scholarly journals The use of the 210Pb method for preliminary evaluating the sedimentation rate in Amazon river mouth

2010 ◽  
Vol 42 (1) ◽  
pp. 149-157
Author(s):  
Sophie Althammer ◽  
Erich Foßhag ◽  
Harald Hoffmann ◽  
José Nery ◽  
Daniel Bonotto
Keyword(s):  
Sedimentation Rate ◽  
River Mouth ◽  
Fine Sand ◽  
Water Volume ◽  
Amazon River ◽  
Atmospheric Conditions ◽  
Linear Rate ◽  
210Pb Method ◽  
Sedimentation Processes ◽  
Made In

The use of the 210Pb method for preliminary evaluating the sedimentation rate in Amazon river mouth This investigation reports the preliminary results for determining the sedimentation rate at the Amazonas River mouth, Brazil, by the 210Pb method. The CIC (constant initial concentration) of unsupported/excess 210Pb model was successfully applied to one sediments core. The measurements were made in a sediments core comprising ten samples 10 cm - thick each. The year of the sampling (2006) was used as reference for the establishment of the rate of sedimentation from the beginning of the top of the testimony. However, the atmospheric conditions and climate in Amapá State, Brazil, claimed for optimization of the results. Because the Channel North is opened into the Atlantic Ocean, it exhibits a huge water volume, causing a permanent motion of sediments and water. So, heavy waves are formed at the water surface, stirring the upper sand strata. Only at a depth of 40-50 cm the profile tends to be more homogeneous, where it is mostly composed by fine sand and very fine sand. Thus, it is reasonable utilize the CIC model from 210Pb data, which allows estimate a sedimentation rate corresponding to 0.61 g/cm2yr and a mean linear rate of 0.8 cm/yr. The 238U and 210Pb activities in the sediments allowed the reconstruction of the sedimentation processes over a period of about 130 years.

The mineralogical composition of some Scottish soils

1925 ◽  
Vol 15 (3) ◽  
pp. 257-271 ◽  
Author(s):  
James Hendrick ◽  
George Newlands
Keyword(s):  
Mineralogical Composition ◽  
Fine Sand ◽  
Plant Food ◽  
Sand Fraction ◽  
Extensive Survey ◽  
North East ◽  
The North ◽  
Local Origin ◽  
East West ◽  
Made In

1. Previous investigations showed that certain Scottish soils were of glacial drift origin, that they were comparatively rich in unweathered silicates and therefore in reserves of plant-food, that they showed considerable variation in such silicates and were capable of classification accordingly. Some indication was also shown that the glacial drift, and hence the resulting soil, was sometimes of local origin, its character being determined by the underlying rock. In the present investigation a more extensive survey of Scottish soils has been made in order to discover to what extent these preliminary findings might be applicable generally.2. For this purpose soils have been collected from various localities in the north, north-east, west and south of Scotland, and have been analysed mechanically and the “fine sand” fraction examined mineralogically.

Effects of Laser Remelting at Cryogenic Conditions on Microstructure and Wear Resistance of the Ti6Al4V Alloy Applied in Medicine

2011 ◽  
Vol 183 ◽  
pp. 215-224 ◽  
Author(s):  
A. Zieliński ◽  
M. Jażdżewska ◽  
J. Łubiński ◽  
Waldemar Serbiński
Keyword(s):  
Surface Treatment ◽  
Laser Treatment ◽  
Laser Power ◽  
Ti6al4v Alloy ◽  
Laser Remelting ◽  
Linear Rate ◽  
Surface Cracking ◽  
Continuous Work ◽  
Cryogenic Conditions ◽  
Made In

The titanium and its alloys can be subjected to surface treatment, including laser treatment. In this work a new laser treatment at cryogenic conditions of Ti6Al4V alloy has been described. The work has been aimed at establishing whether such surface treatment could be suitable for implants working under wear in biological corrosive environment. The remelting has been made with the use of CO2 continuous work laser at laser power between 3 and 6 kW, at scan rate 0.5 and 1 m/s. The microstructure, surface topography, hardness, microhardness and wear linear rate and mass loss under tribological tests made in Ringer`s solution have been made. The results have shown that despite the surface cracking the tribological properties in simulated body fluid have been substantially improved.

scholarly journals Morphometric Characteristics of the Aziana Valley Basin

2021 ◽  
Vol 32 (2) ◽  
pp. 163-180
Author(s):  
Heba Mohammed Fayyad ◽  
Isaac Saleh Al-Akam
Keyword(s):  
Morphometric Characteristics ◽  
Elongation Ratio ◽  
Large Area ◽  
Parallel Patterns ◽  
Erosion Processes ◽  
Drainage Patterns ◽  
Drainage Networks ◽  
Mixed Sediments ◽  
Sedimentation Processes ◽  
Made In

The present study aims at examining quantitatively the morphometric characteristics of Iziana Valley basin that is located in the northern part of Iraq; particularly in south of Erbil Governorate. This basin is considered one of the small sub-basins where its valleys run on formations of the Triple and Quadrant Ages, which are represented by the Bay Hassan formations, and the sediments and mixed sediments of the cliffs, respectively. The area of ​​the Iziana basin amounts to (36.39 km2) whereas the percentage of its rotation reaches (0.17); a low percentage, which indicates that the basin diverges from the circular to the rectangular shape. The value of the elongation ratio of the basin reaches (0.38) while the terrain ratio of the basin is (0.03), a low percentage that entails the weakness of its erosion processes and the small volume of the carried and transported sediments. As for the relative topography of the basin, it was (1.08), which is also a low value. It indicates a relatively large area of ​​the basin and the impressive strides that it has made in its erosion cycle. The total river levels of the basin reach (5) ranks, and their numbers vary from one rank to another. Moreover, the total length of the drainage networks in the basin reached (187.4 km), and the prevailing drainage patterns in the basin are the tree and parallel patterns. The researcher has adopted spatial, formal, topographical, and river net-work properties for the purpose of first determining the shape of the basin, the stage of its erosion, its secondary basins, and its terrestrial features that have been developed as a result of the contrast between the erosion and sedimentation processes. 

scholarly journals One plausible reason for the change in ENSO characteristics in the 2000s

2013 ◽  
Vol 10 (4) ◽  
pp. 951-984
Author(s):  
V. N. Stepanov
Keyword(s):  
Southern Ocean ◽  
Equatorial Pacific ◽  
Warm Water ◽  
Water Volume ◽  
Atmospheric Conditions ◽  
Enso Events ◽  
Wind Variability ◽  
Western Equatorial Pacific ◽  
Warm Water Volume ◽  
The Tropics

Abstract. It is well known that El Niño Southern Oscillation (ENSO) causes floods, droughts and the collapse of fisheries, therefore forecasting of ENSO is an important task in climate researches. Variations in the equatorial warm water volume of the tropical Pacific and wind variability in the western equatorial Pacific has been considered to be a good ENSO predictor. However, in the 2000s, the interrelationship between these two characteristics and ENSO onsets became weak. This article attempts to find some plausible explanation for this. The results presented here demonstrate a possible link between the variability of atmospheric conditions over the Southern Ocean and their impact on the ocean circulation leading to the amplifying/triggering of ENSO events. It is shown that the variability of the atmospheric conditions upstream of Drake Passage can strongly influence ENSO events. The interrelationship between ENSO and variability in the equatorial warm water volume of the equatorial Pacific, together with wind variability in the western equatorial Pacific has recently weakened. It can be explained by the fact that the process occurred in the Southern Ocean recently became a major contributor amplifying ENSO events (in comparison with the processes of interaction between the atmosphere and the ocean in the tropics of the Pacific). Likely it is due to a warmer ocean state observed from the end of the 1990s that led to smaller atmospheric variability in the tropics and insignificant their changes in the Southern Ocean.

Penetration of a Rate Sensitive Geological Target by the Compaction Ring Theory

2002 ◽  
Author(s):  
Martin R. Gilmore ◽  
S. E. Jones ◽  
Joseph C. Foster
Keyword(s):  
Model Development ◽  
Target Material ◽  
Rate Sensitivity ◽  
Target Strength ◽  
Strain Rates ◽  
Linear Rate ◽  
Cat Scan ◽  
Strain And Strain Rate ◽  
Simplifying Assumptions ◽  
Made In

In an earlier paper, the authors presented a theory for the penetration of geologically based semi-infinite targets [5]. This theory was suitable for application to targets in which compaction due to the crushing of voids is the primary deformation mechanism. This phenomenon has been observed in concrete targets with a ring of dense material around the tunnel region, see figure 1 for a cat scan of a concrete target after penetration. This was the motivation for the model development. A number of simplifying assumptions were made in the application of the theory to data from concrete penetration experiments. One of the assumptions was that the target strength was constant, or independent of strain and strain rate. This assumption leads to generally consistent results for the same ogive nose geometry. However, it was noted that there was a discrepancy between the strength predictions when two different ogive nose geometries were used. This paper investigates the discrepancy by assuming that the target material is rate sensitive. The results indicate that the strain rates in the target are indeed affected by the nose geometry. A detailed analysis for a target material with linear rate sensitivity is provided in the paper and the results provide a favorable comparison with available experimental evidence.

Morphological and molecular characterization of cyanobacterial isolates from the mouth of the Amazon River

Phytotaxa ◽  
2019 ◽  
Vol 387 (4) ◽  
pp. 269 ◽  
Author(s):  
ELANE D. CUNHA DE OLIVEIRA ◽  
ALAN C. DA CUNHA ◽  
NATALINA B. DA SILVA ◽  
RAQUEL CASTELO-BRANCO ◽  
JOÃO MORAIS ◽  
...  
Keyword(s):  
River Mouth ◽  
Taxonomic Revision ◽  
16S Rrna Gene Sequencing ◽  
Gene Clusters ◽  
Toxin Production ◽  
Amazon River ◽  
Rrna Gene ◽  
Cyanobacterial Diversity ◽  
Rrna Gene Sequencing

The Amazon region contains a great diversity of species, and the Amazon River basin accounts for almost 20% of all the freshwater in the world. Despite the favorable environmental conditions in this region, little is known about the cyanobacterial diversity of this waterbody, especially at the mouth of the river. In this paper, we used the polyphasic approach to identify 14 cyanobacterial strains isolated in the Amazon River on the inlet site from a drinking water supply located close to the river mouth. The isolated strains were characterized based on morphology, behavior in culture, 16S rRNA gene sequencing, phylogenetic analysis and potential for toxin production. The isolated strains belong to seven different genera, namely, Alkalinema, Cephalothrix, Limnothrix, Leptolyngbya, Phormidium, Pseudanabaena and an unidentified Nostocales taxa that may represent a new genus. Strikingly, there were no new species, nor detection of gene clusters associated with cyanotoxin production. However, the phylogenetic placements of the Amazonian strains of Limnothrix and Pseudanabaena provide new insight into the taxonomy of these genera, reinforcing the need for taxonomic revision.

scholarly journals Feeding behavior of the cirratulid Cirriformia filigera (Delle Chiaje, 1825) (Annelida: Polychaeta)

2004 ◽  
Vol 64 (2) ◽  
pp. 283-288 ◽  
Author(s):  
E. V. Pardo ◽  
A. C. Z. Amaral
Keyword(s):  
Feeding Behavior ◽  
Substrate Surface ◽  
Fine Sand ◽  
Middle Part ◽  
Sediment Surface ◽  
Ventral Region ◽  
Overlying Water ◽  
Shaped Tube ◽  
Food Particles ◽  
Made In

Observations of the feeding behavior of Cirriformia filigera (Delle Chiaje, 1825) (Annelida: Polychaeta) from the intertidal zone of São Francisco and Engenho D'água beaches (São Sebastião, State of São Paulo) were made in the laboratory. This species, like other cirratulids, is a deposit feeder, feeding mainly on sediment surface with the aid of its grooved and ciliated palps, which are used to capture food particles. The worm lies just beneath the substrate surface in a J-shaped tube. When feeding, it extends up to 4 palps over the sediment surface, capturing food particles which pass down the groove of each palp directly to the mouth. Only fine sand grains are ingested. The worm frequently extends 4 branchial filaments into the overlying water for aeration. When it moves with the prostomium sideways, it collects and transports sand grains that pass backwards along its ventral region until reaching the middle part of its body. Next, the parapodia and palps move the sand grains to the dorsal posterior end of the animal, covering this area with sand. Some sand grains are also ingested as the worm moves.

Tidal controls on the formation of fine-scale sedimentary strata near the Amazon river mouth

1995 ◽  
Vol 125 (3-4) ◽  
pp. 259-281 ◽  
Author(s):  
John M. Jaeger ◽  
Charles A. Nittrouer
Keyword(s):  
River Mouth ◽  
Amazon River ◽  
Fine Scale
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