The article presents data on the feasibility of the concept of a high-efficiency seed cleaner with the consistent use of the air flow in aspiration and the multi-tier placement of the sorting grids ...in grating mills. As a result of modeling, the directions for further improvement of air-screen seed cleaning machines have been identified: an increase in the proportion of sorting grids in the mills up to 70 ... 80% and an increase in the speed of the air flow in the channel of the pre-filter cleaning up to 8.0 m / s. Experiments have established the competence of using mathematical modeling of airflow in the pneumatic system with the use of a finite-volume method for solving hydrodynamic equations for substantiating the basic parameters of the pneumatic system.
Critical to our understanding of the developmental potential of stem cells and subsequent control of their differentiation in vitro and in vivo is a thorough understanding of the genes that control ...stem cell fate. Here, we report that Foxd3, a member of the forkhead family of transcriptional regulators, is required for maintenance of embryonic cells of the early mouse embryo. Foxd3-/- embryos die after implantation at approximately 6.5 days postcoitum with a loss of epiblast cells, expansion of proximal extraembryonic tissues, and a distal, mislocalized anterior organizing center. Moreover, it has not been possible to establish Foxd3-/- ES cell lines or to generate Foxd3-/- teratocarcinomas. Chimera analysis reveals that Foxd3 function is required in the epiblast and that Foxd3-/- embryos can be rescued by a small number of wild-type cells. Foxd3-/- mutant blastocysts appear morphologically normal and express Oct4, Sox2, and Fgf4, but when placed in vitro the inner cell mass initially proliferates and then fails to expand even when Fgf4 is added. These results establish Foxd3 as a factor required for the maintenance of progenitor cells in the mammalian embryo.
The results of a numerical evaluation of the stress-strain state of a RVS-20000 tank in the presence of nonuniform settlement of the outer perimeter of the tank bottom are examined. Relations between ...the length of a sector of the nonuniform settlement zone and the maximum value of the vertical component of the settlement that characterize the structural stiffness of the tank are obtained. The regions where the limit states arise are determined.
The Agrobacterium-mediated transformation of a duckweed plant (
Lemna minor
L.) with the use of the organogenic callus and nucleotide sequence of a gene for hirudin-1 optimized for expression in ...plants has been performed. Eight transgenic plant lines transformed by hirudin and seven lines transformed by the gene for β-glucuronidase were obtained. The expression of the glucuronidase gene was proven by histochemical staining and Western blot. ELISA of the transgenic plants showed that the content of β-glucuronidase in them varied from 0.28 to 1.43% of the total soluble protein. The expression of the hirudin-1 gene was confirmed by RT-PCR, with the maximum hirudin accumulation being equal to 0.02% of the total soluble protein. The results of the study can be used in the development of an expression system using the duckweed plant to obtain hirudin and other recombinant proteins for pharmaceutical use.
When using lead as a primary circuit coolant, certain difficulties arise not only from the side of the reactor plant (structural materials, fuel, etc.) but also from the side of the steam turbine ...cycle. A feature of the second circuit of a lead-cooled NPP is noted, such as the need to maintain a high temperature of the feedwater in front of the steam generator, caused by its melting/freezing temperature. For the pilot demonstration power unit with the BREST-OD-300 reactor plant, it was decided to use a mixing feedwater heater, which entailed the appearance of a second rise in the feed pump circuit. Due to the lack of electric drive pumps for such high parameters, it was proposed to use a hydraulic turbine driven pump as a feed pump behind the mixing feedwater heater. These pumps have a significant impact on efficiency due to the multistage energy conversion, and there is no recommendation for selecting resistance on the control valve of these pumps. A computational study was carried out to determine the optimal pressure drop on the control valve of the hydraulic turbine drive of the feed pump of the power unit with the BREST-OD-300 reactor plant. Optimal is understood as the ultimate minimum differential at which the valve is able to carry out regulation with specified quality criteria and ensure the lowest energy consumption for its own needs. Recommendations are given for choosing the optimal pressure drop on the control valve of the hydraulic turbine drive of the feed pump of a turbine unit with the BREST-OD-300 reactor. A methodology has been developed for solving problems of optimizing pressure drop in units of complex hydraulic systems.
The modified dual-frequency printed quasi-Yagi antenna has been designed. After multi-step optimization, the S
11
parameter of the antenna is as low as −27 and −14 dB at f
01
= 1.7 and f
02
= 2.45 ...GHz, respectively. The antenna directivity is 7.1 and 5 dB at f
01
= 1.7 and f
02
= 2.45 GHz, respectively. The total length of the planar dual-frequency quasi-Yagi antenna is 158 mm. The universal algorithm of the antenna design has been proposed, and the algorithm can be applied to the creation of three-frequency printed quasi-Yagi antennas.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Cherenkov radiation and pulsed cathodoluminescence spectra in the ultraviolet, visible, and near infrared regions generated by a 6-MeV electron beam passing through GE-014 and KU1 quartz plates have ...been experimentally studied. The Cherenkov radiation spectrum has been recorded in the ultraviolet and visible regions and its change is shown at the variation of the angle between the plane of the plate and the direction of the electron beam. The data on the conditions of recording of the Cherenkov radiation spectra at the excitation of plane-parallel plates of quartz, sapphire, and diamond have been presented. It has been shown that the total internal reflection in the crystals with a high refractive index imposes certain conditions on the geometry of the output of Cherenkov radiation into vacuum at electron energies above 500 kev.
The printed dual‐frequency quasi‐Yagi antenna with a monopole driver and one‐side implementation is proposed for central frequencies f01 = 1.765 GHz and f02 = 1.9 GHz. The antenna contains 2 ...directors and one reflector which are used as low‐ and high‐frequency passive elements simultaneously.
It is shown that surface color centers of the same type are formed in the surface layer and in regions with damaged crystal structure inside crystalline lithium fluoride after γ-irradiation. Results ...are presented from a study of the effect of pre-irradiation annealing on the efficiency with which surface centers are formed in lithium fluoride nanocrystals. Raising the temperature for pre-irradiation annealing from room temperature to 250°C leads to a substantial reduction in the efficiency with which these centers are created. Surface color centers are not detected after γ-irradiation for pre-irradiation annealing temperatures of 300°C and above. Adsorption of atmospheric gases on the crystal surface cannot be regarded as a necessary condition for the formation of radiation-induced surface centers.
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