Collective modes and the speed of sound in the Fulde-Ferrell-Larkin-Ovchinnikov state

We consider the density response of a spin-imbalanced ultracold Fermi gas in an optical lattice in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. We calculate the collective mode spectrum of the system in the generalised random phase approximation and find that though the collective modes are damped even at zero tempererature, the damping is weak enough to have well-defined collective modes. We calculate the speed of sound in the gas and show that it is anisotropic due to the anisotropy of the FFLO pairing, which implies an experimental signature for the FFLO state.Comment: 13 pages, 9 figures (revised version

Multi-robot cooperation

Abstract. This bachelor’s thesis familiarizes with multi-robot cooperation. The main interest is in two robot manipulators. This thesis is a literature review. The operation of the robot and the phenomena that act on them while in operation are investigated from kinematics and command architecture point of view. This thesis is based on manuals from two KUKA robots from University of Oulu, so in the future the use and understanding of their cooperation would be easier. The results gave good understanding of robot software calculations for trajectories and geometrics and what other has to consider when controlling a multi-robot system. This is a good base for deeper theoretical research for robot system software and practical testing.Usean robotin yhteiskäyttö. Tiivistelmä. Tässä opinnäytetyössä perehdytään usean robotin yhteiskäyttöön, jossa mielenkiinnon kohteena on kahden robottikäden yhteistoiminta. Työ on kirjallisuuskatsaus. Robottien toimintaa ja niihin vaikuttavia asioita tarkastellaan niin kinematiikan, kuin ohjelmisto- ja käskyarkkitehtuurin kautta. Työn pohjana käytettiin yliopistolla olevien KUKA robottikäsien oppaita, jotta jatkossa niiden yhteiskäyttö olisi helpommin ymmärrettävissä. Työn tulokset avasivat sitä, miten robottien ohjelmisto ohjaa ja laskee tarvittavat liikeradat ja geometriat ja mitä kaikkea usean robotin ohjauksessa pitää ottaa huomioon. Tämä on hyvä pohja syvemmälle teoreettiselle robottiohjelmistolle tai käytännön testaamiselle

Superfluid phases of fermions with hybridized ss and pp orbitals

We explore the superfluid phases of a two-component Fermi mixture with hybridized orbitals in optical lattices. We show that there exists a general mapping of this system to the Lieb lattice. By using simple multiband models with hopping between $s$ and $p$-orbital states, we show that superfluid order parameters can have a $\pi$-phase difference between lattice sites, which is distinct from the case with hopping between $s$-orbitals. If the population imbalance between the two spin species is tuned, the superfluid phase may evolve through various phases due to the interplay between hopping, interactions and imbalance. We show that the rich behavior is observable in experimentally realizable systems.Comment: 13 pages, 11 figures. Published versio

Soil carbon stock increases in the organic layer of boreal middle-aged stands

Changes in the soil carbon stock can potentially have a large influence on global carbon balance between terrestrial ecosystems and atmosphere. Since carbon sequestration of forest soils is influenced by human activities, reporting of the soil carbon pool is a compulsory part of the national greenhouse gas (GHG) inventories. Various soil carbon models are applied in GHG inventories, however, the verification of model-based estimates is lacking. In general, the soil carbon models predict accumulation of soil carbon in the middle-aged stands, which is in good agreement with chronosequence studies and flux measurements of eddy sites, but they have not been widely tested with repeated measurements of permanent plots. The objective of this study was to evaluate soil carbon changes in the organic layer of boreal middle-aged forest stands. Soil carbon changes on re-measured sites were analyzed by using soil survey data that was based on composite samples as a first measurement and by taking into account spatial variation on the basis of the second measurement. By utilizing earlier soil surveys, a long sampling interval, which helps detection of slow changes, could be readily available. <br><br> The range of measured change in the soil organic layer varied from −260 to 1260 g m<sup>−2</sup> over the study period of 16–19 years and 23 ± 2 g m<sup>−2</sup> per year, on average. The increase was significant in 6 out of the 38 plots from which data were available. Although the soil carbon change was difficult to detect at the plot scale, the overall increase measured across the middle-aged stands agrees with predictions of the commonly applied soil models. Further verification of the soil models is needed with larger datasets that cover wider geographical area and represent all age classes, especially young stands with potentially large soil carbon source

Turbulent Vortex Flow Responses at the AB Interface in Rotating Superfluid 3He-B

In a rotating two-phase sample of 3He-B and magnetic-field stabilized 3He-A the large difference in mutual friction dissipation at 0.20 Tc gives rise to unusual vortex flow responses. We use noninvasive NMR techniques to monitor spin down and spin up of the B-phase superfluid component to a sudden change in the rotation velocity. Compared to measurements at low field with no A-phase, where these responses are laminar in cylindrically symmetric flow, spin down with vortices extending across the AB interface is found to be faster, indicating enhanced dissipation from turbulence. Spin up in turn is slower, owing to rapid annihilation of remanent vortices before the rotation increase. As confirmed by both our NMR signal analysis and vortex filament calculations, these observations are explained by the additional force acting on the B-phase vortex ends at the AB interface.Comment: 6 pages, 6 figure

Diabetes Care for Patients with Peripheral Arterial Disease

The number of diabetics will increase almost 70% in developed countries during the next 20 years: peripheral arterial disease is a common and costly complication. The incidence of cardiovascular disease (mortality and morbidity) due to atherosclerosis, is higher among patients with diabetes than in those without diabetes. Intensive management of diabetes, including glycaemic control, treatment of hypertension and dyslipidemia, as well as nonpharmacological interventions, decreases both micro- and macrovascular complications. Aspirin and clopidogrel have less antiplatelet effect in patients with diabetes. Metformin therapy is considered a risk factor for lactic acidosis if not withdrawn 2 days before angiography, but this risk is extremely low in patients with normal renal function. Peri-operative hyperglycaemia and large fluctuations in plasma glucose increase postoperative mortality and morbidity and careful measures are required to minimise these effects

Impacts of land cover data selection and trait parameterisation on dynamic modelling of species' range expansion

Peer reviewedPublisher PD