Migrating silver eels return from the sea to the river of origin after a false start.

The European eel's singular spawning migration from European waters towards the Sargasso Sea remains elusive, including the early phase of migration at sea. During spawning migration, the movement of freshwater resident eels from river to sea has been thought to be irreversible. We report the first recorded incidents of eels returning to the river of origin after spending up to a year in the marine environment. After migrating to the Baltic Sea, 21% of the silver eels, tagged with acoustic transmitters, returned to the Narva River. Half returned 11-12 months after moving to the sea, with 15 km being the longest upstream movement. The returned eels spent up to 33 days in the river and migrated to the sea again. The fastest specimen migrated to the outlet of the Baltic Sea in 68 days after the second start-roughly 1300 km. The surprising occurrence of returning migrants has implications for sustainable management and protection of this critically endangered species.

Disparate movement behavior and feeding ecology in sympatric ecotypes of Atlantic cod.

Coexistence of ecotypes, genetically divergent population units, is a widespread phenomenon, potentially affecting ecosystem functioning and local food web stability. In coastal Skagerrak, Atlantic cod (Gadus morhua) occur as two such coexisting ecotypes. We applied a combination of acoustic telemetry, genotyping, and stable isotope analysis to 72 individuals to investigate movement ecology and food niche of putative local "Fjord" and putative oceanic "North Sea" ecotypes-thus named based on previous molecular studies. Genotyping and individual origin assignment suggested 41 individuals were Fjord and 31 were North Sea ecotypes. Both ecotypes were found throughout the fjord. Seven percent of Fjord ecotype individuals left the study system during the study while 42% of North Sea individuals left, potentially homing to natal spawning grounds. Home range sizes were similar for the two ecotypes but highly variable among individuals. Fjord ecotype cod had significantly higher δ13C and δ15N stable isotope values than North Sea ecotype cod, suggesting they exploited different food niches. The results suggest coexisting ecotypes may possess innate differences in feeding and movement ecologies and may thus fill different functional roles in marine ecosystems. This highlights the importance of conserving interconnected populations to ensure stable ecosystem functioning and food web structures.

Non-greeting rituals in clinical placements.

BACKGROUND: This study aims to generate knowledge about how clinical placements contribute to the creation of sustainable nursing education in Denmark. The article discusses how nursing students feel socially excluded when registered nurses do not recognise them through deviating from culturally appropriate greeting rituals. METHOD: A constructivist grounded theory study of (n = 15) individual semi-structured interviews with nursing students in their first and third years of study. RESULTS: Nursing students feel awkward, alienated and uncomfortable when confronted with a culture where registered nurses do not greet them. They are met by the attitude that Bauman refers to as "appropriate indifference," which means that the registered nurses act as if they neither see nor hear them because they are considered faceless private failures. CONCLUSION: Nurses' non-greeting rituals in clinical placements counteract the creation of sustainable nursing education. The aim of this article is to contribute with knowledge about socially inappropriate non-greeting rituals and recommend friendly and socially sustainable education in clinical placements.

Cortisol predicts migration timing and success in both Atlantic salmon and sea trout kelts.

Kelts - individuals of anadromous fish species which have successfully spawned and may return to sea to repeat the cycle - are perhaps the least studied life stage of iteroparous fish species. To date, our understanding of what makes them successful in their return migration to sea is limited. We investigated the relationship between three physiological parameters (baseline cortisol, baseline glucose and low molecular weight antioxidants) and the timing and success of Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) kelt migration. To do so, we combined blood samples obtained within 3 minutes of capture and acoustic telemetry to track 66 salmon and 72 sea trout as they migrated out of rivers, into fjords and out at sea. We show that baseline cortisol may be a good predictor of migration success. Individuals with high baseline cortisol levels exited the river earlier but were less likely to successfully reach the sea. Similar relationships were not observed with glucose or antioxidants. We provide the first evidence to support the role of physiological status in migration success in Atlantic salmon and sea trout kelts. Our findings contribute to our understanding of the relationship between physiology and fitness in wild animals. Further, we suggest that migration timing is a trade-off between stress and readiness to migrate.

A CT-, PET- and MR-imaging-compatible hyperbaric pressure chamber for baromedical research.

OBJECTIVES: We describe the development of a novel preclinical rodent-sized pressure chamber system compatible with computed tomography (CT), positron emission tomography (PET) and magnetic resonance imaging (MRI) that allows continuous uncompromised and minimally invasive data acquisition throughout hyperbaric exposures. The effect of various pressures on the acquired image intensity obtained with different CT, PET and MRI phantoms are characterised. MATERIAL AND METHODS: Tissue-representative phantom models were examined with CT, PET or MRI at normobaric pressure and hyperbaric pressures up to 1.013 mPa. The relationships between the acquired image signals and pressure were evaluated by linear regression analysis for each phantom. RESULTS: CT and PET showed no effect of pressure per se, except for CT of air, demonstrating an increase in Hounsfield units in proportion to the pressure. For MRI, pressurisation induced no effect on the longitudinal relaxation rate (R1), whereas the transversal relaxation rate (R2) changed slightly. The R2 data further revealed an association between pressure and the concentration of the paramagnetic nuclei gadolinium, the contrast agent used to mimic different tissues in the MRI phantoms. CONCLUSION: This study demonstrates a pressure chamber system compatible with CT, PET and MRI. We found that no correction in image intensity was required with pressurisation up to 1.013 mPa for any imaging modality. CT, PET or MRI can be used to obtain anatomical and physiological information from pressurised model animals in this chamber.

Fabricating Nanoporous Silica Structure on D-Fibres through Room Temperature Self-Assembly.

The room temperature deposition of self-assembling silica nanoparticles onto D-shaped optical fibres ("D-fibre"), drawn from milled preforms fabricated by modified chemical vapour deposition (MCVD), is studied. Vertical dip-and-withdraw produces tapered layers, with one end thicker (surface coverage >0.85) than the other, whilst horizontal dip-and-withdraw produces much more uniform layers over the core region. The propagation of induced fracturing over the core region during drying is overcome using a simple protrusion of the inner cladding. Thick coatings are discernible through thin film interference colouring, but thinner coatings require scanning electron microscopy (SEM) imaging. Here, we show that fluorescence imaging, using Rhodamine B, in this example, can provide some qualitative and speedy assessment of coverage.

Pulsed laser manipulation of an optically trapped bead: averaging thermal noise and measuring the pulsed force amplitude.

An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 µm polystyrene bead, the laser pulse-bead interaction is repeated hundreds of times. Traces with the bead position following the prompt displacement from equilibrium, induced by each laser pulse, are averaged and reveal the underlying deterministic motion of the bead, which is not visible in a single trace due to thermal noise. The motion of the bead is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our experimental method may have implications for microrheology.

Motion analysis of optically trapped particles and cells using 2D Fourier analysis.

Motion analysis of optically trapped objects is demonstrated using a simple 2D Fourier transform technique. The displacements of trapped objects are determined directly from the phase shift between the Fourier transform of subsequent images. Using end- and side-view imaging, the stiffness of the trap is determined in three dimensions. The Fourier transform method is simple to implement and applicable in cases where the trapped object changes shape or where the lighting conditions change. This is illustrated by tracking a fluorescent particle and a myoblast cell, with subsequent determination of diffusion coefficients and the trapping forces.

Relaxed fabrication tolerance for self-imaging photonic crystal waveguide splitters using a tapered multimode interference region.

The power imbalance between different waveguide outputs is compensated by manipulating the dispersion of the guided propagation in the multimode interference (MMI) region. This is attainable using a tapered region at the beginning of the MMI region that has been verified through simulation and experiment. From this, the fabrication tolerance for the diameters of holes in a tapered 1×3 photonic crystal waveguide (PhCW) splitter is relaxed up to a range of at least 27 nm. The output power is well-balanced to within 1 dB. The effective bandwidth of the splitters shifts only around 13 nm, for a reduction of 10 nm in the diameter of the PhCW holes. The optimized component is an outstanding ultracompact 1×3 splitter for the photonic integrated circuit (PIC).

Direct slow-light excitation in photonic crystal waveguides forming ultra-compact splitters.

Based on a series of 1x2 beam splitters, novel direct excitation of slow-light from input- to output-region in photonic crystal waveguides is investigated theoretically and experimentally. The study shows that the slow-light excitation provides over 50 nm bandwidth for TE-polarized light splitting between two output ports, and co-exists together with self-imaging leading to ~20 nm extra bandwidth. The intensity of the direct excitation is qualitatively explained by the overlap integral of the magnetic fields between the ground input- and excited output-modes. The direct excitation of slow light is practically lossless compared with transmission in a W1 photonic crystal waveguides, which broadens the application-field for slow-light and further minimizes the size of a 1x2 splitter.

1x3 beam splitter for TE polarization based on self-imaging phenomena in photonic crystal waveguides.

Based on inspiration from multi-mode interference self-imaging and theoretical FDTD simulations, a 1x3 beam splitter was designed, fabricated and characterized. Measurements show that for TE-polarized incident light the power is distributed equally between the output ports within 1dB in the range from 1541nm to 1552nm, and the total transmission of the 1x3 splitter is equal to the corresponding length of a single-line-defect PhCW within the measurement uncertainty.

Versatile transformations of alkylamine-derivatized glassy carbon electrodes using aryl isocyanates.

The reaction between a nucleophilic 4-(2-aminoethyl)phenyl-tethered glassy carbon surface and various para-substituted aryl isocyanates [ONC-PhX; X = NO(2), COPh, Cl, H, and NMe(2)] has been studied in toluene. It is demonstrated that the nucleophilic addition reaction is relatively fast occurring within two hours while providing an efficient and versatile route for derivatizing alkylamine-functionalized surfaces. An often overlooked issue in surface reactions is the possibility for competing physisorption processes. In such cases, the solution-based reactants become adsorbed to the surface or embedded in the grafted layer rather than chemically bonded to the surface. It is shown that for two of the aryl isocyanates (X = NO(2) and COPh) this physical adhesion can be so strong that even prolonged ultrasonic treatment cannot remove the adsorbant. However, a single potential excursion is capable of desorbing most of the physisorbed layers. The isocyanate-based method is also compared with the well-known approaches involving diazonium salts for assembling similar chemical systems directly. It is concluded that the method can be used advantageously not only in cases, where such approaches should fall short, but also if the goal is to achieve better control of the positioning of, e.g., redox active molecules in a well-defined layer with the ultimate goal of obtaining distinct electrochemical responses.

Direct observation of surface mode excitation and slow light coupling in photonic crystal waveguides.

A scanning near-field optical microscope (SNOM) is used to systematically study the properties of guided modes in linear and slow-light regimes of silicon-on-insulator (SOI)-based photonic crystal waveguides (PhCWs) with different terminations of the photonic lattice. High quality SNOM images are obtained for light at telecom wavelengths propagating in the PhCW, demonstrating directly, for the first time to our knowledge, drastic widening of the PhCW guided mode in the slow-light regime and excitation of surface waves at the PhCW interface along with their feeding into the guided mode for the lattice terminations corresponding to significantly reduced coupling loss.

Refractive Index Measurement within a Photonic Crystal Fibre Based on Short Wavelength Diffraction.

A new class of refractive index sensors using solid core photonic crystal fibres isdemonstrated. Coherent scattering at the cladding lattice is used to optically characterizematerials inserted into the fibre holes. The liquid to solid phase transition of water uponfreezing to ice 1h is characterized by determining the refractive index.

Photonic-crystal waveguide biosensor.

A photonic-crystal waveguide sensor is presented for biosensing. The sensor is applied for refractive index measurements and detection of protein-concentrations. Concentrations around 10 mug/ml (0.15muMolar) are measured with excellent signal to noise ratio, and a broad, dynamic refractive index sensing range extending from air to high viscous fluids is presented.

Mapping the broadband polarization properties of linear 2D SOI photonic crystal waveguides.

Both quasi-TE and TM polarisation spectra for a silicon-on-insulator (SOI) waveguide are recorded over (1100-1700)nm using a broadband supercontinuum source. By studying both the input and output polarisation eigenstates we observe narrowband resonant cross coupling near the lowest quasi-TE mode cut-off. We also observe relatively broadband mixing between the two eigenstates to generate a complete photonic bandgap. By careful analysis of the output polarisation state we report on an inherent non-reciprocity between quasi TE and TM fundamental mode cross coupling. The nature of polarisation distinction in such bandgap structures is discussed in the context of polarisation scattering at an interface.

Strained silicon as a new electro-optic material.

For decades, silicon has been the material of choice for mass fabrication of electronics. This is in contrast to photonics, where passive optical components in silicon have only recently been realized. The slow progress within silicon optoelectronics, where electronic and optical functionalities can be integrated into monolithic components based on the versatile silicon platform, is due to the limited active optical properties of silicon. Recently, however, a continuous-wave Raman silicon laser was demonstrated; if an effective modulator could also be realized in silicon, data processing and transmission could potentially be performed by all-silicon electronic and optical components. Here we have discovered that a significant linear electro-optic effect is induced in silicon by breaking the crystal symmetry. The symmetry is broken by depositing a straining layer on top of a silicon waveguide, and the induced nonlinear coefficient, chi(2) approximately 15 pm V(-1), makes it possible to realize a silicon electro-optic modulator. The strain-induced linear electro-optic effect may be used to remove a bottleneck in modern computers by replacing the electronic bus with a much faster optical alternative.

[Food consumption in Denmark is changing. Positive trends have stagnated during the period 2001-2004]. / Danskernes fødevareforbrug under forandring. Hidtidige positive udvikling delvis stagneret i perioden 2001-2004.

INTRODUCTION: The aim of this study was to describe trends in food consumption habits in Denmark, based on a food frequency survey conducted by the Danish Nutrition Council in 2004, and to compare the results to results from similar surveys in 1995, 1998 and 2001. MATERIALS AND METHODS: A random population sample of 1,093 men and women, (15-92 years of age) were interviewed by telephone. They were asked 16 food frequency questions on nutritionally important foods (yoghurt, milk [2 questions], cheese, rye bread, wheat bread, sandwiches with fish, fish as the main meal, meat as the main meal, potatoes, rice, pasta, vegetables [3 questions], fruit), as well as questions about the type of milk and type of fat spreads most often used. RESULTS: Several positive developments in the period 1995-2001 have slowed down during the 2001-2005, and several negative trends have continued. The previous increase in fruit and vegetable consumption has weakened, and the decrease in consumption of bread and potatoes has continued. Furthermore, the previous increase in the proportion of the population not using any kind of fat spread on their bread has reached a standstill. However, the relative increase in consumption of low-fat milk has continued. DISCUSSION: The results show that the previous positive trends in Danish dietary habits, during the period 1995-2001, have come to a standstill. There is therefore a need for a new and more effective effort to encourage positive changes in food consumption patterns.

Planar glass devices for efficient periodic poling.

We demonstrate that frequency-converting devices of high quality can be realised with glass poling. The devices, made with silica-on-silicon technology, are poled with periodic, embedded electrodes, and used for second-harmonic generation. We obtain precise control of the quasi phase-matching wavelength and bandwidth, and a normalised conversion efficiency of 1.4x10-3 %/W/cm2 which, to our knowledge, is the highest obtained so far with periodic glass poling.