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Sample records for liisi lnemets tnu

  1. Study of the effects of solar activities on the ionosphere as observed by VLF signals recorded at TNU station, Vietnam

    NASA Astrophysics Data System (ADS)

    Tan, L. M.

    2015-12-01

    A SuperSID monitor installed at Tay Nguyen University (TNU), Vietnam is used to detect the temporal variations of Very Low Frequency (VLF) signals during 2013 and 2014 to understand the responses of the ionosphere to sunset/sunrise transitions and solar flares. Two VLF station signals are tracked, JJI/22.2 kHz in Japan and NWC/19.8 kHz in Australia. Results show that the effects of sunrise, sunset and solar flares on the NWC signal are more significantly different than those on the JJI signal. Sunset and sunrise spikes only occur on the JJI-TNU path because of longitudinal differences between the receiver and transmitter. Two sunset dips and three sunrise dips appear on the NWC signal during summer season. During intense solar flares, the dips occur after the maximum disturbance of the VLF signals for the North-South path. The appearance of these dips is explained by modal interference patterns. Observing temporal variations of sunrise and sunset dips or spikes of VLF signals during different seasons enhances the understanding of the behavior of the ionosphere.

  2. Astronomical education in Tajikistan. Project TAJASTRO

    NASA Astrophysics Data System (ADS)

    Ibadinov, Khursandkul I.; Rahmonov, A. A.

    2011-06-01

    The centre of astronomy in Tajikistan is the Institute of Astrophysics of the Academy of Sciences of Tajikistan. This institute carries out scientific research and contributes to the preparation of the astronomical staff and to astronomical education. The reform of education in Tajikistan continues and now astronomy is studied in schools (together with physics) and at universities. The Tajik State Pedagogical University resumed in 2007 the training of teachers in physics and astronomy. Since 1999 the Tajik National University (TNU) offers a a specialty in astronomy. In 2006 is restored the Small Academy of Sciences (SAS) of Tajikistan. There is a planetarium in Khujand and in 2006 the Institute of Astrophysics, TNU and the Astronomical Society of Tajikistan, along with the support IBSP/UNESCO, organised the Training Methodical Center (TMC) ``TAJASTRO'' at the Hisar astronomical observatory for students, graduate students, young scientists, and teachers at secondary schools.

  3. Regional study of the Archean to Proterozoic crust at the Sudbury Neutrino Observatory (SNO+), Ontario: Predicting the geoneutrino flux

    NASA Astrophysics Data System (ADS)

    Huang, Yu; Strati, Virginia; Mantovani, Fabio; Shirey, Steven B.; McDonough, William F.

    2014-10-01

    SNO+ detector that is currently under construction in Ontario, Canada, will be a new kiloton-scale liquid scintillation detector with the capability of recording geoneutrino events that can be used to constrain the strength of the Earth's radiogenic power, and in turn, to test compositional models of the bulk silicate Earth (BSE). We constructed a detailed 3-D model of the regional crust centered at SNO+ from compiled geological, geophysical, and geochemical information. Crustal cross sections obtained from refraction and reflection seismic surveys were used to characterize the crust and assign uncertainties to its structure. The average Moho depth in the study area is 42.3 ± 2.6 km. The upper crust was divided into seven dominant lithologic units on the basis of regional geology. The abundances of U and Th and their uncertainties in each upper crustal lithologic unit were determined from analyses of representative outcrop samples. The average chemical compositions of the middle and lower crust beneath the SNO+ region were determined by coupling local seismic velocity profiles with a global compilation of the chemical compositions of amphibolite and granulite facies rocks. Monte Carlo simulations were used to predict the geoneutrino signal originating from the regional crust at SNO+ and to track asymmetrical uncertainties of U and Th abundances. The total regional crust contribution of the geoneutrino signal at SNO+ is predicted to be 15.6-3.4+5.3 TNU (a Terrestrial Neutrino Unit is one geoneutrino event per 1032 target protons per year), with the Huronian Supergroup near SNO+ dominantly contributing 7.3-3.0+5.0 TNU to this total. Future systematically sampling of this regional unit and denser seismic surveys will better model its composition and structure, and thus reduce the uncertainty on geoneutrino signal at SNO+. The bulk crustal geoneutrino signal at SNO+ is estimated to be 30.7-4.2+6.0 TNU, which is lower than that predicted in a global-scale reference

  4. Earth's Uranium and Thorium content and geoneutrinos fluxes based on enstatite chondrites

    NASA Astrophysics Data System (ADS)

    Javoy, Marc; Kaminski, Edouard

    2014-12-01

    The Earth's thermal evolution is controlled by the amount of heat released by the radioactive decay of 40K, 238U, 235U and 232Th. Their crust and upper mantle content is inferred from direct sampling, whereas estimating the lower mantle concentrations requires indirect constraints, such as those brought by primitive chondrites, or by geoneutrinos. Here we follow the framework of "E-Earth" models, based on the isotopic and chemical composition of E-chondrites (EC), to calculate U and Th concentrations in the Earth's present day mantle, and the corresponding geoneutrinos flux. The model uses a compilation of data of U and Th contents of EC and account for the Earth differentiation and crust extraction. We obtain that the Bulk Silicate Earth (BSE) contains 15.4±1.8 ppb of Uranium and 51.3±4.4 ppb of Thorium, and has an average Th/U mass ratio of 3.4±0.4, with a peak value around 3.15. The prediction of geoneutrinos events originating from the mantle (i.e., without taking into account the local contribution of the crust) is 5.1±1.0 TNU, with 4.3±0.9 TNU coming from Uranium, and 0.8±0.2 TNU from Thorium. These numbers are in good agreement with the most recent KamLAND detector estimate, and compatible with the (higher) Borexino flux. On the other hand, the KamLAND constraints are not consistent with the high content of heat producing elements in the mantle predicted by the simple application of parameterized convection model to the thermal evolution of the Earth's mantle. Since the measurement error in the mantle neutrino flux is currently dominated by the crustal contribution, geoneutrinos cannot for now discriminate between CI-based and EH-base models of the Earth's composition. Further progress is expected if an ocean based geoneutrino detector is deployed.

  5. Influence of the stiffness of testing machines on the adherence of elastomers

    SciTech Connect

    Barquins, M.

    1983-08-01

    It is shown that the introduction of the fracture mechanics concepts, such as the strain energy release rate G, to solve the problem of the adherence of elastomers, the edge of contact being seen as a crack propagating in mode I in the interface, allows one to predict the dependence of the adherence force with stiffness of testing machines. Moreover, it is shown the general equation of the kinetics of adherence proposed in 1978 in Maugis and Barquins, G - w = w(phi)(a/sub T/..nu..), where w is Dupre's work of adhesion and phi a dissipation function characteristic of the material only depending on temperature and crack speed, is confirmed whatever the stiffness of the testing machine and the instantaneous deformation imposed on the system. Experiments realized with a hemispherical glass lens in contact on a polyurethane surface verify theoretical predictions with an accuracy better than 1%.

  6. Total suppression of superconductivity by high magnetic fields in YBa(2)Cu(3)O(6.6).

    PubMed

    Rullier-Albenque, F; Alloul, H; Proust, Cyril; Lejay, P; Forget, A; Colson, D

    2007-07-13

    We have studied the variation of transverse magnetoresistance of underdoped YBCO(6.6) crystals, either pure or with reduced T(c) down to 3.5 K by electron irradiation, in fields up to 60 T. We find evidence that the superconducting fluctuation contribution to the conductivity is suppressed only above a threshold field H(c)'(T), which is found to vanish at T(c)' > T(c). In the pure YBCO(6.6) sample, H(c)' is already 50 T at T(c). We find that increasing disorder weakly depresses H(c)'(0), T(c)', and T(nu), the onset of the Nernst signal. Thus, these energy scales appear more characteristic of the 2D local pairing than the pseudogap temperature which is not modified by disorder. PMID:17678247

  7. Expected geoneutrino signal at JUNO

    NASA Astrophysics Data System (ADS)

    Strati, Virginia; Baldoncini, Marica; Callegari, Ivan; Mantovani, Fabio; McDonough, William F.; Ricci, Barbara; Xhixha, Gerti

    2015-12-01

    Constraints on the Earth's composition and on its radiogenic energy budget come from the detection of geoneutrinos. The Kamioka Liquid scintillator Antineutrino Detector (KamLAND) and Borexino experiments recently reported the geoneutrino flux, which reflects the amount and distribution of U and Th inside the Earth. The Jiangmen Underground Neutrino Observatory (JUNO) neutrino experiment, designed as a 20 kton liquid scintillator detector, will be built in an underground laboratory in South China about 53 km from the Yangjiang and Taishan nuclear power plants, each one having a planned thermal power of approximately 18 GW. Given the large detector mass and the intense reactor antineutrino flux, JUNO aims not only to collect high statistics antineutrino signals from reactors but also to address the challenge of discriminating the geoneutrino signal from the reactor background. The predicted geoneutrino signal at JUNO is terrestrial neutrino unit (TNU), based on the existing reference Earth model, with the dominant source of uncertainty coming from the modeling of the compositional variability in the local upper crust that surrounds (out to approximately 500 km) the detector. A special focus is dedicated to the 6° × 4° local crust surrounding the detector which is estimated to contribute for the 44% of the signal. On the basis of a worldwide reference model for reactor antineutrinos, the ratio between reactor antineutrino and geoneutrino signals in the geoneutrino energy window is estimated to be 0.7 considering reactors operating in year 2013 and reaches a value of 8.9 by adding the contribution of the future nuclear power plants. In order to extract useful information about the mantle's composition, a refinement of the abundance and distribution of U and Th in the local crust is required, with particular attention to the geochemical characterization of the accessible upper crust where 47% of the expected geoneutrino signal originates and this region contributes

  8. Measurement of the W+- + b anti-b cross-section in 695-pb-1 of p anti-p collisions at CDF II.

    SciTech Connect

    Soderberg, Mitchell Paul; /Michigan U.

    2006-09-01

    W{sup {+-}} + b{bar b} events contain the associated production of a W{sup {+-}} boson, a pair of bottom quarks (b{bar b}), and any number of additional partons. This process is of much importance at hadron collider experiments due to its role as a background source in searches for Standard Model Higgs boson and single top-quark production. In this thesis the results are presented for a measurement of the b-jet cross-section in W{sup {+-}} + b{bar b} events containing 1 or 2 jets in 695 pb{sup -1} of {radical}s =1.96 TeV p{bar p} collisions at the CDF experiment. This is the first measurement of the cross-section of W{sup {+-}} b{bar b} performed in any experiment. The cross-section is defined to be proportional to the number of b-jets from W{sup {+-}} b{bar b} events with one or two jets, and a leptonically decaying W{sup {+-}} with decay products passing kinematics cuts (p{sub T}({ell}{sup {+-}}) {ge} 20.0 GeV, |{eta}({ell}{sup {+-}})| {le} 1.1, p{sub T}({nu}) {ge} 25.0 GeV). The invariant mass distribution of jets identified as containing a long-lived hadron is fit with components for bottom, charm, and light-flavor to find the fraction due to true b-decays. Background b-jet sources are subtracted to isolate the contribution of W{sup {+-}} b{bar b} to the data. The cross-section is measured to be 0.90 {+-} 0.20(stat.) {+-} 0.26(syst.)pb, which compares well with the leading order theoretical prediction of 0.74 {+-} 0.18 pb.

  9. Water quality and pollution status of Chambal river in National Chambal Sanctuary, Madhya Pradesh.

    PubMed

    Saksena, D N; Garg, R K; Rao, R J

    2008-09-01

    The physico-chemical characteristics of Chambal river water in National Chambal sanctuary (Madhya Pradesh) have been studied. The stretch of Chambal river contained in the National Chambal sanctuary (located at 25 degrees 23'-26 degrees 52'N, 76 degrees 28'-79 degrees 15'E) is extending up to 600 km downstream from Kota (Rajasthan) to the confluence of the Chambal with Yamuna river (Etawah). The river flow in Madhya Pradesh spans up to approximately 400 km. Three sampling stations viz., Station A--near Palighat, district Sheopurkalan, Station B--near Rajghat, district Morena and Station C--near Baraighat, district Bhind were established for the collection of water samples during April, 2003 to March, 2004. The water quality parameters namely transparency (12.12-110 cm), colour (transparent-very turbid), turbidity (1-178 TNU), electrical conductivity (145.60-884 microS cm(-1)), total dissolved solids (260-500 mgl(-1)), pH (7.60-9.33), dissolved oxygen (4.86-14.59 mgl(-1)), free carbon dioxide (0-16.5 mgl(-1)), total alkalinity (70-290 mgl(-1)), total hardness (42-140 mgl(-1)), chloride (15.62-80.94 mgl(-1)), nitrate (0.008-0.025 mgl(-1)), nitrite (0.002-0.022 mgl(-1)), sulphate (3.50-45 mgl(-1)), phosphate (0.004-0.050 mgl(-1)), silicate (2.80-13.80 mgl(-1)), biochemical oxygen demand (0.60-5.67 mgl(-1)), chemical oxygen demand (2.40-26.80 mgl(-1)), ammonia (nil-0.56 mgl(-1)), sodium (14.30-54.40 mgl(-1)) and potassium (2.10 mgl(-1)-6.30 mgl(-1)) reflects on the pristine nature of the river in National Chambal sanctuary. On the basis of various parameters studied, Chambal river in this stretch can be placed under the category of oligosaprobic. The water quality analysis, indicated that the riverwater in the sanctuary area is pollution free and can serve as a good habitat for many aquatic animals including endangered species. PMID:19295068

  10. Interplay of critical Casimir and dispersion forces.

    PubMed

    Dantchev, Daniel; Schlesener, Frank; Dietrich, S

    2007-07-01

    Using general scaling arguments combined with mean-field theory we investigate the critical (T approximately Tc) and off-critical (T not equal Tc) behavior of the Casimir forces in fluid films of thickness L governed by dispersion forces and exposed to long-ranged substrate potentials which are taken to be equal on both sides of the film. We study the resulting effective force acting on the confining substrates as a function of T and of the chemical potential mu. We find that the total force is attractive both below and above Tc. If, however, the direct substrate-substrate contribution is subtracted, the force is repulsive everywhere except near the bulk critical point (Tc, mu(c)), where critical density fluctuations arise, or except at low temperatures and (L/a)(beta(Delta)(mu))=O(1), with Delta(mu)=mu-mu(c)<0 and a the characteristic distance between the molecules of the fluid, i.e., in the capillary condensation regime. While near the critical point the maximal amplitude of the attractive force if of order of L(-d) in the capillary condensation regime the force is much stronger with maximal amplitude decaying as L(-1). In the latter regime we observe that the long-ranged tails of the fluid-fluid and the substrate-fluid interactions further increase that amplitude in comparison with systems with short-range interactions only. Although in the critical region the system under consideration asymptotically belongs to the Ising universality class with short-ranged forces, we find deviations from the standard finite-size scaling for xi(ln)(xi/xi0(+/-)) >L even for xi, L>xi0(+/-), where xi[t=(T-Tc)/Tc-->+/-0,Delta(mu)=0]=xi0(+/-)/t/-nu, is the bulk correlation length. In this regime the dominant finite-size contributions to the free energy and to the force stem from the long-ranged algebraically decaying tails of the interactions; they are not exponentially small in L, as it is the case there in systems governed by purely short-ranged interactions, but exhibit a power