Some topological dynamics properties of discrete-time control systems

This paper is concerned with the study of certain stabilityproperties of discrete-time systems by means of topologicalmethods. It turns out that suitably defined sets guarantee thestability of the reachable sets in the vicinity of compact sets.Furthermore, special properties about affine control systemsare given.     

Nanoporous metal organic framework materials for hydrogen storage

Hydrogen is expected to play an important role in future transportation as a promising alternative clean energy source to carbon-based fuels.One of the key challenges to commercialize hydrogen energy is to develop appropriate onboard hydrogen storage systems,capable of charging and discharging large quantities of hydrogen with fast enough kinetics to meet commercial requirements.Metal organic framework (MOF) is a new type of inorganic and organic hybrid nanoporous particulate materials.Its diverse networks can enhance hydrogen storage through tuning the structure and property of MOFs.The MOF materials so far developed adsorb hydrogen through weak disperston interactions,which allow significant quantity of hydrogen to be stored at cryogenic temperatures with fast kinetics.Novel MOFs are being developed to strengthen the interactions between hydrogen and MOFs in order to store hydrogen under ambient conditions.This review surveys the development of such candidate materials,their performance and future research needs.     

Chemical Factors That Influence the Production of Conductive and/or Reflective Silver-Doped Polyimide Films

ABSTRACT

Doping a poly(amide acid) resin with a silver containing additive (1,5-cyclooctadiene-hexafluoroacetylacetonato)-silver(I) [Ag(COD) (HFA)] resulted, after thermal cure, in either a highly reflective or highly eléctrically conductive polyimide film. The combination of monomers, which render films with low T_g (~210°C), and contained sulfur, produced films with surface resistance in the range 10^1–10³ ohms. On the other hand, films with specular reflectivity (relative to a silver mirror) in the range of 65–48% were obtained using both high T_g polyimides and polyimides void of sulfur in the polyimide backbone with low T_g. Our understanding regarding the structure-property relationship on these polyimide films and also the characterization of the doped-films are discussed.     

Comparison of all-optical co- and counter-propagating high-speed signal processing in SOA-based Mach–Zehnder interferometers

The all-optical signal processing performance of a Mach–Zehnder interferometer (MZI) is investigated. Calculated switching windows are used to investigate and understand the physical mechanisms limiting the high speed performance. Especially, the co- and counter-propagating operation of the MZI is discussed and important differences in the performance for the two schemes are addressed. The non-regenerative all-optical clear and drop functionality is investigated for a 2, 4 and 8 × 40 Gbit/s signal, showing good performance in the co-propagating case. Regenerative simultaneous clear and drop functionality in a single MZI is demonstrated experimentally and compared to the large signal model predictions.     

Three-photon absorption spectroscopy: the L(1Φ3) and m(3II1) states of HCl and DCl

Analysis of (3+1) REMPI room temperature spectra by use of three-photon absorption modelling allowed, for the first time, identification and characterization of Ω = 3, Φ states (L(¹Φ₃)) in HCl and DCl and of the m(³II₁) state in DCl. Simulation analyses and determination of isotope shifts allowed evaluation of vibrational and rotational spectroscopic parameters for both states and both molecules. The mechanism of three-photon absorption in the m(³II₁) ← X(¹Σ⁺) transition is discussed.     

Practical considerations in T1 mapping of prostate for dynamic contrast enhancement pharmacokinetic analyses

There are many challenges in developing robust imaging biomarkers that can be reliably applied in a clinical trial setting. In the case of dynamic contrast-enhanced (DCE) MRI, one such challenge is to obtain accurate precontrast T₁ maps for subsequent use in two-compartment pharmacokinetic models commonly used to fit the MR enhancement time courses. In the prostate, a convenient and common approach for this task has been to use the same 3D spoiled gradient-echo sequence used to collect the DCE data, but with variable flip angles (VFAs) to collect data suitable for T₁ mapping prior to contrast injection. However, inhomogeneous radiofrequency conditions within the prostate have been found to adversely affect the accuracy of this technique. Herein we demonstrate the sensitivity of DCE pharmacokinetic parameters to precontrast T₁ values and examine methods to improve the accuracy of T₁ mapping with flip angle-corrected VFA SPGR methods, comparing T₁ maps from such methods with “gold standard” reference T₁ maps generated with saturation recovery experiments performed with fast spin-echo (FSE) sequences.     

Multiplicity of solutions for a class of nonsymmetric eigenvalue hemivariational inequalities

The aim of this paper is to establish the influence of a non-symmetric perturbation for a symmetric hemivariational eigenvalue inequality with constraints. The original problem was studied by Motreanu and Panagiotopoulos who deduced the existence of infinitely many solutions for the symmetric case. In this paper it is shown that the number of solutions of the perturbed problem becomes larger and larger if the perturbation tends to zero with respect to a natural topology. Results of this type in the case of semilinear equations have been obtained in [1] Ambrosetti, A. (1974), A perturbation theorem for superlinear boundary value problems, Math. Res. Center, Univ. Wisconsin-Madison, Tech. Sum. Report 1446; and [2] Bahri, A. and Berestycki, H. (1981), A perturbation method in critical point theory and applications, Trans. Am. Math. Soc. 267, 1–32; for perturbations depending only on the argument.