351 research outputs found
Effectiveness of Different Materials as Catalysts for Alkaline Water Electrolysis
We tested the catalytic properties of various nickel and molybdenum electrodes as potential replacements for platinum for usage in alkaline water electrolysis. After initial tests found molybdenum-based electrodes to be significantly more effective than nickel electrodes, we moved to calculate overpotentials. We found nickel electrode overpotentials at ± 10 mA current to be 939 and -960 mV. Conversely, molybdenum electrode overpotentials at the same currents were 244 and -681 mV respectively. While still significantly higher than overpotentials for platinum, these results indicate that, with more testing, molybdenum-based electrodes could eventually emerge as a cheaper, more abundant alternative to platinum electrodes
Swimming Dynamics and Propulsive Efficiency of Squids Throughout Ontogeny
Synopsis Squids encounter vastly different flow regimes throughout ontogeny as they undergo critical morphological changes to their two locomotive systems: the fins and jet. Squid hatchlings (paralarvae) operate at low and intermediate Reynolds numbers (Re) and typically have rounded bodies, small fins, and relatively large funnel apertures whereas juveniles and adults operate at higher Re and generally have more streamlined bodies, larger fins, and relatively small funnel apertures. These morphological changes and varying flow conditions affect swimming performance in squids. To determine how swimming dynamics and propulsive efficiency change throughout ontogeny, digital particle image velocimetry (DPIV) and kinematic data were collected from an ontogenetic range of long-finned squid Doryteuthis pealeii and brief squid Lolliguncula brevis swimming in a holding chamber or water tunnel (Re=20-20 000). Jet and fin wake bulk properties were quantified, and propulsive efficiency was computed based on measurements of impulse and excess kinetic energy in the wakes. Paralarvae relied predominantly oil a vertically directed, high frequency, low velocity jet as they bobbed up and down in the water column. Although sonic spherical vortex rings were observed, most paralarval jets consisted of an elongated vertical region of variable length with no clear pinch-off of a vortex ring from the trailing tail component. Compared with paralarvae, juvenile and adult squid exhibited a more diverse range of swimming strategies, involving greater overall locomotive fin reliance and multiple fin and jet wake modes with better defined vortex rings. Despite greater locomotive flexibility, jet propulsive efficiency of juveniles/adults was significantly lower than that of paralarvae, even when juvenile/adults employed their highest efficiency jet mode involving the production of periodic isolated vortex rings with each jet pulse. When the fins were considered together with the jet for several juvenile/adult swimming sequences, overall propulsive efficiency increased, suggesting that fin contributions are important and Should not be overlooked in analyses of the swimming performance of squids. The fins produced significant thrust and consistently had higher propulsive efficiency than did the jet. One particularly important area of future Study is the determination of coordinated jet/fin wake modes that have the greatest impact oil propulsive efficiency. Although such research would be technically challenging, requiring new, powerful, 3D approaches, it is necessary for a more comprehensive assessment of propulsive efficiency of the squid dual-mode locomotive system
Hydrodynamics of Pulsed Jetting in Juvenile and Adult Brief Squid Lolliguncula Brevis: Evidence of Multiple Jet \u27Modes\u27 and Their Implications for Propulsive Efficiency
The dynamics of pulsed jetting in squids throughout ontogeny is not well understood, especially with regard to the development of vortex rings, which are common features of mechanically generated jet pulses (also known as starting jets). Studies of mechanically generated starting jets have revealed a limiting principle for vortex ring formation characterized in terms of a \u27formation number\u27 (F), which delineates the transition between the formation of isolated vortex rings and vortex rings that have \u27pinched off\u27 from the generating jet. Near F, there exists an optimum in pulse-averaged thrust with (potentially) low energetic cost, raising the question: do squids produce vortex rings and if so, do they fall near F, where propulsive benefits presumably occur? To better understand vortex ring dynamics and propulsive jet efficiency throughout ontogeny, brief squid Lolliguncula brevis ranging from 3.3 to 9.1 cm dorsal mantle length (DML) and swimming at speeds of 2.43-22.2cm s-1 (0.54-3.50 DML s-1) were studied using digital particle image velocimetry (DPIV). A range of jet structures were observed but most structures could be classified as variations of two principal jet modes: (1) jet mode I, where the ejected fluid rolled up into an isolated vortex ring; and (2) jet mode II, where the ejected fluid developed into a leading vortex ring that separated or \u27pinched off\u27 from a long trailing jet. The ratio of jet length [based on the vorticity extent (Lω] to jet diameter [based on peak vorticity locations (Dω] was \u3c3.0 for jet mode I and \u3e 3.0 for jet mode II, placing the transition between modes in rough agreement with F determined in mechanical jet studies. Jet mode II produced greater time-averaged thrust and lift forces and was the jet mode most heavily used whereas jet mode I had higher propulsive efficiency, lower slip, shorter jet periods and a higher frequency of fin activity associated with it. No relationship between Lω/Dω and speed was detected and there was no apparent speed preference for the jet modes within the speed range considered in this study; however, propulsive efficiency did increase with speed partly because of a reduction in slip and jet angle with speed. Trends in higher slip, lower propulsive efficiency and higher relative lift production were observed for squid \u3c5.0 cm DML compared with squid \u3e= 5.0 cm DML. While these trends were observed when jet mode I and II were equally represented among the size classes, there was also greater relative dependence on jet mode I than jet mode II for squid \u3c5.0 cm DML when all of the available jet sequences were examined. Collectively, these results indicate that similar to 5.0 cm DML is an important ontogenetic transition for the hydrodynamics of pulsed jetting in squids. The significance of our findings is that from early juvenile through to adult life stages, L. brevis is capable of producing a diversity of vortex ring-based jet structures, ranging from efficient short pulses to high-force longer duration pulses. Given that some of these structures had Lω/Dωs near F, and F represented the delineation between the two primary jet modes observed, fluid dynamics probably played an integral role in the evolution of squid locomotive systems. When this flexibility in jet dynamics is coupled with the highly versatile fins, which are capable of producing multiple hydrodynamic modes as well, it is clear that squid have a locomotive repertoire far more complex than orignally thought
Squids Use Multiple Escape Jet Patterns Throughout Ontogeny
Throughout their lives, squids are both predators and prey for a multitude of animals, many of which are at the top of ocean food webs, making them an integral component of the trophic structure of marine ecosystems. The escape jet, which is produced by the rapid expulsion of water from the mantle cavity through a funnel, is central to a cephalopod\u27s ability to avoid predation throughout its life. Although squid undergo morphological and behavioral changes and experience remarkably different Reynolds number regimes throughout their development, little is known about the dynamics and propulsive efficiency of escape jets throughout ontogeny. We examine the hydrodynamics and kinematics of escape jets in squid throughout ontogeny using 2D/3D velocimetry and high-speed videography. All life stages of squid produced two escape jet patterns: (1) escape jet I characterized by short rapid pulses resulting in vortex ring formation and (2) escape jet II characterized by long high-volume jets, often with a leading-edge vortex ring. Paralarvae exhibited higher propulsive efficiency than adult squid during escape jet ejection, and propulsive efficiency was higher for escape jet I than escape jet II in adults. These results indicate that although squid undergo major ecological transitions and morphology changes from paralarvae to adults, all life stages demonstrate flexibility in escape jet responses and produce escape jets of surprisingly high propulsive efficiency
Pulsed Jet Dynamics of Squid Hatchlings at Intermediate Reynolds Numbers
Squid paralarvae (hatchlings) rely predominantly on a pulsed jet for locomotion, distinguishing them from the majority of aquatic locomotors at low/intermediate Reynolds numbers (Re), which employ oscillatory/undulatory modes of propulsion. Although squid paralarvae may delineate the lower size limit of biological jet propulsion, surprisingly little is known about the hydrodynamics and propulsive efficiency of paralarval jetting within the intermediate Re realm. To better understand paralarval jet dynamics, we used digital particle image velocimetry (DPIV) and high-speed video to measure bulk vortex properties ( e. g. circulation, impulse, kinetic energy) and other jet features [ e. g. average and peak jet velocity along the jet centerline (Uj and Ujmax, respectively), jet angle, jet length based on the vorticity and velocity extents (Lω and LV, respectively), jet diameter based on the distance between vorticity peaks (Dω), maximum funnel diameter (DF), average and maximum swimming speed (U and Umax, respectively)] in free-swimming Doryteuthis pealeii paralarvae (1.8 mm dorsal mantle length) (Resquid=25-90). Squid paralarvae spent the majority of their time station holding in the water column, relying predominantly on a frequent, high-volume, vertically directed jet. During station holding, paralarvae produced a range of jet structures from spherical vortex rings ( Lω/Dω=2.1, LV/DF=13.6) to more elongated vortex ring structures with no distinguishable pinch-off (Lω/Dω= 4.6, LV/DF=36.0). To swim faster, paralarvae increased pulse duration and Lω/Dω, leading to higher impulse but kept jet velocity relatively constant. Paralarvae produced jets with low slip, i.e. ratio of jet velocity to swimming velocity (Uj/U or Ujmax/Umax), and exhibited propulsive efficiency [ηpd=74.9 +/- 8.83% (+/- s.d.) for deconvolved data] comparable with oscillatory/ undulatory swimmers. As slip decreased with speed, propulsive efficiency increased. The detection of high propulsive efficiency in paralarvae is significant because it contradicts many studies that predict low propulsive efficiency at intermediate Re for inertial forms of locomotion
Correction: New Approaches for Assessing Squid Fin Motions: Coupling Proper Orthogonal Decomposition With Volumetric Particle Tracking Velocimetry (doi:10.1242/jeb.176750)
Squid, which swim using a coupled fin/jet system powered by muscular hydrostats, pose unique challenges for the study of locomotion. The high flexibility of the fins and complex flow fields generated by distinct propulsion systems require innovative techniques for locomotive assessment. For this study, we used proper orthogonal decomposition (POD) to decouple components of the fin motions and defocusing digital particle tracking velocimetry (DDPTV) to quantify the resultant 3D flow fields. Kinematic footage and DDPTV data were collected from brief squid, Lolliguncula brevis [3.1–6.5 cm dorsal mantle length (DML)], swimming freely in a water tunnel at speeds of 0.39–7.20 DML s−1. Both flap and wave components were present in all fin motions, but the relative importance of the wave components was higher for arms-first swimming than for tail-first swimming and for slower versus higher speed swimming. When prominent wave components were present, more complex interconnected vortex ring wakes were observed, while fin movements dominated by flapping resulted in more spatially separated vortex ring patterns. Although the jet often produced the majority of the thrust for steady rectilinear swimming, our results demonstrated that the fins can contribute more thrust than the jet at times, consistently produce comparable levels of lift to the jet during arms-first swimming, and can boost overall propulsive efficiency. By producing significant drag signatures, the fins can also aid in stabilization and maneuvering. Clearly, fins play multiple roles in squid locomotion, and when coupled with the jet, allow squid to perform a range of swimming behaviors integral to their ecological success
The Ontogeny of Muscle Structure and Locomotory Function in the Long-Finned Squid Doryteuthis Pealeii
Understanding the extent to which changes in muscle form and function underlie ontogenetic changes in locomotory behaviors and performance is important in understanding the evolution of musculoskeletal systems and also the ecology of different life stages. We explored ontogenetic changes in the structure, myosin heavy chain (MHC) expression and contractile properties of the circular muscles that provide power for jet locomotion in the long-finned squid Doryteuthis pealeii. The circular muscle fibers of newly hatched paralarvae had different sizes, shapes, thick filament lengths, thin: thick filament ratio, myofilament organization and sarcoplasmic reticulum (SR) distribution than those of adults. Viewed in cross section, most circular muscle cells were roughly triangular or ovoid in shape with a core of mitochondria; however, numerous muscle cells with crescent or other unusual cross-sectional shapes and muscle cells with unequal distributions of mitochondria were present in the paralarvae. The frequency of these muscle cells relative to \u27normal\u27 circular muscle cells ranged from 1: 6 to 1: 10 among the 19 paralarvae we surveyed. The thick filaments of the two types of circular fibers, superficial mitochondria-rich (SMR) and central mitochondria-poor (CMP), differed slightly in length among paralarvae with thick filament lengths of 0.83+/-0.15 μm and 0.71+/-0.1μm for the SMR and CMP fibers, respectively (P 0.05; ANOVA). During ontogeny the thick filament lengths of both the CMP and SMR fibers increased significantly to 1.78+/-0.27 μm and 3.12+/-0.56 μm, respectively, in adults (P-1 (where L0 was the preparation length that generated the peak isometric stress), nearly twice that measured in other studies for the CMP fibers of adults. The mean peak isometric stress was 119+/-15mN mm-2 physiological cross section, nearly half that measured for the CMP fibers of adults. Reverse transcriptase-polymerase chain reaction analysis of paralarval and adult mantle samples revealed very similar expression patterns of the two known isoforms of squid MHC. The ontogenetic differences in the structure and physiology of the circular muscles may result in more rapid mantle movements during locomotion. This prediction is consistent with jet pulse durations observed in other studies, with shorter jet pulses providing hydrodynamic advantages for paralarvae
Volumetric Flow Imaging Reveals the Importance of Vortex Ring Formation in Squid Swimming Tail-First and Arms-First
Squids use a pulsed jet and fin movements to swim both arms-first (forward) and tail-first (backward). Given the complexity of the squid multi-propulsor system, 3D velocimetry techniques are required for the comprehensive study of wake dynamics. Defocusing digital particle tracking velocimetry, a volumetric velocimetry technique, and high-speed videography were used to study arms-first and tail-first swimming of brief squid Lolliguncula brevis over a broad range of speeds [0-10 dorsal mantle lengths (DML) s-1) in a swim tunnel. Although there was considerable complexity in the wakes of these multi-propulsor swimmers, 3D vortex rings and their derivatives were prominent reoccurring features during both tail-first and arms-first swimming, with the greatest jet and fin flow complexity occurring at intermediate speeds (1.5-3.0 DML s-1). The jet generally produced the majority of thrust during rectilinear swimming, increasing in relative importance with speed, and the fins provided no thrust at speeds \u3e4.5 DML s-1. For both swimming orientations, the fins sometimes acted as stabilizers, producing negative thrust (drag), and consistently provided lift at low/intermediate speeds (\u3c2.0 DML s-1) to counteract negative buoyancy. Propulsive efficiency (η) increased with speed irrespective of swimming orientation, and eta for swimming sequences with clear isolated jet vortex rings was significantly greater (η=78.6 +/- 7.6%, mean +/- s.d.) than that for swimming sequences with clear elongated regions of concentrated jet vorticity (η=67.9 +/- 19.2%). This study reveals the complexity of 3D vortex wake flows produced by nekton with hydrodynamically distinct propulsors
Engaging with patient online health information use: a survey of primary health care nurses
Internet health information is used by patients for health care decision making. Research indicates this information is not necessarily disclosed in interactions with health professionals. This study investigated primary health care nurses’ engagement with patient online health information use along with the respondents’ disclosure of online sources to their personal health care provider. A questionnaire was posted to a random sample of 1,000 New Zealand nurses with 630 responses. Half the respondents assessed patients’ online use (n = 324) and had encountered patients who had wrongly interpreted information. Health information quality evaluation activities with patients indicated the need for nursing information literacy skills. A majority of respondents (71%, n = 443) used online sources for personal health information needs; 36.3% (n = 155) of the respondents using online sources did not tell their personal health care provider about information obtained. This study identifies that there are gaps in supporting patient use but more nursing engagement with online sources when compared with earlier studies
Espon-Interstrat. Espon in Integrated Territorial Strategies.
The INTERSTRAT project’s overall aim is “to encourage and facilitate the use of ESPON 2013 Programme findings in the creation and monitoring of Integrated Territorial Development Strategies (ITDS) and to support transnational learning about the actual and potential contribution of ESPON to integrated policy-making.” We defined integrated territorial development as ‘the process of shaping economic, social and environmental change through spatially sensitive policies and programmes’
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