Science.gov

Sample records for oeffentliche bekanntmachung der

  1. Der interstellare Raum.

    NASA Astrophysics Data System (ADS)

    der Time-Life Bücher, Redaktion

    Contents: 1. Löcher im Sternenhimmel. Vom Staubkorn zum Stern. 2. Kartieren von Gas, Staub und Magnetismus. Komplexe Moleküle im All. 3. Die Geburtsstätten der Sterne. Molekulare Verstärker. 4. Jenseits der Galaxien. Der intergalaktische Raum.

  2. Philosophie und Geschichte der Kosmologie.

    NASA Astrophysics Data System (ADS)

    Mainzer, K.

    Contents: 1. Von der Mythologie zum geozentrischen Kosmos. 2. Vom geozentrischen zum heliozentrischen Kosmos (15. - 16. Jahrhundert). 3. Der Kosmos im Zeitalter der klassischen Physik (17. - 19. Jahrhundert). 4. Der Kosmos im Zeitalter der modernen Physik. 5. Zusammenfassung.

  3. Umsetzung der Unternehmensstrategie mit der Balanced Scorecard

    NASA Astrophysics Data System (ADS)

    Crespo, Isabel; Bergmann, Lars; Portmann, Stefan; Lacker, Thomas; Lacker, Michael; Fleischmann, JĂŒrgen; KozĂł, 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).

  4. Meilensteine in der Erforschung der kompakten Objekte

    NASA Astrophysics Data System (ADS)

    Camenzind, Max

    Kompakte Objekte besitzen zum einen eine sehr hohe Dichte, und zum anderen sind sie durch die Tatsache charakterisiert, dass keine nuklearen Reaktionen mehr in ihrem Inneren stattfinden können. Aus diesem Grund können sie im Unterschied zu gewöhnlichen Sternen der Gravitation nicht mehr mit dem Druck des thermischen Gases widerstehen. In den Weißen Zwergen bzw. Neutronensternen wird der Gravitation der Quantendruck eines Elektronengases bzw. einer NeutronenflĂŒssigkeit entgegengesetzt. Ein solches Gas besteht aus Elektronen bzw. Neutronen, die auf ihr niedrigstes Energieniveau zusammengepresst wurden. Durch die daraus resultierende hohe Bewegungsenergie der Fermionen wird der sogenannte Quantendruck erzeugt.

  5. 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: EinfĂŒhrung. R. N. Anshen: Vorwort. F. Hoyle: Kosmische Katastrophen und der Ursprung der Religion - Die Folgen der RespektabilitĂ€t; Eiszeiten und Kometen; Die allgemeine Situation in den Nacheiszeiten; Kometen und der Ursprung der Religionen; Der Übergang zu Mittelalter und Neuzeit. DiskussionsbeitrĂ€ge: 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.

  6. 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 grundsĂ€tzlich als Wahrnehmung der Wirkung dieser Eigenschaften ĂŒber einen oder mehrere WahrnehmungskanĂ€le des Menschen: visuell, auditiv, haptisch, olfaktorisch. Die individuelle Wahrnehmung ist hierbei subjektiv und daher mit rein physikalisch objektiven MessgrĂ¶ĂŸen allein nur unvollstĂ€ndig zu beschreiben. Sie hĂ€ngt 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 WeltmĂ€rkten sehr unterschiedlich erlebt.

  7. Grundlagen der Mechatronik

    NASA Astrophysics Data System (ADS)

    Roddeck, Werner

    Der Begriff Mechatronik ist ein Kunstwort, welches durch Eindeutschung des englischen Wortes "Mechatronics“ entstanden ist. Dieses ist wiederum eine Zusammenziehung der englischen Bezeichnungen fĂŒr "Mechanics“ (Maschinenbau) und "Electronics“ (Elektrotechnik). Der Begriff wurde durch einen japanischen Ingenieur 1969 geprĂ€gt und durch eine japanische Firma bis 1972 als Warenzeichen gehalten.

  8. Der II. Hauptsatz der WĂ€rmelehre

    NASA Astrophysics Data System (ADS)

    Heintze, Joachim

    Wir haben in (4.44) den II. Hauptsatz als empirische Tatsache folgendermaßen formuliert: (i) WĂ€rmeenergie geht von selbst nur von einem wĂ€rmeren Körper auf einen kĂ€lteren ĂŒber, niemals in der umgekehrten Richtung. Nun werden wir beweisen, dass sich aus diesem Prinzip folgende Ă€quivalente Formulierungen fĂŒr den II. Hauptsatz ableiten lassen: (ii) Es ist unmöglich, ein Perpetuum mobile zweiter Art zu bauen, d. h. eine Maschine, die fortlaufend WĂ€rmeenergie vollstĂ€ndig in mechanische Arbeit umsetzen kann. Eine WĂ€rmekraftmaschine, die einen Kreisprozess mit der höchsten Temperatur Tw und der niedrigsten Temperatur Tk durchlĂ€uft, hat höchstens den Carnotschen Wirkungsgrad c = (Tw - Tk)/Tw. Wenn in der Maschine nur reversible Prozesse ablaufen, die gesamte WĂ€rmezufuhr bei der Temperatur Tw erfolgt und ausschließlich bei der Temperatur Tw gekĂŒhlt wird, ist ihr Wirkungsgrad = C. Es gibt keine WĂ€rmekraftmaschine, die eine bessere Ausnutzung der WĂ€rmeenergie ermöglicht. (iv) In jedem thermodynamischen System existiert die ZustandsgrĂ¶ĂŸe Entropie, definiert durch ihr Differential dS = (dQrev)/T . Entropie kann erzeugt, aber nicht vernichtet werden. Bei ZustandsĂ€nderungen, 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 VerstĂ€ndnis der Entropie gelangen. Es zeigt sich, dass die Entropie das eigentliche Bindeglied zwischen Mechanik und WĂ€rmelehre darstellt. Am Ende des Kapitels werden wir einige Anwendungen des II. Hauptsatzes betrachten.

  9. Die ArbeitsunfÀhigkeit in der Statistik der GKV

    NASA Astrophysics Data System (ADS)

    Busch, Klaus

    Der vorliegende Beitrag gibt anhand der Statistiken des Bundesministeriums fĂŒr Gesundheit (BMG) einen Überblick ĂŒber die ArbeitsunfĂ€higkeitsdaten der Gesetzlichen Krankenkassen (GKV). ZunĂ€chst werden die ArbeitsunfĂ€higkeitsstatistiken der Krankenkassen und die Erfassung der ArbeitsunfĂ€higkeit erlĂ€utert. 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. 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 LeistungsfÀhigkeit der damaligen, vorwiegend von Newton geprÀgten Weltsicht. Entstehung, Aufbau und Dynamik der Sonne werden in Kants Theorie ebenso erklÀrt wie etwa das PhÀnomen der Sonnenflecken.

  11. 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 PhÀnomene". 6. Aristotelische Kosmololgie. 7. Aristoteles-Welt und Platon-Welt. 8. Noch einmal: die Göttlichkeit der Welt. 9. Griechischer Idealismus.

  12. Jahr der Geowissenschaften

    NASA Astrophysics Data System (ADS)

    Wohnlich, Stefan

    2002-06-01

    Das System Erde ist Leitthema des "Jahres der Geowissenschaften", das von der Bundesministerin fĂŒr Bildung und Forschung in den Vordergrund der Initiative "Wissenschaft im Dialog" fĂŒr 2002 gestellt wurde. Es soll aufzeigen, dass wir in einer empfindlichen Umwelt leben, die auf die natĂŒrlichen Schwankungen, z. B. des Klimas, genauso empfindlich reagiert wie auf die rĂŒcksichtslose Nutzung der Erde durch den Menschen. Damit rĂŒckt auch das Thema Grundwasser als Teil des globalen Wasserkreislaufes in den Mittelpunkt der derzeitigen Öffentlichkeitsarbeit. Wenn wir uns die bisherige Resonanz auf das Jahr der Geowissenschaften anschauen, dann ist festzustellen, dass gerade die Bereitschaft aus den Medien zur Aufnahme von Geowissenschaftlichen Themen erstaunlich groß ist. Aus dem Bereich des Grund- und Trinkwassers snd vor allem in UniversitĂ€tsstĂ€dten bereits grĂ¶ĂŸere Veranstaltungen durchgefĂŒhrt worden oder stehen noch im Laufe des Jahres aus (Information unter: www.planeterde.de). TatsĂ€chlich ist der Dialog von Wissenschaft und Praxis mit der Öffentlichkeit ein vorrangiges Ziel auch der Fachsektion Hydrogeologie. Nur allzu leicht tritt dieses Ziel im Alltagsbetrieb in den Hintergrund. Die deutschen UniversitĂ€ten und Wissenschaftsorganisationen haben in die Öffentlichkeitsarbeit erst in den letzten Jahren verstĂ€rkt Ideen und Mittel investiert. Dabei ist gerade das VerstĂ€ndnis fĂŒr die Chancen und Risiken der Forschung und damit auch der Hochschullehre in der breiten Öffentlichkeit eine unabdingbare Voraussetzung. Aber nicht nur die wissenschaftliche Organisationen sind auf die Akzeptanz einer breiten Öffentlichkeit fĂŒr wissenschaftlich fundiertes Arbeiten angewiesen, sondern auch die von Fachwissen geprĂ€gten Aufgaben im Umfeld des Grundwassers brauchen das VerstĂ€ndnis fĂŒr ihre oft aufwĂ€ndigen Untersuchungen. Ich habe in den letzten Monaten mehrere VortrĂ€ge an verschiedenen Gymnasien zum Thema "Ressource Grundwasser" gehalten. Die Resonanz war fĂŒr mich ĂŒberwĂ€ltigend positiv. Es gibt hier einen enormen Informationsbedarf bei SchĂŒlern wie auch bei Lehrern, den wir erkennen mĂŒssen und den wir bewusst als einen Weg sehen sollten um das VerstĂ€ndnis fĂŒr einen nachhaltigen Schutz der Ressource Grundwasser zu stĂ€rken. Ein weiterer Aspekt sollte nicht ĂŒbersehen werden: es zeichnet sich ein eklatanter Mangel an qualifizierten HochschulabgĂ€ngern aus unserem Fach ab. Auch hier bietet das Jahr der Geowissenschaften die Möglichkeit, Nachwuchs fĂŒr unser Fach zu werben.

  13. 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 mĂŒssen, gelingt dem Autor etwas Seltenes: einen "lebendigen" Zugang zum IdeengebĂ€ude 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 hĂ€tte ich mir diese gescheiten Essays zum Werden unserer heutigen physikalischen Weltsicht gewĂŒnscht. 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 grĂŒndliches "konventionelles" Studium weder ersetzen wollen noch können, sie vermögen aber, dazu zu ermuntern." #Astronomische Nachrichten (zur englischen Ausgabe)#1

  14. Von der Quantenmechanik zum Materialdesign

    NASA Astrophysics Data System (ADS)

    Eyert, Volker; Eckern, Ulrich

    2000-11-01

    Die enormen Fortschritte der theoretischen Festkörperphysik im 20. Jahrhundert sind eng verknĂŒpft mit der Entdeckung der Quantenmechanik und der Entwicklung von schnellen Verfahren zur Berechnung der elektronischen Struktur kondensierter Materie. Letztere bilden heute die Basis sowohl fĂŒr ein vertieftes VerstĂ€ndnis grundlegender physikalischer Fragestellungen als auch die Herstellung neuer Materialien mit maßgeschneiderten Eigenschaften.

  15. Geologie der terrestrischen Planeten und Monde.

    NASA Astrophysics Data System (ADS)

    Stöffler, D.

    Contents: 1. Inhalt und Aufgabe der Planetologie. 2. Aufbau des Sonnensystems. 3. Methoden der Exploration und Analyse der Planeten und Monde. 4. Geologische Grundprozesse auf den terrestrischen Planeten und Monden. 5. Geologische Formationen der planetaren OberflÀchen. 6. Gesteine und Mineralien der planetaren Krusten. 7. Der innere Aufbau der terrestrischen planetaren Körper. 8. Vergleichende geologische Entwicklungsgeschichte der terrestrischen Planeten und des Mondes. 9. Ursprung und Entstehung der terrestrischen planetaren Körper.

  16. Liberalisierung der Energiemärkte

    NASA Astrophysics Data System (ADS)

    Oehler, H.

    Die extremen Preisschwankungen für Energie Ende der ersten Dekade des 21. Jahrhunderts, gekennzeichnet durch rasant steigende Preise bis zu einem Spitzenwert für Erdöl von knapp unter 150 US- pro Barrel und dem nachfolgenden Absturz aufgrund der Wirtschaftskrise, lassen das Interesse für Mechanismen an den globalen und lokalen Märkten für Energie steigen. In diesem Zusammenhang rücken die Auswirkungen der Liberalisierung der Märkte für leitungsgebundene Energien wieder mehr in das Zentrum des Interesses, wobei häufig einerseits Ursachen und Wirkung vermischt, andererseits aber auch völlig verfehlte Erwartungen an die Liberalisierung, die Unternehmen sowie das Kundenverhalten gestellt werden. Zu beobachten ist außerdem, dass die gewünschten Schwerpunkte bei den erhofften Effekten des Wettbewerbs Schwankungen unterliegen, je nachdem welche Interessen gerade meinungsbestimmend sind, z. B. Versorgungssicherheit oder Preise.

  17. 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.

  18. Repulsive van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Han, Jianing

    2015-05-01

    In this presentation, repulsive van der Waals interactions within ultracold gasses will be presented. Van der Waals interaction is generally used in physics, chemistry, biology, and other fields of science. A common misconception about van der Waals interaction is that the van der Waals interaction is attractive. This is only true for ground state atoms. For excited atoms, van der Waals interactions can be either attractive or repulsive. Since the discovery of the van der Waals interactions by Johannes Diderik van der Waals in the 1870's, it has been known as an attractive interaction. Therefore, repulsive van der Waals interaction has been rarely studied and has never been used. In this presentation, repulsive van der Waals interactions in ultracold atoms between different spins will be investigated. This study will analyze the density range for using ultracold atoms as an alternative energy source.

  19. Der Forsch-Frosch Fred

    NASA Astrophysics Data System (ADS)

    Kaibel, Volker

    Bewegt man sich auf der Suche nach Informationen zu einem bestimmten Thema immer neuen Links folgend durch das World-Wide-Web, so stellt man in der Regel nach einer gewissen Zeit fest, dass man auf manchen Seiten immer wieder gelandet ist. Diese Seiten stellen sich oft als wichtig heraus. Suchmaschinen wie Google machen sich dieses Phänomen zu Nutze, um die Wichtigkeit einzelner Web-Seiten zu bewerten. Dazu lassen sie auf einer beliebigen Web-Seite einen imaginären Surfer starten, der immer zufällig einen der auf seiner aktuell besuchten Seite vorgefundenen Links verfolgt. Der Surfer vollführt einen Random Walk im Netzwerk der Web-Seiten.

  20. Der Strahlenkranz im sonnigen Wasser

    NASA Astrophysics Data System (ADS)

    Schlichting, Hans Joachim

    2000-01-01

    Wie in der Kunst gibt es auch in der Natur neben dem kreisförmigen Heiligenschein einen strahlenförmigen Nimbus um den Kopfschatten "auserwählter" Personen. Er ist in leicht getrübtem Wasser zu beobachten.

  1. van der Waals Forces

    PubMed Central

    Ninham, B. W.; Parsegian, V. A.

    1970-01-01

    A practical method for examining and calculating van der Waals forces is derived from Lifshitz' theory. Rather than treat the total van der Waals energy as a sum of pairwise interactions between atoms, the Lifshitz theory treats component materials as continua in which there are electromagnetic fluctuations at all frequencies over the entire body. It is necessary in principle to use total macroscopic dielectric data from component substances to analyze the permitted fluctuations; in practice it is possible to use only partial information to perform satisfactory calculations. The biologically interesting case of lipid-water systems is considered in detail for illustration. The method gives good agreement with measured van der Waals energy of interaction across a lipid film. It appears that fluctuations at infrared frequencies and microwave frequencies are very important although these are usually ignored in preference to UV contributions. “Retardation effects” are such as to damp out high frequency fluctuation contributions; if interaction specificity is due to UV spectra, this will be revealed only at interactions across <200 angstrom (A). Dependence of van der Waals forces on material electric properties is discussed in terms of illustrative numerical calculations. PMID:5449915

  2. Evaluation der zentralen TUM-Lernplattform

    NASA Astrophysics Data System (ADS)

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

    Die Notwendigkeit der QualitĂ€tssicherung und -kontrolle fĂŒr innovative universitĂ€re Lehr-/Lernszenarien ist in der Praxis unbestritten. Die Wirksamkeit der EinfĂŒhrung der zentralen Lernplattform CLIX Campus der imc AG an der TUM wurde mittels quantitativer und qualitativer Evaluation ĂŒberprĂŒft. Als statistische Bewertungsgrundlage wurde der Erreichungsgrad bestimmter Projektziele herangezogen. Aufbauend auf den theoretischen Grundlagen der Evaluation von Bildungsangeboten gibt diese Studie Aufschluss ĂŒber die Ergebnisse der Datenerhebungen sowie die EinschĂ€tzung der Plattform aus Nutzersicht und belegt die wesentliche Bedeutung der durchgĂ€ngigen IT-Infrastruktur und speziell der einheitlichen VerfĂŒgbarkeit der eLearning Angebote.

  3. [Van der Woude syndrome].

    PubMed

    Calzavara Pinton, P G; Gavazzoni, R; Carlino, A; Leali, C

    1989-04-01

    The familial occurrence of lower lip pits (fistulae, sinuses) with or without the cheilo-gnathouranoschisis complex (cleft lip and/or cleft palate) was first described by A. Van der Woude in 1954. The lip pits syndrome is inherited as an autosomal dominant trait with high penetrance (80%), but its clinical expression is variable. Sometimes there may be microforms with only conical elevation and/or surface openings without any deeper sinuses at the typical sites and without cleft lip/palate. We examined 8 members of an Italian family and we observed one member with lip pits and submucous cleft palate and 4 members with only lip pits. Three of these affected members had congenital absence of second premolars too. The presentation, mode of inheritance, aetiology and genetic significance of lip pits syndrome are reviewed. In our opinion this is the first Italian report of the Van der Woude syndrome. PMID:2807397

  4. Haftung in der Medizintechnik

    NASA Astrophysics Data System (ADS)

    MĂŒller, Ute; LĂŒcker, Volker

    Die Unversehrtheit von Leib und Leben ist das grĂ¶ĂŸte Rechtsgut unserer Gesellschaft. Dies macht schon das Grundgesetz in Art. 2 Abs. Satz 1 GG deutlich. Die Öffentlichkeit zeigt daher grĂ¶ĂŸtes Interesse an Produkten, welche der Gesundheit dienen und Leben retten oder erhalten. Dieses Interesse gilt einerseits der Entwicklung und Bereitstellung leistungsfĂ€higer Medizinprodukte, andererseits zielt es auf deren Sicherheit. Um vor allem letztere zu gewĂ€hrleisten, 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 SchadenersatzansprĂŒchen, 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.

  5. 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.

  6. Zeit im Wandel der Zeit.

    NASA Astrophysics Data System (ADS)

    Aichelburg, P. C.

    Contents: Einleitung(P. C. Aichelburg). 1. Über Zeit, Bewegung und VerĂ€nderung (Aristoteles). 2. Ewigkeit und Zeit (Plotin). 3. Was ist die Zeit? (Augustinus). 4. Von der Zeit (Immanuel Kant). 5. Newtons Ansichten ĂŒber Zeit, Raum und Bewegung (Ernst Mach). 6. Über die mechanische ErklĂ€rung irreversibler VorgĂ€nge (Ludwig Boltzmann). 7. Das Maß der Zeit (Henri PoincarĂ©). 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 ĂŒber die Beziehungen zwischen RelativitĂ€tstheorie und der idealistischen Philosophie (Kurt Gödel). 15. Der zweite Hauptsatz und der Unterschied von Vergangenheit und Zukunft (Carl Friedrich v. WeizsĂ€cker). 16. Zeit als physikalischer Begriff (Friedrich Hund). 17. Zeitmessung und Zeitbegriff in der Astronomie (Otto Heckmann). 18. Kann die Zeit rĂŒckwĂ€rts gehen? (Martin Gardner). 19. Zeit und Zeiten (Ilya Prigogine, Isabelle Stengers). 20. Zeit als dynamische GrĂ¶ĂŸe in der RelativitĂ€tstheorie (P. C. Aichelburg).

  7. Grundlagen und Vollzug der amtlichen Lebensmittelkontrolle in der Schweiz

    NASA Astrophysics Data System (ADS)

    HĂŒbner, 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 grundsÀtzlich 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 prÀzisieren - insbesondere die organisatorischen Aspekte - und Regelungen im nicht harmonisierten Bereich treffen.

  8. Dialektischer Materialismus in der Quantentheorie

    NASA Astrophysics Data System (ADS)

    Fuchs, Klaus

    Der absolute Determinismus der klassischen Mechanik bietet keine Ansatzpunkte fĂŒr eine befriedigende Naturphilosophie. Mit der Quantenmechanik werden nicht lediglich die UnzulĂ€nglichkeiten 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.

  9. Der evolutionÀre 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 MoralitĂ€t evolutionĂ€r bedingt ist, scheint daher auf den ersten Blick ganz ĂŒberzeugend. 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 FĂ€higkeit des Menschen, moralische Normen aufzustellen und gemĂ€ĂŸ ihnen zu handeln, nicht evolutionĂ€r erklĂ€rt werden können? Und warum sollte eine solche evolutionĂ€re ErklĂ€rung der menschlichen MoralitĂ€t irrelevant fĂŒr die Rechtfertigung moralischer Normen sein? Warum sollte die Ethik eine Bastion der Philosophen bleiben, fĂŒr die evolutionsbiologische Forschungsergebnisse ĂŒber den Menschen und seine nĂ€chsten Verwandten keinerlei Relevanz besitzen?

  10. 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.

  11. Profiles of IgE Sensitization to Der f 1, Der f 2, Der f 6, Der f 8, Der f 10, and Der f 20 in Korean House Dust Mite Allergy Patients

    PubMed Central

    Jeong, Kyoung Yong; Lee, June Yong; Son, Mina; Yi, Myung-hee; Yong, Tai-Soon; Shin, Jung U; Lee, Kwang Hoon; Kim, Yoon-Ju; Park, Kyung Hee; Park, Hye Jung; Lee, Jae-Hyun

    2015-01-01

    Purpose Measurement of IgE specific to purified house dust mite (HDM) allergens may improve allergy diagnosis. This study aimed to investigate the sensitization profiles of Korean HDM allergic subjects suffering from respiratory allergy and atopic dermatitis (AD) to Der f 1, Der f 2, Der f 6, Der f 8, Der f 10, and Der f 20. Methods Recombinant HDM allergens were produced in Pichia pastoris (Der f 1) or Escherichia coli (5 allergens). IgE reactivity to the individual recombinant allergens and total extract of mite was assessed by ELISA. Results Der f 1 was recognized by 79.1%, Der f 2 by 79.1%, Der f 6 by 9.3%, Der f 8 by 6.2%, Der f 10 by 6.2%, and Der f 20 by 6.6% of the patients' sera tested, while the prevalence of IgE reactivity to total mite extract was 94.7%. Combination of Der f 1 and Der f 2 had a sensitivity of 87.6%. Specific IgE to Der f 2 alone was detected from 89.4% of HDM-sensitized respiratory allergy subjects and 92.3% to the combination of the 2 major allergens Der f 1 and Der f 2. However, sera from fewer patients with AD, namely 72.4% and 71.0%, recognized Der f 1 and Der f 2, respectively. The combination of 2 major allergens allowed diagnosis of 84.5% of the AD patients. No correlation between sensitization to specific allergens and HDM allergy entity was found. Conclusions Der f 2 was the most frequently sensitized allergen among the HDM-sensitized respiratory and AD patients in Korea, and the combination of the group 1 and 2 major allergens increased the diagnostic sensitivity. Minor allergens did not significantly improve diagnostic sensitivity. However, further studies are needed to analyze the relationship between sensitization to other HDM allergens and the disease entity of the HDM allergy. PMID:25749773

  12. Strategische Planung in der Medizintechnik

    NASA Astrophysics Data System (ADS)

    Leewe, Jörn

    FĂŒr den Aufstieg und den Niedergang der Unternehmen spielt die Über- oder Unterlegenheit der Technologie eine zentrale Rolle. Mindestens im gleichen Maße ist jedoch auch ein umsichtiges Management und eine sorgfĂ€ltige strategische Planung fĂŒr den Erfolg verantwortlich. Nur ein profitables Unternehmen, welches nachhaltige Gewinne erzielt, ist in der Lage, eine Spitzenforschung aus eigener Kraft zu finanzieren. Dies klingt zunĂ€chst trivial. In der langjĂ€hrigen Consulting-Praxis sind wir jedoch diversen Unternehmen begegnet, die diese Maxime vernachlĂ€ssigt haben und aufgrund mangelhafter Planungen eine Insolvenz dann nicht mehr abwenden konnten. Damit es erst gar nicht dazu kommt, sollten unterschiedliche Handlungsalternativen im voraus entwickelt und bewertet werden. Die Strategie, also das systematische Aufbauen von Wettbewerbsvorteilen, sollte regelmĂ€ssig ĂŒberprĂŒft werden und eine finanzielle Entwicklung des Produktes oder des Unternehmens sollte regelmĂ€ĂŸig antizipiert und simuliert werden. Dieser Beitrag soll Einblicke in die strategische Planung erlauben, erhebt allerdings aufgrund der KomplexitĂ€t des Themas keinen Anspruch auf VollstĂ€ndigkeit.

  13. Physik gestern und heute Der Spion, der die WĂ€rme untersuchte

    NASA Astrophysics Data System (ADS)

    Heering, Peter

    2003-11-01

    Der in Massachusetts geborene Benjamin Thompson, der ab 1792 auch den Titel eines Grafen von Rumford fĂŒhrte, ist eine der schillerndsten Figuren der Physikgeschichte. BerĂŒhmt wurde er insbesondere wegen seiner Experimente zur WĂ€rmetheorie.http://www.famousamericans.net/benjaminthompsonrumford

  14. Coronellis Cosmos in der Melker Stiftsbibliothek.

    NASA Astrophysics Data System (ADS)

    Glaßner, Gottfried; PĂ€rr, Nora

    2009-06-01

    Die Melker Stiftsbibliothek besitzt ein Globenpaar des berĂŒhmten 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 ursprĂŒnglichen Ausstattung der 1735 fertig gestellten Barockbibliothek gehörten, wird aber aus der zentralen Stellung deutlich, die dem Globus (Erdglobus und ArmillarphĂ€re) 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 HauptsĂ€len wie auch in der Deckenmalerei von Johann Bergl in der Oberen Bibliothek (1768) und in der Kuppel des Gartenpavillons (1764).

  15. 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.

  16. Der Physik-Nobelpreis vor 100 Jahren: Der vierte Aggregatzustand

    NASA Astrophysics Data System (ADS)

    Jacobi, Manfred

    2005-11-01

    Im Jahr 1905 erhielt der aus Preßburg (dem heutigen Bratislava) stammende Philipp Eduard Lenard (1862 - 1947) den Nobelpreis fĂŒr Physik. Die Schwedische Akademie wĂŒrdigte damit seine Arbeiten ĂŒber die Kathodenstrahlen.

  17. Der Einsatz der Dermatoskopie in der Diagnose und Therapie von nichtmelanozytÀren Hautkrebsformen.

    PubMed

    Deinlein, Teresa; Richtig, Georg; Schwab, Christoph; Scarfi, Federica; Arzberger, Edith; Wolf, Ingrid; Hofmann-Wellenhof, Rainer; Zalaudek, Iris

    2016-02-01

    Die Dermatoskopie stellt heute einen integrativen Teil jeder klinischen Hautkrebsuntersuchung dar, da sie die FrĂŒherkennung von melanozytĂ€ren und nichtmelanozytĂ€ren Hautkrebsformen im Vergleich zur Untersuchung mit dem bloßen Auge deutlich verbessert. Neben ihrem diagnostischen Einsatz nimmt diese nichtinvasive Methode auch eine zunehmende Rolle in der Wahl und Bewertung unterschiedlicher Therapien von nichtmelanozytĂ€ren Hauttumoren wie Basalzellkarzinomen, aktinischen Keratosen, Plattenepithelkarzinomen, aber auch seltenen Tumoren wie dem Merkelzellkarzinom, Angiosarkom oder dem Dermatofibrosarcoma protuberans ein. So ist die Dermatoskopie ein valides Werkzeug zur prĂ€operativen Tumorrandbestimmung von Basalzellkarzinomen, kann aber auch zur Verlaufskontrolle nach erfolgter topischer Therapie von aktinischen Keratosen eingesetzt werden. In diesem Artikel soll ein Überblick ĂŒber den Einsatz der Dermatoskopie in der Diagnose und Therapie unterschiedlicher Formen des nichtmelanozytĂ€ren Hautkrebses gegeben werden. PMID:26819108

  18. 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.

  19. Mit Neutronen auf der Spur der Elektronen: Neutronen-Spektroskopie an Festkörpern

    NASA Astrophysics Data System (ADS)

    Hiess, Arno; Schober, Helmut

    2003-05-01

    Neutronen sind elektrisch neutral und haben ein magnetisches Moment. Deshalb eignen sie sich besonders zur Aufklärung der Struktur und Bewegung der Atome und der magnetischen Momente im Festkörper. Forscher am Institut Laue-Langevin konnten mit der Neutronen-Flugzeitspektroskopie die Rolle der Gitterschwingungen im Supraleiter Magnesium-Diborid aufklären. Diffraktion mit polarisierten Neutronen kann die räumliche Verteilung der Magnetisierungsdichte zum Beispiel in einem Nanomagneten sichtbar machen. Neutronen-Dreiachsspektroskopie und -Kleinwinkelstreuung öffnen den Zugang zum Wechselspiel zwischen Magnetismus und Supraleitung in Hochtemperatur- und Schwere-Fermionen-Supraleitern.

  20. Medizintechnik in der TumororthopÀdie

    NASA Astrophysics Data System (ADS)

    Burgkart, Rainer; Gollwitzer, Hans; Holzapfel, Boris; Rudert, Maximilian; Rechl, Hans; Gradinger, Reiner

    Die Behandlung der Knochentumoren unterlag in den letzten 20 Jahren einem raschen und stetigen Wandel, was zum einen auf die verbesserten Therapieerfolge durch den Einsatz von neoadjuvanten Therapieformen zurĂŒckzufĂŒhren ist, und andererseits von medizintechnischen Entwicklungen bezĂŒglich moderner Schnittbilddiagnostik, neuer 3D Operationsplanungsverfahren wie das Rapid Prototyping und adaptiv modularer Tumorendoprothesensystemen u. a. begleitet wurde. Gerade die technischen Entwicklungen haben dazu gefĂŒhrt, daß im Bereich der ExtremitĂ€ten und der WirbelsĂ€ule radikalere Eingriffe durchgefĂŒhrt werden können, was die lokale Tumorkontrolle wesentlich verbessert hat. In zunehmenden Maße werden deshalb nicht nur Kurzzeiterfolge sondern auch mittel- und langfristige Fortschritte bei der Behandlung der malignen Knochentumoren einschließlich der Metastasenbehandlung erreicht. Grundlage der Therapie ist dabei immer primĂ€r die Sicherung der Diagnose mittels Biopsie und die bildgebende sowie histologische Stadieneinteilung des malignen Tumors. Nach der Tumorresektion kann die Rekonstruktion biologisch oder mit Endoprothesensystemen erfolgen. Gerade die weiterentwickelten modularen Systeme fĂŒhren zu guten funktionellen Ergebnissen mit langen Standzeiten und einer reduzierten Komplikationsrate. Individuell angefertigte Implantate sind vor allem im Bereich der Rekonstruktion komplexer Beckentumoren von großer klinischer Bedeutung.

  1. Das Echo aus der Tiefe

    NASA Astrophysics Data System (ADS)

    Beck, Paul G.; Kallinger, Thomas

    2013-04-01

    Seit nunmehr vier Jahren liefert der NASA-Satellit Kepler Helligkeitsmessungen von mehr als 170 000 Sternen mit nie zuvor erreichter Genauigkeit. Obwohl er fĂŒr die Suche nach extrasolaren Planeten konzipiert ist, sind diese Daten eine wahre Fundgrube fĂŒr die Asteroseismologie. Einen aktuellen Durchbruch im VerstĂ€ndnis entwickelter Sterne, den Roten Riesen, stellt die Entdeckung von "Mixed Modes" dar, welche die Erforschung des tiefen Sterninneren ermöglichen.

  2. Organe der Osmoregulation und Exkretion

    NASA Astrophysics Data System (ADS)

    MĂžbjerg, Nadja

    Die meisten SchĂ€deltiere sind in der Lage, die Wasser- und Ionenkonzentration ihres Innenmilieus zu regulieren, sind also im Hinblick auf ihren Ionenhaushalt weitgehend unabhĂ€ngig von der Umgebung. Sie halten die Konzentration von Wasser und anorganischen Ionen in ihren KörperflĂŒssigkeiten (interstitielle FlĂŒssigkeit und Blut) innerhalb enger Grenzen konstant (Osmoregulierer). Schleim aale (Myxinoida) können zwar die Konzentration einzelner anorganischer Ionen regulieren, sind aber insgesamt der hohen OsmolaritĂ€t 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 SchĂ€deltieren sind die KörperflĂŒssigkeiten zur Umgebung hypoosmotisch (im Meerwasser) — sie halten Wasser zurĂŒck und scheiden anorganiche Ionen aus — oder hyperosmotisch (im SĂŒĂŸwasser), indem sie Wasser abgeben und anorganische Ionen aufnehmen.

  3. Zur RelativitÀt der Beschleunigung

    NASA Astrophysics Data System (ADS)

    Burghardt, R.

    Die RelativitĂ€t der Beschleunigung wird im Lichte der Trederschen Tetradentheorie diskutiert. Die Erscheinungen des Newtonschen Eimerversuchs und Sagnac-Experiments werden feldtheoretisch untersucht und gezeigt, daß beide Experimente nicht im Widerspruch zur RelativitĂ€t der Beschleunigung stehen. Das Prinzip der Konstanz der Lichtgeschwindigkeit behĂ€lt auch im Rahmen der allgemeinen RelativitĂ€tstheorie seine GĂŒltigkeit.Translated AbstractThe Relativity of AccelerationThe validity of the relativity of acceleration is investigated in view of Treder's theory of tetrads. Employing the methods of field theory, the effects of Newton's bucket and Sagnac's experiment are analyzed. The paper proves moreover that the results yielded by the experiments mentioned, do not contradict the basic ideas of the relativity of acceleration. The principle of constancy of light velocity is also valid in general relativity.

  4. Sterblichkeit: der paradoxe Kunstgriff des Lebens - Eine Betrachtung vor dem Hintergrund der modernen Biologie

    NASA Astrophysics Data System (ADS)

    Verbeek, Bernhard

    Leben gibt es auf der Erde seit fast 4 Mio. Jahren, trotz allen Katastrophen. Die Idee des Lebens scheint unsterblich. Der Tod aber offenbar auch. Jedes Lebewesen ist davon bedroht, ja fĂŒr Menschen und andere "höhere“ Lebewesen ist er im Lebensprogramm eingebaut - todsicher. Diese Tatsache ist alles andere als selbstverstĂ€ndlich. Ist sie ĂŒberhaupt kompatibel mit dem Prinzip der Evolution, nach dem der am besten Angepasste ĂŒberlebt?

  5. Tycho Brahe - Instrumentenbauer und Meister der Beobachtungstechnik

    NASA Astrophysics Data System (ADS)

    Wolfschmidt, Gudrun

    Vor der Erfindung des Fernrohrs war der dĂ€nische Astronom Tycho Brahe (1546 - 1601) der bedeutendste beobachtende Astronom. Von seinem Observatorium Uraniborg auf der - damals dĂ€nischen - Insel Hven ist heute noch der Grundriß erkennbar, von Stjerneborg sind die Fundamente erhalten, die Kuppeln in den 1950er Jahren ergĂ€nzt. In der Astronomie-Ausstellung im Deutschen Museum gibt es ein Modell der Sternwarte Uraniborg und der zugehörigen Instrumente (Maßstab 1:10); das grĂ¶ĂŸere 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, ArmillarsphĂ€ren, 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 fĂŒr Tycho um 1600 von Jost BĂŒrgi und Erasmus Habermel, gibt es noch im Nationalmuseum für Technik in Prag. Ähnlichkeiten von Tychos Instrumenten mit Groß-Instrumenten aus dem islamischen Kulturkreis sind auffĂ€llig. Tycho Brahes MeßgerĂ€te markieren einen großen Fortschritt in der Entwicklung astronomischer Instrumente und Meßtechniken und bilden die Grundlage fĂŒr den weiteren Fortschritt der Positionsastronomie und der damit verbundenen Tabellenwerke. Die Nachwirkungen sind bis ins 17. und 18. Jahrhundert nachweisbar.

  6. Technologie-Management in der Medizintechnik

    NASA Astrophysics Data System (ADS)

    Nassauer, Josef; Feigl, Thomas

    In der Industrie wurde in den vergangenen Jahren ein besonderer Schwerpunkt auf die stetige Erhöhung von QualitĂ€t und Effizienz gelegt. Im Zeichen des globalen Wettbewerbes bedeutet hohe ProduktivitĂ€t aber nicht mehr unbedingt einen Wettbewerbsvorsprung, sondern wird zur Grundvoraussetzung, um wettbewerbsfĂ€hig zu bleiben. Unter diesen verschĂ€rften Marktgegebenheiten wird ein Wettbewerbsvorsprung vorwiegend durch Innovation und Geschwindigkeit erzielt. DafĂŒr spricht die positive Entwicklung in der Medizintechnik. Die Hersteller medizinischer Produkte investieren rund 10% ihres Umsatzes in Forschung und Entwicklung. Im Durchschnitt wird 50% des Umsatzes mit Produkten erzielt, die jĂŒnger als 2 Jahre sind. Die Innovationskraft der Branche zeigt sich auch in einem stetigen Anstieg der Patentanmeldungen im medizinischen Bereich. Sie bildet die Grundlage fĂŒr einen Export Deutschlands in Höhe von ca. 15 Mrd. DM und entspricht einem Marktanteil von 14% am gesamten Weltmarkt. Aufgrund der dynamischen technologischen Entwicklung in der Medizintechnik, des zunehmenden Wohlstandes und der Verschiebung der Alterspyramide wird der medizintechnischen Branche auch weiterhin eine positive Entwicklung vorhergesagt. Die prognostizierten Wachstumsraten liegen deutlich ĂŒber denen anderer Branchen wie beispielsweise ĂŒber bislang fĂŒhrende Produktbranchen wie Chemie und Maschinenbau. InterdisziplinĂ€re Kooperationen erlauben BĂŒndelungen von neuestem Wissen und von Kompetenzen.

  7. Kosmische Weiten. Kurze Geschichte der Entfernungsmessung im Weltall.

    NASA Astrophysics Data System (ADS)

    Herrmann, D. B.

    Contents: 1. Einleitung. 2. Trigonometrische (jĂ€hrliche) Fixsternparallaxen. 3. Fotometrische Parallaxen. 4. Überblick ĂŒber weitere Methoden der Entfernungsbestimmung. 5. Entfernungen der extragalaktischen Objekte. 6. Ausblick. 7. Elementare Grundlagen der Entfernungsbestimmung.

  8. Erlebniseinkauf in der Innenstadt mit hoher Akzeptanz

    NASA Astrophysics Data System (ADS)

    Pangels, Rolf

    2002-03-01

    Im Oktober 2000 fĂŒhrte die BAG zum zehnten Mal die ĂŒber die Grenzen des Einzelhandels bekannte Untersuchung "Kundenverkehr" in mehr als hundertfĂŒnfzig deutschen StĂ€dten durch. In Kooperation mit der Swiss Retail Federation sowie mit UnterstĂŒtzung der femged (European Federation of Medium-size and Major Retailers) wurde die Untersuchung erstmals auch in der Schweiz und in Österreich durchgefĂŒhrt. Es beteiligten sich insgesamt 463 Unternehmen an der Untersuchung, die knapp 9,5 Mio. Besucher gezĂ€hlt haben und davon mehr als 360.000 Kunden nach bestimmten Parametern befragten. Die Daten fĂŒr Deutschland wurden, wie in den Jahren zuvor, vom Institut fĂŒr Handelsforschung an der UniversitĂ€t Köln ausgewertet. Die Zahlen der Untersuchung in der Schweiz und Österreich wurden von der wirtschafts- und sozialwissenschaftlichen Beratungsgesellschaft ECON-Consult in Köln zusammengetragen und analysiert.

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

    NASA Astrophysics Data System (ADS)

    Jacobi, Manfred

    2001-11-01

    Werner Heisenberg war eine der prĂ€gendsten Gestalten der Physik des 20. Jahrhunderts. Zu seinen wichtigsten Verdiensten gehören die Grundlegung der Quantenmechanik, die Formulierung der UnschĂ€rferelationen sowie die Beteiligung an der Ausarbeitung der Kopenhagener Deutung der Quantenmechanik. DarĂŒber hinaus lieferte er Arbeiten von fundamentalem Charakter zur Theorie des Atomkerns, zur kosmischen Strahlung und zur Quantenfeldtheorie. WĂ€hrend des Krieges war er an den Arbeiten des Uranvereins beteiligt, der die Möglichkeit einer Entwicklung von Kernwaffen untersuchte, jedoch ĂŒber Vorarbeiten zur Reaktorphysik nicht hinauskam. Wegen dieser TĂ€tigkeit wurde er bei Kriegsende fĂŒr einige Monate in England interniert. Nach seiner RĂŒckkehr widmete er sich vor allem dem Aufbau der Physik in Deutschland, die wĂ€hrend der NS-Zeit nahezu ihrer gesamten Substanz beraubt worden war.

  10. E-Learning an der TUM: Entwicklung - Status Quo - Perspektiven

    NASA Astrophysics Data System (ADS)

    Stross, Manfred; Baume, Matthias; Schulze, Elvira

    E-Learning an der Technischen UniversitĂ€t MĂŒnchen (TUM) hat sich Ă€hnlich wie an den meisten anderen Hochschulen als ein wesentliches Element der Hochschullehre etabliert. Seit mehr als einem Jahrzehnt werden in diesem Themenfeld Erfahrungen gesammelt und Entwicklungen vorangetrieben. Der Artikel beschĂ€ftigt sich zunĂ€chst mit E-Learning aus einer allgemeinen Perspektive und greift unterschiedliche Entwicklungsphasen der vergangenen Jahre auf. Im Anschluss daran wird der Fokus auf die TUM gesetzt. Der Beitrag zeigt die spezifische Entwicklung von E-Learning im Verlauf der vergangenen Jahre auf, nennt Funktionen und Verfahren von E-Learning und beschreibt Zielsetzungen fĂŒr E-Learning an der TUM. Im Anschluss daran wird die aktuelle Situation anhand verschiedener Perspektiven analysiert. Den Abschluss des Beitrags bilden die Darstellung der zukĂŒnftigen Herausforderungen von E-Learning an der TUM und ein Ausblick auf weitere Entwicklungen.

  11. QualitÀtsmanagement 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, erfĂŒllt werden. Also die bestimmte erwartete QualitĂ€t (Leistung) sichergestellt wird. Trotz aller BemĂŒhungen und Anstrengungen der Anbieter, QualitĂ€tsprodukte auf den Markt zu bringen, kames in den letzten Jahren immer wieder zu Lebensmittelskandalen.

  12. Symmetriebrechung und Emergenz in der Kosmologie.

    NASA Astrophysics Data System (ADS)

    Mainzer, K.

    Seit der Antike wird der Aufbau des Universums mit einfachen und regulĂ€ren (symmetrischen) Grundstrukturen verbunden. Diese Annahme liegt selbst noch den Standardmodellen der relativistischen Kosmologie zugrunde. DemgegenĂŒber lĂ€ĂŸt sich die Emergenz neuer Strukturen von den Elementarteilchen ĂŒber MolekĂŒle bis zu den komplexen Systemen des Lebens als Symmetriebrechung verstehen. Symmetriebrechung und strukturelle KomplexitĂ€t bestimmen die kosmische Evolution. Damit zeichnet sich ein fachĂŒbergreifendes Forschungsprogramm von Physik, Chemie und Biologie ab, in dem die Evolution des Universums untersucht werden kann.

  13. Dynamic van der Waals theory.

    PubMed

    Onuki, Akira

    2007-03-01

    We present a dynamic van der Waals theory starting with entropy and energy functional with gradient contributions. The resultant hydrodynamic equations contain the stress arising from the density gradient. It provides a general scheme of two-phase hydrodynamics involving the gas-liquid transition in nonuniform temperature. Some complex hydrodynamic processes with evaporation and condensation are examined numerically. They are (i) adiabatically induced spinodal decomposition, (ii) piston effect with a bubble in liquid, (iii) temperature and velocity profiles around a droplet in heat flow, (iv) efficient latent heat transport at small liquid densities (the mechanism of heat pipes), (v) boiling in gravity with continuous bubble formation and rising, and (vi) spreading and evaporation of liquid on a heated boundary wall. PMID:17500788

  14. Wie entsteht Bewusstsein?: Einfache Modelle der Selbstwahrnehmung

    NASA Astrophysics Data System (ADS)

    Schuster, Heinz Georg

    2003-07-01

    Was ist die funktionale Basis der Entstehung des Bewusstseins? Warum bringt dieses in der Evolution einen Vorteil? Diese Fragen werden anhand von drei Spielen untersucht, in denen die Spieler mathematisch modelliert sind. Im ersten Spiel lernt ein Spieler, seine Stellung in einer Hierarchie aus der Interaktion mit anderen zu erraten. Im zweiten Spiel macht ein Zuwachs des GedĂ€chtnisses einen Spieler zum Gewinner: Das ermöglicht ihm einen Spiel entscheidenden Überblick ĂŒber sein eigenes Verhalten und das seines Gegners. Im dritten Spiel mĂŒssen die Spieler die Farbe des Hutes auf dem eigenen Kopf aus der Reaktion des Gegners erraten. Hier ist die FĂ€higkeit von Vorteil, Inhalte aus dem Langzeit- und KurzzeitgedĂ€chtnis im Geist abbilden und manipulieren zu können.

  15. Genetics Home Reference: van der Woude syndrome

    MedlinePlus

    ... disabilities, or other mild cognitive problems. The average IQ of individuals with van der Woude syndrome is ... 1 Images Reviewed : April 2008 Published : May 17, 2016 The resources on this site should not be ...

  16. Van der Waals Interactions and Exciton Condensation

    PubMed Central

    Handel, P. H.; Kittel, C.

    1971-01-01

    It is shown that the van der Waals interaction can lead at low temperatures to a condensed state of excitons with properties in qualitative agreement with the observations of exciton droplets. Our calculation gives a binding energy of the correct sign and magnitude for the exciton condensate. In a diclectric medium, the strong enhancement of the exciton polarizability leads to a giant van der Waals interaction, and this interaction appears to make possible a condensed exciton phase. PMID:16591958

  17. Wie wissenschaftlich ist der Evolutionsgedanke?

    NASA Astrophysics Data System (ADS)

    Vollmer, Gerhard

    Darwin war ein besonnener Mann; alles Aufsehen war ihm zuwider. Trotzdem hat er eine Revolution ausgelöst, deren Wirkung nicht auf die Biologie beschrĂ€nkt blieb. Seine Theorie lĂ€sst sich in fĂŒnf Teiltheorien zerlegen, die sich durch die Begriffe Artenwandel, Verwandtschaft alles Lebendigen und gemeinsamer Ursprung, Artenaufspaltung und Artenvielfalt, Gradualismus, natĂŒrliche Auslese charakterisieren lassen. Dadurch wurden mehrere religiöse und weitere weltanschauliche Überzeugungen in Frage gestellt. Deshalb wird die Evolutionstheorie auch heute noch vielfach kritisiert, ja bekĂ€mpft. Die VorwĂŒrfe lassen sich ordnen nach den Kriterien, mit denen wir erfahrungswissenschaftliche Theorien beurteilen. Haltbar ist daran nur, dass es fĂŒr die Evolutionstheorie zwar beliebig viele BestĂ€tigungen gibt, aber nur wenige Widerlegungsmöglichkeiten. Durch die neuerdings entwickelten und durchgefĂŒhrten Evolutionsexperimente ist die empirische Situation allerdings deutlich besser geworden. Am (erfahrungs)wissenschaftlichen Charakter der Evolutionstheorie besteht deshalb kein Zweifel.

  18. Adaptive Optik: Der scharfe Blick ins All und ins Auge

    NASA Astrophysics Data System (ADS)

    Hippler, Stefan

    2005-01-01

    Mit adaptiver Optik lassen sich optische Störungen, wie sie beispielsweise von der turbulenten ErdatmosphĂ€re, dem menschlichen Auge oder biologischem Zellmaterial hervorgerufen werden, in Echtzeit korrigieren. Sowohl in der Astronomie, der medizinischen Forschung, der Augenheilkunde, der optischen Informationstechnologie als auch auf dem Gebiet der Hochleistungslaser und militĂ€rischen Luftabwehr sind adaptive Optiken heutzutage eine entscheidende SchlĂŒsseltechnologie. In den nĂ€chsten Jahren wird sich herausstellen, ob sie auch in unser Alltagsleben einziehen werden.

  19. Memristor Based van der Pol Oscillation Circuit

    NASA Astrophysics Data System (ADS)

    Lu, Yimin; Huang, Xianfeng; He, Shaobin; Wang, Dongdong; Zhang, Bo

    The memristor is referred to as the fourth fundamental passive circuit element of which inherent nonlinear properties offer to construct the chaos circuits. In this paper, a flux-controlled memristor circuit is developed, and then a van der Pol oscillator is implemented based on this new memristor circuit. The stability of the circuit, the occurring conditions of Hopf bifurcation and limit circle of the self-excited oscillation are analyzed; meanwhile, under the condition of the circuit with an external exciting source, the circuit exhibits a complicated nonlinear dynamic behavior, and chaos occurs within a certain parameter set. The memristor based van der Pol oscillator, furthermore, has been created by an analog circuit utilizing active elements, and there is a good agreement between the circuit responses and numerical simulations of the van der Pol equation. In the consequence, a new approach has been proposed to generate chaos within a nonautonomous circuit system.

  20. TÜV - Zertifizierungen in der Life Science Branche

    NASA Astrophysics Data System (ADS)

    Schaff, Peter; Gerbl-Rieger, Susanne; Kloth, Sabine; SchĂŒbel, 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 interdisziplinÀre Ausrichtung aus, mit Anwendung wissenschaftlicher Erkenntnisse und Einsatz von Ausgangsstoffen aus der modernen Biologie, Chemie und Humanmedizin sowie gezielter marktwirtschaftlich orientierter Arbeit.

  1. Quantenoptik mit einzelnen optischen Zyklen Der Doppelspaltversuch in moderner Form

    NASA Astrophysics Data System (ADS)

    Paulus, Gerhard G.

    2005-07-01

    Der Doppelspaltversuch gilt als eines der zentralen Experimente der Quantenmechanik. Dies gilt insbesondere auch fĂŒr die 1961 durchgefĂŒhrte Variante mit Elektronen. Physiker in Europa und den USA haben diesen Versuch nun so abgeĂ€ndert, dass die Interferenz nicht im Orts-, sondern im Zeitraum stattfindet.

  2. 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 ĂŒber die Evolution des Menschen und die sexuelle Selektion (Darwin 1871), veröffentlichte Friedrich Engels den berĂŒhmt gewordenen Essay "Anteil der Arbeit an der Menschwerdung des Affen“ (Engels 1876). Die Kernfrage darin lautet in Kurzform: Warum hat der Mensch eigentlich ein BedĂŒrfnis nach Arbeit? Engels Antwort wird nachfolgend nĂ€her betrachtet und vom gegenwĂ€rtigen Kenntnisstand aus beurteilt. Wie sich zeigen wird, beantworten seine Überlegungen die Frage nicht wirklich. Sie ist weiterhin offen. Es können lediglich einige zusĂ€tzliche Anhaltspunkte zur Diskussion gestellt werden. Angesichts des drĂ€ngenden Problems millionenfacher Arbeitslosigkeit und der Forderungen nach einem "Grundrecht auf Arbeit“ kommt den Überlegungen zum möglichen Ursprung des BedĂŒrfnisses nach Arbeit mehr als nur akademisches Interesse zu.

  3. 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,


  4. Obituary for Jan van der Pers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    After a short but valiant struggle against cancer, Jan van der Pers died on 29 April, 2006 in the hospital in Hilversum, The Netherlands, close to his home. Our conversations with Jan during the last months of his life showed the remarkable strength and positive attitude typical of him. Discussions...

  5. Wie verstehen Schülerinnen und Schüler den Begriff der Unendlichkeit?

    NASA Astrophysics Data System (ADS)

    Schimmöller, Tabea

    Wie Hilbert bereits feststellte, wirkt die Idee der Unendlichkeit, wie keine andere, schon seit Zeiten sehr anregend und fruchtbar auf den Verstand und bewegt das Gemüt der Menschen. Der Begriff der Unendlichkeit bedarf aber auch, wie kein anderer, der Aufklärung, denn mit ihm eröffnet sich ein weites Feld, welches nicht nur aus vielen verschiedenen Definitionen besteht, sondern auch aus völlig unterschiedlichen Disziplinen. Physiker suchen immer dringender nach einer "Theorie für Alles" oder einer "Weltformel", Kosmologen beschäftigen sich unter anderem mit der Ewigkeit des Universums, Theologen interessiert eher die Unendlichkeit Gottes, Philosophen diskutieren unter anderem Grenzfragen zwischen Naturwissenschaft und Philosophie und die Mathematiker versuchen den Paradoxien des Unendlichen einen Sinn zu geben. Und so wird ersichtlich, dass nichts abstrakter ist als das Unendliche: Obwohl die Unendlichkeit für die unterschiedlichsten Wissenschaften von großer Bedeutung ist, "[ist] in der Wirklichkeit das Unendliche nirgends zu finden, [egal] was für Erfahrungen und Beobachtungen und welcherlei Wissenschaft wir auch heranziehen".

  6. Über die Methode der physikalischen Naturbeschreibung [33

    NASA Astrophysics Data System (ADS)

    Wenn es zu den Aufgaben der Philosophie und der wissensehaftlicher Theologie gehört, das Warum und Wie unserer Existenz und ihrer Umwelt zu ergrĂŒnden, so muss als ihr Ausgangspunkt eine vollstĂ€ndige und möglichst ĂŒbersichtliche Beschreibung unserer Empfindungen vorliegen. Einen Teil dieser Empfindungen fassen wir unter dem Namen Sinnesempfindungen zusammen. Ob ein solcher Aussehnitt genau abgegrenzt werden kann, soll hier nicht untersucht werden. Es kann sogar mit gewisser Berechtigung behauptet werden, dass eine Unterteilung gar nicht streng durchfĂŒhrbar ist. Der schon in der Philosophie der Antike uns entgegentretende Gedanke, dass die Welt nur in ihrer Gesamtheit rerstĂ€ndlich sein kann, kommt sicherlich der Wahrheit nĂ€her als die philosophischen Systeme des verflossenen Jahrhunderts, welche glaubten, dass alies aus unseren materialistischen Erkenntnissen heraus erklĂ€rt werden könne. Die Entstehung dieser Systeme, ich denke z. Â. an den Monisimis Haeckels, erklĂ€rt sich aus der Hybris, welche die Reaktion der Philosophie auf die bedeutenden Erfolge der exakten Naturwissenschaften war. Die ebenfalls nicht zu imterschĂ€tzenden Fortschritte unserer heutigen Kenntnisse auf diesem Gebiete zwingen din Naturforschung eher zu einer immer steigenden Bescheidenheit den "WeltrĂ€tseln" gegenĂŒber, deren letzte Konsequenz vielleicht darin liegen wird, dass sie die eingangs der Philosophie und Theologie zugewiesene Aufgabe als unlosbar bezeichnen muss..

  7. Disziplingeschichte als wissenschaftliche Selbstreflexion der historischen Wissenschaftsforschung

    NASA Astrophysics Data System (ADS)

    Landsberg, H. E.

    This monograph, Disziplingeschichte als wissenschaftliche Selbstreflexion der historischen Wissenschaftsforschung: Eine Darstellung unter Heranziehung von Fallstudien der Wissenschaftsgeschichte der Geophysik, is principally concerned with the problem of how scientific disciplines develop. The historical aspects of geophysics and meteorology, as they became separated from the classical sciences of geography, physics, and astronomy, are the principal topics of discussion. There are three main sections.In the first the author traces some of the symptoms that characterize the emergence of an independent branch of science. These include establishment of journals specifically focused on advances in the specialty, the appearance of personalities with pioneering research, and organizations devoted to the particular field. In touching on these elements in the context of geophysics, a particular aspect becomes immediately obvious. It is the arising need for international cooperation. In the last century this was demonstrated by the establishment of the International Meteorological Organization in 1873 and the 11-nation venture of the International Polar Year 1882/83. It also becomes clear that geophysics is distinctly different from the laboratory sciences because it is notably steered by external events such as the Krakatoa eruption 1883, major earthquakes, notable floods, etc.

  8. 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. PMID:25615099

  9. Zum WissenschaftsverstÀndnis 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 ĂŒber lĂ€ngere ZeitrĂ€ume hinweg einer stetigen VerĂ€nderung. 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 VerĂ€nderlichkeit 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).

  10. 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 GesprĂ€ch mit einem Mitarbeiter berichten, das ich als junger Vorgesetzter einer Instandhaltungsgruppe 1988 fĂŒhrte. Der engagierte Mitarbeiter feierte damals sein vierzigjĂ€hriges DienstjubilĂ€um 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 SelbstverstĂ€ndlichkeit die selbstbewusste Antwort: "Unser Pferd fĂŒttern und mit dem Pferd die innerbetrieblichen Transporte erledigen“. Als junger, technisch orientierter Vorgesetzter war ich ĂŒber diese Antwort sehr ĂŒberrascht. Gedanklich weit entfernt war die Vorstellung, dass in der Vergangenheit Transporte mit einem Pferd erledigt wurden.

  11. Bereits nach Ablauf der Halbwertszeit droht der vollständige Zerfall Die britische Atomic Scientists’ Association, die Ideologie der „objektiven” Wissenschaft und die H-Bombe

    NASA Astrophysics Data System (ADS)

    Laucht, Christoph

    PrĂ€sident Harry Trumans Verlautbarung vom 31.1.1950, seine Regierung wolle die Entwicklung der Wasserstoffbombe vorantreiben, fand große Beachtung in den britischen Medien. Die illustrierte Zeitschrift Picture Post widmete der HBombe einen Artikel, der unter anderem kurze Stellungnahmen der britischen Atomwissenschaftler Eric Burhop, Kathleen Lonsdale, Harrie Massey, Rudolf Peierls und Maurice Pryce enthielt, die alle Mitglieder der Atomic Scientists' Association (ASA) waren.

  12. Das unsichtbare Universum. An den Grenzen der modernen Astrophysik.

    NASA Astrophysics Data System (ADS)

    Field, G. B.; Chaisson, E. J.; Koch, B. P.

    German translation of the English original "The invisible Universe"; Boston 1985 (39.003.089).Contents: (1) Sichtbare und unsichtbare Strahlungen: Die SchlĂŒssel zum Universum.(2) Der interstellare Raum: Die dunklen Reiche des Nachthimmels. (3) Sonne und Fixsterne: SchauplĂ€tze unsichtbarer Urgewalten. (4) Planeten, Leben und Intelligenz: Sind wir allein? (5) Galaxien: Die großen Bausteine der Natur. (6) Kosmische Urgewalten: Schwarze Löcher, Quasare und der Urgrund. (7) Das Universum: Die großrĂ€umigeStruktur des Weltalls. (8) Die KrĂ€fte der Natur: An den Grenzen unseres Wissens.

  13. Information Interaction Study for DER and DMS Interoperability

    NASA Astrophysics Data System (ADS)

    Liu, Haitao; Lu, Yiming; Lv, Guangxian; Liu, Peng; Chen, Yu; Zhang, Xinhui

    The Common Information Model (CIM) is an abstract data model that can be used to represent the major objects in Distribution Management System (DMS) applications. Because the Common Information Model (CIM) doesn't modeling the Distributed Energy Resources (DERs), it can't meet the requirements of DER operation and management for Distribution Management System (DMS) advanced applications. Modeling of DER were studied based on a system point of view, the article initially proposed a CIM extended information model. By analysis the basic structure of the message interaction between DMS and DER, a bidirectional messaging mapping method based on data exchange was proposed.

  14. PhÀnomenologische Grundlagen der WÀrmelehre

    NASA Astrophysics Data System (ADS)

    Heintze, Joachim

    Die Physik der WĂ€rme lĂ€sst sich auf zweierlei Weise formulieren: Einmal als Mechanik eines Systems, das eine enorm große Zahl von Teilchen enthĂ€lt (statistische Mechanik), und einmal mit Hilfe von ad hoc eingefĂŒhrten GrĂ¶ĂŸen, den sogenannten ZustandsgrĂ¶ĂŸen, die geeignet sind, das Verhalten eines solchen Systems zu beschreiben, ohne dass man die Teilchen selbst und ihre Bewegungen betrachten muss (Thermodynamik). Wir werden beide AnsĂ€tze in ihrer einfachsten und anschaulichsten AusprĂ€gung in Kap. 5 (kinetische Gastheorie) bzw. in Kap. 8 (Grundbegriffe der Thermodynamik) behandeln. Obgleich sich die volle DurchfĂŒhrung des Programms als begrifflich und mathematisch recht schwierig erweist - die Vorlesung "Thermodynamik und Statistik" steht gewöhnlich am Ende der Kursvorlesungen ĂŒber theoretische Physik - werden wir doch auf der Grundlage der Kap. 5 und 8 eine Menge ĂŒber die Physik der WĂ€rme lernen können. Den Ausgangspunkt der WĂ€rmelehre bilden jedoch allemal die Naturerscheinungen, die wir hier in Kap. 4 behandeln wollen: WĂ€rme, KĂ€lte, Temperaturausgleich. Wir werden untersuchen, wie man diese Begriffe quantifizieren kann, und was bei der ErwĂ€rmung oder AbkĂŒhlung eines Körpers vor sich geht. Dabei werden wir auf den I. und II. Hauptsatz der WĂ€rmelehre stoßen.

  15. Die Deutsche Statistische Gesellschaft in der Weimarer Republik und wÀhrend der Nazidiktatur

    NASA Astrophysics Data System (ADS)

    Wilke, JĂŒrgen

    Nach anfĂ€nglichen 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 AktivitĂ€ten 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 MachtĂŒbernahme 1933 durch Adolf Hitler geriet die DStatG in das Fahrwasser nationalsozialistischer Ideologie und Politik (FĂŒhrerprinzip, 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 ĂŒber bereitwilliges MitlĂ€ufertum bis zu bewusster TĂ€terschaft. Besonders die Bevölkerungsstatistik wurde durch die NS- Rassenpolitik auf lange Sicht diskreditiert. Im Rahmen von Wirtschaftsplanung und AufrĂŒstung wurden neue zukunftstrĂ€chtige statistische Modelle (GrĂŒnig, Bramstedt, Leisse) entwickelt.

  16. 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.

  17. KomplexitÀt der Geographie

    NASA Astrophysics Data System (ADS)

    Diekert, Volker; Hertrampf, Ulrich

    Das allgemein als Prototyp eines PSPACE-vollstĂ€ndigen Spiels gesehene Geographiespiel wird bezĂŒglich seiner KomplexitĂ€t 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 KomplexitĂ€t des Standardspiels sondern verwendet eine Verallgemeinerung. Die Aussage in dem Lehrbuch bleibt damit etwas unbefriedigend und hinter den Möglichkeiten. Wir zeigen hier, dass die komplexitĂ€tstheoretische Charakterisierung schon fĂŒr die Standardvariante des Spiels gilt.

  18. Kanban - der Weg ist das Ziel

    NASA Astrophysics Data System (ADS)

    Aull, Florian; Berlak, Joachim; Dickmann, Eva; Dickmann, Philipp; FischĂ€der, Holm; Gerlach, Joachim; Henneberg, Jens; Kapalla, Klaus; Kress, Oliver; Kuttler, Robert; Schneider, Herfried M.; SchĂŒrle, Philipp; Stellpflug, Franz-Josef; Wannenwetsch, Ralph; Wulz, Johannes; ZĂ€h, 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. TatsÀchlich ist Kanban ein integraler Bestandteil moderner Produktionssysteme. Blickt man aber im Rahmen von Prozessanalysen hinter die Fassaden", d. h. in die tÀgliche Praxis der Arbeitsprozesse, wird man schnell desillusioniert - die viel gepriesenen klassischen Kanban-Regeln werden im TagesgeschÀft nicht eingehalten.

  19. Modellierung des Einflusses der Landnutzung auf die Hochwasserentstehung in der Mesoskala

    NASA Astrophysics Data System (ADS)

    Niehoff, Daniel

    2001-10-01

    Seit 1990 waren mehrere der großen Flussgebiete Mitteleuropas wiederholt von extremen Hochwassern betroffen. Da sowohl die LandoberflĂ€che als auch die Flusssysteme weiter Teile Mitteleuropas in der Vergangenheit weitreichenden Eingriffen ausgesetzt gewesen sind, wird bei der Suche nach den Ursachen fĂŒr diese HĂ€ufung von Extremereignissen auch die Frage nach der Verantwortung des Menschen hierfĂŒr diskutiert. GewĂ€sserausbau, FlĂ€chenversiegelung, intensive landwirtschaftliche Bodenbearbeitung, Flurbereinigung und WaldschĂ€den sind nur einige Beispiele und Folgen der anthropogenen Eingriffe in die Landschaft. Aufgrund der Vielfalt der beteiligten Prozesse und deren Wechselwirkungen gibt es allerdings bislang nur SchĂ€tzungen darĂŒber, wie sehr sich die Hochwassersituation hierdurch verĂ€ndert hat. Vorrangiges Ziel dieser Arbeit ist es, mit Hilfe eines hydrologischen Modells systematisch darzustellen, in welcher Weise, in welcher GrĂ¶ĂŸenordnung und unter welchen UmstĂ€nden die Art der Landnutzung auf die Hochwasserentstehung Einfluss nimmt. Dies wird anhand exemplarischer Modellanwendungen in der hydrologischen Mesoskala untersucht. Zu diesem Zweck wurde das deterministische und flĂ€chendifferenzierte hydrologische Modell wasim-eth ausgewĂ€hlt, das sich durch eine ausgewogene Mischung aus physikalisch begrĂŒndeten und konzeptionellen AnsĂ€tzen auszeichnet. Das Modell wurde im Rahmen dieser Arbeit um verschiedene Aspekte erweitert, die fĂŒr die Charakterisierung des Einflusses der Landnutzung auf die Hochwasserentstehung wichtig sind: (1) Bevorzugtes Fließen in Makroporen wird durch eine Zweiteilung des Bodens in Makroporen und Bodenmatrix dargestellt, die schnelle Infiltration und Perkolation jenseits der hydraulischen LeitfĂ€higkeit der Bodenmatrix ermöglicht. (2) VerschlĂ€mmung Ă€ußert sich im Modell abhĂ€ngig von NiederschlagsintensitĂ€t und Vegetationsbedeckungsgrad als Verschlechterung der Infiltrationsbedingungen an der BodenoberflĂ€che. (3) Das heterogene Erscheinungsbild bebauter FlĂ€chen mit einer Mischung aus versiegelten Bereichen und FreiflĂ€chen wird berĂŒcksichtigt, indem jede TeilflĂ€che je nach Versiegelungsgrad in einen unversiegelten Bereich und einen versiegelten Bereich mit Anschluss an die Kanalisation aufgeteilt wird. (4) Dezentraler RĂŒckhalt von Niederschlagswasser kann sowohl fĂŒr natĂŒrliche Mulden als auch fĂŒr gezielt angelegte Versickerungsmulden mit definierten Infiltrationsbedingungen simuliert werden. Das erweiterte Modell wird exemplarisch auf drei mesoskalige Teileinzugsgebiete des Rheins angewandt. Diese drei Gebiete mit einer FlĂ€che von zwischen 100 und 500 kmÂČ wurden im Hinblick darauf ausgewĂ€hlt, dass jeweils eine der drei Hauptlandnutzungskategorien Bebauung, landwirtschaftliche Nutzung oder Wald dominiert. FĂŒr die drei Untersuchungsgebiete sind rĂ€umlich explizite Landnutzungs- und Landbedeckungsszenarien entworfen worden, deren Einfluss auf die Hochwasserentstehung mit Hilfe des erweiterten hydrologischen Modells simuliert wird. Im Einzelnen werden die Auswirkungen von VerstĂ€dterung, Maßnahmen zur Niederschlagsversickerung in Siedlungsgebieten, Stilllegung agrarisch genutzter FlĂ€chen, verĂ€nderter landwirtschaftlicher Bodenbearbeitung, Aufforstung sowie von SturmschĂ€den in WĂ€ldern untersucht. Diese Eingriffe beeinflussen die Interzeption von Niederschlag, dessen Infiltration, die oberflĂ€chennahen unterirdischen Fließprozesse sowie, zum Beispiel im Fall der Kanalisation, auch die Abflusskonzentration. Die hydrologischen Simulationen demonstrieren, dass die Versiegelung einer FlĂ€che den massivsten Eingriff in die natĂŒrlichen VerhĂ€ltnisse darstellt und deshalb die stĂ€rksten (negativen) VerĂ€nderungen der Hochwassersituation hervorbringt. Außerdem wird deutlich, dass eine bloße Änderung des Interzeptionsvermögens zu keinen wesentlichen VerĂ€nderungen fĂŒhrt, da die SpeicherkapazitĂ€t der PflanzenoberflĂ€chen im VerhĂ€ltnis zum Volumen hochwasserauslösender NiederschlĂ€ge eher klein ist. StĂ€rkere VerĂ€nderungen ergeben sich hingegen aus einer Änderung der Infiltrationsbedingungen. Die Grenzen der entwickelten Methodik zeigen sich am deutlichsten bei der Simulation verĂ€nderter landwirtschaftlicher Bewirtschaftungsmethoden, deren mathematische Beschreibung und zahlenmĂ€ĂŸige Charakterisierung aufgrund der KomplexitĂ€t der beteiligten Prozesse mit großen Unsicherheiten behaftet ist. Die Modellierungsergebnisse belegen darĂŒber hinaus, dass pauschale Aussagen zum Einfluss der Landnutzung auf die Hochwasserentstehung aufgrund der entscheidenden Bedeutung der klimatischen und physiographischen Randbedingungen unzulĂ€ssig sind. Zu den klimatischen Randbedingungen zĂ€hlen sowohl NiederschlagsintensitĂ€t und -dauer als auch die Feuchtebedingungen vor einem hochwasserauslösenden Niederschlag. Die physiographischen Randbedingungen sind von der geomorphologischen und geologischen Ausstattung des Gebiets vorgegeben. Weiterhin muss der rĂ€umliche und zeitliche Maßstab, ĂŒber den Aussagen getroffen werden, klar definiert sein, da sich mit steigender EinzugsgebietsgrĂ¶ĂŸe die relative Bedeutung sowohl der verschiedenen Niederschlagstypen als auch der physiographischen Eigenschaften verschiebt. Dies wird in der vorliegenden Arbeit im Gegensatz zu vielen anderen Untersuchungen konsequent berĂŒcksichtigt. In AbhĂ€ngigkeit von Randbedingungen und rĂ€umlichen Maßstab sind aufgrund der gewonnen Erkenntnisse folgende Aussagen zum Einfluss von LandnutzungsĂ€nderungen auf die Hochwasserentstehung möglich: (1) FĂŒr intensive konvektive Niederschlagsereignisse mit tendenziell geringer Vorfeuchte ist der Einfluss der Landnutzung grĂ¶ĂŸer als fĂŒr langanhaltende advektive NiederschlĂ€ge geringer IntensitĂ€t, da im ersten Fall verĂ€nderte Infiltrationsbedingungen stĂ€rker zum Tragen kommen als bei kleinen NiederschlagsintensitĂ€ten. (2) In kleinen Einzugsgebieten, wo kleinrĂ€umige Konvektivzellen zu Hochwassern fĂŒhren können, ist der Einfluss der Landnutzung dementsprechend grĂ¶ĂŸer als in großen Flussgebieten wie dem Rheingebiet, wo vor allem langanhaltende advektive Ereignisse (unter UmstĂ€nden verbunden mit Schneeschmelze) relevant sind. (3) In Gebieten mit guten Speichereigenschaften wie mĂ€chtigen, gut durchlĂ€ssigen Böden und gut durchlĂ€ssigem Gesteinsuntergrund ist der Einfluss der Landnutzung grĂ¶ĂŸer als in Gebieten mit geringmĂ€chtigen Böden und geringdurchlĂ€ssigem Festgestein. Dies ist darin begrĂŒndet, dass in Gebieten mit guten Speichereigenschaften bei einer Verschlechterung der Infiltrationsbedingungen mehr Speicherraum fĂŒr Niederschlag verloren geht als in anderen Gebieten. Since 1990, several of the large European river basins were affected repeatedly by extreme floods. As both the landscape and the river systems in large parts of Central Europe have undergone major changes in the past, during the search for the causes of this accumulation of extreme events also the impact of human activities on flooding has been discussed. River training, surface sealing, intensive agricultural land-use, consolidation of farmland, and damages to forests are only some examples and consequences of the anthropogenic interferences with the landscape. But due to the diversity of the processes and factors involved, by now it can only be estimated how far the flood situation has changed by these interferences. Therefore, the main target of this thesis is to describe systematically in which way, to what extent and under which circumstances the land-use exerts an influence on storm-runoff generation and subsequently the discharge of rivers. This is investigated by means of exemplary model applications at the hydrological meso-scale. For this task, the deterministic and distributed hydrological model wasim-eth was chosen due to its well-balanced mixture of physically-based and conceptual approaches. In the framework of this thesis, the model has been extended in order to cope with several phenomena which are important when aiming at a characterization of the influence of land-use on flood generation: (1) Preferential flow in macropores is treated by a division of the soil into macropores and a soil matrix. This so-called double-porosity approach allows for fast infiltration and percolation beyond the hydraulic conductivity of the soil matrix. (2) Siltation expresses itself within the model as a deterioration of infiltration conditions at the soil surface, depending on precipitation intensity and the degree of vegetation covering. (3) The heterogeneous appearance of built-up areas, consisting of both sealed areas and pervious areas, is taken into account by dividing each partial area into an unsealed part and a sealed part which is connected to the sewer system. (4) Decentralized storage can be simulated for natural depressions as well as for specific infiltration measures with defined infiltration conditions. The extended model is exemplarily applied to three meso-scale tributaries of the Rhine river. These three catchments with an area of between 100 and 500 kmÂČ were chosen with regard to their prevailing land-use, one of them being heavily urbanized, one dominated by agricultural use, and one being mainly forested. For these three catchments, spatially explicit land-use and land-cover scenarios were developed. The impact of these scenarios on storm-runoff generation is being simulated using the extended hydrological model. In this context, namely urbanization, infiltration measures in settlement areas, conversion of farmland to set-aside areas, altered agricultural management practices, affor estation and storm damages in forests are taken into account. These changes influence the interception of rainfall, its infiltration into the soil, the subsurface flow processes next to the soil surface as well as, for example in the case of sewer systems, also runoff concentration. The hydrological simulations demonstrate that sealing of the soil surface is the most intensive intervention in the natural conditions among the ones which are mentioned above. Therefore it results in the strongest (negative) changes of the flooding situation in a catchment. In addition to that, the simulations show that a simple alteration in the interception capacity does not yield significant changes in catchment response, because the storage capacity of vegetation surfaces is rather low compared to the volume of storm events which normally lead to significant floods. More pronounced changes arise from modifications in the infiltration conditions. The limits of the methodology which was chosen for this thesis become obvious when simulating altered agricultural management practices. Due the complexity of the processes involved, mathematical description and parameterization is difficult and therefore afflicted with high uncertainty. In addition to that, the modelling results prove that global statements on the influence of land-use on flood generation are illegitimate because of the paramount importance of the climatic and physiographic boundary conditions. Climatic boundary conditions are precipitation intensity and duration as well as the moisture conditions before a storm event. The physiographic boundary counditions are given by the geomorphological and geological catchment properties. Furthermore, with increasing scale there is a shift in the relative importance of the different types of rainfall as well as the different geophysical catchment properties. Therefore, the spatial and temporal scale for which the results are valid have to be clearly defined. This is taken into account consequently within this thesis - in contrast to many other studies on this topic. Depending on boundary conditions and spatial scale, the findings allow the following statements regarding the influence of land-use changes on storm-runoff generation: (1) For intensive convective storm events with generally low antecedent soil moisture, the influence of land-use is greater than for long-lasting advective storm events with low rainfall intensities, because in the first case changes in the infiltration conditions are more important than during times of low precipitation intensities. (2) In small catchments, where small-scale convective cells can lead to a flood, the influence of land-use is accordingly greater than in large river basins like the Rhine basin, where long-lasting advective rainfalls (possibly in combination with snowmelt) are relevant. (3) In areas with good storage conditions like thick, permeable soils and pervious rock underneath, the influence of land-use is greater than in areas with thin soils and only slightly permeable bedrock. This is due to the fact that in case of deteriorating infiltration conditions, more storage space for precipitation is lost in areas with good storage conditions than in other areas. siehe auch: http://opus.kobv.de/ubp/volltexte/2005/398/

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

    PubMed Central

    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. PMID:23955481

  1. Evaluation of Distribution Analysis Software for DER Applications

    SciTech Connect

    Staunton, RH

    2003-01-23

    The term ''Distributed energy resources'' or DER refers to a variety of compact, mostly self-contained power-generating technologies that can be combined with energy management and storage systems and used to improve the operation of the electricity distribution system, whether or not those technologies are connected to an electricity grid. Implementing DER can be as simple as installing a small electric generator to provide backup power at an electricity consumer's site. Or it can be a more complex system, highly integrated with the electricity grid and consisting of electricity generation, energy storage, and power management systems. DER devices provide opportunities for greater local control of electricity delivery and consumption. They also enable more efficient utilization of waste heat in combined cooling, heating and power (CHP) applications--boosting efficiency and lowering emissions. CHP systems can provide electricity, heat and hot water for industrial processes, space heating and cooling, refrigeration, and humidity control to improve indoor air quality. DER technologies are playing an increasingly important role in the nation's energy portfolio. They can be used to meet base load power, peaking power, backup power, remote power, power quality, as well as cooling and heating needs. DER systems, ranging in size and capacity from a few kilowatts up to 50 MW, can include a number of technologies (e.g., supply-side and demand-side) that can be located at or near the location where the energy is used. Information pertaining to DER technologies, application solutions, successful installations, etc., can be found at the U.S. Department of Energy's DER Internet site [1]. Market forces in the restructured electricity markets are making DER, both more common and more active in the distribution systems throughout the US [2]. If DER devices can be made even more competitive with central generation sources this trend will become unstoppable. In response, energy providers will be forced to both fully acknowledge the trend and plan for accommodating DER [3]. With bureaucratic barriers [4], lack of time/resources, tariffs, etc. still seen in certain regions of the country, changes still need to be made. Given continued technical advances in DER, the time is fast approaching when the industry, nation-wide, must not only accept DER freely but also provide or review in-depth technical assessments of how DER should be integrated into and managed throughout the distribution system. Characterization studies are needed to fully understand how both the utility system and DER devices themselves will respond to all reasonable events (e.g., grid disturbances, faults, rapid growth, diverse and multiple DER systems, large reactive loads). Some of this work has already begun as it relates to operation and control of DER [5] and microturbine performance characterization [6,7]. One of the most urgently needed tools that can provide these types of analyses is a distribution network analysis program in combination with models for various DER. Together, they can be used for (1) analyzing DER placement in distribution networks and (2) helping to ensure that adequate transmission reliability is maintained. Surveys of the market show products that represent a partial match to these needs; specifically, software that has been developed to plan electrical distribution systems and analyze reliability (in a near total absence of DER). The first part of this study (Sections 2 and 3 of the report) looks at a number of these software programs and provides both summary descriptions and comparisons. The second part of this study (Section 4 of the report) considers the suitability of these analysis tools for DER studies. It considers steady state modeling and assessment work performed by ORNL using one commercially available tool on feeder data provided by a southern utility. Appendix A provides a technical report on the results of this modeling effort.

  2. elecTUM: Umsetzung der eLearning-Strategie der Technischen UniversitĂ€t MĂŒnchen

    NASA Astrophysics Data System (ADS)

    Rathmayer, Sabine; Gergintchev, Ivan

    An der TUM wurde ein umfassendes und integriertes eLearning-Konzept umgesetzt, welches PrĂ€senzstudium und eLearning in allen Leistungsbereichen der UniversitĂ€t miteinander verzahnt. Ein besonderer Schwerpunkt lag dabei in der Schaffung einer effizienten und wettbewerbsfĂ€higen integrierten eLearning Infrastruktur in Hinblick auf die noch weiter steigenden StudienanfĂ€ngerzahlen ab dem Jahr 2011 sowie die Umsetzung von eBologna. Die Etablierung einer hochschulweiten Lernplattform stellte eine wesentliche Basis fĂŒr die Umsetzung der eLearning-Strategie dar. Die wissenschaftliche und wirtschaftliche AnschlussfĂ€higkeit im Hinblick auf eine Verwertung der Projektergebnisse wurde durch die aktive Beteiligung an einer Vielzahl hochschulĂŒbergreifender Arbeitskreise, Fachtagungen und Kooperationen, vor allem ĂŒber Organisations- und Dienstleistungsmodelle sowie innovative technische Entwicklungen, sichergestellt.

  3. Spezielle RelativitÀtstheorie Konstanz der Lichtgeschwindigkeit bestÀtigt

    NASA Astrophysics Data System (ADS)

    Braxmaier, Claus; MĂŒller, Holger; Peters, Achim; Schiller, Stephan

    2002-03-01

    Licht breitet sich unabhĂ€ngig von der Bewegung der Strahlungsquelle und des Beobachters mit konstanter Geschwindigkeit aus. Diese zentrale Aussage der Speziellen RelativitĂ€tstheorie wurde jetzt in einer Kooperation der UniversitĂ€ten Konstanz und DĂŒsseldorf mit bisher unerreichter Genauigkeit experimentell bestĂ€tigt

  4. Werner-Syndrom. Eine prototypische Form der segmentalen Progerie

    PubMed Central

    Lessel, D.; Oshima, J.; Kubisch, C.

    2013-01-01

    Das Werner-Syndrom ist eine segmental progeroide Erkrankung mit Beginn in der Adoleszenz oder im frĂŒhen Erwachsenenalter. Typische Symptome, die zum vorgealterten PhĂ€notyp beitragen, sind ein post-pubertĂ€r auftretender Kleinwuchs, Katarakte, eine vorzeitige Ergrauung/AusdĂŒnnung des Haupthaars, sklerodermieĂ€hnliche HautverĂ€nderungen und eine regionale Atrophie des subkutanen Fettgewebes. DarĂŒber hinaus kommt es frĂŒh und gehĂ€uft zu „Alterserkrankungen“ wie z. B. einem Diabetes mellitus Typ 2, einer Osteoporose, einer Atherosklerose sowie verschiedenen malignen Tumoren. Das Werner-Syndrom wird autosomal- rezessiv vererbt und ist durch Mutationen im Werner-Gen (WRN) bedingt. Es wurden bis heute mehr als 70 ĂŒber das gesamte Gen verteilte Mutationen identifiziert, die typischerweise zu einem Verlust der Genfunktion fĂŒhren. WRN kodiert fĂŒr eine RecQ-Typ- Helikase, die u. a. an der DNA-Reparatur und der Aufrechterhaltung der DNA-IntegritĂ€t beteiligt ist, was sich in einer erhöhten genetischen InstabilitĂ€t in Patientenzellen wider-spiegelt. Trotz der relativen Seltenheit ist die Analyse des Werner-Syndroms von allgemeiner Bedeutung, um die Rolle der DNA-StabilitĂ€t und IntegritĂ€t fĂŒr das Altern sowie die Entwicklung altersassoziierter Erkrankungen besser zu verstehen. PMID:25309043

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

    PubMed Central

    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. PMID:27069539

  6. The van der Waals fluid and its role in cosmology

    NASA Astrophysics Data System (ADS)

    Jantsch, Rudinei C. S.; Christmann, Marcus H. B.; Kremer, Gilberto M.

    2016-01-01

    We analyze the properties of a generic cosmological fluid described by the van der Waals equation-of-state. Exact solutions for the energy-density evolution are found as implicit functions of the scale factor for a flat Friedmann-Robertson-Walker (FRW) spacetime. The possible values of the free parameter in the van der Waals equation are selected a posteriori, in accordance with asymptotic behaviors that are physically relevant. The stability of the model against small perturbations is studied through the hydrodynamic perturbations of the fluid for the relevant cases. It is found that a van der Waals fluid seems appropriate to describe noneternal inflationary scenarios.

  7. 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, ĂŒber die Möglichkeit zu sprechen, nahezu alle Menschen zu töten?" Der Fragesteller gehört zu den berĂŒhmtesten Physikern des 20. Jahrhunderts und zu den nach wie vor Umstrittensten. ĂŒber ihn wurde in den 1960er Jahren ein international viel beachtetes TheaterstĂŒck geschrieben, vor wenigen Jahren gar eine Oper.

  8. Nanophysik: WĂ€rmeĂŒbertrag auf der Nanometerskala

    NASA Astrophysics Data System (ADS)

    Kittel, Achim

    2006-01-01

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

  9. van der Waals density functional made accurate

    NASA Astrophysics Data System (ADS)

    Hamada, Ikutaro

    2014-03-01

    I propose a van der Waals density functional (vdW-DF) that improves upon the description of energetics and geometries of molecules, solids, and adsorption systems over the original vdW-DF. The functional is based on the nonlocal correlation for the second version of the vdW-DF [10 Lee et al., Phys. Rev. B 82, 081101(R) (2010), 10.1103/PhysRevB.82.081101] and an exchange functional that recovers the second-order gradient expansion approximation in the slowly varying limit, while reproducing the large density gradient behavior proposed by Becke [16 J. Chem. Phys. 85, 7184 (1986), 10.1063/1.451353]. A systematic assessment of the proposed functional is presented, which demonstrates the applicability of the proposed vdW-DF to a wide range of systems.

  10. 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 EuropĂ€ischen Wissenschaften betrachtet, und insbesondere das Leben in den Klöstern galt lange Zeit als frei von jeglichem Interesse fĂŒr 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 verstĂ€rkt. Diese Epoche fĂ€llt mit der FrĂŒhphase der UniversitĂ€t Wien und der 'ersten Wiener Schule der Astronomie' zusammen. Dieser Artikel beleuchtet ausgewĂ€hlte astronomischen Werke in der Melker Stiftsbibliothek zwischen dem frĂŒhen 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 ĂŒber den Kometen von 1456 sowie die im Stift Melk durchgefĂŒhrte Beobachtung der Mondfinsternis von 1457 durch Regiomontanus und Peuerbach beleuchten. Dieser Beitrag ist der einfĂŒhrende 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 concept, created in Melk Abbey in the 15th century. This epoch coincides with the early phase of the University of Vienna and the first Viennese School of Astronomy. This paper discusses selected pieces of astronomical works between the early 9th and the 18th century. The focus is set on the interaction with the members of the Viennese School of Astronomy, e.g., the transcript of Peuerbach's expertise on the comet of 1456 which was presumably produced by a monk of Melk, and the observations of the lunar eclipse 1457 by Peuerbach and Regiomontanus in Melk Abbey. This paper is the introductory overview article on the exhibition in the monastery library of Melk Abbey for the International Year of Astronomy, IYA2009.

  11. Der Weg von einer produktionsintegrierten Instandhaltung zum erfolgreichen, outgesourcten Dienstleister

    NASA Astrophysics Data System (ADS)

    Luther, Friedrich

    Eine marktorientierte UnternehmensfĂŒhrung verlangt heute auch ein kritisches Überdenken der Dienstleistung Instandhaltung und deren Schnittstellen zu anderen Unternehmensbereichen. Die Instandhaltung als Dienstleistungsabteilung, welche oft zu Unrecht als nicht "produktiver“ Betriebsbereich angesehen wird, sieht sich deshalb vielen Fragen und ÜberprĂŒfungen hinsichtlich ihrer Funktion und Effizienz ausgesetzt. In diesem Beitrag soll beispielhaft der Weg einer solchen Instandhaltung vom produktionsintegrierten Bereich in einem mittelstĂ€ndischen Maschinenbau-Unternehmen des Textilmaschinenbaus ĂŒber den zentralen/dezentralen autonomen Unternehmensbereich zum Profit-Center und letztendlich die Entwicklung zum erfolgreichen externen Dienstleister, eingegliedert in die Piepenbrock Gruppe, dargestellt werden. Dieser Entwicklungsprozess ĂŒberstreicht einen Zeitraum von etwa 60 Jahren, von 1950 bis heute. Die Betrachtung des gesamten Prozessablaufs, die dabei aufgetretenen Probleme und Hindernisse auf dem Weg zum externen Dienstleister werden analysiert und Aspekte der Zusammenarbeit mit den Betreibern aus Sicht der outgesourcten Instandhaltung aufgezeigt.

  12. 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.

  13. Quantifizierung neurodegenerativer VerÀnderungen bei der Alzheimer Krankheit

    NASA Astrophysics Data System (ADS)

    Fritzsche, Klaus H.; Giesel, Frederik L.; Thomann, Philipp A.; Hahn, Horst K.; Essig, Marco; Meinzer, Hans-Peter

    Die objektive Bewertung neurodegenerativer Prozesse stellt fĂŒr die Diagnose und Therapiebegutachtung neuropsychiatrischer Krankheiten eine wichtige Grundlage dar. Computerbasierte radiodiagnostische Verfahren können pathologische VerĂ€nderungen in verschiedenen Hirnarealen quantifizieren und hierbei die rein visuelle Beurteilung der Bilddaten ergĂ€nzen. Inhalt dieser Studie ist die Evaluation einer voll automatischen Methode zur voxelbasierten Messung atrophischer VerĂ€nderungen im Gehirn, wie sie bei der Alzheimer-Demenz (AD) oder der leichten kognitiven Störung (LKS) auftreten. Es wurde eine signifikante Korrelation mit den semiautomatisch extrahierten Volumina der Temporalhörner festgestellt. Die PrĂ€zision, Benutzerfreundlichkeit, Beobachterunabh Ă€ngigkeit sowie die kurze Rechenzeit des automatischen Verfahrens sind wichtige Voraussetzungen fĂŒr den routinemĂ€ĂŸigen klinischen Einsatz.

  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 PrĂ€sentationsintegration, welche durch den Einsatz des Medical Imaging Interaction Toolkit (MITK) erreicht werden, sowie der Daten-, und Kontextintegration ist vor allem die StabilitĂ€t der eingesetzten Algorithmik fĂŒr die Routine-Integrierbarkeit wichtig. Erste StabilitĂ€tsuntersuchungen basieren auf 3 von 100 zufĂ€llig ausgewĂ€hlten CT-DatensĂ€tzen, 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 frĂŒheren Arbeits- und Sozialministers Norbert BlĂŒm klingt heute vielen wie Hohn. Der Altersaufbau der deutschen Bevölkerung erinnert grafisch immer mehr an einen Baum auf dĂŒnnem StĂ€mmchen als an eine Pyramide. Angesichts dessen rĂŒcken demographische Entwicklungen mehr und mehr in den Fokus der Öffentlichkeit. Besonders die neuen BundeslĂ€nder sind massiv von Abwanderung und einem nie dagewesenen GeburtenrĂŒckgang betroffen.DIPL.-GEOGR. UTE C. BAUERsprach mitFRIEDRICH BLUTHundWOLF BEYERĂŒber die Besonderheiten der demographischen Prozesse in Berlin und Brandenburg. Beyer leitete bis Anfang 2004 das brandenburgische Referat fĂŒr Raumbeobachtung. Seine Aufgabe bestand darin, Planungsgrundlagen fĂŒr die Gemeinsame Landesplanung Berlin-Brandenburg(GL) zu schaffen. Dazu zĂ€hlen auch Bevölkerungsprognosen fĂŒr die Kreise und StĂ€dte Brandenburgs. Bluth ist in der Senatsverwaltung fĂŒr Stadtentwicklung Berlin beschĂ€ftigt und leitet dort die Gruppe 〝Stadtwissen, Stadtentwicklungsmonitoring, Bevölkerungsprognose.``

  16. 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 EinfĂŒhrung der Benediktiner in Melk im Jahr 1089 erlebte das Melker Skriptorium unter Abt Erchenfried (1121-1163) seine erste BlĂŒte. Hervorzuheben ist eine im Jahr 1123 angelegte Chronik, die bis in das 16. Jahrhundert durch Annaleneintragungen und andere wichtige Texte zur Geschichte des Klosters ergĂ€nzt 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 Untersuchung der zeitnahen Eintragungen in diese Handschrift gelang es, die TĂ€tigkeit von zumindest drei wichtigen, im 12. Jahrhundert in Melk identifizierbaren, namentlich nicht bekannten Schreibern chronologisch zuzuordnen. Erstmals wurden die nur fragmentarisch als Makulatur in den BucheinbĂ€nden erhaltenen Handschriften in die Untersuchung einbezogen, so dass fĂŒr die Wende vom 12. zum 13. Jahrhundert ein BĂŒcherbestand von 68 Handschriften erschlossen werden konnte. Besonders hervorzuheben ist, dass in der Sonderausstellung von 1996 und im Begleitband erstmals eingehend die Bedeutung der Ă€ltesten Melker Handschrift, Cod. 412 aus dem frĂŒhen 9. Jahrhundert mit naturwissenschaftlichen Texten des Beda Venerabilis, als Vorlage fĂŒr drei weitere Handschriften diente: Vatikan, Cod. Vat. lat. 643, abgeschrieben wahrscheinlich in Melk, davon abhĂ€ngig Zwettl, Cod. 296, und Klosterneuburg, Cod. 685. Die Abschriften der Melker Beda-Handschrift sind inhaltlich fast identisch, allerdings um den im Mittelalter fĂ€lschlicherweise Beda Venerabilis zugeschriebenen Sternbilderkatalog erweitert.

  17. Dielectric Genome of van der Waals Heterostructures

    NASA Astrophysics Data System (ADS)

    Andersen, Kirsten; Latini, Simone; Thygesen, Kristian S.

    2015-07-01

    Vertical stacking of two-dimensional (2D) crystals, such as graphene and hexagonal boron nitride, has recently lead to a new class of materials known as van der Waals heterostructures (vdWHs) with unique and highly tunable electronic properties. Abinitio calculations should in principle provide a powerful tool for modeling and guiding the design of vdWHs, but in their traditional, form such calculations are only feasible for commensurable structures with a few layers. Here we show that the dielectric properties of realistic, incommensurable vdWHs comprising hundreds of layers can be calculated with ab-initio accuracy using a multi-scale approach where the dielectric functions of the individual layers (the dielectric building blocks) are coupled simply via their long-range Coulomb interaction. We use the method to illustrate the 2D- 3D dielectric transition in multi-layer MoS2 crystals, the hybridization of quantum plasmons in large graphene/hBN heterostructures, and to demonstrate the intricate effect of substrate screening on the non-Rydberg exciton series in supported WS2.

  18. Supercurrent in van der Waals Josephson junction

    NASA Astrophysics Data System (ADS)

    Yabuki, Naoto; Moriya, Rai; Arai, Miho; Sata, Yohta; Morikawa, Sei; Masubuchi, Satoru; Machida, Tomoki

    2016-02-01

    Supercurrent flow between two superconductors with different order parameters, a phenomenon known as the Josephson effect, can be achieved by inserting a non-superconducting material between two superconductors to decouple their wavefunctions. These Josephson junctions have been employed in fields ranging from digital to quantum electronics, yet their functionality is limited by the interface quality and use of non-superconducting material. Here we show that by exfoliating a layered dichalcogenide (NbSe2) superconductor, the van der Waals (vdW) contact between the cleaved surfaces can instead be used to construct a Josephson junction. This is made possible by recent advances in vdW heterostructure technology, with an atomically flat vdW interface free of oxidation and inter-diffusion achieved by eliminating all heat treatment during junction preparation. Here we demonstrate that this artificially created vdW interface provides sufficient decoupling of the wavefunctions of the two NbSe2 crystals, with the vdW Josephson junction exhibiting a high supercurrent transparency.

  19. Supercurrent in van der Waals Josephson junction.

    PubMed

    Yabuki, Naoto; Moriya, Rai; Arai, Miho; Sata, Yohta; Morikawa, Sei; Masubuchi, Satoru; Machida, Tomoki

    2016-01-01

    Supercurrent flow between two superconductors with different order parameters, a phenomenon known as the Josephson effect, can be achieved by inserting a non-superconducting material between two superconductors to decouple their wavefunctions. These Josephson junctions have been employed in fields ranging from digital to quantum electronics, yet their functionality is limited by the interface quality and use of non-superconducting material. Here we show that by exfoliating a layered dichalcogenide (NbSe2) superconductor, the van der Waals (vdW) contact between the cleaved surfaces can instead be used to construct a Josephson junction. This is made possible by recent advances in vdW heterostructure technology, with an atomically flat vdW interface free of oxidation and inter-diffusion achieved by eliminating all heat treatment during junction preparation. Here we demonstrate that this artificially created vdW interface provides sufficient decoupling of the wavefunctions of the two NbSe2 crystals, with the vdW Josephson junction exhibiting a high supercurrent transparency. PMID:26830754

  20. Supercurrent in van der Waals Josephson junction

    PubMed Central

    Yabuki, Naoto; Moriya, Rai; Arai, Miho; Sata, Yohta; Morikawa, Sei; Masubuchi, Satoru; Machida, Tomoki

    2016-01-01

    Supercurrent flow between two superconductors with different order parameters, a phenomenon known as the Josephson effect, can be achieved by inserting a non-superconducting material between two superconductors to decouple their wavefunctions. These Josephson junctions have been employed in fields ranging from digital to quantum electronics, yet their functionality is limited by the interface quality and use of non-superconducting material. Here we show that by exfoliating a layered dichalcogenide (NbSe2) superconductor, the van der Waals (vdW) contact between the cleaved surfaces can instead be used to construct a Josephson junction. This is made possible by recent advances in vdW heterostructure technology, with an atomically flat vdW interface free of oxidation and inter-diffusion achieved by eliminating all heat treatment during junction preparation. Here we demonstrate that this artificially created vdW interface provides sufficient decoupling of the wavefunctions of the two NbSe2 crystals, with the vdW Josephson junction exhibiting a high supercurrent transparency. PMID:26830754

  1. 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.

  2. 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.

  3. Dielectric Genome of van der Waals Heterostructures.

    PubMed

    Andersen, Kirsten; Latini, Simone; Thygesen, Kristian S

    2015-07-01

    Vertical stacking of two-dimensional (2D) crystals, such as graphene and hexagonal boron nitride, has recently lead to a new class of materials known as van der Waals heterostructures (vdWHs) with unique and highly tunable electronic properties. Ab initio calculations should in principle provide a powerful tool for modeling and guiding the design of vdWHs, but in their traditional form such calculations are only feasible for commensurable structures with a few layers. Here we show that the dielectric properties of realistic, incommensurable vdWHs comprising hundreds of layers can be efficiently calculated using a multiscale approach where the dielectric functions of the individual layers (the dielectric building blocks) are computed ab initio and coupled together via the long-range Coulomb interaction. We use the method to illustrate the 2D-3D transition of the dielectric function of multilayer MoS2 crystals, the hybridization of quantum plasmons in thick graphene/hBN heterostructures, and to demonstrate the intricate effect of substrate screening on the non-Rydberg exciton series in supported WS2. The dielectric building blocks for a variety of 2D crystals are available in an open database together with the software for solving the coupled electrodynamic equations. PMID:26047386

  4. Picosecond photoresponse in van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Massicotte, M.; Schmidt, P.; Vialla, F.; Schädler, K. G.; Reserbat-Plantey, A.; Watanabe, K.; Taniguchi, T.; Tielrooij, K. J.; Koppens, F. H. L.

    2016-01-01

    Two-dimensional crystals such as graphene and transition-metal dichalcogenides demonstrate a range of unique and complementary optoelectronic properties. Assembling different two-dimensional materials in vertical heterostructures enables the combination of these properties in one device, thus creating multifunctional optoelectronic systems with superior performance. Here, we demonstrate that graphene/WSe2/graphene heterostructures ally the high photodetection efficiency of transition-metal dichalcogenides with a picosecond photoresponse comparable to that of graphene, thereby optimizing both speed and efficiency in a single photodetector. We follow the extraction of photoexcited carriers in these devices using time-resolved photocurrent measurements and demonstrate a photoresponse time as short as 5.5?ps, which we tune by applying a bias and by varying the transition-metal dichalcogenide layer thickness. Our study provides direct insight into the physical processes governing the detection speed and quantum efficiency of these van der Waals heterostuctures, such as out-of-plane carrier drift and recombination. The observation and understanding of ultrafast and efficient photodetection demonstrate the potential of hybrid transition-metal dichalcogenide-based heterostructures as a platform for future optoelectronic devices.

  5. Picosecond photoresponse in van der Waals heterostructures.

    PubMed

    Massicotte, M; Schmidt, P; Vialla, F; Schädler, K G; Reserbat-Plantey, A; Watanabe, K; Taniguchi, T; Tielrooij, K J; Koppens, F H L

    2016-01-01

    Two-dimensional crystals such as graphene and transition-metal dichalcogenides demonstrate a range of unique and complementary optoelectronic properties. Assembling different two-dimensional materials in vertical heterostructures enables the combination of these properties in one device, thus creating multifunctional optoelectronic systems with superior performance. Here, we demonstrate that graphene/WSe2/graphene heterostructures ally the high photodetection efficiency of transition-metal dichalcogenides with a picosecond photoresponse comparable to that of graphene, thereby optimizing both speed and efficiency in a single photodetector. We follow the extraction of photoexcited carriers in these devices using time-resolved photocurrent measurements and demonstrate a photoresponse time as short as 5.5?ps, which we tune by applying a bias and by varying the transition-metal dichalcogenide layer thickness. Our study provides direct insight into the physical processes governing the detection speed and quantum efficiency of these van der Waals heterostuctures, such as out-of-plane carrier drift and recombination. The observation and understanding of ultrafast and efficient photodetection demonstrate the potential of hybrid transition-metal dichalcogenide-based heterostructures as a platform for future optoelectronic devices. PMID:26436565

  6. 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

  7. Modern theory of van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Dobson, John

    2014-03-01

    van der Waals (vdW, dispersion) interactions are important in diverse areas such as colloid, surface and nano science, cohesion of molecular crystals, and biomolecular science. They also provide competition in experiments to discover the fifth fundamental force.While vdW interactions have been understood in principle for a century, their quantitative first-principles prediction and modelling down to chemical contact separations have proven stubbornly difficult because the quantal many-electron problem is involved. After some brief historical material, the current state of the art will be discussed with particular reference to several approaches: pairwise additive, perturbative quantum chemical, vdW-DF, Lifshitz-like scattering, RPA-like, Adiabatic Connection Fluctuation Dissipation / Time Dependent DFT based etc.. A potentially useful classification will be introduced to aid in understanding the physical causes of departures from pairwise additivity, that is from the usual sum of C6R-6 contributions. These departures result in non-standard power law decays of nanostructure vdW interactions as a function of separation D, as well as surprising dependences of the attraction on the number, N, of atoms within each vdW-interacting fragment. Some further recent results on non-additivity will also be presented. Work supported by an Australian Research Council Discovery Grant.

  8. Stufenweise Integration von eLearning an der Technischen UniversitĂ€t MĂŒnchen

    NASA Astrophysics Data System (ADS)

    PĂ€tzold, 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 UniversitĂ€t MĂŒnchen (TUM). Dabei wird sowohl die Konsolidierung mehrfach angebotener FunktionalitĂ€ten und Dienste in den verschiedenen Portalen der UniversitĂ€t als auch die sukzessive Optimierung der AblĂ€ufe aufgezeigt. Gleichzeitig wird auf zukĂŒnftige weitere Entwicklungen hin zu einer vollstĂ€ndigen Integration der IuK, aber auch auf die Probleme in den unterschiedlichen Stadien der Entwicklung eingegangen.

  9. 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 need business model and an independent energy aggregator-business model. The approach of developing two group models of DER energy participation in the market is unique. The Detroit Edison (DECo, Utility)-led team includes: DTE Energy Technologies (Dtech, DER provider), Electrical Distribution Design (EDD, Virginia Tech company supporting EPRI’s Distribution Engineering Workstation, DEW), Systems Integration Specialists Company (SISCO, economic scheduling and real-time protocol integrator), and OSIsoft (PI software system for managing real-time information). This team is focused on developing the application engineering, including software systems necessary for DER’s integration, control and sale into the market place. Phase II Highlights Installed and tested an ICCP link with SSL (security) between DECo, the utility, and DTE Energy Technologies (DTECH), the aggregator, making DER data available to the utility for both monitoring and control. Installed and tested PI process book with circuit & DER operational models for DECo SOC/ROC operator’s use for monitoring of both utility circuit and customer DER parameters. The PI Process Book models also included DER control for the DECo SOC/ROC operators, which was tested and demonstrated control. The DER Tagging and Operating Procedures were developed, which allowed that control to be done in a safe manner, were modified for required MOC/MISO notification procedures. The Distribution Engineering Workstation (DEW) was modified to include temperature normalized load research statistics, using a 30 hour day-ahead weather feed. This allowed day-ahead forecasting of the customer load profile and the entire circuit to determine overload and low voltage problems. This forecast at the point of common coupling was passed to DTech DR SOC for use in their economic dispatch algorithm. Standard Work Instructions were developed for DER notification, sale, and operation into the MISO market. A software mechanism consisting of a suite of new and revised functionality was developed that integrated with the local ISO such that offers can be made electronically without human intervention. A suite of software was developed by DR SOC enabling DER usage in real time and day-ahead: Generation information file exchange with PI and the utility power flow A utility day-ahead information file Energy Offer Web Service Market Result Web Service Real-Time Meter Data Web Service Real-Time Notification Web Service Registered over 20 DER with MISO in Demand Response Market and demonstrated electronic sale to MISO.

  10. 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. PMID:23234868

  11. Topologie und Dynamische Netzwerke: Anwendungen Der Optimierung MIT Zukunft

    NASA Astrophysics Data System (ADS)

    Leugering, GĂŒnter; Martin, Alexander; Stingl, Michael

    Die optimale Auslegung von Infrastrukturen z. B. bei der Verkehrsplanung und bei der Planung von Versorgungssystemen, die optimale Strukturierung bzw. Formgebung von Materialien und WerkstĂŒcken z. B. im Leichtbau sind aktuelle Themen angewandter Forschung. In beiden Bereichen wurde bis in die jĂŒngste Zeit vornehmlich eine simulationsbasierte Optimierung auf der Grundlage einer Parameterjustierung vorgenommen, die oft wenig systematisch und zeit- und kostenintensiv ist. Stattdessen erweisen sich modellbasierte mathematische Optimierungsalgorithmen zusammen mit moderner numerischer Simulations-und Visualisierungstechnologie zunehmend als Katalysator neuer Technologien. Eine so verstandene Mathematische Optimierung kann bereits auf beeindruckende Erfolgsgeschichten verweisen und so den Anspruch als eine Zukunftsdisziplin behaupten. Diesem Anspruch trĂ€gt die Einrichtung des DFG-Schwerpunktprogramms 1253, Optimierung mit partiellen Differentialgleichungen’ im Jahre 2006 Rechnung, in dem ĂŒber 25 Projekte im Bundesgebiet sowohl auf die theoretische Fundierung, als auch und insbesondere auf die Verzahnung zwischen Methodenentwicklung und numerischer Realisierung fokussieren. Forschung im Bereich der mathematischen Optimierung und Steuerung von Prozessen bzw. Eigenschaften, die mit Hilfe partieller Differentialgleichungen, so genannten, verteilten Systemen’, beschrieben werden, erfolgt im Kontext konkreter und exemplarischer Anwendungssituationen, die neue mathematische Herausforderungen markieren: Sicherheitsvorgaben etwa bei der Belastung von Gas- und Frischwasserleitungen oder solche fĂŒr die Belastbarkeit von Verkehrsflugzeugen fĂŒhren auf DruckbeschrĂ€nkungen bzw.

  12. Van der Waals stacked 2D layered materials for optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjing; Wang, Qixing; Chen, Yu; Wang, Zhuo; Wee, Andrew T. S.

    2016-06-01

    The band gaps of many atomically thin 2D layered materials such as graphene, black phosphorus, monolayer semiconducting transition metal dichalcogenides and hBN range from 0 to 6 eV. These isolated atomic planes can be reassembled into hybrid heterostructures made layer by layer in a precisely chosen sequence. Thus, the electronic properties of 2D materials can be engineered by van der Waals stacking, and the interlayer coupling can be tuned, which opens up avenues for creating new material systems with rich functionalities and novel physical properties. Early studies suggest that van der Waals stacked 2D materials work exceptionally well, dramatically enriching the optoelectronics applications of 2D materials. Here we review recent progress in van der Waals stacked 2D materials, and discuss their potential applications in optoelectronics.

  13. Collisional stabilization of van der Waals states of ozone

    NASA Astrophysics Data System (ADS)

    Ivanov, Mikhail V.; Babikov, Dmitri

    2011-05-01

    The mixed quantum-classical theory developed earlier [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)] is employed to treat the collisional energy transfer and the ro-vibrational energy flow in a recombination reaction that forms ozone. Assumption is that the van der Waals states of ozone are formed in the O + O2 collisions, and then stabilized into the states of covalent well by collisions with bath gas. Cross sections for collision induced dissociation of van der Waals states of ozone, for their stabilization into the covalent well, and for their survival in the van der Waals well are computed. The role these states may play in the kinetics of ozone formation is discussed.

  14. Biokompatible Implantate und Neuentwicklungen in der GynÀkologie

    NASA Astrophysics Data System (ADS)

    Jacobs, Volker R.; Kiechle, Marion

    FĂŒr den Einsatz in der GynĂ€kologie stehen heute eine Vielzahl unterschiedlicher, biokompatibler Materialien und Implantate zur VerfĂŒgung. Auf eine Auswahl soll hier nĂ€her eingegangen werden, die die verschiedenen Materialien und Bauweisen reprĂ€sentieren. So sind Brustimplantate seit fast vier Jahrzehnten im Gebrauch fĂŒr die Brustvergrösserung und den Brustwiederaufbau. Material, Bauweisen und medizinische Aspekte einschliesslich der kontroversen Diskussion um Silikon werden im folgenden erlĂ€utert. Neuere Entwicklungen von VerhĂŒtungstechniken fĂŒr permanente Sterilisation wie den Filshie ClipTM fĂŒr transabdominalen und den STOPTM fĂŒr intraluminalen Verschluss der Eileiter oder die intrauterin plazierte Hormonspirale MirenaTM fĂŒr zeitlich begrenzte VerhĂŒtung werden beschrieben. Eine neue Perspektive zur Verhinderung postoperativer intraabdominaler AdhĂ€sionen stellt Spray-GelTM, ein Zweikomponenten Hydrogel aus Polyethylenglykol, dar.

  15. Van der Woude Syndrome with Short Review of the Literature

    PubMed Central

    Deshmukh, Pallavi K.; Deshmukh, Kiran; Mangalgi, Anand; Patil, Subhash; Hugar, Deepa; Kodangal, Saraswathi Fakirappa

    2014-01-01

    Van der Woude syndrome (VWS) is a rare autosomal dominant condition with high penetrance and variable expression. Clinical manifestation of this autosomal dominant clefting syndrome includes bilateral midline lower lip pits, cleft lip, and cleft palate along with hypodontia. These congenital lip pits appear as a malformation in the vermilion border of the lip, with or without excretion. Discomfort caused by spontaneous or induced drainage of saliva/mucus when pressure is applied or during a meal as well as poor aesthetic match is one of the main complaints of patients with congenital lip fistula. The pits are treated by surgical resection. Dentists should be aware of the congenital lip pits as in Van der Woude syndrome because they have been reported to be associated with a variety of malformations or other congenital disorders. Here, the authors report a rare case of Van der Woude syndrome with short review of the literature. PMID:25050184

  16. van der Waals interactions in a magnetodielectric medium

    SciTech Connect

    Spagnolo, S.; Dalvit, D. A. R.; Milonni, P. W.

    2007-05-15

    The van der Waals interaction between two ground-state atoms is calculated for two electrically or magnetically polarizable particles embedded in a dispersive magnetodielectric medium. Unlike previous calculations which infer the atom-atom interaction from the dilute-medium limit of the macroscopic, many-body van der Waals interaction, the interaction is calculated directly for the system of two atoms in a magnetodielectric medium. Two approaches are presented, the first based on the quantized electromagnetic field in a dispersive medium without absorption and the second on Green functions that allow for absorption. We show that the correct van der Waals interactions are obtained regardless of whether absorption in the host medium is explicitly taken into account.

  17. 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.

  18. Einsteins Traum. Expeditionen an die Grenzen der Raumzeit.

    NASA Astrophysics Data System (ADS)

    Hawking, S. W.

    This book is a German translation, by H. Kober, of the English original "Black holes and baby universes and other essays" published in 1993. It is a collection of articles written by the author between 1976 and 1992. Contents: 1. Kindheit. 2. Oxford und Cambridge. 3. Meine Erfahrung mit ALS. 4. Öffentliche Einstellungen zur Wissenschaft. 5. Eine kurze Geschichte der Kurzen Geschichte. 6. Mein Standpunkt. 7. Einsteins Traum. 8. Der Ursprung des Universums. 9. Die Quantenmechanik Schwarzer Löcher. 10. Schwarze Löcher und Baby-Universen. 11. Ist alles vorherbestimmt? 12. Die Zukunft des Universums. 13. Desert Island Discs, ein Interview.

  19. Thermal effects on van der Waals adhesive forces

    NASA Astrophysics Data System (ADS)

    Pinon, A. V.; Wierez-Kien, M.; Craciun, A. D.; Beyer, N.; Gallani, J. L.; Rastei, M. V.

    2016-01-01

    We present an experimental and theoretical study on how thermal energy alters van der Waals adhesion forces in nanoscale contacts stretched by mechanical probes. The force follows a distribution whose density function is an asymmetric bell-shaped curve presenting a temperature-dependent negative skewness. With increasing temperature the asymmetry increases whereas the most probable force value decreases. Using a 2-8 Lennard-Jones interaction potential within the reaction rate theory, we offer a theoretical framework permitting an evaluation of the microscopic parameters governing adhesion in a van der Waals nanocontact subjected to mechanical fluctuations.

  20. Prediction of two-dimensional van der Waals ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Ding, Wenjun; Zhu, Jianbao; Gao, Yanfei; Xiao, Di; Gu, Yi; Zhang, Zhenyu; Zhu, Wenguang

    Based on density functional theory calculations, we discover a class of two-dimensional van der Waals ferroelectric materials with spontaneous out-of-plane electric polarization, and the orientation of the electric polarization can be reversed by a seemly lateral shift of a single atomic layer. We further find that the electronic structures of a bilayer of such two-dimensional ferroelectric materials can be switched to be either semiconducting or metallic, depending on their relative orientations of the electric polarization. This finding expand the family of the two-dimensional materials with ferroelectricity and offers new opportunities to tune the properties of van der Waals heterstructures for practical device applications.

  1. Produktion, Distribution, Konsum und IKT - Auswirkungen auf den Verkehr im Spiegel der Empirie

    NASA Astrophysics Data System (ADS)

    Lenz, Barbara; Menge, Julius; Bochynek, Clemens

    Das heutige Produktionssystem ist gekennzeichnet durch die Spezialisierung der Unternehmen auf spezifische Produkte oder Prozesse innerhalb der Wertschöpfungskette, gekoppelt an den Einsatz neuartiger Produktions- und Beschaffungskonzepte. Um der dadurch gewachsenen KomplexitĂ€t der Beziehungen zwischen den Unternehmen und dem zusĂ€tzlichen Planungs- und Steuerungsbedarf gerecht zu werden, findet die VerknĂŒpfung der Akteure ĂŒber gemeinsame Anwendungen der Informations- und Kommunikationstechnologie (IKT) statt. Die unterschiedlichen Einsatzformen von IKT beinhalten unterschiedliche Anforderungen an IKT-Systeme und -Lösungen und wirken sich in verschiedenartiger Weise auf die Transportkette aus. Die Frage, welche VerĂ€nderungen in produzierenden Unternehmen wĂ€hrend der vergangenen Jahre erfolgten und wie sich dabei IKT bedingte VerĂ€nderungen auf den Verkehr auswirken, kann derzeit im Detail nicht beantwortet werden. Nachvollziehbar sind allerdings die verkehrlichen Auswirkungen, die sich aus organisatorischen VerĂ€nderungen in Unternehmen ergeben haben sowie die Bedeutung von IKT-Anwendungen als Instrument bei der Re-Organisation der Produktion, der EinfĂŒhrung neuer Produktionskonzepte und der Ausweitung der AktionsrĂ€ume.

  2. Web-gestĂŒtztes Social Networking am Beispiel der Plattform Wissensmanagement"

    NASA Astrophysics Data System (ADS)

    Lindstaedt, Stefanie; Thurner, Claudia

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

  3. (Physics and chemistry of van der Waals particles)

    SciTech Connect

    Klots, C.E.

    1990-10-08

    Accounts are given of the two major international conferences on the physics and chemistry of small particles, commonly referred to as van der Waals particles. Details of special interest to Oak Ridge National Laboratory personnel are cited. Information exchanges at Freiburg and Paris are described.

  4. Antike Gläser und versteinertes Elfenbein: Röntgenanalyse in der Kunst

    NASA Astrophysics Data System (ADS)

    Reiche, Ina; Radtke, Martin; Brouder, Christian

    2003-03-01

    Physikalische Methoden der Archäometrie liefern den Kunsthistorikern und Archäologen wichtige Informationen. Materialspezifische Größen geben Aufschluss über Alter, Authentizität, Herkunft und Herstellungstechniken sowie Alterserscheinungen von Gegenständen. Insbesondere die Röntgenanalyse hat in jüngster Zeit wertvolle Beiträge hierzu geliefert. Dabei spannt sich ein weiter Bogen von den Mysterien ägyptischer Augenschminke über die Herstellungstechnik römischer Gläser bis zur Authentizitätsuntersuchung mittelalterlicher Silberstiftzeichnungen.

  5. Der Goldene Topf and Das Marmorbild: A Comparison

    ERIC Educational Resources Information Center

    Mornin, Edward

    1978-01-01

    A contrastive treatment of texts with some common thematic material but by different authors is discussed. The tales, Hoffmann's "Der Goldene Topf" and Eichendorff's "Das Marmorbild" are suited for a third- or fourth-year undergraduate literature survey course. The comparative method can be applied to all genres. (SW)

  6. Visual Narrativity in the Picture Book: Heinrich Hoffmann's Der Struwwelpeter

    ERIC Educational Resources Information Center

    Wesseling, Elisabeth

    2004-01-01

    This article intervenes in the debate about the pedagogical import of Heinrich Hoffmann's Der Struwwelpeter. Should this book be regarded as a typical example of black pedagogy or as a form of subversive children's literature? I argue in favour of the latter point of view, on the basis of a close reading of the interaction between words and


  7. Grundlagen und Vollzug der amtlichen Lebensmittelkontrolle in Österreich

    NASA Astrophysics Data System (ADS)

    Vojir, Franz

    Als Geburtsstunde der amtlichen Lebensmittelkontrolle in Österreich kann die Veröffentlichung des "Gesetzes, betreffend den Verkehr mit Lebensmitteln und einigen GebrauchsgegenstĂ€nden" vom 16. JĂ€nner 1896 im Reichsgesetzblatt (RGBl. Nr. 89/1897) [1] angesehen werden. Es wurde in Anlehnung an das Deutsche Nahrungsmittelgesetz 1879 konzipiert.

  8. Englischsprachige Version der S3-Leitlinie Chronische Pankreatitis.

    PubMed

    Hoffmeister, A; Mayerle, J; Beglinger, C; Büchler, M W; Bufler, P; Dathe, K; Fölsch, U R; Friess, H; Izbicki, J; Kahl, S; Klar, E; Keller, J; Knoefel, W T; Layer, P; Loehr, M; Meier, R; Riemann, J F; Rünzi, M; Schmid, R M; Schreyer, A; Tribl, B; Werner, J; Witt, H; Mössner, J; Lerch, M M

    2015-12-01

    Die chronische Pankreatitis ist eine Erkrankung der Bauchspeicheldrüse, bei der rezidivierende Entzündungsschübe zu einem Ersatz des Pankreasparenchyms durch narbiges Bindegewebe führen. Diese Narbenbildung des Pankreas führt zu einem fortschreitenden Verlust der exokrinen und endokrinen Pankreasfunktion. Darüber hinaus treten typische Komplikationen auf zu denen die Bildung von Pseudozysten, Stenosen im Pankreasgang, Obstruktionen des Zwölffingerdarms, Gefäßkomplikationen, einer Obstruktion des Gallengangs, eine Mangel- und Fehlernährung sowie ein Schmerzsyndrom gehören. Das wichtigste Symptom der chronischen Pankreatitis sind abdominelle Schmerzen. Die chronische Pankreatitis stellt einen Risikofaktor für die Entstehung des Pankreaskarzinoms dar. Die chronische Pankreatitis reduziert sowohl die Lebensqualität als auch die Lebenserwartung betroffener Patienten deutlich. Die hier vorgelegte Leitlinie wurde von 74 Vertretern aus 11 Fachgesellschaften als Basis für eine evidenzbasierte Fort- und Weiterbildung zusammengestellt. Ihr Ziel ist es, die medizinische Versorgung betroffener Patienten sowohl im ambulanten als auch im stationären Bereich zu verbessern. Wegen ihrer Krankheitsschwere, ihrer Häufigkeit, ihres chronischen Verlaufs und ihres deutlich negativen Einflusses auf die Lebensqualität und die Lebenserwartung, bedürfen Patienten mit chronischer Pankreatitis einer angemessenen Diagnostik und systematischen Therapie. PMID:26666283

  9. Van der Waals forces in pNRQED

    NASA Astrophysics Data System (ADS)

    Shtabovenko, Vladyslav

    2016-01-01

    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.

  10. Einstellung und Wissen von Lehramtsstudierenden zur Evolution - ein Vergleich zwischen Deutschland und der TĂŒrkei

    NASA Astrophysics Data System (ADS)

    Graf, Dittmar; Soran, Haluk

    Es wird eine Untersuchung vorgestellt, in der Wissen und Überzeugungen von Lehramtsstudierenden aller FĂ€cher zum Thema Evolution an zwei UniversitĂ€ten in Deutschland und der TĂŒrkei erhoben worden sind. Die Befragung wurde in Dortmund und in Ankara durchgefĂŒhrt. Es stellte sich heraus, dass ausgeprĂ€gte Defizite im VerstĂ€ndnis der Evolutionsmechanismen herrschen. Viele Studierende, insbesondere aus der TĂŒrkei, sind nicht von der FaktizitĂ€t der Evolution ĂŒberzeugt. Dies gilt sowohl fĂŒr Studierende mit Fach Biologie als auch fĂŒr Studierende mit anderen FĂ€chern. NĂ€her untersucht worden sind die Faktoren, die die Überzeugungen zur Evolution beeinflussen können, was ja in Anbetracht der hohen Ablehnungsrate der Evolution von besonderem Interesse ist. Das Vertrauen in die Wissenschaft spielt hierbei eine besondere Rolle: Wer der Wissenschaft vertraut, ist auch eher von der Evolution ĂŒberzeugt, als diejenigen, die skeptisch gegenĂŒber der Wissenschaft sind.

  11. Das Universum der Sterne. Himmelsbeobachtungen und StreifzĂŒge durch die moderne Astronomie.

    NASA Astrophysics Data System (ADS)

    Rowan-Robinson, M.

    This book is a German translation, by M. Röser, of the English original published in 1990 (see 52.003.046). Contents: 1. Der Halleysche Komet. 2. Alpha Centauri - Der sonnennĂ€chste Stern. 3. Sirius und sein Begleiter, ein Weißer Zwerg. 4. Polaris - Der Polarstern. 5. Wega - Ein Planetensystem im Entstehen? 6. Mira - Der erste bekannte verĂ€nderliche Stern. 7. Der Ring-Nebel - "Todeskampf" eines sonnenĂ€hnlichen Sterns. 8. Der Orion-Nebel - Die Geburt neuer Sterne. 9. Delta Cephei - Die Meßlatte des Weltalls. 10. Algol - Der Teufelsstern. 11. Nova Aquilae - Der neue Stern von 1918. 12. Der Krebs-Nebel - Die Supernova des Jahres 1054. 13. Die Hyaden und Plejaden - Sternhaufen. 14. Die Milchstraße - Unsere Galaxis. 15. Die Magellanschen Wolken - Unsere Nachbarn im Weltall. 16. Der Andromeda-Nebel - Zwilling unserer Galaxis. 17. Messier 87 - Eine Radiogalaxie. 18. 3C 273 - RĂ€tselhafter Quasar. 19. Messier 82 - Eine "Starburst"-Galaxie. 20. Der Virgo-Haufen - Ein reicher Galaxienhaufen. 21. Das Universum.

  12. Minimalinvasive endovaskulÀre Stent-Therapie bei Erkrankungen in der thorakalen Aorta

    NASA Astrophysics Data System (ADS)

    Voss, Bernhard; Bauernschmitt, Robert; Brockmann, Gernot; Lange, RĂŒdiger

    Die Inzidenz der Aortenerkrankungen nimmt aufgrund der Überalterung der Bevölkerung stetig zu und hat sich innerhalb der letzten 20 Jahre von 2,9 auf 10,9 pro 100.000 Einwohner mehr als verdreifacht [1]. Bei Aortenerkrankungen muss zwischen Aneurysmen und Dissektionen unterschieden werden. Der Begriff Aneurysma (Abb. 62.1) bezeichnet die Ausweitung eines arteriellen BlutgefĂ€ĂŸes. Sind dabei alle Wandschichten, also innere Schicht (Intima), mittlere Schicht (Media) und Ă€ußere Schicht (Adventitia) betroffen, so spricht man von einem echten Aneurysma (Aneurysma verum). Besteht die Aneurysmawand nur aus adventitiellem Gewebe, spricht man von einem falschen Aneurysma. Ursache fĂŒr ein Aneurysma ist eine SchwĂ€chung der elastischen KrĂ€fte der Media, die dann dem intravaskulĂ€ren Druck nicht mehr standhalten kann.

  13. 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

  14. Expression, purification and characterization of Der f 27, a new allergen from dermatophagoides farinae

    PubMed Central

    Lin, Jianli; Li, Meng; Liu, Yulin; Jiang, Congli; Wu, Yulan; Wang, Yuanyuan; Gao, Anjian; Liu, Zhigang; Yang, Pingchang; Liu, Xiaoyu

    2015-01-01

    The house dust mite (HDM), Dermatophagoidesfarinae (D. farina), is one of the most important indoor allergen sources and a major elicitor of allergic asthma; itscharacterization is important in the diagnosis and immunotherapy of mite allergen-relevant diseases. This study aims to characterize a novel allergen, the D. farinae-derived serpin (Der f 27). In this study, the total RNA of D. farinae was extracted, and the Der f 27 gene was cloned and expressed. The allergenicity of recombinant Der f 27 protein was determined by enzyme-linked immunosorbent assay, and Western-blotting with the sera of asthma patients, and skin prick test (SPT) in allergic human subjects. A r-Der f 27 allergic asthma mouse model was established. The cloned Der f 27 gene has been presented at the Gene Bank with an accession number of KM009995. The IgE levels of r-Der f 27 in the serum from r-Der f 27 SPT positive allergic patients were 3 folds more than healthy subjects. The Der f 27 SPT positive ratewas 42.1% in 19 DM-SPT positive patients. Airway hyperresponsiveness, serum specific IgE, and levels of interleukin-4 in the spleen cell culture supernatant were significantly increased in allergic asthma mice sensitized to r-Der f 27. In conclusion, Der f 27 is a new subtype of house mite allergen. PMID:26328010

  15. Qualifizierung von FachkrÀften in der Instandhaltung mit VR-Technologien

    NASA Astrophysics Data System (ADS)

    Mecking, Paul; Termath, Wilhelm

    In den WerkstĂ€tten des Technik Centers PrimĂ€rtechnik der RWE Rhein-Ruhr GmbH in Wesel werden umfangreiche Instandhaltungsarbeiten an Hochspannungsbetriebsmitteln (Schalter, Trennschalter sowie Netz-Wandertransformatoren bis zu einer Spannungsebene von 380 kV) durchgefĂŒhrt. Die Qualifizierung der InstandhaltungsfachkrĂ€fte erfordert eine möglichst praxisorientierte Methodik zur Vorbereitung auf die verantwortliche DurchfĂŒhrung der Instandhaltungsaufgaben. Die Funktionen und Wirkungsweisen der Betriebsmittel, z. B. in Leistungsschaltern mit hohen elektrischen Spannungen oder in Großtransformatoren, sind in der RealitĂ€t jedoch nicht sichtbar bzw. nur in ihren Auswirkungen erfahrbar. In einer virtuell-interaktiven Lernumgebung können die relevanten technischen AblĂ€ufe und physikalischen Prozesse so visualisiert werden, dass sie zusammen mit der Darstellung und EinĂŒbung von Arbeitsschritten eine wesentliche Verbesserung der Lernerfolge erwarten lassen. Der Beitrag skizziert die Anforderungen an die Qualifizierung der FachkrĂ€fte und zeigt das Potenzial innovativer Lernumgebungen auf Basis der Virtual Reality (VR) fĂŒr die berufliche Weiterbildung auf.

  16. Psychometric Properties of the Persian Version of the Difficulties in Emotion Regulation Scale) DERS-6 & DERS-5- Revised (in an Iranian Clinical Sample

    PubMed Central

    Mazaheri, Mina

    2015-01-01

    Objective: The purpose of this study was to determine the construct validity and reliability of the two forms of the Persian version of the Difficulties in Emotion Regulation Scale (DERS-6 & DERS-5-revised) in a clinical sample. Methods: The clinical sample consisted of 181 patients diagnosed with Functional GI Disorders (FGID) who referred to the digestive psychosomatic clinic in Isfahan in 2012. They were selected by census method (In a given period of time). The Persian version of the DERS, the short form of the DASS, and the TAS-20 were used to collect data. Results: The results of the factor structure or construct validity using principal components analysis with varimax rotation recognized 7 factors for the DERS-6 (Goals, Awarness, Impalse, Non Acceptance, Strategy, Clarity, Recognition), and 6 factors for the DERS-5- revised (Non Acceptance, Goals, Impalse, Strategy, Clarity, Recognition) in the clinical sample. They showed the common variance of 59.51% and 59.15%, respectively. Also, the results showed that the concurrent validity of both forms of the DERS and most of their factors, and their reliability in terms of Cronbach-Alpha were favorable. Discussion: Considering the factor structure and favorable psychometric properties of the two scales of DERS-6 & DERS-5-revised, the scales can be used in clinical samples. PMID:26884788

  17. Zu einer inhaltsorientierten Theorie des Lernens und Lehrens der biologischen Evolution

    NASA Astrophysics Data System (ADS)

    Wallin, Anita

    Der Zweck dieser Studie (zwecks Überblick siehe dazu Abb. 9.1) war zu untersuchen, wie die SchĂŒler der Sekundarstufe II ein VerstĂ€ndnis von der Theorie der biologischen Evolution entwickeln. Vom Ausgangspunkt "Vorurteile der SchĂŒler“ ausgehend wurden Unterrichtssequenzen entwickelt und drei verschiedene Lernexperimente in einem zyklischen Prozess durchgefĂŒhrt. Das Wissen der SchĂŒler wurde vor, wĂ€hrend und nach den Unterrichtssequenzen mit Hilfe von schriftlichen Tests, Interviews und Diskussionsrunden in kleinen Gruppen abgefragt. Etwa 80 % der SchĂŒler hatten vor dem Unterricht alternative Vorstellungen von Evolution, und in dem Nachfolgetest erreichten circa 75 % ein wissenschaftliches Niveau. Die Argumentation der SchĂŒler in den verschiedenen Tests wurde sorgfĂ€ltig unter RĂŒcksichtnahme auf Vorurteile, der konzeptionellen Struktur der Theorie der Evolution und den Zielen des Unterrichts analysiert. Daraus konnten Einsichten in solche Anforderungen an Lehren und Lernen gewonnen werden, die Herausforderungen an SchĂŒler und Lehrer darstellen, wenn sie anfangen, evolutionĂ€re Biologie zu lernen oder zu lehren. Ein wichtiges Ergebnis war, dass das VerstĂ€ndnis existierender Variation in einer Population der SchlĂŒssel zum VerstĂ€ndnis von natĂŒrlicher Selektion ist. Die Ergebnisse sind in einer inhaltsorientierten Theorie zusammengefasst, welche aus drei verschiedenen Aspekten besteht: 1) den inhaltsspezifischen Aspekten, die einzigartig fĂŒr jedes wissenschaftliche Feld sind; 2) den Aspekten, die die Natur der Wissenschaft betreffen; und 3) den allgemeinen Aspekten. Diese Theorie kann in neuen Experimenten getestet und weiter entwickelt werden.

  18. Photovoltaic Effect in an Electrically Tunable van der Waals Heterojunction

    PubMed Central

    2014-01-01

    Semiconductor heterostructures form the cornerstone of many electronic and optoelectronic devices and are traditionally fabricated using epitaxial growth techniques. More recently, heterostructures have also been obtained by vertical stacking of two-dimensional crystals, such as graphene and related two-dimensional materials. These layered designer materials are held together by van der Waals forces and contain atomically sharp interfaces. Here, we report on a type-II van der Waals heterojunction made of molybdenum disulfide and tungsten diselenide monolayers. The junction is electrically tunable, and under appropriate gate bias an atomically thin diode is realized. Upon optical illumination, charge transfer occurs across the planar interface and the device exhibits a photovoltaic effect. Advances in large-scale production of two-dimensional crystals could thus lead to a new photovoltaic solar technology. PMID:25057817

  19. Quantum field theory of van der Waals friction

    SciTech Connect

    Volokitin, A. I.; Persson, B. N. J.

    2006-11-15

    van der Waals friction between two semi-infinite solids, and between a small neutral particle and semi-infinite solid is studied using thermal quantum field theory in the Matsubara formulation. We show that the friction to linear order in the sliding velocity can be obtained from the equilibrium Green functions and that our treatment can be extended for bodies with complex geometry. The calculated friction agrees with the friction obtained using a dynamical modification of the Lifshitz theory, which is based on the fluctuation-dissipation theorem. We show that it should be possible to measure the van der Waals friction in noncontact friction experiment using state-of-the-art equipment.

  20. Spin-Flavor van der Waals Forces and NN interaction

    SciTech Connect

    Alvaro Calle Cordon, Enrique Ruiz Arriola

    2011-12-01

    A major goal in Nuclear Physics is the derivation of the Nucleon-Nucleon (NN) interaction from Quantum Chromodynamics (QCD). In QCD the fundamental degrees of freedom are colored quarks and gluons which are confined to form colorless strongly interacting hadrons. Because of this the resulting nuclear forces at sufficiently large distances correspond to spin-flavor excitations, very much like the dipole excitations generating the van der Waals (vdW) forces acting between atoms. We study the Nucleon-Nucleon interaction in the Born-Oppenheimer approximation at second order in perturbation theory including the Delta resonance as an intermediate state. The potential resembles strongly chiral potentials computed either via soliton models or chiral perturbation theory and has a van der Waals like singularity at short distances which is handled by means of renormalization techniques. Results for the deuteron are discussed.

  1. 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. PMID:25283598

  2. Cyber-Physical Systems - Wissenschaftliche Herausforderungen Bei Der Entwicklung

    NASA Astrophysics Data System (ADS)

    Broy, Manfred

    Cyber-Physical Systems adressieren die enge Verbindung eingebetteter Systeme zur Überwachung und Steuerung physikalischer VorgĂ€nge mittels Sensoren und Aktuatoren ĂŒber Kommunikationseinrichtungen mit den globalen digitalen Netzen (dem Cyberspace"). Dieser Typus von Systemen ermöglicht ĂŒber Wirkketten eine Verbindung zwischen VorgĂ€ngen der physischen RealitĂ€t und den heute verfĂŒgbaren digitalen Netzinfrastrukturen. Dies erlaubt vielfĂ€ltige Applikationen mit hohem wirtschaftlichen Potential, und mit starker Innovationskraft. Die vollstĂ€ndige Ausschöpfung des Potentials erfordert aber gezielte wissenschaftliche Anstrengungen bei der Entwicklung solcher Systeme im Hinblick auf Methodik, Technologie, Kostenbeherrschung und funktionale Angemessenheit.

  3. Van der Waals interaction-tuned heat transfer in nanostructures.

    PubMed

    Sun, Tao; Wang, Jianxiang; Kang, Wei

    2013-01-01

    Interfaces usually impede heat transfer in heterogeneous structures. Recent experiments show that van der Waals (vdW) interactions can significantly enhance thermal conductivity parallel to the interface of a bundle of nanoribbons compared to a single layer of freestanding nanoribbon. In this paper, by simulating heat transfer in nanostructures based on a model of nonlinear one-dimensional lattices interacting via van der Waals interactions, we show that the vdW interface interaction can adjust the thermal conductivity parallel to the interface. The efficiency of the adjustment depends on the intensity of interactions and temperature. The nonlinear dependence of the conductivity on the intensity of interactions agrees well with experimental results for carbon nanotube bundles, multi-walled carbon nanotubes, multi-layer graphene, and nanoribbons. PMID:23147396

  4. van der Waals explosion of cold Rydberg clusters

    NASA Astrophysics Data System (ADS)

    Faoro, R.; Simonelli, C.; Archimi, M.; Masella, G.; Valado, M. M.; Arimondo, E.; Mannella, R.; Ciampini, D.; Morsch, O.

    2016-03-01

    We report on the direct measurement in real space of the effect of the van der Waals forces between individual Rydberg atoms on their external degrees of freedom. Clusters of Rydberg atoms with interparticle distances of around 5 Ό m are created by first generating a small number of seed excitations in a magneto-optical trap, followed by off-resonant excitation that leads to a chain of facilitated excitation events. After a variable expansion time the Rydberg atoms are field ionized, and from the arrival time distributions the size of the Rydberg cluster after expansion is calculated. Our experimental results agree well with a numerical simulation of the van der Waals explosion.

  5. Van der Waals interactions: accuracy of pair potential approximations.

    PubMed

    Cole, Milton W; Kim, Hye-Young; Liebrecht, Michael

    2012-11-21

    Van der Waals interactions between single atoms and solids are discussed for the regime of large separation. A commonly employed approximation is to evaluate this interaction as a sum of two-body interactions between the adatom and the constituent atoms of the solid. The resulting potentials are here compared with known results in various geometries. Analogous comparisons are made for diatomic molecules near either single atoms or semi-infinite surfaces and for triatomic molecules' interactions with single atoms. PMID:23181315

  6. 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.

  7. Twilight of the gods: John Henry Mackay's Der Unschuldige.

    PubMed

    Kennedy, H

    1993-01-01

    The writings of the Scotch-German John Henry Mackay are important for the early cultural history of the modern gay movement. This article recalls this unjustly neglected anarchist writer and advocate of man/boy love by tracing his biography and pointing out his contacts with others in the movement. His late novella Der Unschuldige is analyzed to show that Mackay has encoded homosexuality there in a unique and individual way. PMID:8113599

  8. Van der Waals and Casimir-Polder interactions between neutrons

    NASA Astrophysics Data System (ADS)

    Babb, James F.; Hussein, Mahir S.

    2016-03-01

    We investigate the van der Waals interaction between neutrons using the theory of Casimir and Polder, wherein the potential for asymptotically large separations falls off as the inverse seventh power, and compare it to the similar interaction between a neutron and a proton, for which the asymptotic interaction falls off as the inverse fourth power. Modifications of the formalism to extend the validity to smaller separations using dynamic electric and magnetic dipole polarizability data are discussed.

  9. Nonadiabatic Van der Pol oscillations in molecular transport

    NASA Astrophysics Data System (ADS)

    Kartsev, Alexey; Verdozzi, Claudio; Stefanucci, Gianluca

    2014-01-01

    The force exerted by the electrons on the nuclei of a current-carrying molecular junction can be manipulated to engineer nanoscale mechanical systems. In the adiabatic regime a peculiarity of these forces is negative friction, responsible for Van der Pol oscillations of the nuclear coordinates. In this work we study the robustness of the Van der Pol oscillations against high-frequency sources. For this purpose we go beyond the adiabatic approximation and perform full Ehrenfest dynamics simulations. The numerical scheme implements a mixed quantum-classical algorithm for open systems and is capable to deal with arbitrary time-dependent driving fields. We find that the Van der Pol oscillations are extremely stable. The nonadiabatic electron dynamics distorts the trajectory in the momentum-coordinate phase space but preserves the limit cycles in an average sense. We further show that high-frequency fields change both the oscillation amplitudes and the average nuclear positions. By switching the fields off at different times one obtains cycles of different amplitudes which attain the limit cycle only after considerably long times.

  10. 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.

  11. Dynamisierung und Erstarrung in der modernen Gesellschaft - Das BeschleunigungsphÀnomen

    NASA Astrophysics Data System (ADS)

    Rosa, Hartmut

    Dass die Geschichte der Moderne die Geschichte einer ungeheuren Beschleunigung "des Lebens“, "der Kultur“, "der Geschichte“ oder gar "der Zeit selbst“ sei, ist eine Behauptung, der man in BĂŒchern ĂŒber die Moderne - gelehrten wie ungelehrten - so hĂ€ufig begegnet, dass sie geradezu als eine Binsenweisheit gelten kann. Völlig unklar bleibt dabei jedoch in aller Regel, was sich dabei wirklich beschleunigt hat und welcher Begriff von Beschleunigung dieser Auffassung zugrunde liegt. Ich will im Folgenden zunĂ€chst einen wissenschaftlich vertretbaren Begriff von Beschleunigung entwickeln, um danach mit Hilfe dieses Instruments zu ĂŒberprĂŒfen, inwieweit die Geschichte der Moderne wirklich als eine Beschleunigungsgeschichte aufgefasst werden kann.

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

    DOE PAGESBeta

    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.

  13. Application of diffusion Monte Carlo to materials dominated by van der Waals interactions

    SciTech Connect

    Benali, Anouar; Shulenburger, Luke; Romero, Nichols; Kim, Jeongnim; Von Lilienfeld, Anatole

    2014-01-01

    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.

  14. Physik gestern und heute Das Wiegen der Erde

    NASA Astrophysics Data System (ADS)

    Krenn, Heinz; Granitzer, Petra

    2002-09-01

    Magnetische Halbleiter, in denen die Konzentration und der Spin von LadungstrĂ€gern gemeinsam gesteuert werden können, versprechen neue elektronische Anwendungen: Eine durch elektrische Ströme gesteuerte Spin-Elektronik (Spintronik)ist das Ziel. Weil sie voll integrationsfĂ€hig in Chips sind, eignen sich magnetische Halbleiter besser als andere Materialien. Noch fehlen solche Halbleiter, aber verdĂŒnntmagnetische II-VI-Halbleiter und ferromagnetische Europium-Chalkogenide sind gute Kandidaten. Mangan-substituierte Halbleiter könnten sogar einen stabilen Ferromagnetismus bei Raumtemperatur erreichen. Und magneto-optische Halbleiterbauelemente könnten zur Steuerung schneller optischer Computer eingesetzt werden.

  15. DER Certification Laboratory Pilot, Accreditation Plan, and Interconnection Agreement Handbook

    SciTech Connect

    Key, T.; Sitzlar, H. E.; Ferraro, R.

    2003-11-01

    This report describes the first steps toward creating the organization, procedures, plans and tools for distributed energy resources (DER) equipment certification, test laboratory accreditation, and interconnection agreements. It covers the activities and accomplishments during the first period of a multiyear effort. It summarizes steps taken to outline a certification plan to assist in the future development of an interim plan for certification and accreditation activities. It also summarizes work toward a draft plan for certification, a beta Web site to support communications and materials, and preliminary draft certification criteria.

  16. 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 tĂ€tig wurden. Die Grundlagen dessen, was wir heute Logistik nennen, entstammen dem militĂ€rischen Bereich. So basierte z. B. das römische Imperium in starkem Maße auf militĂ€risch-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

  17. Body-assisted van der Waals interaction between excited atoms.

    PubMed

    Safari, Hassan; Karimpour, Mohammad Reza

    2015-01-01

    We present a formula for the body-assisted van der Waals interaction potential between two atoms, one or both being prepared in an excited energy eigenstate. The presence of an arbitrary arrangement for a material environment is taken into account via the Green function. The resulting formula supports one of two conflicting findings recorded. The consistency of our formula is investigated by applying it for the case of two atoms in free space and comparing the resulting expression with the one found from the limiting Casimir-Polder potential between an excited atom and a small dielectric sphere. PMID:25615467

  18. Ionized van-der-Waals systems: Structure and interactions

    SciTech Connect

    Zuelicke, L.

    1996-12-31

    Ions of molecular systems with internal interactions partly of van-der-Waals type differ significantly from their neutral parent species in binding, structure and dynamics. Theoretical knowledge is still rather scarce. The paper discusses some recent advances from theoretical work in the field concerning (i) electronic and geometric structure of triatomic rare-gas containing cations like Ar{sub 3}{sup +} and ArHCI{sup +}, in ground and excited electronic states; (ii) potential energy surfaces for the interaction of H{sup +} or H{sup -} with diatomic molecules, in ground and excited electronic states; (iii) some features of the dynamics of these systems.

  19. Schröder Triangles, Paths, and Parallelogram Polyominoes

    NASA Astrophysics Data System (ADS)

    Pergola, Elisa; Sulanke, Robert A.

    1998-05-01

    This paper considers combinatorial interpretations for two triangular recurrence arrays containing the SchrĂƒÂƒĂ‚Â¶der numbers s_n = 1, 1, 3, 11, 45 197, ... and r_n = 1, 2, 6, 22, 90, 394, ... , for n = 0, 1, 2, .... These interpretations involve the enumeration of constrained lattice paths and bicolored parallelogram polyominoes, called zebras. In addition to two recent inductive constructions of zebras and their associated generating trees, we present two new ones and a bijection between zebras and constrained lattice paths. We use the constructions with generating function methods to count sets of zebras with respect to natural parameters.

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

    NASA Astrophysics Data System (ADS)

    König, Winfried

    Durch langjĂ€hrige Forschungen bei Kfz-Herstellern, Zulieferfirmen und an Hochschulen sind umfangreiche, aber dennoch lĂŒckenhafte Erkenntnisse ĂŒber 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 fĂŒr derartige Systeme voranzutreiben. Im folgenden Kapitel sollen einige der gewonnenen Kenntnisse dargelegt werden, um die Entwicklung des HMI von FAS zu erleichtern.

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

    NASA Astrophysics Data System (ADS)

    Junker, Thomas

    Die Evolution hat viele spektakulĂ€re PhĂ€nomene hervorgebracht - von der Eleganz des Vogelflugs ĂŒber die gigantischen Körper der Dinosaurier und die farbenprĂ€chtige Vielfalt der Korallenriffe bis hin zu ihrem jĂŒngsten Geniestreich - der menschlichen Kunst. Die schönen KĂŒnste - 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 FĂ€higkeiten und Verhaltensweisen. Im Jahr 1859 hatte er auf den letzten Seiten seines berĂŒhmten Buches ĂŒber die Entstehung der Arten eine kĂŒhne 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 FĂ€higkeit notwendigerweise durch graduelle ÜbergĂ€nge erworben wird“ (Darwin 1859, S. 484, 488; Junker 2008).

  2. Magnetic resonance imaging findings of two sisters with Van der Knaap leukoencephalopathy.

    PubMed

    Koç, Koray; Koç, Pınar; Karaali, Kamil; Olgaç DĂŒndar, Nihal; ƞenol, Utku; Canan, Arzu

    2015-10-01

    Megalencephalic leukoencephalopathy with subcortical cysts, or Van der Knaap leukoencephalopathy, is a rare disease which is characterised by macrocephaly and neurological disorders with autosomal recessive inheritance. Magnetic resonance imaging is very helpful for determining distinctive findings and distinguishing other diseases. We present the radiological findings of two sisters (aged 6 and 10 years) diagnosed with Van der Knaap leukoencephalopathy. PMID:26427893

  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... What information about the DER must employers provide to collectors? As an employer, you must provide... contact about any problems or issues that may arise during the testing process....

  4. 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)

  5. 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.

  6. UnterstĂŒtzung der IT-Service-Management-Prozesse an der Technischen UniversitĂ€t MĂŒnchen durch eine Configuration-Management-Database

    NASA Astrophysics Data System (ADS)

    Knittl, Silvia

    Hochschulprozesse in Lehre und Verwaltung erfordern durch die steigende Integration und IT-UnterstĂŒtzung 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 bewĂ€hrten 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 unterstĂŒtzt so das ITSM. Dieser Bericht beschreibt die Erfahrungen mit der prototypischen EinfĂŒhrung einer CMDB an der Technischen UniversitĂ€t MĂŒnchen.

  7. Hochleistungswerkzeuge fĂŒr die Bohrungsbearbeitung mit MMS: Entwicklungen zur Steigerung der Prozesssicherheit

    NASA Astrophysics Data System (ADS)

    HĂ€nle, Peter

    Um die rasch fortschreitenden AnsprĂŒche der spanenden Industrie nach Reduzierung der Hauptzeiten zu erfĂŒllen, bieten moderne HPC-Werkzeuge die ideale Ausgangsbasis. Um dieser Forderung nach Leistungserhöhung von Zerspanungswerkzeugen gerecht zu werden, wird bei der GÜHRING OHG, Albstadt umfangreiche Grundlagenforschung betrieben, welche direkt bei der Auslegung von Serien- und Sonderbohrwerkzeugen BerĂŒcksichtigung findet. Hierbei wird nicht nur das Werkzeug in seinen leistungsbestimmenden Parametern Schneidstoff, Schicht und Geometrie betrachtet, sondern auch das Umfeld, wie z.B. die WĂ€rmeausbreitung in WerkstĂŒcken und die damit verbundenen Bearbeitungsstrategien, um den thermischen Verzug von WerkstĂŒcken wĂ€hrend der Bearbeitung in Grenzen zu halten.

  8. A New Method for Suppressing Periodic Narrowband Interference Based on the Chaotic van der Pol Oscillator

    NASA Astrophysics Data System (ADS)

    Lu, Jia; Zhang, Xiaoxing; Xiong, Hao

    The chaotic van der Pol oscillator is a powerful tool for detecting defects in electric systems by using online partial discharge (PD) monitoring. This paper focuses on realizing weak PD signal detection in the strong periodic narrowband interference by using high sensitivity to the periodic narrowband interference signals and immunity to white noise and PD signals of chaotic systems. A new approach to removing the periodic narrowband interference by using a van der Pol chaotic oscillator is described by analyzing the motion characteristic of the chaotic oscillator on the basis of the van der Pol equation. Furthermore, the Floquet index for measuring the amplitude of periodic narrowband signals is redefined. The denoising signal processed by the chaotic van der Pol oscillators is further processed by wavelet analysis. Finally, the denoising results verify that the periodic narrowband and white noise interference can be removed efficiently by combining the theory of the chaotic van der Pol oscillator and wavelet analysis.

  9. 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.

  10. 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

  11. Quantum Monte Carlo Simulation of condensed van der Waals Systems

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    Van der Waals forces are as ubiquitous as infamous. While post-Hartree-Fock methods enable accurate estimates of these forces in molecules and clusters, they remain elusive for dealing with many-electron condensed phase systems. We present Quantum Monte Carlo [1,2] results for condensed van der Waals systems. Interatomic many-body contributions to cohesive energies and bulk modulus will be discussed. Numerical evidence is presented for crystals of rare gas atoms, and compared to experiments and methods [3]. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DoE's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.[4pt] [1] J. Kim, K. Esler, J. McMinis and D. Ceperley, SciDAC 2010, J. of Physics: Conference series, Chattanooga, Tennessee, July 11 2011 [0pt] [2] QMCPACK simulation suite, http://qmcpack.cmscc.org (unpublished)[0pt] [3] O. A. von Lillienfeld and A. Tkatchenko, J. Chem. Phys. 132 234109 (2010)

  12. Synthesis and Investigation of van der Waals Heterostructures

    NASA Astrophysics Data System (ADS)

    McCreary, Kathleen; Hanbicki, Aubrey; Culbertson, James; Currie, Marc; Jonker, Berend

    2015-03-01

    The recent isolation of single layers of transition metal dichalcogenides (TMD) has demonstrated that reducing dimensionality can alter the material properties. In particular, MoS2, MoSe2, WS2, and WSe2 exhibit an abrupt transition from indirect to direct bandgap semiconductors at monolayer thickness. Monolayer TMDs are promising materials for electronic components due to their high mobility, high on/off ratio, and low standby power dissipation. Additionally, selective layer-by-layer stacking to form van der Waals (vdW) heterostructures may provide the ability to controllably engineer electronic, optic, and spintronic properties. Recently, several methods were investigated to achieve vdW heterostructures including sequential exfoliation, stacking of chemical vapor deposition (CVD) grown monolayers, and epitaxial growth of bilayers. We detail our CVD synthesis of the monolayer TMDs (MoS2, MoSe2, WS2 and WSe2) and the subsequent fabrication and characterization of vdW heterostructures. In our heterostructures, we observe a dramatic decrease in PL intensity compared to the monolayer constituents. The Raman spectra exhibit clear and distinct differences from a superposition of monolayer spectra, demonstrating that interactions across the van der Waals interface in these heterostructures may significantly modify the net electronic properties. We find the observed behaviors are influenced by many factors, including charge transfer, substrate effects, stacking sequence, as well as intra- and inter-layer exciton formation, which will be discussed here.

  13. Ökologische Grundlagen und limitierende Faktoren der Renaturierung

    NASA Astrophysics Data System (ADS)

    Rosenthal, Gert; Eichberg, Carsten

    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. SpĂ€testens seit den 1970er-Jahren ist daher die Neuschaffung und Wiederherstellung gefĂ€hrdeter LebensrĂ€ume und Biozönosen zunehmend in den Mittelpunkt von Naturschutzmaßnahmen gerĂŒckt (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 durchgefĂŒhrt. Im Vordergrund standen dabei zunĂ€chst die Wiederherstellung adĂ€quater abiotischer Standortbedingungen sowie die Reorganisation traditioneller Nutzungsmanagements. Bei Ersterem ging es neben der WiedervernĂ€ssung entwĂ€sserter Feuchtgebiete (Pfadenhauer und Grootjans 1999) vor allem darum, Eutrophierungseffekte zu beseitigen und die ProduktivitĂ€t des Standortes auf das Niveau der Zielgemeinschaft zurĂŒckzufĂŒhren (Gough und Marrs 1990, Oomes et al. 1996, Snow et al. 1997, Tallowin et al. 1998).

  14. Two-dimensional van der Waals C60 molecular crystal.

    PubMed

    Reddy, C D; Gen Yu, Zhi; Zhang, Yong-Wei

    2015-01-01

    Two-dimensional (2D) atomic crystals, such as graphene and transition metal dichalcogenides et al. have drawn extraordinary attention recently. For these 2D materials, atoms within their monolayer are covalently bonded. An interesting question arises: Can molecules form a 2D monolayer crystal via van der Waals interactions? Here, we first study the structural stability of a free-standing infinite C60 molecular monolayer using molecular dynamic simulations, and find that the monolayer is stable up to 600 K. We further study the mechanical properties of the monolayer, and find that the elastic modulus, ultimate tensile stress and failure strain are 55-100 GPa, 90-155 MPa, and 1.5-2.3%, respectively, depending on the stretching orientation. The monolayer fails due to shearing and cavitation under uniaxial tensile loading. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the monolayer are found to be delocalized and as a result, the band gap is reduced to only 60% of the isolated C60 molecule. Interestingly, this band gap can be tuned up to ±30% using strain engineering. Owing to its thermal stability, low density, strain-tunable semi-conducting characteristics and large bending flexibility, this van der Waals molecular monolayer crystal presents aplenty opportunities for developing novel applications in nanoelectronics. PMID:26183501

  15. Two-dimensional van der Waals C60 molecular crystal

    PubMed Central

    Reddy, C. D.; Gen Yu, Zhi; Zhang, Yong-Wei

    2015-01-01

    Two-dimensional (2D) atomic crystals, such as graphene and transition metal dichalcogenides et al. have drawn extraordinary attention recently. For these 2D materials, atoms within their monolayer are covalently bonded. An interesting question arises: Can molecules form a 2D monolayer crystal via van der Waals interactions? Here, we first study the structural stability of a free-standing infinite C60 molecular monolayer using molecular dynamic simulations, and find that the monolayer is stable up to 600 K. We further study the mechanical properties of the monolayer, and find that the elastic modulus, ultimate tensile stress and failure strain are 55–100 GPa, 90–155 MPa, and 1.5–2.3%, respectively, depending on the stretching orientation. The monolayer fails due to shearing and cavitation under uniaxial tensile loading. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the monolayer are found to be delocalized and as a result, the band gap is reduced to only 60% of the isolated C60 molecule. Interestingly, this band gap can be tuned up to ±30% using strain engineering. Owing to its thermal stability, low density, strain-tunable semi-conducting characteristics and large bending flexibility, this van der Waals molecular monolayer crystal presents aplenty opportunities for developing novel applications in nanoelectronics. PMID:26183501

  16. 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 fĂŒr sich dienstbar gemacht. Im sogenannten nahen und mittleren Infrarot (WellenlĂ€ngen zwischen 1-30 ÎŒm) sowie im Millimeter- und Radio-Regime (WellenlĂ€ngen zwischen 1 mm und 10 m) ist die ErdatmosphĂ€re relativ gut durchlĂ€ssig fĂŒr 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 ÎŒm WellenlĂ€nge) von der Erde aus fast völlig unzugĂ€nglich fĂŒr astronomische Beobachtungen. Selbst fĂŒr die besten BeobachtungsplĂ€tze der Erde bleibt die atmosphĂ€rische Transmission durch die immense Wasserdampf- Absorption auf ein absolutes Minimum beschrĂ€nkt. Jedoch erlaubt uns das FIR Zugang zu Informationen, die sehr nĂŒtzlich sind fĂŒr die astrophysikalische Forschung und komplementĂ€r zu anderen WellenlĂ€ngen-Bereichen.

  17. Van der Waals Epitaxy of Ultrathin Halide Perovkistes

    NASA Astrophysics Data System (ADS)

    Wang, Yiping; Shi, Yunfeng; Shi, Jian

    We present our understanding, with CH3NH3PbX3 as a model system, on the 2D van der Waals growth and kinetics of 3D parent materials. We show the successful synthesis of ultrathin (sub-10 nm), large scale (a few tens of ÎŒm) single crystalline 2D perovskite thin films on layered mica substrate by van der Waals (VDW) epitaxy. Classical nucleation and growth model explaining conventional epitaxy has been modified to interpret the unique 2D results under VDW mechanism. The generalization of our model shows that a 3D crystal with low cohesive energy tends to favor the 2D growth while the one with strong cohesive energy has less kinetic window. With Monte Carlo simulations, we show that the fractal 2D morphology in perovskite precisely manifests the kinetic competition between VDW diffusivity and thermodynamic driving force, a unique phenomenon to VDW growth, suggesting a fundamental limit on the morphology stability of the 2D form of a 3D material. On the other hand, our single crystal thin film growth results and subsequent cryogenic study in the iodide perovskite provide a perfect resource for the exploration of its complex optical and electronic properties and unveiling the origins of its popularity in the energy conversion field.

  18. Two-dimensional van der Waals C60 molecular crystal

    NASA Astrophysics Data System (ADS)

    Reddy, C. D.; Gen Yu, Zhi; Zhang, Yong-Wei

    2015-07-01

    Two-dimensional (2D) atomic crystals, such as graphene and transition metal dichalcogenides et al. have drawn extraordinary attention recently. For these 2D materials, atoms within their monolayer are covalently bonded. An interesting question arises: Can molecules form a 2D monolayer crystal via van der Waals interactions? Here, we first study the structural stability of a free-standing infinite C60 molecular monolayer using molecular dynamic simulations, and find that the monolayer is stable up to 600 K. We further study the mechanical properties of the monolayer, and find that the elastic modulus, ultimate tensile stress and failure strain are 55-100 GPa, 90-155 MPa, and 1.5-2.3%, respectively, depending on the stretching orientation. The monolayer fails due to shearing and cavitation under uniaxial tensile loading. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the monolayer are found to be delocalized and as a result, the band gap is reduced to only 60% of the isolated C60 molecule. Interestingly, this band gap can be tuned up to ±30% using strain engineering. Owing to its thermal stability, low density, strain-tunable semi-conducting characteristics and large bending flexibility, this van der Waals molecular monolayer crystal presents aplenty opportunities for developing novel applications in nanoelectronics.

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

    PubMed Central

    Schmezer, Peter; Plass, Christoph

    2009-01-01

    Zusammenfassung Plattenepithelkarzinome der Kopf-Hals-Region (HNSCC) zĂ€hlen seit Jahren zu den weltweit hĂ€ufigsten Krebsarten. Trotz vieler BemĂŒhungen 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 VerĂ€nderungen haben molekular-zytogenetische Untersuchungen bei HNSCC gezeigt, dass es weitere VerĂ€nderungen gibt, die mit Vermehrung und Verlust chromosomaler Bereiche einhergehen, fĂŒr die jedoch die krankheitsverursachenden Gene bisher nicht identifiziert wurden. DarĂŒberhinaus haben jĂŒngste 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 FrĂŒherkennung von HNSCC genutzt werden und nicht zuletzt dadurch zur Verbesserung von PrĂ€vention und Therapieerfolg beitragen. PMID:18483718

  20. 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

  1. Band Gap Engineering of PbI2 by Incommensurate Van der Waals Epitaxy

    NASA Astrophysics Data System (ADS)

    Wang, Yiping; Shi, Jian

    Van der Waals epitaxial growth had been thought to have trivial contribution on inducing substantial epitaxial strain in thin films due to its weak nature of Van der Waals interfacial energy. Due to this, electrical and optical structure engineering via Van der Waals epitaxial strain has been rarely studied. However, by appropriate film-substrate selection, we show that significant band structure engineering could be achieved in a soft thin film material PbI2 via Van der Waals epitaxy. The thickness dependent photoluminescence of single crystal PbI2 flakes was studied and attributed to the substrate-film coupling effect via incommensurate Van der Waals epitaxy. It is proposed that the Van der Waals strain is resulted from the soft nature of PbI2 and large Van der Waals interaction due to the involvement of heavy elements. Such strain plays vital roles in modifying the band gap of PbI2. The deformation potential theory is used to quantitatively unveil the correlation between thickness, strain and band gap change. Our hypothesis is confirmed by the subsequent mechanical bending test and Raman characterization.

  2. 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 the substrate. And we take several oxides as examples to demonstrate a pathway to integrate 3D functional oxides on 2D layered materials.

  3. 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. PMID:26812600

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

  5. Resource Letter VWCPF-1: van der Waals and Casimir-Polder forces

    NASA Astrophysics Data System (ADS)

    Milton, Kimball A.

    2011-07-01

    This Resource Letter provides a guide to the literature on van der Waals and Casimir-Polder forces. Journal articles, books, and other documents are cited on the following topics: Nonretarded or van der Waals forces, retarded dispersion forces or Casimir-Polder forces between atoms or molecules, Casimir-Polder forces between a molecule and a dielectric or conducting body, the summation of Casimir-Polder forces as leading to the Casimir and Lifshitz forces between conducting and dielectric bodies, Casimir friction, applications to nanotechnology, the nature of the quantum vacuum, and experimental tests of the theory of Casimir and Casimir-Polder and van der Waals forces.

  6. [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. PMID:25185861

  7. 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. PMID:9665748

  8. Coincident-site lattice matching during van der Waals epitaxy.

    PubMed

    Boschker, Jos E; Galves, Lauren A; Flissikowski, Timur; Lopes, Joao Marcelo J; Riechert, Henning; Calarco, Raffaella

    2015-01-01

    Van der Waals (vdW) epitaxy is an attractive method for the fabrication of vdW heterostructures. Here Sb2Te3 films grown on three different kind of graphene substrates (monolayer epitaxial graphene, quasi freestanding bilayer graphene and the SiC (6?3?Ś?6?3)R30° buffer layer) are used to study the vdW epitaxy between two 2-dimensionally (2D) bonded materials. It is shown that the Sb2Te3 /graphene interface is stable and that coincidence lattices are formed between the epilayers and substrate that depend on the size of the surface unit cell. This demonstrates that there is a significant, although relatively weak, interfacial interaction between the two materials. Lattice matching is thus relevant for vdW epitaxy with two 2D bonded materials and a fundamental design parameter for vdW heterostructures. PMID:26658715

  9. 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.

  10. Van der Waals Interactions in Density Functional Theory: Intermolecular Complexes

    NASA Astrophysics Data System (ADS)

    Kannemann, Felix; Becke, Axel

    2010-03-01

    Conventional density functional theory (GGA and hybrid functionals) fails to account for dispersion interactions and is therefore not applicable to systems where van der Waals interactions play a dominant role, such as intermolecular complexes and biomolecules. The exchange-hole dipole moment (XDM) dispersion model of Becke and Johnson [A. D. Becke and E. R. Johnson, J. Chem. Phys. 127, 154108 (2007)] corrects for this deficiency. We have previously shown that the XDM dispersion model can be combined with standard GGA functionals (PW86 for exchange and PBE for correlation) to give accurate binding energy curves for rare-gas diatomics [F. O. Kannemann and A. D. Becke, J. Chem. Theory Comput. 5, 719 (2009)]. Here we present further tests of the GGA-XDM method using benchmark sets including hydrogen bonding, electrostatic, dispersion and stacking interactions, and systems ranging from rare-gas diatomics to biomolecular complexes.

  11. Van der Waals Density Functional Theory with Applications

    NASA Astrophysics Data System (ADS)

    Langreth, David C.

    2004-03-01

    We discuss the development of electronic density functionals that are applicable for weakly bound systems where the van der Waals interaction and its ramifications become important. Our current functionals approach the correct asymptotic dependence at large distances and are seamless at small distances. The first form of the functional, appropriate for layered systems, has been recently applied to graphite, boron nitride, and molybdenum sulfide [H. Rydberg et al., Phys. Rev. Lett. 91, 126402 (2003) and D. C. Langreth, Int. J. Quant. Chem. (submitted), see http//:www.physics.rutgers.edu/ ˜langreth/preprints/dft2003.pdf]. The second form of the functional [M. Dion it et al. (to be published)] is appropriate for arbitrary geometries. Recent results on rare gas dimers and the benzene dimer suggest promise for this method as well.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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 10-13 s from the passage of shock front, lateral collision produces NO2 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 10-12 s, shock normal to multilayers becomes more reactive, producing H2O 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.

  13. 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. PMID:26764692

  14. The history of Werner Spalteholz's Handatlas der Anatomie des Menschen.

    PubMed

    Williams, D J

    1999-12-01

    Werner Spalteholz's Handatlas der Anatomie des Menschen is one of the most elegantly illustrated anatomical atlases of all time. Originally published in Leipzig as three volumes from 1895 to 1903, the atlas is still widely used and remains highly regarded by many. The atlas was remarkably popular during the first half of the 20th century, especially the English version in North America and the UK. Unfortunately, the original illustrations and printing plates for the work disappeared following the Second World War and their fate remains a mystery. And, in spite of the atlas's popularity, little is known to the men who prepared the artwork for Spalteholz. It is commonly believed that Max Brödel contributed illustrations to the atlas, but a close examination of the work does not confirm this. A century after its inception, Spalteholz's atlas remains a classic milestone in the history of anatomical illustration. PMID:10795378

  15. Dynamics of a delayed van der Pol-Mathieu oscillator

    NASA Astrophysics Data System (ADS)

    Sarmah, Dipak; Bora, Madhurjya P.

    2014-02-01

    The dynamics of a van der Pol-Mathieu (vdPM) equation with time delay is considered. The vdPM model can be realized as the governing equation for dust density in a simplified model of dusty plasma. The dynamics of the time-delayed equation is analyzed by separating the time-scales of the system assuming that the fundamental simple harmonic oscillator is at least an ?(?) dominating other terms of the oscillator including time-delay, where ? ? 1. Our analytic prediction of the slow-flow system correctly represents the dynamics of the original system, showing periodic creation and annihilation of multi-periodic limit cycles. The original system is then analyzed using the DDE-Biftool [1] bifurcation analysis tool. We show that for large time-delay, the system undergoes a double-Hopf bifurcation, whereas for small delay, it undergoes a Bogdanov-Takens bifurcation.

  16. 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.

  17. van der Waals Heterostructures with High Accuracy Rotational Alignment.

    PubMed

    Kim, Kyounghwan; Yankowitz, Matthew; Fallahazad, Babak; Kang, Sangwoo; Movva, Hema C P; Huang, Shengqiang; Larentis, Stefano; Corbet, Chris M; Taniguchi, Takashi; Watanabe, Kenji; Banerjee, Sanjay K; LeRoy, Brian J; Tutuc, Emanuel

    2016-03-01

    We describe the realization of van der Waals (vdW) heterostructures with accurate rotational alignment of individual layer crystal axes. We illustrate the approach by demonstrating a Bernal-stacked bilayer graphene formed using successive transfers of monolayer graphene flakes. The Raman spectra of this artificial bilayer graphene possess a wide 2D band, which is best fit by four Lorentzians, consistent with Bernal stacking. Scanning tunneling microscopy reveals no moiré pattern on the artificial bilayer graphene, and tunneling spectroscopy as a function of gate voltage reveals a constant density of states, also in agreement with Bernal stacking. In addition, electron transport probed in dual-gated samples reveals a band gap opening as a function of transverse electric field. To illustrate the applicability of this technique to realize vdW heterostructuctures in which the functionality is critically dependent on rotational alignment, we demonstrate resonant tunneling double bilayer graphene heterostructures separated by hexagonal boron-nitride dielectric. PMID:26859527

  18. Study of diatomic van der Waals complexes in supersonic beams

    NASA Astrophysics Data System (ADS)

    Koperski, JarosƂaw

    2002-10-01

    Laser spectroscopy of van der Waals diatoms produced in supersonic beams is a source of information on the ground- and excited-state interatomic potentials. The goal of this review article is to provide a comprehensive characterization of the MeRG and Me 2 diatoms, where Me and RG are 12-group (Zn,Cd,Hg) and rare gas atoms, respectively. As a result, the ground and a number of excited states of the molecules are characterized over a broad range of internuclear separations. Analytical functions are proposed to represent the potential energy curves in three separate regions of internuclear separation: short-range region, vicinity of the equilibrium internuclear separation, and long-range limit. Several models, trends, and regularities of dispersive interaction in the studied diatoms are observed and described. The molecular characteristics presented here are compared with experimental and ab initio results of other investigators.

  19. Spintronics with Graphene and van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Dash, Saroj; Kamalakar, M. Venkata; Dankert, André; Quantum Device Physics Laboratory Team

    Two-dimensional (2D) atomic crystals provide a large class of materials proposed to be important for nanoelectronics and spintronic. Here we present two important advancements in graphene spintronics by employing 2D materials and heterostructures. Graphene is considered to be an ideal material for spin transport due to the high mobility and long spin lifetime of the carriers. We realized spin transport over a long distance of 16 ”m and spin lifetimes up to 1.2 ns in large area CVD graphene on SiO2/Si substrate at room temperature. Subsequently, using the h-BN tunnel barrier/graphene van der Waals heterostructure; we observe an enhancement in the tunnel spin polarization, and a negative spin signal for thicker h-BN barriers. These findings open a platform for exploring novel spin functionalities in 2D crystal heterostructures and understanding the basic science that control their behavior.

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

    SciTech Connect

    Lee, Gwan-Hyoung; Lee, Chul-Ho; Zande, Arend M. van der; Han, Minyong; Cui, Xu; Arefe, Ghidewon; Hone, James; Nuckolls, Colin; Heinz, Tony F.; 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 MoS{sub 2} heterostructures for memory devices; graphene/MoS{sub 2}/WSe{sub 2}/graphene vertical p-n junctions for photovoltaic devices, and organic crystals on hBN with graphene electrodes for high-performance transistors.

  1. Van der Waals solids: properties and device applications

    NASA Astrophysics Data System (ADS)

    Kaul, Anupama B.

    2015-05-01

    Recently, layered 2D crystals of other materials similar to graphene have been realized which include insulating hexagonal-BN (band gap ~5.5 eV) and transition metal di-chalcogenides which display properties ranging from semiconducting, superconducting, metallic to insulating. The device applications of such van der Waals solids also show promising characteristics where MoS2 transistors have been formed on flexible and transparent substrates, and transistors derived from 2D monolayers of MoS2 show ON/OFF ratios many orders of magnitude larger than the best graphene transistors. In this paper, an overview of the novel properties of these layered 2D nanomaterials is provided that can enable their device applications in electronics, photonics, sensors and other related applications.

  2. [Dingeman van der Vliet, veterinary artist, 1792-1866].

    PubMed

    van der Vliet, Marius

    2003-01-01

    Dingeman van der Vliet (1792-1866) from Zierikzee in province of Zeeland, was one of the first officially trained veterinarians in the Netherlands. He was sent to Paris on the order of Louis Napoleon, king of Holland, at the expense of the Dutch government. In the period of his stay at the Veterinary School in Alfort (1808-1811) he wrote a great number of letters to his parents and friends. His letters give insight in the daily life of the school in Alfort and the festivities in Paris during the reign of the emperor Napoleon Bonaparte. In a second article, the laborious built-up of a veterinary practice in those days will be described. PMID:12756997

  3. Coincident-site lattice matching during van der Waals epitaxy

    PubMed Central

    Boschker, Jos E.; Galves, Lauren A.; Flissikowski, Timur; Lopes, Joao Marcelo J.; Riechert, Henning; Calarco, Raffaella

    2015-01-01

    Van der Waals (vdW) epitaxy is an attractive method for the fabrication of vdW heterostructures. Here Sb2Te3 films grown on three different kind of graphene substrates (monolayer epitaxial graphene, quasi freestanding bilayer graphene and the SiC (6√3 × 6√3)R30° buffer layer) are used to study the vdW epitaxy between two 2-dimensionally (2D) bonded materials. It is shown that the Sb2Te3 /graphene interface is stable and that coincidence lattices are formed between the epilayers and substrate that depend on the size of the surface unit cell. This demonstrates that there is a significant, although relatively weak, interfacial interaction between the two materials. Lattice matching is thus relevant for vdW epitaxy with two 2D bonded materials and a fundamental design parameter for vdW heterostructures. PMID:26658715

  4. 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. PMID:22463330

  5. 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.

  6. Harris-type van der Waals density functional scheme

    NASA Astrophysics Data System (ADS)

    Berland, Kristian; Londero, Elisa; Schröder, Elsebeth; Hyldgaard, Per

    2013-07-01

    Biomolecular systems that involve thousands of atoms are difficult to address with standard density functional theory (DFT) calculations. With the development of sparse-matter methods such as the van der Waals density functional (vdW-DF) method [M. Dion , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.92.246401 92, 246401 (2004)], it is now possible to include the dispersive forces in DFT which are necessary to describe the cohesion and behavior of these systems. vdW-DF implementations can be as efficient as those for traditional DFT. Yet, the computational costs of self-consistently determining the electron wave functions and hence the kinetic-energy repulsion still limit the scope of sparse-matter DFT. We propose to speed up sparse-matter calculations by using the Harris scheme [J. Harris, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.31.1770 31, 1770 (1985)]; that is, we propose to perform electronic relaxations only for separated fragments (molecules) and use a superposition of fragment densities as a starting point to obtain the total energy non-self-consistently. We evaluate the feasibility of this approach for an adaption of the Harris scheme for non-self-consistent vdW-DF (sfd-vdW-DF). We study four molecular dimers with varying degrees of polarity and find that the sfd scheme accurately reproduces standard non-self-consistent vdW-DF for van der Waals dominated systems but is less accurate for those dominated by polar interactions. Results for the S22 set of typical organic molecular dimers are promising.

  7. Birth outcome, not pregnancy process: reply to van der Veen.

    PubMed

    Frisbie, W P; Forbes, D; Hummer, R A; Pullum, S G

    1998-11-01

    In a recent article (Frisbie, Forbes, and Pullum 1996) we documented racial/ethnic differences in birth outcomes according to a more fine-grained classification than has typically been employed in the demographic literature. In his commentary, van der Veen focuses on the measurement of one of the dimensions of that classification, maturity of the infant, as proxied by the fetal growth ratio. The crux of the critique is easily seen in van der Veen's statement that "all of my disagreements with Frisbie et al.'s method arise from their particular use of a postnatal standard for the assessment of intrauterine growth." Our critic misunderstands our objective: He fails to realize our interest in birth outcome, not pregnancy process, and does not perceive that our intent was to extend the research extant in both the demographic and public-health literatures in which patently postnatal (i.e., ex utero) measures are taken as outcomes interesting in their own right and/or as risk factors for infant mortality and infant and childhood morbidity. Specifically, he does recognize that we purposefully expanded our focus to include moderately compromised births to determine if they were at higher risk than the normal births with whom they are conventionally categorized. Our discussion draws on research cited in the original article, on studies cited by our critic, and on a few more recent investigations. Although we have never argued that ours is the only, or even the best approach in all cases, we try to clarify the rationale for, and adduce additional empirical evidence of, the utility of the method we used. PMID:9850476

  8. Regenerative EnergietrÀger im Aufwind: Entwicklung der erneuerbaren Energien

    NASA Astrophysics Data System (ADS)

    Kohl, Harald

    2006-05-01

    2005 kam 4,6 % des deutschen PrimĂ€r-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 WĂ€rmeenergie deckten 2004 die erneuerbaren Energien zu 5,4 %, vor allem aus Biomasse. Die solarthermische WĂ€rmeerzeugung hat sich gegenĂŒber 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 PrimĂ€r-Energieverbrauch die FĂŒnfzigprozentmarke ĂŒberschreiten.

  9. Graphene on boron-nitride: Moiré pattern in the van der Waals energy

    SciTech Connect

    Neek-Amal, M.; Peeters, F. M.

    2014-01-27

    The spatial dependence of the van der Waals (vdW) energy between graphene and hexagonal boron-nitride (h-BN) is investigated using atomistic simulations. The van der Waals energy between graphene and h-BN shows a hexagonal superlattice structure identical to the observed Moiré pattern in the local density of states, which depends on the lattice mismatch and misorientation angle between graphene and h-BN. Our results provide atomistic features of the weak van der Waals interaction between graphene and BN which are in agreement with experiment and provide an analytical expression for the size of the spatial variation of the weak van der Waals interaction. We also found that the A-B-lattice symmetry of graphene is broken along the armchair direction.

  10. Der Physik-Nobelpreis vor 100 Jahren Die Entdeckung des trÀgen 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 fĂŒr seine Untersuchungen ĂŒber die Dichte von Gasen und die Entdeckung des Edelgases Argon.

  11. Die Wirkung als Naturkraft und die Herkunft von Zeit, Raum, Dimensionen, NaturkrÀften, und Gesetzen von Logik, Geometrie und Physik bei der Entstehung der Welt

    NASA Astrophysics Data System (ADS)

    Landgraf, Werner

    2011-02-01

    Das Wirkungs-Welt-Modell enthĂ€lt eine einfache Beschreibung des Anfanges der Welt, wonach, ausgehend vom einfachsten Zustand der logisch notwendigen Bejahung ihrer Existenz innerhalb ihr selbst, alles sukzessiv bewirkt wird, und ihre logischen, geometrischen und physikalischen Eigenschaften Aspekte der Verkörperung und Fortwirkung primordialer Fakten darstellen, ohne externe Schöpfung auszuschließen. Die ersten Dimensionen und sie formal und subjektiv charakterisierenden GrĂ¶ĂŸen sind: Informationsmenge und Wirkung, mit abzĂ€hlbarem Ereignis und Wirkungsquantum; Zeit und Energie, mit deren Planck-Einheiten; Geschwindigkeit oder Strecke und Impuls, mit Lichtgeschwindigkeit oder Planck-LĂ€nge; KrĂŒmmung oder zwei rĂ€umliche Richtungen, mit Gravitationskonstanten, und aus den ihnen entsprechenden primĂ€ren NaturkrĂ€ften setzen sich die uns gelĂ€ufigen zusammen.

  12. 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, the results obtained with DER-CAM illustrate the complexity of interactions between DER and passive measure options, showcasing the need for a holistic optimization approach to effectively optimize energy costs and CO2 emissions. Lastly, the simultaneous optimization of building shell improvements and DER investments enables building owners to take one step further towards nearly zero energy buildings (nZEB) or nearly zero carbon emission buildings (nZCEB), and therefore support the 20/20/20 goals.

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

    DOE PAGESBeta

    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%,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 DER-CAM illustrate the complexity of interactions between DER and passive measure options, showcasing the need for a holistic optimization approach to effectively optimize energy costs and CO2 emissions. Lastly, the simultaneous optimization of building shell improvements and DER investments enables building owners to take one step further towards nearly zero energy buildings (nZEB) or nearly zero carbon emission buildings (nZCEB), and therefore support the 20/20/20 goals.« less

  14. Auswahlleitfaden fĂŒr Montagelösungen in der Leistungselektronik

    NASA Astrophysics Data System (ADS)

    Pfeffer, Michael; Reinhardt, Andreas; Dahl, Bodo; Brosius, Nadja; Zeuß, Hermann; MĂ€rz, Martin; Egelkraut, Sven; Schmauch, Eberhard; Groß, Rainer

    Zur Realisierung einer wettbewerbsfĂ€higen Montage mĂŒssen Lösungen gefunden und verglichen werden, mit denen die Herstellung von leistungselektronischen Baugruppen möglich ist. Das Spektrum der Möglichkeiten erstreckt sich hierbei von der reinen manuellen Montage bis hin zur Vollautomatisierung. Durch gezielte Einflussnahme auf das Produkt oder die verwendeten Bauelemente können jedoch auch Resultate erzielt werden, die bereits durch einfache Anpassungen eine Montageerleichterung darstellen.

  15. Leitlinie Dermatomyositis - Auszug aus der interdisziplinĂ€ren S2k-Leitlinie zu Myositissyndromen der deutschen Gesellschaft fĂŒr Neurologie.

    PubMed

    Sunderkötter, Cord; Nast, Alexander; Worm, Margitta; Dengler, Reinhard; Dörner, Thomas; Ganter, Horst; Hohlfeld, Reinhard; Melms, Arthur; Melzer, Nico; Rösler, Kai; Schmidt, Jens; Sinnreich, Michael; Walter, Maggi C; Wanschitz, Julia; Wiendl, Heinz

    2016-03-01

    Diese Leitlinie fĂŒr Dermatomyositis (DM) ist ein Auszug aus der interdisziplinĂ€ren S2k-Leitlinie der deutschen Gesellschaft fĂŒr Neurologie zu Myositissyndromen. SchlĂŒsselsymptom fĂŒr die Myositis bei DM ist eine proximal-symmetrische MuskelschwĂ€che. Weitere diagnostische Hinweise liefern Creatinkinase, CRP oder BSG, Elektromyographie und Muskelbiopsie. Schluck-, Atem-, Herz- und Nackenmuskulatur können beteiligt sein. Da ca. 30 % der Patienten eine interstitielle Lungenerkrankung haben, sollte auch ein Lungenfunktionstest erfolgen. Die Hauteffloreszenzen sind unterschiedlich, aber in ihrer Zusammenschau ein charakteristisches und entscheidendes Kriterium fĂŒr die DM. In fĂŒnf bis ca. 20 % der FĂ€lle treten typische Hauteffloreszenzen, aber keine klinisch manifeste Muskelbeteiligung auf (amyopathische DM). Etwa 30 % aller DM des Erwachsenen sind tumorassoziiert, die Therapie bei schwerer Myositis sollte aber deshalb nicht verzögert werden. Mittel der ersten Wahl gegen die Myositis sind Glukokortikoide. HĂ€ufig sind zusĂ€tzlich Immunsuppressiva notwendig (Azathioprin, bei Kindern Methotrexat). Bei ungenĂŒgendem Ansprechen sind intravenöse Immunglobuline gerechtfertigt. Der Nutzen von Rituximab konnte nicht abschließend beurteilt werden. Auf die Akuttherapie folgt fĂŒr ca. 1-3 Jahre eine niedrig dosierte Langzeittherapie. Die Hautsymptome sprechen nicht immer ausreichend auf die Myositis-Therapie an. Hier helfen topische Glukokortikoide, mitunter auch Calcineurininhibitoren. Systemisch haben Antimalariamittel (auch kombiniert), Methotrexat und Glukokortikoide Wirksamkeit gezeigt, intravenöse Immunglobuline oder Rituximab können ebenfalls wirksam sein. Sonnenschutz ist eine wichtige prophylaktische Maßnahme. PMID:26972220

  16. 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-BĂ€ndern. 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 FunkvertrĂ€glichkeit dieser Systeme untereinander auf. WĂ€hrend die SRD-Funkmodule auf eine geringe Sendeleistung von ~ +14 dBm beschrĂ€nkt sind (Ralf and Thomas, 2009), betrĂ€gt die maximale LTE-Sendeleistung im Uplink nach (ETSI-Norm, 2011) +23 dBm. Zusammen mit der EinfĂŒhrung von LTE im Frequenzbereich unterhalb 1 GHz als DSL-Ersatz vor allem in lĂ€ndlichen Gebieten, ergibt sich damit als mögliches Störszenario, dass durch die Aussendung des LTE-EndgerĂ€tes im Bereich von ca. 850 MHz die SRD-Funkverbindungen bei 868 MHz insbesondere dann gestört werden, wenn die Antennen beider Funksysteme rĂ€umlich nahe zueinander angeordnet sind und folglich nur eine geringe zusĂ€tzliche Entkopplung der Systeme bieten. In der vorliegenden Arbeit wird das LTE-Störpotential auf SRD-EmpfĂ€nger praxisnah untersucht.

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

    NASA Astrophysics Data System (ADS)

    Geisen, Rolf

    Schimmelpilze kommen ubiquitĂ€r vor und spielen besonders bei pflanzlichen Lebensmitteln und Rohprodukten eine besondere Rolle als Verderbsorganismen. Es wird geschĂ€tzt, dass 20-25 % der jĂ€hrlichen Produktion an pflanzlichen Produkten durch Schimmelpilze verdorben werden (Smith et al., 1994). Viele der lebensmittelrelevanten Schimmelpilze sind zudem in der Lage, Mykotoxine, toxische SekundĂ€rmetabolite, zu bilden, was das Ausmaß des Problems deutlich macht. Die wichtigsten mykotoxinbildenden Spezies gehören zu den Fusarien (Trichothecene, Fumonisine, Zearalenon), Aspergillen (Aflatoxin, Ochratoxin, CyclopiazonsĂ€ure) und Penicillien (Patulin, Ochratoxin). FĂŒr viele Mykotoxine, wie die Aflatoxine, Ochratoxin, Fumonisine und Trichothecene sind Grenzwerte erlassen worden, die die VerkehrsfĂ€higkeit 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 fĂŒr die Anwendung eines HACCP-Ansatzes zur Kontrolle der Mykotoxinbildung nur bedingt geeignet, da sie Endpunktkontrollen darstellen und nur das ĂŒber eine lĂ€ngere Zeit gebildete Mykotoxin bestimmen. Sie sagen daher nichts ĂŒber die biologischen Bedingungen zur Zeit der Bildung durch den Pilz aus.

  18. Surface energy and wettability of van der Waals structures

    NASA Astrophysics Data System (ADS)

    Annamalai, Meenakshi; Gopinadhan, Kalon; Han, Sang A.; Saha, Surajit; Park, Hye Jeong; Cho, Eun Bi; Kumar, Brijesh; Patra, Abhijeet; Kim, Sang-Woo; Venkatesan, T.

    2016-03-01

    The wetting behaviour of surfaces is believed to be affected by van der Waals (vdW) forces; however, there is no clear demonstration of this. With the isolation of two-dimensional vdW layered materials it is possible to test this hypothesis. In this paper, we report the wetting behaviour of vdW heterostructures which include chemical vapor deposition (CVD) grown graphene, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) on few layers of hexagon boron nitride (h-BN) and SiO2/Si. Our study clearly shows that while this class of two-dimensional materials are not completely wetting transparent, there seems to be a significant amount of influence on their wetting properties by the underlying substrate due to dominant vdW forces. Contact angle measurements indicate that graphene and graphene-like layered transitional metal dichalcogenides invariably have intrinsically dispersive surfaces with a dominating London-vdW force-mediated wettability.The wetting behaviour of surfaces is believed to be affected by van der Waals (vdW) forces; however, there is no clear demonstration of this. With the isolation of two-dimensional vdW layered materials it is possible to test this hypothesis. In this paper, we report the wetting behaviour of vdW heterostructures which include chemical vapor deposition (CVD) grown graphene, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) on few layers of hexagon boron nitride (h-BN) and SiO2/Si. Our study clearly shows that while this class of two-dimensional materials are not completely wetting transparent, there seems to be a significant amount of influence on their wetting properties by the underlying substrate due to dominant vdW forces. Contact angle measurements indicate that graphene and graphene-like layered transitional metal dichalcogenides invariably have intrinsically dispersive surfaces with a dominating London-vdW force-mediated wettability. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06705g

  19. Gate tunable WSe2-BP van der Waals heterojunction devices

    NASA Astrophysics Data System (ADS)

    Chen, Peng; Zhang, Ting Ting; Zhang, Jing; Xiang, Jianyong; Yu, Hua; Wu, Shuang; Lu, Xiaobo; Wang, Guole; Wen, Fusheng; Liu, Zhongyuan; Yang, Rong; Shi, Dongxia; Zhang, Guangyu

    2016-02-01

    Due to the weak screening effect, the concentration and type of charge carriers in 2D semiconductor heterostructures can be effectively tuned by electrostatic gating, enabling us to realize different types of heterojunctions in a single device. Such `type tunable' properties are useful for designing novel electrical or optoelectrical devices. Here, we demonstrate a `type tunable' heterojunction device construct with two pieces of ambipolar 2D semiconductors: WSe2 and black phosphorus (BP). This heterojunction could be tuned to either the p-p junction or n-n junction by gate modulation. The p-p junction shows a large current rectification ratio while the n-n junction shows a negligible current rectification ratio, indicating a large valence band offset and a small conduction band offset at the WSe2/BP interface. In the optoelectrical measurements, we found the amplitude and even the polarity of photocurrent could be modulated by electrostatic gating. Our study could further enhance the understanding of designing devices based on these `type tunable' van der Waals heterojunctions. Moreover, the properties of the WSe2/BP interface were also experimentally identified through the electrical and optoelectrical measurements in our study.Due to the weak screening effect, the concentration and type of charge carriers in 2D semiconductor heterostructures can be effectively tuned by electrostatic gating, enabling us to realize different types of heterojunctions in a single device. Such `type tunable' properties are useful for designing novel electrical or optoelectrical devices. Here, we demonstrate a `type tunable' heterojunction device construct with two pieces of ambipolar 2D semiconductors: WSe2 and black phosphorus (BP). This heterojunction could be tuned to either the p-p junction or n-n junction by gate modulation. The p-p junction shows a large current rectification ratio while the n-n junction shows a negligible current rectification ratio, indicating a large valence band offset and a small conduction band offset at the WSe2/BP interface. In the optoelectrical measurements, we found the amplitude and even the polarity of photocurrent could be modulated by electrostatic gating. Our study could further enhance the understanding of designing devices based on these `type tunable' van der Waals heterojunctions. Moreover, the properties of the WSe2/BP interface were also experimentally identified through the electrical and optoelectrical measurements in our study. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09218c

  20. Structural Analysis of Der p 1-Antibody Complexes and Comparison with Complexes of Proteins or Peptides with Monoclonal Antibodies.

    PubMed

    Osinski, Tomasz; Pomés, Anna; Majorek, Karolina A; Glesner, Jill; Offermann, Lesa R; Vailes, Lisa D; Chapman, Martin D; Minor, Wladek; Chruszcz, Maksymilian

    2015-07-01

    Der p 1 is a major allergen from the house dust mite, Dermatophagoides pteronyssinus, that belongs to the papain-like cysteine protease family. To investigate the antigenic determinants of Der p 1, we determined two crystal structures of Der p 1 in complex with the Fab fragments of mAbs 5H8 or 10B9. Epitopes for these two Der p 1-specific Abs are located in different, nonoverlapping parts of the Der p 1 molecule. Nevertheless, surface area and identity of the amino acid residues involved in hydrogen bonds between allergen and Ab are similar. The epitope for mAb 10B9 only showed a partial overlap with the previously reported epitope for mAb 4C1, a cross-reactive mAb that binds Der p 1 and its homolog Der f 1 from Dermatophagoides farinae. Upon binding to Der p 1, the Fab fragment of mAb 10B9 was found to form a very rare α helix in its third CDR of the H chain. To provide an overview of the surface properties of the interfaces formed by the complexes of Der p 1-10B9 and Der p 1-5H8, along with the complexes of 4C1 with Der p 1 and Der f 1, a broad analysis of the surfaces and hydrogen bonds of all complexes of Fab-protein or Fab-peptide was performed. This work provides detailed insight into the cross-reactive and specific allergen-Ab interactions in group 1 mite allergens. The surface data of Fab-protein and Fab-peptide interfaces can be used in the design of conformational epitopes with reduced Ab binding for immunotherapy. PMID:26026055

  1. van der Waals effects at molecule-metal interfaces

    NASA Astrophysics Data System (ADS)

    Rosa, Marta; Corni, Stefano; Di Felice, Rosa

    2014-09-01

    We present the results of plane-wave pseudopotential periodic density functional theory (DFT) calculations on the geometries, energetics, and electronic structure of small molecules on Au(111). The chosen molecules—benzene, ammonia and cytosine—are representative of different adsorption regimes and interaction strengths. The chosen substrate is a prototype noble-metal surface that is widely employed as a support for organic materials. We assess the relevance of van der Waals effects in the adsorption process and the accuracy of different first-principle density functionals that have been recently developed to embody such effects. We find that there is no unique functional that is optimal for any system. In particular, our results reveal that functionals designed to reduce the short-term repulsion between the adsorbate and the substrate usually overestimate the adsorption strength and may even predict the wrong adsorption orientation. We show that an accurate description of the substrate does not ensure an accurate evaluation of the adsorption energetics, while the electronic structure is less sensitive to the specific choice. We propose the best choice for DFT calculations of DNA bases on Au(111) and similar systems in which both short-range and long-range interactions exist.

  2. Surface energy and wettability of van der Waals structures.

    PubMed

    Annamalai, Meenakshi; Gopinadhan, Kalon; Han, Sang A; Saha, Surajit; Park, Hye Jeong; Cho, Eun Bi; Kumar, Brijesh; Patra, Abhijeet; Kim, Sang-Woo; Venkatesan, T

    2016-03-01

    The wetting behaviour of surfaces is believed to be affected by van der Waals (vdW) forces; however, there is no clear demonstration of this. With the isolation of two-dimensional vdW layered materials it is possible to test this hypothesis. In this paper, we report the wetting behaviour of vdW heterostructures which include chemical vapor deposition (CVD) grown graphene, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) on few layers of hexagon boron nitride (h-BN) and SiO2/Si. Our study clearly shows that while this class of two-dimensional materials are not completely wetting transparent, there seems to be a significant amount of influence on their wetting properties by the underlying substrate due to dominant vdW forces. Contact angle measurements indicate that graphene and graphene-like layered transitional metal dichalcogenides invariably have intrinsically dispersive surfaces with a dominating London-vdW force-mediated wettability. PMID:26910437

  3. 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.

  4. Gate tunable WSe2-BP van der Waals heterojunction devices.

    PubMed

    Chen, Peng; Zhang, Ting Ting; Zhang, Jing; Xiang, Jianyong; Yu, Hua; Wu, Shuang; Lu, Xiaobo; Wang, Guole; Wen, Fusheng; Liu, Zhongyuan; Yang, Rong; Shi, Dongxia; Zhang, Guangyu

    2016-02-14

    Due to the weak screening effect, the concentration and type of charge carriers in 2D semiconductor heterostructures can be effectively tuned by electrostatic gating, enabling us to realize different types of heterojunctions in a single device. Such 'type tunable' properties are useful for designing novel electrical or optoelectrical devices. Here, we demonstrate a 'type tunable' heterojunction device construct with two pieces of ambipolar 2D semiconductors: WSe2 and black phosphorus (BP). This heterojunction could be tuned to either the p-p junction or n-n junction by gate modulation. The p-p junction shows a large current rectification ratio while the n-n junction shows a negligible current rectification ratio, indicating a large valence band offset and a small conduction band offset at the WSe2/BP interface. In the optoelectrical measurements, we found the amplitude and even the polarity of photocurrent could be modulated by electrostatic gating. Our study could further enhance the understanding of designing devices based on these 'type tunable' van der Waals heterojunctions. Moreover, the properties of the WSe2/BP interface were also experimentally identified through the electrical and optoelectrical measurements in our study. PMID:26810387

  5. Van der Waals torque induced by external magnetic fields

    SciTech Connect

    Esquivel-Sirvent, R.; Cocoletzi, G. H.; Palomino-Ovando, M.

    2010-01-01

    We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III–IV semiconductors such as InSb, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of InSb. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of InSb increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropicmaterials when the magnetic fields is close to 1 T.

  6. Spatially Correlated Disorder in Epitaxial van der Waals Heterostructures

    NASA Astrophysics Data System (ADS)

    Laanait, Nouamane; Zhang, Zhan; Schleputz, Christian; Liu, Ying; Wojcik, Michael; Myers-Ward, Rachael; Gaskill, D. Kurt; Fenter, Paul; Li, Lian

    The structural cohesion of van der Waals (vdW) heterostructures relies upon a cooperative balance between strong intra-layer bonded interactions and weak inter-layer coupling. The confinement of extended defects to within a single vdW layer and competing interactions introduced by epitaxial constraints could generate fundamentally new structural disorders. Here we report on the presence of spatially correlated and localized disorder states that coexist with the near perfect crystallographic order along the growth direction of epitaxial vdW heterostructure of Bi2Se3/graphene/SiC grown by molecular beam epitaxy. With the depth penetration of hard X-ray diffraction microscopy and high-resolution surface scattering, we imaged local structural configurations from the atomic to mesoscopic length scales, and found that these disorder states result as a confluence of atomic scale modulations in the strength of vdW layer-layer interactions and nanoscale boundary conditions imposed by the substrate. These findings reveal a vast landscape of novel disorder states that can be manifested in epitaxial vdW heterostructures. Supported by the Wigner Fellowship program at Oak Ridge Nat'l Lab.

  7. 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. PMID:20503777

  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. PMID:19382751

  9. Jarzynski equality in van der Pol and Rayleigh oscillators.

    PubMed

    Hasegawa, Hideo

    2011-12-01

    We have studied the Jarzynski equality (JE) in van der Pol and Rayleigh oscillators, which are typical deterministic non-Hamiltonian models but not expected to rigorously satisfy the JE because they are not reversible. Our simulations that calculate the contribution to the work W of an applied ramp force with a duration ? show that the JE approximately holds for a fairly wide range of ? including ? ? 0 and ? ? ?, except for ? ~ T, where T denotes the period of relaxation oscillations in the limit cycle. The work distribution function (WDF) is shown to be non-Gaussian with the U-shaped structure for a strong damping parameter. The ? dependence of R ( = -k(B)(Tln(e)(-?W)) obtained by our simulations is semiquantitatively elucidated with the use of a simple expression for limit-cycle oscillations, where the bracket (·) expresses an average over the WDF. The result obtained in self-excited oscillators is in contrast with the fact that the JE holds in the Nosé-Hoover oscillator, which also belongs to deterministic non-Hamiltonian models. PMID:22304045

  10. Peptide folding driven by Van der Waals interactions.

    PubMed

    Sung, Shen-Shu

    2015-09-01

    Contrary to the widespread view that hydrogen bonding and its entropy effect play a dominant role in protein folding, folding into helical and hairpin-like structures is observed in molecular dynamics (MD) simulations without hydrogen bonding in the peptide-solvent system. In the widely used point charge model, hydrogen bonding is calculated as part of the interaction between atomic partial charges. It is removed from these simulations by setting atomic charges of the peptide and water to zero. Because of the structural difference between the peptide and water, van der Waals (VDW) interactions favor peptide intramolecular interactions and are a major contributing factor to the structural compactness. These compact structures are amino acid sequence dependent and closely resemble standard secondary structures, as a consequence of VDW interactions and covalent bonding constraints. Hydrogen bonding is a short range interaction and it locks the approximate structure into the specific secondary structure when it is included in the simulation. In contrast to standard molecular simulations where the total energy is dominated by charge-charge interactions, these simulation results will give us a new view of the folding mechanism. PMID:26013298

  11. Inflationary magnetogenesis, derivative couplings, and relativistic Van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2015-08-01

    When the gauge fields have derivative couplings to scalars, like in the case of the relativistic theory of Van der Waals (or Casimir-Polder) interactions, conformal invariance is broken but the magnetic and electric susceptibilities are not bound to coincide. We analyze the formation of large-scale magnetic fields in slow-roll inflation and find that they are generated at the level of a few hundredths of a nG and over typical length scales between few Mpc and 100 Mpc. Using a new time parametrization that reduces to conformal time but only for coincident susceptibilities, the gauge action is quantized while the evolution equations of the corresponding mode functions are more easily solvable. The power spectra depend on the normalized rates of variation of the two susceptibilities (or of the corresponding gauge couplings) and on the absolute value of their ratio at the beginning of inflation. We pin down explicit regions in the parameter space where all the physical requirements (i.e., the backreaction constraints, the magnetogenesis bounds and the naturalness of the initial conditions of the scenario) are jointly satisfied. Weakly coupled initial data are favored if the gauge couplings are of the same order at the end of inflation. Duality is systematically used to simplify the analysis of the wide parameter space of the model.

  12. 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 GerĂ€ten ĂŒber den menschlichen Körper werden elektromagnetische StörphĂ€nomene im Klinikbereich betrachtet. FĂŒr die Berechnung dieser komplexen Szenarien wird zum einen die Momentenmethode (MoM) verwendet, die sich in besonderem Maße fĂŒr die BerĂŒcksichtigung metallischer Strukturen und offener Streuprobleme eignet, und zum anderen die Methode der Finiten Elemente (FEM), mit der die Eigenschaften des menschlichen Körpers besser berĂŒcksichtigt werden können. Mit Hilfe des Äquivalenzprinzips lĂ€sst sich das Gesamtproblem in zwei Teile zerlegen, in ein inneres und in ein Ă€ußeres. 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 KörperoberflĂ€che ĂŒber Ă€quivalente OberflĂ€chenströme. Durch Lösen des resultierenden linearen Gleichungssystems fĂŒr das gesamte Problem lassen sich dann die OberflĂ€chenströme und die ĂŒber die KontinuitĂ€tsgleichung miteinander verknĂŒpften elektromagnetischen Felder bestimmen.

  13. High-frequency binding of IgE to the Der p allergen expressed in yeast.

    PubMed

    Chua, K Y; Kehal, P K; Thomas, W R; Vaughan, P R; Macreadie, I G

    1992-01-01

    The production of allergens from cDNA clones will provide a clonally pure source of material for experimental and perhaps clinical studies. Attempts to produce the major mite allergen, Der p I, in a highly antigenic form in bacteria have, to date, had limited success. In this study, a high level of production of Der p I from a Cup1 gene cassette from pYELC5-13T in Saccharomyces cerevisiae is described. Although the protein was insoluble, it could be readily solubilized in a urea solution and remained in solution when it was returned to more physiologic buffers. An amount equivalent to about 1 mg/L of yeast culture could then be isolated by affinity chromatography with an immobilized monoclonal antibody. This product reacted strongly with IgE in 9/11 sera from mite-allergic patients compared to the 50% reactivity achieved for Der p I previously produced as a fusion by bacteria. Similarly, the intensity of binding and ability to absorb out Der p I specificities were much greater for the yeast, pYELC5-13T, product. Studies with monoclonal antibodies also demonstrated the yeast, Der p I, had a high degree of antigenicity, although clear differences with the native allergen were demonstrated. The high frequency of reactivity with IgE of the pYELC5-13T formally demonstrates that a single gene product of Der p I is a major allergen and demonstrates that even for Der p I, which is synthesized from a proenzyme, considerable antigenicity can be obtained by expressing the mature protein. PMID:1730842

  14. FORS am Very Large Telescope der EuropĂ€ischen SĂŒdsternwarte

    NASA Astrophysics Data System (ADS)

    1998-09-01

    Erstes wissenschaftliches Beobachtungsinstrument liefert eindrucksvolle Bilder Entsprechend dem straffen Zeitplan wird das ESO Very Large Teleskop Projekt (VLT-Projekt) auf dem Cerro Paranal in Nord-Chile verwirklicht: die volle Betriebsbereitschaft des ersten der vier 8,2m-Einzelteleskope wird Anfang des nĂ€chsten Jahres erreicht sein. Am 15. September 1998 wurde ein weiterer wichtiger Meilenstein erfolgreich, rechtzeitig und innerhalb des Kostenplans erreicht. Nur wenige Tage nach seiner Montage am ersten 8,2m-Einzelteleskop des VLT (UT1) konnte FORS1 ( FO cal R educer and S pectrograph) als erstes einer Gruppe leistungsfĂ€higer und komplexer wissenschaftlicher Instrumente seine BeobachtungstĂ€tigkeit beginnen. Von Anfang an konnte es eine Reihe exzellenter astronomischer Bilder aufnehmen. Dieses bedeutende Ereignis eröffnet eine FĂŒlle neuer Möglichkeiten fĂŒr die europĂ€ische Astronomie. FORS - ein Höhepunkt an KomplexitĂ€t FORS1 und das zukĂŒnftige Zwillingsinstrument (FORS2) sind das Ergebnis einer der eingehendsten und fortschrittlichsten technologischen Studien, die je fĂŒr ein Instrument der bodengebundenen Astronomie durchgefĂŒhrt wurden. Dieses einzigartige Instrument ist nun im Cassegrain-Fokus installiert und verschwindet beinahe, trotz seiner Dimensionen von 3 x 1.5m (Gewicht 2.3t), unterhalb des riesigen 53 m 2 großen Zerodurspiegels. Um die große SpiegelflĂ€che und die hervorragende BildqualitĂ€t von UT1 optimal auszunĂŒtzen, wurde FORS speziell so konstruiert, daß es die lichtschwĂ€chsten und entferntesten Objekte im Weltall untersuchen kann. Bald wird dieses komplexe VLT-Instrument den europĂ€ischen Astronomen erlauben, die derzeitigen Beobachtungshorizonte entscheidend zu erweitern. Die beiden FORS-Instrumente sind Vielzweck-Beobachtungsinstrumente, die in mehreren unterschiedlichen Beobachtungsarten eingesetzt werden können. Beispielsweise können Bilder mit zwei verschiedenen AbbildungsmaßstĂ€ben (VergrĂ¶ĂŸerungen) sowie Spektren mit unterschiedlicher spektraler Auflösung von einzelnen oder mehreren Objekten aufgenommen werden. Dabei erlaubt der schnelle Wechsel zwischen den unterschiedlichen Beobachtungsarten z.B. zunĂ€chst die Aufnahme und direkt anschließend die Spektroskopie weit entfernter Galaxien. Damit kann dann u.a. die stellare Zusammensetzung und die Entfernung bestimmt werden. Als eines der leistungsfĂ€higsten astronomischen Instrumente seiner Art wird FORS1 ein wahres Arbeitspferd fĂŒr die Untersuchung des fernen Universums darstellen. Der Bau von FORS Das FORS-Projekt wird unter ESO-Kontrakt von einem Konsortium dreier deutscher astronomischer Institute durchgefĂŒhrt, der Landessternwarte Heidelberg und den UniversitĂ€ts-Sternwarten von Göttingen and MĂŒnchen. Bis zur Beendigung des Projekts werden die beteiligten Institute Arbeit im Umfang von ca. 180 Mann-Jahren eingebracht haben. Bei der Landessternwarte Heidelberg lag die Leitung des Projekts. Hier wurde außerdem das gesamte optische System konstruiert, die Beschaffung der Komponenten der abbildenden Optik und der Zusatzoptiken fĂŒr Spektroskopie und Polarimetrie durchgefĂŒhrt und die spezielle Computersoftware geschrieben, mit der die von FORS gelieferten Daten verarbeitet und ausgewertet werden. DarĂŒber hinaus wurde in der Werkstatt der Sternwarte ein Teleskopsimulator gebaut, mit dem alle wesentlichen Funktionen von FORS in Europa getestet werden konnten, bevor das Instrument zum Paranal (Chile) transportiert wurde. An der UniversitĂ€ts-Sternwarte Göttingen wurden Konstruktion, Herstellung und Zusammenbau der gesamten Mechanik von FORS durchgefĂŒhrt. Der grĂ¶ĂŸte Teil der PrĂ€zisionsteile, insbesondere der Multispalteinheit, wurde in der feinmechanischen Werkstatt der Sternwarte hergestellt. Die Beschaffung der großen InstrumentengehĂ€use und Flansche, die Computeranalysen fĂŒr mechanische und thermische StabilitĂ€t des empfindlichen Spektrographen und die Herstellung der speziellen Werkzeuge fĂŒr Handhabung, Wartung und Justierung lag ebenso in der Verantwortung dieser Sternwarte wie die Tests der zahlreichen opto- und elektromechanischen Funktionen. Die UniversitĂ€ts-Sternwarte MĂŒnchen war verantwortlich fĂŒr das Projektmanagement, Integration und Test des gesamten Instruments im Labor, fĂŒr Planung und Einbau aller Elektronik und Elektromechanik, sowie fĂŒr Entwicklung und Test der gesamten Software, die FORS in allen Teilen vollstĂ€ndig per Computer steuert (z.B. Filter- und GrismrĂ€der, VerschlĂŒsse, Spalteinheit fĂŒr die Vielspaltspektroskopie, Masken, alle optischen Komponenten, Elektromotoren, Encoder usw.). ZusĂ€tzlich wurde Computersoftware geschrieben, mit der die komplexen astronomischen Beobachtungen mit FORS vorbereitet werden und das Verhalten des Instruments durch eine stĂ€ndige Kontrolle der gesammelten wissenschaftlichen Daten ĂŒberwacht wird. Als Gegenleistung fĂŒr den Bau von FORS erhalten die Astronomen der drei beteiligten Institute des FORS-Konsortiums eine gewisse Anzahl von NĂ€chten an "garantierter Beobachtungszeit" am VLT. In dieser Beobachtungszeit werden verschiedene Forschungsprojekte durchgefĂŒhrt, deren Themen unter anderem von kleinen Körpern im Ă€ußeren Sonnensystem ĂŒber Untersuchungen von Sternen im Endstadium und den von ihnen abgestoßenen Gaswolken bis zur Erforschung ferner Galaxien und Quasare reichen, die Aufschluß ĂŒber die frĂŒhen Zeiten unseres Universums geben. Erste Tests von FORS1 am VLT-UT1: ein großartiger Erfolg Nach sorgfĂ€ltiger Vorbereitung hat das FORS-Konsortium nun mit der Inbetriebnahme ("Commissioning") des Instruments begonnen. Dazu gehören ein eingehender Nachweis der spezifizierten LeistungsfĂ€higkeit am Teleskop, die ÜberprĂŒfung der korrekten Funktionsweise unter Softwaresteuerung vom Kontrollraum auf Paranal, und am Ende dieses Prozesses eine Demonstration, daß das Instrument seinen angestrebten wissenschaftlichen Zweck erfĂŒllt. WĂ€hrend der DurchfĂŒhrung dieser Tests gelangen dem Commissioning-Team auf Paranal eine Reihe von Aufnahmen verschiedener astronomischer Objekte, von denen einige hier wiedergegeben sind. Sie wurden alle mit FORS in der Standardauflösung gewonnen (BildfeldgrĂ¶ĂŸe 6.8 x 6.8 Bogenminuten, PixelgrĂ¶ĂŸe 0.20 Bogensekunden) und zeigen einige der eindrucksvollen Möglichkeiten, die das neue Instrument bietet. Spiralgalaxie NGC 1288 ESO PR Photo 37a/98 ESO PR Photo 37a/98 [Preview - JPEG: 800 x 908 pix - 224k] [High-Res - JPEG: 3000 x 3406 pix - 1.5Mb] Farbaufnahme der Spiralgalaxie NGC 1288, aufgenommen in der ersten Beobachtungsnacht von FORS ("Nacht des ersten Lichts"). Das erste Photo zeigt eine Dreifarbenaufnahme der schönen Spiralgalaxie NGC 1288 im sĂŒdlichen Sternbild Fornax. PR Photo 37a/98 umfaßt das gesamte Feld, das mit der 2048 x 2048 Pixel großen CCD-Kamera abgebildet wurde. Es wurde aus drei CCD-Aufnahmen zusammengesetzt, die bei gutem Seeing in verschiedenen Farben in der "Nacht des ersten Lichts" (15. September 1998) aufgenommen wurden. Diese Galaxie mit einem Durchmesser von rund 200000 Lichtjahren ist etwa 300 Millionen Lichtjahre entfernt, ihre Fluchtgeschwindigkeit betrĂ€gt 4500 km/sec. Technische Informationen : Photo 37a/98 ist ein Komposit von drei Aufnahmen in den drei Filtern B (420nm, 6 Minuten belichtet), V (530nm, 3 Minuten) und I (800nm, 3 Minuten) wĂ€hrend einer Periode mit 0.7 Bogensekunden Seeing. Das gezeigte Feld ist 6.8 x 6.8 Bogenminuten groß. Norden ist links, Osten unten. Entfernter Galaxienhaufen ESO PR Photo 37b/98 ESO PR Photo 37b/98 [Preview - JPEG: 657 x 800 pix - 248k] [High-Res - JPEG: 2465 x 3000 pix - 1.9Mb] Ein ungewöhnlicher Galaxienhaufen in der Umgebung des Quasars PB5763 . ESO PR Photo 37c/98 ESO PR Photo 37c/98 [Preview - JPEG: 670 x 800 pix - 272k] [High-Res - JPEG: 2512 x 3000 pix - 1.9Mb] VergrĂ¶ĂŸerung von PR Photo 37b/98; sie zeigt mehr Einzelheiten des ungewöhnlichen Galaxienhaufens. Die nĂ€chsten Photos wurden von einer 5-minĂŒtigen Aufnahme im Nahen Infrarot reproduziert, die ebenfalls in der "Nacht des ersten Lichts" von FORS1 (15. September 1998) gewonnen wurde. PR Photo 37b/98 zeigt einen Himmelsausschnitt in der NĂ€he des Quasars PB5763, in dem auch ein ungewöhnlicher, sehr weit entfernter Haufen von Galaxien zu sehen ist. Er besteht aus einer großen Zahl lichtschwacher Galaxien, die bisher noch nicht eingehend untersucht wurden. Dieser Haufen ist ein gutes Beispiel fĂŒr die Art von Objekten, auf die viel Beobachtungszeit mit FORS verwendet werden wird, sobald der regulĂ€re Beobachtungsbetrieb begonnen hat. Eine VergrĂ¶ĂŸerung des gleichen Feldes ist in PR Photo 37c/98 wiedergegeben. Sie zeigt die einzelnen Mitglieder dieses Galaxienhaufens im Detail. Man beachte besonders die interessante spindelförmige Galaxie, die anscheinend einen Ă€quatorialen Ring aufweist. Neben einer schönen Spiralgalaxie sind auch noch viele weitere lichtschwache Galaxien zu erkennen. Sie sind entweder Zwerggalaxien und Mitglieder des Haufens oder befinden sich sehr viel weiter entfernt im Hintergrund des Haufens. Technische Informationen : PR Photos 37b/98 (als Negativ reproduziert) und 37c/98 (Positiv) stammen von einer Aufnahme, die bei 0.8 Bogensekunden Seeing durch ein I-Filter (nahes Infrarot, 800nm) gewonnen wurde. Die Belichtungszeit betrug 5 Minuten, und es wurde eine Flatfield-Korrektur durchgefĂŒhrt. Das gezeigte Feld ist 6.8 x 6.8 Bogenminuten bzw. 2.5 x 2.3 Bogenminuten groß. Norden ist links oben, Osten links unten. Spiralgalaxie NGC 1232 ESO PR Photo 37d/98 ESO PR Photo 37d/98 [Preview - JPEG: 800 x 912 pix - 760k] [High-Res - JPEG: 3000 x 3420 pix - 5.7Mb] Ein Farbbild der Spiralgalaxie NGC 1232, aufgenommen am 21. September 1998. ESO PR Photo 37e/98 ESO PR Photo 37e/98 [Preview - JPEG: 800 x 961 pix - 480k] [High-Res - JPEG: 3000 x 3602 pix - 3.5Mb] VergrĂ¶ĂŸerung des Zentrums von PR Photo 37d/98. Dieses spektakulĂ€re Bild der großen Spiralgalaxie NGC 1232 (Photo 37d/98) wurde am 21. September 1998 unter guten Beobachtungsbedingungen erhalten. Es wurde aus drei Einzelaufnahmen im ultravioletten, blauen und roten Licht zusammengesetzt. Die Farben der verschiedenen Regionen sind deutlich sichtbar: Das Zentralgebiet enthĂ€lt Ă€ltere, rötlich leuchtende Sterne (Photo 37e/98), wĂ€hrend die Spiralarme von jungen, blĂ€ulichen Sternen und roten Sternentstehungsgebieten bevölkert sind. Man beachte die gestörte Begleitgalaxie am linken Rand (Photo 37d/98), die wie der griechische Buchstabe "Theta" aussieht. NGC 1232 liegt 20 Grad sĂŒdlich des HimmelsĂ€quators im Sternbild Eridanus. Obwohl die Entfernung dieser Galaxie ungefĂ€hr 100 Millionen Lichtjahre betrĂ€gt, kann man auf Grund der exzellenten BildqualitĂ€t einen unglaublichen Reichtum an Details erkennen. Bei dieser Entfernung entspricht die KantenlĂ€nge des Bildfeldes etwa 200000 Lichtjahren oder etwa der doppelten GrĂ¶ĂŸe unserer Milchstraße. Technische Informationen : Photos 37d/98 und 37e/98 sind ein Komposit von drei Aufnahmen in den drei Filtern U (360nm, 10 Minuten belichtet), B (420nm, 6 Minuten) und R (600nm, 2 Minuten 30 Sekunden) wĂ€hrend einer Periode mit 0.7 Bogensekunden Seeing. Das gezeigte Feld ist 6.8 x 6.8 Bogenminuten bzw. 1.6 x 1.8 Bogenminuten groß. Norden ist oben, Osten links. Note: [1] Diese Pressemitteilung wird gemeinsam (auf Englisch und Deutsch) von der EuropĂ€ischen SĂŒdsternwarte, der Landessternwarte Heidelberg und den UniversitĂ€ts-Sternwarten Göttingen und MĂŒnchen herausgegeben. An English Version of this Press Release is also available. Zugang zu ESO Presseinformationen ESO Presseinformationen werden im World Wide Web zur VerfĂŒgung gestellt (URL: http://www.eso.org/outreach/press-rel/). ESO Pressephotos dĂŒrfen veröffentlicht werden, wenn die EuropĂ€ische SĂŒdsternwarte als Urheber genannt wird.

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

    PubMed Central

    Mueller, Geoffrey A.; Gosavi, Rajendrakumar A.; Krahn, Joseph M.; Edwards, Lori L.; Cuneo, Matthew J.; Glesner, Jill; Pomés, Anna; Chapman, Martin D.; London, Robert E.; Pedersen, Lars C.

    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 ∌3000 Å3 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. PMID:20534590

  16. Physikalische Probleme der InformationsĂŒbertragung ĂŒber Lichtleiter

    NASA Astrophysics Data System (ADS)

    Junge, Klaus

    Die herkömmliche rein elektrische Übertragungstechnik ĂŒber Kabel lĂ€ĂŸt technische und ökonomische Grenzen erkennen. Die Suche nach neuen KanĂ€len fĂŒhrte unter anderem in den optischen Bereich, zur Lichtleiter-NachrichtenĂŒbertragung. HierfĂŒr sind in den letzten Jahren alle Elemente der ersten Generationen in umfangreicher Forschungsarbeit entwickelt worden. Dabei haben moderne Technologien der Mikroelektronik wesentlich zu den erzielten Ergebnissen bei der Herstellung der Lichtleit-Fasern und der opto-elektronischen Sende- und Empfangsbauelemente beigetragen. Abschließend werden Systemfragen und zukĂŒnftige Zielstellungen behandelt.Translated AbstractPhysical Problems in Optical Fiber CommunicationsConventional electrical transmission of information by means of cables has technical and economic limitations. The search for new channels led, among other things, to the optical region, to optical fiber communications. In the last few years all parts of the first generations have been developed on the basis of extensive research. Modern technologies of microelectronics have thus contributed essentially to achieving the results in producing optical fibers and electro-optical elements for transmitters and receivers. Finally several questions of systems and future objectives are discussed.

  17. 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 ÎŒm 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. PMID:24758201

  18. Van der Waals density functionals applied to solids

    NASA Astrophysics Data System (ADS)

    Klimeš, Ji?í; Bowler, David R.; Michaelides, Angelos

    2011-05-01

    The van der Waals density functional (vdW-DF) of M. Dion [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.92.246401 92, 246401 (2004)] is a promising approach for including dispersion in approximate density functional theory exchange-correlation functionals. Indeed, an improved description of systems held by dispersion forces has been demonstrated in the literature. However, despite many applications, standard general tests on a broad range of materials including traditional “hard” matter such as metals, ionic compounds, and insulators are lacking. Such tests are important not least because many of the applications of the vdW-DF method focus on the adsorption of atoms and molecules on the surfaces of solids. Here we calculate the lattice constants, bulk moduli, and atomization energies for a range of solids using the original vdW-DF and several of its offspring. We find that the original vdW-DF overestimates lattice constants in a similar manner to how it overestimates binding distances for gas-phase dimers. However, some of the modified vdW functionals lead to average errors which are similar to those of PBE or better. Likewise, atomization energies that are slightly better than from PBE are obtained from the modified vdW-DFs. Although the tests reported here are for hard solids, not normally materials for which dispersion forces are thought to be important, we find a systematic improvement in cohesive properties for the alkali metals and alkali halides when nonlocal correlations are accounted for.

  19. 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.

  20. Van der Waals coefficients beyond the classical shell model

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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 C6, SFA and CSM are exactly the same. The higher-order (C8 and C10) terms of the vdW expansion can be almost as important as the C6 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.

  1. 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 neglected, other astronomers? Before the chapter dealing with Aristoteles and other Greek thinkers, the author presents a very good introduction to prehistoric astronomy. Subsequent chapters cover medieval times (Sacrobosco), Copernicus, instruments (Apian), calendars and their makers, telescopes and theological conflicts, women in astronomy and celestial mechanics, "amateur" astronomers (Herschel and Bessel), philosophy and science (Kant and successors). "At the limits of knowledge" is the title of the last, somewhat scanty chapter on 20th century astronomy. The only confusing text is found on p. 43: Die exzentrische Lage der Spharen wurde von Hipparch im 2. Jahrhundert v. Chr. eingefuhrt. Cum grano salis, this is correct; Hipparchos assumed an eccentric orbit for the Sun. Furthermore, die Erde steht im Mittelpunkt des Deferenten, jedoch um den Betrag der Exzentrizitat E vom Mittelpunkt des Exzenters entfernt. A figure showing a deferent circle (and attached epicycle) with center M, and a lower point E called center of world = center of Earth in the caption, tries to illustrate this. The desperate reader does not find the eccenter in the figure, and also does not appreciate why the Earth is in the center of the deferent M when the caption says it is in E. The explanation is that for a planet, having two anomalies, the epicycle does not run on a concentric circle, usually called deferent, but on an eccenter. Thus, in the figure, the circle labelled deferent is the eccenter. In Cellarius' Harmonia Macrocosmica, Table 14, a similar figure explains it all: Eccentricus deferens epicyclum - the eccenter that carries around the epicycle. Since we have switched to Latin, we should mention that on p. 158, we encountered the sentence "in dubia pro res". Perhaps we are permitted to reply "si tacuisses, philosophus mansisses". The reader is cautioned: if this book is used as a road atlas for the history of astronomy, the reader will often find very rough sketches of the progress of astronomy, but from time to time a very detailed map of a very beautiful town or village will be encountered. This well-written and inspiring book can be recommended to everyone who wants to learn about astronomical history somewhat off the beaten track.

  2. Arzt und Hobby-Astronom in stĂŒrmischen Zeiten Der BĂŒchernachlass des Doktor Johannes HĂ€ringshauser, 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 HĂ€ringshauser“ als Besitzer seltener und interessanter astronomischer Werke u.a. von Johannes Regiomontan, Georg von Peuerbach, Michael MĂ€stlin, Johannes Kepler und Daniel Sennert. Weitere in den Jahren 2007-2009 durchgefĂŒhrte Nachforschungen ergaben, dass es sich um den von 1630-1641 in Mistelbach, Niederösterreich, als Landschaftsarzt tĂ€tigen Vater des Melker Konventualen und Bibliothekars Sigismund HĂ€ringshauser (1631-1698) handelt. Er wurde 1603 als Sohn des aus Magdeburg stammenden Apothekers Johannes HĂ€ringshauser geboren und starb 1642 in Mistelbach. Johannes HĂ€ringshauser Sen. bekleidete von 1613-1640 eine Reihe wichtiger Ämter in der Wiener Stadtregierung und starb 1647. Der Studienaufenthalt von Dr. Johannes HĂ€ringshauser Jun. in Padua (1624-1626) dĂŒrfte das Interesse fĂŒr Astronomie geweckt haben, das sich in seiner in die BestĂ€nde 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.

  3. SchlĂŒsselkomponenten fĂŒr Roboter in der Produktion Roboterhaut und Sicherheitskonzept fĂŒr 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 OberflĂ€che der Roboterhaut aufgebracht um Informationen ĂŒber die Umgebung sicher an ein ĂŒbergeordnetes Leitsystem zu ĂŒbertragen. Eine unterlagerte sichere Roboterhaut mit Kontaktdetektion zeigt als einfache SchlĂŒsselkomponente ein analoges Ausschaltverhalten fĂŒr geringe Latenzzeiten. Als Schluss wird auf den Einsatz an einem Industrieroboter in der Produktion ohne trennende Schutzeinrichtungen (OTS) eingegangen.

  4. 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 stÀrker von den Naturwissenschaften durchdrungen und abhÀngiger von ihnen als das 20. Jahrhundert" schreibt Eric Hobsbawn im Kapitel "Zauberer und Lehrlinge: Die Naturwissenschaften" seines Buches "Zeitalter der Extreme".

  5. Simulationsbasierte Optimierung in der Bautechnik — Neue Informatische Lösungskonzepte

    NASA Astrophysics Data System (ADS)

    Hartmann, Dietrich; Baitsch, Matthias; van Nguyen, Vinh

    Ingenieure sind — aufbauend auf grĂŒndlicher Planung, intelligentem Entwurf, solider Konstruktion und sorgfĂ€ltiger Herstellung — seit jeher bestrebt, "optimale“ technische Systeme zu entwickeln. Auch die Prozesse, die von Ingenieuren eingeleitet und verantwortet werden, sind in der Regel so ausgelegt, dass sie planmĂ€ĂŸig, zuverlĂ€ssig, hochgradig effizient und somit ebenfalls möglichst optimal ablaufen. Bei der Umsetzung ihrer Ideen mithilfe von leistungsfĂ€higen Computermodellen sowie gebrauchstauglicher Software sorgt die zielgerichtete Vernetzung mit der Forschung in Mathematik und Angewandter Informatik dafĂŒr, dass sowohl dringende aktuelle Problemstellungen gelöst als auch neue Zukunftsfelder in absehbarer Zeit erfolgreich bearbeitet werden können.

  6. van der Waals interaction between a microparticle and a single-walled carbon nanotube

    SciTech Connect

    Blagov, E. V.; Mostepanenko, V. M.; Klimchitskaya, G. L.

    2007-06-15

    The Lifshitz-type formulas describing the free energy and the force of the van der Waals interaction between an atom (molecule) and a single-walled carbon nanotube are obtained. The single-walled nanotube is considered as a cylindrical sheet carrying a two-dimensional free-electron gas with appropriate boundary conditions on the electromagnetic field. The obtained formulas are used to calculate the van der Waals free energy and force between a hydrogen atom (molecule) and single-walled carbon nanotubes of different radii. Comparison studies of the van der Waals interaction of hydrogen atoms with single-walled and multiwalled carbon nanotubes show that depending on atom-nanotube separation distance, the idealization of graphite dielectric permittivity is already applicable to nanotubes with only two or three walls.

  7. An Insight into LĂŒders Deformation Using Advanced Imaging Techniques

    NASA Astrophysics Data System (ADS)

    Nagarajan, Srinivasan; Narayanaswamy, Raghu; Balasubramaniam, Venkatraman

    2013-10-01

    An investigation to explore the feasibility of simultaneous application of infrared thermography (IRT) and digital image correlation (DIC) for analysis of LĂŒders deformation is carried out. Physical models and proposed concepts explaining the dynamics of deformation localization associated with LĂŒders band phenomenon addressing band-formation mechanism, inhomogeneity in stress-strain distribution across the band front, and strain localization following band front propagation are successfully correlated with the thermal and strain evolutions obtained using IRT and DIC. The studies revealed the potential of using these techniques simultaneously in providing an enhanced understanding of micro mechanisms involved in LĂŒders deformation based on associated macroscopic thermal and strain evolutions in a noncontact, nondestructive manner.

  8. Amerikas EinschÀtzung 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, verfĂŒgten ĂŒber sehr widersprĂŒchliche und großteils falsche Informationen ĂŒber den Fortschritt des deutschen Uranprogramms. Noch nach Kriegsende lĂ€sst sich dies an Aussagen des Leiters der amerikanischen Alsos-Mission, Samuel Goudsmit, festmachen. TatsĂ€chlich 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 PeenemĂŒnder Raketenprojekt.

  9. Quantum vacuum photon modes and repulsive Lifshitz-van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Dellieu, Louis; Deparis, Olivier; Muller, JérÎme; Kolaric, Branko; Sarrazin, Michaël

    2015-12-01

    The bridge between quantum vacuum photon modes and properties of patterned surfaces is currently being established on solid theoretical grounds. Based on these foundations, the manipulation of quantum vacuum photon modes in a nanostructured cavity is theoretically shown to be able to change the Lifshitz-van der Waals forces from attractive to repulsive regime. Since this concept relies on surface nanopatterning instead of chemical composition changes, it drastically relaxes the usual conditions for achieving repulsive Lifshitz-van der Waals forces. As a case study, the potential interaction energy between a nanopatterned polyethylene slab and a flat polyethylene slab with water as the intervening medium is calculated. Extremely small corrugation heights (<10 nm) are shown to be able to change the Lifshitz-van der Waals force from attractive to repulsive, the interaction strength being controlled by the corrugation height. This new approach could lead to various applications in surface science.

  10. 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.

  11. 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

    2016-01-01

    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

  12. Quantum synchronization of quantum van der Pol oscillators with trapped ions

    NASA Astrophysics Data System (ADS)

    Lee, Tony; Sadeghpour, Hossein

    2014-03-01

    Van der Pol oscillators are prototypical driven-dissipative oscillators that have been used to study synchronization phenomena in classical systems. We study the van der Pol oscillator in the quantum limit, when the oscillator is near the quantum ground state, and the behavior is sensitive to the quantization of energy levels. We consider four scenarios: one oscillator with and without an external drive, two coupled oscillators, and an infinite number of oscillators with global coupling. We find that phase-locking is much more robust in the quantum model than in the equivalent classical model. Trapped-ion experiments are ideally suited to simulate van der Pol oscillators in the quantum regime via sideband heating and cooling of motional modes. Phys. Rev. Lett. (in press), arXiv:1306.6359

  13. 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

  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

    2016-01-01

    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

  15. 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.

  16. Van der Waals interactions among alkali Rydberg atoms with excitonic states

    NASA Astrophysics Data System (ADS)

    Zoubi, Hashem

    2015-09-01

    We investigate the influence of the appearance of excitonic states on van der Waals interactions among two Rydberg atoms. The atoms are assumed to be in different Rydberg states, e.g., in the | {ns}> and | {np}> states. The resonant dipole-dipole interactions yield symmetric and antisymmetric excitons, with energy splitting that give rise to new resonances as the atoms approach each other. Only away from these resonances can the van der Waals coefficients, C6sp, be defined. We calculate the C6 coefficients for alkali atoms and present the results for lithium by applying perturbation theory. At short interatomic distances of several Ό {{m}}, we show that the widely used simple model of two-level systems for excitons in Rydberg atoms breaks down, and the correct representation implies multi-level atoms. Even though, at larger distances one can keep the two-level systems but in including van der Waals interactions among the atoms .

  17. P. A. M. Dirac und die BegrĂŒndung der relativistischen Quantentheorie

    NASA Astrophysics Data System (ADS)

    Rompe, Robert; Treder, Hans-JĂŒrgen

    Die Vereinigung von spezieller RelativitĂ€tstheorie und Quantentheorie fĂŒhrte zu neuen Vorstellungen ĂŒber das Vakuum, erklĂ€rte den Spin. Eine grundsĂ€tzliche Analyse zwischen beiden fundamentalen Theorien zeigt jedoch auch Inkonsistenzen, die nicht innerhalb der Quantenmechanik und RelativitĂ€tstheorie gelöst werden können. Sie sind mit der Frage verbunden: Warum ist der Kosmos so groß und sind die Atome so klein?.Translated AbstractP. A. M. Dirac and the Foundation of Relativistic Quantum TheoryThe unification of special relativity and quantum mechanics led to a new understanding of vacuum, declared the spin. A thorough analysis between both fundamental theories, however, shows inconsistencies too, unsolvable in the framework of quantum theory and theory of relativity. The are connected with the question: Why is cosmos so big and are atoms so small?.

  18. 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

  19. Nano-photonic phenomena in van der Waals heterostructures (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Basov, Dmitri N.

    2015-09-01

    van der Waals (vdW) crystals consist of individual atomic planes coupled by vdW interaction, similar to graphene monolayers in bulk graphite. We investigated van der Waals heterostructures assembled from atomically thin layers of graphene and hexagonal boron nitride (hBN). We launched, detected and imaged plasmonic, phonon polaritonic and hybrid plasmon-phonon polariton waves in a setting of an antenna based nano-infrared apparatus. Hyperbolic phonon polaritons in hBN enabled sub-diffractional focusing in infrared frequencies. Because electronic, plasmonic and phonon polaritonic properties in van der Waals heterstructures are intertwined, gate voltage and/or details of layer assembly enable efficient control of nano-photonic effects.

  20. Der p 11 Is a Major Allergen for House Dust Mite-Allergic Patients Suffering from Atopic Dermatitis

    PubMed Central

    Banerjee, Srinita; Resch, Yvonne; Chen, Kuan-Wei; Swoboda, Ines; Focke-Tejkl, Margit; Blatt, Katharina; Novak, Natalija; Wickman, Magnus; van Hage, Marianne; Ferrara, Rosetta; Mari, Adriano; Purohit, Ashok; Pauli, Gabrielle; Sibanda, Elopy N.; Ndlovu, Portia; Thomas, Wayne R.; Krzyzanek, Vladislav; Tacke, Sebastian; Malkus, Ursula; Valent, Peter; Valenta, Rudolf; Vrtala, Susanne

    2015-01-01

    House dust mites (HDMs) belong to the most potent indoor allergen sources worldwide and are associated with allergic manifestations in the respiratory tract and the skin. Here we studied the importance of the high-molecular-weight group 11 allergen from Dermatophagoides pteronyssinus (Der p 11) in HDM allergy. Sequence analysis showed that Der p 11 has high homology to paramyosins from mites, ticks, and other invertebrates. A synthetic gene coding for Der p 11 was expressed in Escherichia coli and rDer p 11 purified to homogeneity as folded, alpha-helical protein as determined by circular dichroism spectroscopy. Using antibodies raised against rDer p 11 and immunogold electron microscopy, the allergen was localized in the muscle beneath the skin of mite bodies but not in feces. IgE reactivity of rDer p 11 was tested with sera from HDM-allergic patients from Europe and Africa in radioallergosorbent test–based dot-blot assays. Interestingly, we found that Der p 11 is a major allergen for patients suffering from atopic dermatitis (AD), whereas it is only a minor allergen for patients suffering from respiratory forms of HDM allergy. Thus, rDer p 11 might be a useful serological marker allergen for the identification of a subgroup of HDM-allergic patients suffering from HDM-associated AD. PMID:24999597

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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

  7. Efficacies of immunotherapy with polypeptide vaccine from ProDer f 1 in asthmatic mice

    PubMed Central

    Li, Chaopin; Li, Qiuyu; Jiang, Yuxin

    2015-01-01

    Allergic asthma is associated with the major house dust mite group 1 allergens Der p 1 and Der f 1, which belongs to the papin-like protease family and is the most potent of indoor allergens and allergen-specific immunotherapy (SIT), is seen as effective intervention for the entity. The current study was designed to verify the SIT efficacies of the enzymatic hydrolysates (papain and trypsin) in mice with asthma. We initially developed the asthmatic mouse models with ProDer f 1, and respectively applied recombinant ProDer f 1 protein and the two kinds of enzymatic hydrolysates for SIT. The results were verified by measuring the contents of IL-4, IL-10, IL-17 and IFN-Îł changed in both bronchoalveolar lavage fluid (BALF) and supernatant of splenocyte culture as well as level changes of specific IgE and IgG2a in the serum. After SIT intervention, the symptoms of allergic inflammation was alleviated significantly in mice treated with ProDer f 1 protein and the two enzymatic hydrolysates via detection of the lung tissue sections, and infiltration of inflammatory cells was also notably depressed as compared with the models, though the epithelial structure in airways remained similar with the PBS group. In addition, we observed lower serum contents of the specific IgE antibody and lower levels of IL-4, IL-17 in BALF and splenic cells in mice undergone SIT, whereas specific IgG2a, IFN-Îł and IL-10 in BALF and supernatant of splenocyte culture were higher as compared to the asthma group. The findings suggest the SIT using the above two kinds of hydrolysates may effectively inhibit the allergic inflammation in the airways of mouse models sensitized with ProDer f 1 protein. PMID:25932130

  8. Anwendung von Methoden der Logistik und Netzplantechnik zur prÀzedenz- und ressourcenbeschrÀnkten Ablaufplanung von Echtzeitsystemen

    NASA Astrophysics Data System (ADS)

    Gumzej, Roman; Lipičnik, Martin

    Grundlegende ZusammenhĂ€nge zwischen Logistik, Netzplantechnik und Echtzeit sowie den zugehörigen Arten der Ablaufplanung und ihrer Nutzung werden dargestellt. Das Echtzeitprinzip beinhaltet Rechtzeitigkeit von AblĂ€ufen, wobei es fĂŒr eine frĂŒhzeitige Beendigung eines Ablaufs keinen Bonus gibt; im Gegensatz zum verspĂ€teten Ablauf, dessen Konsequenzen in der Regel negativ und unabschĂ€tzbar sind. Das Just-in-Time-Prinzip gleicht dem der Echtzeit und wird vor allem in der Logistik zur Bezeichnung reibungsloser AblĂ€ufe in Beschaffungsketten verwendet. In der Netzplantechnik werden die kritischen AktivitĂ€ten binnen eines Projektes bestimmt, die nicht verzögert werden dĂŒrfen, um das Projekt rechtzeitig zu beenden. Außerdem haben die drei Bereiche noch eine Gemeinsamkeit: um realistische Ablaufszenarien darzustellen, mĂŒssen in den Analysen auch begrenzte Ressourcen angemessen berĂŒcksichtigt werden.

  9. Innovation im Mittelstand am Beispiel Der Senkung Von MobilitÀtskosten Durch Schwarmintelligenz"

    NASA Astrophysics Data System (ADS)

    Fischer, Hieronymus

    Die zunehmende Vernetzung von Einzelsystemen im Fahrzeug wird durch den Einsatz weiterer Kommunikationsverbindungen (CAR2X-Kommunikation) zu einer hierarchischen Struktur fĂŒhren, die den Austausch von Informationen zwischen einer Vielzahl von verteilten heterogenen Subsystemen auf mobilen und stationĂ€ren Plattformen ermöglicht. Die primĂ€ren Ziele einer solchen Vernetzung von Cyber-Physical Systems sind die Bereitstellung neuer Dienste im Fahrzeug, die Erhöhung der Verkehrssicherheit sowie die effektive Steuerung der weiter wachsenden Verkehrsströme.

  10. 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.

  11. 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

    2012-02-01

    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. PMID:22157726

  12. 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.

  13. Effect of van der Waals interaction on the mode I fracture characteristics of graphene sheet

    NASA Astrophysics Data System (ADS)

    Parashar, Avinash; Mertiny, Pierre

    2013-11-01

    In this paper a study has been performed to investigate the effect of van der Waals interaction forces on the mode I (opening mode) fracture characteristics of a graphene sheet. Finite element based atomistic approach was employed to perform the investigation, where graphene structure was assumed to behave like a space frame structure. Few graphene sheets were modeled in finite element environment with different set of interlayer spacing. Modified virtual crack closure technique (VCCT) was employed to estimate the strain energy release rate (SERR) under mode I of fracture criteria. Significant effect of van der Waals forces was observed on the mode I fracture characteristics of graphene.

  14. Das Zweikörperproblem in der quantisierten, trÀgheitsfreien Mechanik

    NASA Astrophysics Data System (ADS)

    Kreisel, E.

    Es existieren keine gebundenen ZustÀnde des Zweiteilchensystems in der Riemann-Machschen Quantenmechanik. Das Energie-Spektrum ist notwendig positiv semidefinit und kontinuierlich, in Analogie zum freien Teilchen der Quantenmechanik.Translated AbstractThe Two-Body-Problem in Quantized, Inertia-Free MechanicsThere do not exist bound states of the two-particle-system in Riemann-Machian quantum mechanics. The spectrum of the energy is necessarily positively semidefinite and continuous, in analogy to the free particle of quantum mechanics.

  15. On Attempting to Do What Lord Said Was Impossible: Commentary on van der Linden's "Some Conceptual Issues in Observed-Score Equating"

    ERIC Educational Resources Information Center

    Dorans, Neil J.

    2013-01-01

    van der Linden (this issue) uses words differently than Holland and Dorans. This difference in language usage is a source of some confusion in van der Linden's critique of what he calls equipercentile equating. I address these differences in language. van der Linden maintains that there are only two requirements for score equating. I maintain


  16. Effect of van der Waals interaction on Raman transitions. II

    NASA Astrophysics Data System (ADS)

    Linder, Bruno; Kromhout, Robert A.

    Study of the effect of van der Waals interaction on Raman transitions, begun in a previous paper [R. A. Kromhout and B. Linder, 1987, Molec. Phys., 62, 689] is extended to include the effect of a solid. This necessitates extending the time-dependent perturbation treatment of the transition dipole moment to include third order perturbation. A general expression is developed for the transition dipole of a molecule A, whose initial and final states are nonpolar, perturbed by a nonpolar molecular system B, which may be a single molecule or a collection of molecules as in a solid. The theory is formulated in terms of ordinary and transition (Raman) charge-density susceptibilities and hyper-susceptibilities of the isolated subsystems A and B, interacting through the full (unexpanded) Coulomb potential, which allows for charge interpenetration (overlap). Connection with the dielectric function of a slab is made through the T-tensor expansion of the Coulomb potential, neglecting overlap, which yields an expression for the transition dipole moment in terms of the dielectric properties of the slab, the transition third order hyperpolarizabilities, γba (quadrupole-dipole polarizability), and Gba (the quadrupole-triple-dipole polarizability); the transition first order polarizabilities, αba, (the dipole-dipole polarizability) and Aba (the quadrupole-dipole polarizability) and the ordinary polarizabilities αaa, Aaa, Abb, and αbb of the initial and final states of molecule A. It is shown that the γba and Gba terms describe the effect of dispersion interaction, and that the terms associated with αba and Aba are polarization terms describing the effect of induction. Rough numerical estimates are made of the allowed and forbidden Raman transitions of benzene on a flat silver surface and it is concluded that our theory provides a possible mechanism for the forbidden α2u vibration at 673 cm-1 to become allowed. Comparison is made of our results with theories of electromagnetic enhancement contributions to SERs. The dispersion type terms are lacking in the classical electromagnetic treatments of surface enhanced Raman transitions. Unlike the DID (dipole-induced dipole) terms, the dispersion and Aba polarization terms contribute even for forbidden transitions.

  17. 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 peak demand, in turn, may lower a distribution system peak load such that upgrades are deferred or avoided. This could benefit other consumers by providing them with higher reliability and power quality as well as avoiding their cost share of a distribution system upgrade. In this example, the costs of the DER may be born by the end user, but that user reaps only a share of the benefits. This report, the first product of a study to quantify the value of DER, documents initial project efforts to develop an assessment methodology. The focus of currently available site-specific DER assessment techniques are typically limited to two parties, the owner/user and the local utility. Rarely are the impacts on other stakeholders, including interconnected distribution utilities, transmission system operators, generating system operators, other local utility customers, local and regional industry and business, various levels of government, and the environment considered. The goal of this assessment is to quantify benefits and cost savings that accrue broadly across a region, recognizing that DER installations may have local, regional, or national benefits.

  18. „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 StaatenbĂŒndnis ist es nach weitgehend ĂŒbereinstimmender Auffassung von Politik und Wissenschaft zu danken, dass der "Kalte Krieg" in der zweiten HĂ€lfte des 20. Jahrhunderts nicht zum weltumfassenden FlĂ€chenbrand eskalierte. An der raschen Herstellung dieses Patts waren zwei Dresdner Physiker maßgeblich beteiligt, deren einer im Manhattan-Projekt in den USA gearbeitet hatte und spĂ€ter in England der Spionage fĂŒr die Sowjetunion und des Verrats des Know-how der Atombombe ĂŒberfĂŒhrt wurde.

  19. 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…

  20. Characterization of a new subtype of allergen in dermatophagoides farinae—Der f 28

    PubMed Central

    Lin, Jian-Li; Wang, Yuan-Yuan; Xiao, Xiao-Jun; Wu, Yu-Lan; Sun, Bao-Qing; Gao, An-Jian; Liu, Zhi-Gang

    2015-01-01

    Background House dust mites (HDMs) are the major sources of indoor allergens which induce asthma, dermatitis, rhinitis, and some other allergic diseases. Close to 30 sub-allergens have been identified. Methods Through analyzing the full genome sequence of dust mite, a new allergen whose primary structure belongs to the heat shock protein family was identified. The sequence of this allergen was determined by cDNA cloning. The allergenicity was assayed by skin prick test, Western-blot and enzyme-linked immunosorbent assay (ELISA). Results r-Der f 28 bound to serum IgE from mite allergic patients. Positive responses to r-Der f 28 were shown in 11.5% by skin prick testing from 26 DM-allergic patients. Airway hyperresponsiveness, serum specific IgE and IL-4 were significantly increased in allergic asthma mouse model sensitized to r-Der f 28. Conclusions Der f 28 is a new subtype of allergen in dermatophagoides farinae. PMID:26623108

  1. 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


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

    PubMed

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

    2016-03-01

    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. PMID:26885874

  3. Read the Book or Watch the Movie? "Der Richter und sein Henker" at the Intermediate Level.

    ERIC Educational Resources Information Center

    Hamilton, Elizabeth C.

    2002-01-01

    Examines the debate over the text or media that best enable second-year learners of German to increase their active vocabulary. Suggests the novel "Der Richter und sein Henker" can be enriched by the film adaptation. Classroom tested activities incorporate care fully-sequenced visuals and culminate in analysis of both the book and the film. Sample…

  4. 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. PMID:25689488

  5. 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.

  6. 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.

  7. Regelungen im Verkehr mit Lebensmitteln und BedarfsgegenstÀnden in der EU

    NASA Astrophysics Data System (ADS)

    Riemer, Boris

    Die EG hat die Errichtung eines Binnenmarktes zum Ziel. Dieser ist dadurch geprĂ€gt, dass keine Hindernisse fĂŒr den freien Warenverkehr zwischen den Mitgliedstaaten bestehen. Notwendig ist dazu u. a. die Angleichung der innerstaatlichen Rechtsvorschriften. Bezogen auf das Lebensmittelrecht sind die Ziele eines verbesserten Verbraucherschutzes und eines hohen Gesundheitsschutzes zu beachten.

  8. Von Tondern nach Gotha. Der Astronom Peter Andreas Hansen, 1795 - 1874.

    NASA Astrophysics Data System (ADS)

    Strumpf, M.; Pehlemann, E.; Wolfschmidt, G.

    This companion booklet to an exposition in honor of Peter Andreas Hansen's 200th birthday contains three papers. Contents: 1. Peter Andreas Hansen - Leben und Wirken in Gotha (M. Strumpf). 2. Peter Andreas Hansens wissenschaftliches Werk (E. Pehlemann). 3. Beobachtungsinstrumente der Sternwarte Gotha zur Zeit Hansens (G. Wolfschmidt).

  9. Leistungsmessungen zum Einsatz der J2EE Technologie fĂŒr Feldbussimulationen

    NASA Astrophysics Data System (ADS)

    Garreis, Thorsten; JĂŒrgens, 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. DarĂŒber hinaus können mit Simulationen alternative Lösungen studiert werden, die zu optimierten Verfahren fĂŒhren. In dieser Arbeit werden Leistungstests an der Simulationsumgebung drd-Simulator prĂ€sentiert, die auf der J2EE-Technologie1 basiert. FĂŒr die Messungen wird eine Soft-SPS eingesetzt, deren Feldbus vom Typ ModbusTCP simuliert wird. Erste Messungen zeigen, dass J2EE eine leistungsstarke und skalierbare Plattform fĂŒr die Realisierung von Feldbussimulationen ist. In einem Zyklusbereich ab 100 ms ist das E/A-Verhalten echtzeitfĂ€hig, 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 ergĂ€nzt oder verĂ€ndert werden können.

  10. 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)

  11. Approximating the 3D Character of a Van Der Waals Atom-Solid Potential

    NASA Astrophysics Data System (ADS)

    Bruch, L. W.

    2016-04-01

    A truncated Fourier decomposition of the atom-substrate potential energy is developed for three-dimensional models of van der Waals systems, specifically for adsorption on the basal plane surface of graphite or the (111) face of a face-centered-cubic lattice. This provides a framework for analysis of a priori calculations of physical adsorption energies.

  12. 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


  13. Read the Book or Watch the Movie? "Der Richter und sein Henker" at the Intermediate Level.

    ERIC Educational Resources Information Center

    Hamilton, Elizabeth C.

    2002-01-01

    Examines the debate over the text or media that best enable second-year learners of German to increase their active vocabulary. Suggests the novel "Der Richter und sein Henker" can be enriched by the film adaptation. Classroom tested activities incorporate care fully-sequenced visuals and culminate in analysis of both the book and the film. Sample


  14. Comments on "Some Conceptual Issues in Observed-Score Equating" by Wim J. van der Linden

    ERIC Educational Resources Information Center

    Bradlow, Eric T.

    2013-01-01

    The van der Linden article (this issue) provides a roadmap for future research in equating. My belief is that the roadmap begins and ends with collecting auxiliary data that can be utilized to provide improved equating, especially when data are sparse or equating beyond simple moments is desired.

  15. Comments on van der Linden's Critique and Proposal for Equating

    ERIC Educational Resources Information Center

    Holland, Paul W.

    2013-01-01

    While agreeing with van der Linden (this issue) that test equating needs better theoretical underpinnings, my comments criticize several aspects of his article. His examples are, for the most part, worthless; he does not use well-established terminology correctly; his view of 100 years of attempts to give a theoretical basis for equating is


  16. Bridging the Gap: A Literacy-Oriented Approach to Teaching the Graphic Novel "Der erste Fruhling"

    ERIC Educational Resources Information Center

    Bridges, Elizabeth

    2009-01-01

    This article examines the phenomenon of graphic novels generally, and in particular, their utility in second-language contexts via the example of the graphic adaptation of Klaus Kordoris "Der erste Fruhling." This text lends itself especially to bridging thematic gaps in 20th-century German literature courses, as well as the "language/literature…

  17. 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 ÎČ-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.

  18. Cell-Penetrating Peptide Derived from Human Eosinophil Cationic Protein Inhibits Mite Allergen Der p 2 Induced Inflammasome Activation

    PubMed Central

    Yu, Sheng-Jie; Liao, En-Chih; Tsai, Jaw-Ji

    2015-01-01

    Newly discovered cell penetration peptides derived from human eosinophil cationic proteins (CPPecp) have the characteristic of cell internalization, but the effect of CPPecp on immunomodulation has not been clarified. House dust mite (HDM) major allergen, Der p 2, can induce proinflammatory cytokine production which contributes to airway inflammation and allergic asthma. However, the mechanism of Der p 2 on NLRP3 inflammasome activation remains unclear. The aim of this study was to investigate the immunomodulatory effect of CPPecp on inhibition of Der p 2 induced inflammasome activation. We showed that proinflammatory cytokines IL-1ÎČ, IL-6 and IL-8 were significantly upregulated in peripheral blood mononuclear cells (PBMCs) derived from HDM allergic patients after Der p 2 stimulation. Expression of NLRP3, ASC, Caspase-1, IL-1ÎČ and Caspase-1 activity was upregulated in THP-1 cells after Der p 2 stimulation. Proinflammatory cytokine production, NLRP3 inflammasome activation and caspase-1 activity were downregulated in THP-1 cells and CD14+ cells co-cultured with Der p 2 and CPPecp. The immunomodulatory effect of CPPecp was through upregulation of IFN-α production but not induction of autophagy. These results suggested Der p 2 plays an important role in NLRP3 inflammasome activation and CPPecp has the potential to be a novel anti-inflammatory agent for allergic inflammation treatment in the future. PMID:25807144

  19. Band gap engineering of a soft inorganic compound PbI2 by incommensurate van der Waals epitaxy

    NASA Astrophysics Data System (ADS)

    Wang, Yiping; Sun, Yi-Yang; Zhang, Shengbai; Lu, Toh-Ming; Shi, Jian

    2016-01-01

    Van der Waals epitaxial growth had been thought to have trivial contribution on inducing substantial epitaxial strain in thin films due to its weak nature of van der Waals interfacial energy. Due to this, electrical and optical structure engineering via van der Waals epitaxial strain has been rarely studied. In this report, we show that significant band structure engineering could be achieved in a soft thin film material PbI2 via van der Waals epitaxy. The thickness dependent photoluminescence of single crystal PbI2 flakes was studied and attributed to the substrate-film coupling effect via incommensurate van der Waals epitaxy. It is proposed that the van der Waals strain is resulted from the soft nature of PbI2 and large van der Waals interaction due to the involvement of heavy elements. Such strain plays vital roles in modifying the band gap of PbI2. The deformation potential theory is used to quantitatively unveil the correlation between thickness, strain, and band gap change. Our hypothesis is confirmed by the subsequent mechanical bending test and Raman characterization.

  20. Analysis of T-cell epitopes of Der f3 in Dermatophagoides farina

    PubMed Central

    Li, Na; Xu, Haifeng; Song, Hongyu; Wang, Kexia; Li, Chaopin

    2015-01-01

    House dust mites (HDM) are most important indoor allergens for humans. Der f3, one of the potent allergens with allergenicity, is derived from Dermatophagoides farina (D. farinae), and exhibits strong allergenicity that was confirmed in our previous work. The current study was undertaken to determine the localization of T-cell epitope of Der f3. We initially developed the T-cell fraction from BALB/c mice sensitized with recombinant Der f3 to determine the T-cell epitopes in the murine models, and performed T cell proliferation assay with 25 synthetic overlapping peptides of Der f3. The results indicated that T-cell reactive region of murine were assigned on amino acid range 41-60, 101-120, 161-180 and 201-220, respectively. In addition, we did T-cell proliferation experiment, respectively using the 4 murine T-cell epitope peptide and the human T-cell lines from three patients allergic to mite allergens in order to verify homogenous T-cell epitopes in humans. The results indicated that the amino acid sequences of 41-60, 101-120 and 161-180 had induced T cell proliferation in humans, yet 201-220 failed to. These findings suggest that T-cell epitope in Der f3 is located in the amino acid sequences of 41-60, 101-120 and 161-180, respectively. T-cell epitope localization detected in our study may provide a basis for development of animal therapeutic model and peptide vaccine for asthma. PMID:25755700

  1. 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.

  2. Ökophysik: Plaudereien ĂŒber 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 UniversitĂ€t des Saarlandes in SaarbrĂŒcken. 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 StabilitĂ€t beispielsweise der GrĂ€ser erarbeitet. Lebewesen ĂŒberraschen immer wieder durch ihre "BiodiversitĂ€t", 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

    NASA Astrophysics Data System (ADS)

    Gascooke, Jason R.; Lawrance, Warren D.

    2013-02-01

    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. Über die Möglichkeit der Zustandsvoraussage chaotischer Systeme

    NASA Astrophysics Data System (ADS)

    Leven, R. W.; Pompe, B.

    Deterministische chaotische Systeme reagieren empfindlich auf Störungen ihrer Bewegung. Kennt man im speziellen den Anfangszustand des Systems nicht exakt, so ist eine Voraussage ĂŒber das zukĂŒnftige Verhalten des Systems nur beschrĂ€nkt möglich. Die Transformation IT gibt an, wieviel Information man ĂŒber einen zukĂŒnftigen Zustand hat, wenn man den Anfangszustand mit einer bestimmten Genauigkeit kennt.In dieser Arbeit werden weitere mögliche Interpretationen von IT in Hinblick auf die Beschreibung dynamischer Systeme gegeben. FĂŒr zwei einfache eindimensionale Abbildungen wird IT in AbhĂ€ngigkeit von der Zeit der Voraussage (l) bestimmt: Ein System, das durch die BERNOULLI-Abbildung beschrieben wird, vergißt nach der ersten Iteration 1 bis 1,5 bit von seinem Anfangszustand. VollstĂ€ndiges Vergessen tritt jedoch i. allg. erst fĂŒr l ein. Bei der Logistik-Abbildung vergißt das System seinen Anfangszustand schneller, wenn der Grad des Chaos (d. h. der LJAPUNOV-Exponent) oder die Ă€ußeren Störungen zunehmen.Translated AbstractOn the Possibility of State Prediction of Chaotic SystemsDeterministic chaotic systems show a sensitive response to perturbations of their motion. In particular, if one has not exact knowledge about the initial state of the system, limits are set to the prediction of the system's future behaviour. The transinformation IT is the information obtainable about a future state, if one knows the initial state within a certain precision. In this paper further possible interpretations of IT are given with regard to the description of dynamic systems. IT is determined for different times of prediction (l) in the case of two simple one-dimensional maps: A system described by the BERNOULLI-map forgets after the first iteration 1 to 1.5 bit of its initial state. Nevertheless, in general we have complete loss of memory only for l . In the case of the logistic map the system forgets its initial state faster, if the degree of chaos (i.e. the LYAPUNOV characteristic exponent) or the extrinsic perturbations are increased.

  6. 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

    2014-12-01

    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. PMID:26583215

  7. IntegraTUM Teilprojekt Verzeichnisdienst: Identity & Access Management als technisches RĂŒckgrat der Hochschul-IuK-Infrastruktur

    NASA Astrophysics Data System (ADS)

    Boursas, Latifa; Ebner, Ralf; Hommel, Wolfgang; Knittl, Silvia; Pluta, Daniel

    Als zentrales technisches Teilprojekt konzipiert, implementiert und betreibt Teilprojekt (TP) Verzeichnisdienst ein hochschulweites Identity & Access Management (I&AM) System, das eine Vielzahl daran angebundener Systeme und IT-Dienste mit aktuellen, autoritativen Daten ĂŒber alle fĂŒr sie relevanten Benutzer der TUM versorgt. Dabei wurden sowohl auf andere Hochschulen ĂŒbertragbare Architekturen und Werkzeuge geschaffen als auch eine sehr prĂ€zise auf die Prozesse und Anforderungen der TUM abgestimmte Instanz realisiert, die auf Basis der im sehr erfolgreichen praktischen Betrieb gewonnenen Erfahrungen kontinuierlich verbessert und weiterentwickelt wurde. In diesem Artikel werden die Zielsetzung des Teilprojekts, die technische Architektur des I&AMSystems, ausgewĂ€hlte Aspekte der Hochschul-Prozessintegration, Implementierungs-, Migrations- und Betriebsaspekte sowie die umfassenden AktivitĂ€ten zum Know-How-Transfer von TP Verzeichnisdienst vorgestellt.

  8. GrundsĂ€tze ĂŒber die Anlagen neuer Sternwarten mit Beziehung auf die Sternwarte der UniversitĂ€t Göttingen. Von Georg Heinrich Borheck

    NASA Astrophysics Data System (ADS)

    Beuermann, Klaus; Borheck, Georg Heinrich

    Die Göttinger Sternwarte, WirkungsstĂ€tte des berĂŒhmten Gelehrten Carl Friedrich Gauß, ist ein bedeutendes Baudenkmal. Im Jahre 2005 wird sie gemeinsam von der Georg-August-UniversitĂ€t und der Akademie der Wissenschaften zu Göttingen renoviert, um dann als reprĂ€sentatives GebĂ€ude der UniversitĂ€t und ArbeitsstĂ€tte der Akademie zu dienen. Die Nutzung der historischen RĂ€ume fĂŒr Ausstellungen macht diesen imposanten Bau erstmals der Öffentlichkeit zugĂ€nglich. Die Sternwarte war bei ihrer Errichtung vor 200 Jahren ein nach seinerzeit neuesten wissenschaftlichen Erkenntnissen konzipierter Bau, der die UniversitĂ€t Göttingen in eine der vordersten Stellen Europa rĂŒckte. Auch aufgrund ihrer Architektur ist sie ein großer Wurf des Göttinger UniversitĂ€tsbaumeisters Georg Heinrich Borheck. Durch die Kriegswirren der Napoleonischen Zeit zerschlug sich Borhecks Versuch einer Publikation seiner Beschreibung des Baus der Göttinger Sternwarte 1805. Doch seine Schrift ist auch heute noch aktuell und wird mit diesem Band erstmals einer breiten Öffentlichkeit zugĂ€ngig gemacht. Er zeigt die GrundsĂ€tze, nach denen damals öffentliche Bauten konzipiert wurden, erlĂ€utert die Bedeutung des Baus aus kunst- und wissenschaftshistorischer Sicht und informiert ĂŒber die PlĂ€ne zur Restaurierung der Sternwarte in einem separaten Beitrag und im Geleitwort des PrĂ€sidenten der Georg-August UniversitĂ€t Prof. Dr. Dr. h. c. Kurt von Figura.

  9. Wirkungen biogener Amine auf die Erregungs-Sekretions-Kopplung in der SpeicheldrĂŒse 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 SpeicheldrĂŒse der Schabe Periplaneta americana (L.) untersucht. Die SpeicheldrĂŒse ist von dopaminergen und serotonergen Fasern innerviert (Baumann et al., 2002). Beide Transmitter stimulieren eine unterschiedliche Reaktion der DrĂŒse: Dopamin (DA) stimuliert die P-Zellen der Acini und die AusfĂŒhrgangzellen, wĂ€hrend Serotonin (5-HT) die P- und C-Zellen der Acini stimuliert, nicht jedoch die AusfĂŒhrgangzellen. Der Endspeichel ist nach einer DA-Stimulierung proteinfrei. Dagegen enthĂ€lt 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 FlĂŒssigkeitssekretion gemessen. Damit wollte ich klĂ€ren, welche Transporter an der Sekretion des PrimĂ€rspeichels und an dessen Modifikation beteiligt sind. Ausserdem wollte ich die Rolle der transportaktiven Epithelzellen der AusfĂŒhrgĂ€nge fĂŒr die Modifikation des PrimĂ€rspeichels untersuchen. DafĂŒr habe ich einen Vergleich der Elektrolytkonzentrationen im DA- und 5-HT-stimulierten Endspeichel durchgefĂŒhrt. Der Elektrolytgehalt des DA- und 5-HT-stimulierten Endspeichels unterscheidet sich nicht signifikant voneinander. Er ist nach beiden Stimulierungen hypoosmotisch zum verwendeten Ringer. Die AusfĂŒhrgangzellen werden durch DA stimuliert und modifizieren den PrimĂ€rspeichel durch eine netto-Ionenreabsorption. Meine Versuche zeigen jedoch, dass auch die wĂ€hrend einer 5-HT-Stimulierung der DrĂŒse unstimulierten AusfĂŒhrgangzellen den PrimĂ€rspeichel 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 FlĂŒssigkeitssekretion sowie den Elektrolytgehalt des Endspeichels untersucht. Ich habe gefunden, dass die AktivitĂ€t der Na+-K+-ATPase wichtig fĂŒr die Modifikation des DA-stimulierten PrimĂ€rspeichels ist. Im Gegensatz dazu ist sie fĂŒr die Modifikation des 5-HT-stimulierten PrimĂ€rspeichels nicht von Bedeutung. BezĂŒglich der FlĂŒssigkeitssekretion habe ich keinen Einfluss der Na+-K+-ATPase-AktivitĂ€t auf die DA-stimulierten Sekretionsraten gefunden, dagegen ist die 5-HT-stimulierte Sekretionsrate in Anwesenheit von Ouabain gesteigert. Die AktivitĂ€t des NKCC ist fĂŒr beide sekretorische Prozesse, die Ionen- und die FlĂŒssigkeitssekretion, wichtig. Eine Hemmung des NKCC bewirkt eine signifikante Verringerung der Raten der FlĂŒssigkeitssekretion nach DA- und 5-HT-Stimulierung sowie in beiden FĂ€llen einen signifikanten Abfall der Ionenkonzentrationen im Endspeichel. Im zweiten Teil meiner Arbeit habe ich versucht, Änderungen der intrazellulĂ€ren Ionenkonzentrationen in den Acinuszellen wĂ€hrend einer DA- oder 5-HT-Stimulierung zu messen. Diese Experimente sollten mit der Methode des "ratiometric imaging" durchgefĂŒhrt werden. Messungen mit dem Ca2+-sensitiven Fluoreszenzfarbstoff Fura-2 zeigten keinen globalen Anstieg in der intrazellulĂ€ren Ca2+-Konzentration der P-Zellen. Aufgrund von Problemen mit einer schlechten Beladung der Zellen, einer starken und sich wĂ€hrend der Stimulierung Ă€ndernden Autofluoreszenz der Zellen sowie Änderungen im Zellvolumen wurden keine Messungen mit Na+- und K+-sensitiven Fluoreszenzfarbstoffen durchgefĂŒhrt. Im dritten Teil dieser Arbeit habe ich die intrazellulĂ€ren Signalwege untersucht, die zwischen einer 5-HT-Stimulierung der DrĂŒse und der Proteinsekretion vermitteln. Dazu wurde der Proteingehalt im Endspeichel biochemisch mittels eines modifizierten Bradford Assay gemessen. Eine erstellte Dosis-Wirkungskurve zeigt, dass die Rate der Proteinsekretion von der zur Stimulierung verwendeten 5-HT-Konzentration abhĂ€ngt. In einer Serie von Experimenten habe ich die intrazellulĂ€ren Konzentrationen von Ca2+, cAMP und / oder cGMP erhöht und anschließend den Proteingehalt im Endspeichel gemessen. Ein Anstieg der intrazellulĂ€ren Ca2+-Konzentration aktiviert nur eine geringe Rate der Proteinsekretion. Dagegen kann die Steigerung der intrazellulĂ€ren cAMP-Konzentration eine stĂ€rkere Proteinsekretion aktivieren, die sich nicht signifikant von der nach 5-HT-Stimulierung unterscheidet. Die cAMP-stimulierte Proteinsekretion kann durch gleichzeitige Erhöhung der intrazellulĂ€ren Ca2+-Konzentration weiter gesteigert werden. Dagegen aktivierte eine Erhöhung der intrazellulĂ€ren cGMP-Konzentration die Proteinsekretion nicht. Aufgrund dieser Ergebnisse postuliere ich die Existenz eines die Adenylatcyclase aktivierenden 5-HT-Rezeptors in der Basolateralmembran der C-Zellen. The aim of this PhD-work was to investigate major mechanisms of excitation-secretion coupling in the salivary gland of the cockroach Periplaneta americana (L.). This salivary gland is innervated by dopaminergic and serotonergic fibres (Baumann et al., 2002). The two transmitters stimulate different processes in the gland: Dopamine (DA) stimulates the p-cells of the acini and the salivary duct cells, whereas 5-HT (serotonin) activates the p- and the c-cells of the acini, but not the salivary duct cells. Final saliva is completely protein-free after dopamine stimulation. It contains proteins, which are secreted by the c-cells of the acini, after a 5-HT-stimulation (Just & Walz, 1996). In the first part of my work I measured the electrolytic composition of the final saliva by capillary electrophoretic analysis and measured the rates of fluid secretion, in order to answer the following questions: 1.) Which transporters affect the production of primary saliva and its modification? 2.) What is the function of the transport-active salivary duct cells for the modification of the primary saliva? Electrolytic composition of the DA- and 5-HT-stimulated final saliva is not significantly different from each other, and is hypoosmotic to the Ringer used. Salivary duct cells are stimulated by DA and modify the primary saliva by a netto ion-reabsorption. My experiments also show that the duct cells, which are unstimulated during a 5-HT-stimulation of the gland, modify the primary saliva. In the next series of experiments I investigated the effects of ouabain, an inhibitor of the Na+-K+-ATPase, and bumetanide, an inhibitor of the NKCC on the rates of fluid secretion and the electrolytic composition of the final saliva. I found, that the activity of the Na+-K+-ATPase is important for the modification of DA-stimulated primary saliva during its flow through the stimulated duct system. In contrast, it is not important for modification of the 5-HT-stimulated primary saliva. Inhibition of the Na+-K+-ATPase does not affect rates of DA-stimulated fluid secretion, but it increases the rates of 5-HT-stimulated fluid secretion. Activity of the NKCC is important for both secretory processes: the ion and the fluid secretion. Inhibition of the NKCC results in a significant drop in the rates of fluid secretion after DA- and 5-HT-stimulation, as well as a drop in electrolytic concentrations in the saliva. In the second part of my work, I tried to measure changes in the intracellular ionic concentrations (Ca2+, Na+, and K+) within the acinar cells during a DA- or 5-HT-stimulation. The experiments should be performed by ratiometric imaging. Measurements with the Ca2+-sensitive dye Fura-2 did not show any global increase in the intracellular Ca2+-concentration in the p-cells of the acini. Problems concerning a bad loading of the cells, a strong autofluorescence which changed during the time course of the stimulation, as well as changes in the cell volume were the reason, that no measurements using Na+- or K+-sensitive dyes were performed. In the third part of my work I investigated the intracellular signalling pathways, which activate protein secretion after 5-HT-stimulation of the gland. A modified Bradford Assay was used for measuring the protein content in the final saliva. In a dose-response curve I showed that rates of protein secretion are dependent on the 5-HT-concentrations used to stimulate the glands. In another set of experiments I increased the intracellular concentrations of Ca2+, cAMP and / or cGMP, and measured the protein content in the final saliva. An increase in the intracellular Ca2+-concentration activates only a low rate of protein secretion. After an increase in the intracellular cAMP-concentration a much higher rate of protein secretion can be activated, which is not significantly different from the 5-HT stimulated rate of protein secretion. The cAMP-stimulated protein secretion can be further increased by a simultaneous rise in the intracellular Ca2+-concentration. In contrast, cGMP does not activate protein secretion. Therefore I propose the expression of an adenylyl cyclase activating 5-HT-receptor in the basolateral membrane of the protein secreting c-cells.

  10. 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

    2016-03-01

    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. PMID:26899350

  11. 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.

  12. Nonlocal van der Waals functionals: the case of rare-gas dimers and solids.

    PubMed

    Tran, Fabien; Hutter, JĂŒrg

    2013-05-28

    Recently, the nonlocal van der Waals (vdW) density functionals [M. Dion, H. Rydberg, E. Schröder, D. C. Langreth, and B. I. Lundqvist, Phys. Rev. Lett. 92, 246401 (2004)] have attracted considerable attention due to their good performance for systems where weak interactions are important. Since the physics of dispersion is included in these functionals, they are usually more accurate and show less erratic behavior than the semilocal and hybrid methods. In this work, several variants of the vdW functionals have been tested on rare-gas dimers (from He2 to Kr2) and solids (Ne, Ar, and Kr) and their accuracy compared to standard semilocal approximations, supplemented or not by an atom-pairwise dispersion correction [S. Grimme, J. Antony, S. Ehrlich, and H. Krieg, J. Chem. Phys. 132, 154104 (2010)]. An analysis of the results in terms of energy decomposition is also provided. PMID:23742450

  13. Nuclear spin-spin coupling anisotropy in the van der Waals-bonded 129Xe dimer.

    PubMed

    Jokisaari, Jukka; Vaara, Juha

    2013-07-21

    The spin-spin coupling constant, J, in the van der Waals-bonded (129)Xe-(129)Xe dimer cannot be determined experimentally because of the magnetic equivalence of the two nuclei. In contrast, the anisotropy of the coupling tensor, ΔJ, can be obtained from the so called effective dipole-dipole coupling determined in a solid state inclusion compound whose cages accommodate two xenon atoms. For the determination of the experimental ΔJ((129)Xe, (129)Xe) we exploited the data reported earlier in this journal. [D. H. Brouwer et al., Phys. Chem. Chem. Phys., 2007, 9, 1093.] The experimental value and the value obtained from relativistic first-principles computation are in perfect agreement. To the best of our knowledge this is the first investigation of spin-spin coupling anisotropy in a van der Waals-bonded system. PMID:23743998

  14. 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.

  15. 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.

  16. Response to Sijtsma and van der Ark (2015): "Conceptions of reliability revisited and practical recommendations".

    PubMed

    Gajewski, Byron; Price, Larry R; Bott, Marjorie

    2015-01-01

    Sijtsma and van der Ark present a broad set of models and methods for reliability estimation, and their discussion of similarities and differences provides clear information for nurse researchers to move forward in their instrument development projects. In particular, we applaud the authors' clear exposition of the factor analytic model and its utility for providing a framework for unifying reliability and validity. However, we do not want to be constrained only to the point estimates. We also need to ascertain the uncertainty in the point estimate-usually in the form of a 95% confidence interval-or, as the Bayesians refer to, a credible interval. Another issue not discussed by Sijtsma and van der Ark is conditional standard errors of measurement along the score scale measuring latent traits or true scores. In our response, practical tools for estimating intervals and a brief discussion of conditional standard errors of measurement are presented. PMID:25738625

  17. Two dimensional graphene nanogenerator by coulomb dragging: Moving van der Waals heterostructure

    NASA Astrophysics Data System (ADS)

    Zhong, Huikai; Li, Xiaoqiang; Wu, Zhiqian; Zhang, Shengjiao; Xu, Zhijuan; Chen, Hongsheng; Lin, Shisheng

    2015-06-01

    Harvesting energy from environment is the current focus of scientific community. Here, we demonstrate a graphene nanogenerator, which is based on moving van der Waals heterostructure formed between graphene and two dimensional (2D) graphene oxide (GO). This nanogenerator can convert mechanical energy into electricity with a voltage output of around 10 mV. Systematic experiments reveal the generated electricity originates from the coulomb interaction induced momentum transfer between 2D GO and holes in graphene. 2D boron nitride was also demonstrated to be effective in the framework of moving van der Waals heterostructure nanogenerator. This investigation of nanogenerator based on the interaction between 2D macromolecule materials will be important to understand the origin of the flow-induced potential in nanomaterials and may have great potential in practical applications.

  18. 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. PMID:23196929

  19. Buckling and stability analysis of a piezoelectric viscoelastic nanobeam subjected to van der Waals forces

    NASA Astrophysics Data System (ADS)

    Chen, Changping; Li, Shoujian; Dai, Liming; Qian, ChangZhao

    2014-05-01

    A study on the buckling and dynamic stability of a piezoelectric viscoelastic nanobeam subjected to van der Waals forces is performed in this research. The static and dynamic governing equations of the nanobeam are established with Galerkin method and under Euler-Bernoulli hypothesis. The buckling, post-buckling and nonlinear dynamic stability character of the nanobeam is presented. The quasi-elastic method, Leibnitz's rule, Runge-Kutta method and the incremental harmonic balanced method are employed for obtaining the buckling voltage, post-buckling characteristics and the boundaries of the principal instability region of the dynamic system. Effects of the electrostatic load, van der Waals force, creep quantity, inner damping, geometric nonlinearity and other factors on the post-buckling and the principal region of instability are investigated.

  20. 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

  1. 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.

  2. 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-BÀcklund 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.

  3. Sequence polymorphisms of cDNA clones encoding the mite allergen Der p I.

    PubMed

    Chua, K Y; Kehal, P K; Thomas, W R

    1993-01-01

    Sequence information has been obtained from 5 cDNA clones encoding the major house dust mite allergen Der p I, including one which codes for the full length preproenzyme form of the molecule. All translated sequences were unique with 1-3 differences between each clone. 4/5 of the substitutions found were to residues found in Der f I and two positions had a substitution in more than one clone. The polymorphisms included residues already described to be in T cell epitopes, so as well as being necessary to consider them in the construction of synthetic allergens, the substitutions will be important for the interpretation of experimental and genetic studies. PMID:8353459

  4. Klassifikation von Standardebenen in der 2D-Echokardiographie mittels 2D-3D-Bildregistrierung

    NASA Astrophysics Data System (ADS)

    Bergmeir, Christoph; Subramanian, Navneeth

    Zum Zweck der Entwicklung eines Systems, das einen unerfahrenen Anwender von Ultraschall (US) zur Aufnahme relevanter anatomischer Strukturen leitet, untersuchen wir die Machbarkeit von 2D-US zu 3D-CT Registrierung. Wir verwenden US-Aufnahmen von Standardebenen des Herzens, welche zu einem 3D-CT-Modell registriert werden. Unser Algorithmus unterzieht sowohl die US-Bilder als auch den CT-Datensatz Vorverarbeitungsschritten, welche die Daten durch Segmentierung auf wesentliche Informationen in Form von Labein fĂŒr Muskel und Blut reduzieren. Anschließend werden diese Label zur Registrierung mittels der Match-Cardinality-Metrik genutzt. Durch mehrmaliges Registrieren mit verschiedenen Initialisierungen ermitteln wir die im US-Bild sichtbare Standardebene. Wir evaluierten die Methode auf sieben US-Bildern von Standardebenen. FĂŒnf davon wurden korrekt zugeordnet.

  5. 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.

  6. Stochastic bifurcations induced by correlated noise in a birhythmic van der Pol system

    NASA Astrophysics Data System (ADS)

    Mbakob Yonkeu, R.; Yamapi, R.; Filatrella, G.; Tchawoua, C.

    2016-04-01

    We investigate the effects of exponentially correlated noise on birhythmic van der Pol type oscillators. The analytical results are obtained applying the quasi-harmonic assumption to the Langevin equation to derive an approximated Fokker-Planck equation. This approach allows to analytically derive the probability distributions as well as the activation energies associated to switching between coexisting attractors. The stationary probability density function of the van der Pol oscillator reveals the influence of the correlation time on the dynamics. Stochastic bifurcations are discussed through a qualitative change of the stationary probability distribution, which indicates that noise intensity and correlation time can be treated as bifurcation parameters. Comparing the analytical and numerical results, we find good agreement both when the frequencies of the attractors are about equal or when they are markedly different.

  7. Complexity and Convergence of Electrostatic and van der Waals Energies within PME and Cutoff Methods

    SciTech Connect

    Varekova, Radka S.; Koca, Jaroslav; Zhan, Chang-guo

    2004-04-01

    In this paper, we report a detailed comparison between the popularly used cutoff and Particle Mesh Ewald (PME) methods in terms of the time complexity and the energy convergence of the long-range electrostatic and van der Waals interaction calculations. For the comparison, we performed various calculations on various representative biological molecules, including seven peptides and proteins, eleven oligonucleotides, and three conformations of a nucleotide-sugar. The results provide useful insights into the appropriate choice of the methods (i.e. the cutoff or PME) and that of the cutoff values for the calculations on different kinds of molecules. It has also been demonstrated that for some cases using different cutoff values for calculating the electrostatic and van der Waals interaction energies will be computationally more efficient.

  8. van der Waals Interactions on the Mesoscale: Open-Science Implementation, Anisotropy, Retardation, and Solvent Effects.

    PubMed

    Dryden, Daniel M; Hopkins, Jaime C; Denoyer, Lin K; Poudel, Lokendra; Steinmetz, Nicole F; Ching, Wai-Yim; Podgornik, Rudolf; Parsegian, Adrian; French, Roger H

    2015-09-22

    The self-assembly of heterogeneous mesoscale systems is mediated by long-range interactions, including van der Waals forces. Diverse mesoscale architectures, built of optically and morphologically anisotropic elements such as DNA, collagen, single-walled carbon nanotubes, and inorganic materials, require a tool to calculate the forces, torques, interaction energies, and Hamaker coefficients that govern assembly in such systems. The mesoscale Lifshitz theory of van der Waals interactions can accurately describe solvent and temperature effects, retardation, and optically and morphologically anisotropic materials for cylindrical and planar interaction geometries. The Gecko Hamaker open-science software implementation of this theory enables new and sophisticated insights into the properties of important organic/inorganic systems: interactions show an extended range of magnitudes and retardation rates, DNA interactions show an imprint of base pair composition, certain SWCNT interactions display retardation-dependent nonmonotonicity, and interactions are mapped across a range of material systems in order to facilitate rational mesoscale design. PMID:25815562

  9. Admissible shock waves and shock-induced phase transitions in a van der Waals fluid

    NASA Astrophysics Data System (ADS)

    Zhao, Nanrong; Mentrelli, Andrea; Ruggeri, Tommaso; Sugiyama, Masaru

    2011-08-01

    A complete classification of shock waves in a van der Waals fluid is undertaken. This is in order to gain a theoretical understanding of those shock-related phenomena as observed in real fluids which cannot be accounted for by the ideal gas model. These relate to admissibility of rarefaction shock waves, shock-splitting phenomena, and shock-induced phase transitions. The crucial role played by the nature of the gaseous state before the shock (the unperturbed state), and how it affects the features of the shock wave are elucidated. A full description is given of the characteristics of shock waves propagating in a van der Waals fluid. The strength of these shock waves may range from weak to strong. The study is carried out by means of the theory of hyperbolic systems supported by numerical calculations.

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

    SciTech Connect

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; Liang, Chen; Damien, West; Meunier, Vincent; Zhang, Prof. Shengbai

    2016-01-01

    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. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs.

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

    DOE PAGESBeta

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; Liang, Chen; Damien, West; Meunier, Vincent; Zhang, Prof. Shengbai

    2016-01-01

    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 chargemore » 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. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs.« less

  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. Inelastic transitions of atoms and molecules induced by van der Waals interaction with a surface

    NASA Astrophysics Data System (ADS)

    Baudon, J.; Hamamda, M.; Boustimi, M.; Bocvarski, V.; Taillandier-Loize, T.; Dutier, G.; Perales, F.; Ducloy, M.

    2012-05-01

    Inelastic processes occuring in thermal-velocity metastable atoms and molecules passing at a mean distance (1-100 nm) are investigated. These processes are caused by the quadrupolar part of the van der Waals interaction: fine-structure transitions in atoms (Ar∗, Kr∗), rovibrational transitions in N2∗(3Σu+), transitions among magnetic sub-levels in the presence of a magnetic field.

  14. Reentrant Phase Transitions and van der Waals Behaviour for Hairy Black Holes

    NASA Astrophysics Data System (ADS)

    Hennigar, Robie; Mann, Robert

    2015-12-01

    We study the extended phase space thermodynamics for hairy AdS black hole solutions to Einstein-Maxwell-$\\Lambda$ theory conformally coupled to a scalar field in five dimensions. We find these solutions to exhibit van der Waals behaviour in both the charged/uncharged cases, and reentrant phase transitions in the charged case. This is the first example of reentrant phase transitions in a five dimensional gravitational system which does not include higher curvature corrections.

  15. 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. PMID:21469648

  16. Stability analysis for periodic solutions of the Van der Pol-Duffing forced oscillator

    NASA Astrophysics Data System (ADS)

    Cui, Jifeng; Liang, Jiaming; Lin, Zhiliang

    2016-01-01

    Based on the homotopy analysis method (HAM), the high accuracy frequency response curve and the stable/unstable periodic solutions of the Van der Pol-Duffing forced oscillator with the variation of the forced frequency are obtained and studied. The stability of the periodic solutions obtained is analyzed by use of Floquet theory. Furthermore, the results are validated in the light of spectral analysis and bifurcation theory.

  17. The van der Waals interaction in one, two, and three dimensions

    NASA Astrophysics Data System (ADS)

    Ipsen, A. C.; Splittorff, K.

    2015-02-01

    The van der Waals interaction between two polarizable atoms is considered. In three dimensions, the standard form with an attractive 1/R6 potential is obtained from second-order quantum perturbation theory. When the electron motion is restricted to lower dimensions (but the 1/R Coulomb potential is retained), new terms in the expansion appear and alter both the sign and the R-dependence of the interaction.

  18. 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.

  19. Van der Woude Syndrome Associated with Hypodontia: A Rare Clinical Entity

    PubMed Central

    Soni, Romesh; Vivek, Rajul; Srivastava, Adit; Singh, Ankita; Srivastava, Shalabh; Chaturvedi, T. P.

    2012-01-01

    Van der Woude syndrome (VWS) is usually underreported and frequently not diagnosed. The phenomenon that cleft lip and palate are regularly combined in the same pedigree makes it unique. A meticulous examination of a patient with lip pits may reveal a hidden form of a cleft, for example, submucous. This paper presents a case of VWS in a ten-year-old boy with characteristic orofacial features. Special emphasis has also been given on the need for appropriate genetic counseling. PMID:23326687

  20. Synchronization of coupled van der pole and Kislov-Dmitriev self-oscillators

    NASA Astrophysics Data System (ADS)

    Emel'Yanova, Yu. P.; Kuznetsov, A. P.

    2011-04-01

    The problem of interaction of self-oscillating elements of different origin is considered for a coupled van der Pole oscillator and Kislov-Dmitriev generator. Domains with different types of dynamics in the space of parameters are indicated taking into account the possibility of broadband synchronization of the systems. The case of essentially different control parameters is considered. Chaos stabilization effects and the opposite effect (initiated chaos) are detected in the system under investigation for various values of parameters.

  1. A Drosophila shc gene product is implicated in signaling by the DER receptor tyrosine kinase.

    PubMed Central

    Lai, K M; Olivier, J P; Gish, G D; Henkemeyer, M; McGlade, J; Pawson, T

    1995-01-01

    Antibodies to the human Shc adaptor protein were used to isolate a cDNA encoding a Drosophila Shc protein (dShc) by screening an expression library. The dshc gene, which maps to position 67B-C on the third chromosome, encodes a 45-kDa protein that is widely expressed throughout the Drosophila life cycle. In flies, the dShc protein physically associates with the activated Drosophila epidermal growth factor receptor homolog (DER) and is inducibly phosphorylated on tyrosine by DER. The 45-kDa dShc protein is closely related both in overall organization and in amino acid sequence (46% identity) to the 52-kDa mammalian Shc isoform. In addition to a C-terminal Src homology 2 (SH2) domain, dShc contains an N-terminal phosphotyrosine-binding (PTB) domain, which associates in vitro with the autophosphorylated DER receptor tyrosine kinase and with phosphopeptides containing an Asn-Pro-X-pTyr motif, where pTyr stands for phosphotyrosine. A potential binding site for the dShc PTB domain is located at Tyr-1228 of DER. These results indicate that the shc gene has been conserved in evolution, as have the binding properties of the Shc PTB and SH2 domains. Despite the close relationship between the Drosophila and mammalian Shc proteins, dShc lacks the high-affinity Grb2-binding site found in mammalian Shc, suggesting that Shc proteins may have functions in addition to regulation of the Ras pathway. PMID:7651398

  2. Möglichkeiten und Grenzen der Kompression von Femtosekunden-Lichtimpulsen

    NASA Astrophysics Data System (ADS)

    Wilhelmi, Bernd

    Aus der Wellengleichung werden Beziehungen zur Beschreibung des simultanen Einflusses von Dispersion und NichtlinearitĂ€t verschiedener Ordnung auf ultrakurze Lichtimpulse in Materialien, deren Eigenfrequenzen weit von der Mittenfrequenz des Lichtes entfernt liegen, hergeleitet. Unter bestimmten Voraussetzungen ĂŒber Eingangsimpuls und Material nehmen diese Beziehungen die Struktur der nichtlinearen Schrödinger-Gleichung an, deren Anwendungsbereich dadurch abgesteckt werden kann. Es werden Bedingungen fĂŒr die Erzeugung von komprimierten, chirp-freien Impulsen angegeben und Grenzen fĂŒr die erreichbare Impulsdauer diskutiert.Translated AbstractPossibilities and Limitations of Compression of Femtosecond Light PulsesRelations have been derived that describe the simultaneous action of dispersion and nonlinearities of various orders on ultrashort light pulses in samples, the eigen frequencies of which are far from the center frequency of the incoming light. Under certain assumptions, with respect to input pulse and material, these relations attain the structure of the nonlinear Schrödinger-equation, the application range of which has been estimated in this way. Conditions for the generation of compressed, chirp-free pulses are given and limits for the minimum obtainable pulse duration are discussed.

  3. Physisorption of nucleobases on graphene: a comparative van der Waals study

    NASA Astrophysics Data System (ADS)

    Le, Duy; Kara, Abdelkader; Schröder, Elsebeth; Hyldgaard, Per; Rahman, Talat S.

    2012-10-01

    The physisorption of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) on graphene is studied using several variants of the density functional theory (DFT): the generalized gradient approximation with the inclusion of van der Waals interaction (vdW) based on the TS approach (Tkatchenko and Scheffer 2009 Phys. Rev. Lett. 102 073005) and our simplified version of this approach (here called sTS), the van der Waals density functional vdW-DF (Dion et al 2004 Phys. Rev. Lett. 92 246401) and vdW-DF2 (Lee et al 2010 Phys. Rev. B 82 081101), and DFT-D2 (Grimme 2006 J. Comput. Chem. 27 1787) and DFT-D3 (Grimme et al 2010 J. Chem. Phys. 132 154104) methods. The binding energies of nucleobases on graphene are found to be in the following order: G > A > T > C > U within TS, sTS, vdW-DF, and DFT-D2, and in the following order: G > A > T ˜ C > U within DFT-D3 and vdW-DF2. The binding separations are found to be different within different methods and in the following order: DFT-D2 < TS < DFT-D3 ˜ vdW-DF2 < vdW-DF. We also comment on the efficiency of combining the DFT-D approach and vdW-DF to study systems with van der Waals interactions.

  4. 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 DĂŒrer 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. PMID:25747746

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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/Å2).

  6. Li intercalation in graphite: A van der Waals density-functional study

    NASA Astrophysics Data System (ADS)

    Hazrati, E.; de Wijs, G. A.; Brocks, G.

    2014-10-01

    Modeling layered intercalation compounds from first principles poses a problem, as many of their properties are determined by a subtle balance between van der Waals interactions and chemical or Madelung terms, and a good description of van der Waals interactions is often lacking. Using van der Waals density functionals we study the structures, phonons and energetics of the archetype layered intercalation compound Li-graphite. Intercalation of Li in graphite leads to stable systems with calculated intercalation energies of -0.2 to -0.3 eV/Li atom, (referred to bulk graphite and Li metal). The fully loaded stage 1 and stage 2 compounds LiC6 and Li1 /2C6 are stable, corresponding to two-dimensional √{3 }×√{3 } lattices of Li atoms intercalated between two graphene planes. Stage N >2 structures are unstable compared to dilute stage 2 compounds with the same concentration. At elevated temperatures dilute stage 2 compounds easily become disordered, but the structure of Li3 /16C6 is relatively stable, corresponding to a √{7 }×√{7 } in-plane packing of Li atoms. First-principles calculations, along with a Bethe-Peierls model of finite temperature effects, allow for a microscopic description of the observed voltage profiles.

  7. 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.

  8. Van der Waals Attraction of Vortices in Anisotropic and Layered Superconductors

    NASA Astrophysics Data System (ADS)

    Blatter, Gianni; Geshkenbein, Vadim

    1997-03-01

    In anisotropic or layered superconductors two vortices parallel to the c-axis interact on the scale of the London penetration length λ, whereas the interaction between two planar vortices extends over the much larger length λ/\\varepsilon (\\varepsilon^2 = m/M << 1 denotes the anisotropy parameter). We have found that thermal fluctuations of the vortices produce an attractive potential, which is of the van der Waals type and decays algebraically, ∝ (λ/R)^4 at short distances λ < R < d /\\varepsilon and ∝ (λ/R)^5 at large distances d /\\varepsilon < R < λ/\\varepsilon. The attractive van der Waals potential is relevant in the dilute regime, where it drastically changes the B--T phase diagram as originally proposed by Nelson (1988): At low temperatures the transition at H_c1 is of first-order and takes the Meissner-Ochsenfeld phase directly into a vortex solid phase. For intermediate temperatures, a second-order transition from the Meissner-Ochsenfeld phase to a vortex gas phase is followed by two first-order transitions, first to a liquid and subsequently to a solid phase. Approaching high temperatures, the distinction between the gas and liquid phases vanishes, as is the case in the usual van der Waals gas, and following the second-order transition from the Meissner-Ochsenfeld phase to the vortex gas, the system undergoes a single first-order gas -- solid transition.

  9. A novel nanostructured biosensor for the detection of the dust mite antigen Der p2

    PubMed Central

    Tsai, Jaw-Ji; Bau, I-Jiuan; Chen, He-Tsing; Lin, Yu-Ta; Wang, Gou-Jen

    2011-01-01

    The group 2 allergen, Der p2, has been reported to activate innate toll-like receptors (TLRs) on respiratory epithelial cells and thus aggravate respiratory diseases. In this study, a highly sensitive nanostructured biosensor based on a 3D sensing element with uniformly deposited gold nanoparticles is proposed for the detection of the dust mite antigen Der p2. The barrier layer comprises an anodic aluminum oxide (AAO) film which is used as the template in this highly sensitive nanostructured biosensor. Simple electrochemical deposition without reducing agent and stabilizer was enough to uniformly synthesize gold nanoparticles on the surface of the barrier layer. The size and the distribution density of the nanoparticles can be well controlled by the applied potential during electrochemical deposition. Following this procedure, the dust mite monoclonal antibodies (IgG) were then immobilized through the 11-MUA (11-mercaptoundecanoic acid), (1-ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide)/(N-hydroxysuccinimide) self-assembled monolayer approach for the dust mite antigen Der p2 detection. The detection limit of the proposed 3D gold nanoparticle-based nanostructured biosensor was examined using electrochemical impedance spectroscopy analysis and found to be 1 pg/mL. The dynamic range was found to be 5 ÎŒg/mL. The proposed nanostructured biosensor would be useful for fast detection of rare molecules in a solution. PMID:21822382

  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. SchlĂŒssel zum VerstĂ€ndnis von KrĂ€ften und Materie: Der ATLAS-Detektor am Large Hadron Collider

    NASA Astrophysics Data System (ADS)

    Oberlack, Horst; Schacht, Peter

    2001-07-01

    Der Hadronenspeicherring LHC ermöglicht es, tiefer denn je in das Innere der Materie vorzudringen. Mit einer Schwerpunktsenergie von 14 TeV und Protonenstrahlen von höchster IntensitĂ€t sind Experimente am LHC mit Herausforderungen konfrontiert, die bisher unbezwingbar schienen. In einer weltweiten Zusammenarbeit wird gegenwĂ€rtig an der Fertigstellung des ATLAS-Detektors gearbeitet, die Inbetriebnahme soll im Jahr 2005 erfolgen. Der Detektor kann das hypothetische Higgs-Teilchen bis zu einer Masse von 1 TeV nachweisen. DarĂŒber hinaus steht die Suche nach einer möglichen Substruktur der Quarks und von vorhergesagten supersymmetrischen Teilchen im Vordergrund der zukĂŒnftigen Forschung am CERN.

  12. Herausforderungen fĂŒr kĂŒnftige Lernumgebungen am Beispiel der FakultĂ€t fĂŒr 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, wettbewerbsfĂ€hige hochschulĂŒbergreifende Mechanismen sowie entsprechende organisatorische Rahmenbedingungen zu schaffen. Vor allem die Umsetzung von EBologna und die UnterstĂŒtzung kooperativer Bildungsangebote verstĂ€rken diese Notwendigkeit. Motiviert durch die VerĂ€nderungen im Bereich der Hochschullehre und die Herausforderungen fĂŒr kĂŒnftige Lernumgebungen schlagen wir eine Integrationslösung im Sinne eines Learning Gateway vor, die zur webgestĂŒtzten 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.

  13. 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 ÎČ-sheets in Der f 29b. In conclusion, Derf 29b protein was identified as a novel subtype of dust mite allergen. PMID:27158348

  14. 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

  15. 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

    Yang, Lijun; Hirose, Sakiko; Suzuki, Kazuya; Hiroi, Takachika; Takaiwa, Fumio

    2012-05-01

    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

  16. 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.

  17. 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 sufficiently close to any corrugated—and/or any smooth—surface and thus enforce a strong vdW-type adhesion; it exploits what is then essentially a contact force (dominated by the attraction exerted in the near-surface regions) to defy the pull of gravity on its own bulk. This Journal of Physics: Condensed Matter special issue is dedicated to the memory of David C Langreth. David is a dearly missed friend and mentor who inspired many of us. He was an outstanding condensed matter theorist and a scholar who greatly influenced us through his many-particle-physics based insights into density functional theory (DFT), surface science and related areas. His seminal works range from conserving formulations of interacting nonequilibrium transport [1] and formal-scattering theory [2] to an explicit formulation [3] of the exact DFT exchange-correlation energy in the adiabatic connection formula (ACF), the latter also being derived independently by Gunnarsson and Lundqvist [4]. David's portfolio also includes an analysis [5] that helped catalyze and guide the development of DFT from the local-density approximation (LDA) to the formulations of generalized gradient approximations (GGAs). Another salient contribution of David's is in the area of vdW interactions in materials. He was a key architect of the vdW density functional (vdW-DF) method [6, 7]. This method was developed in a long-standing Rutgers-Chalmers collaboration between David's group and that of Bengt I Lundqvist, later extending to a wider group of researchers on both sides of the Atlantic. Plasmons are collective excitations that depend on electron-density variation. The plasmon response can be seen as defining the nature of the LDA [4] and their description can thus also be seen as contributing to the success of GGA. The vdW-DF method is a regular constraint-based density functional (for ground-state DFT) which is derived within the ACF framework and which emphasizes the electrodynamical nature of the coupling between these collective plasmon excitations. The vdW-DF method thus seeks to utilise the implicit plasmon nature of the LDA/GGA success to also provide a nonempirical account of the fully nonlocal correlations that underpin the vdW bond [8]. The method retains a seamless integration [6] with the semilocal density functional components. We know that David was pleased to see how this quantitative, material-specific theory helped address problems in a broad class of materials that are sparse, i.e., that contain low electron density regions which are of significant consequence in determining material characteristics [9]. In a DFT framework, the vdW-DF method supplements other nonlocal functional descriptions [10] and the DFT-dispersion class of methods, extending GGA-DFT with an atom-based asymptotic description which relies on the vdW interaction coefficients [11]. The recent quest to understand the role of vdW forces in materials has certainly been facilitated and intensified by the set of recent developments in DFT itself. This is because these vdW-aware methods provide an opportunity to deliver a computationally effective account of the quantum-physical behavior even when the materials are sparse. It is the expectation that with such new-found theoretical capability, one may further extend the immense progress already attained by traditional (GGA) DFT calculations in reliably predicting the characteristics of materials and phenomena in materials, nanoscience, chemistry and other related fields [12]. This special issue contains a wealth of exciting contributions, mostly on vdW forces in materials. The special issue was suggested following the well-attended first focused vdW and materials session arranged by the Division of Materials Physics (DMP) of the American Physical Society (APS) at the March Meeting in 2011. The sad and unexpected passing of David in the spring of 2011 caused some rethinking and at the memorial symposium, held by David's colleagues at Rutgers in November 2011, we proposed to dedicate this special issue to David's contributions to the field. We are delighted with the overwhelmingly positive reaction that we received in response to our call for papers. We are also delighted to now be able to bring so many exciting contributions to you. The papers included in this special issue focus, in general, either through experiments or through theoretical characterization, on material properties in which vdW forces represent a central component. These articles contain arguments for and against a broader usage of DFT with vdW to account for material description, as well as establishing benchmarks which measure progress in the field. This special issue also includes fundamental theoretical analysis and suggestions for sensitive experiments that can resolve outstanding issues underlying the nature and role of the interaction. We believe that these papers will help stimulate further material-theory developments and, even more importantly, more discussions and feedback between theory and experiment. Physisorption is important to enable lubrication. This is because physisorption keeps the lubricating molecules at the interface at which a pair of internal surfaces must be free to move relative to each other. In turn, physisorbed (or perhaps weakly chemisorbed) lubricants prevent, for example, the formation of stronger bonding that will impede mechanical operation. However, it is also important to further characterize the nature and dynamics of the vdW bonding of lubricants: while physisorption means a weak binding further from the surface, there are still important friction effects. Walker et al present an experimental study, along with theoretical analysis, that directly determines the frictional heating of a Kr overlayer on graphene through quartz crystal microbalance measurements. The properties of materials reflect their atomic structure and hence indirectly their bonding nature and character. We can explore the role of dispersion forces by examining the impact their inclusion has on predictions of material properties. On the other hand, the experimental and theoretical study of Casimir forces also plays a vital role in the exploration of material behavior. vdW forces are related to the Casimir force but lack retardation effects. While the vdW bonding depends on additional effects (for example, the multipole contributions that reflect image-plane effects), the study of Casimir forces provides direct (and not indirect) measurements of the nature of interactions. Klimchitskaya et al note that to reconcile explicit measurements of the Casmir forces between semiconductor fragments within the Lifshitz description, it is relevant to question the Drude-like description of the contributions from free carriers and instead proceed with a formulation based only on optical observations of the permittivity. This optical response can be seen as a reflection of a more plasmon-like behavior. The authors suggest an experiment involving the study of the impact on the Casimir forces by a Mott transition in doped semiconductors. Such an experiment would permit explicit testing of the validity of the present model for Casimir forces and hence provide additional perspectives on the nature of dispersive interactions. There is an effort to store energy, e.g. H2 or CO2, inside a range of open cage-like structures, such as metal organics frameworks (MOF) or clathrates. The fact that the internal molecular adhesion is dominated by vdW forces suggests that the storage and retrieval costs could perhaps be lowered as compared to an approach that involves more traditional chemical compounds. Nijem et al have provided spectroscopic characterization of vdW interactions of both hydrogen molecules and CO in a specific MOF. The study includes a vdW-DF calculation of structure and a theoretical prediction of expected infrared activity. The potential applications to energy materials have motivated more theoretical characterizations. Li and Thonhauser use the vdW-DF method to investigate the limitations and hydrogen storage potential of hydrogen-methane compounds in a MOF. Similarly, Ihm et al combine vdW-DF studies with a thermodynamics argument to characterize the potential for molecular hydrogen uptake in expanded graphite, for example, through intercalation. The relevance of vdW-aware DFT calculations and the usefulness of such methods reaches beyond the study of molecules, surfaces and adsorption/absorption problems. Moellmann et al present a dispersion-DFT study of TiO2 bulk and surfaces, which illustrates that vdW forces can also play a prominent role when comparing the energies of different oxide structures. Perdew et al present a spherical-shell model and a simplified classical electrodynamical determination of the vdW interaction coefficients that describes the asymptotic interaction between fullerenes or other nearly spherical nanoclusters. The overall modeling framework also permits a formal expression of multipole contributions. Dappe et al used a combination of DFT and second-order perturbation theory to analyze the interactions between graphene layers, thus also exploring the role of dynamical screening in the vdW binding. The work of Sabatini et al extends the vdW-DF description with accounts of the stress tensor, providing the method with the same versatility as one has grown to expect in traditional LDA/GGA-DFT calculations. The method is illustrated with investigations of amino acid crystals under various pressures. The vdW-DF method was originally perceived as computationally more expensive than other approaches. It has now benefited from the development of efficient algorithms so the computational cost is comparable to that of traditional GGA-DFT calculations. As is also the case for some of the dispersion-DFT methods, there is an overhead when these are implemented self-consistently. Noting that sparse-matter structure determination and relaxations may well employ a sequence of methods, Le et al have suggested a simplified (cost-free relative to GGA) formulation of self-consistent dispersion-DFT calculations that is cost-free in the evaluation of forces and yet adapts the atom-centered pair-wise interaction coefficients through the change in local electron distributions. There is a need for continued testing of accuracy in the description of material properties and of the robustness and transferability of predictions across systems and length scales. This need is widely appreciated and is also reflected in the fact that many of the contributions touch on, suggest, or pursue a systematic benchmarking. There is an interest in careful analysis of detailed experiments on the physisorption of inert atoms, light molecules and organic molecules on smooth surfaces. Chen et al investigated the role of vdW forces in noble gas adsorption on various metal surfaces. Londero et al analyzed a set of experimental results for the desorption of n-alkanes from graphene in a program that had undergraduate participation. Lee et al benchmarked the performance of the vdW-DF2 functional and other methods against the physisorption potential curve that can be established from a rich data set of resonant backscattering of hydrogen molecules on various facets of Cu crystals. A few of the investigations included here noted that the vdW-DF method permits a more detailed analysis of the nature of strong physisorption and/or weak chemisorption cases than do DFT-dispersion methods and discussed the ramifications of the fact that GGA-DFT often, and vdW-aware DFT sometimes, pose difficulties for systems with a partial vdW component in the binding. Caciuc et al thus present a combined ab initio and semi-empirical vdW study comparing benzene/triazine/broazine adsorption on graphene and on boron-nitride sheets. On a more strategic note, Lazic et al broadened the discussion of a graphene/Ir(111) system and used the documented limitation of a GGA description to discuss a rationale for considering a more general switch to nonlocal functionals. Graziano et al note that the accuracy in the description of some soft layered systems like graphene and boron-nitride can be increased by changing the exchange description away from what was suggested in the original vdW-DF method. Hanke et al focused on the weak chemisorption of ethene on the various Cu facets that have an increasing degree of openness and provide a method for benchmarking through comparison with experimental observations. Finally, Björkman et al raise the question 'Are we van der Waals ready?' and proceed to test our readiness by benchmarking the performance of a range of vdW-aware methods for the group of 96 known layered structures. We have also included in this special issue one study of nonequilibrium transport which is linked to David's work in formal scattering theory [1, 2] and which observes that vdW forces (and possible generalizations to nonequilibrium transport conditions) will be of central importance in a richer computational characterization of molecular electronics under operational conditions. David was always keen to spearhead the development of tools that improved descriptions of nature and addressed actual experiments. We know that he was happy that DMP started the focused session on vdW and materials in 2011. We know that he would have thoroughly appreciated the articles in this special issue. He would have hoped, as we do, that materials theory may continue to learn how to tackle even more exciting experimental problems and that we may continue to deepen our understanding of materials and their functionality. Bibliography [1]Langreth D C 1976 1975 Nato Advanced Study Institute on Linear and Nonlinear Transport in Solids, Antwerben vol B17 (New York: Plenum) pp 3-32 [2]Langreth D C 1966 Friedel sum rule for Anderson's model of localized impurity states Phys. Rev. 150 516 [3]Langreth D C and Perdew J P 1975 The exchange-correlation energy of a metallic surface Solid State Commun. 17 1425 [4]Gunnarsson O and Lundqvist B I 1976 Exchange and correlation in atoms, molecules, and solids by the spin-density-functional formalism Phys. Rev. B 13 4274 [5]Langreth D C and Mehl M J 1981 Beyond the local-density approximation in calculations of ground-state electronic properties Phys. Rev. B 47 446 [6]Dion M, Rydberg H, Schröder E, Langreth D C and Lundqvist B I 2004 Van der Waals density functional for general geometries Phys. Rev. Lett. 92 246401 Thonhauser T, Cooper V R, Li S, Puzder A, Hyldgaard P and Langreth D C 2007 Van der Waals density functional: self-consistent potential and the nature of the van der Waals bond Phys. Rev. B 76 125112 [7]Lee K, Murray E D, Kong L, Lundqvist B I and Langreth D C 2010 A higher-accuracy van der Waals density functional Phys. Rev. B 82 081101 [8]Rapcewicz K and Ashcroft N W 1991 Fluctuation attraction in condensed matter: a nonlocal functional approach Phys. Rev. B 44 4032 Lundqvist B I, Andersson Y, Shao H, Chan S and Langreth D C 1995 Density functional theory including van der Waals forces Int. J. Quant. Chem. 56 247 [9]Langreth D C et al 2009 A density functional for sparse matter J. Phys.: Condens. Matter 21 084203 [10]For example, Kohn W, Meir Y and Makarov D E 1998 The exchange-correlation energy of a metallic surface Phys. Rev. Lett. 80 4153 Kurth S and Perdew J P 1999 Phys. Rev. B 59 10461 Dobson J F and Wang J 1999 Phys. Rev. Lett. 82 2123 Pitarke J M and Perdew J P 2003 Phys. Rev. B 67 045101 Vydrov O A and van Voorhi T 2009 Phys. Rev. Lett. 103 063004 [11]For example, Grimme S 2004 J. Comput. Phys. 25 1463 Tkatchenko A and Scheffler M 2009 Phys. Rev. Lett. 102 073005 Grimme S, Antony J, Ehrlich S and Krieg H 2010 J. Chem. Phys. 132 154004 [12]Burke K 2012 Perspectives on density functional theory J. Chem. Phys. 136 150901 Van der Waals interactions in advanced materials contents Van der Waals interactions in advanced materials, in memory of David C LangrethPer Hyldgaard and Talat S Rahman Frictional temperature rise in a sliding physisorbed monolayer of Kr/grapheneM Walker, C Jaye, J Krim and Milton W Cole How to modify the van der Waals and Casimir forces without change of the dielectric permittivityG L Klimchitskaya, U Mohideen and V M Mostepanenko Spectroscopic characterization of van der Waals interactions in a metal organic framework with unsaturated metal centers: MOF-74-MgNour Nijem, Pieremanuele Canepa, Lingzhu Kong, Haohan Wu, Jing Li, Timo Thonhauser and Yves J Chabal A theoretical study of the hydrogen-storage potential of (H2)4CH4 in metal organic framework materials and carbon nanotubesQ Li and T Thonhauser The influence of dispersion interactions on the hydrogen adsorption properties of expanded graphiteYungok Ihm, Valentino R Cooper, Lujian Peng and James R Morris A DFT-D study of structural and energetic properties of TiO2 modificationsJonas Moellmann, Stephan Ehrlich, Ralf Tonner and Stefan Grimme Spherical-shell model for the van der Waals coefficients between fullerenes and/or nearly spherical nanoclustersJohn P Perdew, Jianmin Tao, Pan Hao, Adrienn Ruzsinszky, GĂĄbor I Csonka and J M Pitarke Dynamical screening of the van der Waals interaction between graphene layersY J Dappe, P G Bolcatto, J Ortega and F Flores Structural evolution of amino acid crystals under stress from a non-empirical density functionalRiccardo Sabatini, Emine KĂŒĂ§ĂŒkbenli, Brian Kolb, T Thonhauser and Stefano de Gironcoli Physisorption of nucleobases on graphene: a comparative van der Waals studyDuy Le, Abdelkader Kara, Elsebeth Schröder, Per Hyldgaard and Talat S Rahman The role of van der Waals interactions in the adsorption of noble gases on metal surfacesDe-Li Chen, W A Al-Saidi and J Karl Johnson Desorption of n-alkanes from graphene: a van der Waals density functional studyElisa Londero, Emma K Karlson, Marcus Landahl, Dimitri Ostrovskii, Jonatan D Rydberg and Elsebeth Schröder Benchmarking van der Waals density functionals with experimental data: potential-energy curves for H2 molecules on Cu(111), (100) and (110) surfacesKyuho Lee, Kristian Berland, Mina Yoon, Stig Andersson, Elsebeth Schröder, Per Hyldgaard and Bengt I Lundqvist Ab initio and semi-empirical van der Waals study of graphene-boron nitride interaction from a molecular point of viewVasile Caciuc, Nicolae Atodiresei, Martin Callsen, Predrag Lazić and Stefan BlĂŒgel Rationale for switching to nonlocal functionals in density functional theoryP Lazić, N Atodiresei, V Caciuc, R Brako, B Gumhalter and S BlĂŒgel Improved description of soft layered materials with van der Waals density functional theoryGabriella Graziano, Jiƙí KlimeĆĄ, Felix Fernandez-Alonso and Angelos Michaelides Structure and stability of weakly chemisorbed ethene adsorbed on low-index Cu surfaces: performance of density functionals with van der Waals interactionsFelix Hanke, Matthew S Dyer, Jonas Björk and Mats Persson Are we van der Waals ready?T Björkman, A Gulans, A V Krasheninnikov and R M Nieminen Nonequilibrium thermodynamics of interacting tunneling transport: variational grand potential, density functional formulation and nature of steady-state forcesP Hyldgaard

  18. Relationship between propeptide pH unfolding and inhibitory ability during ProDer p 1 activation mechanism.

    PubMed

    Chevigné, Andy; Barumandzadeh, Roya; Groslambert, Sylvie; Cloes, Benoßt; Dehareng, Dominique; Filée, Patrice; Marx, Jean-Claude; FrÚre, Jean-Marie; Matagne, André; Jacquet, Alain; Galleni, Moreno

    2007-11-16

    The major allergen Der p 1 of the house dust mite Dermatophagoides pteronyssinus is a papain-like cysteine protease (CA1) produced as an inactive precursor and associated with allergic diseases. The propeptide of Der p 1 exhibits a specific fold that makes it unique in the CA1 propeptide family. In this study, we investigated the activation steps involved in the maturation of the recombinant protease Der p 1 expressed in Pichia pastoris and the interaction of the full-length and truncated soluble propeptides with their parent enzyme in terms of activity inhibition and BIAcore interaction analysis. According to our results, the activation of protease Der p 1 is a multistep mechanism that is characterized by at least two intermediates. The propeptide strongly inhibits unglycosylated and glycosylated recombinant Der p 1 (K(D)=7 nM) at neutral pH. This inhibition is pH dependent. It decreases from pH 7 to pH 4 and can be related to conformational changes of the propeptide characterized by an increase of its flexibility and formation of a molten globule state. Our results indicate that activation of the zymogen at pH 4 is a compromise between activity preservation and propeptide unfolding. PMID:17916363

  19. 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.

  20. [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. PMID:27089735

  1. 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 field-tunable band gap and extract electronic hopping parameters. In WSe 2, a semiconducting transition metal dichalcogenide, we observe spin and layer polarizations of the charge carriers, representing a coupling of the spin, valley and layer degrees of freedom.

  2. Microwave and ab initio studies of rare gas-methane van der Waals complexes

    NASA Astrophysics Data System (ADS)

    Liu, Yaqian; JĂ€ger, Wolfgang

    2004-05-01

    Rotational spectra of the weakly bound Kr-methane van der Waals complex were recorded using a pulsed molecular beam Fourier transform microwave spectrometer in the range from 3.5 to 18 GHz. Spectra of 25 isotopomers of Kr-methane were assigned and analyzed. For isotopomers containing CH4, 13CH4, and CD4, two sets of transitions with K=0 and one with K=1 were recorded, correlating to the j=0, 1, and 2 rotational levels of free methane, respectively (j is the rotational angular momentum quantum number of the methane monomer). For isotopomers containing CH3D and CHD3, two K=0 components were recorded, correlating to the jk=00 and 11 rotational levels of free methane (k corresponds to the projection of j onto the C3 axis of CH3D and CHD3). The obtained spectroscopic results were used to derive van der Waals bond distance R, van der Waals stretching frequency Îœs, and the corresponding stretching force constant ks. Nuclear spin statistical weights of individual states were obtained from molecular symmetry group analyses and were compared with the observed relative transition intensities. The tentatively assigned j=2 transitions were more intense than predicted from symmetry considerations. This is attributed to a relatively large effective dipole moment of this state, supported by ab initio dipole moment calculations. Ab initio potential energy calculations of Kr-CH4 and Ar-CH4 were done at the coupled cluster level of theory, with single and double excitations and perturbative inclusion of triple excitations, using the aug-cc-pVTZ basis set supplemented with bond functions. The theoretical results show that the angular dynamics of the dimer does not change significantly when the binding partner of methane changes from Ar to Kr. The dipole moment of Ar-CH4 was calculated at various configurations, providing a qualitative explanation for the unsuccessful spectral searches for rotational transitions of Ar-CH4.

  3. Effects of surface roughness on the van der Waals force between macroscopic bodies

    NASA Astrophysics Data System (ADS)

    Maradudin, Alexei A.; Mazur, Paul

    1980-08-01

    We have calculated the van der Waals force between two different, semi-infinite dielectric media, separated by a region of vacuum of nominal thickness l, when the surface of one of the two media is rough. The calculation is carried out by the method of van Kampen, Nijboer, and Schram [

    Phys. Lett. 26A, 307 (1968)
    ] to yield the force at the absolute zero of temperature in the regime lâ‰Șλ, where λ is the smaller of the principal absorption wavelengths of the two dielectric media. The result obtained has the form f(l)=-C3/(la)3-ÎŽ2/a2C4/(la)4+C5/(la)5+⋯+OÎŽ4/a4 in the limit l/a is large. Here a is the transverse correlation length, the mean distance between consecutive peaks and valleys on the rough surface, while ÎŽ is the root-mean-square departure of the surface from flatness. Explicit expressions have been obtained for the coefficients C4 and C5, and numerical estimates of the magnitude of the roughness-induced contribution to the van der Waals force are obtained in the case that the two media are the same, and their common dielectric constant is given by ɛ(ω)=1-(ωp2/ω2), where ωp is a plasma frequency. It is found that surface roughness increases the magnitude of the van der Waals force over its value when the surfaces of both media are flat.

  4. Das Lektin aus der Erbse Pisum sativum : Bindungsstudien, Monomer-Dimer-Gleichgewicht und RĂŒckfaltung aus Fragmenten

    NASA Astrophysics Data System (ADS)

    KĂŒster, Frank

    2002-11-01

    Das Lektin aus Pisum sativum, der Gartenerbse, ist Teil der Familie der Leguminosenlektine. Diese Proteine haben untereinander eine hohe Sequenzhomologie, und die Struktur ihrer Monomere, ein all-ß-Motiv, ist hoch konserviert. Dagegen gibt es innerhalb der Familie eine große Vielfalt an unterschiedlichen QuartĂ€rstrukturen, die Gegenstand kristallographischer und theoretischer Arbeiten waren. Das Erbsenlektin ist ein dimeres Leguminosenlektin mit einer Besonderheit in seiner Struktur: Nach der Faltung in der Zelle wird aus einem Loop eine kurze AminosĂ€uresequenz herausgeschnitten, so dass sich in jeder Untereinheit zwei unabhĂ€ngige Polypeptidketten befinden. Beide Ketten sind aber stark miteinander verschrĂ€nkt und bilden eine gemeinsame strukturelle DomĂ€ne. Wie alle Lektine bindet Erbsenlektin komplexe Oligosaccharide, doch sind seine physiologische Rolle und der natĂŒrliche Ligand unbekannt. In dieser Arbeit wurden Versuche zur Entwicklung eines Funktionstests fĂŒr Erbsenlektin durchgefĂŒhrt und seine Faltung, StabilitĂ€t und Monomer-Dimer-Gleichgewicht charakterisiert. Um die spezifische Rolle der Prozessierung fĂŒr StabilitĂ€t und Faltung zu untersuchen, wurde ein unprozessiertes Konstrukt in E. coli exprimiert und mit der prozessierten Form verglichen. Beide Proteine zeigen die gleiche kinetische StabilitĂ€t gegenĂŒber chemischer Denaturierung. Sie denaturieren extrem langsam, weil nur die isolierten Untereinheiten entfalten können und das Monomer-Dimer-Gleichgewicht bei mittleren Konzentrationen an Denaturierungsmittel auf der Seite der Dimere liegt. Durch die extrem langsame Entfaltung zeigen beide Proteine eine apparente Hysterese im GleichgewichtsĂŒbergang, und es ist nicht möglich, die thermodynamische StabilitĂ€t zu bestimmen. Die StabilitĂ€t und die Geschwindigkeit der Assoziation und Dissoziation in die prozessierten bzw. nichtprozessierten Untereinheiten sind fĂŒr beide Proteine gleich. DarĂŒber hinaus konnte gezeigt werden, dass auch unter nicht-denaturierenden Bedingungen die Untereinheiten zwischen den Dimeren ausgetauscht werden. Die Renaturierung der unprozessierten Variante ist unter stark nativen Bedingungen zu 100 % möglich. Das prozessierte Protein dagegen renaturiert nur zu etwa 50 %, und durch die Prozessierung ist die Faltung stark verlangsamt, der Faltungsprozess ist erst nach mehreren Tagen abgeschlossen. Im Laufe der Renaturierung wird ein Intermediat populiert, in dem die lĂ€ngere der beiden Polypeptidketten ein Homodimer mit nativĂ€hnlicher UntereinheitenkontaktflĂ€che bildet. Der geschwindigkeitsbestimmende Schritt der Renaturierung ist die Assoziation der entfalteten kĂŒrzeren Kette mit diesem Dimer. The lectin from Pisum sativum (garden pea) is a member of the family of legume lectins. These proteins share a high sequence homology, and the structure of their monomers, an all-ß-motif, is highly conserved. Their quaternary structures, however, show a great diversity which has been subject to cristallographic and theoretical studies. Pea lectin is a dimeric legume lectin with a special structural feature: After folding is completed in the cell, a short amino acid sequence is cut out of a loop, resulting in two independent polypeptide chains in each subunit. Both chains are closely intertwined and form one contiguous structural domain. Like all lectins, pea lectin binds to complex oligosaccharides, but its physiological role and its natural ligand are unknown. In this study, experiments to establish a functional assay for pea lectin have been conducted, and its folding, stability and monomer-dimer-equilibrium have been characterized. To investigate the specific role of the processing for stability and folding, an unprocessed construct was expressed in E. coli and compared to the processed form. Both proteins have the same kinetic stability against chemical denaturant. They denature extremely slowly, because only the isolated subunits can unfold, and the monomer-dimer-equilibrium favors the dimer at moderate concentrations of denaturant. Due to the slow unfolding, both proteins exhibit an apparent hysteresis in the denaturation transition. Therefore it has not been possible to determine their thermodynamic stability. For both proteins, the stability and the rates of association and dissociation into processed or unprocessed subunits, respectively, are equal. Furthermore it could be shown that even under non-denaturing conditions the subunits are exchanged between dimers. Renaturation of the unprocessed variants is possible under strongly native conditions with 100 % yield. The processed protein, however, can be renatured with yields of about 50 %, and its refolding is strongly decelerated. The folding process is finished only after several days. During renaturation, an intermediate is populated, in which the longer of the two polypeptide chains forms a homodimer with a native-like subunit interface. The rate limiting step of renaturation is the association of the unfolded short chain with this dimer.

  5. Observing the interplay between surface and bulk optical nonlinearities in thin van der Waals crystals.

    PubMed

    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

  6. Nonadiabatic alignment of van der Waals--force-bound argon dimers by femtosecond laser pulses

    SciTech Connect

    Wu, J.; Vredenborg, A.; Ulrich, B.; Schmidt, L. Ph. H.; Meckel, M.; Voss, S.; Sann, H.; Kim, H.; Jahnke, T.; Doerner, R.

    2011-06-15

    We demonstrated that the weak van der Waals-force-bound argon dimer can be nonadiabatically aligned by nonresonant femtosecond laser pulses, showing periodic alignment and anti-alignment revivals after the extinction of the laser pulse. Based on the measured nonadiabatic alignment trace, the rotational constant of the argon dimer ground state is determined to be B{sub 0}= 0.05756 {+-} 0.00004 cm{sup -1}. Noticeable alignment dependence of frustrated tunneling ionization and bond-softening induced dissociation of the argon dimer are observed.

  7. 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.

  8. 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.

  9. Spectroscopy of DABCO-rare-gas and DABCO-DABCO van der Waals complexes

    NASA Astrophysics Data System (ADS)

    van den Hock, G.; Consalvo, D.; Parker, D. H.; Reuss, J.

    1993-03-01

    The excited electronic origin bands of several DABCO containing van der Waals complexes have been observed via (1+1) resonance enhanced multi-photon ionization. Sharp resonances with widths of about 3 cm-1 are seen for DABCO-Rg n=1,2,3 (Rg is Ar, Kr or Xe), for the DABCO-DABCO dimer and for DABCO-DABCO-Ar. The origins of the rare-gas complexes are blue shifted with respect to the monomer origin. Broad features originating from DABCO-Rg n complexes with high n, appear to higher energies than the complex origins, with widths of 120 cm-1.

  10. Electron transport calculations with Wannier functions in van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Dong, Wushi; Lopez-Bezanilla, Alejandro; Littlewood, Peter; Andreas Roelofs'group at Argonne National Lab Collaboration

    The vertical stacking of 2D materials forming van der Waals heterostructures (vdWHs) exhibits a wide range of interesting properties. A combined approach based on the Green's function formalism and a mean-field description of the electronic structure is used to calculate vertical electron transport in vdWHs. Tight-binding parameters obtained from Maximally Localized Wannier Functions enable us to model quantum electron transport at low computational costs. Our analysis of electron transport efficiencies provides the foundation and motivation for experimental works.

  11. Nanoscopy of Surface-Induced van der Waals-Zeeman Transitions

    NASA Astrophysics Data System (ADS)

    Hamamda, M.; Grucker, J.; Dutier, G.; Perales, F.; Bocvarski, V.; Baudon, J.; Ducloy, M.

    2008-10-01

    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*(3P2) 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.

  12. van der Waals-induced level coupling in metastable atom on surface collisions

    NASA Astrophysics Data System (ADS)

    Boustimi, M.; Viaris de Lesegno, B.; Perales, F.; Reinhardt, J.; Baudon, J.; Robert, J.; Ducloy, M.

    2001-01-01

    The symmetry of atomic wave functions is broken by the quadrupolar component of the van der Waals interaction between the atom and a planar surface. This results into a coupling able to mix levels of same parity such as 3P0 and 3P2 metastable levels of heavy rare gas atoms. The 3P0-3P2 transition in Ar and Kr has been evidenced in a time-of-flight experiment using as a surface the edge of a copper slit.

  13. 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

    2015-01-01

    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. PMID:26088295

  14. Periodic Motion of the van der Pol Equation with Impulsive Effect

    NASA Astrophysics Data System (ADS)

    Zheng, Shasha; Fu, Xilin

    In this paper, we investigate the dynamics of the periodic motion for switched van der Pol equation with impulsive effect, utilizing the theory of mapping dynamics in switching systems. For the optimized problem, we consider such impulsive dynamical model as switched system and analyze its features from a discontinuous point of view. Then, conceptions of switching sets as well as discrete mappings are briefly reviewed. By constructing generic mappings, we analyze the flow's periodic behaviors from the perspective of mapping structures. Finally, we apply our analysis and criterion to a specific impulsive model at fixed points and the periodic motions with impulse to the boundary are illustrated.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Phase synchronization and synchronization frequency of two-coupled van der Pol oscillators with delayed coupling

    NASA Astrophysics Data System (ADS)

    Hossein, Gholizade-Narm; Asad, Azemi; Morteza, Khademi

    2013-07-01

    In this paper, phase synchronization and the frequency of two synchronized van der Pol oscillators with delay coupling are studied. The dynamics of such a system are obtained using the describing function method, and the necessary conditions for phase synchronization are also achieved. Finding the vicinity of the synchronization frequency is the major advantage of the describing function method over other traditional methods. The equations obtained based on this method justify the phenomenon of the synchronization of coupled oscillators on a frequency either higher, between, or lower than the highest, in between, or lowest natural frequency of the aggregate oscillators. Several numerical examples simulate the different cases versus the various synchronization frequency delays.

  20. Storage of methane and freon by interstitial van der Waals confinement.

    PubMed

    Atwood, Jerry L; Barbour, Leonard J; Jerga, Agoston

    2002-06-28

    A known host-guest assembly, organized only by means of relatively weak dispersive forces, exhibits hitherto unappreciated thermal stability. The hexagonal close-packed arrangement of calix[4]arene contains lattice voids that can occlude small, highly volatile molecules. This host-guest system can be exploited to retain a range of freons, as well as methane, not only well above their normal boiling points, but also at relatively high temperatures and low pressures. The usually overlooked van der Waals interactions in organic crystals can indeed be used in a highly stable supramolecular system for gas storage. PMID:12004074

  1. Zwischen Commonsense und Wissenschaft Mathematik in der Erziehungsphilosophie A. N. Whiteheads

    NASA Astrophysics Data System (ADS)

    Sölch, Dennis

    Obwohl Whitehead heute wie selbstverständlich als Philosoph rezipiert wird, so hat er seine wissenschaftliche Laufbahn doch als Mathematiker begonnen. Lange Zeit war er gemeinsam mit Bertrand Russell als Autor der Principia Mathematica unter Mathematikern und mathematischen Logikern deutlich besser bekannt als unter Philosophen. Doch selbst von denjenigen, die sich mit Whiteheads Überlegungen zur Metaphysik, zur Wissenschaftsgeschichte und zur Theologie befassen, werden seine Schriften zur Philosophie von Erziehung und Bildung häufig kaum beachtet. So entgeht es leicht, dass Whitehead nicht nur ein auf theoretischem Gebiet brillanter Mathematiker war, sondern sein theoretisches Fachwissen im Hinblick auf pädagogische und didaktische Relevanz fortwährend reflektiert hat.

  2. [Variable expression of lower lip fistulas in Van der Woude syndrome].

    PubMed

    Opitz, C; Witkowski, R; Tinschert, S

    2000-07-01

    Eight families with the combination of cleft lip and/or cleft palate plus lower lip pits including their microforms were examined with the aim of characterization of microsymptoms. Hypodontia as a further symptom was also taken into consideration. Each of the symptoms was also noted separately in relatives of the patients and are to be considered as a genetic equivalent of the complete form of the autosomal-dominant inherited Van der Woude's syndrome. Knowledge of the variable expression of the basic gene is crucial for risk assessment in family counselling and also for distinguishing from clefts of other genesis with lower recurrence risk. PMID:10994321

  3. Rare and hidden attractors in Van der Pol-Duffing oscillators

    NASA Astrophysics Data System (ADS)

    Brezetskyi, S.; Dudkowski, D.; Kapitaniak, T.

    2015-07-01

    We study the dynamics of the single and coupled van der Pol-Duffing oscillators. Each oscillator is characterized by the multistability (the coexistence of attractors). Some of the coexisting attractors have very small basins of attraction (the rare ones) and some of them do not contain equilibria in their basin of attraction (the hidden ones). We perform the detailed bifurcation analysis of these attractors and investigate how this plethora of states influences the dynamics of the network of coupled oscillators. We have observed the cluster synchronization on different attractors as well as different types of chimera states.

  4. In-plane Van der Waals interactions of molecular self-assembly monolayer

    NASA Astrophysics Data System (ADS)

    Gao, Hong-Ying; Wagner, Hendrik; Held, Philipp Alexander; Du, Shixuan; Gao, Hong-Jun; Studer, Armido; Fuchs, Harald

    2015-02-01

    We demonstrate that the Van der Waals interactions in plane are important to control molecular self-assembly structure as well their phase transition. Using precise chemical modification to mediate such in-plane cohesive interactions, we observed the spontaneous formations of 2D order or disorder molecular self-assembly structures, as well their order-disorder phase transitions by annealing. Interestingly, we identified that the side alkyl chains stand up at surfaces and form the `locked' pairs/windmill structures. Moreover, we realized the covalent coupling based on ethynyl functionality before molecular desorption from metal surfaces, by enhancing the in-plane interactions.

  5. 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

  6. Patch contribution to near-field radiative energy transfer and van der Waals pressure between two half-spaces

    NASA Astrophysics Data System (ADS)

    Zheng, Yi; Narayanaswamy, Arvind

    2014-02-01

    Near-field effects in fluctuational electrodynamics leads to enhancement of radiative energy transfer as well as the emergence of van der Waals and/or Casimir pressure. While much has been learned from the analysis of near-field interactions between two half-spaces separated by a vacuum gap, we shed new light on the problem by finding how much of a surface patch on one of the half-spaces contributes to the energy transfer or van der Waals pressure at any location within the vacuum gap. We show that energy transfer and fluctuation-induced van der Waals pressure at any point on the surface of one half-space are qualitatively and quantitatively different due to the dissimilar zones of influence of interactions. We also show that the contributions from different surface patches are qualitatively similar for half-spaces with dielectric materials (silica, silicon carbide) and half-spaces with metals (gold).

  7. Interallelic Complementation among Der/Flb Alleles: Implications for the Mechanism of Signal Transduction by Receptor-Tyrosine Kinases

    PubMed Central

    Raz, E.; Schejter, E. D.; Shilo, B. Z.

    1991-01-01

    The large number of available embryonic lethal alleles in the Drosophila EGF receptor homolog (DER)/faint little ball locus allowed us to test the possibility of positive or negative interactions among different DER alleles. These interactions were monitored by examining the embryonic cuticular phenotypes of different heteroallelic combinations. Several positive interactions were identified, while negative interactions were restricted to a single allele. This is the first example of positive interactions within the same cell type among alleles of a receptor tyrosine kinase gene. The basis for these interactions is likely to arise from the mechanism of signal transduction by receptor tyrosine kinases, which involves receptor aggregation. A combination of two different DER mutant proteins defective in temporally distinct stages of the signal transduction process, may thus form a functional heterodimer. The mutation sites in four alleles showing positive interactions were localized. They identify regions within the protein which are likely to be important for these temporally distinct signal transduction processes. PMID:1936959

  8. Herausforderungen und Best Practices bei der Speicherung von multi-valued Attributen in LDAP-basierten Verzeichnisdiensten

    NASA Astrophysics Data System (ADS)

    Hommel, Wolfgang; Pluta, Daniel

    LDAP-basierte Verzeichnisdienste unterscheiden sich von relationalen Datenbankmanagementsystemen unter anderem stark bezĂŒglich der Datenmodellierung. Dieser Artikel vertieft eingangs die Herausforderungen bei der LDAP-spezifischen Abbildung von Relationen zwischen mehreren multivalued Attributen. Die Diskussion erfolgt vor dem Hintergrund, dass einerseits Verzeichnisdienste generell nur bedingt zur Speicherung von Relationen geeignet sind und dass andererseits multi-valued Attribute ein mĂ€chtiges LDAP-Instrument sind, zu dem es in relationalen Datenbanksystemen keine direkte Entsprechung gibt. Anschließend werden Lösungskonzepte vorgestellt und mögliche Weiterentwicklungen des IntegraTUM-LDAP-Schemas zu deren Umsetzung skizziert, eine exemplarische Implementierung prĂ€sentiert und die Ergebnisse der bisherigen Entwicklung des IntegraTUM-Schemas gegenĂŒbergestellt.

  9. House dust mite allergen Der f 1 induces IL-8 in human basophilic cells via ROS-ERK and p38 signal pathways.

    PubMed

    Yi, Myung-hee; Kim, Hyoung-Pyo; Jeong, Kyoung Yong; Kim, Chung-Ryul; Kim, Tae Yun; Yong, Tai-Soon

    2015-10-01

    Der f 1, a major house dust mite allergen and member of the papain-like cysteine protease family, can provoke immune responses with its proteolytic activity. To understand the role of Der f 1 in inflammatory immune responses, we studied the mechanism of the regulation of interleukin (IL)-8 expressions in human basophilic cell KU812 by proteolytically active recombinant Der f 1. Not only production of IL-8 mRNA was induced but also the DNA binding activity of activator protein-1 (AP-1) and phosphorylation of NF-ÎșB p65 were increased in Der f 1-treated KU812. Furthermore, Der f 1 induction of IL-8 expression was sensitive to pharmacological inhibition of ERK and p38 mitogen activated protein kinase (MAPK) pathways. Der f 1 also activated ERK and p38 MAPK phosphorylation and rapidly induced reactive oxygen species (ROS) production. The antioxidant N-acetyl-cysteine (NAC) inhibited phosphorylation of ERK, but not p38, suggesting that secretion of IL-8 in KU812 cells treated with Der f 1 is dependent on ROS, ERK MAPK and p38 MAPK. We describe the mechanism of Der f 1-induced IL-8 secretion from human basophilic cells, which are thought to be important for allergic inflammation independent of IgE antibodies. These findings improve our understanding of the inflammatory immune response in human basophils to protease allergens. PMID:26194066

  10. 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 fĂŒr den europĂ€ischen Raum zu schaffen, das eine rasche Publikation der fĂŒr das Festkörpergebiet reprĂ€sentative Arbeiten ermöglicht, wird durch ein internationales Herausgebergremium eine neue wissenschaftliche Zeitschrift gegrĂŒndet.

  11. Supramolecular interactions of anthraquinone networks on Au(1 1 1): Hydrogen bonds and van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Kim, Ji Yeon; Jang, Won Jun; Kim, Howon; Yoon, Jong Keon; Park, Jihun; Kahng, Se-Jong; Lee, Jhinhwan; Han, Seungwu

    2013-03-01

    Intermolecular interactions of supramolecular structures were studied in anthraquinone molecules on Au(1 1 1) using scanning tunneling microscopy. Molecular chains of linear and zigzag structures were observed and explained with simple models of hydrogen bonds. In two-dimensional islands, square and chevron structures were observed, and their molecular models were reproduced by density functional theory calculations. Square structures were made of four hydrogen bonds per molecule, whereas chevron structures were explained with four hydrogen bonds per molecule and additional van der Waals interactions. Our study shows that van der Waals interactions play cooperative roles in determining the hydrogen bonded networks of the system.

  12. 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 ÎŒs) 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.

  13. van der Waals - Zeeman transitions of metastable neon atoms passing through a micro-slit copper grating

    NASA Astrophysics Data System (ADS)

    Karam, J.-C.; Grucker, J.; Boustimi, M.; Perales, F.; Bocvarski, V.; Baudon, J.; Vassilev, G.; Robert, J.; Ducloy, M.

    2006-04-01

    Surface-induced transitions between Zeeman sub-levels of metastable neon atoms traversing a micro-slit copper grating are investigated. The quadrupolar part of the surface van der Waals interaction suddenly perturbs the evolution of the Zeeman sub-levels in a magnetic field B, giving rise to van der Waals - Zeeman transitions. Exothermal inelastic transitions are identified by the related deflection γ. In a diagram (γ, B1/2) the location of the inelastic peaks is fitted by straight lines of slopes proportional to |Δm|-1/2, where Δm is the magnetic number change.

  14. Microwave Spectrum, Van Der Waals Bond Length, and 131Xe Quadrupole Coupling Constant of Xe-SO3

    NASA Astrophysics Data System (ADS)

    Dewberry, Chris; Huff, Anna; Mackenzie, Becca; Leopold, Ken

    2015-06-01

    Nine isotopologues of Xe-SO3 have been observed by pulsed-nozzle Fourier transform microwave spectroscopy. The complex is a symmetric top with a Xe-S van der Waals distance of 3.577(2) Å. The increase in rare gas distance relative to that in Kr-SO3 is equal to the difference in van der Waals radii between Xe and Kr. The 131Xe nuclear quadrupole coupling constant indicates that the electric field gradient at the xenon nucleus is 78% larger than that at the Kr nucleus in Kr-SO3.

  15. Admissible Shock Waves and Shock-Induced Phase Transition in a Van Der Waals Fluid (part i - the Model)

    NASA Astrophysics Data System (ADS)

    Sugiyama, M.; Mentrelli, A.; Ruggeri, T.

    2010-04-01

    An exhaustive analysis of shock admissibility and shock-induced phase transition in a van der Waals fluid is presented. The crucial role played by the unperturbed state (the state before the shock) is put into evidence, leading to a full understanding of some phenomena observable in real gases that cannot be accounted for in the framework of the ideal gas model. The study is carried out by means of the theory of hyperbolic systems and numerical calculations. The paper is divided into three parts; in this part the van der Waals model is presented, along with a discussion concerning the thermodynamic stability and phase transitions.

  16. Epicutaneously applied Der p 2 induces a strong TH2-biased antibody response in C57BL/6 mice, independent of functional TLR4

    PubMed Central

    Stremnitzer, C; Manzano-Szalai, K; Starkl, P; Willensdorfer, A; Schrom, S; Singer, J; Reichart, U; Akira, S; Jensen-Jarolim, E

    2014-01-01

    Background The major house dust mite allergen Der p 2 is a structural and functional homologue of MD-2 within the TLR4–CD14–MD-2 complex. An asthma mouse model in TLR4-deficient mice recently suggested that the allergic immune response against Der p 2 is solely dependent on TLR4 signaling. We investigated whether similar mechanisms are important for Der p 2 sensitization via the skin. Methods In an epicutaneous sensitization model, the response to recombinant Der p 2 in combination with or without lipopolysaccharide (LPS) was compared between C57BL/6 WT and TLR4-deficient mice. We further analyzed possible adjuvant function of exogenous cysteine proteases. Results Sensitization with rDer p 2 induced similar levels of allergen-specific IgG1 and IgE antibodies in both mouse strains. LPS increased the systemic (antibody levels, cytokine release by restimulated splenocytes) and local (infiltration of immune cells into the skin) Th2 immune responses, which against our expectations were stronger in the absence of functional TLR4 expression. Barrier disruption by papain, a protease with structural homology to Der p 1, did not enhance the sensitization capacity of rDer p 2. However, the presence of LPS increased the stability of rDer p 2 against the protease. Conclusion Our data suggest that rDer p 2 alone can cause a strong TH2-biased response via the skin being enhanced in the presence of LPS. This response is not reliant on functional TLR4, but vice versa TLR4 expression rather protects against epicutaneous sensitization to house dust mite allergen Der p 2. PMID:24735481

  17. 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.

  18. Isobaric first-principles molecular dynamics of liquid water with nonlocal van der Waals interactions.

    PubMed

    Miceli, Giacomo; de Gironcoli, Stefano; Pasquarello, Alfredo

    2015-01-21

    We investigate the structural properties of liquid water at near ambient conditions using first-principles molecular dynamics simulations based on a semilocal density functional augmented with nonlocal van der Waals interactions. The adopted scheme offers the advantage of simulating liquid water at essentially the same computational cost of standard semilocal functionals. Applied to the water dimer and to ice Ih, we find that the hydrogen-bond energy is only slightly enhanced compared to a standard semilocal functional. We simulate liquid water through molecular dynamics in the NpH statistical ensemble allowing for fluctuations of the system density. The structure of the liquid departs from that found with a semilocal functional leading to more compact structural arrangements. This indicates that the directionality of the hydrogen-bond interaction has a diminished role as compared to the overall attractions, as expected when dispersion interactions are accounted for. This is substantiated through a detailed analysis comprising the study of the partial radial distribution functions, various local order indices, the hydrogen-bond network, and the selfdiffusion coefficient. The explicit treatment of the van der Waals interactions leads to an overall improved description of liquid water. PMID:25612714

  19. Elastic properties of van der Waals epitaxy grown bismuth telluride 2D nanosheets

    NASA Astrophysics Data System (ADS)

    Guo, Lingling; Yan, Haoming; Moore, Quentarius; Buettner, Michael; Song, Jinhui; Li, Lin; Araujo, Paulo T.; Wang, Hung-Ta

    2015-07-01

    Bismuth telluride (Bi2Te3) two-dimensional (2D) nanosheets prepared by van der Waals epitaxy were successfully detached, transferred, and suspended for nano-indentation measurements to be performed on freestanding circular nanosheets. The Young's modulus acquired by fitting linear elastic behaviors of 26 samples (thickness: 5-14 nm) is only 11.7-25.7 GPa, significantly smaller than the bulk in-plane Young's modulus (50-55 GPa). Compliant and robust Bi2Te3 2D nanosheets suggest the feasibility of the elastic strain engineering of topological surface states.Bismuth telluride (Bi2Te3) two-dimensional (2D) nanosheets prepared by van der Waals epitaxy were successfully detached, transferred, and suspended for nano-indentation measurements to be performed on freestanding circular nanosheets. The Young's modulus acquired by fitting linear elastic behaviors of 26 samples (thickness: 5-14 nm) is only 11.7-25.7 GPa, significantly smaller than the bulk in-plane Young's modulus (50-55 GPa). Compliant and robust Bi2Te3 2D nanosheets suggest the feasibility of the elastic strain engineering of topological surface states. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03282b

  20. Isobaric first-principles molecular dynamics of liquid water with nonlocal van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Miceli, Giacomo; de Gironcoli, Stefano; Pasquarello, Alfredo

    2015-01-01

    We investigate the structural properties of liquid water at near ambient conditions using first-principles molecular dynamics simulations based on a semilocal density functional augmented with nonlocal van der Waals interactions. The adopted scheme offers the advantage of simulating liquid water at essentially the same computational cost of standard semilocal functionals. Applied to the water dimer and to ice Ih, we find that the hydrogen-bond energy is only slightly enhanced compared to a standard semilocal functional. We simulate liquid water through molecular dynamics in the NpH statistical ensemble allowing for fluctuations of the system density. The structure of the liquid departs from that found with a semilocal functional leading to more compact structural arrangements. This indicates that the directionality of the hydrogen-bond interaction has a diminished role as compared to the overall attractions, as expected when dispersion interactions are accounted for. This is substantiated through a detailed analysis comprising the study of the partial radial distribution functions, various local order indices, the hydrogen-bond network, and the selfdiffusion coefficient. The explicit treatment of the van der Waals interactions leads to an overall improved description of liquid water.

  1. Microwave and ab initio studies of the Xe-CH4 van der Waals complex

    NASA Astrophysics Data System (ADS)

    Wen, Qing; JĂ€ger, Wolfgang

    2006-01-01

    An ab initio potential-energy surface of the Xe-CH4 van der Waals complex was constructed at the coupled cluster level of theory with single, double, and perturbatively included triple excitations. The recently developed small-core pseudopotential and augmented correlation-consistent polarized valence quadruple-zeta basis set was used for the xenon atom and Dunning's augmented correlation-consistent polarized valence triple-zeta basis set for the other atoms. The basis sets were supplemented with bond functions. Dipole moments were also calculated at various configurations. Rotational spectra of the Xe-CH4 van der Waals complex were recorded using a pulsed-nozzle Fourier transform microwave spectrometer. The isotopomers studied include those of CH4,CH134,CD4,CH3D, and CHD3 with the five most abundant Xe isotopes. Transitions within three internal rotor states, namely, the j =0,K=0;j=1,K=0; and j =2,K=1 states, were observed and assigned. Nuclear quadrupole hyperfine structures due to the presence of Xe131(I=3/2) were detected and analyzed. It was found that the j =1,K=0 state is perturbed by a Coriolis interaction with a nearby j =1,K=1 state. For isotopomers containing CH3D and CHD3, the j =2 states are no longer metastable and could not be observed. The spectroscopic results were used to derive structural and dynamical information of the Xe-CH4 complex.

  2. Potential-energy surface and van der Waals motions of p-difluorobenzene-argon cation

    NASA Astrophysics Data System (ADS)

    Makarewicz, Jan

    2005-07-01

    The structure and dynamics of the van der Waals complex of argon with the p-difluorobenzene cation are investigated using the ab initio theory. The restricted open-shell MĂžller-Plesset second-order perturbation method combined with the augmented correlation-consistent polarized valence double-ζ basis set is employed to determine the electronic ground-state potential-energy surface of the cationic complex. This surface is extremely flat in a wide region of the configuration space of the Ar atom which moves almost freely over the monomer ring. However, it is bound to the monomer stronger in the cationic than in the neutral complex. Its binding energy is calculated to be 621cm-1 at a distance of 3.445Å from the monomer center. The calculated dissociation energy of 572cm-1 agrees perfectly with the experimental value of 572±6cm-1 [S. M. Belm, R. J. Moulds, and D. Lawrence, J. Chem. Phys. 115, 10709 (2001)]. The effect of a strong coupling of large-amplitude intermolecular motions on the character of van der Waals vibrational states is investigated. The vibrational structure of the spectrum of the complex is explained and its earlier assignment is partly corrected.

  3. Nonlocal van der Waals functionals: The case of rare-gas dimers and solids

    NASA Astrophysics Data System (ADS)

    Tran, Fabien; Hutter, JĂŒrg

    2013-05-01

    Recently, the nonlocal van der Waals (vdW) density functionals [M. Dion, H. Rydberg, E. Schröder, D. C. Langreth, and B. I. Lundqvist, Phys. Rev. Lett. 92, 246401 (2004), 10.1103/PhysRevLett.92.246401] have attracted considerable attention due to their good performance for systems where weak interactions are important. Since the physics of dispersion is included in these functionals, they are usually more accurate and show less erratic behavior than the semilocal and hybrid methods. In this work, several variants of the vdW functionals have been tested on rare-gas dimers (from He2 to Kr2) and solids (Ne, Ar, and Kr) and their accuracy compared to standard semilocal approximations, supplemented or not by an atom-pairwise dispersion correction [S. Grimme, J. Antony, S. Ehrlich, and H. Krieg, J. Chem. Phys. 132, 154104 (2010), 10.1063/1.3382344]. An analysis of the results in terms of energy decomposition is also provided.

  4. Large-area single-layer MoSe2 and its van der Waals heterostructures.

    PubMed

    Shim, Gi Woong; Yoo, Kwonjae; Seo, Seung-Bum; Shin, Jongwoo; Jung, Dae Yool; Kang, Il-Suk; Ahn, Chi Won; Cho, Byung Jin; Choi, Sung-Yool

    2014-07-22

    Layered structures of transition metal dichalcogenides stacked by van der Waals interactions are now attracting the attention of many researchers because they have fascinating electronic, optical, thermoelectric, and catalytic properties emerging at the monolayer limit. However, the commonly used methods for preparing monolayers have limitations of low yield and poor extendibility into large-area applications. Herein, we demonstrate the synthesis of large-area MoSe2 with high quality and uniformity by selenization of MoO3 via chemical vapor deposition on arbitrary substrates such as SiO2 and sapphire. The resultant monolayer was intrinsically doped, as evidenced by the formation of charged excitons under low-temperature photoluminescence analysis. A van der Waals heterostructure of MoSe2 on graphene was also demonstrated. Interestingly, the MoSe2/graphene heterostructures show strong quenching of the characteristic photoluminescence from MoSe2, indicating the rapid transfer of photogenerated charge carriers between MoSe2 and graphene. The development of highly controlled heterostructures of two-dimensional materials will further promote advances in the physics and chemistry of reduced dimensional systems and will provide novel applications in electronics and optoelectronics. PMID:24987802

  5. Nuclear spin-spin coupling in a van der Waals-bonded system: xenon dimer.

    PubMed

    Vaara, Juha; Hanni, Matti; Jokisaari, Jukka

    2013-03-14

    Nuclear spin-spin coupling over van der Waals bond has recently been observed via the frequency shift of solute protons in a solution containing optically hyperpolarized (129)Xe nuclei. We carry out a first-principles computational study of the prototypic van der Waals-bonded xenon dimer, where the spin-spin coupling between two magnetically non-equivalent isotopes, J((129)Xe - (131)Xe), is observable. We use relativistic theory at the four-component Dirac-Hartree-Fock and Dirac-density-functional theory levels using novel completeness-optimized Gaussian basis sets and choosing the functional based on a comparison with correlated ab initio methods at the nonrelativistic level. J-coupling curves are provided at different levels of theory as functions of the internuclear distance in the xenon dimer, demonstrating cross-coupling effects between relativity and electron correlation for this property. Calculations on small Xe clusters are used to estimate the importance of many-atom effects on J((129)Xe - (131)Xe). Possibilities of observing J((129)Xe - (131)Xe) in liquid xenon are critically examined, based on molecular dynamics simulation. A simplistic spherical model is set up for the xenon dimer confined in a cavity, such as in microporous materials. It is shown that the on the average shorter internuclear distance enforced by the confinement increases the magnitude of the coupling as compared to the bulk liquid case, rendering J((129)Xe - (131)Xe) in a cavity a feasible target for experimental investigation. PMID:23514495

  6. Strain-Induced Electronic Structure Changes in Stacked van der Waals Heterostructures.

    PubMed

    He, Yongmin; Yang, Yang; Zhang, Zhuhua; Gong, Yongji; Zhou, Wu; Hu, Zhili; Ye, Gonglan; Zhang, Xiang; Bianco, Elisabeth; Lei, Sidong; Jin, Zehua; Zou, Xiaolong; Yang, Yingchao; Zhang, Yuan; Xie, Erqing; Lou, Jun; Yakobson, Boris; Vajtai, Robert; Li, Bo; Ajayan, Pulickel

    2016-05-11

    Vertically stacked van der Waals heterostructures composed of compositionally different two-dimensional atomic layers give rise to interesting properties due to substantial interactions between the layers. However, these interactions can be easily obscured by the twisting of atomic layers or cross-contamination introduced by transfer processes, rendering their experimental demonstration challenging. Here, we explore the electronic structure and its strain dependence of stacked MoSe2/WSe2 heterostructures directly synthesized by chemical vapor deposition, which unambiguously reveal strong electronic coupling between the atomic layers. The direct and indirect band gaps (1.48 and 1.28 eV) of the heterostructures are measured to be lower than the band gaps of individual MoSe2 (1.50 eV) and WSe2 (1.60 eV) layers. Photoluminescence measurements further show that both the direct and indirect band gaps undergo redshifts with applied tensile strain to the heterostructures, with the change of the indirect gap being particularly more sensitive to strain. This demonstration of strain engineering in van der Waals heterostructures opens a new route toward fabricating flexible electronics. PMID:27120401

  7. Critical Importance of van der Waals Stabilization in Strongly Chemically Bonded Surfaces: Cu(110):O.

    PubMed

    Bamidele, J; Brndiar, J; Gulans, A; Kantorovich, L; Ć tich, I

    2013-12-10

    We provide strong evidence that different reconstructed phases of the oxidized Cu(110) surface are stabilized by the van der Waals (vdW) interactions. These covalently bonded reconstructed surfaces feature templates that are an integral part of the surfaces and are bonded on the bare metal surface by a combination of chemical and physical bonding. The vdW stabilization in this class of systems affects predominantly the intertemplate Cu-O interactions in structures sparsely populated by these templates. The conventional dispersionless density functional theory (DFT) methods fail to model such systems. We find a failure to describe the thermodynamics of the different phases that are formed at different oxygen exposures and spurious minima on the potential energy surface of a diffusing surface adatom. To overcome these issues, we employ a range of different DFT methods that account for the missing vdW correlations. Surprisingly, despite vast conceptual differences in the different formulations of these methods, they yield physically identical results for the Cu(110):O surface phases, provided the massive screening effects in the metal are taken into account. Contrary, the vibrational contribution does not consistently stabilize the experimentally observed surface structures. The van der Waals surface stabilization, so far deemed to play only a minor role in hard-bonded surfaces, is suggested to be a more general key feature for this and other related surfaces. PMID:26592291

  8. Measuring anisotropic resistivity of single crystals using the van der Pauw technique

    NASA Astrophysics Data System (ADS)

    Borup, Kasper A.; Fischer, Karl F. F.; Brown, David R.; Snyder, G. Jeffrey; Iversen, Bo B.

    2015-07-01

    Anisotropy in properties of materials is important in materials science and solid-state physics. Measurement of the full resistivity tensor of crystals using the standard four-point method with bar shaped samples requires many measurements and may be inaccurate due to misalignment of the bars along crystallographic directions. Here an approach to extracting the resistivity tensor using van der Pauw measurements is presented. This reduces the number of required measurements. The theory of the van der Pauw method is extended to extract the tensor from parallelogram shaped samples with known geometry. Methods to extract the tensor for both known and unknown principal axis orientation are presented for broad applicability to single crystals. Numerical simulations of errors are presented to quantify error sources. Several benchmark experiments are performed on isotropic graphite samples to verify the internal consistency of the developed theory, test experimental precision, and characterize error sources. The presented methods are applied to a RuS b2 single crystal at room temperature and the results are discussed based on the error source analysis. Temperature resolved resistivities along the a and b directions are finally reported and briefly discussed.

  9. van der Waals Solids from Self-Assembled Nanoscale Building Blocks.

    PubMed

    Choi, Bonnie; Yu, Jaeeun; Paley, Daniel W; Trinh, M Tuan; Paley, Maria V; Karch, Jessica M; Crowther, Andrew C; Lee, Chul-Ho; Lalancette, Roger A; Zhu, Xiaoyang; Kim, Philip; Steigerwald, Michael L; Nuckolls, Colin; Roy, Xavier

    2016-02-10

    Traditional atomic van der Waals materials such as graphene, hexagonal boron-nitride, and transition metal dichalcogenides have received widespread attention due to the wealth of unusual physical and chemical behaviors that arise when charges, spins, and vibrations are confined to a plane. Though not as widespread as their atomic counterparts, molecule-based two-dimensional (2D) layered solids offer significant benefits; their structural flexibility will enable the development of materials with tunable properties. Here we describe a layered van der Waals solid self-assembled from a structure-directing building block and C60 fullerene. The resulting crystalline solid contains a corrugated monolayer of neutral fullerenes and can be mechanically exfoliated. The absorption spectrum of the bulk solid shows an optical gap of 390 ± 40 meV that is consistent with thermal activation energy obtained from electrical transport measurement. We find that the dimensional confinement of fullerenes significantly modulates the optical and electronic properties compared to the bulk solid. PMID:26829055

  10. When is the mode-summation method of calculating van der Waals force valid?

    NASA Astrophysics Data System (ADS)

    Narayanaswamy, Arvind

    2015-03-01

    Most calculations of van der Waals forces and Casimir forces can be categorized as variations of two ``proto methods'': (1) Lifshitz theory, and (2) mode summation method. In the Lifshitz theory, by which I include the subsequent generalization by Dzyaloshinskii, Lifshitz, and Pitaevskii [Adv. Phys. 10, 165 (1961); See also Zheng and Narayanaswamy, Phys. Rev. A 83, 042504 (2011)] the dispersion force is expressed in terms of the (dyadic) Green's function of the vector Helmholtz equation. In the mode summation method [see Casimir, Proc. Kon. Ned. Akad. Wetensch. 51, 793 (1948); Van Kampen, Nijboer, and Schram, Phys. Lett. A 26, 307 (1968)], the free energy of a configuration of objects is expressed in terms of the sum of the free energies of each of the possible electromagnetic modes. The derivative of this free energy with respect to variation of relative positions between the objects yields the force between two objects. However, we raised questions about the validity of the mode summation method when calculating van der Waals forces in dissipative media [see Narayanaswamy and Zheng, Phys. Rev. A 88, 012502 (2013) and Ninham, Parsegian, and Weiss, J. Stat. Phys. 2, 323 (1970)]. In this talk, I want to start a discussion about the validity of the mode summation method.

  11. Mapping van der Waals forces with frequency modulation dynamic force microscopy

    NASA Astrophysics Data System (ADS)

    Polesel-Maris, J.; Guo, H.; Zambelli, T.; Gauthier, S.

    2006-08-01

    Nanometre-size gold clusters supported on MoS2(0001) are investigated by means of ultrahigh-vacuum frequency modulation dynamic force microscopy. Topography and frequency shift images are simultaneously obtained using the average tunnelling current to regulate the tip-substrate distance. Two families of clusters are observed, giving different frequency shift images. While the topographic and frequency shift profiles have similar shapes on small clusters (size \\lesssim 1 nm), they are quite different near the top of large clusters (size \\gtrsim 4 nm): the topographic profile is rounded, but the frequency shift profile exhibits rather steep edges and a depression near the centre of the island. It is demonstrated that these differences result from the finite range of van der Waals forces. On small islands, the frequency shift is dominated by the interaction of the tip with the substrate. On large islands, it is dominated by the interaction with the island. The particular observed shape results from the geometry of the island. These interpretations are comforted by analytical and numerical calculations. In particular, the characteristic shape of the frequency shift profiles on large islands can be reproduced by introducing realistic parameters and considering only the contribution of van der Waals forces.

  12. Atomically Sharp Interface in an h-BN-epitaxial graphene van der Waals Heterostructure

    NASA Astrophysics Data System (ADS)

    Sediri, Haikel; Pierucci, Debora; Hajlaoui, Mahdi; Henck, Hugo; Patriarche, Gilles; Dappe, Yannick J.; Yuan, Sheng; Toury, Bérangère; Belkhou, Rachid; Silly, Mathieu G.; Sirotti, Fausto; Boutchich, Mohamed; Ouerghi, Abdelkarim

    2015-11-01

    Stacking various two-dimensional atomic crystals is a feasible approach to creating unique multilayered van der Waals heterostructures with tailored properties. Herein for the first time, we present a controlled preparation of large-area h-BN/graphene heterostructures via a simple chemical deposition of h-BN layers on epitaxial graphene/SiC(0001). Van der Waals forces, which are responsible for the cohesion of the multilayer system, give rise to an abrupt interface without interdiffusion between graphene and h-BN, as shown by X-ray Photoemission Spectroscopy (XPS) and direct observation using scanning and High-Resolution Transmission Electron Microscopy (STEM/HRTEM). The electronic properties of graphene, such as the Dirac cone, remain intact and no significant charge transfer i.e. doping, is observed. These results are supported by Density Functional Theory (DFT) calculations. We demonstrate that the h-BN capped graphene allows the fabrication of vdW heterostructures without altering the electronic properties of graphene.

  13. Establishing consistent van der Waals volumes of polyatomic ions from crystal structures.

    PubMed

    Beichel, Witali; Eiden, Philipp; Krossing, Ingo

    2013-10-01

    Based on temperature (T) dependent crystal structure data of seven organic salts, a radii-based scheme for the calculation of the van der Waals volume (V(vdw)) is analyzed. The obtained volumes (V(vdw,r), r=radius-based) are nearly T independent. An ion volume partitioning scheme is proposed by fixing the anion volumes of [Cl](-), [Br](-), [I](-), [BF(4)](-), [PF(6)](-), [OTf](-) and [NTf(2)](-). The van der Waals volumes (V(vdw,r) (+/-)) of 48 ions are established, with low standard deviations (0.2-3.6 Å(3), 0.1-4.5 % of V(vdw,r) (+/-)). The ion volumes are independent of the counterion and one crystal structure already suffices for their derivation. Correlations of the viscosity with V(vdw,r) via a Litovitz ansatz and our recently derived Arrhenius-type approach prove that these volumes are suitable for the volume-based description and prediction of IL properties. The corresponding correlation coefficient for the latter is R(2)=0.86 for 40 ILs (354 data points) in the T range of 253-373 K. PMID:23956232

  14. 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. PMID:25493357

  15. Excitons in one-dimensional van der Waals materials: Sb2S3 nanoribbons

    NASA Astrophysics Data System (ADS)

    Caruso, Fabio; Filip, Marina R.; Giustino, Feliciano

    2015-09-01

    Antimony sulphide Sb2S3 has emerged as a promising material for a variety of energy applications ranging from solar cells to thermoelectrics and solid-state batteries. The most distinctive feature of Sb2S3 is its crystal structure, which consists of parallel 1-nm-wide ribbons held together by weak van der Waals forces. This structure clearly suggests that it should be possible to isolate individual Sb2S3 ribbons using micromechanical or liquid-phase exfoliation techniques. However, it is not clear yet how to identify the ribbons postexfoliation using standard optical probes. Using state-of-the-art first-principles calculations based on many-body perturbation theory, here we show that individual ribbons of Sb2S3 carry optical signatures clearly distinct from those of bulk Sb2S3 . In particular, we find a large blueshift of the optical absorption edge (from 1.38 to 2.30 eV) resulting from the interplay between a reduced screening and the formation of bound excitons. In addition, we observe a transition from an indirect band gap to a direct gap, suggesting an enhanced photoluminescence in the green. These unique fingerprints will enable extending the research on van der Waals materials to the case of one-dimensional chalchogenides.

  16. Transition metals-graphene interaction: the role of the screened van der Waals energy

    NASA Astrophysics Data System (ADS)

    Ambrosetti, Alberto; Silvestrelli, Pier Luigi

    2015-03-01

    The interaction of graphene with transition metals is of particular interest for practical applications, which include for instance the efficient production of high-quality graphene. The accurate theoretical description of transition metals-graphene interfaces, however, is a particularly challenging problem due to the complex interplay between van der Waals (vdW) and hybridization effects. Here we apply the DFT/vdW-WF2s method, which allows to augment semi-local Density Functional Theory through the introduction of screened vdW interactions. Notably, we find that a reliable modeling of the van der Waals interaction should account for complex metal screening effects, that are due to the combined contributions of the p- and s-like quasi-free electrons, and the more localized d-states. The resulting geometry and energetic properties are in good agreement with experimental data and sophisticates theoretical calculations. Moreover, the Maximally Localized Wannier Functions underlying the DFT/vdW-WF2s method allow for an intuitive understanding of the complex binding mechanism.

  17. 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. PMID:25907526

  18. First report of a small supernumerary der(8;14) marker chromosome.

    PubMed

    Guilherme, R S; Dutra, A R N; Perez, A B A; Takeno, S S; Oliveira, M M; Kulikowski, L D; Klein, E; Hamid, A B; Liehr, T; Melaragno, M I

    2013-01-01

    Small supernumerary marker chromosomes (sSMC) are structurally abnormal chromosomes, generally equal in size or smaller than a chromosome 20 of the same metaphase spread. Most of them are unexpectedly detected in routine karyotype analyses, and it is usually not easy to correlate them with a specific clinical picture. A small group of sSMCs is derived from more than one chromosome, called complex sSMCs. Here, we report on a patient with a de novo complex sSMC, derived from chromosomes 8 and 14. Banding karyotype analysis, multiplex ligation-dependent probe amplification (MLPA), single nucleotide polymorphism (SNP)-based array, and fluorescence in situ hybridization (FISH) were performed to investigate its origin. Array and FISH analyses revealed a der(14)t(8;14)(p23.2;q22.1)dn. The propositus presents some clinical features commonly found in patients with partial duplication or triplication of 8p and 14q. This is the first report describing a patient with a congenital der(14)t(8;14)(p23.2;q22.1)dn sSMC. PMID:23548553

  19. Existence of quasi-periodic solutions of fast excited van der Pol-Mathieu-Duffing equation

    NASA Astrophysics Data System (ADS)

    Lu, Lin; Li, Xuemei

    2015-12-01

    The van der Pol-Mathieu-Duffing equation x ̈ + ( Ω0 2 + h 1 cos Ω 1 t + h 2 cos Ω 2 t ) x - ( α - ÎČ x 2 ) x ˙ - h 3 x 3 = h 4 Ω3 2 cos x cos Ω 3 t is considered in this paper, where α, ÎČ, h1, h2, h3, h4, Ω1, Ω2 are small parameters, α, ÎČ > 0, the frequency Ω3 is large compared to Ω1 and Ω2, the above parameters are real. For ∀α, ÎČ > 0, we use KAM (Kolmogorov-Arnold-Moser) theory to prove that the van der Pol-Mathieu-Duffing equation possesses quasi-periodic solutions for most of the parameters Ω0, Ω1, Ω2, Ω3, it verifies some phenomenon of Fahsi and Belhaq [Commun. Nonlinear Sci. 14, 244-253 (2009)] and can be regarded as a extension of Abouhazim et al. [Nonlinear Dyn. 39, 395-409 (2005)].

  20. Exciton–polaritons in van der Waals heterostructures embedded in tunable microcavities

    PubMed Central

    Dufferwiel, S.; Schwarz, S.; Withers, F.; Trichet, A. A. P.; Li, F.; Sich, M.; Del Pozo-Zamudio, O.; Clark, C.; Nalitov, A.; Solnyshkov, D. D.; Malpuech, G.; Novoselov, K. S.; Smith, J. M.; Skolnick, M. S.; Krizhanovskii, D. N.; Tartakovskii, A. I.

    2015-01-01

    Layered materials can be assembled vertically to fabricate a new class of van der Waals heterostructures a few atomic layers thick, compatible with a wide range of substrates and optoelectronic device geometries, enabling new strategies for control of light–matter coupling. Here, we incorporate molybdenum diselenide/hexagonal boron nitride (MoSe2/hBN) quantum wells in a tunable optical microcavity. Part-light–part-matter polariton eigenstates are observed as a result of the strong coupling between MoSe2 excitons and cavity photons, evidenced from a clear anticrossing between the neutral exciton and the cavity modes with a splitting of 20 meV for a single MoSe2 monolayer, enhanced to 29 meV in MoSe2/hBN/MoSe2 double-quantum wells. The splitting at resonance provides an estimate of the exciton radiative lifetime of 0.4 ps. Our results pave the way for room-temperature polaritonic devices based on multiple-quantum-well van der Waals heterostructures, where polariton condensation and electrical polariton injection through the incorporation of graphene contacts may be realized. PMID:26446783

  1. Van der Pauw and Hall Measurements on Ultra Thin Silicon-on-Insulator

    NASA Astrophysics Data System (ADS)

    Peng, Weina; Jiang, Hongquan; Ha, Sangkeun; Thalakulam, Madhu; Savage, Donald; Eriksson, Mark; Lagally, Max

    2008-03-01

    Ultra-thin silicon-on-insulator (UTSOI) provides opportunities to study the role of the surface in electrical transport in Si. Because the Si layers can be as thin as 10 nm, surface states, surface induced band bending, and gap states at the oxide-Si interface dominate the carrier density. Transport measurements provide a sensitive probe of the carriers. Previous measurements of thin Si structures have shown that Si/SiO2 interface traps deplete Si of mobile carriers, and sheet resistances reach 10^11 ohm/sq for a 20 nm thick sample [1]. Thus, any perturbation to the surface that induces even modest carrier densities can be detected in transport. We perform van der Pauw and Hall measurements on UTSOI structures with a variety of surface modifications, including hydrogen termination and epichlorohydrin surface attachment. UTSOI that was extremely resistive with oxide on both sides undergoes a drop in resistance of more than 3 orders of magnitude after surface modification. Hall and van der Pauw measurements, reveal the density and the sign of the carriers. We discuss the mechanisms for this increased conductivity. [1] Zhang P. et al. Nature 439 703 (2006)

  2. Atomically Sharp Interface in an h-BN-epitaxial graphene van der Waals Heterostructure

    PubMed Central

    Sediri, Haikel; Pierucci, Debora; Hajlaoui, Mahdi; Henck, Hugo; Patriarche, Gilles; Dappe, Yannick J.; Yuan, Sheng; Toury, BĂ©rangĂšre; Belkhou, Rachid; Silly, Mathieu G.; Sirotti, Fausto; Boutchich, Mohamed; Ouerghi, Abdelkarim

    2015-01-01

    Stacking various two-dimensional atomic crystals is a feasible approach to creating unique multilayered van der Waals heterostructures with tailored properties. Herein for the first time, we present a controlled preparation of large-area h-BN/graphene heterostructures via a simple chemical deposition of h-BN layers on epitaxial graphene/SiC(0001). Van der Waals forces, which are responsible for the cohesion of the multilayer system, give rise to an abrupt interface without interdiffusion between graphene and h-BN, as shown by X-ray Photoemission Spectroscopy (XPS) and direct observation using scanning and High-Resolution Transmission Electron Microscopy (STEM/HRTEM). The electronic properties of graphene, such as the Dirac cone, remain intact and no significant charge transfer i.e. doping, is observed. These results are supported by Density Functional Theory (DFT) calculations. We demonstrate that the h-BN capped graphene allows the fabrication of vdW heterostructures without altering the electronic properties of graphene. PMID:26585245

  3. Atomically Sharp Interface in an h-BN-epitaxial graphene van der Waals Heterostructure.

    PubMed

    Sediri, Haikel; Pierucci, Debora; Hajlaoui, Mahdi; Henck, Hugo; Patriarche, Gilles; Dappe, Yannick J; Yuan, Sheng; Toury, BĂ©rangĂšre; Belkhou, Rachid; Silly, Mathieu G; Sirotti, Fausto; Boutchich, Mohamed; Ouerghi, Abdelkarim

    2015-01-01

    Stacking various two-dimensional atomic crystals is a feasible approach to creating unique multilayered van der Waals heterostructures with tailored properties. Herein for the first time, we present a controlled preparation of large-area h-BN/graphene heterostructures via a simple chemical deposition of h-BN layers on epitaxial graphene/SiC(0001). Van der Waals forces, which are responsible for the cohesion of the multilayer system, give rise to an abrupt interface without interdiffusion between graphene and h-BN, as shown by X-ray Photoemission Spectroscopy (XPS) and direct observation using scanning and High-Resolution Transmission Electron Microscopy (STEM/HRTEM). The electronic properties of graphene, such as the Dirac cone, remain intact and no significant charge transfer i.e. doping, is observed. These results are supported by Density Functional Theory (DFT) calculations. We demonstrate that the h-BN capped graphene allows the fabrication of vdW heterostructures without altering the electronic properties of graphene. PMID:26585245

  4. RĂ€umlich-statistische Charakterisierung der Hydrogeochemie einer BTEX-Grundwasserkontamination am Standort 〝RETZINA``/Zeitz

    NASA Astrophysics Data System (ADS)

    Wachter, Thorsten; Dethlefsen, Frank; Gödeke, Stefan; Dahmke, Andreas

    Kurzfassung Bei der Erkundung von GrundwasserschadensfĂ€llen werden gewöhnlich punktuell erhobene Messdaten ĂŒber den betrachteten Aquifer interpoliert. Die Reichweite der Autokorrelation der Daten entscheidet dabei ĂŒber ZulĂ€ssigkeit und QualitĂ€t der Interpolation. WĂ€hrend auf regionalem Maßstab Daten vorliegen, gibt es nur sehr wenig Arbeiten ĂŒber KorrelationslĂ€ngen auf lokalem Maßstab. Diese Arbeit untersucht die Interpolationssicherheit am Beispiel der BTEX-Kontamination am Testfeld RETZINA in Zeitz anhand von Variogrammen und Krigingstandardabweichung. Als Datengrundlage dienten Analysenergebnisse aus ĂŒber 50 Grundwassermessstellen und 180 Sedimentproben. FĂŒr Benzol, Methan, Sulfat und AlkalitĂ€t genĂŒgte der mittlere Abstand der Probennahmepunkte von etwa 50 m fĂŒr hinreichende Interpolationssicherheit, im Falle von gelöstem Eisen, gelöstem Mangan und Redoxpotenzial war die vorhandene Datendichte zu gering, fĂŒr die Hauptionen, pH-Wert und elektr. LeitfĂ€higkeit hĂ€tten bereits grĂ¶ĂŸere ProbenabstĂ€nde ausgereicht. Die Reichweiten der Autokorrelation im Sediment sind geringer als die ProbennahmeabstĂ€nde, weshalb die Messwerte der Eisen- und Schwefelbindungsformen nicht regionalisiert werden konnten. Die Ergebnisse sind hinsichtlich der Entwicklung von Probennahmestrategien von Bedeutung. Zur Verbesserung der Übertragbarkeit bedarf es noch Ă€hnlicher Untersuchungen an weiteren Standorten. Investigation of sites with groundwater contamination usually involves interpolation of point-based results across the aquifer under consideration. The range of autocorrelation thereby decides whether the quality of interpolation will be sufficient. While there are investigations on the regional (km) scale, only a few publications exist for correlation lengths at a local (10s to 100s of m) scale. This study investigates the accuracy of interpolation at the example of the BTEX-contaminated aquifer in Zeitz by means of variogram analysis and interpretation of kriging standard deviation. Investigations are based upon analytical results from more than 50 groundwater wells and 180 sediment samples. In the case of benzene, methane, sulphate, and alkalinity, the given sample spacing of about 50 m provided sufficient accuracy of interpolation. For dissolved iron, dissolved manganese, and redox potential the results did not allow interpolation, while for the major ions, pH, and electrical conductivity a wider sampling distance would have been possible. The ranges of autocorrelation in the aquifer's solid phase proved to be smaller than the sampling distances. Therefore, results of iron and sulphur phases could not be regionalized. The results of this study are relevant for the development of sampling strategies and quality management. To improve transferability similar investigations should be done at other sites.

  5. Photoplastic effect in a II-VII semiconductor with van der Waals interlayer bonding (HgI2)

    NASA Astrophysics Data System (ADS)

    Marschall, Jochen; Milstein, Frederick

    1993-05-01

    Experimental evidence of a small, positive photoplastic effect during the shear deformation of single-crystal red mercuric iodide is presented. This is apparently the first observation of a photoplastic effect in a II-VII semiconductor, as well as in a material in which the bonding between slip planes is of van der Waals type.

  6. 10. Freiburger Symposium 2011 der SCG-Division Industrielle Chemie Technology Progress, Success Key for our Production Sites.

    PubMed

    Naef, Olivier

    2012-01-01

    This short paper presents the abstracts of the different presentations during 10. Freiburger Symposium 2011 der SCG-Division Industrielle Chemie: Technology Progress, Success key for our production sites held Thursday and Friday, September 29 and 30, 2011 at the Ecole d'ingénieurs et d'architectes de Fribourg (Switzerland). PMID:22613161

  7. PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES: Phase Behaviour of Purely Repulsive Systems: Violation of Traditional van der Waals Picture

    NASA Astrophysics Data System (ADS)

    Zhou, Shi-Qi

    2008-06-01

    Several purely repulsive potentials (PRP) are investigated theoretically. In contrast to the traditional van der Waals picture, it is found that normal gas-liquid transition emerges only on condition that the PRP as a function of particle separation holds a discontinuous point, or an indifferentiable point, or is differentiable but with an additional length scale besides the hard sphere diameter.

  8. Note on Unconditional and Conditional Hypothesis Testing: A Discussion of an Issue Raised by van der Linden and Sotaridona

    ERIC Educational Resources Information Center

    Lewis, Charles

    2006-01-01

    In the context of reviewing an article for this journal (van der Linden & Sotaridona, this issue, pp. 283-304) the topic of unconditional and conditional hypothesis testing came under consideration. While this is hardly a new issue (consider, for example, arguments regarding the chi square vs. Fisher exact test of independence for a 2 x 2…

  9. Note on Unconditional and Conditional Hypothesis Testing: A Discussion of an Issue Raised by van der Linden and Sotaridona

    ERIC Educational Resources Information Center

    Lewis, Charles

    2006-01-01

    In the context of reviewing an article for this journal (van der Linden & Sotaridona, this issue, pp. 283-304) the topic of unconditional and conditional hypothesis testing came under consideration. While this is hardly a new issue (consider, for example, arguments regarding the chi square vs. Fisher exact test of independence for a 2 x 2


  10. Electronic Properties and Device Applications of van-der-Waals Thin Films

    NASA Astrophysics Data System (ADS)

    Renteria, Jacqueline de Dios

    Successful exfoliation of graphene and discoveries of its unique electrical and thermal properties have motivated searches for other quasi two-dimensional (2D) materials with interesting properties. The layered van der Waals materials can be cleaved mechanically or exfoliated chemically by breaking the relatively weak bonding between the layers. In this dissertation research I addressed a special group of inorganic van der Waals materials -- layered transition metal dichalcogenides (MX2, where M=Mo, W, Nb, Ta or Ti and X=S, Se or Te). The focus of the investigation was electronic properties of thin films of TaSe2 and MoS2 and their device applications. In the first part of the dissertation, I describe the fabrication and performance of all-metallic three-terminal devices with the TaSe2 thin-film conducting channel. The layers of 2H-TaSe2 were exfoliated mechanically from single crystals grown by the chemical vapor transport method. It was established that devices with nanometer-scale thickness channels exhibited strongly non-linear current-voltage characteristics, unusual optical response, and electrical gating at room temperature. It was found that the drain-source current in thin-film 2H-TaSe2--Ti/Au devices reproducibly shows an abrupt transition from a highly resistive to a conductive state, with the threshold tunable via the gate voltage. Such current-voltage characteristics can be used, in principle, for implementing radiation-hard all-metallic logic circuits. In the second part of the dissertation, I describe the fabrication, electrical testing and measurements of the low-frequency 1/f noise in three-terminal devices with the MoS2 thin-film channel (f is the frequency). Analysis of the experimental data allowed us to distinguish channel and contact noise contributions for both as fabricated and aged devices. The noise characteristics of MoS 2--Ti/Au devices are in agreement with the McWhorter model description. The latter is contrary to what is observed in graphene devices, where the noise spectral density does not follow the carrier number fluctuation model. The trap density extracted from the noise measurements is on the order of 1.5x1019 eV-1cm-3 and 2x10 20 eV-1cm-3 for as fabricated and aged samples, respectively. These values are of the same order of magnitude as those in high-k MOSFETS. These results of this dissertation research may lead to new applications of van der Waals materials.

  11. From Canards of Folded Singularities to Torus Canards in a Forced van der Pol Equation

    NASA Astrophysics Data System (ADS)

    Burke, John; Desroches, Mathieu; Granados, Albert; Kaper, Tasso J.; Krupa, Martin; Vo, Theodore

    2015-11-01

    In this article, we study canard solutions of the forced van der Pol equation in the relaxation limit for low-, intermediate-, and high-frequency periodic forcing. A central numerical observation made herein is that there are two branches of canards in parameter space which extend across all positive forcing frequencies. In the low-frequency forcing regime, we demonstrate the existence of primary maximal canards induced by folded saddle nodes of type I and establish explicit formulas for the parameter values at which the primary maximal canards and their folds exist. Then, we turn to the intermediate- and high-frequency forcing regimes and show that the forced van der Pol possesses torus canards instead. These torus canards consist of long segments near families of attracting and repelling limit cycles of the fast system, in alternation. We also derive explicit formulas for the parameter values at which the maximal torus canards and their folds exist. Primary maximal canards and maximal torus canards correspond geometrically to the situation in which the persistent manifolds near the family of attracting limit cycles coincide to all orders with the persistent manifolds that lie near the family of repelling limit cycles. The formulas derived for the folds of maximal canards in all three frequency regimes turn out to be representations of a single formula in the appropriate parameter regimes, and this unification confirms the central numerical observation that the folds of the maximal canards created in the low-frequency regime continue directly into the folds of the maximal torus canards that exist in the intermediate- and high-frequency regimes. In addition, we study the secondary canards induced by the folded singularities in the low-frequency regime and find that the fold curves of the secondary canards turn around in the intermediate-frequency regime, instead of continuing into the high-frequency regime. Also, we identify the mechanism responsible for this turning. Finally, we show that the forced van der Pol equation is a normal form-type equation for a class of single-frequency periodically driven slow/fast systems with two fast variables and one slow variable which possess a non-degenerate fold of limit cycles. The analytic techniques used herein rely on geometric desingularisation, invariant manifold theory, Melnikov theory, and normal form methods. The numerical methods used herein were developed in Desroches et al. (SIAM J Appl Dyn Syst 7:1131-1162, 2008, Nonlinearity 23:739-765 2010).

  12. From Canards of Folded Singularities to Torus Canards in a Forced van der Pol Equation

    NASA Astrophysics Data System (ADS)

    Burke, John; Desroches, Mathieu; Granados, Albert; Kaper, Tasso J.; Krupa, Martin; Vo, Theodore

    2016-04-01

    In this article, we study canard solutions of the forced van der Pol equation in the relaxation limit for low-, intermediate-, and high-frequency periodic forcing. A central numerical observation made herein is that there are two branches of canards in parameter space which extend across all positive forcing frequencies. In the low-frequency forcing regime, we demonstrate the existence of primary maximal canards induced by folded saddle nodes of type I and establish explicit formulas for the parameter values at which the primary maximal canards and their folds exist. Then, we turn to the intermediate- and high-frequency forcing regimes and show that the forced van der Pol possesses torus canards instead. These torus canards consist of long segments near families of attracting and repelling limit cycles of the fast system, in alternation. We also derive explicit formulas for the parameter values at which the maximal torus canards and their folds exist. Primary maximal canards and maximal torus canards correspond geometrically to the situation in which the persistent manifolds near the family of attracting limit cycles coincide to all orders with the persistent manifolds that lie near the family of repelling limit cycles. The formulas derived for the folds of maximal canards in all three frequency regimes turn out to be representations of a single formula in the appropriate parameter regimes, and this unification confirms the central numerical observation that the folds of the maximal canards created in the low-frequency regime continue directly into the folds of the maximal torus canards that exist in the intermediate- and high-frequency regimes. In addition, we study the secondary canards induced by the folded singularities in the low-frequency regime and find that the fold curves of the secondary canards turn around in the intermediate-frequency regime, instead of continuing into the high-frequency regime. Also, we identify the mechanism responsible for this turning. Finally, we show that the forced van der Pol equation is a normal form-type equation for a class of single-frequency periodically driven slow/fast systems with two fast variables and one slow variable which possess a non-degenerate fold of limit cycles. The analytic techniques used herein rely on geometric desingularisation, invariant manifold theory, Melnikov theory, and normal form methods. The numerical methods used herein were developed in Desroches et al. (SIAM J Appl Dyn Syst 7:1131-1162, 2008, Nonlinearity 23:739-765 2010).

  13. A sensitive fluorescent assay for measuring the cysteine protease activity of Der p 1, a major allergen from the dust mite Dermatophagoides pteronyssinus.

    PubMed Central

    Schulz, O; Sewell, H F; Shakib, F

    1998-01-01

    The potent allergenicity of Der p 1, a major allergen of the house dust mite Dermatophagoides pteronyssinus, is thought to be related to its cysteine protease activity. Therefore, there is considerable interest in developing a sensitive assay for measuring Der p 1 activity to screen for specific inhibitors. This study demonstrates for the first time that the activity of Der p 1 can be measured conveniently in a continuous rate assay with the fluorogenic substrate Boc-Gln-Ala-Arg-AMC (K(m) = 280 microM and kcat/K(m) = 4.6 x 10(3)/M/s). PMID:9893750

  14. Die Bedeutung der Volumen- und OberflĂ€cheneigenschaften von Biomaterialien fĂŒr die Adsorption von Proteinen und nachfolgende zellulĂ€re Reaktionen

    NASA Astrophysics Data System (ADS)

    Groth, Thomas

    2003-04-01

    Es ist schon seit lĂ€ngerer Zeit bekannt, dass nach Kontakt des Biomaterials mit der biologischen Umgebung bei Implantation oder extrakorporaler Wechselwirkung zunĂ€chst Proteine aus dem umgebenden Milieu adsorbiert werden, wobei die OberflĂ€cheneigenschaften des Materials die Zusammensetzung der Proteinschicht und die Konformation der darin enthaltenden Proteine determinieren. Die nachfolgende Wechselwirkung von Zellen mit dem Material wird deshalb i.d.R. von der Adsorbatschicht vermittelt. Der Einfluss der OberflĂ€chen auf die Zusammensetzung und Konformation der Proteine und die nachfolgende Wechselwirkung mit Zellen ist von besonderem Interesse, da einerseits eine Aussage ĂŒber die Anwendbarkeit ermöglicht wird, andererseits Erkenntnisse ĂŒber diese ZusammenhĂ€nge fĂŒr die Entwicklung neuer Materialien mit verbesserter BiokompatibilitĂ€t genutzt werden können. In der vorliegenden Habilitationsschrift wurde deshalb der Einfluss der Zusammensetzung von Polymeren bzw. von deren OberflĂ€cheneigenschaften auf die Adsorption von Proteinen, den AktivitĂ€tszustand der plasmatischen Gerinnung und die AdhĂ€sion von Zellen untersucht. Dabei wurden auch Möglichkeiten zur Beeinflussung dieser VorgĂ€nge ĂŒber eine VerĂ€nderung der Volumenzusammensetzung oder durch OberflĂ€chenmodifikationen von Biomaterialien vorgestellt. Erkenntnisse aus diesen Arbeiten konnten fĂŒr die Entwicklung von Membranen fĂŒr Biohybrid-Organe genutzt werden. The implantation of biomaterials or the contact of blood with extracorporal devices leads to the rapid adsorption of proteins from the surrounding biological fluids. The surface properties of materials determine the composition of the adsorption layer and the conformation of adsorbed proteins. Hence, the subsequent interaction of cells with biomaterials is dependent on the adsorption layer of proteins. The detailed knowledge on the role of surface properties in protein adsorption and cellular interactions is a useful means to learn about the biomedical applicability of materials and to develop novel materials with improved biocompatibility. The thesis describes the influence of polymer composition and surface properties on protein adsorption, the activation of blood clotting and adhesion of cells. The thesis presents options to modify the reactions of the biological system by the modification of bulk or surface composition of polymers. Results of these studies have been used to develop polymer membranes for biohybrid organs.

  15. The potential for distributed generation in Japanese prototype buildings: A DER-CAM analysis of policy, tariff design, building energy use, and technology development (Japanese translation)

    SciTech Connect

    Zhou, Nan; Marnay, Chris; Firestone, Ryan; Gao, Weijun; Nishida, Masaru

    2004-10-15

    The August 2003 blackout of the northeastern U.S. and CANADA caused great economic losses and inconvenience to New York City and other affected areas. The blackout was a warning to the rest of the world that the ability of conventional power systems to meet growing electricity demand is questionable. Failure of large power systems can lead to serious emergencies. Introduction of on-site generation, renewable energy such as solar and wind power and the effective utilization of exhaust heat is needed, to meet the growing energy demands of the residential and commercial sectors. Additional benefit can be achieved by integrating these distributed technologies into distributed energy resource (DER) systems. This work demonstrates a method for choosing and designing economically optimal DER systems. An additional purpose of this research is to establish a database of energy tariffs, DER technology cost and performance characteristics, and building energy consumption for Japan. This research builds on prior DER studies at the Ernest Orlando Lawrence Berkeley National Laboratory (LBNL) and with their associates in the Consortium for Electric Reliability Technology Solutions (CERTS) and operation, including the development of the microgrid concept, and the DER selection optimization program, the Distributed Energy Resources Customer Adoption Model (DER-CAM). DER-CAM is a tool designed to find the optimal combination of installed equipment and an idealized operating schedule to minimize a site's energy bills, given performance and cost data on available DER technologies, utility tariffs, and site electrical and thermal loads over a test period, usually an historic year. Since hourly electric and thermal energy data are rarely available, they are typically developed by building simulation for each of six end use loads used to model the building: electric-only loads, space heating, space cooling, refrigeration, water heating, and natural-gas-only loads. DER-CAM provides a global optimization, albeit idealized, that shows how the necessary useful energy loads can be provided for at minimum cost by selection and operation of on-site generation, heat recovery, cooling, and efficiency improvements. This study examines five prototype commercial buildings and uses DER-CAM to select the economically optimal DER system for each. The five building types are office, hospital, hotel, retail, and sports facility. Each building type was considered for both 5,000 and 10,000 square meter floor sizes. The energy consumption of these building types is based on building energy simulation and published literature. Based on the optimization results, energy conservation and the emissions reduction were also evaluated. Furthermore, a comparison study between Japan and the U.S. has been conducted covering the policy, technology and the utility tariffs effects on DER systems installations.

  16. Karl ernst von Baer's 'Uber Entwickelungsgeschichte der Thiere II' and its unpublished drawings.

    PubMed

    Tammiksaar, Erki; Brauckmann, Sabine

    2004-01-01

    In 1828 Karl Ernst von Baer (1792-1876) published his seminal Uber Entwickelungsgeschichte der Thiere. Beobachtung und Reflexion. In the preface he announced that a second volume with one copper plate would be finished 'in a few weeks'. However, it took nine years until the unfinished second volume was released, with four copperplates. In his 'Autobiography', von Baer did not clarify the reasons why he did not finish his research program of comparative embryology. The paper attempts to elucidate them, furnished by archival documents and von Baer's unpublished embryological drawings. Our sketch of a few figures will show that (1) von Baer searched for 'analogies' (homologies) as a unifying principle and (2) explained the mechanisms of embryogenesis by physiological reasoning (electromagnetism). The main objective is to show that technical problems in illustrating and conceptual difficulties impeded von Baer's ambitious research program. PMID:16302690

  17. Adsorption of polyiodobenzene molecules on the Pt(111) surface using van der Waals density functional theory

    NASA Astrophysics Data System (ADS)

    Johnston, Karen; Pekoz, Rengin; Donadio, Davide

    2016-02-01

    Adsorption of aromatic molecules on surfaces is widely studied due to applications in molecular electronics. In this work, the adsorption of iodobenzene molecules on the Pt(111) surface has been studied using density functional theory. Iodobenzene molecules, with various numbers of iodine atoms, have two non-dissociative adsorption minima. One structure exhibits chemisorption between the ring and the surface (short-range) and the other structure exhibits chemisorption between the iodine ions and the surface (long-range). Both structures have a strong van der Waals interaction with the surface. In general, the adsorption energy increases as the number of iodine atoms increases. The dissociated structure of monoiodobenzene was investigated, and the dissociation barrier and the barrier between the short- and long-range states were compared.

  18. Rarefaction waves in van der Waals fluids with an arbitrary number of degrees of freedom

    NASA Astrophysics Data System (ADS)

    Yuen, Albert; Barnard, John J.

    2015-09-01

    The isentropic expansion of an instantaneously and homogeneously heated foil is calculated using a 1D fluid model. The initial temperature and density are assumed to be in the vicinity of the critical temperature and solid density, respectively. The fluid is assumed to satisfy the van der Waals equation of state with an arbitrary number of degrees of freedom. Self-similar Riemann solutions are found. With a larger number of degrees of freedom f , depending on the initial dimensionless entropy s˜0, a richer family of foil expansion behaviors have been found. We calculate the domain in parameter space where these behaviors occur. In total, eight types of rarefaction waves are found and described.

  19. A van der Waals density functional study of chloroform and other trihalomethanes on graphene

    NASA Astrophysics Data System (ADS)

    Ćkesson, Joel; Sundborg, Oskar; Wahlström, Olof; Schröder, Elsebeth

    2012-11-01

    A computational study of chloroform (CHCl3) and other trihalomethanes (THMs) adsorbed on graphene is presented. The study uses the van der Waals density functional method to obtain adsorption energies and adsorption structures for these molecules of environmental concern. In this study, chloroform is found to adsorb with the H atom pointing away from graphene, with adsorption energy 357 meV (34.4 kJ/mol). For the other THMs studied the calculated adsorption energy values vary from 206 meV (19.9 kJ/mol) for fluoroform (CHF3) to 404 meV (39.0 kJ/mol) for bromoform (CHBr3). The corrugation of graphene as seen by the THMs is small, the difference in adsorption energy along the graphene plane is less than 6 meV for chloroform.

  20. A van der Waals density functional study of chloroform and other trihalomethanes on graphene.

    PubMed

    Ćkesson, Joel; Sundborg, Oskar; Wahlström, Olof; Schröder, Elsebeth

    2012-11-01

    A computational study of chloroform (CHCl(3)) and other trihalomethanes (THMs) adsorbed on graphene is presented. The study uses the van der Waals density functional method to obtain adsorption energies and adsorption structures for these molecules of environmental concern. In this study, chloroform is found to adsorb with the H atom pointing away from graphene, with adsorption energy 357 meV (34.4 kJ/mol). For the other THMs studied the calculated adsorption energy values vary from 206 meV (19.9 kJ/mol) for fluoroform (CHF(3)) to 404 meV (39.0 kJ/mol) for bromoform (CHBr(3)). The corrugation of graphene as seen by the THMs is small, the difference in adsorption energy along the graphene plane is less than 6 meV for chloroform. PMID:23145737

  1. Phonon dispersion of acene molecular crystals using van der Waals-corrected density functional theory

    NASA Astrophysics Data System (ADS)

    Altvater, Florian; Rangel, Tonatiuh; Neaton, Jeffrey B.

    2015-03-01

    Acene molecular crystals are interesting testbeds for the study of phenomena relevant to organic optoelectronics, including charge separation and carrier transport. In such processes, scattering from lattice vibrations is an important dissipation mechanism. Despite their central role in dissipation processes, there are few calculations of phonon spectra in acene crystals. Here, we carry out van der Waals-corrected density functional theory calculations of the ground-state structure and phonon band structure of acene molecular crystals, comparing to neutron diffraction data where applicable. We use a finite-differences method, and compare the performance of several approaches - including standard generalized gradient approximations (GGA) such as PBE, PBE plus pair-wise vdW corrections, and vdW density functionals - to experiments for solid naphthalene and pentacene. This work was supported by the DOE; computational resources provided by NERSC.

  2. Phase diagram of van der Waals-like phase separation in a driven granular gas.

    PubMed

    Khain, Evgeniy; Meerson, Baruch; Sasorov, Pavel V

    2004-11-01

    Equations of granular hydrostatics are used to compute the phase diagram of the recently discovered van der Waals-like phase separation in a driven granular gas. The model two-dimensional system consists of smooth hard disks in a rectangular box, colliding inelastically with each other and driven by a "thermal" wall at zero gravity. The spinodal line and the critical point of the phase separation are determined. Close to the critical point, the spinodal and binodal (coexistence) lines are determined analytically. Effects of the finite size of the confining box in the direction parallel to the thermal wall are investigated. These include suppression of the phase separation by heat conduction in the lateral direction and a change from supercritical to subcritical bifurcation. PMID:15600606

  3. Hopf-Bifurcations and Van der Pol Oscillator Models of the Mammalian Cochlea

    NASA Astrophysics Data System (ADS)

    Duifhuis, Hendrikus

    2011-11-01

    The successful modeling of the non-linear behavior in stiffness properties of hair bundles of auditory hair cells in sub-mammals and in vitro preparations of mammalian hair cells has stimulated several investigators to propose far-reaching similarity of the functioning of the mammalian organ of Corti. Models have been proposed that share the common background of a Hopf-bifurcation and its relation to a newly defined class of critical oscillators. Some of the proposals are rather similar to the classical line of nonlinear cochlea models whereas others start with assumptions that put them in a different class. It can be shown that the Hopf-bifurcation and the Van der Pol oscillator belong to the same class of nonlinear models. Differences between the models arise at the physical definition of the parameters, and at the question: how to account for individual SOAE patterns.

  4. Phase diagram of Rydberg atoms with repulsive van der Waals interaction

    SciTech Connect

    Osychenko, O. N.; Astrakharchik, G. E.; Boronat, J.; Lutsyshyn, Y.; Lozovik, Yu. E.

    2011-12-15

    We report a quantum Monte Carlo calculation of the phase diagram of bosons interacting with a repulsive inverse sixth power pair potential, a model for assemblies of Rydberg atoms in the local van der Waals blockade regime. The model can be parametrized in terms of just two parameters, the reduced density and temperature. Solidification happens to the fcc phase. At zero temperature, the transition density is found with the diffusion Monte Carlo method at density {rho}=3.9 (({Dirac_h}/2{pi}){sup 2}/mC{sub 6}){sup 3/4}, where C{sub 6} is the strength of the interaction. The solidification curve at nonzero temperature is studied with the path-integral Monte Carlo approach and is compared with transitions in corresponding harmonic and classical crystals. Relaxation mechanisms are considered in relation to present experiments.

  5. Influence of ultrathin water layer on the van der Waals/Casimir force between gold surfaces

    SciTech Connect

    Palasantzas, G.; Zwol, P. J. van; Svetovoy, V. B.

    2009-06-15

    In this paper we investigate the influence of ultrathin water layer ({approx}1-1.5 nm) on the van der Waals/Casimir force between gold surfaces. Adsorbed water is inevitably present on gold surfaces at ambient conditions as jump-up-to contact during adhesion experiments demonstrate. Calculations based on the Lifshitz theory give very good agreement with the experiment in the absence of any water layer for surface separations d > or approx. 10 nm. However, a layer of thickness h < or approx. 1.5 nm is allowed by the error margin in force measurements. At shorter separations, d < or approx. 10 nm, the water layer can have a strong influence as calculations show for flat surfaces. Nonetheless, in reality the influence of surface roughness must also be considered, and it can overshadow any water layer influence at separations comparable to the total sphere-plate rms roughness w{sub shp}+w.

  6. 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.

  7. 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.

  8. Electrically Tunable van der Waals Interaction in Graphene-Molecule Complex.

    PubMed

    Muruganathan, Manoharan; Sun, Jian; Imamura, Tomonori; Mizuta, Hiroshi

    2015-12-01

    van der Waals (vdW) interactions play a central role in the surface-related physics and chemistry. Tuning of the correlated charge fluctuation in a vdW complex is a plausible way of modulating the molecules interaction at the atomic surface. Here, we report the vdW interaction tunability of the graphene-CO2 complex by combining the first-principles calculations with the vdW density functionals and the time evaluation measurements of CO2 molecules adsorption/desorption on graphene under an external electric field. The field-dependent charge transfer within the complex unveils the controllable tuning of CO2 from acceptor to donor. Meanwhile, the configuration of the adsorbed molecule, the equilibrium distance from graphene and O-C-O bonding angle, is modified accordingly. The range of electrical tunability is a unique feature for each type of molecule. PMID:26562749

  9. Revisiting the adsorption of copper-phthalocyanine on Au(111) including van der Waals corrections

    SciTech Connect

    LĂŒder, Johann; Eriksson, Olle; Sanyal, Biplab; Brena, Barbara

    2014-03-28

    We have studied the adsorption of copper-phthalocyanine on Au(111) by means of van der Waals corrected density functional theory using the Tkatchenko-Scheffler method. We have compared the element and site resolved adsorption distances to recent experimental normal-incident X-ray standing wave measurements. The measured adsorption distances could be reproduced within a deviation of 1% for the Cu atom, 1% for the C atoms, and 2% for the N atoms. The molecule was found to have a magnetic moment of 1 ÎŒ{sub B} distributed over the Cu and the N atoms of the pyrrole ring. Simulated scanning tunnel microscopy images based on the total and on the spin-resolved differential charge densities are provided for bias voltages of −1.45 and 1.45 eV.

  10. Light-Induced Exciton Spin Hall Effect in van der Waals Heterostructures.

    PubMed

    Li, Yun-Mei; Li, Jian; Shi, Li-Kun; Zhang, Dong; Yang, Wen; Chang, Kai

    2015-10-16

    We propose a light-induced spin Hall effect for interlayer exciton gas in monolayer MoSe2-WSe2 van der Waals heterostructure. By applying two infrared, spatially varying laser beams coupled to the exciton internal states, a spin-dependent gauge potential on the exciton center-of-mass motion is induced. This gauge potential deflects excitons in different spin states towards opposite directions, leading to a finite spin current but vanishing mass current. In the Hall bar geometry, the spin-dependent deflection gives rise to spin-dependent chiral edge states with spin-velocity locking. The spin current and chiral edge states of the excitons can be detected by spatially resolved photoluminescence spectroscopy. PMID:26550894

  11. Van der Waals interactions determine selectivity in catalysis by metallic gold.

    PubMed

    Rodriguez-Reyes, Juan Carlos F; Siler, Cassandra G F; Liu, Wei; Tkatchenko, Alexandre; Friend, Cynthia M; Madix, Robert J

    2014-09-24

    To achieve high selectivity for catalytic reactions between two or more reactants on a heterogeneous catalyst, the relative concentrations of the reactive intermediates on the surface must be optimized. If species compete for binding sites, their concentrations depend on their relative binding strengths to the surface. In this article we describe a general framework for predicting the relative stability of organic intermediates involved in oxygen-assisted reactions on metallic gold with broad relevance to catalysis by metals. Combining theory and experiment, we establish that van der Waals interactions between the reactive intermediates and the surface, although weak, determine relative stabilities and thereby dictate the conditions for optimum selectivity. The inclusion of these interactions is essential for predicting these trends. The concepts and methods employed here have broad applicability for determining the stability of intermediates on the surfaces of catalytic metals and specifically demonstrate the critical role of weak interactions in determining reaction selectivity among reactions of complex molecules. PMID:25170677

  12. [Citation characteristics of German authors in "Der Chirurg": hegemony of the impact factor].

    PubMed

    Hasse, W; Fischer, R J

    2010-04-01

    Characteristics of citation and language in publications of German authors from the journal "Der Chirurg" (vol 78, 2007) were analysed. Out of a total of 3,342 citations, 756 (22.62%) were from German authors with 248 (32.8) self-citations. The hegemony of the impact factor in science, research and education is critically discussed. The imbalance between the number of surgeons in the US and United Kingdom (66,032) and surgeons in the German speaking countries in Europe (25,300) is compared with respect to the counting methods used to create the impact factor of a journal. The creation of an independent impact factor in Europe and the development of an EU-based citation data bank which allows unselected access to national language scientific literature are strongly needed. PMID:19760378

  13. Atomically thin resonant tunnel diodes built from synthetic van der Waals heterostructures

    PubMed Central

    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.

    2015-01-01

    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. PMID:26088295

  14. The van der Waals gas EOS for the Lorentz contracted rigid spheres

    NASA Astrophysics Data System (ADS)

    Bugaev, Kyrill A.

    2008-07-01

    The relativistic equation of state (EOS) of the van der Waals gas is suggested and analyzed. In contrast to the usual case, the Lorentz contraction of the sphere's volume is taken into account. It is proven that the suggested EOS obeys the causality in the limit of high densities, i.e., the value of sound velocity of such a media is subluminar. The pressure obtained for the high values of chemical potential has an interesting kinetic interpretation. The suggested EOS shows that for high densities the most probable configuration corresponds to the smallest value of the relativistic excluded volume. In other words, for high densities the configurations with the collinear velocities of the neighboring hard core particles are the most probable ones. This, perhaps, may shed light on the coalescence process of any relativistic hard core constituents.

  15. Generalized Fourier series and limit cycles of generalized van der Pol oscillators

    NASA Astrophysics Data System (ADS)

    Garcia-Margallo, J.; Bejarano, J. D.

    1990-02-01

    A very simple generalization, using Jacobian elliptic functions, of the usual Fourier series, appropriate for non-linear systems, is used to study the first order approximate solution of the generalized van der Pol oscillators áșŒ+AX+2BX 3+ɛ(z 3+z 2X 2+z 1X 4) dotX=0 . A generalized harmonic balance method is used to determine the limit cycles. The cases A > 0, B > 0 and A < 0, B > 0 are considered in some detail. For given values of the parameters zi, the values of A and B for which limit cycles exist are found as functions of m. Numerical values for the radius, frequency, and energy of the limit cycles are given. The presence of zero, one, two, three or four limit cycles depends on the value of the parameters of the equation. Stability, bifurcations of fixed points, and the limit cycle stability are studied qualitatively.

  16. The development of two dimensional group IV chalcogenides, blocks for van der Waals heterostructures.

    PubMed

    Sa, Baisheng; Sun, Zhimei; Wu, Bo

    2016-01-14

    In this work, we introduce a series of two dimensional (2D) group IV chalcogenides (AX)2 with the building block X-A-A-X (A = Si, Ge, Sn, and Pb, and X = Se and Te) on the basis of ab initio calculations. The analysis of energy evaluation, lattice vibration as well as the chemical bonding demonstrate the good stability of these 2D materials. Furthermore, the pictures for the chemical bonding and electronic features of the 2D (AX)2 are drawn. Their narrow gapped semiconducting nature is unraveled. Especially, strong interactions between the electrons and phonons as well as the topological insulating nature in (SiTe)2 are observed. The present results indicate that such remarkable artificial 2D (AX)2 are building blocks for van der Waals heterostructure engineering, which shows potential applications in nanoscaled electronics and optoelectronics. PMID:26667941

  17. Periodic bifurcation of Duffing-van der Pol oscillators having fractional derivatives and time delay

    NASA Astrophysics Data System (ADS)

    Leung, A. Y. T.; Yang, H. X.; Zhu, P.

    2014-04-01

    In this paper, a Duffing-van der Pol oscillator having fractional derivatives and time delays is investigated by the residue harmonic method. The angular frequencies and limit cycles of periodic motions are expanded into a power series of an order-tracking parameter and the unbalanced residues resulting from the truncated Fourier series are considered iteratively to improve the accuracy. The periodic bifurcations are examined using the fractional order, feedback gain and time delay as continuation parameters. It is shown that jumps and hysteresis phenomena can be delayed or removed. Transition from discontinuous bifurcation to continuous bifurcation is observed. The approximations are verified by numerical integration. We find that the proposed method can easily be programmed and can predict accurate periodic approximations while the system parameters being unfolded.

  18. The development of two dimensional group IV chalcogenides, blocks for van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Sa, Baisheng; Sun, Zhimei; Wu, Bo

    2015-12-01

    In this work, we introduce a series of two dimensional (2D) group IV chalcogenides (AX)2 with the building block X-A-A-X (A = Si, Ge, Sn, and Pb, and X = Se and Te) on the basis of ab initio calculations. The analysis of energy evaluation, lattice vibration as well as the chemical bonding demonstrate the good stability of these 2D materials. Furthermore, the pictures for the chemical bonding and electronic features of the 2D (AX)2 are drawn. Their narrow gapped semiconducting nature is unraveled. Especially, strong interactions between the electrons and phonons as well as the topological insulating nature in (SiTe)2 are observed. The present results indicate that such remarkable artificial 2D (AX)2 are building blocks for van der Waals heterostructure engineering, which shows potential applications in nanoscaled electronics and optoelectronics.

  19. Communication: Multiple-property-based diabatization for open-shell van der Waals molecules

    NASA Astrophysics Data System (ADS)

    Karman, Tijs; van der Avoird, Ad; Groenenboom, Gerrit C.

    2016-03-01

    We derive a new multiple-property-based diabatization algorithm. The transformation between adiabatic and diabatic representations is determined by requiring a set of properties in both representations to be related by a similarity transformation. This set of properties is determined in the adiabatic representation by rigorous electronic structure calculations. In the diabatic representation, the same properties are determined using model diabatic states defined as products of undistorted monomer wave functions. This diabatic model is generally applicable to van der Waals molecules in arbitrary electronic states. Application to locating seams of conical intersections and collisional transfer of electronic excitation energy is demonstrated for O2 - O2 in low-lying excited states. Property-based diabatization for this test system included all components of the electric quadrupole tensor, orbital angular momentum, and spin-orbit coupling.

  20. Graphene in ionic liquids: collective van der Waals interaction and hindrance of self-assembly pathway.

    PubMed

    Zhao, Yinghe; Hu, Zhonghan

    2013-09-12

    Over the past decade, there has been much controversy regarding the microscopic mechanism by which the π-electron-rich carbon nanomaterials such as graphene and carbon nanotubes can be dispersed in ionic liquids. Through a combination of a quantum mechanical calculation on the level of density functional theory, an extensive molecular dynamics study on the time scale of microseconds, and a kinetic analysis at the experimental time scale, we have demonstrated that collective van der Waals forces between ionic liquids and graphene are able to describe both the short-ranged cation-π interaction and the long-ranged dispersion interaction and this microscopic interaction drives two graphene plates trapped in their metastable state while two graphene plates easily self-assemble into graphite in water. PMID:23957744

  1. A First-Principles Method of Determining van der Waals Forces in Dissipative Media

    NASA Astrophysics Data System (ADS)

    Zheng, Yi; Narayanaswamy, Arvind

    2012-02-01

    Lifshitz theory of van der Waals (vdW) force and energy between two planar objects is strictly valid when the medium separating two planar objects is vacuum. Generalization of Lifshitz theory to the case when intervening medium is a dissipative material, as opposed to vacuum, is a surprisingly difficult undertaking because there is no expression for the electromagnetic stress tensor in dissipative materials. Here, we derive the expression for vdW energy and pressure in planar multilayered dissipative media by computing the work done in assembling the multilayered structure from its constituent thin films. In doing so, we avoid any calculations of the Maxwell stress tensor in any medium but vacuum. Even though this work has proven to be a corroboration of Dzyaloshinskii, Lifshitz, and Pitaevskii, it has thrown new light on our understanding of vdW forces and suggests that it should be possible to achieve the similar result for objects with arbitrary shapes.

  2. Plasmonic contribution to the van der Waals energy in strongly interacting bilayers

    SciTech Connect

    Tas, Murat; Tanatar, B.

    2010-03-15

    We investigate the van der Waals or interaction energy due to the plasmon modes in bilayer fermion and boson systems for several layer separation and coupling strength values. Interaction effects are studied within the random-phase approximation (RPA), the quasilocalized charge approximation (QLCA), and the Singwi, Tosi, Land, and Sjoelander (STLS) models of the dielectric function formalism. We find that the interaction becomes repulsive at short separation distances for strongly coupled systems described by the QLCA and STLS approaches in contrast to attractive behavior predicted by the RPA. At larger separation distances, the interaction energy changes sign within the QLCA and STLS models leading to an attractive interaction. The evident relation between our calculations and the Casimir effect is emphasized.

  3. Rarefaction waves in van der Waals fluids with an arbitrary number of degrees of freedom.

    PubMed

    Yuen, Albert; Barnard, John J

    2015-09-01

    The isentropic expansion of an instantaneously and homogeneously heated foil is calculated using a 1D fluid model. The initial temperature and density are assumed to be in the vicinity of the critical temperature and solid density, respectively. The fluid is assumed to satisfy the van der Waals equation of state with an arbitrary number of degrees of freedom. Self-similar Riemann solutions are found. With a larger number of degrees of freedom f, depending on the initial dimensionless entropy s[over ?]_{0}, a richer family of foil expansion behaviors have been found. We calculate the domain in parameter space where these behaviors occur. In total, eight types of rarefaction waves are found and described. PMID:26465568

  4. Spatial dependent van der Waals energy between graphene and boron-nitride

    NASA Astrophysics Data System (ADS)

    Neek-Amal, Mehdi; Peeters, Francois; Condensed Matter Group, University of Antwerp Collaboration

    2014-03-01

    The small mismatch between the honeycomb lattices of graphene (GE) and boron nitrate (h-BN) leads to long wavelength Moiré patterns. In order to describe such patterns it will require large size unit cells that are unattainable with ab-initio calculations. Earlier density functional theory calculations imposed lattice matching between graphene and h-BN which induces strain and opens a gap of 4 meV. In previous works the Moiré pattern in GE/h-BN was connected to the van der Waals interaction, but a clear theoretical microscopic analysis is still missing. We used atomistic simulations with very large unit cells to investigate quantitative aspects of the connection between the vdW interaction and the Moiré patterns. The value and symmetry of the spatial dependent vdW energy is obtained which agrees with the recently reported Moiré patterns. Acknowledgement: This work was supported by FWO-Vl, EU-Marie Curie and the Methusalem foundation.

  5. Band Engineering of Dirac Surface States in Topological-Insulator-Based van der Waals Heterostructures.

    PubMed

    Chang, Cui-Zu; Tang, Peizhe; Feng, Xiao; Li, Kang; Ma, Xu-Cun; Duan, Wenhui; He, Ke; Xue, Qi-Kun

    2015-09-25

    The existence of a gapless Dirac surface band of a three dimensional (3D) topological insulator (TI) is guaranteed by the nontrivial topological character of the bulk band, yet the surface band dispersion is mainly determined by the environment near the surface. In this Letter, through in situ angle-resolved photoemission spectroscopy and first-principles calculation on 3D TI-based van der Waals heterostructures, we demonstrate that one can engineer the surface band structures of 3D TIs by surface modifications without destroying their topological nontrivial property. The result provides an accessible method to independently control the surface and bulk electronic structures of 3D TIs, and sheds light on designing artificial topological materials for electronic and spintronic purposes. PMID:26451573

  6. Designed Synthesis of van der Waals Heterostructures: The Power of Kinetic Control.

    PubMed

    Alemayehu, Matti B; Falmbigl, Matthias; Ta, Kim; Ditto, Jeffrey; Medlin, Douglas L; Johnson, David C

    2015-12-14

    Selecting specific 2D building blocks and specific layering sequences of van der Waals heterostructures should allow the formation of new materials with designed properties for specific applications. Unfortunately, the synthetic ability to prepare such structures at will, especially in a manner that can be manufactured, does not exist. Herein, we report the targeted synthesis of new metal-semiconductor heterostructures using the modulated elemental-reactant technique to nucleate specific 2D building blocks, control their thickness, and avoid epitaxial structures with long-range order. The building blocks, VSe2 and GeSe2 , have different crystal structures, which inhibits cation intermixing. The precise control of this approach enabled us to synthesize heterostructures containing GeSe2 monolayers alternating with VSe2 structural units with specific sequences. The transport properties systematically change with nanoarchitecture and a charge-density wave-like transition is observed. PMID:26545566

  7. Strain induced piezoelectric effect in black phosphorus and MoS2 van der Waals heterostructure

    NASA Astrophysics Data System (ADS)

    Huang, Le; Li, Yan; Wei, Zhongming; Li, Jingbo

    2015-11-01

    The structural, electronic, transport and optical properties of black phosphorus/MoS2 (BP/MoS2) van der Waals (vdw) heterostructure are investigated by using first principles calculations. The band gap of BP/MoS2 bilayer decreases with the applied normal compressive strain and a semiconductor-to-metal transition is observed when the applied strain is more than 0.85 Å. BP/MoS2 bilayer also exhibits modulation of its carrier effective mass and carrier concentration by the applied compressive strain, suggesting that mobility engineering and good piezoelectric effect can be realized in BP/MoS2 heterostructure. Because the type-II band alignment can facilitate the separation of photo-excited electrons and holes, and it can benefit from the great absorption coefficient in ultra-violet region, the BP/MoS2 shows great potential to be a very efficient ultra-violet photodetector.

  8. Van der Waals interactions between polymers with sequence-specific polarizabilities: Stiff polymers and Gaussian coils

    NASA Astrophysics Data System (ADS)

    Lu, Bing-Sui; Naji, Ali; Podgornik, Rudolf

    2016-01-01

    We consider the van der Waals interaction between a pair of polymers with quenched heterogeneous sequences of local polarizabilities along their backbones, and study the effective pairwise interaction energy for both stiff polymers and flexible Gaussian coils. In particular, we focus on the cases where the pair of polarizability sequences are (i) distinct and (ii) identical. We find that the pairwise interaction energies of distinct and identical Gaussian coils are both isotropic and exhibit the same decay behavior for separations larger than their gyration radius, in contradistinction to the orientationally anisotropic interaction energies of distinct and identical stiff polymers. For both Gaussian coils and stiff polymers, the attractive interaction between identical polymers is enhanced if the polarizability sequence is more heterogeneous.

  9. Graphene/h-BN/ZnO van der Waals tunneling heterostructure based ultraviolet photodetector.

    PubMed

    Wu, Zhiqian; Li, Xiaoqiang; Zhong, Huikai; Zhang, Shengjiao; Wang, Peng; Kim, Tae-ho; Kwak, Sung Soo; Liu, Cheng; Chen, Hongsheng; Kim, Sang-Woo; Lin, Shisheng

    2015-07-27

    We report a novel ultraviolet photodetector based on graphene/h-BN/ZnO van der Waals heterostructure. Graphene/ZnO heterostructure shows poor rectification behavior and almost no photoresponse. In comparison, graphene/h-BN/ZnO structure shows improved electrical rectified behavior and surprising high UV photoresponse (1350AW(-1)), which is two or three orders magnitude larger than reported GaN UV photodetector (0.2~20AW(-1)). Such high photoresponse mainly originates from the introduction of ultrathin two-dimensional (2D) insulating h-BN layer, which behaves as the tunneling layer for holes produced in ZnO and the blocking layer for holes in graphene. The graphene/h-BN/ZnO heterostructure should be a novel and representative 2D heterostructure for improving the performance of 2D materials/Semiconductor heterostructure based optoelectronic devices. PMID:26367550

  10. A generalization of the van-der-Pol oscillator underlies active signal amplification in Drosophila hearing.

    PubMed

    Stoop, R; Kern, A; Göpfert, M C; Smirnov, D A; Dikanev, T V; Bezrucko, B P

    2006-08-01

    The antennal hearing organs of the fruit fly Drosophila melanogaster boost their sensitivity by an active mechanical process that, analogous to the cochlear amplifier of vertebrates, resides in the motility of mechanosensory cells. This process nonlinearly improves the sensitivity of hearing and occasionally gives rise to self-sustained oscillations in the absence of sound. Time series analysis of self-sustained oscillations now unveils that the underlying dynamical system is well described by a generalization of the van-der-Pol oscillator. From the dynamic equations, the underlying amplification dynamics can explicitly be derived. According to the model, oscillations emerge from a combination of negative damping, which reflects active amplification, and a nonlinear restoring force that dictates the amplitude of the oscillations. Hence, active amplification in fly hearing seems to rely on the negative damping mechanism initially proposed for the cochlear amplifier of vertebrates. PMID:16612585

  11. Rotational spectrum of a salt-containing van der Waals complex: Ar-NaCl

    NASA Astrophysics Data System (ADS)

    Mizoguchi, Asao; Endo, Yasuki; Ohshima, Yasuhiro

    1998-12-01

    The first spectroscopic identification of a van der Waals complex containing salt, Ar-NaCl, has been reported. A cm-region rotational spectrum of the complex has been observed for the 35Cl and 37Cl isotopomers by using a Fourier-transform microwave spectrometer combined with a laser ablation nozzle source. The vibrationally averaged geometry of the complex is of the linear Ar⋯Na-Cl configuration, with the internuclear distance of R(Ar⋯Na)=2.887 Å. An almost fully resolved hyperfine structure in low-J transitions has yielded precise nuclear quadrupole coupling constants associated with both Na and Cl nuclei, which indicate a substantial charge rearrangement in the NaCl molecule by complexation with Ar.

  12. Controlled growth of atomically thin In2Se3 flakes by van der Waals epitaxy.

    PubMed

    Lin, Min; Wu, Di; Zhou, Yu; Huang, Wei; Jiang, Wei; Zheng, Wenshan; Zhao, Shuli; Jin, Chuanhong; Guo, Yunfan; Peng, Hailin; Liu, Zhongfan

    2013-09-11

    The controlled production of high-quality atomically thin III-VI semiconductors poses a challenge for practical applications in electronics, optoelectronics, and energy science. Here, we exploit a controlled synthesis of single- and few-layer In2Se3 flakes on different substrates, such as graphene and mica, by van der Waals epitaxy. The thickness, orientation, nucleation site, and crystal phase of In2Se3 flakes were well-controlled by tuning the growth condition. The obtained In2Se3 flakes exhibit either semiconducting or metallic behavior depending on the crystal structures. Meanwhile, field-effect transistors based on the semiconducting In2Se3 flakes showed an efficient photoresponse. The controlled growth of atomically thin In2Se3 flakes with diverse conductivity and efficient photoresponsivity could lead to new applications in photodetectors and phase change memory devices. PMID:23978251

  13. A van der Waals density functional investigation of carboranethiol self-assembled monolayers on Au(111).

    PubMed

    Mete, Ersen; Yılmaz, AyƟen; DanÄ±ĆŸman, Mehmet Fatih

    2016-05-14

    Isolated and full monolayer adsorption of various carboranethiol (C2B10H12S) isomers on the gold(111) surface has been investigated using both the standard and van der Waals density functional theory calculations. The effect of different molecular dipole moment orientations on the low energy adlayer geometries, the binding characteristics and the electronic properties of the self-assembled monolayers of these isomers has been studied. Specifically, the binding energy and work function changes associated with different molecules show a correlation with their dipole moments. The adsorption is favored for the isomers with dipole moments parallel to the surface. Of the two possible unit cell structures, (5 × 5) was found to be more stable than . PMID:27108565

  14. Guest transport in a nonporous organic solid via dynamic van der Waals cooperativity.

    PubMed

    Atwood, Jerry L; Barbour, Leonard J; Jerga, Agoston; Schottel, Brandi L

    2002-11-01

    A well-known organic host compound undergoes single-crystal-to-single-crystal phase transitions upon guest uptake and release. Despite a lack of porosity of the material, guest transport through the solid occurs readily until a thermodynamically stable structure is achieved. In order to actively facilitate this dynamic process, the host molecules undergo significant positional and/or orientational rearrangement. This transformation of the host lattice is triggered by weak van der Waals interactions between the molecular components. In order for the material to maintain its macroscopic integrity, extensive cooperativity must exist between the molecules throughout the crystal, such that rearrangement can occur in a well-orchestrated fashion. We demonstrate here that even weak dispersive forces can exert a profound influence over solid-state dynamics. PMID:12411698

  15. Physisorption of nucleobases on graphene: the role of van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Le, Duy; Kara, Abdelkader; Rahman, Talat S.

    2010-03-01

    The physisorption of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) on graphene is studied within the generalized gradient approximation (GGA) of the density functional theory (DFT) with the inclusion of van der Waals interaction (vdW) based on the London dispersion equation. We find that the inclusion of the latter interaction increases the binding energy by about 0.5eV (from an almost zero value) and moves these nucleobases by about 0.5ć toward the graphene, as compared to the results obtained with regular DFT-GGA. The binding energies of nucleobases on graphene are found to be in the following order: G>A>T>C>U, with a dispersion of about 200meV. Details of the dynamics (diffusion barriers) and adsorption characteristics of these nucleobases on graphene will be presented as well as the description of their electronic structure and nature of the bonding with the substrate.

  16. Exploring a noisy van der Pol type oscillator with a stochastic approach.

    PubMed

    Yuan, Ruoshi; Wang, Xinan; Ma, Yian; Yuan, Bo; Ao, Ping

    2013-06-01

    Based on conventional Ito or Stratonovich interpretation, zero-mean multiplicative noise can induce shifts of attractors or even changes of topology to a deterministic dynamics. Such phenomena usually introduce additional complications in analysis of these systems. We employ in this paper a new stochastic interpretation leading to a straightforward consequence: The steady state distribution is Boltzmann-Gibbs type with a potential function severing as a Lyapunov function for the deterministic dynamics. It implies that an attractor corresponds to the local extremum of the distribution function and the probability is equally distributed right on an attractor. We consider a prototype of nonequilibrium processes, noisy limit cycle dynamics. Exact results are obtained for a class of limit cycles, including a van der Pol type oscillator. These results provide a new angle for understanding processes without detailed balance and can be verified by experiments. PMID:23848629

  17. Ytterbium in quantum gases and atomic clocks: van der Waals interactions and blackbody shifts.

    PubMed

    Safronova, M S; Porsev, S G; Clark, Charles W

    2012-12-01

    We evaluated the C(6) coefficients of Yb-Yb, Yb-alkali, and Yb-group II van der Waals interactions with 2% uncertainty. The only existing experimental result for such quantities is for the Yb-Yb dimer. Our value, C(6)=1929(39) a.u., is in excellent agreement with the recent experimental determination of 1932(35) a.u. We have also developed a new approach for the calculation of the dynamic correction to the blackbody radiation shift. We have calculated this quantity for the Yb 6s(2) (1)S(0)-6s6p (3)P(0)(o) clock transition with 3.5% uncertainty. This reduces the fractional uncertainty due to the blackbody radiation shift in the Yb optical clock at 300 K to the 10(-18) level. PMID:23368178

  18. Communication: Multiple-property-based diabatization for open-shell van der Waals molecules.

    PubMed

    Karman, Tijs; van der Avoird, Ad; Groenenboom, Gerrit C

    2016-03-28

    We derive a new multiple-property-based diabatization algorithm. The transformation between adiabatic and diabatic representations is determined by requiring a set of properties in both representations to be related by a similarity transformation. This set of properties is determined in the adiabatic representation by rigorous electronic structure calculations. In the diabatic representation, the same properties are determined using model diabatic states defined as products of undistorted monomer wave functions. This diabatic model is generally applicable to van der Waals molecules in arbitrary electronic states. Application to locating seams of conical intersections and collisional transfer of electronic excitation energy is demonstrated for O2 - O2 in low-lying excited states. Property-based diabatization for this test system included all components of the electric quadrupole tensor, orbital angular momentum, and spin-orbit coupling. PMID:27036418

  19. Wavelike charge density fluctuations and van der Waals interactions at the nanoscale.

    PubMed

    Ambrosetti, Alberto; Ferri, Nicola; DiStasio, Robert A; Tkatchenko, Alexandre

    2016-03-11

    Recent experiments on noncovalent interactions at the nanoscale have challenged the basic assumptions of commonly used particle- or fragment-based models for describing van der Waals (vdW) or dispersion forces. We demonstrate that a qualitatively correct description of the vdW interactions between polarizable nanostructures over a wide range of finite distances can only be attained by accounting for the wavelike nature of charge density fluctuations. By considering a diverse set of materials and biological systems with markedly different dimensionalities, topologies, and polarizabilities, we find a visible enhancement in the nonlocality of the charge density response in the range of 10 to 20 nanometers. These collective wavelike fluctuations are responsible for the emergence of nontrivial modifications of the power laws that govern noncovalent interactions at the nanoscale. PMID:26965622

  20. Beyond Graphene: Progress in Novel Two-Dimensional Materials and van der Waals Solids

    NASA Astrophysics Data System (ADS)

    Das, Saptarshi; Robinson, Joshua A.; Dubey, Madan; Terrones, Humberto; Terrones, Mauricio

    2015-07-01

    Interest in 2D materials and van der Waals solids is growing exponentially across various scientific and engineering disciplines owing to their fascinating electrical, optical, chemical, and thermal properties. Whereas the micromechanical exfoliation technique has been adopted for rapid material characterization and demonstration of innovative device ideas based on these 2D systems, significant advances have recently been made in large-scale homogeneous and heterogeneous growth of these materials. This review reflects recent progress and outlines future prospects of these novel 2D materials. We provide a holistic overview of the different synthesis and characterization techniques, electronic and photonic device characteristics, and catalytic properties of transition metal dichalcogenides and their heterostructures. We also comment on the challenges that need to be overcome for full-scale commercial implementation of this novel class of layered materials.

  1. Strain induced piezoelectric effect in black phosphorus and MoS2 van der Waals heterostructure

    PubMed Central

    Huang, Le; Li, Yan; Wei, Zhongming; Li, Jingbo

    2015-01-01

    The structural, electronic, transport and optical properties of black phosphorus/MoS2 (BP/MoS2) van der Waals (vdw) heterostructure are investigated by using first principles calculations. The band gap of BP/MoS2 bilayer decreases with the applied normal compressive strain and a semiconductor-to-metal transition is observed when the applied strain is more than 0.85 Å. BP/MoS2 bilayer also exhibits modulation of its carrier effective mass and carrier concentration by the applied compressive strain, suggesting that mobility engineering and good piezoelectric effect can be realized in BP/MoS2 heterostructure. Because the type-II band alignment can facilitate the separation of photo-excited electrons and holes, and it can benefit from the great absorption coefficient in ultra-violet region, the BP/MoS2 shows great potential to be a very efficient ultra-violet photodetector. PMID:26553370

  2. Strain induced piezoelectric effect in black phosphorus and MoS2 van der Waals heterostructure.

    PubMed

    Huang, Le; Li, Yan; Wei, Zhongming; Li, Jingbo

    2015-01-01

    The structural, electronic, transport and optical properties of black phosphorus/MoS2 (BP/MoS2) van der Waals (vdw) heterostructure are investigated by using first principles calculations. The band gap of BP/MoS2 bilayer decreases with the applied normal compressive strain and a semiconductor-to-metal transition is observed when the applied strain is more than 0.85 Å. BP/MoS2 bilayer also exhibits modulation of its carrier effective mass and carrier concentration by the applied compressive strain, suggesting that mobility engineering and good piezoelectric effect can be realized in BP/MoS2 heterostructure. Because the type-II band alignment can facilitate the separation of photo-excited electrons and holes, and it can benefit from the great absorption coefficient in ultra-violet region, the BP/MoS2 shows great potential to be a very efficient ultra-violet photodetector. PMID:26553370

  3. Generalized method for prediction of saturated liquid volumes using Van der Waals volumes

    SciTech Connect

    Wang, J.; Kabadi, V.N.

    1996-02-01

    The modified Rackett equation represents a simple and very widely used method to predict saturated liquid volumes. In addition to being fairly accurate, this equation is mathematically continuous and renders expressions for first and second derivatives of saturated liquid volume needed for computations of thermodynamic properties such as enthalpies and heat capacities from certain liquid state equations of state that use saturated liquid volume. The objective of this work is to further enhance the applicability of the modified Rackett equation by developing a correlation for the parameter Z{sub RA} with Van der Waals volume of the molecule and with a volume parameter calculated by summing the UNIFAC volume parameters (R) of individual groups making up the molecule. The data used in this work included 124 compounds classified into various families. These compounds included high molecular weight aromatics and heterocycles, phenols, and some amines.

  4. Photodepletion measurements of the Zr⋯F-CH 3 van der Waals complex

    NASA Astrophysics Data System (ADS)

    Soorkia, Satchin; Mestdagh, Jean-Michel; Gaveau, Marc-André; Soep, Benoßt

    2010-05-01

    We report here on the observation of the Zr⋯F-CH 3 van der Waals complexes in a laser ablation - supersonic expansion source. The complexes are studied using a combination of laser spectroscopy and time-of-flight mass spectrometric detection. We show that the (1:1) Zr⋯F-CH 3 complex is stable in the ground electronic state. By a ground state photodepletion method, we have characterized one of the transitions in the 600-700 nm region as correlating asymptotically with the z3F20←a3F2 atomic transition from the ground state of free Zr atom. The corresponding excited state of the Zr⋯F-CH 3 complex is reactive with activation of the C-F bond.

  5. Analytical model for the calculation of molecular van der Waals surfaces and solvent-accessible surfaces

    NASA Astrophysics Data System (ADS)

    Ulmschneider, M.; PĂ©nigault, E.

    1999-04-01

    A new analytical procedure for the approximate calculation of molecular van der Waals and solvent-accessible surface areas is described. It is based on a set of probe points placed around atoms by vector construction, related to atomic hybridization and valence geometries. Surface equivalents are assigned to probe points. Surface inclusion is calculated according to a single distance function. The complete and detailed set of fundamental formulas of the model is given in three steps. The first one is purely geometrical. The second develops an analysis of atomic surfaces inclusions. The third deals with the calculation of first derivatives with respect to atomic coordinates. Un nouveau procĂ©dĂ© analytique de calcul approchĂ© des surfaces molĂ©culaires de van der Waals et accessible au solvant est dĂ©crit. Il met enƓuvre un ensemble de points-sondes, disposĂ©s autour du noyau atomique Ă  l'aide de constructions vectorielles spĂ©cifiques de l'hybri dation et des liaisons de valence. Des Ă©quivalents de surface sont affectĂ©s aux points-sondes. Les inclusions de surface sont estimĂ©es Ă  l'aide d'une fonction simple de la distance. L'ensemble des relations fondamentales du modĂšle sont dĂ©crites en trois parties. La premiĂšre a un caractĂšre purement gĂ©omĂ©trique. La seconde analyse les inclusions de surfaces atomiques. La troisiĂšme rend compte du calcul de dĂ©rivĂ©es premiĂšres par rapport aux coordonnĂ©es atomiques.

  6. The effect of nonpolar solvents on Rydberg states: van der Waals complexes of azabicyclooctanes

    NASA Astrophysics Data System (ADS)

    Shang, Q. Y.; Moreno, P. O.; Dion, C.; Bernstein, E. R.

    1993-05-01

    The effect of solvation by nonpolar solvents on the (n,3s) Rydberg states of 1,4-diazabicyclo[2.2.2]octane (DABCO) and azabicyclo[2.2.2]octane (ABCO) is investigated through mass resolved excitation spectroscopy of their van der Waals complexes. The solute/solvent clusters formed in a supersonic expansion include DABCO and ABCO with Ar, n-CmH2m+2 (m=1-7), and CF4 and C2F6. The resulting spectra are analyzed with the help of empirical potential energy calculations of the cluster binding energies, minimum energy structures, van der Waals modes, and potential barriers between the various cluster minimum energy structures. Good agreement is found between the calculated and experimental results for DABCO and ABCO clustered with argon and methane. The spectra of clusters with all other hydrocarbons can be ascribed to only one major geometry for each cluster stoichiometry, despite the fact that calculations yield many stable geometries for each cluster. This apparent lack of agreement between calculations and experiments can be rationalized based on cluster binding energy, zero point energy, and the potential energy barriers between the cluster minima. The observed blue shift of the cluster 000 transition energy as a function of the n-alkane chain length can be qualitatively modeled by a Lennard-Jones potential for the solute-solvent interaction for both the ground and excited states. The model reveals a strong repulsive interaction between the Rydberg state electronic distribution and the solvent molecule. This repulsion depends on the distance between the solvent molecule and the solute molecule nitrogen atom.

  7. Excitons in van der Waals heterostructures: The important role of dielectric screening

    NASA Astrophysics Data System (ADS)

    Latini, S.; Olsen, T.; Thygesen, K. S.

    2015-12-01

    The existence of strongly bound excitons is one of the hallmarks of the newly discovered atomically thin semiconductors. While it is understood that the large binding energy is mainly due to the weak dielectric screening in two dimensions, a systematic investigation of the role of screening on two-dimensional (2D) excitons is still lacking. Here we provide a critical assessment of a widely used 2D hydrogenic exciton model, which assumes a dielectric function of the form ɛ (q )=1 +2 π α q , and we develop a quasi-2D model with a much broader applicability. Within the quasi-2D picture, electrons and holes are described as in-plane point charges with a finite extension in the perpendicular direction, and their interaction is screened by a dielectric function with a nonlinear q dependence which is computed ab initio. The screened interaction is used in a generalized Mott-Wannier model to calculate exciton binding energies in both isolated and supported 2D materials. For isolated 2D materials, the quasi-2D treatment yields results almost identical to those of the strict 2D model, and both are in good agreement with ab initio many-body calculations. On the other hand, for more complex structures such as supported layers or layers embedded in a van der Waals heterostructure, the size of the exciton in reciprocal space extends well beyond the linear regime of the dielectric function, and a quasi-2D description has to replace the 2D one. Our methodology has the merit of providing a seamless connection between the strict 2D limit of isolated monolayer materials and the more bulk-like screening characteristics of supported 2D materials or van der Waals heterostructures.

  8. Thioarsenides: A case for long-range Lewis acid-base-directed van der Waals interactions

    SciTech Connect

    Gibbs, Gerald V.; Wallace, Adam F.; Downs, R. T.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.

    2011-04-01

    Electron density distributions, bond paths, Laplacian and local energy density properties have been calculated for a number of As4Sn (n = 3,4,5) thioarsenide molecular crystals. On the basis of the distributions, the intramolecular As-S and As-As interactions classify as shared bonded interactions and the intermolecular As-S, As-As and S-S interactions classify as closed-shell van der Waals bonded interactions. The bulk of the intermolecular As-S bond paths link regions of locally concentrated electron density (Lewis base regions) with aligned regions of locally depleted electron density (Lewis acid regions) on adjacent molecules. The paths are comparable with intermolecular paths reported for several other molecular crystals that link aligned Lewis base and acid regions in a key-lock fashion, interactions that classified as long range Lewis acid-base directed van der Waals interactions. As the bulk of the intermolecular As-S bond paths (~70%) link Lewis acid-base regions on adjacent molecules, it appears that molecules adopt an arrangement that maximizes the number of As-S Lewis acid-base intermolecular bonded interactions. The maximization of the number of Lewis acid-base interactions appears to be connected with the close-packed array adopted by molecules: distorted cubic close-packed arrays are adopted for alacrĂĄnite, pararealgar, uzonite, realgar and ÎČ-AsS and the distorted hexagonal close-packed arrays adopted by α- and ÎČ-dimorphite. A growth mechanism is proposed for thioarsenide molecular crystals from aqueous species that maximizes the number of long range Lewis acid-base vdW As-S bonded interactions with the resulting directed bond paths structuralizing the molecules as a molecular crystal.

  9. Communication: Determining the structure of the N{sub 2}Ar van der Waals complex with laser-based channel-selected Coulomb explosion

    SciTech Connect

    Wu, Chengyin Liu, Yunquan; Gong, Qihuang; Collaborative Innovation Center of Quantum Matter, Beijing ; Wu, Cong; Xie, Xiguo; Li, Min; Deng, Yongkai; Song, Di; Su, Hongmei

    2014-04-14

    We experimentally reconstructed the structure of the N{sub 2}Ar van der Waals complex with the technique of laser-based channel-selected Coulomb explosion imaging. The internuclear distance between the N{sub 2} center of mass and the Ar atom, i.e., the length of the van der Waals bond, was determined to be 3.88 Å from the two-body explosion channels. The angle between the van der Waals bond and the N{sub 2} principal axis was determined to be 90° from the three-body explosion channels. The reconstructed structure was contrasted with our high level ab initio calculations. The agreement demonstrated the potential application of laser-based Coulomb explosion in imaging transient molecular structure, particularly for floppy van der Waals complexes, whose structures remain difficult to be determined by conventional spectroscopic methods.

  10. Binding and Diffusion of Lithium in Graphite: Quantum Monte-Carlo benchmarks and validation of van der Waals density functional methods

    DOE PAGESBeta

    Ganesh, Panchapakesan; Kim, Jeongnim; Park, Changwon; Yoon, Mina; Reboredo, Fernando A; Kent, Paul R

    2014-01-01

    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 suchmore » 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.« less

  11. Binding and Diffusion of Lithium in Graphite: Quantum Monte-Carlo benchmarks and validation of van der Waals density functional methods

    SciTech Connect

    Ganesh, Panchapakesan; Kim, Jeongnim; Park, Changwon; Yoon, Mina; Reboredo, Fernando A; Kent, Paul R

    2014-01-01

    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.

  12. Workflow-Management fĂŒr organisationsĂŒbergreifende DatenĂŒbertragung am Beispiel des E-Learning-Systems der TUM

    NASA Astrophysics Data System (ADS)

    Boursas, Latifa

    In diesem Paper werden im ersten Schritt die Voraussetzungen und Anforderungen fĂŒr Workflow-Management zur Bereitstellung einer organisationsĂŒbergreifenden DatenĂŒbertragung ausgefĂŒhrt. Weiter werden auf einfache Art und Weise die Grundlagen des Identity Managements (IDM) und der Provisionierung von Zielsystemen erlĂ€utert sowie die technischen Lösungsideen fĂŒr die genannten Anforderungen eingefĂŒhrt. Am Beispiel des E-Learning-Systems der TU MĂŒnchen zeigen wir zwei LösungsansĂ€tze. Zu jedem Lösungsansatz werden die technischen Workflows genauer betrachtet und der Funktionsumfang erlĂ€utert. Ein paar Uses Cases bei den Datenkonvertierungen, die sich auf die verschiedenen Identity-Management-Schnittstellen beziehen werden auch prĂ€sentiert. Am Ende schließt ein Vergleich der beiden LösungsansĂ€tze die Analyse ab.

  13. Regional assignment of seven loci to 12p 13. 2-pter by PCR analysis of somatic cell hybrids containing the der(12) or the der(X) chromosome from a mesothelioma showing t(X; 12)(q22; p13)

    SciTech Connect

    Aerssens, J.; Chaffanet, M.; Baens, M.; Matthijs, G.; Van Den Berche, H.; Cassiman, J.J.; Marynen, P. )

    1994-03-01

    Two somatic cell hybrids containing the der(12) or the der(X) from a mesothelioma with a translocation t(X;12) (q22;p13) as the only chromosomal change were generated to characterize the region of 12p12 containing the translocation breakpoint. Fluorescence in situ hybridization analysis showed the breakpoint on chromosome 12 to occur between VWF and D12S158. On the linkage map developed by J. Weissenbach et al., the breakpoints were located between DXS1106 and DCS1001 on chromosome X. PCR analysis based on genomic sequences, with DNA from both somatic cell hybrids, enabled mapping of CACNL1A1, FGF6, D12S370, D12S38OE, D12S381E, and D12S382E distally to the 12p13 breakpoint and to VWF. 11 refs., 2 figs., 1 tab.

  14. Influence of van der Waals forces on increasing the strength and toughness in dynamic fracture of nanofibre networks: a peridynamic approach

    NASA Astrophysics Data System (ADS)

    Bobaru, F.

    2007-07-01

    The peridynamic method is used here to analyse the effect of van der Waals forces on the mechanical behaviour and strength and toughness properties of three-dimensional nanofibre networks under imposed stretch deformation. The peridynamic formulation allows for a natural inclusion of long-range forces (such as van der Waals forces) by considering all interactions as 'long-range'. We use van der Waals interactions only between different fibres and do not need to model individual atoms. Fracture is introduced at the microstructural (peridynamic bond) level for the microelastic type bonds, while van der Waals bonds can reform at any time. We conduct statistical studies to determine a certain volume element for which the network of randomly oriented fibres becomes quasi-isotropic and insensitive to statistical variations. This qualitative study shows that the presence of van der Waals interactions and of heterogeneities (sacrificial bonds) in the strength of the bonds at the crosslinks between fibres can help in increasing the strength and toughness of the nanofibre network. Two main mechanisms appear to control the deformation of nanofibre networks: fibre reorientation (caused by deformation and breakage) and fibre accretion (due to van der Waals interaction). Similarities to the observed toughness of polymer adhesive in the abalone shell composition are explained. The author would like to dedicate this work to the 60th anniversary of Professor Subrata Mukherjee.

  15. Gesellschaft, Lebensgemeinschaft, Ökosystem - Über die Kongruenz von politischen und ökologischen Theorien der Entwicklung

    NASA Astrophysics Data System (ADS)

    Voigt, Annette

    Im Jahr 1859 veröffentlichte Charles Darwin "On the Origin of Species“. Seine Evolutionstheorie ist das wohl spektakulĂ€rste Beispiel einer naturwissenschaftlichen Theorie großer gesellschaftlicher Relevanz. Ihre verschiedenen Facetten wurden in der Öffentlichkeit kontrovers diskutiert, unter anderem auch ihre Anwendung zur ErklĂ€rung von ZustĂ€nden und Prozessen menschlicher Gesellschaften. Zum Teil wurde die Seiensweise der Natur - scheinbar unabhĂ€ngig von gesellschaftlichen Interessen - fĂŒr die ErklĂ€rung und Legitimation gesellschaftlicher ZustĂ€nde oder die Legitimation von politischen Ideologien herangezogen (Sozialdarwinismus). Denn Gesellschaft funktioniere ja so, wie Darwin die Natur erklĂ€rt habe: es herrsche z. B. Konkurrenzkampf, Auslese und Arbeitsteilung, Erfolg hĂ€tten diejenigen, die sich an die Bedingungen am Besten anpassten.

  16. Quantum Transport Detected by Strong Proximity Interaction at a Graphene-WS2 van der Waals Interface.

    PubMed

    O'Farrell, E C T; Avsar, A; Tan, J Y; Eda, G; Özyilmaz, B

    2015-09-01

    Magnetotransport measurements demonstrate that graphene in a van der Waals heterostructure is a sensitive probe of quantum transport in an adjacent WS2 layer via strong Coulomb interactions. We observe a large low-field magnetoresistance (≫ e(2)/h) and a -ln T temperature dependence of the resistance. In-plane magnetic field resistance indicates the origin is orbital and nonclassical. We demonstrate a strong electron-hole asymmetry in the mobility and coherence length of graphene demonstrating the presence of localized Coulomb interactions with ionized donors in the WS2 substrate, which ultimately leads to screening as the Fermi level of graphene is tuned toward the conduction band of WS2. This leads us to conclude that graphene couples to quantum localization processes in WS2 via the Coulomb interaction and results in the observed signatures of quantum transport. Our results show that theoretical descriptions of the van der Waals interface should not ignore localized strong correlations. PMID:26258760

  17. GridAgents DER Testing: Cooperative Research and Development Final Report, CRADA Number CRD-08-265

    SciTech Connect

    Harrison, K.

    2012-04-01

    The project objectives are to perform research, development, and pilot-scale testing of advanced, next-generation distribution operational strategies using ConEdison's 3G: Distribution System of the Future and associated infrastructure for the real-world Test Bed (demonstration network) combined with the Infotility GridAgents: Secure Agent Framework for Energy as the software platform for advanced operational strategies development. The objective is to accelerate high-payoff technologies that, because of their risk, are unlikely to be developed in a timely manner without a partnership between industry and the Federal government. NREL will be responsible for the evaluation of equipment design and control methods for DER integration and testing of prototype DER technologies and control equipment at the NREL test facility.

  18. Van der Pol behavior of virtual anode oscillations in the sheath around a grid in a double plasma device

    SciTech Connect

    Klostermann, H.; Rohde, A.; Piel, A.

    1997-07-01

    Experiments are reported on oscillations that arise in a double plasma device when plasma production is restricted to the source chamber and the separating grid between the two chambers is biased negatively. The free oscillating system shows periodic pulling which is a typical behavior of driven van der Pol type oscillators. The second interacting frequency is identified to be half the ion plasma frequency at the sheath edge on the source side. With the help of particle in cell simulations the concept of virtual anode oscillations (VAO{close_quote}s) as the underlying oscillation mechanism is investigated and the van der Pol character of these is revealed. When applied to the experimental conditions, the VAO-model predicts correct oscillation frequencies. It gives a new interpretation of the scaling of these with plasma density and grid bias, and is compatible with earlier findings. {copyright} {ital 1997 American Institute of Physics.}

  19. Distributed Energy Resources Customer Adoption Model (DER-CAM), Investment & Planing Version 3.10.5.m

    SciTech Connect

    2014-04-01

    Version 3.10.5 is a multi-year Decision Support tool for Distributed Generation (DG). 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 heat and electric loads of a single building or microgrid for a typical test year. Now, version 3.10.5.m solves for a multiple-year horizon the technology choice question, the appropriate capacity for each selected technology as well as the operational and investment schedule. Optimized investment decisions are based on techno-economic criteria, along with site information such as energy loads, economic forecast, and technology characterization. Version 3.10.5 contains: 1. a PV and battery degradation model and 2. variable performance for technologies. Efficiency, investment costs, etc. can vary over time and model technology breakthroughs and advancements.

  20. Revealing the Buried Metal-Organic Interface: Restructuring of the First Layer by van der Waals Forces.

    PubMed

    Wagner, Margareta; Berkebile, Stephen; Netzer, Falko P; Ramsey, Michael G

    2015-12-22

    With the use of molecular manipulation in a cryogenic scanning tunneling microscope, the structure and rearrangement of sexiphenyl molecules at the buried interface of the organic film with the Cu(110) substrate surface have been revealed. It is shown that a reconstruction of the first monolayer of flat lying molecules occurs due to the van der Waals pressure from subsequent layers. In this rearrangement, additional sexiphenyl molecules are forced into the established complete monolayer and adopt an edge-on configuration. Incorporation of second layer molecules into the first layer is also demonstrated by purposely pushing sexiphenyl molecules with the STM tip. The results indicate that even chemisorbed organic layers at interfaces can be significantly influenced by external stress from van der Waals forces of subsequent layers. PMID:26505912