548 research outputs found
Mesons in the nuclear Medium
We discuss recent experimental results on the modification of hadron
properties in a nuclear medium. Particular emphasis is placed on an
production experiment performed by the CBELSA/TAPS collaboration at the ELSA
accelerator. The data shows a smaller meson mass together with a
significant increase of its width in the nuclear medium.Comment: Proceedings for CIPANP 2006 Puerto Ric
The role of E+A and post-starburst galaxies – I. Models and model results
‘The definitive version is available at www3.interscience.wiley.com '. Copyright Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.14416.xDifferent compositions of galaxy types in the field in comparison to galaxy clusters as described by the morphology–density relation in the local universe are interpreted as a result of transformation processes from late- to early-type galaxies. This interpretation is supported by the Butcher–Oemler effect. We investigate E+A galaxies as an intermediate state between late-type galaxies in low-density environments and early-type galaxies in high-density environment to constrain the possible transformation processes. For this purpose, we model a grid of post-starburst galaxies by inducing a burst and/or a halting of star formation on the normal evolution of spiral galaxies with our galaxy evolution code galev. From our models, we find that the common E+A criteria exclude a significant number of post-starburst galaxies, and propose that comparing their spectral energy distributions leads to a more sufficient method to investigate post-starburst galaxies. We predict that a higher number of E+A galaxies in the early universe cannot be ascribed solely to a higher number of starburst, but is a result of a lower metallicity and a higher burst strength due to more gas content of the galaxies in the early universe. We find that even galaxies with a normal evolution without a starburst have an Hδ-strong phase at early galaxy ages.Peer reviewe
Synchronized Induction Machine
Import 03/11/2016Tato práce je zaměřena na způsob synchronizování asynchronního motoru, jeho rozbor a vyhodnocení vlastností stroje. Pro pochopení problematiky, je nejdříve obecně rozebrán asynchronní motor (tím se rozumí například konstrukce, princip činnosti, jeho využití v praxi). V další části je uvedeno řešení problematiky, tj. postup pro synchronizaci asynchronního motoru. Po tomto rozebrání tématiky se zde nachází měření na asynchronním motoru jak v asynchronním chodu, tak i v synchronním chodu. To zahrnuje jejich postup, naměřené hodnoty a grafická vyhodnocení. Poslední část je vyhrazena pro vyhodnocení měření, uvedení základních vlastností motoru, jeho hlavní výhody a rozdíl oproti klasickým asynchronním motorům.This thesis focuses on the way induction motors synchronize, their analysis and an evaluation of their features. For the sake of understanding the topic, induction motor is at first described in terms of its construction, principles of operation and its practical usage. The next part provides the steps in the process of induction motor synchronizing. Then an induction motor is measured during both asynchronous and synchronous operation. It involves a description of the procedure, measured values and graphic representation of the results. The final part is concerned with the measurement evaluation, presentation of basic features of the motor, its main advantages and its comparison with respect to usual induction motors.410 - Katedra elektroenergetikyvýborn
Recent Results from 2 pi-zero Photoproduction off the Proton
The reaction has been measured using the TAPS
BaF calorimeter at the tagged photon facility of the Mainz Microtron
accelerator in the beam energy range from threshold up to 820 MeV. Close to
threshold, chiral perturbation theory (ChPT) predicts that this channel is
significantly enhanced compared to double pion final states with charged pions.
The strength is attributed dominantly to pion loops in the 2\Piz{} channel - a
finding that opens new prospects for the test of ChPT. Our measurement is the
first which is sensitive enough for a conclusive comparison with the ChPT
calculation and is in agreement with its prediction. The data are also in
agreement with a calculation in the unitary chiral approach.
In the second resonance region, a recent model interpretation of new GRAAL
data claimed a dominance of the \Roper \to \sigma N reaction process. We
present very accurate invariant mass distributions of {\Piz \Piz} and {\Piz
p} systems, which are in contrast to the intermediate state and
which show a dominance of the intermediate state.Comment: Hadron 2003 Proceeding
Interstellar Interloper 1I/2017 U1: Observations from the NOT and WIYN Telescopes
We present observations of the interstellar interloper 1I/2017 U1 ('Oumuamua)
taken during its 2017 October flyby of Earth. The optical colors B-V =
0.700.06, V-R = 0.450.05, overlap those of the D-type Jovian Trojan
asteroids and are incompatible with the ultrared objects which are abundant in
the Kuiper belt. With a mean absolute magnitude = 22.95 and assuming a
geometric albedo = 0.1, we find an average radius of 55 m. No coma is
apparent; we deduce a limit to the dust mass production rate of only
210 kg s, ruling out the existence of exposed ice
covering more than a few m of the surface. Volatiles in this body, if they
exist, must lie beneath an involatile surface mantle 0.5 m thick,
perhaps a product of prolonged cosmic ray processing in the interstellar
medium. The lightcurve range is unusually large at 2.00.2
magnitudes. Interpreted as a rotational lightcurve the body has semi-axes
230 m 35 m. A 6:1 axis ratio is extreme relative to most
small solar system asteroids and suggests that albedo variations may
additionally contribute to the variability. The lightcurve is consistent with a
two-peaked period 8.26 hr but the period is non-unique as a result of
aliasing in the data. Except for its unusually elongated shape, 1I/2017 U1 is a
physically unremarkable, sub-kilometer, slightly red, rotating object from
another planetary system. The steady-state population of similar, 100 m
scale interstellar objects inside the orbit of Neptune is 10, each
with a residence time 10 yr.Comment: 25 Pages, 2 Tables, 7 Figures; submitted to ApJ
Double Photoproduction off the Proton at Threshold
The reaction has been measured using the TAPS
BaF calorimeter at the tagged photon facility of the Mainz Microtron
accelerator. Chiral perturbation theory (ChPT) predicts that close to threshold
this channel is significantly enhanced compared to double pion final states
with charged pions. In contrast to other reaction channels, the lower order
tree terms are strongly suppressed in 2 photoproduction. The consequence
is the dominance of pion loops in the 2 channel close to threshold - a
result that opens new prospects for the test of ChPT and in particular its
inherent loop terms. The present measurement is the first which is sensitive
enough for a conclusive comparison with the ChPT calculation and is in
agreement with its prediction. The data also show good agreement with a
calculation in the unitary chiral approach.Comment: Submitted to PL
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