Lower bounds on the canonical height associated to the morphism $${\phi(z)= z^d+c}$$

A lower bound is obtained of the canonical height associated to the morphism evaluated at wandering points α. The lower bound is of the form Ch(c), for some constant C depending on the the number of primes of bad reduction for , and the degree of the number field . The author was supported by a PDF grant from NSERC.     

Positron annihilation probing of crystallization effects in TAS-235 glass affected by Ga additions

Crystallization effects in Te₂₀As₃₀Se₅₀ glass known also as TAS-235 affected by Ga additions to Ga₂Te₂₀As₂₈Se₅₀ and Ga₅Te₂₀As₂₅Se₅₀ compositions are probed with positron annihilation spectroscopy in the measuring modes exploring positron lifetimes and Doppler broadening of annihilation line. Occurring of cubic-phase Ga₂Se₃ droplets with character nanoscale sizes in partially-crystallized Ga₂Te₂₀As₂₈Se₅₀ alloy is shown to be associated with agglomeration of intrinsic free-volume voids, this process being enhanced over microcrystalline scale in Ga₅Te₂₀As₂₅Se₅₀ alloy. Crystallization changes in the void structure of TAS-235 glass are considered in terms of free-volume evolution under the same principal chemical environment responsible for positron trapping in amorphous and partially crystallized substances.     

Initial State Interaction in the (π+,3p) Reaction on N, Ar and Xe

The pion absorption reaction (π^{+,3 p} ) on Ar was studied at pion energies of 70, 118, 162 and 239 MeV, and on N and Xe at 239 MeV. The 3p cross section with a 50 MeV cut on the missing energy is presented. The existence of an initial state interaction (ISI) component to the reaction was investigated. The portion of the 3p cross section assigned to the ISI process is less than one half and at lower energies significantly so. Received: 11 December 1997     

Estimating a Cholesky decomposition

For a normal distribution the sample covariance matrix S provides an unbiased estimator of the population covariance matrix Σ. We address the problem of finding an unbiased estimator of the lower triangular matrix Ψ defined by the Cholesky decomposition Σ = ΨΨ′.     

Na+-ion conducting glasses

Na⁺-ion conduction in glass is discussed with the aim of selecting suitable electrolytes for use in Na/S cells operating around 350°C. From an extensive survey of many glass systems including silicates, borates, etc., it is found that the conductivity increases with increasing optical basicity (Λ), while the activation energy falls toward an apparent limiting value of ca. 50 kJ mol^?1. The use of special additives such as NaCl does not lead to any further improvement. Several “optimised ionic conductors” have been identified, where σ ? 10^?2 S cm^?1 at T_g. These are the best materials for use in battery applications provided they are stable in the cell environment.     

Highly Sensitive Silver Nanorod Arrays for Rapid Surface Enhanced Raman Scattering Detection of Acetamiprid Pesticides

The determination of pesticide residue on agricultural products is increasingly important.Exposure to pesticides can cause severe acute reactions in humans, including aplastic anemia and leukemia.In this work, we developed a rapid and sensitive method to detect acetamiprid pesticide residue based on surface-enhanced Raman scattering.Silver nanorod (AgNR) arrays were fabricated by oblique angle deposition technology and were used as SERS substrates.Prior to detection, the AgNR arrays were cleaned with nitric acid solution or a mixture of methanol and acetone.Compared to the unwashed AgNR arrays, the AgNR arrays washed with methanol and acetone shows a signal enhancement 1000 times greater than the unwashed AgNR array due to the effective removal of the impurities on its surface.The limit of detection of acetamiprid was determined to be 0.05 mg/L.In addition, the molecular structure of acetamiprid was simulated and the corresponding vibration modes of the characteristic bands of acetamiprid were calculated by density function theory.To demonstrate its practical application, the AgNRs array substrates were applied successfully to the rapid identification of acetamiprid residue on a cucumber's surface.These results confirmed possibility of utilizing the AgNRs SERS substrates as a new method for highly sensitive pesticide residue detection.     

The use of silver vanadates as absorbents for sulphur dioxide

A new solid absorbent for sulphur dioxide is described which is effective at room temperarures, and which does not absorb carbon dioxide. Exhaustion of the filling is indicated by a change in colour from green to brown.The reagent is prepared by heating molecular quantities of silver oxide and silver metavanadate together at 150° C. Evidence is given that on such treatment the two silver salts combine, forming a product having the same empirical composition as silver orthovanadate but different as regards its properties from the orthovanadate produced by the usual precipi-tation method.