Guiding and reflecting light by boundary material

We study effects of finite height and surrounding material on photonic crystal slabs of one- and two-dimensional photonic crystals with a pseudo-spectral method and finite difference time domain simulation methods. The band gap is shown to be strongly modified by the boundary material. As an application we suggest reflection and guiding of light by patterning the material on top/below the slab.Comment: 12 pages, 7 figure

Erosion-oxidation of pressure vessel steel P265GH

The behaviour of pressure vessel steel P265GH was studied in a centrifugal high-temperature erosion apparatus under impacts by silica (SiO2) particles moving at velocities ranging from 20 to 60 m s-1 and contacting the surface at the angles of 30° and 90°. Besides particle impacts, the steel was simultaneously exposed to air and elevated temperatures of 350 and 450°C. For comparison, the tests were also performed in the absence of erodent particles. After the tests, the material behaviour was evaluated in terms of occurred weight changes and surface characteristics, the latter ones of which were investigated by using, for example, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). In the analysis of the test results, special attention was paid to the composition and microstructure of the used silica particles and how these influence the elemental distribution on the exposed surfaces. The results show that the particle impacts introduce weight losses that follow a ductile angle-dependency, i.e., relatively greater weight losses at the shallow than at the steep impact angle. Although evident oxide scales developed on the surfaces at the test temperatures, they did not provide the steel with protection against particle impacts. Particle debris was detected embedded in the surfaces particularly under impacts at 90°, with softer particle constituents being preferentially deposited. These results are discussed in terms of the erosion-oxidation behaviour of the steel and the consequences of the heterogeneous erodent particle quality

Assessing the discharge instructing in the emergency department : Patient perspective

Objective: The objective of the study is to assess how well the emergency department (ED) personnel succeed in instructing the patient at discharge. Methods: In November and December 2016 at Peijas Hospital ED, Finland, a structured questionnaire was conducted during a phone interview on patients the day after discharge. Results: A total of 132 patients interviewed. Ninety percent had received discharge instructions from the ED staff, most of them (75%) about medication. Almost half of the patients (45%) were satisfied with the communication at discharge, those not satisfied (47%) felt that the staff did not know enough of their background to give discharge instructions. Of the patients, 20% thought that they did not have the opportunity to ask questions during the guidance session, and 41% thought that the session was too short and restricted. Some patients (20%) felt that the instructions were ambiguous, but 63% (83/132) felt they were able to follow them well or very well. Conclusion: The pace of care in the ED is fast and duration of the stay is short. The patients must be able to take responsibility of their self-care. Failure to follow medical discharge instructions could lead to non-compliance. Attention should be paid to enhancing the quality of discharge instructing and the instructions provided by the ED personnel, as recurring visits and inquiry calls add to the ED workload.Peer reviewe

Thermal Control of Plasmonic Surface Lattice Resonances

Plasmonic metasurfaces exhibiting collective responses known as surface lattice resonances (SLRs) show potential for realizing tunable and flat photonic components for wavelength-selective processes, including lasing and optical nonlinearities. However, post-fabrication tuning of SLRs remains challenging, limiting the applicability of SLR-based components. Here, we demonstrate how the properties of high quality factor SLRs are easily modified by breaking the symmetry of the nanoparticle surroundings. We break the symmetry by changing the refractive index of the overlying immersion oil simply by controlling the ambient temperature of the device. We show that already modest temperature changes of 10{\deg}C can increase the quality factor of the investigated SLR from 400 to 750. Our results demonstrate accurate and reversible modification of the properties of the SLRs, paving the way towards tunable SLR-based photonic devices. On a more general level, our results demonstrate how symmetry breaking of the surrounding dielectric environment can be utilized for efficient and potentially ultrafast modification of the SLR properties

Phase-Matched Second-Harmonic Generation from Metasurfaces Inside Multipass Cells

We demonstrate a simple and scalable approach to increase conversion efficiencies of nonlinear metasurfaces by incorporating them into multipass cells and by letting the pump beam to interact with the metasurfaces multiple times. We experimentally show that by metasurface design, the associated phase-matching criteria can be fulfilled. As a proof of principle, we achieve phase matching of second-harmonic generation (SHG) using a metasurface consisting of aluminium nanoparticles deposited on a glass substrate. The phase-matching condition is verified to be achieved by measuring superlinear dependence of the detected SHG as a function of number of passes. We measure an order of magnitude enhancement in the SHG signal when the incident pump traverses the metasurface up to 9 passes. Results are found to agree well with a simple model developed to estimate the generated SHG signals. We also discuss strategies to further scale-up the nonlinear signal generation. Our approach provides a clear pathway to enhance nonlinear optical responses of metasurface-based devices. The generic nature of our approach holds promise for diverse applications in nonlinear optics and photonics

Long-term clinical and economic outcomes in previously untreated paediatric patients with severe haemophilia A : A nationwide real-world study with 700 person-years

AimFor previously untreated patients (PUPs) with severe haemophilia A in Finland for the past 2 decades, the standard practice has been to start early primary prophylaxis. We evaluated the long-term clinical outcomes and costs of treatment with high-dose prophylaxis in PUPs from birth to adolescence, including immune tolerance induction (ITI). MethodsFrom the medical records of all PUPs born between June 1994 and May 2013 in Finland, we retrospectively extracted data on clinical outcomes and healthcare use. Using linear mixed models, we analysed longitudinal clinical outcome data. To analyse skewed cost data, including zero costs, we applied hurdle regression. ResultsAll 62 patients received early regular prophylaxis; totally, they have had treatment for nearly 700 patient-years. The median age of starting home treatment was 1.1years. The mean (SD) annual treatment costs (Europerkg) were 4391Euro (3852). For ages 1-3, ITI comprised over half of the costs; in other groups, prophylactic FVIII treatment dominated. With these high costs, however, clinical outcomes were desirable; median (IQR) ABR was low at 0.19 (0.07-0.46) and so was AJBR at 0.06 (0-0.24). Thirteen (21%) patients developed a clinically significant inhibitor, 10 (16%) with a high titre. All ITIs were successful. The mean costs for ITI were 383448Euro (259085). The expected ITI payback period was 1.81 (95% CI 0.62-12.12) years. ConclusionsEarly high-dose prophylaxis leads to excellent long-term clinical outcomes, and early childhood ITI therapy seems to turn cost-neutral generally already in 2years.Peer reviewe

Nonlinear nonlocal metasurfaces

Optical metasurfaces have recently emerged as the game changer in light manipulation and opened up new perspectives in many subfields of optics and photonics. Recent developments in nonlocal metasurfaces, in which the nanoscale building blocks respond to the incoming light collectively rather than as individual objects, are especially promising for enhancing and controlling the nonlinear optical phenomena. In this article, we provide a brief overview of the basic principles of nonlocal metasurfaces in the context of their nonlinear optical functionalities. We discuss the origin and the regimes of the nonlocal response, covering the aspects of multiple scattering, radiation damping, quality factor, local-field enhancement, and temporal dynamics. Some important aspects are illustrated by computational examples. We also give our personal viewpoint on the selected ideas and research directions in nonlocal and nonlinear metasurfaces, including the role of spatial symmetry in nonlocal interactions, the effects of phase and momentum matching in frequency conversion, as well as the possibilities offered by new material platforms and novel concepts, such as bound states in the continuum, parity-time symmetry, and time-variant metasurfaces.publishedVersionPeer reviewe

Cluster observations of sudden impulses in the magnetotail caused by interplanetary shocks and pressure increases

Sudden impulses (SI) in the tail lobe magnetic field associated with solar wind pressure enhancements are investigated using measurements from Cluster. The magnetic field components during the SIs change in a manner consistent with the assumption that an antisunward moving lateral pressure enhancement compresses the magnetotail axisymmetrically. We found that the maximum variance SI unit vectors were nearly aligned with the associated interplanetary shock normals. For two of the tail lobe SI events during which Cluster was located close to the tail boundary, Cluster observed the inward moving magnetopause. During both events, the spacecraft location changed from the lobe to the magnetospheric boundary layer. During the event on 6 November 2001 the magnetopause was compressed past Cluster. We applied the 2-D Cartesian model developed by collier98 in which a vacuum uniform tail lobe magnetic field is compressed by a step-like pressure increase. The model underestimates the compression of the magnetic field, but it fits the magnetic field maximum variance component well. For events for which we could determine the shock normal orientation, the differences between the observed and calculated shock propagation times from the location of WIND/Geotail to the location of Cluster were small. The propagation speeds of the SIs between the Cluster spacecraft were comparable to the solar wind speed. Our results suggest that the observed tail lobe SIs are due to lateral increases in solar wind dynamic pressure outside the magnetotail boundary

Spatial and temporal variability of a dinoflagellate-cyanobacterium community under a complex hydrodynamical influence:a case study at the entrance to the Gulf of Finland

Variability of nutrients and pelagic biological parameters (primary production and chlorophyll a [chl a] in flagellate and cyanobacterial size fractions, nitrogen fixation, phytoplankton species abundance) was followed for 12 d in July 1996 at an anchor station at the entrance to the Gulf of Finland, Simultaneously, meso-scale physical fields and plankton distribution were mapped over the surrounding 15 x 30 km area. The study period coincided with the intense blooming of a dinoflagellate Heterocapsa triquetra Ehrenberg and cyanobacterium Aphanizomenon flos-aquae (Linné) Ralfs community. A complex background of hydrodynamical processes was observed in the study area, including downwelling, formation and development of an anticyclonic eddy and jet currents. Our hypothesis was that the horizontal scale of patches decreases and the variation of biological parameters increases when moving from the overall community level (chl a) to the size class level and further to the species level. The horizontal distribution of chl a was closely related to the different water masses, but the distribution of the 2 dominant species differed and showed high variability even within water masses. The temporal variability of the pelagic biological parameters at the anchor station (estimated by the coefficient of variation) was between 25 and 95 % and it may be explained by horizontal patchiness. The results confirmed our hypothesis by showing that the coefficient of variation of summational parameters (total chl a, total primary production) was always lower than that of parameters specific to plankton size (chl a and primary production in 20 pm size classes), functional group (diazotrophs) or species. Phytoplankton in the size range equal to or greater than 20 μm exhibited particularly pronounced variability, while the smaller size fractions were less affected