scholarly journals Optical polarised phase function of the HR 4796A dust ring

2019 ◽  
Vol 626 ◽  
pp. A54 ◽  
Author(s):  
J. Milli ◽  
N. Engler ◽  
H. M. Schmid ◽  
J. Olofsson ◽  
F. Ménard ◽  
...  
Keyword(s):  
Phase Function ◽  
Scattered Light ◽  
Dust Particles ◽  
Cometary Dust ◽  
Very Large Telescope ◽  
Wide Range ◽  
Alternative Scenarios ◽  
First Time ◽  
Dust Ring ◽  
Compact Spheres

Context. The scattering properties of the dust originating from debris discs are still poorly known. The analysis of scattered light is however a powerful remote-sensing tool to understand the physical properties of dust particles orbiting other stars. Scattered light is indeed widely used to characterise the properties of cometary dust in the solar system. Aims. We aim to measure the morphology and scattering properties of the dust from the debris ring around HR 4796 A in polarised optical light. Methods. We obtained high-contrast polarimetric images of HR 4796 A in the wavelength range 600–900 nm with the SPHERE/ZIMPOL instrument on the Very Large Telescope. Results. We measured for the first time the polarised phase function of the dust in a debris system over a wide range of scattering angles in the optical. We confirm that it is incompatible with dust particles being compact spheres under the assumption of the Mie theory, and propose alternative scenarios compatible with the observations, such as particles with irregular surface roughness or aggregate particles.

scholarly journals First L band detection of hot exozodiacal dust with VLTI/MATISSE

2020 ◽  
Vol 499 (1) ◽  
pp. L47-L52
Author(s):  
Florian Kirchschlager ◽  
Steve Ertel ◽  
Sebastian Wolf ◽  
Alexis Matter ◽  
Alexander V Krivov
Keyword(s):  
Temporal Variability ◽  
Spectral Energy Distribution ◽  
Flux Ratio ◽  
Spectral Energy ◽  
Large Telescope ◽  
Very Large Telescope ◽  
New Instrument ◽  
L Band ◽  
First Time ◽  
Dust Ring

ABSTRACT For the first time, we observed the emission of hot exozodiacal dust in L band. We used the new instrument MATISSE at the Very Large Telescope Interferometer to detect the hot dust around κ Tuc with a significance of 3σ to 6σ at wavelengths between 3.37 and $3.85\, {\mu {\rm m}}$ and a dust-to-star flux ratio of 5 to $7{{{\ \rm per\ cent}}}$. We modelled the spectral energy distribution based on the new L band data alone and in combination with H band data published previously. In all cases we find $0.58\, {\mu {\rm m}}$ grains of amorphous carbon to fit the κ Tuc observations the best, however, also nanometre or micrometre grains and other carbons or silicates reproduce the observations well. Since the H band data revealed a temporal variability, while our Lband data were taken at a different epoch, we combine them in different ways. Depending on the approach, the best fits are obtained for a narrow dust ring at a stellar distance in the 0.1–029 au range and thus with a temperature between 940 and $1430\, {\rm K}$. Within the 1σ uncertainty dust location and temperature are confined to $0.032{\!-\!}1.18\, {\rm au}$ and $600{\!-\!}2000\, {\rm K}$.

scholarly journals Polarimetric Measurements of Scattered Light by Dust Grains In Earth and Microgravity Conditions. Tentative Interpretation of the Dichotomy between Comets

1996 ◽  
Vol 150 ◽  
pp. 391-394 ◽  
Author(s):  
E. Hadamcik ◽  
A.C. Levasseur-Regourd ◽  
J.C. Worms
Keyword(s):  
Physical Properties ◽  
Phase Angle ◽  
Scattered Light ◽  
Dust Particles ◽  
Laboratory Measurements ◽  
Cometary Dust ◽  
Maximum Value ◽  
Tentative Interpretation ◽  
Microgravity Conditions ◽  
Polarization Of Light

AbstractThe evolution of the polarization of light scattered by dust particles (e.g. cometary dust) with the phase angle is an indicator of the physical properties of the particles. For grains large compared to the wavelength, the maximum value of polarization Pmax increases with increasing size. A dichotomy is pointed out in the cometary poiarimetric phase curves, showing two ranges of values for Pmax. A comparison between laboratory measurements performed under Earth and microgravity conditions is presented. Pmax and the corresponding αmax appear to be smaller in microgravity than for ground based measurements. The comparison between ground based, microgravity and cometary results is then tentatively discussed in term of physical properties of the grains.

Safety assessment of biological raw materials in the system of medicines quality assurance

2020 ◽  
pp. 63-72
Author(s):  
Yu. Olefir ◽  
E. Sakanyan ◽  
I. Osipova ◽  
V. Dobrynin ◽  
M. Smirnova ◽  
...  
Keyword(s):  
Raw Materials ◽  
State Level ◽  
The State ◽  
Spongiform Encephalopathy ◽  
Safety Standards ◽  
Wide Range ◽  
The Russian Federation ◽  
Key Aspects ◽  
First Time ◽  
Medicines Quality

The entry of a wide range of biotechnological products into the pharmaceutical market calls for rein-forcement of the quality, efficacy and safety standards at the state level. The following general monographs have been elaborated for the first time to be included into the State Pharmacopoeia of the Russian Federation, XIV edition: "Viral safety" and "Reduction of the risk of transmitting animal spongiform encephalopathy via medicinal products". These general monographs were elaborated taking into account the requirements of foreign pharmacopoeias and the WHO recommendations. The present paper summarises the key aspects of the monographs.

Innovation in Byzantine Medicine

2020 ◽  
Author(s):  
Petros Bouras-Vallianatos
Keyword(s):  
Human Physiology ◽  
Medical Literature ◽  
Cultural Exchange ◽  
Significant Degree ◽  
Medieval Medicine ◽  
Medieval Latin ◽  
Main Thesis ◽  
Wide Range ◽  
Comprehensive Examination ◽  
First Time

Byzantine medicine is still a little-known and misrepresented field not only in the wider arena of debates on medieval medicine but also among Byzantinists. Byzantine medical literature is often viewed as ‘stagnant’ and mainly preserving ancient ideas; and our knowledge of it continues to be based to a great extent on the comments of earlier authorities, which are often repeated uncritically. This book presents the first comprehensive examination of the medical corpus of, arguably, the most important late Byzantine physician John Zacharias Aktouarios (c.1275–c.1330). The main thesis is that John’s medical works show an astonishing degree of openness to knowledge from outside Byzantium combined with a significant degree of originality, in particular, in the fields of uroscopy, pharmacology, and human physiology. The analysis of John’s edited (On Urines and On Psychic Pneuma) and unedited (Medical Epitome) works is supported for the first time by the consultation of a large number of manuscripts. The study is also informed by evidence from a wide range of medical sources, including previously unpublished ones, and texts from other genres, such as epistolography and merchants’ accounts. The contextualization of John’s works sheds new light on the development of Byzantine medical thought and practice, and enhances our understanding of the late Byzantine social and intellectual landscape. Finally, John’s medical observations are also examined in the light of examples from the medieval Latin and Islamic worlds, placing his medical theories in the wider Mediterranean milieu and highlighting the cultural exchange between Byzantium and its neighbours.

Rebels, Believers, Survivors

2020 ◽  
Author(s):  
Noel Malcolm
Keyword(s):  
Catholic Church ◽  
Religious Conversion ◽  
Late Nineteenth Century ◽  
Napoleonic Wars ◽  
Conversion To Islam ◽  
Wide Range ◽  
History Of ◽  
External Powers ◽  
First Time ◽  
Modern Myth

This book of essays covers a wide range of topics in the history of Albania and Kosovo. Many of the essays illuminate connections between the Albanian lands and external powers and interests, whether political, military, diplomatic or religious. Such topics include the Habsburg invasion of Kosovo in 1689, the manoeuvrings of Britain and France towards the Albanian lands during the Napoleonic Wars, the British interest in those lands in the late nineteenth century, and the Balkan War of 1912. On the religious side, essays examine ‘crypto-Christianity’ in Kosovo during the Ottoman period, the stories of conversion to Islam revealed by Inquisition records, the first theological treatise written in Albanian (1685), and the work of the ‘Apostolic Delegate’ who reformed the Catholic Church in early twentieth-century Albania. Some essays bring to life ordinary individuals hitherto unknown to history: women hauled before the Inquisition, for example, or the author of the first Albanian autobiography. The longest essay, on Ali Pasha, tells for the first time the full story of the role he played in the international politics of the Napoleonic Wars. Some of these studies have been printed before (several in hard-to-find publications, and one only in Albanian), but the greater part of this book appears here for the first time. This is not only a contribution to Albanian and Balkan history it also engages with many broader issues, including religious conversion, methods of enslavement within the Ottoman Empire, and the nature of modern myth-making about national identity.

Recycling and Reuse in the Roman Economy

2020 ◽  
Keyword(s):  
Building Materials ◽  
Computational Modelling ◽  
Late Antique ◽  
Roman Economy ◽  
Wide Range ◽  
The Status ◽  
Recent Developments ◽  
Methodological Approaches ◽  
First Time ◽  
Site Types

The recycling and reuse of materials and objects were extensive in the past, but have rarely been embedded into models of the economy; even more rarely has any attempt been made to assess the scale of these practices. Recent developments, including the use of large datasets, computational modelling, and high-resolution analytical chemistry, are increasingly offering the means to reconstruct recycling and reuse, and even to approach the thorny matter of quantification. Growing scholarly interest in the topic has also led to an increasing recognition of these practices from those employing more traditional methodological approaches, which are sometimes coupled with innovative archaeological theory. Thanks to these efforts, it has been possible for the first time in this volume to draw together archaeological case studies on the recycling and reuse of a wide range of materials, from papyri and textiles, to amphorae, metals and glass, building materials and statuary. Recycling and reuse occur at a range of site types, and often in contexts which cross-cut material categories, or move from one object category to another. The volume focuses principally on the Roman Imperial and late antique world, over a broad geographical span ranging from Britain to North Africa and the East Mediterranean. Last, but not least, the volume is unique in focusing upon these activities as a part of the status quo, and not just as a response to crisis.

scholarly journals Experimental Results on Scattering by Irregular and Meteoritic Dust Particles Related to Photopolarimetry of Zodiacal Light and Comets

1985 ◽  
Vol 85 ◽  
pp. 223-226
Author(s):  
K. Weiss-Wrana ◽  
R.H. Giese ◽  
R.H. Zerull
Keyword(s):  
Light Scattering ◽  
Size Range ◽  
Experimental Results ◽  
Dust Particles ◽  
Dust Grains ◽  
Scattering Function ◽  
Negative Polarization ◽  
Zodiacal Light ◽  
Cometary Dust ◽  
Characteristic Features

AbstractThe investigations of light scattering by larger meteoritic and terrestrial single grains (size range 20 μm to 120 μm ) demonstrate that the scattering properties of irregularly shaped dark opaque particles with very rough surfaces resemble the characteristic features of the empirical scattering function as derived from measurements of the zodiacal light. Purely transparent or translucent irregularly shaped particles show a quite different scattering behaviour. Furthermore irregular and multicomponent fluffy particles in the size range of a few microns were modelled by microwave analog measurements in order to explain positive and negative polarization of the light scattered by cometary dust grains.

scholarly journals A Virtual Telescope for the Open University Science Foundation Course

1998 ◽  
Vol 162 ◽  
pp. 100-105
Author(s):  
Andrew J. Norton ◽  
Mark H. Jones
Keyword(s):  
Social Science ◽  
Open University ◽  
Distance Teaching ◽  
The Arts ◽  
Wide Range ◽  
University Science ◽  
First Time ◽  
Degree Level ◽  
Selection Of

The Open University is the UK's foremost distance teaching university. For over twenty five years we have been presenting courses to students spanning a wide range of degree level and vocational subjects. Since we have no pre-requisites for entry, a major component of our course profile is a selection of foundation courses comprising one each in the Arts, Social Science, Mathematics, Technology and Science faculties. The Science Faculty's foundation course is currently undergoing a substantial revision. The new course, entitled “S103: Discovering Science”, will be presented to students for the first time in 1998.

scholarly journals The Impact of Ambient Atmospheric Mineral-Dust Particles on the Calcification of Lungs

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 125
Author(s):  
Mariola Jabłońska ◽  
Janusz Janeczek ◽  
Beata Smieja-Król
Keyword(s):  
Mineral Dust ◽  
Smoking Habit ◽  
Lower Lobe ◽  
Ambient Air ◽  
Dust Particles ◽  
Masking Effect ◽  
Amorphous Calcium Carbonate ◽  
Calcium Salts ◽  
The Impact ◽  
First Time

For the first time, it is shown that inhaled ambient air-dust particles settled in the human lower respiratory tract induce lung calcification. Chemical and mineral compositions of pulmonary calcium precipitates in the lung right lower-lobe (RLL) tissues of 12 individuals who lived in the Upper Silesia conurbation in Poland and who had died from causes not related to a lung disorder were determined by transmission and scanning electron microscopy. Whereas calcium salts in lungs are usually reported as phosphates, calcium salts precipitated in the studied RLL tissue were almost exclusively carbonates, specifically Mg-calcite and calcite. These constituted 37% of the 1652 mineral particles examined. Mg-calcite predominated in the submicrometer size range, with a MgCO3 content up to 50 mol %. Magnesium plays a significant role in lung mineralization, a fact so far overlooked. The calcium phosphate (hydroxyapatite) content in the studied RLL tissue was negligible. The predominance of carbonates is explained by the increased CO2 fugacity in the RLL. Carbonates enveloped inhaled mineral-dust particles, including uranium-bearing oxides, quartz, aluminosilicates, and metal sulfides. Three possible pathways for the carbonates precipitation on the dust particles are postulated: (1) precipitation of amorphous calcium carbonate (ACC), followed by its transformation to calcite; (2) precipitation of Mg-ACC, followed by its transformation to Mg-calcite; (3) precipitation of Mg-free ACC, causing a localized relative enrichment in Mg ions and subsequent heterogeneous nucleation and crystal growth of Mg-calcite. The actual number of inhaled dust particles may be significantly greater than was observed because of the masking effect of the carbonate coatings. There is no simple correlation between smoking habit and lung calcification.

scholarly journals The effect of stellar multiplicity on protoplanetary discs: a near-infrared survey of the Lupus star-forming region

2020 ◽  
Vol 501 (2) ◽  
pp. 2305-2315
Author(s):  
Alice Zurlo ◽  
Lucas A Cieza ◽  
Megan Ansdell ◽  
Valentin Christiaens ◽  
Sebastián Pérez ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Molecular Cloud ◽  
Near Infrared ◽  
Main Sequence Stars ◽  
Multiple Systems ◽  
Star Forming ◽  
Very Large Telescope ◽  
Pms Stars ◽  
First Time ◽  
Infrared Survey

ABSTRACT We present results from a near-infrared (NIR) adaptive optics (AO) survey of pre-main-sequence stars in the Lupus molecular cloud with NACO at the Very Large Telescope (VLT) to identify (sub)stellar companions down to ∼20-au separation and investigate the effects of multiplicity on circumstellar disc properties. We observe for the first time in the NIR with AO a total of 47 targets and complement our observations with archival data for another 58 objects previously observed with the same instrument. All 105 targets have millimetre Atacama Large Millimetre/sub-millimetre Array (ALMA) data available, which provide constraints on disc masses and sizes. We identify a total of 13 multiple systems, including 11 doubles and 2 triples. In agreement with previous studies, we find that the most massive (Mdust > 50 M⊕) and largest (Rdust > 70 au) discs are only seen around stars lacking visual companions (with separations of 20–4800 au) and that primaries tend to host more massive discs than secondaries. However, as recently shown in a very similar study of >200 PMS stars in the Ophiuchus molecular cloud, the distributions of disc masses and sizes are similar for single and multiple systems for Mdust < 50 M⊕ and radii Rdust < 70 au. Such discs correspond to ∼80–90 per cent of the sample. This result can be seen in the combined sample of Lupus and Ophiuchus objects, which now includes more than 300 targets with ALMA imaging and NIR AO data, and implies that stellar companions with separations >20 au mostly affect discs in the upper 10${{\ \rm per\ cent}}$ of the disc mass and size distributions.

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