Primary tunnel junction thermometry

We describe the concept and experimental demonstration of primary thermometry based on a four probe measurement of a single tunnel junction embedded within four arrays of junctions. We show that in this configuration random sample specific and environment-related errors can be avoided. This method relates temperature directly to Boltzmann constant, which will form the basis of the definition of temperature and realization of official temperature scales in the future

Evidence of Cooper pair pumping with combined flux and voltage control

We have experimentally demonstrated pumping of Cooper pairs in a single-island mesoscopic structure. The island was connected to leads through SQUID (Superconducting Quantum Interference Device) loops. Synchronized flux and voltage signals were applied whereby the Josephson energies of the SQUIDs and the gate charge were tuned adiabatically. From the current-voltage characteristics one can see that the pumped current increases in 1e steps which is due to quasiparticle poisoning on the measurement time scale, but we argue that the transport of charge is due to Cooper pairs.Comment: 4 page

Competition for Popularity in Bipartite Networks

We present a dynamical model for rewiring and attachment in bipartite networks in which edges are added between nodes that belong to catalogs that can either be fixed in size or growing in size. The model is motivated by an empirical study of data from the video rental service Netflix, which invites its users to give ratings to the videos available in its catalog. We find that the distribution of the number of ratings given by users and that of the number of ratings received by videos both follow a power law with an exponential cutoff. We also examine the activity patterns of Netflix users and find bursts of intense video-rating activity followed by long periods of inactivity. We derive ordinary differential equations to model the acquisition of edges by the nodes over time and obtain the corresponding time-dependent degree distributions. We then compare our results with the Netflix data and find good agreement. We conclude with a discussion of how catalog models can be used to study systems in which agents are forced to choose, rate, or prioritize their interactions from a very large set of options.Comment: 13 Pages, 19 Figure

Radio-Frequency Single-Electron Refrigerator

We propose a cyclic refrigeration principle based on mesoscopic electron transport. Synchronous sequential tunnelling of electrons in a Coulomb-blockaded device, a normal metal-superconductor single-electron box, results in a cooling power of $\sim k_{\rm B}T \times f$ at temperature $T$ over a wide range of cycle frequencies $f$. Electrostatic work, done by the gate voltage source, removes heat from the Coulomb island with an efficiency of $\sim k_{\rm B}T/\Delta$, where $\Delta$ is the superconducting gap. The performance is not affected significantly by non-idealities, for instance by offset charges. We propose ways of characterizing the system and of its practical implementation.Comment: 5 pages, 4 figures; corrected typos, language improve

Stability properties of periodically driven overdamped pendula and their implications to physics of semiconductor superlattices and Josephson junctions

We consider the first order differential equation with a sinusoidal nonlinearity and periodic time dependence, that is, the periodically driven overdamped pendulum. The problem is studied in the case that the explicit time-dependence has symmetries common to pure ac-driven systems. The only bifurcation that exists in the system is a degenerate pitchfork bifurcation, which describes an exchange of stability between two symmetric nonlinear modes. Using a type of Prufer transform to a pair of linear differential equations, we derive an approximate condition of the bifurcation. This approximation is in very good agreement with our numerical data. In particular, it works well in the limit of large drive amplitudes and low external frequencies. We demonstrate the usefulness of the theory applying it to the models of pure ac-driven semiconductor superlattices and Josephson junctions. We show how the knowledge of bifurcations in the overdamped pendulum model can be utilized to describe effects of rectification and amplification of electric fields in these microstructures.Comment: 15 pages, 7 figures, Revtex 4.1. Revised and expanded following referee's report. Submitted to journal Chaos

Nonexponential Quantum Decay under Environmental Decoherence

A system prepared in an unstable quantum state generally decays following an exponential law, as environmental decoherence is expected to prevent the decay products from recombining to reconstruct the initial state. Here we show the existence of deviations from exponential decay in open quantum systems under very general conditions. Our results are illustrated with the exact dynamics under quantum Brownian motion and suggest an explanation of recent experimental observationsauthorsversionPeer reviewe

Interstitiaalisen virtsarakkotulehduksen eli virtsarakon kipuoireyhtymän hoito

Kansainvälinen urologityöryhmä on ehdottanut, että termi virtsarakon kipuoireyhtymä korvaisi aiemman interstitiaalinen kystiitti -termin laajan merkityksen. Interstitiaalinen kystiitti tarkoittaisi tällöin yhtä ­kipuoireyhtymän alatyyppiä, jossa on histologisesti varmennettu inflammaatio. Virtsarakon kipuoireyhtymän diagnoosi perustuu kliiniseen oirekuvaan ja muiden samantapaisia oireita ­aiheuttavien tunnettujen sairauksien poissulkemiseen. Koska sairauden etiologiaa ei tunnetta, kaikki virtsarakon kipuoireyhtymän hoitomenetelmätkin ovat ­kokemusperäisiä. Virtsarakon kipuoireyhtymä on krooninen kiputila, jonka ei oleteta paranevan. Oirelääkkeistä ja kokeilevista hoidoista on kuitenkin hyötyä.Peer reviewe

Scots pine litter decomposition along drainage succession and soil nutrient gradients in peatland forests, and the effects of inter-annual weather variation

Peer reviewe

Thermal leptogenesis in a 5D split fermion scenario with bulk neutrinos

We study the thermal leptogenesis in a hybrid model, which combines the so called split fermion model and the bulk neutrino model defined in five dimensional spacetime. This model predicts the existence of a heavy neutrino pair nearly degenerate in mass, whose decays might generate a CP violation large enough for creating the baryon asymmetry of the universe through leptogenesis. We investigate numerically the constraints this sets on the parameters of the model such as the size of the compactified fifth dimension.Comment: 22 pages, 9 figure