Relative Entropy and Error Bounds for Filtering of Markov Processes

This paper considers the relative entropy between the conditional distribution and an incorrectly initialized filter for the estimation of one component of a Markov process given observations of the second component. Using the Markov property, we first establish a decomposition of the relative entropy between the measures on observation path space associated to different initial conditions. Using this decomposition, it is shown that the relative entropy of the optimal filter relative to an incorrectly initialized filter is a positive supermartingale. By applying the decomposition to signals observed in additive, white noise, a relative entropy bound is obtained on the integrated, expected, mean square difference between the optimal and incorrectly initialized estimates of the observation function. Date received: October 6, 1997. Date revised: April 9, 1999.     

Concept formation and concept shifting in frontal lesion and Parkinson's disease patients assessed with the California Card Sorting Test.

Concept formation and shifting abilities of 17 frontal lesion (FL) and 8 Parkinson's disease (PD) patients were assessed with the California Card Sorting Test. FL patients demonstrated a significantly greater number of perseverative responses and deficits in strategy planning, strategy initiation, and concept formation and did not benefit from abstract cues in comparison with their matched normal control (NC) participants. PD patients also demonstrated an increased number of perseverative responses under selected conditions in comparison with their matched NCs, but their ability to explain their sorts, to extract and express the sorting principles, and to sort with the help of abstract and concrete cues depended on their general cognitive status. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of soil compaction and irrigation on the concentrations of selenium and arsenic in wheat grains

Arsenic is a known human carcinogen, whereas Se is essential to human health and human Se intake in some European countries has decreased in recent decades. There have been few reports on the potential effect of soil physical conditions on the uptake of Se and As by food crops. Field experiments were conducted to evaluate the effects of soil compaction and irrigation on Se and As concentrations in wheat grains in two seasons. Grain Se concentration varied from 10 to 115 microg kg(-1), whereas the concentration of As in grain was low (<20 microg kg(-1)). Irrigation significantly decreased grain Se concentration by 30-75%, and the effect was likely due to a dilution as a result of increased grain yield, a competition of sulfate added in the irrigation water on Se uptake and increased leaching losses. Soil compaction significantly decreased grain Se concentration in one season. In contrast, soil compaction increased grain As concentration significantly when the crop was irrigated. The contrasting effects of soil compaction on As and Se uptake are explained by the difference in their mobility in soil and the pathway of ion transport to roots. The observed effect on grain Se is significant for human and animal nutrition, because the concentration varied from sufficient to very low levels in response to the alternation of soil physical conditions in the field. Soil physical conditions have to be taken into account when assessing the bioavailability of the contaminant As or the essential nutrient Se.     

Simulation of special bubble detectors for PICASSO

The PICASSO project is a cold dark matter (CDM) search experiment relying on the superheated droplet technique. The detectors use superheated freon liquid droplets (active material) dispersed and trapped in a polymerised gel. This detection technique is based on the phase transition of superheated droplets at about room temperature and ambient pressure. The phase transition is induced by nuclear recoils when an atomic nucleus in the droplets interacts with incoming subatomic particles. This includes CDM particles candidate as the neutralino (a yet-to-discover particle predicted in extensions of the standard model of particle physics). Simulations performed to understand the detector response to neutrons and alpha particles are presented along with corresponding data obtained at the Montreal Laboratory.     

Current-Induced Degradation of Nickel Ohmic Contacts to SiC

The stability of Ni ohmic contacts to p-type SiC under high current density was investigated. A test structure adapted from the four circular contacts method allowed for vertical stressing and the ability to extract a pre- and post-stressed specific contact resistance. The accuracy of the measured specific contact resistance was verified experimentally through comparisons with more widely used methods and the use of computer modeling. The growth of voids initially produced during the high-temperature ohmic contact anneal was found to be the degradation mechanism, effectively decreasing the area of the contact.     

Exuberant Couture

Is the exuberant confined to architecture? Judith Clark , curator and lecturer in the history and theory of fashion, looks into the sartorial equivalent of digital exuberance. She describes how exuberance in fashion is largely performance-based expressed on the catwalk, as epitomised by Hussein Chalayan's dramatic staging of his shows. Copyright © 2010 John Wiley & Sons, Ltd.     

Blackbody radiation shifts in optical atomic clocks

A review of recent theoretical calculations of blackbody radiation (BBR) shifts in optical atomic clocks is presented. We summarize previous results for monovalent ions that were obtained by a relativistic all-order single-double method, where all single and double excitations of the Dirac- Fock wave function are included to all orders of perturbation theory. A recently developed method for accurate calculations of BBR shifts in divalent atoms is then presented. This approach combines the relativistic all-order method and the configuration interaction method, which provides for accurate treatment of correlation corrections in atoms with two valence electrons. Calculations of the BBR shifts in B+, Al+, and In+ have enabled us to reduce the present fractional uncertainties in the frequencies of their clock transitions as measured at room temperature: to 4 × 10-19 for Al+ and 10-18 for B+ and In+. These uncertainties approach recent estimates of the limits of precision of currently proposed optical atomic clocks. We discuss directions of future theoretical developments for reducing clock uncertainties resulting from blackbody radiation shifts.     

Nanoscale periodic modulations on sodium chloride surface revealed by tuning fork atomic force microscopy

The sodium chloride surface is one of the most common platforms for the study of catalysts, thin film growth, and atmospheric aerosols. Here we report a nanoscale periodic modulation pattern on the surface of a cleaved NaCl single crystal, revealed by non-contact atomic force microscopy with a tuning fork sensor. The surface pattern shows two orthogonal domains, extending over the entire cleavage surface. The spatial modulations exhibit a characteristic period of 5.4 nm, along <110> crystallographic directions of the NaCl. The modulations are robust in vacuum, not affected by the tip-induced electric field or gentle annealing (<300?°C); however, they are eliminated after exposure to water and an atomically flat surface can be recovered by subsequent thermal annealing after water exposure. A strong electrostatic charging is revealed on the cleavage surface which may facilitate the formation of the observed metastable surface reconstruction.     

Molecular Kondo chain

An important development in recent synthesis strategies is the formation of electronically coupled one and two-dimensional organic systems for potential applications in nanoscale molecule-based devices. Here, we assemble one-dimensional spin chains by covalently linking basic molecular building blocks on a Au(111) surface. Their structural properties are studied by scanning tunneling microscopy and the Kondo effect of the basic molecular blocks inside the chains is probed by scanning tunneling spectroscopy. Tunneling spectroscopic images reveal the existence of separate Kondo regions within the chains while density functional theory calculations unveil antiferromagnetic coupling between the spin centers.     

A Consistent Dataset of Kinetic Solubilities for Early‐Phase Drug Discovery

Herein, we describe a new dataset of kinetic aqueous solubilities determined by nephelometry for 711 druglike compounds. The solubilities are reported in twelve classes ranging from <2 μg mL^?1 to >250 μg mL^?1. The measurements were designed to provide the appropriate data for applications in the early phases of drug discovery. Three class classification models (insoluble, moderately soluble, soluble) were built using the random forest algorithm and their performance for this dataset was analyzed.