941 research outputs found
Zoo-FISH in the European mole (Talpa europaea) detects all ancestral Boreo-Eutherian human homologous chromosome associations
Zoo-FISH with human whole-chromosome paint probes delineated syntenic association of human homologous chromosome segments 3-21, 14-15, 16-19, 4-8, 7-16 and 12-22 (twice) in the European mole (Talpa europaea, Talpidae, Eulipotyphla, Mammalia). These segment associations represent shared ancestral Boreo-Eutherian traits, half of which were previously not described for Eulipotyphla. The karyotype of the European mole acquired a minimum of 19 translocations and six inversions compared to the presumed Boreo-Eutherian ancestor. Copyright (c) 2006 S. Karger AG, Basel
Modeling collapse aggresiveness of cavitation bubbles in hydromachinery
A simple model of assessment of collapse aggressiveness of cavitation bubbles suitable for application at pump design stage is proposed. The model is focused on quantifying the energetic effects of single bubble collapses and the emphasis is placed on computational efficiency. The objective of the model is to provide a rapid estimation of the erosion risk for steadystate or near-steady-state flow with traveling bubble cavitation. The proprietary 3-dimensional Navier-Stokes code for turbulent flow in hydrodynamic machinery is coupled with the unreduced Rayleigh-Plesset equation for incompressible liquid by virtue of the iterations of continuity and momentum equations to account for density changes in the bubbly regions (two-way coupling). The model of collapse aggressiveness of the cavitation bubbles is based on the estimation of the energy dissipated between two successive bubble rebounds. The model is tested for a 2- dimensional hydrofoil in the cavitation tunnel of SIGMA Research and Development Institute in LutÃn. The closed-loop tunnel is equipped with the acoustic bubble spectrometer to measure the nuclei population in the test section inlet. The erosion pattern of the hydrofoil surface is monitored using optical profilometry. The results indicate the dominant effect of the first (most energetic) collapses, however, the model overestimates the importance of smaller nuclei mainly due to their large number in the spectra. Introduction of a threshold for the minimum collapse energy required to form any erosive potential seems necessary to rectify this deficiency. The model, although aimed to achieve efficiency and simplicity by relying on the single-bubble dynamics, shows good agreement with the experimental evidence. An attempt to apply the model to the 3-dimensional geometry of a mixedflow pump impeller is also presented. This paper is a report on part one of work in progress. In the second part the results of the ongoing pitting tests will be used to develop a model of erosive potential.http://deepblue.lib.umich.edu/bitstream/2027.42/84306/1/CAV2009-final131.pd
Limits for the application of spectroscopic mode ID methods
Spectroscopic mode identification techiques, which monitor intensity variations across an absorption line, provide the possibility of determining the quantum numbers l and m, the inclination and the intrinsic pulsation amplitude of a star. Of course, the uncertainties of the mode identification are dependent on the quality of the observations and the identification method applied. We have focused on the Pixel-by-pixel method/Direct line profile fitting (Mantegazza 2000) and the Moment method (Balona 1987, Briquet & Aerts 2003) for pinpointing mode parameters and tested the impact of various observational effects and stellar properties on the identification
Spectroscopic Pulsational Frequency Identification and Mode Determination of Gamma Doradus Star HD135825
We present the mode identification of frequencies found in spectroscopic
observations of the Gamma Doradus star HD135825. Four frequencies were
successfully identified: 1.3150 +/- 0.0003 1/d; 0.2902 +/- 0.0004 1/d; 1.4045
+/- 0.0005 1/d; and 1.8829 +/- 0.0005 1/d. These correspond to (l, m) modes of
(1,1), (2,-2), (4,0) and (1,1) respectively. Additional frequencies were found
but they were below the signal-to-noise limit of the Fourier spectrum and not
suitable for mode identification. The rotational axis inclination and vsini of
the star were determined to be 87 degrees (nearly edge-on) and 39.7 km/s
(moderate for Gamma Doradus stars) respectively. A simultaneous fit of these
four modes to the line profile variations in the data gives a reduced chi
square of 12.7. We confirm, based on the frequencies found, that HD135825 is a
bona fide Gamma Doradus star.Comment: Accepted to MNRAS 2012 March
A new method for the spectroscopic identification of stellar non-radial pulsation modes. II. Mode identification of the Delta Scuti star FG Virginis
We present a mode identification based on new high-resolution time-series
spectra of the non-radially pulsating Delta Scuti star FG~Vir (HD 106384, V =
6.57, A5V). From 2002 February to June a global Delta Scuti Network (DSN)
campaign, utilizing high-resolution spectroscopy and simultaneous photometry
has been conducted for FG~Vir in order to provide a theoretical pulsation
model. In this campaign we have acquired 969 Echelle spectra covering 147 hours
at six observatories. The mode identification was carried out by analyzing line
profile variations by means of the Fourier parameter fit method, where the
observational Fourier parameters across the line are fitted with theoretical
values. This method is especially well suited for determining the azimuthal
order m of non-radial pulsation modes and thus complementary with the method of
Daszynska-Daszkiewicz (2002) which does best at identifying the degree l. 15
frequencies between 9.2 and 33.5 c/d were detected spectroscopically. We
determined the azimuthal order m of 12 modes and constrained their harmonic
degree l. Only modes of low degree (l <= 4) were detected, most of them having
axisymmetric character mainly due to the relatively low projected rotational
velocity of FG Vir. The detected non-axisymmetric modes have azimuthal orders
between -2 and 1. We derived an inclination of 19 degrees, which implies an
equatorial rotational rate of 66 km/s.Comment: 14 pages, 26 figure
An asteroseismic study of the beta Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling
We present the results of a spectroscopic multisite campaign for the beta
Cephei star 12 (DD) Lacertae. Our study is based on more than thousand
high-resolution high S/N spectra gathered with 8 different telescopes in a time
span of 11 months. In addition we make use of numerous archival spectroscopic
measurements. We confirm 10 independent frequencies recently discovered from
photometry, as well as harmonics and combination frequencies. In particular,
the SPB-like g-mode with frequency 0.3428 1/d reported before is detected in
our spectroscopy. We identify the four main modes as (l1,m1) = (1, 1), (l2,m2)
= (0, 0), (l3,m3) = (1, 0) and (l4,m4) = (2, 1) for f1 = 5.178964 1/d, f2 =
5.334224 1/d, f3 = 5.066316 1/d and f4 = 5.490133 1/d, respectively. Our
seismic modelling shows that f2 is likely the radial first overtone and that
the core overshooting parameter alpha_ov is lower than 0.4 local pressure scale
heights.Comment: 16 pages, 11 figures, accepted in MNRA
Amplitude variability and multiple frequencies in 44 Tau: 2000 - 2006
This study has three principal aims: (i) to increase the number of detected
pulsation modes of 44 Tau, especially outside the previously known frequency
ranges, (ii) to study the amplitude variability and its systematics, and (iii)
to examine the combination frequencies.
During the 2004/5 and 2005/6 observing seasons, high-precision photometry was
obtained with the Vienna Automatic Photoelectric Telescope in Arizona during 52
nights. Together with previous campaigns, a data base from 2000 to 2006 was
available for multifrequency analyses.
Forty-nine pulsation frequencies are detected, of which 15 are independent
pulsation modes and 34 combination frequencies or harmonics. The newly found
gravity mode at 5.30 c/d extends the known frequency range of instability.
Strong amplitude variability from year to year is found for the \ell = 1 modes,
while the two radial modes have essentially constant amplitudes. Possible
origins of the amplitude variability of the \ell = 1 modes, such as precession
of the pulsation axis, beating and resonance effects are considered. The
amplitudes of the combination frequencies, f_i + f_j, mirror the variations in
the parent modes. The combination parameter, which relates the amplitudes of
the combination frequencies to those of the parent modes, is found to be
different for different parents.Comment: 10 pages, 8 figures, 4 tables, accepted for publication in A&
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