Vertical zonation of the hydroid Dynamena crisioides (Hydrozoa, Sertulariidae) in a mangrove ecosystem at Twin Cays, Belize

1991 ◽  
Vol 69 (12) ◽  
pp. 2993-2999 ◽  
Author(s):  
Dale R. Calder
Keyword(s):  
Intertidal Zone ◽  
Prime Factor ◽  
Good Condition ◽  
Mangrove Ecosystem ◽  
Lower Half ◽  
Upper Limits ◽  
Shallow Subtidal ◽  
Lower Limits ◽  
Transplantation Experiments ◽  
Number Of Branches

Dynamena crisioides is generally restricted to lower intertidal and shallow subtidal habitats along tropical and subtropical coasts. The hydroid was abundant during this study on prop roots of red mangroves (Rhizophora mangle) at Twin Cays, Belize, where it ranged vertically from 1.1 m below mean tide level (MTL) to 2–3 cm above MTL. The estimated percentage cover of the hydroid was maximal in the lower half of the intertidal zone (MTL and 0.1 m below MTL) and declined rapidly above and below that level. Colony height and number of branches per colony were also consistently highest in hydroids from the lower half of the intertidal zone. The percentage of colonies with gonophores was lowest at the lower and upper vertical limits of the species. Field observations and transplantation experiments suggest that the lower limits of D. crisioides are established by competition for space (with algae, sponges, and ascidians), smothering (by algae, sponges, ascidians, and other hydroids), and predation (by fishes). Desiccation was considered the prime factor determining the upper limits of the hydroid. Colonies transplanted to the supratidal zone were in good condition after 24 h, alive but in poor condition after 48 h, and dead after 72 and 96 h of exposure.

scholarly journals Upper limits on the water vapour content of the β Pictoris debris disk

2019 ◽  
Vol 628 ◽  
pp. A127 ◽  
Author(s):  
M. Cavallius ◽  
G. Cataldi ◽  
A. Brandeker ◽  
G. Olofsson ◽  
B. Larsson ◽  
...  
Keyword(s):  
Solar System ◽  
Far Infrared ◽  
Kinetic Temperature ◽  
Line Flux ◽  
Water Vapour Content ◽  
Water Ice ◽  
Upper Limit ◽  
Upper Limits ◽  
Debris Disk ◽  
Lower Limits

Context. The debris disk surrounding β Pictoris has been observed with ALMA to contain a belt of CO gas with a distinct peak at ~85 au. This CO clump is thought to be the result of a region of enhanced density of solids that collide and release CO through vaporisation. The parent bodies are thought to be comparable to solar system comets, in which CO is trapped inside a water ice matrix. Aims. Since H2O should be released along with CO, we aim to put an upper limit on the H2O gas mass in the disk of β Pictoris. Methods. We used archival data from the Heterodyne Instrument for the Far-Infrared (HIFI) aboard the Herschel Space Observatory to study the ortho-H2O 110–101 emission line. The line is undetected. Using a python implementation of the radiative transfer code RADEX, we converted upper limits on the line flux to H2O gas masses. The resulting lower limits on the CO/H2O mass ratio are compared to the composition of solar system comets. Results. Depending on the assumed gas spatial distribution, we find a 95% upper limit on the ortho-H2O line flux of 7.5 × 10−20 W m−2 or 1.2 × 10−19 W m−2. These translate into an upper limit on the H2O mass of 7.4 × 1016–1.1 × 1018 kg depending on both the electron density and gas kinetic temperature. The range of derived gas-phase CO/H2O ratios is marginally consistent with low-ratio solar system comets.

scholarly journals Faint Photometry of Edge-on Spiral Galaxies: A Search for Massive Halos

1987 ◽  
Vol 117 ◽  
pp. 425-425
Author(s):  
Michael F. Skrutskie ◽  
Mark A. Shure ◽  
Steven Beckwith
Keyword(s):  
Spiral Galaxies ◽  
Hydrogen Burning ◽  
Dwarf Stars ◽  
Color Changes ◽  
Upper Limits ◽  
Massive Halos ◽  
Halo Masses ◽  
Stellar Masses ◽  
M Dwarf Stars ◽  
Lower Limits

Upper limits have been set to the luminosity from the massive halos of three late-type edge-on spiral galaxies: NGC 2683 (Sb), NGC 4244 (Scd), and NGC 5907 (Sc). The limits resulted from simultaneous photometry in the visual (V) and 2.2μm (K) photometric bands which is sensitive to both luminosity and color changes along the minor axes of the three galaxies. The 3σ lower limits to the mass-to-light ratios for the halo of NGC 5907 are the largest ever recorded: M/Lv > 2000 and M/Lk > 64 in solar units. Since K band M/L for M-dwarf stars lying just above the hydrogen-burning limit is about 35, the results virtually eliminate the possibility that hydrogen-burning stars comprise more than a fraction of the halo masses. If the halos contain a more realistic spectrum of stellar masses, for example Population II, the visual band measurements imply that these stars account for less than one percent of the halo mass. Similar limits were obtained for NGC 4244 and NGC 2683. Variations of the V-K colors along and perpendicular to the disks show no sign of population changes toward redder objects at large galactocentric radii.

Lower limits and upper limits for tails of random sums supported on

2010 ◽  
Vol 80 (13-14) ◽  
pp. 1111-1120 ◽  
Author(s):  
Changjun Yu ◽  
Yuebao Wang ◽  
Zhaolei Cui
Keyword(s):  
Random Sums ◽  
Upper Limits ◽  
Lower Limits

Numbers of naked amoebae inhabiting the intertidal zone of two geographically separate sandy beaches

2000 ◽  
Vol 80 (4) ◽  
pp. 731-732 ◽  
Author(s):  
Andrew Rogerson ◽  
Fiona Hannah ◽  
Gwen Hauer ◽  
Phillip Cowie
Keyword(s):  
Intertidal Zone ◽  
Sandy Beach ◽  
Sandy Beaches ◽  
Beach Sand ◽  
Cultivation Method ◽  
Future Studies ◽  
Beach Communities ◽  
Shallow Subtidal ◽  
Lower Intertidal Zone ◽  
Naked Amoebae

Numbers of naked amoebae (Gymnamoebae) inhabiting the lower intertidal zone of two sandy beaches were estimated using a novel enrichment cultivation method. Samples were collected between June and September, 1999. Beach sand at Kames Bay, Isle of Cumbrae, Scotland contained on average 2604 amoebae cm−3 while at Dania Beach, Florida, USA, sand harboured 4236 amoebae cm−3. This is the first study to focus on the abundance of naked amoebae inhabiting a sandy beach. These numbers are higher than densities generally reported for shallow subtidal sands and show that amoebae must be considered in future studies on the dynamics of sandy beach communities.

A Limiting Approach for the Evaluation of Geometric Mean Transmittance in a Multidimensional Absorbing and Isotropically Scattering Medium

1984 ◽  
Vol 106 (2) ◽  
pp. 441-447 ◽  
Author(s):  
W. W. Yuen
Keyword(s):  
Geometric Mean ◽  
Accurate Estimate ◽  
Exact Expression ◽  
Integral Function ◽  
Scattering Medium ◽  
Exponential Integral ◽  
Physical Consideration ◽  
Upper Limits ◽  
Lower Limits ◽  
Transmittance Factor

The calculation of the geometric-mean transmittance factor between areas with an intervening absorbing and isotropically scattering medium is considered. While an exact expression for the factor is shown to be quite complicated, the upper and lower limits of the factor can be readily generated from physical consideration. Integral expressions for successively increasing (decreasing) values of the lower (upper) limits are obtained. For two-dimensional systems, these expressions are reduced to integrals involving Sn (x), a class of exponential integral function that has been tabulated in a previous work. Utilizing the kernel substitution technique, these integrals are evaluated analytically in closed form for some selected geometries. For cases with small optical thickness and large scattering albedo, both limits are shown to converge relatively slowly to the actual transmittance factor. But the decreasing difference between the two limits provides accurate estimate of the geometric-mean transmittance factor. Based on these results, some interesting conclusions concerning the effect of scattering on multidimensional radiative transmission are established.

scholarly journals A Search for Recombination Line Emission from the Galactic Equator at 408 MHz

1976 ◽  
Vol 29 (5) ◽  
pp. 419 ◽  
Author(s):  
MJ Batty
Keyword(s):  
Surface Brightness ◽  
Thermal Emission ◽  
Line Emission ◽  
Hii Regions ◽  
Line Of Sight ◽  
Recombination Line ◽  
Upper Limits ◽  
Low Surface Brightness ◽  
Lower Limits ◽  
Galactic Longitude

A search for H 2520( recombination line emission was made by scanning the galactic equator region using the Molonglo radio telescope. Upper limits were established over the range of galactic longitude accessible to the instrument. For the region III ;S 40�, estimates of the background thermal continuum brightness temperature were used to derive lower limits of ~ 2000 K for the electron temperature of the gas along the line of sight. Lower limits for the electron density obtained by considering probable non-LTE effects suggest that the thermal emission over this range is due to low surface brightness HII regions. The observed H 2520( upper limit averaged over the range 270� ;S I ;S 320� just admits the line intensity calculated by Shaver (1975) for the cold cloud component of the general interstellar medium.

scholarly journals Robust and Gradient Thickness Porous Membranes for In Vitro Modeling of Physiological Barriers

2020 ◽  
Author(s):  
Shayan Gholizadeh ◽  
Zahra Allahyari ◽  
Robert Carter ◽  
Luis F. Delgadillo ◽  
Marine Blaquiere ◽  
...  
Keyword(s):  
Cell Attachment ◽  
Porous Membranes ◽  
Parylene C ◽  
Upper Limits ◽  
Critical Separation ◽  
Culture Models ◽  
3D Printed ◽  
Lower Limits

AbstractPorous membranes are fundamental elements for tissue-chip barrier and co-culture models. However, the exaggerated thickness of commonly available membranes impedes an accurate in vitro reproduction of the biological multi-cellular continuum as it occurs in vivo. Existing techniques to fabricate membranes such as solvent cast, spin-coating, sputtering and PE-CVD result in uniform thickness films. To understand critical separation distances for various barrier and co-culture models, a gradient thickness membrane is needed. Here, we developed a robust method to generate ultrathin porous parylene C (UPP) membranes not just with precise thicknesses down to 300 nm, but with variable gradients in thicknesses, while at the same time having porosities up to 25%. We also show surface etching and increased roughness lead to improved cell attachment. Next, we examined the mechanical properties of UPP membranes with varying porosity and thickness and fit our data to previously published models, which can help determine practical upper limits of porosity and lower limits of thickness. Lastly, we validate a straightforward approach allowing the successful integration of the UPP membranes into a prototyped 3D-printed scaffold enabling in vitro barrier modeling and investigation of cell-cell interplay over variable distances using thickness gradients.

Invasive Fucus serratus (Fucaceae, Phaeophyceae) responds to climate change along the Atlantic Coast of Nova Scotia, Canada

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
David J. Garbary ◽  
Megan P. Fass ◽  
Herb Vandermeulen
Keyword(s):  
Climate Change ◽  
Nova Scotia ◽  
Intertidal Zone ◽  
Atlantic Coast ◽  
Dispersal Capacity ◽  
Corallina Officinalis ◽  
Fucus Serratus ◽  
Shallow Subtidal ◽  
South Shore ◽  
Distribution And Ecology

Abstract The distribution and ecology of the invasive brown alga Fucus serratus along the 500 km Atlantic coast of Nova Scotia, Canada, has been poorly explored. We observed significant intertidal penetration at four sites in the southwestern part of the province, and then examined numerous sites along the Atlantic coast of Nova Scotia. Surveys of attached algae in intertidal and shallow subtidal zones and wrack show that F. serratus has become a dominant plant in the low to mid-intertidal zone and can be expected on headlands along the South Shore of Nova Scotia where it can occupy up to 40% of the intertidal zone with cover >75% and mean densities of up to 10 kg m−1. In this zone, F. serratus has replaced Chondrus crispus as the major canopy species, although C. crispus and Corallina officinalis remain primary understory species. At slightly higher elevations, F. serratus was common as an understory beneath Ascophyllum nodosum and Fucus vesiculosus. While geographic spread along the Atlantic coast might reflect the natural dispersal capacity of F. serratus, we hypothesize that the ecological extension into the intertidal zone may be facilitated by harvesting of A. nodosum and by climate change in an ocean-warming hotspot.

scholarly journals The Cosmic Infrared Background

1992 ◽  
Vol 9 ◽  
pp. 291-296 ◽  
Author(s):  
M. G. Hauser
Keyword(s):  
Background Radiation ◽  
Initial Examination ◽  
Submillimeter Wavelength ◽  
Cosmic Background ◽  
Upper Limits ◽  
Infrared Background ◽  
External Galaxies ◽  
Cosmic Infrared Background ◽  
Luminous Objects ◽  
Lower Limits

AbstractCosmic infrared background radiation, expected to carry the radiative record of luminous objects since they first formed, has yet to be detected. The Diffuse Infrared Background Experiment (DIRBE) on the Cosmic Background Explorer (COBE) satellite is designed to search for this primeval background over the spectral range from 1 to 300 μm. Initial examination of data from this experiment show that foreground radiations from the solar system and Galaxy dominate the diffuse infrared sky brightness, with relative minima near 3.5 μm and in the submillimeter wavelength range. DIRBE measurements do not confirm some previous data from rockets and IRAS. Preliminary upper limits on the cosmic infrared background are generally above theoretical expectations for pregalactic and protogalactic sources, and substantially above estimated lower limits based upon observations of external galaxies. Careful foreground modeling is required to reduce these limits or identify an isotropic residual.

Ex-post effects of circuit breakers in crisis and calm markets

2020 ◽  
Vol 47 (2) ◽  
pp. 333-350
Author(s):  
Imtiaz Sifat ◽  
Azhar Mohamad
Keyword(s):  
Circuit Breaker ◽  
Wide Band ◽  
Circuit Breakers ◽  
Price Limits ◽  
Content Type ◽  
Price Limit ◽  
Ex Post ◽  
Upper Limits ◽  
Nonparametric Techniques ◽  
Lower Limits

PurposeDespite regulatory claims of straitening volatility and preventing crashes, evidences on circuit breakers' ability to achieve so are nonconclusive. While previous scholars studies general performances of circuit breakers, the authors examine whether Malaysian price limits aggravate volatility, impede price discovery, and interfere with trading activities in both tranquil and stressful periods.Design/methodology/approachThe study uses a combination of parametric and nonparametric techniques consistent with Kim and Rhee (1997) to examine the major ex-post hypotheses in circuit breaker research.FindingsFor calm markets, the authors find significant success of upper limits in tempering volatility with low trading interference. Lower limits show mixed results. Conversely, in crisis markets limits fare poorly in nearly all aspects, particularly for lower limits.Practical implicationsRamifications of the paper's findings are discussed through highlighting the asymmetric nature of price limits' ex-post effects. The paper also contributes to regulatory debate surrounding the quest for an optimal price limit.Originality/valueThe paper is the first of its kind in documenting long-horizon evidence of ex-post effects of a wide-band price limit. Moreover, the paper is unique in its approach in bifurcating circuit breaker performance along the line of market stability periods.

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