Granite Weathering

2006 ◽  
Author(s):  
Piotr Migon
Keyword(s):  
Solid Rock ◽  
Chemical Change ◽  
Transitional Zone ◽  
Sufficient Evidence ◽  
Small Scale ◽  
Bare Rock ◽  
Moisture Deficit ◽  
Geomorphic Features ◽  
Drying Up ◽  
Physical And Chemical

Weathering is a necessary precursor for landform development. However, in the context of granite it acquires a particular importance for various reasons. First, many granite terrains show an extensive development of deep weathering profiles, which can be extremely varied in terms of their depth, vertical zonation, degree of rock decomposition, and mineralogical and chemical change. Moreover, the transitional zone between the weathering mantle and the solid rock, for which the term ‘weathering front’ is used (Mabbutt, 1961b), may be very thin. There is now sufficient evidence that many geomorphic features of granite landscapes, including boulders, domes, and plains, have been sculpted at the solid rock/weathering mantle interface and they are essentially elements of an exposed weathering front. Therefore, the origin of granite landscapes cannot be satisfactorily explained and understood without a proper understanding of the phenomenon of deep weathering. Second, granites break down via a range of weathering mechanisms, both physical and chemical, which interact to produce an extreme diversity of small-scale surface features and minor landforms. In this respect, it is only limestones and some sandstones which show a similar wealth of weathering-related surface phenomena. Third, both superficial and deep weathering of granite act very selectively, exploiting a variety of structural and textural features, including fractures, microfractures, veins, enclaves, and textural inhomogeneities. In effect, the patterns of rock breakdown may differ very much between adjacent localities, and so the resultant landforms differ. In the context of deep weathering, selectivity is evident in significant changes of profile thickness and its properties over short distances, and in the presence of unweathered compartments (corestones) within an altered rock mass. Fourth, it is emphasized that granites are particularly sensitive to the amount of moisture in the environment (Bremer, 1971; Twidale, 1982). They alter very fast in moist environments, whereas moisture deficit enhances rock resistance and makes it very durable. Hence, a bare rock slope shedding rainwater and drying up quickly after rain will be very much immune to weathering, whereas at its foot a surplus of moisture will accelerate decomposition.

scholarly journals Using network analysis to analyse the complex interaction of factors causing the failure of small-scale water infrastructure (SWI) in the rural areas of South Africa

Water SA ◽  
2018 ◽  
Vol 44 (3 July) ◽  
Author(s):  
DC Sambo ◽  
A Senzanje ◽  
K Dhavu
Keyword(s):  
South Africa ◽  
Rural Communities ◽  
Rural Areas ◽  
Small Scale ◽  
Research Approach ◽  
Water Services ◽  
Systematic Analysis ◽  
Complex Interactions ◽  
Technical Community ◽  
Drying Up

Some parts of the rural areas of South Africa are receiving water services below the legislative standards stipulated in the Water Services Act (1997) of South Africa. This is because small-scale water infrastructures (SWI), including standpipes, handpumps and windmills, are failing to supply adequate water in rural communities for various activities that enhance their livelihoods. This is due to technical, community, institutional, and environmental factors. Literature indicates that these factors are complex in nature. However, research on their complex interactions has been limited. Therefore, the complex interactions of the factors causing SWI failure were investigated and analysed in this study. A qualitative research approach was employed to investigate the factors that cause failure of SWI. The network approach combined with graph theory and the community structure method were used to generate a theme and domain network that allowed for a systematic analysis and interpretation of the causes of SWI failure in the study area. The major causes of failure identified include: (i) the use of a top-down approach to implement water projects in rural communities without consultation, (ii) sharing of SWI in high numbers due to the limited number of SWI available/functional, resulting in overloading and increased breakdowns, and (iii) drying up of water sources due to poor siting leading to vandalism of SWI. Overall, the causes of SWI failure are as a result of the complex interactions of different categories of factors. The theme and domain network is a powerful tool that can be used represent and analyse the complex interactions. It is therefore imperative for interventions aiming to improve rural water supply to analyse the complex interactions of the causes of SWI failure to understand the underlying problems at a level of a system, in order to propose suitable solutions.

Structure of cliff vegetation on exposed cliffs and the effect of rock climbing

1996 ◽  
Vol 74 (4) ◽  
pp. 607-617 ◽  
Author(s):  
Victoria A. Nuzzo
Keyword(s):  
Plant Cover ◽  
Rock Climbing ◽  
Small Scale ◽  
Rock Fracturing ◽  
Community Groups ◽  
Bare Rock ◽  
Lichen Cover ◽  
Cliff Vegetation ◽  
Total Plant ◽  
The Impact

Vegetational structure of exposed dolomitic cliffs in the driftless region of northwest Illinois was quantified from 186 quadrats on five cliffs. All cliffs were sparsely vegetated, with a total of 41 species (14 lichen and 27 vascular) recorded in the upper 6 m. On all cliffs, cover averaged 16.03%, with lichen contributing 10.23% cover and vascular vegetation 5.80% cover. Seventy percent of all vegetation grew within 3 m of the cliff top. Linear regression indicated that both cover and density of vascular, but not lichen, flora increased with increased fracturing and decreased with distance from the cliff top. TWINSPAN arranged the quadrats into five groups that differed in lichen and vascular cover and a sixth group that consisted of bare rock. Spatial distribution of the community groups occurred at a small scale, influenced by small scale differences in rock fracturing, slope, weathering, and likely moisture availability. Climbing significantly reduced lichen cover and lichen species density by 50%, from 13.7% cover and 2.4 species/0.25 m2 on unclimbed cliffs, to 6.7% cover and 1.2 species/0.25 m2 on climbed cliffs. Climbing did not have an apparent effect on vascular vegetation, which ranged from 2.74 to 10.62% cover on individual cliffs. Total plant cover averaged 19.7% on three unclimbed cliffs and 12.3% on two climbed cliffs, because of the impact on lichen cover. Although climbed cliffs had lower lichen cover, distribution of TWINSPAN-defined community groups was similar on both climbed and unclimbed cliffs, indicating that environmental and physical variables were the primary determinants of cliff flora on these vertical exposed cliffs. Keywords: cliff, vegetation, lichen, rock climbing, rock fractures.

Analytical Methodology from Lavoisier to Mendeleev

2014 ◽  
Author(s):  
Marco Fontani ◽  
Mariagrazia Costa ◽  
Mary Virginia Orna
Keyword(s):  
Chemical Change ◽  
Chemical Properties ◽  
Professional Activity ◽  
Analytical Methodology ◽  
Long Run ◽  
Similar Chemical ◽  
Experimental Errors ◽  
Ancient Times ◽  
Almost All ◽  
Physical And Chemical

Within the period covered by Part II, 1789–1869, 37 true elements, almost all of them metals, were discovered. Prior to this time, about 14 metals had been discovered, excluding those that had been known from ancient times. The discovery of the elements during this period of interest is intimately related to the analytical methodologies available to chemists, as well as to a growing consciousness of just what an element is. Because these methods were also available to the less competent who may have lacked the skills to use them or the knowledge to interpret their results, their use also led to as many, if not more, erroneous discoveries in the same period. One can number among the major sources of error faulty interpretation of experimental data, the “rediscovery” of an already known element, sample impurities, very similar chemical properties (as in the case of the rare earths), the presence of an element in nature in very scarce or trace amounts, gross experimental errors, confusion of oxides and earths with their metals, and baseless dogmatic pronouncements by known “authorities” in the field. Antoine Laurent Lavoisier’s conceptualization of what constitutes an element was a radical break from the principles of alchemy. His stipulation that an element is a substance that cannot be further decomposed conferred an operational, pragmatic, concrete definition on what had previously been a more abstract concept. At the other end of the spectrum was the intuition of Dmitri Mendeleev who, contrary to the prevailing acceptance of Lavoisier’s concept, stressed the importance of retaining a more abstract, more fundamental sense of an element—an idea that in the long run enabled the development of the periodic table. What both men had in common is that they defined and named individual elements as those components of substances that could survive chemical change and whose presence in compounds could explain their physical and chemical properties. Mendeleev’s table has been immortalized in every chemistry classroom—and also concretely in Saint Petersburg, the city that saw most of his professional activity, by a spectacular building-sized model The analytical chemist depends on both of these concepts and indeed, analytical practice preceded Lavoisier’s concept by at least a century.

Platelet-rich plasma another add-on treatment getting out of hand? How can clinicians preserve the best interest of their patients?

2019 ◽  
Author(s):  
Bulent Urman ◽  
Aysen Boza ◽  
Basak Balaban
Keyword(s):  
Clinical Trial ◽  
Ovarian Reserve ◽  
Platelet Rich Plasma ◽  
Sufficient Evidence ◽  
Small Scale ◽  
Biological Plausibility ◽  
Best Interest ◽  
Thin Endometrium ◽  
Before And After ◽  
Recent Addition

Abstract Add-on treatments in IVF are utilized to a great extent but without sufficient evidence showing their effectiveness. Since the offered treatments are usually costly and may be associated with yet unknown risks, this practice is not in the best interest of couples that may go to great lengths to conceive and have an offspring carrying their own genetic make-up. A recent addition to this armamentarium is the administration of platelet-rich plasma (PRP) in women with diminished ovarian reserve, implantation failures, and a thin endometrium. The only evidence for PRP comes from small scale and mostly before and after studies with clinically irrelevant end points. PRP has not been subjected to a rigorous clinical trial. It is a typical example of an add-on gaining widespread popularity based on biological plausibility and mind-bending theoretical presumptions. We should be extremely cautious prior to implementing PRP on a widescale and await the results of well-designed studies.

scholarly journals Mapping the physical and chemical properties of the planetary nebula NGC 3242

2011 ◽  
Vol 7 (S283) ◽  
pp. 448-449
Author(s):  
Hektor Monteiro ◽  
Denise Gonçalves ◽  
Marcelo Leal-Ferreira ◽  
Romano Corradi ◽  
Sebastian Sánchez
Keyword(s):  
Planetary Nebula ◽  
Three Dimensional ◽  
Chemical Properties ◽  
Small Scale ◽  
Chemical Abundances ◽  
Electronic Density ◽  
Spatially Resolved ◽  
Integral Field Spectroscopy ◽  
Main Components ◽  
Physical And Chemical

AbstractWe present optical integral field spectroscopy analysis of the main components, with the exception of the halo, as well as of the detected small-scale structures of the planetary nebulae NGC 3242. The observations were obtained with the VIMOS instrument attached to VLT-UT3. Spatially resolved maps of the electronic density (Ne), temperatures (Te) and chemical abundances, i.e., in a pixel to pixel fashion of the small and large-scales structures of this planetary nebula are determined in this work. These diagnostic and abundance maps represent important constraints for future detailed three dimensional photoionization modeling of the nebula, as well as providing important information on biases introduced by traditional slit observations.

scholarly journals Investigation of interaction of particles of pollution and gas bulb in flotation of wastewater waters

2019 ◽  
Vol 135 ◽  
pp. 01032
Author(s):  
Elena Nazimko ◽  
Sergei Malko ◽  
Anna Semenova ◽  
Vladimir Dorovskoy
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Hydrophobic Surface ◽  
Small Scale ◽  
Discrete Elements ◽  
Chemical Factors ◽  
Flotation Method ◽  
Physical And Chemical ◽  
Kinetics Of ◽  
Discrete Elements Method

The interaction of phases is at the basis of many technologies in different industries. Flotation method is used in wastewater treatment plants to capture and remove contaminants from wastewater. In this case, the interaction of air bubbles with particles of pollution with a hydrophobic surface. These interactions are very difficult to investigate because they are dynamic, subject to a large number of physical and chemical factors, and occur on a small scale. The processes mentioned above have traditionally been studied by laboratory experiments. These tests are tedious and time-consuming and show unsatisfactory accuracy. Analytical studies give idealized results. One of the most powerful alternatives for solving this problem is numerical modeling, which combines dynamics, accuracy and consideration of sophisticated details. This model is based on the discrete elements method. In this paper, a computer model for modeling the kinetics of the interaction of phases in wastewater treatment is considered.

The Effects of Scaling and Model Complexity in Simulating the Transport of Inorganic Micropollutants in a Lowland River Reach

2006 ◽  
Vol 41 (1) ◽  
pp. 24-36 ◽  
Author(s):  
Karl-Erich Lindenschmidt ◽  
René Wodrich ◽  
Cornelia Hesse
Keyword(s):  
Large Scale ◽  
Transport Model ◽  
Transport Processes ◽  
Model Complexity ◽  
Scale Model ◽  
Small Scale ◽  
Quality Model ◽  
Large Scale Model ◽  
Iron And Zinc ◽  
Physical And Chemical

Abstract A hypothesis stating that more complex descriptions of processes in models simulate reality better (less error) but with more unreliable predictability (more sensitivity) is tested using a river water quality model. This hypothesis was extended stating that applying the model on a domain of smaller scale requires greater complexity to capture the same accuracy as in large-scale model applications which, however, leads to increased model sensitivity. The sediment and pollutant transport model TOXI, a module in the WASP5 package, was applied to two case studies of different scale: a 90-km course of the 5th order (sensu Strahler 1952) lower Saale river, Germany (large scale), and the lock-and-weir system at Calbe (small scale) situated on the same river course. A sensitivity analysis of several parameters relating to the physical and chemical transport processes of suspended solids, chloride, arsenic, iron and zinc shows that the coefficient, which partitions the total heavy metal mass into its dissolved and sorbed fraction, is a very sensitive parameter. Hence, the complexity of the sorptive process was varied to test the hypotheses.

Physical and chemical change in textbooks: An initial view

1996 ◽  
Vol 26 (1) ◽  
pp. 129-140 ◽  
Author(s):  
Bill Palmer ◽  
David F Treagust
Keyword(s):  
Chemical Change ◽  
Physical And Chemical

scholarly journals Increasing the utilisation of grain when fed whole to ruminants

1999 ◽  
Vol 50 (5) ◽  
pp. 737 ◽  
Author(s):  
A. G. Kaiser
Keyword(s):  
Seed Coat ◽  
Animal Production ◽  
Enzyme Treatment ◽  
Sufficient Evidence ◽  
Whole Grain ◽  
Beneficial Effects ◽  
Grain Damage ◽  
Subsequent Effect ◽  
Physical And Chemical ◽  
The Impact

Feeding grain whole to cattle generally results in a lower digestibility than that obtained with processed grain. If this problem could be overcome, feeding with whole grain would reduce processing costs, and the slower rate of starch digestion in the rumen could improve fibre digestion with potential beneficial effects on intake and animal production. Two strategies are available to increase the digestibility of whole grain. The first, longer term strategy relies on the selection or breeding of feed grains that are efficiently digested by cattle when fed whole. The review considers the chemical and physical properties of grains likely to increase the degree of grain damage during mastication, and increase the digestibility of the seed coat fraction. Research is required to determine the feasibility of selecting feed grains with these characteristics. The second strategy is to treat whole grain with chemicals or enzymes to increase digestibility of the seed coat and consequently whole grain digestion within the rumen. Considerable research has been conducted on the sodium hydroxide (NaOH) treatment of grain, and there is sufficient evidence from cattle experiments to indicate that digestibility, liveweight gain, and milk production on NaOH-treated whole grain can be similar to that on rolled grain, provided sufficient NaOH is applied. However, a number of practical and commercial considerations have limited the more widespread adoption of this technology on farms. Although ammonia treatment offers a more practical alternative to NaOH, digestibility and animal production responses have been highly variable, and research is required to identify effective ammoniation procedures. The increased availability of enzymes for livestock feeding has potentially provided another grain treatment option. The application of fibrolytic enzymes to whole grain prior to high-moisture storage or feeding, and their subsequent effect on grain digestibility, require research. The impact of grain characteristics, both physical and chemical, on the response to alkali or enzyme treatment also requires research.

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