2,086 research outputs found
The Effects of Temperature, Diet, and Other Factors on Development, Survivorship, and Oviposition of Aethina tumida (Coleoptera: Nitidulidae)
Developmental rate and survivorship of small hive beetle, Aethina tumida Murray
(Coleoptera: Nitidulidae), life stages were measured across different temperatures (21, 25, 28, 32 and 35 C) and diets, which included natural and artificial pollen, honey, and bee pupae. Temperature affected hatch success, time to hatching, and larval growth. Eggs hatched in 61 h at 21 C but in 22 h at 35 C. Larvae achieved peak weight in 8 d at 35 C but needed 17 d at 21 C. Diet had comparatively little effect on larval survivorship or maximum weight, although larvae fed only bee pupae had lower survivorship. Access to soil influenced pupation success. Duration of the life stage spent in the soil, during which pupation occurs, was also affected by temperature: adults emerged after 32.7 d at 21C but after only 14.8 d at 35 C, albeit with high mortality. Minimum temperature for development was estimated at 13.5 C for eggs, and 10.0 C for larvae and pupae. Temperature influenced adult longevity and oviposition: on a honey and pollen diet average adult lifespan was 92.8 d at 24 C but only 11.6 d at 35 C. Beetles lived longer at 28 C or lower but produced the most eggs per female, regardless of diet, at 32 C. Beetle density influenced fecundity: beetles kept at three pairs per vial laid 6.7 times more eggs per female than those kept as single pairs. Overall, beetles fared best at 28-32 C with mortality of all stages highest at 35 C
Systematic Blueshift of Line Profiles in the Type IIn Supernova 2010jl: Evidence for Post-Shock Dust Formation?
Type IIn SNe show spectral evidence for strong interaction between their
blast wave and dense circumstellar material (CSM) around the progenitor star.
SN2010jl was the brightest core-collapse SN in 2010, and it was a Type IIn
explosion with strong CSM interaction. Andrews et al. recently reported
evidence for an IR excess in SN2010jl, indicating either new dust formation or
the heating of CSM dust in an IR echo. Here we report multi-epoch spectra of
SN2010jl that reveal the tell-tale signature of new dust formation:
emission-line profiles becoming systematically more blueshifted as the red side
of the line is blocked by increasing extinction. The effect is seen clearly in
the intermediate-width (400--4000 km/s) component of H beginning
roughly 30d after explosion. Moreover, we present near-IR spectra demonstrating
that the asymmetry in the hydrogen-line profiles is wavelength dependent,
appearing more pronounced at shorter wavelengths. This evidence suggests that
new dust grains had formed quickly in the post-shock shell of SN 2010jl arising
from CSM interaction. Since the observed dust temperature has been attributed
to an IR echo and not to new dust, either (1) IR excess emission at m is not a particularly sensitive tracer of new dust formation in SNe, or
(2) some assumptions about expected dust temperatures might require further
study. Lastly, we discuss one possible mechanism other than dust that might
lead to increasingly blueshifted line profiles in SNeIIn, although the
wavelength dependence of the asymmetry argues against this hypothesis in the
case of SN2010jl.Comment: 6 pages, 4 figures, submitted to A
Optical and Infrared Analysis of Type II SN 2006BC
We present nebular phase optical imaging and spectroscopy and near/mid-IR
imaging of the Type II SN 2006bc. Observations reveal the central wavelength of
the symmetric H line profile to be red-shifted with respect to the host
galaxy H emission by day 325. Such an phenomenon has been argued to
result from an asymmetric explosion in the iron-peak elements resulting in a
larger mass of Ni and higher excitation of hydrogen on the far side of
the SN explosion. We also observe a gradual blue-shifting of this H
peak which is indicative of dust formation in the ejecta. Although showing a
normal peak brightness, V -17.2, for a core-collapse SN, 2006bc fades by
6 mag during the first 400 days suggesting either a relatively low
Ni yield, an increase in extinction due to new dust, or both. A short
duration flattening of the light curve is observed from day 416 to day 541
suggesting an optical light echo. Based on the narrow time window of this echo,
we discuss implications on the location and geometry of the reflecting ISM.
With our radiative transfer models, we find an upper limit of 2 x 10
M of dust around SN 2006bc. In the event that all of this dust were
formed during the SN explosion, this quantity of dust is still several orders
of magnitude lower than that needed to explain the large quantities of dust
observed in the early universe.Comment: 6 pages, 10 figures, accepted for publication in Ap
Plasma ACTH, α-MSH and cortisol variations in the dog during the oestrous cycle in different photoperiods
The hypothalamic-pituitary-adrenal axis (HPA) is a complex system regulated by multiple factors.Sexual dimorphism of this axis has been described in different species under physiological conditions and it hasbeen proposed that sexual hormones could have an effect on it. There are only a few reports about sex-linkedvariations in HPA axis hormones in the dog. Thus, studying the impact of sexual hormones on the HPA axis wouldbroaden the knowledge about its function in this species. Therefore, the objective of this study was to determinewhether there are variations in HPA plasma hormones (ACTH, alfa-melanocyte-stimulating hormone [α-MSH]and cortisol) according to the sex and photoperiod (positive or negative photoperiod were considered when theduration of the light hours of the day was more than 12 or less than 12, respectively) under basal conditions (likeanoestrus) and throughout the oestrous cycle in the female dog. The population under study consisted of 11 intactfemale and 14 intact male dogs. Under basal conditions neither ACTH nor α-MSH concentrations showed differencesbetween sexes and different photoperiods. Cortisol showed greater values in the negative photoperiod thanin the positive, both in females and males (P = 0.03 and P = 0.015, respectively). Throughout the oestrous cycle,all the studied hormones showed variations (P < 0.0001). The greatest concentrations of ACTH were observed atproestrus, while α-MSH and cortisol showed their greatest concentrations at oestrus. The three hormones decreasedin diestrus. ACTH and cortisol concentrations were higher in the negative photoperiod (P = 0.04 and P < 0.0001,respectively), while α-MSH concentrations were higher in the positive photoperiod (P = 0.012). In the group offemales oestradiol and progesterone correlated with ACTH (r = 0.75, P < 0.0001; r = 0.34, P < 0.01, respectively),α-MSH (r = 0.49, P < 0.0001; r = 0.52, P < 0.0001, respectively) and cortisol (r = 0.33, P < 0.01; r = 0.5, P < 0.0001,respectively). These results show that in females, HPA axis hormones vary during the oestrous cycle in relation tooestradiol and progesterone fluctuations. The ACTH, α-MSH and cortisol concentrations also showed differencesbetween photoperiods in females, but only cortisol did so in males. These findings suggest that sexual hormonescould have an effect on the HPA axis. Further research needs to be done to fully understand this interaction andthe mechanisms involved.Fil: Gallelli, María Florencia. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; ArgentinaFil: Monachesi, N.. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; ArgentinaFil: Miceli, Diego Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; ArgentinaFil: Cabrera Battler, M. F.. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; ArgentinaFil: Gomez, N. V.. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; ArgentinaFil: Meikle, A.. Universidad de Montevideo; UruguayFil: Castillo, V, A.. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; Argentin
Star formation in the merging Galaxy NGC3256
The central 5 kpc of the ultra-luminous merging galaxy NGC 3256 was mapped at J, H, K, L, and 10 micrometer, and a 2 micrometer spectra of the nuclear region was obtained. This data was used to identify and characterize the super starburst which has apparently been triggered and fuelled by the merger of two gas rich galaxies. It is also shown that the old stellar population has relaxed into a single spheroidal system, and that a supernova driven wind might eventually drive any remaining gas from the system to leave a relic which will be indistinguishable from an elliptical galaxy
A Spitzer Space Telescope Study of SN 2003gd: Still No Direct Evidence that Core-Collapse Supernovae are Major Dust Factories
We present a new, detailed analysis of late-time mid-infrared (IR)
observations of the Type II-P supernova (SN) 2003gd. At about 16 months after
the explosion, the mid-IR flux is consistent with emission from 4 x 10^(-5)
M(solar) of newly condensed dust in the ejecta. At 22 months emission from
point-like sources close to the SN position was detected at 8 microns and 24
microns. By 42 months the 24 micron flux had faded. Considerations of
luminosity and source size rule out the ejecta of SN 2003gd as the main origin
of the emission at 22 months. A possible alternative explanation for the
emission at this later epoch is an IR echo from pre-existing circumstellar or
interstellar dust. We conclude that, contrary to the claim of Sugerman et al.
(2006, Science, 313, 196), the mid-IR emission from SN 2003gd does not support
the presence of 0.02 M(solar) of newly formed dust in the ejecta. There is, as
yet, no direct evidence that core-collapse supernovae are major dust factories.Comment: 26 pages, 2 figures, 2 tables, accepted for publication in
Astrophysical Journa
The Rise Times of High and Low Redshift Type Ia Supernovae are Consistent
We present a self-consistent comparison of the rise times for low- and
high-redshift Type Ia supernovae. Following previous studies, the early light
curve is modeled using a t-squared law, which is then mated with a modified
Leibundgut template light curve. The best-fit t-squared law is determined for
ensemble samples of low- and high-redshift supernovae by fitting simultaneously
for all light curve parameters for all supernovae in each sample. Our method
fully accounts for the non-negligible covariance amongst the light curve
fitting parameters, which previous analyses have neglected. Contrary to Riess
et al. (1999), we find fair to good agreement between the rise times of the
low- and high-redshift Type Ia supernovae. The uncertainty in the rise time of
the high-redshift Type Ia supernovae is presently quite large (roughly +/- 1.2
days statistical), making any search for evidence of evolution based on a
comparison of rise times premature. Furthermore, systematic effects on rise
time determinations from the high-redshift observations, due to the form of the
late-time light curve and the manner in which the light curves of these
supernovae were sampled, can bias the high-redshift rise time determinations by
up to +3.6/-1.9 days under extreme situations. The peak brightnesses - used for
cosmology - do not suffer any significant bias, nor any significant increase in
uncertainty.Comment: 18 pages, 4 figures, Accepted for publication in the Astronomical
Journal. Also available at http://www.lbl.gov/~nugent/papers.html Typos were
corrected and a few sentences were added for improved clarit
A Spitzer Space Telescope study of SN 2002hh: an infrared echo from a Type IIP supernova
We present late-time (590-994 d) mid-IR photometry of the normal, but
highly-reddened Type IIP supernova SN 2002hh. Bright, cool, slowly-fading
emission is detected from the direction of the supernova. Most of this flux
appears not to be driven by the supernova event but instead probably originates
in a cool, obscured star-formation region or molecular cloud along the
line-of-sight. We also show, however, that the declining component of the flux
is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR
emission could also be coming from newly-condensed dust and/or an ejecta/CSM
impact but their contributions are likely to be small. For the case of a CSM-IR
echo, we infer a dust mass of as little as 0.036 M(solar) with a corresponding
CSM mass of 3.6(0.01/r(dg))M(solar) where r(dg) is the dust-to-gas mass ratio.
Such a CSM would have resulted from episodic mass loss whose rate declined
significantly about 28,000 years ago. Alternatively, an IR echo from a
surrounding, dense, dusty molecular cloud might also have been responsible for
the fading component. Either way, this is the first time that an IR echo has
been clearly identified in a Type IIP supernova. We find no evidence for or
against the proposal that Type IIP supernovae produce large amounts of dust via
grain condensation in the ejecta. However, within the CSM-IR echo scenario, the
mass of dust derived implies that the progenitors of the most common of
core-collapse supernovae may make an important contribution to the universal
dust content.Comment: 41 pages, 11 figures, 4 tables, accepted for publication in
Astrophysical Journal (References corrected
The absolute infrared magnitudes of type Ia supernovae
The absolute luminosities and homogeneity of early-time infrared (IR) light
curves of type Ia supernovae are examined. Eight supernovae are considered.
These are selected to have accurately known epochs of maximum blue light as
well as having reliable distance estimates and/or good light curve coverage.
Two approaches to extinction correction are considered. Owing to the low
extinction in the IR, the differences in the corrections via the two methods
are small. Absolute magnitude light curves in the J, H and K-bands are derived.
Six of the events, including five established ``Branch-normal'' supernovae show
similar coeval magnitudes. Two of these, SNe 1989B and 1998bu, were observed
near maximum infrared light. This occurs about 5 days {\it before} maximum blue
light. Absolute peak magnitudes of about -19.0, -18.7 and -18.8 in J, H & K
respectively were obtained. The two spectroscopically peculiar supernovae in
the sample, SNe 1986G and 1991T, also show atypical IR behaviour. The light
curves of the six similar supernovae can be represented fairly consistently
with a single light curve in each of the three bands. In all three IR bands the
dispersion in absolute magnitude is about 0.15 mag, and this can be accounted
for within the uncertainties of the individual light curves. No significant
variation of absolute IR magnitude with B-band light curve decline rate, Delta
m_{15}(B), is seen over the range 0.87<Delta m_{15}(B)<1.31. However, the data
are insufficient to allow us to decide whether or not the decline rate relation
is weaker in the IR than in the optical region. IR light curves of type Ia
supernovae should eventually provide cosmological distance estimates which are
of equal or even superior quality to those obtained in optical studies.Comment: 19 pages, 9 figures, MNRAS in press (includes Referee's changes
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