scholarly journals Transient to stationary radon ( 220 Rn) emissions from a phonolitic rock exposed to subvolcanic temperatures

2019 ◽  
Vol 6 (10) ◽  
pp. 190782
Author(s):  
Silvio Mollo ◽  
Paola Tuccimei ◽  
Michele Soligo ◽  
Gianfranco Galli ◽  
Gianluca Iezzi ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Chemical Properties ◽  
Rapid Expansion ◽  
Temperature Dependent ◽  
Temperature Changes ◽  
Stress And Deformation ◽  
Preferential Pathways ◽  
Host Rocks ◽  
Physical And Chemical ◽  
Active Volcanoes

Rock substrates beneath active volcanoes are frequently subjected to temperature changes caused by the input of new magma from the depth and/or the intrusion of magma bodies of variable thickness within the subvolcanic rocks. The primary effect of the influx of hot magma is the heating of surrounding host rocks with the consequent modification of their physical and chemical properties. To assess mobilization in subvolcanic thermal regimes, we have performed radon ( 220 Rn) thermal experiments on a phonolitic lava exposed to temperatures in the range of 100–900°C. Results from these experiments indicate that transient Rn signals are not unequivocally related to substrate deformation caused by tectonic stresses, but rather to the temperature-dependent diffusion of radionuclides through the structural discontinuities of rocks which serve as preferential pathways for gas release. Intense heating/cooling cycles are accompanied by rapid expansion and contraction of minerals. Rapid thermal cycling produced both inter- and intra-crystal microfracturing, as well as the formation of macroscopic faults. The increased number of diffusion paths dramatically intensified Rn migration, leading to much higher emissions than temperature-dependent transient changes. This geochemical behaviour is analogous to positive anomalies recorded on active volcanoes where dyke injections produce thermal stress and deformation in the host rocks. An increased Rn signal far away from the location of a magmatic intrusion is also consistent with microfracturing of subsurface rocks over long distances via thermal stress propagation and the opening of new pathways.

Study of Whiskers to be Used in Composite Materials

2021 ◽  
Vol 316 ◽  
pp. 51-55
Author(s):  
Tamara I. Shishelova ◽  
Vadim V. Fedchishin ◽  
Mikhail A. Khramovskih
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Chemical Properties ◽  
High Strength ◽  
Rapid Expansion ◽  
Physical And Chemical Properties ◽  
Reinforcement Fiber ◽  
Object Of Study ◽  
Physical And Chemical ◽  
And Chemical Properties

Rapid expansion of technologies poses higher requirements to structural materials and items made of them. Conventional materials are being replaced by composite materials (composites). Different additives enhancing the properties of initial materials are used as reinforcement fibers of composites. Utilization of micro-and nanosize particles for production of present-day materials is paid much attention to. Whiskers are among such materials. These crystals have high strength, high chemical and temperature resistance. But for rational utilization of whickers of different chemical composition in composite materials one should know their physical and chemical properties. Objectives of the paper: to study physical and chemical properties of whiskers in different compounds, their composition and structure; to prove experimentally the feasibility of utilizing whiskers as a reinforcement fiber of composite materials. Object of study: specimens of whiskers of silicon nitride (Si3N4), aluminum oxide (Al2O3), aluminum nitride (AlN), and mullite (Al6Si2O13). Methods of investigation: thermal study of specimens, study of mechanical properties and chemical strength, and IR-spectroscopy. Results of study: specimens of whiskers have been studied and their mechanical properties have been tabulated for comparison. Extensive thermal investigation was followed by deduction of regularities and identification of chemical properties of whiskers. IR-spectra of whiskers have been studied and conclusions on molecular composition and on presence of impurities in some whiskers have been made.

Some physical and chemical properties of the lettuce seed endosperm

1976 ◽  
Vol 54 (13) ◽  
pp. 1512-1522 ◽  
Author(s):  
Henry L. Speer ◽  
A. I. Hsiao
Keyword(s):  
Fluid Layer ◽  
Chemical Properties ◽  
Strong Acid ◽  
Cellulose Membrane ◽  
Lettuce Seed ◽  
Temperature Dependent ◽  
Strong Base ◽  
Lettuce Seeds ◽  
Physical And Chemical ◽  
Osmotic Activity

Lettuce seeds (Lactuca sativa) are shown to be encased in an osmotically active cellulose membrane derived from the endosperm. The osmotic activity of this membrane is maintained in seeds treated with strong acid (4 M HCl), strong base (4.4 M NaOH), organic solvents, and protein solvents, indicating that there is no contribution of lipid, protein, or living cells to the osmotic properties of the membrane. Only cellulose solvents such as xanthate and cellulase were effective in disrupting the membrane.When dry seeds are treated with 50% solutions of methanol, ethanol, or acetone or with 10 mM HgCl2, they become osmotically distended seeds (ods) as a result of the accumulation of soluble molecules in the fluid layer (EEF) between the membrane and embryo. This process is temperature dependent and appears to require enzymatic activity.The molecular exclusion limit of the ods membrane was measured by osmotic equilibration techniques and was found to be about 300 daltons. This then explains previous observations on the impermeability of lettuce seeds to substances such as actinomycin D (mol. wt. 1255.5) during germination. Molecules of molecular weight greater than about 300 daltons will be excluded until the endospermal barrier is ruptured at about 10–12 h after germination onset.

The dissolution mechanisms of water in silicate melts; a synthesis of recent data

2000 ◽  
Vol 64 (3) ◽  
pp. 389-408 ◽  
Author(s):  
S. C. Kohn
Keyword(s):  
Bulk Composition ◽  
Chemical Properties ◽  
Silicate Melts ◽  
Molecular Water ◽  
Temperature Dependent ◽  
Hydrous Silicate ◽  
Physical And Chemical ◽  
Future Work ◽  
Kinetics Of ◽  
Water Speciation

AbstractDissolved water has significant effects on the physical and chemical properties of silicate melts. Some of the different approaches towards understanding these effects are reviewed here. Spectroscopic measurements on hydrous glasses quenched from melts provide good models for the structure of the melts at the glass transition temperature (Tg). Such measurements suggest that the mechanism of dissolution of water in silicate melts varies strongly with the bulk composition. In particular framework aluminosilicate compositions seem to have very different dissolution mechanisms from Al-free compositions. The water speciation reactions are temperature dependent, with some of the molecular water which is present in glasses at room temperature being converted to hydroxyl at high temperatures. This conversion probably occurs only above Tg. Data on the kinetics of the speciation reaction and the dynamics of microscopic processes in hydrous silicate melts are also discussed. Finally some important aims of future work on hydrous silicate melts are suggested

Modeling Changes in Internal Pressure During the Solidification of Hydrous Granitic Intrusives: Implications for the Crystallization of Miarolitic Pegmatites

2021 ◽  
Author(s):  
Issac J. Jacques ◽  
Alan J. Anderson
Keyword(s):  
Internal Pressure ◽  
Fluid Pressure ◽  
Chemical Properties ◽  
Alkali Feldspar ◽  
Aqueous Fluid ◽  
The Body ◽  
Melt And Fluid Inclusions ◽  
Host Rocks ◽  
Physical And Chemical ◽  
Residual Melt

ABSTRACT Volatile exsolution is widely recognized as an important trigger for eruptions from shallow magma reservoirs, but relatively few studies quantify the effects of exsolution on internal pressure within deeper-seated intrusive bodies. We present a model to predict internal pressure changes during the crystallization of a haplogranite melt containing 3 and 5 mass % H2O and with an emplacement pressure of 200 MPa. Mass and volume relations between phases are used to determine internal pressure assuming a closed, constant-volume system. The results indicate that initial crystallization of alkali feldspar and quartz causes a decrease in pressure prior to the exsolution of an aqueous fluid from the residual melt (i.e., resurgent boiling). Further crystallization toward the core of the body in the presence of a separate volatile phase results in a sharp increase in internal pressure. Our model shows that in closed, isochoric systems, the crystallization of the H2O-saturated melt will generate internal pressures that greatly exceed emplacement pressures typical of miarolitic pegmatites. Extreme overpressure modifies the physical and chemical properties of the residual melt and coexisting aqueous fluid, which in turn influences crystallization kinetics and the development of primary textures. Primary melt and fluid inclusions in pocket minerals thus likely represent samples trapped at various pressures in a rapidly evolving melt–fluid system. In most pegmatites, increasing fluid pressure and the formation of large pockets is regulated by the permeability and tensile strength of the enclosing rock. This explains why many miarolitic pegmatites occur within rigid host rocks such as granite, gabbro, and gneiss.

scholarly journals Agate Genesis: A Continuing Enigma

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 953 ◽  
Author(s):  
Terry Moxon ◽  
Galina Palyanova
Keyword(s):  
Amorphous State ◽  
Chemical Properties ◽  
Experimental Investigations ◽  
Scientific Instrumentation ◽  
Silica Source ◽  
Multi Stage ◽  
Stage Process ◽  
Host Rocks ◽  
Physical And Chemical ◽  
And Chemical Properties

This review covers the last 250 years of major scientific contributions on the genesis of agates found in basic igneous host rocks. From 1770 to 1955, the genesis question was frequently limited to discussions based on observations on host rock and agate thick sections. Over the next 25 years, experimental investigations examined phase transformations when silica glass and various forms of amorphous silica were heated to high temperatures. This work demonstrated that the change from the amorphous state into chalcedony was likely to be a multi-stage process. The last 40 years has seen modern scientific instrumentation play a key role in identifying the physical and chemical properties of agate. The outcome of this work has allowed limited evidence-based comment on the conditions of agate formation. There is a general consensus that agates in these basic igneous hosts form at <100 °C. However, the silica source and the nature of the initial deposit remain to be proven.

Statistical criteria of stellar population types

1966 ◽  
Vol 24 ◽  
pp. 101-110
Author(s):  
W. Iwanowska
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Spectrophotometric Study ◽  
Physical And Chemical Properties ◽  
Population Type ◽  
The Galaxy ◽  
Distribution Parameters ◽  
Physical And Chemical ◽  
Statistical Criteria ◽  
And Chemical Properties

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.

Biophysical Measurement of Molecular Weight of Foot-and-Mouth Disease RNA Fragments

1974 ◽  
Vol 32 ◽  
pp. 262-263
Author(s):  
Sydney S. Breese ◽  
Howard L. Bachrach
Keyword(s):  
Chemical Properties ◽  
Foot And Mouth Disease ◽  
Mouth Disease ◽  
Distilled Water ◽  
Bovine Plasma ◽  
Mouth Disease Virus ◽  
Foot And Mouth ◽  
Carbon Coated ◽  
Rna Fragments ◽  
Physical And Chemical

Continuing studies on the physical and chemical properties of foot-and-mouth disease virus (FMDV) have included electron microscopy of RNA strands released when highly purified virus (1) was dialyzed against demlneralized distilled water. The RNA strands were dried on formvar-carbon coated electron microscope screens pretreated with 0.1% bovine plasma albumin in distilled water. At this low salt concentration the RNA strands were extended and were stained with 1% phosphotungstic acid. Random dispersions of strands were recorded on electron micrographs, enlarged to 30,000 or 40,000 X and the lengths measured with a map-measuring wheel. Figure 1 is a typical micrograph and Fig. 2 shows the distributions of strand lengths for the three major types of FMDV (A119 of 6/9/72; C3-Rezende of 1/5/73; and O1-Brugge of 8/24/73.

Tailoring microstructures of materials through biomimetics

1993 ◽  
Vol 51 ◽  
pp. 500-501
Author(s):  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Chemical Properties ◽  
Design And Synthesis ◽  
Structure Sensitive ◽  
Macro Scale ◽  
Methods Of Synthesis ◽  
Successive Level ◽  
Engineering Materials ◽  
Physical And Chemical ◽  
And Chemical Properties ◽  
Synthesis Of Materials

Biomimetics involves investigation of structure, function, and methods of synthesis of biological composite materials. The goal is to apply this information to the design and synthesis of materials for engineering applications.Properties of engineering materials are structure sensitive through the whole spectrum of dimensions from nanometer to macro scale. The goal in designing and processing of technological materials, therefore, is to control microstructural evolution at each of these dimensions so as to achieve predictable physical and chemical properties. Control at each successive level of dimension, however, is a major challenge as is the retention of integrity between successive levels. Engineering materials are rarely fabricated to achieve more than a few of the desired properties and the synthesis techniques usually involve high temperature or low pressure conditions that are energy inefficient and environmentally damaging.In contrast to human-made materials, organisms synthesize composites whose intricate structures are more controlled at each scale and hierarchical order.

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