Size Distribution in Periphyton

1987 ◽  
Vol 44 (11) ◽  
pp. 2025-2028 ◽  
Author(s):  
Antonella Cattaneo
Keyword(s):  
Size Distribution ◽  
Fish Community ◽  
Size Class ◽  
Size Distributions ◽  
Size Classes ◽  
Rule Of Thumb ◽  
Littoral Fish ◽  
Order Of Magnitude ◽  
The Mean

When periphytic organisms growing on artificial plants were grouped in logarithmically increasing size classes, patterns in the distribution of biomass were consistent over the season and under different grazing regimes, despite taxonornical changes in the dominant taxa of algae and invertebrates. The amount in each size class was not constant, and instead, certain classes tended to have values consistently lower or higher than the mean. The locations of these peaks and troughs in the size distributions coincided with those observed in lake plankton. Despite these irregularities, the hypothesis that the biomass in logarithmic size classes is constant apparently applies at a crude level, for the biomass of most size classes lay within an order of magnitude of the mean. This rule of thumb also applies to the littoral fish community, for the minnow biomass was approximately that in a periphyton size class.

Size decrease of detonation nanodiamonds by air annealing investigated by AFM

MRS Advances ◽  
2016 ◽  
Vol 1 (16) ◽  
pp. 1067-1073 ◽  
Author(s):  
Stepan Stehlik ◽  
Daria Miliaieva ◽  
Marian Varga ◽  
Alexander Kromka ◽  
Bohuslav Rezek
Keyword(s):  
Size Distribution ◽  
Annealing Temperature ◽  
Detonation Nanodiamonds ◽  
Particle Analysis ◽  
Detonation Synthesis ◽  
Size Distributions ◽  
Force Microscopy ◽  
Atomic Force ◽  
Mean Size ◽  
The Mean

ABSTRACTNanodiamonds (NDs) represent a novel nanomaterial applicable from biomedicine to spintronics. Here we study ability of air annealing to further decrease the typical 5 nm NDs produced by detonation synthesis. We use atomic force microscopy (AFM) with sub-nm resolution to directly measure individual detonation nanodiamonds (DNDs) on a flat Si substrate. By means of particle analysis we obtain their accurate and statistically relevant size distributions. Using this approach, we characterize evolution of the size distribution as a function of time and annealing temperature: i) at constant time (25 min) with changing temperature (480, 490, 500°C) and ii) at constant temperature (490°C) with changing time (10, 25, 50 min). We show that the mean size of DNDs can be controllably reduced from 4.5 nm to 1.8 nm without noticeable particle loss and down to 1.3 nm with 36% yield. By air annealing the size distribution changes from Gaussian to lognormal with a steep edge around 1 nm, indicating instability of DNDs below 1 nm.

scholarly journals DEVELOPMENT OF AN ALGORITHM FOR IDENTIFYING ORE DISSEMINATION FUNCTION

2019 ◽  
Vol 6 (125) ◽  
pp. 105-112
Author(s):  
Nataliya Pryadko ◽  
Alina Havrilko
Keyword(s):  
Distribution Function ◽  
Content Analysis ◽  
Size Distribution ◽  
Mineral Exploration ◽  
Size Distribution Function ◽  
Size Class ◽  
Valuable Component ◽  
Size Classes

The work is devoted to one of the mineral exploration field for processing - identification of disseminated function. The purpose of the work is to develop a methodology for determining the impregnation function according to the known size classes and the distribution of grains according to the content of valuable mineral in the size classes. An algorithm for determining of the impregnation distribution function by size classes is proposed. Having performed the classification of the crushed product according to size classes the content analysis of the valuable component in each size class is further analyzed, which allows determining the intergrowths distribution function in each size class. It is shown that the dependence of the impregnation distribution function on the size distribution function of the product is nonlinear.

scholarly journals Density and Size Distribution of the Sea Cucumber, Holothuria scabra (Jaeger, 1935), at Six Exploited Sites in Mahout Bay, Sultanate of Oman

2007 ◽  
Vol 12 ◽  
pp. 43 ◽  
Author(s):  
Khalfan M. Al-Rashdi ◽  
Michel R. Claereboudt ◽  
Saud S. Al-Busaidi
Keyword(s):  
Size Distribution ◽  
Sea Cucumber ◽  
Size Distributions ◽  
Sultanate Of Oman ◽  
Population Densities ◽  
Sea Cucumbers ◽  
Holothuria Scabra ◽  
Mean Size ◽  
Males And Females ◽  
The Mean

A rapid survey of the density and size distribution of recently exploited populations of Holothuria scabra in Mahout Bay (Ghubbat Hashish Bay) was carried out at six fishing sites. The results showed that population densities varied between 1170 and 4000 individuals ha-1 and biomass ranged between 393 and 2903 kg ha-1. The mean size of sea cucumbers and population densities were much lower in populations closer to human settlements, suggestive of overfishing. The sex ratio was estimated to be 1:1 and the size distributions of males and females did not differ significantly. The length-weight relationship for both sexes was calculated as W (g) = 0.033 Length (mm) 2.178. 

scholarly journals Ontogenetic Shifts in Oxygen Uptake in Common Mudskipper (Periophthalmus kalolo) and its Role in Microhabitat Selection

2021 ◽  
pp. 1-8
Author(s):  
Wayne A. Bennett ◽  
Jennie Rohrer ◽  
Nadiarti N. Kadir ◽  
Theresa F. Dabruzzi
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Standard Length ◽  
Life Stage ◽  
Size Class ◽  
Metabolic Rates ◽  
Ontogenetic Shifts ◽  
Size Classes ◽  
Consumption Values ◽  
Order Of Magnitude

Aims: The common mudskipper, Periophthalmus kalolo is a tropical, amphibious fish that utilizes both air and water as a respiratory medium. Adult oxygen uptake in water and air is well studied, but requirements of post-metamorphosed fish are virtually unknown. Our study quantifies how ontogenetic shifts across mudskipper life stage affects microhabitat choice. Study Design: metabolic rates in air and water were estimated for common mudskippers with mass values from 0.03 to 28.9 grams. Fish in each media were divided into 5 standard length classes (≤ 2.00, 2.01-4.00, 4.01-6.00, 6.01-8.00, ≥ 8.01 cm). Oxygen consumption for each class was calculated as the mean individual oxygen consumption for the group. Place and Duration of Study: Hoga Research Laboratory, Wakatobi National Park, Sulawesi, Indonesia, between June 14 and August 26, 2005. Methodology: Gilson manometry, and flow-through respirometery was used to determine respective aerial and aquatic oxygen uptake values for common mudskippers. Results: Mudskipper lengths varied by an order of magnitude (1.0 to 10.3 cm) and mass varied by three orders of magnitude (0.03 to 17.3 g). Mass-adjusted aerial metabolic rates of fish 2.00 cm or less in length, consumed up to ten times more oxygen than larger fish. whereas, aerial consumption values for size classes 2.01 cm and above did not differ significantly from each other (ANOVA: F4,112 = 40.29, P < 0.0001; SNK, α = 0.05). Metabolic rates of submerged fish fell into two statistically distinct subsets. mudskippers with lengths of 4.00 cm or less had significantly higher metabolic rates than fish in remaining size classes; however, mean oxygen uptake values of fish within subsets did not differ significantly (ANOVA: F4,87 = 6.89, P < 0.0001; SNK, α = 0.05). When oxygen consumption values at each size class were compared, only the smallest mudskipper size class (£ 2.00 cm) differed significantly between air and water (t-test: df = 34, t = 3.44, P < 0.0001). Mudskippers 2 cm in standard length or smaller consumed over seven times more oxygen in air than water. All other size classes had similar rates of oxygen uptake in air and water and air:water oxygen uptake ratios fell to approximately 1:1. Conclusions: (1) Common mudskippers select different mangal habitats based on developmental life stage. (2) Small, post-metamorphosed fish <2 mm in standard length, prefer cool shaded mangal areas, whereas, larger mudskippers utilize sun-exposed zones. (3) Post-metamorphosed fish, consume 10X more oxygen than all other size groups, confirming that juveniles are well suited to aerial respiration oxygen shortly after hatching. (4) Emerged post-metamorphosed fish exploit cooler, wetter pool habitats, thereby ameliorating problems of desiccation, excretion, and/or predation. (5) Ontogenetic shifts are a key life-history event in P. kalolo that promotes wider mangrove habitat use, and plays an important role in establishing common mudskipper as a key mangal species.

Effects of grain size distribution on Cole-Cole plots of polycrystalline spinels

2001 ◽  
Vol 699 ◽  
Author(s):  
M. P. Gutiérrez-Amador ◽  
R. Valenzuela
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mean Free Path ◽  
Size Distributions ◽  
Frequency Range ◽  
Impedance Response ◽  
Grain Size Distributions ◽  
The Mean ◽  
Different Grain Size

AbstractSpinel ferrites of composition Ni0.5Zn0.5Fe2O4 were prepared by coprecipitation. Different grain size and grain size distributions were obtained by various heat treatments. Their electrical properties were investigated by impedance spectroscopy in the temperature range 25-200°C and in the frequency range of 5Hz-13MHz. A decrease in resistivity was observed as grain size increased, which can be explained by an increase in the mean free path of electrons. Cole-Cole plots showed two well-resolved semicircles for samples with a narrow grain size distribution. As the width of the distribution increased, the semicircles exhibited a deformation and eventually became unresolved. These results are interpreted on the basis of a distribution of time-constant of the impedance response, associated with the grain size distribution.

Characterization of Booming Sands

2002 ◽  
Vol 759 ◽  
Author(s):  
Katherine S. Brantley ◽  
Melany L. Hunt ◽  
Christopher E. Brennen ◽  
Steven S. Gao
Keyword(s):  
United States ◽  
Moisture Content ◽  
Size Distribution ◽  
Sand Dunes ◽  
The United States ◽  
Size Distributions ◽  
Narrow Size Distribution ◽  
Dune Sands ◽  
The Mean

ABSTRACTMany sand dunes – at least seven in the United States – make loud booming noises when they avalanche. Records of the sound are centuries old, but the cause remains a mystery. This study examines properties of both the sand and the sound.Properties of the sand reveal clues about the source of the booming. Sand must be extremely dry to boom, but low moisture content alone is not sufficient to facilitate booming. Although the mean grain diameters of both booming and silent dune sands range from 0.20 – 0.40mm, the booming samples have smaller standard deviations. However, synthetic sands with similar size distributions do not boom, so a narrow size distribution cannot be solely responsible for the booming. Studies of the roundness and sphericity of the grains are currently underway.Air microphone and geophone recordings of the booming indicate that the fundamental frequency varies between 80–105 Hz depending on the dunes. This is consistent with previous measurements. Laboratory recordings of the “burping” sound that booming sand makes when shaken in a jar reveal a broad peak between 150–300 Hz.

scholarly journals Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds

2019 ◽  
Vol 19 (1) ◽  
pp. 639-648 ◽  
Author(s):  
Xiang-Yu Li ◽  
Gunilla Svensson ◽  
Axel Brandenburg ◽  
Nils E. L. Haugen
Keyword(s):  
Reynolds Number ◽  
Water Vapor ◽  
Size Distribution ◽  
Cloud Droplet ◽  
Passive Scalar ◽  
Droplet Growth ◽  
Size Distributions ◽  
Stratiform Clouds ◽  
The Mean ◽  
Condensational Growth

Abstract. Condensational growth of cloud droplets due to supersaturation fluctuations is investigated by solving the hydrodynamic and thermodynamic equations using direct numerical simulations (DNS) with droplets being modeled as Lagrangian particles. The supersaturation field is calculated directly by simulating the temperature and water vapor fields instead of being treated as a passive scalar. Thermodynamic feedbacks to the fields due to condensation are also included for completeness. We find that the width of droplet size distributions increases with time, which is contrary to the classical theory without supersaturation fluctuations, where condensational growth leads to progressively narrower size distributions. Nevertheless, in agreement with earlier Lagrangian stochastic models of the condensational growth, the standard deviation of the surface area of droplets increases as t1∕2. Also, for the first time, we explicitly demonstrate that the time evolution of the size distribution is sensitive to the Reynolds number, but insensitive to the mean energy dissipation rate. This is shown to be due to the fact that temperature fluctuations and water vapor mixing ratio fluctuations increase with increasing Reynolds number; therefore the resulting supersaturation fluctuations are enhanced with increasing Reynolds number. Our simulations may explain the broadening of the size distribution in stratiform clouds qualitatively, where the mean updraft velocity is almost zero.

Narrowing sputtered nanoparticle size distributions

1993 ◽  
Vol 8 (5) ◽  
pp. 995-1000 ◽  
Author(s):  
F.H. Kaatz ◽  
G.M. Chow ◽  
A.S. Edelstein
Keyword(s):  
Size Distribution ◽  
Mean Free Path ◽  
Particle Formation ◽  
Distribution Functions ◽  
Size Distributions ◽  
Narrow Size Distribution ◽  
Linear Arrangement ◽  
Nanocrystalline Particle ◽  
The Mean ◽  
Potential Use

By adjusting the sputtering rate and gas pressure, it is possible to form nanoparticles of different sizes, phases, and materials. We have investigated the spatial distribution of sputtered particle formation using a vertical, linear arrangement of substrates. Collecting the particles soon after they are formed, before they have time to grow and agglomerate, allows one to obtain a narrow size distribution. In the case of molybdenum, a narrow distribution of cubic particles is formed at relatively large distances (8 cm) from the source. These cubic particles collide and self-assemble in the vapor into arrays of larger cubic particles. The particle size histograms are fitted to lognormal distribution functions. How supersaturation occurs is discussed qualitatively as a function of the distance from the substrate, sputtering rate, and the mean free path in the vapor. This method of nanocrystalline particle formation has potential use in magnetic and opto-electronic (quantum dot) applications, where a narrow size distribution is required.

Closure Laws for the Transport Equation of Interfacial Area in Dispersed Flow

2002 ◽  
Author(s):  
X. Rioua ◽  
J. Fabrea ◽  
C. Colin
Keyword(s):  
Transport Equation ◽  
Size Distribution ◽  
Bubble Size ◽  
Interfacial Area ◽  
Bubble Size Distribution ◽  
Bubble Coalescence ◽  
Size Distributions ◽  
Mean Diameter ◽  
The Mean ◽  
Two Fluid

Derivation of a transport equation for the interfacial area concentration. In two-phase flows, the interfacial area is a key parameter since it mainly controls the momentum heat and mass transfers between the phases. An equation of transport of interfacial area may be very useful, especially for the two-fluid models. Such an equation should be able to predict the transition between the flow regimes. With this aim in view, we shall focus our attention on pipe flow. Besides in a first step, our study will be limited to dispersed flows. Different models are used to predict the evolution of bubble sizes. Some models use a population balance that provides a detailed description of the bubble size distributions, but they require as many equations as diameter ranges (Coulaloglou & Tavlarides1). Some others use only one equation for the transport of the mean interfacial area (Hibiki & Ishii2). In that case the bubble size distribution is treated as it would be monodispersed, its mean diameter being equal to the Sauter diameter. An intermediate approach was proposed by Kamp et al.3, in which polydispersed size distributions can be taken into account. It is the starting point of the present study in which: • The choice of an interfacial velocity is discussed. • The sink and source terms due to bubble coalescence, break-up or phase change are established. The model of Kamp et al. consists of transport equations of the various moments of the density probability function P(d) of the bubble diameter. In many experimental situations, P(d) is well predicted by a log-normal law (with two characteristic parameters d00 the central diameter of the distribution and a width parameter): The different moments of order ? of P(d) may be calculated: Sγ=n∫P(d)dγd(d)(1) where n is the bubble number density, S1/n, the mean diameter and S2/?, the interfacial area. A transport equation can be written for each moment: ∂Sγ∂t+∇·(uGSγ)=φγ(2) The lhs of (2) is an advection term by the gas velocity uG and the rhs is a source or sink term due to bubble coalescence, break-up or mass transfer. Since the bubble size distribution is characterised by the two parameters d00 and σˆ, only two transport equations (for S1 and S2) have to be solved to calculate the space-time evolution of the bubble size distribution. These two equations are still too cumbersome for a two-fluid model. Under some hypotheses (σˆ ∼ constant), they are lead to a single equation for the interfacial area. In its dimensionless form the interfacial area ai+ (ai+ = π S2 D, where D is the pipe diameter) reads: d/dt+(ai+)=f(RG,Re,We,ai+)(3) where RG is the gas fraction, Re is the Reynolds number of the mixture, We the Weber number of the mixture and t+ a dimensionless time.

Average relative stem profile comparisons for three size classes of Caribbean pine

1993 ◽  
Vol 23 (12) ◽  
pp. 2594-2598 ◽  
Author(s):  
Paul J. Allen
Keyword(s):  
Form Factor ◽  
Relative Position ◽  
Form Factors ◽  
Size Class ◽  
Polynomial Model ◽  
Relative Height ◽  
Independent Variables ◽  
Size Classes ◽  
The Mean ◽  
Caribbean Pine

A method for determining and comparing average relative stem profiles is described. Under-bark diameters at several points along the stem and the total heights were measured on 572 sample trees of Caribbean pine (Pinuscaribaea Morelet var. hondurensis Barrett & Golfari). For each tree, the total volume and the diameters under bark at several consistent relative positions along the stem (viz. 0.10–0.50 in increments of 0.05) were interpolated. The trees were categorised into three size classes depending on volume. For each tree, a true form factor corresponding to each interpolated relative position was calculated. These form factors were regressed on volume for each size class to determine the most appropriate position along the stem for use in calculating the relative diameters. A polynomial model was fitted to each size class, using relative diameter as the dependent variable and powers of relative height as the independent variables. Differences between the three equations describing the mean relative profiles were statistically significant. Mean errors for the relative diameters are also presented to indicate the accuracy of the three equations.

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