Essai de domestication de lentinus squarrosulus mont. a partir d’une souche du Gabon

Dans le cadre d’un vaste programme de valorisation des ressources biologiques initié par les autorités gabonaises en vue de garantir la sécurité alimentaire des populations locales, une souche sauvage de Lentinus squarrosulus récoltée au nord du Gabon, a été mise en culture en utilisant essentiellement des matériaux locaux. Au cours de ce processus, cinq principales étapes ont été mise en œuvre; il s’agit notamment de la production du blanc de semis et du substrat de culture, du lardage du substrat, de l’incubation et de la  fructification du champignon. La production du blanc regroupe les étapes qui ont obligatoirement été exécutées dans un laboratoire parfaitement équipé en vue de garantir des conditions d’asepsie rigoureuses, tandis que la production du substrat de culture, l’inoculation et l’incubation ont parfaitement été réalisées à l’échelle villageoise en utilisant du matériel de fabrication traditionnelle; notamment une unité de pasteurisation constituée d’un fût en aluminium de 250 litres muni d’étagères et d’une chambre contenant de l’eau, ainsi qu’une armoire traditionnelle d’inoculation. Par ce processus, quatre-vingt sacs de 1kg ont été inoculés dont quatorze ont montré un très bon envahissement mycélien et une fructification satisfaisante; ce qui donne un rendement en terme de sac d’environ 17 %. Cependant, cinquante-six sacs n’ont pas été bien envahis par le mycélium et n’ont donc pas donné de champignon, de plus dix sacs ont été contaminés. Mots clés : domestication, souche sauvage, Lentinus squarrosulus, matériaux locaux, Gabon English title: Domestication test of lentinus squarrosulus mont. from a Gabon strain As part of a vast program to develop biological resources initiated by the Gabonese authorities with a view to guaranteeing food security for local populations, a wild strain of Lentinus squarrosulus harvested in northern Gabon was cultivated using mainly local materials. During this process, five main steps were implemented; these include the production of seedling white and growing medium, larding of the substrate, incubation and fruiting of the fungus. The production of the blank includes the steps which must have been carried out in a perfectly equipped laboratory in order to guarantee rigorous aseptic conditions, while the production of the culture substrate, inoculation and incubation have been perfectly carried out at village scale using traditional manufacturing  equipment; including a pasteurization unit consisting of a 250-liter aluminum drum with shelves and a chamber containing water, as well as a traditional inoculation cabinet. By this method, eighty bags (1kg) were inoculated, fourteen of which showed very good mycelial invasion and satisfactory fruiting; which gives a yield of around 17%. However, fifty-six bags were not well invaded by the mycelium and therefore did not give a fungus, and ten bags were contaminated. Keywords: domestication, wild strain, Lentinus squarrosulus, local materials, Gabo

Photothermal heterodyne imaging of individual nonfluorescent nanoclusters and nanocrystals

We introduce a new, highly sensitive, and simple heterodyne optical method for imaging individual nonfluorescent nanoclusters and nanocrystals. A 2 order of magnitude improvement of the signal is achieved compared to previous methods. This allows for the unprecedented detection of individual small absorptive objects such as metallic clusters (of 67 atoms) or nonluminescent semiconductor nanocrystals. The measured signals are in agreement with a calculation based on the scattering field theory from a photothermal-induced modulated index of refraction profile around the nanoparticle

Resolved diffraction patterns from a reflection grating for atoms

We have studied atomic diffraction at normal incidence from an evanescent standing wave with a high resolution using velocity selective Raman transitions. We have observed up to 3 resolved orders of diffraction, which are well accounted for by a scalar diffraction theory. In our experiment the transverse coherence length of the source is greater than the period of the diffraction grating.Comment: 8 pages, 4 figure

Using atomic interference to probe atom-surface interaction

We show that atomic interference in the reflection from two suitably polarized evanescent waves is sensitive to retardation effects in the atom-surface interaction for specific experimental parameters. We study the limit of short and long atomic de Broglie wavelength. The former case is analyzed in the semiclassical approximation (Landau-Zener model). The latter represents a quantum regime and is analyzed by solving numerically the associated coupled Schroedinger equations. We consider a specific experimental scheme and show the results for rubidium (short wavelength) and the much lighter meta-stable helium atom (long wavelength). The merits of each case are then discussed.Comment: 11 pages, including 6 figures, submitted to Phys. Rev. A, RevTeX sourc

Modeling and Optimization of Lactic Acid Synthesis by the Alkaline Degradation of Fructose in a Batch Reactor

The present work deals with the determination of the optimal operating conditions of lactic acid synthesis by the alkaline degradation of fructose. It is a complex transformation for which detailed knowledge is not available. It is carried out in a batch or semi-batch reactor. The ‘‘Tendency Modeling’’ approach, which consists of the development of an approximate stoichiometric and kinetic model, has been used. An experimental planning method has been utilized as the database for model development. The application of the experimental planning methodology allows comparison between the experimental and model response. The model is then used in an optimization procedure to compute the optimal process. The optimal control problem is converted into a nonlinear programming problem solved using the sequencial quadratic programming procedure coupled with the golden search method. The strategy developed allows simultaneously optimizing the different variables, which may be constrained. The validity of the methodology is illustrated by the determination of the optimal operating conditions of lactic acid production

Photothermal Heterodyne Imaging of Individual Metallic Nanoparticles: Theory versus Experiments

We present the theoretical and detailed experimental characterizations of Photothermal Heterodyne Imaging. An analytical expression of the photothermal heterodyne signal is derived using the theory of light scattering from a fluctuating medium. The amplitudes of the signals detected in the backward and forward configurations are compared and their frequency dependences are studied. The application of the Photothermal Heterodyne detection technique to the absorption spectroscopy of individual gold nanoparticles is discussed and the detection of small individual silver nanoparticles is demonstrated

Optimal design of multi-channel microreactor for uniform residence time distribution

Multi-channel microreactors can be used for various applications that require chemical or electrochemical reactions in either liquid, gaseous or multi phase. For an optimal control of the chemical reactions, one key parameter for the design of such microreactors is the residence time distribution of the fluid, which should be as uniform as possible in the series of microchannels that make up the core of the reactor. Based on simplifying assumptions, an analytical model is proposed for optimizing the design of the collecting and distributing channels which supply the series of rectangular microchannels of the reactor, in the case of liquid flows. The accuracy of this analytical approach is discussed after comparison with CFD simulations and hybrid analytical-CFD calculations that allow an improved refinement of the meshing in the most complex zones of the flow. The analytical model is then extended to the case of microchannels with other cross-sections (trapezoidal or circular segment) and to gaseous flows, in the continuum and slip flow regimes. In the latter case, the model is based on second-order slip flow boundary conditions, and takes into account the compressibility as well as the rarefaction of the gas flow

Carbon nanotubes adhesion and nanomechanical behavior from peeling force spectroscopy

Applications based on Single Walled Carbon Nanotube (SWNT) are good example of the great need to continuously develop metrology methods in the field of nanotechnology. Contact and interface properties are key parameters that determine the efficiency of SWNT functionalized nanomaterials and nanodevices. In this work we have taken advantage of a good control of the SWNT growth processes at an atomic force microscope (AFM) tip apex and the use of a low noise (1E-13 m/rtHz) AFM to investigate the mechanical behavior of a SWNT touching a surface. By simultaneously recording static and dynamic properties of SWNT, we show that the contact corresponds to a peeling geometry, and extract quantities such as adhesion energy per unit length, curvature and bending rigidity of the nanotube. A complete picture of the local shape of the SWNT and its mechanical behavior is provided