1,096 research outputs found
The Effects of Monetary Policy in the Czech Republic: An Empirical Study
within VAR, structural VAR, and the Factor-Augmented VAR framework. We document a well-functioning transmission mechanism similar to the euro area countries, especially in terms of persistence of monetary policy shocks. Subject to various sensitivity tests, we find that contractionary monetary policy shock has a negative effect on the degree of economic activity and price level, both with a peak response after one year or so. Regarding the prices at the sectoral level, tradables adjust faster than non-tradables, which is in line with microeconomic evidence on price stickiness. There is no price puzzle, as our data come from single monetary policy regime. There is a rationale in using the real-time output gap instead of current GDP growth as using the former results in much more precise estimates. The results indicate a rather persistent appreciation of domestic currency after monetary tightening with a gradual depreciation afterwards.http://deepblue.lib.umich.edu/bitstream/2027.42/64350/1/wp922.pd
The Effects of Monetary Policy in the Czech Republic: An Empirical Study
within VAR, structural VAR, and the Factor-Augmented VAR framework. We document a well-functioning transmission mechanism similar to the euro area countries, especially in terms of persistence of monetary policy shocks. Subject to various sensitivity tests, we find that contractionary monetary policy shock has a negative effect on the degree of economic activity and price level, both with a peak response after one year or so. Regarding the prices at the sectoral level, tradables adjust faster than non-tradables, which is in line with microeconomic evidence on price stickiness. There is no price puzzle, as our data come from single monetary policy regime. There is a rationale in using the real-time output gap instead of current GDP growth as using the former results in much more precise estimates. The results indicate a rather persistent appreciation of domestic currency after monetary tightening with a gradual depreciation afterwards.monetary policy transmission, VAR, real-time data, sectoral prices
A study of the Sunyaev-Zel'dovich increment using archival SCUBA data
In a search for evidence of the short wavelength increment in the
Sunyaev-Zel'dovich (SZ) effect, we have analyzed archival galaxy cluster data
from the Sub-millimetre Common User Bolometer Array (SCUBA) on the James Clerk
Maxwell Telescope, resulting in the most complete pointed survey of clusters at
850 microns to date. SCUBA's 850 microns passband overlaps the peak of the SZ
increment. The sample consists of 44 galaxy clusters in the range 0 < z < 1.3.
Maps of each of the clusters have been made and sources have been extracted; as
an ancillary product we generate the most thorough galaxy cluster point source
list yet from SCUBA. Seventeen of these clusters are free of obvious AGN and
have data deep enough to provide interesting measurements of the expected SZ
signal. Specialized analysis techniques are employed to extract the SZ effect
signal from these SCUBA data, including using SCUBA's short wavelength band as
an atmospheric monitor and fitting the long wavelength channel to a model of
the spatial distribution of each cluster's SZ effect. By explicitly excising
the exact cluster centre from our analysis we demonstrate that emission from
galaxies within the cluster does not contaminate our measurement. The SZ
amplitudes from our measurements are consistently higher than the amplitudes
inferred from low frequency measurements of the SZ decrement.Comment: 27 pages, 6 figures, replacement matches version published in MNRA
Sub-mm counterparts to Lyman-break galaxies
We summarize the main results from our SCUBA survey of Lyman-break galaxies
(LBGs) at z~3. Analysis of our sample of LBGs reveals a mean flux of
S850=0.60.2 mJy, while simple models of emission based on the UV
properties predict a mean flux about twice as large. Known populations of LBGs
are expected to contribute flux to the weak sub-mm source portion of the far-IR
background, but are not likely to comprise the bright source (S850>5 mJy) end
of the SCUBA-detected source count. The detection of the LBG, Westphal-MM8, at
1.9 mJy suggests that deeper observations of individual LBGs in our sample
could uncover detections at similar levels, consistent with our UV-based
predictions. By the same token, many sub-mm selected sources with S850<2 mJy
could be LBGs. The data are also consistent with the FarIR/ relation
holding at z=3.Comment: 6 pages, 1 figure, contributed talk at UMass/INAOE Conference ``Deep
Millimeter Surveys'
350 Micron Observations of Ultraluminous Infrared Galaxies at Intermediate Redshifts
We present 350micron observations of 36 ultraluminous infrared galaxies
(ULIRGs) at intermediate redshifts (0.089 <= z <= 0.926) using the
Submillimeter High Angular Resolution Camera II (SHARC-II) on the Caltech
Submillimeter Observatory (CSO). In total, 28 sources are detected at S/N >= 3,
providing the first flux measurements longward of 100micron for a statistically
significant sample of ULIRGs in the redshift range of 0.1 < z < 1.0. Combining
our 350micron flux measurements with the existing IRAS 60 and 100micron data,
we fit a single-temperature model to the spectral energy distribution (SED),
and thereby estimate dust temperatures and far-IR luminosities. Assuming an
emissivity index of beta = 1.5, we find a median dust temperature and far-IR
luminosity of Td = 42.8+-7.1K and log(Lfir/Lsolar) = 12.2+-0.5, respectively.
The far-IR/radio correlation observed in local star-forming galaxies is found
to hold for ULIRGs in the redshift range 0.1 < z < 0.5, suggesting that the
dust in these sources is predominantly heated by starbursts. We compare the
far-IR luminosities and dust temperatures derived for dusty galaxy samples at
low and high redshifts with our sample of ULIRGs at intermediate redshift. A
general Lfir-Td relation is observed, albeit with significant scatter, due to
differing selection effects and variations in dust mass and grain properties.
The relatively high dust temperatures observed for our sample compared to that
of high-z submillimeter-selected starbursts with similar far-IR luminosities
suggest that the dominant star formation in ULIRGs at moderate redshifts takes
place on smaller spatial scales than at higher redshifts.Comment: (24 pages in preprint format, 1 table, 7 figures, accepted for
publication in ApJ
Evolving spiking neural networks for temporal pattern recognition in the presence of noise
Creative Commons - Attribution-NonCommercial-NoDerivs 3.0 United StatesNervous systems of biological organisms use temporal patterns of spikes to encode sensory input, but the mechanisms that underlie the recognition of such patterns are unclear. In the present work, we explore how networks of spiking neurons can be evolved to recognize temporal input patterns without being able to adjust signal conduction delays. We evolve the networks with GReaNs, an artificial life platform that encodes the topology of the network (and the weights of connections) in a fashion inspired by the encoding of gene regulatory networks in biological genomes. The number of computational nodes or connections is not limited in GReaNs, but here we limit the size of the networks to analyze the functioning of the networks and the effect of network size on the evolvability of robustness to noise. Our results show that even very small networks of spiking neurons can perform temporal pattern recognition in the presence of input noiseFinal Published versio
Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states
CdSe/CdS nanocrystal tetrapods are interesting building blocks for excitonic circuits, where the flow of excitation energy is gated by an external stimulus. The physical morphology of the nanoparticle, along with the electronic structure, which favors electron delocalization between the two semiconductors, suggests that all orientations of a particle relative to an external electric field will allow for excitons to be dissociated, stored, and released at a later time. While this approach, in principle, works, and fluorescence quenching of over 95% can be achieved electrically, we find that discrete trap states within the CdS are required to dissociate and store the exciton. These states are rapidly filled up with increasing excitation density, leading to a dramatic reduction in quenching efficiency. Charge separation is not instantaneous on the CdS excitonic antennae in which light absorption occurs, but arises from the relaxed exciton following hole localization in the core. Consequently, whereas strong electromodulation of the core exciton is observed, the core multiexciton and the CdS arm exciton are not affected by an external electric field
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