693 research outputs found
Energy dependence of current noise in superconducting/normal metal junctions
Interference of electronic waves undergoing Andreev reflection in diffusive
conductors determines the energy profile of the conductance on the scale of the
Thouless energy. A similar dependence exists in the current noise, but its
behavior is known only in few limiting cases. We consider a metallic diffusive
wire connected to a superconducting reservoir through an interface
characterized by an arbitrary distribution of channel transparencies. Within
the quasiclassical theory for current fluctuations we provide a general
expression for the energy dependence of the current noise.Comment: 5 pages, 1 Figur
Frequency dispersion of photon-assisted shot noise in mesoscopic conductors
We calculate the low-frequency current noise for AC biased mesoscopic chaotic
cavities and diffusive wires. Contrary to what happens for the admittance, the
frequency dispersion is not dominated by the electric response time (the "RC"
time of the circuit), but by the time that electrons need to diffuse through
the structure (dwell time or diffusion time). Frequency dispersion of noise
stems from fluctuations of the Fermi distribution function that preserve charge
neutrality. Our predictions can be verified with present experimental
technology.Comment: 5 pages, 3 Figure
Current-current correlations in hybrid superconducting and normal metal multiterminal structures
We consider a hybrid system consisting of two normal metal leads weakly
connected to a superconductor. Current-current correlations of the normal leads
are studied in the tunneling limit at subgap voltages and temperatures. We find
that only two processes contribute to the cross-correlation: the crossed
Andreev reflection (emission of electrons in different leads) and the elastic
cotunneling. Both processes are possible due to the finite size of the Cooper
pair. Noise measurements can thus be used to probe directly the superconducting
wave function without the drawbacks appearing in average current measurements
where the current is dominated by direct Andreev reflection processes. By
tuning the voltages it is possible to change the sign of the cross correlation.
Quantitative predictions are presented both in the diffusive and ballistic
regimes.Comment: 7 pages, 2 Figure
Pair Wave Functions in Atomic Fermi Condensates
Recent experiments have observed condensation behavior in a strongly
interacting system of fermionic atoms. We interpret these observations in terms
of a mean-field version of resonance superfluidity theory. We find that the
objects condensed are not bosonic molecules composed of bound fermion pairs,
but are rather spatially correlated Cooper pairs whose coherence length is
comparable to the mean spacing between atoms. We propose experiments that will
help to further probe these novel pairs
The charge shuttle as a nanomechanical ratchet
We consider the charge shuttle proposed by Gorelik {\em et al.} driven by a
time-dependent voltage bias. In the case of asymmetric setup, the system
behaves as a rachet. For pure AC drive, the rectified current shows a complex
frequency dependent response characterized by frequency locking at fracional
values of the external frequency. Due to the non-linear dynamics of the
shuttle, the rachet effect is present also for very low frequencies.Comment: 4 pages, 4 figure
Anaerobic Digestion of Spoiled Milk in Batch Reactors: Technical and Economic Feasibility☆
Abstract The economic feasibility of the energy conversion through anaerobic digestion of spoiled milk was assessed for the microscale biogas production and heating value was determined experimentally on a pilot plant with a mixture of spoiled milk and an inoculum previously optimized with Anaerobic Biomethanation Potential tests. Results shows that the feasibility of a 100 kWel plant is characterized by a quite short return time of the investment. Considering a discount rate of 5% and a timespan of investment equal to 20 years, payback period is equal to 8-9 years, Net Present Value is equal to 806,903 € and Internal Rate of Return is equal to 16%
BCS-Bose Crossover in Color Superconductivity
It is shown that the onset of the color superconducting phase occurs in the
BCS-BE crossover region.Comment: 5 pages, LaTeX, references adde
i rexfo life an innovative business model to reduce food waste
Abstract Every year the food produced and wasted consumes a volume of water equal to 250 km3, requires around 30% of the world agricultural land, and it is responsible for the emission of 3,3 billion tons of greenhouse gases. The direct economic consequences of food waste are ranging around 750 billion dollars per year (FAO source). i-REXFO designs an innovative business model with the objective of reducing significantly the amount of landfilled food waste. The actions are economically sustained by public incentives, tax reductions and private revenues from energy valorization of residual food waste. Uptaking the good practices from other EU countries (Denmark) the project will develop a tool to design the integrated model, optimize it from a technical, economic and environmental point of view and transfer it to other EU regions. i-REXFO will increase consumer awareness on food waste reduction in retail malls and HORECA while facilitating the sale and donation to charities and food banks of close to expiration and aesthetically not adequate food; it will also remove the barriers that hamper the use of food residues in biogas plants. The actions are economically sustained from energy valorization of food waste in biogas plant that use the digestate as fertilizer, closing the cycle. I-REXFO will achieve an overall reduction of 17000 tons/year of food waste landfilled during the project duration and in the after life phase. This will correspond to an overall reduction of 41000 tons of CO2 equivalent emissions
- …