scholarly journals Climatic control on the occurrence of high-coercivity magnetic minerals and preservation of greigite in a 640 ka sediment sequence from Lake Ohrid (Balkans)

2015 ◽  
Vol 12 (16) ◽  
pp. 14215-14243 ◽  
Author(s):  
J. Just ◽  
N. Nowaczyk ◽  
A. Francke ◽  
L. Sagnotti ◽  
B. Wagner
Keyword(s):  
Time Scales ◽  
Environmental Conditions ◽  
Strong Relationship ◽  
Magnetic Mineral ◽  
High Coercivity ◽  
Lake Ohrid ◽  
Magnetic Minerals ◽  
High Concentration ◽  
Magnetic Studies ◽  
Summer Insolation

Abstract. The bulk magnetic mineral record from Lake Ohrid, spanning the past ca. 640 ka, shows a strong relationship to environmental conditions on glacial–interglacial and millennial time scales. During extremely cold glacials, a lower accumulation of organic matter and likely enhanced mixing of the water-column coincides with the presence of greigite, whereas greigite is absent in sediments deposited during less severe glacials. Those "non-greigite" glacial sediments are characterized by high concentration of high-coercivity magnetic minerals, which relates to enhanced erosion of soils that had formed during the preceding interglacials. In contrast, magnetite dominated magnetic mineral assemblages characterize interglacial deposits and most likely originate from detrital particles of physically weathered rocks. Superimposed on the glacial–interglacial behavior are millennial scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Likewise to the process on glacial–interglacial time-scales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both, environmental conditions on land and intra-lacustrine processes.

scholarly journals Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans)

2016 ◽  
Vol 13 (7) ◽  
pp. 2093-2109 ◽  
Author(s):  
Janna Just ◽  
Norbert R. Nowaczyk ◽  
Leonardo Sagnotti ◽  
Alexander Francke ◽  
Hendrik Vogel ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Environmental Control ◽  
Magnetic Mineral ◽  
High Coercivity ◽  
Water Volume ◽  
Iron Sulfides ◽  
Lake Ohrid ◽  
Magnetic Minerals ◽  
The Core ◽  
Summer Insolation

Abstract. The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial–interglacial and millennial timescales. A shift in the formation of early diagenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before  ∼  320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe / Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high- to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial–interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial–interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes.

EFFECT OF MEAN ION SIZE AND SPATIAL SPIN DISORDERS FOR (La1-xYx)2/3Ca1/3MnO3 MANGANITES

2004 ◽  
Vol 18 (26) ◽  
pp. 3451-3464 ◽  
Author(s):  
JINCANG ZHANG ◽  
YUFENG ZHANG ◽  
SHIXUN CAO ◽  
CHAO JING
Keyword(s):  
Single Phase ◽  
Bond Angle ◽  
Gradual Increase ◽  
High Concentration ◽  
Magnetic Studies ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Average Ionic Radius ◽  
Lower Temperature ◽  
Ion Size

The structure and transport properties of perovskite ( La 1-x Y x)2/3 Ca 1/3 MnO 3 (0≤x≤0.3) systems are systematically investigated. It is found that all the specimens show a single-phase structure and reveal a direct relationship between the Curie temperature Tc and the average ionic radius <rA> of La site. With increasing Y 3+ doped content, the metal-insulator transition temperature T MI (M-I) shifts to lower temperature. While the relevant resistivity peak ρp is sharp increased, for the specimens with large doping content, x=0.3, it has enhanced eight orders of magnitudes larger than the non-doped samples (x=0.0). At high concentration area, that is to say, when x>0.1, magnetic studies show a gradual increase of antiferromagnetic interaction with an increase of x, ultimately leading to a spatial-spin disorders, that is, spin-glass-like state for x=0.2 and x=0.3 compounds at about 35 K. The results show that it has connected a reduction of Tc and an increase in magnetoresistance with a decrease in the microstructural Mn - O - Mn bond angle.

Analysis of Strong-Field Hysteresis in High Coercivity Magnetic Minerals

2019 ◽  
pp. 127-142 ◽  
Author(s):  
A. Kosterov ◽  
E. S. Sergienko ◽  
A. G. Iosifidi ◽  
P. V. Kharitonskii ◽  
S. Yu. Yanson
Keyword(s):  
Strong Field ◽  
High Coercivity ◽  
Magnetic Minerals

scholarly journals Relationship of Personal Hygiene and Environmental Conditions with Complaints of Skin Disease

2021 ◽  
Vol 4 (1) ◽  
pp. 90-101
Author(s):  
Sumantri Alikhan Sains
Keyword(s):  
Environmental Conditions ◽  
Skin Diseases ◽  
Strong Relationship ◽  
Simple Random Sampling ◽  
Personal Hygiene ◽  
Chi Square ◽  
Natural Lighting ◽  
Chi Square Test ◽  
Relationship Of ◽  
The Village

Based on data from the Tikep Health Center, for the last three years Waturempe Village has become the village with the highest incidence of skin diseases and accounts for almost 50% of skin diseases. The aim of this study was to determine the relationship between personal hygiene and environmental conditions in Waturempe Village. The population in this study were all heads who live in Waturempe Village as many as 120 heads of families (KK). The sample size was 92 respondents, taken by simple random sampling. The data were obtained using a questionnaire then analyzed descriptively and inferentially using the chi square test. The results showed that there was a strong relationship between personal hygiene (X²hit=39,21 2> X²tab = 3,841), moisture (X²hit=36,655 > X²tab=3,841), temperature (X²hit=45,126 > X²tab=3,841), natural lighting (X²hit=29,362> X²tab=3,841), and occupancy density (X²hit=27,273 > X²tab=3,841) with complaints of skin diseases. There was a moderate relationship between water quality and complaints of skin diseases (X²hit=19,354 > X²tab=3,841). It is expected that the community always maintains personal hygiene and improves condition of the home environment and is always aware of the transmission of skin diseases.

scholarly journals Analisis Paparan Co Dan So2 Pada Petugas Parkir di Basement Mall Ska di Kota Pekanbaru

2016 ◽  
Vol 3 (1) ◽  
pp. 47
Author(s):  
Damri Damri ◽  
Mirna Ilza ◽  
Dedi Afandi
Keyword(s):  
Environmental Conditions ◽  
High Concentration ◽  
Parking Lot ◽  
The Impact

Abstrak: The objectives in research on the effects of CO and SO2 to ilness parking attendant is to analyze ilness suffered a parking attendant at the Mall SKA Pekanbaru in working on indoor parking. The description of the illness suffered a parking attendant at SKA Pekanbaru Mall is 21.3% feel the illness, sometimes reaching 33.2% and 45.4% never reached. Exposure to CO over high concentration at night and exposure to SO2 evenly in the morning, afternoon and evening. There is a real impact concentration of CO exposure to the pain felt by the parking attendant. This pain can be perceived from the parking attendants to the environmental conditions the parking lot itself. The condition is more common at night. Then the results related to the impact of SO2 exposure to pain proved to be a significant impact on the illnes parking attendant. 

Paleomagnetic history of the Mealy dykes of Labrador, Canada

1983 ◽  
Vol 20 (12) ◽  
pp. 1818-1833 ◽  
Author(s):  
J. K. Park ◽  
R. F. Emslie
Keyword(s):  
The Other ◽  
Magnetic Mineral ◽  
Magnetic Minerals ◽  
Linear Distribution ◽  
Tectonic Zone ◽  
Magnetic Components ◽  
History Of ◽  
Component C ◽  
A Site

Paleomagnetic analysis of the Mealy diabase dykes of Labrador reveals magnetizations that predate the Grenville event at about 1000 Ma. These dykes intrude the Mealy Mountains anorthositic complex in the Grenville Structural Province. They are well south of the Grenville Front Tectonic Zone, but were apparently never subjected to temperatures as high as 500 °C during their post-consolidation history.Four distinct magnetic components were uncovered by thermal and alternating field treatments and a fifth remained unresolved. The major magnetic mineral present, titanomagnetite, is thought to record two magnetic directions acquired during cooling from magmatic temperatures. These are B (D = 305°, I = −76°; N = 18 sites; κ = 12; α95 = 11°) and A (D = 095°, I = +52°; N = 20 sites; κ = 46; α95 = 5°). Component B has much within-site dispersion. The other two components, C (D = 274°, I = −47°; N = 10 sites; κ = 15; α95 = 13°) and D (D = 292°, I = −74°; κ = 5; α95 = 31°), probably reside in magnetite and pyrrhotite, respectively. Component C, antiparallel to A, was probably acquired at about the same time as A. We suggest that C and A represent the first stable magnetizations retained by the dykes following an extensive period of cooling and re-equilibration of the magnetic minerals. Components B and D, which agree in direction, represent a later stage of cooling.Component B has a pole at 148°E, 34°S (δp = 18°, δm = 19°) in agreement with regional metamorphic poles from the Grenville; A, however, has a pole at 173°W, 23°S (δp = 5°, δm = 7°), which apparently "sees through" the peak in Grenville activity. The A site poles have a linear distribution along the Keweenawan Track and probably relate to an age between 1000 and 1150 Ma.

High-coercivity magnetic minerals in archaeological baked clay and bricks

2020 ◽  
Vol 224 (2) ◽  
pp. 1256-1271
Author(s):  
Andrei Kosterov ◽  
Mary Kovacheva ◽  
Maria Kostadinova-Avramova ◽  
Pavel Minaev ◽  
Natalia Salnaia ◽  
...  
Keyword(s):  
Parent Material ◽  
High Coercivity ◽  
Firing Process ◽  
Magnetic Minerals ◽  
Magnetic Mineralogy ◽  
Archaeological Ceramics ◽  
Mineral Phases ◽  
Initial Magnetic Susceptibility ◽  
Magnetically Hard ◽  
Saturation Remanence

SUMMARY The thorough understanding of magnetic mineralogy is a prerequisite of any successful palaeomagnetic or archaeomagnetic study. Magnetic minerals in archaeological ceramics and baked clay may be inherited from the parent material or, more frequently, formed during the firing process. The resulting magnetic mineralogy may be complex, including ferrimagnetic phases not commonly encountered in rocks. Towards this end, we carried out a detailed rock magnetic study on a representative collection of archaeological ceramics (baked clay from combustion structures and bricks) from Bulgaria and Russia. Experiments included measurement of isothermal remanence acquisition and demagnetization as a function of temperature between 20 and &gt;600 °C. For selected samples, low-temperature measurements of saturation remanence and initial magnetic susceptibility between 1.8 and 300 K have been carried out. All studied samples contain a magnetically soft mineral identified as maghemite probably substituted by Ti, Mn and/or Al. Stoichiometric magnetite has never been observed, as evidenced by the absence of the Verwey phase transition. In addition, one or two magnetically hard mineral phases have been detected, differing sharply in their respective unblocking temperatures. One of these unblocking between 540 and 620 °C is believed to be substituted hematite. Another phase unblocks at much lower temperatures, between 140 and 240 °C, and its magnetic properties correspond to an enigmatic high coercivity, stable, low-unblocking temperature (HCSLT) phase reported earlier. In a few samples, high- and low unblocking temperature, magnetically hard phases appear to coexist; in the others, the HCSLT phase is the only magnetically hard mineral present.

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