Search results for "Stability."
showing 10 items of 3015 documents
Pressure-Induced High Spin State in [Fe(btr)2(NCS)2]·H2O (btr = 4,4′-bis-1,2,4-triazole)
2000
Application of hydrostatic pressure (≤ 10.5 kbar) on the two-dimensional spin transition compound [Fe(btr)2(NCS)2]·H2O (btr = 4,4‘-bis-1,2,4-triazole) results in an unexpected stabilization of the HS state. On release of the pressure, the HS state is found to be partially trapped. After thermal relaxation of the metastable HS state obtained by the LIESST effect (light-induced excited spin state trapping), a pure LS state is obtained in contrast to the pressure experiments. This different behavior supports a structural phase transition as the likely basis of the pressure-induced HS state.
A spin transition molecular material with a wide bistability domain.
2002
International audience; [Fe(hyptrz)3](4-chloro-3-nitrophenylsulfonate)22 H2O (1; hyptrz=4-(3-hydroxypropyl)-1,2,4-triazole) has been synthesized and its physical properties have been investigated by several physical techniques including magnetic susceptibility measurements, calorimetry, and Mössbauer, optical, and EXAFS spectroscopy. Compound 1 exhibits a spin transition below room temperature, together with a very wide thermal hysteresis of about 50 K. This represents the widest hysteresis loop ever observed for an FeII-1,2,4-triazole spin transition material. The cooperativity is discussed on the basis of temperature-dependent EXAFS studies and of the structural features of a CuII analogu…
Kinetics of phase separation in thin films: simulations for the diffusive case.
2005
We study the diffusion-driven kinetics of phase separation of a symmetric binary mixture (AB), confined in a thin-film geometry between two parallel walls. We consider cases where (a) both walls preferentially attract the same component (A), and (b) one wall attracts A and the other wall attracts B (with the same strength). We focus on the interplay of phase separation and wetting at the walls, which is referred to as {\it surface-directed spinodal decomposition} (SDSD). The formation of SDSD waves at the two surfaces, with wave-vectors oriented perpendicular to them, often results in a metastable layered state (also referred to as ``stratified morphology''). This state is reminiscent of th…
Self-assembly of a bioelastomeric structure: solution dynamics and the spinodal and coacervation lines.
1990
The stability, metastability, and instability regions of aqueous solutions of a representative synthetic bioelastomeric polymer, poly (Val-Pro-Gly-Val-Gly), were determined by a combined use of elastic and quasi-elastic light scattering experiments. The approach followed here offers the attractive advantage of singling out the relevant contributions to the total scattering even in the presence of traces of noninteracting larger sized impurities. Conclusions so reached were checked by means of independent experiments. The present results provide descriptions of the very early events in the physics of bioelastogenesis in terms of general polymer science and phase transitions, and in terms of …
Protein aggregation/crystallization and minor structural changes: universal versus specific aspects.
2007
AbstractProtein association covers wide interests in biophysics, protein science, and biotechnologies, and it is often viewed as governed by conformation details. More recently, the existence of a universal physical principle governing aggregation/crystallization processes has been suggested by a series of experiments and shown to be linked to the universal scaling properties of concentration fluctuations occurring in the proximity of a phase transition (spinodal demixing in the specific case). Such properties have provided a quantitative basis for capturing kinetic association data on a universal master curve, ruled by the normalized distance of the state of the system from its instability…
Ultrafast Photo-Dynamics of a Reversible Photochromic Spiropyran
2002
We report the first ultrafast ring closure kinetics of the merocyanine (MC) of a reverse photochromic spiropyran 1‘,3‘,3‘-trimethyl-6,8-dinitrospiro[2H-1-benzopyran-2,2-indoline] (6,8-dinitro BIPS) and its 1‘-(2-carboxyethyl) substituted derivative. The reaction is fast and essentially over in a few hundred picoseconds. The rate of MC-S1 state decay evaluated from transient absorbance can be correlated directly with the MC-S1 state lifetime as determined using stimulated and ordinary emission measurements. The recovery of the MC-S0 state from MC-S1 has a component with a lifetime of 60−78 ps in acetonitrile with a second component of 350−470 ps probably due to a metastable intermediate. We …
Some efficient algorithms for the solution of a single nonlinear equation
1981
High order methods for the numerical solution of nonlinear scalar equations are proposed which are more efficient than known procedures, and a unified approach to various methods suggested in literature is given.
Chapter 3 Giant Siliceous Spicules From the Deep‐sea Glass Sponge Monorhaphis chuni
2009
Only 13 years after realizing, during a repair of a telegraph cable pulled out from the deep sea, that the depth of the ocean is plentifully populated with a highly diverse fauna and flora, the Challenger expedition (1873-1876) treasured up a rich collection of vitreous sponges (Hexactinellida). They had been described by Schulze and represent the phylogenetically oldest class of siliceous sponges (phylum Porifera); they are eye-catching because of their distinct body plan, which relies on a filigree skeleton. It is constructed by an array of morphologically determined elements, the spicules. Soon after, during the German Deep Sea Expedition "Valdivia" (1898-1899), Schulze could describe th…
Albumin-driven disassembly of lipidic nanoparticles: the specific case of the squalene-adenosine nanodrug
2020
International audience; In the field of nanomedicine, nanostructured nanoparticles (NPs) made of self-assembling prodrugs emerged in the recent years with promising properties. In particular, squalene-based drug nanoparticles have already shown their efficiency through in vivo experiments. However, a complete pattern of their stability and interactions in the blood stream is still lacking. In this work we assess the behavior of squalene-adenosine (SQAd) nanoparticles-whose neuroprotective effect has already been demonstrated in murine models-in the presence of fetal bovine serum (FBS) and of bovine serum albumin (BSA), the main protein of blood plasma. Extensive physicochemical characteriza…
Critical temperature of the LIESST effect in iron(II) spin crossover compounds
1999
Abstract The light-induced crossover in a series of iron(II) compounds has been investigated by irradiating the sample at 10 K with a Kr + laser coupled to an optical fiber within a SQUID cavity. The temperature dependence of the molar fraction of the light-induced metastable HS state has been recorded for 22 compounds. The critical LIESST temperature, T c (LIESST), has been defined as the temperature for which the light-induced HS information was erased in the SQUID cavity. The dependence of T c (LIESST) as a function of the thermal spin crossover temperature, T 1/2 , has been discussed. The effect of cooperation has been analyzed and the influence of horizontal and vertical displacements …