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  • 1
    Electronic Resource
    Electronic Resource
    Effects of Injected Volume and Applied Voltage on Column Efficiency in Capillary Electrochromatography with Open Tubular Columns of 10 μm i. d. (2000)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 373-378 
    Details
    ISSN: 0935-6304
    Keywords: Open tubular columns ; capillary electrochromatography ; column efficiency ; injected volume ; applied voltage ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of some instrumental parameters on column efficiency in open tubular capillary electrochromatography (OTCEC) has been evaluated. First, it was investigated whether band broadening due to the sample injection process is within a tolerable range when an open tubular column (OTC) of about 10 μm i. d. is used. As a result of the small injection profile factor (K2 = 1.3), injected volumes must be sufficiently small (less than 10 pL) to avoid a significant efficiency loss (〉5%) when hydrodynamic injection by siphoning is employed. Secondly, the kinetic performance of OTCs in a CEC system was estimated from the variation of the reduced plate height (h) with the reduced linear velocity (ν) which was controlled by the voltage applied. Reasonable agreement was obtained between the theoretical h versus ν curve and the experimental values for a group of polycyclic aromatic hydrocarbons used as test compounds. Values of 0.25 for minimum h at an optimum ν of 16 are estimated, which permit separations with around 400,000 plates per meter to be obtained in less than 5 min. Finally, the possibility of estimating the diffusion coefficients of the solutes in the mobile phase from the plot of the height of a theoretical plate versus electroosmotic flow velocity is shown.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of New Seven-Membered Ring Cyclic Dipeptides From Functionalized β-Amino Acids (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 251-255 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; coupling ; N-Substituted amide ; Cyclizations ; Cyclic dipeptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A short synthesis of new, functionalized seven-membered ring cyclic dipeptides is described. After the coupling of N-protected β-amino acids to N-substituted α-amino tert-butyl esters, the protective groups of the terminal functions were removed and the cyclization took place diastereoselectively in the presence of the coupling agent BOP. Amide substitution was found to be effective in promoting the cyclization of linear dipeptides.
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of Silaproline, a New Proline Surrogate (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 807-811 
    Details
    ISSN: 1434-193X
    Keywords: Proline analogues ; Asymmetric synthesis ; Schöllkopf's method ; Silicon ; Amino acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The asymmetric synthesis of a new proline surrogate, incorporating the dimethylsilyl group at position 4 of proline using Schöllkopf's bis-lactim ether method, is described.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Reductive Cleavage of Potential Cholinomimetics Thiadiazolidinones: A New Family of Spiro Compounds (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 675-680 
    Details
    ISSN: 1434-193X
    Keywords: Thiadiazolidinones ; Spiro compounds ; Thiazoles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The design, synthesis and evaluation of a series of 1,2,4-thiadiazolidinones with potential muscarinic receptor binding properties has been performed. During the synthesis of the target compounds, we observed an interesting reductive cleavage of the thiadiazolidinone system which leads to the formation of the novel piperidine spiro triazine heterocycle. The synthesis, structural elucidation (NMR spectroscopy and X-ray diffraction) and biological evaluation of the new compounds are described. With the structures unequivocally established, a mechanism for the formation of the spiro compound is proposed.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/099462_s.pdf or from the author.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanisms of Cyclopalladation Reactions in Acetic Acid: Not So Simple One-Pot Processes (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 217-224 
    Details
    ISSN: 1434-1948
    Keywords: Reaction mechanisms ; Cyclopalladation ; Acetic acid ; Pd-C bond stability ; Polynuclear species ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The processes operating during the synthetic cyclopalladation reactions of imines in acetic acid have been studied from a kinetico-mechanistic point of view. These reactions include a fast initial coordination to the palladium through the N-donor atom of the imine, followed by the proper C-H bond activation to produce the acetato bridged dimeric species. At this point, the lability of the bridging acetato groups, the hydrolysis of the C-Pd bonds, and/or the hydrolysis of C=N exo bonds contribute to the generation of dark red polynuclear compounds. The processes occurring after the C-H activation have been followed kinetically, both from palladium acetate plus imine, and the synthetically pure isolated acetato dimers as starting materials. The kinetic and activation parameters have been found identical within experimental error whatever the starting material was (k323 = 1.5 × 10-4 s-1; ΔH# = 51 kJ mol-1; ΔS# = -163 JK-1 mol-1 ΔV# = +19 cm3 mol-1 for the 4-ClC6H4-CH=N-CH2-C6H5 imine derivative 1a). Acidolysis of C-Pd bonds has been found to occur in these polynuclear species. When alternative monomeric Cbenzylic-Pd bond-containing complexes are possible follow ups of the reactions produce them as final dead-end complexes (k323 = 2.2 × 10-5 s-1; ΔH# = 61 kJ mol-1; ΔS# = JK-1 mol-1 ΔV# ≈ 0 cm3 cm-1 for the [2,4,6-(CH3)3]C6H2-CH=N-CH2-[2-(CH3]C6[H4] imine derivative 3d). The same study has been carried out with primary amines in order to check the validity of the data if C=N bond hydrolysis is taking place in the imine derivatives with exo C=N bonds. For complexes with similar type of metallacycles, the results agree reasonably well with the proposed mechanism [k323 = 1.2·10-4 s-1, ΔH# = 46 kJ·mol-1, ΔS# = -180 J·K-1mol-1, ΔV# = -16 cm3·mol-1 for the polynuclear formation of the C6H5-CH2-NH2 derivative 4e; k323 = 3.0·10-4 s-1, ΔH# = 55 kJ·mol-1, ΔS
    Additional Material: 1 Ill.
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  • 6
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    Climate-driven basin-scale decadal oscillations of oceanic phytoplankton (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-12-08
    Description: Phytoplankton--the microalgae that populate the upper lit layers of the ocean--fuel the oceanic food web and affect oceanic and atmospheric carbon dioxide levels through photosynthetic carbon fixation. Here, we show that multidecadal changes in global phytoplankton abundances are related to basin-scale oscillations of the physical ocean, specifically the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation. This relationship is revealed in approximately 20 years of satellite observations of chlorophyll and sea surface temperature. Interaction between the main pycnocline and the upper ocean seasonal mixed layer is one mechanism behind this correlation. Our findings provide a context for the interpretation of contemporary changes in global phytoplankton and should improve predictions of their future evolution with climate change.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Martinez, Elodie -- Antoine, David -- D'Ortenzio, Fabrizio -- Gentili, Bernard -- New York, N.Y. -- Science. 2009 Nov 27;326(5957):1253-6. doi: 10.1126/science.1177012.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉UPMC University of Paris 06, UMR 7093, Laboratoire d'Oceanographie de Villefranche (LOV), 06230 Villefranche-sur-Mer, France. martinez@obs-vlfr.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19965473" target="_blank"〉PubMed〈/a〉
    Keywords: Atlantic Ocean ; Biomass ; Chlorophyll/*analysis ; *Climate ; *Ecosystem ; Global Warming ; Indian Ocean ; Oceans and Seas ; Pacific Ocean ; Phytoplankton/*physiology ; Population Dynamics ; Seasons ; *Seawater/chemistry ; Temperature ; Time Factors
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Calidad ambiental de la zona costera del Golfo de Batabanó, Cuba (2008)
    CONyMA
    Details
    Publication Date: 2021-05-19
    Description: The anthropogenic affectation was evaluated on the coast N of the Gulf of Batabanó in May 2003 (corresponding to the provinces of Matanzas and Havana), in areas located in the line of the coast. The results were compared with the historical information of the sector. In the coast N and the Ensenada of the Broa, the parameters oxygen saturation, DBO5 and DQO showed characteristic high values of eutrofication. The biggest contribution in the Cianoficies was in the near coastal areas to sources of organic contamination. In the case of the nutrients they show specific data of mesothrofic waters with tendency to the eutrofization and the silts presented a high affectation for toxic metals. The area near to Guanímar is distinguished to present conditions of organic contamination that favor heterothrofic conditions, corroborated by a prevalence of the processes of mineralization of the organic matter over primary production and lows values of fitoplankton concentration. On the contrary, in the region of Surgidero of Batabanó, the processes of synthesis of organic matter prevail suggested by a high primary production, and concentration of fitoplankton, with low breathing levels and mineralization of the organic matter, that indicates that the system is behaving autothrofically. In a general way, this sector is very affected by the anthropogenic impact. The information obtained is of great importance for the development of the fishing and tourist industries in the area.
    Description: Published
    Keywords: Phytoplankton ; Water quality ; Primary production ; Chemistry ; Environmental monitoring ; Phytoplankton ; Water quality ; Primary production ; Chemistry ; Environmental monitoring
    Repository Name: AquaDocs
    Type: Proceedings Paper
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  • 8
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    Ocurrencia de gallineta con joroba, Prionotus stephanophrys Lockington (Pisces: Triglidae) en aguas ecuatorianas, y aspectos de su comportamiento, biología y utilización (2009)
    INP (Ecuador)
    Details
    Publication Date: 2021-05-19
    Description: The occurrence of gurnard Prionotus stephanophrys was studied in the course of a series of fisheries research cruises on the Ecuadorian continental shelf between 1980 and 1985. The species is common in coastal waters south of 1°S . Its abundance is very variable, possibly associated with sea temperatures. Normally densities are between 0.8 and 1.6 t.km-2. The standing stock varies between 13,000 and 150,000 t wich it is estimated can sustain catches of around 4,000 t pet year, and up to 40,000 t in times of great abundance. P. stephanophyrs is found in large shoals on the bottom during the day but a night moves up into mid-water to feed on euphausids. The fish caught had size range of 12 cm to 37 cm, but the majority were between 16 cm and 21 cm in total length. The growth parameters and natural mortality were calculated. The present fisheries catch large quantities of these gurnards, but most is discarded at sea and the small amounts landed are only used for fish meal production. However, the flesh is of good quality and could easily be used for human consumption.
    Description: Published
    Keywords: Biomass ; Catch composition ; Biomass ; Abundance ; Catch composition ; Natural mortality
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 9
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    Los recursos de peces demersales de la Plataforma Continental del Ecuador. Parte uno. Distribución, abundancia y variaciones (2009)
    INP (Ecuador)
    Details
    Publication Date: 2021-05-19
    Description: A survey of demersal fish resources of the Continental Shelf of Ecuador was carried out between October 1980 an July 1985 by the National Fisheries Institute of Ecuador, with British Technical Cooperation. This report deals with the stock assessment part of the work. In the course of seven cruises, 366 valid diurnal hauls were made with a high-opening bottom trawl. The demersal fish resources were estimated by swept area methods and the results are presented. The overall average standing stock of demersal fish was 78 000 t of which 22 000 t was good fish, but 36 000 t were gurnards (Triglidae) and 3 000 t of unusable fish. The main stocks were gurnards, grunts and croakers, sharks and corvinas Cynoscion spp. The southern areas especially the Gulf of Guayaquil had the highest densities of fish (9,6 t.Km-2 or 4,0 t.Km-2 excluding gurnards). There was a massive abundance of the gurnard, Prionotus stephanophys in 1984 and 1985. There was a general decrease and other changes in the demersal stocks due to the effects of the ”El Niño” in 1983.
    Description: Published
    Keywords: Demersal fisheries ; Geographical distribution ; Biomass ; Demersal fisheries ; Geographical distribution ; Abundance ; Biomass
    Repository Name: AquaDocs
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  • 10
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    Variación mensual y mareal del zooplancton en una estación fija del estero del Muerto, Golfo de Guayaquil (2008)
    Instituto Oceanográfico de la Armada, Guayaquil, Ecuador
    Details
    Publication Date: 2021-05-19
    Description: Durante los meses de Marzo de 1983 a Febrero de 1984, se llevaron a cabo muestreos de 24 horas consecutivas en las fases llenas lunares en una estación fija en la región interior del Golfo de Guayaquil. Con esta información se han determinado variaciones mensuales y mareales del zooplancton, así como de otros parámetros ambientales, encontrándose una estrecha relación entre la abundancia de organismos y los valores de salinidad. La mayor biomasa planctónica estuvo asociada con los meses secos de alta salinidad. Analizando la variación mareal, se ha determinado que durante las mareas, existe aporte de material nutritivo desde el interior del estuario hacia la región exterior.
    Description: Incl. ref.bibl., grafs., ilus.
    Description: Published
    Keywords: Zooplankton ; Biomass ; Seasonal variations ; Zooplankton ; Biomass
    Repository Name: AquaDocs
    Type: Journal Contribution
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