Magnetic hysteresis of magnetite, pyrrhotite and hematite at high temperature

2020 ◽  
Author(s):  
David J Dunlop
Keyword(s):  
Curie Point ◽  
Domain Walls ◽  
Magnetic Hysteresis ◽  
Ambient Temperatures ◽  
The Earth ◽  
Structure Changes ◽  
Permanent Memory ◽  
Almost All ◽  
Saturation Remanence ◽  
Iron Bearing

Summary The magnetic properties of iron-bearing minerals at above ambient temperatures control their magnetic expression at depth in the Earth and other planets, as well as the permanent memory they retain as thermoremanence or thermochemical remanence when brought to the surface and cooled. This paper reports magnetic hysteresis parameters measured at temperatures up to the Curie point TC for natural pyrrhotite and hematite and for suites of sized magnetites, both natural and synthesized. Domain structure changes can be inferred from the ratio of saturation remanence Mrs to saturation magnetization Ms In almost all magnetites and pyrrhotites studied, Mrs decreases more rapidly with increasing measurement temperature T than Ms, indicating thermal unblocking or vortex development in single-domain grains and addition or remobilization of domain walls at high T in multidomain grains. During cooling of a rock, iron minerals might then denucleate domains or vortices. Coercive force Hc, a measure of stability against changing magnetic fields, also decreases with increasing measurement T, usually at a rate similar to that of Mrs, but often retains a finite value near the Curie point.

Magnetic hysteresis of 0.6–110 μm magnetites across the Verwey transition

2019 ◽  
Vol 56 (9) ◽  
pp. 958-972 ◽  
Author(s):  
David J. Dunlop ◽  
Özden Özdemir ◽  
Song Xu
Keyword(s):  
Magnetic Hysteresis ◽  
Magnetic Domain ◽  
Hysteresis Loops ◽  
Single Domain ◽  
Magnetic Domains ◽  
Verwey Transition ◽  
Electron Microscopic ◽  
Structure Changes ◽  
Saturation Remanence ◽  
Major Domain

We report saturation magnetization, Ms, saturation remanence, Mrs, coercive force, Hc, and remanence coercivity, Hcr, as a function of grain size, d, and temperature, T, for 0.6–135 μm magnetites. Five annealed and four unannealed samples were measured at 5–10 K intervals from 300 to 20 K. Mrs and Hc increase by factors of 1.5–4 in cooling through the Verwey transition (TV ≈ 120 K) and by smaller amounts around 50 K. Hysteresis properties change continuously over ≈20 K below TV or for annealed 0.6, 3, and 6 μm grains, within ≈10 K below TV. Hc(d) changes for annealed magnetites from ∼d–0.5 at 300 K to ∼d–0.6–d–0.7 at 120–130 K to ∼d–0.3 at 80–100 K. Day plots of Mrs(T)/Ms(T) versus Hcr(T)/Hc(T) indicate major domain structure changes with T, e.g., 6 μm grains change from large pseudo-single-domain (PSD) at 300 K to multidomain (MD) just above TV and return to PSD below TV, evolving to higher Mrs and Hc down to 20 K. Hysteresis loops change from normal at 300 K to slightly constricted near TV to severely constricted below 50 K. We interpret these results in the light of electron microscopic observations by Kasama et al. (2010 , 2012) . Hardening of magnetic hysteresis below TV and the evolution from MD to PSD, and even to single-domain in the finest grains, results from subdivision of grains by monoclinic twinning, reduced magnetic domain sizes in monoclinic magnetite, and confinement of magnetic domains within twin domains. Constricted hysteresis loops indicate coexisting magnetically hard and soft phases, initially growing monoclinic regions and residual cubic magnetite.

scholarly journals Phase separation during blood spreading

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Houssine Benabdelhalim ◽  
David Brutin
Keyword(s):  
Phase Separation ◽  
Relative Humidity ◽  
Whole Blood ◽  
Crime Scene ◽  
Blood Pool ◽  
Ambient Temperatures ◽  
Surrounding Environment ◽  
Crime Scene Investigators ◽  
Almost All ◽  
Pool Area

AbstractBlood pools can spread on several types of substrates depending on the surrounding environment and conditions. Understanding the influence of these parameters on the spreading of blood pools can provide crime scene investigators with useful information. The focus of the present study is on phase separation, that is, when the serum spreads outside the main blood pool. For this purpose, blood pools with constant initial masses on wooden floors that were either varnished or not were created at ambient temperatures of $$21~^{\circ }\hbox {C}$$ 21 ∘ C , $$29~^{\circ }\hbox {C}$$ 29 ∘ C , and $$37~^{\circ }\hbox {C}$$ 37 ∘ C with a relative humidity varying from 20 to 90%. The range $$21~^{\circ }\hbox {C}$$ 21 ∘ C to $$37~^{\circ }\hbox {C}$$ 37 ∘ C covers almost all worldwide indoor cases. The same whole blood from the same donor was used for all experiments. As a result, an increase in relative humidity was found to result in an increase in the final pool area. In addition, at the three different experimental temperatures, the serum spread outside the main pool at relative humidity levels above 50%. This phase separation is more significant on varnished substrates, and does not lead to any changes in the drying morphology. This phenomenon is explained by the competition between coagulation and evaporation.

Stars and stripes. Nanoscale misfit dislocation patterns on surfaces

2002 ◽  
Vol 74 (9) ◽  
pp. 1663-1671 ◽  
Author(s):  
Raghani Pushpa ◽  
Shobhana Narasimhan
Keyword(s):  
Surface Structure ◽  
Misfit Dislocation ◽  
Domain Walls ◽  
Chemical Potential ◽  
Model System ◽  
Misfit Dislocations ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Structure Changes ◽  
Face Centered

Close-packed metal surfaces and heteroepitaxial systems frequently display a structure consisting of regularly spaced misfit dislocations, with a network of domain walls separating face-centered cubic (fcc) and hexagonal close-packed (hcp) domains. These structures can serve as templates for growing regularly spaced arrays of nanoislands. We present a theoretical investigation of the factors controlling the size and shape of the domains, using Pt(111) as a model system. Upon varying the chemical potential, the surface structure changes from being unreconstructed to the honeycomb, wavy triangles, "bright stars", or Moiré patterns observed experimentally on Pt(111) and other systems. For the particular case of Pt(111), isotropically contracted star-like patterns are favored over uniaxially contracted stripes.

The Earth Scientist’s Periodic Table of the Elements and Their Ions: A New Periodic Table Founded on Non-Traditional Concepts

2018 ◽  
Author(s):  
L. Bruce Railsback
Keyword(s):  
Periodic Table ◽  
General Concept ◽  
First Century ◽  
Arid Environments ◽  
Geological Society ◽  
The Earth ◽  
Science Stories ◽  
Science News ◽  
Almost All ◽  
Scientific Fields

The Earth Scientist’s Periodic Table of the Elements and Their Ions is a fundamentally new table that was first published in 2003 in the Geological Society of America’s (GSA) prominent journal Geology (Railsback 2003). The new table was reported in Nature, it was featured in a cover article by Science News, it was included among Discover magazine’s 100 Top Science Stories of 2003, and its publication was noted in many other magazines and online outlets. GSA sold a large number of reprints of the 2003 paper and then, in 2004, published a revised version of the table in GSA’s Map and Chart Series (Railsback 2004). When GSA’s printed stock ran low, the Society published a further revised version of the table in its Map and Chart Series in 2011 (Railsback 2011). The table has been translated into Chinese (Jin 2006), Spanish (Bernal and Railsback 2008), Portuguese (Franco de Souza Lima and Railsback 2012), and German. The original 2003 paper has been cited in journals ranging from Journal of Mathematical Chemistry to Carbohydrate Research to Geomicrobiology Journal to Journal of Arid Environments to Resource Geology to Reviews in Geophysics, and it has proven useful in understanding the topology of the periodic table (Restrepo et al. 2006). The success of the new Earth Scientist’s Periodic Table of the Elements and Their Ions across the past decade suggests that the periodic table, as a general concept, is not a static document but instead is still subject to evolution, especially as scientific fields beyond traditional chemistry increasingly use chemical perspectives. It further suggests that volumes like this one are not simply retrospective ruminations on a nineteenth-century invention, but instead they can be part of an ongoing process to find new meaning in the periodic concept and to make it more applicable in broader contexts in the twenty-first century. Despite the diversity of periodic tables produced over the last 140 years (e.g., Mazurs 1974), the Earth Scientist’s Periodic Table of the Elements and Their Ions differs both in conceptual origin and in form from almost all previous versions.

scholarly journals Experimental evidence for silica-enriched Earth’s lower mantle with ferrous iron dominant bridgmanite

2020 ◽  
Vol 117 (45) ◽  
pp. 27899-27905
Author(s):  
Izumi Mashino ◽  
Motohiko Murakami ◽  
Nobuyoshi Miyajima ◽  
Sylvain Petitgirard
Keyword(s):  
Sound Velocity ◽  
Lower Mantle ◽  
Mantle Convection ◽  
Brillouin Scattering ◽  
Seismic Structure ◽  
The Earth ◽  
Diamond Anvil ◽  
Evolution Dynamics ◽  
Iron Bearing

Determination of the chemical composition of the Earth’s mantle is of prime importance to understand the evolution, dynamics, and origin of the Earth. However, there is a lack of experimental data on sound velocity of iron-bearing Bridgmanite (Brd) under relevant high-pressure conditions of the whole mantle, which prevents constraints on the mineralogical model of the lower mantle. To uncover these issues, we have conducted sound-velocity measurement of iron-bearing Brd in a diamond-anvil cell (DAC) up to 124 GPa using Brillouin scattering spectroscopy. Here we show that the sound velocities of iron-bearing Brd throughout the whole pressure range of lower mantle exhibit an apparent linear reduction with the iron content. Our data fit remarkably with the seismic structure throughout the lower mantle with Fe2+-enriched Brd, indicating that the greater part of the lower mantle could be occupied by Fe2+-enriched Brd. Our lower-mantle model shows a distinctive Si-enriched composition with Mg/Si of 1.14 relative to the upper mantle (Mg/Si = 1.25), which implies that the mantle convection has been inefficient enough to chemically homogenize the Earth’s whole mantle.

scholarly journals Investigation of GPS draconitic year effect on GPS time series of eliminated eclipsing GPS satellite data

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
A. Allahverdi-zadeh ◽  
J. Asgari ◽  
A.R. Amiri-Simkooei
Keyword(s):  
Time Series ◽  
Original Position ◽  
Year Effect ◽  
The Earth ◽  
Gps Satellites ◽  
Position Time Series ◽  
The Difference ◽  
Original Time ◽  
Almost All ◽  
New Time

AbstractGPS draconitic signal (351.6 ± 0.2 days) and its higher harmonics are observed at almost all IGS products such as position time series of IGS permanent stations. Orbital error and multipath are known as two possible sources of these signals. The effect of Earth shadow crossing of GPS satellites is another suspect for this signal. Up to now there is no serious attempt to investigate this dependence. AMATLAB toolbox is developed and used to determine the satellites located at the earth shadow. RINEX observation files and precise ephemeris are imported to the toolbox and a cylindrical model is used to detect the shadow regions. Data of these satellites were removed from the RINEX observation files of three IGS permanent stations (GRAZ,ONSAandWSRT) and new RINEX observation fileswere created. The time span of these data is about 11 years. The new and original fileswere then processed using precise point positioning (PPP) method to determine position time series, for further analysis. Both the original and new time series were analyzed using the least squares harmonic estimation (LS-HE) in the following steps. The 1st step is the validation of the draconitic harmonics signature in the original position time series of the three stations. The 2nd step does the same for the new time series. It confirms that the power spectrum at the draconitic signals decreases to some extent for the new time series. The difference between the original and new time series (difference between all three position quantity (X, Y and Z)) is then analyzed in the 3rd step. Signature of the draconitic harmonics is also observed to the differences. The results represent that all eight harmonics of GPS draconitic period do exist at the residuals and mainly they decrease. All of the three stations were then processed together using the multivariate LS-HE method. At the 4th step, the difference of the spectral values between the original time series and new times serieswere analyzed. Decreasing of the spectral values at most harmonics (e.g. 1st, 2nd, 4th, 6th, 7th and 8th) represents the effect of removing satellite observations at shadow of the earth on draconitic harmonics. At least, five harmonics among seven shows the amelioration of results (draconitic error reduction) after removing the earth shadowed data from RINEX raw data. The results show that the draconitic year’s component of data is in part due to eclipsing satellites.

scholarly journals In situ Investigations from Spinels under high pressure and high Temperatures

2014 ◽  
Vol 70 (a1) ◽  
pp. C398-C398
Author(s):  
Michael Wehber ◽  
Frank Schilling ◽  
Christian Lathe ◽  
Hans Mueller
Keyword(s):  
High Pressure ◽  
Volume Change ◽  
X Ray Diffraction ◽  
Ambient Temperatures ◽  
The Earth ◽  
Deep Interior ◽  
State Apparatus ◽  
Temperature And Pressure ◽  
Murnaghan Equation

Spinels seem to be important constituents of the deep interior of the Earth while transition with spinel or pseudospinel structure strongly influence the dynamic of the mantle. On the other hand, spinels are widely used as artificial material. The spinels Magnetite, Franklinite, and Gahnite are investigated at the Hamburger Synchrotron Laboratory (HASYLAB) at Hamburg. The experiments were carried out using the high pressure multi anvil devices MAX80 (F2.1 Beamline) and MAX200x (W2 Beamline). The MAX80 is a single state apparatus located at a bending magnet, MAX200x is a double state system located at a wiggler. Energy-dispersive X-ray diffraction in combination with Rietveld refinement [1, 2] was used to determine the pressure and temperature induced volume change. Isothermal experiments were performed up to 15 GPa at ambient temperature. The temperature and pressure dependent volume change were derived from compression experiments using MAX80 apparatus up to 5 GPa at temperatures of 298, 500, 700, 900 and 1100 K. Bulk moduli at ambient temperatures using a Birch-Murnaghan equation of state result in KT=184(7) GPa with K'=4.5(2) for Magnetite, KT =178(6) with K'=4.6(4) for Franklinite, and KT =204(9) with K'=4.9(6) for Gahnite.

scholarly journals PESTICIDE USE AND ITS IMPACTS ON HUMAN HEALTH AND ENVIRONMENT

2020 ◽  
Vol 4 (1) ◽  
pp. 47-51
Author(s):  
Suraj Poudel ◽  
Bikash Poudel ◽  
Birochan Acharya ◽  
Puspa Poudel
Keyword(s):  
Human Health ◽  
Management Practices ◽  
Pesticide Use ◽  
Journal Articles ◽  
Research Papers ◽  
Safe Production ◽  
The Earth ◽  
Long Run ◽  
Almost All ◽  
Chemical Pesticides

Every lay farmer as well the commercial growers use chemical pesticides to kill pests and weeds and to get rid of diseases in their farm with aim of increasing production. Though the use of pesticides has some advantages of increase in yield, its haphazard and excessive use also create a serious impact on the environmental components and human health. The present scenario of pesticide use doesn’t seem to be satisfactory, so-called safe pesticides are also showing their ill effects in the long run and the problems such as bio-accumulation, bio-magnification are being magnified day after day. Almost all the corners of the earth and organisms living in it and those who are yet to be born have already been affected by so-called boons to pest control. This study attempts to study the present pesticides use scenario of Nepal and also the ill-effects of pesticides on human health as well as on the environment. The relevant data and information were collected from the thorough study of the journal articles, research papers, reports and various literatures. This paper pleads and sensitizes the readers to get directed toward more holistic, sustainable, natural and safe production and management practices.

scholarly journals THE LAW OF INTERMITTENT EVOLUTION AND SELF-HEALING OF THE LIVING NATURE OF EARTH

2020 ◽  
Vol 3 (9(78)) ◽  
pp. 36-43
Author(s):  
A. Tetior
Keyword(s):  
Self Healing ◽  
Mass Extinctions ◽  
Mass Destruction ◽  
Information Base ◽  
Technological Revolution ◽  
The Earth ◽  
Biodiversity Restoration ◽  
Living Nature ◽  
Almost All ◽  
First Time

The living nature of the Earth has an amazing property: its evolution is intermittent, it develops in separate stages, with the mass destruction of a large part of wildlife at the end of each stage, and with the subsequent selfhealing of almost all biodiversity for hundreds of thousands or millions of years. Self-healing was due to the presence of an information base - preserved wildlife. Several major natural mass extinctions of animals and plants are known, apparently related to volcanism, space influences, etc. After mass extinctions inevitably followed periods of biodiversity restoration. This development is in line with the author's concept of branching development. Therefore, the tree of evolution is multi-tiered, step-by-step. Extinctions served as natural filters, stopping the development of unpromising species, and supporting the emergence and development of promising species. But the coming period of man-made extinction is fundamentally different from the previous ones in that there used to be a base for biodiversity restoration - natural nature. For the first time, large man-made changes in the Earth's landscapes occurred in the last 150 - 200 years, during the scientific - technological revolution; they're in a good place ...in the components of landscapes ((e.g., the vital composition of air, water, extreme foresting, the limit of the development of nature, etc.).

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