13,707 research outputs found
Market Efficiency in Foreign Exchange Markets
We investigate the relative market efficiency in financial market data, using
the approximate entropy(ApEn) method for a quantification of randomness in time
series. We used the global foreign exchange market indices for 17 countries
during two periods from 1984 to 1998 and from 1999 to 2004 in order to study
the efficiency of various foreign exchange markets around the market crisis. We
found that on average, the ApEn values for European and North American foreign
exchange markets are larger than those for African and Asian ones except Japan.
We also found that the ApEn for Asian markets increase significantly after the
Asian currency crisis. Our results suggest that the markets with a larger
liquidity such as European and North American foreign exchange markets have a
higher market efficiency than those with a smaller liquidity such as the
African and Asian ones except Japan
Nonparametric Bayesian identification of jump systems with sparse dependencies
Many nonlinear dynamical phenomena can be effectively modeled by a system that switches among a set of conditionally linear dynamical modes. We consider two such Markov jump linear systems: the switching linear dynamical system (SLDS) and the switching vector autoregressive (S-VAR) process. In this paper, we present a nonparametric Bayesian approach to identifying an unknown number of persistent, smooth dynamical modes by utilizing a hierarchical Dirichlet process prior. We additionally employ automatic relevance determination to infer a sparse set of dynamic dependencies. The utility and flexibility of our models are demonstrated on synthetic data and a set of honey bee dances.United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative (Grant FA9550-06-1-0324)United States. Army Research Office (Grant W911NF-06-1- 0076
A high-resolution spectroscopic search for multiple populations in the 2 Gyr old cluster NGC 1846
We present detailed C, O, Na, Mg, Si, Ca, Ti, V, Fe, Zr, Ba, and Eu abundance
measurements for 20 red giant branch (RGB) stars in the LMC star cluster NGC
1846 ([Fe/H] = -0.59). This cluster is 1.95 Gyr old and lies just below the
supposed lower age limit (2 Gyr) for the presence of multiple populations in
massive star clusters. Our measurements are based on high and low-resolution
VLT/FLAMES spectra combined with photometric data from HST. Corrections for
non-local thermodynamic equilibrium effects are also included for O, Na, Mg,
Si, Ca, Fe and Ba. Our results show that there is no evidence for multiple
populations in this cluster based on the lack of any intrinsic star-to-star
spread in the abundances of Na and O: we place 95 \% confidence limits on the
intrinsic dispersion for these elements of and dex,
respectively. However, we do detect a significant spread in the carbon
abundances, indicating varying evolutionary mixing occurring on the RGB that
increases with luminosity. Overall, the general abundance patterns for NGC 1846
are similar to those seen in previous studies of intermediate-age LMC star
clusters and field stars
The Quality of Life Questionnaire Core 30 (QLQ-C30) and Functional Assessment of Cancer - General (FACT-G) differ in responsiveness, relative efficiency, and therefore required sample size
The SkyMapper search for extremely metal-poor stars in the Large Magellanic Cloud
We present results of a search for extremely metal-poor (EMP) stars in the
Large Magellanic Cloud, which can provide crucial information about the
properties of the first stars as well as on the formation conditions prevalent
during the earliest stages of star formation in dwarf galaxies. Our search
utilised SkyMapper photometry, together with parallax and proper motion cuts
(from Gaia), colour-magnitude cuts (by selecting the red giant branch region)
and finally a metallicity-sensitive cut. Low-resolution spectra of a sample of
photometric candidates were taken using the ANU 2.3m telescope/WiFeS
spectrograph, from which 7 stars with [Fe/H] -2.75 were identified, two
of which have [Fe/H] -3. Radial velocities, derived from the CaII
triplet lines, closely match the outer rotation curve of the LMC for the
majority of the candidates in our sample. Therefore, our targets are robustly
members of the LMC based on their 6D phase-space information (coordinates,
spectrophotometric distance, proper motions and radial velocities), and they
constitute the most metal-poor stars so far discovered in this galaxy.Comment: Accepted for publication in MNRA
Critical behavior of the planar magnet model in three dimensions
We use a hybrid Monte Carlo algorithm in which a single-cluster update is
combined with the over-relaxation and Metropolis spin re-orientation algorithm.
Periodic boundary conditions were applied in all directions. We have calculated
the fourth-order cumulant in finite size lattices using the single-histogram
re-weighting method. Using finite-size scaling theory, we obtained the critical
temperature which is very different from that of the usual XY model. At the
critical temperature, we calculated the susceptibility and the magnetization on
lattices of size up to . Using finite-size scaling theory we accurately
determine the critical exponents of the model and find that =0.670(7),
=1.9696(37), and =0.515(2). Thus, we conclude that the
model belongs to the same universality class with the XY model, as expected.Comment: 11 pages, 5 figure
Cosmic Microwave Background Anisotropy Window Functions Revisited
The primary results of most observations of cosmic microwave background (CMB)
anisotropy are estimates of the angular power spectrum averaged through some
broad band, called band-powers. These estimates are in turn what are used to
produce constraints on cosmological parameters due to all CMB observations.
Essential to this estimation of cosmological parameters is the calculation of
the expected band-power for a given experiment, given a theoretical power
spectrum. Here we derive the "band power" window function which should be used
for this calculation, and point out that it is not equivalent to the window
function used to calculate the variance. This important distinction has been
absent from much of the literature: the variance window function is often used
as the band-power window function. We discuss the validity of this assumed
equivalence, the role of window functions for experiments that constrain the
power in {\it multiple} bands, and summarize a prescription for reporting
experimental results. The analysis methods detailed here are applied in a
companion paper to three years of data from the Medium Scale Anisotropy
Measurement.Comment: 5 pages, 1 included .eps figure, PRD in press---final published
versio
How well can we measure and understand foregrounds with 21 cm experiments?
Before it becomes a sensitive probe of the Epoch of Reionization, the Dark
Ages, and fundamental physics, 21 cm tomography must successfully contend with
the issue of foreground contamination. Broadband foreground sources are
expected to be roughly four orders of magnitude larger than any cosmological
signals, so precise foreground models will be necessary. Such foreground models
often contain a large number of parameters, reflecting the complicated physics
that governs foreground sources. In this paper, we concentrate on spectral
modeling (neglecting, for instance, bright point source removal from spatial
maps) and show that 21 cm tomography experiments will likely not be able to
measure these parameters without large degeneracies, simply because the
foreground spectra are so featureless and generic. However, we show that this
is also an advantage, because it means that the foregrounds can be
characterized to a high degree of accuracy once a small number of parameters
(likely three or four, depending on one's instrumental specifications) are
measured. This provides a simple understanding for why 21 cm foreground
subtraction schemes are able to remove most of the contaminants by suppressing
just a small handful of simple spectral forms. In addition, this suggests that
the foreground modeling process should be relatively simple and will likely not
be an impediment to the foreground subtraction schemes that are necessary for a
successful 21 cm tomography experiment.Comment: 15 pages, 9 figures, 2 tables; Replaced with accepted MNRAS version
(slight quantitative changes to plots and tables, no changes to any
conclusions
Reproductive isolation between two populations of Aglaoctenus lagotis , a funnel-web wolf spider
Aglaoctenus lagotis (Lycosidae: Sosippinae) is a spider that, in contrast to the predominant wandering habit of the family, constructs funnel webs. The species is widely distributed throughout the Neotropics and is credited with high levels of intraspecific variation. Here, we evaluate whether reproductive isolating barriers operate between some populations of A. lagotis. We used heterotypic encounters between individuals from two distant localities: southern Uruguay (SU) and Central Argentina (CA). Additionally, we used spiders from an ntermediate locality, western Uruguay (WU), where both forms of the species overlap (SU.WU was used to describe individuals from WU reminiscent of those from SU; and CA.WU was used to describe individuals from WU reminiscent of those from CA). No copulations occurred between SU and CA individuals, whereas a single and atypical copulation occurred between SU.WU and CA.WU individuals. Attacks (only by females on males) were rare. In tests of choice based on silk cues, SU males did not prefer homotypic cues but almost did not court CA females, whereas CA males preferred homotypic cues but usually courted heterotypic females. These findings, with a previously reported temporal asynchrony between populations, suggest the occurrence of reproductive isolation between both spider forms and a speciation process favoured by the wide distribution and plasticity of the species.Fil: González Pérez, María de la Macarena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Animal I; ArgentinaFil: Peretti, Alfredo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Animal I; ArgentinaFil: Costa, Fernando G.. Instituto de Investigaciones Biológicas "Clemente Estable"; Urugua
Acupuncture in Oncology: The Effectiveness of Acupuncture May Not Depend on Needle Retention Duration
© 2017, © The Author(s) 2017. Background. Guidelines surrounding optimum needle retention duration in acupuncture have not been established, despite a growing evidence base for acupuncture over recent decades. This retrospective study explored the effect of varying acupuncture needle retention durations in cancer patients. Method. Patients received either 2 (n = 35), 10 (n = 53), or 20 minutes (n = 54) of acupuncture once a week for 6 weeks. Outcomes of anxiety and depression, stress, fatigue, and quality of life (QOL), with the Hospital Anxiety and Depression Scale, Perceived Stress Scale, Functional Assessment of Cancer Therapy–Fatigue, and European Organization for Research and Treatment of Cancer Quality of Life, were measured at baseline and at 6 weeks following the intervention. Results. The mean age of participants was 58 years (n = 152). The majority were female, diagnosed with breast cancer. Depression, stress, fatigue, and QOL were significantly improved in all 3 groups at 6 weeks postintervention. No significant differences in all outcomes were found between the 3 groups (≤2 vs 10 minutes vs 20 minutes). There were no differences with the satisfaction of the acupuncture services and perceived efficacy of acupuncture among the 3 groups. More than 95% of participants indicated that they would recommend acupuncture to other cancer patients, friends, and their family members. Conclusion. The efficacy of acupuncture may not only depend on needle retention duration, but may also be associated with multiple factors. Considering the limitations of this study design, robust randomized controlled studies are warranted to confirm the findings
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