171 research outputs found
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The Brexit vote and currency markets
This paper studies the effect of the Brexit vote on the intraday correlation and volatility transmission among major currencies. We find that the vote causes an increase in the correlation among the safe-haven currencies of the Swiss franc and Japanese yen as well as gold, and also find a decrease in their correlation with the directly involved currencies of British sterling and the Euro. These changes are due to the appreciation of the former group and the depreciation of the latter group which represents a flight to quality of investors. We also observe a substantial decrease in volatility transmission between British sterling and the Euro following the Brexit vote due to lower levels of market integration. However the volatility transmission among the currencies has increased in general and their net spillover is positively correlated with their level of volatility and trading activities. Therefore we document the significant impact of the politically important Brexit vote on the high frequency correlation and volatility spillover in the foreign exchange market
Magnetic fields in Herbig Ae stars
Herbig Ae stars are young A-type stars in the pre-main sequence evolutionary
phase with masses of ~1.5-3 M_o. They show rather intense surface activity
(Dunkin et al. 1997) and infrared excess related to the presence of
circumstellar disks. Because of their youth, primordial magnetic fields
inherited from the parent molecular cloud may be expected, but no direct
evidence for the presence of magnetic fields on their surface, except in one
case (Donati et al. 1997), has been found until now. Here we report
observations of optical circular polarization with FORS 1 at the VLT in the
three Herbig Ae stars HD 139614, HD 144432 and HD 144668. A definite
longitudinal magnetic field at 4.8 sigma level, =-450+-93 G, has been
detected in the Herbig Ae star HD 139614. This is the largest magnetic field
ever diagnosed for a Herbig Ae star. A hint of a weak magnetic field is found
in the other two Herbig Ae stars, HD 144432 and HD 144668, for which magnetic
fields are measured at the ~1.6 sigma and ~2.5 sigma level respectively.
Further, we report the presence of circular polarization signatures in the Ca
II K line in the V Stokes spectra of HD 139614 and HD 144432, which appear
unresolved at the low spectral resolution achievable with FORS 1. We suggest
that models involving accretion of matter from the disk to the star along a
global stellar magnetic field of a specific geometry can account for the
observed Zeeman signatures.Comment: 4 pages, 3 figures, accepted for publication as a letter in A&
A VLT/NACO Survey for Triple and Quadruple Systems among Visual Pre-Main Sequence Binaries
This paper describes a systematic search for high-order multiplicity among
wide visual Pre-Main Sequence (PMS) binaries. We conducted an Adaptive Optics
survey of a sample of 58 PMS wide binaries from various star-forming regions,
which include 52 T Tauri systems with mostly K- and M-type primaries, with the
NIR instrument NACO at the VLT. Of these 52 systems, 7 are found to be triple
(2 new) and 7 quadruple (1 new). The new close companions are most likely
physically bound based on their probability of chance projection and, for some
of them, on their position on a color-color diagram. The corresponding degree
of multiplicity among wide binaries (number of triples and quadruples divided
by the number of systems) is 26.9 +/- 7.2% in the projected separation range
0.07-12 arcsec, with the largest contribution from the Taurus-Auriga cloud. We
also found that this degree of multiplicity is twice in Taurus compared to
Ophiuchus and Chamaeleon for which the same number of sources are present in
our sample. Considering a restricted sample composed of systems at distance
140-190pc, the degree of multiplicity is 26.8 +/- 8.1%, in the separation range
10/14 AU - 1700/2300 AU (30 binaries, 5 triples, 6 quadruples). The observed
frequency agrees with results from previous multiplicity surveys within the
uncertainties, although a significant overabundance of quadruple systems
compared to triple systems is apparent. Tentatively including the spectroscopic
pairs in our restricted sample and comparing the multiplicity fractions to
those measured for solar-type main-sequence stars in the solar neighborhood
leads to the conclusion that both the ratio of triples to binaries and the
ratio of quadruples to triples seems to be in excess among young stars. [...]Comment: 24 pages, accepted for publication in Astronomy & Astrophysic
The PAV trial: Does lactobacillus prevent post-antibiotic vulvovaginal candidiasis? Protocol of a randomised controlled trial [ISRCTN24141277]
BACKGROUND: Complementary and alternative medicines are used by many consumers, and increasingly are being incorporated into the general practitioner's armamentarium. Despite widespread usage, the evidence base for most complementary therapies is weak or non-existent. Post-antibiotic vulvovaginitis is a common problem in general practice, for which complementary therapies are often used. A recent study in Melbourne, Australia, found that 40% of women with a past history of vulvovaginitis had used probiotic Lactobacillus species to prevent or treat post-antibiotic vulvovaginitis. There is no evidence that this therapy is effective. This study aims to test whether oral or vaginal lactobacillus is effective in the prevention of post-antibiotic vulvovaginitis. METHODS/DESIGN: A randomised placebo-controlled blinded 2 × 2 factorial design is being used. General practitioners or pharmacists approach non-pregnant women, aged 18–50 years, who present with a non-genital infection requiring a short course of oral antibiotics, to participate in the study. Participants are randomised in a four group factorial design either to oral lactobacillus powder or placebo and either vaginal lactobacillus pessaries or placebo. These interventions are taken while on antibiotics and for four days afterwards or until symptoms of vaginitis develop. Women self collect a vaginal swab for culture of Candida species and complete a survey at baseline and again four days after completing their study medications. The sample size (a total of 496 – 124 in each factorial group) is calculated to identify a reduction of half in post-antibiotic vulvovaginitis from 23%, while allowing for a 25% drop-out. An independent Data Monitoring Committee is supervising the trial. Analysis will be intention-to-treat, with two pre-specified main comparisons: (i) oral lactobacillus versus placebo and (ii) vaginal lactobacillus versus placebo
Issues of ideology in English language education worldwide: an overview
The relatively limited consideration of ideology in mainstream theory and research of teaching the English language to speakers of other languages has arguably prevented the problematization of many taken-for-granted perceptions and practices of the field. In this article I attempt to bring part of this marginalized body of scholarship on issues of ideology in the area of English language teaching (ELT) to highlight its potential insights for the field. The article sets out from a view of ideology as the most fundamental beliefs in any social practice, which may provide a less-formidable conception of the term and lessen the divergence among the minority of ELT researchers and professionals that do concern themselves with ideology. Then, after a brief sketch of the notion of ideology of language (education), I present an overview of aspects of this marginal but vibrant stream of thought on issues of ideology in ELT worldwide. Overall, the discussion is aimed to act as a call for the further understanding and embracement of sociopolitically-sensitive and ideologically-informed approaches to ELT theory, research, and practice
Future directions in international financial integration research. A crowdsourced perspective
This paper is the result of a crowdsourced effort to surface perspectives on
the present and future direction of international finance. The authors are
researchers in financial economics who attended the INFINITI 2017 conference
in the University of Valencia in June 2017 and who participated in the
crowdsourcing via the Overleaf platform. This paper highlights the actual
state of scientific knowledge in a multitude of fields in finance and proposes
different directions for future research
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Stylized facts of intraday precious metals
This paper examines the stylized facts, correlation and interaction between volatility and returns at the 5-minute frequency for gold, silver, platinum and palladium from May 2000 to April 2015. We study the full sample period, as well as three subsamples to determine how high-frequency data of precious metals have developed over time. We find that over the full sample, the number of trades has increased substantially over time for each precious metal, while the bid-ask spread has narrowed over time, indicating an increase in liquidity and price efficiency. We also find strong evidence of periodicity in returns, volatility, volume and bid- ask spread. Returns and volume both experience strong intraday periodicity linked to the opening and closing of major markets around the world while the bid-ask spread is at its low- est when European markets are open. We also show a bilateral Granger causality between returns and volatility of each precious metal, which holds for the vast majority subsamples
X-rays from jet-driving protostars and T Tauri stars
(abridged:) We study X-rays from jet-driving protostars and T Tau stars. We
seek soft spectral components that may be due to shock emission, and
shock-induced emission displaced from the stellar position. Two stellar samples
are used, the first consisting of lightly absorbed T Tau stars with strong
jets, the other containing protostars with disks seen nearly edge-on. The
former sample was observed in the XMM-Newton Extended Survey of the Taurus
Molecular Cloud (XEST), while Chandra archival data provided observations of
the latter. We confirm the previously identified peculiar spectrum of DG Tau A
and find similar phenomenology in GV Tau and DP Tau, suggesting a new class of
X-ray spectra. These consist of a lightly absorbed, very soft component and a
strongly absorbed, very hard component. The latter is flaring while little
variability is detected in the former. The absorption of the harder component
is about an order of magnitude higher than expected from the optical extinction
assuming a standard gas-to-dust mass ratio. The flaring hard component
represents active coronal emission. Its strong absorption is attributed to mass
inflow from the accretion disk. The optical extinction is small because the
dust has sublimated at larger distances. The weakly absorbed soft component
cannot originate from the same location. Because the stars drive strong jets,
we propose that the X-rays are generated in shocks in the jets. We find that
for the three peculiar X-ray sources, the luminosity of the soft component
roughly scales with the equivalent width of the [OI] 6300A line formed in the
jets, and with the mass outflow rate. In the more strongly obscured protostars,
the soft component is entirely absorbed, and only the hard, coronal component
penetrates the envelope or the near-edge-on disk.Comment: 17 pages, 27 figures, A&A style. Accepted by A&A, to appear in a
special section/issue dedicated to the XMM-Newton Extended Survey of the
Taurus Molecular Cloud (XEST). Version with higher resolution figures
available at http://www.issibern.ch/teams/Taurus/papers.html or
http://www.astro.phys.ethz.ch/papers/guedel/guedel_p_nf.htm
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