Digital tools in aquatic sciences education

info:eu-repo/semantics/publishedVersio

Measuring every particle's size from three-dimensional imaging experiments

Often experimentalists study colloidal suspensions that are nominally monodisperse. In reality these samples have a polydispersity of 4-10%. At the level of an individual particle, the consequences of this polydispersity are unknown as it is difficult to measure an individual particle size from microscopy. We propose a general method to estimate individual particle radii within a moderately concentrated colloidal suspension observed with confocal microscopy. We confirm the validity of our method by numerical simulations of four major systems: random close packing, colloidal gels, nominally monodisperse dense samples, and nominally binary dense samples. We then apply our method to experimental data, and demonstrate the utility of this method with results from four case studies. In the first, we demonstrate that we can recover the full particle size distribution {\it in situ}. In the second, we show that accounting for particle size leads to more accurate structural information in a random close packed sample. In the third, we show that crystal nucleation occurs in locally monodisperse regions. In the fourth, we show that particle mobility in a dense sample is correlated to the local volume fraction.Comment: 7 pages, 5 figure

Fitness & Sports Medicine

Aim: The aim of the present study was to investigate the reactions of oxygen consumption (VO2), heart rate (HR) and lactate accumulation (La) when running on lower body positive pressure treadmills (LBPPT).Methods: 15 well-trained male athletes (VO2peak: 60.23.8ml kg-1 min-1) completed in randomized order three analogous maximal incremental treadmill tests,recording spiroergometrical data using breath-by-breath analysis. Two tests were held on a LBPPT, with 80% and 60% body weight (80% BWSet and 60% BWSet), respectively. The third test was completed on a conventional treadmill (100% BWSet).Results: Average of all running speed stages from 10 to 18 kmh-1, VO2 decreased significantly from 48.18.4 via 39.76.8 to 33.57.3ml kg-1 min-1 at 100%, 80% and 60% BWSet (p<0.001). HR was on average 15 bpm and 27 bpm lower at 80% and 60% BWSetcompared to 100% BWSet (p<0.001), while La decreased from 2.52.3 via 1.51.1 to 1.10.5 mmol l-1 (p<0.001). Conclusion: VO2, HR and La are clearly changed by LBPPT running. Furthermore, regression analyses showed that training at a fixed VO2stimulus leads to higher lactate values on the LBPPT compared to the conventional treadmill, which may indicate a change in energy contributions.KEY WORDS: AlterG, Hypogravity, LBPPT, Anti-Gravity, Oxygen Consumptio

Monolithic integration of focused 2D GMR spin valve magnetic field sensor for high-sensitivity (compass) applications

We have designed and fabricated 2D GMR spin valve sensors on the basis of IrMn/CoFe/Cu/CoFe/NiFe nanolayers in monolithic integration for high sensitivity applications. For a maximum signal-to-noise ratio, we realize a focused double full bridge layout featuring an antiparallel exchange bias pinning for neighbouring meanders and an orthogonal pinning for different bridges. This precise alignment is achieved with microscopic precision by laser heating and subsequent in-field cooling. Striving for maximum signal sensitivity and minimum hysteresis, we study in detail the impact of single meander geometry on the total magnetic structure and electronic transport properties. The investigated geometrical parameters include stripe width, stripe length, cross bar material and total meander length. In addition, the influence of the relative alignment between reference magnetization (pinned layer) and shape anisotropy (free layer) is studied. The experimentally obtained data are moreover compared to the predictions of tailored micromagnetic simulations. Using a set of optimum parameters, we demonstrate that our sensor may readily be employed to measure small magnetic fields, such as the ambient (geomagnetic) field, in terms of a 2D vector with high spatial (~200 μm) and temporal (~1 ms) resolution

High-performance giant magnetoresistive sensorics on flexible Si membranes

We fabricate high-performance giant magnetoresistive (GMR) sensorics on Si wafers, which are subsequently thinned down to 100 mu m or 50 mu m to realize mechanically flexible sensing elements. The performance of the GMR sensors upon bending is determined by the thickness of the Si membrane. Thus, bending radii down to 15.5mm and 6.8mm are achieved for the devices on 100 mu m and 50 mu m Si supports, respectively. The GMR magnitude remains unchanged at the level of (15.3 +/- 0.4)% independent of the support thickness and bending radius. However, a progressive broadening of the GMR curve is observed associated with the magnetostriction of the containing Ni81Fe19 alloy, which is induced by the tensile bending strain generated on the surface of the Si membrane. An effective magnetostriction value of lambda(s) = 1.7 x 10(-6) is estimated for the GMR stack. Cyclic bending experiments showed excellent reproducibility of the GMR curves during 100 bending cycles

Monolithic microelectronic spin valve compass for autonomous MEMS navigation in geomagnetic field

The natural geomagnetic field has been used for millions of years by various organisms for navigation. The determination of the local field direction (in terms of magnetic north and inclination) enables, for instance, migratory birds to find their annual routes from one continent to another and back home, or magnetotactic bacteria to move towards soil areas rich in nutrients. In analogy, for microelectromechanical systems (MEMS), the capability of detecting the local direction of the geomagnetic field as a 2D or 3D vector enables a reliable autonomous navigation through environments with a complex or unknown topology while being independent of GPS or any other radio-based navigation system (and thus being operable also in obstructed or shielded environments). Such mobile MEMS applications demand, however, a very low power consumption and a high miniaturizability of the sensor, as well as a very fast sensor response time. In the following, we present an innovative 2D GMR spin valve sensor on the basis of exchange-biased NiFe- CoFe / Cu / CoFe / IrMn nanolayers in monolithic integration that fulfils all these requirements. For a maximum signal-to-noise ratio, we have realized a focused double full-bridge layout with an antiparallel alignment of the pinned layers of neighbouring meanders by means of microscopic laser heating and subsequent in-field cooling. A systematic optimization of geometry and magnetic structure further contributed to a maximum signal level and a minimum sensor hysteresis. On the basis of fabricated prototypes with a size of 1.5 mm times we demonstrate that these sensors are readily employed to detect the geomagnetic field as a 2D vector with temporal ( 1 ms) resolution

J. Phys.: Condens. Matter

Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it—without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed

Communication between scientists, fishery managers and recreational fishers: lessons learned from a comparative analysis of international case studies

The management of recreational fisheries benefits from good collaboration between scientists, managers and recreational fishers. However, the level of collaboration largely depends on the levels of effective communication among the different stakeholders. This paper presents the views of scientists, managers and fishers concerning the quality of communication in eleven case studies of recreational fisheries. Case studies were synthesised and common reasons why communication did not always flow as intended were identified. The prevalent barriers to good communication, and therefore collaboration included a lack of rigorous scientific information transfer from scientists to fishers and managers, a fear from fishers that management actions will limit fishing opportunities, pre-existing antagonism between commercial and recreational fisheries, and fishers' suspicion of science. Overcoming these issues is paramount to improve collaboration and participatory processes that help lead to robust, well-accepted management action