Isolation and Characterization of a Toxic Moiety of Low Molecular Weight from Clostridium botulinum Type A

PubMed Central

Gerwing, Julia; Dolman, Claude E.; Bains, Hardial S.

1965-01-01

Gerwing, Julia (The University of British Columbia, Vancouver, B.C., Canada), Claude E. Dolman, and Hardial S. Bains. Isolation and characterization of a toxic moiety of low molecular weight from Clostridium botulinum type A. J. Bacteriol. 89:1383–1386. 1965.—A toxic moiety of low molecular weight has been isolated from a type A strain of Clostridium botulinum, by a method involving ammonium sulfate precipitation and elution through diethylaminoethyl cellulose at pH 5.6. By means of electrophoresis and ultracentrifugation, the toxic substance was shown to be homogeneous; a molecular weight of 12,200 was calculated. Images PMID:14293025

Growth of BaIn2S4 layers through the hot-wall-epitaxy method and their electric/optical properties

NASA Astrophysics Data System (ADS)

Hong, K. J.; Jeong, T. S.; Youn, C. J.

2016-01-01

The epitaxial growth of photoconductive BaIn2S4 layers was first achieved through the hot-wall-epitaxy method. In spite of an existing large lattice mismatch between the substrate and layer, BaIn2S4 layers were epitaxially grown along the (440) direction onto a GaAs (100) substrate. Thus, the lattice mismatch was well interpreted through a coincidence site lattice model. From the relationship between the reciprocal temperature and the carrier concentration, the three donor levels were found to be 1.3, 20.2, and 78.3 meV below the conduction band. These donor levels are caused by the native defects originating from slight stoichiometric deviations. From the temperature dependence of the Hall mobility, two specific scatterings were observed. One, at high temperatures ranging over 180 K, is mainly due to the acoustic phonon mode of lattice vibrations through a deformation potential. The other, at low temperatures ranging below 100 K, is ascribed to the dislocation scattering. From the photocurrent (PC) measurement, three PC peaks due to band-to-band transitions were observed. Also, based on the analysis of optical absorption and PC spectra, the optical band gap has been compared and matched well with Eg(T)=Eg(0)-3.95×10-3T2/(T+499), where Eg(0) is estimated to be 3.0597, 3.2301, and 3.2606 eV for the transitions corresponding to the valence band states of peaks A, B and C, respectively.

76 FR 76710 - Baine, Edward H.; Notice of Filing

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-08

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ID-6541-001] Baine, Edward H.; Notice of Filing Take notice that on December 1, 2011, Edward H. Baine submitted for filing, an application for authority to hold interlocking positions, pursuant to section 305(b) of the Federal Power Act...

Characterization of coarse bainite transformation in low carbon steel during simulated welding thermal cycles

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

Lan, Liangyun, E-mail: lanly@me.neu.edu.cn; State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819; Kong, Xiangwei

2015-07-15

Coarse austenite to bainite transformation in low carbon steel under simulated welding thermal cycles was morphologically and crystallographically characterized by means of optical microscope, transmission electron microscope and electron backscattered diffraction technology. The results showed that the main microstructure changes from a mixture of lath martensite and bainitic ferrite to granular bainite with the increase in cooling time. The width of bainitic laths also increases gradually with the cooling time. For a welding thermal cycle with relatively short cooling time (e.g. t{sub 8/5} is 30 s), the main mode of variant grouping at the scale of individual prior austenite grainsmore » changes from Bain grouping to close-packed plane grouping with the progress of phase transformation, which results in inhomogeneous distribution of high angle boundaries. As the cooling time is increased, the Bain grouping of variants becomes predominant mode, which enlarges the effective grain size of product phase. - Highlights: • Main microstructure changes and the width of lath structure increases with cooling time. • Variant grouping changes from Bain zone to close-packed plane grouping with the transformation. • The change of variant grouping results in uneven distribution of high angle grain boundary. • Bain grouping is main mode for large heat input, which lowers the density of high angle boundary.« less

78 FR 21365 - Ocean Transportation Intermediary License Applicants

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-10

...), Application Type: QI Change. Morgan USA Logistics Inc (NVO), 16 Birchwood Park Drive, Syosset, NY 11791... Hull Logistics, LLC (NVO & OFF), 17890 Cedarwood Drive, Riverside, CA 92803, Officers: Stanley J... Baines, Chairman of the Board, Application Type: New NVO & OFF License. Point Global Logistics, LLC (OFF...

77 FR 24491 - Change in Bank Control Notices; Acquisitions of Shares of a Bank or Bank Holding Company

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-24

... Board of Governors. Interested persons may express their views in writing to the Reserve Bank indicated... co-trustee of the RMB 2012 Family Trust; trustee of the Ray Mark Bain 2007 Trust; and trustee of the Ray Mark Bain Children's Trusts; Michael Lewis Bain, Canyon, Texas, individually, as co-trustee of the...

78 FR 31549 - Change in Bank Control Notices; Acquisitions of Shares of a Bank or Bank Holding Company

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-24

... Board of Governors. Interested persons may express their views in writing to the Reserve Bank indicated..., Dallas, Texas 75201-2272: 1. Ray Mark Bain, Lubbock, Texas, individually, as co-trustee of the RMB 2012 Family Trust, trustee of the Ray Mark Bain 2007 Trust, and trustee of the Ray Mark Bain Children's Trust...

Energy barrier of bcc-fcc phase transition via the Bain path in Yukawa system

NASA Astrophysics Data System (ADS)

Kiyokawa, Shuji

2018-05-01

In the Yukawa system with the dimensionless screening parameter κ>1.5 , when bcc-fcc transition occurs via Bain path, we show that spontaneous transitions do not occur even if the system temperature reaches the transition point of bcc-fcc because it is necessary to increase once the free energy in the process of transition from bcc to fcc through Bain deformation. Here, we refer the temporary increment of the free energy during Bain deformation as Bain barrier. Since there are the Bain barriers at the transitions between bcc and fcc phases, these phases may coexist as metastable state in the wide region (not a coexistence line) of κ and the coupling constant Γ. We study the excess energy of the system and the free energy difference between bcc and fcc phases by the Monte Carlo method, where the simulation box is divided into a large number of elements with small volume and a particle in the box is restricted be placed in one of these elements. By this method, we can tabulate the values of the interparticle potential and can calculate the internal energy fast and precisely.

Functional properties of slow and fast gastrocnemius muscle fibers after a 17-day spaceflight

NASA Technical Reports Server (NTRS)

Widrick, J. J.; Romatowski, J. G.; Norenberg, K. M.; Knuth, S. T.; Bain, J. L.; Riley, D. A.; Trappe, S. W.; Trappe, T. A.; Costill, D. L.; Fitts, R. H.

2001-01-01

The purpose of this investigation was to study the effects of a 17-day spaceflight on the contractile properties of individual fast- and slow-twitch fibers isolated from biopsies of the fast-twitch gastrocnemius muscle of four male astronauts. Single chemically skinned fibers were studied during maximal Ca2+-activated contractions with fiber myosin heavy chain (MHC) isoform expression subsequently determined by SDS gel electrophoresis. Spaceflight had no significant effect on the mean diameter or specific force of single fibers expressing type I, IIa, or IIa/IIx MHC, although a small reduction in average absolute force (P(o)) was observed for the type I fibers (0.68 +/- 0.02 vs. 0.64 +/- 0.02 mN, P < 0.05). Subject-by-flight interactions indicated significant intersubject variation in response to the flight, as postflight fiber diameter and P(o) where significantly reduced for the type I and IIa fibers obtained from one astronaut and for the type IIa fibers from another astronaut. Average unloaded shortening velocity [V(o), in fiber lengths (FL)/s] was greater after the flight for both type I (0.60 +/- 0.03 vs. 0.76 +/- 0.02 FL/s) and IIa fibers (2.33 +/- 0.25 vs. 3.10 +/- 0.16 FL/s). Postflight peak power of the type I and IIa fibers was significantly reduced only for the astronaut experiencing the greatest fiber atrophy and loss of P(o). These results demonstrate that 1) slow and fast gastrocnemius fibers show little atrophy and loss of P(o) but increased V(o) after a typical 17-day spaceflight, 2) there is, however, considerable intersubject variation in these responses, possibly due to intersubject differences in in-flight physical activity, and 3) in these four astronauts, fiber atrophy and reductions in P(o) were less for slow and fast fibers obtained from the phasic fast-twitch gastrocnemius muscle compared with slow and fast fibers obtained from the slow antigravity soleus [J. J. Widrick, S. K. Knuth, K. M. Norenberg, J. G. Romatowski, J. L. W. Bain, D. A. Riley, M. Karhanek, S. W. Trappe, T. A. Trappe, D. L. Costill, and R. H. Fitts. J Physiol (Lond) 516: 915-930, 1999].

Laser femtoseconde, filamentation, nuage et orage

NASA Astrophysics Data System (ADS)

Courvoisier, F.; Boutou, V.; Kasparian, J.; Salmon, E.; Méjean, G.; Yu, J.; Wolf, J.-P.

2005-06-01

Les applications telles que le contrôle de foudre grâce aux filaments autoguidés générés par un laser femtoseconde nécessitent de propager un tel filament à travers des aérosols de gouttes d'eau. Nous montrons qu'un filament survit à son interaction avec une goutte de diamètre comparable au sien (95 μ m), ainsi qu'à des nuages d'épaisseur optique 3,2, soit 5% de transmission. Cette transmission est permise par la présence d'un “bain de photons” autour du filament. Ce bain forme un réservoir contenant une part importante de l'énergie du faisceau, en équilibre avec le filament, et favorisant son alimentation.

Optimality of general lattice transformations with applications to the Bain strain in steel

NASA Astrophysics Data System (ADS)

Koumatos, K.; Muehlemann, A.

2016-04-01

This article provides a rigorous proof of a conjecture by E. C. Bain in 1924 on the optimality of the so-called Bain strain based on a criterion of least atomic movement. A general framework that explores several such optimality criteria is introduced and employed to show the existence of optimal transformations between any two Bravais lattices. A precise algorithm and a graphical user interface to determine this optimal transformation is provided. Apart from the Bain conjecture concerning the transformation from face-centred cubic to body-centred cubic, applications include the face-centred cubic to body-centred tetragonal transition as well as the transformation between two triclinic phases of terephthalic acid.

Optimality of general lattice transformations with applications to the Bain strain in steel

PubMed Central

Koumatos, K.

2016-01-01

This article provides a rigorous proof of a conjecture by E. C. Bain in 1924 on the optimality of the so-called Bain strain based on a criterion of least atomic movement. A general framework that explores several such optimality criteria is introduced and employed to show the existence of optimal transformations between any two Bravais lattices. A precise algorithm and a graphical user interface to determine this optimal transformation is provided. Apart from the Bain conjecture concerning the transformation from face-centred cubic to body-centred cubic, applications include the face-centred cubic to body-centred tetragonal transition as well as the transformation between two triclinic phases of terephthalic acid. PMID:27274692

Synthesis, structure, and bonding of BaTl4. Size effects on encapsulation of cations in electron-poor metal networks.

PubMed

Dai, Jing-Cao; Gupta, Shalabh; Corbett, John D

2011-01-03

The synthesis, structure, and bonding of BaTl(4) are described [C2/m, Z = 4, a = 12.408(3), b = 5.351(1), c = 10.383(2) Å, β = 116.00(3)°]. Pairs of edge-sharing Tl pentagons are condensed to generate a network of pentagonal biprisms along b that encapsulate Ba atoms. Alternating levels of prisms along c afford six more bifunctional Tl atoms about the waists of the biprisms, giving Ba a coordination number of 16. Each Tl atom is bonded to five to seven other Tl atoms and to three to five Ba atoms. There is also strong evidence that Hg substitutes preferentially in the shared edges of the Tl biprisms in BaHg(0.80)Tl(3.20) to generate more strongly bound Hg(2) dimers. Cations that are too small relative to the dimensions of the surrounding polyanionic network make this BaTl(4) structure (and for SrIn(4) and perhaps EuIn(4) as well) one stable alternative to tetragonal BaAl(4)-type structures in which cations are bound in larger hexagon-faced nets, as for BaIn(4) and SrGa(4). Characteristic condensation and augmentation of cation-centered prismatic units is common among many relatively cation- and electron-poor, polar derivatives of Zintl phases gain stability. At the other extreme, the large family of Frank-Kasper phases in which the elements exhibit larger numbers of bonded neighbors are sometimes referred to as orbitally rich.

Genetics Home Reference: 22q11.2 duplication

MedlinePlus

... Bean LJH, Bird TD, Ledbetter N, Mefford HC, Smith RJH, Stephens K, editors. GeneReviews® [Internet]. Seattle (WA): ... Citation on PubMed Yu S, Cox K, Friend K, Smith S, Buchheim R, Bain S, Liebelt J, Thompson E, Bratkovic ...

The Determination of Phytotoxicity.

DTIC Science & Technology

1981-01-01

Fluorides. National Academy of Sciences, Washington, DC. BIOASSAY TESIS Brancato, F.P. and N.S. Golding. 11953. The diameter of the mold colony as a...1963. Influence of pesticide residues on soil microbiological and chemicail properties. Residue Rev. 4:96-129. Martini, J.P., R.C. Baines, and J.0

Mapleson's Breathing Systems.

PubMed

Kaul, Tej K; Mittal, Geeta

2013-09-01

Mapleson breathing systems are used for delivering oxygen and anaesthetic agents and to eliminate carbon dioxide during anaesthesia. They consist of different components: Fresh gas flow, reservoir bag, breathing tubes, expiratory valve, and patient connection. There are five basic types of Mapleson system: A, B, C, D and E depending upon the different arrangements of these components. Mapleson F was added later. For adults, Mapleson A is the circuit of choice for spontaneous respiration where as Mapleson D and its Bains modifications are best available circuits for controlled ventilation. For neonates and paediatric patients Mapleson E and F (Jackson Rees modification) are the best circuits. In this review article, we will discuss the structure of the circuits and functional analysis of various types of Mapleson systems and their advantages and disadvantages.

Association of Supply Type with Fecal Contamination of Source Water and Household Stored Drinking Water in Developing Countries: A Bivariate Meta-analysis

PubMed Central

Bain, Robert E.S.; Cronk, Ryan; Wright, Jim A.; Bartram, Jamie

2015-01-01

Background Access to safe drinking water is essential for health. Monitoring access to drinking water focuses on water supply type at the source, but there is limited evidence on whether quality differences at the source persist in water stored in the household. Objectives We assessed the extent of fecal contamination at the source and in household stored water (HSW) and explored the relationship between contamination at each sampling point and water supply type. Methods We performed a bivariate random-effects meta-analysis of 45 studies, identified through a systematic review, that reported either the proportion of samples free of fecal indicator bacteria and/or individual sample bacteria counts for source and HSW, disaggregated by supply type. Results Water quality deteriorated substantially between source and stored water. The mean percentage of contaminated samples (noncompliance) at the source was 46% (95% CI: 33, 60%), whereas mean noncompliance in HSW was 75% (95% CI: 64, 84%). Water supply type was significantly associated with noncompliance at the source (p < 0.001) and in HSW (p = 0.03). Source water (OR = 0.2; 95% CI: 0.1, 0.5) and HSW (OR = 0.3; 95% CI: 0.2, 0.8) from piped supplies had significantly lower odds of contamination compared with non-piped water, potentially due to residual chlorine. Conclusions Piped water is less likely to be contaminated compared with other water supply types at both the source and in HSW. A focus on upgrading water services to piped supplies may help improve safety, including for those drinking stored water. Citation Shields KF, Bain RE, Cronk R, Wright JA, Bartram J. 2015. Association of supply type with fecal contamination of source water and household stored drinking water in developing countries: a bivariate meta-analysis. Environ Health Perspect 123:1222–1231; http://dx.doi.org/10.1289/ehp.1409002 PMID:25956006

Langmuir-Gibbs Surface Phases and Transitions

NASA Astrophysics Data System (ADS)

Ocko, Benjamin; Sloutskin, Eli; Sapir, Zvi; Tamam, Lilach; Deutsch, Moshe; Bain, Colin

2007-03-01

Recent synchrotron x-ray measurements reveal surface ordering transitions in films of medium-length linear hydrocarbons (alkanes), spread on the water surface. Alkanes longer than hexane do not spread on the free surface of water. However, sub-mM concentrations of some anionic surfactants (e.g. CTAB) induce formation of thermodynamically stable alkane monolayers, through a ``pseudo-partial wetting'' phenomenon[1]. The monolayers, incorporating both water-insoluble alkanes (Langmuir) and water-soluble CTAB molecules (Gibbs) are called Langmuir-Gibbs (LG) films. The films formed by alkanes with n <=17 exhibit ordering transition upon cooling [2], below which the molecules are normal to the water surface and hexagonally packed, with CTAB molecules randomly mixed inside the quasi-2D crystal. Alkanes with n>17 can not form ordered LG monolayers, due to the repulsion from the n=16 tails of CTAB. This repulsion arises from the two chains' length mismatch. A demixing transition occurs upon ordering, with a pure alkane quasi-2D crystal forming on top of disordered alkyl tails of CTAB molecules. [1] K.M. Wilkinson et al., Chem. Phys. Phys. Chem. 6, 547 (2005). [2] E. Sloutskin, Z. Sapir, L. Tamam, B.M. Ocko, C.D. Bain, and M. Deutsch, Thin Solid Films, in press; K.M. Wilkinson, L. Qunfang, and C.D. Bain, Soft Matter 2, 66 (2006).

Law Library Service in the 1990's.

ERIC Educational Resources Information Center

The Bookmark, 1990

1990-01-01

This issue of "The Bookmark" presents 20 articles focusing on various aspects of law library services in New York State. The articles are: (1) "Law Library Services in the 1990's" (Christine Bain); (2) "A Librarian's View of Legal Publishing Today" (Margaret Maes Axtmann); (3) "Legal Publishing--A Publisher's View" (Kenneth Lee Halajian); (4)…

Lyndon Baines Johnson signs the Wilderness Act into law

Treesearch

Susan A. Fox

2016-01-01

President Lyndon Baines Johnson signed the Wilderness Act into law on Sept. 3, 1964. In this photo, LBJ hands the pen he used to Alice Zahniser while naturalist, author, adventurer, and conservationist Mardy Murie (standing behind her) looks on.

Beleaguered by Bains and Bureaucrats

ERIC Educational Resources Information Center

Rowan, Patricia

1977-01-01

The Bains Report was meant to produce order out of chaos in local government. But Avon's corporate management row last autumn suggested it may have done more harm than good. This article, the first in a two-part series, reports on its impact elsewhere. (Editor/RK)

Looking to a future of improved diabetes management: interview with Professor Steve Bain.

PubMed

Bain, Steve

2016-12-01

Steve Bain talks to Francesca Lake, Managing Editor: Steve is currently a Professor at Swansea University Medical School (Wales), Assistant Medical Director for Research & Development for ABM University Health Board and Clinical Lead for the Diabetes Research Unit, Wales. His clinical training included research into the genetics of Type 1 diabetes, with his current clinical interests surrounding exercise in Type 1 diabetes, new therapies and the provision of diabetes services. His background has led him to be Principal Investigator for several multicenter trials, and to be involved in various ethical committees concerning genetics. He led the UK Human Genetics Commission's report on DNA testing in 2009, and in 2007 was invited to sit on the National DNA Database Ethics Group, established by the Secretary of State for the Home Department. Steve is also a member of the Wales Diabetes & Endocrine Society executive committee and chairs the Specialist Training Committee for Diabetes & Endocrinology for Wales. He also chairs the Board that oversees the Institute of Life Science Joint Clinical Research Facility, the premier clinical research institute in Wales.

Specific features of basalts from the western part of Andrew Bain Fault, Southwest Indian Ridge

NASA Astrophysics Data System (ADS)

Peyve, A. A.; Skolotnev, S. G.

2017-12-01

This paper reports original data on the composition of volcanic rocks in the western part of the Andrew Bain Fault of the South-West Indian Ridge obtained in the 23rd voyage of R/V Akademik Nikolai Strakhov. In accordance with high La/Th and low Nb/U ratios, the basalt compositions of stations S2317, S2318, and S2330 could result from melting of the DM-type source with HIMU traces. Meanwhile, the enriched samples of station S2326 correspond to a mantle source with a considerable contribution of recycled sediments (EM). Sample S2326/35, which is composed of a melt almost completely depleted in EM material, corresponds to the volcanic rocks of the Marion and Prince Edward islands. The obtained and available data on the SWIR segment from Bouvet Island to Andrew Bain Fault are indicative of small mantle heterogeneities in this region. Two possible variants of their origin are considered: either preservation of the enriched material fragments in the depleted mantle during the split of Gondwana or "contamination" of the mantle with plume material with the formation of vein irregularities before opening of the ocean in this region. In the latter case, the plume material could cover a huge area not constrained by the young plume magmatism regions on Bouvet, Marion, and Prince Edward islands.

Experimental and Theoretical Evidences of p-Type Conductivity in Nickel Carbodiimide Nanoparticles with a Delafossite Structure Type.

PubMed

Jiang, Tengfei; Polteau, Baptiste; Farré, Yoann; Cario, Laurent; Latouche, Camille; Pellegrin, Yann; Boujtita, Mohammed; Odobel, Fabrice; Tessier, Franck; Cheviré, François; Jobic, Stéphane

2017-07-17

Nickel carbodiimide (NiCN 2 ) was synthesized using a two-step precipitation-decomposition route leading to a brown powder with gypsum-flower-like morphology and a large specific surface area (75 m 2 /g). This layered material crystallizes in the 2H structure type of delafossite (space group P6 3 /mmc), which is built upon infinite 2 / ∞ [NiN 2 ] layers connected by linear carbodiimide ([N═C═N] 2- ) bridges. An X-ray diffraction Rietveld refinement and thermal analyses pointed out some nickel deficiencies in the material, and band structure calculations carried out on the defect compound predicted p-type conductivity in relation to a slight amount of N 2- . This p-type conductivity was demonstrated by electrochemical impedance spectroscopy measurements, and a flat band potential of 0.90 V vs SCE at pH 9.4 was measured. This value, which is more positive than those of CuGaO 2 and CuCrO 2 delafossite oxides and NiO, prompted us to test NiCN 2 nanoparticles as a photocathode in p-type dye-sensitized solar cells.

A Malleable Body--Revelations from an Elite Australian Swimmer

ERIC Educational Resources Information Center

McMahon, Jenny; DinanThompson, Maree

2008-01-01

Australian Swimming functions on meritocratic principles as athletes are immersed in a culture that focuses on achievement. Meritocratic principles are accompanied by a technocentric ideology where a "swimmer body" is a commodity "viewed as an instrument and object for manipulation" (Baine, 1990, p. 29) in order to achieve…

Alexander Bain's CUE in the Post-Modern World: Unity Revisited.

ERIC Educational Resources Information Center

Dryden, Phyllis

In 1866, Alexander Bain proposed that by evaluating unity, coherence, and emphasis (which he brought together under the acronym "CUE"), students could judge the effectiveness of their written paragraphs. One hundred twenty-five years later, the proposition is still central to composition instruction. A review of modern writing textbooks…

Identification of spectral units on Phoebe

USGS Publications Warehouse

Coradini, A.; Tosi, F.; Gavrishin, A.I.; Capaccioni, F.; Cerroni, P.; Filacchione, G.; Adriani, A.; Brown, R.H.; Bellucci, G.; Formisano, V.; D'Aversa, E.; Lunine, J.I.; Baines, K.H.; Bibring, J.-P.; Buratti, B.J.; Clark, R.N.; Cruikshank, D.P.; Combes, M.; Drossart, P.; Jaumann, R.; Langevin, Y.; Matson, D.L.; McCord, T.B.; Mennella, V.; Nelson, R.M.; Nicholson, P.D.; Sicardy, B.; Sotin, Christophe; Hedman, M.M.; Hansen, G.B.; Hibbitts, C.A.; Showalter, M.; Griffith, C.; Strazzulla, G.

2008-01-01

We apply a multivariate statistical method to the Phoebe spectra collected by the VIMS experiment onboard the Cassini spacecraft during the flyby of June 2004. The G-mode clustering method, which permits identification of the most important features in a spectrum, is used on a small subset of data, characterized by medium and high spatial resolution, to perform a raw spectral classification of the surface of Phoebe. The combination of statistics and comparative analysis of the different areas using both the VIMS and ISS data is explored in order to highlight possible correlations with the surface geology. In general, the results by Clark et al. [Clark, R.N., Brown, R.H., Jaumann, R., Cruikshank, D.P., Nelson, R.M., Buratti, B.J., McCord, T.B., Lunine, J., Hoefen, T., Curchin, J.M., Hansen, G., Hibbitts, K., Matz, K.-D., Baines, K.H., Bellucci, G., Bibring, J.-P., Capaccioni, F., Cerroni, P., Coradini, A., Formisano, V., Langevin, Y., Matson, D.L., Mennella, V., Nicholson, P.D., Sicardy, B., Sotin, C., 2005. Nature 435, 66-69] are confirmed; but we also identify new signatures not reported before, such as the aliphatic CH stretch at 3.53 ??m and the ???4.4 ??m feature possibly related to cyanide compounds. On the basis of the band strengths computed for several absorption features and for the homogeneous spectral types isolated by the G-mode, a strong correlation of CO2 and aromatic hydrocarbons with exposed water ice, where the uniform layer covering Phoebe has been removed, is established. On the other hand, an anti-correlation of cyanide compounds with CO2 is suggested at a medium resolution scale. ?? 2007 Elsevier Inc. All rights reserved.

Lyndon Baines Johnson (LBJ) High School. Evaluation Design. 1974-1975.

ERIC Educational Resources Information Center

Austin Independent School District, TX. Office of Research and Evaluation.

The Lyndon Baines Johnson High School in Austin, Texas, was designed to provide a responsive, individualized instructional climate at the high school level, partly because of tensions accompanying desegregation, high drop-out rates, and low achievement rates in basic skills. Evaluation of this program is intended to determine whether the…

A Member of the Supporting Cast

ERIC Educational Resources Information Center

St. Jarre, Kevin

2008-01-01

In this article, the author responds to the comments made by Robert Bain and Jesus Garcia to his article entitled "Reinventing Social Studies." He says instead of discussing his suggested solutions to the problem, Bain tells everyone that there are and have been no problems in social studies education, that American citizens are well prepared, and…

A Curandera of Art

ERIC Educational Resources Information Center

Warwick, Sharon

2010-01-01

This article features artist Amalia Mesa-Baines and discusses her background and influences, her creative style, and her cultural connection. Mesa-Baines is the director of Visual and Public Art at California State University, Monterey Bay. She is an independent artist, a cultural critic, and an author of scholarly research. She is also a McArthur…

Nutritional Relationships in Schistosomiasis.

DTIC Science & Technology

1978-07-01

to presence of ou~bain, phlorizin, phloretin . 1lexose mediated accumulation is Na coupled. Accession For NTIS GREA&I DDC TAB Unannounced...mediat,!d system is apparently Na + dependent and sensitive to presence of ouabain, phlorizin, phloretin . Hexose mediated accumulation is Na+ coupled. i...decreased Na+, ouabain, phiorizin phloretin and other sugars. Studies with Na22 suggest that the accumulation of 2-deoxyglucose and Na+ were coupled

From the Secondary Section: Green Pens, Marginal Notes--Rethinking Writing and Student Engagement

ERIC Educational Resources Information Center

Chadwick, Jocelyn A.

2012-01-01

In his foundational work, "English Composition and Rhetoric," Alexander Bain set forth the framework for what students and teachers now routinely refer to as the five-paragraph essay. Teachers were so inculcated with Bain's paradigm for the "perfect" essay format, they in turn have inculcated their students, and they just say now, "Write an…

CORRELATION BETWEEN MARKERS OF PERIPHERAL NERVE FUNCTION AND STRUCTURE IN TYPE 1 DIABETES.

PubMed

Borire, Adeniyi A; Issar, Tushar; Kwai, Natalie C; Visser, Leo H; Simon, Neil G; Poynten, Ann M; Kiernan, Matthew C; Krishnan, Arun V

2018-06-01

Clinical and experimental studies in patients with type 1 and type 2 diabetes have demonstrated changes in ion channel function and nerve structure. In this study, we investigated the relationship between axonal dysfunction and morphological change in diabetic polyneuropathy using neuromuscular ultrasound and nerve excitability techniques. We also explored possible differences in this relationship between type 1 and type 2 diabetes. Nerve ultrasound and corresponding motor excitability studies were undertaken in 110 diabetes patients (50 type 1;60 type 2) and 60 age-matched controls (30 for each group). Neuropathy severity was assessed using Total Neuropathy Score. Median and tibial nerve cross-sectional areas were measured at non-entrapment sites using high resolution linear probe. Median and tibial nerve cross-sectional areas were significantly higher in diabetes patients compared to controls: Type1 (Median=7.6±0.2mm 2 vs. 6.3±0.1mm 2 ; Tibial=14.5±0.7mm 2 vs. 10.8±0.3mm 2 ,p<0.05) and Type 2 (Median=9.1±0.3mm 2 vs. 7.2±0.1mm 2 ; Tibial=18.5±1.0mm 2 vs. 12.8±0.5mm 2 ,p<0.05). In the type 1 cohort, significant correlations were found between nerve cross-sectional area and excitability parameters including resting current-threshold slope (Median: r=0.523,p<0.0001; Tibial: r=-0.571,p=0.004) and depolarizing threshold electrotonus at 90-100ms (Median: 0.424,p<0.01; Tibial: r=0.435,p=0.030). In contrast, there was no relationship between excitability values and nerve cross-sectional area in the type 2 cohort. This study has identified correlation between markers of axonal membrane function and structural abnormalities in peripheral nerves of type 1 diabetes patients. The differential relationship in nerve function and structure between Type 1 and Type 2 diabetes provides clinical evidence that different pathophysiological mechanisms underlie the development of neuropathy in these patient groups. This article is protected by copyright. All rights reserved.

Possible metastable rhombohedral states of the bcc transition metals

NASA Astrophysics Data System (ADS)

Mehl, Michael; Finkenstadt, Daniel

2007-03-01

The energy E(c/a) for a bcc element stretched along its [001] axis (the Bain path) has a minimum at c/a = 1, a maximum at c/a = √2, and an elastically unstable local minimum at c/a > √2. A rhombohedral strain is an alternative method of connecting the bcc and fcc structures. The primitive lattice keeps R3m symmetry, with the angle α changing from 109.4^o (bcc), to 90^o (simple cubic), to 60^o (fcc). We studied this path for the non-magnetic bcc transition metals (V, Nb, Mo, Ta, and W) using both a full-potential LAPW and PAW VASP. Except for Ta, the energy E(α) has a local maximum at α=60^o, with local minima near 55^o and 70^o, the later having lower energy. We studied the elastic stability of the 70^o minimum structure. Only W is elastically stable in this structure, with the smallest eigenvalue of the elastic tensor at 4 GPa, while the other three elements are unstable. We discuss the possibility that Tungsten is actually metastable in this structure. We also consider the possible epitaxial growth of this structure. M. J. Mehl, A. Aguayo, L. L. Boyer, and R. De Coss, Phys. Rev. B 70, 014105 (2004).

Situation Tracking in Large Data Streams

DTIC Science & Technology

2015-02-01

Pike, R. 1989: Different Ways to Cue a Coherent Memory System: A Theory for Episodic , Semantic , and Procedural Tasks. Psychological Review, 96(2), 208...to extract general concept models, such as Latent Semantic Indexing. This technique generally extracts a single topic model, and does not extract a...2001. Semantic leaps: frame-shifting and conceptual blending in meaning construction. Cambridge University Press. Humphreys, M. S, Bain, J. D

Theoretical calculations of high-pressure phases of NiF2: An ab initio constant-pressure study

NASA Astrophysics Data System (ADS)

Kürkçü, Cihan; Merdan, Ziya; Öztürk, Hülya

2016-12-01

We have studied the structural properties of the antiferromagnetic NiF2 tetragonal structure with P42/ mnm symmetry using density functional theory (DFT) under rapid hydrostatic pressure up to 400 GPa. For the exchange correlation energy we used the local density approximation (LDA) of Ceperley and Alder (CA). Two phase transformations are successfully observed through the simulations. The structures of XF2-type compounds crystallize in rutile-type structure. NiF2 undergoes phase transformations from the tetragonal rutile-type structure with space group P42/ mnm to orthorhombic CaCl2-type structure with space group Pnnm and from this orthorhombic phase to monoclinic structure with space group C2/ m at 152 GPa and 360 GPa, respectively. These phase changes are also studied by total energy and enthalpy calculations. According to these calculations, we perdict these phase transformations at about 1.85 and 30 GPa.

AAuAl (A = Ca, Sc, and Ti): Peierls Distortion, Atomic Coloring, and Structural Competition

DOE PAGES

Pham, Joyce; Miller, Gordon J.

2018-04-02

Using density functional theory, the crystal structure variation of AAuAl (A = Ca, Sc, and Ti) from orthorhombic Co 2Si-type to distorted hexagonal Fe 2P-type and then Ni 2In-type structures is shown to correlate with their electronic structures and valence electron counts, sizes of the active metals A, and site preferences for Au and Al atoms, which are arranged to maximize Au–Al nearest neighbor contacts. An evaluation of chemical pressure imposed by the varying A metals using total energy vs volume calculations indicates that larger unit cell volumes favor the orthorhombic structure, whereas smaller volumes favor the hexagonal structures. Themore » electronic origin of the Mg 2Ga-type crystal structure of ScAuAl, refined as a distorted Fe 2P-type supercell doubled along the c-axis, indicates a Peierls-type distortion mechanism of the Au chains along the c-axis.« less

AAuAl (A = Ca, Sc, and Ti): Peierls Distortion, Atomic Coloring, and Structural Competition

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

Pham, Joyce; Miller, Gordon J.

Using density functional theory, the crystal structure variation of AAuAl (A = Ca, Sc, and Ti) from orthorhombic Co 2Si-type to distorted hexagonal Fe 2P-type and then Ni 2In-type structures is shown to correlate with their electronic structures and valence electron counts, sizes of the active metals A, and site preferences for Au and Al atoms, which are arranged to maximize Au–Al nearest neighbor contacts. An evaluation of chemical pressure imposed by the varying A metals using total energy vs volume calculations indicates that larger unit cell volumes favor the orthorhombic structure, whereas smaller volumes favor the hexagonal structures. Themore » electronic origin of the Mg 2Ga-type crystal structure of ScAuAl, refined as a distorted Fe 2P-type supercell doubled along the c-axis, indicates a Peierls-type distortion mechanism of the Au chains along the c-axis.« less

A Method for the Preparation of Chicken Liver Pâté that Reliably Destroys Campylobacters.

PubMed

Hutchison, Mike; Harrison, Dawn; Richardson, Ian; Tchórzewska, Monika

2015-04-28

This study devised a protocol for the manufacture of commercial quantities of chicken liver pâté that reliably destroyed campylobacters. A literature search identified 40 pâté manufacture recipes. Recipes stages with a potential to be antimicrobial were assembled to form a new protocol that included washing with organic acid, freeze-thaw and flambé in alcohol. Naturally-contaminated, high-risk livers were obtained from clearance flocks at slaughter and the effect of each stage of the protocol on Campylobacter populations was determined. Organic acid washing changed the color of the liver surfaces. However, there were no significant differences between liver surface color changes when a range of concentrations of lactic acid and ethanoic acid washes were compared by reflective spectrophotometry. A 5% (w/v) acid wash reduced numbers of indigenous campylobacters by around 1.5 log₁₀ CFU/g for both acids. The use of a Bain Marie was found to more reproducibly apply heat compared with pan-frying. Antimicrobial recipe stages reduced the numbers of campylobacters, but not significantly if thermal processing was ineffective. Cooking to 63°C was confirmed to be a critical control point for campylobacters cooked in a Bain Marie. Organoleptic and sensory assessment of pâté determined an overall preference for pâté made from frozen livers.

A Method for the Preparation of Chicken Liver Pâté that Reliably Destroys Campylobacters

PubMed Central

Hutchison, Mike; Harrison, Dawn; Richardson, Ian; Tchórzewska, Monika

2015-01-01

This study devised a protocol for the manufacture of commercial quantities of chicken liver pâté that reliably destroyed campylobacters. A literature search identified 40 pâté manufacture recipes. Recipes stages with a potential to be antimicrobial were assembled to form a new protocol that included washing with organic acid, freeze-thaw and flambé in alcohol. Naturally-contaminated, high-risk livers were obtained from clearance flocks at slaughter and the effect of each stage of the protocol on Campylobacter populations was determined. Organic acid washing changed the color of the liver surfaces. However, there were no significant differences between liver surface color changes when a range of concentrations of lactic acid and ethanoic acid washes were compared by reflective spectrophotometry. A 5% (w/v) acid wash reduced numbers of indigenous campylobacters by around 1.5 log10 CFU/g for both acids. The use of a Bain Marie was found to more reproducibly apply heat compared with pan-frying. Antimicrobial recipe stages reduced the numbers of campylobacters, but not significantly if thermal processing was ineffective. Cooking to 63°C was confirmed to be a critical control point for campylobacters cooked in a Bain Marie. Organoleptic and sensory assessment of pâté determined an overall preference for pâté made from frozen livers. PMID:25927478

Nearly metastable rhombohedral phases of bcc metals

NASA Astrophysics Data System (ADS)

Mehl, Michael J.; Finkenstadt, Daniel

2008-02-01

The energy E(c/a) for a bcc element stretched along its [001] axis (the Bain path) has a minimum at c/a=1 , a maximum at c/a=2 , and an elastically unstable local minimum at c/a>2 . An alternative path connecting the bcc and fcc structures is the rhombohedral lattice. The primitive lattice has R3¯m symmetry, with the angle α changing from 109.4° (bcc), to 90° (simple cubic), to 60 ° (fcc). We study this path for the non-magnetic bcc transition metals (V, Nb, Mo, Ta, and W) using both all-electron linearized augmented plane wave and projector augmented wave VASP codes. Except for Ta, the energy E(α) has a local maximum at α=60° , with local minima near 55° and 70° , the latter having lower energy, suggesting the possibility of a metastable rhombohedral state for these materials. We first examine the elastic stability of the 70° minimum structure, and determine that only W is elastically stable in this structure, with the smallest eigenvalue of the elastic tensor at 4GPa . We then consider the possibility that tungsten is actually metastable in this structure by looking at its vibrational and third-order elastic stability.

Spring 2009 Water Mass Distribution, Mixing and Transport in the Southern Adriatic after a Low Production of Winter Dense Waters

DTIC Science & Technology

2013-05-21

A.E. Rice et al. / Continental Shelf Research 64 (2013) 33–5050oceanografici in Mare Adriatico (R/V Urania, 24 Febbbraio–2 Marzo 2009). ISMAR-CNR...Carmack, 1976 ; Baines and Condie, 1998), in the Ross Sea (Russo et al., 2011), and in the Barents Sea (Blindheim, 1989), among other regions. In mid...three consecutive research cruises aboard the Italian National Research Council (CNR) R/V Urania in the Adriatic Sea: VELTUR09 (February 24 – March 2

Crystal structures of the new ternary stannides La3Mg4-xSn2+x and LaMg3-xSn2

NASA Astrophysics Data System (ADS)

Solokha, P.; De Negri, S.; Minetti, R.; Proserpio, D. M.; Saccone, A.

2016-01-01

Synthesis and structural characterization of the two new lanthanum-magnesium-stannides La3Mg4-xSn2+x (0.12≤x≤0.40) and LaMg3-xSn2 (0.33≤x≤0.78) are reported. The crystal structures of these intermetallics were determined by single crystal X-ray diffraction analysis and confirmed by Rietveld refinement of powder X-ray diffraction patterns of the corresponding samples. The La3Mg4-xSn2+x phase crystallizes in the hexagonal Zr3Cu4Si2 structure type (P6bar2m, hP9, Z=3, x=0.12(1), a=7.7974(7), c=4.8384(4) Å), which represents an ordered derivative of the hP9-ZrNiAl prototype, ubiquitous among equiatomic intermetallics. The LaMg3-xSn2 phase is the second representative of the trigonal LaMg3-xGe2 type, which is a superstructure of the LaLi3Sb2 structure type (P3bar1c, hP34-0.12, Z=6, x=0.35(1), a=8.3222(9), c=14.9546(16) Å). The scheme describing the symmetry reduction/coloring with respect to the parent type is reported here with the purpose to discuss the LaMg3-xSn2 off-stoichiometry from the geometrical point of view. Structural relationships between the La-Mg-Sn ternary phases, including the already known equiatomic LaMgSn compound (oP12-TiNiSi), are presented in the framework of the AlB2-related compounds family and discussed with the aid of group-subgroup relations in the Bärnighausen formalism.

Thorium Copper Phosphides: More Diverse Metal-Phosphorus and Phosphorus-Phosphorus Interactions than U analogues

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

Jin, Geng Bang; Malliakas, Christos D.; Lin, Jian

To explore the chemical analogy between thorium and heavier actinides in soft anionic environments, three new thorium phosphides (ThCuP 2, beta-ThCu 2P 2, and ThCu 5P 3) have been prepared through solid-state reactions using CuI as a reaction promoter. The structure of ThCuP 2 can be described as a filled UTe 2-type with both dimeric P 2 4- and monomeric P 3- anions, in which Th is coordinated by eight P atoms in a bicapped trigonal prismatic arrangement and Cu is tetrahedrally coordinated by four P atoms. β-ThCu 2P 2 contains only P 3- anions and is isostructural with BaCumore » 2S 2. In this structure, Th is coordinated by seven P atoms in monocapped trigonal prismatic geometry and Cu is tetrahedrally coordinated by four P atoms. ThCu 5P 3 adopts the YCo 5P 3-type structure consisting of P 3- anions. This structure contains Th atoms coordinated by six P atoms in a trigonal prismatic arrangement and Cu atoms that are either tetrahedrally coordinated by four P atoms or square pyramidally coordinated by five P atoms. Electric resistivity measurements and electronic structure calculations on β-ThCu 2P 2 indicate a metal. These new compounds may be charge-balanced and formulated as Th 4+Cu +(P 2 4-) 1/2P 3-, Th 4+(Cu +) 2(P 3-) 2, and Th 4+(Cu +) 5(P 3-) 3, respectively. The structural, bonding, and property relationships between these Th compounds and related actinide and rare-earth phases are discussed. In conclusion, titled compounds display more diverse ion-ion interactions and different electronic structures from those in UCuP 2 and UCu 2P 2 that were synthesized under similar experimental conditions, suggesting divergence of thorium-phosphide chemistry from uranium-phosphide chemistry.« less

Thorium Copper Phosphides: More Diverse Metal-Phosphorus and Phosphorus-Phosphorus Interactions than U analogues

DOE PAGES

Jin, Geng Bang; Malliakas, Christos D.; Lin, Jian

2017-09-28

To explore the chemical analogy between thorium and heavier actinides in soft anionic environments, three new thorium phosphides (ThCuP 2, beta-ThCu 2P 2, and ThCu 5P 3) have been prepared through solid-state reactions using CuI as a reaction promoter. The structure of ThCuP 2 can be described as a filled UTe 2-type with both dimeric P 2 4- and monomeric P 3- anions, in which Th is coordinated by eight P atoms in a bicapped trigonal prismatic arrangement and Cu is tetrahedrally coordinated by four P atoms. β-ThCu 2P 2 contains only P 3- anions and is isostructural with BaCumore » 2S 2. In this structure, Th is coordinated by seven P atoms in monocapped trigonal prismatic geometry and Cu is tetrahedrally coordinated by four P atoms. ThCu 5P 3 adopts the YCo 5P 3-type structure consisting of P 3- anions. This structure contains Th atoms coordinated by six P atoms in a trigonal prismatic arrangement and Cu atoms that are either tetrahedrally coordinated by four P atoms or square pyramidally coordinated by five P atoms. Electric resistivity measurements and electronic structure calculations on β-ThCu 2P 2 indicate a metal. These new compounds may be charge-balanced and formulated as Th 4+Cu +(P 2 4-) 1/2P 3-, Th 4+(Cu +) 2(P 3-) 2, and Th 4+(Cu +) 5(P 3-) 3, respectively. The structural, bonding, and property relationships between these Th compounds and related actinide and rare-earth phases are discussed. In conclusion, titled compounds display more diverse ion-ion interactions and different electronic structures from those in UCuP 2 and UCu 2P 2 that were synthesized under similar experimental conditions, suggesting divergence of thorium-phosphide chemistry from uranium-phosphide chemistry.« less

Polymorphism of the bivalent metal vanadates MeV 2O 6 ( Me = Mg, Ca, Mn, Co, Ni, Cu, Zn, Cd)

NASA Astrophysics Data System (ADS)

Mocała, Krzysztof; Ziółkowski, Jacek

1987-08-01

Based on the literature data, our former findings and additional DTA and high-temperature X-ray studies performed for CdV 2O 6, MgV 2O 6, and MnV 2O 6, a consistent scheme of the phase transformations of the MeV 2O 6 ( Me = Mg, Ca, Mn, Co, Ni, Cu, Zn, Cd) metavanadates is constructed at normal pressure between room temperature and melting points. Three types of structures exist for the considered compounds: brannerite type (B), pseudobrannerite type (P), and NiV 2O 6 type (N). The following phase transformations have been observed: Me = Mg, B → P at 535°C; Me = Mn, B → P at 540°C; Me = Co, N → B at 660°C; Me = Cu, B (with triclinic distortion) → B at 625°C (secondary order); and Me = Cd, B → P at 170°. CaV 2O 6P, NiV 2O 6N, and ZnV 2O 6B exist in unique form in the entire temperature range. P-form seems to be favored by Me of larger ionic radii. N-form seems to appear at a peculiar d-shell structure and small Me size. Preliminary explanation of the dependence of the structure type on Me size is offered. New X-ray data are given for CdV 2O 6B, CdV 2O 6P, MgV 2O 6B, MgV 2O 6P, and MnV 2O 6P.

COM-GEOM Interactive Display Debugger (CIDD)

DTIC Science & Technology

1984-08-01

necessery and Identify by block nlum.ber) Target Description GIFT interactive Computer Graphics SolIi d Geone t ry Combintatorial Gecometry * COM-GLOM 120...program was written to speed up the process of formulating the Com-Geom data used by the Geometric Information for Targets ( GIFT ) 1,2 computer code...Polyhedron Lawrence W. Bain, Mathew J. Reisinger, "The GIFT Code User Manual; Volume I, Introduction and Input Requirements (u)," BRL Report No. 1802

Army Communicator. Volume 35, Number 2

DTIC Science & Technology

2010-01-01

official U.S. Army position and does not change or supersede any information in other official U.S. Army publications. Use of news items constitutes...familiar with the Bain electrochemical telegraph system. Myer used this experience to devise A New Sign Language for Deaf Mutes, the subject of his...Signal officer on 27 June thus becoming the first Signal officer in the U.S. Army. Myer tested his wigwag system during operations in New

Multi-spectral remote sensing of the vortex formerly known as White Oval BA: Temperature structure and cloud properties

NASA Astrophysics Data System (ADS)

Orton, G.; Parrish, P.; Yanamandra-Fisher, P.; Baines, K.; Mousis, O.; Pantin, E.; Fujiyoshi, T.; Fuse, T.; Simon-Miller, A.

White Oval BA: Temperature structure and cloud properties G. Orton, P. Parrish, P. Yanamandra-Fisher, K. Baines (1), O. Mousis (2), E. Pantin (3), T. Fuse, T. Fujiyoshi (4), A. Simon-Miller (5) (1) Jet Propulsion Laboratory, Calif. Inst. of Technology, USA, (2) Obs. de Besancon, France, (3) C.E.A., France, (4) Subaru National Astron. Obs., Japan, (5) NASA Goddard Space Flight Center, USA. (Glenn.Orton@jpl.nasa.gov) White Oval BA, constituted from 3 predecessor vortices (known as Jupiter's "classical" White Ovals) after successive mergers in 1998 and 2000, became second-largest vortex in the atmosphere of Jupiter (and possibly the solar system) at the time of its formation. While it continues in this distinction, it required a name change after a 2005 December through 2006 February transformation which made it appear visually the same color as the Great Red Spot. Our campaign to understand the changes involved examination of the detailed color and wind field using Hubble Space Telescope instrumentation on several orbits in April. The field of temperatures, ammonia distribution and clouds were also examined using the mid-infrared VISIR camera/spectrometer on ESO's 8.2-m Very Large Telescope (3), the NASA Infrared telescope with the mid-infrared MIRSI instrument and the refurbished near-infrared facility camera NSFCam2. High-resolution images of the Oval were made before the color change with the COMICS mid-infrared facility on the Subaru telescope. We are using these data, and possibly others to be acquired during the summer, to characterize the extent to which changes in storm strength (vorticity, positive vertical motion) influenced (i) the depth from which colored cloud particles may have been "dredged up" from depth or (ii) the altitude to which particles may have been lofted and subject to high-energy UV radiation which caused a color change, as alternative explanations for the phenomenon. Clues to this will provide clues to the chemistry of Jupiter's cloud system and its well-known colors in general.

Use of a Novel Artificial Intelligence Platform on Mobile Devices to Assess Dosing Compliance in a Phase 2 Clinical Trial in Subjects With Schizophrenia.

PubMed

Bain, Earle E; Shafner, Laura; Walling, David P; Othman, Ahmed A; Chuang-Stein, Christy; Hinkle, John; Hanina, Adam

2017-02-21

Accurately monitoring and collecting drug adherence data can allow for better understanding and interpretation of the outcomes of clinical trials. Most clinical trials use a combination of pill counts and self-reported data to measure drug adherence, despite the drawbacks of relying on these types of indirect measures. It is assumed that doses are taken, but the exact timing of these events is often incomplete and imprecise. The objective of this pilot study was to evaluate the use of a novel artificial intelligence (AI) platform (AiCure) on mobile devices for measuring medication adherence, compared with modified directly observed therapy (mDOT) in a substudy of a Phase 2 trial of the α7 nicotinic receptor agonist (ABT-126) in subjects with schizophrenia. AI platform generated adherence measures were compared with adherence inferred from drug concentration measurements. The mean cumulative pharmacokinetic adherence over 24 weeks was 89.7% (standard deviation [SD] 24.92) for subjects receiving ABT-126 who were monitored using the AI platform, compared with 71.9% (SD 39.81) for subjects receiving ABT-126 who were monitored by mDOT. The difference was 17.9% (95% CI -2 to 37.7; P=.08). Using drug levels, this substudy demonstrates the potential of AI platforms to increase adherence, rapidly detect nonadherence, and predict future nonadherence. Subjects monitored using the AI platform demonstrated a percentage change in adherence of 25% over the mDOT group. Subjects were able to use the technology successfully for up to 6 months in an ambulatory setting with early termination rates that are comparable to subjects outside of the substudy. ClinicalTrials.gov NCT01655680 https://clinicaltrials.gov/ct2/show/NCT01655680?term=NCT01655680. ©Earle E Bain, Laura Shafner, David P Walling, Ahmed A Othman, Christy Chuang-Stein, John Hinkle, Adam Hanina. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 21.02.2017.

Structure and mechanism of Zn2+-transporting P-type ATPases

PubMed Central

Wang, Kaituo; Sitsel, Oleg; Meloni, Gabriele; Autzen, Henriette Elisabeth; Andersson, Magnus; Klymchuk, Tetyana; Nielsen, Anna Marie; Rees, Douglas C.; Nissen, Poul; Gourdon, Pontus

2014-01-01

Zinc is an essential micronutrient for all living organisms, required for signaling and proper function of a range of proteins involved in e.g. DNA-binding and enzymatic catalysis1. In prokaryotes and photosynthetic eukaryotes Zn2+-transporting P-type ATPases of class IB (ZntA) are crucial for cellular redistribution and detoxification of Zn2+ and related elements2,3. Here we present crystal structures representing the phosphoenzyme ground state (E2P) and a dephosphorylation intermediate (E2.Pi) of ZntA from Shigella sonnei, determined at 3.2 and 2.7 Å resolution, respectively. The structures reveal a similar fold as the Cu+-ATPases with an amphipathic helix at the membrane interface. A conserved electronegative funnel connects this region to the intramembranous high-affinity ion-binding site and may promote specific uptake of cellular Zn2+ ions. The E2P structure displays a wide extracellular release pathway reaching the invariant residues at the high-affinity site, including Cys392, Cys394 and Asp714. The pathway closes in the E2.Pi state where Asp714 interacts with the conserved Lys693, which possibly stimulates Zn2+ release as a built-in counter-ion, as also proposed for H+-ATPases. Indeed, transport studies in liposomes provide experimental support for ZntA activity without counter-transport. These findings suggest a mechanistic link between PIB-type Zn2+-ATPases and PIII-type H+-ATPases, and show at the same time structural features of the extracellular release pathway that resemble the PII-type ATPases such as the sarco(endo)plasmic reticulum Ca2+-ATPase4,5 (SERCA) and Na+,K+-ATPase6. PMID:25132545

Electronic structure of p-type transparent conducting oxide CuAlO2

NASA Astrophysics Data System (ADS)

Mo, Sung-Kwan; Yoon, Joonseok; Liu, Xiaosong; Yang, Wanli; Mun, Bongjin; Ju, Honglyoul

2014-03-01

CuAlO2 is a prototypical p-type transparent conducting oxide. Despite its importance for potential applications and number of studies on its band structure and gap characteristics, experimental study on the momentum-resolved electronic structure has been lacking. We present angle-resolved photoemission data on single crystalline CuAlO2 using synchrotron light source to reveal complete band structure. Complemented by the x-ray absorption and emission spectra, we also study band gap characteristics and compare them with theory.

New type of borophosphate anionic radical in the crystal structure of CsAl2BP6O20

NASA Astrophysics Data System (ADS)

Shvanskaya, L. V.; Yakubovich, O. V.; Belik, V. I.

2016-09-01

The crystal structure of a new borophosphate CsAl2BP6O20 obtained by spontaneous crystallization in a multicomponent Cs-Cu-B-P-O system is determined by X-ray diffraction ( a = 11.815(2), b = 10.042(2), and c = 26.630(4) Å; space group Pbca, Z = 8, V = 3159.5(10) Å3; R 1 = 0.043). A new type of borophosphate anionic 2D radical characterized by the lowest B: P = 1: 6 ratio and containing P3O10 phosphate groups is found in the compound. A mixed-type anionic framework consisting of vertex-sharing BO4 and PO4 tetrahedra and AlO6 octahedra is distinguished in the structure. Large cesium atoms are located in the channels of the framework. Topological relationships are revealed between the structures of the CsAl3(P3O10)2 and CsAl2BP6O20 phases having different cationic compositions. These compounds can be considered quasi-polytypic phases.

Hole conduction pathways in transparent amorphous tin oxides

NASA Astrophysics Data System (ADS)

Wahila, Matthew; Lebens-Higgins, Zachary; Quackenbush, Nicholas; Piper, Louis; Butler, Keith; Hendon, Christopher; Walsh, Aron; Watson, Graeme

P-type transparent amorphous oxide semiconductors (TAOS) have yet to be sufficiently demonstrated or commercialized, severely limiting the possible device architecture of transparent and flexible oxide electronics. The lack of p-type amorphous oxide candidates mainly originates from the directional oxygen 2 p character of their topmost valence states. Previous attempts to create p-type oxides have involved hybridization of the O 2 p with metal orbitals, such as with CuAlO2 and its Cu 3 d - O 2 p hybridization. However, the highly directional nature of the utilized orbitals means that structural disorder inhibits hybridization and severely disrupts hole-conduction pathways. Crystalline stannous oxide (SnO) and other lone-pair active post-transition metal oxides can have reduced localization at the valence band edge due to complex hybridization between the O 2 p, metal p, and spherical metal s-orbitals. I will discuss our investigation of structural disorder in SnO. Using a combination of synchrotron spectroscopy, and atomistic calculations, our investigation elucidates the important interplay between atomistic and electronic structure in establishing continuous hole conduction pathways at the valence band edge of transparent amorphous oxides.

High resolution crystal structure of the Grb2 SH2 domain with a phosphopeptide derived from CD28.

PubMed

Higo, Kunitake; Ikura, Teikichi; Oda, Masayuki; Morii, Hisayuki; Takahashi, Jun; Abe, Ryo; Ito, Nobutoshi

2013-01-01

Src homology 2 (SH2) domains play a critical role in cellular signal transduction. They bind to peptides containing phosphotyrosine (pY) with various specificities that depend on the flanking amino-acid residues. The SH2 domain of growth-factor receptor-bound protein 2 (Grb2) specifically recognizes pY-X-N-X, whereas the SH2 domains in phosphatidylinositol 3-kinase (PI3K) recognize pY-X-X-M. Binding of the pY site in CD28 (pY-M-N-M) by PI3K and Grb2 through their SH2 domains is a key step that triggers the CD28 signal transduction for T cell activation and differentiation. In this study, we determined the crystal structure of the Grb2 SH2 domain in complex with a pY-containing peptide derived from CD28 at 1.35 Å resolution. The peptide was found to adopt a twisted U-type conformation, similar to, but distinct from type-I β-turn. In all previously reported crystal structures, the peptide bound to the Grb2 SH2 domains adopts a type-I β-turn conformation, except those with a proline residue at the pY+3 position. Molecular modeling also suggests that the same peptide bound to PI3K might adopt a very different conformation.

Phase equilibria in the La–Mg–Ge system at 500 °C and crystal structure of the new ternary compounds La{sub 11}Mg{sub 2}Ge{sub 7} and LaMg{sub 3−x}Ge{sub 2}

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

De Negri, S., E-mail: serena.denegri@unige.it; Solokha, P.; Skrobańska, M.

2014-10-15

The whole 500 °C isothermal section of the La–Mg–Ge ternary system was constructed. The existence and crystal structure of three ternary compounds were confirmed: La{sub 2+x}Mg{sub 1−x}Ge{sub 2} (τ{sub 2}, P4/mbm, tP10–Mo{sub 2}FeB{sub 2}, 0≤x≤0.25), La{sub 4}Mg{sub 5}Ge{sub 6} (τ{sub 3}, Cmc2{sub 1}, oS60–Gd{sub 4}Zn{sub 5}Ge{sub 6}) and La{sub 4}Mg{sub 7}Ge{sub 6} (τ{sub 4}, C2/m, mS34, own structure type). Five novel compounds were identified and structurally characterized: La{sub 11}Mg{sub 2}Ge{sub 7} (τ{sub 1}, P4{sub 2}/ncm, tP88-8, own structure type, a=1.21338(5), c=1.57802(6) nm), LaMg{sub 3−x}Ge{sub 2} (τ{sub 5}, P3{sup ¯}1c, hP34-0.44, own structure type, x=0.407(5), a=0.78408(4), c=1.45257(7) nm), La{sub 6}Mg{sub 23}Gemore » (τ{sub 6}, Fm3{sup ¯}m, cF120–Zr{sub 6}Zn{sub 23}Si, a=1.46694(6) nm), La{sub 4}MgGe{sub 10−x} (τ{sub 7}, x=0.37(1), C2/m, mS60-1.46, own structure type, a=0.88403(8), b=0.86756(8), c=1.7709(2) nm, β=97.16°(1) and La{sub 2}MgGe{sub 6} (τ{sub 8}, Cmce, oS72–Ce{sub 2}(Ga{sub 0.1}Ge{sub 0.9}){sub 7}, a=0.8989(2), b=0.8517(2), c=2.1064(3) nm). Disordering phenomena were revealed in several La–Mg–Ge phases in terms of partially occupied sites. The crystal structures of La{sub 11}Mg{sub 2}Ge{sub 7} and LaMg{sub 3−x}Ge{sub 2} are discussed in details. The latter is a √3a×√3a×2c superstructure of the LaLi{sub 3}Sb{sub 2} structure type; the symmetry reduction scheme is shown in the Bärnighausen formalism terms. - Graphical abstract: La–Mg–Ge isothermal section at 500 °C and group–subgroup relation between the LaLi{sub 3}Sb{sub 2} (parent type) and LaMg{sub 3−x}Ge{sub 2} (derivative) structures. - Highlights: • Novel La−Mg−Ge compounds structure determination from X-ray single crystal data. • Disordering phenomena as common features of the studied germanides. • Bärnighausen formalism as a useful tool for accurate structure determination. • Full isothermal section of the La–Mg–Ge ternary system at 500 °C.« less

A new triclinic modification of the pyrochlore-type KOs{sub 2}O{sub 6} superconductor

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

Katrych, S.; Gu, Q.F.; Bukowski, Z.

2009-03-15

A new modification of KOs{sub 2}O{sub 6}, the representative of a new structural type (Pearson symbol aP18, a=5.5668(1) A, b=6.4519(2) A, c=7.2356(2) A, {alpha}=65.377(3){sup o}, {beta}=70.572(3){sup o}, {gamma}=75.613(2){sup o} space group P-1, no. 2 was synthesized employing high pressure technique. Its structure was determined by single-crystal X-ray diffraction. The structure can be described as two OsO{sub 6} octahedral chains relating to each other through inversion and forming big voids with K atoms inside. Quantum chemical calculations were performed on the novel compound and structurally related cubic compound. High-pressure X-ray study showed that cubic KOs{sub 2}O{sub 6} phase was stable upmore » to 32.5(2) GPa at room temperature. - Graphical abstract: A new modification of KOs{sub 2}O{sub 6}, the representative of a new structural type (Pearson symbol aP18, a=5.5668(1) A, b=6.4519(2) A, c=7.2356(2) A, {alpha}=65.377(3){sup o}, {beta}=70.572(3){sup o}, {gamma}=75.613(2){sup o} space group P-1, no. 2 was synthesized employing high pressure technique. The structure can be described as two OsO{sub 6} octahedral chains relating to each other through inversion and forming big voids with K atoms inside.« less

Bismuth zinc vanadate, BiZn{sub 2}VO{sub 6}: New crystal structure type and electronic structure

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

Eliziario Nunes, Sayonara; Department of Materials Engineering, Federal University of São Carlos, 13565-905 São Carlos, SP; Wang, Chun-Hai

2015-02-15

We report a combined experimental and computational study of the crystal structure and electronic properties of bismuth zinc vanadate, BiZn{sub 2}VO{sub 6}, known for its visible light photocatalytic activity. The crystal structure has been solved from laboratory powder X-ray diffraction data using the repeated minimisations from random starting values method. BiZn{sub 2}VO{sub 6} adopts a new structure type, based on the following building blocks: corner- and edge-sharing ZnO{sub 4} tetrahedra, ZnO{sub 6} octahedra and VO{sub 4} tetrahedra, and Bi{sub 2}O{sub 12} dimers. It is the only known member of the BiM{sub 2}AO{sub 6} (M=Pb, Ca, Cd, Mn, Zn, Mg, Cu;more » A=V, P, As) family which does not appear to be structurally closely related to others. The electronic structure of BiZn{sub 2}VO{sub 6}, calculated by DFT methods, shows that it is an indirect gap semiconductor with a calculated band gap of 1.6 eV, which compares favourably to the experimentally measured value of 2.4 eV. - Graphical abstract: The crystal structure of BiZn{sub 2}VO{sub 6}, a new structure type in the BiM{sub 2}AO{sub 6} (M=Mg, Ca, Cd, Cu, Pb, Mn, Zn; A=V, P, As) family. - Highlights: • Structure solution from PXRD data by repeated minimisations from random starting values. • New structure type in the BiM{sub 2}AO{sub 6} (M=Pb, Ca, Cd, Mn, Zn, Mg, Cu; A=V, P, As) family. • Electronic structure calculation.« less

Orcas in Puget Sound

DTIC Science & Technology

2007-01-01

Whales. Poster presented for the Society for Marine Mam- mal Meeting. Bain, D.E. 2002. A model linking energetic effects of whale watching to killer...P.L. Tyack, and H. Whitehead (eds.). Cetacean societies : field studies of dolphins and whales. University of Chicago Press, Chicago, IL. Baird, R.W...The feeding ecology of killer whales (Orcinus orca) in the Pacific Northwest. Pages 113-147 in K. Pryor and K.S. Norris (eds.). Dolphin societies

Functional Requirements of a Target Description System for Vulnerability Analysis

DTIC Science & Technology

1979-11-01

called GIFT .1,2 Together the COMGEOM description model and GIFT codes make up the BRL’s target description system. The significance of a target...and modifying target descriptions are described. 1 Lawrence W. Bain, Jr. and Mathew J. Reisinger, "The GIFT Code User Manual; Volume 1...34The GIFT Code User Manual; Volume II, The Output Options," unpublished draft of BRL report. II. UNDERLYING PHILOSOPHY The BRL has a computer

A Combinatorial Geometry Computer Description of the XR311 Vehicle

DTIC Science & Technology

1978-04-01

cards or magnetic tape. The shot line output of the GRID subroutine of the GIFT code is also stored on magnetic tape for future vulnera- bility...descriptions as processed by the Geometric Information For Targets ( GIFT )2 computer code. This report documents the COM-GEOM target description for all...72, March 1974. ’L.W. Bains and M.J. Reisinger, "The GIFT Code User Manual, VOL 1, Introduction and Input Requirements, " Ballistic Research

Oxygen Breathing Accelerates Decompression from Saturation at 40 msw in 70-kg Swine

DTIC Science & Technology

2010-07-01

2010 0 2 AFfER A DEEP SATURATION DIVE-PETERSEN ET AL. REFERENCES 1. Bain SA, Tmg J, Simeonovic CJ, Wilson JO. Technique of venous catheterization ...was catheterized with a 16-gauge by 20.3-cm single lumen catheter (Braun Certofix; B. Braun Medical Inc., Bethlehem, PA) via the modified Seldinger...respiratory distress, as evidenced by open-mouthed, labored breathing, central cyanosis, or the production of frothy white sputum. The onset of se- vere

Monoclinic 122-Type BaIr2Ge2 with a Channel Framework: A Structural Connection between Clathrate and Layered Compounds

DOE PAGES

Gui, Xin; Chang, Tay-Rong; Kong, Tai; ...

2017-07-18

A new 122-type phase, monoclinic BaIr2Ge2 is successfully synthesized by arc melting; X-ray diffraction and scanning electron microscopy are used to purify the phase and determine its crystal structure. BaIr2Ge2 adopts a clathrate-like channel framework structure of the monoclinic BaRh2Si2-type, with space group P21/c. Structural comparisons of clathrate, ThCr2Si2, CaBe2Ge2, and BaRh2Si2 structure types indicate that BaIr2Ge2 can be considered as an intermediate between clathrate and layered compounds. Magnetic measurements show it to be diamagnetic and non-superconducting down to 1.8 K. Different from many layered or clathrate compounds, monoclinic BaIr2Ge2 displays a metallic resistivity. Electronic structure calculations performed for BaIr2Ge2more » support its observed structural stability and physical properties.« less

Monoclinic 122-Type BaIr2Ge2 with a Channel Framework: A Structural Connection between Clathrate and Layered Compounds

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

Gui, Xin; Chang, Tay-Rong; Kong, Tai

A new 122-type phase, monoclinic BaIr2Ge2 is successfully synthesized by arc melting; X-ray diffraction and scanning electron microscopy are used to purify the phase and determine its crystal structure. BaIr2Ge2 adopts a clathrate-like channel framework structure of the monoclinic BaRh2Si2-type, with space group P21/c. Structural comparisons of clathrate, ThCr2Si2, CaBe2Ge2, and BaRh2Si2 structure types indicate that BaIr2Ge2 can be considered as an intermediate between clathrate and layered compounds. Magnetic measurements show it to be diamagnetic and non-superconducting down to 1.8 K. Different from many layered or clathrate compounds, monoclinic BaIr2Ge2 displays a metallic resistivity. Electronic structure calculations performed for BaIr2Ge2more » support its observed structural stability and physical properties.« less

Structural and Molecular Modeling Features of P2X Receptors

PubMed Central

Alves, Luiz Anastacio; da Silva, João Herminio Martins; Ferreira, Dinarte Neto Moreira; Fidalgo-Neto, Antonio Augusto; Teixeira, Pedro Celso Nogueira; de Souza, Cristina Alves Magalhães; Caffarena, Ernesto Raúl; de Freitas, Mônica Santos

2014-01-01

Currently, adenosine 5′-triphosphate (ATP) is recognized as the extracellular messenger that acts through P2 receptors. P2 receptors are divided into two subtypes: P2Y metabotropic receptors and P2X ionotropic receptors, both of which are found in virtually all mammalian cell types studied. Due to the difficulty in studying membrane protein structures by X-ray crystallography or NMR techniques, there is little information about these structures available in the literature. Two structures of the P2X4 receptor in truncated form have been solved by crystallography. Molecular modeling has proven to be an excellent tool for studying ionotropic receptors. Recently, modeling studies carried out on P2X receptors have advanced our knowledge of the P2X receptor structure-function relationships. This review presents a brief history of ion channel structural studies and shows how modeling approaches can be used to address relevant questions about P2X receptors. PMID:24637936

Advanced Joining of Aerospace Metallic Materials.

DTIC Science & Technology

1986-07-01

uniaxial tensile test with varying temperature and cyclic loading. This simple test problem excercises maray aspects of the phenomena. suOn- ,Ual Yield...6vidence Ia seconde configuration apparait plus n~ faste . 5.3. Ents-e-igne-men-t-s s-u r a dyna-mique de. bain-s de fu-sion A lusage il svest r~vle que la...scanning system for fast and exact alignment of the EB-qun is used. In a fixture the cleaned detail parts are positioned exactly and clamped for welding. At

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

Yang, Meng; Wang, Yachun; Yao, Jinlei

MnB{sub 4} was newly synthesized to crystallize in a monoclinic P2{sub 1}/c structure, different from previous experimental and theoretical reports. Here, based on first-principles calculations, we perform a comparative study of geometric and energetic features, mechanical behaviors, electronic property and chemical bonding of the experimentally identified monoclinic MnB{sub 4}, as well as orthorhombic CrB{sub 4} and FeB{sub 4}. The results demonstrate that the presence of distorted rhomboidal-B{sub 4} units and one-dimensional Mn chains in the monoclinic MnB{sub 4} breaks the structural symmetry and lowers the total energy in comparison to the orthorhombic phase. The opening of band gap in MnB{submore » 4} is induced by Peierls-paired Mn atoms, differing from the metallic behaviors of recently studied tetraborides. Specifically, the preservations of covalent bonding in distorted boron-rhomboids in MnB{sub 4} explain the relatively higher incompressibility and hardness. - Graphical abstract: P2{sub 1}/c-type structure for MnB{sub 4} characterizes rhomboid-B{sub 4} units and alternately short and long Mn–Mn chains. - Highlights: • The novel P2{sub 1}/c-type MnB{sub 4} compound is studied by first-principles calculations. • P2{sub 1}/c-type MnB{sub 4} has lower total energy and relatively higher stability. • An energy gap opening is found for P2{sub 1}/c-type MnB{sub 4} induced by Mn atom pairs. • P2{sub 1}/c-type MnB{sub 4} exhibits excellent mechanical properties. • The mechanical properties of TcB{sub 4} and ReB{sub 4} in P2{sub 1}/c structure are also studied.« less

P-type ATPases as drug targets: tools for medicine and science.

PubMed

Yatime, Laure; Buch-Pedersen, Morten J; Musgaard, Maria; Morth, J Preben; Lund Winther, Anne-Marie; Pedersen, Bjørn P; Olesen, Claus; Andersen, Jens Peter; Vilsen, Bente; Schiøtt, Birgit; Palmgren, Michael G; Møller, Jesper V; Nissen, Poul; Fedosova, Natalya

2009-04-01

P-type ATPases catalyze the selective active transport of ions like H+, Na+, K+, Ca2+, Zn2+, and Cu2+ across diverse biological membrane systems. Many members of the P-type ATPase protein family, such as the Na+,K+-, H+,K+-, Ca2+-, and H+-ATPases, are involved in the development of pathophysiological conditions or provide critical function to pathogens. Therefore, they seem to be promising targets for future drugs and novel antifungal agents and herbicides. Here, we review the current knowledge about P-type ATPase inhibitors and their present use as tools in science, medicine, and biotechnology. Recent structural information on a variety of P-type ATPase family members signifies that all P-type ATPases can be expected to share a similar basic structure and a similar basic machinery of ion transport. The ion transport pathway crossing the membrane lipid bilayer is constructed of two access channels leading from either side of the membrane to the ion binding sites at a central cavity. The selective opening and closure of the access channels allows vectorial access/release of ions from the binding sites. Recent structural information along with new homology modeling of diverse P-type ATPases in complex with known ligands demonstrate that the most proficient way for the development of efficient and selective drugs is to target their ion transport pathway.

Silicene-terminated surface of calcium and strontium disilicides: properties and comparison with bulk structures by computational methods

NASA Astrophysics Data System (ADS)

Brázda, Petr; Mutombo, Pingo; Ondráček, Martin; Corrêa, Cinthia Antunes; Kopeček, Jaromír; Palatinus, Lukáš

2018-05-01

The bulk and surface structures of calcium and strontium disilicides are investigated by computational methods using density functional theory. The investigated structures are R6, R3 and P1-CaSi2 and P1-SrSi2. The investigated properties are the cleavage energy at the silicene sheet, buckling of the bulk and surface silicene layers, charge transfer from calcium to silicon, band structure of bulk and surface-terminated structures and adsorption energies on H atoms and H2 molecules on the silicene-terminated surface of the R3 phase. The cleavage energy at the silicene surface is low in all cases. Structures P1-CaSi2 and R3-CaSi2 contain silicene sheets with different coordination to Ca, while R6-CaSi2 contains both types of the sheets. It is shown that the properties of the two types of silicene-like sheets in R6-CaSi2 are similar to those of the corresponding sheets in P1-CaSi2 and R3-CaSi2, and the thermodynamically stable R6 phase is a good candidate for experimental investigation of silicene-terminated surface in calcium disilicide.

Magnetic phase transitions and magnetic structures in RTxX2, RSn1+xGe1-x and RSn2 compounds

NASA Astrophysics Data System (ADS)

Gil, Alina

2018-02-01

The work presents the review of magnetic properties of the RTxX2, RSn1+xGe1-x and RSn2 compounds. The RTxX2 (where R - rare earth, T - 3d-metal, X - p-electron element: Si, Ge, Sn, and 1 ≥ x > 0) and RSn1+xGe1-x compounds (where x ≈ 0.1) crystallize in the orthorhombic crystal structure of CeNiSi2-type and RSn2 compounds crystallize in ZrSi2-type structure. Both structures are described by the space group Cmcm. The RSn1+xGe1-x compounds seem to be interesting due to the replacement of d-metal to p-electron element. The non-stoichiometric CeNiSi2-type of RTxX2 compounds may be regarded as partially filled ZrSi2-type compounds. The transitions from paramagnetic to antiferromagnetic or ferromagnetic states are observed at low temperatures and there are lots of variants of magnetic structures ranging from simple collinear to the sine-modulated structures with commensurate or incommensurate propagation vector. The comparison of magnetic properties of these compounds may help to find answers to questions concerning mechanisms of interaction between the magnetic moments.

Crystal structures of the new ternary stannides La{sub 3}Mg{sub 4−x}Sn{sub 2+x} and LaMg{sub 3−x}Sn{sub 2}

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

Solokha, P., E-mail: pavlo.solokha@unige.it; De Negri, S.; Minetti, R.

2016-01-15

Synthesis and structural characterization of the two new lanthanum–magnesium–stannides La{sub 3}Mg{sub 4−x}Sn{sub 2+x} (0.12≤x≤0.40) and LaMg{sub 3−x}Sn{sub 2} (0.33≤x≤0.78) are reported. The crystal structures of these intermetallics were determined by single crystal X-ray diffraction analysis and confirmed by Rietveld refinement of powder X-ray diffraction patterns of the corresponding samples. The La{sub 3}Mg{sub 4−x}Sn{sub 2+x} phase crystallizes in the hexagonal Zr{sub 3}Cu{sub 4}Si{sub 2} structure type (P6¯2m, hP9, Z=3, x=0.12(1), a=7.7974(7), c=4.8384(4) Å), which represents an ordered derivative of the hP9-ZrNiAl prototype, ubiquitous among equiatomic intermetallics. The LaMg{sub 3–x}Sn{sub 2} phase is the second representative of the trigonal LaMg{sub 3−x}Ge{sub 2}more » type, which is a superstructure of the LaLi{sub 3}Sb{sub 2} structure type (P3¯1c, hP34-0.12, Z=6, x=0.35(1), a=8.3222(9), c=14.9546(16) Å). The scheme describing the symmetry reduction/coloring with respect to the parent type is reported here with the purpose to discuss the LaMg{sub 3−x}Sn{sub 2} off-stoichiometry from the geometrical point of view. Structural relationships between the La–Mg–Sn ternary phases, including the already known equiatomic LaMgSn compound (oP12-TiNiSi), are presented in the framework of the AlB{sub 2}-related compounds family and discussed with the aid of group-subgroup relations in the Bärnighausen formalism. - Graphical abstract: Crystal structure of LaMg{sub 3−x}Sn{sub 2} viewed along the (001) direction together with the puckered layer of Mg and Sn atoms hosting Mg2, Mg3 and vacancy □. - Highlights: • Crystal structures of the new La{sub 3}Mg{sub 4−x}Sn{sub 2+x} and LaMg{sub 3−x}Sn{sub 2} phases were determined. • The off-stoichiometry of LaMg{sub 3−x}Sn{sub 2} was discussed from geometrical point of view. • Structural relations between the known La–Mg–Sn phases were established. • The studied compounds are related to the AlB{sub 2} type by symmetry reduction.« less

Synthesis, characterization and assembly of metal pnictide nanoparticles, and evaluation of their physicochemical (catalytic, magnetic, and semiconducting) properties

NASA Astrophysics Data System (ADS)

Senevirathne, Keerthisinghe

Synthesis of transition metal phosphide (Ni2P) and arsenide (MnAs) discrete nanoparticles was conducted by following a solution-phase arrested precipitation route and the size- and structure-dependent physicochemical properties of these materials were explored. Furthermore, the assembly of metal phosphide nanoparticles into a network structure via a sol-gel process and the evaluation of their structure related properties also was conducted. The surface ligation chemistry of unsupported Ni2P nanoparticles prepared by arrested precipitation was found to strongly impact the structural integrity and the hydrodesulfurization (HDS) catalytic activity of Ni 2P nanoparticles. The HDS activity of unsupported surface modified Ni2P nanoparticles is higher than that of unsupported Ni2P prepared by temperature programmed reduction (TPR) but considerably lower than silica-supported Ni2P prepared by TPR. However, by supporting the pre-formed Ni 2P nanoparticles on silica, activity comparable to that of silica-supported Ni2P prepared by TPR can be achieved. The synthetic control offered by the Ni2P nanoparticle preparation, not achieved by TPR methods, is expected to enable a systematic study of particle size and shape effects on HDS activity. By using arrested precipitation reactions, for the first time, discrete and dispersible MnAs nanoparticles have been prepared and their magnetic properties evaluated. Syntheses were developed to target both the thermodynamically stable alpha-type (hexagonal) and the metastable beta-type (orthorhombic) MnAs nanoparticles. Surprisingly, both types of ˜25 nm particles exhibit nearly identical ferromagnetic behavior with blocking temperatures, T B, in the region ˜275-310 K, TC's of 315 K and room temperature coercivities of HC ˜ 190-320 Oe. No evidence of the expected structural transition from alpha to beta-MnAs at TC is observed. Oxidative sol-gel assembly of nanoparticles to make nanoparticulate gels was successfully employed to Ni2P nanoparticles, and further extended to MnP and InP nanoparticles, for the first time. The gels were transformed into highly porous, high surface area (175-270 m2/g) 3-D structures (aerogels) via CO2 supercritical drying. Relative to discrete nanoparticles, Ni2P aerogels are less active to HDS, MnP aerogels have similar magnetic properties, and InP aerogels exhibit a greater degree of quantum confinement.

Computer Aided Design of Polyhedron Solids to Model Air in Com-Geom Descriptions

DTIC Science & Technology

1983-08-01

34The GIFT Code User Manual, Volume I, Introduction and Input Requirements," BRL Report No. 1802, July 1975 (Unclassified). (AD B0060Z7LK 2G...Kuehl, L. Bain and M. Reisinger, "The GIFT Code User Manual, Volume II, The Output Options," BRL Report ARBRL-TR-02189, September 1979...is generated from the GIFT code under op- tion XSECT. This option produces plot files which define cross- sectional views of the COM-GEOM

Utilization of Patch/Triangular Target Description Data in BRL Parallel Ray Vulnerability Assessment Codes

DTIC Science & Technology

1979-09-01

KEY WORDS (Continue on revmrem elde It necmmemry and Identity by block number) Target Descriptions GIFT Code C0MGE0M Descriptions FASTGEN Code...which accepts the COMGEOM target description and 1 2 produces the shotline data is the GIFT ’ code. The GIFT code evolved 3 4 from and has...the COMGEOM/ GIFT methodology, while the Navy and Air Force use the PATCH/SHOTGEN-FASTGEN methodology. Lawrence W. Bain, Mathew J. Heisinger

Superconductivity in layered ZrP2-x Se x with PbFCl-type structure

NASA Astrophysics Data System (ADS)

Ishida, Shigeyuki; Fujihisa, Hiroshi; Hase, Izumi; Yanagi, Yousuke; Kawashima, Kenji; Oka, Kunihiko; Gotoh, Yoshito; Yoshida, Yoshiyuki; Iyo, Akira; Eisaki, Hiroshi; Kito, Hijiri

2016-05-01

We performed a systematic study of the crystal structure, physical properties, and electronic structure of PbFCl-type ZrP2-x Se x (0.3 ≤ x ≤ 0.9). We successfully synthesized single-phase polycrystalline samples for the Se substitution range of 0.4 ≤ x ≤ 0.8. The crystal structure of the compound is characterized by the alternate stacking of a two-dimensional P square net and a Zr-(P1-x Se x ) network. ZrP2-x Se x exhibits a dome-like superconductivity phase diagram and has a maximum superconducting transition temperature (T c) of 6.3 K for x ≈ 0.6. Resistivity and Hall measurements indicated that electron-phonon scattering plays a dominant role and that electron-type carriers dominate charge transport. Specific heat measurements confirmed that ZrP2-x Se x exhibits bulk superconductivity. Further, the value of the specific heat jump at T c (ΔC/γT c ≈ 1.35) is in keeping with the BCS weak-coupling model. These facts suggest a rather conventional pairing mechanism in ZrP2-x Se x . The x dependence of T c can be explained on the basis of the density of states (DOS) for x ≤ 0.7, whereas the decrease in T c with an increase in the DOS for x = 0.8 needs further investigation. One possible reason for the suppression of superconductivity is that the PbFCl-type structure becomes unstable for x ≥ 0.8. The results of electronic structure calculations agree reasonably well with those of the experimental observations, suggesting that the Zrd band plays a primary role in determining the physical properties. Further, the calculations predict a significant change in the Fermi-surface topology for x ≥ 0.8 this is a probable reason for the decrease in T c as well as the instability of the PbFCl-type structure.

Prime Contractors with Awards Over $25,000 by Name, Location, and Contract Number. Part 2 (BAIN MXRARY BAIN-CONSOLIDATED PRODUCTS CORP)

DTIC Science & Technology

1990-01-01

5’ -DOF t’- -- F 0 M C)0 co loc. ’m toF mN NO NO F o w r-44( cu 4) 04- F00 0FO0F 0 0 F 3: u) F.F I >z zL)L UL CL F C’ CFF 0 F FO F CC . ~~FF ’-F aF ...0 ot 0 I-L o oL 0~~ It<A1 tII <( , Ca 4 .,wt u m 0 z Hmm m0 IMP 4m o z 0 .1 o a)O 0 1 af m~ r-oma I~U im I (I US 0 00 05) I03 d~L.I 0 0jJ𔃾 . 0 0 u...0u a) 04 t -C/. a)C 00w <-t o o. ~ ~ O to~t to0C) LC o 0. Do) CA x )o >o C 0 ) 4g -. u)I z3 - (0 0 -. 0 I . (0 o oo czt 0.. to ClL 0) 0 .0t ) 0 H 0

Pt-Bi Antibonding Interaction: The Key Factor for Superconductivity in Monoclinic BaPt2Bi2.

PubMed

Gui, Xin; Xing, Lingyi; Wang, Xiaoxiong; Bian, Guang; Jin, Rongying; Xie, Weiwei

2018-02-19

In the search for superconductivity in a BaAu 2 Sb 2 -type monoclinic structure, we have successfully synthesized the new compound BaPt 2 Bi 2 , which crystallizes in the space group P2 1 /m (No. 11; Pearson symbol mP10) according to a combination of powder and single-crystal X-ray diffraction and scanning electron microscopy. A sharp electrical resistivity drop and large diamagnetic magnetization below 2.0 K indicates it owns superconducting ground state. This makes BaPt 2 Bi 2 the first reported superconductor in a monoclinic BaAu 2 Sb 2 -type structure, a previously unappreciated structure for superconductivity. First-principles calculations considering spin-orbit coupling indicate that Pt-Bi antibonding interaction plays a critical role in inducing superconductivity.

Structural basis of nSH2 regulation and lipid binding in PI3Kα.

PubMed

Miller, Michelle S; Schmidt-Kittler, Oleg; Bolduc, David M; Brower, Evan T; Chaves-Moreira, Daniele; Allaire, Marc; Kinzler, Kenneth W; Jennings, Ian G; Thompson, Philip E; Cole, Philip A; Amzel, L Mario; Vogelstein, Bert; Gabelli, Sandra B

2014-07-30

We report two crystal structures of the wild-type phosphatidylinositol 3-kinase α (PI3Kα) heterodimer refined to 2.9 Å and 3.4 Å resolution: the first as the free enzyme, the second in complex with the lipid substrate, diC4-PIP₂, respectively. The first structure shows key interactions of the N-terminal SH2 domain (nSH2) and iSH2 with the activation loop that suggest a mechanism by which the enzyme is inhibited in its basal state. In the second structure, the lipid substrate binds in a positively charged pocket adjacent to the ATP-binding site, bordered by the P-loop, the activation loop and the iSH2 domain. An additional lipid-binding site was identified at the interface of the ABD, iSH2 and kinase domains. The ability of PI3Kα to bind an additional PIP₂ molecule was confirmed in vitro by fluorescence quenching experiments. The crystal structures reveal key differences in the way the nSH2 domain interacts with wild-type p110α and with the oncogenic mutant p110αH1047R. Increased buried surface area and two unique salt-bridges observed only in the wild-type structure suggest tighter inhibition in the wild-type PI3Kα than in the oncogenic mutant. These differences may be partially responsible for the increased basal lipid kinase activity and increased membrane binding of the oncogenic mutant.

A sodium gadolinium phosphate with two different types of tunnel structure: Synthesis, crystal structure, and optical properties of Na 3GdP 2O 8

NASA Astrophysics Data System (ADS)

Fang, M.; Cheng, W.-D.; Zhang, H.; Zhao, D.; Zhang, W.-L.; Yang, S.-L.

2008-09-01

A sodium gadolinium phosphate crystal, Na 3GdP 2O 8, has been synthesized by a high-temperature solution reaction, and it exhibits a new structural family of the alkali-metal-rare-earth phosphate system. Although many compounds with formula M 3LnP 2O 8 have been reported, but they were shown to be orthorhombic [R. Salmon, C. Parent, M. Vlasse, G. LeFlem, Mater. Res. Bull. 13 (1978) 439] rather than monoclinic as shown in this paper. Single-crystal X-ray diffraction analysis shows the structure to be monoclinic with space group C2/ c and the cell parameters: a=27.55 (25), b=5.312 (4), c=13.935(11) Å, β=91.30(1)°, and V=2038.80 Å 3, Z=4. Its structure features a three-dimensional GdP 2O 83- anionic framework with two different types of interesting tunnels at where Na atoms are located by different manners. The framework is constructed by Gd polyhedra and isolated PO 4 tetrahedra. It is different from the structure of K 3NdP 2O 8 [R. Salmon, C. Parent, M. Vlasse, G. LeFlem, Mater. Res. Bull. 13 (1978) 439] with space group P2 1/ m that shows only one type of tunnel. The emission spectrum and the absorption spectrum of the compound have been investigated. Additionally, the calculations of band structure, density of states, dielectric constants, and refractive indexes have been also performed with the density functional theory method. The obtained results tend to support the experimental data.

New Intermetallic Ternary Phosphide Chalcogenide AP2-xXx (A = Zr, Hf; X = S, Se) Superconductors with PbFCl-Type Crystal Structure

NASA Astrophysics Data System (ADS)

Kitô, Hijiri; Yanagi, Yousuke; Ishida, Shigeyuki; Oka, Kunihiko; Gotoh, Yoshito; Fujihisa, Hiroshi; Yoshida, Yoshiyuki; Iyo, Akira; Eisaki, Hiroshi

2014-07-01

We have synthesized a series of intermetallic ternary phosphide chalcogenide superconductors, AP2-xXx (A = Zr, Hf; X = S, Se), using the high-pressure synthesis technique. These materials have a PbFCl-type crystal structure (space group P4/nmm) when x is greater than 0.3. The superconducting transition temperature Tc changes systematically with x, yielding dome-like phase diagrams. The maximum Tc is achieved at approximately x = 0.7, at which point the Tc is 6.3 K for ZrP2-xSex (x = 0.75), 5.5 K for HfP2-xSex (x = 0.7), 5.0 K for ZrP2-xSx (x = 0.675), and 4.6 K for Hfp2-xSx (x = 0.5). They are typical type-II superconductors and the upper and lower critical fields are estimated to be 2.92 T at 0 K and 0.021 T at 2 K for ZrP2-xSex (x = 0.75), respectively.

Synthesis and Characterization of a Heterometallic Extended Architecture Based on a Manganese(II)-Substituted Sandwich-Type Polyoxotungstate

PubMed Central

Ibrahim, Masooma; Moreno-Pineda, Eufemio; Anson, Christopher E.; Powell, Annie K.

2018-01-01

The reaction of [α-P2W15O56]12− with MnII and DyIII in an aqueous basic solution led to the isolation of an all inorganic heterometallic aggregate Na10(OH2)42[{Dy(H2O)6}2Mn4P4W30O112(H2O)2]·17H2O (Dy2Mn4-P2W15). Single-crystal X-ray diffraction revealed that Dy2Mn4-P2W15 crystallizes in the triclinic system with space group P1¯, and consists of a tetranuclear manganese(II)-substituted sandwich-type phosphotungstate [Mn4(H2O)2(P2W15O56)2]16− (Mn4-P2W15), Na, and DyIII cations. Compound Dy2Mn4-P2W15 exhibits a 1D ladder-like chain structure based on sandwich-type segments and dysprosium cations as linkers, which are further connected into a three-dimensional open framework by sodium cations. The title compound was structurally and compositionally characterized in solid state by single-crystal XRD, powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric (TGA), and elemental analyses. Further, the absorption and emission electronic spectra in aqueous solutions of Dy2Mn4-P2W15 and Mn4-P2W15 were studied. Also, magnetic properties were studied and compared with the magnetic behavior of [Mn4(H2O)2(P2W15O56)2]16−. PMID:29342122

An O3-type Oxide with Low Sodium Content as the Phase-Transition-Free Anode for Sodium-Ion Batteries.

PubMed

Zhao, Chenglong; Avdeev, Maxim; Chen, Liquan; Hu, Yong-Sheng

2018-06-11

Layered transition metal oxides Na x MO 2 (M=transition metal) with P2 or O3 structure have attracted attention in sodium-ion batteries (NIBs). A universal law is found to distinguish structural competition between P2 and O3 types based on the ratio of interlayer distances of the alkali metal layer d (O-Na-O) and transition-metal layer d (O-M-O) . The ratio of about 1.62 can be used as an indicator. O3-type Na 0.66 Mg 0.34 Ti 0.66 O 2 oxide is prepared as a stable anode for NIBs, in which the low Na-content (ca. 0.66) usually undergoes a P2-type structure with respect to Na x MO 2 . This material delivers an available capacity of about 98 mAh g -1 within a voltage range of 0.4-2.0 V and exhibits a better cycling stability (ca. 94.2 % of capacity retention after 128 cycles). In situ X-ray diffraction reveals a single-phase reaction in the discharge-charge process, which is different from the common phase transitions reported in O3-type electrodes, ensuring long-term cycling stability. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Oh, Seung-Min; Oh, Pilgun; Kim, Sang-Ok

A low-cost sodium-ion full cell with a O3-type layered Na[Cu 0.2(Fe 1/3Mn2/3) 0.8]O 2 cathode and an alloy-type P-TiP2-C anode is presented. The cathode is synthesized by an oxalate coprecipitation method and optimized cathodes shows a high specific capacity of 135 mAh g -1 at 0.1C rate with a high rate capability of 90 mAh g-1 at 1C rate and 70 mAh g -1 at 2C rate with good cyclability. The full cell exhibits better capacity retention than the half cell with the cathode due to the elimination of the degradation caused by sodium-metal anode. The dramatically enhanced electrochemical performancemore » of the Na[Cu 0.2(Fe 1/3Mn 2/3) 0.8]O 2 / P-TiP 2-C full cell compared to that of the sample with no Cu is attributed to the structural stabilization imparted by Cu by suppressing the phase change from the O3 structure to the P3 structure during cycling.« less

Design of ternary alkaline-earth metal Sn(II) oxides with potential good p-type conductivity

DOE PAGES

Du, Mao -Hua; Singh, David J.; Zhang, Lijun; ...

2016-04-19

Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn 2O 3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn 2O 3 andmore » BaSn 2O 3, which can be stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO 3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn 2O 3) to 3.15 (SrSn 2O 3) eV, and hole effective masses ranging from 0.87 (BaSn 2O 3) to above 6.0 (SrSn 2O 3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.« less

A Cultural Resources Survey of the Proposed Recreational Development Areas and Wildlife Subimpoundments at the B. Everett Jordan Dam and Lake. Volume 1.

DTIC Science & Technology

1984-03-01

containing flow banding, light-gray felsite, felsic- porphyries , crystal tuffs, and rare mafic porphyries and crystal tuffs (Conley and Bain 1965:12Z). The...goods are also present in the form of glass beads, gunflints, iron axes, copper hawk bells and white clay trade pipes. HISTORICAL BACKGROUND The...points manufactured on two rock types occur most frequently: andesitic felsite in the lower valley and grey latite porphyry in the upper valley. The

Automatic procedure for stable tetragonal or hexagonal structures: application to tetragonal Y and Cd

NASA Astrophysics Data System (ADS)

Marcus, P. M.; Jona, F.

2005-05-01

A simple effective procedure (MNP) for finding equilibrium tetragonal and hexagonal states under pressure is described and applied. The MNP procedure finds a path to minima of the Gibbs free energy G at T=0 K (G=E+pV, E=energy per atom, p=pressure, V=volume per atom) for tetragonal and hexagonal structures by using the approximate expansion of G in linear and quadratic strains at an arbitrary initial structure to find a change in the strains which moves toward a minimum of G. Iteration automatically proceeds to a minimum within preset convergence criteria on the calculation of the minimum. Comparison is made with experimental results for the ground states of seven metallic elements in hexagonal close-packed (hcp), face- and body-centered cubic structures, and with a previous procedure for finding minima based on tracing G along the epitaxial Bain path (EBP) to a minimum; the MNP is more easily generalized than the EBP procedure to lower symmetry and more atoms in the unit cell. Comparison is also made with a molecular-dynamics program for crystal equilibrium structures under pressure and with CRYSTAL, a program for crystal equilibrium structures at zero pressure. Application of MNP to the elements Y and Cd, which have hcp ground states at zero pressure, finds minima of E at face-centered cubic (fcc) structure for both Y and Cd. Evaluation of all the elastic constants shows that fcc Y is stable, hence a metastable phase, but fcc Cd is unstable.

Crystal Growth and Characterization of the Narrow-Band-Gap Semiconductors OsPn 2 (Pn = P, As, Sb)

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

Bugaris, Daniel E.; Malliakas, Christos D.; Shoemaker, Daniel P.

2014-09-15

Using metal fluxes, crystals of the binary osmium dipnictides OsPn(2) (Pn = P, As, Sb) have been grown for the first time. Single-crystal X-ray diffraction confirms that these compounds crystallize in the marcasite structure type with orthorhombic space group Pnnm. The structure is a three-dimensional framework of corner- and edge-sharing OsPn(6) octahedra, as well as [Pn(2)(-4)] anions. Raman spectroscopy shows the presence of PP single bonds, consistent with the presence of [Pn(2)(-4)] anions and formally Os4+ cations. Optical-band-gap and high-temperature electrical resistivity measurements indicate that these materials are narrow-band-gap semiconductors. The experimentally determined Seebeck coefficients reveal that nominally undoped OsP2more » and OsSb2 are n-type semiconductors, whereas OsAs2 is p-type. Electronic band structure using density functional theory calculations shows that these compounds are indirect narrow-band-gap semiconductors. The bonding p orbitals associated with the Pn(2) dimer are below the Fermi energy, and the corresponding antibonding states are above, consistent with a PnPn single bond. Thermopower calculations using Boltzmann transport theory and constant relaxation time approximation show that these materials are potentially good thermoelectrics, in agreement with experiment.« less

Three dimensional-stacked complementary thin-film transistors using n-type Al:ZnO and p-type NiO thin-film transistors.

PubMed

Lee, Ching-Ting; Chen, Chia-Chi; Lee, Hsin-Ying

2018-03-05

The three dimensional inverters were fabricated using novel complementary structure of stacked bottom n-type aluminum-doped zinc oxide (Al:ZnO) thin-film transistor and top p-type nickel oxide (NiO) thin-film transistor. When the inverter operated at the direct voltage (V DD ) of 10 V and the input voltage from 0 V to 10 V, the obtained high performances included the output swing of 9.9 V, the high noise margin of 2.7 V, and the low noise margin of 2.2 V. Furthermore, the high performances of unskenwed inverter were demonstrated by using the novel complementary structure of the stacked n-type Al:ZnO thin-film transistor and p-type nickel oxide (NiO) thin-film transistor.

Ternary chalcogenides C s 2 Z n 3 S e 4 and C s 2 Z n 3 T e 4 : Potential p -type transparent conducting materials

DOE PAGES

Shi, Hongliang; Saparov, Bayrammurad; Singh, David J.; ...

2014-11-11

Here we report prediction of two new ternary chalcogenides that can potentially be used as p-type transparent conductors along with experimental synthesis and initial characterization of these previously unknown compounds, Cs 2Zn 3Ch 4 (Ch = Se, Te). In particular, the structures are predicted based on density functional calculations and confirmed by experiments. Phase diagrams, electronic structure, optical properties, and defect properties of Cs 2Zn 3Se 4 and Cs 2Zn 3Te 4 are calculated to assess the viability of these materials as p-type TCMs. Cs 2Zn 3Se 4 and Cs 2Zn 3Te 4, which are stable under ambient air, displaymore » large optical band gaps (calculated to be 3.61 and 2.83 eV, respectively) and have small hole effective masses (0.5-0.77 m e) that compare favorably with other proposed p-type TCMs. Defect calculations show that undoped Cs2Zn3Se4 and Cs2Zn3Te4 are p-type materials. However, the free hole concentration may be limited by low-energy native donor defects, e.g., Zn interstitials. Lastly, non-equilibrium growth techniques should be useful for suppressing the formation of native donor defects, thereby increasing the hole concentration.« less

The in vitro effect of Antimicrobial Photodynamic Therapy on dental microcosm biofilms from partially erupted permanent molars: A pilot study.

PubMed

de Oliveira, Fabiana Sodré; Cruvinel, Thiago; Cusicanqui Méndez, Daniela Alejandra; Dionísio, Evandro José; Rios, Daniela; Machado, Maria Aparecida Andrade Moreira

2018-03-01

Antimicrobial Photodynamic Therapy (aPDT) could enhance the prevention of dental caries lesions in pits and fissures of partially erupted molars, by killing microorganisms from complex dental biofilms. This pilot study aimed to evaluate the effect of Antimicrobial Photodynamic Therapy (aPDT) on the viability of specific microorganism groups of dental microcosm biofilms from occlusal surfaces of first permanent molars in eruption. Dental microcosm biofilms grown on bovine enamel blocks, from dental plaque collected on occlusal surfaces of a partially erupted lower right first permanent molar, with McBain medium plus 1% sucrose in anaerobic condition at 37 °C for 72 h. The experiments were performed in eight groups: L-P- = no treatment (control), L18.75P- = 18.75 J/cm 2 LED, L37.5P- = 37.5 J/cm 2 LED, L75P- = 75 J/cm 2 LED, L-P+ = 200 mM TBO, L18.75P+ = 200 mM TBO + 18.75 J/cm 2 LED, L37.5P+ = 200 mM TBO + 37.5 J/cm 2 LED, and L75P+ = 200 mM TBO + 75 J/cm 2 LED. The counts of total microorganisms, total streptococci and mutans streptococci were determined on selective media agar plates by colony-forming units per mL. The log-transformed counts were analyzed by Kruskal-Wallis and post-hoc Dunn's test (P < 0.05). The counts of all microorganisms treated in the group L75P+ were statistically lower than those treated in L-P-. The aPDT promoted a significant reduction of microorganisms, with a trend of dose-dependent effect. TBO-mediated aPDT was effective in reducing the viability of specific microbial groups in dental microcosm biofilms originated from occlusal of permanent molars in eruption. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis, structure, and polymorphism of A{sub 3}LnSi{sub 2}O{sub 7} (A=Na, K; Ln=Sm, Ho, Yb)

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

Latshaw, Allison M.; Yeon, Jeongho; Smith, Mark D.

2016-03-15

Four new members of the A{sub 3}LnSi{sub 2}O{sub 7} family, K{sub 3}SmSi{sub 2}O{sub 7}, Na{sub 3}HoSi{sub 2}O{sub 7}, and two polymorphs of Na{sub 3}YbSi{sub 2}O{sub 7}, are reported. K{sub 3}SmSi{sub 2}O{sub 7} crystallizes in the hexagonal space group P6{sub 3}/mcm, Na{sub 3}HoSi{sub 2}O{sub 7} and Na{sub 3}YbSi{sub 2}O{sub 7} crystallize in the hexagonal space group P6{sub 3}/m, and Na{sub 3}YbSi{sub 2}O{sub 7} crystallizes in the trigonal space group P31c. The Na{sub 3}YbSi{sub 2}O{sub 7} composition that crystallizes in P31c is a new structure type. The magnetic properties for the Ho and Yb analogs are reported. - Graphical abstract: The differentmore » structure types and polymorphs of the A{sub 3}LnSi{sub 2}O{sub 7} family reported. - Highlights: • Four new members of the A{sub 3}LnSi{sub 2}O{sub 7} family are presented. • Na{sub 3}YbSi{sub 2}O{sub 7} is reported as two polymorphs, one is a new structure type. • Crystals synthesized out of molten fluoride fluxes.« less

The fcc - bcc structural transition: I. A band theoretical study for Li, K, Rb, Ca, Sr, and the transition metals Ti and V

NASA Astrophysics Data System (ADS)

Sliwko, V. L.; Mohn, P.; Schwarz, K.; Blaha, P.

1996-02-01

Employing a high-precision band structure method (FP LAPW - full potential linearized augmented plane wave) we calculate the total energy variation along the tetragonal distortion path connecting the body centred cubic (bcc) and the face centred cubic (fcc) structures. The total energy along this Bain transformation is calculated, varying c/a and volume, providing a first-principles energy surface which has two minima as a function of c/a. These are shallow and occur for the sp metals at the two cubic structures, while Ti (V) has a minimum at fcc (bcc) but a saddle point (i.e. a minimum in volume and a maximum with respect to c/a) at the other cubic structure. These features can be analysed in terms of an interplay between the Madelung contribution and the band energies. Our total energy results allow us to calculate the elastic constants 0953-8984/8/7/006/img1 and 0953-8984/8/7/006/img2 and to study the influence of pressure on the phase stability. These energy surfaces will be used in part II of this paper to investigate finite-temperature effects by mapping them to a Landau - Ginzburg expansion.

Evidence for Sequence Scrambling and Divergent H/D Exchange Reactions of Doubly-Charged Isobaric b-Type Fragment Ions

NASA Astrophysics Data System (ADS)

Zekavat, Behrooz; Miladi, Mahsan; Al-Fdeilat, Abdullah H.; Somogyi, Arpad; Solouki, Touradj

2014-02-01

To date, only a limited number of reports are available on structural variants of multiply-charged b-fragment ions. We report on observed bimodal gas-phase hydrogen/deuterium exchange (HDX) reaction kinetics and patterns for substance P b10 2+ that point to presence of isomeric structures. We also compare HDX reactions, post-ion mobility/collision-induced dissociation (post-IM/CID), and sustained off-resonance irradiation-collision induced dissociation (SORI-CID) of substance P b10 2+ and a cyclic peptide with an identical amino acid (AA) sequence order to substance P b10. The observed HDX patterns and reaction kinetics and SORI-CID pattern for the doubly charged head-to-tail cyclized peptide were different from either of the presumed isomers of substance P b10 2+, suggesting that b10 2+ may not exist exclusively as a head-to-tail cyclized structure. Ultra-high mass measurement accuracy was used to assign identities of the observed SORI-CID fragment ions of substance P b10 2+; over 30 % of the observed SORI-CID fragment ions from substance P b10 2+ had rearranged (scrambled) AA sequences. Moreover, post-IM/CID experiments revealed the presence of two conformer types for substance P b10 2+, whereas only one conformer type was observed for the head-to-tail cyclized peptide. We also show that AA sequence scrambling from CID of doubly-charged b-fragment ions is not unique to substance P b10 2+.

Evidence for sequence scrambling and divergent H/D exchange reactions of doubly-charged isobaric b-type fragment ions.

PubMed

Zekavat, Behrooz; Miladi, Mahsan; Al-Fdeilat, Abdullah H; Somogyi, Arpad; Solouki, Touradj

2014-02-01

To date, only a limited number of reports are available on structural variants of multiply-charged b-fragment ions. We report on observed bimodal gas-phase hydrogen/deuterium exchange (HDX) reaction kinetics and patterns for substance P b10(2+) that point to presence of isomeric structures. We also compare HDX reactions, post-ion mobility/collision-induced dissociation (post-IM/CID), and sustained off-resonance irradiation-collision induced dissociation (SORI-CID) of substance P b10(2+) and a cyclic peptide with an identical amino acid (AA) sequence order to substance P b10. The observed HDX patterns and reaction kinetics and SORI-CID pattern for the doubly charged head-to-tail cyclized peptide were different from either of the presumed isomers of substance P b10(2+), suggesting that b10(2+) may not exist exclusively as a head-to-tail cyclized structure. Ultra-high mass measurement accuracy was used to assign identities of the observed SORI-CID fragment ions of substance P b10(2+); over 30% of the observed SORI-CID fragment ions from substance P b10(2+) had rearranged (scrambled) AA sequences. Moreover, post-IM/CID experiments revealed the presence of two conformer types for substance P b10(2+), whereas only one conformer type was observed for the head-to-tail cyclized peptide. We also show that AA sequence scrambling from CID of doubly-charged b-fragment ions is not unique to substance P b10(2+).

Vertical MoSe2-MoO x p-n heterojunction and its application in optoelectronics.

PubMed

Chen, Xiaoshuang; Liu, Guangbo; Hu, Yunxia; Cao, Wenwu; Hu, PingAn; Hu, Wenping

2018-01-26

The hybrid n-type 2D transition-metal dichalcogenide (TMD)/p-type oxide van der Waals (vdW) heterojunction nanosheets consist of 2D layered MoSe 2 (the n-type 2D material) and MoO x (the p-type oxide) which are grown on SiO 2 /Si substrates for the first time via chemical vapor deposition technique, displaying the regular hexagon structures with the average length dimension of sides of ∼8 μm. Vertical MoSe 2 -MoO x p-n heterojunctions demonstrate obviously current-rectifying characteristic, and it can be tuned via gate voltage. What is more, the photodetector based on vertical MoSe 2 -MoO x heterojunctions displays optimal photoresponse behavior, generating the responsivity, detectivity, and external quantum efficiency to 3.4 A W -1 , 0.85 × 10 8 Jones, and 1665.6%, respectively, at V ds  = 5 V with the light wavelength of 254 nm under 0.29 mW cm -2 . These results furnish a building block on investigating the flexible and transparent properties of vdW and further optimizing the structure of the devices for better optoelectronic and electronic performance.

Vertical MoSe2-MoO x p-n heterojunction and its application in optoelectronics

NASA Astrophysics Data System (ADS)

Chen, Xiaoshuang; Liu, Guangbo; Hu, Yunxia; Cao, Wenwu; Hu, PingAn; Hu, Wenping

2018-01-01

The hybrid n-type 2D transition-metal dichalcogenide (TMD)/p-type oxide van der Waals (vdW) heterojunction nanosheets consist of 2D layered MoSe2 (the n-type 2D material) and MoO x (the p-type oxide) which are grown on SiO2/Si substrates for the first time via chemical vapor deposition technique, displaying the regular hexagon structures with the average length dimension of sides of ˜8 μm. Vertical MoSe2-MoO x p-n heterojunctions demonstrate obviously current-rectifying characteristic, and it can be tuned via gate voltage. What is more, the photodetector based on vertical MoSe2-MoO x heterojunctions displays optimal photoresponse behavior, generating the responsivity, detectivity, and external quantum efficiency to 3.4 A W-1, 0.85 × 108 Jones, and 1665.6%, respectively, at V ds = 5 V with the light wavelength of 254 nm under 0.29 mW cm-2. These results furnish a building block on investigating the flexible and transparent properties of vdW and further optimizing the structure of the devices for better optoelectronic and electronic performance.

How To Design a Successful p53-MDM2/X Interaction Inhibitor: A Thorough Overview Based on Crystal Structures.

PubMed

Estrada-Ortiz, Natalia; Neochoritis, Constantinos G; Dömling, Alexander

2016-04-19

A recent therapeutic strategy in oncology is based on blocking the protein-protein interaction between the murine double minute (MDM) homologues MDM2/X and the tumor-suppressor protein p53. Inhibiting the binding between wild-type (WT) p53 and its negative regulators MDM2 and/or MDMX has become an important target in oncology to restore the antitumor activity of p53, the so-called guardian of our genome. Interestingly, based on the multiple disclosed compound classes and structural analysis of small-molecule-MDM2 adducts, the p53-MDM2 complex is perhaps the best studied and most targeted protein-protein interaction. Several classes of small molecules have been identified as potent, selective, and efficient inhibitors of the p53-MDM2/X interaction, and many co-crystal structures with the protein are available. Herein we review the properties as well as preclinical and clinical studies of these small molecules and peptides, categorized by scaffold type. A particular emphasis is made on crystallographic structures and the observed binding modes of these compounds, including conserved water molecules present. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electronic and elastic properties of new semiconducting oP(12)-type RuB(2) and OsB(2).

PubMed

Hao, Xianfeng; Xu, Yuanhui; Gao, Faming

2011-03-30

Using first-principles total energy calculations we investigate the structural, elastic and electronic properties of new hypothetical oP(12)-type phase RuB(2) and OsB(2). The calculations indicate that the oP(12)-type phase RuB(2) and OsB(2) are thermodynamically and mechanically stable. Remarkably, the new phases RuB(2) and OsB(2) are predicted to be semiconductors, and the appearance of band gaps is ascribed to the enhanced B-B covalent hybridization. Compared to metallic oP(6)-type RuB(2) and OsB(2) phases, the new phases possess similar mechanical properties and hardness. The combination of the probability of tunable electronic properties, strong stiffness and high hardness make RuB(2) and OsB(2) attractive and interesting for advanced applications. © 2011 IOP Publishing Ltd

New silicate-germanate Cs2Pb2[(Si0.6Ge0.4)2O7] from the series A2Pb2[B2O7], A = K, Cs, B = Si, Ge with the umbrella-like [PbO3]4- group

NASA Astrophysics Data System (ADS)

Belokoneva, Elena L.; Morozov, Ivan A.; Volkov, Anatoly S.; Dimitrova, Olga V.; Stefanovich, Sergey Yu.

2018-04-01

New silicate-germanate Cs2Pb2[(Si0.6Ge0.4)2O7] was synthesized in multi-components hydrothermal solution with 20 w.% concentration of Cs2CO3 mineralizer, pH = 10. Novel mixed compound belongs to the structure type A2Pb2[B2O7] previously indicated for powders with A = K, B=Si or Ge. Singe crystal structure determination of Cs2Pb2[(Si0.6Ge0.4)2O7] revealed the need for the correction of the space group of the earlier suggested structural model from P-3 to P-3m1, as well as for the splitting of the Pb-atom position. Umbrella-like groups [PbO3]4- are located between [(Si,Ge)O4]4- tetrahedra in mica-like honeycomb layers and play the role of tetrahedra with the Pb-lone-pair as the forth apex. Crystal chemical comparison revealed similarities and differences with the classical structure type of α-celsian Ba[Al2Si2O8] with the tetrahedral double layer. Recently investigated nonlinear optical acentric borates Pb2(BO3)(NO3) and Pb2(BO3)Cl are both related to this structural type, possessing umbrella-like groups [PbO3]4- and honeycomb layers [Pb2(BO3)]+ with the BO3-triangles on the tetrahedral positions.

New cyclic sulfides extracted from Allium sativum: garlicnins P, J2, and Q.

PubMed

Nohara, Toshihiro; Ono, Masateru; Nishioka, Naho; Masuda, Fuka; Fujiwara, Yukio; Ikeda, Tsuyoshi; Nakano, Daisuke; Kinjo, Junei

2018-01-01

Two atypical cyclic-type sulfides, garlicnin P (1) and garlicnin J 2 (2), and one thiabicyclic-type sulfide, garlicnin Q (3), were isolated from the acetone extracts of garlic, Allium sativum, bulbs cultivated in the Kumamoto city area, and their structures characterized. Their production pathways are also discussed.

Spectroscopic characterization and O2 reactivity of the trinuclear Cu cluster of mutants of the multicopper oxidase Fet3p.

PubMed

Palmer, Amy E; Quintanar, Liliana; Severance, Scott; Wang, Tzu-Pin; Kosman, Daniel J; Solomon, Edward I

2002-05-21

Fet3p is a multicopper oxidase that uses four copper ions (one type 1, one type 2, and one type 3 binuclear site) to couple substrate oxidation to the reduction of O(2) to H(2)O. The type 1 Cu site shuttles electrons between the substrate and the type 2/type 3 Cu sites which form a trinuclear Cu cluster that is the active site for O(2) reduction. This study extends the spectroscopic and reactivity studies that have been conducted with type 1-substituted Hg (T1Hg) laccase to Fet3p and a mutant of Fet3p in which the trinuclear Cu cluster is perturbed. To examine the reaction between the trinuclear Cu cluster and O(2), the type 1 Cu Cys(484) was mutated to Ser, resulting in a type 1-depleted (T1D) form of the enzyme. Additional His to Gln mutations were made at the trinuclear cluster to further probe specific contributions to reactivity. One of these mutants (His(126)Gln) produces the first stable but perturbed trinuclear Cu cluster (T1DT3' Fet3p). Spectroscopic characterization (absorption, circular dichroism, magnetic circular dichroism, and electron paramagnetic resonance) of the resting trinuclear sites in T1D and T1DT3' Fet3p reveal that the His(126)Gln mutation changes the electronic structure of both the type 3 and type 2 Cu sites. The trinuclear clusters in T1D and T1DT3' Fet3p react with O(2) to produce peroxide intermediates analogous to that observed in T1Hg laccase. Spectroscopic data on the peroxide intermediates in the three forms provide further insight into the structure of this intermediate. In T1D Fet3p, the decay of this peroxide intermediate is pH-dependent, and the rate of decay is 10-fold higher at low pH. In T1DT3' Fet3p, the decay of the peroxide intermediate is pH-independent and is slow at all pH's. This change in the pH dependence provides new insight into the mechanism of intermediate decay involving reductive cleavage of the O-O bond.

Effects of Structured Versus Usual Care on Renal Endpoint in Type 2 Diabetes: The SURE Study

PubMed Central

Chan, Juliana C.; So, Wing-Yee; Yeung, Chun-Yip; Ko, Gary T.; Lau, Ip-Tim; Tsang, Man-Wo; Lau, Kam-Piu; Siu, Sing-Chung; Li, June K.; Yeung, Vincent T.; Leung, Wilson Y.; Tong, Peter C.

2009-01-01

OBJECTIVE Multifaceted care has been shown to reduce mortality and complications in type 2 diabetes. We hypothesized that structured care would reduce renal complications in type 2 diabetes. RESEARCH DESIGN AND METHODS A total of 205 Chinese type 2 diabetic patients from nine public hospitals who had plasma creatinine levels of 150–350 μmol/l were randomly assigned to receive structured care (n = 104) or usual care (n = 101) for 2 years. The structured care group was managed according to a prespecified protocol with the following treatment goals: blood pressure <130/80 mmHg, A1C <7%, LDL cholesterol <2.6 mmol/l, triglyceride <2 mmol/l, and persistent treatment with renin-angiotensin blockers. The primary end point was death and/or renal end point (creatinine >500 μmol/l or dialysis). RESULTS Of these 205 patients (mean ± SD age 65 ± 7.2 years; disease duration 14 ± 7.9 years), the structured care group achieved better control than the usual care group (diastolic blood pressure 68 ± 12 vs. 71 ± 12 mmHg, respectively, P = 0.02; A1C 7.3 ± 1.3 vs. 8.0 ± 1.6%, P < 0.01). After adjustment for age, sex, and study sites, the structured care (23.1%, n = 24) and usual care (23.8%, n = 24; NS) groups had similar end points, but more patients in the structured care group attained ≥3 treatment goals (61%, n = 63, vs. 28%, n = 28; P < 0.001). Patients who attained ≥3 treatment targets (n = 91) had reduced risk of the primary end point (14 vs. 34; relative risk 0.43 [95% CI 0.21–0.86] compared with that of those who attained ≤2 targets (n = 114). CONCLUSIONS Attainment of multiple treatment targets reduced the renal end point and death in type 2 diabetes. In addition to protocol, audits and feedback are needed to improve outcomes. PMID:19460913

Effects of structured versus usual care on renal endpoint in type 2 diabetes: the SURE study: a randomized multicenter translational study.

PubMed

Chan, Juliana C; So, Wing-Yee; Yeung, Chun-Yip; Ko, Gary T; Lau, Ip-Tim; Tsang, Man-Wo; Lau, Kam-Piu; Siu, Sing-Chung; Li, June K; Yeung, Vincent T; Leung, Wilson Y; Tong, Peter C

2009-06-01

Multifaceted care has been shown to reduce mortality and complications in type 2 diabetes. We hypothesized that structured care would reduce renal complications in type 2 diabetes. A total of 205 Chinese type 2 diabetic patients from nine public hospitals who had plasma creatinine levels of 150-350 micromol/l were randomly assigned to receive structured care (n = 104) or usual care (n = 101) for 2 years. The structured care group was managed according to a prespecified protocol with the following treatment goals: blood pressure <130/80 mmHg, A1C <7%, LDL cholesterol <2.6 mmol/l, triglyceride <2 mmol/l, and persistent treatment with renin-angiotensin blockers. The primary end point was death and/or renal end point (creatinine >500 micromol/l or dialysis). Of these 205 patients (mean +/- SD age 65 +/- 7.2 years; disease duration 14 +/- 7.9 years), the structured care group achieved better control than the usual care group (diastolic blood pressure 68 +/- 12 vs. 71 +/- 12 mmHg, respectively, P = 0.02; A1C 7.3 +/- 1.3 vs. 8.0 +/- 1.6%, P < 0.01). After adjustment for age, sex, and study sites, the structured care (23.1%, n = 24) and usual care (23.8%, n = 24; NS) groups had similar end points, but more patients in the structured care group attained >or=3 treatment goals (61%, n = 63, vs. 28%, n = 28; P < 0.001). Patients who attained >or=3 treatment targets (n = 91) had reduced risk of the primary end point (14 vs. 34; relative risk 0.43 [95% CI 0.21-0.86] compared with that of those who attained

New high-pressure polymorph of In{sub 2}S{sub 3} with defect Th{sub 3}P{sub 4}-type structure

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

Lai, Xiaojing; Zhu, Feng; Wu, Ye

The high pressure behavior of β-In{sub 2}S{sub 3} (I4{sub 1}/amd and Z=16) has been studied by in situ synchrotron radiation X-ray diffraction combined with diamond anvil cell up to 71.7 GPa. Three pressure-induced phase transitions are evidenced at ∼6.6 GPa, ∼11.1 GPa at room temperature and 35.6 GPa after the high-temperature annealing using a portable laser heating system. The new polymorph of In{sub 2}S{sub 3} at 35.6 GPa is assigned to the denser cubic defect Th{sub 3}P{sub 4} structure (I4¯3d and Z=5.333), whose unit-cell parameters are a=7.557(1) Å and V=431.6(2) Å{sup 3}. The Th{sub 3}P{sub 4}-type phase can be stablemore » at least up to 71.7 GPa and cannot be preserved at ambient pressure. The pressure–volume relationship is well described by the second-order Birch–Murnaghan Equation of State, which yields B{sub 0}=63(3) GPa and B{sub 0}′=4 (fixed) for the β-In{sub 2}S{sub 3} phase and B{sub 0}=87(3) GPa and B{sub 0}′=4 (fixed) for the defect Th{sub 3}P{sub 4}-type phase respectively. - Graphical abstract: The structure and Rietveld refinement of new polymorph the defect Th{sub 3}P{sub 4}-type In{sub 2}S{sub 3}. This structure was observed at 35.6 GPa after laser heating by X-ray diffraction. Display Omitted - Highlights: Three pressure-induced phase transitions of β-In{sub 2}S{sub 3} were observed. β-In{sub 2}S{sub 3} was stable up to 6.6 GPa. The defect Th{sub 3}P{sub 4}-type In{sub 2}S{sub 3} was identified at 35.6 GPa after laser heating and was stable up to 71.7 GPa. Elastic properties of β-In{sub 2}S{sub 3} and Th{sub 3}P{sub 4}-type In{sub 2}S{sub 3} are well presented by Birch–Murnaghan EoS.« less

Actinomyces naeslundii Displays Variant fimP and fimA Fimbrial Subunit Genes Corresponding to Different Types of Acidic Proline-Rich Protein and β-Linked Galactosamine Binding Specificity

PubMed Central

Hallberg, K.; Holm, C.; Öhman, U.; Strömberg, N.

1998-01-01

Actinomyces naeslundii genospecies 1 and 2 bind to acidic proline-rich proteins (APRPs) and statherin via type 1 fimbriae and to β-linked galactosamine (GalNAcβ) structures via type 2 fimbriae. In addition, A. naeslundii displays two types of binding specificity for both APRPs-statherin and GalNAcβ, while Actinomyces odontolyticus binds to unknown structures. To study the molecular basis for these binding specificities, DNA fragments spanning the entire or central portions of fimP (type 1) and fimA (type 2) fimbrial subunit genes were amplified by PCR from strains of genospecies 1 and 2 and hybridized with DNA from two independent collections of oral Actinomyces isolates. Isolates of genospecies 1 and 2 and A. odontolyticus, but no other Actinomyces species, were positive for hybridization with fimP and fimA full-length probes irrespective of binding to APRPs and statherin, GalNAcβ, or unknown structures. Isolates of genospecies 1 and 2, with deviating patterns of GalNAcβ1-3Galα-O-ethyl-inhibitable coaggregation with Streptococcus oralis Ss34 and MPB1, were distinguished by a fimA central probe from genospecies 1 and 2, respectively. Furthermore, isolates of genospecies 1 and 2 displaying preferential binding to APRPs over statherin were positive with a fimP central probe, while a genospecies 2 strain with the opposite binding preference was not. The sequences of fimP and fimA central gene segments were highly conserved among isolates with the same, but diversified between those with a variant, binding specificity. In conclusion, A. naeslundii exhibits variant fimP and fimA genes corresponding to diverse APRP and GalNAcβ specificities, respectively, while A. odontolyticus has a genetically related but distinct adhesin binding specificity. PMID:9712794

A power device material of corundum-structured α-Ga2O3 fabricated by MIST EPITAXY® technique

NASA Astrophysics Data System (ADS)

Kaneko, Kentaro; Fujita, Shizuo; Hitora, Toshimi

2018-02-01

Corundum-structured oxides have been attracting much attention as next-generation power device materials. A corundum-structured α-Ga2O3 successfully demonstrated power device operations of Schottky barrier diodes (SBDs) with the lowest on-resistance of 0.1 mΩ cm2. The SBDs as a mounting device of TO220 also showed low switching-loss properties with a capacitance of 130 pF. Moreover, the thermal resistance was 13.9 °C/W, which is comparable to that of the SiC TO220 device (12.5 °C/W). On the other hand, corundum-structured α-(Rh,Ga)2O3 showed p-type conductivity, which was confirmed by Hall effect measurements. The Hall coefficient, carrier density, and mobility were 8.22 cm3/C, 7.6 × 1017/cm3, and 1.0 cm2 V-1 s-1, respectively. These values were acceptable for the p-type layer of pn diodes based on α-Ga2O3.

Studies on Ammonia Spectral Signatures Relevant to Jupiter's Clouds

NASA Astrophysics Data System (ADS)

Kalogerakis, Konstantinos S.; Oza, A. U.; Marschall, J.; Wong, M. H.

2006-09-01

Observational evidence and thermochemical models indicate an abundance of ammonia ice clouds in Jupiter's atmosphere. However, spectrally identifiable ammonia ice clouds are found covering less than 1% of Jupiter's atmosphere, notably in turbulent areas [1,2]. Current literature suggests two possible explanations: coating by a hydrocarbon haze and/or photochemical processing ("tanning") [2,3]. We are pursuing a research program investigating the above hypotheses. In the experiments, thin films of ammonia ices are deposited in a cryogenic apparatus, coated with hydrocarbons, and characterized by infrared spectroscopy. The ice films can be irradiated by ultraviolet light to study their photochemistry. The spectroscopic measurements aim to identify the processes that control the optical properties of the ice mixtures and quantify their dependence on the identity of the coating, the temperature, and the ice composition. We have observed a consistent suppression of the ammonia absorption feature at 3 μm with coverage by thin layers of hydrocarbons. Modeling calculations of the multi-layer thin films assist in the interpretation of the experimental results and reveal the role of optical interference in masking the aforementioned ammonia spectral feature. The implications of these results for Jupiter's atmosphere will be discussed. Funding from the NSF Planetary Astronomy Program under grant AST-0206270 and from the NASA Outer Planets Research Program under grant NNG06GF37G is gratefully acknowledged. The participation of Anand Oza (Princeton University) was made possible by the NSF Research Experiences for Undergraduates Program under grant PHY-0353745. 1. S. K. Atreya, A.-S. Wong, K. H. Baines, M. H. Wong, T. C. Owen, Planet. Space Science 53, 498 (2005). 2. K. H. Baines, R. W. Carlson, and L. W. Kamp, Icarus 159, 74 (2002). 3. A.-S. Wong, Y. L. Yung, and A. J. Friedson, Geophys. Res. Lett. 30, 1447 (2003).

Infrared Spectroscopy of Ammonia - Hydrocarbon Ices Relevant to Jupiter's Clouds

NASA Astrophysics Data System (ADS)

Engel, P. A.; Kalogerakis, K. S.

2005-12-01

Observational evidence and thermochemical models indicate an abundance of ammonia ice clouds in Jupiter's atmosphere. However, spectrally identifiable ammonia ice clouds are found covering less than 1% of Jupiter's atmosphere, notably in turbulent areas.1,2 This discrepancy highlights an important gap in our understanding of ammonia and its spectral signatures in Jupiter's atmosphere. Current literature suggests two possible explanations: coating by a hydrocarbon haze and/or photochemical processing ("tanning").2,3 We are performing laboratory experiments that investigate the above hypotheses. Thin films of ammonia ices are deposited in a cryogenic apparatus, coated with hydrocarbons, and characterized by infrared spectroscopy. The ice films can be irradiated by ultraviolet light. These spectroscopic measurements aim to identify the photophysical and chemical processes that control the optical properties of the ice mixtures and quantify their dependence on the identity of the coating, the temperature, and the ice composition. Our current results indicate a consistent suppression of the ammonia absorption feature at 3 μm with coverage by thin layers of hexane, cyclohexane, and benzene. Furthermore, strongest suppression is observed in the case of benzene, followed in magnitude by hexane and cyclohexane. Funding from the NSF Planetary Astronomy Program under grant AST-0206270 is gratefully acknowledged. The participation of Patricia A. Engel was made possible by the NSF Research Experiences for Undergraduates Program under grant PHY-0353745. 1. S. K. Atreya, A.-S. Wong, K. H. Baines, M. H. Wong, T. C. Owen, Planet. Space Science 53, 498 (2005). 2. K. H. Baines, R. W. Carlson, and L. W. Kamp, Icarus 159, 74 (2002). 3. A.-S. Wong, Y. L. Yung, and A. J. Friedson, Geophys. Res. Lett. 30, 1447 (2003).

Studies on Ammonia Spectral Signatures Relevant to Jupiter's Clouds

NASA Astrophysics Data System (ADS)

Oza, A. U.; Marschall, J.; Wong, M. H.; Kalogerakis, K. S.

2006-12-01

Observational evidence and thermochemical models indicate an abundance of ammonia ice clouds in Jupiter's atmosphere. However, spectrally identifiable ammonia ice clouds are found covering less than 1% of Jupiter's atmosphere, notably in turbulent areas [1,2]. Current literature suggests two possible explanations: coating by a hydrocarbon haze and/or photochemical processing ("tanning")[2,3]. We are pursuing a research program investigating the above hypotheses. In the experiments, thin films of ammonia ices are deposited in a cryogenic apparatus, coated with hydrocarbons, and characterized by infrared spectroscopy. The ice films can be irradiated by ultraviolet light to study their photochemistry. The spectroscopic measurements aim to identify the processes that control the optical properties of the ice mixtures and quantify their dependence on the identity of the coating, the temperature, and the ice composition. We have observed a consistent suppression of the ammonia absorption feature at 3 μm with coverage by thin layers of hydrocarbons. Modeling calculations of the multi-layer thin films assist in the interpretation of the experimental results and reveal the role of optical interference in masking the aforementioned ammonia spectral feature. The implications of these results for Jupiter's atmosphere will be discussed. Funding from the NSF Planetary Astronomy Program under grant AST-0206270 and from the NASA Outer Planets Research Program under grant NNG06GF37G is gratefully acknowledged. The participation of Anand Oza (Princeton University) was made possible by the NSF Research Experiences for Undergraduates Program under grant PHY-0353745. 1. S. K. Atreya, A.-S. Wong, K. H. Baines, M. H. Wong, T. C. Owen, Planet. Space Science 53, 498 (2005). 2. K. H. Baines, R. W. Carlson, and L. W. Kamp, Icarus 159, 74 (2002). 3. A.-S. Wong, Y. L. Yung, and A. J. Friedson, Geophys. Res. Lett. 30, 1447 (2003).

Molecular Dynamics Simulations to Investigate the Influences of Amino Acid Mutations on Protein Three-Dimensional Structures of Cytochrome P450 2D6.1, 2, 10, 14A, 51, and 62.

PubMed

Fukuyoshi, Shuichi; Kometani, Masaharu; Watanabe, Yurie; Hiratsuka, Masahiro; Yamaotsu, Noriyuki; Hirono, Shuichi; Manabe, Noriyoshi; Takahashi, Ohgi; Oda, Akifumi

2016-01-01

Many natural mutants of the drug metabolizing enzyme cytochrome P450 (CYP) 2D6 have been reported. Because the enzymatic activities of many mutants are different from that of the wild type, the genetic polymorphism of CYP2D6 plays an important role in drug metabolism. In this study, the molecular dynamics simulations of the wild type and mutants of CYP2D6, CYP2D6.1, 2, 10, 14A, 51, and 62 were performed, and the predictions of static and dynamic structures within them were conducted. In the mutant CYP2D6.10, 14A, and 61, dynamic properties of the F-G loop, which is one of the components of the active site access channel of CYP2D6, were different from that of the wild type. The F-G loop acted as the "hatch" of the channel, which was closed in those mutants. The structure of CYP2D6.51 was not converged by the simulation, which indicated that the three-dimensional structure of CYP2D6.51 was largely different from that of the wild type. In addition, the intramolecular interaction network of CYP2D6.10, 14A, and 61 was different from that of the wild type, and it is considered that these structural changes are the reason for the decrease or loss of enzymatic activities. On the other hand, the static and dynamic properties of CYP2D6.2, whose activity was normal, were not considerably different from those of the wild type.

Synthesis, Crystal and Electronic Structures of the Pnictides AE 3TrPn 3 (AE = Sr, Ba; Tr = Al, Ga; Pn = P, As)

DOE PAGES

Stoyko, Stanislav; Voss, Leonard; He, Hua; ...

2015-09-24

New ternary arsenides AE 3TrAs 3 (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr 3GaP 3 and Ba 3AlP 3 have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr 3AlAs 3 and Ba 3AlAs 3 adopt the Ba 3AlSb 3-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr 3GaP 3 and Ba 3AlP 3. Likewise, the compounds Sr 3GaAs 3 and Ba 3GaAs 3 crystallize with the Ba 3GaSb 3-type structure (Pearson symbol oP56, space groupmore » Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn 4 and GaPn 4 tetrahedra (Pn = pnictogen, i.e., P or As), separated by the alkaline-earth Sr 2+ and Ba 2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE 2+] 3[Tr 3+][Pn 3-] 3, or rather [AE 2+] 6[Tr 2Pn 6] 12-, i.e., as Zintl phases.« less

A High-Performance Sodium-Ion Full Cell with a Layered Oxide Cathode and a Phosphorous-Based Composite Anode

DOE PAGES

Oh, Seung-Min; Oh, Pilgun; Kim, Sang-Ok; ...

2016-12-29

A low-cost sodium-ion full cell with a O3-type layered Na[Cu 0.2(Fe 1/3Mn2/3) 0.8]O 2 cathode and an alloy-type P-TiP2-C anode is presented. The cathode is synthesized by an oxalate coprecipitation method and optimized cathodes shows a high specific capacity of 135 mAh g -1 at 0.1C rate with a high rate capability of 90 mAh g-1 at 1C rate and 70 mAh g -1 at 2C rate with good cyclability. The full cell exhibits better capacity retention than the half cell with the cathode due to the elimination of the degradation caused by sodium-metal anode. The dramatically enhanced electrochemical performancemore » of the Na[Cu 0.2(Fe 1/3Mn 2/3) 0.8]O 2 / P-TiP 2-C full cell compared to that of the sample with no Cu is attributed to the structural stabilization imparted by Cu by suppressing the phase change from the O3 structure to the P3 structure during cycling.« less

n/p-Type changeable semiconductor TiO2 prepared from NTA

NASA Astrophysics Data System (ADS)

Li, Qiuye; Wang, Xiaodong; Jin, Zhensheng; Yang, Dagang; Zhang, Shunli; Guo, Xinyong; Yang, Jianjun; Zhang, Zhijun

2007-10-01

A novel kind of nano-sized TiO2 (anatase) was obtained by high-temperature (400-700°C) dehydration of nanotube titanic acid (H2Ti2O4(OH)2, NTA). The high-temperature (400-700°C) dehydrated nanotube titanic acids (HD-NTAs) with a unique defect structure exhibited a p-type semiconductor behavior under visible-light irradiation (λ≥420 nm, E photon=2.95 eV), whereas exhibited an n-type semiconductor behavior irradiated with UV light (λ=365 nm, E photon=3.40 eV).

Electronic, structural and magnetic studies of niobium borides of group 8 transition metals, Nb2MB2 (M=Fe, Ru, Os) from first principles calculations

NASA Astrophysics Data System (ADS)

Touzani, Rachid St.; Fokwa, Boniface P. T.

2014-03-01

The Nb2FeB2 phase (U3Si2-type, space group P4/mbm, no. 127) is known for almost 50 years, but until now its magnetic properties have not been investigated. While the synthesis of Nb2OsB2 (space group P4/mnc, no. 128, a twofold superstructure of U3Si2-type) with distorted Nb-layers and Os2-dumbbells was recently achieved, "Nb2RuB2" is still not synthesized and its crystal structure is yet to be revealed. Our first principles density functional theory (DFT) calculations have confirmed not only the experimental structures of Nb2FeB2 and Nb2OsB2, but also predict "Nb2RuB2" to crystalize with the Nb2OsB2 structure type. According to chemical bonding analysis, the homoatomic B-B interactions are optimized and very strong, but relatively strong heteroatomic M-B, B-Nb and M-Nb bonds (M=Fe, Ru, Os) are also found. These interactions, which together build a three-dimensional network, are mainly responsible for the structural stability of these ternary borides. The density-of-states at the Fermi level predicts metallic behavior, as expected, from metal-rich borides. Analysis of possible magnetic structures concluded preferred antiferromagnetic ordering for Nb2FeB2, originating from ferromagnetic interactions within iron chains and antiferromagnetic exchange interactions between them.

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.

Isoelectronic tungsten doping in monolayer MoSe 2 for carrier type modulation

DOE PAGES

Li, Xufan; Lin, Ming -Wei; Basile, Leonardo; ...

2016-07-06

Doping and alloying are effective ways to engineer the band structure and modulate the optoelectronic functionality of monolayer transition metal dichalcogenides (TMDs). In this work, we explore the synthesis and electronic properties of monolayer Mo 1-xW xSe 2 (0 < x < 0.18) alloys with almost 100% alloying degree. The isoelectronic substitutional doping of tungsten for molybdenum in the monolayer MoSe 2 is shown to suppress its intrinsically n-type conduction behavior, with p-type conduction gradually emerging to become dominant with increasing W concentration in the alloys. Atomic resolution Z-contrast electron microscopy show that W is shown to substitute directly formore » Mo without the introduction of noticeable vacancy or interstitial defects, however with randomly-distributed W-rich regions ~2 nm in diameter. Scanning tunneling microscopy/spectroscopy measurements reveal that these W-rich regions exhibit a local band structure with the valence band maximum (VBM) closer to the Fermi level as compared with the Mo-rich regions in the monolayer Mo 1-xW xSe 2 crystal. These localized upshifts of the VBM in the local band structure appear responsible for the overall p-type behavior observed for the monolayer Mo 1-xW xSe 2 crystals. Stacked monolayers of n-type MoSe 2 and p-type Mo 1-xW xSe 2 were demonstrated to form atomically thin, vertically stacked p n homojunctions with gate-tunable characteristics, which appear useful for future optoelectronic applications. Lastly, these results indicate that alloying with isoelectronic dopant atoms appears to be an effective and advantageous alternate strategy to doping or alloying with electron donors or acceptors in two-dimensional TMDs.« less

Theoretical predictions on the electronic structure and charge carrier mobility in 2D Phosphorus sheets

PubMed Central

Xiao, Jin; Long, Mengqiu; Zhang, Xiaojiao; Ouyang, Jun; Xu, Hui; Gao, Yongli

2015-01-01

We have investigated the electronic structure and carrier mobility of four types of phosphorous monolayer sheet (α-P, β-P,γ-P and δ-P) using density functional theory combined with Boltzmann transport method and relaxation time approximation. It is shown that α-P, β-P and γ-P are indirect gap semiconductors, while δ-P is a direct one. All four sheets have ultrahigh carrier mobility and show anisotropy in-plane. The highest mobility value is ~3 × 105 cm2V−1s−1, which is comparable to that of graphene. Because of the huge difference between the hole and electron mobilities, α-P, γ-P and δ-P sheets can be considered as n-type semiconductors, and β-P sheet can be considered as a p-type semiconductor. Our results suggest that phosphorous monolayer sheets can be considered as a new type of two dimensional materials for applications in optoelectronics and nanoelectronic devices. PMID:26035176

Antiferromagnetism in EuCu 2As 2 and EuCu 1.82Sb 2 single crystals

DOE PAGES

Anand, V. K.; Johnston, D. C.

2015-05-07

Single crystals of EuCu 2As 2 and EuCu 2Sb 2 were grown from CuAs and CuSb self-flux, respectively. The crystallographic, magnetic, thermal, and electronic transport properties of the single crystals were investigated by room-temperature x-ray diffraction (XRD), magnetic susceptibility χ versus temperature T, isothermal magnetization M versus magnetic field H, specific heat C p(T), and electrical resistivity ρ(T) measurements. EuCu 2As 2 crystallizes in the body-centered tetragonal ThCr 2Si 2-type structure (space group I4/mmm), whereas EuCu 2Sb 2 crystallizes in the related primitive tetragonal CaBe 2Ge 2-type structure (space group P4/nmm). The energy-dispersive x-ray spectroscopy and XRD data for themore » EuCu 2Sb 2 crystals showed the presence of vacancies on the Cu sites, yielding the actual composition EuCu 1.82Sb 2. The ρ(T) and C p(T) data reveal metallic character for both EuCu 2As 2 and EuCu 1.82Sb 2. Antiferromagnetic (AFM) ordering is indicated from the χ(T),C p(T), and ρ(T) data for both EuCu 2As 2 (T N = 17.5 K) and EuCu 1.82Sb 2 (T N = 5.1 K). In EuCu 1.82Sb 2, the ordered-state χ(T) and M(H) data suggest either a collinear A-type AFM ordering of Eu +2 spins S = 7/2 or a planar noncollinear AFM structure, with the ordered moments oriented in the tetragonal ab plane in either case. This ordered-moment orientation for the A-type AFM is consistent with calculations with magnetic dipole interactions. As a result, the anisotropic χ(T) and isothermal M(H) data for EuCu 2As 2, also containing Eu +2 spins S = 7/2, strongly deviate from the predictions of molecular field theory for collinear AFM ordering and the AFM structure appears to be both noncollinear and noncoplanar.« less

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

Du, Mao -Hua; Singh, David J.; Zhang, Lijun

Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn 2O 3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn 2O 3 andmore » BaSn 2O 3, which can be stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO 3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn 2O 3) to 3.15 (SrSn 2O 3) eV, and hole effective masses ranging from 0.87 (BaSn 2O 3) to above 6.0 (SrSn 2O 3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.« less

From Spintronics to CFD/ContractForDifferences

NASA Astrophysics Data System (ADS)

Maksoed, W. H.

2015-11-01

Involve the CFD/Computational Fluid Dynamics & HCCI/Homogeneous Charge Compression Ignition - Marcine Frackowiak, dissertation, 2009, for CFD/Contract For Differences accompanied by ``One Man's Crusade to Exonerate Hydrogen for Hindenburg Disaster'' of Addison BAIN, APS News, v. 9, n.7 (July 2000) concludes ``ignition of the blaze'' are responsible to those May, 1937 Accidents. Spintronics their selves include active control & manipulation of spin degree of freedom ever denotes: the nano-obelisk of scanning electron microscopy of galliumnitride/GaN nanostructures-Yong-Hon Cho et al.:``Novel Photonic Device using core-shell nanostructures'', SPIE-newsroom,10.1117/2.1201503.005864. Herewith commercial activated carbon/C can be imaged directly using abberation-corrected transmission electron microscopy[PJF Harris et al.: ``Imaging the Atomic Structures of activated C'', J. Phys. Condens. Matt, 20 (2008) in fig b & c- images networks of hexagonal rings can be clearly be seen depicts equal etchings of 340 px Akhenaten, Nefertiti & their childrens. Incredible acknowledgments to Minister of Education & Culture RI 1998-1999 HE. Mr. Prof. Ir. WIRANTO ARISMUNANDAR, MSME.

New members of the A2 M ‧ M2″ structure family (A=Ca, Sr, Yb, La; M ‧ = In , Sn , Pb; M ″ = Si , Ge)

NASA Astrophysics Data System (ADS)

Jehle, Michael; Dürr, Ines; Fink, Saskia; Lang, Britta; Langenmaier, Michael; Steckhan, Julia; Röhr, Caroline

2015-01-01

The new mixed tetrelides Sr2PbGe2 and Yb2SnGe2, several mixed Ca/Sr (AII) germanides A2II (Sn, Pb)Ge2 and two polymorphs of La2 InSi2 represent new members of the general structure family of ternary alkaline-earth/lanthanoid main group silicides/germanides A2 M ‧ M2″ (M ‧ = In , Sn , Pb ; M ″ = Si , Ge). All compounds were synthesized from melts of the elements and their crystal structures have been determined by means of single crystal X-ray diffraction. Sr2PbGe2 (Cmmm, a=402.36(11), b=1542.3(4), c=463.27(10) pm) crystallizes with the Mn2AlB2 -type structure. In exhibiting infinite planar Ge zig-zag chains, it represents one border of the compound series. The other borderline case, where only [Ge2 ] dumbbells are left as Ge building units, is represented by the Ca/Yb tin germanides Ca2SnGe2 and Yb2SnGe2 (Mo2FeB2 -type; P4/mbm, a=748.58(13)/740.27(7), c=445.59(8)/435.26(5) pm). In between these two border structures compounds with variable Si/Ge chain lengths could be obtained by varying the averaged size of the AII cations: Ca0.45Sr1.55PbGe2 (new structure type; Pbam, a=791.64(5), b=2311.2(2), c=458.53(3) pm) contains planar six-membered chain segments [Ge6 ]. Tetrameric pieces [Ge4 ] are the conspicuous structure elements in Ca1.16Sr0.84SnGe2 and La2 InSi2 (La2InNi2 -type; Pbam, a=781.01(2)/762.01(13), b=1477.95(3)/1494.38(6), c=457.004(9)/442.1(3) pm). The tetragonal form of 'La2 In Si2‧ (exact composition: La2In1.07Si1.93, P4/mbm, a=1309.11(12), c=443.32(4) pm) also crystallizes in a new structure type, containing only [Si3 ] trimers as cutouts of the planar chains. In all structures the Si/Ge zig-zag chains/chain segments are connected by In/Sn/Pb atoms to form planar M layers, which are separated by pure A layers. Band structure calculations within the FP-LAPW DFT approach together with the Zintl formalism, extended by the presence of hypervalent bonding of the heavier M ‧ elements, give insight into the chemical bonding of this series of p-block metallides. An analysis of the band structure for the border phases Sr2PbGe2 and Ca2SnGe2 shows the considerable π bonding contributions within the Ge building units, which also become apparent from the short Ge-Ge bond lengths.

Discovery and Cocrystal Structure of Benzodiazepinedione HDM2 Antagonists that Activate

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

Grasberger,B.; Lu, T.; Schubert, C.

2005-01-01

HDM2 binds to an {alpha}-helical transactivation domain of p53, inhibiting its tumor suppressive functions. A miniaturized thermal denaturation assay was used to screen chemical libraries, resulting in the discovery of a novel series of benzodiazepinedione antagonists of the HDM2-p53 interaction. The X-ray crystal structure of improved antagonists bound to HDM2 reveals their {alpha}-helix mimetic properties. These optimized molecules increase the transcription of p53 target genes and decrease proliferation of tumor cells expressing wild-type p53.

The New Superconductor tP-SrPd2Bi2: Structural Polymorphism and Superconductivity in Intermetallics.

PubMed

Xie, Weiwei; Seibel, Elizabeth M; Cava, Robert J

2016-04-04

We consider a system where structural polymorphism suggests the possible existence of superconductivity through the implied structural instability. SrPd2Bi2 has two polymorphs, which can be controlled by the synthesis temperature: a tetragonal form (CaBe2Ge2-type) and a monoclinic form (BaAu2Sb2-type). Although the crystallographic difference between the two forms may, at first, seem trivial, we show that tetragonal SrPd2Bi2 is superconducting at 2.0 K, whereas monoclinic SrPd2Bi2 is not. We rationalize this finding and place it in context with other 1-2-2 phases.

Interaction of tantalum, chromium, and phosphorus at 1070 K: Phase diagram and structural chemistry

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

Lomnytska, Ya.; Babizhetskyy, V., E-mail: v.babizhetskyy@googlemail.com; Oliynyk, A.

2016-03-15

Solid-state phase equilibria have been established in the Ta–Cr–P system in the region of 0–67 at% P at 1070 K through powder X-ray diffraction analysis. Mutual substitution of Ta and Cr in binary phosphides gives rise to significant homogeneity ranges in Ta{sub 1.00–0.66}Cr{sub 0–0.34}P (NbAs-type; a=3.332(3)–3.1366(3) Å, c=11.386(4)–11.364(2) Å), Ta{sub 3.0–2.1}Cr{sub 0–0.9}P (Ti{sub 3}P-type, a=10.156(2)–9.9992(2) Å, c=5.015(1)–4.956(2) Å), and Cr{sub 3.0–2.4}Ta{sub 0–0.6}P (Ni{sub 3}P-type, a=9.186(5)–9.217(4) Å, c=4.557(3)–4.5911(3) Å). A limited homogeneity range is found in the ternary phase Ta{sub 1.0–0.8}Cr{sub 1.0–1.2}P (TiNiSi-type, a=6.2344(5)–6.141(2) Å, b=3.5034(3)–3.3769(6) Å, c=7.3769(6)–7.357(2) Å). The OsGe{sub 2}-type structures (space group C2/m) of a new P-rich compound,more » Ta{sub 0.92(2)}Cr{sub 0.08(2)}P{sub 2} (a=8.8586(3) Å, b=3.2670(2) Å, c=7.4871(2) Å, β=119.315(2)°) as well as of the Ti-containing analogue Ta{sub 0.93(3)}Ti{sub 0.07(3)}P{sub 2} (a=8.8592(5) Å, b=3.2663(3) Å, c=7.4870(5) Å, β=119.309(2)°) were refined from powder X-ray diffraction data. - Graphical abstract: Solid-state phase equilibria have been established in the Ta–Cr–P system in the region of 0–67 at% P at 1070 K through powder X-ray diffraction analysis. Mutual substitution of Ta and Cr in binary phosphides gives rise to significant homogeneity ranges in Ta{sub 1.00–0.66}Cr{sub 0–0.34}P, Ta{sub 3.0–2.1}Cr{sub 0–0.9}P, and Cr{sub 3.0–2.4}Ta{sub 0–0.6}P. A limited homogeneity range is found in the ternary phase Ta{sub 1.0–0.8}Cr{sub 1.0–1.2}P. The OsGe{sub 2}-type structures of a new P-rich compound, Ta{sub 0.92(2)}Cr{sub 0.08(2)}P{sub 2} as well as of the Ti-containing analogue Ta{sub 0.93(3)}Ti{sub 0.07(3)}P{sub 2} were establish from powder X-ray diffraction data. No homogeneity ranges for binary compounds Cr{sub 12}P{sub 7}, Cr{sub 2}P, Ta{sub 5}P{sub 3} were detected. - Highlights: • The phase diagram of Ta–Cr–P at 1070 K has been constructed. • New ternary compounds Ta{sub 0.92(2)}Cr{sub 0.08(2)}P{sub 2} and Ta{sub 0.93(3)}Ti{sub 0.07(3)}P{sub 2} were established. • Ta{sub 1.0−0.8}Cr{sub 1.0−1.2}P and Ta{sub 0.86+x}Ti{sub 0.15-x}P{sub 2}(x= 0−0.07) exhibit homogeneity ranges. • The binary compounds reveal homogeneity ranges by Ta/Cr and Cr/Ta substitutions.« less

A study of structural, electrical, and optical properties of p-type Zn-doped SnO2 films versus deposition and annealing temperature

NASA Astrophysics Data System (ADS)

Le, Tran; Phuc Dang, Huu; Luc, Quang Ho; Hieu Le, Van

2017-04-01

This study presents a detailed investigation of the structural, electrical, and optical properties of p-type Zn-doped SnO2 versus the deposition and annealing temperature. Using a direct-current (DC) magnetron sputtering method, p-type transparent conductive Zn-doped SnO2 (ZTO) films were deposited on quartz glass substrates. Zn dopants incorporated into the SnO2 host lattice formed the preferred dominant SnO2 (1 0 1) and (2 1 1) planes. X-ray photoelectron spectroscopy (XPS) was used for identifying the valence state of Zn in the ZTO film. The electrical property of ZTO films changed from n-type to p-type at the threshold temperature of 400 °C, and the films achieved extremely high conductivity at the optimum annealing temperature of 600 °C after annealing for 2 h. The best conductive property of the film was obtained on a 10 wt% ZnO-doped SnO2 target with a resistivity, hole concentration, and hole mobility of 0.22 Ω · cm, 7.19  ×  1018 cm-3, and 3.95 cm2 V-1 s-1, respectively. Besides, the average transmission of films was  >84%. The surface morphology of films was examined using scanning electron microscopy (SEM). Moreover, the acceptor level of Zn2+ was identified using photoluminescence spectra at room temperature. Current-voltage (I-V) characteristics revealed the behavior of a p-ZTO/n-Si heterojunction diode.

Phase relations in the system In{sub 2}O{sub 3}-TiO{sub 2}-Fe{sub 2}O{sub 3} at 1100 C in air

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

Brown, F.; Flores, M.J.R.; Kimizuka, N.

1999-04-01

Phase relations in the system In{sub 2}O{sub 3}-TiO{sub 2}-Fe{sub 2}O{sub 3} at 1100 C in air are determined by means of a classic quenching method. There exist In{sub 2}TiO{sub 5}, Fe{sub 2}TiO{sub 5} having a pseudo-Brookite-type phase and a new phase, In{sub 3}Ti{sub 2}FeO{sub 10} having a solid solution range from In{sub 2}O{sub 3}:TiO{sub 2}:Fe{sub 2}O{sub 3} = 4:6:1 to In{sub 2}O{sub 3}:TiO{sub 2}:Fe{sub 2}O{sub 3} = 0.384:0.464:0.152 (mole ratio) on the line InFeO{sub 3}-In{sub 2}Ti{sub 2}O{sub 7}. The crystal structures of In{sub 3}Ti{sub 2}FeO{sub 10} are pyrochlore related with a{sub m} = 5.9171 (5) {angstrom}, b{sub m} = 3.3696more » (3) {angstrom}, c{sub m} = 6.3885 (6) {angstrom}, and {beta} = 108.02 (1){degree} in a monoclinic crystal system at 1100 C, and a{sub 0} = 5.9089 (5) {angstrom}, b{sub 0} = 3.3679 (3) {angstrom}, and c{sub 0} = 12.130 (1) {angstrom} in an orthorhombic system at 1200 C. The relationship between the lattice constants of these phases and those of the cubic pyrochlore type are approximately as follows: a{sub m} = {minus}{1/4}a{sub p} + ({minus}{1/2})b{sub p} + ({minus}{1/4})c{sub p}, b{sub m} = {minus}{1/4}a{sub p} + (0)b{sub p} + ({1/4})c{sub p}, c{sub m} = {1/4}a{sub p} + ({minus}{1/2})b{sub p} + ({1/4})c{sub p} and {beta} = 109.47{degree} in the monoclinic system, and a{sub 0} = {minus}{1/4}a{sub p} + ({minus}{1/2})b{sub p} + ({minus}{1/4})c{sub p}, b{sub 0} = {minus}{1/4}a{sub p} + (0)b{sub p} + ({1/4})c{sub p}, and c{sub 0} = 2/3a{sub p} + ({minus}2/3)b{sub p} + (2/3)c{sub p} in the orthorhombic system, where a{sub p} = b{sub p} = c{sub p} = 9.90 ({angstrom}) are the lattice constants of In{sub 2}Ti{sub 2}O{sub 7} having the cubic pyrochlore type. All solid solutions of In{sub 3}Ti{sub 2}FeO{sub 10} have incommensurate structures with a periodicity of q {times} b{sup *} (q = 0.281--0.356) along the b{sup *} axis and the stoichiometric phase has q = 1/3. In FeO{sub 3} having a layered structure type is unstable between 750 and 1100 C.« less

Copper-transporting P-type ATPases use a unique ion-release pathway

PubMed Central

Andersson, Magnus; Mattle, Daniel; Sitsel, Oleg; Nielsen, Anna Marie; White, Stephen H.; Nissen, Poul; Gourdon, Pontus

2014-01-01

Heavy metals in cells are typically regulated by PIB-type ATPases such as the copper transporting Cu+-ATPases. The first crystal structure of a Cu+-ATPase (LpCopA) was trapped in a transition state of dephosphorylation (E2.Pi) and inferred to be occluded. The structure revealed a PIB-specific topology and suggested a copper transport pathway across the membrane. Here we show by molecular dynamics (MD) simulations that extracellular water solvates the transmembrane (TM) domain, indicative of a pathway for Cu+ release. Furthermore, a new LpCopA crystal structure determined at 2.8 Å resolution, trapped in the E2P state (which is associated with extracellular exchange in PII-type ATPases), delineates the same conduit as also further supported by site-directed mutagenesis. The E2P and E2.Pi states therefore appear equivalent and open to the extracellular side, in contrast to PII-type ATPases where the E2.Pi state is occluded. This indicates that Cu+-ATPases couple dephosphorylation differently to the conformational changes associated with ion extrusion. The ion pathway may explain why Menkes’ and Wilson’s disease mutations at the extracellular side impair protein function, and points to an accessible site for novel inhibitors targeting Cu+-ATPases of pathogens. PMID:24317491

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

Meng, Jiang Ping; Yan, Zhi Shuo; Long, Ji Ying

By using a rigid dicarboxylate ligand, 4,5-di(4′-carboxylphenyl)benzene (H{sub 2}L), two complexes formulated as SrL(DMF)(H{sub 2}O)·(CH{sub 3}CN) (DMF=N,N′-dimethylformamide) (1) and BaL(H{sub 2}O){sub 2} (2) were solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 2 display two-dimensional (2D) layer structures. The two complexes exhibit different electrochemical and photoelectrochemical properties. Their thermal stabilities, cyclic voltammograms, UV–vis absorption and diffuse reflectance spectra and photoluminescence properties have been investigated. The band structures, the total density of states (TDOS) and partial density of states (PDOS) of the two complexes were calculated by CASTEP program. Complex 2 exhibits much higher photocurrent density thanmore » complex 1. The Mott–Schottky plots reveal that complexes 1 and 2 both are p-type semiconductors, which are in agreement with their band structure calculations. - Graphical abstract: Two alkaline earth metal(II) complexes with 2D layer structures are p-type semiconductors, they possess different band structures and density of states. And the Ba(II) complex 2 exhibits much higher photocurrent density than the Sr(II) complex 1.« less

Cu/Cu2O nanocomposite films as a p-type modified layer for efficient perovskite solar cells.

PubMed

Chen, You-Jyun; Li, Ming-Hsien; Huang, Jung-Chun-Andrew; Chen, Peter

2018-05-16

Cu/Cu 2 O films grown by ion beam sputtering were used as p-type modified layers to improve the efficiency and stability of perovskite solar cells (PSCs) with an n-i-p heterojunction structure. The ratio of Cu to Cu 2 O in the films can be tuned by the oxygen flow ratio (O 2 /(O 2  + Ar)) during the sputtering of copper. Auger electron spectroscopy was performed to determine the elemental composition and chemical state of Cu in the films. Ultraviolet photoelectron spectroscopy and photoluminescence spectroscopy revealed that the valence band maximum of the p-type Cu/Cu 2 O matches well with the perovskite. The Cu/Cu 2 O film not only acts as a p-type modified layer but also plays the role of an electron blocking buffer layer. By introducing the p-type Cu/Cu 2 O films between the low-mobility hole transport material, spiro-OMeTAD, and the Ag electrode in the PSCs, the device durability and power conversion efficiency (PCE) were effectively improved as compared to the reference devices without the Cu/Cu 2 O interlayer. The enhanced PCE is mainly attributed to the high hole mobility of the p-type Cu/Cu 2 O film. Additionally, the Cu/Cu 2 O film serves as a protective layer against the penetration of humidity and Ag into the perovskite active layer.

Codoping method for the fabrication of low-resistivity wide band-gap semiconductors in p-type GaN, p-type AlN and n-type diamond: prediction versus experiment

NASA Astrophysics Data System (ADS)

Katayama-Yoshida, H.; Nishimatsu, T.; Yamamoto, T.; Orita, N.

2001-10-01

We review our new valence control method of a co-doping for the fabrication of low-resistivity p-type GaN, p-type AlN and n-type diamond. The co-doping method is proposed based upon ab initio electronic structure calculation in order to solve the uni-polarity and the compensation problems in the wide band-gap semiconductors. In the co-doping method, we dope both the acceptors and donors at the same time by forming the meta-stable acceptor-donor-acceptor complexes for the p-type or donor-acceptor-donor complexes for the n-type under thermal non-equilibrium crystal growth conditions. We propose the following co-doping method to fabricate the low-resistivity wide band-gap semiconductors; p-type GaN: [Si + 2 Mg (or Be)], [H + 2 Mg (or Be)], [O + 2 Mg (or Be)], p-type AlN: [O + 2 C] and n-type diamond: [B + 2 N], [H + S], [H + 2 P]. We compare our prediction of the co-doping method with the recent successful experiments to fabricate the low-resistivity p-type GaN, p-type AlN and n-type diamond. We show that the co-doping method is the efficient and universal doping method by which to avoid carrier compensation with an increase of the solubility of the dopant, to increase the activation rate by decreasing the ionization energy of acceptors and donors, and to increase the mobility of the carrier.

Prediction for electronic, vibrational and thermoelectric properties of chalcopyrite AgX(X=In,Ga)Te2: PBE + U approach

PubMed Central

Yang, Jianhui; Cheng, Xinlu

2017-01-01

The electronic, vibrational and thermoelectric transport characteristics of AgInTe2 and AgGaTe2 with chalcopyrite structure have been investigated. The electronic structures are calculated using the density-functional theory within the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof functional considering the Hubbard-U exchange correlation. The band-gaps of AgInTe2 and AgGaTe2 are much larger than previous standard GGA functional results and agree well with the existing experimental data. The effective mass of the hole and the shape of density of states near the edge of the valence band indicate AgInTe2 and AgGaTe2 are considerable p-type thermoelectric materials. An analysis of lattice dynamics shows the low thermal conductivities of AgInTe2 and AgGaTe2. The thermoelectric transport properties' dependence on carrier concentration for p-type AgInTe2 and AgGaTe2 in a wide range of temperatures has been studied in detail. The results show that p-type AgInTe2 and AgGaTe2 at 800 K can achieve the merit values of 0.91 and 1.38 at about 2.12 × 1020 cm−3 and 1.97 × 1020 cm−3 carrier concentrations, respectively. This indicates p-type AgGaTe2 is a potential thermoelectric material at high temperature. PMID:29134079

Prediction for electronic, vibrational and thermoelectric properties of chalcopyrite AgX(X=In,Ga)Te2: PBE + U approach.

PubMed

Yang, Jianhui; Fan, Qiang; Cheng, Xinlu

2017-10-01

The electronic, vibrational and thermoelectric transport characteristics of AgInTe 2 and AgGaTe 2 with chalcopyrite structure have been investigated. The electronic structures are calculated using the density-functional theory within the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof functional considering the Hubbard-U exchange correlation. The band-gaps of AgInTe 2 and AgGaTe 2 are much larger than previous standard GGA functional results and agree well with the existing experimental data. The effective mass of the hole and the shape of density of states near the edge of the valence band indicate AgInTe 2 and AgGaTe 2 are considerable p-type thermoelectric materials. An analysis of lattice dynamics shows the low thermal conductivities of AgInTe 2 and AgGaTe 2 . The thermoelectric transport properties' dependence on carrier concentration for p-type AgInTe 2 and AgGaTe 2 in a wide range of temperatures has been studied in detail. The results show that p-type AgInTe 2 and AgGaTe 2 at 800 K can achieve the merit values of 0.91 and 1.38 at about 2.12 × 10 20  cm -3 and 1.97 × 10 20  cm -3 carrier concentrations, respectively. This indicates p-type AgGaTe 2 is a potential thermoelectric material at high temperature.

Activities of the Department of Astronomy and McDonald Observatory of the University of Texas at Austin

NASA Technical Reports Server (NTRS)

Smith, H. J.

1986-01-01

McDonald Observatory of the University of Texas at Austin reports on its activities during the period 1 Jan. 1986 to 30 June 1986. Extensive observations of Halley's Comet were obtained. The comet exhibited large variability; moreover, its variability was much more rapid than can be accounted for by water vaporization as the sole controller of activity. Jupiter satellite Io's atmosphere was found to be distended by more than the equilibrium scale height but less than for unimpeded streaming into space. The atmosphere is at least temporarily bound to IO. Uranus' (3-0) H2 quadrupole line shapes require a modification of Baines and Bergstralh's standard model which incorporates at high altitude absorbing haze in addition to the lower haze layer. A fraction of normal H2 equal to 0.25 + or 0.10 is derived, in good agreement with the standard model. This result is unchanged when the preliminary temperature structure derived by the Voyager Radio Occultation Experiment is used instead of Appleby's model c. Out of the six Pluto-Charon mutual events observed this year, data were obtained on four. Preliminary analysis is yielding improved estimates for the diameters, masses, densities, and albedos of these objects.

Structure and spectral features of H+(H2O)7: Eigen versus Zundel forms.

PubMed

Shin, Ilgyou; Park, Mina; Min, Seung Kyu; Lee, Eun Cheol; Suh, Seung Bum; Kim, Kwang S

2006-12-21

The two dimensional (2D) to three dimensional (3D) transition for the protonated water cluster has been controversial, in particular, for H(+)(H(2)O)(7). For H(+)(H(2)O)(7) the 3D structure is predicted to be lower in energy than the 2D structure at most levels of theory without zero-point energy (ZPE) correction. On the other hand, with ZPE correction it is predicted to be either 2D or 3D depending on the calculational levels. Although the ZPE correction favors the 3D structure at the level of coupled cluster theory with singles, doubles, and perturbative triples excitations [CCSD(T)] using the aug-cc-pVDZ basis set, the result based on the anharmonic zero-point vibrational energy correction favors the 2D structure. Therefore, the authors investigated the energies based on the complete basis set limit scheme (which we devised in an unbiased way) at the resolution of the identity approximation Moller-Plesset second order perturbation theory and CCSD(T) levels, and found that the 2D structure has the lowest energy for H(+)(H(2)O)(7) [though nearly isoenergetic to the 3D structure for D(+)(D(2)O)(7)]. This structure has the Zundel-type configuration, but it shows the quantum probabilistic distribution including some of the Eigen-type configuration. The vibrational spectra of MP2/aug-cc-pVDZ calculations and Car-Parrinello molecular dynamics simulations, taking into account the thermal and dynamic effects, show that the 2D Zundel-type form is in good agreement with experiments.

Structure and spectral features of H+(H2O)7: Eigen versus Zundel forms

NASA Astrophysics Data System (ADS)

Shin, Ilgyou; Park, Mina; Min, Seung Kyu; Lee, Eun Cheol; Suh, Seung Bum; Kim, Kwang S.

2006-12-01

The two dimensional (2D) to three dimensional (3D) transition for the protonated water cluster has been controversial, in particular, for H+(H2O)7. For H+(H2O)7 the 3D structure is predicted to be lower in energy than the 2D structure at most levels of theory without zero-point energy (ZPE) correction. On the other hand, with ZPE correction it is predicted to be either 2D or 3D depending on the calculational levels. Although the ZPE correction favors the 3D structure at the level of coupled cluster theory with singles, doubles, and perturbative triples excitations [CCSD(T)] using the aug-cc-pVDZ basis set, the result based on the anharmonic zero-point vibrational energy correction favors the 2D structure. Therefore, the authors investigated the energies based on the complete basis set limit scheme (which we devised in an unbiased way) at the resolution of the identity approximation Møller-Plesset second order perturbation theory and CCSD(T) levels, and found that the 2D structure has the lowest energy for H+(H2O)7 [though nearly isoenergetic to the 3D structure for D+(D2O)7]. This structure has the Zundel-type configuration, but it shows the quantum probabilistic distribution including some of the Eigen-type configuration. The vibrational spectra of MP2/aug-cc-pVDZ calculations and Car-Parrinello molecular dynamics simulations, taking into account the thermal and dynamic effects, show that the 2D Zundel-type form is in good agreement with experiments.

On the anomalous adsorption of [Pd(edta)]2- at the water/Goethite interface: spectroscopic evidence for two types of surface complexes.

PubMed

Kaplun, Marina; Nordin, Agneta; Persson, Per

2008-01-15

The structure of palladium(II) ethylenediaminetetraacetate (edta) in aqueous solutions and its adsorption on the surface of goethite (alpha-FeOOH) were studied using extended X-ray absorption fine structure spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy. The obtained results show that in aqueous solutions, Pd-edta exists as a 1:1 complex, [Pd(edta)]2-, with edta acting as a quadridentate ligand. On the surface of goethite, [Pd(edta)]2- forms two different types of complexes over a pH range of 3.40-8.12. At pH < 5, [Pd(edta)]2- adsorbs as an outer-sphere species with possible hydrogen bonding. At higher pH values, the formation of inner-sphere complexes of the cation-type sets in after a cleavage of one glycinate ring and the formation of an (edta)Pd-O-Fe linkage.

Structure change of β-hairpin induced by turn optimization: an enhanced sampling molecular dynamics simulation study.

PubMed

Shao, Qiang; Yang, Lijiang; Gao, Yi Qin

2011-12-21

Our previous study showed that for the tested polypeptides which have similar β-hairpin structures but different sequences, their folding free energy pathways are dominantly determined by the turn conformational propensity. In this study, we study how the turn conformational propensity affects the structure of hairpins. The folding of two mutants of GB1p peptide (GB1m2 and GB1m3), which have the optimized turn sequence ((6)DDATK(11)T → (6)NPATG(11)K) with native structures unsolved, were simulated using integrated tempering sampling molecular dynamics simulations and the predicted stable structures were compared to wild-type GB1p. It was observed that the turn optimization of GB1p generates a more favored 5-residue type I(') turn in addition to the 6-residue type I turn in wild-type GB1p. As a result two distinctly different hairpin structures are formed corresponding to the "misfolded" (M) and the "folded" (F) states. M state is a one-residue-shifted asymmetric β-hairpin structure whereas F state has the similar symmetric hairpin structure as wild-type GB1p. The formation of the favored type I(') turn has a small free energy barrier and leads to the shifted β-hairpin structure, following the modified "zipping" model. The presence of disfavored type I turn structure makes the folding of a β-hairpin consistent with the "hydrophobic-core-centric" model. On the other hand, the folding simulations on other two GB1p mutants (GB1r1 and GBr2), which have the position of the hydrophobic core cluster further away from the turn compared to wild-type GB1p, showed that moving the hydrophobic core cluster away from the turn region destabilizes but does not change the hairpin structure. Therefore, the present study showed that the turn conformational propensity is a key factor in affecting not only the folding pathways but also the stable structure of β-hairpins, and the turn conformational change induced by the turn optimization leads to significant changes of β-hairpin structure.

A review of primary writing tremor.

PubMed

Rana, Abdul Qayyum; Vaid, Haris M

2012-03-01

A task-specific tremor (TST) is a rare form of movement disorder that appears while performing or attempting to perform a particular task. Primary writing tremor (PWT) is the most common form of TST which only occurs during the act of writing and hinders it. (Bain PG, Findley LJ, Britton TC, Rothwell JC, Gresty MA, Thompson PD, Marsden CD. MRC Human Movement, and Balance Unit, Institute of Neurology, London, UK. Primary writing tremor. Brain. 1995;118(6):1461-72.) Primary writing tremor type B is present not only during the act of writing but also when the hand assumes a writing posture. (Bain PG, Findley LJ, Britton TC, Rothwell JC, Gresty MA, Thompson PD, Marsden CD. MRC Human Movement and Balance Unit, Institute of Neurology, London, UK. Primary writing tremor. Brain. 1995;118(6):1461-72.) We first of all describe a remarkable case study of a 50-year old, right-handed male who started experiencing a primary writing tremor in his right hand about a year ago. This case was found to be of particular interest because the patient had it relatively difficult when attempting to write numbers as opposed to writing letters. This review further discusses the clinical manifestations of PWT. In addition, three main hypotheses have been proposed for the causation of PWT, although the exact pathophysiology of PWT still remains unknown. It has been suggested that PWT is a separate entity, a variant of essential tremor and not a separate entity, or a type of dystonia. The various treatment options for PWT are discussed including botulinum toxin and oral pharmacotherapy.

Solid state coordination chemistry: structural consequences of variations in tether length in the oxovanadium-copper-bisterpy-[O3P(CH2)nPO3]4- system, n= 1-6 (bisterpy = 2,2':4',4'':2'',2'''-quarterpyridyl-6',6''-di-2-pyridine).

PubMed

Ouellette, Wayne; Koo, Bon-Kweon; Burkholder, Eric; Golub, Vladimir; O'Connor, C J; Zubieta, Jon

2004-05-21

Hydrothermal reactions of Na3VO4, an appropriate Cu(II) source, bisterpy and an organodiphosphonate, H2O3P(CH2)nPO3H2 (n = 1-6) yielded a family of materials of the type [Cu2(bisterpy)]4+/VxOy(n-)/[O3P(CH2)nPO3]4-. This family of bimetallic oxides is characterized by an unusual structural diversity. The oxides [[Cu2(bisterpy)]V2O4[O3PCH2PO3H]2] (1), [[Cu2(bisterpy)(H2O)]VO2[O3P(CH2)3PO3][HO3P(CH2)3PO3H2

Improving the ohmic properties of contacts to P-GaN by adding p-type dopants into the metallization layer

NASA Astrophysics Data System (ADS)

Liday, Jozef; Vogrinčič, Peter; Vincze, Andrej; Breza, Juraj; Hotový, Ivan

2012-12-01

The work investigates an increase of the density of free charge carriers in the sub-surface region of p-GaN by adding p-type dopants into the Ni-O layer of an Au/Ni-O metallization structure. We have examined electrical properties and concentration depth profiles of contact structures Au/Ni-Mg-O/p-GaN and Au/Ni-Zn-O/p-GaN, thus with magnesium and zinc as p-type dopants. The metallization layers were deposited on p-GaN by DC reactive magnetron sputtering in an atmosphere with a low concentration of oxygen (0.2 at%). The contacts were annealed in N2 . We have found that the structures containing magnesium or zinc exhibit lower values of contact resistivity in comparison with otherwise identical contacts without Mg or Zn dopants. In our opinion, the lower values of contact resistivity of the structures containing of Mg or Zn are caused by an increased density of holes in the sub-surface region of p-GaN due to diffusion of Mg or Zn from the deposited doped contact layers.

Perspectives on Queer Music Therapy: A Qualitative Analysis of Music Therapists' Reactions to Radically Inclusive Practice.

PubMed

Boggan, Catherine E; Grzanka, Patrick R; Bain, Candice L

2018-01-13

The queer music therapy model was designed by Bain, Grzanka, and Crowe in 2016 as a novel therapeutic approach to affirm and empower LGBTQ+ identity through music. No data have been generated on how this model might actually be implemented, or the strengths and limitations of the model according to music therapy professionals. The purpose of this study was to build on Bain and colleagues' work by collecting music therapists' perspectives on queer music therapy and using these data to critically evaluate the model. Semi-structured qualitative interviews were conducted with twelve music therapists who identify as LGBTQ+ or have experience working with LGBTQ+ clients. Participants were prompted to discuss their music therapy backgrounds, experiences with LGBTQ+ clients, and reactions to the queer music therapy model. Interviews were analyzed using a critical discourse analysis approach. The qualitative findings revealed major strengths of the queer music therapy model and ways in which it could be improved by attending to: (a) the structural limitations of the music therapy discipline, including the demographic composition of the field and lack of critical perspectives in music therapy training; and (b) intersectional considerations of ageism and ableism within diverse LGBTQ+ populations. Queer music therapy has positive implications for future work with LGBTQ+ individuals, but it must more substantively integrate intersectionality theory to serve a diverse range of LGBTQ+ clients. Further, it must critically attend to the structural limitations of the music therapy discipline itself. © The Author(s) 2018. Published by Oxford University Press on behalf of American Music Therapy Association. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

Study of the Structural Stability in Intermetallics Using Displacive Transformation Paths

NASA Astrophysics Data System (ADS)

Sob, M.; Wang, L. G.; Vitek, V.

1997-03-01

Relative structural stability of TiAl, FeAl, NiAl and NiTi is studied by investigating displacive phase transformation paths. These include the well known tetragonal (Bain's) and trigonal deformation paths which correspond to large homogeneous straining, and also more complex paths that include the shuffling of atomic planes. The results of full-potential APW total energy calculations show that all higher-energy cubic structures studied are locally unstable with respect to some deformation modes. There may or may not be symmetry-dictated energy extrema corresponding to cubic lattices depending on the atomic ordering. However, other energy extrema that are not imposed by symmetry requirements occur along the transformation paths. Configurations corresponding to energy minima may represent metastable structures that can play an important role in interfaces and other extended defects.

Electronic structure and p-type doping of ZnSnN2

NASA Astrophysics Data System (ADS)

Wang, Tianshi; Janotti, Anderson; Ni, Chaoying

ZnSnN2 is a promising solar-cell absorber material composed of earth abundant elements. Little is known about doping, defects, and how the valence and conduction bands in this material align with the bands in other semiconductors. Using density functional theory with the the Heyd-Scuseria-Ernzerhof hybrid functional (HSE06), we investigate the electronic structure of ZnSnN2, its band alignment to other semiconductors, such as GaN and ZnO, the possibility of p-type doping, and the possible causes of the observed unintentional n-type conductivity. We find that the position of the valence-band maximum of ZnSnN2 is 0.55 eV higher than that of GaN, yet the conduction-band minimum is close to that in ZnO. As possible p-type dopants, we explore Li, Na, and K substituting on the Zn site. Finally, we discuss the cause of unintentional n-type conductivity by analyzing the position of the conduction-band minimum with respect to that of GaN and ZnO.

STUDIES ON THE FORMATION AND IONIZATION OF THE COMPOUNDS OF CASEIN WITH ALKALI

PubMed Central

Greenberg, David M.; Schmidt, Carl L. A.

1924-01-01

1. The results of conductivity experiments with alkali caseinate solutions are given and a graphical method of extrapolation, which gives a straight line, is described. The results of the conductivity experiments are shown to be in accord with the results of the previous transference experiments. 2. The change of conductivity of the alkali caseinate solutions with temperature is shown to follow a straight line relationship. 3. The high value of the mobility which was obtained for the casein ion and the high temperature gradient are discussed in relation to McBain's theory of colloidal electrolytes. PMID:19872136

Ba 2TeO as an optoelectronic material: First-principles study

DOE PAGES

Sun, Jifeng; Shi, Hongliang; Du, Mao-Hua; ...

2015-05-21

The band structure, optical and defects properties of Ba 2TeO are systematically investigated using density functional theory with a view to understanding its potential as an optoelectronic or transparent conducting material. Ba 2TeO crystallizes with tetragonal structure (space group P4/nmm) and with a 2.93 eV optical band gap1. We find relatively modest band masses for both electrons and holes suggesting applications. Optical properties show a infrared-red absorption when doped. This could potentially be useful for combining wavelength filtering and transparent conducting functions. Furthermore, our defect calculations show that Ba 2TeO is intrinsically p-type conducting under Ba-poor condition. However, the spontaneousmore » formation of the donor defects may constrain the p-type transport properties and would need to be addressed to enable applications.« less

Crystal structures of the ionic conductors Bi{sub 46}M{sub 8}O{sub 89} (M=P, V) related to the fluorite-type structure

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

Darriet, J.; Launay, J.C.; Zuniga, F.J.

2005-06-15

The crystal structures of the two oxides Bi{sub 46}M{sub 8}O{sub 89} (M=P, V) have been solved from single crystals X-ray data at room temperature. Bi{sub 46}P{sub 8}O{sub 89} crystallizes in the monoclinic symmetry (space group C2/m) with the cell parameters a=19.6073(4)A, b=11.4181(4)A, c=21.1119(4)A and {beta}=112.14(3){sup o}. The symmetry of Bi{sub 46}V{sub 8}O{sub 89} is also monoclinic but the space group is P2{sub 1}/c with the unit-cell parameters: a=20.0100(4)A, b=11.6445(4)A, c=20.4136(4)A and {beta}=107.27(3){sup o}. Both structures derive from an oxygen deficient fluorite-type structure where the Bi and M cations (M=P, V) are ordered in the framework. The structures are characterised bymore » isolated MO{sub 4} tetrahedra (M=P, V) which contradicts the previous results. The difference between the two structures is only due to a different order of the M atoms (M=P, V) in the fluorite-type superstructure. It will be shown that some oxygen sites are partially occupied in both structures which can explain the ion conduction properties of these phases. A structural building principle will be proposed that can explain the large domain of solid solution related to the fluorite-type observed in both systems.« less

Design, Synthesis, and Biological and Structural Evaluations of Novel HIV-1 Protease Inhibitors To Combat Drug Resistance

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

Parai, Maloy Kumar; Huggins, David J.; Cao, Hong

2012-09-11

A series of new HIV-1 protease inhibitors (PIs) were designed using a general strategy that combines computational structure-based design with substrate-envelope constraints. The PIs incorporate various alcohol-derived P2 carbamates with acyclic and cyclic heteroatomic functionalities into the (R)-hydroxyethylamine isostere. Most of the new PIs show potent binding affinities against wild-type HIV-1 protease and three multidrug resistant (MDR) variants. In particular, inhibitors containing the 2,2-dichloroacetamide, pyrrolidinone, imidazolidinone, and oxazolidinone moieties at P2 are the most potent with Ki values in the picomolar range. Several new PIs exhibit nanomolar antiviral potencies against patient-derived wild-type viruses from HIV-1 clades A, B, and Cmore » and two MDR variants. Crystal structure analyses of four potent inhibitors revealed that carbonyl groups of the new P2 moieties promote extensive hydrogen bond interactions with the invariant Asp29 residue of the protease. These structure-activity relationship findings can be utilized to design new PIs with enhanced enzyme inhibitory and antiviral potencies.« less

Half-collision analysis of far-wing diffuse structure in Cs-Xe

NASA Technical Reports Server (NTRS)

Exton, R. J.; Hillard, M. E.; Lempert, W. R.

1987-01-01

Laser excitation in the far red wing of the second principal series doublet of Cs mixed with Xe revealed a diffuse structure associated with the 2P(3/2) component. The structure is thought to originate from a reflection type of spectrum between the weakly bound E 2Sigma(1/2) excited state and the X 2Sigma(1/2) repulsive ground state of CsXe.

Design of a highly sensitive ethanol sensor using a nano-coaxial p-Co3O4/n-TiO2 heterojunction synthesized at low temperature.

PubMed

Liang, Y Q; Cui, Z D; Zhu, S L; Li, Z Y; Yang, X J; Chen, Y J; Ma, J M

2013-11-21

In this paper, we describe the design, fabrication and gas-sensing tests of nano-coaxial p-Co3O4/n-TiO2 heterojunction. Specifically, uniform TiO2 nanotubular arrays have been assembled by anodization and used as templates for generation of the Co3O4 one-dimensional nanorods. The structure morphology and composition of as-prepared products have been characterized by SEM, XRD, TEM, and XPS. A possible growth mechanism governing the formation of such nano-coaxial heterojunctions is proposed. The TiO2 nanotube sensor shows a normal n-type response to reducing ethanol gas, whereas TiO2-Co3O4 exhibits p-type response with excellent sensing performances. This conversion of sensing behavior can be explained by the formation of p-n heterojunction structures. A possible sensing mechanism is also illustrated, which can provide theoretical guidance for the further development of advanced gas-sensitive materials with p-n heterojunction.

The effects of obesity and type 2 diabetes mellitus on cardiac structure and function in adolescents and young adults.

PubMed

Shah, A S; Khoury, P R; Dolan, L M; Ippisch, H M; Urbina, E M; Daniels, S R; Kimball, T R

2011-04-01

We sought to evaluate the effects of obesity and obesity-related type 2 diabetes mellitus on cardiac geometry (remodelling) and systolic and diastolic function in adolescents and young adults. Cardiac structure and function were compared by echocardiography in participants who were lean, obese or obese with type 2 diabetes (obese diabetic), in a cross sectional study. Group differences were assessed using ANOVA. Independent determinants of cardiac outcome measures were evaluated with general linear models. Adolescents with obesity and obesity-related type 2 diabetes were found to have abnormal cardiac geometry compared with lean controls (16% and 20% vs <1%, p < 0.05). These two groups also had increased systolic function. Diastolic function decreased from the lean to obese to obese diabetic groups with the lowest diastolic function observed in the obese diabetic group (p < 0.05). Regression analysis showed that group, BMI z score (BMIz), group × BMIz interaction and systolic BP z score (BPz) were significant determinants of cardiac structure, while group, BMIz, systolic BPz, age and fasting glucose were significant determinants of the diastolic function (all p < 0.05). Adolescents with obesity and obesity-related type 2 diabetes demonstrate changes in cardiac geometry consistent with cardiac remodelling. These two groups also demonstrate decreased diastolic function compared with lean controls, with the greatest decrease observed in those with type 2 diabetes. Adults with diastolic dysfunction are known to be at increased risk of progressing to heart failure. Therefore, our findings suggest that adolescents with obesity-related type 2 diabetes may be at increased risk of progressing to early heart failure compared with their obese and lean counterparts.

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

Li, D.F.; Zhang, X.M.; Gautier, E.

The morphology and crystallography of deformation-induced martensites formed during isothermal tensile tests in Fe-30Ni-0.34C and Fe-25Ni-0.66C alloys were investigated by means of optical, transmission electron and scanning electron microscopy. Transitions in morphology from thin plate to coupled plate, to lenticular coupled-plate martensite and from thin plate to lenticular to compact martensite have been observed with increasing deformation. Stress favors the growth of martensite when concurrent plastic strain allows accommodation of macroscopic transformation strains and the change of the Bain strain accommodation mechanism. Mobile dislocations and emission dislocations are directly related to the change of the Bain strain accommodation mechanism frommore » twinning to slip.« less

Compositional analysis of Hyperion with the Cassini Visual and Infrared Mapping Spectrometer

NASA Astrophysics Data System (ADS)

Brad Dalton, J.; Cruikshank, Dale P.; Clark, Roger N.

2012-08-01

Compositional mapping of the surface of Hyperion using Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations reveals a heterogeneous surface dominated by water ice accompanied by additional materials. Carbon dioxide, as evidenced by a prominent absorption band centered at 4.26 μm, is distributed over most of the surface, including icy regions. This does not represent exposures of pure CO2 ice, but concentrations of CO2 molecules adsorbed on other materials or complexed in H2O, perhaps as a clathrate (Cruikshank, D.P., Meyer, A.W., Brown, R.H., Clark, R.N., Jaumann, R., Stephan, K., Hibbitts, C.A., Sandford, S.A., Mastrapa, R., Filacchione, G., Dalle Ore, C.M., Nicholson, P.D., Buratti, B.J., McCord, T.B., Nelson, R.M., Dalton, J.B., Baines, K.H., Matson, D.L., The VIMS Team [2010]. Icarus 206, 561-572). Localized deposits of low-albedo material in subcircular depressions exhibit spectral absorptions indicative of C-H in aromatic (3.29 μm) and aliphatic (3.35-3.50 μm) hydrocarbons. An absorption band at 2.42 μm that is also seen on other saturnian satellites, tentatively identified as H2 (Clark, R.N. et al. [2011]. In: Proc. AAS-DPS Meeting, 43, 1563; Clark et al., in preparation, 2012) adsorbed on dark material grains, is also prominent. Our best spectral models included H2O and CO2 ice, with small amounts of nanophase Fe and Fe2O3. Weaker and more spatially scattered absorption features are also found at 4.48, 4.60, and 4.89 μm, although no clear molecular identifications have yet been made. While strongest in the low-albedo deposits, the CO2, hydrocarbon and putative H2 bands vary in strength throughout the icy regions, as do the 4.48-, 4.60- and 4.89-μm bands, suggesting that this background ice is laced with a complex mixture of non-ice compounds.

Metastable phases of silver and gold in hexagonal structure

NASA Astrophysics Data System (ADS)

Jona, F.; Marcus, P. M.

2004-07-01

Metastable phases of silver and gold in hexagonal close-packed structures are investigated by means of first-principles total-energy calculations. Two different methods are employed to find the equilibrium states: determination of the minima along the hexagonal epitaxial Bain path, and direct determination of minima of the total energy by a new minimum-path procedure. Both metals have two equilibrium states at different values of the hexagonal axial ratio c/a. For both metals, the elastic constants show that the high-c/a states are stable, hence, since the ground states are face-centred cubic, these states represent hexagonal close-packed metastable phases. The elastic constants of the low-c/a states show that they are unstable.

Dependence of the third-order coefficients in Landau free energies for bcc --> fcc structural transition on hydrogen concentration in zirconium hydrides

NASA Astrophysics Data System (ADS)

Ashida, Yuh; Yamamoto, Masahiro; Naito, Shizuo; Mabuchi, Mahito; Hashino, Tomoyasu

1997-08-01

Young's modulus E and the modulus of rigidity G of zirconium hydrides ZrHx(0.9⩽x⩽1.65) at 941 and 1001 K have been obtained as a function of hydrogen concentration c by measuring resonance frequencies for bending and torsion vibrations of a polycrystalline wire. As c increases, observed E and G increase in the bcc β phase, slightly increase linearly in the β+δ phase, and then decrease in the fcc δ phase. On the basis of a phenomenological free energy in terms of strain components taking account of space group symmetry, two types of Landau expansion of the free energies for the β phase in terms of the strain components which play an important role in the structural phase transition between the β and the δ phases are examined. The observed E and G are assumed to be the same as the second-order coefficients of the free energy for the Bain distortions, which occur at the structural phase transition. The dependence of the third-order coefficients on c permits the expanded free energies to describe the fact that the β phase is more stable than the δ phase at low c.

X-ray diffraction and spectroscopy study of nano-Eu 2O 3 structural transformation under high pressure

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

Yu, Zhenhai; Wang, Qinglin; Ma, Yanzhang

Nanoscale materials exhibit properties that are quite distinct from those of bulk materials because of their size restricted nature. Here, we investigated the high-pressure structural stability of cubic (C-type) nano-Eu2O3 using in situ synchrotron X-ray diffraction (XRD), Raman and luminescence spectroscopy, and impedance spectra techniques. Our high-pressure XRD experimental results revealed a pressure-induced structural phase transition in nano-Eu2O3 from the C-type phase (space group: Ia-3) to a hexagonal phase (A-type, space group: P-3m1). Our reported transition pressure (9.3 GPa) in nano-Eu2O3 is higher than that of the corresponding bulk-Eu2O3 (5.0 GPa), which is contrary to the preceding reported experimental result.more » After pressure release, the A-type phase of Eu2O3 transforms into a new monoclinic phase (B-type, space group: C2/m). Compared with bulk-Eu2O3, C-type and A-type nano-Eu2O3 exhibits a larger bulk modulus. Our Raman and luminescence findings and XRD data provide consistent evidence of a pressure-induced structural phase transition in nano-Eu2O3. To our knowledge, we have performed the first high-pressure impedance spectra investigation on nano-Eu2O3 to examine the effect of the structural phase transition on its transport properties. We propose that the resistance inflection exhibited at ~12 GPa results from the phase boundary between the C-type and A-type phases. Besides, we summarized and discussed the structural evolution process by the phase diagram of lanthanide sesquioxides (Ln2O3) under high pressure.« less

A single amino acid substitution makes ERK2 susceptible to pyridinyl imidazole inhibitors of p38 MAP kinase.

PubMed Central

Fox, T.; Coll, J. T.; Xie, X.; Ford, P. J.; Germann, U. A.; Porter, M. D.; Pazhanisamy, S.; Fleming, M. A.; Galullo, V.; Su, M. S.; Wilson, K. P.

1998-01-01

Mitogen-activated protein (MAP) kinases are serine/threonine kinases that mediate intracellular signal transduction pathways. Pyridinyl imidazole compounds block pro-inflammatory cytokine production and are specific p38 kinase inhibitors. ERK2 is related to p38 in sequence and structure, but is not inhibited by pyridinyl imidazole inhibitors. Crystal structures of two pyridinyl imidazoles complexed with p38 revealed these compounds bind in the ATP site. Mutagenesis data suggested a single residue difference at threonine 106 between p38 and other MAP kinases is sufficient to confer selectivity of pyridinyl imidazoles. We have changed the equivalent residue in human ERK2, Q105, into threonine and alanine, and substituted four additional ATP binding site residues. The single residue change Q105A in ERK2 enhances the binding of SB202190 at least 25,000-fold compared to wild-type ERK2. We report enzymatic analyses of wild-type ERK2 and the mutant proteins, and the crystal structure of a pyridinyl imidazole, SB203580, bound to an ERK2 pentamutant, I103L, Q105T, D106H, E109G. T110A. These ATP binding site substitutions induce low nanomolar sensitivity to pyridinyl imidazoles. Furthermore, we identified 5-iodotubercidin as a potent ERK2 inhibitor, which may help reveal the role of ERK2 in cell proliferation. PMID:9827991

Crystal structure of Rb{sub 2}Mn{sub 3}(H{sub 2}O){sub 2}[P{sub 2}O{sub 7}]{sub 2}, a new representative of the family of hydrated diphosphates

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

Kiriukhina, G. V., E-mail: g-biralo@yandex.ru; Yakubovich, O. V.; Dimitrova, O. V.

2016-09-15

The crystal structure of Rb{sub 2}Mn{sub 3}(H{sub 2}O){sub 2}[P{sub 2}O{sub 7}]{sub 2}, a new phase obtained in the form of single crystals under hydrothermal conditions in the MnCl{sub 2}–Rb{sub 3}PO{sub 4}–H{sub 2}O system, is determined by X-ray diffraction (Xcalibur-S-CCD diffractometer, R = 0.0270): a = 9.374(2), b = 8.367(2), c = 9.437(2) Å, ß = 99.12(2)°, space group P2{sub 1}/c, Z = 2, D{sub x} = 3.27 g/cm{sup 3}. A correlation between the unit-cell parameters and the size of cations forming the crystal structures of isostructural A{sub 2}M{sub 3}(H{sub 2}O){sub 2}[P{sub 2}O{sub 7}]{sub 2} diphosphates (A = K, NH{sub 4},more » Rb, or Na; {sub M} = Mn, Fe, Co, or Ni) is revealed. It is shown that, due to the topological similarity, the structures of diphosphates and orthophosphates of the farringtonite structural type can undergo mutual transformations.« less

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.

A medium range order structural connection to the configurational heat capacity of borate-silicate mixed glasses.

PubMed

Liu, Hao; Smedskjaer, Morten M; Tao, Haizheng; Jensen, Lars R; Zhao, Xiujian; Yue, Yuanzheng

2016-04-28

It has been reported that the configurational heat capacity (C(p,conf)) first increases and then becomes saturated with increasing B2O3/SiO2 ratio in borate-silicate mixed glasses. Through Raman spectroscopy measurements, we have, in this work, found an implication for the intermediate range order (IRO) structural connection to the composition dependence of the C(p,conf) of borate-silicate mixed glasses. In the silica-rich compositions, the C(p,conf) rapidly increases with increasing B2O3 content. This is attributed to the increase of the content of the B-O-Si network units ([B2Si2O8](2-)) and 6-membered borate rings with 1 or 2 B(4). In the boron-rich compositions, the C(p,conf) is almost constant, independent of the increase in the B2O3/SiO2 ratio. This is likely attributed to the counteraction between the decrease of the fraction of two types of metaborate groups and the increase of the fraction of other borate superstructural units (particularly 6-membered borate rings). The overall results suggest that the glasses containing more types of superstructural units have a larger C(p,conf).

Superconductivity in YTE2Ge2 compounds (TE = d-electron transition metal)

NASA Astrophysics Data System (ADS)

Chajewski, G.; Samsel-Czekała, M.; Hackemer, A.; Wiśniewski, P.; Pikul, A. P.; Kaczorowski, D.

2018-05-01

Polycrystalline samples of YTE2Ge2 with TE = Co, Ni, Ru, Rh, Pd and Pt were synthesized and characterized by means of X-ray powder diffraction and low-temperature electrical resistivity and specific heat measurements, supplemented by fully relativistic full-potential local-orbital band structure calculations. We confirm that most of the compounds studied crystallize in a body-centered tetragonal ThCr2S2 -type structure (space group I 4 / mmm) and have three-dimensional Fermi surfaces, while only one of them (YPt2Ge2) forms with a primitive tetragonal CaBe2Ge2 -type unit cell (space group P 4 / nmm) and possesses quasi-two-dimensional Fermi surface sheets with some nesting. Physical properties data show conventional superconductivity in the phases with TE = Co, Pd and Pt, i.e. independently of the structure type (and hence the dimensionality of the Fermi surface).

Structure and Electric Conduction in Pulsed Laser-Deposited ZnO Thin Films Individually Doped with N, P, or Na

NASA Astrophysics Data System (ADS)

Jiao, D. L.; Zhong, X. C.; Qiu, W. Q.; Zhang, H.; Liu, Z. W.; Zhang, G. Q.

2018-03-01

N-, P-, and Na-doped ZnO films with c-axis orientation were produced by pulsed laser deposition using N2O or O2 as the reaction gas. The effects of deposition temperature and deposition pressure on the lattice structure, morphology, and electric conduction have been investigated. High gas pressure leads to large-sized grains with large grain barriers, which cause a reduced mobility. P acts as an acceptor and the number of compensating defects in the P-doped film is reduced under high O2 pressure. Na also acts as an acceptor, and the effects of high temperature on Na-doped films are encouraging as the solubility of the dopant is high. However, high temperature may cause less incorporation of N and P in the film. In the present work, p-type conduction has not been obtained in N- and P-doped films despite a wide range of processing parameters employed. Na-doped films display an increasing trend towards p-type films at high temperatures and high O2 pressures. These results provide an insight on how these dopants behave in ZnO films and indicate that the careful selection of the deposition conditions is necessary in order to obtain p-type films by pulsed laser deposition.

Site-selective As-P substitution and hydrogen bonding in the crystal structure of philipsburgite, Cu5Zn((As,P)O4)2(OH)6·H2O

NASA Astrophysics Data System (ADS)

Krivovichev, Sergey V.; Zhitova, Elena S.; Ismagilova, Rezeda M.; Zolotarev, Andrey A.

2018-05-01

Philipsburgite, Cu5Zn((As,P)O4)2(OH)6·H2O, from the Middle Pit, Gold Hill Mine, Tooele Co., Utah, USA, was studied by single-crystal X-ray diffraction and scanning electron microscopy. The empirical formula of the studied sample is (Cu4.69Zn1.23)(As0.86P0.18O4)2(OH)5.61·H2O, which agrees well with the previous reports on the mineral. Philipsburgite is monoclinic, P21/c, a = 12.385(6), b = 9.261(4), c = 10.770(5) Å, β = 97.10(1)o, V = 1225.7(9) Å3 (at 100 K), and Z = 4. The crystal structure was refined to R 1 = 0.046 for 2563 unique observed reflections with |F o| ≥ 4σ F . The crystal structure of philipsburgite is isotypic to that of kipushite and can be considered as a complex three-dimensional framework consisting of two types of layers stacked parallel to the a-axis. The A-type layer is formed by the edge-sharing Jahn-Teller-distorted Cuφ6 octahedra [φ = O2-, (OH)-, H2O]. Two adjacent octahedral layers are linked via (As2O4) tetrahedra. The B-type layer is built by corner-sharing (ZnO4) and (As1O4) tetrahedra and is formed by the four- and eight-membered tetrahedral rings. The A:B ratio of the A and B layers is equal to 2:1. The hydrogen bonding network in philipsburgite is rather complex and consists of two- and three-center hydrogen bonds. The As1 site accommodates ca. 18% of P and is a preferable position for the P substitution in philipsburgite. The observed selectivity of the As1 site for P may indicate that, for the intermediate compositions with the P:As ratios close to 1:1, there is a fully ordered species with P prevalent at the As1 site and As prevalent at the As2 site. The intermediate composition would, therefore, be Cu5Zn(AsO4)(PO4)(OH)6·H2O and such a mineral can be considered as a separate species, according to the rules of the International Mineralogical Association (IMA). Philipsburgite should be considered as structurally complex with the Shannon information contents of 4.954 bits/atom and 614.320 bits/cell. The obvious reason for the structural complexity of the mineral is its modularity, i.e., the presence of two structurally distinct modules, the octahedral-tetrahedral (A) and tetrahedral (B) layers.

Syntheses, Raman spectroscopy and crystal structures of alkali hexa­fluorido­rhenates(IV) revisited

PubMed Central

Louis-Jean, James; Salamat, Ashkan; Pham, Chien Thang; Poineau, Frederic

2018-01-01

The A 2[ReF6] (A = K, Rb and Cs) salts are isotypic and crystallize in the trigonal space group type P m1, adopting the K2[GeF6] structure type. Common to all A 2[ReF6] structures are slightly distorted octa­hedral [ReF6]2− anions with an average Re—F bond length of 1.951 (8) Å. In those salts, symmetry lowering on the local [ReF6]2− anions from Oh (free anion) to D 3d (solid-state structure) occur. The distortions of the [ReF6]2− anions, as observed in their Raman spectra, are correlated to the size of the counter-cations.

Halogen bonds in some dihalogenated phenols: applications to crystal engineering.

PubMed

Mukherjee, Arijit; Desiraju, Gautam R

2014-01-01

3,4-Dichlorophenol (1) crystallizes in the tetragonal space group I41/a with a short axis of 3.7926 (9) Å. The structure is unique in that both type I and type II Cl⋯Cl interactions are present, these contact types being distinguished by the angle ranges of the respective C-Cl⋯Cl angles. The present study shows that these two types of contacts are utterly different. The crystal structures of 4-bromo-3-chlorophenol (2) and 3-bromo-4-chlorophenol (3) have been determined. The crystal structure of (2) is isomorphous to that of (1) with the Br atom in the 4-position participating in a type II interaction. However, the monoclinic P21/c packing of compound (3) is different; while the structure still has O-H⋯O hydrogen bonds, the tetramer O-H⋯O synthon seen in (1) and (2) is not seen. Rather than a type I Br⋯Br interaction which would have been mandated if (3) were isomorphous to (1) and (2), Br forms a Br⋯O contact wherein its electrophilic character is clearly evident. Crystal structures of the related compounds 4-chloro-3-iodophenol (4) and 3,5-dibromophenol (5) were also determined. A computational survey of the structural landscape was undertaken for (1), (2) and (3), using a crystal structure prediction protocol in space groups P21/c and I41/a with the COMPASS26 force field. While both tetragonal and monoclinic structures are energetically reasonable for all compounds, the fact that (3) takes the latter structure indicates that Br prefers type II over type I contacts. In order to differentiate further between type I and type II halogen contacts, which being chemically distinct are expected to have different distance fall-off properties, a variable-temperature crystallography study was performed on compounds (1), (2) and (4). Length variations with temperature are greater for type II contacts compared with type I. The type II Br⋯Br interaction in (2) is stronger than the corresponding type II Cl⋯Cl interaction in (1), leading to elastic bending of the former upon application of mechanical stress, which contrasts with the plastic deformation of (1). The observation of elastic deformation in (2) is noteworthy; in that it finds an explanation based on the strengths of the respective halogen bonds, it could also be taken as a good starting model for future property design. Cl/Br isostructurality is studied with the Cambridge Structural Database and it is indicated that this isostructurality is based on shape and size similarity of Cl and Br, rather than arising from any chemical resemblance.

The coordination behaviour of ferrocene-based pyridylphosphine ligands towards Zn(II), Cd(II) and Hg(II).

PubMed

Siemeling, Ulrich; Klemann, Thorsten; Bruhn, Clemens; Schulz, Jiří; Štěpnička, Petr

2011-05-07

The reaction of Group 12 metal dihalides MX(2) with the P,N-ligands [Fe(C(5)H(4)-PPh(2))(C(5)H(4)-2-py)] (1) (2-py = pyrid-2-yl), [Fe(C(5)H(4)-PPh(2))(C(5)H(4)-CH(2)-2-py)] (2) and [Fe(C(5)H(4)-PPh(2))(C(5)H(4)-3-py)] (3) (3-py = pyrid-3-yl) was investigated. For a 1 : 1 molar ratio of MX(2) and the respective ligand, three structure types were found in the solid state, viz. chelate, cyclic dimer and chain-like coordination polymer. The M(II) coordination environment is distorted pseudo-tetrahedral in each case. The P-M-N angle is much larger in the chelates (≥119°) than in the ligand-bridged structures (≤109°). 1 prefers the formation of chelates [MX(2)(1-κ(2)N,P)]. 3 forms coordination polymers [MX(2)(μ-3)](n). With the more flexible 2 all three structure types can occur. Dynamic coordination equilibria were observed in solution for the molecular complexes obtained with 1 and 2. NMR data indicate that the N- and P-donor sites interact most strongly with Zn(II) and Hg(II), respectively. While the formation of bis(phosphine)mercury complexes (soft-soft) was easily achieved, no bis(pyridine)zinc complex (borderline-borderline) could be obtained, which is surprising in view of the HSAB principle.

Molecular Structure and Regulation of P2X Receptors With a Special Emphasis on the Role of P2X2 in the Auditory System.

PubMed

Mittal, Rahul; Chan, Brandon; Grati, M'hamed; Mittal, Jeenu; Patel, Kunal; Debs, Luca H; Patel, Amit P; Yan, Denise; Chapagain, Prem; Liu, Xue Zhong

2016-08-01

The P2X purinergic receptors are cation-selective channels gated by extracellular adenosine 5'-triphosphate (ATP). These purinergic receptors are found in virtually all mammalian cell types and facilitate a number of important physiological processes. Within the past few years, the characterization of crystal structures of the zebrafish P2X4 receptor in its closed and open states has provided critical insights into the mechanisms of ligand binding and channel activation. Understanding of this gating mechanism has facilitated to design and interpret new modeling and structure-function experiments to better elucidate how different agonists and antagonists can affect the receptor with differing levels of potency. This review summarizes the current knowledge on the structure, activation, allosteric modulators, function, and location of the different P2X receptors. Moreover, an emphasis on the P2X2 receptors has been placed in respect to its role in the auditory system. In particular, the discovery of three missense mutations in P2X2 receptors could become important areas of study in the field of gene therapy to treat progressive and noise-induced hearing loss. J. Cell. Physiol. 231: 1656-1670, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Bis(dicyclohexylselenophosphinyl)selenide, [Cy2P(Se)]2Se: Synthesis, molecular structure and application for self-assembly of a tetrahedral Cu(I) cluster

NASA Astrophysics Data System (ADS)

Artem'ev, Alexander V.; Doronina, Evgeniya P.; Bagryanskaya, Irina Yu; Klyba, Lyudmila V.

2018-05-01

The molecular structure of the selenides of [R2P(Se)]2Se type has been systematically studied on example of bis(dicyclohexylselenophosphinyl)selenide, [Cy2P(Se)]2Se. This selenide has been synthesized in 65% yield by oxidation of Cy2PH with elemental selenium in 1:2 M ratio. Its structure has been investigated by X-ray diffractometry (XRD), NMR, FT-IR and MALDI-TOF/MS techniques. In the solid, the Se1sbnd Psbnd Se2sbnd Psbnd Se3 chain of (Cy2P = Se)2Se molecule adopts a syn-anti conformation with the Se1sbnd Psbnd Se2sbnd P and Psbnd Se2sbnd Psbnd Se3 torsion angles of -179.64 (3)° and 4.69 (4)°. The vibrational band assignments, performing at B3LYP/6-311++G (d,p) theory level, are in a good agreement with the experimental FT-IR frequencies. The synthetic utility of the prepared selenide has been exemplified by its reaction with CuCl2 resulted in the formation of [Cu4(Se2PCy2)4] cluster in 53% yield. The structure of latter is formed by a Cu4 tetrahedron, wherein each triangular face is bridged by a [Se2PCy2] ligand in a trimetallic triconnective (μ2, μ1) pattern.

Fourier transform infrared microspectroscopic analysis of the effects of cereal type and variety within a type of grain on structural makeup in relation to rumen degradation kinetics.

PubMed

Walker, Amanda M; Yu, Peiqiang; Christensen, Colleen R; Christensen, David A; McKinnon, John J

2009-08-12

The objectives of this study were to use Fourier transform infrared microspectroscopy (FTIRM) to determine structural makeup (features) of cereal grain endosperm tissue and to reveal and identify differences in protein and carbohydrate structural makeup between different cereal types (corn vs barley) and between different varieties within a grain (barley CDC Bold, CDC Dolly, Harrington, and Valier). Another objective was to investigate how these structural features relate to rumen degradation kinetics. The items assessed included (1) structural differences in protein amide I to nonstructural carbohydrate (NSC, starch) intensity and ratio within cellular dimensions; (2) molecular structural differences in the secondary structure profile of protein, alpha-helix, beta-sheet, and their ratio; (3) structural differences in NSC to amide I ratio profile. From the results, it was observed that (1) comparison between grain types [corn (cv. Pioneer 39P78) vs barley (cv. Harrington)] showed significant differences in structural makeup in terms of NSC, amide I to NSC ratio, and rumen degradation kinetics (degradation ratio, effective degradability of dry matter, protein and NSC) (P < 0.05); (2) comparison between varieties within a grain (barley varieties) also showed significant differences in structural makeup in terms of amide I, NSC, amide I to NSC ratio, alpha-helix and beta-sheet protein structures, and rumen degradation kinetics (effective degradability of dry matter, protein, and NSC) (P < 0.05); (3) correlation analysis showed that the amide I to NSC ratio was strongly correlated with rumen degradation kinetics in terms of the degradation rate (R = 0.91, P = 0.086) and effective degradability of dry matter (R = 0.93, P = 0.071). The results suggest that with the FTIRM technique, the structural makeup differences between cereal types and between different varieties within a type of grain could be revealed. These structural makeup differences were related to the rate and extent of rumen degradation.

Controlling the electronic and geometric structures of 2D insertions to realize high performance metal/insertion-MoS2 sandwich interfaces.

PubMed

Su, Jie; Feng, Liping; Zeng, Wei; Liu, Zhengtang

2017-06-08

Metal/insertion-MoS 2 sandwich interfaces are designed to reduce the Schottky barriers at metal-MoS 2 interfaces. The effects of geometric and electronic structures of two-dimensional (2D) insertion materials on the contact properties of metal/insertion-MoS 2 interfaces are comparatively studied by first-principles calculations. Regardless of the geometric and electronic structures of 2D insertion materials, Fermi level pinning effects and charge scattering at the metal/insertion-MoS 2 interface are weakened due to weak interactions between the insertion and MoS 2 layers, no gap states and negligible structural deformations for MoS 2 layers. The Schottky barriers at metal/insertion-MoS 2 interfaces are induced by three interface dipoles and four potential steps that are determined by the charge transfers and structural deformations of 2D insertion materials. The lower the electron affinities of 2D insertion materials, the more are the electrons lost from the Sc surface, resulting in lower n-type Schottky barriers at Sc/insertion-MoS 2 interfaces. The larger the ionization potentials and the thinner the thicknesses of 2D insertion materials, the fewer are the electrons that accumulate at the Pt surface, leading to lower p-type Schottky barriers at Pt/insertion-MoS 2 interfaces. All Sc/insertion-MoS 2 interfaces exhibited ohmic characters. The Pt/BN-MoS 2 interface exhibits the lowest p-type Schottky barrier of 0.52 eV due to the largest ionization potential (∼6.88 eV) and the thinnest thickness (single atomic layer thickness) of BN. These results in this work are beneficial to understand and design high performance metal/insertion-MoS 2 interfaces through 2D insertion materials.

Intensive structured self-monitoring of blood glucose and glycemic control in noninsulin-treated type 2 diabetes: the PRISMA randomized trial.

PubMed

Bosi, Emanuele; Scavini, Marina; Ceriello, Antonio; Cucinotta, Domenico; Tiengo, Antonio; Marino, Raffaele; Bonizzoni, Erminio; Giorgino, Francesco

2013-10-01

We aimed to evaluate the added value of intensive self-monitoring of blood glucose (SMBG), structured in timing and frequency, in noninsulin-treated patients with type 2 diabetes. The 12-month, randomized, clinical trial enrolled 1,024 patients with noninsulin-treated type 2 diabetes (median baseline HbA1c, 7.3% [IQR, 6.9-7.8%]) at 39 diabetes clinics in Italy. After standardized education, 501 patients were randomized to intensive structured monitoring (ISM) with 4-point glycemic profiles (fasting, preprandial, 2-h postprandial, and postabsorptive measurements) performed 3 days/week; 523 patients were randomized to active control (AC) with 4-point glycemic profiles performed at baseline and at 6 and 12 months. Two primary end points were tested in hierarchical order: HbA1c change at 12 months and percentage of patients at risk target for low and high blood glucose index. Intent-to-treat analysis showed greater HbA1c reductions over 12 months in ISM (-0.39%) than in AC patients (-0.27%), with a between-group difference of -0.12% (95% CI, -0.210 to -0.024; P=0.013). In the per-protocol analysis, the between-group difference was -0.21% (-0.331 to -0.089; P=0.0007). More ISM than AC patients achieved clinically meaningful reductions in HbA1c (>0.3, >0.4, or >0.5%) at study end (P<0.025). The proportion of patients reaching/maintaining the risk target at month 12 was similar in ISM (74.6%) and AC (70.1%) patients (P=0.131). At visits 2, 3, and 4, diabetes medications were changed more often in ISM than in AC patients (P<0.001). Use of structured SMBG improves glycemic control and provides guidance in prescribing diabetes medications in patients with relatively well-controlled noninsulin-treated type 2 diabetes.

p-type zinc-blende GaN on GaAs substrates

NASA Astrophysics Data System (ADS)

Lin, M. E.; Xue, G.; Zhou, G. L.; Greene, J. E.; Morkoç, H.

1993-08-01

We report p-type cubic GaN. The Mg-doped layers were grown on vicinal (100) GaAs substrates by plasma-enhanced molecular beam epitaxy. Thermally sublimed Mg was, with N2 carrier gas, fed into an electron-cyclotron resonance source. p-type zinc-blende-structure GaN films were achieved with hole mobilities as high as 39 cm2/V s at room temperature. The cubic nature of the films were confirmed by x-ray diffractometry. The depth profile of Mg was investigated by secondary ions mass spectroscopy.

Syntheses and structures of ruthenium(II) N,S-heterocyclic carbene diphosphine complexes and their catalytic activity towards transfer hydrogenation.

PubMed

Ding, Nini; Hor, T S Andy

2011-06-06

Phosphine exchange of [Ru(II) Br(MeCOO)(PPh(3))(2)(3-RBzTh)] (3-RBzTh=3-benzylbenzothiazol-2-ylidene) with a series of diphosphines (bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethylene (dppv), 1,1'-bis(diphenylphosphino)ferrocene (dppf), 1,4-bis(diphenylphosphino)butane (dppb), and 1,3-(diphenylphosphino)propane (dppp)) gave mononuclear and neutral octahedral complexes [RuBr(MeCOO)(η(2)-P(2))(3-RBzTh)] (P(2)=dppm (2), dppv (3), dppf (4), dppb (5), or dppp (6)), the coordination spheres of which contained four different ligands, namely, a chelating diphosphine, carboxylate, N,S-heterocyclic carbene (NSHC), and a bromide. Two geometric isomers of 6 (6a and 6b) have been isolated. The structures of these products, which have been elucidated by single-crystal X-ray crystallography, show two structural types, I and II, depending on the relative dispositions of the ligands. Type I structures contain a carbenic carbon atom trans to the oxygen atom, whereas two phosphorus atoms are trans to bromine and oxygen atoms. The type II system comprises a carbene carbon atom trans to one of the phosphorus atoms, whereas the other phosphorus is trans to the oxygen atom, with the bromine trans to the remaining oxygen atom. Complexes 2, 3, 4, and 6a belong to type I, whereas 5 and 6b are of type II. The kinetic product 6b eventually converts into 6a upon standing. These complexes are active towards catalytic reduction of para-methyl acetophenone by 2-propanol at 82 °C under 1% catalyst load giving the corresponding alcohols. The dppm complex 2 shows the good yields (91-97%) towards selected ketones. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure and biological activity of protopanaxatriol-type saponins from the roots of Panax notoginseng.

PubMed

Sun, Hongxiang; Yang, Zhigang; Ye, Yiping

2006-01-01

The further purification of the total saponins from the roots of Panax notoginseng by using ordinary and reversed-phase silica-gel, as well as Sephadex LH-20 chromatography afford seven adjuvant active protopanaxatriol-type saponins (PTS), ginsenosides-Rh1 (Rh1),-Rh4 (Rh4),-Rg1 (Rg1),-Re (Re), notoginsenosides-R1 (R1),-R2 (R2),-U (U). These saponins were evaluated for their haemolytic activities and adjuvant potentials on the cellular and humoral immune responses of ICR mice against ovalbumin (OVA). The effect of the substitution pattern of these PTS on their biological activities was investigated and structure-activity relationships were established. Among seven PTS, the haemolytic activity of Rh1 was higher than that of other six compounds (p<0.001) The HD50 values of Rh4 and U were significantly bigger than those of R2, Rg1 and Re (p<0.05 or p<0.01). Seven PTS could significantly increase the concanavalin A (Con A)-, lipopolysaccharide (LPS)- and OVA-induced splenocyte proliferation in the OVA-immunized mice (p<0.01 or p<0.001). The OVA-specific IgG, IgG1, IgG2a and IgG2b antibody levels in serum were also significantly enhanced by seven PTS compared with OVA control group (p<0.01 or p<0.001). The structure-activity relationship studies suggested that the number, the length and the position of sugar side chains, and the type of glucosyl group in the structure of PTS could not only affect their haemolytic activities and adjuvant potentials, but have significant effects on the nature of the immune responses. The information about this structure/function relationship might be useful for developing semisynthetic tetracyclic triterpenoid saponin derivatives with immunological adjuvant activity, as well as a reference to the distribution of the functional groups composing the saponin molecule.

Electronic structures and superconductivity in LuTE2Si2 phases (TE = d-electron transition metal)

NASA Astrophysics Data System (ADS)

Samsel-Czekała, M.; Chajewski, G.; Wiśniewski, P.; Romanova, T.; Hackemer, A.; Gorzelniak, R.; Pikul, A. P.; Kaczorowski, D.

2018-05-01

In the course of our search for unconventional superconductors amidst the 1:2:2 phases, we have re-investigated the LuTE2Si2 compounds with TE = Fe, Co, Ni, Ru, Pd and Pt. In this paper, we present the results of our fully relativistic ab initio calculations of the band structures, performed using the full-potential local-orbital code. The theoretical data are supplemented by the results of low-temperature electrical transport and specific heat measurements performed down to 0.35 K. All the materials studied but LuPt2Si2 crystallize with the body-centered tetragonal ThCr2Si2-type structure (space group I4/mmm). Their Fermi surfaces exhibit a three-dimensional multi-band character. In turn, the Pt-bearing compound adopts the primitive tetragonal CaBe2Ge2-type structure (space group P4/nmm), and its Fermi surface consists of predominantly quasi-two-dimensional sheets. Bulk superconductivity was found only in LuPd2Si2 and LuPt2Si2 (independent of the structure type and dimensionality of the Fermi surface). The key superconducting characteristics indicate a fully-gapped BCS type character. Though the electronic structure of LuFe2Si2 closely resembles that of the unconventional superconductor YFe2Ge2, this Lu-based silicide exhibits neither superconductivity nor spin fluctuations at least down to 0.35 K.

Impact of structured self-monitoring of blood glucose on the quality of life of insulin-treated Chinese patients with type 2 diabetes mellitus: Results from the COMPASS study.

PubMed

Gao, L; Ji, L; Su, Q; Feng, B; Shan, Z; Hu, R; Xing, X; Xue, Y

2016-02-01

To evaluate the effect of structured self-monitoring of blood glucose (SMBG) regimen on quality of life (QoL) in poorly controlled insulin-treated patients with type 2 diabetes. Phase II of the COMPASS trial was a 6-month, multicenter, prospective, single-arm, interventional study. This study recruited 820 outpatients from 19 clinical sites in China who met the following inclusion criteria: type 2 diabetes, insulin treatment for ≥ 3 months, and age 18-65 years, an HbA1c >8.0% (64 mmol/mol), and willingness to perform SMBG. Subjects were advised to follow a structured SMBG regimen specific to their insulin regimen, and were trained to respond to SMBG readings via lifestyle changes and insulin dose self-adjustment. QoL assessments (SF-36) were performed at baseline and 6 months. Patients with a mean age of 55.13 ± 9.77 years had an average diabetes duration of 9.83 ± 7.05 years and had been receiving insulin therapy for a mean of 45.4 ± 46.79 months. All QoL parameters were significantly improved following structured SMBG after 6 months, most notably the physical role functioning (p<0.0001) and emotional role functioning (p<0.0001) component scores. Overall, 40.6% of patients rated their overall QoL as 'a bit' or a lot better' after structured SMBG compared with 16.5% prior to the intervention (p<0.0001). SMBG also improved overall feelings of wellbeing, with 39.13% of patients believing that their health was deteriorating prior to SMBG compared with only 14.4% of patients after the intervention (p<0.0001). The structured SMBG program in insulin-treated Chinese outpatients with type 2 diabetes significantly improved QoL outcomes. Physical and emotional role functioning are the 2 QoL scales that demonstrate the largest improvement with SMBG. Copyright © 2016. Published by Elsevier Ireland Ltd.

Final visual acuity results in the early treatment for retinopathy of prematurity study.

PubMed

Good, William V; Hardy, Robert J; Dobson, Velma; Palmer, Earl A; Phelps, Dale L; Tung, Betty; Redford, Maryann

2010-06-01

To compare visual acuity at 6 years of age in eyes that received early treatment for high-risk prethreshold retinopathy of prematurity (ROP) with conventionally managed eyes. Infants with symmetrical, high-risk prethreshold ROP (n = 317) had one eye randomized to earlier treatment at high-risk prethreshold disease and the other eye managed conventionally, treated if ROP progressed to threshold severity. For asymmetric cases (n = 84), the high-risk prethreshold eye was randomized to either early treatment or conventional management. The main outcome measure was ETDRS visual acuity measured at 6 years of age by masked testers. Retinal structure was assessed as a secondary outcome. Analysis of all subjects with high-risk prethreshold ROP showed no statistically significant benefit for early treatment (24.3% vs 28.6% [corrected] unfavorable outcome; P = .15). Analysis of 6-year visual acuity results according to the Type 1 and 2 clinical algorithm showed a benefit for Type 1 eyes (25.1% vs 32.8%; P = .02) treated early but not Type 2 eyes (23.6% vs 19.4%; P = .37). Early-treated eyes showed a significantly better structural outcome compared with conventionally managed eyes (8.9% vs 15.2% unfavorable outcome; P < .001), with no greater risk of ocular complications. Early treatment for Type 1 high-risk prethreshold eyes improved visual acuity outcomes at 6 years of age. Early treatment for Type 2 high-risk prethreshold eyes did not. Application to Clinical Practice Type 1 eyes, not Type 2 eyes, should be treated early. These results are particularly important considering that 52% of Type 2 high-risk prethreshold eyes underwent regression of ROP without requiring treatment. Trial Registration clinicaltrials.gov Identifier: NCT00027222.

The structure of Na{sub 3}SbTe{sub 3}: How ionic and covalent bonding forces work together

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

Lin, Jianhua; Miller, G.J.

1994-12-01

The compound Na{sub 3}SbTe{sub 3} has been synthesized from the elements and characterized by single crystal X-ray diffraction. Na{sub 3}SbTe{sub 3} is cubic, crystallizing in the cP28 structure type (isomorphous with Na{sub 3}AsS{sub 3}); space group P2{sub 1}3 (No. 198); a=9.6114(9) {angstrom}; Z = 4; R1 = 0.0324; wR2 = 0.0561 (I {le} 2{sigma}(I)). The structure consists of isolated sodium cations and trigonal pyramidal [SbTe{sub 3}]{sup {minus}3} anions with a Sb-Te bond length of 2.787(1) {angstrom} and a Te-Sb-Te bond angle of 100.0(1){degrees}. The structure is related to both the Li{sub 3}Bi and K{sub 3}AsS{sub 4}-type structures. Both lattice energymore » and semiempirical electronic structure calculations are utilized to evaluate various local and long-range structural aspects of this Zintl phase.« less

The effect of user experience and inflation technique on endotracheal tube cuff pressure using a feline airway simulator.

PubMed

White, Donna M; Redondo, José I; Mair, Alastair R; Martinez-Taboada, Fernando

2017-09-01

The effect of user experience and inflation technique on endotracheal tube cuff pressure using a feline airway simulator. Prospective, experimental clinical study. Participants included veterinary students at the beginning (group S1) and end (group S2) of their 2-week anaesthesia rotation and veterinary anaesthetists (group A). The feline airway simulator was designed to simulate an average size feline trachea, intubated with a 4.5 mm low-pressure, high-volume cuffed endotracheal tube, connected to a Bain breathing system with oxygen flow of 2 L minute -1 . Participants inflated the on-endotracheal tube cuff by pilot balloon palpation and by instilling the minimum occlusive volume (MOV) required for loss of airway leaks during manual ventilation. Intracuff pressures were measured by manometers obscured to participants and ideally were 20-30 cm H 2 O. Student t, Fisher exact, and Chi-squared tests were used where appropriate to analyse data (p < 0.05). Participants were 12 students and eight anaesthetists. Measured intracuff pressures for palpation and MOV, respectively, were 19 ± 12 and 29 ± 19 cm H 2 O for group S1, 10 ± 5 and 20 ± 11 cm H 2 O for group S2 and 13 ± 6 and 29 ± 18 cm H 2 O for group A. All groups performed poorly at achieving intracuff pressures within the ideal range. There was no significant difference in intracuff pressures between techniques. Students administered lower (p = 0.02) intracuff pressures using palpation after their training. When using palpation and MOV for cuff inflation operators rarely achieved optimal intracuff pressures. Experience had no effect on this skill and, as such, a cuff manometer is recommended. Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

Solid-state (127)I NMR and GIPAW DFT study of metal iodides and their hydrates: structure, symmetry, and higher-order quadrupole-induced effects.

PubMed

Widdifield, Cory M; Bryce, David L

2010-10-14

Central-transition (127)I solid-state nuclear magnetic resonance (SSNMR) spectra are presented for several anhydrous group 2 metal iodides (MgI(2), CaI(2), SrI(2), and BaI(2)), hydrates (BaI(2)·2H(2)O and SrI(2)·6H(2)O), and CdI(2) (4H polytype). Variable offset cumulative spectrum data acquisition coupled with echo pulse sequences and an 'ultrahigh' applied field of 21.1 T were usually suitable to acquire high-quality spectra. Spectral analysis revealed iodine-127 nuclear quadrupole coupling constants (C(Q)((127)I)) ranging in magnitude from 43.5 (CaI(2)) to 214 MHz (one site in SrI(2)). For very large C(Q), analytical second-order perturbation theory could not be used to reliably extract chemical shifts and a treatment which includes quadrupolar effects exactly was required (Bain, A. D. Mol. Phys. 2003, 101, 3163). Differences between second-order and exact modeling allowed us to observe 'higher-order' quadrupole-induced effects for the first time. This finding will have implications for the interpretation of SSNMR spectra of quadrupolar nuclei with large quadrupole moments. In favorable situations (i.e., C(Q)((127)I) < 120 MHz), measurements were also performed at 11.75 T which when combined with the 21.1 T data allowed us to measure iodine chemical shift (CS) tensor spans in the range from 60 (BaI(2)·2H(2)O) to 300 ppm (one site in BaI(2)). These measurements represent the first complete characterizations (i.e., electric field gradient and CS tensors as well as their relative orientation) of noncubic iodide sites using (127)I SSNMR. In select cases, the SSNMR data are supported with (127)I NQR measurements. We also summarize a variety of trends in the halogen SSNMR parameters for group 2 metal halides. Gauge-including projector-augmented wave DFT computations are employed to complement the experimental observations, to predict potential structures for the two hydrates, and to highlight the sensitivity of C(Q)((127)I) to minute structural changes, which has potential applications in NMR crystallography.

High-pressure behavior of iron-nickel-cobalt phosphides and its implications for meteorites and planetary cores

NASA Astrophysics Data System (ADS)

Dera, P.; Lavina, B.; Borkowski, L. A.; Downs, R. T.; Prewitt, C. T.; Prakapenka, V.; Rivers, M. L.; Sutton, S.; Boctor, N.

2008-12-01

Minerals with composition (Fe,Ni)xP, are rare, but important accessory phases present in iron and chondrite meteorites. The occurrence of these minerals in meteoritic samples is believed to originate either from the equilibrium condensation of protoplanetary materials taking place in solar nebulae or from crystallization processes in the cores of parent bodies. Fe-Ni phosphides are considered an important candidate for a minor phase present in Earth's core, and at least partially responsible for the observed core density deficit with respect to pure Fe. We report results of high-pressure high-temperature single-crystal X- ray diffraction experiments with end-members belonging to the (Fe,Ni,Co)2P family, including Fe2P, Ni2P and Co2P. A new phase transition to the Co2Si-type structure (allabogdanite) has been found in Fe2P barringerite at 8.0 GPa, upon heating. The high-pressure phase can be quenched metastably to ambient conditions and then, if heated again, it transforms back to barringerite. Ni2P barringerite does not undergo transformation to allabogdanite structure up to 50 GPa, but instead exhibits incongruent melting with formation of pyrite-type NiP2 and Ni-P glass. Our results indicate that the presence of allabogdanite in meteoritic samples places two important constraints on the thermodynamic history of the meteorite. First, it imposes a minimum pressure and temperature for the formation of the Fe2P, and additionally rules out any higher temperature low pressure alterations. If present in the Earth's core, Fe2P will have the allabogdanite rather than the barringerite structure. Crystal chemical trends in the compressibility of (Fe,Ni,Co)2P minerals, as well as polymorphic transition paths are analyzed in the context of Earth and planetary core composition and properties.

Crystal structures of dye-decolorizing peroxidase with ascorbic acid and 2,6-dimethoxyphenol.

PubMed

Yoshida, Toru; Tsuge, Hideaki; Hisabori, Toru; Sugano, Yasushi

2012-12-14

The structure of dye-decolorizing peroxidase (DyP)-type peroxidase differs from that of other peroxidase families, indicating that DyP-type peroxidases have a different reaction mechanism. We have determined the crystal structures of DyP with ascorbic acid and 2,6-dimethoxyphenol at 1.5 and 1.4Å, respectively. The common binding site for both substrates was located at the entrance of the second cavity leading from the DyP molecular surface to heme. This resulted in a hydrogen bond network connection between each substrate and the heme distal side. This network consisted of water molecules occupying the second cavity, heme 6-propionate, Arg329, and Asn313. This network is consistent with the proton transfer pathway from substrate to DyP. Copyright © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Effect of Mg substitution on crystal structure and hydrogenation of Ce{sub 2}Ni{sub 7}-type Pr{sub 2}Ni{sub 7}

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

Iwase, Kenji, E-mail: fbiwase@mx.ibaraki.ac.jp; Mori, Kazuhiro; Terashita, Naoyoshi

2017-03-15

The effect of Pr being substituted by Mg in Pr{sub 2}Ni{sub 7} with a Ce{sub 2}Ni{sub 7}-type structure was investigated by X-ray diffraction (XRD) and pressure−composition (P−C) isotherm measurements. The maximum hydrogen capacity of Pr{sub 2}Ni{sub 7} reached 1.24 H/M in the first absorption process. However, 0.61 H/M hydrogen remained in the sample after the first desorption and the reversible hydrogen capacity decreased to 0.63 H/M. Severe peak broadening was observed in the XRD profile of Pr{sub 2}Ni{sub 7}H{sub 5.4} after the first P−C isotherm cycle. The metal sublattice of Pr{sub 2}Ni{sub 7}H{sub 5.4} is deformed and changes from themore » Ce{sub 2}Ni{sub 7}-type structure to a lower symmetry during hydrogenation, with no detection of an amorphous phase. Pr{sub 1.5}Mg{sub 0.5}Ni{sub 7} consists of two phases: 80% Gd{sub 2}Co{sub 7}-type and 20% PuNi{sub 3}-type phases. Mg substitution leads to the relative stability of the Gd{sub 2}Co{sub 7}-type and PuNi{sub 3}-type structures. The Gd{sub 2}Co{sub 7}-type and PuNi{sub 3}-type structures are retained after the P-C isotherm. The reversible hydrogen capacity reached 1.05 H/M. The structural change during the hydrogen absorption−desorption cycle and the hydrogenation characteristics are changed by Mg atoms replacing Pr in the MgZn{sub 2}-type cell. - Graphical abstract: The maximum hydrogen capacity is 1.2 H/M in the first absorption process and the reversible capacity is 0.63 H/M.« less

Structure Determination of an Inter-strand-type cis-anti Cyclobutane Thymine Dimer Produced in High Yield by UVB Light in an Oligodeoxynucleotide at Acidic pH

PubMed Central

Su, Dian G. T.; Kao, Jeffrey L.-F.; Gross, Michael L.; Taylor, John-Stephen A.

2009-01-01

UVB irradiation of DNA produces photodimers in adjacent DNA bases and on rare occasions in non-adjacent bases. UVB irradiation (312 nm) of d(GTATCATGAGGTGC) gave rise to an unknown DNA photoproduct in approximately 40% yield at acidic pH of about 5. This product has a much shorter retention time in reverse phase HPLC compared to known dipyrimidine photoproducts of this sequence. A large upfield shift of two thymine H6 NMR signals and photoreversion to the parent ODN upon irradiation with 254 nm light indicates that the photoproduct is a cyclobutane thymine dimer. Exonuclease-coupled MS assay establishes that the photodimer forms between T2 and T7, which was confirmed by tandem mass spectrometric MS/MS identification of the endonuclease P1 digestion product d(T2[A3])=pd(T7[G8]). Acidic hydrolysis of the photoproduct gave a product with the same retention time on reverse phase HPLC and the same MS/MS fragmentation pattern as authentic Thy[c,a]Thy. 2D NOE NMR data are consistent with a cis-anti cyclobutane dimer between the 3′-sides of T2 and T7 in anti glycosyl conformations that had to have arisen from an inter-stand type reaction. In addition to pH-dependent, the photoproduct yield is highly sequence specific and concentration dependent, indicating that it results from a higher order folded structure. The efficient formation of this inter-strand-type photoproduct suggests the existence of a new type of folding motif and the possibility that this type of photoproduct might also form in other folded structures, such as G-quadruplexes and i-motif structures which can be now studied by the methods described. PMID:18680367

cis-trans Germanium chains in the intermetallic compounds ALi{sub 1-x}In{sub x}Ge{sub 2} and A{sub 2}(Li{sub 1-x}In{sub x}){sub 2}Ge{sub 3} (A=Sr, Ba, Eu)-experimental and theoretical studies

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

You, Tae-Soo; Bobev, Svilen, E-mail: bobev@udel.ed

Two types of strontium-, barium- and europium-containing germanides have been synthesized using high temperature reactions and characterized by single-crystal X-ray diffraction. All reported compounds also contain mixed-occupied Li and In atoms, resulting in quaternary phases with narrow homogeneity ranges. The first type comprises EuLi{sub 0.91(1)}In{sub 0.09}Ge{sub 2}, SrLi{sub 0.95(1)}In{sub 0.05}Ge{sub 2} and BaLi{sub 0.99(1)}In{sub 0.01}Ge{sub 2}, which crystallize in the orthorhombic space group Pnma (BaLi{sub 0.9}Mg{sub 0.1}Si{sub 2} structure type, Pearson code oP16). The lattice parameters are a=7.129(4)-7.405(4) A; b=4.426(3)-4.638(2) A; and c=11.462(7)-11.872(6) A. The second type includes Eu{sub 2}Li{sub 1.36(1)}In{sub 0.64}Ge{sub 3} and Sr{sub 2}Li{sub 1.45(1)}In{sub 0.55}Ge{sub 3}, whichmore » adopt the orthorhombic space group Cmcm (Ce{sub 2}Li{sub 2}Ge{sub 3} structure type, Pearson code oC28) with lattice parameters a=4.534(2)-4.618(2) A; b=19.347(8)-19.685(9) A; and c=7.164(3)-7.260(3) A. The polyanionic sub-structures in both cases feature one-dimensional Ge chains with alternating Ge-Ge bonds in cis- and trans-conformation. Theoretical studies using the tight-binding linear muffin-tin orbital (LMTO) method provide the rationale for optimizing the overall bonding by diminishing the {pi}-p delocalization along the Ge chains, accounting for the experimentally confirmed substitution of Li forIn. -- Graphical abstract: Presented are the single-crystal structures of two types of closely related intermetallics, as well as their band structures, calculated using tight-binding linear muffin-tin orbital (TB-LMTO-ASA) method. Display Omitted« less

Study of nanoparticles TiO2 thin films on p-type silicon substrate using different alcoholic solvents

NASA Astrophysics Data System (ADS)

Muaz, A. K. M.; Hashim, U.; Arshad, M. K. Md.; Ruslinda, A. R.; Ayub, R. M.; Gopinath, Subash C. B.; Voon, C. H.; Liu, Wei-Wen; Foo, K. L.

2016-07-01

In this paper, sol-gel method spin coating technique is adopted to prepare nanoparticles titanium dioxide (TiO2) thin films. The prepared TiO2 sol was synthesized using titanium butoxide act as a precursor and subjected to deposited on the p-type silicon oxide (p-SiO2) and glass slide substrates under room temperature. The effect of different alcoholic solvents of methanol and ethanol on the structural, morphological, optical and electrical properties were systematically investigated. The coated TiO2 thin films were annealed in furnace at 773 K for 1 h. The structural properties of the TiO2 films were examined with X-ray Diffraction (XRD). From the XRD analysis, both solvents showing good crystallinity with anatase phase were the predominant structure. Atomic Force Microscopy (AFM) was employed to study the morphological of the thin films. The optical properties were investigated by Ultraviolet-visible (UV-Vis) spectroscopy were found that ethanol as a solvent give a higher optical transmittance if compare to the methanol solvent. The electrical properties of the nanoparticles TiO2 thin films were measured using two-point-probe technique.

InP-based type-I quantum well lasers up to 2.9 μm at 230 K in pulsed mode on a metamorphic buffer

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

Gu, Y.; Zhang, Y. G., E-mail: ygzhang@mail.sim.ac.cn; Ma, Y. J.

This work reports on up to 2.9 μm lasing at 230 K of InP-based type-I quantum well lasers. This record long wavelength lasing is achieved by applying InP-based Sb-free structures with eight periods of strain-compensated InAs quantum wells grown on metamorphic In{sub 0.8}Al{sub 0.2}As template layers. The continuous-wave threshold current density is 797 A/cm{sup 2} and the idealized extrapolated threshold current density for infinite cavity length is as low as 58 A/cm{sup 2} per quantum well at 120 K. This scheme is a promising pathway for extending the wavelength range of type-I quantum well lasers on InP substrates.

New superhindered polydentate polyphosphine ligands P(CH2CH2P(t)Bu2)3, PhP(CH2CH2P(t)Bu2)2, P(CH2CH2CH2P(t)Bu2)3, and their ruthenium(II) chloride complexes.

PubMed

Gilbert-Wilson, Ryan; Field, Leslie D; Bhadbhade, Mohan M

2012-03-05

The synthesis and characterization of the extremely hindered phosphine ligands, P(CH(2)CH(2)P(t)Bu(2))(3) (P(2)P(3)(tBu), 1), PhP(CH(2)CH(2)P(t)Bu(2))(2) (PhP(2)P(2)(tBu), 2), and P(CH(2)CH(2)CH(2)P(t)Bu(2))(3) (P(3)P(3)(tBu), 3) are reported, along with the synthesis and characterization of ruthenium chloro complexes RuCl(2)(P(2)P(3)(tBu)) (4), RuCl(2)(PhP(2)P(2)(tBu)) (5), and RuCl(2)(P(3)P(3)(tBu)) (6). The bulky P(2)P(3)(tBu) (1) and P(3)P(3)(tBu) (3) ligands are the most sterically encumbered PP(3)-type ligands so far synthesized, and in all cases, only three phosphorus donors are able to bind to the metal center. Complexes RuCl(2)(PhP(2)P(2)(tBu)) (5) and RuCl(2)(P(3)P(3)(tBu)) (6) were characterized by crystallography. Low temperature solution and solid state (31)P{(1)H} NMR were used to demonstrate that the structure of RuCl(2)(P(2)P(3)(tBu)) (4) is probably analogous to that of RuCl(2)(PhP(2)P(2)(tBu)) (5) which had been structurally characterized.

(Pt1-xCux)3Cu2B and Pt9Cu3B5, the first examples of copper platinum borides. Observation of superconductivity in a novel boron filled β-Mn-type compound

NASA Astrophysics Data System (ADS)

Salamakha, Leonid P.; Sologub, Oksana; Stöger, Berthold; Michor, Herwig; Bauer, Ernst; Rogl, Peter F.

2015-09-01

New ternary copper platinum borides have been synthesized by arc melting of pure elements followed by annealing at 600 °C. The structures have been studied by X-ray single crystal and powder diffraction. (Pt1-xCux)3Cu2B (x=0.33) forms a B-filled β-Mn-type structure (space group P4132; a=0.6671(1) nm). Cu atoms are distributed preferentially on the 8c atom sites, whereas the 12d site is randomly occupied by Pt and Cu atoms (0.670(4) Pt±0.330(4) Cu). Boron is located in octahedral voids of the parent β-Mn-type structure. Pt9Cu3B5 (space group P-62m; a=0.9048(3) nm, c=0.2908(1) nm) adopts the Pt9Zn3B5-δ-type structure. It has a columnar architecture along the short translation vector exhibiting three kinds of [Pt6] trigonal prism columns (boron filled, boron semi-filled and empty) and Pt channels with a pentagonal cross section filled with Cu atoms. The striking structural feature is a [Pt6] cluster in form of an empty trigonal prism at the origin of the unit cell, which is surrounded by coupled [BPt6] and [Pt6] trigonal prisms, rotated perpendicularly to the central one. There is no B-B contact as well as Cu-B contact in the structure. The relationships of Pt9Cu3B5 structure with the structure of Ti1+xOs2-xRuB2 as well as with the structure families of metal sulfides and aluminides have been elucidated. (Pt1-xCux)3Cu2B (x=0.3) (B-filled β-Mn-type structure) is a bulk superconductor with a transition temperature of about 2.06 K and an upper critical field μ0HC2(0)WHH of 1.2 T, whereas no superconducting transition has been observed up to 0.3 K in Pt9Cu3B5 (Pt9Zn3B5-δ-type structure) from electrical resistivity measurements.

Synthesis and structural characterization of the Zintl phases Na{sub 3}Ca{sub 3}TrPn{sub 4}, Na{sub 3}Sr{sub 3}TrPn{sub 4}, and Na{sub 3}Eu{sub 3}TrPn{sub 4} (Tr=Al, Ga, In; Pn=P, As, Sb)

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

Wang, Yi; Suen, Nian-Tzu; College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002

15 new quaternary Zintl phases have been synthesized by solid-state reactions from the respective elements, and their structures have been determined by single-crystal X-ray diffraction. Na{sub 3}E{sub 3}TrPn{sub 4} (E=Ca, Sr, Eu; Tr=Al, Ga, In; Pn=P, As, Sb) crystallize in the hexagonal crystal system with the non-centrosymmetric space group P6{sub 3}mc (No. 186). The structure represents a variant of the K{sub 6}HgS{sub 4} structure type (Pearson index hP22) and features [TrPn{sub 4}]{sup 9–} tetrahedral units, surrounded by Na{sup +} and Ca{sup 2+}, Sr{sup 2+}, Eu{sup 2+} cations. The nominal formula rationalization [Na{sup +}]{sub 3}[E{sup 2+}]{sub 3}[TrPn{sub 4}]{sup 9–} follows themore » octet rule, suggesting closed-shell configurations for all atoms and intrinsic semiconducting behavior. However, structure refinements for several members hint at disorder and mixing of cations that potentially counteract the optimal valence electron count. - Graphical abstract: The hexagonal, non-centrosymmetric structure of Na{sub 3}E{sub 3}TrPn{sub 4} (E=Ca, Sr, Eu; Tr=Al, Ga, In; Pn=P, As, Sb) features [TrPn{sub 4}]{sup 9–} tetrahedral units, surrounded by Na{sup +} and Ca{sup 2+}, Sr{sup 2+}, Eu{sup 2+} cations. - Highlights: • 15 quaternary phosphides, arsenides, and antimonides are synthesized and structurally characterized. • The structure is a variant of the hexagonal K{sub 6}HgS{sub 4}-type, with distinctive pattern for the cations. • Occupational and/or positional disorder of yet unknown origin exists for some members of the series.« less

Structural similarity and distribution of small cryptic plasmids of Lactobacillus curvatus and L. sake.

PubMed

Vogel, R F; Lohmann, M; Weller, A N; Hugas, M; Hammes, W P

1991-11-15

Plasmid profiles of strains of Lactobacillus curvatus and L. sake isolated from meat or sauerkraut were analysed to investigate plasmid homology and distribution in relation to the ecology of these organisms in fermenting foods. A hybridisation probe was constructed by cloning of pLc2, a cryptic, 2.6-kbp plasmid from L. curvatus LTH683, into the Escherichia coli plasmid pRV50. In Southern hybridisations with the digoxygenine labeled pLc2 probe, pLc2-related small plasmids were frequently detected in meat-borne strains of L. casei subsp. pseudoplantarum, L. curvatus, L. sake, L. alimentarius, L. farciminis and L. halotolerans and in L. curvatus and L. sake isolated from sauerkraut. Among 27 Lactobacillus type strains originally isolated from habitats other than meat this type of homology was detected only with plasmids of L. buchneri and L. mali. Restriction-enzyme mapping of six small cryptic plasmids from L. curvatus and L. sake revealed strong structural homology but no similarity to previously characterized plasmids of lactobacilli. The presence of a variable region in addition to a conserved one and the occurrence of deletions during cloning of pLc2 suggest that vectors derived from these plasmids are likely to be structurally unstable.

Influence of nitrogen-doping concentration on the electronic structure of CuAlO2 by first-principles studies

NASA Astrophysics Data System (ADS)

Liu, Wei-wei; Chen, Hong-xia; Liu, Cheng-lin; Wang, Rong

2017-02-01

Effect of N doping concentration on the electronic structure of N-doped CuAlO2 was investigated by density functional theory based on generalized-gradient approximation plus orbital potential. Lattice parameters a and c both increase with increasing N-doping concentration. Formation energies increase with increasing N doping concentration and all N-doped CuAlO2 were structurally stable. The calculated band gaps for N-doped CuAlO2 narrowed compared to pure CuAlO2, which was attributed to the stronger hybridization between Cu-3d and N-2p states and the downward shift of Cu-3p states in conduction bands. The higher the N-doping concentration is, the narrower the band gap. N-doped CuAlO2 shows a typical p-type semiconductor. The band structure changed from indirect to direct after N doping which will benefit the application of the CuAlO2 materials in optoelectronic and electronic devices.

Antiferromagnetism in semiconducting SrMn 2 Sb 2 and BaMn 2 Sb 2 single crystals

DOE PAGES

Sangeetha, N. S.; Smetana, V.; Mudring, A. -V.; ...

2018-01-03

Here, crystals of SrMn 2Sb 2 and BaMn 2Sb 2 were grown using Sn flux and characterized by powder and single-crystal x-ray diffraction, respectively, and by single-crystal electrical resistivity ρ, heat capacity C p, and magnetic susceptibility χ measurements versus temperature T, and magnetization versus field M(H) isotherm measurements. SrMn 2Sb 2 adopts the trigonal CaAl 2Si 2-type structure, whereas BaMn 2Sb 2 crystallizes in the tetragonal ThCr 2Si 2-type structure. The ρ(T) data indicate semiconducting behaviors for both compounds with activation energies of ≳0.35 eV for SrMn 2Sb 2 and 0.16 eV for BaMn 2Sb 2. The χ(T) andmore » C p(T) data reveal antiferromagnetic (AFM) ordering at T N = 110 K for SrMn 2Sb 2 and 450 K for BaMn 2Sb 2. The anisotropic χ(T≤T N) data also show that the ordered moments in SrMn 2Sb 2 are aligned in the hexagonal ab plane, whereas the ordered moments in BaMn 2Sb 2 are aligned collinearly along the tetragonal c axis. The ab-plane M(H) data for SrMn 2Sb 2 exhibit a continuous metamagnetic transition at low fields 02Sb 2 exhibits no metamagnetic transitions up to 5.5 T. The χ(T) and C p(T) data for both SrMn 2Sb 2 and BaMn 2Sb 2 indicate strong dynamic short-range AFM correlations above their respective T N up to at least 900 K within a local-moment picture, corresponding to quasi-two-dimensional magnetic behavior. The present results and a survey of the literature for Mn pnictides with the CaAl 2Si 2 and ThCr 2Si 2 crystal structures show that the T N values for the CaAl 2Si 2-type compounds are much smaller than those for the ThCr 2Si 2-type materials.« less

Investigation of trapping levels in p-type Zn3P2 nanowires using transport and optical properties

NASA Astrophysics Data System (ADS)

Lombardi, G. A.; de Oliveira, F. M.; Teodoro, M. D.; Chiquito, A. J.

2018-05-01

Here, we report the synthesis and structural characterization of high-quality Zn3P2 nanowires via chemical vapour deposition. Structural and morphological characterization studies revealed a reliable growth process of long, uniform, and single-crystalline nanowires. From temperature dependent transport and photoluminescence measurements, we have observed the contribution of different acceptor levels (15, 50, 70, 90, and 197 meV) to the conduction mechanisms. These levels were associated with zinc vacancies and phosphorous interstitial atoms which assigned a p-type character to this semiconductor. From time resolved photoluminescence experiments, a 91 ps lifetime decay was found. Such a fast lifetime decay is in agreement with the exciton transition along the bulk emission from high quality crystalline nanowires.

First principles study of crystal Si-doped Ge2Sb2Te5

NASA Astrophysics Data System (ADS)

Yan, Beibei; Yang, Fei; Chen, Tian; Wang, Minglei; Chang, Hong; Ke, Daoming; Dai, Yuehua

2017-02-01

Ge2Sb2Te5 (GST) and Si-doped GST with hexagonal structure were investigated by means of First-principles calcucations. We performed many kinds of doping types and studied the electronic properties of Si-doped GST with various Si concentrations. The theoretical calculations show that the lowest formation energy appeared when Si atoms substitute the Sb atoms (SiSb). With the increasing of Si concentrations from 10% to 30%, the impurity states arise around the Fermi level and the band gap of the SiSb structure broadens. Meanwhile, the doping supercell has the most favorable structure when the doping concentration keeps in 20%. The Si-doped GST exhibits p-type metallic characteristics more distinctly owing to the Fermi level moves toward the valence band. The Te p, d-orbitals electrons have greater impact on electronic properties than that of Te s-orbitals.

Characterization of a recombinant type II 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Helicobacter pylori.

PubMed

Webby, Celia J; Patchett, Mark L; Parker, Emily J

2005-08-15

DAH7P (3-Deoxy-D-arabino-heptulosonate 7-phosphate) synthase catalyses the condensation reaction between phosphoenolpyruvate (PEP) and D-erythrose 4-phosphate (E4P) as the first committed step in the biosynthesis of aromatic compounds in plants and micro-organisms. Previous work has identified two families of DAH7P synthases based on sequence similarity and molecular mass, with the majority of the mechanistic and structural studies being carried out on the type I paralogues from Escherichia coli. Whereas a number of organisms possess genes encoding both type I and type II DAH7P synthases, the pathogen Helicobacter pylori has only a single, type II, enzyme. Recombinant DAH7P synthase from H. pylori was partially solubilized by co-expression with chaperonins GroEL/GroES in E. coli, and purified to homogeneity. The enzyme reaction follows an ordered sequential mechanism with the following kinetic parameters: K(m) (PEP), 3 microM; K(m) (E4P), 6 microM; and kcat, 3.3 s(-1). The enzyme reaction involves interaction of the si face of PEP with the re face of E4P. H. pylori DAH7P synthase is not inhibited by phenylalanine, tyrosine, tryptophan or chorismate. EDTA inactivates the enzyme, and activity is restored by a range of bivalent metal ions, including (in order of decreasing effectiveness) Co2+, Mn2+, Ca2+, Mg2+, Cu2+ and Zn2+. Analysis of type II DAH7P synthase sequences reveals several highly conserved motifs, and comparison with the type I enzymes suggests that catalysis by these two enzyme types occurs on a similar active-site scaffold and that the two DAH7P synthase families may indeed be distantly related.

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

Sangeetha, N. S.; Smetana, V.; Mudring, A. -V.

Here, crystals of SrMn 2Sb 2 and BaMn 2Sb 2 were grown using Sn flux and characterized by powder and single-crystal x-ray diffraction, respectively, and by single-crystal electrical resistivity ρ, heat capacity C p, and magnetic susceptibility χ measurements versus temperature T, and magnetization versus field M(H) isotherm measurements. SrMn 2Sb 2 adopts the trigonal CaAl 2Si 2-type structure, whereas BaMn 2Sb 2 crystallizes in the tetragonal ThCr 2Si 2-type structure. The ρ(T) data indicate semiconducting behaviors for both compounds with activation energies of ≳0.35 eV for SrMn 2Sb 2 and 0.16 eV for BaMn 2Sb 2. The χ(T) andmore » C p(T) data reveal antiferromagnetic (AFM) ordering at T N = 110 K for SrMn 2Sb 2 and 450 K for BaMn 2Sb 2. The anisotropic χ(T≤T N) data also show that the ordered moments in SrMn 2Sb 2 are aligned in the hexagonal ab plane, whereas the ordered moments in BaMn 2Sb 2 are aligned collinearly along the tetragonal c axis. The ab-plane M(H) data for SrMn 2Sb 2 exhibit a continuous metamagnetic transition at low fields 02Sb 2 exhibits no metamagnetic transitions up to 5.5 T. The χ(T) and C p(T) data for both SrMn 2Sb 2 and BaMn 2Sb 2 indicate strong dynamic short-range AFM correlations above their respective T N up to at least 900 K within a local-moment picture, corresponding to quasi-two-dimensional magnetic behavior. The present results and a survey of the literature for Mn pnictides with the CaAl 2Si 2 and ThCr 2Si 2 crystal structures show that the T N values for the CaAl 2Si 2-type compounds are much smaller than those for the ThCr 2Si 2-type materials.« less

Optoelectronic properties of novel amorphous CuAlO2/ZnO NWs based heterojunction

NASA Astrophysics Data System (ADS)

Bu, Ian Y. Y.

2013-08-01

Amorphous p-type CuAlO2 thin films were grown onto n-type crystalline ZnO NWs forming a heterojunction through the combination of sol-gel process and hydrothermal growth method. The effects of temperature on structure and optoelectronic properties of CuAlO2 thin films were investigated through various measurement techniques. It was found that the derived CuAlO2 is Al-rich with thin film. UV-Vis measurements showed that the deposited CuAlO2 films are semi-transparent with maximum transmittance ∼82% at 500 nm. Electrical characterization and integration into pn junction confirms that the amorphous CuAlO2 is p-type and exhibited photovoltaic behavior.

Copper Selenidophosphates Cu4P2Se6, Cu4P3Se4, Cu4P4Se3, and CuP2Se, Featuring Zero-, One-, and Two-Dimensional Anions.

PubMed

Kuhn, Alexander; Schoop, Leslie M; Eger, Roland; Moudrakovski, Igor; Schwarzmüller, Stefan; Duppel, Viola; Kremer, Reinhard K; Oeckler, Oliver; Lotsch, Bettina V

2016-08-15

Five new compounds in the Cu/P/Se phase diagram have been synthesized, and their crystal structures have been determined. The crystal structures of these compounds comprise four previously unreported zero-, one-, and two-dimensional selenidophosphate anions containing low-valent phosphorus. In addition to two new modifications of Cu4P2Se6 featuring the well-known hexaselenidohypodiphosphate(IV) ion, there are three copper selenidophosphates with low-valent P: Cu4P3Se4 contains two different new anions, (i) a monomeric (zero-dimensional) selenidophosphate anion [P2Se4](4-) and (ii) a one-dimensional selenidophosphate anion [Formula: see text], which is related to the well-known gray-Se-like [Formula: see text] Zintl anion. Cu4P4Se3 contains one-dimensional [Formula: see text] polyanions, whereas CuP2Se contains the 2D selenidophosphate [Formula: see text] polyanion. It consists of charge-neutral CuP2Se layers separated by a van der Waals gap which is very rare for a Zintl-type phase. Hence, besides black P, CuP2Se constitutes a new possible source of 2D oxidized phosphorus containing layers for intercalation or exfoliation experiments. Additionally, the electronic structures and some fundamental physical properties of the new compounds are reported. All compounds are semiconducting with indirect band gaps of the orders of around 1 eV. The phases reported here add to the structural diversity of chalcogenido phosphates. The structural variety of this family of compounds may translate into a variety of tunable physical properties.

Synthesis, structures, and phase transitions of barium bismuth iridium oxide perovskites Ba{sub 2}BiIrO{sub 6} and Ba{sub 3}BiIr{sub 2}O{sub 9}

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

Ling, Chris D., E-mail: c.ling@chem.usyd.edu.a; Bragg Institute, ANSTO, PMB 1, Menai 2234; Kennedy, Brendan J.

The Ba-Bi-Ir-O system is found to contain two distinct perovskite-type phases: a rock-salt ordered double perovskite Ba{sub 2}BiIrO{sub 6}; and a 6H-type hexagonal perovskite Ba{sub 3}BiIr{sub 2}O{sub 9}. Ba{sub 2}BiIrO{sub 6} undergoes a series of symmetry-lowering phase transitions on cooling Fm3-barm->R3-barc->12/m(C2/m)->I1-bar(P1-bar), all of which are second order except the rhombohedral->monoclinic one, which is first order. The monoclinic phase is only observed in a 2-phase rhombohedral+monoclinic regime. The transition and 2-phase region lie very close to 300 K, making the room-temperature X-ray diffraction patterns extremely complex and potentially explaining why Ba{sub 2}BiIrO{sub 6} had not previously been identified and reported. Amore » solid solution Ba{sub 2}Bi{sub 1+x}Ir{sub 1-x}O{sub 6}, analogous to Ba{sub 2}Bi{sub 1+x}Ru{sub 1-x}O{sub 6}, 0<=x<=2/3, was not observed. The 6H-type phase Ba{sub 3}BiIr{sub 2}O{sub 9} undergoes a clean second-order phase transition P6{sub 3}/mmc->C2/c at 750 K, unlike 6H-type Ba{sub 3}LaIr{sub 2}O{sub 9}, the P6{sub 3}/mmc structure of which is highly strained below {approx}750 K but fails to distort coherently to the monoclinic phase. - Graphical abstract: Structure of Ba{sub 3}BiIr{sub 2}O{sub 9} at 300 K. BiO{sub 6} octahedra are purple, IrO{sub 6} octahedra are gold, and Ba atoms are green. Thermal ellipsoids at 90% probability.« less

Metal Organic Framework-Templated Chemiresistor: Sensing Type Transition from P-to-N Using Hollow Metal Oxide Polyhedron via Galvanic Replacement.

PubMed

Jang, Ji-Soo; Koo, Won-Tae; Choi, Seon-Jin; Kim, Il-Doo

2017-08-30

Facile synthesis of porous nanobuilding blocks with high surface area and uniform catalyst functionalization has always been regarded as an essential requirement for the development of highly sensitive and selective chemical sensors. Metal-organic frameworks (MOFs) are considered as one of the most ideal templates due to their ability to encapsulate ultrasmall catalytic nanoparticles (NPs) in microporous MOF structures in addition to easy removal of the sacrificial MOF scaffold by calcination. Here, we introduce a MOFs derived n-type SnO 2 (n-SnO 2 ) sensing layer with hollow polyhedron structures, obtained from p-n transition of MOF-templated p-type Co 3 O 4 (p-Co 3 O 4 ) hollow cubes during galvanic replacement reaction (GRR). In addition, the Pd NPs encapsulated in MOF and residual Co 3 O 4 clusters partially remained after GRR led to uniform functionalization of efficient cocatalysts (PdO NPs and p-Co 3 O 4 islands) on the porous and hollow polyhedron SnO 2 structures. Due to high gas accessibility through the meso- and macrosized pores in MOF-templated oxides and effective modulation of electron depletion layer assisted by the creation of numerous p-n junctions, the GRR-treated SnO 2 structures exhibited 21.9-fold higher acetone response (R air /R gas = 22.8 @ 5 ppm acetone, 90%RH) compared to MOF-templated p-Co 3 O 4 hollow structures. To the best of our knowledge, the selectivity and response amplitudes reported here for the detection of acetone are superior to those MOF derived metal oxide sensing layers reported so far. Our results demonstrate that highly active MOF-derived sensing layers can be achieved via p-n semiconducting phase transition, driven by a simple and versatile GRR process combined with MOF templating route.

Beyond the structure-property relationship paradigm: influence of the crystal structure and microstructure on the Li+ conductivity of La2/3Li(x)Ti(1-x)Al(x)O3 Oxides.

PubMed

García-Martín, Susana; Morata-Orrantía, Ainhoa; Alario-Franco, Miguel A; Rodríguez-Carvajal, Juan; Amador, Ulises

2007-01-01

The crystal structures of several oxides of the La(2/3)Li(x)Ti(1-x)Al(x)O(3) system have been studied by selected-area electron diffraction, high-resolution transmission electron microscopy, and powder neutron diffraction, and their lithium conductivity has been by complex impedance spectroscopy. The compounds have a perovskite-related structure with a unit cell radical2 a(p)x2 a(p)x radical2 a(p) (a(p)=perovskite lattice parameter) due to the tilting of the (Ti/Al)O(6) octahedra and the ordering of lanthanum and lithium ions and vacancies along the 2 a(p) axis. The Li(+) ions present a distorted square-planar coordination and are located in interstitial positions of the structure, which could explain the very high ionic conductivity of this type of material. The lithium conductivity depends on the oxide composition and its crystal microstructure, which varies with the thermal treatment of the sample. The microstructure of these titanates is complex due to formation of domains of ordering and other defects such as strains and compositional fluctuations.

Engineering birnessite-type MnO2 nanosheets on fiberglass for pH-dependent degradation of methylene blue

NASA Astrophysics Data System (ADS)

Xin Zhang, Yu; Long Guo, Xiao; Huang, Ming; Dong Hao, Xiao; Yuan, Yuan; Hua, Chao

2015-08-01

We construct hierarchical MnO2 nanosheets @ fiberglass nanostructures via one-pot hydrothermal method without any surfactants. The morphology and structure of MnO2-modified fiberglass composites are examined by focus ion beam scanning electron microscopy (FIB/SEM), X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The birnessite-type MnO2 nanosheets are observed to grow vertically on the surface of fiberglass. Furthermore, the birnessite-type MnO2-fiberglass composites exhibit good ability for degradation of methylene blue (MB) in different pH levels. In neutral solution (pH 6.5-7.0), it achieves a high removal rate of 96.1% (2 h, at 60 °C) in the presence of H2O2; and in acidic environment (pH 1.5), 96.8% of MB solution (20 mg/L, 100 mL) is decomposed by oxidation within only 5 min. In principles, the rational design of MnO2 nanosheets-decorated fiberglass architectures demonstrated the suitability of the low-cost MnO2-modified fiberglass nanostructure for water treatment.

Polymorphism of a widely used building block for halogen-bonded assemblies: 1,3,5-trifluoro-2,4,6-triiodobenzene.

PubMed

Raffo, Pablo A; Suárez, Sebastián; Fantoni, Adolfo C; Baggio, Ricardo; Cukiernik, Fabio D

2017-09-01

After reporting the structure of a new polymorph of 1,3,5-trifluoro-2,4,6-triiodobenzene (denoted BzF3I3), C 6 F 3 I 3 , (I), which crystallized in the space group P2 1 /c, we perform a comparative analysis with the already reported P2 1 /n polymorph, (II) [Reddy et al. (2006). Chem. Eur. J. 12, 2222-2234]. In polymorph (II), type-II I...I halogen bonds and I...π interactions connect molecules in such a way that a three-dimensional structure is formed; however, the way in which molecules are connected in polymorph (I), through type-II I...I halogen bonds and π-π interactions, gives rise to an exfoldable lamellar structure, which looks less tightly bound than that of (II). In agreement with this structural observation, both the melting point and the melting enthalpy of (I) are lower than those of (II).

Structure-Induced Reversible Anionic Redox Activity in Na Layered Oxide Cathode

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

Rong, Xiaohui; Liu, Jue; Hu, Enyuan

Anionic redox reaction (ARR) in lithium- and sodium-ion batteries is under hot discussion, mainly regarding how oxygen anion participates and to what extent oxygen can be reversibly oxidized and reduced. In this paper, a P3-type Na 0.6[Li 0.2Mn 0.8]O 2 with reversible capacity from pure ARR was studied. The interlayer O-O distance (peroxo-like O-O dimer, 2.506(3) Å), associated with oxidization of oxygen anions, was directly detected by using a neutron total scattering technique. Finally, different from Li 2RuO 3 or Li 2IrO 3 with strong metal-oxygen (M-O) bonding, for P3-type Na 0.6[Li 0.2Mn 0.8]O 2 with relatively weak Mn-O covalentmore » bonding, crystal structure factors might play an even more important role in stabilizing the oxidized species, as both Li and Mn ions are immobile in the structure and thus may inhibit the irreversible transformation of the oxidized species to O 2 gas.« less

Structure-Induced Reversible Anionic Redox Activity in Na Layered Oxide Cathode

DOE PAGES

Rong, Xiaohui; Liu, Jue; Hu, Enyuan; ...

2017-11-01

Anionic redox reaction (ARR) in lithium- and sodium-ion batteries is under hot discussion, mainly regarding how oxygen anion participates and to what extent oxygen can be reversibly oxidized and reduced. In this paper, a P3-type Na 0.6[Li 0.2Mn 0.8]O 2 with reversible capacity from pure ARR was studied. The interlayer O-O distance (peroxo-like O-O dimer, 2.506(3) Å), associated with oxidization of oxygen anions, was directly detected by using a neutron total scattering technique. Finally, different from Li 2RuO 3 or Li 2IrO 3 with strong metal-oxygen (M-O) bonding, for P3-type Na 0.6[Li 0.2Mn 0.8]O 2 with relatively weak Mn-O covalentmore » bonding, crystal structure factors might play an even more important role in stabilizing the oxidized species, as both Li and Mn ions are immobile in the structure and thus may inhibit the irreversible transformation of the oxidized species to O 2 gas.« less

Binding of Diverse Environmental Chemicals with Human Cytochromes P450 2A13, 2A6, and 1B1 and Enzyme Inhibition

PubMed Central

Shimada, Tsutomu; Kim, Donghak; Murayama, Norie; Tanaka, Katsuhiro; Takenaka, Shigeo; Nagy, Leslie D.; Folkman, Lindsay M.; Foroozesh, Maryam K.; Komori, Masayuki; Yamazaki, Hiroshi; Guengerich, F. Peter

2014-01-01

A total of 68 chemicals including derivatives of naphthalene, phenanthrene, fluoranthene, pyrene, biphenyl, and flavone were examined for their abilities to interact with human P450s 2A13 and 2A6. Fifty-one of these 68 chemicals induced stronger Type I binding spectra (iron low- to high-spin state shift) with P450 2A13 than those seen with P450 2A6, i.e. the spectral binding intensities (ΔAmax/Ks ratio) determined with these chemicals were always higher for P450 2A13. In addition, benzo[c]phenanthrene, fluoranthene, 2,3-dihydroxy-2,3-dihydrofluoranthene, pyrene, 1-hydroxypyrene, 1-nitropyrene, 1-acetylpyrene, 2-acetylpyrene, 2,5,2’,5’-tetrachlorobiphenyl, 7-hydroxyflavone, chrysin, and galangin were found to induce a Type I spectral change only with P450 2A13. Coumarin 7-hydroxylation, catalyzed by P450 2A13, was strongly inhibited by 2’-methoxy-5,7-dihydroxyflavone, 2-ethynylnaphthalene, 2’-methoxyflavone, 2-naphththalene propargyl ether, acenaphthene, acenaphthylene, naphthalene, 1-acetylpyrene, flavanone, chrysin, 3-ethynylphenanthrene, flavone, and 7-hydroxyflavone; these chemicals induced Type I spectral changes with low Ks values. On the basis of the intensities of the spectral changes and inhibition of P450 2A13, we classified the 68 chemicals into eight groups based on the order of affinities for these chemicals and inhibition of P450 2A13. The metabolism of chemicals by P450 2A13 during the assays explained why some of the chemicals that bound well were poor inhibitors of P450 2A13. Finally, we compared the 68 chemicals for their abilities to induce Type I spectral changes of P450 2A13 with the Reverse Type I binding spectra observed with P450 1B1: 45 chemicals interacted with both P450s 2A13 and 1B1, indicating that the two enzymes have some similarty of structural features regarding these chemicals. Molecular docking analyses suggest similarities at the active sites of these P450 enzymes. These results indicate that P450 2A13, as well as Family 1 P450 enzymes, is able to catalyze many detoxication and activation reactions with chemicals of environmental interest. PMID:23432429

The Electronic Structure and Formation Energies of Ni-doped CuAlO2 by Density Functional Theory Calculation

NASA Astrophysics Data System (ADS)

Xu, Ying; Li, Fei; Sheng, Wei; Nie, Guo-Zheng; Yuan, Ding-Wang

2014-03-01

The electronic structure and formation energies of Ni-doped CuAlO2 are calculated by first-principles calculations. Our results show that Ni is good for p-type doping in CuAlO2. When Ni is doped into CuAlO2, it prefers to substitute Al-site. NiAl is a shallow acceptor, while NiCu is a deep acceptor and its formation energy is high. Further electronic structure calculations show that strong hybridization happens between Ni-3d and O-2p states for Ni substituting Al-site, while localized Ni-3d states are found for Ni substituting Cu-site.

Second-sphere coordination in anion binding: Synthesis, characterization and X-ray structures of bis(diethylenetriamine)cobalt(III) complexes containing benzoates

NASA Astrophysics Data System (ADS)

Bala, Ritu; Kaur, Amrinder; Kashyap, Monika; Janzen, Daron E.

2014-04-01

New complexes of composition s-fac-[Co(dien)2]Cl2(Bz)·H2O (1), s-fac-[Co(dien)2]Cl(p-CBz)2·4.5H2O (2) and mer-[Co(dien)2](p-NBz)3·3H2O (3) were obtained by reacting aqueous solutions of bis(diethylenetriamine)cobalt(III) chloride and sodium salts of benzoates ((Bz = benzoate, CBz = p-chlorobenzoate, NBz = p-nitrobenzoate)) in 1:3 molar ratio. These complexes were characterized by TG analysis and spectroscopic studies (IR, NMR and UV-vis). IR and NMR studies were used for the isomeric identification of [Co(dien)2]3+ in new complexes. This cation, contains ligand diethylenetriamine (dien) bearing H-bond donors, capable of forming hydrogen bonds and its binding properties with benzoates have been studied using standard UV-vis spectroscopic titrations in aqueous medium (log k for Bz = 2.11, p-CBz = 3.64 and p-NBz = 3.66). Single crystal X-ray study of complex 2 and 3 reveals that both the structures are dominantly stabilized by second-sphere coordination through H-bonding interactions of type-NH (dien)⋯O (benzoates) and H (water)⋯O (benzoates) in addition to the electrostatic forces of attractions. Further, the NH (dien)⋯Cl- (counter ion) and NH (dien)⋯O (water) types of interactions are also playing a dominant role to stabilize the crystal lattice in complex 2 and 3 respectively.

Phosphorylation of the human respiratory syncytial virus P protein mediates M2-2 regulation of viral RNA synthesis, a process that involves two P proteins.

PubMed

Asenjo, Ana; Villanueva, Nieves

2016-01-04

The M2-2 protein regulates the balance between human respiratory syncytial virus (HRSV) transcription and replication. Here it is shown that M2-2 mediated transcriptional inhibition is managed through P protein phosphorylation. Transcription inhibition by M2-2 of the HRSV based minigenome pRSVluc, required P protein phosphorylation at serines (S) in positions 116, 117, 119 and increased inhibition is observed if S232 or S237 is also phosphorylated. Phosphorylation of these residues is required for viral particle egression from infected cells. Viral RNA synthesis complementation assays between P protein variants, suggest that two types of P proteins participate in the process as components of RNA dependent RNA polymerase (RdRp). Type I is only functional when, as a homotetramer, it is bound to N and L proteins through residues 203-241. Type II is functionally independent of these interactions and binds to N protein at a region outside residues 232-241. P protein type I phosphorylation at S116, S117 and S119, did not affect the activity of RdRp but this phosphorylation in type II avoids its interaction with N protein and impairs RdRp functionality for transcription and replication. Structural changes in the RdRp, mediated by phosphorylation turnover at the indicated residues, in the two types of P proteins, may result in a fine adjustment, late in the infectious cycle, of transcription, replication and progression in the morphogenetic process that ends in egression of the viral particles from infected cells. Copyright © 2015 Elsevier B.V. All rights reserved.

Atomic resolution view into the structure–function relationships of the human myelin peripheral membrane protein P2

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

Ruskamo, Salla; University of Oulu, Oulu; Yadav, Ravi P.

2014-01-01

The structure of the human myelin peripheral membrane protein P2 has been refined at 0.93 Å resolution. In combination with functional experiments in vitro, in vivo and in silico, the fine details of the structure–function relationships in P2 are emerging. P2 is a fatty acid-binding protein expressed in vertebrate peripheral nerve myelin, where it may function in bilayer stacking and lipid transport. P2 binds to phospholipid membranes through its positively charged surface and a hydrophobic tip, and accommodates fatty acids inside its barrel structure. The structure of human P2 refined at the ultrahigh resolution of 0.93 Å allows detailed structuralmore » analyses, including the full organization of an internal hydrogen-bonding network. The orientation of the bound fatty-acid carboxyl group is linked to the protonation states of two coordinating arginine residues. An anion-binding site in the portal region is suggested to be relevant for membrane interactions and conformational changes. When bound to membrane multilayers, P2 has a preferred orientation and is stabilized, and the repeat distance indicates a single layer of P2 between membranes. Simulations show the formation of a double bilayer in the presence of P2, and in cultured cells wild-type P2 induces membrane-domain formation. Here, the most accurate structural and functional view to date on P2, a major component of peripheral nerve myelin, is presented, showing how it can interact with two membranes simultaneously while going through conformational changes at its portal region enabling ligand transfer.« less

The Primary Patency and Fracture Rates of Self-Expandable Nitinol Stents Placed in the Popliteal Arteries, Especially in the P2 and P3 Segments, in Korean Patients

PubMed Central

Chang, Il Soo; Park, Sang Woo; Yun, Ik Jin; Hwang, Jae Joon; Lee, Song Am; Kim, Jun Seok; Chang, Seong-Hwan; Jung, Hong Geun

2011-01-01

Objective We wanted to evaluate the status of self-expandable nitinol stents implanted in the P2 and P3 segments of the popliteal artery in Korean patients. Materials and Methods We retrospectively analyzed 189 consecutive patients who underwent endovascular treatment for stenoocclusive lesions in the femoropopliteal artery from July 2003 to March 2009, and 18 patients who underwent stent placement in popliteal arterial P2 and P3 segments were finally enrolled. Lesion patency was evaluated by ultrasound or CT angiography, and stent fracture was assessed by plain X-rays at 1, 3, 6 and 12 months and annually thereafter. Results At the 1-month follow-up, stent fracture (Type 2) was seen in one limb (up to P3, 1 of 18, 6%) and it was identified in seven limbs at the 3-month follow-up (Type 2, Type 3, Type 4) (n = 1: up to P2; n = 6: P3). At the 6-month follow-up, one more fracture (Type 1) (up to P3) was noted. At the 1-year follow-up, there were no additional stent fractures. Just four limbs (up to P2) at the 2-year follow-up did not have stent fracture. The primary patency was 94%, 61% and 44% at 1, 3 and 6 months, respectively, and the group with stent implantation up to P3 had a higher fracture rate than that of the group that underwent stenting up to P2 (p < 0.05). Conclusion We suggest that stent placement up to the popliteal arterial P3 segment and over P2 in an Asian population can worsen the stent patency owing to stent fracture. It may be necessary to develop a stent design and structure for the Asian population that can resist the bending force in the knee joint. PMID:21430937

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.

An ab initio study of Cu-based delafossites as an alternative to nickel oxide in photocathodes: effects of Mg-doping and surface electronic features.

PubMed

Schiavo, Eduardo; Latouche, Camille; Barone, Vincenzo; Crescenzi, Orlando; Muñoz-García, Ana B; Pavone, Michele

2018-05-23

CuMO2 delafossites (M = Al, Ga, and Cr) are p-type semiconductor oxides that have been recently proposed as the electrode in p-type dye-sensitized solar cells (p-DSSC) which is an alternative to the standard, low-performing nickel oxide. To assess this potential application of delafossites, we report here a DFT-based investigation of the structural and electronic properties of CuAlO2, CuGaO2 and CuCrO2. In particular, we address the role of Mg doping to obtain the p-type semiconducting character: the substitution of an M3+ cation with Mg2+ is easier with Ga than with Al and Cr, and, in all cases, the hole introduced by Mg2+ leads to the formation of Cu2+ species. Moreover, we address surface electronic features in order to characterize the most exposed delafossite surface termination and, more importantly, to predict the valence band maximum energy value, which determines the p-DSSC open circuit potential. From analysis of all our results, CuGaO2 emerges as the most promising system that can boost the development of new photocathodes for p-DSSCs.

Synthesis and characterization of novel barium iron phosphates: Insight into new structure types tailored by hydrogen atoms

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

Sun, Li-Zhi, E-mail: tslz2007@163.com; Sun, Wei, E-mail: 421221789@qq.com; Ren, Wei-Jian, E-mail: 935428502@qq.com

A significant gap in our knowledge of phosphate crystal chemistry is the lack of understanding of what controls the depolymerization of [PO{sub 4}] tetrahedra. A new route using phosphoric acid without any added water at 240 °C has been developed to synthesize two new compounds Ba{sub 2}Fe{sub 2}[H(PO{sub 3}OH){sub 2}][H(P{sub 2}O{sub 7}){sub 2}] and Ba{sub 2}Fe[H(P{sub 2}O{sub 7}){sub 2}], as well as a new polymorph β-BaFe{sub 2}(P{sub 2}O{sub 7}){sub 2} from annealing the former at ≥500 °C. Structural characterizations show that Ba{sub 2}Fe{sub 2}[H(PO{sub 3}OH){sub 2}][H(P{sub 2}O{sub 7}){sub 2}] features a novel 2D {sup 2}{sub ∞}([Fe{sub 2}[H(PO{sub 3}OH){sub 2}][H(P{sub 2}O{submore » 7}){sub 2}

Crystal Structure of Ribosome-Inactivating Protein Ricin A Chain in Complex with the C-Terminal Peptide of the Ribosomal Stalk Protein P2.

PubMed

Shi, Wei-Wei; Tang, Yun-Sang; Sze, See-Yuen; Zhu, Zhen-Ning; Wong, Kam-Bo; Shaw, Pang-Chui

2016-10-13

Ricin is a type 2 ribosome-inactivating protein (RIP), containing a catalytic A chain and a lectin-like B chain. It inhibits protein synthesis by depurinating the N-glycosidic bond at α-sarcin/ricin loop (SRL) of the 28S rRNA, which thereby prevents the binding of elongation factors to the GTPase activation center of the ribosome. Here, we present the 1.6 Å crystal structure of Ricin A chain (RTA) complexed to the C-terminal peptide of the ribosomal stalk protein P2, which plays a crucial role in specific recognition of elongation factors and recruitment of eukaryote-specific RIPs to the ribosomes. Our structure reveals that the C-terminal GFGLFD motif of P2 peptide is inserted into a hydrophobic pocket of RTA, while the interaction assays demonstrate the structurally untraced SDDDM motif of P2 peptide contributes to the interaction with RTA. This interaction mode of RTA and P protein is in contrast to that with trichosanthin (TCS), Shiga-toxin (Stx) and the active form of maize RIP (MOD), implying the flexibility of the P2 peptide-RIP interaction, for the latter to gain access to ribosome.

Synthesis and structural characterization of polyoxometalates incorporating with anilinium cations and facile preparation of hybrid film

NASA Astrophysics Data System (ADS)

Fukaya, Keisuke; Srifa, Atthapon; Isikawa, Eri; Naruke, Haruo

2010-08-01

The self-assembly reaction of tungstate and copper(II) in the presence of aniline (ANI) and phosphoric acid led to the formation of an anilinium (ANIH +) salt of mono-substituted Keggin-type polyoxotungstophosphate (ANIH) 5[PCu(H 2O)W 11O 39](ANI)·8H 2O ( 1), while the reaction of heptamolybdate in the coexistence of copper(II), phosphoric acid and ANI yielded an ANIH + salt of Strandberg-type pentamolybdodiphosphate, (ANIH) 2[(PO 4) 2Mo 5O 15{Cu(ANI) 2(H 2O)} 2](ANI)·2H 2O ( 2). These compounds were characterized by elemental analysis, infrared spectroscopy and X-ray single-crystal analysis. The compound 1, crystallizing in trigonal, P3¯,a = 13.883(4), c = 10.187(3) Å, Z = 1, consists of copper mono-substituted Keggin-typed [PCu(H 2O)W 11O 39] 5- anion surrounded by six ANI molecules, of which five are protonated (ANIH +). The compound 2, crystallizing in triclinic, P1¯,a = 13.98(2), b = 14.73(1), c = 16.24(1) Å, α = 111.27(3), β = 97.42(3), γ = 99.54(4)°, Z = 2, consists of Strandberg-type pentamolybdodiphospate [(PO 4) 2Mo 5O 15] 6- anions interconnected by two Cu(ANI) 2(H 2O) linkers to form a 1D-chain structure. A potentiostatic electrolysis of 1 in aqueous solution gave rise to electropolymerization of the ANIH + cations (and ANI) and deposition with the [PCu(H 2O)W 11O 39] 5- anion on an ITO electrode, forming a nano-structured polyaniline/[PCu(H 2O)W 11O 39] 5- hybrid thin film.

Analysis of interphase node proteins in fission yeast by quantitative and superresolution fluorescence microscopy

PubMed Central

Akamatsu, Matthew; Lin, Yu; Bewersdorf, Joerg; Pollard, Thomas D.

2017-01-01

We used quantitative confocal microscopy and FPALM superresolution microscopy of live fission yeast to investigate the structures and assembly of two types of interphase nodes—multiprotein complexes associated with the plasma membrane that merge together and mature into the precursors of the cytokinetic contractile ring. During the long G2 phase of the cell cycle, seven different interphase node proteins maintain constant concentrations as they accumulate in proportion to cell volume. During mitosis, the total numbers of type 1 node proteins (cell cycle kinases Cdr1p, Cdr2p, Wee1p, and anillin Mid1p) are constant even when the nodes disassemble. Quantitative measurements provide strong evidence that both types of nodes have defined sizes and numbers of constituent proteins, as observed for cytokinesis nodes. Type 1 nodes assemble in two phases—a burst at the end of mitosis, followed by steady increase during interphase to double the initial number. Type 2 nodes containing Blt1p, Rho-GEF Gef2p, and kinesin Klp8p remain intact throughout the cell cycle and are constituents of the contractile ring. They are released from the contractile ring as it disassembles and then associate with type 1 nodes around the equator of the cell during interphase. PMID:28539404

Immunohistochemical Mapping of Sensory Nerve Endings in the Human Triangular Fibrocartilage Complex.

PubMed

Rein, Susanne; Semisch, Manuel; Garcia-Elias, Marc; Lluch, Alex; Zwipp, Hans; Hagert, Elisabet

2015-10-01

The triangular fibrocartilage complex is the main stabilizer of the distal radioulnar joint. While static joint stability is constituted by osseous and ligamentous integrity, the dynamic aspects of joint stability chiefly concern proprioceptive control of the compressive and directional muscular forces acting on the joint. Therefore, an investigation of the pattern and types of sensory nerve endings gives more insight in dynamic distal radioulnar joint stability. We aimed to (1) analyze the general distribution of sensory nerve endings and blood vessels; (2) examine interstructural distribution of sensory nerve endings and blood vessels; (3) compare the number and types of mechanoreceptors in each part; and (4) analyze intrastructural distribution of nerve endings at different tissue depth. The subsheath of the extensor carpi ulnaris tendon sheath, the ulnocarpal meniscoid, the articular disc, the dorsal and volar radioulnar ligaments, and the ulnolunate and ulnotriquetral ligaments were dissected from 11 human cadaver wrists. Sensory nerve endings were counted in five levels per specimen as total cell amount/cm(2) after staining with low-affinity neurotrophin receptor p75, protein gene product 9.5, and S-100 protein and thereafter classified according to Freeman and Wyke. All types of sensory corpuscles were found in the various structures of the triangular fibrocartilage complex with the exception of the ulnolunate ligament, which contained only Golgi-like endings, free nerve endings, and unclassifiable corpuscles. The articular disc had only free nerve endings. Furthermore, free nerve endings were the predominant sensory nerve ending (median, 72.6/cm(2); range, 0-469.4/cm(2)) and more prevalent than all other types of mechanoreceptors: Ruffini (median, 0; range, 0-5.6/cm(2); difference of medians, 72.6; p < 0.001), Pacini (median, 0; range, 0-3.8/cm(2); difference of medians, 72.6; p < 0.001), Golgi-like (median, 0; range, 0-2.1/cm(2); difference of medians, 72.6; p < 0.001), and unclassifiable corpuscles (median, 0; range, 0-2.5/cm(2); difference of medians, 72.6; p < 0.001). The articular disc contained fewer free nerve endings (median, 1.8; range, 0-17.8/cm(2)) and fewer blood vessels (median, 29.8; range, 0-112.2/cm(2); difference of medians: 255.9) than all other structures of the triangular fibrocartilage complex (p ≤ 0.001, respectively) except the ulnolunate ligament. More blood vessels were seen in the volar radioulnar ligament (median, 363.62; range, 117.8-871.8/cm(2)) compared with the ulnolunate ligament (median, 107.7; range, 15.9-410.3/cm(2); difference of medians: 255.91; p = 0.002) and the dorsal radioulnar ligament (median, 116.2; range, 53.9-185.1/cm(2); difference of medians: 247.47; p = 0.001). Free nerve endings were obtained in each structure more often than all other types of sensory nerve endings (p < 0.001, respectively). The intrastructural analysis revealed no differences in mechanoreceptor distribution in all investigated specimens with the numbers available, showing a homogenous distribution of proprioceptive qualities in all seven parts of the triangular fibrocartilage complex. Nociception has a primary proprioceptive role in the neuromuscular stability of the distal radioulnar joint. The articular disc and ulnolunate ligament rarely are innervated, which implies mainly mechanical functions, whereas all other structures have pronounced proprioceptive qualities, prerequisite for dynamic joint stability. Lesions of the volar and dorsal radioulnar ligaments have immense consequences not only for mechanical but also for dynamic stability of the distal radioulnar joint, and surgical reconstruction in instances of radioulnar ligament injury is important.

The interplay between tissue plasminogen activator domains and fibrin structures in the regulation of fibrinolysis: kinetic and microscopic studies

PubMed Central

Thelwell, Craig; Williams, Stella C.; Silva, Marta M. C. G.; Szabó, László; Kolev, Krasimir

2011-01-01

Regulation of tissue-type plasminogen activator (tPA) depends on fibrin binding and fibrin structure. tPA structure/function relationships were investigated in fibrin formed by high or low thrombin concentrations to produce a fine mesh and small pores, or thick fibers and coarse structure, respectively. Kinetics studies were performed to investigate plasminogen activation and fibrinolysis in the 2 types of fibrin, using wild-type tPA (F-G-K1-K2-P, F and K2 binding), K1K1-tPA (F-G-K1-K1-P, F binding), and delF-tPA (G-K1-K2-P, K2 binding). There was a trend of enzyme potency of tPA > K1K1-tPA > delF-tPA, highlighting the importance of the finger domain in regulating activity, but the differences were less apparent in fine fibrin. Fine fibrin was a better surface for plasminogen activation but more resistant to lysis. Scanning electron and confocal microscopy using orange fluorescent fibrin with green fluorescent protein-labeled tPA variants showed that tPA was strongly associated with agglomerates in coarse but not in fine fibrin. In later lytic stages, delF-tPA-green fluorescent protein diffused more rapidly through fibrin in contrast to full-length tPA, highlighting the importance of finger domain-agglomerate interactions. Thus, the regulation of fibrinolysis depends on the starting nature of fibrin fibers and complex dynamic interaction between tPA and fibrin structures that vary over time. PMID:20966169

Screening of medicinal plant phytochemicals as natural antagonists of p53-MDM2 interaction to reactivate p53 functioning.

PubMed

Riaz, Muhammad; Ashfaq, Usman A; Qasim, Muhammad; Yasmeen, Erum; Ul Qamar, Muhammad T; Anwar, Farooq

2017-10-01

In most types of cancer, overexpression of murine double minute 2 (MDM2) often leads to inactivation of p53. The crystal structure of MDM2, with a 109-residue amino-terminal domain, reveals that MDM2 has a core hydrophobic region to which p53 binds as an amphipathic α helix. The interface depends on the steric complementarity between MDM2 and the hydrophobic region of p53. Especially, on p53's triad, amino acids Phe19, Trp23 and Leu26 bind to the MDM2 core. Results from studies suggest that the structural motif of both p53 and MDM2 can be attributed to similarities in the amphipathic α helix. Thus, in the current investigation it is hypothesized that the similarity in the structural motif might be the cause of p53 inactivation by MDM2. Hence, molecular docking and phytochemical screening approaches are appraised to inhibit the hydrophobic cleft of MDM2 and to stop p53-MDM2 interaction, resulting in reactivation of p53 activity. For this purpose, a library of 2295 phytochemicals were screened against p53-MDM2 to find potential candidates. Of these, four phytochemicals including epigallocatechin gallate, alvaradoin M, alvaradoin E and nordihydroguaiaretic acid were found to be potential inhibitors of p53-MDM2 interaction. The screened phytochemicals, derived from natural extracts, may have negligible side effects and can be explored as potent antagonists of p53-MDM2 interactions, resulting in reactivation of the normal transcription of p53.

Layered P2-Na 2/3 Co 1/2 Ti 1/2 O 2 as a high-performance cathode material for sodium-ion batteries

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

Sabi, Noha; Doubaji, Siham; Hashimoto, Kazuki

Layered oxides are regarded as promising cathode materials for sodium-ion batteries. We present Na2/3Co1/2Ti1/2O2 as a potential new cathode material for sodium-ion batteries. The crystal features and morphology of the pristine powder were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The cathode material is evaluated in galvanostatic charge-discharge and galvanostatic intermittent titration tests, as well as ex-situ X-ray diffraction analysis. Synthesized by a high-temperature solid state reaction, Na2/3Co1/2Ti1/2O2 crystallizes in P2-type structure with P6(3)/mmc space group. The material presents reversible electrochemical behavior and delivers a specific discharge capacity of 100 mAh g(-1) when tested in Na halfmore » cells between 2.0 and 4.2 V (vs. Na+/Na), with capacity retention of 98% after 50 cycles. Furthermore, the electrochemical cycling of this titanium-containing material evidenced a reduction of the potential jumps recorded in the NaxCoO2 parent phase, revealing a positive impact of Ti substitution for Co. The ex-situ XRD measurements confirmed the reversibility and stability of the material. No structural changes were observed in the XRD patterns, and the P2-type structure was stable during the charge/discharge process between 2.0 and 4.2 V vs. Na+/Na. These outcomes will contribute to the progress of developing low cost electrode materials for sodium-ion batteries. (C) 2017 Elsevier B.V. All rights reserved.« less

Ternary Bismuthide SrPtBi 2: Computation and Experiment in Synergism to Explore Solid-State Materials

DOE PAGES

Gui, Xin; Zhao, Xin; Sobczak, Zuzanna; ...

2018-02-14

A combination of theoretical calculation and the experimental synthesis to explore the new ternary compound is demonstrated in the Sr–Pt–Bi system. Because Pt–Bi is considered as a new critical charge-transfer pair for superconductivity, it inspired us to investigate the Sr–Pt–Bi system. With a thorough calculation of all the known stable/metastable compounds in the Sr–Pt–Bi system and crystal structure predictions, the thermodynamic stability of hypothetical stoichiometry, SrPtBi2, is determined. Following the high-temperature synthesis and crystallographic analysis, the first ternary bismuthide in Sr–Pt–Bi, SrPtBi2 was prepared, and the stoichiometry was confirmed experimentally. SrPtBi 2 crystallizes in the space group Pnma (S.G. 62,more » Pearson Symbol oP48), which matches well with theoretical prediction using an adaptive genetic algorithm. Using first-principles calculations, we demonstrate that the orthorhombic structure has lower formation energies than other 112 structure types, such as tetragonal BaMnBi 2 (CuSmP 2) and LaAuBi 2 (CuHfSi 2) structure types. The bonding analysis indicates that the Pt–Bi interactions play a critical role in structural stability. The physical property measurements show the metallic properties at the low temperature, which agrees with the electronic structure assessment.« less

New members of the A{sub 2}M′M{sub 2}{sup ″} structure family (A=Ca, Sr, Yb, La; M′=In,Sn,Pb; M″=Si,Ge)

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

Jehle, Michael; Dürr, Ines; Fink, Saskia

The new mixed tetrelides Sr{sub 2}PbGe{sub 2} and Yb{sub 2}SnGe{sub 2}, several mixed Ca/Sr (A{sup II}) germanides A{sub 2}{sup II}(Sn,Pb)Ge{sub 2} and two polymorphs of La{sub 2}InSi{sub 2} represent new members of the general structure family of ternary alkaline-earth/lanthanoid main group silicides/germanides A{sub 2}M′M{sub 2}{sup ″}(M′=In,Sn,Pb;M″=Si,Ge). All compounds were synthesized from melts of the elements and their crystal structures have been determined by means of single crystal X-ray diffraction. Sr{sub 2}PbGe{sub 2} (Cmmm, a=402.36(11), b=1542.3(4), c=463.27(10) pm) crystallizes with the Mn{sub 2}AlB{sub 2}-type structure. In exhibiting infinite planar Ge zig-zag chains, it represents one border of the compound series. Themore » other borderline case, where only [Ge{sub 2}] dumbbells are left as Ge building units, is represented by the Ca/Yb tin germanides Ca{sub 2}SnGe{sub 2} and Yb{sub 2}SnGe{sub 2} (Mo{sub 2}FeB{sub 2}-type; P4/mbm, a=748.58(13)/740.27(7), c=445.59(8)/435.26(5) pm). In between these two border structures compounds with variable Si/Ge chain lengths could be obtained by varying the averaged size of the A{sup II} cations: Ca{sub 0.45}Sr{sub 1.55}PbGe{sub 2} (new structure type; Pbam, a=791.64(5), b=2311.2(2), c=458.53(3) pm) contains planar six-membered chain segments [Ge{sub 6}]. Tetrameric pieces [Ge{sub 4}] are the conspicuous structure elements in Ca{sub 1.16}Sr{sub 0.84}SnGe{sub 2} and La{sub 2}InSi{sub 2} (La{sub 2}InNi{sub 2}-type; Pbam, a=781.01(2)/762.01(13), b=1477.95(3)/1494.38(6), c=457.004(9)/442.1(3) pm). The tetragonal form of ’La{sub 2}InSi{sub 2}{sup ′} (exact composition: La{sub 2}In{sub 1.07}Si{sub 1.93}, P4/mbm, a=1309.11(12), c=443.32(4) pm) also crystallizes in a new structure type, containing only [Si{sub 3}] trimers as cutouts of the planar chains. In all structures the Si/Ge zig-zag chains/chain segments are connected by In/Sn/Pb atoms to form planar M layers, which are separated by pure A layers. Band structure calculations within the FP-LAPW DFT approach together with the Zintl formalism, extended by the presence of hypervalent bonding of the heavier M′ elements, give insight into the chemical bonding of this series of p-block metallides. An analysis of the band structure for the border phases Sr{sub 2}PbGe{sub 2} and Ca{sub 2}SnGe{sub 2} shows the considerable π bonding contributions within the Ge building units, which also become apparent from the short Ge–Ge bond lengths. - Graphical abstract: Example of one of the mixed metallides A{sub 2}(In/Sn/Pb)(Si/Ge){sub 2} with planar Si/Ge zig-zag chain segments of variable lengths. - Highlights: • Mixed metallides A{sub 2}(In/Sn/Pb)(Si/Ge){sub 2} were prepared for A=Ca, Sr, Yb, La. • The structures exhibit planar Si/Ge zig-zag chain segments of variable lengths. • In, Sn and Pb atoms are connecting the Si/Ge anions to planar nets. • Atomic size effects are investigated by the synthesis of mixed Ca/Sr germanides. • Bandstructure calculations indicate Si/Ge–Si/Ge π bonding contributions.« less

Synthesis and crystal structures of (2 E )-1,4-bis(4-chlorophenyl)but-2-ene-1,4-dione and (2 E )-1,4-bis(4-bromophenyl)but-2-ene-1,4-dione

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

Lastovickova, Dominika N.; La Scala, John J.; Sausa, Rosario C.

The molecular structure of (2 E )-1,4-bis(4-chlorophenyl)but-2-ene-1,4-dione [C 16 H 10 Cl 2 O 2 , ( 1 )] is composed of two p -chlorophenyl rings, each bonded on opposite ends to a near planar 1,4- trans enedione moiety [–C(=O)—CH=CH—(C=O)–] [r.m.s. deviation = 0.003 (1) Å]. (2 E )-1,4-Bis(4-bromophenyl)but-2-ene-1,4-dione [C 16 H 10 Br 2 O 2 , ( 2 )] has a similar structure to ( 1 ), but with two p -bromophenyl rings and a less planar enedione group [r.m.s. deviation = 0.011 (1) Å]. Both molecules sit on a center of inversion, thus Z ′ = 0.5. The dihedral angles between themore » ring and the enedione group are 16.61 (8) and 15.58 (11)° for ( 1 ) and ( 2 ), respectively. In the crystal, molecules of ( 1 ) exhibit C—Cl...Cl type I interactions, whereas molecules of ( 2 ) present C—Br...Br type II interactions. van der Waals-type interactions contribute to the packing of both molecules, and the packing reveals face-to-face ring stacking with similar interplanar distances of approximately 3.53 Å.« less

Synthesis and crystal structures of (2 E )-1,4-bis(4-chlorophenyl)but-2-ene-1,4-dione and (2 E )-1,4-bis(4-bromophenyl)but-2-ene-1,4-dione

DOE PAGES

Lastovickova, Dominika N.; La Scala, John J.; Sausa, Rosario C.

2018-02-13

The molecular structure of (2 E )-1,4-bis(4-chlorophenyl)but-2-ene-1,4-dione [C 16 H 10 Cl 2 O 2 , ( 1 )] is composed of two p -chlorophenyl rings, each bonded on opposite ends to a near planar 1,4- trans enedione moiety [–C(=O)—CH=CH—(C=O)–] [r.m.s. deviation = 0.003 (1) Å]. (2 E )-1,4-Bis(4-bromophenyl)but-2-ene-1,4-dione [C 16 H 10 Br 2 O 2 , ( 2 )] has a similar structure to ( 1 ), but with two p -bromophenyl rings and a less planar enedione group [r.m.s. deviation = 0.011 (1) Å]. Both molecules sit on a center of inversion, thus Z ′ = 0.5. The dihedral angles between themore » ring and the enedione group are 16.61 (8) and 15.58 (11)° for ( 1 ) and ( 2 ), respectively. In the crystal, molecules of ( 1 ) exhibit C—Cl...Cl type I interactions, whereas molecules of ( 2 ) present C—Br...Br type II interactions. van der Waals-type interactions contribute to the packing of both molecules, and the packing reveals face-to-face ring stacking with similar interplanar distances of approximately 3.53 Å.« less

Synthesis and crystal structures of (2E)-1,4-bis-(4-chloro-phen-yl)but-2-ene-1,4-dione and (2E)-1,4-bis-(4-bromo-phen-yl)but-2-ene-1,4-dione.

PubMed

Lastovickova, Dominika N; La Scala, John J; Sausa, Rosario C

2018-03-01

The mol-ecular structure of (2 E )-1,4-bis-(4-chloro-phen-yl)but-2-ene-1,4-dione [C 16 H 10 Cl 2 O 2 , ( 1 )] is composed of two p -chlorophenyl rings, each bonded on opposite ends to a near planar 1,4- trans enedione moiety [-C(=O)-CH=CH-(C=O)-] [r.m.s. deviation = 0.003 (1) Å]. (2 E )-1,4-Bis(4-bromo-phen-yl)but-2-ene-1,4-dione [C 16 H 10 Br 2 O 2 , ( 2 )] has a similar structure to ( 1 ), but with two p -bromophenyl rings and a less planar enedione group [r.m.s. deviation = 0.011 (1) Å]. Both mol-ecules sit on a center of inversion, thus Z ' = 0.5. The dihedral angles between the ring and the enedione group are 16.61 (8) and 15.58 (11)° for ( 1 ) and ( 2 ), respectively. In the crystal, mol-ecules of ( 1 ) exhibit C-Cl⋯Cl type I inter-actions, whereas mol-ecules of ( 2 ) present C-Br⋯Br type II inter-actions. van der Waals-type inter-actions contribute to the packing of both mol-ecules, and the packing reveals face-to-face ring stacking with similar inter-planar distances of approximately 3.53 Å.

Synthesis and characterizaton of inorganic materials for sodium-ion batteries

NASA Astrophysics Data System (ADS)

Shanmugam, Rengarajan

Development of low-cost energy storage devices is critical for wide-scale implementation of intermittent renewable energy technologies and improving the electricity grid. Commercial devices remain prohibitively expensive or lack the performance specifications for a wider market reach. Na-ion batteries would perfectly suited for these large-scale applications as the raw materials (such as soda ash, salt, etc.) are plentiful, inexpensive and geographically unconstrained. However, extensive materials research on insertion electrodes is required for better understanding of the electrochemical and structural properties and engineering high performance Na-ion batteries. This thesis research involves exploratory study on new insertion materials with various crystallographic structure-types and extensive characterization of promising new inorganic compositions. Tunnel-type materials, sodium nickel phosphate-Na4Ni7(PO4)6, and sodium cobalt titanate- Na0.8Co0.4Ti1.6O4, were investigated to capitalize on the intrinsic structural stability offered by framework materials. Sol-gel and solid-state reaction synthetic techniques were employed for inorganic powder synthesis. Galvanostatic and potentiostatic testing confirm reversible sodium insertion/de-insertion reactions albeit with inadequate electrochemical characteristics (high voltage hysteresis> 1V). Subsequent efforts involved investigating layer-structured materials supporting fast ionic transport for better electrochemical performance. P2-sodium nickel titanate, Na2/3[Ni1/3Ti2/3]O2 (P2NT), with prismatic sodium co-ordination, was synthesized by solid-state technique. The 'bifunctional' oxide contains Ni2+/4+ and Ti4+/3+ redox couples with redox potentials of 3.6 V, 0.7 V vs. Na/Na+, respectively. This bifunctional approach would simplify electrode processing and provide cost reduction opportunities in battery manufacturing. The structural changes monitored using ex-situ XRD demonstrate a favorably broad solid-solution domain. Manganese substitution, to form P2-Na2/3[Ni1/3Mn1/3Ti1/3]O2 (P2NMT), provides an enhanced high-current performance due to faster interfacial kinetics and accelerated charge carrier transport as shown by impedance spectroscopy and DC testing. Structural properties of P2NT material were studied using neutron diffraction and atomisitic simulations. Rietveld refinement shows that Naf sites have lower site occupancy than Nae sites due to unfavorable repulsive interactions from inline transition metal atoms. Buckingham and Morse-type models accurately predicted the experimental lattice parameters. The energy landscape was explored using energy minimization runs on disordered supercells. The simulated density maps are in agreement with the experiment densities with evidence of stacking fault formation. O3-sodium nickel titanate, Na0.9[Ni0.45Ti0.55]O2 (O3NT) with octahedral sodium co-ordination was synthesized by solid-state reaction technique. The influence of titanium on the poor cycleability of the O3-type electrodes was investigated. Ex-situ XRD shows two phase regions, comprised of O3+P3 phases, and a solid solution region, comprised of P3 phase. O3NT provides an excellent capacity retention of 99% for 115 cycles at C/2 rate. The good cycleability is attributed to the relative invariance of net impedance during electrode cycling using impedance spectroscopy.

Crystal structures of OrfX2 and P47 from a Botulinum neurotoxin OrfX-type gene cluster.

PubMed

Gustafsson, Robert; Berntsson, Ronnie P-A; Martínez-Carranza, Markel; El Tekle, Geniver; Odegrip, Richard; Johnson, Eric A; Stenmark, Pål

2017-11-01

Botulinum neurotoxins are highly toxic substances and are all encoded together with one of two alternative gene clusters, the HA or the OrfX gene cluster. Very little is known about the function and structure of the proteins encoded in the OrfX gene cluster, which in addition to the toxin contains five proteins (OrfX1, OrfX2, OrfX3, P47, and NTNH). We here present the structures of OrfX2 and P47, solved to 2.1 and 1.8 Å, respectively. We show that they belong to the TULIP protein superfamily, which are often involved in lipid binding. OrfX1 and OrfX2 were both found to bind phosphatidylinositol lipids. © 2017 Federation of European Biochemical Societies.

Metal-loaded pollucite-like aluminophosphates: dissymmetrisation of crystal structures and physical properties

NASA Astrophysics Data System (ADS)

Shvanskaya, L. V.; Yakubovich, O. V.; Koshelev, A. V.; Vasiliev, A. N.

2018-02-01

Two aluminophosphate analogues of the mineral pollucite with the general formula Cs2(M,Al)3P3O12 (where M = Cu or Mn) have been synthesized by high-temperature flux and structurally characterized using the single-crystal X-ray diffraction. Both samples crystallize in cubic I4132 space group, Z = 8, with a = 13.5911(5) and a = 13.8544(7) for Cu- and Mn-loaded phases, respectively. Their framework structures are based on the ANA-type topology and exhibit the partial ordering of the metal (M/Al) and phosphorus (P) cations over the tetrahedral sites. The regular changes in cell dimensions and volumes in the row Cs2(Cu,Al)3P3O12→Cs2(Mn,Al)3P3O12 obviously correspond to increasing radii of the transition metal. The crystal chemical analysis of both pollucite-like phases show correlations between the difference in the radii size of tetrahedral cations and the degree of distortion of flexible ANA-type framework due to decreasing of the intertetrahedral angles (T-O-T). Magnetic susceptibility measurements indicate that both compounds are paramagnets in the temperature range of 2-300 K.

Simultaneous control of thermoelectric properties in p- and n-type materials by electric double-layer gating: New design for thermoelectric device

NASA Astrophysics Data System (ADS)

Takayanagi, Ryohei; Fujii, Takenori; Asamitsu, Atsushi

2015-05-01

We report a novel design of a thermoelectric device that can control the thermoelectric properties of p- and n-type materials simultaneously by electric double-layer gating. Here, p-type Cu2O and n-type ZnO were used as the positive and negative electrodes of the electric double-layer capacitor structure. When a gate voltage was applied between the two electrodes, holes and electrons accumulated on the surfaces of Cu2O and ZnO, respectively. The thermopower was measured by applying a thermal gradient along the accumulated layer on the electrodes. We demonstrate here that the accumulated layers worked as a p-n pair of the thermoelectric device.

Hierarchical heterostructures of p-type bismuth oxychloride nanosheets on n-type zinc ferrite electrospun nanofibers with enhanced visible-light photocatalytic activities and magnetic separation properties.

PubMed

Sun, Yucong; Shao, Changlu; Li, Xinghua; Guo, Xiaohui; Zhou, Xuejiao; Li, Xiaowei; Liu, Yichun

2018-04-15

P-type bismuth oxychloride (p-BiOCl) nanosheets were uniformly grown on n-type zinc ferrite (n-ZnFe 2 O 4 ) electrospun nanofibers via a solvothermal technique to form hierarchical heterostructures of p-BiOCl/n-ZnFe 2 O 4 (p-BiOCl/n-ZnFe 2 O 4 H-Hs). The density and loading amounts of the BiOCl nanosheets with exposed {0 0 1} facets were easily controlled by adjusting the reactant concentration in the solvothermal process. The p-BiOCl/n-ZnFe 2 O 4 H-Hs exhibited enhanced visible-light photocatalytic activities for the degradation of Rhodamine B (RhB). The apparent first-order rate of the p-BiOCl/n-ZnFe 2 O 4 H-Hs and its normalized constant were about 12.6- and 8-fold higher than pure ZnFe 2 O 4 nanofibers. This suggests that both the improved charge separation efficiency from the uniform p-n heterojunctions and the enlarged active surface sites from the hierarchical structures increase the photocatalytic performances. Furthermore, the p-BiOCl/n-ZnFe 2 O 4 H-Hs could be efficiently separated from the solution with an external magnetic field via the ferromagnetic behavior of ZnFe 2 O 4 nanofibers. The magnetic p-BiOCl/n-ZnFe 2 O 4 H-Hs with enhanced visible-light photocatalytic performances might have potential applications in water treatment. Copyright © 2018. Published by Elsevier Inc.

Pressure-induced structural transition in chalcopyrite ZnSiP2

NASA Astrophysics Data System (ADS)

Bhadram, Venkata S.; Krishna, Lakshmi; Toberer, Eric S.; Hrubiak, Rostislav; Greenberg, Eran; Prakapenka, Vitali B.; Strobel, Timothy A.

2017-05-01

The pressure-dependent phase behavior of semiconducting chalcopyrite ZnSiP2 was studied up to 30 GPa using in situ X-ray diffraction and Raman spectroscopy in a diamond-anvil cell. A structural phase transition to the rock salt type structure was observed between 27 and 30 GPa, which is accompanied by soft phonon mode behavior and simultaneous loss of Raman signal and optical transmission through the sample. The high-pressure rock salt type phase possesses cationic disorder as evident from broad features in the X-ray diffraction patterns. The behavior of the low-frequency Raman modes during compression establishes a two-stage, order-disorder phase transition mechanism. The phase transition is partially reversible, and the parent chalcopyrite structure coexists with an amorphous phase upon slow decompression to ambient conditions.

Combined use of EPR and 23Na MAS NMR spectroscopy for assessing the properties of the mixed cobalt-nickel-manganese layers of P3-NayCo1-2xNixMnxO2.

PubMed

Kalapsazova, M; Ivanova, S; Kukeva, R; Simova, S; Wegner, S; Zhecheva, E; Stoyanova, R

2017-10-11

Knowledge on the formation of mixed transition metal layers on lithium and sodium transition metal oxides, Li/Na(Co,Ni,Mn,)O 2 , determines the ability to control their electrochemical properties as electrode materials in alkaline ion batteries. Taking this into account, herein we combine the EPR and 23 Na MAS NMR spectroscopic techniques to gain insights into the structural peculiarities of the mixed cobalt-nickel-manganese layers of Na y Co 1-2x Ni x Mn x O 2 with a three-layer stacking (P3-type) structure. Two types of compositions are examined where diamagnetic Co 3+ and paramagnetic Ni 3+ and Mn 4+ are stabilized: Na 2/3 Co 1/3 Ni 1/3 Mn 1/3 O 2 and Na 1/2 Ni 1/2 Mn 1/2 O 2 . EPR spectroscopy operating in the X- and Q-band region is applied with an aim to improve the spectra resolution and, on the other hand, to provide straightforward information on the coordination of the transition metal ions inside the layers. The analysis of EPR spectra is based on the reference for the Mn 4+ and Ni 2+ ions occurring simultaneously in oxides with two layer stacking, P2-Na 2/3 Ni 1/3 Mn 2/3 O 2 . Complementary to EPR, 23 Na MAS NMR spectroscopy at high spinning rates is undertaken to assess the local structure of the Na nucleus in the layered P3-Na y Co 1-2x Ni x Mn x O 2 oxides. All results are discussed taking into account the EPR and NMR data for the well-known lithium analogues O3-LiCo 1/3 Ni 1/3 Mn 1/3 O 2 and O3-LiNi 1/2 Mn 1/2 O 2 . Finally, the structure peculiarities of the transition metal layers extracted from the EPR and NMR methods are demonstrated by electrochemical intercalation of Li + ions into P3-Na y Co 1-2x Ni x Mn x O 2 .

Origin of polymorphism of the two-dimensional group-IV monochalcogenides

NASA Astrophysics Data System (ADS)

Wu, Minghui; Wei, Su-Huai; Huang, Li

2017-11-01

Unlike other two-dimensional (2D) isovalent materials, the 2D group IV monochalcogenides, M X (M =Si , Ge, Sn, and Pb; X =S , Se, and Te), are found to be either in a black phosphorene-derived distorted NaCl-type (d -NaCl) structure or a recently predicted P m a 2 structure. Both M and X atoms in the d -NaCl structure are threefold coordinated, whereas M and X in the P m a 2 structure are fourfold and twofold coordinated, respectively. Using first-principles total energy and electronic structure calculations and a global structural search technique, we systematically investigated the mechanism underlying the polymorphism of the 2D group-IV monochalcogenides. Our analysis show that the relative stability of the two distinct crystallographic phases depends on the strength of the M -M covalent bond and the electronegativity difference between the constituent elements M and X . For small cations, the covalency plays more important role, whereas for large cations the Coulomb interaction becomes more dominant. Therefore, the Si X and Ge X compounds assume the P m a 2 structure, whereas the M X compounds with heavy cation elements (M =Sn and Pb) tend to adopt the d -NaCl structure.

Quantitative separation of murine leukemia virus proteins by reversed-phase high-pressure liquid chromatography reveals newly described gag and env cleavage products.

PubMed Central

Henderson, L E; Sowder, R; Copeland, T D; Smythers, G; Oroszlan, S

1984-01-01

The structural proteins of murine type C retroviruses are proteolytic cleavage products of two different precursor polyproteins coded by the viral gag and env genes. To further investigate the nature and number of proteolytic cleavages involved in virus maturation, we quantitatively isolated the structural proteins of the Rauscher and Moloney strains of type C murine leukemia virus (R-MuLV and M-MuLV, respectively) by reversed-phase high-pressure liquid chromatography. Proteins and polypeptides isolated from R-MuLV included p10, p12, p15, p30, p15(E), gp69, and gp71 and three previously undescribed virus components designated here as p10', p2(E), and p2(E). Homologous proteins and polypeptides were isolated from M-MuLV. Complete or partial amino acid sequences of all the proteins listed above were either determined in this study or were available in previous reports from this laboratory. These data were compared with those from the translation of the M-MuLV proviral DNA sequence (Shinnick et al., Nature [London] 293:543-548, 1981) to determine the exact nature of proteolytic cleavages for all the structural proteins described above and to determine the origin of p10' and p2(E)s. The results showed that, during proteolytic processing of gp80env from M-MuLV (M-gp 80env), a single Arg residue was excised between gp70 and p15(E) and a single peptide bond was cleaved between p15(E) and p2(E). The structure of M-gPr80env is gp70-(Arg)-p15(E)-p2(E). The data suggest that proteolytic cleavage sites in R-gp85env are identical to corresponding cleavage sites in M-gp80env. The p2(E)s are shown to be different genetic variants of p2(E) present in the uncloned-virus preparations. The data for R- and M-p10's shows that they are cleavage products of the gag precursor with the structure p10-Thr-Leu-Asp-Asp-OH. The complete structure of Pr65gag is p15-p12-p30-p10'. Stoichiometries of the gag and env cleavage products in mature R- and M-MuLV were determined. In each virus, gag cleavage products (p15, p12, p30, and p10 plus p10') were found in equimolar amounts and p15(E)s were equimolar with p2(E)s. The stoichiometry of gag to env cleavage products was 4:1. These data are consistent with the proposal that proteolytic processing of precursor polyproteins occurs after virus assembly and that the C-terminal portion of Pr15(E) [i.e., p15(E)-p2(E)] is located on the inner side of the lipid bilayer of the virus. Images PMID:6333515

Study of nanoparticles TiO{sub 2} thin films on p-type silicon substrate using different alcoholic solvents

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

Muaz, A. K. M.; Ruslinda, A. R.; Ayub, R. M.

2016-07-06

In this paper, sol-gel method spin coating technique is adopted to prepare nanoparticles titanium dioxide (TiO{sub 2}) thin films. The prepared TiO{sub 2} sol was synthesized using titanium butoxide act as a precursor and subjected to deposited on the p-type silicon oxide (p-SiO{sub 2}) and glass slide substrates under room temperature. The effect of different alcoholic solvents of methanol and ethanol on the structural, morphological, optical and electrical properties were systematically investigated. The coated TiO{sub 2} thin films were annealed in furnace at 773 K for 1 h. The structural properties of the TiO{sub 2} films were examined with X-raymore » Diffraction (XRD). From the XRD analysis, both solvents showing good crystallinity with anatase phase were the predominant structure. Atomic Force Microscopy (AFM) was employed to study the morphological of the thin films. The optical properties were investigated by Ultraviolet-visible (UV-Vis) spectroscopy were found that ethanol as a solvent give a higher optical transmittance if compare to the methanol solvent. The electrical properties of the nanoparticles TiO{sub 2} thin films were measured using two-point-probe technique.« less

Influence of valence electron concentration on Laves phases: Structures and phase stability of pseudo-binary MgZn 2-xPd x

DOE PAGES

Thimmaiah, Srinivasa; Miller, Gordon J.

2015-06-03

A series of pseudo-binary compounds MgZn 2-xPd x (0.15 ≤ x ≤ 1.0) were synthesized and structurally characterized to understand the role of valence electron concentration (vec) on the prototype Laves phase MgZn 2 with Pd-substitution. Three distinctive phase regions were observed with respect to Pd content, all exhibiting fundamental Laves phase structures: 0.1 ≤ x ≤ 0.3 (MgNi 2-type, hP24; MgZn 1.80Pd 0.20(2)), 0.4 ≤ x ≤ 0.6 (MgCu 2-type, cF24; MgZn 1.59Pd 0.41(2)), and 0.62 ≤ x ≤ 0.8 (MgZn 2-type, hP12: MgZn 1.37Pd 0.63(2)). Refinements from single-crystal X-ray diffraction indicated nearly statistical distributions of Pd and Znmore » atoms among the majority atom sites in these structures. Interestingly, the MgZn 2-type structure re-emerges in MgZn 2–xPd x at x ≈ 0.7 with the refined composition MgZn 1.37(2)Pd 0.63 and a c/a ratio of 1.59 compared to 1.64 for binary MgZn 2. Electronic structure calculations on a model “MgZn 1.25Pd 0.75” yielded a density of states (DOS) curve showing enhancement of a pseudogap at the Fermi level as a result of electronic stabilization due to the Pd addition. Moreover, integrated crystal orbital Hamilton population values show significant increases of orbital interactions for (Zn,Pd)–(Zn,Pd) atom pairs within the majority atom substructure, i.e., within the Kagomé nets as well as between a Kagomé net and an apical site, from binary MgZn 2 to the ternary “MgZn 1.25Pd 0.75”. Multi-centered bonding is evident from electron localization function plots for “MgZn 1.25Pd 0.75”, an outcome which is in accordance with analysis of other Laves phases.« less

Optical and electrical properties of p-type transparent conducting CuAlO2 thin film synthesized by reactive radio frequency magnetron sputtering technique

NASA Astrophysics Data System (ADS)

Saha, B.; Thapa, R.; Jana, S.; Chattopadhyay, K. K.

2010-10-01

Thin films of p-type transparent conducting CuAlO2 have been synthesized through reactive radio frequency magnetron sputtering on silicon and glass substrates at substrate temperature 300°C. Reactive sputtering of a target fabricated from Cu and Al powder (1:1.5) was performed in Ar+O2 atmosphere. The deposition parameters were optimized to obtain phase pure, good quality CuAlO2 thin films. The films were characterized by studying their structural, morphological, optical and electrical properties.

The critical role of sodium content on structure, morphology and electrochemical performance of layered P2-type NaxNi0.167Co0.167Mn0.67O2 for sodium ion batteries

NASA Astrophysics Data System (ADS)

Bao, Shuo; Luo, Shaohua; Wang, Zhiyuan; Wang, Qing; Hao, Aimin; Zhang, Yahui; Wang, Yingling

2017-09-01

P2-type manganese-based ternary transition metal oxides have triggered extensive researches as potential cathode materials for sodium ion batteries. However, these kinds of materials display the large difference in electrochemical performance with sodium content varying from 0.45 to 0.8, the relevant investigations on effects of sodium content are insufficient. In this work, we synthesize a series of spherical P2-type cathode materials NaxNi0.167Co0.167Mn0.67O2 with different sodium content (x = 0.45, 0.55, 0.67, 0.8, 0.9, 1) and investigate the effects of sodium content on structure and electrochemical performance. The results reveal that NaxNi0.167Co0.167Mn0.67O2 (x = 0.45, 0.55) consist of P2-phase and P3-phase, while NaxNi0.167Co0.167Mn0.67O2 (x = 0.67, 0.8, 0.9, 1) exhibit pure P2-phase. Na0.45Ni0.167Co0.167Mn0.67O2 delivers an initial discharge capacity of 143 mAh g-1, while a fast capacity decay is observed after 50 cycles. In comparison, Na0.67Ni0.167Co0.167Mn0.67O2 shows excellent cycling stability and rate performance. The significant difference in electrochemical performance is attributed to the initial sodium content, which leads to the existence of P3-phase. Moreover, higher sodium content promotes primary particles to grow larger and thicker, which is not favorable for the diffusion of Na+. Generally, Na0.67Ni0.167Co0.167Mn0.67O2 is favored by suitable sodium content, offers excellent electrochemical performance in terms of capacity, rate performance and cycling stability.

Achilles tendon adaptation in cross-country runners across a competitive season.

PubMed

Stanley, L E; Lucero, A; Mauntel, T C; Kennedy, M; Walker, N; Marshall, S W; Padua, D A; Berkoff, D J

2018-01-01

Ultrasound tissue characterization (UTC) is an imaging tool used to quantify tendon structural integrity. UTC has quantified Achilles tendon (AT) acute response to load in athletes; however, AT response to cumulative load over a season is unknown. The purpose of this study was to evaluate AT response across a four-month competitive season in collegiate cross-country (XC) runners. Participants (n=21; male=9, female=12; age=19.8±1.2 years; height=171.9±8.9 cm; weight=60.2±8.5 kg) were imaged using the UTC device with a 10-MHz linear-array transducer mounted in a tracking device. The device captures images at 0.2 mm intervals along the AT. UTC algorithms quantified the stability of pixel brightness over every 17 contiguous transverse images into four echo types (I-IV). A total of 168 scans (n=21, bilateral limbs) were performed monthly across the four-month season (Aug=M1, Sep=M2, Oct=M3, Nov=M4). Echo-type percentages (%) were calculated from each scan. Generalized estimating equations (GEE) linear regression models evaluated echo-type % change (β) over the season (M1=reference). Type I increased from M1 to M4 (β=9.10, P<.01; 95%CI: 7.01, 11.21) and Type II decreased from M1 to M3 (β=-2.71, P=.018; 95%CI: -4.96, -0.47) and M1 to M4 (β=-10.19, P<.01; 95%CI: -12.22, -8.17). Type III increased from M1 to M3 (β=0.42, P=.003; 95%CI: 0.19, 0.65) and M1 to M4 (β=0.49, P=.002; 95%CI: 0.18, 0.81), Type IV increased from M1 to M4 (β=0.57, P<.01; 95%CI: 0.29, 0.84). A positive adaptation in AT structural integrity was observed over the XC season, with a ~10% shift from Type II to Type I UTC echo types, suggesting AT resilience to a competitive season of repetitive loading in highly trained runners. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Self-trapping of holes in p-type oxides: Theory for small polarons in MnO

NASA Astrophysics Data System (ADS)

Peng, Haowei; Lany, Stephan

2012-02-01

Employing the p-d repulsion to increase the valence band dispersion and the energy of the VBM is an important design principle for p-type oxides, as manifested in prototypical p-type oxides like Cu2O or CuAlO2 which show a strong Cu-d/O-p interaction. An alternative opportunity to realize this design principle occurs for Mn(+II) compounds, where the p-d orbital interaction occurs dominantly in the fully occupied d^5 majority spin direction of Mn. However, the ability of Mn to change the oxidation state from +II to +III can lead to a small polaron mechanism for hole transport which hinders p-type conductivity. This work addresses the trends of hole self-trapping for MnO between octahedral (rock-salt structure) and tetrahedral coordination (zinc-blende structure). We employ an on-site hole-state potential so to satisfy the generalized Koopmans condition. This approach avoids the well-known difficulty of density-functional calculations to describe correctly the localization of polaronic states, and allows to quantitatively predict the self-trapping energies. We find that the tetrahedrally coordinated Mn is less susceptible to hole self-trapping than the octahedrally coordinated Mn.

Theoretical prediction of a self-forming gallium oxide layer at an n-type GaN/SiO2 interface

NASA Astrophysics Data System (ADS)

Chokawa, Kenta; Narita, Tetsuo; Kikuta, Daigo; Kachi, Tetsu; Shiozaki, Koji; Shiraishi, Kenji

2018-03-01

We examine the energy band diagram at the n-type GaN (n-GaN)/SiO2 interface and show that electron transfer from n-GaN to SiO2 leads to the formation of negatively charged oxygen vacancies in the SiO2, resulting in the self-formation of an n-GaN/Ga2O3/SiO2 structure. On the other hand, it is difficult to automatically form Ga2O3 at a p-type GaN (p-GaN)/SiO2 interface. This electron-transfer-induced self-formation of Ga2O3 causes an interface dipole, which leads to band bending, resulting in an increase in the conduction band offset between GaN and SiO2. Accordingly, by using this self-forming phenomenon, GaN MOSFETs with lower leakage current can be realized.

Models of metal binding structures in fulvic acid from the Suwannee River, Georgia

USGS Publications Warehouse

Leenheer, J.A.; Brown, G.K.; MacCarthy, P.; Cabaniss, S.E.

1998-01-01

Fulvic acid, isolated from the Suwannee River, Georgia, was assessed for its ability to bind Ca2+, Cd2+, Cu2+, Ni2+, and Zn2+ ions at pH 6 before and after extensive fractionation that was designed to reveal the nature of metal binding functional groups. The binding constant for Ca2+ ion had the greatest increase of all the ions in a metal binding fraction that was selected for intensive characterization for the purpose of building quantitative average model structures. The 'metal binding' fraction was characterized by quantitative 13C NMR, 1H NMR, and FT-1R spectrometry and elemental, titrimetric, and molecular weight determinations. The characterization data revealed that carboxyl groups were clustered in short- chain aliphatic dibasic acid structures. The Ca2+ binding data suggested that ether-substituted oxysuccinic acid structures are good models for the metal binding sites at pH 6. Structural models were derived based upon oxidation and photolytic rearrangements of cutin, lignin, and tannin precursors. These structural models rich in substituted dibasic acid structures revealed polydentate binding sites with the potential for both inner-sphere and outer-sphere type binding. The majority of the fulvic acid molecule was involved with metal binding rather than a small substructural unit.Fulvic acid, isolated from the Suwannee River, Georgia, was assessed for its ability to bind Ca2+, Cd2+, Cu2+, Ni2+, and Zn2+ ions at pH 6 before and after extensive fractionation that was designed to reveal the nature of metal binding functional groups. The binding constant for Ca2+ ion had the greatest increase of all the ions in a metal binding fraction that was selected for intensive characterization for the purpose of building quantitative average model structures. The `metal binding' fraction was characterized by quantitative 13C NMR, 1H NMR, and FT-IR spectrometry and elemental, titrimetric, and molecular weight determinations. The characterization data revealed that carboxyl groups were clustered in short-chain aliphatic dibasic acid structures. The Ca2+ binding data suggested that ether-substituted oxysuccinic acid structures are good models for the metal binding sites at pH 6. Structural models were derived based upon oxidation and photolytic rearrangements of cutin, lignin, and tannin precursors. These structural models rich in substituted dibasic acid structures revealed polydentate binding sites with the potential for both inner-sphere and outer-sphere type binding. The majority of the fulvic acid molecule was involved with metal binding rather than a small substructural unit.

Contactless electroreflectance study of the Fermi level pinning on GaSb surface in n-type and p-type GaSb Van Hoof structures

NASA Astrophysics Data System (ADS)

Kudrawiec, R.; Nair, H. P.; Latkowska, M.; Misiewicz, J.; Bank, S. R.; Walukiewicz, W.

2012-12-01

Contactless electroreflectance (CER) has been applied to study the Fermi-level position on GaSb surface in n-type and p-type GaSb Van Hoof structures. CER resonances, followed by strong Franz-Keldysh oscillation of various periods, were clearly observed for two series of structures. This period was much wider (i.e., the built-in electric field was much larger) for n-type structures, indicating that the GaSb surface Fermi level pinning position is closer to the valence-band than the conduction-band. From analysis of the built-in electric fields in undoped GaSb layers, it was concluded that on GaSb surface the Fermi-level is located ˜0.2 eV above the valence band.

Crystal structure of the plasma membrane proton pump.

PubMed

Pedersen, Bjørn P; Buch-Pedersen, Morten J; Morth, J Preben; Palmgren, Michael G; Nissen, Poul

2007-12-13

A prerequisite for life is the ability to maintain electrochemical imbalances across biomembranes. In all eukaryotes the plasma membrane potential and secondary transport systems are energized by the activity of P-type ATPase membrane proteins: H+-ATPase (the proton pump) in plants and fungi, and Na+,K+-ATPase (the sodium-potassium pump) in animals. The name P-type derives from the fact that these proteins exploit a phosphorylated reaction cycle intermediate of ATP hydrolysis. The plasma membrane proton pumps belong to the type III P-type ATPase subfamily, whereas Na+,K+-ATPase and Ca2+-ATPase are type II. Electron microscopy has revealed the overall shape of proton pumps, however, an atomic structure has been lacking. Here we present the first structure of a P-type proton pump determined by X-ray crystallography. Ten transmembrane helices and three cytoplasmic domains define the functional unit of ATP-coupled proton transport across the plasma membrane, and the structure is locked in a functional state not previously observed in P-type ATPases. The transmembrane domain reveals a large cavity, which is likely to be filled with water, located near the middle of the membrane plane where it is lined by conserved hydrophilic and charged residues. Proton transport against a high membrane potential is readily explained by this structural arrangement.

Predictors for switch from unipolar major depressive disorder to bipolar disorder type I or II: a 5-year prospective study.

PubMed

Holma, K Mikael; Melartin, Tarja K; Holma, Irina A K; Isometsä, Erkki T

2008-08-01

In this naturalistic study, we investigated the rate, time course, and predictors of a diagnostic switch from unipolar major depressive disorder (MDD) to bipolar disorder type I or II during a 5-year follow-up. The Vantaa Depression Study included at baseline 269 psychiatric outpatients (82.9%) and inpatients (17.1%) with DSM-IV MDD, diagnosed using structured and semi-structured interviews and followed up at 6 months, 18 months, and 5 years between February 1, 1997 and April 30, 2004. Information on 248 MDD patients (92.2%) was available for analyses of the risk of diagnostic switch. Cox proportional hazards models were used. Twenty-two subjects (8.9%) with previous unipolar MDD switched to bipolar disorder type II and 7 (2.8%) to type I. Median time for switch to bipolar type I was significantly shorter than to type II. In Cox proportional hazards analyses, severity of MDD (hazard ratio [HR] = 1.08, 95% CI = 1.00 to 1.15, p = .036), obsessive-compulsive disorder (OCD) (HR = 5.00, 95% CI = 2.04 to 12.5, p < .001), social phobia (HR = 2.33, 95% CI = 1.00 to 5.26, p = .050), and large number of cluster B personality disorder symptoms (HR = 1.10, 95% CI = 1.02 to 1.20, p = .022) predicted switch. Among outpatients with MDD in secondary level psychiatric settings, diagnostic switch to bipolar disorder usually refers to type II rather than type I. The few switching to bipolar type I do so relatively early. Predictors for diagnostic switch include not only features of mood disorder, such as severity, but may also include some features of psychiatric comorbidity, such as concurrent social phobia, OCD, and symptoms of cluster B personality disorders.

Optical and electrical properties of CuMO2 transparent p-type conductors

NASA Astrophysics Data System (ADS)

Draeseke, A. D.; Jayaraj, M. K.; Ulbrich, T.; Kroupp, M.; Tate, J.; Nagarajan, R.; Oblezov, A.; Sleight, A. W.

2001-03-01

Wide band gap oxides of the type CuMO2 with the delafossite structure are p-type conductors and many of them are transparent. Films of these p-type oxides have been grown by sputtering and thermal evaporation, and characterized electrically and optically. We present transport and optical transmission measurements for CuY_1-xCa_xO_2, CuScO_2+x and other similar materials. Conductivities are in the range 1 200 S/cm and depend on details of film preparation. The carriers are p-type as determined by thermopower measurements, and typical Seebeck coefficients are several hundred µV/K. Optical transparency varies considerably, but is about 40% at 550 nm for the highest conductivity films. Excellent transparency can be achieved at the expense of conductivity, and optimization is being studied. Band gaps derived from optical transmission are larger than 3.1 eV. Prototype all-oxide pn diodes have been fabricated. This work was partially supported by the NSF under DMR-0071727 and by the Research Corporation under RA0291.

Role of low O 2 pressure and growth temperature on electrical transport of PLD grown ZnO thin films on Si substrates

NASA Astrophysics Data System (ADS)

Pandis, Ch.; Brilis, N.; Tsamakis, D.; Ali, H. A.; Krishnamoorthy, S.; Iliadis, A. A.

2006-06-01

Undoped ZnO thin films have been grown on (100) Si substrates by pulsed laser deposition. The effect of growth parameters such as temperature, O 2 partial pressure and laser fluence on the structural and electrical properties of the films has been investigated. It is shown that the well-known native n-type conductivity, attributed to the activation of hydrogenic donor states, exhibits a conversion from n-type to p-type when the O 2 partial pressure is reduced from 10 -4 to 10 -7 Torr at growth temperatures lower than 400 °C. The p-type conductivity could be attributed to the dominant role of the acceptor Zn vacancies for ZnO films grown at very low O 2 pressures.

Au/n-InP Schottky diodes using an Al2O3 interfacial layer grown by atomic layer deposition

NASA Astrophysics Data System (ADS)

Kim, Hogyoung; Kim, Min Soo; Yoon, Seung Yu; Choi, Byung Joon

2017-02-01

We investigated the effect of an Al2O3 interfacial layer grown by atomic layer deposition on the electrical properties of Au Schottky contacts to n-type InP. Considering barrier inhomogeneity, modified Richardson plots yielded a Richardson constant of 8.4 and 7.5 Acm-2K-2, respectively, for the sample with and without the Al2O3 interlayer (theoretical value of 9.4 Acm-2K-2 for n-type InP). The dominant reverse current flow for the sample with an Al2O3 interlayer was found to be Poole-Frenkel emission. From capacitance-voltage measurements, it was observed that the capacitance for the sample without the Al2O3 interlayer was frequency dependent. Sputter-induced defects as well as structural defects were passivated effectively with an Al2O3 interlayer.

Structural, electronic and vibrational properties of LaF3 according to density functional theory and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Oreshonkov, A. S.; Roginskii, E. M.; Krylov, A. S.; Ershov, A. A.; Voronov, V. N.

2018-06-01

Crystal structure of LaF3 single crystal is refined in tysonite-type trigonal unit cell P c1 using density functional theory calculations and Raman spectroscopy. It is shown that trigonal structure with P c1 space group is more energy-efficient than hexagonal structure with space group P63 cm. Simulated Raman spectra obtained using LDA approximation is in much better agreement with experimental data than that obtained with PBE and PBEsol functionals of GGA. The calculated frequency value of silent mode B 2 in case of hexagonal structure P63 cm was found to be imaginary (unstable mode), thus the energy surface obtains negative curvature with respect to the corresponding normal coordinates of the mode which leads to instability of the hexagonal structure in harmonic approximation. The A 1g line at 214 cm‑1 in Raman spectra of LaF3 related to the translation of F2 ions along c axis can be connected with F2 ionic conductivity.

Insights into the Effects of Zinc Doping on Structural Phase Transition of P2-Type Sodium Nickel Manganese Oxide Cathodes for High-Energy Sodium Ion Batteries.

PubMed

Wu, Xuehang; Xu, Gui-Liang; Zhong, Guiming; Gong, Zhengliang; McDonald, Matthew J; Zheng, Shiyao; Fu, Riqiang; Chen, Zonghai; Amine, Khalil; Yang, Yong

2016-08-31

P2-type sodium nickel manganese oxide-based cathode materials with higher energy densities are prime candidates for applications in rechargeable sodium ion batteries. A systematic study combining in situ high energy X-ray diffraction (HEXRD), ex situ X-ray absorption fine spectroscopy (XAFS), transmission electron microscopy (TEM), and solid-state nuclear magnetic resonance (SS-NMR) techniques was carried out to gain a deep insight into the structural evolution of P2-Na0.66Ni0.33-xZnxMn0.67O2 (x = 0, 0.07) during cycling. In situ HEXRD and ex situ TEM measurements indicate that an irreversible phase transition occurs upon sodium insertion-extraction of Na0.66Ni0.33Mn0.67O2. Zinc doping of this system results in a high structural reversibility. XAFS measurements indicate that both materials are almost completely dependent on the Ni(4+)/Ni(3+)/Ni(2+) redox couple to provide charge/discharge capacity. SS-NMR measurements indicate that both reversible and irreversible migration of transition metal ions into the sodium layer occurs in the material at the fully charged state. The irreversible migration of transition metal ions triggers a structural distortion, leading to the observed capacity and voltage fading. Our results allow a new understanding of the importance of improving the stability of transition metal layers.

Novel high-pressure phase of ZrO{sub 2}: An ab initio prediction

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

Durandurdu, Murat, E-mail: murat.durandurdu@agu.edu.tr

2015-10-15

The high-pressure behavior of the orthorhombic cotunnite type ZrO{sub 2} is explored using an ab initio constant pressure technique. For the first time, a novel hexagonal phase (Ni{sub 2}In type) within P6{sub 3}/mmc symmetry is predicted through the simulation. The Ni{sub 2}In type crystal is the densest high-pressure phase of ZrO{sub 2} proposed so far and has not been observed in other metal dioxides at high pressure before. The phase transformation is accompanied by a small volume drop and likely to occur around 380 GPa in experiment. - Graphical abstract: Post-cotunnite Ni{sub 2}In type hexagonal phase forms in zirconia atmore » high pressure. - Highlights: • A post-cotunnite phase is predicted for ZrO{sub 2} through an ab initio simulation. • Cotunnite ZrO{sub 2} adopts the Ni{sub 2}In type structure at high pressure. • The Ni{sub 2}In type structure is the densest high-pressure phase of ZrO{sub 2} proposed so far. • The preferred mechanism in ZrO{sub 2} differs from the other metal dioxides.« less

Reticulated shallow etch mesa isolation for controlling surface leakage in GaSb-based infrared detectors

NASA Astrophysics Data System (ADS)

Nolde, J. A.; Jackson, E. M.; Bennett, M. F.; Affouda, C. A.; Cleveland, E. R.; Canedy, C. L.; Vurgaftman, I.; Jernigan, G. G.; Meyer, J. R.; Aifer, E. H.

2017-07-01

Longwave infrared detectors using p-type absorbers composed of InAs-rich type-II superlattices (T2SLs) nearly always suffer from high surface currents due to carrier inversion on the etched sidewalls. Here, we demonstrate reticulated shallow etch mesa isolation (RSEMI): a structural method of reducing surface currents in longwave single-band and midwave/longwave dual-band detectors with p-type T2SL absorbers. By introducing a lateral shoulder to increase the separation between the n+ cathode and the inverted absorber surface, a substantial barrier to surface electron flow is formed. We demonstrate experimentally that the RSEMI process results in lower surface current, lower net dark current, much weaker dependence of the current on bias, and higher uniformity compared to mesas processed with a single deep etch. For the structure used, a shoulder width of 2 μm is sufficient to block surface currents.

Electronic structure of the metal center in the Cd(2+), Zn(2+), and Cu(2+) substituted forms of KDO8P synthase: implications for catalysis.

PubMed

Kona, Fathima; Tao, Peng; Martin, Philip; Xu, Xingjue; Gatti, Domenico L

2009-04-28

Aquifex aeolicus 3-deoxy-d-manno-octulosonate 8-phosphate synthase (KDO8PS) is active with a variety of different divalent metal ions bound in the active site. The Cd(2+), Zn(2+), and Cu(2+) substituted enzymes display similar values of k(cat) and similar dependence of K(m)(PEP) and K(m)(A5P) on both substrate and product concentrations. However, the flux-control coefficients for some of the catalytically relevant reaction steps are different in the presence of Zn(2+) or Cu(2+), suggesting that the type of metal bound in the active site affects the behavior of the enzyme in vivo. The type of metal also affects the rate of product release in the crystal environment. For example, the crystal structure of the Cu(2+) enzyme incubated with phosphoenolpyruvate (PEP) and arabinose 5-phosphate (A5P) shows the formed product, 3-deoxy-d-manno-octulosonate 8-phosphate (KDO8P), still bound in the active site in its linear conformation. This observation completes our structural studies of the condensation reaction, which altogether have provided high-resolution structures for the reactants, the intermediate, and the product bound forms of KDO8PS. The crystal structures of the Cd(2+), Zn(2+), and Cu(2+) substituted enzymes show four residues (Cys-11, His-185, Glu-222, and Asp-233) and a water molecule as possible metal ligands. Combined quantum mechanics/molecular mechanics (QM/MM) geometry optimizations reveal that the metal centers have a delocalized electronic structure, and that their true geometry is square pyramidal for Cd(2+) and Zn(2+) and distorted octahedral or distorted tetrahedral for Cu(2+). These geometries are different from those obtained by QM optimization in the gas phase (tetrahedral for Cd(2+) and Zn(2+), distorted tetrahedral for Cu(2+)) and may represent conformations of the metal center that minimize the reorganization energy between the substrate-bound and product-bound states. The QM/MM calculations also show that when only PEP is bound to the enzyme the electronic structure of the metal center is optimized to prevent a wasteful reaction of PEP with water.

l en configuration dite de "Bridgman verticale" avec un tirage vers le haut. Pour des valeurs élevées du nombre de Rayleigh solutal, nous suivons les diverses branches de solutions stationnaires jusqu'aux seuils d'apparition des phénomènes instationnaires. Ces transitions à l'instationnarité sont étudiées en fonction du confinement et, le long de ces nouvelles branches de solution, nous estimons l'ordre de grandeur de la fluctuation temporelle de la composition à l'interface. Cette dernière étant responsable d'une striation qui est incorporée par le solide lors de sa croissance, nous caractérisons ce phénomène en termes d'amplitude de striation (i.e. intensité de la fluctuation de composition) et de période spatiale de striation.

NASA Astrophysics Data System (ADS)

Haldenwang, P.; Guérin, R.; Le Marec, C.

1999-06-01

2-D unsteady flow patterns in upward Bridgman solidification are numerically investigated. The alloy under study is Pb-30%Tl. The purpose of the contribution is to characterise the striations induced by unsteadiness in the growing crystal. Unsteady solution branches are studied from onset threshold of unsteadiness to chaos. We report two examples for which time behaviour of a given solution branch is studied versus Rayleigh number. We then estimate the magnitude of the time fluctuations in solute composition that the crystal incorporates. The period of the striations is also discussed. Nous étudions numériquement les structures hydrodynamiques de la convection solutale dans le bain fondu, lors de la solidification dirigée d'alliages binaires. Plus précisément, cette étude porte

Acemetacin cocrystal structures by powder X-ray diffraction.

PubMed

Bolla, Geetha; Chernyshev, Vladimir; Nangia, Ashwini

2017-05-01

Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM), p -aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM-NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid-amide dimer three-point synthon R 3 2 (9) R 2 2 (8) R 3 2 (9) with three different syn amides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I) or syn (type II). ACM hydrate, ACM-NAM, ACM-NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O⋯H, N⋯H, Cl⋯H and C⋯H interactions. The physicochemical properties of these cocrystals are under study.

Acemetacin cocrystal structures by powder X-ray diffraction

PubMed Central

Bolla, Geetha

2017-01-01

Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM), p-aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthon R 3 2(9)R 2 2(8)R 3 2(9) with three different syn amides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I) or syn (type II). ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O⋯H, N⋯H, Cl⋯H and C⋯H interactions. The physicochemical properties of these cocrystals are under study. PMID:28512568

Materials Design of the Codoping for the Fabrication of Low-Resistivity p-Type ZnSe and GaN by ab-initio Electronic Structure Calculation

NASA Astrophysics Data System (ADS)

Katayama-Yoshida, H.; Yamamoto, T.

1997-08-01

We propose an effective doping method, the codoping (doping with n- and p-type dopants at the same time) method, for the fabrication of low-resistivity p-type ZnSe and GaN with wide-band-gap based upon ab-initio electronic band structure calculations. p-type doping eminently leads to an increase in the electrostatic energy, called the Madelung energy, which shifts the Se 4p levels for p-type doped ZnSe and the N 2p levels for p-type doped GaN materials towards higher energy regions. This leads to a destabilization of ionic charge distributions in p-type ZnSe and p-type GaN crystals, resulting in the self-compensation of anion intrinsic defects. For ZnSe crystals, we propose the codoping of n-type In donors at Zn sites and p-type N acceptors at Se sites based on the calculation. In addition, we propose the codoping of n-type Si-donors at Ga sites (n-type O donors at N sites) and p-type Be- or Mg acceptors at Ga sites. The codoping decreases the Madelung energy and leads to an increase in the net acceptor carrier density.

Optical gain spectra of 1.55 μm GaAs/GaN.58yAs1-1.58yBiy/GaAs single quantum well

NASA Astrophysics Data System (ADS)

Guizani, I.; Bilel, C.; Habchi, M. M.; Rebey, A.

2017-02-01

The optical gain spectra of doped lattice-matched GaNAsBi-based single quantum well (SQW) was theoretically investigated using a (16 × 16) band anti-crossing (BAC) model combined with self-consistent calculation. For the sake of comparison, we computed the optical gain of both (i-n-i) and (i-p-i) doped well types in GaAs/GaNAsBi/GaAs quantum structure. The highest obtained material gain Gmax was 1.2 ×104 cm-1 for (i-n-i) type doped with N2Dd = 2.5 ×1012 cm-2 . We proposed investigating the p-i-n type structure to enhance the optical performance of GaAs/GaNAsBi/GaAs SQW. The Bi composition was optimized in order to obtain Te 1 - h 1 = 1.55 μ m . The effect of well width on optical gain spectra was also discussed.

Recognition of a novel type X═N-Hal···Hal (X = C, S, P; Hal = F, Cl, Br, I) halogen bonding.

PubMed

Gushchin, Pavel V; Kuznetsov, Maxim L; Haukka, Matti; Kukushkin, Vadim Yu

2013-04-04

The chlorination of the eight-membered platinum(II) chelates [PtCl2{NH═C(NR2)N(Ph)C(═NH)N(Ph)C(NR2)═NH}] (R = Me (1); R2 = (CH2)5 (2)) with uncomplexed imino group with Cl2 gives complexes bearing the ═N-Cl moiety [PtCl4{NH═C(NR2)N(Ph)C(═NCl)N(Ph)C(NR2)═NH}] (R = Me (3); R2 = (CH2)5 (4)). X-ray study for 3 revealed a novel type intermolecular halogen bonding ═N-Cl···Cl(-), formed between the Cl atom of the chlorinated imine and the chloride bound to the platinum(IV) center. The processing relevant structural data retrieved from the Cambridge Structural Database (CSDB) shows that this type of halogen bonding is realized in 18 more molecular species having X═N-Hal moieties (X = C, P, S, V, W; Hal = Cl, Br, I), but this weak ═N-Hal···Hal(-) bonding was totally neglected in the previous works. The presence of the halogen bonding in 3 was confirmed by theoretical calculations at the density functional theory (DFT, M06-2X) level, and its nature was analyzed.

36 CFR 1253.9 - Federal holidays.

Code of Federal Regulations, 2011 CFR

2011-07-01

... closed on Thanksgiving and December 25. (c) The Presidential library museums are open every day except Thanksgiving, December 25, and January 1 (with the exception of the Lyndon Baines Johnson Library which is only...

Coccolithophore community response to increasing pCO2 in Mediterranean oligotrophic waters

NASA Astrophysics Data System (ADS)

Oviedo, A. M.; Ziveri, P.; Gazeau, F.

2017-02-01

The effects of elevated partial pressure of CO2 (pCO2) on plankton communities in oligotrophic ecosystems were studied during two mesocosm experiments: one during summer 2012 in the Bay of Calvi, France, and another during winter 2013 in the Bay of Villefranche, France. Here we report on the relative abundances of coccolithophores versus siliceous phytoplankton, coccolithophore community structure, Emiliania huxleyi coccolith morphology and calcification degree. A pCO2 mediated succession of phytoplankton groups did not occur. During both experiments, coccolithophore abundance and community structure varied with time independently of pCO2 levels. Changes in the community structure were partly explained by the concentration of phosphate during the winter experiment. During the summer experiment, it was not clearly related to any of the parameters measured but possibly to changes in temperature. Phenological changes in the community and an attenuated response due to the low biomass building during the winter experiment could have masked the response to pCO2. E. huxleyi dominated the coccolithophore community in winter; it was not affected by elevated pCO2 at any time. In contrast, the abundance of Rabdosphaera clavigera, the dominant species in summer, increased with time and this increase was affected at elevated pCO2. Thus, a different coccolithophore community response based on species-specific sensitivities to pCO2 is still likely. Finally, elevated pCO2 had no traceable effect on E. huxleyi (type A) coccolith morphology or on the degree of coccolith calcification. Our results highlight the possibility that, in oligotrophic regions, nutrient availability, temperature or intrinsic phenological changes might exert larger constrains on the coccolithophore community structure than high pCO2 does solely.

A Spinel-integrated P2-type Layered Composite: High-rate Cathode for Sodium-ion Batteries

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

Zheng, Jianming; Yan, Pengfei; Kan, Wang Hay

2016-01-14

Sodium-ion batteries (SIB) are being intensively investigated, owing to the natural abundance and low cost of Na resources. However, the SIBs still suffer from poor rate capability due to the large ionic radius of Na+ ion and the significant kinetic barrier to Na+-ion transport. Here, we present an Fd-3m spinel-integrated P2-type layered composite (P2 + Fd-3m) material as a high-rate cathode for SIBs. The P2 + Fd-3m composite material Na0.50Ni1/6Co1/6Mn2/3O2 shows significantly enhanced discharge capacity, energy density, and rate capability as compared to the pure P2-type counterpart. The composite delivers a high capacity of 85 mA h g-1 when dischargingmore » at a very high current density of 1500 mA g-1 (10C rate) between 2.0 and 4.5 V, validating it as a promising cathode candidate for high-power SIBs. The superior performance is ascribed to the improved kinetics in the presence of the integrated-spinel phase, which facilitates fast electron transport to coordinate with the timely Na+-ion insertion/extraction. The findings of this work also shed light on the importance of developing lattice doping, surface coating, and electrolyte additives to further improve the structural and interfacial stability of P2-type cathode materials and fully realize their practical applications in sodium-ion batteries.« less

Thermoelectric properties of AMg 2X 2, AZn 2Sb 2 (A = Ca, Sr, Ba; X = Sb, Bi), and Ba 2ZnX 2 (X = Sb, Bi) Zintl compounds

DOE PAGES

Sun, Jifeng; Singh, David J.

2017-04-03

In this paper, we report a theoretical investigation of the electronic structure and transport properties of eleven Zintl compounds including nine 122 phases (AMg 2X 2, AZn 2Sb 2 (A = Ca, Sr, Ba; X = Sb, Bi)) and two 212 phases (Ba 2ZnX 2 (X = Sb, Bi)). The electronic structures and electrical transport properties are studied using ab initio calculations and semi-classical Boltzmann theory within the constant relaxation time approximation. All the compounds are semiconducting. We find that the n-type 122 phases with the CaAl 2Si 2 structure type show better performance than p-type materials due to themore » multi-valley degeneracy with anisotropic carrier pockets at and near the conduction band minimum. The pocket anisotropy is beneficial in achieving high conductivity and Seebeck coefficient simultaneously. This mechanism yields substantial improvement in the power factor. Finally, the general performance of 212 phases is inferior to that of the 122 phases, with the Ba 2ZnSb 2 compound showing better performance.« less

Synthesis, crystal structures and ionic conductivities of Bi{sub 14}P{sub 4}O{sub 31} and Bi{sub 50}V{sub 4}O{sub 85}. Two members of the series Bi{sub 18-4m}M{sub 4m}O{sub 27+4m} (M=P, V) related to the fluorite-type structure

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

Mauvy, F.; Launay, J.C.; Darriet, J.

2005-06-15

The two hitherto unknown compounds Bi{sub 14}P{sub 4}O{sub 31} and Bi{sub 50}V{sub 4}O{sub 85} were prepared by the direct solid-state reaction of Bi{sub 2}O{sub 3} and (NH{sub 4})H{sub 2}PO{sub 4} or V{sub 2}O{sub 5}, respectively. Bi{sub 14}P{sub 4}O{sub 31} crystallizes in a C-centred monoclinic symmetry (C2/c space group) with the unit-cell parameters: a=19.2745(2)A, b=11.3698(1)A, c=52.4082(2)A and {beta}=93.63(1){sup o} (Z=16). The symmetry of Bi{sub 50}V{sub 4}O{sub 85} is also monoclinic (I2/m space group) with lattice parameters of a=11.8123(3)A, b=11.7425(2)A, c=16.5396(2)A and {beta}=90.14(1){sup o} (Z=2). Both structures correspond to a fluorite-type superstructure where the Bi and P or V atoms are orderedmore » in the framework. An idealized structural model is proposed where the structures result of the stacking of mixed atomic layers of composition [Bi{sub 14}M{sub 4}O{sub 31}] and [Bi{sub 18}O{sub 27}] respectively. This new family can be formulated Bi{sub 18-4m}M{sub 4m}O{sub 27+4m} with M=P, V and where the parameter m (0=

Pressure-induced structural transition in chalcopyrite ZnSiP 2

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

Bhadram, Venkata S.; Krishna, Lakshmi; Toberer, Eric S.

The pressure-dependent phase behavior of semiconducting chalcopyrite ZnSiP 2 was studied up to 30 GPa using in situ X-ray diffraction and Raman spectroscopy in a diamond-anvil cell. A structural phase transition to the rock salt type structure was observed between 27 and 30 GPa, which is accompanied by soft phonon mode behavior and simultaneous loss of Raman signal and optical transmission through the sample. The high-pressure rock salt type phase possesses cationic disorder as evident from broad features in the X-ray diffraction patterns. The behavior of the low-frequency Raman modes during compression establishes a two-stage, order-disorder phase transition mechanism. Themore » phase transition is partially reversible, and the parent chalcopyrite structure coexists with an amorphous phase upon slow decompression to ambient conditions.« less

SiP monolayers: New 2D structures of group IV-V compounds for visible-light photohydrolytic catalysts

NASA Astrophysics Data System (ADS)

Ma, Zhinan; Zhuang, Jibin; Zhang, Xu; Zhou, Zhen

2018-06-01

Because of graphene and phosphorene, two-dimensional (2D) layered materials of group IV and group V elements arouse great interest. However, group IV-V monolayers have not received due attention. In this work, three types of SiP monolayers were computationally designed to explore their electronic structure and optical properties. Computations confirm the stability of these monolayers, which are all indirect-bandgap semiconductors with bandgaps in the range 1.38-2.21 eV. The bandgaps straddle the redox potentials of water at pH = 0, indicating the potential of the monolayers for use as watersplitting photocatalysts. The computed optical properties demonstrate that certain monolayers of SiP 2D materials are absorbers of visible light and would serve as good candidates for optoelectronic devices.

New intermetallic MIrP (M=Ti, Zr, Nb, Mo) and MgRuP compounds related with MoM'P (M'=Ni and Ru) superconductor

NASA Astrophysics Data System (ADS)

Kito, Hijiri; Iyo, Akira; Wada, Toshimi

2011-01-01

Using a cubic-anvil high-pressure apparatus, ternary iridium phosphides MIrP (M=Ti, Zr, Nb, Mo) and MgRuP have been prepared by reaction of stoichiometric amounts of each metal and phosphide powders at around 2 Gpa and above 1523 K for the first time. The structure of these compounds prepared at high-pressure has been characterized by X-ray powder diffraction. Diffraction lines of these compounds are assigned by the index of the Co2Si-type structure. The electrical resistivity and the d.c magnetic susceptibility of MIrP (M=Ti, Zr, Nb, Mo) have measured at low temperatures. Unfortunately, no superconducting transition for MIrP (M=Ti, Zr, Nb, Mo) and MgRuP are observed down to 2 K.

Evaluation of optimal control type models for the human gunner in an Anti-Aircraft Artillery (AAA) system

NASA Technical Reports Server (NTRS)

Phatak, A. V.; Kessler, K. M.

1975-01-01

The selection of the structure of optimal control type models for the human gunner in an anti aircraft artillery system is considered. Several structures within the LQG framework may be formulated. Two basic types are considered: (1) kth derivative controllers; and (2) proportional integral derivative (P-I-D) controllers. It is shown that a suitable criterion for model structure determination can be based on the ensemble statistics of the tracking error. In the case when the ensemble tracking steady state error is zero, it is suggested that a P-I-D controller formulation be used in preference to the kth derivative controller.

Effects of P3HT concentration on the electrical properties of the Au/PEDOT:PSS/P3HT/n-GaN hybrid junction structure

NASA Astrophysics Data System (ADS)

Noh, Ji-yeon; Lee, Ha Young; Lim, Kyung-won; Ahn, Hyung Soo; Yi, Sam Nyung; Jeon, Hunsoo; Shin, Min Jeong; Yu, Young Moon; Ha, Dong Han

2017-09-01

An inorganic-organic hybrid junction has been fabricated by spin coating the p-type poly(3- hexylthiophene-2,5-diyl)(P3HT) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) on an n-type GaN layer. The GaN layer was formed on Al2O3 by metal organic chemical vapor deposition(MOCVD) method. To investigate the effects of P3HT concentration on the electrical properties, we changed P3HT solution concentration and speed of spin coater. The currentvoltage (I-V ) characteristic of Au/PEDOT:PSS/P3HT/n-GaN shows rectifying behavior. The I-V characteristic was examined in the frame work of the thermionic emission model. The most proper rectifying behavior was obtained for 0.6 wt% and thickness below 65 nm of P3HT used diode. We expect that such hybrid structures, suitably developed, might be enable the fabrication of highquality electronic and optoelectronic devices.

Tuning the p-type Schottky barrier in 2D metal/semiconductor interface:boron-sheet on MoSe2, and WSe2

NASA Astrophysics Data System (ADS)

Couto, W. R. M.; Miwa, R. H.; Fazzio, A.

2017-10-01

Van der Waals (vdW) metal/semiconductor heterostructures have been investigated through first-principles calculations. We have considered the recently synthesized borophene (Mannix et al 2015 Science 350 1513), and the planar boron sheets (S1 and S2) (Feng et al 2016 Nat. Chem. 8 563) as the 2D metal layer, and the transition metal dichalcogenides (TMDCs) MoSe2, and WSe2 as the semiconductor monolayer. We find that the energetic stability of those 2D metal/semiconductor heterojunctions is mostly ruled by the vdW interactions; however, chemical interactions also take place in borophene/TMDC. The electronic charge transfer at the metal/semiconductor interface has been mapped, where we find a a net charge transfer from the TMDCs to the boron sheets. Further electronic structure calculations reveal that the metal/semiconductor interfaces, composed by planar boron sheets S1 and S2, present a p-type Schottky barrier which can be tuned to a p-type ohmic contact by an external electric field.

Designing small molecule polyaromatic p- and n-type semiconductor materials for organic electronics

NASA Astrophysics Data System (ADS)

Collis, Gavin E.

2015-12-01

By combining computational aided design with synthetic chemistry, we are able to identify core 2D polyaromatic small molecule templates with the necessary optoelectronic properties for p- and n-type materials. By judicious selection of the functional groups, we can tune the physical properties of the material making them amenable to solution and vacuum deposition. In addition to solubility, we observe that the functional group can influence the thin film molecular packing. By developing structure-property relationships (SPRs) for these families of compounds we observe that some compounds are better suited for use in organic solar cells, while others, varying only slightly in structure, are favoured in organic field effect transistor devices. We also find that the processing conditions can have a dramatic impact on molecular packing (i.e. 1D vs 2D polymorphism) and charge mobility; this has implications for material and device long term stability. We have developed small molecule p- and n-type materials for organic solar cells with efficiencies exceeding 2%. Subtle variations in the functional groups of these materials produces p- and ntype materials with mobilities higher than 0.3 cm2/Vs. We are also interested in using our SPR approach to develop materials for sensor and bioelectronic applications.

Metal Oxide Nanowire Preparation and Their Integration into Chemical Sensing Devices at the SENSOR Lab in Brescia

PubMed Central

Bertuna, Angela; Faglia, Guido; Ferroni, Matteo; Kaur, Navpreet; Munasinghe Arachchige, Hashitha M. M.; Sberveglieri, Giorgio; Comini, Elisabetta

2017-01-01

Metal oxide 1D nanowires are probably the most promising structures to develop cheap stable and selective chemical sensors. The purpose of this contribution is to review almost two-decades of research activity at the Sensor Lab Brescia on their preparation during by vapor solid (n-type In2O3, ZnO), vapor liquid solid (n-type SnO2 and p-type NiO) and thermal evaporation and oxidation (n-type ZnO, WO3 and p-type CuO) methods. For each material we’ve assessed the chemical sensing performance in relation to the preparation conditions and established a rank in the detection of environmental and industrial pollutants: SnO2 nanowires were effective in DMMP detection, ZnO nanowires in NO2, acetone and ethanol detection, WO3 for ammonia and CuO for ozone. PMID:28468310

Long-term impact of a structured group-based inpatient-education program for intensive insulin therapy in patients with diabetes mellitus.

PubMed

Göbl, Christian S; Dobes, Barbara; Luger, Anton; Bischof, Martin G; Krebs, Michael

2010-06-01

Structured patient education aiming to improve self-management strategies might be beneficial for insulin-treated diabetic patients. However, in previous studies the extent of the benefit has been inconsistent in different subgroups of patients. The aim of the present study was to assess the potential benefit of a structured inpatient-education program for intensive insulin therapy according to the basal-bolus concept with particular emphasis on self-management strategies. We included 81 diabetic patients (59 with type 1, 14 with type 2, eight with other forms) in this retrospective longitudinal study; all had completed the training program on eight consecutive days at a university clinic between 2003 and 2005. Data assessment included HbA1c, LDL-cholesterol, HDL-cholesterol and BMI at baseline (0-15 months before the training) and after 0-5, 5-10 and 10-20 months. A transient decrease of HbA1c (0.2%, 95% CI: 0.04-0.37, P = 0.017) and LDL-cholesterol levels (9.95 mg/dl, 95% CI: 2.24-17.76, P = 0.013) between baseline and the first follow-up examination was observed in the group overall. Thereafter, HbA1c and LDL-cholesterol were similar to baseline, whereas a persistent increase in HDL-cholesterol (P = 0.025) was evident in the multivariable analysis. No changes in BMI were observed. A significant type-by-time interaction (P = 0.008) in HbA1c suggests a long-term benefit in glycemic control in patients with type 2 diabetes. A diabetes training program for intensive insulin therapy with particular emphasis on self-management skills was followed by a moderate and transient improvement of glycemic control and LDL-cholesterol and by a persistent increase in HDL-cholesterol. Long-term improvement in glycemic control was observed only in patients with type 2 diabetes.

Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values

NASA Astrophysics Data System (ADS)

Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

2017-06-01

We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values.

PubMed

Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

2017-06-02

We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO 2 -SiO 2 ) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO 2 -SiO 2 ) composite nanofibers. Such flexible inorganic TiO 2 -SiO 2 and CuO-TiO 2 -SiO 2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO 2 -SiO 2 and CuO-TiO 2 -SiO 2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO 2 -SiO 2 /PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO 2 -SiO 2 /PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO 2 , and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO 2 -SiO 2 /PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

The cytological manifestation of gene amplification in multidrug-resistant mouse leukemia P388 sublines is correlated with amplicon content

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

Il`inskaya, G.V.; Kopnin, B.P.; Demidova, N.S.

1995-10-01

Previously, we showed that development of multidrug resistance (MDR) in mouse P388 leukemia cells is often associated with the appearance of newly-formed chromosomelike structures that contain amplified copies of the mdr1 gene. In the present study, we compared amplicon content in P388 sublines showing different types of these structures. A strong correlation between the formation of specific acentric markers consisting of two identical arms and the absence of the sorcin gene coamplification was found. In all the sublines containing other types of chromosomelike structures, the sorcin gene is coamplified. 9 refs., 2 figs., 1 tab.

The role of regioregularity, crystallinity, and chain orientation on electron transport in a high-mobility n-type copolymer.

PubMed

Steyrleuthner, Robert; Di Pietro, Riccardo; Collins, Brian A; Polzer, Frank; Himmelberger, Scott; Schubert, Marcel; Chen, Zhihua; Zhang, Shiming; Salleo, Alberto; Ade, Harald; Facchetti, Antonio; Neher, Dieter

2014-03-19

We investigated the correlation between the polymer backbone structural regularity and the charge transport properties of poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} [P(NDI2OD-T2)], a widely studied semiconducting polymer exhibiting high electron mobility and an unconventional micromorphology. To understand the influence of the chemical structure and crystal packing of conventional regioregular P(NDI2OD-T2) [RR-P(NDI2OD-T2)] on the charge transport, the corresponding regioirregular polymer RI-P(NDI2OD-T2) was synthesized. By combining optical, X-ray, and transmission electron microscopy data, we quantitatively characterized the aggregation, crystallization, and backbone orientation of all of the polymer films, which were then correlated to the electron mobilities in electron-only diodes. By carefully selecting the preparation conditions, we were able to obtain RR-P(NDI2OD-T2) films with similar crystalline structure along the three crystallographic axes but with different orientations of the polymer chains with respect to the substrate surface. RI-P(NDI2OD-T2), though exhibiting a rather similar LUMO structure and energy compared with the regioregular counterpart, displayed a very different packing structure characterized by the formation of ordered stacks along the lamellar direction without detectible π-stacking. Vertical electron mobilities were extracted from the space-charge-limited currents in unipolar devices. We demonstrate the anisotropy of the charge transport along the different crystallographic directions and how the mobility depends on π-stacking but is insensitive to the degree or coherence of lamellar stacking. The comparison between the regioregular and regioirregular polymers also shows how the use of large planar functional groups leads to improved charge transport, with mobilities that are less affected by chemical and structural disorder with respect to classic semicrystalline polymers such as poly(3-hexylthiophene).

Differential inhibition of Ca2+ channels in mature rat cerebellar Purkinje cells by sFTX-3.3 and FTX-3.3.

PubMed

Dupere, J R; Moya, E; Blagbrough, I S; Usowicz, M M

1996-01-01

Synthetic funnel web spider toxin (sFTX-3.3) is a polyamine amide analogue of FTX, a toxin fraction isolated from the venom of the funnel web spider, Agelenopsis aperta, that blocks P-type Ca2+ channels. The structures of these polyamine containing compounds are not identical: sFTX-3.3 contains an amide carbonyl oxygen that is absent from the predicted structure of native FTX. Recently, a compound called FTX-3.3 was synthesized with the structure predicted for native FTX. We have compared the effects of polyamine amide sFTX-3.3 and polyamine FTX-3.3, on Ca2+ channel currents in the soma of mature rat cerebellar Purkinje neurons, in which the predominant Ca2+ channels are defined as P-type. Differential inhibition by sFTX-3.3 and FTX-3.3 revealed three populations of Ca2+ channels. One group, mediating approximately 66% of the current, was blocked by sFTX-3.3 with an IC50 (concentration producing half maximal inhibition) of 33 nM or by FTX-3.3 with an IC50 of 55 pM. A second population (5-25% of the total current) was inhibited by sFTX-3.3 with an IC50 of 33 nM, but was insensitive to FTX-3.3, while a third (10-30%) was blocked by FTX-3.3 with an IC50 of 125 nM and was resistant to sFTX-3.3. These channels also showed distinctive current-voltage relationships. Our results suggest that P-type Ca2+ channels in mature rat cerebellar Purkinje cells may be subdivided according to pharmacological and biophysical properties.

Differential effects of arginine, glutamate and phosphoarginine on Ca(2+)-activation properties of muscle fibres from crayfish and rat.

PubMed

Jame, David W; West, Jan M; Dooley, Philip C; Stephenson, D George

2004-01-01

The effects of two amino acids, arginine which has a positively charged side-chain and glutamate which has a negatively charged side-chain on the Ca2+-activation properties of the contractile apparatus were examined in four structurally and functionally different types of skeletal muscle; long- and short-sarcomere fibres from the claw muscle of the yabby (a freshwater decapod crustacean), and fast- and slow-twitch fibres from limb muscles of the rat. Single skinned fibres were activated in carefully balanced solutions of different pCa (-log10[Ca2+]) that either contained the test solute ("test") or not ("control"). The effect of phosphoarginine, a phosphagen that bears a nett negative charge, was also compared to the effects of arginine. Results show that (i) arginine (33-36 mmol l(-1)) significantly shifted the force-pCa curve by 0.08-0.13 pCa units in the direction of increased sensitivity to Ca2+-activated contraction in all fibre types; (ii) phosphoarginine (9-10 mmol l(-1)) induced a significant shift of the force-pCa curve by 0.18-0.24 pCa units in the direction of increased sensitivity to Ca2+ in mammalian fast- and slow-twitch fibres, but had no significant effects on the force-pCa relation in either long- or short-sarcomere crustacean fibres; (iii) glutamate (36-40 mmol l(-1)), like arginine affected the force-pCa relation of all fibre types investigated, but in the opposite direction, causing a significant decrease in the sensitivity to Ca2+-activated contraction by 0.08-0.19 pCa units; (iv) arginine, phosphoarginine and glutamate had little or no effect on the maximum Ca2+-activated force of crustacean and mammalian fibres. The results suggest that the opposing effects of glutamate and arginine are not related to simply their charge structure, but must involve complex interactions between these molecules, Ca2+ and the regulatory and other myofibrillar proteins.

A systematic study of (NH4)2S passivation (22%, 10%, 5%, or 1%) on the interface properties of the Al2O3/In0.53Ga0.47As/InP system for n-type and p-type In0.53Ga0.47As epitaxial layers

NASA Astrophysics Data System (ADS)

O'Connor, É.; Brennan, B.; Djara, V.; Cherkaoui, K.; Monaghan, S.; Newcomb, S. B.; Contreras, R.; Milojevic, M.; Hughes, G.; Pemble, M. E.; Wallace, R. M.; Hurley, P. K.

2011-01-01

In this work, we present the results of an investigation into the effectiveness of varying ammonium sulphide (NH4)2S concentrations in the passivation of n-type and p-type In0.53Ga0.47As. Samples were degreased and immersed in aqueous (NH4)2S solutions of concentrations 22%, 10%, 5%, or 1% for 20 min at 295 K, immediately prior to atomic layer deposition of Al2O3. Multi-frequency capacitance-voltage (C-V) results on capacitor structures indicate that the lowest frequency dispersion over the bias range examined occurs for n-type and p-type devices treated with the 10%(NH4)2S solution. The deleterious effect on device behavior of increased ambient exposure time after removal from 10%(NH4)2S solution is also presented. Estimations of the interface state defect density (Dit) for the optimum 10%(NH4)2S passivated In0.53Ga0.47As devices extracted using an approximation to the conductance method, and also extracted using the temperature-modified high-low frequency C-V method, indicate that the same defect is present over n-type and p-type devices having an integrated Dit of ˜2.5×1012 cm-2 (±1×1012 cm-2) with the peak density positioned in the middle of the In0.53Ga0.47As band gap at approximately 0.37 eV (±0.03 eV) from the valence band edge. Both methods used for extracting Dit show very good agreement, providing evidence to support that the conductance method can be applied to devices incorporating high-k oxides on In0.53Ga0.47As.

Alkali metal complexes of a phosphine-borane-stabilised carbanion: influence of co-ligands on structure.

PubMed

Izod, Keith; Wills, Corinne; Clegg, William; Harrington, Ross W

2007-09-07

The adducts [[(Me(3)Si)(2){Me(2)P(BH(3))}C]K(L)(n)](m) [L = THF, n = 0.5, m = infinity (2a); L = tmeda (2b), pmdeta (2c), n = 1, m = 2] may be synthesised by treatment of solvent-free [[(Me(3)Si)(2){Me(2)P(BH(3))}C]K](infinity) (2) with the corresponding Lewis base (tmeda = N,N,N',N'-tetramethylethylenediamine; pmdeta = N,N,N',N'',N''-pentamethyldiethylenetriamine). X-Ray crystallography reveals that, whereas 2 crystallises with a complex 2-dimensional sheet structure, 2a crystallises as a ribbon-type one-dimensional polymer and both 2b and 2c crystallise as dimers. The corresponding complex with 12-crown-4, [K(12-crown-4)(2)][(Me(3)Si)(2){Me(2)P(BH(3))}C] (2d) crystallises as a separated ion pair. The complexes [[(Me(3)Si)(2){Me(2)P(BH(3))}C]M(pmdeta)](n) [M = Na, n = 1 (6); M = Rb, n = 2 (7)] may be synthesised by treatment of [(Me(3)Si)(2){Me(2)P(BH(3))}C]M with pmdeta. Whereas crystallises as a discrete monomer, compound 7 crystallises as a dimer. Compounds 2, 2a-2d, 6, 7 and the corresponding caesium derivative [[(Me(3)Si)(2){Me(2)P(BH(3))}C]Cs(pmdeta)](2) () provide an opportunity to consider the influence of the ionic radius of the metal and the nature of the co-ligands on the structures of alkali metal complexes of a phosphine-borane-stabilised carbanion.

Crystallization and preliminary characterization of a highly thermostable lectin from Trichosanthes dioica and comparison with other Trichosanthes lectins

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

Dharkar, Poorva D.; Anuradha, P.; Gaikwad, Sushama M.

2006-03-01

A lectin from Trichosanthes dioica seeds has been purified and crystallized using 25%(w/v) PEG 2K MME, 0.2 M ammonium acetate, 0.1 M Tris–HCl pH 8.5 and 50 µl 0.5%(w/v) n-octyl β-d-glucopyranoside as thick needles belonging to hexagonal space group P6{sub 4}. A lectin from Trichosanthes dioica seeds has been purified and crystallized using 25%(w/v) PEG 2K MME, 0.2 M ammonium acetate, 0.1 M Tris–HCl pH 8.5 and 50 µl 0.5%(w/v) n-octyl β-d-glucopyranoside as thick needles belonging to hexagonal space group P6{sub 4}. Unit-cell parameters were a = b = 167.54, c = 77.42 Å. The crystals diffracted to a Braggmore » spacing of 2.8 Å. Both the structures of abrin-a and T. kirilowii lectin could be used as a model in structure determination using the molecular-replacement method; however, T. kirilowii lectin coordinates gave better values of reliability and correlation parameters. The thermal, chemical and pH stability of this lectin have also been studied. When heated, its haemagglutination activity remained unaffected up to 363 K. Other stability studies show that 4 M guanidinium hydrochloride (Gdn–HCl) initiates unfolding and that the protein is completely unfolded at 6 M Gdn–HCl. Treatment with urea resulted in a total loss of activity at higher concentrations of denaturant with no major structural changes. The protein remained stable over a wide pH range, from pH 6 to pH 12, except for partial unfolding at extremely alkaline pH. The role of disulfide bonds in the protein stability was found to be insignificant. Rayleigh light-scattering studies showed no molecular aggregation in any of the extreme treated conditions. The unusual stability of this lectin resembles that of type II ribosome-inactivating proteins (type II RIPs), which is also supported by structure determination. The structural features observed in a preliminary electron-density map were compared with the other two available Trichosanthes lectin structures.« less

Conformational Dissection of a Viral Intrinsically Disordered Domain Involved in Cellular Transformation

PubMed Central

Perrone, Sebastián; Salvay, Andres G.; Chemes, Lucía B.; de Prat-Gay, Gonzalo

2013-01-01

Intrinsic disorder is abundant in viral genomes and provides conformational plasticity to its protein products. In order to gain insight into its structure-function relationships, we carried out a comprehensive analysis of structural propensities within the intrinsically disordered N-terminal domain from the human papillomavirus type-16 E7 oncoprotein (E7N). Two E7N segments located within the conserved CR1 and CR2 regions present transient α-helix structure. The helix in the CR1 region spans residues L8 to L13 and overlaps with the E2F mimic linear motif. The second helix, located within the highly acidic CR2 region, presents a pH-dependent structural transition. At neutral pH the helix spans residues P17 to N29, which include the retinoblastoma tumor suppressor LxCxE binding motif (residues 21–29), while the acidic CKII-PEST region spanning residues E33 to I38 populates polyproline type II (PII) structure. At pH 5.0, the CR2 helix propagates up to residue I38 at the expense of loss of PII due to charge neutralization of acidic residues. Using truncated forms of HPV-16 E7, we confirmed that pH-induced changes in α-helix content are governed by the intrinsically disordered E7N domain. Interestingly, while at both pH the region encompassing the LxCxE motif adopts α-helical structure, the isolated 21–29 fragment including this stretch is unable to populate an α-helix even at high TFE concentrations. Thus, the E7N domain can populate dynamic but discrete structural ensembles by sampling α-helix-coil-PII-ß-sheet structures. This high plasticity may modulate the exposure of linear binding motifs responsible for its multi-target binding properties, leading to interference with key cell signaling pathways and eventually to cellular transformation by the virus. PMID:24086265

(Pt{sub 1–x}Cu{sub x}){sub 3}Cu{sub 2}B and Pt{sub 9}Cu{sub 3}B{sub 5}, the first examples of copper platinum borides. Observation of superconductivity in a novel boron filled β-Mn-type compound

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

Salamakha, Leonid P.; Sologub, Oksana, E-mail: oksana.sologub@univie.ac.at; Stöger, Berthold

New ternary copper platinum borides have been synthesized by arc melting of pure elements followed by annealing at 600 °C. The structures have been studied by X-ray single crystal and powder diffraction. (Pt{sub 1−x}Cu{sub x}){sub 3}Cu{sub 2}B (x=0.33) forms a B-filled β-Mn-type structure (space group P4{sub 1}32; a=0.6671(1) nm). Cu atoms are distributed preferentially on the 8c atom sites, whereas the 12d site is randomly occupied by Pt and Cu atoms (0.670(4) Pt±0.330(4) Cu). Boron is located in octahedral voids of the parent β-Mn-type structure. Pt{sub 9}Cu{sub 3}B{sub 5} (space group P-62m; a=0.9048(3) nm, c=0.2908(1) nm) adopts the Pt{sub 9}Zn{submore » 3}B{sub 5–δ}-type structure. It has a columnar architecture along the short translation vector exhibiting three kinds of [Pt{sub 6}] trigonal prism columns (boron filled, boron semi-filled and empty) and Pt channels with a pentagonal cross section filled with Cu atoms. The striking structural feature is a [Pt{sub 6}] cluster in form of an empty trigonal prism at the origin of the unit cell, which is surrounded by coupled [BPt{sub 6}] and [Pt{sub 6}] trigonal prisms, rotated perpendicularly to the central one. There is no B–B contact as well as Cu–B contact in the structure. The relationships of Pt{sub 9}Cu{sub 3}B{sub 5} structure with the structure of Ti{sub 1+x}Os{sub 2−x}RuB{sub 2} as well as with the structure families of metal sulfides and aluminides have been elucidated. (Pt{sub 1–x}Cu{sub x}){sub 3}Cu{sub 2}B (x=0.3) (B-filled β-Mn-type structure) is a bulk superconductor with a transition temperature of about 2.06 K and an upper critical field μ{sub 0}H{sub C2}(0){sup WHH} of 1.2 T, whereas no superconducting transition has been observed up to 0.3 K in Pt{sub 9}Cu{sub 3}B{sub 5} (Pt{sub 9}Zn{sub 3}B{sub 5–δ}-type structure) from electrical resistivity measurements. - Highlights: • First two copper platinum borides, (Pt{sub 0.67}Cu{sub 0.33}){sub 3}Cu{sub 2}B and Pt{sub 9}Cu{sub 3}B{sub 5} were obtained. • (Pt{sub 0.67}Cu{sub 0.33}){sub 3}Cu{sub 2}B forms a B-filled β-Mn-type structure. • Pt{sub 9}Cu{sub 3}B{sub 5} adopts a Pt{sub 9}Zn{sub 3}B{sub 5–δ}-type structure. • Boron atoms exhibit octahedral and trigonal prismatic coordination. • (Pt{sub 1–x}Cu{sub x})3Cu{sub 2}B (x=0.3) is a bulk superconductor with T{sub c} 2.06 K.« less

Use of proline mutants to help solve the NMR solution structure of type III antifreeze protein.

PubMed Central

Chao, H.; Davies, P. L.; Sykes, B. D.; Sönnichsen, F. D.

1993-01-01

To help understand the structure/function relationships in antifreeze proteins (AFP), and to define the motifs required for ice binding, a Type III AFP suitable for two-dimensional (2D) NMR studies was produced in Escherichia coli. A synthetic gene for one of the Type III AFP isoforms was assembled in a T7 polymerase-directed expression vector. The 67-amino acid-long gene product differed from the natural AFP by inclusion of an N-terminal methionine but was indistinguishable in activity. The NMR spectra of this AFP were complicated by cis-trans proline isomerization from the C-terminal sequence YPPA. Substitution of this sequence by YAA eliminated isomer signals without altering the activity or structure of the mutant AFP. This variant (rQAE m1.1) was selected for sequential assignment and the secondary structure determination using 2D 1H NMR spectroscopy. Nine beta-strands are paired to form two triple-stranded antiparallel sheets and one double-stranded antiparallel sheet. Two further proline replacements, P29A and P33A, were made to delineate the role of conserved prolines in Type III AFP. These mutants were valuable in clarifying ambiguous NMR spectral assignments amongst the remaining six prolines of rQAE m1.1. In contrast to the replacement of the C-terminal prolyl residues, the exchange of P29 and P33 caused some structural changes and significantly decreased protein solubility and antifreeze activity. PMID:8401227

Investigation of anodic and chemical oxides grown on p-type InP with applications to surface passivation for n(+)-p solar cell fabrication

NASA Technical Reports Server (NTRS)

Faur, Maria; Faur, Mircea; Goradia, Manju; Goradia, Chandra; Jenkins, Phillip; Jayne, Douglas; Weinberg, Irving

1991-01-01

Most of the previously reported InP anodic oxides were grown on a n-type InP with applications to fabrication of MISFET structures and were described as a mixture of In2O3 and P2O5 stoichiometric compounds or nonstoichiometric phases which have properties similar to crystalline compounds In(OH)3, InPO4, and In(PO3)3. Details of the compositional change of the anodic oxides grown under different anodization conditions were previously reported. The use of P-rich oxides grown either by anodic or chemical oxidation are investigated for surface passivation of p-type InP and as a protective cap during junction formation by closed-ampoule sulfur diffusion. The investigation is based on but not limited to correlations between PL intensity and X-ray photoelectron spectroscopy (XPS) chemical composition data.

Effect of reflective p-type ohmic contact on thermal reliability of vertical InGaN/GaN LEDs

NASA Astrophysics Data System (ADS)

Son, Jun Ho; Song, Yang Hee; Kim, Buem Joon; Lee, Jong-Lam

2014-11-01

We report on the enhanced thermal reliability of vertical-LEDs (VLEDs) using novel reflective p-type ohmic contacts with good thermal stability. The reflective p-type ohmic contacts with Ni/Ag-Cu alloy multi-layer structure shows low contact resistivity, as low as 9.3 × 10-6 Ωcm2, and high reflectance of 86% after annealing at 450°C. The V-LEDs with Ni/Ag-Cu alloy multi-layer structure show good thermal reliability with stress time at 300°C in air ambient. The improved thermal stability of the reflective ohmic contacts to p-type GaN is believed to play a critical role in the thermal reliability of V-LEDs. [Figure not available: see fulltext.

Novel and Recurrent MYO7A Mutations in Usher Syndrome Type 1 and Type 2

PubMed Central

Liu, Yani; Liu, Xiaoxing; Ha, Shaoping; Liu, Wenzhou; Kang, Xiaoli; Sheng, Xunlun; Zhao, Chen

2014-01-01

Usher syndrome (USH) is a group of disorders manifested as retinitis pigmentosa and bilateral sensorineural hearing loss, with or without vestibular dysfunction. Here, we recruited three Chinese families affected with autosomal recessive USH for detailed clinical evaluations and for mutation screening in the genes associated with inherited retinal diseases. Using targeted next-generation sequencing (NGS) approach, three new alleles and one known mutation in MYO7A gene were identified in the three families. In two families with USH type 1, novel homozygous frameshift variant p.Pro194Hisfs*13 and recurrent missense variant p.Thr165Met were demonstrated as the causative mutations respectively. Crystal structural analysis denoted that p.Thr165Met would very likely change the tertiary structure of the protein encoded by MYO7A. In another family affected with USH type 2, novel biallelic mutations in MYO7A, c.[1343+1G>A];[2837T>G] or p.[?];[Met946Arg], were identified with clinical significance. Because MYO7A, to our knowledge, has rarely been correlated with USH type 2, our findings therefore reveal distinguished clinical phenotypes associated with MYO7A. We also conclude that targeted NGS is an effective approach for genetic diagnosis for USH, which can further provide better understanding of genotype-phenotype relationship of the disease. PMID:24831256

Novel and recurrent MYO7A mutations in Usher syndrome type 1 and type 2.

PubMed

Rong, Weining; Chen, Xue; Zhao, Kanxing; Liu, Yani; Liu, Xiaoxing; Ha, Shaoping; Liu, Wenzhou; Kang, Xiaoli; Sheng, Xunlun; Zhao, Chen

2014-01-01

Usher syndrome (USH) is a group of disorders manifested as retinitis pigmentosa and bilateral sensorineural hearing loss, with or without vestibular dysfunction. Here, we recruited three Chinese families affected with autosomal recessive USH for detailed clinical evaluations and for mutation screening in the genes associated with inherited retinal diseases. Using targeted next-generation sequencing (NGS) approach, three new alleles and one known mutation in MYO7A gene were identified in the three families. In two families with USH type 1, novel homozygous frameshift variant p.Pro194Hisfs*13 and recurrent missense variant p.Thr165Met were demonstrated as the causative mutations respectively. Crystal structural analysis denoted that p.Thr165Met would very likely change the tertiary structure of the protein encoded by MYO7A. In another family affected with USH type 2, novel biallelic mutations in MYO7A, c.[1343+1G>A];[2837T>G] or p.[?];[Met946Arg], were identified with clinical significance. Because MYO7A, to our knowledge, has rarely been correlated with USH type 2, our findings therefore reveal distinguished clinical phenotypes associated with MYO7A. We also conclude that targeted NGS is an effective approach for genetic diagnosis for USH, which can further provide better understanding of genotype-phenotype relationship of the disease.

Novel Binding Motif and New Flexibility Revealed by Structural Analyses of a Pyruvate Dehydrogenase-Dihydrolipoyl Acetyltransferase Subcomplex from the Escherichia coli Pyruvate Dehydrogenase Multienzyme Complex*

PubMed Central

Arjunan, Palaniappa; Wang, Junjie; Nemeria, Natalia S.; Reynolds, Shelley; Brown, Ian; Chandrasekhar, Krishnamoorthy; Calero, Guillermo; Jordan, Frank; Furey, William

2014-01-01

The Escherichia coli pyruvate dehydrogenase multienzyme complex contains multiple copies of three enzymatic components, E1p, E2p, and E3, that sequentially carry out distinct steps in the overall reaction converting pyruvate to acetyl-CoA. Efficient functioning requires the enzymatic components to assemble into a large complex, the integrity of which is maintained by tethering of the displaced, peripheral E1p and E3 components to the E2p core through non-covalent binding. We here report the crystal structure of a subcomplex between E1p and an E2p didomain containing a hybrid lipoyl domain along with the peripheral subunit-binding domain responsible for tethering to the core. In the structure, a region at the N terminus of each subunit in the E1p homodimer previously unseen due to crystallographic disorder was observed, revealing a new folding motif involved in E1p-E2p didomain interactions, and an additional, unexpected, flexibility was discovered in the E1p-E2p didomain subcomplex, both of which probably have consequences in the overall multienzyme complex assembly. This represents the first structure of an E1p-E2p didomain subcomplex involving a homodimeric E1p, and the results may be applicable to a large range of complexes with homodimeric E1 components. Results of HD exchange mass spectrometric experiments using the intact, wild type 3-lipoyl E2p and E1p are consistent with the crystallographic data obtained from the E1p-E2p didomain subcomplex as well as with other biochemical and NMR data reported from our groups, confirming that our findings are applicable to the entire E1p-E2p assembly. PMID:25210042

Novel binding motif and new flexibility revealed by structural analyses of a pyruvate dehydrogenase-dihydrolipoyl acetyltransferase subcomplex from the Escherichia coli pyruvate dehydrogenase multienzyme complex.

PubMed

Arjunan, Palaniappa; Wang, Junjie; Nemeria, Natalia S; Reynolds, Shelley; Brown, Ian; Chandrasekhar, Krishnamoorthy; Calero, Guillermo; Jordan, Frank; Furey, William

2014-10-24

The Escherichia coli pyruvate dehydrogenase multienzyme complex contains multiple copies of three enzymatic components, E1p, E2p, and E3, that sequentially carry out distinct steps in the overall reaction converting pyruvate to acetyl-CoA. Efficient functioning requires the enzymatic components to assemble into a large complex, the integrity of which is maintained by tethering of the displaced, peripheral E1p and E3 components to the E2p core through non-covalent binding. We here report the crystal structure of a subcomplex between E1p and an E2p didomain containing a hybrid lipoyl domain along with the peripheral subunit-binding domain responsible for tethering to the core. In the structure, a region at the N terminus of each subunit in the E1p homodimer previously unseen due to crystallographic disorder was observed, revealing a new folding motif involved in E1p-E2p didomain interactions, and an additional, unexpected, flexibility was discovered in the E1p-E2p didomain subcomplex, both of which probably have consequences in the overall multienzyme complex assembly. This represents the first structure of an E1p-E2p didomain subcomplex involving a homodimeric E1p, and the results may be applicable to a large range of complexes with homodimeric E1 components. Results of HD exchange mass spectrometric experiments using the intact, wild type 3-lipoyl E2p and E1p are consistent with the crystallographic data obtained from the E1p-E2p didomain subcomplex as well as with other biochemical and NMR data reported from our groups, confirming that our findings are applicable to the entire E1p-E2p assembly. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Study of the Crystal Structures of Sodium Magnesium and Sodium Nickel Diphosphates

NASA Astrophysics Data System (ADS)

Erragh, Fatima; Boukhari, Ali; Abraham, Francis; Elouadi, Brahim

2000-07-01

Single-crystal X-ray crystallography studies have shown that diphosphates Na3.64Mg2.18(P2O7)2 and Na3.64Ni2.18(P2O7)2 crystallize with the same structural type and the same space group Poverline1. Their triclinic lattice parameters are equal to a=10.901 (2), b=9.765 (2), c=6.382 (1) Å, α=112.43 (1)°, β=99.64 (1)°, γ=107.53 (1)°, Z=2 and a=10.889 (5), b=9.705 (4), c=6.358 (4) Å, α=112.46 (4)°, β=99.92 (4)°, γ=107.54 (4)°, Z=2, respectively. The structure could be regarded as a packing of diphosphate groups [P2O7]4- and [MO6] octahedra (M=Mg, Ni) delimiting cavities and tunnels which host sodium cations. The tunnels are running along [001]. The structure is characterized by mixed (Na, M) sites with an occupation factor ratio equal to ca. 0.82/0.18. Sodium cations are located in five different sites: two cavities (one penta- and the other octa-coordinated) totally occupied and three octahedral interstices, which are partially filled by Na(3), Na(4), and Na(5) according to the respective occupation factors of 0.15, 0.42, and 0.25 for Na3.64Mg2.18(P2O7)2 and 0.13, 0.40, and 0.29 in the case of Na3.64Ni2.18(P2O7)2.

Electrical and structural characterization of plasma polymerized polyaniline/TiO2 heterostructure diode: a comparative study of single and bilayer TiO2 thin film electrode.

PubMed

Ameen, Sadia; Akhtar, M Shaheer; Kimi, Young Soon; Yang, O-Bong; Shin, Hyung-Shik

2011-04-01

A heterostructure was fabricated using p-type plasma polymerized polyaniline (PANI) and n-type (single and bilayer) titanium dioxide (TiO2) thin film on FTO glass. The deposition of single and bilayer TiO2 thin film on FTO substrate was achieved through doctor blade followed by dip coating technique before subjected to plasma enhanced polymerization. To fabricate p-n heterostructure, a plasma polymerization of aniline was conducted using RF plasma at 13.5 MHz and at the power of 120 W on the single and bilayer TiO2 thin film electrodes. The morphological, optical and the structural characterizations revealed the formation of p-n heterostructures between PANI and TiO2 thin film. The PANI/bilayer TiO2 heterostructure showed the improved current-voltage (I-V) characteristics due to the substantial deposition of PANI molecules into the bilayer TiO2 thin film which provided good conducting pathway and reduced the degree of excitons recombination. The change of linear I-V behavior of PANI/TiO2 heterostructure to non linear behavior with top Pt contact layer confirmed the formation of Schottky contact at the interfaces of Pt layer and PANI/TiO2 thin film layers.

Astilbe thunbergii reduces postprandial hyperglycemia in a type 2 diabetes rat model via pancreatic alpha-amylase inhibition by highly condensed procyanidins.

PubMed

Kato, Eisuke; Kushibiki, Natsuka; Inagaki, Yosuke; Kurokawa, Mihoko; Kawabata, Jun

2017-09-01

Type 2 diabetes mellitus (T2DM) is a common global health problem. Prevention of this disease is an important task, and functional food supplements are considered an effective method. We found potent pancreatic α-amylase inhibition in Astilbe thunbergii root extract (AT) and confirmed that AT treatment in a T2DM rat model reduces post-starch administration blood glucose levels. Activity-guided isolation revealed procyanidin (AT-P) as the α-amylase inhibitory component with IC 50  = 1.7 μg/mL against porcine pancreatic α-amylase. Structure analysis of AT-P revealed it is a B-type procyanidin comprised of four types of flavan-3-ols, some with a galloyl group, and catechin attached as the terminal unit. The abundant AT-P content and its comparable α-amylase inhibition to acarbose, the anti-diabetic medicine, suggest that AT is a promising food supplement for diabetes prevention.

First-principles study of nitrogen-doped CuAlO2

NASA Astrophysics Data System (ADS)

Xu, Ying; Ao, Zhi Min; Yuan, Ding Wang

2012-08-01

The electronic structure and formation energies of N-doped CuAlO2 are studied using first-principles calculations. It is found that, when a N atom is doped into CuAlO2, the N atom prefers to substitute an O atom rather than to occupy an interstitial site of the Cu layer. The NO acts as a shallow accepter while the Ni acts as a deep accepter. The results of the electronic structure show that the N-doping doesn't alter the band gap of CuAlO2 for the both cases. In the substitutional case, the N impurity states occur at the top of valance band maximum (VBM), which provides holes and increases the p-type conductivity. However, in the interstitial case, the N impurity states occur in the middle of the band gap, which are more localized and this indicates that it is not good for p-type conductivity.

Fabrication of gold dot, ring, and corpuscle arrays from block copolymer templates via a simple modification of surface energy

NASA Astrophysics Data System (ADS)

Cho, Heesook; Choi, Sinho; Kim, Jin Young; Park, Soojin

2011-12-01

We demonstrate a simple method for tuning the morphologies of as-spun micellar thin films by modifying the surface energy of silicon substrates. When a polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer dissolved in o-xylene was spin-coated onto a PS-modified surface, a dimple-type structure consisting of a thick PS shell and P2VP core was obtained. Subsequently, when the films were immersed in metal precursor solutions at certain periods of time and followed by plasma treatment, metal individual dots in a ring-shaped structure, metal nanoring, and metal corpuscle arrays were fabricated, depending on the loading amount of metal precursors. In contrast, when PS-b-P2VP films cast onto silicon substrates with a native oxide were used as templates, only metal dotted arrays were obtained. The combination of micellar thin film and surface energy modification offers an effective way to fabricate various nanostructured metal or metal oxide films.We demonstrate a simple method for tuning the morphologies of as-spun micellar thin films by modifying the surface energy of silicon substrates. When a polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer dissolved in o-xylene was spin-coated onto a PS-modified surface, a dimple-type structure consisting of a thick PS shell and P2VP core was obtained. Subsequently, when the films were immersed in metal precursor solutions at certain periods of time and followed by plasma treatment, metal individual dots in a ring-shaped structure, metal nanoring, and metal corpuscle arrays were fabricated, depending on the loading amount of metal precursors. In contrast, when PS-b-P2VP films cast onto silicon substrates with a native oxide were used as templates, only metal dotted arrays were obtained. The combination of micellar thin film and surface energy modification offers an effective way to fabricate various nanostructured metal or metal oxide films. Electronic supplementary information (ESI) available: AFM images of Au nanorings prepared from a mixed solvent and characterization of PS-b-P2VP micellar films. See DOI: 10.1039/c1nr11075f

REDUCED CHORIOCAPILLARIS FLOW IN EYES WITH TYPE 3 NEOVASCULARIZATION AND AGE-RELATED MACULAR DEGENERATION.

PubMed

Borrelli, Enrico; Souied, Eric H; Freund, K Bailey; Querques, Giuseppe; Miere, Alexandra; Gal-Or, Orly; Sacconi, Riccardo; Sadda, SriniVas R; Sarraf, David

2018-04-30

To study choriocapillaris (CC) flow in eyes with Type 3 neovascularization (NV) and age-related macular degeneration, using optical coherence tomography angiography analysis. In this multicenter, retrospective, observational study, we collected data from 21 patients with unilateral Type 3 NV and age-related macular degeneration, based on clinical examination, structural optical coherence tomography, and fluorescein angiography when available. An additional group of 20 nonneovascular age-related macular degeneration eyes with unilateral Type 1 or Type 2 NV due to age-related macular degeneration was included for comparison. En face optical coherence tomography angiography imaging (3 × 3 mm scans) with quantitative microvascular analysis of the CC was performed. Main outcome measures were: 1) the percent nonperfused choriocapillaris area; and 2) the average CC signal void size. We included 21 patients with unilateral Type 3 NV (15 female, 71.5%) and 20 patients with unilateral Type 1 or 2 NV (9 female, 45.0% P = 0.118). Mean ± SD age was 82.1 ± 7.4 years in the unilateral Type 3 patients and 78.3 ± 8.1 in unilateral Type 1/2 NV subjects (P = 0.392). The percent nonperfused choriocapillaris area was 56.3 ± 8.1% in eyes with Type 3 NV and 51.9 ± 4.3% in the fellow eyes (P = 0.016). The average signal void size was also increased in those eyes with Type 3 NV (939.9 ± 680.9 μm), compared with the fellow eyes (616.3 ± 304.2 μm, P = 0.039). The number of signal voids was reduced in the Type 3 NV eyes (604.5 ± 282.9 vs. 747.3 ± 195.8, P = 0.046). The subfoveal choroidal thickness was 135.9 ± 54.2 μm in eyes with Type 3 NV and 167.2 ± 65.4 μm in the fellow eyes (P = 0.003). In addition, the fellow eyes of patients with unilateral Type 3 NV displayed more significant CC flow abnormalities versus the fellow eyes with unilateral Type 1/2 NV (percent nonperfused choriocapillaris area = 51.9 ± 4.3% vs. 46.0 ± 2.1%, respectively, P < 0.0001; and average signal void size 616.3 ± 304.2 μm versus 351.4 ± 65.5 μm, respectively, P < 0.0001; and number of signal voids 747.3 ± 195.8 vs. 998.5 ± 147.3, respectively, P < 0.0001). Eyes with unilateral Type 3 NV illustrated increased CC nonperfusion versus fellow nonneovascular eyes. These results suggest that choroidal ischemia may play an important role in the development of Type 3 NV.

p-π Conjugated Polymers Based on Stable Triarylborane with n-Type Behavior in Optoelectronic Devices.

PubMed

Meng, Bin; Ren, Yi; Liu, Jun; Jäkle, Frieder; Wang, Lixiang

2018-02-19

p-π conjugation with embedded heteroatoms offers unique opportunities to tune the electronic structure of conjugated polymers. An approach is presented to form highly electron-deficient p-π conjugated polymers based on triarylboranes, demonstrate their n-type behavior, and explore device applications. By combining alternating [2,4,6-tris(trifluoromethyl)phenyl]di(thien-2-yl)borane (FBDT) and electron-deficient isoindigo (IID)/pyridine-flanked diketopyrrolopyrrole (DPPPy) units, we achieve low-lying lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels, high electron mobilities, and broad absorptions in the visible region. All-polymer solar cells with these polymers as electron acceptors exhibit encouraging photovoltaic performance with power conversion efficiencies of up to 2.83 %. These results unambiguously prove the n-type behavior and demonstrate the photovoltaic applications of p-π conjugated polymers based on triarylborane. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatially Restricted and Developmentally Dynamic Expression of Engrailed Genes in Multiple Cerebellar Cell Types

PubMed Central

Wilson, Sandra L.; Kalinovsky, Anna; Orvis, Grant D.

2011-01-01

The cerebellum is a highly organized structure partitioned into lobules along the anterior–posterior (A-P) axis and into striped molecular domains along the medial–lateral (M-L) axis. The Engrailed (En) homeobox genes are required for patterning the morphological and molecular domains along both axes, as well as for the establishment of the normal afferent topography required to generate a fully functional cerebellum. As a means to understand how the En genes regulate multiple levels of cerebellum construction, we characterized En1 and En2 expression around birth and at postnatal day (P)21 during the period when the cerebellum undergoes a remarkable transformation from a smooth ovoid structure to a highly foliated structure. We show that both En1 and En2 are expressed in many neuronal cell types in the cerebellum, and expression persists until at least P21. En1 and En2 expression, however, undergoes profound changes in their cellular and spatial distributions between embryonic stages and P21, and their expression domains become largely distinct. Comparison of the distribution of En-expressing Purkinje cells relative to early- and late-onset Purkinje cell M-L stripe proteins revealed that although En1- and En2-expressing Purkinje cell domains do not strictly align with those of ZEBRINII at P21, a clear pattern exists that is most evident at E17.5 by an inverse correlation between the level of En2 expression and PLCβ4 and EPHA4. PMID:21431469

Graphene oxide quantum dot-sensitized porous titanium dioxide microsphere: Visible-light-driven photocatalyst based on energy band engineering.

PubMed

Zhang, Yu; Qi, Fuyuan; Li, Ying; Zhou, Xin; Sun, Hongfeng; Zhang, Wei; Liu, Daliang; Song, Xi-Ming

2017-07-15

We report a novel graphene oxide quantum dot (GOQD)-sensitized porous TiO 2 microsphere for efficient photoelectric conversion. Electro-chemical analysis along with the Mott-Schottky equation reveals conductivity type and energy band structure of the two semiconductors. Based on their energy band structures, visible light-induced electrons can transfer from the p-type GOQD to the n-type TiO 2 . Enhanced photocurrent and photocatalytic activity in visible light further confirm the enhanced separation of electrons and holes in the nanocomposite. Copyright © 2017 Elsevier Inc. All rights reserved.

Insight into the impact of two structural calcium ions on the properties of Pleurotus eryngii versatile ligninolytic peroxidase.

PubMed

Gao, Yu; Zheng, Lanyan; Li, Jian-Jun; Du, Yuguang

2016-12-15

Two structural Ca 2+ (proximal and distal) is known to be important for ligninolytic peroxidases. However, few studies toward impact of residues involved in two Ca 2+ on properties of ligninolytic peroxidases have been done, especially the proximal one. In this study, mutants of nine residues involved in liganding two Ca 2+ of Pleurotus eryngii versatile peroxidase (VP) were investigated. Most mutants almost completely lost activities, except the mutants of proximal Ca 2+ - S170A and V192T. In comparison with WT (wild type), optimal pH values of S170A, S170D, and V192T shifted from pH 3.0 to pH 3.5. The order of thermal and pH stabilities of WT, V192T, S170A, and S170D is similar to that of their specific activities: WT > V192T > S170A > S170D. The CD (circular dichroism) results of WT and several mutants indicated that mutations had some effects on secondary structures. For the first time, it was observed that the thermostability of ligninolytic peroxidases is related with proximal Ca 2+ too, and the mutant containing distal Ca 2+ only was obtained. Our results clearly demonstrated that enzymatic activities, pH and thermal stabilities, Ca 2+ content, and secondary structures of VP have close relationship with the residues involved in two structural Ca 2+ . Copyright © 2016 Elsevier Inc. All rights reserved.

Structural building principles of complex face-centered cubic intermetallics.

PubMed

Dshemuchadse, Julia; Jung, Daniel Y; Steurer, Walter

2011-08-01

Fundamental structural building principles are discussed for all 56 known intermetallic phases with approximately 400 or more atoms per unit cell and space-group symmetry F43m, Fd3m, Fd3, Fm3m or Fm3c. Despite fundamental differences in chemical composition, bonding and electronic band structure, their complex crystal structures show striking similarities indicating common building principles. We demonstrate that the structure-determining elements are flat and puckered atomic {110} layers stacked with periodicities 2p. The atoms on this set of layers, which intersect each other, form pentagon face-sharing endohedral fullerene-like clusters arranged in a face-centered cubic packing (f.c.c.). Due to their topological layer structure, all these crystal structures can be described as (p × p × p) = p(3)-fold superstructures of a common basic structure of the double-diamond type. The parameter p, with p = 3, 4, 7 or 11, is determined by the number of layers per repeat unit and the type of cluster packing, which in turn are controlled by chemical composition.

Gating, Regulation, and Structure in K2P K+ Channels: In Varietate Concordia?

PubMed

Niemeyer, María Isabel; Cid, L Pablo; González, Wendy; Sepúlveda, Francisco V

2016-09-01

K2P K(+) channels with two pore domains in tandem associate as dimers to produce so-called background conductances that are regulated by a variety of stimuli. Whereas gating in K2P channels has been poorly understood, recent developments have provided important clues regarding the gating mechanism for this family of proteins. Two modes of gating present in other K(+) channels have been considered. The first is the so-called activation gating that occurs by bundle crossing and the splaying apart of pore-lining helices commanding ion passage. The second mode involves a change in conformation at the selectivity filter (SF), which impedes ion flow at this narrow portion of the conduction pathway and accounts for extracellular pH modulation of several K2P channels. Although some evidence supports the existence of an activation gate in K2P channels, recent results suggest that perhaps all stimuli, even those sensed at a distant location in the protein, are also mediated by SF gating. Recently resolved crystal structures of K2P channels in conductive and nonconductive conformations revealed that the nonconductive state is reached by blockade by a lipid acyl chain that gains access to the channel cavity through intramembrane fenestrations. Here we discuss whether this novel type of gating, proposed so far only for membrane tension gating, might mediate gating in response to other stimuli or whether SF gating is the only type of opening/closing mechanism present in K2P channels. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Design, Synthesis and Evaluation of 2,5-Diketopiperazines as Inhibitors of the MDM2-p53 Interaction.

PubMed

Pettersson, Mariell; Quant, Maria; Min, Jaeki; Iconaru, Luigi; Kriwacki, Richard W; Waddell, M Brett; Guy, R Kiplin; Luthman, Kristina; Grøtli, Morten

2015-01-01

The transcription factor p53 is the main tumour suppressor in cells and many cancer types have p53 mutations resulting in a loss of its function. In tumours that retain wild-type p53 function, p53 activity is down-regulated by MDM2 (human murine double minute 2) via a direct protein-protein interaction. We have designed and synthesised two series of 2,5-diketopiperazines as inhibitors of the MDM2-p53 interaction. The first set was designed to directly mimic the α-helical region of the p53 peptide, containing key residues in the i, i+4 and i+7 positions of a natural α-helix. Conformational analysis indicated that 1,3,6-trisubstituted 2,5-diketopiperazines were able to place substituents in the same spatial orientation as an α-helix template. The key step of the synthesis involved the cyclisation of substituted dipeptides. The other set of tetrasubstituted 2,5-diketopiperazines were designed based on structure-based docking studies and the Ugi multicomponent reaction was used for the synthesis. This latter set comprised the most potent inhibitors which displayed micromolar IC50-values in a biochemical fluorescence polarisation assay.

Design, Synthesis and Evaluation of 2,5-Diketopiperazines as Inhibitors of the MDM2-p53 Interaction

PubMed Central

Pettersson, Mariell; Quant, Maria; Min, Jaeki; Iconaru, Luigi; Kriwacki, Richard W.; Waddell, M. Brett; Guy, R. Kiplin; Luthman, Kristina; Grøtli, Morten

2015-01-01

The transcription factor p53 is the main tumour suppressor in cells and many cancer types have p53 mutations resulting in a loss of its function. In tumours that retain wild-type p53 function, p53 activity is down-regulated by MDM2 (human murine double minute 2) via a direct protein—protein interaction. We have designed and synthesised two series of 2,5-diketopiperazines as inhibitors of the MDM2-p53 interaction. The first set was designed to directly mimic the α-helical region of the p53 peptide, containing key residues in the i, i+4 and i+7 positions of a natural α-helix. Conformational analysis indicated that 1,3,6-trisubstituted 2,5-diketopiperazines were able to place substituents in the same spatial orientation as an α-helix template. The key step of the synthesis involved the cyclisation of substituted dipeptides. The other set of tetrasubstituted 2,5-diketopiperazines were designed based on structure-based docking studies and the Ugi multicomponent reaction was used for the synthesis. This latter set comprised the most potent inhibitors which displayed micromolar IC50-values in a biochemical fluorescence polarisation assay. PMID:26427060

From thermoelectric bulk to nanomaterials: Current progress for Bi 2 Te 3 and CoSb 3: From thermoelectric bulk to nanomaterials

DOE PAGES

Peranio, N.; Eibl, O.; Bäßler, S.; ...

2015-10-29

We synthesized Bi 2Te 3 and CoSb 3 based nanomaterials and their thermoelectric, structural, and vibrational properties analyzed to assess and reduce ZT-limiting mechanisms. The same preparation and/or characterization methods were applied in the different materials systems. Single-crystalline, ternary p-type Bi 15Sb 29Te 56, and n-type Bi 38Te 55Se 7 nanowires with power factors comparable to nanostructured bulkmaterialswere prepared by potential-pulsed electrochemical deposition in a nanostructured Al 2O 3 matrix. p-type Sb 2Te 3, n-type Bi 2Te 3, and n-type CoSb 3 thin films were grown at room temperature using molecular beam epitaxy and were subsequently annealed at elevated temperatures.more » It yielded polycrystalline, single phase thin films with optimized charge carrier densities. In CoSb 3 thin films the speed of sound could be reduced by filling the cage structure with Yb and alloying with Fe yielded p-type material. Bi 2(Te 0.91Se 0.09) 3/SiC and (Bi 0.26Sb 0.74) 2Te 3/SiC nanocomposites with low thermal conductivities and ZT values larger than 1 were prepared by spark plasma sintering. Nanostructure, texture, chemical composition, as well as electronic and phononic excitations were investigated by X-ray diffraction, nuclear resonance scattering, inelastic neutron scattering, M ossbauer spectroscopy, and transmission electron microscopy. Furthermore, for Bi 2Te 3 materials, ab-initio calculations together with equilibrium and non-equilibrium molecular dynamics simulations for point defects yielded their formation energies and their effect on lattice thermal conductivity, respectively. Current advances in thermoelectric Bi 2Te 3 and CoSb 3 based nanomaterials are summarized. Advanced synthesis and characterization methods and theoreticalmodelingwere combined to assess and reduce ZT-limiting mechanisms in these materials.« less

A Memorial to a President

ERIC Educational Resources Information Center

Castro, Nash

1974-01-01

This document describes the plan for a living memorial to commemorate Lyndon Baines Johnson, 36th President of the United States: a 15-acre grove with hike and bike paths, white pine trees, rhododendrons, and other flowering shrubs. (JA)

Crystal and molecular structure of 2,6-dibromo-3-chloro-4-fluoroaniline

NASA Astrophysics Data System (ADS)

Betz, R.

2015-12-01

The crystal and molecular structure of 2,6-dibromo-3-chloro-4-fluoroaniline is determined. The crystals are monoclinic, a = 3.8380(3), b = 13.1010(12), c = 8.0980(8) Å, β = 96.010(4)°, V = 404.94(6) Å3, Z = 2, sp. gr. P21. Classical intra- and intermolecular hydrogen bonds of the N-H··· Hal type are observed next to a series of dispersive halogen···halogen interactions in the crystal structure.

Insights into the Effects of Zinc Doping on Structural Phase Transition of P2-Type Sodium Nickel Manganese Oxide Cathodes for High-Energy Sodium Ion Batteries

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

Wu, Xuehang; Xu, Gui-Liang; Zhong, Guiming

P2-type sodium nickel manganese oxide-based cathode materials with higher energy densities are prime candidates for applications in rechargeable sodium ion batteries. A systematic study combining in situ high energy X-ray diffraction (HEXRD), ex situ Xray absorption fine spectroscopy (XAFS), transmission electron microscopy (TEM), and solid-state nuclear magnetic resonance (SSNMR) techniques was carried out to gain a deep insight into the structural evolution of P2-Na 0.66Ni 0.33-xZn xMn 0.67O 2 (x = 0, 0.07) during cycling. In situ HEXRD and ex situ TEM measurements indicate that an irreversible phase transition occurs upon sodium insertion-extraction of Na 0.66Ni 0.33Mn 0.67O 2. Zincmore » doping of this system results in a high structural reversibility. XAFS measurements indicate that both materials are almost completely dependent on the Ni 4+/Ni 3+/ Ni 2+ redox couple to provide charge/discharge capacity. SS-NMR measurements indicate that both reversible and irreversible migration of transition metal ions into the sodium layer occurs in the material at the fully charged state. The irreversible migration of transition metal ions triggers a structural distortion, leading to the observed capacity and voltage fading. Our results allow a new understanding of the importance of improving the stability of transition metal layers.« less

Superconductivity, Magnetoresistance, Magnetic Anomaly and Crystal Structure of New Phases of Topological Insulators Bi2Se3 and Sb2Te3

NASA Astrophysics Data System (ADS)

Kulbachinskii, V. A.; Buga, S. G.; Serebryanaya, N. R.; Perov, N. S.; Kytin, V. G.; Tarelkin, S. A.; Bagramov, R. H.; Eliseev, N. N.; Blank, V. D.

2018-03-01

We synthesized a new metastable phase of Bi2Se3 topological insulator by a rapid quenching after a high-pressure-high-temperature treatment at P≈7.7 GPa; 673

Type 1, type 2 and gestational diabetes mellitus differentially impact placental pathologic characteristics of uteroplacental malperfusion.

PubMed

Huynh, Jennifer; Yamada, Jessica; Beauharnais, Catherine; Wenger, Julia B; Thadhani, Ravi I; Wexler, Deborah; Roberts, Drucilla J; Bentley-Lewis, Rhonda

2015-10-01

During a pregnancy complicated by diabetes, the placenta undergoes a number of functional and structural pathologic changes. However, differences across studies may reflect pathophysiologic differences of diabetes types under investigation. We examined placental pathology from women ages 18-40 years with self-identified race/ethnicity; singleton, live births; and type 1 (T1DM; n = 36), type 2 (T2DM; n = 37), or gestational diabetes mellitus (GDM; n = 126). Clinical data were abstracted from medical records. Placental diagnoses were independently re-reviewed by a perinatal pathologist. Multivariable analyses adjusting for race, gestational weight gain, gestational age, and systolic blood pressure were conducted. Women with T1DM compared with either T2DM or GDM had higher gestational weight gain (mean ± SD, T1DM vs. T2DM: 28.5 ± 12.4 vs. 20.5 ± 13.4 kg, p = 0.03; or GDM: 21.3 ± 12.7 kg, p = 0.009) and insulin use (T2DM: 100.0% vs. 85.3%, p = 0.02; or GDM: 4.0%, p < 0.001). Women with T1DM compared with either T2DM or GDM also had a similarly lower prevalence of placental infarcts in univariate analyses; however, these findings did not remain significant after multivariable adjustment. Also, placentas from women with T2DM compared to GDM had higher rates of decidual vasculopathy when excluding women with preeclampsia (10.3 vs. 1.6%, p = 0.049) and diffuse chorangiosis (62.2 vs. 32.5%, p < 0.001) but a lower rate of villous immaturity (10.8 vs. 90.5%, p = 0.007) after full adjustment. Placental vasculopathic abnormalities differ by maternal diabetes type, potentially reflecting underlying pathophysiologic mechanisms. Further research on placental pathology and metabolic derangements is warranted. Copyright © 2015 Elsevier Ltd. All rights reserved.

Structural Characterization and Determinants of Specificity of Single-Chain Antibody Inhibitors of Membrane-Type Serine Protease 1

DTIC Science & Technology

2008-03-01

Colman, P. M. (1993). Shape complementarity at protein / protein interfaces . J Mol Biol 234, 946-50. 26. Huang, M., Syed, R., Stura, E. A., Stone, M. J...Å2 of surface area (Table 1). In the apo MT-SP1 structure20, Asp96 forms the bottom of the S4 pocket, allowing a positively charged substrate P4...of surface area that E2 buries on MT-SP1 is larger than the typical antibody/ protein antigen interaction, which averages about 875 Å2 26; 27. This

A new oxytelluride: Perovskite and CsCl intergrowth in Ba 3Yb 2O 5Te

DOE PAGES

Whalen, J. B.; Besara, T.; Vasquez, R.; ...

2013-04-27

The new oxytelluride Ba 3Yb 2O 5Te was obtained from an alkaline earth flux. Ba3Yb2O5Te crystallizes in the tetragonal space group P4/ mmm (#123), with a=4.3615(3) Å and c=11.7596(11) angstrom, Z=1. The structure combines two distinct building blocks, a Ba 2Yb 2O 5 perovskite-like double layer with square bipyramidal coordination of the ytterbium ions, and a CsCl-type BaTe layer. Short range magnetic order is apparent at below 5 K, with the magnetic behavior above this temperature dominated by crystal field effects. The structure may be considered as an analog to the Ruddlesden-Popper phases, where the NaCl-type layer has been replacedmore » by the CsCl-type layer. Finally, the two-dimensional magnetic behavior is expected based on the highly anisotropic nature of the structure.« less

(H3O)2TiF6

NASA Astrophysics Data System (ADS)

Villars, P.; Cenzual, K.; Daams, J.; Gladyshevskii, R.; Shcherban, O.; Dubenskyy, V.; Kuprysyuk, V.; Savysyuk, I.

This document is part of Subvolume A8 `Structure Types. Part 8: Space Groups (156) P3m1 - (148) R-3' of Volume 43 `Crystal Structures of Inorganic Compounds' of Landolt-Börnstein - Group III `Condensed Matter'.

Schottky barrier tuning of the graphene/SnS2 van der Waals heterostructures through electric field

NASA Astrophysics Data System (ADS)

Zhang, Fang; Li, Wei; Ma, Yaqiang; Dai, Xianqi

2018-03-01

Combining the electronic structures of two-dimensional monolayers in ultrathin hybrid nanocomposites is expected to display new properties beyond their single components. The effects of external electric field (Eext) on the electronic structures of monolayer SnS2 with graphene hybrid heterobilayers are studied by using the first-principle calculations. It is demonstrated that the intrinsic electronic properties of SnS2 and graphene are quite well preserved due to the weak van der Waals (vdW) interactions. We find that the n-type Schottky contacts with the significantly small Schottky barrier are formed at the graphene/SnS2 interface. In the graphene/SnS2 heterostructure, the vertical Eext can control not only the Schottky barriers (n-type and p-type) but also contact types (Schottky contact or Ohmic contact) at the interface. The present study would open a new avenue for application of ultrathin graphene/SnS2 heterostructures in future nano- and optoelectronics.

Layered Na‐Ion Cathodes with Outstanding Performance Resulting from the Synergetic Effect of Mixed P‐ and O‐Type Phases

PubMed Central

Keller, Marlou

2015-01-01

Herein, the synthesis of new quaternary layered Na‐based oxides of the type NaxMnyNizFe0.1Mg0.1O2 (0.67≤ x ≤ 1.0; 0.5≤ y ≤ 0.7; 0.1≤ z ≤ 0.3) is described. The synthesis can be tuned to obtain P2‐ and O3‐type as well as mixed P‐/O‐type phases as demonstrated by structural, morphological, and electrochemical properties characterization. Although all materials show good electrochemical performance, the simultaneous presence of the P‐ and O‐type phases is found to have a synergetic effect resulting in outstanding performance of the mixed phase material as a sodium‐ion cathode. The mixed P3/P2/O3‐type material, having an average elemental composition of Na0.76Mn0.5Ni0.3Fe0.1Mg0.1O2, overcomes the specific drawbacks associated with the P2‐ and O3‐type materials, allowing the outstanding electrochemical performance. In detail, the mixed phase material is able to deliver specific discharge capacities of up to 155 mAh g−1 (18 mA g−1) in the potential range of 2.0–4.3 V. In the narrower potential range of 2.5–4.3 V the material exhibits high average discharge potential (3.4 V versus Na/Na+), exceptional average coulombic efficiencies (>99.9%), and extraordinary capacity retention (90.2% after 601 cycles). The unexplored class of P‐/O‐type mixed phases introduces new perspectives for the development of layered positive electrode materials and powerful Na‐ion batteries. PMID:27134617

Forest canopy structural controls over throughfall affect soil microbial community structure in an epiphyte-laden maritime oak stand

NASA Astrophysics Data System (ADS)

Van Stan, J. T., II; Rosier, C. L.; Schrom, J. O.; Wu, T.; Reichard, J. S.; Kan, J.

2014-12-01

Identifying spatiotemporal influences on soil microbial community (SMC) structure is critical to understanding of patterns in nutrient cycling and related ecological services. Since forest canopy structure alters the spatiotemporal patterning of precipitation water and solute supplies to soils (via the "throughfall" mechanism), is it possible changes in SMC structure variability could arise from modifications in canopy elements? Our study investigates this question by monitoring throughfall water and dissolved ion supply to soils beneath a continuum of canopy structure: from a large gap (0% cover) to heavy Tillandsia usneoides L. (Spanish moss) canopy (>90% cover). Throughfall water supply diminished with increasing canopy cover, yet increased washoff/leaching of Na+, Cl-, PO43-, and SO42- from the canopy to the soils (p < 0.01). Presence of T. usneoides diminished throughfall NO3-, but enhanced NH4+, concentrations supplied to subcanopy soils. The mineral soil horizon (0-10 cm) from canopy gaps, bare canopy, and T. usneoides-laden canopy significantly differed (p < 0.05) in soil chemistry parameters (pH, Ca2+, Mg2+, CEC). PCR-DGGE banding patterns beneath similar canopy covers (experiencing similar throughfall dynamics) also produced high similarities per ANalyses Of SIMilarity (ANO-SIM), and clustered together when analyzed by Nonmetric Multidimensional Scaling (NMDS). Correlation analysis of DGGE banding patterns, throughfall dynamics, and soil chemistry yielded significant correlations (p < 0.05) between fungal communities and soil chemical properties significantly differing between canopy cover types (pH: r2 = 0.50; H+ %-base saturation: r2 = 0.48; Ca2+ %-base saturation: r2 = 0.43). Bacterial community structure correlated with throughfall NO3-, NH4+, and Ca2+ concentrations (r2 = 0.37, p = 0.16). These results suggest that modifications of forest canopy structures are capable of affecting mineral-soil horizon SMC structure via the throughfall mechanism when canopies' biomass distribution is highly heterogeneous.

Cluster self-organization of inorganic crystal-forming systems: Templated nanocluster precursors and self-assembly of framework MT structures of A/B,Zr silicates (A = Na, K; B = Ca, Sr)

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

Ilyushin, G. D., E-mail: ilyushin@ns.crys.ras.ru

The basic concepts that are used to describe crystallization as a phenomenon of the hierarchical (cluster) self-organization of a chemical system are considered. The templation of theoretically possible nan-ocluster precursors composed of M octahedra and T tetrahedra by atoms of (A) alkaline and (B) alkaline earth metals is considered for the first time. A relationship between the A/B,M,T composition of templated nanocluster precursors with the composition of A/B,M silicates is established. The model that is developed is used to search for nanocluster precursors in framework MT structures of A/B,Zr silicates. Computer methods (TOPOS 4.0 program package) were used to performmore » complete 3D reconstruction of the self-assembly of all (four) structural types of A/B,Zr silicates (A = Na, K; B = Ca, Sr) with frameworks of the MT{sub 2}O{sub 7} type: nan-ocluster precursor S{sub 3}{sup 0}-primary chain S{sub 3}{sup 1}-microlayer S{sub 3}{sup 2}-microframework S{sub 3}{sup 3}. The invariant type of mono-cyclic nanocluster precursor M{sub 2}T{sub 4} (with the point symmetries 1-bar and 2), stabilized by one or two template cations (A and B), is determined. Bifurcations of the paths of evolution at the S{sub 3}{sup 1} level (structural branching point) are established for the self-assembly of the following frameworks: MT-1 in CaZrSi{sub 2}O{sub 7} (gittinsite, C2), MT-2 in SrZrSi{sub 2}O{sub 7} (P2{sub 1}/c); MT-3 in Na{sub 2}ZrSi{sub 2}O{sub 7} (parakeldyshite,), K{sub 2}ZrSi{sub 2}O{sub 7} (khibinskite, P2{sub 1}/b), and K{sub 2}ZrGe{sub 2}O{sub 7} (C2/c); and MT-4 in Na{sub 2}ZrSi{sub 2}O{sub 7} (H{sub 2}O)(C2/c), Na{sub 3}ScSi{sub 2}O{sub 7} (Pbnm), and K{sub 3}ScSi{sub 2}O{sub 7} (P6{sub 3}/mmc).« less

Low temperature p-type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes

NASA Astrophysics Data System (ADS)

Malinverni, M.; Lamy, J.-M.; Martin, D.; Feltin, E.; Dorsaz, J.; Castiglia, A.; Rossetti, M.; Duelk, M.; Vélez, C.; Grandjean, N.

2014-12-01

We demonstrate state-of-the-art p-type (Al)GaN layers deposited at low temperature (740 °C) by ammonia molecular beam epitaxy (NH3-MBE) to be used as top cladding of laser diodes (LDs) with the aim of further reducing the thermal budget on the InGaN quantum well active region. Typical p-type GaN resistivities and contact resistances are 0.4 Ω cm and 5 × 10-4 Ω cm2, respectively. As a test bed, we fabricated a hybrid laser structure emitting at 400 nm combining n-type AlGaN cladding and InGaN active region grown by metal-organic vapor phase epitaxy, with the p-doped waveguide and cladding layers grown by NH3-MBE. Single-mode ridge-waveguide LD exhibits a threshold voltage as low as 4.3 V for an 800 × 2 μm2 ridge dimension and a threshold current density of ˜5 kA cm-2 in continuous wave operation. The series resistance of the device is 6 Ω and the resistivity is 1.5 Ω cm, confirming thereby the excellent electrical properties of p-type Al0.06Ga0.94N:Mg despite the low growth temperature.

Structural characterization of 2,6-dichloro-p-hydroquinone 1,2-dioxygenase (PcpA) from Sphingobium chlorophenolicum, a new type of aromatic ring-cleavage enzyme.

PubMed

Hayes, Robert P; Green, Abigail R; Nissen, Mark S; Lewis, Kevin M; Xun, Luying; Kang, Chulhee

2013-05-01

PcpA (2,6-dichloro-p-hydroquinone 1,2-dioxygenase) from Sphingobium chlorophenolicum, a non-haem Fe(II) dioxygenase capable of cleaving the aromatic ring of p-hydroquinone and its substituted variants, is a member of the recently discovered p-hydroquinone 1,2-dioxygenases. Here we report the 2.6 Å structure of PcpA, which consists of four βαβββ motifs, a hallmark of the vicinal oxygen chelate superfamily. The secondary co-ordination sphere of the Fe(II) centre forms an extensive hydrogen-bonding network with three solvent exposed residues, linking the catalytic Fe(II) to solvent. A tight hydrophobic pocket provides p-hydroquinones access to the Fe(II) centre. The p-hydroxyl group is essential for the substrate-binding, thus phenols and catechols, lacking a p-hydroxyl group, do not bind to PcpA. Site-directed mutagenesis and kinetic analysis confirm the critical catalytic role played by the highly conserved His10, Thr13, His226 and Arg259. Based on these results, we propose a general reaction mechanism for p-hydroquinone 1,2-dioxygenases. © 2013 Blackwell Publishing Ltd.

Structural characterization of 2,6-dichloro-p-hydroquinone 1,2-dioxygenase (PcpA) from Sphingobium chlorophenolicum, a new type of aromatic ring-cleavage enzyme

PubMed Central

Hayes, Robert P.; Green, Abigail R.; Nissen, Mark S.; Lewis, Kevin M.; Xun, Luying; Kang, ChulHee

2014-01-01

Summary PcpA (2,6-dichloro-p-hydroquinone 1,2-dioxygenase) from Sphingobium chlorophenolicum, a non-haem Fe(II) dioxygenase capable of cleaving the aromatic ring of p-hydroquinone and its substituted variants, is a member of the recently discovered p-hydroquinone 1,2-dioxygenases. Here we report the 2.6 Å structure of PcpA, which consists of four βαβββ motifs, a hallmark of the vicinal oxygen chelate superfamily. The secondary co-ordination sphere of the Fe(II) centre forms an extensive hydrogen-bonding network with three solvent exposed residues, linking the catalytic Fe(II) to solvent. A tight hydrophobic pocket provides p-hydroquinones access to the Fe(II) centre. The p-hydroxyl group is essential for the substrate-binding, thus phenols and catechols, lacking a p-hydroxyl group, do not bind to PcpA. Site-directed mutagenesis and kinetic analysis confirm the critical catalytic role played by the highly conserved His10, Thr13, His226 and Arg259. Based on these results, we propose a general reaction mechanism for p-hydroquinone 1,2-dioxygenases. PMID:23489289

Structure-Function of the Cytochrome b 6f Complex of Oxygenic Photosynthesis

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

Cramer, W. A.; Yamashita, E.; Baniulis, D.

2014-03-20

Structure–function of the major integral membrane cytochrome b 6f complex that functions in cyanobacteria, algae, and green plants to transfer electrons between the two reaction center complexes in the electron transport chain of oxygenic photosynthesis is discussed in the context of recently obtained crystal structures of the complex and soluble domains of cytochrome f and the Rieske iron–sulfur protein. The energy-transducing function of the complex, generation of the proton trans-membrane electrochemical potential gradient, centers on the oxidation/reduction pathways of the plastoquinol/plastoquinone (QH 2/Q), the proton donor/acceptor within the complex. These redox reactions are carried out by five redox prosthetic groupsmore » embedded in each monomer, the high potential two iron–two sulfur cluster and the heme of cytochrome f on the electropositive side (p) of the complex, two noncovalently bound b-type hemes that cross the complex and the membrane, and a covalently bound c-type heme (c n) on the electronegative side (n). These five redox-active groups are organized in high- (cyt f/[2Fe–2S] and low-potential (hemes b p, b n, c n) electron transport pathways that oxidize and reduce the quinol and quinone on the p- and n-sides in a Q-cycle-type mechanism, while translocating as many as 2 H + to the p-side aqueous side for every electron transferred through the high potential chain to the photosystem I reaction center. The presence of heme c n and the connection of the n-side of the membrane and b 6f complex to the cyclic electron transport chain indicate that the Q cycle in the oxygenic photosynthetic electron transport chain differs from those connected to the bc 1 complex in the mitochondrial respiratory chain and the chain in photosynthetic bacteria. Inferences from the structure and C2 symmetry of the complex for the pathway of QH 2/Q transfer within the complex, problems posed by the presence of lipid in the inter-monomer cavity, and the narrow portal for QH2 passage through the p-side oxidation site proximal to the [2Fe–2S] cluster are discussed.« less

Insight into Ca-Substitution Effects on O3-Type NaNi1/3 Fe1/3 Mn1/3 O2 Cathode Materials for Sodium-Ion Batteries Application.

PubMed

Sun, Liqi; Xie, Yingying; Liao, Xiao-Zhen; Wang, Hong; Tan, Guoqiang; Chen, Zonghai; Ren, Yang; Gim, Jihyeon; Tang, Wan; He, Yu-Shi; Amine, Khalil; Ma, Zi-Feng

2018-04-18

O3-type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NaNFM) is well investigated as a promising cathode material for sodium-ion batteries (SIBs), but the cycling stability of NaNFM still needs to be improved by using novel electrolytes or optimizing their structure with the substitution of different elements sites. To enlarge the alkali-layer distance inside the layer structure of NaNFM may benefit Na + diffusion. Herein, the effect of Ca-substitution is reported in Na sites on the structural and electrochemical properties of Na 1- x Ca x /2 NFM (x = 0, 0.05, 0.1). X-ray diffraction (XRD) patterns of the prepared Na 1- x Ca x /2 NFM samples show single α-NaFeO 2 type phase with slightly increased alkali-layer distance as Ca content increases. The cycling stabilities of Ca-substituted samples are remarkably improved. The Na 0.9 Ca 0.05 Ni 1/3 Fe 1/3 Mn 1/3 O 2 (Na 0.9 Ca 0.05 NFM) cathode delivers a capacity of 116.3 mAh g -1 with capacity retention of 92% after 200 cycles at 1C rate. In operando XRD indicates a reversible structural evolution through an O3-P3-P3-O3 sequence of Na 0.9 Ca 0.05 NFM cathode during cycling. Compared to NaNMF, the Na 0.9 Ca 0.05 NFM cathode shows a wider voltage range in pure P3 phase state during the charge/discharge process and exhibits better structure recoverability after cycling. The superior cycling stability of Na 0.9 Ca 0.05 NFM makes it a promising material for practical applications in sodium-ion batteries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of types of some species of “Filaria” (Nematoda) parasites of small mammals described by von Linstow and Molin

PubMed Central

Guerrero, R.; Bain, O.

2011-01-01

Parasitic nematodes from the Berlin (ZMB) and Vienna (NMW) Museum collections referred to the genus Filaria Mueller, 1787 by von Linstow or Molin were studied. Three samples were in good condition and the specimens redescribed. Litomosa hepatica (von Linstow, 1897) n. comb., sample ZMB Vermes Entozoa 3368, from the megachiropteran Pteropus neohibernicus, Bismarck Archipelago, resembles L. maki Tibayrenc, Bain & Ramanchandran, 1979, from Pteropus vampyrus, in Malaysia, but the buccal capsule differs. Both species display particular morphological characters which differ from species of Litomosa parasitic in microchiropterans. The remaining material originates from Brazil. The spicule morphology of Litomosoides circularis (von Linstow, 1899) Chandler, 1931, sample ZMB Vermes Entozoa 1059 from Hesperomys spec. (= Holochilus brasiliensis), Porto Alegre, confirms that it belongs to the sigmodontis group; the microfilaria presents characters of the genus Litomosoides, e.g. body attenuated at both extremities and salient cephalic hook. Taxonomic discussions by others confirm that species of Litomosoides belonging to the sigmodontis group and described subsequently are distinct from L. circularis. Litomosoides serpicula (Molin, 1858) Guerrero, Martin, Gardner & Bain, 2002, is redescribed, sample NMW 6323 from the bat Phyllostoma spiculatum (= Sturnira lilium), Ypanema. It is very close to L. brasiliensis Almeida, 1936, type host Moytis sp., but distinguished by a single ring in the buccal capsule, rather than two, supporting previous conclusions that the taxon L. brasiliensis, as generally regarded, may represent a complex of species. Samples NMW 6322 and NMW 6324, from other bats and also identified by Molin (1858) as Filaria serpicula, contain unidentifiable fragments of Litomosoides incertae sedis. Filaria hyalina von Linstow, 1890, sample ZMB Vermes Entozoa Q 3905 from Sorex vulgaris (= Sorex araneus), is incertae sedis because it contains two unidentifiable posterior parts of male, which might be an acuarid, Stammerinema sp. Filaria vesperuginis von Linstow, 1885, sample ZMB Vermes Entozoa Q 3929, from the bat Vesperugo serotinus (= Eptesicus serotinus), contains encysted nematode larvae and is a nomen dubium. PMID:21678791

Mutations in exons 10 and 11 of human glucokinase result in conformational variations in the active site of the structure contributing to poor substrate binding - explains hyperglycemia in type 2 diabetic patients.

PubMed

Yellapu, Nandakumar; Mahto, Manoj Kumar; Valasani, Koteswara Rao; Sarma, P V G K; Matcha, Bhaskar

2015-01-01

Mutations in the glucokinase (GK) gene play a critical role in the establishment of type 2 diabetes. In our earlier study, R308K mutation in GK in a clinically proven type 2 diabetic patient showed, structural and functional variations that contributed immensely to the hyperglycemic condition. In the extension of this work, a cohort of 30 patients with established type 2 diabetic condition were chosen and the exons 10 and 11 of GK were PCR-amplified and sequenced. The sequence alignment showed A379S, D400Y, E300A, E395A, E395G, H380N, I348N, L301M, M298I, M381G, M402R, R308K, R394P, R397S, and S398R mutations in 12 different patients. The structural analysis of these mutated GKs, showed a variable number of β-α-β units, hairpins, β-bulges, strands, helices, helix-helix interactions, β-turns, and γ-turns along with the RMSD variations when compared to wild-type GK. Molecular modeling studies revealed that the substrate showed variable binding orientations and could not fit into the active site of these mutated structures; moreover, it was expelled out of the conformations. Therefore, these structural variations in GK due to mutations could be one of the strongest reasons for the hyperglycemic levels in these type 2 diabetic patients.

New stable ternary alkaline-earth metal Pb(II) oxides: Ca / Sr / BaPb 2 O 3 and BaPbO 2

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

Li, Yuwei; Zhang, Lijun; Singh, David J.

The different but related chemical behaviors of Pb(II) oxides compared to Sn(II) oxides, and the existence of known alkali/alkali-earth metal Sn(II) ternary phases, suggest that there should be additional ternary Pb(II) oxide phases. Here, we report structure searches on the ternary alkaline-earth metal Pb(II) oxides leading to four new phases. These are two ternary Pb(II) oxides, SrPb 2O 3 and BaPb 2O 3, which have larger chemical potential stability ranges compared with the corresponding Sn(II) oxides, and additionally two other ternary Pb(II) oxides, CaPb 2O 3 and BaPbO 2, for which there are no corresponding Sn(II) oxides. Those Pb(II) oxidesmore » are stabilized by Pb-rich conditions. These structures follow the Zintl behavior and consist of basic structural motifs of (PbO 3) 4- anionic units separated and stabilized by the alkaline-earth metal ions. They show wide band gaps ranging from 2.86 to 3.12 eV, and two compounds (CaPb 2O 3 and SrPb 2O 3) show rather light hole effective masses (around 2m 0). The valence band maxima of these compounds have a Pb-6s/O-2p antibonding character, which may lead to p-type defect (or doping) tolerant behavior. This then suggests alkaline-earth metal Pb(II) oxides may be potential p-type transparent conducting oxides.« less

New stable ternary alkaline-earth metal Pb(II) oxides: Ca / Sr / BaPb 2 O 3 and BaPbO 2

DOE PAGES

Li, Yuwei; Zhang, Lijun; Singh, David J.

2017-10-16

The different but related chemical behaviors of Pb(II) oxides compared to Sn(II) oxides, and the existence of known alkali/alkali-earth metal Sn(II) ternary phases, suggest that there should be additional ternary Pb(II) oxide phases. Here, we report structure searches on the ternary alkaline-earth metal Pb(II) oxides leading to four new phases. These are two ternary Pb(II) oxides, SrPb 2O 3 and BaPb 2O 3, which have larger chemical potential stability ranges compared with the corresponding Sn(II) oxides, and additionally two other ternary Pb(II) oxides, CaPb 2O 3 and BaPbO 2, for which there are no corresponding Sn(II) oxides. Those Pb(II) oxidesmore » are stabilized by Pb-rich conditions. These structures follow the Zintl behavior and consist of basic structural motifs of (PbO 3) 4- anionic units separated and stabilized by the alkaline-earth metal ions. They show wide band gaps ranging from 2.86 to 3.12 eV, and two compounds (CaPb 2O 3 and SrPb 2O 3) show rather light hole effective masses (around 2m 0). The valence band maxima of these compounds have a Pb-6s/O-2p antibonding character, which may lead to p-type defect (or doping) tolerant behavior. This then suggests alkaline-earth metal Pb(II) oxides may be potential p-type transparent conducting oxides.« less

A Helical Short-Peptide Fusion Inhibitor with Highly Potent Activity against Human Immunodeficiency Virus Type 1 (HIV-1), HIV-2, and Simian Immunodeficiency Virus

PubMed Central

Xiong, Shengwen; Borrego, Pedro; Ding, Xiaohui; Zhu, Yuanmei; Martins, Andreia; Chong, Huihui

2016-01-01

ABSTRACT Human immunodeficiency virus type 2 (HIV-2) has already spread to different regions worldwide, and currently about 1 to 2 million people have been infected, calling for new antiviral agents that are effective on both HIV-1 and HIV-2 isolates. T20 (enfuvirtide), a 36-mer peptide derived from the C-terminal heptad repeat region (CHR) of gp41, is the only clinically approved HIV-1 fusion inhibitor, but it easily induces drug resistance and is not active on HIV-2. In this study, we first demonstrated that the M-T hook structure was also vital to enhancing the binding stability and inhibitory activity of diverse CHR-based peptide inhibitors. We then designed a novel short peptide (23-mer), termed 2P23, by introducing the M-T hook structure, HIV-2 sequences, and salt bridge-forming residues. Promisingly, 2P23 was a highly stable helical peptide with high binding to the surrogate targets derived from HIV-1, HIV-2, and simian immunodeficiency virus (SIV). Consistent with this, 2P23 exhibited potent activity in inhibiting diverse subtypes of HIV-1 isolates, T20-resistant HIV-1 mutants, and a panel of primary HIV-2 isolates, HIV-2 mutants, and SIV isolates. Therefore, we conclude that 2P23 has high potential to be further developed for clinical use, and it is also an ideal tool for exploring the mechanisms of HIV-1/2- and SIV-mediated membrane fusion. IMPORTANCE The peptide drug T20 is the only approved HIV-1 fusion inhibitor, but it is not active on HIV-2 isolates, which have currently infected 1 to 2 million people and continue to spread worldwide. Recent studies have demonstrated that the M-T hook structure can greatly enhance the binding and antiviral activities of gp41 CHR-derived inhibitors, especially for short peptides that are otherwise inactive. By combining the hook structure, HIV-2 sequence, and salt bridge-based strategies, the short peptide 2P23 has been successfully designed. 2P23 exhibits prominent advantages over many other peptide fusion inhibitors, including its potent and broad activity on HIV-1, HIV-2, and even SIV isolates, its stability as a helical, oligomeric peptide, and its high binding to diverse targets. The small size of 2P23 would benefit its synthesis and significantly reduce production cost. Therefore, 2P23 is an ideal candidate for further development, and it also provides a novel tool for studying HIV-1/2- and SIV-mediated cell fusion. PMID:27795437

Magneto-transport phenomena in metal/SiO2/n(p)-Si hybrid structures

NASA Astrophysics Data System (ADS)

Volkov, N. V.; Tarasov, A. S.; Rautskii, M. V.; Lukyanenko, A. V.; Bondarev, I. A.; Varnakov, S. N.; Ovchinnikov, S. G.

2018-04-01

Present review touches upon a subject of magnetotransport phenomena in hybrid structures which consist of ferromagnetic or nonmagnetic metal layer, layer of silicon oxide and silicon substrate with n- or p-type conductivity. Main attention will be paid to a number gigantic magnetotransport effects discovered in the devices fabricated on the base of the M/SiO2/n(p)-Si (M is ferromagnetic or paramagnetic metal) hybrid structures. These effects include bias induced dc magnetoresistance, gigantic magnetoimpedance, dc magnetoresistance induced by an optical irradiation and lateral magneto-photo-voltaic effect. The magnetoresistance ratio in ac and dc modes for some of our devices can exceed 106% in a magnetic field below 1 T. For lateral magneto-photo-voltaic effect, the relative change of photo-voltage in magnetic field can reach 103% at low temperature. Two types of mechanisms are responsible for sensitivity of the transport properties of the silicon based hybrid structures to magnetic field. One is related to transformation of the energy structure of the (donor) acceptor states including states near SiO2/n(p)-Si interface in magnetic field. Other mechanism is caused by the Lorentz force action. The features in behaviour of magnetotransport effects in concrete device depend on composition of the used structure, device topology and experimental conditions (bias voltage, optical radiation and others). Obtained results can be base for design of some electronic devices driven by a magnetic field. They can also provide an enhancement of the functionality for existing sensors.

Synthesis Strategies for Ultrastable Zeolite GIS Polymorphs as Sorbents for Selective Separations.

PubMed

Oleksiak, Matthew D; Ghorbanpour, Arian; Conato, Marlon T; McGrail, B Peter; Grabow, Lars C; Motkuri, Radha Kishan; Rimer, Jeffrey D

2016-11-02

Designing zeolites with tunable physicochemical properties can substantially impact their performance in commercial applications, such as adsorption, separations, catalysis, and drug delivery. Zeolite synthesis typically requires an organic structure-directing agent to produce crystals with specific pore topology. Attempts to remove organics from syntheses to achieve commercially viable methods of preparing zeolites often lead to the formation of impurities. Herein, we present organic-free syntheses of two polymorphs of the small-pore zeolite P (GIS), P1 and P2. Using a combination of adsorption measurements and density functional theory calculations, we show that GIS polymorphs are selective adsorbents for H 2 O relative to other light gases (e.g., H 2 , N 2 , CO 2 ). Our findings refute prior theoretical studies postulating that GIS-type zeolites are excellent materials for CO 2 separation/sequestration. We also show that P2 is significantly more thermally stable than P1, which broadens the operating conditions for GIS-type zeolites in commercial applications and opens new avenues for exploring their potential use in processes such as catalysis. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lithium ion insertion and extraction reactions with Hollandite-type manganese dioxide free from any stabilizing cations in its tunnel cavity

NASA Astrophysics Data System (ADS)

Kijima, Norihito; Takahashi, Yasuhiko; Akimoto, Junji; Awaka, Junji

2005-09-01

Lithium ion insertion and extraction reactions with a hollandite-type α-MnO 2 specimen free from any stabilizing cations in its tunnel cavity were investigated, and the crystal structure of a Li+-inserted α-MnO 2 specimen was analyzed by Rietveld refinement and whole-pattern fitting based on the maximum-entropy method (MEM). The pH titration curve of the α-MnO 2 specimen displayed a monobasic acid behavior toward Li+, and an ion-exchange capacity of 3.25 meq/g was achieved at pH>11. The Li/Mn molar ratio of the Li+-inserted α-MnO 2 specimen showed that about two Li+ ions can be chemically inserted into one unit cell of the hollandite-type structure. As the amount of Li content was increased, the lattice parameter a increased while c hardly changed. On the other hand, the mean oxidation number of Mn decreased slightly regardless of Li content whenever ions were exchanged. The Li+-inserted α-MnO 2 specimen reduced topotactically in one phase when it was used as an active cathode material in a liquid organic electrolyte (1:1 EC:DMC, 1 mol/dm 3 LiPF 6) lithium cell. An initial discharge with a capacity of approximately 230 mAh/g was achieved, and the reaction was reversible, whereas the capacity fell steadily upon cycling. About six Li+ ions could be electrochemically inserted into one unit cell of the hollandite-type structure. By contrast, the parent α-MnO 2 specimen showed a poor discharge property although no cationic residues or residual H 2O molecules remained in the tunnel space. Rietveld refinement from X-ray powder diffraction data for a Li+-inserted specimen of (Li 2O) 0.12MnO 2 showed it to have the hollandite-type structure (tetragonal; space group I4/m; a=9.993(11) and c=2.853(3) Å; Z=8; Rwp=6.12%, Rp=4.51%, RB=1.41%, and RF=0.79%; S=1.69). The electron-density distribution images in (Li 2O) 0.12MnO 2 showed that Li 2O molecules almost fill the tunnel space. These findings suggest that the presence of stabilizing atoms or molecules within the tunnel of a hollandite-type structure is necessary to facilitate the diffusion of Li+ ions during cycling.

Hydrodynamic Coating of a Fiber

NASA Astrophysics Data System (ADS)

Quéré, D.; de Ryck, A.

We discuss how a solid (especially a fiber) is coated when drawn out of a bath of liquid. 1. For slow withdrawals out of pure viscous liquids, the data are found to be fitted by the famous Landau law: then, the coating results from a balance between viscosity and capillarity. For quicker withdrawals, the thickness of the entrained film suddenly diverges, at a velocity on order 1 m/s. Inertia is shown to be responsible for this effect. At still higher velocities, the thickness decreases with the velocity because the solid can only entrain the viscous boundary layer. 2. For complex fluids, surface effects are found in the low velocity regime: out of a surfactant solution, films are thicker than predicted by Landau, by a factor of order 2. The thickening factor is shown to be fixed by the Marangoni flow due to the presence of surfactants; out of an emulsion, the film can be enriched with oil , which can be understood by a simple model of capture; out of a polymer solution, a strong swelling of the film is observed if normal stresses are present. Hence, the problem has two families of solution: (i) at low velocity, the thickness of the layer is fixed by a balance between viscous and surface forces and thus is sensitive to the presence of surfactants, or other heterogeneities; (ii) at high velocity, inertia must be considered and the film thickness is fixed by the bulk properties of the liquid (density and viscosity). In these regimes, it is not affected by the presence of surfactants in the bath. Nous décrivons le dépôt de liquide sur un solide (le plus souvent une fibre) qui advient quand on tire ce solide d'un bain. 1. Si le retrait se fait lentement hors d'un liquide pur et visqueux, les données expérimentales suivent la loi de Landau : le dépôt résulte d'un compromis entre forces visqueuses et forces capillaires. Pour des retraits plus rapides, on observe que l'épaisseur du dépôt diverge, pour une vitesse de l'ordre du mètre par seconde. Nous montrons comment l'inertie du fluide engendre un tel effet. Plus vite encore, l'épaisseur décroît lentement avec la vitesse, le solide ne parvenant à entraîner avec lui que la couche limite visqueuse qu'il a mis en mouvement. 2. Pour des liquides complexes, des effets de surface sont observés dans le régime basse vitesse : hors d'une solution de tensioactifs, les films sont plus épais que ce que prévoit la loi de Landau, d'un facteur 2 environ. Nous montrons que l'épaississement est déterminé par l'écoulement Marangoni dû à la présence des tensioactifs ; hors d'une émulsion, le film peut être enrichi en huile, ce que l'on peut interpréter à l'aide d'un modèle de capture ; hors d'une solution de polymère, on observe un fort gonflement du film dès que la solution est semi-diluée, à cause de l'effet des contraintes normales (effet Weissenberg). Le problème étudié a donc deux familles de solution : (i) à basse vitesse, le dépôt résulte d'un compromis entre viscosité et capillarité, si bien qu'il est sensible à la présence dans le bain d'hétérogénéités (tensioactifs, gouttes d'huile) ; (ii) à plus grande vitesse, l'inertie doit être prise en compte et l'épaisseur du film est alors liée aux propriétés de volume du liquide (densité et viscosité).

Theoretical study of thermoelectric properties of few-layer MoS2 and WSe2.

PubMed

Huang, Wen; Luo, Xin; Gan, Chee Kwan; Quek, Su Ying; Liang, Gengchiau

2014-06-14

Molybdenum disulfide (MoS2) and tungsten diselenide (WSe2) are prototypical layered two-dimensional transition metal dichalcogenide materials, with each layer consisting of three atomic planes. We refer to each layer as a trilayer (TL). We study the thermoelectric properties of 1-4TL MoS2 and WSe2 using a ballistic transport approach based on the electronic band structures and phonon dispersions obtained from first-principles calculations. Our results show that the thickness dependence of the thermoelectric properties is different under n-type and p-type doping conditions. Defining ZT1st peak as the first peak in the thermoelectric figure of merit ZT as doping levels increase from zero at 300 K, we found that ZT1st peak decreases as the number of layers increases for MoS2, with the exception of 2TL in n-type doping, which has a slightly higher value than 1TL. However, for WSe2, 2TL has the largest ZT1st peak in both n-type and p-type doping, with a ZT1st peak value larger than 1 for n-type WSe2. At high temperatures (T > 300 K), ZT1st peak dramatically increases when the temperature increases, especially for n-type doping. The ZT1st peak of n-type 1TL-MoS2 and 2TL-WSe2 can reach 1.6 and 2.1, respectively.

Association of comorbid depression, anxiety, and stress disorders with Type 2 diabetes in Bahrain, a country with a very high prevalence of Type 2 diabetes.

PubMed

Almawi, W; Tamim, H; Al-Sayed, N; Arekat, M R; Al-Khateeb, G M; Baqer, A; Tutanji, H; Kamel, C

2008-11-01

This study examined the association of depression, anxiety, and stress with Type 2 diabetes (T2DM) in Bahrain, an island-country with a very high prevalence of T2DM. This was a cross-sectional study involving administering Depression Anxiety Stress Scales (DASS)-21 structured depression, anxiety, and stress scale to 143 T2DM patients and 132 healthy controls. Higher proportion of T2DM patients were found in the mild-moderate and severe- extremely severe depression (p=0.002), anxiety (p<0.001), and stress (p<0.001) groups. Chronic disease and disease duration were significantly associated with the 3 disturbances, while employment status was associated with anxiety and depression. Logistic regression analysis showed that anxiety, depression, and stress were associated with T2DM after adjusting for all variables, while age was the only significant variable associated with stress. These results suggest a positive contribution of T2DM to increased depressive and/or anxiety and/or stress disorders among the patients examined, thereby recommending counseling for T2DM patients.

Band alignment and p -type doping of ZnSnN2

NASA Astrophysics Data System (ADS)

Wang, Tianshi; Ni, Chaoying; Janotti, Anderson

2017-05-01

Composed of earth-abundant elements, ZnSnN2 is a promising semiconductor for photovoltaic and photoelectrochemical applications. However, basic properties such as the precise value of the band gap and the band alignment to other semiconductors are still unresolved. For instance, reported values for the band gap vary from 1.4 to 2.0 eV. In addition, doping in ZnSnN2 remains largely unexplored. Using density functional theory with the Heyd-Scuseria-Ernzerhof hybrid functional, we investigate the electronic structure of ZnSnN2, its band alignment to GaN and ZnO, and the possibility of p -type doping. We find that the position of the valence-band maximum of ZnSnN2 is 0.39 eV higher than that in GaN, yet the conduction-band minimum is close to that in ZnO, which suggests that achieving p -type conductivity is likely as in GaN, yet it may be difficult to control unintentional n -type conductivity as in ZnO. Among possible p -type dopants, we explore Li, Na, and K substituting on the Zn site. We show that while LiZn is a shallow acceptor, NaZn and KZn are deep acceptors, which we trace back to large local relaxations around the Na and K impurities due to the atomic size mismatches.

Directory of Federal Contacts on Environmental Protection,

DTIC Science & Technology

1982-01-01

Director D. M. Hannemann 111B 0362 Energy Coordinator D. K. Bain f1IP 0102 Support Services W. E. Elgin 1111 0102 Head, Management Branch E. E. Hoover... Hannemann , D. M................................................. 8 Ilannesslager, R.............................................. ... 76 Hansen, A.J

Phase stabilities at a glance: Stability diagrams of nickel dipnictides

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

Bachhuber, F.; School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland; Rothballer, J.

2013-12-07

In the course of the recent advances in chemical structure prediction, a straightforward type of diagram to evaluate phase stabilities is presented based on an expedient example. Crystal structures and energetic stabilities of dipnictides NiPn{sub 2} (Pn = N, P, As, Sb, Bi) are systematically investigated by first principles calculations within the framework of density functional theory using the generalized gradient approximation to treat exchange and correlation. These dipnictides show remarkable polymorphism that is not yet understood systematically and offers room for the discovery of new phases. Relationships between the concerned structures including the marcasite, the pyrite, the arsenopyrite/CoSb{sub 2},more » and the NiAs{sub 2} types are highlighted by means of common structural fragments. Electronic stabilities of experimentally known and related AB{sub 2} structure types are presented graphically in so-called stability diagrams. Additionally, competing binary phases are taken into consideration in the diagrams to evaluate the stabilities of the title compounds with respect to decomposition. The main purpose of the stability diagrams is the introduction of an image that enables the estimation of phase stabilities at a single glance. Beyond that, some of the energetically favored structure types can be identified as potential new phases.« less

Controlling Magnetism via Transition Metal Exchange in the Series of Intermetallics Eu( T1, T2)5In ( T = Cu, Ag, Au)

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

Mudring, Anja -Verena; Smetana, Volodymyr; Pecharsky, Vitalij K.

Three series of intermetallic compounds Eu( T1, T2) 5In (T = Cu, Ag, Au) have been investigated in full compositional ranges. Single crystals of all compounds have been obtained by self-flux and were analyzed by single X-ray diffraction revealing the representatives to fall into two structure types: CeCu 6 ( oP28, Pnma, a = 8.832(3)–9.121(2) Å, b = 5.306(2)–5.645(1) Å, c = 11.059(4)–11.437(3) Å, V = 518.3(3)–588.9(2) Å 3) and YbMo2Al4 ( t I14, I4/ mmm, a = 5.417(3)–5.508(1) Å, c = 7.139(2)– 7.199(2) Å, V = 276.1(2)–285.8(1) Å 3). The structural preference was found to depend on the cation/anionmore » size ratio, while the positional preference within the CeCu 6 type structure shows an apparent correlation with the anion size. Chemical compression, hence, a change in cell volume, which occurs upon anion substitution appears to be the main driving force for the change of magnetic ordering. While EuAg 5In shows antiferromagnetic behavior at low temperatures, mixing Cu and Au within the same type of structure results in considerable changes in the magnetism. The Eu(Cu,Au) 5In alloys with CeCu 6 structure show complex magnetic behaviors and strong magnetic field-induced spin-reorientation transition with the critical field of the transition being dependent on Cu/Au ratio. The alloys adopting the YbMo 2Al 4 type structure are ferromagnets exhibiting unusually high magnetic moments. The heat capacity of EuAu 2.66Cu 2.34In reveals a double-peak structure evolving with the magnetic field. Furthermore, low-temperature X-ray powder diffraction does not show a structural transition.« less

Controlling Magnetism via Transition Metal Exchange in the Series of Intermetallics Eu( T1, T2)5In ( T = Cu, Ag, Au)

DOE PAGES

Mudring, Anja -Verena; Smetana, Volodymyr; Pecharsky, Vitalij K.; ...

2017-11-24

Three series of intermetallic compounds Eu( T1, T2) 5In (T = Cu, Ag, Au) have been investigated in full compositional ranges. Single crystals of all compounds have been obtained by self-flux and were analyzed by single X-ray diffraction revealing the representatives to fall into two structure types: CeCu 6 ( oP28, Pnma, a = 8.832(3)–9.121(2) Å, b = 5.306(2)–5.645(1) Å, c = 11.059(4)–11.437(3) Å, V = 518.3(3)–588.9(2) Å 3) and YbMo2Al4 ( t I14, I4/ mmm, a = 5.417(3)–5.508(1) Å, c = 7.139(2)– 7.199(2) Å, V = 276.1(2)–285.8(1) Å 3). The structural preference was found to depend on the cation/anionmore » size ratio, while the positional preference within the CeCu 6 type structure shows an apparent correlation with the anion size. Chemical compression, hence, a change in cell volume, which occurs upon anion substitution appears to be the main driving force for the change of magnetic ordering. While EuAg 5In shows antiferromagnetic behavior at low temperatures, mixing Cu and Au within the same type of structure results in considerable changes in the magnetism. The Eu(Cu,Au) 5In alloys with CeCu 6 structure show complex magnetic behaviors and strong magnetic field-induced spin-reorientation transition with the critical field of the transition being dependent on Cu/Au ratio. The alloys adopting the YbMo 2Al 4 type structure are ferromagnets exhibiting unusually high magnetic moments. The heat capacity of EuAu 2.66Cu 2.34In reveals a double-peak structure evolving with the magnetic field. Furthermore, low-temperature X-ray powder diffraction does not show a structural transition.« less

Energy band engineering and controlled p-type conductivity of CuAlO2 thin films by nonisovalent Cu-O alloying

NASA Astrophysics Data System (ADS)

Yao, Z. Q.; He, B.; Zhang, L.; Zhuang, C. Q.; Ng, T. W.; Liu, S. L.; Vogel, M.; Kumar, A.; Zhang, W. J.; Lee, C. S.; Lee, S. T.; Jiang, X.

2012-02-01

The electronic band structure and p-type conductivity of CuAlO2 films were modified via synergistic effects of energy band offset and partial substitution of less-dispersive Cu+ 3d10 with Cu2+ 3d9 orbitals in the valence band maximum by alloying nonisovalent Cu-O with CuAlO2 host. The Cu-O/CuAlO2 alloying films show excellent electronic properties with tunable wide direct bandgaps (˜3.46-3.87 eV); Hall measurements verify the highest hole mobilities (˜11.3-39.5 cm2/Vs) achieved thus far for CuAlO2 thin films and crystals. Top-gate thin film transistors constructed on p-CuAlO2 films were presented, and the devices showed pronounced performance with Ion/Ioff of ˜8.0 × 102 and field effect mobility of 0.97 cm2/Vs.

Heteromeric assembly of P2X subunits

PubMed Central

Saul, Anika; Hausmann, Ralf; Kless, Achim; Nicke, Annette

2013-01-01

Transcripts and/or proteins of P2X receptor (P2XR) subunits have been found in virtually all mammalian tissues. Generally more than one of the seven known P2X subunits have been identified in a given cell type. Six of the seven cloned P2X subunits can efficiently form functional homotrimeric ion channels in recombinant expression systems. This is in contrast to other ligand-gated ion channel families, such as the Cys-loop or glutamate receptors, where homomeric assemblies seem to represent the exception rather than the rule. P2XR mediated responses recorded from native tissues rarely match exactly the biophysical and pharmacological properties of heterologously expressed homomeric P2XRs. Heterotrimerization of P2X subunits is likely to account for this observed diversity. While the existence of heterotrimeric P2X2/3Rs and their role in physiological processes is well established, the composition of most other P2XR heteromers and/or the interplay between distinct trimeric receptor complexes in native tissues is not clear. After a description of P2XR assembly and the structure of the intersubunit ATP-binding site, this review summarizes the distribution of P2XR subunits in selected mammalian cell types and the biochemically and/or functionally characterized heteromeric P2XRs that have been observed upon heterologous co-expression of P2XR subunits. We further provide examples where the postulated heteromeric P2XRs have been suggested to occur in native tissues and an overview of the currently available pharmacological tools that have been used to discriminate between homo- and heteromeric P2XRs. PMID:24391538

Synthesis and some coordination chemistry of the PSnP pincer-type stannylene Sn(NCH2PtBu2)2C6H4, attempts to prepare the PSiP analogue, and the effect of the E atom on the molecular structures of E(NCH2PtBu2)2C6H4 (E = C, Si, Ge, Sn).

PubMed

Brugos, Javier; Cabeza, Javier A; García-Álvarez, Pablo; Pérez-Carreño, Enrique; Polo, Diego

2018-03-26

The non-donor-stabilized PSnP pincer-type stannylene Sn(NCH2PtBu2)2C6H4 (1) has been prepared by treating SnCl2 with Li2(NCH2PtBu2)2C6H4. All attempts to synthesize the analogous PSiP silylene by reduction of the (previously unknown) silanes SiCl2(NCH2PtBu2)2C6H4 (2), SiHCl(NCH2PtBu2)2C6H4 (3) and SiH(HMDS)(NCH2PtBu2)2C6H4 (4; HMDS = N(SiMe3)2) have been unsuccessful. The almost planar (excluding the tert-butyl groups) molecular structure of stannylene 1 (determined by X-ray crystallography) has been rationalized with the help of DFT calculations, which have shown that, in the series of diphosphanetetrylenes E(NCH2PtBu2)2C6H4 (E = C, Si, Ge, Sn), the most stable conformation of the compounds with E = Ge and Sn has both P atoms very close to the EN2C6H4 plane, near (interacting with) the E atom, whereas for the compounds with E = C and Si, both phosphane groups are located at one side of the EN2C6H4 plane and far away from the E atom. The size of the E atom and the strength of stabilizing donor-acceptor PE interactions (both increase on going down in group 14) are key factors in determining the molecular structures of these diphosphanetetrylenes. The syntheses of the chloridostannyl complexes [Rh{κ2Sn,P-SnCl(NCH2PtBu2)2C6H4}(η4-cod)] (5), [RuCl{κ2Sn,P-SnCl(NCH2PtBu2)2C6H4}(η6-cym)] (6) and [IrCl{κ2Sn,P-SnCl(NCH2PtBu2)2C6H4}(η5-C5Me5)] (7) have demonstrated the tendency of stannylene 1 to insert its Sn atom into M-Cl bonds of transition metal complexes and the preference of the resulting PSnP chloridostannyl group to act as a κ2Sn,P-chelating ligand, maintaining an uncoordinated phosphane fragment. X-ray diffraction data (of 6), 31P{1H} NMR data (of 5-7) and DFT calculations (on 6) are consistent with the existence of a weak PSn interaction involving the non-coordinated P atom of complexes 5-7, similar to that found in stannylene 1.

NMR study of B-2p Fermi-level density of states in the transition metal diborides

NASA Astrophysics Data System (ADS)

Lue, C. S.; Lai, W. J.

2005-04-01

We present a systematic study of the AlB2-type transition metal diborides by measuring the 11B NMR spin-lattice relaxation rate on TiB2, VB2, ZrB2, NbB2, HfB2, as well as TaB2. For all studied materials, the observed relaxation at B nuclei is mainly due to the p-electrons. The comparison with theoretical calculations allows the experimental determination of the partial B-2p Fermi-level density of states (DOS). In addition, the extracted B-2p Fermi-level DOS values in TiB2, ZrB2, and HfB are consistently smaller than in VB2, NbB2, and TaB2. We connect this trend to the rigid-band scenario raised by band structure calculations.

Yb14MgBi11: structure, thermoelectric properties and the effect of the structure on low lattice thermal conductivity.

PubMed

Hu, Yufei; Kauzlarich, Susan M

2017-03-21

Zintl phases Yb 14 MnSb 11 and Yb 14 MgSb 11 , which share the same complex structure type, have been demonstrated as the best p-type thermoelectric materials for the high temperature region (800-1200 K). A new iso-structural compound, Yb 14 MgBi 11 , was synthesized in order to investigate the structure and thermoelectric properties of the Bi analogs. Yb 14 MgBi 11 crystallizes in the Ca 14 AlSb 11 structure-type with the space group I4 1 /acd [a = 16.974(2) Å, c = 22.399(4) Å, V = 6454(2) Å 3 , R 1 /wR 2 = 0.0238/0.0475]. The structure follows the previous description of this structure type and the trend observed in previous analogs. Thermoelectric properties of Yb 14 MgBi 11 are measured together with Yb 14 MnBi 11 and both compounds are metallic. Compared to Yb 14 MgSb 11 , Yb 14 MgBi 11 has a higher carrier concentration with a similar mobility and effective mass. The lattice thermal conductivity of Yb 14 MgBi 11 is extremely low, which is as low as 0.16-0.36 W(mK) -1 . The zT values of Yb 14 MgBi 11 and Yb 14 MnBi 11 reach 0.2 at 875 K.

Configuring PSx tetrahedral clusters in Li-excess Li7P3S11 solid electrolyte

NASA Astrophysics Data System (ADS)

Jung, Wo Dum; Yun, Bin-Na; Jung, Hun-Gi; Choi, Sungjun; Son, Ji-Won; Lee, Jong-Ho; Lee, Jong-Heun; Kim, Hyoungchul

2018-04-01

We demonstrate that the Li-ion conductivity can be improved by adding a certain amount of Li (x = 0.25-0.5) as a charge carrier to the composition of glass-ceramic Li7+xP3S11. Structural analysis clarified that the structural changes caused by the ratio of ortho-thiophosphate tetrahedra PS43- and pyro-thiophosphate ditetrahedra P2S74- affect the Li-ion conductivity. The ratio of PS43- and P2S74- varies depending on x and the highest Li-ion conductivity (2.5 × 10-3 S cm-1) at x = 0.25. All-solid-state LiNi0.8Co0.15Al0.05O2/Li7.25P3S11/In-metal cell exhibits the discharge capacity of 106.2 mAh g-1. This ion conduction enhancement from excess Li is expected to contribute to the future design of sulfide-type electrolytes.

Effect of Te substitution on crystal structure and transport properties of AgBiSe2 thermoelectric material.

PubMed

Goto, Y; Nishida, A; Nishiate, H; Murata, M; Lee, C H; Miura, A; Moriyoshi, C; Kuroiwa, Y; Mizuguchi, Y

2018-02-20

Silver bismuth diselenide (AgBiSe 2 ) has attracted much attention as an efficient thermoelectric material, owing to its intrinsically low lattice thermal conductivity. While samples synthesized using a solid-state reaction showed n-type conductivity and their dimensionless figure of merit (ZT) reached ∼1 by electron doping, theoretical calculations predicted that a remarkably high thermoelectric performance can be achieved in p-type AgBiSe 2 . In this paper, we present the effect of Te substitution on the crystal structure and thermoelectric properties of AgBiSe 2 , expecting p-type conductivity due to the shallowing of the energy potential of the valence band. We found that all AgBiSe 2-x Te x (x = 0-0.8) prepared using a solid-state reaction exhibits n-type conductivity from 300 to 750 K. The room-temperature lattice thermal conductivity decreased to as low as 0.3 W m -1 K -1 by Te substitution, which was qualitatively described using the point defect scattering model for the solid solution. We show that ZT reaches ∼0.6 for x = 0.8 at a broad range of temperatures, from 550 to 750 K, due to the increased power factor, although the carrier concentration has not been optimized yet.

Optional elements and variant structures in the productions of bei2 'to give' dative constructions in Cantonese-speaking adults and three-year-old children.

PubMed

Wong, Anita M-Y; Chow, Dorcas C-C; McBride-Cheng, Catherine; Stokes, Stephanie F

2010-01-01

To express object transfer, Cantonese-speakers use a 'ditransitive' ([V-R-T] or [V-T-R] where V=Verb, T=Theme, R=Recipient), or a more complex prepositional/serial-verb (P/SV) construction. Clausal elements in Cantonese datives can be optional (resulting in 'full' versus 'non-full' forms) or appear in variant orders (full non-canonical and full canonical). We report on usage of dative constructions with the word bei2 'to give' in 86 parents and 53 three-year-old children during conversations. The parents used more P/SV than ditransitive bei2-datives, and vice versa for the children. Both groups showed a similar usage pattern of optional elements and variant structures in their ditransitive and P/SV bei2-datives. The roles of multiple construction types, optional elements and variant structures in children's learning of bei2-dative constructions are described.

Magnetic characteristics of polymorphic single crystal compounds DyIr2Si2

NASA Astrophysics Data System (ADS)

Uchima, Kiyoharu; Shigeoka, Toru; Uwatoko, Yoshiya

2018-05-01

We have confirmed that the tetragonal ternary compound DyIr2Si2 shows polymorphism; the ThCr2Si2-type structure as a low temperature phase (I-phase) and the CaBe2Ge2-type one as a high temperature phase (P-phase) exist. A comparative study on magnetic characteristics of the morphs was performed on the I- and P-phase single crystals in order to elucidate how magnetic properties are influenced by crystallographic symmetry. The magnetic behavior changes drastically depending on the structure. The DyIr2Si2(I) shows an antiferromagnetic ordering below TN = 30 K, additional magnetic transitions of T1 = 17 K and T2 = 10 K, and a strong uniaxial magnetic anisotropy with the easy [001] direction. The [001] magnetization shows four metamagnetic transitions at low temperatures. On the other hand, the DyIr2Si2(P) has comparatively low ordering temperature of TN1 = 9.4 K and an additional transition temperature of TN2 = 3.0 K, and exhibits an easy-plane magnetic anisotropy with the easy [110] direction. Two metamagnetic transitions appear in the basal plane magnetization processes. In both the morphs, the χ-T behavior suggests the existence of component-separated magnetic transitions. The ab-component of magnetic moments orders at the higher transition temperature TN1 for the P-phase compound, which is contrast to the I-phase behavior; the c-component orders firstly at TN. The crystalline electric field (CEF) analysis was made, and the difference in magnetic behaviors between both the morphs is explained by the CEF effects.

Mechanistic and Structural Analyses of the Role of His67 in the Yeast Polyamine Oxidase Fms1†

PubMed Central

Adachi, Mariya S.; Taylor, Alexander B.; Hart, P. John; Fitzpatrick, Paul F.

2012-01-01

The flavoprotein oxidase Fms1 from Saccharomyces cerevisiae catalyzes the oxidation of spermine and N1-acetylspermine to spermidine and 3-aminopropanal or N-acetyl-3-aminopropanal. Within the active site of Fms1, His67 is positioned to form hydrogen bonds with the polyamine substrate. This residue is also conserved in other polyamine oxidases. The catalytic properties of H67Q, H67N, and H67A Fms1 have been characterized to evaluate the role of this residue in catalysis. With both spermine and N1-acetylspermine as the amine substrate, the value of the first-order rate constant for flavin reduction decreases 2–3 orders of magnitude, with the H67Q mutation having the smallest effect and H67N the largest. The kcat/KO2 value changes very little upon mutation with N1-acetylspermine as the amine substrate and decreases only an order of magnitude with spermine. The kcat/KM-pH profiles with N1-acetylspermine are bell-shaped for all the mutants; the similarity to the profile of the wild-type enzyme rules out His67 as being responsible for either of the pKa values. The pH profiles for the rate constant for flavin reduction for all the mutant enzymes similarly show the same pKa as wild-type Fms1, about ~7.4; this pKa is assigned to the substrate N4. The kcat/KO2-pH profiles for wild-type Fms1 and the H67A enzyme both show a pKa of about ~6.9; this suggests His67 is not responsible for this pH behaviour. With the H67Q, H67N, and H67A enzymes the kcat value decreases when a single residue is protonated, as is the case with the wild-type enzyme. The structure of H67Q Fms1 has been determined at a resolution of 2.4 Å. The structure shows that the mutation disrupts a hydrogen bond network in the active site, suggesting that His67 is important both for direct interactions with the substrate and to maintain the overall active site structure. PMID:22642831

Mechanistic and structural analyses of the role of His67 in the yeast polyamine oxidase Fms1.

PubMed

Adachi, Mariya S; Taylor, Alexander B; Hart, P John; Fitzpatrick, Paul F

2012-06-19

The flavoprotein oxidase Fms1 from Saccharomyces cerevisiae catalyzes the oxidation of spermine and N(1)-acetylspermine to spermidine and 3-aminopropanal or N-acetyl-3-aminopropanal. Within the active site of Fms1, His67 is positioned to form hydrogen bonds with the polyamine substrate. This residue is also conserved in other polyamine oxidases. The catalytic properties of H67Q, H67N, and H67A Fms1 have been characterized to evaluate the role of this residue in catalysis. With both spermine and N(1)-acetylspermine as the amine substrate, the value of the first-order rate constant for flavin reduction decreases 2-3 orders of magnitude, with the H67Q mutation having the smallest effect and H67N the largest. The k(cat)/K(O2) value changes very little upon mutation with N(1)-acetylspermine as the amine substrate and decreases only an order of magnitude with spermine. The k(cat)/K(M)-pH profiles with N(1)-acetylspermine are bell-shaped for all the mutants; the similarity to the profile of the wild-type enzyme rules out His67 as being responsible for either of the pK(a) values. The pH profiles for the rate constant for flavin reduction for all the mutant enzymes similarly show the same pK(a) as wild-type Fms1, about ∼7.4; this pK(a) is assigned to the substrate N4. The k(cat)/K(O2)-pH profiles for wild-type Fms1 and the H67A enzyme both show a pK(a) of about ∼6.9; this suggests His67 is not responsible for this pH behavior. With the H67Q, H67N, and H67A enzymes the k(cat) value decreases when a single residue is protonated, as is the case with the wild-type enzyme. The structure of H67Q Fms1 has been determined at a resolution of 2.4 Å. The structure shows that the mutation disrupts a hydrogen bond network in the active site, suggesting that His67 is important both for direct interactions with the substrate and to maintain the overall active site structure.

Altered Volume, Morphology and Composition of the Pancreas in Type 2 Diabetes

PubMed Central

Macauley, Mavin; Percival, Katie; Thelwall, Peter E.; Hollingsworth, Kieren G.; Taylor, Roy

2015-01-01

Objective Although impairment in pancreatic insulin secretion is known to precede the clinical diagnosis of type 2 diabetes by up to a decade, fasting blood glucose concentration only rises abnormally once the impairment reaches a critical threshold. Despite its centrality to the pathogenesis of type 2 diabetes, the pancreas is the least studied organ due to its inaccessible anatomical position. Previous ultrasound and CT studies have suggested a possible decrease in pancreatic volume in type 2 diabetes. However, ultrasound techniques are relatively insensitive while CT uses ionizing radiation, making these modalities unsuitable for precise, longitudinal studies designed to explore the underlying mechanisms of type 2 diabetes. Hence there is a need to develop a non-invasive, safe and precise method to quantitate pancreas volume. Methods We developed and applied magnetic resonance imaging at 3.0T to obtain balanced turbo field echo (BTFE) structural images of the pancreas, together with 3-point Dixon images to quantify pancreatic triglyceride content. Pancreas volume, morphology and triglyceride content was quantified in a group of 41 subjects with well-controlled type 2 diabetes (HbA1c ≤ 7.6%) taking only metformin (duration of T2DM 5.7±0.7years), and a control group of 14 normal glucose tolerance subjects matched for age, weight and sex. Results The mean pancreatic volume was found to be 33% less in type 2 diabetes than in normal glucose tolerant subjects (55.5±2.8 vs. 82.6±4.8cm3; p<0.0001). Pancreas volume was positively correlated with HOMA-β in the type 2 diabetes subjects (r = 0.31; p = 0.03) and controls (r = 0.46; p = 0.05) considered separately; and in the whole population studied (r = 0.37; p = 0.003). In type 2 diabetes, the pancreas was typically involuted with a serrated border. Pancreatic triglyceride content was 23% greater (5.4±0.3 vs. 4.4±0.4%; p = 0.02) in the type 2 diabetes group. Conclusion This study describes for the first time gross abnormalities of the pancreas in early type 2 diabetes and quantifies the decrease in pancreas size, the irregular morphology and increase in fat content. PMID:25950180

RuO2 pH Sensor with Super-Glue-Inspired Reference Electrode

PubMed Central

Wajrak, Magdalena; Alameh, Kamal

2017-01-01

A pH-sensitive RuO2 electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO2 working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO2 pH-sensitive working electrode and a SiO2-PVB junction-modified RuO2 reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a drift below 2.2 mV/h. The developed sensor structure opens the way towards the development of a simple, cost effective, and robust pH sensor for pH analysis in various sample matrices. PMID:28878182

Demonstration of high-performance p-type tin oxide thin-film transistors using argon-plasma surface treatments

NASA Astrophysics Data System (ADS)

Bae, Sang-Dae; Kwon, Soo-Hun; Jeong, Hwan-Seok; Kwon, Hyuck-In

2017-07-01

In this work, we investigated the effects of low-temperature argon (Ar)-plasma surface treatments on the physical and chemical structures of p-type tin oxide thin-films and the electrical performance of p-type tin oxide thin-film transistors (TFTs). From the x-ray photoelectron spectroscopy measurement, we found that SnO was the dominant phase in the deposited tin oxide thin-film, and the Ar-plasma treatment partially transformed the tin oxide phase from SnO to SnO2 by oxidation. The resistivity of the tin oxide thin-film increased with the plasma-treatment time because of the reduced hole concentration. In addition, the root-mean-square roughness of the tin oxide thin-film decreased as the plasma-treatment time increased. The p-type oxide TFT with an Ar-plasma-treated tin oxide thin-film exhibited excellent electrical performance with a high current on-off ratio (5.2 × 106) and a low off-current (1.2 × 10-12 A), which demonstrates that the low-temperature Ar-plasma treatment is a simple and effective method for improving the electrical performance of p-type tin oxide TFTs.

Back-gated Nb-doped MoS2 junctionless field-effect-transistors

NASA Astrophysics Data System (ADS)

Mirabelli, Gioele; Schmidt, Michael; Sheehan, Brendan; Cherkaoui, Karim; Monaghan, Scott; Povey, Ian; McCarthy, Melissa; Bell, Alan P.; Nagle, Roger; Crupi, Felice; Hurley, Paul K.; Duffy, Ray

2016-02-01

Electrical measurements were carried out to measure the performance and evaluate the characteristics of MoS2 flakes doped with Niobium (Nb). The flakes were obtained by mechanical exfoliation and transferred onto 85 nm thick SiO2 oxide and a highly doped Si handle wafer. Ti/Au (5/45 nm) deposited on top of the flake allowed the realization of a back-gate structure, which was analyzed structurally through Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). To best of our knowledge this is the first cross-sectional TEM study of exfoliated Nb-doped MoS2 flakes. In fact to date TEM of transition-metal-dichalcogenide flakes is extremely rare in the literature, considering the recent body of work. The devices were then electrically characterized by temperature dependent Ids versus Vds and Ids versus Vbg curves. The temperature dependency of the device shows a semiconductor behavior and, the doping effect by Nb atoms introduces acceptors in the structure, with a p-type concentration 4.3 × 1019 cm-3 measured by Hall effect. The p-type doping is confirmed by all the electrical measurements, making the structure a junctionless transistor. In addition, other parameters regarding the contact resistance between the top metal and MoS2 are extracted thanks to a simple Transfer Length Method (TLM) structure, showing a promising contact resistivity of 1.05 × 10-7 Ω/cm2 and a sheet resistance of 2.36 × 102 Ω/sq.

H2 gas sensing properties of a ZnO/CuO and ZnO/CuO/Cu2O Heterostructures

NASA Astrophysics Data System (ADS)

Ababii, N.; Postica, V.; Hoppe, M.; Adelung, R.; Lupan, O.; Railean, S.; Pauporté, T.; Viana, B.

2017-03-01

The most important parameters of gas sensors are sensitivity and especially high selectivity to specific chemical species. To improve these parameters we developed sensor structures based on layered semiconducting oxides, namely CuO/Cu2O, CuO:Zn/Cu2O:Zn, NiO/ZnO. In this work, the ZnO/CuxO (where x = 1, 2) bi-layer heterostructure were grown via a simple synthesis from chemical solution (SCS) at relatively low temperatures (< 95 °C), representing a combination of layered n-type and p-type semiconducting oxides which are widely used as sensing material for gas sensors. The main advantages of the developed device structures are given by simplicity of the synthesis and technological cost-efficiency. Structural investigations showed high crystallinity of synthesized layers confirming the presence of zinc oxide nanostructures on the surface of the copper oxide film deposited on glass substrate. Structural changes in morphology of grown nanostructures induced by post-grown thermal annealing were observed by scanning electron microscopy (SEM) investigations, and were studied in detail. The influence of thermal annealing type on the optical properties was also investigated. As an example of practical applications, the ZnO/CuxO bi-layer heterojunctions and ZnO/CuO/Cu2O three-layered structures were integrated into sensor structures and were tested to different types of reducing gases at different operating temperatures (OPT), showing promising results for fabrication of selective gas sensors.

Electronic structure and phase separation of superconducting and nonsuperconducting KxFe2-ySe2 revealed by x-ray photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Oiwake, M.; Ootsuki, D.; Noji, T.; Hatakeda, T.; Koike, Y.; Horio, M.; Fujimori, A.; Saini, N. L.; Mizokawa, T.

2013-12-01

We have investigated the electronic structure of superconducting (SC) and nonsuperconducting (non-SC) KxFe2-ySe2 using x-ray photoemission spectroscopy (XPS). The spectral shape of the Fe 2p XPS is found to depend on the amount of Fe vacancies. The Fe 2p3/2 peak of the SC and non-SC Fe-rich samples is accompanied by a shoulder structure on the lower binding energy side, which can be attributed to the metallic phase embedded in the Fe2+ insulating phase. The absence of the shoulder structure in the non-SC Fe-poor sample allows us to analyze the Fe 2p spectra using a FeSe4 cluster model. The Fe 3d-Se 4p charge-transfer energy of the Fe2+ insulating phase is found to be ˜2.3 eV which is smaller than the Fe 3d-Fe 3d Coulomb interaction of ˜3.5 eV. This indicates that the Fe2+ insulating state is the charge-transfer type in the Zaanen-Sawatzky-Allen scheme. We also find a substantial change in the valence-band XPS as a function of Fe content and temperature. The metallic state at the Fermi level is seen in the SC and non-SC Fe-rich samples and tends to be enhanced with cooling in the SC sample.

X-ray and neutron diffraction study of the defect crystal structure of the as-grown nonstoichiometric phase Y{sub 0.715}Ca{sub 0.285}F{sub 2.715}

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

Bolotina, N. B., E-mail: bolotina@ns.crys.ras.ru; Kalyukanov, A. I.; Chernaya, T. S.

This work begins a series of papers aimed at studying the defect structure of nonstoichiometric phases R{sub 1-y}Ca{sub y}F{sub 3-y} with a tysonite-type (LaF{sub 3}) structure. In the single-crystal structure of Y{sub 0.715}Ca{sub 0.285}F{sub 2.715} with a tysonite-type small unit cell (sp. gr. P6{sub 3}/mmc, a = 3.9095(2) A, c = 6.9829(2) A; Z = 2; R{sub w} = 2.16%), the displacements of Y{sup 3+} cations and F{sup 2-} anions from 6{sub 3} symmetry axes were observed for the first time. The X-ray diffraction pattern shows weak satellites insufficient for structural calculations. The LaF{sub 3} structure type is stabilized upmore » and down on the temperature scale due to anion vacancies and the symmetrizing effect of Ca{sup 2+} cations lying on 6{sub 3} symmetry axes. At 120 Degree-Sign C the fluoride-ion conductivity in the nonstoichiometric phase Y{sub 0.715}Ca{sub 0.285}F{sub 2.715} is five orders of magnitude higher than that in the stoichiometric phase {beta}-YF{sub 3}. The transition to a superionic state is caused by a deviation from stoichiometry and is not associated with reconstructive phase transformation.« less

Two aspartate residues at the putative p10 subunit of a type II metacaspase from Nicotiana tabacum L. may contribute to the substrate-binding pocket.

PubMed

Acosta-Maspons, Alexis; Sepúlveda-García, Edgar; Sánchez-Baldoquín, Laura; Marrero-Gutiérrez, Junier; Pons, Tirso; Rocha-Sosa, Mario; González, Lien

2014-01-01

Metacaspases are cysteine proteases present in plants, fungi, prokaryotes, and early branching eukaryotes, although a detailed description of their cellular function remains unclear. Currently, three-dimensional (3D) structures are only available for two metacaspases: Trypanosoma brucei (MCA2) and Saccharomyces cerevisiae (Yca1). Furthermore, metacaspases diverged from animal caspases of known structure, which limits straightforward homology-based interpretation of functional data. We report for the first time the identification and initial characterization of a metacaspase of Nicotiana tabacum L., NtMC1. By combining domain search, multiple sequence alignment (MSA), and protein fold-recognition studies, we provide compelling evidences that NtMC1 is a plant metacaspase type II, and predict its 3D structure using the crystal structure of two type I metacaspases (MCA2 and Yca1) and Gsu0716 protein from Geobacter sulfurreducens as template. Analysis of the predicted 3D structure allows us to propose Asp353, at the putative p10 subunit, as a new member of the aspartic acid triad that coordinates the P1 arginine/lysine residue of the substrate. Nevertheless, site-directed mutagenesis and expression analysis in bacteria and Nicotiana benthamiana indicate the functionality of both Asp348 and Asp353. Through the co-expression of mutant and wild-type proteins by transient expression in N. benthamiana leaves we found that polypeptide processing seems to be intramolecular. Our results provide the first evidence in plant metacaspases concerning the functionality of the putative p10 subunit.

Identification of antipsychotic drug fluspirilene as a potential p53-MDM2 inhibitor: a combined computational and experimental study

NASA Astrophysics Data System (ADS)

Patil, Sachin P.; Pacitti, Michael F.; Gilroy, Kevin S.; Ruggiero, John C.; Griffin, Jonathan D.; Butera, Joseph J.; Notarfrancesco, Joseph M.; Tran, Shawn; Stoddart, John W.

2015-02-01

The inhibition of tumor suppressor p53 protein due to its direct interaction with oncogenic murine double minute 2 (MDM2) protein, plays a central role in almost 50 % of all human tumor cells. Therefore, pharmacological inhibition of the p53-binding pocket on MDM2, leading to p53 activation, presents an important therapeutic target against these cancers expressing wild-type p53. In this context, the present study utilized an integrated virtual and experimental screening approach to screen a database of approved drugs for potential p53-MDM2 interaction inhibitors. Specifically, using an ensemble rigid-receptor docking approach with four MDM2 protein crystal structures, six drug molecules were identified as possible p53-MDM2 inhibitors. These drug molecules were then subjected to further molecular modeling investigation through flexible-receptor docking followed by Prime/MM-GBSA binding energy analysis. These studies identified fluspirilene, an approved antipsychotic drug, as a top hit with MDM2 binding mode and energy similar to that of a native MDM2 crystal ligand. The molecular dynamics simulations suggested stable binding of fluspirilene to the p53-binding pocket on MDM2 protein. The experimental testing of fluspirilene showed significant growth inhibition of human colon tumor cells in a p53-dependent manner. Fluspirilene also inhibited growth of several other human tumor cell lines in the NCI60 cell line panel. Taken together, these computational and experimental data suggest a potentially novel role of fluspirilene in inhibiting the p53-MDM2 interaction. It is noteworthy here that fluspirilene has a long history of safe human use, thus presenting immediate clinical potential as a cancer therapeutic. Furthermore, fluspirilene could also serve as a structurally-novel lead molecule for the development of more potent, small-molecule p53-MDM2 inhibitors against several types of cancer. Importantly, the combined computational and experimental screening protocol presented in this study may also prove useful for screening other commercially-available compound databases for identification of novel, small molecule p53-MDM2 inhibitors.

Resonant photoemission study of pyrite-type NiS2, CoS2 and FeS2

NASA Astrophysics Data System (ADS)

Fujimori, A.; Mamiya, K.; Mizokawa, T.; Miyadai, T.; Sekiguchi, T.; Takahashi, H.; Môri, N.; Suga, S.

1996-12-01

The electronic structure of pyrite-type NiS2, CoS2, and FeS2 has been studied by photoemission spectroscopy. From resonant photoemission studies and configuration-interaction cluster-model analysis of the spectra, NiS2 is found to be a charge-transfer-type insulator, the band gap of which is formed between the occupied S 3p and the empty Ni 3d states. Cluster-model calculations indicate that the short Fe-S distance favors the low-spin (S=0) ground state in FeS2 compared to the high-spin FeS. Resonant photoemission results indicate a sign of electron correlation in the nonmagnetic semiconductor FeS2.

Growth and Properties of MERCURY(1-X) Cadmium (x) Tellurium Alloys and Quantum Well Structures

NASA Astrophysics Data System (ADS)

Han, Jeong-Whan

1990-01-01

Photoassisted molecular beam epitaxy was employed to grow Hg-based films, which include Hg_{1-x}Cd_{x}Te alloys, modulation-doped HgCdTe, modulation-doped HgCdTe quantum well structures and HgCdTe heterostructures. The structural, electrical and optical properties of these films were studied. A series of Hg_{1 -x}Cd_{x}Te films were deposited on lattice-matched (111)B CdZnTe substrates. The rm Hg_{1-x}Cd_{x}Te films grown under the optimum growth conditions exhibited both high structural perfections and outstanding electrical properties, which can be attributed to the role played by the photons in the growth process. For the first time, conducting p-type and n-type modulation-doped HgCdTe were successfully prepared using arsenic and indium as the p-type and n-type dopants, respectively. Most of them exhibited both excellent structural qualities and very sharp interfaces. The hole concentrations of p-type samples showed no evidence of carrier freeze-out at low temperatures. The electron concentrations of n-type samples also exhibited temperature independence up to 300K. PL measurements exhibited two peaks due to the subband transitions. Many of the modulation-doped HgCdTe superlattices samples exhibited very bright and narrow PL peaks at 4.2K. Both electron and hole mobilities of modulation-doped HgCdTe superlattices increase monotonically with decreasing temperature. The electrical properties of n-type modulation-doped HgCdTe heterostructures having spacer layers were also studied. A series of p-type HgTe-Hg_ {0.15}Cd_{0.85}Te superlattices were grown on (100) CdTe substrates by MBE for an extensive study of the optical and electrical properties of such structures. The absorption coefficient versus photon energy spectra show consecutive rises and plateaus characteristic of two-dimensional quantum structures. Temperature-dependent free carrier mobilities and densities were obtained from a mixed-conduction analysis of the Hall and resistivity data as a function of magnetic field. The experimental results were compared with theoretical tight-binding calculation of the superlattice band structure. Hg-based quantum well structures were grown on (100) CdZnTe substrates at 170^circ C. Stimulated emission at 2.8 mu m was observed for the first time in these quantum well structures where the active regions are HgCdTe. A cw Nd:YAG laser was used as an optical pumping source for the laser cavities. Stimulated emission cavity modes were seen at cw laser power densities as low as 3.4 kW/cm ^2 and at temperatures >=q 60K.

Long-wavelength stimulated emission and carrier lifetimes in HgCdTe-based waveguide structures with quantum wells

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

Rumyantsev, V. V., E-mail: rumyantsev@ipm.sci-nnov.ru; Fadeev, M. A.; Morozov, S. V.

2016-12-15

The interband photoconductivity and photoluminescence in narrow-gap HgCdTe-based waveguide structures with quantum wells (QWs) (designed for long-wavelength stimulated emission under optical pumping) are investigated. The photoconductivity relaxation times in n-type structures reach several microseconds, due to which stimulated emission at a wavelength of 10.2 μm occurs at a low threshold pump intensity (~100 W/cm{sup 2}) at 20 K. In the p-type structures obtained by annealing (to increase the mercury vacancy concentration), even spontaneous emission from the QWs is not detected because of a dramatic decrease in the carrier lifetime with respect to Shockley–Read–Hall nonradiative recombination.

A High-Throughput Cell-Based Screen Identified a 2-[(E)-2-Phenylvinyl]-8-Quinolinol Core Structure That Activates p53

PubMed Central

Bechill, John; Zhong, Rong; Zhang, Chen; Solomaha, Elena

2016-01-01

p53 function is frequently inhibited in cancer either through mutations or by increased degradation via MDM2 and/or E6AP E3-ubiquitin ligases. Most agents that restore p53 expression act by binding MDM2 or E6AP to prevent p53 degradation. However, fewer compounds directly bind to and activate p53. Here, we identified compounds that shared a core structure that bound p53, caused nuclear localization of p53 and caused cell death. To identify these compounds, we developed a novel cell-based screen to redirect p53 degradation to the Skip-Cullin-F-box (SCF) ubiquitin ligase complex in cells expressing high levels of p53. In a multiplexed assay, we coupled p53 targeted degradation with Rb1 targeted degradation in order to identify compounds that prevented p53 degradation while not inhibiting degradation through the SCF complex or other proteolytic machinery. High-throughput screening identified several leads that shared a common 2-[(E)-2-phenylvinyl]-8-quinolinol core structure that stabilized p53. Surface plasmon resonance analysis indicated that these compounds bound p53 with a KD of 200 ± 52 nM. Furthermore, these compounds increased p53 nuclear localization and transcription of the p53 target genes PUMA, BAX, p21 and FAS in cancer cells. Although p53-null cells had a 2.5±0.5-fold greater viability compared to p53 wild type cells after treatment with core compounds, loss of p53 did not completely rescue cell viability suggesting that compounds may target both p53-dependent and p53-independent pathways to inhibit cell proliferation. Thus, we present a novel, cell-based high-throughput screen to identify a 2-[(E)-2-phenylvinyl]-8-quinolinol core structure that bound to p53 and increased p53 activity in cancer cells. These compounds may serve as anti-neoplastic agents in part by targeting p53 as well as other potential pathways. PMID:27124407

Comparative study on degradation and trap density-of-states of p type and n type organic semiconductors

NASA Astrophysics Data System (ADS)

Shijeesh, M. R.; Vikas, L. S.; Jayaraj, M. K.; Puigdollers, J.

2014-10-01

The OTFTs with both p type and n type channel layers were fabricated using the inverted-staggered (top contact) structure by thermal vapour deposition on Si/SiO2 substrate. Pentacene and N,N'-Dioctyl- 3,4,9,10- perylenedicarboximide (PTCDI-C8) were used as channel layer for the fabrications of p type and n type OTFTs respectively. A comparative study on the degradation and density of states (DOS) of p type and n type organic semiconductors have been carried out. In order to compare the stability and degradation of pentacene and PTCDI-C8 OTFTs, the devices were exposed to air for 2 h before performing electrical measurements in air. The DOS measurements revealed that a level with defect density of 1020 cm-3 was formed only in PTCDI C8 layer on exposure to air. The oxygen adsorption into the PTCDI-C8 active layer can be attributed to the formation of this level at 0.15 eV above the LUMO level. The electrical charge transport is strongly affected by the oxygen traps and hence n type organic materials are less stable than p type organic materials.

Transcription factor RBP-J-mediated signalling regulates basophil immunoregulatory function in mouse asthma model.

PubMed

Qu, Shuo-Yao; He, Ya-Long; Zhang, Jian; Wu, Chang-Gui

2017-09-01

Basophils (BA) play an important role in the promotion of aberrant T helper type 2 (Th2) immune responses in asthma. It is not only the effective cell, but also modulates the initiation of Th2 immune responses. We earlier demonstrated that Notch signalling regulates the biological function of BAin vitro. However, whether this pathway plays the same role in vivo is not clear. The purpose of the present study was to investigate the effect of Notch signalling on BA function in the regulation of allergic airway inflammation in a murine model of asthma. Bone marrow BA were prepared by bone marrow cell culture in the presence of recombinant interleukin-3 (rIL-3; 300 pg/ml) for 7 days, followed by isolation of the CD49b + microbeads. The recombination signal binding protein J (RBP-J -/- ) BA were co-cultured with T cells, and the supernatant and the T-cell subtypes were examined. The results indicated disruption of the capacity of BA for antigen presentation alongside an up-regulation of the immunoregulatory function. This was possibly due to the low expression of OX40L in the RBP-J -/- BA. Basophils were adoptively transferred to ovalbumin-sensitized recipient mice, to establish an asthma model. Lung pathology, cytokine profiles of brobchoalveolar fluid, airway hyperactivity and the absolute number of Th1/Th2 cells in lungs were determined. Overall, our results indicate that the RBP-J-mediated Notch signalling is critical for BA-dependent immunoregulation. Deficiency of RBP-J influences the immunoregulatory functions of BA, which include activation of T cells and their differentiation into T helper cell subtypes. The Notch signalling pathway is a potential therapeutic target for BA-based immunotherapy against asthma. © 2017 John Wiley & Sons Ltd.

Subunit arrangement in P2X receptors.

PubMed

Jiang, Lin-Hua; Kim, Miran; Spelta, Valeria; Bo, Xuenong; Surprenant, Annmarie; North, R Alan

2003-10-01

ATP-gated ionotropic receptors (P2X receptors) are distributed widely in the nervous system. For example, a hetero-oligomeric receptor containing both P2X2 and P2X3 subunits is involved in primary afferent sensation. Each subunit has two membrane-spanning domains. We have used disulfide bond formation between engineered cysteines to demonstrate close proximity between the outer ends of the first transmembrane domain of one subunit and the second transmembrane domain of another. After expression in HEK 293 cells of such modified P2X2 or P2X4 subunits, the disulfide bond formation is evident because an ATP-evoked channel opening requires previous reduction with dithiothreitol. In the hetero-oligomeric P2X2/3 receptor the coexpression of doubly substituted subunits with wild-type partners allows us to deduce that the hetero-oligomeric channel contains adjacent P2X3 subunits but does not contain adjacent P2X2 subunits. The results suggest a "head-to-tail" subunit arrangement in the quaternary structure of P2X receptors and show that a trimeric P2X2/3 receptor would have the composition P2X2(P2X3)2.

Poor structural social support is associated with an increased risk of Type 2 diabetes mellitus: findings from the MONICA/KORA Augsburg cohort study.

PubMed

Altevers, J; Lukaschek, K; Baumert, J; Kruse, J; Meisinger, C; Emeny, R T; Ladwig, K H

2016-01-01

Several psychosocial factors have been shown to increase the risk of Type 2 diabetes mellitus. This study investigated the association between structural social support and incidence of Type 2 diabetes mellitus in men and women. Data were derived from three population-based MONICA/KORA surveys conducted in 1984-1995 in the Augsburg region (southern Germany) and followed up by 2009. The study population comprised 8952 participants (4669 men/4283 women) aged 30-74 years without diabetes at baseline. Structural social support was assessed using the Social Network Index. Sex-specific hazard ratios were estimated from Cox proportional hazard models. Within follow-up, 904 incident Type 2 diabetes mellitus cases (558 men, 346 women) were observed. Crude incidence rates for Type 2 diabetes mellitus per 10 000 person-years were substantially higher in poor compared with good structural social support (men: 94 vs. 69, women: 58 vs. 43). After adjustment for age, survey, parental history of diabetes, smoking status, alcohol intake, physical activity, hypertension, dyslipidaemia, BMI, education, sleep complaints and depressed mood, risk of Type 2 diabetes mellitus for participants with poor compared with good structural social support was 1.31 [95% confidence interval (CI) = 1.11-1.55] in men and 1.10 (95% CI = 0.88-1.37) in women. Stratified analyses revealed a hazard ratio of 1.50 (95% CI = 1.23-1.83) in men with a low level of education and 0.87 (95% CI = 0.62-1.22) in men with a high level of education (P for interaction: 0.0082). Poor structural social support is associated with Type 2 diabetes mellitus in men. This association is independent of risk factors at baseline and is particularly pronounced in men with a low level of education. © 2015 The Authors. Diabetic Medicine © 2015 Diabetes UK.

Vertical GaN power diodes with a bilayer edge termination

DOE PAGES

Dickerson, Jeramy R.; Allerman, Andrew A.; Bryant, Benjamin N.; ...

2015-12-07

Vertical GaN power diodes with a bilayer edge termination (ET) are demonstrated. The GaN p-n junction is formed on a low threading dislocation defect density (10 4 - 10 5 cm -2) GaN substrate, and has a 15-μm-thick n-type drift layer with a free carrier concentration of 5 × 10 15 cm -3. The ET structure is formed by N implantation into the p+-GaN epilayer just outside the p-type contact to create compensating defects. The implant defect profile may be approximated by a bilayer structure consisting of a fully compensated layer near the surface, followed by a 90% compensated (p)more » layer near the n-type drift region. These devices exhibit avalanche breakdown as high as 2.6 kV at room temperature. In addition simulations show that the ET created by implantation is an effective way to laterally distribute the electric field over a large area. This increases the voltage at which impact ionization occurs and leads to the observed higher breakdown voltages.« less

Single Crystal X-ray Study of 6-Phenyl-4-( p-tolyl)pyridin-2(1 H)-one

NASA Astrophysics Data System (ADS)

Khajuria, Rajni; Sharma, Suresh; Kapoor, Kamal K.; Gupta, Vivek K.

2017-12-01

The title compound 6-phenyl-4-( p-tolyl)pyridin-2(1 H)-one was synthesized via one-pot, three component reaction of ( E)-1-phenyl-3-( p-tolyl)-2-propen-1-one, ethyl 2-nitroacetate and ammonium acetate in refluxing ethanol, as a shiny green crystalline solid in 83% yield. Its structure was characterized by spectral studies and unambiguously corroborated by X-ray diffraction crystallography. The crystals of title compound are monoclinic, sp. gr. P21/ n, a = 11.8346(7) Å, b = 13.4413(9) Å, c = 17.7626(10) Å, β = 99.479(5)°, and Z = 8. All the rings in molecule of the title compound are planar. Hydrogen interactions play significant role in stabilizing the crystal structure and the supramolecular aggregate of molecules is facilitated by strong N-H···O and C-H···O type of hydrogen interactions.

Impacts of ESD Reliability by Different Layout Engineering in the 0.25-μm 60-V High-Voltage LDMOS Devices

NASA Astrophysics Data System (ADS)

Chen, Shen-Li; Lin, Chun-Ju; Yu-Ting, Huang

2018-02-01

How to effectively enhance the reliability robustness in high-voltage (HV) BCD [(bipolar) complementary metal-oxide semiconductor (CMOS) diffusion metaloxide semiconductor (DMOS)] processes is an important issue. Influences of layouttype dependences on anti-electrostatic discharge (ESD) robustness in a 0.25-μm 60-V process will be studied in this chapter, which includes, in part (1), the traditional striped-type n-channel lateral-diffused MOSFET (nLDMOS), waffle-type nLDMOS, and nLDMOS embedded with a "p-n-p"-arranged silicon-controlled rectifier (SCR) devices in the drain side; and in part (2) a p-channel LDMOS (pLDMOS) with an embedded "p-n-p-n-p"-arranged-type SCR in the drain side (diffusion regions of the drain side is P+-N+-P+-N+-P+). Then, these LDMOS devices are used to evaluate the influence of layout architecture on trigger voltage (Vt1), holding voltage (Vh), and secondary breakdown current (It2). Eventually, the sketching of the layout pattern of a HV LDMOS is a very important issue in the anti-ESD consideration. Also, in part (1), the waffle-type nLDMOS DUT contributes poorly to It2 robustness due to the non-uniform turned-on phenomenon and a narrow channel width per unit finger. Therefore, the It2 robustness of a waffle-type nLDMOS device is decreased about 17% as compared to a traditional striped-type nLDMOS device (reference DUT-1). The ESD abilities of traditional stripedtype and waffle-type nLDMOS devices with an embedded SCR ("p-n-p"-manner arrangement in the drain side) are better than a traditional nLDMOS 224.4% in average. Noteworthy, the nLDMOS-SCR with the "p-n-p" -arranged-type in the drainend is a good structure for the anti-ESD reliability especially in HV usages. Furthermore, in part (2) this layout manner of P+ discrete-island distributions in the drain-side have some impacts on the anti-ESD and anti-latch-up (LU) immunities. All of their It2 values have reached above 6 A; however, the major repercussion is that the Vh value will be decreased about 66.7 73.7%.

Rb3TlBr6•1.14H2O

NASA Astrophysics Data System (ADS)

Villars, P.; Cenzual, K.; Daams, J.; Gladyshevskii, R.; Shcherban, O.; Dubenskyy, V.; Kuprysyuk, V.; Savysyuk, I.; Zaremba, R.

This document is part of Subvolume A10 'Structure Types. Part 10: Space Groups (140) I4/mcm - (136) P42/mnm' of Volume 43 'Crystal Structures of Inorganic Compounds' of Landolt-Börnstein - Group III 'Condensed Matter'.

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

Morozkin, A.V., E-mail: morozkin@general.chem.msu.r; Mozharivskyj, Yu.; SvitlyK, V.

The magnetic ordering of the Fe{sub 2}P-type Tb{sub 6}FeTe{sub 2}, Tb{sub 6}CoTe{sub 2} Tb{sub 6}NiTe{sub 2} and Er{sub 6}FeTe{sub 2} phases (space group P6-bar 2m) has been investigated through magnetization measurement and neutron powder diffraction. Tb{sub 6}FeTe{sub 2}, Tb{sub 6}CoTe{sub 2} and Tb{sub 6}NiTe{sub 2} demonstrate high-temperature ferromagnetic and low-temperature spin reorientation transitions, whereas Er{sub 6}FeTe{sub 2} shows antiferromagnetic transition, only. The Tb{sub 6}FeTe{sub 2} and Tb{sub 6}NiTe{sub 2} phases show same high-temperature collinear ferromagnetic structure, whereas Tb{sub 6}FeTe{sub 2} is the commensurate non-collinear ferromagnet and Tb{sub 6}NiTe{sub 2} is the canted ferromagnetic cone with K{sub 1}=[0, 0, {+-}3/10] andmore » K{sub 2}=[{+-}2/9, {+-}2/9, 0] wave vectors at 2 K. The magnetic structure of Er{sub 6}FeTe{sub 2} is a flat spiral with K{sub 1}=[0, 0, {+-}1/10] at 2 K. The magnetic entropy change for Tb{sub 6}NiTe{sub 2} is {Delta}S{sub m}=-4.86 J/kg K at 229 K for the field change {Delta}{mu}{sub 0}H=0-5 T. In addition, novel Fe{sub 2}P-type Gd{sub 6}FeTe{sub 2}, Zr{sub 6}FeTe{sub 2}, Hf{sub 6}FeTe{sub 2}, Dy{sub 6}NiTe{sub 2}, Zr{sub 6}NiTe{sub 2} and Hf{sub 6}NiTe{sub 2} phases have been obtained. -- Graphical abstract: The novel Fe{sub 2}P-type Tb{sub 6{l_brace}}Fe, Co, Te{r_brace}Te{sub 2} and Er{sub 6}FeTe{sub 2} phases (space group P6-bar 2m) show the complex magnetic ordering below 18-228 K. The magnetocaloric effect for Tb{sub 6}NiTe{sub 2} in terms of the isothermal entropy change, -{Delta}S{sub m}, has the maximum value of 4.86 J/kg K at 229 K for the 0-5 T field change.« less

Structural and computational characterization of 4‧,4‧,6‧,6‧-tetrachloro-3-(2-methoxyethyl)-3H,4H-spiro-1,3,2-benzoxaza phosphinine-2,2‧- [1,3,5,2,4,6] triazatriphosphinine

NASA Astrophysics Data System (ADS)

Işıklan, Muhammet; Yıldırım, Erdem Kamil; Atiş, Murat; Sonkaya, Ömer; Çoşut, Bünyemin

2016-08-01

In this study a new monospirocyclic phosphazene derivative, 4‧,4‧,6‧,6‧-tetrachloro-3-(2-methoxyethyl)-3H,4H-spiro [1,3,2-benzoxazaphosphinine-2,2‧- [1,3,5,2,4,6] triazatriphosphinine] (SP1) was synthesized from the reaction of hexachlorocyclotriphosphazene (N3P3Cl6) with N/O donor-type, 2-{[(2-Metoxyethyl) amino]methyl}phenol. The structural investigations of the compound were verified by elemental analyses, MS, FTIR, 1H, 13C, 31P NMR spectroscopy and the single crystal X-ray diffraction analysis. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (DFT) using 6-311++G (d, p) basis set. The complete assignments of all vibrational modes were performed on the basis of the total energy distributions (TED). Isotropic chemical shifts (31P, 1H and 13C NMR) were calculated using the gauge-invariant atomic orbital (GIAO) method. Theoretical calculations of bond parameters, harmonic vibration frequencies and nuclear magnetic resonance are in good agreement with experimental results. The electrophilic and nucleophilic attack centers in SP1 were predicted with the local softness values (sk+, and sk-) of individual atoms and it is confirmed that P atoms of the PCl2 groups are nucleophilic attack centers.

Structure-function relationship in the globular type III antifreeze protein: identification of a cluster of surface residues required for binding to ice.

PubMed Central

Chao, H.; Sönnichsen, F. D.; DeLuca, C. I.; Sykes, B. D.; Davies, P. L.

1994-01-01

Antifreeze proteins (AFPs) depress the freezing point of aqueous solutions by binding to and inhibiting the growth of ice. Whereas the ice-binding surface of some fish AFPs is suggested by their linear, repetitive, hydrogen bonding motifs, the 66-amino-acid-long Type III AFP has a compact, globular fold without any obvious periodicity. In the structure, 9 beta-strands are paired to form 2 triple-stranded antiparallel sheets and 1 double-stranded antiparallel sheet, with the 2 triple sheets arranged as an orthogonal beta-sandwich (Sönnichsen FD, Sykes BD, Chao H, Davies PL, 1993, Science 259:1154-1157). Based on its structure and an alignment of Type III AFP isoform sequences, a cluster of conserved, polar, surface-accessible amino acids (N14, T18, Q44, and N46) was noted on and around the triple-stranded sheet near the C-terminus. At 3 of these sites, mutations that switched amide and hydroxyl groups caused a large decrease in antifreeze activity, but amide to carboxylic acid changes produced AFPs that were fully active at pH 3 and pH 6. This is consistent with the observation that Type III AFP is optimally active from pH 2 to pH 11. At a concentration of 1 mg/mL, Q44T, N14S, and T18N had 50%, 25%, and 10% of the activity of wild-type antifreeze, respectively. The effects of the mutations were cumulative, such that the double mutant N14S/Q44T had 10% of the wild-type activity and the triple mutant N14S/T18N/Q44T had no activity. All mutants with reduced activity were shown to be correctly folded by NMR spectroscopy. Moreover, a complete characterization of the triple mutant by 2-dimensional NMR spectroscopy indicated that the individual and combined mutations did not significantly alter the structure of these proteins. These results suggest that the C-terminal beta-sheet of Type III AFP is primarily responsible for antifreeze activity, and they identify N14, T18, and Q44 as key residues for the AFP-ice interaction. PMID:7849594

In-Situ Grown P-N Junctions in MERCURY(1-X) Cadmium(x) Telluride for IR Detectors.

NASA Astrophysics Data System (ADS)

Rao, Vithal Rajaram

In-situ grown p-n junctions in mercury cadmium telluride (Hg_{1-x}Cd _{x}Te with x between 0.2-0.3) were fabricated and characterized in this study. Fabrication of these junctions involved the growth of p-n structures at 370^circC on CdTe substrates by Organometallic Vapor Phase Epitaxy. P-type doping with arsenic was achieved by using tertiarybutylarsine as the precursor. N-type doping was obtained either with indium, using trimethylindium as the precursor or by leaving the layer undoped. These p-n structures were processed to fabricate photodiodes. Their electrical performance was evaluated and conclusions regarding current mechanisms which determine their behavior were drawn. By varying the Hg pressure between 0.07-0.13 atm, p-type doping level in the 10^{16 }/cm^3-rm2times10 ^{17}/cm^3 range was achieved. At higher values of Hg pressure, the arsenic doping level in the layer increased significantly. This is possibly due to an increase in Te vacancies, allowing arsenic to occupy more group VI sites where they behave as acceptors. The activation efficiency of arsenic in the layers was measured to be equal to 50%. A high temperature anneal at 415 ^circC for 15 minutes did not result in any increase in the activation efficiency, possibly indicating the presence of stable As-complexes in the layer. Growth of p^+n structures was carried out in a single run. The acceptor concentration in the p-type cap layer was 5-rm10times10 ^{16}/cm^3. Indium doped n-type base layers had a carrier concentration of 1- rm2times10^{16}/cm^3 , while undoped layers had a n-type background carrier concentration of 4-rm6times10^ {14}/cm^3. The cap layer was 3 μm thick with x = 0.30, while the base layer was 8mum thick with x = 0.26. Under the growth conditions, arsenic showed a diffusion coefficient of rm2times10 ^{13}cm^2/s, which was higher than the interdiffusion coefficient of the alloy junction. This resulted in placement of the p-n junction in the lower bandgap base layer, which is necessary for high quantum efficiency devices. Photodiodes showed a cutoff wavelength of 7.5 mum, which correlates with the alloy composition of the base layer. Measured R_0 A of these diodes varied between 1-100 ohm-cm ^2. In the lower R_0A diodes, reverse bias was dominated by surface currents, possibly due to degradation of the passivating layer. Diodes with higher R_0A showed under reverse bias that trap assisted tunneling current dominated their performance. The origin of these traps is process related and could correspond to the presence of inactivated arsenic close to the p-n junction. Forward bias was dominated by diffusion and recombination currents, while the presence of additional leakage currents was evident.

A new nonlinear optical silicate carbonate K2Ca[Si2O5](CO3) with a hybrid structure of kalsilite and soda-like layered fragments

NASA Astrophysics Data System (ADS)

Belokoneva, Elena L.; Stefanovich, Sergey Yu.; Volkov, Anatoly S.; Dimitrova, Olga V.

2016-10-01

Single crystals of a new silicate carbonate, K2Ca[Si2O5](CO3), have been synthesized in a multi-components hydrothermal solution with a pH value close to neutral and a high concentration of a carbonate mineralizer. The new compound has an axial structure (s.g. P6322) with unit cell parameters a = 5.04789 (15), c = 17.8668 (6) Å. Pseudosymmetry of the structure corresponds to s.g. P63/mmc which is broken only by one oxygen position. The structure consists of two layered fragments: one of the type of the mineral kalsilite (KAlSiO4) and the other of the high-temperature soda-like α-Na2CO3, Ca substituting for Na. The electro-neutral layer K2[Si2O5] (denoted K) as well as the layer Ca(CO3) (denoted S) may separately correspond to individual structures. In K2Ca[Si2O5](CO3) the S-K layers are connected together via Ca-O interactions between Ca atoms from the carbonate layer and apical O atoms from the silicate one, and also via K-O interlayer interactions. A hypothetical acentric structure, sp.gr. P-62c, is predicted on the basis of the order-disorder theory. It presents another symmetrical option for the arrangement of K-layers relative to S-layers. The K,Ca-silicate-carbonate powder produces a moderate SHG signal that is two times larger that of the α-quartz powder standard and close to other silicates with acentric structures and low electronic polarizability.

Room temperature electrical properties of solution derived p-type Cu{sub 2}ZnSnS{sub 4} thin films

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

Gupta, Goutam Kumar; Dixit, Ambesh, E-mail: ambesh@iitj.ac.in

2016-05-06

Electrical properties of solution processed Cu{sub 2}ZnSnS{sub 4} (CZTS) compound semiconductor thin film structures on molybdenum (Mo) coated glass substrates are investigated using Mott-Schottky and Impedance spectroscopy measurements at room temperature. These measurements are carried out in sodium sulfate (Na{sub 2}SO{sub 4}) electrolytic medium at pH ~ 9.5. The inversion/depletion/accumulation regions are clearly observed in CZTS semiconductor −Na{sub 2}SO{sub 4} electrolyte interface and measured flat band potential is ~ −0.27 V for CZTS thin film electrode. The positive slope of the depletion region confirms the intrinsic p-type characteristics of CZTS thinfilms with ~ 2.5× 10{sup 19} holes/m{sup 3}. The high frequencymore » impedance measurements showed ~ 30 Ohm electrolyte resistance for the investigated configuration.« less

Transparent conductive p-type lithium-doped nickel oxide thin films deposited by pulsed plasma deposition

NASA Astrophysics Data System (ADS)

Huang, Yanwei; Zhang, Qun; Xi, Junhua; Ji, Zhenguo

2012-07-01

Transparent p-type Li0.25Ni0.75O conductive thin films were prepared on conventional glass substrates by pulsed plasma deposition. The effects of substrate temperature and oxygen pressure on structural, electrical and optical properties of the films were investigated. The electrical resistivity decreases initially and increases subsequently as the substrate temperature increases. As the oxygen pressure increases, the electrical resistivity decreases monotonically. The possible physical mechanism was discussed. And a hetero p-n junction of p-Li0.25Ni0.75O/n-SnO2:W was fabricated by depositing n-SnO2:W on top of the p-Li0.25Ni0.75O, which exhibits typical rectifying current-voltage characteristics.

Structural diversity of three Cu(II) compounds based on a new tripodal zwitterionic ligand: Syntheses, structures and properties

NASA Astrophysics Data System (ADS)

Zhou, Jie; Zhao, Jing-Song; Feng, Jing; Zhang, Xiao-Feng; Xu, Jian; Du, Lin; Xie, Ming-Jin; Zhao, Qi-Hua

2018-03-01

An exploration of reactions of 1,1‧,1″-(benzene-1,3,5-triyltris(methylene))tris(4-carboxypyridinium)-tribromide (H3LBr3) with Cu(II) salt under different pH conditions has led to the formation of three complexes, [Cu(HL)2(H2O)3]·4(ClO4)·3H2O (1), [Cu2(HL)(μ3-OH)(μ2-H2O)(H2O)2]·4(ClO4)·6H2O (2), and [Cu3(L)2Cl6(H2O)4]·4H2O (3). Single-crystal X-ray analyses revealed that complex 1 displays a discrete mononuclear structure with the ligand in a bowl-shaped configuration. Complex 2 possesses a tetranuclear 1D beaded chain structure. While complex 3 features a discrete trinuclear 'H-type' structure with the ligand in a chair-like configuration. The distinct compositions and structures of 1-3 are mainly ascribed to the different pH values of the reaction solution, the influences of anions, as well as the configurations which the zwitterion ligands adopt. The magnetic properties of 2, and the photoluminescence properties of 2, and 3 have been investigated. Moreover, powder X-ray diffraction, infrared spectroscopy, and elemental analysis were also performed.

Oxygen trapped by rare earth tetrahedral clusters in Nd4FeOS6: Crystal structure, electronic structure, and magnetic properties

NASA Astrophysics Data System (ADS)

Lin, Qisheng; Taufour, Valentin; Zhang, Yuemei; Wood, Max; Drtina, Thomas; Bud'ko, Sergey L.; Canfield, Paul C.; Miller, Gordon J.

2015-09-01

Single crystals of Nd4FeOS6 were grown from an Fe-S eutectic solution. Single crystal X-ray diffraction analysis revealed a Nd4MnOSe6-type structure (P63mc, a=9.2693(1) Å, c=6.6650(1)Å, V=495.94(1) Å3, Z=2), featuring parallel chains of face-sharing [FeS6×1/2]4- trigonal antiprisms and interlinked [Nd4OS3]4+ cubane-like clusters. Oxygen atoms were found to be trapped by Nd4 clusters in the [Nd4OS3]4+ chains. Structural differences among Nd4MnOSe6-type Nd4FeOS6 and the related La3CuSiS7- and Pr8CoGa3-type structures have been described. Magnetic susceptibility measurements on Nd4FeOS6 suggested the dominance of antiferromagnetic interactions at low temperature, but no magnetic ordering down to 2 K was observed. Spin-polarized electronic structure calculations revealed magnetic frustration with dominant antiferromagnetic interactions.

Hardness of AISI type 410 martensitic steels after high temperature irradiation via nanoindentation

NASA Astrophysics Data System (ADS)

Waseem, Owais Ahmed; Jeong, Jong-Ryul; Park, Byong-Guk; Maeng, Cheol-Soo; Lee, Myoung-Goo; Ryu, Ho Jin

2017-11-01

The hardness of irradiated AISI type 410 martensitic steel, which is utilized in structural and magnetic components of nuclear power plants, is investigated in this study. Proton irradiation of AISI type 410 martensitic steel samples was carried out by exposing the samples to 3 MeV protons up to a 1.0 × 1017 p/cm2 fluence level at a representative nuclear reactor coolant temperature of 350 °C. The assessment of deleterious effects of irradiation on the micro-structure and mechanical behavior of the AISI type 410 martensitic steel samples via transmission electron microscopy-energy dispersive spectroscopy and cross-sectional nano-indentation showed no significant variation in the microscopic or mechanical characteristics. These results ensure the integrity of the structural and magnetic components of nuclear reactors made of AISI type 410 martensitic steel under high-temperature irradiation damage levels up to approximately 5.2 × 10-3 dpa.

Unexpected Binding Mode of a Potent Indeno[1,2-b]indole-Type Inhibitor of Protein Kinase CK2 Revealed by Complex Structures with the Catalytic Subunit CK2α and Its Paralog CK2α′

PubMed Central

Hochscherf, Jennifer; Lindenblatt, Dirk; Witulski, Benedict; Birus, Robin; Aichele, Dagmar

2017-01-01

Protein kinase CK2, a member of the eukaryotic protein kinase superfamily, is associated with cancer and other human pathologies and thus an attractive drug target. The indeno[1,2-b]indole scaffold is a novel lead structure to develop ATP-competitive CK2 inhibitors. Some indeno[1,2-b]indole-based CK2 inhibitors additionally obstruct ABCG2, an ABC half transporter overexpressed in breast cancer and co-responsible for drug efflux and resistance. Comprehensive derivatization studies revealed substitutions of the indeno[1,2-b]indole framework that boost either the CK2 or the ABCG2 selectivity or even support the dual inhibition potential. The best indeno[1,2-b]indole-based CK2 inhibitor described yet (IC50 = 25 nM) is 5-isopropyl-4-(3-methylbut-2-enyl-oxy)-5,6,7,8-tetrahydroindeno[1,2-b]indole-9,10-dione (4p). Herein, we demonstrate the membrane permeability of 4p and describe co-crystal structures of 4p with CK2α and CK2α′, the paralogs of human CK2 catalytic subunit. As expected, 4p occupies the narrow, hydrophobic ATP site of CK2α/CK2α′, but surprisingly with a unique orientation: its hydrophobic substituents point towards the solvent while its two oxo groups are hydrogen-bonded to a hidden water molecule. An equivalent water molecule was found in many CK2α structures, but never as a critical mediator of ligand binding. This unexpected binding mode is independent of the interdomain hinge/helix αD region conformation and of the salt content in the crystallization medium. PMID:29236079

The relationship between the electronic structure and thermoelectric properties of Zintl compounds M2Zn5As4 (M = K, Rb).

PubMed

Yang, Gui; Yang, Jueming; Yan, Yuli; Wang, Yuanxu

2014-03-28

The electronic structure and the thermoelectric properties of M2Zn5As4 (M = K, Rb) are studied by the first principles and the semiclassical BoltzTraP theory. It is determined that they are semiconductors with an indirect band gap of about 1 eV, which is much larger than that of Ca5Al2Sb6 (0.50 eV). The calculated electronic localization function indicates that they are typical Zintl bonding compounds. The combination of heavy and light bands near the valence band maximum may improve their thermoelectric performance. Rb2Zn5As4 exhibits relatively large Seebeck coefficients, high electrical conductivities, and the large "maximum" thermoelectric figures of merit (ZeT). Compared with Ca5Al2Sb6, the highest ZeT of Rb2Zn5As4 appears at relatively low carrier concentration. For Rb2Zn4As5, the p-type doping may achieve a higher thermoelectric performance than n-type doping. The thermoelectric properties of Rb2Zn5As4 are possibly superior to those of Ca5Al2Sb6.

Complex magnetic phase diagram with multistep spin-flop transitions in L a0.25P r0.75C o2P2

NASA Astrophysics Data System (ADS)

Tan, Xiaoyan; Garlea, V. Ovidiu; Kovnir, Kirill; Thompson, Corey M.; Xu, Tongshuai; Cao, Huibo; Chai, Ping; Tener, Zachary P.; Yan, Shishen; Xiong, Peng; Shatruk, Michael

2017-01-01

L a0.25P r0.75C o2P2 crystallizes in the tetragonal ThC r2S i2 structure type and shows multiple magnetic phase transitions driven by changes in temperature and magnetic field. The nature of these transitions was investigated by a combination of magnetic and magnetoresistance measurements and both single crystal and powder neutron diffraction. The Co magnetic moments order ferromagnetically (FM) parallel to the c axis at 282 K, followed by antiferromagnetic (AFM) ordering at 225 K. In the AFM structure, the Co magnetic moments align along the c axis with FM [C o2P2] layers arranged in an alternating sequence, ↑↑↓↓ , which leads to the doubling of the c axis in the magnetic unit cell. Another AFM transition is observed at 27 K, due to the ordering of a half of Pr moments in the a b plane. The other half of Pr moments undergoes AFM ordering along the c axis at 11 K, causing simultaneous reorientation of the previously ordered Pr moments into an AFM structure with the moments being canted with respect to the c axis. This AFM transition causes an abrupt decrease in electrical resistivity at 11 K. Under applied magnetic field, two metamagnetic transitions are observed in the Pr sublattice at 0.8 and 5.4 T. They correlate with two anomalies in magnetoresistance measurements at the same critical fields. A comparison of the temperature- and field-dependent magnetic properties of L a0.25P r0.75C o2P2 to the magnetic behavior of PrC o2P2 is provided.

Chemical and biological characterization of pectin-like polysaccharides from the bark of the Malian medicinal tree Cola cordifolia.

PubMed

Austarheim, Ingvild; Christensen, Bjørn E; Hegna, Ida K; Petersen, Bent O; Duus, Jens O; Bye, Ragnar; Michaelsen, Terje E; Diallo, Drissa; Inngjerdingen, Marit; Paulsen, Berit S

2012-06-05

The bark of Cola cordifolia used in Malian traditional medicine contains unusual types of polysaccharides with immunomodulating activities. We report for the first time on the structure of a polymer designated CC1P1 having the repeating structure [2→)[α-D-Gal(1→3)]α-L-Rha(1→4)α-d-GalA(1→] as determined by NMR and GC/MS. α-Linked Gal is unusual in pectins. The Mw of 135 kDa was determined by SEC-MALLS. CC1P2 (1400 kDa), another polymer, having the same backbone, but this was substituted with α-4-OMe-GlcA, α-2-OMe-Gal and α-Gal as terminal units. CC1P1 shows a high complement-fixing activity, IC₅₀ being 2.2 times lower than the positive pectin control PMII (IC₅₀ appr. 71 μg/mL) while IC₅₀ of CC1P2 is 1.8 times lower. The simple structure of CC1P1 did not activate macrophages, while CC1P2 (100 μg/mL) showed the same potency as the positive controls PMII (100 μg/mL) and LPS (500 ng/mL). No cytotoxicity was detected. Copyright © 2012 Elsevier Ltd. All rights reserved.

Hydrothermal Synthesis and Characterization of Novel Brackebuschite-Type Transition Metal Vanadates: Ba 2 M(VO 4 ) 2 (OH), M = V 3+ , Mn 3+ , and Fe 3+ , with Interesting Jahn–Teller and Spin-Liquid Behavior

DOE PAGES

Sanjeewa, Liurukara D.; McGuire, Michael A.; Garlea, Vasile O.; ...

2015-07-08

In a new series of transition metal vanadates, namely, Ba 2M(VO 4) 2(OH) (M = V 3+, Mn 3+, and Fe 3+), was synthesized as large single crystals hydrothermally in 5 M NaOH solution at 580 °C and 1 kbar. This new series of compounds is structurally reminiscent of the brackebuschite mineral type. The structure of Ba 2V(VO 4) 2(OH) is monoclinic in space group P2 1/m, a = 7.8783(2) Å, b = 6.1369(1) Å, c = 9.1836(2) Å, β = 113.07(3)°, V = 408.51(2) Å 3. Moreover, the other structures are similar and consist of one-dimensional trans edge-shared distortedmore » octahedral chains running along the b-axis. The vanadate groups bridge across edges of their tetrahedra. Structural analysis of the Ba 2Mn(VO 4) 2(OH) analogue yielded a new understanding of the Jahn–Teller effect in this structure type. Raman and infrared spectra were investigated to observe the fundamental vanadate and hydroxide vibrational modes. Finally, single-crystal temperature-dependent magnetic studies on Ba 2V(VO 4) 2(OH) reveal a broad feature over a wide temperature range with maximum at ~100 K indicating that an energy gap could exist between the antiferromagnetic singlet ground state and excited triplet states, making it potentially of interest for quantum magnetism studies.« less

Band gap narrowing in n-type and p-type 3C-, 2H-, 4H-, 6H-SiC, and Si

NASA Astrophysics Data System (ADS)

Persson, C.; Lindefelt, U.; Sernelius, B. E.

1999-10-01

Doping-induced energy shifts of the conduction band minimum and the valence band maximum have been calculated for n-type and p-type 3C-, 2H-, 4H-, 6H-SiC, and Si. The narrowing of the fundamental band gap and of the optical band gap are presented as functions of ionized impurity concentration. The calculations go beyond the common parabolic treatments of the ground state energy dispersion by using energy dispersion and overlap integrals from band structure calculations. The nonparabolic valence band curvatures influence strongly the energy shifts especially in p-type materials. The utilized method is based on a zero-temperature Green's function formalism within the random phase approximation with local field correction according to Hubbard. We have parametrized the shifts of the conduction and the valence bands and made comparisons with recently published results from a semi-empirical model.

Neocortical maturation during adolescence: change in neuronal soma dimension.

PubMed

Rabinowicz, Theodore; Petetot, Jean Macdonald-Comber; Khoury, Jane C; de Courten-Myers, Gabrielle M

2009-03-01

During adolescence, cognitive abilities increase robustly. To search for possible related structural alterations of the cerebral cortex, we measured neuronal soma dimension (NSD = width times height), cortical thickness and neuronal densities in different types of neocortex in post-mortem brains of five 12-16 and five 17-24 year-olds (each 2F, 3M). Using a generalized mixed model analysis, mean normalized NSD comparing the age groups shows layer-specific change for layer 2 (p < .0001) and age-related differences between categorized type of cortex: primary/primary association cortex (BA 1, 3, 4, and 44) shows a generalized increase; higher-order regions (BA 9, 21, 39, and 45) also show increase in layers 2 and 5 but decrease in layers 3, 4, and 6 while limbic/orbital cortex (BA 23, 24, and 47) undergoes minor decrease (BA 1, 3, 4, and 44 vs. BA 9, 21, 39, and 45: p = .036 and BA 1, 3, 4, and 44 vs. BA 23, 24, and 47: p = .004). These data imply the operation of cortical layer- and type-specific processes of growth and regression adding new evidence that the human brain matures during adolescence not only functionally but also structurally.

Converting the Conducting Behavior of Graphene Oxides from n-Type to p-Type via Electron-Beam Irradiation.

PubMed

Mirzaei, Ali; Kwon, Yong Jung; Wu, Ping; Kim, Sang Sub; Kim, Hyoun Woo

2018-02-28

We studied the effects of electron-beam irradiation (EBI) on the structural and gas-sensing properties of graphene oxide (GO). To understand the effects of EBI on the structure and gas-sensing behavior of irradiated GO, the treated GO was compared with nonirradiated GO. Characterization results indicated an enhancement in the number of oxygen functional groups that occurs with EBI exposure at 100 kGy and then decreases with doses in the range of 100-500 kGy. Data from Raman spectra indicated that EBI could generate defects, and NO 2 -sensing results at room temperature showed a decreased NO 2 response after exposure to EBI at 100 kGy; further increasing the dose to 500 kGy resulted in p-type semiconducting conductivity. The conversion of GO from n-type to p-type via EBI is explained not only through the generation of holes but also the variation in the amount of residual functional groups, including carboxyl (COOH) and hydroxyl groups (C-OH). The obtained results suggest that EBI can be a useful tool to convert GO into a diverse range of sensing devices.

Transform Faults and Lithospheric Structure: Insights from Numerical Models and Shipboard and Geodetic Observations

NASA Astrophysics Data System (ADS)

Takeuchi, Christopher S.

In this dissertation, I study the influence of transform faults on the structure and deformation of the lithosphere, using shipboard and geodetic observations as well as numerical experiments. I use marine topography, gravity, and magnetics to examine the effects of the large age-offset Andrew Bain transform fault on accretionary processes within two adjacent segments of the Southwest Indian Ridge. I infer from morphology, high gravity, and low magnetization that the extremely cold and thick lithosphere associated with the Andrew Bain strongly suppresses melt production and crustal emplacement to the west of the transform fault. These effects are counteracted by enhanced temperature and melt production near the Marion Hotspot, east of the transform fault. I use numerical models to study the development of lithospheric shear zones underneath continental transform faults (e.g. the San Andreas Fault in California), with a particular focus on thermomechanical coupling and shear heating produced by long-term fault slip. I find that these processes may give rise to long-lived localized shear zones, and that such shear zones may in part control the magnitude of stress in the lithosphere. Localized ductile shear participates in both interseismic loading and postseismic relaxation, and predictions of models including shear zones are within observational constraints provided by geodetic and surface heat flow data. I numerically investigate the effects of shear zones on three-dimensional postseismic deformation. I conclude that the presence of a thermally-activated shear zone minimally impacts postseismic deformation, and that thermomechanical coupling alone is unable to generate sufficient localization for postseismic relaxation within a ductile shear zone to kinematically resemble that by aseismic fault creep (afterslip). I find that the current record geodetic observations of postseismic deformation do not provide robust discriminating power between candidate linear and power-law rheologies for the sub-Mojave Desert mantle, but longer observations may potentially allow such discrimination.

Synthesis of phosphinoferrocene amides and thioamides from carbamoyl chlorides and the structural chemistry of Group 11 metal complexes with these mixed-donor ligands.

PubMed

Fernandes, Tiago A; Solařová, Hana; Císařová, Ivana; Uhlík, Filip; Štícha, Martin; Štěpnička, Petr

2015-02-21

The reaction of in situ generated 1'-(diphenylphosphino)-1-lithioferrocene with carbamoyl chlorides, ClC(E)NMe2, affords the corresponding (thio)amides, Ph2PfcC(E)NMe2 (E = O (), S (); fc = ferrocene-1,1'-diyl). These compounds as well as their analogues, Ph2PfcC(O)NHMe () and Ph2PfcC(O)NH2 (), prepared from 1'-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) were studied as ligands for the Group 11 metal ions. In the reactions with [Cu(MeCN)4][BF4], the amides give rise to bis-chelate complexes of the type [Cu(L-κ(2)O,P)2][BF4]. Similar products, [Ag(L-κ(2)O,P)2]ClO4, are obtained from silver(i) perchlorate and , or . In contrast, the reaction of AgClO4 with produces a unique molecular dimer [Ag()(ClO4-κO)]2, where the metal centres are bridged by the sulfur atoms of the P,S-chelating thioamides. The reactions of with [AuCl(tht)] (tht = tetrahydrothiophene) afford the expected gold(i)-phosphine complexes, [AuCl(L-κP)], containing uncoordinated (thio)amide moieties. Hemilabile coordination of the phosphinoamide ligands in complexes with the soft Group 11 metal ions is established by the crystal structure of a solvento complex, [Cu(-κ(2)O,P)(-κP)(CHCl3-κCl)][BF4], which was isolated serendipitously during an attempted crystallisation of [Cu(-κ(2)O,P)2][BF4]. All of the compounds are characterised by spectroscopic methods, and the structures of several representatives of both the free phosphinoamides and their complexes are determined by X-ray diffraction analysis and further studied by DFT calculations and cyclic voltammetry.

P-type transparent conducting oxides.

PubMed

Zhang, Kelvin H L; Xi, Kai; Blamire, Mark G; Egdell, Russell G

2016-09-28

Transparent conducting oxides constitute a unique class of materials combining properties of electrical conductivity and optical transparency in a single material. They are needed for a wide range of applications including solar cells, flat panel displays, touch screens, light emitting diodes and transparent electronics. Most of the commercially available TCOs are n-type, such as Sn doped In2O3, Al doped ZnO, and F doped SnO2. However, the development of efficient p-type TCOs remains an outstanding challenge. This challenge is thought to be due to the localized nature of the O 2p derived valence band which leads to difficulty in introducing shallow acceptors and large hole effective masses. In 1997 Hosono and co-workers (1997 Nature 389 939) proposed the concept of 'chemical modulation of the valence band' to mitigate this problem using hybridization of O 2p orbitals with close-shell Cu 3d (10) orbitals. This work has sparked tremendous interest in designing p-TCO materials together with deep understanding the underlying materials physics. In this article, we will provide a comprehensive review on traditional and recently emergent p-TCOs, including Cu(+)-based delafossites, layered oxychalcogenides, nd (6) spinel oxides, Cr(3+)-based oxides (3d (3)) and post-transition metal oxides with lone pair state (ns (2)). We will focus our discussions on the basic materials physics of these materials in terms of electronic structures, doping and defect properties for p-type conductivity and optical properties. Device applications based on p-TCOs for transparent p-n junctions will also be briefly discussed.

Structural analysis of a class III preQ1 riboswitch reveals an aptamer distant from a ribosome-binding site regulated by fast dynamics

PubMed Central

Liberman, Joseph A.; Suddala, Krishna C.; Aytenfisu, Asaminew; Chan, Dalen; Belashov, Ivan A.; Salim, Mohammad; Mathews, David H.; Spitale, Robert C.; Walter, Nils G.; Wedekind, Joseph E.

2015-01-01

PreQ1-III riboswitches are newly identified RNA elements that control bacterial genes in response to preQ1 (7-aminomethyl-7-deazaguanine), a precursor to the essential hypermodified tRNA base queuosine. Although numerous riboswitches fold as H-type or HLout-type pseudoknots that integrate ligand-binding and regulatory sequences within a single folded domain, the preQ1-III riboswitch aptamer forms a HLout-type pseudoknot that does not appear to incorporate its ribosome-binding site (RBS). To understand how this unusual organization confers function, we determined the crystal structure of the class III preQ1 riboswitch from Faecalibacterium prausnitzii at 2.75 Å resolution. PreQ1 binds tightly (KD,app 6.5 ± 0.5 nM) between helices P1 and P2 of a three-way helical junction wherein the third helix, P4, projects orthogonally from the ligand-binding pocket, exposing its stem-loop to base pair with the 3′ RBS. Biochemical analysis, computational modeling, and single-molecule FRET imaging demonstrated that preQ1 enhances P4 reorientation toward P1–P2, promoting a partially nested, H-type pseudoknot in which the RBS undergoes rapid docking (kdock ∼0.6 s−1) and undocking (kundock ∼1.1 s−1). Discovery of such dynamic conformational switching provides insight into how a riboswitch with bipartite architecture uses dynamics to modulate expression platform accessibility, thus expanding the known repertoire of gene control strategies used by regulatory RNAs. PMID:26106162

Attenuation of the Atmospheric Migration Ability of Polychlorinated Naphthalenes (PCN-2) Based on Three-dimensional QSAR Models with Full Factor Experimental Design.

PubMed

Gu, Wenwen; Chen, Ying; Li, Yu

2017-08-01

Based on the experimental subcooled liquid vapor pressures (P L ) of 17 polychlorinated naphthalene (PCN) congeners, one type of three-dimensional quantitative structure-activity relationship (3D-QSAR) models, comparative molecular similarity indices analysis (CoMSIA), was constructed with Sybyl software. Full factor experimental design was used to obtain the final regulation scheme for PCN, and then carry out modification of PCN-2 to significantly lower its P L . The contour maps of CoMSIA model showed that the migration ability of PCN decreases when the Cl atoms at the 2-, 3-, 4-, 5-, 6-, 7- and 8-positions of PCNs are replaced by electropositive groups. After modification of PCN-2, 12 types of new modified PCN-2 compounds were obtained with lnP L values two orders of magnitude lower than that of PCN-2. In addition, there are significant differences between the calculated total energies and energy gaps of the new modified compounds and those of PCN-2.

General Practitioners' Barriers to Prescribe Physical Activity: The Dark Side of the Cluster Effects on the Physical Activity of Their Type 2 Diabetes Patients.

PubMed

Lanhers, Charlotte; Duclos, Martine; Guttmann, Aline; Coudeyre, Emmanuel; Pereira, Bruno; Ouchchane, Lemlih

2015-01-01

To describe barriers to physical activity (PA) in type 2 diabetes patients and their general practitioners (GPs), looking for practitioner's influence on PA practice of their patients. We conducted a cross-sectional study on GPs (n = 48) and their type 2 diabetes patients (n = 369) measuring respectively barriers to prescribe and practice PA using a self-assessment questionnaire: barriers to physical activity in diabetes (BAPAD). Statistical analysis was performed accounting hierarchical data structure. Similar practitioner's patients were considered a cluster sharing common patterns. The higher the patient's BAPAD score, the higher the barriers to PA, the higher the risk to declare practicing no PA (p<0.001), low frequency and low duration of PA (p<0.001). A high patient's BAPAD score was also associated with a higher risk to have HbA1c ≥7% (53 mmol/mol) (p = 0.001). The intra-class correlation coefficient between type 2 diabetes patients and GPs was 34%, indicating a high cluster effect. A high GP's BAPAD score, regarding the PA prescription, is predictive of a high BAPAD score with their patients, regarding their practice (p = 0.03). Type 2 diabetes patients with lower BAPAD score, thus lower barriers to physical activity, have a higher PA level and a better glycemic control. An important and deleterious cluster effect between GPs and their patients is demonstrated: the higher the GP's BAPAD score, the higher the type 2 diabetes patients' BAPAD score. This important cluster effect might designate GPs as a relevant lever for future interventions regarding patient's education towards PA and type 2 diabetes management.

Exploration of the binding modes of buffalo PGRP1 receptor complexed with meso-diaminopimelic acid and lysine-type peptidoglycans by molecular dynamics simulation and free energy calculation.

PubMed

Sahoo, Bikash Ranjan; Dubey, Praveen Kumar; Goyal, Shubham; Bhoi, Gopal Krushna; Lenka, Santosh Kumar; Maharana, Jitendra; Pradhan, Sukanta Kumar; Kataria, Ranjit Singh

2014-09-05

The peptidoglycan recognition proteins (PGRPs) are the key components of innate-immunity, and are highly specific for the recognition of bacterial peptidoglycans (PGN). Among different mammalian PGRPs, the PGRP1 binds to murein PGN of Gram-positive bacteria (lysine-type) and also have bactericidal activity towards Gram-negative bacteria (diaminopimelic acid or Dap-type). Buffaloes are the major sources of milk and meat in Asian sub-continents and are highly exposed to bacterial infections. The PGRP activates the innate-immune signaling, but their studies has been confined to limited species due to lack of structural and functional information. So, to understand the structural constituents, 3D model of buffalo PGRP1 (bfPGRP1) was constructed and conformational and dynamics properties of bfPGRP1 was studied. The bfPGRP1 model highly resembled human and camel PGRP structure, and shared a highly flexible N-terminus and centrally placed L-shaped cleft. Docking simulation of muramyl-tripeptide, tetrapeptide, pentapeptide-Dap-(MTP-Dap, MTrP-Dap and MPP-Dap) and lysine-type (MTP-Lys, MTrP-Lys and MPP-Lys) in AutoDock 4.2 and ArgusLab 4.0.1 anticipated β1, α2, α4, β4, and loops connecting β1-α2, α2-β2, β3-β4 and α4-α5 as the key interacting domains. The bfPGRP1-ligand complex molecular dynamics simulation followed by free binding energy (BE) computation conceded BE values of -18.30, -35.53, -41.80, -25.03, -24.62 and -22.30 kJ mol(-1) for MTP-Dap, MTrP-Dap, MPP-Dap, MTP-Lys, MTrP-Lys and MPP-Lys, respectively. The groove-surface and key binding residues involved in PGN-Dap and Lys-type interaction intended by the molecular docking, and were also accompanied by significant BE values directed their importance in pharmacogenomics, and warrants further in vivo studies for drug targeting and immune signaling pathways exploration. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Phosphorus-Rich Copper Phosphide Nanowires for Field-Effect Transistors and Lithium-Ion Batteries.

PubMed

Li, Guo-An; Wang, Chiu-Yen; Chang, Wei-Chung; Tuan, Hsing-Yu

2016-09-27

Phosphorus-rich transition metal phosphide CuP2 nanowires were synthesized with high quality and high yield (∼60%) via the supercritical fluid-liquid-solid (SFLS) growth at 410 °C and 10.2 MPa. The obtained CuP2 nanowires have a high aspect ratio and exhibit a single crystal structure of monoclinic CuP2 without any impurity phase. CuP2 nanowires have progressive improvement for semiconductors and energy storages compared with bulk CuP2. Being utilized for back-gate field effect transistor (FET) measurement, CuP2 nanowires possess a p-type behavior intrinsically with an on/off ratio larger than 10(4) and its single nanowire electrical transport property exhibits a hole mobility of 147 cm(2) V(-1) s(-1), representing the example of a CuP2 transistor. In addition, CuP2 nanowires can serve as an appealing anode material for a lithium-ion battery electrode. The discharge capacity remained at 945 mA h g(-1) after 100 cycles, showing a good capacity retention of 88% based on the first discharge capacity. Even at a high rate of 6 C, the electrode still exhibited an outstanding result with a capacity of ∼600 mA h g(-1). Ex-situ transmission electron microscopy and CV tests demonstrate that the stability of capacity retention and remarkable rate capability of the CuP2 nanowires electrode are attributed to the role of the metal phosphide conversion-type lithium storage mechanism. Finally, CuP2 nanowire anodes and LiFePO4 cathodes were assembled into pouch-type lithium batteries offering a capacity over 60 mA h. The full cell shows high capacity and stable capacity retention and can be used as an energy supply to operate electronic devices such as mobile phones and mini 4WD cars.

Defining the minimal structural requirements for partial agonism at the type I myo-inositol 1,4,5-trisphosphate receptor.

PubMed

Wilcox, R A; Fauq, A; Kozikowski, A P; Nahorski, S R

1997-02-03

The novel synthetic analogues D-3-fluoro-myo-inositol 1,5-bisphosphate-4-phosphorothioate, [3F-Ins(1,5)P2-4PS], D-3-fluoro-myo-inositol 1,4-bisphosphate-5-phosphorothioate [3F-Ins(1,4)P2-5PS], and D-3-fluoro-myo-inositol 1-phosphate-4,5-bisphosphorothioate [3F-Ins(1)P-(4,5)PS2] were utilised to define the structure-activity relationships which could produce partial agonism at the Ca2+ mobilising myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] receptor. Based on prior structure-activity data we hypothesised that the minimal structural requirements for lns(1,4,5)P3 receptor partial agonism, were phosphorothioate substitution of the crucial vicinal 4,5-bisphosphate pair accompanied by another structural perturbation, such fluorination of 3-position of the myo-inositol ring. All the analogues fully displaced [3H]Ins(1,4,5)P3 from a single Ins(1,4,5)P3 binding site in pig cerebellar membranes [3F-Ins(1,5)P2-4PS (1C50 = 26 nM), 3F-Ins(1,4)P2-5PS (IC50 = 80 nM) and 3F-Ins(1)P-(4,5)PS2 (IC50 = 109 nM) cf. Ins(1,4,5)P3 (IC50 = 11 nM)]. In contrast, 3F-Ins(1,5)P2-4PS (IC50 = 424 nM) and 3F-Ins(1,4)P2-5PS (IC50 = 3579 nM) were weak full agonists at the Ca2+ mobilising Ins(1,4,5)P3 receptor of permeabilised SH-SY5Y neuroblastoma cells, being respectively 4- and 36-fold less potent than Ins(1,4,5)P3 (EC50 = 99 nM). While 3F-Ins(1)P-(4,5)PS2 (EC50 = 11345 nM) was a partial agonist releasing only 64.3 +/- 1.9% of the Ins(1,4,5)P3-sensitive intracellular Ca2+ pools. 3F-Ins(1)P-(4,5)PS2 was unique among the Ins(1,4,5)P3 receptor partial agonists so far identified in having a relatively high affinity for the Ins(1,4,5)P3 binding site, accompanied by a significant loss of intrinsic activity for Ca2+ mobilisation. This improved affinity was probably due to the retention of the 1-position phosphate, which enhances interaction with the Ins-(1,4,5)P3 receptor. 3F-Ins(1)P-(4,5)PS2 may be an important lead compound for the development of efficient Ins(1,4,5)P3 receptor antagonists.

Atomic Structure of Type VI Contractile Sheath from Pseudomonas aeruginosa.

PubMed

Salih, Osman; He, Shaoda; Planamente, Sara; Stach, Lasse; MacDonald, James T; Manoli, Eleni; Scheres, Sjors H W; Filloux, Alain; Freemont, Paul S

2018-02-06

Pseudomonas aeruginosa has three type VI secretion systems (T6SSs), H1-, H2-, and H3-T6SS, each belonging to a distinct group. The two T6SS components, TssB/VipA and TssC/VipB, assemble to form tubules that conserve structural/functional homology with tail sheaths of contractile bacteriophages and pyocins. Here, we used cryoelectron microscopy to solve the structure of the H1-T6SS P. aeruginosa TssB1C1 sheath at 3.3 Å resolution. Our structure allowed us to resolve some features of the T6SS sheath that were not resolved in the Vibrio cholerae VipAB and Francisella tularensis IglAB structures. Comparison with sheath structures from other contractile machines, including T4 phage and R-type pyocins, provides a better understanding of how these systems have conserved similar functions/mechanisms despite evolution. We used the P. aeruginosa R2 pyocin as a structural template to build an atomic model of the TssB1C1 sheath in its extended conformation, allowing us to propose a coiled-spring-like mechanism for T6SS sheath contraction. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Structure of nerve growth factor complexed with the shared neurotrophin receptor p75.

PubMed

He, Xiao-Lin; Garcia, K Christopher

2004-05-07

Neurotrophins are secreted growth factors critical for the development and maintenance of the vertebrate nervous system. Neurotrophins activate two types of cell surface receptors, the Trk receptor tyrosine kinases and the shared p75 neurotrophin receptor. We have determined the 2.4 A crystal structure of the prototypic neurotrophin, nerve growth factor (NGF), complexed with the extracellular domain of p75. Surprisingly, the complex is composed of an NGF homodimer asymmetrically bound to a single p75. p75 binds along the homodimeric interface of NGF, which disables NGF's symmetry-related second p75 binding site through an allosteric conformational change. Thus, neurotrophin signaling through p75 may occur by disassembly of p75 dimers and assembly of asymmetric 2:1 neurotrophin/p75 complexes, which could potentially engage a Trk receptor to form a trimolecular signaling complex.

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

Kogawa, M.; Watson, E. B.; Ewing, R. C.

Lead-doped zircon crystals, which were synthesized under three different conditions (Watson et al. 1997): dry at 1430 °C at atmospheric pressure without P2O5; wet at 900 °C at 1.5 GPa in the presence of P2O5; and wet at 800 °C at 1.0 GPa without P2O5, have been investigated to understand the mechanisms of Pb incorporation into zircon at the sub-micrometer scale, using various electron microscopy techniques including high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Four different mechanisms in which Pb may be incorporated into zircon have been identified. In the P-free synthesis, Pb-oxidemore » hydrate particles, 50–200 nm in size, are embedded in zircon. Each Pb-particle is associated with a single vesicle, ~50 nm. Lead in the zircon structure is possibly incorporated under the detection limit value of energy-dispersive X-ray analysis (EDX) by means of: (1) Zr4+ = Pb2+ + 2H+ at less than ~0.1 wt%. In the system with P, Pb-phases occur in three different forms: Pb-rich domains concentrated along cleavage planes or grain boundaries without any evident crystal form; numerous Pb-phosphate particles, as large as 100 nm, embedded heterogeneously in the zircon crystal; and homogeneous distribution of Pb in the zircon structure at less than ~1 wt% as determined by EDX. These results suggest that charge balance is maintained by the xenotime-type coupled substitution: (2) Zr4+ + 2Si4+ = Pb2+ + 2P5+ with a possible minor contribution from mechanism 1. The apparent solubility limit of Pb, <1 wt%, is constrained mainly by the xenotime-type coupled substitution mechanism, which is probably due to increasing strain at higher Pb-concentrations. The presence of Pb2+ in natural zircon is consistent with the low-level Pb allowed by substitution mechanism 2, with only a minor contribution from substitution mechanism 1, the latter of which causes distortion in the local structure.« less

Printed thin film transistors and CMOS inverters based on semiconducting carbon nanotube ink purified by a nonlinear conjugated copolymer

NASA Astrophysics Data System (ADS)

Xu, Wenya; Dou, Junyan; Zhao, Jianwen; Tan, Hongwei; Ye, Jun; Tange, Masayoshi; Gao, Wei; Xu, Weiwei; Zhang, Xiang; Guo, Wenrui; Ma, Changqi; Okazaki, Toshiya; Zhang, Kai; Cui, Zheng

2016-02-01

Two innovative research studies are reported in this paper. One is the sorting of semiconducting carbon nanotubes and ink formulation by a novel semiconductor copolymer and second is the development of CMOS inverters using not the p-type and n-type transistors but a printed p-type transistor and a printed ambipolar transistor. A new semiconducting copolymer (named P-DPPb5T) was designed and synthesized with a special nonlinear structure and more condensed conjugation surfaces, which can separate large diameter semiconducting single-walled carbon nanotubes (sc-SWCNTs) from arc discharge SWCNTs according to their chiralities with high selectivity. With the sorted sc-SWCNTs ink, thin film transistors (TFTs) have been fabricated by aerosol jet printing. The TFTs displayed good uniformity, low operating voltage (+/-2 V) and subthreshold swing (SS) (122-161 mV dec-1), high effective mobility (up to 17.6-37.7 cm2 V-1 s-1) and high on/off ratio (104-107). With the printed TFTs, a CMOS inverter was constructed, which is based on the p-type TFT and ambipolar TFT instead of the conventional p-type and n-type TFTs. Compared with other recently reported inverters fabricated by printing, the printed CMOS inverters demonstrated a better noise margin (74% 1/2 Vdd) and was hysteresis free. The inverter has a voltage gain of up to 16 at an applied voltage of only 1 V and low static power consumption.Two innovative research studies are reported in this paper. One is the sorting of semiconducting carbon nanotubes and ink formulation by a novel semiconductor copolymer and second is the development of CMOS inverters using not the p-type and n-type transistors but a printed p-type transistor and a printed ambipolar transistor. A new semiconducting copolymer (named P-DPPb5T) was designed and synthesized with a special nonlinear structure and more condensed conjugation surfaces, which can separate large diameter semiconducting single-walled carbon nanotubes (sc-SWCNTs) from arc discharge SWCNTs according to their chiralities with high selectivity. With the sorted sc-SWCNTs ink, thin film transistors (TFTs) have been fabricated by aerosol jet printing. The TFTs displayed good uniformity, low operating voltage (+/-2 V) and subthreshold swing (SS) (122-161 mV dec-1), high effective mobility (up to 17.6-37.7 cm2 V-1 s-1) and high on/off ratio (104-107). With the printed TFTs, a CMOS inverter was constructed, which is based on the p-type TFT and ambipolar TFT instead of the conventional p-type and n-type TFTs. Compared with other recently reported inverters fabricated by printing, the printed CMOS inverters demonstrated a better noise margin (74% 1/2 Vdd) and was hysteresis free. The inverter has a voltage gain of up to 16 at an applied voltage of only 1 V and low static power consumption. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00015k

Fine structure in plasma waves and radiation near the plasma frequency in Earth's foreshock

NASA Technical Reports Server (NTRS)

Cairns, Iver H.

1994-01-01

Novel observations are presented of intrunsic fine structure in the frequency spectrum of electomagnetic (EM) radiation and plasma waves near the electron plasma frequency f(sub p) during a period of unusually high interplanetary magnetic field strength. Measured using the wideband receiver on the International Sun-Earth Explorer (ISEE) 1 spacecraft, fine-structured emissions are observed both in the solar wind and the foreshock, The fine structure is shown to correspond to emissions spaced above f(sub p) near half harmonies of the electon cyclotron frequency f(sub ce), i.e., near f(sub p) + nf(sub ce)/2. These appear to be the first space physics observations of emissions spaced by f(sub ce)/2. Indirect but strong arguments are used to discriminate between EM and electrostatic (ES) signals, to identify whether ISEE 1 is in the solar wind or the foreshock, and to determine the relative frequencies of the emissions and the local f(sub p). The data are consistent with generation of the ES and EM emissions in the foreshock, with subsequent propagation of the EM emissions into the solar wind. It remains possible that some emissions currently identified as ES have significant EM character. The ES and EM emisions often merge into one another with minimal changes in frequency, arguing that their source regions and generation mechanisms are related and imposing significant constraints on theories. The f(sub ce)/2 ES and EM fine structures observed may be intrinsic to the emission mechanisms or to superposition of two series of signals with f(sub ce) spacing that differ in starting frequency by f(sub ce)/2. Present theories for nonlinear wave coupling processes, cyclotron maser emission, and other linear instability processes are all unable to explain multiple EM and/or ES components spaced by approximately f(sub ce)/2 above f(sub p) for f(sub p)/f(sub ce) much greater than 1 and typical for shock beams parameters. Suitable avenues for further theoretical research are identified. Empirically, the observed fine structures appear very similar to those in split bnad and multiple-lane type II solar radio bursts; interpretation of both these type II fine structures in terms of f(sub ce)/2 splitting is suggested, thereby supporting and generalizing a suggestion by Wild (1950). A possible application to continuum radiation is mentioned. The ubiquity of these fine structures in the Earth's f(sub p) radiation and foreshock waves remains unknown. Only the ISEE 1 wideband receiver has sufficient frequency resolution (approximately less than or equal to 100 Hz) to perform a dedicated search. Further study of the ubiquity of these fine structures, of how reliably the splitting corresponds to f(sub ce)/2, and of the other interpretations above is necessary.

Design consideration of high voltage Ga2O3 vertical Schottky barrier diode with field plate

NASA Astrophysics Data System (ADS)

Choi, J.-H.; Cho, C.-H.; Cha, H.-Y.

2018-06-01

Gallium oxide (Ga2O3) based vertical Schottky barrier diodes (SBDs) were designed for high voltage switching applications. Since p-type Ga2O3 epitaxy growth or p-type ion implantation technique has not been developed yet, a field plate structure was employed in this study to maximize the breakdown voltage by suppressing the electric field at the anode edge. TCAD simulation was used for the physical analysis of Ga2O3 SBDs from which it was found that careful attention must be paid to the insulator under the field plate. Due to the extremely high breakdown field property of Ga2O3, an insulator with both high permittivity and high breakdown field must be used for the field plate formation.

The high pressure crystal structures of tin sulphate: a case study for maximal information recovery from 2D powder diffraction data

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

Hinrichsen, Bernd; Dinnebier, Robert E.; Liu, Haozhe

2008-12-09

Our recently proposed method for automatic detection, calibration and evaluation of Debye-Scherrer ellipses using pattern recognition techniques and advanced signal filtering was applied to 2D powder diffraction data of tin sulphate in dependence on pressure. Three phase transitions towards higher pressure could be identified, and their respective crystal structures have been determined. The high pressure behaviour of the stereoactive lone pair of Sn{sup 2+} was investigated. At ambient conditions, SnSO{sub 4} crystallizes in a strongly distorted Barite structure type in space group Pnma (phase I). In the pressure range between P = 0.15 and P = 0.2 GPa, it exhibitsmore » a displacive second order phase transition into a structure with space group P112{sub 1}/a (phase II at P = 0.2 GPa: a = 8.7022(9) {angstrom}, b = 5.3393(5) {angstrom}, c = 7.0511(6) A, y = 89.90(1){sup o}). A second displacive phase transition occurs between P = 4.40 and P = 5.07 GPa into another structure with space group PI (phase III at P = 13.5 GPa: a = 8.067(3) {angstrom}, b = 5.141(2) {angstrom}, c = 6.609(2) {angstrom}, a = 90.56(3){sup o}, {beta} = 90.65(2){sup o}, y = 89.46(2){sup o}). A third displacive phase transition towards another crystal structure in space group P1 occurs between P = 13.6 and P = 15.3 GPa (phase IV at P = 20.5 GPa: a = 7.889(5) {angstrom}, b = 5.028(3) {angstrom}, c = 6.462(3) {angstrom}, a = 90.99(3){sup o}, {beta}=91.01(3){sup o}, y = 89.89(4){sup o}). A non-linear compression behaviour over the entire pressure range is observed, which can be described by three Vinet relations in the ranges from P = 0.21 to 4.4 GPa, from P = 5.07 to 13.55 GPa and from P = 15.26 to 20.5 GPa. The extrapolated bulk moduli of the high-pressure phases were determined to K{sub 0} = 48(1) GPa for phase II, K{sub 0} = 56(2) GPa for phase III, and K{sub 0} = 51(13) GPa for phase IV. The crystal structures of all phases are refined against X-ray powder diffraction data measured at several pressures between 0.15 and 20.5 GPa. The structural phase transitions of SnSO{sub 4} are mainly characterized by a reorientation of the SO{sub 4} tetrahedra, in order to optimize crystal packing. With increasing pressure, the lone pair which is localized at Sn{sup 2+} increasingly adopts pure s-character.« less

Phosphide oxides RE2AuP2O (RE = La, Ce, Pr, Nd): synthesis, structure, chemical bonding, magnetism, and 31P and 139La solid state NMR.

PubMed

Bartsch, Timo; Wiegand, Thomas; Ren, Jinjun; Eckert, Hellmut; Johrendt, Dirk; Niehaus, Oliver; Eul, Matthias; Pöttgen, Rainer

2013-02-18

Polycrystalline samples of the phosphide oxides RE(2)AuP(2)O (RE = La, Ce, Pr, Nd) were obtained from mixtures of the rare earth elements, binary rare earth oxides, gold powder, and red phosphorus in sealed silica tubes. Small single crystals were grown in NaCl/KCl fluxes. The samples were studied by powder X-ray diffraction, and the structures were refined from single crystal diffractometer data: La(2)AuP(2)O type, space group C2/m, a = 1515.2(4), b = 424.63(8), c = 999.2(2) pm, β = 130.90(2)°, wR2 = 0.0410, 1050 F(2) values for Ce(2)AuP(2)O, and a = 1503.6(4), b = 422.77(8), c = 993.0(2) pm, β = 130.88(2)°, wR2 = 0.0401, 1037 F(2) values for Pr(2)AuP(2)O, and a = 1501.87(5), b = 420.85(5), c = 990.3(3) pm, β = 131.12(1)°, wR2 = 0.0944, 1143 F(2) values for Nd(2)AuP(2)O with 38 variables per refinement. The structures are composed of [RE(2)O](4+) polycationic chains of cis-edge-sharing ORE(4/2) tetrahedra and polyanionic strands [AuP(2)](4-), which contain gold in almost trigonal-planar phosphorus coordination by P(3-) and P(2)(4-) entities. The isolated phosphorus atoms and the P(2) pairs in La(2)AuP(2)O could clearly be distinguished by (31)P solid state NMR spectroscopy and assigned on the basis of a double quantum NMR technique. Also, the two crystallographically inequivalent La sites could be distinguished by static (139)La NMR in conjunction with theoretical electric field gradient calculations. Temperature-dependent magnetic susceptibility measurements show diamagnetic behavior for La(2)AuP(2)O. Ce(2)AuP(2)O and Pr(2)AuP(2)O are Curie-Weiss paramagnets with experimental magnetic moments of 2.35 and 3.48 μ(B) per rare earth atom, respectively. Their solid state (31)P MAS NMR spectra are strongly influenced by paramagnetic interactions. Ce(2)AuP(2)O orders antiferromagnetically at 13.1(5) K and shows a metamagnetic transition at 11.5 kOe. Pr(2)AuP(2)O orders ferromagnetically at 7.0 K.

Thermal Stability of Zone Melting p-Type (Bi, Sb)2Te3 Ingots and Comparison with the Corresponding Powder Metallurgy Samples

NASA Astrophysics Data System (ADS)

Jiang, Chengpeng; Fan, Xi'an; Hu, Jie; Feng, Bo; Xiang, Qiusheng; Li, Guangqiang; Li, Yawei; He, Zhu

2018-04-01

During the past few decades, Bi2Te3-based alloys have been investigated extensively because of their promising application in the area of low temperature waste heat thermoelectric power generation. However, their thermal stability must be evaluated to explore the appropriate service temperature. In this work, the thermal stability of zone melting p-type (Bi, Sb)2Te3-based ingots was investigated under different annealing treatment conditions. The effect of service temperature on the thermoelectric properties and hardness of the samples was also discussed in detail. The results showed that the grain size, density, dimension size and mass remained nearly unchanged when the service temperature was below 523 K, which suggested that the geometry size of zone melting p-type (Bi, Sb)2Te3-based materials was stable below 523 K. The power factor and Vickers hardness of the ingots also changed little and maintained good thermal stability. Unfortunately, the thermal conductivity increased with increasing annealing temperature, which resulted in an obvious decrease of the zT value. In addition, the thermal stabilities of the zone melting p-type (Bi, Sb)2Te3-based materials and the corresponding powder metallurgy samples were also compared. All evidence implied that the thermal stabilities of the zone-melted (ZMed) p-type (Bi, Sb)2Te3 ingots in terms of crystal structure, geometry size, power factor (PF) and hardness were better than those of the corresponding powder metallurgy samples. However, their thermal stabilities in terms of zT values were similar under different annealing temperatures.

Search and design of nonmagnetic centrosymmetric layered crystals with large local spin polarization

NASA Astrophysics Data System (ADS)

Liu, Qihang; Zhang, Xiuwen; Jin, Hosub; Lam, Kanber; Im, Jino; Freeman, Arthur J.; Zunger, Alex

2015-06-01

Until recently, spin polarization in nonmagnetic materials was the exclusive territory of noncentrosymmetric structures. It was recently shown that a form of "hidden spin polarization" (named the "Rashba-2" or "R-2" effect) could exist in globally centrosymmetric crystals provided the individual layers belong to polar point group symmetries. This realization could considerably broaden the range of materials that might be considered for spin-polarization spintronic applications to include the hitherto "forbidden spintronic compound" that belongs to centrosymmetric symmetries. Here we take the necessary steps to transition from such general, material-agnostic condensed matter theory arguments to material-specific "design principles" that could aid future laboratory search of R-2 materials. Specifically, we (i) classify different prototype layered structures that have been broadly studied in the literature in terms of their expected R-2 behavior, including the B i2S e3 -structure type (a prototype topological insulator), Mo S2 -structure type (a prototype valleytronic compound), and LaBiO S2 -structure type (a host of superconductivity upon doping); (ii) formulate the properties that ideal R-2 compounds should have in terms of combination of their global unit cell symmetries with specific point group symmetries of their constituent "sectors"; and (iii) use first-principles band theory to search for compounds from the prototype family of LaOBi S2 -type structures that satisfy these R-2 design metrics. We initially consider both stable and hypothetical M'O M X2 (M': Sc, Y, La, Ce, Pr, Nd, Al, Ga, In, Tl; M: P, As, Sb, Bi; X: S, Se, Te) compounds to establish an understanding of trends of R-2 with composition, and then indicate the predictions that are expected to be stable and synthesizable. We predict large spin splittings (up to ˜200 meV for holes in LaOBiT e2 ) as well as surface Rashba states. Experimental testing of such predictions is called for.

Thermoelectric Behavior of Low Thermal Conductivity Cu-based and IV-V Chalcogenides

NASA Astrophysics Data System (ADS)

Olvera, Alan Anthony

In an ever-changing global environment, energy-related issues have become a central feature in the day-to-day conversations of the general public. A niche field that has recently made major advancements in conversion performance is thermoelectric (TE) energy conversion, where progress in material optimization has resulted in the highest efficiency thermoelectric materials to date. This includes superionic copper chalcogenides and IV-VI selenide compounds, such as Cu2Se and PbSe. Hence, this work focuses on the reliable synthesis and characterization of thermoelectric Cu-based and IV-V compounds. The electronic and optical properties of Cu-based energy conversion materials are greatly affected by synthesis-induced defects. To alleviate this issue, a novel method is developed using the topochemical redox reaction of CuSe 2 into the desired material. It is predicted that CuSe2 -serves as a sacrificial structural template for the facile synthesis of structurally related materials. This was specifically verified in the case of CuInSe 2, where CuSe2 is gradually transformed into CuInSe 2 when reacted with elemental indium. Evidently, this synthetic method is a potential avenue for new material prediction and fabrication of novel composite materials. Using the method described, a composite of CuInSe2 and the known TE material, Cu2Se, is formed. Considering the structural similarity of both compounds, the efficiency of Cu2Se is drastically increased due to enhanced carrier mobility provided by tetrahedral indium subunits. These subunits simultaneously disrupt phonon propagation which result in reduced thermal conductivity and increased TE efficiency (ZT ≈ 2.6 at 850K). More significant is the increased chemical stability of Cu2Se while under applied current and temperature. It is observed that 1 mol % indium stabilizes Cu-ion migration, encouraging the commercialization of Cu 2Se. Currently, CuAgSe is the only promising n-type Cu-based superionic TE material. Accordingly, to find a compatible material for p-type Cu2Se at high temperatures, a series of materials with the formula Cu4-xAgxSe2 were synthesized. It was found that the composition of Cu3AgSe2 ( x = 1) is a two-phase mixture at low temperatures but becomes a single-phase p-type superionic material above 440 K. On the other hand, CuAg 3Se2 (x = 3) remains a two-phase n-type mixture throughout the measured temperature range, contrary to reports of CuAg3Se2 as a single-phase high temperature material. The most important finding is the high temperature n-type behavior of CuAgSe (x = 2), which is the first instance of CuAgSe as an n-type superionic material above 470 K. It is proposed that off-stoichiometry leads to p-type behavior of CuAgSe. Moving to IV-V compounds, a detailed experimental and computational study of the material Pb7Bi4Se13 shows excellent thermoelectric properties for a non-optimized system. It behaves as an n-type material with a small band gap of about 0.23 eV, which is confirmed by band structure calculations and experimental results. It demonstrates ultralow thermal conductivity largely due to the complex atomic-scale structure and heavy constituent atoms. This results in a ZT of approximately 0.9 at 775 K, which is a promising value for further optimization. Additional results from CuSe2 structural template reactions show that several composite materials and new materials can be predicted and synthesized. This includes Cu2Se-Cu(Ga,Al)Se2 composites and new materials such as Cu(Zn,Ni)1.5Se2 and CuPb 0.75Se2. Further work in Sn-Bi-Se compounds is discussed due their complex crystal structure that may result in promising thermoelectric properties. Finally, the preliminary results of high entropy chalcogenides are presented with discussion on future development.

Full color stop bands in hybrid organic/inorganic block copolymer photonic gels by swelling-freezing.

PubMed

Kang, Changjoon; Kim, Eunjoo; Baek, Heeyoel; Hwang, Kyosung; Kwak, Dongwoo; Kang, Youngjong; Thomas, Edwin L

2009-06-10

We report a facile way of fabricating hybrid organic/inorganic photonic gels by selective swelling and subsequent infiltration of SiO(2) into one type of lamellar microdomain previously self-assembled from modest-molecular-weight block copolymers. Transparent, in-plane lamellar films were first prepared by assembly of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP), and subsequently the P2VP domains were swollen with a selective solvent, methanol. The swollen structures were then fixated by synthesizing SiO(2) nanoparticles within P2VP domains. The resulting frozen photonic gels (f-photonic gels) exhibited strong reflective colors with stop bands across the visible region of wavelengths.

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

Lolicato, Marco; Arrigoni, Cristina; Mori, Takahiro

Polymodal thermo- and mechanosensitive two-pore domain potassium (K2P) channels of the TREK1 subfamily generate ‘leak’ currents that regulate neuronal excitability, respond to lipids, temperature and mechanical stretch, and influence pain, temperature perception and anaesthetic responses1, 2, 3. These dimeric voltage-gated ion channel (VGIC) superfamily members have a unique topology comprising two pore-forming regions per subunit4, 5, 6. In contrast to other potassium channels, K2P channels use a selectivity filter ‘C-type’ gate7, 8, 9, 10 as the principal gating site. Despite recent advances3, 11, 12, poor pharmacological profiles of K2P channels limit mechanistic and biological studies. Here we describe a classmore » of small-molecule TREK activators that directly stimulate the C-type gate by acting as molecular wedges that restrict interdomain interface movement behind the selectivity filter. Structures of K2P2.1 (also known as TREK-1) alone and with two selective K2P2.1 (TREK-1) and K2P10.1 (TREK-2) activators—an N-aryl-sulfonamide, ML335, and a thiophene-carboxamide, ML402—define a cryptic binding pocket unlike other ion channel small-molecule binding sites and, together with functional studies, identify a cation–π interaction that controls selectivity. Together, our data reveal a druggable K2P site that stabilizes the C-type gate ‘leak mode’ and provide direct evidence for K2P selectivity filter gating.« less

Large electron capture-cross-section of the major nonradiative recombination centers in Mg-doped GaN epilayers grown on a GaN substrate

NASA Astrophysics Data System (ADS)

Chichibu, S. F.; Shima, K.; Kojima, K.; Takashima, S.; Edo, M.; Ueno, K.; Ishibashi, S.; Uedono, A.

2018-05-01

Complementary time-resolved photoluminescence and positron annihilation measurements were carried out at room temperature on Mg-doped p-type GaN homoepitaxial films for identifying the origin and estimating the electron capture-cross-section ( σ n ) of the major nonradiative recombination centers (NRCs). To eliminate any influence by threading dislocations, free-standing GaN substrates were used. In Mg-doped p-type GaN, defect complexes composed of a Ga-vacancy (VGa) and multiple N-vacancies (VNs), namely, VGa(VN)2 [or even VGa(VN)3], are identified as the major intrinsic NRCs. Different from the case of 4H-SiC, atomic structures of intrinsic NRCs in p-type and n-type GaN are different: VGaVN divacancies are the major NRCs in n-type GaN. The σ n value approximately the middle of 10-13 cm2 is obtained for VGa(VN)n, which is larger than the hole capture-cross-section (σp = 7 × 10-14 cm2) of VGaVN in n-type GaN. Combined with larger thermal velocity of an electron, minority carrier lifetime in Mg-doped GaN becomes much shorter than that of n-type GaN.

Electronic structure of the [MNH2]+ (M = Sc-Cu) complexes.

PubMed

Hendrickx, Marc F A; Clima, Sergiu

2006-11-23

B3LYP geometry optimizations for the [MNH2]+ complexes of the first-row transition metal cations (Sc+-Cu+) were performed. Without any exception the ground states of these unsaturated amide complexes were calculated to possess planar geometries. CASPT2 binding energies that were corrected for zero-point energies and including relativistic effects show a qualitative trend across the series that closely resembles the experimental observations. The electronic structures for the complexes of the early and middle transition metal cations (Sc+-Co+) differ from the electronic structures derived for the complexes of the late transition metal cations (Ni+ and Cu+). For the former complexes the relative higher position of the 3d orbitals above the singly occupied 2p(pi) HOMO of the uncoordinated NH2 induces an electron transfer from the 3d shell to 2p(pi). The stabilization of the 3d orbitals from the left to the right along the first-row transition metal series causes these orbitals to become situated below the HOMO of the NH2 ligand for Ni+ and Cu+, preventing a transfer from occurring in the [MNH2]+ complexes of these metal cations. Analysis of the low-lying states of the amide complexes revealed a rather unique characteristic of their electronic structures that was found across the entire series. Rather exceptionally for the whole of chemistry, pi-type interactions were calculated to be stronger than the corresponding sigma-type interactions. The origin of this extraordinary behavior can be ascribed to the low-lying sp2 lone pair orbital of the NH2 ligand with respect to the 3d level.

Superconductivity and role of pnictogen and Fe substitution in 112-LaPdxP n2 (P n =Sb ,Bi )

NASA Astrophysics Data System (ADS)

Retzlaff, Reiner; Buckow, Alexander; Komissinskiy, Philipp; Ray, Soumya; Schmidt, Stefan; Mühlig, Holger; Schmidl, Frank; Seidel, Paul; Kurian, Jose; Alff, Lambert

2015-03-01

We report on the epitaxial growth of As-free and phase-pure thin films of the 112-pnictide compounds LaPdxP n2 (P n =Sb ,Bi ) grown on (100) MgO substrates by molecular beam epitaxy. X-ray diffraction, reflection high-energy electron diffraction, and x-ray photoelectron spectroscopy confirm the HfCuSi2 structure of the material with a peculiar pnictogen square net layer. The superconducting transition temperature Tc varies little with Pd concentration. LaPdxSb2 has a higher Tc (3.2 K) by about 20% compared with LaPdxBi2 (2.7 K). Fe substitution of Pd leads to a rapid decay of superconductivity, suggesting that these superconductors are conventional type II.

Synthesis, crystal structure and electrical properties of the tetrahedral quaternary chalcogenides CuM{sub 2}InTe{sub 4} (M=Zn, Cd)

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

Nolas, George S., E-mail: gnolas@usf.edu; Hassan, M. Shafiq; Dong, Yongkwan

Quaternary chalcogenides form a large class of materials that continue to be of interest for energy-related applications. Certain compositions have recently been identified as possessing good thermoelectric properties however these materials typically have the kesterite structure type with limited variation in composition. In this study we report on the structural, optical and electrical properties of the quaternary chalcogenides CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} which crystallize in the modified zinc-blende crystal structure, and compare their properties with that of CuZn{sub 2}InSe{sub 4}. These p-type semiconductors have direct band gaps of about 1 eV resulting in relatively high Seebeck coefficientmore » and resistivity values. This work expands on the research into quaternary chalcogenides with new compositions and structure types in order to further the fundamental investigation of multinary chalcogenides for potential thermoelectrics applications. - Graphical abstract: The structural, optical and electrical properties of the quaternary chalcogenides CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} are reported for the first time. The unique crystal structure allows for relatively good electrical transports and therefore potential for thermoelectric applications. - Highlights: • The physical properties of CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} are reported for the first time. • These materials have potential for thermoelectric applications. • Their direct band gaps also suggest potential for photovoltaics applications.« less

p-Type Transparent Electronics

DTIC Science & Technology

2003-09-25

thin - film transistors (TTFTs) reported to date in the literature are summarized. 2.2.1 Thin - Film Transistor Structure and Fabrication A TFT ...is incapable of controlling the TFT regardless of gate voltage, as described in Sec. 2.2.3.1. 2.2.4 Transparent Thin - Film Transistors (TTFTs...Transparent thin - film transistors (TTFTs) described in the literature to date are all n-channel devices. Several n-channel TTFTs (n-TTFTs) based on

A 2 TiO 5 (A = Dy, Gd, Er, Yb) at High Pressure

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

Park, Sulgiye; Rittman, Dylan R.; Tracy, Cameron L.

The structural evolution of lanthanide A2TiO5 (A = Dy, Gd, Yb, and Er) at high pressure is investigated using synchrotron X-ray diffraction. The effects of A-site cation size and of the initial structure are systematically examined by varying the composition of the isostructural lanthanide titanates, and the structure of dysprosium titanate polymorphs (orthorhombic, hexagonal and cubic), respectively. All samples undergo irreversible high pressure phase transformations, but with different onset pressures depending on the initial structure. While individual phase exhibits different phase transformation histories, all samples commonly experience a sluggish transformation to a defect cotunnite-like (Pnma) phase for a certain pressuremore » range. Orthorhombic Dy2TiO5 and Gd2TiO5 form P21am at pressures below 9 GPa and Pnma above 13 GPa. Pyrochlore-type Dy2TiO5 and Er2TiO5 as well as defect-fluorite-type Yb2TiO5 form Pnma at ~ 21 GPa, followed by Im-3m. Hexagonal Dy2TiO5 forms Pnma directly, although a small amount of remnants of hexagonal Dy2TiO5 is observed even at the highest pressure (~ 55 GPa) reached, indicating a kinetic limitations in the hexagonal Dy2TiO5 phase transformations at high pressure. Decompression of these materials leads to different metastable phases. Most interestingly, a high pressure cubic X-type phase (Im-3m) is confirmed using highresolution transmission electron microscopy on recovered pyrochlore-type Er2TiO5. The kinetic constraints on this metastable phase yield a mixture of both the X-type phase and amorphous domains upon pressure release. This is the first observation of an X-type phase for an A2BO5 composition at high pressure.« less

Incorporation of rare earth elements in titanite: Stabilization of the A2/a dimorph by creation of antiphase boundaries

USGS Publications Warehouse

Hughes, J.M.; Bloodaxe, E.S.; Hanchar, J.M.; Foord, E.E.

1997-01-01

The atomic arrangement of a natural rare-earth-rich titanite and two synthetic rare-earth-doped titanites have been refined in space group A2/a, and the atomic arrangement of an undoped P21/a synthetic titanite was also refined for comparison. Previous work has shown that titanite possesses a domain structure, with domains formed of like-displaced Ti atoms in the [100] octahedral chains. P21/a titanite results when the crystal is formed of a single domain, but as Ti-reversal sites occur in the octahedral chain the apparent A2/a structure results from the average of antiphase domains. Antiphase boundaries occur at O1, which is alternately overbonded or underbonded at the boundaries, depending on the displacement of the neighboring Ti atoms. Type 2 antiphase boundaries exist where two Ti atoms are displaced away from the intervening O1 atom and are energetically unfavorable because of underbonding of that O1 atom. However, substitution of a trivalent rare earth element in the adjacent Ca2+ site relieves that underbonding, favoring the creation of type 2 antiphase boundaries and stabilization of the A2/a dimorph. The results of high-precision crystal structure analyses demonstrate that rare earth substituents for Ca stabilize the A2/a dimorph at lower substitution levels than required for octahedral substitutions.

Diffusion-weighted imaging of mucinous carcinoma of the breast: evaluation of apparent diffusion coefficient and signal intensity in correlation with histologic findings.

PubMed

Woodhams, Reiko; Kakita, Satoko; Hata, Hirofumi; Iwabuchi, Keiichi; Umeoka, Shigeaki; Mountford, Carolyn E; Hatabu, Hiroto

2009-07-01

The purposes of this study were to compare the apparent diffusion coefficient (ADC) of mucinous carcinoma of the breast with that of other breast tumors and to analyze correlations between signal intensity on diffusion-weighted images and the histologic features of mucinous carcinoma. Two hundred seventy-six patients with 277 lesions, including 15 mucinous carcinomas (13 pure type, two mixed type), 204 other malignant tumors, and 58 benign lesions, were examined with 1.5-T MRI at b values of 0 and 1,500 s/mm(2). The correlations between cellularity and ADC, homogeneity of signal intensity on diffusion-weighted images, and histopathologic findings were analyzed. The difference was statistically significant (p < 0.05). The mean ADC of mucinous carcinoma (1.8 +/- 0.4 x 10(-3) mm(2)/s) was statistically higher than that of benign lesions (1.3+/- 0.3 x 10(-3) mm(2)/s) and other malignant tumors (0.9 +/- 0.2 x 10(-3) mm(2)/s) (p < 0.001). The ADC of pure type mucinous carcinoma (1.8 +/- 0.3 x 10(-3) mm(2)/s) was higher than that of mixed type mucinous carcinoma (1.2 +/- 0.2 x 10(-3) mm(2)/s) (p < 0.001) and other histologic types (p > 0.05). The correlation between mean cellularity and the ADC of mucinous carcinoma was significant (rho(s) = -0.754; p = 0.001). The homogeneity of signal intensity on diffusion-weighted images correlated with the homogeneity of histologic structures of mucinous carcinoma (p < 0.001; kappa = 0.826). Mucinous carcinoma can be clearly differentiated from other breast tumors on the basis of ADC. The low signal intensity of mucinous carcinoma on diffusion-weighted images appears to reflect the presence of mucin and low cellularity. High signal intensity on diffusion-weighted images may reflect the presence of fibrovascular bundles, increased cell density, or a combination of these features.

New ternary phosphides and arsenides. Syntheses, crystal structures, physical properties of Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}

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

Wang, Jian; Xia, Sheng-Qing, E-mail: shqxia@sdu.edu.cn; Tao, Xu-Tang

2013-09-15

Three new europium pnictides Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3} have been synthesized and their structures were determined by single-crystal X-ray diffraction. Eu{sub 2}ZnP{sub 2} is isotypic with Yb{sub 2}CdSb{sub 2} (Cmc2{sub 1} (No. 36); cell parameters a=4.1777(7) Å, b=15.925(3) Å, c=7.3008(12) Å), while the latter two compounds crystallize with the Ba{sub 2}Cd{sub 2}Sb{sub 3} structure type (C2/m (No. 12); cell parameters a=15.653(5)/16.402(1) Å, b=4.127(1)/4.445(4) Å, c=11.552(4)/12.311(1) Å and β=126.647(4)/126.515(7)° for Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}, respectively). Magnetic susceptibility measurements in the interval 5–300 K confirm paramagnetic behavior and effectivemore » magnetic moments characteristic of Eu{sup 2+} ([Xe] 4f{sup 7}) ground states. Temperature-dependent electrical conductivity measurements also prove that Eu{sub 2}Cd{sub 2}As{sub 3} is a semiconducting compound with a narrow band gap of 0.059 eV below 100 K. According to TG/DSC analyses, Eu{sub 2}Cd{sub 2}As{sub 3} starts to decompose at about 950 K. - Graphical abstract: A polyhedral view of the crystal structure of new pnictides Eu{sub 2}T{sub 2}Pn{sub 3} (T=Zn or Cd; Pn=P or As). Display Omitted - Highlights: • Three new ternary pnictide Zintl compounds, Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}, have been synthesized and characterized. • The europium cations are divalent and ferromagnetically coupled in both Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}. • Eu{sub 2}Cd{sub 2}As{sub 3} has a very small band gap of 0.06 eV and starts to decompose over 950 K.« less

Second moment scaling and the relationship of geometric and electronic structure

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

Hoistad, L.M.

1993-01-01

Extended Hueckel band calculations were used to show the ditellurides in the CdI[sub 2] structure type with more than 16 valence electrons/MTe[sub 2] unit should have an instability due to their electronic structure. Single crystal X-ray diffraction studies of the electron rich Ta[sub 1[minus]x]Ti[sub x]Te[sub 2] (x = 0.2, 0.3, 0.4 and 0.5) show that a statistical distortion of the CdI[sub 2] structure type has indeed occurred for these compounds confirming the theoretical calculations. Second Moment Scaled Hueckel theory was used to examine the basis of the Hume-Rothery phases are face centered cubic, hexagonal closest packed ([zeta], [epsilon] and [eta]-hcp),more » body centered cubic, [beta]-Mn and [gamma]-brass structures. Good agreement between the experimental and theoretically predicted electron concentration ranges was achieved when an s, p and contracted d orbital model was used. The results presented in this thesis were the first theoretical calculations that corroborate the entire set of Hume-Rothery electron concentration rules. Second Moment Scaled Hueckel energies were used for constructing structure maps for intermetallic compounds with stoichiometry ZA[sub 2], ZA[sub 3] and ZA[sub 6]. Calculations were performed only on the covalent network of the A atoms. The structure types considered were SmSb[sub 2], ZrSi[sub 2], Cu[sub 2]Sb, AuCu[sub 3], TiNi[sub 3], TiCu[sub 3], BiF[sub 3], SnNi[sub 3], NdTe[sub 3], TiS[sub 3], SmAu[sub 6], CeCu[sub 6] and PuGa[sub 6]. The bond distance variation found for closo-borohydrides B[sub 8]H[sub 8][sup 2[minus

Crystal structure of a complex of HIV-1 protease with a dihydroxyethylene-containing inhibitor: comparisons with molecular modeling.

PubMed Central

Thanki, N.; Rao, J. K.; Foundling, S. I.; Howe, W. J.; Moon, J. B.; Hui, J. O.; Tomasselli, A. G.; Heinrikson, R. L.; Thaisrivongs, S.; Wlodawer, A.

1992-01-01

The structure of a crystal complex of recombinant human immunodeficiency virus type 1 (HIV-1) protease with a peptide-mimetic inhibitor containing a dihydroxyethylene isostere insert replacing the scissile bond has been determined. The inhibitor is Noa-His-Hch psi [CH(OH)CH(OH)]Vam-Ile-Amp (U-75875), and its Ki for inhibition of the HIV-1 protease is < 1.0 nM (Noa = 1-naphthoxyacetyl, Hch = a hydroxy-modified form of cyclohexylalanine, Vam = a hydroxy-modified form of valine, Amp = 2-pyridylmethylamine). The structure of the complex has been refined to a crystallographic R factor of 0.169 at 2.0 A resolution by using restrained least-squares procedures. Root mean square deviations from ideality are 0.02 A and 2.4 degrees, for bond lengths and angles, respectively. The bound inhibitor diastereomer has the R configurations at both of the hydroxyl chiral carbon atoms. One of the diol hydroxyl groups is positioned such that it forms hydrogen bonds with both the active site aspartates, whereas the other interacts with only one of them. Comparison of this X-ray structure with a model-built structure of the inhibitor, published earlier, reveals similar positioning of the backbone atoms and of the side-chain atoms in the P2-P2' region, where the interaction with the protein is strongest. However, the X-ray structure and the model differ considerably in the location of the P3 and P3' end groups, and also in the positioning of the second of the two central hydroxyl groups. Reconstruction of the central portion of the model revealed the source of the hydroxyl discrepancy, which, when corrected, provided a P1-P1' geometry very close to that seen in the X-ray structure. PMID:1304383

Enhanced photocatalytic performance from NiS/TiO2 p-n heterojunction nanosheet arrays

NASA Astrophysics Data System (ADS)

Qian, Long-Long; Li, Yan; Li, Jian-feng; Wang, Cheng-Wei

2018-05-01

A novel p-n heterostructural film photocatalyst of oriented NiS/TiO2 nanosheet arrays were designed and successfully fabricated via a simple two-step hydrothermal process, and its photodegradation activities of methyl orange (MO) were detailedly investigated. Combining p-type NiS nanoparticles with n-type TiO2 nanosheets to construct distributed p-n heterojunctions, the absorption edge of NiS/TiO2 red-shifted to about 471 nm and its photoresponse in visible range significantly enhanced. Compared with pure TiO2 nanosheet arrays (NSAs), the assembled NiS/TiO2 p-n heterostructural arrays with 0.003 M NiS in hydrothermal precursor solution showed an optimal degradation rate of k = 0.7368 h-1 for MO, achieving 76.3% photocatalytic efficiency within 120 min, which is about 2.34 times higher than that of pure TiO2 nanosheet arrays (k = 0.3144 h-1). Such enhanced photocatalytic activities should be attributed to both the high efficiency of photogenerated charge separation by the built-in electric field at interfaces of NiS-TiO2 and the oriented thin nanosheet structures for smoothly charge transportation for redox reactions at surfaces of NiS/TiO2.

Control of conduction type in ferromagnetic (Zn,Sn,Mn)As2 thin films by changing Mn content and effect of annealing on thin films with n-type conduction

NASA Astrophysics Data System (ADS)

Minamizawa, Yuto; Kitazawa, Tomohiro; Hidaka, Shiro; Toyota, Hideyuki; Nakamura, Shin-ichi; Uchitomi, Naotaka

2018-04-01

The conduction type in (Zn,Sn,Mn)As2 thin films grown by molecular beam epitaxy (MBE) on InP substrates was found to be controllable from p-type to n-type as a function of Mn content. n-type (Zn,Sn,Mn)As2 thin films were obtained by Mn doping of more than approximately 11 cat.%. It is likely that Mn interstitials (MnI) incorporated by excess Mn doping are located at tetrahedral hollow spaces surrounded by Zn and Sn cation atoms and four As atoms, which are expected to act as donors in (Zn,Sn,Mn)As2, resulting in n-type conduction. The effect of annealing on the structural, electrical and magnetic properties of n-type (Zn,Sn,Mn)As2 thin films was investigated as functions of annealing temperature and time. It was revealed that even if the annealing temperature is considerably higher than the growth temperature of 320 °C, the magnetic properties of the thin films remain stable. This suggests that a MnI complex surrounded by Zn and Sn atoms is thermally stable during high-temperature annealing. The n-type (Zn,Sn,Mn)As2 thin films may be suitable for application as n-type spin-polarized injectors.

modeling lunar seisms in class

NASA Astrophysics Data System (ADS)

Blancou, Emmanuelle

2017-04-01

Students are taught that the internal structure of the Earth has been described by analyzing seismometer data collected at the surface of the Earth. With this in mind, a group of 17-years old students asked whether lunar seisms could be used to explore the internal structure of the Moon. Seismometers placed during Apollo 12, 14, 15 and 16 missions recorded many seismic events. The signals obtained on the Moon are different form those recorded on Earth and are due to meteorite impact, lunar tides and thermal variations. Students tried to model meteorite impacts and thermal moonquakes to determine whether they can be distinguished based on their seismic signature. To this aim, the impact of meteorites were modeled by a metallic ball falling in sand and thermal moonquakes were modeled by storing hydrates rocks on a freezer during a week and then upon a bain marie. Signal were collected in both conditions with microphones. Data showed distinctive feature depending on vibration origin.

Lack of Methylated Hopanoids Renders the Cyanobacterium Nostoc punctiforme Sensitive to Osmotic and pH Stress

PubMed Central

Garby, Tamsyn J.; Matys, Emily D.; Ongley, Sarah E.; Salih, Anya; Larkum, Anthony W. D.; Walter, Malcolm R.

2017-01-01

ABSTRACT To investigate the function of 2-methylhopanoids in modern cyanobacteria, the hpnP gene coding for the radical S-adenosyl methionine (SAM) methylase protein that acts on the C-2 position of hopanoids was deleted from the filamentous cyanobacterium Nostoc punctiforme ATCC 29133S. The resulting ΔhpnP mutant lacked all 2-methylhopanoids but was found to produce much higher levels of two bacteriohopanepentol isomers than the wild type. Growth rates of the ΔhpnP mutant cultures were not significantly different from those of the wild type under standard growth conditions. Akinete formation was also not impeded by the absence of 2-methylhopanoids. The relative abundances of the different hopanoid structures in akinete-dominated cultures of the wild-type and ΔhpnP mutant strains were similar to those of vegetative cell-dominated cultures. However, the ΔhpnP mutant was found to have decreased growth rates under both pH and osmotic stress, confirming a role for 2-methylhopanoids in stress tolerance. Evidence of elevated photosystem II yield and NAD(P)H-dependent oxidoreductase activity in the ΔhpnP mutant under stress conditions, compared to the wild type, suggested that the absence of 2-methylhopanoids increases cellular metabolic rates under stress conditions. IMPORTANCE As the first group of organisms to develop oxygenic photosynthesis, Cyanobacteria are central to the evolutionary history of life on Earth and the subsequent oxygenation of the atmosphere. To investigate the origin of cyanobacteria and the emergence of oxygenic photosynthesis, geobiologists use biomarkers, the remnants of lipids produced by different organisms that are found in geologic sediments. 2-Methylhopanes have been considered indicative of cyanobacteria in some environmental settings, with the parent lipids 2-methylhopanoids being present in many contemporary cyanobacteria. We have created a Nostoc punctiforme ΔhpnP mutant strain that does not produce 2-methylhopanoids to assess the influence of 2-methylhopanoids on stress tolerance. Increased metabolic activity in the mutant under stress indicates compensatory alterations in metabolism in the absence of 2-methylhopanoids. PMID:28455341

Lack of Methylated Hopanoids Renders the Cyanobacterium Nostoc punctiforme Sensitive to Osmotic and pH Stress.

PubMed

Garby, Tamsyn J; Matys, Emily D; Ongley, Sarah E; Salih, Anya; Larkum, Anthony W D; Walter, Malcolm R; Summons, Roger E; Neilan, Brett A

2017-07-01

To investigate the function of 2-methylhopanoids in modern cyanobacteria, the hpnP gene coding for the radical S -adenosyl methionine (SAM) methylase protein that acts on the C-2 position of hopanoids was deleted from the filamentous cyanobacterium Nostoc punctiforme ATCC 29133S. The resulting Δ hpnP mutant lacked all 2-methylhopanoids but was found to produce much higher levels of two bacteriohopanepentol isomers than the wild type. Growth rates of the Δ hpnP mutant cultures were not significantly different from those of the wild type under standard growth conditions. Akinete formation was also not impeded by the absence of 2-methylhopanoids. The relative abundances of the different hopanoid structures in akinete-dominated cultures of the wild-type and Δ hpnP mutant strains were similar to those of vegetative cell-dominated cultures. However, the Δ hpnP mutant was found to have decreased growth rates under both pH and osmotic stress, confirming a role for 2-methylhopanoids in stress tolerance. Evidence of elevated photosystem II yield and NAD(P)H-dependent oxidoreductase activity in the Δ hpnP mutant under stress conditions, compared to the wild type, suggested that the absence of 2-methylhopanoids increases cellular metabolic rates under stress conditions. IMPORTANCE As the first group of organisms to develop oxygenic photosynthesis, Cyanobacteria are central to the evolutionary history of life on Earth and the subsequent oxygenation of the atmosphere. To investigate the origin of cyanobacteria and the emergence of oxygenic photosynthesis, geobiologists use biomarkers, the remnants of lipids produced by different organisms that are found in geologic sediments. 2-Methylhopanes have been considered indicative of cyanobacteria in some environmental settings, with the parent lipids 2-methylhopanoids being present in many contemporary cyanobacteria. We have created a Nostoc punctiforme Δ hpnP mutant strain that does not produce 2-methylhopanoids to assess the influence of 2-methylhopanoids on stress tolerance. Increased metabolic activity in the mutant under stress indicates compensatory alterations in metabolism in the absence of 2-methylhopanoids. Copyright © 2017 American Society for Microbiology.

Using p-type PbS Quantum Dots to Quench Photocurrent of Fullerene-Au NP@MoS2 Composite Structure for Ultrasensitive Photoelectrochemical Detection of ATP.

PubMed

Li, Meng-Jie; Zheng, Ying-Ning; Liang, Wen-Bin; Yuan, Ruo; Chai, Ya-Qin

2017-12-06

Ultrasensitive and rapid quantification of the universal energy currency adenosine triphosphate (ATP) is an extremely critical mission in clinical applications. In this work, a "signal-off" photoelectrochemical (PEC) biosensor was designed for ultrasensitive ATP detection based on a fullerene (C 60 )-decorated Au nanoparticle@MoS 2 (C 60 -Au NP@MoS 2 ) composite material as a signal indicator and a p-type PbS quantum dot (QD) as an efficient signal quencher. Modification of wide band gap C 60 with narrow band gap MoS 2 to form an ideal PEC signal indicator was proposed, which could significantly improve photocurrent conversion efficiency, leading to a desirable PEC signal. In the presence of p-type PbS QDs, the PEC signal of n-type C 60 -Au NP@MoS 2 was effectively quenched because p-type PbS QDs could compete with C 60 -Au NP@MoS 2 to consume light energy and electron donor. Besides, the conversion of a limited amount of target ATP into an amplified output PbS QD-labeled short DNA sequence (output S 1 ) was achieved via target-mediated aptazyme cycling amplification strategy, facilitating ultrasensitive ATP detection. The proposed signal-off PEC strategy exhibited a wide linear range from 1.00 × 10 -2 pM to 100 nM with a low detection limit of 3.30 fM. Importantly, this proposed strategy provides a promising platform to detect ATP at ultralow levels and has potential applications, including diagnosis of ATP-related diseases, monitoring of diseases progression and evaluation of prognosis.

Fabrication of SOI structures with buried cavities using Si wafer direct bonding and electrochemical etch-stop

NASA Astrophysics Data System (ADS)

Chung, Gwiy-Sang

2003-10-01

This paper describes the fabrication of SOI structures with buried cavities using SDB and electrochemical etch-stop. These methods are suitable for thick membrane fabrication with accurate thickness, uniformity, and flatness. After a feed-through hole for supplied voltage and buried cavities was formed on a handle Si wafer with p-type, the handle wafer was bonded to an active Si wafer consisting of a p-type substrate with an n-type epitaxial layer corresponding to membrane thickness. The bonded pair was then thinned until electrochemical etch-stop occurred at the pn junction during electrochemical etchback. By using the SDB SOI structure with buried cavities, active membranes, which have a free standing structure with a dimension of 900×900 μm2, were fabricated. It is confirmed that the fabrication process of the SDB SOI structure with buried cavities is a powerful and versatile technology for new MEMS applications.

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

Rettie, Alexander J. E.; Sturza, Mihai; Malliakas, Christos D.

The two-dimensional material KCu 3–xSe 2 was synthesized using both a K 2Se 3 flux and directly from the elements. It crystallizes in the CsAg 3S 2 structure (monoclinic space group C2/m with a = 15.417(3) Å, b = 4.0742(8) Å, c = 8.3190(17) Å, and β = 112.94(3)°), and single-crystal refinement revealed infinite copper-deficient [Cu 3–xSe 2]– layers separated by K + ions. Thermal analysis indicated that KCu 3–xSe 2 melts congruently at ~755 °C. UV–vis spectroscopy showed an optical band gap of ~1.35 eV that is direct in nature, as confirmed by electronic structure calculations. Electronic transport measurementsmore » on single crystals yielded an in-plane resistivity of ~6 × 10 –1 Ω cm at 300 K that has a complex temperature dependence. The results of Seebeck coefficient measurements were consistent with a doped p-type semiconductor (S = +214 μV K –1 at 300 K), with doping being attributed to copper vacancies. Transport is dominated by low-mobility (on the order of 1 cm 2 V –1 s –1) holes caused by relatively flat valence bands with substantial Cu 3d character and a significant concentration of Cu ion vacancy defects (p ~ 10 19 cm –3) in this material. In conclusion, electronic band structure calculations showed that electrons should be significantly more mobile in this structure type.« less

P2Y6 Receptor Activation Promotes Inflammation and Tissue Remodeling in Pulmonary Fibrosis

PubMed Central

Müller, Tobias; Fay, Susanne; Vieira, Rodolfo Paula; Karmouty-Quintana, Harry; Cicko, Sanja; Ayata, Cemil Korcan; Zissel, Gernot; Goldmann, Torsten; Lungarella, Giuseppe; Ferrari, Davide; Di Virgilio, Francesco; Robaye, Bernard; Boeynaems, Jean-Marie; Lazarowski, Eduardo R.; Blackburn, Michael R.; Idzko, Marco

2017-01-01

Idiopathic pulmonary fibrosis (IPF) is a disease with a poor prognosis and very few available treatment options. The involvement of the purinergic receptor subtypes P2Y2 and P2X7 in fibrotic lung disease has been demonstrated recently. In this study, we investigated the role of P2Y6 receptors in the pathogenesis of IPF in humans and in the animal model of bleomycin-induced lung injury. P2Y6R expression was upregulated in lung structural cells but not in bronchoalveolar lavage (BAL) cells derived from IPF patients as well as in animals following bleomycin administration. Furthermore, BAL fluid levels of the P2Y6R agonist uridine-5′-diphosphate were elevated in animals with bleomycin-induced pulmonary fibrosis. Inflammation and fibrosis following bleomycin administration were reduced in P2Y6R-deficient compared to wild-type animals confirming the pathophysiological relevance of P2Y6R subtypes for fibrotic lung diseases. Experiments with bone marrow chimeras revealed the importance of P2Y6R expression on lung structural cells for pulmonary inflammation and fibrosis. Similar effects were obtained when animals were treated with the P2Y6R antagonist MRS2578. In vitro studies demonstrated that proliferation and secretion of the pro-inflammatory/pro-fibrotic cytokine IL-6 by lung fibroblasts are P2Y6R-mediated processes. In summary, our results clearly demonstrate the involvement of P2Y6R subtypes in the pathogenesis of pulmonary fibrosis. Thus, blocking pulmonary P2Y6 receptors might be a new target for the treatment of IPF. PMID:28878780

Systems of conservation laws with third-order Hamiltonian structures

NASA Astrophysics Data System (ADS)

Ferapontov, Evgeny V.; Pavlov, Maxim V.; Vitolo, Raffaele F.

2018-06-01

We investigate n-component systems of conservation laws that possess third-order Hamiltonian structures of differential-geometric type. The classification of such systems is reduced to the projective classification of linear congruences of lines in P^{n+2} satisfying additional geometric constraints. Algebraically, the problem can be reformulated as follows: for a vector space W of dimension n+2, classify n-tuples of skew-symmetric 2-forms A^{α } \\in Λ^2(W) such that φ _{β γ }A^{β }\\wedge A^{γ }=0, for some non-degenerate symmetric φ.

Copper-Based OHMIC Contracts for the Si/SiGe Heterojunction Bipolar Transistor Structure

NASA Technical Reports Server (NTRS)

Das, Kalyan; Hall, Harvey

1999-01-01

Silicon based heterojunction bipolar transistors (HBT) with SiGe base are potentially important devices for high-speed and high-frequency microelectronics. These devices are particularly attractive as they can be fabricated using standard Si processing technology. However, in order to realize the full potential of devices fabricated in this material system, it is essential to be able to form low resistance ohmic contacts using low thermal budget process steps and have full compatibility with VLSI/ULSI processing. Therefore, a study was conducted in order to better understand the contact formation and to develop optimized low resistance contacts to layers with doping densities corresponding to the p-type SiGe base and n-type Si emitter regions of the HBTS. These as-grown doped layers were implanted with BF(sub 2) up to 1 X 10(exp 16)/CM(exp 2) and As up to 5 x 10(exp 15)/CM2, both at 30 keV for the p-type SiGe base and n-type Si emitter layers, respectively, in order to produce a low sheet resistance surface layer. Standard transfer length method (TLM) contact pads on both p and n type layers were deposited using an e-beam evaporated trilayer structure of Ti/CufTi/Al (25)A/1500A/250A/1000A). The TLM pads were delineated by a photoresist lift-off procedure. These contacts in the as-deposited state were ohmic, with specific contact resistances for the highest implant doses of the order of 10(exp -7) ohm-CM2 and lower.

A Review of SnSe: Growth and Thermoelectric Properties

NASA Astrophysics Data System (ADS)

Nguyen, Van Quang; Kim, Jungdae; Cho, Sunglae

2018-04-01

SnSe is a 2D semiconductor with an indirect energy gap of 0.86 - 1 eV; it is widely used in solar cell, optoelectronics, and electronic device applications. Recently, SnSe has been considered as a robust candidate for energy conversion applications due to its high thermoelectric performance ( ZT = 2.6 in p-type and 2.2 in n-type), which is assigned mainly to its anhamornic bonding leading to an ultralow thermal conductivity. In this review, we first discuss the crystalline and electronic structures of SnSe and the source of its p-type characteristic. Then, some typical single crystal and polycrystal growth techniques, as well as an epitaxial thin film growth technique, are outlined. The reported thermoelectric properties of SnSe grown by using each technique are also reviewed. Finally, we will describe some remaining issues concerning the use of SnSe for thermoelectric applications.

Serving Business in an Information Economy.

ERIC Educational Resources Information Center

The Bookmark, 1988

1988-01-01

The 23 articles in this theme issue focus on various aspects of library services to business in an information economy: "Serving Business in an Information Economy" (C. Bain); "New York's Resurging Economy and State Economic Development Information" (R. G. Paolino); "Department of Economic Development Library: Services to…

HIV/AIDS and Children in the English Speaking Caribbean.

ERIC Educational Resources Information Center

Dicks, Barbara A., Ed.

This collection of papers addresses the HIV/AIDS situation among English-speaking children in the Caribbean. Papers include: "Preface" (C. James Hospedales); "Introduction"; (Barbara A. Dicks); "HIV/AIDS: Challenging a Monster" (Brendan Bain); "HIV/AIDS in Caribbean Children and Adolescents" (Noreen Jack);…

Fabrication of a two-dimensional piezoelectric micromachined ultrasonic transducer array using a top-crossover-to-bottom structure and metal bridge connections

NASA Astrophysics Data System (ADS)

Jung, Joontaek; Kim, Sangwon; Lee, Wonjun; Choi, Hongsoo

2013-12-01

A new design methodology and fabrication process for two-dimensional (2D) piezoelectric micromachined ultrasonic transducer (pMUT) arrays using a top-crossover-to-bottom (TCTB) structure was developed. Individual sensing and actuation of pMUT elements from a small number of connection lines was enabled by the TCTB structure, and the parasitic coupling capacitance of the array was significantly reduced as a result. A 32 × 32 pMUT array with a TCTB structure was fabricated, resulting in 64 connection lines over an area of 4.8 × 4.8 mm2. The top electrodes for each pMUT element were re-connected by metal bridging after bottom-electrode etching caused them to become disconnected. A deep reactive ion etching process was used to compactify the array. Each pMUT element was a circular-shaped K31-type ultrasonic transducer using a 1 µm thick sol-gel lead zirconate titanate (PZT: Pb1.10 Zr0.52 Ti0.48) thin film. To characterize a single element in the 2D pMUT array, the resonant frequency and coupling coefficient of 20 pMUT elements were averaged to 3.85 MHz and 0.0112, respectively. The maximum measured ultrasound intensity in water, measured at a distance of 4 mm, was 4.6 µW cm-2 from a single pMUT element driven by a 5 Vpp sine wave at 2.22 MHz. Potential applications for development of a TCTB-arranged 2D pMUT array include ultrasonic medical imaging, ultrasonic communication, ultrasonic range-finding and handwriting input systems.

Lattice dynamics of Cs2NaYbF6 and Cs2NaYF6 elpasolites: Ab initio calculation

NASA Astrophysics Data System (ADS)

Chernyshev, V. A.; Petrov, V. P.; Nikiforov, A. E.; Zakir'yanov, D. O.

2015-06-01

The ab initio calculations of the crystal structure and the phonon spectrum of Cs2NaYbF6 and Cs2NaYF6 crystals with the elpasolite structure have been performed. The frequencies and types of fundamental vibrations have been determined. The calculations have been performed in the framework of the density functional theory using the molecular orbital method with hybrid functionals in the CRYSTAL09 program developed for the simulation of periodic structures. The outer 5 s and 5 p shells of the rare-earth ion have been described in Gaussian-type basis sets. The influence of inner shells, including 4 f electron shells, on the outer shells has been described using the pseudopotential. It has been shown that this approach allows the description of the phonon spectrum with the inclusion of the splitting of the longitudinal and transverse optical modes.

Structural Characterization of AgGaS2-type Photocatalysts for Hydrogen Production from Water Under Visible Light

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

Choi, Sun Hee; Shin, Namsoo; Jang, Jum Suk

Bulky AgGaS2 was synthesized as a p-type semiconductor photocatalyst by a conventional solid state reaction under N2 flow for hydrogen production under visible light. To remove the impurity phase involved in the synthesized material and improve its crystallinity, the material was treated at various temperatures of 873-1123 K under H2S flow. Impurity phases were identified as {beta}-Ga2O3 and Ag9GaS6 with Rietveld analysis of XRD, and the local coordination structure around gallium atom in AgGaS2 was investigated by EXAFS. As the H2S-treatment temperature increased, the contribution from impurity phase was diminished. When the temperature reached 1123 K, the impurity phases weremore » completely removed and the material showed the highest photocatalytic activity.« less

Modified band alignment effect in ZnO/Cu2O heterojunction solar cells via Cs2O buffer insertion

NASA Astrophysics Data System (ADS)

Eom, Kiryung; Lee, Dongyoon; Kim, Seunghwan; Seo, Hyungtak

2018-02-01

The effects of a complex buffer layer of cesium oxide (Cs2O) on the photocurrent response in oxide heterojunction solar cells (HSCs) were investigated. A p-n junction oxide HSC was fabricated using p-type copper (I) oxide (Cu2O) and n-type zinc oxide (ZnO); the buffer layer was inserted between the Cu2O and fluorine-doped tin oxide (FTO). Ultraviolet-visible (UV-vis) and x-ray and ultraviolet photoelectron spectroscopy analyses were performed to characterize the electronic band structures of cells, both with and without this buffer layer. In conjunction with the measured band electronic structures, the significantly improved visible-range photocurrent spectra of the buffer-inserted HSC were analyzed in-depth. As a result, the 1 sun power conversion efficiency was increased by about three times by the insertion of buffer layer. The physicochemical origin of the photocurrent enhancement was mainly ascribed to the increased photocarrier density in the buffer layer and modified valence band offset to promote the effective hole transfer at the interface to FTO on the band-alignment model.

Magnetic colloidal superparticles of Co, Mn and Ni ferrite featured with comb-type and/or linear amphiphilic polyelectrolytes; NMR and MRI relaxometry.

PubMed

Menelaou, Melita; Iatridi, Zacharoula; Tsougos, Ioannis; Vasiou, Katerina; Dendrinou-Samara, Catherine; Bokias, Georgios

2015-06-28

The ability to encapsulate hydrophobic ferrites in colloidal superparticle structures of an a-telechelic hexadecyl-functionalized poly(methacrylic acid) (C16H33-PMAA) polymer with a linear architecture was investigated and compared with that of two amphiphilic comb-type water-soluble copolymers, namely, P(ANa-co-DAAm) and P(MANa-co-DMA), which are comprised of a poly(sodium acrylate) or poly(sodium methacrylate) backbone and pendent dodecyl acrylamide or dodecyl methacrylate chains, respectively. In the case of C16H33-PMAA, the pH-sensitive self-assembly behavior, which was studied through Nile Red probing and TEM, was related to its encapsulation properties. Hydrophobic MFe2O4 nanoparticles coated with oleylamine (MFe2O4@OAm MNPs, where M = Co, Mn, Ni) with a similar shape and size (∼9 nm) and magnetization values of 87.4, 63.1 and 55.0 emu g(-1) for CoFe2O4@OAm, MnFe2O4@OAm and NiFe2O4@OAm, respectively, were successfully encapsulated into the hydrophobic cores of spherical micellar structures formed by the copolymers in an aqueous solution through a solvent mixing procedure. The synthesized magnetic colloidal superparticles fell in the static dephasing regime (SDR). NMR relaxivity measurements of MFe2O4@P(ANa-co-DAAm), MFe2O4@P(MANa-co-DMA) and MFe2O4@C16H33-PMAA at pH = 4.5 and pH = 7 (where M = Co, Mn, Ni) at 11.7 T were recorded and the transverse relaxivity (r2) (mM(-1) s(-1)) was determined. Among all, the CoFe2O4@polymers demonstrated the highest r2 relaxivity values, ranging from 61.6 for CoFe2O4@C16H33-PMAA (pH = 7) to 316.0 mM(-1) s(-1) for CoFe2O4@P(ANa-co-DAAm). The relaxation efficiency (r1 and r2) of CoFe2O4@P(ANa-co-DAAm) was investigated further by magnetic resonance imaging (MRI) at 1.5 T and 3 T and the r2/r1 ratios were found to be 16.5 and 18.2, respectively, indicating its potential use as a T2 contrast agent.

The catalytic mechanism of dye-decolorizing peroxidase DyP may require the swinging movement of an aspartic acid residue.

PubMed

Yoshida, Toru; Tsuge, Hideaki; Konno, Hiroki; Hisabori, Toru; Sugano, Yasushi

2011-07-01

The dye-decolorizing peroxidase (DyP)-type peroxidase family is a unique heme peroxidase family. The primary and tertiary structures of this family are obviously different from those of other heme peroxidases. However, the details of the structure-function relationships of this family remain poorly understood. We show four high-resolution structures of DyP (EC1.11.1.19), which is representative of this family: the native DyP (1.40 Å), the D171N mutant DyP (1.42 Å), the native DyP complexed with cyanide (1.45 Å), and the D171N mutant DyP associated with cyanide (1.40 Å). These structures contain four amino acids forming the binding pocket for hydrogen peroxide, and they are remarkably conserved in this family. Moreover, these structures show that OD2 of Asp171 accepts a proton from hydrogen peroxide in compound I formation, and that OD2 can swing to the appropriate position in response to the ligand for heme iron. On the basis of these results, we propose a swing mechanism in compound I formation. When DyP reacts with hydrogen peroxide, OD2 swings towards an optimal position to accept the proton from hydrogen peroxide bound to the heme iron. © 2011 The Authors Journal compilation © 2011 FEBS.

Structural basis of dual Ca2+/pH regulation of the endolysosomal TRPML1 channel

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

Li, Minghui; Zhang, Wei K.; Benvin, Nicole M.

The activities of organellar ion channels are often regulated by Ca2+ and H+, which are present in high concentrations in many organelles. Here we report a structural element critical for dual Ca2+/pH regulation of TRPML1, a Ca2+-release channel crucial for endolysosomal function. TRPML1 mutations cause mucolipidosis type IV (MLIV), a severe lysosomal storage disorder characterized by neurodegeneration, mental retardation and blindness. We obtained crystal structures of the 213-residue luminal domain of human TRPML1 containing three missense MLIV-causing mutations. This domain forms a tetramer with a highly electronegative central pore formed by a novel luminal pore loop. Cysteine cross-linking and cryo-EMmore » analyses confirmed that this architecture occurs in the full-length channel. Structure–function studies demonstrated that Ca2+ and H+ interact with the luminal pore and exert physiologically important regulation. The MLIV-causing mutations disrupt the luminal-domain structure and cause TRPML1 mislocalization. Our study reveals the structural underpinnings of TRPML1's regulation, assembly and pathogenesis.« less

The Composition and Structure of Biofilms Developed by Propionibacterium acnes Isolated from Cardiac Pacemaker Devices.

PubMed

Okuda, Ken-Ichi; Nagahori, Ryuichi; Yamada, Satomi; Sugimoto, Shinya; Sato, Chikara; Sato, Mari; Iwase, Tadayuki; Hashimoto, Kazuhiro; Mizunoe, Yoshimitsu

2018-01-01

The present study aimed to understand the biofilm formation mechanism of Propionibacterium acnes by analyzing the components and structure of the biofilms. P. acnes strains were isolated from the surface of explanted cardiac pacemaker devices that exhibited no clinical signs of infection. Culture tests using a simple stamp culture method (pressing pacemakers against the surface of agar plates) revealed frequent P. acnes colonization on the surface of cardiac pacemaker devices. P . acnes was isolated from 7/31 devices, and the isolates were categorized by multilocus sequence typing into five different sequence types (STs): ST4 (JK18.2), ST53 (JK17.1), ST69 (JK12.2 and JK13.1), ST124 (JK5.3), ST125 (JK6.2), and unknown ST (JK19.3). An in vitro biofilm formation assay using microtiter plates demonstrated that 5/7 isolates formed biofilms. Inhibitory effects of DNase I and proteinase K on biofilm formation varied among isolates. In contrast, dispersin B showed no inhibitory activity against all isolates. Three-dimensional live/dead imaging of P. acnes biofilms with different biochemical properties using confocal laser microscopy demonstrated different distributions and proportions of living and dead cells. Additionally, it was suggested that extracellular DNA (eDNA) plays a role in the formation of biofilms containing living cells. Ultrastructural analysis of P. acnes biofilms using a transmission electron microscope and atmospheric scanning electron microscope revealed leakage of cytoplasmic components along with cell lysis and fibrous structures of eDNA connecting cells. In conclusion, the biochemical properties and structures of the biofilms differed among P. acnes isolates. These findings may provide clues for establishing countermeasures against biofilm-associated infection by P. acnes .

The Composition and Structure of Biofilms Developed by Propionibacterium acnes Isolated from Cardiac Pacemaker Devices

PubMed Central

Okuda, Ken-ichi; Nagahori, Ryuichi; Yamada, Satomi; Sugimoto, Shinya; Sato, Chikara; Sato, Mari; Iwase, Tadayuki; Hashimoto, Kazuhiro; Mizunoe, Yoshimitsu

2018-01-01

The present study aimed to understand the biofilm formation mechanism of Propionibacterium acnes by analyzing the components and structure of the biofilms. P. acnes strains were isolated from the surface of explanted cardiac pacemaker devices that exhibited no clinical signs of infection. Culture tests using a simple stamp culture method (pressing pacemakers against the surface of agar plates) revealed frequent P. acnes colonization on the surface of cardiac pacemaker devices. P. acnes was isolated from 7/31 devices, and the isolates were categorized by multilocus sequence typing into five different sequence types (STs): ST4 (JK18.2), ST53 (JK17.1), ST69 (JK12.2 and JK13.1), ST124 (JK5.3), ST125 (JK6.2), and unknown ST (JK19.3). An in vitro biofilm formation assay using microtiter plates demonstrated that 5/7 isolates formed biofilms. Inhibitory effects of DNase I and proteinase K on biofilm formation varied among isolates. In contrast, dispersin B showed no inhibitory activity against all isolates. Three-dimensional live/dead imaging of P. acnes biofilms with different biochemical properties using confocal laser microscopy demonstrated different distributions and proportions of living and dead cells. Additionally, it was suggested that extracellular DNA (eDNA) plays a role in the formation of biofilms containing living cells. Ultrastructural analysis of P. acnes biofilms using a transmission electron microscope and atmospheric scanning electron microscope revealed leakage of cytoplasmic components along with cell lysis and fibrous structures of eDNA connecting cells. In conclusion, the biochemical properties and structures of the biofilms differed among P. acnes isolates. These findings may provide clues for establishing countermeasures against biofilm-associated infection by P. acnes. PMID:29491850

Correlation between the electrical properties and the interfacial microstructures of TiAl-based ohmic contacts to p-type 4H-SiC

NASA Astrophysics Data System (ADS)

Tsukimoto, S.; Nitta, K.; Sakai, T.; Moriyama, M.; Murakami, Masanori

2004-05-01

In order to understand a mechanism of TiAl-based ohmic contact formation for p-type 4H-SiC, the electrical properties and microstructures of Ti/Al and Ni/Ti/Al contacts, which provided the specific contact resistances of approximately 2×10-5 Ω-cm2 and 7×10-5 Ω-cm2 after annealing at 1000°C and 800°C, respectively, were investigated using x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Ternary Ti3SiC2 carbide layers were observed to grow on the SiC surfaces in both the Ti/Al and the Ni/Ti/Al contacts when the contacts yielded low resistance. The Ti3SiC2 carbide layers with hexagonal structures had an epitaxial orientation relationship with the 4H-SiC substrates. The (0001)-oriented terraces were observed periodically at the interfaces between the carbide layers and the SiC, and the terraces were atomically flat. We believed the Ti3SiC2 carbide layers primarily reduced the high Schottky barrier height at the contact metal/p-SiC interface down to about 0.3 eV, and, thus, low contact resistances were obtained for p-type TiAl-based ohmic contacts.

Vibrational Sum Frequency Study of the Influence of Water-Ionic Liquid Mixtures in the CO2 Electroreduction on Silver Electrodes

NASA Astrophysics Data System (ADS)

Garcia Rey, Natalia; Dlott, Dana

2015-06-01

Understand the molecular dynamics on buried electrodes under electrochemical transformations is of significant interest. There is a big gap of knowledge in the CO2 electroreduction mechanism due to the limitations to access and probe the liquid-metal interfaces [1,2]. Vibrational Sum Frequency Spectroscopy (VSFS) is a non-invasive and surface sensitive technique, with molecular level detection that can be used to probe electrochemical reactions occurring on the electrolyte-electrode interface [2]. We observed the CO2 electroreduction to CO in ionic liquids (ILs) on poly Ag using VSFS synchronized with cyclic voltammetry. In order to follow the CO2 reaction in situ on the ionic liquid-Ag interface; the CO, CO2 and imidazolium vibrational modes (resonant SFS) were monitored as a function of potential. We identified at which potential the CO was produced and how the EMIM-BF4 played an important role in the electron transfer to the CO2, lowering the CO2- energy barrier. A new approach to reveal the double layer dynamics to the electrostatic environment is presented by the study of the nonresonant sum frequency intensity as a function of the applied potential. By this method, we studied the influence of water-ionic liquid mixtures in the CO2 electroreduction on Ag electrode. We observed a shift to lower potentials in the CO2 electroreduction in water-ILs electrolyte. Previous studies in gas diffusion fuel cells have shown the CO2 electroreduction in a water-imidazolium-based ILs on Ag nanoparticles at lower overpotential [3]. Our VSFS study helps to understand the fundamental electrochemical mechanism, showing how the ILs structural transition influences the CO2 electroreduction. [1] Polyansky, D. E.; Electroreduction of Carbon Dioxide, 2014, Encyclopedia of Applied Electrochemistry, Springer New York, pag 431-437. [2] Bain, C. D.; J. Chem. Soc., Faraday Trans., 1995, 91, 1281. [3] Rosen, B. A. et al; Science, 2011, 334 (6056), 643. Rosen, B. A. et al.; J. electrochem. Soc., 2013, 160 (2), H138.

Increased susceptibility to structural acute kidney injury in a mouse model of presymptomatic cardiomyopathy.

PubMed

Pleasant, LaTawnya; Ma, Qing; Devarajan, Mahima; Parameswaran, Priyanka; Drake, Keri; Siroky, Brian; Shay-Winkler, Kritton; Robbins, Jeffrey; Devarajan, Prasad

2017-09-01

The early events that signal renal dysfunction in presymptomatic heart failure are unclear. We tested the hypothesis that functional and mechanistic changes occur in the kidney that precede the development of symptomatic heart failure. We employed a transgenic mouse model with cardiomyocyte-specific overexpression of mutant α-B-crystallin that develops slowly progressive cardiomyopathy. Presymptomatic transgenic mice displayed an increase in serum creatinine (1.17 ± 0.34 vs. wild type 0.65 ± 0.16 mg/dl, P < 0.05) and in urinary neutrophil gelatinase-associated lipocalin (NGAL; 278.92 ± 176.24 vs. wild type 49.11 ± 22.79 ng/ml, P < 0.05) but no renal fibrosis. Presymptomatic transgenic mouse kidneys exhibited a twofold upregulation of the Ren1 gene, marked overexpression of renin protein in the tubules, and a worsened response to ischemia-reperfusion injury based on serum creatinine (2.77 ± 0.66 in transgenic mice vs. 2.01 ± 0.58 mg/dl in wild type, P < 0.05), urine NGAL (9,198.79 ± 3,799.52 in transgenic mice vs. 3,252.94 ± 2,420.36 ng/ml in wild type, P < 0.05), tubule dilation score (3.4 ± 0.5 in transgenic mice vs. 2.6 ± 0.5 in wild type, P < 0.05), tubule cast score (3.2 ± 0.4 in transgenic mice vs. 2.5 ± 0.5 in wild type, P < 0.05), and TdT-mediated dUTP nick-end labeling (TUNEL)-positive nuclei (10.1 ± 2.1 in the transgenic group vs. 5.7 ± 1.6 per 100 cells counted in wild type, P < 0.01). Our findings indicate functional renal impairment, urinary biomarker elevations, and induction of renin gene and protein expression in the kidney that occur in early presymptomatic heart failure, which increase the susceptibility to subsequent acute kidney injury. Copyright © 2017 the American Physiological Society.

Off-great-circle paths in transequatorial propagation: 1. Discrete and diffuse types

NASA Astrophysics Data System (ADS)

Tsunoda, Roland T.; Maruyama, Takashi; Tsugawa, Takuya; Yokoyama, Tatsuhiro; Ishii, Mamoru; Nguyen, Trang T.; Ogawa, Tadahiko; Nishioka, Michi

2016-11-01

There is mounting evidence that plasma structure in nighttime equatorial F layer evolves from large-scale wave structure (LSWS) in the bottomside F layer. This process cannot be ignored because equatorial plasma bubbles (EPBs) arise from large-amplitude LSWS; and, because intense radiowave scintillations are associated with EPBs, understanding the LSWS-to-EPB process is a crucial step toward reliable Space Weather Forecasting. In this regard, the transequatorial propagation (TEP) experiment appears to be the most useful among available research instruments. After a lapse of 30 years, the TEP experiment has been resurrected; a goal of this research is to understand TEP measurements well enough so that they can be used to diagnose the LSWS-to-EPB process. Toward this end, new results are presented in two companion papers. Herein (P1), off-great-circle (OGC) propagation paths are shown to consist of two types, discrete and diffuse. The new findings include the following: (1) a generalized multireflection model that can explain most of the observed properties; (2) the discrete type is supported by multireflections from an unstructured upwelling, (3) the diffuse type is supported by reflections from plasma structure in EPBs; and (4) the observed east-west (EW) asymmetry can be explained in terms of a distorted upwelling or plasma structure along the west wall of an upwelling. In Paper 2 (P2), a second form of observed EW asymmetry is explained in terms of plasma structure, which is not aligned with the geomagnetic field. The findings strongly confirm a close relationship between upwellings, ESF patches, and OGC paths.

Characterization of metal-ferroelectric-insulator-semiconductor structures based on ferroelectric Langmuir-Blodgett polyvinylidene fluoride copolymer films for nondestructive random access memory applications

NASA Astrophysics Data System (ADS)

Reece, Timothy James

Ferroelectric field effect transistors (FeFETs) have attracted much attention recently because of their ability to combine high speed, low power consumption, and fast nondestructive readout with the potential for high density nonvolatile memory. The polarization of the ferroelectric is used to switch the channel at the silicon surface between states of high and low conductance. Among the ferroelectric thin films used in FET devices; the ferroelectric copolymer of Polyvinylidene fluoride, PVDF (C2H2F 2), with trifluoroethylene, TrFE (C2HF3), has distinct advantages, including low dielectric constant, low processing temperature, low cost and compatibility with organic semiconductors. By employing the Langmuir-Blodgett technique, films as thin as 1.8 nm can be deposited, reducing the operating voltage. An MFIS structure consisting of aluminum, 170 nm P(VDF-TrFE), 100 nm silicon oxide and n-type silicon exhibited low leakage current (˜1x10 -8 A/cm2), a large memory window (4.2 V) and operated at 35 Volts. The operating voltage was lowered through use of high k insulators like cerium oxide. A sample consisting of 25 nm P(VDF-TrFE), 30 nm cerium oxide and p-type silicon exhibited a 1.9 V window with 7 Volt gate amplitude. The leakage current in this case was considerably higher (1x10 -6 A/cm2). The characterization, modeling, and fabrication of metal-ferroelectricinsulator semiconductor (MFIS) structures based on these films are discussed.

Soft X-ray magnetic circular dichroism of Heusler-type alloy Co 2MnGe

NASA Astrophysics Data System (ADS)

Miyamoto, K.; Iori, K.; Kimura, A.; Xie, T.; Taniguchi, M.; Qiao, S.; Tsuchiya, K.

2003-10-01

Co and Mn 2p core absorption (XAS) and X-ray magnetic circular dichroism (XMCD) spectra have been measured for the ferromagnetic ternary alloy Co 2MnGe. The observed Co 2p XAS spectrum can be understood on the basis of the unoccupied Co 3d partial density of states, whereas the overall features of the Mn 2p XAS and XMCD spectra have been partly reproduced by the Mn 2p 53d 6 final state multiplets. We have found that the orbital polarization of the Co 3d and even the Mn 3d states are recognizable, which suggests that a spin-orbit coupling should be taken into account in the energy band structure in order to reproduce the half metallic nature of this alloy.

p-n Junction Diodes Fabricated on Si-Si/Ge Heteroepitaxial Films

NASA Technical Reports Server (NTRS)

Das, K.; Mazumder, M. D. A.; Hall, H.; Alterovitz, Samuel A. (Technical Monitor)

2000-01-01

A set of photolithographic masks was designed for the fabrication of diodes in the Si-Si/Ge material system. Fabrication was performed on samples obtained from two different wafers: (1) a complete HBT structure with an n (Si emitter), p (Si/Ge base), and an n/n+ (Si collector/sub-collector) deposited epitaxially (MBE) on a high resistivity p-Si substrate, (2) an HBT structure where epitaxial growth was terminated after the p-type base (Si/Ge) layer deposition. Two different process runs were attempted for the fabrication of Si-Si/Ge (n-p) and Si/Ge-Si (p-n) junction diodes formed between the emitter-base and base-collector layers, respectively, of the Si-Si/Ge-Si HBT structure. One of the processes employed a plasma etching step to expose the p-layer in the structure (1) and to expose the e-layer in structure (2). The Contact metallization used for these diodes was a Cu-based metallization scheme that was developed during the first year of the grant. The plasma-etched base-collector diodes on structure (2) exhibited well-behaved diode-like characteristics. However, the plasma-etched emitter-base diodes demonstrated back-to-back diode characteristics. These back-to back characteristics were probably due to complete etching of the base-layer, yielding a p-n-p diode. The deep implantation process yielded rectifying diodes with asymmetric forward and reverse characteristics. The ideality factor of these diodes were between 1.6 -2.1, indicating that the quality of the MBE grown epitaxial films was not sufficiently high, and also incomplete annealing of the implantation damage. Further study will be conducted on CVD grown films, which are expected to have higher epitaxial quality.

Structural and optical characterization of p-type highly Fe-doped SnO2 thin films and tunneling transport on SnO2:Fe/p-Si heterojunction

NASA Astrophysics Data System (ADS)

Ben Haj Othmen, Walid; Ben Hamed, Zied; Sieber, Brigitte; Addad, Ahmed; Elhouichet, Habib; Boukherroub, Rabah

2018-03-01

Nanocrystalline highly Fe-doped SnO2 thin films were prepared using a new simple sol-gel method with iron amounts of 5, 10, 15 and 20%. The obtained gel offers a long durability and high quality allowing to reach a sub-5 nm nanocrystalline size with a good crystallinity. The films were structurally characterized through X-ray diffraction (XRD) that confirms the formation of rutile SnO2. High Resolution Transmission Electron Microscopy (HRTEM) images reveals the good crystallinity of the nanoparticles. Raman spectroscopy shows that the SnO2 rutile structure is maintained even for high iron concentration. The variation of the PL intensity with Fe concentration reveals that iron influences the distribution of oxygen vacancies in tin oxide. The optical transmittance results indicate a redshift of the SnO2 band gap when iron concentration increases. The above optical results lead us to assume the presence of a compensation phenomenon between oxygen vacancies and introduced holes following Fe doping. From current-voltage measurements, an inversion of the conduction type from n to p is strongly predicted to follow the iron addition. Electrical characterizations of SnO2:Fe/p-Si and SnO2:Fe/n-Si heterojunctions seem to be in accordance with this deduction. The quantum tunneling mechanism is expected to be important at high Fe doping level, which was confirmed by current-voltage measurements at different temperatures. Both optical and electrical properties of the elaborated films present a particularity for the same iron concentration and adopt similar tendencies with Fe amount, which strongly correlate the experimental observations. In order to evaluate the applicability of the elaborated films, we proceed to the fabrication of the SnO2:Fe/SnO2 homojunction for which we note a good rectifying behavior.

Crystallization and preliminary X-ray analysis of pyruvate kinase from Bacillus stearothermophilus

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

Suzuki, Kenichiro; Ito, Sohei; Shimizu-Ibuka, Akiko

2005-08-01

This report describes the crystallization and X-ray diffraction data collection of three types (wild-type, W416F/V435W and C9S/C268S) of B. stearothermophilus. Crystals of C9S/C268S belonged to space group P6{sub 2}22 and diffracted to a resolution of 2.4 Å. Pyruvate kinase (PK) from a moderate thermophile, Bacillus stearothermophilus (BstPK), is an allosteric enzyme activated by AMP and ribose 5-phosphate but not by fructose 1,6-bisphosphate (FBP). However, almost all other PKs are activated by FBP. The wild-type and W416F/V435W mutant BstPKs were crystallized by the hanging-drop vapour-diffusion method. However, they were unsuitable for structural analysis because their data sets exhibited low completeness. Amore » crystal suitable for structural analysis was obtained using C9S/C268S enzyme. The crystal belonged to space group P6{sub 2}22, with unit-cell parameters a = b = 145.97, c = 118.03 Å.« less

Nb2OsB2, with a new twofold superstructure of the U3Si2 type: Synthesis, crystal chemistry and chemical bonding

NASA Astrophysics Data System (ADS)

Mbarki, Mohammed; Touzani, Rachid St.; Fokwa, Boniface P. T.

2013-07-01

The new ternary metal-rich boride, Nb2OsB2, was synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere. The compound was characterized from single-crystal X-ray data and EDX measurements. It crystallizes as a new superstructure (space group P4/mnc, no. 128) of the tetragonal U3Si2-structure type with lattice parameters a=5.922(1) Å and c=6.879(2) Å. All of the B atoms are involved in B2 dumbbells with B-B distances of 1.89(4) Å. Structure relaxation using VASP (Vienna ab intio Simulation Package) has confirmed the space group and the lattice parameters. According to electronic structure calculations (TB-LMTO-ASA), the homoatomic B-B interactions are optimized and very strong, but relatively strong heteroatomic Os-B, Nb-B and Nb-Os bonds are also found: These interactions, which together build a three-dimensional network, are mainly responsible for the structural stability of this new phase. The density of state at the Fermi level predicts metallic behavior, as expected, from this metal-rich boride.

Silicon nanowire array architecture for heterojunction electronics

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

Solovan, M. M., E-mail: m.solovan@chnu.edu.ua; Brus, V. V.; Mostovyi, A. I.

2017-04-15

Photosensitive nanostructured heterojunctions n-TiN/p-Si were fabricated by means of titanium nitride thin films deposition (n-type conductivity) by the DC reactive magnetron sputtering onto nano structured single crystal substrates of p-type Si (100). The temperature dependencies of the height of the potential barrier and series resistance of the n-TiN/p-Si heterojunctions were investigated. The dominant current transport mechanisms through the heterojunctions under investigation were determined at forward and reverse bias. The heterojunctions under investigation generate open-circuit voltage V{sub oc} = 0.8 V, short-circuit current I{sub sc} = 3.72 mA/cm{sup 2} and fill factor FF = 0.5 under illumination of 100 mW/cm{sup 2}.

Transient oscillation of shape and membrane conductivity changes by field pulse-induced electroporation in nano-sized phospholipid vesicles.

PubMed

Dimitrov, Vasil; Kakorin, Sergej; Neumann, Eberhard

2013-05-07

The results of electrooptical and conductometrical measurements on unilamellar lipid vesicles (of mean radius a = 90 nm), filled with 0.2 M NaCl solution, suspended in 0.33 M sucrose solution of 0.2 mM NaCl, and exposed to a stepwise decaying electric field (time constant τE = 154 μs) in the range 10 ≤ E0 (kV cm(-1)) ≤ 90, are analyzed in terms of cyclic changes in vesicle shape and vesicle membrane conductivity. The two peaks in the dichroitic turbidity relaxations reflect two cycles of rapid membrane electroporation and slower resealing of long-lived electropores. The field-induced changes reflect structural transitions between closed (C) and porated (P) membrane states, qualified by pores of type P1 and of type P2, respectively. The transient change in the membrane conductivity and the transient shape oscillation are based on changes in the pore density of the (larger) P2-pores along a hysteresis cycle. The P2-pore formation leads to transient net ion flows across the P2-pores and to transient changes in the membrane field. The kinetic data are numerically processed in terms of coupled structural relaxation modes. Using the torus-hole pore model, the mean inner pore radii are estimated to be r1 = 0.38 (±0.05) nm and r2 = 1.7 (±0.1) nm, respectively. The observation of a transient oscillation of membrane electroporation and of shape changes in a longer lasting external field pulse is suggestive of potential resonance enhancement, for instance, of electro-uptake by, and of electro-release of biogenic molecules from, biological cells in trains of long-lasting low-intensity voltage pulses.

Strain-induced enhancement of thermoelectric performance of TiS2 monolayer based on first-principles phonon and electron band structures

NASA Astrophysics Data System (ADS)

Li, Guanpeng; Yao, Kailun; Gao, Guoying

2018-01-01

Using first-principle calculations combined with Boltzmann transport theory, we investigate the biaxial strain effect on the electronic and phonon thermal transport properties of a 1 T (CdI2-type) structural TiS2 monolayer, a recent experimental two-dimensional (2D) material. It is found that the electronic band structure can be effectively modulated and that the band gap experiences an indirect-direct-indirect transition with increasing tensile strain. The band convergence induced by the tensile strain increases the Seebeck coefficient and the power factor, while the lattice thermal conductivity is decreased under the tensile strain due to the decreasing group velocity and the increasing scattering chances between the acoustic phonon modes and the optical phonon modes, which together greatly increase the thermoelectric performance. The figure of merit can reach 0.95 (0.82) at an 8 percent tensile strain for the p-type (n-type) doping, which is much larger than that without strain. The present work suggests that the TiS2 monolayer is a good candidate for 2D thermoelectric materials, and that biaxial strain is a powerful tool with which to enhance thermoelectric performance.

Strain-induced enhancement of thermoelectric performance of TiS2 monolayer based on first-principles phonon and electron band structures.

PubMed

Li, Guanpeng; Yao, Kailun; Gao, Guoying

2018-01-05

Using first-principle calculations combined with Boltzmann transport theory, we investigate the biaxial strain effect on the electronic and phonon thermal transport properties of a 1 T (CdI 2 -type) structural TiS 2 monolayer, a recent experimental two-dimensional (2D) material. It is found that the electronic band structure can be effectively modulated and that the band gap experiences an indirect-direct-indirect transition with increasing tensile strain. The band convergence induced by the tensile strain increases the Seebeck coefficient and the power factor, while the lattice thermal conductivity is decreased under the tensile strain due to the decreasing group velocity and the increasing scattering chances between the acoustic phonon modes and the optical phonon modes, which together greatly increase the thermoelectric performance. The figure of merit can reach 0.95 (0.82) at an 8 percent tensile strain for the p-type (n-type) doping, which is much larger than that without strain. The present work suggests that the TiS 2 monolayer is a good candidate for 2D thermoelectric materials, and that biaxial strain is a powerful tool with which to enhance thermoelectric performance.

Synthesis, structure and NMR characterization of a new monomeric aluminophosphate [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4 containing four different types of monophosphates

NASA Astrophysics Data System (ADS)

Chen, Peng; Li, Jiyang; Xu, Jun; Duan, Fangzheng; Deng, Feng; Xu, Ruren

2009-03-01

A new zero-dimensional (0D) aluminophosphate monomer [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4 (designated AlPO-CJ38) with Al/P ratio of 1/6 has been solvothermally prepared by using racemic cobalt complex dl-Co(en) 3Cl 3 as the template. The Al atom is octahedrally linked to six P atoms via bridging oxygen atoms, forming a unique [Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2] 6- monomer. Notably, there exists intramolecular symmetrical O⋯H⋯O bonds, which results in pseudo-4-rings stabilized by the strong H-bonding interactions. The structure is also featured by the existence of four different types of monophosphates that have been confirmed by 31P NMR and 1H NMR spectra. The crystal data are as follows: AlPO-CJ38, [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4, M = 1476.33, monoclinic, C2/ c (No. 15), a = 36.028(7) Å, b = 8.9877(18) Å, c = 16.006(3) Å, β = 100.68(3)°, U = 5093.2(18) Å 3,Z = 4, R1 = 0.0509 ( I > 2 σ( I)) and wR2 = 0.1074 (all data). CCDC number 689491.

The Cryoelectron Microscopy Structure of the Type 1 Chaperone-Usher Pilus Rod.

PubMed

Hospenthal, Manuela K; Zyla, Dawid; Costa, Tiago R D; Redzej, Adam; Giese, Christoph; Lillington, James; Glockshuber, Rudi; Waksman, Gabriel

2017-12-05

Adhesive chaperone-usher pili are long, supramolecular protein fibers displayed on the surface of many bacterial pathogens. The type 1 and P pili of uropathogenic Escherichia coli (UPEC) play important roles during urinary tract colonization, mediating attachment to the bladder and kidney, respectively. The biomechanical properties of the helical pilus rods allow them to reversibly uncoil in response to flow-induced forces, allowing UPEC to retain a foothold in the unique and hostile environment of the urinary tract. Here we provide the 4.2-Å resolution cryo-EM structure of the type 1 pilus rod, which together with the previous P pilus rod structure rationalizes the remarkable "spring-like" properties of chaperone-usher pili. The cryo-EM structure of the type 1 pilus rod differs in its helical parameters from the structure determined previously by a hybrid approach. We provide evidence that these structural differences originate from different quaternary structures of pili assembled in vivo and in vitro. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Loss of Function of P2X7 Receptor Scavenger Activity in Aging Mice: A Novel Model for Investigating the Early Pathogenesis of Age-Related Macular Degeneration.

PubMed

Vessey, Kirstan A; Gu, Ben J; Jobling, Andrew I; Phipps, Joanna A; Greferath, Ursula; Tran, Mai X; Dixon, Michael A; Baird, Paul N; Guymer, Robyn H; Wiley, James S; Fletcher, Erica L

2017-08-01

Age-related macular degeneration (AMD) is a leading cause of irreversible, severe vision loss in Western countries. Recently, we identified a novel pathway involving P2X7 receptor scavenger function expressed on ocular immune cells as a risk factor for advanced AMD. In this study, we investigate the effect of loss of P2X7 receptor function on retinal structure and function during aging. P2X7-null and wild-type C57bl6J mice were investigated at 4, 12, and 18 months of age for macrophage phagocytosis activity, ocular histological changes, and retinal function. Phagocytosis activity of blood-borne macrophages decreased with age at 18 months in the wild-type mouse. Lack of P2X7 receptor function reduced phagocytosis at all ages compared to wild-type mice. At 12 months of age, P2X7-null mice had thickening of Bruchs membrane and retinal pigment epithelium dysfunction. By 18 months of age, P2X7-null mice displayed phenotypic characteristics consistent with early AMD, including Bruchs membrane thickening, retinal pigment epithelium cell loss, retinal functional deficits, and signs of subretinal inflammation. Our present study shows that loss of function of the P2X7 receptor in mice induces retinal changes representing characteristics of early AMD, providing a valuable model for investigating the role of scavenger receptor function and the immune system in the development of this age-related disease. Copyright © 2017 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

Cryo-EM of the pathogenic VCP variant R155P reveals long-range conformational changes in the D2 ATPase ring

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

Mountassif, Driss; Fabre, Lucien; Zaid, Younes

Single amino acid mutations in valosin containing protein (VCP/p97), a highly conserved member of the ATPases associated with diverse cellular activities (AAA) family of ATPases has been linked to a severe degenerative disease affecting brain, muscle and bone tissue. Previous studies have demonstrated the role of VCP mutations in altering the ATPase activity of the D2 ring; however the structural consequences of these mutations remain unclear. In this study, we report the three-dimensional (3D) map of the pathogenic VCP variant, R155P, as revealed by single-particle Cryo-Electron Microscopy (EM) analysis at 14 Å resolution. We show that the N-terminal R155P mutation inducesmore » a large structural reorganisation of the D2 ATPase ring. Results from docking studies using crystal structure data of available wild-type VCP in the EM density maps indicate that the major difference is localized at the interface between two protomers within the D2 ring. Consistent with a conformational change, the VCP R155P variant shifted the isoelectric point of the protein and reduced its interaction with its well-characterized cofactor, nuclear protein localization-4 (Npl4). Together, our results demonstrate that a single amino acid substitution in the N-terminal domain can relay long-range conformational changes to the distal D2 ATPase ring. Our results provide the first structural clues of how VCP mutations may influence the activity and function of the D2 ATPase ring. - Highlights: • p97{sub R155P} and p97{sub A232E} decrease the ability of p97 to bind to its co-factor Npl4. • p97{sub R155P} has a different isoelectric point than that of p97{sub R95G}, p97{sub A232E} and p97{sub WT}. • Mutation R155P changes principally the conformation of the D2 ring. • Mutation R155P modifies the interface between two protomers within the D2 ring.« less

Threshold voltage tuning in AlGaN/GaN HFETs with p-type Cu2O gate synthesized by magnetron reactive sputtering

NASA Astrophysics Data System (ADS)

Wang, Lei; Li, Liuan; Xie, Tian; Wang, Xinzhi; Liu, Xinke; Ao, Jin-Ping

2018-04-01

In present study, copper oxide films were prepared at different sputtering powers (10-100 W) using magnetron reactive sputtering. The crystalline structure, surface morphologies, composition, and optical band gap of the as-grown films are dependent on sputtering power. As the sputtering power decreasing from 100 to 10 W, the composition of films changed from CuO to quasi Cu2O domination. Moreover, when the sputtering power is 10 W, a relative high hole carrier density and high-surface-quality quasi Cu2O thin film can be achieved. AlGaN/GaN HFETs were fabricated with the optimized p-type quasi Cu2O film as gate electrode, the threshold voltage of the device shows a 0.55 V positive shift, meanwhile, a lower gate leakage current, a higher ON/OFF drain current ratio of ∼108, a higher electron mobility (1465 cm2/Vs), and a lower subthreshold slope of 74 mV/dec are also achieved, compared with the typical Ni/Au-gated HFETs. Therefore, Cu2O have a great potential to develop high performance p-type gate AlGaN/GaN HFETs.

Benefits of Carrier-Pocket Anisotropy to Thermoelectric Performance: The Case of p -Type AgBiSe 2

DOE PAGES

Parker, David S.; May, Andrew F.; Singh, David J.

2015-06-05

Here we study theoretically the effects of anisotropy on the thermoelectric performance of p-type AgBiSe 2. We present an apparent realization of the thermoelectric benefits of one-dimensional plate-like carrier pocket anisotropy in the valence band of this material. Based on first principles calculations we find a substantial anisotropy in the electronic structure, likely favorable for thermoelectric performance, in the valence bands of the hexagonal phase of the silver chalcogenide thermoelectric AgBiSe 2, while the conduction bands are more isotropic, and in our experiments do not attain high performance. AgBiSe 2 has already exhibited a ZT value of 1.5 in amore » high-temperature disordered fcc phase, but room-temperature performance has not been demonstrated. We develop a theory for the ability of anisotropy to decouple the density-of-states and conductivity effective masses, pointing out the influence of this effect in the high performance thermoelectrics Bi 2Te 3 and PbTe. From our first principles and Boltzmann transport calculations we find that p-type AgBiSe 2 has substantial promise as a room temperature thermoelectric, and estimate its performance.« less

Phase equillibria and solidification behaviour in the vanillin- p-anisidine system

NASA Astrophysics Data System (ADS)

Singh, N. B.; Das, S. S.; Gupta, Preeti; Dwivedi, M. K.

2008-12-01

Phase diagram of the vanillin- p-anisidine system has been studied by the thaw melt method. Congruent melting-type phase diagram exhibiting two eutectic points was obtained. Vanillin and p-anisidine react in 1:1 M ratio and form N-(4-methoxy phenyl)-4-hydroxy-3-methoxy phenyl methanimine (NHM) and water. Heats of fusion of pure components and the eutectic mixtures ( E1 and E2) were obtained from DSC studies. Jackson's roughness parameters ( α) were calculated. Excess Gibbs free energy ( GE), excess entropy ( SE) and excess enthalpy ( HE) of mixing of pre-, post- and eutectic mixtures were also calculated by using activity coefficient data. Linear velocities of solidification of components and eutectic mixtures were determined at different undercoolings. The values of excess thermodynamic functions and linear velocity data have indicated the non-ideal nature of the eutectic mixtures. Interaction energies in the gaseous state, calculated from computer simulation, have also indicated that the eutectics are non-ideal mixtures. Microstructural studies of vanillin, p-anisidine and NHM show the formation of broken lamellar type structures. However, for the eutectic E1, an irregular type and for the eutectic E2, a lamellar type structures were obtained. The effect of impurity on the microstructures of eutectic mixtures was also studied.

5-Ethynyl-2'-deoxycytidine: a DNA building block with a 'clickable' side chain.

PubMed

Seela, Frank; Mei, Hui; Xiong, Hai; Budow, Simone; Eickmeier, Henning; Reuter, Hans

2012-10-01

The title compound [systematic name: 4-amino-1-(2-deoxy-β-D-erythro-pentofuranosyl)-5-ethynylpyrimidin-2(1H)-one], C(11)H(13)N(3)O(4), shows two conformations in the crystalline state. The N-glycosylic bonds of both conformers adopt similar conformations, with χ = -149.2 (1)° for conformer (I-1) and -151.4 (1)° for conformer (I-2), both in the anti range. The sugar residue of (I-1) shows a C2'-endo envelope conformation ((2)E, S-type), with P = 164.7 (1)° and τ(m) = 36.9 (1)°, while (I-2) shows a major C3'-exo sugar pucker (C3'-exo-C2'-endo, (3)T(2), S-type), with P = 189.2 (1)° and τ(m) = 33.3 (1)°. Both conformers participate in the formation of a layered three-dimensional crystal structure with a chain-like arrangement of the conformers. The ethynyl groups do not participate in hydrogen bonding, but are arranged in proximal positions.

Mechanistic and Structural Analyses of the Role of His67 in the Yeast Polyamine Oxidase Fms1

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

Adachi, Mariya S.; Taylor, Alexander B.; Hart, P. John

2012-07-25

The flavoprotein oxidase Fms1 from Saccharomyces cerevisiae catalyzes the oxidation of spermine and N1-acetylspermine to spermidine and 3-aminopropanal or N-acetyl-3-aminopropanal. Within the active site of Fms1, His67 is positioned to form hydrogen bonds with the polyamine substrate. This residue is also conserved in other polyamine oxidases. The catalytic properties of H67Q, H67N, and H67A Fms1 have been characterized to evaluate the role of this residue in catalysis. With both spermine and N1-acetylspermine as the amine substrate, the value of the first-order rate constant for flavin reduction decreases 2-3 orders of magnitude, with the H67Q mutation having the smallest effect andmore » H67N the largest. The k{sub cat}/K{sub O2} value changes very little upon mutation with N{sup 1}-acetylspermine as the amine substrate and decreases only an order of magnitude with spermine. The k{sub cat}/K{sub M}-pH profiles with N{sup 1}-acetylspermine are bell-shaped for all the mutants; the similarity to the profile of the wild-type enzyme rules out His67 as being responsible for either of the pK{sub a} values. The pH profiles for the rate constant for flavin reduction for all the mutant enzymes similarly show the same pK{sub a} as wild-type Fms1, about {approx}7.4; this pK{sub a} is assigned to the substrate N4. The k{sub cat}/K{sub O2}-pH profiles for wild-type Fms1 and the H67A enzyme both show a pK{sub a} of about {approx}6.9; this suggests His67 is not responsible for this pH behavior. With the H67Q, H67N, and H67A enzymes the k{sub cat} value decreases when a single residue is protonated, as is the case with the wild-type enzyme. The structure of H67Q Fms1 has been determined at a resolution of 2.4 {angstrom}. The structure shows that the mutation disrupts a hydrogen bond network in the active site, suggesting that His67 is important both for direct interactions with the substrate and to maintain the overall active site structure.« less

Synthesis of CaO-SiO2-P2O5 mesoporous bioactive glasses with high P2O5 content by evaporation induced self assembly process.

PubMed

Zhao, Shan; Li, Yanbao; Li, Dongxu

2011-02-01

Mesoporous bioactive glasses (MBGs) of the CaO-SiO(2)-P(2)O(5) system containing relatively high P(2)O(5) contents (10-30 mol%) were prepared from a sol-gel. An evaporation-induced self-assembly (EISA) technique was used with poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (EO(20)-PO(70)-EO(20), P123) acting as a template. The structural, morphological and textural properties of MBGs were investigated by small-angle X-ray diffraction (SAXRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and a N(2) sorption/desorption technique. SAXRD and TEM results display the reduced long-range ordering of mesopores with increasing P(2)O(5) content. N(2) sorption/desorption analysis shows that all three samples exhibit a type IV isotherm with type H1 hysteresis loops, characteristic of independent cylindrical slim pore channels and this material has a Barret-Joyner-Halenda (BJH) model pore size of ~4 nm and BET specific surface area ~430 m(2)/g. NMR results indicate a more condensed framework for samples with 30 mol% P(2)O(5) than samples with 10 mol% P(2)O(5). For in vitro bioactivity tests where samples were soaked in simulated body fluid (SBF), samples with 30 mol% P(2)O(5) showed higher crystallinity than those with lower P(2)O(5) contents Silicon concentration increased in SBF solution during the soaking period, which indicates MBGs can be degradable in SBF solution.

Crystallization and preliminary X-ray analysis of Ebola VP35 interferon inhibitory domain mutant proteins

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

Leung, Daisy W.; Borek, Dominika; Farahbakhsh, Mina

2010-06-21

VP35 is one of seven structural proteins encoded by the Ebola viral genome and mediates viral replication, nucleocapsid formation and host immune suppression. The C-terminal interferon inhibitory domain (IID) of VP35 is critical for dsRNA binding and interferon inhibition. The wild-type VP35 IID structure revealed several conserved residues that are important for dsRNA binding and interferon antagonism. Here, the expression, purification and crystallization of recombinant Zaire Ebola VP35 IID mutants R312A, K319A/R322A and K339A in space groups P6{sub 1}22, P2{sub 1}2{sub 1}2{sub 1} and P2{sub 1}, respectively, are described. Diffraction data were collected using synchrotron sources at the Advanced Lightmore » Source and the Advanced Photon Source.« less

Redox-linked ionization of sulredoxin, an archaeal Rieske-type [2Fe-2S] protein from Sulfolobus sp. strain 7.

PubMed

Iwasaki, T; Imai, T; Urushiyama, A; Oshima, T

1996-11-01

"Sulredoxin" of Sulfolobus sp. strain 7 is an archaeal soluble Rieske-type [2Fe-2S] protein and was initially characterized by several spectroscopic techniques (Iwasaki, T., Isogai, T., Iizuka, T. , and Oshima, T. (1995) J. Bacteriol. 177, 2576-2582). It appears to have tightly linked ionization affecting the redox properties of the protein, which is characteristic of the Rieske FeS proteins found as part of the respiratory chain. Sulredoxin had an Em(low pH) value of +188 +/- 9 mV, and the slope of pH dependence of the midpoint redox potential indicated two ionization equilibria in the oxidized form with pKa(ox1) of 6.23 +/- 0.22 and pKa(ox2) of 8.57 +/- 0.20. The absorption, CD, and resonance Raman spectra of oxidized sulredoxin are consistent with the proposed St2FeSb2Fe[N(His)]t2 core structure, and deprotonation of one of the two putative coordinated histidine imidazoles, having the pKa(ox2) of 8.57 +/- 0.20, causes a decrease in the midpoint redox potential, the change in the optical and CD spectra, and the appearance of a new Raman transition at 278 cm-1, without major structural rearrangement of the [2Fe-2S] cluster as well as the overall protein conformation. The redox-linked ionization of sulredoxin is also contributed by local changes involving another ionizable group having the pKa(ox1) of 6.23 +/- 0. 22, which is probably attributed to a certain positively charged amino acid residue that may not be a ligand by itself but located very close to the cluster. We suggest that sulredoxin provides a new tractable model of the membrane-bound homologue of the respiratory chain, the Rieske FeS proteins of the cytochrome bc1-b6f complexes.

Off-great-circle paths in transequatorial propagation: 2. Nonmagnetic-field-aligned reflections

NASA Astrophysics Data System (ADS)

Tsunoda, Roland T.; Maruyama, Takashi; Tsugawa, Takuya; Yokoyama, Tatsuhiro; Ishii, Mamoru; Nguyen, Trang T.; Ogawa, Tadahiko; Nishioka, Michi

2016-11-01

There is considerable evidence that plasma structure in nighttime equatorial F layer develops from large-scale wave structure (LSWS) in bottomside F layer. However, crucial details of how this process proceeds, from LSWS to equatorial plasma bubbles (EPBs), remain to be sorted out. A major obstacle to success is the paucity of measurements that provide a space-time description of the bottomside F layer over a broad geographical region. The transequatorial propagation (TEP) experiment is one of few methods that can do so. New findings using a TEP experiment, between Shepparton (SHP), Australia, and Oarai (ORI), Japan, are presented in two companion papers. In Paper 1 (P1), (1) off-great-circle (OGC) paths are described in terms of discrete and diffuse types, (2) descriptions of OGC paths are generalized from a single-reflection to a multiple-reflection process, and (3) discrete type is shown to be associated with an unstructured but distorted upwelling, whereas the diffuse type is shown to be associated with EPBs. In Paper 2 (P2), attention is placed on differences in east-west (EW) asymmetry, found between OGC paths from the SHP-ORI experiment and those from another near-identical TEP experiment. Differences are reconciled by allowing three distinct sources for the EW asymmetries: (1) reflection properties within an upwelling (see P1), (2) OGC paths that depend on magnetic declination of geomagnetic field (B), and (3) OGC paths supported by non-B-aligned reflectors at latitudes where inclination of B is finite.

Efficient triple helix formation by oligodeoxyribonucleotides containing alpha- or beta-2-amino-5-(2-deoxy-D-ribofuranosyl) pyridine residues.

PubMed

Bates, P J; Laughton, C A; Jenkins, T C; Capaldi, D C; Roselt, P D; Reese, C B; Neidle, S

1996-11-01

Triple helices containing C+xGxC triplets are destabilised at physiological pH due to the requirement for base protonation of 2'-deoxycytidine (dC), which has a pKa of 4.3. The C nucleoside 2-amino-5-(2'-deoxy-beta-D-ribofuranosyl)pyridine (beta-AP) is structurally analogous to dC but is considerably more basic, with a pKa of 5.93. We have synthesised 5'-psoralen linked oligodeoxyribonucleotides (ODNs) containing thymidine (dT) and either beta-AP or its alpha-anomer (alpha-AP) and have assessed their ability to form triplexes with a double-stranded target derived from standard deoxynucleotides (i.e. beta-anomers). Third strand ODNs derived from dT and beta-AP were found to have considerably higher binding affinities for the target than the corresponding ODNs derived from dT and either dC or 5-methyl-2'-deoxycytidine (5-Me-dC). ODNs containing dT and alpha-AP also showed enhanced triplex formation with the duplex target and, in addition are more stable in serum-containing medium than standard oligopyrimidine-derived ODNs or ODNs derived from dT and beta-AP. Molecular modelling studies showed that an alpha-anomeric AP nucleotide can be accommodated within an otherwise beta-anomeric triplex with only minor perturbation of the triplex structure. Molecular dynamics (MD) simulations on triplexes containing either the alpha- or beta-anomer of (N1-protonated) AP showed that in both cases the base retained two standard hydrogen bonds to its associated guanine when the 'A-type' model of the triplex was used as the start-point for the simulation, but that bifurcated hydrogen bonds resulted when the alternative 'B-type' triplex model was used. The lack of a differential stability between alpha-AP- and beta-AP-containing triplexes at pH >7, predicted from the behaviour of the B-type models, suggests that the A-type models are more appropriate.

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu 3–xSe 2

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

Rettie, Alexander J. E.; Sturza, Mihai; Malliakas, Christos D.

The two-dimensional material KCu 3–xSe 2 was synthesized using both a K 2Se 3 flux and directly from the elements. It crystallizes in the CsAg 3S 2 structure (monoclinic space group C2/m with a = 15.417(3) Å, b = 4.0742(8) Å, c = 8.3190(17) Å, and β = 112.94(3)°), and single-crystal refinement revealed infinite copper-deficient [Cu 3–xSe 2]– layers separated by K + ions. Thermal analysis indicated that KCu 3–xSe 2 melts congruently at ~755 °C. UV–vis spectroscopy showed an optical band gap of ~1.35 eV that is direct in nature, as confirmed by electronic structure calculations. Electronic transport measurementsmore » on single crystals yielded an in-plane resistivity of ~6 × 10 –1 Ω cm at 300 K that has a complex temperature dependence. The results of Seebeck coefficient measurements were consistent with a doped p-type semiconductor (S = +214 μV K –1 at 300 K), with doping being attributed to copper vacancies. Transport is dominated by low-mobility (on the order of 1 cm 2 V –1 s –1) holes caused by relatively flat valence bands with substantial Cu 3d character and a significant concentration of Cu ion vacancy defects (p ~ 10 19 cm –3) in this material. In conclusion, electronic band structure calculations showed that electrons should be significantly more mobile in this structure type.« less

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu 3–xSe 2

DOE PAGES

Rettie, Alexander J. E.; Sturza, Mihai; Malliakas, Christos D.; ...

2017-06-21

The two-dimensional material KCu 3–xSe 2 was synthesized using both a K 2Se 3 flux and directly from the elements. It crystallizes in the CsAg 3S 2 structure (monoclinic space group C2/m with a = 15.417(3) Å, b = 4.0742(8) Å, c = 8.3190(17) Å, and β = 112.94(3)°), and single-crystal refinement revealed infinite copper-deficient [Cu 3–xSe 2]– layers separated by K + ions. Thermal analysis indicated that KCu 3–xSe 2 melts congruently at ~755 °C. UV–vis spectroscopy showed an optical band gap of ~1.35 eV that is direct in nature, as confirmed by electronic structure calculations. Electronic transport measurementsmore » on single crystals yielded an in-plane resistivity of ~6 × 10 –1 Ω cm at 300 K that has a complex temperature dependence. The results of Seebeck coefficient measurements were consistent with a doped p-type semiconductor (S = +214 μV K –1 at 300 K), with doping being attributed to copper vacancies. Transport is dominated by low-mobility (on the order of 1 cm 2 V –1 s –1) holes caused by relatively flat valence bands with substantial Cu 3d character and a significant concentration of Cu ion vacancy defects (p ~ 10 19 cm –3) in this material. In conclusion, electronic band structure calculations showed that electrons should be significantly more mobile in this structure type.« less

Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structures

NASA Technical Reports Server (NTRS)

Chatterjee, B.; Ringel, S. A.; Hoffman, R., Jr.

1995-01-01

High-efficiency, heteroepitaxial (HE) InP solar cells, grown on GaAs, Si or Ge substrates, are desirable for their mechanically strong, light-weight and radiation-hard properties. However, dislocations, caused by lattice mismatch, currently limit the performance of the HE cells. This occurs through shunting paths across the active photovoltaic junction and by the formation of deep levels. In previous work we have demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of dislocations in specially designed HE InP test structures. In this work, we present the first report of successful hydrogen passivation in actual InP cell structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). We have found that a 2 hour exposure to a 13.56 MHz hydrogen plasma at 275 C reduces the deep level concentration in HE n+n InP cell structures from as-grown values of approximately 10(exp 15)/cm(exp -3), down to 1-2 x 10(exp 13)/cm(exp -3). The deep levels in the p-type base region of the cell structure match those of our earlier p-type test structures, which were attributed to dislocations or related point defect complexes. All dopants were successfully reactivated by a 400 C, 5 minute anneal with no detectable activation of deep levels. I-V analysis indicated a subsequent approximately 10 fold decrease in reverse leakage current at -1 volt reverse bias, and no change in the forward biased series resistance of the cell structure which indicates complete reactivation of the n+ emitter. Furthermore, electrochemical C-V profiling indicates greatly enhanced passivation depth, and hence hydrogen diffusion, for heteroepitaxial structures when compared with identically processed homoepitaxial n+p InP structures. An analysis of hydrogen diffusion in dislocated InP will be discussed, along with comparisons of passivation effectiveness for n+p versus p+n heteroepitaxial cell configurations. Preliminary hydrogen-passivated HE InP cell results will also be presented.

Structural analysis of a class III preQ 1 riboswitch reveals an aptamer distant from a ribosome-binding site regulated by fast dynamics

DOE PAGES

Liberman, Joseph A.; Suddala, Krishna C.; Aytenfisu, Asaminew; ...

2015-06-23

PreQ 1-III riboswitches are newly identified RNA elements that control bacterial genes in response to preQ 1 (7-aminomethyl-7-deazaguanine), a precursor to the essential hypermodified tRNA base queuosine. Although numerous riboswitches fold as H-type or HL out-type pseudoknots that integrate ligand-binding and regulatory sequences within a single folded domain, the preQ 1-III riboswitch aptamer forms a HL out-type pseudoknot that does not appear to incorporate its ribosome-binding site (RBS). To understand how this unusual organization confers function, in this paper we determined the crystal structure of the class III preQ 1 riboswitch from Faecalibacterium prausnitzii at 2.75 Å resolution. PreQ 1more » binds tightly (K D,app 6.5 ± 0.5 nM) between helices P1 and P2 of a three-way helical junction wherein the third helix, P4, projects orthogonally from the ligand-binding pocket, exposing its stem-loop to base pair with the 3' RBS. Biochemical analysis, computational modeling, and single-molecule FRET imaging demonstrated that preQ 1 enhances P4 reorientation toward P1–P2, promoting a partially nested, H-type pseudoknot in which the RBS undergoes rapid docking (k dock ~0.6 s -1) and undocking (k undock ~1.1 s -1). Finally, discovery of such dynamic conformational switching provides insight into how a riboswitch with bipartite architecture uses dynamics to modulate expression platform accessibility, thus expanding the known repertoire of gene control strategies used by regulatory RNAs.« less

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

Leenheer, J.A.; Brown, G.K.; Cabaniss, S.E.

Fulvic acid, isolated from the Suwannee River, Georgia, was assessed for its ability to bind Ca{sup 2+}, Cd{sup 2+}, Cu{sup 2+}, Ni{sup 2+}, and Zn{sup 2+} ions at pH 6 before and after extensive fractionation that was designed to reveal the nature of metal binding functional groups. The binding constant for Ca{sup 2+} ion had the greatest increase of all the ions in a metal binding fraction that was selected for intensive characterization for the purpose of building quantitative average model structures. The metal binding fraction was characterized by quantitative {sup 13}C NMR, {sup 1}H NMR, and FT-IR spectrometry andmore » elemental, titrimetric, and molecular weight determinations. The characterization data revealed that carboxyl groups were clustered in short-chain aliphatic dibasic acid structures. The Ca{sup 2+} binding data suggested that ether-substituted oxysuccinic acid structures are good models for the metal binding sites at pH 6. Structural models were derived based upon oxidation and photolytic rearrangements of cutin, lignin, and tannin precursors. These structural models rich in substituted dibasic acid structures revealed polydentate binding sites with the potential for both inner-sphere and outer-sphere type binding. The majority of the fulvic acid molecule was involved with metal binding rather than a small substructural unit.« less

Utilizing Co 2+/Co 3+ Redox Couple in P2-Layered Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 Cathode for Sodium-Ion Batteries

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

Wang, Qin-Chao; Hu, Enyuan; Pan, Yang

Developing sodium-ion batteries for large-scale energy storage applications is facing big challenges of the lack of high-performance cathode materials. Here, a series of new cathode materials Na 0.66Co xMn 0.66–xTi 0.34O 2 for sodium-ion batteries are designed and synthesized aiming to reduce transition metal-ion ordering, charge ordering, as well as Na+ and vacancy ordering. An interesting structure change of Na 0.66Co xMn 0.66–xTi 0.34O 2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 with a P2-type layered structure delivers a reversible capacity of 120more » mAh g -1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g -1 can still be obtained, indicating a promising rate capability. The low valence Co 2+ substitution results in the formation of average Mn 3.7+ valence state in Na 0.66Co 0.22Mn 0.44Ti 0.34O 2, effectively suppressing the Mn3+-induced Jahn–Teller distortion, and in turn stabilizing the layered structure. X-ray absorption spectroscopy results suggest that the charge compensation of Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 during charge/discharge is contributed by Co 2.2+/Co 3+ and Mn 3.3+/Mn 4+ redox couples. This is the first time that the highly reversible Co 2+/Co 3+ redox couple is observed in P2-layered cathodes for sodium-ion batteries. This finding may open new approaches to design advanced intercalation-type cathode materials.« less