scholarly journals Spectrophotometrical researches of the subnuclear area of 46P/WIRTANEN comet

2018 ◽  
pp. 3-8
Author(s):  
V. Ponomarenko ◽  
K. Chiuryumov ◽  
O. Sergeev
Keyword(s):  
Energy Flux ◽  
Cometary Nucleus ◽  
Physical Parameters ◽  
Neutral Gas ◽  
Short Period Comet ◽  
Short Period ◽  
Total Energy Flux ◽  
Physical Quantities ◽  
Observation Period

The observations and research of the short-period comet 46P/Wirtanen by optical spectra with an average resolution (λ/Δλ ≈ 1400) are presented. Spectra in January 2008 at the Peak Terskol mountain observatory with the Zeiss-2000 telescope (D = 2.0 m; F2 = 16 m) were obtained. On the basis of the received spectral material, the identification of emission bands was carried out. The distribution of the total energy flux, reflected energy flux and the spectrophotometric gradient in the spectral range λλ = 4850–7650 ÅÅ are constructed. The quality of the received spectral material allowed estimating with high accuracy the gas productivity of the molecules C2, NH2 and the relative dust productivity in cometary filters GC, RC. The relative dust productivity (Afρ), the gas productivity (Q) for the molecular emissions of C2 and NH2, as well as some other physical parameters of the neutral gas cometary atmosphere were evaluated. The resulting values of physical quantities are characteristic for Jupiter family comets. The gas productivity of 46P/Wirtanen during the observation period QC2 = 3.97–4.12 × 1025 mol/s, QNH2 = 2.06–2.97 × 1025 mol/s. The obtained values of gas and dust productivity characterize the cometary coma of 46P/Wirtanen as dust-rich. In comparison with the data of 1998, a significant decrease in production in the atmosphere of the comet of the NH2 molecule was recorded. The spectrophotometric gradient obtained for comet Wirtanen is characteristic for other JFC and is 8.6 % per 1000 Å. The relative dust productivity (Afρ) at the time of observations in January 2008 was significantly higher than in previous passages of perihelion. The obtained results may be the consequence of evolution of the upper layers of the cometary nucleus and require further experimental confirmation.

Covering of cometary nucleus by refractory crust and its evolution into asteroid-like body

1999 ◽  
Vol 173 ◽  
pp. 365-370
Author(s):  
Kh.I. Ibadinov
Keyword(s):  
Laboratory Experiments ◽  
Cometary Nucleus ◽  
Sublimation Rate ◽  
Cometary Nuclei ◽  
Short Period Comet ◽  
Short Period ◽  
Brightness Decrease ◽  
Crust Thickness ◽  
Ice Sublimation ◽  
Period Comet

AbstractFrom the established dependence of the brightness decrease of a short-period comet dependence on the perihelion distance of its orbit it follows that part of the surface of these cometary nuclei gradually covers by a refractory crust. The results of cometary nucleus simulation show that at constant insolation energy the crust thickness is proportional to the square root of the insolation time and the ice sublimation rate is inversely proportional to the crust thickness. From laboratory experiments resulted the thermal regime, the gas productivity of the nucleus, covering of the nucleus by the crust, and the tempo of evolution of a short-period comet into the asteroid-like body studied.

scholarly journals The Kuiper Belt

1994 ◽  
Vol 160 ◽  
pp. 31-44
Author(s):  
Jane Luu
Keyword(s):  
Solar System ◽  
Kuiper Belt ◽  
Cometary Nucleus ◽  
Outer Solar System ◽  
Short Period Comet ◽  
Short Period ◽  
Lower Limits ◽  
Period Comet

The existence of a belt of comets in the outer solar system (the “Kuiper belt”) has been postulated for a variety of reasons, including the need for a source for the short-period comets. The existence of the belt seems supported by the discoveries of the trans-Neptunian objects 1992 QB1, 1993 FW, 1993 RO, 1993 RP, 1993 SB, and 1993 SC. If these objects are members of the Kuiper belt, crude lower limits on the belt population can be established from the discoveries. The Kuiper belt comets are likely to be primordial remnants of the disk from which the solar system accreted. According to the current theories of cometary nucleus evolution, these objects are expected to possess mantles (“irradiation mantles”) which are different from mantles of comets which have been heated to the point of sublimation (“rubble mantles”). Kuiper belt comets on their way to short-period comet orbits may exist among the Centaur objects.

Climatology of very high ionospheric electron temperature occurrences as observed by Swarm constellation

2021 ◽  
Author(s):  
Igino Coco ◽  
Giuseppe Consolini ◽  
Paola De Michelis ◽  
Fabio Giannattasio ◽  
Michael Pezzopane ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Physical Parameters ◽  
High Electron ◽  
Langmuir Probes ◽  
Swarm Satellites ◽  
High Electron Temperature ◽  
Physical Quantities ◽  
Very High

<p>After more than seven years in orbit, the ESA Swarm satellites have provided an already large statistics of measurements of several important physical parameters of the ionosphere. In particular, electron density and temperature are measured by pairs of Langmuir Probes, and the quality of such data is now considered good enough for many studies, either science cases or climatological characterisations. Concerning specifically the electron temperature, a rather elusive parameter which is quite difficult to correctly characterize “in situ”, and for which the past literature is not so abundant with respect to other ionospheric physical quantities, the overall distributions observed by Swarm are qualitatively consistent with expectations from theory and past observations. However, a non-negligible amount of high and very high electron temperature values is regularly observed, whose distributions and properties are not trivial. In this study we aim at characterizing such features statistically as a function of latitude, local time, and season.</p>

scholarly journals Meteoroid-stream complex originating from comet 2P/Encke

2019 ◽  
Vol 623 ◽  
pp. A13 ◽  
Author(s):  
D. Tomko ◽  
L. Neslušan
Keyword(s):  
Dynamical Evolution ◽  
Meteor Shower ◽  
Meteoroid Stream ◽  
The Past ◽  
Test Particles ◽  
Short Period Comet ◽  
Short Period ◽  
The Mean ◽  
Period Comet

Aims. We present a study of the meteor complex of the short-period comet 2P/Encke. Methods. For five perihelion passages of the parent comet in the past, we modeled the associated theoretical stream. Specifically, each of our models corresponds to a part of the stream characterized with a single value of the evolutionary time and a single value of the strength of the Poynting–Robertson effect. In each model, we follow the dynamical evolution of 10 000 test particles via a numerical integration. The integration was performed from the time when the set of test particles was assumed to be ejected from the comet’s nucleus up to the present. At the end of the integration, we analyzed the mean orbital characteristics of those particles that approached the Earth’s orbit, and thus created a meteor shower or showers. Using the mean characteristics of the predicted shower, we attempted to select its real counterpart from each of five considered databases (one photographic, three video, and one radio-meteor). If at least one attempt was successful, the quality of the prediction was evaluated. Results. The modeled stream of 2P approaches the Earth’s orbit in several filaments with the radiant areas grouped in four cardinal directions of ecliptical showers. These groups of radiant areas are situated symmetrically with respect to the apex of the Earth’s motion around the Sun. Specifically, we found that showers #2, #17, #156, #172, #173, #215, #485, #624, #626, #628, #629, #632, #634, #635, #636, and #726 in the IAU-MDC list of all showers are dynamically related to 2P. In addition, we found five new 2P-related showers in the meteor databases considered.

Models of comets with strongly variable nongravitational effects

1999 ◽  
Vol 173 ◽  
pp. 381-387
Author(s):  
M. Królikowska ◽  
G. Sitarski ◽  
S. Szutowicz
Keyword(s):  
Cometary Nucleus ◽  
Spin Axis ◽  
Reactive Force ◽  
Orbital Elements ◽  
Cometary Nuclei ◽  
Short Period ◽  
Basic Parameters ◽  
Polar Radius ◽  
Cometary Activity ◽  
Nongravitational Effects

AbstractThe nongravitational motion of five “erratic” short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes, and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force,Aand of maximum of cometary activity with respect to perihelion time. The present precession models impose some contraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.32 (equatorial to polar radius of 1.46) is the most oblate among five investigated comets.

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

scholarly journals Metabolic phases during the development of granulation tissue

1967 ◽  
Vol 105 (1) ◽  
pp. 333-341 ◽  
Author(s):  
Kirsti Lampiaho ◽  
E. Kulonen
Keyword(s):  
Granulation Tissue ◽  
Collagen Synthesis ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Pentose Phosphate ◽  
Acid Cycle ◽  
Short Period ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Observation Period

1. The metabolism of incubated slices of sponge-induced granulation tissue, harvested 4–90 days after the implantation, was studied with special reference to the capacity of collagen synthesis and to the energy metabolism. Data are also given on the nucleic acid contents during the observation period. Three metabolic phases were evident. 2. The viability of the slices for the synthesis of collagen was studied in various conditions. Freezing and homogenization destroyed the capacity of the tissue to incorporate proline into collagen. 3. Consumption of oxygen reached the maximum at 30–40 days. There was evidence that the pentose phosphate cycle was important, especially during the phases of the proliferation and the involution. The formation of lactic acid was maximal at about 20 days. 4. The capacity to incorporate proline into collagen hydroxyproline in vitro was limited to a relatively short period at 10–30 days. 5. The synthesis of collagen was dependent on the supply of oxygen and glucose, which latter could be replaced in the incubation medium by other monosaccharides but not by the metabolites of glucose or tricarboxylic acid-cycle intermediates.

Risks of the Digitalization of Life of the Population and Ways of Decreasing Them

2021 ◽  
Vol 13 (4-1) ◽  
pp. 180-203
Author(s):  
Elena Stukalenko ◽  
Keyword(s):  
Quality Of Life ◽  
Digital Technologies ◽  
Well Being ◽  
Digital Economy ◽  
Digital Transformation ◽  
Negative Consequences ◽  
Short Period ◽  
The World ◽  
The Impact

Digital technologies, ubiquitous in our daily life, have radically changed the way we work, communicate, and consume in a short period of time. They affect all components of quality of life: well-being, work, health, education, social connections, environmental quality, the ability to participate and govern civil society, and so on. Digital transformation creates both opportunities and serious risks to the well-being of people. Researchers and statistical agencies around the world are facing a major challenge to develop new tools to analyze the impact of digital transformation on the well-being of the population. The risks are very diverse in nature and it is very difficult to identify the key factor. All researchers conclude that secure digital technologies significantly improve the lives of those who have the skills to use them and pose a serious risk of inequality for society, as they introduce a digital divide between those who have the skills to use them and those who do not. In the article, the author examines the risks created by digital technologies for some components of the quality of life (digital component of the quality of life), which are six main components: the digital quality of the population, providing the population with digital benefits, the labor market in the digital economy, the impact of digitalization on the social sphere, state electronic services for the population and the security of information activities. The study was carried out on the basis of the available statistical base and the results of research by scientists from different countries of the world. The risks of the digital economy cannot be ignored when pursuing state social policy. Attention is paid to government regulation aimed at reducing the negative consequences of digitalization through the prism of national, federal projects and other events.

A Comparative Study between Conventional and Modified Leishman Stain

2021 ◽  
Vol 8 (2) ◽  
pp. 5-12
Author(s):  
Rizwana Abdul Hye ◽  
Bindiya Gisuthan ◽  
Indira Kariveettil
Keyword(s):  
Conventional Method ◽  
Peripheral Blood ◽  
Cross Sectional Study ◽  
Mean Value ◽  
Health Care Centre ◽  
Cross Sectional ◽  
Modified Method ◽  
Present Cross Sectional Study ◽  
Short Period

Introduction: Leishman stain has been used as the stain of choice for peripheral blood films since many decades .But it has a disadvantage of consuming 15 minutes for the procedure alone thereby increasing the turn around time of peripheral smear reporting. In this study modified Leishman stain was made by adding phenol to conventional Leishman to reduce the staining time to 3 minutes without interfering with the quality of stain. Aim: To study the quality of modified Leishman stain in comparison with conventional preparation on peripheral blood smears. Materials and Methods: The present cross-sectional study was carried out in Central Haematology laboratory of a tertiary health care centre in Southern India. A pilot study was done to determine the ideal ratio of phenol to Leishman powder in preparing modified stain without compromising the staining quality. After obtaining consent, the blood sample was collected in anticoagulated vials. Sample size was calculated to be 85.Two thin wedge smears were prepared from each sample and one was stained with conventional Leishman stain and other with modified Leishman stain. The staining characteristics were assessed and scored by an experienced pathologist in terms of 6 parameters- RBC pattern, nuclear pattern, neutrophil granules, eosinophil granules, platelets and background staining. The grades were 1, 2, 3 & 4 (poor, satisfied, good and excellent). Smears each with grades 2, 3 and 4 were selected for study. The results were analysed by Statistical Package for the Social Sciences (SPSS) software version 16.0. Result: The mean value for the staining quality using conventional method was 4.73 and for modified method was 5.39, and the total score possible is 6. Photomicrograph showed excellent results with modified Leishman stain. Thus from these values we can interpret that modified method gave much more acceptable results than that of conventional method. Conclusion: Unlike the conventional method which requires a total of 15 minutes, to complete the staining process, modified Leishman staining techniques takes only 3 minutes. Blood films can be stained within a short period of time thus aiding in rapid diagnosis and treatment of patients. Keywords: Leishman stain, Modified Leishman stain, Phenol.

Radiation of internal waves from groups of surface gravity waves

2017 ◽  
Vol 829 ◽  
pp. 280-303 ◽  
Author(s):  
S. Haney ◽  
W. R. Young
Keyword(s):  
Internal Waves ◽  
Energy Flux ◽  
Gravity Waves ◽  
Three Dimensions ◽  
Stokes Drift ◽  
Surface Gravity ◽  
Fourth Power ◽  
Buoyancy Frequency ◽  
Surface Gravity Waves ◽  
Short Period

Groups of surface gravity waves induce horizontally varying Stokes drift that drives convergence of water ahead of the group and divergence behind. The mass flux divergence associated with spatially variable Stokes drift pumps water downwards in front of the group and upwards in the rear. This ‘Stokes pumping’ creates a deep Eulerian return flow that sets the isopycnals below the wave group in motion and generates a trailing wake of internal gravity waves. We compute the energy flux from surface to internal waves by finding solutions of the wave-averaged Boussinesq equations in two and three dimensions forced by Stokes pumping at the surface. The two-dimensional (2-D) case is distinct from the 3-D case in that the stratification must be very strong, or the surface waves very slow for any internal wave (IW) radiation at all. On the other hand, in three dimensions, IW radiation always occurs, but with a larger energy flux as the stratification and surface wave (SW) amplitude increase or as the SW period is shorter. Specifically, the energy flux from SWs to IWs varies as the fourth power of the SW amplitude and of the buoyancy frequency, and is inversely proportional to the fifth power of the SW period. Using parameters typical of short period swell (e.g. 8 s SW period with 1 m amplitude) we find that the energy flux is small compared to both the total energy in a typical SW group and compared to the total IW energy. Therefore this coupling between SWs and IWs is not a significant sink of energy for the SWs nor a source for IWs. In an extreme case (e.g. 4 m amplitude 20 s period SWs) this coupling is a significant source of energy for IWs with frequency close to the buoyancy frequency.

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