782 research outputs found
Livestock Guardian Dogs and Cattle Protection: Opportunities, Challenges, and Methods
Producer interest in using livestock guardian dogs (Canis lupus familiaris; LGDs) to protect domestic cattle (Bos taurus) is driven by expanding large carnivore predator populations and increased public concerns regarding lethal predator control in North America. However, few resources exist to guide livestock producers regarding the use of LGDs to protect cattle. This paper summarizes published information and personal ranch experiences regarding the use of LGDs to protect cattle, describes livestock-producer identified challenges to more widespread adoption of this method to deter predators, and provides guidelines for introducing pups to LGD-naïve cattle herds. I recommend more extensive research on the use of LGDs with cattle, increased development of programs to place LGDs with cattle herds, as well as educational efforts targeting resource managers, livestock producers, and the general public
Statistical analysis of inter-arrival times of rainfall events for Italian Sub-Alpine and Mediterranean areas
Abstract. In this work a set of time-series of inter-arrival times of rainfall events, at daily scale, was analysed, with the aim to verify the issue of increasing duration of dry periods. The set consists of 12 time-series recorded at rain gauges in 1926–2005, six of them belong to an Italian Sub-Alpine area (Piedmont) and six to a Mediterranean one (Sicily). In order to overcome the problem related to limited sample size for high values of inter-arrival times, the discrete probability polylog-series distribution was used to fit the empirical data from partial (20 yr) time-series. Moreover, a simple qualitative trend analysis was applied to some high quantiles of inter-arrival times as well as to the average extent of rain clusters. The preliminary analysis seems to confirm the issue of increasing duration of dry periods for both environments, which is limited to the ''cold'' season
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
MOST light-curve analysis of the gamma Dor pulsator HR 8799, showing resonances and amplitude variations
Context: The central star of the HR 8799 system is a gamma Doradus-type
pulsator. The system harbours four planetary-mass companions detected by direct
imaging, and is a good solar system analogue. The masses of the companions are
not known accurately, because the estimation depends strongly on the age of the
system, which is also not known with sufficient accuracy. Asteroseismic studies
of the star might help to better constrain the age of HR 8799. We organized an
extensive photometric and multi-site spectroscopic observing campaign for
studying the pulsations of the central star.
Aims: The aim of the present study is to investigate the pulsation properties
of HR 8799 in detail via the ultra-precise 47-d-long nearly continuous
photometry obtained with the MOST space telescope, and to find as many
independent pulsation modes as possible, which is the prerequisite of an
asteroseismic age determination.
Methods: We carried out Fourier analysis of the wide-band photometric time
series.
Results: We find that resonance and sudden amplitude changes characterize the
pulsation of HR 8799. The dominant frequency is always at f1 = 1.978 c/d. Many
multiples of one ninth of the dominant frequency appear in the Fourier spectrum
of the MOST data: n/9 f1, where n={1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 14, 17,
18}. Our analysis also reveals that many of these peaks show strong amplitude
decrease and phase variations even on the 47-d time-scale. The dependencies
between the pulsation frequencies of HR 8799 make the planned subsequent
asteroseismic analysis rather difficult. We point out some resemblance between
the light curve of HR 8799 and the modulated pulsation light curves of Blazhko
RR Lyrae stars.Comment: Accepted for publication in Astronomy and Astrophysics. 8 pages, 4
figure
Paper Session I-A - Modeling Current and Future Launch Vehicle Processing Using Object-Oriented Simulation Techniques
STARSIM, an acronym for Space Transportation Activities and Resources Simulation, is an objectoriented, menu-driven, user-friendly, decision support system for simulating National Space Transportation System (NSTS) processing, as well as Personnel Launch System (PLS)-National Launch System (NLS), PLS-Proton, PLS-Titan IV, Hermes-Ariane 5 and Cargo Transfer Return Vehicle (CTRV) processing. For each launch system modeled, output is displayed numerically (for global statistical information), in pie chart form (to visualize percentages of subcategories associated with a main category) and in Gantt chart form (for visualizing when and where each launch vehicle experiences waiting, processing, blocking and maintenance periods, and the reasons for blocking). Users may input a comprehensive set of system parameters (e.g., number of launch vehicles, processing times at each facility, number of bays at a particular facility) using a window-based environment, or by supplying an existing input data file. Data for existing launch systems and representative data for proposed systems are used to illustrate output for the models mentioned above. The object-oriented methodology employed in the initial model (i.e., NSTS processing) permitted additional models to be implemented in a minimum amount of time and effort
The classification of frequencies in the {\gamma} Doradus / {\delta} Scuti hybrid star HD 49434
Hybrid stars of the {\gamma} Doradus and {\delta} Scuti pulsation types have
great potential for asteroseismic analysis to explore their interior structure.
To achieve this, mode identi- fications of pulsational frequencies observed in
the stars must be made, a task which is far from simple. In this work we begin
the analysis by scrutinizing the frequencies found in the CoRoT photometric
satellite measurements and ground-based high-resolution spectroscopy of the
hybrid star HD 49434. The results show almost no consistency between the
frequencies found using the two techniques and no characteristic period
spacings or couplings were identified in either dataset. The spectroscopic data
additionally show no evidence for any long term (5 year) variation in the
dominant frequency. The 31 spectroscopic frequencies identified have standard
deviation profiles suggesting multiple modes sharing (l, m) in the {\delta}
Scuti frequency region and several skewed modes sharing the same (l, m) in the
{\gamma} Doradus frequency region. In addition, there is a clear frequency in
the {\gamma} Doradus frequency region that appears to be unrelated to the
others. We conclude HD 49434 remains a {\delta} Scuti/ {\gamma} Doradus
candidate hybrid star but more sophisticated models dealing with rotation are
sought to obtain a clear picture of the pulsational behaviour of this star.Comment: Accepted for publication in MNRAS December 201
KIC 4768731: a bright long-period roAp star in theKeplerfield
We report the identification of 61.45 d−1 (711.2 μHz) oscillations, with amplitudes of 62.6 μmag, in KIC 4768731 (HD 225914) using Kepler photometry. This relatively bright (V = 9.17) chemically peculiar star with spectral type A5 Vp SrCr(Eu) has previously been found to exhibit rotational modulation with a period of 5.21 d. Fourier analysis reveals a simple dipole pulsator with an amplitude that has remained stable over a 4-yr time span, but with a frequency that is variable. Analysis of high-resolution spectra yields stellar parameters of Teff = 8100 ± 200 K, log g = 4.0 ± 0.2, [Fe/H] = +0.31 ± 0.24 and v sin i = 14.8 ± 1.6 km s−1.
Line profile variations caused by rotation are also evident. Lines of Sr, Cr, Eu, Mg and Si are strongest when the star is brightest, while Y and Ba vary in antiphase with the other elements. The abundances of rare earth elements are only modestly enhanced compared to other roAp stars of similar Teff and log g. Radial velocities in the literature suggest a significant change over the past 30 yr, but the radial velocities presented here show no significant change over a period of 4 yr
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