scholarly journals Marine snow, zooplankton and thin layers: indications of a trophic link from small-scale sampling with the Video Plankton Recorder

2012 ◽  
Vol 468 ◽  
pp. 57-69 ◽  
Author(s):  
KO Möller ◽  
M St John ◽  
A Temming ◽  
J Floeter ◽  
AF Sell ◽  
...  
Keyword(s):  
Thin Layers ◽  
Small Scale ◽  
Marine Snow ◽  
Trophic Link

scholarly journals Gravity-wave effects on tracer gases and stratospheric aerosol concentrations during the 2013 ChArMEx campaign

2016 ◽  
Author(s):  
Fabrice Chane Ming ◽  
Damien Vignelles ◽  
Fabrice Jegou ◽  
Gwenael Berthet ◽  
Jean-Batiste Renard ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Lower Stratosphere ◽  
Weather Forecasting ◽  
Stratospheric Aerosol ◽  
Thin Layers ◽  
Vertical Wind ◽  
Specific Humidity ◽  
Small Scale ◽  
Strong Activity ◽  
Dynamical Parameters

Abstract. Coupled balloon-borne observations of Light Optical Aerosol Counter (LOAC), M10 meteorological global positioning system (GPS) sondes, ozonesondes and GPS radio occultation data, are examined to identify gravity-wave (GW) induced fluctuations on tracer gases and on the vertical distribution of stratospheric aerosol concentrations during the 2013 ChArMEx (Chemistry-Aerosol Mediterranean Experiment) campaign. Observations reveal signatures of GWs with short vertical wavelengths less than 4 km in dynamical parameters and tracer constituents which are also correlated with the presence of thin layers of strong local enhancements of aerosol concentrations in the upper troposphere and the lower stratosphere. In particular, this is evident from a case study above Ile du Levant (43.02 °N, 6.46 °E) on 26–29 July 2013. Observations show a strong activity of dominant mesoscale inertia GWs with horizontal and vertical wavelengths of 370–510 km and 2–3 km respectively, and periods of 10–13 h propagating southward at altitudes of 13–20 km and eastward above 20 km during 27–28 July which is also captured by the European Center for Medium range Weather Forecasting (ECMWF) analyses. Ray-tracing experiments indicate the jet-front system to be the source of observed GWs. Simulated vertical profiles of dynamical parameters with large stratospheric vertical wind maximum oscillations ± 40 mms−1 are produced for the dominant mesoscale GW using the simplified linear GW theory. Parcel advection method reveals signatures of GWs in the ozone mixing ratio and the specific humidity. Simulated vertical wind perturbations of the dominant GW and small-scale perturbations of aerosol concentration (aerosol size of 0.2–0.7 μm) are in phase in the lower stratosphere. Present results support the importance of vertical wind perturbations in the GW-aerosol relation. The observed mesoscale GW induces a strong modulation of the amplitude of tracer gases and the stratospheric aerosol background.

scholarly journals Small-Scale variability of physical properties and structural characteristics of Antarctic fast ice

1994 ◽  
Vol 20 ◽  
pp. 61-66 ◽  
Author(s):  
A.L. Veazey ◽  
M.O. Jeffries ◽  
K. Morris
Keyword(s):  
Physical Properties ◽  
Structural Characteristics ◽  
Austral Summer ◽  
Ice Cores ◽  
Thin Layers ◽  
Small Scale ◽  
Axis Orientation ◽  
Layer Spacing ◽  
Frazil Ice ◽  
Fast Ice

The small-scale variability of physical properties and structural characteristics of multiple pairs of fast-ice cores obtained during the austral summer of 1991-92 at two Antarctic sites, McMurdo Sound (MCM) and Pine Island Bay (PIB), are examined and discussed with respect to the growth and decay of the sea ice. The ice at the MCM site was thicker than that at the PIB site and was covered by a somewhat thinner snowpack. While mean salinity and temperature of the ice at the two sites were similar, small-scale variations in both salinity and temperature were greater at PIB than at MCM. The ice sheet at MCM was a two-layer medium consisting of congelation ice overlying platelet ice. The ice from the PIB site, however, was composed of mainly frazil ice and layers of congelation ice with occasional thin layers of snow-ice at the surface of the cores. Crystal sub-structure measurements, c-axis orientation and brine-layer spacing from the MCM cores revealed that the congelation ice had moderately aligned, horizontally oriented c axes, suggesting that east-west currents off the southwest tip of Hut Point Peninsula control crystal-growth orientation.d others: Variability of physical and structural characteristics of Antarctic fast ice

Marine Snow: Microplankton Habitat and Source of Small-Scale Patchiness in Pelagic Populations

Science ◽  
1978 ◽  
Vol 201 (4353) ◽  
pp. 371-373 ◽  
Author(s):  
M. W. SILVER ◽  
A. L. SHANKS ◽  
J. D. TRENT
Keyword(s):  
Small Scale ◽  
Marine Snow

scholarly journals Modulation of ecdysal cyst and toxin dynamics of two <i>Alexandrium</i> (Dinophyceae) species under small-scale turbulence

2007 ◽  
Vol 4 (4) ◽  
pp. 559-567 ◽  
Author(s):  
L. Bolli ◽  
G. Llaveria ◽  
E. Garcés ◽  
Ò. Guadayol ◽  
K. van Lenning ◽  
...  
Keyword(s):  
Growth Rate ◽  
Toxin Production ◽  
Thin Layers ◽  
Small Scale ◽  
Alexandrium Minutum ◽  
Cell Numbers ◽  
Cyst Production ◽  
Net Growth Rate ◽  
Scale Turbulence ◽  
Orbital Shaker

Abstract. Some dinoflagellate species have shown different physiological responses to certain turbulent conditions. Here we investigate how two levels of turbulent kinetic energy dissipation rates (ε = 0.4 and 27 cm² s−3) affect the PSP toxins and ecdysal cyst dynamics of two bloom forming species, Alexandrium minutum and A. catenella. The most striking responses were observed at the high ε generated by an orbital shaker. In the cultures of the two species shaken for more than 4 days, the cellular GTX(1+4) toxin contents were significantly lower than in the still control cultures. In A. minutum this trend was also observed in the C(1+2) toxin content. For the two species, inhibition of ecdysal cyst production occurred during the period of exposure of the cultures to stirring (4 or more days) at any time during their growth curve. Recovery of cyst abundances was always observed when turbulence stopped. When shaking persisted for more than 4 days, the net growth rate significantly decreased in A. minutum (from 0.25±0.01 day−1 to 0.19±0.02 day−1) and the final cell numbers were lower (ca. 55.4%) than in the still control cultures. In A. catenella, the net growth rate was not markedly modified by turbulence although under long exposure to shaking, the cultures entered earlier in the stationary phase and the final cell numbers were significantly lower (ca. 23%) than in the control flasks. The described responses were not observed in the experiments performed at the low turbulence intensities with an orbital grid system, where the population development was favoured. In those conditions, cells appeared to escape from the zone of the influence of the grids and concentrated in calmer thin layers either at the top or at the bottom of the containers. This ecophysiological study provides new evidences about the sensitivity to high levels of small-scale turbulence by two life cycle related processes, toxin production and encystment, in dinoflagellates. This can contribute to the understanding of the dynamics of those organisms in nature.

Formation Electrical Anisotropy Derived From Induction-Log Measurements in a Horizontal Well

2001 ◽  
Vol 4 (06) ◽  
pp. 483-488
Author(s):  
Jon Bang ◽  
Arne Solstad ◽  
Svein Mjaaland
Keyword(s):  
Magnetic Permeability ◽  
Horizontal Well ◽  
Empirical Relation ◽  
Deposition Process ◽  
Thin Layers ◽  
Wave Number ◽  
Electrical Anisotropy ◽  
Small Scale ◽  
Anisotropy Ratio ◽  
Resistivity Logs

Summary An existing theory describes how electrical anisotropy in the formationaffects the response of resistivity logging tools. We have related this theory to the processing of logging while drilling (LWD) induction logs and are thus able to calculate the anisotropic resistivities directly from the logs. The method has been demonstrated by application to logs from a horizontal well section. Anisotropy ratios of 2 to 5, and occasionally higher values, were obtained for this formation. We also addressed the accuracy of these numbers by using independent sets of input logs. The results indicate that the logs are influenced by factors like invasion, in addition to the anisotropy. Our approach provides a fast and efficient computer algorithm. The output is calculated at the depths of the input logs; hence, the resulting anisotropy becomes a depth-dependent formation property. Introduction Electrical anisotropy has gained considerable attention in recent years. If present in the formation, neglection of this property when interpreting resistivity logs may lead to erroneous saturation estimates and may thus have great consequences upon development and production strategies and the overall economic situation. Electrical anisotropy denotes that the resistivity shows directional dependence. In sedimentary formations, it is commonly assumed that the anisotropy is caused by the deposition process, which yields different small-scale (grain and pore-size scale) structural properties in the vertical and horizontal directions. Anisotropy may also occur on a lithology scale[i.e., as a result of thin layers (compared to the extension of the electricfield) having individual isotropic properties]. Because the effect is determined by the sedimentary structure, a formation can be expected to show anisotropy in several properties, such as electric, acoustic, and fluid-flow resistance (permeability) properties, simultaneously. A common way of describing anisotropy is to distinguish between the vertical direction and directions in the horizontal plane. In this paper, we shall denote the resistivities in these directions by RV andRH, respectively. However, the terms "vertical" and"horizontal" refer to the original deposition process and may no longer correspond to the actual orientation of the formation owing to small- or large-scale geological activity. For dipping beds, it is common practice to assume one resistivity (R H) in the bedding plane and one (RV) in the direction normal to the bed, unless evidence of intrabed disturbances suggests other orientations of the anisotropy. Numerous publications have addressed the influence of electrical anisotropy on resistivity logs. Among the effects that have been studied are anisotropy in dipping and thinly laminated formations1–3 and in crossbedded formations.4 Effort has been put on theoretical tool response modeling and simulation 5–7 and on anisotropy corrections to logs.8,9 From field cases, anisotropy ratios(RV/R H) up to the order of 5 to 10 have been reported.7,8,10 In this paper, we demonstrate a method for calculating the electrical anisotropy directly from well logs, based on the theory developed by Hagiwara.6 The method has been implemented and applied to log data from a horizontal North Sea well. Theory Hagiwara6 has analyzed the resistivity log's response in anisotropic formations. According to this reference, two different measurements are sufficient to determine the anisotropy unambiguously, as long as the anisotropy orientation is known. The measurements may differ with respect to one or more of the following:antenna spacing (which is a prerequisite for phase- and attenuation-derived resistivity),frequency, ordeviation angle between tool axis and anisotropy orientation. In our work, we consider the LWD induction response. For this instrument class, Hagiwara shows that the complex voltage V recorded by one transmitter-receiver pair of electrodes isEquation 1 where i=the imaginary unit (i=-11/2) and L=the antenna spacing. Further,Equation 2 where a2= RH/RV is the anisotropy ratio between horizontal and vertical resistivitiesRH and RV, and ?=the deviation of tool direction from the R V direction. Notice the interpretation of the terms "vertical" and "horizontal," as discussed in the introduction. The wave number k is defined byEquation 3 where ?=the measurement angular frequency, µ=the magnetic permeability, andeH=the horizontal dielectric constant. In this study, we used the free space magnetic permeability µ=µ0=4p×10–7 N/A, and approximated eH from the logged resistivity through an empirical relation. Both these approximations are considered to have negligible influence on the results.

Multiscale Finite Element Methods for Flows on Rough Surfaces

2013 ◽  
Vol 14 (4) ◽  
pp. 979-1000 ◽  
Author(s):  
Yalchin Efendiev ◽  
Juan Galvis ◽  
M. Sebastian Pauletti
Keyword(s):  
Finite Element ◽  
Coarse Grid ◽  
Numerical Results ◽  
Basis Functions ◽  
Thin Layers ◽  
Reference Configuration ◽  
Small Scale ◽  
Global Information ◽  
Reference Surface ◽  
Multiscale Finite Element

AbstractIn this paper, we present the Multiscale Finite Element Method (MsFEM) for problems on rough heterogeneous surfaces. We consider the diffusion equation on oscillatory surfaces. Our objective is to represent small-scale features of the solution via multiscale basis functions described on a coarse grid. This problem arises in many applications where processes occur on surfaces or thin layers. We present a unified multiscale finite element framework that entails the use of transformations that map the reference surface to the deformed surface. The main ingredients of MsFEM are (1) the construction of multiscale basis functions and (2) a global coupling of these basis functions. For the construction of multiscale basis functions, our approach uses the transformation of the reference surface to a deformed surface. On the deformed surface, multiscale basis functions are defined where reduced (1D) problems are solved along the edges of coarse-grid blocks to calculate nodal multiscale basis functions. Furthermore, these basis functions are transformed back to the reference configuration. We discuss the use of appropriate transformation operators that improve the accuracy of the method. The method has an optimal convergence if the transformed surface is smooth and the image of the coarse partition in the reference configuration forms a quasiuniform partition. In this paper, we consider such transformations based on harmonic coordinates (following H. Owhadi and L. Zhang [Comm. Pure and Applied Math., LX(2007), pp. 675-723]) and discuss gridding issues in the reference configuration. Numerical results are presented where we compare the MsFEM when two types of deformations are used for multiscale basis construction. The first deformation employs local information and the second deformation employs a global information. Our numerical results show that one can improve the accuracy of the simulations when a global information is used.

scholarly journals Small-Scale variability of physical properties and structural characteristics of Antarctic fast ice

1994 ◽  
Vol 20 ◽  
pp. 61-66 ◽  
Author(s):  
A.L. Veazey ◽  
M.O. Jeffries ◽  
K. Morris
Keyword(s):  
Physical Properties ◽  
Structural Characteristics ◽  
Austral Summer ◽  
Ice Cores ◽  
Thin Layers ◽  
Small Scale ◽  
Axis Orientation ◽  
Layer Spacing ◽  
Frazil Ice ◽  
Fast Ice

The small-scale variability of physical properties and structural characteristics of multiple pairs of fast-ice cores obtained during the austral summer of 1991-92 at two Antarctic sites, McMurdo Sound (MCM) and Pine Island Bay (PIB), are examined and discussed with respect to the growth and decay of the sea ice. The ice at the MCM site was thicker than that at the PIB site and was covered by a somewhat thinner snowpack. While mean salinity and temperature of the ice at the two sites were similar, small-scale variations in both salinity and temperature were greater at PIB than at MCM. The ice sheet at MCM was a two-layer medium consisting of congelation ice overlying platelet ice. The ice from the PIB site, however, was composed of mainly frazil ice and layers of congelation ice with occasional thin layers of snow-ice at the surface of the cores. Crystal sub-structure measurements, c-axis orientation and brine-layer spacing from the MCM cores revealed that the congelation ice had moderately aligned, horizontally oriented c axes, suggesting that east-west currents off the southwest tip of Hut Point Peninsula control crystal-growth orientation.d others: Variability of physical and structural characteristics of Antarctic fast ice

scholarly journals Variability of sporadic E-layer semi transparency (<i>f<sub>o</sub>E<sub>s</sub></i><i>-f<sub>b</sub>E<sub>s</sub></i>)with magnitude and distance from earthquake epicenters to vertical sounding stations

2003 ◽  
Vol 3 (3/4) ◽  
pp. 279-284 ◽  
Author(s):  
E. V. Liperovskaya ◽  
O. A. Pokhotelov ◽  
Y. Hobara ◽  
M. Parrot
Keyword(s):  
Plasma Turbulence ◽  
Thin Layers ◽  
Shallow Depth ◽  
Small Scale ◽  
Turbulence Level ◽  
Before And After ◽  
Sporadic E Layer ◽  
Sporadic E

Abstract. Variations of the Es-layer semi transparency co-efficient were analyzed for more than 100 earthquakes with magnitudes M > 4 and depths h < 100 km. Data of mid latitude vertical sounding stations (Kokubunji, Akita, and Yam-agawa) have been used for several decades before and after earthquake occurrences. The semi-transparency coefficient of Es-layer X = (foEs – fbEs)/fbEs can characterize, for thin layers, the presence of small scale plasma turbulence. It is shown that the turbulence level decreases by ~ 10% during three days before earthquakes probably due to the heating of the atmosphere. On the contrary, the turbulence level increases by the same value from one to three days after the shocks. For earthquakes with magnitudes M > 5 the effect exists at distances up to 300 km from the epicenters. The effect could also exist for weak (M ~ 4) and shallow (depth < 50 km) earthquakes at a distance smaller than 200 km from the epicenters.

scholarly journals A Review of Holography in the Aquatic Sciences: In situ Characterization of Particles, Plankton, and Small Scale Biophysical Interactions

2021 ◽  
Vol 7 ◽  
Author(s):  
Aditya R. Nayak ◽  
Ed Malkiel ◽  
Malcolm N. McFarland ◽  
Michael S. Twardowski ◽  
James M. Sullivan
Keyword(s):  
Machine Learning Algorithms ◽  
Thin Layers ◽  
Particle Orientation ◽  
Small Scale ◽  
Research Areas ◽  
Aquatic Sciences ◽  
And Behavior ◽  
Biophysical Interactions

The characterization of particle and plankton populations, as well as microscale biophysical interactions, is critical to several important research areas in oceanography and limnology. A growing number of aquatic researchers are turning to holography as a tool of choice to quantify particle fields in diverse environments, including but not limited to, studies on particle orientation, thin layers, phytoplankton blooms, and zooplankton distributions and behavior. Holography provides a non-intrusive, free-stream approach to imaging and characterizing aquatic particles, organisms, and behavior in situ at high resolution through a 3-D sampling volume. Compared to other imaging techniques, e.g., flow cytometry, much larger volumes of water can be processed over the same duration, resolving particle sizes ranging from a few microns to a few centimeters. Modern holographic imaging systems are compact enough to be deployed through various modes, including profiling/towed platforms, buoys, gliders, long-term observatories, or benthic landers. Limitations of the technique include the data-intensive hologram acquisition process, computationally expensive image reconstruction, and coherent noise associated with the holograms that can make post-processing challenging. However, continued processing refinements, rapid advancements in computing power, and development of powerful machine learning algorithms for particle/organism classification are paving the way for holography to be used ubiquitously across different disciplines in the aquatic sciences. This review aims to provide a comprehensive overview of holography in the context of aquatic studies, including historical developments, prior research applications, as well as advantages and limitations of the technique. Ongoing technological developments that can facilitate larger employment of this technique toward in situ measurements in the future, as well as potential applications in emerging research areas in the aquatic sciences are also discussed.

Forced Convection Heat Transfer and Hydraulic Losses in Graphitic Foam

2006 ◽  
Vol 129 (9) ◽  
pp. 1237-1245 ◽  
Author(s):  
A. G. Straatman ◽  
N. C. Gallego ◽  
Q. Yu ◽  
L. Betchen ◽  
B. E. Thompson
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aluminum Foam ◽  
Solid Phase ◽  
Thin Layers ◽  
Small Scale ◽  
Hydraulic Loss ◽  
Base Temperature ◽  
Extended Surface ◽  
Graphitic Foam

Experiments and computations are presented to quantify the convective heat transfer and the hydraulic loss that is obtained by forcing water through blocks of graphitic foam (GF) heated from one side. Experiments have been conducted in a small-scale water tunnel instrumented to measure the pressure drop and the temperature rise of water passing through the foam and the base temperature and heat flux into the foam block. The experimental data were then used to calibrate a thermal non-equilibrium finite-volume model to facilitate comparisons between GF and aluminum foam. Comparisons of the pressure drop indicate that both normal and compressed aluminum foams are significantly more permeable than GF. Results of the heat transfer indicate that the maximum possible heat dissipation from a given surface is reached using very thin layers of aluminum foam due to the inability of the foam to entrain heat into its internal structure. In contrast, graphitic foam is able to entrain heat deep into the foam structure due to its high extended surface efficiency and thus much more heat can be transferred from a given surface area. The higher extended surface efficiency is mainly due to the combination of moderate porosity and higher solid-phase conductivity.

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