Gatekeeping layer effect: a poly(lactic acid)-coated mesoporous silica nanosphere-based fluorescence probe for detection of amino-containing neurotransmitters

We have synthesized a poly(lactic acid) coated MCM-41-type mesoporous silica nanosphere (PLA-MSN) material can serve as a fluorescence sensor system for detection of amino-containing neurotransmitters in neutral aqueous buffer. Utilizing the PLA layer as a gatekeeper, we investigated the molecular recognition events between several structurally simple neurotransmitters, i.e., dopamine, tyrosine, and glutamic acid and a pore surface-anchored o-phthalic hemithioacetal (OPTA) group, which functions as a fluorescence-sensing group that can react with the neurotransmitters with primary amine groups and form the corresponding fluorescent isoindole products. The poly(lactic acid) layer of the PLA-MSN sensor showed a unique "sieving" effect that regulates the rates of diffusion of the amino acid-based neurotransmitters into the sensor mesopores of the material.     

Vortices in a 2d rotating Bose–Einstein condensate

We investigate the physical model for a two dimensional rotating Bose–Einstein condensate. We minimize a Gross–Pitaevskii functional defined in ${\mathbb{R}}^2$ under the unit mass constraint. We estimate the critical rotational speeds ${\Omega }_d$ for having d vortices in the condensate and we determine the location of the vortices. This relies on an asymptotic expansion of the energy. To cite this article: R. Ignat, V. Millot, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Reversing the training effect in exchange biased CoO/Co bilayers

We performed a detailed study of the training effect in exchange biased CoO/Co bilayers. High-resolution measurements of the anisotropic magnetoresistance (AMR) display an asymmetry in the first magnetization reversal process and training in the subsequent reversal processes. Surprisingly, the AMR measurements as well as magnetization measurements reveal that it is possible to partially reinduce the untrained state by performing a hysteresis measurement with an in-plane external field perpendicular to the cooling field. Indeed, the next hysteresis loop obtained in a field parallel to the cooling field resembles the initial asymmetric hysteresis loop, but with a reduced amount of spin rotation occurring at the first coercive field. This implies that the antiferromagnetic domains, which are created during the first reversal after cooling, can be partially erased.     

Elucidation of the structure of a highly efficient blue electroluminescent material

We determined that the structure of the previously published highly efficient blue electroluminescent borate complex, lithium tetra(2-methyl-8-hydroxyquinolato) boron, does not contain boron. Rather, it is the lithium salt of 2-methyl-8-hydroxyquinoline.     

Selective NMR excitation in strongly inhomogeneous magnetic fields

The NMR-MOUSE is a unilateral and mobile NMR sensor which operates with highly inhomogeneous magnetic fields. To produce a mobile NMR unit, RF excitation is sought, which can be produced with the most simple equipment, in particular nonlinear, low-power amplifiers, and to observe a free induction decay in strongly inhomogeneous fields, the excitation needs to be selective. The possibility to produce selective excitation by sequences of hard low-power radiofrequency pulses in the strongly inhomogeneous magnetic fields of the NMR-MOUSE is explored. The use of the DANTE sequence for selection of magnetization from parts of the sensitive volume was investigated for longitudinal and transverse magnetization by computer simulations and experiments. The spectra of the recorded FIDs and echo signals are in good agreement with those simulated for the excitation, which verifies the concept of the DANTE excitation. The results obtained are an important step towards a low-power operation of the NMR-MOUSE to improve its mobility.     

The beginnings of Analytical Chemistry in Romania

The early time of Analytical Chemistry in Romania is presented. Starting from 1920, the famous schools of chemical analysis in the University of Cluj, Bucharest and Iassy were established. As an example, the team headed by Professor G. Spacu introduced the use of complex compounds as reagents in analytical chemistry. In this way many macro and micro gravimetric methods for elemental determination were proposed. Received: 1 March 1996 / Accepted: 20 May 1996     

The commutator method for form-relatively compact perturbations

We present a variant of the conjugate operator method which can be used when the group generated by the conjugate operator leaves invariant only the form domain of the Hamiltonian. As an example, we get detailed spectral properties and a large class of locally smooth operators for two-body Schrödinger Hamiltonians with form-relatively compact potentials.     

Lie Symmetries for Hamiltonian Systems Methodological Approach

This paper proposes an algorithm for the Lie symmetries investigation in the case of a 2D Hamiltonian system. General Lie operators are deduced firstly and, in the the next step, the associated Lie invariants are derived. The 2D Yang-Mills mechanical model is chosen as a test model for this method. PACS: 05.45.-a; 02.30.Ik     

Generalized contraction mapping principles in probabilistic metric spaces

We give an improvement of Theorem 1 from [2] with a quite different approach, which enable us to prove that the fixed point is also globally attractive. In Theorem 2.11 a further generalization is obtained for a complete Menger space (S,F,T), where T belongs to a more general class of continuous t-norms than in the previous case where T=T _M (=min). Theorem 3.2 is a generalization of Theorem 2 from [2]. Thereafter the notion of a generalized C-contraction of Krasnoselski's type is introduced and a fixed point theorem for such mappings is proved. An application in the space S(Ω, K, P) is given.