13 research outputs found
Selection of stable growth conditions for the parabolic dendrite tip in crystallization of multicomponent melts
Free growth of a dendrite crystal in a stationary multicomponent melt is investigated. A mathematical model of the process is developed and its analytic solution is constructed. A stability criterion is obtained for a 2D parabolic dendrite and the refined relation is derived for the growth rate of the dendrite tip taking into account the anisotropy of surface tension at the solid phase-melt interface. It is shown that the accumulation of impurity in the front of a dendrite makes it tip thinner and reduces its velocity. The theory contains limiting transitions to the familiar dendrite growth criteria for one-component and binary systems. © 2013 Pleiades Publishing, Ltd
On the theory of dendritic growth: Soret and temperature-dependent diffusion effects
An analytical solution is found for the problem of the growth of an isolated dendrite in a convective binary melt with allowance for the Soret and temperature-dependent diffusion effects. Nonlinear impurity transport is shown to radically change the impurity concentration in front of the growing crystal and, correspondingly, the concentration supercooling, which is responsible for the condition of choosing the dendrite tip growth rate. © 2013 Pleiades Publishing, Ltd
The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis
Astrometric observations performed by the Gaia Follow-Up Network for Solar
System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects
first detected by ESA's Gaia mission remain recoverable after their discovery.
An observation campaign on the potentially hazardous asteroid (99 942) Apophis
was conducted during the asteroid's latest period of visibility, from
12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall
performance of the Gaia-FUN-SSO . The 2732 high quality astrometric
observations acquired during the Gaia-FUN-SSO campaign were reduced with the
Platform for Reduction of Astronomical Images Automatically (PRAIA), using the
USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric
reduction process and the precision of the newly obtained measurements are
discussed. We compare the residuals of astrometric observations that we
obtained using this reduction process to data sets that were individually
reduced by observers and accepted by the Minor Planet Center. We obtained 2103
previously unpublished astrometric positions and provide these to the
scientific community. Using these data we show that our reduction of this
astrometric campaign with a reliable stellar catalog substantially improves the
quality of the astrometric results. We present evidence that the new data will
help to reduce the orbit uncertainty of Apophis during its close approach in
2029. We show that uncertainties due to geolocations of observing stations, as
well as rounding of astrometric data can introduce an unnecessary degradation
in the quality of the resulting astrometric positions. Finally, we discuss the
impact of our campaign reduction on the recovery process of newly discovered
asteroids.Comment: Accepted for publication in A&
Selection of stable growth conditions for the parabolic dendrite tip in crystallization of multicomponent melts
The astrometric Gaia-FUN-SSO observation campaign of 99942 Apophis
© 2015 ESO. Aims. Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO. Methods. The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center. Results. We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community. Using these data we show that our reduction of this astrometric campaign with a reliable stellar catalog substantially improves the quality of the astrometric results. We present evidence that the new data will help to reduce the orbit uncertainty of Apophis during its close approach in 2029. We show that uncertainties due to geolocations of observing stations, as well as rounding of astrometric data can introduce an unnecessary degradation in the quality of the resulting astrometric positions. Finally, we discuss the impact of our campaign reduction on the recovery process of newly discovered asteroids
Remote Study of Aufeis along the ‘Power of Siberia’ Gas Pipeline in the Aldan River Basin
The ‘Power of Siberia’ gas pipeline route passes through the territories of South-West and South Yakutia, where the natural conditions are characterized by severe climatic, complex engineering geological and geocryological conditions. A variety of environmental conditions are mandatory for construction and operation in different areas with long-term soil and hazardous geocryological processes: debris flow formation, aufeis formation, soil heaving, thermokarst, thermosuffosion. Aufeis formation processes will be of particular importance during the construction of the pipeline. As a degree of their occurrence in the Republic of Sakha (Yakutia), it should be mentioned the Aldan upland. Aufeis occur almost in the majority of local stream valleys as a small areas of ice formations, basically confined to floodplain and riverbed.
Aufeis areas had been identified in trace areas by the method of deciphering satellite images within the territory of the hydrogeological zones of the Lena-Amur interfluve. As a result of remote studies, territorial and quantitative distributions in hydrogeological zones have been identified. As a result of the monitoring results the areas of each aufeis are determined and their contours are decoded due to satellite images of recent years (2018-2020)
Interaction of Peptides Containing CRAC Motifs with Lipids in Membranes of Various Composition
The response of a human tumour xenograft to chemotherapy: intrinsic variation between tumours and its significance in planning experiments.
© 2015 ESO. Aims. Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO. Methods. The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center. Results. We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community. Using these data we show that our reduction of this astrometric campaign with a reliable stellar catalog substantially improves the quality of the astrometric results. We present evidence that the new data will help to reduce the orbit uncertainty of Apophis during its close approach in 2029. We show that uncertainties due to geolocations of observing stations, as well as rounding of astrometric data can introduce an unnecessary degradation in the quality of the resulting astrometric positions. Finally, we discuss the impact of our campaign reduction on the recovery process of newly discovered asteroids