scholarly journals What is diatomite?

2020 ◽  
Vol 96 ◽  
pp. 48-52
Author(s):  
Petra Zahajská ◽  
Sophie Opfergelt ◽  
Sherilyn C. Fritz ◽  
Johanna Stadmark ◽  
Daniel J. Conley
Keyword(s):  
Sediment Type ◽  
Aquatic Environments ◽  
Burial Depth ◽  
Science Literature ◽  
Precise Description ◽  
Unicellular Algae ◽  
Large Numbers ◽  
Different Types ◽  
Siliceous Algae ◽  
Biogenic Remains

AbstractDifferent types of biogenic remains, ranging from siliceous algae to carbonate precipitates, accumulate in the sediments of lakes and other aquatic ecosystems. Unicellular algae called diatoms, which form a siliceous test or frustule, are an ecologically and biogeochemically important group of organisms in aquatic environments and are often preserved in lake or marine sediments. When diatoms accumulate in large numbers in sediments, the fossilized remains can form diatomite. In sedimentological literature, “diatomite” is defined as a friable, light-coloured, sedimentary rock with a diatom content of at least 50%, however, in the Quaternary science literature diatomite is commonly used as a description of a sediment type that contains a “large” quantity of diatom frustules without a precise description of diatom abundance. Here we pose the question: What is diatomite? What quantity of diatoms define a sediment as diatomite? Is it an uncompacted sediment or a compacted sediment? We provide a short overview of prior practices and suggest that sediment with more than 50% of sediment weight comprised of diatom SiO2 and having high (>70%) porosity is diatomaceous ooze if unconsolidated and diatomite if consolidated. Greater burial depth and higher temperatures result in porosity loss and recrystallization into porcelanite, chert, and pure quartz.

scholarly journals Streptococcus pyogenes vulvovaginitis in children in Nottingham

1991 ◽  
Vol 106 (3) ◽  
pp. 459-465 ◽  
Author(s):  
F. E. Donald ◽  
R. C. B. Slack ◽  
G. Colman
Keyword(s):  
Public Health ◽  
Streptococcus Pyogenes ◽  
Public Health Laboratory ◽  
Large Numbers ◽  
Highly Sensitive ◽  
Vaginal Swabs ◽  
Different Types ◽  
Winter Peak ◽  
The Common

SUMMARYIsolates of Streptococcus pyogenes from vaginal swabs of children with vulvovaginitis received at Nottingham Public Health Laboratory during 1986–9 were studied. A total of 159 isolates was made during the 4 years, increasing from 17 in 1986 to 64 in 1989 and accounting for 11% of all vaginal swabs received from children. The numbers of throat swabs yielding S. pyogenes also showed an increase from 974 in 1986 to 1519 in 1989. A winter peak of isolates was noted for both vaginal swabs and throat swabs. A total of 98 strains from vaginal swabs were serotyped: 22 different types were identified, 61% of which were the common types M4, M6, R28 and M12. Erythromycin sensitivity was done on 89 strains; 84% were highly sensitive (MIC < 0·03 mg/1). There are no other reports of such large numbers in the literature; the reason for seeing this increase in Nottingham is unclear.

The habits and habitats of the opisthobranch molluscs of the British Solomon Islands

1969 ◽  
Vol 255 (800) ◽  
pp. 541-548 ◽  
Keyword(s):  
Natural History ◽  
Solomon Islands ◽  
Gut Contents ◽  
Numerical Evidence ◽  
Large Numbers ◽  
Different Types ◽  
Opisthobranch Molluscs ◽  
First Time ◽  
Reef Formation

Often bizarre in shape and gaudily coloured, the opisthobranchs of the tropical IndoPacific have always been attractive subjects for the specialist worker and for writers of popular natural history. There is certainly no lack of papers describing their anatomy and systematics (Marcus & Burch (1965) give a fairly full bibliography), but only in those by Risbec (1928 a, b , 1951, 1953) are there descriptions of where or how they live and his statements are brief and rather vague. I collected opisthobranchs so as to record them for the British Solomon Islands for the first time and, whenever possible, I noted their habits and habitats. My observations on gut contents are rather scanty as I did not wish to damage any of the few specimens of each species collected. From an examination of ten different types of reef formation I discovered that opisthobranchs are common in only two places; (1) the crest of a semi-exposed reef where algae occur in pools, and (2) the flat of a sheltered or semi-sheltered reef. At each of these sites several distinct habitats can be distinguished. Unfortunately my recognition of these habitats is not supported by strong numerical evidence as none of the 55 species occurred in large numbers.

scholarly journals How many species of cladocerans (Crustacea, Branchiopoda) are found in Brazilian Federal District?

2013 ◽  
Vol 24 (4) ◽  
pp. 351-362 ◽  
Author(s):  
Francisco Diogo Rocha Sousa ◽  
Lourdes Maria Abdu Elmoor-Loureiro
Keyword(s):  
Urban Areas ◽  
Aquatic Vegetation ◽  
Federal District ◽  
Water Bodies ◽  
Aquatic Environments ◽  
Number Of Species ◽  
Different Types ◽  
Local Extinctions ◽  
Richness Estimators ◽  
Selection Of

AIM: This study aimed provides a checklist of cladocerans and also an evaluation of richness and species composition in the Federal District, Brazil. METHODS: Checklist of cladocerans was obtained evaluating data from the literature, from taxonomic collection (Elmoor-Loureiro's collection) and from fauna surveys conducted over more than three decades in different types of aquatic environments. RESULTS: The 57 water bodies studied showed 56 species, of which 14 are new records. The number of species contained in the list displayed corresponds to 85% of what was expected for richness estimators. The highest number of species was observed in the lentic water bodies (52), which also presented the specific composition of fauna (R = 0.110; p = 0.016), possibly because there were samples taken among the aquatic vegetation. According to our understanding, some species may be subject to local extinctions because they inhabit water bodies located exclusively in urban areas, which can lead to a decline in richness. CONCLUSION: Thus, the results of this study can assist in monitoring aquatic environments and in selection of new areas for surveys of cladocerans in the Federal District.

scholarly journals The Degree Analysis of an Inhomogeneous Growing Network with Two Types of Vertices

2014 ◽  
Vol 2014 ◽  
pp. 1-13
Author(s):  
Huilin Huang
Keyword(s):  
Probability Distribution ◽  
Law Of Large Numbers ◽  
Joint Probability ◽  
Joint Probability Distribution ◽  
Degree Sequences ◽  
Strong Law ◽  
Large Numbers ◽  
Different Types ◽  
Azuma's Inequality ◽  
Growing Network

We consider an inhomogeneous growing network with two types of vertices. The degree sequences of two different types of vertices are investigated, respectively. We not only prove that the asymptotical degree distribution of typesfor this process is power law with exponent2+1+δqs+β1-qs/αqs, but also give the strong law of large numbers for degree sequences of two different types of vertices by using a different method instead of Azuma’s inequality. Then we determine asymptotically the joint probability distribution of degree for pairs of adjacent vertices with the same type and with different types, respectively.

scholarly journals The Nature of the Ice-Rock Interface: The Results of Investigation on 20000m2 of the Rock Bed of Temperate Glaciers

1980 ◽  
Vol 25 (92) ◽  
pp. 267-277 ◽  
Author(s):  
Robert Vivian
Keyword(s):  
Surface Velocity ◽  
Sliding Velocity ◽  
Water Drainage ◽  
Precise Description ◽  
Surface Movement ◽  
The Third ◽  
Cavitation Phenomenon ◽  
Different Types ◽  
Rock Bed ◽  
Rock Interface

AbstractThis paper reviews the results of 10 years study of the only four subglacial sites which are permanently accessible due to activity by hydro-electrical companies. All the sites occur beneath temperate ice. The first part is devoted to the study of the ice-rock interface as a glaciological phenomenon, and emphasizes the dynamic conditions for separation of the ice from the rock bed. This glaciological cavitation phenomenon occurs when tan α &gt;Vi/Hi. Another phenomenon, “regressive cavitation” refers to the existence up-stream of the large permanent cavities, of a series of small cavities which although they are not permanent are fundamentally important because they control the subglacial water drainage allowing the water to penetrate new routes. The second part analyses the sliding movement of the ice on the rock bed. The deformation of the cavities depends mainly on variations in the velocity of the glacier. The sliding velocity measured at the interface accounts for 60 to 80% of the surface movement of the glacier; 80 to 90% of the surface velocity movement is attained a few metres above the glacier-bed interface. The third part describes the characteristics of subglacial drainage which are necessary to understand the nature of the ice-rock interface. The fourth part is devoted to the precise description of the different types of interface as they appeared in the subglacial sites.

Individual Differences Among Users

2011 ◽  
pp. 1-24 ◽  
Author(s):  
Madeleine Keehner ◽  
Peter Khooshabeh ◽  
Mary Hegarty
Keyword(s):  
Individual Differences ◽  
Three Dimensional ◽  
Structure And Function ◽  
Science Literature ◽  
Interactive Behavior ◽  
Different Types ◽  
Interactive Visualizations ◽  
Cognitive Benefits ◽  
Sophisticated User ◽  
And Function

This chapter examines human factors associated with using interactive three-dimensional (3D) visualizations. Virtual representations of anatomical structure and function, often with sophisticated user control capabilities, are growing in popularity in medicine for education, training, and simulation. This chapter reviews the cognitive science literature and introduces issues such as theoretical ideas related to using interactive visualizations, different types and levels of interactivity, effects of different kinds of control interfaces, and potential cognitive benefits of these tools. The authors raise the question of whether all individuals are equally capable of using 3D visualizations effectively, focusing particularly on two variables: (1) individual differences in spatial abilities, and (2) individual differences in interactive behavior. The chapter draws together findings from the authors’ own studies and from the wider literature, exploring recent insights into how individual differences among users can impact the effectiveness of different types of external visualizations for different kinds of tasks. The chapter offers recommendations for design, such as providing transparent affordances to support users’ meta-cognitive understanding, and employing personalization to complement the capabilities of different individuals. Finally, the authors suggest future directions and approaches for research, including the use of methodology such as needs analysis and contextual enquiry to better understand the cognitive processes and capacities of different kinds of users.

An efficient method for collecting large samples of live copepods free from detritus

2010 ◽  
Vol 61 (5) ◽  
pp. 621 ◽  
Author(s):  
Carl J. Svensson ◽  
Glenn A. Hyndes ◽  
Paul S. Lavery
Keyword(s):  
Fatty Acids ◽  
Food Web ◽  
Trophic Levels ◽  
Aquatic Systems ◽  
New Method ◽  
Aquatic Environments ◽  
Web Studies ◽  
Large Samples ◽  
Large Numbers ◽  
Harpacticoid Copepods

Meiofauna are often important in the transfer of organic material to higher trophic levels in aquatic environments. However, in food web analysis the group is frequently pooled or ignored owing to the difficulty in isolating individual components of the assemblage. In this study, we developed and tested a new method for extracting photopositive and detritus-free copepod samples from sediments, and compared this method to a previous technique (Couch 1989). In our initial trials, ∼400 copepods (all orders included) were collected in 15 min compared with 60 copepods using Couch’s method. In subsequent trials that focussed on specific orders of copepods, our method was at least 10 times more efficient than Couch’s method at collecting cyclopoid and harpacticoid copepods from sediments. The new method requires very little supervision and there is no requirement for a particular intensity of light. This method can increase the collection of large numbers of photopositive copepods in aquatic systems, and thereby facilitate the inclusion of this important component into future food web studies, particularly those using biomarkers such as stable isotopes or fatty acids.

Targeting Corporate Political Strategy: Theory and Evidence from the U.S. Accounting Industry

2007 ◽  
Vol 9 (2) ◽  
pp. 1-31 ◽  
Author(s):  
Richard G. Vanden Bergh ◽  
Guy L.F. Holburn
Keyword(s):  
Empirical Support ◽  
Auditor Independence ◽  
Science Literature ◽  
Political Strategy ◽  
Political Campaign ◽  
Accounting Firms ◽  
Political Environments ◽  
Policy Making Process ◽  
Different Types ◽  
Corporate Political Strategy

By analyzing the interaction between a business firm and multiple government institutions (including a regulatory agency, an executive and a bicameral legislature), we develop predictions about how firms target their political strategies at different branches of government when seeking more favorable public policies. The core of our argument is that firms will target their resources at the institution that is ‘pivotal’ in the policy-making process. We develop a simple framework, drawing on the political science literature, which identifies pivotal institutions in different types of political environments. We find empirical support for our thesis in an analysis of how U.S. accounting firms shifted their political campaign contributions between the House and Senate in response to the threat of new regulations governing auditor independence during the 1990s.

An introduction to balanced sequential arrays on the square grid

2009 ◽  
Vol 59 (2) ◽  
Author(s):  
Anne Street ◽  
Marks Nester
Keyword(s):  
Publishing House ◽  
Temporal Analysis ◽  
Rectangular Grid ◽  
Regular Grid ◽  
Light Water ◽  
Square Grid ◽  
Large Numbers ◽  
Spatial And Temporal Analysis ◽  
Nearest Neighbours ◽  
Different Types

AbstractPlants grown in large numbers for commercial purposes are usually set out on a regular grid, triangular, square or hexagonal, or possibly a rectangular grid. We need to understand their behaviour when they compete with each other for light, water and nutrients. In a greenhouse, there may be a lamp over each plant, half the plants having their lamps on and half off. The intensity of light falling on any particular plant is determined mainly by whether its own lamp is on, next by the number of its nearest neighbours whose lamps are on, and perhaps also by the number of its second-nearest neighbours whose lamps are on.Such arrays are also used to study competition among different types of plants and, with some extra restrictions, to design field layouts as well. The problem of constructing suitable arrays was introduced in [CORMACK, R. M.: Spatial aspects of competition beween individuals. In: Spatial and Temporal Analysis in Ecology (R. M. Cormack and J. K. Ord, eds.), International Co-operative Publishing House, Fairland, Maryland, USA, 1979] and discussed in [GATES, D. J.: Competition between two types of plants with specified neighbour configurations, Math. Biosci. 48 (1980), 195–209]. Here we consider only the square grid.

scholarly journals The Nature of the Ice-Rock Interface: The Results of Investigation on 20 000 m2 of the Rock Bed of Temperate Glaciers

1979 ◽  
Vol 23 (89) ◽  
pp. 413-414
Author(s):  
Robert Vivian
Keyword(s):  
Surface Velocity ◽  
Sliding Velocity ◽  
Water Drainage ◽  
Future Issue ◽  
Precise Description ◽  
The Third ◽  
Cavitation Phenomenon ◽  
Different Types ◽  
Rock Bed ◽  
Rock Interface

AbstractThis paper reviews the results of ten years study of the only four subglacial sites which are permanently accessible thanks to the work of hydro-electrical companies. All the sites occur beneath temperate ice. The first part is devoted to the study of the rock-ice interface as a glaciological phenomenon. The dynamic conditions for separation of the ice from the rock bed are considered. This cavitation phenomenon occurs when tan α > Vi/Hi. “Regressive cavitation” explains the existence up-stream of large permanent cavities and of a series of small cavities which, although they are not permanent, are fundamental because they control sub-glacial water drainage. The second part analyses the sliding movement of ice on a rock bed. Indeed the deformation of the cavities depends mainly on the variations in the velocity of the glacier. The sliding velocity measured at the interface accounts for 60 to 80% of the surface movement of the glacier. 80 to 90% of the surface velocity is attained a few metres above the glacier-bed interface. The third part describes the characteristics of subglacial drainage which are necessary to understand the nature of the ice-rock interface. The fourth part is devoted to the precise description of the different types of interface as they appeared in the subglacial sites.This paper has been accepted for publication in full in a future issue of the Journal of Glaciology.

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