Noise-Activated Escape from a Sloshing Potential Well

We treat the noise-activated escape from a one-dimensional potential well of an overdamped particle, to which a periodic force of fixed frequency is applied. We determine the boundary layer behavior, and the physically relevant length scales, near the oscillating well top. We show how stochastic behavior near the well top generalizes the behavior first determined by Kramers, in the case without forcing. Both the case when the forcing dies away in the weak noise limit, and the case when it does not, are examined. We also discuss the relevance of various scaling regimes to recent optical trap experiments.Comment: 9 pages, no figures, REVTeX, expanded versio

Salmonella Typhimurium Strain ATCC14028 Requires H-2-Hydrogenases for Growth in the Gut, but Not at Systemic Sites

Salmonella enterica is a common cause of diarrhea. For eliciting disease, the pathogen has to colonize the gut lumen, a site colonized by the microbiota. This process/initial stage is incompletely understood. Recent work established that one particular strain, Salmonella enterica subspecies 1 serovar Typhimurium strain SL1344, employs the hyb H-2-hydrogenase for consuming microbiota-derived H-2 to support gut luminal pathogen growth: Protons from the H-2-splitting reaction contribute to the proton gradient across the outer bacterial membrane which can be harvested for ATP production or for import of carbon sources. However, it remained unclear, if other Salmonella strains would use the same strategy. In particular, earlier work had left unanswered if strain ATCC14028 might use H-2 for growth at systemic sites. To clarify the role of the hydrogenases, it seems important to establish if H-2 is used at systemic sites or in the gut and if Salmonella strains may differ with respect to the host sites where they require H-2 in vivo. In order to resolve this, we constructed a strain lacking all three H-2-hydrogenases of ATCC14028 (14028(hyd3)) and performed competitive infection experiments. Upon intragastric inoculation, 14028(hyd3) was present at 100-fold lower numbers than 14028(WT) in the stool and at systemic sites. In contrast, i.v. inoculation led to equivalent systemic loads of 14028(hyd3) and the wild type strain. However, the pathogen population spreading to the gut lumen featured again up to 100-fold attenuation of 14028(hyd3). Therefore, ATCC14028 requires H-2-hydrogenases for growth in the gut lumen and not at systemic sites. This extends previous work on ATCC14028 and supports the notion that H-2-utilization might be a general feature of S. Typhimurium gut colonization

Salmonella Typhimurium Strain ATCC14028 Requires H-2-Hydrogenases for Growth in the Gut, but Not at Systemic Sites

Salmonella enterica is a common cause of diarrhea. For eliciting disease, the pathogen has to colonize the gut lumen, a site colonized by the microbiota. This process/initial stage is incompletely understood. Recent work established that one particular strain, Salmonella enterica subspecies 1 serovar Typhimurium strain SL1344, employs the hyb H-2-hydrogenase for consuming microbiota-derived H-2 to support gut luminal pathogen growth: Protons from the H-2-splitting reaction contribute to the proton gradient across the outer bacterial membrane which can be harvested for ATP production or for import of carbon sources. However, it remained unclear, if other Salmonella strains would use the same strategy. In particular, earlier work had left unanswered if strain ATCC14028 might use H-2 for growth at systemic sites. To clarify the role of the hydrogenases, it seems important to establish if H-2 is used at systemic sites or in the gut and if Salmonella strains may differ with respect to the host sites where they require H-2 in vivo. In order to resolve this, we constructed a strain lacking all three H-2-hydrogenases of ATCC14028 (14028(hyd3)) and performed competitive infection experiments. Upon intragastric inoculation, 14028(hyd3) was present at 100-fold lower numbers than 14028(WT) in the stool and at systemic sites. In contrast, i.v. inoculation led to equivalent systemic loads of 14028(hyd3) and the wild type strain. However, the pathogen population spreading to the gut lumen featured again up to 100-fold attenuation of 14028(hyd3). Therefore, ATCC14028 requires H-2-hydrogenases for growth in the gut lumen and not at systemic sites. This extends previous work on ATCC14028 and supports the notion that H-2-utilization might be a general feature of S. Typhimurium gut colonization

Circular Optical Nanoantennas: An Analytical Theory

An entirely analytical theory is provided for describing the resonance properties of optical nanoantennas made of a stack of homogeneous discs, i.e. circular patch nanoantennas. It consists in analytically calculating the phase accumulation of surface plasmon polaritons across the resonator and an additional contribution from the complex reflection coefficient at the antenna termination. This makes the theory self-contained with no need for fitting parameters. The very antenna resonances are then explained by a simple Fabry-Perot resonator model. Predictions are compared to rigorous simulations and show excellent agreement. Using this analytical model, circular antennas can be tuned by varying the composition of the stack

Multiparametric immunoimaging maps inflammatory signatures in murine myocardial infarction models

In the past 2 decades, research on atherosclerotic cardiovascular disease has uncovered inflammation to be a key driver of the pathophysiological process. A pressing need therefore exists to quantitatively and longitudinally probe inflammation, in preclinical models and in cardiovascular disease patients, ideally using non-invasive methods and at multiple levels. Here, we developed and employe

Helicobacter Pylori Hydrogenase Accessory Protein HypA and Urease Accessory Protein UreG Compete with Each Other for UreE Recognition

Background: The gastric pathogen Helicobacter pylori relies on nickel-containing urease and hydrogenase enzymes in order to colonize the host. Incorporation of Ni2+ into urease is essential for the function of the enzyme and requires the action of several accessory proteins, including the hydrogenase accessory proteins HypA and HypB and the urease accessory proteins UreE, UreF, UreG and UreH. Methods: Optical biosensing methods (biolayer interferometry and plasmon surface resonance) were used to screen for interactions between HypA, HypB, UreE and UreG. Results: Using both methods, affinity constants were found to be 5nM and 13nM for HypA–UreE and 8μM and 14μM for UreG-UreE. Neither Zn2+ nor Ni2+ had an effect on the kinetics or stability of the HypA–UreE complex. By contrast, addition of Zn2+, but not Ni2+, altered the kinetics and greatly increased the stability of the UreE–UreG complex, likely due in part to Zn2+-mediated oligomerization of UreE. Finally our results unambiguously show that HypA, UreE and UreG cannot form a heterotrimeric protein complex in vitro; instead, HypA and UreG compete with each other for UreE recognition. General significance: Factors influencing the pathogen\u27\u27s nickel budget are important to understand pathogenesis and for future drug design

An open-architecture metal powder bed fusion system for in-situ process measurements

We report the design of a metal powder bed fusion system for in-situ monitoring of the build process during additive manufacture. Its open-architecture design was originally determined to enable access for x-rays to the melt pool, but it also provides access to the build area for a range of other in-situ measurement techniques. The system is sufficiently automated to enable single tracks and high-density, multiple layer components to be built. It is easily transportable to enable measurements at different measurement facilities and its modular design enables straightforward modification for the specific measurements being made. We demonstrate that the system produces components with >99% density. Hence the build conditions are representative to observe process fundamentals and to develop process control strategies

Second harmonic generation from strongly coupled localized and propagating phonon-polariton modes

We experimentally investigate second harmonic generation from strongly coupled localized and propagative phonon polariton modes in arrays of silicon carbide nanopillars. Our results clearly demonstrate the hybrid nature of the system's eigenmodes and distinct manifestation of strong coupling in the linear and nonlinear response. While in linear reflectivity the intensity of the two strongly-coupled branches is essentially symmetric and well explained by their respective localized or propagative components, the second harmonic signal presents a strong asymmetry. Analyzing it in detail, we reveal the importance of interference effects between the nonlinear polarization terms originating in the bulk and in the phonon polariton modes, respectively.Comment: 7 pages, 4 figure