Role Of Quartz Research Articles

The effect of mineralogy and textural characteristics on the strength of crystalline igneous rocks using image-based textural quantification

The attempts made to understand and quantify the relationship between rock texture and engineering properties have been accompanied by some ambiguities and uncertainties, and the majority of the approaches, though focusing on particular rock types, have not been so successful for even the same rock types from other regions. This study, therefore, was aimed to investigate the relationship between the texture and strength properties of a wide range of crystalline igneous rocks along with more aspects of textural analysis. For this purpose, fifteen fresh samples of crystalline igneous rocks belonging to the stone quarries of the NW Iran were collected and subjected to compressive and tensile strength tests (UCS and BTS). Thin sections of the samples were used to prepare the full mosaic image layers in three different optical conditions. About 18,000 mineral grains were manually traced on the processed images and the obtained vector data was used for the quantification of various textural parameters including size metrics, shape descriptors, microfabric indices and mineral content. Different phase considerations (full-phasic, monophasic, multiphasic and phase-ratio) were applied to derive the textural characteristics of the individual and multiple minerals and their proportional ratio. Finally, simple linear regression analysis was performed to evaluate the relationship between the texture and strength properties. The results indicated that the newly developed quartz to feldspar size ratio (QFSR) indicator was the only textural parameter that could be significantly correlated with both compressive and tensile strength in a wide range of rock types. The results also highlighted the fact that the role of quartz and feldspar encountered with different rock failure mechanisms could be different; In fact, the tensile strength was obviously affected by the size and content of K-feldspar, while the compressive strength showed a more complicated mechanism and seemed to be controlled by the interference effects of plagioclase and quartz textural properties. Furthermore, the study indicated that the influence of grain size on the rock strength was more important than the grain shape or mineral content.

Correlation analysis between expression of NF-κB and quartz's deposit in non-small cell lung cancer in Xuanwei, Yunnan province

Objective To evaluate the relationship between quartz's deposit and expression of NF-κB in non-small cell lung cancer (NSCLC) lung tissues in Xuanwei, Yunnan Province, and to clarify the role of quartz in Xuanwei NSCLC's carcinogenic mechanism. Methods As research objects, the lung tissues of NSCLC and lung benign lesions after surgical resection were collected from July 2009 to September 2015 at the Third Affiliated Hospital of Kunming Medical University. Firstly, the transmission electron microscopic (TEM) with energy dispersive X-ray analyzer (EDS) was used for observation of crystalline deposit and local pathological changes. Secondly, expression level of NF-κB had been analysed and a correlation analysis with particle size of SiO2 crystal in the same lung sample was made. Results The occurrence rates of quartz in Xuanwei NSCLC lung tissues were above non-Xuanwei NSCLC and benign lung tissues (P 0.05). The expression level of NF-κB was generally increasing when quartz's size became smaller. Conclusion Quartz's deposit may play a certain role in carcinogenic mechanism of lung cancer in Xuanwei, the smaller the particle size, the greater the cytotoxicity. Key words: Carcinoma, non-small-cell lung; Quartz; NF-kappa B

Heterogeneous ice nucleation on dust particles sourced from nine deserts worldwide – Part 1: Immersion freezing

Abstract. Desert dust is one of the most abundant ice nucleating particle types in the atmosphere. Traditionally, clay minerals were assumed to determine the ice nucleation ability of desert dust and constituted the focus of ice nucleation studies over several decades. Recently some feldspar species were identified to be ice active at much higher temperatures than clay minerals, redirecting studies to investigate the contribution of feldspar to ice nucleation on desert dust. However, so far no study has shown the atmospheric relevance of this mineral phase.For this study four dust samples were collected after airborne transport in the troposphere from the Sahara to different locations (Crete, the Peloponnese, Canary Islands, and the Sinai Peninsula). Additionally, 11 dust samples were collected from the surface from nine of the biggest deserts worldwide. The samples were used to study the ice nucleation behavior specific to different desert dusts. Furthermore, we investigated how representative surface-collected dust is for the atmosphere by comparing to the ice nucleation activity of the airborne samples. We used the IMCA-ZINC setup to form droplets on single aerosol particles which were subsequently exposed to temperatures between 233 and 250 K. Dust particles were collected in parallel on filters for offline cold-stage ice nucleation experiments at 253–263 K. To help the interpretation of the ice nucleation experiments the mineralogical composition of the dusts was investigated. We find that a higher ice nucleation activity in a given sample at 253 K can be attributed to the K-feldspar content present in this sample, whereas at temperatures between 238 and 245 K it is attributed to the sum of feldspar and quartz content present. A high clay content, in contrast, is associated with lower ice nucleation activity. This confirms the importance of feldspar above 250 K and the role of quartz and feldspars determining the ice nucleation activities at lower temperatures as found by earlier studies for monomineral dusts. The airborne samples show on average a lower ice nucleation activity than the surface-collected ones. Furthermore, we find that under certain conditions milling can lead to a decrease in the ice nucleation ability of polymineral samples due to the different hardness and cleavage of individual mineral phases causing an increase of minerals with low ice nucleation ability in the atmospherically relevant size fraction. Comparison of our data set to an existing desert dust parameterization confirms its applicability for climate models. Our results suggest that for an improved prediction of the ice nucleation ability of desert dust in the atmosphere, the modeling of emission and atmospheric transport of the feldspar and quartz mineral phases would be key, while other minerals are only of minor importance.

The role of quartz in Neolithic lithic traditions: a case study from the Thornhill Early Neolithic palisaded enclosure, Co. Londonderry, Northern Ireland

The role of quartz in Neolithic lithic traditions: a case study from the Thornhill Early Neolithic palisaded enclosure, Co. Londonderry, Northern Ireland

The role of quartz in Neolithic lithic traditions: a case study from the Thornhill Early Neolithic palisaded enclosure, Co. Londonderry, Northern Ireland

The role of quartz in Neolithic lithic traditions: a case study from the Thornhill Early Neolithic palisaded enclosure, Co. Londonderry, Northern Ireland

Controls on solid-phase inclusion during porphyroblast growth: insights from the Barrovian sequence (Scottish Dalradian)

A series of Barrovian sequence samples ranging from garnet to sillimanite zones were investigated to infer their porphyroblast-forming reactions and mineral inclusion histories. Quartz is overgrown and partly consumed during garnet formation and remains as inclusion-rich layers in porphyroblasts of the garnet zone. Staurolite crystals in the staurolite zone display sharp transitions between inclusion-rich and inclusion-free areas, suggesting two stages of growth with a different role of quartz in each. The inclusion-rich domains formed similarly to those in garnet by simple overgrowth and resorption of matrix minerals, with thermodynamic constraints suggesting that this staurolite-forming reaction required the presence of chloritoid that is now absent from the examined samples. The participation of garnet was limited in staurolite formation, with chloritoid breakdown supplying sufficient material to form the large amounts (c. 25 vol%) of staurolite found in the rock. This reaction produces an excess of SiO2, which leaves the crystal domain as SiO2aq and thus caused the formation of the inclusion-free areas in the staurolite and precipitation of quartz in the matrix. In the sillimanite zone, staurolite is consumed forming new garnet. The newly formed garnet has less quartz inclusions than its core due to a proportionally greater consumption of quartz by the second garnet-forming reaction than by the initial, garnet-grade reactions. Textural and thermodynamic data both suggest that inclusions in these porphyroblasts represent leftovers of a preferentially overgrown matrix than co-products of the porphyroblast-forming reaction.

Synthesis and Characterization of Maillard Compounds Formed under Sterile Conditions on Sand‐ and Silt‐Sized Mineral Substrates

Maillard compounds were synthesized from D‐glucose and glycine to mimic the separation of particles during a volcanic eruption so that the role of quartz and volcanic ash, fractionated into silt‐ and sand‐size particles, could be tested under sterile conditions. The obtained polymers were separated into two fractions of 1000–8000 and >8000 Daltons. The results evidence the formation of humus‐like polymers from simple compounds and show the importance of substrate mineralogy. Specifically, a) humic‐like polymers can form in the absence of microbial life, b) the role of particle size is important, c) mineral substrates enhance their yields, d) the polymers on volcanic ash and quartz show differences, e) their structure changes with time, f) at the end of the experiments there is an increase of unsaturation while the aliphaticity decreases, and g) the yields of the compounds of 1000–8000 Daltons decrease with time unlike those >8000.

Declining soil quality in South Africa: effects of land use on soil organic matter and surface crusting

Soil conservation in South Africa has historically focussed on preventing soil erosion. Effective maintenance of the soil resource requires, in addition to erosion control, an understanding of how land use practices affect more subtle indicators of soil quality. This review outlines how land use in South Africa can rapidly result in a marked reduction in soil organic matter (SOM) content and a greater tendency of soils to crust. Removal of a cover of vegetation whether by ploughing, grazing or burning tends to reduce SOM due to reduced organic matter inputs and enhanced soil microbe activity. Loss of SOM, particularly from the top few centimetres of soil (named here the pedoderm) has a disproportionately large effect on soil infiltrability and nutrient supply. The mineralogy of the clay fraction also has great bearing on the response of soil to land use effects. The unexpected role of quartz in soil dispersion and crusting in South Africa has only recently been unveiled. Apart from SOM effects, land use can lead to subtle changes in soil chemistry. Plantation forestry has resulted in an increase in soil nitrate in many areas, possibly due to greater mineralisation under forests than grasslands. Annual burning in the Kruger National Park bushveld has been shown to increase clay dispersibility and crusting of the pedoderm, which was ascribed to a reduction in electrical conductivity and SOM as well as an increase in the exchangeable sodium percentage. Soil quality is a multifaceted concept. One aspect stands out, however, as critical and that is the conservation and replenishment of nitrogen which is all important for retaining humus and maintaining soil quality.

The role of quartz in the origin of optical activity on earth.

A thorough analysis of literature data on distribution of right and left quartz in many locations on the surface of Earth indicates that quartz enantiomorph crystals are distributed in equal amounts in all locations. Therefore optically active quartz crystals of one or the other enantiomorph could not serve as the source of homochirality in the evolution of biosphere. Hence the calculation of a PVED based on published 'small excess of left quartz crystals' on Earth lacks a sound physical basis.

The role of quartz- and coal mine dust induced mediators from human macrophages in pathogenesis of silicosis

The role of quartz- and coal mine dust induced mediators from human macrophages in pathogenesis of silicosis

The role of quartz in the development of coal workers' pneumoconiosis.

The role of quartz in the development of coal workers' pneumoconiosis.

Amphibole Paragenesis in the Birrimian series of the Winneba district of Ghana

The rocks of the Birrimian Series in the Winneba District of Ghana have been progressively metamorphosed during the emplacement of the early and late orogenic granitic masses. The “Z” axial colours of the amphiboles generated in the hypabyssal and extrusive rocks of the Series can be broadly correlated with the grade of metamorphism as indicated by the mineral assemblages. A possible classification for amphibolites is discussed and the role of quartz indicated.