Detecting and modeling nonlinearity in the gas furnace data

Using a modification of the Hinich, J Time Ser Anal 3(3):169–176, (1982) bispectrum test for nonlinearity and Gaussianity, the residuals of the Tiao and Box, J Am Stat Assoc 76:802–816, (1981) constrained and unconstrained VAR models for the gas furnace data reject the assumption of Gaussianity and linearity over a grid of bandwidths for estimating the bispectrum. These findings call into question the specification of the linear VAR and VARMA models assumed by Tiao and Box, J Am Stat Assoc 76:802–816, (1981). Utilizing the alternative Hinich J Nonparametr Stat 6:205–221, (1996) nonlinearity test, the residuals of the VAR model were shown to exhibit episodic nonlinearity. The sensitivity of the findings to outliers is investigated by estimating and testing the residuals of L1 and MINIMAX models from 1–6 lags. Building on the linear dynamic specification, a multivariate adaptive regression splines (MARS) model is estimated, using two software implementations, and shown to remove the nonlinearity in the residuals. Leverage plots were used to illustrate the “cost” of imposing a linearity assumption. Out-of-sample forecasting tests from 1–6 periods ahead found that using the sum-of-squared errors criteria, the MARS model out performed ACE, GAM and projection pursuit models.     

Effects of noise on speech production: acoustic and perceptual analyses

Acoustical analyses were carried out on a set of utterances produced by two male speakers talking in quiet and in 80, 90, and 100 dB SPL of masking noise. In addition to replicating previous studies demonstrating increases in amplitude, duration, and vocal pitch while talking in noise, these analyses also found reliable differences in the formant frequencies and short-term spectra of vowels. Perceptual experiments were also conducted to assess the intelligibility of utterances produced in quiet and in noise when they were presented at equal S/N ratios for identification. In each experiment, utterances originally produced in noise were found to be more intelligible than utterances produced in the quiet. The results of the acoustic analyses showed clear and consistent differences in the acoustic-phonetic characteristics of speech produced in quiet versus noisy environments. Moreover, these accounts differences produced reliable effects on intelligibility. The findings are discussed in terms of: (1) the nature of the acoustic changes that taken place when speakers produce speech under adverse conditions such as noise, psychological stress, or high cognitive load: (2) the role of training and feedback in controlling and modifying a talker's speech to improve performance of current speech recognizers; and (3) the development of robust algorithms for recognition of speech in noise.     

The generation of tunable near IR radiation using a nitrogen laser pumped dye laser

Excitation transfer between the two components of a dye mixture has allowed a near IR dye laser to be pumped by a nitrogen laser. Several dye mixtures were employed to achieve lasing at all wavelengths within the range 6400–7720 Å. The output pulse powers were in excess of 10 kW over most of this range.     

Simple cubic super crystals containing PbTe nanocubes and their core-shell building blocks

We report a preparation of high-quality cubic PbTe nanocrystals and their assembly into both square-array, two-dimensional patterns and three-dimensional simple cubic super crystals. The influence of oleylamine in the nanocrystal synthesis and core-shell formation through an anion-exchange mechanism was also studied. The simple cubic super crystals together with two-dimensional assembly patterns containing PbTe nanocubes and their core-shell building blocks were examined using TEM, SEM, AFM, XRD, SAXS, and FTIR. Such super crystals consisting of cubic structural building blocks may allow engineering of more complex materials from which novel properties may emerge.     

Squaraines as unique reporters for SERRS multiplexing

Modified anilino squaraine dyes provide unique SERRS spectra that can be identified at low concentrations within any mixture of current reporters using longer, biologically compatible wavelengths of excitation.     

Cu−NHC Complex for Chan-Evans-Lam Cross-Coupling Reactions of N-Heterocyclic Compounds and Arylboronic Acids

An efficient copper(II) N-heterocyclic carbene (NHC) complex with an NCN coordination mode was optimized to catalyze the Chan–Evans-Lam (CEL) cross-coupling reaction of imidazole and other N-heterocyclic nucleophiles with arylboronic acid. This air-stable copper catalyst shows robust catalytic performance and tolerates a diverse array of functional groups on both the N-nucleophile and arylboronic acid coupling partners in C−N bond forming reactions with up to 95 % yield. Formation of the Cu−NHC complex in situ generated similar catalytic performance for CEL coupling. Alternative metal ions (Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Zn²⁺, Ru²⁺, and Pd²⁺) were also screened in the presence of the NHC precursor as CEL catalysts.     

Immunoassay for P38 MAPK using surface enhanced resonance Raman spectroscopy (SERRS)

A micro-bead sandwich assay for P38 mitogen-activated protein kinase using surface enhanced resonance Raman spectroscopy (SERRS) detection is reported. Monoclonal capture antibodies were immobilised on a solid phase of magnetic micro-beads with secondary detection using a rhodamine-labelled antibody. Quantitative SERRS detection of the secondary antibody was possible with a limit of detection of 9.5 x 10(-12) mol dm(-3). The sandwich assay was quantitative and sensitive to 6 ng ml(-1). The mechanism of the SERRS detection in the immunoassay was investigated. The addition of SERRS aggregating agents causes the dissociation of the immuno-complex from the magnetic beads. Scanning electron microscopy images indicate that the colloidal suspension rather than adsorbed silver nanoparticles on the beads provide the SERRS signals, that the aggregate size is partially controlled and that there is some inhomogeneity in the distribution of organic matter on the nanoscale.     

Negative ions of nitroethane and its clusters

Valence and dipole-bound negative ions of the nitroethane (NE) molecule and its clusters are studied using photoelectron spectroscopy (PES), Rydberg electron transfer (RET) techniques, and ab initio methods. Valence adiabatic electron affinities (EA(a)s) of NE, C(2)H(5)NO(2), and its clusters, (C(2)H(5)NO(2))(n), n=2-5, are estimated using vibrationally unresolved PES to be 0.3+/-0.2 eV (n=1), 0.9+/-0.2 eV (n=2), 1.5+/-0.2 eV (n=3), 1.9+/-0.2 eV (n=4), and 2.1+/-0.2 eV (n=5). These energies were then used to determine stepwise anion-neutral solvation energies and compared with previous literature values. Vertical detachment energies for (C(2)H(5)NO(2))(n)(-) were also measured to be 0.92+/-0.10 eV (n=1), 1.63+/-0.10 eV (n=2), 2.04+/-0.10 eV (n=3), and 2.3+/-0.1 eV (n=4). RET experiments show that Rydberg electrons can be attached to NE both as dipole-bound and valence bound anion states. The results are similar to those found for nitromethane (NM), where it was argued that the diffuse dipole state act as a "doorway state" to the more tightly bound valence anion. Using previous models for relating the maximum in the RET dependence of the Rydberg effective principle number n(max)(*), the dipole-bound electron affinity is predicted to be approximately 25 meV. However, a close examination of the RET cross section data for NE and a re-examination of such data for NM finds a much broader dependence on n(*) than is seen for RET in conventional dipole bound states and, more importantly, a pronounced [l] dependence is found in n(max)(*) (n(max)(*) increases with [l]). Ab initio calculations agree well with the experimental results apart from the vertical electron affinity value associated with the dipole bound state which is predicted to be 8 meV. Moreover, the calculations help to visualize the dramatic difference in the distributions of the excess electron for dipole-bound and valence states, and suggest that NE clusters form only anions where the excess electron localizes on a single monomer.