Endogenous production and detoxification of a potent cytotoxin, nitric oxide, in Salmonella enterica serovar Typhimurium and Escherichia coli

Salmonella serovars are harmful enteric pathogens of economical and clinical importance that possess sophisticated strategies to rapidly adapt to various host (human and animal) and non-host (soil, water and industrial) environments. Nitrosative stress, in the form of RNS such as the potent cytotoxin NO, is an important stress in the Salmonella lifecycle. Salmonella is exposed to exogenous NO, produced by activated macrophages as part of the host immune response and to endogenous NO, produced during anaerobic nitrate respiration. Salmonella employs three known enzymes (HmpA, NrfA and NorVW) to detoxify NO to less toxic compounds, including the neuropharmacological agent and greenhouse gas N2O. The production of endogenous NO and N2O have been predominantly studied in denitrifying soil bacteria and have been widely neglected in enteric bacteria. Here, the physiological and molecular mechanisms involved in endogenous NO production and detoxification were examined in the pathogenic Salmonella enterica serovar Typhimurium and laboratory Escherichia coli (E. coli) strains. Significant differences in N2O production were observed between the two genera and between the tested E. coli strains, although they possess identical nitrate respiration systems. The reason for this was found to be transcriptional, with narG expression having the major impact. In addition, our results indicate that a weak nitrous oxide reductase exists in Salmonella; a process that was believed to be restricted to certain soil bacteria, archaea and fungi that possess the enzyme NosZ. Furthermore, the contribution of selected NsrR regulon genes, to endogenous N2O production of Salmonella was determined and revealed that HmpA and the Hcp-Hcr operon are both crucial for high N2O levels. These findings provide new insights into host-pathogen interactions, which could potentially lead to new treatment strategies for Salmonella infections, help to increase food safety and provide new mitigation strategies to reduce global warming

Defect flows in minimal models

In this paper we study a simple example of a two-parameter space of renormalisation group flows of defects in Virasoro minimal models. We use a combination of exact results, perturbation theory and the truncated conformal space approach to search for fixed points and investigate their nature. For the Ising model, we confirm the recent results of Fendley et al. In the case of central charge close to one, we find six fixed points, five of which we can identify in terms of known defects and one of which we conjecture is a new non-trivial conformal defect. We also include several new results on exact properties of perturbed defects and on the renormalisation group in the truncated conformal space approach.Comment: 35 pages, 21 figures. 1 reference adde

Einführung: Die ungeheuerliche Raumphilosophie von Peter Sloterdijk

This article serves as introduction for a themed issue on Peter Sloterdijk's enormous philosophy of space. It invites scholars from various disciplines to critically engage with Sloterdijk's thought and discusses briefly the contributions made in this special issue. The paper gives some orientation on the anthropological and social philosophy Sloterdijk deploys within his oeuvre, and illuminates the various fields of social and cultural research his ideas have informed so far. The editorial identifies four possible fields of interest within human geography that could gain by engaging with Sloterdijk's thought, namely urban and architectural theory, new technologies, political geographies and critical social geography. The article also discusses the necessity of a critical distance to the philosophical premises on which Sloterdijk grounds his philosophy as well as his role as notorious commentator on political issues in Germany.</p

Twisted boundary states in c=1 coset conformal field theories

We study the mutual consistency of twisted boundary conditions in the coset conformal field theory G/H. We calculate the overlap of the twisted boundary states of G/H with the untwisted ones, and show that the twisted boundary states are consistently defined in the diagonal modular invariant. The overlap of the twisted boundary states is expressed by the branching functions of a twisted affine Lie algebra. As a check of our argument, we study the diagonal coset theory so(2n)_1 \oplus so(2n)_1/so(2n)_2, which is equivalent with the orbifold S^1/\Z_2. We construct the boundary states twisted by the automorphisms of the unextended Dynkin diagram of so(2n), and show their mutual consistency by identifying their counterpart in the orbifold. For the triality of so(8), the twisted states of the coset theory correspond to neither the Neumann nor the Dirichlet boundary states of the orbifold and yield the conformal boundary states that preserve only the Virasoro algebra.Comment: 44 pages, 1 figure; (v2) minor change in section 2.3, references adde

Height variables in the Abelian sandpile model: scaling fields and correlations

We compute the lattice 1-site probabilities, on the upper half-plane, of the four height variables in the two-dimensional Abelian sandpile model. We find their exact scaling form when the insertion point is far from the boundary, and when the boundary is either open or closed. Comparing with the predictions of a logarithmic conformal theory with central charge c=-2, we find a full compatibility with the following field assignments: the heights 2, 3 and 4 behave like (an unusual realization of) the logarithmic partner of a primary field with scaling dimension 2, the primary field itself being associated with the height 1 variable. Finite size corrections are also computed and successfully compared with numerical simulations. Relying on these field assignments, we formulate a conjecture for the scaling form of the lattice 2-point correlations of the height variables on the plane, which remain as yet unknown. The way conformal invariance is realized in this system points to a local field theory with c=-2 which is different from the triplet theory.Comment: 68 pages, 17 figures; v2: published version (minor corrections, one comment added

Time Resolved Experiments at the Frankfurt 14 GHz ECR Ion Source

To investigate the basic production processes of highly charged ions and combined phenomena of an ECRIS plasma (e. g. influence of secondary electrons and plasma instabilities) time resolved experiments have been carried out at the Frankfurt 14 GHz ECRIS [1] (see also the contributions to this workshop by O. Hohn et al. and V. Mironov et al.). We report time resolved measurements of the extracted ion currents by pulsing the biased disk voltage [2]. The measurements have shown that the extracted ion currents respond too fast to explain the "biased disk effect" (i. e. the intensity increase of highly charged ions) by enhanced ion breeding. Furthermore the influence of the pulsed biased disk on plasma instabilities has been investigated. It has also been shown that this method can be used to extract pulsed ion beams from an ECRIS

Status of the Frankfurt 14 GHz-ECRIS-(ve)RFQ Facility

The accelerator facility installed at the Institut fuer Kernphysik (IKF) combines a 14 GHz electron cyclotron resonance ion source (ECRIS) and a variable energy radio frequency quadrupole accelerator (ve-RFQ)[1,2]. The provided highly charged ions have an energy range between a few keV - using the beam delivered from the source - up to 200 keV/u by using the post acceleration of the ve-RFQ. The setup is designed to deliver a wide spectrum of ions in sufficiently high charged states for atomic physics and materials research. Besides this the ion source is used for studies of the production of highly charged ions with the intention to improve quality and intensity of ion beams. In addition to these activities there are some special topics which deal with the investigation of phenomena on the ECRIS plasma and the production of metal ions by laser ablation technique (see also contributions to this workshop S. Runkel et al. And V. Mironov et. al). The present status and further activities of the facility and a view of the different projects will be reported

Influence of damping on the excitation of the double giant resonance

We study the effect of the spreading widths on the excitation probabilities of the double giant dipole resonance. We solve the coupled-channels equations for the excitation of the giant dipole resonance and the double giant dipole resonance. Taking Pb+Pb collisions as example, we study the resulting effect on the excitation amplitudes, and cross sections as a function of the width of the states and of the bombarding energy.Comment: 8 pages, 3 figures, corrected typo

Energy Quantisation in Bulk Bouncing Tachyon

We argue that the closed string energy in the bulk bouncing tachyon background is to be quantised in a simple manner as if strings were trapped in a finite time interval. We discuss it from three different viewpoints; (1) the timelike continuation of the sinh-Gordon model, (2) the dual matrix model description of the (1+1)-dimensional string theory with the bulk bouncing tachyon condensate, (3) the c_L=1 limit of the timelike Liouville theory with the dual Liouville potential turned on. There appears to be a parallel between the bulk bouncing tachyon and the full S-brane of D-brane decay. We find the critical value \lambda_c of the bulk bouncing tachyon coupling which is analogous to \lambda_o=1/2 of the full S-brane coupling, at which the system is thought to be at the bottom of the tachyon potential.Comment: 25 pages, minor changes, one reference adde