An approximate maximum likelihood estimation for non-Gaussian non-minimum phase moving average processes

An approximate maximum likelihood procedure is proposed for the estimation of parameters in possibly nonminimum phase (noninvertible) moving average processes driven by independent and identically distributed non-Gaussian noise. Under appropriate conditions, parameter estimates that are solutions of likelihood-like equations are consistent and are asymptotically normal. A simulation study for MA(2) processes illustrates the estimation procedure.     

Equivalent invariant measures

LetG be a finitely-generated group of non-singular measurable transformations of a measure space (X, β,p). FixA∈β withp(A)>0. A general technique for groups gives sufficient conditions for there to exist aG-invariant measure ν equivalent top with ν((A)=1. These conditions are phrased in terms of the growth behavior ofg→p(gB) forB∈β. The question of necessity is handled in some special cases.     

Estimation for a class of nonstationary processes

Random processes with almost periodic covariance function are considered from a spectral outlook. Given suitable conditions, spectral estimation problems are discussed for Gaussian processes of this type that are neither stationary nor locally stationary. Spectral mass is concentrated on lines parallel to the main diagonal in the spectral plane. A method of estimation of the support of spectral mass under appropriate restraints is considered. Some open questions are discussed. Extension of the methods for a class of nonGaussian nonstationary processes with mean value function a trigonometric regression is given. Consistent estimates for frequency, amplitude and phase of the regression are noted when the residual process is zero mean almost periodic. The resulting estimation of the spectral mass of the residual is also considered.     

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.     

Kinetics of Repair of UV-induced DNA Damage in Repair-proficient and -deficient Cells as Determined by Quantitative Polymerase Chain Reaction

Abstract— Advances in methodologies to monitor gene-specific repair in human cells have facilitated a detailed understanding of the complexity of the nucleotide excision repair system. One of these procedures, quantitative polymerase chain reaction (QPCR), holds significant promise for dissecting the fine structure of the repair of UV-induced DNA damage. This assay was used to study the repair of UV photoproducts in both actively transcribed and nontranscribed genes from human cells that were capable of (1) repair of both cyclobutane pyrimidine dimers and 6-4 photoproducts; (2) removal of neither dinners nor 6-4 photoproducts; (3) strong preferential repair of 6-4 photoproducts relative to dimers; and (4) severely depressed rates of 6-4 photoproducts and dimers. Detailed kinetic analyses revealed that repair of both active and inactive genes can be studied with a very fine degree of precision and that the repair status of the cells can easily be detected by use of the procedures described.