The relentless variability of Mrk 421 from the TeV to the radio

The origin of the gamma-ray emission of the blazar Mrk 421 is still a matter of debate. We used 5.5 years of unbiased observing campaign data, obtained using the FACT telescope and the Fermi LAT detector at TeV and GeV energies, the longest and densest so far, together with contemporaneous multi-wavelength observations, to characterise the variability of Mrk 421 and to constrain the underlying physical mechanisms. We studied and correlated light curves obtained by ten different instruments and found two significant results. The TeV and X-ray light curves are very well correlated with a lag of <0.6 days. The GeV and radio (15 Ghz band) light curves are widely and strongly correlated. Variations of the GeV light curve lead those in the radio. Lepto-hadronic and purely hadronic models in the frame of shock acceleration predict proton acceleration or cooling timescales that are ruled out by the short variability timescales and delays observed in Mrk 421. Instead the observations match the predictions of leptonic models.Comment: 10 pages, 8 figures, 1 tabl

Actin and microtubules drive differential aspects of planar cell polarity in multiciliated cells

Actin dynamics are required for proper cilia spacing, global coordination of cilia polarity, and coordination of metachronic cilia beating, whereas cytoplasmic microtubule dynamics are required for local coordination of polarity between neighboring cilia

Fractional variability—a tool to study blazar variability

Active Galactic Nuclei emit radiation over the whole electromagnetic spectrum up to TeV energies. Blazars are one subtype with their jets pointing towards the observer. One of their typical features is extreme variability on timescales, from minutes to years. The fractional variability is an often used parameter for investigating the degree of variability of a light curve. Different detection methods and sensitivities of the instruments result in differently binned data and light curves with gaps. As they can influence the physics interpretation of the broadband variability, the effects of these differences on the fractional variability need to be studied. In this paper, we study the systematic effects of completeness in time coverage and the sampling rate. Using public data from instruments monitoring blazars in various energy ranges, we study the variability of the bright TeV blazars Mrk 421 and Mrk 501 over the electromagnetic spectrum, taking into account the systematic effects, and compare our findings with previous results. Especially in the TeV range, the fractional variability is higher than in previous studies, which can be explained by the much longer (seven years compared to few weeks) and more complete data sample

Analysis of Instant Messaging Applications for Usage in Security-related Business Areas

Die vorliegende Bachelorarbeit thematisiert Instant-Messenger-Applikationen und inwieweit sie in sicherheitsrelevanten Unternehmensbereichen eingesetzt werden können. Im ersten Teil wird ein fiktives Beispielunternehmen vorgestellt, das eine Liste an Ausschlusskriterien vorgibt. Diese Ausschlusskriterien dienen zur Vorauswahl vor der eigentlichen Nutzwertanalyse. Im zweiten Teil werden sicherheitsrelevante Kriterien ausgearbeitet, anhand derer die Nutzwertanalyse die Sicherheitsstandards der Applikationen bewertet.This bachelor thesis deals with instant messenger applications and their usefulness in securityrelated environments. The first section introduces a functional company that specifies a list of exclusion criteria. These criteria are used for pre-selection before a cost-benefit analysis is used to evaluate the provided applications. In the second section, safety criteria are outlined, which are applied in the cost-benefit analysis to evaluate security standards in instant messaging applications

Twisted patterns in large subsets of ZN

Let E ? ZN be a set of positive upper Banach density, and let

Spatial distribution of polarization in polyethylene ac aged in humid enviroment

The present paper reports the preliminary results of an investigation of the dielectric properties in the frequency range of ~10-5 to 104 Hz, growth of water tree density and the spatial behavior of polarization in LDPE films aged in 0.1M NaCl solution for a time period <or=454 hours with an AC field of 6 kV/mm at 1 kHz at room temperature and at 65 degrees C by the laser intensity modulation method (LIMM).status: publishe