The locomotion of the comatulid Florometra serratissima (Echinodermata: Crinoidea) and its adaptive significance

1990 ◽  
Vol 68 (5) ◽  
pp. 942-950 ◽  
Author(s):  
G. D. Shaw ◽  
A. R. Fontaine
Keyword(s):  
Invertebrate Species ◽  
Behavioral Adaptations ◽  
Feeding Modes ◽  
Contact Behaviour ◽  
Primary Means ◽  
Oral Surface ◽  
Functional Regionalization ◽  
Ambient Currents ◽  
Made In

Swimming and crawling activities are described from observations made in situ during SCUBA diving and in aquaria. Initial vertical swimming lifts the crinoid to 29 cm mean height. Subsequently, horizontal swimming displaces the crinoid, oral surface foremost, at a mean speed of 6.8 cm/s. Horizontal swimming is achieved by differential arm extension. Behavioral adaptations make use of ambient currents to augment displacement. Swimming mechanics are based on sequential repetition of arm strokes made approximately simultaneously by three coordinated groups of arms, verified experimentally by selective arm removal. The Reynolds number while swimming is calculated to be 8112, with a drag coefficient of 0.0148. Swimming occurs in short, repeatable bursts of 10–30 s. Continuous swimming beyond 4 min provokes a refractory period lasting 5–17 min during which individuals are incapable of swimming. Spontaneous swimming was never observed in situ nor in aquaria, but was elicited by mechanical stimulation or contact with potential predators. Trials with 17 cooccurring invertebrate species of diverse feeding modes show that swimming is provoked by opportunistic carnivores, notably asteroids. Swimming is an escape response against potential predators. Crawling is the primary means of moving from place to place. Crawling is induced by directional currents and by intraspecific contact. Spacing out of individuals within an aggregation may be accomplished by crawling following agonistic contact behaviour. Functional regionalization of the arms is discussed in relation to autotomy and predation.

Engaging with the science and politics of biodiversity futures: a literature review

2021 ◽  
pp. 1-8
Author(s):  
Carina Wyborn ◽  
Elena Louder ◽  
Mike Harfoot ◽  
Samantha Hill
Keyword(s):  
Human Life ◽  
Global Environmental Change ◽  
Life Forms ◽  
Trade Offs ◽  
Global Environmental ◽  
Science And Politics ◽  
Science Community ◽  
Impact On Biodiversity ◽  
Made In

Summary Future global environmental change will have a significant impact on biodiversity through the intersecting forces of climate change, urbanization, human population growth, overexploitation, and pollution. This presents a fundamental challenge to conservation approaches, which seek to conserve past or current assemblages of species or ecosystems in situ. This review canvases diverse approaches to biodiversity futures, including social science scholarship on the Anthropocene and futures thinking alongside models and scenarios from the biophysical science community. It argues that charting biodiversity futures requires processes that must include broad sections of academia and the conservation community to ask what desirable futures look like, and for whom. These efforts confront political and philosophical questions about levels of acceptable loss, and how trade-offs can be made in ways that address the injustices in the distribution of costs and benefits across and within human and non-human life forms. As such, this review proposes that charting biodiversity futures is inherently normative and political. Drawing on diverse scholarship united under a banner of ‘futures thinking’ this review presents an array of methods, approaches and concepts that provide a foundation from which to consider research and decision-making that enables action in the context of contested and uncertain biodiversity futures.

scholarly journals Sources and sinks of acetone, methanol, and acetaldehyde in North Atlantic marine air

2005 ◽  
Vol 5 (7) ◽  
pp. 1963-1974 ◽  
Author(s):  
A. C. Lewis ◽  
J. R. Hopkins ◽  
L. J. Carpenter ◽  
J. Stanton ◽  
K. A. Read ◽  
...  
Keyword(s):  
North Atlantic ◽  
Degradation Mechanism ◽  
Chemical Degradation ◽  
Oh Radical ◽  
Detailed Model ◽  
Atmospheric Lifetime ◽  
Sources And Sinks ◽  
Marine Air ◽  
Made In

Abstract. Measurements of acetone, methanol, acetaldehyde and a range of non-methane hydrocarbons have been made in North Atlantic marine air at the Mace Head observatory. Under maritime conditions the combination of OVOCs (acetone, methanol and acetaldehyde) contributed up to 85% of the total mass of measured non methane organics in air and up to 80% of the OH radical organic sink, when compared with the sum of all other organic compounds including non-methane hydrocarbons, DMS and OH-reactive halocarbons (trichloromethane and tetrachloroethylene). The observations showed anomalies in the variance and abundance of acetaldehyde and acetone over that expected for species with a remote terrestrial emission source and OH controlled chemical lifetime. A detailed model incorporating an explicit chemical degradation mechanism indicated in situ formation during air mass transport was on timescales longer than the atmospheric lifetime of precursor hydrocarbons or primary emission. The period over which this process was significant was similar to that of airmass motion on intercontinental scales, and formation via this route may reproduce that of a widespread diffuse source. The model indicates that continued short chain OVOC formation occurs many days from the point of emission, via longer lived intermediates of oxidation such as organic peroxides and long chain alcohols.

scholarly journals Progress on Coronal, Interplanetary, Foreshock, and Outer Heliospheric Radio Emissions

2000 ◽  
Vol 17 (1) ◽  
pp. 22-34 ◽  
Author(s):  
Iver H. Cairns ◽  
P. A. Robinson ◽  
G. P. Zank
Keyword(s):  
Solar Wind ◽  
Plasma Waves ◽  
Recent Theory ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Radio Emissions ◽  
Source Regions ◽  
Earth’S Bow Shock ◽  
Made In

AbstractType II and III solar radio bursts are associated with shock waves and streams of energetic electrons, respectively, which drive plasma waves and radio emission at multiples of the electron plasma frequency as they move out from the corona into the interplanetary medium. Analogous plasma waves and radiation are observed from the foreshock region upstream of Earth's bow shock. In situ spacecraft observations in the solar wind have enabled major progress to be made in developing quantitative theories for these phenomena that are consistent with available data. Similar processes are believed responsible for radio emissions at 2–3 kHz that originate in the distant heliosphere, from where the solar wind interacts with the local interstellar medium. The primary goal of this paper is to review the observations and theories for these four classes of emissions, focusing on recent progress in developing detailed theories for the plasma waves and radiation in the source regions. The secondary goal is to introduce and review stochastic growth theory, a recent theory which appears quantitatively able to explain the wave observations in type III bursts and Earth's foreshock and is a natural theory to apply to type II bursts, the outer heliospheric emissions, and perhaps astrophysicalemissions.

scholarly journals The Rise of the OM-LoC: Opto-Microfluidic Enabled Lab-on-Chip

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1467
Author(s):  
Harry Dawson ◽  
Jinane Elias ◽  
Pascal Etienne ◽  
Sylvie Calas-Etienne
Keyword(s):  
Low Cost ◽  
Optical Components ◽  
New Era ◽  
Lab On Chip ◽  
Highly Sensitive ◽  
Multiple Challenges ◽  
On Chip ◽  
Optical Circuits ◽  
Made In

The integration of optical circuits with microfluidic lab-on-chip (LoC) devices has resulted in a new era of potential in terms of both sample manipulation and detection at the micro-scale. On-chip optical components increase both control and analytical capabilities while reducing reliance on expensive laboratory photonic equipment that has limited microfluidic development. Notably, in-situ LoC devices for bio-chemical applications such as diagnostics and environmental monitoring could provide great value as low-cost, portable and highly sensitive systems. Multiple challenges remain however due to the complexity involved with combining photonics with micro-fabricated systems. Here, we aim to highlight the progress that optical on-chip systems have made in recent years regarding the main LoC applications: (1) sample manipulation and (2) detection. At the same time, we aim to address the constraints that limit industrial scaling of this technology. Through evaluating various fabrication methods, material choices and novel approaches of optic and fluidic integration, we aim to illustrate how optic-enabled LoC approaches are providing new possibilities for both sample analysis and manipulation.

Nanotechnology Enabled In Situ Orthopaedic Sensors for Personalized Medicine

2012 ◽  
Vol 86 ◽  
pp. 40-50
Author(s):  
Sirinrath Sirivisoot ◽  
Thomas J. Webster
Keyword(s):  
Bone Growth ◽  
Electrochemical Sensors ◽  
Electrochemical Analysis ◽  
Matrix Proteins ◽  
Implant Design ◽  
Implant Surface ◽  
Cellular Events ◽  
Bone Deposition ◽  
Made In

Although improvements have been made in implant design to increase bone formation and promote successful osseointegration using nanotechnology, the clinical diagnosis of early bone growth surrounding implants remains problematic. The development of a device allowing doctors to monitor the healing cascade and to diagnose potential infection or inflammation is necessary. Biological detection can be examined by the electrochemical analysis of electron transfer (or redox) reactions of extracellular matrix proteins involved in bone deposition and resorption. The use of nanomaterials as signal amplifiers in electrochemical sensors has greatly improved the sensitivity of detection. Nanotechnology-enabled electrochemical sensors that can be placed on the implant surface itself show promise as self-diagnosing devices in situ, possibly to detect new bone growth surrounding the implant and other cellular events to ensure implant success.

scholarly journals Hurricane Kinetic Energy Spectra from In Situ Aircraft Observations

2018 ◽  
Vol 75 (8) ◽  
pp. 2523-2532 ◽  
Author(s):  
P. Trent Vonich ◽  
Gregory J. Hakim
Keyword(s):  
Air Force ◽  
Weather Forecasting ◽  
Power Spectra ◽  
Spectral Slope ◽  
Cyclone Intensity ◽  
Storm Intensity ◽  
Air Force Reserve ◽  
Aircraft Data ◽  
Made In

Abstract Since the pioneering paper by Nastrom and Gage on aircraft-derived power spectra, significant progress has been made in understanding the wavenumber distribution of energy in Earth’s atmosphere and its implications for the intrinsic limits of weather forecasting. Improvements in tropical cyclone intensity predictions have lagged those of global weather forecasting, and limited intrinsic predictability may be partially responsible. In this study, we construct power spectra from aircraft data of over 1200 missions carried out by the National Oceanic and Atmospheric Administration (NOAA) and Air Force Reserve Command (AFRC) Hurricane Hunters. Each mission is parsed into distinct flight legs, and legs meeting a specified set of criteria are used for spectral analysis. Here, we produce power spectra composites for each category of the Saffir–Simpson scale, revealing a systematic relationship between spectral slope and storm intensity. Specifically, as storm intensity increases, we find that 1) spectral slope becomes steeper across scales from 10 to 160 km and 2) the transition zone where spectral slope begins to steepen shifts downscale.

Observations on the Performance of Vibration-Isolated Railway Track

1997 ◽  
Author(s):  
Hugh E. M. Hunt
Keyword(s):  
Travelling Waves ◽  
Surrounding Medium ◽  
Railway Track ◽  
Relative Speed ◽  
Tunnel Wall ◽  
Infinite Beam ◽  
Slab Track ◽  
Torsional Response ◽  
Made In

Abstract Vibration generated by underground railways is difficult to control because of the very limited space available in a tunnel. A popular approach is to use ‘floating slab track’ whereby the rails are fixed to a large concrete foundation separated from the tunnel wall by a resilient material. This paper investigates some of the vibration characteristics of floating slab track from measurements made in situ. These measurements are compared with the theoretical response of an infinite beam on an elastic foundation taking into account the torsional response of the beam. The transmission of vibration through the tunnel wall and into the surrounding medium is discussed with reference to the relative speed of travelling waves and the coincidence frequencies.

scholarly journals Cascading effects in freshwater microbial food webs by predatory Cercozoa, Katablepharidacea and ciliates feeding on aplastidic bacterivorous cryptophytes

2020 ◽  
Vol 96 (10) ◽  
Author(s):  
Karel Šimek ◽  
Vesna Grujčić ◽  
Indranil Mukherjee ◽  
Vojtěch Kasalický ◽  
Jiří Nedoma ◽  
...  
Keyword(s):  
Food Webs ◽  
Grazing Pressure ◽  
Heterotrophic Nanoflagellates ◽  
Cascading Effects ◽  
Microbial Food Webs ◽  
Feeding Modes ◽  
Hybridization Probes ◽  
Food Vacuoles ◽  
Freshwater Reservoir

ABSTRACT Heterotrophic nanoflagellates (HNF) are considered as major planktonic bacterivores, however, larger HNF taxa can also be important predators of eukaryotes. To examine this trophic cascading, natural protistan communities from a freshwater reservoir were released from grazing pressure by zooplankton via filtration through 10- and 5-µm filters, yielding microbial food webs of different complexity. Protistan growth was stimulated by amendments of five Limnohabitans strains, thus yielding five prey-specific treatments distinctly modulating protistan communities in 10- versus 5-µm fractions. HNF dynamics was tracked by applying five eukaryotic fluorescence in situ hybridization probes covering 55–90% of total flagellates. During the first experimental part, mainly small bacterivorous Cryptophyceae prevailed, with significantly higher abundances in 5-µm treatments. Larger predatory flagellates affiliating with Katablepharidacea and one Cercozoan lineage (increasing to up to 28% of total HNF) proliferated towards the experimental endpoint, having obviously small phagocytized HNF in their food vacuoles. These predatory flagellates reached higher abundances in 10-µm treatments, where small ciliate predators and flagellate hunters also (Urotricha spp., Balanion planctonicum) dominated the ciliate assemblage. Overall, our study reports pronounced cascading effects from bacteria to bacterivorous HNF, predatory HNF and ciliates in highly treatment-specific fashions, defined by both prey-food characteristics and feeding modes of predominating protists.

scholarly journals Solar and Interplanetary Dynamics (Symposium Summary)

1980 ◽  
Vol 91 ◽  
pp. 547-552 ◽  
Author(s):  
M. Kuperus
Keyword(s):  
Solar Atmosphere ◽  
Interplanetary Medium ◽  
Temporal Variations ◽  
Magnetic Structures ◽  
Solar Observations ◽  
The Earth ◽  
The Subject ◽  
Physical Phenomena ◽  
Made In

Solar and interplanetary dynamics comprises dynamic and plasma-physical phenomena in the solar atmosphere, the corona and the interplanetary medium in the broadest sense. In this symposium, however, one has essentially tried to restrict the subject matter to the study of the propagation of a disturbance, produced in the solar atmosphere, through the corona and the interplanetary medium. In studying solar and interplanetary dynamical phenomena we find ourselves in the unique position, with respect to other astrophysical disciplines, to be able to relate solar observations obtained with the highest possible spectral, spatial and time resolution with in situ measurements made in the interplanetary medium. It has now turned out that the two fundamental questions to be answered are:a) How does the medium in between the sun and the earth and beyond the earth's orbit, the socalled heliosphere, look like? Does a basic undisturbed heliosphere actually exist, and is one able to model its observed magnetic structures and plasma motions with their spatial and temporal variations?b) How and where in the solar atmosphere are the disturbances generated and what are the characteristic time scales, geometries and energies involved?

Small vessel membrane potential, sympathetic input, and electrogenic pump rate in SHR

1986 ◽  
Vol 250 (4) ◽  
pp. C547-C556 ◽  
Author(s):  
W. J. Stekiel ◽  
S. J. Contney ◽  
J. H. Lombard
Keyword(s):  
Jejunal Loop ◽  
Physiological Salt Solution ◽  
Mesenteric Vessel ◽  
Small Arteries ◽  
Wistar Kyoto ◽  
6 Hydroxydopamine ◽  
Arteries And Veins ◽  
Made In

Comparative measurements of transmembrane potential (Em) were made in situ in vascular smooth muscle cells (VSM) of mesenteric small principal arteries and veins with innervation and circulation intact. Vessels were in an externalized, topically suffused jejunal loop in 4- to 5-wk-old (initial hypertension) and 12- to 15-wk-old (established hypertension) anesthetized, spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) normotensive control rats. Comparable in vitro measurements of Em were also made in VSM of isolated intact small mesenteric vessel segments (from the 12- to 15-wk-old animals) maintained at their in situ lengths and suffused with physiological salt solution (PSS). During suffusion in situ with control PSS, VSM of both small veins and arteries in older (but not younger)SHR were less polarized than in WKY. Local chemical sympathetic denervation in situ (with 6-hydroxydopamine) hyperpolarized VSM of both vessel types in older (but not younger) SHR to the same Em levels measured in situ in respective WKY vessels. After local denervation, VSM of small arteries (but not veins) of both SHR and WKY remained less polarized in situ than in vitro, suggesting the presence of one or more circulating factors with a specific depolarizing action on the arterial side in both animal types. In vitro, VSM of both small arteries and veins from WKY but not SHR were depolarized immediately by 10(-3) M ouabain. In contrast, reduction of the PSS suffusate temperature to 16 degrees C caused a significantly greater depolarization in VSM of SHR vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Sign in / Sign up

Export Citation Format

Share Document