2,656 research outputs found
Interagency report - Astrogeology 18. A proposed scheme for lunar geologic description
Method for lunar geologic descriptio
Long photometric cycle and disk evolution in the Lyrae type binary OGLE-BLG-ECL-157529
The subtype of hot algol semidetached binaries dubbed Double Periodic
Variables (DPVs) are characterized by a photometric cycle longer than the
orbital one, whose nature has been related to a magnetic dynamo in the donor
component controlling the mass transfer rate. We aim to understand the
morphologic changes observed in the light curve of OGLE-BLG-ECL-157529 that are
linked to the long cycle. In particular, we want to explain the changes in
relative depth of primary and secondary eclipses. We analyze and -band
OGLE photometric times series spanning 18.5 years and model the orbital light
curve. We find that OGLE-BLG-ECL-157529 is a new eclipsing Galactic DPV of
orbital period 24\fd8, and that its long cycle length decreases in amplitude
and length during the time baseline. We show that the changes of the orbital
light curve can be reproduced considering an accretion disk of variable
thickness and radius, surrounding the hottest stellar component. Our models
indicate changes in the temperatures of hot spot and bright spot during the
long cycle, and also in the position of the bright spot. This, along with the
changes in disk radius might indicate a variable mass transfer in this system.Comment: 8 pages, 14 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
Manipulation of Ag nanoparticles utilizing noncontact atomic force microscopy
We have developed a scheme to manipulate metallic aerosol particles on silicon dioxide substrates using an atomic force microscope. The method utilizes the noncontact mode both for locating and moving nanoparticles of size 10–100 nm. The main advantage of our technique is the possibility of “seeing” the moving particle in real time. Our method avoids well sticking problems that typically hamper the manipulation in the contact mode.Peer reviewe
Magnetic Field Amplification by Small-Scale Dynamo Action: Dependence on Turbulence Models and Reynolds and Prandtl Numbers
The small-scale dynamo is a process by which turbulent kinetic energy is
converted into magnetic energy, and thus is expected to depend crucially on the
nature of turbulence. In this work, we present a model for the small-scale
dynamo that takes into account the slope of the turbulent velocity spectrum
v(l) ~ l^theta, where l and v(l) are the size of a turbulent fluctuation and
the typical velocity on that scale. The time evolution of the fluctuation
component of the magnetic field, i.e., the small-scale field, is described by
the Kazantsev equation. We solve this linear differential equation for its
eigenvalues with the quantum-mechanical WKB-approximation. The validity of this
method is estimated as a function of the magnetic Prandtl number Pm. We
calculate the minimal magnetic Reynolds number for dynamo action, Rm_crit,
using our model of the turbulent velocity correlation function. For Kolmogorov
turbulence (theta=1/3), we find that the critical magnetic Reynolds number is
approximately 110 and for Burgers turbulence (theta=1/2) approximately 2700.
Furthermore, we derive that the growth rate of the small-scale magnetic field
for a general type of turbulence is Gamma ~ Re^((1-theta)/(1+theta)) in the
limit of infinite magnetic Prandtl numbers. For decreasing magnetic Prandtl
number (down to Pm approximately larger than 10), the growth rate of the
small-scale dynamo decreases. The details of this drop depend on the
WKB-approximation, which becomes invalid for a magnetic Prandtl number of about
unity.Comment: 13 pages, 8 figures; published in Phys. Rev. E 201
Mycoplasma hyopneumoniae resides intracellularly within porcine epithelial cells
© 2018, The Author(s). Enzootic pneumonia incurs major economic losses to pork production globally. The primary pathogen and causative agent, Mycoplasma hyopneumoniae, colonises ciliated epithelium and disrupts mucociliary function predisposing the upper respiratory tract to secondary pathogens. Alleviation of disease is reliant on antibiotics, vaccination, and sound animal husbandry, but none are effective at eliminating M. hyopneumoniae from large production systems. Sustainable pork production systems strive to lower reliance on antibiotics but lack of a detailed understanding of the pathobiology of M. hyopneumoniae has curtailed efforts to develop effective mitigation strategies. M. hyopneumoniae is considered an extracellular pathogen. Here we show that M. hyopneumoniae associates with integrin β1 on the surface of epithelial cells via interactions with surface-bound fibronectin and initiates signalling events that stimulate pathogen uptake into clathrin-coated vesicles (CCVs) and caveosomes. These early events allow M. hyopneumoniae to exploit an intracellular lifestyle by commandeering the endosomal pathway. Specifically, we show: (i) using a modified gentamicin protection assay that approximately 8% of M. hyopneumoniae cells reside intracellularly; (ii) integrin β1 expression specifically co-localises with the deposition of fibronectin precisely where M. hyopneumoniae cells assemble extracellularly; (iii) anti-integrin β1 antibodies block entry of M. hyopneumoniae into porcine cells; and (iv) M. hyopneumoniae survives phagolysosomal fusion, and resides within recycling endosomes that are trafficked to the cell membrane. Our data creates a paradigm shift by challenging the long-held view that M. hyopneumoniae is a strict extracellular pathogen and calls for in vivo studies to determine if M. hyopneumoniae can traffic to extrapulmonary sites in commercially-reared pigs
DTS-100G — a versatile heterogeneous MPSoC board for cryogenic sensor readout
Heterogeneous devices such as the Multi-Processor System-on-Chip (MPSoC) from Xilinx are extremely valuable in custom instrumentation systems. This contribution presents the joint development of a heterogeneous MPSoC board called DTS-100G by DESY and KIT. The board is built around a Xilinx Zynq Ultrascale+ chip offering all available high-speed transceivers using QSFP28, 28 Gbps FireFly, FMC, and FMC+ interfaces. The board is not designed for a particular application, but can be used as a generic DAQ platform for a variety of physics experiments. The DTS-100G board was successfully developed, built and commissioned. ECHo-100k is the first experiment which will employ the board. This contribution shows the system architecture and explains how the DTS-100G board is a crucial component in the DAQ chain
The Actinome of Dictyostelium discoideum in Comparison to Actins and Actin-Related Proteins from Other Organisms
Actin belongs to the most abundant proteins in eukaryotic cells which harbor usually many conventional actin isoforms as well as actin-related proteins (Arps). To get an overview over the sometimes confusing multitude of actins and Arps, we analyzed the Dictyostelium discoideum actinome in detail and compared it with the genomes from other model organisms. The D. discoideum actinome comprises 41 actins and actin-related proteins. The genome contains 17 actin genes which most likely arose from consecutive gene duplications, are all active, in some cases developmentally regulated and coding for identical proteins (Act8-group). According to published data, the actin fraction in a D. discoideum cell consists of more than 95% of these Act8-type proteins. The other 16 actin isoforms contain a conventional actin motif profile as well but differ in their protein sequences. Seven actin genes are potential pseudogenes. A homology search of the human genome using the most typical D. discoideum actin (Act8) as query sequence finds the major actin isoforms such as cytoplasmic beta-actin as best hit. This suggests that the Act8-group represents a nearly perfect actin throughout evolution. Interestingly, limited data from D. fasciculatum, a more ancient member among the social amoebae, show different relationships between conventional actins. The Act8-type isoform is most conserved throughout evolution. Modeling of the putative structures suggests that the majority of the actin-related proteins is functionally unrelated to canonical actin. The data suggest that the other actin variants are not necessary for the cytoskeleton itself but rather regulators of its dynamical features or subunits in larger protein complexes
Dust observations of Comet 9P/Tempel 1 at the time of the Deep Impact
On 4 July 2005 at 05:52 UT, the impactor of NASA's Deep Impact (DI) mission
crashed into comet 9P/Tempel 1 with a velocity of about 10 km/s. The material
ejected by the impact expanded into the normal coma, produced by ordinary
cometary activity.
The characteristics of the non-impact coma and cloud produced by the impact
were studied by observations in the visible wavelengths and in the near-IR. The
scattering characteristics of the "normal" coma of solid particles were studied
by comparing images in various spectral regions, from the UV to the near-IR.
For the non-impact coma, a proxy of the dust production has been measured in
various spectral regions. The presence of sublimating grains has been detected.
Their lifetime was found to be about 11 hours. Regarding the cloud produced by
the impact, the total geometric cross section multiplied by the albedo was
measured as a function of the color and time. The projected velocity appeared
to obey a Gaussian distribution with the average velocity of the order of 115
m/s. By comparing the observations taken about 3 hours after the impact, we
have found a strong decrease in the cross section in J filter, while that in Ks
remained almost constant. This is interpreted as the result of sublimation of
grains dominated by particles of sizes of the order of some microns.Comment: Accepted by A&
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