703 research outputs found

    Mesospheric anomalous diffusion during noctilucent clouds

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    The Andenes specular meteor radar shows meteor-trail diffusion rates increasing on average by ~ 20% at times and locations where a lidar observes noctilucent clouds (NLCs). This high-latitude effect has been attributed to the presence of charged NLC but this study shows that such behaviors result predominantly from thermal tides. To make this claim, the current study evaluates data from three stations, at high-, mid-, and low-latitudes, for the years 2012 to 2016, comparing diffusion to show that thermal tides correlate strongly with the presence of NLCs. This data also shows that the connection between meteor-trail diffusion and thermal tide occurs at all altitudes in the mesosphere, while the NLC influence exists only at high-latitudes and at around peak of NLC layer. This paper discusses a number of possible explanations for changes in the regions with NLCs and leans towards the hypothesis that relative abundance of background electron density plays the leading role. A more accurate model of the meteor trail diffusion around NLC particles would help researchers determine mesospheric temperature and neutral density profiles from meteor radars.Public versio

    Association of hydrophobically-modified poly(ethylene glycol) with fusogenic liposomes

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    AbstractWe present results on using cooperative interactions to shield liposomes by incorporating multiple hydrophobic anchoring sites on polyethylene glycol (PEG) polymers. The hydrophobically-modified PEGs (HMPEGs) are comb-graft polymers with strictly alternating monodisperse PEG blocks (Mw=6, 12, or 35 kDa) bonded to C18 stearylamide hydrophobes. Cooperativity is varied by changing the degree of oligomerization at a constant ratio of PEG to stearylamide. Fusogenic liposomes prepared from N-C12-DOPE:DOPC 7:3 (mol:mol) were equilibrated with HMPEGs. Affinity for polymer association to liposomes increases with the degree of oligomerization; equilibrium constants (given as surface coverage per equilibrium concentration of free polymer) for 6 kDa PEG increased from 6.1±0.8 (mg/m2)/(mg/ml) for 2.5 loops to 78.1±12.2 (mg/m2)/(mg/ml) for 13 loops. In contrast, the equilibrium constant for distearoylphosphatidylethanolamine-poly(ethylene glycol) (DSPE-PEG5k) was 0.4±0.1 (mg/m2)/(mg/ml).The multi-loop HMPEGs demonstrate higher levels of protection from complement binding than DSPE-PEG5k. Greater protection does not correlate with binding strength alone. The best shielding was by HMPEG6k-DP3 (with three 6 kDa PEG loops), suggesting that PEG chains with adequate surface mobility provide optimal protection from complement opsonization. Complement binding at 30 min and 12 h demonstrates that protection by multi-looped PEGs is constant whereas DSPE-PEG5k initially protects but presumably partitions off of the surface at longer times

    Stripping and scrubbing of ammonium using common fractionating columns to prove ammonium inhibition during anaerobic digestion

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    Anaerobic digestion to produce biogas is generally considered as one of the most sustainable technologies for the production of renewable energy. During this microbial process, organically bound nitrogen is released as ammonium that ends up in the digestate and finally may inhibit the process. In this study, it is investigated if ammonium can be removed and recovered out of the liquid fraction of a thermophilic digestate from a potato processor. This is achieved at laboratory scale through an easy and self-designed stripping and scrubbing process using Vigreux and Dufton columns, which are commonly used laboratory fractionating columns. The stripping is performed at pH 8.5 and at 323.15K (50 degrees C), which results in the volatilization of the ammonium present in ammonia. Subsequently, the stripping gas charged with ammonia is put into contact with a sulphuric acid solution, resulting in (NH4)(2)SO4, which can be used as an N-S fertilizer. In addition, the digestion experiments have demonstrated that the biogas yield is 36% higher after removal of the ammonium from the digestate compared to the untreated digestate

    Observing binary inspiral in gravitational radiation: One interferometer

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    We investigate the sensitivity of individual LIGO/VIRGO-like interferometers and the precision with which they can determine the characteristics of an inspiralling binary system. Since the two interferometers of the LIGO detector share nearly the same orientation, their joint sensitivity is similar to that of a single, more sensitive interferometer. We express our results for a single interferometer of both initial and advanced LIGO design, and also for the LIGO detector in the limit that its two interferometers share exactly the same orientation. We approximate the evolution of a binary system as driven exclusively by leading order quadrupole gravitational radiation. To assess the sensitivity, we calculate the rate at which sources are expected to be observed, the range to which they are observable, and the precision with which characteristic quantities describing the observed binary system can be determined. Assuming a conservative rate density for coalescing neutron star binary systems we expect that the advanced LIGO detector will observe approximately 69~yr−1{}^{-1} with an amplitude SNR greater than 8. Of these, approximately 7~yr−1{}^{-1} will be from binaries at distances greater than 950~Mpc. We explore the sensitivity of these results to a tunable parameter in the interferometer design (the recycling frequency). The optimum choice of the parameter is dependent on the goal of the observations, e.g., maximizing the rate of detections or maximizing the precision of measurement. We determine the optimum parameter values for these two cases.Comment: 40 pages (plus 7 figures), LaTeX/REVTEX3.0, NU-GR-

    Development of a BelRAI screening instrument for correctional facilities preparatory phase for testing

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    Commissioned by the Belgian federal government, a BelRAI screening tool for the detention context was developed. The aim of this screening instrument is to collect all information necessary for care providers inside prison to decide whether a penitentiary care trajectory is needed

    Increased aerobic capacity reduces susceptibility to acute high‐fat diet‐induced weight gain

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134165/1/oby21564.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134165/2/oby21564_am.pd

    Detection, Measurement and Gravitational Radiation

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    Here I examine how to determine the sensitivity of the LIGO, VIRGO, and LAGOS gravitational wave detectors to sources of gravitational radiation by considering the process by which data are analyzed in a noisy detector. By constructing the probability that the detector output is consistent with the presence of a signal, I show how to (1) quantify the uncertainty that the output contains a signal and is not simply noise, and (2) construct the probability distribution that the signal parameterization has a certain value. From the distribution and its mode I determine volumes V(P)V(P) in parameter space such that actual signal parameters are in V(P)V(P) with probability PP. If we are {\em designing} a detector, or determining the suitability of an existing detector for observing a new source, then we don't have detector output to analyze but are interested in the ``most likely'' response of the detector to a signal. I exploit the techniques just described to determine the ``most likely'' volumes V(P)V(P) for detector output corresponding to the source. Finally, as an example, I apply these techniques to anticipate the sensitivity of the LIGO and LAGOS detectors to the gravitational radiation from a perturbed Kerr black hole.Comment: 37 pages (plus 6 figures), LaTeX/REVTE

    Gravitational waves from coalescing binaries: detection strategies and Monte Carlo estimation of parameters

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    The paper deals with issues pertaining the detection of gravitational waves from coalescing binaries. We introduce the application of differential geometry to the problem of optimal detection of the `chirp signal'. We have also carried out extensive Monte Carlo simulations to understand the errors in the estimation of parameters of the binary system. We find that the errors are much more than those predicted by the covariance matrix even at a high SNR of 10-15. We also introduce the idea of using the instant of coalescence rather than the time of arrival to determine the direction to the source.Comment: 28 pages, REVTEX, 12 figures (bundled via uufiles command along with this paper) submitted to Phys. Rev.
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