Correlation between biological activity and energies of electronic transitions in benzodiazepines. Negative ion mass spectrometry and ultraviolet absorption spectroscopy study of some derivatives

A correlation between the energies of electronic singlet transitions in benzodiazepines and their biological activity, which was revealed earlier by means of negative ion mass spectrometry with resonance electron capture, has been verified with a UV absorption spectroscopy investigation. Also, it has been noted that the energies of electronic singlet transitions in benzodiazepines are close in value to the ionization energies of atoms Cs, Rb, K, Na, Li and Tl, the cations of which are known to play an important role in nerve cell excitation processes. Copyright 1999 John Wiley & Sons, Ltd.     

Lower rim amide (1,3) functionalised calix[4]arene amido-thiourea derivatives as dimetallic Zn(II) coordination complexes for anion recognition/sensing

The synthesis of two amido-thiourea based receptors/sensors 1 and 2, formed by functionalisation of the lower rim of a calix[4]arene, and the photophysical analysis of these with Zn(II) and various anions is described. The two structures, differing by the substituent on the thiourea moiety, were found to bind Zn(II) effectively in ethanol (EtOH); the recognition giving rise to significant changes in the UV-vis absorption spectra, which was red-shifted for both chemosensors. The changes in the absorption spectra were further analysed using nonlinear regression analysis programme (using the global analysis software ReactLab? Equilibria), which revealed high binding constants for both systems. The resulting dimetallic complexes (1,2)–Zn₂ were (pre-formed and) then used to coordinate anionic species such as AcO^? , H₂PO₄^?  and Br^?  through electrostatic interactions, showing high affinity towards these anions. In all cases, nonlinear regression analysis showed both 1:1 or 1:2 sensor:anion depending on the anion used. Although the 2-Zn₂ complex showed high affinity for acetate, phosphate and bromide, the 1-Zn₂ complex showed selectivity towards the recognition of phosphate in EtOH.     

Femtosecond laser writing of optical waveguides with controllable core size in high refractive index glass

Optical waveguides have been produced by femtosecond-laser writing in a high linear and nonlinear refractive index glass (SF57). Light guiding occurs nearby a central damaged zone due to the collateral densification caused by shockwaves generated in the focal volume. High pulse energies are required to induce a modified region capable of supporting a guided mode. An alternative processing method, based on using multiple structures, has been successfully used for the production of waveguides with controllable core size at low energies. PACS 42.82.Et; 42.65.Re; 42.70.Ce; 81.20.–n     

Visible upconversion emission and non-radiative direct Yb to Er energy transfer processes in nanocrystalline ZrO2:Yb,Er

Wide band gap Yb³⁺ and Er³⁺ codoped ZrO₂ nanocrystals have been synthesized by a modified sol-gel method. Under 967 nm excitation strong green and red upconversion emission is observed for several Er³⁺ to Yb³⁺ ions concentration ratios. A simple microscopic rate equation model is used to study the effects of non-radiative direct Yb³⁺ to Er³⁺ energy transfer processes on the visible and near infrared fluorescence decay trends of both Er³⁺ and Yb³⁺ ions. The microscopic rate equation model takes into account the crystalline phase as well as the size of nanocrystals. Nanocrystals phase and size were estimated from XRD patterns. The rate equation model succeeds to fit simultaneously all visible and near infrared fluorescence decay profiles. The dipole-dipole interaction parameters that drive the non-radiative energy transfer processes depend on doping concentration due to crystallite phase changes. In addition the non-radiative relaxation rate (⁴I_11/2→⁴I_13/2) is found to be greater than that estimated by the Judd-Ofelt parameters due to the action of surface impurities. Results suggest that non-radiative direct Yb³⁺ to Er³⁺ energy transfer processes in ZrO₂:Yb,Er are extremely efficient.     

Multiple One-Dimensional Search (MODS) algorithm for fast optimization of laser–matter interaction by phase-only fs-laser pulse shaping

In this work, we have developed and implemented a powerful search strategy for optimization of nonlinear optical effects by means of femtosecond pulse shaping, based on topological concepts derived from quantum control theory. Our algorithm [Multiple One-Dimensional Search (MODS)] is based on deterministic optimization of a single solution rather than pseudo-random optimization of entire populations as done by commonly used evolutionary algorithms. We have tested MODS against a genetic algorithm in a nontrivial problem consisting in optimizing the Kerr gating signal (self-interaction) of a shaped laser pulse in a detuned Michelson interferometer configuration. The obtained results show that our search method (MODS) strongly outperforms the genetic algorithm in terms of both convergence speed and quality of the solution. These findings demonstrate the applicability of concepts of quantum control theory to nonlinear laser–matter interaction problems, even in the presence of significant experimental noise.     

Oscillatory behavior in discrete slow power-law models

Nonlinear Dynamics - Discrete mathematical slow oscillatory models are proposed to describe biological interactions between two populations by considering power-law functions. Conditions for slow...     

Null screen quasi-conformal hypersurfaces in semi-Riemannian manifolds and applications

We introduce a class of null hypersurfaces of a semi-Riemannian manifold, namely, screen quasi-conformal hypersurfaces, whose geometry may be studied through the geometry of its screen distribution. In particular, this notion allows us to extend some results of previous works to the case in which the sectional curvature of the ambient space is different from zero. As applications, we study umbilical, isoparametric and Einstein null hypersurfaces in Lorentzian space forms and provide several classification results.     

Numerical modeling of the immune response to human papillomavirus infection

In this work, we develop mathematical models describing the interactions between Human papillomavirus (HPV)-infected cells and the immune system. We start with simple models in order to capture the most important features of such interactions. Then, we proceed to consider fundamental immunological characteristics for the models. For the numerical counterpart, we develop and implement efficient numerical discretizations of our models in order to illustrate the behavior of the schemes using different initial conditions, which represent the degree of infection of the disease. Understanding such interactions is of paramount importance for the prevention and the potential eradication of the infection. One main goal of this research is to analyze how and under what circumstances the immune system succeeds in eliminating HPV-infected cells.     

Flexible linear polyelectrolytes in multivalent salt solutions: Solubility conditions

Single- and double-stranded DNA and many biological and synthetic polyelectrolytes undergo two structural transitions upon increasing the concentration of multivalent salt or molecules. First, the expanded-stretched chains in low monovalent salt solutions collapse into nearly neutral compact structures when the density of multivalent salt approaches that of the monomers. With further addition of multivalent salt the chains redissolve acquiring expanded-coiled conformations. We study the redissolution transition using a two-state model (F.J. Solis, M. Olvera de la Cruz, J. Chem. Phys. 112, 2030 (2000)). The redissolution occurs when there is a high degree of screening of the electrostatic interactions between monomers, thus reducing the energy of the expanded state. The transition is determined by the chemical potential of the multivalent ions in the solution, μ and the inverse screening length, κ. The transition point also depends on the charge distribution along the chain but is nearly independent of the molecular weight and degree of flexibility of the polyelectrolytes. We generate a diagram of μversusκ² where we find two regions of expanded conformations, one with charged chains and the other with overcharged (inverted charge) chains, separated by a collapsed nearly neutral conformation region. The collapse and redissolution transitions occur when the trajectory of the properties of the salt crosses the boundaries between these regions. We find that in most cases the redissolution occurs within the same expanded branch from which the chain precipitates. Received 15 May 2000 and Received in final form 28 June 2000     

A high-sensitivity in situ optical diagnostic technique for laser cleaning of transparent substrates

A differential optical transmission technique has been used to monitor in situ the efficiency of laser cleaning for the removal of sub-micrometer-sized particles on substrates transparent at the monitoring wavelength. This technique has been applied to the removal of sub-micrometer polystyrene particles on polyimide substrates using laser pulses of 30 ps duration at 292 nm while probing the material transmission at 633 nm. The sensitivity achieved -1/10⁴ for the transmission changes induced upon single-pulse laser exposure – allows us to monitor the removal of just a few sub-micron-sized particles from the probed region inside the irradiated area. Received: 2 October 2002 / Accepted: 7 October 2002 / Published online: 29 January 2003 RID="*" ID="*"Corresponding author. Fax: +33-3/87844082, E-mail: nchaoui@iut.univ-metz.fr RID="**" ID="**"Present address: Laboratoire de Chimie et Applications, Institut Universitaire de Technologie de Metz, Département Chimie, Rue Victor Demange, 57500 Saint-Avold, France