4,147 research outputs found
Diversity and Abundance of Hymenopterous Parasitoids Associated with Anastrepha fraterculus (Diptera: Tephritidae) in Native and Exotic Host Plants in Misiones, Northeastern Argentina
Some Major host species used by the tephritid fruit flies Anastrepha
fraterculus (Wiede-mann) and Ceratitis capitata (Wiedemann), including
Acca sellowiana (O. Berg) Burret, Campomanesia xanthocarpa O. Berg,
Psidium guajava L., Prunus persica (L.) Batsch, Eriobotrya japonica (Thunb.) Lindl., Citrus reticulata Blanco var. Murcott, C. aurantium L., C. paradisi
Macfadyen var. Dalan Dan, and C. paradisi var. Sudashi, were sampled for fruit fly
larvae between Feb and Dec 2000 in the northernmost section of the Paranaense forest, in the Province of Misiones, NE Argentina. Both A. fraterculus and C. capitata were obtained from these host plant species, with A. fraterculus accounting for 93% of all tephritid puparia identified. Ten species of larval-pupal parasitoids were recovered from A. fraterculus; Doryctobracon areolatus (Szépligeti), D. brasiliensis (Szépligeti), Utetes anastrephae (Viereck), Opius bellus (Gahan), Diachasmimorpha longicaudata (Ashmead) (Opiinae, raconidae),
Odontosema anastrephae Borgmeier, Lopheucoila anastrephae (Rohwer),
Aganaspis pelleranoi (Brèthes) (Eucoilinae, Figitidae), Asobara anastrephae
(Muessebeck) (Alyssinae, Braconidae), and Aceratoneuromyia indica
(Silvestri) (Tetrastichinae, Eulophidae). All these parasitoids, with the exception of D. longicaudata and A. indica, are native to the Neotropical region. No parasitoids were recovered from C. capitata puparia. Asobara anastrephae
and O. anastrephae are newly recorded in Argentina, whereas D. brasiliensis,
U. anastrephae, and L. anastrephae are newly reported in Misiones. The eucoiline
A. pelleranoi wasthe most abundant parasitoid species. Acca sellowiana and P.
guajava harbored the highest parasitoid abundance and diversity.Fil: Schliserman, Pablo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro de Investigaciones y Transferencia de Catamarca. Universidad Nacional de Catamarca. Centro de Investigaciones y Transferencia de Catamarca; ArgentinaFil: Ovruski Alderete, Sergio Marcelo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Decoll, Olga. Instituto Nacional de TecnologÃa Agropecuaria. Centro Regional Misiones; ArgentinaFil: Wharton, Robert. Texas A&M University; Estados Unido
The Antarctic dry valley lakes: Relevance to Mars
The similarity of the early environments of Mars and Earth, and the biological evolution which occurred on early Earth, motivates exobiologists to seriously consider the possiblity of an early Martian biota. Environments are being identified which could contain Martian life and areas which may presently contain evidence of this former life. Sediments which were thought to be deposited in large ice-covered lakes are present on Mars. Such localities were identified within some of the canyons of the Valles Marineris and more recently in the ancient terrain in the Southern Hemisphere. Perennially ice-covered Antarctic lakes are being studied in order to develop quantitative models that relate environmental factors to the nature of the biological community and sediment forming processes. These models will be applied to the Martian paleolakes to establish the scientific rationale for the exobiological study of ancient Martian sediments
High frequency study of FRB 20180916B using the 100-m Effelsberg radio telescope
FRB 20180916B is a repeating fast radio burst (FRB) with an activity period
of 16.33 days. In previous observations ranging from MHz, the
activity window was found to be frequency dependent, with lower frequency
bursts occurring later. In this work, we present the highest-frequency
detections of bursts from this FRB, using the 100-m Effelsberg Radio Telescope
at 48 GHz. We present the results from two observing campaigns. We performed
the first campaign over an entire activity period which resulted in no
detections. The second campaign was in an active window at 48 GHz which we
predicted from our modelling of chromaticity, resulting in eight burst
detections. The bursts were detected in a window of 1.35 days, 3.6 days
preceding the activity peak seen by CHIME, suggesting the chromaticity extends
to higher frequency. The detected bursts have narrower temporal widths and
larger spectral widths compared to lower frequencies. All of them have flat
polarization position angle sweeps and high polarization fractions. The bursts
also exhibit diffractive scintillation due to the Milky Way, following a
scaling, and vary significantly over time. We find that burst
rate across frequency scales as . Lastly, we examine
implications of the frequency dependency on the source models.Comment: 11 pages, 8 figures, comments welcome, submitted to MNRA
Modelling Annual Scintillation Velocity Variations of FRB 20201124A
Compact radio sources exhibit scintillation, an interference pattern arising
from propagation through inhomogeneous plasma, where scintillation patterns
encode the relative distances and velocities of the source, scattering
material, and Earth. In Main et al. 2022, we showed that the scintillation
velocity of the repeating fast radio burst FRB20201124A can be measured by
correlating pairs of burst spectra, and suggested that the scattering was
nearby the Earth at kpc from the low values of the scintillation
velocity and scattering timescale. In this work, we have measured the
scintillation velocity at 10 epochs spanning a year, observing an annual
variation which strongly implies the screen is within the Milky Way. Modelling
the annual variation with a 1D anisotropic or 2D isotropic screen results in a
screen distance pc or pc from
Earth respectively, possibly associated with the Local Bubble or the edge of
the Orion-Eridanus Superbubble. Continued monitoring, and using measurements
from other telescopes particularly at times of low effective velocity will help
probe changes in screen properties, and distinguish between screen models.
Where scintillation of an FRB originates in its host galaxy or local
environment, these techniques could be used to detect orbital motion, and probe
the FRB's local ionized environment.Comment: 5 pages, 5 Figures, submitted to MNRAS Letter
The Effects of Neutral Inertia on Ionospheric Currents in the High-Latitude Thermosphere Following a Geomagnetic Storm
Results of an experimental and theoretical investigation into the effects of the time dependent neutral wind flywheel on high-latitude ionospheric electrodynamics are presented. The results extend our previous work which used the National Center for Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) to theoretically simulate flywheel effects in the aftermath of a geomagnetic storm. The previous results indicated that the neutral circulation, set up by ion-neutral momentum coupling in the main phase of a geomagnetic storm, is maintained for several hours after the main phase has ended and may dominate height-integrated Hall currents and field-aligned currents for up to 4-5 hours. We extend the work of Deng et al. to include comparisons between the calculated time-dependent ionospheric Hall current system in the storm-time recovery period and that measured by instruments on board the Dynamics Explorer 2 (DE 2) satellite. Also, comparisons are made between calculated field-aligned currents and those derived from DE 2 magnetometer measurements. These calculations also allow us to calculate the power transfer rate (sometimes called the Poynting flux) between the magnetosphere and ionosphere. The following conclusions have been drawn: (1) Neutral winds can contribute significantly to the horizontal ionospheric current system in the period immediately following the main phase of a geomagnetic storm, especially over the magnetic polar cap and in regions of ion drift shear. (2) Neutral winds drive Hall currents that flow in the opposite direction to those driven by ion drifts. (3) The overall morphology of the calculated field-aligned current system agrees with previously published observations for the interplanetary magnetic field (IMF) B(sub Z) southward conditions, although the region I and region 2 currents are smeared by the TI(ICM model grid resolution. (4) Neutral winds can make significant contributions to the field-aligned current system when B(sub Z) northward conditions prevail following the main phase of a storm, but can account for only a fraction of the observed currents. (5) DE 2 measurements provide a demonstration of "local" (satellite-altitude) flywheel effects. (6) On the assumption that the magnetosphere acts as an insulator, we calculate neutral-wind-induced polarization electric fields of approx. 20-30 kV in the period immediately following the geomagnetic storm
Rotation measure variations in Galactic Centre pulsars
We report the results of an observational campaign using the Effelsberg 100-m
telescope of the pulsars J17462849, J17462850, J17462856 and
J17452912 located in the Central Molecular Zone (CMZ) close to the Galactic
centre in order to study rotation measure (RM) variations. We report for the
first time the RM value of PSR J17462850 to be rad
m. This pulsar shows significant variations of RM of rad
m over the course of months to years that suggest a strongly magnetized
environment. The structure function analysis of the RM of PSR J17462850
revealed a steep power-law index of comparable to the
value expected for isotropic turbulence. This pulsar also showed large
dispersion measure (DM) variation of pc cm in an event lasting
a few months where the RM increased by rad m. The large
difference in RM between PSR J17462849 and PSR J17462850 despite the
small angular separation reveals the presence of a magnetic field of at least
70 G in the CMZ and can explain the lack of polarization in the radio
images of the region. These results contribute to our understanding of the
magnetic field in the CMZ and show similarities between the RM behaviours of
these pulsars and some fast radio bursts (FRBs).Comment: Accepted for publication on Monthly Notices of the Royal Astronomical
Society, 13 pages, 7 figure
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