Magnetism in Graphene Induced by Single-Atom Defects

We study from first principles the magnetism in graphene induced by single carbon atom defects. For two types of defects considered in our study, the hydrogen chemisorption defect and the vacancy defect, the itinerant magnetism due to the defect-induced extended states has been observed. Calculated magnetic moments are equal to 1 $\mu_B$ per hydrogen chemisorption defect and 1.12$-$1.53 $\mu_B$ per vacancy defect depending on the defect concentration. The coupling between the magnetic moments is either ferromagnetic or antiferromagnetic, depending on whether the defects correspond to the same or to different hexagonal sublattices of the graphene lattice, respectively. The relevance of itinerant magnetism in graphene to the high-$T_C$ magnetic ordering is discussed.Comment: 5 pages, 6 figure

Low temperature transport on surface conducting diamond

Magneto-transport measurements were performed on surface conducting hydrogen-terminated diamond (100) hall bars at temperatures between 0.1-5 K in magnetic fields up to 8T.Comment: 2 pages Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2012 Conferenc

Coherent nuclear motion in a condensed-phase environment: Wave-packet approach and pump-probe spectroscopy

A quantum-mechanical Gaussian wave-packet approach to the theoretical description of nuclear motions in a condensed-phase environment is developed. General expressions for the time-dependent reduced density matrix are given for a harmonic potential surface, and the exact quantum dynamics is found for a microscopic system-plus-bath model. Particular attention is devoted to the influence of initial correlations between system and bath for the outcome of a pump-probe experiment. We show that the standard factorized preparation, compared to a more realistic correlated preparation, leads to significantly different stimulated emission spectra at high temperatures. Recent experiments for the reaction center are analyzed using this formalism

Identification of epidermal Pdx1 expression discloses different roles of Notch1 and Notch2 in murine KrasG12D-induced skin carcinogenesis in vivo

Background The Ras and Notch signaling pathways are frequently activated during development to control many diverse cellular processes and are often dysregulated during tumorigenesis. To study the role of Notch and oncogenic Kras signaling in a progenitor cell population, Pdx1-Cre mice were utilized to generate conditional oncogenic KrasG12D mice with ablation of Notch1 and/or Notch2. Methodology/Principal Findings Surprisingly, mice with activated KrasG12D and Notch1 but not Notch2 ablation developed skin papillomas progressing to squamous cell carcinoma providing evidence for Pdx1 expression in the skin. Immunostaining and lineage tracing experiments indicate that PDX1 is present predominantly in the suprabasal layers of the epidermis and rarely in the basal layer. Further analysis of keratinocytes in vitro revealed differentiation-dependent expression of PDX1 in terminally differentiated keratinocytes. PDX1 expression was also increased during wound healing. Further analysis revealed that loss of Notch1 but not Notch2 is critical for skin tumor development. Reasons for this include distinct Notch expression with Notch1 in all layers and Notch2 in the suprabasal layer as well as distinctive p21 and β-catenin signaling inhibition capabilities. Conclusions/Significance Our results provide strong evidence for epidermal expression of Pdx1 as of yet not identified function. In addition, this finding may be relevant for research using Pdx1-Cre transgenic strains. Additionally, our study confirms distinctive expression and functions of Notch1 and Notch2 in the skin supporting the importance of careful dissection of the contribution of individual Notch receptors

PEGylated DOTA-AHA-based Gd(III) chelates – A relaxometric study

Three PEGylated derivatives of 1,4,7,10-tetraazacyclododecane-1-((6-amino)hexanoic)-4,7,10-triacetic acid) (DOTA-AHA) with different molecular weights were prepared and characterized. Their Gd(III) chelates were studied in aqueous solution using variable-temperature 1H nuclear magnetic relaxation dispersion (NMRD) and 17ONMR spectroscopy in view of the determination of their relaxivity and the parameters that govern it. The relaxivity varied from 5.1 to 6.5 mM-1.s-1 (37 ºC and 60 MHz) with the increasing molecular weight of the PEG chain, being slightly higher than that of the parent chelate Gd(DOTA-AHA), due to a small contribution of a slow global rotation of the complexes. A variable temperature 1H NMR study of several Ln(III) chelates of DOTA-A(PEG750)HA allowed the determination of the isomeric M/m ratio (M = square antiprismatic isomer and m = twisted square antiprismatic isomer, the latter presenting a much faster water exchange) which for the Gd(III) chelate was estimated in circa 1:0.2, very close to that of [Gd(DOTA)]-. This explains why the PEGylated Gd(III) chelate has a water rate exchange similar to that of [Gd(DOTA)]-. The predominance of the M isomer is a consequence of the bulky PEG moiety which does not favor the stabilization of the m isomer in sterically crowded systems at the substituent site, contrary to what happens with less packed asymmetrical DOTA-type chelates with substitution in one of the four acetate C(α) atoms.The authors thank the Foundation for Science and Technology (FCT–Portugal) for financial support through the NMR Portuguese network (Bruker 400 Avance III-Univ Minho); FCT and FEDER (European Fund for Regional Development)-COMPETE/QREN/EU for financial support through the research unity PEst-C/QUI/UI686/2013 and the PhD grant attributed to André Fontes (SFRH/BD/63676/2009) also financed by the POPH and FSE

The Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Nucleon

The Gerasimov-Drell-Hearn sum rule is one of several dispersive sum rules that connect the Compton scattering amplitudes to the inclusive photoproduction cross sections of the target under investigation. Being based on such universal principles as causality, unitarity, and gauge invariance, these sum rules provide a unique testing ground to study the internal degrees of freedom that hold the system together. The present article reviews these sum rules for the spin-dependent cross sections of the nucleon by presenting an overview of recent experiments and theoretical approaches. The generalization from real to virtual photons provides a microscope of variable resolution: At small virtuality of the photon, the data sample information about the long range phenomena, which are described by effective degrees of freedom (Goldstone bosons and collective resonances), whereas the primary degrees of freedom (quarks and gluons) become visible at the larger virtualities. Through a rich body of new data and several theoretical developments, a unified picture of virtual Compton scattering emerges, which ranges from coherent to incoherent processes, and from the generalized spin polarizabilities on the low-energy side to higher twist effects in deep inelastic lepton scattering.Comment: 32 pages, 19 figures, review articl

Long-term dynamics of adaptive evolution in a globally important phytoplankton species to ocean acidification

Marine phytoplankton may adapt to ocean change, such as acidification or warming, because of their large population sizes and short generation times. Long-term adaptation to novel environments is a dynamic process, and phenotypic change can take place thousands of generations after exposure to novel conditions. We conducted a long-term evolution experiment (4 years = 2100 generations), starting with a single clone of the abundant and widespread coccolithophore Emiliania huxleyi exposed to three different CO2 levels simulating ocean acidification (OA). Growth rates as a proxy for Darwinian fitness increased only moderately under both levels of OA [+3.4% and +4.8%, respectively, at 1100 and 2200 μatm partial pressure of CO2 (Pco2)] relative to control treatments (ambient CO2, 400 μatm). Long-term adaptation to OA was complex, and initial phenotypic responses of ecologically important traits were later reverted. The biogeochemically important trait of calcification, in particular, that had initially been restored within the first year of evolution was later reduced to levels lower than the performance of nonadapted populations under OA. Calcification was not constitutively lost but returned to control treatment levels when high CO2–adapted isolates were transferred back to present-day control CO2 conditions. Selection under elevated CO2 exacerbated a general decrease of cell sizes under long-term laboratory evolution. Our results show that phytoplankton may evolve complex phenotypic plasticity that can affect biogeochemically important traits, such as calcification. Adaptive evolution may play out over longer time scales (>1 year) in an unforeseen way under future ocean conditions that cannot be predicted from initial adaptation responses

Die Schweineweide als Lebensraum für Vögel (Aves) und Laufkäfer (Coleoptera: Carabidae) : dargestellt am Beispiel des Echeler Bruches in der Warburger Börde (Kreis Höxter)

Das Verbundforschungsvorhaben “Schweinefreilandhaltung im Rahmender Landschaftspflege“ hat sich in den Jahren 1999-2003 mit der Frage beschäftigt, inwieweit die extensive Haltung von Hausschweinen einen Beitrag zum Erhalt gefährdeter Offenlandstandorte leisten kann, bzw. ob und in welchem Umfang gefährdete Arten von der Wühltätigkeit der Tiereprofitieren. Am Beispiel einer bis zur Einrichtung der Schweineweide brachliegenden Niedermoorfläche in der Warburger Börde(Kr. Höxter, Ostwestfalen) werden die Auswirkungen der Schweinebeweidung auf tierische Lebensgemeinschaften am Beispiel der Vögel und Laufkäfer erörtert und die Wertigkeiten der Zönosen im Vergleich zu benachbarten Brachflächen bzw.konventionell genutzten Feuchtgrünländern diskutiert. Trotz gewisser Einschränkungen aufgrund der relativ geringen Flächengrößen der Untersuchungsfläche und der damit einhergehenden Randeffekte sowie fehlender Versuchswiederholungen könnenbezüglich der Avifauna folgende Schlussfolgerungen gezogen werden: Extensiv genutzte Schweineweiden in Feuchtgebieten bieten ganzjährig geeignete Habitate und Strukturen für Vogelarten des Offenlandes, der Feuchtwiesen und der Röhrichte bzw. Hochstaudenfluren. Aufgrund der engen Verzahnung unterschiedlichster Strukturen geschieht dies selbst auf vergleichsweise kleinen Flächen in einem Umfang, wie es von anderen landwirtschaftlichen Nutzungen nicht gewährleistet wird. Insbesondere zur Förderung der in Mitteleuropa stark gefährdeten Wiesenbrüter stellt die Schweinebeweidung in Abhängigkeit von den standörtlichen Parametern eine geeignete Nutzungsform dar. Bezüglich der Laufkäferfauna ist festzuhalten, dass die Artengemeinschaft in erster Linie von der Bodenfeuchte bzw. der Dauer der Überstauung bestimmt wird – dies spiegelt sich auch bei der Betrachtung ausgewählter funktioneller Merkmale wider. Erst an zweiter Stelle wirkt sich die Nutzung der Flächen auf die Zusammensetzung der Lebensgemeinschaft aus. Insbesondere die Strukturparameter "Offenbodenanteil" und "Vegetationshöhe/-dichte" beeinflussen die Laufkäferzönosen maßgeblich. Die Schweineweide wies mit 41 nachgewiesenen Laufkäferarten im Vergleich zu benachbarten Brachen (36 Arten) eine höhere Diversität auf– die Käfer zeigten dort ebenfalls höhere Aktivitätsdichten. Typische Feuchtgrünlandsbzw. Niedermoorarten waren überwiegend auf den lange überstauten,nassen Teilbereichen der Untersuchungsflächen anzutreffen,wobei mehrere Arten – darunter der seltene Elaphrusuliginosus – Präferenzen für die Schweineweide zeigten. Demgegenüber drangen auf die frisch-feuchten Teilbereiche vermehrt euryöke Grünlands- und Ackerarten vor. Der Vergleich mit nahe gelegenen, als Wiesen genutzten Niedermoorresten ergab nur sehr geringe Übereinstimmungen. Hierfür dürfte die unterschiedliche Nutzungsgeschichte, aber auch die verschiedene Erfassungsmethodik eine Rolle spielen. Insgesamt kann aus Sicht der untersuchten Tiergruppen die neu eingeführte extensive, saisonale Schweinebeweidung im Bereich des degradierten Niedermoores als erfolgreich bewertet werden. Die charakteristischen Artengemeinschaften konnten erhalten bzw. neu etabliert werden, darüber hinaus profitierten einige selten bzw. gefährdete Arten von der neuen Nutzungsform. 98 Wichtige Ziele des Naturschutzes, wie die Förderung der Biodiversität oder die Schaffung geeigneter Lebensräume für gefährdete Arten, konnten somit realisiert werden

Subset- and tissue-defined STAT5 thresholds control homeostasis and function of innate lymphoid cells

Innate lymphoid cells (ILCs) patrol environmental interfaces to defend against infection and protect barrier integrity. Using a genetic tuning model, we demonstrate that the signal-dependent transcription factor (TF) STAT5 is critical for accumulation of all known ILC subsets in mice and reveal a hierarchy of STAT5 dependency for populating lymphoid and nonlymphoid tissues. We apply transcriptome and genomic distribution analyses to define a STAT5 gene signature in natural killer (NK) cells, the prototypical ILC subset, and provide a systems-based molecular rationale for its key functions downstream of IL-15. We also uncover surprising features of STAT5 behavior, most notably the wholesale redistribution that occurs when NK cells shift from tonic signaling to acute cytokine-driven signaling, and genome-wide coordination with T-bet, another key TF in ILC biology. Collectively, our data position STAT5 as a central node in the TF network that instructs ILC development, homeostasis, and function and provide mechanistic insights on how it works at cellular and molecular levels