Sharp Deviations Research Articles

Visualization of anomalous penetrant transport in glassy poly(methyl methacrylate) utilizing high-resolution X-ray computed tomography

High-resolution X-ray computed tomography, a completely non-destructive technique that can be used to visualize features in the interior of opaque solids, was successfully adapted in a novel manner to examine the transport dynamics of methanol into glassy poly(methyl methacrylate) discs synthesized by an iniferter-mediated free radical polymerization. In addition to tracking methanol absorption and dimensional swelling, the time-dependent concentration profiles within the polymer disc were determined with higher resolution, lower scanning times, and no major geometry restrictions compared to previous state-of-the-art techniques. These profiles indicated non-Fickian transport behavior with sharp penetrant fronts and deviations from previously reported swelling profiles.

Interpreting deviations from covered interest parity during the financial market turmoil of 2007–08

This paper investigates the spillover effects of money market turbulence in 2007–08 on the short-term covered interest parity (CIP) condition between the US dollar and the euro through the foreign exchange (FX) swap market. Sharp and persistent deviations from the CIP condition observed during the turmoil are found to be significantly associated with differences in the counterparty risk between European and US financial institutions. Furthermore, evidence is found that US dollar term funding auctions by the ECB, supported by US dollar swap lines with the Federal Reserve, alleviated the level of dislocations, as well as the instability, of the FX swap market.

Interpreting Deviations from Covered Interest Parity During the Financial Market Turmoil of 2007-08

This paper investigates the spillover effects of money market turbulence in 2007-08 on the short-term covered interest parity (CIP) condition between the US dollar and the euro through the foreign exchange (FX) swap market. Sharp and persistent deviations from the CIP condition observed during the turmoil are found to be significantly associated with differences in the counterparty risk between European and US financial institutions. Furthermore, evidence is found that dollar term funding auctions by the ECB, supported by dollar swap lines with the Federal Reserve, have stabilized the FX swap market by lowering the volatility of deviations from CIP.

Trends in Party System Indicators for the July 2007 Turkish Elections

The stellar success of the Justice and Development Party (AKP) has led to the interpretation of the 2002 and 2007 elections as sharp deviations from past political trends. Through an analysis of national and regional‐level party system indicators in the post‐1980 period, the authors find that the success of the AKP should rather be seen as the continuation of trends that started in the early 1990s. Throughout the 1990s, the pro‐Islamist and nationalist bloc had already established a strong base in Central Anatolia, and the success of the AKP is due to its expansion of this voter base to Western regions and some of the predominantly Kurdish provinces in the southeast.

Interpreting Deviations from Covered Interest Parity during the Financial Market Turmoil of 2007-08

This paper investigates the spillover effects of money market turbulence in 2007-08 on the short-term covered interest parity (CIP) condition between the US dollar and the euro through the foreign exchange (FX) swap market. Sharp and persistent deviations from the CIP condition observed during the turmoil are found to be significantly associated with differences in the counterparty risk between European and US financial institutions. Furthermore, evidence is found that dollar term funding auctions by the ECB, supported by dollar swap lines with the Federal Reserve, have stabilized the FX swap market by lowering the volatility of deviations from CIP.

Dynamical backreaction of relic gravitons

The dynamical effects of the tensor modes of the geometry are investigated in the context of curvature bounces. Since the bouncing behaviour implies sharp deviations from a radiation-dominated evolution, significant back-reaction effects of relic gravitons may be expected at short wavelengths. After developing a general iterative framework for the calculation of dynamical back-reaction effects, explicit analytical and numerical examples are investigated for different parametrizations of the energy-momentum pseudo-tensor(s) of the produced gravitons. The reported results suggest that dynamical back-reaction effects are a necessary ingredient for a consistent description of bouncing models at late times.

Determinants of Venezuela's Equilibrium Real Exchange Rate

The Venezuelan Bolivar is pegged to the U.S. dollar and supported by foreign exchange restrictions. To assess the appropriateness of the peg during the current period of high oil export earnings and the likely consequences of a liberalization, this paper attempts to disentangle the effects of oil prices from other factors underlying the equilibrium real exchange rate, and examines the role of foreign exchange controls by extending the application of a vector error correction (VEC) model to parallel market exchange rates. Several findings are worth noting. First, oil prices have indeed played a significant role in determining a time-varying equilibrium real exchange rate path. Second, oil prices are not the only important determinant of the real effective exchange rate: declining productivity is also a key factor. Third, appreciation pressures are rising. Finally, the speed of convergence of a VEC model using parallel rather than official rates is higher, suggesting that the government has been able to maintain sharp deviations between the official and equilibrium rates because of Venezuela's oil dependency and the concentration of oil income in government hands.

Determinants of Venezuela'S Equilibrium Real Exchange Rate

The Venezuelan Bolivar is pegged to the U.S. dollar and supported by foreign exchange restrictions. To assess the appropriateness of the peg during the current period of high oil export earnings and the likely consequences of a liberalization, this paper attempts to disentangle the effects of oil prices from other factors underlying the equilibrium real exchange rate, and examines the role of foreign exchange controls by extending the application of a vector error correction (VEC) model to parallel market exchange rates. Several findings are worth noting. First, oil prices have indeed played a significant role in determining a time-varying equilibrium real exchange rate path. Second, oil prices are not the only important determinant of the real effective exchange rate: declining productivity is also a key factor. Third, appreciation pressures are rising. Finally, the speed of convergence of a VEC model using parallel rather than official rates is higher, suggesting that the government has been able to maintain sharp deviations between the official and equilibrium rates because of Venezuela's oil dependency and the concentration of oil income in government hands.

On diffusion paths with “horns” and the formation of single phase layers in multiphase diffusion couples

The current study using DICTRA finite difference software predicts sharp deviations from the linear zigzag diffusion paths predicted by an error function model for multiphase diffusion couples. The deviations appear as “horns” that protrude from the linear paths. It was found that the horn length is proportional to the composition vector component along the major eigenvector of the effective diffusivity matrix. Applying these results to a study on Ni–Cr–Al diffusion couples prepared from γ + β alloys, it was also found that the formation of single phase β layers could be attributed to the horns pointing away from each other, in which case the diffusion path could intersect the single phase β region of the phase diagram.

Non-Gaussian resistance noise near electrical breakdown in granular materials

The distribution of resistance fluctuations of conducting thin films with granular structure near electrical breakdown is studied by numerical simulations. The film is modeled as a resistor network in a steady state determined by the competition between two biased processes, breaking and recovery. Systems of different sizes and with different levels of internal disorder are considered. Sharp deviations from a Gaussian distribution are found near breakdown and the effect increases with the degree of internal disorder. We show that in general this non-Gaussianity is related to the finite size of the system and vanishes in the large size limit. Nevertheless, near the critical point of the conductor–insulator transition, deviations from Gaussianity persist when the size is increased and the distribution of resistance fluctuations is well fitted by the universal Bramwell–Holdsworth–Pinton distribution.

Palaeoclimatic variation, adaptation and biogeography of inversion polymorphisms in natural populations of Drosophila robusta

Studies of natural and sexual selection in wild populations of Drosophila have historically provided strong inference for the maintenance of inversion polymorphism. Analysis of geographical variation in the Drosophila robusta chromosomal data collected over more than 50 years from 133 natural populations across eastern North America has confirmed several north–south and east–west clines in the frequencies of some gene arrangements and linked arrangement combinations. Patterns of geographical variation, including several north–south clines, revealed by regression and spatial autocorrelation analyses are concordant with palaeoclimatic shifts, Pleistocene glaciations and historical changes in the composition of North American forest communities. Because D. robusta is a sap-breeder, using the microbe-infested sap exudates of a number of deciduous tree species in which they carry out their life cycle, shifts in climate and palaeovegetation types since the formation of the eastern deciduous forests in the Miocene are hypothesized to be major factors influencing patterns of inversion polymorphisms across the range of this drosophilid species. In areas where sharp deviations in frequencies have been observed, particularly in the mid-western and western portions of the range, these divisions parallel historical geographical disjunctions in the species range that have yet to promote divergence and species formation despite the long history of D. robusta in North America.

Intracranial pressure processing with artificial neural networks: prediction of ICP trends.

It is well known that intracranial pressure (ICP) is influenced by an array of predictable and unpredictable factors, which gives rise to a signal heavily loaded with stochastic, i.e. random components. Hence, statistical modelling of this signal has proved to be of limited utility, in spite of the very sophisticated mathematical methods applied. In recent years, neural network algorithms (ANN), which are an alternative to statistical methods, have proved their effectiveness in the prediction of trends, as applied in a variety of medical and non-medical tasks. We therefore attempted to test the efficiency of neural models in the on-line prediction of ICP values, compare their effectiveness to statistically oriented algorithms and combine ANN methods with some newer signal processing algorithms, like wavelet decomposition. Prediction horizons of up to 5 minutes have been tested with various architectures of the neural predictor. For a 3 minute prediction horizon, a satisfactory accuracy of forecasting has been achieved with "plain" ANN, as expressed by the "average relative variance coefficient". This was measured by the ratio of the prediction error obtained, in relation to the error which would occur if a current value were taken as the forecasted one. The prediction quality with statistical autoregressive models has proved unsatisfactory, whilst the result obtained using the ANN model with the wavelet transform incorporated, performed significantly better than the ANN models alone. The prediction quality obtained with the ANN methodology seems to be satisfactory over a short time horizon, though no conclusion can be derived at this stage of the study, as to the clinical utility of this method. In particular, even with this methodology, it is not possible to forecast any sudden dehiscencies of the ICP signal with any practical reliability. From the point of view of modelling theory, such sharp deviations of the signal may be regarded as a "catastrophe". This implies the necessity for a different approach to the ICP signal analysis with the artificial intelligence methodology; one, that is more oriented towards the global properties of the signal.

Mean Reversion of Real Exchange Rates in High‐Inflation Countries

We test for mean reversion in real exchange rates using data from five countries, four of which have experienced episodes of high inflation. Using monthly data for Argentina, Brazil, Chile, Colombia, and Israel, we find that a stochastic unit root model is typically appropriate (Brazil is the exception). Kalman filter estimates of the stochastic unit roots show sharp deviations from unity associated with high inflation episodes. This suggests that stochastic unit root models are a more appropriate way to model mean reversion in real exchange rates for high inflation countries than models with fixed rates of mean reversion.

Mean Reversion of Real Exchange Rates in High-Inflation Countries

We test for mean reversion in real exchange rates using data from five countries, four of which have experienced episodes of high inflation. Using monthly data for Argentina, Brazil, Chile, Colombia, and Israel, we find that a stochastic unit root model is typically appropriate (Brazil is the exception). Kalman filter estimates of the stochastic unit roots show sharp deviations from unity associated with high inflation episodes. This suggests that stochastic unit root models are a more appropriate way to model mean reversion in real exchange rates for high inflation countries than models with fixed rates of mean reversion.

Nanoscale electronic devices on carbon nanotubes

Conductivity measurements were performed on bundles of single-walled carbon nanotubes with the aid of a scanning tunneling microscope (STM). Semimetallic current-voltage (I-V) characteristics generally indicated the bundles to be electronically similar to graphite. However, by moving the STM tip along the length of the nanotubes, sharp deviations in the I-V characteristics could also be observed. Well-defined positions were found at which the nanotube transport current changed abruptly from a graphitic response to one that is highly nonlinear and asymmetric, including near-perfect rectification. This abrupt change in the nanotube transport suggests that the STM tip had passed a region of the nanotube which acts less like a wire than it does a Schottky barrier or other heterojunction. Similar on-tube nanodevices have been theoretically predicted for point defects in individual carbon nanotubes and are consistent with our observations.

Molecular dynamics and order of microconfined liquid crystals

A new technique based on the dipolar-correlation effect was applied in combination with field-cycling-relaxometry to study ordering effects and slow director fluctuations in a nematic liquid crystal confined in porous glasses. Both methods demonstrate a strong influence of geometrical confinements on the distribution of director fluctuation modes. The mean-squared fluctuation estimated from the dipolar-correlation effect decreases exponentially with decreasing pore diameter. The critical mean pore size for the onset of bulk behaviour was found to be of the order of 120 nm. Frequency dependences of spin-lattice relaxation times exhibit sudden sharp deviations from the square root law at frequencies below the MHz-range. These changes are assumed to reflect the lack of long wavelength fluctuations in the spectrum of director fluctuation modes due to finite pore sizes.

A class of robust entropic functionals for image restoration

This paper considers the concept of robust estimation in regularized image restoration. Robust functionals are employed for the representation of both the noise and the signal statistics. Such functionals allow the efficient suppression of a wide variety of noise processes and permit the reconstruction of sharper edges than their quadratic counterparts. A new class of robust entropic functionals is introduced, which operates only on the high-frequency content of the signal and reflects sharp deviations in the signal distribution. This class of functionals can also incorporate prior structural information regarding the original image, in a way similar to the maximum information principle. The convergence properties of robust iterative algorithms are studied for continuously and noncontinuously differentiable functionals. The definition of the robust approach is completed by introducing a method for the optimal selection of the regularization parameter. This method utilizes the structure of robust estimators that lack analytic specification. The properties of robust algorithms are demonstrated through restoration examples in different noise environments.

Gamma-ray emission and electron acceleration in solar flares

view Abstract Citations (31) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gamma-Ray Emission and Electron Accleration in Solar Flares Petrosian, Vahe ; McTiernan, James M. ; Marschhauser, Holger Abstract Recent observations have extended the spectra of the impulsive phase of flares to the GeV range. Such high-energy photons can be produced either by electron bremsstrahlung or by decay of pions produced by accelerated protons. In this paper we investigate the effects of processes which become important at high energies. We examine the effects of synchrotron losses during the transport of electrons as they travel from the acceleration region in the corona to the gamma-ray emission sites deep in the chromosphere and photosphere, and the effects of scattering and absorption of gamma rays on their way from the photosphere to space instruments. These results are compared with the spectra from so-called electron-dominated flares, observed by GRS on the Solar Maximum Mission, which show negligible or no detectable contribution from accelerated protons. The spectra of these flares show a distinct steepening at energies below 100 keV and a rapid falloff at energies above 50 MeV. Following our earlier results based on lower energy gamma-ray flare emission we have modeled these spectra. We show that neither the radiative transfer effects, which are expected to become important at higher energies, nor the transport effects (Coulomb collisions, synchrotron losses, or magnetic field convergence) can explain such sharp spectral deviations from a simple power law. These spectral deviations from a power law are therefore attributed to the acceleration process. In a stochastic acceleration model the low-energy steepening can be attributed to Coulomb collision and the rapid high-energy steepening can result from synchrotron losses during the acceleration process. Publication: The Astrophysical Journal Pub Date: October 1994 DOI: 10.1086/174777 Bibcode: 1994ApJ...434..747P Keywords: Bremsstrahlung; Coulomb Collisions; Electron Acceleration; Gamma Ray Astronomy; Gamma Ray Spectra; Pions; Radiative Transfer; Solar Flares; Solar Protons; Stellar Models; Synchrotron Radiation; Transport Properties; Chromosphere; Gamma Ray Observatory; Photosphere; Solar Corona; Solar Maximum Mission; Solar Physics; ACCELERATION OF PARTICLES; RADIATION MECHANISMS: MISCELLANEOUS; SUN: FLARES; SUN: X-RAYS; GAMMA RAYS full text sources ADS |

A prototype system for short-term supply planning

Short-term supply planning is concerned with the anticipation of sharp deviations in actual customer demand, resulting in unseen loading of manufacturing plants, within the MPS planning horizon. A high level of accuracy in master production scheduling is normally achieved by effective collaboration of the production, distribution, sales and marketing functions of manufacturing industries. However, attemps to guarantee 100% on-time delivery, while maintaining minimum finished goods inventory, can create sharp fluctuations in near-term demand (especially in a volatile market environment) signals received by manufacturing plants. This paper presents a prototype supply planning system, which can be used to enhance the demand forecast within the MPS horizon, and addresses the difficulties with frequent re-scheduling and sharp fluctuations is near-term demand. The prototype combines expert system and decision support system technology in an integrated supply planners' workbench. The workbench functionality, technical specifications and architecture are presented, in addition to a discussion of the forecasting and rulesbase rationale.

Ethylene and ethane evolution during cold acclimation and deacclimation of ponderosa pine

Greenhouse container-grown ponderosa pine (Pinusponderosa var. scopulorum Engelm.) were cold acclimated and deacclimated in growth chambers during a 19-week regime. Seedling cold hardiness, bud dormancy, and ethylene and ethane evolution from excised needles were measured weekly. Ethylene and ethane evolution and the ethane/ethylene ratio declined from bud set to bud break and did not parallel changes in cold hardiness. Large standard errors of the ethylene evolution means made detecting statistical differences over time difficult. Significant deviations in the ethane evolution means were observed, however, and indicated a sharp decrease and recovery at the start of cold acclimation and a peak at the start of deacclimation. The ethane/ethylene ratio accentuated the declining trend from bud set to bud break and the two sharp deviations in the trend at the start of acclimation and deacclimation.