Signals of confinement in Green functions of SU(2) Yang-Mills theory

The vortex picture of confinement is employed to explore the signals of confinement in Yang-Mills Green functions. By using SU(2) lattice gauge theory, it has been well established that the removal of the center vortices from the lattice configurations results in the loss of confinement. The running coupling constant, the gluon and the ghost form factors are studied in Landau gauge for both cases, the full and the vortex removed theory. In the latter case, a strong suppression of the running coupling constant and the gluon form factor at low momenta is observed. At the same time, the singularity of the ghost form factor at vanishing momentum disappears. This observation establishes an intimate correlation between the ghost singularity and confinement. The result also shows that a removal of the vortices generates a theory for which Zwanziger's horizon condition for confinement is no longer satisfied.Comment: 4 pages, 4 figure

Nucleon Electromagnetic Form Factors from Lattice QCD using 2+1 Flavor Domain Wall Fermions on Fine Lattices and Chiral Perturbation Theory

We present a high-statistics calculation of nucleon electromagnetic form factors in $N_f=2+1$ lattice QCD using domain wall quarks on fine lattices, to attain a new level of precision in systematic and statistical errors. Our calculations use $32^3 \times 64$ lattices with lattice spacing a=0.084 fm for pion masses of 297, 355, and 403 MeV, and we perform an overdetermined analysis using on the order of 3600 to 7000 measurements to calculate nucleon electric and magnetic form factors up to $Q^2 \approx$ 1.05 GeV$^2$. Results are shown to be consistent with those obtained using valence domain wall quarks with improved staggered sea quarks, and using coarse domain wall lattices. We determine the isovector Dirac radius $r_1^v$, Pauli radius $r_2^v$ and anomalous magnetic moment $\kappa_v$. We also determine connected contributions to the corresponding isoscalar observables. We extrapolate these observables to the physical pion mass using two different formulations of two-flavor chiral effective field theory at one loop: the heavy baryon Small Scale Expansion (SSE) and covariant baryon chiral perturbation theory. The isovector results and the connected contributions to the isoscalar results are compared with experiment, and the need for calculations at smaller pion masses is discussed.Comment: 44 pages, 40 figure

The band structure of BeTe - a combined experimental and theoretical study

Using angle-resolved synchrotron-radiation photoemission spectroscopy we have determined the dispersion of the valence bands of BeTe(100) along $\Gamma X$, i.e. the [100] direction. The measurements are analyzed with the aid of a first-principles calculation of the BeTe bulk band structure as well as of the photoemission peaks as given by the momentum conserving bulk transitions. Taking the calculated unoccupied bands as final states of the photoemission process, we obtain an excellent agreement between experimental and calculated spectra and a clear interpretation of almost all measured bands. In contrast, the free electron approximation for the final states fails to describe the BeTe bulk band structure along $\Gamma X$ properly.Comment: 21 pages plus 4 figure

Polyhedral units and network connectivity in calcium aluminosilicate glasses from high-energy x-ray diffraction

Structure factors for Cax/2AlxSi1-xO2 glasses (x=0,0.25,0.5,0.67) extended to a wave vector of magnitude Q= 40 1/A have been obtained by high-energy x-ray diffraction. For the first time, it is possible to resolve the contributions of Si-O, Al-O and Ca-O coordination polyhedra to the experimental atomic pair distribution functions (PDF). It has been found that both Si and Al are four-fold coordinated and so participate in a continuous tetrahedral network at low values of x. The number of network breaking defects in the form of non-bridging oxygens (NBO's) increases slowly with x until x=0.5 (NBO's ~ 10% at x=0.5). By x=0.67 the network breaking defects become significant as evidenced by the significant drop in the average coordination number of Si. By contrast, Al-O tetrahedra remain free of NBO's and fully integrated in the Al/Si-O network for all values of x. Calcium maintains a rather uniform coordination sphere of approximately 5 oxygen atoms for all values of x. The results suggest that not only Si/Al-O tetrahedra but Ca-O polyhedra, too, play a role in determining the glassy structure

En route towards panchromatic light harvesting: photophysical and electrochemical properties of Bodipy–porphyrazine conjugates

The concept of panchromatic light harvesting, that is, broad absorption cross sections throughout most of the visible range and excited state funnelling, has been realized in a novel set of porphyrazines. On one hand, zinc, copper, or magnesium ions were complexed by porphyrazines to tune their ground and excited state features. On the other hand, up to eight Bodipys were covalently attached to the periphery of the porphyrazines to enhance the ground state absorption. The corresponding star-shaped conjugates were probed by advanced photophysical measurements, that is, time-resolved fluorescence and femtosecond transient absorption spectroscopy. From the latter we derive spectroscopic and kinetic evidence in support of a fast and unidirectional energy transfer from the photoexcited Bodipy at the periphery to the porphyrazine at the core. In addition, the impact of the different metal centers is demonstrated

Hydroxylated fluorescent dyes for live-cell labeling: Synthesis, spectra and super-resolution STED.

Hydroxylated rhodamines, carbopyronines, silico- and germanorhodamines with absorption maxima in the range of 530-640 nm were prepared and applied in specific labeling of living cells. The direct and high-yielding entry to germa- and silaxanthones tolerates the presence of protected heteroatoms and may be considered for the syntheses of various sila- and germafluoresceins, as well as -rhodols. Application in stimulated emission depletion (STED) fluorescence microscopy revealed a resolution of 50-75 nm in one- and two-color imaging of vimentin-HaloTag fused protein and native tubulin. The established structure-property relationships allow prediction of the spectral properties and the positions of spirolactone/zwitterion equilibria for the new analogs of rhodamines, carbo-, silico- and germanorhodamines using simple additive schemes

Identifying climate change information needs for the himalayan region: Results from the GLACINDIA Stakeholder Workshop and Training Program

Here we present results of a workshop designed to bring together stakeholders from different states of the Indian side of the Himalayan arc and an international group of climate scientists in order to discuss how climate change research for this region can be tailored toward the needs of local communities. The stakeholder workshop was jointly organized by the Jawaharlal Nehru University (JNU), New Delhi, India, and the Climate Service Center 2.0, Hamburg, Germany, within the framework of the multidisciplinary international research project GLACINDIA. The project focuses on the water-related effects of changes in glacier mass balance and river runoff in western Himalayas. Given the research focus of the GLACINDIA project, the initial focus of the workshop was on glacier-related hydrological information. During stakeholder interactions the resulting discussion covered a much broader range of urgent climate change information needs for the Himalayan region.publishedVersio

Metavinculin modulates force transduction in cell adhesion sites

Vinculin is a ubiquitously expressed protein, crucial for the regulation of force transduction in cells. Muscle cells express a vinculin splice-isoform called metavinculin, which has been associated with cardiomyopathies. However, the molecular function of metavinculin has remained unclear and its role for heart muscle disorders undefined. Here, we have employed a set of piconewton-sensitive tension sensors to probe metavinculin mechanics in cells. Our experiments reveal that metavinculin bears higher molecular forces but is less frequently engaged as compared to vinculin, leading to altered force propagation in cell adhesions. In addition, we have generated knockout mice to investigate the consequences of metavinculin loss in vivo. Unexpectedly, these animals display an unaltered tissue response in a cardiac hypertrophy model. Together, the data reveal that the transduction of cell adhesion forces is modulated by expression of metavinculin, yet its role for heart muscle function seems more subtle than previously thought. Muscle cells express an adhesion molecule called metavinculin, which has been associated with cardiomyopathies. Here, the authors employed molecular tension sensors to reveal that metavinculin expression modulates cell adhesion mechanics and they develop a mouse model to demonstrate that the presence of metavinculin is not as critical for heart muscle function as previously thought