8,586 research outputs found
Exchange Rate Mean Reversion within a Target Zone: Evidence from a Country on the Periphery of the ERM
The aim of this study is to assess to what extent the Portuguese participation in the European Monetary System (EMS) has been characterized by mean reverting behaviour, as predicted by the exchange rate target zone model developed by Krugman (1991). For this purpose, a new class of mean reversion tests is introduced. The empirical analysis of mean reversion in the Portuguese exchange rate shows that most of the traditional unit root and stationarity tests point to the nonstationarity of the exchange rate within the band. However, using a set of variance-ratio tests, it was possible to detect the presence of a martingale difference sequence. This suggests that the Portuguese foreign exchange market has functioned efficiently, allowing us to conclude that the adoption of an exchange rate target zone regime has contributed decisively to the creation of the macroeconomic stability conditions necessary for the participation of Portugal in the euro area.difference sequence, mean reversion, stationarity, target zones and unit roots
VarDict: a novel and versatile variant caller for next-generation sequencing in cancer research
Accurate variant calling in next generation sequencing (NGS) is critical to understand cancer genomes better. Here we present VarDict, a novel and versatile variant caller for both DNA- and RNA-sequencing data. VarDict simultaneously calls SNV, MNV, InDels, complex and structural variants, expanding the detected genetic driver landscape of tumors. It performs local realignments on the fly for more accurate allele frequency estimation. VarDict performance scales linearly to sequencing depth, enabling ultra-deep sequencing used to explore tumor evolution or detect tumor DNA circulating in blood. In addition, VarDict performs amplicon aware variant calling for polymerase chain reaction (PCR)-based targeted sequencing often used in diagnostic settings, and is able to detect PCR artifacts. Finally, VarDict also detects differences in somatic and loss of heterozygosity variants between paired samples. VarDict reprocessing of The Cancer Genome Atlas (TCGA) Lung Adenocarcinoma dataset called known driver mutations in KRAS, EGFR, BRAF, PIK3CA and MET in 16% more patients than previously published variant calls. We believe VarDict will greatly facilitate application of NGS in clinical cancer research
High-performance 3D waveguide architecture for astronomical pupil-remapping interferometry
The detection and characterisation of extra-solar planets is a major theme
driving modern astronomy, with the vast majority of such measurements being
achieved by Doppler radial-velocity and transit observations. Another technique
-- direct imaging -- can access a parameter space that complements these
methods, and paves the way for future technologies capable of detailed
characterization of exoplanetary atmospheres and surfaces. However achieving
the required levels of performance with direct imaging, particularly from
ground-based telescopes which must contend with the Earth's turbulent
atmosphere, requires considerable sophistication in the instrument and
detection strategy. Here we demonstrate a new generation of photonic
pupil-remapping devices which build upon the interferometric framework
developed for the {\it Dragonfly} instrument: a high contrast waveguide-based
device which recovers robust complex visibility observables. New generation
Dragonfly devices overcome problems caused by interference from unguided light
and low throughput, promising unprecedented on-sky performance. Closure phase
measurement scatter of only has been achieved, with waveguide
throughputs of . This translates to a maximum contrast-ratio
sensitivity (between the host star and its orbiting planet) at
(1 detection) of (when a conventional
adaptive-optics (AO) system is used) or (for typical
`extreme-AO' performance), improving even further when random error is
minimised by averaging over multiple exposures. This is an order of magnitude
beyond conventional pupil-segmenting interferometry techniques (such as
aperture masking), allowing a previously inaccessible part of the star to
planet contrast-separation parameter space to be explored
Modelling large motion events in fMRI studies of patients with epilepsy
EEG-correlated fMRI can provide localisation information on the generators of epileptiform discharges in patients with focal epilepsy. To increase the technique's clinical potential, it is important to consider ways of optimising the yield of each experiment while minimizing the risk of false-positive activation. Head motion can lead to severe image degradation and result in false-positive activation and is usually worse in patients than in healthy subjects. We performed general linear model fMRI data analysis on simultaneous EEG–fMRI data acquired in 34 cases with focal epilepsy. Signal changes associated with large inter-scan motion events (head jerks) were modelled using modified design matrices that include ‘scan nulling’ regressors. We evaluated the efficacy of this approach by mapping the proportion of the brain for which F-tests across the additional regressors were significant. In 95% of cases, there was a significant effect of motion in 50% of the brain or greater; for the scan nulling effect, the proportion was 36%; this effect was predominantly in the neocortex. We conclude that careful consideration of the motion-related effects in fMRI studies of patients with epilepsy is essential and that the proposed approach can be effective
Modeling Changes in Measured Conductance of Thin Boron Carbide Semiconducting Films Under Irradiation
Semiconducting, p-type, amorphous partially dehydrogenated boron carbide films (a-B10C2+x:Hy) were deposited utilizing plasma enhanced chemical vapor deposition (PECVD) onto n-type silicon thus creating a heterojunction diode. A model was developed for the conductance of the device as a function of perturbation frequency (��) that incorporates changes of the electrical properties for both the a-B10C2+x:Hy film and the silicon substrate when irradiated. The virgin model has 3 independent variables (R1, C1, R3), and 1 dependent variable (��). Samples were then irradiated with 200 keV He+ ions, and the conductance model was matched to the measured data. It was found that initial irradiation (0.1 displacements per atom (dpa) equivalent) resulted in a decrease in the parallel junction resistance parameter from 6032 Ω to 2705 Ω. Further irradiation drastically increased the parallel junction resistance parameter to 39000 Ω (0.2 dpa equivalent), 77440 Ω (0.3 dpa equivalent), and 190000 Ω (0.5 dpa equivalent). It is believed that the initial irradiation causes type inversion of the silicon substrate changing the original junction from a p-n to a p-p+ with a much lower barrier height leading to a lower junction resistance component between the a-B10C2+x:Hy and irradiated silicon. Additionally, it was found that after irradiation, a second parallel resistor and capacitor component is required for the model, introducing 2 additional independent variables (R2, C2). This is interpreted as the junction between the irradiated and virgin silicon near ion end of range
Energy-efficient acceleration of MPEG-4 compression tools
We propose novel hardware accelerator architectures for the most computationally demanding algorithms of the MPEG-4 video compression standard-motion estimation, binary motion estimation (for shape coding), and the forward/inverse discrete cosine transforms (incorporating shape adaptive modes). These accelerators have been designed using general low-energy design philosophies at the algorithmic/architectural abstraction levels. The themes of these philosophies are avoiding waste and trading area/performance for power and energy gains. Each core has been synthesised targeting TSMC 0.09
μm TCBN90LP technology, and the experimental results presented in this paper show that the proposed cores improve upon the prior art
The Crucial Role of Counties in the Health of Californians: An Overview
Examines county programs and services including indigent health care, public health, mental health, and substance abuse treatment, as well as challenges and considerations for federal healthcare reform, innovation, and realignment of government services
Axion Cosmology
1. Introduction 2. Models: the QCD axion; the strong CP problem; PQWW, KSVZ,
DFSZ; anomalies, instantons and the potential; couplings; axions in string
theory 3. Production and I.C.'s: SSB and non-perturbative physics; the axion
field during inflation and PQ SSB; cosmological populations - decay of parent,
topological defects, thermal production, vacuum realignment 4. The Cosmological
Field: action; background evolution; misalignment for QCD axion and ALPs;
cosmological perturbation theory - i.c.'s, early time treatment, axion sound
speed and Jeans scale, transfer functions and WDM; the Schrodinger picture;
simualting axions; BEC 5. CMB and LSS: Primary anisotropies; matter power;
combined constraints; Isocurvature and inflation 6. Galaxy Formation; halo mass
function; high-z and the EOR; density profiles; the CDM small-scale crises 7.
Accelerated expansion: the c.c. problem; axion inflation (natural and
monodromy) 8. Gravitational interactions with black holes and pulsars 9.
Non-gravitational interactions: stellar astrophysics; LSW; vacuum
birefringence; axion forces; direct detection with ADMX and CASPEr; Axion
decays; dark radiation; astrophysical magnetic fields; cosmological
birefringence 10. Conclusions A Theta vacua of gauge theories B EFT for
cosmologists C Friedmann equations D Cosmological fluids E Bayes Theorem and
priors F Degeneracies and sampling G Sheth-Tormen HMFComment: v2 greatly extended: 111 pages, 38 figures. Accepted for publication
in Physics Report
Specific Aspects in the Adaptation of Human Eye-Hand-Coordination
Sensorimotor control, especially eye-hand-coordination, enables us to interact with our environment. In my dissertation I describe and discuss three specific aspects of the adaptation of eye-hand-coordination: 1) the relative weight of visual and proprioceptive adaptation, 2) spatial and proprioceptive generalization of adaptation, and 3) acquisition of alternative mappings with repeated adaptations. The first aspect of sensorimotor adaptation is how an ambiguous mismatch between visual and proprioceptive coordinate systems is resolved. In my experiment I showed that an auditory pacing signal is an important factor facilitating visual adaptation. As a second aspect I examined the generalization of prism adaptation over space. Based on my results I can explain all previous results as an underestimation of change in the guiding system. The third aspect is the acquisition of alternate mappings (dual-adaptation) together with learning to learn. Confirming the involvement of learning to learn, I also found that the efficiency of dual-adaptation only depends on the total number of trials irrespective of their segmentation in blocks of differing lengths
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