A route to possible civil engineering materials: the case of high-pressure phases of lime.

PubMed

Bouibes, A; Zaoui, A

2015-07-23

Lime system has a chemical composition CaO, which is known as thermodynamically stable. The purpose here is to explore further possible phases under pressure, by means of variable-composition ab initio evolutionary algorithm. The present investigation shows surprisingly new stable compounds of lime. At ambient pressure we predict, in addition to CaO, CaO2 as new thermodynamically stable compound. The latter goes through two phases transition from C2/c space group structure to Pna21 at 1.5 GPa, and Pna21 space group structure to I4/mcm at 23.4 GPa. Under increasing pressure, further compounds such as CaO3 become the most stable and stabilize in P-421m space group structure above 65 GPa. For the necessary knowledge of the new predicted compounds, we have computed their mechanical and electronic properties in order to show and to explain the main reasons leading to the structural changes.

Rapid and high throughput fabrication of high temperature stable structures through PDMS transfer printing

NASA Astrophysics Data System (ADS)

Hohenberger, Erik; Freitag, Nathan; Korampally, Venumadhav

2017-07-01

We report on a facile and low cost fabrication approach for structures—gratings and enclosed nanochannels, through simple solution processed chemistries in conjunction with nanotransfer printing techniques. The ink formulation primarily consisting of an organosilicate polymeric network with a small percentage of added 3-aminopropyl triethoxysilane crosslinker allows one to obtain robust structures that are not only stable towards high temperature processing steps as high as 550 °C but also exhibit exceptional stability against a host of organic solvent washes. No discernable structure distortion was observed compared to the as-printed structures (room temperature processed) when printed structures were subjected to temperatures as high as 550 °C. We further demonstrate the applicability of this technique towards the fabrication of more complex nanostructures such as enclosed channels through a double transfer method, leveraging the exceptional room temperature cross-linking ability of the printed structures and their subsequent resistance to dissolution in organic solvent washes. The exceptional temperature and physico-chemical stability of the nanotransfer printed structures makes this a useful fabrication tool that may be applied as is, or integrated with conventional lithographic techniques for the large area fabrication of functional nanostructures and devices.

Structure and Ferroelectric Properties of High Tc BiScO3-PbTiO3 Epitaxial Thin Films.

PubMed

Wasa, Kiyotaka; Yoshida, Shinya; Hanzawa, Hiroaki; Adachi, Hideaki; Matsunaga, Toshiyuki; Tanaka, Shuji

2016-10-01

Piezoelectric ceramics of new composition with higher Curie temperature T c are extensively studied for better piezoelectric microelectromechanical systems (MEMS). Apart from the compositional research, enhanced T c could be achieved in a modified structure. We have considered that a designed laminated structure of Pb(Zr, Ti)O 3 (PZT)-based thin film, i.e., relaxed heteroepitaxial epitaxial thin film, is one of the promising modified structures to enhance T c . This structure exhibits an extraordinarily high T c , i.e., [Formula: see text] (bulk [Formula: see text]). In this paper, we have fabricated the designed laminated structure of high T c (1-x)BiScO 3 -xPbTiO 3 . T c of BS-0.8PT thin films was found to be extraordinarily high, i.e., [Formula: see text] (bulk T c , [Formula: see text]). Their ferroelectric performances were comparable to those of PZT-based thin films. The present BS-xPT thin films have a high potential for fabrication of high-temperature-stable piezoelectric MEMS. The mechanism of the enhanced T c is probably the presence of the mechanically stable interface to temperature in the laminated structure. We believe this designed laminated structure can extract fruitful properties of bulk ferroelectric ceramics.

From Coordination Cages to a Stable Crystalline Porous Hydrogen-Bonded Framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ju, Zhanfeng; Liu, Guoliang; Chen, Yu-Sheng

2017-03-20

A stable framework has been constructed through multiple charge-assisted H-bonds between cationic coordination cages and chloride ions. The framework maintained its original structure upon desolvation, which has been established by single-crystal structure analysis. This is the first fully characterized stable porous framework based on coordination cages after desolvation, with a moderately high Brunauer–Emmett–Teller (BET) surface area of 1201 m2 g-1. This work will not only give a light to construct stable porous frameworks based on coordination cages and thus broaden their applications, but will also provide a new avenue to the assembly of other porous materials such as porous organicmore » cages and hydrogen-bonded organic frameworks (HOFs) through non covalent bonds.« less

Structure of high-index GaAs surfaces - the discovery of the stable GaAs(2511) surface

NASA Astrophysics Data System (ADS)

Jacobi, K.; Geelhaar, L.; Márquez, J.

We present a brief overview of surface structures of high-index GaAs surfaces, putting emphasis on recent progress in our own laboratory. By adapting a commercial scanning tunneling microscope (STM) to our molecular beam epitaxy and ultra high vacuum analysis chamber system, we have been able to atomically resolve the GaAs( {1} {1} {3})B(8 ×1), (114)Aα2(2×1), (137), (3715), and (2511) surface structures. In cooperation with P. Kratzer and M. Scheffler from the Theory Department of the Fritz-Haber Institute we determined the structure of some of these surfaces by comparing total-energy calculations and STM image simulations with the atomically resolved STM images. We present the results for the {112}, {113}, and {114} surfaces. Then we describe what led us to proceed into the inner parts of the stereographic triangle and to discover the hitherto unknown stable GaAs(2511) surface.

Sequence Tolerance of a Highly Stable Single Domain Antibody: Comparison of Computational and Experimental Profiles

DTIC Science & Technology

2016-09-09

evaluating 18 mutants using either the A or B conformer is only r = ~ 0.2. Given the poor performance of approximating the observed experimental ...1    Sequence Tolerance of a Highly Stable Single Domain Antibody: Comparison of Computational and Experimental Profiles Mark A. Olson,1 Patricia...unusually high thermal stability is explored by a combined computational and experimental study. Starting with the crystallographic structure

Childhood Family Structure and Intergenerational Income Mobility in the United States.

PubMed

Bloome, Deirdre

2017-04-01

The declining prevalence of two-parent families helped increase income inequality over recent decades. Does family structure also condition how economic (dis)advantages pass from parents to children? If so, shifts in the organization of family life may contribute to enduring inequality between groups defined by childhood family structure. Using National Longitudinal Survey of Youth data, I combine parametric and nonparametric methods to reveal how family structure moderates intergenerational income mobility in the United States. I find that individuals raised outside stable two-parent homes are much more mobile than individuals from stable two-parent families. Mobility increases with the number of family transitions but does not vary with children's time spent coresiding with both parents or stepparents conditional on a transition. However, this mobility indicates insecurity, not opportunity. Difficulties maintaining middle-class incomes create downward mobility among people raised outside stable two-parent homes. Regardless of parental income, these people are relatively likely to become low-income adults, reflecting a new form of perverse equality. People raised outside stable two-parent families are also less likely to become high-income adults than people from stable two-parent homes. Mobility differences account for about one-quarter of family-structure inequalities in income at the bottom of the income distribution and more than one-third of these inequalities at the top.

Reconstructive structural phase transitions in dense Mg

NASA Astrophysics Data System (ADS)

Yao, Yansun; Klug, Dennis D.

2012-07-01

The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) → body centered cubic (bcc) or hcp → double hexagonal close-packed (dhcp) → bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp → dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp → bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp → bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied.

Reconstructive structural phase transitions in dense Mg.

PubMed

Yao, Yansun; Klug, Dennis D

2012-07-04

The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) → body centered cubic (bcc) or hcp → double hexagonal close-packed (dhcp) → bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp → dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp → bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp → bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied.

High pressure ices.

PubMed

Hermann, Andreas; Ashcroft, N W; Hoffmann, Roald

2012-01-17

H(2)O will be more resistant to metallization than previously thought. From computational evolutionary structure searches, we find a sequence of new stable and meta-stable structures for the ground state of ice in the 1-5 TPa (10 to 50 Mbar) regime, in the static approximation. The previously proposed Pbcm structure is superseded by a Pmc2(1) phase at p = 930 GPa, followed by a predicted transition to a P2(1) crystal structure at p = 1.3 TPa. This phase, featuring higher coordination at O and H, is stable over a wide pressure range, reaching 4.8 TPa. We analyze carefully the geometrical changes in the calculated structures, especially the buckling at the H in O-H-O motifs. All structures are insulating--chemistry burns a deep and (with pressure increase) lasting hole in the density of states near the highest occupied electronic levels of what might be component metallic lattices. Metallization of ice in our calculations occurs only near 4.8 TPa, where the metallic C2/m phase becomes most stable. In this regime, zero-point energies much larger than typical enthalpy differences suggest possible melting of the H sublattice, or even the entire crystal.

Spatial variations in food web structures with alternative stable states: evidence from stable isotope analysis in a large eutrophic lake

NASA Astrophysics Data System (ADS)

Li, Yunkai; Zhang, Yuying; Xu, Jun; Zhang, Shuo

2018-03-01

Food web structures are well known to vary widely among ecosystems. Moreover, many food web studies of lakes have generally attempted to characterize the overall food web structure and have largely ignored internal spatial and environmental variations. In this study, we hypothesize that there is a high degree of spatial heterogeneity within an ecosystem and such heterogeneity may lead to strong variations in environmental conditions and resource availability, in turn resulting in different trophic pathways. Stable carbon and nitrogen isotopes were employed for the whole food web to describe the structure of the food web in different sub-basins within Taihu Lake. This lake is a large eutrophic freshwater lake that has been intensively managed and highly influenced by human activities for more than 50 years. The results show significant isotopic differences between basins with different environmental characteristics. Such differences likely result from isotopic baseline differences combining with a shift in food web structure. Both are related to local spatial heterogeneity in nutrient loading in waters. Such variation should be explicitly considered in future food web studies and ecosystem-based management in this lake ecosystem.

SAIL--stereo-array isotope labeling.

PubMed

Kainosho, Masatsune; Güntert, Peter

2009-11-01

Optimal stereospecific and regiospecific labeling of proteins with stable isotopes enhances the nuclear magnetic resonance (NMR) method for the determination of the three-dimensional protein structures in solution. Stereo-array isotope labeling (SAIL) offers sharpened lines, spectral simplification without loss of information and the ability to rapidly collect and automatically evaluate the structural restraints required to solve a high-quality solution structure for proteins up to twice as large as before. This review gives an overview of stable isotope labeling methods for NMR spectroscopy with proteins and provides an in-depth treatment of the SAIL technology.

Exotic stable cesium polynitrides at high pressure

DOE PAGES

Peng, Feng; Han, Yunxia; Liu, Hanyu; ...

2015-11-19

New polynitrides containing metastable forms of nitrogen are actively investigated as potential high energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN 3, we identified five new stoichiometric compounds (Cs 3N, Cs 2N, CsN, CsN 2, and CsN 5) with interesting structures that may be experimentally synthesizable at modest pressures (i.e., less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N 2, N 3 , Nmore » 4, N 5, N 6) and chains (N ∞). Polymeric chains of nitrogen were found in the high-pressure C2/c phase of CsN 2. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N 4 4- anion. In conclusion, to our best knowledge, this is the first time a charged N 4 species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure.« less

Exotic stable cesium polynitrides at high pressure

PubMed Central

Peng, Feng; Han, Yunxia; Liu, Hanyu; Yao, Yansun

2015-01-01

New polynitrides containing metastable forms of nitrogen are actively investigated as potential high-energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN3, we identified five new stoichiometric compounds (Cs3N, Cs2N, CsN, CsN2, and CsN5) with interesting structures that may be experimentally synthesizable at modest pressures (i.e., less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N2, N3, N4, N5, N6) and chains (N∞). Polymeric chains of nitrogen were found in the high-pressure C2/c phase of CsN2. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N44− anion. To our best knowledge, this is the first time a charged N4 species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure. PMID:26581175

Relaxation mechanisms, structure and properties of semi-coherent interfaces

DOE PAGES

Shao, Shuai; Wang, Jian

2015-10-15

In this work, using the Cu–Ni (111) semi-coherent interface as a model system, we combine atomistic simulations and defect theory to reveal the relaxation mechanisms, structure, and properties of semi-coherent interfaces. By calculating the generalized stacking fault energy (GSFE) profile of the interface, two stable structures and a high-energy structure are located. During the relaxation, the regions that possess the stable structures expand and develop into coherent regions; the regions with high-energy structure shrink into the intersection of misfit dislocations (nodes). This process reduces the interface excess potential energy but increases the core energy of the misfit dislocations and nodes.more » The core width is dependent on the GSFE of the interface. The high-energy structure relaxes by relative rotation and dilatation between the crystals. The relative rotation is responsible for the spiral pattern at nodes. The relative dilatation is responsible for the creation of free volume at nodes, which facilitates the nodes’ structural transformation. Several node structures have been observed and analyzed. In conclusion, the various structures have significant impact on the plastic deformation in terms of lattice dislocation nucleation, as well as the point defect formation energies.« less

Thermodynamic Stability of Low- and High-Index Spinel LiMn 2 O 4 Surface Terminations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warburton, Robert E.; Iddir, Hakim; Curtiss, Larry A.

2016-05-04

Density functional theory calculations are performed within the generalized gradient approximation (GGA+U) to determine stable terminations of both low- and high-index spinel LiMn2O4 (LMO) surfaces. A grand canonical thermodynamic approach is employed, permitting a direct comparison of offstoichiometric surfaces with previously reported stoichiometric surface terminations at various environmental conditions. Within this formalism, we have identified trends in the structure of the low-index surfaces as a function of the Li and O chemical potentials. The results suggest that, under a range of chemical potentials for which bulk LMO is stable, Li/O and Li-rich (111) surface terminations are favored, neither of whichmore » adopts an inverse spinel structure in the subsurface region. This thermodynamic analysis is extended to identify stable structures for certain high-index surfaces, including (311), (331), (511), and (531), which constitute simple models for steps or defects that may be present on real LMO particles. The low- and high-index results are combined to determine the relative stability of each surface facet under a range of environmental conditions. The relative surface energies are further employed to predict LMO particle shapes through a Wulff construction approach, which suggests that LMO particles will adopt either an octahedron or a truncated octahedron shape at conditions in which LMO is thermodynamically stable. These results are in agreement with the experimental observations of LMO particle shapes.« less

Lone pair effect, structural distortions, and potential for superconductivity in Tl perovskites.

PubMed

Schoop, Leslie M; Müchler, Lukas; Felser, Claudia; Cava, R J

2013-05-06

Drawing the analogy to BaBiO3, we investigate via ab initio electronic structure calculations potential new superconductors of the type ATlX3 with A = Rb and Cs and X = F, Cl, and Br, with a particular emphasis on RbTlCl3. On the basis of chemical reasoning, supported by the calculations, we show that Tl-based perovskites have structural and charge instabilities driven by the lone pair effect, similar to the case of BaBiO3, effectively becoming A2Tl(+)Tl(3+)X6. We find that upon hole doping of RbTlCl3, structures without Tl(+) and Tl(3+) charge disproportionation become more stable, although the ideal cubic perovskite, often viewed as the best host for superconductivity, should not be the most stable phase in the system. The known superconductor (Sr,K)BiO3 and hole doped RbTlCl3, predicted to be most stable in the same tetragonal structure, display highly analogous calculated electronic band structures.

Phase relation of CaSO4 at high pressure and temperature up to 90 GPa and 2300 K

NASA Astrophysics Data System (ADS)

Fujii, Taku; Ohfuji, Hiroaki; Inoue, Toru

2016-05-01

Calcium sulfate (CaSO4), one of the major sulfate minerals in the Earth's crust, is expected to play a major role in sulfur recycling into the deep mantle. Here, we investigated the crystal structure and phase relation of CaSO4 up to ~90 GPa and 2300 K through a series of high-pressure experiments combined with in situ X-ray diffraction. CaSO4 forms three thermodynamically stable polymorphs: anhydrite (stable below 3 GPa), monazite-type phase (stable between 3 and ~13 GPa) and barite-type phase (stable up to at least 93 GPa). Anhydrite to monazite-type phase transition is induced by pressure even at room temperature, while monazite- to barite-type transition requires heating at least to 1500 K at ~20 GPa. The barite-type phase cannot always be quenched from high temperature and is distorted to metastable AgMnO4-type structure or another modified barite structure depending on pressure. We obtained the pressure-volume data and density of anhydrite, monazite- and barite-type phases and found that their densities are lower than those calculated from the PREM model in the studied P-T conditions. This suggests that CaSO4 is gravitationally unstable in the mantle and fluid/melt phase into which sulfur dissolves and/or sulfate-sulfide speciation may play a major role in the sulfur recycling into the deep Earth.

Formation of highly stable chimeric trimers by fusion of an adenovirus fiber shaft fragment with the foldon domain of bacteriophage t4 fibritin.

PubMed

Papanikolopoulou, Katerina; Forge, Vincent; Goeltz, Pierrette; Mitraki, Anna

2004-03-05

The folding of beta-structured, fibrous proteins is a largely unexplored area. A class of such proteins is used by viruses as adhesins, and recent studies revealed novel beta-structured motifs for them. We have been studying the folding and assembly of adenovirus fibers that consist of a globular C-terminal domain, a central fibrous shaft, and an N-terminal part that attaches to the viral capsid. The globular C-terminal, or "head" domain, has been postulated to be necessary for the trimerization of the fiber and might act as a registration signal that directs its correct folding and assembly. In this work, we replaced the head of the fiber by the trimerization domain of the bacteriophage T4 fibritin, termed "foldon." Two chimeric proteins, comprising the foldon domain connected at the C-terminal end of four fiber shaft repeats with or without the use of a natural linker sequence, fold into highly stable, SDS-resistant trimers. The structural signatures of the chimeric proteins as seen by CD and infrared spectroscopy are reported. The results suggest that the foldon domain can successfully replace the fiber head domain in ensuring correct trimerization of the shaft sequences. Biological implications and implications for engineering highly stable, beta-structured nanorods are discussed.

Multifunctional Binary Monolayers Ge xP y: Tunable Band Gap, Ferromagnetism, and Photocatalyst for Water Splitting.

PubMed

Li, Pengfei; Zhang, Wei; Li, Dongdong; Liang, Changhao; Zeng, Xiao Cheng

2018-06-04

The most stable structures of two-dimensional Ge x P y and Ge x As y monolayers with different stoichiometries (e.g., GeP, GeP 2 , and GeP 3 ) are explored systematically through the combination of the particle-swarm optimization technique and density functional theory optimization. For GeP 3 , we show that the newly predicted most stable C2/ m structure is 0.16 eV/atom lower in energy than the state-of-the-art P3̅m1 structure reported previously ( Nano Lett. 2017, 17, 1833). The computed electronic band structures suggest that all the stable and metastable monolayers of Ge x P y are semiconductors with highly tunable band gaps under the biaxial strain, allowing strain engineering of their band gaps within nearly the whole visible-light range. More interestingly, the hole doping can convert the C2/ m GeP 3 monolayer from nonmagnetic to ferromagnetic because of its unique valence band structure. For the GeP 2 monolayer, the predicted most stable Pmc2 1 structure is a (quasi) direct-gap semiconductor that possesses a high electron mobility of ∼800 cm 2 V -1 s -1 along the k a direction, which is much higher than that of MoS 2 (∼200 cm 2 V -1 s -1 ). More importantly, the Pmc2 1 GeP 2 monolayer not only can serve as an n-type channel material in field-effect transistors but also can be an effective catalyst for splitting water.

Structure prediction of boron-doped graphene by machine learning

NASA Astrophysics Data System (ADS)

M. Dieb, Thaer; Hou, Zhufeng; Tsuda, Koji

2018-06-01

Heteroatom doping has endowed graphene with manifold aspects of material properties and boosted its applications. The atomic structure determination of doped graphene is vital to understand its material properties. Motivated by the recently synthesized boron-doped graphene with relatively high concentration, here we employ machine learning methods to search the most stable structures of doped boron atoms in graphene, in conjunction with the atomistic simulations. From the determined stable structures, we find that in the free-standing pristine graphene, the doped boron atoms energetically prefer to substitute for the carbon atoms at different sublattice sites and that the para configuration of boron-boron pair is dominant in the cases of high boron concentrations. The boron doping can increase the work function of graphene by 0.7 eV for a boron content higher than 3.1%.

Structural Search for High Pressure CS2 and Xe-Cl Compounds

NASA Astrophysics Data System (ADS)

Zarifi, Niloofar; Tse, John S.

2018-04-01

The recent successful implementation of several methodologies for the prediction of crystal structures based on the first-principles electronic structure have ushered in a new area of computational chemistry. In this study, the two most popular methods, namely genetic evolution and particle swarm optimization, were applied to the investigation of stable crystalline polymorphs of solid carbon disulfide and xenon halides at high pressure. It was found that both methods have their own merits. However, there are subtleties that need to be considered for the proper execution of the methods. We found a two-dimensional (2D) layered structure that may be responsible for the superconductivity in CS2. Except for XeCl2, no thermodynamically stable crystalline Xe halides were found under 60 GPa in the halide-rich region of the phase diagram.

Pressure-induced structural phase transition in transition metal carbides TMC (TM = Ru, Rh, Pd, Os, Ir, Pt): a DFT study

NASA Astrophysics Data System (ADS)

Manikandan, M.; Rajeswarapalanichamy, R.; Iyakutti, K.

2018-03-01

First-principles calculations based on density functional theory was performed to analyse the structural stability of transition metal carbides TMC (TM = Ru, Rh, Pd, Os, Ir, Pt). It is observed that zinc-blende phase is the most stable one for these carbides. Pressure-induced structural phase transition from zinc blende to NiAs phase is predicted at the pressures of 248.5 GPa, 127 GPa and 142 GPa for OsC, IrC and PtC, respectively. The electronic structure reveals that RuC exhibits a semiconducting behaviour with an energy gap of 0.7056 eV. The high bulk modulus values of these carbides indicate that these metal carbides are super hard materials. The high B/G value predicts that the carbides are ductile in their most stable phase.

The Structure of the Protonated Serine Octamer.

PubMed

Scutelnic, Valeriu; Perez, Marta A S; Marianski, Mateusz; Warnke, Stephan; Gregor, Aurelien; Rothlisberger, Ursula; Bowers, Michael T; Baldauf, Carsten; von Helden, Gert; Rizzo, Thomas R; Seo, Jongcheol

2018-06-20

The amino acid serine has long been known to form a protonated "magic-number" cluster containing eight monomer units that shows an unusually high abundance in mass spectra and has a remarkable homochiral preference. Despite many experimental and theoretical studies, there is no consensus on a Ser 8 H + structure that is in agreement with all experimental observations. Here, we present the structure of Ser 8 H + determined by a combination of infrared spectroscopy and ab initio molecular dynamics simulations. The three-dimensional structure that we determine is ∼25 kcal mol -1 more stable than the previous most stable published structure and explains both the homochiral preference and the experimentally observed facile replacement of two serine units.

Generation of efficient 33 GHz optical combs using cascaded stimulated Brillouin scattering effects in optical fiber

NASA Astrophysics Data System (ADS)

Al-Mansoori, M. H.; Al-Sheriyani, A.; Al-Nassri, S.; Hasoon, F. N.

2017-06-01

In this paper, we demonstrate a multi-wavelength Brillouin-erbium fiber laser (BEFL) with ~33 GHz frequency spacing using cascaded stimulated Brillouin scattering effects in optical fiber. The proposed laser structure exhibits a stable output channel with a tuning range of 19 nm, from 1549 nm to 1568 nm. The number of stable output channels produced is six channels with a triple-Brillouin frequency spacing. The output channels exhibit high output power and high optical signal-to-noise ratios (OSNRs). The laser structure has the potential to be used as a multi-wavelength source for optical communication systems.

Childhood Family Structure and Intergenerational Income Mobility in the United States

PubMed Central

2018-01-01

The declining prevalence of two-parent families helped increase income inequality over recent decades. Does family structure also condition how economic (dis)advantages pass from parents to children? If so, shifts in the organization of family life may contribute to enduring inequality between groups defined by childhood family structure. Using National Longitudinal Survey of Youth data, I combine parametric and nonparametric methods to reveal how family structure moderates intergenerational income mobility in the United States. I find that individuals raised outside stable two-parent homes are much more mobile than individuals from stable two-parent families. Mobility increases with the number of family transitions but does not vary with children’s time spent coresiding with both parents or stepparents conditional on a transition. However, this mobility indicates insecurity, not opportunity. Difficulties maintaining middle-class incomes create downward mobility among people raised outside stable two-parent homes. Regardless of parental income, these people are relatively likely to become low-income adults, reflecting a new form of perverse equality. People raised outside stable two-parent families are also less likely to become high-income adults than people from stable two-parent homes. Mobility differences account for about one-quarter of family-structure inequalities in income at the bottom of the income distribution and more than one-third of these inequalities at the top. PMID:28315158

Acousto-optical and SAW propagation characteristics of temperature stable multilayered structures based on LiNbO3 and diamond

NASA Astrophysics Data System (ADS)

Shandilya, Swati; Sreenivas, K.; Gupta, Vinay

2008-01-01

Theoretical studies on the surface acoustic wave (SAW) properties of c-axis oriented LiNbO3/IDT/diamond and diamond/IDT/128° rotated Y-X cut LiNbO3 multilayered structures have been considered. Both layered structures exhibit a positive temperature coefficient of delay (TCD) characteristic, and a zero TCD device is obtained after integrating with an over-layer of either tellurium dioxide (TeO2) or silicon dioxide (SiO2). The presence of a TeO2 over-layer enhanced the electromechanical coupling coefficients of both multilayered structures, which acts as a better temperature compensation layer than SiO2. The temperature stable TeO2/LiNbO3/IDT/diamond layered structure exhibits good electromechanical coefficient and higher phase velocity for SAW device applications. On the other hand, a high acousto-optical (AO) figure of merit (30-37) × 10-15 s3 kg-1 has been obtained for the temperature stable SiO2/diamond/IDT/LiNbO3 layered structure indicating a promising device structure for AO applications.

Structural transition and enhanced phase transition properties of Se doped Ge2Sb2Te5 alloys

NASA Astrophysics Data System (ADS)

Vinod, E. M.; Ramesh, K.; Sangunni, K. S.

2015-01-01

Amorphous Ge2Sb2Te5 (GST) alloy, upon heating crystallize to a metastable NaCl structure around 150°C and then to a stable hexagonal structure at high temperatures (>=250°C). It has been generally understood that the phase change takes place between amorphous and the metastable NaCl structure and not between the amorphous and the stable hexagonal phase. In the present work, it is observed that the thermally evaporated (GST)1-xSex thin films (0 <= x <= 0.50) crystallize directly to the stable hexagonal structure for x >= 0.10, when annealed at temperatures >= 150°C. The intermediate NaCl structure has been observed only for x < 0.10. Chemically ordered network of GST is largely modified for x >= 0.10. Resistance, thermal stability and threshold voltage of the films are found to increase with the increase of Se. The contrast in electrical resistivity between the amorphous and crystalline phases is about 6 orders of magnitude. The increase in Se shifts the absorption edge to lower wavelength and the band gap widens from 0.63 to 1.05 eV. Higher resistance ratio, higher crystallization temperature, direct transition to the stable phase indicate that (GST)1-xSex films are better candidates for phase change memory applications.

Stability of fluorite-type La 2Ce 2O 7 under extreme conditions

DOE PAGES

Zhang, F. X.; Tracy, C. L.; Lang, M.; ...

2016-03-03

Here, the structural stability of fluorite-type La 2Ce 2O 7 was studied at pressure up to ~40 GPa and under hydrothermal conditions (~1 GPa, 350 °C), respectively, using synchrotron x-ray diffraction (XRD) and Raman scattering measurements. XRD measurements indicated that fluorite-type La 2Ce 2O 7 is not stable at pressures greater than 22.6 GPa and slowly transforms to a high-pressure phase. The high-pressure phase is not stable and changes back to the fluorite-type structure when pressure is released. The La 2Ce 2O 7 fluorite is also not stable under hydrothermal conditions and begins to react with water at 200~250 °C.more » Both Raman and XRD results suggest that lanthanum hydroxide La(OH) 3 and La 3+-doped CeO 2 fluorite are the dominant products after hydrothermal treatment.« less

Lithium storage in structurally tunable carbon anode derived from sustainable source

DOE PAGES

Lim, Daw Gen; Kim, Kyungho; Razdan, Mayuri; ...

2017-09-01

Here, a meticulous solid state chemistry approach has been developed for the synthesis of carbon anode from a sustainable source. The reaction mechanism of carbon formation during pyrolysis of sustainable feed-stock was studied in situ by employing Raman microspectroscopy. No Raman spectral changes observed below 160°C (thermally stable precursor) followed by color change, however above 280°C characteristic D and G bands of graphitic carbon are recorded. Derived carbon particles exhibited high specific surface area with low structural ordering (active carbons) to low specific surface area with high graphitic ordering as a function of increasing reaction temperature. Carbons synthesized at 600°Cmore » demonstrated enhanced reversible lithiation capacity (390 mAh g -1), high charge-discharge rate capability, and stable cycle life. On the contrary, carbons synthesized at higher temperatures (>1200°C) produced more graphite-like structure yielding longer specific capacity retention with lower reversible capacity.« less

Stability and Structure of Star-Shape Granules

NASA Astrophysics Data System (ADS)

Zhao, Yuchen; Bares, Jonathan; Liu, Kevin; Zheng, Matthew; Dierichs, Karola; Menges, Achim; Behringer, Robert

Columns made of convex noncohesive grains like sand collapse after being released from a confining container. While various architectures built by concave grains are stable. We explore why these structures are stable, and how stable they can be. We performed experiments by randomly pouring identical star-shape particles into hollow cylinders resting on glass or a roughened base, and then observed how stable these granular columns were after carefully lifting the cylinders. We used particles that are made of acrylics and have six 9 mm arms, which extend symmetrically in xyz directions. We investigated the probability of creating a stable column and other mechanical stability aspects. We define r as the weight fraction of particles that fall out of the column after the confining cylinder is removed. r gradually increases as the column height increases, or the column diameter decreases. We found high column stability when the inter-particle friction was greater. We also explored experiment conditions such as initial vibration of columns when they were confined and loading on the top. In order to understand the inner structure leading to stability, we obtained 3D CT reconstruction data of stable columns. We will discuss coordination number and orientation, etc. We acknowledge supports from W.M.Keck Foundation and Research Triangle MRSEC.

System Theoretic Models for High Density VLSI Structures

DTIC Science & Technology

1989-01-01

vector is also called a stable We first present a simple example to help visualize how vector of the AMN. The set of all stable vectors is denoted these...New York: Springer- Verlag. 1978. 1980 [34] B. De Finetti. "Funtzione catatteristica di un fenomeno aleato- , [16] W A Little. "The existence of

Synthesis, characterization, and thermal stability of SiO2/TiO2/CR-Ag multilayered nanostructures

NASA Astrophysics Data System (ADS)

Díaz, Gabriela; Chang, Yao-Jen; Philipossian, Ara

2018-06-01

The controllable synthesis and characterization of novel thermally stable silver-based particles are described. The experimental approach involves the design of thermally stable nanostructures by the deposition of an interfacial thick, active titania layer between the primary substrate (SiO2 particles) and the metal nanoparticles (Ag NPs), as well as the doping of Ag nanoparticles with an organic molecule (Congo Red, CR). The nanostructured particles were composed of a 330-nm silica core capped by a granular titania layer (10 to 13 nm in thickness), along with monodisperse 5 to 30 nm CR-Ag NPs deposited on top. The titania-coated support (SiO2/TiO2 particles) was shown to be chemically and thermally stable and promoted the nucleation and anchoring of CR-Ag NPs, which prevented the sintering of CR-Ag NPs when the structure was exposed to high temperatures. The thermal stability of the silver composites was examined by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Larger than 10 nm CR-Ag NPs were thermally stable up to 300 °C. Such temperature was high enough to destabilize the CR-Ag NPs due to the melting point of the CR. On the other hand, smaller than 10 nm Ag NPs were stable at temperatures up to 500 °C because of the strong metal-metal oxide binding energy. Energy dispersion X-ray spectroscopy (EDS) was carried out to qualitatively analyze the chemical stability of the structure at different temperatures which confirmed the stability of the structure and the existence of silver NPs at temperatures up to 500 °C.

Nb-doped SrTiO3 glass-ceramics as high temperature stable n-type oxide thermoelectrics

NASA Astrophysics Data System (ADS)

Lingner, Julian; Jakob, Gerhard; Letz, Martin

2012-06-01

Niobium doped SrTiO3 is known for its high potential as an oxide thermoelectric material and is one of the possible candidates for the n-type site in an oxidic thermoelectric module. The high thermal conductivity [1] and the lack of high-temperature stability of the oxygen vacancies [2] limit its properties in the ceramic systems. Glass-ceramics are intrinsic nano-structured systems and provide crystal phases densely embedded in a glass matrix which prevents the material from detoriation at high temperatures. In particular, the glass-matrix prevents an uncontrolled reoxidization as well as an uncontrolled grain growth therefore retaining the nano-structure even at high temperatures. Here, measurements and results of first glass-ceramic systems are presented, which show a low thermal conductivity due to the residue glass phase. Furthermore a stable thermal cycling up to 650 °C is demonstrated.

Structure and phase composition of ultrafine-grained TiNb alloy after high-temperature annealings

NASA Astrophysics Data System (ADS)

Eroshenko, Anna Yu.; Glukhov, Ivan A.; Mairambekova, Aikol; Tolmachev, Alexey I.; Sharkeev, Yurii P.

2017-12-01

The paper presents the experimental data observed in the microstructure and phase composition of ultrafine-grained Ti-40 mass % Nb (Ti40Nb) alloy after high-temperature annealings. The ultrafine-grained Ti40Nb alloy is produced by severe plastic deformation (SPD). This method includes multiple abc-pressing and multi-pass rolling followed by further pre-recrystallizing annealing which, in its turn, enhances the formation of ultrafine-grained structures with mean size of 0.28 µm involving stable β- and α-phase and metastable nanosized ω-phase in the alloy. It is shown that annealing at 500°C preserves the ultrafine-grained structure and phase composition. In cases of annealing at 800°C the ultrafine-grained state transforms into the coarse-grained state. The stable β-phase and the nanosized metastable ω-phase have been identified in the coarse-grained structure.

New insight in the structural features of haloadaptation in α-amylases from halophilic Archaea following homology modeling strategy: folded and stable conformation maintained through low hydrophobicity and highly negative charged surface

NASA Astrophysics Data System (ADS)

Zorgani, Mohamed Amine; Patron, Kevin; Desvaux, Mickaël

2014-07-01

Proteins from halophilic archaea, which live in extreme saline conditions, have evolved to remain folded, active and stable at very high ionic strengths. Understanding the mechanism of haloadaptation is the first step toward engineering of halostable biomolecules. Amylases are one of the main enzymes used in industry. Yet, no three-dimensional structure has been experimentally resolved for α-amylases from halophilic archaea. In this study, homology structure modeling of α-amylases from the halophilic archaea Haloarcula marismortui, Haloarcula hispanica, and Halalkalicoccus jeotgali were performed. The resulting models were subjected to energy minimization, evaluation, and structural analysis. Calculations of the amino acid composition, salt bridges and hydrophobic interactions were also performed and compared to a set of non-halophilic counterparts. It clearly appeared that haloarchaeal α-amylases exhibited lower propensities for helix formation and higher propensities for coil-forming regions. Furthermore, they could maintain a folded and stable conformation in high salt concentration through highly negative charged surface with over representation of acidic residues, especially Asp, and low hydrophobicity with increase of salt bridges and decrease in hydrophobic interactions on the protein surface. This study sheds some light on the stability of α-amylases from halophilic archaea and provides strong basis not only to understand haloadaptation mechanisms of proteins in microorganisms from hypersalines environments but also for biotechnological applications.

New insight in the structural features of haloadaptation in α-amylases from halophilic Archaea following homology modeling strategy: folded and stable conformation maintained through low hydrophobicity and highly negative charged surface.

PubMed

Zorgani, Mohamed Amine; Patron, Kevin; Desvaux, Mickaël

2014-07-01

Proteins from halophilic archaea, which live in extreme saline conditions, have evolved to remain folded, active and stable at very high ionic strengths. Understanding the mechanism of haloadaptation is the first step toward engineering of halostable biomolecules. Amylases are one of the main enzymes used in industry. Yet, no three-dimensional structure has been experimentally resolved for α-amylases from halophilic archaea. In this study, homology structure modeling of α-amylases from the halophilic archaea Haloarcula marismortui, Haloarcula hispanica, and Halalkalicoccus jeotgali were performed. The resulting models were subjected to energy minimization, evaluation, and structural analysis. Calculations of the amino acid composition, salt bridges and hydrophobic interactions were also performed and compared to a set of non-halophilic counterparts. It clearly appeared that haloarchaeal α-amylases exhibited lower propensities for helix formation and higher propensities for coil-forming regions. Furthermore, they could maintain a folded and stable conformation in high salt concentration through highly negative charged surface with over representation of acidic residues, especially Asp, and low hydrophobicity with increase of salt bridges and decrease in hydrophobic interactions on the protein surface. This study sheds some light on the stability of α-amylases from halophilic archaea and provides strong basis not only to understand haloadaptation mechanisms of proteins in microorganisms from hypersalines environments but also for biotechnological applications.

Long-lived groupers require structurally stable reefs in the face of repeated climate change disturbances

NASA Astrophysics Data System (ADS)

Karkarey, R.; Kelkar, N.; Lobo, A. Savio; Alcoverro, T.; Arthur, R.

2014-06-01

Benthic recovery from climate-related disturbances does not always warrant a commensurate functional recovery for reef-associated fish communities. Here, we examine the distribution of benthic groupers (family Serranidae) in coral reef communities from the Lakshadweep archipelago (Arabian Sea) in response to structural complexity and long-term habitat stability. These coral reefs that have been subject to two major El Niño Southern Oscillation-related coral bleaching events in the last decades (1998 and 2010). First, we employ a long-term (12-yr) benthic-monitoring dataset to track habitat structural stability at twelve reef sites in the archipelago. Structural stability of reefs was strongly driven by exposure to monsoon storms and depth, which made deeper and more sheltered reefs on the eastern aspect more stable than the more exposed (western) and shallower reefs. We surveyed groupers (species richness, abundance, biomass) in 60 sites across the entire archipelago, representing both exposures and depths. Sites were selected along a gradient of structural complexity from very low to high. Grouper biomass appeared to vary with habitat stability with significant differences between depth and exposure; sheltered deep reefs had a higher grouper biomass than either sheltered shallow or exposed (deep and shallow) reefs. Species richness and abundance showed similar (though not significant) trends. More interestingly, average grouper biomass increased exponentially with structural complexity, but only at the sheltered deep (high stability) sites, despite the availability of recovered structure at exposed deep and shallow sites (lower-stability sites). This trend was especially pronounced for long-lived groupers (life span >10 yrs). These results suggest that long-lived groupers may prefer temporally stable reefs, independent of the local availability of habitat structure. In reefs subject to repeated disturbances, the presence of structurally stable reefs may be critical as refuges for functionally important, long-lived species like groupers.

Emergence of a few distinct structures from a single formal structure type during high-throughput screening for stable compounds: The case of RbCuS and RbCuSe

NASA Astrophysics Data System (ADS)

Trimarchi, Giancarlo; Zhang, Xiuwen; DeVries Vermeer, Michael J.; Cantwell, Jacqueline; Poeppelmeier, Kenneth R.; Zunger, Alex

2015-10-01

Theoretical sorting of stable and synthesizable "missing compounds" from those that are unstable is a crucial step in the discovery of previously unknown functional materials. This active research area often involves high-throughput (HT) examination of the total energy of a given compound in a list of candidate formal structure types (FSTs), searching for those with the lowest energy within that list. While it is well appreciated that local relaxation methods based on a fixed list of structure types can lead to inaccurate geometries, this approach is widely used in HT studies because it produces answers faster than global optimization methods (that vary lattice vectors and atomic positions without local restrictions). We find, however, a different failure mode of the HT protocol: specific crystallographic classes of formal structure types each correspond to a series of chemically distinct "daughter structure types" (DSTs) that have the same space group but possess totally different local bonding configurations, including coordination types. Failure to include such DSTs in the fixed list of examined candidate structures used in contemporary high-throughput approaches can lead to qualitative misidentification of the stable bonding pattern, not just quantitative inaccuracies. In this work, we (i) clarify the understanding of the general DST-FST relationship, thus improving current discovery HT approaches, (ii) illustrate this failure mode for RbCuS and RbCuSe (the latter being a yet unreported compound and is predicted here) by developing a synthesis method and accelerated crystal-structure determination, and (iii) apply the genetic-algorithm-based global space-group optimization (GSGO) approach which is not vulnerable to the failure mode of HT searches of fixed lists, demonstrating a correct identification of the stable DST. The broad impact of items (i)-(iii) lies in the demonstrated predictive ability of a more comprehensive search strategy than what is currently used—use HT calculations as the preliminary broad screening followed by unbiased GSGO of the final candidates.

Evolution of the bi-stable wake of a square-back automotive shape

NASA Astrophysics Data System (ADS)

Pavia, Giancarlo; Passmore, Martin; Sardu, Costantino

2018-01-01

Square-back shapes are popular in the automotive market for their high level of practicality. These geometries, however, are usually characterised by high drag and their wake dynamics present aspects, such as the coexistence of a long-time bi-stable behaviour and short-time global fluctuating modes that are not fully understood. In the present paper, the unsteady behaviour of the wake of a generic square-back car geometry is characterised with an emphasis on identifying the causal relationship between the different dynamic modes in the wake. The study is experimental, consisting of balance, pressure, and stereoscopic PIV measurements. Applying wavelet and cross-wavelet transforms to the balance data, a quasi-steady correlation is demonstrated between the forces and bi-stable modes. This is investigated by applying proper orthogonal decomposition to the pressure and velocity data sets and a new structure is proposed for each bi-stable state, consisting of a hairpin vortex that originates from one of the two model's vertical trailing edges and bends towards the opposite side as it merges into a single streamwise vortex downstream. The wake pumping motion is also identified and for the first time linked with the motion of the bi-stable vortical structure in the streamwise direction, resulting in out-of-phase pressure variations between the two vertical halves of the model base. A phase-averaged low-order model is also proposed that provides a comprehensive description of the mechanisms of the switch between the bi-stable states. It is demonstrated that, during the switch, the wake becomes laterally symmetric and, at this point, the level of interaction between the recirculating structures and the base reaches a minimum, yielding, for this geometry, a 7% reduction of the base drag compared to the time-averaged result.

Stiff, Thermally Stable and Highly Anisotropic Wood-Derived Carbon Composite Monoliths for Electromagnetic Interference Shielding.

PubMed

Yuan, Ye; Sun, Xianxian; Yang, Minglong; Xu, Fan; Lin, Zaishan; Zhao, Xu; Ding, Yujie; Li, Jianjun; Yin, Weilong; Peng, Qingyu; He, Xiaodong; Li, Yibin

2017-06-28

Electromagnetic interference (EMI) shielding materials for electronic devices in aviation and aerospace not only need lightweight and high shielding effectiveness, but also should withstand harsh environments. Traditional EMI shielding materials often show heavy weight, poor thermal stability, short lifetime, poor tolerance to chemicals, and are hard-to-manufacture. Searching for high-efficiency EMI shielding materials overcoming the above weaknesses is still a great challenge. Herein, inspired by the unique structure of natural wood, lightweight and highly anisotropic wood-derived carbon composite EMI shielding materials have been prepared which possess not only high EMI shielding performance and mechanical stable characteristics, but also possess thermally stable properties, outperforming those metals, conductive polymers, and their composites. The newly developed low-cost materials are promising for specific applications in aerospace electronic devices, especially regarding extreme temperatures.

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

NASA Astrophysics Data System (ADS)

Zhao, Jie; Zhou, Guangmin; Yan, Kai; Xie, Jin; Li, Yuzhang; Liao, Lei; Jin, Yang; Liu, Kai; Hsu, Po-Chun; Wang, Jiangyan; Cheng, Hui-Ming; Cui, Yi

2017-10-01

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed LixM (M = Si, Sn, or Al) nanoparticles encapsulated by large graphene sheets. With the protection of graphene sheets, the large and freestanding LixM/graphene foils are stable in different air conditions. With fully expanded LixSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). This foil is also paired with high-capacity Li-free V2O5 and sulfur cathodes to achieve stable full-cell cycling.

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

DOE PAGES

Zhao, Jie; Zhou, Guangmin; Yan, Kai; ...

2017-07-10

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed Li xM (M = Si, Sn, or Al) nanoparticles encapsulated by largemore » graphene sheets. With the protection of graphene sheets, the large and freestanding Li xM/graphene foils are stable in different air conditions. With fully expanded Li xSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). As a result, this foil is also paired with high-capacity Li-free V 2O 5 and sulfur cathodes to achieve stable full-cell cycling.« less

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Jie; Zhou, Guangmin; Yan, Kai

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed Li xM (M = Si, Sn, or Al) nanoparticles encapsulated by largemore » graphene sheets. With the protection of graphene sheets, the large and freestanding Li xM/graphene foils are stable in different air conditions. With fully expanded Li xSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). As a result, this foil is also paired with high-capacity Li-free V 2O 5 and sulfur cathodes to achieve stable full-cell cycling.« less

Stable high absorption metamaterial for wide-angle incidence of terahertz wave

NASA Astrophysics Data System (ADS)

Du, Qiujiao; Zeng, Zuoxun; Xiang, Dong; Lv, Tao; Zhang, Guangyong; Yang, Hongwu

2014-04-01

We propose a metamaterial based on metallic Jerusalem cross and cross-wire structures for realizing relatively stable high absorption with respect to the wide angle incidence of both polarized terahertz (THz) waves. Numerical simulations are carried out to verify the proposed absorber. For both transverse electric and transverse magnetic polarizations, absorptions around 0.93 THz reach nearly up to unity under normal incidence and maintain above 97% over a wide incidence angle range. The THz absorber can be easily micro-fabricated due to a thickness about 40 times smaller than operating wavelength. The proposed metamaterial is a promising candidate as absorbing element in THz thermal imager, due to its wide angle, stable high absorption and very thin thickness.

Mental health trajectories among women in Australia as they age.

PubMed

Tran, Thach; Hammarberg, Karin; Ryan, Joanne; Lowthian, Judy; Freak-Poli, Rosanne; Owen, Alice; Kirkman, Maggie; Curtis, Andrea; Rowe, Heather; Brown, Helen; Ward, Stephanie; Britt, Carlene; Fisher, Jane

2018-05-23

To ascertain the trajectories of mental health among women in Australia assessed in repeat waves from their early 70 s to the end of their lives or their mid 80 s. Secondary analysis of data contributed by the 1921-26 cohort of the Australian Longitudinal Study of Women's Health Waves 1-6. Primary outcome was the 4-item SF-36 Vitality Subscale, which assesses mental health as life satisfaction, social participation, energy and enthusiasm. Structural, individual and intermediary factors were assessed using study-specific and standardised measures. Trajectories were identified using Growth Mixture Modelling and associations with baseline characteristics with Structural Equation Modelling. 12,432 women completed Survey One. Three mental health trajectories: stable high (77%); stable low (18.2%) and declining from high to low (4.8%) were identified. Compared to the stable high group, women in the stable low group were significantly less physically active, had more nutritional risks, more recent adverse life events, fewer social interactions and less social support, reported more stress and were more likely to have a serious illness or disability at Survey One. The declining group had similar characteristics to the stable high group, but were significantly more likely to report at baseline that they had experienced recent financial, physical and emotional elder abuse. These interact, but not directly with socioeconomic position and marital status. Mental health among older women is related to social relationships, general health, access to physical activity and healthy nutrition, coincidental adverse life events and experiences of interpersonal violence, in particular elder abuse.

Predicting New Materials for Hydrogen Storage Application

PubMed Central

Vajeeston, Ponniah; Ravindran, Ponniah; Fjellvåg, Helmer

2009-01-01

Knowledge about the ground-state crystal structure is a prerequisite for the rational understanding of solid-state properties of new materials. To act as an efficient energy carrier, hydrogen should be absorbed and desorbed in materials easily and in high quantities. Owing to the complexity in structural arrangements and difficulties involved in establishing hydrogen positions by x-ray diffraction methods, the structural information of hydrides are very limited compared to other classes of materials (like oxides, intermetallics, etc.). This can be overcome by conducting computational simulations combined with selected experimental study which can save environment, money, and man power. The predicting capability of first-principles density functional theory (DFT) is already well recognized and in many cases structural and thermodynamic properties of single/multi component system are predicted. This review will focus on possible new classes of materials those have high hydrogen content, demonstrate the ability of DFT to predict crystal structure, and search for potential meta-stable phases. Stabilization of such meta-stable phases is also discussed.

Sea-Sponge-like Structure of Nano-Fe3O4 on Skeleton-C with Long Cycle Life under High Rate for Li-Ion Batteries.

PubMed

Chen, Shipei; Wu, Qingnan; Wen, Ming; Wu, Qingsheng; Li, Jiaqi; Cui, Yi; Pinna, Nicola; Fan, Yafei; Wu, Tong

2018-06-13

To meet the demands of long cycle life under high rate for lithium-ion batteries, the advancement of anode materials with stable structural properties is necessarily demanded. Such promotion needs to design reasonable structure to facilitate the transportation of electron and lithium ions (Li + ). Herein, a novel C/Fe 3 O 4 sea-sponge-like structure was synthesized by ultrasonic spray pyrolysis following thermal decomposition process. On the basis of sea-sponge carbon (SSC) excellences in electronic conductivity and short Li + diffusion pathway, nano-Fe 3 O 4 anchored on stable SSC skeleton can deliver high electrochemical performance with long cycle life under high rate. During electrochemical cycling, well-dispersed nano-Fe 3 O 4 in ∼6 nm not only averts excessive pulverization and is enveloped by solid electrolyte interphase film, but also increases Li + diffusion efficiency. The much improved electrochemical properties showed a capacity of around 460 mAh g -1 at a high rate of 1.5C with a retention rate of 93%, which is maintained without degradation up to 1000 cycles (1C = 1000 mA g -1 ).

Electrotransfection of Polyamine Folded DNA Origami Structures.

PubMed

Chopra, Aradhana; Krishnan, Swati; Simmel, Friedrich C

2016-10-12

DNA origami structures are artificial molecular nanostructures in which DNA double helices are forced into a closely packed configuration by a multitude of DNA strand crossovers. We show that three different types of origami structures (a flat sheet, a hollow tube, and a compact origami block) can be formed in magnesium-free buffer solutions containing low (<1 mM) concentrations of the condensing agent spermidine. Much like in DNA condensation, the amount of spermidine required for origami folding is proportional to the DNA concentration. At excessive amounts, the structures aggregate and precipitate. In contrast to origami structures formed in conventional buffers, the resulting structures are stable in the presence of high electric field pulses, such as those commonly used for electrotransfection experiments. We demonstrate that spermidine-stabilized structures are stable in cell lysate and can be delivered into mammalian cells via electroporation.

Chemoselective synthesis of functional homocysteine residues in polypeptides and peptides.

PubMed

Gharakhanian, Eric G; Deming, Timothy J

2016-04-18

A methodology was developed for efficient, chemoselective transformation of methionine residues into stable, functional homocysteine derivatives. Methionine residues can undergo highly chemoselective alkylation reactions at low pH to yield stable sulfonium ions, which could then be selectively demethylated to give stable alkyl homocysteine residues. This mild, two-step process is chemoselective, efficient, tolerates many functional groups, and provides a means for creation of new functional biopolymers, site-specific peptide tagging, and synthesis of biomimetic and structural analogs of peptides.

Band structure and phonon properties of lithium fluoride at high pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panchal, J. M., E-mail: amitjignesh@yahoo.co.in; Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat; Joshi, Mitesh

2016-05-23

High pressure structural and electronic properties of Lithium Fluoride (LiF) have been studied by employing an ab-initio pseudopotential method and a linear response scheme within the density functional theory (DFT) in conjunction with quasi harmonic Debye model. The band structure and electronic density of states conforms that the LiF is stable and is having insulator behavior at ambient as well as at high pressure up to 1 Mbar. Conclusions based on Band structure, phonon dispersion and phonon density of states are outlined.

Highly scalable multichannel mesh electronics for stable chronic brain electrophysiology

PubMed Central

Fu, Tian-Ming; Hong, Guosong; Viveros, Robert D.; Zhou, Tao

2017-01-01

Implantable electrical probes have led to advances in neuroscience, brain−machine interfaces, and treatment of neurological diseases, yet they remain limited in several key aspects. Ideally, an electrical probe should be capable of recording from large numbers of neurons across multiple local circuits and, importantly, allow stable tracking of the evolution of these neurons over the entire course of study. Silicon probes based on microfabrication can yield large-scale, high-density recording but face challenges of chronic gliosis and instability due to mechanical and structural mismatch with the brain. Ultraflexible mesh electronics, on the other hand, have demonstrated negligible chronic immune response and stable long-term brain monitoring at single-neuron level, although, to date, it has been limited to 16 channels. Here, we present a scalable scheme for highly multiplexed mesh electronics probes to bridge the gap between scalability and flexibility, where 32 to 128 channels per probe were implemented while the crucial brain-like structure and mechanics were maintained. Combining this mesh design with multisite injection, we demonstrate stable 128-channel local field potential and single-unit recordings from multiple brain regions in awake restrained mice over 4 mo. In addition, the newly integrated mesh is used to validate stable chronic recordings in freely behaving mice. This scalable scheme for mesh electronics together with demonstrated long-term stability represent important progress toward the realization of ideal implantable electrical probes allowing for mapping and tracking single-neuron level circuit changes associated with learning, aging, and neurodegenerative diseases. PMID:29109247

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells

PubMed Central

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-01-01

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm−1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm−2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm−2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode. PMID:26648509

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-12-01

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm-1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm-2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm-2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells.

PubMed

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-12-09

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm(-1) in 5% H2 and peak power densities of 1.72 and 0.54 W cm(-2) using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm(-2). To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

The phase diagrams of KCaF3 and NaMgF3 by ab initio simulations

NASA Astrophysics Data System (ADS)

Jakymiw, Clément; Vočadlo, Lidunka; Dobson, David P.; Bailey, Edward; Thomson, Andrew R.; Brodholt, John P.; Wood, Ian G.; Lindsay-Scott, Alex

2018-04-01

ABF3 compounds have been found to make valuable low-pressure analogues for high-pressure silicate phases that are present in the Earth's deep interior and that may also occur in the interiors of exoplanets. The phase diagrams of two of these materials, KCaF3 and NaMgF3, have been investigated in detail by static ab initio computer simulations based on density functional theory. Six ABF3 polymorphs were considered, as follows: the orthorhombic perovskite structure (GdFeO3-type; space group Pbnm); the orthorhombic CaIrO3 structure ( Cmcm; commonly referred to as the "post-perovskite" structure); the orthorhombic Sb2S3 and La2S3 structures (both Pmcn); the hexagonal structure previously suggested in computer simulations of NaMgF3 ( P63/ mmc); the monoclinic structure found to be intermediate between the perovskite and CaIrO3 structures in CaRhO3 ( P21/ m). Volumetric and axial equations of state of all phases considered are presented. For KCaF3, as expected, the perovskite phase is shown to be the most thermodynamically stable at atmospheric pressure. With increasing pressure, the relative stability of the KCaF3 phases then follows the sequence: perovskite → La2S3 structure → Sb2S3 structure → P63/ mmc structure; the CaIrO3 structure is never the most stable form. Above about 2.6 GPa, however, none of the KCaF3 polymorphs are stable with respect to dissociation into KF and CaF2. The possibility that high-pressure KCaF3 polymorphs might exist metastably at 300 K, or might be stabilised by chemical substitution so as to occur within the standard operating range of a multi-anvil press, is briefly discussed. For NaMgF3, the transitions to the high-pressure phases occur at pressures outside the normal range of a multi-anvil press. Two different sequences of transitions had previously been suggested from computer simulations. With increasing pressure, we find that the relative stability of the NaMgF3 phases follows the sequence: perovskite → CaIrO3 structure → Sb2S3 structure → P63/ mmc structure. However, only the perovskite and CaIrO3 structures are stable with respect to dissociation into NaF and MgF2.

Changes in Age Structure and Rural Community Growth.

ERIC Educational Resources Information Center

McGranahan, David A.

1985-01-01

Whatever migration patterns evolve, changes in the age structure mean that rural communities in general can expect fairly stable elementary school population, reduced high school population, slower growth in new business and employment, and continued increase in the elderly population. (JHZ)

Blurred Palmprint Recognition Based on Stable-Feature Extraction Using a Vese–Osher Decomposition Model

PubMed Central

Hong, Danfeng; Su, Jian; Hong, Qinggen; Pan, Zhenkuan; Wang, Guodong

2014-01-01

As palmprints are captured using non-contact devices, image blur is inevitably generated because of the defocused status. This degrades the recognition performance of the system. To solve this problem, we propose a stable-feature extraction method based on a Vese–Osher (VO) decomposition model to recognize blurred palmprints effectively. A Gaussian defocus degradation model is first established to simulate image blur. With different degrees of blurring, stable features are found to exist in the image which can be investigated by analyzing the blur theoretically. Then, a VO decomposition model is used to obtain structure and texture layers of the blurred palmprint images. The structure layer is stable for different degrees of blurring (this is a theoretical conclusion that needs to be further proved via experiment). Next, an algorithm based on weighted robustness histogram of oriented gradients (WRHOG) is designed to extract the stable features from the structure layer of the blurred palmprint image. Finally, a normalized correlation coefficient is introduced to measure the similarity in the palmprint features. We also designed and performed a series of experiments to show the benefits of the proposed method. The experimental results are used to demonstrate the theoretical conclusion that the structure layer is stable for different blurring scales. The WRHOG method also proves to be an advanced and robust method of distinguishing blurred palmprints. The recognition results obtained using the proposed method and data from two palmprint databases (PolyU and Blurred–PolyU) are stable and superior in comparison to previous high-performance methods (the equal error rate is only 0.132%). In addition, the authentication time is less than 1.3 s, which is fast enough to meet real-time demands. Therefore, the proposed method is a feasible way of implementing blurred palmprint recognition. PMID:24992328

Blurred palmprint recognition based on stable-feature extraction using a Vese-Osher decomposition model.

PubMed

Hong, Danfeng; Su, Jian; Hong, Qinggen; Pan, Zhenkuan; Wang, Guodong

2014-01-01

As palmprints are captured using non-contact devices, image blur is inevitably generated because of the defocused status. This degrades the recognition performance of the system. To solve this problem, we propose a stable-feature extraction method based on a Vese-Osher (VO) decomposition model to recognize blurred palmprints effectively. A Gaussian defocus degradation model is first established to simulate image blur. With different degrees of blurring, stable features are found to exist in the image which can be investigated by analyzing the blur theoretically. Then, a VO decomposition model is used to obtain structure and texture layers of the blurred palmprint images. The structure layer is stable for different degrees of blurring (this is a theoretical conclusion that needs to be further proved via experiment). Next, an algorithm based on weighted robustness histogram of oriented gradients (WRHOG) is designed to extract the stable features from the structure layer of the blurred palmprint image. Finally, a normalized correlation coefficient is introduced to measure the similarity in the palmprint features. We also designed and performed a series of experiments to show the benefits of the proposed method. The experimental results are used to demonstrate the theoretical conclusion that the structure layer is stable for different blurring scales. The WRHOG method also proves to be an advanced and robust method of distinguishing blurred palmprints. The recognition results obtained using the proposed method and data from two palmprint databases (PolyU and Blurred-PolyU) are stable and superior in comparison to previous high-performance methods (the equal error rate is only 0.132%). In addition, the authentication time is less than 1.3 s, which is fast enough to meet real-time demands. Therefore, the proposed method is a feasible way of implementing blurred palmprint recognition.

High Entropy Alloys: Criteria for Stable Structure

NASA Astrophysics Data System (ADS)

Tripathy, Snehashish; Gupta, Gaurav; Chowdhury, Sandip Ghosh

2018-01-01

An effort has been made to reassess the phase predicting capability of various thermodynamic and topological parameters across a wide range of HEA systems. These parameters are valence electron concentration, atomic mismatch ( δ), electronegativity difference (Δ χ), mixing entropy (Δ S mix), entropy of fusion (Δ S f), and mismatch entropy ( S σ ). In continuation of that, two new parameters (a) Modified Darken-Gurry parameter ( A = Sσ * χ) and (b) Modified Mismatch Entropy parameter ( B = δ* Sσ) have been designed to predict the stable crystal structure that would form in the HEA systems considered for assessment.

Evolution of the Structure of Cu-1% Sn Bronze under High Pressure Torsion and Subsequent Annealing

NASA Astrophysics Data System (ADS)

Popov, V. V.; Popova, E. N.; Stolbovsky, A. V.; Falahutdinov, R. M.

2018-04-01

The evolution of the structure of tin bronze under the room-temperature high-pressure torsion with different degrees of deformation and the subsequent annealing has been investigated. The thermal stability of the structure formed, namely, its behavior upon annealing in the temperature range of 150-400°C has been studied. The possibility of alloying copper with tin has been analyzed with the purpose of obtaining a thermally stable nanostructure with high strength characteristics.

High temperature glass thermal control structure and coating. [for application to spacecraft reusable heat shielding

NASA Technical Reports Server (NTRS)

Stewart, D. A.; Goldstein, H. E.; Leiser, D. B. (Inventor)

1983-01-01

A high temperature stable and solar radiation stable thermal control coating is described which is useful either as such, applied directly to a member to be protected, or applied as a coating on a re-usable surface insulation (RSI). It has a base coat layer and an overlay glass layer. The base coat layer has a high emittance, and the overlay layer is formed from discrete, but sintered together glass particles to give the overlay layer a high scattering coefficient. The resulting two-layer space and thermal control coating has an absorptivity-to-emissivity ratio of less than or equal to 0.4 at room temperature, with an emittance of 0.8 at 1200 F. It is capable of exposure to either solar radiation or temperatures as high as 2000 F without significant degradation. When used as a coating on a silica substrate to give an RSI structure, the coatings of this invention show significantly less reduction in emittance after long term convective heating and less residual strain than prior art coatings for RSI structures.

Influence of heating procedures on the surface structure of stabilized polyacrylonitrile fibers

NASA Astrophysics Data System (ADS)

Zhao, Rui-Xue; Sun, Peng-fei; Liu, Rui-jian; Ding, Zhan-hui; Li, Xiang-shan; Liu, Xiao-yang; Zhao, Xu-dong; Gao, Zhong-min

2018-03-01

The stabilized polyacrylonitrile (PAN) fibers were obtained after heating the precursor PAN fibers under air atmosphere by different procedures. The surface structures and compositions of as-prepared stabilized PAN fibers have been investigated by SEM, SSNMR, XPS and Raman spectroscopy. The results show that 200 °C, 220 °C, 250 °C, and 280 °C are key temperatures for the preparation of stabilized PAN fibers. The effect of heating gradient on the structure of stabilized PAN fibers has been studied. The possible chemical structural formulas for the PAN fibers is provided, which include the stable and unstable structure. The stable structure (α-type) could endure the strong chemical reactions and the unstable structure (β- or γ-type) could mitigate the drastic oxidation reactions. The inferences of chemical formula of stabilized PAN fibers are benefit to the design of appropriate surface structure for the production for high quality carbon fibers.

Pressure-induced phase transition in titanium alloys

NASA Astrophysics Data System (ADS)

Murugeswari, R.; Rajeswarapalanichamy, R.; Benial, A. Milton Franklin

2018-05-01

The structural, elastic, magnetic and electronic properties of titanium-based ferromagnetic (FM) TiX (X = Fe, Co, Ni) alloys are investigated by the first principles calculations based on density functional theory using the Vienna ab initio simulation code. At ambient pressure, all the three alloys TiFe, TiCo and TiNi are highly stable in CsCl structure. The calculated lattice parameters and ground state properties are in good agreement with the available theoretical and experimental results. The density of states explains that these alloys possess the metallic nature at normal and high pressures. A pressure-induced structural phase transitions from CsCl to NaCl phase at 46 GPa and NaCl to ZB phase at 49 GPa in TiFe, CsCl to ZB phase in TiCo at 52 GPa, CsCl to hexagonal phase at 22 GPa and hexagonal to ZB phase at 66 GPa in TiNi are observed. The calculated Debye temperatures of TiX (X = Fe, Co, Ni) alloys are in good agreement with earlier reports. Binding energy shows that the TiCo is the most stable alloy. The magnetic property of TiX (X = Fe, Co, Ni) alloys reveals that TiFe is stable in nonmagnetic phase and the other two alloys, TiCo and TiNi, are stable in FM phase at normal pressure.

A coarse grained molecular dynamics simulation study on the structural properties of carbon nanotube-dendrimer composites.

PubMed

Kavyani, Sajjad; Dadvar, Mitra; Modarress, Hamid; Amjad-Iranagh, Sepideh

2018-04-25

By employing coarse grained (CG) molecular dynamics (MD) simulation, the effect of the size and hydrophilic/hydrophobic properties of the interior/exterior structures of the dendrimers in carbon nanotube (CNT)-dendrimer composites has been studied, to find a stable composite with high solubility in water and the capability to be used in drug delivery applications. For this purpose, composites consisting of core-shell dendrimer complexes including: [PPI{core}-PAMAM{shell}], [PAMAM{core}-polyethyleneglycol (PEG){shell}] and [PAMAM{core}-fattyacid (FTA){shell}] were constructed. A new CG model for the fatty acid (FTA) molecules as functionalized to the dendrimer was developed, which, unlike the previous models, could generate the structural conformations of the FTA properly. The obtained results indicated that the dendrimer complexes with short FTA chains can form stable composites with the CNT. Also, it was found that the pristine PAMAM and PPI-PAMAM with small PPI, and PAMAM-PEG dendrimers with short PEG chains, can distribute their chains into the water medium and interact with the CNT efficiently, to form a stable water-soluble CNT-dendrimer composite. The results demonstrated that the structural difference between the interior and exterior of a core-shell dendrimer complex can prevent the core and the interior layers of the dendrimer complex from interacting with the CNT. An overall analysis of the results manifested that the CNT-PAMAM:4-PEG:4 is the most stable composite, due to strong binding of the dendrimer with the CNT while also having high solubility in water, and its core retains its structure properly and unchanged, suitable for encapsulating drugs in the targeted delivery applications.

Crystal Structure and Superconductivity of PH 3 at High Pressures

DOE PAGES

Liu, Hanyu; Li, Yinwei; Gao, Guoying; ...

2016-01-20

Here, we performed systematic structure search on solid PH 3 at high pressures using particle swarm optimization method. Furthermore, at 100-200 GPa, the search led to two structures consisting of P-P bonds that different from these predicted for H 2S. Phonon and electron-phonon calculations indicate both structures are dynamically stable and superconductive. Particularly, the estimated critical temperature for the monoclinic (C2/m) phase of 83 K at 200 GPa is in excellent agreement with a recent experimental report.

Highly active thermally stable nanoporous gold catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biener, Juergen; Wittstock, Arne; Biener, Monika M.

In one embodiment, a system includes a nanoporous gold structure and a plurality of oxide particles deposited on the nanoporous gold structure; the oxide particles are characterized by a crystalline phase. In another embodiment, a method includes depositing oxide nanoparticles on a nanoporous gold support to form an active structure and functionalizing the deposited oxide nanoparticles.

Patterns of Change in Collaboration Are Associated with Baseline Characteristics and Predict Outcome and Dropout Rates in Treatment of Multi-Problem Families. A Validation Study

PubMed Central

Bachler, Egon; Fruehmann, Alexander; Bachler, Herbert; Aas, Benjamin; Nickel, Marius; Schiepek, Guenter K.

2017-01-01

Objective: The present study validates the Multi-Problem Family (MPF)-Collaboration Scale), which measures the progress of goal directed collaboration of patients in the treatment of families with MPF and its relation to drop-out rates and treatment outcome. Method: Naturalistic study of symptom and competence-related changes in children of ages 4–18 and their caregivers. Setting: Integrative, structural outreach family therapy. Measures: The data of five different groups of goal directed collaboration (deteriorating collaboration, stable low collaboration, stable medium collaboration, stable high collaboration, improving collaboration) were analyzed in their relation to treatment expectation, individual therapeutic goals (ITG), family adversity index, severity of problems and global assessment of a caregiver’s functioning, child, and relational aspects. Results: From N = 810 families, 20% displayed stable high collaboration (n = 162) and 21% had a pattern of improving collaboration. The families with stable high or improving collaboration rates achieved significantly more progress throughout therapy in terms of treatment outcome expectancy (d = 0.96; r = 0.43), reaching ITG (d = 1.17; r = 0.50), family adversities (d = 0.55; r = 0.26), and severity of psychiatric symptoms (d = 0.31; r = 0.15). Furthermore, families with stable high or improving collaboration maintained longer treatments and had a bigger chance of finishing the therapy as planned. The odds of having a stable low or deteriorating collaboration throughout treatment were significantly higher for subjects who started treatment with low treatment expectation or high family-related adversities. Conclusion: The positive outcomes of homebased interventions for multi-problem families are closely related to “stable high” and an “improving” collaboration as measured with the MPF-Collaboration Scale. Patients who fall into these groups have a high treatment outcome expectancy and reduce psychological stress. For therapeutic interventions with multi-problem families it seems beneficial to maintain a stable high collaboration or help the collaboration, e.g., by fostering treatment expectation. PMID:28785232

Highly Active and Stable Pt–Pd Alloy Catalysts Synthesized by Room‐Temperature Electron Reduction for Oxygen Reduction Reaction

PubMed Central

Wang, Wei; Wang, Zongyuan; Wang, Jiajun; Zhong, Chuan‐Jian

2017-01-01

Carbon‐supported platinum (Pt) and palladium (Pd) alloy catalyst has become a promising alternative electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. In this work, the synthesis of highly active and stable carbon‐supported Pt–Pd alloy catalysts is reported with a room‐temperature electron reduction method. The alloy nanoparticles thus prepared show a particle size around 2.6 nm and a core–shell structure with Pt as the shell. With this structure, the breaking of O–O bands and desorption of OH are both promoted in electrocatalysis of ORR. In comparison with the commercial Pt/C catalyst prepared by conventional method, the mass activity of the Pt–Pd/C catalyst for ORR is shown to increase by a factor of ≈4. After 10 000‐cycle durability test, the Pt–Pd/C catalyst is shown to retain 96.5% of the mass activity, which is much more stable than that of the commercial Pt/C catalyst. PMID:28435780

Fear of predation drives stable and differentiated social relationships in guppies

PubMed Central

Heathcote, Robert J. P.; Darden, Safi K.; Franks, Daniel W.; Ramnarine, Indar W.; Croft, Darren P.

2017-01-01

Social relationships can have important consequences for fitness in animals. Whilst numerous studies have shown that individuals often join larger groups in response to perceived predation risk (i.e. fear of predation), the importance of predation risk in driving the formation and stability of social relationships within groups has been relatively ignored. We experimentally tested how predation threat influenced fine-scale social network structure using Trinidadian guppies (Poecilia reticulata). When perceived predation risk was high, individuals developed stable and more differentiated social ties compared to when perceived risk was low. Intriguingly, social differentiation coincided with shoals being somewhat smaller under high-perceived risk, suggesting a possible conflict between forming stable social relationships and larger social groups. Individuals most at risk of predation (large and bold individuals) showed the most exaggerated responses in several social measures. Taken together, we provide the first experimental evidence that proximate risk of predation can increase the intensity of social relationships and fine-scale social structure in animal populations. PMID:28150706

Fear of predation drives stable and differentiated social relationships in guppies.

PubMed

Heathcote, Robert J P; Darden, Safi K; Franks, Daniel W; Ramnarine, Indar W; Croft, Darren P

2017-02-02

Social relationships can have important consequences for fitness in animals. Whilst numerous studies have shown that individuals often join larger groups in response to perceived predation risk (i.e. fear of predation), the importance of predation risk in driving the formation and stability of social relationships within groups has been relatively ignored. We experimentally tested how predation threat influenced fine-scale social network structure using Trinidadian guppies (Poecilia reticulata). When perceived predation risk was high, individuals developed stable and more differentiated social ties compared to when perceived risk was low. Intriguingly, social differentiation coincided with shoals being somewhat smaller under high-perceived risk, suggesting a possible conflict between forming stable social relationships and larger social groups. Individuals most at risk of predation (large and bold individuals) showed the most exaggerated responses in several social measures. Taken together, we provide the first experimental evidence that proximate risk of predation can increase the intensity of social relationships and fine-scale social structure in animal populations.

Thermal, Structural, and Optical Analysis of a Balloon-Based Imaging System

NASA Astrophysics Data System (ADS)

Borden, Michael; Lewis, Derek; Ochoa, Hared; Jones-Wilson, Laura; Susca, Sara; Porter, Michael; Massey, Richard; Clark, Paul; Netterfield, Barth

2017-03-01

The Subarcsecond Telescope And BaLloon Experiment, STABLE, is the fine stage of a guidance system for a high-altitude ballooning platform designed to demonstrate subarcsecond pointing stability over one minute using relatively dim guide stars in the visible spectrum. The STABLE system uses an attitude rate sensor and the motion of the guide star on a detector to control a Fast Steering Mirror to stabilize the image. The characteristics of the thermal-optical-mechanical elements in the system directly affect the quality of the point-spread function of the guide star on the detector, so a series of thermal, structural, and optical models were built to simulate system performance and ultimately inform the final pointing stability predictions. This paper describes the modeling techniques employed in each of these subsystems. The results from those models are discussed in detail, highlighting the development of the worst-case cold and hot cases, the optical metrics generated from the finite element model, and the expected STABLE residual wavefront error and decenter. Finally, the paper concludes with the predicted sensitivities in the STABLE system, which show that thermal deadbanding, structural pre-loading, and self-deflection under different loading conditions, and the speed of individual optical elements were particularly important to the resulting STABLE optical performance.

Stability, Elastic Properties, and Deformation of LiBN2: A Potential High-Energy Material.

PubMed

Zhu, Chunye; Zhu, Wenjun; Yang, Yanqiang

2018-05-15

Searching for high-energy-density materials is of great interest in scientific research and for industrial applications. Using an unbiased structure prediction method and first-principles calculations, we investigated the phase stability of LiBN 2 from 0 to100 GPa. Two new structures with space groups P4̅2 1 m and Pnma were discovered. The theoretical calculations revealed that Pnma LiBN 2 is stable with respect to a mixture of 1 / 3 Li 3 N, BN, and 1 / 3 N 2 above 22 GPa. The electronic band structure revealed that Pnma LiBN 2 has an indirect band gap of 2.3 eV, which shows a nonmetallic feature. The Pnma phase has a high calculated bulk modulus and shear modulus, indicating its incompressible nature. The microscopic mechanism of the structural deformation was demonstrated by ideal tensile shear strength calculations. It is worth mentioning that Pnma LiBN 2 is dynamically stable under ambient conditions. The decomposition of this phase is exothermic, releasing an energy of approximately 1.23 kJ/g at the PBE level. The results provide new thoughts for designing and synthesizing novel high-energy compounds in ternary systems.

Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating.

PubMed

Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

2016-03-15

Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium-scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with "lithiophilic" coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm(2) over 80 cycles.

Stable interstitial layer to alleviate fatigue fracture of high nickel cathode for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Yang, Chengkai; Shao, Ruiwen; Mi, Yingying; Shen, Lanyao; Zhao, Binglu; wang, Qian; Wu, Kai; Lui, Wen; Gao, Peng; Zhou, Henghui

2018-02-01

High nickel cathodes can deliver higher capacity with lower cost than conventional LiCoO2, however, the irreversible structural and morphology degradation with long-term cycling hinder their further application. In this paper, LiNi0.815Co0.15Al0.035O2 agglomerates are treated by LiNi0.333Co0.333Mn0.333O2 coating to get a stable interstitial layer without capacity loss. The interstitial layer is about 10 nm in thickness and has a layered (R-3m) structure, which can improve the chemical and mechanical stability of cathode materials with capacity retention of 88.5% after 200 cycles. The structural analysis and in-situ compression test proves that the morphology degradation is a fatigue process within long-term electrochemical reaction, and the coated sample has an excellent elastic recovery capacity thus leading to long cycle life.

A Hollow-Structured Manganese Oxide Cathode for Stable Zn-MnO₂ Batteries.

PubMed

Guo, Xiaotong; Li, Jianming; Jin, Xu; Han, Yehu; Lin, Yue; Lei, Zhanwu; Wang, Shiyang; Qin, Lianjie; Jiao, Shuhong; Cao, Ruiguo

2018-05-05

Aqueous rechargeable zinc-manganese dioxide (Zn-MnO₂) batteries are considered as one of the most promising energy storage devices for large scale-energy storage systems due to their low cost, high safety, and environmental friendliness. However, only a few cathode materials have been demonstrated to achieve stable cycling for aqueous rechargeable Zn-MnO₂ batteries. Here, we report a new material consisting of hollow MnO₂ nanospheres, which can be used for aqueous Zn-MnO₂ batteries. The hollow MnO₂ nanospheres can achieve high specific capacity up to ~405 mAh g −1 at 0.5 C. More importantly, the hollow structure of birnessite-type MnO₂ enables long-term cycling stability for the aqueous Zn-MnO₂ batteries. The excellent performance of the hollow MnO₂ nanospheres should be due to their unique structural properties that enable the easy intercalation of zinc ions.

Research on the Problem of High-Precision Deployment for Large-Aperture Space-Based Science Instruments

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Peterson, Lee D.; Hachkowski, M. Roman; Hinkle, Jason D.; Hardaway, Lisa R.

1998-01-01

The present paper summarizes results from an ongoing research program conducted jointly by the University of Colorado and NASA Langley Research Center since 1994. This program has resulted in general guidelines for the design of high-precision deployment mechanisms, and tests of prototype deployable structures incorporating these mechanisms have shown microdynamically stable behavior (i.e., dimensional stability to parts per million). These advancements have resulted from the identification of numerous heretofore unknown microdynamic and micromechanical response phenomena, and the development of new test techniques and instrumentation systems to interrogate these phenomena. In addition, recent tests have begun to interrogate nanomechanical response of materials and joints and have been used to develop an understanding of nonlinear nanodynamic behavior in microdynamically stable structures. The ultimate goal of these efforts is to enable nano-precision active control of micro-precision deployable structures (i.e., active control to a resolution of parts per billion).

Scallop-Inspired Shell Engineering of Microparticles for Stable and High Volumetric Capacity Battery Anodes.

PubMed

Zhang, Xinghao; Guo, Ruiying; Li, Xianglong; Zhi, Linjie

2018-06-01

Building stable and efficient electron and ion transport pathways are critically important for energy storage electrode materials and systems. Herein, a scallop-inspired shell engineering strategy is proposed and demonstrated to confine high volume change silicon microparticles toward the construction of stable and high volumetric capacity binder-free lithium battery anodes. As for each silicon microparticle, the methodology involves an inner sealed but adaptable overlapped graphene shell, and an outer open hollow shell consisting of interconnected reduced graphene oxide, mimicking the scallop structure. The inner closed shell enables simultaneous stabilization of the interfaces of silicon with both carbon and electrolyte, substantially facilitates efficient and rapid transport of both electrons and lithium ions from/to silicon, the outer open hollow shell creates stable and robust transport paths of both electrons and lithium ions throughout the electrode without any sophisticated additives. The resultant self-supported electrode has achieved stable cycling with rapidly increased coulombic efficiency in the early stage, superior rate capability, and remarkably high volumetric capacity upon a facile pressing process. The rational design and engineering of graphene shells of the silicon microparticles developed can provide guidance for the development of a wide range of other high capacity but large volume change electrochemically active materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A highly-active and stable hydrogen evolution catalyst based on pyrite-structured cobalt phosphosulfide

DOE PAGES

Liu, Wen; Hu, Enyuan; Jiang, Hong; ...

2016-02-19

Rational design and controlled synthesis of hybrid structures comprising multiple components with distinctive functionalities are an intriguing and challenging approach to materials development for important energy applications like electrocatalytic hydrogen production, where there is a great need for cost effective, active and durable catalyst materials to replace the precious platinum. Here we report a structure design and sequential synthesis of a highly active and stable hydrogen evolution electrocatalyst material based on pyrite-structured cobalt phosphosulfide nanoparticles grown on carbon nanotubes. The three synthetic steps in turn render electrical conductivity, catalytic activity and stability to the material. The hybrid material exhibits superiormore » activity for hydrogen evolution, achieving current densities of 10 mA cm –2 and 100 mA cm –2 at overpotentials of 48 mV and 109 mV, respectively. Lastly, phosphorus substitution is crucial for the chemical stability and catalytic durability of the material, the molecular origins of which are uncovered by X-ray absorption spectroscopy and computational simulation.« less

New Polymorph of Fe3O4 Stable at Core-Mantle Boundary Conditions

NASA Astrophysics Data System (ADS)

Greenberg, E.; Prakapenka, V. B.

2017-12-01

Magnetite Fe3O4 (and its high-pressure polymorphs) is one of the most studied iron bearing minerals. One reason for the interest in magnetite is that it contains both Fe2+ and Fe3+, which is especially important for understanding the physical and chemical properties of Earth's deep interior. Early studies on magnetite debated the nature of the structural phase transition at 35 GPa [1-4]. This high-pressure structure was shown to be of the CaTi2O4-type [5], but with Fe3+ occupying multiple sites. Furthermore, at pressures above 65 GPa a second structural transition to a Pmma space group was shown to take place [5], similar to that in Fe3-xTixO4 solid solution [6]. Other studies have focused on the P-T stability of Fe3O4. Early studies by Lazor et al. [7] predicted that Fe3O4 might disproportionate into FeO and h-Fe2O3 at 50 GPa. Other studies suggested that the high-pressure phase should be stable up to 100 GPa [3]. A more recent experimental study by Ricolleau and Fei [8] revealed that Fe3O4 is stable at least up to 103 GPa. Thus far, structural studies of Fe3O4 have been limited to pressures below 105 GPa. We have studied Fe3O4 up to pressures of 175 GPa and temperatures above 4000K, using diamond anvil cells in combination with synchrotron x-ray diffraction and an online pulsed laser-heating system to study the stability of Fe3O4 at relevant pressure-temperature conditions. Our results show that Fe3O4 is stable up to at least 176 GPa and 4200 K. We have discovered a new polymorph of Fe3O4 at these high P-T conditions. This new phase is stable in the pressure range of at least 100

Towards Stable CuZnAl Slurry Catalysts for the Synthesis of Ethanol from Syngas

NASA Astrophysics Data System (ADS)

Dong, Weibing; Gao, Zhihua; Zhang, Qian; Huang, Wei

2018-07-01

A stable CuZnAl slurry catalyst for the synthesis of ethanol from syngas has been developed by adjusting the heat treatment conditions of the complete liquid-phase method. The activity evaluation results showed that the CuZnAl catalyst, when heat-treated under a high pressure and temperature, was a stable catalyst for the synthesis of ethanol. The selectivity of ethanol using the CuZnAl slurry catalyst, which was heat-treated at 553 K under 4.0 MPa, increased continuously with time and was stable at approximately 26.00% after 144 h. The characterization results indicated that the CuZnAl slurry catalyst heat-treated under high pressure conditions could facilitate the formation of a more perfect structure with a larger specific surface area. The prepared catalyst contained a balance of strong and weak acid sites, an appropriate form of Cu2O and a high Cu/Zn atomic ratio at the catalyst surface, providing its stability in ethanol synthesis from syngas.

Evolutionary Dynamics on Protein Bi-stability Landscapes can Potentially Resolve Adaptive Conflicts

PubMed Central

Sikosek, Tobias; Bornberg-Bauer, Erich; Chan, Hue Sun

2012-01-01

Experimental studies have shown that some proteins exist in two alternative native-state conformations. It has been proposed that such bi-stable proteins can potentially function as evolutionary bridges at the interface between two neutral networks of protein sequences that fold uniquely into the two different native conformations. Under adaptive conflict scenarios, bi-stable proteins may be of particular advantage if they simultaneously provide two beneficial biological functions. However, computational models that simulate protein structure evolution do not yet recognize the importance of bi-stability. Here we use a biophysical model to analyze sequence space to identify bi-stable or multi-stable proteins with two or more equally stable native-state structures. The inclusion of such proteins enhances phenotype connectivity between neutral networks in sequence space. Consideration of the sequence space neighborhood of bridge proteins revealed that bi-stability decreases gradually with each mutation that takes the sequence further away from an exactly bi-stable protein. With relaxed selection pressures, we found that bi-stable proteins in our model are highly successful under simulated adaptive conflict. Inspired by these model predictions, we developed a method to identify real proteins in the PDB with bridge-like properties, and have verified a clear bi-stability gradient for a series of mutants studied by Alexander et al. (Proc Nat Acad Sci USA 2009, 106:21149–21154) that connect two sequences that fold uniquely into two different native structures via a bridge-like intermediate mutant sequence. Based on these findings, new testable predictions for future studies on protein bi-stability and evolution are discussed. PMID:23028272

Single-crystal structure determination of hydrous minerals and insights into a wet deep lower mantle

NASA Astrophysics Data System (ADS)

Zhang, L.; Yuan, H.; Meng, Y.; Popov, D.

2017-12-01

Water enters the Earth's interior through hydrated subducting slabs. How deep within the lower mantle (670-2900 km depth) can water be transported down and stored depends upon the availability of hydrous phases that is thermodynamically stable under the high P-T conditions and have a sufficiently high density to sink through the lower mantle. Phase H [MgSiH2O4] (1) and the δ-AlOOH (2) form solid solutions that are stable in the deep lower mantle (3), but the solid solution phase is 10% lighter than the corresponding lower mantle. Recent experimental discoveries of the pyrite (Py) structured FeO2 and FeOOH (4-6) suggest that these Fe-enriched phases can be transported to the deepest lower mantle owing to their high density. We have further discovered a very dense hydrous phase in (Fe,Al)OOH with a previously unknown hexagonal symmetry and this phase is stable relative to the Py-phase under extreme high P-T conditions in the deep lower mantle. Through in situ multigrain analysis (7) and single-crystal structure determination of the hydrous minerals at P-Tconditions of the deep lower mantle, we can obtain detailed structure information of the hydrous phases and therefore provide insights into the hydration mechanism in the deep lower mantle. These highly stable hydrous minerals extend the water cycle at least to the depth of 2900 km. 1. M. Nishi et al., Nature Geoscience 7, 224-227 (2014). 2. E. Ohtani, K. Litasov, A. Suzuki, T. Kondo, Geophysical Research Letters 28, 3991-3993 (2001). 3. I. Ohira et al., Earth and Planetary Science Letters 401, 12-17 (2014). 4. Q. Hu et al., Proceedings of the National Academy of Sciences of the United States of America 114, 1498-1501 (2017). 5. M. Nishi, Y. Kuwayama, J. Tsuchiya, T. Tsuchiya, Nature 547, 205-208 (2017). 6. Q. Hu et al., Nature 534, 241-244 (2016). 7. L. Zhang et al., American Mineralogist 101, 231-234 (2016).

Highly scalable multichannel mesh electronics for stable chronic brain electrophysiology.

PubMed

Fu, Tian-Ming; Hong, Guosong; Viveros, Robert D; Zhou, Tao; Lieber, Charles M

2017-11-21

Implantable electrical probes have led to advances in neuroscience, brain-machine interfaces, and treatment of neurological diseases, yet they remain limited in several key aspects. Ideally, an electrical probe should be capable of recording from large numbers of neurons across multiple local circuits and, importantly, allow stable tracking of the evolution of these neurons over the entire course of study. Silicon probes based on microfabrication can yield large-scale, high-density recording but face challenges of chronic gliosis and instability due to mechanical and structural mismatch with the brain. Ultraflexible mesh electronics, on the other hand, have demonstrated negligible chronic immune response and stable long-term brain monitoring at single-neuron level, although, to date, it has been limited to 16 channels. Here, we present a scalable scheme for highly multiplexed mesh electronics probes to bridge the gap between scalability and flexibility, where 32 to 128 channels per probe were implemented while the crucial brain-like structure and mechanics were maintained. Combining this mesh design with multisite injection, we demonstrate stable 128-channel local field potential and single-unit recordings from multiple brain regions in awake restrained mice over 4 mo. In addition, the newly integrated mesh is used to validate stable chronic recordings in freely behaving mice. This scalable scheme for mesh electronics together with demonstrated long-term stability represent important progress toward the realization of ideal implantable electrical probes allowing for mapping and tracking single-neuron level circuit changes associated with learning, aging, and neurodegenerative diseases. Copyright © 2017 the Author(s). Published by PNAS.

Electrodeposited Structurally Stable V2O5 Inverse Opal Networks as High Performance Thin Film Lithium Batteries.

PubMed

Armstrong, Eileen; McNulty, David; Geaney, Hugh; O'Dwyer, Colm

2015-12-09

High performance thin film lithium batteries using structurally stable electrodeposited V2O5 inverse opal (IO) networks as cathodes provide high capacity and outstanding cycling capability and also were demonstrated on transparent conducting oxide current collectors. The superior electrochemical performance of the inverse opal structures was evaluated through galvanostatic and potentiodynamic cycling, and the IO thin film battery offers increased capacity retention compared to micron-scale bulk particles from improved mechanical stability and electrical contact to stainless steel or transparent conducting current collectors from bottom-up electrodeposition growth. Li(+) is inserted into planar and IO structures at different potentials, and correlated to a preferential exposure of insertion sites of the IO network to the electrolyte. Additionally, potentiodynamic testing quantified the portion of the capacity stored as surface bound capacitive charge. Raman scattering and XRD characterization showed how the IO allows swelling into the pore volume rather than away from the current collector. V2O5 IO coin cells offer high initial capacities, but capacity fading can occur with limited electrolyte. Finally, we demonstrate that a V2O5 IO thin film battery prepared on a transparent conducting current collector with excess electrolyte exhibits high capacities (∼200 mAh g(-1)) and outstanding capacity retention and rate capability.

Spontaneous magnetization-induced phonons stability in γ‧-Fe4N crystalline alloys and high-pressure new phase

NASA Astrophysics Data System (ADS)

Cheng, Tai-min; Yu, Guo-liang; Su, Yong; Zhu, Lin; Li, Lin

2018-04-01

The stability of lattice dynamics and the magnetism of the ordered γ‧-Fe4N crystalline alloy at high pressures were studied by first-principle calculations based on density-functional theory. The dynamical stable new phase P2/m-Fe4N at high pressures was found by conducting the softening phenomenon at the point M (0.5 0.5 0) of the acoustic phonon at 10 GPa in the γ‧-Fe4N via soft-mode phase transition theory. Compared to the phonon spectrum of γ‧-Fe4N without considering electronic spin polarization, the ground-state lattice dynamical stability of the ferromagnetic phase γ‧-Fe4N is induced by the spontaneous magnetization at pressures below 1 GPa. However, P2/m-Fe4N is more thermodynamically stable than γ‧-phase at pressures below 1 GPa, and the magnetic moments of the two phases are almost the same. The ground-state structure of P2/m phase is more stable than that of γ‧-phase in the pressure range from 2.9 to 19 GPa. The magnetic moments of the two phases are almost the same in the pressure range from 20 to 214 GPa, but the ground-state structure of γ‧-phase is more stable than that of P2/m phase in the pressure range from 143.8 to 214 GPa. On the contrary, the ground-state structure of P2/m phase is more stable when the pressure is above 214 GPa. In the pressure range from 214 to 300 GPa, the magnetic moment of P2/m phase is lower than that of γ‧-phase, and the magnetic moments of the two phase tend to be consistent when the pressure exceeds 300 GPa.

Synthesis, characterization and air stable semiconductor properties of thiophene-condensed pyrene derivatives

NASA Astrophysics Data System (ADS)

Moriguchi, Tetsuji; Higashi, Makoto; Yakeya, Daisuke; Jalli, Venkataprasad; Tsuge, Akihiko; Okauchi, Tatsuo; Nagamatsu, Shuichi; Takashima, Wataru

2017-01-01

New and simple polyaromatic compounds containing two thiophene rings were prepared via photo-cyclization and their structural and photophysical properties were evaluated via 1H NMR spectroscopy and X-ray crystallographic analysis. On the basis of X-ray analysis, it was determined that the molecular structure of the compound was highly strained and that they contain two hetero [4] helicene moieties. The compounds were investigated as active layer in p-type organic field-effect transistors (p-OFET) in top contact type devices. Notably, the compound containing two thiophene components exhibited very stable p-type semiconducting behavior in moist air.

The engine of microtubule dynamics comes into focus.

PubMed

Mitchison, T J

2014-05-22

In this issue, Alushin et al. report high-resolution structures of three states of the microtubule lattice: GTP-bound, which is stable to depolymerization; unstable GDP-bound; and stable Taxol and GDP-bound. By comparing these structures at near-atomic resolution, they are able to propose a detailed model for how GTP hydrolysis destabilizes the microtubule and thus powers dynamic instability and chromosome movement. Destabilization of cytoskeleton filaments by nucleotide hydrolysis is an important general principle in cell dynamics, and this work represents a major step forward on a problem with a long history. Copyright © 2014 Elsevier Inc. All rights reserved.

Strengthening of stable Cr-Ni austenitic stainless steel under thermomechanical treatments

NASA Astrophysics Data System (ADS)

Akkuzin, S. A.; Litovchenko, I. Yu.; Tyumentsev, A. N.

2017-12-01

The features of microstructure and mechanical properties of stable austenitic steel after thermomechanical treatment consisted of low-temperature deformation, deformation in the temperature range T = 273-873 K, and subsequent annealing were investigated. It is shown that under such treatment direct (γ → α')- and reverse (α'→γ)-martensitic transformations occur in the steel. As a result of the thermomechanical treatment submicrocrystalline structural states with high density of micro- and nanotwins and localized deformation bands are formed. The strength of the steel in these structural states is several times higher than that in the initial state.

Effects of hydrophobic and dipole-dipole interactions on the conformational transitions of a model polypeptide

NASA Astrophysics Data System (ADS)

Mu, Yan; Gao, Yi Qin

2007-09-01

We studied the effects of hydrophobicity and dipole-dipole interactions between the nearest-neighbor amide planes on the secondary structures of a model polypeptide by calculating the free energy differences between different peptide structures. The free energy calculations were performed with low computational costs using the accelerated Monte Carlo simulation (umbrella sampling) method, with a bias-potential method used earlier in our accelerated molecular dynamics simulations. It was found that the hydrophobic interaction enhances the stability of α helices at both low and high temperatures but stabilizes β structures only at high temperatures at which α helices are not stable. The nearest-neighbor dipole-dipole interaction stabilizes β structures under all conditions, especially in the low temperature region where α helices are the stable structures. Our results indicate clearly that the dipole-dipole interaction between the nearest neighboring amide planes plays an important role in determining the peptide structures. Current research provides a more unified and quantitative picture for understanding the effects of different forms of interactions on polypeptide structures. In addition, the present model can be extended to describe DNA/RNA, polymer, copolymer, and other chain systems.

Mechanical Properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 Refractory High Entropy Alloys (Postprint)

DTIC Science & Technology

2011-05-01

Mn, Fe, Co, Ni and Cu. Since metallic alloys for high temperature load bearing structures and thermal protection systems remain in high demand for aer...condition. These results indicate that the BCC crystal structure formed in both alloys during solidification is stable upon heating at least up to 1400 C... solidification (Fig. 5b). Higher magnification images reveal a dendritic structure in both alloys (Fig. 5c and d). Uneven Z contrast inside the grains indicates

Elaboration and properties of hierarchically structured optical thin films of MIL-101(Cr).

PubMed

Demessence, Aude; Horcajada, Patricia; Serre, Christian; Boissière, Cédric; Grosso, David; Sanchez, Clément; Férey, Gérard

2009-12-14

Stable nanoparticles dispersions of the porous hybrid MIL-101(Cr) allow dip-coating of high quality optical thin films with dual hierarchical porous structure. Moreover, for the first time, mechanical and sorption properties of mesoporous MOFs based thin films are evaluated.

High-level ab initio studies of NO(X2Π)-O2(X3Σg -) van der Waals complexes in quartet states

NASA Astrophysics Data System (ADS)

Grein, Friedrich

2018-05-01

Geometry optimisations were performed on nine different structures of NO(X2Π)-O2(X3Σg-) van der Waals complexes in their quartet states, using the explicitly correlated RCCSD(T)-F12b method with basis sets up to the cc-pVQZ-F12 level. For the most stable configurations, counterpoise-corrected optimisations as well as extrapolations to the complete basis set (CBS) were performed. The X structure in the 4A‧ state was found to be most stable, with a CBS binding energy of -157 cm-1. The slipped tilted structures with N closer to O2 (Slipt-N), as well as the slipped parallel structure with O of NO closer to O2 (Slipp-O) in 4A″ states have binding energies of about -130 cm-1. C2v and linear complexes are less stable. According to calculated harmonic frequencies, the X isomer is bound. Isotropic hyperfine coupling constants of the complex are compared with those of the monomers.

Optimal physiological structure of small neurons to guarantee stable information processing

NASA Astrophysics Data System (ADS)

Zeng, S. Y.; Zhang, Z. Z.; Wei, D. Q.; Luo, X. S.; Tang, W. Y.; Zeng, S. W.; Wang, R. F.

2013-02-01

Spike is the basic element for neuronal information processing and the spontaneous spiking frequency should be less than 1 Hz for stable information processing. If the neuronal membrane area is small, the frequency of neuronal spontaneous spiking caused by ion channel noise may be high. Therefore, it is important to suppress the deleterious spontaneous spiking of the small neurons. We find by simulation of stochastic neurons with Hodgkin-Huxley-type channels that the leakage system is critical and extremely efficient to suppress the spontaneous spiking and guarantee stable information processing of the small neurons. However, within the physiological limit the potassium system cannot do so. The suppression effect of the leakage system is super-exponential, but that of the potassium system is quasi-linear. With the minor physiological cost and the minimal consumption of metabolic energy, a slightly lower reversal potential and a relatively larger conductance of the leakage system give the optimal physiological structure to suppress the deleterious spontaneous spiking and guarantee stable information processing of small neurons, dendrites and axons.

Structural transformations in Ge{sub 2}Sb{sub 2}Te{sub 5} under high pressure and temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mio, A. M.; Privitera, S., E-mail: stefania.privitera@imm.cnr.it; D'Arrigo, G.

2015-08-14

The structural transformations occurring in Ge{sub 2}Sb{sub 2}Te{sub 5} films heated at temperature up to 400 °C, and under hydrostatic pressure up to 12 GPa, have been investigated through in-situ X ray diffraction measurements. The adopted experimental conditions are close to those experienced by the phase change material during the SET (crystallization)/RESET (amorphization) processes in a nonvolatile memory device. The compression enhances the thermal stability of the amorphous phase, which remains stable up to 180 °C at 8 GPa and to 230 °C at 12 GPa. The structure of the crystalline phases is also modified, with the formation of a CsCl-type structure instead of rock-salt andmore » of a GeS-type structure at the temperature at which usually the trigonal stable phase is formed. Overall, the stability of the stable phase appears to be more affected by the compression. We argue that the presence of weak bonds associated to the van der Waals gaps is a determining factor for the observed reduced stability.« less

Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating

PubMed Central

Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

2016-01-01

Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium–scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with “lithiophilic” coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm2 over 80 cycles. PMID:26929378

New multifunctional tungsten nitride with energetic N6 and extreme hardness predicted from first principles

NASA Astrophysics Data System (ADS)

Li, Qian; Sha, Lei; Zhu, Chunye; Yao, Yansun

2017-05-01

We report a new member to the family of tungsten nitrides, WN6, predicted from the structure search. Ground-state convex hull calculation reveals that crystalline WN6 is thermodynamically stable at pressures above 16 GPa, but remains dynamically stable at ambient conditions. The predicted high-pressure WN6 structure contains chaired \\text{cyclo-N}6{6-} rings isoelectronic to cyclo-hexasulfur (S6), which is unprecedented in nitrogen. In the \\text{cyclo-N}6{6-} unit all nitrogen atoms are singly bonded and therefore contain a high energy density. By means of efficiently packing the covalent-bonded species, WN6 is estimated to have extremely high Vickers hardness greater than 40 GPa at ambient conditions, placing it as one of the hardest materials. The present results reveal that WN6 may be used as a superhard material but simultaneously maintaining other desirable properties, which represents an interesting example of multifunctional materials.

Nanoparticle self-assembly by a highly stable recombinant spider wrapping silk protein subunit.

PubMed

Xu, Lingling; Tremblay, Marie-Laurence; Orrell, Kathleen E; Leclerc, Jérémie; Meng, Qing; Liu, Xiang-Qin; Rainey, Jan K

2013-10-01

Artificial spider silk proteins may form fibers with exceptional strength and elasticity. Wrapping silk, or aciniform silk, is the toughest of the spider silks, and has a very different protein composition than other spider silks. Here, we present the characterization of an aciniform protein (AcSp1) subunit named W1, consisting of one AcSp1 199 residue repeat unit from Argiope trifasciata. The structural integrity of recombinant W1 is demonstrated in a variety of buffer conditions and time points. Furthermore, we show that W1 has a high thermal stability with reversible denaturation at ∼71°C and forms self-assembled nanoparticle in near-physiological conditions. W1 therefore represents a highly stable and structurally robust module for protein-based nanoparticle formation. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

High-wafer-yield, high-performance vertical cavity surface-emitting lasers

NASA Astrophysics Data System (ADS)

Li, Gabriel S.; Yuen, Wupen; Lim, Sui F.; Chang-Hasnain, Constance J.

1996-04-01

Vertical cavity surface emitting lasers (VCSELs) with very low threshold current and voltage of 340 (mu) A and 1.5 V is achieved. The molecular beam epitaxially grown wafers are grown with a highly accurate, low cost and versatile pre-growth calibration technique. One- hundred percent VCSEL wafer yield is obtained. Low threshold current is achieved with a native oxide confined structure with excellent current confinement. Single transverse mode with stable, predetermined polarization direction up to 18 times threshold is also achieved, due to stable index guiding provided by the structure. This is the highest value reported to data for VCSELs. We have established that p-contact annealing in these devices is crucial for low voltage operation, contrary to the general belief. Uniform doping in the mirrors also appears not to be inferior to complicated doping engineering. With these design rules, very low threshold voltage VCSELs are achieved with very simple growth and fabrication steps.

Highly stable thin film transistors using multilayer channel structure

NASA Astrophysics Data System (ADS)

Nayak, Pradipta K.; Wang, Zhenwei; Anjum, D. H.; Hedhili, M. N.; Alshareef, H. N.

2015-03-01

We report highly stable gate-bias stress performance of thin film transistors (TFTs) using zinc oxide (ZnO)/hafnium oxide (HfO2) multilayer structure as the channel layer. Positive and negative gate-bias stress stability of the TFTs was measured at room temperature and at 60 °C. A tremendous improvement in gate-bias stress stability was obtained in case of the TFT with multiple layers of ZnO embedded between HfO2 layers compared to the TFT with a single layer of ZnO as the semiconductor. The ultra-thin HfO2 layers act as passivation layers, which prevent the adsorption of oxygen and water molecules in the ZnO layer and hence significantly improve the gate-bias stress stability of ZnO TFTs.

Stability of cavitation structures in a thin liquid layer.

PubMed

Wu, Pengfei; Bai, Lixin; Lin, Weijun; Yan, Jiuchun

2017-09-01

The inception and evolution of acoustic cavitation structures in thin liquid layers under different conditions and perturbations are investigated experimentally with high speed photography. The stability and characterization of cavitation structures are quantified by image analysis methods. It is found that cavitation structures (shape of bubble cloud and number of bubbles) are stable under unaltered experimental conditions, and the cavitation bubble cloud will return to the original structure and remain stable even in the face of large perturbations. When the experimental conditions are altered (for example, acoustic intensity, cavitation nuclei, boundary), the cavitation structures will vary correspondingly. Further analysis implies that the stability of cavitation structures is closely related to the number of bubbles in the cavitation bubble cloud. There are two mechanisms acting simultaneously in the cavitation bubble cloud evolution, one "bubble production" and the other "bubble disappearance". We propose that the two mechanisms acting together constitute the most likely explanation for the stability of cavitation structures and their transformation. Copyright © 2017 Elsevier B.V. All rights reserved.

High-Temperature Storage Testing of ACF Attached Sensor Structures

PubMed Central

Lahokallio, Sanna; Hoikkanen, Maija; Vuorinen, Jyrki; Frisk, Laura

2015-01-01

Several electronic applications must withstand elevated temperatures during their lifetime. Materials and packages for use in high temperatures have been designed, but they are often very expensive, have limited compatibility with materials, structures, and processing techniques, and are less readily available than traditional materials. Thus, there is an increasing interest in using low-cost polymer materials in high temperature applications. This paper studies the performance and reliability of sensor structures attached with anisotropically conductive adhesive film (ACF) on two different organic printed circuit board (PCB) materials: FR-4 and Rogers. The test samples were aged at 200 °C and 240 °C and monitored electrically during the test. Material characterization techniques were also used to analyze the behavior of the materials. Rogers PCB was observed to be more stable at high temperatures in spite of degradation observed, especially during the first 120 h of aging. The electrical reliability was very good with Rogers. At 200 °C, the failures occurred after 2000 h of testing, and even at 240 °C the interconnections were functional for 400 h. The study indicates that, even though these ACFs were not designed for use in high temperatures, with stable PCB material they are promising interconnection materials at elevated temperatures, especially at 200 °C. However, the fragility of the structure due to material degradation may cause reliability problems in long-term high temperature exposure. PMID:28793735

Nickel Ferrite Nanoparticles Anchored onto Silica Nanofibers for Designing Magnetic and Flexible Nanofibrous Membranes.

PubMed

Hong, Feifei; Yan, Chengcheng; Si, Yang; He, Jianxin; Yu, Jianyong; Ding, Bin

2015-09-16

Many applications proposed for magnetic silica nanofibers require their assembly into a cellular membrane structure. The feature to keep structure stable upon large deformation is crucial for a macroscopic porous material which functions reliably. However, it remains a key issue to realize robust flexibility in two-dimensional (2D) magnetic silica nanofibrous networks. Here, we report that the combination of electrospun silica nanofibers with zein dip-coating can lead to the formation of flexible, magnetic, and hierarchical porous silica nanofibrous membranes (SNM). The 290 nm diameter silica nanofibers act as templates for the uniform anchoring of nickel ferrite nanoparticles (size of 50 nm). Benefiting from the homogeneous and stable nanofiber-nanoparticle composite structure, the resulting magnetic SNM can maintain their structure integrity under repeated bending as high as 180° and can facilely recover. The unique hierarchical structure also provides this new class of silica membrane with integrated properties of ultralow density, high porosity, large surface area, good magnetic responsiveness, robust dye adsorption capacity, and effective emulsion separation performance. Significantly, the synthesis of such fascinating membranes may provide new insight for further application of silica in a self-supporting, structurally adaptive, and 2D membrane form.

Phonon dispersions, band structures, and dielectric functions of BeO and BeS polymorphs

NASA Astrophysics Data System (ADS)

Wang, Ke-Long; Gao, Shang-Peng

2018-07-01

Structures, phonon dispersions, electronic structures, and dielectric functions of beryllium oxide (BeO) and beryllium sulfide (BeS) polymorphs are investigated by density functional theory and many-body perturbation theory. Phonon calculations indicate that both wurtzite (w-) and zincblende (zb-) structures are dynamically stable for BeO and BeS, whereas rocksalt (rs-) structures for both BeO and BeS have imaginary phonon frequencies and thus are dynamically unstable at zero pressure. Band structures for the 4 dynamically stable phases show that only w-BeO has a direct band gap. Both the one-shot G0W0 and quasiparticle self-consistent GW methods are used to correct band energies at high symmetry k-points. Bethe-Salpeter equation (BSE), which considers Coulomb correlated electron-hole pairs, is employed to deal with the computation of macroscopic dielectric functions. It is shown that BSE calculation, employing scissors operator derived by self-consistent GW method, can give dielectric functions agreeing very well with experimental measurement of w-BeO. Weak anisotropic characters can be observed for w-BeO and w-BeS. Both zb-BeS and w-BeS show high optical transition probabilities within a narrow ultraviolet energy range.

High-pressure phases of Mg2Si from first principles

NASA Astrophysics Data System (ADS)

Huan, Tran Doan; Tuoc, Vu Ngoc; Le, Nam Ba; Minh, Nguyen Viet; Woods, Lilia M.

2016-03-01

First-principles calculations are presented to resolve the possible pressure-dependent phases of Mg2Si . Although previous reports show that Mg2Si is characterized by the cubic antifluorite F m 3 ¯m structure at low pressures, the situation at higher pressures is less clear with many contradicting results. Here we utilize several methods to examine the stability, electron, phonon, and transport properties of this material as a function of pressure and temperature. We find that Mg2Si is thermodynamically stable at low and high pressures. Between 6 and 24 GPa, Mg2Si can transform into Mg9Si5 , a defected compound, and vice versa, without energy cost. Perhaps this result is related to the aforementioned inconsistency in the structures reported for Mg2Si within this pressure range. Focusing solely on Mg2Si , we find a new monoclinic C 2 /m structure of Mg2Si , which is stable at high pressures within thermodynamical considerations. The calculated electrical conductivity and Seebeck coefficient taking into account results from the electronic structure calculations help us understand better how transport can be affected in this material by modulating pressure and temperature.

High pressure transport and structural studies on Nb 3Ga superconductor

DOE PAGES

Mkrtcheyan, Vahe; Kumar, Ravhi; Baker, Jason; ...

2014-11-24

We investigated the crystal structure of A-15 superconductor Nb 3Ga with a critical temperature T c = 16.5 K by high pressure x-ray diffraction (HPXRD) using synchrotron x-rays and a diamond anvil cell under Ne pressure medium. Furthermore, the high pressure structural results indicate that Nb 3Ga is stable up to 41 GPa. The P-V plot shows an anomaly around 15 GPa even though there are no pressure induced structural transitions are observed. High pressure resistance measurements were performed up to 0.5 GPa to understand the variation of T c under pressure. Finally, our results show a positive pressure effectmore » on T c.« less

Micelle-Triggered β-Hairpin to α-Helix Transition in a 14-Residue Peptide from a Choline-Binding Repeat of the Pneumococcal Autolysin LytA

PubMed Central

Zamora-Carreras, Héctor; Maestro, Beatriz; Strandberg, Erik; Ulrich, Anne S; Sanz, Jesús M; Jiménez, M Ángeles

2015-01-01

Choline-binding modules (CBMs) have a ββ-solenoid structure composed of choline-binding repeats (CBR), which consist of a β-hairpin followed by a short linker. To find minimal peptides that are able to maintain the CBR native structure and to evaluate their remaining choline-binding ability, we have analysed the third β-hairpin of the CBM from the pneumococcal LytA autolysin. Circular dichroism and NMR data reveal that this peptide forms a highly stable native-like β-hairpin both in aqueous solution and in the presence of trifluoroethanol, but, strikingly, the peptide structure is a stable amphipathic α-helix in both zwitterionic (dodecylphosphocholine) and anionic (sodium dodecylsulfate) detergent micelles, as well as in small unilamellar vesicles. This β-hairpin to α-helix conversion is reversible. Given that the β-hairpin and α-helix differ greatly in the distribution of hydrophobic and hydrophilic side chains, we propose that the amphipathicity is a requirement for a peptide structure to interact and to be stable in micelles or lipid vesicles. To our knowledge, this “chameleonic” behaviour is the only described case of a micelle-induced structural transition between two ordered peptide structures. PMID:25917218

Extremely Stable Sodium Metal Batteries Enabled by Localized High-Concentration Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jianming; Chen, Shuru; Zhao, Wengao

Sodium (Na) metal is a promising anode for Na ion batteries. However, the high reactivity of Na metal with electrolytes and the low Na metal cycling efficiency have limited its practical application in rechargeable Na metal batteries. High concentration electrolytes (HCE, ≥4 M) consisting of sodium bis(fluorosulfonyl)imide (NaFSI) and ether solvent could ensure the stable cycling of Na metal with high coulombic efficiency, but suffer from high viscosity, poor wetting ability, and high salt cost. Here, we report that the salt concentration could be significantly reduced (≤ 1.5 M) by diluting with a hydrofluoroether (HFE) as ‘inert’ diluent, which maintainsmore » the solvation structures of HCE, thereby forming a localized high concentration electrolyte (LHCE). A LHCE (2.1 M NaFSI/DME-BTFE (solvent molar ratio 1:2)) has been demonstrated to enable the dendrite-free Na deposition with high coulombic efficiency of > 99%, fast-charging (20C) and stable cycling (90.8% retention after 40,000 cycles) of Na||Na3V2(PO4)3 batteries.« less

Surface engineering of hierarchical platinum-cobalt nanowires for efficient electrocatalysis

DOE PAGES

Bu, Lingzheng; Guo, Shaojun; Zhang, Xu; ...

2016-06-29

Despite intense research in past decades, the lack of high-performance catalysts for fuel cell reactions remains a challenge in realizing fuel cell technologies for transportation applications. Here we report a facile strategy for synthesizing hierarchical platinum-cobalt nanowires with high-index, platinum-rich facets and ordered intermetallic structure. These structural features enable unprecedented performance for the oxygen reduction and alcohol oxidation reactions. The specific/mass activities of the platinum-cobalt nanowires for oxygen reduction reaction are 39.6/33.7 times higher than commercial Pt/C catalyst, respectively. Density functional theory simulations reveal that the active threefold hollow sites on the platinum-rich high-index facets provide an additional factor inmore » enhancing oxygen reduction reaction activities. The nanowires are stable in the electrochemical conditions and also thermally stable. Furthermore, this work may represent a key step towards scalable production of high performance platinum-based nanowires for applications in catalysis and energy conversion.« less

Glycoprotein production for structure analysis with stable, glycosylation mutant CHO cell lines established by fluorescence-activated cell sorting.

PubMed

Wilke, Sonja; Krausze, Joern; Gossen, Manfred; Groebe, Lothar; Jäger, Volker; Gherardi, Ermanno; van den Heuvel, Joop; Büssow, Konrad

2010-06-01

Stable mammalian cell lines are excellent tools for the expression of secreted and membrane glycoproteins. However, structural analysis of these molecules is generally hampered by the complexity of N-linked carbohydrate side chains. Cell lines with mutations are available that result in shorter and more homogenous carbohydrate chains. Here, we use preparative fluorescence-activated cell sorting (FACS) and site-specific gene excision to establish high-yield glycoprotein expression for structural studies with stable clones derived from the well-established Lec3.2.8.1 glycosylation mutant of the Chinese hamster ovary (CHO) cell line. We exemplify the strategy by describing novel clones expressing single-chain hepatocyte growth factor/scatter factor (HGF/SF, a secreted glycoprotein) and a domain of lysosome-associated membrane protein 3 (LAMP3d). In both cases, stable GFP-expressing cell lines were established by transfection with a genetic construct including a GFP marker and two rounds of cell sorting after 1 and 2 weeks. The GFP marker was subsequently removed by heterologous expression of Flp recombinase. Production of HGF/SF and LAMP3d was stable over several months. 1.2 mg HGF/SF and 0.9 mg LAMP3d were purified per litre of culture, respectively. Homogenous glycoprotein preparations were amenable to enzymatic deglycosylation under native conditions. Purified and deglycosylated LAMP3d protein was readily crystallized. The combination of FACS and gene excision described here constitutes a robust and fast procedure for maximizing the yield of glycoproteins for structural analysis from glycosylation mutant cell lines.

Chain-like structure elements in Ni40Ta60 metallic glasses observed by scanning tunneling microscopy

PubMed Central

Pawlak, Rémy; Marot, Laurent; Sadeghi, Ali; Kawai, Shigeki; Glatzel, Thilo; Reimann, Peter; Goedecker, Stefan; Güntherodt, Hans-Joachim; Meyer, Ernst

2015-01-01

The structure of metallic glasses is a long-standing question because the lack of long-range order makes diffraction based techniques difficult to be applied. Here, we used scanning tunneling microscopy with large tunneling resistance of 6 GΩ at low temperature in order to minimize forces between probe and sample and reduce thermal fluctuations of metastable structures. Under these extremely gentle conditions, atomic structures of Ni40Ta60 metallic glasses are revealed with unprecedented lateral resolution. In agreement with previous models and experiments, icosahedral-like clusters are observed. The clusters show a high degree of mobility, which explains the need of low temperatures for stable imaging. In addition to icosahedrons, chain-like structures are resolved and comparative density functional theory (DFT) calculations confirm that these structures are meta-stable. The co-existence of icosahedral and chain-like structures might be an key ingredient for the understanding of the mechanical properties of metallic glasses. PMID:26268430

Crystal Structure and Superconductivity of PH 3 at High Pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Hanyu; Li, Yinwei; Gao, Guoying

2016-02-04

We have performed a systematic structure search on solid PH3 at high pressures using the particle swarm optimization method. At 100–200 GPa, the search led to two structures which along with others have P–P bonds. These structures are structurally and chemically distinct from those predicted for the high-pressure superconducting H2S phase, which has a different topology (i.e., does not contain S–S bonds). Phonon and electron–phonon coupling calculations indicate that both structures are dynamically stable and superconducting. The pressure dependence and critical temperature for the monoclinic (C2/m) phase of 83 K at 200 GPa are in excellent agreement with a recentmore » experimental report.« less

Cholecystokinin octapeptide analogues stable to brain proteolysis.

PubMed

Knight, M; Barone, P; Tamminga, C A; Steardo, L; Chase, T N

1985-01-01

Based on recent findings identifying the initial degradative cleavage of CCK-8 at the Met3-Gly4 bond by a metalloendopeptidase, two analogues of CCK-8 with D-Ala and D-Trp substitutions at the Gly4 position were synthesized as stable analogues. Their stability to proteolysis by brain membranes and their binding potency at central CCK receptors were quantified. Both peptides are stable to degradation by peptidases in cortical synaptic membrane preparations. The analogues are nearly equipotent to CCK-8 in their affinities for inhibition of 125I-CCK-33 binding to guinea pig cortical membranes. L-Ala and L-Trp substituted peptides were synthesized for comparison. Both these peptides are degraded by synaptic membranes and the L-Trp substituted peptide possesses a greatly reduced affinity for central CCK receptors. Therefore, the structure of CCK due to the D conformation of Gly is more capable of interacting with brain CCK receptors. Further conformational analysis will establish whether the stabilized structure is a beta-bend or a beta-turn. Since these peptides are highly potent and stable to brain proteolysis they may be useful as stable CCK analogues for in vivo application.

Toward highly efficient electrocatalyst for Li–O 2 batteries using biphasic N-doping cobalt@graphene multiple-capsule heterostructures

DOE PAGES

Tan, Guoqiang; Chong, Lina; Amine, Rachid; ...

2017-04-12

To promote lithium-oxygen batteries available for practical applications, the development of advanced cathode catalysts with low-cost, high activity and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport, and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@graphene multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium-oxygen cells. The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electro-active zones possible; furthermore, the colander-like porous electrode facilitates themore » oxygen diffusion, catalytic reaction, and stable deposition of discharge products. Finally, the electrode exhibits much improved electrocatalytic properties associated with unique morphologies of electrochemically grown lithium peroxides.« less

Toward Highly Efficient Electrocatalyst for Li–O 2 Batteries Using Biphasic N-Doping Cobalt@Graphene Multiple-Capsule Heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Guoqiang; Chong, Lina; Amine, Rachid

For the promotion of lithium oxygen batteries available for :practical applications, the development of advanced cathode catalysts with low-high activity, and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@grapbene Multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium oxygen cells. 'The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electroactive zones possible; furthermore the colander-like porousmore » electrode facilitates the oxygen diffusion, catalytic reaction,and stable deposition of discharge products. As a result, the electrode exhibits much improved electrocatalytic properties associated with unique morphologies of electrochemically grown lithium peroxides.« less

Toward highly efficient electrocatalyst for Li–O 2 batteries using biphasic N-doping cobalt@graphene multiple-capsule heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Guoqiang; Chong, Lina; Amine, Rachid

To promote lithium-oxygen batteries available for practical applications, the development of advanced cathode catalysts with low-cost, high activity and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport, and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@graphene multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium-oxygen cells. The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electro-active zones possible; furthermore, the colander-like porous electrode facilitates themore » oxygen diffusion, catalytic reaction, and stable deposition of discharge products. Finally, the electrode exhibits much improved electrocatalytic properties associated with unique morphologies of electrochemically grown lithium peroxides.« less

Toward Highly Efficient Electrocatalyst for Li-O2 Batteries Using Biphasic N-Doping Cobalt@Graphene Multiple-Capsule Heterostructures.

PubMed

Tan, Guoqiang; Chong, Lina; Amine, Rachid; Lu, Jun; Liu, Cong; Yuan, Yifei; Wen, Jianguo; He, Kun; Bi, Xuanxuan; Guo, Yuanyuan; Wang, Hsien-Hau; Shahbazian-Yassar, Reza; Al Hallaj, Said; Miller, Dean J; Liu, Dijia; Amine, Khalil

2017-05-10

For the promotion of lithium-oxygen batteries available for practical applications, the development of advanced cathode catalysts with low-cost, high activity, and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@graphene multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium-oxygen cells. The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electroactive zones possible; furthermore, the colander-like porous electrode facilitates the oxygen diffusion, catalytic reaction, and stable deposition of discharge products. As a result, the electrode exhibits much improved electrocatalytic properties associated with unique morphologies of electrochemically grown lithium peroxides.

A flexible metal-organic framework with a high density of sulfonic acid sites for proton conduction

NASA Astrophysics Data System (ADS)

Yang, Fan; Xu, Gang; Dou, Yibo; Wang, Bin; Zhang, Heng; Wu, Hui; Zhou, Wei; Li, Jian-Rong; Chen, Banglin

2017-11-01

The design of stable electrolyte materials with high proton conductivity for use in proton exchange membrane fuel cells remains a challenge. Most of the materials explored have good conductivity at high relative humidity (RH), but significantly decreased conductivity at reduced RH. Here we report a chemically stable and structurally flexible metal-organic framework (MOF), BUT-8(Cr)A, possessing a three-dimensional framework structure with one-dimensional channels, in which high-density sulfonic acid (-SO3H) sites arrange on channel surfaces for proton conduction. We propose that its flexible nature, together with its -SO3H sites, could allow BUT-8(Cr)A to self-adapt its framework under different humid environments to ensure smooth proton conduction pathways mediated by water molecules. Relative to other MOFs, BUT-8(Cr)A not only has a high proton conductivity of 1.27 × 10-1 S cm-1 at 100% RH and 80 °C but also maintains moderately high proton conductivity at a wide range of RH and temperature.

Highly stable and self-repairing membrane-mimetic 2D nanomaterials assembled from lipid-like peptoids

DOE PAGES

Jin, Haibao; Jiao, Fang; Daily, Michael D.; ...

2016-07-12

Two-dimensional (2D) materials with molecular-scale thickness have attracted increasing interest for separation, electronic, catalytic, optical, energy and biomedical applications. Although extensive research on 2D materials, such as graphene and graphene oxide, has been performed in recent years, progress is limited on self-assembly of 2D materials from sequence-specific macromolecules, especially from synthetic sequences that could exhibit lipid-like self-assembly of bilayer sheets and mimic membrane proteins for functions. The creation of such new class of materials could enable development of highly stable biomimetic membranes that exhibit cell-membrane-like molecular transport with exceptional selectively and high transport rates. Here we demonstrate self-assembly of lipid-likemore » 12-mer peptoids into extremely stable, crystalline, flexible and free-standing 2D membrane materials. As with cell membranes, upon exposure to external stimuli, these materials exhibit changes in thickness, varying from 3.5 nm to 5.6 nm. We find that self-assembly occurs through a facile crystallization process, in which inter-peptoid hydrogen bonds and enhanced hydrophobic interactions drive the formation of a highly-ordered structure. Molecular simulation confirms this is the energetically favored structure. Displaying functional groups at arbitrary locations of membrane-forming peptoids produces membranes with similar structures. This research further shows that single-layer membranes can be coated onto substrate surfaces. Moreover, membranes with mechanically-induced defects can self-repair. Given that peptoids are sequence-specific and exhibit protein-like molecular recognition with enhanced stability, we anticipate our membranes to be a robust platform tailored to specific applications.« less

Highly stable and self-repairing membrane-mimetic 2D nanomaterials assembled from lipid-like peptoids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Haibao; Jiao, Fang; Daily, Michael D.

Two-dimensional (2D) materials with molecular-scale thickness have attracted increasing interest for separation, electronic, catalytic, optical, energy and biomedical applications. Although extensive research on 2D materials, such as graphene and graphene oxide, has been performed in recent years, progress is limited on self-assembly of 2D materials from sequence-specific macromolecules, especially from synthetic sequences that could exhibit lipid-like self-assembly of bilayer sheets and mimic membrane proteins for functions. The creation of such new class of materials could enable development of highly stable biomimetic membranes that exhibit cell-membrane-like molecular transport with exceptional selectively and high transport rates. Here we demonstrate self-assembly of lipid-likemore » 12-mer peptoids into extremely stable, crystalline, flexible and free-standing 2D membrane materials. As with cell membranes, upon exposure to external stimuli, these materials exhibit changes in thickness, varying from 3.5 nm to 5.6 nm. We find that self-assembly occurs through a facile crystallization process, in which inter-peptoid hydrogen bonds and enhanced hydrophobic interactions drive the formation of a highly-ordered structure. Molecular simulation confirms this is the energetically favored structure. Displaying functional groups at arbitrary locations of membrane-forming peptoids produces membranes with similar structures. This research further shows that single-layer membranes can be coated onto substrate surfaces. Moreover, membranes with mechanically-induced defects can self-repair. Given that peptoids are sequence-specific and exhibit protein-like molecular recognition with enhanced stability, we anticipate our membranes to be a robust platform tailored to specific applications.« less

Shrink-wrapping water to conduct protons

NASA Astrophysics Data System (ADS)

Shimizu, George K. H.

2017-11-01

For proton-conducting metal-organic frameworks (MOFs) to find application as the electrolyte in proton-exchange membrane fuel cells, materials with better stability and conductivity are required. Now, a structurally flexible MOF that is also highly stable is demonstrated to possess high proton conductivity over a range of humidities.

In-situ, Gate Bias Dependent Study of Neutron Irradiation Effects on AlGaN/GaN HFETs

DTIC Science & Technology

2010-03-01

band gap and high breakdown field, AlGaN devices can operate at very high temperature and operating frequency. AlGaN/GaN based structures, have been...stable under ambient conditions [3]. GaN has a wide, direct band gap of 3.4 eV. It is therefore suitable for high temperature devices. Its high...also be grown with a wurtzite crystal structure and has a band - gap of 6.1 eV. Aluminum, due to having smaller atoms than gallium, forms a smaller

A novel stable 3D luminescent uranyl complex for highly efficient and sensitive recognition of Ru3+ and biomolecules

NASA Astrophysics Data System (ADS)

Tian, Hong-Hong; Chen, Liang-Ting; Zhang, Rong-Lan; Zhao, Jian-She; Liu, Chi-Yang; Weng, Ng Seik

2018-02-01

A novel highly stable 3D luminescent uranyl coordination polymer, namely {[UO2(L)]·DMA}n (1), was assembled with uranyl salt and a glycine-derivative ligand [6-(carboxymethyl-amino)-4-oxo-4,5-dihydro-[1,3,5]triazin-2-ylamino]-acetic acid (H2L) under solvothermal reaction. Besides, It was found that complex 1 possesses excellent luminescent properties, particularly the efficient selectivity and sensitivity in the recognition of Ru3+, biomacromolecule bovine serum albumin (BSA), biological small molecules dopamine (DA), ascorbic acid (AA) and uric acid (UA) in the water solution based on a "turn-off" mechanism. Accordingly, the luminescent explorations also demonstrated that complex 1 could be acted as an efficient luminescent probe with high quenching efficiency and low detection limit for selectively detecting Ru3+ and biomolecules (DA, AA, UA and BSA). It was noted that the framework structure of complex 1 still remains highly stable after quenching, which was verified by powder X-ray diffraction (PXRD).

First-principles calculations of high-pressure iron-bearing monoclinic dolomite and single-cation carbonates with internally-consistent Hubbard U

NASA Astrophysics Data System (ADS)

Solomatova, N. V.; Asimow, P. D.

2017-12-01

It has been proposed that iron has a significant effect on the relative stability of carbonate phases at high pressures, possibly even stabilizing double-cation carbonates (e.g., dolomite) with respect to single-cation carbonates (e.g., magnesite, aragonite and siderite). X-ray diffraction experiments have shown that dolomite transforms at 35 GPa to a high-pressure polymorph that is stable to decomposition; however, there has been disagreement on the structure of the high-pressure phase [1,2]. Ab initio calculations interfaced with an evolutionary structure prediction algorithm demonstrated that a C2/c polymorph of pure CaMg(CO3)2 dolomite is more stable than previously reported structures [3]. In this study, we calculate the relative enthalpies up to 80 GPa for a set of carbonate phases including Fe-bearing solutions and endmembers, using the generalized gradient approximation and a Hubbard U parameter calculated through linear response theory to accurately characterize the electronic structure of Fe. When calculated with a constant U of 4 eV, the spin transition pressure of (Mg,Fe)CO3 agrees well with experiments, whereas an internally-consistent U overestimates the spin transition pressure by 50 GPa. However, whether we use constant or internally-consistent U values, a higher iron concentration increases the stability field of dolomite C2/c with respect to single-cation carbonate assemblages, but iron-free dolomite is not stable with respect to single-cation carbonates at any pressure. Thus, high-pressure polymorphs of Fe-bearing dolomite could in fact represent an important reservoir for carbon storage within oxidized sections of Earth's mantle. [1] Mao, Z. et al. (2011) Geophysical Research Letters, 38. [2] Merlini, M. et al. (2012) Proceedings of the National Academy of Sciences, 109, 13509-13514. [3] Solomatova, N. V. and Asimow, P. D. (2017) American Mineralogist, 102, 210-215.

Automated structure determination of proteins with the SAIL-FLYA NMR method.

PubMed

Takeda, Mitsuhiro; Ikeya, Teppei; Güntert, Peter; Kainosho, Masatsune

2007-01-01

The labeling of proteins with stable isotopes enhances the NMR method for the determination of 3D protein structures in solution. Stereo-array isotope labeling (SAIL) provides an optimal stereospecific and regiospecific pattern of stable isotopes that yields sharpened lines, spectral simplification without loss of information, and the ability to collect rapidly and evaluate fully automatically the structural restraints required to solve a high-quality solution structure for proteins up to twice as large as those that can be analyzed using conventional methods. Here, we describe a protocol for the preparation of SAIL proteins by cell-free methods, including the preparation of S30 extract and their automated structure analysis using the FLYA algorithm and the program CYANA. Once efficient cell-free expression of the unlabeled or uniformly labeled target protein has been achieved, the NMR sample preparation of a SAIL protein can be accomplished in 3 d. A fully automated FLYA structure calculation can be completed in 1 d on a powerful computer system.

Two-Dimensional Phosphorus Oxides as Energy and Information Materials.

PubMed

Luo, Wei; Xiang, Hongjun

2016-07-18

Phosphorene is a rising star in electronics. Recently, 2D phosphorus oxides with higher stability have been synthesized. In this study, we theoretically explored the structures and properties of 2D phosphorus oxides. We found that the structural features of Px Oy vary with the oxygen content. When the oxygen content is low, the most stable Px Oy material can be obtained by the adsorption of O atoms on phosphorene. Otherwise, stable structures are no longer based on phosphorene and will contain P-O-P motifs. We found that P4 O4 has a direct band gap (about 2.24 eV), good optical absorption, and high stability in water, so it may be suitable for photochemical water splitting. P2 O3 adopts two possible stable ferroelectric structures (P2 O3 -I and P2 O3 -II) with electric polarization perpendicular and parallel to the lateral plane, respectively, as the lowest-energy configurations, depending on the layer thickness. We propose that P2 O3 could be used in novel nanoscale multiple-state memory devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of intense THz radiation on spin state of photoswitchable compound Cu(hfac)2L(Pr).

PubMed

Veber, Sergey L; Fedin, Matvey V; Maryunina, Ksenia Yu; Boldyrev, Kirill N; Sheglov, Mikhail A; Kubarev, Vitaly V; Shevchenko, Oleg A; Vinokurov, Nikolay A; Kulipanov, Gennady N; Sagdeev, Renad Z; Ovcharenko, Victor I; Bagryanskaya, Elena G

2013-02-21

The family of magnetoactive compounds Cu(hfac)(2)L(R) exhibits thermo- and photoswitching phenomena promising for various applications. Photoswitching of the Cu(hfac)(2)L(Pr) compound can be observed at temperatures below 20 K and is accompanied by transition to metastable structural state. Reverse conversion to stable structure could not be induced by light of near-IR-vis-UV regions up to date. The far-IR spectra of metastable and stable structural states are different and show characteristic absorption lines in the range of 170-240 cm(-1). These frequencies are accessible by NovoFEL - high-power THz free-electron laser user facility in Novosibirsk. We investigate selective influence of THz radiation on relaxation processes from metastable to stable structural state, which can be monitored by electron paramagnetic resonance (EPR). For this purpose, the experimental station based on X-band EPR spectrometer has been constructed by the THz beamline of NovoFEL and equipped with multimodal THz waveguide allowing to fed radiation directly into the EPR resonator. It has been found that irradiation of studied compound with high-power THz light causes significant but nondestructive increase of its temperature. Apart from this effect, no resonant influence of THz irradiation on relaxation processes has been observed. The experimental results have been rationalized taking into account vibrational relaxation times of the studied compound. Further experiments based on pulse heating by THz radiation have been proposed.

Molecular Dynamic Simulation of Space and Earth-Grown Crystal Structures of Thermostable T1 Lipase Geobacillus zalihae Revealed a Better Structure.

PubMed

Ishak, Siti Nor Hasmah; Aris, Sayangku Nor Ariati Mohamad; Halim, Khairul Bariyyah Abd; Ali, Mohd Shukuri Mohamad; Leow, Thean Chor; Kamarudin, Nor Hafizah Ahmad; Masomian, Malihe; Rahman, Raja Noor Zaliha Raja Abd

2017-09-25

Less sedimentation and convection in a microgravity environment has become a well-suited condition for growing high quality protein crystals. Thermostable T1 lipase derived from bacterium Geobacillus zalihae has been crystallized using the counter diffusion method under space and earth conditions. Preliminary study using YASARA molecular modeling structure program for both structures showed differences in number of hydrogen bond, ionic interaction, and conformation. The space-grown crystal structure contains more hydrogen bonds as compared with the earth-grown crystal structure. A molecular dynamics simulation study was used to provide insight on the fluctuations and conformational changes of both T1 lipase structures. The analysis of root mean square deviation (RMSD), radius of gyration, and root mean square fluctuation (RMSF) showed that space-grown structure is more stable than the earth-grown structure. Space-structure also showed more hydrogen bonds and ion interactions compared to the earth-grown structure. Further analysis also revealed that the space-grown structure has long-lived interactions, hence it is considered as the more stable structure. This study provides the conformational dynamics of T1 lipase crystal structure grown in space and earth condition.

Ferroelectric behavior and reproducible Bi-stable resistance switching property in K-doped ZnO thin films as candidate for application in non-volatile memories

NASA Astrophysics Data System (ADS)

Lee, J. W.; Subramaniam, N. G.; Kang, T. W.; Shon, Yoon; Kim, E. K.

2015-05-01

Potassium-doped ZnO thin films electrodeposited on indium tin oxide (ITO) coated glass substrates exhibited ferroelectric behavior with a remnant polarization of 0.2 μC/cm2. Especially, wave forms showing the applied input voltage Vi and output voltage Vo were obtained for Al/ZnO:K/ITO structure. It exhibits a superposition of Vi (input) and Vo (output) signal from Al/ZnO:K/ITO structure with a clear phase shift between the two wave forms which again confirms that the observed ferroelectric hysteresis curve is not related to leaky dielectric materials. The current-voltage characteristics of Al/ZnO:K/ITO structures measured for several cycles revealed bi-stable switching characteristics. The reproducible bi-stable switching characteristics for the mentioned structures had good retention in one particular resistance state. Around one order of switching was realized between low and high resistance states. The switching property thought to be polarization induced originating out from the ferroelectric properties of the potassium doped ZnO thin film. The switching between ZnO:K/ITO interface is assumed to be critical for stability in switching for several cycles. Possible application of this structure in non-volatile memories is explored.

Entropy stable high order discontinuous Galerkin methods for ideal compressible MHD on structured meshes

NASA Astrophysics Data System (ADS)

Liu, Yong; Shu, Chi-Wang; Zhang, Mengping

2018-02-01

We present a discontinuous Galerkin (DG) scheme with suitable quadrature rules [15] for ideal compressible magnetohydrodynamic (MHD) equations on structural meshes. The semi-discrete scheme is analyzed to be entropy stable by using the symmetrizable version of the equations as introduced by Godunov [32], the entropy stable DG framework with suitable quadrature rules [15], the entropy conservative flux in [14] inside each cell and the entropy dissipative approximate Godunov type numerical flux at cell interfaces to make the scheme entropy stable. The main difficulty in the generalization of the results in [15] is the appearance of the non-conservative "source terms" added in the modified MHD model introduced by Godunov [32], which do not exist in the general hyperbolic system studied in [15]. Special care must be taken to discretize these "source terms" adequately so that the resulting DG scheme satisfies entropy stability. Total variation diminishing / bounded (TVD/TVB) limiters and bound-preserving limiters are applied to control spurious oscillations. We demonstrate the accuracy and robustness of this new scheme on standard MHD examples.

First-Principles Prediction of Thermodynamically Stable Two-Dimensional Electrides

DOE PAGES

Ming, Wenmei; Yoon, Mina; Univ. of Tennessee, Knoxville, TN; ...

2016-10-21

Two-dimensional (2D) electrides, emerging as a new type of layered material whose electrons are confined in interlayer spaces instead of at atomic proximities, are receiving interest for their high performance in various (opto)electronics and catalytic applications. Experimentally, however, 2D electrides have been only found in a couple of layered nitrides and carbides. We report new thermodynamically stable alkaline-earth based 2D electrides by using a first-principles global structure optimization method, phonon spectrum analysis, and molecular dynamics simulation. The method was applied to binary compounds consisting of alkaline-earth elements as cations and group VA, VIA, or VIIA nonmetal elements as anions. Wemore » also revealed that the stability of a layered 2D electride structure is closely related to the cation/anion size ratio; stable 2D electrides possess a sufficiently large cation/anion size ratio to minimize electrostatic energy among cations, anions, and anionic electrons. This work demonstrates a new avenue to the discovery of thermodynamically stable 2D electrides beyond experimental material databases and provides new insight into the principles of electride design.« less

On the dynamical structure of the Trojan group of asteroids

NASA Technical Reports Server (NTRS)

Zagretdinov, R. V.; Williams, I. P.; Yoshikawa, M.

1992-01-01

Using a semi-analytical approach, domains of possible motion for Trojan asteroids were established. It is shown that stable librating motion is possible for both high inclination and high eccentricity. Frequency distributions were also produced for real Trojan asteroids, against differing libration amplitudes and libration periods.

ALD anti-reflection coatings at 1ω, 2ω, 3ω, and 4ω for high-power ns-laser application

NASA Astrophysics Data System (ADS)

Liu, Hao; Jensen, Lars; Ma, Ping; Ristau, Detlev

2018-04-01

Atomic layer deposition (ALD) facilitates the deposition of coatings with precise thickness, high surface conformity, structural uniformity, and nodular-free structure, which are properties desired in high-power laser coatings. ALD was studied to produce uniform and stable Al2O3 and HfO2 single layers and was employed to produce anti-reflection coatings for the harmonics (1ω, 2ω, 3ω, and 4ω) of the Nd:YAG laser. In order to qualify the ALD films for high-power laser applications, the band gap energy, absorption, and element content of single layers were characterized. The damage tests of anti-reflection coatings were carried out with a laser system operated at 1ω, 2ω, 3ω, and 4ω, respectively. The damage mechanism was discussed by analyzing the damage morphology and electric field intensity difference. ALD coatings exhibit stable growth rates, low absorption, and rather high laser-induced damage threshold (LIDT). The LIDT is limited by HfO2 as the employed high-index material. These properties indicate the high versatility of ALD films for applications in high-power coatings.

Glasses of three alkyl phosphates show a range of kinetic stabilities when prepared by physical vapor deposition

NASA Astrophysics Data System (ADS)

Beasley, M. S.; Tylinski, M.; Chua, Y. Z.; Schick, C.; Ediger, M. D.

2018-05-01

In situ AC nanocalorimetry was used to characterize vapor-deposited glasses of three phosphates with increasing lengths of alkyl side chains: trimethyl phosphate, triethyl phosphate, and tributyl phosphate. The as-deposited glasses were assessed in terms of their reversing heat capacity, onset temperature, and isothermal transformation time. Glasses with a range of kinetic stabilities were prepared, including kinetically stable glasses, as indicated by high onset temperatures and long transformation times. Trimethyl phosphate forms kinetically stable glasses, similar to many other organic molecules, while triethyl phosphate and tributyl phosphate do not. Triethyl phosphate and tributyl phosphate present the first examples of non-hydrogen bonding systems that are unable to form stable glasses via vapor deposition at 0.2 nm/s. Based on experiments utilizing different deposition rates, we conclude that triethyl phosphate and tributyl phosphate lack the surface mobility required for stable glass formation. This may be related to their high enthalpies of vaporization and the internal structure of the liquid state.

Designed protein reveals structural determinants of extreme kinetic stability

PubMed Central

Broom, Aron; Ma, S. Martha; Xia, Ke; Rafalia, Hitesh; Trainor, Kyle; Colón, Wilfredo; Gosavi, Shachi; Meiering, Elizabeth M.

2015-01-01

The design of stable, functional proteins is difficult. Improved design requires a deeper knowledge of the molecular basis for design outcomes and properties. We previously used a bioinformatics and energy function method to design a symmetric superfold protein composed of repeating structural elements with multivalent carbohydrate-binding function, called ThreeFoil. This and similar methods have produced a notably high yield of stable proteins. Using a battery of experimental and computational analyses we show that despite its small size and lack of disulfide bonds, ThreeFoil has remarkably high kinetic stability and its folding is specifically chaperoned by carbohydrate binding. It is also extremely stable against thermal and chemical denaturation and proteolytic degradation. We demonstrate that the kinetic stability can be predicted and modeled using absolute contact order (ACO) and long-range order (LRO), as well as coarse-grained simulations; the stability arises from a topology that includes many long-range contacts which create a large and highly cooperative energy barrier for unfolding and folding. Extensive data from proteomic screens and other experiments reveal that a high ACO/LRO is a general feature of proteins with strong resistances to denaturation and degradation. These results provide tractable approaches for predicting resistance and designing proteins with sufficient topological complexity and long-range interactions to accommodate destabilizing functional features as well as withstand chemical and proteolytic challenge. PMID:26554002

Thermodynamic stability and structure of cuprous chloride surfaces: a DFT investigation.

PubMed

Suleiman, Ibrahim A; Radny, Marian W; Gladys, Michael J; Smith, Phillip V; Mackie, John C; Kennedy, Eric M; Dlugogorski, Bogdan Z

2015-03-14

Density functional theory together with ab initio atomistic thermodynamics has been utilized to study the structures and stabilities of the low index CuCl surfaces. It is shown that the Cl-terminated structures are more stable than the Cu-terminated configurations, and that the defective CuCl(110)-Cu structure is more stable than the stoichiometric CuCl(110) surface. The equilibrium shape of a cuprous chloride nanostructure terminated by low-index CuCl surfaces has also been predicted using a Wulff construction. It was found that the (110) facets dominate at low chlorine concentration. As the chlorine concentration is increased, however, the contributions of the (100) and (111) facets to the Wulff construction also increase giving the crystal a semi-prism shape. At high chlorine concentration, and close to the rich limit, the (111) facets were found to be the only contributors to the Wulff construction, resulting in prismatic nanocrystals.

A cost-effective protocol for the over-expression and purification of fully-functional and more stable Erwinia chrisanthemi ligand-gated ion channel

PubMed Central

Elberson, Benjamin W.; Whisenant, Ty E.; Cortes, D. Marien; Cuello, Luis G.

2017-01-01

The Erwinia chrisanthemi ligand-gated ion channel, ELIC, is considered an excellent structural and functional surrogate for the whole pentameric ligand-gated ion channel family. Despite its simplicity, ELIC is structurally capable of undergoing ligand-dependent activation and a concomitant desensitization process. To determine at the molecular level the structural changes underlying ELIC’s function, it is desirable to produce large quantities of protein. This protein should be properly folded, fully-functional and amenable to structural determinations. In the current paper, we report a completely new protocol for the expression and purification of milligram quantities of fully-functional, more stable and crystallizable ELIC. The use of an autoinduction media and inexpensive detergents during ELIC extraction, in addition to the high-quality and large quantity of the purified channel, are the highlights of this improved biochemical protocol. PMID:28279818

First principles study of structural and magnetic properties of transition metal nitrides TMN (TM = Cr, Mn)

NASA Astrophysics Data System (ADS)

Rajeswarapalanichamy, R.; Amudhavalli, A.; Manikandan, M.; Kavitha, M.; Iyakutti, K.

2017-09-01

The structural stability of chromium nitride (CrN) and manganese nitride (MnN) is investigated among four different structures, namely, NaCl (Fm3m), zinc blende (F4-3m), orthorhombic (Pnma) and tetragonal (I4/mmm). It is found that the most stable phase is the zinc blende phase for CrN and MnN. The structural phase transition from zinc blende to orthorhombic phase is predicted at high pressure. At normal pressure, CrN and MnN are found to be antiferromagnetic. As the pressure is increased, antiferromagnetic-to-nonmagnetic phase transition is observed at the pressures of 169.5 GPa in CrN and 206 GPa in MnN. The elastic constants obey the Born-Huang criteria, suggesting that they are mechanically stable. The calculated B/G values indicate that CrN and MnN are ductile in nature.

High-Performance WSe2 Complementary Metal Oxide Semiconductor Technology and Integrated Circuits.

PubMed

Yu, Lili; Zubair, Ahmad; Santos, Elton J G; Zhang, Xu; Lin, Yuxuan; Zhang, Yuhao; Palacios, Tomás

2015-08-12

Because of their extraordinary structural and electrical properties, two-dimensional materials are currently being pursued for applications such as thin-film transistors and integrated circuit. One of the main challenges that still needs to be overcome for these applications is the fabrication of air-stable transistors with industry-compatible complementary metal oxide semiconductor (CMOS) technology. In this work, we experimentally demonstrate a novel high performance air-stable WSe2 CMOS technology with almost ideal voltage transfer characteristic, full logic swing and high noise margin with different supply voltages. More importantly, the inverter shows large voltage gain (∼38) and small static power (picowatts), paving the way for low power electronic system in 2D materials.

Expected distributions of root-mean-square positional deviations in proteins.

PubMed

Pitera, Jed W

2014-06-19

The atom positional root-mean-square deviation (RMSD) is a standard tool for comparing the similarity of two molecular structures. It is used to characterize the quality of biomolecular simulations, to cluster conformations, and as a reaction coordinate for conformational changes. This work presents an approximate analytic form for the expected distribution of RMSD values for a protein or polymer fluctuating about a stable native structure. The mean and maximum of the expected distribution are independent of chain length for long chains and linearly proportional to the average atom positional root-mean-square fluctuations (RMSF). To approximate the RMSD distribution for random-coil or unfolded ensembles, numerical distributions of RMSD were generated for ensembles of self-avoiding and non-self-avoiding random walks. In both cases, for all reference structures tested for chains more than three monomers long, the distributions have a maximum distant from the origin with a power-law dependence on chain length. The purely entropic nature of this result implies that care must be taken when interpreting stable high-RMSD regions of the free-energy landscape as "intermediates" or well-defined stable states.

Computational Discovery of New Materials Under Pressure

NASA Astrophysics Data System (ADS)

Zurek, Eva

The pressure variable opens the door towards the synthesis of materials with unique properties, ie. superconductivity, hydrogen storage media, high-energy density and superhard materials, to name a few. Indeed, recently superconductivity has been observed below 203 K and 103 K in samples of compressed sulfur dihydride and phosphine, respectively. Under pressure elements that would not normally combine may form stable compounds, or may mix in novel proportions. As a result using our chemical intuition developed at 1 atm to theoretically predict stable phases is bound to fail. In order to enable our search for superconducting hydrogen-rich systems under pressure, we have developed XtalOpt, an open-source evolutionary algorithm for crystal structure prediction. New advances in XtalOpt that enable the prediction of unit cells with greater complexity will be described. XtalOpt has been employed to find the most stable structures of hydrides with unique stoichiometries under pressure. The electronic structure and bonding of the predicted phases has been analyzed by detailed first-principles calculations based on density functional theory. The results of our computational experiments are helping us to build chemical and physical intuition for compressed solids.

Biochemical and Spectroscopic Characterization of Highly Stable Photosystem II Supercomplexes from Arabidopsis*

PubMed Central

Crepin, Aurelie; Santabarbara, Stefano; Caffarri, Stefano

2016-01-01

Photosystem II (PSII) is a large membrane supercomplex involved in the first step of oxygenic photosynthesis. It is organized as a dimer, with each monomer consisting of more than 20 subunits as well as several cofactors, including chlorophyll and carotenoid pigments, lipids, and ions. The isolation of stable and homogeneous PSII supercomplexes from plants has been a hindrance for their deep structural and functional characterization. In recent years, purification of complexes with different antenna sizes was achieved with mild detergent solubilization of photosynthetic membranes and fractionation on a sucrose gradient, but these preparations were only stable in the cold for a few hours. In this work, we present an improved protocol to obtain plant PSII supercomplexes that are stable for several hours/days at a wide range of temperatures and can be concentrated without degradation. Biochemical and spectroscopic properties of the purified PSII are presented, as well as a study of the complex solubility in the presence of salts. We also tested the impact of a large panel of detergents on PSII stability and found that very few are able to maintain the integrity of PSII. Such new PSII preparation opens the possibility of performing experiments that require room temperature conditions and/or high protein concentrations, and thus it will allow more detailed investigations into the structure and molecular mechanisms that underlie plant PSII function. PMID:27432883

Group-Based Modeling of Time Spent in Structured Activity Trajectories from Middle Childhood into Early Adolescence

ERIC Educational Resources Information Center

Mata, Andrea D.; van Dulmen, Manfred H. M.

2012-01-01

This study investigated trajectories of time spent in structured activities from middle childhood to early adolescence by using data from the National Institute of Child Health & Human Development (NICHD) Study of Early Child Care. We used latent class growth analyses and identified five trajectories (stable low, increasing high, decreasing low,…

Prediction of novel stable compounds in the Mg-Si-O system under exoplanet pressures

PubMed Central

Niu, Haiyang; Oganov, Artem R.; Chen, Xing-Qiu; Li, Dianzhong

2015-01-01

The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO2 phases, we have found two extraordinary silicon oxides, SiO3 and SiO, which become stable at pressures above 0.51 TPa and 1.89 TPa, respectively. In the Mg-O system, we have found one new compound, MgO3, which becomes stable at 0.89 TPa. We find that not only the (MgO)x·(SiO2)y compounds, but also two (MgO3)x·(SiO3)y compounds, MgSi3O12 and MgSiO6, have stability fields above 2.41 TPa and 2.95 TPa, respectively. The highly oxidized MgSi3O12 can form in deep mantles of mega-Earths with masses above 20 M⊕ (M⊕:Earth’s mass). Furthermore, the dissociation pathways of pPv-MgSiO3 are also clarified, and found to be different at low and high temperatures. The low-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ SiO2 + Mg2SiO4 ⇒ MgO + SiO2, while the high-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ MgO + MgSi2O5 ⇒ MgO + SiO2. Present results are relevant for models of the internal structure of giant exoplanets, and for understanding the high-pressure behavior of materials. PMID:26691903

Atomically precise metal nanoclusters: stable sizes and optical properties

NASA Astrophysics Data System (ADS)

Jin, Rongchao

2015-01-01

Controlling nanoparticles with atomic precision has long been a major dream of nanochemists. Breakthroughs have been made in the case of gold nanoparticles, at least for nanoparticles smaller than ~3 nm in diameter. Such ultrasmall gold nanoparticles indeed exhibit fundamentally different properties from those of the plasmonic counterparts owing to the quantum size effects as well as the extremely high surface-to-volume ratio. These unique nanoparticles are often called nanoclusters to distinguish them from conventional plasmonic nanoparticles. Intense work carried out in the last few years has generated a library of stable sizes (or stable stoichiometries) of atomically precise gold nanoclusters, which are opening up new exciting opportunities for both fundamental research and technological applications. In this review, we have summarized the recent progress in the research of thiolate (SR)-protected gold nanoclusters with a focus on the reported stable sizes and their optical absorption spectra. The crystallization of nanoclusters still remains challenging; nevertheless, a few more structures have been achieved since the earlier successes in Au102(SR)44, Au25(SR)18 and Au38(SR)24 nanoclusters, and the newly reported structures include Au20(SR)16, Au24(SR)20, Au28(SR)20, Au30S(SR)18, and Au36(SR)24. Phosphine-protected gold and thiolate-protected silver nanoclusters are also briefly discussed in this review. The reported gold nanocluster sizes serve as the basis for investigating their size dependent properties as well as the development of applications in catalysis, sensing, biological labelling, optics, etc. Future efforts will continue to address what stable sizes are existent, and more importantly, what factors determine their stability. Structural determination and theoretical simulations will help to gain deep insight into the structure-property relationships.

Molecular dynamics study of the structural and dynamic characteristics of the polyextremophilic short-chain dehydrogenase from the Thermococcus sibiricus archaeon and its homologues

NASA Astrophysics Data System (ADS)

Popinako, Anna V.; Antonov, Mikhail Yu.; Bezsudnova, Ekaterina Yu.; Prokopiev, Georgiy A.; Popov, Vladimir O.

2017-11-01

The study of structural adaptations of proteins from polyextremophilic organisms using computational molecular dynamics method is appealing because the obtained knowledge can be applied to construction of synthetic proteins with high activity and stability in polyextreme media which is useful for many industrial applications. To investigate molecular adaptations to high temperature, we have focused on a superthermostable short-chain dehydrogenase TsAdh319 from the Thermococcus sibiricus polyextremophilic archaeon and its closest structural homologues. Molecular dynamics method is widely used for molecular structure refinement, investigation of biological macromolecules motion, and, consequently, for interpreting the results of certain biophysical experiments. We performed molecular dynamics simulations of the proteins at different temperatures. Comparison of root mean square fluctuations (RMSF) of the atoms in thermophilic alcohol dehydrogenases (ADHs) at 300 K and 358 K revealed the existence of stable residues at 358 K. These residues surround the active site and form a "nucleus of rigidity" in thermophilic ADHs. The results of our studies suggest that the existence of the "nucleus of rigidity" is crucial for the stability of TsAdh319. Absence of the "nucleus of rigidity" in non-thermally stable proteins causes fluctuations throughout the protein, especially on the surface, triggering the process of denaturation at high temperatures.

Engineering Hollow Carbon Architecture for High-Performance K-Ion Battery Anode.

PubMed

Bin, De-Shan; Lin, Xi-Jie; Sun, Yong-Gang; Xu, Yan-Song; Zhang, Ke; Cao, An-Min; Wan, Li-Jun

2018-05-31

K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K + , stable electrode materials capable of sustaining the repeated K + intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extraordinary capacity (340 mAh g -1 at 0.1 C) together with a superior cycling stability (no obvious fading over 150 cycles at 0.5 C).

Structure-based Engineering of a Plant-Fungal Hybrid Peroxidase for Enhanced Temperature and pH Tolerance.

PubMed

Kohler, Amanda C; Simmons, Blake A; Sale, Kenneth L

2018-04-28

In an age of ever-increasing biotechnological and industrial demand for new and specialized biocatalysts, rational protein engineering offers a direct approach to enzyme design and innovation. Heme peroxidases, as indispensable oxidative biocatalysts, provide a relatively mild alternative to the traditional harsh, and often toxic, chemical catalysts, and subsequently, have found widespread application throughout industry. However, the potential for these enzymes is far greater than their present use, as processes are currently restricted to the more stable, but less catalytically powerful, subset of peroxidases. Here we describe the structure-guided, rational engineering of a plant-fungal hybrid peroxidase built to overcome the application barrier of these high-reduction potential peroxidases. This engineered enzyme has the catalytic versatility and oxidative ability of a high-reduction potential versatile peroxidase, with enhanced temperature and pH tolerance similar to that of a highly stable plant peroxidase. Copyright © 2018 Elsevier Ltd. All rights reserved.

Phosphorous dimerization in GaP high-pressure polymorph

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavina, Barbara; Kim, Eunja; Cynn, Hyunchae

We report on the experimental and theoretical characterization of a novel GaP polymorph formed by laser heating of a single crystal of GaP-II in its stable region near 43 GPa. Thereby formed unstrained multigrain sample at 43 GPa and 1300 K, allowed high-resolution crystallographic analysis. We find an oS24 as an energetically optimized crystal structure contrary to oS8 reported by Nelmes et al. (1997). Our DFT calculation confirms a stable existence of oS24 between 18 – 50 GPa. The emergence of the oS24 structure is related to the differentiation of phosphorous atoms between those forming P-P dimers and those formingmore » P-Ga bonds only. Bonding anisotropy explains the symmetry lowering with respect to what is generally expected for semiconductors high-pressure polymorphs. The metallization of GaP does not occur through a uniform change of the nature of its bonds but through the formation of an anisotropic phase containing different bond types.« less

A field-shaping multi-well avalanche detector for direct conversion amorphous selenium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldan, A. H.; Zhao, W.

2013-01-15

Purpose: A practical detector structure is proposed to achieve stable avalanche multiplication gain in direct-conversion amorphous selenium radiation detectors. Methods: The detector structure is referred to as a field-shaping multi-well avalanche detector. Stable avalanche multiplication gain is achieved by eliminating field hot spots using high-density avalanche wells with insulated walls and field-shaping inside each well. Results: The authors demonstrate the impact of high-density insulated wells and field-shaping to eliminate the formation of both field hot spots in the avalanche region and high fields at the metal-semiconductor interface. Results show a semi-Gaussian field distribution inside each well using the field-shaping electrodes,more » and the electric field at the metal-semiconductor interface can be one order-of-magnitude lower than the peak value where avalanche occurs. Conclusions: This is the first attempt to design a practical direct-conversion amorphous selenium detector with avalanche gain.« less

Exceptionally High Proton and Lithium Cation Gas-Phase Basicity of the Anti-Diabetic Drug Metformin.

PubMed

Raczyńska, Ewa D; Gal, Jean-François; Maria, Pierre-Charles; Michalec, Piotr; Zalewski, Marcin

2017-11-16

Substituted biguanides are known for their biological effect, and a few of them are used as drugs, the most prominent example being metformin (1,1-dimethylbiguanide, IUPAC name: N,N-dimethylimidodicarbonimidic diamide). Because of the presence of hydrogen atoms at the amino groups, biguanides exhibit a multiple tautomerism. This aspect of their structures was examined in detail for unsubstituted biguanide and metformin in the gas phase. At the density functional theory (DFT) level {essentially B3LYP/6-311+G(d,p)}, the most stable structures correspond to the conjugated, push-pull, system (NR 2 )(NH 2 )C═N-C(═NH)NH 2 (R = H, CH 3 ), further stabilized by an internal hydrogen bond. The structural and energetic aspects of protonation and lithium cation adduct formation of biguanide and metformin was examined at the same level of theory. The gas-phase protonation energetics reveal that the more stable tautomer is protonated at the terminal imino C═NH site, still with an internal hydrogen bond maintaining the structure of the neutral system. The calculated proton affinity and gas-phase basicity of the two molecules reach the domain of superbasicity. By contrast, the lithium cation prefers to bind the less stable, not fully conjugated, tautomer (NR 2 )C(═NH)-NH-C(═NH)NH 2 of biguanides, in which the two C═NH groups are separated by NH. This less stable form of biguanides binds Li + as a bidentate ligand, in agreement with what was reported in the literature for other metal cations in the solid phase. The quantitative assessment of resonance in biguanide, in metformin and in their protonated forms, using the HOMED and HOMA indices, reveals an increase in electron delocalization upon protonation. On the contrary, the most stable lithium cation adducts are less conjugated than the stable neutral biguanides, because the metal cation is better coordinated by the not-fully conjugated bidentate tautomer.

A computational study of open-chain epothilone analogue

NASA Astrophysics Data System (ADS)

Kamel, Karol; Rusinska-Roszak, Danuta

Molecular mechanics (MM/Ambers) calculations were applied to probe the conformational profile of open-chain epothilone analogue [Org Lett 2006, 8, 685], cytotoxic against some cell lines. Geometries of the most stable conformers were optimized at DFT level using the B3LYP functional and then compared to known both experimental and virtual conformers of epothilone. One of the most stable structures is III (1.47 kcal/mol above global minimum) which represents high similarity to the appropriate fragment of the Taylor's model of epothilone A, but two other conformers: XIV and XX, although they have almost the same conformation as the mother structure, are very unstable (6.7 and 12.4 kcal/mol above the global minimum).0

Beam control of high-power broad-area photonic crystal lasers using ladderlike groove structure

NASA Astrophysics Data System (ADS)

Wang, Tao; Wang, Lijie; Shu, Shili; Tian, Sicong; Lu, Zefeng; Hou, Guanyu; Lu, Huanyu; Tong, Cunzhu; Wang, Lijun

2017-06-01

The high-power broad-area (BA) photonic bandgap crystal (PBC) diode laser is promising as a high-brightness laser source, however, it suffers from poor lateral beam quality owing to the intrinsic drawback of BA lasers. In this paper, a ladderlike groove structure (LLGS) was proposed to improve both the lateral beam quality and emission power of BA PBC lasers. An approximately 15.4% improvement in output power and 25.2% decrease in the lateral beam parameter product (BPP) were realized and the underlying mechanism was discussed. On the basis of the one-dimensional PBC epitaxial structure, a stable vertical far field was demonstrated.

Hierarchical structure in sharply divided phase space for the piecewise linear map

NASA Astrophysics Data System (ADS)

Akaishi, Akira; Aoki, Kazuki; Shudo, Akira

2017-05-01

We have studied a two-dimensional piecewise linear map to examine how the hierarchical structure of stable regions affects the slow dynamics in Hamiltonian systems. In the phase space there are infinitely many stable regions, each of which is polygonal-shaped, and the rest is occupied by chaotic orbits. By using symbolic representation of stable regions, a procedure to compute the edges of the polygons is presented. The stable regions are hierarchically distributed in phase space and the edges of the stable regions show the marginal instability. The cumulative distribution of the recurrence time obeys a power law as ˜t-2 , the same as the one for the system with phase space, which is composed of a single stable region and chaotic components. By studying the symbol sequence of recurrence trajectories, we show that the hierarchical structure of stable regions has no significant effect on the power-law exponent and that only the marginal instability on the boundary of stable regions is responsible for determining the exponent. We also discuss the relevance of the hierarchical structure to those in more generic chaotic systems.

Robust and Stable Cu Nanowire@Graphene Core-Shell Aerogels for Ultraeffective Electromagnetic Interference Shielding.

PubMed

Wu, Shiting; Zou, Mingchu; Li, Zhencheng; Chen, Daqin; Zhang, Hui; Yuan, Yongjun; Pei, Yongmao; Cao, Anyuan

2018-06-01

Cu nanowires (CuNWs) are considered as a promising candidate to develop high performance metal aerogels, yet the construction of robust and stable 3D porous structures remains challenging which severely limits their practical applications. Here, graphene-hybridized CuNW (CuNW@G) core-shell aerogels are fabricated by introducing a conformal polymeric coating and in situ transforming it into multilayered graphene seamlessly wrapped around individual CuNWs through a mild thermal annealing process. The existence of the outer graphene shell reinforces the 3D bulk structure and significantly slows down the oxidation process of CuNWs, resulting in improved mechanical property and highly stable electrical conductivity. When applied in electromagnetic interference shielding, the CuNW@G core-shell aerogels exhibit an average effectiveness of ≈52.5 dB over a wide range (from 8.2 to 18 GHz) with negligible degradation under ambient conditions for 40 d. Mechanism analysis reveals that the graphene shell with functional groups enables dual reflections on the core-shell and a multiple dielectric relaxation process, leading to enhanced dielectric loss and energy dissipation within the core-shell aerogels. The flexible core-shell-structured CuNW@G aerogels, with superior mechanical robustness and electrical stability, have potential applications in many areas such as advanced energy devices and functional composites. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrathin dendrimer-graphene oxide composite film for stable cycling lithium-sulfur batteries.

PubMed

Liu, Wen; Jiang, Jianbing; Yang, Ke R; Mi, Yingying; Kumaravadivel, Piranavan; Zhong, Yiren; Fan, Qi; Weng, Zhe; Wu, Zishan; Cha, Judy J; Zhou, Henghui; Batista, Victor S; Brudvig, Gary W; Wang, Hailiang

2017-04-04

Lithium-sulfur batteries (Li-S batteries) have attracted intense interest because of their high specific capacity and low cost, although they are still hindered by severe capacity loss upon cycling caused by the soluble lithium polysulfide intermediates. Although many structure innovations at the material and device levels have been explored for the ultimate goal of realizing long cycle life of Li-S batteries, it remains a major challenge to achieve stable cycling while avoiding energy and power density compromises caused by the introduction of significant dead weight/volume and increased electrochemical resistance. Here we introduce an ultrathin composite film consisting of naphthalimide-functionalized poly(amidoamine) dendrimers and graphene oxide nanosheets as a cycling stabilizer. Combining the dendrimer structure that can confine polysulfide intermediates chemically and physically together with the graphene oxide that renders the film robust and thin (<1% of the thickness of the active sulfur layer), the composite film is designed to enable stable cycling of sulfur cathodes without compromising the energy and power densities. Our sulfur electrodes coated with the composite film exhibit very good cycling stability, together with high sulfur content, large areal capacity, and improved power rate.

Polymorphism in a high-entropy alloy

DOE PAGES

Zhang, Fei; Wu, Yuan; Lou, Hongbo; ...

2017-06-01

Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiationmore » X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. Lastly, as pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.« less

Strategy for designing stable and powerful nitrogen-rich high-energy materials by introducing boron atoms.

PubMed

Wu, Wen-Jie; Chi, Wei-Jie; Li, Quan-Song; Li, Ze-Sheng

2017-06-01

One of the most important aims in the development of high-energy materials is to improve their stability and thus ensure that they are safe to manufacture and transport. In this work, we theoretically investigated open-chain N 4 B 2 isomers using density functional theory in order to find the best way of stabilizing nitrogen-rich molecules. The results show that the boron atoms in these isomers are aligned linearly with their neighboring atoms, which facilitates close packing in the crystals of these materials. Upon comparing the energies of nine N 4 B 2 isomers, we found that the structure with alternating N and B atoms had the lowest energy. Structures with more than one nitrogen atom between two boron atoms had higher energies. The energy of N 4 B 2 increases by about 50 kcal/mol each time it is rearranged to include an extra nitrogen atom between the two boron atoms. More importantly, our results also show that boron atoms stabilize nitrogen-rich molecules more efficiently than carbon atoms do. Also, the combustion of any isomer of N 4 B 2 releases more heat than the corresponding isomer of N 4 C 2 does under well-oxygenated conditions. Our study suggests that the three most stable N 4 B 2 isomers (BN13, BN24, and BN34) are good candidates for high-energy molecules, and it outlines a new strategy for designing stable boron-containing high-energy materials. Graphical abstract The structural characteristics, thermodynamic stabilities, and exothermic properties of nitrogen-rich N 4 B 2 isomers were investigated by means of density functional theory.

Immobilization of actinides in stable mineral type and ceramic materials (high temperature synthesis)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Starkov, O.; Konovalov, E.

1996-05-01

Alternative vitrification technologies are being developed in the world for the immobilization of high radioactive waste in materials with improved thermodynamic stability, as well as improved chemical and thermal stability and stability to radiation. Oxides, synthesized in the form of analogs to rock-forming minerals and ceramics, are among those materials that have highly stable properties and are compatible with the environment. In choosing the appropriate material, we need to be guided by its geometric stability, the minimal number of cations in the structure of the material and the presence of structural elements in the mineral that are isomorphs of uraniummore » and thorium, actinoids found in nature. Rare earth elements, yttrium, zirconium and calcium are therefore suitable. The minerals listed in the table (with the exception of the zircon) are pegatites by origin, i.e. they are formed towards the end of the magma crystallization of silicates form the residual melt, enriched with Ta, Nb, Ti, Zr, Ce, Y, U and Th. Uranium and thorium in the form of isomorphic admixtures form part of the lattice of the mineral. These minerals, which are rather simple in composition and structure and are formed under high temperatures, may be viewed as natural physio-chemical systems that are stable and long-lived in natural environments. The similarity of the properties of actinoids and lanthanoids plays an important role in the geochemistry of uranium and thorium; however, uranium (IV) is closer to the {open_quotes}heavy{close_quotes} group of lanthanoids (the yttrium group) while thorium (IV) is closer to the {open_quotes}light{close_quotes} group (the cerium group). That is why rare earth minerals contain uranium and thorium in the form of isomorphic admixtures.« less

Jealousy Graphs: Structure and Complexity of Decentralized Stable Matching

DTIC Science & Technology

2013-01-01

REPORT Jealousy Graphs: Structure and Complexity of Decentralized Stable Matching 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: The stable matching...Franceschetti 858-822-2284 3. DATES COVERED (From - To) Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 - Jealousy Graphs: Structure and...market. Using this structure, we are able to provide a ner analysis of the complexity of a subclass of decentralized matching markets. Jealousy

Tetragonal bismuth bilayer: A stable and robust quantum spin hall insulator

DOE PAGES

Kou, Liangzhi; Tan, Xin; Ma, Yandong; ...

2015-11-23

In this study, topological insulators (TIs) exhibit novel physics with great promise for new devices, but considerable challenges remain to identify TIs with high structural stability and large nontrivial band gap suitable for practical applications. Here we predict by first-principles calculations a two-dimensional (2D) TI, also known as a quantum spin Hall (QSH) insulator, in a tetragonal bismuth bilayer (TB-Bi) structure that is dynamically and thermally stable based on phonon calculations and finite-temperature molecular dynamics simulations. Density functional theory and tight-binding calculations reveal a band inversion among the Bi-p orbits driven by the strong intrinsic spin–orbit coupling, producing a largemore » nontrivial band gap, which can be effectively tuned by moderate strains. The helical gapless edge states exhibit a linear dispersion with a high Fermi velocity comparable to that of graphene, and the QSH phase remains robust on a NaCl substrate. These remarkable properties place TB-Bi among the most promising 2D TIs for high-speed spintronic devices, and the present results provide insights into the intriguing QSH phenomenon in this new Bi structure and offer guidance for its implementation in potential applications.« less

Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

PubMed Central

Corbin, Perry S.; Lawless, Laurence J.; Li, Zhanting; Ma, Yuguo; Witmer, Melissa J.; Zimmerman, Steven C.

2002-01-01

Hydrogen bond-mediated self-assembly is a powerful strategy for creating nanoscale structures. However, little is known about the fidelity of assembly processes that must occur when similar and potentially competing hydrogen-bonding motifs are present. Furthermore, there is a continuing need for new modules and strategies that can amplify the relatively weak strength of a hydrogen bond to give more stable assemblies. Herein we report quantitative complexation studies on a ureidodeazapterin-based module revealing an unprecedented stability for dimers of its self-complementary acceptoracceptor-donor-donor (AADD) array. Linking two such units together with a semirigid spacer that carries a first-, second-, or third-generation Fréchet-type dendron affords a ditopic structure programmed to self assemble. The specific structure that is formed depends both on the size of the dendron and the solvent, but all of the assemblies have exceptionally high stability. The largest discrete nanoscale assembly is a hexamer with a molecular mass of about 17.8 kDa. It is stabilized by 30 hydrogen bonds, including six AADD⋅DDAA contacts. The hexamer forms and is indefinitely stable in the presence of a hexamer containing six ADD⋅DAA hydrogen-bonding arrays. PMID:11917113

Tough, high performance, addition-type thermoplastic polymers

NASA Technical Reports Server (NTRS)

Pater, Ruth H. (Inventor)

1992-01-01

A tough, high performance polyimide is provided by reacting a triple bond conjugated with an aromatic ring in a bisethynyl compound with the active double bond in a compound containing a double bond activated toward the formation of a Diels-Adler type adduct, especially a bismaleimide, a biscitraconimide, or a benzoquinone, or mixtures thereof. Addition curing of this product produces a high linear polymeric structure and heat treating the highly linear polymeric structure produces a thermally stable aromatic addition-type thermoplastic polyimide, which finds utility in the preparation of molding compounds, adhesive compositions, and polymer matrix composites.

Structural transformations of heat treated Co-less high entropy alloys

NASA Astrophysics Data System (ADS)

Mitrica, D.; Tudor, A.; Rinaldi, A.; Soare, V.; Predescu, C.; Berbecaru, A.; Stoiciu, F.; Badilita, V.

2018-03-01

Co is considered to be one of the main ingredients in superalloys. Co is considered a critical element and its substitution is difficult due to its unique ability to form high temperature stable structures with high mechanical and corrosion/oxidation resistance. High entropy alloys (HEA) represent a relatively new concept in material design. HEA are characterised by a high number of alloying elements, in unusually high proportion. Due to their specific particularities, high entropy alloys tend to form predominant solid solution structures that develop potentially high chemical, physical and mechanical properties. Present paper is studying Co-less high entropy alloys with high potential in severe environment applications. The high entropy alloys based on Al-Cr-Fe-Mn-Ni system were prepared by induction melting and casting under protective atmosphere. The as-cast specimens were heat treated at various temperatures to determine the structure and property behaviour. Samples taken before and after heat treatment were investigated for chemical, physical, structural and mechanical characteristics. Sigma phase composition and heat treatment parameters had major influence over the resulted alloy structure and properties.

Interplay of local structure, charge, and spin in bilayered manganese perovskites

NASA Astrophysics Data System (ADS)

Rybicki, Damian; Sikora, Marcin; Przewoznik, Janusz; Kapusta, Czesław; Mitchell, John F.

2018-03-01

Chemical doping is a reliable method of modification of the electronic properties of transition metal compounds. In manganese perovskites, it leads to charge transfer and peculiar ordering phenomena. However, depending on the interplay of the local crystal structure and electronic properties, synthesis of stable compounds in the entire doping range is often impossible. Here, we show results of high-energy resolution x-ray absorption and emission spectroscopies on a La2 -2 xSr1 +2 xMn2O7 family of bilayered manganites in a broad doping range (0.5 ≤x ≤1 ). We established a relation between local Mn charge and Mn-O distances as a function of doping. Based on a comparison of such relation with other manganites, we suggest why stable structures cannot be realized for certain doping levels of bilayered compounds.

Highly oxidized superconductors

DOEpatents

Morris, D.E.

1994-09-20

Novel superconducting materials in the form of compounds, structures or phases are formed by performing otherwise known synthesis in a highly oxidizing atmosphere rather than that created by molecular oxygen at atmospheric pressure or below. This leads to the successful synthesis of novel superconducting compounds which are thermodynamically stable at the conditions under which they are formed. 16 figs.

Highly oxidized superconductors

DOEpatents

Morris, Donald E.

1994-01-01

Novel superconducting materials in the form of compounds, structures or phases are formed by performing otherwise known syntheses in a highly oxidizing atmosphere rather than that created by molecular oxygen at atmospheric pressure or below. This leads to the successful synthesis of novel superconducting compounds which are thermodynamically stable at the conditions under which they are formed.

Nano-sized Superlattice Clusters Created by Oxygen Ordering in Mechanically Alloyed Fe Alloys

NASA Astrophysics Data System (ADS)

Hu, Yong-Jie; Li, Jing; Darling, Kristopher A.; Wang, William Y.; Vanleeuwen, Brian K.; Liu, Xuan L.; Kecskes, Laszlo J.; Dickey, Elizabeth C.; Liu, Zi-Kui

2015-07-01

Creating and maintaining precipitates coherent with the host matrix, under service conditions is one of the most effective approaches for successful development of alloys for high temperature applications; prominent examples include Ni- and Co-based superalloys and Al alloys. While ferritic alloys are among the most important structural engineering alloys in our society, no reliable coherent precipitates stable at high temperatures have been found for these alloys. Here we report discovery of a new, nano-sized superlattice (NSS) phase in ball-milled Fe alloys, which maintains coherency with the BCC matrix up to at least 913 °C. Different from other precipitates in ferritic alloys, this NSS phase is created by oxygen-ordering in the BCC Fe matrix. It is proposed that this phase has a chemistry of Fe3O and a D03 crystal structure and becomes more stable with the addition of Zr. These nano-sized coherent precipitates effectively double the strength of the BCC matrix above that provided by grain size reduction alone. This discovery provides a new opportunity for developing high-strength ferritic alloys for high temperature applications.

Highly stable silica-coated manganese ferrite nanoparticles as high-efficacy T2 contrast agents for magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Ahmad, Ashfaq; Bae, Hongsub; Rhee, Ilsu

2018-05-01

Highly stable silica-coated manganese ferrite nanoparticles were fabricated for application as magnetic resonance imagining (MRI) contrast agents. The manganese ferrite nanoparticles were synthesized using a hydrothermal technique and coated with silica. The particle size was investigated using transmission electron microscopy and was found to be 40-60 nm. The presence of the silica coating on the particle surface was confirmed by Fourier transform infrared spectroscopy. The crystalline structure was investigated by X-ray diffraction, and the particles were revealed to have an inverse spinel structure. Superparamagnetism was confirmed by the magnetic hysteresis curves obtained using a vibrating sample magnetometer. The efficiency of the MRI contrast agents was investigated by using aqueous solutions of the particles in a 4.7 T MRI scanner. The T1 and T2 relaxivities of the particles were 1.42 and 60.65 s-1 mM-1, respectively, in water. The ratio r2/r1 was 48.91, confirming that the silica-coated manganese ferrite nanoparticles were suitable high-efficacy T2 contrast agents.

Wearable, wireless gas sensors using highly stretchable and transparent structures of nanowires and graphene.

PubMed

Park, Jihun; Kim, Joohee; Kim, Kukjoo; Kim, So-Yun; Cheong, Woon Hyung; Park, Kyeongmin; Song, Joo Hyeb; Namgoong, GyeongHo; Kim, Jae Joon; Heo, Jaeyeong; Bien, Franklin; Park, Jang-Ung

2016-05-19

Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the 'Internet of Things' area.

Pressure-induced structural phase transformation and superconducting properties of titanium mononitride

NASA Astrophysics Data System (ADS)

Li, Qian; Guo, Yanan; Zhang, Miao; Ge, Xinlei

2018-03-01

In this work, we have systematically performed the first-principles structure search on titanium mononitride (TiN) within Crystal Structure AnaLYsis by Particle Swarm Optimization (CALYPSO) methodology at high pressures. Here, we have confirmed a phase transition from cubic rock-salt (fcc) phase to CsCl (bcc) phase of TiN at ∼348 GPa. Further simulations reveal that the bcc phase is dynamically stable, and could be synthesized experimentally in principle. The calculated elastic anisotropy decreases with the phase transformation from fcc to bcc structure under high pressures, and the material changes from ductile to brittle simultaneously. Moreover, we found that both structures are superconductive with the superconducting critical temperature of 2-12 K.

Meta-stable magnetic transitions and its field dependence in Co2.75Fe0.25O4 ferrite

NASA Astrophysics Data System (ADS)

Aswathi M., C.; Bhowmik, R. N.

2018-04-01

The Co2.75Fe0.25O4 ferrite has been prepared by chemical co-precipitation route. The as-prepared sample has been annealed at 500° C. X-ray diffraction pattern indicated cubic spinel structure in the sample. The sample showed ferrimagnetic nature with magnetic irreversibility and hysteresis loop. Magnetization data revealed high anisotropic nature and at least two prominent meta-stable magnetic transitions below the highest measurement temperature 350 K.

Synthesis of stable TiO2 nanotubes: effect of hydrothermal treatment, acid washing and annealing temperature.

PubMed

López Zavala, Miguel Ángel; Lozano Morales, Samuel Alejandro; Ávila-Santos, Manuel

2017-11-01

Effect of hydrothermal treatment, acid washing and annealing temperature on the structure and morphology of TiO 2 nanotubes during the formation process was assessed. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy analysis were conducted to describe the formation and characterization of the structure and morphology of nanotubes. Hydrothermal treatment of TiO 2 precursor nanoparticles and acid washing are fundamental to form and define the nanotubes structure. Hydrothermal treatment causes a change in the crystallinity of the precursor nanoparticles from anatase phase to a monoclinic phase, which characterizes the TiO 2 nanosheets structure. The acid washing promotes the formation of high purity nanotubes due to Na + is exchanged from the titanate structure to the hydrochloric acid (HCl) solution. The annealing temperature affects the dimensions, structure and the morphology of the nanotubes. Annealing temperatures in the range of 400 °C and 600 °C are optimum to maintain a highly stable tubular morphology of nanotubes. Additionally, nanotubes conserve the physicochemical properties of the precursor Degussa P25 nanoparticles. Temperatures greater than 600 °C alter the morphology of nanotubes from tubular to an irregular structure of nanoparticles, which are bigger than those of the precursor material, i.e., the crystallinity turn from anatase phase to rutile phase inducing the collapse of the nanotubes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fei; Wu, Yuan; Lou, Hongbo

Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiationmore » X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. Lastly, as pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.« less

Finding the Stable Structures of N1-xWx with an Ab Initio High-Throughput Approach

DTIC Science & Technology

2015-05-26

W. These include borides , carbides, oxides, and other nitrides. We also invented many structures to mimic the random pattern of vacancies on both the...structures. These include nitrides, oxides, borides , and carbides, as well as supercells of standard structures with atoms removed to mimic the random patter...1930). [15] R. Kiessling and Y. H. Liu, Thermal stability of the chromium, iron, and tungsten borides in streaming ammonia and the existence of a new

Stable 293 T and CHO cell lines expressing cleaved, stable HIV-1 envelope glycoprotein trimers for structural and vaccine studies.

PubMed

Chung, Nancy P Y; Matthews, Katie; Kim, Helen J; Ketas, Thomas J; Golabek, Michael; de Los Reyes, Kevin; Korzun, Jacob; Yasmeen, Anila; Sanders, Rogier W; Klasse, Per Johan; Wilson, Ian A; Ward, Andrew B; Marozsan, Andre J; Moore, John P; Cupo, Albert

2014-04-25

Recombinant soluble, cleaved HIV-1 envelope glycoprotein SOSIP.664 gp140 trimers based on the subtype A BG505 sequence are being studied structurally and tested as immunogens in animals. For these trimers to become a vaccine candidate for human trials, they would need to be made in appropriate amounts at an acceptable quality. Accomplishing such tasks by transient transfection is likely to be challenging. The traditional way to express recombinant proteins in large amounts is via a permanent cell line, usually of mammalian origin. Making cell lines that produce BG505 SOSIP.664 trimers requires the co-expression of the Furin protease to ensure that the cleavage site between the gp120 and gp41 subunits is fully utilized. We designed a vector capable of expressing Env and Furin, and used it to create Stable 293 T and CHO Flp-In™ cell lines through site-specific recombination. Both lines produce high quality, cleaved trimers at yields of up to 12-15 mg per 1 × 109 cells. Trimer expression at such levels was maintained for up to 30 days (10 passages) after initial seeding and was consistently superior to what could be achieved by transient transfection. Electron microscopy studies confirm that the purified trimers have the same native-like appearance as those derived by transient transfection and used to generate high-resolution structures. They also have appropriate antigenic properties, including the presentation of the quaternary epitope for the broadly neutralizing antibody PGT145. The BG505 SOSIP.664 trimer-expressing cell lines yield proteins of an appropriate quality for structural studies and animal immunogenicity experiments. The methodology is suitable for making similar lines under Good Manufacturing Practice conditions, to produce trimers for human clinical trials. Moreover, any env gene can be incorporated into this vector system, allowing the manufacture of SOSIP trimers from multiple genotypes, either by transient transfection or from stable cell lines.

Benchmark Design and Installation: A synthesis of Existing Information.

DTIC Science & Technology

1987-07-01

casings (15 ft deep) drilled to rock and filled with concrete. Disks - 1 . Set on vertically stable structures (e.g., dam monoliths). 2 . Set in rock ...Structural movement survey 1 . Rock outcrops (first choice) -- chiseled square on high point. 2 . Massive concrete structure (second choice) - cut square on...bolt marker (type 2 ). 58,. % %--"% %I 1 ± 4 -I,.- Table Cl. Recomnded benchmarks. Type of condition or terrain Type of markert Bedrock, rock outcrops

Middle School Improvement and Reform: Development and Validation of a School-Level Assessment of Climate, Cultural Pluralism, and School Safety.

ERIC Educational Resources Information Center

Brand, Stephen; Felner, Robert; Shim, Minsuk; Seitsinger, Anne; Dumas, Thaddeus

2003-01-01

Examines the structure of perceived school climate and the relationship of climate dimensions to adaptation of students who attend middle-grade-level schools. The climate scales exhibited a stable dimensional structure, high levels of internal consistency, and moderate levels of stability. Ratings of multiple climate dimensions were associated…

An Army Force Structure for the Future

DTIC Science & Technology

1992-03-31

realization: deterring aggression; ensuring access to foreign markets , energy, mineral resources, the oceans, and space; maintaining stable regional...establish the optimum organisational mix for independent and highly flexible operational-level activity." 7 Two factors are driving this structural change...armored forces; and optimizing the force mix of the three. However, before describing the specific changes needed to shape the future Army, a delineation

Static network structure can stabilize human cooperation.

PubMed

Rand, David G; Nowak, Martin A; Fowler, James H; Christakis, Nicholas A

2014-12-02

The evolution of cooperation in network-structured populations has been a major focus of theoretical work in recent years. When players are embedded in fixed networks, cooperators are more likely to interact with, and benefit from, other cooperators. In theory, this clustering can foster cooperation on fixed networks under certain circumstances. Laboratory experiments with humans, however, have thus far found no evidence that fixed network structure actually promotes cooperation. Here, we provide such evidence and help to explain why others failed to find it. First, we show that static networks can lead to a stable high level of cooperation, outperforming well-mixed populations. We then systematically vary the benefit that cooperating provides to one's neighbors relative to the cost required to cooperate (b/c), as well as the average number of neighbors in the network (k). When b/c > k, we observe high and stable levels of cooperation. Conversely, when b/c ≤ k or players are randomly shuffled, cooperation decays. Our results are consistent with a quantitative evolutionary game theoretic prediction for when cooperation should succeed on networks and, for the first time to our knowledge, provide an experimental demonstration of the power of static network structure for stabilizing human cooperation.

Static network structure can stabilize human cooperation

PubMed Central

Rand, David G.; Nowak, Martin A.; Fowler, James H.; Christakis, Nicholas A.

2014-01-01

The evolution of cooperation in network-structured populations has been a major focus of theoretical work in recent years. When players are embedded in fixed networks, cooperators are more likely to interact with, and benefit from, other cooperators. In theory, this clustering can foster cooperation on fixed networks under certain circumstances. Laboratory experiments with humans, however, have thus far found no evidence that fixed network structure actually promotes cooperation. Here, we provide such evidence and help to explain why others failed to find it. First, we show that static networks can lead to a stable high level of cooperation, outperforming well-mixed populations. We then systematically vary the benefit that cooperating provides to one’s neighbors relative to the cost required to cooperate (b/c), as well as the average number of neighbors in the network (k). When b/c > k, we observe high and stable levels of cooperation. Conversely, when b/c ≤ k or players are randomly shuffled, cooperation decays. Our results are consistent with a quantitative evolutionary game theoretic prediction for when cooperation should succeed on networks and, for the first time to our knowledge, provide an experimental demonstration of the power of static network structure for stabilizing human cooperation. PMID:25404308

Metastable solidification of hypereutectic Co 2Si-CoSi composition: Microstructural studies and in-situ observations

DOE PAGES

Wang, Yeqing; Gao, Jianrong; Kolbe, Matthias; ...

2017-09-18

Metastable solidification of undercooled Co 60Si 40 melts was investigated by microstructural studies and in-situ high-energy X-ray diffraction. Five solidification paths were identified. Three of them were observed at low undercoolings, which show uncoupled and coupled growth of stable β-Co 2Si and CoSi compounds. The other paths were observed at high undercoolings, which show peritectic and primary crystallization of a metastable Co 5Si 3 compound. The β-Co 2Si and Co 5Si 3 compounds crystallize into a hexagonal crystal structure and experience solid-state decomposition. Microstructure formation depends on solidification path. The coupled and uncoupled growth of the stable compounds produces amore » regular lamellar eutectic structure and an anomalous eutectic structure, respectively. The crystallization and solid-state decomposition of the metastable Co 5Si 3 compound brings about a fine-grained two-phase mixture, which represents another type of anomalous eutectic structure. Here, the results provide proof of two rare mechanisms of anomalous eutectic formation and shed light onto metastable phase relations in the undercooled region of the Co-Si system.« less

Metastable solidification of hypereutectic Co 2Si-CoSi composition: Microstructural studies and in-situ observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yeqing; Gao, Jianrong; Kolbe, Matthias

Metastable solidification of undercooled Co 60Si 40 melts was investigated by microstructural studies and in-situ high-energy X-ray diffraction. Five solidification paths were identified. Three of them were observed at low undercoolings, which show uncoupled and coupled growth of stable β-Co 2Si and CoSi compounds. The other paths were observed at high undercoolings, which show peritectic and primary crystallization of a metastable Co 5Si 3 compound. The β-Co 2Si and Co 5Si 3 compounds crystallize into a hexagonal crystal structure and experience solid-state decomposition. Microstructure formation depends on solidification path. The coupled and uncoupled growth of the stable compounds produces amore » regular lamellar eutectic structure and an anomalous eutectic structure, respectively. The crystallization and solid-state decomposition of the metastable Co 5Si 3 compound brings about a fine-grained two-phase mixture, which represents another type of anomalous eutectic structure. Here, the results provide proof of two rare mechanisms of anomalous eutectic formation and shed light onto metastable phase relations in the undercooled region of the Co-Si system.« less

Structure, stability, thermodynamic properties, and IR spectra of the protonated water decamer H+(H2O)10.

PubMed

Karthikeyan, S; Kim, Kwang S

2009-08-13

Protonated water clusters H+(H2O)n favor two-dimensional (2D) structures for n < or = 7 at low temperatures. At 0 K, the 2D and three-dimensional (3D) structures for n = 8 are almost isoenergetic, and the 3D structures for n > 9 tend to be more stable. However, for n = 9, the netlike structures are likely to be more stable above 150 K. In this regard, we investigate the case of n = 10 to find which structure is more stable between the 3D structure and the netlike structure around 150 and 250 K. We use density functional theory, Møller-Plesset second-order perturbation theory, and coupled cluster theory with single, double, and perturbative triple excitations (CCSD(T)). At the complete basis set limit for the CCSD(T) level of theory, three isomers of 3D cage structure are much more stable in zero point energy corrected binding energy and in free binding energies at 150 K than the lowest energy netlike structures, while the netlike structure would be more stable around approximately 250 K. The predicted vibrational spectra are in good agreement with the experiment. One of the three isomers explains the experimental IR observation of an acceptor (A) type peak of a dangling hydrogen atom.

Designing Air-Stable O 3-Type Cathode Materials by Combined Structure Modulation for Na-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, Hu-Rong; Wang, Peng-Fei; Gong, Yue

As promising high-capacity cathode materials for Na-ion batteries, O 3-type Na-based metal oxides always suffer from their poor air stability originating from the spontaneous extraction of Na and oxidation of transition metals when exposed to air. Here, a combined structure modulation is proposed to tackle concurrently the two handicaps via reducing Na layers spacing and simultaneously increasing valence state of transition metals. Guided by density functional theory calculations, we demonstrate such a modulation can be subtly realized through cosubstitution of one kind of heteroatom with comparable electronegativity and another one with substantially different Fermi level, by adjusting the structure ofmore » NaNi 0.5Mn 0.5O 2 via Cu/Ti codoping. The as-obtained NaNi 0.45Cu 0.05Mn 0.4Ti 0.1O 2 exhibits an increase of 20 times in stable air-exposure period and 9 times in capacity retention after 500 cycles, and even retains its structure and capacity after being soaked in water. In such a simple and effective structure modulation reveals a new avenue for high-performance O 3-type cathodes and pushes the large-scale industrialization of Na-ion batteries a decisive step forward.« less

Designing Air-Stable O 3-Type Cathode Materials by Combined Structure Modulation for Na-Ion Batteries

DOE PAGES

Yao, Hu-Rong; Wang, Peng-Fei; Gong, Yue; ...

2017-06-09

As promising high-capacity cathode materials for Na-ion batteries, O 3-type Na-based metal oxides always suffer from their poor air stability originating from the spontaneous extraction of Na and oxidation of transition metals when exposed to air. Here, a combined structure modulation is proposed to tackle concurrently the two handicaps via reducing Na layers spacing and simultaneously increasing valence state of transition metals. Guided by density functional theory calculations, we demonstrate such a modulation can be subtly realized through cosubstitution of one kind of heteroatom with comparable electronegativity and another one with substantially different Fermi level, by adjusting the structure ofmore » NaNi 0.5Mn 0.5O 2 via Cu/Ti codoping. The as-obtained NaNi 0.45Cu 0.05Mn 0.4Ti 0.1O 2 exhibits an increase of 20 times in stable air-exposure period and 9 times in capacity retention after 500 cycles, and even retains its structure and capacity after being soaked in water. In such a simple and effective structure modulation reveals a new avenue for high-performance O 3-type cathodes and pushes the large-scale industrialization of Na-ion batteries a decisive step forward.« less

Structuring unbreakable hydrophobic barriers in paper

NASA Astrophysics Data System (ADS)

Nargang, Tobias M.; Kotz, Frederik; Rapp, Bastian E.

2018-02-01

Hydrophobic barriers are one of the key elements of microfluidic paper based analytical devices (μPADs).μPADs are simple and cost efficient and they can be carried out without the need of high standard laboratories. To carry out such a test a method is needed to create stable hydrophobic barriers. Commonly used methods like printing wax or polystyrene have the major drawback that these barriers are stiff and break if bended which means they will no longer be able to retain a liquid sample. Here we present silanes to structure hydrophobic barriers via polycondensation and show a silanization method which combines the advantages of flexible silane/siloxane layers with the short processing times of UV-light based structuring. The barriers are created by using methoxy silanes which are mixed with a photo acid generator (PAG) as photoinitiator. Also a photosensitizer was given to the mixture to increase the effectiveness of the PAG. After the PAG is activated by UV-light the silane is hydrolyzed and coupled to the cellulose via polycondensation. The created hydrophobic barriers are highly stable and do not break if being bended.

Recent development in deciphering the structure of luminescent silver nanodots

NASA Astrophysics Data System (ADS)

Choi, Sungmoon; Yu, Junhua

2017-05-01

Matrix-stabilized silver clusters and stable luminescent few-atom silver clusters, referred to as silver nanodots, show notable difference in their photophysical properties. We present recent research on deciphering the nature of silver clusters and nanodots and understanding the factors that lead to variations in luminescent mechanisms. Due to their relatively simple structure, the matrix-stabilized clusters have been well studied. However, the single-stranded DNA (ssDNA)-stabilized silver nanodots that show the most diverse emission wavelengths and the best photophysical properties remain mysterious species. It is clear that their photophysical properties highly depend on their protection scaffolds. Analyses from combinations of high-performance liquid chromatography, inductively coupled plasma-atomic emission spectroscopy, electrophoresis, and mass spectrometry indicate that about 10 to 20 silver atoms form emissive complexes with ssDNA. However, it is possible that not all of the silver atoms in the complex form effective emission centers. Investigation of the nanodot structure will help us understand why luminescent silver nanodots are stable in aqueous solution and how to further improve their chemical and photophysical properties.

New two-dimensional V-V binary compounds with a honeycomb-like structure: a first-principles study

NASA Astrophysics Data System (ADS)

Xiao, Wen-Zhi; Xiao, Gang; Rong, Qing-Yan; Wang, Ling-Ling

2018-03-01

We systematically search for the stable structures of two-dimensional (2D) V-V binary compounds with honeycomb-like structure by using the first-principles calculation. We identify 26 stable structures out of 54 2D V-V compounds based on various assessments of stabilities: total energy, thermodynamics, and mechanics. Among them, 12 2D V-V compounds are previously unrecognized structures. For each class V-V isomer, the most stable structures are found to be β-AsP, β-SbAs, α-BiAs, α-BiSb, α 2-SbP, and α 2-BiP. For all isomers of the AsP, they are always stable, and hence PAs monolayer is most likely to be prepared experimentally. All the stable structures are semiconductors with bandgaps ranging from 0.06 eV to 2.52 eV at the Heyd-Scuseria-Ernzerhof level. Therefore, they are potential materials for versatile semiconductor devices. Our findings provide a new clue to facilitate the design of 2D materials for potential applications.

Computational Redesign of Thioredoxin Is Hypersensitive toward Minor Conformational Changes in the Backbone Template

PubMed Central

Christensen, Signe; Horowitz, Scott; Bardwell, James C.A.; Olsen, Johan G.; Willemoës, Martin; Lindorff-Larsen, Kresten; Ferkinghoff-Borg, Jesper; Hamelryck, Thomas; Winther, Jakob R.

2017-01-01

Despite the development of powerful computational tools, the full-sequence design of proteins still remains a challenging task. To investigate the limits and capabilities of computational tools, we conducted a study of the ability of the program Rosetta to predict sequences that recreate the authentic fold of thioredoxin. Focusing on the influence of conformational details in the template structures, we based our study on 8 experimentally determined template structures and generated 120 designs from each. For experimental evaluation, we chose six sequences from each of the eight templates by objective criteria. The 48 selected sequences were evaluated based on their progressive ability to (1) produce soluble protein in Escherichia coli and (2) yield stable monomeric protein, and (3) on the ability of the stable, soluble proteins to adopt the target fold. Of the 48 designs, we were able to synthesize 32, 20 of which resulted in soluble protein. Of these, only two were sufficiently stable to be purified. An X-ray crystal structure was solved for one of the designs, revealing a close resemblance to the target structure. We found a significant difference among the eight template structures to realize the above three criteria despite their high structural similarity. Thus, in order to improve the success rate of computational full-sequence design methods, we recommend that multiple template structures are used. Furthermore, this study shows that special care should be taken when optimizing the geometry of a structure prior to computational design when using a method that is based on rigid conformations. PMID:27659562

Computational Redesign of Thioredoxin Is Hypersensitive toward Minor Conformational Changes in the Backbone Template.

PubMed

Johansson, Kristoffer E; Tidemand Johansen, Nicolai; Christensen, Signe; Horowitz, Scott; Bardwell, James C A; Olsen, Johan G; Willemoës, Martin; Lindorff-Larsen, Kresten; Ferkinghoff-Borg, Jesper; Hamelryck, Thomas; Winther, Jakob R

2016-10-23

Despite the development of powerful computational tools, the full-sequence design of proteins still remains a challenging task. To investigate the limits and capabilities of computational tools, we conducted a study of the ability of the program Rosetta to predict sequences that recreate the authentic fold of thioredoxin. Focusing on the influence of conformational details in the template structures, we based our study on 8 experimentally determined template structures and generated 120 designs from each. For experimental evaluation, we chose six sequences from each of the eight templates by objective criteria. The 48 selected sequences were evaluated based on their progressive ability to (1) produce soluble protein in Escherichia coli and (2) yield stable monomeric protein, and (3) on the ability of the stable, soluble proteins to adopt the target fold. Of the 48 designs, we were able to synthesize 32, 20 of which resulted in soluble protein. Of these, only two were sufficiently stable to be purified. An X-ray crystal structure was solved for one of the designs, revealing a close resemblance to the target structure. We found a significant difference among the eight template structures to realize the above three criteria despite their high structural similarity. Thus, in order to improve the success rate of computational full-sequence design methods, we recommend that multiple template structures are used. Furthermore, this study shows that special care should be taken when optimizing the geometry of a structure prior to computational design when using a method that is based on rigid conformations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structural insights into methanol-stable variants of lipase T6 from Geobacillus stearothermophilus.

PubMed

Dror, Adi; Kanteev, Margarita; Kagan, Irit; Gihaz, Shalev; Shahar, Anat; Fishman, Ayelet

2015-11-01

Enzymatic production of biodiesel by transesterification of triglycerides and alcohol, catalyzed by lipases, offers an environmentally friendly and efficient alternative to the chemically catalyzed process while using low-grade feedstocks. Methanol is utilized frequently as the alcohol in the reaction due to its reactivity and low cost. However, one of the major drawbacks of the enzymatic system is the presence of high methanol concentrations which leads to methanol-induced unfolding and inactivation of the biocatalyst. Therefore, a methanol-stable lipase is of great interest for the biodiesel industry. In this study, protein engineering was applied to substitute charged surface residues with hydrophobic ones to enhance the stability in methanol of a lipase from Geobacillus stearothermophilus T6. We identified a methanol-stable variant, R374W, and combined it with a variant found previously, H86Y/A269T. The triple mutant, H86Y/A269T/R374W, had a half-life value at 70 % methanol of 324 min which reflects an 87-fold enhanced stability compared to the wild type together with elevated thermostability in buffer and in 50 % methanol. This variant also exhibited an improved biodiesel yield from waste chicken oil compared to commercial Lipolase 100L® and Novozyme® CALB. Crystal structures of the wild type and the methanol-stable variants provided insights regarding structure-stability correlations. The most prominent features were the extensive formation of new hydrogen bonds between surface residues directly or mediated by structural water molecules and the stabilization of Zn and Ca binding sites. Mutation sites were also characterized by lower B-factor values calculated from the X-ray structures indicating improved rigidity.

An isopropanol-assisted fabrication strategy of pinhole-free perovskite films in air for efficient and stable planar perovskite solar cells

NASA Astrophysics Data System (ADS)

Ren, Ziqiu; Zhu, Menghua; Li, Xin; Dong, Cunku

2017-09-01

As a promising photovoltaic device, perovskite solar cells have attracted numerous attention in recent years, where forming a compact and pinhole-free perovskite film in air is of great importance. Herein, we evaluate highly efficient and air stable planar perovskite solar cells in air (relative humidity over 50%) with the modified two-step sequential deposition method by adjusting the CH3NH3I (MAI) concentrations and regulating the crystallization process of the perovskite film. The optimum MAI concentration is 60 mg mL-1 in isopropanol. With a planar structure of FTO/TiO2/MAPbI3/spiro-OMeTAD/Au, the efficient devices composed of compact and pinhole-free perovskite films are constructed in air, achieving a high efficiency of up to 15.10% and maintaining over 80% after 20 days storing without any encapsulation in air. With a facile fabrication process and high photovoltaic performance, this work represents a promising method for fabricating low-cost, highly efficient and stable photovoltaic device.

Automated, high-throughput platform for protein solubility screening using a split-GFP system

PubMed Central

Listwan, Pawel; Terwilliger, Thomas C.

2010-01-01

Overproduction of soluble and stable proteins for functional and structural studies is a major bottleneck for structural genomics programs and traditional biochemistry laboratories. Many high-payoff proteins that are important in various biological processes are “difficult to handle” as protein reagents in their native form. We have recently made several advances in enabling biochemical technologies for improving protein stability (http://www.lanl.gov/projects/gfp/), allowing stratagems for efficient protein domain trapping, solubility-improving mutations, and finding protein folding partners. In particular split-GFP protein tags are a very powerful tool for detection of stable protein domains. Soluble, stable proteins tagged with the 15 amino acid GFP fragment (amino acids 216–228) can be detected in vivo and in vitro using the engineered GFP 1–10 “detector” fragment (amino acids 1–215). If the small tag is accessible, the detector fragment spontaneously binds resulting in fluorescence. Here, we describe our current and on-going efforts to move this process from the bench (manual sample manipulation) to an automated, high-throughput, liquid-handling platform. We discuss optimization and validation of bacterial culture growth, lysis protocols, protein extraction, and assays of soluble and insoluble protein in multiple 96 well plate format. The optimized liquid-handling protocol can be used for rapid determination of the optimal, compact domains from single ORFS, collections of ORFS, or cDNA libraries. PMID:19039681

The stable clustering ansatz, consistency relations and gravity dual of large-scale structure

NASA Astrophysics Data System (ADS)

Munshi, Dipak

2018-02-01

Gravitational clustering in the nonlinear regime remains poorly understood. Gravity dual of gravitational clustering has recently been proposed as a means to study the nonlinear regime. The stable clustering ansatz remains a key ingredient to our understanding of gravitational clustering in the highly nonlinear regime. We study certain aspects of violation of the stable clustering ansatz in the gravity dual of Large Scale Structure (LSS). We extend the recent studies of gravitational clustering using AdS gravity dual to take into account possible departure from the stable clustering ansatz and to arbitrary dimensions. Next, we extend the recently introduced consistency relations to arbitrary dimensions. We use the consistency relations to test the commonly used models of gravitational clustering including the halo models and hierarchical ansätze. In particular we establish a tower of consistency relations for the hierarchical amplitudes: Q, Ra, Rb, Sa,Sb,Sc etc. as a functions of the scaled peculiar velocity h. We also study the variants of popular halo models in this context. In contrast to recent claims, none of these models, in their simplest incarnation, seem to satisfy the consistency relations in the soft limit.

The long-sought seventeen-electron radical [(C6Me6)Cr(CO)3](+): isolation, crystal structure and substitution reaction.

PubMed

Wang, Wenqing; Wang, Xingyong; Zhang, Zaichao; Yuan, Ningning; Wang, Xinping

2015-05-18

A highly air-sensitive seventeen-electron half-sandwich radical, [(C6Me6)Cr(CO)3](+), which has been long sought over 40 years, was isolated and structurally characterized. EPR spectroscopy and theoretical calculations indicate that the spin density mainly resides on the chromium atom. The radical can undergo a substitution reaction with PPh3 to form a more stable cation, [(C6Me6)Cr(CO)2(PPh3)](+). This work provides a direct observation of the radical process for CO-substitution reactions found in (arene)M(CO)3 (M = Cr, Mo, or W) systems, and suggests that other stable radicals of the type [(arene)M(CO)3](+) are accessible.

High-temperature-measuring device

DOEpatents

Not Available

1981-01-27

A temperature measuring device for very high design temperatures (to 2000/sup 0/C) is described. The device comprises a homogenous base structure preferably in the form of a sphere or cylinder. The base structure contains a large number of individual walled cells. The base structure has a decreasing coefficient of elasticity within the temperature range being monitored. A predetermined quantity of inert gas is confined within each cell. The cells are dimensonally stable at the normal working temperature of the device. Increases in gaseous pressure within the cells will permanently deform the cell walls at temperatures within the high temperature range to be measured. Such deformation can be correlated to temperature by calibrating similarly constructed devices under known time and temperature conditions.

High temperature measuring device

DOEpatents

Tokarz, Richard D.

1983-01-01

A temperature measuring device for very high design temperatures (to 2,000.degree. C.). The device comprises a homogenous base structure preferably in the form of a sphere or cylinder. The base structure contains a large number of individual walled cells. The base structure has a decreasing coefficient of elasticity within the temperature range being monitored. A predetermined quantity of inert gas is confined within each cell. The cells are dimensionally stable at the normal working temperature of the device. Increases in gaseous pressure within the cells will permanently deform the cell walls at temperatures within the high temperature range to be measured. Such deformation can be correlated to temperature by calibrating similarly constructed devices under known time and temperature conditions.

Si-FeSi2/C nanocomposite anode materials produced by two-stage high-energy mechanical milling

NASA Astrophysics Data System (ADS)

Yang, Yun Mo; Loka, Chadrasekhar; Kim, Dong Phil; Joo, Sin Yong; Moon, Sung Whan; Choi, Yi Sik; Park, Jung Han; Lee, Kee-Sun

2017-05-01

High capacity retention Silicon-based nanocomposite anode materials have been extensively explored for use in lithium-ion rechargeable batteries. Here we report the preparation of Si-FeSi2/C nanocomposite through scalable a two-stage high-energy mechanical milling process, in which nano-scale Si-FeSi2 powders are besieged by the carbon (graphite/amorphous phase) layer; and investigation of their structure, morphology and electrochemical performance. Raman analysis revealed that the carbon layer structure comprised of graphitic and amorphous phase rather than a single amorphous phase. Anodes fabricated with the Si-FeSi2/C showed excellent electrochemical behavior such as a first discharge capacity of 1082 mAh g-1 and a high capacity retention until the 30th cycle. A remarkable coulombic efficiency of 99.5% was achieved within a few cycles. Differential capacity plots of the Si-FeSi2/C anodes revealed a stable lithium reaction with Si for lithiation/delithiation. The enhanced electrochemical properties of the Si-FeSi2/C nanocomposite are mainly attributed to the nano-size Si and stable solid electrolyte interface formation and highly conductive path driven by the carbon layer.

High-Temperature Adhesives for Thermally Stable Aero-Assist Technologies

NASA Technical Reports Server (NTRS)

Eberts, Kenneth; Ou, Runqing

2013-01-01

Aero-assist technologies are used to control the velocity of exploration vehicles (EVs) when entering Earth or other planetary atmospheres. Since entry of EVs in planetary atmospheres results in significant heating, thermally stable aero-assist technologies are required to avoid the high heating rates while maintaining low mass. Polymer adhesives are used in aero-assist structures because of the need for high flexibility and good bonding between layers of polymer films or fabrics. However, current polymer adhesives cannot withstand temperatures above 400 C. This innovation utilizes nanotechnology capabilities to address this need, leading to the development of high-temperature adhesives that exhibit high thermal conductivity in addition to increased thermal decomposition temperature. Enhanced thermal conductivity will help to dissipate heat quickly and effectively to avoid temperature rising to harmful levels. This, together with increased thermal decomposition temperature, will enable the adhesives to sustain transient high-temperature conditions.

The nucleotide-free state of heterotrimeric G proteins α-subunit adopts a highly stable conformation.

PubMed

Andhirka, Sai Krishna; Vignesh, Ravichandran; Aradhyam, Gopala Krishna

2017-08-01

Deciphering the mechanism of activation of heterotrimeric G proteins by their cognate receptors continues to be an intriguing area of research. The recently solved crystal structure of the ternary complex captured the receptor-bound α-subunit in an open conformation, without bound nucleotide has improved our understanding of the activation process. Despite these advancements, the mechanism by which the receptor causes GDP release from the α-subunit remains elusive. To elucidate the mechanism of activation, we studied guanine nucleotide-induced structural stability of the α-subunit (in response to thermal/chaotrope-mediated stress). Inherent stabilities of the inactive (GDP-bound) and active (GTP-bound) forms contribute antagonistically to the difference in conformational stability whereas the GDP-bound protein is able to switch to a stable intermediate state, GTP-bound protein loses this ability. Partial perturbation of the protein fold reveals the underlying influence of the bound nucleotide providing an insight into the mechanism of activation. An extra stable, pretransition intermediate, 'empty pocket' state (conformationally active-state like) in the unfolding pathway of GDP-bound protein mimics a gating system - the activation process having to overcome this stable intermediate state. We demonstrate that a relatively more complex conformational fold of the GDP-bound protein is at the core of the gating system. We report capturing this threshold, 'metastable empty pocket' conformation (the gate) of α-subunit of G protein and hypothesize that the receptor activates the G protein by enabling it to achieve this structure through mild structural perturbation. © 2017 Federation of European Biochemical Societies.

Finding the Stable Structures of WxN1-x with an ab-initio High-Throughput Approach

DTIC Science & Technology

2014-03-13

cubic boron nitride[4], carbonitrides,[5] and transition metal borides .[6, 7] Over the past several years there has been considerable theoretical...include ionic and covalent structures which seem chemically similar to W-N. These include borides , carbides, oxides, and other nitrides. In this paper we...metallic alloys, [23–27] we extended it to include over fifty new structures. These include nitrides, oxides, borides , and carbides. The important

Superior Thermally Stable and Nonflammable Porous Polybenzimidazole Membrane with High Wettability for High-Power Lithium-Ion Batteries.

PubMed

Li, Dan; Shi, Dingqin; Xia, Yonggao; Qiao, Lin; Li, Xianfeng; Zhang, Huamin

2017-03-15

Separators with high security, reliability, and rate capacity are in urgent need for the advancement of high power lithium ion batteries. The currently used porous polyolefin membranes are critically hindered by their low thermal stability and poor electrolyte wettability, which further lead to low rate capacity. Here we present a novel promising porous polybenzimidazole (PBI) membrane with super high thermal stability and electrolyte wettability. The rigid structure and functional groups in the PBI chain enable membranes to be stable at temperature as high as 400 °C, and the unique flame resistance of PBI could ensure the high security of a battery as well. In particular, the prepared membrane owns 328% electrolyte uptake, which is more than two times higher than commercial Celgard 2325 separator. The unique combination of high thermal stability, high flame resistance and super high electrolyte wettability enable the PBI porous membranes to be highly promising for high power lithium battery.

Investigation on structural, thermal, optical and sensing properties of meta-stable hexagonal MoO(3) nanocrystals of one dimensional structure.

PubMed

Chithambararaj, Angamuthuraj; Bose, Arumugam Chandra

2011-01-01

Hexagonal molybdenum oxide (h-MoO(3)) was synthesized by a solution based chemical precipitation technique. Analysis by X-ray diffraction (XRD) confirmed that the as-synthesized powder had a metastable hexagonal structure. The characteristic vibrational band of Mo-O was identified from Fourier transform infrared spectroscopy (FT-IR). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images clearly depicted the morphology and size of h-MoO(3.) The morphology study showed that the product comprises one-dimensional (1D) hexagonal rods. From the electron energy loss spectroscopy (EELS) measurement, the elemental composition was investigated and confirmed from the characteristic peaks of molybdenum and oxygen. Thermogravimetric (TG) analysis on metastable MoO(3) revealed that the hexagonal phase was stable up to 430 °C and above this temperature complete transformation into a highly stable orthorhombic phase was achieved. The optical band gap energy was estimated from the Kubelka-Munk (K-M) function and was found to be 2.99 eV. Finally, the ethanol vapor-sensing behavior was investigated and the sensing response was found to vary linearly as a function of ethanol concentration in the parts per million (ppm) range.

SAW propagation characteristics of TeO3/3C-SiC/LiNbO3 layered structure

NASA Astrophysics Data System (ADS)

Soni, Namrata D.

2018-04-01

Surface acoustic wave (SAW) devices based on Lithium Niobate (LiNbO3) single crystal are advantageous because of its high SAW phase velocity, electromechanical coupling coefficient and cost effectiveness. In the present work a new multi-layered TeO3/3C-SiC/128° Y-X LiNbO3 SAW device has been proposed. SAW propagation properties such as phase velocity, coupling coefficient and temperature coefficient of delay (TCD) of the TeO3/SiC/128° Y-X LiNbO3 multi layered structure is examined using theoretical calculations. It is found that the integration of 0.09λ thick 3C-SiC over layer on 128° Y-X LiNbO3 increases its electromechanical coupling coefficient from 5.3% to 9.77% and SAW velocity from 3800 ms‑1 to 4394 ms‑1. The SiC/128° Y-X LiNbO3 bilayer SAW structure exhibits a high positive TCD value. A temperature stable layered SAW device could be obtained with introduction of 0.007λ TeO3 over layer on SiC/128° Y-X LiNbO3 bilayer structure without sacrificing the efficiency of the device. The proposed TeO3/3C-SiC/128° Y-X LiNbO3 multi-layered SAW structure is found to be cost effective, efficient, temperature stable and suitable for high frequency application in harsh environment.

Interplay of local structure, charge, and spin in bilayered manganese perovskites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rybicki, Damian; Sikora, Marcin; Przewoznik, Janusz

Chemical doping is a reliable method of modification of the electronic properties of transition metal compounds. In manganese perovskites, it leads to charge transfer and peculiar ordering phenomena. However, depending on the interplay of the local crystal structure and electronic properties, synthesis of stable compounds in the entire doping range is often impossible. In this paper, we show results of high-energy resolution x-ray absorption and emission spectroscopies on amore » $${\\mathrm{La}}_{2{-}2x}{\\mathrm{Sr}}_{1+2x}{\\mathrm{Mn}}_{2}{\\mathrm{O}}_{7}$$ family of bilayered manganites in a broad doping range $$(0.5{\\le}x{\\le}1)$$. We established a relation between local Mn charge and Mn-O distances as a function of doping. Finally, based on a comparison of such relation with other manganites, we suggest why stable structures cannot be realized for certain doping levels of bilayered compounds.« less

Stable diffraction-management soliton in a periodic structure with alternating left-handed and right-handed media

NASA Astrophysics Data System (ADS)

Zhang, Jinggui

2017-09-01

In this paper, we first derive a modified two-dimensional non-linear Schrödinger equation including high-order diffraction (HOD) suitable for the propagation of optical beam near the low-diffraction regime in Kerr non-linear media with spatial dispersion. Then, we apply our derived physical model to a designed two-dimensional configuration filled with alternate layers of a left-handed material (LHM) and a right-handed media by employing the mean-field theory. It is found that the periodic structure including LHM may experience diminished, cancelled, and even reversed diffraction behaviours through engineering the relative thickness between both media. In particular, the variational method analytically predicts that close to the zero-diffraction regime, such periodic structure can support stable diffraction-management solitons whose beamwidth and peak amplitude evolve periodically with the help of HOD effect. Numerical simulation based on the split-step Fourier method confirms the analytical results.

Interplay of local structure, charge, and spin in bilayered manganese perovskites

DOE PAGES

Rybicki, Damian; Sikora, Marcin; Przewoznik, Janusz; ...

2018-03-27

Chemical doping is a reliable method of modification of the electronic properties of transition metal compounds. In manganese perovskites, it leads to charge transfer and peculiar ordering phenomena. However, depending on the interplay of the local crystal structure and electronic properties, synthesis of stable compounds in the entire doping range is often impossible. In this paper, we show results of high-energy resolution x-ray absorption and emission spectroscopies on amore » $${\\mathrm{La}}_{2{-}2x}{\\mathrm{Sr}}_{1+2x}{\\mathrm{Mn}}_{2}{\\mathrm{O}}_{7}$$ family of bilayered manganites in a broad doping range $$(0.5{\\le}x{\\le}1)$$. We established a relation between local Mn charge and Mn-O distances as a function of doping. Finally, based on a comparison of such relation with other manganites, we suggest why stable structures cannot be realized for certain doping levels of bilayered compounds.« less

Soft template strategy to synthesize iron oxide-titania yolk-shell nanoparticles as high-performance anode materials for lithium-ion battery applications.

PubMed

Lim, Joohyun; Um, Ji Hyun; Ahn, Jihoon; Yu, Seung-Ho; Sung, Yung-Eun; Lee, Jin-Kyu

2015-05-18

Yolk-shell-structured nanoparticles with iron oxide core, void, and a titania shell configuration are prepared by a simple soft template method and used as the anode material for lithium ion batteries. The iron oxide-titania yolk-shell nanoparticles (IO@void@TNPs) exhibit a higher and more stable capacity than simply mixed nanoparticles of iron oxide and hollow titania because of the unique structure obtained by the perfect separation between iron oxide nanoparticles, in combination with the adequate internal void space provided by stable titania shells. Moreover, the structural effect of IO@void@TNPs clearly demonstrates that the capacity retention value after 50 cycles is approximately 4 times that for IONPs under harsh operating conditions, that is, when the temperature is increased to 80 °C. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Computational evidence for stable inorganic fullerene-like structures of ceramic and semiconductor materials

NASA Astrophysics Data System (ADS)

Chang, Ch; Patzer, A. B. C.; Sedlmayr, E.; Steinke, T.; Sülzle, D.

2001-12-01

Theoretical electronic structure techniques have become an indispensible and powerful means for predicting molecular properties and designing new materials. Based on a density functional approach and guided by geometric considerations we provide evidence for some specific inorganic fullerene-like cage molecules of ceramic and semiconductor materials which exhibit high energetic stability and point group symmetry as well as nearly perfect spherical shape.

Superconductivity in Hydrides Doped with Main Group Elements Under Pressure

NASA Astrophysics Data System (ADS)

Shamp, Andrew; Zurek, Eva

2017-01-01

A priori crystal structure prediction techniques have been used to explore the phase diagrams of hydrides of main group elements under pressure. A number of novel phases with the chemical formulas MHn, n > 1 and M = Li, Na, K, Rb, Cs; MHn, n > 2 and M= Mg, Ca, Sr, Ba; HnI with n > 1 and PH, PH2, PH3 have been predicted to be stable at pressures achievable in diamond anvil cells. The hydrogenic lattices within these phases display a number of structural motifs including H2δ- , H-, H-3 , as well as one-dimensional and three-dimensional extended structures. A wide range of superconducting critical temperatures, Tcs, are predicted for these hydrides. The mechanism of metallization and the propensity for superconductivity are dependent upon the structural motifs present in these phases, and in particular on their hydrogenic sublattices. Phases that are thermodynamically unstable, but dynamically stable, are accessible experimentally. The observed trends provide insight on how to design hydrides that are superconducting at high temperatures.

The closo-Si{sub 12}C{sub 12} molecule from cluster to crystal: A theoretical prediction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Xiaofeng F., E-mail: xiaofeng.duan@wpafb.af.mil, E-mail: larry.burggraf@us.af.mil; Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio 45433; Burggraf, Larry W., E-mail: xiaofeng.duan@wpafb.af.mil, E-mail: larry.burggraf@us.af.mil

2016-03-21

The structure of closo-Si{sub 12}C{sub 12} is unique among stable Si{sub n}C{sub m} isomers (n, m > 4) because of its high symmetry, π–π stacking of C{sub 6} rings and unsaturated silicon atoms at symmetrical peripheral positions. Dimerization potential surfaces reveal various dimerization reactions that form between two closo-Si{sub 12}C{sub 12} molecules through Si–Si bonds at unsaturated Si atoms. As a result the closo-Si{sub 12}C{sub 12} molecule is capable of polymerization to form stable 1D polymer chains, 2D crystal layers, and 3D crystals. 2D crystal structures formed by side-side polymerization satisfy eight Si valences on each monomer without large distortionmore » of the monomer structure. 3D crystals are formed by stacking 2D structures in the Z direction, preserving registry of C{sub 6} rings in monomer moiety.« less

Insights into MHC class I peptide loading from the structure of the tapasin/ERp57 heterodimer

PubMed Central

Dong, Gang; Wearsch, Pamela A.; Peaper, David R.; Cresswell, Peter; Reinisch, Karin M.

2009-01-01

SUMMARY Tapasin is a glycoprotein critical for loading Major Histocompatibility Complex (MHC) class I molecules with high affinity peptides. It functions within the multimeric peptide-loading complex (PLC) as a disulfide-linked, stable heterodimer with the thiol oxidoreductase ERp57, and this covalent interaction is required to support optimal PLC activity. Here we present the 2.6 Å resolution structure of the tapasin/ERp57 core of the PLC. The structure reveals the basis for the stable dimerization of tapasin and ERp57 and provides the first example of a protein disulfide isomerase family member interacting with a substrate. Mutational analysis identified a conserved surface on tapasin that interacts with MHC class I molecules and is critical for the peptide loading and editing function of the tapasin-ERp57 heterodimer. By combining the tapasin/ERp57 structure with those of other defined PLC components we present a molecular model that illuminates the processes involved in MHC class I peptide loading. PMID:19119025

Engineering Interface Structures and Thermal Stabilities via SPD Processing in Bulk Nanostructured Metals

DOE PAGES

Zheng, Shijian; Carpenter, John S.; McCabe, Rodney J.; ...

2014-02-27

Nanostructured metals achieve extraordinary strength but suffer from low thermal stability, both a consequence of a high fraction of interfaces. Overcoming this tradeoff relies on making the interfaces themselves thermally stable. In this paper, we show that the atomic structures of bi-metal interfaces in macroscale nanomaterials suitable for engineering structures can be significantly altered via changing the severe plastic deformation (SPD) processing pathway. Two types of interfaces are formed, both exhibiting a regular atomic structure and providing for excellent thermal stability, up to more than half the melting temperature of one of the constituents. Most importantly, the thermal stability ofmore » one is found to be significantly better than the other, indicating the exciting potential to control and optimize macroscale robustness via atomic-scale bimetal interface tuning. As a result, we demonstrate an innovative way to engineer pristine bimetal interfaces for a new class of simultaneously strong and thermally stable materials.« less

Nitrogen and sulfur co-doping of partially exfoliated MWCNTs as 3-D structured electrocatalysts for the oxygen reduction reaction

DOE PAGES

Wang, Jie; Wu, Zexing; Han, Lili; ...

2016-03-14

Preventing the stacking of graphene sheets is of vital importance for highly efficient and stable fuel cell electrocatalysts. Here, we report a 3-D structured carbon nanotube intercalated graphene nanoribbon with N/S co-doping. The nanocomposite is obtained by using high temperature heat-treated thiourea with partially unzipped multi-walled carbon nanotubes. This unique structure preserves both the properties of carbon nanotubes and graphene, exhibiting excellent catalytic performance for the ORR with similar onset and half-wave potentials to those of Pt/C electrocatalysts. Furthermore, the stereo structured composite exhibits distinct advantages in long-term stability and methanol poisoning tolerance in comparison to Pt/C.

Iron-antimony-based hybrid oxides as high-performance anodes for lithium-ion storage

NASA Astrophysics Data System (ADS)

Nguyen, Tuan Loi; Kim, Doo Soo; Hur, Jaehyun; Park, Min Sang; Yoon, Sukeun; Kim, Il Tae

2018-06-01

We report a facile approach to synthesize Fe-Sb-based hybrid oxides nanocomposites consisting of Sb, Sb2O3, and Fe3O4 for use as new anode materials for lithium-ion batteries. The composites are synthesized via galvanic replacement between Fe3+ and Sb at high temperature in triethylene glycol medium. The phase, morphology, and composition changes of the composites involved in the various stages of the replacement reaction are characterized using X-ray diffractometry, high-resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy. The as-prepared composites have different compositions with very small particle sizes (<< 10 nm). The FexSbyOz-18 h composite, for instance, exhibits high capacity, better cyclic stability, and rate performance than other composites, with a highly stable specific capacity of 434 mAh g-1 at 500 cycles. The excellent electrochemical performance can be ascribed to the high interfacial contact area between the nanocomposite and electrolyte, stable structure of the composites owing to a mixture of inactive phases generated by the conversion reaction between Li+ and oxide metal-whose structure serves as an electron conductor, inhibits agglomeration of Sb particles, and acts as an effective buffer against volume change of Sb during cycling-and high Li+ diffusion ability.

Atom by atom: HRTEM insights into inorganic nanotubes and fullerene-like structures

PubMed Central

Sadan, Maya Bar; Houben, Lothar; Enyashin, Andrey N.; Seifert, Gotthard; Tenne, Reshef

2008-01-01

The characterization of nanostructures down to the atomic scale is essential to understand some physical properties. Such a characterization is possible today using direct imaging methods such as aberration-corrected high-resolution transmission electron microscopy (HRTEM), when iteratively backed by advanced modeling produced by theoretical structure calculations and image calculations. Aberration-corrected HRTEM is therefore extremely useful for investigating low-dimensional structures, such as inorganic fullerene-like particles and inorganic nanotubes. The atomic arrangement in these nanostructures can lead to new insights into the growth mechanism or physical properties, where imminent commercial applications are unfolding. This article will focus on two structures that are symmetric and reproducible. The first structure that will be dealt with is the smallest stable symmetric closed-cage structure in the inorganic system, a MoS2 nanooctahedron. It is investigated by means of aberration-corrected microscopy which allowed validating the suggested DFTB-MD model. It will be shown that structures diverging from the energetically most stable structures are present in the laser ablated soot and that the alignment of the different shells is parallel, unlike the bulk material where the alignment is antiparallel. These findings correspond well with the high-energy synthetic route and they provide more insight into the growth mechanism. The second structure studied is WS2 nanotubes, which have already been shown to have a unique structure with very desirable mechanical properties. The joint HRTEM study combined with modeling reveals new information regarding the chirality of the different shells and provides a better understanding of their growth mechanism. PMID:18838681

Atom by atom: HRTEM insights into inorganic nanotubes and fullerene-like structures.

PubMed

Bar Sadan, Maya; Houben, Lothar; Enyashin, Andrey N; Seifert, Gotthard; Tenne, Reshef

2008-10-14

The characterization of nanostructures down to the atomic scale is essential to understand some physical properties. Such a characterization is possible today using direct imaging methods such as aberration-corrected high-resolution transmission electron microscopy (HRTEM), when iteratively backed by advanced modeling produced by theoretical structure calculations and image calculations. Aberration-corrected HRTEM is therefore extremely useful for investigating low-dimensional structures, such as inorganic fullerene-like particles and inorganic nanotubes. The atomic arrangement in these nanostructures can lead to new insights into the growth mechanism or physical properties, where imminent commercial applications are unfolding. This article will focus on two structures that are symmetric and reproducible. The first structure that will be dealt with is the smallest stable symmetric closed-cage structure in the inorganic system, a MoS(2) nanooctahedron. It is investigated by means of aberration-corrected microscopy which allowed validating the suggested DFTB-MD model. It will be shown that structures diverging from the energetically most stable structures are present in the laser ablated soot and that the alignment of the different shells is parallel, unlike the bulk material where the alignment is antiparallel. These findings correspond well with the high-energy synthetic route and they provide more insight into the growth mechanism. The second structure studied is WS(2) nanotubes, which have already been shown to have a unique structure with very desirable mechanical properties. The joint HRTEM study combined with modeling reveals new information regarding the chirality of the different shells and provides a better understanding of their growth mechanism.

Facile synthesis of 3D MnNi-layered double hydroxides (LDH)/graphene composites from directly graphites for pseudocapacitor and their electrochemical analysis

NASA Astrophysics Data System (ADS)

Lee, Ilbok; Jeong, Gyoung Hwa; An, Soyeon; Kim, Sang-Wook; Yoon, Songhun

2018-01-01

Herein, MnNi-layered double hydroxides (LDH) were imbibed within the interlayers of graphene nanosheets. The anionic surfactant, sodium dodecyl sulfate played a role of graphite exfoliator adding interaction with metal cations. Using this process, layered MnNi-LDH-graphene nanocomposite was prepared without formation of graphene oxide. When applied into pseudocapacitor electrode, LDH-graphene with optimal ratio between Mn and Ni exhibited very stable cycle with 90% at 1400 cycles and high energy 47.29 Wh kg-1 at the power density of 7473 W kg-1, which was attributed to highly stable layered LDH structure within conductive graphene layers.

High-pressure phase transitions of nitinol NiTi to a semiconductor with an unusual topological structure

NASA Astrophysics Data System (ADS)

Liu, Guangtao; Liu, Hanyu; Feng, Xiaolei; Redfern, Simon A. T.

2018-04-01

Systematic ab initio structure simulations have been used to explore the high-pressure behavior of nitinol (NiTi) at zero temperature. Our crystal structure prediction and first-principles calculations reveal that the known B 19 phase is dynamically unstable, and an orthorhombic structure (Pbcm) and a face-centered-cubic B 32 structure (F d 3 ¯m ) become stable above ˜4 and 29 GPa, respectively. The predicted, highest-pressure, B 32 phase is composed of two interpenetrating diamond structures, with a structural topology that is quite distinct from that of the other phases of NiTi. Interestingly, the B 32 phase shows an unusual semiconducting characteristic as a result of its unique band structure and the nature of 3 d orbitals localization, whose expected synthesis pressure is accessible to current experimental techniques.

Unraveling Crystalline Structure of High-Pressure Phase of Silicon Carbonate

NASA Astrophysics Data System (ADS)

Zhou, Rulong; Qu, Bingyan; Dai, Jun; Zeng, Xiao Cheng

2014-03-01

Although CO2 and SiO2 both belong to group-IV oxides, they exhibit remarkably different bonding characteristics and phase behavior at ambient conditions. At room temperature, CO2 is a gas, whereas SiO2 is a covalent solid with rich polymorphs. A recent successful synthesis of the silicon-carbonate solid from the reaction between CO2 and SiO2 under high pressure [M. Santoro et al., Proc. Natl. Acad. Sci. U.S.A. 108, 7689 (2011)] has resolved a long-standing puzzle regarding whether a SixC1-xO2 compound between CO2 and SiO2 exists in nature. Nevertheless, the detailed atomic structure of the SixC1-xO2 crystal is still unknown. Here, we report an extensive search for the high-pressure crystalline structures of the SixC1-xO2 compound with various stoichiometric ratios (SiO2:CO2) using an evolutionary algorithm. Based on the low-enthalpy structures obtained for each given stoichiometric ratio, several generic structural features and bonding characteristics of Si and C in the high-pressure phases are identified. The computed formation enthalpies show that the SiC2O6 compound with a multislab three-dimensional (3D) structure is energetically the most favorable at 20 GPa. Hence, a stable crystalline structure of the elusive SixC1-xO2 compound under high pressure is predicted and awaiting future experimental confirmation. The SiC2O6 crystal is an insulator with elastic constants comparable to typical hard solids, and it possesses nearly isotropic tensile strength as well as extremely low shear strength in the 2D plane, suggesting that the multislab 3D crystal is a promising solid lubricant. These valuable mechanical and electronic properties endow the SiC2O6 crystal for potential applications in tribology and nanoelectronic devices, or as a stable solid-state form for CO2 sequestration.

Bound states and interactions of vortex solitons in the discrete Ginzburg-Landau equation

NASA Astrophysics Data System (ADS)

Mejía-Cortés, C.; Soto-Crespo, J. M.; Vicencio, Rodrigo A.; Molina, Mario I.

2012-08-01

By using different continuation methods, we unveil a wide region in the parameter space of the discrete cubic-quintic complex Ginzburg-Landau equation, where several families of stable vortex solitons coexist. All these stationary solutions have a symmetric amplitude profile and two different topological charges. We also observe the dynamical formation of a variety of “bound-state” solutions composed of two or more of these vortex solitons. All of these stable composite structures persist in the conservative cubic limit for high values of their power content.

Evaluating the Energetic Driving Force for Cocrystal Formation.

PubMed

Taylor, Christopher R; Day, Graeme M

2018-02-07

We present a periodic density functional theory study of the stability of 350 organic cocrystals relative to their pure single-component structures, the largest study of cocrystals yet performed with high-level computational methods. Our calculations demonstrate that cocrystals are on average 8 kJ mol -1 more stable than their constituent single-component structures and are very rarely (<5% of cases) less stable; cocrystallization is almost always a thermodynamically favorable process. We consider the variation in stability between different categories of systems-hydrogen-bonded, halogen-bonded, and weakly bound cocrystals-finding that, contrary to chemical intuition, the presence of hydrogen or halogen bond interactions is not necessarily a good predictor of stability. Finally, we investigate the correlation of the relative stability with simple chemical descriptors: changes in packing efficiency and hydrogen bond strength. We find some broad qualitative agreement with chemical intuition-more densely packed cocrystals with stronger hydrogen bonding tend to be more stable-but the relationship is weak, suggesting that such simple descriptors do not capture the complex balance of interactions driving cocrystallization. Our conclusions suggest that while cocrystallization is often a thermodynamically favorable process, it remains difficult to formulate general rules to guide synthesis, highlighting the continued importance of high-level computation in predicting and rationalizing such systems.

Disentangling the surface and bulk electronic structures of LaOFeAs

DOE PAGES

Zhang, P.; Ma, J.; Qian, T.; ...

2016-09-20

We performed a comprehensive angle-resolved photoemission spectroscopy study of the electronic band structure of LaOFeAs single crystals. We found that samples cleaved at low temperature show an unstable and very complicated band structure, whereas samples cleaved at high temperature exhibit a stable and clearer electronic structure. Using in situ surface doping with K and supported by first-principles calculations, we identify both surface and bulk bands. Our assignments are confirmed by the difference in the temperature dependence of the bulk and surface states.

The mitochondrial genomes of Campodea fragilis and C. lubbocki(Hexapoda: Diplura): high genetic divergence in a morphologically uniformtaxon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Podsiadlowski, L.; Carapelli, A.; Nardi, F.

2005-12-01

Mitochondrial genomes from two dipluran hexapods of the genus Campodea have been sequenced. Gene order is the same as in most other hexapods and crustaceans. Secondary structures of tRNAs reveal specific structural changes in tRNA-C, tRNA-R, tRNA-S1 and tRNA-S2. Comparative analyses of nucleotide and amino acid composition, as well as structural features of both ribosomal RNA subunits, reveal substantial differences among the analyzed taxa. Although the two Campodea species are morphologically highly uniform, genetic divergence is larger than expected, suggesting a long evolutionary history under stable ecological conditions.

Metabolism of Penicillins to Penicilloic Acids and 6-Aminopenicillanic Acid in Man and Its Significance in Assessing Penicillin Absorption

PubMed Central

Cole, M.; Kenig, M. D.; Hewitt, Valerie A.

1973-01-01

Penicillins can be metabolized to penicilloic acids in man, the extent being dependent on the penicillin structure. In the phenoxy penicillin series, phenoxymethyl penicillin was found to be particularly unstable, but the higher homologues were more stable. In the isoxazolyl series, oxacillin was unstable, and progressive insertion of halogen in the phenyl ring increased stability. Ampicillin and amoxycillin showed some instability, ampicillin possibly being the more stable. After intramuscular administration, carbenicillin was very stable in the body, ampicillin was fairly stable, and benzyl penicillin was unstable. It is important to take into account the penicilloic acid content of urine when estimating total absorption of a penicillin. Increased stability in the body as well as slower renal clearance can lead to high concentrations in the serum. Penicilloic acids seemed to be more slowly cleared from the body than penicillins. The liver is probably the site of inactivation. PMID:4364176

Heat treatment giving a stable high temperature micro-structure in cast austenitic stainless steel

DOEpatents

Anton, Donald L.; Lemkey, Franklin D.

1988-01-01

A novel micro-structure developed in a cast austenitic stainless steel alloy and a heat treatment thereof are disclosed. The alloy is based on a multicomponent Fe-Cr-Mn-Mo-Si-Nb-C system consisting of an austenitic iron solid solution (.gamma.) matrix reinforced by finely dispersed carbide phases and a heat treatment to produce the micro-structure. The heat treatment includes a prebraze heat treatment followed by a three stage braze cycle heat treatment.

High-Temperature Stable Anatase Titanium Oxide Nanofibers for Lithium-Ion Battery Anodes.

PubMed

Lee, Sangkyu; Eom, Wonsik; Park, Hun; Han, Tae Hee

2017-08-02

Control of the crystal structure of electrochemically active materials is an important approach to fabricating high-performance electrodes for lithium-ion batteries (LIBs). Here, we report a methodology for controlling the crystal structure of TiO 2 nanofibers by adding aluminum isopropoxide to a common sol-gel precursor solution utilized to create TiO 2 nanofibers. The introduction of aluminum cations impedes the phase transformation of electrospun TiO 2 nanofibers from the anatase to the rutile phase, which inevitably occurs in the typical annealing process utilized for the formation of TiO 2 crystals. As a result, high-temperature stable anatase TiO 2 nanofibers were created in which the crystal structure was well-maintained even at high annealing temperatures of up to 700 °C. Finally, the resulting anatase TiO 2 nanofibers were utilized to prepare LIB anodes, and their electrochemical performance was compared to pristine TiO 2 nanofibers that contain both anatase and rutile phases. Compared to the electrode prepared with pristine TiO 2 nanofibers, the electrode prepared with anatase TiO 2 nanofibers exhibited excellent electrochemical performances such as an initial Coulombic efficiency of 83.9%, a capacity retention of 89.5% after 100 cycles, and a rate capability of 48.5% at a current density of 10 C (1 C = 200 mA g -1 ).

Aromatic polyimides containing a dimethylsilane-linked dianhydride

NASA Technical Reports Server (NTRS)

St.clair, Anne K. (Inventor); St.clair, Terry L. (Inventor); Pratt, J. Richard (Inventor)

1989-01-01

A high-temperature stable, optically transparent, low dielectric aromatic polyimide is prepared by chemically combining equimolar quantities of an aromatic dianhydride reactant and an aromatic diamine reactant, which are selected so that one reactant contains at least one Si(CH3)2 group in its molecular structure, and the other reactant contains at least one -CF3 group in its molecular structure. The reactants are chemically combined in a solvent medium to form a solution of a high molecular weight polyamic acid, which is then converted to the corresponding polyimide.

Aromatic polyimides containing a dimethylsilane-linked dianhydride

NASA Technical Reports Server (NTRS)

St. Clair, Anne K. (Inventor); St. Clair, Terry L. (Inventor); Pratt, J. Richard (Inventor)

1992-01-01

A high-temperature stable, optically transparent, low dielectric aromatic polyimide is prepared by chemically combining equimolar quantities of an aromatic dianhydride reactant and an aromatic diamine reactant, which are selected so that one reactant contains at least one Si(CH.sub.3).sub.2 group in its molecular structure, and the other reactant contains at least one --CH.sub.3 group in its molecular structure. The reactants are chemically combined in a solvent medium to form a solution of a high molecular weight polyamic acid, which is then converted to the corresponding polyimide.

High pressure–low temperature phase diagram of barium: Simplicity versus complexity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desgreniers, Serge; Tse, John S., E-mail: John.Tse@usask.ca; State Key Laboratory of Superhard Materials, Jilin University, 130012 Changchun

2015-11-30

Barium holds a distinctive position among all elements studied upon densification. Indeed, it was the first example shown to violate the long-standing notion that high compression of simple metals should preserve or yield close-packed structures. From modest pressure conditions at room temperature, barium transforms at higher pressures from its simple structures to the extraordinarily complex atomic arrangements of the incommensurate and self-hosting Ba-IV phases. By a detailed mapping of the pressure/temperature structures of barium, we demonstrate the existence of another crystalline arrangement of barium, Ba-VI, at low temperature and high pressure. The simple structure of Ba-VI is unlike that ofmore » complex Ba-IV, the phase encountered in a similar pressure range at room temperature. First-principles calculations predict Ba-VI to be stable at high pressure and superconductive. The results illustrate the complexity of the low temperature-high pressure phase diagram of barium and the significant effect of temperature on structural phase transformations.« less

Lithium amide (LiNH2) under pressure.

PubMed

Prasad, Dasari L V K; Ashcroft, N W; Hoffmann, Roald

2012-10-11

Static high pressure lithium amide (LiNH(2)) crystal structures are predicted using evolutionary structure search methodologies and intuitive approaches. In the process, we explore the relationship of the structure and properties of solid LiNH(2) to its molecular monomer and dimer, as well as its valence-isoelectronic crystalline phases of methane, water, and ammonia all under pressure. A NaNH(2) (Fddd) structure type is found to be competitive for the ground state of LiNH(2) above 6 GPa with the P = 1 atm I4[overline] phase. Three novel phases emerge at 11 (P4[overline]2(1)m), 13 (P4(2)/ncm), and 46 GPa (P2(1)2(1)2(1)), still containing molecular amide anions, which begin to form N-H···N hydrogen bonds. The P2(1)2(1)2(1) phase remains stable over a wide pressure range. This phase and another Pmc2(1) structure found at 280 GPa have infinite ···(H)N···H···N(H)···H polymeric zigzag chains comprising symmetric N···H···N hydrogen bonds with one NH bond kept out of the chain, an interesting general feature found in many of our high pressure (>280 GPa) LiNH(2) structures, with analogies in high pressure H(2)O-ices. All the predicted low enthalpy LiNH(2) phases are calculated to be enthalpically stable with respect to their elements but resist metallization with increasing pressure up to several TPa. The possibility of Li sublattice melting in the intermediate pressure range structures is raised.

Hydrothermal recrystallization of transition metal nitroprussides. Formation of the most stable phases

NASA Astrophysics Data System (ADS)

Echevarría, F.; Reguera, L.; González M, M.; Galicia, J.; Ávila, M.; Reguera, E.

2018-02-01

Hydrothermal recrystallization appears to be an appropriate treatment to explore the structural diversity of porous coordination polymers. In this contribution, such a post-synthesis treatment is applied to divalent transition metal nitroprussides, T[Fe(CN)5NO]•xH2O with T =Mn, Fe, Co, Ni, Cu, Zn, Cd. This family of compounds forms an interesting series of nanoporous coordination polymers with a wide structural diversity, related to the synthesis route used and the solid hydration degree (x). The effect of a hydrothermal recrystallization of previously prepared fine powders using the precipitation method, on their crystal structure and related properties is herein discussed. In this series of coordination polymers, for Fe, Co, Ni the precipitated powders are obtained as cubic phase, with a high porosity related to presence of systematic vacancies for building unit [Fe(CN)5NO]. For Fe and Co a structural transition, from cubic to orthorhombic, was observed, which is associated to formation of a most compact structure. The crystal structure for the new orthorhombic phases was refined from the collected powder HR-XRD patterns. For Ni, the cubic phase remains stable even for large heating time, which is ascribed to the high polarizing power of this metal. The high porosity for the cubic phase allows an easy accommodation for the local deformations around the Ni atom coordination sphere. The structural information from XRD was complemented with CO2 and H2 adsorption and TG data, IR and UV-vis spectra, and magnetic measurements. The magnetic data, through the presence of spin-orbit coupling for Fe and Co in the two phases, provide fine details on the coordination environment for the metal linked at the N ends of the CN group.

Stabilizing benzene-like planar N6 rings to form a single atomic honeycomb BeN3 sheet with high carrier mobility.

PubMed

Li, Xiaoyin; Zhang, Shunhong; Zhang, Cunzhi; Wang, Qian

2018-01-18

It is a longstanding quest to use the planar N 6 ring as a structural unit to build stable atomic sheets. However, unlike C 6 H 6 , the neutral N 6 ring is unstable due to the strong repulsion of the lone-pair of electrons. Using first-principles calculations and the global structure search method, we show that the N 6 unit can be stabilized by the linkage of Be atoms, forming a h-BeN 3 honeycomb monolayer, in which the geometry and the π-molecular orbitals of the N 6 rings are well kept. This sheet is not only energetically, dynamically and thermally stable, but also can withstand high temperatures up to 1000 K. Band structure calculation combined with a group theory analysis and a tight-binding model uncover that h-BeN 3 has a π-band dominated band structure with an indirect band gap of 1.67 eV. While it possesses a direct band gap of 2.07 eV at the Γ point lying in the photon energy region of visual light, its interband dipole transition is symmetrically allowed so that electrons can be excited by photons free of phonons. Based on deformation potential theory, a systematic study of the transport properties reveals that the h-BeN 3 sheet possesses a high carrier mobility of ∼10 3 cm 2 V -1 s -1 , superior to the extensively studied transition metal dichalcogenide monolayers. We further demonstrate that this sheet can be rolled up into either zigzag or armchair nanotubes. These nanotubes are also dynamically stable, and are all direct band gap semiconductors with carrier mobility comparable to that of their 2D counterparts, regardless of their chirality and diameter. The robust stability and novel electronic and transport properties of the h-BeN 3 sheet and its tubular derivatives endow them with great potential for applications in nanoelectronic devices.

The high Andes, gene flow and a stable hybrid zone shape the genetic structure of a wide-ranging South American parrot

PubMed Central

2011-01-01

Background While the gene flow in some organisms is strongly affected by physical barriers and geographical distance, other highly mobile species are able to overcome such constraints. In southern South America, the Andes (here up to 6,900 m) may constitute a formidable barrier to dispersal. In addition, this region was affected by cycles of intercalating arid/moist periods during the Upper/Late Pleistocene and Holocene. These factors may have been crucial in driving the phylogeographic structure of the vertebrate fauna of the region. Here we test these hypotheses in the burrowing parrot Cyanoliseus patagonus (Aves, Psittaciformes) across its wide distributional range in Chile and Argentina. Results Our data show a Chilean origin for this species, with a single migration event across the Andes during the Upper/Late Pleistocene, which gave rise to all extant Argentinean mitochondrial lineages. Analyses suggest a complex population structure for burrowing parrots in Argentina, which includes a hybrid zone that has remained stable for several thousand years. Within this zone, introgression by expanding haplotypes has resulted in the evolution of an intermediate phenotype. Multivariate regressions show that present day climatic variables have a strong influence on the distribution of genetic heterogeneity, accounting for almost half of the variation in the data. Conclusions Here we show how huge barriers like the Andes and the regional environmental conditions imposed constraints on the ability of a parrot species to colonise new habitats, affecting the way in which populations diverged and thus, genetic structure. When contact between divergent populations was re-established, a stable hybrid zone was formed, functioning as a channel for genetic exchange between populations. PMID:21672266

Metastable Polymeric Nitrogen: The Ultimate Green High-Energy-Density Material

NASA Astrophysics Data System (ADS)

Ciezak, Jennifer

2007-06-01

High-energy-high-density materials offering increased stability, vulnerability, and environmental safety are being aggressively pursued to meet the requirements of the DoD Joint Visions and Future Force. Nearly two decades ago, it was proposed that polymeric nitrogen would exceed all of these requirements and possess nearly five times the energy of any conventional energetic material in use today. The present study details an investigation into nitrogen polymerization using a novel high-pressure approach utilizing sodium azide as the starting material. Due to the weaker bonding structure of the anionic azide chains in comparison to a N-N triple bond, one expects that the azide chains will create single-covalently bonded polymeric networks more easily than diatomic nitrogen. A polymeric form of sodium azide was synthesized at high pressures, but the material was not metastable at ambient conditions, which precluded performance testing. Quantum chemical calculations have indicated stabilization of the polymeric structure at ambient conditions may be possible with the addition of hydrogen. Vibrational spectroscopic characterization suggests that a meta-stable polymeric form of nitrogen has been synthesized under high-pressure using sodium azide/hydrogen as the starting materials. This material remains stable at ambient conditions upwards of two weeks depending on the storage conditions.

Method of producing highly oxidized superconductors containing barium, copper, and a third metal

DOEpatents

Morris, Donald E.

1996-01-01

Novel superconducting materials in the form of compounds, structures or phases are formed by performing otherwise known syntheses in a highly oxidizing atmosphere rather than that created by molecular oxygen at atmospheric pressure or below. This leads to the successful synthesis of novel superconducting compounds which are thermodynamically stable at the conditions under which they are formed.

Wire-type MnO2/Multilayer graphene/Ni electrode for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Hu, Minglei; Liu, Yuhao; Zhang, Min; Wei, Helin; Gao, Yihua

2016-12-01

Commercially available wearable energy storage devices need a wire-type electrode with high strength, conductivity and electrochemical performance, as well as stable structure under deformation. Herein, we report a novel wire-type electrode of hierarchically structure MnO2 on Ni wire with multilayer graphene (MGr) as a buffer layer to enhance the electrical conductivity of the MnO2 and interface contact between the MnO2 and Ni wire. Thus, the wire-type MnO2/MGr/Ni electrode has a stable and high quality interface. The wire-type supercapacitor (WSC) based on wire-type MnO2/MGr/Ni electrode exhibits good electrochemical performance, high rate capability, extraordinary flexibility, and superior cycle lifetime. Length (area, volumetric) specific capacitance of the WSC reaches 6.9 mF cm-1 (73.2 mF cm-2, 9.8 F cm-3). Maximum length (volumetric) energy density of the WSC based on MnO2/MGr/Ni reaches 0.62 μWh cm-1 (0.88 mWh cm-3). Furthermore, the WSC has a short time constant (0.5-400 ms) and exhibits minimal change in capacitance under different bending shapes.

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

NASA Astrophysics Data System (ADS)

Choi, Won-Mi; Jo, Yong Hee; Sohn, Seok Su; Lee, Sunghak; Lee, Byeong-Joo

2018-01-01

Although high-entropy alloys (HEAs) are attracting interest, the physical metallurgical mechanisms related to their properties have mostly not been clarified, and this limits wider industrial applications, in addition to the high alloy costs. We clarify the physical metallurgical reasons for the materials phenomena (sluggish diffusion and micro-twining at cryogenic temperatures) and investigate the effect of individual elements on solid solution hardening for the equiatomic CoCrFeMnNi HEA based on atomistic simulations (Monte Carlo, molecular dynamics and molecular statics). A significant number of stable vacant lattice sites with high migration energy barriers exists and is thought to cause the sluggish diffusion. We predict that the hexagonal close-packed (hcp) structure is more stable than the face-centered cubic (fcc) structure at 0 K, which we propose as the fundamental reason for the micro-twinning at cryogenic temperatures. The alloying effect on the critical resolved shear stress (CRSS) is well predicted by the atomistic simulation, used for a design of non-equiatomic fcc HEAs with improved strength, and is experimentally verified. This study demonstrates the applicability of the proposed atomistic approach combined with a thermodynamic calculation technique to a computational design of advanced HEAs.

Defect states of complexes involving a vacancy on the boron site in boronitrene

NASA Astrophysics Data System (ADS)

Ngwenya, T. B.; Ukpong, A. M.; Chetty, N.

2011-12-01

First principles calculations have been performed to investigate the ground state properties of freestanding monolayer hexagonal boronitrene (h-BN). We have considered monolayers that contain native point defects and their complexes, which form when the point defects bind with the boron vacancy on the nearest-neighbor position. The changes in the electronic structure are analyzed to show the extent of localization of the defect-induced midgap states. The variations in formation energies suggest that defective h-BN monolayers that contain carbon substitutional impurities are the most stable structures, irrespective of the changes in growth conditions. The high energies of formation of the boron vacancy complexes suggest that they are less stable, and their creation by ion bombardment would require high-energy ions compared to point defects. Using the relative positions of the derived midgap levels for the double vacancy complex, it is shown that the quasi-donor-acceptor pair interpretation of optical transitions is consistent with stimulated transitions between electron and hole states in boronitrene.

Combined crystal structure prediction and high-pressure crystallization in rational pharmaceutical polymorph screening

PubMed Central

Neumann, M. A.; van de Streek, J.; Fabbiani, F. P. A.; Hidber, P.; Grassmann, O.

2015-01-01

Organic molecules, such as pharmaceuticals, agro-chemicals and pigments, frequently form several crystal polymorphs with different physicochemical properties. Finding polymorphs has long been a purely experimental game of trial-and-error. Here we utilize in silico polymorph screening in combination with rationally planned crystallization experiments to study the polymorphism of the pharmaceutical compound Dalcetrapib, with 10 torsional degrees of freedom one of the most flexible molecules ever studied computationally. The experimental crystal polymorphs are found at the bottom of the calculated lattice energy landscape, and two predicted structures are identified as candidates for a missing, thermodynamically more stable polymorph. Pressure-dependent stability calculations suggested high pressure as a means to bring these polymorphs into existence. Subsequently, one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib. PMID:26198974

Engineering of Nanoscale Antifouling and Hydrophobic Surfaces on Naval Structural Steel HY-80 by Anodizing

DTIC Science & Technology

2015-06-01

examination of the morphologies of the nanoporous structures and the evaluation of the anodization parameters such as anodization potential, time... sponges , anemones, tunicates, and hydroids, whilst hard fouling comprises invertebrates such as barnacles, mussels, and tubeworms. The specific...of metals by making them more stable and highly resistant, but also to modify the surface by giving it a desired morphology . Ferrous alloys such as

Sphere-Shaped Hierarchical Cathode with Enhanced Growth of Nanocrystal Planes for High-Rate and Cycling-Stable Li-Ion Batteries

DOE PAGES

Zhang, Linjing; Li, Ning; Wu, Borong; ...

2015-01-14

High-energy and high-power Li-ion batteries have been intensively pursued as power sources in electronic vehicles and renewable energy storage systems in smart grids. With this purpose, developing high-performance cathode materials is urgently needed. Here we report an easy and versatile strategy to fabricate high-rate and cycling-stable hierarchical sphered cathode Li 1.2Ni 0.13Mn 0.54Co 0.13O 2, by using an ionic interfusion method. The sphere-shaped hierarchical cathode is assembled with primary nanoplates with enhanced growth of nanocrystal planes in favor of Li+ intercalation/deintercalation, such as (010), (100), and (110) planes. This material with such unique structural features exhibits outstanding rate capability, cyclability,more » and high discharge capacities, achieving around 70% (175 mAh g–1) of the capacity at 0.1 C rate within about 2.1 min of ultrafast charging. Such cathode is feasible to construct high-energy and high-power Li-ion batteries.« less

Sphere-shaped hierarchical cathode with enhanced growth of nanocrystal planes for high-rate and cycling-stable li-ion batteries.

PubMed

Zhang, Linjing; Li, Ning; Wu, Borong; Xu, Hongliang; Wang, Lei; Yang, Xiao-Qing; Wu, Feng

2015-01-14

High-energy and high-power Li-ion batteries have been intensively pursued as power sources in electronic vehicles and renewable energy storage systems in smart grids. With this purpose, developing high-performance cathode materials is urgently needed. Here we report an easy and versatile strategy to fabricate high-rate and cycling-stable hierarchical sphered cathode Li(1.2)Ni(0.13)Mn(0.54)Co(0.13)O2, by using an ionic interfusion method. The sphere-shaped hierarchical cathode is assembled with primary nanoplates with enhanced growth of nanocrystal planes in favor of Li(+) intercalation/deintercalation, such as (010), (100), and (110) planes. This material with such unique structural features exhibits outstanding rate capability, cyclability, and high discharge capacities, achieving around 70% (175 mAh g(-1)) of the capacity at 0.1 C rate within about 2.1 min of ultrafast charging. Such cathode is feasible to construct high-energy and high-power Li-ion batteries.

Solution structure of a highly stable DNA duplex conjugated to a minor groove binder.

PubMed Central

Kumar, S; Reed, M W; Gamper, H B; Gorn, V V; Lukhtanov, E A; Foti, M; West, J; Meyer, R B; Schweitzer, B I

1998-01-01

The tripeptide 1,2-dihydro-(3 H )-pyrrolo[3,2- e ]indole-7-carboxylate (CDPI3) binds to the minor groove of DNA with high affinity. When this minor groove binder is conjugated to the 5'-end of short oligonucleotides the conjugates form unusually stable hybrids with complementary DNA and thus may have useful diagnostic and/or therapeutic applications. In order to gain an understanding of the structural interactions between the CDPI3minor groove binding moiety and the DNA, we have determined and compared the solution structure of a duplex consisting of oligodeoxyribonucleotide 5'-TGATTATCTG-3' conjugated at the 5'-end to CDPI3 and its complementary strand to an unmodified control duplex of the same sequence using nuclear magnetic resonance techniques. Thermal denaturation studies indicated that the hybrid of this conjugate with its complementary strand had a melting temperature that was 30 degrees C higher compared with the unmodified control duplex. Following restrained molecular dynamics and relaxation matrix refinement, the solution structure of the CDPI3-conjugated DNA duplex demonstrated that the overall shape of the duplex was that of a straight B-type helix and that the CDPI3moiety was bound snugly in the minor groove, where it was stabilized by extensive van der Waal's interactions. PMID:9443977

Solution structure of a highly stable DNA duplex conjugated to a minor groove binder.

PubMed

Kumar, S; Reed, M W; Gamper, H B; Gorn, V V; Lukhtanov, E A; Foti, M; West, J; Meyer, R B; Schweitzer, B I

1998-02-01

The tripeptide 1,2-dihydro-(3 H )-pyrrolo[3,2- e ]indole-7-carboxylate (CDPI3) binds to the minor groove of DNA with high affinity. When this minor groove binder is conjugated to the 5'-end of short oligonucleotides the conjugates form unusually stable hybrids with complementary DNA and thus may have useful diagnostic and/or therapeutic applications. In order to gain an understanding of the structural interactions between the CDPI3minor groove binding moiety and the DNA, we have determined and compared the solution structure of a duplex consisting of oligodeoxyribonucleotide 5'-TGATTATCTG-3' conjugated at the 5'-end to CDPI3 and its complementary strand to an unmodified control duplex of the same sequence using nuclear magnetic resonance techniques. Thermal denaturation studies indicated that the hybrid of this conjugate with its complementary strand had a melting temperature that was 30 degrees C higher compared with the unmodified control duplex. Following restrained molecular dynamics and relaxation matrix refinement, the solution structure of the CDPI3-conjugated DNA duplex demonstrated that the overall shape of the duplex was that of a straight B-type helix and that the CDPI3moiety was bound snugly in the minor groove, where it was stabilized by extensive van der Waal's interactions.

Composite Li metal anode with vertical graphene host for high performance Li-S batteries

NASA Astrophysics Data System (ADS)

Zhang, Y. J.; Liu, S. F.; Wang, X. L.; Zhong, Y.; Xia, X. H.; Wu, J. B.; Tu, J. P.

2018-01-01

Efficient and stable operation of a lithium metal anode has become the enabling factor for next-generation high energy density storage system. Here, vertical graphene (VG) arrays are used as the scaffold structure for high performance Li metal batteries. The melt infusion method is employed to encapsulate Li inside the VG scaffold structure, and the lithiophilic Si layer is coated onto the array surface by magnetron sputtering to assist this melt-infusion process. The porous scaffold structure can control the volume expansion and inhibit the formation of dendritic lithium significantly, leading to the excellent electrochemical performance of the Li composite anode. In addition, the Li-S full batteries with the composite anode display enhanced cycling reversibility.

Sapphire Fabry-Perot high-temperature sensor study

NASA Astrophysics Data System (ADS)

Yao, Yi-qiang; Liang, Wei-long; Gui, Xinwang; Fan, Dian

2017-04-01

A new structure sapphire fiber Fabry-Perot (F-P) high-temperature sensor based on sapphire wafer was proposed and fabricated. The sensor uses the sapphire fiber as a transmission waveguide, the sapphire wafer as an Fabry-Perot (F-P) interferometer and the new structure of "Zirconia ferrule-Zirconia tube" as the sensor fixing structure of the sensor. The reflection spectrum of the interferometer was demodulated by a serial of data processing including FIR bandpass filter, FFT (Fast Fourier Transformation) estimation and LSE (least squares estimation) compensation to obtain more precise OPD. Temperature measurement range is from 20 to 1000°C in experiment. The experimental results show that the sensor has the advantages of small size, low cost, simple fabrication and high repeatability. It can be applied for longterm, stable and high-precision high temperature measurement in harsh environments.

Novel penta-graphene nanotubes: strain-induced structural and semiconductor–metal transitions

DOE PAGES

Wang, Zhanyu; Cao, Xinran; Qiao, Chong; ...

2017-11-17

Research into novel one-dimensional (1D) materials and associated structural transitions is of significant scientific interest. It is widely accepted that a 1D system with a short-range interaction cannot have 1D phase transition at finite temperature. In this paper, we propose a series of new stable carbon nanotubes by rolling up penta-graphene sheets, which exhibit fascinating well-defined 1D phase transitions triggered by axial strain. Our first-principles calculations show that such penta-graphene nanotubes (PGNTs) are dynamically stable by phonon calculations, but transform from a tri-layer structure to a highly defective single-walled nanotube at low temperature in molecular dynamics simulations. We show thatmore » moderate compressive strains can drive structural transitions of (4,4), (5,5), and (6,6) PGNTs, during which the distances of neighboring carbon dimers in the inner shell have a sudden drop, corresponding to dimer–dimer nonbonding to bonding transitions. After such transition, the tubes become much more thermally stable and undergo semiconductor–metal transitions under increasing strain. The band gaps of PGNTs are not sensitive to chirality whereas they can be tuned effectively from visible to short-wavelength infrared by appropriate strain, making them appealing materials for flexible nano-optoelectronics. In conclusion, these findings provide useful insight into unusual phase transitions in low-dimensional systems.« less

Novel penta-graphene nanotubes: strain-induced structural and semiconductor–metal transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhanyu; Cao, Xinran; Qiao, Chong

Research into novel one-dimensional (1D) materials and associated structural transitions is of significant scientific interest. It is widely accepted that a 1D system with a short-range interaction cannot have 1D phase transition at finite temperature. In this paper, we propose a series of new stable carbon nanotubes by rolling up penta-graphene sheets, which exhibit fascinating well-defined 1D phase transitions triggered by axial strain. Our first-principles calculations show that such penta-graphene nanotubes (PGNTs) are dynamically stable by phonon calculations, but transform from a tri-layer structure to a highly defective single-walled nanotube at low temperature in molecular dynamics simulations. We show thatmore » moderate compressive strains can drive structural transitions of (4,4), (5,5), and (6,6) PGNTs, during which the distances of neighboring carbon dimers in the inner shell have a sudden drop, corresponding to dimer–dimer nonbonding to bonding transitions. After such transition, the tubes become much more thermally stable and undergo semiconductor–metal transitions under increasing strain. The band gaps of PGNTs are not sensitive to chirality whereas they can be tuned effectively from visible to short-wavelength infrared by appropriate strain, making them appealing materials for flexible nano-optoelectronics. In conclusion, these findings provide useful insight into unusual phase transitions in low-dimensional systems.« less

Three-Dimensional Rebar Graphene.

PubMed

Sha, Junwei; Salvatierra, Rodrigo V; Dong, Pei; Li, Yilun; Lee, Seoung-Ki; Wang, Tuo; Zhang, Chenhao; Zhang, Jibo; Ji, Yongsung; Ajayan, Pulickel M; Lou, Jun; Zhao, Naiqin; Tour, James M

2017-03-01

Free-standing robust three-dimensional (3D) rebar graphene foams (GFs) were developed by a powder metallurgy template method with multiwalled carbon nanotubes (MWCNTs) as a reinforcing bar, sintered Ni skeletons as a template and catalyst, and sucrose as a solid carbon source. As a reinforcement and bridge between different graphene sheets and carbon shells, MWCNTs improved the thermostability, storage modulus (290.1 kPa) and conductivity (21.82 S cm -1 ) of 3D GF resulting in a high porosity and structurally stable 3D rebar GF. The 3D rebar GF can support >3150× the foam's weight with no irreversible height change, and shows only a ∼25% irreversible height change after loading >8500× the foam's weight. The 3D rebar GF also shows stable performance as a highly porous electrode in lithium ion capacitors (LICs) with an energy density of 32 Wh kg -1 . After 500 cycles of testing at a high current density of 6.50 mA cm -2 , the LIC shows 78% energy density retention. These properties indicate promising applications with 3D rebar GFs in devices requiring stable mechanical and electrochemical properties.

Optimization and development of stable w/o/w cosmetic multiple emulsions by means of the Quality by Design approach.

PubMed

Kovács, A; Erős, I; Csóka, I

2016-04-01

The aim of our present work was to develop stable water-in-oil-in-water (w/o/w) cosmetic multiple emulsions that are proper for cosmetic use and can also be applied on the skin as pharmaceutical vehicles by means of Quality by Design (QbD) concept. This product design concept consists of a risk assessment step and also the 'predetermination' of the critical material attributes and process parameters of a stable multiple emulsion system. We have set up the hypothesis that the stability of multiple emulsions can be improved by the development based on such systematic planning - making a map of critical product parameters - so their industrial usage can be increased. The risk assessment and the determination of critical physical-chemical stability parameters of w/o/w multiple emulsions to define critical control points were performed by means of quality tools and the leanqbd(™) (QbD Works LLC, Fremont, CA, U.S.A.) software. Critical materials and process parameters: Based on the results of preformulation experiments, three factors, namely entrapped active agent, preparation methodology and shear rate, were found to be highly critical factors for critical quality attributes (CQAs) and for stability, whereas the nature of oil was found a medium level risk factor. The results of the risk assessment are the following: (i) droplet structure and size distribution should be evaluated together to be able to predict the stability issues, (ii) the presence of entrapped active agents had a great impact on droplet structure, (iii) the viscosity curves represent the structural changes during storage, if the decrease in relative viscosity is >15% the emulsion disintegrates, and (iv) it is enough to use the shear rate between 34g and 116g relative centrifugal force (RCF). CQAs: By risk assessment, we discovered that four factors should be considered to be high-risk variables as compared to others: droplet size, droplet structure, viscosity and multiple character were found to be highly critical attributes. The preformulation experiment is the part of a development plan. On the basis of these results, the control strategy can be defined and a stable multiple emulsion can be ensured that meets the relevant stakeholders' quality expectations. © 2015 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

High performance sandwich structured Si thin film anodes with LiPON coating

NASA Astrophysics Data System (ADS)

Luo, Xinyi; Lang, Jialiang; Lv, Shasha; Li, Zhengcao

2018-06-01

The sandwich structured silicon thin film anodes with lithium phosphorus oxynitride (LiPON) coating are synthesized via the radio frequency magnetron sputtering method, whereas the thicknesses of both layers are in the nanometer range, i.e. between 50 and 200 nm. In this sandwich structure, the separator simultaneously functions as a flexible substrate, while the LiPON layer is regarded as a protective layer. This sandwich structure combines the advantages of flexible substrate, which can help silicon release the compressive stress, and the LiPON coating, which can provide a stable artificial solid-electrolyte interphase (SEI) film on the electrode. As a result, the silicon anodes are protected well, and the cells exhibit high reversible capacity, excellent cycling stability and good rate capability. All the results demonstrate that this sandwich structure can be a promising option for high performance Si thin film lithium ion batteries.

Theoretical studies on a TeO2/ZnO/diamond-layered structure for zero TCD SAW devices

NASA Astrophysics Data System (ADS)

Dewan, Namrata; Sreenivas, K.; Gupta, Vinay

2008-08-01

High-frequency surface acoustic wave (SAW) devices based on diamond substrate are useful because of their very high SAW velocity. In the present work, SAW propagation characteristics, such as phase velocity, coupling coefficient and temperature coefficient of delay (TCD) of a TeO2/ZnO/diamond-layered structure, are examined using theoretical calculations. The ZnO/diamond bi-layer structure is found to exhibit a high positive TCD value. A zero TCD device structure is obtained after integration with a TeO2 over layer having a negative TCD value. Introduction of a non-piezoelectric TeO2 over layer on the bi-layer structure (ZnO/diamond) increases the coupling coefficient. A relatively low thickness of TeO2 thin film (~(1.6-3.1) × 10-3λ) is required to achieve temperature-stable SAW devices based on diamond.

High performance sandwich structured Si thin film anodes with LiPON coating

NASA Astrophysics Data System (ADS)

Luo, Xinyi; Lang, Jialiang; Lv, Shasha; Li, Zhengcao

2018-04-01

The sandwich structured silicon thin film anodes with lithium phosphorus oxynitride (LiPON) coating are synthesized via the radio frequency magnetron sputtering method, whereas the thicknesses of both layers are in the nanometer range, i.e. between 50 and 200 nm. In this sandwich structure, the separator simultaneously functions as a flexible substrate, while the LiPON layer is regarded as a protective layer. This sandwich structure combines the advantages of flexible substrate, which can help silicon release the compressive stress, and the LiPON coating, which can provide a stable artificial solidelectrolyte interphase (SEI) film on the electrode. As a result, the silicon anodes are protected well, and the cells exhibit high reversible capacity, excellent cycling stability and good rate capability. All the results demonstrate that this sandwich structure can be a promising option for high performance Si thin film lithium ion batteries.

Carbon nanotube-embedded advanced aerospace composites for early-stage damage sensing

NASA Astrophysics Data System (ADS)

Nataraj, Latha; Coatney, Michael; Cain, Jason; Hall, Asha

2018-03-01

Fiber reinforced polymer (FRP) composites featuring outstanding fatigue performance, high specific stiffness and strength, and low density have evolved as critical structural materials in aerospace applications. Microscale damage such as fiber breakage, matrix cracking, and delamination could occur in layered composites compromising structural integrity, emphasizing the critical need to monitor structural health. Early damage detection would lead to enhanced reliability, lifetime, and performance while minimizing maintenance time, leading to enormous scientific and technical interest in realizing physically stable, quick responding, and cost effective strain sensing materials, devices, and techniques with high sensitivity over a broad range of the practical strain spectrum. Today's most commonly used strain sensing techniques are metal foil strain gauges and optical fiber sensors. Metal foil gauges offer high stability and cost-effectiveness but can only be surface-mounted and have a low gauge factor. Optical fibers require expensive instrumentation, are mostly insensitive to cracks parallel to the fiber orientation and may lead to crack initiation as the diameter is larger than that of the reinforcement fibers. Carbon nanotubes (CNTs) have attracted much attention due to high aspect ratio and superior electrical, thermal, and mechanical properties. CNTs embedded in layered composites have improved performance. A variety of CNT architectures and configurations have shown improved piezoresistive behavior and stability for sensing applications. However, scaling up and commercialization remain serious challenges. The current study investigates a simple, cost effective and repeatable technique for highly sensitive, stable, linear and repeatable strain sensing for damage detection by integrating CNT laminates into composites.

Co-Percolating Graphene-Wrapped Silver Nanowire Network for High Performance, Highly Stable, Transparent Conducting Electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Ruiyi; Das, Suprem R; Jeong, Changwook

Transparent conducting electrodes (TCEs) require high transparency and low sheet resistance for applications in photovoltaics, photodetectors, flat panel displays, touch screen devices, and imagers. Indium tin oxide (ITO), or other transparent conductive oxides, have been used, and provide a baseline sheet resistance (RS) vs. transparency (T) relationship. Several alternative material systems have been investigated. The development of high-performance hybrid structures provides a route towards robust, scalable and low-cost approaches for realizing high-performance TCE.

77 FR 68773 - FIFRA Scientific Advisory Panel; Notice of Public Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-16

... for physical chemical properties that cannot be easily tested in in vitro systems or stable enough for.... Quantitative structural-activity relationship (QSAR) models and estrogen receptor (ER) expert systems development. High-throughput data generation and analysis (expertise focused on how this methodology can be...

Novel AlInN/GaN integrated circuits operating up to 500 °C

NASA Astrophysics Data System (ADS)

Gaska, R.; Gaevski, M.; Jain, R.; Deng, J.; Islam, M.; Simin, G.; Shur, M.

2015-11-01

High electron concentration in 2DEG channel of AlInN/GaN devices is remarkably stable over a broad temperature range, enabling device operation above 500 °C. The developed IC technology is based on three key elements: (1) exceptional quality AlInN/GaN heterostructure with very high carrier concentration and mobility enables IC fast operation in a broad temperature range; (2) heterostructure field effect transistor approach t provides fully planar IC structure which is easy to scale and to combine with the other high temperature electronic components; (3) fabrication advancements including novel metallization scheme and high-K passivation/gate dielectrics enable high temperature operation. The feasibility of the developed technology was confirmed by fabrication and testing of the high temperature inverter and differential amplifier ICs using AlInN/GaN heterostructures. The developed ICs showed stable performance with unit-gain bandwidth above 1 MHz and internal response time 45 ns at temperatures as high as 500 °C.

A stable solution-processed polymer semiconductor with record high-mobility for printed transistors

PubMed Central

Li, Jun; Zhao, Yan; Tan, Huei Shuan; Guo, Yunlong; Di, Chong-An; Yu, Gui; Liu, Yunqi; Lin, Ming; Lim, Suo Hon; Zhou, Yuhua; Su, Haibin; Ong, Beng S.

2012-01-01

Microelectronic circuits/arrays produced via high-speed printing instead of traditional photolithographic processes offer an appealing approach to creating the long-sought after, low-cost, large-area flexible electronics. Foremost among critical enablers to propel this paradigm shift in manufacturing is a stable, solution-processable, high-performance semiconductor for printing functionally capable thin-film transistors — fundamental building blocks of microelectronics. We report herein the processing and optimisation of solution-processable polymer semiconductors for thin-film transistors, demonstrating very high field-effect mobility, high on/off ratio, and excellent shelf-life and operating stabilities under ambient conditions. Exceptionally high-gain inverters and functional ring oscillator devices on flexible substrates have been demonstrated. This optimised polymer semiconductor represents a significant progress in semiconductor development, dispelling prevalent skepticism surrounding practical usability of organic semiconductors for high-performance microelectronic devices, opening up application opportunities hitherto functionally or economically inaccessible with silicon technologies, and providing an excellent structural framework for fundamental studies of charge transport in organic systems. PMID:23082244

First-principle study of pressure-induced phase transitions and electronic properties of electride Y2C

NASA Astrophysics Data System (ADS)

Feng, Caihui; Shan, Jingfeng; Xu, Aoshu; Xu, Yang; Zhang, Meiguang; Lin, Tingting

2017-10-01

Trigonal yttrium hypocarbide (Y2C), crystallizing in a layered hR3 structure, is an intriguing quasi-two-dimensional electride metal with potential application for the next generation of electronics. By using an efficient structure search method in combination with first-principles calculations, we have extensively explored the phase transitions and electronic properties of Y2C in a wide pressure range of 0-200 GPa. Three structural transformations were predicted, as hR3 → oP12 → tI12 → mC12. Calculated pressures of phase transition are 20, 118, and 126 GPa, respectively. The high-pressure oP12 phase exhibits a three-dimensional extended C-Y network built up from face- and edge-sharing CY8 hendecahedrons, whereas both the tI12 and mC12 phases are featured by the presence of C2 units. No anionic electrons confined to interstitial spaces have been found in the three predicted high-pressure phases, indicating that they are not electrides. Moreover, Y2C is dynamically stable and also energetically stable relative to the decomposition into its elemental solids.

Evolutions of lamellar structure during melting and solidification of Fe9577 nanoparticle from molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Wu, Yongquan; Shen, Tong; Lu, Xionggang

2013-03-01

A structural evolution during solidification and melting processes of nanoparticle Fe9577 was investigated from MD simulations. A perfect lamellar structure, consisting alternately of fcc and hcp layers, was obtained from solidification process. A structural heredity of early embryo is proposed to explain the structural preference of solidification. Defects were found inside the solid core and play the same role as surface premelting on melting. hcp was found more stable than fcc in high temperature. The difference between melting and solidification points can be deduced coming fully from the overcoming of thermodynamic energy barrier, instead of kinetic delay of structural relaxation.

Structural models of inorganic fullerene-like structures

NASA Astrophysics Data System (ADS)

Ascencio, J. A.; Perez-Alvarez, M.; Molina, L. M.; Santiago, P.; José-Yacaman, M.

2003-03-01

In the study of fullerene-like structures, some of the more interesting systems are the inorganic cages, made of MoS 2 (usually named inorganic fullerenes), which have many important potential applications as lubricant and catalysts. In the present work, we report calculations for structural models of closed cage of inorganic fullerene-like structures for MoS 2 system. Three cage shapes were found to be the most stable: triangular pyramid, octahedron and dodecahedron. High resolution TEM images of MoS 2 cages structures were calculated to be compared with experimental data. Some examples of triangular pyramid and polyhedron in experimental MoS 2 samples are presented.

Ground state structure of high-energy-density polymeric carbon monoxide

NASA Astrophysics Data System (ADS)

Xia, Kang; Sun, Jian; Pickard, Chris J.; Klug, Dennis D.; Needs, Richard J.

2017-04-01

Crystal structure prediction methods and first-principles calculations have been used to explore low-energy structures of carbon monoxide (CO). Contrary to the standard wisdom, the most stable structure of CO at ambient pressure was found to be a polymeric structure of P n a 21 symmetry rather than a molecular solid. This phase is formed from six-membered (four carbon + two oxygen) rings connected by C=C double bonds with two double-bonded oxygen atoms attached to each ring. Interestingly, the polymeric P n a 21 phase of CO has a much higher energy density than trinitrotoluene (TNT). On compression to about 7 GPa, P n a 21 is found to transform into another chainlike phase of C c symmetry which has similar ring units to P n a 21 . On compression to 12 GPa, it is energetically favorable for CO to polymerize into a purely single bonded C m c a phase, which is stable over a wide pressure range and transforms into the previously known C m c m phase at around 100 GPa. Thermodynamic stability of these structures was verified using calculations with different density functionals, including hybrid and van der Waals corrected functionals.

The crystal structure of the calcium-bound con-G[Q6A] peptide reveals a novel metal-dependent helical trimer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cnudde, Sara E.; Prorok, Mary; Jia, Xaofei

2012-02-15

The ability to form and control both secondary structure and oligomerization in short peptides has proven to be challenging owing to the structural instability of such peptides. The conantokin peptides are a family of {gamma}-carboxyglutamic acid containing peptides produced in the venoms of predatory sea snails of the Conus family. They are examples of short peptides that form stable helical structures, especially in the presence of divalent cations. Both monomeric and dimeric conantokin peptides have been identified and represent a new mechanism of helix association, 'the metallozipper motif' that is devoid of a hydrophobic interface between monomers. In the presentmore » study, a parallel/antiparallel three-helix bundle was identified and its crystal structure determined at high resolution. The three helices are almost perfectly parallel and represent a novel helix-helix association. The trimer interface is dominated by metal chelation between the three helices, and contains no interfacial hydrophobic interactions. It is now possible to produce stable monomeric, dimeric, or trimeric metallozippers depending on the peptide sequence and metal ion. Such structures have important applications in protein design.« less

Rare-metal-free high-performance Ga-Sn-O thin film transistor

NASA Astrophysics Data System (ADS)

Matsuda, Tokiyoshi; Umeda, Kenta; Kato, Yuta; Nishimoto, Daiki; Furuta, Mamoru; Kimura, Mutsumi

2017-03-01

Oxide semiconductors have been investigated as channel layers for thin film transistors (TFTs) which enable next-generation devices such as high-resolution liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, flexible electronics, and innovative devices. Here, high-performance and stable Ga-Sn-O (GTO) TFTs were demonstrated for the first time without the use of rare metals such as In. The GTO thin films were deposited using radiofrequency (RF) magnetron sputtering. A high field effect mobility of 25.6 cm2/Vs was achieved, because the orbital structure of Sn was similar to that of In. The stability of the GTO TFTs was examined under bias, temperature, and light illumination conditions. The electrical behaviour of the GTO TFTs was more stable than that of In-Ga-Zn-O (IGZO) TFTs, which was attributed to the elimination of weak Zn-O bonds.

Rare-metal-free high-performance Ga-Sn-O thin film transistor

PubMed Central

Matsuda, Tokiyoshi; Umeda, Kenta; Kato, Yuta; Nishimoto, Daiki; Furuta, Mamoru; Kimura, Mutsumi

2017-01-01

Oxide semiconductors have been investigated as channel layers for thin film transistors (TFTs) which enable next-generation devices such as high-resolution liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, flexible electronics, and innovative devices. Here, high-performance and stable Ga-Sn-O (GTO) TFTs were demonstrated for the first time without the use of rare metals such as In. The GTO thin films were deposited using radiofrequency (RF) magnetron sputtering. A high field effect mobility of 25.6 cm2/Vs was achieved, because the orbital structure of Sn was similar to that of In. The stability of the GTO TFTs was examined under bias, temperature, and light illumination conditions. The electrical behaviour of the GTO TFTs was more stable than that of In-Ga-Zn-O (IGZO) TFTs, which was attributed to the elimination of weak Zn-O bonds. PMID:28290547

Rare-metal-free high-performance Ga-Sn-O thin film transistor.

PubMed

Matsuda, Tokiyoshi; Umeda, Kenta; Kato, Yuta; Nishimoto, Daiki; Furuta, Mamoru; Kimura, Mutsumi

2017-03-14

Oxide semiconductors have been investigated as channel layers for thin film transistors (TFTs) which enable next-generation devices such as high-resolution liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, flexible electronics, and innovative devices. Here, high-performance and stable Ga-Sn-O (GTO) TFTs were demonstrated for the first time without the use of rare metals such as In. The GTO thin films were deposited using radiofrequency (RF) magnetron sputtering. A high field effect mobility of 25.6 cm 2 /Vs was achieved, because the orbital structure of Sn was similar to that of In. The stability of the GTO TFTs was examined under bias, temperature, and light illumination conditions. The electrical behaviour of the GTO TFTs was more stable than that of In-Ga-Zn-O (IGZO) TFTs, which was attributed to the elimination of weak Zn-O bonds.

Stable propagation of mechanical signals in soft media using stored elastic energy.

PubMed

Raney, Jordan R; Nadkarni, Neel; Daraio, Chiara; Kochmann, Dennis M; Lewis, Jennifer A; Bertoldi, Katia

2016-08-30

Soft structures with rationally designed architectures capable of large, nonlinear deformation present opportunities for unprecedented, highly tunable devices and machines. However, the highly dissipative nature of soft materials intrinsically limits or prevents certain functions, such as the propagation of mechanical signals. Here we present an architected soft system composed of elastomeric bistable beam elements connected by elastomeric linear springs. The dissipative nature of the polymer readily damps linear waves, preventing propagation of any mechanical signal beyond a short distance, as expected. However, the unique architecture of the system enables propagation of stable, nonlinear solitary transition waves with constant, controllable velocity and pulse geometry over arbitrary distances. Because the high damping of the material removes all other linear, small-amplitude excitations, the desired pulse propagates with high fidelity and controllability. This phenomenon can be used to control signals, as demonstrated by the design of soft mechanical diodes and logic gates.

Stable propagation of mechanical signals in soft media using stored elastic energy

PubMed Central

Raney, Jordan R.; Nadkarni, Neel; Daraio, Chiara; Lewis, Jennifer A.; Bertoldi, Katia

2016-01-01

Soft structures with rationally designed architectures capable of large, nonlinear deformation present opportunities for unprecedented, highly tunable devices and machines. However, the highly dissipative nature of soft materials intrinsically limits or prevents certain functions, such as the propagation of mechanical signals. Here we present an architected soft system composed of elastomeric bistable beam elements connected by elastomeric linear springs. The dissipative nature of the polymer readily damps linear waves, preventing propagation of any mechanical signal beyond a short distance, as expected. However, the unique architecture of the system enables propagation of stable, nonlinear solitary transition waves with constant, controllable velocity and pulse geometry over arbitrary distances. Because the high damping of the material removes all other linear, small-amplitude excitations, the desired pulse propagates with high fidelity and controllability. This phenomenon can be used to control signals, as demonstrated by the design of soft mechanical diodes and logic gates. PMID:27519797

Changes in microbial communities, photosynthesis and calcification of the coral Acropora gemmifera in response to ocean acidification.

PubMed

Zhou, Guowei; Yuan, Tao; Cai, Lin; Zhang, Weipeng; Tian, Renmao; Tong, Haoya; Jiang, Lei; Yuan, Xiangcheng; Liu, Sheng; Qian, Peiyuan; Huang, Hui

2016-10-27

With the increasing anthropogenic CO 2 concentration, ocean acidification (OA) can have dramatic effects on coral reefs. However, the effects of OA on coral physiology and the associated microbes remain largely unknown. In the present study, reef-building coral Acropora gemmifera collected from a reef flat with highly fluctuating environmental condition in the South China Sea were exposed to three levels of partial pressure of carbon dioxide (pCO 2 ) (i.e., 421, 923, and 2070 μatm) for four weeks. The microbial community structures associated with A. gemmifera under these treatments were analyzed using 16S rRNA gene barcode sequencing. The results revealed that the microbial community associated with A. gemmifera was highly diverse at the genus level and dominated by Alphaproteobacteria. More importantly, the microbial community structure remained rather stable under different pCO 2 treatments. Photosynthesis and calcification in A. gemmifera, as indicated by enrichment of δ 18 O and increased depletion of δ 13 C in the coral skeleton, were significantly impaired only at the high pCO 2 (2070 μatm). These results suggest that A. gemmifera can maintain a high degree of stable microbial communities despite of significant physiological changes in response to extremely high pCO 2 .

Changes in microbial communities, photosynthesis and calcification of the coral Acropora gemmifera in response to ocean acidification

NASA Astrophysics Data System (ADS)

Zhou, Guowei; Yuan, Tao; Cai, Lin; Zhang, Weipeng; Tian, Renmao; Tong, Haoya; Jiang, Lei; Yuan, Xiangcheng; Liu, Sheng; Qian, Peiyuan; Huang, Hui

2016-10-01

With the increasing anthropogenic CO2 concentration, ocean acidification (OA) can have dramatic effects on coral reefs. However, the effects of OA on coral physiology and the associated microbes remain largely unknown. In the present study, reef-building coral Acropora gemmifera collected from a reef flat with highly fluctuating environmental condition in the South China Sea were exposed to three levels of partial pressure of carbon dioxide (pCO2) (i.e., 421, 923, and 2070 μatm) for four weeks. The microbial community structures associated with A. gemmifera under these treatments were analyzed using 16S rRNA gene barcode sequencing. The results revealed that the microbial community associated with A. gemmifera was highly diverse at the genus level and dominated by Alphaproteobacteria. More importantly, the microbial community structure remained rather stable under different pCO2 treatments. Photosynthesis and calcification in A. gemmifera, as indicated by enrichment of δ18O and increased depletion of δ13C in the coral skeleton, were significantly impaired only at the high pCO2 (2070 μatm). These results suggest that A. gemmifera can maintain a high degree of stable microbial communities despite of significant physiological changes in response to extremely high pCO2.

Changes in microbial communities, photosynthesis and calcification of the coral Acropora gemmifera in response to ocean acidification

PubMed Central

Zhou, Guowei; Yuan, Tao; Cai, Lin; Zhang, Weipeng; Tian, Renmao; Tong, Haoya; Jiang, Lei; Yuan, Xiangcheng; Liu, Sheng; Qian, Peiyuan; Huang, Hui

2016-01-01

With the increasing anthropogenic CO2 concentration, ocean acidification (OA) can have dramatic effects on coral reefs. However, the effects of OA on coral physiology and the associated microbes remain largely unknown. In the present study, reef-building coral Acropora gemmifera collected from a reef flat with highly fluctuating environmental condition in the South China Sea were exposed to three levels of partial pressure of carbon dioxide (pCO2) (i.e., 421, 923, and 2070 μatm) for four weeks. The microbial community structures associated with A. gemmifera under these treatments were analyzed using 16S rRNA gene barcode sequencing. The results revealed that the microbial community associated with A. gemmifera was highly diverse at the genus level and dominated by Alphaproteobacteria. More importantly, the microbial community structure remained rather stable under different pCO2 treatments. Photosynthesis and calcification in A. gemmifera, as indicated by enrichment of δ18O and increased depletion of δ13C in the coral skeleton, were significantly impaired only at the high pCO2 (2070 μatm). These results suggest that A. gemmifera can maintain a high degree of stable microbial communities despite of significant physiological changes in response to extremely high pCO2. PMID:27786309

[Circular RNA in human disease and their potential clinic significance].

PubMed

Chen, Yonghua; Li, Cheng; Tan, Chunlu; Mai, Gang; Liu, Xubao

2017-02-10

Circular RNAs (circ RNAs) are a novel type of RNA that, unlike linear RNAs, form a covalently closed continuous loop and are highly represented in the eukaryotic transcriptome. They share a stable structure, high expression and often exhibit tissue/developmental-stage-specific expression. Emerging evidence indicates that circRNAs might play important roles in human disease, such as cancer, neurological disorders and atherosclerotic vascular disease risk. The huge potentials of circRNAs are recently being discovered from the laboratory to the clinic. CircRNAs might be developed as a potential novel and stable biomarker and potential drugs used in disease diagnosis and treatment. Here, we review the current understanding of the roles of circRNAs in human disease and their potential clinic significance in disease.

Nonequilibrium Phase Chemistry in High Temperature Structure Alloys

NASA Technical Reports Server (NTRS)

Wang, R.

1991-01-01

Titanium and nickel aluminides of nonequilibrium microstructures and in thin gauge thickness were identified, characterized and produced for potential high temperature applications. A high rate sputter deposition technique for rapid surveillance of the microstructures and nonequilibrium phase is demonstrated. Alloys with specific compositions were synthesized with extended solid solutions, stable dispersoids, and specific phase boundaries associated with different heat treatments. Phase stability and mechanical behavior of these nonequilibrium alloys were investigated and compared.

Development and molecular-genetic characterization of a stable Brassica allohexaploid.

PubMed

Gupta, Mehak; Atri, Chhaya; Agarwal, Neha; Banga, Surinder Singh

2016-11-01

We report first-time synthesis of a stable Brassica allohexaploid. It may evolve into a new species and also advance our understanding of pairing regulation and genome evolution in complex allopolyploids. Crop Brassicas include both monogenomic and digenomic species. A trigenomic Brassica (AABBCC) is not known to exist in nature. Past attempts to synthesize a stable allohexaploid were not successful due to aberrant meiosis and very high proportion of aneuploid plants in the selfed progenies. We report the development of a stable allohexaploid Brassica (2n = 54; AABBCC). Genomic in situ hybridization confirmed the complete assemblage of three genomes. Only allohexaploids involving B. rapa cv. R01 (2n = 20; AA) as pollinator with a set of B. carinata (2n = 34; BBCC) were stable. These exhibited a high proportion (0.78-0.94) of pollen mother cells with normal meiosis and an excellent hexaploid ratio (0.80-0.94) in the selfed progenies. Stability of two allohexaploid combinations was demonstrated from H 1 to H 4 generations at two very diverse locations in India. Graphical genotyping of allohexaploids allowed detection of chromosome fragment exchanges among three genomes. These were much smaller for meiotically stable allohexaploids as compared to unstable ones. The putative hexaploids were morphologically closer to the female donor, B. carinata, for leaf morphology, inflorescence structure and flower shape. The newly formed allohexaploid may also provide unique opportunities to investigate the immediate genetic and genomic consequences of a Brassica allohexaploid with three resident genomes.

Enthalpy and high temperature relaxation kinetics of stable vapor-deposited glasses of toluene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, Deepanjan; Sadtchenko, Vlad, E-mail: vlad@gwu.edu

Stable non-crystalline toluene films of micrometer and nanometer thicknesses were grown by vapor deposition at distinct rates and probed by fast scanning calorimetry. Fast scanning calorimetry is shown to be extremely sensitive to the structure of the vapor-deposited phase and was used to characterize simultaneously its kinetic stability and its thermodynamic properties. According to our analysis, transformation of vapor-deposited samples of toluene during heating with rates in excess 10{sup 5} K s{sup −1} follows the zero-order kinetics. The transformation rate correlates strongly with the initial enthalpy of the sample, which increases with the deposition rate according to sub-linear law. Analysismore » of the transformation kinetics of vapor-deposited toluene films of various thicknesses reveal a sudden increase in the transformation rate for films thinner than 250 nm. The change in kinetics seems to correlate with the surface roughness scale of the substrate. The implications of these findings for the formation mechanism and structure of vapor-deposited stable glasses are discussed.« less

An equilibrium ab initio atomistic thermodynamics study of chlorine adsorption on the Cu(001) surface.

PubMed

Suleiman, Ibrahim A; Radny, Marian W; Gladys, Michael J; Smith, Phillip V; Mackie, John C; Kennedy, Eric M; Dlugogorski, Bogdan Z

2011-06-07

The effect of chlorine (Cl) chemisorption on the energetics and atomic structure of the Cu(001) surface over a wide range of chlorine pressures and temperatures has been studied using equilibrium ab initio atomistic thermodynamics to elucidate the formation of cuprous chloride (CuCl) as part of the Deacon reaction on copper metal. The calculated surface free energies show that the 1/2 monolayer (ML) c(2 × 2)-Cl phase with chlorine atoms adsorbed at the hollow sites is the most stable structure for a wide range of Cl chemical potential, in agreement with experimental observations. It is also found that at very low pressure and exposure, but elevated temperature, the 1/9 ML and 1/4 ML phases become the most stable. By contrast, a high coverage of Cl does not lead to thermodynamically stable geometries. The subsurface adsorption of Cl atoms, however, dramatically increases the stability of the 1 ML and 2 ML adsorption configurations providing a possible pathway for the formation of the bulk-chloride surface phases in the kinetic regime.

Green, stable and earth abundant ionic PV absorbers based on chalcogenide perovskite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Hao

Searching for inexpensive, environment-friendly, and air-stable absorber materials for thin film solar cells has become a key thrust of PV research. Supported by this one-year award, the UB-RPI team aims to develop a novel class of semiconductors — chalcogenide perovskites. Sharing some similarities to the widely researched halide perovskites, and unlike most conventional semiconductors, the chalcogenide perovskites are strongly ionic. Such characteristics is expected to provide intrinsic defect properties favorable for charge transport in PV absorbers. In this one-year project, we confirmed structural stability of the BaZrS3 material through high pressure Raman studies. We find no evidence that the perovskitemore » structure of BaZrS3 undergoes any phase changes under hydrostatic pressure to at least 8.9 GPa. Our results indicate the robust structural stability of BaZrS3, and suggest cation alloying as a viable approach for band-gap engineering for photovoltaic and other applications. We also achieved reduced band gap to 1.45 eV by Ti-alloying of BaZrS3, which is close to the optimal value for a single junction solar cell. We further synthesized BaZrS3 thin films with desired crystal structure and band gap. The optical absorption is high as expected. The carrier mobility is moderate. The high processing temperature limits its ability for device integration. We are working on deposition of chalcogenide perovskite thin films using molecular beam epitaxy.« less

Structural characterization of recombinant IAV polymerase reveals a stable complex between viral PA-PB1 heterodimer and host RanBP5.

PubMed

Swale, Christopher; Monod, Alexandre; Tengo, Laura; Labaronne, Alice; Garzoni, Frédéric; Bourhis, Jean-Marie; Cusack, Stephen; Schoehn, Guy; Berger, Imre; Ruigrok, Rob W H; Crépin, Thibaut

2016-04-20

The genome of influenza A virus (IAV) comprises eight RNA segments (vRNA) which are transcribed and replicated by the heterotrimeric IAV RNA-dependent RNA-polymerase (RdRp). RdRp consists of three subunits (PA, PB1 and PB2) and binds both the highly conserved 3'- and 5'-ends of the vRNA segment. The IAV RdRp is an important antiviral target, but its structural mechanism has remained largely elusive to date. By applying a polyprotein strategy, we produced RdRp complexes and define a minimal human IAV RdRp core complex. We show that PA-PB1 forms a stable heterodimeric submodule that can strongly interact with 5'-vRNA. In contrast, 3'-vRNA recognition critically depends on the PB2 N-terminal domain. Moreover, we demonstrate that PA-PB1 forms a stable and stoichiometric complex with host nuclear import factor RanBP5 that can be modelled using SAXS and we show that the PA-PB1-RanPB5 complex is no longer capable of 5'-vRNA binding. Our results provide further evidence for a step-wise assembly of IAV structural components, regulated by nuclear transport mechanisms and host factor binding.

Pnma-BN: Another Boron Nitride Polymorph with Interesting Physical Properties

PubMed Central

Ma, Zhenyang; Han, Zheng; Liu, Xuhong; Yu, Xinhai; Wang, Dayun; Tian, Yi

2016-01-01

Structural, mechanical, electronic properties, and stability of boron nitride (BN) in Pnma structure were studied using first-principles calculations by Cambridge Serial Total Energy Package (CASTEP) plane-wave code, and the calculations were performed with the local density approximation and generalized gradient approximation in the form of Perdew–Burke–Ernzerhof. This BN, called Pnma-BN, contains four boron atoms and four nitrogen atoms buckled through sp3-hybridized bonds in an orthorhombic symmetry unit cell with Space group of Pnma. Pnma-BN is energetically stable, mechanically stable, and dynamically stable at ambient pressure and high pressure. The calculated Pugh ratio and Poisson’s ratio revealed that Pnma-BN is brittle, and Pnma-BN is found to turn brittle to ductile (~94 GPa) in this pressure range. It shows a higher mechanical anisotropy in Poisson’s ratio, shear modulus, Young’s modulus, and the universal elastic anisotropy index AU. Band structure calculations indicate that Pnma-BN is an insulator with indirect band gap of 7.18 eV. The most extraordinary thing is that the band gap increases first and then decreases with the increase of pressure from 0 to 60 GPa, and from 60 to 100 GPa, the band gap increases first and then decreases again. PMID:28336837

Conjugation in multi-tetrazole derivatives: a new design direction for energetic materials.

PubMed

Sun, Shuyang; Lu, Ming

2018-06-23

Multi-tetrazole derivatives with conjugated structures were designed and investigated in this study. Using quantum chemistry methods, the crystal structures, electrostatic potentials (ESPs), multicenter bond orders, HOMO-LUMO energy gaps, and detonation properties of the derivatives were calculated. As expected, these molecules with conjugated structures showed low energies of their crystal structures, molecular layering in their crystals, high average ESPs, high multicenter bond order values, and enhanced detonation properties. The derivative 1,2-di(1H-tetrazol-5-yl)diazene (N2) was predicted to have the best density (1.87 g/cm 3 ), detonation velocity (9006 m/s), and detonation pressure (36.8 GPa) of the designed molecules, while its total crystal energy was low, suggesting that it is relatively stable. Its sensitivity was also low, as the molecular stacking that occurs in its crystal allows external forces to be dissipated into movements of crystal layers. Finally, its multicenter bond order was high, indicating a highly conjugated structure.

Rational design of Fe3O4@C yolk-shell nanorods constituting a stable anode for high-performance Li/Na-ion batteries.

PubMed

Wang, Beibei; Zhang, Xing; Liu, Xiaojie; Wang, Gang; Wang, Hui; Bai, Jintao

2018-05-24

In the current research project, we have prepared a novel Fe 3 O 4 @mesoporous carbon nanorod (denoted as Fe 3 O 4 @C) anode with yolk-shell structure for Li/Na-ion batteries via one-pot and surfactant-free synthesis strategy. The yolk-shell structure consists of Fe 3 O 4 nanorod yolk completely protected by a well-conductive mesoporous carbon shell. The substantial void space in the Fe 3 O 4 @C yolk-shell nanorod can not only accommodate the full volume expansion of inner Fe 3 O 4 nanorod, but also preserve the structural integrity of the Fe 3 O 4 @C anode and develop a stable SEI film on the outside mesoporous carbon shell during the repeated Li + /Na + insertion/extraction processes. As for lithium storage, the Fe 3 O 4 @C electrode exhibits a high specific capacity (1247 mAh g -1 ), stable cycling performance (a specific capacity of 954 mAh g -1 after 200 cycles at a current density of 0.5 A g -1 ) and excellent rate capability (specific capabilities of 1122, 958, 783, 577, and 374 mAh g -1 at 0.5, 1, 2, 4, and 8 A g -1 , respectively). As for sodium storage, the Fe 3 O 4 @C yolk-shell nanorods also maintain a reversible capacity of approximate 424 mAh g -1 at 0.1 A g -1 after 100 cycles. Copyright © 2018. Published by Elsevier Inc.

Self-Reconstructed Formation of a One-Dimensional Hierarchical Porous Nanostructure Assembled by Ultrathin TiO2 Nanobelts for Fast and Stable Lithium Storage.

PubMed

Liu, Yuan; Yan, Xiaodong; Xu, Bingqing; Lan, Jinle; Yu, Yunhua; Yang, Xiaoping; Lin, Yuanhua; Nan, Cewen

2018-06-06

Owing to their unique structural advantages, TiO 2 hierarchical nanostructures assembled by low-dimensional (LD) building blocks have been extensively used in the energy-storage/-conversion field. However, it is still a big challenge to produce such advanced structures by current synthetic techniques because of the harsh conditions needed to generate primary LD subunits. Herein, a novel one-dimensional (1D) TiO 2 hierarchical porous fibrous nanostructure constructed by TiO 2 nanobelts is synthesized by combining a room-temperature aqueous solution growth mechanism with the electrospinning technology. The nanobelt-constructed 1D hierarchical nanoarchitecture is evolves directly from the amorphous TiO 2 /SiO 2 composite fibers in alkaline solutions at ambient conditions without any catalyst and other reactant. Benefiting from the unique structural features such as 1D nanoscale building blocks, large surface area, and numerous interconnected pores, as well as mixed phase anatase-TiO 2 (B), the optimum 1D TiO 2 hierarchical porous nanostructure shows a remarkable high-rate performance when tested as an anode material for lithium-ion batteries (107 mA h g -1 at ∼10 A g -1 ) and can be used in a hybrid lithium-ion supercapacitor with very stable lithium-storage performance (a capacity retention of ∼80% after 3000 cycles at 2 A g -1 ). The current work presents a scalable and cost-effective method for the synthesis of advanced TiO 2 hierarchical materials for high-power and stable energy-storage/-conversion devices.

Method of producing highly oxidized superconductors containing barium, copper, and a third metal

DOEpatents

Morris, D.E.

1996-02-20

Novel superconducting materials in the form of compounds, structures or phases are formed by performing otherwise known syntheses in a highly oxidizing atmosphere rather than that created by molecular oxygen at atmospheric pressure or below. This leads to the successful synthesis of novel superconducting compounds which are thermodynamically stable at the conditions under which they are formed. 16 figs.

Mechanically stable, hierarchically porous Cu3(btc)2 (HKUST-1) monoliths via direct conversion of copper(II) hydroxide-based monoliths.

PubMed

Moitra, Nirmalya; Fukumoto, Shotaro; Reboul, Julien; Sumida, Kenji; Zhu, Yang; Nakanishi, Kazuki; Furukawa, Shuhei; Kitagawa, Susumu; Kanamori, Kazuyoshi

2015-02-28

The synthesis of highly crystalline macro-meso-microporous monolithic Cu3(btc)2 (HKUST-1; btc(3-) = benzene-1,3,5-tricarboxylate) is demonstrated by direct conversion of Cu(OH)2-based monoliths while preserving the characteristic macroporous structure. The high mechanical strength of the monoliths is promising for possible applications to continuous flow reactors.

Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition.

PubMed

Potapov, Anton M; Tiunov, Alexei V; Scheu, Stefan

2018-06-19

Despite the major importance of soil biota in nutrient and energy fluxes, interactions in soil food webs are poorly understood. Here we provide an overview of recent advances in uncovering the trophic structure of soil food webs using natural variations in stable isotope ratios. We discuss approaches of application, normalization and interpretation of stable isotope ratios along with methodological pitfalls. Analysis of published data from temperate forest ecosystems is used to outline emerging concepts and perspectives in soil food web research. In contrast to aboveground and aquatic food webs, trophic fractionation at the basal level of detrital food webs is large for carbon and small for nitrogen stable isotopes. Virtually all soil animals are enriched in 13 C as compared to plant litter. This 'detrital shift' likely reflects preferential uptake of 13 C-enriched microbial biomass and underlines the importance of microorganisms, in contrast to dead plant material, as a major food resource for the soil animal community. Soil organic matter is enriched in 15 N and 13 C relative to leaf litter. Decomposers inhabiting mineral soil layers therefore might be enriched in 15 N resulting in overlap in isotope ratios between soil-dwelling detritivores and litter-dwelling predators. By contrast, 13 C content varies little between detritivores in upper litter and in mineral soil, suggesting that they rely on similar basal resources, i.e. little decomposed organic matter. Comparing vertical isotope gradients in animals and in basal resources can be a valuable tool to assess trophic interactions and dynamics of organic matter in soil. As indicated by stable isotope composition, direct feeding on living plant material as well as on mycorrhizal fungi is likely rare among soil invertebrates. Plant carbon is taken up predominantly by saprotrophic microorganisms and channelled to higher trophic levels of the soil food web. However, feeding on photoautotrophic microorganisms and non-vascular plants may play an important role in fuelling soil food webs. The trophic niche of most high-rank animal taxa spans at least two trophic levels, implying the use of a wide range of resources. Therefore, to identify trophic species and links in food webs, low-rank taxonomic identification is required. Despite overlap in feeding strategies, stable isotope composition of the high-rank taxonomic groups reflects differences in trophic level and in the use of basal resources. Different taxonomic groups of predators and decomposers are likely linked to different pools of organic matter in soil, suggesting different functional roles and indicating that trophic niches in soil animal communities are phylogenetically structured. During last two decades studies using stable isotope analysis have elucidated the trophic structure of soil communities, clarified basal food resources of the soil food web and revealed links between above- and belowground ecosystem compartments. Extending the use of stable isotope analysis to a wider range of soil-dwelling organisms, including microfauna, and a larger array of ecosystems provides the perspective of a comprehensive understanding of the structure and functioning of soil food webs. © 2018 Cambridge Philosophical Society.

Sharper Graph-Theoretical Conditions for the Stabilization of Complex Reaction Networks

PubMed Central

Knight, Daniel; Shinar, Guy; Feinberg, Martin

2015-01-01

Across the landscape of all possible chemical reaction networks there is a surprising degree of stable behavior, despite what might be substantial complexity and nonlinearity in the governing differential equations. At the same time there are reaction networks, in particular those that arise in biology, for which richer behavior is exhibited. Thus, it is of interest to understand network-structural features whose presence enforces dull, stable behavior and whose absence permits the dynamical richness that might be necessary for life. We present conditions on a network’s Species-Reaction Graph that ensure a high degree of stable behavior, so long as the kinetic rate functions satisfy certain weak and natural constraints. These graph-theoretical conditions are considerably more incisive than those reported earlier. PMID:25600138

Behavioral Dimensions in One-Year-Olds and Dimensional Stability in Infancy.

ERIC Educational Resources Information Center

Hagekull, Berit; And Others

1980-01-01

The dimensional structure of infants' behavioral repertoire was shown to be highly stable over 3 to 15 months of age. Factor analysis of parent questionnaire data produced seven factors named Intensity/Activity, Regularity, Approach-Withdrawal, Sensory Sensitivity, Attentiveness, Manageability and Sensitivity to New Food. An eighth factor,…

Station Magnitude Bias - Its Determination, Causes, and Effects

DTIC Science & Technology

1977-04-29

TSK Tsukuba, Honshu, Japan TUC (W) Tucson, Arizona TUL (W) Tulsa, Oklahoma TVO Taravao, French Polynesia UBO* Uinta Basin , Utah VAH Vaihoa...8217 structures such as the western US, and lowest in stable regions such as shields and deep ocean basins . High attenuation further appears to be well

Prediction of new high pressure structural sequence in thorium carbide: A first principles study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahoo, B. D., E-mail: bdsahoo@barc.gov.in; Joshi, K. D.; Gupta, Satish C.

2015-05-14

In the present work, we report the detailed electronic band structure calculations on thorium monocarbide. The comparison of enthalpies, derived for various phases using evolutionary structure search method in conjunction with first principles total energy calculations at several hydrostatic compressions, yielded a high pressure structural sequence of NaCl type (B1) → Pnma → Cmcm → CsCl type (B2) at hydrostatic pressures of ∼19 GPa, 36 GPa, and 200 GPa, respectively. However, the two high pressure experimental studies by Gerward et al. [J. Appl. Crystallogr. 19, 308 (1986); J. Less-Common Met. 161, L11 (1990)] one up to 36 GPa and other up to 50 GPa, onmore » substoichiometric thorium carbide samples with carbon deficiency of ∼20%, do not report any structural transition. The discrepancy between theory and experiment could be due to the non-stoichiometry of thorium carbide samples used in the experiment. Further, in order to substantiate the results of our static lattice calculations, we have determined the phonon dispersion relations for these structures from lattice dynamic calculations. The theoretically calculated phonon spectrum reveal that the B1 phase fails dynamically at ∼33.8 GPa whereas the Pnma phase appears as dynamically stable structure around the B1 to Pnma transition pressure. Similarly, the Cmcm structure also displays dynamic stability in the regime of its structural stability. The B2 phase becomes dynamically stable much below the Cmcm to B2 transition pressure. Additionally, we have derived various thermophysical properties such as zero pressure equilibrium volume, bulk modulus, its pressure derivative, Debye temperature, thermal expansion coefficient and Gruneisen parameter at 300 K and compared these with available experimental data. Further, the behavior of zero pressure bulk modulus, heat capacity and Helmholtz free energy has been examined as a function temperature and compared with the experimental data of Danan [J. Nucl. Mater. 57, 280 (1975)].« less

Electron beam enhanced surface modification for making highly resolved structures

DOEpatents

Pitts, John R.

1986-01-01

A method for forming high resolution submicron structures on a substrate is provided by direct writing with a submicron electron beam in a partial pressure of a selected gas phase characterized by the ability to dissociate under the beam into a stable gaseous leaving group and a reactant fragment that combines with the substrate material under beam energy to form at least a surface compound. Variations of the method provide semiconductor device regions on doped silicon substrates, interconnect lines between active sites, three dimensional electronic chip structures, electron beam and optical read mass storage devices that may include color differentiated data areas, and resist areas for use with selective etching techniques.

Electron beam enhanced surface modification for making highly resolved structures

DOEpatents

Pitts, J.R.

1984-10-10

A method for forming high resolution submicron structures on a substrate is provided by direct writing with a submicron electron beam in a partial pressure of a selected gas phase characterized by the ability to dissociate under the beam into a stable gaseous leaving group and a reactant fragment that combines with the substrate material under beam energy to form at least a surface compound. Variations of the method provide semiconductor device regions on doped silicon substrates, interconnect lines between active sites, three dimensional electronic chip structures, electron beam and optical read mass storage devices that may include color differentiated data areas, and resist areas for use with selective etching techniques.

Fabrication of three-dimensional collagen scaffold using an inverse mould-leaching process.

PubMed

Ahn, SeungHyun; Lee, SuYeon; Cho, Youngseok; Chun, Wook; Kim, GeunHyung

2011-09-01

Natural biopolymers, such as collagen or chitosan, are considered ideal for biomedical scaffolds. However, low processability of the materials has hindered the fabrication of designed pore structures controlled by various solid freeform-fabrication methods. A new technique to fabricate a biomedical three-dimensional collagen scaffold, supplemented with a sacrificial poly(ethylene oxide) mould is proposed. The fabricated collagen scaffold shows a highly porous surface and a three-dimensional structure with high porosity as well as mechanically stable structure. To show its feasibility for biomedical applications, fibroblasts/keratinocytes were co-cultured on the scaffold, and the cell proliferation and cell migration of the scaffold was more favorable than that obtained with a spongy-type collagen scaffold.

Discovery of a Superconducting Cu-Bi Intermetallic Compound by High-Pressure Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clarke, Samantha M.; Walsh, James P. S.; Amsler, Maximilian

A new intermetallic compound, the first to be structurally identified in the Cu-Bi binary system, is reported. This compound is accessed by high-pressure reaction of the elements. Its detailed characterization, physical property measurements, and ab initio calculations are described. The commensurate crystal structure of Cu 11Bi 7 is a unique variation of the NiAs structure type. Temperature-dependent electrical resistivity and heat capacity measurements reveal a bulk superconducting transition at T c=1.36 K. Density functional theory calculations further demonstrate that Cu 11Bi 7 can be stabilized (relative to decomposition into the elements) at high pressure and temperature. These results highlight themore » ability of high-pressure syntheses to allow for inroads into heretofore-undiscovered intermetallic systems for which no thermodynamically stable binaries are known.« less

Formation of the –N(NO)N(NO)– polymer at high pressure and stabilization at ambient conditions

PubMed Central

Xiao, Hai; An, Qi; Goddard, William A.; Liu, Wei-Guang; Zybin, Sergey V.

2013-01-01

A number of exotic structures have been formed through high-pressure chemistry, but applications have been hindered by difficulties in recovering the high-pressure phase to ambient conditions (i.e., one atmosphere and 300 K). Here we use dispersion-corrected density functional theory [PBE-ulg (Perdew-Burke-Ernzerhof flavor of DFT with the universal low gradient correction for long range London dispersion)] to predict that above 60 gigapascal (GPa) the most stable form of N2O (the laughing gas in its molecular form) is a one-dimensional polymer with an all-nitrogen backbone analogous to cis-polyacetylene in which alternate N are bonded (ionic covalent) to O. The analogous trans-polymer is only 0.03∼0.10 eV/molecular unit less stable. Upon relaxation to ambient conditions, both polymers relax below 14 GPa to the same stable nonplanar trans-polymer. The predicted phonon spectrum and dissociation kinetics validates the stability of this trans-poly-NNO at ambient conditions, which has potential applications as a type of conducting nonlinear optical polymer with all-nitrogen chains and as a high-energy oxidizer for rocket propulsion. This work illustrates in silico materials discovery particularly in the realm of extreme conditions (very high pressure or temperature). PMID:23503849

Titanium α-ω phase transformation pathway and a predicted metastable structure

DOE PAGES

Zarkevich, Nickolai A.; Johnson, Duane D.

2016-01-15

A titanium is a highly utilized metal for structural lightweighting and its phases, transformation pathways (transition states), and structures have scientific and industrial importance. Using a proper solid-state nudged elastic band method employing two climbing images combined with density functional theory DFT + U methods for accurate energetics, we detail the pressure-induced α (ductile) to ω (brittle) transformation at the coexistence pressure. We also find two transition states along the minimal-enthalpy path and discover a metastable body-centered orthorhombic structure, with stable phonons, a lower density than the end-point phases, and decreasing stability with increasing pressure.

Chemical structural analysis of diamondlike carbon films: II. Raman analysis

NASA Astrophysics Data System (ADS)

Takabayashi, Susumu; Ješko, Radek; Shinohara, Masanori; Hayashi, Hiroyuki; Sugimoto, Rintaro; Ogawa, Shuichi; Takakuwa, Yuji

2018-02-01

The chemical structure of diamondlike carbon (DLC) films, synthesized by photoemission-assisted glow discharge, has been analyzed by Raman spectroscopy. Raman analysis in conjunction with the sp2 cluster model clarified the film structure. The sp2 clusters in DLC films synthesized at low temperature preferred various aliphatic structures. Sufficient argon-ion assist allowed for formation of less strained DLC films containing large amounts of hydrogen. As the synthesis temperature was increased, thermal desorption of hydrogen left carbon dangling bonds with active unpaired electrons in the films, and the reactions that followed created strained films containing aromatic sp2 clusters. In parallel, the desorption of methane molecules from the growing surface by chemisorption of hydrogen radicals prevented the action of argon ions, promoting internal strain of the films. However, in synthesis at very high temperature, where sp2 clusters are sufficiently dominant, the strain was dissolved gradually. In contrast, the DLC films synthesized at low temperature were more stable than other films synthesized at the same temperature because of stable hydrogen-carbon bonds in the films.

First-principles study of native defects in bulk Sm2CuO4 and its (001) surface structure

NASA Astrophysics Data System (ADS)

Zheng, Fubao; Zhang, Qinfang; Meng, Qiangqiang; Wang, Baolin; Song, Fengqi; Yunoki, Seiji; Wang, Guanghou

2018-04-01

Using the first-principles calculations based on the density functional theory, we have studied the bulk defect formation and surface structures of Sm2CuO4. To ensure the accuracy of calculations, the spin order of Cu atoms is rechecked and it is the well-known nearest-neighbor antiferromagnetic ground state, which can be attributed to the hole-mediated superexchange through the strong pdσ hybridization interaction between Cu dx2-y2 electron and the neighboring oxygen px (or py) electron. Under each present experimental condition, the Sm vacancy has a very high formation energy and is unlikely to be stable. The Cu vacancy is a shallow acceptor, which is preferred under O-rich conditions, whereas the O vacancy is a donor and energetically favorable under O-poor conditions. To construct its (001) surface structure, CuOO, CuO, and Cu terminated surfaces are found to be most favorable under different experimental conditions. The stable surface structures are always accompanied by significant surface atomic reconstructions and electron charge redistribution, which are intimately correlated to each other.

Improving Self-Assembly by Varying the Temperature Periodically with Time

NASA Astrophysics Data System (ADS)

Raz, Oren; Jarzynski, Christopher

Self-assembly (SA) is the process by which basic components organize into a larger structure without external guidance. These processes are common in Nature, and also have technological applications, e.g. growing a crystal with a specific structure. So far, artificial SA processes have been designed mostly using diffusive building blocks with high specificity and directionality. The formation of the self-assembled structures is then driven by free-energy minimization into a thermodynamically stable state. In an alternative approach to SA, macroscopic parameters such as temperature, pressure, pH, magnetic field etc., are varied periodically with time. In this case, the SA structures are the stable periodic states of the driven system. Currently there are no design principles for periodically driven SA, other than in the limits of fast or weak driving. We present guiding ideas for self-assembly under periodic driving. As an example, we show a particular case in which self-assembly errors can be dramatically reduced by varying a system's temperature periodically with time. James S. McDonnell Foundation, and the US National Science Foundation: DMR-1506969.

Two distinct crystallization processes in supercooled liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tane, Masakazu, E-mail: mtane@sanken.osaka-u.ac.jp; Kimizuka, Hajime; Ichitsubo, Tetsu

2016-05-21

Using molecular dynamics simulations we show that two distinct crystallization processes, depending on the temperature at which crystallization occurs, appear in a supercooled liquid. As a model for glass-forming materials, an Al{sub 2}O{sub 3} model system, in which both the glass transition and crystallization from the supercooled liquid can be well reproduced, is employed. Simulations in the framework of an isothermal-isobaric ensemble indicate that the calculated time-temperature-transformation curve for the crystallization to γ(defect spinel)-Al{sub 2}O{sub 3} exhibited a typical nose shape, as experimentally observed in various glass materials. During annealing above the nose temperature, the structure of the supercooled liquidmore » does not change before the crystallization, because of the high atomic mobility (material transport). Thus, the crystallization is governed by the abrupt crystal nucleation, which results in the formation of a stable crystal structure. In contrast, during annealing below the nose temperature, the structure of the supercooled liquid gradually changes before the crystallization, and the formed crystal structure is less stable than that formed above the nose temperature, because of the restricted material transport.« less

First-principles study of Al2Sm intermetallic compound on structural, mechanical properties and electronic structure

NASA Astrophysics Data System (ADS)

Lin, Jingwu; Wang, Lei; Hu, Zhi; Li, Xiao; Yan, Hong

2017-02-01

The structural, thermodynamic, mechanical and electronic properties of cubic Al2Sm intermetallic compound are investigated by the first-principles method on the basis of density functional theory. In light of the strong on-site Coulomb repulsion between the highly localized 4f electrons of Sm atoms, the local spin density approximation approach paired with additional Hubbard terms is employed to achieve appropriate results. Moreover, to examine the reliability of this study, the experimental value of lattice parameter is procured from the analysis of the TEM image and diffraction pattern of Al2Sm phase in the AZ31 alloy to verify the authenticity of the results originated from the computational method. The value of cohesive energy reveals Al2Sm to be a stable in absolute zero Kelvin. According to the stability criteria, the subject of this work is mechanically stable. Afterward, elastic moduli are deduced by performing Voigt-Reuss-Hill approximation. Furthermore, elastic anisotropy and anisotropy of sound velocity are discussed. Finally, the calculation of electronic density of states is implemented to explore the underlying mechanism of structural stability.

Dimensionally stable composite structures and composite mirrors for spaceborne optical instruments

NASA Astrophysics Data System (ADS)

Sippel, Rudolf; Stute, Thomas; Erdl, Günther

2018-04-01

This paper, "Dimensionally stable composite structures and composite mirrors for spaceborne optical instruments," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Interaction of an ultrarelativistic electron bunch train with a W-band accelerating structure: High power and high gradient

DOE PAGES

Wang, D.; Antipov, S.; Jing, C.; ...

2016-02-05

Electron beam interaction with high frequency structures (beyond microwave regime) has a great impact on future high energy frontier machines. We report on the generation of multimegawatt pulsed rf power at 91 GHz in a planar metallic accelerating structure driven by an ultrarelativistic electron bunch train. This slow-wave wakefield device can also be used for high gradient acceleration of electrons with a stable rf phase and amplitude which are controlled by manipulation of the bunch train. To achieve precise control of the rf pulse properties, a two-beam wakefield interferometry method was developed in which the rf pulse, due to themore » interference of the wakefields from the two bunches, was measured as a function of bunch separation. As a result, measurements of the energy change of a trailing electron bunch as a function of the bunch separation confirmed the interferometry method.« less

Computational Modeling of Allosteric Regulation in the Hsp90 Chaperones: A Statistical Ensemble Analysis of Protein Structure Networks and Allosteric Communications

PubMed Central

Blacklock, Kristin; Verkhivker, Gennady M.

2014-01-01

A fundamental role of the Hsp90 chaperone in regulating functional activity of diverse protein clients is essential for the integrity of signaling networks. In this work we have combined biophysical simulations of the Hsp90 crystal structures with the protein structure network analysis to characterize the statistical ensemble of allosteric interaction networks and communication pathways in the Hsp90 chaperones. We have found that principal structurally stable communities could be preserved during dynamic changes in the conformational ensemble. The dominant contribution of the inter-domain rigidity to the interaction networks has emerged as a common factor responsible for the thermodynamic stability of the active chaperone form during the ATPase cycle. Structural stability analysis using force constant profiling of the inter-residue fluctuation distances has identified a network of conserved structurally rigid residues that could serve as global mediating sites of allosteric communication. Mapping of the conformational landscape with the network centrality parameters has demonstrated that stable communities and mediating residues may act concertedly with the shifts in the conformational equilibrium and could describe the majority of functionally significant chaperone residues. The network analysis has revealed a relationship between structural stability, global centrality and functional significance of hotspot residues involved in chaperone regulation. We have found that allosteric interactions in the Hsp90 chaperone may be mediated by modules of structurally stable residues that display high betweenness in the global interaction network. The results of this study have suggested that allosteric interactions in the Hsp90 chaperone may operate via a mechanism that combines rapid and efficient communication by a single optimal pathway of structurally rigid residues and more robust signal transmission using an ensemble of suboptimal multiple communication routes. This may be a universal requirement encoded in protein structures to balance the inherent tension between resilience and efficiency of the residue interaction networks. PMID:24922508

Computational modeling of allosteric regulation in the hsp90 chaperones: a statistical ensemble analysis of protein structure networks and allosteric communications.

PubMed

Blacklock, Kristin; Verkhivker, Gennady M

2014-06-01

A fundamental role of the Hsp90 chaperone in regulating functional activity of diverse protein clients is essential for the integrity of signaling networks. In this work we have combined biophysical simulations of the Hsp90 crystal structures with the protein structure network analysis to characterize the statistical ensemble of allosteric interaction networks and communication pathways in the Hsp90 chaperones. We have found that principal structurally stable communities could be preserved during dynamic changes in the conformational ensemble. The dominant contribution of the inter-domain rigidity to the interaction networks has emerged as a common factor responsible for the thermodynamic stability of the active chaperone form during the ATPase cycle. Structural stability analysis using force constant profiling of the inter-residue fluctuation distances has identified a network of conserved structurally rigid residues that could serve as global mediating sites of allosteric communication. Mapping of the conformational landscape with the network centrality parameters has demonstrated that stable communities and mediating residues may act concertedly with the shifts in the conformational equilibrium and could describe the majority of functionally significant chaperone residues. The network analysis has revealed a relationship between structural stability, global centrality and functional significance of hotspot residues involved in chaperone regulation. We have found that allosteric interactions in the Hsp90 chaperone may be mediated by modules of structurally stable residues that display high betweenness in the global interaction network. The results of this study have suggested that allosteric interactions in the Hsp90 chaperone may operate via a mechanism that combines rapid and efficient communication by a single optimal pathway of structurally rigid residues and more robust signal transmission using an ensemble of suboptimal multiple communication routes. This may be a universal requirement encoded in protein structures to balance the inherent tension between resilience and efficiency of the residue interaction networks.

Lidar Observation of Aerosol and Temperature Stratification over Urban Area During the Formation of a Stable Atmospheric PBL

NASA Technical Reports Server (NTRS)

Kolev, I.; Parvanov, O.; Kaprielov, B.; Mitev, V.; Simeonov, V.; Grigorov, I.

1992-01-01

In recent years, the processes in the atmospheric planetary boundary layer (PBL) over urban areas were intensely investigated, due to ecological problems related to the air, soil, and water pollution. New pollution sources in new residential districts, when in contradiction to the microclimate and topography requirements of that region, create a number of considerable hazards and problems. The present study is a continuation of our preceding investigations and aims at revealing the aerosol structure and stratification during the transition after sunset as measured by two lidars. Such observation of the nocturnal, stable PBL formation over an urban area in Bulgaria has not been reported before. The lidars' high time and spatial resolutions allow the changes of the internal structure of the PBL's part located above the surface layer to be observed.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

PubMed Central

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-01-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10–40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage. PMID:24145684

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors.

PubMed

Oakes, Landon; Westover, Andrew; Mares, Jeremy W; Chatterjee, Shahana; Erwin, William R; Bardhan, Rizia; Weiss, Sharon M; Pint, Cary L

2013-10-22

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-10-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

In situ TEM observation of FCC Ti formation at elevated temperatures

DOE PAGES

Yu, Qian; Kacher, Josh; Gammer, Christoph; ...

2017-07-04

Pure Ti traditionally exhibits the hexagonal closed packed (HCP) crystallographic structure under ambient conditions and the body centered cubic (BCC) structure at elevated temperatures. In addition to these typical structures for Ti alloys, the presence of a face centered cubic (FCC) phase associated with thin films, interfaces, or high levels of plastic deformation has occasionally been reported. Here in this paper we show that small FCC precipitates form in freestanding thin foils during in situ transmission electron microscope (TEM) heating and we discuss the potential origins of the FCC phase in light of the in situ observations. This FCC phasemore » was found to be stable upon cooling and under ambient conditions, which allowed us to explore its mechanical properties and stability via nanomechanical in situ TEM testing. It was found that FCC platelets within the HCP matrix phase were stable under mechanical deformation and exhibited similar mechanical deformation behavior as the parent HCP phase.« less

In situ TEM observation of FCC Ti formation at elevated temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Qian; Kacher, Josh; Gammer, Christoph

Pure Ti traditionally exhibits the hexagonal closed packed (HCP) crystallographic structure under ambient conditions and the body centered cubic (BCC) structure at elevated temperatures. In addition to these typical structures for Ti alloys, the presence of a face centered cubic (FCC) phase associated with thin films, interfaces, or high levels of plastic deformation has occasionally been reported. Here in this paper we show that small FCC precipitates form in freestanding thin foils during in situ transmission electron microscope (TEM) heating and we discuss the potential origins of the FCC phase in light of the in situ observations. This FCC phasemore » was found to be stable upon cooling and under ambient conditions, which allowed us to explore its mechanical properties and stability via nanomechanical in situ TEM testing. It was found that FCC platelets within the HCP matrix phase were stable under mechanical deformation and exhibited similar mechanical deformation behavior as the parent HCP phase.« less

Long-term stable water vapor permeation barrier properties of SiN/SiCN/SiN nanolaminated multilayers grown by plasma-enhanced chemical vapor deposition at extremely low pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Bum Ho, E-mail: bhchoi@kitech.re.kr; Lee, Jong Ho

2014-08-04

We investigated the water vapor permeation barrier properties of 30-nm-thick SiN/SiCN/SiN nanolaminated multilayer structures grown by plasma enhanced chemical vapor deposition at 7 mTorr. The derived water vapor transmission rate was 1.12 × 10{sup −6} g/(m{sup 2} day) at 85 °C and 85% relative humidity, and this value was maintained up to 15 000 h of aging time. The X-ray diffraction patterns revealed that the nanolaminated film was composed of an amorphous phase. A mixed phase was observed upon performing high resolution transmission electron microscope analysis, which indicated that a thermodynamically stable structure was formed. It was revealed amorphous SiN/SiCN/SiN multilayer structures that are freemore » from intermixed interface defects effectively block water vapor permeation into active layer.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manikandan, M.; Santhosh, M.; Rajeswarapalanichamy, R., E-mail: rrpalanichamy@gmail.com

Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of actinide carbides AnC (An=U, Np) for three different crystal structures, namely NaCl, CsCl and ZnS. Among the considered structures, NaCl structure is found to be the most stable structure for these carbides at normal pressure. A pressure induced structural phase transition from NaCl to ZnS is observed. The electronic structure reveals that these carbides are metals. The calculated elastic constants indicate that these carbides are mechanically stable at normal pressure.

Ab-initio study of high temperature lattice dynamics of BCC zirconium (β-Zr) and uranium (γ-U)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Partha S., E-mail: parthasarathi13@gmail.com; Arya, A., E-mail: parthasarathi13@gmail.com; Dey, G. K., E-mail: parthasarathi13@gmail.com

2014-04-24

Using self consistent ab-initio lattice dynamics calculations, we show that bcc structures of Zr and U phases become stable at high temperature by phonon-phonon interactions. The calculated temperature dependent phonon dispersion curve (PDC) of β-Zr match excellently with experimental PDC. But the calculated PDC for γ-U shows negative phonon frequencies even at solid to liquid transition temperature. We show that this discrepancy is due to an overestimation of instability depth of bcc U phase which is removed by incorporation of spin-orbit coupling in the electronic structure calculations.

Atomic force microscope studies of fullerene films - Highly stable C60 fcc (311) free surfaces

NASA Technical Reports Server (NTRS)

Snyder, Eric J.; Tong, William M.; Williams, R. S.; Anz, Samir J.; Anderson, Mark S.

1991-01-01

Atomic force microscopy and X-ray diffractometry were used to study 1500 A-thick films of pure C60 grown by sublimation in ultrahigh vacuum onto a CaF2 (111) substrte. Topographs of the films did not reveal the expected close-packed structures, but they showed instead large regions that correspond to a face-centered cubic (311) surface and distortions of this surface. The open (311) structure may have a relatively low free energy because the low packing density contributes to a high entropy of the exposed surface.

Stabilization of flat aromatic Si6 rings analogous to benzene: ab initio theoretical prediction.

PubMed

Zdetsis, Aristides D

2007-12-07

It is shown by ab initio calculations, based on density functional (DFT/B3LYP), and high level coupled-cluster [CCSD(T)] and quadratic CI [QCISD(T)] methods, that flat aromatic silicon structures analogous to benzene (C6H6) can be stabilized in the presence of lithium. The resulting planar Si6Li6 structure is both stable and aromatic, sharing many key characteristics with benzene. To facilitate possible synthesis and characterization of these species, routes of formation with high exothermicity are suggested and several spectral properties (including optical absorption, infrared, and Raman) are calculated.

Technology update: Tethered aerostat structural design and material developments

NASA Technical Reports Server (NTRS)

Witherow, R. G.

1975-01-01

Requirements exist for an extremely stable, high performance, all-weather tethered aerostat system. This requirement has been satisfied by a 250,000 cubic foot captive buoyant vehicle as demonstrated by over a year of successful field operations. This achievement required significant advancements in several technology areas including composite materials design, aerostatics and aerodynamics, structural design, electro-mechanical design, vehicle fabrication and mooring operations. This paper specifically addresses the materials and structural design aspects of pressurized buoyant vehicles as related to the general class of Lighter Than Air vehicles.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Degtyarenko, N. N.; Mazur, E. A., E-mail: eugen-mazur@mail.ru

The structural, electronic, phonon, and other characteristics of the normal phases of phosphorus hydrides with stoichiometry PH{sub k} are analyzed. The properties of the initial substance, namely, diphosphine are calculated. In contrast to phosphorus hydrides with stoichiometry PH{sub 3}, a quasi-two-dimensional phosphorus-stabilized lattice of metallic hydrogen can be formed in this substance during hydrostatic compression at a high pressure. The formed structure with H–P–H elements is shown to be locally stable in phonon spectrum, i.e., to be metastable. The properties of diphosphine are compared with the properties of similar structures of sulfur hydrides.

Synthetic surfactant- and cross-linker-free preparation of highly stable lipid-polymer hybrid nanoparticles as potential oral delivery vehicles.

PubMed

Wang, Taoran; Xue, Jingyi; Hu, Qiaobin; Zhou, Mingyong; Chang, Chao; Luo, Yangchao

2017-06-05

The toxicity associated with concentrated synthetic surfactants and the poor stability at gastrointestinal condition are two major constraints for practical applications of solid lipid nanoparticles (SLN) as oral delivery vehicles. In this study, a synthetic surfactant-free and cross-linker-free method was developed to fabricate effective, safe, and ultra-stable lipid-polymer hybrid nanoparticles (LPN). Bovine serum albumin (BSA) and dextran varying in molecular weights were first conjugated through Maillard reaction and the conjugates were exploited to emulsify solid lipid by a solvent diffusion and sonication method. The multilayer structure was formed by self-assembly of BSA-dextran micelles to envelope solid lipid via a pH- and heating-induced facile process with simultaneous surface deposition of pectin. The efficiency of different BSA-dextran conjugates was systematically studied to prepare LPN with the smallest size, the most homogeneous distribution and the greatest stability. The molecular interactions were characterized by Fourier transform infrared and fluorescence spectroscopies. Both nano spray drying and freeze-drying methods were tested to produce spherical and uniform pectin-coated LPN powders that were able to re-assemble nanoscale structure when redispersed in water. The results demonstrated the promise of a synthetic surfactant- and cross-linker-free technique to prepare highly stable pectin-coated LPN from all natural biomaterials as potential oral delivery vehicles.

Bulk Al-Al3Zr composite prepared by mechanical alloying and hot extrusion for high-temperature applications

NASA Astrophysics Data System (ADS)

Pourkhorshid, E.; Enayati, M. H.; Sabooni, S.; Karimzadeh, F.; Paydar, M. H.

2017-08-01

Bulk Al/Al3Zr composite was prepared by a combination of mechanical alloying (MA) and hot extrusion processes. Elemental Al and Zr powders were milled for up to 10 h and heat treated at 600°C for 1 h to form stable Al3Zr. The prepared Al3Zr powder was then mixed with the pure Al powder to produce an Al-Al3Zr composite. The composite powder was finally consolidated by hot extrusion at 550°C. The mechanical properties of consolidated samples were evaluated by hardness and tension tests at room and elevated temperatures. The results show that annealing of the 10-h-milled powder at 600°C for 1 h led to the formation of a stable Al3Zr phase. Differential scanning calorimetry (DSC) results confirmed that the formation of Al3Zr began with the nucleation of a metastable phase, which subsequently transformed to the stable tetragonal Al3Zr structure. The tension yield strength of the Al-10wt%Al3Zr composite was determined to be 103 MPa, which is approximately twice that for pure Al (53 MPa). The yield stress of the Al/Al3Zr composite at 300°C is just 10% lower than that at room temperature, which demonstrates the strong potential for the prepared composite to be used in high-temperature structural applications.

Strategy to approach stable production of recombinant nattokinase in Bacillus subtilis.

PubMed

Chen, Po Ting; Chiang, Chung-Jen; Chao, Yun-Peng

2007-01-01

Bacillus subtilis (B. subtilis) is widely accepted as an excellent host cell for the secretory production of recombinant proteins. In this study, a shuttle vector was constructed by fusion of Staphylococcus aureus (S. aureus) plasmid pUB110 with Escherichia coli (E. coli) plasmid pUC18 and used for the expression of nattokinase in B. subtilis. The pUB110/pUC-based plasmid was found to exhibit high structural instability with the identification of a DNA deletion between two repeated regions. An initial attempt was made to eliminate the homologous site in the plasmid, whereas the stability of the resulting plasmid was not improved. In an alternative way, the pUC18-derived region in this hybrid vector was replaced by the suicidal R6K plasmid origin of E. coli. As a consequence, the pUB110/R6K-based plasmid displayed full structural stability, leading to a high-level production of recombinant nattokinase in the culture broth. This was mirrored by the detection of a very low level of high molecular weight DNAs generated by the plasmid. Moreover, 2-fold higher nattokinase production was obtained by B. subtilis strain carrying the pUB110/R6K-based plasmid as compared to the cell with the pAMbeta1-derived vector, a plasmid known to have high structural stability. Overall, it indicates the feasibility of the approach by fusing two compatible plasmid origins for stable and efficient production of recombinant nattokinase in B. subtilis.

Wearable, wireless gas sensors using highly stretchable and transparent structures of nanowires and graphene

NASA Astrophysics Data System (ADS)

Park, Jihun; Kim, Joohee; Kim, Kukjoo; Kim, So-Yun; Cheong, Woon Hyung; Park, Kyeongmin; Song, Joo Hyeb; Namgoong, Gyeongho; Kim, Jae Joon; Heo, Jaeyeong; Bien, Franklin; Park, Jang-Ung

2016-05-01

Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the `Internet of Things' area.Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the `Internet of Things' area. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01468b

Fabrication and lithium storage performance of sugar apple-shaped SiOx@C nanocomposite spheres

NASA Astrophysics Data System (ADS)

Li, Mingqi; Zeng, Ying; Ren, Yurong; Zeng, Chunmei; Gu, Jingwei; Feng, Xiaofang; He, Hongyan

2015-08-01

Nonstoichiometric SiOx is a kind of very attractive anode material for high-energy lithium-ion batteries because of a high specific capacity and facile synthesis. However, the poor electrical conductivity and unstable electrode structure of SiOx severely limit its electrochemical performance as anode in lithium-ion batteries. In this work, highly durable sugar apple-shaped SiOx@C nanocomposite spheres are fabricated to achieve significantly improved electrochemical performance. The composite is synthesized by homogenous one-pot synthesis, using ethyltriethoxysilanes (EtSi(OEt)3) and resorcinol/formaldehyde (RF) as starting materials. The morphology, composition and structure of the composite are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis (EA) and X-ray photoelectron spectroscopy (XPS). At a current density of 50 mA g-1, the sugar apple-shaped SiOx@C spheres exhibit a stable discharge capacity of about 630 mAh g-1 calculated on the total mass of both SiOx and C. At a current density of 100 mA g-1, a stable discharge capacity of about 550 mAh g-1 is obtained and the capacity has been kept up to 400 cycles. The excellent cycling performance is attributed to the homogeneous dispersion of SiOx in disordered carbon at the nanometer scale and the unique structure of the composite.

The high-pressure behavior of spherocobaltite (CoCO3): a single crystal Raman spectroscopy and XRD study

NASA Astrophysics Data System (ADS)

Chariton, Stella; Cerantola, Valerio; Ismailova, Leyla; Bykova, Elena; Bykov, Maxim; Kupenko, Ilya; McCammon, Catherine; Dubrovinsky, Leonid

2018-01-01

Magnesite (MgCO3), calcite (CaCO3), dolomite [(Ca, Mg)CO3], and siderite (FeCO3) are among the best-studied carbonate minerals at high pressures and temperatures. Although they all exhibit the calcite-type structure ({R}\\bar{3}{c}) at ambient conditions, they display very different behavior at mantle pressures. To broaden the knowledge of the high-pressure crystal chemistry of carbonates, we studied spherocobaltite (CoCO3), which contains Co2+ with cation radius in between those of Ca2+ and Mg2+ in calcite and magnesite, respectively. We synthesized single crystals of pure spherocobaltite and studied them using Raman spectroscopy and X-ray diffraction in diamond anvil cells at pressures to over 55 GPa. Based on single crystal diffraction data, we found that the bulk modulus of spherocobaltite is 128 (2) GPa and K' = 4.28 (17). CoCO3 is stable in the calcite-type structure up to at least 56 GPa and 1200 K. At 57 GPa and after laser heating above 2000 K, CoCO3 partially decomposes and forms CoO. In comparison to previously studied carbonates, our results suggest that at lower mantle conditions carbonates can be stable in the calcite-type structure if the radius of the incorporated cation(s) is equal or smaller than that of Co2+ (i.e., 0.745 Å).

Tailoring gadolinium-doped ceria-based solid oxide fuel cells to achieve 2 W cm(-2) at 550 °C.

PubMed

Lee, Jin Goo; Park, Jeong Ho; Shul, Yong Gun

2014-06-04

Low-temperature operation is necessary for next-generation solid oxide fuel cells due to the wide variety of their applications. However, significant increases in the fuel cell losses appear in the low-temperature solid oxide fuel cells, which reduce the cell performance. To overcome this problem, here we report Gd0.1Ce0.9O1.95-based low-temperature solid oxide fuel cells with nanocomposite anode functional layers, thin electrolytes and core/shell fibre-structured Ba0.5Sr0.5Co0.8Fe0.2O3-δ-Gd0.1Ce0.9O1.95 cathodes. In particular, the report describes the use of the advanced electrospinning and Pechini process in the preparation of the core/shell-fibre-structured cathodes. The fuel cells show a very high performance of 2 W cm(-2) at 550 °C in hydrogen, and are stable for 300 h even under the high current density of 1 A cm(-2). Hence, the results suggest that stable and high-performance solid oxide fuel cells at low temperatures can be achieved by modifying the microstructures of solid oxide fuel cell components.

Electrochemistry and electrochemiluminescence from a redox-active metal-organic framework.

PubMed

Xu, Yang; Yin, Xue-Bo; He, Xi-Wen; Zhang, Yu-Kui

2015-06-15

The marriage of metal-organic frameworks (MOFs) and electrochemiluminescence (ECL) can combine their merits together. Designing ECL-active MOF with a high electron transfer capacity and high stability is critical for ECL emission. Here we reported the ECL from a redox-active MOF prepared from {Ru[4,4'-(HO2C)2-bpy]2bpy}(2+) and Zn(2+); a property of MOFs has not been reported previously. The MOF structure is independent of its charge and is therefore stable electrochemically. The redox-activity and well-ordered porous structure of the MOF were confirmed by its electrochemical properties and ECL emission. The high ECL emission indicated the ease of electron transfer between the MOF and co-reactants. Furthermore, the MOF exhibited permselectivity, charge selectivity, and catalytic selectivity along with a stable and concentration-dependent ECL emission toward co-reactants. ECL mechanism was proposed based on the results. The detection and recovery of cocaine in the serum sample was used to validate the feasibility of MOF- based ECL system. The information obtained in this study provides a better understanding of the redox properties of MOFs and their potential electrochemical applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Ultra-stable, low phase noise dielectric resonator stabilized oscillators for military and commercial systems

NASA Technical Reports Server (NTRS)

Mizan, Muhammad; Higgins, Thomas; Sturzebecher, Dana

1993-01-01

EPSD has designed, fabricated and tested, ultra-stable, low phase noise microwave dielectric resonator oscillators (DRO's) at S, X, Ku, and K-bands, for potential application to high dynamic range and low radar cross section target detection radar systems. The phase noise and the temperature stability surpass commercially available DROs. Low phase noise signals are critical for CW Doppler radars, at both very close-in and large offset frequencies from the carrier. The oscillators were built without any temperature compensation techniques and exhibited a temperature stability of 25 parts per million (ppm) over an extended temperature range. The oscillators are lightweight, small and low cost compared to BAW & SAW oscillators, and can impact commercial systems such as telecommunications, built-in-test equipment, cellular phone and satellite communications systems. The key to obtaining this performance was a high Q factor resonant structure (RS) and careful circuit design techniques. The high Q RS consists of a dielectric resonator (DR) supported by a low loss spacer inside a metal cavity. The S and the X-band resonant structures demonstrated loaded Q values of 20,300 and 12,700, respectively.

First-principles study of high-pressure structural phase transitions of magnesium

NASA Astrophysics Data System (ADS)

Liu, Qiuxiang; Fan, Changzeng; Zhang, Ruijun

2009-06-01

The structural phase transitions for the hcp, bcc, dhcp, and fcc of magnesium at hydrostatic pressures larger than about 200 GPa at zero temperature are studied by first-principles total energy calculations. The plane-wave basis pseudopotential method has been adopted, in which the generalized gradient approximation implanted in the CASTEP code is employed. By comparing the enthalpy differences of the hcp structure with other three structures under different pressures, it can be seen that when the pressure becomes higher than about 65, 130, and 190 GPa, the bcc, dhcp, and fcc structures become more stable relative to the hcp structure, respectively. Due to the lowest enthalpy value of the bcc structure above 65 GPa, it can be deduced that magnesium may transform to the bcc structure from the ground state hcp structure around 65 GPa, but no further phase transitions occur without additionally applying high temperature. In addition, the equation of state of magnesium is calculated, indicating that bcc structure is the softest phase.

Complex topological structures of frustrated liquid crystals with potential for optics and photonics (Presentation Recording)

NASA Astrophysics Data System (ADS)

Žumer, Slobodan; Čančula, Miha; Čopar, Simon; Ravnik, Miha

2015-10-01

Geometrical constrains and intrinsic chirality in nematic mesophases enable formation of stable and metastable complex defect structures. Recently selected knotted and linked disclinations have been formed using laser manipulation of nematic braids entangling colloidal particles in nematic colloids [Tkalec et al., Science 2011; Copar et al., PNAS 2015]. In unwinded chiral nematic phases stable and metastable toron and hopfion defects have been implemented by laser tweezers [Smalyukh et al., Nature Materials 2010; Chen et al., PRL2013] and in chiral nematic colloids particles dressed by solitonic deformations [Porenta et al., Sci. Rep. 2014]. Modelling studies based on the numerical minimisation of the phenomenological free energy, supported with the adapted topological theory [Copar and Zumer, PRL 2011; Copar, Phys. Rep. 2014] allow describing the observed nematic defect structures and also predicting numerous structures in confined blue phases [Fukuda and Zumer, Nature Comms 2011 and PRL 2011] and stable knotted disclinations in cholesteric droplets with homeotropic boundary [Sec et al., Nature Comms 2014]. Coupling the modeling with finite difference time domain light field computation enables understanding of light propagation and light induced restructuring in these mesophases. The method was recently demonstrated for the description of low intensity light beam changes during the propagation along disclination lines [Brasselet et al., PRL 2009; Cancula et al., PRE 2014]. Allowing also high intensity light an order restructuring is induced [Porenta et al., Soft Matter 2012; Cancula et al., 2015]. These approaches help to uncover the potential of topological structures for beyond-display optical and photonic applications.

Quinone-based stable isotope probing for assessment of 13C substrate-utilizing bacteria

NASA Astrophysics Data System (ADS)

Kunihiro, Tadao; Katayama, Arata; Demachi, Toyoko; Veuger, Bart; Boschker, Henricus T. S.; van Oevelen, Dick

2015-04-01

In this study, we attempted to establish quinone-stable-isotope probing (SIP) technique to link substrate-utilizing bacterial group to chemotaxonomic group in bacterial community. To identify metabolically active bacterial group in various environments, SIP techniques combined with biomarkers have been widely utilized as an attractive method for environmental study. Quantitative approaches of the SIP technique have unique advantage to assess substrate-incorporation into bacteria. As a most major quantitative approach, SIP technique based on phospholipid-derived fatty acids (PLFA) have been applied to simultaneously assess substrate-incorporation rate into bacteria and microbial community structure. This approach is powerful to estimate the incorporation rate because of the high sensitivity due to the detection by a gas chromatograph-combustion interface-isotope ratio mass spectrometer (GC-c-IRMS). However, its phylogenetic resolution is limited by specificity of a compound-specific marker. We focused on respiratory quinone as a biomarker. Our previous study found a good correlation between concentrations of bacteria-specific PLFAs and quinones over several orders of magnitude in various marine sediments, and the quinone method has a higher resolution (bacterial phylum level) for resolving differences in bacterial community composition more than that of bacterial PLFA. Therefore, respiratory quinones are potentially good biomarkers for quantitative approaches of the SIP technique. The LC-APCI-MS method as molecular-mass based detection method for quinone was developed and provides useful structural information for identifying quinone molecular species in environmental samples. LC-MS/MS on hybrid triple quadrupole/linear ion trap, which enables to simultaneously identify and quantify compounds in a single analysis, can detect high molecular compounds with their isotope ions. Use of LC-MS/MS allows us to develop quinone-SIP based on molecular mass differences due to 13C abundance in the quinone. In this study, we verified carbon stable isotope of quinone compared with bulk carbon stable isotope of bacterial culture. Results indicated a good correlation between carbon stable isotope of quinone compared with bulk carbon stable isotope. However, our measurement conditions for detection of quinone isotope-ions incurred underestimation of 13C abundance in the quinone. The quinone-SIP technique needs further optimization for measurement conditions of LC-MS/MS.

Electronic and Morphological Dual Modulation of Cobalt Carbonate Hydroxides by Mn Doping toward Highly Efficient and Stable Bifunctional Electrocatalysts for Overall Water Splitting.

PubMed

Tang, Tang; Jiang, Wen-Jie; Niu, Shuai; Liu, Ning; Luo, Hao; Chen, Yu-Yun; Jin, Shi-Feng; Gao, Feng; Wan, Li-Jun; Hu, Jin-Song

2017-06-21

Developing bifunctional efficient and durable non-noble electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly desirable and challenging for overall water splitting. Herein, Co-Mn carbonate hydroxide (CoMnCH) nanosheet arrays with controllable morphology and composition were developed on nickel foam (NF) as such a bifunctional electrocatalyst. It is discovered that Mn doping in CoCH can simultaneously modulate the nanosheet morphology to significantly increase the electrochemical active surface area for exposing more accessible active sites and tune the electronic structure of Co center to effectively boost its intrinsic activity. As a result, the optimized Co 1 Mn 1 CH/NF electrode exhibits unprecedented OER activity with an ultralow overpotential of 294 mV at 30 mA cm -2 , compared with all reported metal carbonate hydroxides. Benefited from 3D open nanosheet array topographic structure with tight contact between nanosheets and NF, it is able to deliver a high and stable current density of 1000 mA cm -2 at only an overpotential of 462 mV with no interference from high-flux oxygen evolution. Despite no reports about effective HER on metal carbonate hydroxides yet, the small overpotential of 180 mV at 10 mA cm -2 for HER can be also achieved on Co 1 Mn 1 CH/NF by the dual modulation of Mn doping. This offers a two-electrode electrolyzer using bifunctional Co 1 Mn 1 CH/NF as both anode and cathode to perform stable overall water splitting with a cell voltage of only 1.68 V at 10 mA cm -2 . These findings may open up opportunities to explore other multimetal carbonate hydroxides as practical bifunctional electrocatalysts for scale-up water electrolysis.

Extremely strong self-assembly of a bimetallic salen complex visualized at the single-molecule level.

PubMed

Salassa, Giovanni; Coenen, Michiel J J; Wezenberg, Sander J; Hendriksen, Bas L M; Speller, Sylvia; Elemans, Johannes A A W; Kleij, Arjan W

2012-04-25

A bis-Zn(salphen) structure shows extremely strong self-assembly both in solution as well as at the solid-liquid interface as evidenced by scanning tunneling microscopy, competitive UV-vis and fluorescence titrations, dynamic light scattering, and transmission electron microscopy. Density functional theory analysis on the Zn(2) complex rationalizes the very high stability of the self-assembled structures provoked by unusual oligomeric (Zn-O)(n) coordination motifs within the assembly. This coordination mode is strikingly different when compared with mononuclear Zn(salphen) analogues that form dimeric structures having a typical Zn(2)O(2) central unit. The high stability of the multinuclear structure therefore holds great promise for the development of stable self-assembled monolayers with potential for new opto-electronic materials.

High-resolution stable isotope signature of a land-falling atmospheric river in Southern Norway

NASA Astrophysics Data System (ADS)

Weng, Yongbiao; Sodemann, Harald

2017-04-01

Gathering observational evidence of the long-range moisture versus local source contributions remains a scientific challenge, but is critical for understanding how hydrological extremes develop. Moisture transport to the west coast of Norway is often connected to elongated meridional structures of high water vapour flux known as Atmospheric Rivers. It is still an open question how well moisture sources estimated by different numerical models for such events of long-range transport correspond with reality. In this study, we present high resolution stable isotope information collected during a land-falling Atmospheric River in Southern Norway during winter 2016, and analyse the data with the aim to differentiate between moisture source signatures and below-cloud processes affecting the stable isotope composition. The precipitation characterised by a pronounced warm front was sampled manually on a rooftop platform at a 10-20 minute interval during the 24h of the event and later measured by a laser spectrometer (Picarro L2140-i) in the lab for δ18O, δD, and d-excess. Simultaneously, the stable isotope composition of water vapor was continuously measured at high resolution. To that end, ambient air was continuously pumped from a nearby inlet at 25 m above the ground and measured by another laser spectrometer (Picarro L2130-i). Stable water isotope measurements were supplemented by detailed precipitation parameters from a laser disdrometer (OTT Parsivel2), Micro Rain Radar (MRR-2), Total Precipitation Sensor (TPS-3100), and a nearby weather station. Measurements show a signature of two depletion periods in the main stable isotope parameters that are not apparent in precipitation amount and atmospheric temperature measurements. The deuterium excess in rainfall responds differently, with first and increase and then a decrease during these depletion periods. We interpret this as a combined consequence of airmass change, cloud microphysics, and below-cloud effects. Moisture sources identified during the atmospheric river event show a clear transition that points to the need to constrain this kind of analysis by additional stable water isotope observations en route and upstream.

Structure of β-AgGaO{sub 2}; ternary I–III–VI{sub 2} oxide semiconductor with a wurtzite-derived structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagatani, Hiraku; Suzuki, Issei; Kita, Masao

2015-02-15

The structure of the wurtzite-derived β-AgGaO{sub 2} was refined by Rietveld analysis of high-resolution powder diffraction data obtained using synchrotron X-ray radiation. The space group of the crystal is Pna2{sub 1} with lattice parameters of a{sub 0}=5.56175 Å, b{sub 0}=7.14749 Å, and c{sub 0}=5.46875 Å. The deviation of O–Ag–O and M–O–M bond angles from the regular tetrahedral angle of 109.5° was very large at ∼8° and ∼11°, respectively. The electronic structure of β-AgGaO{sub 2} is discussed based on its structure, and the indirect band gap of β-AgGaO{sub 2} was related to significant tetrahedral distortion. Although β-AgGaO{sub 2} decomposes into metallicmore » silver and Ga{sub 2}O{sub 3} at a high temperature in any atmosphere, β-AgGaO{sub 2} is stable up to 690 °C under an O{sub 2} atmosphere. No direct transformation from the wurtzite-derived phase to a delafossite phase occurs in β-AgGaO{sub 2}. - Graphical abstract: Crystal structure of β-AgGaO{sub 2} was refined by Rietveld analysis. AgO{sub 4} and O(Ag,Ga){sub 4} tetrahedra are significantly distorted from ideal tetrahedron. - Highlights: • Orthorhombic β-AgGaO{sub 2} with a wurtzite-derived β-NaFeO{sub 2} structure was synthesized. • Its structure was refined by Rietveld analysis of high-resolution XRD data. • Silver and oxygen tetrahedra are significantly distorted from an ideal tetrahedron. • The extent of this tetrahedral distortion is related to the band gap nature. • β-AgGaO{sub 2} is a metastable phase but is stable up to 690 °C in an O{sub 2} atmosphere.« less

The denaturation and degradation of stable enzymes at high temperatures.

PubMed Central

Daniel, R M; Dines, M; Petach, H H

1996-01-01

Now that enzymes are available that are stable above 100 degrees C it is possible to investigate conformational stability at this temperature, and also the effect of high-temperature degradative reactions in functioning enzymes and the inter-relationship between degradation and denaturation. The conformational stability of proteins depends upon stabilizing forces arising from a large number of weak interactions, which are opposed by an almost equally large destabilizing force due mostly to conformational entropy. The difference between these, the net free energy of stabilization, is relatively small, equivalent to a few interactions. The enhanced stability of very stable proteins can be achieved by an additional stabilizing force which is again equivalent to only a few stabilizing interactions. There is currently no strong evidence that any particular interaction (e.g. hydrogen bonds, hydrophobic interactions) plays a more important role in proteins that are stable at 100 degrees C than in those stable at 50 degrees C, or that the structures of very stable proteins are systematically different from those of less stable proteins. The major degradative mechanisms are deamidation of asparagine and glutamine, and succinamide formation at aspartate and glutamate leading to peptide bond hydrolysis. In addition to being temperature-dependent, these reactions are strongly dependent upon the conformational freedom of the susceptible amino acid residues. Evidence is accumulating which suggests that even at 100 degrees C deamidation and succinamide formation proceed slowly or not at all in conformationally intact (native) enzymes. Whether this is the case at higher temperatures is not yet clear, so it is not known whether denaturation of degradation will set the upper limit of stability for enzymes. PMID:8694749

Spectral structure and stability studies on microstructure-fiber continuum

NASA Astrophysics Data System (ADS)

Gu, Xun; Kimmel, Mark; Zeek, Erik; Shreenath, Aparna P.; Trebino, Rick P.; Windeler, Robert S.

2003-07-01

Although previous direct measurements of the microstructure-fiber continuum have all showed a smooth and stable spectrum, our cross-correlation frequency-resolved optical gating (XFROG) full-intensity-and-phase characterization of the continuum pulse, utilizing sum-frequency-generation with a pre-characterized reference pulse and the angle-dithered-crystal technique, indicates that fine-scale spectral structure exists on a single-shot basis, contrary to previous observations. In particular, deep and fine oscillations are found in the retrieved spectrum, and the retrieved trace contains a "measles" pattern, whereas the measured trace and the independently-measured spectrum are rather smooth. The discrepancy is shown to be the result of unstable single-shot spectral structure. Although the XFROG measurement is not able to directly measure the single-shot fine structure in the trace, the redundancy of information in FROG traces enables the retrieval algorithm to correctly recognize the existence of the spectral fine structure, and restore the structure in the retrieved trace and spectrum. Numerical simulations have supported our hypothesis, and we directly observed the fine spectral structure in single-shot measurements of the continuum spectrum and the structure was seen to be highly unstable, the continuum spectrum appearing smooth only when many shots are averaged. Despite the structure and instability in the continuum spectrum, coherence experiments also reveal that the spectral phase is rather stable, being able to produce well-defined spectral fringes across the entire continuum bandwidth.

Materials for Adaptive Structural Acoustic Control. Volume 3

DTIC Science & Technology

1994-04-11

criteria have been met for a partcular application, it then becomes advantageous to reduce costs by miniaturizing and/or reducing the power delivered...MAELSG FRintended to develop motion or vibration. such as high power COUPLING sonar, while a high g constant is desirable for sensor Histor of...which is another stable chips, which must be adjusted using solid- power and miniaturization. crystal slate in which the relative positions stale

Tough, High-Performance, Thermoplastic Addition Polymers

NASA Technical Reports Server (NTRS)

Pater, Ruth H.; Proctor, K. Mason; Gleason, John; Morgan, Cassandra; Partos, Richard

1991-01-01

Series of addition-type thermoplastics (ATT's) exhibit useful properties. Because of their addition curing and linear structure, ATT polymers have toughness, like thermoplastics, and easily processed, like thermosets. Work undertaken to develop chemical reaction forming stable aromatic rings in backbone of ATT polymer, combining high-temperature performance and thermo-oxidative stability with toughness and easy processibility, and minimizing or eliminating necessity for tradeoffs among properties often observed in conventional polymer syntheses.

Structural, electronic and photocatalytic properties of atomic defective BiI3 monolayers

NASA Astrophysics Data System (ADS)

Yan, Huang; Ziyu, Hu; Xu, Gong; Xiaohong, Shao

2018-01-01

The structural, electronic and photocatalytic properties of five vacancy-containing 2D BiI3 monolayers are investigated by the first-principle calculations. The electronic structures show that the five structures are stable and have comparable binding energies to that of the pristine BiI3 monolayer, and the defects can tune the band gaps. Optical spectra indicate that the five structures retain high absorption capacity for visible light. The spin-orbit coupling (SOC) effect is found to play an important role in the band edge of defective structures, and the VBi and VBi-I3 defective BiI3 monolayers can make absolute band edges straddle water redox potentials more easily.

New frontiers in water purification: highly stable amphopolycarboxyglycinate-stabilized Ag-AgCl nanocomposite and its newly discovered potential

NASA Astrophysics Data System (ADS)

Krutyakov, Yurii A.; Zherebin, Pavel M.; Kudrinskiy, Alexey A.; Zubavichus, Yan V.; Presniakov, Mikhail Yu; Yapryntsev, Alexey D.; Karabtseva, Anastasia V.; Mikhaylov, Dmitry M.; Lisichkin, Georgii V.

2016-09-01

A simple synthetic procedure for high-stable dispersions of porous composite Ag/AgCl nanoparticles stabilized with amphoteric surfactant sodium tallow amphopolycarboxyglycinate has been proposed for the first time. The prepared samples were characterized by UV-vis spectroscopy, x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy, small area electron diffraction (SAED), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electron probe micro-analysis. In addition, measurements (carried out at the Kurchatov synchrotron radiation source stations) of the Ag K-edge extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) spectra and XRD of the prepared nanoparticles have been performed. The obtained results suggest that small-sized Ag clusters are homogeneously distributed in the mass of the AgCl nanoparticle (~80 nm) formed during the synthesis. The Ag/AgCl dispersion demonstrates photocatalytic activity (with respect to methyl orange) and high bactericidal activity against E. coli. This activity is superior to the activity of both Ag and AgCl nanoparticles stabilized by the same surfactant. Thus, porous composite Ag/AgCl nanoparticles can be used as a multifunctional agent that is able to remove both pollutants and bacterium from water.

Structural phase transitions of (Bi 1$-$xSb x ) 2(Te 1$-$y Se y) 3 compounds under high pressure and the influence of the atomic radius on the compression processes of tetradymites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Jinggeng; Yu, Zhenhai; Hu, Qingyang

Recently, A 2B 3-type tetradymites have developed into a hot topic in physical and material research fields, where the A and B atoms represent V and VI group elements, respectively. In this study, in situ angle-dispersive X-ray diffraction measurements were performed on Bi 2Te 2Se, BiSbTeSe 2, and Sb 2Te 2Se tetradymites under high pressure. Bi 2Te 2Se transforms from a layered rhombohedral structure (phase I) into 7-fold monoclinic (phase II) and body-centered tetragonal (phase IV) structures at about 8.0 and 14.3 GPa, respectively, without an 8-fold monoclinic structure (phase III) similar to that in Bi 2Te 3. Thus, themore » compression behavior of Bi 2Te 2Se is the same as that of Bi 2Se 3, which could also be obtained from first-principles calculations and in situ high-pressure electrical resistance measurements. Under high pressure, BiSbTeSe 2 and Sb 2Te 2Se undergo similar structural phase transitions to Bi 2Te 2Se, which indicates that the compression process of tellurides can be modulated by doping Se in Te sites. According to these high-pressure investigations of A 2B 3-type tetradymites, the decrease of the B-site atomic radius shrinks the stable pressure range of phase III and expands that of phase II, whereas the decrease of the A-site atomic radius induces a different effect, i.e. expanding the stable pressure range of phase III and shrinking that of phase II. Lastly, the influence of the atomic radius on the compression process of tetradymites is closely related to the chemical composition and the atom arrangement in the quintuple layer.« less

Structural phase transitions of (Bi 1$-$xSb x ) 2(Te 1$-$y Se y) 3 compounds under high pressure and the influence of the atomic radius on the compression processes of tetradymites

DOE PAGES

Zhao, Jinggeng; Yu, Zhenhai; Hu, Qingyang; ...

2016-12-14

Recently, A 2B 3-type tetradymites have developed into a hot topic in physical and material research fields, where the A and B atoms represent V and VI group elements, respectively. In this study, in situ angle-dispersive X-ray diffraction measurements were performed on Bi 2Te 2Se, BiSbTeSe 2, and Sb 2Te 2Se tetradymites under high pressure. Bi 2Te 2Se transforms from a layered rhombohedral structure (phase I) into 7-fold monoclinic (phase II) and body-centered tetragonal (phase IV) structures at about 8.0 and 14.3 GPa, respectively, without an 8-fold monoclinic structure (phase III) similar to that in Bi 2Te 3. Thus, themore » compression behavior of Bi 2Te 2Se is the same as that of Bi 2Se 3, which could also be obtained from first-principles calculations and in situ high-pressure electrical resistance measurements. Under high pressure, BiSbTeSe 2 and Sb 2Te 2Se undergo similar structural phase transitions to Bi 2Te 2Se, which indicates that the compression process of tellurides can be modulated by doping Se in Te sites. According to these high-pressure investigations of A 2B 3-type tetradymites, the decrease of the B-site atomic radius shrinks the stable pressure range of phase III and expands that of phase II, whereas the decrease of the A-site atomic radius induces a different effect, i.e. expanding the stable pressure range of phase III and shrinking that of phase II. Lastly, the influence of the atomic radius on the compression process of tetradymites is closely related to the chemical composition and the atom arrangement in the quintuple layer.« less

Toward high-resolution computational design of helical membrane protein structure and function

PubMed Central

Barth, Patrick; Senes, Alessandro

2016-01-01

The computational design of α-helical membrane proteins is still in its infancy but has made important progress. De novo design has produced stable, specific and active minimalistic oligomeric systems. Computational re-engineering can improve stability and modulate the function of natural membrane proteins. Currently, the major hurdle for the field is not computational, but the experimental characterization of the designs. The emergence of new structural methods for membrane proteins will accelerate progress PMID:27273630

Replication of butterfly wing and natural lotus leaf structures by nanoimprint on silica sol-gel films.

PubMed

Saison, Tamar; Peroz, Christophe; Chauveau, Vanessa; Berthier, Serge; Sondergard, Elin; Arribart, Hervé

2008-12-01

An original and low cost method for the fabrication of patterned surfaces bioinspired from butterfly wings and lotus leaves is presented. Silica-based sol-gel films are thermally imprinted from elastomeric molds to produce stable structures with superhydrophobicity values as high as 160 degrees water contact angle. The biomimetic surfaces are demonstrated to be tuned from superhydrophobic to superhydrophilic by annealing between 200 degrees C and 500 degrees C.

Toward high-resolution computational design of the structure and function of helical membrane proteins.

PubMed

Barth, Patrick; Senes, Alessandro

2016-06-07

The computational design of α-helical membrane proteins is still in its infancy but has already made great progress. De novo design allows stable, specific and active minimal oligomeric systems to be obtained. Computational reengineering can improve the stability and function of naturally occurring membrane proteins. Currently, the major hurdle for the field is the experimental characterization of the designs. The emergence of new structural methods for membrane proteins will accelerate progress.

An Investigation of the Dynamic Response of a Seismically Stable Platform

DTIC Science & Technology

1982-08-01

PAD. The controls on the -9system are of two types. A low frequency tilt control, with a 10 arc second sensitivity, 2-axis tiltmeter as sensor ...Inertial Sensors Structural Analysis Holloman AFB, NiM. Support to this effort includes structural analyses toward active servo frequency band. This report...controlled to maintain a null position of a sensitive height sensor . The 6-degree-of- freedom high frequency controls are based on seismometers as sensors

Partially coherent axiconic surface plasmon polariton fields

NASA Astrophysics Data System (ADS)

Chen, Yahong; Norrman, Andreas; Ponomarenko, Sergey A.; Friberg, Ari T.

2018-04-01

We introduce a class of structured polychromatic surface electromagnetic fields, reminiscent of conventional optical axicon fields, through a judicious superposition of partially correlated surface plasmon polaritons. We show that such partially coherent axiconic surface plasmon polariton fields are structurally stable and statistically highly versatile with regard to spectral density, polarization state, energy flow, and degree of coherence. These fields can be created by plasmon coherence engineering and may prove instrumental broadly in surface physics and in various nanophotonics applications.

Effect of severe plastic deformation on the structure and mechanical properties of Al-Cu-Mg alloy

NASA Astrophysics Data System (ADS)

Khafizova, E.; Islamgaliev, R.

2014-08-01

Aluminum Al-Cu-Mg alloy has been subjected to high pressure torsion (HPT) and equal-channel angular pressing (ECAP) at various temperatures. An ultrafine-grained (UFG) structure thermally stable up to a temperature of 175 °C was produced in all the investigated samples. Simultaneous increase in strength and ductility has been demonstrated in an ECAPed sample in comparison with a coarse-grained sample subjected to standard treatment.

Spectroscopic and first-principles calculation studies of the chemical forms of palladium ion in nitric acid solution for development of disposal of high-level radioactive nuclear wastes

NASA Astrophysics Data System (ADS)

Watanabe, Shinta; Sato, Toshikazu; Yoshida, Tomoko; Nakaya, Masato; Yoshino, Masahito; Nagasaki, Takanori; Inaba, Yusuke; Takeshita, Kenji; Onoe, Jun

2018-04-01

We have investigated the chemical forms of palladium (Pd) ion in nitric acid solution, using XAFS/UV-vis spectroscopic and first-principles methods in order to develop the disposal of high-level radioactive nuclear liquid wastes (HLLW: radioactive metal ions in 2 M nitric acid solution). The results of theoretical calculations and XAFS/UV-vis spectroscopy indicate that Pd is a divalent ion and forms a square-planar complex structure coordinated with four nitrate ions, [Pd(NO3)4]2-, in nitric acid solution. This complex structure is also thermodynamically predicted to be most stable among complexes [Pd(H2O)x(NO3)4-x]x-2 (x = 0-4). Since the overall feature of UV-vis spectra of the Pd complex was independent of nitric acid concentration in the range 1-6 M, the structure of the Pd complex remains unchanged in this range. Furthermore, we examined the influence of γ-ray radiation on the [Pd(NO3)4]2- complex, using UV-vis spectroscopy, and found that UV-vis spectra seemed not to be changed even after 1.0 MGy irradiation. This implies that the Pd complex structure will be still stable in actual HLLW. These findings obtained above are useful information to develop the vitrification processes for disposal of HLLW.

The Role of Teak Leaves (Tectona grandis), Rhizobium, and Vesicular-Arbuscular Mycorrhizae on Improving Soil Structure and Soil Nutrition

NASA Astrophysics Data System (ADS)

Yuliani; Rahayu, Y. S.

2018-01-01

Calcium is the largest mineral in calcareous soils. High levels of calcium carbonate lead to phosphate deposition. Nutrient deficiencies in calcareous soil (mainly Phosphate and Nitrogen) resulted only certain crops with a wide range of tolerances that can grow. Meanwhile, dynamics nutrient in calcareous soils also depend on the topography and decomposition of the litter in the growing vegetation. The purpose of this study was to describe the pattern of nutrient enhancement and soil-texture structures on calcareous soils after littering the teak leaves, Rhizobium and Vesicular Arbuscular Mycorrhiza. The research parameters were the concentration of N, P, K; C/N ratio, humid acid content, and soil structure, which measured at days 30, 60, and 85 of soil decomposition process. The results showed that at days 30, the texture and structure of the soil tend to be stable (porosity 31.2, DMR 1.93, moisture content 0.36, sandy clay) while at days 85 has been very stable (porosity 49.8; Water content 0.28, sandy clay). While C and N organic, N and K concentration at days 30 showed low value (C organic 1.03, N 0.12, K 0.49, C / N ratio 9). This condition is almost unchanged at days 85. While the P value shows very high value (60.53) at days 30 although after 60 days the P content showed a decrease.

Rheology Gradients at the Base of the Lithosphere and the Stabilization of Deep Mantle Plumes in Stagnant-Lid Planets

NASA Astrophysics Data System (ADS)

King, S. D.

2017-12-01

In high-Rayleigh-number, spherical-shell convection, such as one expects to find in the interiors of large silicate planetary bodies, plumes will migrate unless they are anchored to fixed structures. Within the Earth LLSVPs or core-mantle boundary topography have been proposed to anchor deep mantle plumes, fixing the location of hotspots. The relative stability of volcanic features on Mars and Venus, which are thought to be related to mantle plumes, have not be satisfactorily explained. Thus, it is surprising to see high-Rayleigh-number, stagnant-lid, spherical-shell convection calculations where plumes seeded by the structure of the initial condition persist in a stable configuration for more than 1 Gyr. By comparing calculations with a fixed lithospheric rheology structure with a lithosphere rheology determined by temperature and pressure, I show that in these calculations, topography on the base of the stagnant lid (i.e., the lithosphere-asthenosphere boundary) is responsible for the spatial stability of the plumes. If there is symmetry in the plume distribution, this symmetry can prevent the lithosphere becoming unstable and overturning, leading to a significantly over-thickened lithosphere relative to predictions based on scaling laws. This is confirmed by considering an identical calculation where the symmetry in the plume distribution is broken. I discuss geological and geophysical implications for planetary bodies resulting of long-lived, stable, mantle structures.

Convergent evolution of plant and animal embryo defences by hyperstable non-digestible storage proteins.

PubMed

Pasquevich, María Yanina; Dreon, Marcos Sebastián; Qiu, Jian-Wen; Mu, Huawei; Heras, Horacio

2017-11-20

Plants have evolved sophisticated embryo defences by kinetically-stable non-digestible storage proteins that lower the nutritional value of seeds, a strategy that have not been reported in animals. To further understand antinutritive defences in animals, we analysed PmPV1, massively accumulated in the eggs of the gastropod Pomacea maculata, focusing on how its structure and structural stability features affected its capacity to withstand passage through predator guts. The native protein withstands >50 min boiling and resists the denaturing detergent sodium dodecyl sulphate (SDS), indicating an unusually high structural stability (i.e., kinetic stability). PmPV1 is highly resistant to in vitro proteinase digestion and displays structural stability between pH 2.0-12.0 and 25-85 °C. Furthermore, PmPV1 withstands in vitro and mice digestion and is recovered unchanged in faeces, supporting an antinutritive defensive function. Subunit sequence similarities suggest a common origin and tolerance to mutations. This is the first known animal genus that, like plant seeds, lowers the nutritional value of eggs by kinetically-stable non-digestible storage proteins that survive the gut of predators unaffected. The selective pressure of the harsh gastrointestinal environment would have favoured their appearance, extending by convergent evolution the presence of plant-like hyperstable antinutritive proteins to unattended reproductive stages in animals.

Novel synthesis approach for stable sodium superoxide (NaO2) nanoparticles for LPG sensing application

NASA Astrophysics Data System (ADS)

Nemade, Kailash; Waghuley, Sandeep

2017-05-01

The synthesis of stable superoxide is still great challenge for the researchers working in the field of materials science. Through this letter, we report the novel and simple synthesis approach for the preparation of stable sodium superoxide (NaO2) nanoparticles. NaO2 nanoparticles were prepared by a spray pyrolysis technique, under oxygen rich environment for gas sensing application. The texture characterizations show that as-obtained NaO2 nanoparticles have high structural purity. Most importantly, NaO2 nanoparticles exhibits higher sensing response, shorter response time and recovery time, low operating temperature and good stability during sensing of liquefied petroleum gas (LPG). The main accomplishment of present work is that as-fabricated sensor has low operating temperature (423 K), which is below auto-ignition temperature of LPG. The gas sensing mechanism of NaO2 nanoparticles was discussed without the conventional oxygen bridging mechanism. Through this short communication, LPG sensing application of stable sodium superoxide nanoparticle is explored.

Formation and structure of stable aggregates in binary diffusion-limited cluster-cluster aggregation processes

NASA Astrophysics Data System (ADS)

López-López, J. M.; Moncho-Jordá, A.; Schmitt, A.; Hidalgo-Álvarez, R.

2005-09-01

Binary diffusion-limited cluster-cluster aggregation processes are studied as a function of the relative concentration of the two species. Both, short and long time behaviors are investigated by means of three-dimensional off-lattice Brownian Dynamics simulations. At short aggregation times, the validity of the Hogg-Healy-Fuerstenau approximation is shown. At long times, a single large cluster containing all initial particles is found to be formed when the relative concentration of the minority particles lies above a critical value. Below that value, stable aggregates remain in the system. These stable aggregates are composed by a few minority particles that are highly covered by majority ones. Our off-lattice simulations reveal a value of approximately 0.15 for the critical relative concentration. A qualitative explanation scheme for the formation and growth of the stable aggregates is developed. The simulations also explain the phenomenon of monomer discrimination that was observed recently in single cluster light scattering experiments.

Iron-titanium oxyhydroxides which transport water into the deep upper mantle and mantle transition zone

NASA Astrophysics Data System (ADS)

Matsukage, K. N.; Nishihara, Y.

2015-12-01

We experimentally discovered a new hydrous phase in the system FeOOH-TiO2 at pressures of 10-16 GPa and temperatures of 1000-1600°C which corresponds to conditions of the deep upper mantle and the Earth's mantle transition zone. Seven different compositions in the FeOOH-TiO2 system having molar ratios of x = Ti/(Fe + Ti) = 0, 0.125, 0.25, 0.375, 0.5, 0.75 that were prepared by mixing reagent grade a-FeOOH (goethite) and TiO2 (anatase) powders were used as starting materials. High-pressure and high-temperature experiments were carried out using Kawai-type multi-anvil apparatus (Orange-1000 at Ehime University and SPI-1000 at Tokyo Institute of Technology). In this system, we identified two stable iron-titanium oxyhydroxide phases whose estimated composition is expressed by (FeH)1 - xTixO2 . One is the Fe-rich solid solution (x < 0.23) with e-FeOOH type crystal structure (e-phase, orthorhombic, P21nm) that was described by the previous studies (e.g., Suzuki 2010), and the other is the more Ti-rich solid solution (x > 0.35) with a-PbO2 type structure (a-phase, orthorhombic, Pbcn). The a-phase is stable up to 1500ºC for a composition of x = 0.5 and at least to 1600ºC for x = 0.75. Our result means that this phase is stable at average mantle temperature in the Earth's mantle transition zone. The Iron-titanium-rich hydrous phases was possible to stable in basalt + H2O system (e.g., Hashimoto and Matsukage 2013). Therefore our findings suggest that water transport in the Earth's deep interior is probably much more efficient than had been previously thought.

The Free Jet Microwave Spectrum of 2-PHENYLETHYLAMINE-WATER

NASA Astrophysics Data System (ADS)

Melandri, Sonia; Giuliano, B. Michela; Maris, Assimo; Caminati, Walther

2009-06-01

2-Phenylethylamine (PEA) is the parent structure for a variety of important compounds including dopamine, tyrosine, anphetamine and adrenaline. Due to the flexibility of the side chain, the conformational hypersurface of the isolated molecule contains several minima at relatively low energy. The conformational surface was studied by various spectroscopic and theoretical techniques and four of the five stable conformers were detected. The most stable conformers observed in isolated conditions are those in which the methylene side chain is folded into a gauche structure and the amino hydrogen is oriented towards the aromatic ring to form a weakly hydrogen bonded structure, while in the less stable conformers the amino group is in the anti position, thus the energy difference between the gauche and anti conformers (ca 4 kJ mol^{-1}) represents the energy associated with this weak interaction. Since bioactive molecules can be found in different environments including aqueous media and rotational spectroscopy coupled with high level ab initio calculations gives the most detailed structural picture, we studied the free jet microwave spectrum of the adducts formed between PEA and water in the region 60-78 GHz. The dominant spectrum is that of the 1:1 adduct of PEA and water where PEA is in its most stable gauche conformation and the water molecole is bound to the nitrogen lone pair. The orientation of the water molecole is such that the oxygen atom is closest (ca 2.5 Å) and equidistant from the ring and chain hydrogen atoms. The experimental data were complemented by ab initio calculations at the MP2/6311++G** level of theory; several stable conformations of the PEA-W have been characterized and the observed structure corresponds to the global minimum. The bonding of water seems to affect only slightly the structure of isolated PEA and the main structural parameters of the flexible amino side chain remain basically unaltered. Some lines still remain unassigned in the spectrum and we are hoping to assign them to a second conformational species of PEA-W. (a) S. J. Martinez, J. C. Alfano and D. H. Levy J. Mol. Struct. 158 82 1993. (b)P. D. Godfrey,L. D. Hatherley and R. D. Brown J. Am. Chem. Soc. 117 8204 1995. (c)S. Sun and E. R. Bernstein J. Am. Chem. Soc. 118 5086 1996. (d) J. A. Dickinson, M. R. Hockridge, R. T. Kroemer, E. G. Robertson, J. P. Simons, J. McCombie and M. Walker J. Am. Chem. Soc. 120 2622 1998. (e) J. C. Lopez, V. Cortijo, S. Blanco and J. Alonso PCCP 9 4521 2007.

High-temperature-stable and regenerable catalysts: platinum nanoparticles in aligned mesoporous silica wells.

PubMed

Xiao, Chaoxian; Maligal-Ganesh, Raghu V; Li, Tao; Qi, Zhiyuan; Guo, Zhiyong; Brashler, Kyle T; Goes, Shannon; Li, Xinle; Goh, Tian Wei; Winans, Randall E; Huang, Wenyu

2013-10-01

We report the synthesis, structural characterization, thermal stability study, and regeneration of nanostructured catalysts made of 2.9 nm Pt nanoparticles sandwiched between a 180 nm SiO2 core and a mesoporous SiO2 shell. The SiO2 shell consists of 2.5 nm channels that are aligned perpendicular to the surface of the SiO2 core. The nanostructure mimics Pt nanoparticles that sit in mesoporous SiO2 wells (Pt@MSWs). By using synchrotron-based small-angle X-ray scattering, we were able to prove the ordered structure of the aligned mesoporous shell. By using high-temperature cyclohexane dehydrogenation as a model reaction, we found that the Pt@MSWs of different well depths showed stable activity at 500 °C after the induction period. Conversely, a control catalyst, SiO2 -sphere-supported Pt nanoparticles without a mesoporous SiO2 shell (Pt/SiO2 ), was deactivated. We deliberately deactivated the Pt@MSWs catalyst with a 50 nm deep well by using carbon deposition induced by a low H2 /cyclohexane ratio. The deactivated Pt@MSWs catalyst was regenerated by calcination at 500 °C with 20 % O2 balanced with He. After the regeneration treatments, the activity of the Pt@MSWs catalyst was fully restored. Our results suggest that the nanostructured catalysts-Pt nanoparticles confined inside mesoporous SiO2 wells-are stable and regenerable for treatments and reactions that require high temperatures. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nickel-free austenitic stainless steels for medical applications.

PubMed

Yang, Ke; Ren, Yibin

2010-02-01

The adverse effects of nickel ions being released into the human body have prompted the development of high-nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel in medical stainless steels, the advantages of nitrogen in stainless steels, and emphatically, the development of high-nitrogen nickel-free stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength and good plasticity, better corrosion and wear resistances, and superior biocompatibility compared to the currently used 316L stainless steel, the newly developed high-nitrogen nickel-free stainless steel is a reliable substitute for the conventional medical stainless steels.

Nickel-free austenitic stainless steels for medical applications

PubMed Central

Yang, Ke; Ren, Yibin

2010-01-01

The adverse effects of nickel ions being released into the human body have prompted the development of high-nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel in medical stainless steels, the advantages of nitrogen in stainless steels, and emphatically, the development of high-nitrogen nickel-free stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength and good plasticity, better corrosion and wear resistances, and superior biocompatibility compared to the currently used 316L stainless steel, the newly developed high-nitrogen nickel-free stainless steel is a reliable substitute for the conventional medical stainless steels. PMID:27877320

Calculation of Half-Metal, Debye and Curie Temperatures of Co2VAl Compound: First Principles Study

NASA Astrophysics Data System (ADS)

Arash, Boochani; Heidar, Khosravi; Jabbar, Khodadadi; Shahram, Solaymani; Masoud Majidiyan, Sarmazdeh; Rohollah Taghavi, Mendi; Sayed, Mohammad Elahi

2015-05-01

By FP-LAPW calculations, the structural, elastic, Debye and Curie temperatures, electronic and magnetic properties of Co2 VAl are investigated. The results indicate that Ferromagnetic (FM) phase is more stable than Anti-Ferromagnetic (AFM) and Non-magnetic (NM) ones. In addition, C11-C12 > 0, C44 > 0, and B > 0 so Co2VAl is an elastically stable material with high Debye temperature. Also, the B/G ratio exhibits a ductility behavior. The relatively high Curie temperature provides it as a favorable material for spintronic application. It's electronic and magnetic properties are studied by GGA+U approach leading to a 100% spin polarization at Fermi level. Supported by the simulation of Nano Physics Lab center of Kermanshah Branch, Islamic Azad University

Na4Mn9O18/Carbon Nanotube Composite as a High Electrochemical Performance Material for Aqueous Sodium-Ion Batteries.

PubMed

Yin, Fuxing; Liu, Zhengjun; Yang, Shuang; Shan, Zhenzhen; Zhao, Yan; Feng, Yuting; Zhang, Chengwei; Bakenov, Zhumabay

2017-10-17

The aqueous sodium-ion battery (ASIB) is one of the promising new energy storage systems owing to the abundant resources of sodium as well as efficiency and safety of electrolyte. Herein, we report an ASIB system with Na 4 Mn 9 O 18 /carbon nanotube (NMO/CNT) as cathode, metal Zn as anode and a novel Na + /Zn 2+ mixed ion as electrolyte. The NMO/CNT with microspherical structure is prepared by a simple spray-drying method. The prepared battery delivers a high reversible specific capacity and stable cyclability. Furthermore, the battery displays a stable reversible discharge capacity of 53.2 mAh g -1 even at a high current rate of 4 C after 150 cycles. Our results confirm that the NMO/CNT composite is a promising electrode cathode material for ASIBs.

Nano-laminate-based ignitors

DOEpatents

Barbee, Jr., Troy W.; Simpson, Randall L.; Gash, Alexander E.; Satcher, Jr., Joe H.

2012-12-11

Sol-gel chemistry is used to prepare igniters comprising energetic multilayer structures coated with energetic materials. These igniters can be tailored to be stable to environmental aging, i.e., where the igniters are exposed to extremes of both hot and cold temperatures (-30 C to 150 C) and both low (0%) and high relative humidity (100%).

Nano-laminate-based ignitors

DOEpatents

Barbee, Jr., Troy W.; Simpson, Randall L [Livermore, CA; Gash, Alexander E [Brentwood, CA; Satcher, Jr., Joe H.

2011-05-31

Sol-gel chemistry is used to prepare igniters comprising energetic multilayer structures coated with energetic booster materials. These igniters can be tailored to be stable to environmental aging, i.e., where the igniters are exposed to extremes of both hot and cold temperatures (-30 C to 150 C) and both low (0%) and high relative humidity (100%).

Genome-Wide Prediction of Intrinsic Disorder; Sequence Alignment of Intrinsically Disordered Proteins

ERIC Educational Resources Information Center

Midic, Uros

2012-01-01

Intrinsic disorder (ID) is defined as a lack of stable tertiary and/or secondary structure under physiological conditions in vitro. Intrinsically disordered proteins (IDPs) are highly abundant in nature. IDPs possess a number of crucial biological functions, being involved in regulation, recognition, signaling and control, e.g. their functional…

Sensitivity of bandpass filters using recirculating delay-line structures

NASA Astrophysics Data System (ADS)

Heyde, Eric C.

1996-12-01

Recirculating delay lines have value notably as sensors and optical signal processors. Most useful applications depend on a high-finesse response from a network. A proof that, with given response parameters, more complex systems can produce behavior that is more stable to the effects of nonidealities than a single recirculating loop is presented.

Stable and rigid DTPA-like paramagnetic tags suitable for in vitro and in situ protein NMR analysis.

PubMed

Chen, Jia-Liang; Zhao, Yu; Gong, Yan-Jun; Pan, Bin-Bin; Wang, Xiao; Su, Xun-Cheng

2018-02-01

Organic synthesis of a ligand with high binding affinities for paramagnetic lanthanide ions is an effective way of generating paramagnetic effects on proteins. These paramagnetic effects manifested in high-resolution NMR spectroscopy are valuable dynamic and structural restraints of proteins and protein-ligand complexes. A paramagnetic tag generally contains a metal chelating moiety and a reactive group for protein modification. Herein we report two new DTPA-like tags, 4PS-PyDTTA and 4PS-6M-PyDTTA that can be site-specifically attached to a protein with a stable thioether bond. Both protein-tag adducts form stable lanthanide complexes, of which the binding affinities and paramagnetic tensors are tunable with respect to the 6-methyl group in pyridine. Paramagnetic relaxation enhancement (PRE) effects of Gd(III) complex on protein-tag adducts were evaluated in comparison with pseudocontact shift (PCS), and the results indicated that both 4PS-PyDTTA and 4PS-6M-PyDTTA tags are rigid and present high-quality PREs that are crucially important in elucidation of the dynamics and interactions of proteins and protein-ligand complexes. We also show that these two tags are suitable for in-situ protein NMR analysis.

Time-varying and time-invariant dimensions of depression in children and adolescents: Implications for cross-informant agreement.

PubMed

Cole, David A; Martin, Joan M; Jacquez, Farrah M; Tram, Jane M; Zelkowitz, Rachel; Nick, Elizabeth A; Rights, Jason D

2017-07-01

The longitudinal structure of depression in children and adolescents was examined by applying a Trait-State-Occasion structural equation model to 4 waves of self, teacher, peer, and parent reports in 2 age groups (9 to 13 and 13 to 16 years old). Analyses revealed that the depression latent variable consisted of 2 longitudinal factors: a time-invariant dimension that was completely stable over time and a time-varying dimension that was not perfectly stable over time. Different sources of information were differentially sensitive to these 2 dimensions. Among adolescents, self- and parent reports better reflected the time-invariant aspects. For children and adolescents, peer and teacher reports better reflected the time-varying aspects. Relatively high cross-informant agreement emerged for the time-invariant dimension in both children and adolescents. Cross-informant agreement for the time-varying dimension was high for adolescents but very low for children. Implications emerge for theoretical models of depression and for its measurement, especially when attempting to predict changes in depression in the context of longitudinal studies. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Resolving phase stability in the Ti-O binary with first-principles statistical mechanics methods

NASA Astrophysics Data System (ADS)

Gunda, N. S. Harsha; Puchala, Brian; Van der Ven, Anton

2018-03-01

The Ti-O system consists of a multitude of stable and metastable oxides that are used in wide ranging applications. In this work we investigate phase stability in the Ti-O binary from first principles. We perform a systematic search for ground state structures as a function of oxygen concentration by considering oxygen-vacancy and/or titanium-vacancy orderings over four parent crystal structures: (i) hcp Ti, (ii) ω -Ti, (iii) rocksalt, and (iv) hcp oxygen containing interstitial titanium. We explore phase stability at finite temperature using cluster expansion Hamiltonians and Monte Carlo simulations. The calculations predict a high oxygen solubility in hcp Ti and the stability of suboxide phases that undergo order-disorder transitions upon heating. Vacancy ordered rocksalt phases are also predicted at low temperature that disorder to form an extended solid solution at high temperatures. Predicted stable and metastable phase diagrams are qualitatively consistent with experimental observations, however, important discrepancies are revealed between first-principles density functional theory predictions of phase stability and the current understanding of phase stability in this system.

Performance evaluation of a non-woven lithium ion battery separator prepared through a paper-making process

NASA Astrophysics Data System (ADS)

Huang, Xiaosong

2014-06-01

Porous separator functions to electrically insulate the negative and positive electrodes yet communicate lithium ions between the two electrodes when infiltrated with a liquid electrolyte. The separator must fulfill numerous requirements (e.g. permeability, wettability, and thermal stability) in order to optimize the abuse tolerance and electrochemical performance of a battery. Non-woven mat separators have advantages such as high porosity and heat resistance. However, their applications in lithium ion batteries are very limited as their inadequate pore structures could cause accelerated battery performance degradation and even internal short. This work features the development of thermally stable non-woven composite separators using a low cost paper-making process. The composite separators offer significantly improved thermal dimensional stability and exhibit superior wettability by the liquid electrolyte compared to a conventional polypropylene separator. The open porous structures of the non-woven composite separators also resulted in high effective ionic conductivities. The electrochemical performance of the composite separators was tested in coin cells. Stable cycle performances and improved rate capabilities have been observed for the coin cells with these composite separators.

Protein nanocrystallography: growth mechanism and atomic structure of crystals induced by nanotemplates.

PubMed

Pechkova, E; Vasile, F; Spera, R; Fiordoro, S; Nicolini, C

2005-11-01

Protein nanocrystallography, a new technology for crystal growth based on protein nanotemplates, has recently been shown to produce diffracting, stable and radiation-resistant lysozyme crystals. This article, by computing these lysozyme crystals' atomic structures, obtained by the diffraction patterns of microfocused synchrotron radiation, provides a possible mechanism for this increased stability, namely a significant decrease in water content accompanied by a minor but significant alpha-helix increase. These data are shown to be compatible with the circular dichroism and two-dimensional Fourier transform spectra of high-resolution H NMR of proteins dissolved from the same nanotemplate-based crystal versus those from a classical crystal. Finally, evidence for protein direct transfer from the nanotemplate to the drop and the participation of the template proteins in crystal nucleation and growth is provided by high-resolution NMR spectrometry and mass spectrometry. Furthermore, the lysozyme nanotemplate appears stable up to 523 K, as confirmed by a thermal denaturation study using spectropolarimetry. The overall data suggest that heat-proof lysozyme presence in the crystal provides a possible explanation of the crystal's resistance to synchrotron radiation.

Biocellulose-based flexible magnetic paper

NASA Astrophysics Data System (ADS)

Barud, H. S.; Tercjak, A.; Gutierrez, J.; Viali, W. R.; Nunes, E. S.; Ribeiro, S. J. L.; Jafellici, M.; Nalin, M.; Marques, R. F. C.

2015-05-01

Biocellulose or bacterial cellulose (BC) is a biocompatible (nano) material produced with a three-dimensional network structure composed of microfibrils having nanometric diameters obtained by the Gluconacetobacter xylinus bacteria. BC membranes present relatively high porosity, allowing the incorporation or synthesis in situ of inorganic nanoparticles for multifunctional applications and have been used as flexible membranes for incorporation of magnetic nanocomposite. In this work, highly stable superparamagnetic iron oxide nanoparticles (SPION), functionalized with polyethylene glycol (PEG), with an average diameter of 5 nm and a saturation magnetization of 41 emu/g at 300 K were prepared. PEG-Fe2O3 hybrid was dispersed by mixing a pristine BC membrane in a stable aqueous dispersion of PEG-SPION. The PEG chains at PEG-SPION's surface provide a good permeability and strong affinity between the BC chains and SPION through hydrogen-bonding interactions. PEG-SPION also allow the incorporation of higher content of nanoparticles without compromising the mechanical properties of the nanocomposite. Structural and magnetic properties of the composite have been characterized by XRD, SEM, energy-dispersive X-ray spectroscopy (EDX), magnetization, Raman spectroscopy, and magnetic force microscopy.

Self-Healing Textile: Enzyme Encapsulated Layer-by-Layer Structural Proteins.

PubMed

Gaddes, David; Jung, Huihun; Pena-Francesch, Abdon; Dion, Genevieve; Tadigadapa, Srinivas; Dressick, Walter J; Demirel, Melik C

2016-08-10

Self-healing materials, which enable an autonomous repair response to damage, are highly desirable for the long-term reliability of woven or nonwoven textiles. Polyelectrolyte layer-by-layer (LbL) films are of considerable interest as self-healing coatings due to the mobility of the components comprising the film. In this work mechanically stable self-healing films were fabricated through construction of a polyelectrolyte LbL film containing squid ring teeth (SRT) proteins. SRTs are structural proteins with unique self-healing properties and high elastic modulus in both dry and wet conditions (>2 GPa) due to their semicrystalline architecture. We demonstrate LbL construction of multilayers containing native and recombinant SRT proteins capable of self-healing defects. Additionally, we show these films are capable of utilizing functional biomolecules by incorporating an enzyme into the SRT multilayer. Urease was chosen as a model enzyme of interest to test its activity via fluorescence assay. Successful construction of the SRT films demonstrates the use of mechanically stable self-healing coatings, which can incorporate biomolecules for more complex protective functionalities for advanced functional fabrics.

Efficient Red-Emitting Platinum Complex with Long Operational Stability.

PubMed

Fleetham, Tyler; Li, Guijie; Li, Jian

2015-08-05

A tetradentate cyclometalated Pt(II) complex, PtN3N-ptb, was developed as an emissive dopant for stable and efficient red phosphorescent OLEDs. Devices employing PtN3N-ptb in electrochemically stable device architectures achieved long operational lifetimes with estimated LT97, of over 600 h at luminances of 1000 cd/m(2). Such long operational lifetimes were achieved utilizing only literature reported host, transporting and blocking materials with known molecular structures. Additionally, a thorough study of the effects of various host and transport materials on the efficiency, turn on voltage, and stability of the devices was carried out. Ultimately, maximum forward viewing EQEs as high as 21.5% were achieved, demonstrating that Pt(II) complexes can act as stable and efficient dopants with operational lifetimes comparable or superior to those of the best literature-reported Ir(III) complexes.

Decadal stability in genetic variation and structure in the intertidal seaweed Fucus serratus (Heterokontophyta: Fucaceae).

PubMed

Jueterbock, Alexander; Coyer, James A; Olsen, Jeanine L; Hoarau, Galice

2018-06-15

The spatial distribution of genetic diversity and structure has important implications for conservation as it reveals a species' strong and weak points with regard to stability and evolutionary capacity. Temporal genetic stability is rarely tested in marine species other than commercially important fishes, but is crucial for the utility of temporal snapshots in conservation management. High and stable diversity can help to mitigate the predicted northward range shift of seaweeds under the impact of climate change. Given the key ecological role of fucoid seaweeds along rocky shores, the positive effect of genetic diversity may reach beyond the species level to stabilize the entire intertidal ecosystem along the temperate North Atlantic. In this study, we estimated the effective population size, as well as temporal changes in genetic structure and diversity of the seaweed F. serratus using 22 microsatellite markers. Samples were taken across latitudes and a range of temperature regimes at seven locations with decadal sampling (2000 and 2010). Across latitudes, genetic structure and diversity remained stable over 5-10 generations. Stable small-scale structure enhanced regional diversity throughout the species' range. In accordance with its biogeographic history, effective population size and diversity peaked in the species' mid-range in Brittany (France), and declined towards its leading and trailing edge to the north and south. At the species' southern edge, multi-locus-heterozygosity displayed a strong decline from 1999 to 2010. Temporally stable genetic structure over small spatial scales is a potential driver for local adaptation and species radiation in the genus Fucus. Survival and adaptation of the low-diversity leading edge of F. serratus may be enhanced by regional gene flow and 'surfing' of favorable mutations or impaired by the accumulation of deleterious mutations. Our results have clear implications for the conservation of F. serratus at its genetically unique southern edge in Northwest Iberia, where increasing temperatures are likely the major cause for the decline not only of F. serratus, but also other intertidal and subtidal macroalgae. We expect that F. serratus will disappear from Northwest Iberia by 2100 if genetic rescue is not induced by the influx of genetic variation from Brittany.

First principles study of LiAlO2: new dense monoclinic phase under high pressure

NASA Astrophysics Data System (ADS)

Liu, Guangtao; Liu, Hanyu

2018-03-01

In this work, we have systematically explored the crystal structures of LiAlO2 at high pressures using crystal structure prediction method in combination with the density functional theory calculations. Besides the reported α, β, γ, δ and ɛ-phases, here we propose a new monoclinic ζ-LiAlO2 (C2/m) structure, which becomes thermodynamically and dynamically stable above 27 GPa. It is found that the cation coordination number increases from 4 to 6 under compression. Consisting of the compact {LiO6} and {AlO6} octahedrons, the newly-discovered ζ-phase possesses a very high density. Further electronic calculations show that LiAlO2 is still an insulator up to 60 GPa, and its bandgap increases upon compression. The present study advances our understanding on the crystal structures and high-pressure phase transitions of LiAlO2 that may trigger applications in multiple areas of industry and provoke more related basic science research.

Anomalous anisotropic compression behavior of superconducting CrAs under high pressure

PubMed Central

Yu, Zhenhai; Wu, Wei; Hu, Qingyang; Zhao, Jinggeng; Li, Chunyu; Yang, Ke; Cheng, Jinguang; Luo, Jianlin; Wang, Lin; Mao, Ho-kwang

2015-01-01

CrAs was observed to possess the bulk superconductivity under high-pressure conditions. To understand the superconducting mechanism and explore the correlation between the structure and superconductivity, the high-pressure structural evolution of CrAs was investigated using the angle-dispersive X-ray diffraction (XRD) method. The structure of CrAs remains stable up to 1.8 GPa, whereas the lattice parameters exhibit anomalous compression behaviors. With increasing pressure, the lattice parameters a and c both demonstrate a nonmonotonic change, and the lattice parameter b undergoes a rapid contraction at ∼0.18−0.35 GPa, which suggests that a pressure-induced isostructural phase transition occurs in CrAs. Above the phase transition pressure, the axial compressibilities of CrAs present remarkable anisotropy. A schematic band model was used to address the anomalous compression behavior of CrAs. The present results shed light on the structural and related electronic responses to high pressure, which play a key role toward understanding the superconductivity of CrAs. PMID:26627230

The cross-national structure of mental disorders: results from the World Mental Health Surveys.

PubMed

de Jonge, Peter; Wardenaar, Klaas J; Lim, Carmen C W; Aguilar-Gaxiola, Sergio; Alonso, Jordi; Andrade, Laura Helena; Bunting, Brendan; Chatterji, Somnath; Ciutan, Marius; Gureje, Oye; Karam, Elie G; Lee, Sing; Medina-Mora, Maria Elena; Moskalewicz, Jacek; Navarro-Mateu, Fernando; Pennell, Beth-Ellen; Piazza, Marina; Posada-Villa, José; Torres, Yolanda; Kessler, Ronald C; Scott, Kate

2017-12-19

The patterns of comorbidity among mental disorders have led researchers to model the underlying structure of psychopathology. While studies have suggested a structure including internalizing and externalizing disorders, less is known with regard to the cross-national stability of this model. Moreover, little data are available on the placement of eating disorders, bipolar disorder and psychotic experiences (PEs) in this structure. We evaluated the structure of mental disorders with data from the World Health Organization Composite International Diagnostic Interview, including 15 lifetime mental disorders and six PEs. Respondents (n = 5478-15 499) were included from 10 high-, middle- and lower middle-income countries across the world aged 18 years or older. Confirmatory factor analyses (CFAs) were used to evaluate and compare the fit of different factor structures to the lifetime disorder data. Measurement invariance was evaluated with multigroup CFA (MG-CFA). A second-order model with internalizing and externalizing factors and fear and distress subfactors best described the structure of common mental disorders. MG-CFA showed that this model was stable across countries. Of the uncommon disorders, bipolar disorder and eating disorder were best grouped with the internalizing factor, and PEs with a separate factor. These results indicate that cross-national patterns of lifetime common mental-disorder comorbidity can be explained with a second-order underlying structure that is stable across countries and can be extended to also cover less common mental disorders.

Robust high pressure stability and negative thermal expansion in sodium-rich antiperovskites Na 3OBr and Na 4OI 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yonggang; Wen, Ting; Park, Changyong

2016-01-14

The structure stability under high pressure and thermal expansion behavior of Na 3OBr and Na 4OI 2, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temp. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na 3OBr and Na 4OI 2, resp. The cubic Na 3OBr structure and tetragonal Na 4OI 2 with intergrowth K 2NiF 4 structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na 4OI 2 exhibits nearly isotropic compressibility. Neg. thermal expansion wasmore » obsd. at low temp. range (20-80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined. and confirmed by first-principles calculations. among various possible polymorphisms qualitatively. The results provide in-depth understanding of the neg. thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.« less

Improving the apo-state detergent stability of NTS1 with CHESS for pharmacological and structural studies.

PubMed

Scott, Daniel J; Kummer, Lutz; Egloff, Pascal; Bathgate, Ross A D; Plückthun, Andreas

2014-11-01

The largest single class of drug targets is the G protein-coupled receptor (GPCR) family. Modern high-throughput methods for drug discovery require working with pure protein, but this has been a challenge for GPCRs, and thus the success of screening campaigns targeting soluble, catalytic protein domains has not yet been realized for GPCRs. Therefore, most GPCR drug screening has been cell-based, whereas the strategy of choice for drug discovery against soluble proteins is HTS using purified proteins coupled to structure-based drug design. While recent developments are increasing the chances of obtaining GPCR crystal structures, the feasibility of screening directly against purified GPCRs in the unbound state (apo-state) remains low. GPCRs exhibit low stability in detergent micelles, especially in the apo-state, over the time periods required for performing large screens. Recent methods for generating detergent-stable GPCRs, however, offer the potential for researchers to manipulate GPCRs almost like soluble enzymes, opening up new avenues for drug discovery. Here we apply cellular high-throughput encapsulation, solubilization and screening (CHESS) to the neurotensin receptor 1 (NTS1) to generate a variant that is stable in the apo-state when solubilized in detergents. This high stability facilitated the crystal structure determination of this receptor and also allowed us to probe the pharmacology of detergent-solubilized, apo-state NTS1 using robotic ligand binding assays. NTS1 is a target for the development of novel antipsychotics, and thus CHESS-stabilized receptors represent exciting tools for drug discovery. Copyright © 2014 Elsevier B.V. All rights reserved.

Thermodynamic analysis of water molecules at the surface of proteins and applications to binding site prediction and characterization.

PubMed

Beuming, Thijs; Che, Ye; Abel, Robert; Kim, Byungchan; Shanmugasundaram, Veerabahu; Sherman, Woody

2012-03-01

Water plays an essential role in determining the structure and function of all biological systems. Recent methodological advances allow for an accurate and efficient estimation of the thermodynamic properties of water molecules at the surface of proteins. In this work, we characterize these thermodynamic properties and relate them to various structural and functional characteristics of the protein. We find that high-energy hydration sites often exist near protein motifs typically characterized as hydrophilic, such as backbone amide groups. We also find that waters around alpha helices and beta sheets tend to be less stable than waters around loops. Furthermore, we find no significant correlation between the hydration site-free energy and the solvent accessible surface area of the site. In addition, we find that the distribution of high-energy hydration sites on the protein surface can be used to identify the location of binding sites and that binding sites of druggable targets tend to have a greater density of thermodynamically unstable hydration sites. Using this information, we characterize the FKBP12 protein and show good agreement between fragment screening hit rates from NMR spectroscopy and hydration site energetics. Finally, we show that water molecules observed in crystal structures are less stable on average than bulk water as a consequence of the high degree of spatial localization, thereby resulting in a significant loss in entropy. These findings should help to better understand the characteristics of waters at the surface of proteins and are expected to lead to insights that can guide structure-based drug design efforts. Copyright © 2011 Wiley Periodicals, Inc.

Construction of proteins with molecular recognition capabilities using α3β3 de novo protein scaffolds.

PubMed

Okura, Hiromichi; Mihara, Hisakazu; Takahashi, Tsuyoshi

2013-10-01

The molecular recognition ability of proteins is essential in biological systems, and therefore a considerable amount of effort has been devoted to constructing desired target-binding proteins using a variety of naturally occurring proteins as scaffolds. However, since generating a binding site in a native protein can often affect its structural properties, highly stable de novo protein scaffolds may be more amenable than the native proteins. We previously reported the generation of de novo proteins comprising three α-helices and three β-strands (α3β3) from a genetic library coding simplified amino acid sets. Two α3β3 de novo proteins, vTAJ13 and vTAJ36, fold into a native-like stable and molten globule-like structures, respectively, even though the proteins have similar amino acid compositions. Here, we attempted to create binding sites for the vTAJ13 and vTAJ36 proteins to prove the utility of de novo designed artificial proteins as a molecular recognition tool. Randomization of six amino acids at two linker sites of vTAJ13 and vTAJ36 followed by biopanning generated binding proteins that recognize the target molecules, fluorescein and green fluorescent protein, with affinities of 10(-7)-10(-8) M. Of note, the selected proteins from the vTAJ13-based library tended to recognize the target molecules with high specificity, probably due to the native-like stable structure of vTAJ13. Our studies provide an example of the potential of de novo protein scaffolds, which are composed of a simplified amino acid set, to recognize a variety of target compounds.

Theoretical investigation of stabilities and optical properties of Si12C12 clusters

NASA Astrophysics Data System (ADS)

Duan, Xiaofeng F.; Burggraf, Larry W.

2015-01-01

By sorting through hundreds of globally stable Si12C12 isomers using a potential surface search and using simulated annealing, we have identified low-energy structures. Unlike isomers knit together by Si-C bonds, the lowest energy isomers have segregated carbon and silicon regions that maximize stronger C-C bonding. Positing that charge separation between the carbon and silicon regions would produce interesting optical absorption in these cluster molecules, we used time-dependent density functional theory to compare the calculated optical properties of four isomers representing structural classes having different types of silicon and carbon segregation regions. Absorptions involving charge transfer between segregated carbon and silicon regions produce lower excitation energies than do structures having alternating Si-C bonding for which frontier orbital charge transfer is exclusively from separated carbon atoms to silicon atoms. The most stable Si12C12 isomer at temperatures below 1100 K is unique as regards its high symmetry and large optical oscillator strength in the visible blue. Its high-energy and low-energy visible transitions (1.15 eV and 2.56 eV) are nearly pure one-electron silicon-to-carbon transitions, while an intermediate energy transition (1.28 eV) is a nearly pure carbon-to-silicon one-electron charge transfer.

Reversible structural transformation and enhanced performance of PEDOT:PSS-based hybrid solar cells driven by light intensity.

PubMed

Thomas, Joseph Palathinkal; Srivastava, Saurabh; Zhao, Liyan; Abd-Ellah, Marwa; McGillivray, Donald; Kang, Jung Soo; Rahman, Md Anisur; Moghimi, Nafiseh; Heinig, Nina F; Leung, Kam Tong

2015-04-15

Hybrid solar cells made of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) and appropriate amounts of a cosolvent and a fluorosurfactant on planar n-type silicon substrates showed a photoconversion efficiency (PCE) of above 13%. These cells also exhibited stable, reproducible, and high external quantum efficiency (EQE) that was not sensitive to light-bias intensity (LBI). In contrast, solar cells made of pristine PSS showed low PCE and high EQE only under certain measurement conditions. The EQE was found to degrade with increasing LBI. Here we report that the LBI-sensitive variation of EQE of the low-PCE cells is related to a reversible structural transformation from a quinoid to a benzoid structure of PEDOT.

Structural, stability, and vibrational properties of BinPm clusters

NASA Astrophysics Data System (ADS)

Shen, Wanting; Han, Lihong; Liang, Dan; Zhang, Chunfang; Ruge, Quhe; Wang, Shumin; Lu, Pengfei

2018-04-01

An in-depth investigation is performed on stability mechanisms, electronic and optical properties of III-V semiconductor vapor phases clusters. First principles electronic structure calculations of CAM-B3LYP are performed on neutral BinPm (n + m ≤ 14) clusters. The geometrical evolution of all stable structures remains amorphous as the clusters size increases. Binding energies (BEs), energy gains and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gaps confirm that all four-atom structures of BinPm clusters have more stable optical properties. Orbitals composition and vibrational spectra of stable clusters are analyzed. Our calculations will contribute to the study of diluted bismuth alloys and compounds.

Production, Characterization, and Flocculation Mechanism of Cation Independent, pH Tolerant, and Thermally Stable Bioflocculant from Enterobacter sp. ETH-2

PubMed Central

Tang, Wei; Song, Liyan; Li, Dou; Qiao, Jing; Zhao, Tiantao; Zhao, Heping

2014-01-01

Synthetic high polymer flocculants, frequently utilized for flocculating efficiency and low cost, recently have been discovered as producing increased risk to human health and the environment. Development of a more efficient and environmentally sound alternative flocculant agent is investigated in this paper. Bioflocculants are produced by microorganisms and may exhibit a high rate of flocculation activity. The bioflocculant ETH-2, with high flocculating activity (2849 mg Kaolin particle/mg ETH-2), produced by strain Enterobacter sp. isolated from activated sludge, was systematically investigated with regard to its production, characterization, and flocculation mechanism. Analyses of microscopic observation, zeta potential and ETH-2 structure demonstrates the bridging mechanism, as opposed to charge neutralization, was responsible for flocculation of the ETH-2. ETH-2 retains high molecular weight (603 to 1820 kDa) and multi-functional groups (hydroxyl, amide and carboxyl) that contributed to flocculation. Polysaccharides mainly composed of mannose, glucose, and galactose, with a molar ratio of 1∶2.9∶9.8 were identified as the active constituents in bioflocculant. The structure of the long backbone with active sites of polysaccharides was determined as a primary basis for the high flocculation activity. Bioflocculant ETH-2 is cation independent, pH tolerant, and thermally stable, suggesting a potential fit for industrial application. PMID:25485629

Experimental investigation of broadband energy harvesting of a bi-stable composite piezoelectric plate

NASA Astrophysics Data System (ADS)

Pan, Diankun; Ma, Benbiao; Dai, Fuhong

2017-03-01

In this work, a bi-stable vibration energy harvester is presented to scavenge energy from ambient vibrations over a wide frequency range. This bi-stable harvester consists of a bi-stable hybrid composite plate as host structure and several pieces of piezoelectric ceramics. Three linear harvesters with the same geometry were employed as the control samples to illustrate the advantages of this bi-stable harvester. The voltage-frequency responses were measured with different g-level excitations, and the output powers across various resistances were measured at different frequencies and accelerations. Unlike the linear harvesters which are effective only near their natural frequencies, the obvious nonlinearities of this bi-stable harvester broaden its working bandwidth. Additionally, the characteristics of this bi-stable host structure contribute to the output power. Under the same condition, when this bi-stable harvester is under cross-well oscillation pattern the maximum output powers are several times higher than those of the linear harvesters. The measured highest output power of this bi-stable harvester is 36.2 mW with 38 Hz frequency and 5g acceleration (g = 9.8 m s-2).

High pressure hydrogen stabilised by quantum nuclear motion

NASA Astrophysics Data System (ADS)

Needs, Richard; Monserrat, Bartomeu; Pickard, Chris

Hydrogen under extreme pressures is of fundamental interest, as it might exhibit exotic physical phenomena, and of practical interest, as it is a major component of many astrophysical objects. Structure searches have been successful at identifying promising candidates for the known phases of high pressure hydrogen. However, these searches have so far been restricted to the location of minima of the potential energy landscape. In this talk, we will describe a new structure searching method, ``saddle-point ab initio random structure searching'' (sp-AIRSS), that allows us to identify structures associated with saddle points of the potential energy landscape. Using sp-AIRSS, we find two new high-pressure hydrogen structures that exhibit a harmonic dynamical instability, but quantum and thermal anharmonic motion render them dynamically stable. These structures are formed by mixed layers of strongly and softly bound hydrogen molecules, and become thermodynamically competitive at the highest pressures reached in experiment. The experimental implications of these new structures will also be discussed. BM is supported by Robinson College, Cambridge, and the Cambridge Philosophical Society. RJN and CJP are supported by the Engineering and Physical Sciences Research Council (EPSRC) of the UK.

Heterogeneous network promotes species coexistence: metapopulation model for rock-paper-scissors game.

PubMed

Nagatani, Takashi; Ichinose, Genki; Tainaka, Kei-Ichi

2018-05-04

Understanding mechanisms of biodiversity has been a central question in ecology. The coexistence of three species in rock-paper-scissors (RPS) systems are discussed by many authors; however, the relation between coexistence and network structure is rarely discussed. Here we present a metapopulation model for RPS game. The total population is assumed to consist of three subpopulations (nodes). Each individual migrates by random walk; the destination of migration is randomly determined. From reaction-migration equations, we obtain the population dynamics. It is found that the dynamic highly depends on network structures. When a network is homogeneous, the dynamics are neutrally stable: each node has a periodic solution, and the oscillations synchronize in all nodes. However, when a network is heterogeneous, the dynamics approach stable focus and all nodes reach equilibriums with different densities. Hence, the heterogeneity of the network promotes biodiversity.

Precursor polymer compositions comprising polybenzimidazole

DOEpatents

Klaehn, John R.; Peterson, Eric S.; Orme, Christopher J.

2015-07-14

Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

Polymer compositions, polymer films and methods and precursors for forming same

DOEpatents

Klaehn, John R; Peterson, Eric S; Orme, Christopher J

2013-09-24

Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

Highly Stable Double-Stranded DNA Containing Sequential Silver(I)-Mediated 7-Deazaadenine/Thymine Watson-Crick Base Pairs.

PubMed

Santamaría-Díaz, Noelia; Méndez-Arriaga, José M; Salas, Juan M; Galindo, Miguel A

2016-05-17

The oligonucleotide d(TX)9 , which consists of an octadecamer sequence with alternating non-canonical 7-deazaadenine (X) and canonical thymine (T) as the nucleobases, was synthesized and shown to hybridize into double-stranded DNA through the formation of hydrogen-bonded Watson-Crick base pairs. dsDNA with metal-mediated base pairs was then obtained by selectively replacing W-C hydrogen bonds by coordination bonds to central silver(I) ions. The oligonucleotide I adopts a duplex structure in the absence of Ag(+) ions, and its stability is significantly enhanced in the presence of Ag(+) ions while its double-helix structure is retained. Temperature-dependent UV spectroscopy, circular dichroism spectroscopy, and ESI mass spectrometry were used to confirm the selective formation of the silver(I)-mediated base pairs. This strategy could become useful for preparing stable metallo-DNA-based nanostructures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Inexpensive, Stable, and Accurate Relative Humidity Measurement Method for Challenging Environments

PubMed Central

Zhang, Wei; Ma, Hong; Yang, Simon X.

2016-01-01

In this research, an improved psychrometer is developed to solve practical issues arising in the relative humidity measurement of challenging drying environments for meat manufacturing in agricultural and agri-food industries. The design in this research focused on the structure of the improved psychrometer, signal conversion, and calculation methods. The experimental results showed the effect of varying psychrometer structure on relative humidity measurement accuracy. An industrial application to dry-cured meat products demonstrated the effective performance of the improved psychrometer being used as a relative humidity measurement sensor in meat-drying rooms. In a drying environment for meat manufacturing, the achieved measurement accuracy for relative humidity using the improved psychrometer was ±0.6%. The system test results showed that the improved psychrometer can provide reliable and long-term stable relative humidity measurements with high accuracy in the drying system of meat products. PMID:26999161

An Inexpensive, Stable, and Accurate Relative Humidity Measurement Method for Challenging Environments.

PubMed

Zhang, Wei; Ma, Hong; Yang, Simon X

2016-03-18

In this research, an improved psychrometer is developed to solve practical issues arising in the relative humidity measurement of challenging drying environments for meat manufacturing in agricultural and agri-food industries. The design in this research focused on the structure of the improved psychrometer, signal conversion, and calculation methods. The experimental results showed the effect of varying psychrometer structure on relative humidity measurement accuracy. An industrial application to dry-cured meat products demonstrated the effective performance of the improved psychrometer being used as a relative humidity measurement sensor in meat-drying rooms. In a drying environment for meat manufacturing, the achieved measurement accuracy for relative humidity using the improved psychrometer was ±0.6%. The system test results showed that the improved psychrometer can provide reliable and long-term stable relative humidity measurements with high accuracy in the drying system of meat products.

Dioxane contributes to the altered conformation and oligomerization state of a designed engrailed homeodomain variant

PubMed Central

Hom, Geoffrey K.; Lassila, J. Kyle; Thomas, Leonard M.; Mayo, Stephen L.

2005-01-01

Our goal was to compute a stable, full-sequence design of the Drosophila melanogaster engrailed homeodomain. Thermal and chemical denaturation data indicated the design was significantly more stable than was the wild-type protein. The data were also nearly identical to those for a similar, later full-sequence design, which was shown by NMR to adopt the homeodomain fold: a three-helix, globular monomer. However, a 1.65 Å crystal structure of the design described here turned out to be of a completely different fold: a four-helix, rodlike tetramer. The crystallization conditions included ~25% dioxane, and subsequent experiments by circular dichroism and sedimentation velocity analytical ultracentrifugation indicated that dioxane increases the helicity and oligomerization state of the designed protein. We attribute at least part of the discrepancy between the target fold and the crystal structure to the presence of a high concentration of dioxane. PMID:15741348

Atomic sites and stability of Cs+ captured within zeolitic nanocavities

PubMed Central

Yoshida, Kaname; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Nakahira, Atsushi; Kurata, Hiroki; Ikuhara, Yumi H.; Sasaki, Yukichi

2013-01-01

Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations. PMID:23949184

Super Stable Ferroelectrics with High Curie Point.

PubMed

Gao, Zhipeng; Lu, Chengjia; Wang, Yuhang; Yang, Sinuo; Yu, Yuying; He, Hongliang

2016-04-07

Ferroelectric materials are of great importance in the sensing technology due to the piezoelectric properties. Thermal depoling behavior of ferroelectrics determines the upper temperature limit of their application. So far, there is no piezoelectric material working above 800 °C available. Here, we show Nd2Ti2O7 with a perovskite-like layered structure has good resistance to thermal depoling up to 1400 °C. Its stable behavior is because the material has only 180° ferroelectric domains, complex structure change at Curie point (Tc) and their sintering temperature is below their Tc, which avoided the internal stresses produced by the unit cell volume change at Tc. The phase transition at Tc shows a first order behavior which involving the tilting and rotation of the octahedron. The Curie - Weiss temperature is calculated, which might explain why the thermal depoling starts at about 1400 °C.

Super Stable Ferroelectrics with High Curie Point

PubMed Central

Gao, Zhipeng; Lu, Chengjia; Wang, Yuhang; Yang, Sinuo; Yu, Yuying; He, Hongliang

2016-01-01

Ferroelectric materials are of great importance in the sensing technology due to the piezoelectric properties. Thermal depoling behavior of ferroelectrics determines the upper temperature limit of their application. So far, there is no piezoelectric material working above 800 °C available. Here, we show Nd2Ti2O7 with a perovskite-like layered structure has good resistance to thermal depoling up to 1400 °C. Its stable behavior is because the material has only 180° ferroelectric domains, complex structure change at Curie point (Tc) and their sintering temperature is below their Tc, which avoided the internal stresses produced by the unit cell volume change at Tc. The phase transition at Tc shows a first order behavior which involving the tilting and rotation of the octahedron. The Curie – Weiss temperature is calculated, which might explain why the thermal depoling starts at about 1400 °C. PMID:27053338

Non-flammable polyimide materials for aircraft and spacecraft applications

NASA Technical Reports Server (NTRS)

Gagliani, J.; Supkis, D. E.

1979-01-01

Recent developments in polyimide chemistry show promise for producing materials with very low flammability and a wide range of mechanical properties. Polyimide foams can be synthesized to provide fire safety without detectable formation of smoke or toxic byproducts below 204 C (400 F), thus avoiding an environment which is lethal to human habitation. This work has been and is currently being performed under development programs, the objective of which is to provide cost effective processes for producing thermally stable, polyimide flexible resilient foams, thermal-acoustical insulating materials, rigid low density foam panels, and high strength foam structures. The chemical and physical properties demonstrated by these materials represent a technological advancement in the art of thermally stable polyimide polymers which are expected to insure fire protection of structures and components used in air transportation and space exploration. Data compiled to date on thermal, physical and functional properties of these materials are presented.

Crystal-Structure-Guided Design of Self-Assembling RNA Nanotriangles.

PubMed

Boerneke, Mark A; Dibrov, Sergey M; Hermann, Thomas

2016-03-14

RNA nanotechnology uses RNA structural motifs to build nanosized architectures that assemble through selective base-pair interactions. Herein, we report the crystal-structure-guided design of highly stable RNA nanotriangles that self-assemble cooperatively from short oligonucleotides. The crystal structure of an 81 nucleotide nanotriangle determined at 2.6 Å resolution reveals the so-far smallest circularly closed nanoobject made entirely of double-stranded RNA. The assembly of the nanotriangle architecture involved RNA corner motifs that were derived from ligand-responsive RNA switches, which offer the opportunity to control self-assembly and dissociation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Se substitution on the phase change properties of Ge2Sb2Te5

NASA Astrophysics Data System (ADS)

Shekhawat, Roopali; Rangappa, Ramanna; Gopal, E. S. R.; Ramesh, K.

2018-05-01

Ge2Sb2Te5 popularly known as GST is being explored for non-volatile phase change random access memory(PCRAM) applications. Under high electric field, thin films of amorphous GST undergo a phase change from amorphous to crystalline with a high contrast in electrical resistivity (about 103). The phase change is between amorphous and metastable NaCl structure occurs at about 150°C and not to the stable hexagonal phase which occurs at a high temperature (> 250 °C). In GST, about 50 % of Te substituted by Se (Ge2Sb2Te2.5Se2.5) is found to increase the contrast in electrical resistivity by 7 orders of magnitude (about 4 orders of magnitude higher than GST). The phase transition in Se added GST also found to be between amorphous and the stable hexagonal structure. The threshold voltage at which the Ge2Sb2Te2.5Se2.5 switches to the high conducting state increases to 9V as compared to 2V in GST. Interestingly, the threshold current decrease to 1mA as compared to 1.8mA in GST indicating the Se substitution reduces the power needed for switching between the low and high conducting states. The reduction in power needed for phase change, high contrast in electrical resistivity with high thermal stability makes Ge2Sb2Te2.5Se2.5 as a better candidate for PCRAM.

Porphyrinoids as a platform of stable radicals

PubMed Central

Shimizu, Daiki

2018-01-01

The non-innocent ligand nature of porphyrins was observed for compound I in enzymatic cycles of cytochrome P450. Such porphyrin radicals were first regarded as reactive intermediates in catabolism, but recent studies have revealed that porphyrinoids, including porphyrins, ring-contracted porphyrins, and ring-expanded porphyrins, display excellent radical-stabilizing abilities to the extent that radicals can be handled like usual closed-shell organic molecules. This review surveys four types of stable porphyrinoid radical and covers their synthetic methods and properties such as excellent redox properties, NIR absorption, and magnetic properties. The radical-stabilizing abilities of porphyrinoids stem from their unique macrocyclic conjugated systems with high electronic and structural flexibilities. PMID:29675188

Dual-band frequency selective surface with large band separation and stable performance

NASA Astrophysics Data System (ADS)

Zhou, Hang; Qu, Shao-Bo; Peng, Wei-Dong; Lin, Bao-Qin; Wang, Jia-Fu; Ma, Hua; Zhang, Jie-Qiu; Bai, Peng; Wang, Xu-Hua; Xu, Zhuo

2012-05-01

A new technique of designing a dual-band frequency selective surface with large band separation is presented. This technique is based on a delicately designed topology of L- and Ku-band microwave filters. The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface, respectively. A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings. Based on this technique, a dual-band frequency selective surface with large band separation is designed, which possesses large band separation, high selectivity, and stable performance under various incident angles and different polarizations.

REVIEWS OF TOPICAL PROBLEMS: Global phase-stable radiointerferometric systems

NASA Astrophysics Data System (ADS)

Dravskikh, A. F.; Korol'kov, Dimitrii V.; Pariĭskiĭ, Yu N.; Stotskiĭ, A. A.; Finkel'steĭn, A. M.; Fridman, P. A.

1981-12-01

We discuss from a unitary standpoint the possibility of building a phase-stable interferometric system with very long baselines that operate around the clock with real-time data processing. The various problems involved in the realization of this idea are discussed: the methods of suppression of instrumental and tropospheric phase fluctuations, the methods for constructing two-dimensional images and determining the coordinates of radio sources with high angular resolution, and the problem of the optimal structure of the interferometric system. We review in detail the scientific problems from the various branches of natural science (astrophysics, cosmology, geophysics, geodynamics, astrometry, etc.) whose solution requires superhigh angular resolution.

On stability of the structure of implicit personality theory over situations.

PubMed

Hochwälder, J

1995-12-01

In the present study, the following (hitherto unaddressed) question was posed: "Is the structure of implicit personality theory stable over situations?". In order to answer this question, correlation coefficients were computed between different aspects of two trait-structures obtained under different situational conditions. The results seem to indicate that the structure of IPT is stable over situations. The results are discussed in the light of some methodological considerations.

Synthesis, structure and topological analysis of glycine templated highly stable cadmium sulfate framework: A New Lewis Acid catalyst

NASA Astrophysics Data System (ADS)

Paul, Avijit Kumar

2018-04-01

One new open-framework two-dimensional layer, [Cd(NH3CH2COO)(SO4)], I, has been synthesized using amino acid as templating agent. Single crystal structural analysis shows that the compound crystallizes in monoclinic cell with non-centrosymmetric space group P21, a = 4.9513(1) Å, b = 7.9763(2) Å, c = 8.0967(2) Å, β = 105.917(1)° and V = 307.504(12) Å3. The compound has connectivity between the Cd-centers and the sulfate units forming a two-dimensional layer structure. Sulfate unit is coordinated to metal center with η3, μ4 mode possessing a coordination free oxygen atom. The zwitterionic form of glycine molecule is present in the structure bridging with two metal centers through μ2-mode by carboxylate oxygens. The topological analysis reveals that the two-dimensional network is formed with a novel 4- and 6-connected binodal net of (32,42,52)(34,44,54,63) topology. Although one end of the glycine molecule is free from coordination, the structure is highly stable up to 350 °C. Strong N-H⋯ O hydrogen bonding interactions play an important role in the stabilization and formation of three-dimensional supramolecular structure. The cyanosilylation of imines using the present compounds as heterogeneous catalyst indicates good catalytic behavior. The present study illustrates the usefulness of the amino acid for the structure building in less studied sulfate based framework materials as well as designing of new heterogeneous catalysts for the broad application. The compound has also been characterized through elemental analysis, PXRD, IR, SEM and TG-DT studies.

High Water Tolerance of a Core-Shell-Structured Zeolite for CO2 Adsorptive Separation under Wet Conditions.

PubMed

Miyamoto, Manabu; Ono, Shumpei; Kusukami, Kodai; Oumi, Yasunori; Uemiya, Shigeyuki

2018-06-11

Dehumidification in CO 2 adsorptive separation processes is an important issue, owing to its high energy consumption. However, available adsorbents such as low-silica zeolites show a significant decrease in CO 2 adsorption capacity when water vapor is present. A core-shell-structured MFI-type zeolite with a hydrophilic ZSM-5 coated with a hydrophobic silicalite-1 shell layer was applied in CO 2 adsorptive separation under wet conditions. This hybrid material demonstrated remarkably high water tolerance with stable CO 2 adsorption performance without additional thermal treatment for regeneration, whereas a significant decrease in the CO 2 adsorption amount because of water vapor was observed on the parent ZSM-5. The core-shell structure of zeolites with high pore volumes, such as LTA or CHA, could also be suitable candidates for high CO 2 adsorption capacity and high water tolerance for practical applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural properties of iron and nickel mixed oxide nano particles.

NASA Astrophysics Data System (ADS)

Dehipawala, Sunil; Samarasekara, Pubudu; Gafney, Harry

Small scale magnets have very high technological importance today. Instead of traditional expensive methods, scientists are exploring new low cost methods to produce micro magnets. We synthesized thin film magnets containing iron and nickel oxides. Films will be synthesized using sol-gel method and spin coating technique. Several different precursor concentrations were tested to find out the ideal concentrations for stable thin films. Structural properties of iron and nickel oxide particles were investigated using X-ray absorption and Mossbauer spectroscopy. PSC-CUNY.

Natural shorelines promote the stability of fish communities in an urbanized coastal system.

PubMed

Scyphers, Steven B; Gouhier, Tarik C; Grabowski, Jonathan H; Beck, Michael W; Mareska, John; Powers, Sean P

2015-01-01

Habitat loss and fragmentation are leading causes of species extinctions in terrestrial, aquatic and marine systems. Along coastlines, natural habitats support high biodiversity and valuable ecosystem services but are often replaced with engineered structures for coastal protection or erosion control. We coupled high-resolution shoreline condition data with an eleven-year time series of fish community structure to examine how coastal protection structures impact community stability. Our analyses revealed that the most stable fish communities were nearest natural shorelines. Structurally complex engineered shorelines appeared to promote greater stability than simpler alternatives as communities nearest vertical walls, which are among the most prevalent structures, were most dissimilar from natural shorelines and had the lowest stability. We conclude that conserving and restoring natural habitats is essential for promoting ecological stability. However, in scenarios when natural habitats are not viable, engineered landscapes designed to mimic the complexity of natural habitats may provide similar ecological functions.

Advances in high gradient normal conducting accelerator structures

DOE PAGES

Simakov, Evgenya Ivanovna; Dolgashev, Valery A.; Tantawi, Sami G.

2018-03-09

Here, this paper reviews the current state-of-the-art in understanding the phenomena of ultra-high vacuum radio-frequency (rf) breakdown in accelerating structures and the efforts to improve stable operation of the structures at accelerating gradients above 100 MV/m. Numerous studies have been conducted recently with the goal of understanding the dependence of the achievable accelerating gradients and breakdown rates on the frequency of operations, the geometry of the structure, material and method of fabrication, and operational temperature. Tests have been conducted with single standing wave accelerator cells as well as with the multi-cell traveling wave structures. Notable theoretical effort was directed atmore » understanding the physical mechanisms of the rf breakdown and its statistical behavior. Finally, the achievements presented in this paper are the result of the large continuous self-sustaining collaboration of multiple research institutions in the United States and worldwide.« less

Advances in high gradient normal conducting accelerator structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simakov, Evgenya Ivanovna; Dolgashev, Valery A.; Tantawi, Sami G.

Here, this paper reviews the current state-of-the-art in understanding the phenomena of ultra-high vacuum radio-frequency (rf) breakdown in accelerating structures and the efforts to improve stable operation of the structures at accelerating gradients above 100 MV/m. Numerous studies have been conducted recently with the goal of understanding the dependence of the achievable accelerating gradients and breakdown rates on the frequency of operations, the geometry of the structure, material and method of fabrication, and operational temperature. Tests have been conducted with single standing wave accelerator cells as well as with the multi-cell traveling wave structures. Notable theoretical effort was directed atmore » understanding the physical mechanisms of the rf breakdown and its statistical behavior. Finally, the achievements presented in this paper are the result of the large continuous self-sustaining collaboration of multiple research institutions in the United States and worldwide.« less

Natural Shorelines Promote the Stability of Fish Communities in an Urbanized Coastal System

PubMed Central

Scyphers, Steven B.; Gouhier, Tarik C.; Grabowski, Jonathan H.; Beck, Michael W.; Mareska, John; Powers, Sean P.

2015-01-01

Habitat loss and fragmentation are leading causes of species extinctions in terrestrial, aquatic and marine systems. Along coastlines, natural habitats support high biodiversity and valuable ecosystem services but are often replaced with engineered structures for coastal protection or erosion control. We coupled high-resolution shoreline condition data with an eleven-year time series of fish community structure to examine how coastal protection structures impact community stability. Our analyses revealed that the most stable fish communities were nearest natural shorelines. Structurally complex engineered shorelines appeared to promote greater stability than simpler alternatives as communities nearest vertical walls, which are among the most prevalent structures, were most dissimilar from natural shorelines and had the lowest stability. We conclude that conserving and restoring natural habitats is essential for promoting ecological stability. However, in scenarios when natural habitats are not viable, engineered landscapes designed to mimic the complexity of natural habitats may provide similar ecological functions. PMID:26039407

Formation mechanism of Ruddlesden-Popper-type antiphase boundaries during the kinetically limited growth of Sr rich SrTiO3 thin films

PubMed Central

Xu, Chencheng; Du, Hongchu; van der Torren, Alexander J. H.; Aarts, Jan; Jia, Chun-Lin; Dittmann, Regina

2016-01-01

We elucidated the formation process for Ruddlesden-Popper-type defects during pulsed laser deposition of Sr rich SrTiO3 thin films by a combined analysis of in-situ atomic force microscopy, low energy electron diffraction and high resolution scanning transmission electron microscopy. At the early growth stage of 1.5 unit cells, the excess Sr results in the formation of SrO on the surface, resulting in a local termination change from TiO2 to SrO, thereby forming a Sr rich (2 × 2) surface reconstruction. With progressive SrTiO3 growth, islands with thermodynamically stable SrO rock-salt structure are formed, coexisting with TiO2 terminated islands. During the overgrowth of these thermodynamically stable islands, both lateral as well as vertical Ruddlesden-Popper-type anti-phase boundaries are formed, accommodating the Sr excess of the SrTiO3 film. We suggest the formation of thermodynamically stable SrO rock-salt structures as origin for the formation of Ruddlesden-Popper-type antiphase boundaries, which are as a result of kinetic limitations confined to certain regions on the surface. PMID:27922069

Calcium titanium silicate based glass-ceramic for nuclear waste immobilisation

NASA Astrophysics Data System (ADS)

Sharma, K.; Srivastav, A. P.; Goswami, M.; Krishnan, Madangopal

2018-04-01

Titanate based ceramics (synroc) have been studied for immobilisation of nuclear wastes due to their high radiation and thermal stability. The aim of this study is to synthesis glass-ceramic with stable phases from alumino silicate glass composition and study the loading behavior of actinides in glass-ceramics. The effects of CaO and TiO2 addition on phase evolution and structural properties of alumino silicate based glasses with nominal composition x(10CaO-9TiO2)-y(10Na2O-5 Al2O3-56SiO2-10B2O3); where z = x/y = 1.4-1.8 are reported. The glasses are prepared by melt-quench technique and characterized for thermal and structural properties using DTA and Raman Spectroscopy. Glass transition and peak crystallization temperatures decrease with increase of CaO and TiO2 content, which implies the weakening of glass network and increased tendency of glasses towards crystallization. Sphene (CaTiSiO5) and perovskite (CaTiO3) crystalline phases are confirmed from XRD which are well known stable phase for conditioning of actinides. The microsturcture and elemental analysis indicate the presence of actinide in stable crystalline phases.

Formation mechanism of Ruddlesden-Popper-type antiphase boundaries during the kinetically limited growth of Sr rich SrTiO3 thin films

NASA Astrophysics Data System (ADS)

Xu, Chencheng; Du, Hongchu; van der Torren, Alexander J. H.; Aarts, Jan; Jia, Chun-Lin; Dittmann, Regina

2016-12-01

We elucidated the formation process for Ruddlesden-Popper-type defects during pulsed laser deposition of Sr rich SrTiO3 thin films by a combined analysis of in-situ atomic force microscopy, low energy electron diffraction and high resolution scanning transmission electron microscopy. At the early growth stage of 1.5 unit cells, the excess Sr results in the formation of SrO on the surface, resulting in a local termination change from TiO2 to SrO, thereby forming a Sr rich (2 × 2) surface reconstruction. With progressive SrTiO3 growth, islands with thermodynamically stable SrO rock-salt structure are formed, coexisting with TiO2 terminated islands. During the overgrowth of these thermodynamically stable islands, both lateral as well as vertical Ruddlesden-Popper-type anti-phase boundaries are formed, accommodating the Sr excess of the SrTiO3 film. We suggest the formation of thermodynamically stable SrO rock-salt structures as origin for the formation of Ruddlesden-Popper-type antiphase boundaries, which are as a result of kinetic limitations confined to certain regions on the surface.

Frequency-Dependent Selection: The High Potential for Permanent Genetic Variation in the Diallelic, Pairwise Interaction Model

PubMed Central

Asmussen, M. A.; Basnayake, E.

1990-01-01

A detailed analytic and numerical study is made of the potential for permanent genetic variation in frequency-dependent models based on pairwise interactions among genotypes at a single diallelic locus. The full equilibrium structure and qualitative gene-frequency dynamics are derived analytically for a symmetric model, in which pairwise fitnesses are chiefly determined by the genetic similarity of the individuals involved. This is supplemented by an extensive numerical investigation of the general model, the symmetric model, and nine other special cases. Together the results show that there is a high potential for permanent genetic diversity in the pairwise interaction model, and provide insight into the extent to which various forms of genotypic interactions enhance or reduce this potential. Technically, although two stable polymorphic equilibria are possible, the increased likelihood of maintaining both alleles, and the poor performance of protected polymorphism conditions as a measure of this likelihood, are primarily due to a greater variety and frequency of equilibrium patterns with one stable polymorphic equilibrium, in conjunction with a disproportionately large domain of attraction for stable internal equilibria. PMID:2341034

Perceptual Learning Immediately Yields New Stable Motor Coordination

ERIC Educational Resources Information Center

Wilson, Andrew D.; Snapp-Childs, Winona; Bingham, Geoffrey P.

2010-01-01

Coordinated rhythmic movement is specifically structured in humans. Movement at 0[degrees] mean relative phase is maximally stable, 180[degrees] is less stable, and other coordinations can, but must, be learned. Variations in perceptual ability play a key role in determining the observed stabilities so we investigated whether stable movements can…

Imaging initial formation processes of nanobubbles at the graphite-water interface through high-speed atomic force microscopy

NASA Astrophysics Data System (ADS)

Liao, Hsien-Shun; Yang, Chih-Wen; Ko, Hsien-Chen; Hwu, En-Te; Hwang, Ing-Shouh

2018-03-01

The initial formation process of nanobubbles at solid-water interfaces remains unclear because of the limitations of current imaging techniques. To directly observe the formation process, an astigmatic high-speed atomic force microscope (AFM) was modified to enable imaging in the liquid environment. By using a customized cantilever holder, the resonance of small cantilevers was effectively enhanced in water. The proposed high-speed imaging technique yielded highly dynamic quasi-two-dimensional (2D) gas structures (thickness: 20-30 nm) initially at the graphite-water interface. The 2D structures were laterally mobile mainly within certain areas, but occasionally a gas structure might extensively migrate and settle in a new area. The 2D structures were often confined by substrate step edges in one lateral dimension. Eventually, all quasi-2D gas structures were transformed into cap-shaped nanobubbles of higher heights and reduced lateral dimensions. These nanobubbles were immobile and remained stable under continuous AFM imaging. This study demonstrated that nanobubbles could be stably imaged at a scan rate of 100 lines per second (640 μm/s).

Stable, concentrated solutions of high molecular weight polyaniline and articles therefrom

DOEpatents

Mattes, Benjamin R.; Wang, Hsing-Lin

2000-01-01

Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (>15% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

The stability of aluminium oxide monolayer and its interface with two-dimensional materials

NASA Astrophysics Data System (ADS)

Song, Ting Ting; Yang, Ming; Chai, Jian Wei; Callsen, Martin; Zhou, Jun; Yang, Tong; Zhang, Zheng; Pan, Ji Sheng; Chi, Dong Zhi; Feng, Yuan Ping; Wang, Shi Jie

2016-07-01

The miniaturization of future electronic devices requires the knowledge of interfacial properties between two-dimensional channel materials and high-κ dielectrics in the limit of one atomic layer thickness. In this report, by combining particle-swarm optimization method with first-principles calculations, we present a detailed study of structural, electronic, mechanical, and dielectric properties of Al2O3 monolayer. We predict that planar Al2O3 monolayer is globally stable with a direct band gap of 5.99 eV and thermal stability up to 1100 K. The stability of this high-κ oxide monolayer can be enhanced by substrates such as graphene, for which the interfacial interaction is found to be weak. The band offsets between the Al2O3 monolayer and graphene are large enough for electronic applications. Our results not only predict a stable high-κ oxide monolayer, but also improve the understanding of interfacial properties between a high-κ dielectric monolayer and two-dimensional material.

Highly Stable and Red-Emitting Nanovesicles Incorporating Lipophilic Diketopyrrolopyrroles for Cell Imaging.

PubMed

Veciana, Jaume; Ardizzone, Antonio; Blasi, Davide; Grimaldi, Natascia; Sala, Santi; Ratera, Imma; Vona, Danilo; Rosspeintner, Arnulf; Punzi, Angela; Altamura, Emiliano; Vauthey, Eric; Farinola, Gianluca M; Ventosa, Nora

2018-06-05

Diketopyrrolopyrroles (DPPs) have recently attracted large interest as highly bright and photostable red-emitting molecules. However, their tendency to form non-fluorescent aggregates in water via the so-called Aggregation Caused Quenching (ACQ) effect is a major issue that limits their application under the microscope. In this work, two DPP molecules have been incorporated in the membrane of highly stable and water-soluble Quatsomes (QS, nanovesicles made by surfactants and sterols), allowing their nanostructuration in water limiting at the same time the ACQ effect. The obtained fluorescent organic nanoparticles (FONs) showed superior structural homogeneity along with long-time colloidal and optical stability. A thorough one- (1P) and two-photon (2P) fluorescence characterization revealed the promising photophysical features of these fluorescent nanovesicles, which showed a high 1P and 2P brightness. Finally, the fluorescent QSs were used for the in vitro bioimaging of Saos-2 osteosarcoma cell lines, demonstrating their potential as nanomaterials for bioimaging applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new concept for active bistable twisting structures

NASA Astrophysics Data System (ADS)

Schultz, Marc R.

2005-05-01

A novel type of morphing structure capable of a large change in shape with a small energy input is discussed in this paper. The considered structures consist of two curved shells that are joined in a specific manner to form a bistable airfoil-like structure. The two stable shapes have a difference in axial twist, and the structure may be transformed between the stable shapes by a simple snap-through action. The benefit of a bistable structure of this type is that, if the stable shapes are operational shapes, power is needed only to transform the structure from one shape to another. The discussed structures could be used in aerodynamic applications such as morphing wings, or as aerodynamic control surfaces. The investigation discussed in this paper considers both experiment and finite-element analysis. Several graphite-epoxy composite and one steel device were created as proof-of-concept models. To demonstrate active control of these structures, piezocomposite actuators were applied to one of the composite structures and used to transform the structure between stable shapes. The analysis was used to compare the predicted shapes with the experimental shapes, and to study how changes to the geometric input values affected the shape and operational characteristics of the structures. The predicted shapes showed excellent agreement with the experimental shapes, and the results of the parametric study suggest that the shapes and the snap-through characteristics can be easily tailored to meet specific needs.

Characterisation of the Interaction between Toroidal Vortex Structures and Flame Front Propagation

NASA Astrophysics Data System (ADS)

Long, E. J.; Hargrave, G. K.; Jarvis, S.; Justham, T.; Halliwell, N.

2006-07-01

Experimental laser diagnostic data is presented for flame characterisation during interactions with toroidal vortices generated in the wake of an annular obstacle. A novel twin section combustion chamber has been utilised to allow the controlled formation of stable eddy structures into which a flame front can propagate. High speed laser sheet visualisation was employed to record the flow field and flame front temporal development and high-speed digital particle image velocimetry was used to quantify the velocity field of the unburnt mixture ahead of the flame front. Results provide characterisation of the toroidal vortex/flame front interaction for a range of vortex scales of and recirculation strengths.

Solution-proceed Air-stable Copper Bismuth Iodide CuBiI₄ for Photovoltaics.

PubMed

Hu, Zhaosheng; Wang, Zhen; Kapil, Gaurav; Ma, Tingli; Iikubo, Satoshi; Minemoto, Takashi; Yoshino, Kenji; Toyoda, Taro; Shen, Qing; Hayase, Shuzi

2018-06-19

Bismuth based solar cells have been under intensive interest as an efficient non-toxic absorber in photovoltaics. Within this new family of semiconductors, we herein, report a new, long-term stable material copper bismuth iodide (CuBiI₄). A solution-processed method is provided under air atmosphere. The adopted HI assisted Dimethylacetamide (DMA) co-solvent can completely dissolve CuI and BiI₃ powders with high concentration compared to other organic solvent. Moreover, high vapor pressure of Tributyl phosphate, we select for the solvent vapor annealing (SVA), enables the whole low-temperature (≤70⁰C) film preparation. It results in a stable, uniform dense CuBiI₄ film. The average grains size increasing with precursor concentration, greatly enlarge the PL life time and hall mobility. And carrier lifetime of 3.03 ns as well as an appreciable hall mobility of 110 cm²/Vs were obtained. X-ray diffraction illustrates that the crystal structure is cubic (space group Fd3m) and favored in [1, 1, 1] direction. Moreover, the photovoltaic performance of CuBiI₄ was also investigated. A wide-bandgap (2.67 eV) solar cell with 0.82 % performance is presented, which shows an excellent long-term stability at least over 1008 hours under ambient conditions. This air-stable material may give an application in future tandem solar cells as a stable short-wavelength light absorber. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

p-Type Transparent Conducting Oxide/n-Type Semiconductor Heterojunctions for Efficient and Stable Solar Water Oxidation.

PubMed

Chen, Le; Yang, Jinhui; Klaus, Shannon; Lee, Lyman J; Woods-Robinson, Rachel; Ma, Jie; Lum, Yanwei; Cooper, Jason K; Toma, Francesca M; Wang, Lin-Wang; Sharp, Ian D; Bell, Alexis T; Ager, Joel W

2015-08-05

Achieving stable operation of photoanodes used as components of solar water splitting devices is critical to realizing the promise of this renewable energy technology. It is shown that p-type transparent conducting oxides (p-TCOs) can function both as a selective hole contact and corrosion protection layer for photoanodes used in light-driven water oxidation. Using NiCo2O4 as the p-TCO and n-type Si as a prototypical light absorber, a rectifying heterojunction capable of light driven water oxidation was created. By placing the charge separating junction in the Si using a np(+) structure and by incorporating a highly active heterogeneous Ni-Fe oxygen evolution catalyst, efficient light-driven water oxidation can be achieved. In this structure, oxygen evolution under AM1.5G illumination occurs at 0.95 V vs RHE, and the current density at the reversible potential for water oxidation (1.23 V vs RHE) is >25 mA cm(-2). Stable operation was confirmed by observing a constant current density over 72 h and by sensitive measurements of corrosion products in the electrolyte. In situ Raman spectroscopy was employed to investigate structural transformation of NiCo2O4 during electrochemical oxidation. The interface between the light absorber and p-TCO is crucial to produce selective hole conduction to the surface under illumination. For example, annealing to produce more crystalline NiCo2O4 produces only small changes in its hole conductivity, while a thicker SiOx layer is formed at the n-Si/p-NiCo2O4 interface, greatly reducing the PEC performance. The generality of the p-TCO protection approach is demonstrated by multihour, stable, water oxidation with n-InP/p-NiCo2O4 heterojunction photoanodes.

Structure, Elastic Constants and XRD Spectra of Extended Solids under High Pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batyrev, I. G.; Coleman, S. P.; Ciezak-Jenkins, J. A.

We present results of evolutionary simulations based on density functional calculations of a potentially new type of energetic materials called extended solids: P-N and N-H. High-density structures with covalent bonds generated using variable and fixed concentration methods were analysed in terms of thermo-dynamical stability and agreement with experimental X-ray diffraction (XRD) spectra. X-ray diffraction spectra were calculated using a virtual diffraction algorithm that computes kinematic diffraction intensity in three-dimensional reciprocal space before being reduced to a two-theta line profile. Calculated XRD patterns were used to search for the structure of extended solids present at experimental pressures by optimizing data accordingmore » to experimental XRD peak position, peak intensity and theoretically calculated enthalpy. Elastic constants has been calculated for thermodynamically stable structures of P-N system.« less

Local Nash equilibrium in social networks.

PubMed

Zhang, Yichao; Aziz-Alaoui, M A; Bertelle, Cyrille; Guan, Jihong

2014-08-29

Nash equilibrium is widely present in various social disputes. As of now, in structured static populations, such as social networks, regular, and random graphs, the discussions on Nash equilibrium are quite limited. In a relatively stable static gaming network, a rational individual has to comprehensively consider all his/her opponents' strategies before they adopt a unified strategy. In this scenario, a new strategy equilibrium emerges in the system. We define this equilibrium as a local Nash equilibrium. In this paper, we present an explicit definition of the local Nash equilibrium for the two-strategy games in structured populations. Based on the definition, we investigate the condition that a system reaches the evolutionary stable state when the individuals play the Prisoner's dilemma and snow-drift game. The local Nash equilibrium provides a way to judge whether a gaming structured population reaches the evolutionary stable state on one hand. On the other hand, it can be used to predict whether cooperators can survive in a system long before the system reaches its evolutionary stable state for the Prisoner's dilemma game. Our work therefore provides a theoretical framework for understanding the evolutionary stable state in the gaming populations with static structures.

Local Nash Equilibrium in Social Networks

PubMed Central

Zhang, Yichao; Aziz-Alaoui, M. A.; Bertelle, Cyrille; Guan, Jihong

2014-01-01

Nash equilibrium is widely present in various social disputes. As of now, in structured static populations, such as social networks, regular, and random graphs, the discussions on Nash equilibrium are quite limited. In a relatively stable static gaming network, a rational individual has to comprehensively consider all his/her opponents' strategies before they adopt a unified strategy. In this scenario, a new strategy equilibrium emerges in the system. We define this equilibrium as a local Nash equilibrium. In this paper, we present an explicit definition of the local Nash equilibrium for the two-strategy games in structured populations. Based on the definition, we investigate the condition that a system reaches the evolutionary stable state when the individuals play the Prisoner's dilemma and snow-drift game. The local Nash equilibrium provides a way to judge whether a gaming structured population reaches the evolutionary stable state on one hand. On the other hand, it can be used to predict whether cooperators can survive in a system long before the system reaches its evolutionary stable state for the Prisoner's dilemma game. Our work therefore provides a theoretical framework for understanding the evolutionary stable state in the gaming populations with static structures. PMID:25169150

Local Nash Equilibrium in Social Networks

NASA Astrophysics Data System (ADS)

Zhang, Yichao; Aziz-Alaoui, M. A.; Bertelle, Cyrille; Guan, Jihong

2014-08-01

Nash equilibrium is widely present in various social disputes. As of now, in structured static populations, such as social networks, regular, and random graphs, the discussions on Nash equilibrium are quite limited. In a relatively stable static gaming network, a rational individual has to comprehensively consider all his/her opponents' strategies before they adopt a unified strategy. In this scenario, a new strategy equilibrium emerges in the system. We define this equilibrium as a local Nash equilibrium. In this paper, we present an explicit definition of the local Nash equilibrium for the two-strategy games in structured populations. Based on the definition, we investigate the condition that a system reaches the evolutionary stable state when the individuals play the Prisoner's dilemma and snow-drift game. The local Nash equilibrium provides a way to judge whether a gaming structured population reaches the evolutionary stable state on one hand. On the other hand, it can be used to predict whether cooperators can survive in a system long before the system reaches its evolutionary stable state for the Prisoner's dilemma game. Our work therefore provides a theoretical framework for understanding the evolutionary stable state in the gaming populations with static structures.

Generation of T-cell receptors targeting a genetically stable and immunodominant cytotoxic T-lymphocyte epitope within hepatitis C virus non-structural protein 3.

PubMed

Pasetto, Anna; Frelin, Lars; Brass, Anette; Yasmeen, Anila; Koh, Sarene; Lohmann, Volker; Bartenschlager, Ralf; Magalhaes, Isabelle; Maeurer, Markus; Sällberg, Matti; Chen, Margaret

2012-02-01

Hepatitis C virus (HCV) is a major cause of severe liver disease, and one major contributing factor is thought to involve a dysfunction of virus-specific T-cells. T-cell receptor (TCR) gene therapy with HCV-specific TCRs would increase the number of effector T-cells to promote virus clearance. We therefore took advantage of HLA-A2 transgenic mice to generate multiple TCR candidates against HCV using DNA vaccination followed by generation of stable T-cell-BW (T-BW) tumour hybrid cells. Using this approach, large numbers of non-structural protein 3 (NS3)-specific functional T-BW hybrids can be generated efficiently. These predominantly target the genetically stable HCV genotype 1 NS3(1073-1081) CTL epitope, frequently associated with clearance of HCV in humans. These T-BW hybrid clones recognized the NS3(1073) peptide with a high avidity. The hybridoma effectively recognized virus variants and targeted cells with low HLA-A2 expression, which has not been reported previously. Importantly, high-avidity murine TCRs effectively redirected human non-HCV-specific T-lymphocytes to recognize human hepatoma cells with HCV RNA replication driven by a subgenomic HCV replicon. Taken together, TCR candidates with a range of functional avidities, which can be used to study immune recognition of HCV-positive targets, have been generated. This has implications for TCR-related immunotherapy against HCV.

Structure Elucidation of the Diagnostic Product Ion at m/z 97 Derived from Androst-4-en-3-One-Based Steroids by ESI-CID and IRMPD Spectroscopy

NASA Astrophysics Data System (ADS)

Thevis, Mario; Beuck, Simon; Höppner, Sebastian; Thomas, Andreas; Held, Joseph; Schäfer, Mathias; Oomens, Jos; Schänzer, Wilhelm

2012-03-01

Structure elucidation of steroids by mass spectrometry has been of great importance to various analytical arenas and numerous studies were conducted to provide evidence for the composition and origin of (tandem) mass spectrometry-derived product ions used to characterize and identify steroidal substances. The common product ion at m/z 97 generated from androst-4-ene-3-one analogs has been subject of various studies, including stable isotope-labeling and (high resolution/high accuracy) tandem mass spectrometry, but its gas-phase structure has never been confirmed. Using high resolution/high accuracy mass spectrometry and low resolution tandem mass spectrometry, density functional theory (DFT) calculation, and infrared multiple photon dissociation (IRMPD) spectroscopy employing a free electron laser, the structure of m/z 97 derived from testosterone was assigned to protonated 3-methyl-2-cyclopenten-1-one. This ion was identified in a set of six cyclic C6H9O+ isomers as computed at the B3LYP/6-311++G(2d,2p) level of theory (protonated 3-methyl-2-cyclopenten-1-one, 2-methyl-2-cyclopenten-1-one and 2-cyclohexen-1-one). Product ions of m/z 97 obtained from MS2 and MS3 experiments of protonated 3-methyl-2-cyclopenten-1-one, 2-methyl-2-cyclopenten-1-one, 2-cyclohexen-1-one, and testosterone corroborated the suggested gas-phase ion structure, which was eventually substantiated by IRMPD spectroscopy yielding a spectrum that convincingly matched the predicted counterpart. Finally, the dissociation pathway of the protonated molecule of testosterone to m/z 97 was revisited and an alternative pathway was suggested that considers the exclusion of C-10 along with the inclusion of C-5, which was experimentally demonstrated with stable isotope labeling.

Visual search for object categories is predicted by the representational architecture of high-level visual cortex

PubMed Central

Alvarez, George A.; Nakayama, Ken; Konkle, Talia

2016-01-01

Visual search is a ubiquitous visual behavior, and efficient search is essential for survival. Different cognitive models have explained the speed and accuracy of search based either on the dynamics of attention or on similarity of item representations. Here, we examined the extent to which performance on a visual search task can be predicted from the stable representational architecture of the visual system, independent of attentional dynamics. Participants performed a visual search task with 28 conditions reflecting different pairs of categories (e.g., searching for a face among cars, body among hammers, etc.). The time it took participants to find the target item varied as a function of category combination. In a separate group of participants, we measured the neural responses to these object categories when items were presented in isolation. Using representational similarity analysis, we then examined whether the similarity of neural responses across different subdivisions of the visual system had the requisite structure needed to predict visual search performance. Overall, we found strong brain/behavior correlations across most of the higher-level visual system, including both the ventral and dorsal pathways when considering both macroscale sectors as well as smaller mesoscale regions. These results suggest that visual search for real-world object categories is well predicted by the stable, task-independent architecture of the visual system. NEW & NOTEWORTHY Here, we ask which neural regions have neural response patterns that correlate with behavioral performance in a visual processing task. We found that the representational structure across all of high-level visual cortex has the requisite structure to predict behavior. Furthermore, when directly comparing different neural regions, we found that they all had highly similar category-level representational structures. These results point to a ubiquitous and uniform representational structure in high-level visual cortex underlying visual object processing. PMID:27832600

Multiscale description of mercury intrusion curves from an Oxisol and the residual saprolite left after deep profile excavation

NASA Astrophysics Data System (ADS)

Vidal Vázquez, Eva; Kitamura, Aline E.; Alves, Marlene C.; Miranda, José G. V.; Paz Ferreiro, Jorge

2010-05-01

Oxisols are highly weathered soils with a thick profile that are found primarily in the intertropical regions of the world. Brazilian Oxisols are characterized by 1:1 low activity clays a weak macrostructure and a strong microgranular structure, which results in very stable aggregates (pseudosand) at the

The thermal stability of the nanograin structure in a weak solute segregation system.

PubMed

Tang, Fawei; Song, Xiaoyan; Wang, Haibin; Liu, Xuemei; Nie, Zuoren

2017-02-08

A hybrid model that combines first principles calculations and thermodynamic evaluation was developed to describe the thermal stability of a nanocrystalline solid solution with weak segregation. The dependence of the solute segregation behavior on the electronic structure, solute concentration, grain size and temperature was demonstrated, using the nanocrystalline Cu-Zn system as an example. The modeling results show that the segregation energy changes with the solute concentration in a form of nonmonotonic function. The change in the total Gibbs free energy indicates that at a constant solute concentration and a given temperature, a nanocrystalline structure can remain stable when the initial grain size is controlled in a critical range. In experiments, dense nanocrystalline Cu-Zn alloy bulk was prepared, and a series of annealing experiments were performed to examine the thermal stability of the nanograins. The experimental measurements confirmed the model predictions that with a certain solute concentration, a state of steady nanograin growth can be achieved at high temperatures when the initial grain size is controlled in a critical range. The present work proposes that in weak solute segregation systems, the nanograin structure can be kept thermally stable by adjusting the solute concentration and initial grain size.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egli, Martin; Pallan, Pradeep S.; Pattanayek, Rekha

An experimental rationalization of the structure type encountered in DNA and RNA by systematically investigating the chemical and physical properties of alternative nucleic acids has identified systems with a variety of sugar-phosphate backbones that are capable of Watson-Crick base pairing and in some cases cross-pairing with the natural nucleic acids. The earliest among the model systems tested to date, (4{prime} {yields} 6{prime})-linked oligo(2{prime},3{prime}-dideoxy-{beta}-d-glucopyranosyl)nucleotides or homo-DNA, shows stable self-pairing, but the pairing rules for the four natural bases are not the same as those in DNA. However, a complete interpretation and understanding of the properties of the hexapyranosyl (4{prime} {yields} 6{prime})more » family of nucleic acids has been impeded until now by the lack of detailed 3D-structural data. We have determined the crystal structure of a homo-DNA octamer. It reveals a weakly twisted right-handed duplex with a strong inclination between the hexose-phosphate backbones and base-pair axes, and highly irregular values for helical rise and twist at individual base steps. The structure allows a rationalization of the inability of allo-, altro-, and glucopyranosyl-based oligonucleotides to form stable pairing systems.« less

Large and stable reversible lithium-ion storages from mesoporous SnO2 nanosheets with ultralong lifespan over 1000 cycles

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Jiang, Bin; Guo, Jinxue; Xie, Yaping; Tang, Lin

2014-12-01

The major challenge to promote the commercialization of SnO2 anode materials is to construct unique structures and/or composites that could alleviate the volume effect and extend the lifespan. This study develops an efficient synthetic solution for the preparation of mesoporous SnO2 nanosheets, which involves an evaporation-induced selfassembly process and the following thermal treatment. Surfactant F127 is used as the soft template to form abundant cores. The as-prepared sample intrinsically inherits flexible sheet-like structure and porous features, as characterized with XRD, SEM, TEM and BET techniques. Based on these combining structural benefits, the sample is utilized as anode materials for lithium-ion batteries and exhibits excellent Li+ storage performance such as large and stable reversible capacity, good rate capability, and especially the outstanding durable cycling life of over 1000 cycles, which meets the demands of practical applications. The structural changes of SnO2 nanosheets are observed from the decomposed electrodes after different electrochemical cycles. Moreover, this synthesis strategy may offer an alternative and universal approach for synthesis of other transitional metal oxides or their binary composites as high-performance anode materials for lithium-ion batteries.

High-pressure polymorphism of As2S3 and new AsS2 modification with layered structure

NASA Astrophysics Data System (ADS)

Bolotina, N. B.; Brazhkin, V. V.; Dyuzheva, T. I.; Katayama, Y.; Kulikova, L. F.; Lityagina, L. V.; Nikolaev, N. A.

2014-01-01

At normal pressure, the As2S3 compound is the most stable equilibrium modification with unique layered structure. The possibility of high-pressure polymorphism of this substance remains questionable. Our research showed that the As2S3 substance was metastable under pressures P > 6 GPa decomposing into two high-pressure phases: As2S3 → AsS2 + AsS. New AsS2 phase can be conserved in the single crystalline form in metastable state at room pressure up to its melting temperature (470 K). This modification has the layered structure with P1211 monoclinic symmetry group; the unit-cell values are a = 7.916(2) Å, b = 9.937(2) Å, c = 7.118(1) Å, β = 106.41° ( Z = 8, density 3.44 g/cm3). Along with the recently studied AsS high-pressure modification, the new AsS2 phase suggests that high pressure polymorphism is a very powerful tool to create new layered-structure phases with "wrong" stoichiometry.

Liquid-Infused Smooth Surface for Improved Condensation Heat Transfer.

PubMed

Tsuchiya, Hirotaka; Tenjimbayashi, Mizuki; Moriya, Takeo; Yoshikawa, Ryohei; Sasaki, Kaichi; Togasawa, Ryo; Yamazaki, Taku; Manabe, Kengo; Shiratori, Seimei

2017-09-12

Control of vapor condensation properties is a promising approach to manage a crucial part of energy infrastructure conditions. Heat transfer by vapor condensation on superhydrophobic coatings has garnered attention, because dropwise condensation on superhydrophobic surfaces with rough structures leads to favorable heat-transfer performance. However, pinned condensed water droplets within the rough structure and a high thermodynamic energy barrier for nucleation of superhydrophobic surfaces limit their heat-transfer increase. Recently, slippery liquid-infused surfaces (SLIPS) have been investigated, because of their high water sliding ability and surface smoothness originating from the liquid layer. However, even on SLIPS, condensed water droplets are eventually pinned to degrade their heat-transfer properties after extended use, because the rough base layer is exposed as infused liquid is lost. Herein, we report a liquid-infused smooth surface named "SPLASH" (surface with π electron interaction liquid adsorption, smoothness, and hydrophobicity) to overcome the problems derived from the rough structures in previous approaches to obtain stable, high heat-transfer performance. The SPLASH displayed a maximum condensation heat-transfer coefficient that was 175% higher than that of an uncoated substrate. The SPLASH also showed higher heat-transfer performance and more stable dropwise condensation than superhydrophobic surfaces and SLIPS from the viewpoints of condensed water droplet mobility and the thermodynamic energy barrier for nucleation. The effects of liquid-infused surface roughness and liquid viscosity on condensation heat transfer were investigated to compare heat-transfer performance. This research will aid industrial applications using vapor condensation.

ZnS-Sb2S3@C Core-Double Shell Polyhedron Structure Derived from Metal-Organic Framework as Anodes for High Performance Sodium Ion Batteries.

PubMed

Dong, Shihua; Li, Caixia; Ge, Xiaoli; Li, Zhaoqiang; Miao, Xianguang; Yin, Longwei

2017-06-27

Taking advantage of zeolitic imidazolate framework (ZIF-8), ZnS-Sb 2 S 3 @C core-double shell polyhedron structure is synthesized through a sulfurization reaction between Zn 2+ dissociated from ZIF-8 and S 2- from thioacetamide (TAA), and subsequently a metal cation exchange process between Zn 2+ and Sb 3+ , in which carbon layer is introduced from polymeric resorcinol-formaldehyde to prevent the collapse of the polyhedron. The polyhedron composite with a ZnS inner-core and Sb 2 S 3 /C double-shell as anode for sodium ion batteries (SIBs) shows us a significantly improved electrochemical performance with stable cycle stability, high Coulombic efficiency and specific capacity. Peculiarly, introducing a carbon shell not only acts as an important protective layer to form a rigid construction and accommodate the volume changes, but also improves the electronic conductivity to optimize the stable cycle performance and the excellent rate property. The architecture composed of ZnS inner core and a complex Sb 2 S 3 /C shell not only facilitates the facile electrolyte infiltration to reduce the Na-ion diffusion length to improve the electrochemical reaction kinetics, but also prevents the structure pulverization caused by Na-ion insertion/extraction. This approach to prepare metal sulfides based on MOFs can be further extended to design other nanostructured systems for high performance energy storage devices.

Stretchable Platinum Network-Based Transparent Electrodes for Highly Sensitive Wearable Electronics.

PubMed

Wang, Yuting; Cheng, Jing; Xing, Yan; Shahid, Muhammad; Nishijima, Hiroki; Pan, Wei

2017-07-01

A platinum network-based transparent electrode has been fabricated by electrospinning. The unique nanobelt structured electrode demonstrates low sheet resistance (about 16 Ω sq -1 ) and high transparency of 80% and excellent flexibility. One of the most interesting demonstrations of this Pt nanobelt electrode is its excellent reversibly resilient characteristic. The electric conductivity of the flexible Pt electrode can recover to its initial value after 160% extending and this performance is repeatable and stable. The good linear relationship between the resistance and strain of the unique structured Pt electrode makes it possible to assemble a wearable high sensitive strain sensor. Present reported Pt nanobelt electrode also reveals potential applications in electrode for flexible fuel cells and highly transparent ultraviolet (UV) sensors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Medieval Horse Stable; The Results of Multi Proxy Interdisciplinary Research

PubMed Central

Dejmal, Miroslav; Lisá, Lenka; Fišáková Nývltová, Miriam; Bajer, Aleš; Petr, Libor; Kočár, Petr; Kočárová, Romana; Nejman, Ladislav; Rybníček, Michal; Sůvová, Zdenka; Culp, Randy; Vavrčík, Hanuš

2014-01-01

A multi proxy approach was applied in the reconstruction of the architecture of Medieval horse stable architecture, the maintenance practices associated with that structure as well as horse alimentation at the beginning of 13th century in Central Europe. Finally, an interpretation of the local vegetation structure along Morava River, Czech Republic is presented. The investigated stable experienced two construction phases. The infill was well preserved and its composition reflects maintenance practices. The uppermost part of the infill was composed of fresh stabling, which accumulated within a few months at the end of summer. Horses from different backgrounds were kept in the stable and this is reflected in the results of isotope analyses. Horses were fed meadow grasses as well as woody vegetation, millet, oat, and less commonly hemp, wheat and rye. Three possible explanations of stable usage are suggested. The stable was probably used on a temporary basis for horses of workers employed at the castle, courier horses and horses used in battle. PMID:24670874

The facile fabrication of tunable plasmonic gold nanostructure arrays using microwave plasma

NASA Astrophysics Data System (ADS)

Hsu, Chuen-Yuan; Huang, Jing-Wen; Gwo, Shangjr; Lin, Kuan-Jiuh

2010-01-01

Fabrication of isolated noble metal nanoparticles embedded in transparent substrates is the fasting growing demand for innovative plasmonic technologies. Here we report a simple and effective methodology for the preparation of highly stable plasmonic nanoparticles embedded in a glass surface. Size-controllable (10-70 nm) Au nanoparticles were rapidly prepared when subjected to the home-microwave plasma. Accordingly, the optical extinction maximum of the localized surface plasmon resonance (LSPR) can be systematically tuned in the range 532-586 nm. We find that the plasmonic structures are exceedingly stable toward immersion in ethanol solvents and pass successfully the adhesive tape test, which makes our system highly promising for efficient transmission-LSPR nanosensors. Besides, the attractive features of substrate-bound plasmonic nanostructures include its low cost, versatility, robustness, reusability and a promising ability to make a multi-arrayed LSPR biochip.

Radiative engineering with refractory epsilon-near-zero metamaterials (Conference Presentation)

NASA Astrophysics Data System (ADS)

Dyachenko, Pavel N.; Molesky, Sean; Petrov, Alexander Y.; Störmer, Michael; Krekeler, Tobias; Lang, Slawa; Ritter, Martin; Jacob, Zubin; Eich, Manfred

2016-04-01

Improvement in high-temperature stable spectrally selective absorbers and emitters is integral for the further development of thermophotovoltaic (TPV), lighting and solar thermal applications. However, the high operational temperatures (T>1000oC) required for efficient energy conversion, along with application specific criteria such as the operational range of low bandgap semiconductors, greatly restrict what can be accomplished with natural materials. Motivated by this challenge, we demonstrate the first example of high temperature thermal radiation engineering with metamaterials. By employing the naturally selective thermal excitation of radiative modes that occurs near topological transitions, we show that thermally stable highly selective emissivity features are achieved for temperatures up to 1000°C with low angular dependence in a sub-micron thick refractory tungsten/hafnium dioxide epsilon-near-zero (ENZ) metamaterial. We also investigate the main mechanisms of thermal degradation of the fabricated refractory metamaterial both in terms of optical performance and structural stability using spectral analysis and energy-dispersive X-ray spectroscopy (EDS) techniques. Importantly, we observe chemical stability of the constituent materials for temperatures up to 1000°C and structural stability beyond 1100°C. The scalable fabrication, requiring magnetron sputtering, and thermally robust optical properties of this metamaterial approach are ideally suited to high temperature emitter applications such as lighting or TPV. Our findings provide a first concrete proof of radiative engineering with high temperature topological transition in ENZ metamaterials, and establish a clear path for implementation in TPV energy harvesting applications.

Properties of radiation stable insulation composites for fusion magnet

NASA Astrophysics Data System (ADS)

Wu, Zhixiong; Huang, Rongjin; Huang, Chuanjun; Li, Laifeng

2017-09-01

High field superconducting magnets made of Nb3Al will be a suitable candidate for future fusion device which can provide magnetic field over 15T without critical current degradation caused by strain. The higher magnetic field and the larger current will produce a huge electromagnetic force. Therefore, it is necessary to develop high strength cryogenic structural materials and electrical insulation materials with excellent performance. On the other hand, superconducting magnets in fusion devices will experience significant nuclear radiation exposure during service. While typical structural materials like stainless steel and titanium have proven their ability to withstand these conditions, electrical insulation materials used in these coils have not fared as well. In fact, recent investigations have shown that electrical insulation breakdown is a limiting factor in the performance of high field magnets. The insulation materials used in the high field fusion magnets should be characterized by excellent mechanical properties, high radiation resistivity and good thermal conductivity. To meet these objectives, we designed various insulation materials based on epoxy resins and cyanate ester resins and investigated their processing characteristic and mechanical properties before and after irradiation at low temperature. In this paper, the recent progress of the radiation stable insulation composites for high field fusion magnet is presented. The materials have been irradiated by 60Co γ-ray irradiation in air at ambient temperature with a dose rate of 300 Gy/min. The total doses of 1 MGy, 5 MGy and 10 MGy were selected to the test specimens.

Hierarchical MoS2 tubular structures internally wired by carbon nanotubes as a highly stable anode material for lithium-ion batteries

PubMed Central

Chen, Yu Ming; Yu, Xin Yao; Li, Zhen; Paik, Ungyu; Lou, Xiong Wen (David)

2016-01-01

Molybdenum disulfide (MoS2), a typical two-dimensional material, is a promising anode material for lithium-ion batteries because it has three times the theoretical capacity of graphite. The main challenges associated with MoS2 anodes are the structural degradation and the low rate capability caused by the low intrinsic electric conductivity and large strain upon cycling. Here, we design hierarchical MoS2 tubular structures internally wired by carbon nanotubes (CNTs) to tackle these problems. These porous MoS2 tubular structures are constructed from building blocks of ultrathin nanosheets, which are believed to benefit the electrochemical reactions. Benefiting from the unique structural and compositional characteristics, these CNT-wired MoS2 tubular structures deliver a very high specific capacity of ~1320 mAh g−1 at a current density of 0.1 A g−1, exceptional rate capability, and an ultralong cycle life of up to 1000 cycles. This work may inspire new ideas for constructing high-performance electrodes for electrochemical energy storage. PMID:27453938

Bioinspired Omnidirectional Self-Stable Reflectors with Multiscale Hierarchical Structures.

PubMed

Han, Zhiwu; Mu, Zhengzhi; Li, Bo; Feng, Xiaoming; Wang, Ze; Zhang, Junqiu; Niu, Shichao; Ren, Luquan

2017-08-30

Structured surfaces, demonstrating various wondrous physicochemical performances, are ubiquitous phenomena in nature. Butterfly wings with impressive structural colors are an interesting example for multiscale hierarchical structures (MHSs). However, most natural structural colors are relatively unstable and highly sensitive to incident angles, which limit their potential practical applications to a certain extent. Here, we reported a bioinspired color reflector with omnidirectional reflective self-stable (ORS) properties, which is inspired by the wing scales of Papilio palinurus butterfly. Through experimental exploration and theoretical analysis, it was found that the vivid colors of such butterfly wings are structure-based and possess novel ORS properties, which attributes to the multiple optical actions between light and the complex structures coupling the inverse opal-like structures (IOSs) and stacked lamellar ridges (SLRs). On the basis of this, we designed and successfully fabricated the SiO 2 -based bioinspired color reflectors (BCRs) through a facile and effective biotemplate method. It was confirmed that the MHSs in biotemplate are inherited by the obtained SiO 2 -based BCRs. More importantly, the SiO 2 -based BCRs also demonstrated the similar ORS properties in a wide wavelength range. We forcefully anticipate that the reported MHS-based ORS performance discovered in butterfly wing scales here could offer new thoughts for scientists to solve unstable reflection issues in particular optical field. The involved biotemplate fabrication method offers a facile and effective strategy for fabricating functional nanomaterials or bioinspired nanodevices with 3D complex nanostructures, such as structured optical devices, displays, and optoelectronic equipment.

Single frequency free-running low noise compact extended-cavity semiconductor laser at high power level

NASA Astrophysics Data System (ADS)

Garnache, Arnaud; Myara, Mikhaël.; Laurain, A.; Bouchier, Aude; Perez, J. P.; Signoret, P.; Sagnes, I.; Romanini, D.

2017-11-01

We present a highly coherent semiconductor laser device formed by a ½-VCSEL structure and an external concave mirror in a millimetre high finesse stable cavity. The quantum well structure is diode-pumped by a commercial single mode GaAs laser diode system. This free running low noise tunable single-frequency laser exhibits >50mW output power in a low divergent circular TEM00 beam with a spectral linewidth below 1kHz and a relative intensity noise close to the quantum limit. This approach ensures, with a compact design, homogeneous gain behaviour and a sufficiently long photon lifetime to reach the oscillation-relaxation-free class-A regime, with a cut off frequency around 10MHz.

Switching dynamics of TaOx-based threshold switching devices

NASA Astrophysics Data System (ADS)

Goodwill, Jonathan M.; Gala, Darshil K.; Bain, James A.; Skowronski, Marek

2018-03-01

Bi-stable volatile switching devices are being used as access devices in solid-state memory arrays and as the active part of compact oscillators. Such structures exhibit two stable states of resistance and switch between them at a critical value of voltage or current. A typical resistance transient under a constant amplitude voltage pulse starts with a slow decrease followed by a rapid drop and leveling off at a low steady state value. This behavior prompted the interpretation of initial delay and fast transition as due to two different processes. Here, we show that the entire transient including incubation time, transition time, and the final resistance values in TaOx-based switching can be explained by one process, namely, Joule heating with the rapid transition due to the thermal runaway. The time, which is required for the device in the conducting state to relax back to the stable high resistance one, is also consistent with the proposed mechanism.

Requirement of GM2 ganglioside activator for phospholipase D activation

PubMed Central

Nakamura, Shun-ichi; Akisue, Toshihiro; Jinnai, Hitoshi; Hitomi, Tomohiro; Sarkar, Sukumar; Miwa, Noriko; Okada, Taro; Yoshida, Kimihisa; Kuroda, Shun’ichi; Kikkawa, Ushio; Nishizuka, Yasutomi

1998-01-01

Sequence analysis of a heat-stable protein necessary for the activation of ADP ribosylation factor-dependent phospholipase D (PLD) reveals that this protein has a structure highly homologous to the previously known GM2 ganglioside activator whose deficiency results in the AB-variant of GM2 gangliosidosis. The heat-stable activator protein indeed has the capacity to enhance enzymatic conversion of GM2 to GM3 ganglioside that is catalyzed by β-hexosaminidase A. Inversely, GM2 ganglioside activator purified separately from tissues as described earlier [Conzelmann, E. & Sandhoff, K. (1987) Methods Enzymol. 138, 792–815] stimulates ADP ribosylation factor-dependent PLD in a dose-dependent manner. At higher concentrations of ammonium sulfate, the PLD activator protein apparently substitutes for protein kinase C and phosphatidylinositol 4,5-bisphosphate, both of which are known as effective stimulators of the PLD reaction. The mechanism of action of the heat-stable PLD activator protein remains unknown. PMID:9770472

An In Situ One-Pot Synthetic Approach towards Multivariate Zirconium MOFs.

PubMed

Sun, Yujia; Sun, Lixian; Feng, Dawei; Zhou, Hong-Cai

2016-05-23

Chemically highly stable MOFs incorporating multiple functionalities are of great interest for applications under harsh environments. Herein, we presented a facile one-pot synthetic strategy to incorporate multiple functionalities into stable Zr-MOFs from mixed ligands of different geometry and connectivity. Via our strategy, tetratopic tetrakis(4-carboxyphenyl)porphyrin (TCPP) ligands were successfully integrated into UiO-66 while maintaining the crystal structure, morphology, and ultrahigh chemical stability of UiO-66. The amount of incorporated TCPP is controllable. Through various combinations of BDC derivatives and TCPP, 49 MOFs with multiple functionalities were obtained. Among them, MOFs modified with FeTCPPCl were demonstrated to be catalytically active for the oxidation of ABTS. We anticipate our strategy to provide a facile route to introduce multiple functionalities into stable Zr-MOFs for a wide variety of potential applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Irradiation effects in UO2 and CeO2

NASA Astrophysics Data System (ADS)

Ye, Bei; Oaks, Aaron; Kirk, Mark; Yun, Di; Chen, Wei-Ying; Holtzman, Benjamin; Stubbins, James F.

2013-10-01

Single crystal CeO2, as a surrogate material to UO2, was irradiated with 500 keV xenon ions at 800 °C while being observed using in situ transmission electron microscopy (TEM). Experimental results show the formation and growth of defect clusters including dislocation loops and cavities as a function of increasing atomic displacement dose. At high dose, the dislocation loop structure evolves into an extended dislocation line structure, which appears to remain stable to the high dose levels examined in this study. A high concentration of cavities was also present in the microstructure. Despite high atomic displacement doses, the specimen remained crystalline to a cumulated dose of 5 × 1015 ions/cm2, which is consistent with the known stability of the fluorite structure under high dose irradiation. Kinetic Monte Carlo calculations show that oxygen mobility is substantially higher in hypo-stoichiometric UO2/CeO2 than hyper-stoichiometric systems. This result is consistent with the ability of irradiation damage to recover even at intermediate irradiation temperatures.

High-Q Wafer Level Package Based on Modified Tri-Layer Anodic Bonding and High Performance Getter and Its Evaluation for Micro Resonant Pressure Sensor.

PubMed

Wang, Liying; Du, Xiaohui; Wang, Lingyun; Xu, Zhanhao; Zhang, Chenying; Gu, Dandan

2017-03-16

In order to achieve and maintain a high quality factor (high-Q) for the micro resonant pressure sensor, this paper presents a new wafer level package by adopting cross-layer anodic bonding technique of the glass/silicon/silica (GSS) stackable structure and integrated Ti getter. A double-layer structure similar to a silicon-on-insulator (SOI) wafer is formed after the resonant layer and the pressure-sensitive layer are bonded by silicon direct bonding (SDB). In order to form good bonding quality between the pressure-sensitive layer and the glass cap layer, the cross-layer anodic bonding technique is proposed for vacuum package by sputtering Aluminum (Al) on the combination wafer of the pressure-sensitive layer and the resonant layer to achieve electrical interconnection. The model and the bonding effect of this technique are discussed. In addition, in order to enhance the performance of titanium (Ti) getter, the prepared and activation parameters of Ti getter under different sputtering conditions are optimized and discussed. Based on the optimized results, the Ti getter (thickness of 300 nm to 500 nm) is also deposited on the inside of the glass groove by magnetron sputtering to maintain stable quality factor (Q). The Q test of the built testing system shows that the number of resonators with a Q value of more than 10,000 accounts for more than 73% of the total. With an interval of 1.5 years, the Q value of the samples remains almost constant. It proves the proposed cross-layer anodic bonding and getter technique can realize high-Q resonant structure for long-term stable operation.

Topology-Scaling Identification of Layered Solids and Stable Exfoliated 2D Materials.

PubMed

Ashton, Michael; Paul, Joshua; Sinnott, Susan B; Hennig, Richard G

2017-03-10

The Materials Project crystal structure database has been searched for materials possessing layered motifs in their crystal structures using a topology-scaling algorithm. The algorithm identifies and measures the sizes of bonded atomic clusters in a structure's unit cell, and determines their scaling with cell size. The search yielded 826 stable layered materials that are considered as candidates for the formation of two-dimensional monolayers via exfoliation. Density-functional theory was used to calculate the exfoliation energy of each material and 680 monolayers emerge with exfoliation energies below those of already-existent two-dimensional materials. The crystal structures of these two-dimensional materials provide templates for future theoretical searches of stable two-dimensional materials. The optimized structures and other calculated data for all 826 monolayers are provided at our database (https://materialsweb.org).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Ruixue; Chen, Kezheng, E-mail: dxb@sdu.edu.cn; Liao, Zhongmiao

Highlights: ► Hydroxyapatite hierarchical microstructures have been synthesized by a facile method. ► The morphology and size of the building units of 3D structures can be controlled. ► The hydroxyapatite with 3D structure is morphologically and structurally stable up to 800 °C. - Abstract: Hydroxyapatite (HAp) hierarchical microstructures with novel 3D morphology were prepared through a template- and surfactant-free hydrothermal homogeneous precipitation method. Field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the morphology and composition of the synthesized products. Interestingly, the obtained HAp with 3D structure is composed ofmore » one-dimensional (1D) nanorods or two-dimensional (2D) nanoribbons, and the length and morphology of these building blocks can be controlled through controlling the pH of the reaction. The building blocks are single crystalline and have different preferential orientation growth under different pH conditions. At low pH values, octacalcium phosphate (OCP) phase formed first and then transformed into HAp phase due to the increased pH value caused by the decomposition of urea. The investigation on the thermal stability reveals that the prepared HAp hierarchical microstructures are morphologically and structurally stable up to 800 °C.« less

Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution

PubMed Central

Bergmann, Arno; Martinez-Moreno, Elias; Teschner, Detre; Chernev, Petko; Gliech, Manuel; de Araújo, Jorge Ferreira; Reier, Tobias; Dau, Holger; Strasser, Peter

2015-01-01

Water splitting catalysed by earth-abundant materials is pivotal for global-scale production of non-fossil fuels, yet our understanding of the active catalyst structure and reactivity is still insufficient. Here we report on the structurally reversible evolution of crystalline Co3O4 electrocatalysts during oxygen evolution reaction identified using advanced in situ X-ray techniques. At electrode potentials facilitating oxygen evolution, a sub-nanometre shell of the Co3O4 is transformed into an X-ray amorphous CoOx(OH)y which comprises di-μ-oxo-bridged Co3+/4+ ions. Unlike irreversible amorphizations, here, the formation of the catalytically-active layer is reversed by re-crystallization upon return to non-catalytic electrode conditions. The Co3O4 material thus combines the stability advantages of a controlled, stable crystalline material with high catalytic activity, thanks to the structural flexibility of its active amorphous oxides. We propose that crystalline oxides may be tailored for generating reactive amorphous surface layers at catalytic potentials, just to return to their stable crystalline state under rest conditions. PMID:26456525

Investigation of exotic stable calcium carbides using theory and experiment

DOE PAGES

Li, Yan-Ling; Wang, Sheng-Nan; Oganov, Artem R.; ...

2015-05-11

It is well known that pressure causes profound changes in the properties of atoms and chemical bonding, leading to the formation of many unusual materials. Here we systematically explore all stable calcium carbides at pressures from ambient to 100 GPa using variable-composition evolutionary structure predictions. We find that Ca 5C 2, Ca 2C, Ca 3C 2, CaC, Ca 2C 3, and CaC 2 have stability fields on the phase diagram. Among these, Ca2C and Ca2C3 are successfully synthesized for the first time via high-pressure experiments with excellent structural correspondence to theoretical predictions. Of particular significance are the base-centered monoclinic phasemore » (space group C 2/m) of Ca 2C, a quasi-two-dimensional metal with layers of negatively charged calcium atoms, and the primitive monoclinic phase (space group P21/c) of CaC with zigzag C 4 groups. Interestingly, strong interstitial charge localization is found in the structure of R-3m-Ca 5C 2 with semimetallic behaviour.« less

Record of C4 Photosynthesis Through the Late Neogene and Pleistocene

NASA Astrophysics Data System (ADS)

Cerling, T. E.

2016-12-01

C4 photosynthesis is an adaptation to the low atmospheric carbon dioxide concentrations experienced in the Neogene; it is found principally in tropical to sub-tropical/temperate regions where temperatures are high in the growing season. Although C4 photosynthesis makes up about 50% of Net Primary Productivity in tropical regions, its macroscopic fossil record is extremely sparse. Therefore, inferences to its significance in local ecosystems are based primarily on stable isotopes, with phytoliths become more important as phytolith morphology becomes better associated with plant structure and classification. Stable isotopes have been the principal recorder for understanding the history of C4 photosynthesis; however, different materials record different aspects of the C4 contribution to ecosystem structure and thus are telling different parts of the same story. With the fossil record so poorly known, we often assume similar ecosystem structures and functions as we observe in modern analogues. It is likely that large evolutionary changes have taken place within C4 plants as they went from < 1% tropical NPP to > 50% tropical NPP in the late Neogene.

Universal quinone electrodes for long cycle life aqueous rechargeable batteries

NASA Astrophysics Data System (ADS)

Liang, Yanliang; Jing, Yan; Gheytani, Saman; Lee, Kuan-Yi; Liu, Ping; Facchetti, Antonio; Yao, Yan

2017-08-01

Aqueous rechargeable batteries provide the safety, robustness, affordability, and environmental friendliness necessary for grid storage and electric vehicle operations, but their adoption is plagued by poor cycle life due to the structural and chemical instability of the anode materials. Here we report quinones as stable anode materials by exploiting their structurally stable ion-coordination charge storage mechanism and chemical inertness towards aqueous electrolytes. Upon rational selection/design of quinone structures, we demonstrate three systems that coupled with industrially established cathodes and electrolytes exhibit long cycle life (up to 3,000 cycles/3,500 h), fast kinetics (>=20C), high anode specific capacity (up to 200-395 mAh g-1), and several examples of state-of-the-art specific energy/energy density (up to 76-92 Wh kg-1/ 161-208 Wh l-1) for several operational pH values (-1 to 15), charge carrier species (H+, Li+, Na+, K+, Mg2+), temperature (-35 to 25 °C), and atmosphere (with/without O2), making them a universal anode approach for any aqueous battery technology.

Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution.

PubMed

Bergmann, Arno; Martinez-Moreno, Elias; Teschner, Detre; Chernev, Petko; Gliech, Manuel; de Araújo, Jorge Ferreira; Reier, Tobias; Dau, Holger; Strasser, Peter

2015-10-12

Water splitting catalysed by earth-abundant materials is pivotal for global-scale production of non-fossil fuels, yet our understanding of the active catalyst structure and reactivity is still insufficient. Here we report on the structurally reversible evolution of crystalline Co3O4 electrocatalysts during oxygen evolution reaction identified using advanced in situ X-ray techniques. At electrode potentials facilitating oxygen evolution, a sub-nanometre shell of the Co3O4 is transformed into an X-ray amorphous CoOx(OH)y which comprises di-μ-oxo-bridged Co(3+/4+) ions. Unlike irreversible amorphizations, here, the formation of the catalytically-active layer is reversed by re-crystallization upon return to non-catalytic electrode conditions. The Co3O4 material thus combines the stability advantages of a controlled, stable crystalline material with high catalytic activity, thanks to the structural flexibility of its active amorphous oxides. We propose that crystalline oxides may be tailored for generating reactive amorphous surface layers at catalytic potentials, just to return to their stable crystalline state under rest conditions.

Making sense of the conflicting magic numbers in WSi{sub n} clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abreu, Marissa Baddick; Reber, Arthur C.; Khanna, Shiv N.

2015-08-21

First principles studies on the geometric structure, stability, and electronic structure of WSi{sub n} clusters, n = 6-16, have been carried out to show that the observed differing “magic sizes” for WSi{sub n} clusters are associated with the nature of the growth processes. The WSi{sub 12} cluster, observed as a magic species in experiments reacting transition metal ions with silane, is not stable due to a filled shell of 18 electrons, as previously proposed, but due to its atomic structure that arrests further growth because of an endohedral transition metal site. In fact, it is found that all of thesemore » clusters, n = 6-16, have filled 5d shells except for WSi{sub 12}, which has a 5d{sup 8} configuration that is caused by crystal field splitting. The stability of WSi{sub 15}{sup +}, observed as highly stable in clusters generated by vaporizing silicon and metal carbonyls, is shown to be associated with a combination of geometric and electronic features. The findings are compared with previous results on CrSi{sub n} clusters.« less

Designing of new structure PID controller of boost converter for solar photovoltaic stability

NASA Astrophysics Data System (ADS)

Shabrina, Hanifati Nur; Setiawan, Eko Adhi; Sabirin, Chip Rinaldi

2017-03-01

Nowadays, the utilization of renewable energy as the source on distributed generation system is increasing. It aims to reduce reliance and power losses from utility grid and improve power stability in near loads. One example of renewable energy technology that have been highly proven on the market is solar photovoltaic (PV). This technology converts photon from sunlight into electricity. However, the fluctuation of solar radiation that often occurs become the main problem for this system. Due to this condition, the power conversion is needed to convert the change frequently in photovoltaic panel into a stable voltage to the system. Developing control of boost converter has important role to keep ability of system stabilization. A conventional PID (Proportional, Integral, Derivative) control is mostly used to achieve this goal. In this research, a design of new structure PID controller of boost converter is offered to better optimize system stability comparing to the conventional PID. Parameters obtained from this PID structure have been successfully yield a stable boost converter output at 200 V with 10% overshoot, 1.5 seconds of settling time, and 1.5% of steady-state error.

An alkaline active xylanase: insights into mechanisms of high pH catalytic adaptation.

PubMed

Mamo, Gashaw; Thunnissen, Marjolein; Hatti-Kaul, Rajni; Mattiasson, Bo

2009-09-01

The alkaliphilic bacterium, Bacillus halodurans S7, produces an alkaline active xylanase (EC 3.2.1.8), which differs from many other xylanases in being operationally stable under alkaline conditions as well as at elevated temperature. Compared to non-alkaline active xylanases, this enzyme has a high percent composition of acidic amino acids which results in high ratio of negatively to positively charged residues. A positive correlation was observed between the charge ratio and the pH optima of xylanases. The recombinant xylanase was crystallized using a hanging drop diffusion method. The crystals belong to the space group P2(1)2(1)2(1) and the structure was determined at a resolution of 2.1 A. The enzyme has the common eight-fold TIM-barrel structure of family 10 xylanases; however, unlike non-alkaline active xylanases, it has a highly negatively charged surface and a deeper active site cleft. Mutational analysis of non-conserved amino acids which are close to the acid/base residue has shown that Val169, Ile170 and Asp171 are important to hydrolyze xylan at high pH. Unlike the wild type xylanase which has optimum pH at 9-9.5, the triple mutant xylanase (V169A, I170F and D171N), which was constructed using sequence information of alkaline sensitive xylanses was optimally active around pH 7. Compared to non-alkaline active xylanases, the alkaline active xylanases have highly acidic surfaces and fewer solvent exposed alkali labile residues. Based on these results obtained from sequence, structural and mutational analysis, the possible mechanisms of high pH stability and catalysis are discussed. This will provide useful information to understand the mechanism of high pH adaptation and engineering of enzymes that can be operationally stable at high pH.

Hydrogen Clathrate Structures in Rare Earth Hydrides at High Pressures: Possible Route to Room-Temperature Superconductivity

NASA Astrophysics Data System (ADS)

Peng, Feng; Sun, Ying; Pickard, Chris J.; Needs, Richard J.; Wu, Qiang; Ma, Yanming

2017-09-01

Room-temperature superconductivity has been a long-held dream and an area of intensive research. Recent experimental findings of superconductivity at 200 K in highly compressed hydrogen (H) sulfides have demonstrated the potential for achieving room-temperature superconductivity in compressed H-rich materials. We report first-principles structure searches for stable H-rich clathrate structures in rare earth hydrides at high pressures. The peculiarity of these structures lies in the emergence of unusual H cages with stoichiometries H24 , H29 , and H32 , in which H atoms are weakly covalently bonded to one another, with rare earth atoms occupying the centers of the cages. We have found that high-temperature superconductivity is closely associated with H clathrate structures, with large H-derived electronic densities of states at the Fermi level and strong electron-phonon coupling related to the stretching and rocking motions of H atoms within the cages. Strikingly, a yttrium (Y) H32 clathrate structure of stoichiometry YH10 is predicted to be a potential room-temperature superconductor with an estimated Tc of up to 303 K at 400 GPa, as derived by direct solution of the Eliashberg equation.

High-Throughput Synthesis and Structure of Zeolite ZSM-43 with Two-Directional 8-Ring Channels.

PubMed

Willhammar, Tom; Su, Jie; Yun, Yifeng; Zou, Xiaodong; Afeworki, Mobae; Weston, Simon C; Vroman, Hilda B; Lonergan, William W; Strohmaier, Karl G

2017-08-07

The aluminosilicate zeolite ZSM-43 (where ZSM = Zeolite Socony Mobil) was first synthesized more than 3 decades ago, but its chemical structure remained unsolved because of its poor crystallinity and small crystal size. Here we present optimization of the ZSM-43 synthesis using a high-throughput approach and subsequent structure determination by the combination of electron crystallographic methods and powder X-ray diffraction. The synthesis required the use of a combination of both inorganic (Cs + and K + ) and organic (choline) structure-directing agents. High-throughput synthesis enabled a screening of the synthesis conditions, which made it possible to optimize the synthesis, despite its complexity, in order to obtain a material with significantly improved crystallinity. When both rotation electron diffraction and high-resolution transmission electron microscopy imaging techniques are applied, the structure of ZSM-43 could be determined. The structure of ZSM-43 is a new zeolite framework type and possesses a unique two-dimensional channel system limited by 8-ring channels. ZSM-43 is stable upon calcination, and sorption measurements show that the material is suitable for adsorption of carbon dioxide as well as methane.

Hydrogen Clathrate Structures in Rare Earth Hydrides at High Pressures: Possible Route to Room-Temperature Superconductivity.

PubMed

Peng, Feng; Sun, Ying; Pickard, Chris J; Needs, Richard J; Wu, Qiang; Ma, Yanming

2017-09-08

Room-temperature superconductivity has been a long-held dream and an area of intensive research. Recent experimental findings of superconductivity at 200 K in highly compressed hydrogen (H) sulfides have demonstrated the potential for achieving room-temperature superconductivity in compressed H-rich materials. We report first-principles structure searches for stable H-rich clathrate structures in rare earth hydrides at high pressures. The peculiarity of these structures lies in the emergence of unusual H cages with stoichiometries H_{24}, H_{29}, and H_{32}, in which H atoms are weakly covalently bonded to one another, with rare earth atoms occupying the centers of the cages. We have found that high-temperature superconductivity is closely associated with H clathrate structures, with large H-derived electronic densities of states at the Fermi level and strong electron-phonon coupling related to the stretching and rocking motions of H atoms within the cages. Strikingly, a yttrium (Y) H_{32} clathrate structure of stoichiometry YH_{10} is predicted to be a potential room-temperature superconductor with an estimated T_{c} of up to 303 K at 400 GPa, as derived by direct solution of the Eliashberg equation.

Highly Stretchable Superhydrophobic Composite Coating Based on Self-Adaptive Deformation of Hierarchical Structures.

PubMed

Hu, Xin; Tang, Changyu; He, Zhoukun; Shao, Hong; Xu, Keqin; Mei, Jun; Lau, Woon-Ming

2017-05-01

With the rapid development of stretchable electronics, functional textiles, and flexible sensors, water-proof protection materials are required to be built on various highly flexible substrates. However, maintaining the antiwetting of superhydrophobic surface under stretching is still a big challenge since the hierarchical structures at hybridized micro-nanoscales are easily damaged following large deformation of the substrates. This study reports a highly stretchable and mechanically stable superhydrophobic surface prepared by a facile spray coating of carbon black/polybutadiene elastomeric composite on a rubber substrate followed by thermal curing. The resulting composite coating can maintain its superhydrophobic property (water contact angle ≈170° and sliding angle <4°) at an extremely large stretching strain of up to 1000% and can withstand 1000 stretching-releasing cycles without losing its superhydrophobic property. Furthermore, the experimental observation and modeling analysis reveal that the stable superhydrophobic properties of the composite coating are attributed to the unique self-adaptive deformation ability of 3D hierarchical roughness of the composite coating, which delays the Cassie-Wenzel transition of surface wetting. In addition, it is first observed that the damaged coating can automatically recover its superhydrophobicity via a simple stretching treatment without incorporating additional hydrophobic materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

para-Azaquinodimethane: A Compact Quinodimethane Variant as an Ambient Stable Building Block for High-Performance Low Band Gap Polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xuncheng; He, Bo; Anderson, Christopher L.

Quinoidal structures incorporating expanded para-quinodimethane (p-QM) units have garnered great interest as functional organic electronic, optical, and magnetic materials. The direct use of the compact p-QM unit as an electronic building block, however, has been inhibited by the high reactivity conveyed by its biradical character. Herein, we introduce a stable p-QM variant, namely p-azaquinodimethane (p-AQM), that incorporates nitrogen atoms in the central ring and alkoxy substituents on the periphery to increase the stability of the quinoidal structure. The succinct synthesis from readily available precursors leads to regio- and stereospecific p-AQMs that can be readily integrated into the backbone of conjugatedmore » polymers. The quinoidal character of the p-AQM unit endows the resulting polymers with narrow band gaps and high carrier transport mobilities. The study of a series of copolymers employing different numbers of thiophene units revealed an unconventional trend in band gaps, which is distinct from the widely adopted donor-acceptor approach to tuning the band gaps of conjugated polymers. Theoretical calculations have shed light on the nature of this trend, which may provide a unique class of conjugated polymers with promising optical and electronic properties.« less

para-Azaquinodimethane: A Compact Quinodimethane Variant as an Ambient Stable Building Block for High-Performance Low Band Gap Polymers

DOE PAGES

Liu, Xuncheng; He, Bo; Anderson, Christopher L.; ...

2017-05-24

Quinoidal structures incorporating expanded para-quinodimethane (p-QM) units have garnered great interest as functional organic electronic, optical, and magnetic materials. The direct use of the compact p-QM unit as an electronic building block, however, has been inhibited by the high reactivity conveyed by its biradical character. Herein, we introduce a stable p-QM variant, namely p-azaquinodimethane (p-AQM), that incorporates nitrogen atoms in the central ring and alkoxy substituents on the periphery to increase the stability of the quinoidal structure. The succinct synthesis from readily available precursors leads to regio- and stereospecific p-AQMs that can be readily integrated into the backbone of conjugatedmore » polymers. The quinoidal character of the p-AQM unit endows the resulting polymers with narrow band gaps and high carrier transport mobilities. The study of a series of copolymers employing different numbers of thiophene units revealed an unconventional trend in band gaps, which is distinct from the widely adopted donor-acceptor approach to tuning the band gaps of conjugated polymers. Theoretical calculations have shed light on the nature of this trend, which may provide a unique class of conjugated polymers with promising optical and electronic properties.« less

Three-Dimensional Flexible Complementary Metal-Oxide-Semiconductor Logic Circuits Based On Two-Layer Stacks of Single-Walled Carbon Nanotube Networks.

PubMed

Zhao, Yudan; Li, Qunqing; Xiao, Xiaoyang; Li, Guanhong; Jin, Yuanhao; Jiang, Kaili; Wang, Jiaping; Fan, Shoushan

2016-02-23

We have proposed and fabricated stable and repeatable, flexible, single-walled carbon nanotube (SWCNT) thin film transistor (TFT) complementary metal-oxide-semiconductor (CMOS) integrated circuits based on a three-dimensional (3D) structure. Two layers of SWCNT-TFT devices were stacked, where one layer served as n-type devices and the other one served as p-type devices. On the basis of this method, it is able to save at least half of the area required to construct an inverter and make large-scale and high-density integrated CMOS circuits easier to design and manufacture. The 3D flexible CMOS inverter gain can be as high as 40, and the total noise margin is more than 95%. Moreover, the input and output voltage of the inverter are exactly matched for cascading. 3D flexible CMOS NOR, NAND logic gates, and 15-stage ring oscillators were fabricated on PI substrates with high performance as well. Stable electrical properties of these circuits can be obtained with bending radii as small as 3.16 mm, which shows that such a 3D structure is a reliable architecture and suitable for carbon nanotube electrical applications in complex flexible and wearable electronic devices.

Physico-Chemical Evaluation of Rationally Designed Melanins as Novel Nature-Inspired Radioprotectors

PubMed Central

Schweitzer, Andrew D.; Howell, Robertha C.; Jiang, Zewei; Bryan, Ruth A.; Gerfen, Gary; Chen, Chin-Cheng; Mah, Dennis; Cahill, Sean

2009-01-01

Background Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melanized microorganisms against high doses of ionizing radiation. However, the physics of melanin interaction with ionizing radiation is unknown. Methodology/Principal Findings We rationally designed melanins from either 5-S-cysteinyl-DOPA, L-cysteine/L-DOPA, or L-DOPA with diverse structures as shown by elemental analysis and HPLC. Sulfur-containing melanins had higher predicted attenuation coefficients than non-sulfur-containing melanins. All synthetic melanins displayed strong electron paramagnetic resonance (2.14·1018, 7.09·1018, and 9.05·1017 spins/g, respectively), with sulfur-containing melanins demonstrating more complex spectra and higher numbers of stable free radicals. There was no change in the quality or quantity of the stable free radicals after high-dose (30,000 cGy), high-energy (137Cs, 661.6 keV) irradiation, indicating a high degree of radical stability as well as a robust resistance to the ionizing effects of gamma irradiation. The rationally designed melanins protected mammalian cells against ionizing radiation of different energies. Conclusions/Significance We propose that due to melanin's numerous aromatic oligomers containing multiple π-electron system, a generated Compton recoil electron gradually loses energy while passing through the pigment, until its energy is sufficiently low that it can be trapped by stable free radicals present in the pigment. Controlled dissipation of high-energy recoil electrons by melanin prevents secondary ionizations and the generation of damaging free radical species. PMID:19789711

Physico-chemical evaluation of rationally designed melanins as novel nature-inspired radioprotectors.

PubMed

Schweitzer, Andrew D; Howell, Robertha C; Jiang, Zewei; Bryan, Ruth A; Gerfen, Gary; Chen, Chin-Cheng; Mah, Dennis; Cahill, Sean; Casadevall, Arturo; Dadachova, Ekaterina

2009-09-30

Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melanized microorganisms against high doses of ionizing radiation. However, the physics of melanin interaction with ionizing radiation is unknown. We rationally designed melanins from either 5-S-cysteinyl-DOPA, L-cysteine/L-DOPA, or L-DOPA with diverse structures as shown by elemental analysis and HPLC. Sulfur-containing melanins had higher predicted attenuation coefficients than non-sulfur-containing melanins. All synthetic melanins displayed strong electron paramagnetic resonance (2.14.10(18), 7.09.10(18), and 9.05.10(17) spins/g, respectively), with sulfur-containing melanins demonstrating more complex spectra and higher numbers of stable free radicals. There was no change in the quality or quantity of the stable free radicals after high-dose (30,000 cGy), high-energy ((137)Cs, 661.6 keV) irradiation, indicating a high degree of radical stability as well as a robust resistance to the ionizing effects of gamma irradiation. The rationally designed melanins protected mammalian cells against ionizing radiation of different energies. We propose that due to melanin's numerous aromatic oligomers containing multiple pi-electron system, a generated Compton recoil electron gradually loses energy while passing through the pigment, until its energy is sufficiently low that it can be trapped by stable free radicals present in the pigment. Controlled dissipation of high-energy recoil electrons by melanin prevents secondary ionizations and the generation of damaging free radical species.

Population pressures: threat to democracy.

PubMed

1992-06-01

The desire for political freedom and representative government is spreading throughout the world. The stability of democratic bodies is dependent on wise leaders, foreign aid, and slowing population growth. Rapid population growth strains political institutions and increases pressure on services. A Population Crisis Committee study found that only a few democratic countries with serious demographic pressures remained stable. The most stable countries were ones with lower levels of population pressure. Most of the 31 unstable countries were in Africa and in a band stretching from the Middle East to South Asia, and almost all had serious demographic pressures. Only 5 stable countries had high or very high demographic pressures. Since countries in the world are interdependent, population pressures have adverse consequences everywhere. Population pressures in the developing world are considered enhanced by the rapid growth of cities. Both the developed and the developing world face the problems of clogged highways, loss of wilderness, polluted lakes and streams, and stifling smog and acid rain conditions. The sociopolitical implications of demographic changes vary from country to country, but rapid growth and maldistribution of population strains existing political, social, and economic structures and relations between nations. Urban areas are the arena for clashes of cultures, competition for scarce housing and jobs, the breakdown of traditional family and social structures, and juxtapositions of extreme wealth next to extreme poverty. The growth of independent nation states since the 1940s has not allowed much time for development of effective political institutions. There are many obstacles to national unity and popular political participation. The potential for political instability is correlated with a number of factors: large youth populations in overcrowded cities with too high expectations and limited opportunities, diverse and intense ethnic and religious factors, and oppressive governments which violate human rights. Rapid growth has a harmful impact on the environment.

Protein chainmail variants in dsDNA viruses

PubMed Central

Zhou, Z. Hong; Chiou, Joshua

2017-01-01

First discovered in bacteriophage HK97, biological chainmail is a highly stable system formed by concatenated protein rings. Each subunit of the ring contains the HK97-like fold, which is characterized by its submarine-like shape with a 5-stranded β sheet in the axial (A) domain, spine helix in the peripheral (P) domain, and an extended (E) loop. HK97 capsid consists of covalently-linked copies of just one HK97-like fold protein and represents the most effective strategy to form highly stable chainmail needed for dsDNA genome encapsidation. Recently, near-atomic resolution structures enabled by cryo electron microscopy (cryoEM) have revealed a range of other, more complex variants of this strategy for constructing dsDNA viruses. The first strategy, exemplified by P22-like phages, is the attachment of an insertional (I) domain to the core 5-stranded β sheet of the HK97-like fold. The atomic models of the Bordetella phage BPP-1 showcases an alternative topology of the classic HK97 topology of the HK97-like fold, as well as the second strategy for constructing stable capsids, where an auxiliary jellyroll protein dimer serves to cement the non-covalent chainmail formed by capsid protein subunits. The third strategy, found in lambda-like phages, uses auxiliary protein trimers to stabilize the underlying non-covalent chainmail near the 3-fold axis. Herpesviruses represent highly complex viruses that use a combination of these strategies, resulting in four-level hierarchical organization including a non-covalent chainmail formed by the HK97-like fold domain found in the floor region. A thorough understanding of these structures should help unlock the enigma of the emergence and evolution of dsDNA viruses and inform bioengineering efforts based on these viruses. PMID:29177192

Structure and variability of symbiotic assemblages associated with feather stars (Crinoidea: Comatulida) Himerometra robustipinna

NASA Astrophysics Data System (ADS)

Britayev, T. A.; Beksheneva, L. F.; Deart, Yu. V.; Mekhova, E. S.

2016-09-01

The paper considers the influence of the geographical position and local conditions on the structure and abundance of symbiotic communities (SCs) associated with the crinoid Himerometra robustipinna. Two water areas at the coast of Vietnam (Nhatrang Bay and the Anthoy Archipelago; our data), Hansa Bay (Papua, New Guinea; Deyen et al., 2006), and the Great Barrier Reef (Australia; Fabricius and Dale, 1993) were compared. We found a similarity in the contribution from the main taxa to the structure of SCs between geographically distant water areas—Nhatrang Bay, Hansa Bay, and the Great Barrier Reef (GBR)—and strong differences between the two Vietnamese water areas. A possible reason for the differences in the SC structure in these water areas is not their geographical location, but the environmental conditions, which are more stable in the seaward part of Nhatrang Bay and less stable in the Anthoy Archipelago. The abundances of symbionts in the water areas of the coast of Vietnam are similar to each other and strongly different from Hansa Bay and the GBR. We suppose that a factor regulating the abundance of symbionts is their consumption by predatory fishes. A low abundance of fishes in the area of active coastal fishery (the coast of Vietnam) makes possible the existence of SCs with a high abundance. In Hansa Bay and the GBR where fishery pressure is low, a high number of predators leads to a low abundance of symbionts.

Solar cell module lamination process

DOEpatents

Carey, Paul G.; Thompson, Jesse B.; Aceves, Randy C.

2002-01-01

A solar cell module lamination process using fluoropolymers to provide protection from adverse environmental conditions and thus enable more extended use of solar cells, particularly in space applications. A laminate of fluoropolymer material provides a hermetically sealed solar cell module structure that is flexible and very durable. The laminate is virtually chemically inert, highly transmissive in the visible spectrum, dimensionally stable at temperatures up to about 200.degree. C. highly abrasion resistant, and exhibits very little ultra-violet degradation.

Toward highly stable solid-state unconventional thin-film battery-supercapacitor hybrid devices: Interfacing vertical core-shell array electrodes with a gel polymer electrolyte

NASA Astrophysics Data System (ADS)

Pandey, Gaind P.; Klankowski, Steven A.; Liu, Tao; Wu, Judy; Li, Jun

2017-02-01

A novel solid-state battery-supercapacitor hybrid device is fabricated for high-performance electrical energy storage using a Si anode and a TiO2 cathode in conjunction with a flexible, solid-like gel polymer electrolyte film as the electrolyte and separator. The electrodes were fabricated as three-dimensional nanostructured vertical arrays by sputtering active materials as conformal shells on vertically aligned carbon nanofibers (VACNFs) which serve as the current collector and structural template. Such nanostructured vertical core-shell array-electrodes enable short Li-ion diffusion path and large pseudocapacitive contribution by fast surface reactions, leading to the hybrid features of batteries and supercapacitors that can provide high specific energy over a wide range of power rates. Due to the improved mechanical stability of the infiltrated composite structure, the hybrid cell shows excellent cycling stability and is able to retain more than 95% of the original capacity after 3500 cycles. More importantly, this solid-state device can stably operate in a temperature range from -20 to 60 °C with a very low self-discharge rate and an excellent shelf life. This solid-state architecture is promising for the development of highly stable thin-film hybrid energy storage devices for unconventional applications requiring largely varied power, wider operation temperature, long shelf-life and higher safety standards.

Extreme Genetic Structure in a Small-Bodied Freshwater Fish, the Purple Spotted Gudgeon, Mogurnda adspersa (Eleotridae)

PubMed Central

Hughes, Jane M.; Real, Kathryn M.; Marshall, Jonathan C.; Schmidt, Daniel J.

2012-01-01

Freshwater fish are a group that is especially susceptible to biodiversity loss as they often exist naturally in small, fragmented populations that are vulnerable to habitat degradation, pollution and introduction of exotic species. Relatively little is known about spatial dynamics of unperturbed populations of small-bodied freshwater fish species. This study examined population genetic structure of the purple spotted gudgeon (Mogurnda adspersa, Eleotridae), a small-bodied freshwater fish that is widely distributed in eastern Australia. The species is threatened in parts of its range but is common in coastal streams of central Queensland where this study took place. Microsatellite (msat) and mitochondrial DNA (mtDNA) variation was assessed for nine sites from four stream sections in two drainage basins. Very high levels of among population structure were observed (msat F ST = 0.18; mtDNA ΦST = 0.85) and evidence for contemporary migration among populations was rare and limited to sites within the same section of stream. Hierarchical structuring of variation was best explained by stream section rather than by drainage basin. Estimates of contemporary effective population size for each site was low (range 28 – 63, Sibship method), but compared favorably with similar estimates for other freshwater fish species, and there was no genetic evidence for inbreeding or recent population bottlenecks. In conclusion, within a stable part of its range, M adspersa exists as a series of small, demographically stable populations that are highly isolated from one another. Complimentary patterns in microsatellites and mtDNA indicate this structuring is the result of long-term processes that have developed over a remarkably small spatial scale. High population structure and limited dispersal mean that recolonisation of locally extinct populations is only likely to occur from closely situated populations within stream sections. Limited potential for recolonisation should be considered as an important factor in conservation and management of this species. PMID:22808190

Structural Transformation Detection Contributes to Screening of Behaviorally Active Compounds: Dynamic Binding Process Analysis of DhelOBP21 from Dastarcus helophoroides.

PubMed

Yang, Rui-Nan; Li, Dong-Zhen; Yu, Guangqiang; Yi, Shan-Cheng; Zhang, Yinan; Kong, De-Xin; Wang, Man-Qun

2017-12-01

In light of reverse chemical ecology, the fluorescence competitive binding assays of functional odorant binding proteins (OBPs) is a recent advanced approach for screening behaviorally active compounds of insects. Previous research on Dastareus helophoroides identified a minus-C OBP, DhelOBP21, which preferably binds to several ligands. In this study, only (+)-β-pinene proved attractive to unmated adult beetles. To obtain a more in-depth explanation of the lack of behavioral activity of other ligands we selected compounds with high (camphor) and low (β-caryophyllene) binding affinities. The structural transformation of OBPs was investigated using well-established approaches for studying binding processes, such as fluorescent quenching assays, circular dichroism, and molecular dynamics. The dynamic binding process revealed that the flexibility of DhelOBP21 seems conducive to binding specific ligands, as opposed to broad substrate binding. The compound (+)-β-pinene and DhelOBP21 formed a stable complex through a secondary structural transformation of DhelOBP21, in which its amino-terminus transformed from random coil to an α-helix to cover the binding pocket. On the other hand, camphor could not efficiently induce a stable structural transformation, and its high binding affinities were due to strong hydrogen-bonding, compromising the structure of the protein. The other compound, β-caryophyllene, only collided with DhelOBP21 and could not be positioned in the binding pocket. Studying structural transformation of these proteins through examining the dynamic binding process rather than using approaches that just measure binding affinities such as fluorescence competitive binding assays can provide a more efficient and reliable approach for screening behaviorally active compounds.

Patterns and Predictors of Language and Literacy Abilities 4-10 Years in the Longitudinal Study of Australian Children.

PubMed

Zubrick, Stephen R; Taylor, Catherine L; Christensen, Daniel

2015-01-01

Oral language is the foundation of literacy. Naturally, policies and practices to promote children's literacy begin in early childhood and have a strong focus on developing children's oral language, especially for children with known risk factors for low language ability. The underlying assumption is that children's progress along the oral to literate continuum is stable and predictable, such that low language ability foretells low literacy ability. This study investigated patterns and predictors of children's oral language and literacy abilities at 4, 6, 8 and 10 years. The study sample comprised 2,316 to 2,792 children from the first nationally representative Longitudinal Study of Australian Children (LSAC). Six developmental patterns were observed, a stable middle-high pattern, a stable low pattern, an improving pattern, a declining pattern, a fluctuating low pattern, and a fluctuating middle-high pattern. Most children (69%) fit a stable middle-high pattern. By contrast, less than 1% of children fit a stable low pattern. These results challenged the view that children's progress along the oral to literate continuum is stable and predictable. Multivariate logistic regression was used to investigate risks for low literacy ability at 10 years and sensitivity-specificity analysis was used to examine the predictive utility of the multivariate model. Predictors were modelled as risk variables with the lowest level of risk as the reference category. In the multivariate model, substantial risks for low literacy ability at 10 years, in order of descending magnitude, were: low school readiness, Aboriginal and/or Torres Strait Islander status and low language ability at 8 years. Moderate risks were high temperamental reactivity, low language ability at 4 years, and low language ability at 6 years. The following risk factors were not statistically significant in the multivariate model: Low maternal consistency, low family income, health care card, child not read to at home, maternal smoking, maternal education, family structure, temperamental persistence, and socio-economic area disadvantage. The results of the sensitivity-specificity analysis showed that a well-fitted multivariate model featuring risks of substantive magnitude did not do particularly well in predicting low literacy ability at 10 years.

A Reinvestigation of the Dimer of para-Benzoquinone with Pyrimidine with MP2, CCSD(T) and DFT using Functionals including those Designed to Describe Dispersion

PubMed Central

Marianski, Mateusz; Oliva, Antoni

2012-01-01

We reevaluate the interaction of pyridine and p-benzoquinone using functionals designed to treat dispersion. We compare the relative energies of four different structures: stacked, T-shaped (identified for the first time) and two planar H-bonded geometries using these functionals (B97-D, ωB97x-D, M05, M05-2X, M06, M06L, M06-2X), other functionals (PBE1PBE, B3LYP, X3LYP), MP2 and CCSD(T) using basis sets as large as cc-pVTZ. The functionals designed to treat dispersion behave erratically as the predictions of the most stable structure vary considerably. MP2 predicts the experimentally observed structure (H-bonded) to be the least stable, while single point CCSD(T) at the MP2 optimized geometry correctly predicts the observed structure to be most stable. We have confirmed the assignment of the experimental structure using new calculations of the vibrational frequency shifts previously used to identify the structure. The MP2/cc-pVTZ vibrational calculations are in excellent agreement with the observations. All methods used to calculate the energies provide vibrational shifts that agree with the observed structure even though most do not predict this structure to be most stable. The implications for evaluating possible π-stacking in biologically important systems are discussed. PMID:22765283