1,781 research outputs found
Stabilizing intergovernmental transfers in Latin America : a complement to national/subnational fiscal rules?
The traditional theory of fiscal federalism assigns the role of macroeconomic stabilization to the federal government. In addition to this long-standing theoretical result, there is empirical observation that federal governments in developing countries typically have cheaper and more stable access to capital markets, relative to subnational governments. Drawing on the recent experience of four large federal countries in Latin America-Argentina, Brazil, Colombia, and Mexico--the authors examine how intergovernmental transfers affect the division of the burden of stabilization across the levels of government, when the nation as a whole faces economic fluctuations. Imposing stabilizing rules on federal transfers that protect subnational governments from fluctuations in the business cycle can serve two purposes. During boom periods, stabilizing rules prevent subnational governments'tendency to increase inflexible expenditures. And during downturns, stabilizing rules place the burden of borrowing at the federal level-the level most appropriate for macroeconomic stabilization and often the level with superior access to credit. Despite the logic of these rules, recent experience of the four countries reveals that these rules can be risky, particularly inthe face of high GDP volatility. Protection against falling revenues in the downturn constitutes a contingent liability for the central government. Argentina's stabilizing rule contributed to fiscal and political tensions during its ongoing crisis. Colombia is beginning to implement similar rules. Meanwhile, Brazilian and Mexican transfers do not implement such rules and fiscal and economic results do not appear to have fared any worse for this absence. The authors draw on the country experience to establish that certain conditions should be in place before establishing a stabilization rule to federal-to-subnational fiscal transfers-in particular the elimination of long-term structural fiscal imbalances, either within levels of government or across levels of government.Municipal Financial Management,Public Sector Economics&Finance,Public&Municipal Finance,Banks&Banking Reform,Urban Economics,Banks&Banking Reform,National Governance,Public Sector Economics&Finance,Municipal Financial Management,Urban Economics
Electrical Nanoprobing of Semiconducting Carbon Nanotubes using an Atomic Force Microscope
We use an Atomic Force Microscope (AFM) tip to locally probe the electronic
properties of semiconducting carbon nanotube transistors. A gold-coated AFM tip
serves as a voltage or current probe in three-probe measurement setup. Using
the tip as a movable current probe, we investigate the scaling of the device
properties with channel length. Using the tip as a voltage probe, we study the
properties of the contacts. We find that Au makes an excellent contact in the
p-region, with no Schottky barrier. In the n-region large contact resistances
were found which dominate the transport properties.Comment: 4 pages, 5 figure
Kinetics of Phase Transition in An Anticlinic Liquid Crystal Induced by a Uniform Temperature Field: Growth in One Dimension
It is experimentally demonstrated that a transition from a synclinic to an anticlinic liquid crystal phase occurs via stable domain wall propagation after quenching in a uniform temperature field. Such a one-dimensional growth may be explained in terms of a nonlinear diffusion equation. The experiment provides the first example of free, one-dimensional growth in a system subjected to a pure and uniform temperature field
Amenable actions, free products and a fixed point property
We investigate the class of groups admitting an action on a set with an
invariant mean. It turns out that many free products admit such an action. We
give a complete characterisation of such free products in terms of a strong
fixed point property.Comment: 12 page
Syntactic discriminative language model rerankers for statistical machine translation
This article describes a method that successfully exploits syntactic features for n-best translation candidate reranking using perceptrons. We motivate the utility of syntax by demonstrating the superior performance of parsers over n-gram language models in differentiating between Statistical Machine Translation output and human translations. Our approach uses discriminative language modelling to rerank the n-best translations generated by a statistical machine translation system. The performance is evaluated for Arabic-to-English translation using NIST’s MT-Eval benchmarks. While deep features extracted from parse trees do not consistently help, we show how features extracted from a shallow Part-of-Speech annotation layer outperform a competitive baseline and a state-of-the-art comparative reranking approach, leading to significant BLEU improvements on three different test sets
Better-than-chance classification for signal detection
The estimated accuracy of a classifier is a random quantity with variability. A common practice in supervised machine learning, is thus to test if the estimated accuracy is significantly better than chance level. This method of signal detection is particularly popular in neuroimaging and genetics. We provide evidence that using a classifier's accuracy as a test statistic can be an underpowered strategy for finding differences between populations, compared to a bona fide statistical test. It is also computationally more demanding than a statistical test. Via simulation, we compare test statistics that are based on classification accuracy, to others based on multivariate test statistics. We find that the probability of detecting differences between two distributions is lower for accuracy-based statistics. We examine several candidate causes for the low power of accuracy-tests. These causes include: the discrete nature of the accuracy-test statistic, the type of signal accuracy-tests are designed to detect, their inefficient use of the data, and their suboptimal regularization. When the purpose of the analysis is the evaluation of a particular classifier, not signal detection, we suggest several improvements to increase power. In particular, to replace V-fold cross-validation with the Leave-One-Out Bootstrap.Development and application of statistical models for medical scientific researc
Polar Smectic Films
We report on a new experimental procedure for forming and studying polar
smectic liquid crystal films. A free standing smectic film is put in contact
with a liquid drop, so that the film has one liquid crystal/liquid interface
and one liquid crystal/air interface. This polar environment results in changes
in the textures observed in the film, including a boojum texture and a
previously unobserved spiral texture in which the winding direction of the
spiral reverses at a finite radius from its center. Some aspects of these
textures are explained by the presence of a Ksb term in the bulk elastic free
energy density that favors a combination of splay and bend deformations.Comment: 4 pages, REVTeX, 3 figures, submitted to PR
Electron-Phonon Scattering in Metallic Single-Walled Carbon Nanotubes
Electron scattering rates in metallic single-walled carbon nanotubes are
studied using an atomic force microscope as an electrical probe. From the
scaling of the resistance of the same nanotube with length in the low and high
bias regimes, the mean free paths for both regimes are inferred. The observed
scattering rates are consistent with calculations for acoustic phonon
scattering at low biases and zone boundary/optical phonon scattering at high
biases.Comment: 4 pages, 5 figure
Photocurrent Imaging of p-n Junctions and Local Defects in Ambipolar Carbon Nanotube Transistors
We use scanning photocurrent microscopy (SPCM) to investigate the properties
of internal p-n junctions as well as local defects in ambipolar carbon nanotube
(CNT) transistors. Our SPCM images show strong signals near metal contacts
whose polarity and positions change depending on the gate bias. SPCM images
analyzed in conjunction with the overall conductance also indicate the
existence and gate-dependent evolution of internal p-n junctions near contacts
in the n-type operation regime. To determine the p-n junction position and the
depletion width with a nanometer scale resolution, a Gaussian fit was used. We
also measure the electric potential profile of CNT devices at different gate
biases, which shows that both local defects and induced electric fields can be
imaged using the SPCM technique. Our experiment clearly demonstrates that SPCM
is a valuable tool for imaging and optimizing electrical and optoelectronic
properties of CNT based devices.Comment: 5 pages, 5 figure
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