2,539 research outputs found
First direct identification of the barlens vertical structure in galaxy models
Applying spectral dynamics methods to one typical -body model with a
barlens, we dissect the modelled bar into separate components supported by
completely different types of orbits. We identify at least four components: a
narrow elongated bar, a boxy bar, and two components contributing to the
barlens. We analyse the vertical structure of all components that make up the
thick part of the bar, which has a boxy/peanut shape (B/P bulge). We show that
the `peanut' shape is mainly due to the orbits that assemble the boxy part of
the face-on bar. We associate the X-shape with the narrow and elongated bar.
The wider part of the barlens with square-like isophotes contributes to the
boxy shape of the B/P bulge when we observe the galaxy edge-on. However, the
part of the barlens with rounded isophotes in the face-on view is a rather flat
structure in the vertical direction without any significant off-centre
protrusions. Thus, for the first time, we demonstrate that the rounded face-on
barlens cannot be entirely associated with the B/P bulge.Comment: 5 pages, 5 figures, accepted to Astronomy and Astrophysics on March
26, 202
B/PS bulges and barlenses from a kinematic viewpoint. I
A significant part of barred disc galaxies exhibits boxy/peanut-shaped
structures (B/PS bulges) at high inclinations. Another structure also
associated with the bar is a barlens, often observed in galaxies in a position
close to face-on. At this viewing angle, special kinematic tests are required
to detect a 3D extension of the bars in the vertical direction (B/PS bulges).
We use four pure -body models of galaxies with B/PS bulges, which have
different bar morphology from bars with barlenses to the so-called face-on
peanut bars. We analyse the kinematics of our models to establish how the
structural features of B/PS bulges manifest themselves in the kinematics for
galaxies at intermediate inclinations and whether these features are related to
the barlenses. We apply the dissection of the bar into different orbital groups
to determine which of them are responsible for the features of the LOSVD
(line-of-sight velocity distribution), i.e., for the deep minima of the
parameter along the major axis of the bar. As a result, we claim that for our
models at the face-on position, the kinematic signatures of a `peanut' indeed
track the vertical density distribution features. We conclude that orbits
responsible for such kinematic signatures differ from model to model. We pay
special attention to the barlens model. We show that orbits assembled into
barlens are not responsible for the kinematic signatures of B/PS bulges. The
results presented in this work are applicable to the interpretation of IFU
observations of real galaxies.Comment: 18 page
Barless flocculent galaxies: a dynamic puzzle
We draw attention to the bright galaxies that do not show a bar in their
structure but have a flocculent spiral structure. Using the THINGS' and
HERACLES' kinematic data for four barless galaxies (NGC~2841, NGC~3512,
NGC~5055, NGC~7331) we built their mass models including dark halos. We
concluded that the fraction of the dark matter does not exceed 50\% within the
optical radii of the galaxies. This is too little to explain the lack of a bar
in these galaxies. In an attempt to understand the featureless structure of
these galaxies we constructed several -body models with an initially reduced
content of dark matter. We concluded that, in addition to the low mass of the
dark halo, the decisive factor that leads to a barless disc is the start from
an initially unstable state. An isolated dynamically cold disc (with the Toomre
parameter ) settled into rotational equilibrium passes trough the
short stage of violent instability with fragmentation and formation of stellar
clumps. After that, it evolves passively and ends up with a featureless
structure. We assume that the barless flocculent galaxies studied in the
present work may be descendants of galaxies at high redshifts with rotation
curves which are consistent with the high mass fraction of baryons relative to
the total dark matter halo.Comment: 18 page
Wiring surface loss of a superconducting transmon qubit
Quantum processors using superconducting qubits suffer from dielectric loss
leading to noise and dissipation. Qubits are usually designed as large
capacitor pads connected to a non-linear Josephson junction (or SQUID) by a
superconducting thin metal wiring. Here, we report on finite-element simulation
and experimental results confirming that more than 50% of surface loss in
transmon qubits can originated from Josephson junctions wiring and can limit
qubit relaxation time. Extracting dielectric loss tangents capacitor pads and
wiring based on their participation ratios, we show dominant surface loss of
wiring can occur for real qubits designs. Then, we simulate a qubit coupled to
a bath of individual TLS defects and show that only a small fraction (~18%) of
coupled defects is located within the wiring interfaces, however, their
coupling strength is much higher due to stronger electromagnetic field.
Finally, we fabricate six tunable floating transmon qubits and experimentally
demonstrate up to 20% improvement in qubit quality factor by wiring design
optimization.Comment: 17 pages, 8 figure
The role of endoscopic ultrasonography in the differential diagnosis of biliary obstructions
Dispensarul Oncologic Regional, Secţia Endoscopie, St.Petersburg, Rusia, 2 IMSP SR ACSR, Secţia endoscopie şi chirurgie miniinvazivă Chişinău, Republica Moldova, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Tehnologiile moderne modifică tot mai semnificativ evaluarea diagnostică a pacienților cu obstrucțiile biliare.
Aplicarea UltraSonografiei Endoscopice (USEnd) este una dintre metodele de ultimă oră în depistarea diferitor maladii, ce
contribuie la obstrucţii biliare.
Scopul: Cercetarea actuală a fost orientată spre aprecierea rolului USEnd în diagnosticarea patologiilor ce pot provoca
dezvoltarea obstrucţiilor biliare.
Rezultate: Au fost studiate fişele de examinare a 42 pacienţi evaluați prin USEnd din evidenţa Dispensarului Oncologic
Regional din St.Petersburg.
Concluzie: USEnd, este o metodă promiţătoare de diagnostic diferenţial în optimizarea algoritmului managementului
obstrucţiilor biliare.Introduction: The emergent imaging technologies increasingly modify the diagnostic evaluation of the patients with biliary
obstructions. One of the recently investigated improvements pertains to the use of Endoscopic Ultrasonography (USEnd) in the
hepatobiliary imaging.
Aim: This study is oriented towards the appreciation of the role of USEnd in the diagnosis of the pathologies pertaining to biliary
obstruction.
Results: The results obtained at the St.Petersburg Regional Oncologic Dispensary after the application of USEnd for 42
patients were analysed.
Conclusion: The possibilities of USEnd in the differential diagnosis for patients with biliary obstructions may optimize the
diagnosis and treatment algorithms
Pulse dynamics in SESAM-free electrically pumped VECSEL
Self-starting pulsed operation in an electrically pumped (EP) vertical-external-cavity surface-emitting-laser (VECSEL) without intracavity saturable absorber is demonstrated. A linear hemispherical cavity design, consisting of the EP-VECSEL chip and a 10% output-coupler, is used to obtain picosecond output pulses with energies of 2.8 pJ and pulse widths of 130 ps at a repetition rate of 1.97 GHz. A complete experimental analysis of the generated output pulse train and of the transition from continuous-wave to pulsed operation is presented. Numerical simulations based on a delay-differential-equation (DDE) model of mode-locked semiconductor lasers are used to reproduce the pulse dynamics and identify different laser operation regimes. From this, the measured single pulse operation is attributed to FM-type mode-locking. The pulse formation is explained by strong amplitude-phase coupling and spectral filtering inside the EP-VECSEL
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