192 research outputs found
Fundamental and financial influences on the co-movement of oil and gas prices
As speculative flows into commodity futures are expected to link commodity prices more strongly to equity indices, we investigate whether this process also creates increased correlations amongst the commodities themselves. Considering U.S. oil and gas futures, we investigate whether common factors, derived from a large international data set of real and nominal macroeconomic variables by means of the large approximate factor models methodology, are able to explain both returns and whether, beyond these fundamental common factors, the residuals remain correlated. We further investigate a possible explanation for this residual correlation by using some proxies for trading intensity derived from CFTC publicly available data, showing most notably that the proxy for speculation in the oil market increases the oil-gas correlation. We thus identify the central role
of financial activities in shaping the link between oil and gas returns
The VIRMOS deep imaging survey: I. overview and survey strategy
This paper presents the CFH12K-VIRMOS survey: a deep B, V, R and I imaging
survey in four fields totalling more than 17 deg^2, conducted with the 30x40
arcmin^2 field CFH-12K camera. The survey is intended to be a multi-purpose
survey used for a variety of science goals, including surveys of very high
redshift galaxies and weak lensing studies.
Four high galactic latitude fields, each 2x2 deg^2, have been selected along
the celestial equator: 0226-04, 1003+01, 1400+05, and 2217+00. The 16 deg^2 of
the "wide" survey are covered with exposure times of 2h, 1.5h, 1h, 1h, while
the 1.3x1 deg^2 area of the "deep" survey at the center of the 0226-04 field is
covered with exposure times of 7h, 4.5h, 3h, 3h, in B,V,R and I respectively.
The data is pipeline processed at the Terapix facility at the Institut
d'Astrophysique de Paris to produce large mosaic images. The catalogs produced
contain the positions, shape, total and aperture magnitudes for the 2.175
million objects. The depth measured (3sigma in a 3 arc-second aperture) is
I_{AB}=24.8 in the ``Wide'' areas, and I_{AB}=25.3 in the deep area. Careful
quality control has been applied on the data as described in joint papers.
These catalogs are used to select targets for the VIRMOS-VLT Deep Survey, a
large spectroscopic survey of the distant universe (Le F\`evre et al., 2003).
First results from the CFH12K-VIRMOS survey have been published on weak lensing
(e.g. van Waerbeke & Mellier 2003).
Catalogs and images are available through the VIRMOS database environment
under Oracle ({\tt http://www.oamp.fr/virmos}). They will be open for general
use on July 1st, 2003.Comment: 17 pages including 9 figures, submitted to A&
Cosmic Shear Statistics and Cosmology
We report a measurement of cosmic shear correlations using an effective area
of 6.5 sq. deg. of the VIRMOS deep imaging survey in progress at the
Canada-France-Hawaii Telescope. We measured various shear correlation
functions, the aperture mass statistic and the top-hat smoothed variance of the
shear with a detection significance exceeding 12 sigma for each of them. We
present results on angular scales from 3 arc-seconds to half a degree. The
consistency of different statistical measures is demonstrated and confirms the
lensing origin of the signal through tests that rely on the scalar nature of
the gravitational potential. For Cold Dark Matter models we find at the 95% confidence level. The
measurement over almost three decades of scale allows to discuss the effect of
the shape of the power spectrum on the cosmological parameter estimation. The
degeneracy on sigma_8-Omega_0 can be broken if priors on the shape of the
linear power spectrum (that can be parameterized by Gamma) are assumed. For
instance, with Gamma=0.21 and at the 95% confidence level, we obtain
0.60.65 and
Omega_0<0.4 for flat (Lambda-CDM) models. From the tangential/radial modes
decomposition we can set an upper limit on the intrinsic shape alignment, which
was recently suggested as a possible contribution to the lensing signal. Within
the error bars, there is no detection of intrinsic shape alignment for scales
larger than 1'.Comment: 13 pages, submitted to A&
Cosmic Shear Analysis with CFHTLS Deep data
We present the first cosmic shear measurements obtained from the T0001
release of the Canada-France-Hawaii Telescope Legacy Survey. The data set
covers three uncorrelated patches (D1, D3 and D4) of one square degree each
observed in u*, g', r', i' and z' bands, out to i'=25.5. The depth and the
multicolored observations done in deep fields enable several data quality
controls. The lensing signal is detected in both r' and i' bands and shows
similar amplitude and slope in both filters. B-modes are found to be
statistically zero at all scales. Using multi-color information, we derived a
photometric redshift for each galaxy and separate the sample into medium and
high-z galaxies. A stronger shear signal is detected from the high-z subsample
than from the low-z subsample, as expected from weak lensing tomography. While
further work is needed to model the effects of errors in the photometric
redshifts, this results suggests that it will be possible to obtain constraints
on the growth of dark matter fluctuations with lensing wide field surveys. The
various quality tests and analysis discussed in this work demonstrate that
MegaPrime/Megacam instrument produces excellent quality data. The combined Deep
and Wide surveys give sigma_8= 0.89 pm 0.06 assuming the Peacock & Dodds
non-linear scheme and sigma_8=0.86 pm 0.05 for the halo fitting model and
Omega_m=0.3. We assumed a Cold Dark Matter model with flat geometry.
Systematics, Hubble constant and redshift uncertainties have been marginalized
over. Using only data from the Deep survey, the 1 sigma upper bound for w_0,
the constant equation of state parameter is w_0 < -0.8.Comment: 14 pages, 16 figures, accepted A&
Cost-Effectiveness of Highly Active Antiretroviral Therapy in South Africa
BACKGROUND: Little information exists on the impact of highly active antiretroviral therapy (HAART) on health-care provision in South Africa despite increasing scale-up of access to HAART and gradual reduction in HAART prices. METHODS AND FINDINGS: Use and cost of services for 265 HIV-infected adults without AIDS (World Health Organization [WHO] stage 1, 2, or 3) and 27 with AIDS (WHO stage 4) receiving HAART between 1995 and 2000 in Cape Town were compared with HIV-infected controls matched for baseline WHO stage, CD4 count, age, and socioeconomic status, who did not receive antiretroviral therapy (ART; No-ART group). Costs of service provision (January 2004 prices, US730 per patient-year (PPY), whereas scenario 2 was based on the anticipated public-sector price for locally manufactured drug of 950 for the No-ART group versus 793 PPY for the HAART group for scenario 1 and 2, respectively, whereas the incremental cost per life-year gained (LYG) was 675 for scenario 2. For patients with AIDS, mean inpatients days PPY was 2.04 (95% CI: 1.63–2.52) for the HAART versus 15.36 (95% CI: 13.97–16.85) for the No-ART group. Mean outpatient visits PPY was 7.62 (95% CI: 6.81–8.49) compared with 6.60 (95% CI: 5.69–7.62) respectively. Average service provision PPY was 1,513 and 1,557 to 111 for patients with AIDS. CONCLUSION: HAART is a cost-effective intervention in South Africa, and cost saving when HAART prices are further reduced. Our estimates, however, were based on direct costs, and as such the actual cost saving might have been underestimated if indirect costs were also included
piRNAs Can Trigger a Multigenerational Epigenetic Memory in the Germline of C. elegans
SummaryTransgenerational effects have wide-ranging implications for human health, biological adaptation, and evolution; however, their mechanisms and biology remain poorly understood. Here, we demonstrate that a germline nuclear small RNA/chromatin pathway can maintain stable inheritance for many generations when triggered by a piRNA-dependent foreign RNA response in C.elegans. Using forward genetic screens and candidate approaches, we find that a core set of nuclear RNAi and chromatin factors is required for multigenerational inheritance of environmental RNAi and piRNA silencing. These include a germline-specific nuclear Argonaute HRDE1/WAGO-9, a HP1 ortholog HPL-2, and two putative histone methyltransferases, SET-25 and SET-32. piRNAs can trigger highly stable long-term silencing lasting at least 20 generations. Once established, this long-term memory becomes independent of the piRNA trigger but remains dependent on the nuclear RNAi/chromatin pathway. Our data present a multigenerational epigenetic inheritance mechanism induced by piRNAs.Graphical AbstractHighlights► Multigenerational inheritance and piRNAs converge on same nuclear silencing pathway ► HRDE1/WAGO-9 and chromatin factors required for inheritance of piRNA silencing ► piRNAs can induce multigenerational silencing for more than 20 generations. ► Long-term memory independent of piRNA triggers but remains dependent on nuclear pathwayMultigenerational inheritance and piRNAs converge on same silencing pathway, in which both nuclear WAGOs and chromatin factors are required. The piRNA trigger can be lost, but the nuclear silencing pathway maintains the silencing for more than 20 generations
Combined Discrete-Continuum Analysis for Ballasted Rail Tracks
A study on the load-deformation behaviour of railway ballast aggregates subjected to cyclic loadings using a combined discrete-continuum modelling approach is presented. Discrete ballast particles are simulated in the DEM and the continuum-based subgrade is simulated by the FDM. Interface elements are generated to transmit contact forces and displacements between the two domains (i.e. discrete and continuum) whereby the DEM exchanges contact forces to the FDM, and then the FDM transfers the displacement back to the DEM. Distributions of contact forces, coordination number, stress contours on the subgrade and corresponding number of broken bonds (representing ballast breakage) are analysed
Acute weight gain, gender, and therapeutic response to antipsychotics in the treatment of patients with schizophrenia
BACKGROUND: Previous research indicated that women are more vulnerable than men to adverse psychological consequences of weight gain. Other research has suggested that weight gain experienced during antipsychotic therapy may also psychologically impact women more negatively. This study assessed the impact of acute treatment-emergent weight gain on clinical and functional outcomes of patients with schizophrenia by patient gender and antipsychotic treatment (olanzapine or haloperidol). METHODS: Data were drawn from the acute phase (first 6-weeks) of a double-blind randomized clinical trial of olanzapine versus haloperidol in the treatment of 1296 men and 700 women with schizophrenia-spectrum disorders. The associations between weight change and change in core schizophrenia symptoms, depressive symptoms, and functional status were examined post-hoc for men and women and for each medication group. Core schizophrenia symptoms (positive and negative) were measured with the Brief Psychiatric Rating Scale (BPRS), depressive symptoms with the BPRS Anxiety/Depression Scale and the Montgomery-Asberg Depression Rating Scale, and functional status with the mental and physical component scores on the Medical Outcome Survey-Short Form 36. Statistical analysis included methods that controlled for treatment duration. RESULTS: Weight gain during 6-week treatment with olanzapine and haloperidol was significantly associated with improvements in core schizophrenia symptoms, depressive symptoms, mental functioning, and physical functioning for men and women alike. The conditional probability of clinical response (20% reduction in core schizophrenia symptom), given a clinically significant weight gain (at least 7% of baseline weight), showed that about half of the patients who lost weight responded to treatment, whereas three-quarters of the patients who had a clinically significant weight gain responded to treatment. The positive associations between therapeutic response and weight gain were similar for the olanzapine and haloperidol treatment groups. Improved outcomes were, however, more pronounced for the olanzapine-treated patients, and more olanzapine-treated patients gained weight. CONCLUSIONS: The findings of significant relationships between treatment-emergent weight gain and improvements in clinical and functional status at 6-weeks suggest that patients who have greater treatment-emergent weight gain are more likely to benefit from treatment with olanzapine or haloperidol regardless of gender
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