2,016 research outputs found
Milliradian precision ultrafast pulse control for spectral phase metrology
A pulse-shaper-based method for spectral phase measurement and compression with milliradian precision is proposed and tested experimentally. Measurements of chirp and third-order dispersion are performed and compared to theoretical predictions. The single-digit milliradian accuracy is benchmarked by a group velocity dispersion measurement of fused silica
Analyzing the Complex Regulatory Landscape of Hfq â an Integrative, Multi-Omics Approach
The ability of bacteria to respond to environmental change is based on the ability to coordinate, redirect and fine-tune their genetic repertoire as and when required. While we can learn a great deal from reductive analysis of individual pathways and global approaches to gene regulation, a deeper understanding of these complex signaling networks requires the simultaneous consideration of several regulatory layers at the genome scale. To highlight the power of this approach we analyzed the Hfq transcriptional/translational regulatory network in the model bacterium Pseudomonas fluorescens. We first used extensive âomicsâ analyses to assess how hfq deletion affects mRNA abundance, mRNA translation and protein abundance. The subsequent, multi-level integration of these datasets allows us to highlight the discrete contributions by Hfq to gene regulation at different levels. The integrative approach to regulatory analysis we describe here has significant potential, for both dissecting individual signaling pathways and understanding the strategies bacteria use to cope with external challenges
The CRIRES Search for Planets Around the Lowest-Mass Stars. I. High-Precision Near-Infrared Radial Velocities with an Ammonia Gas Cell
Radial velocities measured from near-infrared spectra are a potentially
powerful tool to search for planets around cool stars and sub-stellar objects.
However, no technique currently exists that yields near-infrared radial
velocity precision comparable to that routinely obtained in the visible. We
describe a method for measuring high-precision relative radial velocities of
these stars from K-band spectra. The method makes use of a glass cell filled
with ammonia gas to calibrate the spectrograph response similar to the "iodine
cell" technique that has been used very successfully in the visible. Stellar
spectra are obtained through the ammonia cell and modeled as the product of a
Doppler-shifted template spectrum of the object and a spectrum of the cell,
convolved with a variable instrumental profile model. A complicating factor is
that a significant number of telluric absorption lines are present in the
spectral regions containing useful stellar and ammonia lines. The telluric
lines are modeled simultaneously as well using spectrum synthesis with a
time-resolved model of the atmosphere over the observatory. The free parameters
in the complete model are the wavelength scale of the spectrum, the
instrumental profile, adjustments to the water and methane abundances in the
atmospheric model, telluric spectrum Doppler shift, and stellar Doppler shift.
Tests of the method based on the analysis of hundreds of spectra obtained for
late M dwarfs over six months demonstrate that precisions of ~5 m/s are
obtainable over long timescales, and precisions of better than 3 m/s can be
obtained over timescales up to a week. The obtained precision is comparable to
the predicted photon-limited errors, but primarily limited over long timescales
by the imperfect modeling of the telluric lines.Comment: Accepted for publication in Ap
Stickstoffdynamik im Umfeld von Rinderanlagen
An zwei sĂ€chsischen Rinderanlagen in WaldnĂ€he wurde zwei Jahre lang der Einfluss der Ammoniakemission auf die rĂ€umliche und zeitliche Dynamik der Stickstoffbelastung im Umfeld der Betriebe durch Messung von Immission, Deposition und Transmissionsbedingungen untersucht. Zur Anwendung kam eine neue Methode, die auf Basis kontinuierlicher Messungen von Ammoniakimmissionen und meteorologischen Parametern die RĂŒckrechnung auf anlagenbezogene Emissionen ermöglicht. Dabei wurden zwei Messverfahren bewertet: DOAS-Trasse und Passivsammler.
Alle Messpunkte im Umfeld der Betriebe zeigten einen deutlich erhöhten Ammoniumanteil am anorganischen Stickstoffeintrag. An den Referenzpunkten im Freiland wurden ca. 15 kg/(ha a) höhere Stickstoffdepositionen als an den DauerbeobachtungsflÀchen des lÀndlichen Hintergrunds ermittelt.
Die Stickstoffgesamtdeposition lag an allen Messpunkten deutlich ĂŒber den fĂŒr Nadelwald definierten empirischen Critical Loads. Dennoch sind die WĂ€lder bisher nicht geschĂ€digt
Organizational Mortality of Small Firms: The Effects of Entrepreneurial Age and Human Capital
This paper addresses the issue of internal determination of organizational outcomes. It is argued that in small and simply structured organizations a considerable proportion of the variance in organizational activities and outcomes is associated with individuals. In particular, the paper uses human capital theory to derive hypotheses about individual determinants of organizational mortality. These hypotheses are tested with event-history data of firm registrations and de-registrations in a West German region. The hypotheses are corroborated by the data, but the effects may nonetheless be due to processes linking individual characteristics with organizational performance other than those suggested by the human capital approach
Translocation of Inhaled Ultrafine Manganese Oxide Particles to the Central Nervous System
BACKGROUND: Studies in monkeys with intranasally instilled gold ultrafine particles (UFPs; < 100 nm) and in rats with inhaled carbon UFPs suggested that solid UFPs deposited in the nose travel along the olfactory nerve to the olfactory bulb. METHODS: To determine if olfactory translocation occurs for other solid metal UFPs and assess potential health effects, we exposed groups of rats to manganese (Mn) oxide UFPs (30 nm; ~ 500 Όg/m(3)) with either both nostrils patent or the right nostril occluded. We analyzed Mn in lung, liver, olfactory bulb, and other brain regions, and we performed gene and protein analyses. RESULTS: After 12 days of exposure with both nostrils patent, Mn concentrations in the olfactory bulb increased 3.5-fold, whereas lung Mn concentrations doubled; there were also increases in striatum, frontal cortex, and cerebellum. Lung lavage analysis showed no indications of lung inflammation, whereas increases in olfactory bulb tumor necrosis factor-α mRNA (~ 8-fold) and protein (~ 30-fold) were found after 11 days of exposure and, to a lesser degree, in other brain regions with increased Mn levels. Macrophage inflammatory protein-2, glial fibrillary acidic protein, and neuronal cell adhesion molecule mRNA were also increased in olfactory bulb. With the right nostril occluded for a 2-day exposure, Mn accumulated only in the left olfactory bulb. Solubilization of the Mn oxide UFPs was < 1.5% per day. CONCLUSIONS: We conclude that the olfactory neuronal pathway is efficient for translocating inhaled Mn oxide as solid UFPs to the central nervous system and that this can result in inflammatory changes. We suggest that despite differences between human and rodent olfactory systems, this pathway is relevant in humans
The Added Value of Large-Eddy and Storm-Resolving Models for Simulating Clouds and Precipitation
More than one hundred days were simulated over very large domains with fine (0.156 km to 2.5 km) grid spacing for realistic conditions to test the hypothesis that storm (kilometer) and large-eddy (hectometer) resolving simulations would provide an improved representation of clouds and precipitation in atmospheric simulations. At scales that resolve convective storms (storm-resolving for short), the vertical velocity variance becomes resolved and a better physical basis is achieved for representing clouds and precipitation. Similarly to past studies we found an improved representation of precipitation at kilometer scales, as compared to models with parameterized convection. The main precipitation features (location, diurnal cycle and spatial propagation) are well captured already at kilometer scales, and refining resolution to hectometer scales does not substantially change the simulations in these respects. It does, however, lead to a reduction in the precipitation on the time-scales considered â most notably over the ocean in the tropics. Changes in the distribution of precipitation, with less frequent extremes are also found in simulations incorporating hectometer scales. Hectometer scales appear to be more important for the representation of clouds, and make it possible to capture many important aspects of the cloud field, from the vertical distribution of cloud cover, to the distribution of cloud sizes, and to the diel (daily) cycle. Qualitative improvements, particularly in the ability to differentiate cumulus from stratiform clouds, are seen when one reduces the grid spacing from kilometer to hectometer scales. At the hectometer scale new challenges arise, but the similarity of observed and simulated scales, and the more direct connection between the circulation and the unconstrained degrees of freedom make these challenges less daunting. This quality, combined with already improved simulation as compared to more parameterized models, underpins our conviction that the use and further development of storm-resolving models offers exciting opportunities for advancing understanding of climate and climate change
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