Gluon spectral functions and transport coefficients in Yang--Mills theory

We compute non-perturbative gluon spectral functions at finite temperature in quenched QCD with the maximum entropy method. We also provide a closed loop equation for the spectral function of the energy-momentum tensor in terms of the gluon spectral function. This setup is then used for computing the shear viscosity over entropy ratio $\eta/s$ in a temperature range from about $0.4\, T_c$ to $4.5\, T_c$. The ratio $\eta /s$ has a minimum at about $1.25\, T_c$ with the value of about 0.115. We also discuss extensions of the present results to QCD.Comment: 5 pages, 4 figure

Heterogeneous Firms and Substitution by Tasks: the Productivity Effect of Migrants

Economic debate about the consequences of immigration in Germany has largely focused on the wage effects for natives at an aggregate level. Especially the role of imperfect substitutability of migrants and natives gained importance. A new micro oriented approach is to focus on the firm level by estimating production functions in an equilibrium framework to gain more detailed information including firm heterogeneity. Another branch of recent literature emphasizes the role of task dimension of occupations additionally to the qualification of workers: migrants work in different jobs than natives do and are concentrated in agglomerations. The task approach is thus a key to understand imperfect substitution on the firm level. Our contribution in this article is manifold: we examine the effects of the relative (dis-)advantages in performing certain tasks and their implications on the labor market outcomes. Using this framework we construct a general equilibrium model with monopolistic competition a la Dixit-Stiglitz considering heterogeneous firms with different productivity levels and two types of jobs for migrants and natives. Firms differ in the ability to employ migrants which gives rise to wage differences between natives and migrants. Therefore firms with a higher share of migrants realize wage cost advantages. In the long run equilibrium only those firms survive in the market which are highly productive or are able to compensate their lower productivity level by wage cost advantages. We show that a higher migrant share is able to explain the increase of productivity. Further, the heterogeneous distribution of migrants in our model is the source of regional disparities. Thus part of the agglomeration advantages can be explained by the empirical stable observation that migrants tend to move to cities. The conclusions of the model are in line with three empirical facts in Germany. Firstly, the average productivity of firms is higher in cities. Secondly, the wage difference between migrants and natives in a region is increasing in the share of migrants in that region. Thirdly, less productive firms are more likely to employ a higher share of migrants, as wage advantages and productivity acts as a substitute. keywords: immigration, firm heterogeneity, skills, tasks, regional labor markets JEL: R23, J15, J24, J6

lntracluster rearrangement of protonated nitric acid: Infrared spectroscopic studies of H^+(HNO_3)(H_2O)_n

Infrared spectra of clusters of protonated nitric acid and water exhibit a marked change with cluster size, indicating that an intracluster reaction occurs with sufficient solvation. In small clusters, H_2O binds to a nitronium ion core, but at a critical cluster size the NO^+_2 reacts. A lower bound of 174 kcal/mol is found for the proton affinity of HNO_3

Poststructuralist fiddling while the world burns: Exiting the self made crisis of “architectural culture”

We critique the current crisis for the environmental design professions: facing urgent ecological, social and economic imperatives, key leadership has become mired in the confusions of do nothing postmodernist artistic doctrine. The result is a self made state of paralysis, leaving the egregious mistakes of the past to be endlessly repeated, while it only matters that they are cloaked in ever more aesthetically extravagant artistic garb. We argue that this self excusing paralysis arises because, under a poststructuralist infatuation with ambiguity, multiplicity and constructed meaning, an effective shared framework to address the urgent challenges of the built environment becomes impossible. This paralysis is rewarded, however, because it serves narrow economic interests, which are happy to find rationalisations for projects that might otherwise be rejected as of inferior quality. We conclude with the hopeful observation that the ingredients of such a framework are indeed emerging from the biological sciences and other fields. However, to make use of them, we argue, professionals must learn to critique, and finally to dispense with, the misapplications of non productive forms of thinking, a number of which we specify herein. We hope this paper will serve as one small step on that important path

Vibrational spectroscopy of NO^+(H_2O)_n: Evidence for the intracluster reaction NO^+(H_2O)_n→H_3O^+(H_2O)_(n-2)(HONO) at n≥4

Infrared spectra of mass‐selected clusters NO^+(H_2O)_n for n=1 to 5 were recorded from 2700 to 3800 cm^(−1) by vibrational predissociation spectroscopy. Vibrational frequencies and intensities were also calculated for n=1 and 2 at the second‐order Møller–Plesset (MP2) level, to aid in the interpretation of the spectra, and at the singles and doubles coupled cluster (CCSD) level energies of n=1 isomers were computed at the MP2 geometries. The smaller clusters (n=1 to 3) were complexes of H_2O ligands bound to a nitrosonium ion NO^+ core. They possessed perturbed H_2O stretch bands and dissociated by loss of H_2O. The H_2O antisymmetric stretch was absent in n=1 and gradually increased in intensity with n. In the n=4 clusters, we found evidence for the beginning of a second solvation shell as well as the onset of an intracluster reaction that formed HONO. These clusters exhibited additional weak, broad bands between 3200 and 3400 cm^(−1) and two new minor photodissociation channels, loss of HONO and loss of two H_2O molecules. The reaction appeared to go to completion within the n=5 clusters. The primary dissociation channel was loss of HONO, and seven vibrational bands were observed. From an analysis of the spectrum, we concluded that the n=5 cluster rearranged to form H_3O^+(H_2O)_3(HONO), i.e., an adduct of the reaction products

Rheological Behavior of a Dispersion of Small Lipid Bilayer Vesicles

Rheological behavior of a dispersion of small nearly-unilamellar phospholipid bilayer vesicles has been investigated. We conducted steady-state shear experiments and linear viscoelastic experiments. In the dilute and semidilute regime the rheological behavior is similar to that of a hard-sphere dispersion as reported in the literature for viscoelastic measurements, but now also observed in steady shear experiments. The effect of the main acyl-chain phase transition, taking place at 23 °C, can be described with an increase of the effective volume fraction. As a result, with temperature variation one can obtain effective volume fractions larger than the maximum packing fraction for hard spheres. Near and above the maximum packing fraction a dynamic yield stress ty and a frequency independent storage modulus G' develop. In this concentration regime the rheological behavior is determined by the interplay between vesicle deformation and the intervesicle interaction, and so far, there is no indication which phenomenon is dominant. A comparison with recently reported measurements suggests that G' is proportional to a-3, where a is the vesicle radius. Furthermore, we show that ty = γcG' which is in agreement with theory. Here tγ is the dynamic yield stress and γc the critical strain which indicates the transition to nonlinear behavior in a viscoelastic experiment. There is a striking resemblance between our high concentration results and those reported in literature for vesicles in the so-called onion phase. To the best of our knowledge this is the first rheological study for concentrated nearly-unilamellar vesicle dispersions with volume fraction and temperature as variables