WorldWideScience

Sample records for non-negligible defect densities

  1. Morganella morganii, a non-negligent opportunistic pathogen.

    Science.gov (United States)

    Liu, Hui; Zhu, Junmin; Hu, Qiwen; Rao, Xiancai

    2016-09-01

    Morganella morganii belongs to the tribe Proteeae of the Enterobacteriaceae family. This species is considered as an unusual opportunistic pathogen that mainly causes post-operative wound and urinary tract infections. However, certain clinical M. morganii isolates present resistance to multiple antibiotics by carrying various resistant genes (such as blaNDM-1, and qnrD1), thereby posing a serious challenge for clinical infection control. Moreover, virulence evolution makes M. morganii an important pathogen. Accumulated data have demonstrated that M. morganii can cause various infections, such as sepsis, abscess, purple urine bag syndrome, chorioamnionitis, and cellulitis. This bacterium often results in a high mortality rate in patients with some infections. M. morganii is considered as a non-negligent opportunistic pathogen because of the increased levels of resistance and virulence. In this review, we summarized the epidemiology of M. morganii, particularly on its resistance profile and resistant genes, as well as the disease spectrum and risk factors for its infection.

  2. Morganella morganii, a non-negligent opportunistic pathogen

    Directory of Open Access Journals (Sweden)

    Hui Liu

    2016-09-01

    Full Text Available Morganella morganii belongs to the tribe Proteeae of the Enterobacteriaceae family. This species is considered as an unusual opportunistic pathogen that mainly causes post-operative wound and urinary tract infections. However, certain clinical M. morganii isolates present resistance to multiple antibiotics by carrying various resistant genes (such as blaNDM-1, and qnrD1, thereby posing a serious challenge for clinical infection control. Moreover, virulence evolution makes M. morganii an important pathogen. Accumulated data have demonstrated that M. morganii can cause various infections, such as sepsis, abscess, purple urine bag syndrome, chorioamnionitis, and cellulitis. This bacterium often results in a high mortality rate in patients with some infections. M. morganii is considered as a non-negligent opportunistic pathogen because of the increased levels of resistance and virulence. In this review, we summarized the epidemiology of M. morganii, particularly on its resistance profile and resistant genes, as well as the disease spectrum and risk factors for its infection.

  3. Perturbed Newtonian description of the Lemaître model with non-negligible pressure

    Science.gov (United States)

    Yamamoto, Kazuhiro; Marra, Valerio; Mukhanov, Viatcheslav; Sasaki, Misao

    2016-03-01

    We study the validity of the Newtonian description of cosmological perturbations using the Lemaître model, an exact spherically symmetric solution of Einstein's equation. This problem has been investigated in the past for the case of a dust fluid. Here, we extend the previous analysis to the more general case of a fluid with non-negligible pressure, and, for the numerical examples, we consider the case of radiation (P=ρ/3). We find that, even when the density contrast has a nonlinear amplitude, the Newtonian description of the cosmological perturbations using the gravitational potential ψ and the curvature potential phi is valid as long as we consider sub-horizon inhomogeneities. However, the relation ψ+phi=Script O(phi2)—which holds for the case of a dust fluid—is not valid for a relativistic fluid, and an effective anisotropic stress is generated. This demonstrates the usefulness of the Lemaître model which allows us to study in an exact nonlinear fashion the onset of anisotropic stress in fluids with non-negligible pressure. We show that this happens when the characteristic scale of the inhomogeneity is smaller than the sound horizon and that the deviation is caused by the nonlinear effect of the fluid's fast motion. We also find that ψ+phi= [Script O(phi2),Script O(cs2phi δ)] for an inhomogeneity with density contrast δ whose characteristic scale is smaller than the sound horizon, unless w is close to -1, where w and cs are the equation of state parameter and the sound speed of the fluid, respectively. On the other hand, we expect ψ+phi=Script O(phi2) to hold for an inhomogeneity whose characteristic scale is larger than the sound horizon, unless the amplitude of the inhomogeneity is large and w is close to -1.

  4. Background Defect Density Reduction Using Automated Defect Inspection And Analysis

    Science.gov (United States)

    Weirauch, Steven C.

    1988-01-01

    Yield maintenance and improvement is a major area of concern in any integrated circuit manufacturing operation. A major aspect of this concern is controlling and reducing defect density. Obviously, large defect excursions must be immediately addressed in order to maintain yield levels. However, to enhance yields, the subtle defect mechanisms must be reduced or eliminated as well. In-line process control inspections are effective for detecting large variations in the defect density on a real time basis. Examples of in-line inspection strategies include after develop or after etch inspections. They are usually effective for detecting when a particular process segment has gone out of control. However, when a process is running normally, there exists a background defect density that is generally not resolved by in-line process control inspections. The inspection strategies that are frequently used to monitor the background defect density are offline inspections. Offline inspections are used to identify the magnitude and characteristics of the background defect density. These inspections sample larger areas of product wafers than the in-line inspections to allow identification of the defect generating mechanisms that normally occur in the process. They are used to construct a database over a period of time so that trends may be studied. This information enables engineering efforts to be focused on the mechanisms that have the greatest impact on device yield. Once trouble spots in the process are identified, the data base supplies the information needed to isolate and solve them. The key aspect to the entire program is to utilize a reliable data gathering mechanism coupled with a flexible information processing system. This paper describes one method of reducing the background defect density using automated wafer inspection and analysis. The tools used in this evaluation were the KLA 2020 Wafer Inspector, KLA Utility Terminal (KLAUT), and a new software package developed

  5. Perturbed Newtonian description of the Lema\\^itre model with non-negligible pressure

    CERN Document Server

    Yamamoto, Kazuhiro; Mukhanov, Viatcheslav; Sasaki, Misao

    2015-01-01

    We study the validity of the Newtonian description of cosmological perturbations using the Lemaitre model, an exact spherically symmetric solution of Einstein's equation. This problem has been investigated in the past for the case of a dust fluid. Here, we extend the previous analysis to the more general case of a fluid with non-negligible pressure, and, for the numerical examples, we consider the case of radiation (P=\\rho/3). We find that, even when the density contrast has a nonlinear amplitude, the Newtonian description of the cosmological perturbations using the gravitational potential \\psi and the curvature potential \\phi is valid as long as we consider sub-horizon inhomogeneities. However, the relation \\psi+\\phi={\\cal O}(\\phi^2), which holds for the case of a dust fluid, is not valid for a relativistic fluid and effective anisotropic stress is generated. This demonstrates the usefulness of the Lemaitre model which allows us to study in an exact nonlinear fashion the onset of anisotropic stress in fluids...

  6. Performance model to predict overall defect density

    Directory of Open Access Journals (Sweden)

    J Venkatesh

    2012-08-01

    Full Text Available Management by metrics is the expectation from the IT service providers to stay as a differentiator. Given a project, the associated parameters and dynamics, the behaviour and outcome need to be predicted. There is lot of focus on the end state and in minimizing defect leakage as much as possible. In most of the cases, the actions taken are re-active. It is too late in the life cycle. Root cause analysis and corrective actions can be implemented only to the benefit of the next project. The focus has to shift left, towards the execution phase than waiting for lessons to be learnt post the implementation. How do we pro-actively predict defect metrics and have a preventive action plan in place. This paper illustrates the process performance model to predict overall defect density based on data from projects in an organization.

  7. Non-Negligible Diffusio-Osmosis Inside an Ion Concentration Polarization Layer

    Science.gov (United States)

    Cho, Inhee; Kim, Wonseok; Kim, Junsuk; Kim, Ho-Young; Lee, Hyomin; Kim, Sung Jae

    2016-06-01

    The first experimental and theoretical evidence was provided for the non-negligible role of a diffusio-osmosis in the ion concentration polarization (ICP) layer, which had been reported to be in a high Peclet number regime. Under the assumption that the hydrated shells of cations were stripped out with the amplified electric field inside the ICP layer, its concentration profile possessed a steep concentration gradient at the stripped location. Since the concentration gradient drove a strong diffusio-osmosis, the combination of electro-osmotic and diffusio-osmotic slip velocity had a form of an anomalous nonmonotonic function with both a single- and multiple-cationic solution. A direct measurement of electrolytic concentrations around the layer quantitatively validated our new investigations. This non-negligible diffusio-osmotic contribution in a micro- and nanofluidic platform or porous medium would be essential for clarifying the fundamental insight of nanoscale electrokinetics as well as guiding the engineering of ICP-based electrochemical systems.

  8. γ radiation caused graphene defects and increased carrier density

    Institute of Scientific and Technical Information of China (English)

    Han Mai-xing; Ji Zhuo-Yu; Shang Li-Wei; Chen Ying-Ping; Wang Hong; Liu Xin; Li Dong-Mei; Liu Ming

    2011-01-01

    We report on a micro-Raman investigation of inducing defects in mono-layer,bi-layer and tri-layer graphene by γ ray radiation.It is found that the radiation exposure results in two-dimensional(2D)and G band position evolution with the layer number increasing and D and D' bands rising,suggesting the presence of defects and related crystal lattice deformation in graphene.Bi-layer graphene is more stable than mono-and tri-layer graphene,indicating that the former is a better candidate in the application of radiation environments.Also,the DC electrical property of the mono-layer graphene device shows that the defects increase the carrier density.

  9. A comparative study of density functional and density functional tight binding calculations of defects in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Zobelli, Alberto [Laboratoire de Physique des Solides, Univ. Paris Sud, CNRS UMR, Orsay (France); Ivanovskaya, Viktoria; Wagner, Philipp; Yaya, Abu; Ewels, Chris P. [Institut des Materiaux Jean Rouxel (IMN), CNRS UMR, University of Nantes (France); Suarez-Martinez, Irene [Nanochemistry Research Institute, Curtin University of Technology, Perth, Western Australia (Australia)

    2012-02-15

    The density functional tight binding approach (DFTB) is well adapted for the study of point and line defects in graphene based systems. After briefly reviewing the use of DFTB in this area, we present a comparative study of defect structures, energies, and dynamics between DFTB results obtained using the dftb+ code, and density functional results using the localized Gaussian orbital code, AIMPRO. DFTB accurately reproduces structures and energies for a range of point defect structures such as vacancies and Stone-Wales defects in graphene, as well as various unfunctionalized and hydroxylated graphene sheet edges. Migration barriers for the vacancy and Stone-Wales defect formation barriers are accurately reproduced using a nudged elastic band approach. Finally we explore the potential for dynamic defect simulations using DFTB, taking as an example electron irradiation damage in graphene. DFTB-MD derived sputtering energy threshold map for a carbon atom in a graphene plane. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. H2 Adsorbed Site-to-Site Electronic Delocalization within IRMOF-1: Understanding Non-Negligible Interactions at High Pressure

    Science.gov (United States)

    Wu, Jian; Kucukkal, Mustafa U.; Clark, Aurora E.

    2016-01-01

    Isoreticular metal organic frameworks (IRMOFs) have shown high uptake capabilities for storage of H2 (11.5 wt % at 77 K and 170 bar). A significant literature has employed fragment models and a single adsorbed H2 to identify adsorption sites within IRMOFs, as well as the necessary adsorbate–adsorbent interactions needed to reach sufficient adsorption enthalpy for practical usage, however at high pressures it remains to be seen if H2···H2 intermolecular interactions may influence the energetics. This study focuses upon IRMOF-1 (also known as MOF-5), and examines the individual H2 stabilization energies at different sites using Möller–Plesset perturbation theory and density functional theory alongside chemical models that consist of isolated fragment models and a cubic super cell cluster consisting of both the face- and edge-cube’s of IRMOF-1. Optimization of twenty stable configurations of singly adsorbed H2 in the super-cell cluster is observed to be essential to obtain energy ordering of the five primary sites consistent with experiment and prior benchmark calculations (α >> β > γ > δ ≈ ε). To examine site-to-site interactions that may occur in the high-pressure regime, 64 co-adsorbed H2 within a super-cell cluster have been studied (a theoretical maximum of all adsorption sites, 14 wt %). There, delocalization and/or charge transfer of electrons is observed from the σ orbitals of the H2 bound at the γ positions into the σ* orbitals of H2 bound at the α sites leads to stabilization of the interaction of H2 at the γ, by 1.4 kJ/mol, respectively (using M06-2X/LANL2DZ). This effect has been confirmed to be charge transfer, and not a manifestation of enhanced dispersion at high loading, through natural bond order (NBO) analysis and by comparisons of the square of off-diagonal NBO Fock matrix elements for both density functionals that account for dispersion interactions and Hartree–Fock calculations that ignore dispersion. PMID:28773699

  11. H₂ Adsorbed Site-to-Site Electronic Delocalization within IRMOF-1: Understanding Non-Negligible Interactions at High Pressure.

    Science.gov (United States)

    Wu, Jian; Kucukkal, Mustafa U; Clark, Aurora E

    2016-07-15

    Isoreticular metal organic frameworks (IRMOFs) have shown high uptake capabilities for storage of H₂ (11.5 wt % at 77 K and 170 bar). A significant literature has employed fragment models and a single adsorbed H₂ to identify adsorption sites within IRMOFs, as well as the necessary adsorbate-adsorbent interactions needed to reach sufficient adsorption enthalpy for practical usage, however at high pressures it remains to be seen if H₂···H₂ intermolecular interactions may influence the energetics. This study focuses upon IRMOF-1 (also known as MOF-5), and examines the individual H₂ stabilization energies at different sites using Möller-Plesset perturbation theory and density functional theory alongside chemical models that consist of isolated fragment models and a cubic super cell cluster consisting of both the face- and edge-cube's of IRMOF-1. Optimization of twenty stable configurations of singly adsorbed H₂ in the super-cell cluster is observed to be essential to obtain energy ordering of the five primary sites consistent with experiment and prior benchmark calculations (α > β > γ > δ ≈ ε). To examine site-to-site interactions that may occur in the high-pressure regime, 64 co-adsorbed H₂ within a super-cell cluster have been studied (a theoretical maximum of all adsorption sites, 14 wt %). There, delocalization and/or charge transfer of electrons is observed from the σ orbitals of the H₂ bound at the γ positions into the σ* orbitals of H₂ bound at the α sites leads to stabilization of the interaction of H₂ at the γ, by 1.4 kJ/mol, respectively (using M06-2X/LANL2DZ). This effect has been confirmed to be charge transfer, and not a manifestation of enhanced dispersion at high loading, through natural bond order (NBO) analysis and by comparisons of the square of off-diagonal NBO Fock matrix elements for both density functionals that account for dispersion interactions and Hartree-Fock calculations that ignore dispersion.

  12. H2 Adsorbed Site-to-Site Electronic Delocalization within IRMOF-1: Understanding Non-Negligible Interactions at High Pressure

    Directory of Open Access Journals (Sweden)

    Jian Wu

    2016-07-01

    Full Text Available Isoreticular metal organic frameworks (IRMOFs have shown high uptake capabilities for storage of H2 (11.5 wt % at 77 K and 170 bar. A significant literature has employed fragment models and a single adsorbed H2 to identify adsorption sites within IRMOFs, as well as the necessary adsorbate–adsorbent interactions needed to reach sufficient adsorption enthalpy for practical usage, however at high pressures it remains to be seen if H2···H2 intermolecular interactions may influence the energetics. This study focuses upon IRMOF-1 (also known as MOF-5, and examines the individual H2 stabilization energies at different sites using Möller–Plesset perturbation theory and density functional theory alongside chemical models that consist of isolated fragment models and a cubic super cell cluster consisting of both the face- and edge-cube’s of IRMOF-1. Optimization of twenty stable configurations of singly adsorbed H2 in the super-cell cluster is observed to be essential to obtain energy ordering of the five primary sites consistent with experiment and prior benchmark calculations (α >> β > γ > δ ≈ ε. To examine site-to-site interactions that may occur in the high-pressure regime, 64 co-adsorbed H2 within a super-cell cluster have been studied (a theoretical maximum of all adsorption sites, 14 wt %. There, delocalization and/or charge transfer of electrons is observed from the σ orbitals of the H2 bound at the γ positions into the σ* orbitals of H2 bound at the α sites leads to stabilization of the interaction of H2 at the γ, by 1.4 kJ/mol, respectively (using M06-2X/LANL2DZ. This effect has been confirmed to be charge transfer, and not a manifestation of enhanced dispersion at high loading, through natural bond order (NBO analysis and by comparisons of the square of off-diagonal NBO Fock matrix elements for both density functionals that account for dispersion interactions and Hartree–Fock calculations that ignore dispersion.

  13. Point defect absorption by grain boundaries in α -iron by atomic density function modeling

    Science.gov (United States)

    Kapikranian, O.; Zapolsky, H.; Patte, R.; Pareige, C.; Radiguet, B.; Pareige, P.

    2015-12-01

    Using the atomic density function theory (ADFT), we examine the point defect absorption at [110] symmetrical tilt grain boundaries in body-centered cubic iron. It is found that the sink strength strongly depends on misorientation angle. We also show that the ADFT is able to reproduce reasonably well the elastic properties and the point defect formation volume in α -iron.

  14. Dissociation and diffusion of hydrogen on defect-free and vacancy defective Mg (0001) surfaces: A density functional theory study

    Science.gov (United States)

    Han, Zongying; Chen, Haipeng; Zhou, Shixue

    2017-02-01

    First-principles calculations with the density functional theory (DFT) have been carried out to study dissociation and diffusion of hydrogen on defect-free and vacancy defective Mg (0001) surfaces. Results show that energy barriers of 1.42 eV and 1.28 eV require to be overcome for H2 dissociation on defect-free and vacancy defective Mg (0001) surfaces respectively, indicating that reactivity of Mg (0001) surface is moderately increased due to vacancy defect. Besides, the existence of vacancy defect changes the preferential H atom diffusion entrance to the subsurface and reduces the diffusion energy barrier. An interesting remark is that the minimum energy diffusion path of H atom from magnesium surface into bulk is a spiral channel formed by staggered octahedral and tetrahedral interstitials. The diffusion barriers computed for H atom penetration from the surface into inner-layers are all less than 0.70 eV, which is much smaller than the activation energy for H2 dissociation on the Mg (0001) surface. This suggests that H2 dissociation is more likely than H diffusion to be rate-limiting step for magnesium hydrogenation.

  15. Current density and conductivity through modified gravity in the graphene with defects

    CERN Document Server

    Sepehri, Alireza; Bamba, Kazuharu; Capozziello, Salvatore; Saridakis, Emmanuel N

    2016-01-01

    We propose a model describing the evolution of the free electron current density in graphene. Based on the concept of Mp-branes, we perform the analysis using the difference between curvatures of parallel and antiparallel spins. In such a framework an effective graviton emerges in the form of gauge field exchange between electrons. In a plain graphene system, the curvatures produced by both kinds of spins neutralize each other. However, in the presence of defects, the inequality between curvatures leads to the emergence of current density, modified gravity and conductivity. Depending on the type of the defects, the resulting current density can be negative or positive.

  16. Effects of CZSi furnace modification on density of grown-in defects

    Institute of Scientific and Technical Information of China (English)

    REN; Bingyan(任丙彦); ZHANG; Zhicheng(张志成); LIU; Caichi(刘彩池); HAO; Qiuyan(郝秋燕); WANG; Meng(王猛)

    2002-01-01

    During large diameter Czochralski silicon growth, heat zone and argon flow influence the formation of defects in silicon crystal by changing the distribution of temperature. Different silicon crys tals with various density of grown-in defects were grown by replacing the popular heater with the com posite heater and changing the popular argon flow into a controlled flow. The experimental results have been explained well by the numeric simulation of argon flow.

  17. VV and VO2 defects in silicon studied with hybrid density functional theory

    KAUST Repository

    Christopoulos, Stavros Richard G

    2014-12-07

    The formation of VO (A-center), VV and VO2 defects in irradiated Czochralski-grown silicon (Si) is of technological importance. Recent theoretical studies have examined the formation and charge states of the A-center in detail. Here we use density functional theory employing hybrid functionals to analyze the formation of VV and VO2 defects. The formation energy as a function of the Fermi energy is calculated for all possible charge states. For the VV and VO2 defects double negatively charged and neutral states dominate, respectively.

  18. Assessing climate model software quality: a defect density analysis of three models

    Directory of Open Access Journals (Sweden)

    J. Pipitone

    2012-08-01

    Full Text Available A climate model is an executable theory of the climate; the model encapsulates climatological theories in software so that they can be simulated and their implications investigated. Thus, in order to trust a climate model, one must trust that the software it is built from is built correctly. Our study explores the nature of software quality in the context of climate modelling. We performed an analysis of defect reports and defect fixes in several versions of leading global climate models by collecting defect data from bug tracking systems and version control repository comments. We found that the climate models all have very low defect densities compared to well-known, similarly sized open-source projects. We discuss the implications of our findings for the assessment of climate model software trustworthiness.

  19. Bond length and charge density variations within extended arm chair defects in graphene.

    Science.gov (United States)

    Warner, Jamie H; Lee, Gun-Do; He, Kuang; Robertson, Alex W; Yoon, Euijoon; Kirkland, Angus I

    2013-11-26

    Extended linear arm chair defects are intentionally fabricated in suspended monolayer graphene using controlled focused electron beam irradiation. The atomic structure is accurately determined using aberration-corrected transmission electron microscopy with monochromation of the electron source to achieve ∼80 pm spatial resolution at an accelerating voltage of 80 kV. We show that the introduction of atomic vacancies in graphene disrupts the uniformity of C-C bond lengths immediately surrounding linear arm chair defects in graphene. The measured changes in C-C bond lengths are related to density functional theory (DFT) calculations of charge density variation and corresponding DFT calculated structural models. We show good correlation between the DFT predicted localized charge depletion and structural models with HRTEM measured bond elongation within the carbon tetragon structure of graphene. Further evidence of bond elongation within graphene defects is obtained from imaging a pair of 5-8-5 divacancies.

  20. Analysis of electronic models for solar cells including energy resolved defect densities

    Energy Technology Data Exchange (ETDEWEB)

    Glitzky, Annegret

    2010-07-01

    We introduce an electronic model for solar cells including energy resolved defect densities. The resulting drift-diffusion model corresponds to a generalized van Roosbroeck system with additional source terms coupled with ODEs containing space and energy as parameters for all defect densities. The system has to be considered in heterostructures and with mixed boundary conditions from device simulation. We give a weak formulation of the problem. If the boundary data and the sources are compatible with thermodynamic equilibrium the free energy along solutions decays monotonously. In other cases it may be increasing, but we estimate its growth. We establish boundedness and uniqueness results and prove the existence of a weak solution. This is done by considering a regularized problem, showing its solvability and the boundedness of its solutions independent of the regularization level. (orig.)

  1. A sublinear-scaling approach to density-functional-theory analysis of crystal defects

    Science.gov (United States)

    Ponga, M.; Bhattacharya, K.; Ortiz, M.

    2016-10-01

    We develop a sublinear-scaling method, referred to as MacroDFT, for the study of crystal defects using ab-initio Density Functional Theory (DFT). The sublinear scaling is achieved using a combination of the Linear Scaling Spectral Gauss Quadrature method (LSSGQ) and a Coarse-Graining approach (CG) based on the quasi-continuum method. LSSGQ reformulates DFT and evaluates the electron density without computing individual orbitals. This direct evaluation is possible by recourse to Gaussian quadrature over the spectrum of the linearized Hamiltonian operator. Furthermore, the nodes and weights of the quadrature can be computed independently for each point in the domain. This property is exploited in CG, where fields of interest are computed at selected nodes and interpolated elsewhere. In this paper, we present the MacroDFT method, its parallel implementation and an assessment of convergence and performance by means of test cases concerned with point defects in magnesium.

  2. Leveling coatings for reducing the atomic oxygen defect density in protected graphite fiber epoxy composites

    Science.gov (United States)

    Jaworske, D. A.; Degroh, K. K.; Podojil, G.; Mccollum, T.; Anzic, J.

    1992-01-01

    Pinholes or other defect sites in a protective oxide coating provide pathways for atomic oxygen in low Earth orbit to reach underlying material. One concept for enhancing the lifetime of materials in low Earth orbits is to apply a leveling coating to the material prior to applying any reflective and protective coatings. Using a surface tension leveling coating concept, a low viscosity epoxy was applied to the surface of several composite coupons. A protective layer of 1000 A of SiO2 was deposited on top of the leveling coating, and the coupons were exposed to an atomic oxygen environment in a plasma asher. Pinhole populations per unit area were estimated by counting the number of undercut sites observed by scanning electron microscopy. Defect density values of 180,000 defects/sq cm were reduced to about 1000 defects/sq cm as a result of the applied leveling coating. These improvements occur at a mass penalty of about 2.5 mg/sq cm.

  3. Determination of Defect Densities in High Electron Mobility Transistors Using Current Transient DLTS

    Science.gov (United States)

    Palma, John; Mil'shtein, Samson

    2011-12-01

    Since its introduction, Deep Level Transient Spectroscopy (DLTS) has become the preferred tool for investigating semiconductor defects. The limitations of measuring the small changes in gate capacitance in transistors led to the advent of current transient DLTS where the defects manifest themselves as a small change in drain current. However, this method was introduced at a time when heterostructure devices, such as High Electron Mobility Transistors (HEMTs), were non-existent and fails in determining defect concentrations in these modern devices. This study establishes a method by which defect concentrations can be determined in HEMT structures using current transient DLTS. First, the relationship between the change in the trap charge and the transistor drain current is established. Then, a computer aided technique is described which determines the volume within the device where the Fermi level crosses the trap energy. The result is that trap densities and their locations can be determined. DLTS measurements revealed two traps with ET = 0.43 and Nt = 1.1×1017cm-3, and ET = 0.19 and Nt = 3.1×1017 cm-3 for a tested HEMT.

  4. Investigation of oxygen defects in wurtzite InN by using density functional theory

    Science.gov (United States)

    Hattori, Y.; Chubaci, J. F. D.; Matsuoka, M.; Freitas, J. A.; da Silva, A. Ferreira

    2016-12-01

    Density Functional Theory based on ab initio calculations was employed to investigate single and complex defects of oxygen in indium nitride and their influence on the optical properties. Different oxygen contents (x=1.38%, 4.16%, 5.55% and 11.11%) were considered in our study by using PBEsol-GGA and TB-mBJ for the treatment of exchange-correlation energy and potential. It was found that oxygen is energetically favorable to exist mainly as singly charged isolated defect. The results using TB-mBJ approximation predicts a narrowing of the VBM (valence band maximum) and CBM (conduction band minimum) as oxygen content increases. Nevertheless, the larger contribution of the Moss-Burstein effect leads to an effective band-gap increase, yielding absorption edge values larger than that of the intrinsic bulk indium nitride.

  5. Doping and defects in YBa2Cu3O7: Results from hybrid density functional theory

    KAUST Repository

    Schwingenschlögl, Udo

    2012-06-21

    Modified orbital occupation and inhomogeneous charge distribution in high-Tc oxide compounds due to doping and/or defects play a huge role for the material properties. To establish insight into the charge redistribution, we address metallic YBa2Cu3O7 in two prototypical configurations: Ca doped (hole doping) and O deficient (electron doping). By means of first principles calculations for fully relaxed structures, we evaluate the orbital occupations. We find that the change of the charge density, in particular in the CuO2 planes, shows a complex spatial pattern instead of the expected uniform (de-)population of the valence states.

  6. Interlayer vacancy defects in AA-stacked bilayer graphene: density functional theory predictions

    Science.gov (United States)

    Vuong, A.; Trevethan, T.; Latham, C. D.; Ewels, C. P.; Erbahar, D.; Briddon, P. R.; Rayson, M. J.; Heggie, M. I.

    2017-04-01

    AA-stacked graphite and closely related structures, where carbon atoms are located in registry in adjacent graphene layers, are a feature of graphitic systems including twisted and folded bilayer graphene, and turbostratic graphite. We present the results of ab initio density functional theory calculations performed to investigate the complexes that are formed from the binding of vacancy defects across neighbouring layers in AA-stacked bilayers. As with AB stacking, the carbon atoms surrounding lattice vacancies can form interlayer structures with sp 2 bonding that are lower in energy than in-plane reconstructions. The sp 2 interlayer bonding of adjacent multivacancy defects in registry creates a type of stable sp 2 bonded ‘wormhole’ or tunnel defect between the layers. We also identify a new class of ‘mezzanine’ structure characterised by sp 3 interlayer bonding, resembling a prismatic vacancy loop. The V 6 hexavacancy variant, where six sp 3 carbon atoms sit midway between two carbon layers and bond to both, is substantially more stable than any other vacancy aggregate in AA-stacked layers. Our focus is on vacancy generation and aggregation in the absence of extreme temperatures or intense beams.

  7. Thermodynamic and kinetic properties of hydrogen defect pairs in SrTiO3 from density functional theory

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Bonanos, Nikolaos; Rossmeisl, Jan

    2011-01-01

    A density functional theory investigation of the thermodynamic and kinetic properties of hydrogen–hydrogen defect interactions in the cubic SrTiO3 perovskite is presented. We find a net attraction between two hydrogen atoms with an optimal separation of ∼2.3 Å. The energy gain is ca. 0.33 e......V compared to two non-interacting H defects. The main cause of the net attractive potential is elastic defect interactions through lattice deformation. Two possible diffusion paths for the hydrogen defect pair are investigated and are both determined to be faster than the corresponding diffusion path...

  8. Study of CO adsorption on perfect and defective pyrite(100)surfaces by density functional theory

    Institute of Scientific and Technical Information of China (English)

    Yudong Du; Wenkai Chen; Yongfan Zhang; Xin Guo

    2011-01-01

    First-principles calculations based on density functional theory(DFT)and the generalized gradient approximation(GGA)have been used to study the adsorption of CO molecule on the perfect and defective FeS2(100)surfaces.The defective Fe2S(100)surfaces are caused by sulfur deficiencies.Slab geometry and periodic boundary conditions are employed with partial relaxations of atom positions in calculations.Two molecular orientations,C-and O-down,at various distinct sites have been considered.Total energy calculations indicated that no matter on perfect or deficient surfaces,the Fe position is relatively more favored than the S site with the predicted binding energies of 120.8 kJ/mol and 140.8 kJ/mol,respectively.Moreover,CO was found to be bound to Fe atom in vertical configuration.The analysis of density of states and vibrational frequencies before and after adsorption showed clear changes of the C-O bond.

  9. Dependability of the Exemplary Technical System for Assumed Functions of Defect Density

    Directory of Open Access Journals (Sweden)

    Stępień Sławomir

    2016-12-01

    Full Text Available The analysis of structural dependability of technical system, especially determining the change in dependability over time, requires knowledge on density function or the understanding of cumulative distribution function of components belonging to the structure. Based on previously registered data concerning component defect, it is relatively easy to establish the average uptime of component as well as the standard deviation for this time. However, defining distribution shape gives rise to some difficulties. Usually, we do not have the sufficient number of data at our disposal to verify the hypothesis regarding the distribution shape. Due to this fact, it is a common practice, depending on the case under consideration, to apply the function of defect density. However, the question arises: Does the incorrect determination of types of distributions of components leads to the big error of estimation results of dependability and system durability? This article will not respond to this question in whole, but one will conduct a comparison of calculation results for a few cases. The calculations were conducted for the exemplary technical system.

  10. Density functional theory calculations of defect and fission gas properties in U-Si fuels

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Anders David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-02-03

    Accident tolerant fuels (ATF) are being developed in response to the Fukushima Daiichi accident in Japan. One of the options being pursued is U-Si fuels, such as the U3Si2 and U3Si5 compounds, which benefit from high thermal conductivity (metallic) compared to the UO2 fuel (insulator or semi-conductor) used in current Light Water Reactors (LWRs). The U-Si fuels also have higher fissile density. In order to perform meaningful engineering scale nuclear fuel performance simulations, the material properties of the fuel, including the response to irradiation environments, must be known. Unfortunately, the data available for U-Si fuels are rather limited, in particular for the temperature range where LWRs would operate. The ATF HIP is using multi-scale modeling and simulations to address this knowledge gap. The present study investigates point defect and fission gas properties in U3Si2, which is one of the main fuel candidates, using density functional theory (DFT) calculations. Based on a few assumption regarding entropy contributions, defect and fission diffusivities are predicted. Even though uranium silicides have been shown to amorphize easily at low temperature, we assume that U3Si2 remains crystalline under the conditions expected in Light Water Reactors (LWRs). The temperature and dose where amorphization occurs has not yet been well established.

  11. The influence of critical current density of Bi-2212 superconductors by defects after Yb-doping

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Tianni [State key Laboratory for Mechanical Behavior of Materials of Xi' an Jiaotong University, Xi' an 710014 (China); SMRC, Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China); Zhang, Cuiping [SMRC, Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China); Guo, Shengwu [State key Laboratory for Mechanical Behavior of Materials of Xi' an Jiaotong University, Xi' an 710014 (China); Wu, Yifang [State key Laboratory for Mechanical Behavior of Materials of Xi' an Jiaotong University, Xi' an 710014 (China); SMRC, Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China); Li, Chengshan, E-mail: csli368@126.com [SMRC, Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China); Zhou, Lian [State key Laboratory for Mechanical Behavior of Materials of Xi' an Jiaotong University, Xi' an 710014 (China); SMRC, Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China)

    2015-12-15

    Highlights: • Ca substituting Yb element in Bi-2212 single crystal. • The critical current density of this sample is the highest without the optimal Tc value. • The Cu–O{sub 2} and Ca–O layers in pure and doping samples are observed using HRTEM. • The optimal defect density is calculated. - Abstract: Bi{sub 2}Sr{sub 2}Ca{sub 1−x}Yb{sub x}Cu{sub 2}O{sub 8+δ} (Bi-2212) single crystals with x = 0.000, 0.005, 0.010 and 0.020 have been prepared by self-flux method. The influences of Yb doping on the formation of the dislocations in the lattice structures, as well as the related current carrying capability are investigated. Due to the SQUID measurement and the Bean model calculation, the maximum critical current density (Jc) is obtained when the Yb doping content is x = 0.010, though the Tc and the carrier concentration are not in the optimal region. Based on the HRTEM analyses of the Ca–O and Cu–O{sub 2} layers, the optimal dislocation density in the Cu–O{sub 2} layers is deduced according to the number of the dislocations per unit area. Besides, the sizes of the dislocations also prove the effectiveness of Yb substitution on the enhancement of the current carrying capability in Bi-2212 single crystals.

  12. Spectroscopic properties of doped and defective semiconducting oxides from hybrid density functional calculations.

    Science.gov (United States)

    Di Valentin, Cristiana; Pacchioni, Gianfranco

    2014-11-18

    CONSPECTUS: Very rarely do researchers use metal oxides in their pure and fully stoichiometric form. In most of the countless applications of these compounds, ranging from catalysis to electronic devices, metal oxides are either doped or defective because the most interesting chemical, electronic, optical, and magnetic properties arise when foreign components or defects are introduced in the lattice. Similarly, many metal oxides are diamagnetic materials and do not show a response to specific spectroscopies such as electron paramagnetic resonance (EPR) spectroscopy. However, doped or defective oxides may exhibit an interesting and informative paramagnetic behavior. Doped and defective metal oxides offer an expanding range of applications in contemporary condensed matter science; therefore researchers have devoted enormous effort to the understanding their physical and chemical properties. The interplay between experiment and computation is particularly useful in this field, and contemporary simulation techniques have achieved high accuracies with these materials. In this Account, we show how the direct comparison between spectroscopic experimental and computational data for some selected and relevant materials provides ways to understand and control these complex systems. We focus on the EPR properties and electronic transitions that arise from the presence of dopants and defects in bulk metal oxide materials. We analyze and compare the effect of nitrogen doping in TiO2 and ZnO (two semiconducting oxides) and MgO (a wide gap insulator) and examine the effect of oxygen deficiency in the semiconducting properties of TiO2-x, ZnO1-x, and WO3-x materials. We chose these systems because of their relevance in applications including photocatalysis, touch screens, electrodes in magnetic random access memories, and smart glasses. Density functional theory (DFT) provides the general computational framework used to illustrate the electronic structure of these systems. However

  13. Density functional calculations of multiphonon capture cross sections at defects in semiconductors

    Science.gov (United States)

    Barmparis, Georgios D.; Puzyrev, Yevgeniy S.; Zhang, X.-G.; Pantelides, Sokrates T.

    2014-03-01

    The theory of electron capture cross sections by multiphonon processes in semiconductors has a long and controversial history. Here we present a comprehensive theory and describe its implementation for realistic calculations. The Born-Oppenheimer and the Frank-Condon approximations are employed. The transition probability of an incoming electron is written as a product of an instantaneous electronic transition in the initial defect configuration and the line shape function (LSF) that describes the multiphonon processes that lead to lattice relaxation. The electronic matrix elements are calculated using the Projector Augmented Wave (PAW) method which yields the true wave functions while still employing a plane-wave basis. The LSF is calculated by employing a Monte Carlo method and the real phonon modes of the defect, calculated using density functional theory in the PAW scheme. Initial results of the capture cross section for a prototype system, namely a triply hydrogenated vacancy in Si are presented. The results are relevant for modeling device degradation by hot electron effects. This work is supported in part by the Samsung Advanced Institute of Technology (SAIT)'s Global Research Outreach (GRO) Program and by the LDRD program at ORNL.

  14. On the near-threshold peak structure in the differential cross section of $\\phi$-meson photoproduction: missing resonance with non-negligible strangeness content?

    CERN Document Server

    Kiswandhi, Alvin

    2011-01-01

    The details of the analysis, with more extensive results, of the near-threshold bump structure in the forward differential cross section of the phi-meson photoproduction to determine whether it is a signature of a resonance are presented. The analysis is carried out in an effective Lagrangian approach which includes Pomeron and (pi, eta) exchanges in the t channel, and contributions from the s- and u-channel excitation of a postulated nucleon resonance. In addition to the differential cross sections, we use the nine spin-density matrix elements as recently measured, instead of the phi-meson decay angular distributions which depend only on six spin-density matrix elements as was done before, to constrain the resonance parameters. We conclude that indeed the bump structure as reported by LEPS, can only be explained with an assumption of the excitation of a resonance of spin 3/2, as previously reported. However, both parities of +/- can account for the data equally well with almost identical mass of 2.08 +/- 0.0...

  15. Riboflavin crosslinked high-density collagen gel for the repair of annular defects in intervertebral discs: An in vivo study.

    Science.gov (United States)

    Grunert, Peter; Borde, Brandon H; Towne, Sara B; Moriguchi, Yu; Hudson, Katherine D; Bonassar, Lawrence J; Härtl, Roger

    2015-10-01

    Open annular defects compromise the ability of the annulus fibrosus to contain nuclear tissue in the disc space, and therefore lead to disc herniation with subsequent degenerative changes to the entire intervertebral disc. This study reports the use of riboflavin crosslinked high-density collagen gel for the repair of annular defects in a needle-punctured rat-tail model. High-density collagen has increased stiffness and greater hydraulic permeability than conventional low-density gels; riboflavin crosslinking further increases these properties. This study found that treating annular defects with crosslinked high-density collagen inhibited the progression of disc degeneration over 18 weeks compared to untreated control discs. Histological sections of FITC-labeled collagen gel revealed an early tight attachment to host annular tissue. The gel was subsequently infiltrated by host fibroblasts which remodeled it into a fibrous cap that bridged the outer disrupted annular fibers and partially repaired the defect. This repair tissue enhanced retention of nucleus pulposus tissue, maintained physiological disc hydration, and preserved hydraulic permeability, according to MRI, histological, and mechanical assessments. Degenerative changes were partially reversed in treated discs, as indicated by an increase in nucleus pulposus size and hydration between weeks 5 and 18. The collagen gel appeared to work as an instant sealant and by enhancing the intrinsic healing capabilities of the host tissue.

  16. Stress and density of defects in Si-doped GaN

    Energy Technology Data Exchange (ETDEWEB)

    Chine, Z.; Rebey, A.; Touati, H.; Jani, B.El [Unite de Recherche sur l' Heteroepitaxie et Applications, Faculte des Sciences, Monastir 5000 (Tunisia); Goovaerts, E. [Physics Department, University of Antwerp (U.I.A), Universiteitsplein 1, 2610 Wilrijk-Antwerpen (Belgium); Oueslati, M. [Unite de Recherche de Spectroscopie Raman, Departement de Physique, Faculte des Sciences, Tunis 1002 (Tunisia); Laugt, S. [Centre de Recherche sur l' Heteroepitaxie et Applications, CNRS, Rue Bernard Gregory, 06560 Valbonne (France)

    2006-06-15

    We report a study by photoluminescence (PL), Raman scattering, and highly resolved X-ray diffraction (HRXRD) of a series of Si-doped n-type GaN layers grown by metalorganic vapor phase epitaxy (MOVPE) on sapphire (0001) with the carrier concentration of 2.3 x 10{sup 17}-9 x 10{sup 18} cm{sup -3}. We found that the band gap reduction deduced from the PL spectra analysis is due to both band gap narrowing (BGN) effect and change of the nature of stress in the GaN:Si layers. The HRXRD spectra show that at high Si-doping levels (>1.6 x 10{sup 18} cm{sup -3}) the GaN films become under tensile stress. Progressive decreases of the E{sub 2} Raman mode frequency with Si concentration confirm this observation. The stress induced E{sub 2} mode frequency shift is estimated to 1.6 cm{sup -1}/GPa. Additionally, dislocation densities are determined by HRXRD by employing a model that uses the line width of X-ray rocking curves. Atomic force microscopy (AFM) is also used to investigate the defect surface structures of GaN:Si layers which are dominated by pinned steps and surface depressions related to threading dislocations. We find that dislocation densities given by AFM measurements are in agreement with those obtained from rocking curve line widths. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Control of morphology and defect density in zinc oxide for improved dye-sensitized solar cells.

    Science.gov (United States)

    Kim, Seul Ah; Abbas, Muhammad Awais; Lee, Lanlee; Kang, Byungwuk; Kim, Hahkjoon; Bang, Jin Ho

    2016-11-09

    While zinc oxide (ZnO) with a mesoporous network has long been explored for adsorption of dyes and as an electron-transporting medium in dye-sensitized solar cells (DSSCs), the performance of ZnO-based DSSCs remains unsatisfactory. Despite the importance of understanding the surface characteristics of ZnO in DSSC applications, most of the studies relevant to ZnO-based DSSCs are focused on the synthesis of unique nanostructures of ZnO. In this study, we not only introduce a novel disk-shaped ZnO nanostructure, but also provide insight into the distinctive surface properties of ZnO and its influence on DSSC performance. When utilized in DSSCs, the mesoporous ZnO nanodisk yields 60% better power conversion efficiency (PCE) compared to commercial ZnO nanoparticles, which is attributed to less surface and bulk trap densities as concluded by an in-depth open-circuit voltage decay (OCVD) analysis and electrochemical impedance spectroscopy (EIS). Another aspect that contributes to the higher PCE is the better connectivity of primary particles that join together to form secondary disk-shaped particles. Furthermore, a 40% improvement in the PCE was observed by coating the mesoporous ZnO nanodisk with TiO2, which results from the passivation of the surface defects that aid in suppressing the interfacial charge recombination.

  18. Defect properties of CuCrO2: A density functional theory calculation

    Institute of Scientific and Technical Information of China (English)

    Fang Zhi-Jie; Zhu Ji-Zhen; Zhou Jiang; Mo Man

    2012-01-01

    Using the first-principles methods,we study the formation energetics properties of intrinsic defects,and the charge doping properties of extrinsic defects in transparent conducting oxides CuCrO2.Intrinsic defects,some typical acceptortype,and donor-type extrinsic defects in their relevant charge state are considered.By systematically calculating the formation energies and transition energy,the results of calculation show that,Vcu,Oi,and OCu are the relevant intrinsic defects in CuCrO2; among these intrinsic defects,VCu is the most efficient acceptor in CuCrO2.It is found that all the donor-type extrinsic defects have difficulty in inducing n-conductivity in CuCrO2 because of their deep transition energy level.For all the acceptor-type extrinsic defects,substituting Mg for Cr is the most prominent doping acceptor with relative shallow transition energy levels in CuCrO2.Our calculation results are expected to be a guide for preparing promising n-type and p-type materials in CuCrO2.

  19. Order and creep in flux lattices and charge density wave pinned by planar defects.

    Science.gov (United States)

    Petković, Aleksandra; Nattermann, Thomas

    2008-12-31

    The influence of randomly distributed point impurities and planar defects on the order and transport in type-II superconductors and related systems is considered theoretical. For random planar defects of identical orientation, the flux line lattice exhibits a new glassy phase with diverging shear and tilt modulus, a transverse Meissner effect, large sample to sample fluctuations of the susceptibility, and an exponential decay of translational long range order. The flux creep resistivity for currents J parallel to the defects is p(J) to approximately exp-(J0/J)mu with mu = 3/2. Strong disorder enforces an array of dislocations to relax shear

  20. Nematic liquid crystals on spherical surfaces: Control of defect configurations by temperature, density, and rod shape

    Science.gov (United States)

    Dhakal, Subas; Solis, Francisco J.; Olvera de la Cruz, Monica

    2012-07-01

    Recent experiments have shown that defect conformations in spherical nematic liquid crystals can be controlled through variations of temperature, shell thickness, and other environmental parameters. These modifications can be understood as a result of the induced changes in the effective elastic constants of the system. To characterize the relation between defect conformations and elastic anisotropy, we carry out Monte Carlo simulations of a nematic on a spherical surface. As the anisotropy is increased, the defects flow from a tetrahedral arrangement to two coalescing pairs and then to a great circle configuration. We also analyze this flow using a variational method based on harmonic configurations.

  1. Controlling the cytotoxicity of CdSe magic-sized quantum dots as a function of surface defect density.

    Science.gov (United States)

    Silva, Anielle Christine Almeida; Silva, Marcelo José Barbosa; da Luz, Felipe Andrés Cordero; Silva, Danielle Pereira; de Deus, Samantha Luara Vieira; Dantas, Noelio Oliveira

    2014-09-10

    Quantum dots are potentially very useful as fluorescent probes in biological systems. However, they are inherently cytotoxic because of their constituents. We controlled the cytotoxicity of CdSe magic-sized quantum dots (MSQDs) as a function of surface defect density by altering selenium (Se) concentration during synthesis. Higher Se concentrations reduced the cytotoxicity of the CdSe MSQDs and diminished mRNA expression of methallothionein because of the low cadmium ions (Cd(2+)) concentration adsorbed on the surface of the MSQDs. These results agree with luminescence spectra, which show that higher Se concentrations decrease the density of surface defects. Therefore, our results describe for the first time a simple way of controlling the cytotoxicity of CdSe MSQDs and making them safer to use as fluorescence probes in biological systems.

  2. Correlating the Local Defect-Level Density with the Macroscopic Composition and Energetics of Chalcopyrite Thin-Film Surfaces.

    Science.gov (United States)

    Bröker, Sebastian; Kück, Dennis; Timmer, Alexander; Lauermann, Iver; Ümsür, Bünyamin; Greiner, Dieter; Kaufmann, Christian A; Mönig, Harry

    2015-06-17

    The unusual defect chemistry of polycrystalline Cu(In,Ga)Se2 (CIGSe) thin films is a main issue for a profound understanding of recombination losses in chalcopyrite thin-film solar cells. Especially, impurity-driven passivation of electronic levels due to point defects segregating at the surface and at grain boundaries is extensively debated. By combining current imaging tunneling spectroscopy with photoelectron spectroscopy, the local defect-level density and unusual optoelectronic grain-boundary properties of this material are correlated with the macroscopic energy levels and surface composition. Vacuum annealing of different CIGSe materials provides evidence that Na diffusion from the glass substrate does not affect the surface defect passivation or grain-boundary properties of standard Cu-poor materials. Furthermore, we find no major impact on the observed thermally activated dipole compensation or the accompanying change in surface band bending (up to 0.6 eV) due to Na. In contrast, Cu-rich CIGSe shows an opposing surface defect chemistry with only minor heat-induced band bending. Our results lead to a comprehensive picture, where the highly desirable type inversion at the p/n interface in standard chalcopyrite thin-film solar cells is dominated by band bending within the CIGSe absorber rather than the result of Na impurities or an n-type defect phase segregating at the interface. This is in accordance with recent studies suggesting a surface reconstruction as the origin for Cu depletion and band-gap widening at the surface of chalcopyrite thin films.

  3. Huge Critical Current Density and Tailored Superconducting Anisotropy in SmFeAsO(0.8)F(0.15) by Low Density Columnar-Defect Incorporation

    Science.gov (United States)

    Welp, U.; Fang, L.; Jia, Y.; Mishra, V.; Chaparro, C.; Vlasko-Vlasov, V. K.; Koshelev, A. E.; Crabtree, G. W.; Zhu, S. F.; Zhigadlo, N. D.; Katrych, S.; Karpinski, J.; Kwok, W. K.

    2014-03-01

    SmFeAsO(0.8)F(0.15) is of great interest because it has the highest transition temperature of all the iron-based superconductors. We find that the introduction of a low density of correlated nano-scale defects enhances the critical current density up to 2 × 107A/cm2 at 5 K without any suppression in the high superconducting transition temperature of 50 K and amounting to 20 % of the theoretical depairing current density. We also observed a surprising reduction in the thermodynamic superconducting anisotropy from 8 to 4 upon irradiation. A model based on anisotropic electron scattering predicts that the superconducting anisotropy can be tailored via correlated defects in semi-metallic, fully gapped type II superconductors. - We acknowledge support by the Center for Emergent Superconductivity, an EFRC funded by the US DOE, Office of Basic Energy Sciences (LF, YJ, VM, AEK, WKK, GWC), by the DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 (CC, VKV, UW), by the EC Research Council project SuperIron (JK, SK), and by the Swiss National Science Foundation and the National Center of Competence in Research MaNEP (NDZ).

  4. Effects of Wavelength and Defect Density on the Efficiency of (In,Ga)N-Based Light-Emitting Diodes

    Science.gov (United States)

    Pristovsek, Markus; Bao, An; Oliver, Rachel A.; Badcock, Tom; Ali, Muhammad; Shields, Andrew

    2017-06-01

    We measure the electroluminescence of light-emitting diodes (LEDs) on substrates with low dislocation densities (LDD) at 106 cm-2 and low 108 cm-2 , and compare them to LEDs on substrates with high dislocation densities (HDD) closer to 1010 cm-2 . The external quantum efficiencies (EQEs) are fitted using the A B C model with and without localization. The nonradiative-recombination (NR) coefficient A is constant for HDD LEDs, indicating that the NR is dominated by dislocations at all wavelengths. However, A strongly increases for LDD LEDs by a factor of 20 when increasing the emission wavelength from 440 to 540 nm. We attribute this to an increased density of point defects due to the lower growth temperatures used for longer wavelengths. The radiative recombination coefficient B follows the squared wave-function overlap for all samples. Using the observed coefficients, we calculate the peak efficiency as a function of the wavelength. For HDD LEDs the change of wave-function overlap (i.e., B ) is sufficient to reduce the EQE as observed, while for LDD LEDs also the NR coefficient A must increase to explain the observed EQEs. Thus, reducing NR is important to improving the EQEs of green LEDs, but this cannot be achieved solely by reducing the dislocation density: point defects must also be addressed.

  5. Evaluation of defect density by top-view large scale AFM on metamorphic structures grown by MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Gocalinska, Agnieszka, E-mail: agnieszka.gocalinska@tyndall.ie; Manganaro, Marina; Dimastrodonato, Valeria; Pelucchi, Emanuele

    2015-09-15

    Highlights: • Metamorphic buffer layers of In{sub x}Ga{sub 1−x}As were grown by MOVPE and characterised by AFM and TEM. • It was found that AFM provides sufficient information to estimate threading defect density in metamorphic structures, even when significant roughness is present. • When planar-view TEM is lacking, a combination of cross-sectional TEM and large scale AFM can provide good evaluation of the material quality. • It is fast, cheap and non-destructive – can be very useful in development process of complicated structures, requiring multiple test growths and characterisation. - Abstract: We demonstrate an atomic force microscopy based method for estimation of defect density by identification of threading dislocations on a non-flat surface resulting from metamorphic growth. The discussed technique can be applied as an everyday evaluation tool for the quality of epitaxial structures and allow for cost reduction, as it lessens the amount of the transmission electron microscopy analysis required at the early stages of projects. Metamorphic structures with low surface defectivities (below 10{sup 6}) were developed successfully with the application of the technique, proving its usefulness in process optimisation.

  6. Effects of Nb and Si on densities of valence electrons in bulk and defects of Fe3Al alloys

    Institute of Scientific and Technical Information of China (English)

    邓文; 钟夏平; 黄宇阳; 熊良钺; 王淑荷; 郭建亭; 龙期威

    1999-01-01

    Positron lifetime measurements have been performed in binary Fe3Al and Fe3Al doping with Nb or Si alloys. The densities of valence electrons of the bulk and microdefects in all tested samples have been calculated by using the positron lifetime parameters. Density of valence electron is low in the bulk of Fe3Al alloy. It indicates that, the 3d electrons in a Fe atom have strong-localized properties and tend to form covalent bonds with Al atoms, and the bonding nature in Fe3Al is a mixture of metallic and covalent bonds. The density of valence electron is very low in the defects of Fe3Al grain boundary, which makes the bonding cohesion in grain boundary quite weak. The addition of Si to Fe3Al gives rise to the decrease of the densities of valence electrons in the bulk and the grain boundary thus the metallic bonding cohesion. This makes the alloy more brittle. The addition of Nb to Fe3Al results in the decrease of the ordering energy of the alloy and increases the density of valence electron and th

  7. Intracellular transport of low density lipoprotein-derived cholesterol is defective in Niemann-Pick type C fibroblasts

    Energy Technology Data Exchange (ETDEWEB)

    Liscum, L.; Ruggiero, R.M.; Faust, J.R.

    1989-05-01

    Niemann-Pick disease type C (NPC) is characterized by substantial intracellular accumulation of unesterified cholesterol. The accumulation of unesterified cholesterol in NPC fibroblasts cultured with low density lipoprotein (LDL) appears to result from the inability of LDL to stimulate cholesterol esterification in addition to impaired LDL-mediated downregulation of LDL receptor activity and cellular cholesterol synthesis. Although a defect in cholesterol transport in NPC cells has been inferred from previous studies, no experiments have been reported that measure the intracellular movement of LDL-cholesterol specifically. We have used four approaches to assess intracellular cholesterol transport in normal and NPC cells and have determined the following: (a) mevinolin-inhibited NPC cells are defective in using LDL-cholesterol for growth. However, exogenously added mevalonate restores cell growth equally in normal and NPC cells; (b) the transport of LDL-derived (3H)cholesterol to the plasma membrane is slower in NPC cells, while the rate of appearance of (3H)acetate-derived, endogenously synthesized (3H)cholesterol at the plasma membrane is the same for normal and NPC cells; (c) in NPC cells, LDL-derived (3H)cholesterol accumulates in lysosomes to higher levels than normal, resulting in defective movement to other cell membranes; and (d) incubation of cells with LDL causes an increase in cholesterol content of NPC lysosomes that is threefold greater than that observed in normal lysosomes. Our results indicate that a cholesterol transport defect exists in NPC that is specific for LDL-derived cholesterol.

  8. A laser scanning vibrometer for the monitoring of stiffness and density defects in fibre-reinforced plastics

    Science.gov (United States)

    Cianciafara, P.; Visco, A. M.; Torrisi, L.

    2010-10-01

    Laser scanning vibrometry (LSV) is a non-contact technique for precise measurements of elastic wave parameters. In particular, the measurements of the wave velocity and dissipation deliver information on a material's stiffness and imperfections. In this paper, LSV was applied to monitor the stiffness and density of defects in composite laminate specimens cured at various exposures to microwave radiation. The specimens were supported by nylon wires and excited by a loudspeaker. Its driving frequency was swept and the frequency response of the specimens was measured by a laser vibrometer. The frequency shift of the fundamental flexural mode due to stiffness variation was measured as a function of the microwave exposure. To evaluate the dissipation factor, which is related to the density of defects, a short pulse was used for acoustic excitation. The temporal decay of the vibrations (reverberation) was measured by LSV and interpolated with an exponential function. The results obtained enable monitoring of the deterioration of the composite properties with the increase in the microwave exposure.

  9. Sperm-associated antigen 6 (SPAG6 deficiency and defects in ciliogenesis and cilia function: polarity, density, and beat.

    Directory of Open Access Journals (Sweden)

    Maria E Teves

    Full Text Available SPAG6, an axoneme central apparatus protein, is essential for function of ependymal cell cilia and sperm flagella. A significant number of Spag6-deficient mice die with hydrocephalus, and surviving males are sterile because of sperm motility defects. In further exploring the ciliary dysfunction in Spag6-null mice, we discovered that cilia beat frequency was significantly reduced in tracheal epithelial cells, and that the beat was not synchronized. There was also a significant reduction in cilia density in both brain ependymal and trachea epithelial cells, and cilia arrays were disorganized. The orientation of basal feet, which determines the direction of axoneme orientation, was apparently random in Spag6-deficient mice, and there were reduced numbers of basal feet, consistent with reduced cilia density. The polarized epithelial cell morphology and distribution of intracellular mucin, α-tubulin, and the planar cell polarity protein, Vangl2, were lost in Spag6-deficient tracheal epithelial cells. Polarized epithelial cell morphology and polarized distribution of α-tubulin in tracheal epithelial cells was observed in one-week old wild-type mice, but not in the Spag6-deficient mice of the same age. Thus, the cilia and polarity defects appear prior to 7 days post-partum. These findings suggest that SPAG6 not only regulates cilia/flagellar motility, but that in its absence, ciliogenesis, axoneme orientation, and tracheal epithelial cell polarity are altered.

  10. NO2 interaction with Au atom adsorbed on perfect and defective MgO(100) surfaces: density functional theory calculations.

    Science.gov (United States)

    Ammar, H Y; Eid, Kh M

    2013-10-01

    The interactions of nitrogen dioxide molecule (NO2) on Au atom adsorbed on the surfaces of metal oxide MgO (100) on both anionic (O2-) and defect (F(s) and F(s)(+)-centers) sites have been studied using the Density Functional Theory (DFT) in combination with embedded cluster model. The adsorption energies of NO2 molecule (N-down as well as O-down) on O(-2), F(s) and F(s)(+)-sites were considered. Full optimization for the additive materials and partial optimization for MgO substrate surfaces have been done. The formation energies were evaluated for F(s) and F(s)(+) of MgO substrate surfaces. Some parameters, the Ionization Potential (IP) and electron Affinity (eA), for defect free and defect containing surfaces have been calculated. The interaction properties of NO2 have been analyzed in terms of the adsorption energy, the electron donation (basicity), the elongation of N-O bond length and the charge distribution by using Natural Bond Orbital (NBO) analysis. The adsorption properties were examined by calculation of the Density of State (DOS). The presence of the Au atom increases the surface chemistry of the anionic O(2-)-site of MgO substrate surfaces. On the other hand, the presence of the Au atom decreases the surface chemistry of the F(s) and F(s)(+)-sites of MgO substrate surfaces. Generally, the NO2 molecule is strongly adsorbed (chemisorption) on the MgO substrate surfaces containing F(s) and F(s)(+)-centers.

  11. Density functional theory study of phase stability and defect thermodynamics in iron-oxyhydroxide mineral materials

    Science.gov (United States)

    Pinney, Nathan Douglas

    Due to their high surface area and reactivity toward a variety of heavy metal and oxyanion species of environmental concern, Fe-(oxyhydr)oxide materials play an important role in the geochemical fate of natural and anthropogenic contaminants in soils, aquifers and surface water environments worldwide. In this research, ab initio simulations describe the bulk structure, magnetic properties, and relative phase stability of major Fe-(oxyhydr)oxide materials, including hematite, goethite, lepidocrocite, and ferrihydrite.These bulk models are employed in further studies of point defect and alloy/dopant thermodynamics in these materials, allowing construction of a phase stability model that better replicates the structure and composition of real materials. Li + adsorption at the predominant goethite (101) surface is simulated using ab initio methods, offering energetic and structural insight into the binding mechanisms of metal cations over a range of surface protonation conditions.

  12. High-density G-centers, light-emitting point defects in silicon crystal

    Directory of Open Access Journals (Sweden)

    Koichi Murata

    2011-09-01

    Full Text Available We propose a new method of creating light-emitting point defects, or G-centers, by modifying a silicon surface with hexamethyldisilazane followed by laser annealing of the surface region. This laser annealing process has two advantages: creation of highly dense G-centers by incorporating carbon atoms into the silicon during heating; freezing in the created G-centers during rapid cooling. The method provides a surface region of up to 200 nm with highly dense carbon atoms of up to 4 × 1019 cm−3 to create G-centers, above the solubility limit of carbon atoms in silicon crystal (3 × 1017 cm−3. Photoluminescence measurement reveals that the higher-speed laser annealing produces stronger G-center luminescence. We demonstrate electrically-driven emission from the G-centers in samples made using our new method.

  13. Direct determination of defect density of states in organic bulk heterojunction solar cells

    Science.gov (United States)

    Verma, Upkar K.; Tripathi, Durgesh C.; Mohapatra, Y. N.

    2016-09-01

    The measurement of the occupied trap density of states (DOS) is important for optimization of organic bulk heterojunction solar cells. We demonstrate a direct method for obtaining it from the trap related peak in capacitance-voltage characteristics under different levels of illumination, and its correlation with the dark current density-voltage characteristics. We use the method to measure the parameters of DOS, occupied trap distribution, and its temperature dependence for poly(3-hexathiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) based solar cells. The total occupied trap concentration is approximately 7 × 1015 cm-3 with a standard deviation for a truncated Gaussian distribution varying between 32 and 44 meV in the temperature range of 310-270 K within a total Gaussian DOS with a standard deviation of 92 meV.

  14. EFFECT OF THE DEFECT STATES DENSITY ON OPTICAL BAND GAP OF CdIn2O4 THIN FILM

    Institute of Scientific and Technical Information of China (English)

    H.S. San; Z.G. Wu; B. Li; B.X. Feng

    2005-01-01

    Transparent conducting oxides CdIn2O4 thin films were prepared by radio-frequency reactive sputtering from a Cd-In alloy target in Ar+O2 atmosphere. By transmission spectrum and Hall measurement for different samples prepared at different substrate temperatures, it could be found that the carrier concentration would increase with the decrease of substrate temperature, but absorption edge showed an abrupt variation from a blue shift to a red shift.Theoretically, the paper formulated the effect of high-density point defects on band structures; it embodied the formation of band tailing, Burstein-Moss shift and band-gap narrowing. The density of holes will influence the magnitude of optical band gap and transmittance of light. Since extrapolation method does not fit degenerate semiconductor materials, a more accurate method of obtaining optical band gap is curve fitting. In addition, ionized impurities scattering is the main damping mechanism of the free electrons in CdIn2O4 films, the density of ionized impurities induced by altering substrate temperature will affect the carriers mobility.

  15. Defects Energetics and Electronic Properties of Li Doped ZnO: A Hybrid Hartree-Fock and Density Functional Study

    Institute of Scientific and Technical Information of China (English)

    Xu Sun; You-song Gu; Xue-qiang Wang; Yue Zhang

    2012-01-01

    The electronic properties and stability of Li-doped ZnO with various defects have been studied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Hartree-Fock and density functional methods.The results from formation energy calculations show that Li pair complexes have the lowest formation energy in most circumstances and they consume most of the Li content in Li doped ZnO,which make the p-type conductance hard to obtain.The formation of Li pair complexes is the main obstacle to realize p-type conductance in Li doped ZnO.However,the formation energy of Lizn decreases as environment changes from Zn-rich to O-rich and becomes more stable than that of Li-pair complexes at highly O-rich environment.Therefore,p-type conductance can be obtained by Li doped ZnO grown or post annealed in oxygen rich atmosphere.

  16. The influence of critical current density of Bi-2212 superconductors by defects after Yb-doping

    Science.gov (United States)

    Lu, Tianni; Zhang, Cuiping; Guo, Shengwu; Wu, Yifang; Li, Chengshan; Zhou, Lian

    2015-12-01

    Bi2Sr2Ca1-xYbxCu2O8+δ (Bi-2212) single crystals with x = 0.000, 0.005, 0.010 and 0.020 have been prepared by self-flux method. The influences of Yb doping on the formation of the dislocations in the lattice structures, as well as the related current carrying capability are investigated. Due to the SQUID measurement and the Bean model calculation, the maximum critical current density (Jc) is obtained when the Yb doping content is x = 0.010, though the Tc and the carrier concentration are not in the optimal region. Based on the HRTEM analyses of the Ca-O and Cu-O2 layers, the optimal dislocation density in the Cu-O2 layers is deduced according to the number of the dislocations per unit area. Besides, the sizes of the dislocations also prove the effectiveness of Yb substitution on the enhancement of the current carrying capability in Bi-2212 single crystals.

  17. Iron-oxygen vacancy defect centers in PbTi O3 : Newman superposition model analysis and density functional calculations

    Science.gov (United States)

    Meštrić, H.; Eichel, R.-A.; Kloss, T.; Dinse, K.-P.; Laubach, So.; Laubach, St.; Schmidt, P. C.; Schönau, K. A.; Knapp, M.; Ehrenberg, H.

    2005-04-01

    The Fe3+ center in ferroelectric PbTiO3 together with an oxygen vacancy forms a charged defect associate, oriented along the crystallographic c axis. Its microscopic structure has been analyzed in detail comparing results from a semiempirical Newman superposition model analysis based on fine-structure data and from calculations using density functional theory. Both methods give evidence for a substitution of Fe3+ for Ti4+ as an acceptor center. The position of the iron ion in the ferroelectric phase is found to be similar to the B site in the paraelectric phase. Partial charge compensation is locally provided by a directly coordinated oxygen vacancy. Using high-resolution synchrotron powder diffraction, it was verified that lead titanate remains tetragonal down to 12K , exhibiting a c/a ratio of 1.0721.

  18. Role of zinc interstitials and oxygen vacancies of ZnO in photocatalysis: a bottom-up approach to control defect density.

    Science.gov (United States)

    Kayaci, Fatma; Vempati, Sesha; Donmez, Inci; Biyikli, Necmi; Uyar, Tamer

    2014-09-07

    Oxygen vacancies (V(O)s) in ZnO are well-known to enhance photocatalytic activity (PCA) despite various other intrinsic crystal defects. In this study, we aim to elucidate the effect of zinc interstitials (Zn(i)) and V(O)s on PCA, which has applied as well as fundamental interest. To achieve this, the major hurdle of fabricating ZnO with controlled defect density requires to be overcome, where it is acknowledged that defect level control in ZnO is significantly difficult. In the present context, we fabricated nanostructures and thoroughly characterized their morphological (SEM, TEM), structural (XRD, TEM), chemical (XPS) and optical (photoluminescence, PL) properties. To fabricate the nanostructures, we adopted atomic layer deposition (ALD), which is a powerful bottom-up approach. However, to control defects, we chose polysulfone electrospun nanofibers as a substrate on which the non-uniform adsorption of ALD precursors is inevitable because of the differences in the hydrophilic nature of the functional groups. For the first 100 cycles, Zn(i)s were predominant in ZnO quantum dots (QDs), while the presence of V(O)s was negligible. As the ALD cycle number increased, V(O)s were introduced, whereas the density of Zn(i) remained unchanged. We employed PL spectra to identify and quantify the density of each defect for all the samples. PCA was performed on all the samples, and the percent change in the decay constant for each sample was juxtaposed with the relative densities of Zn(i)s and V(O)s. A logical comparison of the relative defect densities of Zn(i)s and V(O)s suggested that the former are less efficient than the latter because of the differences in the intrinsic nature and the physical accessibility of the defects. Other reasons for the efficiency differences were elaborated.

  19. Crystal Engineering for Low Defect Density and High Efficiency Hybrid Chemical Vapor Deposition Grown Perovskite Solar Cells.

    Science.gov (United States)

    Ng, Annie; Ren, Zhiwei; Shen, Qian; Cheung, Sin Hang; Gokkaya, Huseyin Cem; So, Shu Kong; Djurišić, Aleksandra B; Wan, Yangyang; Wu, Xiaojun; Surya, Charles

    2016-12-07

    Synthesis of high quality perovskite absorber is a key factor in determining the performance of the solar cells. We demonstrate that hybrid chemical vapor deposition (HCVD) growth technique can provide high level of versatility and repeatability to ensure the optimal conditions for the growth of the perovskite films as well as potential for batch processing. It is found that the growth ambient and degree of crystallization of CH3NH3PbI3 (MAPI) have strong impact on the defect density of MAPI. We demonstrate that HCVD process with slow postdeposition cooling rate can significantly reduce the density of shallow and deep traps in the MAPI due to enhanced material crystallization, while a mixed O2/N2 carrier gas is effective in passivating both shallow and deep traps. By careful control of the perovskite growth process, a champion device with power conversion efficiency of 17.6% is achieved. Our work complements the existing theoretical studies on different types of trap states in MAPI and fills the gap on the theoretical analysis of the interaction between deep levels and oxygen. The experimental results are consistent with the theoretical predictions.

  20. Systematic defect donor levels in III-V and II-VI semiconductors revealed by hybrid functional density-functional theory

    Science.gov (United States)

    Petretto, Guido; Bruneval, Fabien

    2015-12-01

    The identification of defect levels from photoluminescence spectroscopy is a useful but challenging task. Density-functional theory (DFT) is a highly valuable tool to this aim. However, the semilocal approximations of DFT that are affected by a band gap underestimation are not reliable to evaluate defect properties, such as charge transition levels. It is now established that hybrid functional approximations to DFT improve the defect description in semiconductors. Here we demonstrate that the use of hybrid functionals systematically stabilizes donor defect states in the lower part of the band gap for many defects, impurities or vacancies, in III-V and in II-VI semiconductors, even though these defects are usually considered as acceptors. These donor defect states are a very general feature and, to the best of our knowledge, have been overlooked in previous studies. The states we identify here may challenge the older assignments to photoluminescent peaks. Though appealing to screen quickly through the possible stable charge states of a defect, semilocal approximations should not be trusted for that purpose.

  1. Structural and electronic properties of the adsorbed and defected Cu nanowires: A density-functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Ying-Ni [College of Physics and Information Technology, Shaanxi Normal University, Xian 710062, Shaanxi (China); Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830011, Xinjiang (China); Zhang, Jian-Min, E-mail: jianm_zhang@yahoo.com [College of Physics and Information Technology, Shaanxi Normal University, Xian 710062, Shaanxi (China); Fan, Xiao-Xi [Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830011, Xinjiang (China); Xu, Ke-Wei [College of Physics and Mechanical and Electronic Engineering, Xian University of Arts and Science, Xian 710065, Shaanxi (China)

    2014-12-01

    Using first-principles calculations based on density-functional theory, we systematically investigate the influence of adsorbates (CO molecule and O atom) and defects (adsorb one extra Cu atom and monovacancy) on the structural and electronic properties of Cu{sub 5-1}NW and Cu{sub 6-1}NW. For both nanowires, CO molecule prefers to adsorb on the top site, while O atom prefers to adsorb on the center site. The hybridization between the CO and Cu states is dominated by the donation–backdonation process, which leads to the formation of bonding/antibonding pairs, 5σ{sub b}/5σ{sub a} and 2π{sub b}{sup ⁎}/2π{sub a}{sup ⁎}. The larger adsorption energies, larger charge transfers to O adatom and larger decrease in quantum conductance 3G{sub 0} for an O atom adsorbed on the Cu{sub 5-1}NW and Cu{sub 6-1}NW show both Cu{sub 5-1}NW and Cu{sub 6-1}NW can be used as an O sensor. Furthermore, the decrease in quantum conductance 1G{sub 0} for a CO molecule adsorbed on the Cu{sub 6-1}NW also shows the Cu{sub 6-1}NW can be used to detect CO molecule. So we expect these results may have implications for CuNW based chemical sensing. High adsorption energy of one extra Cu atom and relatively low formation energy of a monovacancy suggest that these two types of defects are likely to occur in the fabrication of CuNWs. One extra Cu atom does not decrease the quantum conductance, while a Cu monovacancy leads to a drop of the quantum conductance.

  2. Histomorphometric Analysis of Periodontal Tissue Regeneration by the Use of High Density Polytetrafluoroethylen Membrane in Grade II Furcation Defects of Dogs

    Directory of Open Access Journals (Sweden)

    Raoofi S

    2015-09-01

    Full Text Available Statement of Problem: There are limited histomorphometric studies on biologic efficacy of high density tetrafluoroethylen (d-PTFE membrane. Objectives: To investigate the healing of surgically induced grade II furcation defects in dogs following the use of dense polytetrafluoroethylene as the barrier membrane and to compare the results with the contra lateral control teeth without the application of any membrane. Materials andMethods: Mandibular and maxillary 3rd premolar teeth of 18 young adult male mongrel dogs were used for the experiment. The furcation defects were created during the surgery. 5 weeks later, regenerative surgery was performed. The third premolar teeth were assigned randomly to control and test groups. In the test group, after a full thickness flap reflection, the d-PTFE membrane was placed over furcation defects. In the control group, no membrane was placed over the defect. 37 tissue blocks containing the teeth and surrounding hard and soft tissues were obtained three months post-regenerative surgery. The specimens were demineralized, serially sectioned, mounted and stained with Hematoxylin and Eosin staining technique. From each tissue block, 35-45 sections of 10 μm thickness within 60μm interval captured the entire surgically created defect. The histological images were transferred to computer and then the linear measurement ranges of the defects area, interadicular alveolar bone, epithelial attachment and coronal extension of the new cementum were done. Then, the volume and area of aforementioned parameters were calculated considering the thickness and interval of the sections. To compare the parameters between the control and test teeth, we calculated the amount of each one proportionally to the original amount of defects. Results: The mean interradicular root surface areas of original defects covered with new cementum was 74.46% and 29.59% for the membrane and control defects, respectively (p < 0.0001. Corresponding

  3. Quantification of Valleys of Randomly Textured Substrates as a Function of Opening Angle: Correlation to the Defect Density in Intrinsic nc-Si:H.

    Science.gov (United States)

    Kim, Do Yun; Hänni, Simon; Schüttauf, Jan-Willem; van Swaaij, René A C M M; Zeman, Miro

    2016-08-17

    Optical and electrical properties of hydrogenated nanocrystalline silicon (nc-Si:H) solar cells are strongly influenced by the morphology of underlying substrates. By texturing the substrates, the photogenerated current of nc-Si:H solar cells can increase due to enhanced light scattering. These textured substrates are, however, often incompatible with defect-less nc-Si:H growth resulting in lower Voc and FF. In this study we investigate the correlation between the substrate morphology, the nc-Si:H solar-cell performance, and the defect density in the intrinsic layer of the solar cells (i-nc-Si:H). Statistical surface parameters representing the substrate morphology do not show a strong correlation with the solar-cell parameters. Thus, we first quantify the line density of potentially defective valleys of randomly textured ZnO substrates where the opening angle is smaller than 130° (ρSi:H (ρdefect), which is obtained by fitting external photovoltaic parameters from experimental results and simulations. We confirm that when ρ<130 increases the Voc and FF significantly drops. It is also observed that ρdefect increases following a power law dependence of ρ<130. This result is attributed to more frequently formed defective regions for substrates having higher ρ<130.

  4. The stability and electronic structures of Si/O/Al/P atom doped (5,0)boron nitrogen nanotubes with Stone-Wales defects: Density functional theory studies

    Science.gov (United States)

    Li, KeJing; Ye, JinQian; Zhang, Juan; Wang, XiYuan; Shao, QingYi

    2017-03-01

    Using density functional theory, we have investigated Si/O/Al/P atoms doped (5,0)BNNTs with SW defects. We have mainly found that Si/O/Al/P have improved the stability of (5,0)BNNTs with SW defects. In view of Mulliken charge, we have thought Si/O/Al/P atoms have donated electrons (charge +e state or charge -e state) to nanotubes, contributing BNNTs with SW defects to stable. Meanwhile, from the aspect of energy band structure and DOS, we have further explained the reason. We have considerred that stability of doped structures has related to hybridization between doped atom and BNNTs. The stability has changed with changing the degree of hybridization. Moreover, B atom can play a crucial role in the insertion of Si/O/Al/P atom into (5,0)BNNTs with SW defects.

  5. Influence of point defects on the phonon thermal conductivity and phonon density of states of Bi{sub 2}Te{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Bedoya-Martinez, O.N.; Hashibon, A.; Elsaesser, C. [Fraunhofer IWM, Freiburg (Germany)

    2016-03-15

    The influence of point defects on the lattice thermal conductivity and vibrational properties of Bi{sub 2}Te{sub 3} were studied by using equilibrium and non-equilibrium molecular-dynamics simulations. Three types of point defects at various concentrations were considered, namely Bi and Te vacancies and Bi anti-sites. It is shown that point defects can result in a reduction of up to 80% of the bulk thermal conductivity. A detailed analysis of the phonon density of states (PDOS) of the studied systems is provided. Element (Bi or Te) and orientation (in-plane or cross-plane) resolved PDOS were calculated. In agreement with experimental observations and other simulations, features in the PDOS were identified with specific atomic and orientation contributions. Systems containing point defects exhibit a broadening of the PDOS peaks as the defect concentration increases, which is due to the disorder induced by the defects. Such disorder leads to a higher phonon scattering and thus to a lower lattice thermal conductivity. Tuning the point defect type and concentrations during growth may, therefore, provide a route for optimizing Bi{sub 2}Te{sub 3} based thermoelectric devices. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Adsorption of SF6 decomposed gas on anatase (101) and (001) surfaces with oxygen defect: a density functional theory study.

    Science.gov (United States)

    Zhang, Xiaoxing; Chen, Qinchuan; Tang, Ju; Hu, Weihua; Zhang, Jinbin

    2014-04-23

    The detection of partial discharge by analyzing the components of SF6 gas in gas-insulated switchgears is important to the diagnosis and assessment of the operational state of power equipment. A gas sensor based on anatase TiO2 is used to detect decomposed gases in SF6. In this paper, first-principle density functional theory calculations are adopted to analyze the adsorption of SO2, SOF2, and SO2F2, the primary decomposition by-products of SF6 under partial discharge, on anatase (101) and (001) surfaces. Simulation results show that the perfect anatase (001) surface has a stronger interaction with the three gases than that of anatase (101), and both surfaces are more sensitive and selective to SO2 than to SOF2 and SO2F2. The selection of a defect surface to SO2, SOF2, and SO2F2 differs from that of a perfect surface. This theoretical result is corroborated by the sensing experiment using a TiO2 nanotube array (TNTA) gas sensor. The calculated values are analyzed to explain the results of the Pt-doped TNTA gas sensor sensing experiment. The results imply that the deposited Pt nanoparticles on the surface increase the active sites of the surface and the gas molecules may decompose upon adsorption on the active sites.

  7. Reduced defect density at the CZTSSe/CdS interface by atomic layer deposition of Al2O3

    Science.gov (United States)

    Erkan, Mehmet Eray; Chawla, Vardaan; Scarpulla, Michael A.

    2016-05-01

    The greatest challenge for improving the power conversion efficiency of Cu2ZnSn(S,Se)4 (CZTSSe)/CdS/ZnO thin film solar cells is increasing the open circuit voltage (VOC). Probable leading causes of the VOC deficit in state-of-the-art CZTSSe devices have been identified as bulk recombination, band tails, and the intertwined effects of CZTSSe/CdS band offset, interface defects, and interface recombination. In this work, we demonstrate the modification of the CZTSSe absorber/CdS buffer interface following the deposition of 1 nm-thick Al2O3 layers by atomic layer deposition (ALD) near room temperature. Capacitance-voltage profiling and quantum efficiency measurements reveal that ALD-Al2O3 interface modification reduces the density of acceptor-like states at the heterojunction resulting in reduced interface recombination and wider depletion width. Indications of increased VOC resulting from the modification of the heterojunction interface as a result of ALD-Al2O3 treatment are presented. These results, while not conclusive for application to state-of-the-art high efficiency CZTSSe devices, suggest the need for further studies as it is probable that interface recombination contributes to reduced VOC even in such devices.

  8. [Regeneration processes in bone defects after implantation of composite material of different density of polylactide origin filled with HAP (experimental-morphological study)].

    Science.gov (United States)

    Kulakov, A A; Grigor'ian, A S; Krotova, L I; Popov, V K; Volozhin, A I; Losev, V F

    2009-01-01

    In experimental-morphological study on 6 dogs the dynamics of regenerate formation in ulna and mandible defects after implantation in them composite material of different density (0.46-0.50 and 0.38-0.42 g/cm(3)) of polylactide (PL) origin filled with HAP was followed at the terms of 6 and 9 months. Histologic study and structural determinant distribution analysis in the content of regenerate showed that optimal results according to the bone defect substitution by bone regenerate criterion at 9th month of the experiment were received after composite material from PL and HAP with the density of 0.38-0.42 g/cm(3) implantation. Newly formed trabecular bone tissue was seen in the regenerate and as well as strong tendency for bone matrix maturation. It was confirmed by the appearance of lamellar structures in newly formed bone trabecules situated in peripheral zones of bone defect. In bone mandible defects the substitution process of the implants from PL with HAP by the bone tissue was much slower than in ulna defects.

  9. A comparative study of the density of defect states in bulk samples and thin films of glassy Se$_{90}$Sb$_{10}$

    Indian Academy of Sciences (India)

    KUMAR ANJANI; DWIVEDI PRABHAT K; SHUKLA R K; KUMAR A

    2016-05-01

    The present paper reports the comparative study of density of defect states (DOS) between bulk samples and thin films of glassy Se$_{90}$Sb$_{10}$. These glasses have been prepared by the quenching technique. Thin films of these glasses have been prepared by vacuum evaporation technique. Space-charge-limited conduction (SCLC) has been measured at different temperatures.The density of localized states near Fermi level is calculated by fitting the data to the theory of SCLC for the case of uniform distribution of localized states for bulk as well as for thin films. A comparison has been made between the density of states calculated in these two cases.

  10. Analysis of defects in externally driven dust-density wavefronts in cogenerated dusty plasma using the time-resolved Hilbert-Huang transform

    Science.gov (United States)

    Sarkar, Sanjib; Barman, Chiranjib; Mondal, Malay; Bose, M.; Mukherjee, S.

    2016-05-01

    Analysis of defects in externally driven dust-density wavefronts (DDWs) in cogenerated dusty plasma has been carried out. The DDWs are excited for threshold positive bias through another T-shaped electrode which is placed inbetween two main discharge electrodes. Spatiotemporal evolution of the DDWs reveals a wave defect and non-propagating wave mode in the DDW field. A space-time plot and the time-resolved Hilbert-Huang transform (HHT) were employed to analyze the spatiotemporal wave data at a specific location in the wave field.

  11. Relationship between optical coherence tomography sector peripapillary angioflow-density and Octopus visual field cluster mean defect values

    Science.gov (United States)

    2017-01-01

    Purpose To compare the relationship of Octopus perimeter cluster mean-defect (cluster MD) values with the spatially corresponding optical coherence tomography (OCT) sector peripapillary angioflow vessel-density (PAFD) and sector retinal nerve fiber layer thickness (RNFLT) values. Methods High quality PAFD and RNFLT images acquired on the same day with the Angiovue/RTVue-XR Avanti OCT (Optovue Inc., Fremont, USA) on 1 eye of 27 stable early-to-moderate glaucoma, 22 medically controlled ocular hypertensive and 13 healthy participants were analyzed. Octopus G2 normal visual field test was made within 3 months from the imaging. Results Total peripapillary PAFD and RNFLT showed similar strong positive correlation with global mean sensitivity (r-values: 0.6710 and 0.6088, P<0.0001), and similar (P = 0.9614) strong negative correlation (r-values: -0.4462 and -0.4412, P≤0.004) with global MD. Both inferotemporal and superotemporal sector PAFD were significantly (≤0.039) lower in glaucoma than in the other groups. No significant difference between the corresponding inferotemporal and superotemporal parameters was seen. The coefficient of determination (R2) calculated for the relationship between inferotemporal sector PAFD and superotemporal cluster MD (0.5141, P<0.0001) was significantly greater than that between inferotemporal sector RNFLT and superotemporal cluster MD (0.2546, P = 0.0001). The R2 values calculated for the relationships between superotemporal sector PAFD and RNFLT, and inferotemporal cluster MD were similar (0.3747 and 0.4037, respectively, P<0.0001). Conclusion In the current population the relationship between inferotemporal sector PAFD and superotemporal cluster MD was strong. It was stronger than that between inferotemporal sector RNFLT and superotemporal cluster MD. Further investigations are necessary to clarify if our results are valid for other populations and can be usefully applied for glaucoma research. PMID:28152106

  12. Huge critical current density and tailored superconducting anisotropy in SmFeAsO0.8F0.15 by low-density columnar-defect incorporation

    Science.gov (United States)

    Fang, L.; Jia, Y.; Mishra, V.; Chaparro, C.; Vlasko-Vlasov, V. K.; Koshelev, A. E.; Welp, U.; Crabtree, G. W.; Zhu, S.; Zhigadlo, N. D.; Katrych, S.; Karpinski, J.; Kwok, W. K.

    2013-11-01

    Iron-based superconductors could be useful for electricity distribution and superconducting magnet applications because of their relatively high critical current densities and upper critical fields. SmFeAsO0.8F0.15 is of particular interest as it has the highest transition temperature among these materials. Here we show that by introducing a low density of correlated nano-scale defects into this material by heavy-ion irradiation, we can increase its critical current density to up to 2 × 107 A cm-2 at 5 K—the highest ever reported for an iron-based superconductor—without reducing its critical temperature of 50 K. We also observe a notable reduction in the thermodynamic superconducting anisotropy, from 8 to 4 upon irradiation. We develop a model based on anisotropic electron scattering that predicts that the superconducting anisotropy can be tailored via correlated defects in semimetallic, fully gapped type II superconductors.

  13. A defect density-based constitutive crystal plasticity framework for modeling the plastic deformation of Fe-Cr-Al cladding alloys subsequent to irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Patra, Anirban [Los Alamos National Laboratory; Wen, Wei [Los Alamos National Laboratory; Martinez Saez, Enrique [Los Alamos National Laboratory; Tome, Carlos [Los Alamos National Laboratory

    2016-02-05

    It is essential to understand the deformation behavior of these Fe-Cr-Al alloys, in order to be able to develop models for predicting their mechanical response under varied loading conditions. Interaction of dislocations with the radiation-induced defects governs the crystallographic deformation mechanisms. A crystal plasticity framework is employed to model these mechanisms in Fe-Cr-Al alloys. This work builds on a previously developed defect density-based crystal plasticity model for bcc metals and alloys, with necessary modifications made to account for the defect substructure observed in Fe-Cr-Al alloys. The model is implemented in a Visco-Plastic Self Consistent (VPSC) framework, to predict the mechanical behavior under quasi-static loading.

  14. Atomic defects and dopants in ternary Z-phase transition-metal nitrides Cr M N with M =V , Nb, Ta investigated with density functional theory

    Science.gov (United States)

    Urban, Daniel F.; Elsässer, Christian

    2017-09-01

    A density functional theory study of atomic defects and dopants in ternary Z-phase transition-metal nitrides Cr M N with M =V , Nb, or Ta is presented. Various defect formation energies of native point defects and of substitutional atoms of other metal elements which are abundant in the steel as well are evaluated. The dependence thereof on the thermodynamic environment, i.e., the chemical conditions of a growing Z-phase precipitate, is studied, and different growth scenarios are compared. The results obtained may help to relate results of experimental atomic-scale analysis by atom probe tomography or transmission electron microscopy to the theoretical modeling of the formation process of the Z phase from binary transition-metal nitrides.

  15. Substrate preparation effects on defect density in molecular beam epitaxial growth of CdTe on CdTe (100) and (211)B

    Energy Technology Data Exchange (ETDEWEB)

    Burton, George L.; Diercks, David R.; Perkins, Craig L.; Barnes, Teresa M.; Ogedengbe, Olanrewaju S.; Jayathilaka, Pathiraja A.; Edirisooriya, Madhavie; Wang, Alice; Myers, Thomas H.; Gorman, Brian P.

    2017-07-01

    Recent studies have demonstrated that growth of CdTe on CdTe (100) and (211)B substrates via molecular beam epitaxy (MBE) results in planar defect densities 2 and 3 orders of magnitude higher than growth on InSb (100) substrates, respectively. To understand this shortcoming, MBE growth on CdTe substrates with a variety of substrate preparation methods is studied by scanning electron microscopy, secondary ion mass spectrometry, x-ray photoelectron spectroscopy, cross sectional transmission electron microscopy, and atom probe tomography (APT). Prior to growth, carbon is shown to remain on substrate surfaces even after atomic hydrogen cleaning. APT revealed that following the growth of films, trace amounts of carbon remained at the substrate/film interface. This residual carbon may lead to structural degradation, which was determined as the main cause of higher defect density.

  16. Bone density of defects treated with lyophilized amniotic membrane versus collagen membrane: a tomographic and histomorfogenic study in rabbit´s femur

    Directory of Open Access Journals (Sweden)

    Liz Katty Ríos

    2014-09-01

    Full Text Available ABSTRACT The aim of this study was to compare the bone density of bone defects treated with lyophilizated amniotic membrane (LAM and collagen Membrane (CM, at 3 and 5 weeks. Two bone defects of 4 mm in diameter and 6 mm deep were created in left distal femoral diaphysis of New Zealand rabbits (n = 12. The animals were randomly divided into 2 groups. One of the defects was covered with lyophilized amniotic membrane (Rosa Chambergo Tissue Bank/National Institute of Child Health-IPEN, Lima, Peru or collagen Membrane (Dentium Co, Seoul, Korea. The second was left uncovered (NC. The rabbits were killed after 3 and 5 weeks (3 rabbits/period. The results showed a high bone density and repair of the defect by new bone. The tomographic study revealed that the bone density of the defects treated with LAM at 3 weeks was equivalent to the density obtained with CM and higher density compared with NC (p 0.05. The results show that lyophilizated amniotic membrane provides bone density equal or higher to the collagen membrane. RESUMEN El propósito de este estudio fue comparar la densidad ósea (DO de defectos óseos tratados con membrana amniótica liofilizada (MAL y membrana de colágeno (MC, a las 3 y 5 semanas. Se crearon dos defectos óseos, de 4 mm de diámetro y 6 mm de profundidad, en la diáfisis femoral distal izquierda de conejos Nueva Zelanda (n=12. Los animales fueron divididos aleatoriamente en 2 grupos. Uno de los defectos fue cubierto con membrana amniótica liofilizada (Banco de tejidos Rosa Chambergo/INSN-IPEN, Lima, Perú o membrana de colágeno (Dentium Co, Seoul, Korea. El segundo se dejó sin cubrir (NC. Los conejos fueron sacrificados después de 3 y 5 semanas (3 conejos/periodo. Los resultados mostraron una alta DO y reparación del defecto por hueso neoformado. El estudio tomográfico reveló que la DO de los defectos tratados con MAL a las 3 semanas fue comparable a la densidad obtenida con MC y mayor comparado con la densidad de NC (p

  17. Low-dislocation-density epitatial layers grown by defect filtering by self-assembled layers of spheres

    Science.gov (United States)

    Wang, George T.; Li, Qiming

    2013-04-23

    A method for growing low-dislocation-density material atop a layer of the material with an initially higher dislocation density using a monolayer of spheroidal particles to bend and redirect or directly block vertically propagating threading dislocations, thereby enabling growth and coalescence to form a very-low-dislocation-density surface of the material, and the structures made by this method.

  18. Defect properties of the two-dimensional (CH3NH3)2Pb(SCN)2I2 perovskite: a density-functional theory study.

    Science.gov (United States)

    Xiao, Zewen; Meng, Weiwei; Wang, Jianbo; Yan, Yanfa

    2016-10-07

    Recently, solar cells based on 2D (CH3NH3)2Pb(SCN)2I2 perovskite have realized a power conversion efficiency of 3.23%. In this work, we study the defect properties of (CH3NH3)2Pb(SCN)2I2 through density-functional theory calculations. It is found that the lower crystal structure dimensionality of (CH3NH3)2Pb(SCN)2I2 makes the valence band maximum lower and the conduction band minimum higher as compared to its 3D CH3NH3PbI3 perovskite counterpart, resulting in relatively deeper defect transition levels. Our calculated defect formation energies suggest that if the 2D (CH3NH3)2Pb(SCN)2I2 perovskite absorbers are synthesized under Pb-poor and I-rich conditions, the dominant defects should be Pb vacancies, which create shallow levels. The resultant perovskite films are expected to exhibit p-type conductivity with a relatively long carrier lifetime.

  19. Local charge neutrality condition, Fermi level and majority carrier density of a semiconductor with multiple localized multi-level intrinsic/impurity defects

    Institute of Scientific and Technical Information of China (English)

    Ken K. Chin

    2011-01-01

    For semiconductors with localized intrinsic/impurity defects,intentionally doped or unintentionally incorporated,that have multiple transition energy levels among charge states,the general formulation of the local charge neutrality condition is given for the determination of the Fermi level and the majority carrier density.A graphical method is used to illustrate the solution of the problem.Relations among the transition energy levels of the multi-level defect are derived using the graphical method.Numerical examples are given for p-doping of the CdTe thin film used in solar panels and semi-insulating Si to illustrate the relevance and importance of the issues discussed in this work.

  20. Defect density in multiwalled carbon nanotubes influences ovalbumin adsorption and promotes macrophage activation and CD4(+) T-cell proliferation.

    Science.gov (United States)

    Bai, Wei; Raghavendra, Achyut; Podila, Ramakrishna; Brown, Jared M

    Carbon nanotubes (CNTs) are of great interest for the development of drugs and vaccines due to their unique physicochemical properties. The high surface area to volume ratio and delocalized pi-electron cloud of CNTs promote binding of proteins to the surface forming a protein corona. This unique feature of CNTs has been recognized for potential delivery of antigens for strong and long-lasting antigen-specific immune responses. Based on an earlier study that demonstrated increased protein binding, we propose that carboxylated multiwalled CNTs (MWCNTs) can function as an improved carrier to deliver antigens such as ovalbumin (OVA). To test this hypothesis, we coated carboxylated MWCNTs with OVA and measured uptake and activation of antigen-presenting cells (macrophages) and their ability to stimulate CD4(+) T-cell proliferation. We employed two types of carboxylated MWCNTs with different surface areas and defects (MWCNT-2 and MWCNT-30). MWCNT-2 and MWCNT-30 have surface areas of ~215 m(2)/g and 94 m(2)/g, respectively. The ratios of D- to G-band areas (I D/I G) were 0.97 and 1.37 for MWCNT-2 and MWCNT-30, respectively, samples showing that MWCNT-30 contained more defects. The increase in defects in MWCNT-30 led to increased binding of OVA as compared to MWCNT-2 (1,066±182 μg/mL vs 582±41 μg/mL, respectively). Both types of MWCNTs, along with MWCNT-OVA complexes, showed no observable toxicity to bone-marrow-derived macrophages up to 5 days. Surprisingly, we found that MWCNT-OVA complex significantly increased the expression of major histocompatibility complex class II on macrophages and production of pro-inflammatory cytokines (tumor necrosis factor-α and interleukin 6), while MWCNTs without OVA protein corona did not. The coculture of MWCNT-OVA-complex-treated macrophages and OVA-specific CD4(+) T-cells isolated from OT-II mice demonstrated robust proliferation of CD4(+) T-cells. This study provides strong evidence for a role for defects in carboxylated MWCNTs

  1. Lean Thinking in Systems with Non-Negligible Process Variability

    DEFF Research Database (Denmark)

    Nielsen, Erland Hejn; Simons, David

    2000-01-01

    (Stalk and Hout) is a key weapon in attacking this waste. By compressing time, quality issues are revealed driving improvement and cost reduction. When the value stream is mapped (Hines and Rich), inventory is usually the largest target for time compression. As inventory is removed from process buffers......, Time, Centralisation and Structure. Control focuses on removing variability from the information and physical flows through standardisation of processes. Empirical evidence from automotive after-sales demonstrated that simulation could identify the areas of variability with greatest leverage on cost...

  2. Lean Thinking in systems with non-negligible process variability

    DEFF Research Database (Denmark)

    Nielsen, Erland Hejn; Simons, David

    2000-01-01

    and Hout) is a key weapon in attacking this waste. By compressing time, quality issues are revealed driving improvement and cost reduction. When the value stream is mapped (Hines and Rich), inventory is usually the largest target for time compression. As inventory is removed from process buffers, process......, Time, Centralisation and Structure. Control focuses on removing variability from the information and physical flows through standardisation of processes. Empirical evidence from automotive after-sales demonstrated that simulation could identify the areas of variability with greatest leverage on cost...

  3. Lean Thinking in systems with non-negligible process variability

    DEFF Research Database (Denmark)

    Nielsen, Erland Hejn; Simons, David

    2000-01-01

    /excess of buffer capacity in such systems. The findings are put into a long-term perspective based on Lean Thinking recommendations. Based on systems thinking (Towill and Naim), four generic sequential steps to Lean Supply and Distribution have been developed within the Lean Paradigm (Simons and Kiff) - Control......Lean Thinking (Womack and Jones) improves quality, cost and delivery through the relentless elimination of wastes. For example, the exemplar of Lean, the Toyota Production system, focuses on improvement through the continual elimination of seven categorised wastes (Ohno). Time compression (Stalk......). For this system this paper makes two contributions: 1. Simulates the relationship between buffer size and throughput performance. 2. Investigates the potential for improvement through Lean Thinking There is an intricate relationship between loss of throughput and allowed inventory buffer sizes along...

  4. Lean Thinking in Systems with Non-Negligible Process Variability

    DEFF Research Database (Denmark)

    Nielsen, Erland Hejn; Simons, David

    2000-01-01

    /excess of buffer capacity in such systems. The findings are put into a long-term perspective based on lean thinking recommendations. Based on systems thinking (Towill and Naim), four generic sequential steps to Lean Supply and Distribution have been developed within the Lean Paradigm (Simons and Kiff) - Control......Lean Thinking (Womack and Jones) improves quality, cost and delivery through the relentless elimination of the wastes. For example, the exemplar of Lean, the Toyota Production system, focuses on improvement through the continual elimination of seven categorised wastes (Ohno). Time compression......). For this system this paper makes two contributions: - 1. Simulates the relationship between buffer size and throughput performance. 2. Investigates the potential for improvement through Lean Thinking There is an intricate relationship between loss of throughput and allowed inventory buffer sizes along...

  5. Fibroblast cholesterol efflux to plasma from metabolic syndrome subjects is not defective despite low high-density lipoprotein cholesterol

    NARCIS (Netherlands)

    R.P.F. Dullaart (Robin); A. Groen (Albert); G.M. Dallinga-Thie (Geesje); R. de Vries (Rindert); W. Sluiter (Wim); A. van Tol (Arie)

    2008-01-01

    textabstractObjective: We tested whether in metabolic syndrome (MetS) subjects the ability of plasma to stimulate cellular cholesterol efflux, an early step in the anti-atherogenic reverse cholesterol transport pathway, is maintained despite low high-density lipoprotein (HDL) cholesterol. Design: In

  6. An investigation of the role of the time averaged ion beam current density upon the defect densities in thin film SIMOX

    Science.gov (United States)

    Nejim, A.; Marsh, C. D.; Giles, L. F.; Hemment, P. L. F.; Li, Y.; Chater, RJ.; Kilner, J. A.; Booker, G. R.

    1994-02-01

    The effect of the time averaged ion beam current density on the material quality of thin film SIMOX has been investigated. Thin film SOI/SIMOX material has been produced by 200 keV oxygen implantation into 3 in. Fz wafers with a background temperature of 680°C. The dose range of 5 × 10 17-7 × 10 17O+/ cm2 was selected to be near the dose threshold for the formation of a continuous buried oxide after implantation and annealing which is thought to be between 5 × 10 17 and 6 × 10 17 O +/cm 2 for 200 keV [A.E. White et al., Appl. Phys. Lett. 50 (1987) 19; P.L.F. Hemment et al., Vacuum 36 (1986) 877; Y. Li et al., in: Proc. V Int. Symp. on SOI Technology and Devices (The Electrochemical Society, 1992) p. 368 [1-3

  7. Density functional study of NO adsorption on undefected and oxygen defective Au–BaO(1 0 0) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Añez, Rafael, E-mail: ranez@ivic.gob.ve [Laboratorio de Química Física y Catálisis Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Sierraalta, Aníbal; Bastardo, Anelisse [Laboratorio de Química Física y Catálisis Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Coll, David [Laboratorio de Físico Química Teórica de Materiales, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Garcia, Belkis [Instituto Universitario de Tecnología de Valencia IUTVAL, Valencia, Edo. Carabobo (Venezuela, Bolivarian Republic of)

    2014-07-01

    A periodic density functional approach has been used in order to explore the interaction of NO with undoped and Au doped BaO(1 0 0) surface. Due to oxygen vacancies increase the interaction between the doping metal and the surface, F{sub S} and F{sub S}{sup +} vacancies were studied and compared with the results obtained on the undefected doped BaO(1 0 0). Our results indicate that the high basicity of the BaO surface, besides the electron density changes produced by the oxygen vacancies, modify considerably how the Au atom interacts with the surface increasing the ionic character of the interaction. F{sub S} vacancy shows to be a promise center to activate de NO bond on the BaO(1 0 0) surface.

  8. Point defect dynamics in sodium aluminum hydrides - a combined quasielastic neutron scattering and density functional theory study

    DEFF Research Database (Denmark)

    Shi, Qing; Voss, Johannes; Jacobsen, H.S.

    2007-01-01

    we study hydrogen dynamics in undoped and TiCl3-doped samples of NaAlH4 and Na3AlH6 using a combination of density functional theory calculations and quasielastic neutron scattering. Hydrogen dynamics is found to be limited and mediated by hydrogen vacancies in both alanate phases, requiring......Understanding the catalytic role of titanium-based additives on the reversible hydrogenation of complex metal hydrides is an essential step towards developing hydrogen storage materials for the transport sector. Improved bulk diffusion of hydrogen is one of the proposed catalytic effects, and here...

  9. Time-dependent density-functional theory simulation of local currents in pristine and single-defect zigzag graphene nanoribbons

    Science.gov (United States)

    He, Shenglai; Russakoff, Arthur; Li, Yonghui; Varga, Kálmán

    2016-07-01

    The spatial current distribution in H-terminated zigzag graphene nanoribbons (ZGNRs) under electrical bias is investigated using time-dependent density-functional theory solved on a real-space grid. A projected complex absorbing potential is used to minimize the effect of reflection at simulation cell boundary. The calculations show that the current flows mainly along the edge atoms in the hydrogen terminated pristine ZGNRs. When a vacancy is introduced to the ZGNRs, loop currents emerge at the ribbon edge due to electrons hopping between carbon atoms of the same sublattice. The loop currents hinder the flow of the edge current, explaining the poor electric conductance observed in recent experiments.

  10. Performance potential of low-defect density silicon thin-film solar cells obtained by electron beam evaporation and laser crystallisation

    Directory of Open Access Journals (Sweden)

    Kim K. H.

    2013-01-01

    Full Text Available A few microns thick silicon films on glass coated with a dielectric intermediate layer can be crystallised by a single pass of a line-focused diode laser beam. Under favorable process conditions relatively large linear grains with low defect density are formed. Most grain boundaries are defect-free low-energy twin-boundaries. Boron-doped laser crystallised films are processed into solar cells by diffusing an emitter from a phosphorous spin-on-dopant source, measuring up to 539 mV open-circuit voltage prior to metallisation. After applying a point-contact metallisation the best cell achieves 7.8% energy conversion efficiency, open-circuit voltage of 526 mV and short-circuit current of 26 mA/cm2. The efficiency is significantly limited by a low fill-factor of 56% due to the simplified metallisation approach. The internal quantum efficiency of laser crystallised cells is consistent with low front surface recombination. By improving cell metallisation and enhancing light-trapping the efficiencies of above 13% can be achieved.

  11. Linear-scaling density-functional simulations of charged point defects in Al2O3 using hierarchical sparse matrix algebra.

    Science.gov (United States)

    Hine, N D M; Haynes, P D; Mostofi, A A; Payne, M C

    2010-09-21

    We present calculations of formation energies of defects in an ionic solid (Al(2)O(3)) extrapolated to the dilute limit, corresponding to a simulation cell of infinite size. The large-scale calculations required for this extrapolation are enabled by developments in the approach to parallel sparse matrix algebra operations, which are central to linear-scaling density-functional theory calculations. The computational cost of manipulating sparse matrices, whose sizes are determined by the large number of basis functions present, is greatly improved with this new approach. We present details of the sparse algebra scheme implemented in the ONETEP code using hierarchical sparsity patterns, and demonstrate its use in calculations on a wide range of systems, involving thousands of atoms on hundreds to thousands of parallel processes.

  12. The role of interfacial defects in enhancing the critical current density of YBa2Cu3O7-delta coatings

    Energy Technology Data Exchange (ETDEWEB)

    Foltyn, Stephen R [Los Alamos National Laboratory; Wang, Haiyan [Los Alamos National Laboratory; Civale, Leonardo [Los Alamos National Laboratory; Maiorov, Boris A [Los Alamos National Laboratory; Jia, Quanxi [Los Alamos National Laboratory

    2009-01-01

    The critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}0{sub 7-{delta}} (YBCO) films can approach 10 MA/cm{sup 2} at 77 K in self field , but only for very thin films. We have shown previously that strong thickness dependence results if J{sub c} is enhanced near the film-substrate interface. In the present work we investigate interfacial enhancement using laser-deposited YBCO films on NdGaO{sub 3} substrates, and find that we can adjust deposition conditions to switch the enhancement on and off. Interestingly, we find that the 'on' state is accompanied by interfacial misfit dislocations, establishing an unambiguous correlation between enhanced J{sub c} and dislocations at the film-substrate interface.

  13. Hybrid density functional calculations of the defect properties of ZnO:Rh and ZnO:Ir

    Energy Technology Data Exchange (ETDEWEB)

    Muñoz Ramo, David, E-mail: dm586@cam.ac.uk; Bristowe, Paul D., E-mail: pdb1000@cam.ac.uk

    2014-03-31

    We report density functional calculations of the atomic and electronic structure of the spinel phases ZnRh{sub 2}O{sub 4} and ZnIr{sub 2}O{sub 4} as well as crystalline ZnO lightly doped (1 at.%) with Rh and Ir ions using the B3LYP hybrid functional. Calculations for the spinels show band gaps (∼ 3 eV) and lattice parameters (∼ 2% difference) in reasonable agreement with experimental data. Incorporation of the transition metals into ZnO induces local distortions in the lattice and the appearance of metal d levels in the low gap region and near the conduction band minimum, with a d–d splitting of about 2 eV, which reduces the effective transparency of the material. Addition of a hole to the simulation cell of both spinels and doped ZnO leads to charge localization in the neighbourhood of Rh/Ir accompanied by local lattice deformations to form a small polaron which may lead to low hole mobility. We calculate polaron diffusion barriers in the spinels and obtain values around 0.02–0.03 eV. These very low barrier energies suggest that at high Rh/Ir concentrations polaron hopping is not going to be detected at room temperature. - Highlights: • Rh/Ir incorporation into ZnO at low doping induces local distortions in the lattice. • Localized levels appear in the gap of ZnO:Rh/ZnO:Ir near band edges. • Hole trapping is found in ZnO:Rh/ZnO:Ir and in the ZnRh{sub 2}O{sub 4}/ZnIr{sub 2}O{sub 4} spinels. • Hole diffusion barriers in the spinels are very small.

  14. Observation of lower defect density in CH{sub 3}NH{sub 3}Pb(I,Cl){sub 3} solar cells by admittance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Minlin; Lan, Fei; Tao, Quan; Li, Guangyong, E-mail: gaod@pitt.edu, E-mail: gul6@pitt.edu [Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Zhao, Bingxin [Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Key Laboratory of Advanced Functional Materials, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Wu, Jiamin; Gao, Di, E-mail: gaod@pitt.edu, E-mail: gul6@pitt.edu [Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

    2016-06-13

    The introduction of Cl into CH{sub 3}NH{sub 3}PbI{sub 3} precursors is reported to enhance the performance of CH{sub 3}NH{sub 3}PbI{sub 3} solar cell, which is attributed to the significantly increased diffusion lengths of carriers in CH{sub 3}NH{sub 3}Pb(I,Cl){sub 3} solar cell. It has been assumed but never experimentally approved that the defect density in CH{sub 3}NH{sub 3}Pb(I,Cl){sub 3} solar cell should be reduced according to the higher carrier lifetime observed from photoluminescence (PL) measurement. We have fabricated CH{sub 3}NH{sub 3}Pb(I,Cl){sub 3} solar cell by adding a small amount of Cl source into CH{sub 3}NH{sub 3}PbI{sub 3} precursor. The performance of CH{sub 3}NH{sub 3}Pb(I,Cl){sub 3} solar cell is significantly improved from 15.39% to 18.60%. Results from scanning electron microscopy and X-ray diffraction indicate that the morphologies and crystal structures of CH{sub 3}NH{sub 3}PbI{sub 3} and CH{sub 3}NH{sub 3}Pb(I,Cl){sub 3} thin films remain unchanged. Open circuit voltage decay and admittance spectroscopy characterization jointly approve that Cl plays an extremely important role in suppressing the formation of defects in perovskite solar cells.

  15. Simple benzene derivatives adsorption on defective single-walled carbon nanotubes: a first-principles van der Waals density functional study.

    Science.gov (United States)

    Ganji, Masoud Darvish; Mohseni, Maryam; Bakhshandeh, Anahita

    2013-03-01

    We have investigated the interaction between open-ended zig-zag single-walled carbon nanotube (SWCNT) and a few benzene derivatives using the first-principles van der Waals density functional (vdW-DF) method, involving full geometry optimization. Such sp (2)-like materials are typically investigated using conventional DFT methods, which significantly underestimate non-local dispersion forces (vdW interactions), therefore affecting interactions between respected molecules. Here, we considered the vdW forces for the interacting molecules that originate from the interacting π electrons of the two systems. The -0.54 eV adsorption energy reveals that the interaction of benzene with the side wall of the SWCNT is typical of the strong physisorption and comparable with the experimental value for benzene adsorption onto the graphene sheet. It was found that aromatics are physisorbed on the sidewall of perfect SWCNTs, as well as at the edge site of the defective nanotube. Analysis of the electronic structures shows that no orbital hybridization between aromatics and nanotubes occurs in the adsorption process. The results are relevant in order to identify the potential applications of noncovalent functionalized systems.

  16. High current density GaAs/Si rectifying heterojunction by defect free Epitaxial Lateral overgrowth on Tunnel Oxide from nano-seed

    Science.gov (United States)

    Renard, Charles; Molière, Timothée; Cherkashin, Nikolay; Alvarez, José; Vincent, Laetitia; Jaffré, Alexandre; Hallais, Géraldine; Connolly, James Patrick; Mencaraglia, Denis; Bouchier, Daniel

    2016-05-01

    Interest in the heteroepitaxy of GaAs on Si has never failed in the last years due to the potential for monolithic integration of GaAs-based devices with Si integrated circuits. But in spite of this effort, devices fabricated from them still use homo-epitaxy only. Here we present an epitaxial technique based on the epitaxial lateral overgrowth of micrometer scale GaAs crystals on a thin SiO2 layer from nanoscale Si seeds. This method permits the integration of high quality and defect-free crystalline GaAs on Si substrate and provides active GaAs/Si heterojunctions with efficient carrier transport through the thin SiO2 layer. The nucleation from small width openings avoids the emission of misfit dislocations and the formation of antiphase domains. With this method, we have experimentally demonstrated for the first time a monolithically integrated GaAs/Si diode with high current densities of 10 kA.cm‑2 for a forward bias of 3.7 V. This epitaxial technique paves the way to hybrid III–V/Si devices that are free from lattice-matching restrictions, and where silicon not only behaves as a substrate but also as an active medium.

  17. Reduced defect density at the CZTSSe/CdS interface by atomic layer deposition of Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Erkan, Mehmet Eray [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Chawla, Vardaan [AQT Solar, Inc., Sunnyvale, California 94086 (United States); Scarpulla, Michael A., E-mail: scarpulla@eng.utah.edu [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 (United States)

    2016-05-21

    The greatest challenge for improving the power conversion efficiency of Cu{sub 2}ZnSn(S,Se){sub 4} (CZTSSe)/CdS/ZnO thin film solar cells is increasing the open circuit voltage (V{sub OC}). Probable leading causes of the V{sub OC} deficit in state-of-the-art CZTSSe devices have been identified as bulk recombination, band tails, and the intertwined effects of CZTSSe/CdS band offset, interface defects, and interface recombination. In this work, we demonstrate the modification of the CZTSSe absorber/CdS buffer interface following the deposition of 1 nm-thick Al{sub 2}O{sub 3} layers by atomic layer deposition (ALD) near room temperature. Capacitance-voltage profiling and quantum efficiency measurements reveal that ALD-Al{sub 2}O{sub 3} interface modification reduces the density of acceptor-like states at the heterojunction resulting in reduced interface recombination and wider depletion width. Indications of increased V{sub OC} resulting from the modification of the heterojunction interface as a result of ALD-Al{sub 2}O{sub 3} treatment are presented. These results, while not conclusive for application to state-of-the-art high efficiency CZTSSe devices, suggest the need for further studies as it is probable that interface recombination contributes to reduced V{sub OC} even in such devices.

  18. Determination of the density of the defect states in Hf0.5Zr0.5O2 high-k film Deposited by using rf-magnetron sputtering technique

    Directory of Open Access Journals (Sweden)

    W. Lu

    2014-08-01

    Full Text Available A memory structure Pt/Al2O3/Hf0.5Zr0.5O2/Al2O3/p-Si was fabricated by using atomic layer deposition and rf-magnetron sputtering techniques, and its microstructure has been investigated by using the high resolution transmission electron microscopy (HRTEM. By measuring the applied gate voltage dependence of the capacitance for the memory structure, the planar density of the trapped charges in Hf0.5Zr0.5O2 high-k film was estimated as 6.63 × 1012 cm−2, indicating a body defect density of larger than 2.21 × 1019 cm−3. It is observed that the post-annealing in N2 can reduces the defect density in Hf0.5Zr0.5O2 film, which was ascribed to the occupancy of oxygen vacancies by nitrogen atoms.

  19. Elaboration of massive SiC monocrystals for power electronics. Reduction of the density of defects; Elaboration de monocristaux de SiC massifs pour l'electronique de puissance. Reduction de la densite de defauts

    Energy Technology Data Exchange (ETDEWEB)

    Moulin, C. [CEA Grenoble, LETI, 38 - Grenoble (France)

    2001-07-01

    This study deals with the elaboration of massive SiC monocrystals using a vapor-phase physical transport method. It treats more precisely of the reduction of the density of defects in SiC monocrystals. The method used allows to reach a substrate quality close to the specifications established for the different contracts. The obtention of substrates with larger diameters remains the main step to reach before the industrialization of the method. (J.S.)

  20. Birth Defects

    Science.gov (United States)

    A birth defect is a problem that happens while a baby is developing in the mother's body. Most birth defects happen during the first 3 months of ... in the United States is born with a birth defect. A birth defect may affect how the ...

  1. Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

    Science.gov (United States)

    Alnoor, Hatim; Pozina, Galia; Khranovskyy, Volodymyr; Liu, Xianjie; Iandolo, Donata; Willander, Magnus; Nur, Omer

    2016-04-01

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (˜575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.

  2. Analyzing topological defects in disordered charge density waves in transition-metal dichalcogenides TaSe2 and TaS2 using scanning tunneling microscopy

    Science.gov (United States)

    Schaper, Danielle; McElroy, Kyle; Calleja, Eduardo; Dai, Jixia; Li, Lijun; Lu, Wenjian; Sun, Yuping; Zhu, Xiangde

    2014-03-01

    Charged ordered states are becoming a common feature in the phase diagrams of correlated materials. In many cased there are indications that doping controlled quantum critical points between the CO state and others are related to interesting properties including superconductivity. An interesting test case is the ordered 2D CDW found in the transition metal dichalcogenides. We performed an analytical study on the dichalcogenides tantalum disulfide (TaS2) and tantalum diselenide (TaSe2) to observe how CDWs present in the material can be melted as disorder is introduced into the system via copper doping. Data was taken using a scanning tunneling microscope (STM) below the transition to the CDW state, both with and without copper dopants added. The resulting topographs were then analyzed to investigate the relationship between the phase and the amplitude of the disordered CDW. We found that the copper doping caused disorder in the CDW state characterized by phase wanderings and 2 π phase winding ``point defects'' in the CDW not present in the undoped parent compound. The locations of these point defects and windings were, in turn, found to have the characteristics of topological defects. Implications for studies of other disordered CO states seen in STM will be discussed.

  3. Contingent kernel density estimation.

    Directory of Open Access Journals (Sweden)

    Scott Fortmann-Roe

    Full Text Available Kernel density estimation is a widely used method for estimating a distribution based on a sample of points drawn from that distribution. Generally, in practice some form of error contaminates the sample of observed points. Such error can be the result of imprecise measurements or observation bias. Often this error is negligible and may be disregarded in analysis. In cases where the error is non-negligible, estimation methods should be adjusted to reduce resulting bias. Several modifications of kernel density estimation have been developed to address specific forms of errors. One form of error that has not yet been addressed is the case where observations are nominally placed at the centers of areas from which the points are assumed to have been drawn, where these areas are of varying sizes. In this scenario, the bias arises because the size of the error can vary among points and some subset of points can be known to have smaller error than another subset or the form of the error may change among points. This paper proposes a "contingent kernel density estimation" technique to address this form of error. This new technique adjusts the standard kernel on a point-by-point basis in an adaptive response to changing structure and magnitude of error. In this paper, equations for our contingent kernel technique are derived, the technique is validated using numerical simulations, and an example using the geographic locations of social networking users is worked to demonstrate the utility of the method.

  4. A study of the dependence of electron-induced defects on the doping impurity density in n-type germanium by deep-level transient spectroscopy (DLTS)

    Energy Technology Data Exchange (ETDEWEB)

    Nyamhere, Cloud [Department of Physics, Univeristy of Pretoria, Pretoria 0002 (South Africa)], E-mail: cloud.nyamhere@up.ac.za; Auret, F.D. [Department of Physics, Univeristy of Pretoria, Pretoria 0002 (South Africa); Das, A.G.M. [School of Information Technology, Monash South Africa, Roodepoort 1725 (South Africa); Chawanda, A. [Department of Physics, Univeristy of Pretoria, Pretoria 0002 (South Africa)

    2007-12-15

    We have measured the electrical characteristics of electron irradiation-induced defects in n-type (1 1 0), (1 1 1) and (1 0 0) germanium doped with antimony (Sb) by deep-level transient spectroscopy (DLTS) and Laplace-DLTS. The following electron traps at 0.04, 0.15, 0.20, 0.21, 0.23, 0.31 and 0.38 eV below the conduction band were observed and two hole traps at 0.09 and 0.30 eV above the valence band were recorded in the low doping (10{sup 14} cm{sup -3}) samples. In the higher doping (10{sup 15} cm{sup -3}) samples, similar electron traps were observed but the electron trap at 0.04 eV below the conduction band and hole trap at 0.09 eV above the valence band was not observed. The electron trap at 0.38 eV is identified as the (V-Sb){sup --/-} center and the hole trap at 0.30 eV assigned the (V-Sb){sup 0/-} appeared in almost equal concentrations in the higher-doped samples but in the lowest-doped samples the hole trap (V-Sb){sup 0/-} was more dominant. We have also presented the annealing behavior of these electron-induced defects.

  5. A study of the dependence of electron-induced defects on the doping impurity density in n-type germanium by deep-level transient spectroscopy (DLTS)

    Science.gov (United States)

    Nyamhere, Cloud; Auret, F. D.; Das, A. G. M.; Chawanda, A.

    2007-12-01

    We have measured the electrical characteristics of electron irradiation-induced defects in n-type (1 1 0), (1 1 1) and (1 0 0) germanium doped with antimony (Sb) by deep-level transient spectroscopy (DLTS) and Laplace-DLTS. The following electron traps at 0.04, 0.15, 0.20, 0.21, 0.23, 0.31 and 0.38 eV below the conduction band were observed and two hole traps at 0.09 and 0.30 eV above the valence band were recorded in the low doping (10 14 cm -3) samples. In the higher doping (10 15 cm -3) samples, similar electron traps were observed but the electron trap at 0.04 eV below the conduction band and hole trap at 0.09 eV above the valence band was not observed. The electron trap at 0.38 eV is identified as the (V-Sb) --/- center and the hole trap at 0.30 eV assigned the (V-Sb) 0/- appeared in almost equal concentrations in the higher-doped samples but in the lowest-doped samples the hole trap (V-Sb) 0/- was more dominant. We have also presented the annealing behavior of these electron-induced defects.

  6. Elaboration of massive silicon carbide monocrystals for power electronics applications. Reduction of the density of defects; Elaboration de monocristaux de carbure de silicium massifs pour l'electronique de puissance - reduction de la densite de defauts

    Energy Technology Data Exchange (ETDEWEB)

    Moulin, C. [CEA Grenoble, LETI, 38 - Grenoble (France)

    2001-07-01

    Thanks to its exceptional physical properties, SiC is a semiconductor material of prime importance for average and high power, high frequency and high temperature electronic applications. However, the SiC technology requires large diameter substrates (50 mm) with a density of micro-defects (micro-pipes or micro-tubes) lower than 10/cm{sup 2}. The present study deals with the reduction of the defects density in massive SiC crystals elaborated using a modified version of Lely's method. The method consists in the sublimation of a SiC powder and to the condensation of vapor species onto a SiC monocrystal germ. A thermal gradient is established between the powder and the germ which favors the transport of species from the powder to the germ. A study of the crystals characteristics and of the growth properties has permitted to identify the sensible parameters and to significantly improve the quality of the obtained crystals. Short note. (J.S.)

  7. Density of electronic states and dispersion of optical functions of defect chalcopyrite CdGa{sub 2}X{sub 4} (X = S, Se): DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H. [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Khan, Saleem Ayaz, E-mail: sayaz_usb@yahoo.com [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic)

    2013-11-15

    Graphical abstract: - Highlights: • FPLAPW method is used for calculating the electronic and optical properties of CdGa{sub 2}X{sub 4}. • Electronic and optical properties were calculated using LDA, GGA, EVGGA and mBJ. • Band gap conformed that CdGa{sub 2}X{sub 4} are semiconductors fit for UV and visible light. • The ECD shows that change in the bond length and bond nature affect the band gap. • The dielectric tensor components and its derivatives show considerable anisotropy. - Abstract: A density functional theory (DFT) based on full potential linear augmented plane wave (FPLAPW) was used for calculating the electronic structure, charge density and optical properties of CdGa{sub 2}X{sub 4} (X = S, Se) compounds. Local density approximation (LDA), generalized gradient approximation (GGA), Engle Vasko generalized gradient approximation (EVGGA) and recently modified Becke–Johnson (mBJ) were applied to calculate the band structure, total and partial density of states. The investigation of band structures and density of states of CdGa{sub 2}X{sub 4} (X = S, Se) elucidate that mBJ potential show close agreement to the experimental results. The mBJ potential was selected for further explanation of optical properties of CdGa{sub 2}X{sub 4} (X = S, Se). The study of electronic charge density contours shows that change in the bond lengths and bond nature affect the band gap of the compounds. The two non-zero dielectric tensor components and its derivatives show considerable anisotropy between the perpendicular and parallel components. The present work provide accurate information about the combination (hybridization) of orbital, formation of bands and dispersion of non-zero tensor components of CdGa{sub 2}X{sub 4} (X = S, Se)

  8. Paravaginal defect

    DEFF Research Database (Denmark)

    Arenholt, Louise T S; Pedersen, Bodil Ginnerup; Glavind, Karin;

    2016-01-01

    , arcus tendineus fascia pelvis (ATFP), pubocervical fascia, and uterosacral/cardinal ligaments. Studies conclude that physical examination is inconsistent in detecting paravaginal defects. Ultrasound (US) and magnetic resonance imaging (MRI) have been used to describe patterns in the appearance...

  9. Effects of nanoscale defects on critical current density of (Y{sub 1-x}Eu{sub x})Ba{sub 2}Cu{sub 3}O{sub 7-d}elta thin films

    Energy Technology Data Exchange (ETDEWEB)

    Goswami, R., E-mail: ramasis.goswami@nrl.navy.mi [US Naval Research Laboratory, Washington, DC 20375 (United States); Science Applications International Corporation (SAIC), Washington, DC 20375 (United States); Haugan, T.J.; Barnes, P.N. [Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433 (United States); Spanos, G.; Holtz, R.L. [US Naval Research Laboratory, Washington, DC 20375 (United States)

    2010-03-01

    In pulsed laser deposition of YBa{sub 2}Cu{sub 3}O{sub 7-d}elta films, defect introduction into the films tends to anisotropically improve the pinning along the H||c direction due to the columnar growth mode of the process. In Eu-substituted samples, however, even though an increase in critical current density (J{sub c}) in the H||c direction was observed for low fields (H = 0.2 T), the improvement was more notable for the H||ab-plane at both low and higher fields. Herein we present detailed TEM microstructural studies to understand these new trends in J{sub c}(H), which are markedly different than flux pinning increases achieved with other methods, for example, with nanoparticle additions. Threading dislocations, observed in the Eu-substituted samples along the c-axis, account for J{sub c} enhancement with H||c at low field. The enhanced ab-planar pinning in the Eu-substituted samples is attributed to the extensive bending of the left brace0 0 1right brace lattice planes throughout the film, and the crystal lattice defects with excess Cu-O planes, that were effective in increasing the J{sub c} for H||ab at both low and high fields.

  10. Defects and defect processes in nonmetallic solids

    CERN Document Server

    Hayes, W

    2004-01-01

    This extensive survey covers defects in nonmetals, emphasizing point defects and point-defect processes. It encompasses electronic, vibrational, and optical properties of defective solids, plus dislocations and grain boundaries. 1985 edition.

  11. Assessing EUV mask defectivity

    Science.gov (United States)

    Okoroanyanwu, Uzodinma; Tchikoulaeva, Anna; Ackmann, Paul; Wood, Obert; La Fontaine, Bruno; Bubke, Karsten; Holfeld, Christian; Peters, Jan Hendrik; Kini, Sumanth; Watson, Sterling; Lee, Isaac; Mu, Bo; Lim, Phillip; Raghunathan, Sudhar; Boye, Carol

    2010-04-01

    This paper assesses the readiness of EUV masks for pilot line production. The printability of well characterized reticle defects, with particular emphasis on those reticle defects that cause electrical errors on wafer test chips, is investigated. The reticles are equipped with test marks that are inspected in a die-to-die mode (using DUV inspection tool) and reviewed (using a SEM tool), and which also comprise electrically testable patterns. The reticles have three modules comprising features with 32 nm ground rules in 104 nm pitch, 22 nm ground rules with 80 nm pitch, and 16 nm ground rules with 56 nm pitch (on the wafer scale). In order to determine whether specific defects originate from the substrate, the multilayer film, the absorber stack, or from the patterning process, the reticles were inspected after each fabrication step. Following fabrication, the reticles were used to print wafers on a 0.25 NA full-field ASML EUV exposure tool. The printed wafers were inspected with state of the art bright-field and Deep UV inspection tools. It is observed that the printability of EUV mask defects down to a pitch of 56 nm shows a trend of increased printability as the pitch of the printed pattern gets smaller - a well established trend at larger pitches of 80 nm and 104 nm, respectively. The sensitivity of state-of-the-art reticle inspection tools is greatly improved over that of the previous generation of tools. There appears to be no apparent decline in the sensitivity of these state-of-the-art reticle inspection tools for higher density (smaller) patterns on the mask, even down to 56nm pitch (1x). Preliminary results indicate that a blank defect density of the order of 0.25 defects/cm2 can support very early learning on EUV pilot line production at the 16nm node.

  12. Simple intrinsic defects in InAs :

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter Andrew

    2013-03-01

    This Report presents numerical tables summarizing properties of intrinsic defects in indium arsenide, InAs, as computed by density functional theory using semi-local density functionals, intended for use as reference tables for a defect physics package in device models.

  13. Packing defects into ordered structures

    DEFF Research Database (Denmark)

    Bechstein, R.; Kristoffersen, Henrik Høgh; Vilhelmsen, L.B.

    2012-01-01

    We have studied vicinal TiO2(110) surfaces by high-resolution scanning tunneling microscopy and density functional theory calculations. On TiO2 surfaces characterized by a high density of ⟨11̅ 1⟩ steps, scanning tunneling microscopy reveals a high density of oxygen-deficient strandlike adstructur...... because building material is available at step sites. The strands on TiO2(110) represent point defects that are densely packed into ordered adstructures....

  14. Directed self-assembly defectivity assessment. Part II

    Science.gov (United States)

    Bencher, Chris; Yi, He; Zhou, Jessica; Cai, Manping; Smith, Jeffrey; Miao, Liyan; Montal, Ofir; Blitshtein, Shiran; Lavi, Alon; Dotan, Kfir; Dai, Huixiong; Cheng, Joy Y.; Sanders, Daniel P.; Tjio, Melia; Holmes, Steven

    2012-03-01

    The main concern for the commercialization of directed self-assembly (DSA) for semiconductor manufacturing continues to be the uncertainty in capability and control of defect density. Our research investigates the defect densities of various DSA process applications in the context of a 300mm wafer fab cleanroom environment; this paper expands substantially on the previously published DSA defectivity study by reporting a defect density process window relative to chemical epitaxial pre-pattern registration lines; as well as investigated DSA based contact hole shrinking and report critical dimension statistics for the phase separated polymers before and after etch, along with positional accuracy measurements and missing via defect density.

  15. Non-negligible Contributions to Thermal Conductivity From Localized Modes in Amorphous Silicon Dioxide

    Science.gov (United States)

    Lv, Wei; Henry, Asegun

    2016-10-01

    Thermal conductivity is important for almost all applications involving heat transfer. The theory and modeling of crystalline materials is in some sense a solved problem, where one can now calculate their thermal conductivity from first principles using expressions based on the phonon gas model (PGM). However, modeling of amorphous materials still has many open questions, because the PGM itself becomes questionable when one cannot rigorously define the phonon velocities. In this report, we used our recently developed Green-Kubo modal analysis (GKMA) method to study amorphous silicon dioxide (a-SiO2). The predicted thermal conductivities exhibit excellent agreement with experiments and anharmonic effects are included in the thermal conductivity calculation for all the modes in a-SiO2 for the first time. Previously, localized modes (locons) have been thought to have a negligible contribution to thermal conductivity, due to their highly localized nature. However, in a-SiO2 our results indicate that locons contribute more than 10% to the total thermal conductivity from 400 K to 800 K and they are largely responsible for the increase in thermal conductivity of a-SiO2 above room temperature. This is an effect that cannot be explained by previous methods and therefore offers new insight into the nature of phonon transport in amorphous/glassy materials.

  16. Electroosmotic fluid motion and late-time solute transport at non-negligible zeta potentials

    Energy Technology Data Exchange (ETDEWEB)

    S. K. Griffiths; R. H. Nilson

    1999-12-01

    Analytical and numerical methods are employed to determine the electric potential, fluid velocity and late-time solute distribution for electroosmotic flow in a tube and channel when the zeta potential is not small. The electric potential and fluid velocity are in general obtained by numerical means. In addition, new analytical solutions are presented for the velocity in a tube and channel in the extremes of large and small Debye layer thickness. The electroosmotic fluid velocity is used to analyze late-time transport of a neutral non-reacting solute. Zeroth and first-order solutions describing axial variation of the solute concentration are determined analytically. The resulting expressions contain eigenvalues representing the dispersion and skewness of the axial concentration profiles. These eigenvalues and the functions describing transverse variation of the concentration field are determined numerically using a shooting technique. Results are presented for both tube and channel geometries over a wide range of the normalized Debye layer thickness and zeta potential. Simple analytical approximations to the eigenvalues are also provided for the limiting cases of large and small values of the Debye layer thickness. The methodology developed here for electroosmotic flow is also applied to the Taylor problem of late-time transport and dispersion in pressure-driven flows.

  17. Revisiting the Logan plot to account for non-negligible blood volume in brain tissue

    National Research Council Canada - National Science Library

    Schain, Martin; Fazio, Patrik; Mrzljak, Ladislav; Amini, Nahid; Al-Tawil, Nabil; Fitzer-Attas, Cheryl; Bronzova, Juliana; Landwehrmeyer, Bernhard; Sampaio, Christina; Halldin, Christer; Varrone, Andrea

    2017-01-01

    .... The bias extent depends on the amount of radioactivity in the blood vessels. In this study, we seek to revisit the well-established Logan plot and derive alternative formulations that provide estimation of distribution volume ratios (DVRs...

  18. Non-negligible Contributions to Thermal Conductivity From Localized Modes in Amorphous Silicon Dioxide.

    Science.gov (United States)

    Lv, Wei; Henry, Asegun

    2016-10-21

    Thermal conductivity is important for almost all applications involving heat transfer. The theory and modeling of crystalline materials is in some sense a solved problem, where one can now calculate their thermal conductivity from first principles using expressions based on the phonon gas model (PGM). However, modeling of amorphous materials still has many open questions, because the PGM itself becomes questionable when one cannot rigorously define the phonon velocities. In this report, we used our recently developed Green-Kubo modal analysis (GKMA) method to study amorphous silicon dioxide (a-SiO2). The predicted thermal conductivities exhibit excellent agreement with experiments and anharmonic effects are included in the thermal conductivity calculation for all the modes in a-SiO2 for the first time. Previously, localized modes (locons) have been thought to have a negligible contribution to thermal conductivity, due to their highly localized nature. However, in a-SiO2 our results indicate that locons contribute more than 10% to the total thermal conductivity from 400 K to 800 K and they are largely responsible for the increase in thermal conductivity of a-SiO2 above room temperature. This is an effect that cannot be explained by previous methods and therefore offers new insight into the nature of phonon transport in amorphous/glassy materials.

  19. Painless causality in defect calculations

    CERN Document Server

    Cheung, C; Cheung, Charlotte; Magueijo, Joao

    1997-01-01

    Topological defects must respect causality, a statement leading to restrictive constraints on the power spectrum of the total cosmological perturbations they induce. Causality constraints have for long been known to require the presence of an under-density in the surrounding matter compensating the defect network on large scales. This so-called compensation can never be neglected and significantly complicates calculations in defect scenarios, eg. computing cosmic microwave background fluctuations. A quick and dirty way to implement the compensation are the so-called compensation fudge factors. Here we derive the complete photon-baryon-CDM backreaction effects in defect scenarios. The fudge factor comes out as an algebraic identity and so we drop the negative qualifier ``fudge''. The compensation scale is computed and physically interpreted. Secondary backreaction effects exist, and neglecting them constitutes the well-defined approximation scheme within which one should consider compensation factor calculatio...

  20. Experimental and numerical response of rigid slender blocks with geometrical defects under seismic excitation

    Directory of Open Access Journals (Sweden)

    Mathey Charlie

    2015-01-01

    Full Text Available The present work investigates on the influence of small geometrical defects on the behavior of slender rigid blocks. A comprehensive experimental campaign was carried out on one of the shake tables of CEA/Saclay in France. The tested model was a massive steel block with standard manufacturing quality. Release, free oscillations tests as well as shake table tests revealed a non-negligible out-of-plane motion even in the case of apparently plane initial conditions or excitations. This motion exhibits a highly reproducible part for a short duration that was used to calibrate a numerical geometrically asymmetrical model. The stability of this model when subjected to 2 000 artificial seismic horizontal bidirectional signals was compared to the stability of a symmetrical one. This study showed that the geometrical imperfections slightly increase the rocking and overturning probabilities under bidirectional seismic excitations in a narrow range of peak ground acceleration.

  1. Topological Defects in Liquid Crystal Films

    Institute of Scientific and Technical Information of China (English)

    DUAN Yi-Shi; ZHAO Li; ZHANG Xin-Hui; SI Tie-Yan

    2007-01-01

    A topological theory of liquid crystal films in the presence of defects is developed based on the φ-mapping topological current theory. By generalizing the free-energy density in "one-constant" approximation, a covariant freeenergy density is obtained, from which the U(1) gauge field and the unified topological current for monopoles and strings in liquid crystals are derived. The inner topological structure of these topological defects is characterized by the winding numbers of φ-mapping.

  2. Density of states controls Anderson localization in disordered photonic crystal waveguides

    DEFF Research Database (Denmark)

    Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren

    2010-01-01

    -of-plane losses are non-negligible, ℓe can be approximated to be the localization length ξ. The extinction mean-free path shows a fivefold variation between the low- and the high-DOS regime, and it becomes shorter than the sample length thus giving rise to strongly confined modes. The dispersive behavior of ℓe......We prove Anderson localization in a disordered photonic crystal waveguide by measuring the ensemble-averaged extinction mean-free path, ℓe, which is controlled by the dispersion in the photon density of states (DOS) of the photonic crystal waveguide. Except for the very low DOS case, where out...

  3. Topological defects from the multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jun [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Blanco-Pillado, Jose J. [Department of Theoretical Physics, University of the Basque Country UPV/EHU, 48080 Bilbao (Spain); IKERBASQUE, Basque Foundation for Science, 48013, Bilbao (Spain); Garriga, Jaume [Departament de Fisica Fonamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, 08028, Barcelona (Spain); Vilenkin, Alexander [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)

    2015-05-28

    Many theories of the early universe predict the existence of a multiverse where bubbles continuously nucleate giving rise to observers in their interior. In this paper, we point out that topological defects of several dimensionalities will also be produced in de Sitter like regions of the multiverse. In particular, defects could be spontaneously nucleated in our parent vacuum. We study the evolution of these defects as they collide with and propagate inside of our bubble. We estimate the present distribution of defects in the observable part of the universe. The expected number of such nearby defects turns out to be quite small, even for the highest nucleation rate. We also study collisions of strings and domain walls with our bubble in our past light cone. We obtain simulated full-sky maps of the loci of such collisions, and find their angular size distribution. Similarly to what happens in the case of bubble collisions, the prospect of detecting any collisions of our bubble with ambient defects is greatly enhanced in the case where the cosmological constant of our parent vacuum is much higher than the vacuum energy density during inflation in our bubble.

  4. Topological defects from the multiverse

    Science.gov (United States)

    Zhang, Jun; Blanco-Pillado, Jose J.; Garriga, Jaume; Vilenkin, Alexander

    2015-05-01

    Many theories of the early universe predict the existence of a multiverse where bubbles continuously nucleate giving rise to observers in their interior. In this paper, we point out that topological defects of several dimensionalities will also be produced in de Sitter like regions of the multiverse. In particular, defects could be spontaneously nucleated in our parent vacuum. We study the evolution of these defects as they collide with and propagate inside of our bubble. We estimate the present distribution of defects in the observable part of the universe. The expected number of such nearby defects turns out to be quite small, even for the highest nucleation rate. We also study collisions of strings and domain walls with our bubble in our past light cone. We obtain simulated full-sky maps of the loci of such collisions, and find their angular size distribution. Similarly to what happens in the case of bubble collisions, the prospect of detecting any collisions of our bubble with ambient defects is greatly enhanced in the case where the cosmological constant of our parent vacuum is much higher than the vacuum energy density during inflation in our bubble.

  5. Ventricular septal defect (image)

    Science.gov (United States)

    Ventricular septal defect is a congenital defect of the heart, that occurs as an abnormal opening in ... wall that separates the right and left ventricles. Ventricular septal defect may also be associated with other ...

  6. Facts about Birth Defects

    Science.gov (United States)

    ... Button Information For… Media Policy Makers Facts about Birth Defects Language: English (US) Español (Spanish) Recommend ... having a baby born without a birth defect. Birth Defects Are Common Every 4 ½ minutes, a ...

  7. Neural Tube Defects

    Science.gov (United States)

    Neural tube defects are birth defects of the brain, spine, or spinal cord. They happen in the ... that she is pregnant. The two most common neural tube defects are spina bifida and anencephaly. In ...

  8. Using Defects in Materials to Store Energy: a Theoretical Study

    Science.gov (United States)

    Lu, I.-Te; Bernardi, Marco

    We study the energy stored by defects in materials using density functional theory (DFT) calculations. Leveraging experimental data to estimate the energy density of defects, expressed as the defect formation energy per unit volume (units of MJ/L) or weight (units of MJ/kg), we identify candidates for high energy density storage, including tungsten, diamond, graphite, silicon, and graphene. DFT calculations are applied to these materials to study the formation energy of vacancies, interstitials, and Frenkel pairs. Our results indicate that the energy density stored by defects in these materials, with experimentally accessible non-equilibrium defect concentrations, can be higher than that of common energy storage technologies such as lithium batteries and supercapacitors. We discuss storage of solar energy and electrical energy (through ion bombardment) using defects.

  9. Inspection of directed self-assembly defects

    Science.gov (United States)

    Ito, Chikashi; Durant, Stephane; Lange, Steve; Harukawa, Ryota; Miyagi, Takemasa; Nagaswami, Venkat; Rincon Delgadillo, Paulina; Gronheid, Roel; Nealey, Paul

    2014-03-01

    Directed Self-Assembly (DSA) is considered as a potential patterning solution for future generation devices. One of the most critical challenges for translating DSA into high volume manufacturing is to achieve low defect density in the DSA patterning process. The defect inspection capability is fundamental to defect reduction in any process, particularly the DSA process, as it provides engineers with information on the numbers and types of defects. While the challenges of other candidates of new generation lithography are well known (for example, smaller size, noise level due to LER etc.), the DSA process causes certain defects that are unique. These defects are nearly planar and in a material which produces very little defect scattering signal. These defects, termed as "dislocation" and "disclination" have unique shapes and have very little material contrast. While large clusters of these unique defects are easy to detect, single dislocation and disclination defects offer considerable challenge during inspection. In this investigation, etching the DSA pattern into a silicon (Si) substrate structure to enhance defect signal and Signal-to-Noise Ratio (SNR) is studied. We used a Rigorous Coupled-Wave Analysis (RCWA) method for solving Maxwell's equations to simulate the DSA unique defects and calculate inspection parameters. Controllable inspection parameters include various illumination and collection apertures, wavelength band, polarization, noise filtering, focus, pixel size, and signal processing. From the RCWA simulation, we compared SNR between "Post-SiN etch" and "Post-SiN+Si-substrate etch" steps. The study is also extended to investigate wafer-level data at post etch inspection. Both the simulations and inspection tool results showed dramatic signal and SNR improvements when the pattern was etched into the SiN+Si substrate allowing capture of DSA unique defect types.

  10. Defect and functionalized graphene for supercapacitor electrodes

    Science.gov (United States)

    Taluja, Yogita; SanthiBhushan, Boddepalli; Yadav, Shekhar; Srivastava, Anurag

    2016-10-01

    The structural, electronic and transport properties of defected (single vacancy and double vacancy) and nitrogen functionalized graphene sheets have been analysed within the framework of Density Functional Theory (DFT) and non-equilibrium Green's function (NEGF) formalism for their possible application as supercapacitor electrodes. Formation energy calculations reveal the increasing stability of defect with nitrogen functional doping concentration at its edges. The extracted electronic properties reveal the presence of acceptor-type energy levels at Fermi level in the defected and functionalized sheets. Transport studies portray remarkable increase in electrical conductivity of graphene sheet after the formation of single vacancy defect and its functionalization. Especially, the Single Vacancy Trimerized pyridine-type defect (SVT) configuration has demonstrated superior thermodynamic stability as well as electrical conductance in comparison to all the other configurations.

  11. Congenital platelet function defects

    Science.gov (United States)

    ... storage pool disorder; Glanzmann's thrombasthenia; Bernard-Soulier syndrome; Platelet function defects - congenital ... Congenital platelet function defects are bleeding disorders that ... function, even though there are normal platelet numbers. Most ...

  12. Birth Defects: Cerebral Palsy

    Science.gov (United States)

    ... defects, premature birth and infant mortality. Solving premature birth Featured articles Accomplishments and lessons learned since the ... and pregnancy Folic acid Medicine safety and pregnancy Birth defects prevention Learn how to help reduce your ...

  13. Atrioventricular Canal Defect

    Science.gov (United States)

    ... doctor See your doctor if you or your child develops signs or symptoms of atrioventricular canal defect. Atrioventricular canal defect occurs before birth when a baby's heart is developing. Some factors, such as Down syndrome, might increase the risk of atrioventricular canal defect. ...

  14. Defect production in ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J. [Oak Ridge National Lab., TN (United States); Kinoshita, C. [Kyushu Univ. (Japan)

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  15. Oxygen defect processes in silicon and silicon germanium

    KAUST Repository

    Chroneos, A.

    2015-06-18

    Silicon and silicon germanium are the archetypical elemental and alloy semiconductor materials for nanoelectronic, sensor, and photovoltaic applications. The investigation of radiation induced defects involving oxygen, carbon, and intrinsic defects is important for the improvement of devices as these defects can have a deleterious impact on the properties of silicon and silicon germanium. In the present review, we mainly focus on oxygen-related defects and the impact of isovalent doping on their properties in silicon and silicon germanium. The efficacy of the isovalent doping strategies to constrain the oxygen-related defects is discussed in view of recent infrared spectroscopy and density functional theory studies.

  16. Oxygen defect processes in silicon and silicon germanium

    Energy Technology Data Exchange (ETDEWEB)

    Chroneos, A., E-mail: alexander.chroneos@imperial.ac.uk [Faculty of Engineering and Computing, Coventry University, Priory Street, Coventry CV1 5FB (United Kingdom); Department of Materials, Imperial College London, London SW7 2BP (United Kingdom); Sgourou, E. N.; Londos, C. A. [Solid State Section, Physics Department, University of Athens, Panepistimiopolis, Zografos, 157 84 Athens (Greece); Schwingenschlögl, U. [PSE Division, KAUST, Thuwal 23955-6900 (Saudi Arabia)

    2015-06-15

    Silicon and silicon germanium are the archetypical elemental and alloy semiconductor materials for nanoelectronic, sensor, and photovoltaic applications. The investigation of radiation induced defects involving oxygen, carbon, and intrinsic defects is important for the improvement of devices as these defects can have a deleterious impact on the properties of silicon and silicon germanium. In the present review, we mainly focus on oxygen-related defects and the impact of isovalent doping on their properties in silicon and silicon germanium. The efficacy of the isovalent doping strategies to constrain the oxygen-related defects is discussed in view of recent infrared spectroscopy and density functional theory studies.

  17. First principles studies of extrinsic and intrinsic defects in boron nitride nanotubes

    CSIR Research Space (South Africa)

    Mashapa, MG

    2012-10-01

    Full Text Available Spin polarized density functional theory has been used to investigate the structural stability and electronic properties of extrinsic and intrinsic defects in boron nitride nanotubes. Carbon substitutional defects under nitrogen rich and boron...

  18. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel.

    Science.gov (United States)

    Gilbert, C A; Smith, R; Kenny, S D; Murphy, S T; Grimes, R W; Ball, J A

    2009-07-08

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters.

  19. Coulomb screening in graphene with topological defects

    Science.gov (United States)

    Chakraborty, Baishali; Gupta, Kumar S.; Sen, Siddhartha

    2015-06-01

    We analyze the screening of an external Coulomb charge in gapless graphene cone, which is taken as a prototype of a topological defect. In the subcritical regime, the induced charge is calculated using both the Green's function and the Friedel sum rule. The dependence of the polarization charge on the Coulomb strength obtained from the Green's function clearly shows the effect of the conical defect and indicates that the critical charge itself depends on the sample topology. Similar analysis using the Friedel sum rule indicates that the two results agree for low values of the Coulomb charge but differ for the higher strengths, especially in the presence of the conical defect. For a given subcritical charge, the transport cross-section has a higher value in the presence of the conical defect. In the supercritical regime we show that the coefficient of the power law tail of polarization charge density can be expressed as a summation of functions which vary log periodically with the distance from the Coulomb impurity. The period of variation depends on the conical defect. In the presence of the conical defect, the Fano resonances begin to appear in the transport cross-section for a lower value of the Coulomb charge. For both sub and supercritical regime we derive the dependence of LDOS on the conical defect. The effects of generalized boundary condition on the physical observables are also discussed.

  20. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua

    2015-02-19

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm \\'2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  1. CAD/CAM技术辅助下使用Medpor®精确修复下颌轮廓凹陷%Using computer-aided design and manufacture (CAD/CAM) techniques to accurately reconstruct defects of mandibular con-tour with high-density porous polyethylene(Medpor®)

    Institute of Scientific and Technical Information of China (English)

    张轶群; 章臻; 胡静; 李翔; 李蔚; 李继华

    2016-01-01

    Objective To report a semi-digital technique to get an optimal fitting custom-made high-density porous polyethylene ( Medpor) for reconstruction of mandibular contour defects with the help of CAD/CAM and reverse engineering technology. Methods 17 patients suffering from defects of mandibular contour registered for the novel techniques to reconstruct the mandibular contour. For each patient, computed tomography ( CT) data were collected, CAD/CAM, reverse engineering and rapid prototyping ( RP) by three-dimensional (3D) printing were used to fabricate the preoperative individualized geometric model. The mandibular contour defected ar-eas were reconstructed by modeling and implanting Medpor. Results All cases, except one with delayed infection whose implantation material was removed later on, recovered quite well. The follow-up observation showed that the previous defect zones had been accu-rately reconstructed, and a symmetric bony contour as well as an appealing facial appearance was acquired. Conclusion Individual-ized Medpor implant based on CAD/CAM can accurately reconstruct defect of mandibular contour.%目的:报导一种通过个体化Medpor®来重塑下颌骨轮廓的方法,评价其治疗效果并讨论适应证。方法选取四川大学华西口腔医院下颌骨轮廓凹陷病例17例,采集其CT数据,运用CAD/CAM、镜像反求、快速成型及3D打印技术设计并精确制作出手术模板,雕刻塑形出个性化Medpor®,并指导准确植入体内,修复下颌凹陷畸形。结果除1例植入体因迟发性感染取出外,其余患者恢复良好,复查定位照相对比示:患者下颌轮廓凹陷均得到较好修复,对称性得到明显改善,医患均对手术效果感到满意。结论在CAD/CAM技术辅助下,运用Medpor®可以精确修复下颌骨轮廓凹陷,是一种值得推广的方法。

  2. Defects in semiconductors

    CERN Document Server

    Romano, Lucia; Jagadish, Chennupati

    2015-01-01

    This volume, number 91 in the Semiconductor and Semimetals series, focuses on defects in semiconductors. Defects in semiconductors help to explain several phenomena, from diffusion to getter, and to draw theories on materials' behavior in response to electrical or mechanical fields. The volume includes chapters focusing specifically on electron and proton irradiation of silicon, point defects in zinc oxide and gallium nitride, ion implantation defects and shallow junctions in silicon and germanium, and much more. It will help support students and scientists in their experimental and theoret

  3. Imaging defects and dopants

    Directory of Open Access Journals (Sweden)

    H.Philipp Ebert

    2003-06-01

    With the invention of the transistor, a revolution in the development of semiconductor-based electronic devices began. However, even in the very early stages, the importance of defects and dopant atoms became obvious. In fact, if one incorporates the right defects and dopant atoms into semiconductor materials, one can tune their electrical properties such that optimal device characteristics are achieved. Unfortunately, counteractive defects are often also formed unintentionally during semiconductor processing, leading to unfavorable electronic properties. Considerable research efforts have, therefore, focused on understanding the nanoscale physics that governs the formation of point defects, the incorporation behavior of impurities, and their respective electronic properties.

  4. A Constraint on Defect and Boundary Renormalization Group Flows

    CERN Document Server

    Jensen, Kristan

    2015-01-01

    A conformal field theory (CFT) in dimension $d\\geq 3$ coupled to a planar, two-dimensional, conformal defect is characterized in part by a "central charge" $b$ that multiplies the Euler density in the defect's Weyl anomaly. For defect renormalization group flows, under which the bulk remains critical, we use reflection positivity to show that $b$ must decrease or remain constant from ultraviolet to infrared. Our result applies also to a CFT in $d=3$ flat space with a planar boundary.

  5. Constraint on Defect and Boundary Renormalization Group Flows.

    Science.gov (United States)

    Jensen, Kristan; O'Bannon, Andy

    2016-03-04

    A conformal field theory (CFT) in dimension d≥3 coupled to a planar, two-dimensional, conformal defect is characterized in part by a "central charge" b that multiplies the Euler density in the defect's Weyl anomaly. For defect renormalization group flows, under which the bulk remains critical, we use reflection positivity to show that b must decrease or remain constant from the ultraviolet to the infrared. Our result applies also to a CFT in d=3 flat space with a planar boundary.

  6. Point defect reduction in wide bandgap semiconductors by defect quasi Fermi level control

    Science.gov (United States)

    Reddy, P.; Hoffmann, M. P.; Kaess, F.; Bryan, Z.; Bryan, I.; Bobea, M.; Klump, A.; Tweedie, J.; Kirste, R.; Mita, S.; Gerhold, M.; Collazo, R.; Sitar, Z.

    2016-11-01

    A theoretical framework for a general approach to reduce point defect density in materials via control of defect quasi Fermi level (dQFL) is presented. The control of dQFL is achieved via excess minority carrier generation. General guidelines for controlling dQFL that lead to a significant reduction in compensating point defects in any doped material is proposed. The framework introduces and incorporates the effects of various factors that control the efficacy of the defect reduction process such as defect level, defect formation energy, bandgap, and excess minority carrier density. Modified formation energy diagrams are proposed, which illustrate the effect of the quasi Fermi level control on the defect formation energies. These formation energy diagrams provide powerful tools to determine the feasibility and requirements to produce the desired reduction in specified point defects. An experimental study of the effect of excess minority carriers on point defect incorporation in GaN and AlGaN shows an excellent quantitative agreement with the theoretical predictions. Illumination at energies larger than the bandgap is employed as a means to generate excess minority carriers. The case studies with CN in Si doped GaN, H and VN in Mg doped GaN and VM-2ON in Si doped Al0.65Ga0.35N revealed a significant reduction in impurities in agreement with the proposed theory. Since compensating point defects control the material performance (this is particularly challenging in wide and ultra wide bandgap materials), dQFL control is a highly promising technique with wide scope and may be utilized to improve the properties of various materials systems and performance of devices based upon them.

  7. Photonic crystals with topological defects

    Science.gov (United States)

    Liew, Seng Fatt; Knitter, Sebastian; Xiong, Wen; Cao, Hui

    2015-02-01

    We introduce topological defects to a square lattice of elliptical cylinders. Despite the broken translational symmetry, the long-range positional order of the cylinders leads to a residual photonic band gap in the local density of optical states. However, the band-edge modes are strongly modified by the spatial variation of the ellipse orientation. The Γ -X band-edge mode splits into four regions of high intensity and the output flux becomes asymmetric due to the formation of crystalline domains with different orientation. The Γ -M band-edge mode has the energy flux circulating around the topological defect center, creating an optical vortex. By removing the elliptical cylinders at the center, we create localized defect states, which are dominated by either clockwise or counterclockwise circulating waves. The flow direction can be switched by changing the ellipse orientation. The deterministic aperiodic variation of the unit cell orientation adds another dimension to the control of light in photonic crystals, enabling the creation of a diversified field pattern and energy flow landscape.

  8. Defect complexes in carbon and boron nitride nanotubes

    CSIR Research Space (South Africa)

    Mashapa, MG

    2012-05-01

    Full Text Available The effect of defect complexes on the stability, structural and electronic properties of single-walled carbon nanotubes and boron nitride nanotubes is investigated using the ab initio pseudopotential density functional method implemented...

  9. Defects in Human Nature

    Institute of Scientific and Technical Information of China (English)

    黄靓

    2008-01-01

    By tracing the defects of society back to the defects of human nature, humanity's essence is proved to be inherent evil. Man's natural tendency to do evil remain harnessed through the controls and conventions imposed by civilization, however, when rules or civilization are weakened, man' s dark side is unleashed.

  10. Birth Defects (For Parents)

    Science.gov (United States)

    ... this virus during pregnancy, her child may have low birth weight, intellectual disability (mental retardation) or learning disabilities, ... and central nervous system problems. A child with late congenital syphilis may have abnormalities of the ... Diagnosing Birth Defects Many birth defects are diagnosed even before ...

  11. Defects at oxide surfaces

    CERN Document Server

    Thornton, Geoff

    2015-01-01

    This book presents the basics and characterization of defects at oxide surfaces. It provides a state-of-the-art review of the field, containing information to the various types of surface defects, describes analytical methods to study defects, their chemical activity and the catalytic reactivity of oxides. Numerical simulations of defective structures complete the picture developed. Defects on planar surfaces form the focus of much of the book, although the investigation of powder samples also form an important part. The experimental study of planar surfaces opens the possibility of applying the large armoury of techniques that have been developed over the last half-century to study surfaces in ultra-high vacuum. This enables the acquisition of atomic level data under well-controlled conditions, providing a stringent test of theoretical methods. The latter can then be more reliably applied to systems such as nanoparticles for which accurate methods of characterization of structure and electronic properties ha...

  12. Cosmic defects and cosmology

    CERN Document Server

    Magueijo, J; Magueijo, Joao; Brandenberger, Robert

    2000-01-01

    We provide a pedagogical overview of defect models of structure formation. We first introduce the concept of topological defect, and describe how to classify them. We then show how defects might be produced in phase transitions in the Early Universe and approach non-pathological scaling solutions. A very heuristic account of structure formation with defects is then provided, following which we introduce the tool box required for high precision calculations of CMB and LSS power spectra in these theories. The decomposition into scalar vector and tensor modes is reviewed, and then we introduce the concept of unequal-time correlator. We use isotropy and causality to constrain the form of these correlators. We finally show how these correlators may be decomposed into eigenmodes, thereby reducing a defect problem to a series of ``inflation'' problems. We conclude with a short description of results in these theories and how they fare against observations. We finally describe yet another application of topological d...

  13. Spatial and frequency domain effects of defects in 1D photonic crystal

    CERN Document Server

    Rudziński, A; Szczepański, P; 10.1007/s11082-007-9095-3

    2009-01-01

    The aim of this paper is to present the analysis of influence of defects in 1D photonic crystal (PC) on the density of states and simultaneously spontaneous emission, in both spatial and frequency domains. In our investigations we use an analytic model of 1D PC with defects. Our analysis reveals how presence of a defect causes a defect mode to appear. We show that a defect in 1D PC has local character, being negligible in regions of PC situated far from the defected elementary cell. We also analyze the effect of multiple defects, which lead to photonic band gap splitting.

  14. Exploring pentagon-heptagon pair defects in the triangular graphene quantum dots: A computational study

    Energy Technology Data Exchange (ETDEWEB)

    Ghafouri, Reza, E-mail: reghafouri@gmail.com

    2016-06-01

    We have applied density functional calculations to investigate Stone Wales (SW) and carbon ad-dimer (CD) defect formation in triangular graphene quantum dots (GQDs). According to our results, defect formation energies depend on the positions of SW defects, such that the rotation of the C−C bond located near the vertex of triangular GQD is easier than the rotation of other C−C bonds. Therefore, the multiply defective GQDs with isolated SW defect sites are the most favorable while the formation of pentalene like structures in the connected SW defect sites costs larger formation energies. Introducing of carbon dimer defects on a triangular GQD induces a curvature at the defective sites, which leads to a more complex defect configuration with cone-like structure in the CD defective GQD with three defective sites. Then, formation energies for CD defective GQDs are higher than those for SW defective ones. The electrophilicity values calculated for SW and CD defective GQDs are greater than those for pristine GQDs. Moreover, perturbation of strong sp{sup 2} bonding network of graphitic carbons on the GQD, leading to the formation of more localized C−C bonds, results in further electron deficiency of multiply SW and CD defective GQDs with increasing of electrophilicity values. - Highlights: • Defect formation energy depends on positions of SW defects. • Defective GQDs with isolated SW defects are the most favorable. • Introducing of CD defects induces a curvature leading to cone-like structure. • Defect formation energies for CD defective GQDs are higher than those for SW ones. • Electrophilicity: CD defective GQDs > SW defective GQDs > perfect GQDs.

  15. Reduction in Defect Content of ODS Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ritherdon, J

    2001-05-15

    The work detailed within this report is a continuation of earlier work carried out under contract number 1DX-SY382V. The earlier work comprises a literature review of the sources and types of defects found principally in Fe-based ODS alloys as well as experimental work designed to identify defects in the prototype ODS-Fe{sub 3}Al alloy, deduce their origins and to recommend methods of defect reduction. The present work is an extension of the experimental work already reported and concentrates on means of reduction of defects already identified rather than the search for new defect types. This report also includes results gathered during powder separation trials, conducted by the University of Groningen, Netherlands and coordinated by the University of Liverpool, involving the separation of different metallic powders in terms of their differing densities. The scope and objectives of the present work were laid out in the technical proposal ''Reduction in Defect Content in ODS Alloys-III''. All the work proposed in the ''Statement of Work'' section of the technical proposal has been carried out and all work extra to the ''Statement of Work'' falls within the context of an ODS-Fe{sub 3}Al alloy of improved overall quality and potential creep performance in the consolidated form. The outturn of the experimental work performed is reported in the following sections.

  16. Diabetes mellitus and birth defects

    Science.gov (United States)

    Correa, Adolfo; Gilboa, Suzanne M.; Besser, Lilah M.; Botto, Lorenzo D.; Moore, Cynthia A.; Hobbs, Charlotte A.; Cleves, Mario A.; Riehle-Colarusso, Tiffany J.; Waller, D. Kim; Reece, E. Albert

    2016-01-01

    OBJECTIVE The purpose of this study was to examine associations between diabetes mellitus and 39 birth defects. STUDY DESIGN This was a multicenter case-control study of mothers of infants who were born with (n = 13,030) and without (n = 4895) birth defects in the National Birth Defects Prevention Study (1997–2003). RESULTS Pregestational diabetes mellitus (PGDM) was associated significantly with noncardiac defects (isolated, 7/23 defects; multiples, 13/23 defects) and cardiac defects (isolated, 11/16 defects; multiples, 8/16 defects). Adjusted odds ratios for PGDM and all isolated and multiple defects were 3.17 (95% CI, 2.20–4.99) and 8.62 (95% CI, 5.27–14.10), respectively. Gestational diabetes mellitus (GDM) was associated with fewer noncardiac defects (isolated, 3/23 defects; multiples, 3/23 defects) and cardiac defects (isolated, 3/16 defects; multiples, 2/16 defects). Odds ratios between GDM and all isolated and multiple defects were 1.42 (95% CI, 1.17–1.73) and 1.50 (95% CI, 1.13–2.00), respectively. These associations were limited generally to offspring of women with prepregnancy body mass index ≥25 kg/m2. CONCLUSION PGDM was associated with a wide range of birth defects; GDM was associated with a limited group of birth defects. PMID:18674752

  17. Intrinsic Defects and H Doping in WO3

    Science.gov (United States)

    Zhu, Jiajie; Vasilopoulou, Maria; Davazoglou, Dimitris; Kennou, Stella; Chroneos, Alexander; Schwingenschlögl, Udo

    2017-01-01

    WO3 is widely used as industrial catalyst. Intrinsic and/or extrinsic defects can tune the electronic properties and extend applications to gas sensors and optoelectonics. However, H doping is a challenge to WO3, the relevant mechanisms being hardly understood. In this context, we investigate intrinsic defects and H doping by density functional theory and experiments. Formation energies are calculated to determine the lowest energy defect states. O vacancies turn out to be stable in O-poor environment, in agreement with X-ray photoelectron spectroscopy, and O-H bond formation of H interstitial defects is predicted and confirmed by Fourier transform infrared spectroscopy. PMID:28098210

  18. Defect-induced loading of Pt nanoparticles on carbon nanotubes

    Science.gov (United States)

    Kim, Sung Jin; Park, Yong Jin; Ra, Eun Ju; Kim, Ki Kang; An, Kay Hyeok; Lee, Young Hee; Choi, Jae Young; Park, Chan Ho; Doo, Seok Kwang; Park, Min Ho; Yang, Cheol Woong

    2007-01-01

    Carbon nanotubes-supported Pt nanoparticles were loaded using a microwave oven on the defective carbon nanotubes generated by an additional oxidant during acid treatment. The authors' Raman spectra and x-ray diffraction analysis demonstrated that defects created during oxidation and microwave treatment acted as nucleation seeds for Pt adsorption. The generated Pt nanoparticles had the size distributions of 2-3nm and were uniformly distributed on the defects of carbon nanotubes. The authors' density functional calculations showed that the adsorption of Pt atom on the vacancy of nanotube was significantly stronger by s-p hybridization with carbon atoms near the defect site.

  19. Intrinsic Defects and H Doping in WO3

    KAUST Repository

    Zhu, Jiajie

    2017-01-18

    WO3 is widely used as industrial catalyst. Intrinsic and/or extrinsic defects can tune the electronic properties and extend applications to gas sensors and optoelectonics. However, H doping is a challenge to WO3, the relevant mechanisms being hardly understood. In this context, we investigate intrinsic defects and H doping by density functional theory and experiments. Formation energies are calculated to determine the lowest energy defect states. O vacancies turn out to be stable in O-poor environment, in agreement with X-ray photoelectron spectroscopy, and O-H bond formation of H interstitial defects is predicted and confirmed by Fourier transform infrared spectroscopy.

  20. A computational framework for automation of point defect calculations

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, Anuj; Gorai, Prashun; Peng, Haowei; Lany, Stephan; Stevanović, Vladan

    2017-04-01

    A complete and rigorously validated open-source Python framework to automate point defect calculations using density functional theory has been developed. The framework provides an effective and efficient method for defect structure generation, and creation of simple yet customizable workflows to analyze defect calculations. The package provides the capability to compute widely-accepted correction schemes to overcome finite-size effects, including (1) potential alignment, (2) image-charge correction, and (3) band filling correction to shallow defects. Using Si, ZnO and In2O3 as test examples, we demonstrate the package capabilities and validate the methodology.

  1. Intrinsic Defects and H Doping in WO3

    Science.gov (United States)

    Zhu, Jiajie; Vasilopoulou, Maria; Davazoglou, Dimitris; Kennou, Stella; Chroneos, Alexander; Schwingenschlögl, Udo

    2017-01-01

    WO3 is widely used as industrial catalyst. Intrinsic and/or extrinsic defects can tune the electronic properties and extend applications to gas sensors and optoelectonics. However, H doping is a challenge to WO3, the relevant mechanisms being hardly understood. In this context, we investigate intrinsic defects and H doping by density functional theory and experiments. Formation energies are calculated to determine the lowest energy defect states. O vacancies turn out to be stable in O-poor environment, in agreement with X-ray photoelectron spectroscopy, and O-H bond formation of H interstitial defects is predicted and confirmed by Fourier transform infrared spectroscopy.

  2. Defects and oxidation resilience in InSe

    Science.gov (United States)

    Xiao, K. J.; Carvalho, A.; Castro Neto, A. H.

    2017-08-01

    We use density functional theory to study intrinsic defects and oxygen related defects in indium selenide. We find that InSe is prone to oxidation, but however not reacting with oxygen as strongly as phosphorene. The dominant intrinsic defects in In-rich material are the In interstitial, a shallow donor, and the Se vacancy, which introduces deep traps. The latter can be passivated by oxygen, which is isoelectronic with Se. The dominant intrinsic defects in Se-rich material have comparatively higher formation energies.

  3. Defects and diffusion in semiconductors XIV

    CERN Document Server

    Fisher, David J

    2012-01-01

    This 14th volume in the series covers the latest results in the field of Defects and Diffusion in Semiconductor. The issue also includes some original papers: An Experimental Study of the Thermal Properties of Modified 9Cr-1Mo Steel; Physico-Mechanical Properties of Sintered Iron-Silica Sand Nanoparticle Composites: A Preliminary Study; Defect and Dislocation Density Parameters of 5251 Al Alloy Using Positron Annihilation Lifetime Technique; A Novel Computational Strategy to Enhance the Ability of Elaborate Search by Entire Swarm to Find the Best Solution in Optimization of AMCs; Synthesis and

  4. What Are Neural Tube Defects?

    Science.gov (United States)

    ... NICHD Research Information Clinical Trials Resources and Publications Neural Tube Defects (NTDs): Condition Information Skip sharing on social media links Share this: Page Content What are neural tube defects? Neural (pronounced NOOR-uhl ) tube defects are ...

  5. What Are Congenital Heart Defects?

    Science.gov (United States)

    ... page from the NHLBI on Twitter. What Are Congenital Heart Defects? Congenital (kon-JEN-ih-tal) heart defects are problems ... carry blood to the heart or the body Congenital heart defects change the normal flow of blood through the ...

  6. H2 Adsorbed Site-to-Site Electronic Delocalization within IRMOF-1: Understanding Non-Negligible Interactions at High Pressure

    OpenAIRE

    Jian Wu; Mustafa U. Kucukkal; Aurora E. Clark

    2016-01-01

    Isoreticular metal organic frameworks (IRMOFs) have shown high uptake capabilities for storage of H2 (11.5 wt % at 77 K and 170 bar). A significant literature has employed fragment models and a single adsorbed H2 to identify adsorption sites within IRMOFs, as well as the necessary adsorbate–adsorbent interactions needed to reach sufficient adsorption enthalpy for practical usage, however at high pressures it remains to be seen if H2···H2 intermolecular interactions may influence the energetic...

  7. Dipole and multipole models of dielectrophoresis for a non-negligible particle size-simulations and experiments.

    Science.gov (United States)

    Michálek, Tomáš; Zemánek, Jiří

    2017-03-16

    Mathematical models of dielectrophoresis play an important role in the design of experiments, analysis of results, and even operation of some devices. In this paper, we test the accuracy of existing models in both simulations and laboratory experiments. We test the accuracy of the most common model that involves a point-dipole approximation of the induced field, when the small-particle assumption is broken. In simulations, comparisons against a model based on the Maxwell stress tensor show that even the point-dipole approximation provides good results for a large particle close to the electrodes. In addition, we study a refinement of the model offered by multipole approximations (quadrupole, and octupole). We also show that the voltages on the electrodes influence the error of the model because they affect the positions of the field nulls and the nulls of the higher-order derivatives. Experiments with a parallel electrode array and a polystyrene microbead reveal that the models predict the force with an error that cannot be eliminated even with the most accurate model. Nonetheless, it is acceptable for some purposes such as a model-based control system design. This article is protected by copyright. All rights reserved.

  8. The avalanche process of the fiber bundle model with defect

    Science.gov (United States)

    Hao, Da-Peng; Tang, Gang; Xia, Hui; Xun, Zhi-Peng; Han, Kui

    2017-04-01

    In order to explore the impacts of defect on the tensile fracture process of materials, the fiber bundle model with defect is constructed based on the classical fiber bundle model. In the fiber bundle model with defect, the two key parameters are the mean size and the density of defects. In both uniform and Weibull threshold distributions, the mean size and density all bring impacts on the threshold distribution of fibers. By means of analytical approximation and numerical simulation, we show that the two key parameters of the model have substantial effects on the failure process of the bundle. From macroscopic view, the defect described by the altering of threshold distribution of fibers will has a significant impact on the mechanical properties of the bundle. While in microscopic scale, the statistical properties of the model are still harmonious with the classical fiber bundle model.

  9. Road density

    Data.gov (United States)

    U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...

  10. Neural tube defects

    Directory of Open Access Journals (Sweden)

    M.E. Marshall

    1981-09-01

    Full Text Available Neural tube defects refer to any defect in the morphogenesis of the neural tube, the most common types being spina bifida and anencephaly. Spina bifida has been recognised in skeletons found in north-eastern Morocco and estimated to have an age of almost 12 000 years. It was also known to the ancient Greek and Arabian physicians who thought that the bony defect was due to the tumour. The term spina bifida was first used by Professor Nicolai Tulp of Amsterdam in 1652. Many other terms have been used to describe this defect, but spina bifida remains the most useful general term, as it describes the separation of the vertebral elements in the midline.

  11. Probing bulk defect energy bands using generalized charge pumping method

    Science.gov (United States)

    Masuduzzaman, Muhammad; Weir, Bonnie; Alam, Muhammad Ashraful

    2012-04-01

    The multifrequency charge pumping (CP) technique has long been used to probe the density of defects at the substrate-oxide interface, as well as in the bulk of the oxide of MOS transistors. However, profiling the energy levels of the defects has been more difficult due to the narrow scanning range of the voltage of a typical CP signal, and the uncertainty associated with the defect capture cross-section. In this paper, we discuss a generalized CP method that can identify defect energy bands within a bulk oxide, without requiring separate characterization of the defect capture cross-section. We use the new technique to characterize defects in both fresh and stressed samples of various dielectric compositions. By quantifying the way defects are generated as a function of time, we gain insight into the nature of defect generation in a particular gate dielectric. We also discuss the relative merits of voltage, time, and other variables of CP to probe bulk defect density, and compare the technique with related characterization approaches.

  12. Defect Prevention Based on 5 Dimensions of Defect Origin

    Directory of Open Access Journals (Sweden)

    Sakthi Kumaresh

    2012-08-01

    Full Text Available “Discovering the unexpected is more important than confirming the known [7]. In software development,the “unexpected” one relates to defects. These defects when unattended would cause failure to the productand risk to the users. The increasing dependency of society on software and the crucial consequences that afailure can cause requires the need to find out the defects at the origin itself. Based on the lessons learntfrom the earlier set of projects, a defect framework highlighting the 5 Dimensions (Ds of defect origin isproposed in this work. The defect framework is based on analyzing the defects that had emerged fromvarious stages of software development like Requirements, Design, Coding, Testing and Timeline (defectsdue to lack of time during development. This study is not limited to just identifying the origin of defects atvarious phases of software development but also finds out the reasons for such defects, and defectpreventive (DP measures are proposed for each type of defect. This work can help practitioners chooseeffective defect avoidance measures.In addition to arriving at defect framework, this work also proposes a defect injection metric based onseverity of the defect rather than just defect count, which gives the number of adjusted defects produced bya project at various phases. The defect injection metric value, once calculated, serves as a yardstick tomake a comparison in the improvements made in the software process development between similar set ofprojects

  13. Defect reaction network in Si-doped InAs. Numerical predictions.

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-05-01

    This Report characterizes the defects in the def ect reaction network in silicon - doped, n - type InAs predicted with first principles density functional theory. The reaction network is deduced by following exothermic defect reactions starting with the initially mobile interstitial defects reacting with common displacement damage defects in Si - doped InAs , until culminating in immobile reaction p roducts. The defect reactions and reaction energies are tabulated, along with the properties of all the silicon - related defects in the reaction network. This Report serves to extend the results for the properties of intrinsic defects in bulk InAs as colla ted in SAND 2013 - 2477 : Simple intrinsic defects in InAs : Numerical predictions to include Si - containing simple defects likely to be present in a radiation - induced defect reaction sequence . This page intentionally left blank

  14. Structural phase transitions and topological defects in ion Coulomb crystals

    Energy Technology Data Exchange (ETDEWEB)

    Partner, Heather L. [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany); Nigmatullin, Ramil [Institute of Quantum Physics, Albert-Einstein Allee-11, Ulm University, 89069 Ulm (Germany); Burgermeister, Tobias; Keller, Jonas; Pyka, Karsten [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany); Plenio, Martin B. [Center for Integrated Quantum Science and Technology, Albert-Einstein-Allee 11, Ulm University, 89069 Ulm (Germany); Institute for Theoretical Physics, Albert-Einstein-Allee 11, Ulm University, 89069 Ulm (Germany); Retzker, Alex [Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Givat Ram (Israel); Zurek, Wojciech H. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Campo, Adolfo del [Department of Physics, University of Massachusetts Boston, Boston, MA 02125 (United States); Mehlstäubler, Tanja E., E-mail: tanja.mehlstaeubler@ptb.de [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)

    2015-03-01

    We use laser-cooled ion Coulomb crystals in the well-controlled environment of a harmonic radiofrequency ion trap to investigate phase transitions and defect formation. Topological defects in ion Coulomb crystals (kinks) have been recently proposed for studies of nonlinear physics with solitons and as carriers of quantum information. Defects form when a symmetry breaking phase transition is crossed nonadiabatically. For a second order phase transition, the Kibble–Zurek mechanism predicts that the formation of these defects follows a power law scaling in the rate of the transition. We demonstrate a scaling of defect density and describe kink dynamics and stability. We further discuss the implementation of mass defects and electric fields as first steps toward controlled kink preparation and manipulation.

  15. Structural phase transitions and topological defects in ion Coulomb crystals

    Energy Technology Data Exchange (ETDEWEB)

    Partner, Heather L. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Nigmatullin, Ramil [Institute of Quantum Physics, Ulm Univ., Ulm (Germany); Burgermeister, Tobias [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Keller, Jonas [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Pyka, Karsten [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Plenio, Martin B. [Center for Integrated Quantum Science and Technology, Ulm Univ., Ulm, (Germany):Institute for Theoretical Physics, Ulm Univ.,Ulm, (Germany); Retzker, Alex [Racah Institute of Physics, The Hebrew University of Jerusalem, Givat Ram (Israel); Zurek, Wojciech Hubert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); del Campo, Adolfo [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Physics; Mehlstaubler, Tanja E. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

    2014-11-19

    We use laser-cooled ion Coulomb crystals in the well-controlled environment of a harmonic radiofrequency ion trap to investigate phase transitions and defect formation. Topological defects in ion Coulomb crystals (kinks) have been recently proposed for studies of nonlinear physics with solitons and as carriers of quantum information. Defects form when a symmetry breaking phase transition is crossed non-adiabatically. For a second order phase transition, the Kibble-Zurek mechanism predicts that the formation of these defects follows a power law scaling in the rate of the transition. We demonstrate a scaling of defect density and describe kink dynamics and stability. We further discuss the implementation of mass defects and electric fields as first steps toward controlled kink preparation and manipulation.

  16. Norwegian Pitched Roof Defects

    Directory of Open Access Journals (Sweden)

    Lars Gullbrekken

    2016-06-01

    Full Text Available The building constructions investigated in this work are pitched wooden roofs with exterior vertical drainpipes and wooden load-bearing system. The aim of this research is to further investigate the building defects of pitched wooden roofs and obtain an overview of typical roof defects. The work involves an analysis of the building defect archive from the research institute SINTEF Building and Infrastructure. The findings from the SINTEF archive show that moisture is a dominant exposure factor, especially in roof constructions. In pitched wooden roofs, more than half of the defects are caused by deficiencies in design, materials, or workmanship, where these deficiencies allow moisture from precipitation or indoor moisture into the structure. Hence, it is important to increase the focus on robust and durable solutions to avoid defects both from exterior and interior moisture sources in pitched wooden roofs. Proper design of interior ventilation and vapour retarders seem to be the main ways to control entry from interior moisture sources into attic and roof spaces.

  17. Lung density

    DEFF Research Database (Denmark)

    Garnett, E S; Webber, C E; Coates, G

    1977-01-01

    The density of a defined volume of the human lung can be measured in vivo by a new noninvasive technique. A beam of gamma-rays is directed at the lung and, by measuring the scattered gamma-rays, lung density is calculated. The density in the lower lobe of the right lung in normal man during quiet...... breathing in the sitting position ranged from 0.25 to 0.37 g.cm-3. Subnormal values were found in patients with emphsema. In patients with pulmonary congestion and edema, lung density values ranged from 0.33 to 0.93 g.cm-3. The lung density measurement correlated well with the findings in chest radiographs...... but the lung density values were more sensitive indices. This was particularly evident in serial observations of individual patients....

  18. Topological Point Defects in Relaxor Ferroelectrics

    Science.gov (United States)

    Nahas, Y.; Prokhorenko, S.; Kornev, I.; Bellaiche, L.

    2016-03-01

    First-principles-based effective Hamiltonian simulations are used to reveal the hidden connection between topological defects (hedgehogs and antihedgehogs) and relaxor behavior. Such defects are discovered to predominantly lie at the border of polar nanoregions in both Ba (Zr0.5 Ti0.5 )O3 (BZT) and Pb (Sc0.5 Nb0.5 )O3 (PSN) systems, and the temperature dependency of their density allows us to distinguish between noncanonical (PSN) and canonical (BZT) relaxor behaviors (via the presence or absence of a crossing of a percolation threshold). This density also possesses an inflection point at precisely the temperature for which the dielectric response peaks. Moreover, hedgehogs and antihedgehogs are found to be mobile excitations, and the dynamical nature of their annihilation is demonstrated (using simple hydrodynamical arguments) to follows laws, such as those of Vogel-Fulcher and Arrhenius, that are characteristic of dipolar relaxation kinetics of relaxor ferroelectrics.

  19. Electronic Defect States in Polyaniline.

    Science.gov (United States)

    Ginder, John Matthew

    The electronic defect states of the conducting polymer polyaniline are studied by a variety of magnetic and optical techniques. The insulating emeraldine base form (EB) of polyaniline can be converted to the conducting emeraldine salt form (ES) by treatment with aqueous acids such as HCl. This "protonic acid doping" process occurs via the bonding of protons to the polymer chain, without altering the number of chain electrons. Magnetic susceptibility studies reveal that a roughly linear growth of the Pauli paramagnetic susceptibility, and an increase in the density of Curie-like spins, accompanies this conversion. Consequently, the protonation-induced defects are mainly spin-1/2 polarons; further, the linear growth of the Pauli susceptibility suggests that fully protonated regions--metallic islands --grow with increasing doping level. The electronic structure of the metallic phase is proposed to be that of a polaron lattice with electronic bandwidth ~0.4 eV and polaron decay length ~2 A. The defects which accomodate excess charge in EB were also studied by near-steady-state photoinduced absorption experiments. Upon photoexcitation into the 2 eV absorption band in EB, several photoinduced features evolved. Induced bleachings of the existing transitions at 2.0 and 3.7 eV were observed; induced absorptions were found at 0.9, 1.4, and 3.0 eV. The 2.0 eV bleaching is consistent with the production of molecular charge-transfer excitons, which may relax to a different ring conformation causing long-lived bleaching, or to two separate charges on a single chain. Indeed, the induced absorptions at 1.4 and 3.0 eV are, by analogy with similar protonation -induced absorptions and by their bimolecular recombination kinetics, assigned to photoexcited polarons. Light-induced electron spin resonance experiments confirm the presence of photogenerated spins upon pumping into the excitonic absorption. Near-steady-state photoconductivity measurements on EB reveal a very small induced

  20. First principles defect energetics for simulations of silicon carbide under irradiation: Kinetic mechanisms of silicon di-interstitials

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Ting [CEA, DEN, Service de Recherche de Métallurgie Physique, F-91191 Gif-sur-Yvette (France); Theory and Computation Group, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072 (Australia); Roma, Guido, E-mail: roma@uni-mainz.de [CEA, DEN, Service de Recherche de Métallurgie Physique, F-91191 Gif-sur-Yvette (France); Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg Universität, D-55128 Mainz (Germany)

    2014-05-01

    Understanding the modification of the properties of silicon carbide under irradiation from the very fundamental point of view of atomic bonds and electronic structure can become possible in the next few years, thanks to the effort made in the last two decades to understand point defects from first principles calculations, but also thanks to the coupling of these results with simulation tools designed to describe larger spatial (and temporal) scales. We discuss some of the missing tiles that would allow to advance in this direction, in particular the incomplete data on defect clusters, and we present some first principles results for small silicon aggregates. We examine the stability, migration and structural evolution of Si di-interstitials in SiC. A triangular configuration is found to be the most stable in cubic SiC. Relatively small energy barriers, ranging from 0.25 to 1.2 eV, are found for the transformation of Si di-interstitials through reorientations, migration, and compact to extended transitions. We discuss the source of errors affecting our calculations as well as previous published results, which are still non-negligible.

  1. Algebraic approach to multiple defects on the line and application to Casimir force

    CERN Document Server

    Mintchev, M

    2007-01-01

    An algebraic framework for quantization in presence of arbitrary number of point-like defects on the line is developed. We consider a scalar field which interacts with the defects and freely propagates away of them. As an application we compute the Casimir force both at zero and finite temperature. We derive also the charge density in the Gibbs state of a complex scalar field with defects. The example of two delta-defects is treated in detail.

  2. Discrete torsion defects

    CERN Document Server

    Brunner, Ilka; Plencner, Daniel

    2014-01-01

    Orbifolding two-dimensional quantum field theories by a symmetry group can involve a choice of discrete torsion. We apply the general formalism of `orbifolding defects' to study and elucidate discrete torsion for topological field theories. In the case of Landau-Ginzburg models only the bulk sector had been studied previously, and we re-derive all known results. We also introduce the notion of `projective matrix factorisations', show how they naturally describe boundary and defect sectors, and we further illustrate the efficiency of the defect-based approach by explicitly computing RR charges. Roughly half of our results are not restricted to Landau-Ginzburg models but hold more generally, for any topological field theory. In particular we prove that for a pivotal bicategory, any two objects of its orbifold completion that have the same base are orbifold equivalent. Equivalently, from any orbifold theory (including those based on nonabelian groups) the original unorbifolded theory can be be obtained by orbifo...

  3. Mask Blank Defect Detection

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, M A; Sommargren, G E

    2000-02-04

    Mask blanks are the substrates that hold the master patterns for integrated circuits. Integrated circuits are semiconductor devices, such as microprocessors (mPs), dynamic random access memory (DRAMs), and application specific integrated circuits (ASICs) that are central to the computer, communication, and electronics industries. These devices are fabricated using a set of master patterns that are sequentially imaged onto light-sensitive coated silicon wafers and processed to form thin layers of insulating and conductive materials on top of the wafer. These materials form electrical paths and transistors that control the flow of electricity through the device. For the past forty years the semiconductor industry has made phenomenal improvements in device functionality, compactness, speed, power, and cost. This progress is principally due to the exponential decrease in the minimum feature size of integrated circuits, which has been reduced by a factor of {radical}2 every three years. Since 1992 the Semiconductor Industry Association (SIA) has coordinated the efforts of producing a technology roadmap for semiconductors. In the latest document, ''The International Technology Roadmap for Semiconductors: 1999'', future technology nodes (minimum feature sizes) and targeted dates were specified and are summarized in Table 1. Lithography is the imaging technology for producing a de-magnified image of the mask on the wafer. A typical de-magnification factor is 4. Mask blank defects as small as one-eighth the equivalent minimum feature size are printable and may cause device failure. Defects might be the result of the surface preparation, such as polishing, or contamination due to handling or the environment. Table 2 shows the maximum tolerable defect sizes on the mask blank for each technology node. This downward trend puts a tremendous burden on mask fabrication, particularly in the area of defect detection and reduction. A new infrastructure for mask

  4. Statistical relation between particle contaminations in ultra pure water and defects generated by process tools

    NARCIS (Netherlands)

    Wali, F.; Knotter, D. Martin; Wortelboer, Ronald; Mud, Auke

    2007-01-01

    Ultra pure water supplied inside the Fab is used in different tools at different stages of processing. Data of the particles measured in ultra pure water was compared with the defect density on wafers processed on these tools and a statistical relation is found Keywords— Yield, defect density,

  5. Defect formation energy in pyrochlore: the effect of crystal size

    Science.gov (United States)

    Wang, Jianwei; Ewing, Rodney C.; Becker, Udo

    2014-09-01

    Defect formation energies of point defects of two pyrochlores Gd2Ti2O7 and Gd2Zr2O7 as a function of crystal size were calculated. Density functional theory with plane-wave basis sets and the projector-augmented wave method were used in the calculations. The results show that the defect formation energies of the two pyrochlores diverge as the size decreases to the nanometer range. For Gd2Ti2O7 pyrochlore, the defect formation energy is higher at nanometers with respect to that of the bulk, while it is lower for Gd2Zr2O7. The lowest defect formation energy for Gd2Zr2O7 is found at 15-20 Å. The different behaviors of the defect formation energies as a function of crystal size are caused by different structural adjustments around the defects as the size decreases. For both pyrochlore compositions at large sizes, the defect structures are similar to those of the bulk. As the size decreases, for Gd2Ti2O7, additional structure distortions appear at the surfaces, which cause the defect formation energy to increase. For Gd2Zr2O7, additional oxygen Frenkel pair defects are introduced, which reduce the defect formation energy. As the size further decreases, increased structure distortions occur at the surfaces, which cause the defect formation energy to increase. Based on a hypothesis that correlates the energetics of defect formation and radiation response for complex oxides, the calculated results suggest that at nanometer range Gd2Ti2O7 pyrochlore is expected to have a lower radiation tolerance, and those of Gd2Zr2O7 pyrochlore to have a higher radiation tolerance. The highest radiation tolerance for Gd2Zr2O7 pyrochlore is expected to be found at ˜2 nanometers.

  6. C-V and DLTS studies of radiation induced Si-SiO2 interface defects

    Science.gov (United States)

    Capan, I.; Janicki, V.; Jacimovic, R.; Pivac, B.

    2012-07-01

    Interface traps at the Si-SiO2 interface have been and will be an important performance limit in many (future) semiconductor devices. In this paper, we present a study of fast neutron radiation induced changes in the density of Si-SiO2 interface-related defects. Interface related defects (Pb centers) are detected before and upon the irradiation. The density of interface-related defects is increasing with the fast neutron fluence.

  7. Congenital Abdominal Wall Defects

    DEFF Research Database (Denmark)

    Risby, Kirsten; Jakobsen, Marianne Skytte; Qvist, Niels

    2016-01-01

    complications were seen in five (15%) children: four had detachment of the mesh and one patient developed abdominal compartment syndrome. Mesh related clinical infection was observed in five children. In hospital mortality occurred in four cases (2 gastroschisis and 2 omphalocele) and was not procedure......OBJECTIVE: To evaluate the clinical utility of GORE® DUALMESH (GDM) in the staged closure of large congenital abdominal wall defects. MATERIALS AND METHODS: Data of patients with congenital abdominal wall defects managed with GDM was analyzed for outcome regarding complete fascial closure; mesh...

  8. Supersymmetric k-defects

    CERN Document Server

    Koehn, Michael

    2015-01-01

    In supersymmetric theories, topological defects can have nontrivial behaviors determined purely by whether or not supersymmetry is restored in the defect core. A well-known example of this is that some supersymmetric cosmic strings are automatically superconducting, leading to important cosmological effects and constraints. We investigate the impact of nontrivial kinetic interactions, present in a number of particle physics models of interest in cosmology, on the relationship between supersymmetry and supercurrents on strings. We find that in some cases it is possible for superconductivity to be disrupted by the extra interactions.

  9. Do the Defects Make It Work? Defect Engineering in Pi-Conjugated Polymers and Their Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Wang, D.; Reese, M.; Kopidakis N.; Gregg, B. A.

    2008-05-01

    The charged defect density in common pi-conjugated polymers such as poly(3-hexylthiophene), P3HT, is around 1018 cm-3. Despite, or perhaps because of, this huge defect density, bulk heterojunction solar cells made from these polymers and a C60 derivative such as PCBM exhibit some of the highest efficiencies (~5%) yet obtained in solid state organic photovoltaic cells. We discuss defects in molecular organic semiconductors and in pi-conjugated polymers. These defects can be grouped in two categories, covalent and noncovalent. Somewhat analogous to treating amorphous silicon with hydrogen, we introduce chemical methods to modify the density and charge of the covalent defects in P3HT by treating it with electrophiles such as dimethyl sulfate and nucleophiles such as sodium methoxide. The effects of these treatments on the electrical and photovoltaic properties and stability of organic PV cells is discussed in terms of the change in the number and chemical properties of the defects. Finally, we address the question of whether the efficiency of OPV cells requires the presence of these defects which function as adventitious p-type dopants. Their presence relieves the resistance limitations usually encountered in cleaner organic semiconductors and can create built-in electric fields at junctions.

  10. Quantum computing with defects.

    Science.gov (United States)

    Weber, J R; Koehl, W F; Varley, J B; Janotti, A; Buckley, B B; Van de Walle, C G; Awschalom, D D

    2010-05-11

    Identifying and designing physical systems for use as qubits, the basic units of quantum information, are critical steps in the development of a quantum computer. Among the possibilities in the solid state, a defect in diamond known as the nitrogen-vacancy (NV(-1)) center stands out for its robustness--its quantum state can be initialized, manipulated, and measured with high fidelity at room temperature. Here we describe how to systematically identify other deep center defects with similar quantum-mechanical properties. We present a list of physical criteria that these centers and their hosts should meet and explain how these requirements can be used in conjunction with electronic structure theory to intelligently sort through candidate defect systems. To illustrate these points in detail, we compare electronic structure calculations of the NV(-1) center in diamond with those of several deep centers in 4H silicon carbide (SiC). We then discuss the proposed criteria for similar defects in other tetrahedrally coordinated semiconductors.

  11. CLASSIFICATION OF DEFECTS IN SOFTWARE USING DECISION TREE ALGORITHM

    Directory of Open Access Journals (Sweden)

    M. SURENDRA NAIDU

    2013-06-01

    Full Text Available Software defects due to coding errors continue to plague the industry with disastrous impact, especially in the enterprise application software category. Identifying how much of these defects are specifically due to coding errors is a challenging problem. Defect prevention is the most vivid but usually neglected aspect of softwarequality assurance in any project. If functional at all stages of software development, it can condense the time, overheads and wherewithal entailed to engineer a high quality product. In order to reduce the time and cost, we will focus on finding the total number of defects if the test case shows that the software process not executing properly. That has occurred in the software development process. The proposed system classifying various defects using decision tree based defect classification technique, which is used to group the defects after identification. The classification can be done by employing algorithms such as ID3 or C4.5 etc. After theclassification the defect patterns will be measured by employing pattern mining technique. Finally the quality will be assured by using various quality metrics such as defect density, etc. The proposed system will be implemented in JAVA.

  12. Contact angle hysteresis generated by strong dilute defects.

    Science.gov (United States)

    Reyssat, Mathilde; Quéré, David

    2009-03-26

    Water on solid decorated with hydrophobic defects (such as micropillars) often stays at the top of the defects in a so-called fakir state, which explains the superhydrophobicity observed in such case, provided that the density of defects is small enough. Here we show that this situation provides an ideal frame for studying the contact angle hysteresis; the phase below the liquid is "perfect" and slippery (it is air), contrasting with pillars' tops whose edges form strong pining sites for the contact line. This model system thus allows us to study the hysteresis as a function of the density of defects and to compare it to the classical theory by Joanny and de Gennes, which is based on very similar hypothesis.

  13. Freestanding silicon nanocrystals with extremely low defect content

    Science.gov (United States)

    Pereira, R. N.; Rowe, D. J.; Anthony, R. J.; Kortshagen, U.

    2012-08-01

    The future exploitation of the exceptional properties of freestanding silicon nanocrystals (Si NCs) in marketable applications relies upon our ability to produce large amounts of defect-free Si NCs by means of a low-cost method. Here, we demonstrate that Si NCs fabricated by scalable rf plasma-assisted decomposition of silane with additional hydrogen gas injected into the afterglow region of the plasma exhibit immediately after synthesis the lowest reported defect density, corresponding to a value of only about 0.002-0.005 defects per NC for Si NCs of 4 nm size. In addition, the virtually perfect hydrogen termination of these Si NCs yields an enhanced resistance against natural oxidation in comparison to Si NCs with nearly one order of magnitude larger initial defect density.

  14. Point Defect Characterization in CdZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Gul,R.; Li, Z.; Bolotnikov, A.; Keeter, K.; Rodriguez, R.; James, R.

    2009-03-24

    Measurements of the defect levels and performance testing of CdZnTe detectors were performed by means of Current Deep Level Transient Spectroscopy (I-DLTS), Transient Charge Technique (TCT), Current versus Voltage measurements (I-V), and gamma-ray spectroscopy. CdZnTe crystals were acquired from different commercial vendors and characterized for their point defects. I-DLTS studies included measurements of defect parameters such as energy levels in the band gap, carrier capture cross sections, and defect densities. The induced current due to laser-generated carriers was measured using TCT. The data were used to determine the transport properties of the detectors under study. A good correlation was found between the point defects in the detectors and their performance.

  15. On the material geometry of continuously defective corrugated graphene sheets

    OpenAIRE

    Trzesowski, Andrzej

    2014-01-01

    Geometrical objects describing the material geometry of continuously defective graphene sheets are introduced and their compatibility conditions are formulated. Effective edge dislocations embedded in the Riemann-Cartan material space and defined by their scalar density and by local Burgers vectors, are considered. The case of secondary curvature-type defects created by this distribution of dislocations is analysed in terms of the material space. The variational geometry of the material space...

  16. Electrical Characterization of Defects in SiC Schottky Barriers

    Science.gov (United States)

    Schnabel, C. M.; Tabib-Azar, M.; Raffaelle, R. P.; Su, H. B.; Dudley, M.; Neudeck, P. G.; Bailey, S.

    2005-01-01

    We have been investigating the effect of screw dislocation and other structural defects on the electrical properties of SiC. SiC is a wide-bandgap semiconductor that is currently received much attention due to its favorable high temperature behavior and high electric field breakdown strength. Unfortunately, the current state-of-the-art crystal growth and device processing methods produce material with high defect densities, resulting in a limited commercial viability

  17. Low temperature diffusivity of self-interstitial defects in tungsten

    Science.gov (United States)

    Swinburne, Thomas D.; Ma, Pui-Wai; Dudarev, Sergei L.

    2017-07-01

    The low temperature diffusivity of nanoscale crystal defects, where quantum mechanical fluctuations are known to play a crucial role, are essential to interpret observations of irradiated microstructures conducted at cryogenic temperatures. Using density functional theory calculations, quantum heat bath molecular dynamics and open quantum systems theory, we evaluate the low temperature diffusivity of self-interstitial atom clusters in tungsten valid down to temperatures of 1 K. Due to an exceptionally low defect migration barrier, our results show that interstitial defects exhibit very high diffusivity of order {10}3 μ {{{m}}}2 {{{s}}}-1 over the entire range of temperatures investigated.

  18. Types of Congenital Heart Defects

    Science.gov (United States)

    ... heart develops. Examples of Simple Congenital Heart Defects Holes in the Heart (Septal Defects) The septum is ... Google+ SITE INDEX ACCESSIBILITY PRIVACY STATEMENT FOIA NO FEAR ACT OIG CONTACT US National Institutes of Health ...

  19. Adults with Congenital Heart Defects

    Science.gov (United States)

    ... Disease Venous Thromboembolism Aortic Aneurysm More Web Booklet: Adults With Congenital Heart Defects Updated:Aug 29,2017 ... the list below to learn more. Web Booklet: Adults With Congenital Heart Defects Introduction Introduction: Adults with ...

  20. Reconstructions of eyelid defects

    Directory of Open Access Journals (Sweden)

    Nirmala Subramanian

    2011-01-01

    Full Text Available Eyelids are the protective mechanism of the eyes. The upper and lower eyelids have been formed for their specific functions by Nature. The eyelid defects are encountered in congenital anomalies, trauma, and postexcision for neoplasm. The reconstructions should be based on both functional and cosmetic aspects. The knowledge of the basic anatomy of the lids is a must. There are different techniques for reconstructing the upper eyelid, lower eyelid, and medial and lateral canthal areas. Many a times, the defects involve more than one area. For the reconstruction of the lid, the lining should be similar to the conjunctiva, a cover by skin and the middle layer to give firmness and support. It is important to understand the availability of various tissues for reconstruction. One layer should have the vascularity to support the other layer which can be a graft. A proper plan and execution of it is very important.

  1. Wetting on smooth micropatterned defects

    OpenAIRE

    Debuisson, Damien; Dufour, Renaud; Senez, Vincent; Arscott, Steve

    2011-01-01

    We develop a model which predicts the contact angle hysteresis introduced by smooth micropatterned defects. The defects are modeled by a smooth function and the contact angle hysteresis is explained using a tangent line solution. When the liquid micro-meniscus touches both sides of the defect simultaneously, depinning of the contact line occurs. The defects are fabricated using a photoresist and experimental results confirm the model. An important point is that the model is scale-independent,...

  2. Effect of native defects and laser-induced defects on multi-shot laser-induced damage in multilayer mirrors

    Institute of Scientific and Technical Information of China (English)

    Ying Wang; Yuanan Zhao; Tanda Shao; Zhengxiu Fan

    2011-01-01

    The roles of laser-induced defects and native defects in multilayer mirrors under multi-shot irradiation condition are investigated. The HfO2/SiO2 dielectric mirrors are deposited by electron beam evaporation (EBE). Laser damage testing is carried out on both the 1-on-l and S-on-1 regimes using 355-nm pulsed laser at a duration of 8 ns. It is found that the single-shot laser-induced damage threshold (LIDT) is much higher than the multi-shot LIDT. In the multi-shot mode, the main factor influencing LIDT is the accumulation of irreversible laser-induced defects and native defects. The surface morphologies of the samples are observed by optical microscopy. Moreover, the number of laser-induced defects affects the damage probability of the samples. A correlative model based on critical conduction band (CB) electron density (ED) is presented to simulate the multi-shot damage behavior.%@@ The roles of laser-induced defects and native defects in multilayer mirrors under multi-shot irradiation condition are investigated.The Hf02/SiO2 dielectric mirrors are deposited by electron beam evaporation (EBE).Laser damage testing is carried out on both the 1-on-1 and S-on-1 regimes using 355-nn pulsed laser at a duration of 8 us.It is found that the single-shot laser-induced damage threshold(LIDT)is much higher than the multi-shot LIDT.In the multi-shot mode,the main factor influencing LIDT is the accumulation of irreversible laser-induced defects and native defects.The surface morphologies of the samples are observed by optical microscopy.Moreover,the number of laser-induced defects affects the damage probability of the samples.A correlative model based on critical conduction band(CB)electron density(ED)is presented to simulate the multi-shot damage behavior.

  3. Congenital Heart Defects (For Parents)

    Science.gov (United States)

    ... Old Feeding Your 1- to 2-Year-Old Congenital Heart Defects KidsHealth > For Parents > Congenital Heart Defects A A A What's in this article? How ... a Problem en español Anomalías cardíacas congénitas A congenital heart defect is a problem in the heart's structure that ...

  4. Oxygen defects in Fe-substituted Tl-system superconductors

    Institute of Scientific and Technical Information of China (English)

    李阳; 曹国辉; 王耘波; 马庆珠; 熊小涛; 陈宁; 马如璋; 郭应焕; 许祝安; 王劲松; 张小俊; 焦正宽; 彭获田; 周思海

    1996-01-01

    For Fe-doped T1-1223 phase,the excess oxygen defects induced by Fe dopants are studied by means of Hall coefficient,thermogravimetric measurements,Mossbauer spectroscopy,and the model calculation of the effective bond valence.The extra oxygen defects have effects on carrier density and microstructure of the superconductors.In the light doping level of Fe (x=0-0.05),the superconducting transition and carrier density have significant corresponding relation--the zero resistance temperature Tco and carrier densities decrease linearly with Fe dopants increasing.The thermogravimetric measurements show that the Fe3+ ions’ substituting for Cu2+ ions can bring the extra oxygen into the lattice to form extra oxygen defects.The calculation of the effective bond valence shows that the decrease of carrier density originates the strongly localized binding of the extra oxygen defects.The distortion of Cu-O layer induced by the extra oxygen defects decreases the superconductive transition temperature.The microstructure

  5. Understanding of Defect Physics in Polycrystalline Photovoltaic Materials: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Y.

    2011-07-01

    The performance of thin-film solar cells is influenced by the quality of interfaces and formation of defects such as point defects, stacking faults, twins, dislocations, and grain boundaries. It is important to understand the defect physics so that appropriate methods may be developed to suppress the formation of harmful defects. Here, we review our understanding of defect physics in thin-film photovoltaic (PV) materials such as Si, CdTe, Cu(In,Ga)Se2 (CIGS), Cu2ZnSnSe2 (CZTSe), and Cu2ZnSnS2 (CZTS) using the combination of nanoscale electron microscopy characterization and density-functional theory (DFT). Although these thin-film PV materials share the same basic structural feature - diamond structure based - the defect physics in them could be very different. Some defects, such as stacking faults and special twins, have similar electronic properties in these thin-film materials. However, some other defects, such as grain boundaries and interfaces, have very different electronic properties in these materials. For example, grain boundaries produce harmful deep levels in Si and CdTe, but they do not produce significant deep levels in CIGS, CZTSe, and CZTS. These explain why passivation is critical for Si and CdTe solar cells, but is less important in CIS and CZTS solar cells. We further provide understanding of the effects of interfaces on the performance of solar cells made of these PV materials.

  6. Unraveling the luminescence signatures of chemical defects in polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Lihua; Tran, Huan Doan; Wang, Chenchen; Ramprasad, Rampi, E-mail: rampi.ramprasad@uconn.edu [Department of Materials Science and Engineering, Institute of Materials Science, University of Connecticut, 97 North Eagleville Road, Storrs, Connecticut 06269 (United States)

    2015-09-28

    Chemical defects in polyethylene (PE) can deleteriously downgrade its electrical properties and performance. Although these defects usually leave spectroscopic signatures in terms of characteristic luminescence peaks, it is nontrivial to make unambiguous assignments of the peaks to specific defect types. In this work, we go beyond traditional density functional theory calculations to determine intra-defect state transition and charge recombination process derived emission and absorption energies in PE. By calculating the total energy differences of the neutral defect at excited and ground states, the emission energies from intra-defect state transition are obtained, reasonably explaining the photoluminescence peaks in PE. In order to study the luminescence emitted in charge recombination processes, we characterize PE defect levels in terms of thermodynamic and optical charge transition levels that involve total energy calculations of neutral and charged defects. Calculations are performed at several levels of theory including those involving (semi)local and hybrid electron exchange-correlation functionals, and many-body perturbation theory. With these critical elements, the emission energies are computed and further used to clarify and confirm the origins of the observed electroluminescence and thermoluminescence peaks.

  7. Neoclassical transport in density pedestals with non-trace impurities

    Science.gov (United States)

    Buller, Stefan; Pusztai, Istvan; Landreman, Matt

    2016-10-01

    We study neoclassical transport in steady-state density pedestals with non-trace impurities using the Eulerian δf code Perfect, with an emphasis on radially global effects and the effects of impurities. To properly describe transport in a tokamak pedestal, radial coupling must be included, which strongly affects the transport. We find that radial coupling reduces the pedestal heat flux compared to local predictions. Furthermore, the influence of the pedestal persists several orbit widths into the core. The electron flux is significant in the pedestal, and global neoclassical transport is not intrinsically ambipolar. Thus, the impurity flux is not simply opposing the ion flux. The resulting radial current gives a torque that is balanced by a non-negligible radial transport of toroidal momentum. The effective Prandtl number is comparable to typical turbulent values in the core (0.1 - 0.3), and is sensitive to the impurity content. Global effects have a strong contribution to the poloidal flows of low- Z ions, which give rise to larger in-out flow asymmetries. Supported by the INCA Grant of Vetenskapsrådet (Dnr. 330-2014-6313). ML is supported by the USDoE Grants DEFG0293ER54197 and DEFC0208ER54964. The simulations used computational resources of Hebbe at C3SE (C3SE2016-1-10 & SNIC2016-1-161).

  8. Point defect engineering strategies to retard phosphorous diffusion in germanium

    KAUST Repository

    Tahini, H. A.

    2013-01-01

    The diffusion of phosphorous in germanium is very fast, requiring point defect engineering strategies to retard it in support of technological application. Density functional theory corroborated with hybrid density functional calculations are used to investigate the influence of the isovalent codopants tin and hafnium in the migration of phosphorous via the vacancy-mediated diffusion process. The migration energy barriers for phosphorous are increased significantly in the presence of oversized isovalent codopants. Therefore, it is proposed that tin and in particular hafnium codoping are efficient point defect engineering strategies to retard phosphorous migration. © the Owner Societies 2013.

  9. Wetting on smooth micropatterned defects

    CERN Document Server

    Debuisson, Damien; Senez, Vincent; Arscott, Steve

    2011-01-01

    We develop a model which predicts the contact angle hysteresis introduced by smooth micropatterned defects. The defects are modeled by a smooth function and the contact angle hysteresis is explained using a tangent line solution. When the liquid micro-meniscus touches both sides of the defect simultaneously, depinning of the contact line occurs. The defects are fabricated using a photoresist and experimental results confirm the model. An important point is that the model is scale-independent, i.e. the contact angle hysteresis is dependent on the aspect ratio of the function, not on its absolute size; this could have implications for natural surface defects.

  10. Characterization of lacunar defects by positrons annihilation

    CERN Document Server

    Barthe, M F; Blondiaux, G

    2003-01-01

    Among the nondestructive methods for the study of matter, the positrons annihilation method allows to sound the electronic structure of materials by measuring the annihilation characteristics. These characteristics depend on the electronic density as seen by the positon, and on the electron momentums distribution which annihilate with the positon. The positon is sensible to the coulombian potential variations inside a material and sounds preferentially the regions away from nuclei which represent potential wells. The lacunar-type defects (lack of nuclei) represent deep potential wells which can trap the positon up to temperatures close to the melting. This article describes the principles of this method and its application to the characterization of lacunar defects: 1 - positrons: matter probes (annihilation of electron-positon pairs, annihilation characteristics, positrons sources); 2 - positrons interactions in solids (implantation profiles, annihilation states, diffusion and trapping, positon lifetime spec...

  11. Research on Defects Inspection of Solder Balls Based on Eddy Current Pulsed Thermography

    Science.gov (United States)

    Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe

    2015-01-01

    In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique. PMID:26473871

  12. Point-Defect Mediated Bonding of Pt Clusters on (5,5) Carbon Nanotubes

    DEFF Research Database (Denmark)

    Wang, J. G.; Lv, Y. A.; Li, X. N.;

    2009-01-01

    The adhesion of various sizes of Pt clusters on the metallic (5,5) carbon nanotubes (CNTs) with and without the point defect has been investigated by means of density functional theory (DFT). The calculations show that the binding energies of Pt-n (n = 1-6) clusters on the defect free CNTs are more......). The stronger orbital hybridization between the Pt atom and the carbon atom shows larger charge transfers on the defective CNTs than on the defect free CNTs, which allows the strong interaction between Pt clusters and CNTs. On the basis of DFT calculations, CNTs with point defect can be used as the catalyst...

  13. Study on defects associated with interstitial oxygen in PbWO4 crystal

    Institute of Scientific and Technical Information of China (English)

    Liu Feng-song; Gu Mu; Zhang Rui

    2004-01-01

    The defects associated with interstitial oxygen in lead tungstate crystals (PbWO4) are investigated by the relativistic self-consistent discrete variational embedded cluster method. The research work is focused on the density of states of interstitial oxygen defects and relational Frankel defects. The transition state method is used to calculate excitation energy of different electron orbits. Simulation results show that the existence of defects related to interstitial oxygen can diminish the bandwidth of the WO2-4 group, and it might produce the green luminescence. Frankel defects associated with interstitial oxygen could result in the absorption at 420nm.

  14. Research on defects inspection of solder balls based on eddy current pulsed thermography.

    Science.gov (United States)

    Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe

    2015-10-13

    In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique.

  15. Research on Defects Inspection of Solder Balls Based on Eddy Current Pulsed Thermography

    Directory of Open Access Journals (Sweden)

    Xiuyun Zhou

    2015-10-01

    Full Text Available In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT. Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique.

  16. Penta-hepta defect chaos in a model for rotating hexagonal convection.

    Science.gov (United States)

    Young, Yuan-Nan; Riecke, Hermann

    2003-04-01

    In a model for rotating non-Boussinesq convection with mean flow, we identify a regime of spatiotemporal chaos that is based on a hexagonal planform and is sustained by the induced nucleation of dislocations by penta-hepta defects. The probability distribution function for the number of defects deviates substantially from the usually observed Poisson-type distribution. It implies strong correlations between the defects in the form of density-dependent creation and annihilation rates of defects. We extract these rates from the distribution function and also directly from the defect dynamics.

  17. Defect Recognition in Thermosonic Imaging

    Institute of Scientific and Technical Information of China (English)

    CHEN Dapeng; WU Naiming; ZHANG Zheng

    2012-01-01

    This work is aimed at developing an effective method for defect recognition in thermosonic imaging.The heat mechanism of thermosonic imaging is introduced,and the problem for defect recognition is discussed.For this purpose,defect existing in the inner wall of a metal pipeline specimen and defects embedded in a carbon fiber reinforced plastic (CFRP) laminate are tested.The experimental data are processed by pulse phase thermography (PPT) method to show the phase images at different frequencies,and the characteristic of phase angle vs frequency curve of thermal anomalies and sound area is analyzed.A binary image,which is based on the characteristic value of defects,is obtained by a new recognition algorithm to show the defects.Results demonstrate good defect recognition performance for thermosonic imaging,and the reliability of this technique can be improved by the method.

  18. Topological defect lasers

    CERN Document Server

    Knitter, Sebastian; Xiong, Wen; Guy, Mikhael I; Solomon, Glenn S; Cao, Hui

    2014-01-01

    We demonstrate topological defect lasers in a GaAs membrane with embedded InAs quantum dots. By introducing a disclination to a square-lattice of elliptical air holes, we obtain spatially confined optical resonances with high quality factor. Such resonances support powerflow vortices, and lase upon optical excitation of quantum dots, embedded in the structure. The spatially inhomogeneous variation of the unit cell orientation adds another dimension to the control of a lasing mode, enabling the manipulation of its field pattern and energy flow landscape.

  19. Thermographic Imaging of Defects in Anisotropic Composites

    Science.gov (United States)

    Plotnikov, Y. A.; Winfree, W. P.

    2000-01-01

    Composite materials are of increasing interest to the aerospace industry as a result of their weight versus performance characteristics. One of the disadvantages of composites is the high cost of fabrication and post inspection with conventional ultrasonic scanning systems. The high cost of inspection is driven by the need for scanning systems which can follow large curve surfaces. Additionally, either large water tanks or water squirters are required to couple the ultrasonics into the part. Thermographic techniques offer significant advantages over conventional ultrasonics by not requiring physical coupling between the part and sensor. The thermographic system can easily inspect large curved surface without requiring a surface following scanner. However, implementation of Thermal Nondestructive Evaluations (TNDE) for flaw detection in composite materials and structures requires determining its limit. Advanced algorithms have been developed to enable locating and sizing defects in carbon fiber reinforced plastic (CFRP). Thermal Tomography is a very promising method for visualizing the size and location of defects in materials such as CFRP. However, further investigations are required to determine its capabilities for inspection of thick composites. In present work we have studied influence of the anisotropy on the reconstructed image of a defect generated by an inversion technique. The composite material is considered as homogeneous with macro properties: thermal conductivity K, specific heat c, and density rho. The simulation process involves two sequential steps: solving the three dimensional transient heat diffusion equation for a sample with a defect, then estimating the defect location and size from the surface spatial and temporal thermal distributions (inverse problem), calculated from the simulations.

  20. Carrier providers or killers: The case of Cu defects in CdTe

    Science.gov (United States)

    Yang, Ji-Hui; Metzger, Wyatt K.; Wei, Su-Huai

    2017-07-01

    Defects play important roles in semiconductors for optoelectronic applications. Common intuition is that defects with shallow levels act as carrier providers and defects with deep levels are carrier killers. Here, taking the Cu defects in CdTe as an example, we show that relatively shallow defects can play both roles. Using first-principles calculation methods combined with thermodynamic simulations, we study the dialectic effects of Cu-related defects on hole density and lifetime in bulk CdTe. Because CuCd can form a relatively shallow acceptor, we find that increased Cu incorporation into CdTe indeed can help achieve high hole density; however, too much Cu can cause significant non-radiative recombination. We discuss strategies to balance the contradictory effects of Cu defects based on the calculated impact of Cd chemical potential, copper defect concentrations, and annealing temperature on lifetime and hole density. These findings advance the understanding of the potential complex defect behaviors of relatively shallow defect states in semiconductors.

  1. Carrier providers or killers: The case of Cu defects in CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ji-Hui; Metzger, Wyatt K.; Wei, Su-Huai

    2017-07-24

    Defects play important roles in semiconductors for optoelectronic applications. Common intuition is that defects with shallow levels act as carrier providers and defects with deep levels are carrier killers. Here, taking the Cu defects in CdTe as an example, we show that relatively shallow defects can play both roles. Using first-principles calculation methods combined with thermodynamic simulations, we study the dialectic effects of Cu-related defects on hole density and lifetime in bulk CdTe. Because CuCd can form a relatively shallow acceptor, we find that increased Cu incorporation into CdTe indeed can help achieve high hole density; however, too much Cu can cause significant non-radiative recombination. We discuss strategies to balance the contradictory effects of Cu defects based on the calculated impact of Cd chemical potential, copper defect concentrations, and annealing temperature on lifetime and hole density. These findings advance the understanding of the potential complex defect behaviors of relatively shallow defect states in semiconductors.

  2. Neutral-depletion-induced asymmetric plasma density profile and momentum transport in a helicon thruster

    Science.gov (United States)

    Takahashi, Kazunori; Takao, Yoshinori; Chiba, Aiki; Ando, Akira

    2016-09-01

    Axial momentum lost to a lateral wall of a helicon source is directly measured by using a pendulum force balance, where only the lateral wall is attached to the balance immersed in 60-cm-diam and 1.4-m-long vacuum tank (pumping speed of 300-400 L/s). When operating the source with highly ionized krypton and xenon, the strong density decay along the axis is observed inside the source tube, which seems to be due to the neutral depletion. Under such a condition, a non-negligible loss of the axial momentum to the lateral wall is detected. The presently detected loss of the axial momentum indicates the presence of the ions which are axially accelerated by the electric field in the plasma core and then lost to the lateral wall. Furthermore, the helicon thruster immersed in 1-m-diam and 2-m-long vacuum tank (pumping speed of 4000-5000 L/s) is operated at high rf power up to 5 kW in argon, to demonstrate the neutral-depletion-induced axially asymmetric density profile. Combination between the Langmuir probe and the optical diagnosis indicates that the neutral density at the axial center of the source is reduced to 20% of the initial neutral density. This work is partially supported by grant-in-aid for scientific research (16H04084 and 26247096) from the Japan Society for the Promotion of Science.

  3. Dipole defects in beryl

    Energy Technology Data Exchange (ETDEWEB)

    Holanda, B A; Cordeiro, R C; Blak, A R, E-mail: bruna.holanda@usp.br, E-mail: renan.cordeiro@usp.br, E-mail: anablak@if.usp.br

    2010-11-15

    Dipole defects in gamma irradiated and thermally treated beryl (Be{sub 3}Al{sub 2}Si{sub 6}O{sub 18}) samples have been studied using the Thermally Stimulated Depolarization Currents (TSDC) technique. TSDC experiments were performed in pink (morganite), green (emerald), blue (aquamarine) and colourless (goshenite) natural beryl. TSDC spectra present dipole peaks at 190K, 220K, 280K and 310K that change after gamma irradiation and thermal treatments. In morganite samples, for thermal treatments between 700K and 1100K, the 280K peak increase in intensity and the band at 220K disappears. An increase of the 280K peak and a decrease of the 190K peak were observed in the TSDC spectra of morganite after a gamma irradiation of 25kGy performed after the thermal treatments. In the case of emerald samples, thermal treatments enhanced the 280K peak and gamma irradiation partially destroyed this band. The goshenite TSDC spectra present only one band at 280K that is not affected either by thermal treatments or by gamma irradiation. All the observed peaks are of dipolar origin because the intensity of the bands is linearly dependent on the polarization field, behaviour of dipole defects. The systematic study, by means of TSDC measurements, of ionizing irradiation effects and thermal treatments in these crystals makes possible a better understanding of the role played by the impurities in beryl crystals.

  4. Defect passivation in hybrid perovskite solar cells using quaternary ammonium halide anions and cations

    Science.gov (United States)

    Zheng, Xiaopeng; Chen, Bo; Dai, Jun; Fang, Yanjun; Bai, Yang; Lin, Yuze; Wei, Haotong; Zeng, Xiao Cheng; Huang, Jinsong

    2017-07-01

    The ionic defects at the surfaces and grain boundaries of organic-inorganic halide perovskite films are detrimental to both the efficiency and stability of perovskite solar cells. Here, we show that quaternary ammonium halides can effectively passivate ionic defects in several different types of hybrid perovskite with their negative- and positive-charged components. The efficient defect passivation reduces the charge trap density and elongates the carrier recombination lifetime, which is supported by density-function-theory calculation. The defect passivation reduces the open-circuit-voltage deficit of the p-i-n-structured device to 0.39 V, and boosts the efficiency to a certified value of 20.59 ± 0.45%. Moreover, the defect healing also significantly enhances the stability of films in ambient conditions. Our findings provide an avenue for defect passivation to further improve both the efficiency and stability of solar cells.

  5. Topological defect motifs in two-dimensional Coulomb clusters

    CERN Document Server

    Radzvilavičius, A; 10.1088/0953-8984/23/38/385301

    2012-01-01

    The most energetically favourable arrangement of low-density electrons in an infinite two-dimensional plane is the ordered triangular Wigner lattice. However, in most instances of contemporary interest one deals instead with finite clusters of strongly interacting particles localized in potential traps, for example, in complex plasmas. In the current contribution we study distribution of topological defects in two-dimensional Coulomb clusters with parabolic lateral confinement. The minima hopping algorithm based on molecular dynamics is used to efficiently locate the ground- and low-energy metastable states, and their structure is analyzed by means of the Delaunay triangulation. The size, structure and distribution of geometry-induced lattice imperfections strongly depends on the system size and the energetic state. Besides isolated disclinations and dislocations, classification of defect motifs includes defect compounds --- grain boundaries, rosette defects, vacancies and interstitial particles. Proliferatio...

  6. A general route towards defect and pore engineering in graphene.

    Science.gov (United States)

    Xie, Guibai; Yang, Rong; Chen, Peng; Zhang, Jing; Tian, Xuezeng; Wu, Shuang; Zhao, Jing; Cheng, Meng; Yang, Wei; Wang, Duoming; He, Congli; Bai, Xuedong; Shi, Dongxia; Zhang, Guangyu

    2014-06-12

    Defect engineering in graphene is important for tailoring graphene's properties thus applicable in various applications such as porous membranes and ultra-capacitors. In this paper, we report a general route towards defect- and pore- engineering in graphene through remote plasma treatments. Oxygen plasma irradiation was employed to create homogenous defects in graphene with controllable density from a few to ≈10(3) (μm(-2)). The created defects can be further enlarged into nanopores by hydrogen plasma anisotropic etching with well-defined pore size of a few nm or above. The achieved smallest nanopores are ≈2 nm in size, showing the potential for ultra-small graphene nanopores fabrication. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Detecting Defects in Aircraft Materials by Nuclear Technique (pas)

    Science.gov (United States)

    Badawi, Emad. A.

    Positron annihilation spectroscopy (PAS) is one of the nuclear techniques used in material science. The present measurements are used to study the behavior of defect concentration in one of the most important materials aluminum alloys which is the 7075 alloy. It has been shown that positrons can become trapped at imperfect locations in solids and their mean lifetime can be influenced by changes in the concentration of such defects. No changes have been observed in the mean lifetime values after the saturation of defect concentration. The mean lifetime and trapping rates are studied for samples deformed up to 58.3%. The concentration of defect range vary from 1015 to 1018cm-3 at the thickness reduction from 2.3 to 58.3%. The dislocation density varies from 108 to 1011cm/cm3.

  8. Modeling equilibrium concentrations of Bjerrum and molecular point defects and their complexes in ice I(h)

    OpenAIRE

    de Koning, Maurice; Antonelli, Alex

    2008-01-01

    We present a model for the determination of the thermal equilibrium concentrations of Bjerrum defects, molecular point defects, and their aggregates in ice I(h). First, using a procedure which minimizes the free energy of an ice crystal with respect to the numbers of defect species, we derive a set of equations for the equilibrium concentrations of free Bjerrum and point defects, as well their complexes. Using density-functional-theory calculations, we then evaluate the binding energies of Bj...

  9. Defects in new protective aprons

    Energy Technology Data Exchange (ETDEWEB)

    Glaze, S.; LeBlanc, A.D.; Bushong, S.C.

    1984-07-01

    Upon careful examination, several defects have been detected in new protective aprons. The nature of the defects is identified and described. Although the occurrence of such defects has not exceeded 5%, they are significant enough to warrant return of the lead apron to the supplier. It is recommended that the integrity of all new protective aprons be verified upon receipt as well as at yearly intervals.

  10. Structural – Electrical property correlation in defect induced nanostructured off-stoichiometric bismuth ferrite: A defect analysis

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, R.K. [Department of Physics and Material Science & Engineering, Jaypee Institute of Information Technology, Noida, U. P. 201307 (India); Jha, Pardeep K., E-mail: pardeepjha.jiit@gmail.com [Department of Physics and Material Science & Engineering, Jaypee Institute of Information Technology, Noida, U. P. 201307 (India); Jha, Priyanka A. [Department of Physics and Material Science & Engineering, Jaypee Institute of Information Technology, Noida, U. P. 201307 (India); Department of Applied Sciences, HMR Institute of Technology and Management, GGSIPU, New Delhi 110036 (India); Kumar, Pawan [School of Basic and Applied Sciences, K. R. Mangalam University, Sohna Road, Gurgaon, Haryana 122103 (India); Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2015-08-15

    In order to increase magnetization, an attempt has been made to synthesize nanostructured bismuth ferrite using high energy planetary ball milling (HEPBM). In this process local heating in HEPBM and Bi-volatility has eventually led to the formation of BiFe{sub 5}O{sub 12} (off stoichiometric bismuth iron garnet (BIG)). Electrical characterization has been done in order to identify the nature of defects and diffusion mechanism which has been supported by high resolution transmission electron microscopy and selected area electron diffraction images. The simultaneous analysis of current density-applied voltage (J–V) and current density-frequency (J–ν) curves gives insight mechanism for defect formation and how surface charge density depends on relaxation time and frequency of field applied. - Highlights: • Dielectric analysis has been carried out to analyse the defect mechanism. • RBS and EdX study confirm the elemental constituents. • Correlation between observed J-V-f behaviour and defects has been established. • HRTEM, SAED pattern and impedance analysis supports the defect analysis.

  11. RUPTURING OF POLYMER FILMS WITH RUBBING-INDUCED SURFACE DEFECTS

    Institute of Scientific and Technical Information of China (English)

    B.Du; F.C.Xie; Y.J.Wang; O.K.C.Tsui

    2003-01-01

    It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaces wherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or heterogeneous nucleation. In this experiment, we use a simple method to make the distinction through introduction of topographical defects of the films by rubbing the sample surface with a rayon cloth. Spinodal dewetting is identified for those films that dewet by a characteristic wavevector, q*, independent of the density of rubbing-induced defects. Heterogeneous nucleation, on the other hand, is identified for those with q* increasing with increasing density of defects. Our result shows that PS films on oxide coated silicon with thickness less than ≈ 13 nm are dominated by spinodal dewetting, but the thicker films are dominated by nucleation dewetting. We also confirm that spinodal dewetting does not necessarily lead to a bicontinuous morphology in the dewetting film, contrary to the classic theory of Cahn.

  12. C-V and DLTS studies of radiation induced Si-SiO{sub 2} interface defects

    Energy Technology Data Exchange (ETDEWEB)

    Capan, I., E-mail: capan@irb.hr [Rudjer Boskovic Institute, 10000 Zagreb (Croatia); Janicki, V. [Rudjer Boskovic Institute, 10000 Zagreb (Croatia); Jacimovic, R. [Jozef Stefan Institute, 1000 Ljubljana (Slovenia); Pivac, B. [Rudjer Boskovic Institute, 10000 Zagreb (Croatia)

    2012-07-01

    Interface traps at the Si-SiO{sub 2} interface have been and will be an important performance limit in many (future) semiconductor devices. In this paper, we present a study of fast neutron radiation induced changes in the density of Si-SiO{sub 2} interface-related defects. Interface related defects (P{sub b} centers) are detected before and upon the irradiation. The density of interface-related defects is increasing with the fast neutron fluence.

  13. First principles predictions of intrinsic defects in aluminum arsenide, AlAs : numerical supplement.

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter Andrew

    2012-04-01

    This Report presents numerical tables summarizing properties of intrinsic defects in aluminum arsenide, AlAs, as computed by density functional theory. This Report serves as a numerical supplement to the results published in: P.A. Schultz, 'First principles predictions of intrinsic defects in Aluminum Arsenide, AlAs', Materials Research Society Symposia Proceedings 1370 (2011; SAND2011-2436C), and intended for use as reference tables for a defect physics package in device models.

  14. Native defects and the dehydrogenation of NaBH4

    NARCIS (Netherlands)

    Cakir, Deniz; de Wijs, Gilles A.; Brocks, G.

    2011-01-01

    Chemical reactions of hydrogen storage materials often involve mass transport through a bulk solid. Diffusion in crystalline solids proceeds by means of lattice defects. Using density functional theory (DFT) calculations, we identify the stability and the mobility of the most prominent lattice

  15. Extreme ultraviolet induced defects on few-layer graphene

    NARCIS (Netherlands)

    Gao, A.; Rizo, P. J.; Zoethout, E.; Scaccabarozzi, L.; Lee, C. J.; Banine, V.; F. Bijkerk,

    2013-01-01

    We use Raman spectroscopy to show that exposing few-layer graphene to extreme ultraviolet (EUV, 13.5 nm) radiation, i.e., relatively low photon energy, results in an increasing density of defects. Furthermore, exposure to EUV radiation in a H2 background increases the graphene dosage sensitivity, du

  16. Preparation and characterization of low-defect surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, T.O.

    1991-12-01

    Silver crystal surfaces with low defect densities were prepared electrochemically from aqueous solutions using capillary-growth techniques. These surfaces had low rates for the nucleation of new silver layers. The impedance of these inert silver/aqueous silver nitrate interfaces was used to determine silver adatom concentration and water dipole reorientation energetics.

  17. Studies of defects and defect agglomerates by positron annihilation spectroscopy

    DEFF Research Database (Denmark)

    Eldrup, Morten Mostgaard; Singh, B.N.

    1997-01-01

    and with other experimental methods (in particular transmission electron microscopy) forms the basis for the use of PAS to quantitatively characterize defects and defect complexes, both visible and invisible is transmission electron microscopes: this is illustrated by some examples. Finally, the advantages...

  18. Defect Tolerance in Methylammonium Lead Triiodide Perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Steirer, K. Xerxes; Schulz, Philip; Teeter, Glenn; Stevanovic, Vladan; Yang, Mengjin; Zhu, Kai; Berry, Joseph J.

    2016-08-12

    Photovoltaic applications of perovskite semiconductor material systems have generated considerable interest in part because of predictions that primary defect energy levels reside outside the bandgap. We present experimental evidence that this enabling material property is present in the halide-lead perovskite, CH3NH3PbI3 (MAPbI3), consistent with theoretical predictions. By performing X-ray photoemission spectroscopy, we induce and track dynamic chemical and electronic transformations in the perovskite. These data show compositional changes that begin immediately with exposure to X-ray irradiation, whereas the predominant electronic structure of the thin film on compact TiO2 appears tolerant to the formation of compensating defect pairs of VI and VMA and for a large range of I/Pb ratios. Changing film composition is correlated with a shift of the valence-band maximum only as the halide-lead ratio drops below 2.5. This delay is attributed to the invariance of MAPbI3 electronic structure to distributed defects that can significantly transform the electronic density of states only when in high concentrations.

  19. Topological defects control collective dynamics in neural progenitor cell cultures

    Science.gov (United States)

    Kawaguchi, Kyogo; Kageyama, Ryoichiro; Sano, Masaki

    2017-04-01

    Cultured stem cells have become a standard platform not only for regenerative medicine and developmental biology but also for biophysical studies. Yet, the characterization of cultured stem cells at the level of morphology and of the macroscopic patterns resulting from cell-to-cell interactions remains largely qualitative. Here we report on the collective dynamics of cultured murine neural progenitor cells (NPCs), which are multipotent stem cells that give rise to cells in the central nervous system. At low densities, NPCs moved randomly in an amoeba-like fashion. However, NPCs at high density elongated and aligned their shapes with one another, gliding at relatively high velocities. Although the direction of motion of individual cells reversed stochastically along the axes of alignment, the cells were capable of forming an aligned pattern up to length scales similar to that of the migratory stream observed in the adult brain. The two-dimensional order of alignment within the culture showed a liquid-crystalline pattern containing interspersed topological defects with winding numbers of +1/2 and -1/2 (half-integer due to the nematic feature that arises from the head-tail symmetry of cell-to-cell interaction). We identified rapid cell accumulation at +1/2 defects and the formation of three-dimensional mounds. Imaging at the single-cell level around the defects allowed us to quantify the velocity field and the evolving cell density; cells not only concentrate at +1/2 defects, but also escape from -1/2 defects. We propose a generic mechanism for the instability in cell density around the defects that arises from the interplay between the anisotropic friction and the active force field.

  20. Selective sulfur dioxide adsorption on crystal defect sites on an isoreticular metal organic framework series

    Science.gov (United States)

    Rodríguez-Albelo, L. Marleny; López-Maya, Elena; Hamad, Said; Ruiz-Salvador, A. Rabdel; Calero, Sofia; Navarro, Jorge A. R.

    2017-02-01

    The widespread emissions of toxic gases from fossil fuel combustion represent major welfare risks. Here we report the improvement of the selective sulfur dioxide capture from flue gas emissions of isoreticular nickel pyrazolate metal organic frameworks through the sequential introduction of missing-linker defects and extra-framework barium cations. The results and feasibility of the defect pore engineering carried out are quantified through a combination of dynamic adsorption experiments, X-ray diffraction, electron microscopy and density functional theory calculations. The increased sulfur dioxide adsorption capacities and energies as well as the sulfur dioxide/carbon dioxide partition coefficients values of defective materials compared to original non-defective ones are related to the missing linkers enhanced pore accessibility and to the specificity of sulfur dioxide interactions with crystal defect sites. The selective sulfur dioxide adsorption on defects indicates the potential of fine-tuning the functional properties of metal organic frameworks through the deliberate creation of defects.

  1. Simulation of the diffusion features of point defects in bcc metals

    NARCIS (Netherlands)

    Chirkov, AS; Nazarov, AV; Bokstein, BS; Straumal, BB

    2006-01-01

    This work is devoted to simulation of the diffusion features of point defects in bee metals. The properties of point defects have been investigated with the usage of many-body interatomic potentials. This approach, based on the density-functional theory, permitted us to derive more adequate

  2. Simulation of the diffusion features of point defects in bcc metals

    NARCIS (Netherlands)

    Chirkov, AS; Nazarov, AV; Bokstein, BS; Straumal, BB

    2006-01-01

    This work is devoted to simulation of the diffusion features of point defects in bee metals. The properties of point defects have been investigated with the usage of many-body interatomic potentials. This approach, based on the density-functional theory, permitted us to derive more adequate diffusio

  3. Platinum Clusters on Vacancy-Type Defects of Nanometer-Sized Graphene Patches

    Directory of Open Access Journals (Sweden)

    Hisayoshi Kobayashi

    2012-07-01

    Full Text Available Density functional theory calculations found that spin density distributions of platinum clusters adsorbed on nanometer-size defective graphene patches with zigzag edges deviate strongly from those in the corresponding bare clusters, due to strong Pt-C interactions. In contrast, platinum clusters on the pristine patch have spin density distributions similar to the bare cases. The different spin density distributions come from whether underlying carbon atoms have radical characters or not. In the pristine patch, center carbon atoms do not have spin densities, and they cannot influence radical characters of the absorbed cluster. In contrast, radical characters appear on the defective sites, and thus spin density distributions of the adsorbed clusters are modulated by the Pt-C interactions. Consequently, characters of platinum clusters adsorbed on the sp2 surface can be changed by introducing vacancy-type defects.

  4. Birth Defects Research and Tracking

    Science.gov (United States)

    ... used data from the National Birth Defects Prevention Study (NBDPS) to examine maternal asthma medication use during pregnancy and the risk of certain birth defects. (Published October 22, 2014) World Down Syndrome Day Read one mother’s reflection on the birth ...

  5. Calculating charged defects using CRYSTAL

    Science.gov (United States)

    Bailey, Christine L.; Liborio, Leandro; Mallia, Giuseppe; Tomić, Stanko; Harrison, Nicholas M.

    2010-07-01

    The methodology for the calculation of charged defects using the CRYSTAL program is discussed. Two example calculations are used to illustrate the methodology: He+ ions in a vacuum and two intrinsic charged defects, Cu vacancies and Ga substitution for Cu, in the chalcopyrite CuGaS2.

  6. Facts about Atrial Septal Defect

    Science.gov (United States)

    ... Living With Heart Defects Data & Statistics Tracking & Research Articles & Key Findings Free Materials Multimedia and Tools Links to Other Websites Information For... Media Policy Makers Facts about Atrial Septal Defect Language: English Español (Spanish) Recommend on Facebook Tweet Share Compartir ...

  7. Facts about Ventricular Septal Defect

    Science.gov (United States)

    ... Living With Heart Defects Data & Statistics Tracking & Research Articles & Key Findings Free Materials Multimedia and Tools Links to Other Websites Information For... Media Policy Makers Facts about Ventricular Septal Defect Language: English Español (Spanish) Recommend on Facebook Tweet Share Compartir ...

  8. Irradiation Defects in Silicon Crystal

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The application of irradiation in silicon crystal is introduced.The defects caused by irradiation are reviewed and some major ways of studying defects in irradiated silicon are summarized.Furthermore the problems in the investigation of irradiated silicon are discussed as well as its properties.

  9. Holographic Chern-Simons Defects

    CERN Document Server

    Fujita, Mitsutoshi; Meyer, Rene; Sugimoto, Shigeki

    2016-01-01

    We study SU(N) Yang-Mills-Chern-Simons theory in the presence of defects that shift the Chern-Simons level from a holographic point of view by embedding the system in string theory. The model is a D3-D7 system in Type IIB string theory, whose gravity dual is given by the AdS soliton background with probe D7-branes attaching to the AdS boundary along the defects. We holographically renormalize the free energy of the defect system with sources, from which we obtain the correlation functions for certain operators naturally associated to these defects. We find interesting phase transitions when the separation of the defects as well as the temperature are varied. We also discuss some implications for the Fractional Quantum Hall Effect and for two-dimensional QCD.

  10. Defects and defect generation in oxide layer of ion implanted silicon-silicon dioxide structures

    CERN Document Server

    Baraban, A P

    2002-01-01

    One studies mechanism of generation of defects in Si-SiO sub 2 structure oxide layer as a result of implantation of argon ions with 130 keV energy and 10 sup 1 sup 3 - 3.2 x 10 sup 1 sup 7 cm sup - sup 2 doses. Si-SiO sub 2 structures are produced by thermal oxidation of silicon under 950 deg C temperature. Investigations were based on electroluminescence technique and on measuring of high-frequency volt-farad characteristics. Increase of implantation dose was determined to result in spreading of luminosity centres and in its maximum shifting closer to boundary with silicon. Ion implantation was shown, as well, to result in increase of density of surface states at Si-SiO sub 2 interface. One proposed model of defect generation resulting from Ar ion implantation into Si-SiO sub 2

  11. Trifocal distraction osteogenesis for reconstruction of skull defect

    Institute of Scientific and Technical Information of China (English)

    Ke Ke; Hai-Song Xu; Zhi-Hong Fan

    2013-01-01

    Objective:To apply trifocal distraction osteogenesis in canine model of skull segmental defects and to provide reference for clinical treatment. Methods:Six labrador dogs were selected in this study and divided into observation group and control group randomly. Each group contained 3 dogs. Skull segmental defects models were established by surgery, and dogs in bservation group received trifocal distraction osteogenesis treatment. Bone density was observed and compared between two groups during treatment. Results: There were no significant difference in bone density between two groups on th 1st day (P>0.05). The bone density of observation group on the 30th day, and 60th day were higher than that of control group (P<0.01). Conclusions: Trifocal distraction osteogenesis has significant clinical effect, and it would be widely used in clinical treatment.

  12. 2010 Defects in Semiconductors GRC

    Energy Technology Data Exchange (ETDEWEB)

    Shengbai Zhang

    2011-01-06

    Continuing its tradition of excellence, this Gordon Conference will focus on research at the forefront of the field of defects in semiconductors. The conference will have a strong emphasis on the control of defects during growth and processing, as well as an emphasis on the development of novel defect detection methods and first-principles defect theories. Electronic, magnetic, and optical properties of bulk, thin film, and nanoscale semiconductors will be discussed in detail. In contrast to many conferences, which tend to focus on specific semiconductors, this conference will deal with point and extended defects in a broad range of electronic materials. This approach has proved to be extremely fruitful for advancing fundamental understanding in emerging materials such as wide-band-gap semiconductors, oxides, sp{sup 2} carbon based-materials, and photovoltaic/solar cell materials, and in understanding important defect phenomena such as doping bottleneck in nanostructures and the diffusion of defects and impurities. The program consists of about twenty invited talks and a number of contributed poster sessions. The emphasis should be on work which has yet to be published. The large amount of discussion time provides an ideal forum for dealing with topics that are new and/or controversial.

  13. Software Defect Detection with Rocus

    Institute of Scientific and Technical Information of China (English)

    Yuan Jiang; Ming Li; Zhi-Hua Zhou

    2011-01-01

    Software defect detection aims to automatically identify defective software modules for efficient software test in order to improve the quality of a software system. Although many machine learning methods have been successfully applied to the task, most of them fail to consider two practical yet important issues in software defect detection. First, it is rather difficult to collect a large amount of labeled training data for learning a well-performing model; second, in a software system there are usually much fewer defective modules than defect-free modules, so learning would have to be conducted over an imbalanced data set. In this paper, we address these two practical issues simultaneously by proposing a novel semi-supervised learning approach named Rocus. This method exploits the abundant unlabeled examples to improve the detection accuracy, as well as employs under-sampling to tackle the class-imbalance problem in the learning process. Experimental results of real-world software defect detection tasks show that Rocgs is effective for software defect detection. Its performance is better than a semi-supervised learning method that ignores the class-imbalance nature of the task and a class-imbalance learning method that does not make effective use of unlabeled data.

  14. Laser annealing of silicon surface defects for photovoltaic applications

    Science.gov (United States)

    Sun, Zeming; Gupta, Mool C.

    2016-10-01

    High power lasers are increasingly used for low cost fabrication of solar cell devices. High power laser processes generate crystal defects, which lower the cell efficiency. This study examines the effect of low power laser annealing for the removal of high power laser induced surface defects. The laser annealing behavior is demonstrated by the significant decrease of photoluminescence generated from dislocation-induced defects and the increase of band-to-band emission. This annealing effect is further confirmed by the X-ray diffraction peak reversal. The dislocation density is quantified by observing etch pits under the scanning electron microscope (SEM). For as-melted samples, the dislocation density is decreased to as low as 1.01 × 106 cm- 2 after laser annealing, resulting in an excellent surface carrier lifetime of 920 μs that is comparable to the value of 1240 μs for the silicon starting wafer. For severely defective samples, the dislocation density is decreased by 4 times and the surface carrier lifetime is increased by 5 times after laser annealing.

  15. Crystal defect studies using x-ray diffuse scattering

    Energy Technology Data Exchange (ETDEWEB)

    Larson, B.C.

    1980-01-01

    Microscopic lattice defects such as point (single atom) defects, dislocation loops, and solute precipitates are characterized by local electronic density changes at the defect sites and by distortions of the lattice structure surrounding the defects. The effect of these interruptions of the crystal lattice on the scattering of x-rays is considered in this paper, and examples are presented of the use of the diffuse scattering to study the defects. X-ray studies of self-interstitials in electron irradiated aluminum and copper are discussed in terms of the identification of the interstitial configuration. Methods for detecting the onset of point defect aggregation into dislocation loops are considered and new techniques for the determination of separate size distributions for vacancy loops and interstitial loops are presented. Direct comparisons of dislocation loop measurements by x-rays with existing electron microscopy studies of dislocation loops indicate agreement for larger size loops, but x-ray measurements report higher concentrations in the smaller loop range. Methods for distinguishing between loops and three-dimensional precipitates are discussed and possibilities for detailed studies considered. A comparison of dislocation loop size distributions obtained from integral diffuse scattering measurements with those from TEM show a discrepancy in the smaller sizes similar to that described above.

  16. DEFECTS SIMULATION OF ROLLING STRIP

    Directory of Open Access Journals (Sweden)

    Rudolf Mišičko

    2009-06-01

    Full Text Available The defects in the continuous casting slabs can be developed or kept down in principle by rolling technology, especially depend to sort, size and distribution of primary defects, as well as used of rolling parameters. Scope of the article is on observation behavior artificial surface and undersurface defects (scores without filler (surface defects and filling by oxides and casting powder (subsurface defects. First phase of hot rolling process have been done by software simulation DEFORM 3D setting to the limited condition for samples with surface defects. Samples of material with low-carbon steel of sizes h x b x l have been chosen and the surface defects shape „U” and „V” of scores have been injected artificially by software. The process of rolling have been simulated on the deformation temperatures 1200°C and 900°C, whereas on the both of this deformation temperatures have been applied amount of deformation 10 and 50 %. With respect to the process of computer simulation, it is not possible to truthful real oxidation condition (physical – chemical process during heat of metal, in the second phase of our investigation have been observed influence of oxides and casting powders inside the scores for a defect behavior in plastic deformation process (hot and cold rolling process in laboratory condition. The basic material was STN steel class 11 375, cladding material was steel on the bases C-Mn-Nb-V. Scores have been filled by scales to get from the heating temperatures (1100°C a 1250°C, varied types of casting powders, if you like mixture of scale and casting powders in the rate 1:4. The joint of the basic and cladding material have been done by peripheral welded joint. Experiment results from both phases are pointed on the evolution of original typology defects in rolling process.

  17. Self-regulation of charged defect compensation and formation energy pinning in semiconductors

    Science.gov (United States)

    Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Wei, Su-Huai

    2015-11-01

    Current theoretical analyses of defect properties without solving the detailed balance equations often estimate Fermi-level pinning position by omitting free carriers and assume defect concentrations can be always tuned by atomic chemical potentials. This could be misleading in some circumstance. Here we clarify that: (1) Because the Fermi-level pinning is determined not only by defect states but also by free carriers from band-edge states, band-edge states should be treated explicitly in the same footing as the defect states in practice; (2) defect formation energy, thus defect density, could be pinned and independent on atomic chemical potentials due to the entanglement of atomic chemical potentials and Fermi energy, in contrast to the usual expectation that defect formation energy can always be tuned by varying the atomic chemical potentials; and (3) the charged defect compensation behavior, i.e., most of donors are compensated by acceptors or vice versa, is self-regulated when defect formation energies are pinned. The last two phenomena are more dominant in wide-gap semiconductors or when the defect formation energies are small. Using NaCl and CH3NH3PbI3 as examples, we illustrate these unexpected behaviors. Our analysis thus provides new insights that enrich the understanding of the defect physics in semiconductors and insulators.

  18. Defect-induced Raman spectroscopy in single-layer graphene with boron and nitrogen substitutional defects by theoretical investigation

    Science.gov (United States)

    Jiang, Jie; Pachter, Ruth; Islam, Ahmad E.; Maruyama, Benji; Boeckl, John J.

    2016-10-01

    Although advances in heteroatom incorporation into the single-layer graphene lattice resulted in films with large carrier densities, careful characterization by Raman spectroscopy is important for assessment of the material's quality. We investigated theoretically I(D)/I(D‧) Raman intensity ratios induced by B- and N- substitutional doping, demonstrated to be consistent with measurements. Calculated Fermi level shifts showed that for a moderate doping density results are comparable to electrolyte gating, while analytical analysis of the electron-defect scattering provided insight into changes of cross-sections. Effects of doping density on the D band intensity and broadening were quantified, and will assist in graphene characterization.

  19. Microscopic studies of defect formation under dense electronic excitation in insulators

    Energy Technology Data Exchange (ETDEWEB)

    Tanimura, Katsumi; Itoh, Noriaki

    1988-05-01

    Current experimental studies carried out to elucidate the lattice relaxation that occurs under dense electronic excitation in insulators are surveyed. The experimental observation treated includes defect formation by cascade-excitation of self-trapped excitons and by interaction between free and self-trapped excitons. It is pointed out that in certain solids defect generation by electronic excitation occurs only under dense electronic excitation, while in some others the defect yield depends on the density of excitation to a lesser extent. The mechanism of the effects of dense electronic excitation varies depending on the materials. Some of the crucial steps for defect formation under dense electronic excitation are presented.

  20. Magnetization of two-dimensional superconductors with defects

    CERN Document Server

    Kashurnikov, V A; Zyubin, M V

    2002-01-01

    The new method for modeling the layered high-temperature superconductors magnetization with defects, based on the Monte-Carlo algorithm, is developed. Minimization of the free energy functional of the vortex two-dimensional system made it possible to obtain the equilibrium vortex density configurations and calculate the magnetization of the superconductor with the arbitrary defects distribution in the wide range of temperatures. The magnetic induction profiles and magnetic flux distribution inside the superconductor, proving the applicability of the Bean model, are calculated

  1. Five Facts about Congenital Heart Defects

    Science.gov (United States)

    ... Button Past Emails CDC Features Five Facts about Congenital Heart Defects Language: English Español (Spanish) Recommend on Facebook Tweet Share Compartir Congenital heart defects are the most common types of birth defects. ...

  2. Defect chemistry in ferroelectric perovskites: long standing issues and recent advances.

    Science.gov (United States)

    Maglione, M; Philippot, G; Levasseur, D; Payan, S; Aymonier, C; Elissalde, C

    2015-08-14

    Accurate control of residual defect density is required for reliable investigation and use of ferroelectric materials. After reviewing the long term endeavor to decrease defect contributions in bulk materials, which reached mass production decades ago, recent challenges are underlined. These mostly result from the continuous trend towards integration which has reached the nanometre range. The contribution of solid state chemistry is of key relevance for improving the present processing routes and suggesting alternative ones, for example by controlling a large density of charged defects to reach unprecedented functionalities. Some of these breakthroughs are reviewed.

  3. Thermal conductivity of graphene with defects induced by electron beam irradiation

    Science.gov (United States)

    Malekpour, Hoda; Ramnani, Pankaj; Srinivasan, Srilok; Balasubramanian, Ganesh; Nika, Denis L.; Mulchandani, Ashok; Lake, Roger K.; Balandin, Alexander A.

    2016-07-01

    We investigate the thermal conductivity of suspended graphene as a function of the density of defects, ND, introduced in a controllable way. High-quality graphene layers are synthesized using chemical vapor deposition, transferred onto a transmission electron microscopy grid, and suspended over ~7.5 μm size square holes. Defects are induced by irradiation of graphene with the low-energy electron beam (20 keV) and quantified by the Raman D-to-G peak intensity ratio. As the defect density changes from 2.0 × 1010 cm-2 to 1.8 × 1011 cm-2 the thermal conductivity decreases from ~(1.8 +/- 0.2) × 103 W mK-1 to ~(4.0 +/- 0.2) × 102 W mK-1 near room temperature. At higher defect densities, the thermal conductivity reveals an intriguing saturation-type behavior at a relatively high value of ~400 W mK-1. The thermal conductivity dependence on the defect density is analyzed using the Boltzmann transport equation and molecular dynamics simulations. The results are important for understanding phonon - point defect scattering in two-dimensional systems and for practical applications of graphene in thermal management.We investigate the thermal conductivity of suspended graphene as a function of the density of defects, ND, introduced in a controllable way. High-quality graphene layers are synthesized using chemical vapor deposition, transferred onto a transmission electron microscopy grid, and suspended over ~7.5 μm size square holes. Defects are induced by irradiation of graphene with the low-energy electron beam (20 keV) and quantified by the Raman D-to-G peak intensity ratio. As the defect density changes from 2.0 × 1010 cm-2 to 1.8 × 1011 cm-2 the thermal conductivity decreases from ~(1.8 +/- 0.2) × 103 W mK-1 to ~(4.0 +/- 0.2) × 102 W mK-1 near room temperature. At higher defect densities, the thermal conductivity reveals an intriguing saturation-type behavior at a relatively high value of ~400 W mK-1. The thermal conductivity dependence on the defect density is

  4. Air density dependence of the response of the PTW SourceCheck 4pi ionization chamber for (125)I brachytherapy seeds.

    Science.gov (United States)

    Torres Del Río, J; Tornero-López, A M; Guirado, D; Pérez-Calatayud, J; Lallena, A M

    2017-06-01

    To analyze the air density dependence of the response of the new SourceCheck 4pi ionization chamber, manufactured by PTW. The air density dependence of three different SourceCheck 4pi chambers was studied by measuring (125)I sources. Measurements were taken by varying the pressure from 746.6 to 986.6hPa in a pressure chamber. Three different HDR 1000 Plus ionization chambers were also analyzed under similar conditions. A linear and a potential-like function of the air density were fitted to experimental data and their achievement in describing them was analyzed. SourceCheck 4pi chamber response showed a residual dependence on the air density once the standard pressure and temperature factor was applied. The chamber response was overestimated when the air density was below that under normal atmospheric conditions. A similar dependence was found for the HDR 1000 Plus chambers analyzed. A linear function of the air density permitted a very good description of this residual dependence, better than with a potential function. No significant variability between the different specimens of the same chamber model studied was found. The effect of overestimation observed in the chamber responses once they are corrected for the standard pressure and temperature may represent a non-negligible ∼4% overestimation in high altitude cities as ours (700m AMSL). This overestimation behaves linearly with the air density in all cases analyzed. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  5. Ventricular Septal Defect (For Parents)

    Science.gov (United States)

    ... Child What Kids Say About: Handling Stress Anxiety, Fears, and Phobias Community Service: A Family's Guide to ... septal defect (VSD) — sometimes referred to as a hole in the heart — is a type of congenital ...

  6. Defective Autophagy Initiates Malignant Transformation.

    Science.gov (United States)

    Galluzzi, Lorenzo; Bravo-San Pedro, José Manuel; Kroemer, Guido

    2016-05-19

    In this issue of Molecular Cell, Park et al. (2016) elegantly demonstrate that a partial defect in autophagy supports malignant transformation as it favors the production of genotoxic reactive oxygen species by mitochondria.

  7. Screening Tests for Birth Defects

    Science.gov (United States)

    ... 21 (Down syndrome) . Other trisomies include trisomy 13 (Patau syndrome) and trisomy 18 (Edwards syndrome) . A monosomy is ... which there is an extra chromosome. Trisomy 13 (Patau Syndrome): A genetic disorder that causes serious heart defects ...

  8. Atrial Septal Defect (For Teens)

    Science.gov (United States)

    ... septal defect (pronounced: AY-tree-ul SEP-tul DEE-fekt), or ASD for short, is sometimes referred ... can be treated with cardiac catheterization (pronounced: CAR-dee-ack cath-uh-turr-ih-ZAY-shun), in ...

  9. Low quantum defect laser performance

    Science.gov (United States)

    Bowman, Steven R.

    2017-01-01

    Low quantum defect lasers are possible using near-resonant optical pumping. This paper examines the laser material performance as the quantum defect of the laser is reduced. A steady-state model is developed, which incorporates the relevant physical processes in these materials and predicts extraction efficiency and waste heat generation. As the laser quantum defect is reduced below a few percent, the impact of fluorescence cooling must be included in the analysis. The special case of a net zero quantum defect laser is examined in detail. This condition, referred to as the radiation balance laser (RBL), is shown to provide two orders of magnitude lower heat generation at the cost of roughly 10% loss in extraction efficiency. Numerical examples are presented with the host materials Yb:YAG and Yb:Silica. The general conditions, which yield optimal laser efficiency, are derived and explored.

  10. Congenital heart defect - corrective surgery

    Science.gov (United States)

    ... Hypoplastic left heart repair; Tetralogy of Fallot repair; Coarctation of the aorta repair; Atrial septal defect repair; ... done in the neonatal intensive care unit (NICU). Coarctation of the aorta repair: Coarctation of the aorta ...

  11. Point defect determination by photoluminescence and capacitance—voltage characterization in a GaN terahertz Gunn diode

    Science.gov (United States)

    Li, Liang; Yang, Lin-An; Zhou, Xiao-Wei; Zhang, Jin-Cheng; Hao, Yue

    2013-08-01

    Photoluminescence (PL) measurement is used to study the point defect distribution in a GaN terahertz Gunn diode, which is able to the degrade high-field transport characteristic during further device operation. PL, secondary ion mass spectroscopy (SIMS), transmission electron microscope (TEM), and capacitance—voltage (C—V) measurements are used to discuss the origin of point defects responsible for the yellow luminescence in structures. The point defect densities of about 1011 cm-2 in structures are extracted by analysis of C—V characterization. After thermal annealing treatment, diminishments of point defect densities in structures are efficiently demonstrated by PL and C—V results.

  12. Low Bone Density

    Science.gov (United States)

    ... Information › Bone Density Exam/Testing › Low Bone Density Low Bone Density Low bone density is when your ... compared to people with normal bone density. Detecting Low Bone Density A bone density test will determine ...

  13. Stable line defects in silicene

    Science.gov (United States)

    Ghosh, Dibyajyoti; Parida, Prakash; Pati, Swapan K.

    2015-11-01

    Line defects in two-dimensional (2D) materials greatly modulate various properties of their pristine form. Using ab initio molecular dynamics (AIMD) simulations, we investigate the structural reconstructions of different kinds of grain boundaries in the silicene sheets. It is evident that depending upon the presence of silicon adatoms and edge shape of grain boundaries (i.e., armchair or zigzag), stable extended line defects (ELDs) can be introduced in a controlled way. Further studies show the stability of these line-defects in silicene, grown on Ag(111) surface at room-temperature. Importantly, unlike most of the 2D sheet materials such as graphene and hexagonal boron nitride, 5-5-8 line defects modify the nonmagnetic semimetallic pristine silicene sheet to spin-polarized metal. As ferromagnetically ordered magnetic moments remain strongly localized at the line defect, a one-dimensional spin channel gets created in silicene. Interestingly, these spin channels are quite stable because, unlike the edge of nanoribbons, structural reconstruction or contamination cannot destroy the ordering of magnetic moments here. Zigzag silicene nanoribbons with a 5-5-8 line defect also exhibit various interesting electronic and magnetic properties depending upon their width as well as the nature of the magnetic coupling between edge and defect spin states. Upon incorporation of other ELDs, such as 4-4-4 and 4-8 defects, 2D sheets and nanoribbons of silicene show a nonmagnetic metallic or semiconducting ground state. Highlighting the controlled formation of ELDs and consequent emergence of technologically important properties in silicene, we propose new routes to realize silicene-based nanoelectronic and spintronic devices.

  14. Topological Defects from the Multiverse

    CERN Document Server

    Zhang, Jun; Garriga, Jaume; Vilenkin, Alexander

    2015-01-01

    Many theories of the early universe predict the existence of a multiverse where bubbles continuously nucleate giving rise to observers in their interior. In this paper, we point out that topological defects of several dimensionalities will also be produced in de Sitter like regions of the multiverse. In particular, defects could be spontaneously nucleated in our parent vacuum. We study the evolution of these defects as they collide with and propagate inside of our bubble. We estimate the present distribution of defects in the observable part of the universe. The expected number of such nearby defects turns out to be quite small, even for the highest nucleation rate. We also study collisions of strings and domain walls with our bubble in our past light cone. We obtain simulated full-sky maps of the loci of such collisions, and find their angular size distribution. Similarly to what happens in the case of bubble collisions, the prospect of detecting any collisions of our bubble with ambient defects is greatly e...

  15. Intrauterine Infections and Birth Defects

    Institute of Scientific and Technical Information of China (English)

    XIAO-YING ZHENG; XIN-MING SONG; LI-HUA PANG; YING JI; HONG-MEI SUN; LEI ZHANG; JU-FEN LIU; YAN-LING GUO; YAN ZHANG; TING ZHANG; YI-FEI WANG; CHEN XU; GONG CHEN; RUOLEI XIN; JIA-PENG CHEN; XU-MEI HU; QING YANG

    2004-01-01

    Intrauterine infection is an important cause of some birth defects worldwide. The most common pathogens include rubella virus, cytomegaloviurs, ureaplasma urealyticum, toxoplasma, etc. General information about these pathogens in epidemiology, consequence of birth defects, and the possible mechanisms in the progress of birth defects, and the interventions to prevent or treat these pathogens' infections are described. The infections caused by rubella virus, cytomegaloviurs, ureaplasma urealyticum, toxoplasma, etc. are common, yet they are proved to be fatal during the pregnant period, especially during the first trimester. These infections may cause sterility, abortion, stillbirth, low birth weight, and affect multiple organs that may induce loss of hearing and vision, even fetal deformity and the long-term effects. These pathogens' infections may influence the microenvironment of placenta, including levels of enzymes and cytokines, and affect chondriosome that may induce the progress of birth defect. Early diagnosis of infections during pregnancy should be strengthened. There are still many things to be settled, such as the molecular mechanisms of birth defects, the effective vaccines to certain pathogens. Birth defect researches in terms of etiology and the development of applicable and sensitive pathogen detection technology and methods are imperative.

  16. Electrical fingerprint of pipeline defects

    Energy Technology Data Exchange (ETDEWEB)

    Mica, Isabella [STMicroelectronics Srl, via C.Olivetti 2, 20041 Agrate Brianza (Italy)]. E-mail: isabella.mica@st.com; Polignano, Maria Luisa [STMicroelectronics Srl, via C.Olivetti 2, 20041 Agrate Brianza (Italy); Marco, Cinzia De [STMicroelectronics Srl, via C.Olivetti 2, 20041 Agrate Brianza (Italy)

    2004-12-15

    Pipeline defects are dislocations that connect the source region of the transistor with the drain region. They were widely reported to occur in CMOS, BiCMOS devices and recently in SOI technologies. They can reduce device yield either by affecting the devices functionality or by increasing the current consumption under stand-by conditions. In this work the electrical fingerprint of these dislocations is studied, its purpose is to enable us to identify these defects as the ones responsible for device failure. It is shown that the pipeline defects are responsible for a leakage current from source to drain in the transistors. This leakage has a resistive characteristic and it is lightly modulated by the body bias. It is not sensitive to temperature; vice versa the off-current of a good transistor exhibits the well-known exponential dependence on 1/T. The emission spectrum of these defects was studied and compared with the spectrum of a good transistor. The paper aims to show that the spectrum of a defective transistor is quite peculiar; it shows well defined peaks, whereas the spectrum of a good transistor under saturation conditions is characterized by a broad spectral light emission distribution. Finally the deep-level transient spectroscopy (DLTS) is tried on defective diodes.

  17. Relic density of wino-like dark matter in the MSSM

    CERN Document Server

    Beneke, M; Dighera, F; Hellmann, C; Hryczuk, A; Recksiegel, S; Ruiz-Femenia, P

    2016-01-01

    The relic density of TeV-scale wino-like neutralino dark matter in the MSSM is subject to potentially large corrections as a result of the Sommerfeld effect. A recently developed framework enables us to calculate the Sommerfeld-enhanced relic density in general MSSM scenarios, properly treating mixed states and multiple co-annihilating channels as well as including off-diagonal contributions. Using this framework, including on-shell one-loop mass splittings and running couplings and taking into account the latest experimental constraints, we perform a thorough study of the regions of parameter space surrounding the well known pure-wino scenario: namely the effect of sfermion masses being non-decoupled and of allowing non-negligible Higgsino or bino components in the lightest neutralino. We further perform an investigation into the effect of thermal corrections and show that these can safely be neglected. The results reveal a number of phenomenologically interesting but so far unexplored regions where the Somm...

  18. Defective graphene as promising anode material for Na-ion battery and Ca-ion battery

    CERN Document Server

    Datta, Dibakar; Shenoy, Vivek B

    2013-01-01

    We have investigated adsorption of Na and Ca on graphene with divacancy (DV) and Stone-Wales (SW) defect. Our results show that adsorption is not possible on pristine graphene. However, their adsorption on defective sheet is energetically favorable. The enhanced adsorption can be attributed to the increased charge transfer between adatoms and underlying defective sheet. With the increase in defect density until certain possible limit, maximum percentage of adsorption also increases giving higher battery capacity. For maximum possible DV defect, we can achieve maximum capacity of 1459 mAh/g for Na-ion batteries (NIBs) and 2900 mAh/g for Ca-ion batteries (CIBs). For graphene full of SW defect, we find the maximum capacity of NIBs and CIBs is around 1071 mAh/g and 2142 mAh/g respectively. Our results will help create better anode materials with much higher capacity and better cycling performance for NIBs and CIBs.

  19. Actinic defect counting statistics over 1 cm2 area of EUVL mask blank

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Seongtae; Lai, Chih-Wei; Rekawa, Seno; Walton, Chris W.; Bokor, Jeffrey

    2000-02-18

    As a continuation of comparison experiments between EUV inspection and visible inspection of defects on EUVL mask blanks, we report on the result of an experiment where the EUV defect inspection tool is used to perform at-wavelength defect counting over 1 cm{sup 2} of EUVL mask blank. Initial EUV inspection found five defects over the scanned area and the subsequent optical scattering inspection was able to detect all of the five defects. Therefore, if there are any defects that are only detectable by EUV inspection, the density is lower than the order of unity per cm2. An upgrade path to substantially increase the overall throughput of the EUV inspection system is also identified in the manuscript.

  20. Possible mechanism for d0 ferromagnetism mediated by intrinsic defects

    KAUST Repository

    Zhang, Zhenkui

    2014-01-01

    We examine the effects of several intrinsic defects on the magnetic behavior of ZnS nanostructures using hybrid density functional theory to gain insights into d0 ferromagnetism. Previous studies have predicted that the magnetism is due to a coupling between partially filled defect states. By taking into account the electronic correlations, we find an additional splitting of the defect states in Zn vacancies and thus the possibility of gaining energy by preferential filling of hole states, establishing ferromagnetism between spin polarized S 3p holes. We demonstrate a crucial role of neutral S vacancies in promoting ferromagnetism between positively charged S vacancies. S dangling bonds on the nanoparticle surface also induce ferromagnetism. This journal is

  1. CRYSTAL DEFECTS IN PLASMA NITRIDED LAYER CATALYZED BY RARE EARTH

    Institute of Scientific and Technical Information of China (English)

    F.S. Chen; Y.X. Liu; D.K. Liang; L.M. Xiao

    2002-01-01

    The microstructure of plasma nitrided layer catalyzed by rare-earth elements has beenstudied with TEM. The results show that the grains of γ'-Fe4N phase are refinedby rare-earth elements and the plane defects in boundary are increased by rare-earthelements. The addition of rare-earth element increases the bombardment effect andthe number of crystal defects such as vacancies, dislocation loops, twins and stackingfaults in γ'-Fe4N phase and can produce the high-density dislocations in the ferrite ofdiffusion layer at a distance 0. 08mm from the surface. The production of a numberof crystal defects is one of important reasons why rare-earth element accelerates thediffusion of nitrogen atoms during plasma-nitridiug.

  2. Characterization of the defect levels in copper indium diselenide

    Energy Technology Data Exchange (ETDEWEB)

    Abou-Elfotouh, F.A.; Moutinho, H.; Bakry, A.; Coutts, T.J.; Kazmerski, L.L. (Solar Energy Research Inst., Golden, CO (USA))

    1991-05-01

    High-resolution photoluminescence (PL) measurements were carried out at 10 K to identify the energy levels associated with the various defect states dominating the semiconductor CuInSe{sub 2} (CIS). PL measurements were taken on the bare surfaces of both thin film and single-crystal (polished and cleaved) samples and through a (Cd, Zn)S window layer deposited by thermal co-evaporation onto the CIS absorber surface. A complete energy band diagram is proposed which identifies the origin of the 12 intrinsic defect states expected in this material. The effects of surface and heat treatments, used in device fabrication processing, on the existence and generation of defect states (deep and shallow) are identified and correlated with the device performance. The inferior single-crystal device performance is correlated with presence of a high density of process-generated radiative surface recombination states and trap levels. (orig.).

  3. UNIVERSALITY OF PHASE TRANSITION DYNAMICS: TOPOLOGICAL DEFECTS FROM SYMMETRY BREAKING

    Energy Technology Data Exchange (ETDEWEB)

    Zurek, Wojciech H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Del Campo, Adolfo [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-02-13

    In the course of a non-equilibrium continuous phase transition, the dynamics ceases to be adiabatic in the vicinity of the critical point as a result of the critical slowing down (the divergence of the relaxation time in the neighborhood of the critical point). This enforces a local choice of the broken symmetry and can lead to the formation of topological defects. The Kibble-Zurek mechanism (KZM) was developed to describe the associated nonequilibrium dynamics and to estimate the density of defects as a function of the quench rate through the transition. During recent years, several new experiments investigating formation of defects in phase transitions induced by a quench both in classical and quantum mechanical systems were carried out. At the same time, some established results were called into question. We review and analyze the Kibble-Zurek mechanism focusing in particular on this surge of activity, and suggest possible directions for further progress.

  4. Delineation of Crystalline Extended Defects on Multicrystalline Silicon Wafers

    Directory of Open Access Journals (Sweden)

    Mohamed Fathi

    2007-01-01

    Full Text Available We have selected Secco and Yang etch solutions for the crystalline defect delineation on multicrystalline silicon (mc-Si wafers. Following experimentations and optimization of Yang and Secco etching process parameters, we have successfully revealed crystalline extended defects on mc-Si surfaces. A specific delineation process with successive application of Yang and Secco agent on the same sample has proved the increased sensitivity of Secco etch to crystalline extended defects in mc-Si materials. The exploration of delineated mc-Si surfaces indicated that strong dislocation densities are localized mainly close to the grain boundaries and on the level of small grains in size (below 1 mm. Locally, we have observed the formation of several parallel dislocation lines, perpendicular to the grain boundaries. The overlapping of several dislocations lines has revealed particular forms for etched pits of dislocations.

  5. Atomic Defects and Doping of Monolayer NbSe2.

    Science.gov (United States)

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J P; Lawlor, Sean; Sanchez, Ana M; Sloan, Jeremy; Gorbachev, Roman V; Grigorieva, Irina V; Krasheninnikov, Arkady V; Haigh, Sarah J

    2017-02-24

    We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

  6. Defect Detection Techniques for Airbag Production Sewing Stages

    Directory of Open Access Journals (Sweden)

    Raluca Brad

    2014-01-01

    Full Text Available Airbags are subjected to strict quality control in order to ensure passengers safety. The quality of fabric and sewing thread influences the final product and therefore, sewing defects must be early and accurately detected, in order to remove the item from production. Airbag seams assembly can take various forms, using linear and circle primitives, with threads of different colors and length densities, creating lockstitch or double threads chainstitch. The paper presents a framework for the automatic detection of defects occurring during the airbag sewing stage. Types of defects as skipped stitch, missed stitch, or superimposed seam for lockstitch and two threads chainstitch are detected and marked. Using image processing methods, the proposed framework follows the seams path and determines if a color pattern of the considered stitches is valid.

  7. Point defects in thorium nitride: A first-principles study

    Science.gov (United States)

    Pérez Daroca, D.; Llois, A. M.; Mosca, H. O.

    2016-11-01

    Thorium and its compounds (carbides and nitrides) are being investigated as possible materials to be used as nuclear fuels for Generation-IV reactors. As a first step in the research of these materials under irradiation, we study the formation energies and stability of point defects in thorium nitride by means of first-principles calculations within the framework of density functional theory. We focus on vacancies, interstitials, Frenkel pairs and Schottky defects. We found that N and Th vacancies have almost the same formation energy and that the most energetically favorable defects of all studied in this work are N interstitials. These kind of results for ThN, to the best authors' knowledge, have not been obtained previously, neither experimentally, nor theoretically.

  8. Microstructural defects in EUROFER 97 after different neutron irradiation conditions

    Directory of Open Access Journals (Sweden)

    Christian Dethloff

    2016-12-01

    Full Text Available Characterization of irradiation induced microstructural evolution is essential for assessing the applicability of structural steels like the Reduced Activation Ferritic/Martensitic steel EUROFER 97 in upcoming fusion reactors. In this work Transmission Electron Microscopy (TEM is used to determine the defect microstructure after different neutron irradiation conditions. In particular dislocation loops, voids and precipitates are analyzed concerning defect nature, density and size distribution after irradiation to 15 dpa at 300 °C in the mixed spectrum High Flux Reactor (HFR. New results are combined with previously obtained data from irradiation in the fast spectrum BOR-60 reactor (15 and 32 dpa, 330 °C, which allows for assessment of dose and dose rate effects on the aforementioned irradiation induced defects and microstructural characteristics.

  9. Defects formation and wave emitting from defects in excitable media

    Science.gov (United States)

    Ma, Jun; Xu, Ying; Tang, Jun; Wang, Chunni

    2016-05-01

    Abnormal electrical activities in neuronal system could be associated with some neuronal diseases. Indeed, external forcing can cause breakdown even collapse in nervous system under appropriate condition. The excitable media sometimes could be described by neuronal network with different topologies. The collective behaviors of neurons can show complex spatiotemporal dynamical properties and spatial distribution for electrical activities due to self-organization even from the regulating from central nervous system. Defects in the nervous system can emit continuous waves or pulses, and pacemaker-like source is generated to perturb the normal signal propagation in nervous system. How these defects are developed? In this paper, a network of neurons is designed in two-dimensional square array with nearest-neighbor connection type; the formation mechanism of defects is investigated by detecting the wave propagation induced by external forcing. It is found that defects could be induced under external periodical forcing under the boundary, and then the wave emitted from the defects can keep balance with the waves excited from external forcing.

  10. Defects Mediated Corrosion in Graphene Coating Layer.

    Science.gov (United States)

    Lei, Jincheng; Hu, Yaowu; Liu, Zishun; Cheng, Gary J; Zhao, Kejie

    2017-04-05

    Mixed results were reported on the anticorrosion of graphene-coated metal surfaces-while graphene serves as an effective short-term barrier against corrosion and oxidation due to its low permeability to gases, the galvanic cell between graphene and the metal substrate facilitates extensive corrosion in the long run. Defects in the graphene layer provide pathways for the permeation of oxidizing species. We study the role of defects in graphene in the anticorrosion using first-principles theoretical modeling. Experiments in the highly reactive environment indicate that the oxidized products primarily distribute along the grain boundaries of graphene. We analyze the thermodynamics of the absorption of S and O on the grain boundaries of graphene on the basis of density functional theory. The insertion of S and O at the vacancy sites is energetically favorable. The interstitial impurities facilitate structural transformation of graphene and significantly decrease the mechanical strength of the graphene layer. Furthermore, the presence of the interstitial S and O reduces the chemical stability of graphene by enhancing the formation of vacancies and promoting dispersive growth of corrosive reactants along the grain boundaries.

  11. Supersymmetric defect models and mirror symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Hook, Anson; Kachru, Shamit; Torroba, Gonzalo

    2013-11-01

    We study supersymmetric field theories in three space-time dimensions doped by various configurations of electric charges or magnetic fluxes. These are supersymmetric avatars of impurity models. In the presence of additional sources such configurations are shown to preserve half of the supersymmetries. Mirror symmetry relates the two sets of configurations. We discuss the implications for impurity models in 3d NN = 4 QED with a single charged hypermultiplet (and its mirror, the theory of a free hypermultiplet) as well as 3d NN = 2 QED with one flavor and its dual, a supersymmetric Wilson-Fisher fixed point. Mirror symmetry allows us to find backreacted solutions for arbitrary arrays of defects in the IR limit of NN = 4 QED. Our analysis, complemented with appropriate string theory brane constructions, sheds light on various aspects of mirror symmetry, the map between particles and vortices and the emergence of ground state entropy in QED at finite density.

  12. Supersymmetric Defect Models and Mirror Symmetry

    CERN Document Server

    Hook, Anson; Torroba, Gonzalo

    2013-01-01

    We study supersymmetric field theories in three space-time dimensions doped by various configurations of electric charges or magnetic fluxes. These are supersymmetric avatars of impurity models. In the presence of additional sources such configurations are shown to preserve half of the supersymmetries. Mirror symmetry relates the two sets of configurations. We discuss the implications for impurity models in 3d N=4 QED with a single charged hypermultiplet (and its mirror, the theory of a free hypermultiplet) as well as 3d N=2 QED with one flavor and its dual, a supersymmetric Wilson-Fisher fixed point. Mirror symmetry allows us to find backreacted solutions for arbitrary arrays of defects in the IR limit of N=4 QED. Our analysis, complemented with appropriate string theory brane constructions, sheds light on various aspects of mirror symmetry, the map between particles and vortices and the emergence of ground state entropy in QED at finite density.

  13. Quantitative Testing of Defect for Gun Barrels

    Institute of Scientific and Technical Information of China (English)

    WANG Chang-long; JI Feng-zhu; WANG Jin; CHEN Zheng-ge

    2007-01-01

    The magnetic flux leakage (MFL) method is commonly used in the nondestructive evaluation (NDE) of gun barrels. The key point of MFL testing is to estimate the crack geometry parameters based on the measured signal. The analysis of magnetic leakage fields can be obtained by solving Maxwell's equations using finite element method (FEM).The radial component of magnetic flux density is measured in MFL testing. The peak-peak value, the separation distance between positive and negative peaks of signal and the lift-off value of Hall-sensor are used as the main features of every sample. This paper establishes the multi-regression equations related to the width (the depth) of crack and the main characteristic values. The regression model is tested by use of the magnetic leakage data. The experimental results indicate that the regression equations can accurately predict the 2-D defect geometry parameters and the MFL quantitative testing can be achieved.

  14. Distribution of Topological Defects on Axisymmetric Surface

    Institute of Scientific and Technical Information of China (English)

    SI Tie-Yan; DUAN Yi-Shi

    2006-01-01

    We propose a general method of determining the distribution of topological defects on axisymmetric surface,and study the distribution of topological defects on biconcave-discoid surface, which is the geometric configuration of red blood cell. There are three most possible cases of the distribution of the topological defects on the biconcave surface:four defects charged with 1/2, two defects charged with +1, or one defect charged with 2. For the four defect charged with 1/2, they sit at the vertices of a square imbedded in the equator of biconcave surface.

  15. Step density waves on growing vicinal crystal surfaces - Theory and experiment

    Science.gov (United States)

    Ranguelov, Bogdan; Müller, Pierre; Metois, Jean-Jacques; Stoyanov, Stoyan

    2017-01-01

    The Burton, Cabrera and Frank (BCF) theory plays a key conceptual role in understanding and modeling the crystal growth of vicinal surfaces. In BCF theory the adatom concentration on a vicinal surface obeys to a diffusion equation, generally solved within quasi-static approximation where the adatom concentration at a given distance x from a step has a steady state value n (x) . Recently, we show that going beyond this approximation (Ranguelov and Stoyanov, 2007) [6], for fast surface diffusion and slow attachment/detachment kinetics of adatoms at the steps, a train of fast-moving steps is unstable against the formation of steps density waves. More precisely, the step density waves are generated if the step velocity exceeds a critical value related to the strength of the step-step repulsion. This theoretical treatment corresponds to the case when the time to reach a steady state concentration of adatoms on a given terrace is comparable to the time for a non-negligible change of the step configuration leading to a terrace adatom concentration n (x , t) that depends not only on the terrace width, but also on its "past width". This formation of step density waves originates from the high velocity of step motion and has nothing to do with usual kinetic instabilities of step bunching induced by Ehrlich-Schwoebel effect, surface electromigration and/or the impact of impurities on the step rate. The so-predicted formation of step density waves is illustrated by numerical integration of the equations for step motion. In order to complete our previous theoretical treatment of the non-stationary BCF problem, we perform an in-situ reflection electron microscopy experiment at specific temperature interval and direction of the heating current, in which, for the first time, the step density waves instability is evidenced on Si(111) surface during highest possible Si adatoms deposition rates.

  16. Defect-related electronic metastabilities in chalcopyrite compounds

    Energy Technology Data Exchange (ETDEWEB)

    Hammer, Maria S., E-mail: maria.hammer@uni-oldenburg.de [Energy and Semiconductor Research Laboratory, Department of Physics, University of Oldenburg, 26111 Oldenburg (Germany); Neugebohrn, Nils; Riediger, Julia; Neerken, Janet; Ohland, Jörg; Riedel, Ingo [Energy and Semiconductor Research Laboratory, Department of Physics, University of Oldenburg, 26111 Oldenburg (Germany); Kiowski, Oliver; Wischmann, Wiltraud [Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Industriestr. 6, 70565 Stuttgart (Germany)

    2014-04-15

    So far, in Cu(In,Ga)Se{sub 2} solar cells the metastable behavior of the key parameters, i.e. open circuit voltage, short circuit current and fill factor, and the corresponding defect physics were typically investigated independently. In order to contribute to this issue, we systematically varied between annealed and light soaked state and investigated the influence of these processes on the solar cell parameters as well as on the defect physics. In this work, we attempt to correlate the key parameters of the solar cells and the defect physics by discussing experimental results obtained from temperature dependent current–voltage measurements (IVT) as well as from capacitance voltage (CV), admittance (AS) and deep-level transient spectroscopy (DLTS). A commonly observed defect contribution in Cu(In,Ga)Se{sub 2} solar cells is the so-called N1 signature. The activation energy of this signature was found to increase upon air-annealing in the dark which goes along with a decrease in the open circuit voltage and the effective doping density. In this paper we will discuss the correlation between annealing-induced shifting of defect energies and the variation of the key parameters.

  17. Revisiting the reasons for contact fatigue defects in rails

    Directory of Open Access Journals (Sweden)

    Darenskiy Alexander

    2017-01-01

    Full Text Available As it is known rail is one of the most significant elements of the whole railway construction. Operation under alternating loads from wheels of the rolling stock and different ambient temperatures lead to appearance and development of rail defects and damages. A great variety of operational factors (freight traffic density, axial loads, traffic speeds, track layout and profile as well as special features of manufacturing and thermal treatment of rails create certain difficulties while identifying reasons for defects and damages. The article deals with an attempt to estimate influence of track layout and lateral forces on appearance of defects and damages in rails on the base of long-term observations of rail operation in Kharkiv Metro. On the basis of the vehicle/track mathematical model which considers structural features of both rolling stock and permanent way in underground systems, the level of lateral forces in curves was calculated. The coefficients of correlation between the track curvature, the level of forces and the amount of defected rails removed were later obtained, that made it possible to determine the dominant factor which may lead to appearance and development of contact fatigue defects in rails laid in curves.

  18. Atomistic stimulation of defective oxides

    CERN Document Server

    Minervini, L

    2000-01-01

    defect processes. The predominant intrinsic disorder reaction and the mechanism by which excess oxygen is accommodated are established. Furthermore, the most favourable migration mechanism and pathway for oxygen ions is predicted. Chapters 7 and 8 investigate pyrochlore oxides. These materials are candidates for solid oxide fuel cell components and as actinide host phases. Such applications require a detailed understanding of the defect processes. The defect energies, displayed as contour maps, are able to account for structure stability and, given an appropriate partial charge potential model, to accurately determine the oxygen positional parameter. In particular, the dependence of the positional parameter on intrinsic disorder is predicted. It is demonstrated, by radiation damage experiments, that these results are able to predict the radiation performance of pyrochlore oxides. Atomistic simulation calculations based on energy minimization techniques and classical pair potentials are used to study several i...

  19. Defect CFTs and holographic multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Fiol, Bartomeu, E-mail: bfiol@ub.edu [Departament de Física Fonamental i Institut de Ciències del Cosmos, Universitat de Barcelona, Martí i Franquès 1, 08193 Barcelona (Spain)

    2010-07-01

    We investigate some aspects of a recent proposal for a holographic description of the multiverse. Specifically, we focus on the implications on the suggested duality of the fluctuations of a bubble separating two universes with different cosmological constants. We do so by considering a similar problem in a 2+1 CFT with a codimension one defect, obtained by an M5-brane probe embedding in AdS{sub 4} × S{sup 7}, and studying its spectrum of fluctuations. Our results suggest that the kind of behavior required by the spectrum of bubble fluctuations is not likely to take place in defect CFTs with an AdS dual, although it might be possible if the defect supports a non-unitary theory.

  20. Congenital heart defects and medical imaging.

    Science.gov (United States)

    Gehin, Connie; Ragsdale, Lisa

    2013-01-01

    Radiologic technologists perform imaging studies that are useful in the diagnosis of congenital heart defects in infants and adults. These studies also help to monitor congenital heart defect repairs in adults. This article describes the development and functional anatomy of the heart, along with the epidemiology and anatomy of congenital heart defects. It also discusses the increasing population of adults who have congenital heart defects and the most effective modalities for diagnosing, evaluating, and monitoring congenital heart defects.

  1. Defect reduction in seeded aluminum nitride crystal growth

    Science.gov (United States)

    Bondokov, Robert T.; Morgan, Kenneth E.; Schowalter, Leo J.; Slack, Glen A.

    2017-06-06

    Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density .ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

  2. Defect reduction in seeded aluminum nitride crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Bondokov, Robert T.; Morgan, Kenneth E.; Schowalter, Leo J.; Stack, Glen A.

    2017-04-18

    Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density.ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

  3. First-principles study of defect behavior in irradiated uranium monocarbide

    Science.gov (United States)

    Ducher, R.; Dubourg, R.; Barrachin, M.; Pasturel, A.

    2011-03-01

    Ab initio electron theory based on the projector-augmented-wave method in the generalized gradient approximation of the density functional theory is used for calculating formation and migration energies of point defects in uranium monocarbide (UC). The use of the Hubbard term to describe the 5f electrons of uranium is discussed on the basis of the density of states and cohesive energies. A formalism allowing the “raw” calculated energies to be normalized is proposed to take into account the compositional dependence of defective crystals. Such formation energies are then used to determine the population of predominant defects as a function of nonstoichiometry. We identify the most stable defects as uranium antisites and carbon vacancies for UC1-x, and dimers C2 for UC1+x. The most stable thermal defects are obtained, in turn, by formation of complex defects associating dimer C2 and carbon vacancies whereas carbon Frenkel pairs and Schottky defects require larger formation energies. The migration energies are also calculated for different mechanisms, using as diffusion vectors both thermal vacancy sources and preexisting constitutional defects in the case of off-stoichiometric alloys. We compare the calculated diffusion paths with available experimental data proposed by Matzke [J. Less-Common Met.JCOMAH0022-508810.1016/0022-5088(86)90573-4 121, 537 (1986)].

  4. Behavior of deep level defects on voltage-induced stress of Cu(In,Ga)Se{sub 2} solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.W.; Cho, S.E. [Department of Physics and Semiconductor Science, Dongguk University, Seoul (Korea, Republic of); Jeong, J.H. [Solar Cell Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); Cho, H.Y., E-mail: hycho@dongguk.edu [Department of Physics and Semiconductor Science, Dongguk University, Seoul (Korea, Republic of)

    2015-05-01

    The behavior of deep level defects by a voltage-induced stress for CuInGaSe{sub 2} (CIGS) solar cells has been investigated. CIGS solar cells were used with standard structures which are Al-doped ZnO/i-ZnO/CdS/CIGSe{sub 2}/Mo on soda lime glass, and that resulted in conversion efficiencies as high as 16%. The samples with the same structure were isothermally stressed at 100 °C under the reverse voltages. The voltage-induced stressing in CIGS samples causes a decrease in the carrier density and conversion efficiency. To investigate the behavior of deep level defects in the stressed CIGS cells, photo-induced current transient spectroscopy was utilized, and normally 3 deep level defects (including 2 hole traps and 1 electron trap) were found to be located at 0.18 eV and 0.29 eV above the valence band maximum (and 0.36 eV below the conduction band). In voltage-induced cells, especially, it was found that the decrease of the hole carrier density could be responsible for the increase of the 0.29 eV defect, which is known to be observed in less efficient CIGS solar cells. And the carrier density and the defects are reversible at least to a large extent by resting at room-temperature without the bias voltage. From optical capture kinetics in photo-induced current transient spectroscopy measurement, the types of defects could be distinguished into the isolated point defect and the extended defect. In this work, it is suggested that the increase of the 0.29 eV defect by voltage-induced stress could be due to electrical activation accompanied by a loss of positive ion species and the activated defect gives rise to reduction of the carrier density. - Highlights: • We investigated behavior of deep level defects by voltage-induced stress. • Defect generation could affect the decrease of the conversion efficiency of cells. • Defect generation could be electrically activated by a loss of positive ion species. • Type of defects could be studied with models of point defects

  5. Alarming Rise In Birth Defects

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A rapid rise in birth defects has prompted China to look for causes and solutionsEvery 60 seconds two children are born in China with a handicap.It’s an alarming fact,but one that young adults across the country who hope to have children face every day. At a conference on the prevention of birth defects in Chengdu of Sichuan Province in September,Vice Minister of the National Population and Family Planning Commission Jiang Fan revealed this inconvenient truth, supported by shocking statistics.

  6. Atrial – Ventricular Septal Defect

    Directory of Open Access Journals (Sweden)

    T Panagiotopoulos

    2009-05-01

    Full Text Available Atrial and ventricular septal defect constitute the most common congenital heart disease.Aim: Τhe aim of the present retrospective study was to record data and factors that affect atrial and ventricular septal defect.Method and material: The sample study included patients of both sexes who were hospitalized with diagnosis atrial and ventricular septal defect in a Cardiac Surgery hospital of Athens. A specially constructed printed form was used for data collection, where were recorded the demographic and personal variables, the pathological, surgical, cardiology and obstetric history, the habits of adults, as well as the personal characteristics of mothers. Analysis of data was performed by descriptive statistical analysis.Results: The sample study consisted of 101 individuals with diagnosis atrial or ventricular Septal Defect, of which 40% were boys and 60% girls. The 70% of the sample study suffered from atrial Septal Defect and the 30% suffered from ventricular Septal Defect. Regarding age, 12% of the sample study was 0-1 years old, 35% was >1 years old, 8% was >12-18 years old and 45% over than 18 years old. Regarding educational status of the adult participants, 9% was of 0-6 years education, 22%>6 -12 years, 13%>12 years. 14% of the adult paticipants smoked, 4% consumed alcohol and 5% smoked in conjunction with alcohol. In terms of the obstetric history of the sample studied, 32% of the cases had normal birth, 4% had a twin birth and 1% had a triplet one. According to the variables related to mothers, the mean age of the mother was 30 years and 3 months, 10% were smokers at pregnancy and 3% used chemical substance and mainly hair color. Also, the results of the present study showed that individuals of 12-18 and >18 years old did not suffer from ventricular Septal Defect, whereas the infants 0-1 years old did not suffer from Atrial Septal Defect. The mean value of age at the admission in intensive care unit was 7 months (12% for the infants

  7. Moduli inflation with large scale structure produced by topological defects

    CERN Document Server

    Freese, Katherine; Umeda, H; Freese, Katherine; Gherghetta, Tony; Umeda, Hideyuki

    1996-01-01

    It is tempting to inflate along one of the many flat directions that arise in supersymmetric theories. The required flatness of the potential to obtain sufficient inflation and to not overproduce density fluctuations occurs naturally. However, the density perturbations (in the case of a single moduli field) that arise from inflaton quantum fluctuations are too small for structure formation. Here we propose that topological defects (such as cosmic strings), which arise during a phase transition near the end of moduli inflation can provide an alternative source of structure. The strings produced will be `fat', yet have the usual evolution by the time of nucleosynthesis. Possible models are discussed.

  8. G-centers in irradiated silicon revisited: A screened hybrid density functional theory approach

    KAUST Repository

    Wang, H.

    2014-05-13

    Electronic structure calculations employing screened hybrid density functional theory are used to gain fundamental insight into the interaction of carbon interstitial (Ci) and substitutional (Cs) atoms forming the CiCs defect known as G-center in silicon (Si). The G-center is one of the most important radiation related defects in Czochralski grown Si. We systematically investigate the density of states and formation energy for different types of CiCs defects with respect to the Fermi energy for all possible charge states. Prevalence of the neutral state for the C-type defect is established.

  9. Facts about Upper and Lower Limb Reduction Defects

    Science.gov (United States)

    ... Heart Defects Atrial Septal Defect Atrioventricular Septal Defect Coarctation of the Aorta D-Transposition of the Great ... Defects Fetal Alcohol Syndrome Disorders Gastroschisis Heart Defects Coarctation of the Aorta Hypoplastic left heart syndrome Tetralogy ...

  10. Hamiltonian monodromy as lattice defect

    OpenAIRE

    Zhilinskii, B.

    2003-01-01

    The analogy between monodromy in dynamical (Hamiltonian) systems and defects in crystal lattices is used in order to formulate some general conjectures about possible types of qualitative features of quantum systems which can be interpreted as a manifestation of classical monodromy in quantum finite particle (molecular) problems.

  11. Ocular defects in cerebral palsy

    Directory of Open Access Journals (Sweden)

    Katoch Sabita

    2007-01-01

    Full Text Available There is a high prevalence of ocular defects in children with developmental disabilities. This study evaluated visual disability in a group of 200 cerebral palsy (CP patients and found that 68% of the children had significant visual morbidity. These findings emphasize the need for an early ocular examination in patients with CP.

  12. Brane Inflation and Defect Formation

    CERN Document Server

    Davis, A C; Van de Bruck, C

    2008-01-01

    Brane inflation and the production of topological defects at the end of the inflationary phase are discussed. After a description of the inflationary setup we discuss the properties of the cosmic strings produced at the end of inflation. Specific examples of brane inflation are described: $D-\\bar D$ inflation, $D3/D7$ inflation and modular inflation

  13. Nuclear Pasta: Topology and Defects

    Science.gov (United States)

    da Silva Schneider, Andre; Horowitz, Charles; Berry, Don; Caplan, Matt; Briggs, Christian

    2015-04-01

    A layer of complex non-uniform phases of matter known as nuclear pasta is expected to exist at the base of the crust of neutron stars. Using large scale molecular dynamics we study the topology of some pasta shapes, the formation of defects and how these may affect properties of neutron star crusts.

  14. Genetic defects of iron transport.

    Science.gov (United States)

    Bannerman, R M

    1976-09-01

    Five genetic traits in man and laboratory animals have major effects on iron transport. The heterogeneous condition, hemochromatosis, in some families appears to segregate as a Mendelian trait, and is associated with defective control of intestinal iron absorption. In the very rare human autosomal recessive trait, atransferrinemia, there is an almost total lack of transferrin and gross maldistribution of iron through the body. In mice, sex-linked anemia (an X-linked recessive trait) causes iron deficiency through defective iron absorption, at the "exit" step; a similar defect probably exists in placental iron transfer. In microcytic anemia of mice, an autosomal recessive trait, iron absorption is also impaired because of a defect of iron entry into cells, which is probably generalized. Belgrade rat anemia, less understood at present, also may involve a major disorder of iron metabolism. Study of these mutations has provided new knowledge of iron metabolism and its genetic control Their phenotypic interaction with nutritional factors, especially the form and quantity of iron in the diet, may provide new insights for the study of nutrition.

  15. Mass transport through defected bentonite plugs

    Energy Technology Data Exchange (ETDEWEB)

    Oscarson, D.W.; Dixon, D.A.; Hume, H.B

    1996-07-01

    Compacted bentonite-based materials are important barriers in many waste containment strategies. To function as effective barriers, however, these materials must maintain their low water permeability and molecular diffusivity for long periods of time under a variety of environmental conditions. Here we examine the permeability and diffusivity of compacted bentonite plugs that were either slotted, to mimic fractures, parallel to the direction of mass flow or heated at 150 and 250{sup o}C for several weeks at various moisture contents before testing. The dry density of the plugs ranged from about 0.9 to 1.3 Mg/m{sup 3}. The results show that the saturated hydraulic conductivity and diffusivity (for I{sup -} and Cs{sup +}) of the treated or 'defected' bentonite plugs are essentially the same as those of untreated plugs at similar densities. This provides confidence that compacted bentonitic materials can function effectively as barriers for long periods of time under a range of environmental conditions. (author)

  16. Transport-reaction model for defect and carrier behavior within displacement cascades in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Wampler, William R.; Myers, Samuel Maxwell,

    2014-02-01

    A model is presented for recombination of charge carriers at displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers and defects within a representative spherically symmetric cluster. The initial radial defect profiles within the cluster were chosen through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Charging of the defects can produce high electric fields within the cluster which may influence transport and reaction of carriers and defects, and which may enhance carrier recombination through band-to-trap tunneling. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to pulsed neutron irradiation.

  17. Modelling water vapour permeability through atomic layer deposition coated photovoltaic barrier defects

    Energy Technology Data Exchange (ETDEWEB)

    Elrawemi, Mohamed, E-mail: Mohamed.elrawemi@hud.ac.uk [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom); Blunt, Liam; Fleming, Leigh [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom); Bird, David, E-mail: David.Bird@uk-cpi.com [Centre for Process Innovation Limited, Sedgefield, County Durham (United Kingdom); Robbins, David [Centre for Process Innovation Limited, Sedgefield, County Durham (United Kingdom); Sweeney, Francis [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom)

    2014-11-03

    Transparent barrier films such as Al{sub 2}O{sub 3} used for prevention of oxygen and/or water vapour permeation are the subject of increasing research interest when used for the encapsulation of flexible photovoltaic modules. However, the existence of micro-scale defects in the barrier surface topography has been shown to have the potential to facilitate water vapour ingress, thereby reducing cell efficiency and causing internal electrical shorts. Previous work has shown that small defects (≤ 3 μm lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (≥ 3 μm lateral dimension) seem to be more detrimental to the barrier functionality. Experimental results based on surface topography segmentation analysis and a model presented in this paper will be used to test the hypothesis that the major contributing defects to water vapour transmission rate are small numbers of large defects. The model highlighted in this study has the potential to be used for gaining a better understanding of photovoltaic module efficiency and performance. - Highlights: • A model of water vapour permeation through barrier defects is presented. • The effect of the defects on the water vapour permeability is investigated. • Defect density correlates with water vapour permeability. • Large defects may dominate the permeation properties of the barrier film.

  18. COMPARISON BETWEEN WOOD DRYING DEFECT SCORES: SPECIMEN TESTING X ANALYSIS OF KILN-DRIED BOARDS

    Directory of Open Access Journals (Sweden)

    Djeison Cesar Batista

    2015-04-01

    Full Text Available It is important to develop drying technologies for Eucalyptus grandis lumber, which is one of the most planted species of this genus in Brazil and plays an important role as raw material for the wood industry. The general aim of this work was to assess the conventional kiln drying of juvenile wood of three clones of Eucalyptus grandis. The specific aims were to compare the behavior between: i drying defects indicated by tests with wood specimens and conventional kiln-dried boards; and ii physical properties and the drying quality. Five 11-year-old trees of each clone were felled, and only flatsawn boards of the first log were used. Basic density and total shrinkage were determined, and the drying test with wood specimens at 100 °C was carried out. Kiln drying of boards was performed, and initial and final moisture content, moisture gradient in thickness, drying stresses and drying defects were assessed. The defect scoring method was used to verify the behavior between the defects detected by specimen testing and the defects detected in kiln-dried boards. As main results, the drying schedule was too severe for the wood, resulting in a high level of boards with defects. The behavior between the defects in the drying test with specimens and the defects of kiln-dried boards was different, there was no correspondence, according to the defect scoring method.

  19. Effect of tin doping on oxygen- and carbon-related defects in Czochralski silicon

    Energy Technology Data Exchange (ETDEWEB)

    Chroneos, A. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Londos, C. A.; Sgourou, E. N. [University of Athens, Solid State Physics Section, Panepistimiopolis Zografos, Athens 157 84 (Greece)

    2011-11-01

    Experimental and theoretical techniques are used to investigate the impact of tin doping on the formation and the thermal stability of oxygen- and carbon-related defects in electron-irradiated Czochralski silicon. The results verify previous reports that Sn doping reduces the formation of the VO defect and suppresses its conversion to the VO{sub 2} defect. Within experimental accuracy, a small delay in the growth of the VO{sub 2} defect is observed. Regarding carbon-related defects, it is determined that Sn doping leads to a reduction in the formation of the C{sub i}O{sub i}, C{sub i}C{sub s}, and C{sub i}O{sub i}(Si{sub I}) defects although an increase in their thermal stability is observed. The impact of strain induced in the lattice by the larger tin substitutional atoms, as well as their association with intrinsic defects and carbon impurities, can be considered as an explanation to account for the above observations. The density functional theory calculations are used to study the interaction of tin with lattice vacancies and oxygen- and carbon-related clusters. Both experimental and theoretical results demonstrate that tin co-doping is an efficient defect engineering strategy to suppress detrimental effects because of the presence of oxygen- and carbon-related defect clusters in devices.

  20. Interactions of structural defects with metallic impurities in multicrystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    McHugo, S.A.; Thompson, A.C. [Lawrence Berkeley National Lab., CA (United States); Hieslmair, H. [Univ. of California, Berkeley, CA (United States)] [and others

    1997-04-01

    Multicrystalline silicon is one of the most promising materials for terrestrial solar cells. It is critical to getter impurities from the material as well as inhibit contamination during growth and processing. Standard processing steps such as, phosphorus in-diffusion for p-n junction formation and aluminum sintering for backside ohmic contact fabrication, intrinsically possess gettering capabilities. These processes have been shown to improve L{sub n} values in regions of multicrystalline silicon with low structural defect densities but not in highly dislocated regions. Recent Deep Level Transient Spectroscopy (DLTS) results indirectly reveal higher concentrations of iron in highly dislocated regions while further work suggests that the release of impurities from structural defects, such as dislocations, is the rate limiting step for gettering in multicrystalline silicon. The work presented here directly demonstrates the relationship between metal impurities, structural defects and solar cell performance in multicrystalline silicon. Edge-defined Film-fed Growth (EFG) multicrystalline silicon in the as-grown state and after full solar cell processing was used in this study. Standard solar cell processing steps were carried out at ASE Americas Inc. Metal impurity concentrations and distributions were determined by use of the x-ray fluorescence microprobe (beamline 10.3.1) at the Advanced Light Source, Lawrence Berkeley National Laboratory. The sample was at atmosphere so only elements with Z greater than silicon could be detected, which includes all metal impurities of interest. Structural defect densities were determined by preferential etching and surface analysis using a Scanning Electron Microscope (SEM) in secondary electron mode. Mapped areas were exactly relocated between the XRF and SEM to allow for direct comparison of impurity and structural defect distributions.

  1. First-Principles Study of Electronic Properties in PbS((1)OO) with Vacancy Defect

    Institute of Scientific and Technical Information of China (English)

    DING Zong-Ling; XING Huai-Zhong; XU Sheng-Lan; HUANG Yan; CHEN Xiao-Shuang

    2007-01-01

    Electronic properties of both Pb and S vacancy defects in PbS(100) have been studied using the first-principles density functional theory (DFT) calculations with the plane-wave pseudopotentials. It is found that the density of states (DOS) near the top of the valence band and the bottom of the conduction band is significantly modified by these defects. Our calculation indicates that in the case of S vacancy defects the Fermi energy shifts to the conduction band making it as an n-type PbS (donor). However, in the case of Pb vacancy, because of the appreciable change of the DOS, the system acts as a p-type PbS (accepter). In addition, the structural relaxation shows that the defect leads to outward relaxation of the nearest-neighbouring atoms and inward relaxation of the next-nearest neighbouring atoms.

  2. Electron Density Determination, Bonding and Properties of Tetragonal Ferromagnetic Intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Wiezorek, Jorg [Univ. of Pittsburgh, PA (United States)

    2016-09-01

    . This implies that onsite Coulomb repulsion effects become non-negligible as the d-orbitals fill. The use of now easily measured low-order structure factors as an additional experimental metric in validation of DFT calculation of electronic structures of crystals offers potential to capture better both total energy related properties and details of the interatomic bonding in system with d-electron orbital contributions. This effort advanced the state of the art in quantitative TEM experimentation, provides original experimental data uniquely suited for new validation approaches of DFT calculations of d-electron affected transition metals and intermetallics.

  3. Casting defects analysis by the Pareto method

    Directory of Open Access Journals (Sweden)

    B. Borowiecki

    2011-07-01

    Full Text Available On the basis of receive results formed of diagram Pareto Lorenz. On the basis of receive graph it affirmed, that for 70% general number casting defects answered 3 defects (9 contribution – 100% defects. For 70% general number defects of influence it has three type of causes: sand holes, porosity and slaginclusions. Thedefects show that it is necessary to take up construction gatingsystem. The remaining 8 causes have been concerned only 25%, with general number of casting defects. Analysis of receive results permit to determine of direction of correct actions in order to eliminate or to limit the most defects.

  4. Independent Modulation of Omnidirectional Defect Modes in Single-Negative Materials Photonic Crystal with Multiple Defects

    Institute of Scientific and Technical Information of China (English)

    WANG Qiong; YAN Chang-Chun; ZHANG Ling-Ling; CUI Yi-Ping

    2008-01-01

    @@ Single-negative materials based on photonic crystal with multiple defect layers are designed and the free modulation of defect modes is studied. The results show that the multi-defect structure can avoid the interference between the defect states. Therefore, the designed double defect modes in the zero effective-phase gap can be adjusted independently by changing the thickness of different defect layers. In addition, the two tunable defect modes have the omnidirectional characteristics. This multi-defect structure with above-mentioned two advantages has potential applications in modern optical devices such as tunable omnidirectional filters.

  5. Effect of radiation-induced substrate defects on microstrip gas chamber gain behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Pallares, A.; Brom, J.M.; Bergdolt, A.M.; Coffin, J.; Eberle, H.; Sigward, M.H. [Institute de Recherches Subatomiques, 67 - Strasbourg (France); Fontaine, J.C. [Universite de Haute Alsace, GRPHE, 61 rue Albert Camus, 68093 Mulhouse Cedex (France); Barthe, S.; Schunck, J.P. [Laboratoire PHASE (UPR 292 du CNRS), 23 rue du Loess, BP 28, 67037 Strasbourg Cedex 2 (France)

    1998-08-01

    The aim of this work was to quantify the influence of radiation-induced substrate defects on microstrip gas chamber (MSGC) gain behaviour. The first part of this paper focuses on radiation effects on a typical MSGC substrate: Desag D263 glass. Defect generation was studied for Desag D263 with pure silica (Suprasil 1) as a reference. We studied the evolution of defect concentration with respect to accumulated doses up to 480 kGy. Annealing studies of defects in Desag D263 were also performed. In the second part, the radiation sensitivity of Desag D263 glass has been linked to the behaviour of the detector under irradiation. Comparative gain measurements were taken before and after substrate irradiation at 10 and 80 kGy the minimal dose received during LHC operation and the dose for which defect density is maximum (respectively). (orig.) 26 refs.

  6. A study of defects on EUV mask using blank inspection, patterned mask inspection, and wafer inspection

    Energy Technology Data Exchange (ETDEWEB)

    Huh, S.; Ren, L.; Chan, D.; Wurm, S.; Goldberg, K. A.; Mochi, I.; Nakajima, T.; Kishimoto, M.; Ahn, B.; Kang, I.; Park, J.-O.; Cho, K.; Han, S.-I.; Laursen, T.

    2010-03-12

    The availability of defect-free masks remains one of the key challenges for inserting extreme ultraviolet lithography (EUVL) into high volume manufacturing. yet link data is available for understanding native defects on real masks. In this paper, a full-field EUV mask is fabricated to investigate the printability of various defects on the mask. The printability of defects and identification of their source from mask fabrication to handling were studied using wafer inspection. The printable blank defect density excluding particles and patterns is 0.63 cm{sup 2}. Mask inspection is shown to have better sensitivity than wafer inspection. The sensitivity of wafer inspection must be improved using through-focus analysis and a different wafer stack.

  7. Effect of vacancy defects on generalized stacking fault energy of fcc metals.

    Science.gov (United States)

    Asadi, Ebrahim; Zaeem, Mohsen Asle; Moitra, Amitava; Tschopp, Mark A

    2014-03-19

    Molecular dynamics (MD) and density functional theory (DFT) studies were performed to investigate the influence of vacancy defects on generalized stacking fault (GSF) energy of fcc metals. MEAM and EAM potentials were used for MD simulations, and DFT calculations were performed to test the accuracy of different common parameter sets for MEAM and EAM potentials in predicting GSF with different fractions of vacancy defects. Vacancy defects were placed at the stacking fault plane or at nearby atomic layers. The effect of vacancy defects at the stacking fault plane and the plane directly underneath of it was dominant compared to the effect of vacancies at other adjacent planes. The effects of vacancy fraction, the distance between vacancies, and lateral relaxation of atoms on the GSF curves with vacancy defects were investigated. A very similar variation of normalized SFEs with respect to vacancy fractions were observed for Ni and Cu. MEAM potentials qualitatively captured the effect of vacancies on GSF.

  8. Impact of Interfacial Defects on the Properties of Monolayer Transition Metal Dichalcogenide Lateral Heterojunctions

    KAUST Repository

    Cao, Zhen

    2017-03-25

    We explored the impact of interfacial defects on the stability and optoelectronic properties of monolayer transition metal dichalcogenide lateral heterojunctions using a density functional theory approach. As a prototype, we focused on the MoS2-WSe2 system and found that even a random alloy-like interface with a width of less than 1 nm has only a minimal impact on the band gap and alignment compared to the defect-less interface. The largest impact is on the evolution of the electrostatic potential across the monolayer. Similar to defect-less interfaces, a small number of defects results in an electrostatic potential profile with a sharp change at the interface, which facilitates exciton dissociation. Differently, a large number of defects results in an electrostatic potential profile switching smoothly across the interface, which is expected to reduce the capability of the heterojunction to promote exciton dissociation. These results are generalizable to other transition metal dichalcogenide lateral heterojunctions.

  9. Comparative theoretical study of adsorption of lithium polysulfides (Li2Sx) on pristine and defective graphene

    Science.gov (United States)

    Jand, Sara Panahian; Chen, Yanxin; Kaghazchi, Payam

    2016-03-01

    Adsorption of Li2Sx on pristine and defective (Stone-Wales (SW) and vacancy) graphene is studied using density functional theory. Results show that the interaction between Li2Sx and graphene is dominated by dispersion interaction (physisorption), which depends on the size of molecule as well as the existence and type of defect sites on graphene. We find that single Li2Sx molecules interact only slightly stronger to the SW sites than to the defect-free sites, but they interact very strongly with single-vacant defects. In the later cases, the vacant site catches one S atom from the Li2Sx molecule, leading to the formation of a Li2Sx-1 molecule, which adsorbs weakly on the created S-doped graphene. This study suggests that defect sites can not improve the ability of graphene to catch lithium polysulfides in Li-S batteries.

  10. Spectroscopic investigation of native defect induced electron-phonon coupling in GaN nanowires

    Science.gov (United States)

    Parida, Santanu; Patsha, Avinash; Bera, Santanu; Dhara, Sandip

    2017-07-01

    The integration of advanced optoelectronic properties in nanoscale devices of group III nitride can be realized by understanding the coupling of charge carriers with optical excitations in these nanostructures. The native defect induced electron-phonon coupling in GaN nanowires are reported using various spectroscopic studies. The GaN nanowires having different native defects are grown in an atmospheric pressure chemical vapor deposition technique. X-ray photoelectron spectroscopic analysis revealed the variation of Ga/N ratios in nanowires having possible native defects, with respect to their growth parameters. The analysis of the characteristic features of electron-phonon coupling in the Raman spectra show the variations in carrier density and mobility, with respect to the native defects in unintentionally doped GaN nanowires. The radiative recombination of donor acceptor pair transitions and the corresponding LO phonon replicas observed in photoluminescence studies further emphasize the role of native defects in electron-phonon coupling.

  11. Anomalous Enhancement of Mechanical Properties in the Ammonia Adsorbed Defective Graphene

    Science.gov (United States)

    Ma, Fengxian; Jiao, Yalong; Gu, Yuantong; Bilic, Ante; Chen, Ying; Chen, Zhongfang; Du, Aijun

    2016-01-01

    Pure graphene is known as the strongest material ever discovered. However, the unavoidable defect formation in the fabrication process renders the strength of defective graphene much lower (~14%) than that of its perfect counterpart. By means of density functional theory computations, we systematically explored the effect of gas molecules (H2, N2, NH3, CO, CO2 and O2) adsorption on the mechanical strength of perfect/defective graphene. The NH3 molecule is found to play a dominant role in enhancing the strength of defective graphene by up to ~15.6%, while other gas molecules decrease the strength of graphene with varying degrees. The remarkable strength enhancement can be interpreted by the decomposition of NH3, which saturates the dangling bond and leads to charge redistribution at the defect site. The present work provides basic information for the mechanical failure of gas-adsorbed graphene and guidance for manufacturing graphene-based electromechanical devices. PMID:27667709

  12. Anisotropic mechanical properties and Stone-Wales defects in graphene monolayer: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Fan, B.B. [School of Materials Science and Engineering, Zhengzhou University, Henan 450001 (China); Yang, X.B. [Department of Physics, South China University of Technology, Guangzhou 510640 (China); Zhang, R., E-mail: zhangray@zzu.edu.c [School of Materials Science and Engineering, Zhengzhou University, Henan 450001 (China); Zhengzhou Institute of Aeronautical Industry Management, Henan 450046 (China)

    2010-06-14

    We investigate the mechanical properties of graphene monolayer via the density functional theoretical (DFT) method. We find that the strain energies are anisotropic for the graphene under large strain. We attribute the anisotropic feature to the anisotropic sp{sup 2} hybridization in the hexagonal lattice. We further identify that the formation energies of Stone-Wales (SW) defects in the graphene monolayer are determined by the defect concentration and also the direction of applied tensile strain, correlating with the anisotropic feature.

  13. Control of defect-mediated tunneling barrier heights in ultrathin MgO films

    OpenAIRE

    Kim, D. J; Choi, W S; Schleicher, F.; Shin, R. H.; Boukari, S.; Davesne, V.; Kieber, C.; Arabski, J.; Schmerber, G.; Beaurepaire, E.; Jo, W.; Bowen, M.

    2010-01-01

    The impact of oxygen vacancies on local tunneling properties across rf-sputtered MgO thin films was investigated by optical absorption spectroscopy and conducting atomic force microscopy. Adding O$_2$ to the Ar plasma during MgO growth alters the oxygen defect populations, leading to improved local tunneling characteristics such as a lower density of current hotspots and a lower tunnel current amplitude. We discuss a defect-based potential landscape across ultrathin MgO barriers.

  14. Point defects in crystals (including grouped defects). Report No. 4548

    Energy Technology Data Exchange (ETDEWEB)

    Seidman, D.N.

    1981-08-01

    The fundamental properties of point defects, vacancies and self-interstitial atoms, in pure fcc and bcc metals is reviewed. Point defects created by both thermally-activated and irradiation processes are considered. The roles played by vacancies and self-interstitial atoms in thermal equilibrium are discussed and the best values of the enthalpy of formation of these point defects, in a number of metals, are given. Methods for obtaining fundamental properties of vacancies, such as activation volumes, mobilities, and binding enthalpies are discussed. Selected best values of mobilities and binding enthalpies of vacancies, as deduced from recovery experiments on a number of different quenched metals are listed. The problem of the production of single self-interstitial atoms and their configuration(s) is discussed. The clustering of single self-interstitials into small clusters is also considered. The physical origin of the extremely high low-temperature mobility of self-interstitials in the so-called Stage I recovery regime is also discussed.

  15. Structure and energy of point defects in TiC: An ab initio study

    Science.gov (United States)

    Sun, Weiwei; Ehteshami, Hossein; Korzhavyi, Pavel A.

    2015-04-01

    We employ first-principles calculations to study the atomic and electronic structure of various point defects such as vacancies, interstitials, and antisites in the stoichiometric as well as slightly off-stoichiometric Ti1 -cCc (including both C-poor and C-rich compositions, 0.49 ≤c ≤0.51 ). The atomic structure analysis has revealed that both interstitial and antisite defects can exist in split conformations involving dumbbells. To characterize the electronic structure changes caused by a defect, we introduce differential density of states (dDOS) defined as a local perturbation of the density of states (DOS) on the defect site and its surrounding relative to the perfect TiC. This definition allows us to identify the DOS peaks characteristic of the studied defects in several conformations. So far, characteristic defect states have been discussed only in connection with carbon vacancies. Here, in particular, we have identified dDOS peaks of carbon interstitials and dumbbells, which can be used for experimental detection of such defects in TiC. The formation energies of point defects in TiC are derived in the framework of a grand-canonical formalism. Among the considered defects, carbon vacancies and interstitials are shown to have, respectively, the lowest and the second-lowest formation energies. Their formation energetics are consistent with the thermodynamic data on the phase stability of nonstoichiometric TiC. A cluster type of point defect is found to be next in energy, a titanium [100] dumbbell terminated by two carbon vacancies.

  16. Quantitative digital subtraction radiography for assessment of bone density changes following periodontal guided tissue regeneration.

    Science.gov (United States)

    Christgau, M; Wenzel, A; Hiller, K A; Schmalz, G

    1996-01-01

    The quantitative assessment of alveolar bone density changes in periodontal defects following guided tissue regeneration (GTR). Twelve patients with 30 intrabony lesions and 16 furcation defects took part. Standardized radiographic and clinical examinations were carried out immediately before and then 5 and 13 months after surgery. Intra-oral radiographs were evaluated by means of digital subtraction radiography (DSR). Within the subtraction images, a window ('experimental region') was defined covering the visible density changes in the defect area. Background noise was measured by using a similarly sized window ('control region') located in an area not affected by GTR. Bone density changes were quantitatively evaluated by calculation of the mean, standard deviation and maximum and minimum values of the grey-level histogram within these windows. DSR revealed significant bone density gain after GTR in intrabony and furcation defects. While a continuous increase was observed over the 13 month period in intrabony defects, changes in furcation defects occurred mostly in the 5-13 month period. Clinically, a distinct vertical and horizontal attachment gain was found. The correlation coefficients between changes in radiographic density and clinical parameters were low, indicating a difference in the information obtained by the two diagnostic methods. Quantitative DSR is a valuable, non-invasive, objective method to obtain information on density changes in intrabony and furcation defects treated by GTR. However, a full assessment of soft and hard tissue changes requires both clinical evaluation and DSR.

  17. Topology-induced anomalous defect production by crossing a quantum critical point.

    Science.gov (United States)

    Bermudez, A; Patanè, D; Amico, L; Martin-Delgado, M A

    2009-04-03

    We study the influence of topology on the quench dynamics of a system driven across a quantum critical point. We show how the appearance of certain edge states, which fully characterize the topology of the system, dramatically modifies the process of defect production during the crossing of the critical point. Interestingly enough, the density of defects is no longer described by the Kibble-Zurek scaling, but determined instead by the nonuniversal topological features of the system. Edge states are shown to be robust against defect production, which highlights their topological nature.

  18. Defect-Induced Changes in the Spectral Properties of HIGH-Tc Cuprates

    Science.gov (United States)

    Vobornik, I.; Berger, H.; Rullier-Albenque, F.; Margaritondo, G.; Pavuna, D.; Grioni, L. Forroand M.

    Superconductivity in high-Tc cuprates is particularly sensitive to disorder due to the unconventional d-wave pairing symmetry. We investigated effects of disorder on the spectral properties of Bi2Sr2CaCu2O8+x high-Tc superconductor. We found that already small defect densities suppress the characteristic spectral signature of the superconducting state. The spectral line shape clearly reflects new excitations within the gap, as expected for defect-induced pair breaking. At the lowest defect concentrations the normal state remains unaffected, while increased disorder leads to suppression of the normal quasiparticle peaks.

  19. Chemical stability and defect formation in CaHfO3

    KAUST Repository

    Alay-E-Abbas, Syed Muhammad

    2014-04-01

    Defects in CaHfO3 are investigated by ab initio calculations based on density functional theory. Pristine and anion-deficient CaHfO 3 are found to be insulating, whereas cation-deficient CaHfO 3 is hole-doped. The formation energies of neutral and charged cation and anion vacancies are evaluated to determine the stability in different chemical environments. Moreover, the energies of the partial and full Schottky defect reactions are computed. We show that clustering of anion vacancies in the HfO layers is energetically favorable for sufficiently high defect concentrations and results in metallicity. © 2014 EPLA.

  20. Probabilistic distributions of pinhole defects in atomic layer deposited films on polymeric substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yersak, Alexander S., E-mail: alexander.yersak@colorado.edu; Lee, Yung-Cheng [Department of Mechanical Engineering, University of Colorado at Boulder, 1045 Regent Drive, 422 UCB, Boulder, Colorado 80309-0422 (United States)

    2016-01-15

    Pinhole defects in atomic layer deposition (ALD) coatings were measured in an area of 30 cm{sup 2} in an ALD reactor, and these defects were represented by a probabilistic cluster model instead of a single defect density value with number of defects over area. With the probabilistic cluster model, the pinhole defects were simulated over a manufacturing scale surface area of ∼1 m{sup 2}. Large-area pinhole defect simulations were used to develop an improved and enhanced design method for ALD-based devices. A flexible thermal ground plane (FTGP) device requiring ALD hermetic coatings was used as an example. Using a single defect density value, it was determined that for an application with operation temperatures higher than 60 °C, the FTGP device would not be possible. The new probabilistic cluster model shows that up to 40.3% of the FTGP would be acceptable. With this new approach the manufacturing yield of ALD-enabled or other thin film based devices with different design configurations can be determined. It is important to guide process optimization and control and design for manufacturability.

  1. Revealing origin of quasi-one dimensional current transport in defect rich two dimensional materials

    Energy Technology Data Exchange (ETDEWEB)

    Lotz, Mikkel R.; Boll, Mads; Bøggild, Peter; Petersen, Dirch H., E-mail: dirch.petersen@nanotech.dtu.dk [Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); Hansen, Ole [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); Danish National Research Foundation' s Center for Individual Nanoparticle Functionality (CINF), Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Kjær, Daniel [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); CAPRES A/S, Scion-DTU, Building 373, DK-2800 Kgs. Lyngby (Denmark)

    2014-08-04

    The presence of defects in graphene have for a long time been recognized as a bottleneck for its utilization in electronic and mechanical devices. We recently showed that micro four-point probes may be used to evaluate if a graphene film is truly 2D or if defects in proximity of the probe will lead to a non-uniform current flow characteristic of lower dimensionality. In this work, simulations based on a finite element method together with a Monte Carlo approach are used to establish the transition from 2D to quasi-1D current transport, when applying a micro four-point probe to measure on 2D conductors with an increasing amount of line-shaped defects. Clear 2D and 1D signatures are observed at low and high defect densities, respectively, and current density plots reveal the presence of current channels or branches in defect configurations yielding 1D current transport. A strong correlation is found between the density filling factor and the simulation yield, the fraction of cases with 1D transport and the mean sheet conductance. The upper transition limit is shown to agree with the percolation threshold for sticks. Finally, the conductance of a square sample evaluated with macroscopic edge contacts is compared to the micro four-point probe conductance measurements and we find that the micro four-point probe tends to measure a slightly higher conductance in samples containing defects.

  2. Piezoresistive effects in controllable defective HFTCVD graphene-based flexible pressure sensor.

    Science.gov (United States)

    Mohammad Haniff, Muhammad Aniq Shazni; Muhammad Hafiz, Syed; Wahid, Khairul Anuar Abd; Endut, Zulkarnain; Wah Lee, Hing; Bien, Daniel C S; Abdul Azid, Ishak; Abdullah, Mohd Zulkifly; Ming Huang, Nay; Abdul Rahman, Saadah

    2015-10-01

    In this work, the piezoresistive effects of defective graphene used on a flexible pressure sensor are demonstrated. The graphene used was deposited at substrate temperatures of 750, 850 and 1000 °C using the hot-filament thermal chemical vapor deposition method in which the resultant graphene had different defect densities. Incorporation of the graphene as the sensing materials in sensor device showed that a linear variation in the resistance change with the applied gas pressure was obtained in the range of 0 to 50 kPa. The deposition temperature of the graphene deposited on copper foil using this technique was shown to be capable of tuning the sensitivity of the flexible graphene-based pressure sensor. We found that the sensor performance is strongly dominated by the defect density in the graphene, where graphene with the highest defect density deposited at 750 °C exhibited an almost four-fold sensitivity as compared to that deposited at 1000 °C. This effect is believed to have been contributed by the scattering of charge carriers in the graphene networks through various forms such as from the defects in the graphene lattice itself, tunneling between graphene islands, and tunneling between defect-like structures.

  3. Expert Network for Die Casing Defect Analysis

    Institute of Scientific and Technical Information of China (English)

    Jiadi WANG; Yongfeng JIANG; Chen LU; Wenjiang DING

    2003-01-01

    Due to the competition and high cost associated with die casting defects, it is urgent to adopt a rapid and effective method for defect analysis. In this research, a novel expert network approach was proposed to avoid some disadvantages of rulebased expert system. The main objective of the system is to assist die casting engineer in identifying defect, determining the probable causes of defect and proposing remedies to eliminate the defect. 14 common die casting defects could be identified quickly by expert system on the basis of their characteristics. BP neural network in combination with expert system was applied to map the complex relationship between causes and defects, and further explained the cause determination process.Cause determination gives due consideration to practical process conditions. Finally, corrective measures were recommended to eliminate the defect and implemented in the sequence of difficulty.

  4. National Birth Defects Prevention Study (NBDPS)

    Science.gov (United States)

    ... Submit Button Information For… Media Policy Makers National Birth Defects Prevention Study (NBDPS) Recommend on Facebook Tweet ... NBDPS is one of the largest studies on birth defects ever undertaken in the United States. This ...

  5. Cellular Defect May Be Linked to Parkinson's

    Science.gov (United States)

    ... 160862.html Cellular Defect May Be Linked to Parkinson's: Study Abnormality might apply to all forms of ... that may be common to all forms of Parkinson's disease. The defect plays a major role in ...

  6. Automatic classification of blank substrate defects

    Science.gov (United States)

    Boettiger, Tom; Buck, Peter; Paninjath, Sankaranarayanan; Pereira, Mark; Ronald, Rob; Rost, Dan; Samir, Bhamidipati

    2014-10-01

    Mask preparation stages are crucial in mask manufacturing, since this mask is to later act as a template for considerable number of dies on wafer. Defects on the initial blank substrate, and subsequent cleaned and coated substrates, can have a profound impact on the usability of the finished mask. This emphasizes the need for early and accurate identification of blank substrate defects and the risk they pose to the patterned reticle. While Automatic Defect Classification (ADC) is a well-developed technology for inspection and analysis of defects on patterned wafers and masks in the semiconductors industry, ADC for mask blanks is still in the early stages of adoption and development. Calibre ADC is a powerful analysis tool for fast, accurate, consistent and automatic classification of defects on mask blanks. Accurate, automated classification of mask blanks leads to better usability of blanks by enabling defect avoidance technologies during mask writing. Detailed information on blank defects can help to select appropriate job-decks to be written on the mask by defect avoidance tools [1][4][5]. Smart algorithms separate critical defects from the potentially large number of non-critical defects or false defects detected at various stages during mask blank preparation. Mechanisms used by Calibre ADC to identify and characterize defects include defect location and size, signal polarity (dark, bright) in both transmitted and reflected review images, distinguishing defect signals from background noise in defect images. The Calibre ADC engine then uses a decision tree to translate this information into a defect classification code. Using this automated process improves classification accuracy, repeatability and speed, while avoiding the subjectivity of human judgment compared to the alternative of manual defect classification by trained personnel [2]. This paper focuses on the results from the evaluation of Automatic Defect Classification (ADC) product at MP Mask

  7. Correlation functions on conical defects

    CERN Document Server

    Smolkin, Michael

    2015-01-01

    We explore the new technique developed recently in \\cite{Rosenhaus:2014woa} and suggest a correspondence between the $N$-point correlation functions on spacetime with conical defects and the $(N+1)$-point correlation functions in regular Minkowski spacetime. This correspondence suggests a new systematic way to evaluate the correlation functions on spacetimes with conical defects. We check the correspondence for the expectation value of a scalar operator and of the energy momentum tensor in a conformal field theory and obtain the exact agreement with the earlier derivations for cosmic string spacetime. We then use this correspondence and do the computations for a generic scalar operator and a conserved vector current. For generic unitary field theory we compute the expectation value of the energy momentum tensor using the known spectral representation of the $2$-point correlators of stress-energy tensor in Minkowski spacetime.

  8. Cooperation and defection in ghetto

    CERN Document Server

    Kulakowski, K

    2006-01-01

    We consider ghetto as a community of people ruled against their will by an external power. Members of the community feel that their laws are broken. However, attempts to leave ghetto makes their situation worse. We discuss the relation of the ghetto inhabitants to the ruling power in context of their needs, organized according to the Maslow hierarchy. Decisions how to satisfy successive needs are undertaken in cooperation with or defection the ruling power. This issue allows to construct the tree of decisions and to adopt the pruning technique from the game theory. Dynamics of decisions can be described within the formalism of fundamental equations. The result is that the strategy of defection is stabilized by the estimated payoff.

  9. Defects of mitochondrial DNA replication.

    Science.gov (United States)

    Copeland, William C

    2014-09-01

    Mitochondrial DNA is replicated by DNA polymerase γ in concert with accessory proteins such as the mitochondrial DNA helicase, single-stranded DNA binding protein, topoisomerase, and initiating factors. Defects in mitochondrial DNA replication or nucleotide metabolism can cause mitochondrial genetic diseases due to mitochondrial DNA deletions, point mutations, or depletion, which ultimately cause loss of oxidative phosphorylation. These genetic diseases include mitochondrial DNA depletion syndromes such as Alpers or early infantile hepatocerebral syndromes, and mitochondrial DNA deletion disorders, such as progressive external ophthalmoplegia, ataxia-neuropathy, or mitochondrial neurogastrointestinal encephalomyopathy. This review focuses on our current knowledge of genetic defects of mitochondrial DNA replication (POLG, POLG2, C10orf2, and MGME1) that cause instability of mitochondrial DNA and mitochondrial disease.

  10. Cooperation and Defection in Ghetto

    Science.gov (United States)

    Kułakowski, Krzysztof

    We consider ghetto as a community of people ruled against their will by an external power. Members of the community feel that their laws are broken. However, attempts to leave ghetto makes their situation worse. We discuss the relation of the ghetto inhabitants to the ruling power in context of their needs, organized according to the Maslow hierarchy. Decisions how to satisfy successive needs are undertaken in cooperation with or defection the ruling power. This issue allows to construct the tree of decisions and to adopt the pruning technique from the game theory. Dynamics of decisions can be described within the formalism of fundamental equations. The result is that the strategy of defection is stabilized by the estimated payoff.

  11. Confining crack propagation in defective graphene.

    Science.gov (United States)

    López-Polín, Guillermo; Gómez-Herrero, Julio; Gómez-Navarro, Cristina

    2015-03-11

    Crack propagation in graphene is essential to understand mechanical failure in 2D materials. We report a systematic study of crack propagation in graphene as a function of defect content. Nanoindentations and subsequent images of graphene membranes with controlled induced defects show that while tears in pristine graphene span microns length, crack propagation is strongly reduced in the presence of defects. Accordingly, graphene oxide exhibits minor crack propagation. Our work suggests controlled defect creation as an approach to avoid catastrophic failure in graphene.

  12. Diabetic angiopathy and angiogenic defects

    Directory of Open Access Journals (Sweden)

    Xu Ling

    2012-08-01

    Full Text Available Abstract Diabetes is one of the most serious health problems in the world. A major complication of diabetes is blood vessel disease, termed angiopathy, which is characterized by abnormal angiogenesis. In this review, we focus on angiogenesis abnormalities in diabetic complications and discuss its benefits and drawbacks as a therapeutic target for diabetic vascular complications. Additionally, we discuss glucose metabolism defects that are associated with abnormal angiogenesis in atypical diabetic complications such as cancer.

  13. Algorithms for defects in nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Chan, T.-L.; Tiago, Murilo L. [Center for Computational Materials, Institute for Computational Engineering and Sciences, University of Texas, Austin, Texas 78712 (United States); Chelikowsky, James R. [Center for Computational Materials, Institute for Computational Engineering and Sciences, University of Texas, Austin, Texas 78712 (United States); Departments of Physics and Chemical Engineering, University of Texas, Austin, Texas 78712 (United States)], E-mail: jrc@ices.utexas.edu

    2007-12-15

    We illustrate recent progress in developing algorithms for solving the Kohn-Sham problem. Key ingredients of our algorithm include pseudopotentials implemented on a real space grid and the use of damped-Chebyshev polynomial filtered subspace iteration. This procedure allows one to predict electronic properties for many materials across the nano-regime, i.e., from atoms to nanocrystals of sufficient size to replicate bulk properties. We will illustrate this method for large silicon quantum dots doped with phosphorus defect.

  14. Electricity Surcharges: Defects and Suggestions

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Since 1980s, the government has decided to levy certain surcharges attached to electricity tariff collected by power grid corporations as government revenue for specific social public welfare purposes. These surcharges presently include the Three Gorges construction fund, urban construction surcharge, rural power grid debt service fund, as well as the newly-added post supporting fund for water reservoirs immigrants and renewable energy surcharge, etc. Yet the legal defects on surcharge policy have brought about operational risks on power grid enterprises.

  15. The role of point defects in PbS, PbSe and PbTe: a first principles study.

    Science.gov (United States)

    Li, Wun-Fan; Fang, Chang-Ming; Dijkstra, Marjolein; van Huis, Marijn A

    2015-09-09

    Intrinsic defects are of central importance to many physical and chemical processes taking place in compound nanomaterials, such as photoluminescence, accommodation of off-stoichiometry and cation exchange. Here, the role of intrinsic defects in the above mentioned processes inside rock salt (RS) lead chalcogenide systems PbS, PbSe and PbTe (PbX) was studied systematically using first principles density functional theory. Vacancy, interstitial, Schottky and Frenkel defects were considered. Rock salt PbO was included for comparison. The studied physical properties include defect formation energy, local geometry relaxation, Bader charge analysis, and electronic structure. The defect formation energies show that monovacancy defects and Schottky defects are favoured over interstitial and Frenkel defects. Schottky dimers, where the cation vacancy and anion vacancy are adjacent to each other, have the lowest defect formation energies at 1.27 eV, 1.29 eV and 1.21 eV for PbS, PbSe and PbTe, respectively. Our results predict that a Pb monovacancy gives rise to a shallow acceptor state, while an X vacancy generates a deep donor state, and Schottky defects create donor-acceptor pairs inside the band gap. The surprisingly low formation energy of Schottky dimers suggests that they may play an important role in cation exchange processes, in contrast to the current notion that only single point defects migrate during cation exchange.

  16. Designing defect spins for wafer-scale quantum technologies

    Energy Technology Data Exchange (ETDEWEB)

    Koehl, William F. [Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Chicago, IL (United States); Seo, Hosung [Univ. of Chicago, IL (United States); Galli, Giulia [Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Chicago, IL (United States); Awschalom, David D. [Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Chicago, IL (United States)

    2015-11-27

    The past decade has seen remarkable progress in the development of the nitrogen-vacancy (NV) defect center in diamond, which is one of the leading candidates for quantum information technologies. The success of the NV center as a solid-state qubit has stimulated an active search for similar defect spins in other technologically important and mature semiconductors, such as silicon carbide. If successfully combined with the advanced microfabrication techniques available to such materials, coherent quantum control of defect spins could potentially lead to semiconductor-based, wafer-scale quantum technologies that make use of exotic quantum mechanical phenomena like entanglement. In this article, we describe the robust spin property of the NV center and the current status of NV center research for quantum information technologies. We then outline first-principles computational modeling techniques based on density functional theory to efficiently search for potential spin defects in nondiamond hosts suitable for quantum information applications. The combination of computational modeling and experimentation has proven invaluable in this area, and we describe the successful interplay between theory and experiment achieved with the divacancy spin qubit in silicon carbide.

  17. EPR identification of intrinsic defects in SiC

    Energy Technology Data Exchange (ETDEWEB)

    Umeda, T.; Mizuochi, N. [University of Tsukuba, Tsukuba 305-8550 (Japan); Son, N.T.; Janzen, E. [Department of Physics, Chemistry and Biology, Linkoeping University, Linkoeping (Sweden); Ohshima, T. [Japan Atomic Energy Agency, Takasaki 370-1292 (Japan); Isoya, J.

    2008-07-15

    The structure determination of intrinsic defects in 4H-SiC, 6H-SiC, and 3C-SiC by means of EPR is based on measuring the angular dependence of the {sup 29}Si/{sup 13}C hyperfine (HF) satellite lines, from which spin densities, sp-hybrid ratio, and p-orbital direction can be determined over major atoms comprising a defect. In most cases, not only the assignment of the variety due to the inequivalent sites (h- and k-sites in 4H-SiC) but also the identification of the defect species is accomplished through the comparison of the obtained HF parameters with those obtained from first principles calculations. Our works of identifying vacancy-related defects such as the monovacancies, divacancies, and antisite-vacancy pairs in 4H-SiC are reviewed. In addition, it is demonstrated that the observation of the central line of the T{sub V2a} center of S=3/2 has been achieved by pulsed-ELDOR. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Ultrasonic sensor based defect detection and characterisation of ceramics.

    Science.gov (United States)

    Kesharaju, Manasa; Nagarajah, Romesh; Zhang, Tonzhua; Crouch, Ian

    2014-01-01

    Ceramic tiles, used in body armour systems, are currently inspected visually offline using an X-ray technique that is both time consuming and very expensive. The aim of this research is to develop a methodology to detect, locate and classify various manufacturing defects in Reaction Sintered Silicon Carbide (RSSC) ceramic tiles, using an ultrasonic sensing technique. Defects such as free silicon, un-sintered silicon carbide material and conventional porosity are often difficult to detect using conventional X-radiography. An alternative inspection system was developed to detect defects in ceramic components using an Artificial Neural Network (ANN) based signal processing technique. The inspection methodology proposed focuses on pre-processing of signals, de-noising, wavelet decomposition, feature extraction and post-processing of the signals for classification purposes. This research contributes to developing an on-line inspection system that would be far more cost effective than present methods and, moreover, assist manufacturers in checking the location of high density areas, defects and enable real time quality control, including the implementation of accept/reject criteria. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. Chronic Kidney Disease Impairs Bone Defect Healing in Rats.

    Science.gov (United States)

    Liu, Weiqing; Kang, Ning; Seriwatanachai, Dutmanee; Dong, Yuliang; Zhou, Liyan; Lin, Yunfeng; Ye, Ling; Liang, Xing; Yuan, Quan

    2016-03-09

    Chronic kidney disease (CKD) has been regarded as a risk for bone health. The aim of this study was to evaluate the effect of CKD on bone defect repair in rats. Uremia was induced by subtotal renal ablation, and serum levels of BUN and PTH were significantly elevated four weeks after the second renal surgery. Calvarial defects of 5-mm diameter were created and implanted with or without deproteinized bovine bone mineral (DBBM). Micro-CT and histological analyses consistently revealed a decreased newly regenerated bone volume for CKD rats after 4 and 8 weeks. In addition, 1.4-mm-diameter cortical bone defects were established in the distal end of femora and filled with gelatin sponge. CKD rats exhibited significantly lower values of regenerated bone and bone mineral density (BMD) within the cortical gap after 2 and 4 weeks. Moreover, histomorphometric analysis showed an increase in both osteoblast number (N.Ob/B.Pm) and osteoclast number (N.Oc/B.Pm) in CKD groups due to hyperparathyroidism. Notably, collagen maturation was delayed in CKD rats as verified by Masson's Trichrome staining. These data indicate that declined renal function negatively affects bone regeneration in both calvarial and femoral defects.

  20. Ensemble v-representable ab-initio density functional calculation of energy and spin in atoms: atest of exchange-correlation approximations

    CERN Document Server

    Kraisler, Eli; Kelson, Itzhak

    2010-01-01

    The total energies and the spin states for atoms and their first ions with Z = 1-86 are calculated within the the local spin-density approximation (LSDA) and the generalized-gradient approximation (GGA) to the exchange-correlation (xc) energy in density-functional theory. Atoms and ions for which the ground-state density is not pure-state v-representable, are treated as ensemble v- representable with fractional occupations of the Kohn-Sham system. A newly developed algorithm which searches over ensemble v-representable densities [E. Kraisler et al., Phys. Rev. A 80, 032115 (2009)] is employed in calculations. It is found that for many atoms the ionization energies obtained with the GGA are only modestly improved with respect to experimental data, as compared to the LSDA. However, even in those groups of atoms where the improvement is systematic, there remains a non-negligible difference with respect to the experiment. The ab-initio electronic configuration in the Kohn-Sham reference system does not always equ...

  1. Theoretical study on the interaction of pristine, defective and strained graphene with Fen and Nin (n = 13, 38, 55) clusters

    Science.gov (United States)

    Song, Wei; Jiao, Menggai; Li, Kai; Wang, Ying; Wu, Zhijian

    2013-11-01

    The structural and electronic properties of Fen and Nin (n = 13, 38, 55) clusters interacting with pristine, defective and strained graphene are investigated by means of self-consistent charge density-functional tight binding (SCC-DFTB) method. The cluster size dependence, defect influence, and strain effect are discussed. We found that the defects play an important role in stabilizing metal clusters by forming metal-carbon σ bonds. Large charge redistribution of Fen compared to Nin lead to stronger interaction in Fen@graphene. The results suggested that tuning the morphological level of the substrate defect and cluster size could affect the catalytic activity of the metal cluster.

  2. Density matrix renormalization group (DMRG) method as a common tool for large active-space CASSCF/CASPT2 calculations

    Science.gov (United States)

    Nakatani, Naoki; Guo, Sheng

    2017-03-01

    This paper describes an interface between the density matrix renormalization group (DMRG) method and the complete active-space self-consistent field (CASSCF) method and its analytical gradient, as well as an extension to the second-order perturbation theory (CASPT2) method. This interfacing allows large active-space multi-reference computations to be easily performed. The interface and its extension are both implemented in terms of reduced density matrices (RDMs) which can be efficiently computed via the DMRG sweep algorithm. We also present benchmark results showing that, in practice, the DMRG-CASSCF calculations scale with active-space size in a polynomial manner in the case of quasi-1D systems. Geometry optimization of a binuclear iron-sulfur cluster using the DMRG-CASSCF analytical gradient is demonstrated, indicating that the inclusion of the valence p-orbitals of sulfur and double-shell d-orbitals of iron lead to non-negligible changes in the geometry compared to the results of small active-space calculations. With the exception of the selection of M values, many computational settings in these practical DMRG calculations have been tuned and black-boxed in our interface, and so the resulting DMRG-CASSCF and DMRG-CASPT2 calculations are now available to novice users as a common tool to compute strongly correlated electronic wavefunctions.

  3. Signs and Symptoms of Congenital Heart Defects

    Science.gov (United States)

    ... Twitter. What Are the Signs and Symptoms of Congenital Heart Defects? Many congenital heart defects cause few or no signs and symptoms. A ... lips, and fingernails) Fatigue (tiredness) Poor blood circulation Congenital heart defects don't cause chest pain or other painful ...

  4. Care and Treatment for Congenital Heart Defects

    Science.gov (United States)

    ... Thromboembolism Aortic Aneurysm More Care and Treatment for Congenital Heart Defects Updated:Oct 26,2015 Not all people with ... supports you in your pursuit of heart health. Congenital Heart Defects • Home • About Congenital Heart Defects • The Impact of ...

  5. RUPTURING OF POLYMER FILMS WITH RUBBING—INDUCED SURFACE DEFECTS

    Institute of Scientific and Technical Information of China (English)

    B.Du; F.C.Xie; Y.J.Wang; O.K.C.Tsui; O.K.C.Tsui

    2003-01-01

    It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaces wherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or heterogeneous nucleation.In this experiment,we use a simple method to make the distinction through introduction of topographical defects of the films by rubbing the sample surface with a rayon cloth.Spinodal dewetting is identified for those films that dewet by a characteristic wavevector,q,independent of the density of rubbing-induced defects.Heterogeneous nucleation,on the other hand,is identified for those with q increasing with increasing density of defects.Our result shows that PS films on oxide coated silicon with thickness less than≈13nm are dominated by spinodal dewetting,but the thicker films are dominated by nucleation dewetting.We also confirm that spinodal dewetting does not necessarily lead to a bicontinuous morphology in the dewetting film,contrary to the classic theory of Cahn.

  6. Laboratory Density Functionals

    OpenAIRE

    Giraud, B. G.

    2007-01-01

    We compare several definitions of the density of a self-bound system, such as a nucleus, in relation with its center-of-mass zero-point motion. A trivial deconvolution relates the internal density to the density defined in the laboratory frame. This result is useful for the practical definition of density functionals.

  7. Laboratory Density Functionals

    OpenAIRE

    Giraud, B G

    2007-01-01

    We compare several definitions of the density of a self-bound system, such as a nucleus, in relation with its center-of-mass zero-point motion. A trivial deconvolution relates the internal density to the density defined in the laboratory frame. This result is useful for the practical definition of density functionals.

  8. Tunnelling characteristics of Stone-Wales defects in monolayers of Sn and group-V elements

    Science.gov (United States)

    Jamdagni, Pooja; Kumar, Ashok; Thakur, Anil; Pandey, Ravindra; Ahluwalia, P. K.

    2017-10-01

    Topological defects in ultrathin layers are often formed during synthesis and processing, thereby strongly influencing the electronic properties of layered systems. For the monolayers of Sn and group-V elements, we report the results based on density functional theory determining the role of Stone-Wales (SW) defects in modifying their electronic properties. The calculated results find the electronic properties of the Sn monolayer to be strongly dependent on the concentration of SW defects, e.g. defective stanene has nearly zero band gap (≈0.03 eV) for the defect concentration of 2.2  ×  1013 cm-2 which opens up to 0.2 eV for the defect concentration of 3.7  ×  1013 cm-2. In contrast, SW defects appear to induce conduction states in the semiconducting monolayers of group-V elements. These conduction states act as channels for electron tunnelling, and the calculated tunnelling characteristics show the highest differential conductance for the negative bias with the asymmetric current-voltage characteristics. On the other hand, the highest differential conductance was found for the positive bias in stanene. Simulated STM topographical images of stanene and group-V monolayers show distinctly different features in terms of their cross-sectional views and distance-height profiles. These distinctive features can serve as fingerprints to identify the topological defects in experiments for the monolayers of group-IV and group-V elements.

  9. Defect aggregates in the Sr2MgSi2O7 persistent luminescence material

    Institute of Scientific and Technical Information of China (English)

    JormaH(o)ls(a); Taneli Laamanen; Mika Lastusaari; Pavel Novák

    2011-01-01

    The crystal and electronic structure of the Eu2+ doped and defect containing Sr2MgSi2O7 persistent luminescence material were studied using the density functional theory (DFT).The defects may act as energy storage or even luminescence quenching centres in these materials,however their role is very difficult to confirm experimentally.The probability of vacancy formation was studied using the total energy of the defect containing host.Significant structural modifications in the environment of the isolated defects,especially the strontinm vacancy,as well as defect aggregetes were found.The experimental band gap energy of Sr2MgSi2O7 was well reproduced by the calculations.The defect induced electron traps close to the host's conduction band were found to act as energy storage sites contributing to its efficient persistent luminescence.The interactions between the defects were found to modify both the Eu2+ 4f7 ground state energy as well as the trap structure.The effect of charge compensation induced by the rare earth co-doping on the defect structure and energy storage properties of the persistent luminescence materials was discussed.

  10. In situ study of defect accumulation in zirconium under heavy ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Idrees, Y. [Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, Canada K7L 3N6 (Canada); Yao, Z., E-mail: yaoz@me.queensu.ca [Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, Canada K7L 3N6 (Canada); Kirk, M.A. [Material Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Daymond, M.R. [Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, Canada K7L 3N6 (Canada)

    2013-02-15

    In this study, we report direct observations on heavy ion (Kr{sup 2+}) irradiation induced changes in microstructures of pure Zr at different temperatures using intermediate voltage electron microscopy. Thin TEM foils were irradiated with 1 MeV Kr{sup 2+} ions. Materials have been irradiated to different damage levels ranging from 0.008 dpa to 1 dpa at different temperatures ranging from 300 °C to 500 °C. We particularly concentrate on yield of small defects directly occurring from cascade collapse at very low doses, and their evolution as the dose increases. In situ observation of growth and evolution of these small defects into complex defect structures at high dose has been carried out. Irradiation of materials at different temperatures provided an opportunity to investigate the temperature dependence of defect accumulation in Zr during irradiation. The differences in defect structures, defect densities, and therefore dynamic growth have been discussed in detail as a function of irradiation parameters (dose, temperature). Interaction of irradiation induced defects with existing microstructure and other defects is discussed.

  11. The effects of hyper velocity impact phenomena on radiation induced defects

    Science.gov (United States)

    Yamanaka, C.; Ikeya, M.

    1994-06-01

    Effects of high speed impacts on radiation-induced defects were investigated with a plasma rail-gun. Vitreous quartz targets irradiated by γ-ray were shocked with polycarbonate projectiles at a speed of 7 km/s, then the remaining destroyed pieces were examined by ESR spectroscopy to investigate the degree of "impact-annealing". The white substance from the impact point showed a trace of melting and no ESR signal, while the rest of the scattered pieces showed a decrease of E' center density to 50 ± 10% of the initial density. The defect production efficiency for the impacted silica was almost two-third of the original material.

  12. Probing Crystallinity of Graphene Samples via the Vibrational Density of States

    NARCIS (Netherlands)

    Jain, Sandeep K.; Juricic, Vladimir; Barkema, Gerard T.

    2015-01-01

    The purity of graphene samples is of crucial importance for their experimental and practical use. In this regard, the detection of the defects is of direct relevance. Here, we show that structural defects in graphene samples give rise to clear signals in the vibrational density of states (VDOS) at

  13. First-principles study of point defects in thorium carbide

    Science.gov (United States)

    Pérez Daroca, D.; Jaroszewicz, S.; Llois, A. M.; Mosca, H. O.

    2014-11-01

    Thorium-based materials are currently being investigated in relation with their potential utilization in Generation-IV reactors as nuclear fuels. One of the most important issues to be studied is their behavior under irradiation. A first approach to this goal is the study of point defects. By means of first-principles calculations within the framework of density functional theory, we study the stability and formation energies of vacancies, interstitials and Frenkel pairs in thorium carbide. We find that C isolated vacancies are the most likely defects, while C interstitials are energetically favored as compared to Th ones. These kind of results for ThC, to the best authors' knowledge, have not been obtained previously, neither experimentally, nor theoretically. For this reason, we compare with results on other compounds with the same NaCl-type structure.

  14. First-principles study of point defects in thorium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Pérez Daroca, D., E-mail: pdaroca@tandar.cnea.gov.ar [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, (1033) Buenos Aires (Argentina); Jaroszewicz, S. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM-CNEA, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Llois, A.M. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, (1033) Buenos Aires (Argentina); Mosca, H.O. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM-CNEA, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina)

    2014-11-15

    Thorium-based materials are currently being investigated in relation with their potential utilization in Generation-IV reactors as nuclear fuels. One of the most important issues to be studied is their behavior under irradiation. A first approach to this goal is the study of point defects. By means of first-principles calculations within the framework of density functional theory, we study the stability and formation energies of vacancies, interstitials and Frenkel pairs in thorium carbide. We find that C isolated vacancies are the most likely defects, while C interstitials are energetically favored as compared to Th ones. These kind of results for ThC, to the best authors’ knowledge, have not been obtained previously, neither experimentally, nor theoretically. For this reason, we compare with results on other compounds with the same NaCl-type structure.

  15. Software Defects, Scientific Computation and the Scientific Method

    CERN Document Server

    CERN. Geneva

    2011-01-01

    Computation has rapidly grown in the last 50 years so that in many scientific areas it is the dominant partner in the practice of science. Unfortunately, unlike the experimental sciences, it does not adhere well to the principles of the scientific method as espoused by, for example, the philosopher Karl Popper. Such principles are built around the notions of deniability and reproducibility. Although much research effort has been spent on measuring the density of software defects, much less has been spent on the more difficult problem of measuring their effect on the output of a program. This talk explores these issues with numerous examples suggesting how this situation might be improved to match the demands of modern science. Finally it develops a theoretical model based on an amalgam of statistical mechanics and Hartley/Shannon information theory which suggests that software systems have strong implementation independent behaviour and supports the widely observed phenomenon that defects clust...

  16. Defects and microstructural evolution of proton irradiated titanium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Dickerson, Clayton, E-mail: cdickerson@anl.gov [Material Science Program, University of Wisconsin - Madison, Madison, WI 53706 (United States); Yang, Yong; Allen, Todd R. [Department of Engineering Physics, University of Wisconsin - Madison, Madison, WI 53706 (United States)

    2012-05-15

    Titanium carbide has been identified as a candidate material for advanced coated nuclear fuel components, however little is known about the response of TiC to particle irradiation at elevated temperatures. To understand the radiation effects in TiC, proton irradiations were conducted to three doses (0.17, 0.34, and 0.80 dpa) at three temperatures (600 Degree-Sign C, 800 Degree-Sign C, and 900 Degree-Sign C), and post irradiation examination was performed with a number of TEM techniques to evaluate the irradiated microstructures. The predominant irradiation induced aggregate defects found by high resolution TEM and diffraction contrast TEM were interstitial Frank-type loops, while unfaulted loops were also identified. By monitoring the loop sizes and densities and accounting for the interstitials which formed the loops, a marked increase in vacancy point defect mobility was observed around 800 Degree-Sign C.

  17. Selecting the best defect reduction methodology

    Energy Technology Data Exchange (ETDEWEB)

    Hinckley, C.M. [Sandia National Labs., Albuquerque, NM (United States); Barkan, P. [Stanford Univ., CA (United States)

    1994-04-01

    Defect rates less than 10 parts per million, unimaginable a few years ago, have become the standard of world-class quality. To reduce defects, companies are aggressively implementing various quality methodologies, such as Statistical Quality Control Motorola`s Six Sigma, or Shingo`s poka-yok. Although each quality methodology reduces defects, selection has been based on an intuitive sense without understanding their relative effectiveness in each application. A missing link in developing superior defect reduction strategies has been a lack of a general defect model that clarifies the unique focus of each method. Toward the goal of efficient defect reduction, we have developed an event tree which addresses a broad spectrum of quality factors and two defect sources, namely, error and variation. The Quality Control Tree (QCT) predictions are more consistent with production experience than obtained by the other methodologies considered independently. The QCT demonstrates that world-class defect rates cannot be achieved through focusing on a single defect source or quality control factor, a common weakness of many methodologies. We have shown that the most efficient defect reduction strategy depend on the relative strengths and weaknesses of each organization. The QCT can help each organization identify the most promising defect reduction opportunities for achieving its goals.

  18. Electron beam generation and structure of defects in carbon and boron nitride nano-tubes

    Energy Technology Data Exchange (ETDEWEB)

    Zobelli, A

    2007-10-15

    The nature and role of defects is of primary importance to understand the physical properties of C and BN (boron nitride) single walled nano-tubes (SWNTs). Transmission electron microscopy (TEM) is a well known powerful tool to study the structure of defects in materials. However, in the case of SWNTs, the electron irradiation of the TEM may knock out atoms. This effect may alter the native structure of the tube, and has also been proposed as a potential tool for nano-engineering of nano-tubular structures. Here we develop a theoretical description of the irradiation mechanism. First, the anisotropy of the emission energy threshold is obtained via density functional based calculations. Then, we numerically derive the total Mott cross section for different emission sites of carbon and boron nitride nano-tubes with different chiralities. Using a dedicated STEM (Scanning Transmission Electron Microscope) microscope with experimental conditions optimised on the basis of derived cross-sections, we are able to control the generation of defects in nano-tubular systems. Either point or line defects can be obtained with a spatial resolution of a few nanometers. The structure, energetics and electronics of point and line defects in BN systems have been investigated. Stability of mono- and di- vacancy defects in hexagonal boron nitride layers is investigated, and their activation energies and reaction paths for diffusion have been derived using the nudged elastic band method (NEB) combined with density functional based techniques. We demonstrate that the appearance of extended linear defects under electron irradiation is more favorable than a random distribution of point defects and this is due to the existence of preferential sites for atom emission in the presence of pre-existing defects, rather than thermal vacancy nucleation and migration. (author)

  19. Atomic Approaches to Defect Thermochemistry

    Science.gov (United States)

    1992-04-30

    ATOMIC APPROACHES TO DEFECT THERMOCHEMISTRY (AFOSR-89-0309) for period 1 April 1989 to 31 March 1992 Submitted by Professor James A. Van Vechten and...could be very much less. Thus, the GaAs lattice is indeed found to be stiff. Positron annihilation experiments (17) also teach us that GaAs samples...to be less for Si than for Ge. Experience with chemical trends of bond strengths, as well as the empirical literature, teach us that the H bond

  20. Developmental defects of the lungs

    Energy Technology Data Exchange (ETDEWEB)

    DaCosta, H.; Pathak, A.; Noronha, O.; Dalal, S.; Shah, K.; Merchant, S.

    1981-06-01

    Poor lung development was first noted on scintigraphy using sup(99m)Tc-phytate in 32 children. They had all been referred for a hepatosplenic scan but the initial circulatory phase of the radiopharmaceutical was also recorded as a routine procedure. In 3 patients it revealed aplasia of an entire lung; bilateral pulmonary hypolplasia was observed in 14 of 16 patients with diaphragmatic herniae. Six patients with congenital heart enlargement showed a poorly developed ipsilateral lung; 5 of 6 patients with dextrocardia without an intracardiac defect had a larger left lung compared with the right lung; both pulmonary beds appeared equal in a patient with mesocardia.

  1. Determination of the extinction factor in function of the density of dislocations; Determinacion del factor de extincion en funcion de la densidad de dislocaciones

    Energy Technology Data Exchange (ETDEWEB)

    Macias B, L.R

    1991-12-15

    There are exist three basic types of crystalline lattice defects: point, line (or dislocations) and surface defects. Such defects may be incorporated intentionally to produce desired mechanical and physical properties. This report presents a FORTRAN language program to calculate the extinction factor in samples of polycrystalline copper as function of the dislocations density. (Author)

  2. Effects of line defects on spin-dependent electronic transport of zigzag MoS{sub 2} nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xin-Mei; Yang, Kai-Wei; Zhang, Dan; Ding, Jia-Feng; Xu, Hui, E-mail: xuhui@csu.edu.cn [Institute of Super-microstructure and Ultrafast Process in Advanced Materials & Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083 (China); Long, Meng-Qiu, E-mail: mqlong@csu.edu.cn [Institute of Super-microstructure and Ultrafast Process in Advanced Materials & Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083 (China); Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China); Cui, Li-Ling [Institute of Super-microstructure and Ultrafast Process in Advanced Materials & Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083 (China); School of Science, Hunan University of Technology, Zhuzhou 412007 (China)

    2016-01-15

    The nonlinear spin-dependent transport properties in zigzag molybdenum-disulfide nanoribbons (ZMNRs) with line defects are investigated systematically using nonequilibrium Green’s function method combined with density functional theory. The results show that the line defects can enhance the electronic transfer ability of ZMNRs. The types and locations of the line defects are found critical in determining the spin polarization and the current-voltage (I-V) characteristics of the line defected ZMNRs. For the same defect type, the total currents of the ribbons with the line defects in the centers are lager than those on the edges. And for the same location, the total currents of the systems with the sulfur (S) line defect are larger than the according systems with the molybdenum (Mo) line defect. All the considered systems present magnetism properties. And in the S line defected systems, the spin reversal behaviors can be observed. In both the spin-up and spin-down states of the Mo line defected systems, there are obvious negative differential resistance behaviors. The mechanisms are proposed for these phenomena.

  3. Effects of line defects on spin-dependent electronic transport of zigzag MoS2 nanoribbons

    Directory of Open Access Journals (Sweden)

    Xin-Mei Li

    2016-01-01

    Full Text Available The nonlinear spin-dependent transport properties in zigzag molybdenum-disulfide nanoribbons (ZMNRs with line defects are investigated systematically using nonequilibrium Green’s function method combined with density functional theory. The results show that the line defects can enhance the electronic transfer ability of ZMNRs. The types and locations of the line defects are found critical in determining the spin polarization and the current-voltage (I-V characteristics of the line defected ZMNRs. For the same defect type, the total currents of the ribbons with the line defects in the centers are lager than those on the edges. And for the same location, the total currents of the systems with the sulfur (S line defect are larger than the according systems with the molybdenum (Mo line defect. All the considered systems present magnetism properties. And in the S line defected systems, the spin reversal behaviors can be observed. In both the spin-up and spin-down states of the Mo line defected systems, there are obvious negative differential resistance behaviors. The mechanisms are proposed for these phenomena.

  4. Future Road Density

    Data.gov (United States)

    U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...

  5. Defect visualization of Cu(InGa)(SeS)2 thin films using DLTS measurement

    Science.gov (United States)

    Heo, Sung; Chung, Jaegwan; Lee, Hyung-Ik; Lee, Junho; Park, Jong-Bong; Cho, Eunae; Kim, Kihong; Kim, Seong Heon; Park, Gyeong Su; Lee, Dongho; Lee, Jaehan; Nam, Junggyu; Yang, Jungyup; Lee, Dongwha; Cho, Hoon Young; Kang, Hee Jae; Choi, Pyung-Ho; Choi, Byoung-Deog

    2016-08-01

    Defect depth profiles of Cu (In1‑x,Gax)(Se1‑ySy)2 (CIGSS) were measured as functions of pulse width and voltage via deep-level transient spectroscopy (DLTS). Four defects were observed, i.e., electron traps of ~0.2 eV at 140 K (E1 trap) and 0.47 eV at 300 K (E2 trap) and hole traps of ~0.1 eV at 100 K (H1 trap) and ~0.4 eV at 250 K (H2 trap). The open circuit voltage (VOC) deteriorated when the trap densities of E2 were increased. The energy band diagrams of CIGSS were also obtained using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and DLTS data. These results showed that the valence band was lowered at higher S content. In addition, it was found that the E2 defect influenced the VOC and could be interpreted as an extended defect. Defect depth profile images provided clear insight into the identification of defect state and density as a function of depth around the space charge region.

  6. Kibble-Zurek Scaling during Defect Formation in a Nematic Liquid Crystal.

    Science.gov (United States)

    Fowler, Nicholas; Dierking, Dr Ingo

    2017-04-05

    Symmetry-breaking phase transitions are often accompanied by the formation of topological defects, as in cosmological theories of the early universe, superfluids, liquid crystals or solid-state systems. This scenario is described by the Kibble-Zurek mechanism, which predicts corresponding scaling laws for the defect density ρ. One such scaling law suggests a relation ρ≈τQ(-1/2) with τQ the change of rate of a control parameter. In contrast to the scaling of the defect density during annihilation with ρ≈t(-1) , which is governed by the attraction of defects of the same strength but opposite sign, the defect formation process, which depends on the rate of change of a physical quantity initiating the transition, has only rarely been investigated. Herein, we use nematic liquid crystals as a different system to demonstrate the validity of the predicted scaling relation for defect formation. It is found that the scaling exponent is independent of temperature and material employed, thus universal, as predicted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Various categories of defects after surface alloying induced by high current pulsed electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Dian [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Tang, Guangze, E-mail: oaktang@hit.edu.cn [School of Material Science & Engineering, Harbin Institute of Technology, Harbin 150001 (China); Ma, Xinxin [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Gu, Le [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Sun, Mingren [School of Material Science & Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Liqin [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-10-01

    Highlights: • Four kinds of defects are found during surface alloying by high current electron beam. • Exploring the mechanism how these defects appear after irradiation. • Increasing pulsing cycles will help to get good surface quality. • Choosing proper energy density will increase surface quality. - Abstract: High current pulsed electron beam (HCPEB) is an attractive advanced materials processing method which could highly increase the mechanical properties and corrosion resistance. However, how to eliminate different kinds of defects during irradiation by HCPEB especially in condition of adding new elements is a challenging task. In the present research, the titanium and TaNb-TiW composite films was deposited on the carburizing steel (SAE9310 steel) by DC magnetron sputtering before irradiation. The process of surface alloying was induced by HCPEB with pulse duration of 2.5 μs and energy density ranging from 3 to 9 J/cm{sup 2}. Investigation of the microstructure indicated that there were several forms of defects after irradiation, such as surface unwetting, surface eruption, micro-cracks and layering. How the defects formed was explained by the results of electron microscopy and energy dispersive spectroscopy. The results also revealed that proper energy density (∼6 J/cm{sup 2}) and multi-number of irradiation (≥50 times) contributed to high quality of alloyed layers after irradiation.

  8. Crowding and Density

    Science.gov (United States)

    Design and Environment, 1972

    1972-01-01

    Three-part report pinpointing problems and uncovering solutions for the dual concepts of density (ratio of people to space) and crowding (psychological response to density). Section one, A Primer on Crowding,'' reviews new psychological and social findings; section two, Density in the Suburbs,'' shows conflict between status quo and increased…

  9. Yellow luminescence of gallium nitride generated by carbon defect complexes.

    Science.gov (United States)

    Demchenko, D O; Diallo, I C; Reshchikov, M A

    2013-02-22

    We demonstrate that yellow luminescence often observed in both carbon-doped and pristine GaN is the result of electronic transitions via the C(N)-O(N) complex. In contrast to common isolated defects, the C(N)-O(N) complex is energetically favorable, and its calculated optical properties, such as absorption and emission energies, a zero phonon line, and the thermodynamic transition level, all show excellent agreement with measured luminescence data. Thus, by combining hybrid density functional theory and experimental measurements, we propose a solution to a long-standing problem of the GaN yellow luminescence.

  10. Elastic and Electronic Properties of Point Defects in Titanium Carbide

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Daebok [Kyungsung Univ., Busan (Korea, Republic of)

    2013-12-15

    A theoretical study of the electronic structures of TiC{sub 1-x} and Ti{sub -1-x}W{sub x}C (x = 0, 0.25) is presented. The density of states and crystal orbital overlap population calculations were used to interpret variations of elastic properties induced by carbon vacancies and alloying substitutions. Our results show why the introduction of vacancies into TiC reduces bulk moduli, while W substitution at a Ti site increases the elastic modulus. The effect of the point defects on the bonding in TiC is investigated by means of extended Huckel tight-binding band calculations.

  11. Effects of in-cascade defect clustering on near-term defect evolution

    Energy Technology Data Exchange (ETDEWEB)

    Heinisch, H.L. [Pacific Northwest National Lab., Richland, WA (United States)

    1997-08-01

    The effects of in-cascade defect clustering on the nature of the subsequent defect population are being studied using stochastic annealing simulations applied to cascades generated in molecular dynamics (MD) simulations. The results of the simulations illustrates the strong influence of the defect configuration existing in the primary damage state on subsequent defect evolution. The large differences in mobility and stability of vacancy and interstitial defects and the rapid one-dimensional diffusion of small, glissile interstitial loops produced directly in cascades have been shown to be significant factors affecting the evolution of the defect distribution. In recent work, the effects of initial cluster sizes appear to be extremely important.

  12. Surface defects and temperature on atomic friction

    Energy Technology Data Exchange (ETDEWEB)

    Fajardo, O Y; Mazo, J J, E-mail: yovany@unizar.es [Departamento de Fisica de la Materia Condensada and Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain)

    2011-09-07

    We present a theoretical study of the effect of surface defects on atomic friction in the stick-slip dynamical regime of a minimalistic model. We focus on how the presence of defects and temperature change the average properties of the system. We have identified two main mechanisms which modify the mean friction force of the system when defects are considered. As expected, defects change the potential profile locally and thus affect the friction force. But the presence of defects also changes the probability distribution function of the tip slip length and thus the mean friction force. We corroborated both effects for different values of temperature, external load, dragging velocity and damping. We also show a comparison of the effects of surface defects and surface disorder on the dynamics of the system. (paper)

  13. FABRIC DEFECT DETECTION USING STEERABLE PYRAMID

    Directory of Open Access Journals (Sweden)

    S. Mythili

    2011-05-01

    Full Text Available In this paper, a novel idea is proposed for fabric defect detection. De- fects are detected in the fabric using steerable pyramid along with a defect detection algorithm. Various steerable pyramid of four size 256*256, 128*128, 64*64, 32*32 and with four orientation bands 00,450, 900, 1350 are used. Utilizing a Steerable pyramid proved ade- quate in the representation of fabric images in multi-scale and multi- orientations; thus allowing defect detection algorithms to run more effectively. Defect detection algorithm identifies and locates the im- perfection in the defective sample using the statistics mean and stan- dard deviation. This statistics represents the relative amount of inten- sity in the texture and is sufficient to measure defects in the current model .The obtained result are compared with the existing methods wavelet based system and with Gaussian and Laplacian pyramid.

  14. Primordial inhomogeneities from massive defects during inflation

    Science.gov (United States)

    Firouzjahi, Hassan; Karami, Asieh; Rostami, Tahereh

    2016-10-01

    We consider the imprints of local massive defects, such as a black hole or a massive monopole, during inflation. The massive defect breaks the background homogeneity. We consider the limit that the physical Schwarzschild radius of the defect is much smaller than the inflationary Hubble radius so a perturbative analysis is allowed. The inhomogeneities induced in scalar and gravitational wave power spectrum are calculated. We obtain the amplitudes of dipole, quadrupole and octupole anisotropies in curvature perturbation power spectrum and identify the relative configuration of the defect to CMB sphere in which large observable dipole asymmetry can be generated. We observe a curious reflection symmetry in which the configuration where the defect is inside the CMB comoving sphere has the same inhomogeneous variance as its mirror configuration where the defect is outside the CMB sphere.

  15. Primordial inhomogeneities from massive defects during inflation

    CERN Document Server

    Firouzjahi, Hassan; Rostami, Tahereh

    2016-01-01

    We consider the imprints of local massive defects, such as a black hole or a massive monopole, during inflation. The massive defect breaks the background homogeneity. We consider the limit that the physical Schwarzschild radius of the defect is much smaller than the inflationary Hubble radius so a perturbative analysis is allowed. The inhomogeneities induced in scalar and gravitational wave power spectrum are calculated. We obtain the amplitudes of dipole, quadrupole and octupole anisotropies in curvature perturbation power spectrum and identify the relative configuration of the defect to CMB sphere in which large observable dipole asymmetry can be generated. We observe a curious reflection symmetry in which the configuration where the defect is inside the CMB comoving sphere has the same inhomogeneous variance as its mirror configuration where the defect is outside the CMB sphere.

  16. Little String Origin of Surface Defects

    CERN Document Server

    Haouzi, Nathan

    2016-01-01

    We derive the codimension-two defects of 4d $\\mathcal{N} = 4$ Super Yang-Mills (SYM) theory from the (2, 0) little string. The origin of the little string is type IIB theory compactified on an ADE singularity. The defects are D-branes wrapping the 2-cycles of the singularity. We use this construction to make contact with the description of SYM defects due to Gukov and Witten [arXiv:hep-th/0612073]. Furthermore, we derive from a geometric perspective the complete nilpotent orbit classification of codimension-two defects, and the connection to ADE-type Toda CFT. The only data needed to specify the defects is a set of weights of the algebra obeying certain constraints, which we give explicitly. We highlight the differences between the defect classification in the little string theory and its (2, 0) CFT limit.

  17. Geometric Defects in Quantum Hall States

    CERN Document Server

    Gromov, Andrey

    2016-01-01

    We describe a geometric (or gravitational) analogue of the Laughlin quasiholes in the fractional quantum Hall states. Analogously to the quasiholes these defects can be constructed by an insertion of an appropriate vertex operator into the conformal block representation of a trial wavefunction, however, unlike the quasiholes these defects are extrinsic and do not correspond to true excitations of the quantum fluid. We construct a wavefunction in the presence of such defects and explain how to assign an electric charge and a spin to each defect, and calculate the adiabatic, non-abelian statistics of the defects. The defects turn out to be equivalent to the genons in that their adiabatic exchange statistics can be described in terms of representations of the mapping class group of an appropriate higher genus Riemann surface. We present a general construction that, in principle, allows to calculate the statistics of $\\mathbb Z_n$ genons for any "parent" topological phase. We illustrate the construction on the ex...

  18. Reconstruction of partial laryngopharyngectomy defects.

    Science.gov (United States)

    Anthony, J P; Neligan, P C; Rotstein, L E; Coleman, J

    1997-09-01

    As our contributors to this section have pointed out, there are at present two main methods of reconstructing defects of the pharynx and cervical esophagus: free jejunal transfer (FJT) and tubed radial forearm flap. The advantage of the FJT is that it is a tube, thus limiting the enteric suture lines to proximal and distal. The radial forearm flap requires not only the proximal and distal suture lines but a long longitudinal suture line to create the tube. This increase the possibility for fistula formation. The controversy surrounding this case concerns what to do with a remaining mucosal strip after a subtotal laryngectomy. Traditional reconstructive principles would dictate that normal tissue should not be sacrificed, but some would argue that the remaining mucosa should be sacrificed to allow for use of a FJT. The other alternative would be use of a radical forearm skin flap tubed to 270 degrees. At the University of Texas M. D. Anderson Cancer Center, we preferentially use the FJT for almost all defects and would probably have sacrificed the remaining mucosal strip in this particular case. We have used skin flaps to patch pharyngeal defects and prevent stricture in a number of cases. This is usually done however when the remaining pharyngeal mucosa approaches 50% or greater. Although we do not routinely use the tubed radial forearm flap because of the increased rate of fistula formation, there are some definite indications for its use. The first important indication is in patients in whom speech rehabilitation is desired or indicated. The skin flap provides a stiffer resonating chamber for the speech production and does not have the peristalsis or the mucus production associated with the jejunal flap. Another indication for use of radial forearm flap would be when there is a contraindication to celiotomy, ie, patients with hepatic cirrhosis and associated ascites or other abdominal conditions precluding abdominal exploration. In this situation, avoiding an

  19. Kinetic Monte Carlo of transport processes in Al/AlOx/Au-layers: Impact of defects

    Directory of Open Access Journals (Sweden)

    Benedikt Weiler

    2016-09-01

    Full Text Available Ultrathin films of alumina were investigated by a compact kMC-model. Experimental jV-curves from Al/AlOx/Au-junctions with plasma- and thermal-grown AlOx were fitted by simulated ones. We found dominant defects at 2.3-2.5 eV below CBM for AlOx with an effective mass mox∗=0.35 m0 and a barrier EB,Al/AlOx≈2.8 eV in agreement with literature. The parameterization is extended to varying defect levels, defect densities, injection barriers, effective masses and the thickness of AlOx. Thus, dominant charge transport processes and implications on the relevance of defects are derived and AlOx parameters are specified which are detrimental for the operation of devices.

  20. Measuring nonlinear stresses generated by defects in 3D colloidal crystals

    CERN Document Server

    Lin, Neil Y C; Schall, Peter; Sethna, James P; Cohen, Itai

    2016-01-01

    The mechanical, structural and functional properties of crystals are determined by their defects and the distribution of stresses surrounding these defects has broad implications for the understanding of transport phenomena. When the defect density rises to levels routinely found in real-world materials, transport is governed by local stresses that are predominantly nonlinear. Such stress fields however, cannot be measured using conventional bulk and local measurement techniques. Here, we report direct and spatially resolved experimental measurements of the nonlinear stresses surrounding colloidal crystalline defect cores, and show that the stresses at vacancy cores generate attractive interactions between them. We also directly visualize the softening of crystalline regions surrounding dislocation cores, and find that stress fluctuations in quiescent polycrystals are uniformly distributed rather than localized at grain boundaries, as is the case in strained atomic polycrystals. Nonlinear stress measurements ...

  1. Ordering and defects in self-assembled monolayers on nanoporous gold

    Science.gov (United States)

    Patel, Dipna A.; Weller, Andrew M.; Chevalier, Robert B.; Karos, Constantine A.; Landis, Elizabeth C.

    2016-11-01

    Self-assembled monolayers are commonly used to tailor nanoporous structures for applications, and they also provide a model system for determining the effects of nanoscale structure on self-assembly. We have investigated the ordering and defects in alkanethiol self-assembled monolayers on nanoporous gold, a high surface area mesoporous material. Infrared reflection absorption spectroscopy was used to characterize the effects of alkyl chain length and nanoporous gold pore size on molecular layer ordering. Cyclic voltammetry was used to characterize the monolayer density and ordering, with ferrocenylalkylthiolates used to quantify and characterize defect sites. We find that dense and well-ordered molecular layers form quickly with low defect levels. However, we do not observe differences in molecular layer ordering or defects with changes in pore size.

  2. TEM study of layered defects in high J_c MTG-YBCO

    Institute of Scientific and Technical Information of China (English)

    王葛亚; 施天生; 傅耀先; 蔡传兵; 杨宏川

    1995-01-01

    The microstructure and defects in melt-textured growth (MTG) YBa2Cu3O7-x (YBCO) bulk material have been studied systematically using high resolution transmission electron microscopy (HREM), and the relationship between the anisotropic critical current density Jc and the microstructure has been explored. The results indicate that there are numerous dense and nonunifonnly-distributed intergrowth-type layered defects orienting parallel to the ab plane in MTG-YBCO. These defects may serve as effective flux pinning centres for H//ab. The layered defects parallel to the ab plane together with the {110} twin boundaries are probably responsible for the anisotiopic behaviour of Jc depending upon the orientation of the external magnetic field.

  3. Kinetic Monte Carlo of transport processes in Al/AlOx/Au-layers: Impact of defects

    Science.gov (United States)

    Weiler, Benedikt; Haeberle, Tobias; Gagliardi, Alessio; Lugli, Paolo

    2016-09-01

    Ultrathin films of alumina were investigated by a compact kMC-model. Experimental jV-curves from Al/AlOx/Au-junctions with plasma- and thermal-grown AlOx were fitted by simulated ones. We found dominant defects at 2.3-2.5 eV below CBM for AlOx with an effective mass mox ∗= 0.35 m0 and a barrier EB ,A l /A l O x≈2.8 eV in agreement with literature. The parameterization is extended to varying defect levels, defect densities, injection barriers, effective masses and the thickness of AlOx. Thus, dominant charge transport processes and implications on the relevance of defects are derived and AlOx parameters are specified which are detrimental for the operation of devices.

  4. Comparison of defect cluster accumulation and pattern formation in irradiated copper and nickel

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J.; Snead, L.L. [Oak Ridge National Lab., TN (United States); Edwards, D.J. [Pacific Northwest Lab., Richland, WA (United States)] [and others

    1995-04-01

    The objective of this study is to compare the contrasting behavior of defect cluster formation in neutron-irradiated copper and nickel specimens. Transmission electron microscopy was used to examine the density and spatial distribution of defect clusters produced in copper and nickel as the result of fission neutron irradiation to damage levels of 0.01 to 0.25 displacements per atom (dpa) at irradiation temperature between 50 and 230{degrees}C. A comparison with published results in the literature indicates that defect cluster wall formation occurs in nickel irradiated at 0.2 to 0.4 T{sub M} in a wide variety of irradiation spectra. Defect cluster wall formation apparently only occurs in copper during low temperature irradiation with electrons and light ions. These results are discussed in terms of the thermal spike model for energetic displacement cascades.

  5. Kinetics of Schottky defect formation and annihilation in single crystal TlBr.

    Science.gov (United States)

    Bishop, Sean R; Tuller, Harry L; Kuhn, Melanie; Ciampi, Guido; Higgins, William; Shah, Kanai S

    2013-07-28

    The kinetics for Schottky defect (Tl and Br vacancy pair) formation and annihilation in ionically conducting TlBr are characterized through a temperature induced conductivity relaxation technique. Near room temperature, defect generation-annihilation was found to take on the order of hours before equilibrium was reached after a step change in temperature, and that mechanical damage imparted on the sample rapidly increases this rate. The rate limiting step to Schottky defect formation-annihilation is identified as being the migration of lower mobility Tl (versus Br), with an estimate for source-sink density derived from calculated diffusion lengths. This study represents one of the first investigations of Schottky defect generation-annihilation kinetics and demonstrates its utility in quantifying detrimental mechanical damage in radiation detector materials.

  6. Identification of defect-related emissions in ZnO hybrid materials

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Wei; Wang, Xuefeng, E-mail: xfwang@nju.edu.cn; Ye, Jiandong; Gu, Shulin; Shi, Yi; Zhang, Rong [National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Zhu, Hao [National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, and Department of Physics, Nanjing University, Nanjing 210093 (China); Department of Materials Science and Engineering, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093 (China); Song, Fengqi [National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, and Department of Physics, Nanjing University, Nanjing 210093 (China); Zhou, Jianfeng [Department of Materials Science and Engineering, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093 (China); Xu, Yongbing [National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York YO10 5DD (United Kingdom)

    2015-07-13

    ZnO hybrid materials with singly precipitated ZnO nanocrystals embedded in the glass surface were fabricated by melt-quenching method followed by the annealing process. A series of samples containing different densities and species of intrinsic defects were obtained under different annealing conditions in a controllable manner, which was an ideal platform to identify the complicated defect origins. By employing photoluminescence (PL), excitation-dependent PL, PL excitation (PLE), and Raman spectroscopy, the radiative transitions of visible emission bands at around 401, 490, and 528 nm were unambiguously involved with zinc interstitial-related defect levels as initial states, and the corresponding terminal states were suggested to be valence band, oxygen vacancies, and zinc vacancies, respectively. This study may deepen the fundamental understanding of defect-related emissions and physics in ZnO and benefit potential applications of ZnO hybrid materials in optoelectronics.

  7. An atomistic vision of the Mass Action Law: Prediction of carbon/oxygen defects in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Brenet, G.; Timerkaeva, D.; Caliste, D.; Pochet, P. [CEA, INAC-SP2M, Atomistic Simulation Laboratory, F-38000 Grenoble (France); Univ. Grenoble Alpes, INAC-SP2M, L-Sim, F-38000 Grenoble (France); Sgourou, E. N.; Londos, C. A. [University of Athens, Solid State Physics Section, Panepistimiopolis Zografos, Athens 157 84 (Greece)

    2015-09-28

    We introduce an atomistic description of the kinetic Mass Action Law to predict concentrations of defects and complexes. We demonstrate in this paper that this approach accurately predicts carbon/oxygen related defect concentrations in silicon upon annealing. The model requires binding and migration energies of the impurities and complexes, here obtained from density functional theory (DFT) calculations. Vacancy-oxygen complex kinetics are studied as a model system during both isochronal and isothermal annealing. Results are in good agreement with experimental data, confirming the success of the methodology. More importantly, it gives access to the sequence of chain reactions by which oxygen and carbon related complexes are created in silicon. Beside the case of silicon, the understanding of such intricate reactions is a key to develop point defect engineering strategies to control defects and thus semiconductors properties.

  8. Multi-scale model for point defects behaviour in uranium mononitride

    Science.gov (United States)

    Starikov, S.; Kuksin, A.; Smirnova, D.

    2017-01-01

    A multiscale approach was used to study the properties of point defects in uranium mononitride (UN). In this work we used combination of several methods: ab initio calculations; molecular dynamics simulations with a new interatomic potential; thermodynamic model. Density functional theory (DFT) calculations are used for fitting of the parameters of the angular-dependent interatomic potential, as well as for evaluation of the defects formation and migration energies. Molecular dynamics (MD) simulations are applied to analyze what migration/formation mechanisms are activated at finite temperatures and to calculate diffusion coefficients of point defects. The thermodynamic model for description of concentrations and diffusivities for point defects in non-stoichiometric UN1+x is proposed.

  9. First principles study on defectives BN nanotubes for water splitting and hydrogen storage

    Science.gov (United States)

    Bevilacqua, Andressa C.; Rupp, Caroline J.; Baierle, Rogério J.

    2016-06-01

    First principles calculations within the spin polarized density functional approximation have been addressed to investigate the energetic stability, electronic and optical properties of defective BN nanotubes. Our results show that the presence of carbon impurities interacting with vacancies gives rise to defective electronic levels inside the nanotube band gap. By calculating the absorbance index, we have obtained a strong inter-band optical absorption in the visible region (around 2.1 eV) showing that defective BN nanotubes could be an efficient catalytic semiconductor material to be used within solar energy for water splitting. In addition, we observe that the adsorption energy for one and two H2 molecules on the defective surface is in the desired window for the system to be useful as a hydrogen storage medium.

  10. Defect Characterization Using Two-Dimensional Arrays

    Science.gov (United States)

    Velichko, A.; Wilcox, P. D.

    2011-06-01

    2D arrays are able to `view' a given defect from a range of angles leading to the possibility of obtaining richer characterization detail than possible with 1D arrays. In this paper a quantitative comparison of 2D arrays with different element layouts is performed. A technique for extracting the scattering matrix of a defect from the raw 2D array data is also presented. The method is tested on experimental data for characterization of various volumetric defects.

  11. Folding defect affine Toda field theories

    CERN Document Server

    Robertson, C

    2013-01-01

    A folding process is applied to fused a^(1)_r defects to construct defects for the non-simply laced affi?ne Toda ?field theories of c^(1)_n, d^(2)_n and a^(2)_n at the classical level. Support for the hypothesis that these defects are integrable in the folded theories is provided by the observation that transmitted solitons retain their form. Further support is given by the demonstration that energy and momentum are conserved.

  12. Theory and Phenomenology of Spacetime Defects

    CERN Document Server

    Hossenfelder, Sabine

    2014-01-01

    Whether or not space-time is fundamentally discrete is of central importance for the development of the theory of quantum gravity. If the fundamental description of space-time is discrete, typically represented in terms of a graph or network, then the apparent smoothness of geometry on large scales should be imperfect -- it should have defects. Here, we review a model for space-time defects and summarize the constraints on the prevalence of these defects that can be derived from observation.

  13. Detection of Surface Defects on Compact Discs

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Stoustrup, Jakob; Andersen, Palle

    2007-01-01

    Online detection of surface defects on optical discs is of high importance for the accommodation schemes handling these defects. These surface defects introduce fault components to the position measurements of focus and radial tracking positions. The respective controllers will accordingly try to...... in order to inspect the importance and consequences of the size of the detection delay, from which it can be seen that focus and radial position errors increase significantly due to the fault as the detection delay increases....

  14. Welding defects at friction stir welding

    Directory of Open Access Journals (Sweden)

    P. Podržaj

    2015-04-01

    Full Text Available The paper presents an overview of different types of defects at friction stir welding. In order to explain the reasons for their occurrence a short theoretical background of the process is given first. The main emphasis is on the parameters that influence the process. An energy supply based division of defects into three disjoint groups was used. The occurring defects are demonstrated on various materials.

  15. Topological defects in two-dimensional crystals

    OpenAIRE

    Chen, Yong; Qi, Wei-Kai

    2008-01-01

    By using topological current theory, we study the inner topological structure of the topological defects in two-dimensional (2D) crystal. We find that there are two elementary point defects topological current in two-dimensional crystal, one for dislocations and the other for disclinations. The topological quantization and evolution of topological defects in two-dimensional crystals are discussed. Finally, We compare our theory with Brownian-dynamics simulations in 2D Yukawa systems.

  16. Phosphorous–vacancy–oxygen defects in silicon

    KAUST Repository

    Wang, Hao

    2013-07-30

    Electronic structure calculations employing the hybrid functional approach are used to gain fundamental insight in the interaction of phosphorous with oxygen interstitials and vacancies in silicon. It recently has been proposed, based on a binding energy analysis, that phosphorous–vacancy–oxygen defects may form. In the present study we investigate the stability of this defect as a function of the Fermi energy for the possible charge states. Spin polarization is found to be essential for the charge neutral defect.

  17. Emerging Diluted Ferromagnetism in High-Tc Superconductors Driven by Point Defect Clusters.

    Science.gov (United States)

    Gazquez, Jaume; Guzman, Roger; Mishra, Rohan; Bartolomé, Elena; Salafranca, Juan; Magén, Cesar; Varela, Maria; Coll, Mariona; Palau, Anna; Valvidares, S Manuel; Gargiani, Pierluigi; Pellegrin, Eric; Herrero-Martin, Javier; Pennycook, Stephen J; Pantelides, Sokrates T; Puig, Teresa; Obradors, Xavier

    2016-06-01

    Defects in ceramic materials are generally seen as detrimental to their functionality and applicability. Yet, in some complex oxides, defects present an opportunity to enhance some of their properties or even lead to the discovery of exciting physics, particularly in the presence of strong correlations. A paradigmatic case is the high-temperature superconductor YBa2Cu3O7-δ (Y123), in which nanoscale defects play an important role as they can immobilize quantized magnetic flux vortices. Here previously unforeseen point defects buried in Y123 thin films that lead to the formation of ferromagnetic clusters embedded within the superconductor are unveiled. Aberration-corrected scanning transmission microscopy has been used for exploring, on a single unit-cell level, the structure and chemistry resulting from these complex point defects, along with density functional theory calculations, for providing new insights about their nature including an unexpected defect-driven ferromagnetism, and X-ray magnetic circular dichroism for bearing evidence of Cu magnetic moments that align ferromagnetically even below the superconducting critical temperature to form a dilute system of magnetic clusters associated with the point defects.

  18. Radiation defect dynamics in Si at room temperature studied by pulsed ion beams

    Science.gov (United States)

    Wallace, J. B.; Charnvanichborikarn, S.; Bayu Aji, L. B.; Myers, M. T.; Shao, L.; Kucheyev, S. O.

    2015-10-01

    The evolution of radiation defects after the thermalization of collision cascades often plays the dominant role in the formation of stable radiation disorder in crystalline solids of interest to electronics and nuclear materials applications. Here, we explore a pulsed-ion-beam method to study defect interaction dynamics in Si crystals bombarded at room temperature with 500 keV Ne, Ar, Kr, and Xe ions. The effective time constant of defect interaction is measured directly by studying the dependence of lattice disorder, monitored by ion channeling, on the passive part of the beam duty cycle. The effective defect diffusion length is revealed by the dependence of damage on the active part of the beam duty cycle. Results show that the defect relaxation behavior obeys a second order kinetic process for all the cases studied, with a time constant in the range of ˜4-13 ms and a diffusion length of ˜15-50 nm. Both radiation dynamics parameters (the time constant and diffusion length) are essentially independent of the maximum instantaneous dose rate, total ion dose, and dopant concentration within the ranges studied. However, both the time constant and diffusion length increase with increasing ion mass. This demonstrates that the density of collision cascades influences not only defect production and annealing efficiencies but also the defect interaction dynamics.

  19. Transport Effects on Capacitance-Frequency Analysis for Defect Characterization in Organic Photovoltaic Devices

    Science.gov (United States)

    Xu, Liang; Wang, Jian; Hsu, Julia W. P.

    2016-12-01

    Using capacitance-frequency (C -f ) analysis to characterize the density-of-states (DOS) distribution of defects has been well established for inorganic thin-film photovoltaic devices. While C -f analysis has also been applied to bulk-heterojunction (BHJ) organic photovoltaic (OPV) devices, we show that the low carrier mobility in the BHJ material can severely alter the C -f behaviors and lead to misinterpretations. Because of the complicated nature of disorders in organic materials, artifacts from an erroneous C -f analysis are difficult to identify. Here we compare drift-diffusion simulations with experiments to reveal situations when the validity of C -f analysis for defect characterization breaks down. When a flat-band region is present in the low-mobility active layer, the capacitive response cannot follow the electrical modulation and behaves as if the active layer is a dielectric at frequencies higher than the characteristic frequency determined by carrier mobility and thickness. The transition produces a fictitious shallow defect when defect analysis is applied. Even in fully depleted devices, the defect distributions derived from C -f analysis can appear at spuriously deeper energies if the mobility is too low. Through simulations, we determine the ranges of mobility and thickness for which the C -f analysis can effectively yield credible defect DOS information. Insight from this study also sheds light on transport limitation when using capacitance spectroscopy for defect characterization in general.

  20. Fluence dependence of defect evolution in austenitic stainless steels during fission neutron irradiation

    Science.gov (United States)

    Watanabe, H.; Muroga, T.; Yoshida, N.

    To understand microstructural evolution during fission neutron irradiation, a pure Fe-Cr-Ni ternary alloy, phosphorus-containing model austenitic stainless steels and SUS316 were irradiated in a Japanese Material Testing Reactor (JMTR) at 493 and 613 K. At 493 K, the density of defect cluster increased with the irradiation dose, but there was no significant change in loop density and loop size among all the materials. At 613 K, on the other hand, interstitial type dislocation loops and phosphides were formed in pure ternary and phosphorus-containing alloys, respectively, by an early stage of irradiation. These results suggest that the defect cluster formation at 493 and 613 K is mainly controlled by the cascade damage and long-range migration of free point defects, respectively.

  1. DFT study of formaldehyde adsorption on vacancy defected graphene doped with B, N, and S

    Science.gov (United States)

    Zhou, Qingxiao; Yuan, Lei; Yang, Xi; Fu, Zhibing; Tang, Yongjian; Wang, Chaoyang; Zhang, Hong

    2014-08-01

    The adsorption of formaldehyde (H2CO) on modified graphene sheets, combining vacancy and dopants (B, N, and S), was investigated by employing the density functional theory (DFT). It was found that the vacancy-defected graphene was more sensitive to absorb H2CO molecule compared with the pristine one. Furthermore, the H2CO molecule tended to be chemisorbed on vacancy-defected graphene with dopants, which exhibited larger adsorption energy and net charge transfer than that of one without dopants. The results of partial electronic density of states (PDOS) indicated that the defect-dopant combination effect on the adsorption process was mainly owing to the contribution of the hybridization between dopants and C atoms around the vacancy. We hope our results will be useful for the application of graphene for chemical sensors to detect formaldehyde gas.

  2. Purity and Defect Characterization of Single-Wall Carbon Nanotubes Using Raman Spectroscopy

    Directory of Open Access Journals (Sweden)

    Yasumitsu Miyata

    2011-01-01

    Full Text Available We investigated the purity and defects of single-wall carbon nanotubes (SWCNTs produced by various synthetic methods including chemical vapor deposition, arc discharge, and laser ablation. The SWCNT samples were characterized using scanning electron microscopy (SEM, thermogravimetric analysis (TGA, and Raman spectroscopy. Quantitative analysis of SEM images suggested that the G-band Raman intensity serves as an index for the purity. By contrast, the intensity ratio of G-band to D-band (G/D ratio reflects both the purity and the defect density of SWCNTs. The combination of G-band intensity and G/D ratio is useful for a quick, nondestructive evaluation of the purity and defect density of a SWCNT sample.

  3. Defect interactions within a group of subcascades

    Energy Technology Data Exchange (ETDEWEB)

    Heinisch, H.L. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    The evolution of the defect distributions within high energy cascades that contain multiple subcascades is studied as a function of temperature for cascades in copper. Low energy cascades generated with molecular dynamics are placed in close proximity to simulate the arrangement of subcascades within a high energy event, then the ALSOME code follows the evolution of the cascade damage during short term annealing. The intersubcascade defect interactions during the annealing stage are found to be minimal. However, no conclusions regarding effects of subcascades on defect production should be drawn until intersubcascade defect interactions during the quenching stage are examined.

  4. Antigravity from a spacetime defect

    CERN Document Server

    Klinkhamer, F R

    2013-01-01

    A nonsingular localized static classical solution is constructed for standard Einstein gravity coupled to an SO(3)\\times SO(3) chiral model of scalars [Skyrme model]. The construction proceeds in three steps. First, an Ansatz is presented for a solution with nontrivial topology of the spacetime manifold. Second, an exact vacuum solution of the reduced field equations is obtained. Third, matter fields are included and a numerical solution is found. This numerical solution has a negative effective mass, meaning that the gravitational force on a distant point mass is repulsive. The origin of the negative effective mass must lie in the surgery needed to create the "defect" from Minkowski spacetime, but this process involves topology change and lies outside the realm of classical Einstein gravity.

  5. Renyi entropy and conformal defects

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, Lorenzo [Humboldt-Univ. Berlin (Germany). Inst. fuer Physik; Hamburg Univ. (Germany). II. Inst. fuer Theoretische Physik; Meineri, Marco [Scuola Normale Superiore, Pisa (Italy); Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); Istituto Nazionale di Fisica Nucleare, Pisa (Italy); Myers, Robert C. [Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); Smolkin, Michael [California Univ., Berkely, CA (United States). Center for Theoretical Physics and Department of Physics

    2016-04-18

    We propose a field theoretic framework for calculating the dependence of Renyi entropies on the shape of the entangling surface in a conformal field theory. Our approach rests on regarding the corresponding twist operator as a conformal defect and in particular, we define the displacement operator which implements small local deformations of the entangling surface. We identify a simple constraint between the coefficient defining the two-point function of the displacement operator and the conformal weight of the twist operator, which consolidates a number of distinct conjectures on the shape dependence of the Renyi entropy. As an example, using this approach, we examine a conjecture regarding the universal coefficient associated with a conical singularity in the entangling surface for CFTs in any number of spacetime dimensions. We also provide a general formula for the second order variation of the Renyi entropy arising from small deformations of a spherical entangling surface, extending Mezei's results for the entanglement entropy.

  6. Influence of microgravity on Ce-doped Bi12SiO20 crystal defect

    Indian Academy of Sciences (India)

    Y F Zhou; J Y Xu; Y Liu; L D Chen; Y Y Huang; W X Huang

    2007-06-01

    Space grown BSO crystal doped with Ce was characterized by means of X-ray fluorescence spectra, X-ray topography, dislocation density etc. Influence of microgravity on Ce-doped BSO crystal defect was studied by comparing space grown BSO crystal with ground grown one. These results show that compositional homogeneity and structural perfection of crystal can be improved under microgravity conditions.

  7. Probability densities and Lévy densities

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler

    For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated.......For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated....

  8. Probability densities and Lévy densities

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler

    For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated.......For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated....

  9. Contact angle hysteresis and pinning at periodic defects in statics

    Science.gov (United States)

    Iliev, Stanimir; Pesheva, Nina; Nikolayev, Vadim S.

    2014-07-01

    This article deals with the theoretical prediction of the wetting hysteresis on nonideal solid surfaces in terms of the surface heterogeneity parameters. The spatially periodical chemical heterogeneity is considered. We propose precise definitions for both the advancing and the receding contact angles for the Wilhelmy plate geometry. It is well known that in such a system, a multitude of metastable states of the liquid meniscus occurs for each different relative position of the defect pattern on the plate with respect to the liquid level. As usual, the static advancing and receding angles are assumed to be a consequence of the preceding contact line motion in the respective direction. It is shown how to select the appropriate states among all metastable states. Their selection is discussed. The proposed definitions are applicable to both the static and the dynamic contact angles on heterogeneous surfaces. The static advancing and receding angles are calculated for two examples of periodic heterogeneity patterns with sharp borders: the horizontal alternating stripes of a different wettability (studied analytically) and the doubly periodic pattern of circular defects on a homogeneous base (studied numerically). The wetting hysteresis is determined as a function of the defect density and the spatial period. A comparison with the existing results is carried out.

  10. Ab initio studies of niobium defects in uranium

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, S; Huang, H; Hsiung, L

    2007-06-01

    Uranium (U), with the addition of small amount of niobium (Nb), is stainless. The Nb is fully miscible with the high temperature phase of U and tends to segregate upon cooling below 647 C. The starting point of segregation is the configuration of Nb substitutional or interstitial defects. Using density-functional-theory based ab initio calculations, the authors find that the formation energy of a single vacancy is 1.08 eV, that of Nb substitution is 0.59 eV, that of Nb interstitial at octahedral site is 1.58 eV, and that of Nb interstitial at tetrahedral site is 2.35 eV; all with reference to a reservoir of {gamma} phase U and pure Nb. The formation energy of Nb defects correlates with the local perturbation of electron distribution; higher formation energy to larger perturbation. Based on this study, Nb atoms thermodynamically prefer to occupy substitutional sites in {gamma} phase U, and they prefer to be in individual substitutional defects than clusters.

  11. Point Defects in Binary Laves-Phase Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, P.K.; Liu, C.T.; Pike, L.M.; Zhu, J.H.

    1999-01-11

    Point defects in the binary C15 NbCrQ and NbCoz, and C 14 NbFe2 systems on both sides of stoichiometry were studied by both bulk density and X-ray Iattiee parameter measurements. It was found that the vacancy concentrations in these systems after quenching from 1000"C are essentially zero. The constitutional defects on both sides of stoichiometry for these systems were found to be of the anti-site type in comparison with the model predictions. Thermal vacancies exhibiting a maximum at the stoichiometric composition were obtained in NbCr2 Laves phase alloys after quenching from 1400"C. However, there are essentially no thermal vacancies in NbFe2 alloys after quenching from 1300oC. Anti-site hardening was found on both sides of stoichiometry for all the tie Laves phase systems studied, while the thermal vacancies in NbCr2 alloys quenched from 1400'C were found to soften the Laves phase. The anti-site hardening of the Laves phases is similar to that of the B2 compounds and the thermal vacancy softening is unique to the Laves phase. Neither the anti-site defects nor the thermal vacancies affect the fracture toughness of the Laves phases significantly.

  12. Contact angle hysteresis and pinning at periodic defects in statics.

    Science.gov (United States)

    Iliev, Stanimir; Pesheva, Nina; Nikolayev, Vadim S

    2014-07-01

    This article deals with the theoretical prediction of the wetting hysteresis on nonideal solid surfaces in terms of the surface heterogeneity parameters. The spatially periodical chemical heterogeneity is considered. We propose precise definitions for both the advancing and the receding contact angles for the Wilhelmy plate geometry. It is well known that in such a system, a multitude of metastable states of the liquid meniscus occurs for each different relative position of the defect pattern on the plate with respect to the liquid level. As usual, the static advancing and receding angles are assumed to be a consequence of the preceding contact line motion in the respective direction. It is shown how to select the appropriate states among all metastable states. Their selection is discussed. The proposed definitions are applicable to both the static and the dynamic contact angles on heterogeneous surfaces. The static advancing and receding angles are calculated for two examples of periodic heterogeneity patterns with sharp borders: the horizontal alternating stripes of a different wettability (studied analytically) and the doubly periodic pattern of circular defects on a homogeneous base (studied numerically). The wetting hysteresis is determined as a function of the defect density and the spatial period. A comparison with the existing results is carried out.

  13. Point Defects in Binary Laves-Phase Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, P.K.; Liu, C.T.; Pike, L.M.; Zhu, J.H.

    1998-11-30

    Point defect mechanisms in the binary C15 NbCr{sub 2} and NbCo{sub 2}, and C14 NbFe{sub 2} systems on both sides of stoichiometry was studied and clarified by both bulk density and X-ray lattice parameter measurements. It was found that the vacancy concentrations in these systems after quenching from 1000 C are essentially zero. The constitutional defects on both sides of stoichiometry for these systems were found to be of the anti-site type in comparison with the model predictions. However, thermal vacancies exhibiting a maximum at the stoichiometric composition were obtained in NbCr{sub 2} laves phase alloys after quenching from 1400 C. These could be completely eliminated by annealing at 1000 C. Anti-site hardening was found on both sides of stoichiometry for all three Laves phase systems studied. Furthermore, the thermal vacancies in NbCr{sub 2} alloys after quenching from 1400 C were found to soften the Laves phase. The anti-site hardening of the Laves phases is similar to that of the B2 compounds, while the thermal vacancy softening is unique to the Laves phase. Both the anti-site defects and thermal vacancies do not significantly affect the fracture toughness of the Laves phases.

  14. Paternal occupation and birth defects: findings from the National Birth Defects Prevention Study.

    NARCIS (Netherlands)

    Desrosiers, T.A.; Herring, A.H.; Shapira, S.K.; Hooiveld, M.; Luben, T.J.; Herdt-Losavio, M.L.; Lin, S.; Olshan, A.F.

    2012-01-01

    Objectives: Several epidemiological studies have suggested that certain paternal occupations may be associated with an increased prevalence of birth defects in offspring. Using data from the National Birth Defects Prevention Study, the authors investigated the association between paternal occupation

  15. Topological conformal defects with tensor networks

    Science.gov (United States)

    Hauru, Markus; Evenbly, Glen; Ho, Wen Wei; Gaiotto, Davide; Vidal, Guifre

    2016-09-01

    The critical two-dimensional classical Ising model on the square lattice has two topological conformal defects: the Z2 symmetry defect Dɛ and the Kramers-Wannier duality defect Dσ. These two defects implement antiperiodic boundary conditions and a more exotic form of twisted boundary conditions, respectively. On the torus, the partition function ZD of the critical Ising model in the presence of a topological conformal defect D is expressed in terms of the scaling dimensions Δα and conformal spins sα of a distinct set of primary fields (and their descendants, or conformal towers) of the Ising conformal field theory. This characteristic conformal data {Δα,sα}D can be extracted from the eigenvalue spectrum of a transfer matrix MD for the partition function ZD. In this paper, we investigate the use of tensor network techniques to both represent and coarse grain the partition functions ZDɛand ZD σ of the critical Ising model with either a symmetry defect Dɛ or a duality defect Dσ. We also explain how to coarse grain the corresponding transfer matrices MDɛand MD σ, from which we can extract accurate numerical estimates of {Δα,sα}Dɛ and {Δα,sα}Dσ. Two key ingredients of our approach are (i) coarse graining of the defect D , which applies to any (i.e., not just topological) conformal defect and yields a set of associated scaling dimensions Δα, and (ii) construction and coarse graining of a generalized translation operator using a local unitary transformation that moves the defect, which only exist for topological conformal defects and yields the corresponding conformal spins sα.

  16. Modeling the relationships among internal defect features and external Appalachian hardwood log defect indicators

    Science.gov (United States)

    R. Edward. Thomas

    2009-01-01

    As a hardwood tree grows and develops, surface defects such as branch stubs and wounds are overgrown. Evidence of these defects remain on the log surface for decades and in many instances for the life of the tree. As the tree grows the defect is encapsulated or grown over by new wood. During this process the appearance of the defect in the tree's bark changes. The...

  17. Paternal occupation and birth defects: findings from the National Birth Defects Prevention Study

    OpenAIRE

    Desrosiers, T.A.; Herring, A H; Shapira, S K; Hooiveld, M.; Luben, T.J.; Herdt-Losavio, M.L.; LIN, S.; Olshan, A.F.

    2012-01-01

    Objectives: Several epidemiological studies have suggested that certain paternal occupations may be associated with an increased prevalence of birth defects in offspring. Using data from the National Birth Defects Prevention Study, the authors investigated the association between paternal occupation and birth defects in a case–control study of cases comprising over 60 different types of birth defects (n=9998) and non-malformed controls (n=4066) with dates of delivery between 1997 and 2004. Me...

  18. Method and instrumentation for detection of rail defects, in particular rail top defects

    NARCIS (Netherlands)

    Li, Z.; Molodova, M.

    2011-01-01

    A method and instrumentation for detection of rail defects, in particular rail top defects, in a railway-track by measuring an axle box acceleration signal of a rail vehicle, wherein a longitudinal axle box acceleration signal is used as a measure to detect the occurrence of said rail defects, in pa

  19. Radiographic defect depth and width for prognosis and description of periodontal healing of infrabony defects.

    Science.gov (United States)

    Klein, F; Kim, T S; Hassfeld, S; Staehle, H J; Reitmeir, P; Holle, R; Eickholz, P

    2001-12-01

    The aims of the present study were to evaluate 1) defect depth and width as a prognostic factor and 2) change in defect width as a describing parameter of periodontal healing in infrabony defects treated by regenerative therapy after 6 and 24 months. In 24 patients with advanced periodontitis, 39 infrabony defects were treated by guided tissue regeneration (GTR) using expanded polytetrafluoroethylene (ePTFE) (n = 7) or bioabsorbable barriers (n = 32). Clinical parameters were assessed and 39 standardized radiographs (in triplicate) were taken before and 6 and 24 months after surgery. Using a computer-assisted analysis, the depth, width, and angle of the bony defects were measured. Statistically significant vertical clinical attachment gains (CAL-V: 3.15 +/- 1.63 mm to 3.31 +/- 1.65 mm; P or = 3 mm) infrabony defects bony fill was more pronounced than in wide and shallow defects (P <0.05). Improvement achieved by guided tissue regeneration in infrabony defects can be maintained up to 24 months after surgery. Narrow and deep infrabony defects respond radiographically and to some extent clinically more favorably to GTR therapy than wide and shallow defects. However, depth of the infrabony component was a stronger prognostic parameter than defect angle. Actual smoking impairs the results of GTR therapy in infrabony defects.

  20. Predicting internal white oak (Quercus alba) log defect features using surface defect indicator measurements

    Science.gov (United States)

    Ralph E. Thomas

    2012-01-01

    As hardwood trees grow and develop, surface defects such as limb stubs and wounds are overgrown and encapsulated into the tree. Evidence of these defects can remain on the tree's surface for decades and in many instances for the life of the tree. The location and severity of internal defects dictate the quality and value of products that can be obtained from logs...

  1. The intrinsic defect structure of exfoliated MoS2 single layers revealed by Scanning Tunneling Microscopy

    Science.gov (United States)

    Vancsó, Péter; Magda, Gábor Zsolt; Pető, János; Noh, Ji-Young; Kim, Yong-Sung; Hwang, Chanyong; Biró, László P.; Tapasztó, Levente

    2016-01-01

    MoS2 single layers have recently emerged as strong competitors of graphene in electronic and optoelectronic device applications due to their intrinsic direct bandgap. However, transport measurements reveal the crucial role of defect-induced electronic states, pointing out the fundamental importance of characterizing their intrinsic defect structure. Transmission Electron Microscopy (TEM) is able to image atomic scale defects in MoS2 single layers, but the imaged defect structure is far from the one probed in the electronic devices, as the defect density and distribution are substantially altered during the TEM imaging. Here, we report that under special imaging conditions, STM measurements can fully resolve the native atomic scale defect structure of MoS2 single layers. Our STM investigations clearly resolve a high intrinsic concentration of individual sulfur atom vacancies, and experimentally identify the nature of the defect induced electronic mid-gap states, by combining topographic STM images with ab intio calculations. Experimental data on the intrinsic defect structure and the associated defect-bound electronic states that can be directly used for the interpretation of transport measurements are essential to fully understand the operation, reliability and performance limitations of realistic electronic devices based on MoS2 single layers. PMID:27445217

  2. Defect Engineering and Interface Phenomena in Tin Oxide

    KAUST Repository

    Albar, Arwa

    2017-04-05

    The advance in transparent electronics requires high-performance transparent conducting oxide materials. The microscopic properties of these materials are sensitive to the presence of defects and interfaces and thus fundamental understanding is required for materials engineering. In this thesis, first principles density functional theory is used to investigate the possibility of tuning the structural, electronic and magnetic properties of tin oxide by means of defects and interfaces. Our aim is to reveal unique properties and the parameters to control them as well as to explain the origin of unique phenomena in oxide materials. The stability of native defect in tin monoxide (SnO) under strain is investigated using formation energy calculations. We find that the conductivity (which is controlled by native defects) can be switched from p-type to either n-type or undoped semiconducting by means of applied pressure. We then target inducing magnetism in SnO by 3d transition metal doping. We propose that V doping is efficient to realize spin polarization at high temperature. We discuss different tin oxide interfaces. Metallic states are found to form at the SnO/SnO2 interface with electronic properties that depend on the interface terminations. The origin of these states is explained in terms of charge transfer caused by chemical bonding and band alignment. For the SnO/SnO2 heterostructure, we observe the formation of a two dimensional hole gas at the interface, which is surprising as it cannot be explained by the standard polar catastrophe model. Thus, we propose a charge density discontinuity model to explain our results. The model can be generalized to other polar-polar interfaces. Motivated by technological applications, the electronic and structural properties of the MgO (100)/SnO2 (110) interface are investigated. Depending on the interface termination, we observe the formation of a two dimensional electron gas or spin polarized hole gas. Aiming to identify further

  3. Population Density Modeling Tool

    Science.gov (United States)

    2014-02-05

    194 POPULATION DENSITY MODELING TOOL by Davy Andrew Michael Knott David Burke 26 June 2012 Distribution...MARYLAND NAWCADPAX/TR-2012/194 26 June 2012 POPULATION DENSITY MODELING TOOL by Davy Andrew Michael Knott David Burke...Density Modeling Tool 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Davy Andrew Michael Knott David Burke 5d. PROJECT NUMBER

  4. On varieties with higher osculating defect

    CERN Document Server

    De Poi, Pietro; Ilardi, Giovanna

    2012-01-01

    In this paper, using the method of moving frames, we generalise some of Terracini's results on varieties with tangent defect. In particular, we characterise varieties with higher order osculating defect in terms of Jacobians of higher fundamental forms and moreover we characterise varieties with "small" higher fundamental forms as contained in scrolls.

  5. 30 CFR 56.7002 - Equipment defects.

    Science.gov (United States)

    2010-07-01

    ... Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Drilling § 56.7002 Equipment defects. Equipment defects affecting safety shall be corrected...

  6. 30 CFR 57.7002 - Equipment defects.

    Science.gov (United States)

    2010-07-01

    ... Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Drilling-Surface Only § 57.7002 Equipment defects. Equipment defects affecting...

  7. Unsound defect volume in hardwood pallet cants

    Science.gov (United States)

    Philip Araman; Matt Winn; Firoz Kabir; Xavier Torcheux; Guillaume Loizeaud

    2003-01-01

    A study was conducted to determine the percentage of unsound defect volume to sound/clear wood in pallet cants at selected sawmills in Virginia and West Virginia. Splits,wane, shake, holes, decay, unsound knots, bark pockets, and mechanical defects were all considered to be unsound. Data were collected from seven Appalachian area sawmills for four hardwood species: red...

  8. Birth defects in children with newborn encephalopathy

    NARCIS (Netherlands)

    Felix, JF; Badawi, N; Kurinczuk, JJ; Bower, C; Keogh, JM; Pemberton, PJ

    2000-01-01

    This study was designed to investigate birth defects found in association with newborn encephalopathy. All possible birth defects were ascertained in a population-based study of 276 term infants with moderate or severe encephalopathy and 564 unmatched term control infants. A strong association

  9. 7 CFR 52.780 - Defects.

    Science.gov (United States)

    2010-01-01

    ... PROCESSED FRUITS AND VEGETABLES, PROCESSED PRODUCTS THEREOF, AND CERTAIN OTHER PROCESSED FOOD PRODUCTS 1... cherry. (b) (A) classification. Canned red tart pitted cherries that are practically free from defects...) (B) classification. Canned red tart pitted cherries that are reasonably free from defects may...

  10. Orbital dystopia due to orbital roof defect.

    Science.gov (United States)

    Rha, Eun Young; Joo, Hong Sil; Byeon, Jun Hee

    2013-01-01

    We performed a retrospective review of patients who presented with delayed dystopia as a consequence of an orbital roof defect due to fractures and nontraumatic causes to search for a correlation between orbital roof defect size and surgical indications for the treatment thereof. Retrospective analyses were performed in 7 patients, all of whom presented with delayed dystopia due to orbital roof defects, between January 2001 and June 2011. The causes of orbital roof defects were displaced orbital roof fractures (5 cases), tumor (1 case), and congenital sphenoid dysplasia (1 case). All 7 patients had initially been treated conservatively and later presented with significant dystopia. The sizes of the defects were calculated on computed tomographic scans. Among the 7 patients, aspiration of cerebrospinal fluid, which caused ocular symptoms, in 1 patient with minimal displaced orbital roof and reconstruction with calvarial bone, titanium micromesh, or Medpor in 6 other patients were performed. The minimal size of the orbital roof in patients who underwent orbital roof reconstruction was 1.2 cm (defect height) x 1.0 cm (defect length), 0.94 cm(2). For all patients with orbital dystopia, displacement of the globe was corrected without any complications, regardless of whether the patient was evaluated grossly or by radiology. In this retrospective study, continuous monitoring of clinical signs and active surgical management should be considered for cases in which an orbital roof defect is detected, even if no definite symptoms are noted, to prevent delayed sequelae.

  11. Indicators for Building Process without Final Defects -

    DEFF Research Database (Denmark)

    Jørgensen, Kirsten; Rasmussen, Grane Mikael Gregaard; Thuesen, Christian Langhoff

    2011-01-01

    This article introduces the preliminary data analysis, as well as the underlying theories and methods for identifying the indicators for building process without final defects. Since 2004, the Benchmark Centre for the Danish Construction Sector (BEC) has collected information about legal defects ...

  12. Positron analysis of defects in metals

    NARCIS (Netherlands)

    van Veen, A; Kruseman, AC; Schut, H; Mijnarends, PE; Kooi, BJ; De Hosson, JTM; Jean, YC; Eldrup, M; Schrader, DM; West, RN

    1997-01-01

    New methods are discussed to improve defect analysis. The first method employs mapping of two shape parameters, S and W, of the positron annihilation photopeak. It is demonstrated that the combined use of S and W allows to a better discrimination of defects. The other method is based on background s

  13. Renal acidification defects in medullary sponge kidney

    DEFF Research Database (Denmark)

    Osther, P J; Hansen, A B; Røhl, H F

    1988-01-01

    patients had some form of renal acidification defect; 8 had the distal type of renal tubular acidosis, 2 the complete and 6 the incomplete form. One patient had proximal renal tubular acidosis. These findings, which suggest that renal acidification defects play an important role in the pathogenesis...

  14. Birth defects in children with newborn encephalopathy

    NARCIS (Netherlands)

    Felix, JF; Badawi, N; Kurinczuk, JJ; Bower, C; Keogh, JM; Pemberton, PJ

    2000-01-01

    This study was designed to investigate birth defects found in association with newborn encephalopathy. All possible birth defects were ascertained in a population-based study of 276 term infants with moderate or severe encephalopathy and 564 unmatched term control infants. A strong association betwe

  15. Opioid Use and Neural Tube Defects

    Science.gov (United States)

    ... to start in 2014). These studies work to identify risk factors for birth defects and to answer questions ... Prevention Study. Maternal treatment with opioid analgesics and risk for birth defects. American Journal of Obstetrics and Gynecology . 2011;204(4):314. ...

  16. Line defects and (framed) BPS quivers

    CERN Document Server

    Cirafici, Michele

    2013-01-01

    The BPS spectrum of certain N=2 supersymmetric field theories can be determined algebraically by studying the representation theory of BPS quivers. We introduce methods based on BPS quivers to study line defects. The presence of a line defect opens up a new BPS sector: framed BPS states can be bound to the defect. The defect can be geometrically described in terms of laminations on a curve. To a lamination we associate certain elements of the Leavitt path algebra of the BPS quiver and use them to compute the framed BPS spectrum. We also provide an alternative characterization of line defects by introducing framed BPS quivers. Using the theory of (quantum) cluster algebras, we derive an algorithm to compute the framed BPS spectra of new defects from known ones. Line defects are generated from a framed BPS quiver by applying certain sequences of mutation operations. Framed BPS quivers also behave nicely under a set of "cut and join" rules, which can be used to study how N=2 systems with defects couple to produc...

  17. Microphthalmia with linear skin defects syndrome.

    Science.gov (United States)

    García-Rabasco, Ana; De-Unamuno, Blanca; Martínez, Francisco; Febrer-Bosch, Isabel; Alegre-de-Miquel, Víctor

    2013-01-01

    Microphthalmia with linear skin defects (MLS) or microcornea, dermal aplasia and sclerocornea (MIDAS) syndrome is a rare X-linked-dominant disorder. We present a patient with agenesis of corpus callosum, ocular abnormalities, and multiple skin defects. The cytogenetic studies of the MLS critical region (Xp22.2) were normal, but a skewed X-chromosome inactivation pattern (85:15) was observed.

  18. Ab initio modelling of boron related defects in amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Tiago A.; Torres, Vitor J.B. [Department of Physics, University of Aveiro, Campus Santiago, 3810-193 Aveiro (Portugal)

    2012-10-15

    We have modeled boron related point defects in amorphous silicon, using an ab initio method, the Density functional theory-pseudopotential code Aimpro. The boron atoms were embedded in 64 atom amorphous silicon cubic supercells. The calculations were performed using boron defects in 15 different supercells. These supercells were developed using a modified Wooten-Winer-Weaire bond switching mechanism. In average, the properties of the 15 supercells agree with the observed radial and bond angle distributions, as well the electronic and vibrational density of states and Raman spectra. In amorphous silicon it has been very hard to find real self-interstitials, since for almost all the tested configurations, the amorphous lattice relaxes overall. We found that substitutional boron prefers to be 4-fold coordinated. We find also an intrinsic hole-trap in the non-doped amorphous lattice, which may explain the low efficiency of boron doping. The local vibrational modes are, in average, higher than the correspondent crystalline values (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Point defect determination by photoluminescence and capacitance-voltage characterization in a GaN terahertz Gunn diode

    Institute of Scientific and Technical Information of China (English)

    Li Liang; Yang Lin-An; Zhou Xiao-Wei; Zhang Jin-Cheng; Hao Yue

    2013-01-01

    Photoluminescence (PL) measurement is used to study the point defect distribution in a GaN terahertz Gunn diode,which is able to the degrade high-field transport characteristic during further device operation.PL,secondary ion mass spectroscopy (SIMS),transmission electron microscope (TEM),and capacitance-voltage (C-V) measurements are used to discuss the origin of point defects responsible for the yellow luminescence in structures.The point defect densities of about 1011 cm-2 in structures are extracted by analysis of C-V characterization.After thermal annealing treatment,diminishments of point defect densities in structures are efficiently demonstrated by PL and C-V results.

  20. A collagen defect in homocystinuria.

    Science.gov (United States)

    Kang, A H; Trelstad, R L

    1973-10-01

    the two patients examined, reflecting a functional defect in collagen cross-linking. Although the concentration of homocysteine used in this study to demonstrate these effects in vitro is clearly higher than that which is observed in homocystinuric's plasma, the data do suggest a possible pathogenetic mechanism of connective tissue defect in homocystinuria.

  1. The Doppler peaks from a generic defect

    CERN Document Server

    Magueijo, J

    1996-01-01

    We investigate which of the exotic Doppler peak features found for textures and cosmic strings are generic novelties pertaining to defects. We find that the ``out of phase'' texture signature is an accident. Generic defects, when they generate a secondary peak structure similar to inflation, apply to it an additive shift. It is not necessary for this shift to be ``out of phase''. We also show which factors are responsible for the absence of secondary oscillations found for cosmic strings. Within this general analysis we finally consider the conditions under which topological defects and inflation can be confused. It is argued that only \\Omega=1 inflation and a defect with a horizon size coherence length have a chance to be confused. Any other inflationary or defect model always differ distinctly. (To appear in the proceedings of the XXXIth Moriond meeting, ``Microwave Background Anisotropies'')

  2. Defect-Tolerant Monolayer Transition Metal Dichalcogenides

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Rasmussen, Filip Anselm; Kuhar, Korina;

    2016-01-01

    -principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy, while the TMDs based on group IV metals form only...... shallow defect levels and are thus predicted to be defect-tolerant. Interestingly, all the defect sensitive TMDs have valence and conduction bands with a very similar orbital composition. This indicates a bonding/antibonding nature of the gap, which in turn suggests that dangling bonds will fall inside...... the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within...

  3. Defect studies of ZnSe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Philipose, U; Saxena, Ankur; Ruda, Harry E [Centre for Nanotechnology, University of Toronto, 170 College Street, Toronto, ON, M5S 3E4 (Canada); Simpson, P J [Department of Physics and Astronomy, University of Western Ontario, London, ON, N6A 3K7 (Canada); Wang, Y Q; Kavanagh, K L [Department of Physics, Simon Fraser University, Burnaby, BC, V5A 1S6 (Canada)

    2008-05-28

    During the synthesis of ZnSe nanowires various point and extended defects can form, leading to observed stacking faults and twinning defects, and strong defect related emission in photoluminescence spectra. In this paper, we report on the development of a simple thermodynamic model for estimating the defect concentration in ZnSe nanowires grown under varying Se vapour pressure and for explaining the results of our experimental findings. Positron annihilation spectroscopy was used successfully for the first time for nanowires and the results support predictions from the defect model as well as agreeing well with our structural and optical characterization results. Under very high Se vapour pressure, Se nodules were observed to form on the sidewalls of the nanowire, indicating that beyond a limit, excess Se will begin to precipitate out of the liquid alloy droplet in the vapour-liquid-solid growth of nanowires.

  4. Online isolation of defects in cellular nanocomputers

    Institute of Scientific and Technical Information of China (English)

    Teijiro Isokawa; Shin'ya Kowada; Ferdinand Peper; Naotake Kamiura; Nobuyuki Matsui

    2007-01-01

    Unreliability will be a major issue for computers built from components at nanometer scales.Thus,it's to be expected that such computers will need a high degree of defect-tolerance to overcome components' defects which have arisen during the process of manufacturing.This paper presents a novel approach to defect-tolerance that is especially geared towards nanocomputers based on asynchronous cellular automata.According to this approach,defective cells are detected and isolated by small configurations that move around randomly in cellular space.These configurations,called random flies,will attach to configurations that are static,which is typical for configurations that contain defective cells.On the other hand,dynamic configurations,like those that conduct computations,will not be isolated from the rest of the cellular space by the random flies,and will be able to continue their operations unaffectedly.

  5. INFLUENCE OF PERSONALITY SHORTFALLON THEEFFECTIVENESS OFDEFECT DENSITY IN PAIR PROGRAMMING

    Directory of Open Access Journals (Sweden)

    Mrs. k.s.sunitha

    2016-04-01

    Full Text Available Various software developmental issues in pair programming environment such as,reducing defects, better bug fixing, optimumknowledge combinationofexpertise and thereby reducing developmental time etc.,have been reported in literature. They are however found mostlyoncomparative studies with single programmingofs/w projects.These characteristics arealso found to be dealt withmostly in isolation bythe available literature.Whether certain personality shortfalls among pair programmers in some of the above specified programmer characteristics would influence the efficiency in reducing s/w defects?Thisissue mightdemand forempirical social factors of programmer characteristics for further research purposes.We have reported in our earlier work that defect density (defective codes to overall code ratio has reduced in small sized s/w projects, when domain experts have been paired with conventional programmers.This paper will be an extension of that, which attemptsfor an investigation on delimited personality shortfalls, namely talent in combination with domain job matching. The investigation aims at studying the influence of cross trainingmade on inexperienced programmers (of the pair in cross domains with an objective to determine whether these shortfalls would be rectified and therebythe defect density of small sizeds/w development projects would decrease?Experimental setups, social surveys and the results reported in this paper form a part of a whole research program of the authors, and hence some of the relevant input data have beendrawn from our earlier published work [SunithaK. S &Nirmala, K, 2015]. When s/w defects relate to lines of coding (LOC or in other words the developmental efforts, due to personality shortfalls might directly influencethe concerned paired humans. It is hypothesized that the domain experts (navigators could controland influence the programmers (drivers one anotheror in a combined fashion.The paper presents relational study

  6. Impact of isovalent doping on the formation of the CiOi(SiI)n defects in silicon

    Science.gov (United States)

    Christopoulos, S.-R. G.; Sgourou, E. N.; Vovk, R. V.; Chroneos, A.; Londos, C. A.

    2017-09-01

    It has been determined that carbon-oxygen-self-interstitial defects in silicon (Si) can influence the operation of devices through the concentration of intrinsic point defects. Doping with larger isovalent dopants such as germanium (Ge) and tin (Sn) can impact the formation, energetics and structure of defect clusters in Si. In the present study we use density functional theory calculations to gain insights on the formation and stability of the CiOi(SiI)n (n = 0, 1, 2) defects in Si doped with Ge or Sn. It is calculated that the CiOi(SiI)n defects will preferentially form away from the oversized dopants. This result for the interstitial clusters is opposite to what is expected for vacancy-containing clusters which strongly associate with oversized dopants.

  7. The role of point defects and defect complexes in silicon device processing. Summary report and papers

    Energy Technology Data Exchange (ETDEWEB)

    Sopori, B.; Tan, T.Y.

    1994-08-01

    This report is the summary of the third workshop on the role of point defects and defect complexes in silicon device processing. The workshop was organized: (1) to discuss recent progress in the material quality produced by photovoltaic Si manufacturers, (2) to foster the understanding of point defect issues in Si device processing, (3) to review the effects of inhomogeneities on large- area solar cell performance, (4) to discuss how to improve Si solar cell processing, and (5) to develop a new understanding of gettering, defect passivation, and defect annihilation. Separate abstract were prepared for the individual papers, for the database.

  8. The defective RNAs of Closteroviridae

    Directory of Open Access Journals (Sweden)

    Munir eMawassi

    2013-05-01

    Full Text Available The family Closteroviridae consists of two genera, Closterovirus and Ampelovirus with monopartite genomes transmitted respectively by aphids and mealybugs and the Crinivirus with bipartite genomes transmitted by whiteflies. The Closteroviridae consists of more than thirty virus species, which differ considerably in their phytopathological significance. Some, like Beet yellows virus (BYV and Citrus tristeza virus (CTV were associated for many decades with their respective hosts, sugar beets and citrus. Others, like the grapevine leafroll-associated ampeloviruses 1, and 3 were also associated with their grapevine hosts for long periods; however difficulties in virus isolation hampered their molecular characterization. The majority of the recently identified Closteroviridae were probably associated with their vegetative propagated host plants for long periods and only detected through the considerable advances in dsRNA isolation and sequencing of PCR amplified replicons. Molecular characterization of CTV and several other Closteroviridae revealed that, in addition to genomic and subgenomic RNAs, infected plants contain several different subviral defective RNAs (dRNAs. The roles and biological functions of dRNAs associated with Closteroviridae remain terra incognita.

  9. Symmetry fractionalization and twist defects

    Science.gov (United States)

    Tarantino, Nicolas; Lindner, Netanel H.; Fidkowski, Lukasz

    2016-03-01

    Topological order in two-dimensions can be described in terms of deconfined quasiparticle excitations—anyons—and their braiding statistics. However, it has recently been realized that this data does not completely describe the situation in the presence of an unbroken global symmetry. In this case, there can be multiple distinct quantum phases with the same anyons and statistics, but with different patterns of symmetry fractionalization—termed symmetry enriched topological order. When the global symmetry group G, which we take to be discrete, does not change topological superselection sectors—i.e. does not change one type of anyon into a different type of anyon—one can imagine a local version of the action of G around each anyon. This leads to projective representations and a group cohomology description of symmetry fractionalization, with the second cohomology group {H}2(G,{{ A }}{{abelian}}) being the relevant group. In this paper, we treat the general case of a symmetry group G possibly permuting anyon types. We show that despite the lack of a local action of G, one can still make sense of a so-called twisted group cohomology description of symmetry fractionalization, and show how this data is encoded in the associativity of fusion rules of the extrinsic ‘twist’ defects of the symmetry. Furthermore, building on work of Hermele (2014 Phys. Rev. B 90 184418), we construct a wide class of exactly-solvable models which exhibit this twisted symmetry fractionalization, and connect them to our formal framework.

  10. Roles of crystal defects in the persistent luminescence of Eu2+, Dy3+ co-doped strontium aluminate based phosphors

    Institute of Scientific and Technical Information of China (English)

    L(U) Xingdong; SHU Wangen

    2007-01-01

    The roles of different point defects in persistent luminescence of SrAl2O4:Eu,Dy phosphors were investigated. phors. It can serve as the electron trap of suitable depth for persistent luminescence. V(o) does not serve as the electron trap work as an effective electron trap. The point defect of V"Sr can be hole trap, but the change of its density in crystal matrix does not arouse the obvious change of persistent luminescence.

  11. In situ study of defect migration kinetics and self-healing of twin boundaries in heavy ion irradiated nanotwinned metals.

    Science.gov (United States)

    Li, J; Yu, K Y; Chen, Y; Song, M; Wang, H; Kirk, M A; Li, M; Zhang, X

    2015-05-13

    High energy particles introduce severe radiation damage in metallic materials, such as Ag. Here we report on the study on twin boundary (TB) affected zone in irradiated nanotwinned Ag wherein time accumulative defect density and defect diffusivity are substantially different from those in twin interior. In situ studies also reveal surprising resilience and self-healing of TBs in response to radiation. This study provides further support for the design of radiation-tolerant nanotwinned metallic materials.

  12. Visual Field Defects and Retinal Ganglion Cell Losses in Human Glaucoma Patients

    Science.gov (United States)

    Harwerth, Ronald S.; Quigley, Harry A.

    2007-01-01

    Objective The depth of visual field defects are correlated with retinal ganglion cell densities in experimental glaucoma. This study was to determine whether a similar structure-function relationship holds for human glaucoma. Methods The study was based on retinal ganglion cell densities and visual thresholds of patients with documented glaucoma (Kerrigan-Baumrind, et al.) The data were analyzed by a model that predicted ganglion cell densities from standard clinical perimetry, which were then compared to histologic cell counts. Results The model, without free parameters, produced accurate and relatively precise quantification of ganglion cell densities associated with visual field defects. For 437 sets of data, the unity correlation for predicted vs. measured cell densities had a coefficient of determination of 0.39. The mean absolute deviation of the predicted vs. measured values was 2.59 dB, the mean and SD of the distribution of residual errors of prediction was -0.26 ± 3.22 dB. Conclusions Visual field defects by standard clinical perimetry are proportional to neural losses caused by glaucoma. Clinical Relevance The evidence for quantitative structure-function relationships provides a scientific basis of interpreting glaucomatous neuropathy from visual thresholds and supports the application of standard perimetry to establish the stage of the disease. PMID:16769839

  13. Muscular ventricular septal defects: A reappraisal of the anatomy

    NARCIS (Netherlands)

    Wenink, A.C.G.; Oppenheimer-Dekker, A.; Moulaert, A.J.

    1979-01-01

    Among 79 autopsy specimens of hearts with an isolated ventricular septal defect, there were 29 cases of muscular defect. Among 60 hearts with complete transposition of the great arteries and a ventricular septal defect, there were 13 cases with a muscular defect. All muscular defects could be classi

  14. The defect effects on the signal transport of an excitable soft cable

    Science.gov (United States)

    Liu, Tang-Yu; Chang, Cheng-Hung

    2013-03-01

    How a local perturbation affects a propagating wave traveling in a homogeneous medium is a general physics question widely investigated in condensed materials. Intuitively, one might expect that a perturbation would suppress the transport ability of the medium if it is quasi one dimensional. This is generically true as defects and impurities influence numerous non-excitable systems such as carbon nanotubes, nanowires and DNA double helixes. However, if the system is excitable, such as a neuron, a defect may generate a highly non-trivial dynamical behavior. In this paper, using the Hodgkin-Huxley model, we explored this diversity generated by locally non-uniform ion channel densities caused by toxins, diseases, environmental disorders or artificial manipulations. These channel density defects could induce several exotic behaviors, in contrast with the normal destructive role of defects in solid-state physics. They may behave as an electric signal generator exhibiting spontaneous or stimulated emissions, as well as trap, reflect, rectify, delay or extinguish propagating signals or be switched to different functions by a signal. Nonlinear analysis and phase diagrams were used to quantify this dynamical complexity. The results may contribute to research on signal manipulation in biotechnology, neuronal diseases and damages, channel distribution-related cell functions and defect dynamics in general excitable mathematical models.

  15. Defect-induced selective oxidation of graphene: A first-principles study

    Science.gov (United States)

    Xing, Yu-heng; Lu, Peng-fei; Wang, Jian; Yang, Jin-peng; Chen, Yong-ping

    2017-02-01

    Controlled oxidation of graphene is extremely important for nanopatterning and chemical functionalization. It is generally assumed in experiments that the oxidizing agent in the liquid-phase oxidation first attacks the defective sites in carbon lattices. To explore how the oxidation in the graphene sheet first begins, we have investigated the oxidization process with the structural defect using the density functional theory. Ten reaction pathways in the frame of the transition state theory are considered. We find that the most preferential reaction locus is located at the center of defect. It has also been observed that the preexistence of hydroxyl functional group on the graphene surface substantially decrease energy barrier for oxidization. Such facilitation of oxidation due to hydroxyl can explain how the oxidation process continues after its first oxidation around defects. The uneven redistributions of electron density caused both by defect and by the hydroxyl functional group account for the mechanism of the oxidization process on graphene sheet. Our calculation fully verifies the experimental assumption and is consistent with the recent experimental observations.

  16. Mechanical characterization of the role of defects in sintered FeCrAIY foams

    Institute of Scientific and Technical Information of China (English)

    M. Kepets; T. J. Lu; A. P. Dowling

    2007-01-01

    Open celled metal foams fabricated through metal sintering are a new class of material that offers novel mechanical and acoustic properties. Previously, polymer foams have been widely used as a means of absorbing acous-tic energy. However, the structural applications of these foams are limited. The metal sintering approach offers a cost-effective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys. In this first part of two-paper series, the mechanical properties of open-celled steel alloy (FeCrAlY) foams were characterized under uniaxial compression and shear loading.Compared to predictions from established models, a signi-ficant knockdown in material properties was observed. This knockdown was attributed to the presence of defects throu-ghout the microstructure that result from the unique fabri-cation process. Further in situ tests were carded out in a SEM (scanning electronic microscope) in order to investigate the effects of defects on the properties of the foams. Typi-cally, the onset of plastic yielding was observed to occur at defect locations within the microstructure. At lower relative densities, ligament bending dominates, with the deformation initializing at defects. At higher relative densities, an additional deformation mechanism associated with mem-brane elements was observed. In the follow-up of this paper,a finite element model will be constructed to quantify the effects of defects on the mechanical performance of the open-cell foam.

  17. Effects of defect states on the performance of perovskite solar cells

    Science.gov (United States)

    Fengjuan, Si; Fuling, Tang; Hongtao, Xue; Rongfei, Qi

    2016-07-01

    We built an ideal perovskite solar cell model and investigated the effects of defect states on the solar cell's performance. The verities of defect states with a different energy level in the band gap and those in the absorption layer CH3NH3PbI3 (MAPbI3), the interface between the buffer layer/MAPbI3, and the interface between the hole transport material (HTM) and MAPbI3, were studied. We have quantitatively analyzed these effects on perovskite solar cells' performance parameters. They are open-circuit voltage, short-circuit current, fill factor, and photoelectric conversion efficiency. We found that the performances of perovskite solar cells change worse with defect state density increasing, but when defect state density is lower than 1016 cm-3, the effects are small. Defect states in the absorption layer have much larger effects than those in the adjacent interface layers. The perovskite solar cells have better performance as its working temperature is reduced. When the thickness of MAPbI3 is about 0.3 μm, perovskite solar cells show better comprehensive performance, while the thickness 0.05 μm for Spiro-OMeTAD is enough. Project supported by the National Natural Science Foundation of China (Nos. 11164014, 11364025), the Gansu Science and Technology Pillar Program (No. 1204GKCA057), and the Gansu Supercomputer Center.

  18. Defect-Defect Interaction in Single-Walled Carbon Nanotubes Under Torsional Loading

    Science.gov (United States)

    Huq, Abul M. A.; Bhuiyan, Abuhanif K.; Liao, Kin; Goh, Kheng Lim

    This paper presents an analysis of interactions between a pair of Stone-Wales (SW) defects in a single-walled carbon nanotube (SWCNT) that has been subjected to an external torque. Defect pairs, representing the different combinations of SW defect of A (SW-A) and B (SW-B) modes, were incorporated in SWCNT models of different chirality and diameter and solved using molecular mechanics. Defect-defect interaction was investigated by evaluating the C-C steric interactions in the defect that possesses the highest potential energy, E, as a function of inter-defect distance, D. This study reveals that the deformation of the C-C bond is attributed to bond stretching and bending. In the SW-B defects, there is an additional contributor arising from the dihedral angular deformation. The magnitude of E depends on the type of defect but the profile of the E versus D curve depends on the orientation of the defects. The largest indifference length, D0, beyond which two defects cease to interact, is approximately 30 Å. When the angular displacement of the tube increases two-fold, E increases, but the profile of the E versus D curve is not affected. The sense of rotation affects the magnitude of E but not the profile of the E versus D curve.

  19. Density dependent neurodynamics.

    Science.gov (United States)

    Halnes, Geir; Liljenström, Hans; Arhem, Peter

    2007-01-01

    The dynamics of a neural network depends on density parameters at (at least) two different levels: the subcellular density of ion channels in single neurons, and the density of cells and synapses at a network level. For the Frankenhaeuser-Huxley (FH) neural model, the density of sodium (Na) and potassium (K) channels determines the behaviour of a single neuron when exposed to an external stimulus. The features of the onset of single neuron oscillations vary qualitatively among different regions in the channel density plane. At a network level, the density of neurons is reflected in the global connectivity. We study the relation between the two density levels in a network of oscillatory FH neurons, by qualitatively distinguishing between three regions, where the mean network activity is (1) spiking, (2) oscillating with enveloped frequencies, and (3) bursting, respectively. We demonstrate that the global activity can be shifted between regions by changing either the density of ion channels at the subcellular level, or the connectivity at the network level, suggesting that different underlying mechanisms can explain similar global phenomena. Finally, we model a possible effect of anaesthesia by blocking specific inhibitory ion channels.

  20. On density forecast evaluation

    NARCIS (Netherlands)

    Diks, C.

    2008-01-01

    Traditionally, probability integral transforms (PITs) have been popular means for evaluating density forecasts. For an ideal density forecast, the PITs should be uniformly distributed on the unit interval and independent. However, this is only a necessary condition, and not a sufficient one, as

  1. MEASUREMENT OF WHEAT DENSITY

    Institute of Scientific and Technical Information of China (English)

    冯跟胜; 党金春; 等

    1995-01-01

    A method used for on line determining the change of wheat density with a automatic watering machine in a lqarge flour mill has been studied.The results show that the higher distinguishing ability is obtained when using 241Am as a γ-ray source for measuring the wheat density than using 137Cs.

  2. High energy density in multisoliton collisions

    Science.gov (United States)

    Saadatmand, Danial; Dmitriev, Sergey V.; Kevrekidis, Panayotis G.

    2015-09-01

    Solitons are very effective in transporting energy over great distances and collisions between them can produce high energy density spots of relevance to phase transformations, energy localization and defect formation among others. It is then important to study how energy density accumulation scales in multisoliton collisions. In this study, we demonstrate that the maximal energy density that can be achieved in collision of N slowly moving kinks and antikinks in the integrable sine-Gordon field, remarkably, is proportional to N2, while the total energy of the system is proportional to N . This maximal energy density can be achieved only if the difference between the number of colliding kinks and antikinks is minimal, i.e., is equal to 0 for even N and 1 for odd N and if the pattern involves an alternating array of kinks and antikinks. Interestingly, for odd (even) N the maximal energy density appears in the form of potential (kinetic) energy, while kinetic (potential) energy is equal to zero. The results of the present study rely on the analysis of the exact multisoliton solutions for N =1 ,2 , and 3 and on the numerical simulation results for N =4 ,5 ,6 , and 7. The effect of weak Hamiltonian and non-Hamiltonian perturbations on the maximal energy density in multikink collisions is also discussed as well as that of the collision relative phase. Based on these results one can speculate that the soliton collisions in the sine-Gordon field can, in principle, controllably produce very high energy density. This can have important consequences for many physical phenomena described by the Klein-Gordon equations.

  3. Distribution of Defects in Wind Turbine Blades and Reliability Assessment of Blades Containing Defects

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Branner, Kim; Berring, Peter

    2009-01-01

    on the assumption that one error in the production process tends to trigger several defects. For both models additional information about number, type and size of the defects is included as stochastic variables. The probability of failure for a wind turbine blade will not only depend on variations in the material...... properties and the load but also on potential defects in the blades. As a numerical example the probability of failure is calculated for the main spar both with and without defects in terms of delaminations. The delaminations increase the probability of failure compared to a perfect blade, but by applying......In the present paper two stochastic models for the distribution of defects in wind turbine blades are proposed. The first model assumes that the individual defects are completely randomly distributed in the blade. The second model assumes that the defects occur in clusters of different size based...

  4. Learning Grasp Affordance Densities

    DEFF Research Database (Denmark)

    Detry, Renaud; Kraft, Dirk; Kroemer, Oliver

    2011-01-01

    We address the issue of learning and representing object grasp affordance models. We model grasp affordances with continuous probability density functions (grasp densities) which link object-relative grasp poses to their success probability. The underlying function representation is nonparametric...... and relies on kernel density estimation to provide a continuous model. Grasp densities are learned and refined from exploration, by letting a robot “play” with an object in a sequence of graspand-drop actions: The robot uses visual cues to generate a set of grasp hypotheses; it then executes...... these and records their outcomes. When a satisfactory number of grasp data is available, an importance-sampling algorithm turns these into a grasp density. We evaluate our method in a largely autonomous learning experiment run on three objects of distinct shapes. The experiment shows how learning increases success...

  5. Symmetry energy and density

    CERN Document Server

    Trautmann, Wolfgang; Russotto, Paolo

    2016-01-01

    The nuclear equation-of-state is a topic of highest current interest in nuclear structure and reactions as well as in astrophysics. In particular, the equation-of-state of asymmetric matter and the symmetry energy representing the difference between the energy densities of neutron matter and of symmetric nuclear matter are not sufficiently well constrained at present. The density dependence of the symmetry energy is conventionally expressed in the form of the slope parameter L describing the derivative with respect to density of the symmetry energy at saturation. Results deduced from nuclear structure and heavy-ion reaction data are distributed around a mean value L=60 MeV. Recent studies have more thoroughly investigated the density range that a particular observable is predominantly sensitive to. Two thirds of the saturation density is a value typical for the information contained in nuclear-structure data. Higher values exceeding saturation have been shown to be probed with meson production and collective ...

  6. Spatially-resolved photocapacitance measurements to study defects in a-Si:H based p-i-n particle detectors

    Energy Technology Data Exchange (ETDEWEB)

    Casteleiro, C. [Departamento de Fisica, Instituto Superior Tecnico, Lisboa (Portugal); Schwarz, R. [Departamento de Fisica, Instituto Superior Tecnico, Lisboa (Portugal)], E-mail: rschwarz@fisica.ist.utl.pt; Mardolcar, U. [Departamento de Fisica, Instituto Superior Tecnico, Lisboa (Portugal); Macarico, A.; Martins, J.; Vieira, M. [Departamento de Electronica e Informatica, Instituto Superior de Engenharia de Lisboa, Lisboa (Portugal); Wuensch, F.; Kunst, M. [Hahn-Meitner-Institut, Solare Energetik, Berlin (Germany); Morgado, E. [Departamento de Engenharia Electrotecnica, Instituto Superior Tecnico, Lisboa (Portugal); Stallinga, P.; Gomes, H.L. [Departamento de Electrotecnia, Universidade do Algarve, Faro (Portugal)

    2008-06-02

    Thick large-area particle or X-ray detectors suffer degradation during operation due to creation of defects that act as deep traps. Measuring the photocurrent under homogeneously absorbed weak light can monitor variation in detector performance. We describe how photocapacitance can be used as an alternative method to measure the creation of defects and their energy level after intense irradiation with protons or He ions at 1.5 MeV and after exposure to intense laser pulses. The possibility to detect small areas of high defect density in a large-area detector structure is discussed.

  7. Numerical simulation of intrinsic defects in SiO sub 2 and Si sub 3 N sub 4

    CERN Document Server

    Gritsenko, V A; Shaposhnikov, A V; Morokov, Y N

    2001-01-01

    The electronic structure of main intrinsic defects in SiO sub 2 and Si sub 3 N sub 4 has been studied in the cluster approximation using the MINDO/3 method and the density functional method. The defects which are interesting from the point of view of their possibility to capture electrons and holes, three- and two-coordinated silicon atom, are considered. An energy gain is calculated for the capture of an electron or a hole by defects, taking into account the electronic and atomic relaxation. Experimental and calculated X-ray emission spectra for both materials are compared

  8. Studying post-etching silicon crystal defects on 300mm wafer by automatic defect review AFM

    Science.gov (United States)

    Zandiatashbar, Ardavan; Taylor, Patrick A.; Kim, Byong; Yoo, Young-kook; Lee, Keibock; Jo, Ahjin; Lee, Ju Suk; Cho, Sang-Joon; Park, Sang-il

    2016-03-01

    Single crystal silicon wafers are the fundamental elements of semiconductor manufacturing industry. The wafers produced by Czochralski (CZ) process are very high quality single crystalline materials with known defects that are formed during the crystal growth or modified by further processing. While defects can be unfavorable for yield for some manufactured electrical devices, a group of defects like oxide precipitates can have both positive and negative impacts on the final device. The spatial distribution of these defects may be found by scattering techniques. However, due to limitations of scattering (i.e. light wavelength), many crystal defects are either poorly classified or not detected. Therefore a high throughput and accurate characterization of their shape and dimension is essential for reviewing the defects and proper classification. While scanning electron microscopy (SEM) can provide high resolution twodimensional images, atomic force microscopy (AFM) is essential for obtaining three-dimensional information of the defects of interest (DOI) as it is known to provide the highest vertical resolution among all techniques [1]. However AFM's low throughput, limited tip life, and laborious efforts for locating the DOI have been the limitations of this technique for defect review for 300 mm wafers. To address these limitations of AFM, automatic defect review AFM has been introduced recently [2], and is utilized in this work for studying DOI on 300 mm silicon wafer. In this work, we carefully etched a 300 mm silicon wafer with a gaseous acid in a reducing atmosphere at a temperature and for a sufficient duration to decorate and grow the crystal defects to a size capable of being detected as light scattering defects [3]. The etched defects form a shallow structure and their distribution and relative size are inspected by laser light scattering (LLS). However, several groups of defects couldn't be properly sized by the LLS due to the very shallow depth and low

  9. Hydrogen adsorption and storage of Ca-decorated graphene with topological defects: A first-principles study

    Science.gov (United States)

    Ma, Ling; Zhang, Jian-Min; Xu, Ke-Wei; Ji, Vincent

    2014-09-01

    As a candidate for hydrogen storage medium, geometric stability and hydrogen capacity of Ca-decorated graphene with topological defects are investigated using the first-principle based on density functional theory (DFT), specifically for the experimentally realizable single carbon vacancy (SV), 585 double carbon vacancy (585 DCV) and 555-777 double carbon vacancy (555-777 DCV) defects. It is found that Ca atom can be stabilized on above defective graphenes since Ca's binding energy on vacancy defect is much larger than its cohesive energy. Up to six H2 molecules can stably bind to a Ca atom on defective graphene with the average adsorption energies of 0.17-0.39 eV/H2. The hybridization of the Ca-3d orbitals with H2-σorbitals and the electrostatic interaction between the Ca cation and the induced H2 dipole both contribute to the H2 molecules binding. Double-side Ca-decorated graphene with 585 DCV and 555-777 DCV defects can theoretically reach a gravimetric capacity of 5.2 wt% hydrogen, indicating that Ca-decorated defective graphene can be used as a promising material for high density hydrogen storage.

  10. Elemental redistributions at structural defects in Cu(In,Ga)Se2 thin films for solar cells

    Science.gov (United States)

    Simsek Sanli, E.; Ramasse, Q. M.; Sigle, W.; Abou-Ras, D.; Mainz, R.; Weber, A.; Kleebe, H.-J.; van Aken, P. A.

    2016-11-01

    The microstructural evolution of Cu(In,Ga)Se2 absorber layers during a three-stage-type co-evaporation process was studied to elucidate the effect of a Cu-rich stage on the formation of extended structural defects. Defect densities for two Cu-poor samples, one interrupted before and one after this crucial Cu-rich composition stage, were investigated by scanning transmission electron microscopy (STEM) imaging. The structure and chemical nature of individual defects were investigated by aberration-corrected high-resolution STEM in combination with electron energy-loss spectroscopy on the atomic-scale. In spite of the different defect densities between the two samples, most of the individual defects exhibited similar chemistry. In particular, the elemental distributions of atomic columns at {112} twin planes, which are very frequent in Cu(In,Ga)Se2 thin films, were found to be the same as in the defect-free grain interiors. In contrast, within grain boundaries, dislocation cores, and other structurally more complex defects, elemental redistributions of Cu and In were observed.

  11. An analysis of the temperature dependence of the electron density in CdGeAs sub 2

    CERN Document Server

    Borisenko, S I

    2001-01-01

    Analysis of temperature dependence of electron density in single crystals grown by a new method has been performed. Values of concentration of intrinsic defects and the energy of activation is calculated. It is shown, that the energy of activation has a resonant character, and concentration of intrinsic defects in the investigated range of temperatures 10-500 K considerably exceeds the concentration of electrons

  12. Robust defect segmentation in woven fabrics

    Energy Technology Data Exchange (ETDEWEB)

    Sari-Sarraf, H.; Goddard, J.S. Jr.

    1997-12-01

    This paper describes a robust segmentation algorithm for the detection and localization of woven fabric defects. The essence of the presented segmentation algorithm is the localization of those events (i.e., defects) in the input images that disrupt the global homogeneity of the background texture. To this end, preprocessing modules, based on the wavelet transform and edge fusion, are employed with the objective of attenuating the background texture and accentuating the defects. Then, texture features are utilized to measure the global homogeneity of the output images. If these images are deemed to be globally nonhomogeneous (i.e., defects are present), a local roughness measure is used to localize the defects. The utility of this algorithm can be extended beyond the specific application in this work, that is, defect segmentation in woven fabrics. Indeed, in a general sense, this algorithm can be used to detect and to localize anomalies that reside in images characterized by ordered texture. The efficacy of this algorithm has been tested thoroughly under realistic conditions and as a part of an on-line fabric inspection system. Using over 3700 images of fabrics, containing 26 different types of defects, the overall detection rate of this approach was 89% with a localization accuracy of less than 0.2 inches and a false alarm rate of 2.5%.

  13. Platelet rich fibrin in jaw defects

    Science.gov (United States)

    Nica, Diana; Ianes, Emilia; Pricop, Marius

    2016-03-01

    Platelet rich fibrin (PRF) is a tissue product of autologous origin abundant in growth factors, widely used in regenerative procedures. Aim of the study: Evaluation of the regenerative effect of PRF added in the bony defects (after tooth removal or after cystectomy) Material and methods: The comparative nonrandomized study included 22 patients divided into 2 groups. The first group (the test group) included 10 patients where the bony defects were treated without any harvesting material. The second group included 12 patients where the bony defects were filled with PRF. The bony defect design was not critical, with one to two walls missing. After the surgeries, a close clinically monitoring was carried out. The selected cases were investigated using both cone beam computer tomography (CBCT) and radiographic techniques after 10 weeks postoperatively. Results: Faster bone regeneration was observed in the bony defects filled with PRF comparing with the not grafted bony defects. Conclusions: PRF added in the bony defects accelerates the bone regeneration. This simplifies the surgical procedures and decreases the economic costs.

  14. Modeling of Powder Bed Manufacturing Defects

    Science.gov (United States)

    Mindt, H.-W.; Desmaison, O.; Megahed, M.; Peralta, A.; Neumann, J.

    2017-09-01

    Powder bed additive manufacturing offers unmatched capabilities. The deposition resolution achieved is extremely high enabling the production of innovative functional products and materials. Achieving the desired final quality is, however, hampered by many potential defects that have to be managed in due course of the manufacturing process. Defects observed in products manufactured via powder bed fusion have been studied experimentally. In this effort we have relied on experiments reported in the literature and—when experimental data were not sufficient—we have performed additional experiments providing an extended foundation for defect analysis. There is large interest in reducing the effort and cost of additive manufacturing process qualification and certification using integrated computational material engineering. A prerequisite is, however, that numerical methods can indeed capture defects. A multiscale multiphysics platform is developed and applied to predict and explain the origin of several defects that have been observed experimentally during laser-based powder bed fusion processes. The models utilized are briefly introduced. The ability of the models to capture the observed defects is verified. The root cause of the defects is explained by analyzing the numerical results thus confirming the ability of numerical methods to provide a foundation for rapid process qualification.

  15. Emerging Diluted Ferromagnetism in High‐T c Superconductors Driven by Point Defect Clusters

    Science.gov (United States)

    Guzman, Roger.; Mishra, Rohan; Bartolomé, Elena; Salafranca, Juan; Magén, Cesar; Varela, Maria; Coll, Mariona; Palau, Anna; Valvidares, S. Manuel; Gargiani, Pierluigi; Pellegrin, Eric; Herrero‐Martin, Javier.; Pennycook, Stephen J.; Pantelides, Sokrates T.; Puig, Teresa; Obradors, Xavier

    2016-01-01

    Defects in ceramic materials are generally seen as detrimental to their functionality and applicability. Yet, in some complex oxides, defects present an opportunity to enhance some of their properties or even lead to the discovery of exciting physics, particularly in the presence of strong correlations. A paradigmatic case is the high‐temperature superconductor YBa2Cu3O7‐δ (Y123), in which nanoscale defects play an important role as they can immobilize quantized magnetic flux vortices. Here previously unforeseen point defects buried in Y123 thin films that lead to the formation of ferromagnetic clusters embedded within the superconductor are unveiled. Aberration‐corrected scanning transmission microscopy has been used for exploring, on a single unit‐cell level, the structure and chemistry resulting from these complex point defects, along with density functional theory calculations, for providing new insights about their nature including an unexpected defect‐driven ferromagnetism, and X‐ray magnetic circular dichroism for bearing evidence of Cu magnetic moments that align ferromagnetically even below the superconducting critical temperature to form a dilute system of magnetic clusters associated with the point defects. PMID:27812469

  16. Defect-assisted tuning of electroluminescence from p-GaN/n-ZnO nanorod heterojunction

    Indian Academy of Sciences (India)

    Lawrence S Vikas; C K Sruthi; Madambi K Jayaraj

    2015-08-01

    Growth of nanostructured ZnO by solution process always lead to the formation of various kinds of defects. Defect states also can aid in improving different properties of the material. In the case of light-emitting diodes (LEDs), major research is focused on tuning the emission colour so as to achieve white emission without the use of any phosphors. Vertically aligned ZnO nanorods were grown over Mg:GaN substrate by hydrothermal process. High-resolution X-ray diffraction (HRXRD) analysis confirms the epitaxial growth of nanorods over the substrate. The photoluminescence (PL) studies revealed a narrow near band edge emission and a broad defect-induced deep level emission. The intensity of deep level emissions related to Zni, Vo, Oi defects decreases on annealing. The - characteristics of the heterojunction showed excellent rectifying nature with electroluminescence emission on forward bias. Device fabricated by as-grown ZnO nanorods emits in the UV–blue region and broad emission in the visible region. While the annealed device emitted only in UV–blue region. The emission wavelengths closely matched with that of defect state emissions obtained in the PL studies. By annealing, various defect states density can be controlled, thereby emission colour tuned from white to blue.

  17. Coherent resonance of quantum plasmons in Stone-Wales defected graphene-silver nanowire hybrid system

    Science.gov (United States)

    Liu, Tong; Zhang, Hong; Cheng, Xin-Lu; Xu, Yang

    2017-10-01

    Defected graphene has a more important practical significance than graphene. Silver nanoparticles can modify the optical properties of defected graphene. We present herein a detailed theoretical analysis about the coherent resonance of quantum plasmons in the Stone-Wales (SW) defected graphene-silver nanowire hybrid system by using time-dependent density functional theory. The plasmon coherent effect is mainly attributed to the electromagnetic field coupling between the Stone-Wales defected graphene and silver nanowires. As a result, the optical response of the hybrid system exhibits a remarkable enhancement. Plasmon resonance, which depends on polarization and selectable tuning, is enhanced in wide frequency regions. Moreover, it reveals that the resonance frequency of an optical absorption spectrum depends on the space configuration of the SW defected graphene in the hybrid system. This investigation provides a better understanding of the plasmon enhancement effect used in a graphene-based photoelectric device. The study also offers an effective means of detecting the defects existing in graphene.

  18. Investigation of point and extended defects in electron irradiated silicon—Dependence on the particle energy

    Energy Technology Data Exchange (ETDEWEB)

    Radu, R.; Pintilie, I.; Nistor, L. C. [National Institute of Materials Physics, Atomistilor 105 bis, Magurele 077125 (Romania); Fretwurst, E.; Lindstroem, G. [Institute for Experimental Physics, University of Hamburg, D-22761 Hamburg (Germany); Makarenko, L. F. [Belarusian State University, Independence Ave. 4, 220030 Minsk (Belarus)

    2015-04-28

    This work is focusing on generation, time evolution, and impact on the electrical performance of silicon diodes impaired by radiation induced active defects. n-type silicon diodes had been irradiated with electrons ranging from 1.5 MeV to 27 MeV. It is shown that the formation of small clusters starts already after irradiation with high fluence of 1.5 MeV electrons. An increase of the introduction rates of both point defects and small clusters with increasing energy is seen, showing saturation for electron energies above ∼15 MeV. The changes in the leakage current at low irradiation fluence-values proved to be determined by the change in the configuration of the tri-vacancy (V{sub 3}). Similar to V{sub 3}, other cluster related defects are showing bistability indicating that they might be associated with larger vacancy clusters. The change of the space charge density with irradiation and with annealing time after irradiation is fully described by accounting for the radiation induced trapping centers. High resolution electron microscopy investigations correlated with the annealing experiments revealed changes in the spatial structure of the defects. Furthermore, it is shown that while the generation of point defects is well described by the classical Non Ionizing Energy Loss (NIEL), the formation of small defect clusters is better described by the “effective NIEL” using results from molecular dynamics simulations.

  19. Effect of defects on the burst failure of butt fusion welded polyethylene pipes

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Huan Sheng; Tun, Nwe Ni; Yoon, Kee Bong [Chung-Ang University, Seoul (Korea, Republic of); Kil, Seong Hee [Korea Gas Safety Corporation, Eumseong (Korea, Republic of)

    2016-05-15

    With the increasing demand of Medium density polyethylene (MDPE) pipes for gas transmission, the safety concern related with welding defects is becoming a serious matter. In this paper, experimental burst tests and finite element analyses were employed to study butt fusion welded MDPE pipe joints with spherical and planar defects of various sizes. These defects were used to simulate lack of bonding during the welding. Test results showed that in all pipe test cases, the failure location originated from pipe substrates, even though the defect size was increased to 45% of the pipe's wall thickness. The burst pressure could be estimated by the expression employed in the ASME BPVC, and in the burst pressure, the hoop stress was 20.28 MPa. Simulation results showed that the failure position was not only affected by the defect size, but also by the welding bead. It can be argued that a single welding defect whose maximum size is smaller than 15% of the thickness can be used without failure during short-term usage, even when there is no welding bead in the welded joint.

  20. A high spatial resolution retrieval of NO2 column densities from OMI: method and evaluation

    Directory of Open Access Journals (Sweden)

    R. C. Cohen

    2011-04-01

    Full Text Available We present a new retrieval of tropospheric NO2 vertical column density from the Ozone Monitoring Instrument (OMI based on high spatial and temporal resolution terrain and profile inputs. We find non-negligible impacts on the retrieved NO2 column for terrain pressure (±20%, albedo (±40%, and NO2 vertical profile (−75%–+10%. We compare our NO2 product, the Berkeley High-Resolution (BEHR product, with operational retrievals and find that the operational retrievals are biased high (30% over remote areas and biased low (8% over urban regions. We validate the operational and BEHR products using boundary layer aircraft observations from the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS-CA field campaign which occurred in June 2008 in California. Results indicate that columns derived using our boundary layer extrapolation method show good agreement with satellite observations (R2 = 0.65–0.83; N = 68 and provide a more robust validation of satellite-observed NO2 column than those determined using full vertical spirals (R2 = 0.26; N = 5 as in previous work. Agreement between aircraft observations and the BEHR product (R2 = 0.83 is better than agreement with the operational products (R2 = 0.65–0.72. We also show that agreement between satellite and aircraft observations for all products can be further improved (e.g. BEHR: R2 = 0.91 using cloud information from the Moderate Resolution Imaging Spectroradiometer (MODIS instrument instead of the OMI cloud product. These results indicate that much of the variance in the operational products can be attributed to coarse resolution terrain and profile parameters.