J. Johansson

Reducing Life Cycle Environmental Impacts of Waste Electrical and Electronic Equipment Recycling: Case Study on Dishwashers

Collection and treatment of waste from electrical and electronic equipment (WEEE) is regulated in the European Union by the WEEE Directive. Producers are responsible for take-back and recycling of ...

Random background charges and Coulomb blockade in one-dimensional tunnel junction arrays

We have numerically studied the behavior of one-dimensional tunnel junction arrays when random background charges are included using the orthodox theory of single-electron tunneling. Random backgro ...

Enhanced spin accumulation in a superconductor

A lateral array of ferromagnetic tunnel junctions is used to inject and detect nonequilibrium quasiparticle spin distribution in a superconducting strip made of Al. The strip width and thickness are kept below the quasiparticle spin diffusion length in Al. Nonlocal measurements in multiple parallel and antiparallel magnetic states of the detectors are used to in situ determine the quasiparticle spin diffusion length. A very large increase in the spin accumulation in the superconducting state compared to that in the normal state is observed and is attributed to a diminishing of the quasiparticle population by the opening of the gap below the transition temperature.

Quantum phase transition in one-dimensional Josephson junction arrays

We describe experiments on one-dimensional arrays of small capacitance Josephson junctions which show how the Coulomb blockade of Cooper pair tunneling is influenced by changing the Josephson coupling energy in situ with an externally applied magnetic flux. We show how the zero bias resistance of the array is affected by the length of the array, and we use the length scaling of this resistance to infer that a quantum phase transition occurs as the Josephson coupling energy is changed. The data are qualitatively analyzed in terms of a theoretical model of the quantum phase transition which uses a mapping to the two-dimensional XY model.

Coulomb blockade effects in anodically oxidized titanium wires

We investigate the electrical transport properties of narrow titanium (Ti) wires which are anodically oxidized through a resist mask. At temperatures below 1.2 K the current–voltage characteristics of the resulting Ti/TiOx nanostructures exhibit a zero-current state, characteristic of the Coulomb blockade. The blockade region can be modulated by a capacitively coupled gate electrode. The observed experimental features can be explained in terms of a single electron tunneling model of a multi-island device.

Error propagation in E. coli protein synthesis

A new approach to the error catastrophe theory, proposed by Leslie Orgel, is presented here. Our model is a development of previous models, but differs in several respects: the overall activity is assumed to be dependent on the error level, the effect of errors in the translating system, giving rise to additional errors in the succeeding generation of products, is explicitly included as a special term in our model, and scavenging enzymes are assumed to break down and eliminate products with a loose structure. Their efficiency is dependent on the error level. The model also takes into account the dilution of incorrect ribosomes and enzymes, and is described by a time-dependence in terms of ribosome/enzyme generations. The model and the contribution to the time development are discussed in the light of experiments on E. coli treated with streptomycin.

Hysteretic current-voltage characteristics and Coulomb blockade in 1D-arrays of Josephson junctions

Abstract The IV characteristics (IVC) of 1D-arrays of small capacitance Josephson junctions with EC∼EJ have been measured. The IVC show Coulomb blockade of Cooper pair tunneling and exhibit a pronounced hysteresis which appears to be dual to the well-known resistively shunted junction behavior of ordinary Josephson junctions. A dual serially resistive junction model is used to qualitatively explain the measured data.

Molecular Dynamics Studies of Model Membranes with Alfa Helices

A model membrane with other molecules inserted has been studied by molecular dynamics simulations. The membrane model is a detailed one according to references 1 and 2. The lipids where treated as chains consisting of 15 hydrocarbon pseudo atoms and a head group. Lennard-Jones, dihedral angle and valence angle interactions were included and the bond lengths were kept fixed. The bilayer structure was stabilized whithout water by having a harmonic potential that keeps each head group in an average plane defined by all the head groups. The strength of that potential potential was chosen to allow for a 5–10% fluctuation out of the plane for the head groups. The temperature was kept well above the gel/liquid crystalline phase transition temperature. The lateral density was chosen to 32 or 34 A. The order parameters far away from the inserted molecule were calculated and compared to experimental deuterium NMR order parameters for pure dipalmiotyllecithin measured bye Seelig and Seelig (3). It turned out that the system was quite sensitive to the surface area and that a surface area of 33 A instead of 32 or 34 would have been a better choice.