Giant spin canting in the S = 1/2 antiferromagnetic chain [CuPM(NO3)2(H2O)2]n observed by 13C-NMR

We present a combined experimental and theoretical study on copper pyrimidine dinitrate [CuPM(NO3)2(H2O)2]n, a one-dimensional S = 1/2 antiferromagnet with alternating local symmetry. From the local susceptibility measured by NMR at the three inequivalent carbon sites in the pyrimidine molecule we deduce a giant spin canting, i.e., an additional staggered magnetization perpendicular to the applied external field at low temperatures. The magnitude of the transverse magnetization, the spin canting of 52 degrees at 10 K and 9.3 T and its temperature dependence are in excellent agreement with exact diagonalization calculations.Comment: 5 pages, 6 Postscript figure

Halbheiten in der Überwindung des Leninismus: Zur Leninkritik des Projekts Klassenanalyse (PKA)

Es ist kein Zufall, daß die ausführliche Leninkritik des PKA: ,,Leninismus - neue Stufe des wissenschaftlichen Sozialismus? Zum Verhältnis von Marxscher Theorie, Klassenanalyse und revolutionärer Taktik bei W. I. Lenin, Westberlin 1972" in der bisher spärlichen Lenindiskussion der westdeutschen sozialistischen Opposition fast völlig ignoriert wurde. Dies liegt bestimmt nicht nur an der rein äußerlich durch den Umfang und die vielen Wiederholungen hervorgerufenen mühseligen Lesbarkeit des Buches, sondern hat seinen eigentlichen Grund in der eigentümlichen politischen Stoßrichtung der Argumentation. Nachdem das PKA die DKP zur „distinkten Arbeiterpartei" erhoben und alle linkskommunistische Kritik am Leninismus als sektiererisch verworfen hat, wird nun doch auf Basis der Marxschen Theorie eine systematische und grundsätzliche Kritik an Lenin, dem Idol des Marxismus-Leninismus, eingeschlossen der DKP, geführt. Dabei kommt das PKA nicht umhin, richtige Elemente der linkskommunistischen, luxemburgianischen, trotzkistischen etc. Positionen aufzunehmen, ohne sie natürlich als solche zu kennzeichnen. Doch bleibt auch die Kritik an Lenin eigentümlich ambivalent: einerseits gelingt es dem PKA in vielen entscheidenden Punkten theoretische und taktische Verkürzungen der Marxsehen Theorie von Lenin nachzuweisen, andererseits wird Lenin nichtsdestoweniger als revolutionäres Vorbild gepriesen. Das PKA gebärdet sich so gleichsam als Wolf im Schafspelz, der aber lieber Schaf als Wolf sein will. Diese Haltung erlaubt es aber der DKP, nach ihrem Belieben die Diskussion mit dem PKA zu führen oder eben auch nicht zu führen, und macht es der nicht an die DKP gebundenen sozialistischen Opposition, die selbst in vielen leninistischen Dogmatisierungen steckt, leicht, das PKA als literarische Repräsentanten der DKP abzutun

Mutual independence of critical temperature and superfluid density under pressure in optimally electron-doped superconducting LaFeAsO1−x_{1-x}Fx_{x}

The superconducting properties of LaFeAsO$_{1-x}$F$_{x}$ in conditions of optimal electron-doping are investigated upon the application of external pressure up to $\sim 23$ kbar. Measurements of muon-spin spectroscopy and dc magnetometry evidence a clear mutual independence between the critical temperature $T_{c}$ and the low-temperature saturation value for the ratio $n_{s}/m^{*}$ (superfluid density over effective band mass of Cooper pairs). Remarkably, a dramatic increase of $\sim 30$ % is reported for $n_{s}/m^{*}$ at the maximum pressure value while $T_{c}$ is substantially unaffected in the whole accessed experimental window. We argue and demonstrate that the explanation for the observed results must take the effect of non-magnetic impurities on multi-band superconductivity into account. In particular, the unique possibility to modify the ratio between intra-band and inter-bands scattering rates by acting on structural parameters while keeping the amount of chemical disorder constant is a striking result of our proposed model.Comment: 8 pages (Main text: 5 pages. Paper merged with supplemental information), 5 figure

Transit mapping of a starspot on CoRoT-2 - Probing a stellar surface by planetary transits

We analyze variations in the transit lightcurves of CoRoT-2b, a massive hot Jupiter orbiting a highly active G star. We use one transit lightcurve to eclipse-map a photospheric spot occulted by the planet. In this case study we determine the size and longitude of the eclipsed portion of the starspot and systematically study the corresponding uncertainties. We determine a spot radius between 4.5\degr and 10.5\degr on the stellar surface and the spot longitude with a precision of about $\pm 1$ degree. Given the well-known transit geometry of the CoRoT-2 system, this implies a reliable detection of spots on latitudes typically covered by sunspots; also regarding its size the modelled spot is comparable to large spot groups on the Sun. We discuss the future potential of eclipse mapping by planetary transits for the high-resolution analysis of stellar surface features.Comment: accepted by Astronomy and Astrophysic

Brands in international and multi‐platform expansion strategies: economic and management issues

Powerful media branding has historically facilitated successful international expansion on the part of magazine and other content forms including film and TV formats. Multi-platform expansion is now increasingly central to the strategies of media companies and, as this chapter argues, effective use of branding in order to engage audiences effectively and to secure a prominent presence across digital platforms forms a core part of this. Drawing on original research into the experience of UK media companies, this chapter highlights some of the key economic, management and socio-cultural issues raised by the ever-increasing role of brands and branding in the strategies of international and multi-platform expansion that are increasingly common- place across media

Atacamite Cu2Cl(OH)3: A model compound for the S = 1/2 sawtooth chain?

We present a combined experimental and theoretical study of the mineral atacamite Cu2Cl(OH)3.Based on ab initio band structure calculations, we derive a magnetic coupling scheme of essentially a S = 1/2 sawtooth chain. Experimentally, we fully characterize the long-range antiferromagnetically ordered state and field-induced behavior, here for H k b axis. Magnetic order is suppressed by magnetic fields of ∼ 20 T, while beginning at 31.5 T we observe a wide magnetization plateau at half of the saturation magnetization, Msat/2. Numerical calculations for the magnetization M(H) of the quantum sawtooth chain reveal a plateau at Msat/2, raising the issue of the understandingof its microscopic nature.Fil: Heinze, L.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; AlemaniaFil: Jeschke, H.. Okayama University; Japón. Goethe Universitat Frankfurt; AlemaniaFil: Metavitsiadis, A.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; AlemaniaFil: Reehuis, M.. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH; AlemaniaFil: Feyerherm, R.. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH; AlemaniaFil: Hoffmann, J. U.. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH; AlemaniaFil: Wolter, A. U. B.. Leibniz Institute For Solid State And Materials Researc; AlemaniaFil: Ding, X.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Zapf, V.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Corvalán Moya, Carolina del Huerto. Comisión Nacional de Energía Atómica; Argentina. Los Alamos National High Magnetic Field Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Weickert, F.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Jaime, M.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Rule, K. C.. Australian Nuclear Science And Technology Organisation; AustraliaFil: Menzel, D.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; AlemaniaFil: Valenti, R.. Goethe Universitat Frankfurt; AlemaniaFil: Brenig, W.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; AlemaniaFil: Süllow, S.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; Alemani

High-field magnetization study of the S = 1/2 antiferromagnetic Heisenberg chain [PM Cu(NO3_3)2_2(H2_2O)2_2]n_n with a field-induced gap

We present a high-field magnetization study of the $S$ = 1/2 antiferromagnetic Heisenberg chain [PM Cu(NO$_3$)$_2$(H$_2$O)$_2$]$_n$. For this material, as result of the Dzyaloshinskii-Moriya interaction and a staggered $g$ tensor, the ground state is characterized by an anisotropic field-induced spin excitation gap and a staggered magnetization. Our data reveal the qualitatively different behavior in the directions of maximum and zero spin excitation gap. The data are analyzed via exact diagonalization of a linear spin chain with up to 20 sites and on basis of the Bethe ansatz equations, respectively. For both directions we find very good agreement between experimental data and theoretical calculations. We extract the magnetic coupling strength $J/k_B$ along the chain direction to 36.3(5) K and determine the field dependence of the staggered magnetization component $m_s$.Comment: 5 pages, 2 figures (minor changes to manuscript and figures

The Sedentary Multi-Frequency Survey. I. Statistical Identification and Cosmological Properties of HBL BL Lacs

We have assembled a multi-frequency database by cross-correlating the NVSS catalog of radio sources with the RASSBSC list of soft X-ray sources, obtaining optical magnitude estimates from the Palomar and UK Schmidt surveys as provided by the APM and COSMOS on-line services. By exploiting the nearly unique broad-band properties of High-Energy Peaked (HBL) BL Lacs we have statistically identified a sample of 218 objects that is expected to include about 85% of BL Lacs and that is therefore several times larger than all other published samples of HBLs. Using a subset (155 objects) that is radio flux limited and statistically well-defined we have derived the \vovm distribution and the LogN-LogS of extreme HBLs (fx/fr >= 3E-10 erg/cm2/s/Jansky) down to 3.5 mJy. We find that the LogN-LogS flattens around 20 mJy and that = 0.42 +/- 0.02. This extends to the radio band earlier results, based on much smaller X-ray selected samples, about the anomalous cosmological observational properties of HBL BL Lacs. A comparison with the expected radio LogN-LogS of all BL Lacs (based on a beaming model) shows that extreme HBLs make up roughly 2% of the BL Lac population, independently of radio flux. This result, together with the flatness of the radio logN-logS at low fluxes, is in contrast with the predictions of a recent model which assumes an anti-correlation between peak frequency and bolometric luminosity. The extreme fx/fr flux ratios and high X-ray fluxes of these BL Lacs makes them good candidate TeV sources, some of the brighter (and closer) ones possibly detectable with the current generation of Cerenkov telescopes.Comment: 11 pages, LaTeX, 6 ps figures. Accepted for publication in MNRA