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  • 1
    ISSN: 1573-1111
    Keywords: p-tert-Butylcalix[n]arenes ; amines ; thermodynamics ; electrochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Attention is drawn to the need of detailed thermodynamics in calixarene chemistry. The reasons for increasing efforts in this area are underlined and suggestions for new issues to be addressed are given. The solution thermodynamics ofp-tert-butylcalix[n]arenes (n=4, 6, 8) is discussed with particular reference to transfer Gibbs energies which reflect the selective solvation that the tetramer and the octamer undergo in the various solvents. This is followed by recent solution studies on amine-p-tert-butylcalix[n]arene (n=4, 6, 8) in nitrobenzene and in benzonitrile at 298.15 K which indicate the lower acidic character of the tetramer relative to the hexamer and the octamer in these solvents. As an implication of these results, very low conductivities are observed in studies involving the interaction of the former with amines. Thus, thermodynamic studies suggest thatp-tert-butylcalix[4]arene interacts with triethylamine in benzonitrile and in nitrobenzene through hydrogen bonding or ion-pair formation. A thermodynamic cycle is used to investigate the effect associated with the interaction of the amine with the tetramer in these solvents.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Materials and structures 26 (1993), S. 53-55 
    ISSN: 1359-5997
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 261 (1998), S. 123-126 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2016-08-03
    Description: Previous work has shown that the synthetic lethality of the slt2rim101 mutant results from a combination of factors, including improper functioning of the septum assembly machinery. Here, we identify new multicopy suppressors of this lethality including Kss1, Pcl1 and Sph1, none of which seems to be linked to the upregulation of chitin synthesis. Characterization of the suppression mediated by Kss1 showed that it is independent of the transcriptional response of the CWI signaling response, but efficiently restores the Bni4 localization defects produced by the absence of Slt2. Accordingly, Bni4 interacts physically with both kinases, and its levels of phosphorylation are reduced in the slt2 mutant but increased after Kss1 overexpression. Using an assay based on hypersensitive cells of the cdc10-11 mutant, we have pinpointed several MAP kinase phosphorylatable residues required for Bni4 function. Our results, together with a genetic correlation analysis, strongly support a functional model linking Slt2 MAP kinase and Pcl1, a Pho85 cyclin-dependent kinase, in septum assembly through Bni4. This model, based on the coordinated phosphorylation of Bni4 by both kinases, would be able to integrate cellular signals rapidly to maintain cell integrity during cytokinesis.
    Print ISSN: 1567-1356
    Electronic ISSN: 1567-1364
    Topics: Biology
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  • 5
    Publication Date: 2018
    Description: Collimated outflows and jets play a critical role in shaping planetary nebulae (PNe), especially in the brief transition from a spherical AGB envelope to an aspherical PN, which is called the protoplanetary nebula (pPN) phase. We present UV observations of Hen 3-1475, a bipolar pPN with fast, highly collimated jets, obtained with STIS on board the Hubble Space Telescope (HST). The deep, low-dispersion spectroscopy enabled monochromatic imaging of Hen 3-1475 in different UV nebular emission lines; this is the first of such attempt ever conducted for a pPN. The northwest inner knot (NW1) is resolved into four components in Mg ii λ 2800. Through comparison analysis with the HST optical narrowband images obtained 6 yr earlier, we found that these components of NW1 hardly move, despite of a negative gradient of high radial velocities, from −1550 km s - 1 on the innermost component to ∼−300 km s - 1 on the outermost. These NW1 knot components might thus be quasi-stationary shocks near the tip of the conical outflow of Hen 3-1475.
    Electronic ISSN: 2075-4434
    Topics: Physics
    Published by MDPI
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  • 6
    Publication Date: 2019
    Description: 〈span〉〈div〉Abstract〈/div〉In this work, three samples of the zeolite stilbite from the Faroe Islands have been used to prepare zeolite/hydroxyapatite composite materials that have been tested for the removal of fluoride present as geogenic contaminant in underground water. The Faroe Islands are an archipelago in the North Atlantic that have volcanic origins of Paleocene and early Eocene age. Early reports on the presence of zeolites in the Faroe Islands indicate abundance of chabazite, analcite, mesolite, heulandites, and stilbite, with heulandite and stilbite dominant in the northern and northwestern part of the islands. Further investigations of the Faroese Geological Survey yielded zeolitic phases in Vestmanna, Streymoy, Morkranes, and Eysturoy, as well as in the sea tunnel that connects the island of Eysturoy with the island of Borðoy. Three stilbite samples coming from these locations have been used with the aim of producing composite materials for fluoride removal. For this purpose, the samples were exposed to a phosphate solution at room temperature for selected periods of time, in such a way that a hydroxyapatite layer develops on the surface of the zeolite crystals. The resulting composites consist of approximately 93% zeolite and 7% nano-hydroxyapatite, which is the active phase for fluoride removal. Excess fluoride (above 1.5 mg/L according to WHO) in drinking waters provokes dental or skeletal fluorosis, an endemic health problem in more than 25 countries. The defluoridation studies in our work are performed using real waters from Spain with initial [F〈sup〉–〈/sup〉] of 7.1 mg/L. The capacity of the Faroe Islands stilbite-based adsorbent reaches 0.3 mg F〈sup〉–〈/sup〉/g, showing similar behavior regardless of the stilbite sample used. The impact of the particle size of stilbite in the final defluoridation capacity is remarkable. An increase in the particle size leads to a dramatic decrease in the surface area, affecting the growth of the nano–hydroxyapatite on the zeolite surface and hindering, as a result, its capacity to remove fluoride. Interestingly, electron microscopy and X–ray powder diffraction results clearly show that nano–hydroxyapatite grow on the zeolite surface with a preferential orientation that maximizes the exposure of the (001) face containing the active sites for defluoridation, thus explaining the high F-removal efficiency of these materials.〈/span〉
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences , Physics
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  • 7
    Publication Date: 2011-11-03
    Description: An innovative technique has been developed to assess moisture sources contributing to precipitation. It represents an advance with respect to previously developed methodologies because it allows to discriminate more effectively between terrestrial versus oceanic sources, and also to detect with greater precision the relative importance of remote versus local sources together with the sequence of evaporation associated with a rainfall event. It is based upon the use of a mesoscale model to simulate a selected precipitation episode and a Lagrangian trajectory model to evaluate three-dimensional back-trajectories in order to track the vapor parcels transporting the target precipitation to their surface evaporative sources. An extreme sequence of rainfall events occurred over central Europe between August 11th and 13th is chosen to put the methodology into test. A domain centered in the region and spanning 6372 km in the W–E direction and 5940 km in the N–S direction is chosen to assess moisture sources. Results show the evolving role of various sources throughout the duration of the event, indicating that they shift from the southern to northern and eastern source regions, while a simultaneous decrease of marine sources with respect to terrestrial sources occurs from the onset of the event to its ending phase. The capability of discriminating moisture sources with precision is an important requirement to better understand the mechanisms of extreme rainfalls.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Publication Date: 2011-11-04
    Description: Since the optimal design of dividing wall columns (DWC) is a highly nonlinear and multivariable problem, an appropriate solving tool is required. In this paper a multi-objective genetic algorithm with restrictions is considered to design columns with dividing walls. Also, a methodology is proposed for sizing the DWC. The proposed design methodology allows achieving appropriate designs for columns with two dividing walls. As expected, the physical structures that allow the use of one or two dividing walls are not so different from each other and, as a consequence, the difference in the total annual costs for both systems depends mainly on the energy requirements. For the optimal design of dividing wall columns (DWC), a multi-objective genetic algorithm with restrictions is considered. Additionally, a methodology is proposed for sizing the DWC. The proposed design methodology shows robustness and it allows obtaining an adequate set of optimal designs for complex distillation sequences.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley
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  • 9
    Publication Date: 2007-11-03
    Description: The evolution of insect resistance threatens the effectiveness of Bacillus thuringiensis (Bt) toxins that are widely used in sprays and transgenic crops. Resistance to Bt toxins in some insects is linked with mutations that disrupt a toxin-binding cadherin protein. We show that susceptibility to the Bt toxin Cry1Ab was reduced by cadherin gene silencing with RNA interference in Manduca sexta, confirming cadherin's role in Bt toxicity. Native Cry1A toxins required cadherin to form oligomers, but modified Cry1A toxins lacking one alpha-helix did not. The modified toxins killed cadherin-silenced M. sexta and Bt-resistant Pectinophora gossypiella that had cadherin deletion mutations. Our findings suggest that cadherin promotes Bt toxicity by facilitating toxin oligomerization and demonstrate that the modified Bt toxins may be useful against pests resistant to standard Bt toxins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Soberon, Mario -- Pardo-Lopez, Liliana -- Lopez, Idalia -- Gomez, Isabel -- Tabashnik, Bruce E -- Bravo, Alejandra -- 1R01 AI066014/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 2007 Dec 7;318(5856):1640-2. Epub 2007 Nov 1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Apartado Postal 510-3, Cuernavaca 62250, Morelos, Mexico. mario@ibt.unam.mx〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17975031" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bacterial Proteins/chemistry/*genetics/metabolism/*toxicity ; Bacterial Toxins/chemistry/*genetics/metabolism/*toxicity ; Cadherins/genetics/metabolism ; Endotoxins/chemistry/*genetics/metabolism/*toxicity ; Genetic Engineering ; Hemolysin Proteins/chemistry/*genetics/metabolism/*toxicity ; *Insecticide Resistance ; Larva ; *Manduca/genetics/metabolism ; *Moths/genetics/metabolism ; Mutation ; *Pest Control, Biological ; RNA Interference
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2018
    Description: The study and characterization of the exoplanets’ atmospheres and composition is in its infancy. The large facilities that will make feasible to image an exo-Earth are currently under study. This contribution to the special issue on “detection and characterization of extrasolar planets” is a summary on the current status of the design studies to build large space-based facilities working in the 100–3000 nm range for this purpose. The three basic designs: Fresnel imagers, starshades, and coronagraphs on large space telescopes are described. An outline of the pros and cons for each design is provided. The relevance of transmission spectroscopy to characterize exoplanets atmospheres is pointed out.
    Electronic ISSN: 2076-3263
    Topics: Geosciences
    Published by MDPI
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