On the Definition of Effective Permittivity and Permeability For Thin Composite Layers

The problem of definition of effective material parameters (permittivity and permeability) for composite layers containing only one-two parallel arrays of complex-shaped inclusions is discussed. Such structures are of high importance for the design of novel metamaterials, where the realizable layers quite often have only one or two layers of particles across the sample thickness. Effective parameters which describe the averaged induced polarizations are introduced. As an explicit example, we develop an analytical model suitable for calculation of the effective material parameters $\epsilon_{\rm{eff}}$ and $\mu_{\rm{eff}}$ for double arrays of electrically small electrically polarizable scatterers. Electric and magnetic dipole moments induced in the structure and the corresponding reflection and transmission coefficients are calculated using the local field approach for the normal plane-wave incidence, and effective parameters are introduced through the averaged fields and polarizations. In the absence of losses both material parameters are purely real and satisfy the Kramers-Kronig relations and the second law of thermodynamics. We compare the analytical results to the simulated and experimental results available in the literature. The physical meaning of the introduced parameters is discussed in detail.Comment: 6 pages, 5 figure

Quantum Interference of Tunably Indistinguishable Photons from Remote Organic Molecules

We demonstrate two-photon interference using two remote single molecules as bright solid-state sources of indistinguishable photons. By varying the transition frequency and spectral width of one molecule, we tune and explore the effect of photon distinguishability. We discuss future improvements on the brightness of single-photon beams, their integration by large numbers on chips, and the extension of our experimental scheme to coupling and entanglement of distant molecules

Lean-ajattelu ja lean-päivittäisjohtaminen yliopistosairaaloissa

Terveydenhuollossakin sovellettava lean-ajattelu korostaa jatkuvaa parantamista ja lisäarvon tuottamista asiakkaille. Lean-päivittäisjohtamisen piirteitä ovat mittaamisen ja lean-taulujen avulla tapahtuva visuaalinen seuranta, vastuu toiminnasta ja päivittäiset lyhyet moniammatilliset tiimikokoukset. Tämän tutkimuksen tarkoituksena oli tunnistaa lean-päivittäisjohtamisen piirteitä ja siihen liittyvää osaamista sekä lean-ajattelun hyödynnettävyyttä yliopistosairaaloissa. Aineisto kerättiin neljästä suomalaisesta yliopistosairaalasta lean-ajattelua soveltavilta asiantuntijoilta kyselyillä (N = 41) ja teemahaastatteluilla (N = 15) marraskuun 2017 ja kesäkuun 2018 välillä. Aineistot analysoitiin aineisto- ja teoriaohjaavalla sisällönanalyysilla. Lean-ajattelun periaatteet sopivat yliopistosairaaloihin. Lean-ajattelun systemaattinen soveltaminen terveydenhuollon organisaatioissa edellyttää valmentavaa johtamista, selkeitä strategiassa kuvattuja visiota ja tavoitteita, jalkautussuunnitelmaa sekä johdon ja henkilöstön sitoutumista siihen. Soveltamista rajoittaa osa terveydenhuollon kulttuurin piirteistä: hierarkkisuus, menettelytapojen kankeus ja epäselvät prosessit. Lean-ajattelun periaatteita ja työkaluja käytettäneen tulevaisuudessakin, mutta ajattelumallin odotetaan muokkaantuvan ja hyödyn paranevan, kun lean-ajattelu yhdistetään muihin johtamis- ja kehittämismalleihin. Lean-päivittäisjohtamisen ei arvioitu olevan vakioitunutta yliopistosairaaloissa, mutta sen piirteitä tunnistettiin ja samalla tarve niiden vahvistamiseen. Piirteitä olivat kommunikaatio ja viestintä, mittaaminen ja seuranta, osaamisen hallinta, valmentava johtaminen, tiimityön ja muutoksen tukeminen, jatkuva parantaminen, hukan poistaminen sekä strategian mukainen toiminta ja tavoitteiden asettaminen. Lean-päivittäisjohtamisen vahvistamiseksi tarvitaan jatkuvan parantamisen menettelyjen jaseurantamittareiden systemaattista kehittämistä.</p

Diffusion in periodic potentials with path integral hyperdynamics

We consider the diffusion of Brownian particles in one-dimensional periodic potentials as a test bench for the recently proposed stochastic path integral hyperdynamics (PIHD) scheme [Chen and Horing, J. Chem. Phys. 126, 224103 (2007)]. First, we consider the case where PIHD is used to enhance the transition rate of activated rare events. To this end, we study the diffusion of a single Brownian particle moving in a spatially periodic potential in the high-friction limit at low temperature. We demonstrate that the boost factor as compared to straight molecular dynamics (MD) has nontrivial behavior as a function of the bias force. Instead of growing monotonically with the bias, the boost attains an optimal maximum value due to increased error in the finite path sampling induced by the bias. We also observe that the PIHD method can be sensitive to the choice of numerical integration algorithm. As the second case, we consider parallel resampling of multiple bias force values in the case of a Brownian particle in a periodic potential subject to an external ac driving force. We confirm that there is no stochastic resonance in this system. However, while the PIHD method allows one to obtain data for multiple values of the ac bias, the boost with respect to MD remains modest due to the simplicity of the equation of motion in this case.Peer reviewe

Endorectal magnetic resonance imaging of prostatic cancer: comparison between fat-suppressed T2-weighted fast spin echo and three-dimensional dual-echo, steady-state sequences

Peer reviewe

Effects of Initial Age Structure of Managed Norway Spruce Forest Area on Net Climate Impact of Using Forest Biomass for Energy

We investigated how the initial age structure of a managed, middle boreal (62A degrees N), Norway spruce-dominated (Picea abies L. Karst.) forest area affects the net climate impact of using forest biomass for energy. The model-based analysis used a gap-type forest ecosystem model linked to a life cycle assessment (LCA) tool. The net climate impact of energy biomass refers to the difference in annual net CO2 exchange between the biosystem using forest biomass (logging residues from final felling) and the fossil (reference) system using coal. In the simulations over the 80-year period, the alternative initial age structures of the forest areas were (i) skewed to the right (dominated by young stands), (ii) normally distributed (dominated by middle-aged stands), (iii) skewed to the left (dominated by mature stands), and (iv) evenly distributed (same share of different age classes). The effects of management on net climate impacts were studied using current recommendations as a baseline with a fixed rotation period of 80 years. In alternative management scenarios, the volume of the growing stock was maintained 20% higher over the rotation compared to the baseline, and/or nitrogen fertilization was used to enhance carbon sequestration. According to the results, the initial age structure of the forest area affected largely the net climate impact of using energy biomass over time. An initially right-skewed age structure produced the highest climate benefits over the 80-year simulation period, in contrast to the left-skewed age structure. Furthermore, management that enhanced carbon sequestration increased the potential of energy biomass to replace coal, reducing CO2 emissions and enhancing climate change mitigation.Peer reviewe

COVID-19 cases in spectators returning to Finland from UEFA Euro 2020 matches in Saint Petersburg

UEFA Euro 2020 tournament was scheduled to take place in 2020, but due to the coronavirus disease 2019 (COVID-19) pandemic was rescheduled to start on 11 June 2021. Approximately 4500 Finnish spectators participated, travelling between Finland and Russia during the period of 16 to 30 June to attend matches played on 16 and 21 June. A total of 419 persons returning from Russia or with a connection to Russia were detected positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Of the 321 sequenced samples 303 turned out to be of the Delta variant. None of these cases was hospitalised. In the following weeks findings of the Delta variant increased rapidly. Thus, EURO 2020 travel-related imported cases likely facilitated this rapid surge of Delta variant, but this impact would likely have been seen with the typical increase in the number of travellers entering Finland later in the summer.Peer reviewe