279 research outputs found
N-enlarged Galilei Hopf algebra and its twist deformations
The N-enlarged Galilei Hopf algebra is constructed. Its twist deformations
are considered and the corresponding twisted space-times are derived.Comment: 8 pages, no figure
Complex asteroseismology of the Slowly Pulsating B-type star HD74560
We present the results of complex seismic modelling of the Slowly Pulsating
B-type star HD74560. The star pulsates in five frequencies detected in
photometric observations. For all these frequencies, we identify the mode
degree, . For two of them, found also in spectroscopic data, we are able
to derived the empirical values of the complex nonadiabatic parameter . We
test effects of chemical composition and opacity data. Our results show that
the properties of seismic models of SPB stars differ significantly from those
of the more massive Cephei stars.Comment: 4 pages, 2 figures, conference proceedings, to appear in ASS
Twisted Rindler space-times
The (linearized) noncommutative Rindler space-times associated with
canonical, Lie-algebraic and quadratic twist-deformed Minkowski spaces are
provided. The corresponding deformed Hawking spectra detected by Rindler
observers are derived as well.Comment: 13 pages, no figures, keywords: quantum space-times, Hawking
radiatio
Tension pneumocephalus following suboccipital sitting craniotomy in the pediatric population
Background
Sitting craniotomy often results in entrapment of air in fluid-filled intracranial cavities. Gas under pressure exerts a deleterious effect on adjacent nervous tissue, resulting in clinical deterioration.
Aim of study
To assess the incidence of tension pneumocephalus (TP) and to define risk factors associated therewith.
Material and method
Analysis included 100 consecutive patients (57 boys, 43 girls, mean age 9.7 y) undergoing suboccipital sitting craniotomy since 2012 to 2014.
Results
In our material (n=100) TP was seen in 7 cases, asymptomatic pneumocephalus (AP) in 77 and no pneumocephalus (NP) in 16. Tumor types encountered were typical for pediatric population. In the TP group (n=7) the ratio of low-grade to high-grade tumors was 5:2, in the AP group (n=77) 2:1 and in the NP group (n=16) 1:1. Preoperative hydrocephalus was present in 21 cases (21%, mean incidence), thereof 3 in the TP group (3/7; 42.8%), 12 in AP group (12/77; 15.5%) and 6 in the NP group (6/16; 37.5%). All TP patients received an emergency external drainage, thereof 4 required a permanent ventriculo-peritoneal shunt (57.1%), while AP and NP patients combined (n=93) required a permanent shunt in 4 cases only (4.3%). TP-associated morbidity (n=2) consisted in a significant deterioration of neurological condition.
Conclusions
TP is a relatively rare but potentially serious complication of suboccipital sitting craniotomy. Risk factors for TP are low-grade tumor and pre-existing long-standing hydrocephalus. TP requires emergency decompression by temporary external drainage. TP patients significantly more often require a permanent CSF shunt
Complex asteroseismology of the Cep/SPB pulsator Eridani: constraints on opacities
We undertake another attempt towards seismic modelling of the most intensive
studied main sequence pulsators of the early B spectral type, Eridani.
Our analysis is extended by a requirement of fitting not only pulsational
frequencies but also the complex amplitude of the bolometric flux variation,
, related to each mode frequency. This approach, called {\it complex
asteroseismology}, provides a unique test of stellar parameters, atmospheres
and opacities. In particular, the concordance of the empirical and theoretical
values of we obtained for the high-order g mode opens a new gate in seismic
studies of the main-sequence hybrid pulsators. The most intriguing and
challenging result is that whereas an agreement of the theoretical and
empirical values of for the radial mode can be achieved only with the OPAL
data, a preference for the OP tables is derived from the analysis of the
high-order gravity mode.Comment: 10 pages, 9 figures, accepted for publication in MNRA
-Deformed Statistics and Classical Fourmomentum Addition Law
We consider -deformed relativistic symmetries described algebraically
by modified Majid-Ruegg bicrossproduct basis and investigate the quantization
of field oscillators for the -deformed free scalar fields on
-Minkowski space. By modification of standard multiplication rule, we
postulate the -deformed algebra of bosonic creation and annihilation
operators. Our algebra permits to define the n-particle states with classical
addition law for the fourmomenta in a way which is not in contradiction with
the nonsymmetric quantum fourmomentum coproduct. We introduce -deformed
Fock space generated by our -deformed oscillators which satisfy the
standard algebraic relations with modified -multiplication rule. We
show that such a -deformed bosonic Fock space is endowed with the
conventional bosonic symmetry properties. Finally we discuss the role of
-deformed algebra of oscillators in field-theoretic noncommutative
framework.Comment: LaTeX, 12 pages. V2: second part of chapter 4 changed, new references
and comments added. V3: formula (14) corrected. Some additional explanations
added. V4: further comments about algebraic structure are adde
- …