排序方式: 共有49条查询结果,搜索用时 234 毫秒
41.
Bertrand L Robinet L Cohen SX Sandt C Le Hô AS Soulier B Lattuati-Derieux A Echard JP 《Analytical and bioanalytical chemistry》2011,399(9):3025-3032
The study of varnishes from musical instruments presents the difficulty of analysing very thin layers of heterogeneous materials
on samples most of which are generally brittle and difficult to prepare. Such study is crucial to the understanding of historical
musical instrument varnishing practices since written sources before 1800 are very rare and not precise. Fourier-transform
infrared (FTIR) spectroscopy and imaging methods were applied to identify the major chemical components within the build-up
of the varnish layers on a cello made by one of the most prominent French violin-makers of the eighteenth century (Jacques
Boquay, ca. 1680–1730). Two types of FTIR imaging methods were used: scanning with a synchrotron-based microscope and full-field
imaging using a 2D imager with a conventional source. An interpretation of the results obtained from these studies on the
Boquay cello is that the maker first applied a proteinaceous layer, probably gelatine-based animal glue. He later applied
a second layer based on a mixture of a drying oil and diterpenic resin from Pinaceae sp. From an historical perspective, the results complement previous studies by describing a second technique used for musical
instrument finishes at the beginning of the eighteenth century in Europe. 相似文献
42.
In this paper we studied a non-ideal system with two degrees of freedom consisting of a dumped nonlinear oscillator coupled to a rotatory part. We investigated the stability of the equilibrium point of the system and we obtain, in the critical case, sufficient conditions in order to obtain an appropriate Normal Form. From this, we get conditions for the appearance of Hopf Bifurcation when the difference between the driving torque and the resisting torque is small. It was necessary to use the Bezout Theorem, a classical result of Algebraic Geometry, in the obtaining of the foregoing results. 相似文献
43.
Jean‐Philippe Echard Loïc Bertrand Dr. Alex von Bohlen Dr. Anne‐Solenn Le Hô Dr. Céline Paris Dr. Ludovic Bellot‐Gurlet Dr. Balthazar Soulier Agnès Lattuati‐Derieux Dr. Sylvie Thao Laurianne Robinet Dr. Bertrand Lavédrine Prof. Stéphane Vaiedelich 《Angewandte Chemie (International ed. in English)》2010,49(1):1-1
44.
Jean‐Philippe Echard Loïc Bertrand Dr. Alex von Bohlen Dr. Anne‐Solenn Le Hô Dr. Céline Paris Dr. Ludovic Bellot‐Gurlet Dr. Balthazar Soulier Agnès Lattuati‐Derieux Dr. Sylvie Thao Laurianne Robinet Dr. Bertrand Lavédrine Prof. Stéphane Vaiedelich 《Angewandte Chemie (International ed. in English)》2010,49(1):197-201
45.
Balthazar Toussaint Taslyne Immame Hassane Beck Estelle Surget Vincent Boudy Emmanuel Jaccoulet 《Journal of separation science》2023,46(6):2200766
In this study, we discuss the origin of the slightly increased response of the charged aerosol detector when low-concentration polar drugs formulated with sodium chloride are analyzed by hydrophilic interaction liquid chromatography coupled to the charged aerosol detector. In the case of tromethamine mixed with saline solutions, we investigated several levels including the mobile phase, sample matrix, and detection. We show that the analysis of the rich-salted sample results in both interactions with the mobile phase modifiers and the stationary phase during the run time. With 150 mM NaCl as a compounding solution, a slight increase in the tromethamine peak area was observed (<5.5%). Our study suggests that chloride ions in excess sequentially interact firstly with the counterions from the organic modifiers and secondly with the analyte via the stationary phase and the contribution of hydrophilic interaction liquid chromatography retention mechanisms. Because of these effects, the hydrophilic interaction liquid chromatography-charged aerosol detector analysis of drugs in saline solutions requires particular attention, and a correction factor for quantitative purposes that accounts for formulation ions remains appropriate. 相似文献
46.
Analytical study of the nonlinear behavior of a shape memory oscillator: Part II—resonance secondary
In this work, the response of a single-degree-of-freedom shape memory oscillator subjected to the excitation harmonic has
been investigated. Equation of motion is formulated assuming a polynomial constitutive model to describe the restitution force
of the oscillator. Here the method of multiple scales is used to obtain an approximate solution to the equations of the motion
describing the modulation equations of amplitude and phase, and to investigate theoretically its stability. This work is presented
in two parts. In Part I of this study we showed the modeling of the problem where the free vibration of the oscillator at
low temperature is analyzed, where martensitic phase is stable. Part I also presents the investigation dynamics of the primary
resonance of the pseudoelastic oscillator. Part II of the work is focused on the study in the secondary resonance of a pseudoelastic
oscillator using the model developed in Part I. The analysis of the system in Part I as well as in Part II is accomplished
numerically by means of phase portraits, Lyapunov exponents, power spectrum and Poincare maps. Frequency-response curves are
constructed for shape memory oscillators for various excitation levels and detuning parameter. A rich class of solutions and
bifurcations, including jump phenomena and saddle-node bifurcations, is found. 相似文献
47.
Karina Penedo Carvalho Nathalia Balthazar Martins Ana Rosa Lopes Pereira Ribeiro Taliria Silva Lopes Rodrigo Caciano de Sena Pascal Sommer José Mauro Granjeiro 《Journal of nanoparticle research》2016,18(8):244
Nanoparticles agglomerate when in contact with biological solutions, depending on the solutions’ nature. The agglomeration state will directly influence cellular response, since free nanoparticles are prone to interact with cells and get absorbed into them. In sunscreens, titanium dioxide nanoparticles (TiO2-NPs) form mainly aggregates between 30 and 150 nm. Until now, no toxicological study with skin cells has reached this range of size distribution. Therefore, in order to reliably evaluate their safety, it is essential to prepare suspensions with reproducibility, irrespective of the biological solution used, representing the above particle size distribution range of NPs (30–150 nm) found on sunscreens. Thus, the aim of this study was to develop a unique protocol of TiO2 dispersion, combining these features after dilution in different skin cell culture media, for in vitro tests. This new protocol was based on physicochemical characteristics of TiO2, which led to the choice of the optimal pH condition for ultrasonication. The next step consisted of stabilization of protein capping with acidified bovine serum albumin, followed by an adjustment of pH to 7.0. At each step, the solutions were analyzed by dynamic light scattering and transmission electron microscopy. The final concentration of NPs was determined by inductively coupled plasma-optical emission spectroscopy. Finally, when diluted in dulbecco’s modified eagle medium, melanocytes growth medium, or keratinocytes growth medium, TiO2–NPs displayed a highly reproducible size distribution, within the desired size range and without significant differences among the media. Together, these results demonstrate the consistency achieved by this new methodology and its suitability for in vitro tests involving skin cell cultures. 相似文献
48.
Mathematical modeling and control of population systems: Applications in biological pest control 总被引:1,自引:0,他引:1
The aim of this paper is to apply methods from optimal control theory, and from the theory of dynamic systems to the mathematical modeling of biological pest control. The linear feedback control problem for nonlinear systems has been formulated in order to obtain the optimal pest control strategy only through the introduction of natural enemies. Asymptotic stability of the closed-loop nonlinear Kolmogorov system is guaranteed by means of a Lyapunov function which can clearly be seen to be the solution of the Hamilton–Jacobi–Bellman equation, thus guaranteeing both stability and optimality. Numerical simulations for three possible scenarios of biological pest control based on the Lotka–Volterra models are provided to show the effectiveness of this method. 相似文献
49.
Pauline Legrand Rabah Gahoual Raphaël Benattar Balthazar Toussaint Caroline Roques Nathalie Mignet Sophie Goulay‐Dufaÿ Pascal Houz 《Journal of separation science》2020,43(14):2925-2935
Ascorbic acid is a powerful antioxidant compound involved in many biological functions, and a chronic deficiency is at the origin of scurvy disease. A simple, rapid, and cost‐effective capillary electrophoresis method was developed for the separation and simultaneous quantification of ascorbic acid and the major degradation products: dehydroascorbic acid, furfural, and furoic acid. Systematic optimization of the conditions was performed that enabled baseline separation of the compounds in less than 10 min. In addition to simultaneous quantification of ascorbic acid alongside to the degradation products, stability studies demonstrated the possibility using capillary electrophoresis to separate and identify the major degradation products. Thus, high‐resolution tandem mass spectrometry experiments were conducted in order to identify an unknown degradation product separated by capillary electrophoresis and significantly present in degraded samples. Comparison of mass spectrometry data and capillary electrophoresis electropherograms allowed to identify unambiguously trihydroxy‐keto‐valeraldehyde. Finally, capillary electrophoresis was successfully applied to evaluate the composition of different pharmaceutical preparation of ascorbic acid. Results showed the excellent performance of the capillary electrophoresis method due to the separation of excipients from the compounds of interest, which demonstrated the relevance of using an electrophoretic separation in order to perform comprehensive stability studies of ascorbic acid. 相似文献