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  • ASTROPHYSICS  (5)
  • INSTRUMENTATION AND PHOTOGRAPHY  (2)
  • Primary production  (2)
  • 81.60J  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Dopant-induced excimer laser ablation of Poly(tetrafluoroethylene) (1992)
    Springer
    Applied physics 54 (1992), S. 227-230 
    Details
    ISSN: 1432-0649
    Keywords: 78.65H ; 81.60J
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Poly(tetrafluoroethylene) (PTFE) does not exhibit excimer laser etching behavior at conventional, e.g., single photon absorption, emissions of 193, 248, and 308 nm, due to the lack of polymer/photon interaction. This is not surprising since the electronic transitions available to the PTFE molecule are high energy and thus require short wavelength the radiation However, by incorporating a small quantity of material into the non-absorbing fluoropolymer matrix that interacts strongly with the emitted laser energy, e.g., a dopant, successful ablation, both in terms of etch rate and structuring quality occurs. Specifically, excimer laser ablation of PTFE films containing 5, 10, and 15% polyimide (wt/wt) as a dopant was achieved at 308 nm in a fluence range of 1 to 12 J/cm2. Ablation rates for the materials increased with increasing fluence and, at the polyimide levels investigated, varied inversely with dopant concentration. All compositions exhibited excellent structuring quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325507
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The biomass of an Indian monsoonal wetland before and after being overgrown with Paspalum distichum L. (1993)
    Springer
    Plant ecology 109 (1993), S. 81-90 
    Details
    ISSN: 1573-5052
    Keywords: Cyperus alopecuroides ; Hydrilla verticillata ; Ipomoea aquatica ; Primary production ; Scirpus tuberosus ; Sporobolus helvolus ; Standing crop ; Water level
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Paspalum distichum L. has been the dominant species in the monsoonal wetlands of the Keoladeo National Park in northcentral India since 1982 when grazing by water buffalo and domestic cattle was halted. Maximum water levels in these wetlands occur immediately after the end of the summer monsoon in late September of early October and then decline until the next summer monsoon the following June. After the normal 1985 monsoon, maximum water depths were around 140 cm. After the poor 1986 monsoon, maximum water depths were only around 60 cm. Paspalum distichum maximum aboveground biomass at four sites ranged from 850 g m-2 at the shallowest site to 3400 g m−2 at a deep water site. The maximum biomass of other vegetation types, which had dominated this wetland prior to 1982, ranged from 1400 g m-2 at a deep water site (Ipomoea aquatica Forsk.) to only 240 g m-2 to 400 g m-2 at a deep-water submersed site (Hydrilla verticillata (L. f.) Royle/Cyperus alopecuroides Rottb.) and at a shallow emergent site (Scirpus tuberosus Desf./Sporobolus helvolus (Trin.) Dur. et Schinz). For all vegetation types, biomass changed seasonally in response to changing water levels and temperatures. After the 1986 monsoon, above-ground biomass for all vegetation types was much lower than it had been after the 1985 monsoon. Mean below-ground biomass was very low in all vegetation types (1 to 47 g m-2). Paspalum distichum had a higher aboveground biomass at nearly all water depths in all seasons than that of the pre-1982 vegetation types. Paspalum distichum belowground biomass, however, is comparable to, or less than, that of the pre-1982 vegetation types. During years with an average monsoon, the overall primary production of these wetlands is estimated to have increased 2.5 to 3.5-fold since they were overgrown with Paspalum distichum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149547
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  • 3
    Electronic Resource
    Electronic Resource
    Changes in the composition, structure, and production of plant communities along a perturbed wetland coenocline (1976)
    Springer
    Plant ecology 32 (1976), S. 87-96 
    Details
    ISSN: 1573-5052
    Keywords: Coenocline ; Drawdown ; Emergent zone ; Iowa ; Marsh ; Meadow zone ; Perturbation ; Primary production ; Simpson's index ; Submersed zone ; Wetland ; Zonation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Comparisons of a wetland coenocline before and after a drought-caused drawdown and the refilling of the basin to a higher-than-normal water level revealed that there was little difference in the above ground standing crop or in the floristic composition of the submersed, emergent or meadow zones along the coenocline. However, the position of many species along the coenocline shifted in response to these perturbations.Sagittaria latifolia, Carex spp.,Patamogeton sp. aff.pusillus all were found 2 to 4 m closer to shore.Glyceria grandis is normally found only in the meadow zone; but after the drawdown, it was found along the whole lenght of the coenocline. The drawdown also nearly eliminatedCeratophyllum demersum from the coenocline. Species richness as a result of these perturbations increased in the submersed (3.3 to 5.9) and emergent (3.6 to 4.3) zones, but decreased in the meadow zone (7.6 to 6.0). The Simpson's index in all three zones was not appreciably influenced by the perturbations. The average Simpson's indices for the meadow, emergent and submersed zones were 0.4, 0.7 and 0.5 respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02111903
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  • 4
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    Hydrodynamic effects in the atmosphere of variable stars (1975)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Numerical models of variable stars are established, using a nonlinear radiative transfer coupled hydrodynamics code. The variable Eddington method of radiative transfer is used. Comparisons are for models of W Virginis, beta Doradus, and eta Aquilae. From these models it appears that shocks are formed in the atmospheres of classical Cepheids as well as W Virginis stars. In classical Cepheids, with periods from 7 to 10 days, the bumps occurring in the light and velocity curves appear as the result of a compression wave that reflects from the star's center. At the head of the outward going compression wave, shocks form in the atmosphere. Comparisons between the hydrodynamic motions in W Virginis and classical Cepheids are made. The strong shocks in W Virginis do not penetrate into the interior as do the compression waves formed in classical Cepheids. The shocks formed in W Virginis stars cause emission lines, while in classical Cepheids the shocks are weaker.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Cepheid Modeling; p 71-83
    Format: text
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  • 5
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    Mean colors of Cepheids (1975)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Color observations of Cepheids can be interpreted by a color effective temperature relation to give different T sub e values for each kind of mean color. Here, theoretical colors from numerical integrations of Cepheid pulsations are used to determine the proper method of taking the color mean in order to get, by the color T sub e relation, the correct nonpulsating T sub e.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Cepheid Modeling; p 43-55
    Format: text
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  • 6
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    Theoretical mean colors for RR Lyrae variables (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A hydrodynamically pulsating 0.6 solar mass model of a typical RR Lyrae variable was studied with a radiation transport-hydrodynamic computer program to predict theoretical T sub 3 and colors at many phases and to find the proper methods for getting mean colors and the consequent mean effective temperatures. The variable Eddington radiation approximation method was used with gray and with multifrequency absorption coefficients to represent the radiation flow in the outer optically thin layers. Comparison between observed and computed B-V colors indicate that these low Z population 2 models are reasonably accurate using King 1A composition opacities. The well known Oke, Giver, and Searle relation between B-V and T sub e reproduced. Mean colors were found by four different averaging methods. The method that gives a mean color and the mean T sub e closest to the nonpulsating model was the separate intensity means of B and V.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 293-310
    Format: application/pdf
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  • 7
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    Light curves for bump Cepheids computed with a dynamically zoned pulsation code (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The dynamically zoned pulsation code developed by Castor, Davis, and Davison was used to recalculate the Goddard model and to calculate three other Cepheid models with the same period (9.8 days). This family of models shows how the bumps and other features of the light and velocity curves change as the mass is varied at constant period. The use of a code that is capable of producing reliable light curves demonstrates that the light and velocity curves for 9.8 day Cepheid models with standard homogeneous compositions do not show bumps like those that are observed unless the mass is significantly lower than the 'evolutionary mass.' The light and velocity curves for the Goddard model presented here are similar to those computed independently by Fischel, Sparks, and Karp. They should be useful as standards for future investigators.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 175-186
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  • 8
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    Repeatable electrical measurement instrumentation for use in the accelerated stress testing of thin film solar cells (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Attention is given to the construction, calibration, and performance of a repeatable measurement system for use in conjunction with the accelerated stress testing of a-Si:H cells. A filtered diode array is utilized to approximate the spectral response of any type of solar cell in discrete portions of the spectrum. It is noted that in order to achieve the necessary degree of overall repeatability, it is necessary to pay particular attention to methods of contacting and positioning the cells.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 9
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    On the mass of the Cepheid X Cygni (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Using a new non-Lagrangian hydrodynamic radiation transport code, models of the Cepheid X Cygni have been calculated and compared with new observations. Adopting an effective temperature of 5300 K, the luminosity was varied for stellar masses of 6, 8, and 9 solar masses in order to obtain a period of 16.4d. The results indicate that in order to find reasonable agreement between the light curves as calculated and observed, the mass used in the models must be nearly the evolutionary mass, not some 60% less as found in earlier work for Cepheids with periods from 7d to 10d. In addition, the new observations support the physical reality of the so-called 'artificial viscosity dip'.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 10
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    A new thermal radiation detector using optical heterodyne detection of absorbed energy (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The operating principles of a new kind of room-temperature thermal radiation detector are described. In this device modulated light heats a gas, either directly or by conduction from a thin absorbing membrane, and the resultant change in density of the gas is detected by optical heterodyning. The performance of a membrane device of this kind agrees well with the predictions of theory.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Infrared Physics (ISSN 0020-0891); 23; 177-182
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