1,809 research outputs found
Mise au point d'un microscope à effet tunnel
La conception et la réalisation d'un microscope à effet tunnel sont présentées. On discute de la partie mécanique et de la façon de réaliser l'isolation vis-à-vis des vibrations. Le comportement de la boucle d'asservissement qui contrôle la distance pointe-échantillon est analysée en détail. Les effets parasites dus aux perturbations électriques sont également pris en compte. Les possibilités de ce microscope sont démontrées avec quelques images du graphite et de métaux réalisées à l'air
Determinação de ácido ascórbico em bebidas de abacaxi (Ananas comosus) e beterraba (Beta vulgaris) por titrimetria e cromatografia líquida.
Composição aminoacídica de farinha de semente de abóbora (FSA) (Cucurbita maxima) e de paçoca contendo FSA.
Entropic phase separation of linked beads
We study theoretically a model system of a transient network of microemulsion
droplets connected by telechelic polymers and explain recent experimental
findings. Despite the absence of any specific interactions between either the
droplets or polymer chains, we predict that as the number of polymers per drop
is increased, the system undergoes a first order phase separation into a dense,
highly connected phase, in equilibrium with dilute droplets, decorated by
polymer loops. The phase transition is purely entropic and is driven by the
interplay between the translational entropy of the drops and the
configurational entropy of the polymer connections between them. Because it is
dominated by entropic effects, the phase separation mechanism of the system is
extremely robust and does not depend on the particlular physical realization of
the network. The discussed model applies as well to other polymer linked
particle aggregates, such as nano-particles connected with short DNA linkers
Optimization of control parameters of a hot cold controller by means of Simplex type methods
This paper describes a hot/cold controller for regulating crystallization
operations. The system was identified with a common method (the Broida method) and the parameters were obtained by the Ziegler-Nichols method. The paper shows that this empirical method will only allow a qualitative approach to regulation and that, in some instances, the parameters obtained are unreliable and therefore cannot be used to cancel variations between the set point and the actual values. Optimization methods were used to
determine the regulation parameters and solve this identcation problem. It was found that the weighted centroid method was the best one
Understanding the core density profile in TCV H-mode plasmas
Results from a database analysis of H-mode electron density profiles on the
Tokamak \`a Configuration Variable (TCV) in stationary conditions show that the
logarithmic electron density gradient increases with collisionality. By
contrast, usual observations of H-modes showed that the electron density
profiles tend to flatten with increasing collisionality. In this work it is
reinforced that the role of collisionality alone, depending on the parameter
regime, can be rather weak and in these, dominantly electron heated TCV cases,
the electron density gradient is tailored by the underlying turbulence regime,
which is mostly determined by the ratio of the electron to ion temperature and
that of their gradients. Additionally, mostly in ohmic plasmas, the Ware-pinch
can significantly contribute to the density peaking. Qualitative agreement
between the predicted density peaking by quasi-linear gyrokinetic simulations
and the experimental results is found. Quantitative comparison would
necessitate ion temperature measurements, which are lacking in the considered
experimental dataset. However, the simulation results show that it is the
combination of several effects that influences the density peaking in TCV
H-mode plasmas.Comment: 23 pages, 12 figure
Bebida contendo abacaxi (Ananas comosus) e beterraba (Beta vulgaris) para crianças: tratar termicamente ou não?
Edição dos Resumos do VI Congresso Latinoamericano e XII Congresso Brasileiro de Higienistas de Alimentos, II Encontro Nacional de Vigilância das Zoonoses, IV Encontro do Sistema Brasileiro de Inspeção de Produtos de Origem Animal, Gramado, abr. 2013
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