scholarly journals On Monitoring Physical and Chemical Degradation and Life Estimation Models for Lubricating Greases

Lubricants ◽  
2016 ◽  
Vol 4 (3) ◽  
pp. 34 ◽  
Author(s):  
Asghar Rezasoltani ◽  
M. Khonsari
Keyword(s):  
Chemical Degradation ◽  
Life Estimation ◽  
Physical And Chemical ◽  
Estimation Models

scholarly journals Enzymes Involved in Plastic Degradation

2021 ◽  
pp. 95-110
Author(s):  
S.Z.Z. Cobongela
Keyword(s):  
Polyethylene Terephthalate ◽  
Synthetic Polymers ◽  
Chemical Degradation ◽  
Natural Resistance ◽  
Aquatic Life ◽  
Carbon Backbone ◽  
Catabolic Enzymes ◽  
Plastic Degradation ◽  
Global Increase ◽  
Physical And Chemical

The global increase in production of plastic and accumulation in the environment is becoming a major concern especially to the aquatic life. This is due to the natural resistance of plastic to both physical and chemical degradation. Lack of biodegradability of plastic polymers is linked to, amongst other factors, the mobility of the polymers in the crystalline part of the polyesters as they are responsible for enzyme interaction. There are significantly few catabolic enzymes that are active in breaking down polyesters which are the constituents of plastic. The synthetic polymers widely used in petroleum-based plastics include polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane (PUR), polystyrene (PS), polyamide (PA) and polyethylene terephthalate (PET) being the ones used mostly. Polymers with heteroatomic backbone such as PET and PUR are easier to degrade than the straight carbon-carbon backbone polymers such as PE, PP, PS and PVC.

scholarly journals Leaf wax <i>n</i>-alkanes in modern plants and topsoils from eastern Georgia (Caucasus) – implications for reconstructing regional paleovegetation

2017 ◽  
Author(s):  
Marcel Bliedtner ◽  
Imke K. Schäfer ◽  
Roland Zech ◽  
Hans von Suchodoletz
Keyword(s):  
Regional Scale ◽  
Chemical Degradation ◽  
Vegetation Types ◽  
Terrestrial Plants ◽  
Caucasus Region ◽  
Leaf Wax ◽  
South Eastern Europe ◽  
Southern Caucasus ◽  
Physical And Chemical ◽  
Long Chain

Abstract. Long-chain n-alkanes became increasingly used for paleoenvironmental studies during the last years as they have the great potential to reconstruct past changes in vegetation and climate. They mostly originate from leaf waxes of higher terrestrial plants, are relatively resistant against physical and chemical degradation and can thus serve as valuable biomarkers that are preserved in various sedimentary archives for at least millennial timescales. However, before any robust interpretation of the long-chain n-alkane patterns in sedimentary archives, reference samples from modern vegetation and topsoil material should be investigated at a regional scale. Apart from Central and South-Eastern Europe, such systematic regional studies on modern plant and topsoil material are still largely lacking. To test the potential of leaf wax derived n-alkane patterns for paleoenvironmental studies in the semi-humid to semi-arid southern Caucasus region, we investigated the influence of different vegetation types on the leaf wax n-alkane signal in modern plants and topsoil material (0–5 cm) from eastern Georgia. We sampled (i) sites with grassland that included steppe, cultivated grassland and meadows, and (ii) sites that are dominated by deciduous hornbeam forests. The n-alkane results show distinct and systematic differences between samples from sites with the different vegetation types: n-alkanes derived from sites with grassland are mainly dominated by C31, while n-alkanes derived from sites with deciduous trees show high abundances of C29. Thus, chain-length ratios allow to discriminate between these two different vegetation types and have a great potential when used for regional paleoenvironmental reconstructions. As degradation of organic matter can affect the leaf wax n-alkane distribution, we further present an updated end-member model that includes our results, accounts for degradation effects and enables semi-quantitative reconstruc-tions of past vegetation changes in the southern Caucasus region.

scholarly journals Fire - mechanical behaviour of sandwich composite beam

2020 ◽  
pp. 22-26
Author(s):  
Tran Van Luan, Le Minh Tien Tran
Keyword(s):  
Mechanical Behaviour ◽  
Sandwich Beam ◽  
Extreme Temperature ◽  
Chemical Degradation ◽  
Sandwich Composite ◽  
Composite Sandwich ◽  
Materials Used ◽  
Marine Applications ◽  
Sandwich Materials ◽  
Physical And Chemical

We have analyzed the fire-mechanical behaviour of sandwich composite materials used in marine applications, as a function of the combustion time. In this light, sandwich beam samples are analyzed in terms of fire resistance kinetic and of post-combustion mechanical strength. We have shown that the materials undergo a strong degradation during 100 s of fire exposure at 750 ° C and this degradation is linked to the top skin. Finally, a finite element modelling work is being developed to predict the thermal behavior of composite sandwich materials; this modelling must include all thermal, physical and chemical degradation processes in order to realistically report resistance of materials in extreme temperature environment.

scholarly journals Fractal Metrology for biogeosystems analysis

2010 ◽  
Vol 7 (11) ◽  
pp. 3799-3815 ◽  
Author(s):  
V. Torres-Argüelles ◽  
K. Oleschko ◽  
A. M. Tarquis ◽  
G. Korvin ◽  
C. Gaona ◽  
...  
Keyword(s):  
Measurement Techniques ◽  
Clay Mineralogy ◽  
Chemical Degradation ◽  
Structural Pattern ◽  
Box Counting ◽  
Soil Functioning ◽  
Gray Intensity ◽  
Physical And Chemical ◽  
Contrasting Structure

Abstract. The solid-pore distribution pattern plays an important role in soil functioning being related with the main physical, chemical and biological multiscale and multitemporal processes of this complex system. In the present research, we studied the aggregation process as self-organizing and operating near a critical point. The structural pattern is extracted from the digital images of three soils (Chernozem, Solonetz and "Chocolate" Clay) and compared in terms of roughness of the gray-intensity distribution quantified by several measurement techniques. Special attention was paid to the uncertainty of each of them measured in terms of standard deviation. Some of the applied methods are known as classical in the fractal context (box-counting, rescaling-range and wavelets analyses, etc.) while the others have been recently developed by our Group. The combination of these techniques, coming from Fractal Geometry, Metrology, Informatics, Probability Theory and Statistics is termed in this paper Fractal Metrology (FM). We show the usefulness of FM for complex systems analysis through a case study of the soil's physical and chemical degradation applying the selected toolbox to describe and compare the structural attributes of three porous media with contrasting structure but similar clay mineralogy dominated by montmorillonites.

scholarly journals Establishment of homogeneous zones in a soil of alluvial origin

2019 ◽  
Vol 43 ◽  
Author(s):  
Camilo Ignacio Jaramillo-Barrios ◽  
Andrés Felipe Ortiz-Rico ◽  
Gustavo Alfonso Araujo Carrillo ◽  
Viviana Marcela Varón-Ramírez
Keyword(s):  
Chemical Properties ◽  
Exchange Capacity ◽  
Chemical Degradation ◽  
Acid Sulfate Soils ◽  
Al Content ◽  
Neutralizing Capacity ◽  
Homogeneous Chemical ◽  
Sulfate Soils ◽  
Physical And Chemical ◽  
And Chemical Properties

ABSTRACT Soils have the ability to maintain plant growth and biological activity due to their physical and chemical properties. The aim of this study was to observe the spatial distribution of some chemical properties of the soil, such as pH, organic matter (OM), electrical conductivity (EC), effective cation exchange capacity (ECEC), sulfur (S) and aluminum (Al) content and to establish zones with homogeneous chemical characteristics using the MULTISPATI-PCA technique and the fuzzy c-means algorithm. The study area was located in the Tundama and Sugamuxi Valleys (Boyacá, Colombia) with an area of 8,017 ha. Chemical properties such as pH, OM, EC, S, Al, and ECEC were indicators of the chemical degradation of these soils. Four homogeneous zones were identified. The first zone represents areas with acidity and excessive sulfur, with a pH of 4.54, 15.88% OM, 3.19 dS m-1 EC, 2.47 meq 100 g-1 Al and 365.59 meq 100 g-1 S. In contrast, the second zone represents areas with a high self-neutralizing capacity, with a pH of 5.98, 4.22% OM, 0.75 dS m-1 EC, 0.20 meq 100 g-1 Al and 44.64 meq 100 g-1 S. Zone three showed a high similarity with the first two, except for its EC and S contents. Finally, zone four showed similarity with the first, except in OM, EC and S contents. These data show that S and EC influenced the homogeneous zones because the soils in this area are called acid sulfate soils.

Coastal environments and oil spill residues in Chedabucto Bay, Nova Scotia

1976 ◽  
Vol 13 (7) ◽  
pp. 908-928 ◽  
Author(s):  
E. H. Owens ◽  
M. A. Rashid
Keyword(s):  
Nova Scotia ◽  
Oil Spill ◽  
Littoral Zone ◽  
Wave Activity ◽  
Sediment Supply ◽  
Chemical Degradation ◽  
Coastal Environments ◽  
Sediment Removal ◽  
Natural Processes ◽  
Physical And Chemical

Investigations following the oil spill from the tanker ARROW in Chedabucto Bay, Nova Scotia, in 1970 have focussed on the physical and chemical degradation of the Bunker C oil in different littoral environments and on the effects of sediment removal to restore polluted beaches. Natural processes have restored the beaches effectively on coasts exposed to wave activity. In sheltered, low-energy areas, the oil has undergone relatively little change over the 3-year period and is still present in the littoral zone. The removal of contaminated sediments from exposed beaches has not caused major changes but has resulted in permanent retreat of the beach crest in areas of limited sediment supply.

Resizing: A Brief Review of Restoration and Conservation Literature from the 17th to the 21st Century

2019 ◽  
Vol 40 (3-4) ◽  
pp. 219-237
Author(s):  
Eva Hummert
Keyword(s):  
Twentieth Century ◽  
Mechanical Stability ◽  
Chemical Degradation ◽  
Cellulose Ethers ◽  
V Protein ◽  
Conservation Practice ◽  
Application Techniques ◽  
Aqueous Treatment ◽  
Sizing Agents ◽  
Physical And Chemical

Abstract From the first half of the seventeenth century until the beginning of the twentieth century resizing was common practice after each aqueous treatment to replace the loss of original sizing, but it is used much less frequently today. As already described in early sources, resizing in modern conservation practice still serves three main purposes: increasing mechanical stability, modifying the surface texture of abraded papers by decreasing their surface roughness and consolidating loosened fibres and preparing the paper substrate for inpainting. Today’s practice, however, differentiates more carefully between an improvement in mechanical stability and increased resistance to physical and chemical degradation processes. While previously almost exclusively protein glues were used for resizing, today gelatine and cellulose ethers are among the most commonly used sizing agents. The solution concentrations used for resizing have significantly decreased: gelatine is used in 0.5 % (w/v) to 1 % (w/v) solutions today, while historic literature recommends 1.6 % (w/v) to 3.5 % (w/v) protein glues. Concerning application techniques, mainly immersion, closely related to tub sizing used during paper manufacture and local or overall brush applications were used for historic sizing. Spraying, which was introduced at the beginning of the second half of the twentieth century, is recommended for resizing drawings to prevent friable media from being smudged.

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