ABSTRACT
Statistical analysis of samples of the orbits of celestial bodies is complicated by the fact that the Keplerian orbit is a multidimensional object, the coordinate representation of which ...non-linearly depends on the choice of orbital elements. In this work, using the construction of the Fréchet mean, concepts of mean orbit and dispersion of the orbit family are introduced, consistent with the distance function on the orbit set. The introduced statistical characteristics serve as analogues of sample mean and variance of a one-dimensional random variable. Exact formulas for calculating the elements of mean orbits and dispersion quantities with respect to two metrics on the orbit space are derived. For a large sample of meteoroid orbits from the Geminid stream, numerical simulations of orbit evolution over 20 000 yr in the past were conducted. By analysing the dependency of statistical characteristics on time, estimates for the age of the stream and the gas outflow velocity are obtained under the assumption of the birth of the Geminids due to the rapid destruction of the cometary nucleus. The estimate of the age of the stream lies in the interval from 1200 to 2400 yr, and the speed of gas outflow at perihelion should have been more than 1.2 km s−1.
Primary hyperparathyroidism (PHPT) is a common endocrine disorder caused by a parathyroid tumor or hyperplasia, which is often accompanied with quality of life (QoL) impairment. A parathyroidectomy ...(PTX) is the preferred standard treatment for PHPT patients. In this single center study we aimed to evaluate the impact of PHPT on patient's QoL and identify QoL changes at early and long-term follow-up after surgery.
All the patients underwent routine PTX with the removal of the suspected hyperparathyroid gland(s). Patients filled out generic QoL questionnaire RAND SF-36, specific questionnaire PHPQoL and specific symptom assessment questionnaire PAS upon admission to the hospital before surgery, at 3 months, 12 months and 24 months after surgery.
A total of 92 patients with PHPT (median age was 56 years, 95.7% females) were included in the study. Before PTX patient's QoL by SF-36 scores was significantly lower as compared to healthy controls (p < 0.01). Almost 40% of patients had poor or very poor QoL. The most frequent symptoms by PAS before surgery were as follows: tiredness (97.8% of patients), weakness (94.6%), forgetfulness (94.6%), mood changes (90%), feeling "blue"/depression (88%), joint pains (83.3%), headaches (80.2%), constant irritability (77.2%), bone pains (75%), thirst (70.7%) and trouble getting out of a chair (67.4%). The half of the patients had moderate-to-severe (≥ 40 scores) tiredness, weakness, joint pains, forgetfulness, as well as mood changes. Post-operative QoL changes were analysed in the group of 72 patients. After surgery there was significant improvement in QoL by all scales of SF-36 questionnaire, excluding bodily pain, and the PHPQoL total score (GEE, p < 0.01) as compared with their values before surgery. Also severity of tiredness, mood changes, weakness and forgetfulness significantly decreased after surgery as compared to their baseline values (GEE, p < 0.05). Decreased mental component of QoL by PHPQoL (OR = 0.927, 95%CI = 0.874-0.984, p = 0.013) predicted improved QoL after surgery.
Patients with PHPT demonstrated significantly impaired QoL in physical, psychological and social functioning as well experienced a wide profile of common PHPT symptoms. Successful PTX was accompanied with remarkable QoL improvement and decrease in subjective symptoms for at least 24 months after surgery.
This paper is devoted to dynamic network flows. A phenomenon called dynamic network flow splash is studied (splash is an exceeding of flow value over maximum feasible static flow for the same ...network). Parallel and tree-structured network topology classes are defined. Conditions for occurring network flow splash in the parallel and tree-structured networks are discovered. A formula for computing a value of maximum dynamic network flow splash is obtained. An algorithm for calculating the formula values is presented.
Red-colored pedosediments were described in the sections of the Lori Basin in northern Armenia. The environmental conditions in the period of their formation have been reconstructed. The Early ...Pleistocene pedosediments in Yagdan and Kurtan-IV sections are available for study due to their conservation under the products of volcanic activity, which are dated earlier than 2 and 1.4 Ma, respectively. Prior to burial, the pedosediments were exposed to molten lava, which affected their composition and properties. We used the micromorphological method to study the pedosediments and determined the magnetic susceptibility, particle-size and total chemical composition, the content of carbon and nitrogen, and the biomorphs. Signs of the formation of the studied pedosediments in a humid warm (subtropical) climate were found, which corresponded to the results of earlier studies. Based on the combination of features, soil formations from the Yagdan section were assigned to Cambisols with Argic, Vitric, and Chromic qualifiers. Additional elements were input from the above layer of basalt lava to the sediments: copper, chromium, nickel, cobalt, and vanadium, which was reflected in an increase in the specific magnetic susceptibility and enabled us to specify the soil and sediments by geochemical coefficients. Pedosediments from Kurtan-IV section were characterized by Stagnic and Luvic features. They were also formed in a humid but cooler climate.
Results of an experimental study and numerical simulation of the curing kinetics of an epoxy binder under the conditions of violation of the stoichiometric equilibrium of its components are ...presented. The object of research is a two-component composition of an L epoxy resin and an EPH 161 hardener, certified as a binder for composite materials of aerospace purpose. As the basic model, we used a system of two ordinary differential equations describing the behavior of the resin and hardener during the curing process. The values of material parameters necessary for calculations were obtained by a rheological method, where the viscosity of binder was analyzed as a function of polymerization time and hardener concentration. The estimates of model parameters obtained by processing data of full-scale experiments are presented. The effective values of kinetic parameters at which the calculated time of yield loss is in good agreement with the experimental one are determined. The adequacy of the model was confirmed by direct measurements using the IR spectroscopy.
•Main regularities of the change in MCE value with a change in composition are found.•We find a structural phase transition in Тb0.4Dy0.3Ho0.3Co1.75Fe0.25 at 375 K using XRD.•Mössbauer effect study ...provided data on the hyperfine parameters in the alloys.•Hydrogenation effect on magnetism of alloys is shown.
In this work, the effects of substitutional elements on the magnetism of complex rare-earth-transition metal compounds RT2 with the Laves phase structure are studied with the aim to find new materials with high magnetocaloric effect (MCE) above room temperature. We determine the main regularities in the MCE magnitude variation when varying composition of the Tb-Dy-Ho-Co-Fe alloys and also after hydrogenation. The crystal structure of the compounds is characterized by X-ray diffraction in a wide temperature range while information on the magnetic properties of the 3d-transition metal sublattice is accessed by means of the 57Fe Mössbauer effect studies. We design a series of Tbx(Dy0.5Ho0.5)1-xCo1.75Fe0.25 samples with constant MCE values, suitable for the use as cooling elements of devices operating at elevated temperatures.
The structure and superconducting properties of the Fe
1 –
x
(A)
x
(Se
0.2
Te
0.8
)
0.82
(
x
= 0.1, 0.2) compound, where A is Cu, Zn, Bi or Group IV elements (Pb, Sn, Ge), were studied. It was shown ...that the effect of substitution of some iron atoms on the structure and superconducting properties of the Fe(Se,Te) compound depends on whether a solid solution with a substituting element was formed. If complete dissolution of the replacement element occured (Cu, Zn), then a significant degradation of the superconducting properties was observed. If a separate chalcogenide phase was formed (substitution by Pb, Sn, Ge), then a slight change in the superconducting properties was observed. Such a slight change and even improvement in the superconducting properties upon precipitation of the chalcogenide phase can be associated with both the positive effect of an increase in the relative content of iron and a decrease in the number of iron atoms in the interstitial sites of the β-phase. The preservation of the superconducting properties of the Fe(Se,Te) compound with a small substitution of iron for group IV elements can be used to create wires based on Fe(Se,Te), since impurity chalcogenide particles can act as effective pinning centers.
In the present paper, features and problems of non-destructive testing (NDT) of composite materials with big inside quantity of pores have been discussed. Solutions for issues of NDT of this ...materials have been proposed.
Selection of a land plot is one of the first and most important stages during realization of the vineyard project. The final decision at this stage is determined by many factors, including the cost ...of the land plot, its logistical parameters, tourist attractiveness, etc. The most important among them is the suitability of the plot for grape cultivation, determined by a combination of soil, climatic, and orographic conditions, which are combined in the concept of terroir in the production practice of viticulture and winemaking. An integral assessment of the soil component of the terroir of test plots located in contrasting physical-geographical conditions of France (communes of Le Bignon and Domme) and Russia (villages of Fruktovoe and Beregovoi) was performed. The optimal list of analyzed soil properties based on the parameters taken into account when choosing rootstock varieties—the design solution that most depends on soil conditions—was determined in the course of the work. Then, the procedure of compression of the information on the soil component of the terroir of test plots was performed, and locally oriented weight coefficients were calculated. According to the results of the average integral assessment in the 1-m-deep layer of soil profiles, the following ranked sequence of test plots from the best soil conditions to the worst ones was obtained: the village of Beregovoi (score 0.84), the commune of Le Bignon (score 0.70), the village of Fruktovoe (scores 0.66 and 0.65), and the commune of Domme (score 0.63), the values of which can be compared with other factors at the stage of making a decision on planting vineyards.
We investigate the curing of large shell construction made of epoxy resin/carbon fibers prepreg under free space conditions in solar synchronous Low Earth Orbit. The curing kinetics is described by ...first order kinetic equation with auto-acceleration and deceleration parameters based on the experimental data. Heating of the shell is provided by solar radiation. The heat distribution in the shell is modelled based on partial absorbance of the solar radiation, the prepreg thermal conductivity and thermal capacity, radiation heat transfer between inner surfaces of the shell and the gas thermal conductivity. The iterated algorithm of curing was developed. Three flight regimes based on the circular motion of a construction have been considered: 1 – the axis of a shell lies in the tangent plane to the orbit and makes a constant angle with the tangent; 2 – under conditions (1), a shell rotates around its axis with a constant angular velocity; 3 – under conditions (2), the axis of the shell precesses around the tangent to the orbit. It was found, that the parameters of the motion (i.e. angular velocity of the rotation around the axis, precession angular velocity and precession angle) could be optimised in such way, that the whole shell can be completely cured under the solar radiation.
•Curing of epoxy composite in space is proposed for large space construction.•Solar synchronous Low Earth Orbit is considered for a curing orbit.•Orbital motion with the axis of the shell precesses around the tangent is optimised.
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