362 research outputs found
Essai de domestication de lentinus squarrosulus mont. a partir dâune souche du Gabon
Dans le cadre dâun vaste programme de valorisation des ressources biologiques initiĂ© par les autoritĂ©s gabonaises en vue de garantir la sĂ©curitĂ© alimentaire des populations locales, une souche sauvage de Lentinus squarrosulus rĂ©coltĂ©e au nord du Gabon, a Ă©tĂ© mise en culture en utilisant essentiellement des matĂ©riaux locaux. Au cours de ce processus, cinq principales Ă©tapes ont Ă©tĂ© mise en Ćuvre; il sâagit notamment de la production du blanc de semis et du substrat de culture, du lardage du substrat, de lâincubation et de la fructification du champignon. La production du blanc regroupe les Ă©tapes qui ont obligatoirement Ă©tĂ© exĂ©cutĂ©es dans un laboratoire parfaitement Ă©quipĂ© en vue de garantir des conditions dâasepsie rigoureuses, tandis que la production du substrat de culture, lâinoculation et lâincubation ont parfaitement Ă©tĂ© rĂ©alisĂ©es Ă lâĂ©chelle villageoise en utilisant du matĂ©riel de fabrication traditionnelle; notamment une unitĂ© de pasteurisation constituĂ©e dâun fĂ»t en aluminium de 250 litres muni dâĂ©tagĂšres et dâune chambre contenant de lâeau, ainsi quâune armoire traditionnelle dâinoculation. Par ce processus, quatre-vingt sacs de 1kg ont Ă©tĂ© inoculĂ©s dont quatorze ont montrĂ© un trĂšs bon envahissement mycĂ©lien et une fructification satisfaisante; ce qui donne un rendement en terme de sac dâenviron 17 %. Cependant, cinquante-six sacs nâont pas Ă©tĂ© bien envahis par le mycĂ©lium et nâont donc pas donnĂ© de champignon, de plus dix sacs ont Ă©tĂ© contaminĂ©s.
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 ââTendency Modelingââ 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
- âŠ