Exhaustion of a supersonic underexpanded air jet into air–helium and air–sulfur hexafluoride mixtures is studied experimentally. The air jet escapes from a convergent circular nozzle in the range of ...moderate Reynolds numbers covering the laminar and transitional regimes of the jet flow. The experiments are performed with “cold” and heated jets in a low-pressure jet setup, which allows the Reynolds number of the jet exhaustion from the nozzle, the jet pressure ratio, and the density of the gas surrounding the jet to be maintained independently. A Pitot tube is used to measure the supersonic core length of the air jet as a function of the density of the ambient medium whereto the jet exhausts. In addition, the spatial distributions of the amplitude–frequency characteristics of acoustic oscillations generated by the jet in the ambient space are measured by a moving sensor of pressure fluctuations. The effect of the ratio of the underexpanded air jet density to the ambient medium density on the supersonic core length is demonstrated. It is shown that the mechanism of influence of the ambient medium density is associated with a change in the conditions for the global instability of the underexpanded air jet and, in particular, the conditions for generation of the screech tone.
This paper describes the results of methodical investigations of the effect of the Pitot tube on measurements of gas-dynamic parameters of supersonic axisymmetric underexpanded real and model ...microjets. Particular attention is paid to distortions of Pitot pressure variations on the jet axis associated with the wave structure of the jet and to distortions of the supersonic core length. In experiments with model jets escaping from nozzles with diameters ranging from 0.52 to 1.06 mm into the low-pressure chamber, the measurements are performed by the Pitot tubes 0.05 to 2 mm in diameter. The results are analyzed together with the earlier obtained data for real microjets escaping from nozzles with diameters ranging from 10 to 340 µm where the parameters of real microjets were determined by the Pitot microtube 12 µm in diameter. Interaction of the Pitot tube with an unsteady jet in the laminar-turbulent transition region is investigated; the influence of this interaction on Pitot pressure measurements is determined, and a physical interpretation of this phenomenon is provided.
Hantaviruses are rodent-borne, emerging viruses that cause life-threatening human diseases in Eurasia and the Americas. We detected hantavirus genome sequences in an African wood mouse (Hylomyscus ...simus) captured in Sangassou, Guinea. Sequence and phylogenetic analyses of the genetic material demonstrate a novel hantavirus species, which we propose to name "Sangassou virus."
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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•Temperature across liquid–gas layers are measured at normal atmospheric condition.•Micro-thermocouple with sensor thickness of less than 4μm is used.•The temperature jump at the ...liquid–gas interface is clearly detected.•Jump increases with increasing temperature drop between heater and ambient gas.•Heater temperature is varying in the range 25–60°C.•Jump of 0.2°C is detected for liquid surface temperature of 35.2°C.
The temperature profiles are measured across a liquid–gas two-layers system at normal atmospheric conditions. A thin water layer is locally heated from the bottom substrate and it evaporates from the liquid–gas interface. A micro-thermocouple with sensor thickness of less than 4μm has been specially manufactured for the accurate measurement of the temperature profiles. This micro-thermocouple is displaced with micro-steps near the interface, providing the detailed information on the temperature field. A temperature jump at the liquid–gas interface is clearly detected even for small evaporation rate. This jump is measured for heater temperature varying in the range 25–60°C at normal atmospheric conditions. The temperature jump value is found to increase with increasing the temperature difference between heater and ambient gas, and, hence, with increasing of the evaporation rate. A specific evolution of the temperature profile with increasing of the heater temperature is obtained. Depending on the ambient condition, the temperature in the gas phase near the liquid–gas interface can be higher or lower than that of the liquid. The temperature profiles with negligible temperature jump at liquid–gas interface are observed for some operating conditions. The temperature jump depends not only on evaporation rate, but also on temperature gradients in liquid and gas phases near the interface. The experimental results are found to be qualitatively in agreement with the kinetic theory and quantitatively with classical energy balance on the interface. The reported detailed data on the phase transition phenomena for relatively high heat flux are presented for the first time in the literature. However, more precise measurements of the temperature profiles at the liquid–gas interface should be done further.
Mastomys natalensis and Lassa fever, West Africa Lecompte, Emilie; Fichet-Calvet, Elisabeth; Daffis, Stéphane ...
Emerging infectious diseases,
12/2006, Letnik:
12, Številka:
12
Journal Article
Recenzirano
Odprti dostop
PCR screening of 1,482 murid rodents from 13 genera caught in 18 different localities of Guinea, West Africa, showed Lassa virus infection only in molecularly typed Mastomys natalensis. Distribution ...of this rodent and relative abundance compared with M. erythroleucus correlates geographically with Lassa virus seroprevalence in humans.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Karyotypes of Hapalomys delacouri (Rodentia, Muridae) and Typhlomys cinereus (Rodentia, Platacanthomyidae) from Vietnam are described for the first time. The diploid karyotype of Hapalomys delacouri ...is 38 (NFa=48), consisting of six pairs of bi-armed and 12 pairs of acrocentric autosomes decreasing in size; plus a large metacentric X chromosome and Y chromosome, also metacentric, that is equal in size to the largest pair of acrocentric autosomes. The newly described karyotype differs significantly from that reported for Hapalomys delacouri from northern Thailand. The latter record very likely represents a different species of Hapalomys, possibly the taxon Hapalomys pasquieri described from north-central Laos.The diploid karyotype of Typhlomys cinereus is 38 (NF=48), consisting of five pairs of meta- to submetacentric and 14 pairs of acrocentric chromosomes varying in size from large to small; sex chromosomes were not defined.
At the current stage of digitization of the Russian economy, educational institutions urgently need new, more advanced and effective training technologies that help improve the quality of training of ...highly competent and competitive specialists who comply with the social order of society digital. These technologies should promote the introduction of robotic and cyber-physical systems in the training of future specialists. The article shows that SMART, STEM and STEAM integrated learning technologies that encompass the theoretical and practical components of educational programs with the help of special technological equipment: robotic complexes, virtual learning tools and cyber systems, can be used as technologies in the digital education. It is proven that the practical application of mathematical, physical, engineering and technological knowledge, modeling and design of robotic cybernetic devices and others, allow us to more effectively solve the tasks of the competition-oriented educational paradigm, create additional conditions for the development and realization of the personal potential of the students. The integrative didactic potential of SMART, STEM and STEAM technologies is determined, ensuring the achievement of the synergistic effect in the educational process and increasing the productivity of education subjects through the combination of the individual means of the technologies studied in a single system. The advantages of digital education are analyzed, which are optimized using the integrative teaching potential of SMART, STEM and STEAM technologies. Based on the characteristics of the integrative didactic potential of SMART, STEM and STEAM technologies, it is concluded that they are promising in the era of the digitization of Russian education and viable to use them in order to maintain the effectiveness of the educational process.
Tonkinomys daovantieni was recently described from Northern Vietnam, but very sparse information exists for the taxon. We report for the first time the karyotype of this species and investigate its ...phylogenetic position in the Dacnomys division using both mitochondrial and nuclear genetic data. The diploid chromosome number of the species is 2n=44. This chromosomal set consists of one submetacentric pair, one metacentric pair, and nineteen pairs of subtelocentric/acrocentric autosomes progressively decreasing in size. The X chromosome is submetacentric and approximately equal in size to the largest subtelocentric autosome. The Y chromosome is metacentric and equal in size to the smallest pair of autosomes. The phylogenetic reconstruction based on the Cyt b COI and GHR genes reveals that Saxotilomys paulinae, a species distributed in the karst formations of the Lao PDR, is the closest relative to T. daovantieni. These two taxa are similar not only in a number of morphological characters, but also in their major ecological preferences (both are petrophylic species associated with limestone karst formations). Based on our data, we can conclude that the similarities among the ecological adaptations, natural conditions and habitat preferences of these species are a reflection of their phylogenetic relationship.
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