634 research outputs found
A dark energy view of inflation
Traditionally, inflationary models are analyzed in terms of parameters such
as the scalar spectral index ns and the tensor to scalar ratio r, while dark
energy models are studied in terms of the equation of state parameter w.
Motivated by the fact that both deal with periods of accelerated expansion, we
study the evolution of w during inflation, in order to derive observational
constraints on its value during an earlier epoch likely dominated by a dynamic
form of dark energy. We find that the cosmic microwave background and
large-scale structure data is consistent with w_inflation=-1 and provides an
upper limit of 1+w <~ 0.02. Nonetheless, an exact de Sitter expansion with a
constant w=-1 is disfavored since this would result in ns=1.Comment: 5 pages, 4 figures; v2: minor modifications to match published
versio
On the Topological Resonance Energy of Coumarin and Its Derivates
Topological resonance energies of coumarin and the following
derivatives: 3-hydroxycoumarin, 4-hydroxycoumarin, 3,4-dihydro-.
xycoumarin, 4,6-dihydroxycoumarin, 4,5,7-trihydroxycoumarin, 3-
-carboxy-4-hydroxycoumarin, 3-bromo-4-hydroxycoumarin, and
6-bromo-4-hydroxycoumarin, are reported. Theoretical predictions
that these all coumarins should exhibit aromatic properties are
sustained by the ample experimental evidence. In addition, coumarin
and isocoumarin are predicted to be much more stable than
the corresponding quinonoid isomer
RXJ 0921+4529: a binary quasar or gravitational lens?
We report the new spectroscopic observations of the gravitational lens RXJ
021+4529 with the multi-mode focal reducer SCORPIO of the SAO RAS 6-m
telescope. The new spectral observations were compared with the previously
observed spectra of components A and B of RXJ 0921+4529, i.e. the same
components observed in different epochs. We found a significant difference in
the spectrum between the components that cannot be explained with microlensing
and/or spectral variation. We conclude that RXJ 0921+4529 is a binary quasar
system, where redshifts of quasars A and B are 1.6535 +/- 0.0005 and 1.6625 +/-
0.0015, respectively.Comment: 6 pages, 5 figures, accepted for publication in The Astrophysical
Journal Letter
Transient Stability Simulation by Waveform Relaxation Methods
In this paper, a new methodology for power system dynamic response calculations is presented. The technique known as the waveform relaxation has been extensively used in transient analysis of VLSI circuits and it can take advantage of new architectures in computer systems such as parallel processors. The application in this paper is limited to swing equations of a large power system. Computational results are presented
Revealing the nature of central emission nebulae in the dwarf galaxy NGC 185
In this paper we present new optical observations of the galaxy NGC 185
intended to reveal the status of supernova remnants (SNRs) in this dwarf
companion of the Andromeda galaxy. Previously, it was reported that this galaxy
hosts one SNR. Our deep photometric study with the 2m telescope at Rozhen
National Astronomical Observatory using narrow-band H and [SII] filters
revealed complex structure of the interstellar medium in the center of the
galaxy. To confirm the classification and to study the kinematics of the
detected nebulae, we carried out spectroscopic observations using the SCORPIO
multi-mode spectrograph at the 6m telescope at the Special Astrophysical
Observatory of the Russian Academy of Science, both in low- and high-resolution
modes. We also searched the archival X-ray and radio data for counterparts of
the candidate SNRs identified by our optical observations. Our observations
imply the presence of one more SNR, one possible HII region previously
cataloged as part of an SNR, and the presence of an additional source of shock
ionization in one low-brightness PN. We detected enhanced [SII]/H_alpha and
[NII]/H_alpha line ratios, as well as relatively high (up to 90 km s)
expansion velocities of the two observed nebulae, motivating their
classification as SNRs (with diameters of 45 pc and 50 pc), confirmed by both
photometric and spectral observations. The estimated electron density of
emission nebulae is 30 - 200 cm. Archival XMM-Newton observations
indicate the presence of an extended, low-brightness, soft source in projection
of one of the optical SNRs, whereas the archival VLA radio image shows weak,
unresolved emission in the center of NGC 185.Comment: 15 pages, 14 figures, accepted for publication in A&
An overview of generalized entropic forms
The aim of this focus letter is to present a comprehensive classification of
the main entropic forms introduced in the last fifty years in the framework of
statistical physics and information theory. Most of them can be grouped into
three families, characterized by two-deformation parameters, introduced
respectively by Sharma, Taneja, and Mittal (entropies of degree
)), by Sharma and Mittal (entropies of order
), and by Hanel and Thurner (entropies of class ).
Many entropic forms examined will be characterized systematically by means of
important concepts such as their axiomatic foundations {\em \`{a} la}
Shannon-Khinchin and the consequent composability rule for statistically
independent systems. Other critical aspects related to the Lesche stability of
information measures and their consistency with the Shore-Johnson axioms will
be briefly discussed on a general ground.Comment: 14 pages, 6 tables, no figures, to appear on EPL: Focus Issues
"Progresses on Statistical Physics and Complexity
Homodiegetic narration in the Serbian novel ; Гомодиегетическое повествование в сербском романе.
Рад представља покушај теоријског укрштања два различита
књижевнонаучна приступа: са једне стране непосредно је заснован на
наратолошким поставкама најутицајнијих аутора краја ХХ века (посебно на
Женетовој теорији приповедања), док са друге подразумева јасну
књижевноисторијску перспективу, и то жанровски прецизно профилисану ‒
организован је као једна специфична повест српског романа. Извршено читалачко
истраживање и анализа текстова тежили су да у исто време обухвате и поступке и
облике, односно да испитају примену једне посебне приповедне технике
(хомодијегетичког приповедања) у конкретној прозној форми (роману) у дужој
дијахронијској перспективи. Показало се да је прича о хомодијегетичком роману у исто време и повест српског романа у целини...The work represents an attempt at theoretical cross-section between two
different literary scholarship approaches: on the one hand it is indirectly based on
narrative settings of the most influential authors of the end of the twentieth century
(especially on Genette’s narrative theory), while on the other hand it implies a clear
literary-historical perspective which is organized as a specific history of the Serbian
novel. The carried out book research and text analyses aspired to comprise both
techniques and forms at the same time, i.e. to explore the implementation of a special
narrative technique (homodiegetic narration) in a prose form (novel) in a long-term
diachronic perspective. The story about the homodiegetic novel has proved to be the
history of the Serbian novel at the same time..
Micromorphological characteristics of the distal segment and braches of the radial artery
Hirurške procedure, kao što je odizanje tenarnih režnjeva ili stabla radijalne
arterije, traže detaljno poznavanje anatomije stabla i grana a. radialis (AR). Ciljevi ove
disertacije bili su da se definišu pružanje i šema grananja radijalne arterije i njenih
grana, i da se definišu morfometrijske karakteristike i varijacije radijalne arterije i
njenih grana.
Eksperimentalno istraživanje distalnog segmenta radijalne arterije je obavljeno
na 50 podlaktica i šaka kadavera (leševa) oba pola. Krvni sudovi 15 podlaktica i šaka su
perfundovani toplim fiziološkim rastvorom i neutralnim formalinom (4% neutralni
rastvor formaldehida) nakon čega je izvršeno ubrizgavanje 10% tuš želatina u
proksimalni deo stable radijalne arterije. Ovi preparati su korišćeni za mikrodisekciju
distalnog dela radijalne arterije i njenih grana u cilju proučavanja morfologije,
topografskih odnosa i anastomoza ovih krvnih sudova.
Drugi deo istraživanja je izveden ubrizgavanjem metil metakrilata u arterijski
sistem 35 podlaktica i šaka i naknadno sprovedenom korozijom u 40% rastvoru KOH
što nam je omogućilo da dobijemo plastične odlivke arterijske mreže distalnog dela
radijalne arterije na kojima su vršena merenja istraživanih krvnih sudova. Dalja
mikroanatomska istraživanja su obuhvatala tri dela distalnog segmenta žbične arterije
(a. radialis): 1) stablo distalnog segmenta a. radialis (AR), 2) a. princeps pollicis (APP)
i 3) arcus palmaris profundus (ArcPP). Posebno smo izdvojili r. palmaris superficialis
(RPS) i aa. metacarpales dorsales (AMD).
Prečnik distalnog dela stabla a. radialis (AR) u nivou zgloba ručja iznosio je
prosečno 2,9±0,3 mm. R. palmaris superificialis (RPS) je identifikovan na svim
preparatima (100%). RPS se u većini slučajeva (75% preparata) pružao potkožno i
njegov prosečan dijametar (prečnik) je iznosio 1,42±0,45 mm. Definisali smo postojanje
dva tipa RPS: dobro razvijen RPS (tip A) i hipoplastičan RPS (tip B). Dobro razvijen
RPS (tip A) bio je prisutan na 11 (31,4%) preparata, odlikovale su ga vrednosti
dijametra koje su bile veće od 1,7 mm, pri čemu je vrednost njegovog prosečnog
dijametra iznosila 1,95±0,36 mm. Ovaj tip RPS je učestvovao u vaskularizaciji
kažiprsta, a zavisno od uključenosti u vaskularizaciju palca izdvojili smo podtip A1,
koji je bio prisutan u 6 (17,1%) slučajeva i podtip A2 koji je bio nešto ređi, 4 (11,4%)
slučajeva...Surgical procedures such as the thenar flaps and radial artery (RA) harvesting
call for an detailed anatomical study of the radial artery and its branches. The aims of
this dissertation were to define the extent and branching patterns of the distal segment
and branches of the radial artery, as like as to define the morphometric characteristics
and anatomical variations of these blood vessels.
The distal segment of the RA and its branches were investigated in 50 postmortem
specimens of human forearms and hands. In the first part of our study, 15
specimens of the forearms and hands were perfused with 0.9% saline solution and
buffered formalin (4% neutral solution of formaldehyde), and further injected with
black India ink. These specimens were used for the microdissection of the distal
segment of the RA and its branches in order to investigate the morphology, topographic
relationships and anastomoses of these blood vessels.
Second part of our study was performed in 35 specimens of the forearms and
hands we injected with methyl-methacrylate and afterwards corroded in 40% potassium
hydroxide solution. Using this method we obtained corrosion plastic casts in order to
perform measurements of investigated blood vessels. Further microanatomical studies
covered three parts of the distal segment of the RA: 1) the main stem of the distal
segment of the RA, 2) the princeps pollicis artery (PPA) and 3) the deep palmar arch
(DPA), including the superficial palmar branch and dorsal metacarpal arteries (DMA).
The average diameter of the main stem of the RA distal segment was 2.9±0.3
mm. The superficial palmar branch (SPB) of the RA was always present and in the
majority of cases the course of the SPB was superficial (75%). The mean diameter of
the SPB was 1.42±0.45 mm. We defined two types of the SPB according to its diameter:
well developed SPB (type A) and hypoplastic SPB (type 2). Well developed SPB (type
A) was present in 11 hands (31.4% of cases) with the diameter larger than 1.7 mm
(mean diameter of 1.95±0.36 mm) and it was extending distally in order to continue as
the radialis indicis artery (RIA). This type of the SPB supplied the index finger and it
gave of two important branches to the thumb we further classified as the A1 subtype,
which was present in 6 hands (17.1% of cases) and A2 subtype, which was present in 4
hands (11.4% of cases)..
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