2,681 research outputs found
ENZYMIC EXCHANGE OF LEUCINE BETWEEN DIFFERENT COMPONENTS OF LEUCINE ACCEPTOR RNA IN ESCHERICHIA COLI
JPL field measurements at the Finney County, Kansas, test site, October 1976: Ground-based microwave radiometric measurements
Microwave brightness temperature measurements were made as part of the Joint Soil Moisture Experiment. These measurements are reported with a description of the JPL microwave radiometry van facility. The data will be used with ground truth data from the test site and microwave data from aircraft overflights to investigate the potential of microwave radiometry for soil moisture remote sensing under field conditions
Water vapor radiometry research and development phase
This report describes the research and development phase for eight dual-channel water vapor radiometers constructed for the Crustal Dynamics Project at the Goddard Space Flight Center, Greenbelt, Maryland, and for the NASA Deep Space Network. These instruments were developed to demonstrate that the variable path delay imposed on microwave radio transmissions by atmospheric water vapor can be calibrated, particularly as this phenomenon affects very long baseline interferometry measurement systems. Water vapor radiometry technology can also be used in systems that involve moist air meteorology and propagation studies
Effects of tape covering and vine vigor on development of surface callus in girdle of grapevine
The effects of vine vigor (shoot growth) and covering the girdle surface with plastic tape on the development of a surface callus (SC) in the girdle of grapevine were studied by histological observation. The SC was formed in a tape-covering treatment but was not formed unless the girdle surface was covered with plastic tape (exposing treatment). Histological observation revealed that in the tape-covering treatment, callus cells developed mainly from the ray parenchyma cells on the girdle surface 2 days after girdling (DAG), leading to the formation of the SC, which grew and filled the girdle portion by 7 DAG. When 16 vines were divided into three categories based on scaffold branch length, vines with 7.5 m scaffold branches developed shorter shoots with smaller internode diameters than did vines with 4.5 and 6.0 m scaffold branches. In vines with 7.5 m scaffold branches, the SC covered a smaller area of the girdle surface than in vines with 4.5 and 6.0 m scaffold branches. The length and diameter of the shoot were significantly correlated (r2 = 0.75** and 0.70**, respectively) with the ratio of the girdle area covered by the SC to the whole girdle area (SC covering ratio). These results show that the SC originates mainly from the ray parenchyma cells and that SC development is strongly affected by vine vigor. Consequently, to ensure SC development, girdling should be done by tape covering in vines with shoot diameters larger than 8 mm.
The table mountain 8-mm-wavelength interferometer
The system components, performance, and calibration of two element radio interferometer operating at 8.33 mm wavelength are discussed. The interferometer employs a 5.5 m and a 3 m diameter antenna on an east-west baseline of 60 or 120 m, yielding fringe spacings at transit of 28 or 14 in. respectively. The broad intermediate frequency bandpass of 100 to 350 MHz and the system noise temperature of 500 K provide high sensitivity for the measurement of continuum sources. The interferometer has been used for high resolution studies of the planets and the Sun, and it is currently being adapted to study solar flare emissions at high spatial and time resolution
Dimensionality and Irreversibility Field in YBa_2Cu_3O_7 Films (High Field Superconductors)
In order to investigate the relationship between the flux pinning and dimensionality, the critical current density J_c for YBa_2Cu_3O_7 films was measured as a function of temperature, field and tilt angle between field and c-axis. The kink anomaly in the temperature dependence of J_c for B⊥c was observed as the dimensional crossover from 3D extrinsic pinning to 2D intrinsic pinning. The irreversibility field B_i for B//c was measured in fields up to 23T and estimated to be 90T at 30K using the scaling law of the pinning force densities. The enhancement of B_i from a power law (1-T/T_c)^n with n≈1.5 for B//c was observed below 40K. This suggests the formation of the 2-dimensional pancake vortex in YBa_2Cu_3O_7
Varietal differences in the texture of grape berries measured by penetration tests
Penetration tests were made on 8 mm thick flesh sections from grape berries of 22 cultivars of Vitis vinifera L. and 18 of Vitis labruscana Bailey. Deformation at the first major peak (DFP), maximum force (MF), force at the first major peak (FFP) and work to the first major peak (WFP) were recorded. High correlation coefficients were obtained between the rating of difficulty of breakdown on mastication in the sensory tests and DFP (r=0.86**), and the rating of flesh firmness in the sensory test and MF (r=0.84**). The mean value and variance of DFP and WFP were significantly higher in V. labruscana than in V. vinifera, whereas those of MF were nearly the same. DFP and MF were not correlated for V. vinifera cultivars, but were for V. labruscana cultivars (r=0.68**). These results indicate that the texture of V. labruscana had a wide variation in toughness whereas that of V. vinifera was brittle and did not have a wide variation in toughness; both groups had the same variation in firmness
Comments on Drinfeld Realization of Quantum Affine Superalgebra and its Hopf Algebra Structure
By generalizing the Reshetikhin and Semenov-Tian-Shansky construction to
supersymmetric cases, we obtain Drinfeld current realization for quantum affine
superalgebra . We find a simple coproduct for the quantum
current generators and establish the Hopf algebra structure of this super
current algebra.Comment: Some errors and misprints corrected and a remark in section 4
removed. 12 pages, Latex fil
A Liapunov functional for a matrix neutral difference-differential equation with one delay
AbstractFor the matrix neutral difference-differential equation ẋ(t) + Aẋ(t − τ) Bx(t) + Cx(t − τ) we construct a quadratic Liapunov functional which gives necessary and sufficient conditions for the asymptotic stability of the solutions of that equation. We consider a difference equation approximation of the difference-differential equation, and for this difference equation we construct a Liapunov function from which we obtain the desired Liapunov functional by an appropriate limiting process. The Liapunov functional thus obtained gives the best possible estimate for the rates of growth or decay of the solutions of the matrix neutral difference-differential equation. The results obtained are natural generalizations of previous results obtained for a matrix retarded difference-differential equation with one delay
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