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  • 1
    Electronic Resource
    Electronic Resource
    Calix[4]arene-Based (Hemi)carcerands and Carceplexes: Synthesis, Functionalization, and Molecular Modeling Study (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 639-654 
    Details
    ISSN: 0947-6539
    Keywords: calixarenes ; carcerands ; inclusion compounds ; molecular devices ; resorcinarenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 11 calix[4]arene-based carceplexes obtained by solvent or doped inclusion is reported. Carceplexes with amides, for example, DMF, NMP, and 1,5-dimethyl-2-pyrrolidinone, and sulfoxides, for example, DMSO and thiolane-1-oxide, were obtained by solvent inclusion. In these cases the yield of the carceplex decreases with increasing guest size. Potential guests that do not form carceplexes by solvent inclusion, such as 2-butanone and 3-sulfolene, could be incarcerated by doped inclusion with 1,5-dimethyl-2-pyrrolidinone as a solvent “doped” with 5-15 vol% of potential guest. The amide bridges of the carceplexes were converted into thioamide bridges in essentially quantitative yield by means of Lawesson's reagent in refluxing xylene. The dynamic properties of the incarcerated guests were examined by 2D NMR spectroscopy. Whereas for most guests a preference for one orientation inside the calix[4]arene-based (thia)carcerands was observed, for DMA, NMP, and ethyl methyl sulfoxide inside calix[4]arene-based (thia)carcerands two different orientations were present. The energy barriers for interconversion between the various orientations of DMA, NMP, and ethyl methyl sulfoxide inside calix[4]arene-based (thia)-carcerands were determined with 2D EXSY NMR. The energy barriers are higher for the thiacarcerands than for the corresponding carcerands with amide bridges. This may be due to the stronger hydrogen-bond-donating character of the thioamide group. Furthermore, molecular modeling simulations indicate that in case of the thiacarcerand the cavity is smaller as a result of a smaller diametrical distance between the NH atoms. Our results demonstrate that molecular modeling can be used to estimate the energy barriers for interconversion; the calculated activation energies showed good quantitative agreement with the experimental values.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030421
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Plant endemism in two forests in southern Bahia, Brazil (1998)
    Springer
    Biodiversity and conservation 7 (1998), S. 311-322 
    Details
    ISSN: 1572-9710
    Keywords: Atlantic coastal forest ; Bahia, Brazil ; endemism ; flora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An important factor in determining species rarity is the geographic distribution of species. Estimates were made of the level of endemism of the flora of two sites in the southern Bahian wet forest zone. Estimates were made for endemism in the Atlantic forest biome and for the much more restricted area of southern Bahia and northern Espi´rito Santo and are derived from analyses of the distributions of the species known from each area. The species checklist for each area is based on identified specimens resulting from intensive collecting in a forest near Serra Grande (40km north of Ilhe´us) and the Una Biological Reserve (40km south of Ilhe´us). Slightly less than half of the species (45.2% at Una and 47.7% at Serra Grande) have widespread distributions and 7.4% at each site are disjunct between the coastal forests and Amazonia. In the Una Reserve, 44.1% of the species are endemic to the coastal forest and 28.1% endemic to southern Bahia and northern Espi´rito Santo. At Serra Grande, 41.6% of the species are endemic to the coastal forest and 26.5% endemic to southern Bahia and northern Espi´rito Santo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008825627656
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and Application of Iso(thio)cyanate-Functionalized Calix[4]arenes (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2235-2245 
    Details
    ISSN: 0947-3440
    Keywords: Calix[4]arenes ; Cavitands ; Iso(thio)cyanates ; Carbamates ; (Thio)ureas ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aminocalix[4]arenes 7-12 react with triphosgene and thiophosgene to the corresponding iso(thio)cyanate-functionalized calix[4]arenes 13-20. Carbamate- (21-25) and ureasubstituted calix[4]arenes (26,27) can be obtained via isocyanatocalix[4]arenes using a one-pot synthesis starting from the corresponding aminocalix[4]arenes in moderate to good yields. Isothiocyanate-functionalized calix[4]arenes 16, 18 react selectively with amines to the corresponding thioureas 28-31 in 59-83% yield. Reaction of isothiocyanate-functionalized calix[4]arenes 16, 19, 20 with cavitands 34, 38 gives 2:2 products 42-45 in 35-42% yield.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971110
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  • 4
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    A Review of Technologies and Techniques for Indoor Navigation Systems for the Visually Impaired (2020)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2020-07-15
    Description: Technologies and techniques of location and navigation are advancing, allowing greater precision in locating people in complex and challenging conditions. These advances have attracted growing interest from the scientific community in using indoor positioning systems (IPSs) with a higher degree of precision and fast delivery time, for groups of people such as the visually impaired, to some extent improving their quality of life. Much research brings together various works that deal with the physical and logical approaches of IPSs to give the reader a more general view of the models. These surveys, however, need to be continuously revisited to update the literature on the features described. This paper presents an expansion of the range of technologies and methodologies for assisting the visually impaired in previous works, providing readers and researchers with a more recent version of what was done and the advantages and disadvantages of each approach to guide reviews and discussions about these topics. Finally, we discuss a series of considerations and future trends for the construction of indoor navigation and location systems for the visually impaired.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by Molecular Diversity Preservation International
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    PAPER CURRENT
  • 5
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    Non-Intrusive Velocity Measurements with MTV During DCC Event in the HTTF (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Velocity profiles are measured using molecular tagging velocimetry (MTV) in the high temperature test facility (HTTF) at Oregon State University during a depressurized conduction cooldown (DCC) event. The HTTF is a quarter scale electrically heated nuclear reactor simulator designed to replicate various accident scenarios. During a DCC, a double ended guillotine break results in the reactor pressure vessel (RPV) depressurizing into the reactor cavity and ultimately leading to air ingress in the reactor core (lock-exchange and gas diffusion). It is critical to understand the resulting buoyancy-driven flow to characterize the reactor self-cooling capacity through natural circulation. During tests conducted at ambient pressure and temperature, the RPV containing helium is opened (via the hot and cold legs) to a large vessel filled with nitrogen to simulate the atmosphere. The velocity profile on the hot leg pipe centerline is recorded at 10 Hz with MTV based on NO tracers. The precision of the velocimetry was measured to be 0.02 m/s in quiescent flow prior to the tests. A helium flow from the RPV is initially observed in the top quarter of the pipe. During the first 20 seconds of the event, helium flows out of the RPV with a maximum velocity below 2 m/s. The velocity profile transitions from parabolic to linear in character and decays slowly over the rest of the recording; peak velocities of 0.2 m/s are observed after 30 min. A counter-flow of nitrogen is also observed intermittently, which occurs at lower velocities (〉0.1 m/s).
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NF1676L-26169 , International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17); Sep 03, 2017 - Sep 08, 2017; Xian; China
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Development of a Molecular Tagging Velocimetry Technique for Non-Intrusive Velocity Measurements in Low-Speed Gas Flows (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: N2O molecular tagging velocimetry (N2O-MTV) is developed for use in very-high-temperature reactor environments. Tests were carried out to determine the optimum excitation wavelength, tracer concentration, and timing parameters for the laser system. Using NO tracers obtained from photo-dissociation of N2O, velocity profiles are successfully obtained in air, nitrogen, and helium for a large range of parameters: temperature from 295 to 781 K, pressure from 1 to 3 bars, with a velocity precision of 0.01 m/s. Furthermore, by using two read pulses at adjustable time delays, the velocity dynamic range can be increased. An unprecedented dynamic range of 5,000 has been obtained to successfully resolve the flow during a helium blowdown from 1000 m/s down to 0.2 m/s. This technique is also applied to the high-temperature test facility (HTTF) at Oregon State University (OSU) during a depressurized condition cooldown (DCC) event. Details of these measurements are presented in a companion paper. This technique shows a strong potential for fundamental understanding of gas flows in nuclear reactors and to provide benchmark experimental data to validate numerical simulations.
    Keywords: Instrumentation and Photography
    Type: NF1676L-26170 , International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17); Sep 03, 2017 - Sep 08, 2017; Xian; China
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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