11,076 research outputs found
One-handed hammer-spanner for chucks
Modified spanner wrench with a heavy hammer-piece hinged to its handle allows one hand removal of a tool from a chuck
Rotor burst protection program initial test results, phase 4 Final report
High speed photographic recording of turbine wheel failure in containment devic
The solution space of metabolic networks: producibility, robustness and fluctuations
Flux analysis is a class of constraint-based approaches to the study of
biochemical reaction networks: they are based on determining the reaction flux
configurations compatible with given stoichiometric and thermodynamic
constraints. One of its main areas of application is the study of cellular
metabolic networks. We briefly and selectively review the main approaches to
this problem and then, building on recent work, we provide a characterization
of the productive capabilities of the metabolic network of the bacterium E.coli
in a specified growth medium in terms of the producible biochemical species.
While a robust and physiologically meaningful production profile clearly
emerges (including biomass components, biomass products, waste etc.), the
underlying constraints still allow for significant fluctuations even in key
metabolites like ATP and, as a consequence, apparently lay the ground for very
different growth scenarios.Comment: 10 pages, prepared for the Proceedings of the International Workshop
on Statistical-Mechanical Informatics, March 7-10, 2010, Kyoto, Japa
On the transition to efficiency in Minority Games
The existence of a phase transition with diverging susceptibility in batch
Minority Games (MGs) is the mark of informationally efficient regimes and is
linked to the specifics of the agents' learning rules. Here we study how the
standard scenario is affected in a mixed population game in which agents with
the `optimal' learning rule (i.e. the one leading to efficiency) coexist with
ones whose adaptive dynamics is sub-optimal. Our generic finding is that any
non-vanishing intensive fraction of optimal agents guarantees the existence of
an efficient phase. Specifically, we calculate the dependence of the critical
point on the fraction of `optimal' agents focusing our analysis on three
cases: MGs with market impact correction, grand-canonical MGs and MGs with
heterogeneous comfort levels.Comment: 12 pages, 3 figures; contribution to the special issue "Viewing the
World through Spin Glasses" in honour of David Sherrington on the occasion of
his 65th birthda
Adaptive drivers in a model of urban traffic
We introduce a simple lattice model of traffic flow in a city where drivers
optimize their route-selection in time in order to avoid traffic jams, and
study its phase structure as a function of the density of vehicles and of the
drivers' behavioral parameters via numerical simulations and mean-field
analytical arguments. We identify a phase transition between a low- and a
high-density regime. In the latter, inductive drivers may surprisingly behave
worse than randomly selecting drivers.Comment: 7 pages, final versio
Von Neumann's expanding model on random graphs
Within the framework of Von Neumann's expanding model, we study the maximum
growth rate r achievable by an autocatalytic reaction network in which
reactions involve a finite (fixed or fluctuating) number D of reagents. r is
calculated numerically using a variant of the Minover algorithm, and
analytically via the cavity method for disordered systems. As the ratio between
the number of reactions and that of reagents increases the system passes from a
contracting (r1). These results extend the
scenario derived in the fully connected model (D\to\infinity), with the
important difference that, generically, larger growth rates are achievable in
the expanding phase for finite D and in more diluted networks. Moreover, the
range of attainable values of r shrinks as the connectivity increases.Comment: 20 page
Experimental evidence of laser power oscillations induced by the relative Fresnel (Goos-Haenchen) phase
The amplification of the relative Fresnel (Goos-Haenchen) phase by an
appropriate number of total internal reflections and the choice of favorable
incidence angles allow to observe full oscillations in the power of a DPSS
laser transmitted through sequential BK7 blocks. The experimental results
confirm the theoretical predictions. The optical apparatus used in this letter
can be seen as a new type of two-phase ellipsometric system where the phase of
the complex refractive index is replaced by the relative Fresnel
(Goos-Haenchen) phase.Comment: 7 pages, 3 figures, 1 tabl
Rashba spin-orbit coupling and spin precession in carbon nanotubes
The Rashba spin-orbit coupling in carbon nanotubes and its effect on
spin-dependent transport properties are analyzed theoretically. We focus on
clean non-interacting nanotubes with tunable number of subbands . The
peculiar band structure is shown to allow in principle for Datta-Das
oscillatory behavior in the tunneling magnetoresistance as a function of gate
voltage, despite the presence of multiple bands. We discuss the conditions for
observing Datta-Das oscillations in carbon nanotubes.Comment: 12 pages, published versio
- …