7,688 research outputs found
Reply to `Comment on ``Helmholtz Theorem and the V-Gauge in the Problem of Superluminal and Instantaneous Signals in Classical Electrodynamics" by A. Chubykalo Et Al' by J. A. Heras [FOUND. Phys. Lett. vol. 19(6) p. 579 (2006)]
This is the reply to `COMMENT ON ``HELMHOLTZ THEOREM AND THE V-GAUGE IN THE
PROBLEM OF SUPERLUMINAL AND INSTANTANEOUS SIGNALS IN CLASSICAL ELECTRODYNAMICS"
BY A. CHUBYKALO ET AL' BY J. A. HERAS [FOUND. PHYS. LETT. vol. 19(6) p. 579
(2006)]Comment: 5 pages, submitted to Foundations of Physic
Evaluation of PCR as a diagnostic mass-screening tool to detect Leishmania (Viannia) spp. in domestic dogs (Canis familiaris).
Several studies have suggested that the PCR could be used in epidemiological mass-screening surveys to detect Leishmania (Viannia) spp. infection in human and animal hosts. Dogs from an area of Leishmania braziliensis and Leishmania peruviana endemicity were screened for American cutaneous leishmaniasis (ACL) infection by established PCR-based and enzyme-linked immunosorbent antibody test (ELISA) protocols. PCR detected Leishmania (Viannia) infection in a total of 90 of 1,066 (8.4%) dogs: 32 of 368 (8.7%), 65 of 769 (8.5%), and 7 of 42 (16.7%) dogs were PCR positive by testing of whole blood, buffy coat, and bone marrow aspirates, respectively. ELISA detected infection in 221 of 1,059 (20.9%) tested dogs. The high prevalence of Leishmania (Viannia) detected by PCR and ELISA in both asymptomatic (7.5 and 19.2%, respectively) and symptomatic (32 and 62.5%, respectively) dogs is further circumstantial evidence for their suspected role as reservoir hosts of ACL. However, the low sensitivity of PCR (31%) compared to ELISA (81%) indicates that PCR cannot be used for mass screening of samples in ACL epidemiological studies. Unless more-sensitive PCR protocols were to be developed, its use should be restricted to the diagnosis of active (canine and human) cases and to the parasitological monitoring of patients after chemotherapy
New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools: II. SDSS DR7 vs UKIDSS LAS DR6, SDSS DR7 vs UKIDSS LAS DR8, SDSS DR9 vs UKIDSS LAS DR10, and SDSS DR7 vs 2MASS
We aim at developing an efficient method to search for late-type subdwarfs
(metal-depleted dwarfs with spectral types >M5) to improve the current
statistics. Our objectives are: improve our knowledge of metal-poor low-mass
dwarfs, bridge the gap between the late-M and L types, determine their surface
density, and understand the impact of metallicity on the stellar and substellar
mass function.
We carried out a search cross-matching the SDSS, 2MASS, and UKIDSS using
STILTS, Aladin, and Topcat. We considered different photometric and proper
motion criteria for our selection. We identified 29 and 71 late-type subdwarf
candidates in each cross-correlation over 8826 and 3679 square degrees,
respectively. We obtained low-resolution optical spectra for 71 of our
candidates with GTC, NOT, and VLT and retrieved spectra for 30 candidates from
the SDSS spectroscopic database. We classified 92 candidates based on 101
optical spectra using two methods: spectral indices and comparison with
templates of known subdwarfs.
We confirmed 86% and 94% of the candidates as late-type subdwarfs from the
SDSS vs 2MASS and SDSS vs UKIDSS cross-matches, respectively. These subdwarfs
have spectral types ranging between M5 and L0.5 and SDSS magnitudes in the
r=19.4-23.3 mag range. Our new late-type M discoveries include 49 subdwarfs, 25
extreme subdwarfs, six ultrasubdwarfs, one subdwarf/extreme subdwarf, and two
dwarfs/subdwarfs. We derived a surface density of late-type subdwarfs of
0.040 per square degree in the SDSS DR7 vs UKIDSS LAS DR10
cross-match. We also checked the AllWISE photometry of known and new subdwarfs
and found that mid-infrared colours of M subdwarfs do not appear to differ from
their solar-metallicity counterparts of similar spectral types. However, the
J-W2 and J-W1 colours are bluer for lower metallicity dwarfs. (abstract
strongly abridged)Comment: 28 pages, 4 Tables, 10 figures, 1 appendix. Accepted to A&A.
Photometry and spectra available in a dedicated archive on late-type
subdwarfs at http://svo2.cab.inta-csic.es/vocats/ltsa
Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - VII. V1200 Centauri: a bright triple in the Hyades moving group
We present the orbital and physical parameters of the detached eclipsing
binary V1200~Centauri (ASAS~J135218-3837.3) from the analysis of spectroscopic
observations and light curves from the \textit{All Sky Automated Survey} (ASAS)
and SuperWASP database. The radial velocities were computed from the
high-resolution spectra obtained with the OUC 50-cm telescope and PUCHEROS
spectrograph and with 1.2m Euler telescope and CORALIE spectrograph using the
cross-correlation technique \textsc{todcor}. We found that the absolute
parameters of the system are M, M, R, R.
We investigated the evolutionary status and kinematics of the binary and our
results indicate that V1200~Centauri is likely a member of the Hyades moving
group, but the largely inflated secondary's radius may suggest that the system
may be even younger, around 30 Myr. We also found that the eclipsing pair is
orbited by another, stellar-mass object on a 351-day orbit, which is unusually
short for hierarchical triples. This makes V1200 Cen a potentially interesting
target for testing the formation models of multiple stars.Comment: Accepted for publication in MNRAS, 8 pages, 4 figure
The nova V1369 Cen -- a short review
We briefly present the spectroscopic evolution of the recent outburst of the
classical nova V1369 Cen, and the presence of a narrow absorption line
identified as due to the resonance of neutral lithium at 6708 \AA. We also
discuss the consequences for the chemical evolution of lithium in the Galaxy.Comment: 8 pages, 5 figures, 2 tables. To appear in the proceedings of the
conference "The Golden Age of Cataclysmic Variables and Related Objects -
III" held in Palermo, Italy, 7-12 September 201
The glitch activity of neutron stars
We present a statistical study of the glitch population and the behaviour of
the glitch activity across the known population of neutron stars. An unbiased
glitch database was put together based on systematic searches of radio timing
data of 898 rotation-powered pulsars obtained with the Jodrell Bank and Parkes
observatories. Glitches identified in similar searches of 5 magnetars were also
included. The database contains 384 glitches found in the rotation of 141 of
these neutron stars. We confirm that the glitch size distribution is at least
bimodal, with one sharp peak at approximately , which we
call large glitches, and a broader distribution of smaller glitches. We also
explored how the glitch activity , defined as the mean
frequency increment per unit of time due to glitches, correlates with the spin
frequency , spin-down rate , and various combinations of
these, such as energy loss rate, magnetic field, and spin-down age. It is found
that the activity is insensitive to the magnetic field and that it correlates
strongly with the energy loss rate, though magnetars deviate from the trend
defined by the rotation-powered pulsars. However, we find that a constant ratio
is consistent with the behaviour
of all rotation-powered pulsars and magnetars. This relation is dominated by
large glitches, which occur at a rate directly proportional to .
The only exception are the rotation-powered pulsars with the highest values of
, such as the Crab pulsar and PSR B054069, which exhibit a much
smaller glitch activity, intrinsically different from each other and from the
rest of the population. The activity due to small glitches also shows an
increasing trend with , but this relation is biased by selection
effects.Comment: Accepted for publication in A&
Antiparasitic activity of chicory (Cichorium intybus) and its natural bioactive compounds in livestock: a review
Increasing drug resistance in gastrointestinal (GI) parasites of livestock and concerns about chemical residues in animal products and the environment are driving the development of alternative control strategies that are less reliant on the use of synthetic drugs. An increasingly investigated approach is the use of bioactive forages with antiparasitic properties as part of the animal’s diet (nutraceuticals) or as potential sources of novel, natural parasiticides. Chicory (Cichorium intybus) is a multi-purpose crop and one of the most promising bioactive forages in temperate regions, and numerous in vivo trials have explored its potential against parasitic nematodes in livestock. However, it is unclear whether chicory can induce a direct and broad activity against various GI parasites in different livestock species, and the levels of chicory in the diet that are required to exert an efficient antiparasitic effect. Moreover, the mechanisms leading to the reported parasiticidal activity of chicory are still largely unknown, and its bioactive phytochemicals have only recently been investigated. In this review, we summarise the progress in the study of the antiparasitic activity of chicory and its natural bioactive compounds against GI parasites in livestock, through examination of the published literature. The available evidence indicates that feeding chicory can reduce faecal egg counts and/or worm burdens of abomasal nematodes, but not infections with intestinal worms, in ruminants. Highly chicory-rich diets (≥ 70% of chicory dry matter in the diet) may be necessary to directly affect abomasal parasitism. Chicory is known to synthesise several bioactive compounds with potential antiparasitic activity, but most research has been devoted to the role of sesquiterpene lactones (SL). Recent in vitro studies have confirmed direct and potent activity of SL-rich extracts from chicory against different GI helminths of livestock. Chicory SL have also been reported to exhibit antimalarial properties and its potential antiprotozoal activity in livestock remains to be evaluated. Furthermore, the detailed identification of the main antiparasitic metabolites of chicory and their pharmacokinetics need further confirmation. Research gaps and perspectives on the potential use of chicory as a nutraceutical forage and a source of bioactive compounds for parasite control in livestock are discussed
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