scholarly journals Occurrence of Graphite-Like Carbon in Podiform Chromitites of Greece and Its Genetic Significance

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 152 ◽  
Author(s):  
Maria Economou-Eliopoulos ◽  
George Tsoupas ◽  
Vasilis Skounakis
Keyword(s):  
Subduction Zone ◽  
Mineral Chemistry ◽  
Present Contribution ◽  
Term Evolution ◽  
Wide Range ◽  
Carbon Recycling ◽  
Podiform Chromitites ◽  
Of Greece

The role of post-magmatic processes in the composition of chromitites hosted in ophiolite complexes, the origin of super-reduced phases, and factors controlling the carbon recycling in a supra-subduction zone environment are still unclear. The present contribution compiles the first scanning electron microscope/energy-dispersive (SEM/EDS) data on graphite-like amorphous carbon, with geochemical and mineral chemistry data, from chromitites of the Skyros, Othrys, Pindos, and Veria ophiolites (Greece). The aim of this study was the delineation of potential relationships between the modified composition of chromite and the role of redox conditions, during the long-term evolution of chromitites in a supra-subduction zone environment. Chromitites are characterized by a strong brittle (cataclastic) texture and the presence of phases indicative of super-reducing phases, such as Fe–Ni–Cr-alloys, awaruite (Ni3Fe), and heazlewoodite (Ni3S2). Carbon-bearing assemblages are better revealed on Au-coated unpolished sections. Graphite occurs in association with hydrous silicates (chlorite, serpentine) and Fe2+-chromite, as inclusions in chromite, filling cracks within chromite, or as nodule-like graphite aggregates. X-ray spectra of graphite–silicate aggregates showed the presence of C, Si, Mg, Al, O in variable proportions, and occasionally K and Ca. The extremely low fO2 during serpentinization facilitated the occurrence of methane in microfractures of chromitites, the precipitation of super-reducing phases (metal alloys, awaruite, heazlewoodite), and graphite. In addition, although the origin of Fe–Cu–Ni-sulfides in ultramafic parts of ophiolite complexes is still unclear, in the case of the Othrys chromitites, potential reduction-induced sulfide and/or carbon saturation may drive formation of sulfide ores and graphite-bearing chromitites. The presented data on chromitites covering a wide range in platinum-group element (PGE) content, from less than 100 ppb in the Othrys to 25 ppm ΣPGE in the Veria ores, showed similarity in the abundance of graphite-like carbon. The lack of any relationship between graphite (and probably methane) and the PGE content may be related to the occurrence of the (Ru–Os–Ir) minerals in chromitites, which occur mostly as oxides/hydroxides, and to lesser amounts of laurite, with pure Ru instead activating the stable CO2 molecule and reducing it to methane (experimental data from literature).

Correlation between magnesium and potassium contents in muscle: role of Na(+)-K+ pump

1993 ◽  
Vol 264 (2) ◽  
pp. C457-C463 ◽  
Author(s):  
I. Dorup ◽  
T. Clausen
Keyword(s):  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Deficient Diet ◽  
Young Rats ◽  
Wide Range ◽  
86Rb Influx

In young rats fed a Mg(2+)-deficient diet for 3 wk, Mg2+ and K+ contents in soleus and extensor digitorum longus muscles were significantly reduced and closely correlated. In isolated soleus muscles, Mg2+ depletion induced an even more pronounced loss of K+, and Mg2+ and K+ contents were correlated over a wide range (r = 0.95, P < 0.001). Extracellular Mg2+ (0-1.2 mM) caused no change in total or ouabain-suppressible 86Rb influx. After long-term incubation in Ca(2+)-Mg(2+)-free buffer with EDTA and EGTA, cellular Mg2+ and K+ contents were reduced by 35 and 15%, respectively, without any reduction in ATP and total or ouabain-suppressible 86Rb influx. In Mg(2+)-depleted muscles 42K efflux was increased by up to 42%, and repletion with Mg2+ produced a graded decrease. We conclude that Mg2+ and K+ contents are closely correlated in muscles Mg2+ depleted in vivo or in vitro and that neither extracellular nor moderate intracellular Mg2+ depletion affects total or Na(+)-K+ pump-mediated K+ influx. The reduced K+ content may rather be related to increased K+ efflux from the muscles.

scholarly journals Problems of Muses Education in the Ancient Cities of the Northern Black Sea Coast

2019 ◽  
Keyword(s):  
Black Sea ◽  
Social Background ◽  
Black Sea Region ◽  
Black Sea Coast ◽  
Wide Range ◽  
Archaeological Materials ◽  
Teaching Music ◽  
Teaching Grammar ◽  
Of Greece

The article deals with the problems of education and upbringing in the ancient cities of the Northern Black Sea Littoral. Literary, epigraphic and material data sources characterizing the muses education are systematized. Namely: the study of grammar, literature, arithmetic, music. The inscriptions that can be considered as school exercises, texts of epitaphs, messages from ancient authors, archaeological materials, including funerals are analyzed. The material of the graffiti shows the peculiarities of teaching grammar and literature, the process of forming a unified system for writing throughout the Northern Black Sea Littoral. The process of teaching music and dance is still poorly covered in literature. A wide range of iconographic and archaeological materials have been used to expose this aspect of muses education. According to the author, the content and forms of education in the cities of the Northern Black Sea region were generally the same as in the cities of Greece itself. The possibility of obtaining the highest level of education from the local elite is emphasized. That is confirmed by the data on eminent philosophers from the Northern Black Sea region, such as Bosporan Sopheid, Bion Borisfenit, Posidonius Olviopolit and others. The following forms of organization of school education are considered: questions of school premises and educational accessories, methods of teaching and education, social background of students and teachers. The role of muses agonists and religious holidays as forms of quality control of education is shown. The connection of musical education with physical preparation and influence of political structure of the states on the development of education are considered.

Long-Term Evolution of the Load Curve of the Interconnected System of Greece

1979 ◽  
pp. 537-546
Author(s):  
C.N. Eleftheratos ◽  
C.B. Cassapoglou
Keyword(s):  
Long Term Evolution ◽  
Load Curve ◽  
Interconnected System ◽  
Term Evolution ◽  
Of Greece

scholarly journals Swift/XRT, Chandra, and XMM–Newton observations of IGR J17091–3624 as it returns into quiescence

2020 ◽  
Vol 497 (1) ◽  
pp. 1115-1126
Author(s):  
M Pereyra ◽  
D Altamirano ◽  
J M C Court ◽  
N Degenaar ◽  
R Wijnands ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Time Scales ◽  
Strong Evidence ◽  
Spectral Properties ◽  
X Ray ◽  
Term Evolution ◽  
Wide Range ◽  
Low Mass

ABSTRACT IGR J17091–3624 is a low-mass X-ray binary (LMXB), which received wide attention from the community thanks to its similarities with the bright black hole system GRS 1915+105. Both systems exhibit a wide range of highly structured X-ray variability during outburst, with time-scales from few seconds to tens of minutes, which make them unique in the study of mass accretion in LMXBs. In this work, we present a general overview into the long-term evolution of IGR J17091–3624, using Swift/XRT observations from the onset of the 2011–2013 outburst in 2011 February till the end of the last bright outburst in 2016 November. We found four re-flares during the decay of the 2011 outburst, but no similar re-flares appear to be present in the latter one. We studied, in detail, the period with the lowest flux observed in the last 10 yr, just at the tail end of the 2011–2013 outburst, using Chandra and XMM-Newton observations. We observed changes in flux as high as a factor of 10 during this period of relative quiescence, without strong evidence of softening in the spectra. This result suggests that the source has not been observed at its true quiescence so far. By comparing the spectral properties at low luminosities of IGR J17091–3624 and those observed for a well-studied population of LMXBs, we concluded that IGR J17091–3624 is most likely to host a black hole as a compact companion rather than a neutron star.

Protein Fibrillar Nanopolymers: Molecular-Level Insights into Their Structural, Physical and Mechanical Properties

2015 ◽  
Vol 10 (03) ◽  
pp. 135-156 ◽  
Author(s):  
Valeriya M. Trusova
Keyword(s):  
Protein Misfolding ◽  
Amyloid Fibrils ◽  
Molecular Level ◽  
Physical And Mechanical Properties ◽  
Present Contribution ◽  
Wide Range ◽  
Generic Class ◽  
Protein Fibril

Amyloid fibrils represent a generic class of mechanically strong and stable biomaterials with extremely advantageous properties. Although amyloids were initially associated only with severe neurological disorders, the role of these structures nowadays is shifting from health debilitating to highly beneficial both in biomedical and technological aspects. Intensive involvement of fibrillar assemblies into the wide range of pathogenic and functional processes strongly necessitate the molecular level characterization of the structural, physical and elastic features of protein nanofibrils. In the present contribution, we made an attempt to highlight the up-to-date progress in the understanding of amyloid properties from the polymer physics standpoint. The fundamental insights into protein fibril behavior are essential not only for development of therapeutic strategies to combat the protein misfolding disorders but also for rational and precise design of novel biodegradable protein-based nanopolymers.

scholarly journals Stellar activity and coronal heating: an overview of recent results

2015 ◽  
Vol 373 (2042) ◽  
pp. 20140259 ◽  
Author(s):  
Paola Testa ◽  
Steven H. Saar ◽  
Jeremy J. Drake
Keyword(s):  
Magnetic Activity ◽  
Coronal Heating ◽  
Complementary Information ◽  
Stellar Activity ◽  
X Ray ◽  
Solar Observations ◽  
Term Evolution ◽  
Wide Range ◽  
Stellar Magnetic Fields

Observations of the coronae of the Sun and of solar-like stars provide complementary information to advance our understanding of stellar magnetic activity, and of the processes leading to the heating of their outer atmospheres. While solar observations allow us to study the corona at high spatial and temporal resolution, the study of stellar coronae allows us to probe stellar activity over a wide range of ages and stellar parameters. Stellar studies therefore provide us with additional tools for understanding coronal heating processes, as well as the long-term evolution of solar X-ray activity. We discuss how recent studies of stellar magnetic fields and coronae contribute to our understanding of the phenomenon of activity and coronal heating in late-type stars.

scholarly journals Effects of leptin administration on long-term selected fat mice

1997 ◽  
Vol 69 (3) ◽  
pp. 215-225 ◽  
Author(s):  
LUTZ BÜNGER ◽  
WILLIAM G. HILL
Keyword(s):  
Matter Content ◽  
Control Line ◽  
Dry Matter Content ◽  
Genetic Changes ◽  
Term Selection ◽  
Wide Range ◽  
Selection For ◽  
Phosphate Buffered Saline

To assess the role of genetic changes in sensitivity to leptin hormone in contributing to responses to long-term selection for fatness, leptin was administered to a long-term fat selected (F) and a control line (C) of mice. These lines differ almost three fold in their percentage of fat (fat%) at about 15 weeks of age. Treated (T) animals received twice-daily intraperitoneal injections of 5 mg/kg leptin from 91 to 105 days of age; untreated (U) animals received equivolume injections of phosphate-buffered saline. Treated compared with untreated animals in both lines had significantly (P<0·05) lower mean body weight, food intake and fatness at the end of test (fat%: CT 3%, CU 7·4%, FT 14·9%, FU21·1%). The differences in response between the lines [(CT−CU)−(FT−FU)] were all non-significant (P>0·05), however. There was a very wide range of fatness (estimated from dry matter content) among FT animals (3–29%), much higher than in FU (15–31%), CT (0·7–6·4%) and CU (2–15%) animals. While sensitivity to leptin remains in the fat line, response appears to vary among animals at the dose level used.

scholarly journals Novel Astroviruses in Insectivorous Bats

2008 ◽  
Vol 82 (18) ◽  
pp. 9107-9114 ◽  
Author(s):  
D. K. W. Chu ◽  
L. L. M. Poon ◽  
Y. Guan ◽  
J. S. M. Peiris
Keyword(s):  
Virus Detection ◽  
High Genetic Diversity ◽  
Insectivorous Bats ◽  
Detection Rates ◽  
Human Astroviruses ◽  
Wide Range ◽  
The Family ◽  
Apparently Healthy

ABSTRACT Bats are increasingly recognized to harbor a wide range of viruses, and in most instances these viruses appear to establish long-term persistence in these animals. They are the reservoir of a number of human zoonotic diseases including Nipah, Ebola, and severe acute respiratory syndrome. We report the identification of novel groups of astroviruses in apparently healthy insectivorous bats found in Hong Kong, in particular, bats belonging to the genera Miniopterus and Myotis. Astroviruses are important causes of diarrhea in many animal species, including humans. Many of the bat astroviruses form distinct phylogenetic clusters in the genus Mamastrovirus within the family Astroviridae. Virus detection rates of 36% to 100% and 50% to 70% were found in Miniopterus magnater and Miniopterus pusillus bats, respectively, captured within a single bat habitat during four consecutive visits spanning 1 year. There was high genetic diversity of viruses in bats found within this single habitat. Some bat astroviruses may be phylogenetically related to human astroviruses, and further studies with a wider range of bat species in different geographic locations are warranted. These findings are likely to provide new insights into the ecology and evolution of astroviruses and reinforce the role of bats as a reservoir of viruses with potential to pose a zoonotic threat to human health.

scholarly journals The role of oxidative stress, inflammation and acetaminophen exposure from birth to early childhood in the induction of autism

2017 ◽  
Vol 45 (2) ◽  
pp. 407-438 ◽  
Author(s):  
William Parker ◽  
Chi Dang Hornik ◽  
Staci Bilbo ◽  
Zoie E. Holzknecht ◽  
Lauren Gentry ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Early Childhood ◽  
Early Development ◽  
Long Term Effects ◽  
Small Children ◽  
Factors Associated ◽  
Wide Range ◽  
And Oxidative Stress

The wide range of factors associated with the induction of autism is invariably linked with either inflammation or oxidative stress, and sometimes both. The use of acetaminophen in babies and young children may be much more strongly associated with autism than its use during pregnancy, perhaps because of well-known deficiencies in the metabolic breakdown of pharmaceuticals during early development. Thus, one explanation for the increased prevalence of autism is that increased exposure to acetaminophen, exacerbated by inflammation and oxidative stress, is neurotoxic in babies and small children. This view mandates extreme urgency in probing the long-term effects of acetaminophen use in babies and the possibility that many cases of infantile autism may actually be induced by acetaminophen exposure shortly after birth.

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