Slow-fast hamiltonian dynamics near a ghost separatix loop

We study the behavior of a slow-fast (singularly perturbed) Hamiltonian system with two degrees of freedom, losing one degree of freedom at the singular limit = 0, near its ghost separatrix loop, i.e., a homoclinic orbit to a saddle equilibrium of the slow (one degree of freedom) system. We show that, for small > 0, the system has an equilibrium of the saddle-center type and prove, using the method of Delatte, that the Moser normal form exists in an O()-neighborhood of the equilibrium. Then we show that one-dimensional separatrices of the equilibria are generically split with exponentially small splitting. Also, we demonstrate that out of some exponentially thin neighborhood of the ghost separatrix loop in the level of a Hamiltonian containing a saddle-center, the major part of the phase space is foliated into Diophantine invariant tori.Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 8 , Suzdal Conference—2, 2003.This revised version was published online in April 2005 with a corrected cover date.     

Glass-modified stress waves for adhesion measurement of ultra thin films for device applications

Laser-generated stress wave profiles with rarefaction shocks (almost zero post-peak decay times) have been uncovered in different types of glasses and presented in this communication. The rise time of the pulses was found to increase with their amplitude, with values reaching as high as . This is in contrast to measurements in other brittle crystalline solids where pulses with rise times of and post-peak decay times of were recorded. The formation of rarefaction shock is attributed to the increased compressibility of glasses with increasing pressures. This was demonstrated using a one-dimensional nonlinear elastic wave propagation model in which the wave speed was taken as a function of particle velocity. The technological importance of these pulses in measuring the tensile strength of very thin film interfaces is demonstrated by using a previously developed laser spallation experiment in which a laser-generated compressive stress pulse in the substrate reflects into a tensile wave from the free surface of the film and pries off its interface at a threshold amplitude. Because of the rarefaction shock, glass-modified waves allow generation of substantially higher interfacial tensile stress amplitudes compared with those with finite post-peak decay profiles. Thus, for the first time, tensile strengths of very strong and ultra thin film interfaces can be measured. Results presented here indicate that interfaces of 185-nm-thick films, and with strengths as high as , can be measured. Thus, an important advance has been made that should allow material optimization of ultra thin layer systems that may form the basis of future MEMS-based microelectronic, mechanical and clinical devices.     

Robust exponential acceleration in time-dependent billiards

A class of nonrelativistic particle accelerators in which the majority of particles gain energy at an exponential rate is constructed. The class includes ergodic billiards with a piston that moves adiabatically and is removed adiabatically in a periodic fashion. The phenomenon is robust: deformations that keep the chaotic character of the billiard retain the exponential energy growth. The growth rate is found analytically and is, thus, controllable. Numerical simulations corroborate the analytic predictions with good precision. The acceleration mechanism has a natural thermodynamical interpretation and is applied to a hot dilute gas of repelling particles.     

Battery-operated, argon-hydrogen microplasma on hybrid, postage stamp-sized plastic-quartz chips for elemental analysis of liquid microsamples using a portable optical emission spectrometer

A battery-operated, atmospheric pressure, self-igniting, planar geometry Ar–H₂ microplasma for elemental analysis of liquid microsamples is described. The inexpensive microplasma device (MPD) fabricated for this work was a hybrid plastic–quartz structure that was formed on chips with an area (roughly) equal to that of a small-sized postage stamp (MPD footprint, 12.5-mm width by 38-mm length). Plastic substrates were chosen due to their low cost, for rapid prototyping purposes, and for a speedy microplasma device evaluation. To enhance portability, the microplasma was operated from an 18-V rechargeable battery. To facilitate portability even further, it was demonstrated that the battery can be recharged by a portable solar panel. The battery-supplied dc voltage was converted to a high-voltage ac. The ∼750-μm (diameter) and 12-mm (long) Ar–H₂ (3% H₂) microplasma was formed by applying the high-voltage ac between two needle electrodes. Spectral interference from the electrode materials or from the plastic substrate was not observed. Operating conditions were found to be key to igniting and sustaining a microplasma that was simply “warm” to the touch (thus alleviating the need for cooling or other thermal management) and that had a stable background emission. A small-sized (900 μL internal volume) electrothermal vaporization system (40-W max power) was used for microsample introduction. Microplasma background emission in the spectral region between 200 and 850 nm obtained using a portable fiber-optic spectrometer is reported and the effect of the operating conditions is described. Analyte emission from microliter volumes of dilute single-element standard solutions of Cd, Cu, K, Li, Mg, Mn, Na, Pb, and Zn is documented. The majority of spectral lines observed for the elements tested were from neutral atoms. The relative lack of emission from ion lines simplified the spectra, thus facilitating the use of a portable spectrometer. Despite the relative spectral simplicity, some spectral interference effects were noted when running a multi-element solution. An example of how interference in the spectral domain can be resolved in the time domain using selective thermal vaporization is provided. Analytical utility and performance characteristics are reported; for example, K concentrations in diluted (∼30 times) bottled water were determined to be 4.1 ± 1.0 μg/mL (4 μg/mL was the stated concentration), precision was about 25%, and the estimated detection limits were in the picogram range (or in nanograms per milliliter in relative units).     

From Primary Silylphosphanes and Arsanes to Novel Group 13–15 Clusters

Abstract

The reaction of the primary silylphosphanes and -arsanes 1 with [LiAlH₄] leads. under evolution of H2 and depending on the solvent, to the different unusual clusters 2 and 3. Compound 2 has a rhombododecahedral skeleton. Surprisingly, the same reaction of the starting materials in DME instead of Et₂O as solvent hrnishes the triple ion pair 3.     

Induction of A549 Nonsmall-Cell Lung Cancer Cells Proliferation by Photoreleased Nicotine

Caged compounds comprise the group of artificially synthesized, light-sensitive molecules that enable in situ derivation of biologically active constituents capable of affecting cells, tissues and/or biological processes upon exposure to light. Ruthenium-bispyridine (RuBi) complexes are photolyzed by biologically harmless visible light. In the present study, we show that RuBi-caged nicotine can be used as a source of free nicotine to induce proliferation of A549 nonsmall-cell lung cancer (NSCLC) cells by acting on nicotinic acetylcholine receptors expressed in these cells. RuBi-nicotine was photolyzed using LED light source with the spectrum matching RuBi-absorption. Photorelease of free nicotine ([Nic]_p/r) was quantified by high-performance liquid chromatography (HPLC). 5-s-long light exposure of 10 μm of RuBi-nicotine generated 2 μm [Nic]_p/r which enhanced A549 cell proliferation similarly to the 2 μm of plain nicotine during 72 h of cell culturing. Both RuBi-nicotine per se and its photolysis byproduct exerted no effect on A549 cells. We conclude that RuBi-nicotine can be a good source of free nicotine for inducing short- and long-term biological effects. Photolysis of RuBi-nicotine is quite effective, and can produce biologically relevant concentrations of nicotine at acceptable concentrations of the source material with the use of simple, inexpensive, and easily accessible light sources.