Detection of ozone gas using gold nanoislands and surface plasmon resonance

Gold nanoislands interact with gaseous ozone to produce a surface plasmon resonance shift, similarly to the interaction of ozone and gold nanoparticles in water. Gold nanoislands are produced by sputtering, which significantly simplifies the synthesis and produces controlled size for the gold nanoislands. The shift of surface plasmon resonance peak was monitored while gold nanoislands were exposed to variable concentration of gaseous ozone. The shift was then correlated with ozone concentration. Our current results indicate sensing gaseous ozone at concentration of as low as 20 μg/L is achievable. Gold nanoislands were reversed to their original wavelength and were able to cycle between the wavelengths as ozone was introduced and removed. Potentially, this system can be useful as a sensor that identifies the presence of ozone at low part-per-billion concentrations of ozone in gaseous media.     

Properties of a simple bilinear stochastic model: Estimation and predictability

We analyze the properties of arguably the simplest bilinear stochastic multiplicative process, proposed as a model of financial returns and of other complex systems combining both nonlinearity and multiplicative noise. By construction, it has no linear predictability (zero two-point correlation) but a certain nonlinear predictability (non-zero three-point correlation). It can thus be considered as a paradigm for testing the existence of a possible nonlinear predictability in a given time series. We present a rather exhaustive study of the process, including its ability to produce fat-tailed distributions from Gaussian innovations, the unstable characteristics of the inversion of the key nonlinear parameters and of the two initial conditions necessary for the implementation of a prediction scheme and an analysis of the associated super-exponential sensitivity of the inversion of the innovations in the presence of a large impulse. Our study emphasizes the conditions under which a degree of predictability can be achieved and describe a number of different attempts, which overall illuminates the properties of the process. In conclusion, notwithstanding its remarkable simplicity, the bilinear stochastic process exhibits remarkably rich and complex behavior, which makes it a serious candidate for the modeling of financial time series among others.     

Luminescence of europium ions in lanthanum-magnesium hexaaluminate

The photoluminescence of Eu³⁺ ions in hexagonal lanthanum-magnesium aluminate is studied for the first time. The concentration and temperature dependences of the luminescence intensity and the structure of the spectra of La_1–xEu_xMg·Al₁₁O₁₉ for X = 0.01–1.0 were studied, the existence of several types of luminescence centers (LC) was established. Under excitation, predominantly high-symmetry LC (D_3h) are manifested in the charge-transfer band in the luminescence spectra. A group-theoretical analysis of the structure of the luminescence spectra of europium for possible LC in hexaaluminate with the structural type of magnetoplumbite (space group P6₃/mmc) is carried out.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 45–49, October, 1985.We thank our co-workers at the Laboratory of Vibrations, Institute of General Physics of the USSR Academy of Sciences, for assistance in the experiments on selective laser spectroscopy.     

Errors as Multistable Response Options

Five simulations mimicked benchmark phenomena of intact and dyslexic word naming. Initially, an iterative map was tuned to simulate the frequency × consistency interaction in skilled naming. Subsequently, two model parameters were changed, in turn, to produce the regularization error of surface dyslexia (PINT pronounced to rhyme with /mint/), absent pseudoword (BINT) naming of phonological dyslexia (words are named correctly; pseudowords are not), the semantic error of deep dyslexia (BUSH named as /tree/), and a dissociation in picture naming of spoken versus written responses (the spoken response to a picture of a bush is /tree/, but the written response is BUSH). All errors, except absent pseudoword naming, were simulated as transcritical bifurcations.     

Doping of magic nanoclusters in the submonolayer In/Si(100) system

Si(100)4 x 3-In reconstruction is essentially a superlattice of magic (identical-size) Si7In6 nanoclusters. Using scanning tunneling microscopy (STM) observations, we have found that under appropriate growth conditions up to 35% of these clusters can be modified; namely, two Si atoms in the cluster can be replaced by two In atoms, thus forming a Si5In8 cluster. This modification can be considered as a doping of the magic cluster, as it changes the electronic properties of the cluster from semiconducting towards metallic. The doped cluster is less rigid than the ordinary one and swings in the electrical field of the STM tip. The atomic structure and stability of the doped magic cluster have been examined using first-principles total-energy calculations.