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  1. Amplituden der Kernphasen im Bereich der Kaustik B und Untersuchung der Struktur der Übergangszone zum inneren Erdkern mit spektralen Amplituden der diffraktierten Phase PKP(BC)

    NASA Astrophysics Data System (ADS)

    Wolf, Michael D. C.

    2002-04-01

    ücksichtigt zu werden, da die kumulierte Amplituden-Entfernungskurve anhand der Lage des Maximums auf der Entfernungsachse ausgewertet wird. Folglich wird darauf verzichtet, ein alternatives Q-Modell zu entwickeln. Hinsichtlich der Lage des Kaustikmaximums lassen sich die untersuchten Erdmodelle in zwei Kategorien einteilen. Eine Gruppe besteht aus den Modellen IASP91 und 1066B, deren Maxima bei 144.6 ° und 144.7 ° liegen. Zur zweiten Gruppe von Modellen zählen AK135, PREM und SP6 mit den Maxima bei 145.1 ° und 145.2 ° (SP6). Die gemessene Amplitudenkurve hat ihr Maximum bei 145 °. Alle Entfernungsangaben beziehen sich auf eine Herdtiefe von 200 km. Die Kaustikentfernung für einen Oberflächenherd ist jeweils um 0.454 ° gröer als die angegeben Werte. Damit liegen die Maxima der Modelle AK135 und PREM nur 0.1 ° neben dem der gemessenen kumulierten Amplitudenkurve. Daher wird auf die Erstellung eines eigenen Modells verzichtet, da dieses eine unwesentlich verbesserte Amplitudenkurve aufweisen würde. Das Ergebnis der Untersuchung ist die Erstellung einer gemessenen kumulierten Amplituden-Entfernungskurve für die Kaustik B. Die Kurve legt die Position der Kaustik B für kurzperiodische Daten auf ± 0.15 ° fest und bestimmt damit, welche Erdmodelle für die Beschreibung der Amplituden im Entfernungsbereich der Kaustik B besonders geeignet sind. Die Erdmodelle AK135 und PREM, ergänzt durch ein einheitliches Q-Modell, geben den Verlauf der Amplituden am besten wieder. Da die Amplitudenkurven beider Modelle nahe beieinander liegen, sind sie als gleichwertig zu bezeichnen. Im zweiten Teil der Arbeit wird die Struktur der Übergangszone in den inneren Erdkern anhand des spektralen Abklingens der Phase PKP(BC)diff am Punkt C der Laufzeitkurve untersucht. Der physikalische Proze der Beugung ist für die starke Abnahme der Amplituden dieser Phase verantwortlich. Die Diffraktion beeinflut das Abklingverhalten verschiedener Frequenzanteile des seismischen Signals auf

  2. Van der Waals phase transition in the framework of holography

    NASA Astrophysics Data System (ADS)

    Zeng, Xiao-Xiong; Li, Li-Fang

    2017-01-01

    Phase structure of the quintessence Reissner-Nordström-AdS black hole is probed by the nonlocal observables such as holographic entanglement entropy and two point correlation function. Our result shows that, as the case of the thermal entropy, both the observables exhibit the Van der Waals-like phase transition. To reinforce this conclusion, we further check the equal area law for the first order phase transition and critical exponent of the heat capacity for the second order phase transition. We also discuss the effect of the state parameter on the phase structure of the nonlocal observables.

  3. Evolutionary design of interfacial phase change van der Waals heterostructures.

    PubMed

    Kalikka, Janne; Zhou, Xilin; Behera, Jitendra; Nannicini, Giacomo; Simpson, Robert E

    2016-10-27

    We use an evolutionary algorithm to explore the design space of hexagonal Ge2Sb2Te5; a van der Waals layered two dimensional crystal heterostructure. The Ge2Sb2Te5 structure is more complicated than previously thought. Predominant features include layers of Ge3Sb2Te6 and Ge1Sb2Te4 two dimensional crystals that interact through Te-Te van der Waals bonds. Interestingly, (Ge/Sb)-Te-(Ge/Sb)-Te alternation is a common feature for the most stable structures of each generation's evolution. This emergent rule provides an important structural motif that must be included in the design of high performance Sb2Te3-GeTe van der Waals heterostructure superlattices with interfacial atomic switching capability. The structures predicted by the algorithm agree well with experimental measurements on highly oriented, and single crystal Ge2Sb2Te5 samples. By analysing the evolutionary algorithm optimised structures, we show that diffusive atomic switching is probable by Ge atoms undergoing a transition at the van der Waals interface from layers of Ge3Sb2Te6 to Ge1Sb2Te4 thus producing two blocks of Ge2Sb2Te5. Evolutionary methods present an efficient approach to explore the enormous multi-dimensional design parameter space of van der Waals bonded heterostructure superlattices.

  4. Holographic Van der Waals-like phase transition in the Gauss-Bonnet gravity

    NASA Astrophysics Data System (ADS)

    He, Song; Li, Li-Fang; Zeng, Xiao-Xiong

    2017-02-01

    The Van der Waals-like phase transition is observed in temperature-thermal entropy plane in spherically symmetric charged Gauss-Bonnet-AdS black hole background. In terms of AdS/CFT, the non-local observables such as holographic entanglement entropy, Wilson loop, and two point correlation function of very heavy operators in the field theory dual to spherically symmetric charged Gauss-Bonnet-AdS black hole have been investigated. All of them exhibit the Van der Waals-like phase transition for a fixed charge parameter or Gauss-Bonnet parameter in such gravity background. Further, with choosing various values of charge or Gauss-Bonnet parameter, the equal area law and the critical exponent of the heat capacity are found to be consistent with phase structures in temperature-thermal entropy plane.

  5. Solution phase van der Waals epitaxy of ZnO wire arrays.

    PubMed

    Zhu, Yue; Zhou, Yong; Utama, Muhammad Iqbal Bakti; de la Mata, María; Zhao, Yanyuan; Zhang, Qing; Peng, Bo; Magen, Cesar; Arbiol, Jordi; Xiong, Qihua

    2013-08-21

    As an incommensurate epitaxy, van der Waals epitaxy allows defect-free crystals to grow on substrates even with a large lattice mismatch. Furthermore, van der Waals epitaxy is proposed as a universal platform where heteroepitaxy can be achieved irrespective of the nature of the overlayer material and the method of crystallization. Here we demonstrate van der Waals epitaxy in solution phase synthesis for seedless and catalyst-free growth of ZnO wire arrays on phlogopite mica at low temperature. A unique incommensurate interface is observed even with the incomplete initial wetting of ZnO onto the substrate. Interestingly, the imperfect contacting layer does not affect the crystalline and optical properties of other parts of the wires. In addition, we present patterned growth of a well-ordered array with hexagonal facets and in-plane alignment. We expect our seedless and catalyst-free solution phase van der Waals epitaxy synthesis to be widely applicable in other materials and structures.

  6. Topological phase transition from trigonal warping in van der Waals multilayers

    NASA Astrophysics Data System (ADS)

    Zeng, Junjie; Ren, Yafei; Zhang, Kunhua; Qiao, Zhenhua

    2017-01-01

    In van der Waals multilayers of triangular lattice, trigonal warping occurs universally due to the interlayer hopping. We theoretically investigate the effect of trigonal warping upon distinctive topological phases, such as the quantum anomalous Hall effect (QAHE) and the quantum valley Hall effect (QVHE). Taking Bernal-stacked bilayer graphene as an example, we find that the trigonal warping plays a crucial role in the formation of QAHE in a large exchange field and/or interlayer potential difference by inducing extra band inversion points at a momentum further away from the high-symmetry point. The presence of trigonal warping shrinks the phase space of QAHE and QVHE, leading to the emergence of a valley-polarized QAHE with high Chern numbers ranging from C =-7 to 7 . These results suggest that the universal trigonal warping may play an important role when the Bloch states at momenta deviated from high-symmetry points are involved.

  7. Energy-based analysis of frequency entrainment described by van der Pol and phase-locked loop equations.

    PubMed

    Susuki, Yoshihiko; Yokoi, Yuuichi; Hikihara, Takashi

    2007-06-01

    This paper analyzes frequency entrainment described by van der Pol and phase-locked loop (PLL) equations. The PLL equation represents the dynamics of a PLL circuit that appear in typical phase-locking phenomena. These two equations describe frequency entrainment by a periodic force. The entrainment originates from two different types of limit cycles: libration for the van der Pol equation and rotation for the PLL one. To explore the relationship between the geometry of limit cycles and the mechanism of entrainment, we investigate the entrainment using an energy balance relation. This relation is equivalent to the energy conservation law of dynamical systems with dissipation and input terms. We show response curves for the dc component, harmonic amplitude, phase difference, and energy supplied by a periodic force. The obtained curves indicate that the entrainments for the two equations have different features of supplied energy, and that the entrainment for the PLL equation possibly has the same mechanism as does the regulation of the phase difference for the van der Pol equation.

  8. Energy-based analysis of frequency entrainment described by van der Pol and phase-locked loop equations

    NASA Astrophysics Data System (ADS)

    Susuki, Yoshihiko; Yokoi, Yuuichi; Hikihara, Takashi

    2007-06-01

    This paper analyzes frequency entrainment described by van der Pol and phase-locked loop (PLL) equations. The PLL equation represents the dynamics of a PLL circuit that appear in typical phase-locking phenomena. These two equations describe frequency entrainment by a periodic force. The entrainment originates from two different types of limit cycles: libration for the van der Pol equation and rotation for the PLL one. To explore the relationship between the geometry of limit cycles and the mechanism of entrainment, we investigate the entrainment using an energy balance relation. This relation is equivalent to the energy conservation law of dynamical systems with dissipation and input terms. We show response curves for the dc component, harmonic amplitude, phase difference, and energy supplied by a periodic force. The obtained curves indicate that the entrainments for the two equations have different features of supplied energy, and that the entrainment for the PLL equation possibly has the same mechanism as does the regulation of the phase difference for the van der Pol equation.

  9. National Dam Safety Program. Von Der Ahe Dam (MO 31077), Mississippi - Kaskaskia - St. Louis Basin, Franklin County, Missouri. Phase I Inspection Report.

    DTIC Science & Technology

    1980-06-01

    from Controlling Office) IS. SECURITY CLASS. (of thia rePort) National Darn Safety Program. Von der UNLSSFE(~ Ahe Dam (MO 31V77), Mississippi - ISa ...34;TAT1 MiNT I Apro’,,,, for ;,.blhc yele(so |: ’ --- __ ~ ~~ii[ , - rtu : ’ lrrJl": ’,d PHASE I REPORT NATIONAL DAM SAFETY PROGRAM Name of Dam: Von Der Ahe

  10. Phase change memory devices formed by using 2 dimensional layered Graphene-In2 Se3 van der Waals heterostructure

    NASA Astrophysics Data System (ADS)

    Choi, Min Sup; Yang, Chenxi; Ra, Chang Ho; Yoo, Won Jong

    Indium selenide (In2Se3) is one of the unique materials which have both a layered structure and phase change property. One of the advantages of using 2 dimensional (2D) materials is their potential to form van der Waals heterostructures which enable unique physical properties and novel quantum device functions, which cannot be achieved in 2D material alone. In this study, we fabricated vertically stacked graphene-In2Se3 heterostructured memory devices. The fabricated devices showed a rapid increase of current conduction, which is attributed to the phase transition of In2Se3. The TEM images demonstrated that In2Se3 transformed from polycrystalline to layered structure thanks to the effective thermal confinement effect between graphene and In2Se3, attributed to the low thermal conductivity of layered materials in vertical direction. In addition, the current conduction could be controlled effectively by applying different pulse voltages, showing stable retention and endurance characteristics. It is thought that the differently bonded states contribute to this control process. This study demonstrates the possibility of Graphene-In2Se3 van der Waals heterostructure as 2D based future memory electronics. This work was supported by the National Research Foundation of Korea(NRF) Grant funded by the Korea government(MEST) (No. 2013R1A2A2A01015516).

  11. Nonlinear dipole-dipole interactions and spectroscopic properties of van der waals complexes in the gas phase

    NASA Astrophysics Data System (ADS)

    Bakhshiev, N. G.

    2003-09-01

    We suggest a semiempirical approach to describing the influence of local nonlinear dipole-dipole interactions on the formation of van der Waals complexes of 1: 1 composition in the gas phase. Based on this approach, we quantitatively interpret the experimental data on the patterns of the shift in the electronic (complexes of a 3-aminophthalimide molecule with water and methanol molecules) and vibrational (complexes of a HCl molecule with acetone and acetonitrile molecules) absorption spectra attributable to the processes of complex formation. We confirm the conclusion that a nonlinear dipole-dipole interaction should be considered as one of the most important physical mechanisms that result in the association of molecules both in the gas phase and, under certain conditions, in the condensed state.

  12. A van der Waals-like Transition Between Normal and Cancerous Phases in Cell Populations Dynamics of Colorectal Cancer

    NASA Astrophysics Data System (ADS)

    Qiu, Kang; Wang, Li-Fang; Shen, Jian; Yousif, Alssadig A. M.; He, Peng; Shao, Dan-Dan; Zhang, Xiao-Min; Kirunda, John B.; Jia, Ya

    2016-11-01

    Based on a deterministic continuous model of cell populations dynamics in the colonic crypt and in colorectal cancer, we propose four combinations of feedback mechanisms in the differentiations from stem cells (SCs) to transit cells (TCs) and then to differentiated cells (DCs), the four combinations include the double linear (LL), the linear and saturating (LS), the saturating and linear (SL), and the double saturating (SS) feedbacks, respectively. The relative fluctuations of the population of SCs, TCs, and DCs around equilibrium states with four feedback mechanisms are studied by using the Langevin method. With the increasing of net growth rate of TCs, it is found that the Fano factors of TCs and DCs go to a peak in a transient phase, and then increase again to infinity in the cases of LS and SS feedbacks. The “up-down-up” characteristic on the Fano factor (like the van der Waals loop) demonstrates that there exists a transient phase between the normal and cancerous phases, our novel findings suggest that the mathematical model with LS or SS feedback might be better to elucidate the dynamics of a normal and abnormal (cancerous) phases.

  13. Unterstützung der IT-Service-Management-Prozesse an der Technischen Universität München durch eine Configuration-Management-Database

    NASA Astrophysics Data System (ADS)

    Knittl, Silvia

    Hochschulprozesse in Lehre und Verwaltung erfordern durch die steigende Integration und IT-Unterstützung ein sogenanntes Business Alignment der IT und damit auch ein professionelleres IT-Service-Management (ITSM). Die IT Infrastructure Library (ITIL) mit ihrer Beschreibung von in der Praxis bewährten Prozessen hat sich zum de-facto Standard im ITSM etabliert. Ein solcher Prozess ist das Konfigurationsmanagement. Es bildet die IT-Infrastruktur als Konfigurationselemente und deren Beziehungen in einem Werkzeug, genannt Configuration Management Database (CMDB), ab und unterstützt so das ITSM. Dieser Bericht beschreibt die Erfahrungen mit der prototypischen Einführung einer CMDB an der Technischen Universität München.

  14. Decoupling interface effect on the phase stability of CdS thin films by van der Waals heteroepitaxy

    NASA Astrophysics Data System (ADS)

    Sun, Xin; Wang, Yiping; Seewald, Lucas J.; Chen, Zhizhong; Shi, Jian; Washington, Morris A.; Lu, Toh-Ming

    2017-01-01

    Wurtzite (W) and zinc-blende (ZB) polytypism has long been observed in epitaxial CdS thin films. The present work, based on van der Waals epitaxial CdS thin films, is an attempt to explain which crystal modification, W or ZB, is favored under different growth conditions. In this van der Waals epitaxy system where the substrate influence is considered weak, it is found that the substrate temperature plays a crucial role in determining the crystal modification of CdS, that is, W and ZB CdS are more stable at low and high ends of substrate temperature, respectively. We attribute this temperature effect to the entropy difference (SW < SZB), a conclusion well supported by the thermodynamic hard sphere model formulation of the entropy difference between hexagonal close-packed and face-centered cubic structures. By summarizing other works, we find that the entropy difference model can also be applied to large mismatched (≳3%) CdS-substrate chemical epitaxy systems but not for small mismatched (≲3%) ones. In the latter case, the energy benefit in terms of high density of bonding contributed by the substrate-film interface is believed to be too overwhelming for the intrinsic entropy difference to overcome. Furthermore, the deposition rate is found to affect the crystalline quality and strain level in CdS films but not the crystal modification of the CdS films. Last, Raman and photoluminescence spectroscopies reveal the strain behaviors in the films. The phase change from W to ZB CdS is well-correlated with the observed peak shifts in Raman and photoluminescence spectroscopies.

  15. Beyond the Van Der Waals loop: What can be learned from simulating Lennard-Jones fluids inside the region of phase coexistence

    NASA Astrophysics Data System (ADS)

    Binder, Kurt; Block, Benjamin J.; Virnau, Peter; Tröster, Andreas

    2012-12-01

    As a rule, mean-field theories applied to a fluid that can undergo a transition from saturated vapor at density ρυ to a liquid at density ρℓ yield a van der Waals loop. For example, isotherms of the chemical potential μ(T ,ρ) as a function of the density ρ at a fixed temperature T less than the critical temperature Tc exhibit a maximum and a minimum. Metastable and unstable parts of the van der Waals loop can be eliminated by the Maxwell construction. Van der Waals loops and the corresponding double minimum potentials are mean-field artifacts. Simulations at fixed μ =μcoex for ρυ<ρ <ρℓ yield a loop, but for sufficiently large systems this loop does not resemble the van der Waals loop and reflects interfacial effects on phase coexistence due to finite size effects. In contrast to the van der Waals loop, all parts of the loop found in simulations are thermodynamically stable. The successive umbrella sampling algorithm is described as a convenient tool for seeing these effects. It is shown that the maximum of the loop is not the stability limit of a metastable vapor but signifies the droplet evaporation-condensation transition. The descending part of the loop contains information on Tolman-like corrections to the surface tension, rather than describing unstable states.

  16. van der Waals epitaxial growth of atomically thin Bi₂Se₃ and thickness-dependent topological phase transition.

    PubMed

    Xu, Shuigang; Han, Yu; Chen, Xiaolong; Wu, Zefei; Wang, Lin; Han, Tianyi; Ye, Weiguang; Lu, Huanhuan; Long, Gen; Wu, Yingying; Lin, Jiangxiazi; Cai, Yuan; Ho, K M; He, Yuheng; Wang, Ning

    2015-04-08

    Two-dimensional (2D) atomic-layered heterostructures stacked by van der Waals interactions recently introduced new research fields, which revealed novel phenomena and provided promising applications for electronic, optical, and optoelectronic devices. In this study, we report the van der Waals epitaxial growth of high-quality atomically thin Bi2Se3 on single crystalline hexagonal boron nitride (h-BN) by chemical vapor deposition. Although the in-plane lattice mismatch between Bi2Se3 and h-BN is approximately 65%, our transmission electron microscopy analysis revealed that Bi2Se3 single crystals epitaxially grew on h-BN with two commensurate states; that is, the (1̅21̅0) plane of Bi2Se3 was preferably parallel to the (1̅100) or (1̅21̅0) plane of h-BN. In the case of the Bi2Se3 (2̅110) ∥ h-BN (11̅00) state, the Moiré pattern wavelength in the Bi2Se3/h-BN superlattice can reach 5.47 nm. These naturally formed thin crystals facilitated the direct assembly of h-BN/Bi2Se3/h-BN sandwiched heterostructures without introducing any impurity at the interfaces for electronic property characterization. Our quantum capacitance (QC) measurements showed a compelling phenomenon of thickness-dependent topological phase transition, which was attributed to the coupling effects of two surface states from Dirac Fermions at/or above six quintuple layers (QLs) to gapped Dirac Fermions below six QLs. Moreover, in ultrathin Bi2Se3 (e.g., 3 QLs), we observed the midgap states induced by intrinsic defects at cryogenic temperatures. Our results demonstrated that QC measurements based on h-BN/Bi2Se3/h-BN sandwiched structures provided rich information regarding the density of states of Bi2Se3, such as quantum well states and Landau quantization. Our approach in fabricating h-BN/Bi2Se3/h-BN sandwiched device structures through the combination of bottom-up growth and top-down dry transferring techniques can be extended to other two-dimensional layered heterostructures.

  17. Isomer- and ``phase''-selective spectroscopy of van der Waals solvent clusters

    NASA Astrophysics Data System (ADS)

    Leutwyler, S.; Furlan, A.; Knochenmuss, R.; Schütz, M.; Troxler, T.; Wülfert, S.

    1991-03-01

    At the atomic size level, descriptions of rearrangement of structures and shapes of molecules are couched in chemical terminology (isomerization, racemization, rearrangement, etc.). In bulk solids, structural changes are described on a collective scale as order-disorder transformations and phase transitions (melting). To describe structural changes in atomic and molecular clusters we employ elements of both pictures: (a) local bonding rearrangements in molecules, and (b) collective permutational and/or translational rearrangements in the bulk. Various examples are given of isomerism and collective structural transformations in clusters.

  18. Liquid-vapor phase relations in the Si-O system: A calorically constrained van der Waals-type model

    NASA Astrophysics Data System (ADS)

    Connolly, James A. D.

    2016-09-01

    This work explores the use of several van der Waals (vW)-type equations of state (EoS) for predicting vaporous phase relations and speciation in the Si-O system, with emphasis on the azeotropic boiling curve of SiO2-rich liquid. Comparison with the observed Rb and Hg boiling curves demonstrates that prediction accuracy is improved if the a-parameter of the EoS, which characterizes vW forces, is constrained by ambient pressure heat capacities. All EoS considered accurately reproduce metal boiling curve trajectories, but absent knowledge of the true critical compressibility factor, critical temperatures remain uncertain by ~500 K. The EoS plausibly represent the termination of the azeotropic boiling curve of silica-rich liquid by a critical point across which the dominant Si oxidation state changes abruptly from the tetravalent state characteristic of the liquid to the divalent state characteristic of the vapor. The azeotropic composition diverges from silica toward metal-rich compositions with increasing temperature. Consequently, silica boiling is divariant and atmospheric loss after a giant impact would enrich residual silicate liquids in reduced silicon. Two major sources of uncertainty in the boiling curve prediction are the heat capacity of silica liquid, which may decay during depolymerization from the near-Dulong-Petit limit heat capacity of the ionic liquid to value characteristic of the molecular liquid, and the unknown liquid affinity of silicon monoxide. Extremal scenarios for these uncertainties yield critical temperatures and compositions of 5200-6200 K and Si1.1O2-Si1.4O2. The lowest critical temperatures are marginally consistent with shock experiments and are therefore considered more probable.

  19. National Dam Inspection Program. Lake of the Four Seasons Dam (NDS-ID Number PA-568, DER-ID Number 40-225) Susquehanna River Basin, Oley Creek, Luzerne County, Pennsylvania. Phase I Inspection Report,

    DTIC Science & Technology

    1980-09-01

    A0-AU91 266 KIMBALL (L ROBERT) AND ASSOCIATES EBENSBURG PA F/G 13/13 NATIONAL JAM INSPECTION PROGRAM. LAKE OF THE FOUR SEASONS DAM (--ETC(U) SEP 80 R...PENNSYLVANI LAKE OF THE FOUR SEASONS DA NDS ID NO. PA-568 DER ID NO. 40-225 DIVERSIFIED MORTGAGE INVESTORS INC. PHASE I INSPECTION REPORT v- NATIONAL DAM...OLEY CREEK LUZERNE COUNTY ~ IEPEN NSYL VAN IA-,, LAKE OF THE FOUR SEASONS DAM li0 L __NOS4D14. PA-56! DER 40. 4Y225) A:HASE JINSPE TIO LEP 5 NATIONAL

  20. Umsetzung der Unternehmensstrategie mit der Balanced Scorecard

    NASA Astrophysics Data System (ADS)

    Crespo, Isabel; Bergmann, Lars; Portmann, Stefan; Lacker, Thomas; Lacker, Michael; Fleischmann, Jürgen; Kozó, Hans

    Die Balanced Scorecard (BSC) ist ein Ansatz zum strategischen Management, der neben der Ausrichtung des Unternehmens auf finanzielle Zielwerte ebenso großes Gewicht auf so genannte weiche Faktoren legt, die den wirtschaftlichen Erfolg eines Unternehmens erst ermöglichen. Das entscheidende Merkmal der Balanced Scorecard ist dabei, dass sie ein ausgewogenes System strategischer Ziele herstellt, welches das Unternehmen hinsichtlich der vier Perspektiven Finanzen, Kunden, interne Prozesse und Mitarbeiter und Potenziale strategisch ausrichtet (Kaplan u. Norton 1997).

  1. National Dam Inspection Program. Locklin Pond Dam (NDI ID Number PA-00139, DER ID Number 64-31), Delaware River Basin, Lakeville Creek, Wayne County, Pennsylvania. Phase I Inspection Report.

    DTIC Science & Technology

    1980-07-01

    from a vertical mortared- rockfill wall to a nearly-flat earthen slope. The upstream slope is nearly vertical above normal pool along this part of the dam ...history of the dam . In 1917, the dam was described as being constructed of stone and earth fill. At this time a 150-foot long embankment existed...PENNSYLVANIA NDI ID NO. PA-00139 DER ID NO. 64.31 CLIFTON AND LEWIS LOCKLIN PHASE I INSPECTION REPORT NATIONAL DAM INSPECTION PROGRAM Preae by GANNETT

  2. Magnetic structure and phase stability of the van der Waals bonded ferromagnet Fe3-xGeTe2

    DOE PAGES

    May, Andrew F.; Calder, Stuart A.; Cantoni, Claudia; ...

    2016-01-08

    The magnetic structure and phase diagram of the layered ferromagnetic compound Fe3GeTe2 have been investigated by a combination of synthesis, x-ray and neutron diffraction, high-resolution microscopy, and magnetization measurements. Single crystals were synthesized by self-flux reactions, and single-crystal neutron diffraction finds ferromagnetic order with moments of 1.11(5)μB/Fe aligned along the c axis at 4 K. These flux-grown crystals have a lower Curie temperature Tc ≈ 150 K than crystals previously grown by vapor transport (Tc = 220 K). The difference is a reduced Fe content in the flux-grown crystals, as illustrated by the behavior observed in a series of polycrystallinemore » samples. As Fe content decreases, so do the Curie temperature, magnetic anisotropy, and net magnetization. Furthermore, Hall-effect and thermoelectric measurements on flux-grown crystals suggest that multiple carrier types contribute to electrical transport in Fe3–xGeTe2 and structurally similar Ni3–xGeTe2.« less

  3. Quantenphysikalischer Ursprung der Eichidee

    NASA Astrophysics Data System (ADS)

    Bopp, Fritz

    Vergleichbares leisten.Tatsächlich folgt die EQE aus einer bereits vorhandenen, wenn auch wenig beachteten Symmetrie der empirisch bewährten Diractheorie. Sie ist darum einerseits im Sinne der Newtonschen Definition des Begriffs hypothesenfrei. Andererseits kann sie wegen der erforderlichen Phaseninvarianz kaum wegdiskutiert werden, was immer sie am Ende bedeuten mag. Die Erfindung neuer Symmetrien und die Anerkennung einer Unzahl unabhängiger Spinorkomponenten ist jedenfalls zunächst entbehrlich.Translated AbstractThe Quantum Physical Origin of the Gauge IdeaTo consider quantum physics as an interplay of creation and annihilation processes has the consequence that gauge field theories are not only possible but necessary. Since the complex conjugate phase factors of each pair of fermion creators and annihilators can be arbitrary chosen, quantum field theories must be completely phase invariant.Unfortunately, even globally the Dirac equation for systems of free fermions is not phase invariant. The Dirac matrices are namely transformed, if we multiply the spinor components by different constant phase factors. The Dirac equations before and after the transformation are however physically equivalent. We may therefore say: Systems of free fermions will be completely described, only if we consider the class of all equivalent Dirac equations.Since Dirac's commutation relations are unitarily invariant, the class equivalent Dirac equations is invariant under all transformations of the group U 4. Unitary diagonal matrices yield arbitrary phase transformations. Hence, gauge fields of the group U 4 are compatible with the postulate of general phase invariance. These gauge file are so similar to the QED that we may speak of an extended quantum electrodynamics, EQE.Here, we will show that EQE exists. The invariant subgroup U 1 U 4 yields QED. The complementary subgroup SU 4 includes four subgroups SU 3, there subgroups O 4

  4. Kosmische Katastrophen und der Ursprung der Religion.

    NASA Astrophysics Data System (ADS)

    Hoyle, F.

    This book is a German translation, by V. Delavre, from the English original "The origin of the Universe and the origin of religion", published in 1993. Contents: E. Sens: Die unterbrochene Musikstunde. Einleitung zur deutschen Ausgabe. C. Ryskamp: Einführung. R. N. Anshen: Vorwort. F. Hoyle: Kosmische Katastrophen und der Ursprung der Religion - Die Folgen der Respektabilität; Eiszeiten und Kometen; Die allgemeine Situation in den Nacheiszeiten; Kometen und der Ursprung der Religionen; Der Übergang zu Mittelalter und Neuzeit. Diskussionsbeiträge: Ruth Nanda Anshen, Freeman Dyson, Paul Oscar Kristeller, John Archibald Wheeler, James Schwartz, Roger Shinn, Milton Gatch, Philip Solomon, Norman Newell. F. Hoyle: Schlußwort. A. Tollmann: Nachwort zur deutschen Ausgabe.

  5. Akustikgestaltung in der Fahrzeugentwicklung

    NASA Astrophysics Data System (ADS)

    Pletschen, Bernd

    Die zielgerichtete Entwicklung der Fahrzeugakustik stellt eine hochkomplexe, integrative Aufgabenstellung im Rahmen der Fahrkomfortgestaltung des Automobils dar. Die Wahrnehmung der Komforteigenschaften eines Fahrzeugs erfolgt grundsätzlich als Wahrnehmung der Wirkung dieser Eigenschaften über einen oder mehrere Wahrnehmungskanäle des Menschen: visuell, auditiv, haptisch, olfaktorisch. Die individuelle Wahrnehmung ist hierbei subjektiv und daher mit rein physikalisch objektiven Messgrößen allein nur unvollständig zu beschreiben. Sie hängt einerseits von den Eigenschaften des betrachteten Fahrzeugs oder einer erlebten Situation ab und andererseits außerdem von der Sozialisation des Bewertenden und der Umgebung, in der die Bewertung stattfindet (Wikipedia). Der Fahrkomfort, den ein Fahrzeug Fahrer und Beifahrern bietet, wird also wegen unterschiedlicher Erwartungen des Kunden in den verschiedenen Weltmärkten sehr unterschiedlich erlebt.

  6. National Dam Inspection Program. Crabapple Dam (NDI Number PA 00907, PennDER Number 26-32) Ohio River Basin, Crabapple Run, Fayette County, Pennsylvania. Phase I Inspection Report,

    DTIC Science & Technology

    1980-07-01

    7 D-A091 529 ACKENHEIL AND ASSOCIATES INC PITTSBURGH PA F/6 13/13 NATIONAL DAM INSPECTION PROGRAM. CRABAPPLE DAM (NDI NUMBER PA 0-ETC(U) JUL B8 J P...HANNAN, J E BARRICK DAC 31- BOC-0026 UNCLASSIFIE NLE2IIIIIIIhIIIl EIIIIIIIIIIIII 0OHI0 RIVER BASIN CRABAPPLE RUN FAYETTE COUNTY PENNSYLVANIA NDI No. PA...00907 :E- 1rŘ PENN DER No. 26-32 me CRABAPPLE DAM STEPHEN VINCINSKI and GEORGE THOMAS PHASE I INSPECTION REPORT NATIONAL DAM INSPECTION PROGRAM J 1

  7. National Dam Inspection Program. Flat Rock Dam (NDS I.D. Number PA 00896, DER I.D. Number 51-1), Delaware River Basin, Schuylkill River, Montgomery and Philadelphia Counties, Pennsylvania. Phase I Inspection Report,

    DTIC Science & Technology

    1980-08-01

    engineering characteristics of the dam include the Water Resources Bulletin, Bulletin No. 4, "Water Resources Survey, The Schuylkill River , Pennsylvania...2.8 12.5 iii,,1.0 .0 12 .0*2 1111 L A, 1 .2 1 1 MICROCOPY RESOLUTION TEST CHART 10AIIONA1 0111I AAil 0 IANDAR[1, 101,3 A DELAWARE RIVER BA(IN SNOYLKILL... RIVER UIUTllUERY AND PUILADELPEIA eoNuTIES PENNSYLVANIA lOS I PA. 06816 DER IB 51-1 . t0 II PHASE I INSPECTION REPORT I NATIONAL DAM INSPECTION

  8. Der II. Hauptsatz der Wärmelehre

    NASA Astrophysics Data System (ADS)

    Heintze, Joachim

    Wir haben in (4.44) den II. Hauptsatz als empirische Tatsache folgendermaßen formuliert: (i) Wärmeenergie geht von selbst nur von einem wärmeren Körper auf einen kälteren über, niemals in der umgekehrten Richtung. Nun werden wir beweisen, dass sich aus diesem Prinzip folgende äquivalente Formulierungen für den II. Hauptsatz ableiten lassen: (ii) Es ist unmöglich, ein Perpetuum mobile zweiter Art zu bauen, d. h. eine Maschine, die fortlaufend Wärmeenergie vollständig in mechanische Arbeit umsetzen kann. Eine Wärmekraftmaschine, die einen Kreisprozess mit der höchsten Temperatur Tw und der niedrigsten Temperatur Tk durchläuft, hat höchstens den Carnotschen Wirkungsgrad c = (Tw - Tk)/Tw. Wenn in der Maschine nur reversible Prozesse ablaufen, die gesamte Wärmezufuhr bei der Temperatur Tw erfolgt und ausschließlich bei der Temperatur Tw gekühlt wird, ist ihr Wirkungsgrad = C. Es gibt keine Wärmekraftmaschine, die eine bessere Ausnutzung der Wärmeenergie ermöglicht. (iv) In jedem thermodynamischen System existiert die Zustandsgröße Entropie, definiert durch ihr Differential dS = (dQrev)/T . Entropie kann erzeugt, aber nicht vernichtet werden. Bei Zustandsänderungen, die in einem abgeschlossenen System ablaufen, nimmt die Entropie entweder zu (irreversible Prozesse), oder sie bleibt konstant (reversible Prozesse). Im Anschluss an (iii) werden wir zur Definition der thermodynamischen Temperatur und bei der Diskussion von (iv) zu einem tieferen Verständnis der Entropie gelangen. Es zeigt sich, dass die Entropie das eigentliche Bindeglied zwischen Mechanik und Wärmelehre darstellt. Am Ende des Kapitels werden wir einige Anwendungen des II. Hauptsatzes betrachten.

  9. Die Arbeitsunfähigkeit in der Statistik der GKV

    NASA Astrophysics Data System (ADS)

    Busch, Klaus

    Der vorliegende Beitrag gibt anhand der Statistiken des Bundesministeriums für Gesundheit (BMG) einen Überblick über die Arbeitsunfähigkeitsdaten der Gesetzlichen Krankenkassen (GKV). Zunächst werden die Arbeitsunfähigkeitsstatistiken der Krankenkassen und die Erfassung der Arbeitsunfähigkeit erläutert. Hiernach wird auf die Entwicklung der Fehlzeiten auf GKV-Ebene eingegangen. Ebenfalls wird Bezug auf die Unterschiede der Fehlzeiten zwischen den verschiedenen Kassen genommen.

  10. Application of mixed-mode, solid-phase extraction in environmental and clinical chemistry. Combining hydrogen-bonding, cation-exchange and Van der Waals interactions

    USGS Publications Warehouse

    Mills, M.S.; Thurman, E.M.; Pedersen, M.J.

    1993-01-01

    Silica- and styrene-divinylbenzene-based mixed-mode resins that contain C8, C18 and sulphonated cation-exchange groups were compared for their efficiency in isolation of neutral triazine compounds from water and of the basic drug, benzoylecgonine, from urine. The triazine compounds were isolated by a combination of Van der Waals and hydrogen-bonding interactions, and benzoylecgonine was isolated by Van der Waals interactions and cation exchange. All analytes were eluted with a polar organic solvent contaning 2% ammonium hydroxide. Larger recoveries (95%) were achieved on copolymerized mixed-mode resins where C18 and sulfonic acid are in closer proximity than on 'blended' mixed-mode resins (60-70% recovery).

  11. Kants Theorie der Sonne: Physikgeschichte

    NASA Astrophysics Data System (ADS)

    Jacobi, Manfred

    2005-01-01

    Im Rahmen seiner Kosmogonie entwickelte der junge Immanuel Kant eine Theorie der Sonne. Sie ist ein einzigartiges Zeugnis seiner intuitiven Vorstellungskraft und beweist auch die Leistungsfähigkeit der damaligen, vorwiegend von Newton geprägten Weltsicht. Entstehung, Aufbau und Dynamik der Sonne werden in Kants Theorie ebenso erklärt wie etwa das Phänomen der Sonnenflecken.

  12. Die Kosmologie der Griechen.

    NASA Astrophysics Data System (ADS)

    Mittelstraß, J.

    Contents: 1. Mythische Eier. 2. Thales-Welten. 3. "Alles ist voller Götter". 4. Griechische Astronomie. 5. "Rettung der Phänomene". 6. Aristotelische Kosmololgie. 7. Aristoteles-Welt und Platon-Welt. 8. Noch einmal: die Göttlichkeit der Welt. 9. Griechischer Idealismus.

  13. A mathematical recursive model for accurate description of the phase behavior in the near-critical region by Generalized van der Waals Equation

    NASA Astrophysics Data System (ADS)

    Kim, Jibeom; Jeon, Joonhyeon

    2015-01-01

    Recently, related studies on Equation Of State (EOS) have reported that generalized van der Waals (GvdW) shows poor representations in the near critical region for non-polar and non-sphere molecules. Hence, there are still remains a problem of GvdW parameters to minimize loss in describing saturated vapor densities and vice versa. This paper describes a recursive model GvdW (rGvdW) for an accurate representation of pure fluid materials in the near critical region. For the performance evaluation of rGvdW in the near critical region, other EOS models are also applied together with two pure molecule group: alkane and amine. The comparison results show rGvdW provides much more accurate and reliable predictions of pressure than the others. The calculating model of EOS through this approach gives an additional insight into the physical significance of accurate prediction of pressure in the nearcritical region.

  14. Integrable extended van der Waals model

    NASA Astrophysics Data System (ADS)

    Giglio, Francesco; Landolfi, Giulio; Moro, Antonio

    2016-10-01

    Inspired by the recent developments in the study of the thermodynamics of van der Waals fluids via the theory of nonlinear conservation laws and the description of phase transitions in terms of classical (dissipative) shock waves, we propose a novel approach to the construction of multi-parameter generalisations of the van der Waals model. The theory of integrable nonlinear conservation laws still represents the inspiring framework. Starting from a macroscopic approach, a four parameter family of integrable extended van der Waals models is indeed constructed in such a way that the equation of state is a solution to an integrable nonlinear conservation law linearisable by a Cole-Hopf transformation. This family is further specified by the request that, in regime of high temperature, far from the critical region, the extended model reproduces asymptotically the standard van der Waals equation of state. We provide a detailed comparison of our extended model with two notable empirical models such as Peng-Robinson and Soave's modification of the Redlich-Kwong equations of state. We show that our extended van der Waals equation of state is compatible with both empirical models for a suitable choice of the free parameters and can be viewed as a master interpolating equation. The present approach also suggests that further generalisations can be obtained by including the class of dispersive and viscous-dispersive nonlinear conservation laws and could lead to a new type of thermodynamic phase transitions associated to nonclassical and dispersive shock waves.

  15. Theoretische Konzepte der Physik

    NASA Astrophysics Data System (ADS)

    Longair, Malcolm S.; Simon, B.; Simon, H.

    "Dies ist kein Lehrbuch der theoretischen Physik, auch kein Kompendium der Physikgeschichte ... , vielmehr eine recht anspruchsvolle Sammlung historischer Miniaturen zur Vergangenheit der theoretischen Physik - ihrer "Sternstunden", wenn man so will. Frei vom Zwang, etwas Erschöpfendes vorlegen zu müssen, gelingt dem Autor etwas Seltenes: einen "lebendigen" Zugang zum Ideengebäude der modernen Physik freizulegen, ... zu zeigen, wie Physik in praxi entsteht... Als Vehikel seiner Absichten dienen dem Autor geschichtliche Fallstudien, insgesamt sieben an der Zahl. Aus ihnen extrahiert er das seiner Meinung nach Lehrhafte, dabei bestrebt, mathematische Anachronismen womöglich zu vermeiden... Als Student hätte ich mir diese gescheiten Essays zum Werden unserer heutigen physikalischen Weltsicht gewünscht. Sie sind originell, didaktisch klug und genieren sich auch nicht, von der Faszination zu sprechen, die ... von der Physik ausgeht. Unnötig darauf hinzuweisen, das sie ein gründliches "konventionelles" Studium weder ersetzen wollen noch können, sie vermögen aber, dazu zu ermuntern." #Astronomische Nachrichten (zur englischen Ausgabe)#1

  16. Nomogramme der Sickerwasserprognose

    NASA Astrophysics Data System (ADS)

    Schneider, Wilfried; Stöfen, Heinke

    Kurzfassung Modelle zur Sickerwasserprognose stehen in unterschiedlicher Komplexität zur Verfügung. Komplexe Modelle werden aufgrund der schwierigen Handhabung und des enormen Eingabedatenumfangs in der Praxis kaum angewandt. Grobe Abschätzmethoden sind dagegen nicht ausreichend wissenschaftlich fundiert, um damit justiziable Ergebnisse erzielen zu können. Um die Kluft zwischen komplexer und einfacher, jedoch justiziabler sowie wissenschaftlich fundierter Methode zu schmälern, wurden Nomogramme für Sickerwasserprognosen zur Berücksichtigung der Endlichkeit der Quelle entwickelt. Mithilfe der Nomogramme können ohne Modellierungserfahrung schnell und einfach die zu erwartenden Schadstoffkonzentrationen am Ort der Beurteilung abgeschätzt werden, falls die Endlichkeit der Quelle der hauptsächlich zur Abminderung führende Prozess ist. Die Nomogramme basieren auf analytischen Lösungen der eindimensionalen Advektions-Dispersions-Gleichung. Sie berücksichtigen die Prozesse Advektion, Diffusion in Bodenwasser und -luft, Dispersion, lineare Sorption, Abbau 1. Ordnung innerhalb einer aus mehreren Bodenschichten bestehenden Sickerwasserzone, wobei die Endlichkeit der Schadstoffmasse in der Bodenkontamination einbezogen wird. Die Genauigkeit der Nomogramme wird dargestellt. Models of different complexity are available for groundwater risk assessment. In practice complex models are hardly used, due to their difficult handling and large data requirement. Rough estimation methods are not sufficiently scientifically founded to produce justiciable results. To reduce the gap between complex and easy to use but justiciable and scientifically founded methods we developed nomograms for groundwater risk assessment which take into account the finite mass of contaminant in the source. With the help of the nomograms the expected concentrations at the point of compliance (transition between the unsaturated and saturated zone) can be estimated easily, fast and without any

  17. On the excited state dynamics of vibronic transitions. High-resolution electronic spectra of acenaphthene and its argon van der Waals complex in the gas phase.

    PubMed

    Álvarez-Valtierra, Leonardo; Plusquellic, David F; Yi, John T; Pratt, David W

    2011-09-01

    Rotationally resolved fluorescence excitation spectroscopy has been used to study the dynamics, electronic distribution, and the relative orientation of the transition moment vector in several vibronic transitions of acenaphthene (ACN) and in its Ar van der Waals (vdW) complex. The 0(0)(0) band of the S(1) ← S(0) transition of ACN exhibits a transition moment orientation parallel to its a-inertial axis. However, some of the vibronic bands exhibit a transition moment orientation parallel to the b-inertial axis, suggesting a Herzberg-Teller coupling with the S(2) state. Additionally, some other vibronic bands exhibit anomalous intensity patterns in several of their rotational transitions. A Fermi resonance involving two near degenerate vibrations has been proposed to explain this behavior. The high-resolution electronic spectrum of the ACN-Ar vdW complex has also been obtained and fully analyzed. The results indicate that the weakly attached argon atom is located on top of the plane of the bare molecule at ~3.48 Å away from its center of mass in the S(0) electronic state.

  18. Grundbegriffe der Thermodynamik

    NASA Astrophysics Data System (ADS)

    Heintze, Joachim

    In diesem Kapitel geht es darum, Vorgänge zu analysieren, bei denen der thermische Zustand eines Systems verändert wird: Daher der Name "Thermodynamik". Wir werden zunächst untersuchen, unter welchen Umständen man eine Zustandsänderung im Detail beschreiben kann. Hierbei werden wir zwei grundsätzlich verschiedene Arten, Zustandsänderungen herbeizuführen, kennenlernen: reversible und irreversible Prozesse. Sodann werden wir die Eigenschaften von Zustandsgrößen allgemein definieren und dabei auf eine überaus wichtige neue Zustandsgröße, die Entropie, stoßen.

  19. National Dam Inspection Program. Dyers Run Number 3 Dam (NDI Number PA 00676 DER Number 54-038), Delaware River Basin, Schuykill County, Pennsylvania. Phase I Inspection Report,

    DTIC Science & Technology

    1981-02-01

    34’-’JPRE PARED-- R::R... ..... ’ DEPARTMENT OF THE ARMY Baltimore District, Corps of Engineers Baltimore , Maryland 21203/r > _ BY .,, Berger...Investi- gations. Copies of these guidelines may be obtained from the Office of Chief of Engineers , Washington, D.C. 20314. The purpose of a Phase I...SCHUYLKILL Stream: DYER RUN Date of Inspection: October 21, 1980 Based on the visual inspection, past performance and the available engineering data, the

  20. Update: Therapie der Necrobiosis lipoidica.

    PubMed

    Peckruhn, Melanie; Tittelbach, Jörg; Elsner, Peter

    2017-02-01

    Die Necrobiosis lipoidica ist eine seltene granulomatöse Erkrankung von bisher unzureichend geklärter Ätiologie. Häufig stellt die bei Diabetikern gehäuft zu beobachtende und zur Ulzeration neigende Dermatose eine starke Belastung für die Patienten dar. Bezüglich der Therapie existieren aktuell keine deutschen oder europäischen Leitlinien. Gleichzeitig lässt sich unter der aktuellen Standardtherapie, der lokalen oder intraläsionalen Anwendung von Glukokortikoiden, nicht immer ein zufriedenstellendes Ansprechen beobachten. Daher wurde untersucht, ob seit dem Jahr 2000 publizierte Therapiemodalitäten das Therapiespektrum relevant und erfolgversprechend erweitern. Es erfolgte eine Betrachtung aller Arbeiten im oben genannten Zeitraum, bei denen mehr als ein Einzelfallbericht je Therapiemodalität publiziert wurde. Insgesamt wurden in einem systematischen Review die Daten von 16 verschiedenen, seit 2000 publizierten Therapieverfahren in 49 Publikationen analysiert. Im Ergebnis zeigte sich, dass die meisten Erfahrungen bezüglich der topischen PUVA-Therapie, der photodynamischen Therapie (PDT) und der systemischen Therapie mit Fumarsäureestern vorliegen. Allerdings ist auffällig, dass mit steigender Zahl der pro Behandlungsmodalität behandelten Patienten der Anteil der Patienten, bei denen eine Abheilung bzw. eine teilweise Abheilung berichtet wurde, sinkt. Wir interpretieren diese Beobachtung als Publikationsbias. Daher kann für keines der besprochenen Verfahren eine klare Empfehlung als Therapie der zweiten Wahl nach Versagen der lokalen bzw. intraläsionalen Steroidtherapie gegeben werden.

  1. Zum Stellenwert der Unterdruck-Instillationstherapie in der Dermatologie.

    PubMed

    Müller, Cornelia Sigrid Lissi; Burgard, Barbara; Zimmerman, Monika; Vogt, Thomas; Pföhler, Claudia

    2016-08-01

    Die Methoden zur Behandlung akuter und chronischer Wunden unterliegen einer steten Weiterentwicklung, Reevaluierung und Anwendung innovativer Therapieformen. Die Vakuumtherapie zur Wundbehandlung gehört zu den etablierten Behandlungsmodalitäten. Ein innovatives Verfahren kombiniert die Vakuumtherapie mit der automatisierten, kontrollierten Zufuhr und Drainage wirkstoffhaltiger Lösungen zur topischen Wundbehandlung im Wundbett und auch wirkstofffrei durch Instillation physiologischer Kochsalzlösung (Unterdruck-Instillationstherapie). Hierdurch können die Effekte der konventionellen Vakuumtherapie mit denen der lokalen Antisepsis kombiniert werden. Hierdurch kommt es zu einer Reduktion der Wundfläche, einer Induktion von Granulationsgewebe sowie einer Reduktion der Keimbesiedelung der Wunden. Bisher publizierte Studien konzentrieren sich auf die Anwendung dieses Therapieverfahrens zur Behandlung orthopädisch-chirurgischer Krankheiten. Die Datenlage bezüglich der Vakuum-Instillationstherapie in der Dermatochirurgie beschränkt sich derzeit auf Fallberichte und Einzelfallerfahrungen. Randomisierte, prospektive Studien zum Vergleich der Vakuum-Instillationstherapie zur Behandlung dermatologischer Krankheitsbilder existieren bislang nicht. Ziele des vorliegenden Artikels sind die Vorstellung der Vakuumtherapie mit Instillation einschließlich ihres Wirkprinzips, deren mögliche Komplikationen, die Diskussion erdenklicher Kontraindikationen sowie eine Übersicht über die aktuell verfügbare Datenlage. Zusammenfassend scheint sich die Evidenz zu verdichten, dass mittels Unterdruck-Instillationstherapie sowohl einfache als auch komplizierte Wunden effizient behandelt werden können, was sich in einer deutlichen Beschleunigung der Wundgranulation mit konsekutiv früher möglichem Defektverschluss äußert.

  2. Magnetic structure and phase stability of the van der Waals bonded ferromagnet Fe3-xGeTe2

    SciTech Connect

    May, Andrew F.; Calder, Stuart A.; Cantoni, Claudia; Cao, Huibo; McGuire, Michael A.

    2016-01-08

    The magnetic structure and phase diagram of the layered ferromagnetic compound Fe3GeTe2 have been investigated by a combination of synthesis, x-ray and neutron diffraction, high-resolution microscopy, and magnetization measurements. Single crystals were synthesized by self-flux reactions, and single-crystal neutron diffraction finds ferromagnetic order with moments of 1.11(5)μB/Fe aligned along the c axis at 4 K. These flux-grown crystals have a lower Curie temperature Tc ≈ 150 K than crystals previously grown by vapor transport (Tc = 220 K). The difference is a reduced Fe content in the flux-grown crystals, as illustrated by the behavior observed in a series of polycrystalline samples. As Fe content decreases, so do the Curie temperature, magnetic anisotropy, and net magnetization. Furthermore, Hall-effect and thermoelectric measurements on flux-grown crystals suggest that multiple carrier types contribute to electrical transport in Fe3–xGeTe2 and structurally similar Ni3–xGeTe2.

  3. Excited nucleon as a van der Waals system of partons

    SciTech Connect

    Jenkovszky, L. L.; Muskeyev, A. O. Yezhov, S. N.

    2012-06-15

    Saturation in deep inelastic scattering (DIS) and deeply virtual Compton scattering (DVCS) is associated with a phase transition between the partonic gas, typical of moderate x and Q{sup 2}, and partonic fluid appearing at increasing Q{sup 2} and decreasing Bjorken x. We suggest the van der Waals equation of state to describe properly this phase transition.

  4. Grundlagen der Organisationsgestaltung

    NASA Astrophysics Data System (ADS)

    Spath, Dieter; Koch, Steffen

    In diesem Kapitel werden Grundlagen der Organisationsgestaltung dargestellt. Es scheint nahe liegend, diese Inhalte wie in einem Lehrbuch aufzubereiten. Schließlich handelt es sich um grundlegende Inhalte. Die Neufassung dieses Abschnitts ist aber stärker für Verantwortliche in Unternehmen geschrieben und weniger wissenschaftlich geprägt. Das "Lehrbuchwissen“ wird daher bewusst knapp gehalten. Das betrifft z.B. die Klärung des Organisationsbegriffes und die Fragen nach den Zielsetzungen und den Gestaltungsbereichen von Organisation. Stattdessen widmet sich das Kapitel ausführlicher den Fragen, ob es Trends in der Organisationsgestaltung gibt, welche wichtigen Einflussgrößen existieren und welche übergeordneten und beständigen Leitlinien es gibt.

  5. Haftung in der Medizintechnik

    NASA Astrophysics Data System (ADS)

    Müller, Ute; Lücker, Volker

    Die Unversehrtheit von Leib und Leben ist das größte Rechtsgut unserer Gesellschaft. Dies macht schon das Grundgesetz in Art. 2 Abs. Satz 1 GG deutlich. Die Öffentlichkeit zeigt daher größtes Interesse an Produkten, welche der Gesundheit dienen und Leben retten oder erhalten. Dieses Interesse gilt einerseits der Entwicklung und Bereitstellung leistungsfähiger Medizinprodukte, andererseits zielt es auf deren Sicherheit. Um vor allem letztere zu gewährleisten, nimmt der Gesetzgeber alle Beteiligten in die Pflicht, die auftretenden Risiken auf das geringstmögliche Maß zu begrenzen. Dies spiegelt sich in den rechtlichen Vorgaben ebenso wie in den Haftungsfolgen, die bei Verletzung dieser Vorgaben greifen, wieder. Diese Folgen können dementsprechend gravierend ausfallen, von Geldstrafen bis zu Freiheitsstrafen, von Bußgeldzahlungen bis zum Schadenersatzansprüchen, die schnell ein wirtschaftliches Aus bedeuten können. Den Beteiligten, allen voran den Herstellern, muss deshalb daran gelegen sein, nicht nur die Produkte, sondern auch deren Sicherheit stetig weiter zu entwickeln.

  6. Evaluation der zentralen TUM-Lernplattform

    NASA Astrophysics Data System (ADS)

    Schulze, Elvira; Baume, Matthias; Graf, Stephan; Gergintchev, Ivan

    Die Notwendigkeit der Qualitätssicherung und -kontrolle für innovative universitäre Lehr-/Lernszenarien ist in der Praxis unbestritten. Die Wirksamkeit der Einführung der zentralen Lernplattform CLIX Campus der imc AG an der TUM wurde mittels quantitativer und qualitativer Evaluation überprüft. Als statistische Bewertungsgrundlage wurde der Erreichungsgrad bestimmter Projektziele herangezogen. Aufbauend auf den theoretischen Grundlagen der Evaluation von Bildungsangeboten gibt diese Studie Aufschluss über die Ergebnisse der Datenerhebungen sowie die Einschätzung der Plattform aus Nutzersicht und belegt die wesentliche Bedeutung der durchgängigen IT-Infrastruktur und speziell der einheitlichen Verfügbarkeit der eLearning Angebote.

  7. Critical and near-critical phase behavior and interplay between the thermodynamic Casimir and van der Waals forces in a confined nonpolar fluid medium with competing surface and substrate potentials

    NASA Astrophysics Data System (ADS)

    Valchev, Galin; Dantchev, Daniel

    2015-07-01

    We study, using general scaling arguments and mean-field type calculations, the behavior of the critical Casimir force and its interplay with the van der Waals force acting between two parallel slabs separated at a distance L from each other, confining some fluctuating fluid medium, say a nonpolar one-component fluid or a binary liquid mixture. The surfaces of the slabs are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials ensuring the so-called (+,+) boundary conditions. The slabs, on the other hand, influence the fluid by long-range competing dispersion potentials, which represent irrelevant interactions in renormalization-group sense. Under such conditions, one usually expects attractive Casimir force governed by universal scaling function, pertinent to the extraordinary surface universality class of Ising type systems, to which the dispersion potentials provide only corrections to scaling. We demonstrate, however, that below a given threshold thickness of the system Lcrit for a suitable set of slabs-fluid and fluid-fluid coupling parameters the competition between the effects due to the coatings and the slabs can result in sign change of the Casimir force acting between the surfaces confining the fluid when one changes the temperature T , the chemical potential of the fluid μ , or L . The last implies that by choosing specific materials for the slabs, coatings, and the fluid for L ≲Lcrit one can realize repulsive Casimir force with nonuniversal behavior which, upon increasing L , gradually turns into an attractive one described by a universal scaling function, depending only on the relevant scaling fields related to the temperature and the excess chemical potential, for L ≫Lcrit . We present arguments and relevant data for specific substances in support of the experimental feasibility of the predicted behavior of the force. It can

  8. van der Waals torque

    NASA Astrophysics Data System (ADS)

    Esquivel-Sirvent, Raul; Schatz, George

    2014-03-01

    The theory of generalized van der Waals forces by Lifshtz when applied to optically anisotropic media predicts the existence of a torque. In this work we present a theoretical calculation of the van der Waals torque for two systems. First we consider two isotropic parallel plates where the anisotropy is induced using an external magnetic field. The anisotropy will in turn induce a torque. As a case study we consider III-IV semiconductors such as InSb that can support magneto plasmons. The calculations of the torque are done in the Voigt configuration, that occurs when the magnetic field is parallel to the surface of the slabs. The change in the dielectric function as the magnetic field increases has the effect of decreasing the van der Waals force and increasing the torque. Thus, the external magnetic field is used to tune both the force and torque. The second example we present is the use of the torque in the non retarded regime to align arrays of nano particle slabs. The torque is calculated within Barash and Ginzburg formalism in the nonretarded limit, and is quantified by the introduction of a Hamaker torque constant. Calculations are conducted between anisotropic slabs of materials including BaTiO3 and arrays of Ag nano particles. Depending on the shape and arrangement of the Ag nano particles the effective dielectric function of the array can be tuned as to make it more or less anisotropic. We show how this torque can be used in self assembly of arrays of nano particles. ref. R. Esquivel-Sirvent, G. C. Schatz, Phys. Chem C, 117, 5492 (2013). partial support from DGAPA-UNAM.

  9. Melker Meilensteine auf dem Weg in ein naturwissenschaftliches Zeitalter - Glanzlichter der Ausstellung zum Internationalen Astronomiejahr 2009 in der Melker Stiftsbibliothek.

    NASA Astrophysics Data System (ADS)

    Beck, Paul G.; Zotti, Georg

    2009-06-01

    Das Mittelalter wird weithin als die dunkle Epoche in der Geschichte der Europäischen Wissenschaften betrachtet, und insbesondere das Leben in den Klöstern galt lange Zeit als frei von jeglichem Interesse für Naturwissenschaften abseits der Medizin. Im Mittelalter galt die Astronomie bloß als Mittel zum Zweck, um religiöse und zivile Kalender erstellen zu können. Durch den Bestand der Handschriftenkammer der Melker Stiftsbibliothek eröffnet sich uns eine neue Sichtweise auf das gegen Ende des Mittelalters wachsende Interesse an den Naturwissenschaften. Dies wurde durch die starke Aufwertung der Klosterbibliothek im Rahmen der 'Melker Reform' im 15. Jahrhundert noch weiter verstärkt. Diese Epoche fällt mit der Frühphase der Universität Wien und der 'ersten Wiener Schule der Astronomie' zusammen. Dieser Artikel beleuchtet ausgewählte astronomischen Werke in der Melker Stiftsbibliothek zwischen dem frühen 9 und dem 18. Jahrhundert. Einen Schwerpunkt stellt das Wirken der Wiener Schule der Astronomie dar, wobei wir u.a. die Melker Abschrift von Peuerbachs Gutachten über den Kometen von 1456 sowie die im Stift Melk durchgeführte Beobachtung der Mondfinsternis von 1457 durch Regiomontanus und Peuerbach beleuchten. Dieser Beitrag ist der einführende Übersichtsartikel zum Ausstellungsprojekt in der Melker Stiftsbibliothek im Rahmen des Internationalen Jahres der Astronomie 2009. The medieval period is commonly seen as a dark epoch for science in Europe. Especially monasteries were seen as institutions without interest in natural sciences except for medicine. Astronomy was allegedly only a tool to construct religious and civil calendars. The inventory of the medieval manuscript collection of the library of the Abbey of Melk allows a new view on the growing interest in the exact sciences towards the end of the medieval ages. This interest was intensified through the increased importance of the monastery library due to the monastery reform

  10. Advanced Communication and Control Solutions of Distributed Energy Resources (DER)

    SciTech Connect

    Asgeirsson, Haukur; Seguin, Richard; Sherding, Cameron; de Bruet, Andre, G.; Broadwater, Robert; Dilek, Murat

    2007-01-10

    This report covers work performed in Phase II of a two phase project whose objective was to demonstrate the aggregation of multiple Distributed Energy Resources (DERs) and to offer them into the energy market. The Phase I work (DE-FC36-03CH11161) created an integrated, but distributed, system and procedures to monitor and control multiple DERs from numerous manufacturers connected to the electric distribution system. Procedures were created which protect the distribution network and personnel that may be working on the network. Using the web as the communication medium for control and monitoring of the DERs, the integration of information and security was accomplished through the use of industry standard protocols such as secure SSL,VPN and ICCP. The primary objective of Phase II was to develop the procedures for marketing the power of the Phase I aggregated DERs in the energy market, increase the number of DER units, and implement the marketing procedures (interface with ISOs) for the DER generated power. The team partnered with the Midwest Independent System Operator (MISO), the local ISO, to address the energy market and demonstrate the economic dispatch of DERs in response to market signals. The selection of standards-based communication technologies offers the ability of the system to be deployed and integrated with other utilities’ resources. With the use of a data historian technology to facilitate the aggregation, the developed algorithms and procedures can be verified, audited, and modified. The team has demonstrated monitoring and control of multiple DERs as outlined in phase I report including procedures to perform these operations in a secure and safe manner. In Phase II, additional DER units were added. We also expanded on our phase I work to enhance communication security and to develop the market model of having DERs, both customer and utility owned, participate in the energy market. We are proposing a two-part DER energy market model--a utility

  11. Zeit im Wandel der Zeit.

    NASA Astrophysics Data System (ADS)

    Aichelburg, P. C.

    Contents: Einleitung(P. C. Aichelburg). 1. Über Zeit, Bewegung und Veränderung (Aristoteles). 2. Ewigkeit und Zeit (Plotin). 3. Was ist die Zeit? (Augustinus). 4. Von der Zeit (Immanuel Kant). 5. Newtons Ansichten über Zeit, Raum und Bewegung (Ernst Mach). 6. Über die mechanische Erklärung irreversibler Vorgänge (Ludwig Boltzmann). 7. Das Maß der Zeit (Henri Poincaré). 8. Dauer und Intuition (Henri Bergson). 9. Die Geschichte des Unendlichkeitsproblems (Bertrand Russell). 10. Raum und Zeit (Hermann Minkowski). 11. Der Unterschied von Zeit und Raum (Hans Reichenbach). 12. Newtonscher und Bergsonscher Zeitbegriff (Norbert Wiener). 13. Die Bildung des Zeitbegriffs beim Kinde (JeanPiaget).14. Eine Bemerkung über die Beziehungen zwischen Relativitätstheorie und der idealistischen Philosophie (Kurt Gödel). 15. Der zweite Hauptsatz und der Unterschied von Vergangenheit und Zukunft (Carl Friedrich v. Weizsäcker). 16. Zeit als physikalischer Begriff (Friedrich Hund). 17. Zeitmessung und Zeitbegriff in der Astronomie (Otto Heckmann). 18. Kann die Zeit rückwärts gehen? (Martin Gardner). 19. Zeit und Zeiten (Ilya Prigogine, Isabelle Stengers). 20. Zeit als dynamische Größe in der Relativitätstheorie (P. C. Aichelburg).

  12. Entwicklung und Formulierung der Unternehmensstrategie

    NASA Astrophysics Data System (ADS)

    Crespo, Isabel; Bergmann, Lars; Lacker, Thomas

    Ursprünglich stammt der Begriff "Strategie“ aus dem Altgriechischen: "strategos“ bedeutete "Heer“, "Heeresmacht“ und damit auch "konzentrierte Kraft“; das Wort "agein“ bedeutete "tun, machen, treiben“. Ein Stratege war also eine Person, die ein Heer führte und damit Kraft, Macht und Stärke konzentrierte und einsetzen konnte. Strategie bezeichnete dementsprechend die Maßnahmen, die in dieser Funktion entwickelt wurden. Daher ist es leicht verständlich, dass der Begriff Strategie bis in die Mitte des letzten Jahrhunderts in erster Linie militärisch verstanden wurde. Anschließend wurde der Begriff in weiteren Bereichen, wie beispielsweise der Unternehmensführung, verwendet. Im betriebswirtschaftlichen Sinne bedeutet der Begriff Strategie die langfristig geplante Verhaltensweise eines Unternehmens zur Erreichung seiner Ziele.

  13. Physik-Nobelpreis 2004 Von der Freiheit in der Welt der Quarks

    NASA Astrophysics Data System (ADS)

    Bartels, Jochen

    2004-11-01

    Die Schwedische Akademie der Wissenschaften vergab in diesem Jahr den Physik-Nobelpreis zu gleichen Teilen an die amerikanischen Physiker David Gross, David Politzer und Frank Wilczek. Sie würdigte damit ihre theoretischen Arbeiten zur asymptotischen Freiheit in der starken Wechselwirkung.

  14. Grundlagen und Vollzug der amtlichen Lebensmittelkontrolle in der Schweiz

    NASA Astrophysics Data System (ADS)

    Hübner, Philipp; Spinner, Christoph

    In der Schweiz wird die Mehrheit der hoheitlichen Aufgaben von den 26 Kantonen, die zusammen die schweizerische Eidgenossenschaft bilden, autonom vollzogen. So liegt zum Beispiel die Kompetenz in den Bereichen Steuern, Gesundheit, Schulen oder Polizei grundsätzlich bei den Kantonen. Im Gegensatz dazu ist die Lebensmittelgesetzgebung national durch eidgenössische Erlasse harmonisiert. Die Vollzugsaufgaben liegen aber auch in diesem Bereich, abgesehen vom Vollzug an der Grenze und von einer nationalen Vollzugsaufsicht und Weisungsberechtigung, in kantonaler Kompetenz. Die Kantone können anhand kantonaler Erlasse das Bundesrecht präzisieren - insbesondere die organisatorischen Aspekte - und Regelungen im nicht harmonisierten Bereich treffen.

  15. Statistical complexity, virial expansion, and van der Waals equation

    NASA Astrophysics Data System (ADS)

    Pennini, F.; Plastino, A.

    2016-09-01

    We investigate the notion of LMC statistical complexity with regards to a real gas and in terms of the second virial coefficient. The ensuing results are applied to the van der Waals equation. Interestingly enough, one finds a complexity-interpretation for the associated phase transition.

  16. Verbesserung der Symmetrie von Hirnaufnahmen entlang der Sagittalebene

    NASA Astrophysics Data System (ADS)

    Ens, Konstantin; Wenzel, Fabian; Fischer, Bernd

    Die lokale Symmetrie von Hirnscans entlang der Sagittalebene zu ermitteln und zu modizifieren, ist für eine Reihe neurologischer Anwendungen interessant. Beispielsweise kann der voxelweise Vergleich von rechter und linker Hirnhälfte nur dann Aufschluss über die Lokalisierung von Läsionen geben, wenn durch Transformation ein Hirnscan eine möglichst hohe Symmetrie aufweist. Ein weiteres Anwendungsgebiet ist die Visualisierung von medialen Hirnschnitten, für die die Trennfläche beider Hirnhälfte möglichst eben sein sollte. Diese Arbeit stellt die Entwicklung eines Verfahrens vor, mit dessen Hilfe die Symmetrie von Hirnaufnahmen entlang der Sagittalebene verbessert werden kann. Dies geschieht unter Verwendung von aktiven Konturen, die mit Hilfe einer neuartigen Kostenfunktion gesteuert werden. Experimente am Ende der Arbeit mit strukturellen Kernspinaufnahmen demonstrieren die Leistungsfähigkeit des Verfahrens.

  17. Dialektischer Materialismus in der Quantentheorie

    NASA Astrophysics Data System (ADS)

    Fuchs, Klaus

    Der absolute Determinismus der klassischen Mechanik bietet keine Ansatzpunkte für eine befriedigende Naturphilosophie. Mit der Quantenmechanik werden nicht lediglich die Unzulänglichkeiten einzelner klassischer Begriffe, sondern die des gesamten klassischen Begriffssystems beseitigt.Translated AbstractDialectical Materialism in Quantum TheoryThe absolute determinism of classical mechanics does not provide any base for a satisfactory philosophy of nature. In quantum mechanics the shortcomings of not only some single classical concepts but of the classical description as a whole are removed.

  18. Imaging van der Waals Interactions.

    PubMed

    Han, Zhumin; Wei, Xinyuan; Xu, Chen; Chiang, Chi-Lun; Zhang, Yanxing; Wu, Ruqian; Ho, W

    2016-12-15

    The van der Waals interactions are responsible for a large diversity of structures and functions in chemistry, biology, and materials. Discussion of van der Waals interactions has focused on the attractive potential energy that varies as the inverse power of the distance between the two interacting partners. The origin of the attractive force is widely discussed as being due to the correlated fluctuations of electron charges that lead to instantaneous dipole-induced dipole attractions. Here, we use the inelastic tunneling probe to image the potential energy surface associated with the van der Waals interactions of xenon atoms.

  19. Online Condition Monitoring mit der Stresswellenanalyse

    NASA Astrophysics Data System (ADS)

    Bruderreck, Frank

    Die Anforderungen des heutigen Energiemarkts und damit einhergehende veränderte Einsatzbedingungen für ältere Kraftwerksblöcke haben unvorhergesehene Produktionsausfälle in den letzten Jahren erheblich verteuert. Nach der Optimierung der Kraftwerksprozesse und der Steigerung der Wirkungsgrade richten die Energieversorger ihren Blick daher nun verstärkt auch auf die Verfügbarkeit ihrer Anlagen. Zur Verbesserung der Anlagenverfügbarkeit und der Minimierung der Instandhaltungskosten bietet sich der Einsatz von Condition Monitoring Systemen an. Nach der Erprobung eines Systems zur Vibrationsanalyse setzt die Evonik Steag GmbH jetzt in einem Pilotprojekt die Stresswellenanalyse ein, ein Online Condition Monitoring System auf der Basis von Ultraschallsensoren. Dieser Beitrag erläutert an einem Beispiel die Methode und grenzt sie gegen den De-facto-Standard Vibrationsanalyse ab.

  20. Der evolutionäre Naturalismus in der Ethik

    NASA Astrophysics Data System (ADS)

    Kaiser, Marie I.

    Charles Darwin hat eindrucksvoll gezeigt, dass der Mensch ebenso wie alle anderen Lebewesen ein Produkt der biologischen Evolution ist. Die sich an Darwin anschließende Forschung hat außerdem plausibel gemacht, dass sich nicht nur viele der körperlichen Merkmale des Menschen, sondern auch (zumindest einige) seiner Verhaltensdispositionen in adaptiven Selektionsprozessen herausgebildet haben. Die Vorstellung, dass auch die menschliche Moralität evolutionär bedingt ist, scheint daher auf den ersten Blick ganz überzeugend. Schließlich hat die Evolutionstheorie in den vergangenen Jahrzehnten in vielen Bereichen (auch außerhalb der Biologie) ihre weitreichende Bedeutung unter Beweis gestellt. Warum sollte, so könnte man beispielsweise fragen, gerade die Fähigkeit des Menschen, moralische Normen aufzustellen und gemäß ihnen zu handeln, nicht evolutionär erklärt werden können? Und warum sollte eine solche evolutionäre Erklärung der menschlichen Moralität irrelevant für die Rechtfertigung moralischer Normen sein? Warum sollte die Ethik eine Bastion der Philosophen bleiben, für die evolutionsbiologische Forschungsergebnisse über den Menschen und seine nächsten Verwandten keinerlei Relevanz besitzen?

  1. National Dam Inspection Program. Upper Pigeon Hill Dam. (NDI I.D. Number PA-00340, PennDER I.D. Number 67-5) Susquehanna River Basin, Gitts Run, York County, Pennsylvania. Phase I Inspection Report,

    DTIC Science & Technology

    1980-03-01

    Pennsylvania (PennDER I.D. No. 67-5) County Located: York Stream: Gitts Run Inspection Date: 9 November 1979 Inspection Team: GAI Consultants, Inc. 570 Beatty...is located on Gitts Run in Penn Township, York County, Pennsylvania. The site is situated just off Pennsylvania Route 194 about 3 miles north of...Middle, and Lower Pigeon Hill Dams constructed in series along Gitts Run, just north of Hanover, Pennsylvania. A 1915 state report references the designer

  2. National Dam Inspection Program. Lake Jean Dam. (NDI I.D. Number PA-00570 PennDER I.D. Number 40-16) Susquehanna River Basin, Branch of Kitchen Creek, Luzerne County, Pennsylvania. Phase I Inspection Report,

    DTIC Science & Technology

    1980-07-01

    is formally inspected on an annual basis by state representatives of the PennDER, Division of Com - pleted Projects. Results of past inspections...ftfts dSA 5t- .l 7.dll -, -v * W6D6 S4~ J - ~ SI-, b%~MobUmeeftf. m =Ara~ .j WSJ ~j~7 fara’ - - A6 WsM .fSW cft =M1=1 -I-. 5Tf4M

  3. Auf der Suche nach dem Unendlichen.

    NASA Astrophysics Data System (ADS)

    Fraser, G.; Lillestøl, E.; Sellevåg, I.

    This book is a German translation by C. Ascheron and J. Urbahn, of "The search for infinity: solving the mysteries of the universe", published in 1994. Diese Buch beschreibt anschaulich die Meilensteine, die der Mensch seit der Antike auf der Suche nach dem Unendlichen erreicht und hinter sich gelassen hat. Es enthält Kurzbiographien der wichtigsten Forscher, verständlich geschriebene Texte sowie Erläuterungen der entscheidenen Fachtermini.

  4. Van der Waals quintessence stars

    SciTech Connect

    Lobo, Francisco S. N.

    2007-01-15

    The van der Waals quintessence equation of state is an interesting scenario for describing the late universe, and seems to provide a solution to the puzzle of dark energy, without the presence of exotic fluids or modifications of the Friedmann equations. In this work, the construction of inhomogeneous compact spheres supported by a van der Waals equation of state is explored. These relativistic stellar configurations shall be denoted as van der Waals quintessence stars. Despite of the fact that, in a cosmological context, the van der Waals fluid is considered homogeneous, inhomogeneities may arise through gravitational instabilities. Thus, these solutions may possibly originate from density fluctuations in the cosmological background. Two specific classes of solutions, namely, gravastars and traversable wormholes are analyzed. Exact solutions are found, and their respective characteristics and physical properties are further explored.

  5. National Dam Inspection Program. Butler’s Lake Dam (NDI Number PA-01067, PennDER Number 2-29) Ohio River Basin, Drennen Branch, Allegheny County, Pennsylvania. Phase I Inspection Report.

    DTIC Science & Technology

    1981-05-01

    PENNSYLVANIA 15216 MAY 1981 81 7 0 o 7 OHIO RIVER BASIN BUTLER’S LAKE DAM ALLEGHENY COUNTY, COMMONWEALTH OF PENNSYLVANIA NDI NO. PA 01067 PennDER NO. 2...been affected by small country banks. F1 )1’u nt Vemnur FPm Pmm Bun Vs PPm PIpw pm ’ c-AMST f ~.Indt / t0s. 3 0 -(Fran PPw PmPm c/ 13 vthedale...STRUCTURE CONTOUR MAP1975 DATE: MAY 1981 BUTLER’S LAKE DAM SCALE: 1"-:2000’ NATIONAL DAM INSPECTION PROGRAM I GEOLOGIC DR: JF ICK: j ACKENI4EIL & ASSOCIATES

  6. Aspekte und Probleme der linguistischen Analyse schichtenspezifischen Sprachgebrauchs. Studien und Berichte 31 (Aspects and Problems of the Linguistic Analysis of Language Usage Within Specific Social Levels. Studies and Reports No. 31).

    ERIC Educational Resources Information Center

    Klann, Gisela

    This is a study of linguistic variability among social levels in West Germany and of the problems associated with doing such an analysis. The data, ordered according to sex and social levels, were collected from young children retelling narratives heard on tapes. The report represents a comprehensive study of the children's syntactic performance…

  7. 25 Jahre - Institut fuer Geodaesie, Teil 1: Wissenschaftliche Beitraege und Berichte (25 Years - Institute of Geodesy, Part 1: Scientific Contributions and Reports)

    DTIC Science & Technology

    2000-01-01

    des Dispersionswinkels zur Bestimmung der Refraktion. AVN 100, S. 51-62, 1993 HAMMING, R., W.: Digitale Filter. VCH-Verlag, Weinheim 1987 HAMPEL, F...KRONMOLLER, H.: Digitale Signalverarbeitung. Springer-Verlag, Berlin 1991 KUHLMANN, H.: Ein Beitrag zur Oberwachung von Briickenbauwerken mit...1987), das Europdische Referenzsystem - EUREF (SEEGER/ALTINER/ENGELHARDT/FRANKE/HABRICH/SCHLC- TER 1998) und das Sistema di Referencia del America del

  8. Twisted Van der Waals Systems

    NASA Astrophysics Data System (ADS)

    Gani, Satrio; Rossi, Enrico

    Van der Waals systems formed by two-dimensional (2D) crystals and nanostructures possess electronic properties that make them extremely interesting for basic science and for possible technological applications. By tuning the relative angle (the twist angle) between the layers, or nanostructures, forming the Van der Waals systems experimentalists have been able to control the stacking configuration of such systems. We study the dependence on the twist angle of the electronic properties of two classes of Van der Waals systems: double layers formed by two, one-atom thick, layers of a metal dichalcogenide such as molybdenum disulfide (MoS2), and graphene nanoribbons on a hexagonal boron nitride substrate. We present results that show how, for both classes of systems, the electronic properties can be strongly tuned via the twist angle. Work supported by ACS-PRF-53581-DNI5 and NSF-DMR-1455233.

  9. Coronellis Cosmos in der Melker Stiftsbibliothek.

    NASA Astrophysics Data System (ADS)

    Glaßner, Gottfried; Pärr, Nora

    2009-06-01

    Die Melker Stiftsbibliothek besitzt ein Globenpaar des berühmten venezianischen Globenbauers Vincenzo Coronelli (1650-1718), einen Erdglobus von 1688 und einen Himmelsglobus von 1693. Wie und wann die beiden Globen nach Melk gekommen sind, ist nicht bekannt. Dass sie zur ursprünglichen Ausstattung der 1735 fertig gestellten Barockbibliothek gehörten, wird aber aus der zentralen Stellung deutlich, die dem Globus (Erdglobus und Armillarphäre) in dem von Paul Troger 1732 gemalten Deckenfresko zukommt. Mehrfach begegnet das Motiv des Globus als Attribut der Weisheit bzw. Philosophie, der Geographie bzw. Geometrie und der Astronomie in den beiden Hauptsälen wie auch in der Deckenmalerei von Johann Bergl in der Oberen Bibliothek (1768) und in der Kuppel des Gartenpavillons (1764).

  10. Ancillary Services Provided from DER

    SciTech Connect

    Campbell, J.B.

    2005-12-21

    Distributed energy resources (DER) are quickly making their way to industry primarily as backup generation. They are effective at starting and then producing full-load power within a few seconds. The distribution system is aging and transmission system development has not kept up with the growth in load and generation. The nation's transmission system is stressed with heavy power flows over long distances, and many areas are experiencing problems in providing the power quality needed to satisfy customers. Thus, a new market for DER is beginning to emerge. DER can alleviate the burden on the distribution system by providing ancillary services while providing a cost adjustment for the DER owner. This report describes 10 types of ancillary services that distributed generation (DG) can provide to the distribution system. Of these 10 services the feasibility, control strategy, effectiveness, and cost benefits are all analyzed as in the context of a future utility-power market. In this market, services will be provided at a local level that will benefit the customer, the distribution utility, and the transmission company.

  11. Segmentierung der Papille in Fundusaufnahmen Aktives Kreisbogen-Modell

    NASA Astrophysics Data System (ADS)

    Schmidt, Torsten; Doering, Axel

    In der vorliegenden Arbeit präsentieren wir einen praxistauglichen Algorithmus zur automatischen Segmentierung der Disc-Grenze der Papille in Fundusaufnahmen. Ausgehend von einem lokalisierten Papillenpunkt werden Grauwertverläufe in horizontaler und vertikaler Richtung mittels einer Energiefunktion ausgewertet. In einem iterativen Prozess wird die Ellipse der tatsächlichen Disc-Grenze angenähert. Der Papillenrand konnte im Testdatensatz in 88% der Aufnahmen erfolgreich segmentiert werden. Der Algorithmus ist robust gegenüber der Lage des Startpunktes innerhalb der Papille und soll als Unterstützung bei der Glaukombefundung eingesetzt werden.

  12. The Influence of Surface Roughness and Bubbles on Sea Surface Acoustic Backscattering (Der Einfluss von Seegangsrauhigkeit und Blasen auf die Akustischen Rueckstreueigen-Schaften der Meeresoberflaeche)

    DTIC Science & Technology

    1987-11-12

    s’.gn,,ficant waveheight H1/3 (longer average times arn seicctable), * a plot of the power spectral density averaged over 0.5 hour- or 4 hours...America, vol. 61, no.2, February 1977, pp. 325-337. 5. B. Nuetzel and R. Jacobsen , Beschreibung des Nachhall-Messplatzes, Interner FWG-Bericht 1985-7

  13. Van der Waals like behavior of topological AdS black holes in massive gravity

    NASA Astrophysics Data System (ADS)

    Hendi, S. H.; Mann, R. B.; Panahiyan, S.; Eslam Panah, B.

    2017-01-01

    Motivated by recent developments in black hole thermodynamics, we investigate van der Waals phase transitions of charged black holes in massive gravity. We find that massive gravity theories can exhibit strikingly different thermodynamic behavior compared to that of Einstein gravity, and that the mass of the graviton can generate a range of new phase transitions for topological black holes that are otherwise forbidden.

  14. Organe der Osmoregulation und Exkretion

    NASA Astrophysics Data System (ADS)

    Møbjerg, Nadja

    Die meisten Schädeltiere sind in der Lage, die Wasser- und Ionenkonzentration ihres Innenmilieus zu regulieren, sind also im Hinblick auf ihren Ionenhaushalt weitgehend unabhängig von der Umgebung. Sie halten die Konzentration von Wasser und anorganischen Ionen in ihren Körperflüssigkeiten (interstitielle Flüssigkeit und Blut) innerhalb enger Grenzen konstant (Osmoregulierer). Schleim aale (Myxinoida) können zwar die Konzentration einzelner anorganischer Ionen regulieren, sind aber insgesamt der hohen Osmolarität des Meerwassers angepasst, also isoosmostisch zu diesem. Isoosmotisch oder leic ht hyperosmostisch zur Umgebung sind auch marine Neoselachier und Latimeria chalumnae (Actinistia), die dazu organische Osmolyte (Harnstoff und Trimethylaminoxid) im Blut akkumulieren (Osmokonformer). Bei anderen aquatischen Schädeltieren sind die Körperflüssigkeiten zur Umgebung hypoosmotisch (im Meerwasser) — sie halten Wasser zurück und scheiden anorganiche Ionen aus — oder hyperosmotisch (im Süßwasser), indem sie Wasser abgeben und anorganische Ionen aufnehmen.

  15. Quantitative Analyse und Visualisierung der Herzfunktionen

    NASA Astrophysics Data System (ADS)

    Sauer, Anne; Schwarz, Tobias; Engel, Nicole; Seitel, Mathias; Kenngott, Hannes; Mohrhardt, Carsten; Loßnitzer, Dirk; Giannitsis, Evangelos; Katus, Hugo A.; Meinzer, Hans-Peter

    Die computergestützte bildbasierte Analyse der Herzfunktionen ist mittlerweile Standard in der Kardiologie. Die verfügbaren Produkte erfordern meist ein hohes Maß an Benutzerinteraktion und somit einen erhöhten Zeitaufwand. In dieser Arbeit wird ein Ansatz vorgestellt, der dem Kardiologen eine größtenteils automatische Analyse der Herzfunktionen mittels MRT-Bilddaten ermöglicht und damit Zeitersparnis schafft. Hierbei werden alle relevanten herzphysiologsichen Parameter berechnet und mithilfe von Diagrammen und Graphen visualisiert. Diese Berechnungen werden evaluiert, indem die ermittelten Werte mit manuell vermessenen verglichen werden. Der hierbei berechnete mittlere Fehler liegt mit 2,85 mm für die Wanddicke und 1,61 mm für die Wanddickenzunahme immer noch im Bereich einer Pixelgrösse der verwendeten Bilder.

  16. Friedrich Möglich - sein Beitrag zum Aufbau der Physik in der DDR. Friedrich Möglich - langjähriger Mitherausgeber und Chefredakteur der Annalen der Physik

    NASA Astrophysics Data System (ADS)

    Rompe, Robert

    Friedrich Möglich, ein Schüler von Max von Laue und Erwin Schrödinger, übernahm 1947 die Chefredaktion der Annalen der Physik.Translated AbstractFriedrich Möglich - His Contributions to the Formation of Physics in GDRFriedrich Möglich a student of Max von Laue and Erwin Schrödinger took over as editor in chief of Annalen der Physik in 1947.

  17. Tycho Brahe - Instrumentenbauer und Meister der Beobachtungstechnik

    NASA Astrophysics Data System (ADS)

    Wolfschmidt, Gudrun

    Vor der Erfindung des Fernrohrs war der dänische Astronom Tycho Brahe (1546 - 1601) der bedeutendste beobachtende Astronom. Von seinem Observatorium Uraniborg auf der - damals dänischen - Insel Hven ist heute noch der Grundriß erkennbar, von Stjerneborg sind die Fundamente erhalten, die Kuppeln in den 1950er Jahren ergänzt. In der Astronomie-Ausstellung im Deutschen Museum gibt es ein Modell der Sternwarte Uraniborg und der zugehörigen Instrumente (Maßstab 1:10); das größere Modell wurde dem Technischen Museum in Malmö geschenkt. Die Instrumente, die er in den Observatorien Uraniborg und Stjerneborg benutzte, sind nicht erhalten. Aber es gibt gute Beschreibungen der Instrumente (Halbkreis, Quadranten, Sextanten, Armillarsphären, Triquetrum, Himmelsglobus) in seinem Buch Astronomiae instauratae mechanica (Wandsbek 1598). Eine Nachbildung des großen hölzernen Quadranten kann man im Runden Turm in Kopenhagen sehen. Zwei Sextanten, hergestellt für Tycho um 1600 von Jost Bürgi und Erasmus Habermel, gibt es noch im Nationalmuseum für Technik in Prag. Ähnlichkeiten von Tychos Instrumenten mit Groß-Instrumenten aus dem islamischen Kulturkreis sind auffällig. Tycho Brahes Meßgeräte markieren einen großen Fortschritt in der Entwicklung astronomischer Instrumente und Meßtechniken und bilden die Grundlage für den weiteren Fortschritt der Positionsastronomie und der damit verbundenen Tabellenwerke. Die Nachwirkungen sind bis ins 17. und 18. Jahrhundert nachweisbar.

  18. Towards a more accurate van der Waals density functional

    NASA Astrophysics Data System (ADS)

    Hamada, Ikutaro

    2014-03-01

    The van der Waals density functional (vdW-DF) of Dion et al. [1] has attracted considerable attention, because the functional is able to describe intra- and intermolecular bondings with different natures, e.g., covalent and van der Waals bondings in a seamless fashion within the framework of density functional theory. However, the accuracy of the functional is yet to be improved for the applications to various systems. Here I propose an exchange functional for the second version of vdW-DF [2], which improves the accuracy of vdW-DF. The keys in the improved exchange are the matching to the gradient expansion approximation in the slowly varying limit and the large density gradient behavior set in Becke's exchange (B86b)[3]. Systematic study on gas phase molecules, solids, and molecular adsorption demonstrates the applicability of the proposed functional to a wide variety of materials.

  19. Untersuchung der Richtwirkung der Einkopplung von ebenen Wellen in eine Leitung

    NASA Astrophysics Data System (ADS)

    Magdowski, M.; Vick, R.

    2013-07-01

    Elektrische Leitungen und Kabel stellen häufig die Haupteinfallstore für elektromagnetische Felder in die daran angeschlossenen Geräte und Systeme dar. Für die Einkopplung einer ebenen Welle kann der in eine Leitung eingekoppelte Strom unter bestimmten Voraussetzungen mit Hilfe der Leitungstheorie sehr effizient bestimmt werden. Er hängt dabei von den Abmessungen der Leitung, den Leitungsabschlüssen sowie der Amplitude, der Wellenlänge und der Einfallsrichtung der ebenen Welle ab. In dieser Arbeit wird die Abhängigkeit der Einkopplung von der Einfallsrichtung näher untersucht. Dazu werden Richtdiagramme der Einkopplung berechnet, dargestellt und hinsichtlich der mittleren und maximalen Einkopplung über alle Einfallsrichtungen und Polarisationen ausgewertet. Die Ergebnisse werden genutzt, um die maximale Direktivität der Einkopplung in eine Leitung zu bestimmen. Fasst man die Einkopplung externer Felder in eine Leitung als einen Störfestigkeitstest auf, so kann die maximale Direktivität benutzt werden, um einen Vergleich zwischen unterschiedlichen Messumgebungen wie Absorberhallen und Modenverwirbelungskammern herzustellen.

  20. Numerical integration of nearly-Hamiltonian systems. [Van der Pol oscillator and perturbed Keplerian motion

    NASA Technical Reports Server (NTRS)

    Bond, V. R.

    1978-01-01

    The reported investigation is concerned with the solution of systems of differential equations which are derived from a Hamiltonian function in the extended phase space. The problem selected involves a one-dimensional perturbed harmonic oscillator. The van der Pol equation considered has an exact asymptotic value for its amplitude. Comparisons are made between a numerical solution and a known analytical solution. In addition to the van der Pol problem, known solutions regarding the restricted problem of three bodies are used as examples for perturbed Keplerian motion. The extended phase space Hamiltonian discussed by Stiefel and Scheifele (1971) is considered. A description is presented of two canonical formulations of the perturbed harmonic oscillator.

  1. Sequence polymorphisms of Der f 1, Der p 1, Der f 2 and Der p 2 from Korean house dust mite isolates.

    PubMed

    Jeong, Kyoung Yong; Lee, In-Yong; Yong, Tai-Soon; Lee, Jae-Hyun; Kim, Eun-Jin; Lee, Joo-Shil; Hong, Chein-Soo; Park, Jung-Won

    2012-09-01

    Amino acid sequence variations have possible influences on the allergenicity of allergens and may be important factors in allergen standardization. This study was undertaken to investigate the sequence polymorphisms of group 1 and 2 allergens from Korean isolates of the house dust mites Dermatophagoides farinae and D. pteronyssinus. cDNA sequences encoding group 1 and 2 allergens were amplified by RT-PCR and compared the deduced amino acid sequences. Der f 1.0101, which appeared in 64.0 % of the 50 sequences analyzed, was found to be predominant. Among the Der p 1 sequences, Der p 1.0102 and 1.0105 were predominant (58 %). Among the Der f 2 sequences, Der f 2.0102 (40.7 %) and a new variant with Gly at position 42 (27.8 %) were predominant. The deduced amino acid sequences of 60 Der p 2 clones were examined, and 28 variants with 1-5 amino acid substitutions were found. Interestingly, all of the Der p 2 sequences had Thr instead of Lys at position 49. Two variants (Leu40, Thr49, and Asn114 (26.6 %); Val40, Thr49, and Asn114 (20.0 %)) were found to be the most predominant forms of Der p 2. Der p 1 has a high rate of sporadic substitutions and the group 2 allergens show a more regular pattern with orderly associations of amino acid substitutions. Der f 1 and Der p 2 from Korean mite isolates have unique amino acid sequence polymorphisms. These findings provide important data for house dust mite allergen standardization.

  2. Von Humboldt bis Einstein. Berlin als Weltzentrum der exakten Wissenschaften.

    NASA Astrophysics Data System (ADS)

    Meschkowski, H.

    Contents: 1. Die Anfänge. 2. Die Ära Dirichlet-Jacobi. 3. Der Ausbau der experimentellen Naturwissenschaften. 4. Alexander von Humboldt. 5. Berlin wird "Weltzentrum" der Mathematik. 6. Die Ära Helmholtz. 7. Neue Arbeitsweisen der Astronomie. 8. Chemie: Forschung und Industrie. 9. Max Planck. 10. Ins technische Zeitalter. 11. Zur Mathematik der zwanziger Jahre. 12. Albert Einstein. 13. Fortschritte der Grundlagenforschung. 14. Erwin Schrödinger: Physiker, Philosoph und Poet. 15. Zum Schluß.

  3. Reply to the 'Comment on "Discovery of a tetracontinuous, aqueous lyotropic network phase with unusual 3D-hexagonal symmetry"' by G. Schröder-Turk, M. Fischer and S. Hyde.

    PubMed

    Sorenson, Gregory P; Mahanthappa, Mahesh K

    2015-02-14

    A new calculation by Fischer et al. suggests that the 3etc network phase with 3D-hexagonal symmetry (space group #193: P63/mcm) may be a generic structure adopted by self-assembling soft materials, thereby broadening the context for our recent report of its spontaneous formation in lyotropic liquid crystals. The experimental observation of the 3etc phase further validates previous theoretical models used to predict its stability, provocatively suggesting that other polycontinuous network phases predicted by these methods may be discovered in the future. While these network phase morphologies are often mathematically described in terms of their underlying triply periodic minimal surfaces (TPMS), the numerous potential applications of these functional nanostructured soft materials require the development of a concise, consistent, and unambiguous nomenclature for their complete description. In this comment, we propose adoption of a nomenclature that describes each mesophase more generally in terms of the total number of non-intersecting domains into which three-dimensional space is partitioned.

  4. Der Kalte Krieg in der Peripherie Griechische Physiker und Atomenergie nach dem Zweiten Weltkrieg

    NASA Astrophysics Data System (ADS)

    Vlahakis, George N.

    Die vorliegende Arbeit analysiert Ansichten griechischer Physiker zur Atomenergie und deren mögliche Anwendung nach dem Zweiten Weltkrieg, insbesondere während des Kalten Kriegs. Einerseits werden Ansichten von Physik- Professoren griechischer Universitäten präsentiert - beispielsweise von Dimitrios Hondros, der Student von Arnold Sommerfeld und Mitarbeiter von Peter Debye in München war, und andererseits wird die Politik der griechischen Regierung für die Etablierung eines Forschungsinstitutes diskutiert, das der Entwicklung der Atomenergie dienen sollte; ebenfalls wird eine öffentliche Meinungsumfrage zu diesen Thema, die in den Tageszeitungen der damaligen Zeit präsentiert wurde, diskutiert.

  5. Topika und deren Einsatz in der Dermatologie.

    PubMed

    Wohlrab, Johannes

    2016-11-01

    Grundkenntnisse zur Zusammensetzung und den regulatorischen Hintergründen von Topika gehören zu den alltäglich benötigten Herausforderungen dermatologisch-ärztlichen Handelns. Ein professioneller und indikationsgerechter Umgang bei der Auswahl, Verordnung und Anwendung topischer Präparate ist somit Voraussetzung für eine verantwortungsvolle fachärztliche Tätigkeit. Dabei bereiten die regulatorische Zuordnung (Arzneimittel, Medizinprodukt, Kosmetikum), die Feststellung der Erstattungsfähigkeit durch die GKV und die unzureichende Kennzeichnung des Vehikelsystems einzelner Präparate nicht selten Probleme. Bestreben sollte es sein, neben der Wahl des geeigneten Wirkstoffs und der geeigneten Konzentration ein an die Indikation der Therapie angepasstes galenisches System auszuwählen, um dessen Eigenwirkung für den therapeutischen Effekt nutzen zu können. Bei der Verschreibung von Rezepturarzneimitteln sollte nach Möglichkeit immer auf eine standardisierte Rezeptur (Magistralrezeptur) zurückgegriffen werden. Durch die Vielzahl der möglichen Inhaltsstoffe und der sich daraus ergebenden Komplexität eines galenischen Systems ist eine willkürliche Manipulation durch qualitative oder quantitative Veränderungen einzelner Komponenten mit hohen Risiken für eine Instabilität und damit für Sicherheit und Sinnhaftigkeit verbunden. Eine optimierte Anwendung von Topika setzt zudem Grundlagenkenntnisse zur Pharmakokinetik und zur evidenzbasierten Therapieplanung voraus.

  6. National Dam Inspection Program. Robena Slurry Pond 6 (NDI Number PA 00197, Penn DER Number 30-26), Ohio River Basin, Tributary to Whiteley Creek, Greene County, Pennsylvania. Phase I Inspection Report

    DTIC Science & Technology

    1981-07-01

    not the dam constitutes a hazard to human life or property. 1.2 DESCRIPTION OF PROJECT a. General: Robena Slurry Pond 6 consists of an earth and...Surface Current Top of Dam 27.5 acres* Emergency Spillway Crest 24.7 acres g. Embankment Type Zoned Earth and Coarse Coal Refuse Length 1985 feet Height...CORPORATION RAW MATERIALS DIVISION FRICK DISTRICT PHASE : INSPECTION REPORT NATIONAL DAM INSPECTION PROGRAM liii JAN o 41982 -4 PREPARED FOR - "DPA

  7. Heterologous Expression of Der Homologs in an Escherichia coli der Mutant and Their Functional Complementation

    PubMed Central

    Choi, Eunsil; Kang, Nalae; Jeon, Young; Pai, Hyun-Sook

    2016-01-01

    ABSTRACT The unique Escherichia coli GTPase Der (double Era-like GTPase), which contains tandemly repeated GTP-binding domains, has been shown to play an essential role in 50S ribosomal subunit biogenesis. The depletion of Der results in the accumulation of precursors of 50S ribosomal subunits that are structurally unstable at low Mg2+ concentrations. Der homologs are ubiquitously found in eubacteria. Conversely, very few are conserved in eukaryotes, and none is conserved in archaea. In the present study, to verify their conserved role in bacterial 50S ribosomal subunit biogenesis, we cloned Der homologs from two gammaproteobacteria, Klebsiella pneumoniae and Salmonella enterica serovar Typhimurium; two pathogenic bacteria, Staphylococcus aureus and Neisseria gonorrhoeae; and the extremophile Deinococcus radiodurans and then evaluated whether they could functionally complement the E. coli der-null phenotype. Only K. pneumoniae and S. Typhimurium Der proteins enabled the E. coli der-null strain to grow under nonpermissive conditions. Sucrose density gradient experiments revealed that the expression of K. pneumoniae and S. Typhimurium Der proteins rescued the structural instability of 50S ribosomal subunits, which was caused by E. coli Der depletion. To determine what allows their complementation, we constructed Der chimeras. We found that only Der chimeras harboring both the linker and long C-terminal regions could reverse the growth defects of the der-null strain. Our findings suggest that ubiquitously conserved essential GTPase Der is involved in 50S ribosomal subunit biosynthesis in various bacteria and that the linker and C-terminal regions may participate in species-specific recognition or interaction with the 50S ribosomal subunit. IMPORTANCE In Escherichia coli, Der (double Era-like GTPase) is an essential GTPase that is important for the production of mature 50S ribosomal subunits. However, to date, its precise role in ribosome biogenesis has not been

  8. Reisen im freien Fall - Teil 2: Das Zwillingsparadoxon aus dem Blickwinkel der ART

    NASA Astrophysics Data System (ADS)

    Sonne, Bernd; Weiß, Reinhard

    2013-07-01

    Nachdem wir uns mit den Prinzipien der ART und einigen Beispielen vertraut gemacht haben, kommen wir nun zur Berechnung des Zwillingsparadoxons aus Sicht des reisenden Zwillings. Dabei spielt das Äquivalenzprinzip eine große Rolle. Deshalb wird die Bewegungssituation noch einmal erläutert, diesmal aus Sicht von Katrin. Sie befindet sich in ihrem System S'in Ruhe. In ihrem System läuft die Zeit t'ab. Nach dem Start fühlt Katrin jedoch eine Kraft, die sie als Gravitationskraft interpretieren kann. Sie merkt es daran, dass sie in den Sitz gedrückt wird. Nach einiger Zeit werden die Triebwerke abgeschaltet, und das Raumschiff fliegt mit konstanter Geschwindigkeit weiter, Phase 2. Anschließend wird der Schub der Triebwerke solange umgekehrt, bis das Raumschiff irgendwo mit der Geschwindigkeit null am Umkehrpunkt U landet, Phase 3 (Abb. 15.1). Die Erde, auf der sich Michael befindet, bewegt sich mit x'(t') aus Sicht von Katrin im freien Fall von ihr weg, s. das Experiment mit dem steigenden Fahrstuhl in Abschn. 13.2.1.

  9. Characterization of rarefaction waves in van der Waals fluids.

    PubMed

    Yuen, Albert; Barnard, John J

    2015-12-01

    We calculate the isentropic evolution of an instantaneously heated foil, assuming a van der Waals equation of state with the Maxwell construction. The analysis by Yuen and Barnard [Phys. Rev. E 92, 033019 (2015)] is extended for the particular case of three degrees of freedom. We assume heating to temperatures in the vicinity of the critical point. The self-similar profiles of the rarefaction waves describing the evolution of the foil display plateaus in density and temperature due to a phase transition from the single-phase to the two-phase regime. The hydrodynamic equations are expressed in a dimensionless form and the solutions form a set of universal curves, depending on a single parameter: the dimensionless initial entropy. We characterize the rarefaction waves by calculating how the plateau length, density, pressure, temperature, velocity, internal energy, and sound speed vary with dimensionless initial entropy.

  10. Characterization of rarefaction waves in van der Waals fluids

    NASA Astrophysics Data System (ADS)

    Yuen, Albert; Barnard, John J.

    2015-12-01

    We calculate the isentropic evolution of an instantaneously heated foil, assuming a van der Waals equation of state with the Maxwell construction. The analysis by Yuen and Barnard [Phys. Rev. E 92, 033019 (2015), 10.1103/PhysRevE.92.033019] is extended for the particular case of three degrees of freedom. We assume heating to temperatures in the vicinity of the critical point. The self-similar profiles of the rarefaction waves describing the evolution of the foil display plateaus in density and temperature due to a phase transition from the single-phase to the two-phase regime. The hydrodynamic equations are expressed in a dimensionless form and the solutions form a set of universal curves, depending on a single parameter: the dimensionless initial entropy. We characterize the rarefaction waves by calculating how the plateau length, density, pressure, temperature, velocity, internal energy, and sound speed vary with dimensionless initial entropy.

  11. Qualitätsmanagement in der Lebensmittelindustrie

    NASA Astrophysics Data System (ADS)

    Thorn, Volker

    Die wesentlichen Kunden der Lebensmittelindustrie sind der Einzel- und Großhandel und die Verbraucher. Jedes Unternehmen kann mittel- und langfristig nur existieren, wenn seine Kunden zufrieden sind. Kunden sind zufrieden, wenn ihre Erwartungen, die sie an Produkt, Service und Preis stellen, erfüllt werden. Also die bestimmte erwartete Qualität (Leistung) sichergestellt wird. Trotz aller Bemühungen und Anstrengungen der Anbieter, Qualitätsprodukte auf den Markt zu bringen, kames in den letzten Jahren immer wieder zu Lebensmittelskandalen.

  12. Werner Heisenberg zum 100. Geburtstag: Pionier der Quantenmechanik

    NASA Astrophysics Data System (ADS)

    Jacobi, Manfred

    2001-11-01

    Werner Heisenberg war eine der prägendsten Gestalten der Physik des 20. Jahrhunderts. Zu seinen wichtigsten Verdiensten gehören die Grundlegung der Quantenmechanik, die Formulierung der Unschärferelationen sowie die Beteiligung an der Ausarbeitung der Kopenhagener Deutung der Quantenmechanik. Darüber hinaus lieferte er Arbeiten von fundamentalem Charakter zur Theorie des Atomkerns, zur kosmischen Strahlung und zur Quantenfeldtheorie. Während des Krieges war er an den Arbeiten des Uranvereins beteiligt, der die Möglichkeit einer Entwicklung von Kernwaffen untersuchte, jedoch über Vorarbeiten zur Reaktorphysik nicht hinauskam. Wegen dieser Tätigkeit wurde er bei Kriegsende für einige Monate in England interniert. Nach seiner Rückkehr widmete er sich vor allem dem Aufbau der Physik in Deutschland, die während der NS-Zeit nahezu ihrer gesamten Substanz beraubt worden war.

  13. A high-pressure van der Waals compound in solid nitrogen-helium mixtures

    NASA Technical Reports Server (NTRS)

    Vos, W. L.; Finger, L. W.; Hemley, R. J.; Hu, J. Z.; Mao, H. K.; Schouten, J. A.

    1992-01-01

    A detailed diamond anvil-cell study using synchrotron X-ray diffraction, Raman scattering, and optical microscopy has been conducted for the He-N system, with a view to the weakly-bound van der Waals molecule interactions that can be formed in the gas phase. High pressure is found to stabilize the formation of a stoichiometric, solid van der Waals compound of He(N2)11 composition which may exemplify a novel class of compounds found at high pressures in the interiors of the outer planets and their satellites.

  14. Van der Waals interactions and the limits of isolated atom models at interfaces

    NASA Astrophysics Data System (ADS)

    Kawai, Shigeki; Foster, Adam S.; Björkman, Torbjörn; Nowakowska, Sylwia; Björk, Jonas; Canova, Filippo Federici; Gade, Lutz H.; Jung, Thomas A.; Meyer, Ernst

    2016-05-01

    Van der Waals forces are among the weakest, yet most decisive interactions governing condensation and aggregation processes and the phase behaviour of atomic and molecular matter. Understanding the resulting structural motifs and patterns has become increasingly important in studies of the nanoscale regime. Here we measure the paradigmatic van der Waals interactions represented by the noble gas atom pairs Ar-Xe, Kr-Xe and Xe-Xe with a Xe-functionalized tip of an atomic force microscope at low temperature. Individual rare gas atoms were fixed at node sites of a surface-confined two-dimensional metal-organic framework. We found that the magnitude of the measured force increased with the atomic radius, yet detailed simulation by density functional theory revealed that the adsorption induced charge redistribution strengthened the van der Waals forces by a factor of up to two, thus demonstrating the limits of a purely atomic description of the interaction in these representative systems.

  15. Dynamics of three coupled van der Pol oscillators with application to circadian rhythms

    NASA Astrophysics Data System (ADS)

    Rompala, Kevin; Rand, Richard; Howland, Howard

    2007-08-01

    In this work we study a system of three van der Pol oscillators. Two of the oscillators are identical, and are not directly coupled to each other, but rather are coupled via the third oscillator. We investigate the existence of the in-phase mode in which the two identical oscillators have the same behavior. To this end we use the two variable expansion perturbation method (also known as multiple scales) to obtain a slow flow, which we then analyze using the computer algebra system MACSYMA and the numerical bifurcation software AUTO. Our motivation for studying this system comes from the presence of circadian rhythms in the chemistry of the eyes. We model the circadian oscillator in each eye as a van der Pol oscillator. Although there is no direct connection between the two eyes, they are both connected to the brain, especially to the pineal gland, which is here represented by a third van der Pol oscillator.

  16. Van der Waals interactions and the limits of isolated atom models at interfaces.

    PubMed

    Kawai, Shigeki; Foster, Adam S; Björkman, Torbjörn; Nowakowska, Sylwia; Björk, Jonas; Canova, Filippo Federici; Gade, Lutz H; Jung, Thomas A; Meyer, Ernst

    2016-05-13

    Van der Waals forces are among the weakest, yet most decisive interactions governing condensation and aggregation processes and the phase behaviour of atomic and molecular matter. Understanding the resulting structural motifs and patterns has become increasingly important in studies of the nanoscale regime. Here we measure the paradigmatic van der Waals interactions represented by the noble gas atom pairs Ar-Xe, Kr-Xe and Xe-Xe with a Xe-functionalized tip of an atomic force microscope at low temperature. Individual rare gas atoms were fixed at node sites of a surface-confined two-dimensional metal-organic framework. We found that the magnitude of the measured force increased with the atomic radius, yet detailed simulation by density functional theory revealed that the adsorption induced charge redistribution strengthened the van der Waals forces by a factor of up to two, thus demonstrating the limits of a purely atomic description of the interaction in these representative systems.

  17. Van der Waals interactions and the limits of isolated atom models at interfaces

    PubMed Central

    Kawai, Shigeki; Foster, Adam S.; Björkman, Torbjörn; Nowakowska, Sylwia; Björk, Jonas; Canova, Filippo Federici; Gade, Lutz H.; Jung, Thomas A.; Meyer, Ernst

    2016-01-01

    Van der Waals forces are among the weakest, yet most decisive interactions governing condensation and aggregation processes and the phase behaviour of atomic and molecular matter. Understanding the resulting structural motifs and patterns has become increasingly important in studies of the nanoscale regime. Here we measure the paradigmatic van der Waals interactions represented by the noble gas atom pairs Ar–Xe, Kr–Xe and Xe–Xe with a Xe-functionalized tip of an atomic force microscope at low temperature. Individual rare gas atoms were fixed at node sites of a surface-confined two-dimensional metal–organic framework. We found that the magnitude of the measured force increased with the atomic radius, yet detailed simulation by density functional theory revealed that the adsorption induced charge redistribution strengthened the van der Waals forces by a factor of up to two, thus demonstrating the limits of a purely atomic description of the interaction in these representative systems. PMID:27174162

  18. Modellbasierte interindividuelle Registrierung an der lateralen Schädelbasis

    NASA Astrophysics Data System (ADS)

    Riechmann, M.; Lohnstein, P. U.; Raczkowsky, J.; Klenzner, T.; Schipper, J.; Wörn, H.

    Bei chirurgischen Eingriffen an der lateralen Schädelbasis wird in der zur Zeit gängigen Praxis das Knochengewebe unter optischer Kontrolle großflächig ablativ entfernt, um den Operationssitus freizulegen und konventionell operieren zu können. Prinzipiell soll dabei die Schonung vital und funktional bedeutender Strukturen berücksichtigt werden. Zur weiteren Minimierung der Traumatisierung und zur Erhaltung der strukturellen anatomischen Integrität soll eine alternative endoskopische Operationstechnik entwickelt werden, bei der der Situs durch dünne im Knochen liegende Bohrkanäle erreicht wird. Im Rahmen der Evaluierung der generellen Eignung der geometrischen Ausprägungen der humanen lateralen Schädelbasis wurden Methoden entwickelt, die anhand virtueller Modelle die Zugänglichkeit der anatomischen Zielstrukturen bestimmen können. Ein dabei auftretendes Problem ist die interindividuelle Vergleichbarkeit der Ergebnisse, da aufgrund der anatomischen Variationen eine zuverlässige interindividuelle Registrierung nicht trivial ist. Diese Arbeit beschreibt ein modellbasiertes Verfahren zur automatischen Registrierung mehrerer Felsenbeine zu einander über die prägnante Geometrie der Cochlea.

  19. Checkpoint-Inhibitoren in der Immuntherapie: Ein Meilenstein in der Behandlung des malignen Melanoms.

    PubMed

    Wilden, Sophia M; Lang, Berenice M; Mohr, Peter; Grabbe, Stephan

    2016-07-01

    Seit Jahrzehnten ist bekannt, dass Tumoren vom Immunsystem erkannt und zerstört werden können. Diese, vor allem in Tierversuchen gewonnene Erkenntnis konnte jedoch in der Vergangenheit nicht zum Nutzen unserer Patienten umgesetzt werden, da immunonkologische Therapieansätze in den letzten Jahrzehnten in der Anwendung beim Menschen stets versagt haben. Daher hat, mit Ausnahme der adjuvanten Interferontherapie, keines dieser Verfahren den Einzug in die klinische Versorgung gefunden. Langzeitüberleben unter guter Lebensqualität war dabei sehr wenigen Patienten vorbehalten. Mit den neuen immunologischen Therapieansätzen wird jedoch sowohl das Langzeitüberleben als auch die Lebensqualität onkologischer Patienten neu definiert. Auf die neuen "Immun-Checkpoint-Inhibitoren" spricht erstmals ein relevanter Teil der behandelten Patienten an und diese zeigen in der Regel langandauernde Remissionen bis hin zur Heilung. Schon jetzt ist klar, dass die Immuntherapie in Zukunft eine der wesentlichen Therapiesäulen bei der Behandlung des metastasierten Melanoms und auch vieler anderer fortgeschrittener Tumoren bilden wird. In dieser Übersicht werden die wichtigsten neuen Therapiemodalitäten besprochen und sowohl deren Wirkprinzip als auch klinische Daten zum Therapieansprechen und zu erwartenden Nebenwirkungen der Therapie referiert.

  20. Extended version of the van der Waals capillarity theory.

    PubMed

    Baidakov, V G; Boltachev, G Sh

    2004-11-01

    An extended version of the van der Waals capillarity theory describing the liquid-vapor interface in the temperature range from the triple to the critical point is suggested. A model functional of thermodynamic potential for a two-phase Lennard-Jones system taking into account the effect of the highest degree terms of gradient expansion has been constructed. The identity of the thermodynamic and the mechanical definition of Tolman's length has been proved in the framework of the adopted form of functional. The properties of nuclei of the liquid and the vapor phase are described. The paper determines: the work of formation of a nucleus, density profiles, size dependences of the surface tension, and the parameter delta in the Gibbs-Tolman-Koenig-Buff equation.

  1. Thermohydrodynamics of boiling in a van der Waals fluid.

    PubMed

    Laurila, T; Carlson, A; Do-Quang, M; Ala-Nissila, T; Amberg, G

    2012-02-01

    We present a modeling approach that enables numerical simulations of a boiling Van der Waals fluid based on the diffuse interface description. A boundary condition is implemented that allows in and out flux of mass at constant external pressure. In addition, a boundary condition for controlled wetting properties of the boiling surface is also proposed. We present isothermal verification cases for each element of our modeling approach. By using these two boundary conditions we are able to numerically access a system that contains the essential physics of the boiling process at microscopic scales. Evolution of bubbles under film boiling and nucleate boiling conditions are observed by varying boiling surface wettability. We observe flow patters around the three-phase contact line where the phase change is greatest. For a hydrophilic boiling surface, a complex flow pattern consistent with vapor recoil theory is observed.

  2. Kommunikationsanforderungen an verteilte Echtzeitsysteme in der Fertigungsautomatisierung

    NASA Astrophysics Data System (ADS)

    Just, Roman; Trsek, Henning

    Kommunikationssysteme der Automatisierung müssen hohe zeitliche Anforderungen erfüllen, damit die entsprechenden industriellen Anwendungen realisiert werden können. Im Gegensatz zum IT-Bereich sind diese Anforderungen jedoch häufig nicht genau bekannt, was insbesondere beim Einsatz von drahtlosen Technologien Probleme bereiten kann1. In dieser Arbeit werden Verkehrsmuster einer realen Anlage aus dem Bereich der Fertigungsautomatisierung bestimmt. Die Zwischenankunfts- und Latenzzeiten einzelner Sensorund Aktorsignale ermöglichen Rückschlüsse auf zeitliche Anforderungen und Charakteristiken der untersuchten Anwendung. Im Anschluss werden die erzielten Erkenntnisse hinsichtlich ausgewählter Kommunikationsanforderungen analysiert und aktuell gültige Anforderungen von realen Automatisierungsanlagen abgeleitet. Weiterhin werden sie zukünftig zur Entwicklung realitätsnaher Simulationsmodelle genutzt.

  3. Efficient thermoelectric van der Pauw measurements

    NASA Astrophysics Data System (ADS)

    de Boor, Johannes; Schmidt, Volker

    2011-07-01

    The development of powerful thermoelectric materials requires fast and simple characterization techniques. We combine three measurements to obtain a complete thermoelectric characterization. The electrical conductivity is measured by the van der Pauw method, while ZT is determined directly by means of a Harman measurement. Finally, exploiting the analogy between electrical and thermal physics, a thermal van der Pauw measurement is performed and the sample Seebeck coefficient and thermal conductivity can be determined. No temperature differences need to be measured; all quantities can be deduced from voltage measurements concurrently on the same sample which allows for quick and convenient material screening.

  4. Numerische Berechnung von Wirbelstromproblemen mit der Cell-Methode

    NASA Astrophysics Data System (ADS)

    Frenner, K.; Rucker, W. M.

    2006-09-01

    In dieser Arbeit wird die Cell-Methode auf die quasistatischen Maxwellgleichungen angewendet. Dabei werden für die notwendige Transformation vom Primärgitter auf das duale Gitter reziproke Basisvektoren verwendet. Anhand der Felddiffusion der magnetischen Induktion in einen zylindrischen Leiter werden Ergebnisse der Cell-Methode mit einer analytischen Vergleichsrechnung präsentiert.

  5. TÜV - Zertifizierungen in der Life Science Branche

    NASA Astrophysics Data System (ADS)

    Schaff, Peter; Gerbl-Rieger, Susanne; Kloth, Sabine; Schübel, Christian; Daxenberger, Andreas; Engler, Claus

    Life Sciences [1] (Lebenswissenschaften) sind ein globales Innovationsfeld mit Anwendungen der Bio- und Medizinwissenschaften, der Pharma-, Chemie-, Kosmetik- und Lebensmittelindustrie. Diese Branche zeichnet sich durch eine stark interdisziplinäre Ausrichtung aus, mit Anwendung wissenschaftlicher Erkenntnisse und Einsatz von Ausgangsstoffen aus der modernen Biologie, Chemie und Humanmedizin sowie gezielter marktwirtschaftlich orientierter Arbeit.

  6. Multiple critical points and liquid liquid equilibria from the van der Waals like equations of state

    NASA Astrophysics Data System (ADS)

    Artemenko, Sergey; Lozovsky, Taras; Mazur, Victor

    2008-06-01

    The principal aim of this work is a comprehensive analysis of the phase diagram of water via the van der Waals like equations of state (EoSs) which are considered as superpositions of repulsive and attractive forces. We test more extensively the modified van der Waals EoS (MVDW) proposed by Skibinski et al (2004 Phys. Rev. E 69 061206) and refine this model by introducing instead of the classical van der Waals repulsive term a very accurate hard sphere EoS over the entire stable and metastable regions (Liu 2006 Preprint cond-mat/0605392). It was detected that the simplest form of MVDW EoS displays a complex phase behavior, including three critical points, and identifies four fluid phases (gas, low density liquid (LDL), high density liquid (HDL), and very high density liquid (VHDL)). Moreover the experimentally observed (Mallamace et al 2007 Proc. Natl Acad. Sci. USA 104 18387) anomalous behavior of the density of water in the deeply supercooled region (a density minimum) is reproduced by the MWDW EoS. An improvement of the repulsive part does not change the topological picture of the phase behavior of water in the wide range of thermodynamic variables. The new parameters set for second and third critical points are recognized by thorough analysis of experimental data for the loci of thermodynamic response function extrema.

  7. Darwin, Engels und die Rolle der Arbeit in der biologischen und kulturellen Evolution des Menschen

    NASA Astrophysics Data System (ADS)

    Reichholf, Josef H.

    Im Jahre 1876, 5 Jahre nach Erscheinen von Darwins Buch über die Evolution des Menschen und die sexuelle Selektion (Darwin 1871), veröffentlichte Friedrich Engels den berühmt gewordenen Essay "Anteil der Arbeit an der Menschwerdung des Affen“ (Engels 1876). Die Kernfrage darin lautet in Kurzform: Warum hat der Mensch eigentlich ein Bedürfnis nach Arbeit? Engels Antwort wird nachfolgend näher betrachtet und vom gegenwärtigen Kenntnisstand aus beurteilt. Wie sich zeigen wird, beantworten seine Überlegungen die Frage nicht wirklich. Sie ist weiterhin offen. Es können lediglich einige zusätzliche Anhaltspunkte zur Diskussion gestellt werden. Angesichts des drängenden Problems millionenfacher Arbeitslosigkeit und der Forderungen nach einem "Grundrecht auf Arbeit“ kommt den Überlegungen zum möglichen Ursprung des Bedürfnisses nach Arbeit mehr als nur akademisches Interesse zu.

  8. Note on a van der Waals Gas.

    ERIC Educational Resources Information Center

    Bauman, Robert P.; Harrison, Joseph G.

    1996-01-01

    Discusses the difficulties with the standard model for introduction of attractive forces into the van der Waals equation. Presents an analysis in terms of force and time delays and an alternative analysis for more advanced students in terms of energy. (JRH)

  9. Die Evolution der Religiosität

    NASA Astrophysics Data System (ADS)

    Voland, Eckart

    Ein konsequent darwinischer Blick auf den Menschen bedeutet, auch im Denken, Fühlen und Handeln biologische Anpassungsgeschichte zu suchen, denn auch die psychischen und mentalen Eigenheiten des Homo sapiens unterliegen der natürlichen Selektion. Lässt sich die religiöse Lebenspraxis von Menschen daher auch aus einer Fitnessperspektive betrachten?

  10. The Forced van der Pol Equation

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2009-01-01

    We report on a study of the forced van der Pol equation x + [epsilon](x[superscript 2] - 1)x + x = F cos[omega]t, by solving numerically the differential equation for a variety of values of the parameters [epsilon], F and [omega]. In doing so, many striking and interesting trajectories can be discovered and phenomena such as frequency entrainment,…

  11. Exact traveling wave solutions of the van der Waals normal form for fluidized granular matter

    NASA Astrophysics Data System (ADS)

    Abourabia, A. M.; Morad, A. M.

    2015-11-01

    Analytical solutions of the van der Waals normal form for fluidized granular media have been done to study the phase separation phenomenon by using two different exact methods. The Painlevé analysis is discussed to illustrate the integrability of the model equation. An auto-Bäcklund transformation is presented via the truncated expansion and symbolic computation. The results show that the exact solutions of the model introduce solitary waves of different types. The solutions of the hydrodynamic model and the van der Waals equation exhibit a behavior similar to the one observed in molecular dynamic simulations such that two pairs of shock and rarefaction waves appear and move away, giving rise to the bubbles. The dispersion properties and the relation between group and phase velocities of the model equation are studied using the plane wave assumption. The diagrams are drawn to illustrate the physical properties of the exact solutions, and indicate their stability and bifurcation.

  12. A Van der Waals-like theory of plasma double layers

    NASA Technical Reports Server (NTRS)

    Katz, Ira; Davis, V. A.

    1989-01-01

    A theory describing plasma double layers in terms of multiple roots of the charge density expression is presented. The theory presented uses the fact that equilibrium plasmas shield small potential perturbations linearly; for high potentials, the shielding decreases. The approach is analogous to Van der Waals' theory of simple fluids in which inclusion of approximate expressions for both excluded volume and long range attractive forces sufficiently describes the first-order liquid-gas phase transition.

  13. Thermal response in van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Naidu Gandi, Appala; Alshareef, Husam N.; Schwingenschlögl, Udo

    2017-01-01

    We solve numerically the Boltzmann transport equations of the phonons and electrons to understand the thermoelectric response in heterostructures of M2CO2 (M: Ti, Zr, Hf) MXenes with transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding, contribute significantly to the thermal transport, and compensate for the reduced contributions of the acoustic phonons (increased scattering cross-sections in heterostructures), such that the thermal conductivities turn out to be similar to those of the bare MXenes. Our results indicate that the important superlattice design approach of thermoelectrics (to reduce the thermal conductivity) may be effective for two-dimensional van der Waals materials when used in conjunction with intercalation.

  14. Thermal response in van der Waals heterostructures.

    PubMed

    Gandi, Appala Naidu; Alshareef, Husam N; Schwingenschlögl, Udo

    2017-01-25

    We solve numerically the Boltzmann transport equations of the phonons and electrons to understand the thermoelectric response in heterostructures of M2CO2 (M: Ti, Zr, Hf) MXenes with transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding, contribute significantly to the thermal transport, and compensate for the reduced contributions of the acoustic phonons (increased scattering cross-sections in heterostructures), such that the thermal conductivities turn out to be similar to those of the bare MXenes. Our results indicate that the important superlattice design approach of thermoelectrics (to reduce the thermal conductivity) may be effective for two-dimensional van der Waals materials when used in conjunction with intercalation.

  15. Superlubricity using repulsive van der Waals forces.

    PubMed

    Feiler, Adam A; Bergström, Lennart; Rutland, Mark W

    2008-03-18

    Using colloid probe atomic force microscopy, we show that if repulsive van der Waals forces exist between two surfaces prior to their contact then friction is essentially precluded and supersliding is achieved. The friction measurements presented here are of the same order as the lowest ever recorded friction coefficients in liquid, though they are achieved by a completely different approach. A gold sphere attached to an AFM cantilever is forced to interact with a smooth Teflon surface (templated on mica). In cyclohexane, a repulsive van der Waals force is observed that diverges at short separations. The friction coefficient associated with this system is on the order of 0.0003. When the refractive index of the liquid is changed, the force can be tuned from repulsive to attractive and adhesive. The friction coefficient increases as the Hamaker constant becomes more positive and the divergent repulsive force, which prevents solid-solid contact, gets switched off.

  16. Der Begriff mathematischer Schönheit in einer empirisch informierten Ästhetik der Mathematik

    NASA Astrophysics Data System (ADS)

    Müller-Hill, Eva; Spies, Susanne

    Dieses Zitat des britischen Mathematikers G. H. Hardy bringt pointiert die unter praktizierenden Mathematikern, aber auch unter Philosophen der Mathematik weithin akzeptierte Ansicht zum Ausdruck, dass mathematische Schönheit eine nicht zu vernachlässigende Rolle in der mathematischen Forschungspraxis spielt und sowohl interessante ästhetiktheoretische, epistemische als auch ontologische Aspekte aufweist. Danach beeinflusst also das Verständnis dessen, was mathematische Schönheit ist, auch das Verständnis dessen, was Mathematik ist: "Was sind die Träger mathematischer Schönheit?" ist die Frage nach der Art der Gegenstände, für deren Schönheit Mathematiker sich begeistern und nach der sie streben. "Was sind die Kriterien für mathematische Schönheit?" ist die Frage nach den Kategorien, unter denen Mathematiker ihre Arbeit bewerten. Egal, ob sich das Phänomen mathematischer Schönheit als Ausnahmemerkmal oder als ständiger Begleiter mathematischen Tuns erweist - ein adäquates allgemeines Mathematikverständnis sollte dieses Phänomen berücksichtigen und bestenfalls auch erklären können.

  17. Theory of coherent van der Waals matter.

    PubMed

    Kulić, Igor M; Kulić, Miodrag L

    2014-12-01

    We explain in depth the previously proposed theory of the coherent van der Waals (cvdW) interaction, the counterpart of van der Waals (vdW) force, emerging in spatially coherently fluctuating electromagnetic fields. We show that cvdW driven matter is dominated by many-body interactions, which are significantly stronger than those found in standard van der Waals (vdW) systems. Remarkably, the leading two- and three-body interactions are of the same order with respect to the distance (∝R(-6)), in contrast to the usually weak vdW three-body effects (∝R(-9)). From a microscopic theory we show that the anisotropic cvdW many-body interactions drive the formation of low-dimensional structures such as chains, membranes, and vesicles with very unusual, nonlocal properties. In particular, cvdW chains display a logarithmically growing stiffness with the chain length, while cvdW membranes have a bending modulus growing linearly with their size. We argue that the cvdW anisotropic many-body forces cause local cohesion but also a negative effective "surface tension." We conclude by deriving the equation of state for cvdW materials and propose experiments to test the theory, in particular the unusual three-body nature of cvdW.

  18. Zellulare Nichtlineare Netzwerke: Anwendungen in der Informationstechnologie

    NASA Astrophysics Data System (ADS)

    Tetzlaff, R.

    2007-06-01

    Zellulare Nichtlineare Netzwerke (CNN) wurden 1988 von Chua und Yang (Chua und Yang, 1988) eingeführt. Diese Netzwerke sind dadurch gekennzeichnet, dass eine Zelle, die die kleinste Einheit eines CNN darstellt, nur mit Zellen innerhalb einer bestimmten Umgebung verbunden ist. üblicherweise sind Art und Stärke der Wechselwirkung zwischen zwei Zellen eines CNN translationsinvariant, d.h. sie hängen nur von der relativen Lage beider Zellen zueinander ab. Im Vordergrund aktueller Arbeiten stehen auf derartigen Netzwerken basierende schaltungstechnische Realisierungen mit bis zu 176x144 Zellen, die eine direkte Verbindung zu zweidimensionalen optischen Sensor-Anordnungen aufweisen. Über einen separaten Speicherbereich können die Zellkopplungen eines Netzwerks verändert werden, wodurch eine adaptive Verarbeitung von mehrdimensionalen Sensorsignalen ermöglicht wird. Das kürzlich vorgestellte so genannte EyeRis System (Anafocus Ltd.) enthält zusätzlich noch einen Standardprozessor und stellt (bei einer Größe vergleichbar mit der einer Kreditkarte) daher ein vollständiges superschnelles System zur Informationsverarbeitung dar. In diesem Beitrag sollen, nach einem kurzen Überblick über die Eigenschaften von CNN, aktuelle Realisierungen und exemplarisch eine neuere eigene Anwendung vorgestellt und besprochen werden.

  19. Theory of coherent van der Waals matter

    NASA Astrophysics Data System (ADS)

    Kulić, Igor M.; Kulić, Miodrag L.

    2014-12-01

    We explain in depth the previously proposed theory of the coherent van der Waals (cvdW) interaction, the counterpart of van der Waals (vdW) force, emerging in spatially coherently fluctuating electromagnetic fields. We show that cvdW driven matter is dominated by many-body interactions, which are significantly stronger than those found in standard van der Waals (vdW) systems. Remarkably, the leading two- and three-body interactions are of the same order with respect to the distance (∝R-6) , in contrast to the usually weak vdW three-body effects (∝R-9 ). From a microscopic theory we show that the anisotropic cvdW many-body interactions drive the formation of low-dimensional structures such as chains, membranes, and vesicles with very unusual, nonlocal properties. In particular, cvdW chains display a logarithmically growing stiffness with the chain length, while cvdW membranes have a bending modulus growing linearly with their size. We argue that the cvdW anisotropic many-body forces cause local cohesion but also a negative effective "surface tension." We conclude by deriving the equation of state for cvdW materials and propose experiments to test the theory, in particular the unusual three-body nature of cvdW.

  20. Van der Waals Epitaxy of Functional Oxide Heterostructures

    NASA Astrophysics Data System (ADS)

    Chu, Ying-Hao

    In the diligent pursuit of low-power consumption, multifunctional, and environmentally friendly electronics, more sophisticated requirements on functional materials are on demand. Recently, the discovery of 2D layered materials has created a revolution to this field. Pioneered by graphene, these new 2D materials exhibit abundant unusual physical phenomena that is undiscovered in bulk forms. These materials are characterized with their layer form and almost pure 2D electronic behavior. The confinement of charge and heat transport at such ultrathin planes offers possibilities to overcome the bottleneck of present device development in thickness limitation, and thus push the technologies into next generation. Van der Waals epitaxy, an epitaxial growth method to combine 2D and 3D materials, is one of current reliable manufacturing processes to fabricate 2D materials by growing these 2D materials epitaxially on 3D materials. Then, transferring the 2D materials to the substrates for practical applications. In the mean time, van der Waals epitaxy has also been used to create free-standing 3D materials by growing 3D materials on 2D materials and then removing them from 2D materials since the interfacial boding between 2D and 3D materials should be weak van der Waals bonds. In this study, we intend to take the same concept, but to integrate a family of functional materials in order to open new avenue to flexible electronics. Due to the interplay of lattice, charge, orbital, and spin degrees of freedom, correlated electrons in oxides generate a rich spectrum of competing phases and physical properties. Recently, lots of studies have suggested that oxide heterostructures provide a powerful route to create and manipulate the degrees of freedom and offer new possibilities for next generation devices, thus create a new playground for researchers to investigate novel physics and the emergence of fascinating states of condensed matter. In this talk, we use a 2D layered material as

  1. Jahre Entwicklung der Instandhaltung - von der ausfallorientierten Instandhaltung zum gemeinsamen TPM und RCM

    NASA Astrophysics Data System (ADS)

    Iske, Friedhelm

    Zur Einleitung meines Beitrages möchte ich von einem Gespräch mit einem Mitarbeiter berichten, das ich als junger Vorgesetzter einer Instandhaltungsgruppe 1988 führte. Der engagierte Mitarbeiter feierte damals sein vierzigjähriges Dienstjubiläum und war stolz auf das von ihm Geleistete sowie auf den besonderen Einsatz seiner Altersgruppe, die nach dem Zweiten Weltkrieg das Werk wieder aufgebaut hatte. Auf meine Frage, was denn damals die erste Aufgabe in der Firma war, bekam ich kurz und knapp und mit einer Selbstverständlichkeit die selbstbewusste Antwort: "Unser Pferd füttern und mit dem Pferd die innerbetrieblichen Transporte erledigen“. Als junger, technisch orientierter Vorgesetzter war ich über diese Antwort sehr überrascht. Gedanklich weit entfernt war die Vorstellung, dass in der Vergangenheit Transporte mit einem Pferd erledigt wurden.

  2. Der Telemanipulator daVinci als mechanisches Trackingsystem

    NASA Astrophysics Data System (ADS)

    Käst, Johannes; Neuhaus, Jochen; Nickel, Felix; Kenngott, Hannes; Engel, Markus; Short, Elaine; Reiter, Michael; Meinzer, Hans-Peter; Maier-Hein, Lena

    Der Telemanipulator daVinci (Intuitive Surgical, Sunnyvale, Kalifornien) ist ein M aster-Slave System für roboterassistierte minimalinvasive Chirurgie. Da er über integrierte Gelenksensoren verfügt, kann er unter Verwendung der daVinci-API als mechanisches Trackingsystem verwendet werden. In dieser Arbeit evaluieren wir die Präzision und Genauigkeit eines daVinci mit Hilfe eines Genauigkeitsphantoms mit bekannten Maßen. Der ermittelte Positionierungsfehler liegt in der Größenordnung von 6 mm und ist somit für einen Großteil der medizinischen Fragestellungen zu hoch. Zur Reduktion des Fehlers schlagen wir daher eine Kalibrierung der Gelenksensoren vor.

  3. Zum Wissenschaftsverständnis der modernen Evolutionsbiologie

    NASA Astrophysics Data System (ADS)

    Sommer, Ralf J.

    Die moderne Evolutionsbiologie hat ihren Ursprung in den Arbeiten von Charles Darwin und Alfred Wallace (Darwin 1963). Der gemeinsame Ausgangspunkt des Evolutionsgedanken ist dabei die Beobachtung, dass die biologische Welt nicht konstant ist. Biologische Systeme und alle darin lebenden Organismen unterliegen über längere Zeiträume hinweg einer stetigen Veränderung. Diese grundlegende Eigenschaft biologischer Systeme macht die Biologie zu einer historischen Wissenschaft und stellt einen wichtigen Gegensatz zu großen Teilen der Physik dar. Obwohl die Aussage von der Veränderlichkeit der Arten heute trivial klingt, war sie im 19. Jahrhundert eine Revolution, da die Konstanz der Arten und der Welt eine vorherrschende Stellung im damaligen Weltbild hatte (Amundson 2005).

  4. Exfoliation of natural van der Waals heterostructures to a single unit cell thickness

    PubMed Central

    Velický, Matěj; Toth, Peter S.; Rakowski, Alexander M.; Rooney, Aidan P.; Kozikov, Aleksey; Woods, Colin R.; Mishchenko, Artem; Fumagalli, Laura; Yin, Jun; Zólyomi, Viktor; Georgiou, Thanasis; Haigh, Sarah J.; Novoselov, Kostya S.; Dryfe, Robert A. W.

    2017-01-01

    Weak interlayer interactions in van der Waals crystals facilitate their mechanical exfoliation to monolayer and few-layer two-dimensional materials, which often exhibit striking physical phenomena absent in their bulk form. Here we utilize mechanical exfoliation to produce a two-dimensional form of a mineral franckeite and show that the phase segregation of chemical species into discrete layers at the sub-nanometre scale facilitates franckeite's layered structure and basal cleavage down to a single unit cell thickness. This behaviour is likely to be common in a wider family of complex minerals and could be exploited for a single-step synthesis of van der Waals heterostructures, as an alternative to artificial stacking of individual two-dimensional crystals. We demonstrate p-type electrical conductivity and remarkable electrochemical properties of the exfoliated crystals, showing promise for a range of applications, and use the density functional theory calculations of franckeite's electronic band structure to rationalize the experimental results. PMID:28194026

  5. Exfoliation of natural van der Waals heterostructures to a single unit cell thickness.

    PubMed

    Velický, Matěj; Toth, Peter S; Rakowski, Alexander M; Rooney, Aidan P; Kozikov, Aleksey; Woods, Colin R; Mishchenko, Artem; Fumagalli, Laura; Yin, Jun; Zólyomi, Viktor; Georgiou, Thanasis; Haigh, Sarah J; Novoselov, Kostya S; Dryfe, Robert A W

    2017-02-13

    Weak interlayer interactions in van der Waals crystals facilitate their mechanical exfoliation to monolayer and few-layer two-dimensional materials, which often exhibit striking physical phenomena absent in their bulk form. Here we utilize mechanical exfoliation to produce a two-dimensional form of a mineral franckeite and show that the phase segregation of chemical species into discrete layers at the sub-nanometre scale facilitates franckeite's layered structure and basal cleavage down to a single unit cell thickness. This behaviour is likely to be common in a wider family of complex minerals and could be exploited for a single-step synthesis of van der Waals heterostructures, as an alternative to artificial stacking of individual two-dimensional crystals. We demonstrate p-type electrical conductivity and remarkable electrochemical properties of the exfoliated crystals, showing promise for a range of applications, and use the density functional theory calculations of franckeite's electronic band structure to rationalize the experimental results.

  6. Exfoliation of natural van der Waals heterostructures to a single unit cell thickness

    NASA Astrophysics Data System (ADS)

    Velický, Matěj; Toth, Peter S.; Rakowski, Alexander M.; Rooney, Aidan P.; Kozikov, Aleksey; Woods, Colin R.; Mishchenko, Artem; Fumagalli, Laura; Yin, Jun; Zólyomi, Viktor; Georgiou, Thanasis; Haigh, Sarah J.; Novoselov, Kostya S.; Dryfe, Robert A. W.

    2017-02-01

    Weak interlayer interactions in van der Waals crystals facilitate their mechanical exfoliation to monolayer and few-layer two-dimensional materials, which often exhibit striking physical phenomena absent in their bulk form. Here we utilize mechanical exfoliation to produce a two-dimensional form of a mineral franckeite and show that the phase segregation of chemical species into discrete layers at the sub-nanometre scale facilitates franckeite's layered structure and basal cleavage down to a single unit cell thickness. This behaviour is likely to be common in a wider family of complex minerals and could be exploited for a single-step synthesis of van der Waals heterostructures, as an alternative to artificial stacking of individual two-dimensional crystals. We demonstrate p-type electrical conductivity and remarkable electrochemical properties of the exfoliated crystals, showing promise for a range of applications, and use the density functional theory calculations of franckeite's electronic band structure to rationalize the experimental results.

  7. Devices and applications of van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Li, Chao; Zhou, Peng; Zhang, David Wei

    2017-03-01

    Van der Waals heterostructures, composed of individual two-dimensional material have been developing extremely fast. Synthesis of van der Waals heterostructures without the constraint of lattice matching and processing compatibility provides an ideal platform for fundamental research and new device exploitation. We review the approach of synthesis of van der Waals heterostructures, discuss the property of heterostructures and thoroughly illustrate the functional van der Waals heterostructures used in novel electronic and photoelectronic device. Project supported by the National Key Research and Development Program (No. 2016YFA0203900) and the National Natural Science Foundation of China (Nos. 61376093, 61622401).

  8. Synchronization of two memristively coupled van der Pol oscillators

    NASA Astrophysics Data System (ADS)

    Ignatov, M.; Hansen, M.; Ziegler, M.; Kohlstedt, H.

    2016-02-01

    The objective of this letter is to convey two essential principles of biological computing—synchronization and memory—in an electronic circuit with two van der Pol (vdP) oscillators coupled via a memristive device. The coupling was mediated by connecting the gate terminals of two programmable unijunction transistors through a resistance-capacitance network comprising an Ag-TiOx-Al memristive device. In the high resistance state the memristance was in the order of MΩ, which leads to two independent self-sustained oscillators characterized by the different frequencies f1 and f2 and no phase relation between the oscillations. Depending on the mediated pulse amplitude, the memristive device switched to the low resistance state after a few cycles and a frequency adaptation and phase locking were observed. The experimental results are underlined by theoretically considering a system of two coupled vdP equations. This experiment may pave the way to larger neuromorphic networks in which the coupling parameters (through memristive devices) can vary in time and strength and are able to remember the history of applied electrical potentials.

  9. Die Deutsche Statistische Gesellschaft in der Weimarer Republik und während der Nazidiktatur

    NASA Astrophysics Data System (ADS)

    Wilke, Jürgen

    Nach anfänglichen Schwierigkeiten durch den 1. Weltkrieg erlangte die Deutsche Statistische Gesellschaft (DStatG) unter dem renommierten Statistiker und Vorsitzenden der DStatG, Friedrich Zahn, durch eine Vielzahl von Aktivitäten hohes Ansehen. Es gab Bestrebungen, Statistiker aus allen Arbeitsfeldern der Statistik in die DStatG zu integrieren, wobei die "Mathematische Statistik" nur zögerlich akzeptiert wurde (Konjunkturforschung, Zeitreihenanalyse). Nach der Machtübernahme 1933 durch Adolf Hitler geriet die DStatG in das Fahrwasser nationalsozialistischer Ideologie und Politik (Führerprinzip, Gleichschaltung des Vereinswesens). Damit war eine personelle Umstrukturierung in der DStatG verbunden. Politisch Missliebige und rassisch Verfolgte mussten die DStatG verlassen (Bernstein, Freudenberg, Gumbel u.a.). Unter den Statistikern gab es alle Abstufungen im Verhalten zum Regime von Ablehnung und zwangsweiser Anpassung über bereitwilliges Mitläufertum bis zu bewusster Täterschaft. Besonders die Bevölkerungsstatistik wurde durch die NS- Rassenpolitik auf lange Sicht diskreditiert. Im Rahmen von Wirtschaftsplanung und Aufrüstung wurden neue zukunftsträchtige statistische Modelle (Grünig, Bramstedt, Leisse) entwickelt.

  10. Shock dynamics of phase diagrams

    SciTech Connect

    Moro, Antonio

    2014-04-15

    A thermodynamic phase transition denotes a drastic change of state of a physical system due to a continuous change of thermodynamic variables, as for instance pressure and temperature. The classical van der Waals equation of state is the simplest model that predicts the occurrence of a critical point associated with the gas–liquid phase transition. Nevertheless, below the critical temperature theoretical predictions of the van der Waals theory significantly depart from the observed physical behaviour. We develop a novel approach to classical thermodynamics based on the solution of Maxwell relations for a generalised family of nonlocal entropy functions. This theory provides an exact mathematical description of discontinuities of the order parameter within the phase transition region, it explains the universal form of the equations of state and the occurrence of triple points in terms of the dynamics of nonlinear shock wave fronts. -- Highlights: •A new generalisation of van der Waals equation of state. •Description of phase transitions in terms of shock dynamics of state curves. •Proof of the universality of equations of state for a general class of models. •Interpretation of triple points as confluence of classical shock waves. •Correspondence table between thermodynamics and nonlinear conservation laws.

  11. van der Waals Heterostructures Grown by MBE

    NASA Astrophysics Data System (ADS)

    Hinkle, Christopher

    In this work, we demonstrate the high-quality MBE heterostructure growth of various layered 2D materials by van der Waals epitaxy (VDWE). The coupling of different types of van der Waals materials including transition metal dichalcogenide thin films (e.g., WSe2, WTe2, HfSe2) , insulating hexagonal boron nitride (h-BN), and topological insulators (e.g., Bi2Se3) allows for the fabrication of novel electronic devices that take advantage of unique quantum confinement and spin-based characteristics. The relaxed lattice-matching criteria of van der Waals epitaxy has allowed for high-quality heterostructure growth with atomically abrupt interfaces, allowing us to couple these materials based primarily on their band alignment and electronic properties. We will discuss the impact of sample preparation, surface reactivity, and lattice mismatch of various substrates (sapphire, graphene, TMDs, Bi2Se3) on the growth mode and quality of the films and will discuss our studies of substrate temperature and flux rates on the resultant growth and grain size. Structural and chemical characterization was conducted via reflection high energy electron diffraction (RHEED, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning tunneling microscopy/spectroscopy (STM/S), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Experimentally determined band alignments have been determined and compared with first-principles calculations allowing the design of novel low-power logic and magnetic memory devices. Initial results from the electrical characterization of these grown thin films and some simple devices will also be presented. These VDWE grown layered 2D materials show significant potential for fabricating novel heterostructures with tunable band alignments and magnetic properties for a variety of nanoelectronic and optoelectronic applications.

  12. Kanban - der Weg ist das Ziel

    NASA Astrophysics Data System (ADS)

    Aull, Florian; Berlak, Joachim; Dickmann, Eva; Dickmann, Philipp; Fischäder, Holm; Gerlach, Joachim; Henneberg, Jens; Kapalla, Klaus; Kress, Oliver; Kuttler, Robert; Schneider, Herfried M.; Schürle, Philipp; Stellpflug, Franz-Josef; Wannenwetsch, Ralph; Wulz, Johannes; Zäh, Michael F.

    Wenn man aktuell Produktionsbereiche in Deutschland und Europa besucht, fallen im Zusammenhang mit modernen Produktionsmethoden immer öfter die Begriffe Kanban (jap. Karte, Signal) und Pull-Produktion, und dies nicht ohne Stolz, da diese mit dem schillernden Vorbild des Toyota Produktionssystems in Zusammenhang stehen. Tatsächlich ist Kanban ein integraler Bestandteil moderner Produktionssysteme. Blickt man aber im Rahmen von Prozessanalysen hinter die Fassaden", d. h. in die tägliche Praxis der Arbeitsprozesse, wird man schnell desillusioniert - die viel gepriesenen klassischen Kanban-Regeln werden im Tagesgeschäft nicht eingehalten.

  13. Komplexität der Geographie

    NASA Astrophysics Data System (ADS)

    Diekert, Volker; Hertrampf, Ulrich

    Das allgemein als Prototyp eines PSPACE-vollständigen Spiels gesehene Geographiespiel wird bezüglich seiner Komplexität genauer untersucht. Das Interesse der theoretischen Informatik an diesem Spiel wurde sehr durch die Darstellung in dem Lehrbuch von Papadimitriou [Pap94] gefördert. Allerdings bestimmt dieses Lehrbuch nicht die Komplexität des Standardspiels sondern verwendet eine Verallgemeinerung. Die Aussage in dem Lehrbuch bleibt damit etwas unbefriedigend und hinter den Möglichkeiten. Wir zeigen hier, dass die komplexitätstheoretische Charakterisierung schon für die Standardvariante des Spiels gilt.

  14. A van der Waals-type equation of state for fluids with associating molecules

    PubMed Central

    Heidemann, Robert A.; Prausnitz, J. M.

    1976-01-01

    The basic assumptions of van der Waals theory are contained in two well-known concepts: excluded volume (repulsive forces) and a homogeneous, isotropic field potential (attractive forces). We have superimposed on these, one more well-known concept: the existence of dimers, trimers, etc., at chemical equilibrium. With reasonable simplifying assumptions, we obtain a closed-form equation of state, applicable to all fluid densities, and potentially useful for fluids containing strongly polar or hydrogen-bonded molecules. At all temperatures and at high densities, the equation of state suggests a phase transition where, because of extensive association, a new (solid-like) phase is in equilibrium with a “normal” fluid phase. The boundary between these phases has no critical point. PMID:16592320

  15. Physik gestern und heute: Visualisierung mit der Schlierenmethode

    NASA Astrophysics Data System (ADS)

    Heering, Peter

    2006-07-01

    Der Name des österreichischen Forschers Ernst Mach ist heute noch mit der Schallgeschwindigkeit verbunden. Diese Auszeichnung resultiert aus Machs Untersuchungen, wie sich Projektile mit Überschallgeschwindigkeit durch die Luft bewegen. Gerade in jüngster Zeit hat die Anwendung derartiger Methoden durch technische Modifikationen wieder einen Aufschwung erfahren.

  16. Crystal Structures of Mite Allergens Der f 1 and Der p 1 Reveal Differences in Surface-Exposed Residues that May Influence Antibody Binding

    SciTech Connect

    Chruszcz, Maksymilian; Chapman, Martin D.; Vailes, Lisa D.; Stura, Enrico A.; Saint-Remy, Jean-Marie; Minor, Wladek; Pomés, Anna

    2009-12-01

    The Group 1 mite allergens, Der f 1 and Der p 1, are potent allergens excreted by Dermatophagoides farinae and Dermatophagoides pteronyssinus, respectively. The human IgE antibody responses to the Group 1 allergens show more cross-reactivity than the murine IgG antibody responses which are largely species-specific. Here, we report the crystal structure of the mature form of Der f 1, which was isolated from its natural source, and a new, high-resolution structure of mature recombinant Der p 1. Unlike Der p 1, Der f 1 is monomeric both in the crystalline state and in solution. Moreover, no metal binding is observed in the structure of Der f 1, despite the fact that all amino acids involved in Ca{sup 2+} binding in Der p 1 are completely conserved in Der f 1. Although Der p 1 and Der f 1 share extensive sequence identity, comparison of the crystal structures of both allergens revealed structural features which could explain the differences in murine and human IgE antibody responses to these allergens. There are structural differences between Der f 1 and Der p 1 which are unevenly distributed on the allergens' surfaces. This uneven spatial arrangement of conserved versus altered residues could explain both the specificity and cross-reactivity of antibodies against Der f 1 and Der p 1.

  17. Vollautomatische Segmentierung der Prostata aus 3D-Ultraschallbildern

    NASA Astrophysics Data System (ADS)

    Heimann, Tobias; Simpfendörfer, Tobias; Baumhauer, Matthias; Meinzer, Hans-Peter

    Diese Arbeit beschreibt ein modellbasiertes Verfahren zur Segmentierung der Prostata aus 3D-Ultraschalldaten. Kern der Methode ist ein statistisches Formmodell, das auf Beispieldaten der Prostata trainiert wird. Erster Schritt der Segmentierung ist ein evolutionärer Algorithmus, mit dem das Modell grob im zu segmentierenden Bild positioniert wird. Für die darauf folgende lokale Suche wurden mehrere Varianten des Algorithmus evaluiert, unter anderem Ausreißer-Unterdrückung, freie Deformation und Gewichtung der verwendeten Erscheinungsmodelle nach ihrer Zuverlässigkeit. Alle Varianten wurden auf 35 Ultraschallbildern getestet und mit manuellen Referenzsegmentierungen verglichen. Die beste Variante erreichte eine durchschnittliche Oberflächenabweichung von 1.1 mm.

  18. Scaling laws for van der Waals interactions in nanostructured materials.

    PubMed

    Gobre, Vivekanand V; Tkatchenko, Alexandre

    2013-01-01

    Van der Waals interactions have a fundamental role in biology, physics and chemistry, in particular in the self-assembly and the ensuing function of nanostructured materials. Here we utilize an efficient microscopic method to demonstrate that van der Waals interactions in nanomaterials act at distances greater than typically assumed, and can be characterized by different scaling laws depending on the dimensionality and size of the system. Specifically, we study the behaviour of van der Waals interactions in single-layer and multilayer graphene, fullerenes of varying size, single-wall carbon nanotubes and graphene nanoribbons. As a function of nanostructure size, the van der Waals coefficients follow unusual trends for all of the considered systems, and deviate significantly from the conventionally employed pairwise-additive picture. We propose that the peculiar van der Waals interactions in nanostructured materials could be exploited to control their self-assembly.

  19. Probabilistic characteristics of noisy Van der Pol type oscillator with nonlinear damping

    NASA Astrophysics Data System (ADS)

    Dubkov, A. A.; Litovsky, I. A.

    2016-05-01

    The exact Fokker-Planck equation for the joint probability distribution of amplitude and phase of a Van der Pol oscillator perturbed by both additive and multiplicative noise sources with arbitrary nonlinear damping is first derived by the method of functional splitting of averages. We truncate this equation in the usual manner using the smallness of the damping parameter and obtain a general expression for the stationary probability density function of oscillation amplitude, which is valid for any nonlinearity in the feedback loop of the oscillator. We analyze the dependence of this stationary solution on system parameters and intensities of noise sources for two different situations: (i) Van der Pol generator with soft and hard excitation regimes; (ii) Van der Pol oscillator with negative nonlinear damping. As shown, in the first case the probability distribution of amplitude demonstrates one characteristic maximum, which indicates the presence of a stable limit cycle in the system. The non-monotonic dependence of stationary probability density function on oscillation frequency is also detected. In the second case we examine separately three situations: linear oscillator with two noise sources, nonlinear oscillator with additive noise and nonlinear oscillator with frequency fluctuations. For the last two situations, noise-induced transitions in the system under consideration are found.

  20. elecTUM: Umsetzung der eLearning-Strategie der Technischen Universität München

    NASA Astrophysics Data System (ADS)

    Rathmayer, Sabine; Gergintchev, Ivan

    An der TUM wurde ein umfassendes und integriertes eLearning-Konzept umgesetzt, welches Präsenzstudium und eLearning in allen Leistungsbereichen der Universität miteinander verzahnt. Ein besonderer Schwerpunkt lag dabei in der Schaffung einer effizienten und wettbewerbsfähigen integrierten eLearning Infrastruktur in Hinblick auf die noch weiter steigenden Studienanfängerzahlen ab dem Jahr 2011 sowie die Umsetzung von eBologna. Die Etablierung einer hochschulweiten Lernplattform stellte eine wesentliche Basis für die Umsetzung der eLearning-Strategie dar. Die wissenschaftliche und wirtschaftliche Anschlussfähigkeit im Hinblick auf eine Verwertung der Projektergebnisse wurde durch die aktive Beteiligung an einer Vielzahl hochschulübergreifender Arbeitskreise, Fachtagungen und Kooperationen, vor allem über Organisations- und Dienstleistungsmodelle sowie innovative technische Entwicklungen, sichergestellt.

  1. Van Der Pol model of a Cerenkov maser

    SciTech Connect

    Kleckner, M.; Ron, A.; Botton, M.

    1995-12-31

    A non-linear analysis of a Cerenkov maser is presented. The system consists of a ring configuration of a cylindrical waveguide filled with a dielectric material. A single transverse-magnetic mode is assumed to propagate in the system. A low-density pencil electron beam travels in part of the ring, confined by a strong axial magnetic field. Using the single-particle description for the beam and the wave equation for the field, we obtain a set of two coupled non-linear differential equations describing the slowly varying amplitude and phase of the electromagnetic mode. The gain per path is assumed to be small and the spatial growth of the field is neglected. The resulting time dependent amplitude includes the exponential gain of the linear stage and the saturation to its maximum value. The time dependent frequency is also calculated. The two equations are combined to a single Van Der Pol equation with a non-linear restoring force. This description demonstrates the similarities and differences between the Cerenkov maser and other lasing systems.

  2. Helmholtz's early empiricism and the Erhaltung der Kraft.

    PubMed

    Jurkowitz, Edward

    2010-01-01

    Hermann Helmholtz has often been understood to have started research under the influence of Kant, and then to have made a transition to a later mature empiricist phase. Without claiming that in 1847 Helmholtz held the same positions that he later espoused, I suggest that already in his 1847 'Uber die Erhaltung der Kraft' one may find important aspects of his later empiricism. I highlight the ways in which, from early on, Helmholtz turned Kant to use in developing an empirical program of inquiry into possible basic natural causes. To that end, I indicate how, throughout his arguments, Helmholtz employed, sometimes explicitly, but often tacitly, an empiricist logic, one that ran contrary to any form of transcendental deduction, and even to all a priori knowledge. Instead of deriving aspects about the ultimate constituents of nature, Helmholtz aimed to define the proper project for physical natural science. The first part of the paper describes the context of discussion in which Helmholtz entered. The bulk of the paper then analyzes Helmholtz's arguments in order to make space between (1) Kantian, and other, deductions of characteristics that must be true of nature and (2) Helmholtz's delineation of empirically determinable characteristics of presumed ultimate elements of nature, ones that he meant to be specified and delimited through future experimental research. The paper highlights that throughout his discussion Helmholtz meant to define the proper project for physical natural science, a project rife with empiricist aspects.

  3. Berechnung der auftretenden lokalen Kräfte auf der magnetischen Beschichtung eines magnetischen Rasterkraftmikroskops

    NASA Astrophysics Data System (ADS)

    Preisner, T.; Mathis, W.

    2009-05-01

    Die numerische Berechnung entstehender Kraftwirkungen auf Körper aufgrund magnetischer Wechselwirkungen zwischen diesen, ist in Bezug auf die mechanische Deformation dieser Körper ein noch nicht vollständig gelöstes Problem. In dieser Arbeit wird ein Vergleich vorhandener Kraftberechnungsmethoden hinsichtlich der totalen Kraft anhand eines analytisch berechenbaren Beispiels vorgestellt, sowie Unterschiede der lokalen Kraftdichten dieser Methoden in Anwendung auf die magnetische Beschichtung eines magnetischen Rasterkraftmikroskops aufgezeigt. Due to magnetic interactions between magnetic field inducing bodies, force effects occur on the materials. The numerical computation of those occuring forces with respect to a subsequent structural analysis of a deformable material is still a topic of interest in research. In this paper a comparison between several existent force calculation methods regarding the total force is given for an example with two magnetic cubes. Furthermore, differences are shown concerning the local force densities on the magnetic coating of a magnetic force microscope.

  4. The effect of the London-van der Waals dispersion force on interline heat transfer

    NASA Technical Reports Server (NTRS)

    Wayner, P. C., Jr.

    1978-01-01

    A theoretical procedure to determine the heat transfer characteristics of the interline region (junction of liquid-solid-vapor) from the macroscopic optical and thermophysical properties of the system is outlined. The analysis is based on the premise that the interline transport processes are controlled by the London-van der Waals dispersion force between condensed phases (solid and liquid). Numerical values of the dispersion constant are presented. The procedure is used to compare the relative size of the interline heat sink of various systems using a constant heat flux mode. This solution demonstrates the importance of the interline heat flow number, which is evaluated for various systems.

  5. 3D van der Waals σ-model and its topological excitations

    NASA Astrophysics Data System (ADS)

    Bulgadaev, S. A.

    2001-09-01

    It is shown that the 3D vector van der Waals nonlinear σ-model (NSM) on a sphere S2 has two types of topological excitations: reminiscent vortices and instantons of 2D NSM. The first ones, the hedgehogs, are described by the homotopic group π2(S2) = Z and have logarithmic energies. They are an analog of 2D vortices. The second ones, corresponding to 2D instantons, are the hopfions. They are described by the homotopic group π3(S2) = Z, or the Hopf invariant HinZ, and have finite energy. The possibility of a topological phase transition in this model and its applications are briefly discussed.

  6. Der f 21, a novel allergen from dermatophagoides farina.

    PubMed

    Wu, Yulan; Jiang, Congli; Li, Meng; Yu, Haiqiong; Xiao, Xiaojun; Fan, Xiaoqin; Lin, Jianli; Liu, Xiaoyu; Zhang, Min; Yang, Pingchang; Liu, Zhigang

    2016-01-01

    The Dermatophagoides farina (D. farina) allergens are an important factor contributing to allergic disease. To identify new allergens is important for diagnosis and treatment of allergic diseases. In this study, we sought to characterize the biological activity of Der f 21 of D. farina. The recombinant Der f 21 protein was characterized by western-blot, ELISA and Skin prick test using clinic patient's serum.An allergic asthma mouse model was established with the rDer f 21 as a specific antigen. The results showed that the sera from 28.9% in 38 dust mite allergic children displayed positive results in response to rDer f 21, and 42% in 98 dust mite allergic patients displayed positive response in skin prick test. In addition, Immune inhibition assays showed there was IgE cross-reactivity between rDer f 21 and rDer f 5. Moreover, an allergic asthma mouse model was established. Airway hyperresponsiveness, serum specific IgE, IgG1, eosinophil infiltration in the allergic mice, interleukin-4(IL-4) and interferon-γ (INF-γ) from spleen cells were markedly increased in the allergic mice. The results demonstrate that Der f 21 is a novel allergen.

  7. Direct synthesis of van der Waals solids.

    PubMed

    Lin, Yu-Chuan; Lu, Ning; Perea-Lopez, Nestor; Li, Jie; Lin, Zhong; Peng, Xin; Lee, Chia Hui; Sun, Ce; Calderin, Lazaro; Browning, Paul N; Bresnehan, Michael S; Kim, Moon J; Mayer, Theresa S; Terrones, Mauricio; Robinson, Joshua A

    2014-04-22

    The stacking of two-dimensional layered materials, such as semiconducting transition metal dichalcogenides (TMDs), insulating hexagonal boron nitride (hBN), and semimetallic graphene, has been theorized to produce tunable electronic and optoelectronic properties. Here we demonstrate the direct growth of MoS2, WSe2, and hBN on epitaxial graphene to form large-area van der Waals heterostructures. We reveal that the properties of the underlying graphene dictate properties of the heterostructures, where strain, wrinkling, and defects on the surface of graphene act as nucleation centers for lateral growth of the overlayer. Additionally, we show that the direct synthesis of TMDs on epitaxial graphene exhibits atomically sharp interfaces. Finally, we demonstrate that direct growth of MoS2 on epitaxial graphene can lead to a 10(3) improvement in photoresponse compared to MoS2 alone.

  8. Hyperdislocations in van der Waals Layered Materials.

    PubMed

    Ly, Thuc Hue; Zhao, Jiong; Keum, Dong Hoon; Deng, Qingming; Yu, Zhiyang; Lee, Young Hee

    2016-12-14

    Dislocations are one-dimensional line defects in three-dimensional crystals or periodic structures. It is common that the dislocation networks made of interactive dislocations be generated during plastic deformation. In van der Waals layered materials, the highly anisotropic nature facilitates the formation of such dislocation networks, which is critical for the friction or exfoliation behavior for these materials. By transmission electron microscopy analysis, we found the topological defects in such dislocation networks can be perfectly rationalized in the framework of traditional dislocation theory, which we applied the name "hyperdislocations". Due to the strong pinning effect of hyperdislocations, the state of exfoliation can be easily triggered by 1° twisting between two layers, which also explains the origin of disregistry and frictionlessness for all of the superlubricants that are widely used for friction reduction and wear protection.

  9. Implantate und Verfahren in der Augenheilkunde

    NASA Astrophysics Data System (ADS)

    Neuhann, Tobias H.

    Das in der Medizin mit am häufigsten verwendete Implantat weltweit ist die Intraokulare Linse (IOL). Die Gründe hierfür sind vielschichtig: einmal haben die Operationstechniken in den letzten 30 Jahren eine wesentliche Steigerung an Gleichmäßigkeit, Erfolg und Effizienz erfahren, zum anderen verursachen die gestiegenen Anforderungen des Alltags in den Industrienationen und im Berufsleben den höheren Anspruch an das Sehvermögen. Ist die menschliche Linse Ursache für schlechtes Sehvermögen, besteht meist eine Trübung des Linsenproteins. Diese Trübung nennt wird Volksmund Grauer Star genannt, wissenschaftlich die Katarakt (cataracta). Es gibt unterschiedliche Formen wie angeborene (congenita) oder erworbene, traumatische, krankheitsoder altersbedingte Formen [45]. Wird die eingetrübte Linse nun mittels moderner Operationsverfahren entfernt, muss für Ersatz dieses lichtbrechenden Mediums gesorgt werden [2].

  10. Kernschmelze Der nachhaltige Einfluss von Nuklearwaffen auf Politik und Wirtschaft

    NASA Astrophysics Data System (ADS)

    Greiner, Bernd

    "Was sollen wir von einer Kultur halten, der die Ethik stets als wesentliches Element des menschlichen Lebens galt, die aber - außer in fachlicher oder spieltheoretischer Terminologie - nicht in der Lage war, über die Möglichkeit zu sprechen, nahezu alle Menschen zu töten?" Der Fragesteller gehört zu den berühmtesten Physikern des 20. Jahrhunderts und zu den nach wie vor Umstrittensten. über ihn wurde in den 1960er Jahren ein international viel beachtetes Theaterstück geschrieben, vor wenigen Jahren gar eine Oper.

  11. Einsteins Spuren in den Archiven der Wissenschaft: Physikgeschichte

    NASA Astrophysics Data System (ADS)

    Marx, Werner

    2005-07-01

    Die Erwähnungen und Zitierungen von Einsteins Arbeiten dokumentieren lediglich den quantifizierbaren Anteil von Einsteins Beitrag zur Physik. Gleichwohl belegen sie die außergewöhnliche Resonanz und Langzeitwirkung seiner Arbeiten. Die Häufigkeit der Zitierungen entspricht nicht der allgemeinen Einschätzung ihrer Bedeutung. Insbesondere die Pionierarbeiten werden inzwischen als bekannt vorausgesetzt und nicht mehr explizit zitiert. Interessanterweise ist seine nach 1945 meist zitierte Arbeit nicht eine der Pionierarbeiten zur Quantenphysik oder Relativitätstheorie, sondern jene aus dem Jahr 1935 zum berühmten Einstein-Podolsky-Rosen-Paradoxon.

  12. Nanophysik: Wärmeübertrag auf der Nanometerskala

    NASA Astrophysics Data System (ADS)

    Kittel, Achim

    2006-01-01

    Gegen Ende des 19. Jahrhunderts waren die grundlegenden Prozesse des Wärmeaustauschs verstanden. Die Gesetze dienten dann als Grundlage für die Quantenmechanik. Doch gelten diese Gesetze auch auf der Nanometerskala? In den 1970er-Jahren wurde eine Theorie für den Wärmeübertrag im atomaren Bereich entwickelt. Physiker der Universität Oldenburg überprüften deren Vorhersagen und stießen dabei auf signifikante Abweichungen, welche auf einen Zusammenbruch der klassischen, makroskopischen Elektrodynamik hindeuten.

  13. Isotope separation by photodissociation of Van der Waal's molecules

    DOEpatents

    Lee, Yuan T.

    1977-01-01

    A method of separating isotopes based on the dissociation of a Van der Waal's complex. A beam of molecules of a Van der Waal's complex containing, as one partner of the complex, a molecular species in which an element is present in a plurality of isotopes is subjected to radiation from a source tuned to a frequency which will selectively excite vibrational motion by a vibrational transition or through electronic transition of those complexed molecules of the molecular species which contain a desired isotope. Since the Van der Waal's binding energy is much smaller than the excitational energy of vibrational motion, the thus excited Van der Waal's complex dissociate into molecular components enriched in the desired isotope. The recoil velocity associated with vibrational to translational and rotational relaxation will send the separated molecules away from the beam whereupon the product enriched in the desired isotope can be separated from the constituents of the beam.

  14. Ein routine-integrierbares Planungswerkzeug zur operativen Rekonstruktion der Orbita

    NASA Astrophysics Data System (ADS)

    Kleiner, Melanie; Schulze, Dirk; Voss, Pit Jakob; Deserno, Thomas M.

    Bei Frakturen des Orbitabodens kann ein Titangitter zur Rekonstruktion operativ eingesetzt werden. In dieser Arbeit wird ein Planungswerkzeug entwickelt, welches mit Hilfe eines aktiven Konturmodells die Orbita in CT Daten segmentiert, ihr Volumen berechnet und visualisiert. Neben den technischen Integrationsstufen der Funktions- und Präsentationsintegration, welche durch den Einsatz des Medical Imaging Interaction Toolkit (MITK) erreicht werden, sowie der Daten-, und Kontextintegration ist vor allem die Stabilität der eingesetzten Algorithmik für die Routine-Integrierbarkeit wichtig. Erste Stabilitätsuntersuchungen basieren auf 3 von 100 zufällig ausgewählten CT-Datensätzen, wobei das Volumen mit je 50 verschiedenen Startpunkten berechnet wurde. Die so ermittelten Variationskoeffizienten liegen deutlich unterhalb der kritischen 5 % Schwelle.

  15. Demographische Entwicklung in der Metropolregion Berlin-Brandenburg

    NASA Astrophysics Data System (ADS)

    Beyer, Wolf; Bluth, Friedrich

    〝Denn eins ist sicher: Die Rente.`` Der vielzitierte Satz des früheren Arbeits- und Sozialministers Norbert Blüm klingt heute vielen wie Hohn. Der Altersaufbau der deutschen Bevölkerung erinnert grafisch immer mehr an einen Baum auf dünnem Stämmchen als an eine Pyramide. Angesichts dessen rücken demographische Entwicklungen mehr und mehr in den Fokus der Öffentlichkeit. Besonders die neuen Bundesländer sind massiv von Abwanderung und einem nie dagewesenen Geburtenrückgang betroffen.DIPL.-GEOGR. UTE C. BAUERsprach mitFRIEDRICH BLUTHundWOLF BEYERüber die Besonderheiten der demographischen Prozesse in Berlin und Brandenburg. Beyer leitete bis Anfang 2004 das brandenburgische Referat für Raumbeobachtung. Seine Aufgabe bestand darin, Planungsgrundlagen für die Gemeinsame Landesplanung Berlin-Brandenburg(GL) zu schaffen. Dazu zählen auch Bevölkerungsprognosen für die Kreise und Städte Brandenburgs. Bluth ist in der Senatsverwaltung für Stadtentwicklung Berlin beschäftigt und leitet dort die Gruppe 〝Stadtwissen, Stadtentwicklungsmonitoring, Bevölkerungsprognose.``

  16. Modified Van der Waals equation and law of corresponding states

    NASA Astrophysics Data System (ADS)

    Zhong, Wei; Xiao, Changming; Zhu, Yongkai

    2017-04-01

    It is well known that the Van der Waals equation is a modification of the ideal gas law, yet it can be used to describe both gas and liquid, and some important messages can be obtained from this state equation. However, the Van der Waals equation is not a precise state equation, and it does not give a good description of the law of corresponding states. In this paper, we expand the Van der Waals equation into its Taylor's series form, and then modify the fourth order expansion by changing the constant Virial coefficients into their analogous ones. Via this way, a more precise result about the law of corresponding states has been obtained, and the law of corresponding states can then be expressed as: in terms of the reduced variables, all fluids should obey the same equation with the analogous Virial coefficients. In addition, the system of 3 He with quantum effects has also been taken into consideration with our modified Van der Waals equation, and it is found that, for a normal system without quantum effect, the modification on ideal gas law from the Van der Waals equation is more significant than the real case, however, for a system with quantum effect, this modification is less significant than the real case, thus a factor is introduced in this paper to weaken or strengthen the modification of the Van der Waals equation, respectively.

  17. Die Anfaenge der Melker Bibliothek - Neue Erkenntnisse zu Handschriften und Fragmenten aus der Zeit vor 1200

    NASA Astrophysics Data System (ADS)

    Glaßner, Christine; Haidinger, Alois

    1996-04-01

    Shortly after Benedictine monks started monastic life in Melk in 1089 the scriptorium was flourishing under abbot Erchenfried (1121-1164). Noteworthy is Cod. 391, a manuscript written in its main part in 1123, but used by the monks as a yearbook with handwritten entries up to the 16th century. This manuscript was also an important source for the publication which dealt with the history of the scriptorium in 12th century. By examining the entries in this book the period of the activity of at least three unknwon writers in this era could be identified. It was the first time that not only the intact volumes but also the manuscripts preserved as fragments in the binding were examined. At the beginning of th 13th century the number of books held in the collection according to the result of this examination was 68. Another remarkable point of the exhibition and of the publication refering to the exhibition was Cod. 412, the oldest manuscript of the monastery, written in early 9th century and containing texts on natural sciences and astronomy by Venerable Bede. Three copies of this manuscript were done during 12th century, one of them probably in Melk, all of them with nearly identical consistency except the catalogue of signs of the zodiac which was ascribed erroneously to Venerable Bede in the Middle Ages: Vatican, Cod. Vat. lat. 643, Zwettl, Cod. 296 (copy of the Vatican manuscript), Klosterneuburg, Cod. 685 (copy of the Zwettl manuscript done in Klosterneuburg). Kurz nach Einführung der Benediktiner in Melk im Jahr 1089 erlebte das Melker Skriptorium unter Abt Erchenfried (1121-1163) seine erste Blüte. Hervorzuheben ist eine im Jahr 1123 angelegte Chronik, die bis in das 16. Jahrhundert durch Annaleneintragungen und andere wichtige Texte zur Geschichte des Klosters ergänzt wurde (Cod. 391). Diese Handschrift ist zugleich eine der wichtigsten Quellen zur Geschichte des Melker Skriptoriums im 12. Jahrhundert, dem sich die Publikation widmet. Mit Hilfe einer genaueren

  18. Van der Waals Effects on semiconductor clusters.

    PubMed

    Li, Haisheng; Chen, Weiguang; Han, Xiaoyu; Li, Liben; Sun, Qiang; Guo, Zhengxiao; Jia, Yu

    2015-09-30

    Van der Waals (vdW) interactions play an important role on semiconductors in nanoscale. Here, we utilized first-principles calculations based on density functional theory to demonstrate the growth mode transition from prolate to multiunit configurations for Gen (n = 10-50) clusters. In agreement with the injected ion drift tube techniques that "clusters with n < 70 can be thought of as loosely bound assemblies of small strongly bound fragments (such as Ge7 and Ge10 )," we found these stable fragments are connected by Ge6 , Ge9 , or Ge10 unit (from bulk diamond), via strong covalent bonds. Our calculated cations usually fragment to Ge7 and Ge10 clusters, in accordance with the experiment results that the spectra Ge7 and Ge10 correspond to the mass abundance spectra. By controlling a germanium cluster with vdW interactions parameters in the program or not, we found that the vdW effects strengthen the covalent bond from different units more strikingly than that in a single unit. With more bonds between units than the threadlike structures, the multiunit structures have larger vdW energies, explaining why the isolated nanowires are harder to produce. © 2015 Wiley Periodicals, Inc.

  19. Van der Waals Interactions Involving Proteins

    NASA Technical Reports Server (NTRS)

    Roth, Charles M.; Neal, Brian L.; Lenhoff, Abraham M.

    1996-01-01

    Van der Waals (dispersion) forces contribute to interactions of proteins with other molecules or with surfaces, but because of the structural complexity of protein molecules, the magnitude of these effects is usually estimated based on idealized models of the molecular geometry, e.g., spheres or spheroids. The calculations reported here seek to account for both the geometric irregularity of protein molecules and the material properties of the interacting media. Whereas the latter are found to fall in the generally accepted range, the molecular shape is shown to cause the magnitudes of the interactions to differ significantly from those calculated using idealized models. with important consequences. First, the roughness of the molecular surface leads to much lower average interaction energies for both protein-protein and protein-surface cases relative to calculations in which the protein molecule is approximated as a sphere. These results indicate that a form of steric stabilization may be an important effect in protein solutions. Underlying this behavior is appreciable orientational dependence, one reflection of which is that molecules of complementary shape are found to exhibit very strong attractive dispersion interactions. Although this has been widely discussed previously in the context of molecular recognition processes, the broader implications of these phenomena may also be important at larger molecular separations, e.g., in the dynamics of aggregation, precipitation, and crystal growth.

  20. Van der Waals Interactions in Aspirin

    NASA Astrophysics Data System (ADS)

    Reilly, Anthony; Tkatchenko, Alexandre

    2015-03-01

    The ability of molecules to yield multiple solid forms, or polymorphs, has significance for diverse applications ranging from drug design and food chemistry to nonlinear optics and hydrogen storage. In particular, aspirin has been used and studied for over a century, but has only recently been shown to have an additional polymorphic form, known as form II. Since the two observed solid forms of aspirin are degenerate in terms of lattice energy, kinetic effects have been suggested to determine the metastability of the less abundant form II. Here, first-principles calculations provide an alternative explanation based on free-energy differences at room temperature. The explicit consideration of many-body van der Waals interactions in the free energy demonstrates that the stability of the most abundant form of aspirin is due to a subtle coupling between collective electronic fluctuations and quantized lattice vibrations. In addition, a systematic analysis of the elastic properties of the two forms of aspirin rules out mechanical instability of form II as making it metastable.

  1. Van der Waals Force Assisted Heat Transfer

    NASA Astrophysics Data System (ADS)

    Sasihithlu, K.; Pendry, J. B.; Craster, R. V.

    2017-02-01

    Phonons (collective atomic vibrations in solids) are more effective in transporting heat than photons. This is the reason why the conduction mode of heat transport in nonmetals (mediated by phonons) is dominant compared to the radiation mode of heat transport (mediated by photons). However, since phonons are unable to traverse a vacuum gap (unlike photons), it is commonly believed that two bodies separated by a gap cannot exchange heat via phonons. Recently, a mechanism was proposed [J. B. Pendry, K. Sasihithlu, and R. V. Craster, Phys. Rev. B 94, 075414 (2016)] by which phonons can transport heat across a vacuum gap - through the Van der Waals interaction between two bodies with gap less than the wavelength of light. Such heat transfer mechanisms are highly relevant for heating (and cooling) of nanostructures; the heating of the flying heads in magnetic storage disks is a case in point. Here, the theoretical derivation for modelling phonon transmission is revisited and extended to the case of two bodies made of different materials separated by a vacuum gap. Magnitudes of phonon transmission, and hence the heat transfer, for commonly used materials in the micro- and nano-electromechanical industry are calculated and compared with the calculation of conduction heat transfer through air for small gaps as well as the heat transfer calculation due to photon exchange.

  2. Van der Waals interactions involving proteins.

    PubMed Central

    Roth, C M; Neal, B L; Lenhoff, A M

    1996-01-01

    Van der Waals (dispersion) forces contribute to interactions of proteins with other molecules or with surfaces, but because of the structural complexity of protein molecules, the magnitude of these effects is usually estimated based on idealized models of the molecular geometry, e.g., spheres or spheroids. The calculations reported here seek to account for both the geometric irregularity of protein molecules and the material properties of the interacting media. Whereas the latter are found to fall in the generally accepted range, the molecular shape is shown to cause the magnitudes of the interactions to differ significantly from those calculated using idealized models, with important consequences. First, the roughness of the molecular surface leads to much lower average interaction energies for both protein-protein and protein-surface cases relative to calculations in which the protein molecule is approximated as a sphere. These results indicate that a form of steric stabilization may be an important effect in protein solutions. Underlying this behavior is appreciable orientational dependence, one reflection of which is that molecules of complementary shape are found to exhibit very strong attractive dispersion interactions. Although this has been widely discussed previously in the context of molecular recognition processes, the broader implications of these phenomena may also be important at larger molecular separations, e.g., in the dynamics of aggregation, precipitation, and crystal growth. Images FIGURE 3 PMID:8789115

  3. Microstructure-dependent dynamic stability analysis of torsional NEMS scanner in van der Waals regime

    NASA Astrophysics Data System (ADS)

    Abdi, Javad; Keivani, Maryam; Abadyan, Mohamadreza

    2016-06-01

    The physico-mechanical behavior of nanoscale devices might be microstructure dependent. However, the classical continuum theory cannot correctly predict the microstructure dependency. In this paper, the strain gradient theory is employed to examine the instability characteristics of a nanoscanner with circular geometry. The governing equation of the scanner is derived incorporating the Coulomb and van der Waals (vdW) forces. The influences of applied voltage, squeeze damping and microstructure parameters on the dynamic instability of equilibrium points are studied by plotting the phase portrait and bifurcation diagrams. In the presence of the applied voltage, the phase portrait shows the saddle-node bifurcation while for freestanding scanner a subcritical pitchfork bifurcation is observed. It is concluded that the microstructure parameter enhances the torsional stability.

  4. Stufenweise Integration von eLearning an der Technischen Universität München

    NASA Astrophysics Data System (ADS)

    Pätzold, Sebastian; Graf, Stephan; Gergintchev, Ivan; Pongratz, Hans; Rathmayer, Sabine

    Der vorliegende Beitrag beschreibt als Best Practice Beispiel die stufenweise Integration eines Learning Management Systems (LMS) in die Infrastruktur von Information und Kommunikation (IuK) der Technischen Universität München (TUM). Dabei wird sowohl die Konsolidierung mehrfach angebotener Funktionalitäten und Dienste in den verschiedenen Portalen der Universität als auch die sukzessive Optimierung der Abläufe aufgezeigt. Gleichzeitig wird auf zukünftige weitere Entwicklungen hin zu einer vollständigen Integration der IuK, aber auch auf die Probleme in den unterschiedlichen Stadien der Entwicklung eingegangen.

  5. Van der Waals interaction in uniaxial anisotropic media.

    PubMed

    Kornilovitch, Pavel E

    2013-01-23

    Van der Waals interactions between flat surfaces in uniaxial anisotropic media are investigated in the nonretarded limit. The main focus is the effect of nonzero tilt between the optical axis and the surface normal on the strength of the van der Waals attraction. General expressions for the van der Waals free energy are derived using the surface mode method and the transfer-matrix formalism. To facilitate numerical calculations a temperature-dependent three-band parameterization of the dielectric tensor of the liquid crystal 5CB is developed. A solid slab immersed in a liquid crystal experiences a van der Waals torque that aligns the surface normal relative to the optical axis of the medium. The preferred orientation is different for different materials. Two solid slabs in close proximity experience a van der Waals attraction that is strongest for homeotropic alignment of the intervening liquid crystal for all the materials studied. The results have implications for the stability of plate-like colloids in liquid crystal hosts.

  6. Materials perspective on Casimir and van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Woods, L. M.; Dalvit, D. A. R.; Tkatchenko, A.; Rodriguez-Lopez, P.; Rodriguez, A. W.; Podgornik, R.

    2016-10-01

    Interactions induced by electromagnetic fluctuations, such as van der Waals and Casimir forces, are of universal nature present at any length scale between any types of systems. Such interactions are important not only for the fundamental science of materials behavior, but also for the design and improvement of micro- and nanostructured devices. In the past decade, many new materials have become available, which has stimulated the need for understanding their dispersive interactions. The field of van der Waals and Casimir forces has experienced an impetus in terms of developing novel theoretical and computational methods to provide new insights into related phenomena. The understanding of such forces has far reaching consequences as it bridges concepts in materials, atomic and molecular physics, condensed-matter physics, high-energy physics, chemistry, and biology. This review summarizes major breakthroughs and emphasizes the common origin of van der Waals and Casimir interactions. Progress related to novel ab initio modeling approaches and their application in various systems, interactions in materials with Dirac-like spectra, force manipulations through nontrivial boundary conditions, and applications of van der Waals forces in organic and biological matter are examined. The outlook of the review is to give the scientific community a materials perspective of van der Waals and Casimir phenomena and stimulate the development of experimental techniques and applications.

  7. Phases and Phase Transitions

    NASA Astrophysics Data System (ADS)

    Gitterman, Moshe

    2014-09-01

    In discussing phase transitions, the first thing that we have to do is to define a phase. This is a concept from thermodynamics and statistical mechanics, where a phase is defined as a homogeneous system. As a simple example, let us consider instant coffee. This consists of coffee powder dissolved in water, and after stirring it we have a homogeneous mixture, i.e., a single phase. If we add to a cup of coffee a spoonful of sugar and stir it well, we still have a single phase -- sweet coffee. However, if we add ten spoonfuls of sugar, then the contents of the cup will no longer be homogeneous, but rather a mixture of two homogeneous systems or phases, sweet liquid coffee on top and coffee-flavored wet sugar at the bottom...

  8. A cartography of the van der Waals territories.

    PubMed

    Alvarez, Santiago

    2013-06-28

    The distribution of distances from atoms of a particular element E to a probe atom X (oxygen in most cases), both bonded and intermolecular non-bonded contacts, has been analyzed. In general, the distribution is characterized by a maximum at short E···X distances corresponding to chemical bonds, followed by a range of unpopulated distances--the van der Waals gap--and a second maximum at longer distances--the van der Waals peak--superimposed on a random distribution function that roughly follows a d(3) dependence. The analysis of more than five million interatomic "non-bonded" distances has led to the proposal of a consistent set of van der Waals radii for most naturally occurring elements, and its applicability to other element pairs has been tested for a set of more than three million data, all of them compared to over one million bond distances.

  9. Stabilization of thin liquid films by repulsive van der Waals force.

    PubMed

    Li, Er Qiang; Vakarelski, Ivan U; Chan, Derek Y C; Thoroddsen, Sigurdur T

    2014-05-13

    Using high-speed video recording of bubble rise experiments, we study the stability of thin liquid films trapped between a rising bubble and a surfactant-free liquid-liquid meniscus interface. Using different combinations of nonpolar oils and water that are all immiscible, we investigate the extent to which film stability can be predicted by attractive and repulsive van der Waals (vdW) interactions that are indicated by the relative magnitude of the refractive indices of the liquid combinations, for example, water (refractive index, n = 1.33), perfluorohexane (n = 1.23), and tetradecane (n = 1.43). We show that, when the film-forming phase was oil (perfluorohexane or tetradecane), the stability of the film could always be predicted from the sign of the vdW interaction, with a repulsive vdW force resulting in a stable film and an attractive vdW force resulting in film rupture. However, if aqueous electrolyte is the film-forming bulk phase between the rising air bubble and the upper oil phase, the film always ruptured, even when a repulsive vdW interaction was predicted. We interpret these results as supporting the hypothesis that a short-ranged hydrophobic attraction determines the stability of the thin water film formed between an air phase and a nonpolar oil phase.

  10. The Economics of van der Waals Force Engineering

    NASA Astrophysics Data System (ADS)

    Pinto, Fabrizio

    2008-01-01

    As micro-electro-mechanical system (MEMS) fabrication continues on an ever-decreasing scale, new technological challenges must be successfully negotiated if Moore's Law is to be an even approximately valid model of the future of device miniaturization. Among the most significant obstacles is the existence of strong surface forces related to quantum mechanical van der Waals interatomic interactions, which rapidly diverge as the distance between any two neutral boundaries decreases. The van der Waals force is a contributing factor in several device failures and limitations, including, for instance, stiction and oscillator non-linearities. In the last decade, however, it has been conclusively shown that van der Waals forces are not just a MEMS limitation but can be engineered in both magnitude and sign so as to enable classes of proprietary inventions which either deliver novel capabilities or improve upon existing ones. The evolution of van der Waals force research from an almost exclusively theoretical field in quantum-electro-dynamics to an enabling nanotechnology discipline represents a useful example of the ongoing paradigm shift from government-centered to private-capital funded R&D in cutting-edge physics leading to potentially profitable products. In this paper, we discuss the reasons van der Waals force engineering may lead to the creation of thriving markets both in the short and medium terms by highlighting technical challenges that can be competitively addressed by this novel approach. We also discuss some notable obstacles to the cultural transformation of the academic research community required for the emergence of a functional van der Waals force engineering industry worldwide.

  11. Adsorption by design: Tuning atom-graphene van der Waals interactions via mechanical strain

    NASA Astrophysics Data System (ADS)

    Nichols, Nathan S.; Del Maestro, Adrian; Wexler, Carlos; Kotov, Valeri N.

    2016-05-01

    We aim to understand how the van der Waals force between neutral adatoms and a graphene layer is modified by uniaxial strain and electron correlation effects. A detailed analysis is presented for three atoms (He, H, and Na) and graphene strain ranging from weak to moderately strong. We show that the van der Waals potential can be significantly enhanced by strain, and present applications of our results to the problem of elastic scattering of atoms from graphene. In particular, we find that quantum reflection can be significantly suppressed by strain, meaning that dissipative inelastic effects near the surface become of increased importance. Furthermore, we introduce a method to independently estimate the Lennard-Jones parameters used in an effective model of He interacting with graphene, and determine how they depend on strain. At short distances, we find that strain tends to reduce the interaction strength by pushing the location of the adsorption potential minima to higher distances above the deformed graphene sheet. This opens up the exciting possibility of mechanically engineering an adsorption potential, with implications for the formation and observation of anisotropic low-dimensional superfluid phases.

  12. Understanding corrosion inhibition with van der Waals DFT methods: the case of benzotriazole.

    PubMed

    Gattinoni, Chiara; Michaelides, Angelos

    2015-01-01

    The corrosion of materials is an undesirable and costly process affecting many areas of technology and everyday life. As such, considerable effort has gone into understanding and preventing it. Organic molecule based coatings can in certain circumstances act as effective corrosion inhibitors. Although they have been used to great effect for more than sixty years, how they function at the atomic-level is still a matter of debate. In this work, computer simulation approaches based on density functional theory are used to investigate benzotriazole (BTAH), one of the most widely used and studied corrosion inhibitors for copper. In particular, the structures formed by protonated and deprotonated BTAH molecules on Cu(111) have been determined and linked to their inhibiting properties. It is found that hydrogen bonding, van der Waals interactions and steric repulsions all contribute in shaping how BTAH molecules adsorb, with flat-lying structures preferred at low coverage and upright configurations preferred at high coverage. The interaction of the dehydrogenated benzotriazole molecule (BTA) with the copper surface is instead dominated by strong chemisorption via the azole moiety with the aid of copper adatoms. Structures of dimers or chains are found to be the most stable structures at all coverages, in good agreement with scanning tunnelling microscopy results. Benzotriazole thus shows a complex phase behaviour in which van der Waals forces play an important role and which depends on coverage and on its protonation state and all of these factors feasibly contribute to its effectiveness as a corrosion inhibitor.

  13. Two-dimensional antimonene single crystals grown by van der Waals epitaxy

    NASA Astrophysics Data System (ADS)

    Ji, Jianping; Song, Xiufeng; Liu, Jizi; Yan, Zhong; Huo, Chengxue; Zhang, Shengli; Su, Meng; Liao, Lei; Wang, Wenhui; Ni, Zhenhua; Hao, Yufeng; Zeng, Haibo

    2016-11-01

    Unlike the unstable black phosphorous, another two-dimensional group-VA material, antimonene, was recently predicted to exhibit good stability and remarkable physical properties. However, the synthesis of high-quality monolayer or few-layer antimonenes, sparsely reported, has greatly hindered the development of this new field. Here, we report the van der Waals epitaxy growth of few-layer antimonene monocrystalline polygons, their atomical microstructure and stability in ambient condition. The high-quality, few-layer antimonene monocrystalline polygons can be synthesized on various substrates, including flexible ones, via van der Waals epitaxy growth. Raman spectroscopy and transmission electron microscopy reveal that the obtained antimonene polygons have buckled rhombohedral atomic structure, consistent with the theoretically predicted most stable β-phase allotrope. The very high stability of antimonenes was observed after aging in air for 30 days. First-principle and molecular dynamics simulation results confirmed that compared with phosphorene, antimonene is less likely to be oxidized and possesses higher thermodynamic stability in oxygen atmosphere at room temperature. Moreover, antimonene polygons show high electrical conductivity up to 104 S m-1 and good optical transparency in the visible light range, promising in transparent conductive electrode applications.

  14. ders deformation and superplastic flow of metals extruded by KOBO method

    NASA Astrophysics Data System (ADS)

    Korbel, Andrzej; Bochniak, Włodzimierz

    2013-05-01

    The work brings the results of the study on mechanical properties of some metallic materials subjected to very large plastic deformation by KOBO extrusion. The unexpected features of the KOBO products like Lüders deformation in pure metals and superplastic flow in coarse grain materials are discussed in terms of micro- and nano-scale elements of their structure. The choice to the experiment materials having different crystallographic and phase structure (commercial purity aluminium, multiphase aluminium 7075 alloy, pure zinc and multiphase magnesium AZ91 alloy) and different history (extrusion, casting) allowed to identify the common nano-size elements of the structure generated during the KOBO deformation which seems to be responsible for the mechanical behaviour of these materials. In particular, clusters of point defects (self-interstitials) formed under the KOBO extrusion conditions (cyclic change in the deformation path, high hydrostatic pressure) were found in these materials regardless of grain size and material early history. They correlate with appearance of unstable Lüders-like or even Portevin-LeChatelier deformation at ambient and superplastic flow at elevated temperatures.

  15. Two-dimensional antimonene single crystals grown by van der Waals epitaxy

    PubMed Central

    Ji, Jianping; Song, Xiufeng; Liu, Jizi; Yan, Zhong; Huo, Chengxue; Zhang, Shengli; Su, Meng; Liao, Lei; Wang, Wenhui; Ni, Zhenhua; Hao, Yufeng; Zeng, Haibo

    2016-01-01

    Unlike the unstable black phosphorous, another two-dimensional group-VA material, antimonene, was recently predicted to exhibit good stability and remarkable physical properties. However, the synthesis of high-quality monolayer or few-layer antimonenes, sparsely reported, has greatly hindered the development of this new field. Here, we report the van der Waals epitaxy growth of few-layer antimonene monocrystalline polygons, their atomical microstructure and stability in ambient condition. The high-quality, few-layer antimonene monocrystalline polygons can be synthesized on various substrates, including flexible ones, via van der Waals epitaxy growth. Raman spectroscopy and transmission electron microscopy reveal that the obtained antimonene polygons have buckled rhombohedral atomic structure, consistent with the theoretically predicted most stable β-phase allotrope. The very high stability of antimonenes was observed after aging in air for 30 days. First-principle and molecular dynamics simulation results confirmed that compared with phosphorene, antimonene is less likely to be oxidized and possesses higher thermodynamic stability in oxygen atmosphere at room temperature. Moreover, antimonene polygons show high electrical conductivity up to 104 S m−1 and good optical transparency in the visible light range, promising in transparent conductive electrode applications. PMID:27845327

  16. Curves of growth for van der Waals broadened spectral lines

    NASA Technical Reports Server (NTRS)

    Park, C.

    1980-01-01

    Curves of growth are evaluated for a spectral line broadened by the van der Waals interactions during collisions. The growth of the equivalent widths of such lines is shown to be dependent on the product of the perturber density and the 6/10 power of the van der Waals potential coefficient. When the parameter is small, the widths grow as the 1/2 power of the optical depth as they do for the Voigt profile: but when the parameter is large, they grow as 2/3 power and, hence, faster than the Voigt profile. An approximate analytical expression for the computed growth characteristics is given.

  17. Aufbau und Anpassung der Motorsteuerungs-Software für Otto- und Dieselmotoren

    NASA Astrophysics Data System (ADS)

    Stuhler, Harald; Ricken, Volker; Diener, René

    Die Erfüllung steigender Kundenansprüche und strenger gesetzlicher Vorgaben hinsichtlich der Verringerung des Kraftstoffverbrauchs, der Reduzierung von Schadstoffemissionen, der Erhöhung von Fahrsicherheit, Fahrleistung und Fahrkomfort ist untrennbar mit dem Einzug elektronischer Systeme in moderne Kraftfahrzeuge verbunden. Die elektronischen Systeme bestimmen zunehmend den Kundennutzen und werden für die Differenzierung der Automobilhersteller untereinander immer wichtiger. Daher sind sie ein wesentlicher Erfolgsfaktor moderner Kraftfahrzeuge.

  18. Phase diagram of crushed powders

    NASA Astrophysics Data System (ADS)

    Bodard, Sébastien; Jalbaud, Olivier; Saurel, Richard; Burtschell, Yves; Lapebie, Emmanuel

    2016-12-01

    Compression of monodisperse powder samples in quasistatic conditions is addressed in a pressure range such that particles fragmentation occurs while the solid remains incompressible (typical pressure range of 1-300 MPa for glass powders). For a granular bed made of particles of given size, the existence of three stages is observed during compression and crush up. First, classical compression occurs and the pressure of the granular bed increases along a characteristic curve as the volume decreases. Then, a critical pressure is reached for which fragmentation begins. During the fragmentation process, the granular pressure stays constant in a given volume range. At the end of this second stage, 20%-50% of initial grains are reduced to finer particles, depending on the initial size. Then the compression undergoes the third stage and the pressure increases along another characteristic curve, in the absence of extra fragmentation. The present paper analyses the analogies between the phase transition in liquid-vapour systems and powder compression with crush-up. Fragmentation diagram for a soda lime glass is determined by experimental means. The analogues of the saturation pressure and latent heat of phase change are determined. Two thermodynamic models are then examined to represent the crush-up diagram. The first one uses piecewise functions while the second one is of van der Waals type. Both equations of state relate granular pressure, solid volume fraction, and initial particle diameter. The piecewise functions approach provides reasonable representations of the phase diagram while the van der Waals one fails.

  19. Polymorphism and thermodynamic ground state of silver fulminate studied from van der Waals density functional calculations

    SciTech Connect

    Yedukondalu, N.; Vaitheeswaran, G.

    2014-06-14

    Silver fulminate (AgCNO) is a primary explosive, which exists in two polymorphic phases, namely, orthorhombic (Cmcm) and trigonal (R3{sup ¯}) forms at ambient conditions. In the present study, we have investigated the effect of pressure and temperature on relative phase stability of the polymorphs using planewave pseudopotential approaches based on Density Functional Theory (DFT). van der Waals interactions play a significant role in predicting the phase stability and they can be effectively captured by semi-empirical dispersion correction methods in contrast to standard DFT functionals. Based on our total energy calculations using DFT-D2 method, the Cmcm structure is found to be the preferred thermodynamic equilibrium phase under studied pressure and temperature range. Hitherto Cmcm and R3{sup ¯} phases denoted as α- and β-forms of AgCNO, respectively. Also a pressure induced polymorphic phase transition is seen using DFT functionals and the same was not observed with DFT-D2 method. The equation of state and compressibility of both polymorphic phases were investigated. Electronic structure and optical properties were calculated using full potential linearized augmented plane wave method within the Tran-Blaha modified Becke-Johnson potential. The calculated electronic structure shows that α, β phases are indirect bandgap insulators with a bandgap values of 3.51 and 4.43 eV, respectively. The nature of chemical bonding is analyzed through the charge density plots and partial density of states. Optical anisotropy, electric-dipole transitions, and photo sensitivity to light of the polymorphs are analyzed from the calculated optical spectra. Overall, the present study provides an early indication to experimentalists to avoid the formation of unstable β-form of AgCNO.

  20. Web-gestütztes Social Networking am Beispiel der Plattform Wissensmanagement"

    NASA Astrophysics Data System (ADS)

    Lindstaedt, Stefanie; Thurner, Claudia

    Anhand der Plattform Wissensmanagement, der größten deutschsprachigen Community im Themenfeld Wissensmanagement, werden organisationale Rahmenbedingungen, technische Werkzeuge und Rollen der Moderatorin diskutiert, die Bedingungen für den erfolgreichen Betrieb einer Community im Web 2.0 sind. Weiters wird dargestellt, wie Communities für das betriebliche Wissensmanagement eingesetzt werden können.

  1. Re-entrant phase behavior for systems with competition between phase separation and self-assembly.

    PubMed

    Reinhardt, Aleks; Williamson, Alexander J; Doye, Jonathan P K; Carrete, Jesús; Varela, Luis M; Louis, Ard A

    2011-03-14

    In patchy particle systems where there is a competition between the self-assembly of finite clusters and liquid-vapor phase separation, re-entrant phase behavior can be observed, with the system passing from a monomeric vapor phase to a region of liquid-vapor phase coexistence and then to a vapor phase of clusters as the temperature is decreased at constant density. Here, we present a classical statistical mechanical approach to the determination of the complete phase diagram of such a system. We model the system as a van der Waals fluid, but one where the monomers can assemble into monodisperse clusters that have no attractive interactions with any of the other species. The resulting phase diagrams show a clear region of re-entrance. However, for the most physically reasonable parameter values of the model, this behavior is restricted to a certain range of density, with phase separation still persisting at high densities.

  2. Van der Waals forces in pNRQED

    SciTech Connect

    Shtabovenko, Vladyslav

    2016-01-22

    We report on the calculation of electromagnetic van der Waals forces [1] between two hydrogen atoms using non-relativistic effective field theories (EFTs) of QED for large and small momentum transfers with respect to the intrinsic energy scale of the hydrogen atom. Our results reproduce the well known London and Casimir-Polder forces.

  3. Nonadiabatic corrections to the van der Waals potential

    NASA Technical Reports Server (NTRS)

    Au, C. K.

    1988-01-01

    Closed-form expressions are derived for the finite-mass nonadiabatic corrections to the van der Waals potential in the electric-dipole approximations in terms of London-analog two-center atomic spectral sums. The nonadiabatic corrections to all orders at threshold energy and also those with first-order energy dependence are given.

  4. Applying DER-CAM for IIT Microgrid Explansion Planning

    SciTech Connect

    Shahidehpour, Mohammad; Li, Zuyi; Wang, Jianhui; Chen, Chen

    2016-04-19

    The Distributed Energy Resources Customer Adoption Model (DER-CAM) is an economic and environmental model of customer DER adoption. This model has been in development at the Lawrence Berkeley National Laboratory since 2000. The objective of the model is to find optimal DER investments while minimizing total energy costs or carbon dioxide (CO2) emissions, or achieving a weighted objective that simultaneously considers both criteria. The Illinois Institute of Technology (IIT) Microgrid project started in August 2008, and the majority of the project was completed in May 2013. IIT Microgrid, funded mostly by a grant from the U.S. Department of Energy as well as State and philanthropic contributions, empowers the campus consumers with the objective of establishing a smart microgrid that is highly reliable, economically viable, environmentally friendly, fuel-efficient, and resilient in extreme circumstances with a self-healing capability. In this project, we apply DER-CAM to study the expansion planning of the IIT Microgrid. First, the load data, environmental data, utility data, and technology data for the IIT Microgrid are gathered and organized to follow the DER-CAM input requirements. Then, DERCAM is applied to study the expansion planning of the IIT Microgrid for different cases, where different objectives in DER-CAM and different utility conditions are tested. Case 1 considers the objective of minimizing energy costs with fixed utility rates and 100% electric utility availability. Case 2 considers the objective of minimizing energy costs with real-time utility rates and 4 emergency weeks when the IIT Microgrid does not have access to the electric utility grid and has to operate in island mode. In Case 3, the utility rates are restored to fixed values and 100% electric utility availability is assumed, but a weighted multi-objective (Obj: a × costs + b × CO2 emissions, where a and b are weights for cost minimization and CO2 emissions minimization) is utilized to

  5. 1-D Van der Waals Foams Heated by Ion Beam Energy Deposition

    SciTech Connect

    Zylstra, A; Barnard, J J; More, R M

    2010-03-19

    One dimensional simulations of various initial average density aluminum foams (modeled as slabs of solid metal separated by low density regions) heated by volumetric energy deposition are conducted with a Lagrangian hydrodynamics code using a van der Waals equation of state (EOS). The resulting behavior is studied to facilitate the design of future warm dense matter (WDM) experiments at LBNL. In the simulations the energy deposition ranges from 10 to 30 kJ/g and from 0.075 to 4.0 ns total pulse length, resulting in temperatures from approximately 1 to 4 eV. We study peak pressures and temperatures in the foams, expansion velocity, and the phase evolution. Five relevant time scales in the problem are identified. Additionally, we present a method for characterizing the level of inhomogeneity in a foam target as it is heated and the time it takes for a foam to homogenize.

  6. 1-D Van der Waals Foams Heated by Ion Beam Energy Deposition

    SciTech Connect

    Zylstra, A. B.; Barnard, J. J.; More, R. M.

    2009-12-23

    One dimensional simulations of various initial average density aluminum foams (modeled as slabs of solid metal separated by low density regions) heated by volumetric energy deposition are conducted with a Lagrangian hydrodynamics code using a van der Waals equation of tate (EOS). The resulting behavior is studied to facilitate the design of future warm dense matter (WDM) experiments at LBNL. In the simulations the energy deposition ranges from 10 to 30 kJ/g and from 0.075 to 4.0 ns total pulse length, resulting in temperatures from approximately 1 o 4 eV. We study peak pressures and temperatures in the foams, expansion velocity, and the phase evolution. Five relevant time scales in the problem are identified. Additionally, we present a method for characterizing the level of inhomogeneity in a foam target as it is heated and the time it takes for a foam to homogenize.

  7. Self-consistent van der Waals density functional study of benzene adsorption on Si(100)

    NASA Astrophysics Data System (ADS)

    Hamamoto, Yuji; Hamada, Ikutaro; Inagaki, Kouji; Morikawa, Yoshitada

    2016-06-01

    The adsorption of benzene on the Si(100) surface is studied theoretically using the self-consistent van der Waals density functional (vdW-DF) method. The adsorption energies of two competing adsorption structures, butterfly (BF) and tight-bridge (TB) structures, are calculated with several vdW-DFs at saturation coverage. Our results show that recently proposed vdW-DFs with high accuracy all prefer TB to BF, in accord with more accurate calculations based on exact exchange and correlation within the random-phase approximation. Detailed analyses reveal the important roles played by the molecule-surface interaction and molecular deformation upon adsorption, and we suggest that their precise description is a prerequisite for accurate prediction of the most stable adsorption structure of organic molecules on semiconductor surfaces.

  8. Van der waals-like isotherms in a confined electrolyte by spherical and cylindrical nanopores.

    PubMed

    Aguilar-Pineda, Gabriel E; Jiménez-Angeles, Felipe; Yu, Jiang; Lozada-Cassou, Marcelo

    2007-03-01

    Electrolytes confined by spherical, cylindrical, and slit-like charged nanopores are studied. Results for ionic distribution profiles, pressures of the confined fluid, and absorption isotherms are obtained through the hypernetted chain/mean spherical approximation (HNC/MSA) integral equations theory. In spherical and cylindrical geometries, an inward, non-monotonic behavior of the pressure is found as confinement increases, implying a negative compressibility. The pressure vs volume isotherms resemble liquid-vapor van der Waals-like phase transition diagrams. This effect is correlated with a charge separation inside a spherical pore previously reported (Phys. Rev. Lett., 79, 3656, 1997). Here, the mechanism of charge separation and negative compressibility are explored in detail. When compared with the slit-like pore pressure, important qualitative differences are found.

  9. Der Lebenszyklus von Porphyrostromium obscurum (Bangiophyceae, Rhodophyta)

    NASA Astrophysics Data System (ADS)

    Kornmann, P.

    1987-06-01

    Studies on the sexuality and the heteromorphous life cycle of Erythrotrichia ciliaris provided decisive criteria for the establishment of the genus Erythrotrichopeltis (Kornmann, 1984). This genus was transferred by Wynne (1986) to Porphyrostromium Trevisan 1848. In the present study Erythrotrichia obscura, the original species of Berthold's (1882) classical observations on the sexuality of this genus, is incorporated to Porphyrostromium. Previously regarded as synonyms, Porphyrostromium ciliare (Carm. ex Harv.) Wynne and P. obscurum (Berth.) nov. comb. proved to be distinct species, differing both in the filamentous and in the peltoid phases of their life cycle. The relationship between P. ciliare and P. boryanum (Montagne) Trevisan, type species of the genus, may only be elucidated by future investigations on the basis of field collected material.

  10. Cloning, expression, and characterization of Der f 7, an allergen of Dermatophagoides farinae from China.

    PubMed

    Cui, Yu-bao; Cai, Hong-xing; Zhou, Ying; Gao, Cui-xiang; Shi, Wei-hong; Yu, Ming; Li, Li

    2010-09-01

    A full-length cDNA encoding house dust mite allergen Der f 7 from Dermatophagoides farina (Acari: Pyroglyphidae) from China was cloned, sequenced, and successfully expressed. A reference sequence (GenBank accession AY283292) was used to design polymerase chain reaction primers. Analysis revealed eight mismatched nucleotides in five Der f 7 cDNA clones, and the projected amino acid sequence contained six incompatible residues. These results suggest that the sequence of Der f 7 may be polymorphic. Further bioinformatic analysis revealed that the mature Der f 7 allergen had a molecular mass of approximately 21.88 kDa and a theoretical isoelectric point of 4.90. Der f 7 protein secondary structure was composed of a helix (56.63%), extended strand (5.10%), and random coil (38.27%). Group 7 allergens are present in Pyroglyphidae, Acaridae, and Glycyphagidae families, and homology analysis revealed a 86% similarity between Der f 7 and Der p 7. Furthermore, a phylogenetic tree constructed of group 7 allergens from different mite species revealed that Der f 7 and Der p 7 clustered with 100% bootstrap support. Bioinformatics-driven characterization of Der f 7 allergen as conducted in this study may contribute to diagnostic and therapeutic applications for dust mite allergies.

  11. Characterization of arginine kinase, anovel allergen of dermatophagoides farinae (Der f 20)

    PubMed Central

    Xing, Peng; Yu, Haiqiong; Li, Meng; Xiao, Xiaojun; Jiang, Congli; Mo, Lihua; Zhang, Min; Yang, Pingchang; Liu, Zhigang

    2015-01-01

    Objective: To characterize a novel allergen, the Dermatophagoides farinae-derived arginine kinase (Der f 20). Methods: The protein of Der f 20 was synthesized by genetic engineering approaches. The allergenicity of Der f 20 was tested by enzyme-linked immunosorbent assay and an airway allergy mouse model. Results: The Der f 20 gene was cloned andpresented in the Gene Bank with an accession number of AAP57094. The Der f 20 is an arginine kinase (AK), whichshowed a close relationship with D. pteronyssinus AK and Aleuroglyphusovatus AK. Western-blot and ELISA studies showed the IgE binding capacity of Der f 20 was 66.7% in the sera from 6 dust mite allergic patients. Immune inhibition assayresults showed the IgE cross-reactivity between Der f 20 and DME (Dust mite extract). Positive responses to Der f 20 were 41.2% as shown by skin prick tests in 17 DME-allergic patients. In vitro experimental results showed that Der f 20 induced Th2 cell differentiation and the expression of T cell Ig mucin domain molecule-4 (TIM4) in DCs. Conclusions; The Der f 20 protein is a novel subtype of thedust mite allergen. PMID:26885278

  12. Van der Waals density functional: An appropriate exchange functional

    NASA Astrophysics Data System (ADS)

    Cooper, Valentino R.

    2010-04-01

    In this Rapid Communication, an exchange functional which is compatible with the nonlocal Rutgers-Chalmers correlation functional [van der Waals density functional (vdW-DF)] is presented. This functional, when employed with vdW-DF, demonstrates remarkable improvements on intermolecular separation distances while further improving the accuracy of vdW-DF interaction energies. The key to the success of this three-parameter functional is its reduction in short-range exchange repulsion through matching to the gradient expansion approximation in the slowly varying/high-density limit while recovering the large reduced gradient, s , limit set in the revised Perdew-Burke-Ernzerhof (revPBE) exchange functional. This augmented exchange functional could be a solution to long-standing issues of vdW-DF lending to further applicability of density-functional theory to the study of relatively large, dispersion bound (van der Waals) complexes.

  13. Accurate van der Waals coefficients from density functional theory

    PubMed Central

    Tao, Jianmin; Perdew, John P.; Ruzsinszky, Adrienn

    2012-01-01

    The van der Waals interaction is a weak, long-range correlation, arising from quantum electronic charge fluctuations. This interaction affects many properties of materials. A simple and yet accurate estimate of this effect will facilitate computer simulation of complex molecular materials and drug design. Here we develop a fast approach for accurate evaluation of dynamic multipole polarizabilities and van der Waals (vdW) coefficients of all orders from the electron density and static multipole polarizabilities of each atom or other spherical object, without empirical fitting. Our dynamic polarizabilities (dipole, quadrupole, octupole, etc.) are exact in the zero- and high-frequency limits, and exact at all frequencies for a metallic sphere of uniform density. Our theory predicts dynamic multipole polarizabilities in excellent agreement with more expensive many-body methods, and yields therefrom vdW coefficients C6, C8, C10 for atom pairs with a mean absolute relative error of only 3%. PMID:22205765

  14. Aqueous gating of van der Waals materials on bilayer nanopaper.

    PubMed

    Bao, Wenzhong; Fang, Zhiqiang; Wan, Jiayu; Dai, Jiaqi; Zhu, Hongli; Han, Xiaogang; Yang, Xiaofeng; Preston, Colin; Hu, Liangbing

    2014-10-28

    In this work, we report transistors made of van der Waals materials on a mesoporous paper with a smooth nanoscale surface. The aqueous transistor has a novel planar structure with source, drain, and gate electrodes on the same surface of the paper, while the mesoporous paper is used as an electrolyte reservoir. These transistors are enabled by an all-cellulose paper with nanofibrillated cellulose (NFC) on the top surface that leads to an excellent surface smoothness, while the rest of the microsized cellulose fibers can absorb electrolyte effectively. Based on two-dimensional van der Waals materials, including MoS2 and graphene, we demonstrate high-performance transistors with a large on-off ratio and low subthreshold swing. Such planar transistors with absorbed electrolyte gating can be used as sensors integrated with other components to form paper microfluidic systems. This study is significant for future paper-based electronics and biosensors.

  15. Discrete structure of van der Waals domains in globular proteins.

    PubMed

    Berezovsky, Igor N

    2003-03-01

    Most globular proteins are divisible by domains, distinct substructures of the globule. The notion of hierarchy of the domains was introduced earlier via van der Waals energy profiles that allow one to subdivide the proteins into domains (subdomains). The question remains open as to what is the possible structural connection of the energy profiles. The recent discovery of the loop-n-lock elements in the globular proteins suggests such a structural connection. A direct comparison of the segmentation by van der Waals energy criteria with the maps of the locked loops of nearly standard size reveals a striking correlation: domains in general appear to consist of one to several such loops. In addition, it was demonstrated that a variety of subdivisions of the same protein into domains is just a regrouping of the loop-n-lock elements.

  16. Persistent hysteresis in graphene-mica van der Waals heterostructures.

    PubMed

    Mohrmann, Jens; Watanabe, Kenji; Taniguchi, Takashi; Danneau, Romain

    2015-01-09

    We report the study of electronic transport in graphene-mica van der Waals heterostructures. We have designed various graphene field-effect devices in which mica is utilized as a substrate and/or gate dielectric. When mica is used as a gate dielectric we observe a very strong positive gate voltage hysteresis of the resistance, which persists in samples that were prepared in a controlled atmosphere down to even millikelvin temperatures. In a double-gated mica-graphene-hBN van der Waals heterostructure, we found that while a strong hysteresis occurred when mica was used as a substrate/gate dielectric, the same graphene sheet on mica substrate no longer showed hysteresis when the charge carrier density was tuned through a second gate with the hBN dielectric. While this hysteretic behavior could be useful for memory devices, our findings confirm that the environment during sample preparation has to be controlled strictly.

  17. Grippers Based on Opposing Van Der Waals Adhesive Pads

    NASA Technical Reports Server (NTRS)

    Parness, Aaron (Inventor); Kennedy, Brett A. (Inventor); Heverly, Matthew C (Inventor); Cutkosky, Mark R. (Inventor); Hawkes, Elliot Wright (Inventor)

    2016-01-01

    Novel gripping structures based on van der Waals adhesive forces are disclosed. Pads covered with fibers can be activated in pairs by opposite forces, thereby enabling control of the adhesive force in an ON or OFF state. Pads can be used in groups, each comprising a group of opposite pads. The adhesive structures enable anchoring forces that can resist adverse forces from different directions. The adhesive structures can be used to enable the operation of robots on surfaces of space vehicles.

  18. Structure and dynamics of small van der Waals complexes

    SciTech Connect

    Loreau, J.

    2014-10-06

    We illustrate computational aspects of the calculation of the potential energy surfaces of small (up to five atoms) van der Waals complexes with high-level quantum chemistry techniques such as the CCSD(T) method with extended basis sets. We discuss the compromise between the required accuracy and the computational time. Further, we show how these potential energy surfaces can be fitted and used in dynamical calculations such as non-reactive inelastic scattering.

  19. Astronomen bei der Arbeit - Live-Konferenz mit La Palma

    NASA Astrophysics Data System (ADS)

    Beck, Paul G.

    2012-02-01

    "Wie kann man sich die nächtliche Arbeit eines Astronomen am Teleskop vorstellen?" Diese Frage stellen sich viele wissenschaftlich interessierte Menschen, die noch kein professionelles Observatorium besuchen konnten. Das multimediale Experiment "Call a Scientist" verband Besucher einer österreichischen Amateursternwarte live mit dem Großobservatorium in La Palma und brachte damit einer interessierten Öffentlichkeit seltene Einblicke in die Arbeitsweise der modernen Astronomie nahe.

  20. Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures

    DTIC Science & Technology

    2015-03-30

    electrical characteristics. Both large-area chemical vapor - deposited (CVD) single-crystalline h-BN layers and h-BN microflakes mechanically cleaved from a...dimensional (2D) van der Waals (vdW) materials for the realization of novel quantum electronic states. We employed molecular beam epitaxy (MBE) combined with...novel quantum electronic states. We employed molecular beam epitaxy (MBE) combined with nanofabrication techniques to form functional nanostructures

  1. Helgoland und die Erforschung der marinen Benthosalgen

    NASA Astrophysics Data System (ADS)

    Mollenhauer, D.; Lüning, K.

    1988-09-01

    Early phycological research on the island of Helgoland was performed by amateur phycologists from the adjacent coastal regions of Germany (Bremen, Hamburg, Lower Saxony and Schleswig-Holstein). These pioneers were followed by professionals, and by collectors from the mainland universities, particularly from Berlin. This second phase group includes the naturalist Christian Gottfried Ehrenberg, the zoologists Johannes Müller, Ernst Haeckel and Anton Dohrn, and the botanists Alexander Braun, Nathanael Pringsheim, and Ferdinand Cohn. The leading marine phycologist in Germany, towards the end of the 19th century, was Johannes Reinke, who finally worked at the University of Kiel. Paul Kuckuck's doctoral thesis had been supervised by Reinke who recommended him for the post of the first curator of botany at the Biological Station of Helgoland, which was founded in 1892. Kuckuck worked on the island from 1892 to 1914. After World War I, and after Kuckuck's untimely death, Wilhelm Nienburg became the second curator of botany on Helgoland, from 1921 to 1923. The next permanent phycologist on the island, from 1925 to 1936, was Ernst Schreiber. He was followed in 1936 by Peter Kornmann, who retired in 1972 but still continues as a research worker, together with Paul-Heinz Sahling, who started to work as a technical assistant under the guidance of Ernst Schreiber in 1927.

  2. Scaling Laws for van der Waals Interactions in Nanostructured Materials

    NASA Astrophysics Data System (ADS)

    Gobre, Vivekanand; Tkatchenko, Alexandre

    2014-03-01

    Van der Waals (vdW) forces originate from interactions between fluctuating multipoles in matter and play a significant role in the structure and stability of nanostructured materials. Many models used to describe vdW interactions in nanomaterials are based on a simple pairwise-additive approximation, neglecting the strong electrodynamic response effects caused by long-range fluctuations in matter. We develop and utilize an efficient microscopic method to demonstrate that vdW interactions in nanomaterials act at distances greater than typically assumed, and can be characterized by different scaling laws depending on the dimensionality and size of the system. Specifically, we study the behaviour of vdW interactions in single-layer and multilayer graphene, fullerenes of varying size, single-wall carbon nanotubes and graphene nanoribbons. As a function of nanostructure size, the van der Waals coefficients follow unusual trends for all of the considered systems, and deviate significantly from the conventionally employed pairwise-additive picture. We propose that the peculiar van der Waals interactions in nanostructured materials could be exploited to control their self-assembly.

  3. Laboratory tests of IEC DER object models for grid applications.

    SciTech Connect

    Blevins, John D.; Menicucci, David F.; Byrd, Thomas, Jr.; Gonzalez, Sigifredo; Ginn, Jerry W.; Ortiz-Moyet, Juan

    2007-02-01

    This report describes a Cooperative Research and Development Agreement (CRADA) between Salt River Project Agricultural Improvement and Power District (SRP) and Sandia National Laboratories to jointly develop advanced methods of controlling distributed energy resources (DERs) that may be located within SRP distribution systems. The controls must provide a standardized interface to allow plug-and-play capability and should allow utilities to take advantage of advanced capabilities of DERs to provide a value beyond offsetting load power. To do this, Sandia and SRP field-tested the IEC 61850-7-420 DER object model (OM) in a grid environment, with the goal of validating whether the model is robust enough to be used in common utility applications. The diesel generator OM tested was successfully used to accomplish basic genset control and monitoring. However, as presently constituted it does not enable plug-and-play functionality. Suggestions are made of aspects of the standard that need further development and testing. These problems are far from insurmountable and do not imply anything fundamentally unsound or unworkable in the standard.

  4. Silicon addition to hydroxyapatite increases nanoscale electrostatic, van der Waals, and adhesive interactions.

    PubMed

    Vandiver, Jennifer; Dean, Delphine; Patel, Nelesh; Botelho, Claudia; Best, Serena; Santos, José D; Lopes, Maria A; Bonfield, William; Ortiz, Christine

    2006-08-01

    The normal intersurface forces between nanosized probe tips functionalized with COO(-)-terminated alkanethiol self-assembling monolayers and dense, polycrystalline silicon-substituted synthetic hydroxyapatite (SiHA) and phase pure hydroxyapatite (HA) were measured via a nanomechanical technique called chemically specific high-resolution force spectroscopy. A significantly larger van der Waals interaction was observed for the SiHA compared to HA; Hamaker constants (A) were found to be A(SiHA) = 35 +/- 27 zJ and A(HA) = 13 +/- 12 zJ. Using the Derjaguin-Landau-Verwey-Overbeek approximation, which assumes linear additivity of the electrostatic double layer and van der Waals components, and the nonlinear Poisson-Boltzmann surface charge model for electrostatic double-layer forces, the surface charge per unit area, sigma (C/m(2)), was calculated as a function of position for specific nanosized areas within individual grains. SiHA was observed to be more negatively charged than HA with sigma(SiHA) = -0.024 +/- 0.013 C/m(2), two times greater than sigma(HA) = -0.011 +/- 0.006 C/m(2). Additionally, SiHA was found to have increased surface adhesion (0.7 +/- 0.3 nN) compared to HA (0.5 +/- 0.3 nN). The characterization of the nanoscale variations in surface forces of SiHA and HA will enable an improved understanding of the initial stages of bone-biomaterial bonding.

  5. Jacobus Schroeder van der Kolk (1797-1862): his resistance against materialism.

    PubMed

    Eling, P

    1998-07-01

    Schroeder van der Kolk is regarded as the founder of Dutch psychiatry and neurology. This paper describes his vitalistic views on the relation between body and soul, as formulated by him in a series of lectures. These lectures were intended to counteract the materialistic tendencies of some of Schroeder van der Kolk's French and German contemporaries. It is argued that Schroeder van der Kolk can be regarded as the transition in Holland from the "Naturphilosophie" approach to the modern experimental approach in physiology.

  6. Application of Diffusion Monte Carlo to Materials Dominated by van der Waals Interactions

    SciTech Connect

    Benali, Anouar; Shulenburger, Luke; Romero, Nichols A.; Kim, Jeongnim; von Lilienfeld, O. Anatole

    2014-06-12

    Van der Waals forces are notoriously difficult to account for from first principles. We perform extensive calculation to assess the usefulness and validity of diffusion quantum Monte Carlo when applied to van der Waals forces. We present results for noble gas solids and clusters - archetypical van der Waals dominated assemblies, as well as a relevant pi-pi stacking supramolecular complex: DNA + intercalating anti-cancer drug Ellipticine.

  7. Auf der Suche nach dem Codierungs-Gral für genetische Algorithmen

    NASA Astrophysics Data System (ADS)

    Weicker, Karsten

    Die umstrittene Frage nach dem "wichtigsten" Operator im genetischen Algorithmus - Mutation oder Crossover - hängt eng zusammen mit der Frage nach der richtigen binären Codierung. Gray- und standardbinärer Code bringen unterschiedliche Vor- und Nachteile in einen genetischen Algorithmus ein. Diese Arbeit beschäftigt sich mit der Suche nach einer Codierung, welche die Vorteile beider Codes vereinbart, und berichtet von einem Teilerfolg für mit 4 Bits encodierten Zahlen.

  8. Distributed Energy Resources Customer Adoption Model Plus (DER-CAM+), Version 1.0.0

    SciTech Connect

    Stadler, Michael; Cardorso, Goncalo; Mashayekh, Salman; DeForest, Nicholas

    2016-03-24

    DER-CAM+ v1.0.0 is internally referred to as DER-CAM v5.0.0. Due to fundamental changes from previous versions, a new name (DER-CAM+) will be used for DER-CAM version 5.0.0 and above. DER-CAM+ is a Decision Support Tool for Decentralized Energy Systems that has been tailored for microgrid applications, and now explicitly considers electrical and thermal networks within a microgrid, ancillary services, and operating reserve. DER-CAM was initially created as an exclusively economic energy model, able to find the cost minimizing combination and operation profile of a set of DER technologies that meet energy loads of a building or microgrid for a typical test year. The previous versions of DER-CAM were formulated without modeling the electrical/thermal networks within the microgrid, and hence, used aggregate single-node approaches. Furthermore, they were not able to consider operating reserve constraints, and microgrid revenue streams from participating in ancillary services markets. This new version DER-CAM+ considers these issues by including electrical power flow and thermal flow equations and constraints in the microgrid, revenues from various ancillary services markets, and operating reserve constraints.

  9. Moon Phases

    ERIC Educational Resources Information Center

    Riddle, Bob

    2010-01-01

    When teaching Moon phases, the focus seems to be on the sequence of Moon phases and, in some grade levels, how Moon phases occur. Either focus can sometimes be a challenge, especially without the use of models and observations of the Moon. In this month's column, the author describes some of the lessons that he uses to teach the phases of the Moon…

  10. Enthalpy, geometric volume and logarithmic correction to entropy for van der Waals black hole

    NASA Astrophysics Data System (ADS)

    Pradhan, Parthapratim

    2016-10-01

    If the negative cosmological constant is treated as a dynamical pressure and if the volume is its thermodynamically conjugate variable then the gravitational mass can be expressed as the total gravitational enthalpy rather than the energy. Under these circumtances, a new phenomenon emerges in the context of extended phase space thermodynamics. We examine here these features for the recently discovered van der Waals (VDW) black hole (BH) (Rajagopal A. et al., Phys. Lett. B, 737 (2014) 277) which is analogous to the VDW fluid. We show that the thermodynamic volume is greater than the naive geometric volume. We also show that the Smarr-Gibbs-Duhem relation is satisfied for this BH. Furthermore, by computing the thermal specific heat we find the local thermodynamic stability criterion for this BH. It has been observed that the BH does not possess any kind of second-order phase transition. This is an interesting feature of VDW BH by its own right. Moreover, we also derive the Cosmic-Censorship-Inequality for this class of BH. In addition finally, we compute the logarithmic correction to the entropy of this BH due to the quantum fluctuations around the thermal equilibrium.

  11. The house dust mite allergen Der p 1, unlike Der p 3, stimulates the expression of interleukin-8 in human airway epithelial cells via a proteinase-activated receptor-2-independent mechanism.

    PubMed

    Adam, Emmanuelle; Hansen, Kristina K; Astudillo Fernandez, Olaya; Astudillo, Olaya Fernandez; Coulon, Ludivine; Bex, Françoise; Duhant, Xavier; Jaumotte, Erika; Hollenberg, Morley D; Jacquet, Alain

    2006-03-17

    We investigated and compared the mechanisms by which two dust mite proteolytic allergens, Der p 1 and Der p 3, and a peptide agonist of proteinase-activated receptor 2 (PAR(2)AP) trigger interleukin (IL)-8 release from human pulmonary epithelial cells (A549). Although all three stimuli tested induced the up-regulation of IL-8 (mRNA and protein), the Der p 1-mediated signaling events did not exactly match those induced by PAR(2)AP and Der p 3. First, Der p 1 was less effective in stimulating IL-8 gene transcriptional activity than PAR(2)AP and Der p 3. Second, Der p 1-mediated IL-8 expression was mainly dependent on NF-kappaB, whereas Der p 3 and PAR(2)AP regulated IL-8 expression through the activation of both NF-kappaB and AP-1. Third, although all three MAP kinases, ERK1/2, p38, and JNK, were activated, Der p 1 induced IL-8 release exclusively via the ERK1/2 signaling pathway, whereas PAR(2)AP and Der p 3 also involved the other kinases. Fourth, in HeLa cells, Der p 1 was able to up-regulate IL-8 secretion independent of PAR(2) expression, and in contrast with PAR(2)AP and Der p 3, Der p 1 was unable to affect calcium signaling via PAR(2) in PAR(2)-expressing KNRK cells. Finally, cleavage by Der p 1 of a synthetic peptide representing the N-terminal activation-cleavage site of PAR(2) did not release a high potency activator of PAR(2) as does Der p 3. We conclude that Der p 1 (but not Der p 3)-induced IL-8 production in A549 epithelial cells is independent of PAR(2) activation.

  12. Investigation of the morphology of the van der Waals surface of the InSe single crystal

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. I.; Vishnjak, V. V.; Lashkarev, G. V.; Karbovskyi, V. L.; Kovaljuk, Z. D.; Bahtinov, A. P.

    2011-03-01

    The morphology of the (0001) van der Waals surfaces of the layered single crystal In1.03Se0.97, which were prepared using different techniques, has been investigated by scanning probe microscopy methods. It has been assumed that the van der Waals surface prepared with the use of an adhesive tape oxidizes in air due to the chemisorption of acid agents on dangling bonds of the metal and selenium. An analysis of the current-voltage characteristics of the tunneling current has shown that the composition of natural oxides represents a mixture of phases of the In2O3 oxide and wide-band-gap selenium oxides. In the InSe surface prepared by cleavage with subsequent exposure in air for approximately 2 min, the scanning with a tunneling microscope has revealed a surface ordering in the form of a corrugation of a complex profile with a fine structure. The last fact reflects the charge density redistribution after the chemisorption of gas molecules from air on this surface and its relaxation to the state with a minimum energy. Atoms of the basal plane are observed on the InSe(0001) van der Waals surface prepared by cleavage in an oxygen-free medium. The surface corrugation is absent. Point defects cause a disturbance of the periodic potential of the single crystal, which extends over a distance equal to four lattice spacings and appears as a shadowing. A technique has been proposed for producing In2O3 oxide nanostructures on the surface of the single crystal of the layered semiconductor InSe with the use of an atomic-force microscope probe as a nanoindenter. The ability of the probe to operate in gaseous and liquid media significantly extends the capabilities of the method.

  13. Analyse der Plasmakoma des Kometen P/Halley mittels Bildverarbeitung der Bochumer Photoplatten

    NASA Astrophysics Data System (ADS)

    Voelzke, M. R.

    1993-12-01

    Photographic and photoeletric observations of comet P/Halley's ion gas coma from CO+ at 4250 A were part of the Bochum Halley Monitoring Program, conducted from 1986 February 17, to April 17 at the European Southern Observatory on La Silla (Chile). In this spectral range it is possible to watch the continuous formation, motion and expansion of plasma structures. To observe the morphology of these structures 32 CO+ photos (glass plates) from P/Halley's comet have been analysed. They have a field of view of 28.6 X 28.6 degrees and were obtained from 1986 March 29, to April 17 with exposure times between 20 and 120 minutes. All photos were digitized with a PDS 2020 GM (Photometric Data System) microdensitometer at the Astronomisches Institut der Westfalischen Wilhelms-Universitaet in Muenster (one pixel = 25 X 25 microns approximately 46.88 X 46.88 arcsec). After digitization the data were reduced to relative intensities, and the part with proper calibrations were also converted to absolute intensities, expressed in terms of column densities using the image data systems MIDAS (Munich Image Data Analysis System; ESO - Image Processing Group, 1988) and IHAP (Image Handling And Processing; Middleburg, 1983). With the help of the Stellingwerf-Theta-Minimum-Method (Stellingwerf, 1978) a period of (2.22 +/- 0.09) days result from analysis of structures in the plasma-coma by subtracting subsequent images. The idea behind subtracting subsequent images is that rotation effects are only 10% phenomena on gas distribution. Difference images are than used to supress the static component of the gas cloud. The CO+ column density data (in molecules cm^-2) were compared with the data of CN column density from Schulz (1990) in all common days. The results show that the relations between CO+ and CN in average column density values (N_CO^+/N_CN) are 11.6 for a circular slit with average diameter (Phi) of 6.1 arcminute which corresponds to a distance from the nucleus (rho) equal to 6.3 X

  14. Slidable atomic layers in van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yu; Taniguchi, Takashi; Watanabe, Kenji; Maniwa, Yutaka; Miyata, Yasumitsu

    2017-04-01

    We report the preparation and manipulation of slidable atomic layers in clean, incommensurate van der Waals (vdW) heterostructures. Monolayer and multilayer WS2 grains are grown on graphite and hexagonal boron nitride (hBN) via chemical vapor deposition, and these grains can slide smoothly on graphite and hBN surfaces by manipulation with a tip. Furthermore, this sliding process allows the suspension, tearing, stacking, and connection of the atomic layers. These results demonstrate a novel approach for developing a wide variety of atomic-layer heterostructures with tunable interlayer coupling and an ideal system for studying the superlubricity of incommensurate, highly clean vdW contacts.

  15. Mit Mathematik zu Mehr Intelligenz in der Logistik

    NASA Astrophysics Data System (ADS)

    Möhring, Rolf H.; Schenk, Michael

    Die Lösung logistischer Probleme ist ein wichtiger Aspekt menschlichen Handelns seit Menschen gemeinsam zielgerichtet tätig wurden. Die Grundlagen dessen, was wir heute Logistik nennen, entstammen dem militärischen Bereich. So basierte z. B. das römische Imperium in starkem Maße auf militärisch-logistischen Glanzleistungen. Ob damals bereits mathematische Überlegungen eine Rolle spielten, wissen wir heute nicht. Jedoch versuchte z. B. Napoleon, der mit den bedeutendsten Mathematikern seiner Zeit befreundet war, den Transport seiner Truppen und die Verbreitung von Informationen zu optimieren und strategisch einzusetzen.1,2

  16. Van der Waals interaction between two crossed carbon nanotubes.

    PubMed

    Zhbanov, Alexander I; Pogorelov, Evgeny G; Chang, Yia-Chung

    2010-10-26

    The analytical expressions for the van der Waals potential energy and force between two crossed carbon nanotubes are presented. The Lennard-Jones potential between pairs of carbon atoms and the smeared-out approximation suggested by L. A. Girifalco (J. Phys. Chem. 1992, 96, 858) were used. The exact formula is expressed in terms of rational and elliptical functions. The potential and force for carbon nanotubes were calculated. The uniform potential curves for single- and multiwall nanotubes were plotted. The equilibrium distance, maximal attractive force, and potential energy have been evaluated.

  17. Nutzergerechte Entwicklung der Mensch-Maschine-Interaktion von Fahrerassistenzsystemen

    NASA Astrophysics Data System (ADS)

    König, Winfried

    Durch langjährige Forschungen bei Kfz-Herstellern, Zulieferfirmen und an Hochschulen sind umfangreiche, aber dennoch lückenhafte Erkenntnisse über das Zusammenspiel zwischen FAS und Nutzer gewonnen worden. In deutschen und internationalen Projekten wie z. B. PROMETHEUS, DRIVE, MOTIV, INVENT, RESPONSE und AKTIV haben sich Kfz-Hersteller, Zulieferfirmen, Hochschulen und weitere staatliche und private Forschungseinrichtungen zusammengefunden, um die vorwettbewerbliche Forschung für derartige Systeme voranzutreiben. Im folgenden Kapitel sollen einige der gewonnenen Kenntnisse dargelegt werden, um die Entwicklung des HMI von FAS zu erleichtern.

  18. Spherical and hyperspherical harmonics representation of van der Waals aggregates

    NASA Astrophysics Data System (ADS)

    Lombardi, Andrea; Palazzetti, Federico; Aquilanti, Vincenzo; Grossi, Gaia; Albernaz, Alessandra F.; Barreto, Patricia R. P.; Cruz, Ana Claudia P. S.

    2016-12-01

    The representation of the potential energy surfaces of atom-molecule or molecular dimers interactions should account faithfully for the symmetry properties of the systems, preserving at the same time a compact analytical form. To this aim, the choice of a proper set of coordinates is a necessary precondition. Here we illustrate a description in terms of hyperspherical coordinates and the expansion of the intermolecular interaction energy in terms of hypersherical harmonics, as a general method for building potential energy surfaces suitable for molecular dynamics simulations of van der Waals aggregates. Examples for the prototypical case diatomic-molecule-diatomic-molecule interactions are shown.

  19. Flexible DER Utility Interface System: Final Report, September 2004--May 2006

    SciTech Connect

    Lynch, J.; John, V.; Danial, S. M.; Benedict, E.; Vihinen, I.; Kroposki, B.; Pink, C.

    2006-08-01

    In an effort to accelerate deployment of Distributed Energy Resources (DER) such as wind, solar, and conventional backup generators to our nation's electrical grid, Northern Power Systems (NPS), the California Energy Commission (CEC), and the National Renewable Energy Laboratory (NREL) collaborated to create a prototype universal interconnect device called the DER Switch.

  20. Bifurkationsanalyse eines LC Tank VCOs unter Berücksichtigung der variablen Kapazität

    NASA Astrophysics Data System (ADS)

    Bremer, J.-K.; Zorn, C.; Mathis, W.

    2009-05-01

    In dieser Arbeit präsentieren wir einen neuartigen Ansatz für den systematischen Entwurf von integrierten LC Tank VCO-Schaltungen basierend auf dem Andronov Hopf Theorem und der Störungstheorie. Der Ansatz ermöglicht es, eine Abschätzung des resultierenden Abstimmbereichs, eine Stabilitätsanalyse und eine Berechnung der Amplitude des VCOs im Vorfeld des eigentlichen Entwurfs durchzuführen. Des Weiteren erlaubt die vorgestellte Methode eine Optimierung des VCOs hinsichtlich der in den Spezifikationen geforderte Amplitude und eine Minimierung der höheren Harmonischen. Mit Hilfe eines ladungsbasierten MOS-Modells ist es möglich die spannungsabhängige Kapazität der Varaktortransistoren durch einen analytischen Ausdruck zu beschreiben. Auf Basis dieses analytischen Ausdrucks wird die amplitudenabhängige Großsignalkapazität des VCOs in Abhängigkeit von Designparametern und der Tuningspannung modelliert. Die Gültigkeit der vorgestellte Entwurfsmethode wird anhand eines Beispielentwurfes eines 2.4 GHz VCO unter Verwendung einer 0.25 μm HF-CMOS Technologie verifiziert.

  1. Noch einmal: Zum phonologischen Aspekt in der Lautschulung (Once Again: The Phonological Aspect of Teaching Pronunciation)

    ERIC Educational Resources Information Center

    Germer, Erich

    1973-01-01

    Argues against the dominance of applied phonology in the teaching of English pronunciation. A follow-up to the author's Einige Probleme der Aussprache im Englischunterricht der Hauptschule'' (Some Problems of Pronunciation in English Instruction in the Elementary School), Englisch, Mar 1972. (RS)

  2. Schönheit und andere Provokationen - Eine neue evolutionsbiologische Theorie der Kunst

    NASA Astrophysics Data System (ADS)

    Junker, Thomas

    Die Evolution hat viele spektakuläre Phänomene hervorgebracht - von der Eleganz des Vogelflugs über die gigantischen Körper der Dinosaurier und die farbenprächtige Vielfalt der Korallenriffe bis hin zu ihrem jüngsten Geniestreich - der menschlichen Kunst. Die schönen Künste - Malerei, Bildhauerei und Architektur, Theater, Tanz, Oper und Filmkunst, Musik und Literatur - Produkte der Evolution? Diese Vorstellung mutet vielen Menschen fremd an, aber wie könnte es anders sein? Denn wenn Charles Darwin recht hat, dann sind nicht nur die körperlichen Merkmale der Menschen als Antworten auf die Erfordernisse des Lebens entstanden, sondern auch ihre geistigen Fähigkeiten und Verhaltensweisen. Im Jahr 1859 hatte er auf den letzten Seiten seines berühmten Buches über die Entstehung der Arten eine kühne Prophezeiung gemacht: Durch die Evolutionstheorie werde es "zu einer bemerkenswerten Revolution in der Naturwissenschaft kommen […]. Die Psychologie wird auf die neue Grundlage gestellt, dass jede geistige Kraft und Fähigkeit notwendigerweise durch graduelle Übergänge erworben wird“ (Darwin 1859, S. 484, 488; Junker 2008).

  3. Pressure dependent low temperature kinetics for CN + CH3CN: competition between chemical reaction and van der Waals complex formation.

    PubMed

    Sleiman, Chantal; González, Sergio; Klippenstein, Stephen J; Talbi, Dahbia; El Dib, Gisèle; Canosa, André

    2016-06-01

    The gas phase reaction between the CN radical and acetonitrile CH3CN was investigated experimentally, at low temperatures, with the CRESU apparatus and a slow flow reactor to explore the temperature dependence of its rate coefficient from 354 K down to 23 K. Whereas a standard Arrhenius behavior was found at T > 200 K, indicating the presence of an activation barrier, a dramatic increase in the rate coefficient by a factor of 130 was observed when the temperature was decreased from 168 to 123 K. The reaction was found to be pressure independent at 297 K unlike the experiments carried out at 52 and 132 K. The work was complemented by ab initio transition state theory based master equation calculations using reaction pathways investigated with highly accurate thermochemical protocols. The role of collisional stabilization of a CNCH3CN van der Waals complex and of tunneling induced H atom abstractions were also considered. The experimental pressure dependence at 52 and 132 K is well reproduced by the theoretical calculations provided that an anharmonic state density is considered for the van der Waals complex CH3CNCN and its Lennard-Jones radius is adjusted. Furthermore, these calculations indicate that the experimental observations correspond to the fall-off regime and that tunneling remains small in the low-pressure regime. Hence, the studied reaction is essentially an association process at very low temperature. Implications for the chemistry of interstellar clouds and Titan are discussed.

  4. Insight into the dynamic behaviour of the Van der Pol/Raleigh oscillator using the internal stiffness and damping forces

    NASA Astrophysics Data System (ADS)

    Brennan, M. J.; Tang, B.; Carranza, J. C.

    2016-09-01

    The van der Pol oscillator is an archetypal nonlinear oscillator that has been studied for many years. It is a self-sustaining oscillator that vibrates in a limit cycle, and has the characteristic that it generates energy in the part of the cycle when the displacement is small and dissipates energy in the part of the cycle when the displacement is large. Almost all analyses for this type of oscillator have been conducted in a strict mathematical framework using the displacement and velocity of the mass to describe the motion in the phase plane. Physical insight into the behaviour is then generally only possible for very small or for very large damping nonlinearity. In this paper a fresh approach is taken. The internal forces of the Rayleigh oscillator are studied rather than van der Pol's equation as the key damping force is a function of only velocity. Simulations are presented which show how the stiffness and damping forces vary when the system is vibrating in a steady-state limit cycle.

  5. Electrolytic phototransistor based on graphene-MoS2 van der Waals p-n heterojunction with tunable photoresponse

    NASA Astrophysics Data System (ADS)

    Henck, Hugo; Pierucci, Debora; Chaste, Julien; Naylor, Carl H.; Avila, Jose; Balan, Adrian; Silly, Mathieu G.; Asensio, Maria C.; Sirotti, Fausto; Johnson, A. T. Charlie; Lhuillier, Emmanuel; Ouerghi, Abdelkarim

    2016-09-01

    Van der Waals (vdW) heterostructures obtained by stacking 2D materials offer a promising route for next generation devices by combining different unique properties in completely new artificial materials. In particular, the vdW heterostructures combine high mobility and optical properties that can be exploited for optoelectronic devices. Since the p-n junction is one of the most fundamental units of optoelectronics, we propose an approach for its fabrication based on the intrinsic n doped MoS2 and the p doped bilayer graphene hybrid interfaces. We demonstrate the control of the photoconduction properties using electrolytic gating which ensures a low bias operation. We show that by finely choosing the doping value of each layer, the photoconductive properties of the hybrid system can be engineered to achieve magnitude and sign control of the photocurrent. Finally, we provide a simple phase diagram relating the photoconductive behavior with the chosen doping, which we believe can be very useful for the future design of the van der Waals based photodetectors.

  6. Capillary Condensation in Polymer Blends: an Analysis of Phase Transitions

    NASA Astrophysics Data System (ADS)

    Ilie, Carolina C.; Jira, Nicholas C.; Evans, Ian R.; Cohen, Matthew; D'Rozario, Julia R.; Romano, Marie T.; Sabirianov, Ildar

    We explore herein the capillary condensation for various geometries. Capillary condensation is studied in the presence of van der Waals forces. We derive the grand free energy, and we analyze the phase transitions, the absorption isotherms and the triple point. Phase transitions between full, empty and two films are investigated and the shape of the liquid is calculated. We also analyze an important application of wetting phenomena and capillary condensation in binary polymer blends and investigate the type of wetting transitions presented and the phase diagram. SUNY Oswego SCAC Grant, NSF Noyce Grant.

  7. van der Waals forces influencing adhesion of cells

    PubMed Central

    Kendall, K.; Roberts, A. D.

    2015-01-01

    Adhesion molecules, often thought to be acting by a ‘lock and key’ mechanism, have been thought to control the adhesion of cells. While there is no doubt that a coating of adhesion molecules such as fibronectin on a surface affects cell adhesion, this paper aims to show that such surface contamination is only one factor in the equation. Starting from the baseline idea that van der Waals force is a ubiquitous attraction between all molecules, and thereby must contribute to cell adhesion, it is clear that effects from geometry, elasticity and surface molecules must all add on to the basic cell attractive force. These effects of geometry, elasticity and surface molecules are analysed. The adhesion force measured between macroscopic polymer spheres was found to be strongest when the surfaces were absolutely smooth and clean, with no projecting protruberances. Values of the measured surface energy were then about 35 mJ m−2, as expected for van der Waals attractions between the non-polar molecules. Surface projections such as abrasion roughness or dust reduced the molecular adhesion substantially. Water cut the measured surface energy to 3.4 mJ m−2. Surface active molecules lowered the adhesion still further to less than 0.3 mJ m−2. These observations do not support the lock and key concept. PMID:25533101

  8. Franckeite as a naturally occurring van der Waals heterostructure.

    PubMed

    Molina-Mendoza, Aday J; Giovanelli, Emerson; Paz, Wendel S; Niño, Miguel Angel; Island, Joshua O; Evangeli, Charalambos; Aballe, Lucía; Foerster, Michael; van der Zant, Herre S J; Rubio-Bollinger, Gabino; Agraït, Nicolás; Palacios, J J; Pérez, Emilio M; Castellanos-Gomez, Andres

    2017-02-13

    The fabrication of van der Waals heterostructures, artificial materials assembled by individual stacking of 2D layers, is among the most promising directions in 2D materials research. Until now, the most widespread approach to stack 2D layers relies on deterministic placement methods, which are cumbersome and tend to suffer from poor control over the lattice orientations and the presence of unwanted interlayer adsorbates. Here, we present a different approach to fabricate ultrathin heterostructures by exfoliation of bulk franckeite which is a naturally occurring and air stable van der Waals heterostructure (composed of alternating SnS2-like and PbS-like layers stacked on top of each other). Presenting both an attractive narrow bandgap (<0.7 eV) and p-type doping, we find that the material can be exfoliated both mechanically and chemically down to few-layer thicknesses. We present extensive theoretical and experimental characterizations of the material's electronic properties and crystal structure, and explore applications for near-infrared photodetectors.

  9. A van der Waals DFT Approach to Modeling Water

    NASA Astrophysics Data System (ADS)

    Kolb, Brian; Thonhauser, Timo

    2010-03-01

    We present density functional theory calculations for small water clusters and bulk water including van der Waals interactions via the non-local functional vdW-DF [1]. Historically, standard functionals such as LDA or GGA have been unable to accurately predict vibrational frequencies of small water clusters or the freezing point of bulk water, which has been partly attributed to the lack of van der Waals interactions [2]. We have implemented vdW-DF in the PWscf package, using an efficient convolution approach [3]. Our results for the vibrational frequencies of small water clusters show that vdW-DF gives a significant improvement compared to LDA or GGA. While the discrepancy between experiment and LDA/GGA is as much as 28% for certain modes, vdW-DF reduces this error to only about 6%. We also present results for the vibrational spectrum and Raman spectrum of periodic ice, again showing the advantages of vdW-DF. In addition, we show preliminary results for bulk water from our vdW-DF MD simulations.[4pt] [1] Thonhauser et al., Phys. Rev. B 76, 125112 (2007).[2] H. Sit and N. Marzari, J. Chem. Phys. 122, 204510 (2005). [3] G. Roman-Perez and J. Soler, Phys. Rev. Lett. 103, 096102 (2009).

  10. Ökologische Grundlagen und limitierende Faktoren der Renaturierung

    NASA Astrophysics Data System (ADS)

    Hölzel, N.; Rebele, F.; Rosenthal, G.; Eichberg, C.

    In den dicht besiedelten und agrarisch besonders intensiv genutzten Regionen Mittel- und Westeuropas ist seit Ende des Zweiten Weltkrieges ein fortschreitender Verlust an naturnahen ökosystemen mit hoher biologischer Vielfalt zu verzeichnen. Spätestens seit den 1970er-Jahren ist daher die Neuschaffung und Wiederherstellung gefährdeter Lebensräume und Biozönosen zunehmend in den Mittelpunkt von Naturschutzmaßnahmen gerückt (Bakker 1989, Muller et al. 1998, Bakker und Berendse 1999). Aufgrund fehlender wissenschaftlicher Grundlagen und praktischer Erfahrungen wurden Renaturierungsmaßnahmen anfangs fast durchweg nach dem trial and error-Prinzip durchgeführt. Im Vordergrund standen dabei zunächst die Wiederherstellung adäquater abiotischer Standortbedingungen sowie die Reorganisation traditioneller Nutzungsmanagements. Bei Ersterem ging es neben der Wiedervernässung entwässerter Feuchtgebiete (Pfadenhauer und Grootjans 1999) vor allem darum, Eutrophierungseffekte zu beseitigen und die Produktivität des Standortes auf das Niveau der Zielgemeinschaft zurückzuführen (Gough und Marrs 1990, Oomes et al. 1996, Snow et al. 1997, Tallowin et al. 1998).

  11. Epigenetische Aspekte bei Karzinomen der Kopf-Hals-Region

    PubMed Central

    Schmezer, Peter; Plass, Christoph

    2009-01-01

    Zusammenfassung Plattenepithelkarzinome der Kopf-Hals-Region (HNSCC) zählen seit Jahren zu den weltweit häufigsten Krebsarten. Trotz vieler Bemühungen hat sich das 5-Jahres-Überleben bei Patienten mit HNSCC kaum verbessert. Um einen Fortschritt zu erzielen, ist es notwendig, die der Erkrankung zugrunde liegenden biologischen Prozesse besser zu verstehen. Neben den bekannten genetischen Veränderungen haben molekular-zytogenetische Untersuchungen bei HNSCC gezeigt, dass es weitere Veränderungen gibt, die mit Vermehrung und Verlust chromosomaler Bereiche einhergehen, für die jedoch die krankheitsverursachenden Gene bisher nicht identifiziert wurden. Darüberhinaus haben jüngste Forschungsergebnisse verdeutlicht, dass epigenetische Modifikationen wie die DNA Methylierung eine wichtige Rolle spielen. So konnte gezeigt werden, dass bei HNSCC eine Reihe von Genen (z.B. das Tumorsuppressorgen CDKN2A sowie DAPK1, MGMT, TIMP3, TCF21, und C/EBPα) hypermethylierte Bereiche in regulatorischen DNA Sequenzen aufweisen, wodurch ihre Expression verringert oder unterbunden wird. Die Hypermethylierung solcher Gene könnte als Biomarker zur Früherkennung von HNSCC genutzt werden und nicht zuletzt dadurch zur Verbesserung von Prävention und Therapieerfolg beitragen. PMID:18483718

  12. Franckeite as a naturally occurring van der Waals heterostructure

    NASA Astrophysics Data System (ADS)

    Molina-Mendoza, Aday J.; Giovanelli, Emerson; Paz, Wendel S.; Niño, Miguel Angel; Island, Joshua O.; Evangeli, Charalambos; Aballe, Lucía; Foerster, Michael; van der Zant, Herre S. J.; Rubio-Bollinger, Gabino; Agraït, Nicolás; Palacios, J. J.; Pérez, Emilio M.; Castellanos-Gomez, Andres

    2017-02-01

    The fabrication of van der Waals heterostructures, artificial materials assembled by individual stacking of 2D layers, is among the most promising directions in 2D materials research. Until now, the most widespread approach to stack 2D layers relies on deterministic placement methods, which are cumbersome and tend to suffer from poor control over the lattice orientations and the presence of unwanted interlayer adsorbates. Here, we present a different approach to fabricate ultrathin heterostructures by exfoliation of bulk franckeite which is a naturally occurring and air stable van der Waals heterostructure (composed of alternating SnS2-like and PbS-like layers stacked on top of each other). Presenting both an attractive narrow bandgap (<0.7 eV) and p-type doping, we find that the material can be exfoliated both mechanically and chemically down to few-layer thicknesses. We present extensive theoretical and experimental characterizations of the material's electronic properties and crystal structure, and explore applications for near-infrared photodetectors.

  13. Herschel und die Zukunft der Fern-Infrarot-Astronomie

    NASA Astrophysics Data System (ADS)

    Linz, Hendrik

    2015-06-01

    Schon lange ist die beobachtende Astronomie den engen Grenzen des optisch Sichbaren entwachsen und hat fast alle Bereiche des elektromagnetischen Spektrums für sich dienstbar gemacht. Im sogenannten nahen und mittleren Infrarot (Wellenlängen zwischen 1-30 μm) sowie im Millimeter- und Radio-Regime (Wellenlängen zwischen 1 mm und 10 m) ist die Erdatmosphäre relativ gut durchlässig für elektromagnetische Signale oder hat zumindest eine Vielzahl von spektral begrenzten Transmissionsfenstern, die astronomische Beobachtungen zumindest von höheren Bergen aus möglich machen. Allerdings ist das sogenannte Ferne Infrarot (FIR, 30-300 μm Wellenlänge) von der Erde aus fast völlig unzugänglich für astronomische Beobachtungen. Selbst für die besten Beobachtungsplätze der Erde bleibt die atmosphärische Transmission durch die immense Wasserdampf- Absorption auf ein absolutes Minimum beschränkt. Jedoch erlaubt uns das FIR Zugang zu Informationen, die sehr nützlich sind für die astrophysikalische Forschung und komplementär zu anderen Wellenlängen-Bereichen.

  14. Franckeite as a naturally occurring van der Waals heterostructure

    PubMed Central

    Molina-Mendoza, Aday J.; Giovanelli, Emerson; Paz, Wendel S.; Niño, Miguel Angel; Island, Joshua O.; Evangeli, Charalambos; Aballe, Lucía; Foerster, Michael; van der Zant, Herre S. J.; Rubio-Bollinger, Gabino; Agraït, Nicolás; Palacios, J. J.; Pérez, Emilio M.; Castellanos-Gomez, Andres

    2017-01-01

    The fabrication of van der Waals heterostructures, artificial materials assembled by individual stacking of 2D layers, is among the most promising directions in 2D materials research. Until now, the most widespread approach to stack 2D layers relies on deterministic placement methods, which are cumbersome and tend to suffer from poor control over the lattice orientations and the presence of unwanted interlayer adsorbates. Here, we present a different approach to fabricate ultrathin heterostructures by exfoliation of bulk franckeite which is a naturally occurring and air stable van der Waals heterostructure (composed of alternating SnS2-like and PbS-like layers stacked on top of each other). Presenting both an attractive narrow bandgap (<0.7 eV) and p-type doping, we find that the material can be exfoliated both mechanically and chemically down to few-layer thicknesses. We present extensive theoretical and experimental characterizations of the material's electronic properties and crystal structure, and explore applications for near-infrared photodetectors. PMID:28194037

  15. {InSe}/{GaSe} heterointerfaces prepared by Van der Waals epitaxy

    NASA Astrophysics Data System (ADS)

    Lang, O.; Klein, A.; Schlaf, R.; Löher, T.; Pettenkofer, C.; Jaegermann, W.; Chevy, A.

    1995-01-01

    Epitaxial films of layered substrates can be prepared onto layered substrates even for large lattice mismatch, when the growth is attempted with the Van der Waals surfaces opposing each other (Van der Waals epitaxy). Thin epitaxial InSe(GaSe) films are prepared onto ultrahigh vacuum (UHV) cleaved GaSe(InSe) Van der Waals (0001) surfaces. The films and the heterointerface are characterized by photoelectron spectroscopy, electron diffraction and scanning tunneling microscopy (STM). High quality and stoichiometric films are obtained by direct InSe(GaSe) evaporation from a Knudsen cell at sample temperatures between 520 and 620 K. Despite a 6% lattice mismatch the deposited films are oriented with their c- and α-axis to the hexagonal substrate. The growth mostly follows the Frank-Van der Merwe mode. This rather ideal growth behaviour is related to the specific properties of the Van der Waals plane which contains no dangling bonds.

  16. Improved description of soft layered materials with van der Waals density functional theory.

    PubMed

    Graziano, Gabriella; Klimeš, Jiří; Fernandez-Alonso, Felix; Michaelides, Angelos

    2012-10-24

    The accurate description of van der Waals forces within density functional theory is currently one of the most active areas of research in computational physics and chemistry. Here we report results on the structural and energetic properties of graphite and hexagonal boron nitride, two layered materials where interlayer binding is dominated by van der Waals forces. Results from several density functionals are reported, including the optimized Becke88 van der Waals (optB88-vdW) and the optimized PBE van der Waals (optPBE-vdW) (Klimeš et al 2010 J. Phys.: Condens. Matter 22 022201) functionals. Where comparison to experiment and higher-level theory is possible, the results obtained from the two new van der Waals density functionals are in good agreement. An analysis of the physical nature of the interlayer binding in both graphite and hexagonal boron nitride is also reported.

  17. Implication of Two-Coupled Differential Van der Pol Duffing Oscillator in Weak Signal Detection

    NASA Astrophysics Data System (ADS)

    Peng, Hang-hang; Xu, Xue-mei; Yang, Bing-chu; Yin, Lin-zi

    2016-04-01

    The principle of the Van der Pol Duffing oscillator for state transition and for determining critical value is described, which has been studied to indicate that the application of the Van der Pol Duffing oscillator in weak signal detection is feasible. On the basis of this principle, an improved two-coupled differential Van der Pol Duffing oscillator is proposed which can identify signals under any frequency and ameliorate signal-to-noise ratio (SNR). The analytical methods of the proposed model and the construction of the proposed oscillator are introduced in detail. Numerical experiments on the properties of the proposed oscillator compared with those of the Van der Pol Duffing oscillator are carried out. Our numerical simulations have confirmed the analytical treatment. The results demonstrate that this novel oscillator has better detection performance than the Van der Pol Duffing oscillator.

  18. Zener Tunneling and Photoresponse of a WS2/Si van der Waals Heterojunction.

    PubMed

    Lan, Changyong; Li, Chun; Wang, Shuai; He, Tianying; Jiao, Tianpeng; Wei, Dapeng; Jing, Wenkui; Li, Luying; Liu, Yong

    2016-07-20

    Van der Waals heterostructures built from two-dimensional materials on a conventional semiconductor offer novel electronic and optoelectronic properties for next-generation information devices. Here we report that by simply stacking a vapor-phase-synthesized multilayer n-type WS2 film onto a p-type Si substrate, a high-responsivity Zener photodiode can be achieved. We find that above a small reverse threshold voltage of 0.5 V, the fabricated heterojunction exhibits Zener tunneling behavior which was confirmed by its negative temperature coefficient of the breakdown voltage. The WS2/Si heterojunction working in the Zener breakdown regime shows a stable and linear photoresponse, a broadband photoresponse ranging from 340 to 1100 nm with a maximum photoresponsivity of 5.7 A/W at 660 nm and a fast response speed of 670 μs. Such high performance can be attributed to the ultrathin depletion layer involved in the WS2/Si p-n junction, on which a strong electric field can be created even with a small reverse voltage and thereby enabling an efficient separation of the photogenerated electron-hole pairs.

  19. Towards Efficient and General Method for Many-Body van-der-Waals Interactions

    NASA Astrophysics Data System (ADS)

    Tkatchenko, Alexandre

    2012-02-01

    Van der Waals interactions are intrinsically many-body phenomena, arising from collective electron fluctuations in a given material. Adiabatic connection fluctuation-dissipation theorem (ACFDT) allows to compute the many-body vdW interactions accurately. However, the ACFDT computational cost is prohibitive for real materials, even when the random-phase approximation is employed for the response function. We show how the problem of computing the long-range many-body vdW energy for real systems can be solved efficiently by mapping the system (molecule or condensed matter) onto a collection of quantum harmonic oscillators. Currently, our method, which couples density-functional theory with the many-body dispersion energy (DFT+MBD), is developed for non-metallic system [A. Tkatchenko, R. A. DiStasio Jr., R. Car, M. Scheffler, submitted]. The DFT+MBD method includes the hybridization effects by using the Tkatchenko-Scheffler approach [PRL 102, 073005 (2009)], the long-range Coulomb screening through classical electrodynamics [B. U. Felderhof, Physica 29, 1569 (1974)], and the many-body vdW energy from the coupled-fluctuating dipole model [M. W. Cole et al., Mol. Simul. 35, 849 (2009)]. The successes of the DFT+MBD approach and the many challenges that lie ahead will be discussed.

  20. Van der Waals forces and electron-electron interactions in two strained graphene layers

    NASA Astrophysics Data System (ADS)

    Sharma, Anand; Harnish, Peter; Sylvester, Alexander; Kotov, Valeri N.

    2014-03-01

    We evaluate the van der Waals (vdW) interaction energy at T=0 between two undoped graphene layers which are separated by a finite distance. Our study is carried out within the Random Phase Approximation and the interaction energy is obtained for variation in the strength of effective Coulomb interaction and anisotropy due to applied uniaxial strain. We consider the following three models for the anisotropic case: a) where one of the two layers is uniaxially strained, b) the two layers are strained in the same direction, and c) one of the layers is strained in the perpendicular direction. We find that for all the three models and any given value of the coupling, the vdW interaction energy increases with increasing anisotropy. The effect is most striking for the case when both the layers are strained in the parallel direction where we observe up to an order of magnitude increase in the strained graphene relative to the unstrained case. We also investigate the effect of intra-layer electron-electron interactions in the region of large separation between the strained graphene layers. We conclude that the many-body contributions to the correlation energy are non-negligible and the vdW interaction energy decreases as a function of increasing distance between the layers. Alexander Sylvester acknowledges financial assistance from the Research Experiences for Undergraduates (REU) Program of the National Science Foundation (NSF) focussing on complex materials.

  1. Shaping van der Waals nanoribbons via torsional constraints: Scrolls, folds and supercoils

    PubMed Central

    Shahabi, Alireza; Wang, Hailong; Upmanyu, Moneesh

    2014-01-01

    Interplay between structure and function in atomically thin crystalline nanoribbons is sensitive to their conformations yet the ability to prescribe them is a formidable challenge. Here, we report a novel paradigm for controlled nucleation and growth of scrolled and folded shapes in finite-length nanoribbons. All-atom computations on graphene nanoribbons (GNRs) and experiments on macroscale magnetic thin films reveal that decreasing the end distance of torsionally constrained ribbons below their contour length leads to formation of these shapes. The energy partitioning between twisted and bent shapes is modified in favor of these densely packed soft conformations due to the non-local van der Waals interactions in these 2D crystals; they subvert the formation of supercoils that are seen in their natural counterparts such as DNA and filamentous proteins. The conformational phase diagram is in excellent agreement with theoretical predictions. The facile route can be readily extended for tailoring the soft conformations of crystalline nanoscale ribbons, and more general self-interacting filaments. PMID:25417759

  2. Low-energy universality and scaling of van der Waals forces

    SciTech Connect

    Calle Cordon, A.; Ruiz Arriola, E.

    2010-04-15

    At long distances, interactions between neutral ground-state atoms can be described by the van der Waals potential. In the ultracold regime, atom-atom scattering is dominated by s-waves phase shifts given by an effective range expansion in terms of the scattering length {alpha}{sub 0} and the effective range r{sub 0}. We show that while the scattering length cannot be predicted for these potentials, the effective range is given by the universal low-energy theorem r{sub 0}=A+B/{alpha}{sub 0}+C/{alpha}{sub 0}{sup 2}, where A, B, and C depend on the dispersion coefficients C{sub n} and the reduced diatom mass. We confront this formula to about 100 determinations of r{sub 0} and {alpha}{sub 0} and show why the result is dominated by the leading dispersion coefficient C{sub 6}. Universality and scaling extend much beyond naive dimensional analysis estimates.

  3. COED Transactions, Vol. 8, No. 10, October 1976. The Computer Generation of Thermodynamic Phase Diagrams.

    ERIC Educational Resources Information Center

    Jolls, Kenneth R.; And Others

    A technique is described for the generation of perspective views of three-dimensional models using computer graphics. The technique is applied to models of familiar thermodynamic phase diagrams and the results are presented for the ideal gas and van der Waals equations of state as well as the properties of liquid water and steam from the Steam…

  4. Modified GRAY: An Improved Three-Phase Equation of State for Metals

    DTIC Science & Technology

    1976-04-01

    An improved version of the GRAY three-phase equation of state for metals is presented in this report. The Grover model for liquid metals is modified...representation is incorporated into the modified van der Waals equation of state for the vapor region yielding a model which is physically realistic at

  5. Finite-Size Effects on the Behavior of the Susceptibility in van der Waals Films Bounded by Strongly Absorbing Substrates

    NASA Technical Reports Server (NTRS)

    Dantchev, Daniel; Rudnick, Joseph; Barmatz, M.

    2007-01-01

    We study critical point finite-size effects in the case of the susceptibility of a film in which interactions are characterized by a van der Waals-type power law tail. The geometry is appropriate to a slab-like system with two bounding surfaces. Boundary conditions are consistent with surfaces that both prefer the same phase in the low temperature, or broken symmetry, state. We take into account both interactions within the system and interactions between the constituents of the system and the material surrounding it. Specific predictions are made with respect to the behavior of 3He and 4He films in the vicinity of their respective liquid-vapor critical points.

  6. Crystallographic features related to a van der Waals coupling in the layered chalcogenide FePS3

    NASA Astrophysics Data System (ADS)

    Murayama, Chisato; Okabe, Momoko; Urushihara, Daisuke; Asaka, Toru; Fukuda, Koichiro; Isobe, Masahiko; Yamamoto, Kazuo; Matsushita, Yoshitaka

    2016-10-01

    We investigated the crystallographic structure of FePS3 with a layered structure using transmission electron microscopy and powder X-ray diffraction. We found that FePS3 forms a rotational twin structure with the common axis along the c*-axis. The high-resolution transmission electron microscopy images revealed that the twin boundaries were positioned at the van der Waals gaps between the layers. The narrow bands of dark contrast were observed in the bright-field transmission electron microscopy images below the antiferromagnetic transition temperature, TN ≈ 120 K. Low-temperature X-ray diffraction showed a lattice distortion; the a- and b-axes shortened and lengthened, respectively, as the temperature decreased below TN. We propose that the narrow bands of dark contrast observed in the bright-field transmission electron microscopy images are caused by the directional lattice distortion with respect to each micro-twin variant in the antiferromagnetic phase.

  7. PHASE DETECTOR

    DOEpatents

    Kippenhan, D.O.

    1959-09-01

    A phase detector circuit is described for use at very high frequencies of the order of 50 megacycles. The detector circuit includes a pair of rectifiers inverted relative to each other. One voltage to be compared is applied to the two rectifiers in phase opposition and the other voltage to be compared is commonly applied to the two rectifiers. The two result:ng d-c voltages derived from the rectifiers are combined in phase opposition to produce a single d-c voltage having amplitude and polarity characteristics dependent upon the phase relation between the signals to be compared. Principal novelty resides in the employment of a half-wave transmission line to derive the phase opposing signals from the first voltage to be compared for application to the two rectifiers in place of the transformer commonly utilized for such purpose in phase detector circuits for operation at lower frequency.

  8. Ontogenic Caste Differences in the Van der Vecht Organ of Primitively Eusocial Neotropical Paper Wasps

    PubMed Central

    de Souza, André Rodrigues; Petrocelli, Iacopo; Lino-Neto, José; Santos, Eduardo Fernando; Noll, Fernando Barbosa; Turillazzi, Stefano

    2016-01-01

    Recent studies have reported incipient morphological caste dimorphism in the Van der Vecht organ size of some temperate Polistes paper wasps. Whether species other than the temperate ones show a similar pattern remains elusive. Here, we have studied some Neotropical Polistes species. By comparing females collected through the year, we showed caste related differences in the size of the Van der Vecht organ in P. ferreri (body size corrected Van der Vech organ size of queens = 0.45 ± 0.06, workers = 0.38 ± 0.07 mm2, p = 0.0021), P. versicolor (body size corrected Van der Vech organ size of queens = 0.54 ± 0.11, workers = 0.46 ± 0.09 mm2, p = 0.010), but not P. simillimus (body size corrected Van der Vech organ size of queens = 0.52 ± 0.05, workers = 0.49 ± 0.06 mm2, p = 0.238). Therefore, it seems that queens and workers of some Neotropical Polistes have diverged in their ontogenic trajectory of the Van der Vecht organ size, providing clear evidence for incipient morphological caste dimorphism. As Polistes are distributed mostly in the tropics, we propose that physical caste differences may be widespread in the genus. Also, we highlight that morphological divergence in the queen–worker phenotypes may have started through differential selection of body structures, like the Van der Vecht organ. PMID:27167514

  9. Renormalization and Universality of Van der Waals forces

    NASA Astrophysics Data System (ADS)

    Ruiz Arriola, Enrique; Calle Cordón, Alvaro

    2010-04-01

    Renormalization ideas can profitably be exploited in conjunction with the superposition principle of boundary conditions in the description of model independent and universal scaling features of the singular and long range Van der Waals force between neutral atoms. The dominance of the leading power law is highlighted both in the scattering as well as in the bound state problem. The role of off-shell two-body unitarity and causality within the Effective Field Theory framework on the light of universality and scaling at low energies is analyzed. Presented by E. Ruiz Arriola at 19th International IUPAP Conference On Few-Body Problems In Physics (FB 19) 31 Aug - 5 Sep 2009, Bonn, Germany

  10. Statistical mechanics of simple fluids - Beyond van der Waals

    NASA Astrophysics Data System (ADS)

    Lebowitz, J. L.; Waisman, E. M.

    1980-03-01

    Consideration is given to recent developments in the theory of dense fluids, based on a model fluid of hard spheres. The fluid is treated as consisting of electrically neutral particles interacting through pair potentials dependent only on the distance between their centers, a macroscopic system which can be described by classical statistical mechanics. The van der Waals equation of state and the Maxwell amendment to it for temperatures less than the critical temperature are reviewed, and subsequent rigorous derivations of the amended equation are presented. A relatively simple scheme for approximating a dense, single-component simple classical fluid whose atoms interact via the Lennard-Jones potential, based on the hard sphere model and employing computer calculations is then outlined. It is noted that the approach can be easily generalized to treat quantitatively mixtures of simple fluids, and nonuniform fluids qualitatively, and that there remains much to be done to understand why the schemes presented work as well as they do.

  11. General van der Waals potential for common organic molecules.

    PubMed

    Qi, Rui; Wang, Qiantao; Ren, Pengyu

    2016-10-15

    This work presents a systematic development of a new van der Waals potential (vdW2016) for common organic molecules based on symmetry-adapted perturbation theory (SAPT) energy decomposition. The Buf-14-7 function, as well as Cubic-mean and Waldman-Hagler mixing rules were chosen given their best performance among other popular potentials. A database containing 39 organic molecules and 108 dimers was utilized to derive a general set of vdW parameters, which were further validated on nucleobase stacking systems and testing organic dimers. The vdW2016 potential is anticipated to significantly improve the accuracy and transferability of new generations of force fields for organic molecules.

  12. The vibration of nanosprings affected by van der Waals interactions.

    PubMed

    Zhao, Junhua; Ben, Sudong; Yu, Peishi

    2016-10-01

    The vibration of tightly helical nanosprings affected by van der Waals (vdW) interactions is investigated based on continuum modelling. Explicit solutions are derived to clarify the influence of initial pitch, stiffness and the number of nanosprings on the period, frequency and amplitude of the vibration. Unlike classic linear/nonlinear springs, the waveform of the vibration is always asymmetric for tightly helical nanosprings due to the asymmetry of vdW attraction and repulsion. The at most three equilibrium positions for the nanosprings strongly depend on the deformation due to competition between the vdW interactions and the elastic energy of the nanosprings. This study provides physical insights into the origin of the novel dynamic properties of such nanosprings.

  13. A Scalable Implementation of Van der Waals Density Functionals

    NASA Astrophysics Data System (ADS)

    Wu, Jun; Gygi, Francois

    2010-03-01

    Recently developed Van der Waals density functionals[1] offer the promise to account for weak intermolecular interactions that are not described accurately by local exchange-correlation density functionals. In spite of recent progress [2], the computational cost of such calculations remains high. We present a scalable parallel implementation of the functional proposed by Dion et al.[1]. The method is implemented in the Qbox first-principles simulation code (http://eslab.ucdavis.edu/software/qbox). Application to large molecular systems will be presented. [4pt] [1] M. Dion et al. Phys. Rev. Lett. 92, 246401 (2004).[0pt] [2] G. Roman-Perez and J. M. Soler, Phys. Rev. Lett. 103, 096102 (2009).

  14. A crossover in anisotropic nanomechanochemistry of van der Waals crystals

    SciTech Connect

    Shimamura, Kohei; Misawa, Masaaki; Li, Ying; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Shimojo, Fuyuki

    2015-12-07

    In nanoscale mechanochemistry, mechanical forces selectively break covalent bonds to essentially control chemical reactions. An archetype is anisotropic detonation of layered energetic molecular crystals bonded by van der Waals (vdW) interactions. Here, quantum molecular dynamics simulations reveal a crossover of anisotropic nanomechanochemistry of vdW crystal. Within 10{sup −13} s from the passage of shock front, lateral collision produces NO{sub 2} via twisting and bending of nitro-groups and the resulting inverse Jahn-Teller effect, which is mediated by strong intra-layer hydrogen bonds. Subsequently, as we transition from heterogeneous to homogeneous mechanochemical regimes around 10{sup −12} s, shock normal to multilayers becomes more reactive, producing H{sub 2}O assisted by inter-layer N-N bond formation. These time-resolved results provide much needed atomistic understanding of nanomechanochemistry that underlies a wider range of technologies.

  15. Heterostructures based on inorganic and organic van der Waals systems

    NASA Astrophysics Data System (ADS)

    Lee, Gwan-Hyoung; Lee, Chul-Ho; van der Zande, Arend M.; Han, Minyong; Cui, Xu; Arefe, Ghidewon; Nuckolls, Colin; Heinz, Tony F.; Hone, James; Kim, Philip

    2014-09-01

    The two-dimensional limit of layered materials has recently been realized through the use of van der Waals (vdW) heterostructures composed of weakly interacting layers. In this paper, we describe two different classes of vdW heterostructures: inorganic vdW heterostructures prepared by co-lamination and restacking; and organic-inorganic hetero-epitaxy created by physical vapor deposition of organic molecule crystals on an inorganic vdW substrate. Both types of heterostructures exhibit atomically clean vdW interfaces. Employing such vdW heterostructures, we have demonstrated various novel devices, including graphene/hexagonal boron nitride (hBN) and MoS2 heterostructures for memory devices; graphene/MoS2/WSe2/graphene vertical p-n junctions for photovoltaic devices, and organic crystals on hBN with graphene electrodes for high-performance transistors.

  16. One-dimensional Fermi accelerator model with moving wall described by a nonlinear van der Pol oscillator.

    PubMed

    Botari, Tiago; Leonel, Edson D

    2013-01-01

    A modification of the one-dimensional Fermi accelerator model is considered in this work. The dynamics of a classical particle of mass m, confined to bounce elastically between two rigid walls where one is described by a nonlinear van der Pol type oscillator while the other one is fixed, working as a reinjection mechanism of the particle for a next collision, is carefully made by the use of a two-dimensional nonlinear mapping. Two cases are considered: (i) the situation where the particle has mass negligible as compared to the mass of the moving wall and does not affect the motion of it; and (ii) the case where collisions of the particle do affect the movement of the moving wall. For case (i) the phase space is of mixed type leading us to observe a scaling of the average velocity as a function of the parameter (χ) controlling the nonlinearity of the moving wall. For large χ, a diffusion on the velocity is observed leading to the conclusion that Fermi acceleration is taking place. On the other hand, for case (ii), the motion of the moving wall is affected by collisions with the particle. However, due to the properties of the van der Pol oscillator, the moving wall relaxes again to a limit cycle. Such kind of motion absorbs part of the energy of the particle leading to a suppression of the unlimited energy gain as observed in case (i). The phase space shows a set of attractors of different periods whose basin of attraction has a complicated organization.

  17. Electron response in van der Waals density functionals

    NASA Astrophysics Data System (ADS)

    Hyldgaard, Per

    2013-03-01

    There is significant interest in density functional theory (DFT) of dispersive or van der Waals (vdW) interactions and in DFT studies of sparse systems where vdW forces contribute to the cohesion and behavior. The Rutgers-Chalmers van der Waals density functional (vdW-DF) method [PRL 92, 246401 (2004); PRB 76, 125112 (2007)] is a nonempirical approach to calculate vdW bonding and for DFT characterizations of sparse matter. The vdW-DF framework is defined by a single exchange-correlation density functional that rests on a plasmon-type description for both semilocal components and for a parameter-free evaluation of nonlocal correlation. My talk summarizes a set of vdW-DF studies that seeks to map and analyze details in the vdW-DF electron-response nature. The purpose is in part to extract consequences that can facilitate an experiment-theory comparison that goes beyond binding geometries and energies. The aim is also to seek implications that can help develop the vdW-DF framework. I present an analysis of the relative importance of morphology, screening (image-plane formation), and collective effects in the vdW-DF description of molecular systems. In addition, I compare vdW-DF results with Cu(111) experiments that tests the electron-response behavior in terms of adsorption-induced band shifts, the form of the overall light-molecule physisorption potential, and the corrugation in the kinetic-energy repulsion of molecules at surfaces. Overall, the vdW-DF studies suggest the importance of benchmarking vdW methods across different length scales and by exploring the variation that arise when related structures have a different balance between exchange repulsion and vdW attraction.

  18. High-level expression and purification of the major house dust mite allergen Der p 2 in Escherichia coli.

    PubMed

    Cao, Tuo; Zhang, Zhang; Liu, Zhi-Gao; Dou, Xia; Zhang, Jie; Zhang, Wei; Wu, Bo; Yu, Zhen-Dong; Wei, Zhun; Yu, Bo

    2016-05-01

    Der p 2, a major allergen derived from the house dust mite Dermatophagoides pteronyssinus, is one of the most clinically relevant allergens worldwide. Recombinant Der p 2 (rDer p 2) is useful in clinical diagnosis and disease-specific immunotherapy. However, previous studies showed that Der p 2 can only be expressed in Escherichia coli (E. coli) cells as inclusion bodies, thus protein refolding is required to obtain functional products. Here we report a new method to produce biologically active Der p 2 protein in E. coli. N-terminal hexahistidine- and trigger factor (TF)-tagged Der p 2 was expressed in soluble form in E. coli and purified using a combination of chromatography processes. This procedure produced milligram-level high purity Der p 2 per liter of bacterial culture. Moreover, far-UV region circular dichroism (CD) analysis and serum specific IgE reactivity test demonstrated that the secondary structure and IgE reactivity properties of rDer p 2 produced in our study were almost identical to those of natural Der p 2 (nDer p 2). In conclusion, the method developed in this work provides a useful tool for the production of immunologically active recombinant Der p 2 for clinical applications.

  19. Tuning the van der Waals Interaction of Graphene with Molecules via Doping.

    PubMed

    Huttmann, Felix; Martínez-Galera, Antonio J; Caciuc, Vasile; Atodiresei, Nicolae; Schumacher, Stefan; Standop, Sebastian; Hamada, Ikutaro; Wehling, Tim O; Blügel, Stefan; Michely, Thomas

    2015-12-04

    We use scanning tunneling microscopy to visualize and thermal desorption spectroscopy to quantitatively measure that the binding of naphthalene molecules to graphene, a case of pure van der Waals interaction, strengthens with n and weakens with p doping of graphene. Density-functional theory calculations that include the van der Waals interaction in a seamless, ab initio way accurately reproduce the observed trend in binding energies. Based on a model calculation, we propose that the van der Waals interaction is modified by changing the spatial extent of graphene's π orbitals via doping.

  20. Finite element analysis of resistivity measurement with van der Pauw method in a diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Huang, Xiaowei; Gao, Chunxiao; Han, Yonghao; Li, Ming; He, Chunyuan; Hao, Aimin; Zhang, Dongmei; Yu, Cuiling; Zou, Guangtian; Ma, Yanzhang

    2007-06-01

    Using finite element analysis, the authors studied the steady current field distribution under the configuration of van der Pauw method [L. J. van der Pauw, Philips Tech. Rev. 20, 220 (1958)] for resistivity measurement in a diamond anvil cell. Based on the theoretical analysis, the authors obtained the theoretical accuracy curve of the van der Pauw method. This method provides accurate determination of sample resistivity when the ratio of sample thickness to its diameter is less than 0.45. They found that the contact area between electrode and sample is a key factor in the resistivity measurement accuracy and its size is dependent on the sample diameter for a given measurement accuracy.

  1. [Ernst von der Porten : looking for facts before and after forced emigration].

    PubMed

    Goerig, M; Bruijn, L

    2014-10-01

    The Ernst von der Porten medal has been awarded for many years to exceptional personalities by the Alliance of German Anesthesiologists to honor the outstanding achievements of the physician Ernst von der Porten from Hamburg in the development of anesthesiology as an autonomous discipline Only recent access to hitherto inaccessible documents enabled the reconstruction of his final years. He was persecuted and excluded by the National Socialist (NS) regime due to his Jewish roots and finally forced to emigrate. Records revealed that even in the so-called safe exile, degrading treatment and humiliation continued for Ernst von der Porten and his family. He eventually evaded this situation by committing suicide.

  2. Microstructure Evolution and Mechanical Behavior of a Hot-Rolled High-Manganese Dual-Phase Transformation-Induced Plasticity/Twinning-Induced Plasticity Steel

    NASA Astrophysics Data System (ADS)

    Fu, Liming; Shan, Mokun; Zhang, Daoda; Wang, Huanrong; Wang, Wei; Shan, Aidang

    2017-02-01

    The microstructures and deformation behavior were studied in a high-temperature annealed high-manganese dual-phase (28 vol pct δ-ferrite and 72 vol pct γ-austenite) transformation-induced plasticity/twinning-induced plasticity (TRIP/TWIP) steel. The results showed that the steel exhibits a special Lüders-like yielding phenomenon at room temperature (RT) and 348 K (75 °C), while it shows continuous yielding at 423 K, 573 K and 673 K (150 °C, 300 °C and 400 °C) deformation. A significant TRIP effect takes place during Lüders-like deformation at RT and 348 K (75 °C) temperatures. Semiquantitative analysis of the TRIP effect on the Lüders-like yield phenomenon proves that a softening effect of the strain energy consumption of strain-induced transformation is mainly responsible for this Lüders-like phenomenon. The TWIP mechanism dominates the 423 K (150 °C) deformation process, while the dislocation glide controls the plasticity at 573 K (300 °C) deformation. The delta-ferrite, as a hard phase in annealed dual-phase steel, greatly affects the mechanical stability of austenite due to the heterogeneous strain distribution between the two phases during deformation. A delta-ferrite-aided TRIP effect, i.e., martensite transformation induced by localized strain concentration of the hard delta-ferrite, is proposed to explain this kind of Lüders-like phenomenon. Moreover, the tensile curve at RT exhibits an upward curved behavior in the middle deformation stage, which is principally attributed to the deformation twinning of austenite retained after Lüders-like deformation. The combination of the TRIP effect during Lüders-like deformation and the subsequent TWIP effect greatly enhances the ductility in this annealed high-manganese dual-phase TRIP/TWIP steel.

  3. Non-Gaussian particle number fluctuations in vicinity of the critical point for van der Waals equation of state

    NASA Astrophysics Data System (ADS)

    Vovchenko, V.; Poberezhnyuk, R. V.; Anchishkin, D. V.; Gorenstein, M. I.

    2016-01-01

    The non-Gaussian measures of the particle number fluctuations—skewness Sσ and kurtosis κ {σ }2—are calculated in a vicinity of the critical point (CP). This point corresponds to the end point of the first-order liquid-gas phase transition. The gaseous phase is characterized by the positive values of skewness while the liquid phase has negative skew. The kurtosis appears to be significantly negative at the critical density and supercritical temperatures. The skewness and kurtosis diverge at the CP. The classical van der Waals (VDW) equation of state in the grand canonical ensemble formulation is used in our studies. Neglecting effects of the quantum statistics we succeed to obtain the analytical expressions for the rich structures of the skewness and kurtosis in a wide region around the CP. These results have universal form, i.e., they do not depend on particular values of the VDW parameters a and b. The strongly intensive measures of particle number and energy fluctuations are also considered and show singular behavior in the vicinity of the CP.

  4. Der Physik-Nobelpreis vor 100 Jahren Die Entdeckung des trägen Gases

    NASA Astrophysics Data System (ADS)

    Jacobi, Manfred

    2004-11-01

    Im Jahr 1904 erhielt der britische Physiker Lord Rayleigh (John William Strutt, 1842 bis 1919) den Nobelpreis für seine Untersuchungen über die Dichte von Gasen und die Entdeckung des Edelgases Argon.

  5. van der Waals screening by single-layer graphene and molybdenum disulfide.

    PubMed

    Tsoi, Stanislav; Dev, Pratibha; Friedman, Adam L; Stine, Rory; Robinson, Jeremy T; Reinecke, Thomas L; Sheehan, Paul E

    2014-12-23

    A sharp tip of atomic force microscope is employed to probe van der Waals forces of a silicon oxide substrate with adhered graphene. Experimental results obtained in the range of distances from 3 to 20 nm indicate that single-, double-, and triple-layer graphenes screen the van der Waals forces of the substrate. Fluorination of graphene, which makes it electrically insulating, lifts the screening in the single-layer graphene. The van der Waals force from graphene determined per layer decreases with the number of layers. In addition, increased hole doping of graphene increases the force. Finally, we also demonstrate screening of the van der Waals forces of the silicon oxide substrate by single- and double-layer molybdenum disulfide.

  6. Regenerative Energieträger im Aufwind: Entwicklung der erneuerbaren Energien

    NASA Astrophysics Data System (ADS)

    Kohl, Harald

    2006-05-01

    2005 kam 4,6 % des deutschen Primär-Energieverbrauchs aus erneuerbaren Energiequellen, bei der Stromproduktion lag ihr Anteil bei 10,2 %. Wesentliche Ursache ist der Boom bei der Windkraft, die vor allem durch Offshore-Windparks auf See weiter ausbaubar ist. Die Wasserkraft lieferte in Deutschland traditionell einen großen Beitrag zur Stromerzeugung, doch ihr Ausbaupotenzial ist gering. Die Photovoltaik, die solar- und die geothermische Stromerzeugung spielen derzeit noch eine kleine Rolle. Den deutschen Bedarf an Wärmeenergie deckten 2004 die erneuerbaren Energien zu 5,4 %, vor allem aus Biomasse. Die solarthermische Wärmeerzeugung hat sich gegenüber 2000 mehr als verdoppelt. Im Straßenverkehr spielen biogene Kraftstoffe mit 5,4 % noch eine untergeordnete Rolle. Bis 2050 könnte in Deutschland der Anteil regenerativer Energien am Primär-Energieverbrauch die Fünfzigprozentmarke überschreiten.

  7. NetCoDer: A Retransmission Mechanism for WSNs Based on Cooperative Relays and Network Coding.

    PubMed

    Valle, Odilson T; Montez, Carlos; Medeiros de Araujo, Gustavo; Vasques, Francisco; Moraes, Ricardo

    2016-05-31

    Some of the most difficult problems to deal with when using Wireless Sensor Networks (WSNs) are related to the unreliable nature of communication channels. In this context, the use of cooperative diversity techniques and the application of network coding concepts may be promising solutions to improve the communication reliability. In this paper, we propose the NetCoDer scheme to address this problem. Its design is based on merging cooperative diversity techniques and network coding concepts. We evaluate the effectiveness of the NetCoDer scheme through both an experimental setup with real WSN nodes and a simulation assessment, comparing NetCoDer performance against state-of-the-art TDMA-based (Time Division Multiple Access) retransmission techniques: BlockACK, Master/Slave and Redundant TDMA. The obtained results highlight that the proposed NetCoDer scheme clearly improves the network performance when compared with other retransmission techniques.

  8. Approximation dreidimensionaler Oberflächenmodelle der Lippen-Kiefer-Gaumen-Region durch aktive Polygonnetze

    NASA Astrophysics Data System (ADS)

    Weichert, Frank; Ewerlin, Christoph; Büttner, Christian; Shamaa, Ali; Landes, Constantin; Linder, Roland; Wagner, Mathias

    In dieser Arbeit wird ein Verfahren zur Rekonstruktion eines dreidimensionalen Oberflächenmodells aus Serienschnitten vorgestellt, die sich von Lippen-Kiefer-Gaumenspalten (kurz LKG) ableiten und insbesondere die in der chirurgischen Behandlung relevanten medizinischen Strukturen berücksichtigen. Die Intention ist, ein aktives Polygonnetz (deformierbares Oberflächennetz) zur Rekonstruktion der Struktur zu verwenden. Initial wird ein Netzprototyp als grobe Approximation der Struktur erstellt und dann mithilfe eines Gradient Vector Flow (GVF)-Kraftfeldes deformiert. Inhärenter Aspekt der Deformation ist die Beachtung eines resultierenden überschneidungsfreien Oberflächennetzes. Die rekonstruierte Oberfläche eignet sich aufgrund ausgezeichneter Eigenschaften als Eingabe für eine Kräftesimulation mittels Finite-Elemente-Methoden.

  9. NetCoDer: A Retransmission Mechanism for WSNs Based on Cooperative Relays and Network Coding

    PubMed Central

    Valle, Odilson T.; Montez, Carlos; Medeiros de Araujo, Gustavo; Vasques, Francisco; Moraes, Ricardo

    2016-01-01

    Some of the most difficult problems to deal with when using Wireless Sensor Networks (WSNs) are related to the unreliable nature of communication channels. In this context, the use of cooperative diversity techniques and the application of network coding concepts may be promising solutions to improve the communication reliability. In this paper, we propose the NetCoDer scheme to address this problem. Its design is based on merging cooperative diversity techniques and network coding concepts. We evaluate the effectiveness of the NetCoDer scheme through both an experimental setup with real WSN nodes and a simulation assessment, comparing NetCoDer performance against state-of-the-art TDMA-based (Time Division Multiple Access) retransmission techniques: BlockACK, Master/Slave and Redundant TDMA. The obtained results highlight that the proposed NetCoDer scheme clearly improves the network performance when compared with other retransmission techniques. PMID:27258280

  10. Optimizing Distributed Energy Resources and building retrofits with the strategic DER-CAModel

    SciTech Connect

    Stadler, M.; Groissböck, M.; Cardoso, G.; Marnay, C.

    2014-08-05

    The pressuring need to reduce the import of fossil fuels as well as the need to dramatically reduce CO2 emissions in Europe motivated the European Commission (EC) to implement several regulations directed to building owners. Most of these regulations focus on increasing the number of energy efficient buildings, both new and retrofitted, since retrofits play an important role in energy efficiency. Overall, this initiative results from the realization that buildings will have a significant impact in fulfilling the 20/20/20-goals of reducing the greenhouse gas emissions by 20%, increasing energy efficiency by 20%, and increasing the share of renewables to 20%, all by 2020. The Distributed Energy Resources Customer Adoption Model (DER-CAM) is an optimization tool used to support DER investment decisions, typically by minimizing total annual costs or CO2 emissions while providing energy services to a given building or microgrid site. This document shows enhancements made to DER-CAM to consider building retrofit measures along with DER investment options. Specifically, building shell improvement options have been added to DER-CAM as alternative or complementary options to investments in other DER such as PV, solar thermal, combined heat and power, or energy storage. The extension of the mathematical formulation required by the new features introduced in DER-CAM is presented and the resulting model is demonstrated at an Austrian Campus building by comparing DER-CAM results with and without building shell improvement options. Strategic investment results are presented and compared to the observed investment decision at the test site. Results obtained considering building shell improvement options suggest an optimal weighted average U value of about 0.53 W/(m2K) for the test site. This result is approximately 25% higher than what is currently observed in the building, suggesting that the retrofits made in 2002 were not optimal. Furthermore

  11. EPITOPE-BASED VACCINE FOR THE TREATMENT OF DER F 3 ALLERGY.

    PubMed

    Zhan, Xiaodong; Li, Chaopin; Jiang, Yuxing; Li, Na

    2015-12-01

    Introducción: el asma alérgica está causada por la exposición a los ácaros del polvo casero (HDM). Der f 3 se cree que es uno de los principales alérgenos en los ácaros del asma alérgica. El trabajo consistió en identificar las características inmunológicas de la vacuna basada en epítopo-Der f 3 que contienen las células T y las células B. Métodos: se generaron líneas de células T a partir de células mononucleares de sangre periférica de pacientes alérgicos a Der f 3. Tres epítopos de células T y cinco epítopos de células B de Der f 3, que hemos identificado previamente, fueron seleccionados para diseñar un polipéptido (denominados péptidos Der f 3). Construcciones de DNA que codifican estos péptidos Der f 3 se expresaron en Escherichia coli. Las líneas de células T se estimularon con los péptidos y se utilizaron en el ensayo por su capacidad proliferativa y la producción de citoquinas. Resultados: el plásmido pET28a (+) - Der f 3-péptidos se construyó y se expresaron en E. coli BL21, y la proteína de Der f 3-péptidos se purificó y se confirmaron mediante transferencia de Western. Los Der f 3-péptidos fueron reconocidos por los clones de células T procedentes de pacientes alérgicos. Valor SI de Der f 3 grupo y f grupo 3-péptidos Der eran tanto mayor que la del grupo de PBS (P.

  12. Optimizing Distributed Energy Resources and building retrofits with the strategic DER-CAModel

    DOE PAGES

    Stadler, M.; Groissböck, M.; Cardoso, G.; ...

    2014-08-05

    The pressuring need to reduce the import of fossil fuels as well as the need to dramatically reduce CO2 emissions in Europe motivated the European Commission (EC) to implement several regulations directed to building owners. Most of these regulations focus on increasing the number of energy efficient buildings, both new and retrofitted, since retrofits play an important role in energy efficiency. Overall, this initiative results from the realization that buildings will have a significant impact in fulfilling the 20/20/20-goals of reducing the greenhouse gas emissions by 20%, increasing energy efficiency by 20%, and increasing the share of renewables to 20%,more » all by 2020. The Distributed Energy Resources Customer Adoption Model (DER-CAM) is an optimization tool used to support DER investment decisions, typically by minimizing total annual costs or CO2 emissions while providing energy services to a given building or microgrid site. This document shows enhancements made to DER-CAM to consider building retrofit measures along with DER investment options. Specifically, building shell improvement options have been added to DER-CAM as alternative or complementary options to investments in other DER such as PV, solar thermal, combined heat and power, or energy storage. The extension of the mathematical formulation required by the new features introduced in DER-CAM is presented and the resulting model is demonstrated at an Austrian Campus building by comparing DER-CAM results with and without building shell improvement options. Strategic investment results are presented and compared to the observed investment decision at the test site. Results obtained considering building shell improvement options suggest an optimal weighted average U value of about 0.53 W/(m2K) for the test site. This result is approximately 25% higher than what is currently observed in the building, suggesting that the retrofits made in 2002 were not optimal. Furthermore, the results obtained with

  13. Thermodynamic geometry, phase transitions, and the Widom line.

    PubMed

    Ruppeiner, G; Sahay, A; Sarkar, T; Sengupta, G

    2012-11-01

    A microscopic characterization, based on the thermodynamic curvature R, is proposed for first-order liquid-gas phase transitions. Near the critical point, where R is proportional to the correlation volume ξ(3), we propose that R takes the same value in the coexisting phases. This proposal allows a determination of the liquid-gas coexistence curve with no use of the problematic Maxwell equal area construction. Furthermore, |R| ~ ξ(3) allows a direct determination of the Widom line in the supercritical regime. We illustrate with input from the van der Waals model and the National Institute of Standards and Technology Chemistry WebBook.

  14. On the Law of Inertia. Translation of: Ueber das Beharrungsgesetz

    NASA Astrophysics Data System (ADS)

    Lange, Ludwig

    2014-04-01

    This article is a translation of Ludwig Lange: "Ueber das Beharrungsgesetz" in: Berichte ueber Verhandlungen der Koenigl. Saechsischen Gesellschaft der Wissenschaften, math.-physik. Klasse (Leipzig, 1885), SS. 333-351. Translated by Herbert Pfister, Institut für Theoretische Physik, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen, Germany; herbert.pfister@uni-tuebingen.de. Kind assistance by Julian Barbour is acknowledged.

  15. High broad-band photoresponsivity of mechanically formed InSe-graphene van der Waals heterostructures.

    PubMed

    Mudd, Garry W; Svatek, Simon A; Hague, Lee; Makarovsky, Oleg; Kudrynskyi, Zakhar R; Mellor, Christopher J; Beton, Peter H; Eaves, Laurence; Novoselov, Kostya S; Kovalyuk, Zakhar D; Vdovin, Evgeny E; Marsden, Alex J; Wilson, Neil R; Patanè, Amalia

    2015-07-01

    High broad-band photoresponsivity of mechanically formed InSe-graphene van der Waals heterostructures is achieved by exploiting the broad-band transparency of graphene, the direct bandgap of InSe, and the favorable band line up of InSe with graphene. The photoresponsivity exceeds that for other van der Waals heterostructures and the spectral response extends from the near-infrared to the visible spectrum.

  16. Graphene Substrate for van der Waals Epitaxy of Layer-Structured Bismuth Antimony Telluride Thermoelectric Film.

    PubMed

    Kim, Eun Sung; Hwang, Jae-Yeol; Lee, Kyu Hyoung; Ohta, Hiromichi; Lee, Young Hee; Kim, Sung Wng

    2017-02-01

    Graphene as a substrate for the van der Waals epitaxy of 2D layered materials is utilized for the epitaxial growth of a layer-structured thermoelectric film. Van der Waals epitaxial Bi0.5 Sb1.5 Te3 film on graphene synthesized via a simple and scalable fabrication method exhibits good crystallinity and high thermoelectric transport properties comparable to single crystals.

  17. Enhanced Allergic Inflammation of Der p 2 Affected by Polymorphisms of MD-2 Promoter

    PubMed Central

    Liao, En-Chih; Hsieh, Chia-Wei; Chang, Ching-Yun; Yu, Sheng-Jie; Sheu, Meei-Ling; Wu, Sheng-Mao

    2015-01-01

    Purpose Myeloid differentiation-2 (MD-2) has been associated with endotoxin and inflammatory disorders because it can recognize lipopolysaccharide (LPS) binding and attenuate Toll-like receptor 4 (TLR4)-mediated signaling. However, its role in allergic inflammation has yet to be clarified. We examined whether single nucleotide polymorphisms (SNPs) in MD-2 promoter can affect MD-2 expression and aimed to clarify the relationship between Der p 2 allergy and SNPs of MD-2 promoter. Methods The function of SNPs of MD-2 promoter and the effects of cytokines and immunoglobulin on the secretion and mRNA expression were investigated in 73 allergic subjects with different MD-2 gene promoter variants. Peripheral blood mononuclear cells were cultured with or without LPS in the presence of Dermatophagoides pteronyssinus group 2 allergen (Der p 2), followed by mRNA extraction and cytokine expression analysis. The culture supernatants were collected for cytokine measurement. Results Patients with the MD-2 promoter SNPs (rs1809441/rs1809442) had increased mRNA expressions of MD-2, ε heavy chain of IgE (Cε), and interleukin (IL)-8; however, only MD-2 and IL-8 were further up-regulated after Der p 2 stimulation. Patients with SNPs of MD-2 promoter tended to have high levels of IL-1β, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α after Der p 2 and LPS stimulation. Increased secretions of IL-6, IL-8, and IL-10 were found to be up-regulated by Der p 2 stimulation, and an increased secretion of IFN-γ and decreased secretion of IL-4 were noted after LPS stimulation. Conclusions The high levels of proinflammatory cytokines secreted by Der p 2 were predetermined by MD-2 promoter SNPs (rs1809441/rs1809442). Through cytokine secretion by Der p 2 and LPS, these SNPs may serve as an indicator of the pathological phenotype of Der p 2-induced allergic inflammation. PMID:26122509

  18. Modified van der Pauw method based on formulas solvable by the Banach fixed point method

    NASA Astrophysics Data System (ADS)

    Cieśliński, Jan L.

    2012-11-01

    We propose a modification of the standard van der Pauw method for determining the resistivity and Hall coefficient of flat thin samples of arbitrary shape. Considering a different choice of resistance measurements we derive a new formula which can be numerically solved (with respect to sheet resistance) by the Banach fixed point method for any values of experimental data. The convergence is especially fast in the case of almost symmetric van der Pauw configurations (e.g., clover shaped samples).

  19. Construction of a Der p2-transgenic plant for the alleviation of airway inflammation

    PubMed Central

    Lee, CC; Ho, H; Lee, KT; Jeng, ST; Chiang, BL

    2011-01-01

    In clinical therapy, the amount of antigen administered to achieve oral tolerance for allergic diseases is large, and the cost is a major consideration. In this study, we used tobacco plants to develop a large-scale protein production system for allergen-specific immunotherapy, and we investigated the mechanisms of oral tolerance induced by a transgenic plant-derived antigen. We used plants (tobacco leaves) transgenic for the Dermatophagoides pteronyssinus 2 (Der p2) antigen to produce Der p2. Mice received total protein extract from Der p2 orally once per day over 6 days (days 0–2 and days 6–8). Mice were also sensitized and challenged with yeast-derived recombinant Der p2 (rDer p2), after which the mice were examined for airway hyper-responsiveness and airway inflammation. After sensitization and challenge with rDer p2, mice that were fed with total protein extracted from transgenic plants showed decreases in serum Der p2-specific IgE and IgG1 titers, decreased IL-5 and eotaxin levels in bronchial alveolar lavage fluid, and eosinophil infiltration in the airway. In addition, hyper-responsiveness was also decreased in mice that were fed with total protein extracted from transgenic plants, and CD4+CD25+Foxp3+ regulatory T cells were significantly increased in mediastinal and mesenteric lymph nodes. Furthermore, splenocytes isolated from transgenic plant protein-fed mice exhibited decreased proliferation and increased IL-10 secretion after stimulation with rDer p2. The data here suggest that allergen-expressing transgenic plants could be used for therapeutic purposes for allergic diseases. PMID:21602845

  20. Venus Phasing.

    ERIC Educational Resources Information Center

    Riddle, Bob

    1997-01-01

    Presents a science activity designed to introduce students to the geocentric and heliocentric models of the universe. Helps students discover why phase changes on Venus knocked Earth out of the center of the universe. (DKM)

  1. Sitzungsberichte der Heidelberger Akademie der Wissenschaften> " Jahrgang 1990 Sitzungsber.Heidelberg 90 " "Gott hat die Natur einfältig gemacht, sie aber suchen viel Künste"

    NASA Astrophysics Data System (ADS)

    Zehe, Horst

    Der Aufsatz demonstriert anhand ausgiebig kommentierter zeitgenössischer Zeugnisse Goethes Reaktion auf die Arbeiten Fraunhofers, insbesondere auf die Entdeckung der dunklen Linien im Sonnenspektrum. Den Fehlurteilen Goethes werden dabei die Urteile zeitgenössischer Physiker wie Chladni und J.F.W. Herschel gegenübergestellt. Bislang noch ungedruckte Dokumente aus dem Weimarer Goethe- und Schiller-Archiv belegen, daß sich Goethe nicht nur literarisch mit Fraunhofer beschäftigte, sondern daß er auch dessen Versuche mit Hilfe des Jenaer Universitätsmechanikers Körner getreulich zu wiederholen suchte.

  2. Cloning, bioinformatics analysis, and expression of the dust mite allergen Der f 5 of Dermatophagoides farinae.

    PubMed

    Cui, Yubao; Zhou, Ying; Ma, Guifang; Yang, Li; Wang, Yungang; Shi, Weihong

    2012-08-01

    Crude extracts of house dust mites are used clinically for diagnosis and immunotherapy of allergic diseases, including bronchial asthma, perennial rhinitis, and atopic dermatitis. However, crude extracts are complexes with non-allergenic antigens and lack effective concentrations of important allergens, resulting in several side effects. Dermatophagoides farinae (Hughes; Acari: Pyroglyphidae) is one of the predominant sources of dust mite allergens, which has more than 30 groups of allergen. The cDNA coding for the group 5 allergen of D. farinae from China was cloned, sequenced and expressed. According to alignment using the VECTOR NTI 9.0 software, there were eight mismatched nucleotides in five cDNA clones resulting in seven incompatible amino acid residues, suggesting that the Der f 5 allergen might have sequence polymorphism. Bioinformatics analysis revealed that the matured Der f 5 allergen has a molecular mass of 13604.03 Da, a theoretical pI of 5.43 and is probably hydrophobic and cytoplasmic. Similarities in amino acid sequences between Der f 5 and allergens of other domestic mite species, viz. Der p 5, Blo t 5, Sui m 5, and Lep d 5, were 79, 48, 53, and 37%, respectively. Phylogenetic analysis indicated that Der f 5 and Der p 5 clustered together. Blo t 5 and Ale o 5 also clustered together, although Blomia tropicalis and Aleuroglyphus ovatus belong to different mite families, viz. Echimyopodidae and Acaridae, respectively.

  3. Molekulare Methoden zum Nachweis, zur Quantifizierung und zum Monitoring der Mykotoxinbildung lebensmittelrelevanter Pilze

    NASA Astrophysics Data System (ADS)

    Geisen, Rolf

    Schimmelpilze kommen ubiquitär vor und spielen besonders bei pflanzlichen Lebensmitteln und Rohprodukten eine besondere Rolle als Verderbsorganismen. Es wird geschätzt, dass 20-25 % der jährlichen Produktion an pflanzlichen Produkten durch Schimmelpilze verdorben werden (Smith et al., 1994). Viele der lebensmittelrelevanten Schimmelpilze sind zudem in der Lage, Mykotoxine, toxische Sekundärmetabolite, zu bilden, was das Ausmaß des Problems deutlich macht. Die wichtigsten mykotoxinbildenden Spezies gehören zu den Fusarien (Trichothecene, Fumonisine, Zearalenon), Aspergillen (Aflatoxin, Ochratoxin, Cyclopiazonsäure) und Penicillien (Patulin, Ochratoxin). Für viele Mykotoxine, wie die Aflatoxine, Ochratoxin, Fumonisine und Trichothecene sind Grenzwerte erlassen worden, die die Verkehrsfähigkeit betroffener Produkte regeln. Die Einhaltung der Grenzwerte kann sehr genau durch offizielle chemisch-analytische Methoden, wie HPLC, GC-MS etc. kontrolliert werden. Diese analytischen Methoden sind aber für die Anwendung eines HACCP-Ansatzes zur Kontrolle der Mykotoxinbildung nur bedingt geeignet, da sie Endpunktkontrollen darstellen und nur das über eine längere Zeit gebildete Mykotoxin bestimmen. Sie sagen daher nichts über die biologischen Bedingungen zur Zeit der Bildung durch den Pilz aus.

  4. Comparison of buffers for extraction of mite allergen der p 1 from dust.

    PubMed

    Prester, Ljerka; Kovačić, Jelena; Macan, Jelena

    2012-09-01

    Der p 1 is the main allergen of house dust mite Dermatophagoides pteronyssinus, which has routinely been detected in residential dust. However, the procedure for extracting Der p 1 from reservoir dust has not been well defined. The aim of this study was to compare Der p 1 mass fractions in dust extracts prepared using the following extraction buffers: phosphate (pH 7.4), borate (pH 8.0), and ammonium bicarbonate (pH 8.0), all with 0.05 % Tween 20. Twenty-eight dust samples were divided into three aliquots and each portion was extracted with one of the three buffers at room temperature. Der p 1 mass fractions were measured in a total of 84 dust extracts using the enzyme immunoassay (range: 0.1 μg g-1 to 7.53 μg g-1). Statistical methods including intraclass correlation showed a high agreement between Der p 1 mass fractions irrespective of the extracting medium. Our results suggest that all three buffers are suitable for the extraction of mite allergens and routine Der p 1 analysis in dust.

  5. Physisorption of benzene on a tin dioxide surface: van der Waals interaction

    NASA Astrophysics Data System (ADS)

    Viitala, Matti; Kuisma, Mikael; Rantala, Tapio T.

    2012-02-01

    An adsorption study of the benzene molecule on SnO2 (110) surfaces with the density functional theory is extended to include the van der Waals interaction. We compare adsorption onto two model surfaces of SnO2, oxygen rich (stoichiometric) and oxygen poor (reduced), considered as limiting cases of varying oxygen abundance. With the chosen van der Waals approach [M. Dion, H. Rydberg, E. Schröder, D. C. Langreth, and B. I. Lundqvist, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.92.246401 92, 246401 (2004)] it is found that on the stoichiometric surface, where binding has both a covalent nature and an ionic nature, with the addition of the van der Waals interaction the adsorption energy becomes somewhat stronger. However, on the reduced surface, where binding was earlier predicted to be more physisorptionlike by using a standard generalized gradient approximation (GGA) approach, the van der Waals interaction increases the adsorption energy by a larger factor. Furthermore, three different local-density approximation and GGA functionals are compared, as corrected with the van der Waals scheme. It is found that the correction brings those three to reasonably similar descriptions of adsorption on both surfaces.

  6. Untersuchung der Störwirkung von LTE auf SRD Anwendungen bei 868 MHz

    NASA Astrophysics Data System (ADS)

    Welpot, M.; Wunderlich, S.; Gaspard, I.

    2014-11-01

    Moderne Hausautomatisierungssysteme, Alarmanlagen oder auch Funk-Zugangssysteme in Haus und Automobil setzen auf frei nutzbare Frequenzen in ISM/SRD-Bändern. Die rasante Zunahme an privaten und kommerziell genutzten Applikationen im SRD-Band bei 868 MHz und der Ausbau der LTE-Mobilfunknetze im Frequenzbereich unterhalb von 1 GHz ("Digital Dividend") wirft zunehmend die Frage nach der Funkverträglichkeit dieser Systeme untereinander auf. Während die SRD-Funkmodule auf eine geringe Sendeleistung von ~ +14 dBm beschränkt sind (Ralf and Thomas, 2009), beträgt die maximale LTE-Sendeleistung im Uplink nach (ETSI-Norm, 2011) +23 dBm. Zusammen mit der Einführung von LTE im Frequenzbereich unterhalb 1 GHz als DSL-Ersatz vor allem in ländlichen Gebieten, ergibt sich damit als mögliches Störszenario, dass durch die Aussendung des LTE-Endgerätes im Bereich von ca. 850 MHz die SRD-Funkverbindungen bei 868 MHz insbesondere dann gestört werden, wenn die Antennen beider Funksysteme räumlich nahe zueinander angeordnet sind und folglich nur eine geringe zusätzliche Entkopplung der Systeme bieten. In der vorliegenden Arbeit wird das LTE-Störpotential auf SRD-Empfänger praxisnah untersucht.

  7. Van der Waals interactions in density functional theory

    NASA Astrophysics Data System (ADS)

    Langreth, David C.

    2009-03-01

    The van der Waals density functional which we introduced half a decade agoootnotetextM. Dion et al. Phys. Rev. Lett. 92, 246401 (2004). and its self-consistent generalizationootnotetextT. Thonhauser et al., Phys. Rev. B 76, 125112 (2007). will be briefly reviewed. There are many collaborators in the application review that will follow, not only those who worked in the physics department at Rutgers% ootnotetextMaxime Dion, Aaron Puzder, T. Thonhauser, Valentino R. Cooper, Shen Li, Eamonn Murray, Lingzhu Kong, and Kyuho Lee. and at Chalmers,% ootnotetextHenrik Rydberg, Svetla Chakarova-K"ack, Jesper Kleis, Elsebeth Schr"oder, Per Hyldgaard, and Bengt I. Lundqvist. but also at Denmarks Technical University,% ootnotetextAndrei Kelkkanen, Poul G. Moses, Jesper Kleis, and Bengt I. Lundqvist. the chemistry department at Rutgers,% ootnotetextKonhoa Li, Jing Li, Yves Chabal, and Wilma K. Olson. and most recently at the University of Texas at Dallas.% ootnotetextNour Nijem and Yves Chabal. I will expand on our recent review article,ootnotetextD. C. Langreth et al., J. Phys. Cond. Mat. (in press). which hopefully will be published before the present talk, and include applications by other groups not listed below. If possible, I will also review results from a more recent collaboration to study nucleosomal DNA and beyond.

  8. Consistent van der Waals radii for the whole main group.

    PubMed

    Mantina, Manjeera; Chamberlin, Adam C; Valero, Rosendo; Cramer, Christopher J; Truhlar, Donald G

    2009-05-14

    Atomic radii are not precisely defined but are nevertheless widely used parameters in modeling and understanding molecular structure and interactions. The van der Waals radii determined by Bondi from molecular crystals and data for gases are the most widely used values, but Bondi recommended radius values for only 28 of the 44 main-group elements in the periodic table. In the present Article, we present atomic radii for the other 16; these new radii were determined in a way designed to be compatible with Bondi's scale. The method chosen is a set of two-parameter correlations of Bondi's radii with repulsive-wall distances calculated by relativistic coupled-cluster electronic structure calculations. The newly determined radii (in A) are Be, 1.53; B, 1.92; Al, 1.84; Ca, 2.31; Ge, 2.11; Rb, 3.03; Sr, 2.49; Sb, 2.06; Cs, 3.43; Ba, 2.68; Bi, 2.07; Po, 1.97; At, 2.02; Rn, 2.20; Fr, 3.48; and Ra, 2.83.

  9. Thermionic Energy Conversion Based on Graphene van der Waals Heterostructures

    PubMed Central

    Liang, Shi-Jun; Liu, Bo; Hu, Wei; Zhou, Kun; Ang, L. K.

    2017-01-01

    Seeking for thermoelectric (TE) materials with high figure of merit (or ZT), which can directly converts low-grade wasted heat (400 to 500 K) into electricity, has been a big challenge. Inspired by the concept of multilayer thermionic devices, we propose and design a solid-state thermionic devices (as a power generator or a refrigerator) in using van der Waals (vdW) heterostructure sandwiched between two graphene electrodes, to achieve high energy conversion efficiency in the temperature range of 400 to 500 K. The vdW heterostructure is composed of suitable multiple layers of transition metal dichalcogenides (TMDs), such as MoS2, MoSe2, WS2 and WSe2. From our calculations, WSe2 and MoSe2 are identified as two ideal TMDs (using the reported experimental material’s properties), which can harvest waste heat at 400 K with efficiencies about 7% to 8%. To our best knowledge, this design is the first in combining the advantages of graphene electrodes and TMDs to function as a thermionic-based device. PMID:28387363

  10. Molecular Interactions in Particular Van der Waals Nanoclusters

    NASA Astrophysics Data System (ADS)

    Jungclas, Hartmut; Komarov, Viacheslav V.; Popova, Anna M.; Schmidt, Lothar

    2017-01-01

    A method is presented to analyse the interaction energies in a nanocluster, which is consisting of three neutral molecules bound by non-covalent long range Van der Waals forces. One of the molecules (M0) in the nanocluster has a permanent dipole moment, whereas the two other molecules (M1 and M2) are non-polar. Analytical expressions are obtained for the numerical calculation of the dispersion and induction energies of the molecules in the considered nanocluster. The repulsive forces at short intermolecular distances are taken into account by introduction of damping functions. Dispersion and induction energies are calculated for a nanocluster with a definite geometry, in which the polar molecule M0 is a linear hydrocarbon molecule C5H10 and M1 and M2 are pyrene molecules. The calculations are done for fixed distances between the two pyrene molecules. The results show that the induction energies in the considered three-molecular nanocluster are comparable with the dispersion energies. Furthermore, the sum of induction energies in the substructure (M0, M1) of the considered nanocluster is much higher than the sum of induction energies in a two-molecular nanocluster with similar molecules (M0, M1) because of the absence of an electrostatic field in the latter case. This effect can be explained by the essential intermolecular induction in the three-molecular nanocluster.

  11. Investigation of the distinction between van der Waals interaction and chemical bonding based on the PAEM-MO diagram.

    PubMed

    Zhao, Dong-Xia; Yang, Zhong-Zhi

    2014-05-15

    In recent years, the basic problem of understanding chemical bonding, nonbonded, and/or van der Waals interactions has been intensively debated in terms of various theoretical methods. We propose and construct the potential acting on one electron in a molecule-molecular orbital (PAEM-MO) diagram, which draws the PAEM inserted the MO energy levels with their major atomic orbital components. PAEM-MO diagram is able to show clear distinction of chemical bonding from nonbonded and/or vdW interactions. The rule for this is as follows. Along the line connecting two atoms in a molecule or a complex, the existence of chemical bonding between these two atoms needs to satisfy two conditions: (a) a critical point of PAEM exists and (b) PAEM barrier between the two atoms is lower in energy than the occupied major valence-shell bonding MO which contains in-phase atomic components (positive overlap) of the two considered atoms. In contrast to the chemical bonding, for a nonbonded interaction or van der Waals interaction between two atoms, both conditions (a) and (b) do not be satisfied at the same time. This is demonstrated and discussed by various typical cases, particularly those related to helium atom and H-H bonding in phenanthrene. There are helium bonds in HHeF and HeBeO molecules, whereas no H-H bonding in phenanthrene. The validity and limitation for this rule is demonstrated through the investigations of the curves of the PAEM barrier top and MO energies versus the internuclear distances for He2 , H2 , and He2 (+) systems.

  12. Defining the role of histone deacetylases in the inhibition of mammary carcinogenesis by dietary energy restriction (DER): effects of suberoylanilide hydroxamic acid (SAHA) and DER in a rat model.

    PubMed

    Zhu, Zongjian; Jiang, Weiqin; McGinley, John N; Thompson, Henry J

    2013-04-01

    Dietary energy restriction (DER) inhibits experimentally induced mammary cancer, an effect accompanied by elevated levels of silent information regulator 2 (SIRT1), a class III histone deacetylase (HDAC). However, the effect of DER on targets of other classes of HDACs has not been reported, a highly relevant issue given evidence that HDAC induction favors the development of cancer and tumor growth. Experiments were carried out to determine whether suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor with broad activity, would affect the anti-cancer activity of DER. Female Sprague Dawley rats (n = 30/group) were injected with 1-methyl-1-nitrosourea (50 mg/kg) at 21 days of age and 7 days thereafter were randomized to groups fed: (i) control diet (AIN-93G), (ii) 0.1% SAHA (w/w), (iii) 40% DER, or (iv) 0.1% SAHA + 40% DER. An additional group was fed 0.1% SAHA + 40%DER for 5 weeks and released to control diet for 3 weeks. DER significantly reduced mammary cancer incidence, multiplicity, and cancer burden and prolonged cancer latency (P < 0.01). Cancer inhibition was maintained in SAHA + DER, despite evidence that histone (H2A(Lys9), H2B(Lys5), and H4(Lys5/8/12/16), but not H3(Lys9); P < 0.001) and non-histone protein deacetylation (p53(Lys373) and p53(Lys382); P < 0.001) induced by DER was reversed by SAHA. This indicates that the inhibition of DER of cancer is not dependent on HDAC induction. After releasing rats from DER + SAHA, cancer multiplicity remained lower than control (P < 0.05), consistent with apoptosis-mediated cell deletion. These findings support further investigation of the hypothesis that HDAC induction by DER blunts its anti-carcinogenic impact.

  13. Dynamical screening of van der Waals interactions in nanostructured solids: Sublimation of fullerenes

    NASA Astrophysics Data System (ADS)

    Tao, Jianmin; Yang, Jing; Rappe, Andrew M.

    2015-04-01

    Sublimation energy is one of the most important properties of molecular crystals, but it is difficult to study, because the attractive long-range van der Waals (vdW) interaction plays an important role. Here, we apply efficient semilocal density functional theory (DFT), corrected with the dynamically screened vdW interaction (DFT + vdW), the Rutgers-Chalmers nonlocal vdW-DF, and the pairwise-based dispersion-corrected DFT-D2 developed by Grimme and co-workers, to study the sublimation of fullerenes. We find that the short-range part, which accounts for the interaction due to the orbital overlap between fullerenes, is negligibly small. Our calculation shows that there exists a strong screening effect on the vdW interaction arising from the valence electrons of fullerenes. On the other hand, higher-order contributions can be as important as the leading-order term. The reasons are that (i) the surface of fullerene molecules is metallic and thus highly polarizable, (ii) the band gap of fullerene solids is small (less than 2 eV), and (iii) fullerene molecules in the solid phase are so densely packed, yielding the high valence electron density and small equilibrium intermolecular distances (the first nearest neighbor distance is only about 10 Å for C60). However, these two effects make opposite contributions, leading to significant error cancellation between these two contributions. We demonstrate that, by considering higher-order contributions and the dynamical screening, the DFT + vdW method can yield sublimation energies of fullerenes in good agreement with reference values, followed by vdW-DF and DFT-D2. The insights from this study are important for a better understanding of the long-range nature of vdW interactions in nanostructured solids.

  14. Dynamical screening of van der Waals interactions in nanostructured solids: Sublimation of fullerenes

    SciTech Connect

    Tao, Jianmin; Yang, Jing; Rappe, Andrew M.

    2015-04-28

    Sublimation energy is one of the most important properties of molecular crystals, but it is difficult to study, because the attractive long-range van der Waals (vdW) interaction plays an important role. Here, we apply efficient semilocal density functional theory (DFT), corrected with the dynamically screened vdW interaction (DFT + vdW), the Rutgers-Chalmers nonlocal vdW-DF, and the pairwise-based dispersion-corrected DFT-D2 developed by Grimme and co-workers, to study the sublimation of fullerenes. We find that the short-range part, which accounts for the interaction due to the orbital overlap between fullerenes, is negligibly small. Our calculation shows that there exists a strong screening effect on the vdW interaction arising from the valence electrons of fullerenes. On the other hand, higher-order contributions can be as important as the leading-order term. The reasons are that (i) the surface of fullerene molecules is metallic and thus highly polarizable, (ii) the band gap of fullerene solids is small (less than 2 eV), and (iii) fullerene molecules in the solid phase are so densely packed, yielding the high valence electron density and small equilibrium intermolecular distances (the first nearest neighbor distance is only about 10 Å for C{sub 60}). However, these two effects make opposite contributions, leading to significant error cancellation between these two contributions. We demonstrate that, by considering higher-order contributions and the dynamical screening, the DFT + vdW method can yield sublimation energies of fullerenes in good agreement with reference values, followed by vdW-DF and DFT-D2. The insights from this study are important for a better understanding of the long-range nature of vdW interactions in nanostructured solids.

  15. Comparative study of van der Waals corrections to the bulk properties of graphite

    NASA Astrophysics Data System (ADS)

    Rêgo, Celso R. C.; Oliveira, Luiz N.; Tereshchuk, Polina; Da Silva, Juarez L. F.

    2015-10-01

    Graphite is a stack of honeycomb (graphene) layers bound together by nonlocal, long-range van der Waals (vdW) forces, which are poorly described by density functional theory (DFT) within local or semilocal exchange-correlation functionals. Several approximations have been proposed to add a vdW correction to the DFT total energies (Stefan Grimme (D2 and D3) with different damping functions (D3-BJ), Tkatchenko-Scheffler (TS) without and with self-consistent screening (TS  +  SCS) effects). Those corrections have remarkly improved the agreement between our results and experiment for the interlayer distance (from 3.8 to 0.1%) and high-level random-phase approximation (RPA) calculations for interlayer binding energy (from 56.2 to 0.6%). We report a systematic investigation of various structural, energetic and electron properties with the aforementioned vdW corrections followed by comparison with experimental and theoretical RPA data. Comparison between the resulting relative errors shows that the TS  +  SCS correction provides the best results; the other corrections yield significantly larger errors for at least one of the studied properties. If considerations of computational costs or convergence problems rule out the TS  +  SCS approach, we recommend the D3-BJ correction. Comparison between the computed {πz}Γ\\text{ } -splitting and experimental results shows disagreements of 10% or more with all vdW corrections. Even the computationally more expensive hybrid PBE0 has proved unable to improve the agreement with the measured splitting. Our results indicate that improvements of the exchange-correlation functionals beyond the vdW corrections are necessary to accurately describe the band structure of graphite.

  16. Comparative study of van der Waals corrections to the bulk properties of graphite.

    PubMed

    Rêgo, Celso R C; Oliveira, Luiz N; Tereshchuk, Polina; Da Silva, Juarez L F

    2015-10-21

    Graphite is a stack of honeycomb (graphene) layers bound together by nonlocal, long-range van der Waals (vdW) forces, which are poorly described by density functional theory (DFT) within local or semilocal exchange-correlation functionals. Several approximations have been proposed to add a vdW correction to the DFT total energies (Stefan Grimme (D2 and D3) with different damping functions (D3-BJ), Tkatchenko-Scheffler (TS) without and with self-consistent screening (TS  +  SCS) effects). Those corrections have remarkly improved the agreement between our results and experiment for the interlayer distance (from 3.9 to 0.6%) [corrected] and high-level random-phase approximation (RPA) calculations for interlayer binding energy (from 69.5 to 1.5%). [corrected]. We report a systematic investigation of various structural, energetic and electron properties with the aforementioned vdW corrections followed by comparison with experimental and theoretical RPA data. Comparison between the resulting relative errors shows that the TS  +  SCS correction provides the best results; the other corrections yield significantly larger errors for at least one of the studied properties. If considerations of computational costs or convergence problems rule out the TS  +  SCS approach, we recommend the D3-BJ correction. Comparison between the computed π(z)Γ-splitting and experimental results shows disagreements of 10% or more with all vdW corrections. Even the computationally more expensive hybrid PBE0 has proved unable to improve the agreement with the measured splitting. Our results indicate that improvements of the exchange-correlation functionals beyond the vdW corrections are necessary to accurately describe the band structure of graphite.

  17. Thermodynamic geometry and phase transitions of dyonic charged AdS black holes

    NASA Astrophysics Data System (ADS)

    Chaturvedi, Pankaj; Das, Anirban; Sengupta, Gautam

    2017-02-01

    We investigate phase transitions and critical phenomena of four dimensional dyonic charged AdS black holes in the framework of thermodynamic geometry. In a mixed canonical-grand canonical ensemble with a fixed electric charge and varying magnetic charge these black holes exhibit a liquid-gas like first order phase transition culminating in a second order critical point similar to the van der Waals gas. We show that the thermodynamic scalar curvature R for these black holes follow our proposed geometrical characterization of the R-crossing Method for the first order liquid-gas like phase transition and exhibits a divergence at the second order critical point. The pattern of R crossing and divergence exactly corresponds to those of a van der Waals gas described by us in an earlier work.

  18. Cloning, expression, purification, characterization, crystallization and X-ray crystallographic analysis of recombinant Der f 21 (rDer f 21) from Dermatophagoides farinae.

    PubMed

    Pang, Sze Lei; Ho, Kok Lian; Waterman, Jitka; Teh, Aik Hong; Chew, Fook Tim; Ng, Chyan Leong

    2015-11-01

    Dermatophagoides farinae is one of the major house dust mite (HDM) species that cause allergic diseases. N-terminally His-tagged recombinant Der f 21 (rDer f 21), a group 21 allergen, with the signal peptide truncated was successfully overexpressed in an Escherichia coli expression system. The purified rDer f 21 protein was initially crystallized using the sitting-drop vapour-diffusion method. Well diffracting protein crystals were obtained after optimization of the crystallization conditions using the hanging-drop vapour-diffusion method with a reservoir solution consisting of 0.19 M Tris-HCl pH 8.0, 32% PEG 400 at 293 K. X-ray diffraction data were collected to 1.49 Å resolution using an in-house X-ray source. The crystal belonged to the C-centered monoclinic space group C2, with unit-cell parameters a = 123.46, b = 27.71, c = 90.25 Å, β = 125.84°. The calculated Matthews coefficient (VM) of 2.06 Å(3) Da(-1) suggests that there are two molecules per asymmetric unit, with a solvent content of 40.3%. Despite sharing high sequence identity with Blo t 5 (45%) and Blo t 21 (41%), both of which were determined to be monomeric in solution, size-exclusion chromatography, static light scattering and self-rotation function analysis indicate that rDer f 21 is likely to be a dimeric protein.

  19. On the accuracy of van der Waals inclusive density-functional theory exchange-correlation functionals for ice at ambient and high pressures

    NASA Astrophysics Data System (ADS)

    Santra, Biswajit; Klimeš, Jiří; Tkatchenko, Alexandre; Alfè, Dario; Slater, Ben; Michaelides, Angelos; Car, Roberto; Scheffler, Matthias

    2013-10-01

    Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [B. Santra, J. Klimeš, D. Alfè, A. Tkatchenko, B. Slater, A. Michaelides, R. Car, and M. Scheffler, Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure ice phases pose they should be used in future benchmark studies of simulation methods for water.

  20. On the accuracy of van der Waals inclusive density-functional theory exchange-correlation functionals for ice at ambient and high pressures.

    PubMed

    Santra, Biswajit; Klimes, Jirí; Tkatchenko, Alexandre; Alfè, Dario; Slater, Ben; Michaelides, Angelos; Car, Roberto; Scheffler, Matthias

    2013-10-21

    Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [B. Santra, J. Klimeš, D. Alfè, A. Tkatchenko, B. Slater, A. Michaelides, R. Car, and M. Scheffler, Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure ice phases pose they should be used in future benchmark studies of simulation methods for water.

  1. Kopplung eines auf der Momentenmethode basierenden Computerprogramms mit einem FEM-Algorithmus zur Berechnung von elektromagnetischen Streuproblemen im medizinischen Bereich

    NASA Astrophysics Data System (ADS)

    Schick, M.; Landstorfer, F. M.

    2004-05-01

    Am Beispiel der Verkopplung von medizinischen Geräten über den menschlichen Körper werden elektromagnetische Störphänomene im Klinikbereich betrachtet. Für die Berechnung dieser komplexen Szenarien wird zum einen die Momentenmethode (MoM) verwendet, die sich in besonderem Maße für die Berücksichtigung metallischer Strukturen und offener Streuprobleme eignet, und zum anderen die Methode der Finiten Elemente (FEM), mit der die Eigenschaften des menschlichen Körpers besser berücksichtigt werden können. Mit Hilfe des Äquivalenzprinzips lässt sich das Gesamtproblem in zwei Teile zerlegen, in ein inneres und in ein äußeres. Der Außenraum wird dabei mit der MoM behandelt und das Innere, d.h. der Körper mit der FEM. Die Kopplung der beiden Methoden erfolgt an der Körperoberfläche über äquivalente Oberflächenströme. Durch Lösen des resultierenden linearen Gleichungssystems für das gesamte Problem lassen sich dann die Oberflächenströme und die über die Kontinuitätsgleichung miteinander verknüpften elektromagnetischen Felder bestimmen.

  2. Van der Waals coefficients beyond the classical shell model

    SciTech Connect

    Tao, Jianmin; Fang, Yuan; Hao, Pan; Scuseria, G. E.; Ruzsinszky, Adrienn; Perdew, John P.

    2015-01-14

    Van der Waals (vdW) coefficients can be accurately generated and understood by modelling the dynamic multipole polarizability of each interacting object. Accurate static polarizabilities are the key to accurate dynamic polarizabilities and vdW coefficients. In this work, we present and study in detail a hollow-sphere model for the dynamic multipole polarizability proposed recently by two of the present authors (JT and JPP) to simulate the vdW coefficients for inhomogeneous systems that allow for a cavity. The inputs to this model are the accurate static multipole polarizabilities and the electron density. A simplification of the full hollow-sphere model, the single-frequency approximation (SFA), circumvents the need for a detailed electron density and for a double numerical integration over space. We find that the hollow-sphere model in SFA is not only accurate for nanoclusters and cage molecules (e.g., fullerenes) but also yields vdW coefficients among atoms, fullerenes, and small clusters in good agreement with expensive time-dependent density functional calculations. However, the classical shell model (CSM), which inputs the static dipole polarizabilities and estimates the static higher-order multipole polarizabilities therefrom, is accurate for the higher-order vdW coefficients only when the interacting objects are large. For the lowest-order vdW coefficient C{sub 6}, SFA and CSM are exactly the same. The higher-order (C{sub 8} and C{sub 10}) terms of the vdW expansion can be almost as important as the C{sub 6} term in molecular crystals. Application to a variety of clusters shows that there is strong non-additivity of the long-range vdW interactions between nanoclusters.

  3. BOOK REVIEW: Meilensteine der Astronomie - Von Aristoteles bis Hawking

    NASA Astrophysics Data System (ADS)

    Duerbeck, H. W.; Hamel, J.

    2006-12-01

    A writer, more specific a writer on the history of astronomy, might from time to time look at the collected document folders with all the research material and reprints, and might wonder: has this been all? Especially at a time when recycling is in vogue? And, perhaps with a request or an invitation to submit something, he or she might consider re-using the material before its definitive disposal. Well, such are my feelings when I looked at Jurgen Hamel's new book Milestones of Astronomy - From Aristoteles to Hawking . A slight chance for survival of medium-sized publishers like Kosmos is to offer popular books, and a title must attract potential buyers: Aristoteles means the "old" times, and as concerns the "mad scientist" of modern times, Stephen Hawking has by now dethroned Einstein. In 1998, Hamel had published a Geschichte der Astronomie - Von den Anfangen bis zur Gegenwart (History of astronomy, from the beginnings to the present), which, of course, he could not simply copy. This time, he selected some stones from his research areas - milestones, touchstones, stumbling blocks in the long road of astronomical evolution - and put them between the covers of his new book. So let us look at these (mile)stones . The reader is informed about Aristoteles on 2 pages, but his medieval interpreter Johannes de Sacrobosco gets 8 pages! Copernicus' life and achievements are described on 9 pages, closely followed by his devotee and translator Rothmann with 8 pages; Copernicus' contemporary, Peter Apian, however, gets about 13! Bessel's and Herschel's lifes and works are described on well-deserved 13 and 15 pages, while the achievements of the two Lucasian professors, Isaac Newton and Stephen Hawking, are just outlined in a single paragraph! Thus, importance is sometimes inversely proportional to text length... But let us become serious now. Why should an active historian outline, for the hundreth time, the life of Copernicus, while there are so many interesting, and often

  4. Clamping instability and van der Waals forces in carbon nanotube mechanical resonators.

    PubMed

    Aykol, Mehmet; Hou, Bingya; Dhall, Rohan; Chang, Shun-Wen; Branham, William; Qiu, Jing; Cronin, Stephen B

    2014-05-14

    We investigate the role of weak clamping forces, typically assumed to be infinite, in carbon nanotube mechanical resonators. Due to these forces, we observe a hysteretic clamping and unclamping of the nanotube device that results in a discrete drop in the mechanical resonance frequency on the order of 5-20 MHz, when the temperature is cycled between 340 and 375 K. This instability in the resonant frequency results from the nanotube unpinning from the electrode/trench sidewall where it is bound weakly by van der Waals forces. Interestingly, this unpinning does not affect the Q-factor of the resonance, since the clamping is still governed by van der Waals forces above and below the unpinning. For a 1 μm device, the drop observed in resonance frequency corresponds to a change in nanotube length of approximately 50-65 nm. On the basis of these findings, we introduce a new model, which includes a finite tension around zero gate voltage due to van der Waals forces and shows better agreement with the experimental data than the perfect clamping model. From the gate dependence of the mechanical resonance frequency, we extract the van der Waals clamping force to be 1.8 pN. The mechanical resonance frequency exhibits a striking temperature dependence below 200 K attributed to a temperature-dependent slack arising from the competition between the van der Waals force and the thermal fluctuations in the suspended nanotube.

  5. Der p 5 Crystal Structure Provides Insight into the Group 5 Dust Mite Allergens

    SciTech Connect

    Mueller, G.; Gosavi, R; Krahn, J; Edwards, L; Cuneo, M; Glesner, J; Pomes, A; Chapman, M; London, R; Pedersen, L

    2010-01-01

    Group 5 allergens from house dust mites elicit strong IgE antibody binding in mite-allergic patients. The structure of Der p 5 was determined by x-ray crystallography to better understand the IgE epitopes, to investigate the biologic function in mites, and to compare with the conflicting published Blo t 5 structures, designated 2JMH and 2JRK in the Protein Data Bank. Der p 5 is a three-helical bundle similar to Blo t 5, but the interactions of the helices are more similar to 2JMH than 2JRK. The crystallographic asymmetric unit contains three dimers of Der p 5 that are not exactly alike. Solution scattering techniques were used to assess the multimeric state of Der p 5 in vitro and showed that the predominant state was monomeric, similar to Blo t 5, but larger multimeric species are also present. In the crystal, the formation of the Der p 5 dimer creates a large hydrophobic cavity of {approx}3000 {angstrom}{sup 3} that could be a ligand-binding site. Many allergens are known to bind hydrophobic ligands, which are thought to stimulate the innate immune system and have adjuvant-like effects on IgE-mediated inflammatory responses.

  6. Colossal terahertz nonlinearity of tunneling van der Waals gap (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Bahk, Young-Mi; Kang, Bong Joo; Kim, Yong Seung; Kim, Joon-Yeon; Kim, Won Tae; Kim, Tae Yun; Kang, Taehee; Rhie, Ji Yeah; Han, Sanghoon; Park, Cheol-Hwan; Rotermund, Fabian; Kim, Dai-Sik

    2016-09-01

    We manufactured an array of three angstrom-wide, five millimeter-long van der Waals gaps of copper-graphene-copper composite, in which unprecedented nonlinearity was observed. To probe and manipulate van der Waals gaps with long wavelength electromagnetic waves such as terahertz waves, one is required to fabricate vertically oriented van der Waals gaps sandwiched between two metal planes with an infinite length in the sense of being much larger than any of the wavelengths used. By comparison with the simple vertical stacking of metal-graphene-metal structure, in our structure, background signals are completely blocked enabling all the light to squeeze through the gap without any strays. When the angstrom-sized van der Waals gaps are irradiated with intense terahertz pulses, the transient voltage across the gap reaches up to 5 V with saturation, sufficiently strong to deform the quantum barrier of angstrom gaps. The large transient potential difference across the gap facilitates electron tunneling through the quantum barrier, blocking terahertz waves completely. This negative feedback of electron tunneling leads to colossal nonlinear optical response, a 97% decrease in the normalized transmittance. Our technology for infinitely long van der Waals gaps can be utilized for other atomically thin materials than single layer graphene, enabling linear and nonlinear angstrom optics in a broad spectral range.

  7. Voluntary peer review as innovative tool for quality improvement in the intensive care unit--a retrospective descriptive cohort study in German intensive care units.

    PubMed

    Kumpf, Oliver; Bloos, Frank; Bause, Hanswerner; Brinkmann, Alexander; Deja, Maria; Marx, Gernot; Kaltwasser, Arnold; Dubb, Rolf; Muhl, Elke; Greim, Clemens-A; Weiler, Norbert; Chop, Ines; Jonitz, Günther; Schaefer, Henning; Felsenstein, Matthias; Liebeskind, Ursula; Leffmann, Carsten; Jungbluth, Annemarie; Waydhas, Christian; Pronovost, Peter; Spies, Claudia; Braun, Jan-Peter

    2014-01-01

    Einleitung: Die Verbesserung von Qualität und Sicherheit in der Intensivmedizin gewinnt zunehmend an Bedeutung. Allerdings fehlt ein Goldstandard für die Beurteilung von Qualitätsverbesserung in der Intensivmedizin. Im Jahr 2007 begann ein Pilotprojekt auf deutschen Intensivstationen, das freiwilliges Peer Review als innovatives Instrument zur Qualitätsbewertung und -verbesserung nutzt. Wir beschreiben die Methode des freiwilligen Peer Review und untersuchten ihre Durchführbarkeit. Wir analysierten anonymisierte Peer-Review-Berichte auf die thematischen Schwerpunkte, die in den Berichten hervorgehoben waren. Methode: Retrospektive Datenanalyse von 22 anonymisierten Peer-Review-Berichten. Alle 22 Intensivstationen – mit zusammen mehr als 300 Patientenbetten – hatten sich freiwilligen Peer Reviews unterzogen. Die Daten wurden aus den Berichten der Peer Reviewer und aus den Rückmeldungen der besuchten Intensivstationen gewonnen. Die Daten wurden im Hinblick auf die Anzahl der behandelten Themen und die Ergebnisse der Bewertungsbögen analysiert. Berichte über Stärken, Schwächen, Chancen und Risiken (SWOT-Berichte) dieser Intensivstationen werden vorgestellt. Ergebnisse: Die Bewertung der Struktur, Prozess- und Ergebnisindikatoren zeigte einen hohen Erreichungsgrad der vorgegebenen Qualitätsziele. In den SWOT-Berichten wurden 11 Hauptthemen, die auf allen besuchten Intensivstationen als relevant eingestuft wurden, identifiziert. 58,1% der genannten Themen betrafen Personalfragen, Team- und Kommunikationsfragen sowie Organisation und Behandlungsstandards. Als Schwachstellen wurden die Themen Dokumentation/Reporting, Hygiene und Ethik eingestuft. Fazit: Das freiwillige intensivmedizinische Peer Review stellte sich als einfach anwendbares und wertvolles Instrument für die Qualitätsverbesserung heraus. Die Peer-Review-Berichte behandelten allgemeine Problemschwerpunkte in der Intensivmedizin detaillierter als andere Methoden, wie z.B. die ausschlie

  8. Molecular, Structural and Immunological Characterization of Der p 18, a Chitinase-Like House Dust Mite Allergen

    PubMed Central

    Resch, Yvonne; Blatt, Katharina; Malkus, Ursula; Fercher, Christian; Swoboda, Ines; Focke-Tejkl, Margit; Chen, Kuan-Wei; Seiberler, Susanne; Mittermann, Irene; Lupinek, Christian; Rodriguez-Dominguez, Azahara; Zieglmayer, Petra; Zieglmayer, René; Keller, Walter; Krzyzanek, Vladislav; Valent, Peter; Valenta, Rudolf; Vrtala, Susanne

    2016-01-01

    Background The house dust mite (HDM) allergen Der p 18 belongs to the glycoside hydrolase family 18 chitinases. The relevance of Der p 18 for house dust mite allergic patients has only been partly investigated. Objective To perform a detailed characterization of Der p 18 on a molecular, structural and immunological level. Methods Der p 18 was expressed in E. coli, purified to homogeneity, tested for chitin-binding activity and its secondary structure was analyzed by circular dichroism. Der p 18-specific IgG antibodies were produced in rabbits to localize the allergen in mites using immunogold electron microscopy and to search for cross-reactive allergens in other allergen sources (i.e. mites, crustacea, mollusca and insects). IgE reactivity of rDer p 18 was tested with sera from clinically well characterized HDM-allergic patients (n = 98) and its allergenic activity was analyzed in basophil activation experiments. Results Recombinant Der p 18 was expressed and purified as a folded, biologically active protein. It shows weak chitin-binding activity and partial cross-reactivity with Der f 18 from D. farinae but not with proteins from the other tested allergen sources. The allergen was mainly localized in the peritrophic matrix of the HDM gut and to a lower extent in fecal pellets. Der p 18 reacted with IgE from 10% of mite allergic patients from Austria and showed allergenic activity when tested for basophil activation in Der p 18-sensitized patients. Conclusion Der p 18 is a rather genus-specific minor allergen with weak chitin-binding activity but exhibits allergenic activity and therefore should be included in diagnostic test panels for HDM allergy. PMID:27548813

  9. Arzt und Hobby-Astronom in stürmischen Zeiten Der Büchernachlass des Doktor Johannes Häringshauser, Viertelsmedicus in Mistelbach (1630-1641) in der Melker Stiftsbibliothek.

    NASA Astrophysics Data System (ADS)

    Davison, Giles; Glaßner, Gottfried

    2009-06-01

    Auf der Suche nach astronomischer Literatur stieß Giles Davison in der Melker Stiftsbibliothek auf den Namen "Doctor Johannes Häringshauser“ als Besitzer seltener und interessanter astronomischer Werke u.a. von Johannes Regiomontan, Georg von Peuerbach, Michael Mästlin, Johannes Kepler und Daniel Sennert. Weitere in den Jahren 2007-2009 durchgeführte Nachforschungen ergaben, dass es sich um den von 1630-1641 in Mistelbach, Niederösterreich, als Landschaftsarzt tätigen Vater des Melker Konventualen und Bibliothekars Sigismund Häringshauser (1631-1698) handelt. Er wurde 1603 als Sohn des aus Magdeburg stammenden Apothekers Johannes Häringshauser geboren und starb 1642 in Mistelbach. Johannes Häringshauser Sen. bekleidete von 1613-1640 eine Reihe wichtiger Ämter in der Wiener Stadtregierung und starb 1647. Der Studienaufenthalt von Dr. Johannes Häringshauser Jun. in Padua (1624-1626) dürfte das Interesse für Astronomie geweckt haben, das sich in seiner in die Bestände der Melker Stiftsbibliothek eingegangenen Privatbibliothek widerspiegelt. Der Großteil der 10 dem Fachbereich der Astronomie und Astrologie zuzuweisenden Titel wurde von ihm in den Jahren 1636 und 1637 erworben.

  10. Fault Current Contribution from Single-Phase PV Inverters

    SciTech Connect

    Keller, J.; Kroposki, B.; Bravo, R.; Robles, S.

    2011-01-01

    A significant increase in photovoltaic (PV) system installations is expected to come on line in the near future and as the penetration level of PV increases, the effect of PV may no longer be considered minimal. One of the most important attributions of additional PV is what effect this may have on protection systems. Protection engineers design protection systems to safely eliminate faults from the electric power system. One of the new technologies recently introduced into the electric power system are distributed energy resources (DER). Currently, inverter-based DER contributes very little to the power balance on all but a few utility distribution systems. As DER become prevalent in the distribution system, equipment rating capability and coordination of protection systems merit a closer investigation. A collaborative research effort between the National Renewable Energy Laboratory (NREL) and Southern California Edison (SCE) involved laboratory short-circuit testing single-phase (240 VAC) residential type (between 1.5 and 7kW) inverters. This paper will reveal test results obtained from these short-circuit tests.

  11. Concurrent Van der Woude syndrome and Turner syndrome: A case report.

    PubMed

    Los, Evan; Baines, Hayley; Guttmann-Bauman, Ines

    2017-01-01

    Most cases of Van der Woude syndrome are caused by a mutation to interferon regulatory factor 6 on chromosome 1. Turner syndrome is caused by complete or partial absence of the second sex chromosome in girls. We describe a unique case of the two syndromes occurring concurrently though apparently independently in a girl with Van der Woude syndrome diagnosed at birth and Turner syndrome at 14 years 9 months. Short stature was initially misattributed to Van der Woude syndrome and pituitary insufficiency associated with clefts before correctly diagnosing Turner syndrome. We discuss the prevalence of delayed diagnosis of Turner syndrome, the rarity of reports of concurrent autosomal chromosome mutation and sex chromosome deletion, as well as the need to consider the diagnosis of Turner syndrome in all girls with short stature regardless of prior medical history.

  12. Concurrent Van der Woude syndrome and Turner syndrome: A case report

    PubMed Central

    Los, Evan; Baines, Hayley; Guttmann-Bauman, Ines

    2017-01-01

    Most cases of Van der Woude syndrome are caused by a mutation to interferon regulatory factor 6 on chromosome 1. Turner syndrome is caused by complete or partial absence of the second sex chromosome in girls. We describe a unique case of the two syndromes occurring concurrently though apparently independently in a girl with Van der Woude syndrome diagnosed at birth and Turner syndrome at 14 years 9 months. Short stature was initially misattributed to Van der Woude syndrome and pituitary insufficiency associated with clefts before correctly diagnosing Turner syndrome. We discuss the prevalence of delayed diagnosis of Turner syndrome, the rarity of reports of concurrent autosomal chromosome mutation and sex chromosome deletion, as well as the need to consider the diagnosis of Turner syndrome in all girls with short stature regardless of prior medical history. PMID:28228961

  13. Amerikas Einschätzung der deutschen Atomforschung: Das deutsche Uranprojekt

    NASA Astrophysics Data System (ADS)

    Walker, Mark

    2002-07-01

    Die amerikanischen Wissenschaftler und ihre emigrierten Kollegen, die am Bau der Atombombe beteiligt waren, verfügten über sehr widersprüchliche und großteils falsche Informationen über den Fortschritt des deutschen Uranprogramms. Noch nach Kriegsende lässt sich dies an Aussagen des Leiters der amerikanischen Alsos-Mission, Samuel Goudsmit, festmachen. Tatsächlich war das deutsche Programm hinsichtlich seiner wissenschaftlichen Grundlagen und des Managements nicht so unterlegen, wie vielfach behauptet wurde. Aber die deutschen Behörden waren nicht in der Lage, Geld und Ressourcen in gleichem Maße in das Uranprojekt zu investieren, wie etwa in das Peenemünder Raketenprojekt.

  14. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures.

    PubMed

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; Liang, Liangbo; West, Damien; Meunier, Vincent; Zhang, Shengbai

    2016-05-10

    The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs.

  15. Electron transfer and coupling in graphene-tungsten disulfide van der Waals heterostructures.

    PubMed

    He, Jiaqi; Kumar, Nardeep; Bellus, Matthew Z; Chiu, Hsin-Ying; He, Dawei; Wang, Yongsheng; Zhao, Hui

    2014-11-25

    The newly discovered two-dimensional materials can be used to form atomically thin and sharp van der Waals heterostructures with nearly perfect interface qualities, which can transform the science and technology of semiconductor heterostructures. Owing to the weak van der Waals interlayer coupling, the electronic states of participating materials remain largely unchanged. Hence, emergent properties of these structures rely on two key elements: electron transfer across the interface and interlayer coupling. Here we show, using graphene-tungsten disulfide heterostructures as an example, evidence of ultrafast and highly efficient interlayer electron transfer and strong interlayer coupling and control. We find that photocarriers injected in tungsten disulfide transfer to graphene in 1 ps and with near-unity efficiency. We also demonstrate that optical properties of tungsten disulfide can be effectively tuned by carriers in graphene. These findings illustrate basic processes required for using van der Waals heterostructures in electronics and photonics.

  16. Periodic potentials in hybrid van der Waals heterostructures formed by supramolecular lattices on graphene

    NASA Astrophysics Data System (ADS)

    Gobbi, Marco; Bonacchi, Sara; Lian, Jian X.; Liu, Yi; Wang, Xiao-Ye; Stoeckel, Marc-Antoine; Squillaci, Marco A.; D'Avino, Gabriele; Narita, Akimitsu; Müllen, Klaus; Feng, Xinliang; Olivier, Yoann; Beljonne, David; Samorì, Paolo; Orgiu, Emanuele

    2017-03-01

    The rise of 2D materials made it possible to form heterostructures held together by weak interplanar van der Waals interactions. Within such van der Waals heterostructures, the occurrence of 2D periodic potentials significantly modifies the electronic structure of single sheets within the stack, therefore modulating the material properties. However, these periodic potentials are determined by the mechanical alignment of adjacent 2D materials, which is cumbersome and time-consuming. Here we show that programmable 1D periodic potentials extending over areas exceeding 104 nm2 and stable at ambient conditions arise when graphene is covered by a self-assembled supramolecular lattice. The amplitude and sign of the potential can be modified without altering its periodicity by employing photoreactive molecules or their reaction products. In this regard, the supramolecular lattice/graphene bilayer represents the hybrid analogue of fully inorganic van der Waals heterostructures, highlighting the rich prospects that molecular design offers to create ad hoc materials.

  17. Understanding the nanoscale local buckling behavior of vertically aligned MWCNT arrays with van der Waals interactions.

    PubMed

    Li, Yupeng; Kim, Hyung-ick; Wei, Bingqing; Kang, Junmo; Choi, Jae-boong; Nam, Jae-Do; Suhr, Jonghwan

    2015-09-14

    The local buckling behavior of vertically aligned carbon nanotubes (VACNTs) has been investigated and interpreted in the view of a collective nanotube response by taking van der Waals interactions into account. To the best of our knowledge, this is the first report on the case of collective VACNT behavior regarding van der Waals force among nanotubes as a lateral support effect during the buckling process. The local buckling propagation and development of VACNTs were experimentally observed and theoretically analyzed by employing finite element modeling with lateral support from van der Waals interactions among nanotubes. Both experimental and theoretical analyses show that VACNTs buckled in the bottom region with many short waves and almost identical wavelengths, indicating a high mode buckling. Furthermore, the propagation and development mechanism of buckling waves follow the wave damping effect.

  18. Interoperability - a Key Element for the Grid and DER of the Future

    SciTech Connect

    Hamilton, S.; Gunther, E.; Drummond, R.; Widergren, Steven E.

    2006-05-21

    The information exchange and coordinated control of distributed energy resources (DER) for many different purposes to the benefit of various parties represents a complex problem. The large number of DER devices means that the information exchange approaches, must be scalable, must accommodate a changing variety of communications technologies over time, and lend themselves to safe and reliable distributed decision making schemes. Mainstream information technology (IT) techniques will drive these approaches, but what can be done to facilitate the integration of the vast number of these resources into the larger system so they can interoperate more easily? Establishing a common vision of interoperability principles for the integration of DER in the power system can help address this question.

  19. Photovoltaic DER System Could Save USPS $25,000 per Year in Marina del Rey, California

    SciTech Connect

    Not Available

    2002-11-01

    In numerous projects, government agencies are demonstrating the economic and environmental value of using distributed energy resources (DER) to provide reliable electricity for Federal facilities. These projects also show how renewable DER systems such as photovoltaics (PV) can be effectively integrated into utility power grids to provide added power during peak demand periods in populous regions and states. This four-page case study describes a recent project in which the United States Postal Service (USPS) worked with the U.S. Department of Energy (DOE) Federal Energy Management Program (FEMP), a national laboratory, the local utility, and a private company to install a PV DER system at the USPS Marina Processing and Distribution Center in Inglewood, California. This system is expected to shave 10% off the facility's 1.2-megawatt peak power demand and save more $25,000 per year in utility costs.

  20. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

    PubMed Central

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; Liang, Liangbo; West, Damien; Meunier, Vincent; Zhang, Shengbai

    2016-01-01

    The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs. PMID:27160484

  1. Tunable phonon polaritons in atomically thin van der Waals crystals of boron nitride.

    PubMed

    Dai, S; Fei, Z; Ma, Q; Rodin, A S; Wagner, M; McLeod, A S; Liu, M K; Gannett, W; Regan, W; Watanabe, K; Taniguchi, T; Thiemens, M; Dominguez, G; Castro Neto, A H; Zettl, A; Keilmann, F; Jarillo-Herrero, P; Fogler, M M; Basov, D N

    2014-03-07

    van der Waals heterostructures assembled from atomically thin crystalline layers of diverse two-dimensional solids are emerging as a new paradigm in the physics of materials. We used infrared nanoimaging to study the properties of surface phonon polaritons in a representative van der Waals crystal, hexagonal boron nitride. We launched, detected, and imaged the polaritonic waves in real space and altered their wavelength by varying the number of crystal layers in our specimens. The measured dispersion of polaritonic waves was shown to be governed by the crystal thickness according to a scaling law that persists down to a few atomic layers. Our results are likely to hold true in other polar van der Waals crystals and may lead to new functionalities.

  2. Die Tabellen von Ulugh Beg. Die Sternkataloge des Ptolemäus, Ulugh Beg und Tycho Brahe im Vergleich

    NASA Astrophysics Data System (ADS)

    Schwan, Heiner

    2002-09-01

    Im 15. Jahrhundert schuf Ulugh Beg, der Herrscher von Samarkand (1394 - 1449), ein wichtiges Tabellenwerk. Das Kernstück dieses Werks (Zij Ulugh Beg, "Tabellen Ulugh Begs") ist ein Katalog mit 1018 Sternen, ihren Helligkeiten und Positionen. In diesem Bericht werden die Zij Ulugh Beg mit den großen Katalogen von Ptolemäus und Tycho Brahe verglichen.

  3. Die Pugwash Conferences on Science and World Affairs Ein Beispiel für erfolgreiche „Track-II-Diplomacy“ der Naturwissenschaftler im Kalten Krieg

    NASA Astrophysics Data System (ADS)

    Neuneck, Götz

    "Kein Zeitalter der Geschichte ist stärker von den Naturwissenschaften durchdrungen und abhängiger von ihnen als das 20. Jahrhundert" schreibt Eric Hobsbawn im Kapitel "Zauberer und Lehrlinge: Die Naturwissenschaften" seines Buches "Zeitalter der Extreme".

  4. Schlüsselkomponenten für Roboter in der Produktion Roboterhaut und Sicherheitskonzept für die Mensch-Roboter Kooperation

    NASA Astrophysics Data System (ADS)

    Denkena, B.; Hesse, P.; Friederichs, J.; Wedler, A.

    Vorgestellt wird der Aufbau einer aktiven Sensor-Matrix zur Abstands- und Kontaktdetektion in der Robotik. Diese besteht aus einem Sensornetzwerk zur Fusion und Überlagerung differenter physikalischer Wirkprinzipien. Die Sicherheit der I2C-Bus Kommunikation, der Aufbau der Roboterhaut, Ergebnisse der Abstandsdetektion mit Infrarot-, und Ultraschallsensorik werden dargestellt. Ferner wurden Temperatur-, und Beschleunigungssensoren auf die Oberfläche der Roboterhaut aufgebracht um Informationen über die Umgebung sicher an ein übergeordnetes Leitsystem zu übertragen. Eine unterlagerte sichere Roboterhaut mit Kontaktdetektion zeigt als einfache Schlüsselkomponente ein analoges Ausschaltverhalten für geringe Latenzzeiten. Als Schluss wird auf den Einsatz an einem Industrieroboter in der Produktion ohne trennende Schutzeinrichtungen (OTS) eingegangen.

  5. Understanding the nanoscale local buckling behavior of vertically aligned MWCNT arrays with van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Li, Yupeng; Kim, Hyung-Ick; Wei, Bingqing; Kang, Junmo; Choi, Jae-Boong; Nam, Jae-Do; Suhr, Jonghwan

    2015-08-01

    The local buckling behavior of vertically aligned carbon nanotubes (VACNTs) has been investigated and interpreted in the view of a collective nanotube response by taking van der Waals interactions into account. To the best of our knowledge, this is the first report on the case of collective VACNT behavior regarding van der Waals force among nanotubes as a lateral support effect during the buckling process. The local buckling propagation and development of VACNTs were experimentally observed and theoretically analyzed by employing finite element modeling with lateral support from van der Waals interactions among nanotubes. Both experimental and theoretical analyses show that VACNTs buckled in the bottom region with many short waves and almost identical wavelengths, indicating a high mode buckling. Furthermore, the propagation and development mechanism of buckling waves follow the wave damping effect.The local buckling behavior of vertically aligned carbon nanotubes (VACNTs) has been investigated and interpreted in the view of a collective nanotube response by taking van der Waals interactions into account. To the best of our knowledge, this is the first report on the case of collective VACNT behavior regarding van der Waals force among nanotubes as a lateral support effect during the buckling process. The local buckling propagation and development of VACNTs were experimentally observed and theoretically analyzed by employing finite element modeling with lateral support from van der Waals interactions among nanotubes. Both experimental and theoretical analyses show that VACNTs buckled in the bottom region with many short waves and almost identical wavelengths, indicating a high mode buckling. Furthermore, the propagation and development mechanism of buckling waves follow the wave damping effect. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03581c

  6. Recent Improvements to the Finite-Fault Rupture Detector Algorithm: FinDer II

    NASA Astrophysics Data System (ADS)

    Smith, D.; Boese, M.; Heaton, T. H.

    2015-12-01

    Constraining the finite-fault rupture extent and azimuth is crucial for accurately estimating ground-motion in large earthquakes. Detecting and modeling finite-fault ruptures in real-time is thus essential to both earthquake early warning (EEW) and rapid emergency response. Following extensive real-time and offline testing, the finite-fault rupture detector algorithm, FinDer (Böse et al., 2012 & 2015), was successfully integrated into the California-wide ShakeAlert EEW demonstration system. Since April 2015, FinDer has been scanning real-time waveform data from approximately 420 strong-motion stations in California for peak ground acceleration (PGA) patterns indicative of earthquakes. FinDer analyzes strong-motion data by comparing spatial images of observed PGA with theoretical templates modeled from empirical ground-motion prediction equations (GMPEs). If the correlation between the observed and theoretical PGA is sufficiently high, a report is sent to ShakeAlert including the estimated centroid position, length, and strike, and their uncertainties, of an ongoing fault rupture. Rupture estimates are continuously updated as new data arrives. As part of a joint effort between USGS Menlo Park, ETH Zurich, and Caltech, we have rewritten FinDer in C++ to obtain a faster and more flexible implementation. One new feature of FinDer II is that multiple contour lines of high-frequency PGA are computed and correlated with templates, allowing the detection of both large earthquakes and much smaller (~ M3.5) events shortly after their nucleation. Unlike previous EEW algorithms, FinDer II thus provides a modeling approach for both small-magnitude point-source and larger-magnitude finite-fault ruptures with consistent error estimates for the entire event magnitude range.

  7. Effect of floorcovering construction on content and vertical distribution of house dust mite allergen, Der p I.

    PubMed

    Causer, Simon; Shorter, Caroline; Sercombe, Jason

    2006-04-01

    Domestic floorcoverings often contain appreciable quantities of particulate pollutants, such as house dust mite allergen, Der p I. Exposure to Der p I is a risk factor for the development of mite sensitization and asthma. We investigated whether carpet construction was related to the Der p I content in normal use, and its vertical distribution. We hoped to inform development of methods to remove such material. Along with one hard flooring surface, a range of carpets with differing pile conformations (loop vs. cut), pile heights, yarn twists, and pile densities were placed in houses for 13 months. The carpets were later sectioned to allow profiling of Der p I throughout the pile strata using monoclonal antibody, enzyme-linked immunosorbent assay. Not surprisingly, significantly lower amounts of Der p I were found on hard flooring than any of the carpets, which all contained similar amounts of mite allergen. For all carpets, the Der p I concentration per unit area was found to be inversely related to the distance from the carpet backing. We conclude that carpet construction is not a good predictor of Der p I content in the home. We also suggest that, as carpet construction likely influences ease of disturbance of material within the pile, methods to remove or denature particulate pollutants such as Der p I will be most effective if they are able to target the bulk of allergenic material, found toward the base of the pile.

  8. 49 CFR 40.215 - What information about the DER do employers have to provide to BATs and STTs?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... to provide to BATs and STTs? 40.215 Section 40.215 Transportation Office of the Secretary of... Personnel § 40.215 What information about the DER do employers have to provide to BATs and STTs? As an employer, you must provide to the STTs and BATs the name and telephone number of the appropriate DER (and...

  9. 49 CFR 40.215 - What information about the DER do employers have to provide to BATs and STTs?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... to provide to BATs and STTs? 40.215 Section 40.215 Transportation Office of the Secretary of... Personnel § 40.215 What information about the DER do employers have to provide to BATs and STTs? As an employer, you must provide to the STTs and BATs the name and telephone number of the appropriate DER (and...

  10. 49 CFR 40.215 - What information about the DER do employers have to provide to BATs and STTs?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... to provide to BATs and STTs? 40.215 Section 40.215 Transportation Office of the Secretary of... Personnel § 40.215 What information about the DER do employers have to provide to BATs and STTs? As an employer, you must provide to the STTs and BATs the name and telephone number of the appropriate DER (and...

  11. 49 CFR 40.215 - What information about the DER do employers have to provide to BATs and STTs?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... to provide to BATs and STTs? 40.215 Section 40.215 Transportation Office of the Secretary of... Personnel § 40.215 What information about the DER do employers have to provide to BATs and STTs? As an employer, you must provide to the STTs and BATs the name and telephone number of the appropriate DER (and...

  12. 49 CFR 40.215 - What information about the DER do employers have to provide to BATs and STTs?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... to provide to BATs and STTs? 40.215 Section 40.215 Transportation Office of the Secretary of... Personnel § 40.215 What information about the DER do employers have to provide to BATs and STTs? As an employer, you must provide to the STTs and BATs the name and telephone number of the appropriate DER (and...

  13. Trace elements and REE geochemistry of Middle Devonian carbonate mounds (Maïder Basin, Eastern Anti-Atlas, Morocco): Implications for early diagenetic processes

    NASA Astrophysics Data System (ADS)

    Franchi, Fulvio; Turetta, Clara; Cavalazzi, Barbara; Corami, Fabiana; Barbieri, Roberto

    2016-08-01

    Trace and rare earth elements (REEs) have proven their utility as tools for assessing the genesis and early diagenesis of widespread geological bodies such as carbonate mounds, whose genetic processes are not yet fully understood. Carbonates from the Middle Devonian conical mud mounds of the Maïder Basin (eastern Anti-Atlas, Morocco) have been analysed for their REE and trace element distribution. Collectively, the carbonates from the Maïder Basin mud mounds appear to display coherent REE patterns. Three different geochemical patterns, possibly related with three different diagenetic events, include: i) dyke fills with a normal marine REE pattern probably precipitated in equilibrium with seawater, ii) mound micrite with a particular enrichment of overall REE contents and variable Ce anomaly probably related to variation of pH, increase of alkalinity or dissolution/remineralization of organic matter during early diagenesis, and iii) haematite-rich vein fills precipitated from venting fluids of probable hydrothermal origin. Our results reinforce the hypothesis that these mounds were probably affected by an early diagenesis induced by microbial activity and triggered by abundance of dispersed organic matter, whilst venting may have affected the mounds during a later diagenetic phase.

  14. Near-Unity Absorption in van der Waals Semiconductors for Ultrathin Optoelectronics.

    PubMed

    Jariwala, Deep; Davoyan, Artur R; Tagliabue, Giulia; Sherrott, Michelle C; Wong, Joeson; Atwater, Harry A

    2016-09-14

    We demonstrate near-unity, broadband absorbing optoelectronic devices using sub-15 nm thick transition metal dichalcogenides (TMDCs) of molybdenum and tungsten as van der Waals semiconductor active layers. Specifically, we report that near-unity light absorption is possible in extremely thin (<15 nm) van der Waals semiconductor structures by coupling to strongly damped optical modes of semiconductor/metal heterostructures. We further fabricate Schottky junction devices using these highly absorbing heterostructures and characterize their optoelectronic performance. Our work addresses one of the key criteria to enable TMDCs as potential candidates to achieve high optoelectronic efficiency.

  15. Analyzing Longitudinal Magnetoresistance Asymmetry to Quantify Doping Gradients: Generalization of the van der Pauw Method

    NASA Astrophysics Data System (ADS)

    Zhou, Wang; Yoo, H. M.; Prabhu-Gaunkar, S.; Tiemann, L.; Reichl, C.; Wegscheider, W.; Grayson, M.

    2015-10-01

    A longitudinal magnetoresistance asymmetry (LMA) between a positive and negative magnetic field is known to occur in both the extreme quantum limit and the classical Drude limit in samples with a nonuniform doping density. By analyzing the current stream function in van der Pauw measurement geometry, it is shown that the electron density gradient can be quantitatively deduced from this LMA in the Drude regime. Results agree with gradients interpolated from local densities calibrated across an entire wafer, establishing a generalization of the van der Pauw method to quantify density gradients.

  16. Enhanced and switchable nanoscale thermal conduction due to van der Waals interfaces.

    PubMed

    Yang, Juekuan; Yang, Yang; Waltermire, Scott W; Wu, Xiaoxia; Zhang, Haitao; Gutu, Timothy; Jiang, Youfei; Chen, Yunfei; Zinn, Alfred A; Prasher, Ravi; Xu, Terry T; Li, Deyu

    2011-12-11

    Understanding thermal transport in nanostructured materials is important for the development of energy conversion applications and the thermal management of microelectronic and optoelectronic devices. Most nanostructures interact through van der Waals interactions, and these interactions typically lead to a reduction in thermal transport. Here, we show that the thermal conductivity of a bundle of boron nanoribbons can be significantly higher than that of a single free-standing nanoribbon. Moreover, the thermal conductivity of the bundle can be switched between the enhanced values and that of a single nanoribbon by wetting the van der Waals interface between the nanoribbons with various solutions.

  17. Analyzing Longitudinal Magnetoresistance Asymmetry to Quantify Doping Gradients: Generalization of the van der Pauw Method.

    PubMed

    Zhou, Wang; Yoo, H M; Prabhu-Gaunkar, S; Tiemann, L; Reichl, C; Wegscheider, W; Grayson, M

    2015-10-30

    A longitudinal magnetoresistance asymmetry (LMA) between a positive and negative magnetic field is known to occur in both the extreme quantum limit and the classical Drude limit in samples with a nonuniform doping density. By analyzing the current stream function in van der Pauw measurement geometry, it is shown that the electron density gradient can be quantitatively deduced from this LMA in the Drude regime. Results agree with gradients interpolated from local densities calibrated across an entire wafer, establishing a generalization of the van der Pauw method to quantify density gradients.

  18. van der Pauw method for measuring resistivity of a plane sample with distant boundaries.

    PubMed

    Lim, S H N; McKenzie, D R; Bilek, M M M

    2009-07-01

    In the paper, we derive an algorithm which follows from the original van der Pauw's technique for measuring resistivity with the added advantage of allowing contacts to be positioned a distance away from the boundary. For a large sample area, we show that the resistivity calculated by our algorithm is equivalent to the resistivity calculated by the original van der Pauw's method. In practice, this configuration is easier to achieve and can eliminate errors associated with contacts that are not placed exactly at the edge.

  19. Van der Pauw method on a sample with an isolated hole

    NASA Astrophysics Data System (ADS)

    Szymański, Krzysztof; Cieśliński, Jan L.; Łapiński, Kamil

    2013-03-01

    Explicit results of the van der Pauw method for a sample containing an isolated hole are presented together with experimental confirmation. Results of measurements and numerical analysis strongly suggest that four probe resistivities obey inequality similar in the form to the famous van der Pauw equation. The inequality seems to be valid for any sample with an isolated hole and contacts located on the same edge, however rigorous proof is not given. The inequality can be used for experimental detection of the sample quality.

  20. van der Waals equation of state for a fluid in a nanopore.

    PubMed

    Zarragoicoechea, Guillermo J; Kuz, Víctor A

    2002-02-01

    A generalization of the van der Waals equation of state is presented for a confined fluid in a nanopore. The pressure in the fluid, confined in a narrow pore of infinite length, has tensorial character. From this hypothesis, the Helmholtz free energy is constructed and expressions for the axial and transversal components of the pressure tensor are obtained. The equations predict liquid-vapor equilibria, and a shift of the critical point with respect to that obtained from the van der Waals bulk equation. The results are in good agreement with recent experiments.

  1. Phase Transition of AdS Black Holes with Non Linear Source in the Holographic Framework

    NASA Astrophysics Data System (ADS)

    Moumni, H. El

    2017-02-01

    In this work we investigate the phase transition of AdS black hole solution in the presence of a generalized Maxwell theory, namely power Maxwell invariant (PMI). This phase structure is probed by the nonlocal observables such as holographic entanglement entropy and two point correlation function. We show that the both observables exhibit a Van der Waals-like phase transition as the case of the thermal entropy. By checking the Maxwell's equal area law for different space dimension n and nonlinearity parameter s we confirm this result.

  2. Reduktion der Invasivität bei nadelbasierter Bewegungskompensation für navigierte Eingriffe im Abdomen

    NASA Astrophysics Data System (ADS)

    Maier-Hein, L.; Tekbas, A.; Franz, A. M.; Tetzlaff, R.; Müller, S. A.; Pianka, F.; Wolf, I.; Kauczor, H.-U.; Schmied, B. M.; Meinzer, H.-P.

    Diese Arbeit stellt eine in-vivo Genauigkeitsstudie über das Kombinieren interner und externer Marker für die Bewegungskompensation bei Leberinterventionen vor. Abhängig von der Anzahl und Anordnung der verwendeten Marker sowie der angewandten Echtzeittransformation wurde bei kontinuierlicher Atmung eine Schätzgenauigkeit der Zielposition zwischen 1 und 5 mm erreicht. Das Hinzufügen einer einzigen Hilfsnadel zu einer Menge von Hautmarkern führte zu einer Fehlerreduktion von über 50%. Die Ergebnisse dieser Studie können in der Praxis verwendet werden, um basierend auf dem Tradeoff zwischen geringer Invasivität und hoher Genauigkeit eine geeignete Kombination von internen und externen Markern für eine gegebene Fragestellung zu wählen.

  3. Phase equilibria in molecular hydrogen-helium mixtures at high pressures

    NASA Technical Reports Server (NTRS)

    Streett, W. B.

    1973-01-01

    Experiments on phase behavior in hydrogen-helium mixtures have been carried out at pressures up to 9.3 kilobars, at temperatures from 26 to 100 K. Two distinct fluid phases are shown to exist at supercritical temperatures and high pressures. Both the trend of the experimental results and an analysis based on the van der Waals theory of mixtures suggest that this fluid-fluid phase separation persists at temperatures and pressures beyond the range of these experiments, perhaps even to the limits of stability of the molecular phases. The results confirm earlier predictions concerning the form of the hydrogen-helium phase diagram in the region of pressure-induced solidification of the molecular phases at supercritical temperatures. The implications of this phase diagram for planetary interiors are discussed.

  4. Connecting Distributed Energy Resources to the Grid: Their Benefits to the DER Owner etc.

    SciTech Connect

    Poore, WP

    2003-07-09

    The vision of the Distributed Energy Research Program (DER) program of the U.S. Department of Energy (DOE) is that the United States will have the cleanest and most efficient and reliable energy system in the world by maximizing the use of affordable distributed energy resources. Electricity consumers will be able to choose from a diverse number of efficient, cost-effective, and environmentally friendly distributed energy options and easily connect them into the nation's energy infrastructure while providing benefits to their owners and other stakeholders. The long-term goal of this vision is that DER will achieve a 20% share of new electric capacity additions in the United States by 2010, thereby helping to make the nation's electric power generation and delivery system more efficient, reliable, secure, clean, economical, and diverse in terms of fuel use (oil, natural gas, solar, hydroelectric, etc.) and prime mover resource (solar, wind, gas turbines, etc.). Near- and mid-term goals are to develop new technologies for implementing and operating DER and address barriers associated with DER usage and then to reduce costs and emissions and improve the efficiency and reliability of DER. Numerous strategies for meeting these goals have been developed into a research, development, and demonstration (RD&D) program that supports generation and delivery systems architecture, including modeling and simulation tools. The benefits associated with DER installations are often significant and numerous. They almost always provide tangible economic benefits, such as energy savings or transmission and distribution upgrade deferrals, as well as intangible benefits, such as power quality improvements that lengthen maintenance or repair intervals for power equipment. Also, the benefits routinely are dispersed among end users, utilities, and the public. For instance, an end user may use the DER to reduce their peak demand and save money due to lower demand charges. Reduced end user

  5. Phase-flip and oscillation-quenching-state transitions through environmental diffusive coupling

    NASA Astrophysics Data System (ADS)

    Sharma, Amit; Verma, Umesh Kumar; Shrimali, Manish Dev

    2016-12-01

    We study the dynamics of nonlinear oscillators coupled through environmental diffusive coupling. The interaction between the dynamical systems is maintained through its agents which, in turn, interact globally with each other in the common dynamical environment. We show that this form of coupling scheme can induce an important transition like phase-flip transition as well transitions among oscillation quenching states in identical limit-cycle oscillators. This behavior is analyzed in the parameter plane by analytical and numerical studies of specific cases of the Stuart-Landau oscillator and van der Pol oscillator. Experimental evidences of the phase-flip transition and quenching states are shown using an electronic version of the van der Pol oscillators.

  6. Holographic research on phase transitions for a five dimensional AdS black hole with conformally coupled scalar hair

    NASA Astrophysics Data System (ADS)

    Li, Hui-Ling; Yang, Shu-Zheng; Zu, Xiao-Tao

    2017-01-01

    In the framework of holography, we survey the phase structure for a higher dimensional hairy black hole including the effects of the scalar field hair. It is worth emphasizing that, not only black hole entropy, but also entanglement entropy and two point correlation function exhibit the Van der Waals-like phase transition in a fixed scalar charge ensemble. Furthermore, by making use of numerical computation, we show that the Maxwell's equal area law is valid for the first order phase transition. In addition, we also discuss how the hair parameter affects the black hole's phase transition.

  7. A van der Waals Equation of State for a Dilute Boson Gas

    ERIC Educational Resources Information Center

    Deeney, F. A.; O'Leary, J. P.

    2012-01-01

    An equation of state of a system is a relationship that connects the thermodynamic variables of the system such as pressure and temperature. Such equations are well known for classical gases but less so for quantum systems. In this paper we develop a van der Waals equation of state for a dilute boson gas that may be used to explain the occurrence…

  8. 57. Photocopy of illustration 'Landungsplatz der HamburgAmerika Linie in Hoboken ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    57. Photocopy of illustration 'Landungsplatz der Hamburg-Amerika Linie in Hoboken (1899)'. VIEW OF HAMBURG-AMERICAN TERMINAL AND PIERS, LOOKING EAST. (From an unidentified source. Artist unknown, circa 1899) - Hoboken Piers Headhouse, River Street at Hudson River, Hoboken, Hudson County, NJ

  9. Gas Temperature Determination in Argon-Helium Plasma at Atmospheric Pressure using van der Waals Broadening

    SciTech Connect

    Munoz, Jose; Yubero, Cristina; Calzada, Maria Dolores; Dimitrijevic, Milan S.

    2008-10-22

    The use of the van der Waals broadening of Ar atomic lines to determine the gas temperature in Ar-He plasmas, taking into account both argon and helium atoms as perturbers, has been analyzed. The values of the gas temperature inferred from this broadening have been compared with those obtained from the spectra of the OH molecular species in the discharge.

  10. Erzahlraum im virtuellen Raum: Rewriting Bernhard Schlink's "Der Vorleser" on the Web >.

    ERIC Educational Resources Information Center

    Schaumann, Caroline

    2001-01-01

    Presents a pilot course for the Collaboration in Virtual Space (CiVS) project at Middlebury College. After reading and discussing Bernhard Schlink's "Der Vorleser," students produced in collaborative groups a Web site with information on Schlink, the text's cultural-historical background, and its reception, and they developed an interactive,…

  11. Dynamics of Gold Nanoparticles on Carbon Nanostructures Driven by van der Waals and Electrostatic Interactions.

    PubMed

    La Torre, Alessandro; Gimenez-Lopez, Maria del Carmen; Fay, Michael W; Lucas, Carlos Herreros; Brown, Paul D; Khlobystov, Andrei N

    2015-06-01

    Transmission electron microscopy studies on the assembly and growth of gold nanoparticles on carbon nanotubes supported on few-layer graphene and amorphous carbon reveal a competition between van der Waals forces and electrostatic interactions, enabling controlled positioning and sizing of adsorbed nanoparticles at the nanochannels formed between the carbon nanotube and the few-layer graph-ene surface.

  12. Atomically thin p-n junctions with van der Waals heterointerfaces.

    PubMed

    Lee, Chul-Ho; Lee, Gwan-Hyoung; van der Zande, Arend M; Chen, Wenchao; Li, Yilei; Han, Minyong; Cui, Xu; Arefe, Ghidewon; Nuckolls, Colin; Heinz, Tony F; Guo, Jing; Hone, James; Kim, Philip

    2014-09-01

    Semiconductor p-n junctions are essential building blocks for electronic and optoelectronic devices. In conventional p-n junctions, regions depleted of free charge carriers form on either side of the junction, generating built-in potentials associated with uncompensated dopant atoms. Carrier transport across the junction occurs by diffusion and drift processes influenced by the spatial extent of this depletion region. With the advent of atomically thin van der Waals materials and their heterostructures, it is now possible to realize a p-n junction at the ultimate thickness limit. Van der Waals junctions composed of p- and n-type semiconductors--each just one unit cell thick--are predicted to exhibit completely different charge transport characteristics than bulk heterojunctions. Here, we report the characterization of the electronic and optoelectronic properties of atomically thin p-n heterojunctions fabricated using van der Waals assembly of transition-metal dichalcogenides. We observe gate-tunable diode-like current rectification and a photovoltaic response across the p-n interface. We find that the tunnelling-assisted interlayer recombination of the majority carriers is responsible for the tunability of the electronic and optoelectronic processes. Sandwiching an atomic p-n junction between graphene layers enhances the collection of the photoexcited carriers. The atomically scaled van der Waals p-n heterostructures presented here constitute the ultimate functional unit for nanoscale electronic and optoelectronic devices.

  13. First principles calculations of solid-state thermionic transport in layered van der Waals heterostructures.

    PubMed

    Wang, Xiaoming; Zebarjadi, Mona; Esfarjani, Keivan

    2016-08-21

    This work aims at understanding solid-state energy conversion and transport in layered (van der Waals) heterostructures in contact with metallic electrodes via a first-principles approach. As an illustration, a graphene/phosphorene/graphene heterostructure in contact with gold electrodes is studied by using density functional theory (DFT)-based first principles calculations combined with real space Green's function (GF) formalism. We show that for a monolayer phosphorene, quantum tunneling dominates the transport. By adding more phosphorene layers, one can switch from tunneling-dominated transport to thermionic-dominated transport, resulting in transporting more heat per charge carrier, thus, enhancing the cooling coefficient of performance. The use of layered van der Waals heterostructures has two advantages: (a) thermionic transport barriers can be tuned by changing the number of layers, and (b) thermal conductance across these non-covalent structures is very weak. The phonon thermal conductance of the present van der Waals heterostructure is found to be 4.1 MW m(-2) K(-1) which is one order of magnitude lower than the lowest value for that of covalently-bonded interfaces. The thermionic coefficient of performance for the proposed device is 18.5 at 600 K corresponding to an equivalent ZT of 0.13, which is significant for nanoscale devices. This study shows that layered van der Waals structures have great potential to be used as solid-state energy-conversion devices.

  14. Dynamical screening of the van der Waals interaction between graphene layers.

    PubMed

    Dappe, Y J; Bolcatto, P G; Ortega, J; Flores, F

    2012-10-24

    The interaction between graphene layers is analyzed combining local orbital DFT and second order perturbation theory. For this purpose we use the linear combination of atomic orbitals-orbital occupancy (LCAO-OO) formalism, that allows us to separate the interaction energy as the sum of a weak chemical interaction between graphene layers plus the van der Waals interaction (Dappe et al 2006 Phys. Rev. B 74 205434). In this work, the weak chemical interaction is calculated by means of corrected-LDA calculations using an atomic-like sp(3)d(5) basis set. The van der Waals interaction is calculated by means of second order perturbation theory using an atom-atom interaction approximation and the atomic-like-orbital occupancies. We also analyze the effect of dynamical screening in the van der Waals interaction using a simple model. We find that this dynamical screening reduces by 40% the van der Waals interaction. Taking this effect into account, we obtain a graphene-graphene interaction energy of 70 ± 5 meV/atom in reasonable agreement with the experimental evidence.

  15. van der Waals Metal-Organic Framework as an Excitonic Material for Advanced Photonics.

    PubMed

    Milichko, Valentin A; Makarov, Sergey V; Yulin, Alexey V; Vinogradov, Alexandr V; Krasilin, Andrei A; Ushakova, Elena; Dzyuba, Vladimir P; Hey-Hawkins, Evamarie; Pidko, Evgeny A; Belov, Pavel A

    2017-01-23

    Synergistic combination of organic and inorganic nature in van der Waals metal-organic frameworks supports different types of robust excitons that can be effectively and independently manipulated by light at room temperature, and opens new concepts for all-optical data processing and storage.

  16. Interlayer Interactions in van der Waals Heterostructures: Electron and Phonon Properties.

    PubMed

    Le, Nam B; Huan, Tran Doan; Woods, Lilia M

    2016-03-09

    Artificial van der Waals heterostructures constitute an emerging field that promises to design systems with properties on demand. Stacking patterns and the utilization of different types of chemically inert layers can deliver novel materials and devices. Despite the relatively weak van der Waals interaction, which does not affect the electronic properties around the Fermi level, our first-principles calculations show significant changes in the higher conduction and deeper valence regions in the considered graphene/silicene, graphene/MoS2, and silicene/MoS2 systems. Such changes are linked to strong out-of-plane hybridization effects and van der Waals interactions. We also find that the interface coupling significantly affects the vibrational properties of the heterostructures when compared to the individual constituents. Specifically, the van der Waals coupling is found to be a major factor for the stability of the system. The emergence of shear and breathing modes, as well as the transformation of flexural modes, are also found.

  17. Generalized van der Waals Hamiltonian: periodic orbits and C1 nonintegrability.

    PubMed

    Guirao, Juan L G; Llibre, Jaume; Vera, Juan A

    2012-03-01

    The aim of this paper is to study the periodic orbits of the generalized van der Waals Hamiltonian system. The tool for studying such periodic orbits is the averaging theory. Moreover, for this Hamiltonian system we provide information on its C(1) nonintegrability, i.e., on the existence of a second first integral of class C(1).

  18. Maxwell's Relations for a van der Waals Gas and a Nuclear Paramagnetic System.

    ERIC Educational Resources Information Center

    Herlihy, James; And Others

    1981-01-01

    Since Maxwell's relations are derived in general form from the first to second laws, and students often wonder what they mean and how they are used, appropriate partition functions for van der Waals gas and the nuclear paramagnetic system are used to obtain entropy expressions and equations of state. (Author/SK)

  19. Leistungsmessungen zum Einsatz der J2EE Technologie für Feldbussimulationen

    NASA Astrophysics Data System (ADS)

    Garreis, Thorsten; Jürgens, Hendrik; Schmidtmann, Uwe; von Cölin, Gerd

    Die Flexibilisierung der Fertigung und kurze Produktzyklen setzen einen beschleunigten, möglichst fehlerfreien Entwicklungsprozess voraus. Dieses Ziel kann jedoch nur erreicht werden, wenn bereits parallel zur Hardwareentwicklung die Software mit Hilfe einer Simulation der Hardware entwickelt und getestet werden kann. Darüber hinaus können mit Simulationen alternative Lösungen studiert werden, die zu optimierten Verfahren führen. In dieser Arbeit werden Leistungstests an der Simulationsumgebung drd-Simulator präsentiert, die auf der J2EE-Technologie1 basiert. Für die Messungen wird eine Soft-SPS eingesetzt, deren Feldbus vom Typ ModbusTCP simuliert wird. Erste Messungen zeigen, dass J2EE eine leistungsstarke und skalierbare Plattform für die Realisierung von Feldbussimulationen ist. In einem Zyklusbereich ab 100 ms ist das E/A-Verhalten echtzeitfähig, wobei meherere Steuerungen auf den Bus zugreifen können. Die J2EE-Technologie zeichnet sich zudem durch eine gute Ausfallsicherheit und dynamische Rekonfigurier-barkeit aus, so dass Tests dynamisch zur Laufzeit ergänzt oder verändert werden können.

  20. The first record of Pyxidium tardigradum Van der Land, 1964 (Ciliophora) in Romania.

    PubMed

    Ciobanu, Daniel Adrian; Roszkowska, Milena; Moglan, Ioan; Kaczmarek, Łukasz

    2015-04-02

    In three lichen samples collected from eastern part of Romania, three populations of Ramazzottius cf. oberhaeuseri (Doyère, 1840) infested by Pyxidium tardigradum Van der Land 1964 were found. In this short correspondence we present a first record of P. tardigradum in Romania and infestation rates in studied populations according to the different life stages.

  1. Effect of van der Waals interactions on the structural and binding properties of GaSe

    SciTech Connect

    Sarkisov, Sergey Y.; Kosobutsky, Alexey V.; Shandakov, Sergey D.

    2015-12-15

    The influence of van der Waals interactions on the lattice parameters, band structure, elastic moduli and binding energy of layered GaSe compound has been studied using projector-augmented wave method within density functional theory. We employed the conventional local/semilocal exchange-correlation functionals and recently developed van der Waals functionals which are able to describe dispersion forces. It is found that application of van der Waals density functionals allows to substantially increase the accuracy of calculations of the lattice constants a and c and interlayer distance in GaSe at ambient conditions and under hydrostatic pressure. The pressure dependences of the a-parameter, Ga–Ga, Ga–Se bond lengths and Ga–Ga–Se bond angle are characterized by a relatively low curvature, while c(p) has a distinct downward bowing due to nonlinear shrinking of the interlayer spacing. From the calculated binding energy curves we deduce the interlayer binding energy of GaSe, which is found to be in the range 0.172–0.197 eV/layer (14.2–16.2 meV/Å{sup 2}). - Highlights: • Effects of van der Waals interactions are analyzed using advanced density functionals. • Calculations with vdW-corrected functionals closely agree with experiment. • Interlayer binding energy of GaSe is estimated to be 14.2–16.2 meV/Å{sup 2}.

  2. The Average IQ of Sub-Saharan Africans: Comments on Wicherts, Dolan, and van der Maas

    ERIC Educational Resources Information Center

    Lynn, Richard; Meisenberg, Gerhard

    2010-01-01

    Wicherts, Dolan, and van der Maas (2009) contend that the average IQ of sub-Saharan Africans is about 80. A critical evaluation of the studies presented by WDM shows that many of these are based on unrepresentative elite samples. We show that studies of 29 acceptably representative samples on tests other than the Progressive Matrices give a…

  3. 49 CFR 40.35 - What information about the DER must employers provide to collectors?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false What information about the DER must employers provide to collectors? 40.35 Section 40.35 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Urine Collection Personnel §...

  4. 49 CFR 40.35 - What information about the DER must employers provide to collectors?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 1 2011-10-01 2011-10-01 false What information about the DER must employers provide to collectors? 40.35 Section 40.35 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Urine Collection Personnel §...

  5. 49 CFR 40.35 - What information about the DER must employers provide to collectors?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 1 2013-10-01 2013-10-01 false What information about the DER must employers provide to collectors? 40.35 Section 40.35 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Urine Collection Personnel §...

  6. 49 CFR 40.35 - What information about the DER must employers provide to collectors?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 1 2014-10-01 2014-10-01 false What information about the DER must employers provide to collectors? 40.35 Section 40.35 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Urine Collection Personnel §...

  7. 49 CFR 40.35 - What information about the DER must employers provide to collectors?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 1 2012-10-01 2012-10-01 false What information about the DER must employers provide to collectors? 40.35 Section 40.35 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Urine Collection Personnel §...

  8. van der Waals Density Functional Theory vdW-DFq for Semihard Materials

    NASA Astrophysics Data System (ADS)

    Peng, Qing; de, Suvranu

    There are a large number of materials with mild stiffness, which are not as soft as tissues and not as strong as metals. These semihard materials includes energetic materials, molecular crystals, layered materials, and van der Waals crystals. The integrity and mechanical stability are mainly determined by the interactions between instantaneously induced dipoles, the so called London dispersion force or van der Waals force. It is challenging to accurately model the structural and mechanical properties of these semihard materials in the frame of density functional theory where the non-local correlation functionals are not well known. Here we propose a van der Waals density functional named vdW-DFq to accurately model the density and geometry of semihard materials. Using β-cyclotetramethylene tetranitramine as a prototype, we adjust the enhancement factor of the exchange energy functional with generalized gradient approximations. We find this method to be simple and robust over a wide tuning range when calibrating the functional on-demand with experimental data. With a calibrated value q = 1 . 05 , the proposed vdW-DFq method shows good performance in predicting the geometries of 11 common energetic material molecular crystals and 3 typical layered van der Waals crystals. The authors would like to acknowledge the generous financial support from the Defense Threat Reduction Agency (DTRA) Grant # HDTRA1-13-1-0025.

  9. Control of excitons in multi-layer van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Calman, E. V.; Dorow, C. J.; Fogler, M. M.; Butov, L. V.; Hu, S.; Mishchenko, A.; Geim, A. K.

    2016-03-01

    We report an experimental study of excitons in a double quantum well van der Waals heterostructure made of atomically thin layers of MoS2 and hexagonal boron nitride. The emission of neutral and charged excitons is controlled by gate voltage, temperature, and both the helicity and the power of optical excitation.

  10. van der Waals density functionals built upon the electron-gas tradition: Facing the challenge of competing interactions

    SciTech Connect

    Berland, Kristian; Arter, Calvin A.; Thonhauser, T.; Cooper, Valentino R.; Lee, Kyuho; Lundqvist, Bengt I.; Schröder, Elsebeth; Hyldgaard, Per

    2014-05-14

    The theoretical description of sparse matter attracts much interest, in particular for those ground-state properties that can be described by density functional theory. One proposed approach, the van der Waals density functional (vdW-DF) method, rests on strong physical foundations and offers simple yet accurate and robust functionals. A very recent functional within this method called vdW-DF-cx [K. Berland and P. Hyldgaard, Phys. Rev. B 89, 035412 (2014)] stands out in its attempt to use an exchange energy derived from the same plasmon-based theory from which the nonlocal correlation energy was derived. Encouraged by its good performance for solids, layered materials, and aromatic molecules, we apply it to several systems that are characterized by competing interactions. These include the ferroelectric response in PbTiO{sub 3}, the adsorption of small molecules within metal-organic frameworks, the graphite/diamond phase transition, and the adsorption of an aromatic-molecule on the Ag(111) surface. Our results indicate that vdW-DF-cx is overall well suited to tackle these challenging systems. In addition to being a competitive density functional for sparse matter, the vdW-DF-cx construction presents a more robust general-purpose functional that could be applied to a range of materials problems with a variety of competing interactions.

  11. van der Waals density functionals built upon the electron-gas tradition: Facing the challenge of competing interactions

    SciTech Connect

    Berland, Kristian; Arter, Calvin A; Cooper, Valentino R; Lee, Dr. Kyuho; Lundqvist, Prof. Bengt I.; Schroder, Prof. Elsebeth; Thonhauser, Prof. Timo; Hyldgaard, Per

    2014-01-01

    The theoretical description of sparse matter attracts much interest, in particular for those groundstate properties that can be described by density functional theory (DFT). One proposed approach, the van der Waals density functional (vdW-DF) method, rests on strong physical foundations and offers simple yet accurate and robust functionals. A very recent functional within this method called vdW-DF-cx [K. Berland and P. Hyldgaard, Phys. Rev. B, in print] stands out in its attempt to use an exchange energy derived from the same plasmon-based theory from which the nonlocal correlation energy was derived. Encouraged by its good performance for solids, layered materials, and aromatic molecules, we apply it to several systems that are characterized by competing interactions. These include the ferroelectric response in PbTiO3, the adsorption of small molecules within metal-organic frameworks (MOFs), the graphite/diamond phase transition, and the adsorption of an aromaticmolecule on the Ag(111) surface. Our results indicate that vdW-DF-cx is overall well suited to tackle these challenging systems. In addition to being a competitive density functional for sparse matter, the vdW-DF-cx construction presents a more robust general purpose functional that could be applied to a range of materials problems with a variety of competing interactions.

  12. Application of a Dual-Hybrid Direct Random Phase Approximation to Water Clusters.

    PubMed

    Mezei, Pál D; Ruzsinszky, Adrienn; Csonka, Gábor I

    2016-09-13

    In water clusters, there is a delicate balance of van der Waals interactions and hydrogen bonds. Although semilocal and nonlocal density functional approximations have been recently routinely applied to water in various phases, the accurate description of hydrogen bonds remains a challenge. The most popular density functional approaches fail to predict the correct ordering of the energies of water clusters. To illustrate the required accuracy, the CCSD(T) complete basis set extrapolated dissociation energy difference between the two lowest energy hexamer structures is 0.06 kcal mol(-1) per monomer. In this work, we assessed interaction energies in neutral and ionic water clusters with various density functionals with or without van der Waals correction. Generally, van der Waals approximations play a significant role in clusters with increasing size, while hybrid functionals improve the description of hydrogen bonds. Despite these general trends, none of the tested density functional approximations with or without van der Waals correction and exact exchange mixing can lead to a uniform performance for neutral and ionic water clusters. The recently constructed dual-hybrid dRPA75 approximation is a successful combination of exact and semilocal exchange, and nonlocal correlation in its energy, while utilizing a high fraction of exact exchange. We have shown that the dRPA75 method has a systematic error, which can be efficiently compensated for by the aug-cc-pVTZ basis set for small- and medium-sized water clusters.

  13. Electronic structure and photoabsorption property of pseudocubic perovskites CH3NH3PbX3(X = I, Br) including van der Waals interaction

    NASA Astrophysics Data System (ADS)

    Yu, Chol-Jun; Jong, Un-Gi; Ri, Mun-Hyok; Ri, Gum-Chol; Pae, Yong-Hyon

    2016-11-01

    Using density functional theory with the inclusion of van der Waals (vdW) interaction, we have investigated electronic energy bands, density of states, effective masses of charge carriers, and photo absorption coefficients of pseudo-cubic CH$_3$NH$_3$PbX$_3$ (X=I, Br). Our results confirm the direct bandgap of 1.49 (1.92) eV for X=I (Br) in the pseudo-cubic $Pm$ phase with lattice constant of 6.324 (5.966) \\AA, being agreed well with experiment and indicating the necessity of vdW correction. The calculated photo absorption coefficients for X=I (Br) have the onset at red (orange) color and the first peak around violet (ultraviolet) color in overall agreement with the experiment.

  14. „Überholen ohne einzuholen“ Die Entwicklung von Technologien für übermorgen in Kernenergie und Mikroelektronik der DDR

    NASA Astrophysics Data System (ADS)

    Barkleit, Gerhard

    Dem nuklearen Patt zwischen Ostblock und westlichem Staatenbündnis ist es nach weitgehend übereinstimmender Auffassung von Politik und Wissenschaft zu danken, dass der "Kalte Krieg" in der zweiten Hälfte des 20. Jahrhunderts nicht zum weltumfassenden Flächenbrand eskalierte. An der raschen Herstellung dieses Patts waren zwei Dresdner Physiker maßgeblich beteiligt, deren einer im Manhattan-Projekt in den USA gearbeitet hatte und später in England der Spionage für die Sowjetunion und des Verrats des Know-how der Atombombe überführt wurde.

  15. Phase structure of the Born-Infeld-anti-de Sitter black holes probed by non-local observables

    NASA Astrophysics Data System (ADS)

    Zeng, Xiao-Xiong; Liu, Xian-Ming; Li, Li-Fang

    2016-11-01

    With the non-local observables such as two point correlation function and holographic entanglement entropy, we probe the phase structure of the Born-Infeld-anti-de Sitter black holes. For the case bQ>0.5, where b is the Born-Infeld parameter and Q is the charge of the black hole, the phase structure is found to be similar to that of the Van der Waals phase transition, namely the black hole undergoes a first order phase transition and a second order phase transition before it reaches a stable phase. While for the case bQ<0.5, a new phase branch emerges besides the Van der Waals phase transition. For the first order phase transition, the equal area law is checked, and for the second order phase transition, the critical exponent of the heat capacity is obtained. All these results are found to be the same as that observed in the entropy-temperature plane.

  16. Assessment of (mu)grid distributed energy resource potential using DER-CAM and GIS

    SciTech Connect

    Edwards, Jennifer L.; Marnay, Chris; Bartholomew, Emily; Ouaglal, Boubekeur; Siddiqui, Afzal S.; LaCommare, Kristina S.H.

    2002-01-01

    This report outlines an approach to assess the local potential for deployment of distributed energy resources (DER), small power-generation installations located close to the point where the energy they produce will be consumed. Although local restraints, such as zoning, building codes, and on-site physical barriers are well-known frustrations to DER deployment, no analysis method has been developed to address them within a broad economic analysis framework. The approach developed here combines established economic optimization techniques embedded in the Distributed Energy Resource Customer Adoption Model (DER-CAM) with a geographic information system (GIS) analysis of local land-use constraint. An example case in the San Diego area is developed from a strictly customer perspective, based on the premise that future development of DER may take the form of microgrids ((mu)Grids) under the control of current utility customers. Beginning with assumptions about which customer combinations h ave complementary energy loads, a GIS was used to locate specific neighborhoods in the San Diego area with promising customer combinations. A detailed energy analysis was conducted for the commercial/residential area chosen covering both electrical and heat energy requirements. Under various scenarios, different combinations of natural gas reciprocating engines were chosen by DER-CAM, ranging in size from 25 kW to 500 kW, often with heat recovery or absorption cooling. These generators typically operate throughout the day and are supplemented by purchased electricity during late-night and early-morning hours, when utility time-of-use prices are lowest. Typical (mu)Grid scenarios displaced about 80 percent of their annual gas heat load through CHP. Self-generation together with absorption cooling dramatically reduce electricity purchases, which usually only occur during nighttime hours.

  17. In planta expression of a mature Der p 1 allergen isolated from an Italian strain of Dermatophagoides pteronyssinus.

    PubMed

    Marconi, Gianpiero; Albertini, Emidio; Mari, Adriano; Palazzo, Paola; Porceddu, Andrea; Raggi, Lorenzo; Bolis, Luigi; Lancioni, Hovirag; Palomba, Antonella; Lucentini, Livia; Lanfaloni, Luisa; Marcucci, Francesco; Falcinelli, Mario; Panara, Fausto

    2012-06-01

    European (Dermatophagoides pteronyssinus) and American (Dermatophagoides farinae) house dust mite species are considered the most common causes of asthma and allergic symptoms worldwide. Der p 1 protein, one of the main allergens of D. pteronyssinus, is found in high concentration in mites faecal pellets, which can became easily airborne and, when inhaled, can cause perennial rhinitis and bronchial asthma. Here we report the isolation of the Der p 1 gene from an Italian strain of D. pteronyssinus and the PVX-mediated expression of its mature form (I-rDer p 1) in Nicotiana benthamiana plants. Human sera from characterized allergic patients were used for IgE binding inhibition assays to test the immunological reactivity of I-rDer p 1 produced in N. benthamiana plants. The binding properties of in planta produced I-rDer p 1 versus the IgE of patients sera were comparable to those obtained on Der p 1 preparation immobilized on a microarray. In this paper we provide a proof of concept for the production of an immunologically active form of Der p 1 using a plant viral vector. These results pave the way for the development of diagnostic allergy tests based on in planta produced allergens.

  18. Thermodynamic products in extended phase-space

    NASA Astrophysics Data System (ADS)

    Pradhan, Parthapratim

    We have examined the thermodynamic properties for a variety of spherically symmetric charged-AdS black hole (BH) solutions, including the charged AdS BH surrounded by quintessence dark energy and charged AdS BH in f(R) gravity in extended phase-space. This framework involves treating the cosmological constant as thermodynamic variable (for example: thermodynamic pressure and thermodynamic volume). Then they should behave as an analog of Van-der-Waal (VdW) like systems. In the extended phase-space we have calculated the entropy product and thermodynamic volume product of all horizons. The mass (or enthalpy) independent nature of the said product signals they are universal quantities. The divergence of the specific heat indicates that the second-order phase transition occurs under certain condition. In Appendix A, we have studied the thermodynamic volume products for axisymmetric spacetime and it is shown to be not universal in nature. Finally, in Appendix B, we have studied the P ‑ V criticality of Cauchy horizon for charged-AdS BH and found to be an universal relation of critical values between two horizons as Pc‑ = P c+, vc‑ = v c+, Tc‑ = ‑T c+, ρc‑ = ‑ρ c+. The symbols are defined in the main work.

  19. Effect of the house dust mite allergen Der p 1 on tryptase release from human mast cells.

    PubMed

    Wang, D Q; Shen, Y Y; Xu, J H; Tang, H

    2016-07-14

    This study aimed to investigate the effects of the house dust mite allergen Der p 1 on the secretion of tryptase from the human mast cell line HMC-1. Flow cytometry was used to determine the expression levels of protease-activated receptor-2 (PAR2) on the surface of HMC-1 cells. HMC-1 cells were treated with Der p 1, SLIGRL-NH2 (PAR2 agonist), LRGILS-NH2 (control peptide for PAR2), or Der p 1 + FSLLRY (PAR2 antagonist), and the tryptase levels were measured using enzyme-linked immunosorbent assay. The biological functions of PAR2 were determined using the calcium green indicator, and intracellular calcium fluorescence intensity in the different groups (Der p 1, SLIGRL-NH2, LRGILS- NH2, Der p 1 + FSLLRY, tryptase, tryptase + FSLLRY, or cell culture medium) was detected by laser scanning confocal microscopy. The mast cells expressed PAR2 receptor on their surfaces. Der p 1 alone induced a significant release of intracellular calcium and tryptase in HMC-1 cells compared with the SLIGRL- NH2 treatment group and the control group. The combination of Der p 1 and FSLLRY partly inhibited intracellular calcium and tryptase release in HMC-1 cells compared with the Der p 1 treatment group. Moreover, tryptase induced a significant release of intracellular calcium in the HMC-1 cells. Der p 1 induced HMC-1 cell degranulation and the release of tryptase by activating the PAR2 receptor on the cell surfaces. Tryptase activated the PAR2 receptor and induced intracellular calcium release from the HMC-1 cells in a positive feedback loop.

  20. Characterization of an immunomodulatory Der p 2-FIP-fve fusion protein produced in transformed rice suspension cell culture.

    PubMed

    Su, Chin-Fen; Kuo, I-Chun; Chen, Peng-Wen; Huang, Chiung-Hui; Seow, See Voon; Chua, Kaw Yan; Yu, Su-May

    2012-02-01

    Der p 2, a major allergen of Dermatophagoides pteronyssinus mites, is one of the most clinically relevant allergens to allergic patients worldwide. FIP-fve protein (Fve) from the golden needle mushroom (Flammulina velutipes) is an immunomodulatory protein with potential Th1-skewed adjuvant properties. Here, we produced and immunologically evaluated a Der p 2-Fve fusion protein as a potential immunotherapeutic for allergic diseases. Using an inducible expression system in cultured rice suspension cells, the recombinant Der p 2-Fve fusion protein (designated as OsDp2Fve) was expressed in rice cells under the control of an α-amylase gene (αAmy8) promoter and secreted under sucrose starvation. OsDp2Fve was partially purified from the cultured medium. The conformation of Der p 2 in OsDp2Fve remains intact as reflected by its unaltered allergenicity, as assessed by human IgE ELISA and histamine release assays, compared to non-fusion Der p 2 protein. Furthermore, the Fve protein expressed in OsDp2Fve retains its in vitro lymphoproliferative activity but loses its hemagglutination and lymphoagglutination effects compared to the native protein. Notably, in vivo evaluation showed that mice administered with OsDp2Fve possessed an enhanced production of Der p 2-specific IgG antibodies without potentiating the production of Der p 2-specific IgE and Th2 effector cytokines in comparison with mice co-administered with native Fve and Der p 2 proteins. These results suggest that the recombinant Der p 2-Fve fusion protein produced in rice suspension cell cultures has a great potential for allergy immunotherapy.

  1. In-situ epitaxial growth of graphene/h-BN van der Waals heterostructures by molecular beam epitaxy.

    PubMed

    Zuo, Zheng; Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza; Zheng, Jian-Guo; Liu, Jianlin

    2015-10-07

    Van der Waals materials have received a great deal of attention for their exceptional layered structures and exotic properties, which can open up various device applications in nanoelectronics. However, in situ epitaxial growth of dissimilar van der Waals materials remains challenging. Here we demonstrate a solution for fabricating van der Waals heterostructures. Graphene/hexagonal boron nitride (h-BN) heterostructures were synthesized on cobalt substrates by using molecular beam epitaxy. Various characterizations were carried out to evaluate the heterostructures. Wafer-scale heterostructures consisting of single-layer/bilayer graphene and multilayer h-BN were achieved. The mismatch angle between graphene and h-BN is below 1°.

  2. Ökophysik: Plaudereien über das Leben auf dem Land, im Wasser und in der Luft

    NASA Astrophysics Data System (ADS)

    Nachtigall, W.

    Prof. em. Dr. rer. nat. Werner Nachtigall, geb. 1934, war als Zoophysiologe und Biophysiker Leiter des Zoologischen Instituts der Universität des Saarlandes in Saarbrücken. In Forschung und Ausbildung hat er sich insbesondere mit Aspekten der Technischen Biologie und Bionik befasst und mit seinen Forschergruppen viele Basisdaten insbesondere zur Ökologie, Physiologie und Physik des Fliegens und Schwimmens aber auch zur Stabilität beispielsweise der Gräser erarbeitet. Lebewesen überraschen immer wieder durch ihre "Biodiversität", ihre hochspezifischen Ausgestaltungen und Anpassungen.

  3. In-situ epitaxial growth of graphene/h-BN van der Waals heterostructures by molecular beam epitaxy

    PubMed Central

    Zuo, Zheng; Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza; Zheng, Jian-Guo; Liu, Jianlin

    2015-01-01

    Van der Waals materials have received a great deal of attention for their exceptional layered structures and exotic properties, which can open up various device applications in nanoelectronics. However, in situ epitaxial growth of dissimilar van der Waals materials remains challenging. Here we demonstrate a solution for fabricating van der Waals heterostructures. Graphene/hexagonal boron nitride (h-BN) heterostructures were synthesized on cobalt substrates by using molecular beam epitaxy. Various characterizations were carried out to evaluate the heterostructures. Wafer-scale heterostructures consisting of single-layer/bilayer graphene and multilayer h-BN were achieved. The mismatch angle between graphene and h-BN is below 1°. PMID:26442629

  4. The toluene-Ar complex: S0 and S1 van der Waals modes, changes to methyl rotation, and torsion-van der Waals vibration coupling.

    PubMed

    Gascooke, Jason R; Lawrance, Warren D

    2013-02-28

    The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 ← S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are ∣V3(S1)∣ = 33.4 ± 1.0 cm(-1), ∣V3(S0)∣ = 20.0 ± 1.0 cm(-1), V6(S1) = -10.7 ± 1.0 cm(-1), and V6(S0) = -1.7 ± 1.0 cm(-1). The methyl rotor is also found to couple with van der Waals vibration; specifically, the m(") = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m(") = 1. The coupling constant is determined to be 1.9 cm(-1), which is small compared with the values typically reported for torsion-vibration coupling involving ring modes.

  5. Are non-linear C-H⋯O contacts hydrogen bonds or Van der Waals interactions?. Establishing the limits between hydrogen bonds and Van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Novoa, Juan J.; Lafuente, Pilar; Mota, Fernando

    1998-07-01

    The hydrogen bond nature of angular C-H⋯O contacts is examined to determine when these contacts are better classified as hydrogen bonds or as Van der Waals bonds. To classify the bond we propose to look at the nature of the intermolecular bond critical point present in the electron density of the complex containing the bond. The physics behind this approach is explained using a qualitative orbital overlap model aimed at describing the main changes in the electronic density of the complex produced by the C-H⋯O bending.

  6. Werk und Leben Walter Christallers . Auszüge aus der Festrede anläßlich der Verleihung des Walter-Christaller-Preises 1996

    NASA Astrophysics Data System (ADS)

    Hottes, Ruth

    1997-03-01

    Unter der Betreuung und Federführung von Robert Gradmann promovierte am Erlanger Geographischen Institut 1932 Walter Christaller mit seiner Dissertation `Die Zentralen Orte in Süddeutschland'. Diese mit summa cum laude bewertete Monographie sollte die vielleicht berühmteste geographische Doktorarbeit unseres Jahrhunderts werden. Sie hat in den vergangenen Jahrzehnten einen beispiellosen Siegeszug angetreten. Heute gilt sie für Geographie, Raumwirtschaftslehre, Stadtforschung und Standorttheorie als eine bahnbrechende Grundkonzeption, und sie ist von größter Bedeutung für Raumordnungspolitik und Planungspraxis."

  7. Quantum interference in a macroscopic van der Waals conductor

    NASA Astrophysics Data System (ADS)

    Rischau, C. W.; Wiedmann, S.; Seyfarth, G.; LeBoeuf, D.; Behnia, K.; Fauqué, B.

    2017-02-01

    Quantum corrections to charge transport can give rise to an oscillatory magnetoconductance, typically observed in mesoscopic samples with a length shorter than or comparable to the phase coherence length. Here, we report the observation of magnetoconductance oscillations periodic in magnetic field with an amplitude of the order of e2/h in macroscopic samples of highly oriented pyrolytic graphite (HOPG). The observed effect emerges when all carriers are confined to their lowest Landau levels. We argue that this quantum interference phenomenon can be explained by invoking moiré superlattices with a discrete distribution in periodicity. According to our results, when the magnetic length ℓB, the Fermi wavelength λF, and the length scale of fluctuations in local chemical potential are comparable in a layered conductor, quantum corrections can be detected over centimetric length scales.

  8. Optimization of a van der Waals Density Functional for water

    NASA Astrophysics Data System (ADS)

    Fritz, Michelle; Fernandez-Serra, Marivi; Soler, Jose M.

    2015-03-01

    In particularly delicate systems, like liquid water, ab initio exchange and correlation functionals are simply not accurate enough for many practical applications. In these cases, fitting the functional to reference data is a sensible alternative to empirical interatomic potentials. However, a global optimization requires functional forms that depend on many parameters and the usual trial and error strategy becomes cumbersome and suboptimal. We present a general and powerful optimization scheme called data projection onto parameter space (DPPS). In an arbitrarily large parameter space, DPPS expands the vector of unknown parameters in vectors of known data. Poorly sampled subspaces are determined by the physically-motivated functional shape of ab initio functionals, using Bayes' theory to combine this prior information with reference energies and electron densities of monomers, clusters, and condensed phases of water. We aknowledge support from FIS2012-37549 (MF and JMS) and DOE Early Career Award No. DE-SC0003871 (M.-V.F.-S.)

  9. Phase transitions, magnetism and surface adsorptions assessed by meta-GGA functionals and random phase approximation

    NASA Astrophysics Data System (ADS)

    Xiao, Bing

    The meta-GGA functionals and random phase approximation are tested for phase transitions and a strongly correlated transition metal oxide in this dissertation. One of the latest meta-GGA functionals is also employed to study the van der Waals bound system in surface science. Our main purpose is to reveal the performance of new exchange-correlation functionals on various properties and systems. We are also interested in seeking the possible relationship between the performance of a semilocal functional and its exchange enhancement factor. We have studied the structural phase transitions in crystalline Si (insulator to metal), SiO2 (insulator to insulator) and Zr (metal to metal) systems, as a test of exchange energy semilocal functionals on Jacob's ladder. Our results confirm the energy-geometry delimma of GGAs in three systems. The most sophisticated non-empirical meta-generalized gradient approximations (meta-GGAs) such as TPSS (Tao-Perdew-Staroveov-Scuseria) and revTPSS (revised TPSS) give better lattice constants than PBE, but the phase transition parameters (energy difference and transition pressure) are smaller and less realistic than those from the latter GGA. However, the recent functionals of meta-GGA made simple family (MGGA_MS) behave differently to those previous meta-GGAs, predicting larger and more realistic phase transition parameters. Meanwhile, MGGA_MS also delivers the equilibrium geometry of crystalline materials similar to previous non-empirical meta-GGAs. In contrast to semilocal functionals, the nonlocal functionals such as the range-separated hybrid functional HSE06 (Heyd-Scuseria-Ernzerhof) and non-self consistent random phase approximation (RPA) are not only able to give the accurate equilibrium geometry , but also predict the realistic phase transition parameters for Si and SiO2 systems. The ground state of rutile-type vanadium dioxide (R-VO2) represents a great challenge to the current density functional theory. In this dissertation, we

  10. Binding and Diffusion of Lithium in Graphite: Quantum Monte Carlo Benchmarks and Validation of van der Waals Density Functional Methods.

    PubMed

    Ganesh, P; Kim, Jeongnim; Park, Changwon; Yoon, Mina; Reboredo, Fernando A; Kent, Paul R C

    2014-12-09

    Highly accurate diffusion quantum Monte Carlo (QMC) studies of the adsorption and diffusion of atomic lithium in AA-stacked graphite are compared with van der Waals-including density functional theory (DFT) calculations. Predicted QMC lattice constants for pure AA graphite agree with experiment. Pure AA-stacked graphite is shown to challenge many van der Waals methods even when they are accurate for conventional AB graphite. Highest overall DFT accuracy, considering pure AA-stacked graphite as well as lithium binding and diffusion, is obtained by the self-consistent van der Waals functional vdW-DF2, although errors in binding energies remain. Empirical approaches based on point charges such as DFT-D are inaccurate unless the local charge transfer is assessed. The results demonstrate that the lithium-carbon system requires a simultaneous highly accurate description of both charge transfer and van der Waals interactions, favoring self-consistent approaches.

  11. Cooperative interplay of van der Waals forces and quantum nuclear effects on adsorption: H at graphene and at coronene.

    PubMed

    Davidson, Erlend R M; Klimeš, Jiří; Alfè, Dario; Michaelides, Angelos

    2014-10-28

    The energetic barriers that atoms and molecules often experience when binding to surfaces are incredibly important to a myriad of chemical and physical processes. However, these barriers are difficult to describe accurately with current computer simulation approaches. Two prominent contemporary challenges faced by simulation are the role of van der Waals forces and nuclear quantum effects. Here we examine the widely studied model systems of hydrogen on graphene and coronene using a van der Waals inclusive density functional theory approach together with path integral molecular dynamics at 50 K. We find that both van der Waals and quantum nuclear effects work together in a cooperative manner to dramatically reduce the barriers for hydrogen atoms to adsorb. This suggests that the low temperature hydrogenation of graphene is easier than previously thought and in more general terms that the combined roles of van der Waals and quantum tunnelling can lead to qualitative changes in adsorption.

  12. Binding and Diffusion of Lithium in Graphite: Quantum Monte Carlo Benchmarks and Validation of van der Waals Density Functional Methods

    SciTech Connect

    Ganesh, P.; Kim, Jeongnim; Park, Changwon; Yoon, Mina; Reboredo, Fernando A.; Kent, Paul R. C.

    2014-11-03

    In highly accurate diffusion quantum Monte Carlo (QMC) studies of the adsorption and diffusion of atomic lithium in AA-stacked graphite are compared with van der Waals-including density functional theory (DFT) calculations. Predicted QMC lattice constants for pure AA graphite agree with experiment. Pure AA-stacked graphite is shown to challenge many van der Waals methods even when they are accurate for conventional AB graphite. Moreover, the highest overall DFT accuracy, considering pure AA-stacked graphite as well as lithium binding and diffusion, is obtained by the self-consistent van der Waals functional vdW-DF2, although errors in binding energies remain. Empirical approaches based on point charges such as DFT-D are inaccurate unless the local charge transfer is assessed. Our results demonstrate that the lithium carbon system requires a simultaneous highly accurate description of both charge transfer and van der Waals interactions, favoring self-consistent approaches.

  13. Production of Protonated Methanol Ions Via Intermolecular Reactions within Van der Waals Clusters of Dime Dimethyl Ether. Revision

    DTIC Science & Technology

    1990-02-02

    preparation (17) This result also suggests that the protonated methanol ion is not produced via a reaction between the DME cluster and a water impurity. In...include Security Classification) Production ol Protonated Methanol Ions via "Intermolecular" Reactions within van der Waals Clusters of Dimethyl Ether...2/90 Production of Protonated Methanol Ions via "Intermolecular" Reactions within van der Waals Clusters of Dimethyl Ether M. Todd Coolbaugh, William

  14. van der Waals forces in density functional theory: Perturbational long-range electron-interaction corrections

    SciTech Connect

    Angyan, Janos G.; Gerber, Iann C.; Savin, Andreas; Toulouse, Julien

    2005-07-15

    Long-range exchange and correlation effects, responsible for the failure of currently used approximate density functionals in describing van der Waals forces, are taken into account explicitly after a separation of the electron-electron interaction in the Hamiltonian into short- and long-range components. We propose a 'range-separated hybrid' functional based on a local density approximation for the short-range exchange-correlation energy, combined with a long-range exact exchange energy. Long-range correlation effects are added by a second-order perturbational treatment. The resulting scheme is general and is particularly well adapted to describe van der Waals complexes, such as rare gas dimers.

  15. FAST TRACK COMMUNICATION: A variational principle behind the van der Waals picture of strongly coupled plasmas

    NASA Astrophysics Data System (ADS)

    Frusawa, Hiroshi

    2009-02-01

    Various strong coupling theories of the one-component plasma have successfully predicted the thermodynamic and structural properties by separating the Coulomb potential into short- and long-ranged parts in ad hoc ways. Moreover, it has been demonstrated that the density-density correlation function in a mimic system with only short-ranged interactions resembles that of the full Coulomb system, revealing that the van der Waals picture applies to the strongly coupled Coulomb systems. Here we present a variational theory forming the basis of the van der Waals picture. Our approach provides hybrid formulations which combine both the liquid state theory and statistical field theory; essential use is made of the coarse-grained system with only the long-ranged part of Coulomb interactions as a reference system in introducing both the lower bound variational principle and strong coupling expansion.

  16. A simplified implementation of van der Waals density functionals for first-principles molecular dynamics applications

    NASA Astrophysics Data System (ADS)

    Wu, Jun; Gygi, François

    2012-06-01

    We present a simplified implementation of the non-local van der Waals correlation functional introduced by Dion et al. [Phys. Rev. Lett. 92, 246401 (2004)] and reformulated by Román-Pérez et al. [Phys. Rev. Lett. 103, 096102 (2009)]. The proposed numerical approach removes the logarithmic singularity of the kernel function. Complete expressions of the self-consistent correlation potential and of the stress tensor are given. Combined with various choices of exchange functionals, five versions of van der Waals density functionals are implemented. Applications to the computation of the interaction energy of the benzene-water complex and to the computation of the equilibrium cell parameters of the benzene crystal are presented. As an example of crystal structure calculation involving a mixture of hydrogen bonding and dispersion interactions, we compute the equilibrium structure of two polymorphs of aspirin (2-acetoxybenzoic acid, C9H8O4) in the P21/c monoclinic structure.

  17. Generalization of the van der Pauw Method: Analyzing Longitudinal Magnetoresistance Asymmetry to Quantify Doping Gradients

    NASA Astrophysics Data System (ADS)

    Grayson, M.; Zhou, Wang; Yoo, Heun-Mo; Prabhu-Gaunkar, S.; Tiemann, L.; Reichl, C.; Wegscheider, W.

    A longitudinal magnetoresistance asymmetry (LMA) between a positive and negative magnetic field is known to occur in both the extreme quantum limit and the classical Drude limit in samples with a nonuniform doping density. By analyzing the current stream function in van der Pauw measurement geometry, it is shown that the electron density gradient can be quantitatively deduced from this LMA in the Drude regime. Results agree with gradients interpolated from local densities calibrated across an entire wafer, establishing a generalization of the van der Pauw method to quantify density gradients. Results will be shown of various semoconductor systems where this method is applied, from bulk doped semiconductors, to exfoliated 2D materials. McCormick Catalyst Award from Northwestern University, EECS Bridge Funding, and AFOSR FA9550-15-1-0247.

  18. Electrical and optical properties of SnS2/WSe2 van der Waals Heterojunction FETs

    NASA Astrophysics Data System (ADS)

    Zubair, Ahmad; Nourbakhsh, Amirhasan; Dresselhaus, Mildred; Palacios, Tomas

    Two dimensional crystals based on atomically thin films of transition metal dichalcogenides offer an exciting platform for various optoelectronic applications. Their unique crystal properties make them particularly attractive for van der Waals heterostructures which open up an additional degree of freedom to tailor the material properties into new physics and device applications. In this work, we explore, for the first time, the optoelectronic properties of van der Waals SnS2/WSe2 heterojunction. WSe2 is an ambipolar semiconductor while SnS2 is an n-type wide bandgap semiconductor. We use the pickup and dry transfer methods to fabricate SnS2/WSe2 heterojunction transistors (hetero-FETs). We observe negative differential transconductance in the SnS2/WSe2 hetero-FET. Also, the heterostructure couples strongly to incident light and shows high photovoltaic responsivity which can find applications in nano-devices such as photo-detectors and solar cells.

  19. Measuring the thermal boundary resistance of van der Waals contacts using an individual carbon nanotube.

    PubMed

    Hirotani, Jun; Ikuta, Tatsuya; Nishiyama, Takashi; Takahashi, Koji

    2013-01-16

    Interfacial thermal transport via van der Waals interaction is quantitatively evaluated using an individual multi-walled carbon nanotube bonded on a platinum hot-film sensor. The thermal boundary resistance per unit contact area was obtained at the interface between the closed end or sidewall of the nanotube and platinum, gold, or a silicon dioxide surface. When taking into consideration the surface roughness, the thermal boundary resistance at the sidewall is found to coincide with that at the closed end. A new finding is that the thermal boundary resistance between a carbon nanotube and a solid surface is independent of the materials within the experimental errors, which is inconsistent with a traditional phonon mismatch model, which shows a clear material dependence of the thermal boundary resistance. Our data indicate the inapplicability of existing phonon models when weak van der Waals forces are dominant at the interfaces.

  20. Universal curves for the van der Waals interaction between single-walled carbon nanotubes.

    PubMed

    Pogorelov, Evgeny G; Zhbanov, Alexander I; Chang, Yia-Chung; Yang, Sung

    2012-01-17

    We report very simple and accurate algebraic expressions for the van der Waals (VDW) potentials and the forces between two parallel and crossed carbon nanotubes. The Lennard-Jones potential for two carbon atoms and the method of the smeared-out approximation suggested by Girifalco were used. It is found that the interaction between parallel and crossed tubes is described by two universal curves for parallel and crossed configurations that do not depend on the van der Waals constants, the angle between tubes, and the surface density of atoms and their nature but only on the dimensionless distance. The explicit functions for equilibrium VDW distances, well depths, and maximal attractive forces have been given. These results may be used as a guide for the analysis of experimental data to investigate the interaction between nanotubes of various natures.

  1. Dielectric response variation and the strength of van der Waals interactions.

    PubMed

    Hopkins, Jaime C; Dryden, Daniel M; Ching, Wai-Yim; French, Roger H; Parsegian, V Adrian; Podgornik, Rudolf

    2014-03-01

    Small changes in the dielectric response of a material result in substantial variations in the Hamaker coefficient of the van der Waals interactions, as demonstrated in a simplified approximate model as well as a realistic example of amorphous silica with and without an exciton peak. Variation of the dielectric response spectra at one particular frequency influences all terms in the Matsubara summation, making the total change in the Hamaker coefficient depend on the spectral changes not only at that frequency but also at the rest of the spectrum, properly weighted. The Matsubara terms most affected by the addition of a single peak are not those close to the position of the added peak, but are distributed doubly non-locally over the entire range of frequencies. A possibility of eliminating van der Waals interactions or at least drastically reducing them by spectral variation in a narrow regime of frequencies thus seems very remote.

  2. van der Waals interactions at the nanoscale: the effects of nonlocality.

    PubMed

    Luo, Yu; Zhao, Rongkuo; Pendry, John B

    2014-12-30

    Calculated using classical electromagnetism, the van der Waals force increases without limit as two surfaces approach. In reality, the force saturates because the electrons cannot respond to fields of very short wavelength: polarization charges are always smeared out to some degree and in consequence the response is nonlocal. Nonlocality also plays an important role in the optical spectrum and distribution of the modes but introduces complexity into calculations, hindering an analytical solution for interactions at the nanometer scale. Here, taking as an example the case of two touching nanospheres, we show for the first time, to our knowledge, that nonlocality in 3D plasmonic systems can be accurately analyzed using the transformation optics approach. The effects of nonlocality are found to dramatically weaken the field enhancement between the spheres and hence the van der Waals interaction and to modify the spectral shifts of plasmon modes.

  3. Microwave spectra of van der Waals complexes of importance in planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Suenram, R. D.; Lovas, F. J.

    1990-01-01

    The Fourier-transform Fabry-Perot pulsed-molecular-beam microwave spectrometer at NIST was used to study the microwave spectra of a number of molecular dimers and trimers that may be present in planetary atmospheres. The weak van der Waals bonds associated with these species usually give rise to rotational-tunneling splittings in the microwave spectra. The microwave spectrum of the water dimer species was used to illustrate the complications that can arise in the study of the rotational spectra of these loosely bound species. In addition to the water dimer species, the microwave spectra of the following hydrogen-bonded and van der Waals complexes were studied: (CO2)2-H2O, CO2-(H2O)2, CO2-H2S, N2-H2O, CO-H2O, SO2-H2O, and O3-H2O.

  4. van der Waals interactions at the nanoscale: The effects of nonlocality

    PubMed Central

    Luo, Yu; Zhao, Rongkuo; Pendry, John B.

    2014-01-01

    Calculated using classical electromagnetism, the van der Waals force increases without limit as two surfaces approach. In reality, the force saturates because the electrons cannot respond to fields of very short wavelength: polarization charges are always smeared out to some degree and in consequence the response is nonlocal. Nonlocality also plays an important role in the optical spectrum and distribution of the modes but introduces complexity into calculations, hindering an analytical solution for interactions at the nanometer scale. Here, taking as an example the case of two touching nanospheres, we show for the first time, to our knowledge, that nonlocality in 3D plasmonic systems can be accurately analyzed using the transformation optics approach. The effects of nonlocality are found to dramatically weaken the field enhancement between the spheres and hence the van der Waals interaction and to modify the spectral shifts of plasmon modes. PMID:25468982

  5. Van der Waals heterostructure of phosphorene and hexagonal boron nitride: First-principles modeling

    NASA Astrophysics Data System (ADS)

    Peng, Zhang; Jing, Wang; Xiang-Mei, Duan

    2016-03-01

    We have studied the structural and electronic properties of a hybrid hexagonal boron nitride with phosphorene nanocomposite using ab initio density functional calculations. It is found that the interaction between the hexagonal boron nitride and phosphorene is dominated by the weak van der Waals interaction, with their own intrinsic electronic properties preserved. Furthermore, the band gap of the nanocomposite is dependent on the interfacial distance. Our results could shed light on the design of new devices based on van der Waals heterostructure. Projected supported by the National Natural Science Foundation of China (Grant No. 11574167), the New Century 151 Talents Project of Zhejiang Province,China, and the K. C. Wong Magna Foundation in Ningbo University, China.

  6. [Heinrich Hoffmann's Der Struwwelpeter (1845/1859): a parody on the romantic cult of childhood].

    PubMed

    Wesseling, Lies

    2006-01-01

    This article analyzes the cultural dynamics of the construction and deconstruction of childhood images, by means of a case study of Heinrich Hoffmann's classic picture book, Der Struwwelpeter (1845/1859). Childhood images are the joint product of sciences (especially anthropology, pedagogy and developmental psychology) and arts (especially painting, photography and (children's) literature). These images are historically variable, because childhood is the permanent target of idealization and demystification. This article interprets Der Struwwelpeter as a demystication of Romantic idealizations of childhood as propounded by Romantic Naturphilosophie and, more specifically, the pedagogy of Friedrich Fröbel (1772-1852). In my view, this picture book satirizes the developmentalism and the pastoryl idyll which informed the Romantic image of childhood, through its verbal and visual components. As I argue at length, this satire directly bears upon leading scientific and political controversies of Hoffmann's time.

  7. Van der Waals force: a dominant factor for reactivity of graphene.

    PubMed

    Lee, Jong Hak; Avsar, Ahmet; Jung, Jeil; Tan, Jun You; Watanabe, K; Taniguchi, T; Natarajan, Srinivasan; Eda, Goki; Adam, Shaffique; Castro Neto, Antonio H; Özyilmaz, Barbaros

    2015-01-14

    Reactivity control of graphene is an important issue because chemical functionalization can modulate graphene's unique mechanical, optical, and electronic properties. Using systematic optical studies, we demonstrate that van der Waals interaction is the dominant factor for the chemical reactivity of graphene on two-dimensional (2D) heterostructures. A significant enhancement in the chemical stability of graphene is achieved by replacing the common SiO2 substrate with 2D crystals such as an additional graphene layer, WS2, MoS2, or h-BN. Our theoretical and experimental results show that its origin is a strong van der Waals interaction between the graphene layer and the 2D substrate. This results in a high resistive force on graphene toward geometric lattice deformation. We also demonstrate that the chemical reactivity of graphene can be controlled by the relative lattice orientation with respect to the substrates and thus can be used for a wide range of applications including hydrogen storage.

  8. First principles calculations of solid-state thermionic transport in layered van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoming; Zebarjadi, Mona; Esfarjani, Keivan

    2016-08-01

    This work aims at understanding solid-state energy conversion and transport in layered (van der Waals) heterostructures in contact with metallic electrodes via a first-principles approach. As an illustration, a graphene/phosphorene/graphene heterostructure in contact with gold electrodes is studied by using density functional theory (DFT)-based first principles calculations combined with real space Green's function (GF) formalism. We show that for a monolayer phosphorene, quantum tunneling dominates the transport. By adding more phosphorene layers, one can switch from tunneling-dominated transport to thermionic-dominated transport, resulting in transporting more heat per charge carrier, thus, enhancing the cooling coefficient of performance. The use of layered van der Waals heterostructures has two advantages: (a) thermionic transport barriers can be tuned by changing the number of layers, and (b) thermal conductance across these non-covalent structures is very weak. The phonon thermal conductance of the present van der Waals heterostructure is found to be 4.1 MW m-2 K-1 which is one order of magnitude lower than the lowest value for that of covalently-bonded interfaces. The thermionic coefficient of performance for the proposed device is 18.5 at 600 K corresponding to an equivalent ZT of 0.13, which is significant for nanoscale devices. This study shows that layered van der Waals structures have great potential to be used as solid-state energy-conversion devices.This work aims at understanding solid-state energy conversion and transport in layered (van der Waals) heterostructures in contact with metallic electrodes via a first-principles approach. As an illustration, a graphene/phosphorene/graphene heterostructure in contact with gold electrodes is studied by using density functional theory (DFT)-based first principles calculations combined with real space Green's function (GF) formalism. We show that for a monolayer phosphorene, quantum tunneling dominates the

  9. Effects of a periodic drive and correlated noise on birhythmic van der Pol systems

    NASA Astrophysics Data System (ADS)

    Yonkeu, R. Mbakob; Yamapi, R.; Filatrella, G.; Tchawoua, C.

    2017-01-01

    This paper considers the dynamics of a van der Pol birhythmic oscillator submitted both to colored noise and harmonic excitation. Applying the quasi-harmonic assumption to the corresponding Langevin equation we derive an approximated Fokker-Planck equation, that is compared with the results of computer simulations. We thus derive both the effects of the correlation time and the harmonic excitation on the parameter space where birhythmicity appears. In this region, we find that the multi-limit-cycle van der Pol oscillator reduces to an asymmetric bistable system where the sinusoidal drive intensity plays the role of asymmetric parameter, and noise can lead to stochastic bifurcations, consisting in a qualitative change of the stationary amplitude distribution. Under both influence of noise and harmonic excitation, the dynamics can be well characterized through the concepts of pseudo-potential, that regulates the low noise Arrhenius-like behavior.

  10. Wirkungen biogener Amine auf die Erregungs-Sekretions-Kopplung in der Speicheldrüse von Periplaneta americana (L.)

    NASA Astrophysics Data System (ADS)

    Rietdorf, Katja

    2003-07-01

    In der vorliegenden Arbeit habe ich wichtige Teilmechanismen der Erregungs-Sekretionskopplung in der Speicheldrüse der Schabe Periplaneta americana (L.) untersucht. Die Speicheldrüse ist von dopaminergen und serotonergen Fasern innerviert (Baumann et al., 2002). Beide Transmitter stimulieren eine unterschiedliche Reaktion der Drüse: Dopamin (DA) stimuliert die P-Zellen der Acini und die Ausführgangzellen, während Serotonin (5-HT) die P- und C-Zellen der Acini stimuliert, nicht jedoch die Ausführgangzellen. Der Endspeichel ist nach einer DA-Stimulierung proteinfrei. Dagegen enthält er nach einer 5-HT-Stimulierung Proteine, die von den C-Zellen sezerniert werden (Just & Walz, 1996). Im ersten Teil meiner Arbeit habe ich mittels Kapillarelektrophoretischer Analyse (CE-Analyse) die Elektrolytkonzentrationen im Endspeichel untersucht sowie die Raten der Flüssigkeitssekretion gemessen. Damit wollte ich klären, welche Transporter an der Sekretion des Primärspeichels und an dessen Modifikation beteiligt sind. Ausserdem wollte ich die Rolle der transportaktiven Epithelzellen der Ausführgänge für die Modifikation des Primärspeichels untersuchen. Dafür habe ich einen Vergleich der Elektrolytkonzentrationen im DA- und 5-HT-stimulierten Endspeichel durchgeführt. Der Elektrolytgehalt des DA- und 5-HT-stimulierten Endspeichels unterscheidet sich nicht signifikant voneinander. Er ist nach beiden Stimulierungen hypoosmotisch zum verwendeten Ringer. Die Ausführgangzellen werden durch DA stimuliert und modifizieren den Primärspeichel durch eine netto-Ionenreabsorption. Meine Versuche zeigen jedoch, dass auch die während einer 5-HT-Stimulierung der Drüse unstimulierten Ausführgangzellen den Primärspeichel modifizieren. In einer nachfolgenden Versuchsreihe habe ich den Einfluss von Ouabain, einem Hemmstoff der Na+-K+-ATPase, und Bumetanid, einem Hemmstoff des NKCC, auf die Raten der Flüssigkeitssekretion sowie den Elektrolytgehalt des Endspeichels untersucht. Ich

  11. Black phosphorene/monolayer transition-metal dichalcogenides as two dimensional van der Waals heterostructures: a first-principles study.

    PubMed

    You, Baiqing; Wang, Xiaocha; Zheng, Zhida; Mi, Wenbo

    2016-03-14

    The electronic structure of black phosphorene (BP)/monolayer 1H-XT2 (X = Mo, W; T = S, Se, Te) two dimensional (2D) van der Waals heterostructures have been calculated by the first-principles method. It is found that the electronic band structures of both BP and XT2 are preserved in the combined van der Waals heterostructures. The WSe2/BP van der Waals heterostructure demonstrates a type-I band alignment, but the MoS2/BP, MoSe2/BP, MoTe2/BP, WS2/BP and WTe2/BP van der Waals heterostructures demonstrate a type-II band alignment. In particular, the n-type XT2/p-type BP van der Waals heterostructures can be applied in p-n diode and logical devices. Strong spin splitting appears in all of the heterostructures when considering the spin orbital coupling. Our results play a significant role in the prediction of novel 2D van der Waals heterostructures that have potential applications in spin-filter devices, spin field effect transistors, optoelectronic devices, etc.

  12. EXPERIMENTAL AND THEORETICAL STUDIES OF THE CN-AR VAN DER WAALS COMPLEX

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The CN-Ar van der Waals complex has been observed using B2E+-X2E+ and A2II-X2E+ electronic transitions. The spectra yielded a dissociation energy of D0"=109+2 cm1 and a zero point rational constant of B0"=0.067+0.005 cm-1 for CN(x)-Ar. The dissociation energy for Cn(A)-Ar was found to be D0"=132+2...

  13. Generation and purification of monoclonal antibodies against Der f 2, a major allergen from Dermatophagoides farinae.

    PubMed

    Chen, Huifang; Zhang, Kejun; Wang, Shan; Xu, Chenxia; Zou, Zehong; Tao, Ailin

    Monoclonal antibodies (mAbs) are needed for the quantitation of environmental allergens for precise diagnosis and immunotherapy. In this study, we produced and purified monoclonal antibodies against Der f 2, one of the major allergens of the house dust mite Dermatophagoides farina, in order to develop an assay for the detection of this allergen. BALB/c mice were immunized four times with the protein Der f 2 together with an adjuvant after which splenocytes were collected and fused with SP2/0 (myeloma cells) in the presence of polyethylene glycol (PEG). The fused cells were selected in the presence of Hypoxanthine-Aminopterin-Thymidine (HAT) and then Hypoxanthine-Thymidine (HT) medium. Positive cells were screened with ELISA and subcloned by limited dilution at least three times to achieve stable mAb-producing clones. Four stable mAb-producing clones were obtained. One clone with IgG1 isotype and another with IgG2b isotype were chosen to produce large amounts of mAb by inoculation of the cells into the abdominal cavity of mice. Ascites were collected and the mAbs were purified using protein A affinity chromatography. Testing of the ascites by ELISA showed the titration of IgG1 and IgG2b to be higher than 1/10(6) dilution. The specificity of both antibodies was confirmed by immunoblotting. Thus, we produced two mAb clones against Der f 2 that can be used to create a precise quantitative method to identify allergen components in dust samples and facilitate further study in Der f 2 component-resolved diagnosis (CRD).

  14. Electronic spectroscopy of large van der waals molecules by resonant two-photon ionization

    NASA Astrophysics Data System (ADS)

    Leutwyler, Samuel; Even, Uzi; Jortner, Joshua

    1982-03-01

    Tunable laser two-photon ionization of large van der Waals molecules, combined with time-of-flight mass spectroscopy. was applied to the identification of the electronic origin and of some low vibrational excitations of the S 0 — S 1 electronic transition of fluorene·Ar 1, fluorene·Ar 2 and fluorene·Kr 1 produced in supersonic expansions.

  15. Passivation of Black Phosphorus via Self-Assembled Organic Monolayers by van der Waals Epitaxy.

    PubMed

    Zhao, Yinghe; Zhou, Qionghua; Li, Qiang; Yao, Xiaojing; Wang, Jinlan

    2017-02-01

    An effective passivation approach to protect black phosphorus (BP) from degradation based on multi-scale simulations is proposed. The self-assembly of perylene-3,4,9,10-tetracarboxylic dianhydride monolayers via van der Waals epitaxy on BP does not break the original electronic properties of BP. The passivation layer thickness is only 2 nm. This study opens up a new pathway toward fine passivation of BP.

  16. Offset reduction in Hall effect measurements using a nonswitching van der Pauw technique.

    PubMed

    Riss, O; Shaked, E; Karpovsky, M; Gerber, A

    2008-07-01

    A nonswitching van der Pauw technique, which uses two electrically isolated alternating current sources operating at two different frequencies and two lock-in amplifiers, is suggested for Hall effect measurements. Parasitic offset voltage, typical for this type of measurements, is reduced by averaging two sets of data accumulated simultaneously. Application of the technique is particularly useful when the offset changes on a time scale comparable to the measurement cycle.

  17. Van der Waals equation of state revisited: importance of the dispersion correction.

    PubMed

    de Visser, Sam P

    2011-04-28

    One of the most basic equations of state describing nonideal gases and liquids is the van der Waals equation of state, and as a consequence, it is generally taught in most first year undergraduate chemistry courses. In this work, we show that the constants a and b in the van der Waals equation of state are linearly proportional to the polarizability volume of the molecules in a gas or liquid. Using this information, a new thermodynamic one-parameter equation of state is derived that contains experimentally measurable variables and physics constants only. This is the first equation of state apart from the Ideal Gas Law that contains experimentally measurable variables and physics constants only, and as such, it may be a very useful and practical equation for the description of dilute gases and liquids. The modified van der Waals equation of state describes pV as the sum of repulsive and attractive intermolecular interaction energies that are represented by an exponential repulsion function between the electron clouds of the molecules and a London dispersion component, respectively. The newly derived equation of state is tested against experimental data for several gas and liquid examples, and the agreement is satisfactory. The description of the equation of state as a one-parameter function also has implications on other thermodynamic functions, such as critical parameters, virial coefficients, and isothermal compressibilities. Using our modified van der Waals equation of state, we show that all of these properties are a function of the molecular polarizability volume. Correlations of experimental data confirm the derived proportionalities.

  18. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

    DOE PAGES

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; ...

    2016-05-10

    Here, the success of van der Waals (vdW) heterostructures, made of graphene, metal dichalcogenides, and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that vdW heterostructues can exhibit ultra-fast charge transfer despite the weak binding of the heterostructure. Using time-dependent density functional theory molecular dynamics, we identify a strong dynamic coupling between the vdW layers associated with charge transfer. This dynamic coupling results in rapid nonlinear coherentmore » charge oscillations which constitute a purely electronic phenomenon and are shown to be a general feature of vdW heterostructures provided they have a critical minimum dipole coupling. Application to MoS2/WS2 heterostructure yields good agreement with experiment, indicating near complete charge transfer within a timescale of 100 fs.The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the

  19. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

    SciTech Connect

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; West, Damien; Meunier, Vincent; Zhang, Shengbai; Liang, Linagbo

    2016-05-10

    Here, the success of van der Waals (vdW) heterostructures, made of graphene, metal dichalcogenides, and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that vdW heterostructues can exhibit ultra-fast charge transfer despite the weak binding of the heterostructure. Using time-dependent density functional theory molecular dynamics, we identify a strong dynamic coupling between the vdW layers associated with charge transfer. This dynamic coupling results in rapid nonlinear coherent charge oscillations which constitute a purely electronic phenomenon and are shown to be a general feature of vdW heterostructures provided they have a critical minimum dipole coupling. Application to MoS2/WS2 heterostructure yields good agreement with experiment, indicating near complete charge transfer within a timescale of 100 fs.The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface

  20. Thin Film Evaporation Model with Retarded Van Der Waals Interaction (Postprint)

    DTIC Science & Technology

    2013-11-01

    failing to comply with a collection of information if it does not display a currently valid OMB control number . PLEASE DO NOT RETURN YOUR FORM TO THE...April 2013 4. TITLE AND SUBTITLE THIN FILM EVAPORATION MODEL WITH RETARDED VAN DER WAALS INTERACTION (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b...GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62203F 6. AUTHOR(S) Michael Hanchak, Marlin D. Vangsness, and Jamie S. Ervin (University of Dayton

  1. Quasi-1D van der Waals materials as high current-density local interconnects (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Stolyarov, Maxim; Aytan, Ece; Bloodgood, Matthew; Salguero, Tina T.; Balandin, Alexander A.

    2016-09-01

    The continuous downscaling of interconnect dimensions in combination with the introduction of low-k dielectrics has increased the number of heat dissipation, integration and reliability challenges in modern electronics. As a result, there is a strong need for new materials that have high current-carrying capacity for applications as nanoscale interconnects. In this presentation, we show that quasi-one-dimensional (1D) van der Waals metals such as TaSe3 have excellent breakdown current density exceeding that of 5 MA/cm2. This value is above that currently achievable in conventional copper or aluminum wires. The quasi-1D van der Waals materials are characterized by strong bonds along one dimension and weak van der Waals bonds along two other dimensions. The material for this study was grown by the chemical vapor transport (CVT) method. Both mechanical and chemical exfoliation methods were used to fabricate nanowires with lateral dimensions below 100 nm. The dimensions of the quasi-1D nanowires were verified with scanning electron microscopy (SEM) and atomic force microscopy (AFM). The metal (Ti/Au) contacts for the electrical characterization were deposited using electron beam evaporation (EBE). The measurements were conducted on a number of prototype interconnects with multiple electric contacts to ensure reproducibility. The obtained results suggest that quasi-1D van der Waals metals present a feasible alternative to conventional copper interconnects in terms of the current-carrying capacity and the breakdown current-density. This work was supported, in part, by the SRC and DARPA through STARnet Center for Function Accelerated nanoMaterial Engineering (FAME).

  2. Controlled Synthesis of Organic/Inorganic van der Waals Solid for Tunable Light-Matter Interactions.

    PubMed

    Niu, Lin; Liu, Xinfeng; Cong, Chunxiao; Wu, Chunyang; Wu, Di; Chang, Tay Rong; Wang, Hong; Zeng, Qingsheng; Zhou, Jiadong; Wang, Xingli; Fu, Wei; Yu, Peng; Fu, Qundong; Najmaei, Sina; Zhang, Zhuhua; Yakobson, Boris I; Tay, Beng Kang; Zhou, Wu; Jeng, Horng Tay; Lin, Hsin; Sum, Tze Chien; Jin, Chuanhong; He, Haiyong; Yu, Ting; Liu, Zheng

    2015-12-16

    High-quality organic and inorganic van der Waals (vdW) solids are realized using methylammonium lead halide (CH3 NH3 PbI3 ) as the organic part (organic perovskite) and 2D inorganic monolayers as counterparts. By stacking on various 2D monolayers, the vdW solids exhibit dramatically different light emissions. Futhermore, organic/h-BN vdW solid arrays are patterned for red-light emission.

  3. van der Waals epitaxy and photoresponse of two-dimensional CdSe plates

    NASA Astrophysics Data System (ADS)

    Zhu, Dan-Dan; Xia, Jing; Wang, Lei; Li, Xuan-Ze; Tian, Li-Feng; Meng, Xiang-Min

    2016-06-01

    Here we demonstrate the first growth of two-dimensional (2D) single-crystalline CdSe plates on mica substrates via van der Waals epitaxy. The as-synthesized 2D plates exhibit hexagonal, truncated triangular and triangular shapes with the lateral size around several microns. Photodetectors based on 2D CdSe plates present a fast response time of 24 ms, revealing that 2D CdSe is a promising building block for ultrathin optoelectronic devices.

  4. Phase field modelling of spinodal decomposition in the oil/water/asphaltene system.

    PubMed

    Tóth, Gyula I; Kvamme, Bjørn

    2015-08-21

    In this paper the quantitative applicability of van der Sman/van der Graaf type Ginzburg-Landau theories of surfactant assisted phase separation [van der Sman et al., Rheol. Acta, 2006, 46, 3] is studied for real systems displaying high surfactant concentrations at the liquid-liquid interface. The model is applied for the water/heptane/asphaltene system (a model of heavy crude oil), for which recent molecular dynamics (MD) simulations provide microscopic data needed to calibrate the theory. A list of general requirements is set up first, which is then followed by analytical calculations of the equilibrium properties of the system, such as the equilibrium liquid densities, the adsorption isotherm and the interfacial tension. Based on the results of these calculations, the model parameters are then determined numerically, yielding a reasonable reproduction of the MD density profiles. The results of time-dependent simulations addressing the dynamical behaviour of the system will also be presented. It will be shown that the competition between the diffusion and hydrodynamic time scales can lead to the formation of an emulsion. We also address the main difficulties and limitations of the theory regarding quantitative modelling of surfactant assisted liquid phase separation.

  5. High pressure phase transition in group III nitrides compounds

    NASA Astrophysics Data System (ADS)

    Soni, Shubhangi; Verma, S.; Kaurav, Netram; Choudhary, K. K.

    2016-05-01

    Using an effective interionic interaction potential (EIOP), the pressure induced structural phase transformation from ZnS-type (B3) to NaCl-type (B1) structure in group III Post-Transition Metal Nitrides [TMN; TM=Ga and Tl] were investigated. The long range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction upto second-neighbor ions within the Hafemeister and Flygare approach with modified ionic charge are properly incorporated in the EIOP. The vdW coefficients are computed following the Slater-Kirkwood variational method, as both the ions are polarizable. The estimated value of the phase transition pressure (Pt) and the magnitude of the discontinuity in volume at the transition pressure are consistent as compared to the reported data.

  6. Second Virial Coefficient As Determined from Protein Phase Behavior.

    PubMed

    Platten, Florian; Hansen, Jan; Wagner, Dana; Egelhaaf, Stefan U

    2016-10-06

    We quantitatively link the macroscopic phase behavior of protein solutions to protein-protein interactions based on a coarse-grained colloidal approach. We exploit the extended law of corresponding states and apply the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory in order to infer the second virial coefficient b2, an integral measure of the interaction potential, from the phase behavior, namely, cloud-point temperature (CPT) measurements under conditions favoring protein crystallization. This determination of b2 yields values that quantitatively agree with the results of static light scattering (SLS) experiments. The strength of the attractions is quantified in terms of an effective Hamaker constant, which accounts for van der Waals attractions as well as non-DLVO forces, such as hydration and hydrophobic interactions. Our approach based on simple lab experiments to determine the CPT in combination with the DLVO theory is expected to facilitate further biophysical research on protein-protein interactions in complex solution environments.

  7. Thermal phase transitions of dimensionally continued AdS black holes

    NASA Astrophysics Data System (ADS)

    Kuang, Xiao-Mei; Miskovic, Olivera

    2017-02-01

    We study the thermal phase transitions of charged black holes in dimensionally continued gravity in anti-de Sitter space. We find the van der Waals-like phase transition in the temperature-entropy plane of the black holes with spherical horizons in even dimensions, and there is no such phase transition of the black holes with flat and hyperbolic geometries. Near the critical inflection point, the critical exponent is computed and its value does not depend on the dimension. The Maxwell equal area law is checked to be fulfilled in the temperature-entropy diagram for the first order phase transition. In odd dimensions, there are no thermal phase transitions for the black hole with any geometry of the horizon.

  8. Low-pressure phase diagram of crystalline benzene from quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Azadi, Sam; Cohen, R. E.

    2016-08-01

    We studied the low-pressure (0-10 GPa) phase diagram of crystalline benzene using quantum Monte Carlo and density functional theory (DFT) methods. We performed diffusion quantum Monte Carlo (DMC) calculations to obtain accurate static phase diagrams as benchmarks for modern van der Waals density functionals. Using density functional perturbation theory, we computed the phonon contributions to the free energies. Our DFT enthalpy-pressure phase diagrams indicate that the Pbca and P21/c structures are the most stable phases within the studied pressure range. The DMC Gibbs free-energy calculations predict that the room temperature Pbca to P21/c phase transition occurs at 2.1(1) GPa. This prediction is consistent with available experimental results at room temperature. Our DMC calculations give 50.6 ± 0.5 kJ/mol for crystalline benzene lattice energy.

  9. Phase array calibration orthogonal phase sequence

    NASA Technical Reports Server (NTRS)

    Sorace, Ronald E. (Inventor); Reinhardt, Victor S. (Inventor); Chan, Clinton (Inventor)

    1999-01-01

    Methods and systems for calibrating an array antenna are described. The array antenna has a plurality of antenna elements each having a signal with a phase and an amplitude forming an array antenna signal. For calibration, the phase of each element signal is sequentially switched one at a time through four orthogonal phase states. At each orthogonal phase state, the power of the array antenna signal is measured. A phase and an amplitude error for each of the element signals is determined based on the power of the array antenna signal at each of the four orthogonal phase states. The phase and amplitude of each of the element signals is then adjusted by the corresponding phase and amplitude errors.

  10. Van der Pol and the history of relaxation oscillations: Toward the emergence of a concept

    NASA Astrophysics Data System (ADS)

    Ginoux, Jean-Marc; Letellier, Christophe

    2012-06-01

    Relaxation oscillations are commonly associated with the name of Balthazar van der Pol via his paper (Philosophical Magazine, 1926) in which he apparently introduced this terminology to describe the nonlinear oscillations produced by self-sustained oscillating systems such as a triode circuit. Our aim is to investigate how relaxation oscillations were actually discovered. Browsing the literature from the late 19th century, we identified four self-oscillating systems in which relaxation oscillations have been observed: (i) the series dynamo machine conducted by Gérard-Lescuyer (1880), (ii) the musical arc discovered by Duddell (1901) and investigated by Blondel (1905), (iii) the triode invented by de Forest (1907), and (iv) the multivibrator elaborated by Abraham and Bloch (1917). The differential equation describing such a self-oscillating system was proposed by Poincaré for the musical arc (1908), by Janet for the series dynamo machine (1919), and by Blondel for the triode (1919). Once Janet (1919) established that these three self-oscillating systems can be described by the same equation, van der Pol proposed (1926) a generic dimensionless equation which captures the relevant dynamical properties shared by these systems. Van der Pol's contributions during the period of 1926-1930 were investigated to show how, with Le Corbeiller's help, he popularized the "relaxation oscillations" using the previous experiments as examples and, turned them into a concept.

  11. van der Waals interactions between excited-state atoms and dispersive dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Fichet, M.; Schuller, F.; Bloch, D.; Ducloy, M.

    1995-02-01

    van der Waals interactions between atoms and dielectric surfaces are reinvestigated. To describe the nonretarded interaction potential between a dispersive dielectric surface and an atom in an arbitrary internal energy state, we derive a general expression in terms of an integral, over real frequency, of the combined atom and surface polarizabilities. It is shown that, for excited atoms, the expression is equivalent to the one obtained by Wylie and Sipe [Phys. Rev. A 32, 2030 (1985)]. We thus demonstrate how to extend this approach to excited atoms interacting with birefringent dielectrics. For isotropic dielectrics, a method of integration in closed form allows us to derive an approximate formula for the van der Waals interaction constant in terms of resonance frequencies and oscillator strengths of both the atom and the dielectric. Frequency-dependent ``dielectric reflection'' coefficients are introduced for virtual atomic dipole couplings either in absorption or in emission. In absorption, the reflection coefficient is always positive and smaller than unity. In emission, it may take arbitrary values, positive or negative (corresponding to van der Waals repulsion). Such a behavior is shown to be related to resonant excitation exchange between the atomic system and the dielectric medium, when an atomic transition frequency gets in resonance with a dielectric absorption band. Numerical calculations performed for the cesium-sapphire system are shown to be in good agreement with data obtained by selective-reflection spectroscopy. Finally, experimental tests of the birefringent character of the sapphire response are discussed.

  12. Molecular recognition by van der Waals interaction between polymers with sequence-specific polarizabilities.

    PubMed

    Lu, Bing-Sui; Naji, Ali; Podgornik, Rudolf

    2015-06-07

    We analyze van der Waals interactions between two rigid polymers with sequence-specific, anisotropic polarizabilities along the polymer backbones, so that the dipole moments fluctuate parallel to the polymer backbones. Assuming that each polymer has a quenched-in polarizability sequence which reflects, for example, the polynucleotide sequence of a double-stranded DNA molecule, we study the van der Waals interaction energy between a pair of such polymers with rod-like structure for the cases where their respective polarizability sequences are (i) distinct and (ii) identical, with both zero and non-zero correlation length of the polarizability correlator along the polymer backbones in the latter case. For identical polymers, we find a novel r(-5) scaling behavior of the van der Waals interaction energy for small inter-polymer separation r, in contradistinction to the r(-4) scaling behavior of distinct polymers, with furthermore a pronounced angular dependence favoring attraction between sufficiently aligned identical polymers. Such behavior can assist the molecular recognition between polymers.

  13. The effects of van der Waals attractions on cloud droplet growth by coalescence

    NASA Technical Reports Server (NTRS)

    Rogers, Jan R.; Davis, Robert H.

    1990-01-01

    The inclusion of van der Waals attractions in the interaction between cloud droplets has been recently shown to significantly increase the collision efficiencies of the smaller droplets. In the current work, these larger values for the collision efficiencies are used in a population dynamics model of the droplet size distribution evolution with time, in hopes of at least partially resolving the long-standing paradox in cloud microphysics that predicted rates of the onset of precipitation are generally much lower than those which are observed. Evolutions of several initial cloud droplet spectra have been tracked in time. Size evolutions are compared as predicted from the use of collision efficiencies computed using two different models to allow for droplet-droplet contact: one which considers slip flow effects only, and one which considers the combined effects of van der Waals forces and slip flow. The rate at which the droplet mass density function shifts to larger droplet sizes is increased by typically 20-25 percent, when collision efficiencies which include van der Waals forces are used.

  14. van der Waals torque and force between dielectrically anisotropic layered media.

    PubMed

    Lu, Bing-Sui; Podgornik, Rudolf

    2016-07-28

    We analyse van der Waals interactions between a pair of dielectrically anisotropic plane-layered media interacting across a dielectrically isotropic solvent medium. We develop a general formalism based on transfer matrices to investigate the van der Waals torque and force in the limit of weak birefringence and dielectric matching between the ordinary axes of the anisotropic layers and the solvent. We apply this formalism to study the following systems: (i) a pair of single anisotropic layers, (ii) a single anisotropic layer interacting with a multilayered slab consisting of alternating anisotropic and isotropic layers, and (iii) a pair of multilayered slabs each consisting of alternating anisotropic and isotropic layers, looking at the cases where the optic axes lie parallel and/or perpendicular to the plane of the layers. For the first case, the optic axes of the oppositely facing anisotropic layers of the two interacting slabs generally possess an angular mismatch, and within each multilayered slab the optic axes may either be the same or undergo constant angular increments across the anisotropic layers. In particular, we examine how the behaviors of the van der Waals torque and force can be "tuned" by adjusting the layer thicknesses, the relative angular increment within each slab, and the angular mismatch between the slabs.

  15. Spooky correlations and unusual van der Waals forces between gapless and near-gapless molecules.

    PubMed

    Dobson, John F; Savin, Andreas; Ángyán, János G; Liu, Ru-Fen

    2016-11-28

    We consider the zero-temperature van der Waals (vdW) interaction between two molecules, each of which has a zero or near-zero electronic gap between a ground state and the first excited state, using a toy model molecule (equilateral H3) as an example. We show that the van der Waals energy between two ground state molecules falls off as D(-3) instead of the usual D(-6) dependence, when the molecules are separated by distance D. We show that this is caused by a perfect "spooky" correlation between the two fluctuating electric dipoles. The phenomenon is related to, but not the same as, the "resonant" interaction between an electronically excited and a ground state molecule introduced by Eisenschitz and London in 1930. It is also an example of "type C van der Waals non-additivity" recently introduced by one of us [J. F. Dobson, Int. J. Quantum Chem. 114, 1157 (2014)]. Our toy molecule H3 is not stable, but symmetry considerations suggest that a similar vdW phenomenon may be observable, despite Jahn-Teller effects, in molecules with a discrete rotational symmetry and broken inversion symmetry, such as certain metal atom clusters. The motion of the nuclei will need to be included for a definitive analysis of such cases, however.

  16. The hot pick-up technique for batch assembly of van der Waals heterostructures.

    PubMed

    Pizzocchero, Filippo; Gammelgaard, Lene; Jessen, Bjarke S; Caridad, José M; Wang, Lei; Hone, James; Bøggild, Peter; Booth, Timothy J

    2016-06-16

    The assembly of individual two-dimensional materials into van der Waals heterostructures enables the construction of layered three-dimensional materials with desirable electronic and optical properties. A core problem in the fabrication of these structures is the formation of clean interfaces between the individual two-dimensional materials which would affect device performance. We present here a technique for the rapid batch fabrication of van der Waals heterostructures, demonstrated by the controlled production of 22 mono-, bi- and trilayer graphene stacks encapsulated in hexagonal boron nitride with close to 100% yield. For the monolayer devices, we found semiclassical mean-free paths up to 0.9 μm, with the narrowest samples showing clear indications of the transport being affected by boundary scattering. The presented method readily lends itself to fabrication of van der Waals heterostructures in both ambient and controlled atmospheres, while the ability to assemble pre-patterned layers paves the way for complex three-dimensional architectures.

  17. Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures.

    PubMed

    Pierucci, Debora; Henck, Hugo; Naylor, Carl H; Sediri, Haikel; Lhuillier, Emmanuel; Balan, Adrian; Rault, Julien E; Dappe, Yannick J; Bertran, François; Fèvre, Patrick Le; Johnson, A T Charlie; Ouerghi, Abdelkarim

    2016-06-01

    Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design.

  18. The hot pick-up technique for batch assembly of van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Pizzocchero, Filippo; Gammelgaard, Lene; Jessen, Bjarke S.; Caridad, José M.; Wang, Lei; Hone, James; Bøggild, Peter; Booth, Timothy J.

    2016-06-01

    The assembly of individual two-dimensional materials into van der Waals heterostructures enables the construction of layered three-dimensional materials with desirable electronic and optical properties. A core problem in the fabrication of these structures is the formation of clean interfaces between the individual two-dimensional materials which would affect device performance. We present here a technique for the rapid batch fabrication of van der Waals heterostructures, demonstrated by the controlled production of 22 mono-, bi- and trilayer graphene stacks encapsulated in hexagonal boron nitride with close to 100% yield. For the monolayer devices, we found semiclassical mean-free paths up to 0.9 μm, with the narrowest samples showing clear indications of the transport being affected by boundary scattering. The presented method readily lends itself to fabrication of van der Waals heterostructures in both ambient and controlled atmospheres, while the ability to assemble pre-patterned layers paves the way for complex three-dimensional architectures.

  19. Periodic potentials in hybrid van der Waals heterostructures formed by supramolecular lattices on graphene

    PubMed Central

    Gobbi, Marco; Bonacchi, Sara; Lian, Jian X.; Liu, Yi; Wang, Xiao-Ye; Stoeckel, Marc-Antoine; Squillaci, Marco A.; D'Avino, Gabriele; Narita, Akimitsu; Müllen, Klaus; Feng, Xinliang; Olivier, Yoann; Beljonne, David; Samorì, Paolo; Orgiu, Emanuele

    2017-01-01

    The rise of 2D materials made it possible to form heterostructures held together by weak interplanar van der Waals interactions. Within such van der Waals heterostructures, the occurrence of 2D periodic potentials significantly modifies the electronic structure of single sheets within the stack, therefore modulating the material properties. However, these periodic potentials are determined by the mechanical alignment of adjacent 2D materials, which is cumbersome and time-consuming. Here we show that programmable 1D periodic potentials extending over areas exceeding 104 nm2 and stable at ambient conditions arise when graphene is covered by a self-assembled supramolecular lattice. The amplitude and sign of the potential can be modified without altering its periodicity by employing photoreactive molecules or their reaction products. In this regard, the supramolecular lattice/graphene bilayer represents the hybrid analogue of fully inorganic van der Waals heterostructures, highlighting the rich prospects that molecular design offers to create ad hoc materials. PMID:28322229

  20. Application of the van der Pauw method for samples with holes

    NASA Astrophysics Data System (ADS)

    Oh, Donggeon; Ahn, Cheongeung; Kim, Minchul; Park, Eung-Kyu; Kim, Yong-Sang

    2016-12-01

    Modifications of the original van der Pauw relation were suggested recently. The methods are applicable to samples with a hole, unlike the original van der Pauw relation, but it takes too much time and effort to apply the methods to samples with high randomness. So in this paper we suggest two generalizations of the van der Pauw method which are applicable for two-dimensional homogeneous systems with a finite number of holes. Both methods rely on obtaining a crucial constant of the system, ν. The first method involves setting the probes far from each other while conducting the experiment using a sample with a small hole, approximating a relation that gives ν as a linear function of the area ratio of the hole only. The second method produces an identical sample of known resistivity and thickness to obtain ν, which is believed to be dependent on the geometrical properties only. Unlike the earlier methods, which entailed complex procedures, little in the way of measurements and computation is needed for the new methods. The methods will be very useful in electric experiments or industries which need to measure the resistivity of samples.

  1. Goiter in paintings by Rogier van der Weyden (1399-1464).

    PubMed

    Lazzeri, Davide; Pozzilli, Paolo; Zhang, Yi Xin; Persichetti, Paolo

    2015-05-01

    Figures affected by goiter were only sparsely depicted by Peter Paul Rubens and Albrecht Dürer among Flemish artists, because obvious goiter was not common in regions such as the Netherlands and Belgium. However, the recent observation of two figures with a goiter elegantly depicted by Rogier van der Weyden has raised our interest in this topic. When taking a close look at the paintings of this Flemish Renaissance painter, it is interesting to note that 16 portrayed subjects show an abnormal profile of the neck with swelling, suggestive of a presumptive medico-artistic diagnosis of goiter. Van der Weyden travelled to Italy where he soon acquired great fame and was second only to the other Flemish painter of the time, Jan Van Eyck. It is very likely that in Italy he had the opportunity to look at several female figures depicted with goiter, which may have influenced his paintings. Van der Weyden was appreciated because of his style to mix realistic details with idealized softened features to increase the beauty and appeal of his models. It is also likely that the integration of the goiter may have been part of the Renaissance tendency toward a more realistic and precise representation of subjects. The fact that in almost all cases the goiter was a low-to-moderate grade enlargement of the thyroid may confirm our speculation that perhaps the painter used the same model or the template derived from one model for subsequent paintings.

  2. Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures

    PubMed Central

    Pierucci, Debora; Henck, Hugo; Naylor, Carl H.; Sediri, Haikel; Lhuillier, Emmanuel; Balan, Adrian; Rault, Julien E.; Dappe, Yannick J.; Bertran, François; Fèvre, Patrick Le; Johnson, A. T. Charlie; Ouerghi, Abdelkarim

    2016-01-01

    Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design. PMID:27246929

  3. The hot pick-up technique for batch assembly of van der Waals heterostructures

    PubMed Central

    Pizzocchero, Filippo; Gammelgaard, Lene; Jessen, Bjarke S.; Caridad, José M.; Wang, Lei; Hone, James; Bøggild, Peter; Booth, Timothy J.

    2016-01-01

    The assembly of individual two-dimensional materials into van der Waals heterostructures enables the construction of layered three-dimensional materials with desirable electronic and optical properties. A core problem in the fabrication of these structures is the formation of clean interfaces between the individual two-dimensional materials which would affect device performance. We present here a technique for the rapid batch fabrication of van der Waals heterostructures, demonstrated by the controlled production of 22 mono-, bi- and trilayer graphene stacks encapsulated in hexagonal boron nitride with close to 100% yield. For the monolayer devices, we found semiclassical mean-free paths up to 0.9 μm, with the narrowest samples showing clear indications of the transport being affected by boundary scattering. The presented method readily lends itself to fabrication of van der Waals heterostructures in both ambient and controlled atmospheres, while the ability to assemble pre-patterned layers paves the way for complex three-dimensional architectures. PMID:27305833

  4. Optimierung von FSS-Bandpassfiltern mit Hilfe der Schwarmintelligenz (Particle Swarm Optimization)

    NASA Astrophysics Data System (ADS)

    Wu, G.; Hansen, V.; Kreysa, E.; Gemünd, H.-P.

    2006-09-01

    In diesem Beitrag wird ein neues Verfahren zur Optimierung von Bandpassfiltern aus mehrlagigen frequenzselektiven Schirmen (FSS), die in ein Dielektrikum eingebettet sind, vorgestellt. Das Ziel ist es, die Parameter der gesamten Struktur so zu optimieren, dass ihre Transmissionseigenschaften hohe Filteranforderungen erfüllen. Als Optimierungsverfahren wird die Particle Swarm Optimization (PSO) eingesetzt. PSO ist eine neue stochastische Optimierungsmethode, die in verschieden Gebieten, besonders aber bei der Optimierung nicht linearer Probleme mit mehreren Zielfunktionen erfolgreich eingesetzt wird. In dieser Arbeit wird die PSO in die Spektralbereichsanalyse zur Berechnung komplexer FSS-Strukturen integriert. Die numerische Berechnung basiert auf einer Integralgleichungsformulierung mit Hilfe der spektralen Greenschen Funktion für geschichtete Strukturen. This paper presents a novel procedure for the optimization of band-pass filters consisting of frequency selective surfaces (FSS) embedded in a dielectric. The aim is to optimize the parameters of the complete structure so that the transmission characteristics of the filters fulfill the demanding requirements. The Particle Swarm Optimization (PSO) is used as the optimization procedure. PSO is a new stochastic optimization method that is successfully applied in different areas for the optimization of non-linear problems with several object-functions. In this work, PSO is integrated into the spectral domain analysis for the calculation of the complex FSS structures. The numerical computation is based on the formulation of an integral equation with the help of the spectral Green's function for layered media.

  5. Spooky correlations and unusual van der Waals forces between gapless and near-gapless molecules

    NASA Astrophysics Data System (ADS)

    Dobson, John F.; Savin, Andreas; Ángyán, János G.; Liu, Ru-Fen

    2016-11-01

    We consider the zero-temperature van der Waals (vdW) interaction between two molecules, each of which has a zero or near-zero electronic gap between a ground state and the first excited state, using a toy model molecule (equilateral H3) as an example. We show that the van der Waals energy between two ground state molecules falls off as D-3 instead of the usual D-6 dependence, when the molecules are separated by distance D. We show that this is caused by a perfect "spooky" correlation between the two fluctuating electric dipoles. The phenomenon is related to, but not the same as, the "resonant" interaction between an electronically excited and a ground state molecule introduced by Eisenschitz and London in 1930. It is also an example of "type C van der Waals non-additivity" recently introduced by one of us [J. F. Dobson, Int. J. Quantum Chem. 114, 1157 (2014)]. Our toy molecule H3 is not stable, but symmetry considerations suggest that a similar vdW phenomenon may be observable, despite Jahn-Teller effects, in molecules with a discrete rotational symmetry and broken inversion symmetry, such as certain metal atom clusters. The motion of the nuclei will need to be included for a definitive analysis of such cases, however.

  6. Molecular recognition by van der Waals interaction between polymers with sequence-specific polarizabilities

    NASA Astrophysics Data System (ADS)

    Lu, Bing-Sui; Naji, Ali; Podgornik, Rudolf

    2015-06-01

    We analyze van der Waals interactions between two rigid polymers with sequence-specific, anisotropic polarizabilities along the polymer backbones, so that the dipole moments fluctuate parallel to the polymer backbones. Assuming that each polymer has a quenched-in polarizability sequence which reflects, for example, the polynucleotide sequence of a double-stranded DNA molecule, we study the van der Waals interaction energy between a pair of such polymers with rod-like structure for the cases where their respective polarizability sequences are (i) distinct and (ii) identical, with both zero and non-zero correlation length of the polarizability correlator along the polymer backbones in the latter case. For identical polymers, we find a novel r-5 scaling behavior of the van der Waals interaction energy for small inter-polymer separation r, in contradistinction to the r-4 scaling behavior of distinct polymers, with furthermore a pronounced angular dependence favoring attraction between sufficiently aligned identical polymers. Such behavior can assist the molecular recognition between polymers.

  7. Advanced Communication and Control for Distributed Energy Resource Integration: Phase 2 Scientific Report

    SciTech Connect

    BPL Global

    2008-09-30

    The objective of this research project is to demonstrate sensing, communication, information and control technologies to achieve a seamless integration of multivendor distributed energy resource (DER) units at aggregation levels that meet individual user requirements for facility operations (residential, commercial, industrial, manufacturing, etc.) and further serve as resource options for electric and natural gas utilities. The fully demonstrated DER aggregation system with embodiment of communication and control technologies will lead to real-time, interactive, customer-managed service networks to achieve greater customer value. Work on this Advanced Communication and Control Project (ACCP) consists of a two-phase approach for an integrated demonstration of communication and control technologies to achieve a seamless integration of DER units to reach progressive levels of aggregated power output. Phase I involved design and proof-of-design, and Phase II involves real-world demonstration of the Phase I design architecture. The scope of work for Phase II of this ACCP involves demonstrating the Phase I design architecture in large scale real-world settings while integrating with the operations of one or more electricity supplier feeder lines. The communication and control architectures for integrated demonstration shall encompass combinations of software and hardware components, including: sensors, data acquisition and communication systems, remote monitoring systems, metering (interval revenue, real-time), local and wide area networks, Web-based systems, smart controls, energy management/information systems with control and automation of building energy loads, and demand-response management with integration of real-time market pricing. For Phase II, BPL Global shall demonstrate the Phase I design for integrating and controlling the operation of more than 10 DER units, dispersed at various locations in one or more Independent System Operator (ISO) Control Areas, at

  8. Liquid Crystal Phase Behaviour of Attractive Disc-Like Particles

    PubMed Central

    Wu, Liang; Jackson, George; Müller, Erich A.

    2013-01-01

    We employ a generalized van der Waals-Onsager perturbation theory to construct a free energy functional capable of describing the thermodynamic properties and orientational order of the isotropic and nematic phases of attractive disc particles. The model mesogen is a hard (purely repulsive) cylindrical disc particle decorated with an anisotropic square-well attractive potential placed at the centre of mass. Even for isotropic attractive interactions, the resulting overall inter-particle potential is anisotropic, due to the orientation-dependent excluded volume of the underlying hard core. An algebraic equation of state for attractive disc particles is developed by adopting the Onsager trial function to characterize the orientational order in the nematic phase. The theory is then used to represent the fluid-phase behaviour (vapour-liquid, isotropic-nematic, and nematic-nematic) of the oblate attractive particles for varying values of the molecular aspect ratio and parameters of the attractive potential. When compared to the phase diagram of their athermal analogues, it is seen that the addition of an attractive interaction facilitates the formation of orientationally-ordered phases. Most interestingly, for certain aspect ratios, a coexistence between two anisotropic nematic phases is exhibited by the attractive disc-like fluids. PMID:23965962

  9. State-of-the-art review of phase equilibria

    SciTech Connect

    Prausnitz, J.M.

    1980-03-01

    High-pressure phase-equilibrium calculations using an equation of state are more sensitive to the mixing rules than to details in the effect of density or temperature on pressure. Attention must be given to the problem of how to extend equations of state to mixtures. One possible technique is provided by perturbation theory; another by superposition of chemical equilibria. At low or moderate pressures, vapor-phase corrections are often important. When specific intermolecular forces produce formation of molecular aggregates, strong deviations from ideal-gas behavior can be significant even at pressures well below 1 bar. When vapor-liquid equilibrium data are reduced using conventional expressions for the excess Gibbs energy, the resulting binary parameters tend to be partially correlated, it difficult, but no impossible, to calculate ternary liquid-liquid equilibria using binary parameters only. New models for calculating properties of liquid-phase mixtures mist allow for changes in free volume to give consideration to the effect of mixing on changes in rotational and vibrational degrees of freedom. Liquid-phase volumetric effects are also important in describing the solubilities of gases in solvent mixtures. Therefore, future liquid-phase models should incorporate a liquid-phase equation of state, either of the van der Waals type or, perhaps, as given by the direct-correlation function theory of liquids.

  10. Focus on Phase Electives.

    ERIC Educational Resources Information Center

    Jones, Victor H., Ed.

    1976-01-01

    In this thematic issue, articles focus on the use of phase electives in the English classroom. Discussions include "Death in the Classroom,""Soapbox Operas in the English Classroom,""Language and History in Phase-Elective Programs,""Phase Electives and the Problem of Composition," and "Phase Electives and College Preparation.""Phase Electives Are…

  11. Networking as a Seismograph for Social Development. A Contribution to the Function Expansion of Networks Using the Example of Health Promotion of the Socially Disadvantaged (Netzwerkbildung als Seismograph gesellschaftlicher Entwicklungen: Ein Beitrag zur Funktionserweiterung von Netzwerken am Beispiel der Gesundheitsfoerderung von sozial Benachteiligten)

    DTIC Science & Technology

    2008-03-01

    vollzieht sich in den letzten Jahren Ober eine Vielzahl von Netzwerken, uber die sich unterschiedlichste Akteure miteinander verknQ~pft haben. In...indirekt, politische 2 Akteure zu adressieren und bisherige Handlungsdefizite der Gesundheitsf6rderung bei sozial Benachteiligten auch uber neue...klassischen Sinne der Korporatismusanalyse impliziert, sondern gar eine Form der Einwandvorwegnahme darsteilt. Auf der Grundlage der durch die bislang uber

  12. Modellierungskonzept für MOS Varaktoren zur Minimierung der AM-FM Konversion in VCOs

    NASA Astrophysics Data System (ADS)

    Peikert, T.; Bremer, J.-K.; Mathis, W.

    2010-10-01

    In dieser Arbeit wird ein analytisches Simulationsmodell für MOS Varaktoren zur Entwurfsunterstützung von integrierten CMOS LC-Tank VCO-Schaltungen präsentiert. Das analytische Simulationsmodell wurde auf Basis des EKV-Transistormodells implementiert und beinhaltet ausschließlich Design- und Prozessparameter für die Berechnung der Varaktorkapazität. Dieses Simulationsmodell ermöglicht es, die verwendeten Varaktoren im Vorfeld des VCO-Entwurfs zu dimensionieren, die effektive Großsignalkapazität in Abhängigkeit des Ausgangssignals zu berechnen und einzelne Eigenschaften der Varaktoren, wie z.B. das AM-FM Konversionsverhalten zu optimieren. Die Gültigkeit des vorgestellten analytischen Simulationsmodells zur Beschreibung der Varaktorkapazität in CMOS LC-Tank VCOs, wird anhand von Spectre (Cadence) Simulationen auf Basis eines 0.25 μm CMOS Prozesses der Firma IHP (SGB25) und eines 0.35 μm CMOS Prozesses der Firma AMS (C35) verifiziert. In this work an analytical simulation model for MOS varactors, that can be used in a systematically VCO design flow, is presented. The simulation model is based on the EKV transistor model and includes only design and process parameters of the used CMOS technology. The proposed simulation model allows calculating the required design parameters and the effective large signal capacitance of the varactors incorporated into the VCO as a function of the output signal of the VCO. Based on the expression for the effective large signal capacitance it is possible to optimize the AM-FM conversion behavior of the used varactors. The validity and accuracy of the simulation model is verified by Spectre simulations which are based on a 0.25 μm CMOS process (SGB25) from the company IHP and a 0.35 μm CMOS process (C35) from the company AMS. The simulation results show a good accordance in all transistor operating regions for NMOS varactors as well as PMOS varactors.

  13. Herausforderungen für künftige Lernumgebungen am Beispiel der Fakultät für Medizin

    NASA Astrophysics Data System (ADS)

    Gergintchev, Ivan; Graf, Stephan

    Nach der weit reichenden Etablierung von eLearning in den letzten Jahren stehen nahezu alle deutschen Hochschulen vor der Aufgabe, wettbewerbsfähige hochschulübergreifende Mechanismen sowie entsprechende organisatorische Rahmenbedingungen zu schaffen. Vor allem die Umsetzung von EBologna und die Unterstützung kooperativer Bildungsangebote verstärken diese Notwendigkeit. Motiviert durch die Veränderungen im Bereich der Hochschullehre und die Herausforderungen für künftige Lernumgebungen schlagen wir eine Integrationslösung im Sinne eines Learning Gateway vor, die zur webgestützten Abwicklung von kooperativen Bildungsangeboten in heterogen Lernumgebungen eingesetzt werden kann. Ihre Praxisanwendung verdeutlichen wir anschließend im komplexen Szenario der Medizin an der TUM. Die Evaluierung der Umsetzung belegt den deutlichen Mehrwert des Ansatzes.

  14. Comparing van der Waals DFT methods for water on NaCl(001) and MgO(001)

    NASA Astrophysics Data System (ADS)

    Kebede, Getachew G.; Spângberg, Daniel; Mitev, Pavlin D.; Broqvist, Peter; Hermansson, Kersti

    2017-02-01

    In this work, a range of van der Waals type density functionals are applied to the H2O/NaCl(001) and H2O/MgO(001) interface systems to explore the effect of an explicit dispersion treatment. The functionals we use are the self-consistent vdW functionals vdW-DF, vdW-DF2, optPBE-vdW, optB88-vdW, optB86b-vdW, and vdW-DF-cx, as well as the dispersion-corrected PBE-TS and PBE-D2 methods; they are all compared with the standard PBE functional. For both NaCl(001) and MgO(001), we find that the dispersion-flavoured functionals stabilize the water-surface interface by approximately 20%-40% compared to the PBE results. For NaCl(001), where the water molecules remain intact for all overlayers, the dominant contribution to the adsorption energy from "density functional theory dispersion" stems from the water-surface interactions rather than the water-water interactions. The optPBE-vdW and vdW-DF-cx functionals yield adsorption energies in good agreement with available experimental values for both NaCl and MgO. To probe the strengths of the perturbations of the adsorbed water molecules, we also calculated water dipole moments and found an increase up to 85% for water at the MgO(001) surface and 70% at the NaCl(001) surface, compared to the gas-phase dipole moment.

  15. Comparing van der Waals DFT methods for water on NaCl(001) and MgO(001).

    PubMed

    Kebede, Getachew G; Spångberg, Daniel; Mitev, Pavlin D; Broqvist, Peter; Hermansson, Kersti

    2017-02-14

    In this work, a range of van der Waals type density functionals are applied to the H2O/NaCl(001) and H2O/MgO(001) interface systems to explore the effect of an explicit dispersion treatment. The functionals we use are the self-consistent vdW functionals vdW-DF, vdW-DF2, optPBE-vdW, optB88-vdW, optB86b-vdW, and vdW-DF-cx, as well as the dispersion-corrected PBE-TS and PBE-D2 methods; they are all compared with the standard PBE functional. For both NaCl(001) and MgO(001), we find that the dispersion-flavoured functionals stabilize the water-surface interface by approximately 20%-40% compared to the PBE results. For NaCl(001), where the water molecules remain intact for all overlayers, the dominant contribution to the adsorption energy from "density functional theory dispersion" stems from the water-surface interactions rather than the water-water interactions. The optPBE-vdW and vdW-DF-cx functionals yield adsorption energies in good agreement with available experimental values for both NaCl and MgO. To probe the strengths of the perturbations of the adsorbed water molecules, we also calculated water dipole moments and found an increase up to 85% for water at the MgO(001) surface and 70% at the NaCl(001) surface, compared to the gas-phase dipole moment.

  16. Characterization and analysis of a cDNA coding for the group 29b (Der f 29b) allergen of Dermatophagoides farinae

    PubMed Central

    Lin, Jianli; Wang, Hui; Li, Meng; Liang, Zhilin; Jiang, Congli; Wu, Yulan; Liu, Zhigang; Yang, Pingchang; Liu, Xiaoyu

    2016-01-01

    This study aims to acquire a recombinant allergen of Der f 29b by cloning and expression, and to identify its immunogenicity. In this study, the total RNA of D. farinae was extracted, cloned and expressed based on the Der f 29b gene. The molecular characteristics of Der f 29b was analyzed by the procedures of Bioinformatics. The allergenicity of recombinant Der f 29b protein was examined by western-blotting, ELISA, Immune inhibitory assays and skin prick test. The gene of Der f 29b consisted of 495 bases, derived from its nucleic acid sequence and encoded 164 amino acids. Positive responses to r-Der f 29b were shown in 24.3% by means of skin prick testing with 37 DM-allergic patients. The immunoblotting assays demonstrated that serum IgE from allergic patients reacted to r-Der f 29b protein. The IgE reactivity of r-Der f 29b in the serum from r-Der f 29b allergic patients was increased by more than 2 folds compared with healthy subjects. Immune inhibition assays showed that the IgE cross-reactivity was between r-Der f 29b and DME. Bioinformatics analysis predicted four peptides (13-17, 67-71, 104-109 and 147-155) as the B cell epitopes and five peptides (5-14, 16-31, 35-43, 52-63 and 87-97) as the T cell epitopes. Secondary structure prediction of Der f 29b with software PSIPRED identified two α-helices and seven β-sheets in Der f 29b. In conclusion, Derf 29b protein was identified as a novel subtype of dust mite allergen. PMID:27158348

  17. Expression of hypoallergenic Der f 2 derivatives with altered intramolecular disulphide bonds induces the formation of novel ER-derived protein bodies in transgenic rice seeds

    PubMed Central

    Yang, Lijun; Hirose, Sakiko; Suzuki, Kazuya; Hiroi, Takachika; Takaiwa, Fumio

    2012-01-01

    House dust mites (HDM) are the most common source of indoor allergens and are associated with allergic diseases worldwide. To benefit allergic patients, safer and non-invasive mucosal routes of oral administration are considered to be the best alternative to conventional allergen-specific immunotherapy. In this study, transgenic rice was developed expressing derivatives of the major HDM allergen Der f 2 with reduced Der f 2-specific IgE reactivity by disrupting intramolecular disulphide bonds in Der f 2. These derivatives were produced specifically as secretory proteins in the endosperm tissue of seeds under the control of the endosperm-specific glutelin GluB-1 promoter. Notably, modified Der f 2 derivatives aggregated in the endoplasmic reticulum (ER) lumen and were deposited in a unique protein body (PB)-like structure tentatively called the Der f 2 body. Der f 2 bodies were characterized by their intracellular localization and physico-chemical properties, and were distinct from ER-derived PBs (PB-Is) and protein storage vacuoles (PB-IIs). Unlike ER-derived organelles such as PB-Is, Der f 2 bodies were rapidly digested in simulated gastric fluid in a manner similar to that of PB-IIs. Oral administration in mice of transgenic rice seeds containing Der f 2 derivatives encapsulated in Der f 2 bodies suppressed Der f 2-specific IgE and IgG production compared with that in mice fed non-transgenic rice seeds, and the effect was dependent on the type of Der f 2 derivative expressed. These results suggest that engineered hypoallergenic Der f 2 derivatives expressed in the rice seed endosperm could serve as a basis for the development of viable strategies for the oral delivery of vaccines against HDM allergy. PMID:22378952

  18. Characterization and analysis of a cDNA coding for the group 29b (Der f 29b) allergen of Dermatophagoides farinae.

    PubMed

    Lin, Jianli; Wang, Hui; Li, Meng; Liang, Zhilin; Jiang, Congli; Wu, Yulan; Liu, Zhigang; Yang, Pingchang; Liu, Xiaoyu

    2016-01-01

    This study aims to acquire a recombinant allergen of Der f 29b by cloning and expression, and to identify its immunogenicity. In this study, the total RNA of D. farinae was extracted, cloned and expressed based on the Der f 29b gene. The molecular characteristics of Der f 29b was analyzed by the procedures of Bioinformatics. The allergenicity of recombinant Der f 29b protein was examined by western-blotting, ELISA, Immune inhibitory assays and skin prick test. The gene of Der f 29b consisted of 495 bases, derived from its nucleic acid sequence and encoded 164 amino acids. Positive responses to r-Der f 29b were shown in 24.3% by means of skin prick testing with 37 DM-allergic patients. The immunoblotting assays demonstrated that serum IgE from allergic patients reacted to r-Der f 29b protein. The IgE reactivity of r-Der f 29b in the serum from r-Der f 29b allergic patients was increased by more than 2 folds compared with healthy subjects. Immune inhibition assays showed that the IgE cross-reactivity was between r-Der f 29b and DME. Bioinformatics analysis predicted four peptides (13-17, 67-71, 104-109 and 147-155) as the B cell epitopes and five peptides (5-14, 16-31, 35-43, 52-63 and 87-97) as the T cell epitopes. Secondary structure prediction of Der f 29b with software PSIPRED identified two α-helices and seven β-sheets in Der f 29b. In conclusion, Derf 29b protein was identified as a novel subtype of dust mite allergen.

  19. An Analysis of the DER Adoption Climate in Japan UsingOptimization Results for Prototype Buildings with U.S. Comparisons

    SciTech Connect

    Zhou, Nan; Marnay, Chris; Firestone, Ryan; Gao, Weijun; Nishida,Masaru

    2006-06-16

    This research demonstrates economically optimal distributedenergy resource (DER) system choice using the DER choice and operationsoptimization program, the Distributed Energy Resources Customer AdoptionModel (DER-CAM). DER-CAM finds the optimal combination of installedequipment given prevailing utility tariffs and fuel prices, siteelectrical and thermal loads (including absorption cooling), and a menuof available equipment. It provides a global optimization, albeitidealized, that shows how site useful energy loads can be served atminimum cost. Five prototype Japanese commercial buildings are examinedand DER-CAM is applied to select the economically optimal DER system foreach. Based on the optimization results, energy and emission reductionsare evaluated. Significant decreases in fuel consumption, carbonemissions, and energy costs were seen in the DER-CAM results. Savingswere most noticeable in the prototype sports facility, followed by thehospital, hotel, and office building. Results show that DER with combinedheat and power equipment is a promising efficiency and carbon mitigationstrategy, but that precise system design is necessary. Furthermore, aJapan-U.S. comparison study of policy, technology, and utility tariffsrelevant to DER installation is presented.

  20. CrowdPhase: crowdsourcing the phase problem

    SciTech Connect

    Jorda, Julien; Sawaya, Michael R.; Yeates, Todd O.

    2014-06-01

    The idea of attacking the phase problem by crowdsourcing is introduced. Using an interactive, multi-player, web-based system, participants work simultaneously to select phase sets that correspond to better electron-density maps in order to solve low-resolution phasing problems. The human mind innately excels at some complex tasks that are difficult to solve using computers alone. For complex problems amenable to parallelization, strategies can be developed to exploit human intelligence in a collective form: such approaches are sometimes referred to as ‘crowdsourcing’. Here, a first attempt at a crowdsourced approach for low-resolution ab initio phasing in macromolecular crystallography is proposed. A collaborative online game named CrowdPhase was designed, which relies on a human-powered genetic algorithm, where players control the selection mechanism during the evolutionary process. The algorithm starts from a population of ‘individuals’, each with a random genetic makeup, in this case a map prepared from a random set of phases, and tries to cause the population to evolve towards individuals with better phases based on Darwinian survival of the fittest. Players apply their pattern-recognition capabilities to evaluate the electron-density maps generated from these sets of phases and to select the fittest individuals. A user-friendly interface, a training stage and a competitive scoring system foster a network of well trained players who can guide the genetic algorithm towards better solutions from generation to generation via gameplay. CrowdPhase was applied to two synthetic low-resolution phasing puzzles and it was shown that players could successfully obtain phase sets in the 30° phase error range and corresponding molecular envelopes showing agreement with the low-resolution models. The successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it

  1. Critical behaviors and phase transitions of black holes in higher order gravities and extended phase spaces

    NASA Astrophysics Data System (ADS)

    Sherkatghanad, Zeinab; Mirza, Behrouz; Mirzaiyan, Zahra; Mansoori, Seyed Ali Hosseini

    We consider the critical behaviors and phase transitions of Gauss-Bonnet-Born-Infeld-AdS black holes (GB-BI-AdS) for d = 5, 6 and the extended phase space. We assume the cosmological constant, Λ, the coupling coefficient α, and the BI parameter β to be thermodynamic pressures of the system. Having made these assumptions, the critical behaviors are then studied in the two canonical and grand canonical ensembles. We find “reentrant and triple point phase transitions” (RPT-TP) and “multiple reentrant phase transitions” (multiple RPT) with increasing pressure of the system for specific values of the coupling coefficient α in the canonical ensemble. Also, we observe a reentrant phase transition (RPT) of GB-BI-AdS black holes in the grand canonical ensemble and for d = 6. These calculations are then expanded to the critical behavior of Born-Infeld-AdS (BI-AdS) black holes in the third-order of Lovelock gravity and in the grand canonical ensemble to find a van der Waals (vdW) behavior for d = 7 and a RPT for d = 8 for specific values of potential ϕ in the grand canonical ensemble. Furthermore, we obtain a similar behavior for the limit of β →∞, i.e. charged-AdS black holes in the third-order of the Lovelock gravity. Thus, it is shown that the critical behaviors of these black holes are independent of the parameter β in the grand canonical ensemble.

  2. Serum and salivary IgE, IgA, and IgG4 antibodies to Dermatophagoides pteronyssinus and its major allergens, Der p1 and Der p2, in allergic and nonallergic children.

    PubMed

    Miranda, Diego O; Silva, Deise A O; Fernandes, Jorge F C; Queirós, Meimei G J; Chiba, Hamilton F; Ynoue, Leandro H; Resende, Rafael O; Pena, Janethe D O; Sung, Sun-Sang J; Segundo, Gesmar R S; Taketomi, Ernesto A

    2011-01-01

    Allergic rhinitis (AR) is a public health problem with high prevalence worldwide. We evaluated levels of specific IgE, IgA, and IgG4 antibodies to the Dermatophagoides pteronyssinus (Dpt) house dust mite and to its major allergens (Der p1 and Der p2) in serum and saliva samples from allergic and nonallergic children. A total of 86 children were analyzed, from which 72 had AR and 14 were nonallergic healthy children. Serum IgE and serum/salivary IgG4 levels to Dpt, Der p1, and Der p2 were higher in allergic children whereas serum/salivary IgA levels to all allergens were higher in nonallergic children. IgE levels positively correlated with IgG4 and IgA to all allergens in allergic children, while IgA levels negatively correlated with IgG4 to Dpt and Der p1 in nonallergic children. In conclusion, mite-specific IgA antibodies predominate in the serum and saliva of nonallergic children whereas mite-specific IgE and IgG4 are prevalent in allergic children. The presence of specific IgA appears to have a key role for the healthy immune response to mucosal allergens. Also, specific IgA measurements in serum and/or saliva may be useful for monitoring activation of tolerance-inducing mechanisms during allergen specific immunotherapeutic procedures, especially sublingual immunotherapy.

  3. EDITORIAL: Van der Waals interactions in advanced materials, in memory of David C Langreth Van der Waals interactions in advanced materials, in memory of David C Langreth

    NASA Astrophysics Data System (ADS)

    Hyldgaard, Per; Rahman, Talat S.

    2012-10-01

    The past decade has seen a dramatic rise in interest in exploring the role that van der Waals (vdW) or dispersion forces play in materials and in material behavior. Part of this stems from the obvious fact that vdW interactions (and other weak forces, such as Casimir) underpin molecular recognition, i.e., nature's approach to search for a match between genes and anti-genes and hence enable biological function. Less obvious is the recognition that vdW interactions affect a multitude of properties of a vast variety of materials in general, some of which also have strong technological applications. While for two atom- or orbital-sized material fragments the dispersive contributions to binding are small compared to those from the better known forms (ionic, covalent, metallic), those between sparse materials (spread over extended areas) can be of paramount importance. For example, an understanding of binding in graphite cannot arise solely from a study of the graphene layers individually, but also requires insight from inter-sheet graphene vdW bonding. It is the extended-area vdW bonding that provides sufficient cohesion to make graphite a robust, naturally occurring material. In fact, it is the vdW-bonded graphite, and not the all-covalently bonded diamond, that is the preferred form of pure carbon under ambient conditions. Also important is the understanding that vdW attraction can attain a dramatic relevance even if the material fragments, the building blocks, are not necessarily parallel from the outset or smooth when viewed in isolation (such as a graphene sheet or a carbon nanotube). This can happen if the building blocks have some softness and flexibility and allow an internal relative alignment to emerge. The vdW forces can then cause increasingly larger parts of the interacting fragments to line up at sub-nanometer separations and thus beget more areas with a sizable vdW bonding contribution. The gecko can scale a wall because it can bring its flexible hairs

  4. Gustav Steinmann (1856-1929): Ein deutscher Ordinarius der Kaiserzeit

    NASA Astrophysics Data System (ADS)

    Seibold, Eugen; Seibold, Ilse

    2010-10-01

    Gustav Steinmann (1856-1929) was a typical German professor of the time around the turn of the twentieth century. He was active in all fields of geology, palaeontology and marginally mineralogy with a list of about 200 publications. Unfortunately, only a few documents referring to him exist today. We try to outline some details of his life and his scientific and organisational achievements and discuss some aspects of his somewhat discordant character. The geology (structure, stratigraphy including the Pleistocene) of Chile and Peru was one of his main topics. Extracts from the unpublished fieldbooks of his expeditions (1903/1904 and 1908) are given. Other regional investigations cover the Southern Black Forest, the Swiss folded Jura Mountains and their relationships with the Oberrheingraben, the Alps and Apennines. Another lifelong topic was palaeontology and the theory of evolution. Beside some pioneering scientific discoveries, he published various hypotheses that, however, were purely speculative. By contrast, the discovery of the close association of deep-sea sediments and ophiolites in the Alps and the Apennines (1905, 1927), later named the “Steinmann Trinity”, was to inspire later the theories of seafloor spreading and plate tectonics. He also was the first to prove two phases of glacial activity in the Black Forest. On the other hand, he erroneously believed that Middle Europe was once completely covered with ice and that folding in the Swiss Jura produced empty spaces in the cores of anticlines in analogy to folds in the Andes that were “passively filled by diorites”. His ideas about the evolution of organisms were also extremely speculative if not absurd. He constructed lineages that were based only on morphological appearance thus bringing together, e.g. dinosaurs and giraffes. In 1877, Steinmann finished a dissertation on fossil hydrozoa in Munich, and in 1880, as an assistant at the University of Strasbourg, a habilitation on the Jurassic and

  5. Phase behavior and molecular dynamics simulation studies of new aqueous two-phase separation systems induced by HEPES buffer.

    PubMed

    Taha, Mohamed; Khoiroh, Ianatul; Lee, Ming-Jer

    2013-01-17

    Here, for the first time, we show that with addition of a biological buffer, 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), into aqueous solutions of tetrahydrofuran (THF), 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone, the organic solvent can be excluded from water to form a new liquid phase. The phase diagrams have been determined at ambient temperature. In order to understand why and how a zwitterion solute (HEPES) induced phase separation of the investigated systems, molecular dynamics (MD) simulation studies are performed for HEPES + water + THF system. The MD simulations were conducted for the aqueous mixtures with 12 different compositions. The reliability of the simulation results of HEPES in pure water and beyond the phase separation mixtures was justified by comparing the densities obtained from MD with the experimental values. The simulation results of HEPES in pure THF and in a composition inside the phase separation region were justified qualitatively. Interestingly, all HEPES molecules entirely aggregated in pure THF. This reveals that HEPES is insoluble in pure THF, which is consistent with the experimental results. Even more interestingly, the MD simulation for the mixture with composition inside the phase separation region showed the formation of two phases. The THF molecules are squeezed out from the water network into a new liquid phase. The hydrogen bonds (HBs), HB lifetime, HB Gibbs energy (ΔG), radial distribution functions (RDFs), coordination numbers (CNs), electrostatic interactions, and the van der Waals interactions between the different species have been analyzed. Further, MD simulations for the other phase separation systems by choosing a composition inside the two liquids region for each system were also simulated. Our findings will therefore pave the way for designing new benign separation auxiliary agents.

  6. Crystallization and Preliminary X-ray Analysis of Der f 2, a Potent Allergen Derived from the House Dust Mite

    NASA Technical Reports Server (NTRS)

    Roeber, Dana; Achari, Aniruddha; Takai, Toshiro; Okumura, Yasushi; Scott, David L.; Curreri, Peter (Technical Monitor)

    2002-01-01

    Although a number of allergens have been identified and isolated, the underlying molecular basis for the potent immune response is poorly understood. House dust mites (Dermatophugoides sp.) are particularly ubiquitous contributors to atopy in developed countries. The rhinitis, dermatitis, and asthma associated with allergic reactions to these arthropods are often caused by relatively small (125-129 amino acids) mite proteins of unclear biological function. Der f 2, a major allergen from the mite Dermatophagoides farinae, has been recombinantly expressed and characterized. The Der f 2 protein has been crystallized in our laboratory and a native data set collected at a synchrotron source. The crystals belong to the orthorhombic space group I422 with unit cell parameters of a = 95.2 Angstroms, b = 95.2 Angstroms, and c = 103.3 Angstroms. An essentially complete (97.2%) data set has been collected to 2.4 Angstroms. Attempts to solve the crystal structure of Der f 2 by molecular replacement using the available NMR coordinates for either Der f 2 or Der p 2 (the homologous protein from D. pterovssinus) failed to reveal a creditable solution.

  7. Van der Waals interactions: Evaluations by use of a statistical mechanical method

    NASA Astrophysics Data System (ADS)

    Høye, Johan S.

    2011-10-01

    In this work the induced van der Waals interaction between a pair of neutral atoms or molecules is considered by use of a statistical mechanical method. With use of the Schrödinger equation this interaction can be obtained by standard quantum mechanical perturbation theory to second order. However, the latter is restricted to electrostatic interactions between dipole moments. So with radiating dipole-dipole interaction where retardation effects are important for large separations of the particles, other methods are needed, and the resulting induced interaction is the Casimir-Polder interaction usually obtained by field theory. It can also be evaluated, however, by a statistical mechanical method that utilizes the path integral representation. We here show explicitly by use of this method the equivalence of the Casimir-Polder interaction and the van der Waals interaction based upon the Schrödinger equation. The equivalence is to leading order for short separations where retardation effects can be neglected. In recent works [J. S. Høye, Physica A 389, 1380 (2010), 10.1016/j.physa.2009.12.003; Phys. Rev. E 81, 061114 (2010)], 10.1103/PhysRevE.81.061114, the Casimir-Polder or Casimir energy was added as a correction to calculations of systems like the electron clouds of molecules. The equivalence to van der Waals interactions indicates that the added Casimir energy will improve the accuracy of calculated molecular energies. Thus, we give numerical estimates of this energy including analysis and estimates for the uniform electron gas.

  8. [A Comparative Analysis of Shushi-Sanbaron and the Original German Textbook Lehrbuch der Hebammenkunst].

    PubMed

    Tsukisawa, Miyoko

    2015-12-01

    In this paper we present a comparative analysis of Shushi-Sanbaron (Japanese characters) and the original book, Lehrbuch der Hebammenkunst. After the legal reorganisation of the medical professions in Germany in the mid nineteenth century, the textbook Lehrbuch der Hebammenkunst was published for certified midwives. This book has two distinct characteristics; it was written from the physician's standpoint regarding the importance of the professional hierarchy of obstetricians and midwives, and it also served as a practical educator for midwives. Lehrbuch der Hebammenkunst was translated into Japanese for use as a textbook after the introduction of systematised education for certified midwives by the Tokyo-fu Hospital. It was published between 1877 and 1878 under title Shushi-Sanbaron. We clarify that Shushi-Sanbaron was not a literal translation of the original book, but was largely rewritten by two physicians in order to modify it to the Japanese situation after the introduction of modern medicine. Japanese physicians made serious modifications of the chapters that dealt with deviations from the regular course of birth and abnormal conditions of postpartum women and new-born babies, and they added theoretical explanations about obstetrics. As a result, Shushi-Sanbaron made two contradicting demands to midwives. On the one hand, midwives were urged to attain high-level theoretical knowledge and skill in obstetrics in order to--independently--help pregnant women and new-born babies in a crisis. On the other hand, as lower participants in the medical hierarchy, they were told to assume a dependent and uncritical attitude towards physicians.

  9. Self-consistent van der Waals density functional: Development and Applications

    NASA Astrophysics Data System (ADS)

    Cooper, Valentino

    2008-03-01

    The inability of density functional theory (DFT), with standard exchange-correlation functionals, to correctly describe van der Waals/dispersion (vdW) interactions has severely limited its applicability to sparsely packed systems, such as organic and biological molecules. Numerous attempts have been made to correct these deficiencies; however, many of them either require extensive reparameterization for each new situation or scale poorly with system size. In this paper, I will discuss the development and implementation of an exchange-correlation functional which correctly incorporates non-local vdW interactions within DFT (vdW-DF)ootnotetextM. Dion, H. Rydberg, E. Schröder, B. I. Lundqvist and D. C. Langreth, Phys. Rev. Lett., 92, 246401 (2004). In addition, I will present our recent development of the corresponding exchange- correlation potential (Vxc)ootnotetextT. Thonhauser, V. R. Cooper, S. Li, A. Puzder, P. Hyldgaard, and David C. Langreth, Phys. Rev. B, 76, 125112 (2007). The Vxc gives us the ability to compute Hellmann-Feynman forces, allowing for structural relaxations and molecular dynamics simulation. Using the Vxc I will examine the nature of the van der Waals bond between molecules. Finally, to demonstrate the power of the vdW-DF, I will discuss our relatively large scale application of the functional to study the influence of stacking interactions on the structure and stability of DNA. Here, I will show how these interactions are crucial for defining the twist and base pair separation in DNA and how methyl-nucleobase and methyl-methyl interactions give additional stability to DNA.

  10. Local Probe Spectroscopy of Two-Dimensional van der Waals Heterostructures

    NASA Astrophysics Data System (ADS)

    Yankowitz, Matthew Abraham

    A large family of materials, collectively known as "van der Waals materials", have attracted enormous research attention over the past decade following the realization that they could be isolated into individual crystalline monolayers, with charge carriers behaving effectively two-dimensionally. More recently, an even larger class of composite materials has been realized, made possible by combining the isolated atomic layers of different materials into "van der Waals heterostructures", which can exhibit electronic and optical behaviors not observed in the parent materials alone. This thesis describes efforts to characterize the atomic-scale structural and electronic properties of these van der Waals materials and heterostructures through scanning tunneling microscopy measurements. The majority of this work addresses the properties of monolayer and few-layer graphene, whose charge carriers are described by massless and massive chiral Dirac Hamiltonians, respectively. In heterostructures with hexagonal boron nitride, an insulating isomorph of graphene, we observe electronic interference patterns between the two materials which depend on their relative rotation. As a result, replica Dirac cones are formed in the valence and conduction bands of graphene, with their energy tuned by the rotation. Further, we are able to dynamically drag the graphene lattice in these heterostructures, owing to an interaction between the scanning probe tip and the domain walls formed by the electronic interference pattern. Similar dragging is observed in domain walls of trilayer graphene, whose electronic properties are found to depend on the stacking configuration of the three layers. Scanning tunneling spectroscopy provides a direct method for visualizing the scattering pathways of electrons in these materials. By analyzing the scattering, we can directly infer properties of the band structures and local environments of these heterostructures. In bilayer graphene, we map the electrically

  11. Field Effect in Graphene-Based van der Waals Heterostructures: Stacking Sequence Matters.

    PubMed

    Stradi, Daniele; Papior, Nick R; Hansen, Ole; Brandbyge, Mads

    2017-03-13

    Stacked van der Waals (vdW) heterostructures where semiconducting two-dimensional (2D) materials are contacted by overlaid graphene electrodes enable atomically thin, flexible electronics. We use first-principles quantum transport simulations of graphene-contacted MoS2 devices to show how the transistor effect critically depends on the stacking configuration relative to the gate electrode. We can trace this behavior to the stacking-dependent response of the contact region to the capacitive electric field induced by the gate. The contact resistance is a central parameter and our observation establishes an important design rule for ultrathin devices based on 2D atomic crystals.

  12. Investigation on Dynamics of the Extended Duffing-Van der Pol System

    NASA Astrophysics Data System (ADS)

    Yu, Jun; Li, Jieru

    2009-06-01

    The chaotic motion in periodic self-excited oscillators has been extensively investigated through experiments and computer simulations. However, with the advent of the study of chaotic motion by means of strange attractors, Poincaŕe map, fractal dimension, it has become necessary to seek for a better understanding of nonlinear system with higher order nonlinear terms. In this paper we consider an extended Duffing-Van der Pol oscillator by introducing a nonlinear quintic term. The dynamical behaviour of the system is investigated by using Melnikov analysis and numerical simulation. The results can help one to understand the essence of given nonlinear system.

  13. Observing the interplay between surface and bulk optical nonlinearities in thin van der Waals crystals

    PubMed Central

    Deckoff-Jones, Skylar; Zhang, Jingjing; Petoukhoff, Christopher E.; Man, Michael K.L.; Lei, Sidong; Vajtai, Robert; Ajayan, Pulickel M.; Talbayev, Diyar; Madéo, Julien; Dani, Keshav M.

    2016-01-01

    Van der Waals materials, existing in a range of thicknesses from monolayer to bulk, allow for interplay between surface and bulk nonlinearities, which otherwise dominate only at atomically-thin or bulk extremes, respectively. Here, we observe an unexpected peak in intensity of the generated second harmonic signal versus the thickness of Indium Selenide crystals, in contrast to the quadratic increase expected from thin crystals. We explain this by interference effects between surface and bulk nonlinearities, which offer a new handle on engineering the nonlinear optical response of 2D materials and their heterostructures. PMID:26936437

  14. Virtual Resonance and Frequency Difference Generation by van der Waals Interaction

    NASA Astrophysics Data System (ADS)

    Tetard, L.; Passian, A.; Eslami, S.; Jalili, N.; Farahi, R. H.; Thundat, T.

    2011-05-01

    The ability to explore the interior of materials for the presence of inhomogeneities was recently demonstrated by mode synthesizing atomic force microscopy [L. Tetard, A. Passian, and T. Thundat, Nature Nanotech. 5, 105 (2009).NNAABX1748-338710.1038/nnano.2009.454]. Proposing a semiempirical nonlinear force, we show that difference frequency ω- generation, regarded as the simplest synthesized mode, occurs optimally when the force is tuned to van der Waals form. From a parametric study of the probe-sample excitation, we show that the predicted ω- oscillation agrees well with experiments. We then introduce the concept of virtual resonance to show that probe oscillations at ω- can efficiently be enhanced.

  15. Collision-induced Raman spectra of Hg-rare gas Van der Waals complexes

    NASA Astrophysics Data System (ADS)

    Borysow, A.; Grycuk, T.

    1982-10-01

    An absolute differential scattering cross section is calculated for the Hg-rare gas and pure Hg Van der Waals quasimolecules, taking into account both the free state and bound state contributions to the depolarized Raman spectra of these systems. The calculations are performed using the Maitland-Smith (MS) potential function fitted to available experimental data and assuming the simple dipole-induced dipole (DID) model of anisotropy of the polarizability tensor of a collisional atomic pair. The obtained cross sections are about 100 times greater than those for the pure rare gas calculated and measured by Frommhold et al.

  16. Observing the interplay between surface and bulk optical nonlinearities in thin van der Waals crystals

    NASA Astrophysics Data System (ADS)

    Deckoff-Jones, Skylar; Zhang, Jingjing; Petoukhoff, Christopher E.; Man, Michael K. L.; Lei, Sidong; Vajtai, Robert; Ajayan, Pulickel M.; Talbayev, Diyar; Madéo, Julien; Dani, Keshav M.

    2016-03-01

    Van der Waals materials, existing in a range of thicknesses from monolayer to bulk, allow for interplay between surface and bulk nonlinearities, which otherwise dominate only at atomically-thin or bulk extremes, respectively. Here, we observe an unexpected peak in intensity of the generated second harmonic signal versus the thickness of Indium Selenide crystals, in contrast to the quadratic increase expected from thin crystals. We explain this by interference effects between surface and bulk nonlinearities, which offer a new handle on engineering the nonlinear optical response of 2D materials and their heterostructures.

  17. Interlayer coupling effects on Schottky barrier in the arsenene-graphene van der Waals heterostructures

    SciTech Connect

    Xia, Congxin Xue, Bin; Wang, Tianxing; Peng, Yuting; Jia, Yu

    2015-11-09

    The electronic characteristics of arsenene-graphene van der Waals (vdW) heterostructures are studied by using first-principles methods. The results show that a linear Dirac-like dispersion relation around the Fermi level can be quite well preserved in the vdW heterostructures. Moreover, the p-type Schottky barrier (0.18 eV) to n-type Schottky barrier (0.31 eV) transition occurs when the interlayer distance increases from 2.8 to 4.5 Å, which indicates that the Schottky barrier can be tuned effectively by the interlayer distance in the vdW heterostructures.

  18. Construction of van der Waals magnetic tunnel junction using ferromagnetic layered dichalcogenide

    NASA Astrophysics Data System (ADS)

    Arai, Miho; Moriya, Rai; Yabuki, Naoto; Masubuchi, Satoru; Ueno, Keiji; Machida, Tomoki

    2015-09-01

    We investigate the micromechanical exfoliation and van der Waals (vdW) assembly of ferromagnetic layered dichalcogenide Fe0.25TaS2. The vdW interlayer coupling at the Fe-intercalated plane of Fe0.25TaS2 allows exfoliation of flakes. A vdW junction between the cleaved crystal surfaces is constructed by dry transfer method. We observe tunnel magnetoresistance in the resulting junction under an external magnetic field applied perpendicular to the plane, demonstrating spin-polarized tunneling between the ferromagnetic layered material and the vdW junction.

  19. Nanoscopy of Surface-Induced van der Waals-Zeeman Transitions

    SciTech Connect

    Hamamda, M.; Grucker, J.; Dutier, G.; Perales, F.; Baudon, J.; Ducloy, M.; Bocvarski, V.

    2008-10-22

    van der Waals transitions among magnetic sub-levels of a metastable rare gas atom passing near a surface immersed in a magnetic field, are described. Related transition amplitudes are calculated using both the sudden and the Landau-Zener approximations. Experimental data for Ne*({sup 3}P{sub 2}) atoms traversing a copper grating are presented. For a pair of surfaces (e.g. the opposite edges of a slit) and a sufficiently large coherence width, Fresnel's biprism interference fringes are obtained. From this interference pattern, detailed information about the transition amplitude at a sub-nanometric scale can be derived. The effect of gravity on this pattern is examined.

  20. van der Waals force between positronium and hydrogenic atoms Finite-mass corrections

    NASA Technical Reports Server (NTRS)

    Au, C. K.; Drachman, R. J.

    1986-01-01

    The Feshbach projection-operator formalism is used to derive the asymptotic effective interaction potential between two atoms. Beyond the usual van der Waals potential, falling like x exp -6, three x exp -8 terms are also obtained: an attractive dipole-quadrupole term (absent in the positronium-positronium case because of symmetry), a repulsive energy-dependent term, and a repulsive mass-dependent but energy-independent one. This last term was not obtained by Manson and Ritchie (1985) using an independent method.

  1. A Van Der Waals Homojunction: Ideal p-n Diode Behavior in MoSe2.

    PubMed

    Jin, Youngjo; Keum, Dong Hoon; An, Sung-Jin; Kim, Joonggyu; Lee, Hyun Seok; Lee, Young Hee

    2015-10-07

    A MoSe2 p-n diode with a van der Waals homojunction is demonstrated by stacking undoped (n-type) and Nb-doped (p-type) semiconducting MoSe2 synthesized by chemical vapor transport for Nb substitutional doping. The p-n diode reveals an ideality factor of ≈1.0 and a high external quantum efficiency (≈52%), which increases in response to light intensity due to the negligible recombination rate at the clean homojunction interface.

  2. Electro-photo modulation of the fermi level in WSe2/graphene van der Waals heterojunction

    NASA Astrophysics Data System (ADS)

    Sun, Honghui; Yang, Hang; Fang, Liang; Zhang, Jiangwei; Wang, Zhiyuan; Jiang, Tian

    2017-04-01

    We report an electro-photo double modulation of the fermi level in a WSe2/graphene heterojunction. The heterojunction exhibits high ION/IOFF ratio ( 103) in transfer characteristic in dark and distinct rectification behavior in output characteristic under light illumination, respectively. Time-dependent photoresponse reveals that the heterojunction has a considerable potential in the application of photodetection. Interestingly, an exotic current peak is observed in transfer characteristic under light illumination. This novel behavior is attributed to the tunable fermi level at the WSe2/graphene heterojunction by electro-photo double modulation. The results may be helpful to develop tunable photovoltaic optoelectronics based on van der Waals heterojunctions.

  3. Super-Planckian Electron Cooling in a van der Waals Stack

    NASA Astrophysics Data System (ADS)

    Principi, Alessandro; Lundeberg, Mark B.; Hesp, Niels C. H.; Tielrooij, Klaas-Jan; Koppens, Frank H. L.; Polini, Marco

    2017-03-01

    Radiative heat transfer (RHT) between macroscopic bodies at separations that are much smaller than the thermal wavelength is ruled by evanescent electromagnetic modes and can be orders of magnitude more efficient than its far-field counterpart, which is described by the Stefan-Boltzmann law. In this Letter, we present a microscopic theory of RHT in van der Waals stacks comprising graphene and a natural hyperbolic material, i.e., hexagonal boron nitride (hBN). We demonstrate that RHT between hot carriers in graphene and hyperbolic phonon polaritons in hBN is extremely efficient at room temperature, leading to picosecond time scales for the carrier cooling dynamics.

  4. Recent progress of photodetectors based on MX2/graphene van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Yang, Hang; Qin, Shiqiao; Fang, Jinyue; Peng, Gang; Zhang, Xueao

    2016-10-01

    Recently, heterostructures, combining the unique advantages of both graphene and transition metal dichalcogenides (TMDs, also known as MX2), have exhibited extraordinary photo-electrical properties, thus attracted tremendous interests worldwide. In this paper, we overviewed recent progress of MX2/Graphene van der Waals heterostructures, including the preparation methods, relevant parameters in opto-electronic measurements, physical mechanisms, existing experimental results and encountered problems. Here, we focus to cover the development of entire field, and provide a comprehensive and accurate understanding concerning this field, which may be helpful for interested researchers in this area.

  5. Atomically thin resonant tunnel diodes built from synthetic van der Waals heterostructures.

    PubMed

    Lin, Yu-Chuan; Ghosh, Ram Krishna; Addou, Rafik; Lu, Ning; Eichfeld, Sarah M; Zhu, Hui; Li, Ming-Yang; Peng, Xin; Kim, Moon J; Li, Lain-Jong; Wallace, Robert M; Datta, Suman; Robinson, Joshua A

    2015-06-19

    Vertical integration of two-dimensional van der Waals materials is predicted to lead to novel electronic and optical properties not found in the constituent layers. Here, we present the direct synthesis of two unique, atomically thin, multi-junction heterostructures by combining graphene with the monolayer transition-metal dichalcogenides: molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2). The realization of MoS2-WSe2-graphene and WSe2-MoS2-graphene heterostructures leads to resonant tunnelling in an atomically thin stack with spectrally narrow, room temperature negative differential resistance characteristics.

  6. System for absolute measurement of electrolytic conductivity in aqueous solutions based on van der Pauw's theory

    NASA Astrophysics Data System (ADS)

    Zhang, Bing; Lin, Zhen; Zhang, Xiao; Yu, Xiang; Wei, Jiali; Wang, Xiaoping

    2014-05-01

    Based on an innovative application of van der Pauw's theory, a system was developed for the absolute measurement of electrolytic conductivity in aqueous solutions. An electrolytic conductivity meter was designed that uses a four-electrode system with an axial-radial two-dimensional adjustment structure coupled to an ac voltage excitation source and signal collecting circuit. The measurement accuracy, resolution and repeatability of the measurement system were examined through a series of experiments. Moreover, the measurement system and a high-precision electrolytic conductivity meter were compared using some actual water samples.

  7. Amyloidosis: The Newer Discovered ALECT2 Associated with der7q add(7)

    PubMed Central

    Samal, Priyanka; Chakrabartty, Joydeep

    2016-01-01

    Amyloidosis is characterized by pathological deposition of abnormal protein aggregates in various tissues, AL protein being the commonest. ALECT 2 is the newest protein described, having a predisposition to affect the kidneys, sometimes the liver and rarely other organs. We present a case of renal amyloid ALECT 2 due to leucocyte cell derived chemotaxin 2, a novel amyloidogenic protein. The patient presented with mild proteinuria, scattered plasma cells on bone marrow examination and altered kappa/lambda ratio with associated cytogenetic abnormality of der7q add(7). It is essential to correctly type this protein and differentiate it from AL during diagnosis for appropriate and effective clinical management. PMID:27790444

  8. Stability of an attractive bosonic cloud with van der Waals interaction

    SciTech Connect

    Biswas, Anindya; Das, Tapan Kumar; Salasnich, Luca; Chakrabarti, Barnali

    2010-10-15

    We investigate the structure and stability of Bose-Einstein condensates of {sup 7}Li atoms with realistic van der Waals interactions by using the potential harmonic expansion method. Besides the known low-density metastable solution with a contact {delta}-function interaction, we find a stable branch at a higher density which corresponds to the formation of an atomic cluster. Comparison with the results of a nonlocal effective interaction is also presented. We analyze the effect of trap size on the transition between the two branches of solutions. We also compute the loss rate of a Bose condensate due to two- and three-body collisions.

  9. Erfahrungen im Aufbau des IT Service Desks der Technischen Universität München

    NASA Astrophysics Data System (ADS)

    Vellguth, Karmela

    Durch das Projekt IntegraTUM und die darin eingebettete Einrichtung eines IT Service Desks mit 1st, 2nd und 3rd Level Support gelang eine an ITIL orientierte Neuausrichtung der internen IT-Dienstleistungen. Die vormals existierende Struktur mit einer Vielzahl an Ansprechpartnern bei auftretenden IT-Problemen wurde aufgelöst. Die Nutzer haben nun eine Anlaufstelle erhalten, die sich für die Beantwortung aller Incidents in kürzester Zeit und mit qualitativ hohem Niveau zuständig fühlt.

  10. On the choice of inertial axes for interpreting spectroscopic properties of van der Waals complexes

    NASA Astrophysics Data System (ADS)

    Ernesti, Andreas; Hutson, Jeremy M.

    1994-10-01

    Properties such as the dipole moments and nuclear quadrupole coupling constants of van der Waals complexes are important in the determination of intermolecular potential energy surfaces from high-resolution spectra. The properties are often interpreted in terms of angular expectation values. It is shown that, when calculating such properties, it is important to use an inertial axis system that satisfies the Eckart conditions. Projections onto other axes, such as the intermolecular vector or the instantaneous principal axes, can lead to substantial errors when the individual monomers have large moments of inertia.

  11. Effects of zero van der Waals and zero electrostatic forces on droplet sedimentation

    NASA Technical Reports Server (NTRS)

    Omenyi, S. N.; Snyder, R. S.; Van Oss, C. J.; Absolom, D. R.; Neumann, A. W.

    1981-01-01

    The present investigation provides a confirmation of the dependence of droplet sedimentation on particle concentration. It is shown that it is possible to determine the maximum particle concentration which can remain stable on a given liquid from droplet sedimentation experiments. Droplet sedimentation can be reduced but not totally eliminated by the addition of appropriate amounts of dimethyl sulfoxide (DMSO) to reduce the van der Waals forces to zero. It was found that, at 12% DMSO, a maximum particle concentration of 6.3 x 10 to the 8th cells/ml of glutaraldehyde-fixed human erythrocytes suspended in physiological saline can remain stable on a D2O cushion.

  12. Construction of van der Waals magnetic tunnel junction using ferromagnetic layered dichalcogenide

    SciTech Connect

    Arai, Miho; Moriya, Rai Yabuki, Naoto; Masubuchi, Satoru; Ueno, Keiji; Machida, Tomoki

    2015-09-07

    We investigate the micromechanical exfoliation and van der Waals (vdW) assembly of ferromagnetic layered dichalcogenide Fe{sub 0.25}TaS{sub 2}. The vdW interlayer coupling at the Fe-intercalated plane of Fe{sub 0.25}TaS{sub 2} allows exfoliation of flakes. A vdW junction between the cleaved crystal surfaces is constructed by dry transfer method. We observe tunnel magnetoresistance in the resulting junction under an external magnetic field applied perpendicular to the plane, demonstrating spin-polarized tunneling between the ferromagnetic layered material and the vdW junction.

  13. Sitzungsberichte der Heidelberger Akademie der Wissenschaften¬Jahrgang 1990 Sitzungsber.Heidelberg 90¬"Gott hat die Natur einfältig gemacht, sie aber suchen viel Künste"

    NASA Astrophysics Data System (ADS)

    Zehe, Horst

    Der Aufsatz demonstriert anhand ausgiebig kommentierter zeitgenössischer Zeugnisse Goethes Reaktion auf die Arbeiten Fraunhofers, insbesondere auf die Entdeckung der dunklen Linien im Sonnenspektrum. Den Fehlurteilen Goethes werden dabei die Urteile zeitgenössischer Physiker wie Chladni und J.F.W. Herschel gegenübergestellt. Bislang noch ungedruckte Dokumente aus dem Weimarer Goethe- und Schiller-Archiv belegen, daß sich Goethe nicht nur literarisch mit Fraunhofer beschäftigte, sondern daß er auch dessen Versuche mit Hilfe des Jenaer Universitätsmechanikers Körner getreulich zu wiederholen suchte.

  14. Empirical evaluation of attractive van der Waals potentials for type-purified single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Hobbie, Erik K.; Ihle, Thomas; Harris, John M.; Semler, Matthew R.

    2012-06-01

    van der Waals forces play a critical role in the structure and stability of single-wall carbon nanotube (SWCNT) materials. Thin films assembled from SWCNTs purified by electronic type show particular promise for flexible electronics applications, but mechanical durability remains an unresolved issue. Using transition resonances determined from spectroscopic measurements of type-purified SWCNTs deposited on quartz, coupled with analogous spectroscopic characterization of polydimethylsiloxane (PDMS) substrates, we use the Lifshitz theory of van der Waals dispersion interactions developed by Rajter and co-workers [Rajter , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.76.045417 76, 045417 (2007)] to examine the influence of electronic type on van der Waals contact potentials in polymer-supported nanotube networks. Our results suggest a significantly stronger nanotube-nanotube and nanotube-polymer attraction for the semiconducting SWCNT fractions, consistent with recent measurements of the electronic durability of flexible transparent SWCNT coatings.

  15. Image method in the calculation of the van der Waals force between an atom and a conducting surface

    NASA Astrophysics Data System (ADS)

    de Melo e Souza, Reinaldo; Kort-Kamp, W. J. M.; Sigaud, C.; Farina, C.

    2013-05-01

    After a brief survey of van der Waals forces, we review a method recently proposed by Eberlein and Zietal to compute the dispersion van der Waals interaction between a neutral but polarizable atom and a perfectly conducting surface of arbitrary shape. This method has the advantage of relating the quantum problem to a corresponding classical one in electrostatics in an enlightening way so that all one needs is to compute an appropriate Green function. We show how the image method of electrostatics can be conveniently used together with the Eberlein and Zietal method (when the image solution is known). We then illustrate this method in some simple but important cases, including the atom-sphere system. Finally, we present an original result for the van der Waals force between an atom and a boss hat made of a grounded conducting material.

  16. CrowdPhase: crowdsourcing the phase problem

    PubMed Central

    Jorda, Julien; Sawaya, Michael R.; Yeates, Todd O.

    2014-01-01

    The human mind innately excels at some complex tasks that are difficult to solve using computers alone. For complex problems amenable to parallelization, strategies can be developed to exploit human intelligence in a collective form: such approaches are sometimes referred to as ‘crowdsourcing’. Here, a first attempt at a crowdsourced approach for low-resolution ab initio phasing in macromolecular crystallography is proposed. A collaborative online game named CrowdPhase was designed, which relies on a human-powered genetic algorithm, where players control the selection mechanism during the evolutionary process. The algorithm starts from a population of ‘individuals’, each with a random genetic makeup, in this case a map prepared from a random set of phases, and tries to cause the population to evolve towards individuals with better phases based on Darwinian survival of the fittest. Players apply their pattern-recognition capabilities to evaluate the electron-density maps generated from these sets of phases and to select the fittest individuals. A user-friendly interface, a training stage and a competitive scoring system foster a network of well trained players who can guide the genetic algorithm towards better solutions from generation to generation via gameplay. CrowdPhase was applied to two synthetic low-resolution phasing puzzles and it was shown that players could successfully obtain phase sets in the 30° phase error range and corresponding molecular envelopes showing agreement with the low-resolution models. The successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it possible to extract meaningful information in cases where limited resolution might otherwise prevent initial phasing. PMID:24914965

  17. Europäisches Organ der Festkörperforschung und DDR-Devisenbringer Die Zeitschrift Physica Status Solidi im Kalten Krieg

    NASA Astrophysics Data System (ADS)

    Hoffmann, Dieter

    Mit dem Ziele, ein einheitliches internationales Organ der Festkörperphysik für den europäischen Raum zu schaffen, das eine rasche Publikation der für das Festkörpergebiet repräsentative Arbeiten ermöglicht, wird durch ein internationales Herausgebergremium eine neue wissenschaftliche Zeitschrift gegründet.

  18. Fragwuerdige Luxussteuern: Statusstreben und Demonstratives Konsumverhalten in der Geschichte Oekonomischen Denkens (Questionable Luxury Taxes: Status Seeking and Conspicuous Consumption in the History of Economic Thought)

    DTIC Science & Technology

    2008-05-01

    England immer mehr, und der Markt ffir Luxusgiiter und Mode begann zu florieren. Die Kommerzialisierung des Handels im England des 18. Jahrhunderts...der insbesondere Hirsch (1976) in seinen Social Limits to Growth wieder Nachdruck verleihen sollte. Siehe hierzu Abschnitt 2.9. 5 auf seinen...klassischen Schule ibertriebenes statusbedingtes Konsumverhalten als social waste an und pladiert fdr eine Lenkung statusbedingten Konsumverhaltens in

  19. Hydrogenic Rydberg States of Molecular van der Waals Complexes: Resolved Rydberg Spectroscopy of DABCO-N2

    NASA Astrophysics Data System (ADS)

    Cockett, Martin C.; Watkins, Mark J.

    2004-01-01

    The complementary threshold ionization techniques of MATI and ZEKE spectroscopy have been used to reveal well-resolved, long-lived (>10 μs) hydrogenic Rydberg series (50≤n≤98) in a van der Waals complex formed between a polyatomic molecule and a diatomic molecule for the first time. The series are observed within 50 cm-1 of the adiabatic ionization threshold as well as two core-excited thresholds corresponding to excitation of up to two quanta in the van der Waals vibra­tional mode.

  20. van der Waals-Tonks-type equations of state for hard-hypersphere fluids in four and five dimensions.

    PubMed

    Wang, Xian-Zhi

    2004-04-15

    Recently, we developed accurate van der Waals-Tonks-type equations of state for hard-disk and hard-sphere fluids by using the known virial coefficients. In this paper, we derive the van der Waals-Tonks-type equations of state. We further apply these equations of state to hard-hypersphere fluids in four and five dimensions. In the low-density fluid regime, these equations of state are in good agreement with the simulation results and existing equations of state.