Magneto-responsive hybrid materials based on cellulose nanocrystals

We fabricated self-standing films of cellulose nanocrystals (CNC) and electrospun composite fibers with CNC and polyvinyl alcohol both with magnetic properties arising from cobalt iron oxide nanoparticles in the CNC matrix. Aqueous dispersions of cobalt-iron oxide nanoparticles (10–80 nm diameter) and CNCs (ca. 150 nm length) were used as precursor systems for the films and composite fibers. The properties of the hybrid material were determined by electron and atomic force microscopy, X-ray diffraction, thermogravimetry and magnetometry. The CNC-inorganic system was ferromagnetic, with a saturation magnetization of ca. 20 emu g^?1 of the magnetic phase. We demonstrate potential applications of the precursor dispersions, including magnetic fluid hyperthermia and highlight possible uses of the CNC-based magneto-responsive systems in biomedical and magneto-optical components.     

Rate coefficients for the reactions of O(3P) with selected biogenic Hydrocarbons

The rate coefficients for the reaction of O(³P) with the biogenic hydrocarbons Δ³-carene, α-pinene, and isoprene have been measured using a direct method for the first time. O(³P) was generated from the pulsed photolysis of NO₂ or O₃ at 308 nm, and measured by resonance fluorescence at 131 nm. Rate coefficients at room temperature for the biogenics are similar: (3.4 ± 0.6) × 10^?11, (3.7 ± 0.6) × 10^?11, and (3.5 ± 0.6) × 10^?11 cm³ molec^?1 s^?1, for Δ³-carene, α-pinene, and isoprene, respectively. The rate coefficients for the reaction of O(³P) with NO₂ and ethene were also measured with the same method, and these values are within 4% and 10% of the currently recommended values, respectively. The correlation between OH and O(³P)-alkene reaction rate coefficients is updated and discussed. © 1995 John Wiley & Sons, Inc.     

Recognition of biological systems by mass-resolved laser spectroscopy

Molecular clusters are non-covalent aggregates widely recognized as a new state of matter, whose properties are neither those of the individual constituents nor those of their condensed phases. Tailor made molecular clusters have proved to be ideal systems for modelling molecular recognition phenomena and their applications in many scientific fields interlocking the physical and life sciences are now well assessed. In the last few years, it has become possible, through the use of advanced laser techniques, to study the interactions between individual components of a cluster, produced by laser desorption. The studies were carried out developing laser spectroscopic methodologies, capable of characterizing molecular clusters and probing the chemical bond breaking and forming on an extremely short time scale.This paper deals with chiral recognition in gas phase clusters of biological interest through the application of the mass-resolved Resonant Two Photon Ionization (1 and 2 color R2PI) laser technique.The measurement of the spectroscopic shifts and of the fragmentation thresholds of diasteromeric clusters allows the determination of the nature of the interactions which control the formation of biological material and affect their stability and reactivity.     

Analytical Hartree–Fock gradients with respect to the cell parameter: systems periodic in one and two dimensions

Analytical Hartree–Fock gradients with respect to the cell parameter have been implemented in the electronic structure code CRYSTAL, for the case of one- and two-dimensional periodicity. As in most molecular codes, Gaussian type orbitals are used to express the wavefunction. Examples demonstrate that the gradients have a good.     

A constrained minimization problem with integrals on the entire space

In this paper we consider the question of minimizing functionals defined by improper integrals. Our approach is alternative to the method of concentration-compactness and it does not require the verification of strict subaddivity.Dedicated to the memory of Antonio Gilioli (1945–1989)     

Multilayered metal oxide thin film gas sensors obtained by conventional and RF plasma-assisted laser ablation

Multilayered thin films of In₂O₃ and SnO₂ have been deposited by conventional and RF plasma-assisted reactive pulsed laser ablation, with the aim to evaluate their behaviour as toxic gas sensors. The depositions have been carried out by a frequency doubled Nd-YAG laser (λ = 532 nm, τ = 7 ns) on Si(1 0 0) substrates, in O₂ atmosphere. The thin films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical resistance measurements. A comparison of the electrical response of the simple (indium oxide, tin oxide) and multilayered oxides to toxic gas (nitric oxide, NO) has been performed. The influence on the structural and electrical properties of the deposition parameters, such as substrate temperature and RF power is reported.     

Non-Separating Paths in 4-Connected Graphs

In 1975, Lovász conjectured that for any positive integer k, there exists a minimum positive integer f(k) such that, for any two vertices x, y in any f(k)-connected graph G, there is a path P from x to y in G such that G–V(P) is k-connected. A result of Tutte implies f(1) = 3. Recently, f(2) = 5 was shown by Chen et al. and, independently, by Kriesell. In this paper, we show that f(2) = 4 except for double wheels.Received October 17, 2003