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Sample records for 3c-6h polytypic transition

  1. Polytypism in superhard transition-metal triborides

    PubMed Central

    Liang, Yongcheng; Yang, Jiong; Yuan, Xun; Qiu, Wujie; Zhong, Zheng; Yang, Jihui; Zhang, Wenqing

    2014-01-01

    The quest of novel compounds with special structures and unusual functionalities continues to be a central challenge to modern materials science. Even though their exact structures have puzzled scientists for decades, superhard transition-metal borides (TMBs) have long been believed to exist only in simple crystal structures. Here, we report on a polytypic phenomenon in superhard WB3 and MoB3 with a series of energetically degenerate structures due to the random stacking of metal layers amongst the interlocking boron layers. Such polytypism can create a multiphase solid-solution compound with a large number of interfaces amongst different polytypes, and these interfaces will strongly hinder the interlayer sliding movement within each polytype, thereby further increase the hardness of this particular material. Furthermore, in contrast to the conventional knowledge that intrinsically strong chemical bonds in superhard materials should lead to high lattice thermal conductivity, the polytypic TMB3 manifest anomalously low lattice thermal conductivity due to structural disorders and phonon folding. These findings promise to open a new avenue to searching for novel superhard materials with additional functionalities. PMID:24863493

  2. Trisodium citrate, Na3(C6H5O7)

    PubMed Central

    Rammohan, Alagappa; Kaduk, James A.

    2016-01-01

    The crystal structure of anhydrous tris­odium citrate, Na3(C6H5O7), has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory (DFT). There are two independent five-coordinate Na+ and one six-coordinate Na+ cations in the asymmetric unit. The [NaO5] and [NaO6] polyhedra share edges and corners to form a three-dimensional framework. There are channels parallel to the a and b axes in which the remainder of the citrate anions reside. The only hydrogen bonds are an intra­molecular one between the hy­droxy group and one of the terminal carboxyl­ate O atoms and an intermolecular one between a methylene group and the hydroxyl O atom. PMID:27308044

  3. Vapor-Liquid Equilibrium in the Mixture Trichloromethane CHCl3 + C6H10O Cyclohexanone (EVLM1111, LB5654_E)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume A 'Binary Liquid Systems of Nonelectrolytes I' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Vapor-Liquid Equilibrium in the Mixture Trichloromethane CHCl3 + C6H10O Cyclohexanone (EVLM1111, LB5654_E)' providing data from direct measurement of pressure at variable mole fraction in liquid phase and constant temperature.

  4. Heat of Mixing and Solution of 1,1,2-Trichloroethane C2H3Cl3 + C6H10O Cyclohexanone (HMSD1111, LB3665_H)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume C 'Binary Liquid Systems of Nonelectrolytes III' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'heat of Mixing and Solution of 1,1,2-Trichloroethane C2H3Cl3 + C6H10O Cyclohexanone (HMSD1111, LB3665_H)' providing data from direct low-pressure calorimetric measurement of molar excess enthalpy at variable mole fraction and constant temperature.

  5. Heat of Mixing and Solution of 1,1,1-Trichloroethane C2H3Cl3 + C6H10O Cyclohexanone (HMSD1111, LB3664_H)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume C 'Binary Liquid Systems of Nonelectrolytes III' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'heat of Mixing and Solution of 1,1,1-Trichloroethane C2H3Cl3 + C6H10O Cyclohexanone (HMSD1111, LB3664_H)' providing data from direct low-pressure calorimetric measurement of molar excess enthalpy at variable mole fraction and constant temperature.

  6. Connecting modes of linking ligands containing different terminal groups (pyridyl-amine or pyridyl-pyridyl): Preparation and structures of {[Cd( L1) 2(OH 2) 2]·(ClO 4) 2·(C 6H 6)} ∞, {[Cd( L2) 2(ClO 4) 2]·(CH 3OH) 2} ∞, {[Cd( L3) 2(OH 2) 2]·(ClO 4) 2} ∞, and [Cd( L4) 2(CH 3OH) 2(ClO 4) 2] {( m-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-NH 2 ( m = 3 ( L1) or 4 ( L2)); ( n-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-N dbnd CH-( n-py); ( n = 3 ( L3) or 4 ( L4))}

    NASA Astrophysics Data System (ADS)

    Yun, Sung Yol; Lee, Kyung-Eun; Lee, Soon W.

    2009-10-01

    We prepared four potential linking ligands, [(3-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-NH 2, L1], [(4-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-NH 2, L2], [(3-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-N dbnd CH-(3-py), L3], and [(4-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-N dbnd CH-(4-py), L4], all of which contain an intervening biphenyl fragment. Whereas ligands L1 and L2 have two types of terminal groups (pyridyl-amine), ligands L3 and L4 have a single type of terminal groups (pyridyl-pyridyl). Ligands L1- L4 reacted with cadmium nitrate to produce {[Cd( L1) 2(OH 2) 2]·(ClO 4) 2·(C 6H 6)} ∞ ( 1), {[Cd( L2) 2(ClO 4) 2]·(CH 3OH) 2} ∞ ( 2), {[Cd( L3) 2(OH 2) 2]·(ClO 4) 2} ∞ ( 3), and [Cd( L4) 2(CH 3OH) 2(ClO 4) 2] ( 4), respectively. Whereas compounds 1- 3 are 1-dimensional coordination polymers, compound 4 is a discrete molecular species.

  7. Insights into Hydrocarbon Chain and Aromatic Ring Formation in the Interstellar Medium: Computational Study of the Isomers of C4H3+ C6H3+ and C6H5+ and Their Formation Pathways

    NASA Astrophysics Data System (ADS)

    Peverati, Roberto; Bera, Partha P.; Lee, Timothy J.; Head-Gordon, Martin

    2016-10-01

    Small hydrocarbons such as acetylene is present in circumstellar envelopes of carbon-rich stars, but the processes that yield larger molecules, and eventually polycyclic aromatic hydrocarbons (PAHs), remain poorly understood. To gain additional insight into the early steps of such processes, electronic structure calculations were performed on the potential energy surfaces of {{{C}}}4{{{{H}}}3}+, {{{C}}}6{{{{H}}}3}+ and {{{C}}}6{{{{H}}}5}+. The results establish reactive pathways from acetylene and its ion to formation of the first aromatic ring. We characterize the stable isomers, their spectroscopic properties, and many of the transition structures that represent barriers to isomerization. The pathways to stabilized {{{C}}}4{{{{H}}}3}+ and {{{C}}}6{{{{H}}}3}+ are most likely to arise from unimolecular decomposition of hot {{{C}}}4{{{{H}}}4}+ and {{{C}}}6{{{{H}}}4}+ by H atom elimination. By contrast, we found an ion-molecule pathway to {{{C}}}6{{{{H}}}5}+ to be very stable to fragmentation and elimination reactions even without collisional stabilization. This aromatic species is a good nucleation center for the growth of larger PAHs in interstellar conditions.

  8. Effect of symmetry reduction on the electronic transitions in polytypic GdAl3(BO3)4:Eu:Tb crystals

    NASA Astrophysics Data System (ADS)

    Lengyel, K.; Beregi, E.; Földvári, I.; Corradi, G.; Kovács, L.; Solarz, P.; Ryba-Romanowski, W.

    2016-03-01

    The existence of a recently described monoclinic phase (C2/c, Z = 8) (Beregi et al., 2012) in addition to the well-known Huntite type rhombohedral (R32) polytypic modification of the GdAl3(BO3)4 (GAB) crystal at room temperature provides a unique possibility to investigate the incorporation of rare earth dopants into slightly modified crystal lattice by spectroscopic methods. In these characteristic GAB structures the dopant ions, e.g. Tb3+ or Eu3+, possess slightly different neighbor geometries and local symmetries. The Tb3+: 7F6 → 5D4 and Eu3+: 7F0,1,2 → 5D0,1,2 electronic transitions were successfully identified in the absorption spectra using polarization, concentration and temperature dependent measurements in both polytypic modifications. The positions of the investigated Tb lines are shifted by up to 10 cm-1 due to symmetry changes. In addition, some of the Eu lines show splittings of about 4-30 cm-1 as a consequence of the change of the local environment. From the room temperature absorption measurements some of the low energy crystal field levels of 7F and 5D states of the Eu3+ ions were successfully determined for both modifications.

  9. Crystal structure, DSC and Raman studies in CH 3C 6H 4NH(CH 3) 2·SbCl 4

    NASA Astrophysics Data System (ADS)

    Chaabouni, Slaheddine; Hadrich, Ahmed; Romain, François; Ben Salah, Abdelhamid

    2003-07-01

    The salt para methyl phenyl dimethyl ammonium tetrachloroantimonate (III) crystallizes in the monoclinic system with space group Cc. The unit cell dimensions are: a=13.780(1) Å, b=14.943(2) Å, c=8.192(1) Å, β=113.39(1)°, with Z=4. The structure consists of ammonium cations and polynuclear anions in which distorted SbCl 5 square pyramids sharing a common Cl atom are held together in infinite chains parallel to the c axis. These chains are themselves interconnected by means of the NH⋯Cl hydrogen bonds. Differential scanning calorimetry study was carried out. The Raman of polycrystalline samples have been recorded at different temperatures between 77 and 300 K. A low-temperature phase transition at 230 K of order-disorder type was found.

  10. Vapor-Liquid Equilibrium in the Mixture 1,1,1-Trichloroethane C2H3Cl3 + C6H10O Cyclohexanone (EVLM1111, LB5638_E)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume C 'Binary Liquid Systems of Nonelectrolytes III' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'vapor-Liquid Equilibrium in the Mixture 1,1,1-Trichloroethane C2H3Cl3 + C6H10O Cyclohexanone (EVLM1111, LB5638_E)' providing data from direct measurement of pressure at variable mole fraction in liquid phase and constant temperature.

  11. Volumetric Properties of the Mixture Dimethyl carbonate C3H6O3 + C6H12O3 2,4,6-Trimethyl-1,3,5-trioxane (VMSD1111, LB4518_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume C 'Binary Liquid Systems of Nonelectrolytes III' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Dimethyl carbonate C3H6O3 + C6H12O3 2,4,6-Trimethyl-1,3,5-trioxane (VMSD1111, LB4518_V)' providing data from direct low-pressure measurement of mass density at variable mole fraction and constant temperature, in the single-phase region(s).

  12. Volumetric Properties of the Mixture Dimethyl carbonate C3H6O3 + C6H12O3 2,4,6-Trimethyl-1,3,5-trioxane (VMSD1212, LB4519_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume C 'Binary Liquid Systems of Nonelectrolytes III' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Dimethyl carbonate C3H6O3 + C6H12O3 2,4,6-Trimethyl-1,3,5-trioxane (VMSD1212, LB4519_V)' providing data by calculation of molar excess volume from low-pressure density measurements at variable mole fraction and constant temperature.

  13. Volumetric Properties of the Mixture Dimethyl carbonate C3H6O3 + C6H12O3 2,4,6-Trimethyl-1,3,5-trioxane (VMSD1511, LB4517_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume C 'Binary Liquid Systems of Nonelectrolytes III' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Dimethyl carbonate C3H6O3 + C6H12O3 2,4,6-Trimethyl-1,3,5-trioxane (VMSD1511, LB4517_V)' providing data from direct measurement of low-pressure thermodynamic speed of sound at variable mole fraction and constant temperature, in the single-phase region(s).

  14. Static and dynamic interaction between π and d electrons in organic superconductor β″-(BEDT-TTF)4[(H3O ) Fe (C2O4)3] .C6H5Br studied by 13C NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Ihara, Y.; Futami, Y.; Kawamoto, A.; Matsui, K.; Goto, T.; Sasaki, T.; Benmansour, S.; Gómez-García, C. J.

    2016-08-01

    We present the results of 13C NMR experiments in an organic superconductor with localized Fe spins β″-(BEDT-TTF) 4[(H3O ) Fe (C2O4)3] .C6H5Br . We reveal the antiferromagnetic coupling between Fe d spins and π spins, which creates an exchange field antiparallel to the external field direction at the π electrons. In addition to the static effects of Fe spins, we show from the nuclear spin-lattice relaxation rate measurement that the magnetic fluctuations generated by Fe spins are suppressed at low temperatures and high magnetic fields. These conditions are suitable to stabilize the field-induced superconductivity by the field compensation mechanism. After the suppression of Fe-spin dynamics by a magnetic field of 19 T, we observed the underlying π -electron contribution. We discuss a possible anomaly in the π -electron system.

  15. Synthesis, crystal structure, thermal analysis and vibrational spectroscopy accomplished with DFT calculation of new hybrid compound [2-CH3C6H4NH3]HSO4.H2O

    NASA Astrophysics Data System (ADS)

    Ben Hassen, C.; Boujelbene, M.; Marweni, S.; Bahri, M.; Mhiri, T.

    2015-10-01

    The present paper undertakes the study of a new organic/inorganic hybrid compound [2-CH3C6H4NH3]HSO4.H2O characterized by the X-ray diffraction, TG-DTA, IR and Raman spectroscopy accomplished with DFT calculation. It is crystallized in the monoclinic system with the centrosymmetric space group P 21/c, with a = 9.445 (5) Å, b = 10.499 Å, c = 10.073 Å, β = 90.627 (5)° and Z = 4. The atomic arrangement can be described as inorganic layers built by infinite chains, parallel to the (a c) planes between which the organic cations are inserted. In this atomic arrangement, hydrogen bonds and π-π interactions between the different species have an important role in the tri-dimensional network cohesion. Besides, the X-ray powder diffraction of the title compound confirms the existence of only one phase at room temperature. The thermal decomposition of precursors studied by thermo gravimetric analysis (TGA), the differential thermal analysis (DTA) and the temperature-dependent X-ray diffraction, show crystalline anhydrous compounds upon dehydration. DFT/BHHLYP calculations were performed, using the DZV (d,p) basis set, to determine the harmonic frequencies of the vibrational modes of an optimized cluster structure. The calculated modes were animated using the Molden graphical package to give tentative assignments of the observed IR and Raman spectra.

  16. Synthesis, structural characterization, electrical properties and antioxidant activity of [p-(NH3)C6H4NH3]3P6O18·6H2O

    NASA Astrophysics Data System (ADS)

    Fezai, Ramzi; Mezni, Ali; Kahlaoui, Messaoud; Rzaigui, Mohamed

    2016-09-01

    Single crystals of a novel organic cyclohexaphosphate, [p-(NH3)C6H4NH3]3P6O18.6H2O, have been prepared in aqueous solution. Its crystal structure can be described by a three-dimensional framework where the P6O186- rings are interconnected by hydrogen bonds to form anionic layers between which organic cations are located. Hydrogen bonding network connecting the different components is given. The thermal stability and spectroscopic properties of this material are given too. Its DC and AC electrical conductivities, modulus analysis and dielectric constants have been investigated. The AC conductivity is found to obey the universal power law. The DC electrical conductivity indicates a semiconductor behavior. The kind of the observed conduction is protonic by translocation. X-rays structural and electrical results are correlated. This compound has also been screened for its antioxidant activity, determined in vitro, using 1,1-diphenyl-2-picrylhydrazyl, reducing power, hydroxyl scavenging ability and ferrous ion chelating (FIC) methods and with ascorbic acid as reference.

  17. Linearly arranged polytypic CZTSSe nanocrystals

    PubMed Central

    Fan, Feng-Jia; Wu, Liang; Gong, Ming; Chen, Shi You; Liu, Guang Yao; Yao, Hong-Bin; Liang, Hai-Wei; Wang, Yi-Xiu; Yu, Shu-Hong

    2012-01-01

    Even colloidal polytypic nanostructures show promising future in band-gap tuning and alignment, researches on them have been much less reported than the standard nano-heterostructures because of the difficulties involved in synthesis. Up to now, controlled synthesis of colloidal polytypic nanocrsytals has been only realized in II-VI tetrapod and octopod nanocrystals with branched configurations. Herein, we report a colloidal approach for synthesizing non-branched but linearly arranged polytypic I2-II-IV-VI4 nanocrystals, with a focus on polytypic non-stoichiometric Cu2ZnSnSxSe4−x nanocrystals. Each synthesized polytypic non-stoichiometric Cu2ZnSnSxSe4−x nanocrystal is consisted of two zinc blende-derived ends and one wurtzite-derived center part. The formation mechanism has been studied and the phase composition can be tuned through adjusting the reaction temperature, which brings a new band-gap tuning approach to Cu2ZnSnSxSe4-x nanocrystals. PMID:23233871

  18. Instability of metal 1,3-benzodi(thiophosphinoyl)methandiide complexes: formation of hafnium, tin and zirconium complexes of 1,3-benzodi(thiophosphinoyl)thioketone dianionic ligand [1,3-C6H4(PhPS)2CS](2(-)).

    PubMed

    Yang, Ya-Xiu; Li, Yongxin; Ganguly, Rakesh; So, Cheuk-Wai

    2015-07-28

    The reaction of [LCH2] (1, L = 1,3-C6H4(PhPS)2) and M(NMe2)4 (M = Hf, Zr) in toluene at 110 °C afforded a mixture of group 4 metal complexes [{LC(S)}2M] [M = Hf (2), Zr (3)] and [1,3-C6H4(PhPS)(PhP)CH2]. The reactions appear to proceed through the formation of metal bis(carbene) complexes, [LC=M=CL], which then undergo an intermolecular sulphur transfer reaction with the P=S bond of [LCH2] to form 2 and 3, and the byproduct is [1,3-C6H4(PhPS)(PhP)CH2]. In addition, the reaction of 1, [CH2(PPh2S)2] (4) and M(NMe2)4 in refluxing toluene gave a mixture of [{LC(S)}M(NHMe2){C(PPh2S)2}] [M = Hf (5), Zr (6)], [1,3-C6H4(PhPS)(PhP)CH2] and [CH2(PPh2S)(PPh2)]. Moreover, the intermolecular sulfur transfer reaction is evidenced by the reaction of the tin(ii) 1,3-benzodi(thiophosphinoyl)methandiide complex [{μ-1,3-C6H4(PhPS)2C}Sn]2 (7) with two equivalents of elemental sulfur in CH2Cl2 at ambient temperature to give [{1,3-C6H4(PhPS)2CS}2Sn] (8). Compounds 2, 3, 5, 6, and 8 were characterized by NMR spectroscopy and X-ray crystallography.

  19. Mica polytypes: Systematic description and identification

    USGS Publications Warehouse

    Ross, M.; Takeda, H.; Wones, D.R.

    1966-01-01

    X-ray studies of mica specimens from a variety of geological localities show that biotite and certain lithium-rich mica samples are composed of a mixture of different polytypes. Many of the biotite structures are new complex polytypes not before reported. A new method of designating mica polytypes is proposed. Techniques are described for the systematic generation of all the possible layer-stacking sequences of mica polytypes and for the verification of the stacking sequences in newly discovered forms.

  20. Classification of polytype structures of zinc sulfide

    SciTech Connect

    Laptev, V.I.

    1994-12-31

    It is suggested that the existing classification of polytype structures of zinc sulfide be supplemented with an additional criterion: the characteristic of regular point systems (Wyckoff positions) including their type, number, and multiplicity. The consideration of the Wyckoff positions allowed the establishment of construction principles of known polytype series of different symmetries and the systematization (for the first time) of the polytypes with the same number of differently packed layers. the classification suggested for polytype structures of zinc sulfide is compact and provides a basis for creating search systems. The classification table obtained can also be used for numerous silicon carbide polytypes. 8 refs., 4 tabs.

  1. Polytypism, polymorphism, and superconductivity in TaSe2–xTex

    DOE PAGES

    Luo, Huixia; Xie, Weiwei; Tao, Jing; Inoue, Hiroyuki; Gyenis, András; Krizan, Jason W.; Yazdani, Ali; Zhu, Yimei; Cava, Robert Joseph

    2015-03-03

    Polymorphism in materials often leads to significantly different physical properties - the rutile and anatase polymorphs of TiO₂ are a prime example. Polytypism is a special type of polymorphism, occurring in layered materials when the geometry of a repeating structural layer is maintained but the layer stacking sequence of the overall crystal structure can be varied; SiC is an example of a material with many polytypes. Although polymorphs can have radically different physical properties, it is much rarer for polytypism to impact physical properties in a dramatic fashion. Here we study the effects of polytypism and polymorphism on the superconductivitymore » of TaSe₂, one of the archetypal members of the large family of layered dichalcogenides. We show that it is possible to access 2 stable polytypes and 2 stable polymorphs in the TaSe2-xTex solid solution, and find that the 3R polytype shows a superconducting transition temperature that is between 6 and 17 times higher than that of the much more commonly found 2H polytype. Thus, the reason for this dramatic change is not apparent, but we propose that it arises either from a remarkable dependence of Tc on subtle differences in the characteristics of the single layers present, or from a surprising effect of the layer stacking sequence on electronic properties that instead are expected to be dominated by the properties of a single layer in materials of this kind.« less

  2. Distribution of mica polytypes among space groups.

    NASA Technical Reports Server (NTRS)

    Takeda, H.

    1971-01-01

    All the possible space groups for mica polytypes are deduced by making use of the characteristics of the mica unit layer and stacking mode. The algebraic properties of the vector-stacking symbol of Ross et al. (1966) are examined, and a simple algorithm for deducing the space group from this symbol is presented. A method considered for enumerating all possible stacking sequences of mica polytypes makes use of a computer.

  3. Polytypism, polymorphism, and superconductivity in TaSe2–xTex

    SciTech Connect

    Luo, Huixia; Xie, Weiwei; Tao, Jing; Inoue, Hiroyuki; Gyenis, András; Krizan, Jason W.; Yazdani, Ali; Zhu, Yimei; Cava, Robert Joseph

    2015-03-03

    Polymorphism in materials often leads to significantly different physical properties - the rutile and anatase polymorphs of TiO₂ are a prime example. Polytypism is a special type of polymorphism, occurring in layered materials when the geometry of a repeating structural layer is maintained but the layer stacking sequence of the overall crystal structure can be varied; SiC is an example of a material with many polytypes. Although polymorphs can have radically different physical properties, it is much rarer for polytypism to impact physical properties in a dramatic fashion. Here we study the effects of polytypism and polymorphism on the superconductivity of TaSe₂, one of the archetypal members of the large family of layered dichalcogenides. We show that it is possible to access 2 stable polytypes and 2 stable polymorphs in the TaSe2-xTex solid solution, and find that the 3R polytype shows a superconducting transition temperature that is between 6 and 17 times higher than that of the much more commonly found 2H polytype. Thus, the reason for this dramatic change is not apparent, but we propose that it arises either from a remarkable dependence of Tc on subtle differences in the characteristics of the single layers present, or from a surprising effect of the layer stacking sequence on electronic properties that instead are expected to be dominated by the properties of a single layer in materials of this kind.

  4. Polytypism and mixed layering in minerals

    NASA Astrophysics Data System (ADS)

    de Villiers, J. P. R.

    Polytypes are stacking variations that occur in crystals, forming periodic extended defects, without changing the overall composition. Mineral examples are the different polytypes of micas, kaolinite, talc, graphite. None of the theories that have been proposed to explain the occurrence of short and long period superstructures have met with universal success in explaining their occurrences. Polysomatism is defined as the stacking of compositionally different modules, similar to polytypism. Minerals belonging to a polysomatic series have compositions that are linear combinations of the end members. Structures derived from the bixbyite (Mn2O3) structure are used as examples of a polysomatic series and a number of polysomes in single crystals have been described using HRTEM. The relative stabilities of different polysomes have been modelled with a lattice energy minimization programme. The results show that certain polysomes are significantly more stable than others, and that the contribution of next-nearest neighbour interactions seems to be an important factor in determining polysome stability.

  5. Raman Signatures of Polytypism in Molybdenum Disulfide.

    PubMed

    Lee, Jae-Ung; Kim, Kangwon; Han, Songhee; Ryu, Gyeong Hee; Lee, Zonghoon; Cheong, Hyeonsik

    2016-02-23

    Since the stacking order sensitively affects various physical properties of layered materials, accurate determination of the stacking order is important for studying the basic properties of these materials as well as for device applications. Because 2H-molybdenum disulfide (MoS2) is most common in nature, most studies so far have focused on 2H-MoS2. However, we found that the 2H, 3R, and mixed stacking sequences exist in few-layer MoS2 exfoliated from natural molybdenite crystals. The crystal structures are confirmed by HR-TEM measurements. The Raman signatures of different polytypes are investigated by using three different excitation energies that are nonresonant and resonant with A and C excitons, respectively. The low-frequency breathing and shear modes show distinct differences for each polytype, whereas the high-frequency intralayer modes show little difference. For resonant excitations at 1.96 and 2.81 eV, distinct features are observed that enable determination of the stacking order.

  6. Raman Signatures of Polytypism in Molybdenum Disulfide.

    PubMed

    Lee, Jae-Ung; Kim, Kangwon; Han, Songhee; Ryu, Gyeong Hee; Lee, Zonghoon; Cheong, Hyeonsik

    2016-02-23

    Since the stacking order sensitively affects various physical properties of layered materials, accurate determination of the stacking order is important for studying the basic properties of these materials as well as for device applications. Because 2H-molybdenum disulfide (MoS2) is most common in nature, most studies so far have focused on 2H-MoS2. However, we found that the 2H, 3R, and mixed stacking sequences exist in few-layer MoS2 exfoliated from natural molybdenite crystals. The crystal structures are confirmed by HR-TEM measurements. The Raman signatures of different polytypes are investigated by using three different excitation energies that are nonresonant and resonant with A and C excitons, respectively. The low-frequency breathing and shear modes show distinct differences for each polytype, whereas the high-frequency intralayer modes show little difference. For resonant excitations at 1.96 and 2.81 eV, distinct features are observed that enable determination of the stacking order. PMID:26756836

  7. Copper thiocyanate: polytypes, defects, impurities, and surfaces.

    PubMed

    Tsetseris, Leonidas

    2016-07-27

    Copper thiocyanate (CuSCN) is an established solid state dye in solar cells and has emerged as a key material for applications in transparent conductors and solution-processed thin film transistors. Here we report the results of density-functional theory calculations on several fundamental properties related to the performance of CuSCN in the above-mentioned systems. We describe the structural and electronic properties of CuSCN phases and show that the material is prone to polytypism. We also perform a systematic study on various defects and hydrogen impurities and determine their effect on the electronic properties of the host system, particularly with respect to doping. Finally, we show that non-polar surfaces have low formation energies, suggesting easy cleavage along certain directions. PMID:27248787

  8. Coexistence of multiple metastable polytypes in rhombohedral bismuth

    PubMed Central

    Shu, Yu; Hu, Wentao; Liu, Zhongyuan; Shen, Guoyin; Xu, Bo; Zhao, Zhisheng; He, Julong; Wang, Yanbin; Tian, Yongjun; Yu, Dongli

    2016-01-01

    Derivative structural polytypes coexisting with the rhombohedral A7 structure of elemental bismuth (Bi) have been discovered at ambient condition, based on microstructure analyses of pure Bi samples treated under high pressure and high temperature conditions. Three structures with atomic positions close to those of the A7 structure have been identified through first-principles calculations, showing these polytypes energetically comparable to the A7 structure under ambient condition. Simulated diffraction data are in excellent agreement with the experimental observations. We argue that previously reported some variations of physical properties (e.g., density, electrical conductivity, and magnetism) in bismuth could be due to the formation of these polytypes. The coexistence of metastable derivative structural polytypes may be a widely occurring phenomenon in other elemental materials. PMID:26883895

  9. Epitaxial growth of hexagonal silicon polytypes on sapphire

    SciTech Connect

    Pavlov, D. A.; Pirogov, A. V. Krivulin, N. O.; Bobrov, A. I.

    2015-01-15

    The formation of a single-crystal silicon polytype is observed in silicon-on-sapphire structures by high-resolution transmission electron microscopy. The appearance of inclusions with a structure different from that of diamond is attributed to the formation of strong-twinning regions and the aggregation of stacking faults, which form their own crystal structure in the crystal lattice of silicon. It is demonstrated that the given modification belongs to the 9R silicon polytype.

  10. Polytype control of spin qubits in silicon carbide

    PubMed Central

    Falk, Abram L.; Buckley, Bob B.; Calusine, Greg; Koehl, William F.; Dobrovitski, Viatcheslav V.; Politi, Alberto; Zorman, Christian A.; Feng, Philip X.-L.; Awschalom, David D.

    2013-01-01

    Crystal defects can confine isolated electronic spins and are promising candidates for solid-state quantum information. Alongside research focusing on nitrogen-vacancy centres in diamond, an alternative strategy seeks to identify new spin systems with an expanded set of technological capabilities, a materials-driven approach that could ultimately lead to ‘designer’ spins with tailored properties. Here we show that the 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states, including states in all three with room-temperature quantum coherence. The prevalence of this spin coherence shows that crystal polymorphism can be a degree of freedom for engineering spin qubits. Long spin coherence times allow us to use double electron–electron resonance to measure magnetic dipole interactions between spin ensembles in inequivalent lattice sites of the same crystal. Together with the distinct optical and spin transition energies of such inequivalent states, these interactions provide a route to dipole-coupled networks of separately addressable spins. PMID:23652007

  11. Rhombohedral polytypes of the layered honeycomb delafossites with optical brilliance in the visible.

    PubMed

    Roudebush, John H; Sahasrabudhe, Girija; Bergman, Susanna L; Cava, R J

    2015-04-01

    We report the synthesis of the Delafossite honeycomb compounds Cu3Ni2SbO6 and Cu3Co2SbO6 via a copper topotactic reaction from the layered α-NaFeO2-like precursors Na3Ni2SbO6 and Na3Co2SbO6. The low-temperature exchange reaction exclusively produces the rhombahedral 3R polytype subcell, whereas only the hexagonal 2H polytype subcell has been made by conventional synthesis. The thus-synthesized 3R variants are visually striking; they are bright lime-green (Ni variant) and terracotta-orange (Co variant), while both of the conventionally synthesized 2H variants have a burnt-red color. The new structures are characterized by powder X-ray diffraction and Rietveld analysis as well as magnetic susceptibility, X-ray photoelectron spectroscopy (XPS), and diffuse-reflectance optical spectroscopy. Using thermogravimetric analysis, we identify a second order 3R → 2H phase transition as well as a first-order structural transition associated with rearrangement of the honeycomb stacking layers. The optical absorbance spectra of the samples show discrete edges that correlate well to their visual colors. Exposing Cu3Ni2SbO6 to O2 and heat causes the sample to change color. XPS confirms the presence of Cu(2+) in these samples, which implies that the difference in color between the polytypes is due to oxygen intercalation resulting from their different synthetic routes.

  12. Interband polarized absorption in InP polytypic superlattices

    SciTech Connect

    Faria Junior, P. E.; Sipahi, G. M.; Campos, T.

    2014-11-21

    Recent advances in growth techniques have allowed the fabrication of semiconductor nanostructures with mixed wurtzite/zinc-blende crystal phases. Although the optical characterization of these polytypic structures is well reported in the literature, a deeper theoretical understanding of how crystal phase mixing and quantum confinement change the output linear light polarization is still needed. In this paper, we theoretically investigate the mixing effects of wurtzite and zinc-blende phases on the interband absorption and in the degree of light polarization of an InP polytypic superlattice. We use a single 8 × 8 k⋅p Hamiltonian that describes both crystal phases. Quantum confinement is investigated by changing the size of the polytypic unit cell. We also include the optical confinement effect due to the dielectric mismatch between the superlattice and the vaccum and we show it to be necessary to match experimental results. Our calculations for large wurtzite concentrations and small quantum confinement explain the optical trends of recent photoluminescence excitation measurements. Furthermore, we find a high sensitivity to zinc-blende concentrations in the degree of linear polarization. This sensitivity can be reduced by increasing quantum confinement. In conclusion, our theoretical analysis provides an explanation for optical trends in InP polytypic superlattices, and shows that the interplay of crystal phase mixing and quantum confinement is an area worth exploring for light polarization engineering.

  13. Combinatorial approaches to understanding polytypism in III-V nanowires.

    PubMed

    Johansson, Jonas; Bolinsson, Jessica; Ek, Martin; Caroff, Philippe; Dick, Kimberly A

    2012-07-24

    Polytypism in III-V semiconductor nanowires is a topic that has received considerable attention in recent years. Achieving a pure nanowire crystal phase requires well-controlled and advanced parameter tuning for most III-V materials. Additionally, the new and unusual phases sometimes observed may present unique material properties if they can be controllably fabricated. With the prospect of using nanowires in applications within several different fields (including electronics, photonics, and life science), theoretical models are necessary to explain experimental trends and to attain a high level of crystal phase control. At present, there is no theoretical model (or combination of models) that fully explains how and why nanowire crystal structures commonly include several different polytypes. Here we use combinatorics and interlayer interactions to include higher order polytypes (4H and 6H) with the aim to explain nanowire crystal structure beyond the well-investigated zinc blende-wurtzite polytypism. Predictions from our theoretical models compare well with experimental results. PMID:22681568

  14. Second-harmonic generation in silicon carbide polytypes

    NASA Astrophysics Data System (ADS)

    Niedermeier, S.; Schillinger, H.; Sauerbrey, R.; Adolph, B.; Bechstedt, F.

    1999-08-01

    We report simultaneous measurements and ab initio calculations of the second-order nonlinear coefficients for SiC polytypes. Our measured values for χzzz (χzxx) are 18 (-4) pm/V for 4H SiC and 24 (-4) pm/V for 6H SiC. They are in good agreement with our theoretical results.

  15. Salt-free synthesis of samarium-aluminum mixed-metal alkoxides: X-ray crystal structures of [[(i-Pr-O)(i-Bu)Al(mu-O-i-Pr)(2)Sm(O-i-Pr)(HO-i-Pr)](mu-O-i-Pr)](2), [(THF)(2)Sm(O-t-Bu)(2)(mu-O-t-Bu)(2)Al(i-Bu)(2)], Sm(OAr)(3)(THF)(3) (Ar = 2,4,6-Me(3)C(6)H(2)), [Nd(mu-OAr)(OAr)(2)(py)(2)](2) (Ar = 2,4,6-Me(3)C(6)H(2)), and (ArO)(3)Sm[(mu-O-t-Bu)(2)Al(2)(O-t-Bu)(4)] (Ar = 2,6-i-Pr(2)C(6)H(3)).

    PubMed

    Giesbrecht, Garth R; Gordon, John C; Clark, David L; Scott, Brian L; Watkin, John G; Young, Kenneth J

    2002-12-01

    Reaction of equimolar quantities of Sm[N(SiMe(3))(2)](3) and Al(i-Bu)(3) with 6 equiv of iso-propyl alcohol in toluene leads to the formation of the mixed-metal alkoxide complex [[(i-Pr-O)(i-Bu)Al(mu-O-i-Pr)(2)Sm(O-i-Pr)(HO-i-Pr)](mu-O-i-Pr)](2) (1). An analogous reaction between 1:1 Sm[N(SiMe(3))(2)](3)/Al(i-Bu)(3) and 6 equiv of tert-butyl alcohol, followed by addition of THF, produces the THF adduct [(THF)(2)Sm(O-t-Bu)(2)(mu-O-t-Bu)(2)Al(i-Bu)(2)] (2). Compound 1 crystallizes in the space group P1 while 2 crystallizes in space group Cmcm. Cell parameters for 1: a = 11.028(2) A, b = 12.168(2) A, c = 12.879(2) A, alpha = 82.84(1) degrees, beta = 64.88(1) degrees, gamma = 70.80(1) degrees, Z = 1. Cell parameters for 2: a = 11.304(2) A, b = 22.429(4) A, c = 15.768(2) A, Z = 4. Attempts to prepare the bulkier derivatives result in the formation of lanthanide aryloxide species only; reaction between equimolar amounts of Ln[N(SiMe(3))(2)](3) (Ln = Sm, Nd) and Al(i-Bu)(3) with 6 equiv of HO-2,4,6-Me(3)C(6)H(2), followed by the addition of THF or pyridine, yields the Lewis base adducts Sm(OAr)(3)(THF)(3) (3) and [Nd(mu-OAr)(OAr)(2)(py)(2)](2) (4). Compound 3 crystallizes in the space group Pbca while 4 crystallizes in space group P2(1)/c. Cell parameters for 3: a = 16.5822(9) A, b = 15.5668(9) A, c = 29.902(2) A, Z = 8. Cell parameters for 4: a = 13.4496(8) A, b = 20.034(1) A, c = 16.206(1) A, beta = 113.782(1) degrees, Z = 2. Reaction of Al(2)(O-t-Bu)(6) with [Sm(OAr)(3)](2) (Ar = 2,6-i-Pr(2)C(6)H(3)) yields the adduct (ArO)(3)Sm[(mu-O-t-Bu)(2)Al(2)(O-t-Bu)(4)] (5), which crystallizes in the space group P2(1)/n. Cell parameters for 5: a = 14.0960(7) A, b = 27.3037(15) A, c = 16.7893(9) A, beta = 92.216(1) degrees, Z = 4. PMID:12444780

  16. Polytypic Nanocrystals of Cu-Based Ternary Chalcogenides: Colloidal Synthesis and Photoelectrochemical Properties.

    PubMed

    Wu, Liang; Chen, Shi-You; Fan, Feng-Jia; Zhuang, Tao-Tao; Dai, Chen-Min; Yu, Shu-Hong

    2016-05-01

    Heterocrystalline polytype nanostructured semiconductors have been attracting more and more attention in recent years due to their novel structures and special interfaces. Up to now, controlled polytypic nanostructures are mostly realized in II-VI and III-V semiconductors. Herein, we report the synthesis and photoelectrochemical properties of Cu-based ternary I-III-VI2 chalcogenide polytypic nanocrystals, with a focus on polytypic CuInS2 (CIS), CuInSe2 (CISe), and CuIn(S0.5Se0.5)2 alloy nanocrystals. Each obtained polytypic nanocrystal is constructed with a wurtzite hexagonal column and a zinc blende/chalcopyrite cusp, regardless of the S/Se ratio. The growth mechanisms of polytypic CIS and CISe nanocrystals have been studied by time-dependent experiments. The polytypic nanocrystals are solution-deposited on indium-tin oxide glass substrate and used as a photoelectrode, thus showing stable photoelectrochemical activity in aqueous solution. Density functional theory calculation was used to study the electronic structure and the band gap alignment. This versatile synthetic method provides a new route for synthesis of novel polytypic nanostructured semiconductors with unique properties. PMID:27063512

  17. Characterization of the Waukesha Illite: A mixed-polytype illite in the Clay Mineral Society repository

    USGS Publications Warehouse

    Grathoff, Georg H.; Moore, D.M.

    2002-01-01

    The Waukesha Illite is an excellent example of the illites found in argillaceous rocks, typical for Paleozoic shales that have undergone significant burial diagenesis during their geologic history. It consists of a mixture of detrital 2M1, interpreted to be a residuum of karstification within Silurian carbonates, and diagenetic 1M and 1Md illite. The chemistry and the age of the illite polytypes are different. Extrapolating to 100%, the 1M and 1Md polytypes have an apparent diagenetic age between 295 and 325 Ma. The chemistry of the 1M polytype could not be determined because of its low abundance. The approximate chemical composition of the 1Md polytype is 0.67 K, 3.6 Si, and 1.9 Al per half unit cell. The 2M1 polytype has an apparent detrital age between 440 and 520 Ma, and an approximate chemical composition per half unit cell of 0.78 K, 3.4 Si, and 2.1 Al, all within our margin of error. X-ray diffraction (XRD) results of both random powder and oriented preparations both indicate that the Waukesha Illite consists of a mixture of illites. The XRD patterns of the random powder preparation indicate it is a physical mixture of three different illite polytypes. This result was confirmed using 3 different methods: (1) by measuring illite polytype-specific reflections; (2) by mixing illite polytype reference samples; and (3) by mixing WILDFIRE calculated XRD patterns. Decomposition of the illite 001 XRD peak from oriented preparations also indicates mixtures of illites. However, the proportions of the three illitic components derived from the oriented 001 peak decomposition differ from those results derived from the analysis of the random powder data. Therefore, the shape of the 001 reflection of the Waukesha Illite cannot be explained by mixing the three different illite polytypes.

  18. Thermal expansion and elastic anisotropies of SiC as related to polytype structure

    NASA Technical Reports Server (NTRS)

    Li, Z.; Bradt, R. C.

    1989-01-01

    The concept of the fraction of hexagonal stacking is used to describe the anisotropic thermal expansion coefficients of polytypes of SiC. The single crystal elastic anisotropy for the SiC polytype structures and the temperature dependencies of the anisotropies are examined. The anisotropic thermoelastic stress index for the 3C and 6H SiC polytypes are illustrated graphically. It is shown that this index is useful for predicting the most desirable crystal growth orientations for SiC whisker incorporation into composite matrices.

  19. Complex (Nonstandard) Six-Layer Polytypes of Lizardite Revealed from Oblique-Texture Electron Diffraction Patterns

    SciTech Connect

    Zhukhlistov, A.P.; Zinchuk, N.N.; Kotel'nikov, D.D.

    2004-11-01

    Association of simple (1T and 3R) and two complex (nonstandard) orthogonal polytypes of the serpentine mineral lizardite from the Catoca kimberlite pipe (West Africa) association is revealed from oblique-texture electron diffraction patterns. A six-layer polytype with an ordered superposition of equally oriented layers (notation 3{sub 2}3{sub 2}3{sub 4}3{sub 4}3{sub 6}3{sub 6} or ++ - -00) belonging to the structural group A and a three-layer (336 or I,I,II) or a six-layer (336366 or I,I,II,I,II,II) polytype with alternating oppositely oriented layers and semi-disordered structure are identified using polytype analysis.

  20. Analysis of polytype stability in PVT grown silicon carbide single crystal using competitive lattice model Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Guo, Hui-Jun; Huang, Wei; Liu, Xi; Gao, Pan; Zhuo, Shi-Yi; Xin, Jun; Yan, Cheng-Feng; Zheng, Yan-Qing; Yang, Jian-Hua; Shi, Er-Wei

    2014-09-01

    Polytype stability is very important for high quality SiC single crystal growth. However, the growth conditions for the 4H, 6H and 15R polytypes are similar, and the mechanism of polytype stability is not clear. The kinetics aspects, such as surface-step nucleation, are important. The kinetic Monte Carlo method is a common tool to study surface kinetics in crystal growth. However, the present lattice models for kinetic Monte Carlo simulations cannot solve the problem of the competitive growth of two or more lattice structures. In this study, a competitive lattice model was developed for kinetic Monte Carlo simulation of the competition growth of the 4H and 6H polytypes of SiC. The site positions are fixed at the perfect crystal lattice positions without any adjustment of the site positions. Surface steps on seeds and large ratios of diffusion/deposition have positive effects on the 4H polytype stability. The 3D polytype distribution in a physical vapor transport method grown SiC ingot showed that the facet preserved the 4H polytype even if the 6H polytype dominated the growth surface. The theoretical and experimental results of polytype growth in SiC suggest that retaining the step growth mode is an important factor to maintain a stable single 4H polytype during SiC growth.

  1. Illite polytype quantification using Wildfire© calculated x-ray diffraction patterns

    USGS Publications Warehouse

    Grathoff, Georg H.; Moore, D.M.

    1996-01-01

    Illite polytype quantification allows the differentiation of diagenetic and detrital illite components. In Paleozoic shales from the Illinois Basin, we observe 3 polytypes: 1Md, 1M and 2M1. 1Md and 1M are of diagenetic origin and 2M1 is of detrital origin. In this paper, we compare experimental X-ray diffraction (XRD) traces with traces calculated using WILDFIRE© and quantify mixtures of all 3 polytypes, adjusting the effects of preferred orientation and overlapping peaks. The broad intensity (“illite hump”) around the illite 003, which is very common in illite from shales, is caused by the presence of 1Md illite and mixing of illite polytypes and is not an artifact of sample preparation or other impurities in the sample. Illite polytype quantification provides a tool to extrapolate the K/Ar age and chemistry of the detrital and diagenetic end-members by analysis of different size fractions containing different proportions of diagenetic and detrital illite polytypes.

  2. Strain effects in polytypical wurtzite/zinc-blend nanowhiskers

    NASA Astrophysics Data System (ADS)

    Sipahi, Guilherme; Faria, Paulo

    2012-02-01

    The recent interest on III-V nanowhiskers has led to the growth of high quality samples of systems with two different crystalline structures [1]. The crystals grown in [111]-direction for the zinc-blend (ZB) phase and [0001]-direction for the wurtzite (WZ) phase are very similar and can both be described as stacked hexagonal layers. The effect of two different structural phases coexisting in the same nanostrucure is known as polytypism and creates confinement profiles similar to a heterostructure. One can notice band offsets at the interface and the formation of electronic minibands that can be explored to design systems for device applications. Although some of the III-V compounds do not present WZ structure in bulk form, recent calculations [2] presented a theoretical prediction of their band structure. However, as they considered that ZB and WZ to have the same lattice parameters no strain effects should appear on a first approach. Our theoretical approach introduces strain effects in our previous model [3] by using group theory arguments. It allows the analysis of the biaxial strain effects for both structures in a single matrix. [1] P. Caroff et al. Nature Nanotech. 4, 50, 2009. [2] A. De and C. E. Pryor, Phys. Rev. B 81, 155210, 2010 [3] http://arxiv.org/abs/1012.022

  3. Crystal Phase Effects in Si Nanowire Polytypes and Their Homojunctions.

    PubMed

    Amato, Michele; Kaewmaraya, Thanayut; Zobelli, Alberto; Palummo, Maurizia; Rurali, Riccardo

    2016-09-14

    Recent experimental investigations have confirmed the possibility to synthesize and exploit polytypism in group IV nanowires. Driven by this promising evidence, we use first-principles methods based on density functional theory and many-body perturbation theory to investigate the electronic and optical properties of hexagonal-diamond and cubic-diamond Si NWs as well as their homojunctions. We show that hexagonal-diamond NWs are characterized by a more pronounced quantum confinement effect than cubic-diamond NWs. Furthermore, they absorb more light in the visible region with respect to cubic-diamond ones and, for most of the studied diameters, they are direct band gap materials. The study of the homojunctions reveals that the diameter has a crucial effect on the band alignment at the interface. In particular, at small diameters the band-offset is type-I whereas at experimentally relevant sizes the offset turns up to be of type-II. These findings highlight intriguing possibilities to modulate electron and hole separations as well as electronic and optical properties by simply modifying the crystal phase and the size of the junction. PMID:27530077

  4. Crystal Phase Effects in Si Nanowire Polytypes and Their Homojunctions.

    PubMed

    Amato, Michele; Kaewmaraya, Thanayut; Zobelli, Alberto; Palummo, Maurizia; Rurali, Riccardo

    2016-09-14

    Recent experimental investigations have confirmed the possibility to synthesize and exploit polytypism in group IV nanowires. Driven by this promising evidence, we use first-principles methods based on density functional theory and many-body perturbation theory to investigate the electronic and optical properties of hexagonal-diamond and cubic-diamond Si NWs as well as their homojunctions. We show that hexagonal-diamond NWs are characterized by a more pronounced quantum confinement effect than cubic-diamond NWs. Furthermore, they absorb more light in the visible region with respect to cubic-diamond ones and, for most of the studied diameters, they are direct band gap materials. The study of the homojunctions reveals that the diameter has a crucial effect on the band alignment at the interface. In particular, at small diameters the band-offset is type-I whereas at experimentally relevant sizes the offset turns up to be of type-II. These findings highlight intriguing possibilities to modulate electron and hole separations as well as electronic and optical properties by simply modifying the crystal phase and the size of the junction.

  5. Nanostructural and electronic properties of polytypes in InN nanocolumns

    SciTech Connect

    Kioseoglou, J.; Koukoula, T.; Komninou, Ph.; Kehagias, Th.; Georgakilas, A.; Androulidaki, M.

    2013-08-21

    Transmission electron microscopy techniques and density functional theory calculations were employed to investigate the nanostructural and electronic properties of InN polytypes observed in InN nanocolumns, grown on Si(111) by molecular beam epitaxy. Moiré fringes and alternating hexagonal and cubic lattice stacking sequences along the c-axis, observed among the wurtzite layers, implied the presence of different structures embedded in the basic 2H structure of the nanocolumns. Quantitative electron diffraction analysis and high-resolution image simulations verified the coexistence of the wurtzite structure with the 4H, 6H, and the 3C zinc-blende structural polytypes. Total energies calculations established the 2H wurtzite structure as the most stable polytype. The band gap of all polytypes was found direct with the energies and the band gaps of the 4H (E{sub g} = 0.64 eV) and 6H (E{sub g} = 0.60 eV) structures calculated between the corresponding values of the 2H (E{sub g} = 0.75 eV) and 3C (E{sub g} = 0.49 eV) basic structures. Theoretical and experimental analysis showed that at the initial stages of growth InN nanocolumns were under tensile strain along both the basal plane and growth direction. Structural polytypes were then introduced in the form of embedded inclusions to accommodate the excess tensile strain along the growth direction, allowing the entire process of polymorphism to be the dominant strain relaxation mechanism of InN nanocolumns. Moreover, the lattice and energetic properties and band gap values of InN polytypes showed a linear dependence on hexagonality, while the presence of polytypes led to a characteristic broadening of the photoluminescence emission peak toward lower emission energies.

  6. Metallic VS2 Monolayer Polytypes as Potential Sodium-Ion Battery Anode via ab Initio Random Structure Searching.

    PubMed

    Putungan, Darwin Barayang; Lin, Shi-Hsin; Kuo, Jer-Lai

    2016-07-27

    We systematically investigated the potential of single-layer VS2 polytypes as Na-battery anode materials via density functional theory calculations. We found that sodiation tends to inhibit the 1H-to-1T structural phase transition, in contrast to lithiation-induced transition on monolayer MoS2. Thus, VS2 can have better structural stability in the cycles of charging and discharging. Diffussion of Na atom was found to be very fast on both polytypes, with very small diffusion barriers of 0.085 eV (1H) and 0.088 eV (1T). Ab initio random structure searching was performed in order to explore stable configurations of Na on VS2. Our search found that both the V top and the hexagonal center sites are preferred adsorption sites for Na, with the 1H phase showing a relatively stronger binding. Notably, our random structures search revealed that Na clusters can form as a stacked second layer at full Na concentration, which is not reported in earlier works wherein uniform, single-layer Na adsorption phases were assumed. With reasonably high specific energy capacity (232.91 and 116.45 mAh/g for 1H and 1T phases, respectively) and open-circuit voltage (1.30 and 1.42 V for 1H and 1T phases, respectively), VS2 is a promising alternative material for Na-ion battery anodes with great structural sturdiness. Finally, we have shown the capability of the ab initio random structure searching in the assessment of potential materials for energy storage applications. PMID:27373121

  7. Metallic VS2 Monolayer Polytypes as Potential Sodium-Ion Battery Anode via ab Initio Random Structure Searching.

    PubMed

    Putungan, Darwin Barayang; Lin, Shi-Hsin; Kuo, Jer-Lai

    2016-07-27

    We systematically investigated the potential of single-layer VS2 polytypes as Na-battery anode materials via density functional theory calculations. We found that sodiation tends to inhibit the 1H-to-1T structural phase transition, in contrast to lithiation-induced transition on monolayer MoS2. Thus, VS2 can have better structural stability in the cycles of charging and discharging. Diffussion of Na atom was found to be very fast on both polytypes, with very small diffusion barriers of 0.085 eV (1H) and 0.088 eV (1T). Ab initio random structure searching was performed in order to explore stable configurations of Na on VS2. Our search found that both the V top and the hexagonal center sites are preferred adsorption sites for Na, with the 1H phase showing a relatively stronger binding. Notably, our random structures search revealed that Na clusters can form as a stacked second layer at full Na concentration, which is not reported in earlier works wherein uniform, single-layer Na adsorption phases were assumed. With reasonably high specific energy capacity (232.91 and 116.45 mAh/g for 1H and 1T phases, respectively) and open-circuit voltage (1.30 and 1.42 V for 1H and 1T phases, respectively), VS2 is a promising alternative material for Na-ion battery anodes with great structural sturdiness. Finally, we have shown the capability of the ab initio random structure searching in the assessment of potential materials for energy storage applications.

  8. Perspectives and limitations of symmetric X-ray Bragg reflections for inspecting polytypism in nanowires.

    PubMed

    Köhl, Martin; Schroth, Philipp; Baumbach, Tilo

    2016-03-01

    X-ray diffraction, possibly time-resolved during growth or annealing, is an important technique for the investigation of polytypism in free-standing nanowires. A major advantage of the X-ray diffraction approach for adequately chosen beam conditions is its high statistical significance in comparison with transmission electron microscopy. In this manuscript the interpretation of such X-ray intensity distribution is discussed, and is shown to be non-trivial and non-unique given measurements of the [111]c or [333]c reflection of polytypic nanowires grown in the (111)c direction. In particular, the diffracted intensity distributions for several statistical distributions of the polytypes inside the nanowires are simulated and compared. As an example, polytypic GaAs nanowires are employed, grown on a Si-(111) substrate with an interplanar spacing of the Ga (or As) planes in the wurtzite arrangement that is 0.7% larger than in the zinc blende arrangement along the (111)c direction. Most importantly, ambiguities of high experimental relevance in the case of strongly fluctuating length of the defect-free polytype segments in the nanowires are demonstrated. As a consequence of these ambiguities, a large set of deviations from the widely used Markov model for the stacking sequences of the nanowires cannot be detected in the X-ray diffraction data. Thus, the results here are of high relevance for the proper interpretation of such data. PMID:26917137

  9. Low-temperature production of silicon carbide films of different polytypes

    SciTech Connect

    Semenov, A. V. Puzikov, V. M.; Golubova, E. P.; Baumer, V. N.; Dobrotvorskaya, M. V.

    2009-05-15

    The study is concerned with the effect of temperature on the structure of SiC films formed by deposition of the C and Si ions with the energy 120 eV. On the basis of the X-ray structural studies, it is unambiguously established that the structure of the growing polytype is finely dependent on the substrate temperature. In the temperature range from 1080 deg. C to 1510 deg. C, the sequence of films involving the 21R, 51R, 27R, and 6H polytypes is produced for the first time. The effect of temperature on the silicon-carbon atomic content ratio [Si]/[C] in the deposited films is determined. At optimized parameters of deposition the film structured as the 51R rhombohedral polytype is grown.

  10. Thermal expansion and thermal expansion anisotropy of SiC polytypes

    NASA Technical Reports Server (NTRS)

    Li, Z.; Bradt, R. C.

    1987-01-01

    The principal axial coefficients of thermal expansion for the (3C), (4H), and (6H) polytypes of SiC are considered to identify the structural role of the stacking layer sequence as it affects the thermal expansion. A general equation based on the fractions of cubic and hexagonal layer stacking is developed that expresses the principal axial thermal expansion coefficients of all of the SiC polytypes. It is then applied to address the thermal expansion anisotropy of the noncubic SiC structures.

  11. Two new polytypes of 2,4,6-tri­bromo­benzo­nitrile

    PubMed Central

    Britton, Doyle; Noland, Wayland E.; Tritch, Kenneth J.

    2016-01-01

    Three polymorphs of 2,4,6-tri­bromo­benzo­nitrile (RCN), C7H2Br3N, two of which are novel and one of which is a redetermination of the original structure first determined by Carter & Britton [(1972). Acta Cryst. B28, 945–950] are found to be polytypic. Each has a layer structure which differs only in the stacking of the layers. Each layer is composed of mol­ecules associated through C N⋯Br contacts which form R 2 2(10) rings. Two such rings are associated with each N atom; one with each ortho-Br atom. No new polytypes of 1,3,5-tri­bromo-2-iso­cyano­benzene (RNC) were found but a re-determination of the original structure by Carter et al. [(1977). Cryst. Struct. Commun. 6, 543–548] is presented. RNC was found to be isostructural with one of the novel polytypes of RCN. Unit cells were determined for 23 RCN samples and 11 RNC samples. Polytypes could not be distinguished based on crystal habits. In all four structures, each mol­ecule of the asymmetric unit lies across a mirror plane. PMID:26958382

  12. Discovery of elusive structures of multifunctional transition-metal borides.

    PubMed

    Liang, Yongcheng; Wu, Zhaobing; Yuan, Xun; Zhang, Wenqing; Zhang, Peihong

    2016-01-14

    A definitive determination of crystal structures is an important prerequisite for designing and exploiting new functional materials. Even though tungsten and molybdenum borides (TMBx) are the prototype for transition-metal light-element compounds with multiple functionalities, their elusive crystal structures have puzzled scientists for decades. Here, we discover that the long-assumed TMB2 phases with the simple hP3 structure (hP3-TMB2) are in fact a family of complex TMB3 polytypes with a nanoscale ordering along the axial direction. Compared with the energetically unfavorable and dynamically unstable hP3-TMB2 phase, the energetically more favorable and dynamically stable TMB3 polytypes explain the experimental structural parameters, mechanical properties, and X-ray diffraction (XRD) patterns better. We demonstrate that such a structural and compositional modification from the hP3-TMB2 phases to the TMB3 polytypes originates from the relief of the strong antibonding interaction between d electrons by removing one third of metal atoms systematically. These results resolve the longstanding structural mystery of this class of metal borides and uncover a hidden family of polytypic structures. Moreover, these polytypic structures provide an additional hardening mechanism by forming nanoscale interlocks that may strongly hinder the interlayer sliding movements, which promises to open a new avenue towards designing novel superhard nanocomposite materials by exploiting the coexistence of various polytypes.

  13. An ab initio study of the polytypism in InP

    PubMed Central

    Dacal, Luis C. O.; Cantarero, A.

    2016-01-01

    The existence of polytypism in semiconductor nanostructures gives rise to the appearance of stacking faults which many times can be treated as quantum wells. In some cases, despite of a careful growth, the polytypism can be hardly avoided. In this work, we perform an ab initio study of zincblende stacking faults in a wurtzite InP system, using the supercell approach and taking the limit of low density of narrow stacking faults regions. Our results confirm the type II band alignment between the phases, producing a reliable qualitative description of the band gap evolution along the growth axis. These results show an spacial asymmetry in the zincblende quantum wells, that is expected due to the fact that the wurtzite stacking sequence (ABAB) is part of the zincblende one (ABCABC), but with an unexpected asymmetry between the valence and the conduction bands. We also present results for the complex dielectric function, clearly showing the influence of the stacking on the homostructure values and surprisingly proving that the correspondent bulk results can be used to reproduce the polytypism even in the limit we considered. PMID:27666092

  14. Polytype-selective growth of SiC by supersaturation control in solution growth

    NASA Astrophysics Data System (ADS)

    Seki, Kazuaki; Alexander; Kozawa, Shigeta; Harada, Shunta; Ujihara, Toru; Takeda, Yoshikazu

    2012-12-01

    We realized the polytype-selective growth of 3C-SiC and 6H-SiC on a 6H-SiC (0 0 0 1) seed crystal by controlling the supersaturation. Both 6H-SiC and 3C-SiC grew on the 6H-SiC seed crystal at low supersaturation, but 3C-SiC increased with increasing supersaturation. At high supersaturation, 3C-SiC grew so rapidly that it completely covered the 6H-SiC seed crystal. The growth rates of 3C-SiC and 6H-SiC have different dependences on supersaturation. In the present case, the growth rate of 3C-SiC in 2D nucleation mode is compared with that of 6H-SiC in spiral growth mode. The present kinetic polytype-control technique is based on polytypes having different growth rates and it differs considerably from the conventional technique that is based on "inheritance" of stacking sequence, which is well known as "step-controlled epitaxy".

  15. Electronic bands and excited states of III-V semiconductor polytypes with screened-exchange density functional calculations

    SciTech Connect

    Akiyama, Toru; Nakamura, Kohji; Ito, Tomonori; Freeman, Arthur J.

    2014-03-31

    The electronic band structures and excited states of III-V semiconductors such as GaP, AlP, AlAs, and AlSb for various polytypes are determined employing the screened-exchange density functional calculations implemented in the full-potential linearized augmented plane-wave methods. We demonstrate that GaP and AlSb in the wurtzite (WZ) structure have direct gap while III-V semiconductors in the zinc blende, 4H, and 6H structures considered in this study exhibit an indirect gap. Furthermore, we find that inclusion of Al atoms less than 17% and 83% in the hexagonal Al{sub x}Ga{sub 1−x}P and Al{sub x}Ga{sub 1−x}As alloys, respectively, leads to a direct transition with a gap energy of ∼2.3 eV. The feasibility of III-V semiconductors with a direct gap in WZ structure offers a possible crystal structure engineering to tune the optical properties of semiconductor materials.

  16. The structure of orange HgI2. I. Polytypic layer structure.

    PubMed

    Hostettler, Marc; Birkedal, Henrik; Schwarzenbach, Dieter

    2002-12-01

    The metastable orange crystals of HgI(2) comprise three different crystal structures, all of which are built from corner-linked Hg(4)I(10) supertetrahedra. Two of them are end members with the maximum degree of order (MDO) of a polytypic layer structure; the third shows a three-dimensional linkage. This paper presents the determination from X-ray diffraction data of the tetragonal polytypic structures and their stacking disorder. Diffraction patterns show sharp Bragg reflections and rods of diffuse intensity with pronounced maxima. In a first step, the diffuse intensity was neglected and all maxima were treated as Bragg reflections. The crystal was supposed to be a conglomerate of the two MDO structures diffracting independently, and their parameters and volume ratio were refined against the single data set. The geometries and anisotropic displacement parameters of the layers in the two structures are shown to be nearly identical. Layer contacts in the two stacking modes are identical. The structures are fractal complications of the stable red form of HgI(2). In a second step, the stacking disorder has been quantitatively analyzed with a Markov chain model. Two probabilities describing next-nearest-layer interactions were visually adjusted to observed intensity profiles extracted from image-plate detector data. Results consistently show that the crystal comprises nearly equal volumes of MDO structures with an average domain thickness of about 5 layers or 30 A

  17. Radiometric dating of brittle fault rocks; illite polytype age analysis and application to the Spanish Pyrenees.

    NASA Astrophysics Data System (ADS)

    van der Pluijm, B. A.; Haines, S. H.

    2008-12-01

    A variety of approaches have been available to indirectly date the timing of deformation and motion on faults, but few approaches for direct, radiometric dating of shallow crustal fault rocks were available until recently. The growing recognition of clay neomineralization at low temperatures in many fault rocks, particularly the 1Md illite polytype, allows the successful application of Ar dating to these K-bearing phases. In this presentation we will discuss our recent illite age analysis approach (sampling, treatments, analytical methods), and present new results from fault dating along the Spanish Pyrenean orogenic front as an example. X-ray quantification of polytype ratios in three or more size fractions is used to define a mixing line between (1Md illite) authigenic and (2M illite) detrital end-member phases that constrain the fault age and host rock provenance/cooling age for each fault. The common problem of recoil in clays is addressed by encapsulating samples before irradiation. Nine fault gouge ages in the south-central and south-eastern Pyrenees support several contractional pulses in the Pyrenean orogen: 1) Late Cretaceous thrusting (Boixols), 2) Latest Paleocene-Early Eocene deformation (Nogueres Zone and Freser antiformal stack), 3) Middle-Late Eocene deformation (Ripoll syncline, Vallfogona, Gavernie, Abocador and L'Escala thrusts), and 4) Middle Oligocene thrusting in the central portion of the Axial Zone (Llavorsi-Senet). The late Paleocene-Early Eocene and Middle-Late Eocene events may or may not be one single phase, due to slightly overlapping error estimates. The outboard thrusts give Hercynian ages for the detrital component of the fault rock, while the inboard thrusts, which juxtapose metamorphic units, give Cretaceous ages for the non-authigenic component, reflecting the cooling age of the adjacent wallrocks. Based on our latest work, the illite polytype dating method complements previously developed illite-smectite dating (van der Pluijm et

  18. Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

    SciTech Connect

    Ramesh, Thimmasandra Narayan

    2010-06-15

    The isothermal decomposition of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature leads to the formation of Co{sub 3}O{sub 4}. The phase evolution during the decomposition process was monitored using powder X-ray diffraction. The transformation of cobalt hydroxide to cobalt oxide occurs via three phase mixture while cobalt hydroxynitrate to cobalt oxide occurs through a two phase mixture. The nature of the sample and its preparation method controls the decomposition mechanism. The comparison of topotactical relationship between the precursors to the decomposed product has been reported in relation to polytypism. - Graphical abstract: Isothermal thermal decomposition studies of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature show the metastable phase formed prior to Co{sub 3}O{sub 4} phase.

  19. Crystal structure of Cr-bearing Mg3BeAl8O16, a new polytype of magnesiotaaffeite-2N'2S.

    PubMed

    Malcherek, Thomas; Schlüter, Jochen

    2016-07-01

    The crystal structure of a new polytype of magnesiotaaffeite-2N'2S, ideally Mg3BeAl8O16 (trimagnesium beryllium octa-aluminium hexa-deca-oxide), is described in space-group symmetry P-3m1. It has been identified in a fragment of a mineral sample from Burma (Myanmar). The new polytype is composed of two Mg2Al4O8 (S)- and two BeMgAl4O8 (N')-modules in a stacking sequence N'SSN'' which differs from the N'SN'S-stacking sequence of the known magnesiotaaffeite-2N'2S polytype. The crystal structure can be derived from a close-packed arrangement of O atoms and is discussed with regard to its polytypism and its Cr(3+) chromophore content.

  20. Crystal structure of Cr-bearing Mg3BeAl8O16, a new polytype of magnesiotaaffeite-2N′2S

    PubMed Central

    Malcherek, Thomas; Schlüter, Jochen

    2016-01-01

    The crystal structure of a new polytype of magnesiotaaffeite-2N′2S, ideally Mg3BeAl8O16 (trimagnesium beryllium octa­aluminium hexa­deca­oxide), is described in space-group symmetry P-3m1. It has been identified in a fragment of a mineral sample from Burma (Myanmar). The new polytype is composed of two Mg2Al4O8 (S)- and two BeMgAl4O8 (N′)-modules in a stacking sequence N′SSN′′ which differs from the N′SN′S-stacking sequence of the known magnesiotaaffeite-2N′2S polytype. The crystal structure can be derived from a close-packed arrangement of O atoms and is discussed with regard to its polytypism and its Cr3+ chromophore content. PMID:27555963

  1. Crystal structure of Cr-bearing Mg3BeAl8O16, a new polytype of magnesiotaaffeite-2N'2S.

    PubMed

    Malcherek, Thomas; Schlüter, Jochen

    2016-07-01

    The crystal structure of a new polytype of magnesiotaaffeite-2N'2S, ideally Mg3BeAl8O16 (trimagnesium beryllium octa-aluminium hexa-deca-oxide), is described in space-group symmetry P-3m1. It has been identified in a fragment of a mineral sample from Burma (Myanmar). The new polytype is composed of two Mg2Al4O8 (S)- and two BeMgAl4O8 (N')-modules in a stacking sequence N'SSN'' which differs from the N'SN'S-stacking sequence of the known magnesiotaaffeite-2N'2S polytype. The crystal structure can be derived from a close-packed arrangement of O atoms and is discussed with regard to its polytypism and its Cr(3+) chromophore content. PMID:27555963

  2. Selective epitaxial growth of zinc blende-derivative on wurtzite-derivative: the case of polytypic Cu2CdSn(S1-xSex)4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Wu, Liang; Fan, Feng-Jia; Gong, Ming; Ge, Jin; Yu, Shu-Hong

    2014-02-01

    Polytypic nanocrystals with zinc blende (ZB) cores and wurtzite (WZ) arms, such as tetrapod and octopod nanocrystals, have been widely reported. However, polytypic nanocrystals with WZ cores and ZB arms or ends have been rarely reported. Here, we report a facile, solution-based approach to the synthesis of polytypic Cu2CdSn(S1-xSex)4 (CCTSSe) nanocrystals with ZB-derivative selectively engineered on (000+/-2)WZ facets of WZ-derived cores. Accordingly, two typical morphologies, i.e., bullet-like nanocrystals with a WZ-derivative core and one ZB-derivative end, and rugby ball-like nanocrystals with a WZ-derivative core and two ZB-derivative ends, can be selectively prepared. The epitaxial growth mechanism is confirmed by the time-dependent experiments. The ratio of rugby ball-like and bullet-like polytypic CCTSSe nanocrystals can be tuned through changing the amount of Cd precursor to adjust the reactivity difference between (0002)WZ and (000-2)WZ facets. These unique polytypic CCTSSe nanocrystals may find applications in energetic semiconducting materials for energy conversion in the future.Polytypic nanocrystals with zinc blende (ZB) cores and wurtzite (WZ) arms, such as tetrapod and octopod nanocrystals, have been widely reported. However, polytypic nanocrystals with WZ cores and ZB arms or ends have been rarely reported. Here, we report a facile, solution-based approach to the synthesis of polytypic Cu2CdSn(S1-xSex)4 (CCTSSe) nanocrystals with ZB-derivative selectively engineered on (000+/-2)WZ facets of WZ-derived cores. Accordingly, two typical morphologies, i.e., bullet-like nanocrystals with a WZ-derivative core and one ZB-derivative end, and rugby ball-like nanocrystals with a WZ-derivative core and two ZB-derivative ends, can be selectively prepared. The epitaxial growth mechanism is confirmed by the time-dependent experiments. The ratio of rugby ball-like and bullet-like polytypic CCTSSe nanocrystals can be tuned through changing the amount of Cd precursor

  3. Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

    NASA Astrophysics Data System (ADS)

    Larkin, David J.; Powell, J. Anthony

    1992-11-01

    A method for the controlled growth of single-crystal semiconductor-device-quality films of SiC polytypes on vicinal (0001) SiC wafers with low tilt angles is presented. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

  4. Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

    NASA Astrophysics Data System (ADS)

    Larkin, David J.; Powell, J. Anthony

    1994-11-01

    This invention is a method for the controlled growth of single-crystal semiconductor-device-quality films of SiC polytypes of vicinal (0001) SiC wafers with low tilt angles. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

  5. Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

    NASA Astrophysics Data System (ADS)

    Powell, J. Anthony

    1991-06-01

    This invention is a method for the controlled growth of single-crystal semiconductor device quality films of SiC polytypes on vicinal (0001) SiC wafers with low tilt angles. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

  6. Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony (Inventor)

    1991-01-01

    This invention is a method for the controlled growth of single-crystal semiconductor device quality films of SiC polytypes on vicinal (0001) SiC wafers with low tilt angles. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

  7. Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

    NASA Technical Reports Server (NTRS)

    Larkin, David J. (Inventor); Powell, J. Anthony (Inventor)

    1992-01-01

    A method for the controlled growth of single-crystal semiconductor-device-quality films of SiC polytypes on vicinal (0001) SiC wafers with low tilt angles is presented. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

  8. Rapid and Nondestructive Identification of Polytypism and Stacking Sequences in Few-Layer Molybdenum Diselenide by Raman Spectroscopy

    DOE PAGES

    Lu, Xin; Utama, M. Iqbal Bakti; Lin, Junhao; Luo, Xin; Zhao, Yanyuan; Zhang, Jun; Pantelides, Sokrates T.; Zhou, Wu; Quek, Su Ying; Xiong, Qihua

    2015-07-02

    Various combinations of interlayer shear modes emerge in few-layer molybdenum diselenide grown by chemical vapor deposition depending on the stacking configuration of the sample. Raman measurements may also reveal polytypism and stacking faults, as supported by first principles calculations and high-resolution transmission electron microscopy. Thus, Raman spectroscopy is an important tool in probing stacking-dependent properties in few-layer 2D materials.

  9. Embedded polytypes in Bi2Sr2-xLaxCuO6 thin films grown by laser ablation

    NASA Astrophysics Data System (ADS)

    Cancellieri, C.; Lin, P. H.; Ariosa, D.; Pavuna, D.

    2007-11-01

    We investigate the presence of secondary phases in La-doped Bi-2201 thin films grown by laser ablation. The cation ratios in the target material, the oxygen pressure, and the substrate temperature during the deposition are the main parameters determining the presence of diluted intergrowth and/or polytype aggregates. A statistical model of random intergrowth is used to analyze the x-ray diffraction (XRD) anomalies caused by hidden defects and to characterize the latter. A detailed structural XRD refinement on oriented aggregates allows us to identify the guest phase as a Bi deficient phase, Bi-1201. The occurrence of this particular embedded polytype is accompanied by a global Bi deficiency introduced in the films by the growing process and/or by the annealing treatment. The presence of La favors the Bi-1201 formation mostly as La-rich c -axis oriented aggregates. Bi excess in the target material improves considerably the crystallographic structure of Bi-2201, avoids intergrowth formation, but does not prevent the phase separation of Bi-1201 in La-doped thin films. We also investigate the influence of the deposition parameters on the type of intergrowth as well as their variation with La doping. This work introduces a specific methodology for optimizing the growth of thin films grown by laser ablation, which applies to layered oxides that admit polytypes with close formation enthalpies in their phase diagram.

  10. Transitions.

    ERIC Educational Resources Information Center

    Field, David; And Others

    1992-01-01

    Includes four articles: "Career Aspirations" (Field); "Making the Transition to a New Curriculum" (Baker, Householder); "How about a 'Work to School' Transition?" (Glasberg); and "Technological Improvisation: Bringing CNC to Woodworking" (Charles, McDuffie). (SK)

  11. Facile one-pot synthesis of polytypic (wurtzite-chalcopyrite) CuGaS2

    NASA Astrophysics Data System (ADS)

    Vahidshad, Yaser; Mirkazemi, Seyed Mohammad; Tahir, Muhammad Nawaz; Zad, Azam Iraji; Ghasemzadeh, Reza; Tremel, Wolfgang

    2016-03-01

    In this investigation, monodisperse CuGaS2 nanoparticles intended for use as visible-light-absorbing materials were synthesized using a facile one-step heating method that involved dissolving the precursors copper chloride, gallium acetylacetonate, and thiourea in a solvent consisting of either oleylamine alone or a combination of oleylamine, oleic acid, and 1-octadecene. The shapes of the resulting nanoparticles were either elongated, polygonal, or a mixture of both, depending on whether the crystal structure of the nanoparticles was predominantly wurtzite, predominantly chalcopyrite, or a more balanced mixture of both wurtzite and chalcopyrite (i.e., the nanoparticles were polytypic: both wurtzite and chalcopyrite phases were present). The crystal structure of the synthesized nanoparticles was found to be influenced by the temperature and the solvent applied during synthesis. X-ray diffraction data for the nanoparticles indicated that applying a temperature of 270 °C or using oleylamine, oleic acid solvent, and 1-octadecene during synthesis tended to yield a chalcopyrite phase, whereas applying a somewhat lower temperature (210 °C) or using oleylamine alone during synthesis tended to result in a wurtzite phase. The chemical states of the compounds obtained at different temperatures and using various solvents, as well as their crystal structures, morphologies, and optical properties were characterized via X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, ultraviolet-visible spectroscopy, and photoluminescence.

  12. Characterization of paramagnetic defect centers in three polytypes of dry heat treated, oxidized SiC

    NASA Astrophysics Data System (ADS)

    Macfarlane, P. J.; Zvanut, M. E.

    2000-10-01

    This work describes the characterization of defect centers in 3C-SiC, 4H-SiC, and 6H-SiC. The different SiC crystal structures are examined with electron paramagnetic resonance after thermal oxidation, and after dry (<1 ppm H2O) N2 or O2 heat treatment. The centers are described by g values that range from 2.0025 to 2.0029, which are typical of C dangling bonds. Because the centers are activated in ambients that eliminate H2O and are passivated in ambients that contain H2O, it is suggested that the centers are C dangling bonds created during the dry heat treatment when hydrogen or a hydrogenous species releases from C bonds. The activation characteristics for the centers is the same for both 6H and 3C polytypes; however, centers in the 6H-SiC samples are passivated at lower temperatures than the centers in the 3C-SiC samples. The passivation behavior is attributed to differences in the hydrogen diffusion rates in these materials rather than significant differences in the chemistry of the centers. Etching studies conducted with hydrofluoric acid indicate that the centers are not located in the SiO2, but are located in the SiC at a distance of, at most, 200 nm from the SiO2/SiC interface.

  13. Polytypism and unexpected strong interlayer coupling in two-dimensional layered ReS2.

    PubMed

    Qiao, Xiao-Fen; Wu, Jiang-Bin; Zhou, Linwei; Qiao, Jingsi; Shi, Wei; Chen, Tao; Zhang, Xin; Zhang, Jun; Ji, Wei; Tan, Ping-Heng

    2016-04-21

    Anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and application potential, offer one more dimension than isotropic 2D materials to tune their physical properties. Various physical properties of 2D multi-layer materials are modulated by varying their stacking orders owing to significant interlayer vdW coupling. Multilayer rhenium disulfide (ReS2), a representative anisotropic 2D material, was expected to be randomly stacked and lack interlayer coupling. Here, we demonstrate two stable stacking orders, namely isotropic-like (IS) and anisotropic-like (AI) N layer (NL, N > 1) ReS2 are revealed by ultralow- and high-frequency Raman spectroscopy, photoluminescence and first-principles density functional theory calculation. Two interlayer shear modes are observed in AI-NL-ReS2 while only one shear mode appears in IS-NL-ReS2, suggesting anisotropic- and isotropic-like stacking orders in IS- and AI-NL-ReS2, respectively. This explicit difference in the observed frequencies identifies an unexpected strong interlayer coupling in IS- and AI-NL-ReS2. Quantitatively, the force constants of them are found to be around 55-90% of those of multilayer MoS2. The revealed strong interlayer coupling and polytypism in multi-layer ReS2 may stimulate future studies on engineering physical properties of other anisotropic 2D materials by stacking orders. PMID:27035503

  14. Polytypism and unexpected strong interlayer coupling in two-dimensional layered ReS2

    NASA Astrophysics Data System (ADS)

    Qiao, Xiao-Fen; Wu, Jiang-Bin; Zhou, Linwei; Qiao, Jingsi; Shi, Wei; Chen, Tao; Zhang, Xin; Zhang, Jun; Ji, Wei; Tan, Ping-Heng

    2016-04-01

    Anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and application potential, offer one more dimension than isotropic 2D materials to tune their physical properties. Various physical properties of 2D multi-layer materials are modulated by varying their stacking orders owing to significant interlayer vdW coupling. Multilayer rhenium disulfide (ReS2), a representative anisotropic 2D material, was expected to be randomly stacked and lack interlayer coupling. Here, we demonstrate two stable stacking orders, namely isotropic-like (IS) and anisotropic-like (AI) N layer (NL, N > 1) ReS2 are revealed by ultralow- and high-frequency Raman spectroscopy, photoluminescence and first-principles density functional theory calculation. Two interlayer shear modes are observed in AI-NL-ReS2 while only one shear mode appears in IS-NL-ReS2, suggesting anisotropic- and isotropic-like stacking orders in IS- and AI-NL-ReS2, respectively. This explicit difference in the observed frequencies identifies an unexpected strong interlayer coupling in IS- and AI-NL-ReS2. Quantitatively, the force constants of them are found to be around 55-90% of those of multilayer MoS2. The revealed strong interlayer coupling and polytypism in multi-layer ReS2 may stimulate future studies on engineering physical properties of other anisotropic 2D materials by stacking orders.Anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and application potential, offer one more dimension than isotropic 2D materials to tune their physical properties. Various physical properties of 2D multi-layer materials are modulated by varying their stacking orders owing to significant interlayer vdW coupling. Multilayer rhenium disulfide (ReS2), a representative anisotropic 2D material, was expected to be randomly stacked and lack interlayer coupling. Here, we demonstrate two stable stacking orders, namely isotropic-like (IS) and

  15. Transits

    NASA Astrophysics Data System (ADS)

    Gilliland, Ronald L.

    Transits of the planets Mercury and especially Venus have been exciting events in the development of astronomy over the past few hundred years. Just two years ago the first transiting extra-solar planet, HD 209458b, was discovered, and subsequent studies during transit have contributed fundamental new knowledge. From the photometric light curve during transit one obtains a basic confirmation that the radial velocity detected object is indeed a planet by allowing precise determination of its mass and radius relative to these stellar quantities. From study of spectroscopic changes during transit it has been possible to probe for individual components of the transiting planets atmosphere. Planet transits are likely to become a primary tool for detection of new planets, especially other Earth-like planets with the Kepler Discovery Mission. Looking ahead, the additional aperture of the James Webb Space Space Telescope promises to allow the first possibility of studying the atmosphere of extra-solar Earth-analogue planets, perhaps even providing the first evidence of direct relevance to the search for signs of life on other planets.

  16. Structure and magnetic properties of Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15}, a new 10H-polytype in the Ba-Ce-Mn-O system

    SciTech Connect

    Macias, Mario A.; Mentre, Olivier; Cuello, Gabriel J.; Gauthier, Gilles H.

    2013-02-15

    Based on the peculiar magnetic properties that are observed in pseudo one-dimensional manganites, we decided to synthesize the new Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} compound. The preparation was performed by solid state reaction in air at about 1350 Degree-Sign C, for which we found that the compound crystallizes in a hexagonal symmetry with space group P6{sub 3}/mmc (No-194) and cell parameters a=b=5.7861(2) A and c=23.902(1) A. The structural description was correlated with neutron diffraction and bond valence calculations, confirming the presence of Ce{sup 4+} and Mn{sup 4+} segregated in the different crystallographic positions. Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} displays evidence for strong AFM couplings already set at room temperature. The main arrangement of Mn{sup 4+} in magnetically isolated tetramers of face-sharing octahedra is responsible for a metamagnetic-like transition around 50 K. - Graphical abstract: The new Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} polytype shows strong AFM couplings in magnetically isolated [Ce{sub 0.25}Mn{sub 3.75}O{sub 15}] tetramers of face-sharing octahedral, resulting in a metamagnetic-like transition around 50 K. Highlights: Black-Right-Pointing-Pointer Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15}, a new 10H polytype, has been prepared in the Ba-Ce-Mn-O system. Black-Right-Pointing-Pointer The compound crystallizes in the P6{sub 3}/mmc space group with (cchhh){sub 2} stacking sequence. Black-Right-Pointing-Pointer [Ce{sub 0.25}Mn{sub 3.75}O{sub 15}] tetramers are separated by [CeO{sub 6}] octahedra in the structure. Black-Right-Pointing-Pointer Instead of robust AFM ordering, a metamagnetic-like transition is found around 50 K.

  17. Role of polytypism and degree of hexagonality on the photoinduced optical second harmonic generation in SiC nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Semenov, A.; Puziko, V.; Skorik, S.; Wojciechowski, A.; Fedorchuk, A. O.; Maciąg, A.

    2015-05-01

    Photoinduced optiсal second harmonic generation was studied in nanocrystalline SiC films prepared by the method of direct ion deposition. For the studies were chosen three types of polytypes (with different degree of hexagonality) - 24R with degree hexagonality G=25, 27R-G=44, 33R with - G=36. The bicolor photoinduced treatment was performed by the wavelengths 1064nm/532 nm by 15 ns YAG:Nd laser. The efficiency of the output SHG was evaluated by ratio of the corresponding signal intensities with respect to the references and by the time delay between the SHG and the fundamental maxima. Explanation of the observed effect is given within a framework of the occurrence of the nano-trapping levels in the film crystalline interfaces.

  18. Orientation, alignment, and polytype control in epitaxial growth of SiC nanowires for electronics application in harsh environments

    NASA Astrophysics Data System (ADS)

    Koshka, Yaroslav; Thirumalai, Rooban Venkatesh K. G.; Krishnan, Bharat K.; Levin, Igor; Merrett, J. Neil; Davydov, Albert V.

    2013-09-01

    SiC nanowires (NWs) are attractive building blocks for the next generation electronic devices since silicon carbide is a wide bandgap semiconductor with high electrical breakdown strength, radiation resistance, mechanical strength, thermal conductivity, chemical stability and biocompatibility. Epitaxial growth using metal-catalyst-based vapor-liquid-solid mechanism was employed for SiC NW growth in this work. 4H-SiC substrates having different crystallographic orientations were used in order to control NW alignment and polytype. A new technique based on vapor-phase delivery of the metal catalyst was developed to facilitate control of the NW density. Both 4H and 3C polytypes with a strong stacking disorder were obtained. The 4H and 3C NWs had different orientations with respect to the substrate. 4H NWs grew perpendicular to the c-plane of the substrate. The stacking faults (SFs) in these nanowires were perpendicular to the [0001] nanowire axes. All 3C NWs grew at 20° with respect to the substrate c-plane, and their projections on the c-plane corresponded to one of the six equivalent ⟨101-0⟩ crystallographic directions. All six orientations were obtained simultaneously when growing NWs on the (0001) substrate surface, while only one or two NW orientations were observed when growing NWs on any particular crystallographic plane parallel to the c-axis of the substrate. Growth on {101-0} surfaces resulted in only one NW orientation, thereby producing well-aligned NW arrays. Preliminary measurements of the NW electrical conductivity are reported utilizing two-terminal device geometry.

  19. Time-varying imagery of ice features dynamic scattering in presence climate change: polytypical lakes Ladoga and Peipus as example

    NASA Astrophysics Data System (ADS)

    Melentyev, V.; Melentyev, K.; Pettersson, L.; Mushkudiany, M.

    2009-04-01

    The Problem of dynamical instability of ice conditions and modification of ice regime of polytypical lakes owing to global warming was investigated using time-varying satellite imagery. Deep-water Lake Ladoga and shallow-water Lake Peipus both situated at the north-western part of Russian Federation in moderate climatic zone but possessed different heat capacity were used for comparative studies. The comprehensive analysis of ERS/RADARSAT/Envisat SAR images was provided using the results of long-term studies of thermal structures of these inland water bodies and peculiarities of their variability during open water season as well calculations of heat supply in different weather conditions. 1993-2008 NERSC/NIERSC SAR archive as well materials sub-satellite experiments on board research vessel and research aircraft since 1960-s is used. Shipborne observations were used for validation satellite information. Thematic interpretation of satellite data shows that SAR signature of ice could be applied as tracer of various natural processes and phenomena, including climatically and ecologically important ones. As result dependence of hydrological features and the time of freeze-up and ice destruction in both selected lakes in consequence of climate change and softening of winter severity in nowadays was assessed. Wind regime patterns (speed and direction) were analyzed using algorithm CMOD 4 and in the upshot the increase of seasonal and regional variability of windy weather in studied regions was fixed. In frame of these studies wind cadastre appurtenant to the NW part of RF was composed on the basis of satellite SAR survey. In particular the modification of "wind climate" was disclosed. And what is more: it was revealed that intensification of windy weather resulted in intensification of dynamic range of water and ice exchange between the central part of both studied polytypical lakes and their gulfs. These natural processes took place due to widening duration of the open

  20. Time-varying imagery of ice features dynamic scattering in presence climate change: polytypical lakes Ladoga and Peipus as example

    NASA Astrophysics Data System (ADS)

    Melentyev, V. V.; Melentyev, K. V.; Pettersson, L. H.; Mushkudany, M. I.

    2009-04-01

    Problem of dynamical instability of ice conditions and modification of ice regime of polytypical lakes owing to global warming were investigated using time-varying satellite imagery. Deep-water Lake Ladoga and shallow-water Lake Peipus both situated at the north-western part of Russian Federation in moderate climatic zone but possessed different heat capacity were used for comparative studies. The comprehensive analysis of ERS/RADARSAT/Envisat SAR images was provided using the results of long-term studies of thermal structures of these inland waterbodies and peculiarities of their variability during open water season as well calculations of heat supply in different weather conditions. 1993-2008 NERSC/NIERSC SAR archive as well materials sub-satellite experiments onboard research vessel and research aircraft since 1960-s is used. Shipborne observations were used for validation satellite information. Thematic interpretation of satellite data shows that SAR signature of ice could be applied as tracer of various natural processes and phenomena, including climatically and ecologically important ones. As result dependence of hydrological features and the time of freeze-up and ice destruction in both selected lakes in consequence of climate change and softening of winter severity in nowadays was assessed. Wind regime patterns (speed and direction) were analyzed using algorithm CMOD 4 and in the upshot the increase of seasonal and regional variability of windy weather in studied regions was fixed. In frame of these studies wind cadastre appurtenant to the NW part of RF was composed on the basis of satellite SAR survey. In particular the modification of "wind climate" was disclosed. And what is more: it was revealed that intensification of windy weather resulted in intensification of dynamic range of water and ice exchange between the central part of both studied polytypical lakes and their gulfs. These natural processes took place due to widening duration of the open water

  1. Investigation of the transition layer in 3C-SiC/6H-SiC heterostructures

    SciTech Connect

    Lebedev, A. A.; Zamorianskaya, M. V.; Davydov, S. Yu.; Kirilenko, D. A.; Lebedev, S. P. Sorokin, L. M.; Shustov, D. B.; Scheglov, M. P.

    2013-11-15

    Transmission electron microscopy and the cathodoluminescence method are used to study the transition region in 3C-SiC/6H-SiC heterostructures. It is shown that this region is, as a rule, constituted by alternating 3C-SiC and 6H-SiC layers with the possible inclusion of other silicon carbide polytypes. An assumption is made that this structure of the transition region can be explained in terms of the model of spinodal decomposition.

  2. The Pleistocene glaciations and the evolutionary history of the polytypic snail species Arianta arbustorum (Gastropoda, Pulmonata, Helicidae).

    PubMed

    Gittenberger, E; Piel, W H; Groenenberg, D S J

    2004-01-01

    The evolutionary history of the snail Arianta arbustorum is controversial. This diverse, polytypic species has two distinct forms: one, with a globular shell and closed umbilicus, is found from lowland to high altitudes; the other, with a depressed shell and open umbilicus, is found at a few scattered, high altitude localities. What is the origin of these two forms? Some believe that the depressed shell is a recent, local, ecotypic adaptation to alpine environments. Others believe that this form is a relic of an ancestral condition that may have survived the Pleistocene glaciations on nunatak-like montane refugia, while the globular shell is a derived condition and its presence at high altitudes follows post-Pleistocene recolonisation. We analysed a portion of the mitochondrial gene cytochrome oxidase I for 100 snails of the species A. arbustorum, three additional Arianta species, and nine outgroup taxa from five genera, in order to understand the phylogeographic history of the species. Despite some confounding artefacts that are likely due to introgression among the morphological forms, the resulting phylogeny shows that the depressed shell is plesiomorphic, while the globular shell is derived. Moreover, their disparate histories suggest that the depressed shell variety survived the glaciations in pockets of alpine refugia, while the globular shell variety recolonised the alpine environment post-glacially. PMID:15022758

  3. Measurement of Optical, Mechanical and Transport properties of the hexagonal closed packed 4H polytype of metallic silver

    NASA Astrophysics Data System (ADS)

    Chakraborty, Indrani; Shirodkar, Sharmila N.; Gohil, Smita; Waghmare, Umesh; Ayyub, Pushan

    2013-03-01

    Optical, mechanical and transport property measurements were done on the hexagonal closed packed (hcp) 4H polytype of Ag with stacking sequence ABCBABCB.. grown as bulk films on Al2O3 substrates. Diffused reflectance measurements done on the 4H films showed a general loss of reflectivity amounting to a decrease of 35% as compared to normal fcc (3C) Ag near 500 nm with a blueshift of 5nm in the bulk plasmon frequency, possibly due to the modified electronic structure of the hcp form. Raman spectroscopic measurements showed the appearance of a peak at 64.3 cm-1 at 4K which underwent ``Mode softening,'' that is shifted to lower wave numbers with increase of temperature and disappeared above 350K. Low temperature transport measurements done on 4H films gave the in-plane resistivity value to be 39 times higher than that of a similarly synthesized fcc Ag film at 295 K. Vicker's microhardness measurements done on the 4H films showed that the 4H samples to be almost 5 times harder than the 3C Ag. Density functional theory simulations were done to obtain the phonon dispersion, band structure and nature of Fermi surface for the 4H Ag which corroborated with the experimental observations. The 4H form appears to be a much less metallic, darker and harder form of Ag.

  4. The Pleistocene glaciations and the evolutionary history of the polytypic snail species Arianta arbustorum (Gastropoda, Pulmonata, Helicidae).

    PubMed

    Gittenberger, E; Piel, W H; Groenenberg, D S J

    2004-01-01

    The evolutionary history of the snail Arianta arbustorum is controversial. This diverse, polytypic species has two distinct forms: one, with a globular shell and closed umbilicus, is found from lowland to high altitudes; the other, with a depressed shell and open umbilicus, is found at a few scattered, high altitude localities. What is the origin of these two forms? Some believe that the depressed shell is a recent, local, ecotypic adaptation to alpine environments. Others believe that this form is a relic of an ancestral condition that may have survived the Pleistocene glaciations on nunatak-like montane refugia, while the globular shell is a derived condition and its presence at high altitudes follows post-Pleistocene recolonisation. We analysed a portion of the mitochondrial gene cytochrome oxidase I for 100 snails of the species A. arbustorum, three additional Arianta species, and nine outgroup taxa from five genera, in order to understand the phylogeographic history of the species. Despite some confounding artefacts that are likely due to introgression among the morphological forms, the resulting phylogeny shows that the depressed shell is plesiomorphic, while the globular shell is derived. Moreover, their disparate histories suggest that the depressed shell variety survived the glaciations in pockets of alpine refugia, while the globular shell variety recolonised the alpine environment post-glacially.

  5. Identifying and mapping the polytypes and orientation relationships in ZnO/CdSe core–shell nanowire arrays

    NASA Astrophysics Data System (ADS)

    Consonni, Vincent; Rapenne, Laetitia; Renou, Gilles; Roussel, Hervé; Gérard, Lionel; Cuscó, Ramón; Artús, Lluís; André, Régis; Rauch, Edgar F.

    2016-11-01

    Identifying and mapping the crystalline phases and orientation relationships on the local scale in core–shell ZnO nanowire heterostructures are of primary importance to improve the interface quality, which governs the performances of the nanoscale devices. However, this represents a major difficulty, especially when the expected polytypes exhibit very similar properties as in the case of CdSe. In the present work, we address that issue in ZnO nanowire heterostructures involving a uniform and highly conformal CdSe shell grown by molecular beam epitaxy. It is shown by x-ray diffraction and Raman spectroscopy through the occurrence of the (101¯0) and (101¯1) diffraction peaks and of the {{{{E}}}2}{{low}} mode at 34 cm‑1, respectively, that the CdSe shell is mostly crystallized into the wurtzite phase. By using automated crystal phase and orientation mapping with precession (ASTAR) in a transmission electron microscope and thus by benefiting from highly precise electron diffraction patterns, the CdSe shell is found to crystallize also into the minority zinc blende phase. The wurtzite CdSe shell is epitaxially grown on the top of ZnO nanowires, and some specific orientation relationships are mapped and revealed when grown on their vertical sidewalls. Zinc blende CdSe domains are also formed exclusively in the center of wurtzite CdSe grains located on the vertical sidewalls; both wurtzite and zinc blende CdSe crystalline phases have a strong orientation relationship. These findings reveal that ASTAR is a powerful technique to elucidate the structural properties on the local scale and to gain a deeper insight into their crystalline phases and orientation relationships, which is highly promising for many types of semiconducting nanowire heterostructures.

  6. Polytypes and twins in the diamond-lonsdaleite system formed by high-pressure and high-temperature treatment of graphite.

    PubMed

    Kulnitskiy, Boris; Perezhogin, Igor; Dubitsky, Gennady; Blank, Vladimir

    2013-10-01

    As a result of the high-temperature and high-pressure treatment of graphite we obtained a powder containing diamond and lonsdaleite. The structure and properties of the powder were studied by transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). It was found that the synthesized material contains not only diamond nanoparticles, but also some relatively large (up to several nanometers) fragments of lonsdaleite. 4H and 6H polytypes were found in some of the diamond particles. Incoherent twin boundaries were observed in the diamond particle containing fragments of lonsdaleite.

  7. A study of the dechanneling of protons in SiC polytype crystals in the energy range Ep=400-650 keV

    NASA Astrophysics Data System (ADS)

    Kokkoris, M.; Perdikakis, G.; Kossionides, S.; Petrović, S.; Vlastou, R.; Grötzschel, R.

    2004-06-01

    In the present work, the energy spectra of protons channeled along the (0 0 0 1) axis of SiC polytype crystals (namely 4H and 6H) in the energy range Ep=400-650 keV, in the backscattering geometry, were taken and analyzed. Computer simulations are in very good agreement with the measured spectra. The accurate reproduction of the experimental channeling spectra in the backscattering geometry is strongly based on the investigation of the correct dechanneling function and α, the ratio of the stopping powers in the aligned and random mode. In the present work, the applicability of a Gompertz type sigmoidal dechanneling function, with two parameters, k and xc, which represent characteristic dechanneling rate and range, respectively, is examined, and the results are compared to the ones obtained in the past, concerning the same polytype structures, based on the assumption that the dechanneling of protons follows an exponential law, for the energy range Ep=1.7-2.4 MeV.

  8. Modeling possible structural transitions in aluminum and lead nanoclusters

    NASA Astrophysics Data System (ADS)

    Baidyshev, V. S.; Gafner, Yu. Ya.; Samsonov, V. M.; Bembel, A. G.

    2015-01-01

    The boundaries of thermal stability of the initial fcc phase in aluminum and lead clusters up to 3 nm in diameter have been investigated by the method of molecular dynamics using a modified tight-binding potential TB-SMA. It is shown that in small Al and Pb clusters the initial fcc phase passes into different structural modifications due the temperature factor. The polytype transition temperature has been found to approach the cluster melting temperature with an increase in the nanoparticle size. It is established that geometric "magic" numbers play an important role in the formation of structure of Al clusters (in contrast to Pb clusters).

  9. Synthesis, characterization and sorption properties of functionalized Cr-MIL-101-X (X=-F, -Cl, -Br, -CH3, -C6H4, -F2, -(CH3)2) materials

    NASA Astrophysics Data System (ADS)

    Buragohain, Amlan; Couck, Sarah; Van Der Voort, Pascal; Denayer, Joeri F. M.; Biswas, Shyam

    2016-06-01

    Four existing and three new functionalized chromium terephthalates having MIL-101 topology and denoted as Cr-MIL-101-X (existing ones with X=-F, 1-F; -Cl, 2-Cl; -Br, 3-Br; -CH3, 4-CH3; new ones with X=-C6H4, 5-C6H4; -F2, 6-F2, -(CH3)2, 7-(CH3)2) were synthesized under hydrothermal conditions. All the materials except 5-C6H4 could be prepared by a general synthetic route, in which the mixtures of CrO3, H2BDC-X (BDC=1,4-benzenedicarboxylate) linkers, conc. HCl and water with a molar ratio of 1:1:3.9:222.2 were reacted at 180 °C for 144 h. Compared to the 144 h of synthesis time, three of the compounds, namely 1-Cl, 2-Br and 5-C6H4, could be prepared in much shorter reaction times (12-18 h at 180-210 °C). The materials possess high thermal stability up to 270-300 °C in an air atmosphere. The activated compounds exhibit significant porosity (SBET range: 1273-2135 m2 g-1). At 0 °C and 1 bar, the CO2 adsorption capacities of the compounds fall in the 1.7-2.9 mmol g-1 range. Compounds 1-F and 6-F2 showed enhanced CO2 uptake values compared to parent Cr-MIL-101. The benzene adsorption capacities of the compounds lie in the range of 66.2-139.5 molecules per unit cell at 50 °C and p/p0=0.35. The increased benzene uptake value of 1-F compared to un-functionalized Cr-MIL-101 and 4-CH3 suggests that the fluorination has induced more hydrophobicity in Cr-MIL-101 as compared to the methylation.

  10. Size- and structure-dependence of thermal and mechanical behaviors of single-crystalline and polytypic superlattice ZnS nanowires

    SciTech Connect

    Moon, Junghwan; Cho, Maenghyo; Zhou, Min

    2015-06-07

    Molecular dynamics (MD) simulations are carried out to study the thermal and mechanical behaviors of single-crystalline wurtzite (WZ), zinc-blende (ZB), and polytypic superlattice ZnS nanowires containing alternating WZ and ZB regions with thicknesses between 1.85 nm and 29.62 nm under tensile loading. The wires analyzed have diameters between 1.77 nm and 5.05 nm. The Green-Kubo method is used to calculate the thermal conductivity of the wires at different deformed states. A non-equilibrium MD approach is used to analyze the thermal transport behavior at the interfaces between different structural regions in the superlattice nanowires (SLNWs). The Young's modulus and thermal conductivity of ZB nanowires are approximately 2%–12% and 23%–35% lower than those of WZ nanowires, respectively. The lower initial residual compressive stress due to higher irregularity of surface atoms causes the Young's modulus of ZB nanowires to be lower. The dependence of the thermal conductivity on structure comes from differences in phonon group velocities associated with the different wires. The thermal conductivity of polytypic superlattice nanowires is up to 55% lower than that of single-crystalline nanowires, primarily because of phonon scattering at the interfaces and the resulting lower effective phonon mean free paths for each structural region. As the periodic lengths (1.85–29.62 nm) and specimen lengths (14.81–59.24 nm) of SLNWs decrease, these effects become more pronounced, causing the thermal conductivity to further decrease by up to 30%.

  11. Thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap semiconductors SiC, GaN, and ZnO

    SciTech Connect

    Huang, Zheng; Lü, Tie-Yu; Wang, Hui-Qiong; Zheng, Jin-Cheng

    2015-09-15

    We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type) semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory. Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC. However, for GaN and ZnO, their power factors show a very weak dependence on the polytype. Detailed analysis of the thermoelectric properties with respect to temperature and carrier concentration of 4H-SiC, 2H-GaN, and 2H-ZnO shows that the figure of merit of these three compounds increases with temperature, indicating the promising potential applications of these thermoelectric materials at high temperature. The significant difference of the polytype-dependent thermoelectric properties among SiC, GaN, and ZnO might be related to the competition between covalency and ionicity in these semiconductors. Our calculations may provide a new way to enhance the thermoelectric properties of wide-band-gap semiconductors through atomic structure design, especially hexagonality design for SiC.

  12. Effects of Polytypism on Optical Properties and Band Structure of Individual Ga(N)P Nanowires from Correlative Spatially Resolved Structural and Optical Studies.

    PubMed

    Dobrovolsky, Alexander; Persson, Per O Å; Sukrittanon, Supanee; Kuang, Yanjin; Tu, Charles W; Chen, Weimin M; Buyanova, Irina A

    2015-06-10

    III-V semiconductor nanowires (NWs) have gained significant interest as building blocks in novel nanoscale devices. The one-dimensional (1D) nanostructure architecture allows one to extend band structure engineering beyond quantum confinement effects by utilizing formation of different crystal phases that are thermodynamically unfavorable in bulk materials. It is therefore of crucial importance to understand the influence of variations in the NWs crystal structure on their fundamental physical properties. In this work we investigate effects of structural polytypism on the optical properties of gallium phosphide and GaP/GaNP core/shell NW structures by a correlative investigation on the structural and optical properties of individual NWs. The former is monitored by transmission electron microscopy, whereas the latter is studied via cathodoluminescence (CL) mapping. It is found that structural defects, such as rotational twins in zinc blende (ZB) GaNP, have detrimental effects on light emission intensity at low temperatures by promoting nonradiative recombination processes. On the other hand, formation of the wurtzite (WZ) phase does not notably affect the CL intensity neither in GaP nor in the GaNP alloy. This suggests that zone folding in WZ GaP does not enhance its radiative efficiency, consistent with theoretical predictions. We also show that the change in the lattice structure have negligible effects on the bandgap energies of the GaNP alloys, at least within the range of the investigated nitrogen compositions of <2%. Both WZ and ZB GaNP are found to have a significantly higher efficiency of radiative recombination as compared with that in parental GaP, promising for potential applications of GaNP NWs as efficient nanoscale light emitters within the desirable amber-red spectral range.

  13. Polytype stability, microstructural evolution, and impurities at the interface of homoepitaxial 4H-silicon carbide(1120) thin films grown via hot-wall chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Bishop, Seann M. G.

    replicate the polytype of the underlying substrate exactly. The microstructural evolution of [112¯0]-oriented SiC and III-nitride films was investigated. 4H-SiC (112¯0) films showed evidence of step-flow growth in the sublimation-driven regime, while both step-flow and terrace nucleation and growth were observed in the precursor-driven regime. AlN initially grew via the Stranski-Krastanov mode on 4-HSiC(112¯0), while the Volmer-Weber mode was observed for GaN on AlN(112¯0).

  14. Transition Planning

    ERIC Educational Resources Information Center

    Statfeld, Jenna L.

    2011-01-01

    Post-school transition is the movement of a child with disabilities from school to activities that occur after the completion of school. This paper provides information about: (1) post-school transition; (2) transition plan; (3) transition services; (4) transition planning; (5) vocational rehabilitation services; (6) services that are available…

  15. Boundary conditions for transition-metal dichalcogenide monolayers in the continuum model

    NASA Astrophysics Data System (ADS)

    Péterfalvi, Csaba G.; Kormányos, Andor; Burkard, Guido

    We derive the boundary conditions for MoS2 and similar transition-metal dichalcogenide honeycomb (2H polytype) monolayers with the same type of k . p Hamiltonian within the continuum model around the K points. In an effective 2-band description, the electron-hole symmetry breaking quadratic terms are also taken into account. We model the effect of the edges with a linear edge constraint method that has been applied previously to graphene. Focusing mainly on zigzag edges, we find that different reconstruction geometries with different edge-atoms can generally be described with one scalar parameter varying between 0 and 2 π . We analyze the edge states and their dispersion relation in MoS2 in particular, and we find good agreement with the results of previous density functional theory calculations for various edge types.

  16. Boundary conditions for transition-metal dichalcogenide monolayers in the continuum model

    NASA Astrophysics Data System (ADS)

    Péterfalvi, Csaba G.; Kormányos, Andor; Burkard, Guido

    2015-12-01

    We derive the boundary conditions for MoS2 and similar transition-metal dichalcogenide honeycomb (2H polytype) monolayers with the same type of k .p Hamiltonian within the continuum model around the K points. In an effective two-band description, the electron-hole symmetry breaking quadratic terms are also taken into account. We model the effect of the edges with a linear edge constraint method that has been applied previously to graphene. Focusing mainly on zigzag edges, we find that different reconstruction geometries with different edge atoms can generally be described with one scalar parameter varying between 0 and 2 π . We analyze the edge states and their dispersion relation in MoS2 in particular, and we find good agreement with the results of previous density functional theory calculations for various edge types.

  17. On the stability of the electronic system in transition metal dichalcogenides.

    PubMed

    Faraggi, M N; Zubizarreta, X; Arnau, A; Silkin, V M

    2016-05-11

    Based on first-principles calculations, we prove that the origin of charge-density wave formation in metallic layered transition metal dichalcogenides (TMDC) is not due to an electronic effect, like the Fermi surface (FS) nesting, as it had been proposed. In particular, we consider NbSe2, NbS2, TaSe2, and TaS2 as representative examples of 2H-TMDC polytypes. Our main result consists that explicit inclusion of the matrix elements in first-principles calculations of the electron susceptibility [Formula: see text] removes, due to strong momentum dependence of the matrix elements, almost all the information about the FS topologies in the resulting [Formula: see text]. This finding strongly supports an interpretation in which the momentum dependence of the electron-phonon interaction is the only reason why the phenomenon of charge-density waves appears in this class of materials. PMID:27057801

  18. On the stability of the electronic system in transition metal dichalcogenides.

    PubMed

    Faraggi, M N; Zubizarreta, X; Arnau, A; Silkin, V M

    2016-05-11

    Based on first-principles calculations, we prove that the origin of charge-density wave formation in metallic layered transition metal dichalcogenides (TMDC) is not due to an electronic effect, like the Fermi surface (FS) nesting, as it had been proposed. In particular, we consider NbSe2, NbS2, TaSe2, and TaS2 as representative examples of 2H-TMDC polytypes. Our main result consists that explicit inclusion of the matrix elements in first-principles calculations of the electron susceptibility [Formula: see text] removes, due to strong momentum dependence of the matrix elements, almost all the information about the FS topologies in the resulting [Formula: see text]. This finding strongly supports an interpretation in which the momentum dependence of the electron-phonon interaction is the only reason why the phenomenon of charge-density waves appears in this class of materials.

  19. Ferromagnetism in 4H-GaN polytype doped by non-magnetic light elements Li, Be, B, C, O, F, Ne, Na, and Mg: Ab-initio study

    NASA Astrophysics Data System (ADS)

    Torrichi, M.; Ferhat, M.; Bouhafs, B.

    2016-09-01

    Using density-functional theory within the generalized-gradient approximation, we explore the magnetic behavior induced by nonmagnetic impurity X atoms, such as Li, Be, B, C, O, F, Ne, Na, and Mg on cation site in 4H-GaN polytype. The results reveal that Ne doped 4H-GaN has the highest magnetic moment of 3μB, whereas Mg doped 4H-GaN has the lowest magnetic moment of 0.75μB. Among the systems studied 4H-GaN doped Ne has been found to be half-metallic, whereas 4H-GaN doped F and Na are found to be nearly half-metallic. The partial density of states evidence that magnetism is achieved through a p-p like coupling between the impurity and the host 2p states. Furthermore, we inspect whether there exists a relationship between the spin-polarization and the local structure around the doping X atoms. It is found that for all the compounds studied, the total magnetic moment increases with increasing the X-N bond lengths. Interestingly, 4H-GaN:Be becomes ferromagnetic with increasing the Be-N bond length, whereas 4H-GaN:Na and 4H-GaN:F become half-metallic with increasing Na-N and F-N bond lengths.

  20. Transiting Exoplanets

    NASA Astrophysics Data System (ADS)

    Haswell, Carole A.

    2010-07-01

    1. Our solar system from afar; 2. Exoplanet discoveries by the transit method; 3. What the transit lightcurve tells us; 4. The transiting exoplanet population; 5. Transmission spectroscopy and Rossiter-McLaughlin effect; 6. Secondary eclipses and phase variations; 7. Transit timing variations and orbital dynamics; 8. Brave new worlds: the future; Index.

  1. Hydride VPE: the unexpected process for the fast growth of GaAs and GaN nanowires with record aspect ratio and polytypism-free crystalline structure

    NASA Astrophysics Data System (ADS)

    André, Yamina; Trassoudaine, Agnès.; Avit, Geoffrey; Lekhal, Kaddour; Ramdani, Mohammed R.; Leroux, Christine; Monier, Guillaume; Varenne, Christelle; Hoggan, Philip; Castelluci, Dominique; Bougerol, Catherine; Réveret, François; Leymarie, Joël.; Petit, Elodie; Dubrovskii, Vladimir G.; Gil, Evelyne

    2013-12-01

    Hydride Vapor Phase Epitaxy (HVPE) makes use of chloride III-Cl and hydride V-H3 gaseous growth precursors. It is known as a near-equilibrium process, providing the widest range of growth rates from 1 to more than 100 μm/h. When it comes to metal catalyst-assisted VLS (vapor-liquid-solid) growth, the physics of HVPE growth is maintained: high dechlorination frequency, high axial growth rate of nanowires (NWs) up to 170 μm/h. The remarkable features of NWs grown by HVPE are the untapered morphology with constant diameter and the stacking fault-free crystalline phase. Record pure zinc blende cubic phase for 20 μm long GaAs NWs with radii of 10 and 5 nm is shown. The absence of wurtzite phase in GaAs NWs grown by HVPE whatever the diameter is discussed with respect to surface energetic grounds and kinetics. Ni assisted, Ni-Au assisted and catalyst-free HVPE growth of wurtzite GaN NWs is also addressed. Micro-photoluminescence spectroscopy analysis revealed GaN nanowires of great optical quality, with a FWHM of 1 meV at 10 K for the neutral donor bound exciton transition.

  2. Transitional Care

    ERIC Educational Resources Information Center

    Naylor, Mary; Keating, Stacen A.

    2008-01-01

    Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…

  3. Newborn transition.

    PubMed

    Graves, Barbara W; Haley, Mary Mumford

    2013-01-01

    The transition from intrauterine to extrauterine life is a complex adaptation. Although, in a sense, the entire time in utero is in preparation for this transition, there are many specific anatomic and physiologic changes that take place in the weeks and days leading up to labor that facilitate a healthy transition. Some, including increasing pulmonary vasculature and blood flow, are part of an ongoing process of maturation. Others, such as a reversal in the lung from secreting fluid to absorbing fluid and the secretion of pulmonary surfactant, are associated with the hormonal milieu that occurs when spontaneous labor is impending. Interventions such as elective cesarean birth or induction of labor may interfere with this preparation for birth. Postnatal interventions such as immediate clamping of the umbilical cord and oropharyngeal suction may also compromise the normal process of newborn transition. This article reviews the physiology of the fetal to newborn transition and explores interventions that may facilitate or hinder the optimal process.

  4. Metric transition

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This report describes NASA's metric transition in terms of seven major program elements. Six are technical areas involving research, technology development, and operations; they are managed by specific Program Offices at NASA Headquarters. The final program element, Institutional Management, covers both NASA-wide functional management under control of NASA Headquarters and metric capability development at the individual NASA Field Installations. This area addresses issues common to all NASA program elements, including: Federal, state, and local coordination; standards; private industry initiatives; public-awareness initiatives; and employee training. The concluding section identifies current barriers and impediments to metric transition; NASA has no specific recommendations for consideration by the Congress.

  5. [Humanitarian transition].

    PubMed

    Mattei, Jean-François; Troit, Virginie

    2016-02-01

    In two centuries, modern humanitarian action has experienced several fractures often linked to crises. Although its professionalism and intervention force remain indisputable, it faces, since the 2000s, a new context that limits its ability to act and confronts it with new dilemmas, even though it must deal with needs for aid of unprecedented scale. These difficulties reveal a humanitarian transition period that was not anticipated. This transition period reflects the change from a dominant paradigm of North-South solidarity of Western origin to a much more complex model. This article provides a summary of the current mutations that are dominated by the States' assertion of sovereignty. Among the possible solutions, it argues for an ethical approach and a better integration of the research carried out in the Global South, prerequisites for building a true partnership and placing the victims at the heart of the operations which involve them. PMID:26936180

  6. Eliminating Transitions

    ERIC Educational Resources Information Center

    Gallick, Barb; Lee, Lisa

    2010-01-01

    Adults often find themselves transitioning from one activity to another in a short time span. Most of the time, they do not feel they have a lot of control over their schedules, but wish that they could carve out extended time to relax and focus on one project. Picture a group of children in the block area who have spent 15 or 20 minutes building…

  7. Luminescent transition metal dichalcogenide nanosheets through one-step liquid phase exfoliation

    NASA Astrophysics Data System (ADS)

    Mar Bernal, M.; Álvarez, Lidia; Giovanelli, Emerson; Arnáiz, Adriana; Ruiz-González, Luisa; Casado, Santiago; Granados, Daniel; Pizarro, Ana M.; Castellanos-Gomez, Andres; Pérez, Emilio M.

    2016-09-01

    Liquid phase exfoliation (LPE) from the bulk is an adequate method for the mass-production of thin nanosheets of transition metal dichalcogenides (TMDCs). However, making suspensions in which the extraordinary properties of mechanically exfoliated TMDCs are observable remains a challenge. We describe a mild LPE method to produce luminescent suspensions of MoS2 and WS2 in N-methylpyrrolidone or isopropanol/water mixtures, without the need for a purification step. The key differences in our experimental procedure compared to previously reported LPE methods are the use of mild bath sonication at controlled temperature and the low initial concentration of the parent TMDC. Spectroscopic and AFM data confirm that an overwhelming majority of the sample is composed of ultrathin nanosheets. HREM data support the formation of the luminescent 2H polytype. The ultrathin nanosheets can be transferred to pure water and cell culture medium. Confocal fluorescence microscopy experiments on MCF-7 breast cancer cells exposed to LPE WS2 show that the cells are viable and the photoluminescence of the nanosheets is detectable.

  8. Fabrication of quasi-superlattices at the interface between 3 C-SiC epitaxial layer and substrates of hexagonal SiC polytypes by sublimation epitaxy in vacuum

    NASA Astrophysics Data System (ADS)

    Lebedev, A. A.; Davydov, S. Yu.; Sorokin, L. M.; Shakhov, L. V.

    2015-12-01

    Transmission electron microscopy has been used to study the structure of a transition layer between a hexagonal substrate (6 H-SiC and 4 H-SiC) and a cubic silicon carbide layer grown by sublimation epitaxy in vacuum. It is shown by microdiffraction analysis that the transition layer with a thickness of 210 nm is constituted by alternating layers of cubic (3 C) and hexagonal (6 H) silicon carbide. It is demonstrated that 6 H-SiC/3 C-SiC and 4 H-SiC/3 C-SiC quasi-superlattices can be produced by this method.

  9. Interband Transitions

    NASA Astrophysics Data System (ADS)

    Varma, Shikha

    We have studied thin (1-7 monolayer) overlayers of Hg on Ag(100) and Cu(100) using angle-resolved photoemission and low energy electron diffraction. We have investigated the electronic states of well ordered, disordered and the liquid overlayers of mercury. We show that the electronic structure of the well ordered overlayers is very different than that of the disordered and the liquid overlayers. The well ordered overlayers of Hg on Ag(100) exhibit a new electronic state which is absent for the disordered overlayers of mercury as well as for gaseous mercury. We will argue that this new Hg state is a result of the interaction among the Hg-Hg atoms, when adsorbed on Ag(100). The strain among adlayer atoms also plays a crucial role in the development of the new electronic state. We have used the synchrotron radiation to study the partial cross-section and the branching ratio of the 5d electronic state of Hg. We have measured the partial cross-section and branching ratio of the well-ordered, disordered and liquid overlayers of mercury on Ag(100) and Cu(100). We have observed resonances in the photoemission intensities of the mercury 5d orbitals for thin films of mercury for incident photon energies near the 5p _{3/2}, 4f_{7/2 } and 4f_{5/2} thresholds. The results indicate that interband transitions from the 5p and 4f levels to the 5d orbitals can occur for a thin overlayer of mercury, as a result of final state 5f contributions, though such interband transitions are forbidden for the free isolated Hg atom. These resonances are attributed to the formation of a solid state band structure incorporating new itinerant mercury electronic state. These resonances are absent when the mercury film is disordered or melted. We have measured the branching ratio of the 5d orbital for thin mercury overlayers in the photon energy range between 26 to 105 eV. The branching ratios deviate from the nonrelativistic statistical value of 1.5, reaching values of 8.0. These results indicate

  10. Transitions: A Personal Perspective.

    ERIC Educational Resources Information Center

    Wood, Ann Stace

    1995-01-01

    Distinguishes between unchosen transitions (children maturing and leaving, parents aging, companies downsizing) and chosen ones (moving, divorce, marriage, career changes). Describes the steps one goes through: uneasiness, renewed energy, complaining, exploration, partial transition, and the completed transition. (JOW)

  11. First-principles theory of field-effect doping in transition-metal dichalcogenides: Structural properties, electronic structure, Hall coefficient, and electrical conductivity

    NASA Astrophysics Data System (ADS)

    Brumme, Thomas; Calandra, Matteo; Mauri, Francesco

    2015-04-01

    We investigate how field-effect doping affects the structural properties, the electronic structure, and the Hall coefficient of few-layers transition-metal dichalcogenides by using density-functional theory. We consider monolayers, bilayers, and trilayers of the H polytype of MoS2, MoSe2, MoTe2, WS2, and WSe2 and provide a full database of electronic structures and Hall coefficients for hole and electron doping. We find that, for both electron and hole doping, the electronic structure depends on the number of layers and cannot be described by a rigid band shift. Furthermore, it is important to relax the structure under the asymmetric electric field. Interestingly, while the width of the conducting channel depends on the doping, the number of occupied bands at each given k point is almost uncorrelated with the thickness of the doping-charge distribution. Finally, we calculate within the constant-relaxation-time approximation the electrical conductivity and the inverse Hall coefficient. We demonstrate that in some cases the charge determined by Hall-effect measurements can deviate from the real charge by up to 50%. For hole-doped MoTe2 the Hall charge has even the wrong polarity at low temperature. We provide the mapping between the doping charge and the Hall coefficient. We present more than 250 band structures for all doping levels of the transition-metal dichalcogenides considered within this work.

  12. Order-disorder phase transition in the antiperovskite-type structure of synthetic kogarkoite, Na3SO4F

    NASA Astrophysics Data System (ADS)

    Avdontceva, Margarita S.; Zolotarev, Andrey A.; Krivovichev, Sergey V.

    2015-11-01

    High-temperature phase transition of synthetic kogarkoite, Na3SO4F, has been studied by high-temperature X-ray powder and single-crystal diffraction. The temperature of the phase transition can be estimated as 112.5±12.5 °C. The low-temperature phase, α-Na3SO4F, at 293 K, is monoclinic, P21/m, a=18.065(3), b=6.958(1), c=11.446(1) Å, β=107.711(1)°, Z=12. The structure contains thirteen symmetrically independent Na sites with coordination numbers varying from 6 to 8, and six independent S sites. The high-temperature β-phase at 423 K is rhombohedral, R-3m, a=6.94(1), c=24.58(4) Å, Z=9. The crystal structure of both polymorphs of Na3SO4F can be described as a 9R antiperovskite polytype based upon triplets of face-sharing [FNa6] octahedra linked into a three-dimensional framework by sharing corners. In the α-modification, the SO4 tetrahedra are completely ordered and located in the framework cavities. In the β-modification, there are only two symmetrically independent Na atoms in the structure. The main difference between the structures of the α- and β-phases is the degree of ordering of the SO4 tetrahedra: in the α-modification, they are completely ordered, whereas, in the β-modification, the complete disorder is observed, which is manifested in a number of low-occupied O sites around fully occupied S sites. The phase transition is therefore has an order-disorder character and is associated with the decrease of structural complexity measured as an information content per unit cell [577.528 bits for the low- (α) and 154.830 bits for the high- (β) temperature modifications].

  13. Transition Handbook: Valley Transitional School Program.

    ERIC Educational Resources Information Center

    Virginia State Dept. of Rehabilitation Services, Richmond.

    The handbook was developed by the 3-year Valley Transitional School Project, serving Augusta, Staunton, and Waynesboro schools, all located in Augusta County, Virginia. The purpose of the project was to develop and validate a model which would assist school youth with severe disabilities to make the transition from school to employment, in the…

  14. Gas turbine combustor transition

    DOEpatents

    Coslow, B.J.; Whidden, G.L.

    1999-05-25

    A method is described for converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit. 7 figs.

  15. Gas turbine combustor transition

    DOEpatents

    Coslow, Billy Joe; Whidden, Graydon Lane

    1999-01-01

    A method of converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit.

  16. Conceptualizing Transitions to Adulthood

    ERIC Educational Resources Information Center

    Wyn, Johanna

    2014-01-01

    This chapter provides an overview of theories of the transition to young adulthood. It sets out the argument for conceptual renewal and discusses some implications of new patterns of transition for adult education.

  17. The Managerial Transition.

    ERIC Educational Resources Information Center

    Kneeland, Steven J.

    1980-01-01

    Having identified the problem of managerial transition in a previous article (CE 510 277), the author outlines a strategy for change which includes performance appraisal, definition of the management structure, and counselling for the individual in transition. (SK)

  18. Transition in Turbines

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The concept of a large disturbance bypass mechanism for the initiation of transition is reviewed and studied. This mechanism, or some manifestation thereof, is suspected to be at work in the boundary layers present in a turbine flow passage. Discussion is presented on four relevant subtopics: (1) the effect of upstream disturbances and wakes on transition; (2) transition prediction models, code development, and verification; (3) transition and turbulence measurement techniques; and (4) the hydrodynamic condition of low Reynolds number boundary layers.

  19. Cosmological phase transitions

    SciTech Connect

    Kolb, E.W. |

    1993-10-01

    If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions.

  20. Origins of evolutionary transitions.

    PubMed

    Clarke, Ellen

    2014-04-01

    An 'evolutionary transition in individuality' or 'major transition' is a transformation in the hierarchical level at which natural selection operates on a population. In this article I give an abstract (i.e. level-neutral and substrate-neutral) articulation of the transition process in order to precisely understand how such processes can happen, especially how they can get started. PMID:24736161

  1. Transitivity of Preferences

    ERIC Educational Resources Information Center

    Regenwetter, Michel; Dana, Jason; Davis-Stober, Clintin P.

    2011-01-01

    Transitivity of preferences is a fundamental principle shared by most major contemporary rational, prescriptive, and descriptive models of decision making. To have transitive preferences, a person, group, or society that prefers choice option "x" to "y" and "y" to "z" must prefer "x" to "z". Any claim of empirical violations of transitivity by…

  2. Modeling the transition region

    NASA Technical Reports Server (NTRS)

    Singer, Bart A.

    1993-01-01

    The current status of transition-region models is reviewed in this report. To understand modeling problems, various flow features that influence the transition process are discussed first. Then an overview of the different approaches to transition-region modeling is given. This is followed by a detailed discussion of turbulence models and the specific modifications that are needed to predict flows undergoing laminar-turbulent transition. Methods for determining the usefulness of the models are presented, and an outlook for the future of transition-region modeling is suggested.

  3. Structural phase transition and erasable optically memorized effect in layered γ-In{sub 2}Se{sub 3} crystals

    SciTech Connect

    Ho, Ching-Hwa; Chen, Ying-Cen; Pan, Chia-Chi

    2014-01-21

    We have grown In{sub 2}Se{sub 3} layered-type crystals using chemical vapor transport method with ICl{sub 3} as the transport agent. The as-grown crystals show two different color groups of black shiny for α-phase In{sub 2}Se{sub 3} and red to yellow for γ-phase In{sub 2}Se{sub 3}. High-resolution transmission electron micro scopy verifies crystalline state and structural polytype of the as-grown In{sub 2}Se{sub 3}. The results indicate that the α-In{sub 2}Se{sub 3} crystals present more crystalline states than those of the other amorphous γ-In{sub 2}Se{sub 3}. The amorphous effect on the advancing of optoelectronic property of γ-In{sub 2}Se{sub 3} shows erasable optical-memorized effect in the disordered and polycrystalline γ-In{sub 2}Se{sub 3} layers. Laser-induced photodarkening and annealed-recovery test verified that a reversible structural-phase transition of γ↔α can occur inside the γ-In{sub 2}Se{sub 3}. Thermoreflectance and Raman scattering measurements are carried out to identify the inter-phase transformation of the γ-In{sub 2}Se{sub 3} polycrystals using different heat treatments. Direct band gaps and Raman vibration modes for the γ- and α-In{sub 2}Se{sub 3} crystalline phases are, respectively, characterized and identified. The character of γ↔α inter-phase transition promotes feasible optical and optoelectronic applications of the γ-In{sub 2}Se{sub 3} material in optical memory, optics, and solar-energy devices.

  4. Structural phase transition and erasable optically memorized effect in layered γ-In2Se3 crystals

    NASA Astrophysics Data System (ADS)

    Ho, Ching-Hwa; Chen, Ying-Cen; Pan, Chia-Chi

    2014-01-01

    We have grown In2Se3 layered-type crystals using chemical vapor transport method with ICl3 as the transport agent. The as-grown crystals show two different color groups of black shiny for α-phase In2Se3 and red to yellow for γ-phase In2Se3. High-resolution transmission electron micro scopy verifies crystalline state and structural polytype of the as-grown In2Se3. The results indicate that the α-In2Se3 crystals present more crystalline states than those of the other amorphous γ-In2Se3. The amorphous effect on the advancing of optoelectronic property of γ-In2Se3 shows erasable optical-memorized effect in the disordered and polycrystalline γ-In2Se3 layers. Laser-induced photodarkening and annealed-recovery test verified that a reversible structural-phase transition of γ↔α can occur inside the γ-In2Se3. Thermoreflectance and Raman scattering measurements are carried out to identify the inter-phase transformation of the γ-In2Se3 polycrystals using different heat treatments. Direct band gaps and Raman vibration modes for the γ- and α-In2Se3 crystalline phases are, respectively, characterized and identified. The character of γ↔α inter-phase transition promotes feasible optical and optoelectronic applications of the γ-In2Se3 material in optical memory, optics, and solar-energy devices.

  5. Gifts from Exoplanetary Transits

    NASA Astrophysics Data System (ADS)

    Narita, Norio

    2009-08-01

    The discovery of transiting extrasolar planets has enabled us to do a number of interesting studies. Transit photometry reveals the radius and the orbital inclination of transiting planets, which allows us to learn the true mass and density of the respective planets by the combined information from radial velocity (RV) measurements. In addition, follow-up observations of transiting planets, looking at such things as secondary eclipses, transit timing variations, transmission spectroscopy, and the Rossiter-McLaughlin effect, provide us information about their dayside temperatures, unseen bodies in systems, planetary atmospheres, and the obliquity of planetary orbits. Such observational information, which will provide us a greater understanding of extrasolar planets, is available only for transiting planets. Here, I briefly summarize what we can learn from transiting planets and introduce previous studies.

  6. Gravitationally induced quantum transitions

    NASA Astrophysics Data System (ADS)

    Landry, A.; Paranjape, M. B.

    2016-06-01

    In this paper, we calculate the probability for resonantly inducing transitions in quantum states due to time-dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultracold neutrons, which are organized according to the energy levels of the Schrödinger equation in the presence of the Earth's gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency ω . The driving force is created by oscillating a macroscopic mass in the neighborhood of the system of neutrons. The neutron lifetime is approximately 880 sec while the probability of transitions increases as t2. Hence, the optimal strategy is to drive the system for two lifetimes. The transition amplitude then is of the order of 1.06 ×10-5, and hence with a million ultracold neutrons, one should be able to observe transitions.

  7. Moons over Jupiter: transits and shadow transits

    NASA Astrophysics Data System (ADS)

    Rogers, J. H.; et al.

    2003-06-01

    There is no more beautiful illustration of orbital motions than the movements of Jupiter's satellites. Every six years, their movements are most strikingly displayed, when the jovian system is presented edge-on to Earth. This means that there is a higher frequency of multiple transits over the face of the planet, as all the moons transit across the equatorial zone, whereas in other years Ganymede and Callisto transit near the poles or not at all. Also, for a few months, the satellites pass in front of each other, displaying mutual eclipses and occultations. In 2002/2003 we have been able to observe a fine series of these multiple and mutual events. On the cover, and on these pages, are some of the highest-resolution images received.

  8. Dynamical Transition in polypeptides

    NASA Astrophysics Data System (ADS)

    He, Yunfen; Markelz, Andrea

    2008-03-01

    Two of the possible causes for the so called dynamical transition (the rapid increase in flexibility for biomolecules at ˜ 200 K) are: thermally activated side chain diffusive motions with hydration dependent activation energies; or a glass transition in the biological water directly adjacent to the biomolecule. If the transition is strictly due to side chain activation, it should not depend on protein structure. Previously we demonstrated that the dynamical transition remains after tertiary structure was removed using THz time domain dielectric spectroscopy (0.2 -2.0 THz, 0.5-5ps). Here measurements on polyalanine as a function of chain length show that the dynamical transition does not occur for peptide length shorter than 5. However, the transition is observed for 5 mer and higher. Structural and simulation studies indicate that the 5 mer transiently occupies structured forms [1,2]. These results suggest that A) the dynamical transition is not due to thermally activated side chain motion and B) secondary structure is necessary for the dynamical transition. Secondary structure possibly induces sufficient ordering in the adjacent water to result in a fragile to strong glass transition resulting in increased protein flexibility [3]. [1] KAH Wildman et al. Solid State Nucl. Magn. Reson. 24 (2003) 94-109. [2] Yuguang Mu,et al. Proteins 58, (2005) 45-52. [3] S.H. Chen et al. PNAS (2006) 9012--9016.

  9. Transition to Old Age (Transition to Retirement).

    ERIC Educational Resources Information Center

    Bergman, Simon

    Several conceptualizations and definitions of retirement have been proposed. One of them--the three-stage transition process--can be illustrated from studies in Israel: (1) leaving the old role; (2) going through the act of formal separation; and (3) adjusting to the new situation and role. Today's higher rate of survival into later years means…

  10. Transitioning between Clerkship Directors

    ERIC Educational Resources Information Center

    Soltys, Stephen M.; Pary, Robert J.; Robinson, Stephen W.; Markwell, Stephen J.

    2011-01-01

    Objective: The authors report on succession-planning for mid-level academic positions. Method: The authors describe the process of succession-planning between clerkship directors and the smooth transition resulting in one case. Results: Gradually transitioning allowed a new faculty person to assume the clerkship-director position with minimal…

  11. Transitions in Spousal Caregiving.

    ERIC Educational Resources Information Center

    Burton, Lynda C.; Zdaniuk, Bozena; Schulz, Richard; Jackson, Sharon; Hirsch, Calvin

    2003-01-01

    Describes transitions over 5 years among community-dwelling elderly spouses into and within caregiving roles and associated health outcomes. The trajectory of health outcomes associated with caregiving was generally downward. Those who transitioned to heavy caregiving had more symptoms of depression, and poorer self-reported health and health…

  12. Seamless Transition for All

    ERIC Educational Resources Information Center

    Test, David W.

    2008-01-01

    Postschool outcomes for students with disabilities have been dismal for quite some time now. Although recent data from the National Longitudinal Transition Study 2 indicate some improvement, students with severe intellectual disabilities continue to transition into segregated employment at unacceptable rates in spite of a multitude of studies,…

  13. Matter in transition

    NASA Astrophysics Data System (ADS)

    Anderson, Lara B.; Gray, James; Raghuram, Nikhil; Taylor, Washington

    2016-04-01

    We explore a novel type of transition in certain 6D and 4D quantum field theories, in which the matter content of the theory changes while the gauge group and other parts of the spectrum remain invariant. Such transitions can occur, for example, for SU(6) and SU(7) gauge groups, where matter fields in a three-index antisymmetric representation and the fundamental representation are exchanged in the transition for matter in the two-index antisymmetric representation. These matter transitions are realized by passing through superconformal theories at the transition point. We explore these transitions in dual F-theory and heterotic descriptions, where a number of novel features arise. For example, in the heterotic description the relevant 6D SU(7) theories are described by bundles on K3 surfaces where the geometry of the K3 is constrained in addition to the bundle structure. On the F-theory side, non-standard representations such as the three-index antisymmetric representation of SU( N) require Weierstrass models that cannot be realized from the standard SU( N) Tate form. We also briefly describe some other situations, with groups such as Sp(3), SO(12), and SU(3), where analogous matter transitions can occur between different representations. For SU(3), in particular, we find a matter transition between adjoint matter and matter in the symmetric representation, giving an explicit Weierstrass model for the F-theory description of the symmetric representation that complements another recent analogous construction.

  14. Good Transitions = Great Starts!

    ERIC Educational Resources Information Center

    Our Children: The National PTA Magazine, 2012

    2012-01-01

    The smooth transition of outgoing and incoming board members and officers is of vital importance and can determine the PTA's success for years to come. The transition process is the responsibility of both incoming and outgoing officers and board members. It gives closure to those leaving their positions and allows those coming in to be properly…

  15. Secondary Education Transition Model.

    ERIC Educational Resources Information Center

    Colorado State Univ., Ft. Collins.

    The Secondary Education Transition Model project at Colorado State University-Fort Collins represents a local and state commitment to serve students with severe handicaps who are moving into community work and living roles. These comprehensive transition services begin at the secondary education level and extend into the adult service system. The…

  16. Transitions and Linkages.

    ERIC Educational Resources Information Center

    Ilfeld, Ellen M., Ed.; Hanssen, Elizabeth, Ed.

    1997-01-01

    If children are to benefit from a healthy, supportive early childhood experience, it is important to strengthen transitions between early childhood experiences in educational and care settings and the more formal educational system. This issue of Coordinator's Notebook focuses on strengthening linkages and transitions between home, preschool, and…

  17. Predictability of critical transitions

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaozhu; Kuehn, Christian; Hallerberg, Sarah

    2015-11-01

    Critical transitions in multistable systems have been discussed as models for a variety of phenomena ranging from the extinctions of species to socioeconomic changes and climate transitions between ice ages and warm ages. From bifurcation theory we can expect certain critical transitions to be preceded by a decreased recovery from external perturbations. The consequences of this critical slowing down have been observed as an increase in variance and autocorrelation prior to the transition. However, especially in the presence of noise, it is not clear whether these changes in observation variables are statistically relevant such that they could be used as indicators for critical transitions. In this contribution we investigate the predictability of critical transitions in conceptual models. We study the quadratic integrate-and-fire model and the van der Pol model under the influence of external noise. We focus especially on the statistical analysis of the success of predictions and the overall predictability of the system. The performance of different indicator variables turns out to be dependent on the specific model under study and the conditions of accessing it. Furthermore, we study the influence of the magnitude of transitions on the predictive performance.

  18. Growth mechanisms, polytypism, and real structure of kaolinite microcrystals

    SciTech Connect

    Samotoin, N. D.

    2008-09-15

    The mechanisms of growth of kaolinite microcrystals (0.1-5.0 {mu}m in size) at deposits related to the cluvial weathering crust, as well as to the low-temperature and medium-temperature hydrothermal processes of transformations of minerals in different rocks in Russia, Kazakhstan, Ukraine, Czechia, Vietnam, India, Cuba, and Madagascar, are investigated using transmission electron microscopy and vacuum decoration with gold. It is established that kaolinite microcrystals grow according to two mechanisms: the mechanism of periodic formation of two-dimensional nuclei and the mechanism of spiral growth. The spiral growth of kaolinite microcrystals is dominant and occurs on steps of screw dislocations that differ in sign and magnitude of the Burgers vector along the c axis. The layered growth of kaolinite originates from a widespread source in the form of a step between polar (+ and -) dislocations, i.e., a growth analogue of the Frank-Read dislocation source. The density of growth screw dislocations varies over a wide range and can be as high as {approx}10{sup 9} cm{sup -2}. Layered stepped kaolinite growth pyramids for all mechanisms of growth on the (001) face of kaolinite exhibit the main features of the triclinic 1Tc and real structures of this mineral.

  19. Genetic diversification, vicariance, and selection in a polytypic frog.

    PubMed

    Robertson, Jeanne M; Zamudio, Kelly R

    2009-01-01

    Spatial patterns of heritable phenotypic diversity reflect the relative roles of gene flow and selection in determining geographic variation within a species. We quantified color differentiation and genetic divergence among 20 populations of the red-eyed tree frog (Agalychnis callidryas) in lower Central America. Phylogenetic analyses revealed 5 well-supported mitochondrial DNA clades, and we infer from our phylogeny that geographic barriers have played a large role in structuring populations. Two phenotypic characters varied independently among isolated population groups: Flank coloration distinguished Caribbean from Pacific individuals, whereas leg coloration exhibited a more complex geographic pattern. We detected 3 generalized spatial patterns of genetic and phenotypic diversity: 1) phenotypic differentiation in the presence of historical connectivity, 2) phenotypic uniformity across genetically differentiated regions, and 3) codistribution of genetic and phenotypic characters. These patterns indicate that phenotypic diversification is highly regionalized and can result from spatial variation in localized adaptations, geographic isolation, genetic drift, and/or evolutionary stasis. Although the mode of selection underlying color variation was not the focal objective of this study, we discuss the possible roles of natural and sexual selection in mediating population differentiation. Our study underscores the fact that selection gradients vary across relatively small spatial scales, even in species that occupy relatively homogeneous environments. PMID:19589848

  20. Superconductivity in transition metals.

    PubMed

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified.

  1. The Heliosphere in Transition

    NASA Astrophysics Data System (ADS)

    Kasper, Justin

    2015-04-01

    The heliosphere consists of the connective tissue of particles, fields and photons that mediate our interaction with the Sun and with interstellar space. Exploration of the heliosphere yields clues to the nature of environments we cannot reach ourselves, illuminating the composition of the solar interior, or the acceleration of cosmic rays in the galaxy. The heliosphere is also a laboratory for us to understand the fundamental physics of magnetized plasma, from heating and instabilities to coupling with neutral gas and dust. This talk will review some of the most exciting recent results in the heliosphere with a focus on transitions: what we can learn by exploring transitions within the heliosphere, how the heliosphere is responding to the long term transition in solar activity, and how our very view of the heliosphere is in transition with upcoming missions such as Solar Probe Plus, Solar Orbiter and IMAP.

  2. Superconductivity in transition metals.

    PubMed

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified. PMID:25666075

  3. Alternative fuel transit buses

    SciTech Connect

    Motta, R.; Norton, P.; Kelly, K.

    1996-10-01

    The National Renewable Energy Laboratory (NREL) is a U.S. Department of Energy (DOE) national laboratory; this project was funded by DOE. One of NREL`s missions is to objectively evaluate the performance, emissions, and operating costs of alternative fuel vehicles so fleet managers can make informed decisions when purchasing them. Alternative fuels have made greater inroads into the transit bus market than into any other. Each year, the American Public Transit Association (APTA) surveys its members on their inventory and buying plans. The latest APTA data show that about 4% of the 50,000 transit buses in its survey run on an alternative fuel. Furthermore, 1 in 5 of the new transit buses that members have on order are alternative fuel buses. This program was designed to comprehensively and objectively evaluate the alternative fuels in use in the industry.

  4. Transitions in biofilm formation

    NASA Astrophysics Data System (ADS)

    Gordon, Vernita; Thatcher, Travis; Cooley, Benjamin

    2011-03-01

    Biofilms are multicellular, dynamic communities formed by interacting unicellular organisms bound to a surface. Forming a biofilm is a developmental process, characterized by sequential changes in gene expression and behavior as bacteria and yeast progress from discrete, free-swimming cells though stages that arrive at a mature biofilm. We are developing automated metrics to identify key transitions in early biofilm formation as cells attach to a surface, populate that surface, and adhere to each other to form early microcolonies. Our metrics use high-throughput tracking and analysis of microscopy movies to localize these transitions in space and time. Each of these transitions is associated with a loss of entropy in the bacterial system and, therefore, with biological activity that drives this loss of entropy. Better understanding of these transitions will allow automated determination of the strength and turn-on of attractive cell-surface and cell-cell interactions as biofilm development progresses.

  5. Melting of Transition Metals

    SciTech Connect

    Ross, M; Japel, S; Boehler, R

    2005-04-11

    We review the transition melting studies carried out at Mainz, and describe a recently developed model used to explain that the relatively low melting slopes are due to the partially filled d-bands, and the persistence of the pressure induced s-d transition. The basic tenets of the model have now been reconfirmed by new measurements for Cu and Ni. The measurements show that Cu which has a filled 3d-band, has a melt slope that is about 2.5 greater than its neighbor Ni. In the case of Mo, the apparent discrepancy of DAC melting measurements with shock melting can be explained by accounting for the change in melt slope due to the bcc-cp transition observed in the shock studies. The Fe melt curve is revisited. The possible relevance of the Jahn-Teller effect and recently observed transition metal melts with Icosahedral Short-Range Order (ISRO) is discussed.

  6. Palaeontology: turtles in transition.

    PubMed

    Lee, Michael S Y

    2013-06-17

    One of the major remaining gaps in the vertebrate fossil record concerns the origin of turtles. The enigmatic little reptile Eunotosaurus could represent an important transitional form, as it has a rudimentary shell that resembles the turtle carapace.

  7. Transit Timing Variations

    NASA Video Gallery

    The animation shows the difference between planet transit timing of single and multiple planet system. In tightly packed planetary systems, the gravitational pull of the planets among themselves ca...

  8. Urban guideway transit workshop: Proceedings

    SciTech Connect

    Larsen, H. )

    1992-03-01

    On March 20--21, 1991, EPRI sponsored a workshop on urban guideway transit. The purpose of this workshop was to provide utility managers with increased knowledge about urban guideway transit options, public policy regarding transit, and the effect of transit options on utility operations. With this information utilities should be better prepared to make decisions about transit development in their service areas. The workshop also provided EPRI with ideas and information for developing an R D project plan for urban guideway transit.

  9. Stability, transition and turbulence

    NASA Technical Reports Server (NTRS)

    Hussaini, M. Y.

    1987-01-01

    A glimpse is provided of the research program in stability, transition, and turbulence based on numerical simulations. This program includes both the so-called abrupt and the restrained transition processes. Attention is confined to the prototype problems of channel flow and the parallel boundary layer in the former category and the Taylor-Couette flow in the latter category. It covers both incompressible flows and supersonic flows. Some representative results are presented.

  10. Stability, transition and turbulence

    NASA Technical Reports Server (NTRS)

    Hussaini, M. Y.

    1987-01-01

    A glimpse is provided of the research program in stability, transition and turbulence based on numerical simulations. This program includes both the so-called abrupt and the restrained transition processes. Attention is confined to the prototype problems of channel flow and the parallel boundary layer in the former category and the Taylor-Couette flow in the latter category. It covers both incompressible flows and supersonic flows. Some representative results are presented.

  11. Matter in transition

    DOE PAGES

    Anderson, Lara B.; Gray, James; Raghuram, Nikhil; Taylor, Washington

    2016-04-13

    In this study, we explore a novel type of transition in certain 6D and 4D quantum field theories, in which the matter content of the theory changes while the gauge group and other parts of the spectrum remain invariant. Such transitions can occur, for example, for SU(6) and SU(7) gauge groups, where matter fields in a three-index antisymmetric representation and the fundamental representation are exchanged in the transition for matter in the two-index antisymmetric representation. These matter transitions are realized by passing through superconformal theories at the transition point. We explore these transitions in dual F-theory and heterotic descriptions, wheremore » a number of novel features arise. For example, in the heterotic description the relevant 6D SU(7) theories are described by bundles on K3 surfaces where the geometry of the K3 is constrained in addition to the bundle structure. On the F-theory side, non-standard representations such as the three-index antisymmetric representation of SU(N) require Weierstrass models that cannot be realized from the standard SU(N) Tate form. We also briefly describe some other situations, with groups such as Sp(3), SO(12), and SU(3), where analogous matter transitions can occur between different representations. For SU(3), in particular, we find a matter transition between adjoint matter and matter in the symmetric representation, giving an explicit Weierstrass model for the F-theory description of the symmetric representation that complements another recent analogous construction.« less

  12. Venus Transit 2004

    NASA Astrophysics Data System (ADS)

    Mayo, L. A.; Odenwald, S. F.

    2002-09-01

    December 6th, 1882 was the last transit of the planet Venus across the disk of the sun. It was heralded as an event of immense interest and importance to the astronomical community as well as the public at large. There have been only six such occurrences since Galileo first trained his telescope on the heavens in 1609 and on Venus in 1610 where he concluded that Venus had phases like the moon and appeared to get larger and smaller over time. Many historians consider this the final nail in the coffin of the Ptolemaic, Earth centered solar system. In addition, each transit has provided unique opportunities for discovery such as measurement and refinement of the astronomical unit, calculation of longitudes on the earth, and detection of Venus' atmosphere. The NASA Sun Earth Connection Education Forum in partnership with the Solar System Exploration Forum, DPS, and a number of NASA space missions is developing plans for an international education program centered around the June 8, 2004 Venus transit. The transit will be visible in its entirety from Europe and partially from the East Coast of the United States. We will use a series of robotic observatories including the Telescopes In Education network distributed in latitude to provide observations of the transit that will allow middle and high school students to calculate the A.U. through application of parallax. We will also use Venus transit as a probe of episodes in American history (e.g. 1769: revolutionary era, 1882: post civil war era, and 2004: modern era). Museums and planetariums in the US and Europe will offer real time viewing of the transit and conduct educational programs through professional development seminars, public lectures, and planetarium shows. We are interested in soliciting advice from the research community to coordinate professional research interests with this program.

  13. Examining hydrogen transitions.

    SciTech Connect

    Plotkin, S. E.; Energy Systems

    2007-03-01

    This report describes the results of an effort to identify key analytic issues associated with modeling a transition to hydrogen as a fuel for light duty vehicles, and using insights gained from this effort to suggest ways to improve ongoing modeling efforts. The study reported on here examined multiple hydrogen scenarios reported in the literature, identified modeling issues associated with those scenario analyses, and examined three DOE-sponsored hydrogen transition models in the context of those modeling issues. The three hydrogen transition models are HyTrans (contractor: Oak Ridge National Laboratory), MARKAL/DOE* (Brookhaven National Laboratory), and NEMS-H2 (OnLocation, Inc). The goals of these models are (1) to help DOE improve its R&D effort by identifying key technology and other roadblocks to a transition and testing its technical program goals to determine whether they are likely to lead to the market success of hydrogen technologies, (2) to evaluate alternative policies to promote a transition, and (3) to estimate the costs and benefits of alternative pathways to hydrogen development.

  14. Transition from School to Work.

    ERIC Educational Resources Information Center

    Milner, Eileen R.

    1995-01-01

    This brief informational flyer presents practical information on the transition from school to work for students who are deaf-blind or have other severe disabilities. After defining transition, the flyer offers guidelines on: the age at which transition services should be started, areas that should be considered in a coordinated transition plan,…

  15. Navajo childbirth in transition.

    PubMed

    Waxman, A G

    1990-03-01

    For the Navajo Indians, the transition from home-centered childbearing practices based on religious ritual to biomedically directed childbirth in hospitals was completed over a relatively short time in the middle decades of this century. For Anglo-American society, the acceptance of medically oriented childbirth occurred during an equally short period earlier in the century. The transition was driven for both by many common factors. For Navajo women it was additionally influenced by the social and economic changes that affected the Reservation following the beginning of the Second World War. This paper examines the changes in Navajo childbearing practices and, for comparison, those of the dominant American society. It reviews factors that permitted the acceptance of biomedical childbirth by Navajo women and explores the health implications of the transition. PMID:2233169

  16. UTM: Universal Transit Modeller

    NASA Astrophysics Data System (ADS)

    Deeg, Hans J.

    2014-12-01

    The Universal Transit Modeller (UTM) is a light-curve simulator for all kinds of transiting or eclipsing configurations between arbitrary numbers of several types of objects, which may be stars, planets, planetary moons, and planetary rings. A separate fitting program, UFIT (Universal Fitter) is part of the UTM distribution and may be used to derive best fits to light-curves for any set of continuously variable parameters. UTM/UFIT is written in IDL code and its source is released in the public domain under the GNU General Public License.

  17. Nursing Role Transition Preceptorship

    ERIC Educational Resources Information Center

    Batory, Susan M.

    2014-01-01

    The preceptorship clinical experience in a practical nursing (PN) program at a Midwestern community college is considered crucial to the PN students' transition from novice nurse to professional nurse. However, no research has been available to determine whether the preceptorship clinical accomplishes its purpose. A case study was conducted to…

  18. Indian science in transition.

    PubMed

    Singh, Seema

    2006-10-01

    India is a country in transition, and so is its science. Scientific institutions, researchers, regulatory agencies, and government policies are in a state of flux as changes are instigated to overcome the bureaucracy and inertia that are characteristic of a populous developing nation.

  19. Variational transition state theory

    SciTech Connect

    Truhlar, D.G.

    1993-12-01

    This research program involves the development of variational transition state theory (VTST) and semiclassical tunneling methods for the calculation of gas-phase reaction rates and selected applications. The applications are selected for their fundamental interest and/or their relevance to combustion.

  20. Learning for Life Transitions

    ERIC Educational Resources Information Center

    Varmecky, Jane Hyde

    2012-01-01

    Many adults return to formal learning situations to pursue lifelong learning goals because their lives are in transition from dealing with real-life problems such as divorce and re-marriage. The purpose of this study was to describe what couples learned that contributed to the success of their subsequent marriages and how they learned it. The…

  1. Families in Transition .

    ERIC Educational Resources Information Center

    Bundy, Michael L., Ed.; Gumaer, James, Ed.

    1984-01-01

    Focuses on disrupted families and the role of the school counselor in helping children adjust. Describes characteristics of healthy families, and discusses the transition to the blended family, effects of divorce groups on children's classroom behavior, counseling children in stepfamilies, single-parent families, and parenting strengths of single…

  2. Transitioning to CBT.

    ERIC Educational Resources Information Center

    Molina, Carla A.

    1995-01-01

    Discusses transitional situations of concurrent computer-based training (CBT) that occur in organizations, and provides instructional designers with adaptable checklists to use when communicating with managers and programmers about the tasks performed and the tools needed in designing and developing CBT. Tables present steps, applications,…

  3. The Education of Transition.

    ERIC Educational Resources Information Center

    Castles, Stephen; And Others

    1982-01-01

    The Foundation for Education with Production was organized to help African countries make the transition from colonial economies to socialism by providing an international network of resources to support educational innovations linking education with production. The theoretical basis for the foundation's work and its current activities are…

  4. A Survey Transition Course

    ERIC Educational Resources Information Center

    Johnston, William; McAllister, Alex M.

    2012-01-01

    Successful outcomes for a "Transition Course in Mathematics" have resulted from two unique design features. The first is to run the course as a "survey course" in mathematics, introducing sophomore-level students to a broad set of mathematical fields. In this single mathematics course, undergraduates benefit from an introduction of proof…

  5. Transition at hypersonic speeds

    NASA Technical Reports Server (NTRS)

    Morkovin, Mark V.

    1987-01-01

    Certain conjectures on the physics of instabilities in high-speed flows are discussed and the state of knowledge of hypersonic transition summarized. The case is made for an unpressured systematic research program in this area consisting of controlled microscopic experiments, theory, and numerical simulations.

  6. Transition Is Everyone's Job.

    ERIC Educational Resources Information Center

    Sherman, Jill Z.; Osborn, Sandra R.

    Vocationally at-risk students have one or a combination of handicaps affecting mobility, coordination, communication, self-care and/or cognition which may significantly interfere with the goals of successful student-to-adult transition, namely employment, productive work, and independent community living. A program for students with physical…

  7. String mediated phase transitions

    NASA Technical Reports Server (NTRS)

    Copeland, ED; Haws, D.; Rivers, R.; Holbraad, S.

    1988-01-01

    It is demonstrated from first principles how the existence of string-like structures can cause a system to undergo a phase transition. In particular, the role of topologically stable cosmic string in the restoration of spontaneously broken symmetries is emphasized. How the thermodynamic properties of strings alter when stiffness and nearest neighbor string-string interactions are included is discussed.

  8. Singing Smoothes Classroom Transitions

    ERIC Educational Resources Information Center

    Mathews, Sarah E.

    2012-01-01

    Just as humming a merry tune helped Snow White and her furry animal friends to quickly clean a filthy cottage in the movie "Snow White and the Seven Dwarfs" (Disney & Cottrell, 1937), singing can be an effective way to help keep young children fully engaged during classroom transitions. The purposes of this article are to: (1) consider why…

  9. Families in Transition.

    ERIC Educational Resources Information Center

    Britton, Patti O., Ed.; McGee, Michael, Ed.

    1987-01-01

    This issue of "Emphasis" deals with families in transition, providing some model programs for the new family and some historical perspectives on how families have developed over time. Articles include: (1) "Nostalgia on the Right" (Nancy Theriot); (2) "Heart to Heart" (Nancy Harrington-MacLennan); (3) "The Media Get the Message" (Janet Alyn); (4)…

  10. Water's second glass transition.

    PubMed

    Amann-Winkel, Katrin; Gainaru, Catalin; Handle, Philip H; Seidl, Markus; Nelson, Helge; Böhmer, Roland; Loerting, Thomas

    2013-10-29

    The glassy states of water are of common interest as the majority of H2O in space is in the glassy state and especially because a proper description of this phenomenon is considered to be the key to our understanding why liquid water shows exceptional properties, different from all other liquids. The occurrence of water's calorimetric glass transition of low-density amorphous ice at 136 K has been discussed controversially for many years because its calorimetric signature is very feeble. Here, we report that high-density amorphous ice at ambient pressure shows a distinct calorimetric glass transitions at 116 K and present evidence that this second glass transition involves liquid-like translational mobility of water molecules. This "double Tg scenario" is related to the coexistence of two liquid phases. The calorimetric signature of the second glass transition is much less feeble, with a heat capacity increase at Tg,2 about five times as large as at Tg,1. By using broadband-dielectric spectroscopy we resolve loss peaks yielding relaxation times near 100 s at 126 K for low-density amorphous ice and at 110 K for high-density amorphous ice as signatures of these two distinct glass transitions. Temperature-dependent dielectric data and heating-rate-dependent calorimetric data allow us to construct the relaxation map for the two distinct phases of water and to extract fragility indices m = 14 for the low-density and m = 20-25 for the high-density liquid. Thus, low-density liquid is classified as the strongest of all liquids known ("superstrong"), and also high-density liquid is classified as a strong liquid. PMID:24101518

  11. Transit of Extrasolar Planets

    NASA Technical Reports Server (NTRS)

    Doyle, Laurance R.

    1998-01-01

    During the past five years we have pursued the detection of extrasolar planets by the photometric transit method, i.e. the detection of a planet by watching for a drop in the brightness of the light as it crosses in front of a star. The planetary orbit must cross the line-of-sight and so most systems will not be lined up for such a transit to ever occur. However, we have looked at eclipsing binary systems which are already edge-on. Such systems must be very small in size as this makes the differential light change due to a transit much greater for a given planet size (the brightness difference will be proportional to the area of the transiting planet to the disc area of the star). Also, the planet forming region should be closer to the star as small stars are generally less luminous (that is, if the same thermal regime for planet formation applies as in the solar system). This led to studies of the habitable zone around other stars, as well. Finally, we discovered that our data could be used to detect giant planets without transits as we had been carefully timing the eclipses of the stars (using a GPS antenna for time) and this will drift by being offset by any giant planets orbiting around the system, as well. The best summary of our work may be to just summarize the 21 refereed papers produced during the time of this grant. This will be done is chronological order and in each section separately.

  12. Transition States and transition state analogue interactions with enzymes.

    PubMed

    Schramm, Vern L

    2015-04-21

    Enzymatic transition states have lifetimes of a few femtoseconds (fs). Computational analysis of enzyme motions leading to transition state formation suggests that local catalytic site motions on the fs time scale provide the mechanism to locate transition states. An experimental test of protein fs motion and its relation to transition state formation can be provided by isotopically heavy proteins. Heavy enzymes have predictable mass-altered bond vibration states without altered electrostatic properties, according to the Born-Oppenheimer approximation. On-enzyme chemistry is slowed in most heavy proteins, consistent with altered protein bond frequencies slowing the search for the transition state. In other heavy enzymes, structural changes involved in reactant binding and release are also influenced. Slow protein motions associated with substrate binding and catalytic site preorganization are essential to allow the subsequent fs motions to locate the transition state and to facilitate the efficient release of products. In the catalytically competent geometry, local groups move in stochastic atomic motion on the fs time scale, within transition state-accessible conformations created by slower protein motions. The fs time scale for the transition state motions does not permit thermodynamic equilibrium between the transition state and stable enzyme states. Isotopically heavy enzymes provide a diagnostic tool for fast coupled protein motions to transition state formation and mass-dependent conformational changes. The binding of transition state analogue inhibitors is the opposite in catalytic time scale to formation of the transition state but is related by similar geometries of the enzyme-transition state and enzyme-inhibitor interactions. While enzymatic transition states have lifetimes as short as 10(-15) s, transition state analogues can bind tightly to enzymes with release rates greater than 10(3) s. Tight-binding transition state analogues stabilize the rare but

  13. Alternative fuel transit buses: The Pierce Transit Success Story

    SciTech Connect

    1996-10-01

    The Pierce transit program for operating mass transit buses on compressed natural gas (CNG) is described. Cost, reliability, fuel efficiency, emission of combustion products, and future trends are discussed.

  14. 75 FR 76921 - Tobacco Transition Payment Program; Tobacco Transition Assessments

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-10

    ... Corporation 7 CFR Part 1463 RIN 0560-AH30 Tobacco Transition Payment Program; Tobacco Transition Assessments... Commodity Credit Corporation (CCC) is modifying the regulations for the Tobacco Transition Payment Program (TTPP) to clarify, consistent with current practice and as required by the Fair and Equitable...

  15. Transition Planning: A Team Effort. NICHCY Transition Summary, TS10.

    ERIC Educational Resources Information Center

    Gutierrez, Mary Kate

    This summary on transition planning provides ideas and information on how students, families, school personnel, service providers, and others can work together to help students with a disability make a smooth transition after leaving high school. It focuses on creative transition planning and services that use all the resources that exist in…

  16. LAMPF transition region

    SciTech Connect

    Sander, O.R.

    1982-06-01

    After describing the transition region between the LAMPF drift-tube linac and side-coupled linac, we discuss the function of the region, its present shortcomings, and the need for a redesign. Then we present the new design, its advantages, and its expected performance. Included are detailed results of beam-dynamics studies giving the ranges of input- and output-beam shapes that can be successfully matched in the new transition region. To improve the present operation of the two linacs, we suggest small changes that will allow us to easily match the beam between the two linacs. Finally we describe the methods used in our beam-dynamic studies so that effects of future improvements to the new design can be examined.

  17. Models for transition clinics.

    PubMed

    Carrizosa, Jaime; An, Isabelle; Appleton, Richard; Camfield, Peter; Von Moers, Arpad

    2014-08-01

    Transition is a purposeful, planned process that addresses the medical, psychosocial, educational, and vocational needs of adolescents and young adults with chronic medical conditions, as they advance from a pediatric and family-centered to an adult, individual focused health care provider. This article describes some of the models for transition clinics or services for epilepsy in five countries (Canada, France, Colombia, Germany, and the United Kingdom). These models include joint adult and pediatric clinics, algorithm-driven service, and a check list system in the context of pediatric care. Evaluation of these models is limited, and it is not possible to choose an optimal program. The attitude and motivation of health care providers may be the most important elements. PMID:25209087

  18. Radiative Transitions in Charmonium

    SciTech Connect

    Jozef Dudek; Robert Edwards; David Richards

    2005-10-01

    The form factors for the radiative transitions between charmonium mesons are investigated. We employ an anisotropic lattice using a Wilson gauge action, and domain-wall fermion action. We extrapolate the form factors to Q{sup 2} = 0, corresponding to a real photon, using quark-model-inspired functions. Finally, comparison is made with photocouplings extracted from the measured radiative widths, where known. Our preliminary results find photocouplings commensurate with these experimentally extracted values.

  19. The major evolutionary transitions.

    PubMed

    Szathmáry, E; Smith, J M

    1995-03-16

    There is no theoretical reason to expect evolutionary lineages to increase in complexity with time, and no empirical evidence that they do so. Nevertheless, eukaryotic cells are more complex than prokaryotic ones, animals and plants are more complex than protists, and so on. This increase in complexity may have been achieved as a result of a series of major evolutionary transitions. These involved changes in the way information is stored and transmitted.

  20. High speed transition prediction

    NASA Technical Reports Server (NTRS)

    Gasperas, Gediminis

    1992-01-01

    The main objective of this work period was to develop, acquire and apply state-of-the-art tools for the prediction of transition at high speeds at NASA Ames. Although various stability codes as well as basic state codes were acquired, the development of a new Parabolized Stability Equation (PSE) code was minimal. The time that was initially allocated for development was used on other tasks, in particular for the Leading Edge Suction problem, in acquiring proficiency in various graphics tools, and in applying these tools to evaluate various Navier-Stokes and Euler solutions. The second objective of this work period was to attend the Transition and Turbulence Workshop at NASA Langley in July and August, 1991. A report on the Workshop follows. From July 8, 1991 to August 2, 1991, the author participated in the Transition and Turbulence Workshop at NASA Langley. For purposes of interest here, analysis can be said to consist of solving simplified governing equations by various analytical methods, such as asymptotic methods, or by use of very meager computer resources. From the composition of the various groups at the Workshop, it can be seen that analytical methods are generally more popular in Great Britain than they are in the U.S., possibly due to historical factors and the lack of computer resources. Experimenters at the Workshop were mostly concerned with subsonic flows, and a number of demonstrations were provided, among which were a hot-wire experiment to probe the boundary layer on a rotating disc, a hot-wire rake to map a free shear layer behind a cylinder, and the use of heating strips on a flat plate to control instability waves and consequent transition. A highpoint of the demonstrations was the opportunity to observe the rather noisy 'quiet' supersonic pilot tunnel in operation.

  1. NASA metric transition plan

    NASA Technical Reports Server (NTRS)

    1992-01-01

    NASA science publications have used the metric system of measurement since 1970. Although NASA has maintained a metric use policy since 1979, practical constraints have restricted actual use of metric units. In 1988, an amendment to the Metric Conversion Act of 1975 required the Federal Government to adopt the metric system except where impractical. In response to Public Law 100-418 and Executive Order 12770, NASA revised its metric use policy and developed this Metric Transition Plan. NASA's goal is to use the metric system for program development and functional support activities to the greatest practical extent by the end of 1995. The introduction of the metric system into new flight programs will determine the pace of the metric transition. Transition of institutional capabilities and support functions will be phased to enable use of the metric system in flight program development and operations. Externally oriented elements of this plan will introduce and actively support use of the metric system in education, public information, and small business programs. The plan also establishes a procedure for evaluating and approving waivers and exceptions to the required use of the metric system for new programs. Coordination with other Federal agencies and departments (through the Interagency Council on Metric Policy) and industry (directly and through professional societies and interest groups) will identify sources of external support and minimize duplication of effort.

  2. Youths Transitioning as Adult Learners

    ERIC Educational Resources Information Center

    Davis, C. Amelia

    2014-01-01

    This chapter considers how transitions to adulthood have been historically represented and presents alternative ways of thinking about transitions to adulthood through the context of adult basic education programs.

  3. The Myths of Mass Transit.

    ERIC Educational Resources Information Center

    Burke, Catherine G.

    1982-01-01

    Criticizes eight commonly held notions about the value of mass transit systems in public transportation programs. Alternative approaches for improving the quality and quantity of urban transit systems are discussed. (AM)

  4. The transition to agricultural sustainability

    PubMed Central

    Ruttan, Vernon W.

    1999-01-01

    The transition to sustainable growth in agricultural production during the 21st century will take place within the context of a transition to a stable population and a possible transition to a stable level of material consumption. If the world fails to successfully navigate a transition to sustainable growth in agricultural production, the failure will be due more to a failure in the area of institutional innovation than to resource and environmental constraints. PMID:10339524

  5. Visual Analytics Technology Transition Progress

    SciTech Connect

    Scholtz, Jean; Cook, Kristin A.; Whiting, Mark A.; Lemon, Douglas K.; Greenblatt, Howard

    2009-09-23

    The authors provide a description of the transition process for visual analytic tools and contrast this with the transition process for more traditional software tools. This paper takes this into account and describes a user-oriented approach to technology transition including a discussion of key factors that should be considered and adapted to each situation. The progress made in transitioning visual analytic tools in the past five years is described and the challenges that remain are enumerated.

  6. Reconstructing Transition Knowledge in Taiwan

    ERIC Educational Resources Information Center

    Cheng, Chen-chen

    2012-01-01

    Taking a post-colonial stand and using school to work transition as an example, the author re-examines the special education discourses in Taiwan and attempts to construct alternate understandings of transition from sociological and cultural perspectives. A review of past transition literature and a survey of the educational background of the…

  7. Slow Transit Constipation.

    PubMed

    Wald, Arnold

    2002-08-01

    The diagnosis of slow transit functional constipation is based upon diagnostic testing of patients with idiopathic constipation who responded poorly to conservative measures such as fiber supplements, fluids, and stimulant laxatives. These tests include barium enema or colonoscopy, colonic transit of radio-opaque markers, anorectal manometry, and expulsion of a water-filled balloon. Plain abdominal films can identify megacolon, which can be further characterized by barium or gastrografin studies. Colonic transit of radio-opaque markers identifies patients with slow transit with stasis of markers in the proximal colon. However, anorectal function should be characterized to exclude outlet dysfunction, which may coexist with colonic inertia. Because slow colonic transit is defined by studies during which patients consume a high-fiber diet, fiber supplements are generally not effective, nor are osmotic laxatives that consist of unabsorbed sugars. Stimulant laxatives are considered first-line therapy, although studies often show a diminished colonic motor response to such agents. There is no evidence to suggest that chronic use of such laxatives is harmful if they are used two to three times per week. Polyethylene glycol with or without electrolytes may be useful in a minority of patients, often combined with misoprostol. I prefer to start with misoprostol 200 mg every other morning and increase to tolerance or efficacy. I see no advantage in prescribing misoprostol on a TID or QID basis or even daily because it increases cramping unnecessarily. This drug is not acceptable in young women who wish to become pregnant. An alternative may be colchicine, which is reported to be effective when given as 0.6 mg TID. Long-term efficacy has not been studied. Finally, biofeedback is a risk-free approach that has been reported as effective in approximately 60% of patients with slow transit constipation in the absence of outlet dysfunction. Although difficult to understand

  8. Alameda-Contra Costa Transit District (AC Transit) Fuel Cell Transit Buses: Preliminary Evaluation Results

    SciTech Connect

    Chandler, K.; Eudy, L.

    2007-03-01

    This report provides an evaluation of three prototype fuel cell-powered transit buses operating at AC Transit in Oakland, California, and six baseline diesel buses similar in design to the fuel cell buses.

  9. Transition Metal Switchable Mirror

    SciTech Connect

    2009-08-21

    The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft.

  10. Wetting Transition in Water

    NASA Astrophysics Data System (ADS)

    Friedman, S. R.; Khalil, M.; Taborek, P.

    2013-11-01

    Optical images were used to study the wetting behavior of water on graphite, sapphire, and quartz along the liquid vapor coexistence curve from room temperature to 300°C. Wetting transitions were identified by the temperature at which the contact angle decreased to zero and also by the disappearance of dropwise condensation. These two methods yielded consistent values for the wetting temperatures, which were 185°C, 234°C, and 271°C for water on quartz, sapphire, and graphite, respectively. We compare our results with the theoretical predictions based on a simplified model of the water-substrate potential and sharp interfaces.

  11. Wetting transition in water.

    PubMed

    Friedman, S R; Khalil, M; Taborek, P

    2013-11-27

    Optical images were used to study the wetting behavior of water on graphite, sapphire, and quartz along the liquid vapor coexistence curve from room temperature to 300 °C. Wetting transitions were identified by the temperature at which the contact angle decreased to zero and also by the disappearance of dropwise condensation. These two methods yielded consistent values for the wetting temperatures, which were 185 °C, 234 °C, and 271 °C for water on quartz, sapphire, and graphite, respectively. We compare our results with the theoretical predictions based on a simplified model of the water-substrate potential and sharp interfaces.

  12. Transition Metal Switchable Mirror

    ScienceCinema

    None

    2016-07-12

    The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft. More information at: http://windows.lbl.gov/materials/chromogenics/default.htm

  13. Transition Metal Switchable Mirror

    ScienceCinema

    None

    2016-07-12

    The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft.

  14. MINEHOUND: transition to production

    NASA Astrophysics Data System (ADS)

    Daniels, David J.; Curtis, Paul; Hunt, Nigel; Braunstein, Jürgen; Merz, Armin

    2007-04-01

    The UK Department for International Development (DfID), in collaboration with the German Foreign Ministry (Auswärtiges Amt), contracted ERA Technology to carry out extensive field trials in Cambodia, Bosnia and Angola of an advanced technology, dual sensor, and hand-held landmine detector system called MINEHOUND TM. This detector combines a metal detector with a Ground Penetrating Radar (GPR). As a result of extremely successful trials MINEHOUND TM was developed as a product by ERA Technology and Vallon GmbH and has been available for sale since late 2006. This paper describes the transition to production of the detector.

  15. Electromagnetic transitions in hypernuclei

    SciTech Connect

    Chrien, R.E.

    1986-01-01

    The object of this review is to survey observations of electromagnetic transitions in hypernuclei and to point out contributions of these observations to an understanding of the effective two-body hyperon-nucleon forces in the nucleus. The discussion concentrates on lambda-hyperon nucleon potentials. Future plans for high resolution hypernuclear spectroscopy using Ge diode detectors is discussed, especially regarding the window of utility of such devices. Expected improvements in beam facilities are also reviewed. 9 refs., 4 figs., 1 tab. (DWL)

  16. Transition in Turner's syndrome.

    PubMed

    Saenger, Paul

    2004-06-01

    Management of the chromosomal condition Turner's syndrome requires consistent medical care, especially during the time when affected girls transition from childhood into adulthood. The medical problems that first develop during childhood of a patient with Turner's syndrome such as congenital heart disease, hearing loss, skeletal problems and dental and ophthalmological abnormalities, should be followed into adulthood. Providing the necessary continuum of care will require that medical centers develop teams with the appropriate expertise in treatment of Turner's syndrome. Now more than ever patients with Turner's syndrome have the capability of achieving their full potential, but it requires a multidisciplinary approach toward care throughout their lifetime.

  17. Transition Metal Homeostasis.

    PubMed

    Nies, Dietrich H; Grass, Gregor

    2009-08-01

    This chapter focuses on transition metals. All transition metal cations are toxic-those that are essential for Escherichia coli and belong to the first transition period of the periodic system of the element and also the "toxic-only" metals with higher atomic numbers. Common themes are visible in the metabolism of these ions. First, there is transport. High-rate but low-affinity uptake systems provide a variety of cations and anions to the cells. Control of the respective systems seems to be mainly through regulation of transport activity (flux control), with control of gene expression playing only a minor role. If these systems do not provide sufficient amounts of a needed ion to the cell, genes for ATP-hydrolyzing high-affinity but low-rate uptake systems are induced, e.g., ABC transport systems or P-type ATPases. On the other hand, if the amount of an ion is in surplus, genes for efflux systems are induced. By combining different kinds of uptake and efflux systems with regulation at the levels of gene expression and transport activity, the concentration of a single ion in the cytoplasm and the composition of the cellular ion "bouquet" can be rapidly adjusted and carefully controlled. The toxicity threshold of an ion is defined by its ability to produce radicals (copper, iron, chromate), to bind to sulfide and thiol groups (copper, zinc, all cations of the second and third transition period), or to interfere with the metabolism of other ions. Iron poses an exceptional metabolic problem due its metabolic importance and the low solubility of Fe(III) compounds, combined with the ability to cause dangerous Fenton reactions. This dilemma for the cells led to the evolution of sophisticated multi-channel iron uptake and storage pathways to prevent the occurrence of unbound iron in the cytoplasm. Toxic metals like Cd2+ bind to thiols and sulfide, preventing assembly of iron complexes and releasing the metal from iron-sulfur clusters. In the unique case of mercury, the

  18. Pivotal Transitions - Historical and Today

    NASA Astrophysics Data System (ADS)

    Hurley, M.

    2008-08-01

    The goal of this paper is to enable readers to better "design" successful transitions that move Science and Technology or Research and Development (S&T/R&D) technologies and systems into operational capabilities for users. Transitions from S&T/R&D into acquisition and operations are challenging and critical to providing capab ilities to end users. Two historical examples, the Global Positioning System (GPS) and the Disaster Monitoring Constellation (DMC), are explored. Two current examples are also explored, including one from Operationally Responsive Space (ORS) which is in th e early stages of transition. While transitions are necessary, transition periods are inherently challenging and dynamically changing situations. These situations must be carefully managed and led in order to succeed. Characteristics, approaches, and incentives that foster effective transitions are discussed. Understanding the transition process and the communities involved allows one to maximize the chance of successfully moving an S&T/R&D development into an operational capability supporting end users.

  19. 309 Building transition plan

    SciTech Connect

    Graves, C.E.

    1994-08-31

    The preparation for decontamination and decommissioning (transition) of the 309 Building is projected to be completed by the end of the fiscal year (FY) 1998. The major stabilization and decontamination efforts include the Plutonium Recycle Test Reactor (PRTR), fuel storage and transfer pits, Transfer Waste (TW) tanks and the Ion Exchange Vaults. In addition to stabilizing contaminated areas, equipment, components, records, waste products, etc., will be dispositioned. All nonessential systems, i.e., heating, ventilation, and air conditioning (HVAC), electrical, monitoring, fluids, etc., will be shut down and drained/de-energized. This will allow securing of the process, laboratory, and office areas of the facility. After that, the facility will be operated at a level commensurate with its surveillance needs while awaiting D&D. The implementation costs for FY 1995 through FY 1998 for the transition activities are estimated to be $1,070K, $2,115K, $2,939K, and $4,762K, respectively. Costs include an assumed company overhead of 20% and a 30% out year contingency.

  20. Planet Demographics from Transits

    NASA Astrophysics Data System (ADS)

    Howard, Andrew

    2015-08-01

    From the demographics of planets detected by the Kepler mission, we have learned that there exists approximately one planet per star for planets larger than Earth orbiting inside of 1 AU. We have also learned the relative occurrence of these planets as a function of their orbital periods, sizes, and host star masses and metallicities. In this talk I will review the key statistical findings that the planet size distribution peaks in the range 1-3 times Earth-size, the orbital period distribution is characterized by a power-law cut off at short periods, small planets are more prevalent around small stars, and that approximately 20% of Sun-like stars hosts a planet 1-2 times Earth-size in a habitable zone. Looking forward, I will describe analysis of photometry from the K2 mission that is yielding initial planet discoveries and offering the opportunity to measure planet occurrence in widely separated regions of the galaxy. Finally, I will also discuss recent techniques to discover transiting planets in space-based photometry and to infer planet population properties from the ensemble of detected and non-detected transit signals.

  1. Gait transition cost in humans.

    PubMed

    Usherwood, James R; Bertram, John E A

    2003-11-01

    The energetics of locomotion depend largely on speed, gait and body size. Gait selection for a given speed appears partly, but perhaps not wholly, related to metabolic cost. One cost normally omitted from considerations of locomotion efficiency is the metabolic cost of the transition between gaits. We present the first direct assessment of the metabolic cost for the walk-run/run-walk transition in humans. The average increase in metabolic cost for a step involving a transition is 1.75 times that of a mean non-transition step at a speed where metabolic power requirements are identical for walking and running. Despite this substantial increase in cost for the transition step, the metabolic cost of gait transition is unlikely to have a strong bearing on the process of gait selection as the cost of using a metabolically inappropriate gait, even for only a few steps, will dominate. PMID:14564525

  2. Symmetry in DIET phase transitions

    NASA Astrophysics Data System (ADS)

    Zhang, J. P.; Marks, L. D.

    1989-11-01

    Analysis of the route of the phase transitions in transition metal oxides driven by DIET of oxygen from the surfaces observed by high resolution electron microscopy indicates that there is a symmetry selection rule. The phase transitions are to a structure with a higher point group symmetry where the new phase with a lower oxygen content is either one with a supergroup symmetry with respect to the original phase, or is an amorphous intermediary. The final phase has the highest symmetry and is also a metallic conductor. If a possible lower oxygen content phase does not have the correct supergroup symmetry, it is not formed. It is also found that the point group is conserved during the phase transition if the oxide belongs to the highest groups O h or D 6h. This symmetry selection rule can therefore be used to predict the route of the phase transition. The symmetry rule operates when the phase transition is diffusional.

  3. Maritime in transit care.

    PubMed

    Bott, G; Barnard, J; Prior, K

    2015-01-01

    Operation GRITROCK saw the first operational deployment of the Maritime In Transit Care team from the Role 2 (Enhanced) (R2(E)) Medical Treatment Facility, which is able to provide Damage Control Surgery and the limited holding of patients, situated on board RFA ARGUS. Whilst the Medical Emergency Response Team demonstrated the capability of advanced military Pre-Hospital Emergency Care (PHEC) on Op HERRICK, the need to provide a similar high level of care on contingency operations was recognised. Op GRITROCK allowed for the continued exploration of a maritime capability from an established R2(E) platform whilst providing medical evacuation capability for a significant population at risk distributed over a large Joint Operation Area. Although the patient load during the operation was low, key lessons were learnt and opportunities identified to further develop the newly recognised sub-speciality of PHEC, both medically and logistically, and these will be discussed in this article. PMID:26867404

  4. Hybrid Electric Transit Bus

    NASA Technical Reports Server (NTRS)

    Viterna, Larry A.

    1997-01-01

    A government, industry, and university cooperative is developing an advanced hybrid electric city transit bus. Goals of this effort include doubling the fuel economy compared to current buses and reducing emissions to one-tenth of current EPA standards. Unique aspects of the vehicle's power system include the use of ultra-capacitors as an energy storage system, and a planned natural gas fueled turbogenerator developed from a small jet engine. Power from both the generator and energy storage system is provided to a variable speed electric motor attached to the rear axle. At over 15000 kg gross weight, this is the largest vehicle of its kind ever built using ultra-capacitor energy storage. This paper describes the overall power system architecture, the evolution of the control strategy, and its performance over industry standard drive cycles.

  5. Nonadiabatic transition path sampling

    NASA Astrophysics Data System (ADS)

    Sherman, M. C.; Corcelli, S. A.

    2016-07-01

    Fewest-switches surface hopping (FSSH) is combined with transition path sampling (TPS) to produce a new method called nonadiabatic path sampling (NAPS). The NAPS method is validated on a model electron transfer system coupled to a Langevin bath. Numerically exact rate constants are computed using the reactive flux (RF) method over a broad range of solvent frictions that span from the energy diffusion (low friction) regime to the spatial diffusion (high friction) regime. The NAPS method is shown to quantitatively reproduce the RF benchmark rate constants over the full range of solvent friction. Integrating FSSH within the TPS framework expands the applicability of both approaches and creates a new method that will be helpful in determining detailed mechanisms for nonadiabatic reactions in the condensed-phase.

  6. Transit satellite system timing capabilities

    NASA Technical Reports Server (NTRS)

    Finsod, T. D.

    1978-01-01

    Current time transfer capabilities of the Transit Satellite System are reviewed. Potential improvements in the changes in equipment and operational procedures using operational satellites are discussed.

  7. Transit administration and planning research

    SciTech Connect

    de Corla-Souza; Gupta.

    1989-01-01

    The 10 papers in the report deal with the following areas: Evaluation of demand-management strategies for Toledo's year 2010 transportation plan; Accommodating deaf and hard-of-hearing persons on public transportation systems in Massachusetts; Quick approach to compare highway and bus transit alternatives using the arterial analysis package; Panel survey approach to measuring transit route service elasticity of demand; UMTA and major investments: evaluation process and results; Using early performance to project transit route ridership: comparison of methods; Institutional requirements for competition: labor issues; Updating ride checks with multiple point checks; Producing section 15 service-consumed data: challenge for large transit; Parkrose targeted marketing campaign pass-incentive program.

  8. Quantum phase transition in space

    SciTech Connect

    Damski, Bogdan; Zurek, Wojciech H

    2008-01-01

    A quantum phase transition between the symmetric (polar) phase and the phase with broken symmetry can be induced in a ferromagnetic spin-1 Bose-Einstein condensate in space (rather than in time). We consider such a phase transition and show that the transition region in the vicinity of the critical point exhibits scalings that reflect a compromise between the rate at which the transition is imposed (i.e., the gradient of the control parameter) and the scaling of the divergent healing length in the critical region. Our results suggest a method for the direct measurement of the scaling exponent {nu}.

  9. Essentials of Transition Planning. Brookes Transition to Adulthood Series

    ERIC Educational Resources Information Center

    Wehman, Paul

    2011-01-01

    For young people with disabilities, crossing the bridge to adulthood will be empowering instead of intimidating--when their support teams know the essentials of effective transition planning. Now all the fundamentals of well-crafted transition plans are collected in one concise quick-guide, straight from one of the top authorities on helping young…

  10. Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Preliminary Evaluation Results

    SciTech Connect

    Chandler, K.; Eudy, L.

    2008-10-01

    This report provides preliminary results from a National Renewable Energy Laboratory evaluation of a protoptye fuel cell transit bus operating at Connecticut Transit in Hartford. Included are descriptions of the planned fuel cell bus demonstration and equipment; early results and agency experience are also provided.

  11. Light Scattering in Exoplanet Transits

    NASA Astrophysics Data System (ADS)

    Robinson, Tyler D.; Fortney, Jonathan J.

    2016-10-01

    Transit spectroscopy is currently the leading technique for studying exoplanet atmospheric composition, and has led to the detection of molecular species, clouds, and/or hazes for numerous worlds outside the Solar System. The field of exoplanet transit spectroscopy will be revolutionized with the anticipated launch of NASA's James Webb Space Telescope (JWST) in 2018. Over the course of the design five year mission for JWST, the observatory is expected to provide in-depth observations of many tens of transiting exoplanets, including some worlds in the poorly understood 2–4 Earth-mass regime. As the quality of transit spectrum observations continues to improve, so should models of exoplanet transits. Thus, certain processes initially thought to be of second-order importance should be revisited and possibly added to modeling tools. For example, atmospheric refraction, which was commonly omitted from early transit spectrum models, has recently been shown to be of critical importance in some terrestrial exoplanet transits. Beyond refraction, another process that has seen little study with regards to exoplanet transits is light multiple scattering. In most cases, scattering opacity in exoplanet transits has been treated as equivalent to absorption opacity. However, this equivalence cannot always hold, such as in the case of a strongly forward scattering, weakly absorbing aerosol. In this presentation, we outline a theory of exoplanet transit spectroscopy that spans the geometric limit (used in most modern models) to a fully multiple scattering approach. We discuss a new technique for improving model efficiency that effectively separates photon paths, which tend to vary slowly in wavelength, from photon absorption, which can vary rapidly in wavelength. Using this newly developed approach, we explore situations where cloud or haze scattering may be important to JWST observations of gas giants, and comment on the conditions necessary for scattering to become a major

  12. Detection by Transit Photometry

    NASA Technical Reports Server (NTRS)

    Borucki, William J.; Koch, David G.; Jenkins, Jon M.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    A periodic sequence of planetary transits provides a valid detection of an orbiting planet and provides the relative size of the planet and its orbital period. Ancillary measurements of the stellar spectrum and the variations of the star's radial velocity or position combined with stellar models allow the absolute size of the planet and its mass to be obtained. The results of this approach have already shown that the planet orbiting HD209458 has only 70% of the mass of Jupiter, but is nearly 50% larger in radius. Based on models of planetary structure, these results imply that the planet must have spent most of its lifetime so close to the star that it has not been able to cool and contract as have the giant planets in our Solar System. Thus its density is much less than Jupiter and Saturn and is actually less than that of water; i.e., about 0.4 gr/cu cm. If more sensitive measurements of the light curve of stars with closely orbiting planets can be made that provide the varying amplitude of the light reflected by the planet at various phases in its orbit, then characteristics of the planetary atmosphere can be obtained. Potentially, these data can identify major molecular species present in the atmosphere and tell us if clouds are present and yield the phase function of the aerosols. Although such detail cannot be obtained for Earth-size planets because their signal amplitudes are too small, it is possible to get data critical to the determination of the structure of extrasolar planetary systems. In particular, the size distributions and their orbital distributions can be measured by the transit photometry missions now in development. The COROT mission should be able to find large terrestrial planets in short-period orbits while the more ambitious Kepler and Eddington missions should be able to detect planets even smaller than the Earth and at orbital distances that place them in the habitable zone of their stars.

  13. Partnership Transitions and Maternal Parenting

    ERIC Educational Resources Information Center

    Beck, Audrey N.; Cooper, Carey E.; McLanahan, Sara; Brooks-Gunn, Jeanne

    2010-01-01

    We use data from the Fragile Families and Child Wellbeing Study (N = 1,975) to examine the association between mothers' partnership changes and parenting behavior during the first 5 years of their children's lives. We compare coresidential with dating transitions and recent with more distal transitions. We also examine interactions between…

  14. Adult Transition Program without Walls

    ERIC Educational Resources Information Center

    Moberg, Eric

    2010-01-01

    Best practices in adult transition special education for moderate to severe students suggest student-centered planning that maximizes independence in adult life. Based on the above sources, school districts and governing boards would best serve moderate to severe transition special education students with increasing integration into the community…

  15. Transition Planning for Foster Youth

    ERIC Educational Resources Information Center

    Geenen, Sarah J.; Powers, Laurie E.

    2006-01-01

    The study evaluated the IEPs/Individualized Transition Plans of 45 students who were in special education and foster care, and compared them to the plans of 45 students who were in special education only. Results indicate that the transition plans of foster youth with disabilities were poor in quality, both in absolute terms and in comparison to…

  16. School-to-Work Transition.

    ERIC Educational Resources Information Center

    ERIC Review, 1996

    1996-01-01

    The "ERIC Review" announces research results, publications, and new programs relevant to each issue's theme topic. This issue explores the topic of preparing young people to make the transition from school to work. The lead article by Ray D. Ryan and Susan Imel, "School-to-Work Transition: Genuine Reform or the Latest Fad?," summarizes…

  17. Sampling diffusive transition paths

    SciTech Connect

    F. Miller III, Thomas; Predescu, Cristian

    2006-10-12

    We address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with sampling infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with sampling the coarse features of long paths. The fine-features sampling stiffness is eliminated with the use of the fast sampling algorithm (FSA), and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. We use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature.

  18. Theory of antiferroelectric phase transitions

    NASA Astrophysics Data System (ADS)

    Tolédano, Pierre; Guennou, Mael

    2016-07-01

    At variance with structural ferroic phase transitions which give rise to macroscopic tensors coupled to macroscopic fields, criteria defining antiferroelectric (AFE) phase transitions are still under discussion due to the absence of specific symmetry properties characterizing their existence. They are recognized by the proximity of a ferroelectric (FE) phase induced under applied electric field, with a double hysteresis loop relating the induced polarization to the electric field and a typical anomaly of the dielectric permittivity. Here, we show that there exist indeed symmetry criteria defining AFE transitions. They relate the local symmetry of the polar crystallographic sites emerging at an AFE phase transition with the macroscopic symmetry of the AFE phase. The dielectric properties of AFE transitions are deduced from a Landau theoretical model in which ferroelectric and ferrielectric phases are shown to stabilize as the result of specific symmetry-allowed couplings of the AFE order parameter with the field-induced polarization.

  19. Migraine and the menopausal transition.

    PubMed

    Martin, Vincent T

    2014-05-01

    The menopausal transition or "perimenopause" represents a time period of turbulent changes in ovarian hormones as middle-aged women progress into menopause. The purpose of this article is to review the literature to determine the effect of the menopausal transition on migraine headaches and to develop a rational treatment approach to these patients. The menopausal transition is divided into early and stages based upon patterns of menstruation and specific reproductive hormones. Studies would suggest that the prevalence of migraine and other climacteric symptoms tend to peak during the late menopausal transition particularly in those with a past history of premenstrual stress disorder. Treatment approaches vary by stage of the menopausal transition and include conventional daily preventatives, mini-prophylaxis and hormonal therapies.

  20. Assessing transitional phenomena with the transitional object memory probe.

    PubMed

    Fowler, C; Hilsenroth, M J; Handler, L

    1998-01-01

    Winnicott's concept of transitional relatedness has captured the interest of psychoanalysts because it provides an understanding of the dialectical process occurring between inner and outer reality, and by extension, between analyst and analysand. Clinical observations related to transitional phenomena have led the authors to develop a projective early memory probe that assesses transitional phenomena. The transitional object early memory probe was tested both for its empirical validity and for its clinical utility in psychodynamic psychotherapy. Construct validity was assessed by comparing memory scores to the Rorschach Transitional Object Scale, as well as to therapist ratings of patient behaviors. Results demonstrated moderate correlations between early memory scores and Rorschach scale scores. Equally important was the finding that early memory scores were significantly correlated with therapist ratings of key behavioral patterns in therapy. A case vignette highlights the clinical application of the transitional object probe in assessing the capacity for transitional relatedness. In this case, the data gleaned from the patient's memories provided the therapist with a sharper focus on their role in the patient's growing capacity for more vital and creative contact with reality.

  1. Assessing transitional phenomena with the transitional object memory probe.

    PubMed

    Fowler, C; Hilsenroth, M J; Handler, L

    1998-01-01

    Winnicott's concept of transitional relatedness has captured the interest of psychoanalysts because it provides an understanding of the dialectical process occurring between inner and outer reality, and by extension, between analyst and analysand. Clinical observations related to transitional phenomena have led the authors to develop a projective early memory probe that assesses transitional phenomena. The transitional object early memory probe was tested both for its empirical validity and for its clinical utility in psychodynamic psychotherapy. Construct validity was assessed by comparing memory scores to the Rorschach Transitional Object Scale, as well as to therapist ratings of patient behaviors. Results demonstrated moderate correlations between early memory scores and Rorschach scale scores. Equally important was the finding that early memory scores were significantly correlated with therapist ratings of key behavioral patterns in therapy. A case vignette highlights the clinical application of the transitional object probe in assessing the capacity for transitional relatedness. In this case, the data gleaned from the patient's memories provided the therapist with a sharper focus on their role in the patient's growing capacity for more vital and creative contact with reality. PMID:9810109

  2. Selenophene transition metal complexes

    SciTech Connect

    White, C.J.

    1994-07-27

    This research shows that selenophene transition metal complexes have a chemistry that is similar to their thiophene analogs. Selenophene coordination has been demonstrated and confirmed by molecular structure in both the {eta}{sup 5}- and the {eta}{sup 1}(Se)-coordination modes. The reaction chemistry of selenophene complexes closely resembles that of the analogous thiophene complexes. One major difference, however, is that selenophene is a better donor ligand than thiophene making the selenophene complexes more stable than the corresponding thiophene complexes. The {sup 77}Se NMR chemical shift values for selenophene complexes fall within distinct regions primarily depending on the coordination mode of the selenophene ligand. In the final paper, the C-H bond activation of {eta}{sup 1}(S)-bound thiophenes, {eta}{sup 1}(S)-benzothiophene and {eta}{sup 1}(Se)-bound selenophenes has been demonstrated. The deprotonation and rearrangement of the {eta}{sup 1}(E)-bound ligand to the carbon bound L-yl complex readily occurs in the presence of base. Reprotonation with a strong acid gives a carbene complex that is unreactive towards nucleophilic attack at the carbene carbon and is stable towards exposure to air. The molecular structure of [Cp(NO)(PPh{sub 3})Re(2-benzothioenylcarbene)]O{sub 3}SCF{sub 3} was determined and contains a Re-C bond with substantial double bond character. Methyl substitution for the thienylcarbene or selenylcarbene gives a carbene that rearranges thermally to give back the {eta}{sup 1}(E)-bound complex. Based on these model reactions, a new mechanism for the H/D exchange of thiophene over the hydrodesulfurization catalyst has been proposed.

  3. 22 CFR 41.71 - Transit aliens.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Transit aliens. 41.71 Section 41.71 Foreign... NATIONALITY ACT, AS AMENDED Transit Aliens § 41.71 Transit aliens. (a) Transit aliens—general. An alien is classifiable as a nonimmigrant transit alien under INA 101(a) (15) (C) if the consular officer is...

  4. 22 CFR 41.71 - Transit aliens.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Transit aliens. 41.71 Section 41.71 Foreign... NATIONALITY ACT, AS AMENDED Transit Aliens § 41.71 Transit aliens. (a) Transit aliens—general. An alien is classifiable as a nonimmigrant transit alien under INA 101(a) (15) (C) if the consular officer is...

  5. 22 CFR 41.71 - Transit aliens.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Transit aliens. 41.71 Section 41.71 Foreign... NATIONALITY ACT, AS AMENDED Transit Aliens § 41.71 Transit aliens. (a) Transit aliens—general. An alien is classifiable as a nonimmigrant transit alien under INA 101(a) (15) (C) if the consular officer is...

  6. 22 CFR 41.71 - Transit aliens.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Transit aliens. 41.71 Section 41.71 Foreign... NATIONALITY ACT, AS AMENDED Transit Aliens § 41.71 Transit aliens. (a) Transit aliens—general. An alien is classifiable as a nonimmigrant transit alien under INA 101(a) (15) (C) if the consular officer is...

  7. 22 CFR 41.71 - Transit aliens.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Transit aliens. 41.71 Section 41.71 Foreign... NATIONALITY ACT, AS AMENDED Transit Aliens § 41.71 Transit aliens. (a) Transit aliens—general. An alien is classifiable as a nonimmigrant transit alien under INA 101(a) (15) (C) if the consular officer is...

  8. Jamming transition in hierarchical networks

    NASA Astrophysics Data System (ADS)

    Cheng, Xiang; Boettcher, Stefan

    2014-03-01

    Jamming transitions arise in disordered granular materials where the systems fall out of equilibrium due to an increase in the packing density. A kinetically constrained lattice gas model due to Biroli and Mezard (BM) has connected the jamming transition to an equilibrium phase transition. In this description, before this equilibrium transition can be reached, any experiment or simulation would fall out of equilibrium at a Kauzmann transition. However, this analysis is based on a mean-field calculation which, for disordered systems, may have limited relevance in finite dimensions. We study the BM-model on a lattice-like network, which mixes geometric and mean-field features, to reproduce such a phase transition. Computationally, we use the Wang-Landau algorithm which should be less affected by the jamming near the phase transition. The algorithm produces the density of states and, hence, the entropy directly, in addition to many critical properties, such as packing fraction, compressibility, etc. Also, lattice-like hierarchical networks conveniently allow exact or approximate renormalization group treatments, extending analytical results to the thermodynamic limit. Supported through NSF grant DMR-1207431.

  9. The Visibility of Earth Transits

    NASA Technical Reports Server (NTRS)

    Castellano, Timothy P.; Doyle, Laurance; McIntosh, Dawn; DeVincenzi, Donald (Technical Monitor)

    2000-01-01

    The recent photometric detection of planetary transits of the solar-like star HD 209458 at a distance of 47 parsecs suggest that transits can reveal the presence of Jupiter-size planetary companions in the solar neighborhood. Recent space-based transit searches have achieved photometric precision within an order of magnitude of that required to detect the much smaller transit signal of an earth-size planet across a solar-size star. Laboratory experiments in the presence of realistic noise sources have shown that CCDs can achieve photometric precision adequate to detect the 9.6 E-5 dimming of the Sun due to a transit of the Earth. Space-based solar irradiance monitoring has shown that the intrinsic variability of the Sun would not preclude such a detection. Transits of the Sun by the Earth would be detectable by observers that reside within a narrow band of sky positions near the ecliptic plane, if the observers possess current Earth epoch levels of technology and astronomical expertise. A catalog of solar-like stars that satisfy the geometric condition for Earth transit visibility are presented.

  10. The Visibility of Earth Transits

    NASA Technical Reports Server (NTRS)

    Castellano, Tim; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The recent detection of planetary transits of the solar-like star HD 209458 at a distance of 47 parsecs suggest that transits can reveal the presence of Jupiter-size planetary companions in the solar neighborhood. Recent space-based transit searches have achieved photometric precision within an order of magnitude of that required to detect the much smaller transit signal of an earth-size planet around a solar-size star. Laboratory experiments in the presence of realistic noise sources have shown that CCDs can achieve photometric precision adequate to detect the 9.6 E-5 dimming, of the Sun due to a transit of the Earth. Space-based solar irradiance monitoring has shown that the intrinsic variability of the Sun would not preclude such a detection. Transits of the Sun by the Earth would be detectable by observers that reside within a narrow band of sky positions near the ecliptic plane, if the observers possess current Earth epoch levels of technology and astronomical expertise. A catalog of candidate target stars, their properties, and simulations of the photometric Earth transit signal detectability at each target is presented.

  11. Observational biases for transiting planets

    NASA Astrophysics Data System (ADS)

    Kipping, David M.; Sandford, Emily

    2016-09-01

    Observational biases distort our view of nature, such that the patterns we see within a surveyed population of interest are often unrepresentative of the truth we seek. Transiting planets currently represent the most informative data set on the ensemble properties of exoplanets within 1 AU of their star. However, the transit method is inherently biased due to both geometric and detection-driven effects. In this work, we derive the overall observational biases affecting the most basic transit parameters from first principles. By assuming a trapezoidal transit and using conditional probability, we infer the expected distribution of these terms both as a joint distribution and in a marginalized form. These general analytic results provide a baseline against which to compare trends predicted by mission-tailored injection/recovery simulations and offer a simple way to correct for observational bias. Our results explain why the observed population of transiting planets displays a non-uniform impact parameter distribution, with a bias towards near-equatorial geometries. We also find that the geometric bias towards observed planets transiting near periastron is attenuated by the longer durations which occur near apoastron. Finally, we predict that the observational bias with respect to ratio-of-radii is super-quadratic, scaling as (RP/R⋆)5/2, driven by an enhanced geometric transit probability and modestly longer durations.

  12. Electronic Transitions of Yttrium Monophosphide

    NASA Astrophysics Data System (ADS)

    Cheung, Allan S. C.; Li, Biu Wa; Chan, MAN-CHOR

    2015-06-01

    Electronic transition spectrum of the yttrium monophosphide (YP) molecule in the visible region between 715 nm and 880 nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The YP molecule was produced by reacting laser - ablated yttrium atoms with PH3 seeded in argon. Thirteen vibrational bands were analyzed and five electronic transition systems have identified, namely the [12.2] Ω = 3 - X3 Π_2 transition, [13.3] Ω = 3 - X3 Π_2 transition, [13.4] Ω = 3 - X3 Π_2 transition, [13.5] Ω = 3 - X3 Π_2 transition, and [13.4] Ω = 2 - X3 Π_2 transition. Least squares fits of the measured rotational lines yielded molecular constants for the ground and excited states. The ground state symmetry and the bond length r_0 of the YP molecule have been determined to be a X3 Π_2 state and 2.4413 Å respectively in this work. A molecular orbital energy level diagram has been used to help the assignment of the observed electronic states. This work represents the first experimental investigation of the spectrum of the YP molecule.

  13. Major evolutionary transitions in individuality

    PubMed Central

    West, Stuart A.; Fisher, Roberta M.; Gardner, Andy; Kiers, E. Toby

    2015-01-01

    The evolution of life on earth has been driven by a small number of major evolutionary transitions. These transitions have been characterized by individuals that could previously replicate independently, cooperating to form a new, more complex life form. For example, archaea and eubacteria formed eukaryotic cells, and cells formed multicellular organisms. However, not all cooperative groups are en route to major transitions. How can we explain why major evolutionary transitions have or haven’t taken place on different branches of the tree of life? We break down major transitions into two steps: the formation of a cooperative group and the transformation of that group into an integrated entity. We show how these steps require cooperation, division of labor, communication, mutual dependence, and negligible within-group conflict. We find that certain ecological conditions and the ways in which groups form have played recurrent roles in driving multiple transitions. In contrast, we find that other factors have played relatively minor roles at many key points, such as within-group kin discrimination and mechanisms to actively repress competition. More generally, by identifying the small number of factors that have driven major transitions, we provide a simpler and more unified description of how life on earth has evolved. PMID:25964342

  14. Fluctuation driven electroweak phase transition

    NASA Technical Reports Server (NTRS)

    Gleiser, Marcelo; Kolb, Edward W.

    1991-01-01

    We examine the dynamics of the electroweak phase transition in the early Universe. For Higgs masses in the range 46 less than or = M sub H less than or = 150 GeV and top quark masses less than 200 GeV, regions of symmetric and asymmetric vacuum coexist to below the critical temperature, with thermal equilibrium between the two phases maintained by fluctuations of both phases. We propose that the transition to the asymmetric vacuum is completed by percolation of these subcritical fluctuations. Our results are relevant to scenarios of baryogenesis that invoke a weakly first-order phase transition at the electroweak scale.

  15. Nonradiative transition dynamics in alexandrite

    NASA Technical Reports Server (NTRS)

    Gayen, S. K.; Wang, W. B.; Petricevic, V.; Alfano, R. R.

    1986-01-01

    The first direct picosecond time-resolved measurement of the nonradiative transition dynamics between the excited 4T2 pump band and the metastable 2E storage level of the trivalent chromium ion in alexandrite is reported. The nonradiative relaxation times of 17 ps for intra-4T2 vibrational transitions, and 27 ps for 4T2-2E electronic transition are obtained. The thermal repopulation rate of the 4T2 state from the metastable 2E level is of the order 3.5 x 10 to the 9th per s.

  16. Empowering Students in Transition

    PubMed Central

    Sullivan, Ann-Catherine

    2016-01-01

    The purpose of this study was to (a) identify potential benefits for students with disabilities taking part in a physical activity program with same-age typical peers on a Midwest university campus and (b) to determine if the program impacted the students with disabilities empowerment. Empowerment theory was used to determine how transition students’ attitudes change over the course of the semester while participating in a workout buddy program with same-age college peers. The program was structured to provide a sense of empowerment to students to make their own decisions and learn for themselves so they do not feel a lack of power in their lives. This study implemented elements of a quantitative design but a majority utilized a qualitative design based on the assumptions of the Interpretivist paradigm. The quantitative design elements focused on the analysis of two questionnaires: Sports Questionnaire and the Perceived Control Scale Questionnaire. The analysis of the focus group data revealed the following themes as positive effects of the intervention: positive effect on empowerment, how happy the program made the students, what benefits the students gained from the program, the student’s familiarity with university students, and the environment, and, lastly, the students ability to ask for assistance when need. Findings from the study determined that the empowerment of the students with disabilities was impacted while participating in the program. In general, the findings of gaining empowerment were similar to previous studies in that students with disabilities are able to gain empowerment from participation in fitness and recreation programs. The researcher noted during focus groups that some of the Best of Both Worlds (BOBW) students were not confident in starting conversations with their university peers. Although the BOBW students felt a sense of losing empowerment with this specific instance, there was an overall positive impact on the BOBW students

  17. Immigration and adult transitions.

    PubMed

    Rumbaut, Rubén G; Komaie, Golnaz

    2010-01-01

    Almost 30 percent of the more than 68 million young adults aged eighteen to thirty-four in the United States today are either foreign born or of foreign parentage. As these newcomers make their transitions to adulthood, say Rubén Rumbaut and Golnaz Komaie, they differ significantly not only from one another but also from their native-parentage counterparts, including blacks and whites. The authors document the demographic changes in the United States over the past forty years and describe the ways in which generation and national origin shape the experiences of these newcomers as they become adults. Rumbaut and Komaie point out that immigrant groups experience gaps in social, economic, and legal status that are even greater than the gaps between native whites and blacks. By far the most-educated (Indians) and the least-educated (Mexicans) groups in the United States today are first-generation immigrants, as are the groups with the lowest poverty rate (Filipinos) and the highest poverty rate (Dominicans). These social and economic divides reflect three very different ways immigrants enter the country: through regular immigration channels, without legal authorization, or as state-sponsored refugees. For many ethnic groups, significant progress takes place from the first to the second generation. But, say the authors, for millions of young immigrants, a lack of legal permanent residency status blocks their prospects for social mobility. Having an undocumented status has become all the more consequential with the failure of Congress to pass comprehensive federal immigration reforms. In the coming two decades, as the U.S. native-parentage labor force continues to shrink, immigrants and their children are expected to account for most of the growth of the nation's labor force, with the fastest-growing occupations requiring college degrees. Rumbaut and Komaie stress that one key to the nation's future will be how it incorporates young adults of immigrant origin in its

  18. ISS Update: Transit of Venus

    NASA Video Gallery

    ISS Update commentator Brandi Dean interviews Mario Runco, NASA astronaut, about Venus's transit across the sun on June 5, 2012. Questions? Ask us on Twitter @NASA_Johnson and include the hashtag #...

  19. Adolescent Urology and Transitional Care.

    PubMed

    Woodhouse, Christopher

    2015-11-01

    Babies with the major congenital anomalies of the genito-urinary tract have all-embracing holistic care during childhood. They require the same level of care in adult life. This is the role of transition and adolescent urology.

  20. Moved by a Rapid Transit

    NASA Astrophysics Data System (ADS)

    Bueter, C.

    2013-04-01

    Enticing by virtue of its predictability, historical utility, and spectacle, the transit of Venus is a niche event among astronomical phenomena. Though the value of a transit for scientific purposes is now diminished, the brief appearance of Venus silhouetted against the background of the Sun in 2004 moved the artistic community to celebrate the rare alignment. Artists of all ages combined old traditions with fresh technology to create a 21st-century tapestry of music, sculpture, paintings, glasswork, quilts, sky shows, and digital imagery. A full catalog of transit-related art generated over the centuries would feature the sampling of entries presented here and at the Moved by a Rapid Transit website.

  1. Universal Keplerian state transition matrix

    NASA Technical Reports Server (NTRS)

    Shepperd, S. W.

    1985-01-01

    A completely general method for computing the Keplerian state transition matrix in terms of Goodyear's universal variables is presented. This includes a new scheme for solving Kepler's problem which is a necessary first step to computing the transition matrix. The Kepler problem is solved in terms of a new independent variable requiring the evaluation of only one transcendental function. Furthermore, this transcendental function may be conveniently evaluated by means of a Gaussian continued fraction.

  2. The major synthetic evolutionary transitions.

    PubMed

    Solé, Ricard

    2016-08-19

    Evolution is marked by well-defined events involving profound innovations that are known as 'major evolutionary transitions'. They involve the integration of autonomous elements into a new, higher-level organization whereby the former isolated units interact in novel ways, losing their original autonomy. All major transitions, which include the origin of life, cells, multicellular systems, societies or language (among other examples), took place millions of years ago. Are these transitions unique, rare events? Have they instead universal traits that make them almost inevitable when the right pieces are in place? Are there general laws of evolutionary innovation? In order to approach this problem under a novel perspective, we argue that a parallel class of evolutionary transitions can be explored involving the use of artificial evolutionary experiments where alternative paths to innovation can be explored. These 'synthetic' transitions include, for example, the artificial evolution of multicellular systems or the emergence of language in evolved communicating robots. These alternative scenarios could help us to understand the underlying laws that predate the rise of major innovations and the possibility for general laws of evolved complexity. Several key examples and theoretical approaches are summarized and future challenges are outlined.This article is part of the themed issue 'The major synthetic evolutionary transitions'. PMID:27431528

  3. The major synthetic evolutionary transitions.

    PubMed

    Solé, Ricard

    2016-08-19

    Evolution is marked by well-defined events involving profound innovations that are known as 'major evolutionary transitions'. They involve the integration of autonomous elements into a new, higher-level organization whereby the former isolated units interact in novel ways, losing their original autonomy. All major transitions, which include the origin of life, cells, multicellular systems, societies or language (among other examples), took place millions of years ago. Are these transitions unique, rare events? Have they instead universal traits that make them almost inevitable when the right pieces are in place? Are there general laws of evolutionary innovation? In order to approach this problem under a novel perspective, we argue that a parallel class of evolutionary transitions can be explored involving the use of artificial evolutionary experiments where alternative paths to innovation can be explored. These 'synthetic' transitions include, for example, the artificial evolution of multicellular systems or the emergence of language in evolved communicating robots. These alternative scenarios could help us to understand the underlying laws that predate the rise of major innovations and the possibility for general laws of evolved complexity. Several key examples and theoretical approaches are summarized and future challenges are outlined.This article is part of the themed issue 'The major synthetic evolutionary transitions'.

  4. Transitions in turbulent rotating convection

    NASA Astrophysics Data System (ADS)

    Rajaei, Hadi; Alards, Kim; Kunnen, Rudie; Toschi, Federico; Clercx, Herman; Fluid Dynamics Lab Team

    2015-11-01

    This study aims to explore the flow transition from one state to the other in rotating Rayleigh-Bènard convection using Lagrangian acceleration statistics. 3D particle tracking velocimetry (3D-PTV) is employed in a water-filled cylindrical tank of equal height and diameter. The measurements are performed at the center and close to the top plate at a Rayleigh number Ra = 1.28e9 and Prandtl number Pr = 6.7 for different rotation rates. In parallel, direct numerical simulation (DNS) has been performed to provide detailed information on the boundary layers. We report the acceleration pdfs for different rotation rates and show how the transition from weakly to strongly rotating Rayleigh-Bènard affects the acceleration pdfs in the bulk and boundary layers. We observe that the shapes of the acceleration PDFs as well as the isotropy in the cell center are largely unaffected while crossing the transition point. However, acceleration pdfs at the top show a clear change at the transition point. Using acceleration pdfs and DNS data, we show that the transition between turbulent states is actually a boundary layer transition between Prandtl-Blasius type (typical of non-rotating convection) and Ekman type.

  5. Modelling the transitional boundary layer

    NASA Technical Reports Server (NTRS)

    Narasimha, R.

    1990-01-01

    Recent developments in the modelling of the transition zone in the boundary layer are reviewed (the zone being defined as extending from the station where intermittency begins to depart from zero to that where it is nearly unity). The value of using a new non-dimensional spot formation rate parameter, and the importance of allowing for so-called subtransitions within the transition zone, are both stressed. Models do reasonably well in constant pressure 2-dimensional flows, but in the presence of strong pressure gradients further improvements are needed. The linear combination approach works surprisingly well in most cases, but would not be so successful in situations where a purely laminar boundary layer would separate but a transitional one would not. Intermittency-weighted eddy viscosity methods do not predict peak surface parameters well without the introduction of an overshooting transition function whose connection with the spot theory of transition is obscure. Suggestions are made for further work that now appears necessary for developing improved models of the transition zone.

  6. Boundary layer transition studies

    NASA Technical Reports Server (NTRS)

    Watmuff, Jonathan H.

    1995-01-01

    A small-scale wind tunnel previously used for turbulent boundary layer experiments was modified for two sets of boundary layer transition studies. The first study concerns a laminar separation/turbulent reattachment. The pressure gradient and unit Reynolds number are the same as the fully turbulent flow of Spalart and Watmuff. Without the trip wire, a laminar layer asymptotes to a Falkner & Skan similarity solution in the FPG. Application of the APG causes the layer to separate and a highly turbulent and approximately 2D mean flow reattachment occurs downstream. In an effort to gain some physical insight into the flow processes a small impulsive disturbance was introduced at the C(sub p) minimum. The facility is totally automated and phase-averaged data are measured on a point-by-point basis using unprecedently large grids. The evolution of the disturbance has been tracked all the way into the reattachment region and beyond into the fully turbulent boundary layer. At first, the amplitude decays exponentially with streamwise distance in the APG region, where the layer remains attached, i.e. the layer is viscously stable. After separation, the rate of decay slows, and a point of minimum amplitude is reached where the contours of the wave packet exhibit dispersive characteristics. From this point, exponential growth of the amplitude of the disturbance is observed in the detached shear layer, i.e. the dominant instability mechanism is inviscid. A group of large-scale 3D vortex loops emerges in the vicinity of the reattachment. Remarkably, the second loop retains its identify far downstream in the turbulent boundary layer. The results provide a level of detail usually associated with CFD. Substantial modifications were made to the facility for the second study concerning disturbances generated by Suction Holes for laminar flow Control (LFC). The test section incorporates suction through interchangeable porous test surfaces. Detailed studies have been made using isolated

  7. Phase Transitions and Gravitational Collapse

    NASA Astrophysics Data System (ADS)

    Gentile, Nicholas A.

    1994-01-01

    Results are presented for numerical calculations of gravitational collapses and explosions. Two effects are studied. The first involves aspects of the numerical models used in almost all current gravitational collapse calculations. The second involves phase transitions in the equation of state of dense matter. A (1+1) dimensional general relativistic hydrodynamics code was constructed to investigate both effects. A modification of standard artificial viscosity methods was developed. This extended both the tensor artificial viscosity formulation and the artificial heat conduction formulation to the general relativistic regime. This method shows better results for collapse calculations than the standard scalar artificial viscosity. Numerical collapse calculations were also examined with respect to the number of zones used in the model. These calculations suggest that the number of zones used in current supernova calculations may be insufficient, and that the more sophisticated artificial viscosity methods used may be useful in future core collapse investigations. The second effect studied by this thesis is the impact of phase transitions in dense matter on the results of core collapse in Type 2 supernovae. Two different phase transitions were investigated. The QCD phase transition embodies the prediction of quantum chromodynamics that at high density the constituents of baryonic matter will be free quarks and gluons. The effects on the shock wave formed by core collapse and bounce is studied for various phase transitions. We find that some of the phase transitions modeled significantly increase the shock strength. The second phase transition we study is one from a normal hadronic gas to Q matter. Q matter is a phase of dense baryonic matter that is motivated by soliton models for the nucleus. It has been used to model zero temperature dense matter in static stellar objects, here we extend it to finite temperature, determine the phase transitions with hadronic matter

  8. Transition boiling heat transfer and the film transition regime

    NASA Technical Reports Server (NTRS)

    Ramilison, J. M.; Lienhard, J. H.

    1987-01-01

    The Berenson (1960) flat-plate transition-boiling experiment has been recreated with a reduced thermal resistance in the heater, and an improved access to those portions of the transition boiling regime that have a steep negative slope. Tests have been made in Freon-113, acetone, benzene, and n-pentane boiling on horizontal flat copper heaters that have been mirror-polished, 'roughened', or teflon-coated. The resulting data reproduce and clarify certain features observed by Berenson: the modest surface finish dependence of boiling burnout, and the influence of surface chemistry on both the minimum heat flux and the mode of transition boiling, for example. A rational scheme of correlation yields a prediction of the heat flux in what Witte and Lienhard (1982) previously identified as the 'film-transition boiling' region. It is also shown how to calculate the heat flux at the boundary between the pure-film, and the film-transition, boiling regimes, as a function of the advancing contact angle.

  9. Electronic transitions of cobalt monoboride

    NASA Astrophysics Data System (ADS)

    Ng, Y. W.; Pang, H. F.; Cheung, A. S.-C.

    2011-11-01

    Electronic transition spectrum of cobalt monoboride (CoB) in the visible region between 495 and 560 nm has been observed and analyzed using laser-induced fluorescence spectroscopy. CoB molecule was produced by the reaction of laser-ablated cobalt atom and diborane (B2H6) seeded in argon. Fifteen vibrational bands with resolved rotational structure have been recorded, which included transitions of both Co10B and Co11B isotopic species. Our analysis showed that the observed transition bands are ΔΩ = 0 transitions with Ω″ = 2 and Ω″ = 3 lower states. Four transition systems have been assigned, namely, the [18.1]3Π2-X3Δ2, the [18.3]3Φ3-X3Δ3, the [18.6]3- X3Δ3, and the [19.0]2-X3Δ2 systems. The bond length, ro, of the X 3Δ3 state of CoB is determined to be 1.705 Å. The observed rotational lines showed unresolved hyperfine structure arising from the nuclei, which conforms to the Hund's case (aβ) coupling scheme. This work represents the first experimental investigation of the CoB spectrum.

  10. Transitional care in pediatric urology.

    PubMed

    Lambert, Sarah M

    2015-04-01

    The transition from childhood to adolescence and into adulthood occurs as a natural component of human development. As children progress through school and gain independence, health care practitioners must facilitate a parallel transition from pediatric to adult providers. Modern medicine has succeeded in extending the life expectancy for many children with complex conditions, and adult providers are participating in their medical care through adulthood. Transitioning pediatric urology care to adult urology care is unique to every individual and his or her underlying condition, while the transition process is universal. The objectives of all pediatric urologists include preservation of the kidneys and lower urinary tracts, safe urine storage, safe urine drainage, urinary continence, fertility, sexual function, and genital cosmesis. For some children, these objectives can be attained during childhood, while other children require lifelong maintenance and management. Children with posterior urethral valves, exstrophy-epispadias complex, cloaca, vesicoureteral reflux, neurogenic bladder, disorders of sex development, cancer, hypospadias, nephrolithiasis, undescended testes, varicoceles, ureteropelvic junction obstruction, solitary kidney, and upper tract anomalies all require long-term evaluation and management. The obstacles of altering a patient and caregiver paradigm, locating adult urologists with special expertise, coordinating care with other adult specialties such as nephrology, and navigating the adult health care environment can impede the transition process.

  11. The major synthetic evolutionary transitions

    PubMed Central

    Solé, Ricard

    2016-01-01

    Evolution is marked by well-defined events involving profound innovations that are known as ‘major evolutionary transitions'. They involve the integration of autonomous elements into a new, higher-level organization whereby the former isolated units interact in novel ways, losing their original autonomy. All major transitions, which include the origin of life, cells, multicellular systems, societies or language (among other examples), took place millions of years ago. Are these transitions unique, rare events? Have they instead universal traits that make them almost inevitable when the right pieces are in place? Are there general laws of evolutionary innovation? In order to approach this problem under a novel perspective, we argue that a parallel class of evolutionary transitions can be explored involving the use of artificial evolutionary experiments where alternative paths to innovation can be explored. These ‘synthetic’ transitions include, for example, the artificial evolution of multicellular systems or the emergence of language in evolved communicating robots. These alternative scenarios could help us to understand the underlying laws that predate the rise of major innovations and the possibility for general laws of evolved complexity. Several key examples and theoretical approaches are summarized and future challenges are outlined. This article is part of the themed issue ‘The major synthetic evolutionary transitions’. PMID:27431528

  12. Major transitions in human evolution

    PubMed Central

    Foley, Robert A.; Martin, Lawrence; Mirazón Lahr, Marta; Stringer, Chris

    2016-01-01

    Evolutionary problems are often considered in terms of ‘origins', and research in human evolution seen as a search for human origins. However, evolution, including human evolution, is a process of transitions from one state to another, and so questions are best put in terms of understanding the nature of those transitions. This paper discusses how the contributions to the themed issue ‘Major transitions in human evolution’ throw light on the pattern of change in hominin evolution. Four questions are addressed: (1) Is there a major divide between early (australopithecine) and later (Homo) evolution? (2) Does the pattern of change fit a model of short transformations, or gradual evolution? (3) Why is the role of Africa so prominent? (4) How are different aspects of adaptation—genes, phenotypes and behaviour—integrated across the transitions? The importance of developing technologies and approaches and the enduring role of fieldwork are emphasized. This article is part of the themed issue ‘Major transitions in human evolution’. PMID:27298461

  13. Electronic Transitions of Ruthenium Monoxide

    NASA Astrophysics Data System (ADS)

    Wang, Na; Ng, Y. W.; Cheung, A. S.-C.

    2013-06-01

    The electronic transition spectrum of ruthenium monoxide (RuO) molecule in the spectral region between 545nm to 640nm has been recorded and analyzed using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The RuO molecule was produced by reacting laser- ablated ruthenium atoms with N_{2}O seeded in argon. Nine vibrational bands were recorded and they are identified to be belonging to four electronic transition systems, namely the [18.1]Ω = 4 - X^{5} Δ_4 transition, [16.0]^{5} Φ_5 - X^{5} Δ_4 transition, [18.1]Ω = 3 - X^{5} Δ_3, and [15.8] ^{5} Φ_4 - X^{5} Δ_3 transition. RuO has been determined to have a X^{5} Δ_4 ground state. A least squares fit of the measured rotational lines yielded molecular constants for the ground and the low-lying electronic states. A molecular orbital energy level diagram has been used to help with the assignment of the observed electronic states.

  14. Major transitions in human evolution.

    PubMed

    Foley, Robert A; Martin, Lawrence; Mirazón Lahr, Marta; Stringer, Chris

    2016-07-01

    Evolutionary problems are often considered in terms of 'origins', and research in human evolution seen as a search for human origins. However, evolution, including human evolution, is a process of transitions from one state to another, and so questions are best put in terms of understanding the nature of those transitions. This paper discusses how the contributions to the themed issue 'Major transitions in human evolution' throw light on the pattern of change in hominin evolution. Four questions are addressed: (1) Is there a major divide between early (australopithecine) and later (Homo) evolution? (2) Does the pattern of change fit a model of short transformations, or gradual evolution? (3) Why is the role of Africa so prominent? (4) How are different aspects of adaptation-genes, phenotypes and behaviour-integrated across the transitions? The importance of developing technologies and approaches and the enduring role of fieldwork are emphasized.This article is part of the themed issue 'Major transitions in human evolution'. PMID:27298461

  15. 29 CFR 36.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 1 2010-07-01 2010-07-01 true Transition plans. 36.230 Section 36.230 Labor Office of the... FEDERAL FINANCIAL ASSISTANCE Coverage § 36.230 Transition plans. (a) Submission of plans. An institution... submit either a single transition plan applicable to all such units, or a separate transition...

  16. 10 CFR 5.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Transition plans. 5.230 Section 5.230 Energy NUCLEAR... FEDERAL FINANCIAL ASSISTANCE Coverage § 5.230 Transition plans. (a) Submission of plans. An institution to... either a single transition plan applicable to all such units, or a separate transition plan applicable...

  17. 18 CFR 1317.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 2 2010-04-01 2010-04-01 false Transition plans. 1317... Coverage § 1317.230 Transition plans. (a) Submission of plans. An institution to which § 1317.225 applies... transition plan applicable to all such units, or a separate transition plan applicable to each such unit....

  18. 7 CFR 15a.18 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 1 2012-01-01 2012-01-01 false Transition plans. 15a.18 Section 15a.18 Agriculture... FEDERAL FINANCIAL ASSISTANCE Coverage § 15a.18 Transition plans. (a) Submission of plans. An institution... submit either a single transition plan applicable to all such units, or a separate transition...

  19. 7 CFR 15a.18 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 1 2013-01-01 2013-01-01 false Transition plans. 15a.18 Section 15a.18 Agriculture... FEDERAL FINANCIAL ASSISTANCE Coverage § 15a.18 Transition plans. (a) Submission of plans. An institution... submit either a single transition plan applicable to all such units, or a separate transition...

  20. 7 CFR 15a.18 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 1 2014-01-01 2014-01-01 false Transition plans. 15a.18 Section 15a.18 Agriculture... FEDERAL FINANCIAL ASSISTANCE Coverage § 15a.18 Transition plans. (a) Submission of plans. An institution... submit either a single transition plan applicable to all such units, or a separate transition...

  1. 36 CFR 1211.230 - Transition plans.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Transition plans. 1211.230... FINANCIAL ASSISTANCE Coverage § 1211.230 Transition plans. (a) Submission of plans. An institution to which... a single transition plan applicable to all such units, or a separate transition plan applicable...

  2. 10 CFR 5.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Transition plans. 5.230 Section 5.230 Energy NUCLEAR... FEDERAL FINANCIAL ASSISTANCE Coverage § 5.230 Transition plans. (a) Submission of plans. An institution to... either a single transition plan applicable to all such units, or a separate transition plan applicable...

  3. 7 CFR 15a.18 - Transition plans.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 1 2011-01-01 2011-01-01 false Transition plans. 15a.18 Section 15a.18 Agriculture... FEDERAL FINANCIAL ASSISTANCE Coverage § 15a.18 Transition plans. (a) Submission of plans. An institution... submit either a single transition plan applicable to all such units, or a separate transition...

  4. 29 CFR 36.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 1 2014-07-01 2013-07-01 true Transition plans. 36.230 Section 36.230 Labor Office of the... FEDERAL FINANCIAL ASSISTANCE Coverage § 36.230 Transition plans. (a) Submission of plans. An institution... submit either a single transition plan applicable to all such units, or a separate transition...

  5. 32 CFR 196.230 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 2 2013-07-01 2013-07-01 false Transition plans. 196.230 Section 196.230... FINANCIAL ASSISTANCE Coverage § 196.230 Transition plans. (a) Submission of plans. An institution to which... a single transition plan applicable to all such units, or a separate transition plan applicable...

  6. 36 CFR 1211.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 3 2012-07-01 2012-07-01 false Transition plans. 1211.230... FINANCIAL ASSISTANCE Coverage § 1211.230 Transition plans. (a) Submission of plans. An institution to which... a single transition plan applicable to all such units, or a separate transition plan applicable...

  7. 32 CFR 196.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 2 2012-07-01 2012-07-01 false Transition plans. 196.230 Section 196.230... FINANCIAL ASSISTANCE Coverage § 196.230 Transition plans. (a) Submission of plans. An institution to which... a single transition plan applicable to all such units, or a separate transition plan applicable...

  8. 44 CFR 19.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 44 Emergency Management and Assistance 1 2012-10-01 2011-10-01 true Transition plans. 19.230... RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 19.230 Transition plans. (a) Submission of plans. An... submit either a single transition plan applicable to all such units, or a separate transition...

  9. 45 CFR 2555.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 45 Public Welfare 4 2012-10-01 2012-10-01 false Transition plans. 2555.230 Section 2555.230 Public... Coverage § 2555.230 Transition plans. (a) Submission of plans. An institution to which § 2555.225 applies... transition plan applicable to all such units, or a separate transition plan applicable to each such unit....

  10. 32 CFR 196.230 - Transition plans.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 2 2011-07-01 2011-07-01 false Transition plans. 196.230 Section 196.230... FINANCIAL ASSISTANCE Coverage § 196.230 Transition plans. (a) Submission of plans. An institution to which... a single transition plan applicable to all such units, or a separate transition plan applicable...

  11. 10 CFR 5.230 - Transition plans.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Transition plans. 5.230 Section 5.230 Energy NUCLEAR... FEDERAL FINANCIAL ASSISTANCE Coverage § 5.230 Transition plans. (a) Submission of plans. An institution to... either a single transition plan applicable to all such units, or a separate transition plan applicable...

  12. 33 CFR 401.74 - Transit declaration.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Transit declaration. 401.74... Transit declaration. (a) Seaway Transit Declaration Form (Cargo and Passenger) shall be forwarded to the... ships, within fourteen days after the vessel enters the Seaway on any upbound or downbound transit....

  13. 33 CFR 401.74 - Transit declaration.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Transit declaration. 401.74... Transit declaration. (a) A Seaway Transit Declaration Form (Cargo and Passenger) shall be forwarded to the... bound transit. The form may be obtained from the St. Lawrence Management Corporation, 151 Ecluse...

  14. Individualized Transition Plans (ITP): A National Perspective.

    ERIC Educational Resources Information Center

    Repetto, Jeanne B.; And Others

    1990-01-01

    Information concerning implementation of Individualized Transition Plans (ITP) was collected from 46 states and analyzed to determine documentation used in transition planning, relationship between the ITP and Individualized Education Programs, age for beginning transition planning, individuals involved in transition planning, and issues addressed…

  15. A Plan for Dealing with Transition.

    ERIC Educational Resources Information Center

    Arin-Krupp, Judy

    1984-01-01

    The author describes her plan for dealing with life transitions. The plan has three steps. First, the individual in transition must accurately perceive the situation; second, respond to the situation, change, or transition; and third, reassess his or her perception of the transition. (CT)

  16. 24 CFR 990.225 - Transition determination.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... DEVELOPMENT THE PUBLIC HOUSING OPERATING FUND PROGRAM Transition Policy and Transition Funding § 990.225 Transition determination. The determination of the amount and period of the transition funding shall be based on the difference in subsidy levels between the formula set forth in this part and the formula...

  17. 24 CFR 990.225 - Transition determination.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... DEVELOPMENT THE PUBLIC HOUSING OPERATING FUND PROGRAM Transition Policy and Transition Funding § 990.225 Transition determination. The determination of the amount and period of the transition funding shall be based on the difference in subsidy levels between the formula set forth in this part and the formula...

  18. Family-Directed Transition Planning Guide.

    ERIC Educational Resources Information Center

    Colorado State Dept. of Education, Denver. Div. of Special Education Services.

    This guide to family-directed transition planning is intended to help parents and students with disabilities take leading roles in the process of transition from school to post-school activities. First, a letter to families examines the challenge of change and the transition process. Section 2 examines regulations that affect transition planning,…

  19. Transition metals in superheat melts

    NASA Technical Reports Server (NTRS)

    Jakes, Petr; Wolfbauer, Michael-Patrick

    1993-01-01

    A series of experiments with silicate melts doped with transition element oxides was carried out at atmospheric pressures of inert gas at temperatures exceeding liquidus. As predicted from the shape of fO2 buffer curves in T-fO2 diagrams the reducing conditions for a particular oxide-metal pair can be achieved through the T increase if the released oxygen is continuously removed. Experimental studies suggest that transition metals such as Cr or V behave as siderophile elements at temperatures exceeding liquidus temperatures if the system is not buffered by the presence of other oxide of more siderophile element. For example the presence of FeO prevents the reduction of Cr2O3. The sequence of decreasing siderophility of transition elements at superheat conditions (Mo, Ni, Fe, Cr) matches the decreasing degree of depletion of siderophile elements in mantle rocks as compared to chondrites.

  20. Transitions in individuality through symbiosis.

    PubMed

    Estrela, Sylvie; Kerr, Benjamin; Morris, J Jeffrey

    2016-06-01

    When a more complex, functionally integrated entity emerges from the association of simpler, initially independent entities, a major evolutionary transition has occurred. Transitions that result from the association of different species include the evolution of the eukaryotic cell and some obligate mutualisms. Recent studies are revolutionizing our understanding of how these intimate interspecific associations come to be, revealing how and to what extent each partner contributes to the relationship, and how partners mediate conflict. Here, we review work on the evolution of mutualistic symbioses in the context of transitions in individuality and highlight how a better mechanistic understanding of the ecological drivers of host-symbiont interdependencies can help elucidate the evolutionary path to symbiotic organismality. PMID:27131019

  1. Sliding Over a Phase Transition

    NASA Astrophysics Data System (ADS)

    Tosatti, Erio; Benassi, Andrea; Vanossi, Andrea; Santoro, Giuseppe E.

    2011-03-01

    The frictional response experienced by a stick-slip slider when a phase transition occurs in the underlying solid substrate is a potentially exciting, poorly explored problem. We show, based on 2-dimensional simulations modeling the sliding of a nanotip, that indeed friction may be heavily affected by a continuous structural transition. First, friction turns nonmonotonic as temperature crosses the transition, peaking at the critical temperature Tc where fluctuations are strongest. Second, below Tc friction depends upon order parameter directions, and is much larger for those where the frictional slip can cause a local flip. This may open a route towards control of atomic scale friction by switching the order parameter direction by an external field or strain, with possible application to e.g., displacive ferroelectrics such as BaTi O3 , as well as ferro- and antiferro-distortive materials. Supported by project ESF FANAS/AFRI sponsored by the Italian Research Council (CNR).

  2. Transition in Internally Heated Convection

    NASA Astrophysics Data System (ADS)

    Tasaka, Yuji; Yanagisawa, Takatoshi

    2005-11-01

    Natural convection induced by internal heat generation in a shallow fluid layer was investigated experimentally. Internal heat generation was realized by passing electric current through ionic liquid. Kalliroscope flakes and thermo-chromic liquid crystal were utilized to clarify a transition of the convection with respect to the Rayleigh number, RI. Visualized flow pattern at higher Rayleigh number show two types of deformed cell shape, double cell structure, which has a small cell in a large cell, and spoke like cell structure, where descending flow neat the center of a cell spread like a spoke. Visualized temperature field was converted to temperature field in order to investigate the transition quantitatively. Variation of horizontal temperature fluctuation with respect to RI may show critical Rayleigh number for the transition.

  3. Transitions in individuality through symbiosis.

    PubMed

    Estrela, Sylvie; Kerr, Benjamin; Morris, J Jeffrey

    2016-06-01

    When a more complex, functionally integrated entity emerges from the association of simpler, initially independent entities, a major evolutionary transition has occurred. Transitions that result from the association of different species include the evolution of the eukaryotic cell and some obligate mutualisms. Recent studies are revolutionizing our understanding of how these intimate interspecific associations come to be, revealing how and to what extent each partner contributes to the relationship, and how partners mediate conflict. Here, we review work on the evolution of mutualistic symbioses in the context of transitions in individuality and highlight how a better mechanistic understanding of the ecological drivers of host-symbiont interdependencies can help elucidate the evolutionary path to symbiotic organismality.

  4. Electronic transitions of iridium monophosphide

    NASA Astrophysics Data System (ADS)

    Yang, M.; Chan, Man-Chor; Cheung, A. S.-C.

    2016-05-01

    Laser induced fluorescence spectrum of IrP in the near infrared spectral region between 720 and 820 nm has been recorded and analyzed. Six vibrational bands with resolved rotational structure for both 191IrP and 193IrP were analyzed, they have been grouped into three new electronic transitions: the [13.6] Ω = 2 - a3Π2, the [12.3]1Π1-X1Σ+, and the [12.7]1Π1-X1Σ+ transitions. Ab initio calculation results were used to aid the assignment of the observed transitions. A new triplet state has been observed for the first time. The observed electronic states of IrP are compared with those of the isovalent IrN molecule.

  5. The migration transition in Malaysia.

    PubMed

    Lim, L L

    1996-01-01

    "Exploring the unique experience of migration transition in Malaysia, this paper identifies the turning points in relation to the level and nature of economic and labor market developments in Malaysia. Examining the development dynamics that mark the passage from exporting labor to depending on foreign labor, the paper concludes that such dynamics are influenced not only by economic but also sociocultural, demographic and policy factors. Several lessons from the Malaysian experience are drawn at the end to be utilized by other countries that still have to reach the turning points of the migration transition." PMID:12320775

  6. Theoretical Studies of Atomic Transitions

    SciTech Connect

    Charlotte Froese Fischer

    2005-07-08

    Atomic structure calculations were performed for properties such as energy levels, binding energies, transition probabilities, lifetimes, hyperfine structure, and isotope shifts. Accurate computational procedures were devised so that properties could be predicted even when they could not be obtained from experiment, and to assist in the identification of observed data. The method used was the multiconfiguration Hartree-Fock (MCHF) method, optionally corrected for relativistic effects in the Breit-Pauli approximation. Fully relativistic Dirac-Fock calculations also were performed using the GRASP code A database of energy levels, lifetimes, and transition probabilities was designed and implemented and, at present, includes many results for Be-like to Ar-like.

  7. Space Station transition through Spacelab

    NASA Technical Reports Server (NTRS)

    Craft, Harry G., Jr.; Wicks, Thomas G.

    1990-01-01

    It is appropriate that NASA's Office of Space Science and Application's science management structures and processes that have proven successful on Spacelab be applied and extrapolated to Space Station utilization, wherever practical. Spacelab has many similarities and complementary aspects to Space Station Freedom. An understanding of the similarities and differences between Spacelab and Space Station is necessary in order to understand how to transition from Spacelab to Space Station. These relationships are discussed herein as well as issues which must be dealt with and approaches for transition and evolution from Spacelab to Space Station.

  8. William Crabtree's Venus transit observation

    NASA Astrophysics Data System (ADS)

    Kollerstrom, Nicholas

    2005-04-01

    The close collaboration between the two North-country astronomers Jeremiah Horrocks and William Crabtree gave them special insight into the new astronomy published by the recently-deceased Kepler, whereby Horrocks became the only person to apprehend that the Rudolphine tables were in fact predicting a Venus transit in 1639. This paper focuses especially upon William Crabtree's role and contribution. A comparison is made with an earlier, unsuccessful endeavour by these two concerning a possible transit of Mercury. Much of the record of their work was lost during the civil war. Finally, thanks to Christiaan Huygens, Horrock's manuscript was published by Johannes Hevelius in Danzig, in 1662.

  9. Dynamic Transitions of Generalized Burgers Equation

    NASA Astrophysics Data System (ADS)

    Li, Limei; Ong, Kiah Wah

    2016-03-01

    In this article, we study the dynamic transition for the one dimensional generalized Burgers equation with periodic boundary condition. The types of transition are dictated by the sign of an explicitly given parameter b, which is derived using the dynamic transition theory developed by Ma and Wang (Phase transition dynamics. Springer, New York, 2014). The rigorous result demonstrates clearly the types of dynamics transition in terms of length scale l, dispersive parameter δ and viscosity ν.

  10. Electrical Conductivity in Transition Metals

    ERIC Educational Resources Information Center

    Talbot, Christopher; Vickneson, Kishanda

    2013-01-01

    The aim of this "Science Note" is to describe how to test the electron-sea model to determine whether it accurately predicts relative electrical conductivity for first-row transition metals. In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalised valence…

  11. Preterm Birth: Transition to Adulthood

    ERIC Educational Resources Information Center

    Allen, Marilee C.; Cristofalo, Elizabeth; Kim, Christina

    2010-01-01

    Preterm birth is associated with greater difficulty with transitions from childhood to adolescence to adulthood. Adolescents and young adults born preterm have higher rates of cerebral palsy, intellectual disability, cognitive impairment, learning disability, executive dysfunction, attention deficit disorder, and social-emotional difficulties than…

  12. Leadership Transitions: Keys for Success

    ERIC Educational Resources Information Center

    Goodyear, Marilu; Golden, Cynthia

    2008-01-01

    A leadership transition poses dangers and challenges for both leaders and followers. While each party naturally focuses on the organization's success, time needs to be spent on how the new relationships will develop and mature into effective working relationships. This article discusses the following four areas of interaction between leaders and…

  13. ROLE TRANSITION IN CAREER DEVELOPMENT.

    ERIC Educational Resources Information Center

    MOMENT, DAVID

    ROLE TRANSITIONS IN ADULT CAREER DEVELOPMENT IS PRESENTED IN TERMS OF THE TECHNICAL, SOCIAL, AND DIRECTIVE ROLE ELEMENTS FOUND IN TWO STUDIES OF MANAGERIAL BEHAVIOR AND CAREER DEVELOPMENT. THE INDIVIDUAL'S LIFE SPACE IS THE BASIC FORMULATION OF THIS IDEA. THAT IS, MAJOR CHANGES IN THE CONFIGURATION OF THE INDIVIDUAL'S INTERPERSONAL NETWORK…

  14. Supporting Student Veterans in Transition

    ERIC Educational Resources Information Center

    Rumann, Corey B.; Hamrick, Florence A.

    2009-01-01

    The purpose of this chapter is to offer frameworks and considerations for student affairs professionals seeking to serve the transition needs of the current generation of student veterans. The historical intersections of the military and higher education, particularly with respect to the effects of the draft on students and higher education,…

  15. Narratives about Labour Market Transitions

    ERIC Educational Resources Information Center

    Cort, Pia; Thomsen, Rie

    2014-01-01

    In European Union policy, Denmark is often referred to as a model country in terms of its flexicurity model and provision of financial support and access to education and training during periods of unemployment, i.e. during transitional phases in a working life. However, in the research on flexicurity and its implications for labour market…

  16. Gifted Students' Transition to University

    ERIC Educational Resources Information Center

    Mendaglio, Sal

    2013-01-01

    The transition from school to university presents novel demands for all students. Although this educational milestone has been addressed by scholars, particularly those interested in the study of higher education, there is a dearth of literature regarding gifted students' experience of their handling demands of first-year university. In the…

  17. Structural transitions of encapsidated polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Angelescu, D. G.; Linse, P.; Nguyen, T. T.; Bruinsma, R. F.

    2008-03-01

    Conformations and structural transitions of polyelectrolytes strictly confined onto a spherical 2D surface have been investigated by scaling descriptions based on physical arguments concerning polyelectrolyte adsorption onto planar surface and liquid crystals as well as by Monte Carlo simulations using a bead-spring model with short-range and electrostatic repulsions. In case of the electrostatic screened regime, a disordered-ordered (spiral) transition at increasing persistence length of the chain was found. It was predicted that the transition occurred when the persistence length is comparable with the mean spacing between adjacent strands of the ordered chain. The presence of a non-screened electrostatic repulsion led to a more complex behavior with i) a re-entrant order-disorder transition and ii) a tennis ball texture as an additional smectic/nematic structure. The various competing structures given by the theory were recovered by the Monte Carlo simulations, which also indicated that the tennis ball texture was favored over the spiral structure by the long-range interactions for semi-flexible chains.

  18. N-{Delta} weak transition

    SciTech Connect

    Graczyk, Krzysztof M.

    2011-11-23

    A short review of the Rein-Sehgal and isobar models is presented. The attention is focused on the nucleon-{Delta}(1232) weak transition form-factors. The results of the recent re-analyses of the ANL and BNL bubble chamber neutrino-deuteron scattering data are discussed.

  19. Leadership Transitions during Fundraising Campaigns

    ERIC Educational Resources Information Center

    Nehls, Kimberly

    2012-01-01

    Capital campaigns are intense efforts to build the financial assets of an institution in a specified amount of time. This study provides an empirical view of how changes in leadership affected concomitant capital campaigns at ten colleges and universities. The transitions during these 10 campaigns influenced morale on campus, altered timing of the…

  20. Postsecondary Transitions among Navajo Indians.

    ERIC Educational Resources Information Center

    Jackson, Aaron P.; Smith, Steven A.

    2001-01-01

    A study examining postsecondary transition experiences interviewed 22 Navajos who were recent high school graduates. Prominent themes included family influence and pressures, discrepancy between high school and college learning environments, student-faculty relationships, vague educational and career plans, misconceptions about postsecondary…

  1. Transiting Exoplanet Survey Satellite (TESS)

    NASA Technical Reports Server (NTRS)

    Ricker, G. R.; Clampin, M.; Latham, D. W.; Seager, S.; Vanderspek, R. K.; Villasenor, J. S.; Winn, J. N.

    2012-01-01

    The Transiting Exoplanet Survey Satellite (TESS) will discover thousands of exoplanets in orbit around the brightest stars in the sky. In a two-year survey, TESS will monitor more than 500,000 stars for temporary drops in brightness caused by planetary transits. This first-ever spaceborne all-sky transit survey will identify planets ranging from Earth-sized to gas giants, around a wide range of stellar types and orbital distances. No ground-based survey can achieve this feat. A large fraction of TESS target stars will be 30-100 times brighter than those observed by Kepler satellite, and therefore TESS . planets will be far easier to characterize with follow-up observations. TESS will make it possible to study the masses, sizes, densities, orbits, and atmospheres of a large cohort of small planets, including a sample of rocky worlds in the habitable zones of their host stars. TESS will provide prime targets for observation with the James Webb Space Telescope (JWST), as well as other large ground-based and space-based telescopes of the future. TESS data will be released with minimal delay (no proprietary period), inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the very nearest and brightest main-sequence stars hosting transiting exoplanets, thus providing future observers with the most favorable targets for detailed investigations.

  2. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, V.A.; Iton, L.E.; Pasterczyk, J.W.; Winterer, M.; Krause, T.R.

    1994-04-26

    A zeolite-based catalyst is described for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C[sub 2]+ hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  3. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, Victor A.; Iton, Lennox E.; Pasterczyk, James W.; Winterer, Markus; Krause, Theodore R.

    1994-01-01

    A zeolite based catalyst for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C.sub.2 + hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  4. On Comparing Transition Rate Gains.

    ERIC Educational Resources Information Center

    Reuterberg, Sven-Eric

    This report is about the problem of making transition or enrollment rate gains comparable. It is shown that measures based on the proportions themselves, i.e. the difference between proportions, the proportion ratio and the residual gain ratio do not make the gains comparable. Instead a non-linear transformation has to be done. Two such…

  5. "Mexico in Transition." Curriculum Units.

    ERIC Educational Resources Information Center

    Oregon Univ., Eugene. Foreign Language Resource Center.

    These curriculum units were developed in a National Endowment for the Humanities 1994 summer seminar "Mexico in Transition." The 23 lessons are written in Spanish. Lessons are entitled: (1) "La Migracion Mexicana Vista a Traves del Cuento 'Paso del Norte' de Juan Rulfo" (Jose Jorge Armendariz); (2) "Los Grupos Indigenas de Mexico: Condiciones…

  6. Career Transitions: The Australian Experience.

    ERIC Educational Resources Information Center

    Stevens, Paul

    This book is designed to aid career counselors in Australia help their clients search for enhanced well-being in their occupations and to help organizations and human resource staff members dealing with employees' career development. The book is organized in four parts. Parts 1 and 2 explore the career transition journey that a typical person…

  7. American Higher Education in Transition

    ERIC Educational Resources Information Center

    Ehrenberg, Ronald G.

    2011-01-01

    American higher education is in transition and if there ever was a "golden age" for faculty, it probably is behind us. The best historical data on the composition of faculty is collected annually by the American Mathematical Society. Between 1967 and 2009, the share of full-time faculty with PhDs remained constant at about 90 percent at doctoral…

  8. GLOBAL TRANSITION TO SUSTAINABLE DEVELOPMENT

    EPA Science Inventory

    Global transition to sustainable development is possible but many obstacles lie in the way and it will require acts of political will on the part of both the developed and developing nations to become a reality. In this paper, sustainable development is defined as continuous prog...

  9. Transition Room Program, 1967 Report.

    ERIC Educational Resources Information Center

    Glassner, Leonard E.

    The Transition Room Program of the Pittsburgh Schools was defined and evaluated by the staff, the administration, and a program evaluator from the Office of Research. The definition included general objectives, anticipated outcomes, student criteria and characteristics, staff qualifications and functions, media, student activities, and staff…

  10. Menopause: A Life Cycle Transition.

    ERIC Educational Resources Information Center

    Evarts, Barbara Kess; Baldwin, Cynthia

    1998-01-01

    Family therapists need to address the issue of menopause proactively to be of benefit to couples and families during this transitional period in the family life cycle. Physical, psychological, and psychosocial factors affecting the menopausal woman and her family, and ways to address these issues in counseling are discussed. (Author/EMK)

  11. Flexible Scheduling: Making the Transition

    ERIC Educational Resources Information Center

    Creighton, Peggy Milam

    2008-01-01

    Citing literature that supports the benefits of flexible scheduling on student achievement, the author exhorts readers to campaign for flexible scheduling in their library media centers. She suggests tips drawn from the work of Graziano (2002), McGregor (2006) and Stripling (1997) for making a smooth transition from fixed to flexible scheduling:…

  12. The nature of transition blazars

    SciTech Connect

    Ruan, J. J.; Anderson, S. F.; Plotkin, R. M.; Brandt, W. N.; Schneider, D. P.; Burnett, T. H.; Myers, A. D.

    2014-12-10

    Blazars are classically divided into the BL Lacertae (BLL) and flat-spectrum radio quasar (FSRQ) subclasses, corresponding to radiatively inefficient and efficient accretion regimes, respectively, largely based on the equivalent width (EW) of their optical broad emission lines (BELs). However, EW-based classification criteria are not physically motivated, and a few blazars have previously transitioned' from one subclass to the other. We present the first systematic search for these transition blazars in a sample of 602 unique pairs of repeat spectra of 354 blazars in the Sloan Digital Sky Survey, finding six clear cases. These transition blazars have bolometric Eddington ratios of ∼0.3 and low-frequency synchrotron peaks, and are thus FSRQ-like. We show that the strong EW variability (up to an unprecedented factor of >60) is due to swamping of the BELs from variability in jet continuum emission, which is stronger in amplitude and shorter in timescale than typical blazars. Although these transition blazars appear to switch between FSRQ and BLL according to the phenomenologically based EW scheme, we show that they are most likely rare cases of FSRQs with radiatively efficient accretion flows and especially strongly beamed jets. These results have implications for the decrease of the apparent BLL population at high redshifts, and may lend credence to claims of a negative BLL redshift evolution.

  13. Alkali and transition metal phospholides

    NASA Astrophysics Data System (ADS)

    Bezkishko, I. A.; Zagidullin, A. A.; Milyukov, V. A.; Sinyashin, O. G.

    2014-06-01

    Major tendencies in modern chemistry of alkali and transition metal phospholides (phosphacyclopentadienides) are systematized, analyzed and generalized. Basic methods of synthesis of these compounds are presented. Their chemical properties are considered with a special focus on their complexing ability. Potential applications of phospholides and their derivatives are discussed. The bibliography includes 184 references.

  14. Poland's Transition in Business Education

    ERIC Educational Resources Information Center

    Leven, Bozena

    2010-01-01

    Prior to Poland's transition from central planning to a market system, which began in 1990, schools of business were non-existent in that country. Instead, university level instruction on economics during the socialist period was closely tied to ideological priorities, and limited to imparting skills suitable for planned economy. All universities…

  15. Quantifying macromolecular conformational transition pathways

    NASA Astrophysics Data System (ADS)

    Seyler, Sean; Kumar, Avishek; Thorpe, Michael; Beckstein, Oliver

    2015-03-01

    Diverse classes of proteins function through large-scale conformational changes that are challenging for computer simulations. A range of fast path-sampling techniques have been used to generate transitions, but it has been difficult to compare paths from (and assess the relative strengths of) different methods. We introduce a comprehensive method (pathway similarity analysis, PSA) for quantitatively characterizing and comparing macromolecular pathways. The Hausdorff and Fréchet metrics (known from computational geometry) are used to quantify the degree of similarity between polygonal curves in configuration space. A strength of PSA is its use of the full information available from the 3 N-dimensional configuration space trajectory without requiring additional specific knowledge about the system. We compare a sample of eleven different methods for the closed-to-open transitions of the apo enzyme adenylate kinase (AdK) and also apply PSA to an ensemble of 400 AdK trajectories produced by dynamic importance sampling MD and the Geometrical Pathways algorithm. We discuss the method's potential to enhance our understanding of transition path sampling methods, validate them, and help guide future research toward deeper physical insights into conformational transitions.

  16. Electronic transitions of yttrium monophosphide

    NASA Astrophysics Data System (ADS)

    Li, Biu Wa; Chan, Man-Chor; Cheung, A. S.-C.

    2015-11-01

    The electronic transition spectrum of the yttrium monophosphide (YP) molecule in the near infrared region between 715 nm and 880 nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The YP molecule was produced by reacting laser - ablated yttrium atoms with PH3 gas seeded in argon. Eleven vibrational bands were analyzed and six electronic transitions have been identified, namely the [12.17] Ω = 3 - X3Π2, [13.27] Ω = 3 - X3Π2, [13.44] Ω = 3 - X3Π2, [13.46] Ω = 3 - X3Π2 and [13.40] Ω = 2 - X3Π2 transitions and a [13.69] Ω = 3 - a1Δ2 transition. Least squares fits of the measured rotational lines yielded molecular constants for the ground and excited states. The ground state has been determined to be a X3Π2 state and the bond length ro and vibrational separation, ΔG1/2, were determined to be 2.4413 Å and 390.77 cm-1 respectively. A molecular orbital energy level diagram has been used to aid the assignment of the observed electronic states. This work represents the first experimental investigation of the electronic spectrum of the YP molecule.

  17. Adolescent Urology and Transitional Care.

    PubMed

    Woodhouse, Christopher

    2015-11-01

    Babies with the major congenital anomalies of the genito-urinary tract have all-embracing holistic care during childhood. They require the same level of care in adult life. This is the role of transition and adolescent urology. PMID:26153563

  18. Comparative Habitability of Transiting Exoplanets

    NASA Astrophysics Data System (ADS)

    Barnes, Rory; Meadows, Victoria S.; Evans, Nicole

    2015-12-01

    Exoplanet habitability is traditionally assessed by comparing a planet’s semimajor axis to the location of its host star’s “habitable zone,” the shell around a star for which Earth-like planets can possess liquid surface water. The Kepler space telescope has discovered numerous planet candidates near the habitable zone, and many more are expected from missions such as K2, TESS, and PLATO. These candidates often require significant follow-up observations for validation, so prioritizing planets for habitability from transit data has become an important aspect of the search for life in the universe. We propose a method to compare transiting planets for their potential to support life based on transit data, stellar properties and previously reported limits on planetary emitted flux. For a planet in radiative equilibrium, the emitted flux increases with eccentricity, but decreases with albedo. As these parameters are often unconstrained, there is an “eccentricity-albedo degeneracy” for the habitability of transiting exoplanets. Our method mitigates this degeneracy, includes a penalty for large-radius planets, uses terrestrial mass-radius relationships, and, when available, constraints on eccentricity to compute a number we call the “habitability index for transiting exoplanets” that represents the relative probability that an exoplanet could support liquid surface water. We calculate it for Kepler objects of interest and find that planets that receive between 60% and 90% of the Earth’s incident radiation, assuming circular orbits, are most likely to be habitable. Finally, we make predictions for the upcoming TESS and James Webb Space Telescope missions.

  19. COMPARATIVE HABITABILITY OF TRANSITING EXOPLANETS

    SciTech Connect

    Barnes, Rory; Meadows, Victoria S.; Evans, Nicole

    2015-12-01

    Exoplanet habitability is traditionally assessed by comparing a planet’s semimajor axis to the location of its host star’s “habitable zone,” the shell around a star for which Earth-like planets can possess liquid surface water. The Kepler space telescope has discovered numerous planet candidates near the habitable zone, and many more are expected from missions such as K2, TESS, and PLATO. These candidates often require significant follow-up observations for validation, so prioritizing planets for habitability from transit data has become an important aspect of the search for life in the universe. We propose a method to compare transiting planets for their potential to support life based on transit data, stellar properties and previously reported limits on planetary emitted flux. For a planet in radiative equilibrium, the emitted flux increases with eccentricity, but decreases with albedo. As these parameters are often unconstrained, there is an “eccentricity-albedo degeneracy” for the habitability of transiting exoplanets. Our method mitigates this degeneracy, includes a penalty for large-radius planets, uses terrestrial mass–radius relationships, and, when available, constraints on eccentricity to compute a number we call the “habitability index for transiting exoplanets” that represents the relative probability that an exoplanet could support liquid surface water. We calculate it for Kepler objects of interest and find that planets that receive between 60% and 90% of the Earth’s incident radiation, assuming circular orbits, are most likely to be habitable. Finally, we make predictions for the upcoming TESS and James Webb Space Telescope missions.

  20. Composition of transiting and transiting-only super-Earths

    NASA Astrophysics Data System (ADS)

    Valencia, Diana

    2011-11-01

    The relatively recent detections of the first three transiting super-Earths mark the beginning of a subfield within exoplanets that is both fruitful and challenging. The first step into characterizing these objects is to infer their composition given the degenerate character of the problem. The calculations show that Kepler-10b has a composition between an Earth-like and a Mercury-like (enriched in iron) composition. In contrast, GJ 1214b is too large to be solid, and has to have a volatile envelope. Lastly, while three of the four reported mass estimates of CoRoT-7b allow for a rocky composition, one forbids it and can only be reconciled with significant amounts of water vapor. In addition to these three transiting low-mass planets, there are now more than one thousand Kepler planets with only measured radius. Even without a mass measurement (``transiting-only'') it is still possible to place constraints on the amount of volatile content of the highly-irradiated planets, as their envelopes, if present, are flared. Using Kepler-9d as an example, we estimate its water vapor, or hydrogen and helium content to be less than 50% or 0.1% by mass respectively.

  1. Transitions

    NASA Technical Reports Server (NTRS)

    2006-01-01

    26 May 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a variety of textures observed on a dust-covered plain in the Marte Valles region of Mars. Textural variations across the scene include: areas that are littered with small impact craters, a channel-like feature that is dominated by mounds of a variety of sizes, small ripples and/or ridges, and relatively smooth, unremarkable terrain. The contact between the cratered plain and the area dominated by mounds marks one of the banks along the edge of one of the shallow valleys of the Marte Valles system.

    Location near: 17.7oN, 175.0oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

  2. Venus transits - A French view

    NASA Astrophysics Data System (ADS)

    Débarbat, Suzanne

    2005-04-01

    After a careful study of Mars observations obtained by Tycho Brahé (1546-1601), Kepler (1571-1630) discovered the now-called Kepler's third law. In 1627 he published his famous Tabulae Rudolphinae, a homage to his protector Rudolph II (1552-1612), tables (Kepler 1609, 1627) from which he predicted Mercury and Venus transits over the Sun. In 1629 Kepler published his Admonitio ad Astronomos Advertisement to Astronomers (Kepler 1630), Avertissement aux Astronomes in French Au sujet de phénomènes rares et étonnants de l'an 1631: l'incursion de Vénus et de Mercure sur le Soleil. This was the beginning of the interest of French astronomers, among many others, in such transits, mostly for Venus, the subject of this paper in which dates are given in the Gregorian calendar.

  3. Electronic Transitions of Yttrium Monoxide

    NASA Astrophysics Data System (ADS)

    Ng, Y. W.; Wang, Na; Clark, Andrew B.; Cheung, A. S.-C.

    2013-06-01

    The electronic transition spectrum of yttrium monoxide (YO) in the spectral region between 284nm and 307nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence (LIF) spectroscopy. The YO molecule was produced by reacting laser-ablated yttrium atoms with O_{2} seeded in argon. Twenty transition bands were observed in that region and a few bands were selected for further study using optical-optical double resonance (OODR) spectroscopy. The excited C^{2} Π state has been reached via the intermediate B^{2} Σ^{+} state from the ground X^{2} Σ^{+} state. The excited sub-states observed so far have Ω = 0.5 and 1.5. A least squares fit of the measured rotational lines yielded molecular constants for the newly observed excited states.

  4. Electronic transitions of palladium dimer

    SciTech Connect

    Qian, Yue; Ng, Y. W.; Chen, Zhihua; Cheung, A. S.-C.

    2013-11-21

    The laser induced fluorescence spectrum of palladium dimer (Pd{sub 2}) in the visible region between 480 and 700 nm has been observed and analyzed. The gas-phase Pd{sub 2} molecule was produced by laser ablation of palladium metal rod. Eleven vibrational bands were observed and assigned to the [17.1] {sup 3}II{sub g} - X{sup 3}Σ{sub u}{sup +} transition system. The bond length (r{sub o}) and vibrational frequency (ΔG{sub 1/2}) of the ground X{sup 3}Σ{sub u}{sup +} state were determined to be 2.47(4) Å and 211.4(5) cm{sup −1}, respectively. A molecular orbital energy level diagram was used to understand the observed ground and excited electronic states. This is the first gas-phase experimental investigation of the electronic transitions of Pd{sub 2}.

  5. Articulated transition duct in turbomachine

    SciTech Connect

    Flanagan, James Scott; McMahan, Kevin Weston; LeBegue, Jeffrey Scott; Pentecost, Ronnie Ray

    2014-04-29

    Turbine systems are provided. A turbine system includes a transition duct comprising an inlet, an outlet, and a duct passage extending between the inlet and the outlet and defining a longitudinal axis, a radial axis, and a tangential axis. The outlet of the transition duct is offset from the inlet along the longitudinal axis and the tangential axis. The duct passage includes an upstream portion and a downstream portion. The upstream portion extends from the inlet between an inlet end and an aft end. The downstream portion extends from the outlet between an outlet end and a head end. The turbine system further includes a joint coupling the aft end of the upstream portion and the head end of the downstream portion together. The joint is configured to allow movement of the upstream portion and the downstream portion relative to each other about or along at least one axis.

  6. Charge transfer transitions in cuprates

    NASA Astrophysics Data System (ADS)

    Larsson, Sven

    2010-05-01

    Absorption spectra of cuprates are discussed. Persistent photo-induced conductivity occurs in the visible spectrum (˜2 eV) and is commonly assigned to ligand-metal (LM) charge transfer (CT) transitions. However, LM CT is site local and cannot possibly generate persistent charges. The assignment in this Letter is 'metal to adjacent metal' (MM) CT transitions, while the absorption at hν > 3 eV is still assigned to mainly LM CT. Only MM CT, defining the Mott-Hubbard gap, is exclusively polarized in the CuO 2 plane, as found experimentally. Since MM CT is strongly affected by the local electric field, doping transfers spectral weight to the IR region.

  7. Counting paths with Schur transitions

    NASA Astrophysics Data System (ADS)

    Díaz, Pablo; Kemp, Garreth; Véliz-Osorio, Alvaro

    2016-10-01

    In this work we explore the structure of the branching graph of the unitary group using Schur transitions. We find that these transitions suggest a new combinatorial expression for counting paths in the branching graph. This formula, which is valid for any rank of the unitary group, reproduces known asymptotic results. We proceed to establish the general validity of this expression by a formal proof. The form of this equation strongly hints towards a quantum generalization. Thus, we introduce a notion of quantum relative dimension and subject it to the appropriate consistency tests. This new quantity finds its natural environment in the context of RCFTs and fractional statistics; where the already established notion of quantum dimension has proven to be of great physical importance.

  8. Phase transitions in nuclear matter

    SciTech Connect

    Glendenning, N.K.

    1984-11-01

    The rather general circumstances under which a phase transition in hadronic matter at finite temperature to an abnormal phase in which baryon effective masses become small and in which copious baryon-antibaryon pairs appear is emphasized. A preview is also given of a soliton model of dense matter, in which at a density of about seven times nuclear density, matter ceases to be a color insulator and becomes increasingly color conducting. 22 references.

  9. The PAMELA Transition Radiation Detector

    NASA Astrophysics Data System (ADS)

    Cafagna, Francesco

    A Transition Radiation Detector (TRD) has been developed for the PAMELA instrument. PAMELA is a satellite born magnetic spectrometer; its primary scientific objective is the study of antiparticles in cosmic rays. The TRD detector was developed to provide particle identification, in addition to calorimetric measurements. This detector is composed of 9 active layers made of proportional straw tubes, piled up with interleaved carbon fibers radiator layers. Detector description and test beam performances will be presented.

  10. Shape Coexistence in Transitional Nuclei

    NASA Astrophysics Data System (ADS)

    Kulp, W. D.; Schmelzenbach, P.; Wood, J. L.; Allmond, J. M.; Krane, K. S.; Loats, J.; Stapels, C. J.; Norman, E. B.

    2007-10-01

    The ``transitional'' nuclei near N=90 have long been a focus of experimental and theoretical investigations. We report on a program of study of the N=90 and N=88 nuclei with a focus on the structure of ^150Sm elucidated through new high-statistics, precision γ-ray coincidence spectroscopy and γ-γ angular correlation data from the radioactive decay of ^150Pm (T1/2= 2.68 h, Q^- = 3454 keV, J^π= 1^-) and ^150m,gEu (T1/2= 12.8 h, J^π= 0^- and T1/2= 36.9 y, J^π= 5^(-), respectively, Q^+(g.s.)= 2261 keV). In particular, very weak key collective transitions (e.g., the 2^+2(1046) ->4^+1(773) 272 keV γ ray) are observed and precision δ(E2/M1) mixing ratios are extracted (determining δJ = 0 transitions). This data, when combined with published results from conversion electron measurements, two-neutron transfer studies, and Coulomb excitation supports the results from detailed multiple-spectroscopy studies of ^152Sm [1] indicating that shape coexistence underlies the structure at N=88, 90. [1] W. D. Kulp, et al., arXiv:0706.4129 [nucl-ex].

  11. Major transitions in information technology.

    PubMed

    Valverde, Sergi

    2016-08-19

    When looking at the history of technology, we can see that all inventions are not of equal importance. Only a few technologies have the potential to start a new branching series (specifically, by increasing diversity), have a lasting impact in human life and ultimately became turning points. Technological transitions correspond to times and places in the past when a large number of novel artefact forms or behaviours appeared together or in rapid succession. Why does that happen? Is technological change continuous and gradual or does it occur in sudden leaps and bounds? The evolution of information technology (IT) allows for a quantitative and theoretical approach to technological transitions. The value of information systems experiences sudden changes (i) when we learn how to use this technology, (ii) when we accumulate a large amount of information, and (iii) when communities of practice create and exchange free information. The coexistence between gradual improvements and discontinuous technological change is a consequence of the asymmetric relationship between complexity and hardware and software. Using a cultural evolution approach, we suggest that sudden changes in the organization of ITs depend on the high costs of maintaining and transmitting reliable information.This article is part of the themed issue 'The major synthetic evolutionary transitions'.

  12. Major transitions in information technology.

    PubMed

    Valverde, Sergi

    2016-08-19

    When looking at the history of technology, we can see that all inventions are not of equal importance. Only a few technologies have the potential to start a new branching series (specifically, by increasing diversity), have a lasting impact in human life and ultimately became turning points. Technological transitions correspond to times and places in the past when a large number of novel artefact forms or behaviours appeared together or in rapid succession. Why does that happen? Is technological change continuous and gradual or does it occur in sudden leaps and bounds? The evolution of information technology (IT) allows for a quantitative and theoretical approach to technological transitions. The value of information systems experiences sudden changes (i) when we learn how to use this technology, (ii) when we accumulate a large amount of information, and (iii) when communities of practice create and exchange free information. The coexistence between gradual improvements and discontinuous technological change is a consequence of the asymmetric relationship between complexity and hardware and software. Using a cultural evolution approach, we suggest that sudden changes in the organization of ITs depend on the high costs of maintaining and transmitting reliable information.This article is part of the themed issue 'The major synthetic evolutionary transitions'. PMID:27431527

  13. Transition physics and scaling overview

    SciTech Connect

    Carlstrom, T.N.

    1995-12-01

    This paper presents an overview of recent experimental progress towards understanding H-mode transition physics and scaling. Terminology and techniques for studying H-mode are reviewed and discussed. The model of shear E x B flow stabilization of edge fluctuations at the L-H transition is gaining wide acceptance and is further supported by observations of edge rotation on a number of new devices. Observations of poloidal asymmetries of edge fluctuations and dephasing of density and potential fluctuations after the transition pose interesting challenges for understanding H-mode physics. Dedicated scans to determine the scaling of the power threshold have now been performed on many machines. A dear B{sub t} dependence is universally observed but dependence on the line averaged density is complicated. Other dependencies are also reported. Studies of the effect of neutrals and error fields on the power threshold are under investigation. The ITER threshold database has matured and offers guidance to the power threshold scaling issues relevant to next-step devices.

  14. Saturn as a Transiting Exoplanet

    NASA Astrophysics Data System (ADS)

    Dalba, Paul A.; Muirhead, Philip S.; Fortney, Jonathan J.; Hedman, Matthew M.; Nicholson, Philip D.; Veyette, Mark J.

    2015-11-01

    Previous investigations of exoplanet atmospheres have not targeted those resembling the gas giant planets in our solar system. These types of exoplanets are too cold to be directly imaged or observed in emission, and their low transit probabilities and frequencies make characterization via transmission spectroscopy a challenging endeavor. However, studies of cold giant exoplanets would be highly valuable to our understanding of planet formation and migration and could place the gas giant members of our own solar system in a greater context. Here, we use solar occultations observed by the Visual and Infrared Mapping Spectrometer aboard the Cassini Spacecraft to extract the 1 to 5 μm transmission spectrum of Saturn, as if it were a transiting exoplanet. We detect absorption features from several molecules despite the presence of ammonia clouds. Self-consistent exoplanet atmosphere models show good agreement with Saturn's transmission spectrum but fail to reproduce the largest feature in the spectrum. We also find that atmospheric refraction determines the minimum altitude that could be probed during mid-transit of a Saturn-twin exoplanet around a Sun-like star. These results suggest that transmission spectroscopy of cold, long-period gaseous exoplanets should be possible with current and future observatories.

  15. Electronic transitions of platinum monofluoride

    NASA Astrophysics Data System (ADS)

    Ng, K. F.; Southam, A. M.; Cheung, A. S.-C.

    2016-10-01

    Electronic transition spectrum of platinum monofluoride (PtF) between 431 and 560 nm has been investigated using the technique of laser vaporization/reaction with free jet expansion and laser induced fluorescence spectroscopy. Eight vibrational bands had been observed but only six of them were analyzed, they were grouped into four electronic transitions: the [18.9]2Π3/2 - X2Π3/2, the [18.9]2Π3/2 - [0.04]2Δ5/2, the [19.9]2Δ5/2 - X2Π3/2 and the [23.2]2Δ5/2 - X2Π3/2 transitions. Accurate molecular constants have been determined for the [23.2]2Δ5/2, [19.9]2Δ5/2, [18.9]2Π3/2 and [0.04]2Δ5/2 electronic states. The agreement between experimental determined molecular constants and those from ab initio calculations incorporating the spin-orbit coupling is generally good.

  16. Non-equilibrium phase transitions

    SciTech Connect

    Mottola, E.; Cooper, F.M.; Bishop, A.R.; Habib, S.; Kluger, Y.; Jensen, N.G.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Non-equilibrium phase transitions play a central role in a very broad range of scientific areas, ranging from nuclear, particle, and astrophysics to condensed matter physics and the material and biological sciences. The aim of this project was to explore the path to a deeper and more fundamental understanding of the common physical principles underlying the complex real time dynamics of phase transitions. The main emphasis was on the development of general theoretical tools to deal with non-equilibrium processes, and of numerical methods robust enough to capture the time-evolving structures that occur in actual experimental situations. Specific applications to Laboratory multidivisional efforts in relativistic heavy-ion physics (transition to a new phase of nuclear matter consisting of a quark-gluon plasma) and layered high-temperature superconductors (critical currents and flux flow at the National High Magnetic Field Laboratory) were undertaken.

  17. Trust Transitivity in Social Networks

    PubMed Central

    Richters, Oliver; Peixoto, Tiago P.

    2011-01-01

    Non-centralized recommendation-based decision making is a central feature of several social and technological processes, such as market dynamics, peer-to-peer file-sharing and the web of trust of digital certification. We investigate the properties of trust propagation on networks, based on a simple metric of trust transitivity. We investigate analytically the percolation properties of trust transitivity in random networks with arbitrary in/out-degree distributions, and compare with numerical realizations. We find that the existence of a non-zero fraction of absolute trust (i.e. entirely confident trust) is a requirement for the viability of global trust propagation in large systems: The average pair-wise trust is marked by a discontinuous transition at a specific fraction of absolute trust, below which it vanishes. Furthermore, we perform an extensive analysis of the Pretty Good Privacy (PGP) web of trust, in view of the concepts introduced. We compare different scenarios of trust distribution: community- and authority-centered. We find that these scenarios lead to sharply different patterns of trust propagation, due to the segregation of authority hubs and densely-connected communities. While the authority-centered scenario is more efficient, and leads to higher average trust values, it favours weakly-connected “fringe” nodes, which are directly trusted by authorities. The community-centered scheme, on the other hand, favours nodes with intermediate in/out-degrees, in detriment of the authorities and its “fringe” peers. PMID:21483683

  18. Trust transitivity in social networks.

    PubMed

    Richters, Oliver; Peixoto, Tiago P

    2011-04-05

    Non-centralized recommendation-based decision making is a central feature of several social and technological processes, such as market dynamics, peer-to-peer file-sharing and the web of trust of digital certification. We investigate the properties of trust propagation on networks, based on a simple metric of trust transitivity. We investigate analytically the percolation properties of trust transitivity in random networks with arbitrary in/out-degree distributions, and compare with numerical realizations. We find that the existence of a non-zero fraction of absolute trust (i.e. entirely confident trust) is a requirement for the viability of global trust propagation in large systems: The average pair-wise trust is marked by a discontinuous transition at a specific fraction of absolute trust, below which it vanishes. Furthermore, we perform an extensive analysis of the Pretty Good Privacy (PGP) web of trust, in view of the concepts introduced. We compare different scenarios of trust distribution: community- and authority-centered. We find that these scenarios lead to sharply different patterns of trust propagation, due to the segregation of authority hubs and densely-connected communities. While the authority-centered scenario is more efficient, and leads to higher average trust values, it favours weakly-connected "fringe" nodes, which are directly trusted by authorities. The community-centered scheme, on the other hand, favours nodes with intermediate in/out-degrees, in detriment of the authorities and its "fringe" peers.

  19. Nuclear physics: Elusive transition spotted in thorium

    NASA Astrophysics Data System (ADS)

    Safronova, Marianna

    2016-05-01

    The highly precise atomic clocks used in science and technology are based on electronic transitions in atoms. The discovery of a nuclear transition in thorium-229 raises hopes of making nuclear clocks a reality. See Article p.47

  20. Functions and Requirements for the Transition Project

    SciTech Connect

    YANOCHKO, R.M.

    2000-04-24

    This document describes the functional requirement baseline for the Transition of 100 K Area Facilities Project (Transition Project). This baseline information consists of top-level functions, requirements, concept description, interface description, issues, and enabling assumptions.

  1. Fast flux test facility, transition project plan

    SciTech Connect

    Guttenberg, S.

    1994-11-15

    The FFTF Transition Project Plan, Revision 1, provides changes and project baseline for the deactivation activities necessary to transition the FFTF to a radiologically and industrially safe shutdown condition.

  2. OBSERVATIONAL WINDOW FUNCTIONS IN PLANET TRANSIT SURVEYS

    SciTech Connect

    Von Braun, Kaspar; Kane, Stephen R.; Ciardi, David R. E-mail: skane@ipac.caltech.edu

    2009-09-01

    The probability that an existing planetary transit is detectable in one's data is sensitively dependent upon the window function of the observations. We quantitatively characterize and provide visualizations of the dependence of this probability as a function of orbital period upon several observing strategy and astrophysical parameters, such as length of observing run, observing cadence, length of night, transit duration and depth, and the minimum number of sampled transits. The ability to detect a transit is directly related to the intrinsic noise of the observations. In our simulations of observational window functions, we explicitly address noncorrelated (Gaussian or white) noise and correlated (red) noise and discuss how these two noise components affect transit detectability in fundamentally different manners, especially for long periods and/or small transit depths. We furthermore discuss the consequence of competing effects on transit detectability, elaborate on measures of observing strategies, and examine the projected efficiency of different transit survey scenarios with respect to certain regions of parameter space.

  3. Atomic homodyne detection of weak atomic transitions.

    PubMed

    Gunawardena, Mevan; Elliott, D S

    2007-01-26

    We have developed a two-color, two-pathway coherent control technique to detect and measure weak optical transitions in atoms by coherently beating the transition amplitude for the weak transition with that of a much stronger transition. We demonstrate the technique in atomic cesium, exciting the 6s(2)S(1/2) --> 8s(2)S(1/2) transition via a strong two-photon transition and a weak controllable Stark-induced transition. We discuss the enhancement in the signal-to-noise ratio for this measurement technique over that of direct detection of the weak transition rate, and project future refinements that may further improve its sensitivity and application to the measurement of other weak atomic interactions.

  4. Planets in Transit V Passages of Discovery

    NASA Astrophysics Data System (ADS)

    Castellano, T. P.

    2003-05-01

    Eclipses of the Sun have long influenced culture, history, and science. The analogous but much more subtle phenomena of a transit of the Sun by Mercury was first predicted by Johannes Kepler. Soon, predictions of transits of Venus inspired bold expeditions to better understand the scale of our solar system. These passages of discovery sometimes succeeded scientifically but always captured the public imagination and played an unexpected role in history. The possibility of detecting planets outside the solar system by the transit method was first outlined by Otto Struve in 1952. Early inquiries usually assumed that extrasolar planetary systems would have a distribution of planetary radii and orbital sizes like the solar system. The detection of transits from the ground in such systems would be daunting. The recent, unexpected discovery of a class of extrasolar planets (by the radial velocity technique) with orbital periods less than a week and masses near to the planet Jupiter has resulted in a resurgence of interest in the transit method. These so called "hot Jupiters", can produce transits that are likely enough, frequent enough, the transit method. These so called "hot Jupiters", can produce transits that are likely enough, frequent enough, and deep enough that ground-based transit searches can be successful. In November 1999, a planet orbiting the star HD 209458 was found to transit, and many measurements of the transit have since been made that challenge formation and evolution theories. Numerous ground based searches for transits are now underway. Several planned high precision space-based missions designed to detect transits of earth-sized planets, also have the potential to detect transits of hundreds of "hot Jupiters". These efforts and the upcoming transit of the Sun by Venus on June 8, 2004 present an opportunity for transits to once again capture the public imagination and perhaps play a role in history.

  5. Microscopic Description of Nuclear Quantum Phase Transitions

    SciTech Connect

    Niksic, T.; Vretenar, D.; Lalazissis, G. A.; Ring, P.

    2007-08-31

    The relativistic mean-field framework, extended to include correlations related to restoration of broken symmetries and to fluctuations of the quadrupole deformation, is applied to a study of shape transitions in Nd isotopes. It is demonstrated that the microscopic self-consistent approach, based on global effective interactions, can describe not only general features of transitions between spherical and deformed nuclei, but also the singular properties of excitation spectra and transition rates at the critical point of quantum shape phase transition.

  6. Educational Policies of the Countries in Transition.

    ERIC Educational Resources Information Center

    Birzea, Cesar

    This report discusses the emergence of a new geopolitical reality, that of countries in transition. Although the expression usually refers to former Communist countries, a closer analysis shows that transition is, in fact, a universal historical phenomenon. As used here, countries in transition must evidence the following factors: (1) the…

  7. Analysis of abrupt transitions in ecological systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The occurrence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of abrupt transitions has been advanced by theory, but hindered by the l...

  8. ASD Academic Transitions: Trends in Parental Perspective

    ERIC Educational Resources Information Center

    Lee, Cindy; McCoy, Kathleen M.; Zucker, Stanley H.; Mathur, Sarup R.

    2014-01-01

    Academic transitions are a necessary and important part of an ASD student's life. Parental involvement and perspective is a vital part of each transition planning process. The primary goal of this research was to identify trends in parent perspectives regarding ASD academic transitions through meta-synthesis of current research. The research…

  9. Phase transitions for the Brusselator model

    NASA Astrophysics Data System (ADS)

    Ma, Tian; Wang, Shouhong

    2011-03-01

    Dynamic phase transitions of the Brusselator model is carefully analyzed, leading to a rigorous characterization of the types and structure of the phase transitions of the model from basic homogeneous states. The study is based on the dynamic transition theory developed recently by the authors.

  10. 45 CFR 618.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Transition plans. 618.230 Section 618.230 Public... Coverage § 618.230 Transition plans. (a) Submission of plans. An institution to which § 618.225 applies and... plan applicable to all such units, or a separate transition plan applicable to each such unit....

  11. 34 CFR 106.17 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Transition plans. 106.17 Section 106.17 Education... Coverage § 106.17 Transition plans. (a) Submission of plans. An institution to which § 106.16 applies and... plan applicable to all such units, or a separate transition plan applicable to each such unit....

  12. 31 CFR 28.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Transition plans. 28.230 Section 28... Transition plans. (a) Submission of plans. An institution to which § 28.225 applies and that is composed of more than one administratively separate unit may submit either a single transition plan applicable...

  13. Lost in Transition? Student Food Consumption

    ERIC Educational Resources Information Center

    Blichfeldt, Bodil Stilling; Gram, Malene

    2013-01-01

    Findings from transition studies as well as studies of student food show that the transition from living at home to independent living influences student food consumption and that food consumption might be problematic during this period. Furthermore, both students' enactment of being in transition and the food habits and practices they bring with…

  14. Fluor Hanford (FH) River Corridor Transition Plan

    SciTech Connect

    MCBRIDE, D.J.

    2002-08-28

    This Transition Plan defines the scope and schedule for actions that are critical for a smooth transition of the River Corridor scope of work and to ensure the achievement of transition as planned, with minimal or no impact to ongoing baseline activities.

  15. 34 CFR 106.17 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 34 Education 1 2014-07-01 2014-07-01 false Transition plans. 106.17 Section 106.17 Education... Coverage § 106.17 Transition plans. (a) Submission of plans. An institution to which § 106.16 applies and... plan applicable to all such units, or a separate transition plan applicable to each such unit....

  16. 31 CFR 28.230 - Transition plans.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance: Treasury 1 2011-07-01 2011-07-01 false Transition plans. 28.230 Section 28... Transition plans. (a) Submission of plans. An institution to which § 28.225 applies and that is composed of more than one administratively separate unit may submit either a single transition plan applicable...

  17. 31 CFR 28.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance: Treasury 1 2012-07-01 2012-07-01 false Transition plans. 28.230 Section 28... Transition plans. (a) Submission of plans. An institution to which § 28.225 applies and that is composed of more than one administratively separate unit may submit either a single transition plan applicable...

  18. 45 CFR 618.230 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 3 2013-10-01 2013-10-01 false Transition plans. 618.230 Section 618.230 Public... Coverage § 618.230 Transition plans. (a) Submission of plans. An institution to which § 618.225 applies and... plan applicable to all such units, or a separate transition plan applicable to each such unit....

  19. 15 CFR 8a.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 15 Commerce and Foreign Trade 1 2014-01-01 2014-01-01 false Transition plans. 8a.230 Section 8a... Transition plans. (a) Submission of plans. An institution to which § 8a.225 applies and that is composed of more than one administratively separate unit may submit either a single transition plan applicable...

  20. 40 CFR 7.75 - Transition plan.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 1 2014-07-01 2014-07-01 false Transition plan. 7.75 Section 7.75... of Handicap § 7.75 Transition plan. If structural changes to facilities are necessary to make the program or activity accessible to handicapped persons, a recipient must prepare a transition plan....

  1. 13 CFR 113.230 - Transition plans.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 13 Business Credit and Assistance 1 2011-01-01 2011-01-01 false Transition plans. 113.230 Section... Coverage § 113.230 Transition plans. (a) Submission of plans. An institution to which § 113.225 applies and... plan applicable to all such units, or a separate transition plan applicable to each such unit....

  2. 15 CFR 8a.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 15 Commerce and Foreign Trade 1 2012-01-01 2012-01-01 false Transition plans. 8a.230 Section 8a... Transition plans. (a) Submission of plans. An institution to which § 8a.225 applies and that is composed of more than one administratively separate unit may submit either a single transition plan applicable...

  3. 38 CFR 23.230 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2013-07-01 2013-07-01 false Transition plans. 23.230... Coverage § 23.230 Transition plans. (a) Submission of plans. An institution to which § 23.225 applies and... plan applicable to all such units, or a separate transition plan applicable to each such unit....

  4. A Smoother Transition for Black Teens

    ERIC Educational Resources Information Center

    Holcomb-McCoy, Cheryl

    2011-01-01

    For all students, the transition to high school may lead to lower academic achievement and adjustment problems. Black students are at greater risk for academic and social decline during this transition. Holcomb-McCoy identifies four obstacles that make black students more vulnerable as they navigate the transition into high school: stereotyping in…

  5. The Transition Experiences of Successful Chinese Immigrants

    ERIC Educational Resources Information Center

    Amundson, Norman E.; Yeung, Thomas; Sun, Iris; Chan, Keith; Cheng, Johnny

    2011-01-01

    This article focused on the transition experiences of 20 successful Chinese immigrants, in particular their transition stories and how they accounted for their success (what facilitated and hindered their transition). An enhanced critical incident method was used for data analysis. Four major success categories emerged: having a positive attitude…

  6. Vulnerable Youth and Transitions to Adulthood

    ERIC Educational Resources Information Center

    Xie, Rongbing; Sen, Bisakha; Foster, E. Michael

    2014-01-01

    This chapter focuses on vulnerable youth, the challenges they face during their transitions to adulthood, and the adverse effects of limited support systems on those transitions. The authors offer recommendations on how adult educators can help facilitate smooth transitions into adulthood for vulnerable youth.

  7. Meeting the Needs of Students in Transition

    ERIC Educational Resources Information Center

    Summers, Al; Moehnke, Larry

    2006-01-01

    As our society becomes more mobile, smooth and rewarding student transitions become more important. This article describes a partnership between U. S. Army Child and Youth Services and the Military Child Education Coalition that helps schools ease transitions for thousands of students. The program is based on the principle that transition does not…

  8. On the structure of supercritical phase transition

    SciTech Connect

    Hirata, Y.S. )

    1990-06-10

    A novel physical picture is presented for the normal-to-supercritical phase transition in QED around a large-Z nucleus. The process is described as the decay of the false vacuum in close analogy to the first-order phase transition in statistical mechanics. The irreversible nature of the transition is pointed out and the physical implications of this picture are discussed.

  9. 40 CFR 7.75 - Transition plan.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 1 2012-07-01 2012-07-01 false Transition plan. 7.75 Section 7.75... of Handicap § 7.75 Transition plan. If structural changes to facilities are necessary to make the program or activity accessible to handicapped persons, a recipient must prepare a transition plan....

  10. 40 CFR 7.75 - Transition plan.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 1 2013-07-01 2013-07-01 false Transition plan. 7.75 Section 7.75... of Handicap § 7.75 Transition plan. If structural changes to facilities are necessary to make the program or activity accessible to handicapped persons, a recipient must prepare a transition plan....

  11. 33 CFR 401.89 - Transit refused.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Transit refused. 401.89 Section... TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations General § 401.89 Transit refused. (a) An officer may refuse to allow a vessel to transit when, (1) The vessel is not equipped in accordance with §§ 401.5...

  12. 33 CFR 401.89 - Transit refused.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Transit refused. 401.89 Section... TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations General § 401.89 Transit refused. (a) An officer may refuse to allow a vessel to transit when, (1) The vessel is not equipped in accordance with §§ 401.5...

  13. 33 CFR 401.89 - Transit refused.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Transit refused. 401.89 Section... TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations General § 401.89 Transit refused. (a) An officer may refuse to allow a vessel to transit when, (1) The vessel is not equipped in accordance with §§ 401.5...

  14. 33 CFR 401.89 - Transit refused.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Transit refused. 401.89 Section... TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations General § 401.89 Transit refused. (a) An officer may refuse to allow a vessel to transit when, (1) The vessel is not equipped in accordance with §§ 401.5...

  15. 33 CFR 401.89 - Transit refused.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Transit refused. 401.89 Section... TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations General § 401.89 Transit refused. (a) An officer may refuse to allow a vessel to transit when, (1) The vessel is not equipped in accordance with §§ 401.5...

  16. On transit time instability in liquid jets

    NASA Technical Reports Server (NTRS)

    Grabitz, G.; Meier, G.

    1982-01-01

    A basic transit time instability in flows with disturbances of speed is found. It was shown that the mass distribution is established by and large by the described transit time effects. These transit time effects may also be involved for gas jets.

  17. No Wasted Moments: Planning Purposeful Transitions

    ERIC Educational Resources Information Center

    Nicolucci, Sandra

    2010-01-01

    This article focuses on the nature of the "transitional minutes" in "any" music class. When transitional minutes before, during, and after rehearsals and classes are unplanned and left to chance, much viable and valuable teaching time is lost. When transitional minutes are well structured, learning can proceed efficiently. One tends to remember…

  18. Magnetism and electronic phase transitions in monoclinic transition metal dichalcogenides with transition metal atoms embedded

    NASA Astrophysics Data System (ADS)

    Lin, Xianqing; Ni, Jun

    2016-08-01

    First-principles calculations have been performed to study the energetic, electronic, and magnetic properties of substitutional 3d transition metal dopants in monoclinic transition metal dichalcogenides (TMDs) as topological insulators ( 1 T ' - MX 2 with M = (Mo, W) and X = (S, Se)). We find various favorite features in these doped systems to introduce magnetism and other desirable electronic properties: (i) The Mn embedded monoclinic TMDs are magnetic, and the doped 1 T ' - MoS 2 still maintains the semiconducting character with high concentration of Mn, while an electronic phase transition occurs in other Mn doped monoclinic TMDs with an increasing concentration of Mn. Two Mn dopants prefer the ferromagnetic coupling except for substitution of the nearest Mo atoms in 1 T ' - MoS 2 , and the strength of exchange interaction shows anisotropic behavior with dopants along one Mo zigzag chain having much stronger coupling. (ii) The substitutional V is a promising hole dopant, which causes little change to the energy dispersion around the conduction and valence band edges in most systems. In contrast, parts of the conduction band drop for the electron dopants Co and Ni due to the large structural distortion. Moreover, closing band gaps of the host materials are observed with increasing carrier concentration. (iii) Single Fe dopant has a magnetic moment, but it also dopes electrons. When two Fe dopants have a small distance, the systems turn into nonmagnetic semiconductors. (iv) The formation energies of all dopants are much lower than those in hexagonal TMDs and are all negative in certain growth conditions, suggesting possible realization of the predicted magnetism, electronic phase transitions as well as carrier doping in 1 T ' - MX 2 based topological devices.

  19. Research in bus and rail transit operations

    SciTech Connect

    Chatterjee, A.; Wegmann, F.J.; Ceder, A.; Levinson, H.S.; Hollander, A.

    1989-01-01

    The 10 papers in the report deal with the following areas: Private Sector Involvement in Sponsoring Sunday Bus Service; Optimal Design of Transit Short-Turn Trips; New York City's Unfranchised Buses: Case Study in Deregulation; Critical Factors in Planning Multimodal Passenger Terminals; Use of Travelers' Attitudes in Rail Service Design; Driven, Attended, and Fully Automated Transit; Qualitative Comparison; Impact on Transit Patronage of Cessation or Inauguration of Rail Service; Use of Productivity Factors in Estimating LRT Operating Costs; Simulation Study To Evaluate Spare Ratios in Bus Transit Systems; Statistical Evaluation of Spare Ratio in Transit Rolling Stock.

  20. Work and quantum phase transitions: quantum latency.

    PubMed

    Mascarenhas, E; Bragança, H; Dorner, R; França Santos, M; Vedral, V; Modi, K; Goold, J

    2014-06-01

    We study the physics of quantum phase transitions from the perspective of nonequilibrium thermodynamics. For first-order quantum phase transitions, we find that the average work done per quench in crossing the critical point is discontinuous. This leads us to introduce the quantum latent work in analogy with the classical latent heat of first order classical phase transitions. For second order quantum phase transitions the irreversible work is closely related to the fidelity susceptibility for weak sudden quenches of the system Hamiltonian. We demonstrate our ideas with numerical simulations of first, second, and infinite order phase transitions in various spin chain models.

  1. Possible Structural Phase Transitions in Transition Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Durgun, Engin; Sahin, Hasan; Peeters, Francois

    2014-03-01

    Most of the the transition metal dichalcogenides (TMD) have graphene-like hexagonal crystal structure which are composed of metal atom layers (M) sandwiched between layers of chalcogen atoms (X) and these structures have MX2 stoichiometry. Chalcogen layers can be stacked on top of each other in two different forms: H phase made of trigonal prismatic holes for metal atoms and T phase that consists staggered chalcogen layers forming octahedral holes for metals. Among the TMDs that have been reported to be stable, individual layers of MoS2, MoSe2, WS2 and WSe2 have 1H structure in their ground state while dichalcogens of Ti, V and Ta prefer the 1T phase. In our study we investigate the physical mechanisms underlying for the possible phase transitions in TMDs. Our calculations based on first-principles techniques reveal that in addition to H and T phases various distorted H and T phases can be also stabilized by point defects. These new phases have entirely different electronic properties.

  2. Topological phase transition in layered transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Choe, Duk-Hyun; Sung, Ha-Jun; Chang, Kee Joo

    Despite considerable interests in transition metal dichalcogenides (TMDs), such as MX2 with M = (Mo, W) and X = (S, Se, Te), the physical origin of their topological nature is still in its infancy. The conventional view of topological phase transition (TPT) in TMDs is that the band inversion occurs between the metal d and chalcogen p orbital bands. More precisely, the former is pulled down below the latter. Here we introduce an explicit scheme for analyzing TPT in topological materials and find that the TPT in TMDs is different from the conventional speculation. When the 1T phase undergoes a structural transformation to the 1T' phase in monolayer MX2, the band topology changes from trivial to non-trivial, leading to the TPT. We discuss the exact role of the metal d and chalcogen p orbital bands during the TPT. Our finding would provide clear guidelines for understanding the topological nature not only in TMDs but also in other topological materials yet to be explored.

  3. Metal to semiconductor transition in metallic transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Li, Yan; Tongay, Sefaattin; Yue, Qu; Kang, Jun; Wu, Junqiao; Li, Jingbo

    2013-11-01

    We report on tuning the electronic and magnetic properties of metallic transition metal dichalcogenides (mTMDCs) by 2D to 1D size confinement. The stability of the mTMDC monolayers and nanoribbons is demonstrated by the larger binding energy compared to the experimentally available semiconducting TMDCs. The 2D MX2 (M = Nb, Ta; X = S, Se) monolayers are non-ferromagnetic metals and mechanically softer compared to their semiconducting TMDCs counterparts. Interestingly, mTMDCs undergo metal-to-semiconductor transition when the ribbon width approaches to ˜13 Å and ˜7 Å for zigzag and armchair edge terminations, respectively; then these ribbons convert back to metal when the ribbon widths further decrease. Zigzag terminated nanoribbons are ferromagnetic semiconductors, and their magnetic properties can also be tuned by hydrogen edge passivation, whereas the armchair nanoribbons are non-ferromagnetic semiconductors. Our results display that the mTMDCs offer a broad range of physical properties spanning from metallic to semiconducting and non-ferromagnetic to ferromagnetic that is ideal for applications where stable narrow bandgap semiconductors with different magnetic properties are desired.

  4. Cognition and the menopause transition.

    PubMed

    Maki, Pauline M; Henderson, Victor W

    2016-07-01

    Complaints about forgetfulness, "brain fog," and difficulty concentrating are common in women transitioning through menopause. Women with these cognitive complaints often express concern about whether these problems are normal, related to menopause, or represent a symptom of Alzheimer disease or another serious cognitive disorder. In this Practice Pearl, we provide a brief summary of the scientific literature on the frequency of cognitive complaints in midlife women, the validity of complaints in relation to performance on standardized cognitive tests, and the influence of menopause on cognitive performance. We then offer recommendations for healthcare providers and women to address cognitive concerns. PMID:27272226

  5. Transition section for acoustic waveguides

    DOEpatents

    Karplus, H.H.B.

    1975-10-28

    A means of facilitating the transmission of acoustic waves with minimal reflection between two regions having different specific acoustic impedances is described comprising a region exhibiting a constant product of cross-sectional area and specific acoustic impedance at each cross-sectional plane along the axis of the transition region. A variety of structures that exhibit this feature is disclosed, the preferred embodiment comprising a nested structure of doubly reentrant cones. This structure is useful for monitoring the operation of nuclear reactors in which random acoustic signals are generated in the course of operation.

  6. Low floor mass transit vehicle

    DOEpatents

    Emmons, J. Bruce; Blessing, Leonard J.

    2004-02-03

    A mass transit vehicle includes a frame structure that provides an efficient and economical approach to providing a low floor bus. The inventive frame includes a stiff roof panel and a stiff floor panel. A plurality of generally vertical pillars extend between the roof and floor panels. A unique bracket arrangement is disclosed for connecting the pillars to the panels. Side panels are secured to the pillars and carry the shear stresses on the frame. A unique seating assembly that can be advantageously incorporated into the vehicle taking advantage of the load distributing features of the inventive frame is also disclosed.

  7. Shim for sealing transition pieces

    DOEpatents

    Lacy, Benjamin Paul; Demiroglu, Mehmet; Sarawate, Neelesh Nandkumar

    2012-07-24

    According to one aspect of the invention, a shim for sealing two adjacent turbine transition pieces is disclosed. The shim includes a circumferential member that includes a first lateral flange and a second lateral flange. Further, the first and second lateral flanges each comprise a tab configured to mate to a first surface plane and the first and second lateral flanges are configured to mate to a second surface plane, wherein the first and second surface planes are substantially parallel. In addition, the shim includes a first flange extending substantially perpendicular from the circumferential member.

  8. Radiative transitions in metallic nanoclusters

    NASA Astrophysics Data System (ADS)

    Shalin, A. S.

    2008-02-01

    In this article, a new theoretical approach to studying light-scattering characteristics of nanosized objects based on the solution to the Thomas-Fermi equation and quasi-classical approximation is considered. It is shown that the distribution of valence electrons in the volume of metallic clusters exhibits a specific structure of "spatial zones." With the aid of quasi-classical wave functions, expressions for the appropriate dipole moments of the transitions between the ground and excited states are obtained; the behavior of the spectrum of gold clusters depending on their sizes is studied; a comparison with existing experimental data is carried out.

  9. Conformational Transitions in Molecular Systems

    NASA Astrophysics Data System (ADS)

    Bachmann, M.; Janke, W.

    2008-11-01

    Proteins are the "work horses" in biological systems. In almost all functions specific proteins are involved. They control molecular transport processes, stabilize the cell structure, enzymatically catalyze chemical reactions; others act as molecular motors in the complex machinery of molecular synthetization processes. Due to their significance, misfolds and malfunctions of proteins typically entail disastrous diseases, such as Alzheimer's disease and bovine spongiform encephalopathy (BSE). Therefore, the understanding of the trinity of amino acid composition, geometric structure, and biological function is one of the most essential challenges for the natural sciences. Here, we glance at conformational transitions accompanying the structure formation in protein folding processes.

  10. Transition state structures in solution

    SciTech Connect

    Bertran, J.; Lluch, J. M.; Gonzalez-Lafont, A.; Dillet, V.; Perez, V.

    1995-04-05

    In the present paper the location of transition state structures for reactions in solution has been studied. Continuum model calculations have been carried out on the Friedel-Crafts alkylation reaction and a proton transfer through a water molecule between two oxygen atoms in formic acid. In this model the separation between the chemical system and the solvent has been introduced. On the other hand, the discrete Monte Carlo methodology has also been used to simulate the solvent effect on dissociative electron transfer processes. In this model, the hypothesis of separability is not assumed. Finally, the validity of both approaches is discussed.

  11. Transition state structures in solution

    NASA Astrophysics Data System (ADS)

    Bertrán, J.; Lluch, J. M.; Gonzàlez-Lafont, A.; Dillet, V.; Pérez, V.

    1995-04-01

    In the present paper the location of transition state structures for reactions in solution has been studied. Continuum model calculations have been carried out on the Friedel-Crafts alkylation reaction and a proton transfer through a water molecule between two oxygen atoms in formic acid. In this model the separation between the chemical system and the solvent has been introduced. On the other hand, the discrete Monte Carlo methodology has also been used to simulate the solvent effect on dissociative electron transfer processes. In this model, the hypothesis of separability is not assumed. Finally, the validity of both approaches is discussed.

  12. Transitions in nursing leadership roles.

    PubMed

    Jobes, M; Steinbinder, A

    1996-01-01

    Today's turbulent, chaotic health care environment necessitates dramatic changes in the roles of nurse executives. These role changes are rapidly being cast upon individuals who are pressured to react, accept, and adapt quickly. Previously successful leadership styles no longer serve nurse executives as they assume nonoperational roles without line authority and power. No prescriptive strategies will be effective to assist nurse leaders in their new roles. One nurse executive's story of her own journey will be shared to illustrate how she is creating a successful transition.

  13. TERMS PHOTOMETRY OF KNOWN TRANSITING EXOPLANETS

    SciTech Connect

    Dragomir, Diana; Kane, Stephen R.; Ciardi, David R.; Gelino, Dawn M.; Payne, Alan; Ramirez, Solange V.; Von Braun, Kaspar; Wyatt, Pamela; Pilyavsky, Genady; Mahadevan, Suvrath; Wright, Jason T.; Zachary Gazak, J.; Rabus, Markus

    2011-10-15

    The Transit Ephemeris Refinement and Monitoring Survey conducts radial velocity and photometric monitoring of known exoplanets in order to refine planetary orbits and predictions of possible transit times. This effort is primarily directed toward planets not known to transit, but a small sample of our targets consists of known transiting systems. Here we present precision photometry for six WASP (Wide Angle Search for Planets) planets acquired during their transit windows. We perform a Markov Chain Monte Carlo analysis for each planet and combine these data with previous measurements to redetermine the period and ephemerides for these planets. These observations provide recent mid-transit times which are useful for scheduling future observations. Our results improve the ephemerides of WASP-4b, WASP-5b, and WASP-6b and reduce the uncertainties on the mid-transit time for WASP-29b. We also confirm the orbital, stellar, and planetary parameters of all six systems.

  14. Elaborating transition interface sampling methods

    SciTech Connect

    Erp, Titus S. van . E-mail: bolhuis@science.uva.nl

    2005-05-01

    We review two recently developed efficient methods for calculating rate constants of processes dominated by rare events in high-dimensional complex systems. The first is transition interface sampling (TIS), based on the measurement of effective fluxes through hypersurfaces in phase space. TIS improves efficiency with respect to standard transition path sampling (TPS) rate constant techniques, because it allows a variable path length and is less sensitive to recrossings. The second method is the partial path version of TIS. Developed for diffusive processes, it exploits the loss of long time correlation. We discuss the relation between the new techniques and the standard reactive flux methods in detail. Path sampling algorithms can suffer from ergodicity problems, and we introduce several new techniques to alleviate these problems, notably path swapping, stochastic configurational bias Monte Carlo shooting moves and order-parameter free path sampling. In addition, we give algorithms to calculate other interesting properties from path ensembles besides rate constants, such as activation energies and reaction mechanisms.

  15. Transitional nuclei near shell closures

    SciTech Connect

    Mukherjee, G.

    2014-08-14

    High spin states in Bismuth and Thallium nuclei near the Z = 82 shell closure and Cesium nuclei near the N = 82 shell closure in A = 190 and A = 130 regions, respectively, have been experimentally investigated using heavy-ion fusion evaporation reaction and by detecting the gamma rays using the Indian National Gamma Array (INGA). Interesting shape properties in these transitional nuclei have been observed. The results were compared with the neighboring nuclei in these two regions. The total Routhian surface (TRS) calculations have been performed for a better understanding of the observed properties. In mass region A = 190, a change in shape from spherical to deformed has been observd around neutron number N = 112 for the Bi (Z = 83) isotopes with proton number above the magic gap Z = 82, whereas, the shape of Tl (Z = 81) isotopes with proton number below the magic gap Z = 82 remains stable as a function of neutron number. An important transition from aplanar to planar configuration of angular momentum vectors leading to the occurance of nuclar chirality and magnetic rotation, respectively, has been proposed for the unique parity πh{sub 11/2}⊗νh{sub 11/2} configuration in Cs isotopes in the mass region A ∼ 130 around neutron number N = 79. These results are in commensurate with the TRS calculations.

  16. Photochemistry of Transition Metal Hydrides.

    PubMed

    Perutz, Robin N; Procacci, Barbara

    2016-08-10

    Photochemical reactivity associated with metal-hydrogen bonds is widespread among metal hydride complexes and has played a critical part in opening up C-H bond activation. It has been exploited to design different types of photocatalytic reactions and to obtain NMR spectra of dilute solutions with a single pulse of an NMR spectrometer. Because photolysis can be performed on fast time scales and at low temperature, metal-hydride photochemistry has enabled determination of the molecular structure and rates of reaction of highly reactive intermediates. We identify five characteristic photoprocesses of metal monohydride complexes associated with the M-H bond, of which the most widespread are M-H homolysis and R-H reductive elimination. For metal dihydride complexes, the dominant photoprocess is reductive elimination of H2. Dihydrogen complexes typically lose H2 photochemically. The majority of photochemical reactions are likely to be dissociative, but hydride complexes may be designed with equilibrated excited states that undergo different photochemical reactions, including proton transfer or hydride transfer. The photochemical mechanisms of a few reactions have been analyzed by computational methods, including quantum dynamics. A section on specialist methods (time-resolved spectroscopy, matrix isolation, NMR, and computational methods) and a survey of transition metal hydride photochemistry organized by transition metal group complete the Review.

  17. Preterm birth: Transition to adulthood.

    PubMed

    Allen, Marilee C; Cristofalo, Elizabeth; Kim, Christina

    2010-01-01

    Preterm birth is associated with greater difficulty with transitions from childhood to adolescence to adulthood. Adolescents and young adults born preterm have higher rates of cerebral palsy, intellectual disability, cognitive impairment, learning disability, executive dysfunction, attention deficit disorder, and social-emotional difficulties than their peers born fullterm. Compared to individuals born fullterm, more preterm survivors have major neurodevelopmental or psychiatric disability and need financial supports and societal resources. Neuroimaging studies of adolescents and adults born preterm report higher rates of brain injury, differences in regional brain structure, and different brain circuits than in those born fullterm. Making the transition to adulthood is more difficult for young adults who were born preterm than their peers born fullterm, in that fewer complete high school and higher education, find and keep meaningful employment, and live independently from their parents. As a group, they do not tend to be risk-takers, and they have lower rates of alcohol abuse, use of illicit drugs, and criminal offenses than do their peers. Despite their many challenges, the majority of adults born preterm function well, form personal relationships, integrate well into their community, and are as satisfied with their quality of life as are their peers. Concerns regarding current preterm infants, with more extremely preterm survivors, overwhelming our medical, educational, and societal resources should serve as an impetus for research on prevention of preterm births and brain injury, as well as how to support and promote their ongoing neuromaturation and recovery from injury. PMID:25708075

  18. Phase Transitions in Dipalmitoylphosphatidylcholine Monolayers.

    PubMed

    Zuo, Yi Y; Chen, Rimei; Wang, Xianju; Yang, Jinlong; Policova, Zdenka; Neumann, A Wilhelm

    2016-08-23

    A self-assembled phospholipid monolayer at an air-water interface is a well-defined model system for studying surface thermodynamics, membrane biophysics, thin-film materials, and colloidal soft matter. Here we report a study of two-dimensional phase transitions in the dipalmitoylphosphatidylcholine (DPPC) monolayer at the air-water interface using a newly developed methodology called constrained drop surfactometry (CDS). CDS is superior to the classical Langmuir balance in its capacity for rigorous temperature control and leak-proof environments, thus making it an ideal alternative to the Langmuir balance for studying lipid polymorphism. In addition, we have developed a novel Langmuir-Blodgett (LB) transfer technique that allows the direct transfer of lipid monolayers from the droplet surface under well-controlled conditions. This LB transfer technique permits the direct visualization of phase coexistence in the DPPC monolayer. With these technological advances, we found that the two-dimensional phase behavior of the DPPC monolayer is analogous to the three-dimensional phase transition of a pure substance. This study has implications in the fundamental understanding of surface thermodynamics as well as applications such as self-assembled monolayers and pulmonary surfactant biophysics. PMID:27479299

  19. Energy development: crisis and transition

    SciTech Connect

    Gordon, L.

    1981-04-01

    The historical role of energy use in economic development has not been as clear as were the roles of land, labor, and capital until recent shortages brought it into a clearer perspective. Added to this were ambiguities in the computation of the energy consumption/economic growth relationship that overstated the fuel-conversion efficiencies of developing countries. Energy differs from other raw materials in its pervasiveness, its inability to be recycled, and its low elasticity of substitution, which make it a potential constraint on economic growth. Oil-importing developing countries accumulated large balance-of-payment deficits during the 1970s in addition to drawing down their traditional energy reserves through deforestation and the use of organic wastes as fuels. The management of a long-term energy transition is more acute for developing countries, but international cooperation to keep this transition violence-free will benefit all nations. Arguments are made for a positive response to the call for a global energy strategy. (DCK)

  20. Dynamic transition in supercritical iron

    PubMed Central

    Fomin, Yu. D.; Ryzhov, V. N.; Tsiok, E. N.; Brazhkin, V. V.; Trachenko, K.

    2014-01-01

    Recent advance in understanding the supercritical state posits the existence of a new line above the critical point separating two physically distinct states of matter: rigid liquid and non-rigid gas-like fluid. The location of this line, the Frenkel line, remains unknown for important real systems. Here, we map the Frenkel line on the phase diagram of supercritical iron using molecular dynamics simulations. On the basis of our data, we propose a general recipe to locate the Frenkel line for any system, the recipe that importantly does not involve system-specific detailed calculations and relies on the knowledge of the melting line only. We further discuss the relationship between the Frenkel line and the metal-insulator transition in supercritical liquid metals. Our results enable predicting the state of supercritical iron in several conditions of interest. In particular, we predict that liquid iron in the Jupiter core is in the “rigid liquid” state and is highly conducting. We finally analyse the evolution of iron conductivity in the core of smaller planets such as Earth and Venus as well as exoplanets: as planets cool off, the supercritical core undergoes the transition to the rigid-liquid conducting state at the Frenkel line. PMID:25424664

  1. THE QUASIPERIODIC AUTOMATED TRANSIT SEARCH ALGORITHM

    SciTech Connect

    Carter, Joshua A.; Agol, Eric

    2013-03-10

    We present a new algorithm for detecting transiting extrasolar planets in time-series photometry. The Quasiperiodic Automated Transit Search (QATS) algorithm relaxes the usual assumption of strictly periodic transits by permitting a variable, but bounded, interval between successive transits. We show that this method is capable of detecting transiting planets with significant transit timing variations without any loss of significance-{sup s}mearing{sup -}as would be incurred with traditional algorithms; however, this is at the cost of a slightly increased stochastic background. The approximate times of transit are standard products of the QATS search. Despite the increased flexibility, we show that QATS has a run-time complexity that is comparable to traditional search codes and is comparably easy to implement. QATS is applicable to data having a nearly uninterrupted, uniform cadence and is therefore well suited to the modern class of space-based transit searches (e.g., Kepler, CoRoT). Applications of QATS include transiting planets in dynamically active multi-planet systems and transiting planets in stellar binary systems.

  2. STELLAR TRANSITS IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Beky, Bence; Kocsis, Bence E-mail: bkocsis@cfa.harvard.edu

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 10{sup 6} solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or {approx}10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  3. Stellar Transits in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Béky, Bence; Kocsis, Bence

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 106 solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or ~10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  4. The transition to a sustainable society.

    PubMed Central

    Speth, J G

    1992-01-01

    Transitions in dealing with the root causes of environmental problems are advocated to achieve environmental sustainability. These transformations include (i) a demographic transition, (ii) a technology transition that includes the "green" automobile, (iii) an economic transition to one in which prices reflect full environmental costs, (iv) a transition in social equity, and (v) an institutional transition to different arrangements among governments, businesses, and peoples. Businessmen and environmentalists are urged to work together in the next decade to make the environment a personal issue, to call for government action, to recognize the environmental challenges, and to commit to accountability in order to leave a legacy of hope to the twenty-first century. PMID:11607270

  5. Approximating metal-insulator transitions

    NASA Astrophysics Data System (ADS)

    Danieli, Carlo; Rayanov, Kristian; Pavlov, Boris; Martin, Gaven; Flach, Sergej

    2015-12-01

    We consider quantum wave propagation in one-dimensional quasiperiodic lattices. We propose an iterative construction of quasiperiodic potentials from sequences of potentials with increasing spatial period. At each finite iteration step, the eigenstates reflect the properties of the limiting quasiperiodic potential properties up to a controlled maximum system size. We then observe approximate Metal-Insulator Transitions (MIT) at the finite iteration steps. We also report evidence on mobility edges, which are at variance to the celebrated Aubry-André model. The dynamics near the MIT shows a critical slowing down of the ballistic group velocity in the metallic phase, similar to the divergence of the localization length in the insulating phase.

  6. Cloud regimes as phase transitions

    NASA Astrophysics Data System (ADS)

    Stechmann, Samuel N.; Hottovy, Scott

    2016-06-01

    Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes -- open versus closed cells -- fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. With this new conceptual viewpoint, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions.

  7. Synthesis of transition metal carbonitrides

    DOEpatents

    Munir, Zuhair A. R.; Eslamloo-Grami, Maryam

    1994-01-01

    Transition metal carbonitrides (in particular, titanium carbonitride, TiC.sub.0.5 N.sub.0.5) are synthesized by a self-propagating reaction between the metal (e.g., titanium) and carbon in a nitrogen atmosphere. Complete conversion to the carbonitride phase is achieved with the addition of TiN as diluent and with a nitrogen pressure .gtoreq.0.6 MPa. Thermodynamic phase-stability calculations and experimental characterizations of quenched samples provided revealed that the mechanism of formation of the carbonitride is a two-step process. The first step involves the formation of the nonstoichiometric carbide, TiC.sub.0.5, and is followed by the formation of the product by the incorporation of nitrogen in the defect-structure carbide.

  8. Risks of the oil transition

    NASA Astrophysics Data System (ADS)

    Farrell, A. E.; Brandt, A. R.

    2006-10-01

    The energy system is in the early stages of a transition from conventionally produced oil to a variety of substitutes, bringing economic, strategic, and environmental risks. We argue that these three challenges are inherently interconnected, and that as we act to manage one we cannot avoid affecting our prospects in dealing with the others. We further argue that without appropriate policies, tradeoffs between these risks are likely to be made so as to allow increased environmental disruption in return for increased economic and energy security. Responsible solutions involve developing and deploying environmentally acceptable energy technologies (both supply and demand) rapidly enough to replace dwindling conventional oil production and meet growing demand for transportation while diversifying supply to improve energy security.

  9. Mixing and Transition Control Studied

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Considerable progress in understanding nonlinear phenomena in both unbounded and wallbounded shear flow transition has been made through the use of a combination of high- Reynolds-number asymptotic and numerical methods. The objective of this continuing work is to fully understand the nonlinear dynamics so that ultimately (1) an effective means of mixing and transition control can be developed and (2) the source terms in the aeroacoustic noise problem can be modeled more accurately. Two important aspects of the work are that (1) the disturbances evolve from strictly linear instability waves on weakly nonparallel mean flows so that the proper upstream conditions are applied in the nonlinear or wave-interaction streamwise region and (2) the asymptotic formulations lead to parabolic problems so that the question of proper out-flow boundary conditions--still a research issue for direct numerical simulations of convectively unstable shear flows--does not arise. Composite expansion techniques are used to obtain solutions that account for both mean-flow-evolution and nonlinear effects. A previously derived theory for the amplitude evolution of a two-dimensional instability wave in an incompressible mixing layer (which is in quantitative agreement with available experimental data for the first nonlinear saturation stage for a plane-jet shear layer, a circular-jet shear layer, and a mixing layer behind a splitter plate) have been extended to include a wave-interaction stage with a three-dimensional subharmonic. The ultimate wave interaction effects can either give rise to explosive growth or an equilibrium solution, both of which are intimately associated with the nonlinear self-interaction of the three dimensional component. The extended theory is being evaluated numerically. In contrast to the mixing-layer situation, earlier comparisons of theoretical predictions based on asymptotic methods and experiments in wall-bounded shear-flow transition have been somewhat lacking

  10. Desorption induced by electronic transitions

    NASA Astrophysics Data System (ADS)

    Ageev, V. N.

    1994-10-01

    A survey is presented of the techniques and instruments used in studies of desorption induced by electronic transitions (DIET) that can be stimulated by irradiating a solid surface by electrons (ESD) or photons (PSD). The most general characteristics and aspects of this phenomenon are systematized. An analysis is made of relations between DIET and crystallographic and band structure of the substrate, the nature of adsorption bonding and specific features of desorbing particles. The main DIET models involving various electronic excitations of adsorption bonding and their relaxation as particles escape from the surface are discussed, and their predictions are compared with the available experimental data. Particular attention is focussed on the DIET models involving many-electron excitations. The various applications of DIET techniques to studies of adsorbed layers and of surface processes are considered. The radiation stability of solid surfaces and of film coatings with respect to excitation of their electronic subsystem is discussed.

  11. Picking the right transition strategy.

    PubMed

    Watkins, Michael D

    2009-01-01

    Leaders in transition reflexively rely on the skills and strategies that worked for them in the past. That's a mistake, says Watkins, whose research shows that executives moving into new roles must gain a deep understanding of the situation at hand and adapt to it. To help them accurately assess their organizations and tailor their strategies and styles accordingly, he developed the STARS framework. "STARS" is an acronym for the five common situations leaders move into: start-up, turnaround, accelerated growth, realignment, and sustaining success. Thus, the model outlines the challenges of launching a venture or project; saving a business or initiative that's in serious trouble; dealing with rapid expansion; reenergizing a once-leading company that's now facing problems; and following in the footsteps of a highly regarded leader with a strong legacy of success. Executives can accelerate their immersion in new roles by following certain fundamental principles: Organize to learn about the business, establish A-item priorities, define strategic intent, quickly build the leadership team, secure early wins, and create supportive alliances across the company. But the way those principles should be applied depends very much on the business situation, which the STARS framework can help leaders analyze. Turnarounds and realignments present especially distinct leadership challenges that call for particular transition strategies. Regardless of the business situation, leaders must figure out which things need to happen--perhaps a jump in market share or an expansion into different markets--for their business to achieve its goals. And they must determine which leadership style best fits the new culture they're joining. Armed with such clarity, executives can design effective plans to manage their organizations and themselves.

  12. Nonequilibrium dynamics of phase transitions

    NASA Astrophysics Data System (ADS)

    Gagne, Carmen Jeanne

    2001-11-01

    Phase transitions occur in such diverse and important systems as ferromagnets, liquid crystals and the early Universe. The dynamics of phase transitions such as these have been studied for decades, but the analytical models still need a great deal of improvement before they can adequately describe all time stages and regions under the coexistence curve. Numerical studies can supplement these analytical theories, but they need to accurately describe the continuum equations that they are intended to solve. This thesis describes a method for removing the lattice- spacing and renormalization-mass dependence of Langevin simulations of phase mixing in (2 + 1)-dimensional asymmetric Ginzburg-Landau models with short-ranged interactions. Also, the spread in the order parameter near the critical value of the control parameter due to critical slowing down is used to more accurately determine this value of the control parameter in these simulations. In addition, a new method is proposed for quantifying the departure from equilibrium. The method explores the behavior of the rate of change of the momentum-integrated structure function, ΔStot( t), as it evolves in time. As an illustration, we examine a (1 + 1)-dimensional model of a stochastic Ginzburg-Landau model at varying cooling rates. We show that ΔStot(t) displays a peak which scales with cooling time-scale as t1/2q in the over-damped limit and t1/3q in the underdamped limit. The peak amplitude was found to scale with cooling time-scale as t6/5q in all viscosities studied.

  13. Thermal Phase Transitions in Finite Quantum Systems

    SciTech Connect

    Dean, D.J.

    2001-10-18

    In this Proceedings, the author will describe the behavior of two different quantum-mechanical systems as a function of increasing temperature. While these systems are somewhat different, the questions addressed are very similar, namely, how does one describe transitions in phase of a finite many-body system; how does one recognize these transitions in practical calculations; and how may one obtain the order of the transition.

  14. Observation of transitions in lithiumlike germanium

    NASA Technical Reports Server (NTRS)

    Behring, W. E.; Seely, J. F.; Brown, C. M.; Feldman, U.; Knauer, J. P.

    1989-01-01

    Transitions of the type n = 2-2, n = 2-3 and n = 3-4 in Li-like Ge(29+) have been observed in the spectrum from a laser-produced plasma. The energy levels and ionization energy of Ge(29+) were derived from the observed wavelengths. The wavelength of the 2s 2S1/2-2p 2P3/2 transition is sufficiently accurate to determine the quantum-electrodynamic contribution to the transition energy.

  15. Analysis of Nuclear Quantum Phase Transitions

    SciTech Connect

    Li, Z. P.; Meng, J.; Niksic, T.; Vretenar, D.; Lalazissis, G. A.; Ring, P.

    2009-08-26

    A microscopic analysis, based on nuclear energy density functionals, is presented for shape phase transitions in Nd isotopes. Low-lying excitation spectra and transition probabilities are calculated starting from a five-dimensional Hamiltonian, with parameters determined by constrained relativistic mean-field calculations for triaxial shapes. The results reproduce available data, and show that there is an abrupt change of structure at N = 90, that corresponds to a first-order quantum phase transition between spherical and axially deformed shapes.

  16. Transit station energy impacts. Research report (Interim)

    SciTech Connect

    Coleman, P.; Euritt, M.; Walton, C.M.

    1992-12-01

    Transit trips-when compared with automobile travel-not only relieve congestion, but also offer considerable energy savings per person. Transit trips also affect land use and development patterns that surround a transit station. In the report, a methodology will be developed to estimate the energy savings associated with land use changes in the station areas. Since changes in land use and development in a station area are partially dependent on the type of service offered (rail versus bus rapid, for example), a classification system will be developed for different types of transit stations, a system based on the land use and development changes that occur within the station's zone of influence.

  17. Unidirectional Transition Waves in Bistable Lattices

    NASA Astrophysics Data System (ADS)

    Nadkarni, Neel; Arrieta, Andres F.; Chong, Christopher; Kochmann, Dennis M.; Daraio, Chiara

    2016-06-01

    We present a model system for strongly nonlinear transition waves generated in a periodic lattice of bistable members connected by magnetic links. The asymmetry of the on-site energy wells created by the bistable members produces a mechanical diode that supports only unidirectional transition wave propagation with constant wave velocity. We theoretically justify the cause of the unidirectionality of the transition wave and confirm these predictions by experiments and simulations. We further identify how the wave velocity and profile are uniquely linked to the double-well energy landscape, which serves as a blueprint for transition wave control.

  18. Young Exo-Planet Transit Initiative (YETI)

    NASA Astrophysics Data System (ADS)

    Neuhäuser, Ralph; Errmann, Ronny; Raetz, Stefanie; Chen, Wen-Ping; Hu, Seline; Torres, Guillermo; Kellerer, Aglae; Kitze, Manfred; YETI Team

    2013-07-01

    The Young Exo-Planet Transit Initiative (YETI) uses a network of about 20 telescopes worldwide to monitor several young stellar clusters in order to study all kinds of variability, but primarily to identify planetary transits. We will present first results from the clusters Trumpler-37 and 25 Ori including follow-up imaging and spectroscopy of our first three transit candidates. Discovery of a transiting planet (with direct mass and radius estimates) in a cluster younger than about 10 Myr allows critical tests of planetary formation theories. We will also present additional science results on variability of young stars and eclipsing young binaries.

  19. X-Ray Transition Energies Database

    National Institute of Standards and Technology Data Gateway

    SRD 128 X-Ray Transition Energies Database (Web, free access)   This X-ray transition table provides the energies and wavelengths for the K and L transitions connecting energy levels having principal quantum numbers n = 1, 2, 3, and 4. The elements covered include Z = 10, neon to Z = 100, fermium. There are two unique features of this data base: (1) a serious attempt to have all experimental values on a scale consistent with the International System of measurement (the SI) and (2) inclusion of accurate theoretical estimates for all transitions.

  20. Exposing Baccalaureate Nursing Students to Transitional Care.

    PubMed

    OʼConnor, Melissa; Arcamone, Angelina; Amorim, Frances; Hoban, Mary Beth; Boyd, Regina M; Fowler, Lauren; Marcelli, Theresa; Smith, Jacalyn; Nassar, Kathleen; Fitzpatrick, M Louise

    2016-10-01

    Management and facilitation of care transitions from hospital to alternative settings requires skill and attention to avoid adverse events. Several interprofessional organizations and nurse leaders have called for the expansion and redesign of undergraduate nursing curricula to include care transitions. Yet there is little evidence describing how undergraduate baccalaureate nursing students are educated on this critical topic or how successful they are in improving student knowledge about care transitions. To address this gap, an in-classroom and clinical experience was implemented to prepare students to manage and facilitate care transitions from the hospital to alternative settings-including the home. Perceptions of undergraduate nursing students and home healthcare nurse preceptors were assessed via an electronic survey that was emailed to participants. Forty-eight responses to the survey were received. Students agreed this experience contributed to their understanding of caring for adults and older adults who are experiencing a care transition and they had a good understanding of care transitions to apply to their future nursing courses. Home healthcare nurse preceptors agreed they were able to demonstrate transitional care and that students were engaged. Future work should include expanding transitional care immersion to other care settings as well as the inclusion of additional healthcare disciplines in care transition education.

  1. Dynamics of stimulated L → H transitions

    SciTech Connect

    Miki, K.; Diamond, P. H.; Xiao, W. W.; Hahn, S.-H.; Gürcan, Ö. D.; Tynan, G. R.

    2013-08-15

    We report on model studies of stimulated L → H transitions [K. Miki et al., Phys. Rev. Lett. 110, 195002 (2013)]. These studies use a reduced mesoscale model. Model studies reveal that L → H transition can be triggered by particle injection into a subcritical state (i.e., Ptransition. For low ambient heating, strong injection is predicted to trigger a transient turbulence collapse. Repetitive injection at a period less than the lifetime of the collapsed state can thus maintain the turbulence collapse and so sustain a driven H-mode-like state. The total number of particles required to induce a transition by either injection or gas puffing is estimated. Results indicate that the total number of injected particles required is much smaller than that required for a transition by gas puffing. We thus show that internal injection is more efficient than gas puffing of comparable strength. We also observe that zonal flows do not play a critical role in stimulated transitions. For spontaneous transitions, the spike of the Reynolds work of turbulence on the zonal flow precedes the spike in the mean electric field shear. In contrast, we show that the two are coincident for stimulated transitions, suggesting that there is no causal link between zonal and mean flows for stimulated transitions.

  2. Nonadiabatic transitions in electrostatically trapped ammonia molecules

    SciTech Connect

    Kirste, Moritz; Schnell, Melanie; Meijer, Gerard; Sartakov, Boris G.

    2009-05-15

    Nonadiabatic transitions are known to be major loss channels for atoms in magnetic traps but have thus far not been experimentally reported upon for trapped molecules. We have observed and quantified losses due to nonadiabatic transitions for three isotopologues of ammonia in electrostatic traps by comparing the trapping times in traps with a zero and a nonzero electric field at the center. Nonadiabatic transitions are seen to dominate the overall loss rate even for the present samples that are at relatively high temperatures of 30 mK. It is anticipated that losses due to nonadiabatic transitions in electric fields are omnipresent in ongoing experiments on cold molecules.

  3. The multiuniverse transition in superfluid 3He.

    PubMed

    Bunkov, Yury

    2013-10-01

    The symmetry-breaking phase transitions of the universe and of superfluid (3)He may lead to the formation of different states with different order parameters. In both cases the energy potential below the transition temperature has a complicated multidimensional profile with many local minima and saddle points, which correspond to different states. Consequently, not only topological defects, but also islands of different metastable states can be created. Using (3)He we can analyse the properties and experimental consequences of such transitions and, in particular, the first-order phase transition between the two low symmetry states. PMID:24026020

  4. Negative refraction using Raman transitions and chirality

    SciTech Connect

    Sikes, D. E.; Yavuz, D. D.

    2011-11-15

    We present a scheme that achieves negative refraction with low absorption in far-off resonant atomic systems. The scheme utilizes Raman resonances and does not require the simultaneous presence of an electric-dipole transition and a magnetic-dipole transition near the same wavelength. We show that two interfering Raman tran-sitions coupled to a magnetic-dipole transition can achieve a negative index of refraction with low absorption through magnetoelectric cross-coupling. We confirm the validity of the analytical results with exact numerical simulations of the density matrix. We also discuss possible experimental implementations of the scheme in rare-earth metal atomic systems.

  5. The Helix Coil Transition of DNA

    ERIC Educational Resources Information Center

    Steinert, Roger; Hudson, Bruce

    1973-01-01

    This transition, observed with an inexpensive ultraviolet photometer, is a potentially useful experiment for an advanced freshman class because it introduces several concepts of general physical interest. (DF)

  6. Observations of Extrasolar Planet Transits: What's next?

    NASA Astrophysics Data System (ADS)

    Rauer, H.

    2014-03-01

    Transits of extrasolar planets are a goldmine for our understanding of the physical nature of planets beyond the Solar System. Measurements of radii from transit observations combined with mass determinations from radial velocity spectroscopy, or transit timing variations, have provided the first indications to the planetary composition and interior structure. It turns out that planets show a much richer diversity than found in our own planetary system, considering e.g. the so-called 'super-Earths', 'mini-Neptunes', and inflated giant planets. Transiting exoplanets also allow for spectroscopic observations of their atmospheres, either during transit or near secondary eclipse. Exoplanets showing transits have therefore been identified as key observables, not only for planet detection, but in particular for investigating further planetary nature. As a result, a new generation of instruments (space- and groundbased) for exoplanet transit observations is already in the construction phase and is planned for the near future. Most of these target specifically stars bright enough for spectroscopic follow-up observations, a èlesson learned' from past transit surveys. A clear goal for future investigations of habitable planets is the detection and characterization of terrestrial planets which potentially could harbor life. This talk will review the status and in particular the future of transit observations, with a focus on rocky planets in the habitable zone of their host stars.

  7. NO TRANSIT TIMING VARIATIONS IN WASP-4

    SciTech Connect

    Petrucci, R.; Schwartz, M.; Buccino, A. P.; Mauas, P. J. D.; Jofré, E.; Cúneo, V.; Gómez, M.; Martínez, C.

    2013-12-20

    We present six new transits of the system WASP-4. Together with 28 light curves published in the literature, we perform a homogeneous study of its parameters and search for variations in the transits' central times. The final values agree with those previously reported, except for a slightly lower inclination. We find no significant long-term variations in i or R{sub P} /R {sub *}. The O-C mid-transit times do not show signs of transit timing variations greater than 54 s.

  8. Explosive Percolation Transition is Actually Continuous

    NASA Astrophysics Data System (ADS)

    da Costa, R. A.; Dorogovtsev, S. N.; Goltsev, A. V.; Mendes, J. F. F.

    2010-12-01

    Recently a discontinuous percolation transition was reported in a new “explosive percolation” problem for irreversible systems [D. Achlioptas, R. M. D’Souza, and J. Spencer, Science 323, 1453 (2009)SCIEAS0036-807510.1126/science.1167782] in striking contrast to ordinary percolation. We consider a representative model which shows that the explosive percolation transition is actually a continuous, second order phase transition though with a uniquely small critical exponent of the percolation cluster size. We describe the unusual scaling properties of this transition and find its critical exponents and dimensions.

  9. Kepler Stars with Multiple Transiting Planet Candidates

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack J.

    2012-01-01

    NASA's Kepler spacecraft was launched into an Earth-trailing heliocentric orbit in March of 2009. Kepler is designed to conduct a statistical census of planetary system properties using transit photometry. Among the most exciting early results from Kepler are target stars found to have photometric signatures that suggest the presence of more than one transiting planet. Individual transiting planets provide information on the size and orbital period distributions of exoplanets. Multiple transiting planets provide additional information on the spacing and flatness distributions of planetary systems. Results to d ate and plans for future analysis will be presented.

  10. Many-Body Theory of Atomic Transitions

    NASA Astrophysics Data System (ADS)

    Holmes, Charles Potter

    This dissertation presents a systematic approach to the derivation of transition widths and cross sections for atomic radiative and/or nonradiative processes. By applying the transition theory of Goldberger and Watson ^1, all transition properties are derived from proper solutions of the time-dependent Schrodinger equation. The focus is on situations where initial and final wave functions are nonorthogonal functions that belong to different self-consistent fields. This approach is particularly useful in the treatment of ionizing transitions where the outgoing free electron sees a different atomic potential from that of the initial bound state. Transition amplitudes are expressed as perturbation expansions in which singularities have been removed algebraically. These singularities are due to states which are degenerate with the initial and final states and represent the competing transition channels. The perturbation expansions show clearly the role of the nonorthogonality of the participating states leading to terms representing "shake" processes competing with higher-order electron correlation processes. Transition amplitudes including all second-order processes, are derived for the following transitions: X-ray, Auger, photoionization, radiative recombination, dielectronic recombination, radiative -Auger. Comparisons are made with the expressions frequently used by other workers. Using a Hartree-Fock-Slater model K- and L-shell X-ray and Auger transition widths are calculated for the range 5 <= Z <= 36. These calculations show the effects of initial/final state overlap. ftn^1M. L. Goldberger and K. M. Watson, Collision Theory, (John Wiley & Sons, New York, 1964), Chapter 8, page 424.

  11. Exposing Baccalaureate Nursing Students to Transitional Care.

    PubMed

    OʼConnor, Melissa; Arcamone, Angelina; Amorim, Frances; Hoban, Mary Beth; Boyd, Regina M; Fowler, Lauren; Marcelli, Theresa; Smith, Jacalyn; Nassar, Kathleen; Fitzpatrick, M Louise

    2016-10-01

    Management and facilitation of care transitions from hospital to alternative settings requires skill and attention to avoid adverse events. Several interprofessional organizations and nurse leaders have called for the expansion and redesign of undergraduate nursing curricula to include care transitions. Yet there is little evidence describing how undergraduate baccalaureate nursing students are educated on this critical topic or how successful they are in improving student knowledge about care transitions. To address this gap, an in-classroom and clinical experience was implemented to prepare students to manage and facilitate care transitions from the hospital to alternative settings-including the home. Perceptions of undergraduate nursing students and home healthcare nurse preceptors were assessed via an electronic survey that was emailed to participants. Forty-eight responses to the survey were received. Students agreed this experience contributed to their understanding of caring for adults and older adults who are experiencing a care transition and they had a good understanding of care transitions to apply to their future nursing courses. Home healthcare nurse preceptors agreed they were able to demonstrate transitional care and that students were engaged. Future work should include expanding transitional care immersion to other care settings as well as the inclusion of additional healthcare disciplines in care transition education. PMID:27677063

  12. A liquid-liquid transition can exist in monatomic transition metals with a positive melting slope

    PubMed Central

    Lee, Byeongchan; Lee, Geun Woo

    2016-01-01

    Liquid-liquid transitions under high pressure are found in many elemental materials, but the transitions are known to be associated with either sp-valent materials or f-valent rare-earth elements, in which the maximum or a negative slope in the melting line is readily suggestive of the transition. Here we find a liquid-liquid transition with a positive melting slope in transition metal Ti from structural, electronic, and thermodynamic studies using ab-initio molecular dynamics calculations, showing diffusion anomaly, but no density anomaly. The origin of the transition in liquid Ti is a pressure-induced increase of local structures containing very short bonds with directionality in electronic configurations. This behavior appears to be characteristic of the early transition metals. In contrast, the late transition metal liquid Ni does not show the L-L transition with pressure. This result suggests that the possibility of the L-L transition decreases from early to late transition metals as electronic structures of late transition metals barely have a Jahn-Teller effect and bond directionality. Our results generalize that a phase transition in disordered materials is found with any valence band regardless of the sign of the melting slope, but related to the symmetry of electronic structures of constituent elements. PMID:27762334

  13. Esophageal Transit, Contraction and Perception of Transit After Swallows of Two Viscous Boluses

    PubMed Central

    Dalmazo, Jucileia; Aprile, Lilian Rose Otoboni; Dantas, Roberto Oliveira

    2015-01-01

    Background There have been results showing the influence of bolus viscosities and consistency on esophageal motility and transit. However, there is no description about the influence of two different viscous boluses on esophageal contractions, bolus transit and perception of transit. Our objective in this investigation was to evaluate the esophageal transit and contraction after swallows of two viscous boluses. Methods By impedance and manometric methods, we measured the esophageal transit and contraction after swallows of two viscous boluses of 5 mL volume, 100% barium sulfate and yogurt, swallowed in duplicate in the supine and upright positions. The bolus transit, esophageal contractions and the perception of bolus transit through the esophagus were evaluated in both positions. Impedance and contraction were measured at 5, 10, 15 and 20 cm from the lower esophageal sphincter. After each swallow, the volunteers were asked about the sensation of bolus transit through the esophagus. Results In supine position, the yogurt had a less frequent complete bolus transit than barium. Also in the supine position, the esophageal transit was longer with yogurt than with barium. Esophageal contractions after swallows were similar between barium and yogurt boluses. There was no difference in perception of transit between the two boluses. Conclusion Although both 100% barium sulfate and yogurt are viscous boluses and have similar viscosities, the transit through the esophagus is slower with yogurt bolus than with barium bolus, which suggests that viscosity may be not the sole factor to determine transit.

  14. A Catalog of Transit Timing Posterior Distributions for all Kepler Planet Candidate Transit Events

    NASA Astrophysics Data System (ADS)

    Montet, Benjamin Tyler; Becker, Juliette C.; Johnson, John Asher

    2015-12-01

    Kepler has ushered in a new era of planetary dynamics, enabling the detection of interactions between multiple planets in transiting systems for hundreds of systems. These interactions, observed as transit timing variations (TTVs), have been used to find non-transiting companions to transiting systems and to measure masses, eccentricities, and inclinations of transiting planets. Often, physical parameters are inferred by comparing the observed light curve to the result of a photodynamical model, a time-intensive process that often ignores the effects of correlated noise in the light curve. Catalogs of transit timing observations have previously neglected non-Gaussian uncertainties in the times of transit, uncertainties in the transit shape, and short cadence data. Here, I present a catalog of not only times of transit centers, but also posterior distributions on the time of transit for every planet candidate transit event in the Kepler data, developed through importance sampling of each transit. This catalog allows one to marginalize over uncertainties in the transit shape and incorporate short cadence data, the effects of correlated noise, and non-Gaussian posteriors. Our catalog will enable dynamical studies that reflect accurately the precision of Kepler and its limitations without requiring the computational power to model the light curve completely with every integration. I will also present our open-source N-body photodynamical modeling code, which integrates planetary and stellar orbits accounting for the effects of GR, tidal effects, and Doppler beaming.

  15. Economic transition and health transition: comparing China and Russia.

    PubMed

    Liu, Y; Rao, K; Fei, J

    1998-05-01

    Drawing on experiences from China and Russia (the world's two largest transitional economies), this paper empirically examines the impact of economic reforms on health status. While China's overall health status continued to improve after the economic reform, Russia experienced a serious deterioration in its population health. The observed differences in health performance between China and Russia can be explained by the different impacts of economic reforms on three major socioeconomic determinants of health. Depending on whether or not the reform improves physical environment (as reflected in income level and nutritional status), social environment (including social stability and security system), and health care, we would observe either a positive or a negative net effect on health. Despite remarkable differences in overall health development, China and Russia share some common problems. Mental and social health problems such as suicides and alcohol poisoning have been on the rise in both countries. These problems were much more serious in Russia, where political and social instability was more pronounced, associated with Russia's relatively radical reform process. With their economies moving toward a free market system, health sectors in China and Russia are undergoing marketization, which has had serious detrimental effect on the public health services.

  16. Developing transit availability measures and an index of transit service availability. Research report

    SciTech Connect

    Henk, R.H.; Hubbard, S.M.; Lomax, T.J.; Shunk, G.A.

    1995-07-01

    This study involved the development of an index of transit service availability (ITSA). This index utilizes the factors which most effectively quantify the availability of public transit service (both bus and rail) in an urban area at a macroscopic planning level. The development of the index consisted of applying over 30 prospective measures of transit service availability of 228 urban area transit systems in the United States. The index utilizes three specific measures which quantify transit service coverage, frequency of transit service, and transit system capacity. The index developed in this study is designed to serve as a planning tool -- it is not intended for use in assessing transit system efficiency and/or performance.

  17. Structural transitions in nanoscale systems

    NASA Astrophysics Data System (ADS)

    Yoon, Mina

    In this work I investigate three different materials: nanoscale carbon systems, ferrofluid systems, and molecular-electronic devices. In particular, my study is focused on the theoretical understanding of structural changes and the associated electronic, mechanical, and magnetic properties of these materials. To study the equilibrium packing of fullerenes in carbon nanotube peapods optimization techniques were applied. In agreement with experimental measurements, my results for nanotubes containing fullerenes with 60--84 atoms indicate that the axial separation between the fullerenes is smaller than in the bulk crystal. The reduction of the inter-fullerene distance and also the structural relaxation of fullerenes result from a large internal pressure within the peapods. This naturally induced "static" pressure may qualify nanotubes as nanoscale autoclaves for chemical reactions. Combining total energy calculations with a search of phase space, I investigated the microscopic fusion mechanism of C60 fullerenes. I show that the (2+2) cycloaddition reaction, a necessary precursor for fullerene fusion, can be accelerated inside a nanotube. Fusion occurs along the minimum energy path as a finite sequence of Stone-Wales (SW) transformations. A detailed analysis of the transition states shows that Stone-Wales transformations are multi-step processes. I propose a new microscopic mechanism to explain the unusually fast fusion process of carbon nanotubes. The detailed pathway for two adjacent (5, 5) nanotubes to gradually merge into a (10, 10) tube, and the transition states have been identified. The propagation of the fused region is energetically favorable and proceeds in a morphology reminiscent of a Y-junction via a so called zipper mechanism, involving only SW bond rearrangements with low activation barriers. Using density functional theory, the equilibrium structure, stability, and electronic properties of nanostructured, hydrogen terminated diamond fragments have been

  18. Easing the Transition to School: Administrators' Descriptions of Transition to School Activities

    ERIC Educational Resources Information Center

    Noel, Andrea

    2011-01-01

    This paper details the early childhood transition activities of three schools in southern Queensland, Australia, as reported by school administrators. The transition programs were analysed using the categories of the Transition to School Matrix of the New South Wales (NSW) Department of Education. Activities fell into the first four categories…

  19. Implementing Secondary Transition Evidence-Based Practices: A Multi-State Survey of Transition Service Providers

    ERIC Educational Resources Information Center

    Mazzotti, Valerie L.; Plotner, Anthony J.

    2016-01-01

    Inadequate transition outcomes for youth with disabilities have produced a call for enhanced transition service delivery that includes implementation of evidence-based practices (EBPs). However, research indicates transition service providers still lack the knowledge and skills to effectively implement EBPs to ensure youth with disabilities…

  20. Transformative Learning in Managerial Role Transitions

    ERIC Educational Resources Information Center

    Isopahkala-Bouret, Ulpukka

    2008-01-01

    The purpose of this study is to investigate the nature of learning in work role transitions from specialist roles to managerial roles in a context of a large international technology organisation. Prior theorisation of learning in role transitions has been based on quantitative, psychologically-oriented studies prescribing different role and…

  1. 10 CFR 5.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Transition plans. 5.230 Section 5.230 Energy NUCLEAR... transition plan shall: (1) State the name, address, and Federal Interagency Committee on Education Code of... estimates of the number of students, by sex, expected to apply for, be admitted to, and enter each...

  2. Magnetic fields from the electroweak phase transition

    SciTech Connect

    Tornkvist, O.

    1998-02-01

    I review some of the mechanisms through which primordial magnetic fields may be created in the electroweak phase transition. I show that no magnetic fields are produced initially from two-bubble collisions in a first-order transition. The initial field produced in a three-bubble collision is computed. The evolution of fields at later times is discussed.

  3. The Role of Transitions in ESL Instruction

    ERIC Educational Resources Information Center

    Steinman, Linda

    2013-01-01

    Transitions in ESL contexts generally refer to those linking words placed between sentences and between paragraphs. Transitions in writing (and in speaking) are helpful; they facilitate coherence and cohesion when used correctly. Understanding them when reading allows us to join the writer in seeing why and how idea B follows idea A. In this…

  4. Overview of Transition Programs: Policies and Programs.

    ERIC Educational Resources Information Center

    2003

    There is recent, widespread activity in Australian education and training sectors to improve the transition of young people from initial education to further education and training and employment. Many jurisdictions have conducted high-level reviews of the institutional arrangements underpinning the transition process. The focus has been mainly on…

  5. Energy implications of fixed rail mass transit

    SciTech Connect

    Pikarsky, M.

    1981-01-01

    Major studies on whether mass transit actually saves energy are reviewed. A possible petroleum conservation strategy that focusses on future urban and regional development is then identified. A number of U.S. cities are considered to be prime candidates for rail transit systems for the purpose of energy conservation. 30 refs.

  6. 47 CFR 101.4 - Transition plan.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... part 94 of this chapter as contained in the CFR edition revised as of October 1, 1995 and amended in... 47 Telecommunication 5 2010-10-01 2010-10-01 false Transition plan. 101.4 Section 101.4... SERVICES Applications and Licenses General Filing Requirements § 101.4 Transition plan. (a) All...

  7. 49 CFR 25.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false Transition plans. 25.230 Section 25.230... PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 25.230 Transition plans. (a) Submission of plans. An institution to which § 25.225 applies and that is composed of more than...

  8. 28 CFR 54.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Transition plans. 54.230 Section 54.230... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 54.230 Transition plans. (a) Submission of plans. An institution to which § 54.225 applies and that is composed of more...

  9. 10 CFR 1042.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Transition plans. 1042.230 Section 1042.230 Energy... ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 1042.230 Transition plans. (a) Submission of plans. An institution to which § 1042.225 applies and that is composed of more than one...

  10. 6 CFR 17.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 6 Domestic Security 1 2010-01-01 2010-01-01 false Transition plans. 17.230 Section 17.230 Domestic... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 17.230 Transition plans. (a) Submission of plans. An institution to which § 17.225 applies and that is composed of more...

  11. Transition to School: Revisiting the Bridge Metaphor

    ERIC Educational Resources Information Center

    Huser, Carmen; Dockett, Sue; Perry, Bob

    2016-01-01

    Policymakers, researchers and educators around the world have acknowledged the importance of children's transition to school, both as a significant life event and as a factor in future engagement with education. As a result, much attention has been directed towards researching transition experiences, developing policies to support positive…

  12. Building Bridges: Understanding Student Transition to University

    ERIC Educational Resources Information Center

    Briggs, A. R. J.; Clark, J.; Hall, I.

    2012-01-01

    This article explores challenges in ensuring effective student transition from school or college to university. It examines the complex liaison needed for students to progress to appropriate courses, settle into university life and succeed as higher education learners. Secondary data (international literature on transition and the formation of…

  13. The Supported Teen: Transitioning to High School

    ERIC Educational Resources Information Center

    Dorman, Benton

    2012-01-01

    Transition plans for students with special needs provide support for social and academic success while giving students an accurate picture of what to expect in high school. The Texas Comprehensive Center recommends that schools develop a comprehensive transition plan district-wide. This district plan must include the cooperation of staff from the…

  14. 40 CFR 7.75 - Transition plan.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... the schedule for the steps needed to achieve full accessibility under § 7.65(a), and include a year-by... 40 Protection of Environment 1 2010-07-01 2010-07-01 false Transition plan. 7.75 Section 7.75... of Handicap § 7.75 Transition plan. If structural changes to facilities are necessary to make...

  15. Changes and Exchanges in Marginal Youth Transitions

    ERIC Educational Resources Information Center

    Bottrell, Dorothy; Armstrong, Derrick

    2007-01-01

    While some groups of young people may negotiate successful transitions to work, others are unable or unlikely to do so. The concept of "fair exchange" is pertinent to understanding youth transitions in their formative stages through educational experiences. Patterns of disrupted education challenge the education-work nexus not only because failure…

  16. Energy Transition Initiative: Islands Playbook (Book)

    SciTech Connect

    Not Available

    2015-01-01

    The Island Energy Playbook (the Playbook) provides an action-oriented guide to successfully initiating, planning, and completing a transition to an energy system that primarily relies on local resources to eliminate a dependence on one or two imported fuels. It is intended to serve as a readily available framework that any community can adapt to organize its own energy transition effort.

  17. Bullying and school transition: Context or development?

    PubMed

    Wang, Weijun; Brittain, Heather; McDougall, Patricia; Vaillancourt, Tracy

    2016-01-01

    The relative impact of school transition versus development on peer victimization and bullying perpetration were examined in a natural experiment involving 698 students where half transitioned into middle school from Grade 5 to Grade 6 and the other half remained in their elementary school over the same period. Results indicated that, on average, peer victimization decreased over the transition period while bullying perpetration remained stable for the whole sample. Multilevel modeling was used to investigate the effects of school transition and sex on changes in victimization and perpetration. Results indicated that the effect of transition status on changes in peer victimization was moderated by sex. Middle school transition status predicted decreases in peer victimization for girls, but not for boys, who transitioned. However, school transition status and participants' sex (and their interaction) did not predict changes in perpetration over time. Our findings indicate that changes in student involvement with peer victimization are better understood as a contextual rather than a typical developmental process, whereas bullying perpetration may be better understood as developmental. PMID:26522183

  18. Transition metals activate TFEB in overexpressing cells.

    PubMed

    Peña, Karina A; Kiselyov, Kirill

    2015-08-15

    Transition metal toxicity is an important factor in the pathogenesis of numerous human disorders, including neurodegenerative diseases. Lysosomes have emerged as important factors in transition metal toxicity because they handle transition metals via endocytosis, autophagy, absorption from the cytoplasm and exocytosis. Transcription factor EB (TFEB) regulates lysosomal biogenesis and the expression of lysosomal proteins in response to lysosomal and/or metabolic stresses. Since transition metals cause lysosomal dysfunction, we proposed that TFEB may be activated to drive gene expression in response to transition metal exposure and that such activation may influence transition metal toxicity. We found that transition metals copper (Cu) and iron (Fe) activate recombinant TFEB and stimulate the expression of TFEB-dependent genes in TFEB-overexpressing cells. In cells that show robust lysosomal exocytosis, TFEB was cytoprotective at moderate levels of Cu exposure, decreasing oxidative stress as reported by the expression of heme oxygenase-1 (HMOX1) gene. However, at high levels of Cu exposure, particularly in cells with low levels of lysosomal exocytosis, activation of overexpressed TFEB was toxic, increasing oxidative stress and mitochondrial damage. Based on these data, we conclude that TFEB-driven gene network is a component of the cellular response to transition metals. These data suggest limitations and disadvantages of TFEB overexpression as a therapeutic approach. PMID:26251447

  19. Bullying and school transition: Context or development?

    PubMed

    Wang, Weijun; Brittain, Heather; McDougall, Patricia; Vaillancourt, Tracy

    2016-01-01

    The relative impact of school transition versus development on peer victimization and bullying perpetration were examined in a natural experiment involving 698 students where half transitioned into middle school from Grade 5 to Grade 6 and the other half remained in their elementary school over the same period. Results indicated that, on average, peer victimization decreased over the transition period while bullying perpetration remained stable for the whole sample. Multilevel modeling was used to investigate the effects of school transition and sex on changes in victimization and perpetration. Results indicated that the effect of transition status on changes in peer victimization was moderated by sex. Middle school transition status predicted decreases in peer victimization for girls, but not for boys, who transitioned. However, school transition status and participants' sex (and their interaction) did not predict changes in perpetration over time. Our findings indicate that changes in student involvement with peer victimization are better understood as a contextual rather than a typical developmental process, whereas bullying perpetration may be better understood as developmental.

  20. Sustaining Secondary Transition Programs in Local Schools

    ERIC Educational Resources Information Center

    Benz, M. R.; Lindstrom, L.; Unruh, D.; Waintrup, M.

    2004-01-01

    This article reports on factors that influence the sustainability of secondary transition innovations in local schools. We used a two-stage research process, which combined broad survey methods and an embedded case study design, to investigate the sustainability of a specific school-to-community transition model for youth with disabilities. We…

  1. College Students in Transition: An Annotated Bibliography

    ERIC Educational Resources Information Center

    Foote, Stephanie M., Ed.; Hinkle, Sara M., Ed.; Kranzow, Jeannine, Ed.; Pistilli, Matthew D., Ed.; Miles, LaTonya Rease, Ed.; Simmons, Jannell G., Ed.

    2013-01-01

    The transition from high school to college is an important milestone, but it is only one of many steps in the journey through higher education. This volume is an annotated bibliography of the emerging literature examining the many other transitions students make beyond the first year, including the sophomore year, the transfer experience, and the…

  2. 10 CFR 1042.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 4 2014-01-01 2014-01-01 false Transition plans. 1042.230 Section 1042.230 Energy... ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 1042.230 Transition plans. (a) Submission of plans. An institution to which § 1042.225 applies and that is composed of more than one...

  3. 22 CFR 146.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Transition plans. 146.230 Section 146.230... PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 146.230 Transition plans. (a) Submission of plans. An institution to which § 146.225 applies and that is composed of more than...

  4. 43 CFR 41.230 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Transition plans. 41.230 Section 41.230... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 41.230 Transition plans. (a) Submission of plans. An institution to which § 41.225 applies and that is composed of more...

  5. 22 CFR 229.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Transition plans. 229.230 Section 229.230... PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 229.230 Transition plans. (a) Submission of plans. An institution to which § 229.225 applies and that is composed of more than...

  6. 6 CFR 17.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 6 Domestic Security 1 2014-01-01 2014-01-01 false Transition plans. 17.230 Section 17.230 Domestic... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 17.230 Transition plans. (a) Submission of plans. An institution to which § 17.225 applies and that is composed of more...

  7. 6 CFR 17.230 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 6 Domestic Security 1 2013-01-01 2013-01-01 false Transition plans. 17.230 Section 17.230 Domestic... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 17.230 Transition plans. (a) Submission of plans. An institution to which § 17.225 applies and that is composed of more...

  8. 40 CFR 5.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 1 2014-07-01 2014-07-01 false Transition plans. 5.230 Section 5.230... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 5.230 Transition plans. (a) Submission of plans. An institution to which § 5.225 applies and that is composed of more...

  9. 22 CFR 229.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Transition plans. 229.230 Section 229.230... PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 229.230 Transition plans. (a) Submission of plans. An institution to which § 229.225 applies and that is composed of more than...

  10. 22 CFR 146.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Transition plans. 146.230 Section 146.230... PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 146.230 Transition plans. (a) Submission of plans. An institution to which § 146.225 applies and that is composed of more than...

  11. 22 CFR 229.230 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Transition plans. 229.230 Section 229.230... PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 229.230 Transition plans. (a) Submission of plans. An institution to which § 229.225 applies and that is composed of more than...

  12. 22 CFR 146.230 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Transition plans. 146.230 Section 146.230... PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 146.230 Transition plans. (a) Submission of plans. An institution to which § 146.225 applies and that is composed of more than...

  13. 49 CFR 25.230 - Transition plans.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 1 2014-10-01 2014-10-01 false Transition plans. 25.230 Section 25.230... PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 25.230 Transition plans. (a) Submission of plans. An institution to which § 25.225 applies and that is composed of more than...

  14. 43 CFR 41.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Transition plans. 41.230 Section 41.230... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 41.230 Transition plans. (a) Submission of plans. An institution to which § 41.225 applies and that is composed of more...

  15. Informing Transitions in the Early Years

    ERIC Educational Resources Information Center

    Dunlop, Aline-Wendy; Fabian, Hilary

    2006-01-01

    An increased emphasis on an early start in group day care and educational settings for young children means that by the time children enter statutory education, they may already have had several transitional experiences: each will have an impact. This book explores early transitions from a variety of international perspectives. Each chapter is…

  16. Transition metals activate TFEB in overexpressing cells

    PubMed Central

    Peña, Karina A.; Kiselyov, Kirill

    2015-01-01

    Transition metal toxicity is an important factor in the pathogenesis of numerous human disorders, including neurodegenerative diseases. Lysosomes have emerged as important factors in transition metal toxicity because they handle transition metals via endocytosis, autophagy, absorption from the cytoplasm and exocytosis. Transcription factor EB (TFEB) regulates lysosomal biogenesis and the expression of lysosomal proteins in response to lysosomal and/or metabolic stresses. Since transition metals cause lysosomal dysfunction, we proposed that TFEB may be activated to drive gene expression in response to transition metal exposure and that such activation may influence transition metal toxicity. We found that transition metals copper (Cu) and iron (Fe) activate recombinant TFEB and stimulate the expression of TFEB-dependent genes in TFEB-overexpressing cells. In cells that show robust lysosomal exocytosis, TFEB was cytoprotective at moderate levels of Cu exposure, decreasing oxidative stress as reported by the expression of heme oxygenase-1 (HMOX1) gene. However, at high levels of Cu exposure, particularly in cells with low levels of lysosomal exocytosis, activation of overexpressed TFEB was toxic, increasing oxidative stress and mitochondrial damage. Based on these data, we conclude that TFEB-driven gene network is a component of the cellular response to transition metals. These data suggest limitations and disadvantages of TFEB overexpression as a therapeutic approach. PMID:26251447

  17. 12 CFR 1273.10 - Transition.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 12 Banks and Banking 10 2014-01-01 2014-01-01 false Transition. 1273.10 Section 1273.10 Banks and Banking FEDERAL HOUSING FINANCE AGENCY FEDERAL HOME LOAN BANKS OFFICE OF FINANCE § 1273.10 Transition. (a) Within 45 calendar days of the date on which FHFA first appoints an Independent Director pursuant...

  18. 12 CFR 1273.10 - Transition.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 9 2012-01-01 2012-01-01 false Transition. 1273.10 Section 1273.10 Banks and Banking FEDERAL HOUSING FINANCE AGENCY FEDERAL HOME LOAN BANKS OFFICE OF FINANCE § 1273.10 Transition. (a) Within 45 calendar days of the date on which FHFA first appoints an Independent Director pursuant...

  19. Transitions and the Development of Expertise

    ERIC Educational Resources Information Center

    Hallam, Susan

    2010-01-01

    This paper explores the relationships between the development of expertise and transitions. It sets out what we know about the development of expertise, changes in the brain as expertise develops, and how transitions between different learning contexts and the challenges that they present may impact on developing expertise. It sets out a series of…

  20. Method for dry etching of transition metals

    DOEpatents

    Ashby, C.I.H.; Baca, A.G.; Esherick, P.; Parmeter, J.E.; Rieger, D.J.; Shul, R.J.

    1998-09-29

    A method for dry etching of transition metals is disclosed. The method for dry etching of a transition metal (or a transition metal alloy such as a silicide) on a substrate comprises providing at least one nitrogen- or phosphorus-containing {pi}-acceptor ligand in proximity to the transition metal, and etching the transition metal to form a volatile transition metal/{pi}-acceptor ligand complex. The dry etching may be performed in a plasma etching system such as a reactive ion etching (RIE) system, a downstream plasma etching system (i.e. a plasma afterglow), a chemically-assisted ion beam etching (CAIBE) system or the like. The dry etching may also be performed by generating the {pi}-acceptor ligands directly from a ligand source gas (e.g. nitrosyl ligands generated from nitric oxide), or from contact with energized particles such as photons, electrons, ions, atoms, or molecules. In some preferred embodiments of the present invention, an intermediary reactant species such as carbonyl or a halide ligand is used for an initial chemical reaction with the transition metal, with the intermediary reactant species being replaced at least in part by the {pi}-acceptor ligand for forming the volatile transition metal/{pi}-acceptor ligand complex.

  1. Method for dry etching of transition metals

    DOEpatents

    Ashby, Carol I. H.; Baca, Albert G.; Esherick, Peter; Parmeter, John E.; Rieger, Dennis J.; Shul, Randy J.

    1998-01-01

    A method for dry etching of transition metals. The method for dry etching of a transition metal (or a transition metal alloy such as a silicide) on a substrate comprises providing at least one nitrogen- or phosphorous-containing .pi.-acceptor ligand in proximity to the transition metal, and etching the transition metal to form a volatile transition metal/.pi.-acceptor ligand complex. The dry etching may be performed in a plasma etching system such as a reactive ion etching (RIE) system, a downstream plasma etching system (i.e. a plasma afterglow), a chemically-assisted ion beam etching (CAIBE) system or the like. The dry etching may also be performed by generating the .pi.-acceptor ligands directly from a ligand source gas (e.g. nitrosyl ligands generated from nitric oxide), or from contact with energized particles such as photons, electrons, ions, atoms, or molecules. In some preferred embodiments of the present invention, an intermediary reactant species such as carbonyl or a halide ligand is used for an initial chemical reaction with the transition metal, with the intermediary reactant species being replaced at least in part by the .pi.-acceptor ligand for forming the volatile transition metal/.pi.-acceptor ligand complex.

  2. Factors Affecting Third Culture Kids' (TCKs) Transition

    ERIC Educational Resources Information Center

    Morales, Antonio

    2015-01-01

    (TCKs) transition becomes challenging for both the student and the school. The programs implemented, or lack thereof, are imperative to the successful transition of TCKs into their new, diverse, multicultural environment. Research has been written on the positive effects and challenges faced by TCKs' transient lifestyle. Although international…

  3. Structure and Agency in Transition Research

    ERIC Educational Resources Information Center

    Heinz, Walter R.

    2009-01-01

    Based on the results of transition studies in the UK, Germany, USA and Canada, the virtues of analysing the structural contexts, institutional arrangements and the young peoples' action orientations are presented. In the first decade of the twenty-first century, school and the labour market have become more and more decoupled and transition routes…

  4. Case Studies in Assessment for Transition Planning

    ERIC Educational Resources Information Center

    Trainor, Audrey A.; Patton, James R.; Clark, Gary M.

    2005-01-01

    This book presents a group of case studies to show how to assess students to develop a clear statement of transition service needs and then use that information for goals and objectives in their IEP or ITP (individual transition plan). The case studies format will help you see in a concrete way how assessment procedures relate to young people with…

  5. Branding and Bricolage. Gender, Consumption and Transition

    ERIC Educational Resources Information Center

    Russell, Rachel; Tyler, Melissa

    2005-01-01

    The analysis presented here focuses on the relationship between femininity, transition and consumer culture. It explores the relationship between gender and consumer culture in the context of a discussion of the transition from childhood to teenage status for a group of young girls, and seeks to make a critical contribution to contemporary debates…

  6. Family Perceptions of Transitions in Early Intervention

    ERIC Educational Resources Information Center

    Lovett, David L.; Haring, Kathryn A.

    2003-01-01

    This article explores three broad themes about transitions that have emerged in a naturalistic study of experiences of families with young children with disabilities. Generalizations regarding early transitions include families going through a birth crisis have difficulty understanding all the information they are provided. Not only is their role…

  7. The Chancellor's Role in a Presidential Transition

    ERIC Educational Resources Information Center

    Appleton, James R.; Dorsey, Stuart

    2009-01-01

    Successful transitions involving a formal role for the former president, such as chancellor, are rare enough that the authors think theirs is an exceptional experience and is worth sharing, especially given the bulge of presidential retirements anticipated over the next decade. The authors believe that this model of transition can be successful,…

  8. 14 CFR 1253.230 - Transition plans.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Transition plans. 1253.230 Section 1253.230 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION NONDISCRIMINATION ON THE BASIS OF SEX IN EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 1253.230 Transition...

  9. 14 CFR 1253.230 - Transition plans.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Transition plans. 1253.230 Section 1253.230 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION NONDISCRIMINATION ON THE BASIS OF SEX IN EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 1253.230 Transition...

  10. 14 CFR 1253.230 - Transition plans.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Transition plans. 1253.230 Section 1253.230 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION NONDISCRIMINATION ON THE BASIS OF SEX IN EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 1253.230 Transition...

  11. 14 CFR 1253.230 - Transition plans.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 5 2013-01-01 2013-01-01 false Transition plans. 1253.230 Section 1253.230 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION NONDISCRIMINATION ON THE BASIS OF SEX IN EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 1253.230 Transition...

  12. Transition: Old Wine in New Bottles.

    ERIC Educational Resources Information Center

    Halpern, Andrew S.

    1992-01-01

    The 1980s movement for improved transition of handicapped youth from school to work is considered in light of similar previous movements: (1) the career education movement of the 1970s and (2) the work/study movement of the 1960s. The influence of broad social issues (such as educational reform) on outcomes for the transition movement is stressed.…

  13. Tying Signals: Restoring Classroom Order after Transitions

    ERIC Educational Resources Information Center

    Icbay, Mehmet Ali

    2011-01-01

    This study aimed at publicly demonstrating how classroom order is mutually established by a teacher and students in transition periods. Transitions take place in each instance when a current activity finishes, simultaneously the contextual organisation of the activity changes, and then the previously established order is lost. As a result, the…

  14. Youth in Transition: Are They Adult Learners?

    ERIC Educational Resources Information Center

    Shaw, Lester H.; Conti, Gary J.; Shaw, Brenda S.

    2013-01-01

    Since at-risk youth are in transition to adulthood, major adult learning concepts can be applied to them. The purpose of this study was to describe the learning strategies of youth in transition to adulthood in the urban life skills program of A Pocket Full of Hope®. Both qualitative and quantitative data collecting methods were used. Assessing…

  15. 12 CFR 931.9 - Transition provision.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 7 2010-01-01 2010-01-01 false Transition provision. 931.9 Section 931.9 Banks and Banking FEDERAL HOUSING FINANCE BOARD FEDERAL HOME LOAN BANK RISK MANAGEMENT AND CAPITAL STANDARDS FEDERAL HOME LOAN BANK CAPITAL STOCK § 931.9 Transition provision. (a) In general. Each Bank shall...

  16. 12 CFR 933.4 - Transition provisions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 7 2010-01-01 2010-01-01 false Transition provisions. 933.4 Section 933.4 Banks and Banking FEDERAL HOUSING FINANCE BOARD FEDERAL HOME LOAN BANK RISK MANAGEMENT AND CAPITAL STANDARDS BANK CAPITAL STRUCTURE PLANS § 933.4 Transition provisions. (a) The capital plan of a Bank...

  17. 5 CFR 550.187 - Transitional provisions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Transitional provisions. 550.187 Section 550.187 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PAY ADMINISTRATION (GENERAL) Premium Pay Law Enforcement Availability Pay § 550.187 Transitional provisions....

  18. 5 CFR 550.187 - Transitional provisions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Transitional provisions. 550.187 Section 550.187 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PAY ADMINISTRATION (GENERAL) Premium Pay Law Enforcement Availability Pay § 550.187 Transitional provisions....

  19. Nuclear binding near a quantum phase transition

    NASA Astrophysics Data System (ADS)

    Lee, Dean

    2016-03-01

    I review recent ab initio results by the Nuclear Lattice Effective Field Theory Collaboration showing that nature lies close to a quantum phase transition between an alpha-particle gas and nuclear liquid. I discuss the control parameter of this transition and the implications for clustering in nuclei and improving ab initio nuclear structure calculations.

  20. An Exploratory Study of Transition, Inc.

    ERIC Educational Resources Information Center

    Hogges, Ralph; Hogges, Lilia

    In this paper the Transition, Inc. program of the city of Miami is examined. This program's main concern is to help ex-offenders in their re-socialization process by offering them moral as well as financial support. It is evidenced from the goal and objectives of the Transition, Inc. program, its rehabilitative results and related literature that…