Apertureless scanning near-field optical microscopy: the need for probe-vibration modeling

In apertureless scanning near-field optical microscopy (ASNOM), the probe vibration is often used to increase the detected signal. The useful signal is detected at the probe-vibration frequency by a lock-in amplifier. By comparing two-dimensional numerical results with an experimental scan, we show numerically that, to explain or predict the detected signal, a realistic model of ASNOM should take into account the scan of the probe as well as the probe vibration and the material properties.     

Existence of periodic travelling waves solutions in predator prey model with diffusion

This paper deals with the qualitative analysis of the travelling waves solutions of a reaction diffusion model that refers to the competition between the predator and prey with modified Leslie–Gower and Holling type II schemes. The well posedeness of the problem is proved. We establish sufficient conditions for the asymptotic stability of the unique nontrivial positive steady state of the model by analyzing roots of the forth degree exponential polynomial characteristic equation. We also prove the existence of a Hopf bifurcation which leads to periodic oscillating travelling waves by considering the diffusion coefficient as a parameter of bifurcation. Numerical simulations are given to illustrate the analytical study.     

Quantitative trace analysis of benzene using an array of plasma-treated metal-decorated carbon nanotubes and fuzzy adaptive resonant theory techniques

The functionalization of carbon nanotube sidewalls with metal nanoparticles is exploited here to improve the sensitivity and selectivity of gas sensors operated at room temperature. An array of sensors using oxygen plasma treated multiwalled carbon nanotubes (bare and decorated with Pt, Pd or Rh nanoparticles) is shown to selectively detect traces of benzene (i.e., 100 ppb) in the presence of carbon monoxide, hydrogen sulfide or nitrogen dioxide at different humidity levels. Employing a quantitative fuzzy adaptive resonant theory (ART) network whose inputs are the responses of the sensor array, it is possible to accurately estimate benzene concentration in a changing background. The quantitative fuzzy ART is especially suited for compensating the nonlinear effects in sensor response caused by changes in ambient humidity, which explains why this method clearly outperforms partial least squares calibration models at estimating benzene concentration. These results open the way to design new affordable, wearable, sensitive and selective detectors aimed at the personal protection of workers subject to occupational exposure to benzene, toluene, ethyl benzene and xylenes.     

Light mass galileons: Cosmological dynamics,mass screening and observational constraints

In this Letter, we examine the cosmological viability of a light mass galileon field consistent with local gravity constraints. The minimal, _L3=□?(_∂μ?)²$L_3=\square ?{({\partial }_{\mu }?)}^2$, massless galileon field requires an additional term in order to give rise to a viable ghost free late time acceleration of Universe. The desired cosmological dynamics can either be achieved by incorporating an additional terms in the action such as (_L4,_L5)$(L_4,L_5)$ – the higher order galileon Lagrangians or by considering a light mass field à la galileon field potential. We analyze the second possibility and find that: (1) The model produces a viable cosmology in the regime where the non-linear galileon field is subdominant, (2) the Vainshtein mechanism operates at small scales where the non-linear effects become important and contribution of the field potential ceases to be significant. Also the small mass of the field under consideration is protected against strong quantum corrections thereby providing quantum stability to the system.     

Dynamics and numerical simulations in a production and development of red blood cells model with one delay

In this paper, we study an unstructured model of a cellular population in the spirit of Grabosch and Heijmans [Grabosch A, Heijmans HJAM. Production, development and maturation of red blood cells, A mathematical model. AM-R 8919, ISSN 0924-2953, 1989.] model. The cellular population is described by a system of differential equations with one delay. The basic assumption is that the cell population responsible for the production of blood cells consists of three compartments: the stem cells, the precursor cells, and the blood cells. We prove that the model has two possible steady states and their dynamics (depending on time delay) are studied in term of the local stability, we illustrate these results with numerical simulations for some different values of the time delay.     

Coupling semiconductor lasers into single-mode optical fibers by use of tips grown by photopolymerization

We show that a polymer tip, integrated by free-radical photopolymerization at the end of a telecommunication optical fiber, allows high-efficiency coupling between the fiber and an infrared laser diode. A coupling efficiency of 70% (1.5-dB loss) was achieved. We obtained this result by controlling the radius of curvature of the tip, the origin of which is discussed in terms of the photochemical influence of oxygen during tip formation. The experimental data were found to be in agreement with results of electromagnetic calculations based on the finite-element method.     

Studies on the Selective Reduction of the Amide Link of Acyclic and Macrocyclic Amidoketals: Unexpected Cleavage and trans‐Acetalization with Red‐Al®

Selective reduction of the amide moiety of acyclic and macrocyclic amidoketals was studied in presence of various reagents (BH₃ · Me₂S, iBuAlH₂, Red‐Al^®, LiAlH₄). The best results were obtained with lithium aluminium hydride in the presence of triethylamine traces, whereas borane dimethyl sulfide gave rise to a partial ketal reduction of the acyclic compound and Red‐Al^® to a cleavage of the macrocyclic molecule accompanied by an unexpected trans‐acetalization.