Non-singlet QCD analysis of F_2(x,Q^2) up to NNLO

The significance of NNLO (3-loop) QCD contributions to the flavor non-singlet sector of F_2^ep and F_2^ed has been studied as compared to uncertainties (different factorization schemes, higher twist and QED contributions) of standard NLO (and LO) QCD analyses. The latter effects turn out to be comparable in size to the NNLO contributions. Therefore the minute NNLO effects are not observable with presently available data on non-singlet structure functions.Comment: 14 pages, 2 figure

Horizontal flows concurrent with an X2.2 flare in active region NOAA 11158

Horizontal proper motions were measured with local correlation tracking (LCT) techniques in active region NOAA 11158 on 2011 February 15 at a time when a major (X2.2) solar flare occurred. The measurements are based on continuum images and magnetograms of the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. The observed shear flows along the polarity inversion line were rather weak (a few 100 m/s). The counter-streaming region shifted toward the north after the flare. A small circular area with flow speeds of up to 1.2 km/s appeared after the flare near a region of rapid penumbral decay. The LCT signal in this region was provided by small-scale photospheric brigthenings, which were associated with fast traveling moving magnetic features. Umbral strengthening and rapid penumbral decay was observed after the flare. Both phenomena were closely tied to kernels of white-light flare emission. The white-light flare only lasted for about 15 min and peaked 4 min earlier than the X-ray flux. In comparison to other major flares, the X2.2 flare in active region NOAA 11158 only produced diminutive photospheric signatures.Comment: 6 pages, 4 figures, accepted for publication in Astronomische Nachrichten/A

Single-photon detection and cryogenic reconfigurability in Lithium Niobate nanophotonic circuits

Lithium-Niobate-On-Insulator (LNOI) is emerging as a promising platform for integrated quantum photonic technologies because of its high second-order nonlinearity and compact waveguide footprint. Importantly, LNOI allows for creating electro-optically reconfigurable circuits, which can be efficiently operated at cryogenic temperature. Their integration with superconducting nanowire single-photon detectors (SNSPDs) paves the way for realizing scalable photonic devices for active manipulation and detection of quantum states of light. Here we report the first demonstration of these two key components integrated in a low loss (0.2 dB/cm) LNOI waveguide network. As an experimental showcase of our technology, we demonstrate the combined operation of an electrically tunable Mach-Zehnder interferometer and two waveguide-integrated SNSPDs at its outputs. We show static reconfigurability of our system with a bias-drift-free operation over a time of 12 hours, as well as high-speed modulation at a frequency up to 1 GHz. Our results provide blueprints for implementing complex quantum photonic devices on the LNOI platform

A multi-step nucleation process determines the kinetics of prion-like domain phase separation

The nucleation mechanisms of biological protein phase separation are poorly understood. Here, the authors perform time-resolved SAXS experiments with the low-complexity domain (LCD) of hnRNPA1 and uncover multiple kinetic regimes on the micro- to millisecond timescale. Initially, individual proteins collapse. Nucleation then occurs via two steps distinguished by their protein cluster size distributions

Density Contrast Sedimentation Velocity for the Determination of Protein Partial-Specific Volumes

The partial-specific volume of proteins is an important thermodynamic parameter required for the interpretation of data in several biophysical disciplines. Building on recent advances in the use of density variation sedimentation velocity analytical ultracentrifugation for the determination of macromolecular partial-specific volumes, we have explored a direct global modeling approach describing the sedimentation boundaries in different solvents with a joint differential sedimentation coefficient distribution. This takes full advantage of the influence of different macromolecular buoyancy on both the spread and the velocity of the sedimentation boundary. It should lend itself well to the study of interacting macromolecules and/or heterogeneous samples in microgram quantities. Model applications to three protein samples studied in either H2O, or isotopically enriched H218O mixtures, indicate that partial-specific volumes can be determined with a statistical precision of better than 0.5%, provided signal/noise ratios of 50–100 can be achieved in the measurement of the macromolecular sedimentation velocity profiles. The approach is implemented in the global modeling software SEDPHAT

Partizipation, Dezentralisierung und Geschlechterverhältnisse in Mexiko und Nikaragua

Der Bericht präsentiert die ersten entwicklungssoziologischen bzw. sozialanthropologischen Ergebnisse einer Feldforschung von 2004 in Mexiko und Nicaragua. Den wissenschaftlichen Ausführungen sind die methodologischen Erfahrungen der Feldforscher 'vor Ort' vorangestellt. Die methodologische Grundlage des Forschungsvorhaben bildet die Grounded Theory (Strauss, 1994), die Datenerhebung konzentriert sich auf die qualitative Methode des Interviews. Im ersten Abschnitt gilt das Interesse dem Aspekt der Partizipation an staatlichen Strukturen und den Ausschlussmechanismen. Dabei finden die Aspekte (1) kazikile Strukturen auf der lokalen Ebene, (2) ethnische Identitäten sowie (3) Partizipation, Wissen und Konflikt Berücksichtigung. Der zweite Abschnitt befasst sich mit dem Zusammenhang von Partizipation und Geschlechterverhältnisse. Hierzu werden folgende Punkte beschrieben: (1) Geschlechterdiskurse des (ländlichen) Alltags, (2) Geschlechterstrukturierung sozialer Wirklichkeiten, (3) Geschlechterpolitik als Förderung 'der' Frau, (4) staatliche Institutionen, (5) soziale Bewegungen sowie (6) Handlungsspielräume und Chancen zum Empowerment. Der dritte Abschnitt erörtert abschließend die (Nicht-)Verflechtung von Partizipation und Dezentralisierung in den beiden Ländern. (ICG2

On the role of heavy flavor parton distributions at high energy colliders

We compare `fixed flavor number scheme' (FFNS) and `variable flavor number scheme' (VFNS) parton model predictions at high energy colliders. Based on our recent LO- and NLO-FFNS dynamical parton distributions, we generate radiatively two sets of VFNS parton distributions where also the heavy quark flavors h=c,b,t are considered as massless partons within the nucleon. By studying the role of these distributions in the production of heavy particles (h\bar{h}, t\bar{b}, hW^{+-}, Higgs--bosons, etc.) at high energy ep, p\bar{p} and pp colliders, we show that the VFNS predictions are compatible with the FFNS ones (to within about 10-20% at LHC, depending on the process) when the invariant mass of the produced system far exceeds the mass of the participating heavy quark flavor.Comment: 10 pages, 1 table, 5 figure

Triggering an eruptive flare by emerging flux in a solar active-region complex

A flare and fast coronal mass ejection originated between solar active regions NOAA 11514 and 11515 on July 1, 2012 in response to flux emergence in front of the leading sunspot of the trailing region 11515. Analyzing the evolution of the photospheric magnetic flux and the coronal structure, we find that the flux emergence triggered the eruption by interaction with overlying flux in a non-standard way. The new flux neither had the opposite orientation nor a location near the polarity inversion line, which are favorable for strong reconnection with the arcade flux under which it emerged. Moreover, its flux content remained significantly smaller than that of the arcade (approximately 40 %). However, a loop system rooted in the trailing active region ran in part under the arcade between the active regions, passing over the site of flux emergence. The reconnection with the emerging flux, leading to a series of jet emissions into the loop system, caused a strong but confined rise of the loop system. This lifted the arcade between the two active regions, weakening its downward tension force and thus destabilizing the considerably sheared flux under the arcade. The complex event was also associated with supporting precursor activity in an enhanced network near the active regions, acting on the large-scale overlying flux, and with two simultaneous confined flares within the active regions.Comment: Accepted for publication in Topical Issue of Solar Physics: Solar and Stellar Flares. 25 pages, 12 figure

Single-molecule analysis of 1D diffusion and transcription elongation of T7 RNA polymerase along individual stretched DNA molecules

Using total intrnal reflection fluorescence microscopy, we directly visualize in real-time, the 1D Brownian motion and transcription elongation of T7 RNA polymerase along aligned DNA molecules bound to substrates by molecular combing. We fluorescently label T7 RNA polymerase with antibodies and use flow to convect them orthogonally to the DNA alignment direction, permitting observation and estimation of the protein diffusivity along the DNA at the single-molecule level. Our observations suggest that the 1D diffusion coefficient varies from molecule to molecule over the range 6.1 × 10−11 cm2/s to 4.3 × 10−9 cm2/s. We also observe binding and transcription by T7 RNA polymerases on single combed T7 DNA molecules with an apparent association rate of 1.6 μM−1s−1. From the measured dependence of the rate of transcription on concentration of nucleotide triphosphate, we infer that the combed DNA molecules capable of interacting with proteins are under an average tension of 25 pN