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41.
The SCF FPT method in the INDO approximation of molecular orbital theory is employed for calculations of 1H NMR cisoidal coupling constants in model compounds. Obtained results are used for finding conformational states of α-xylo-, β-lyxo-, and α-2′-deoxyribonucleosides in solution. 相似文献
42.
Alfons Krause Irena Plura L. Ŀomozik 《Monatshefte für Chemie / Chemical Monthly》1965,96(5):1581-1585
Zusammenfassung Basisches Magnesiumcarbonat und basisches Zinkcarbonat erlangen nach Tieftemperaturbehandlung mit flüssiger Luft eine bedeutend größere Oberfläche, die auch bei den betr. oxidischen Abkömmlingen nach ihrer thermischen Beanspruchung bei 800° bestehen bleibt. Ebenfalls tieftemperatur-empfindlich ist das dunkelbraune röntgenamorphe Eisen(III)-hydroxid (Orthohydroxid), während das topochemische röntgenamorphe und ziegelfarbige Eisen(III)-hydroxid (Iso-Orthohydroxid) sowie ein daraus gewonnenes hellgelbes -FeOOH, die schon von sich aus oberflächengroß sind, sich in dieser Hinsicht als indifferent erwiesen. Die aus den verschiedenen Eisen(III)-hydroxiden bei 800° gewonnenen -Oxide hatten eine sehr differente scheinbare Dichte bzw. Oberfläche. 相似文献
43.
We explicitly calculate the normal cones of all monomial primes which define the curves of the form , where . All of these normal cones are reduced and Cohen-Macaulay, and their reduction numbers are independent of the reduction. These monomial primes are new examples of integrally closed ideals for which the product with the maximal homogeneous ideal is also integrally closed.
Substantial use was made of the computer algebra packages Maple and Macaulay2.
44.
Irena Blute Martin Svensson Krister Holmberg Margareta Bergh Ann-Therese Karlberg 《Colloids and surfaces. A, Physicochemical and engineering aspects》1999,150(1-3):105-113
It has previously been shown that alcohol ethoxylates readily undergo autoxidation and that one of the major oxidation products is the surfactant aldehyde, i.e. an ethoxylate carrying a –CH2CHO group at the terminal end of the polyoxyethylene chain. In this work the cloud point, phase behavior and aggregation characteristics of the surfactant aldehyde produced by oxidation of C12H25(OCH2CH2)5OH (C12E5) are determined and compared with the values obtained with the parent surfactant. It was found that the physico–chemical behavior of the two species was very similar, which indicates that a considerable portion of the aldehyde group is in hydrated state, i.e. the surfactant aldehyde consists of a mixture of aldehyde in carbonyl form and the corresponding geminal diol. The cloud point of the surfactant aldehyde decreased rapidly with time, even when it was stored at low temperature. Also the parent surfactant and its homologue C12E6 exhibited a decrease in cloud point during storage. For instance, a 1% aqueous solution of C12E6 showed a cloud point decrease from 62 to 32°C after 4 months storage at 40°C. Such a change in solution behavior can have important practical implications. 相似文献
45.
Irena Gancarz Gryzelda Po?niakMarek Bryjak W?odzimierz Tylus 《European Polymer Journal》2002,38(10):1937-1946
This paper describes some properties of microwave plasma polymers of n-butylamine and allylamine deposited on the surface of polysulfone substrate. Contact angle evaluation, ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy analysis and estimation of pore size distribution of ultrafiltration polysulfone membranes were used. It was found that addition of Ar to the amine vapor significantly stabilized the plasma and converted it to the ablation mode. The surface became more hydrophilic and the surface groups were enriched in oxygen. Both amines gave deposits of various compositions: the n-butylamine polymer was not as enriched in amines as the polymer formed from allylamine. However, the amounts of nitrogen in both deposits indicated allylamine to be the precursor for the preparation of membranes with weakly basic functionalities. When porous membranes are modified, the ultrafilters obtained may be named `fouling protected' as they do not foul so intensively with proteins as their unmodified analogues. To a lesser extent, similar behavior was shown by membranes modified by deposition of plasma-polymerized n-butylamine. 相似文献
46.
This paper proposes a dynamic cascade model to investigate the systemic risk posed by sector-level industries within the U.S. inter-industry network. We then use this model to study the effect of the disruptions presented by Covid-19 on the U.S. economy. We construct a weighted digraph G = (V,E,W) using the industry-by-industry total requirements table for 2018, provided by the Bureau of Economic Analysis (BEA). We impose an initial shock that disrupts the production capacity of one or more industries, and we calculate the propagation of production shortages with a modified Cobb–Douglas production function. For the Covid-19 case, we model the initial shock based on the loss of labor between March and April 2020 as reported by the Bureau of Labor Statistics (BLS). The industries within the network are assigned a resilience that determines the ability of an industry to absorb input losses, such that if the rate of input loss exceeds the resilience, the industry fails, and its outputs go to zero. We observed a critical resilience, such that, below this critical value, the network experienced a catastrophic cascade resulting in total network collapse. Lastly, we model the economic recovery from June 2020 through March 2021 using BLS data. 相似文献
47.
Enhancement of the Efficacy of Photodynamic Inactivation of Candida albicans with the Use of Biogenic Gold Nanoparticles 下载免费PDF全文
Irena Maliszewska Barbara Lisiak Katarzyna Popko Katarzyna Matczyszyn 《Photochemistry and photobiology》2017,93(4):1081-1090
This study reports on successful photodynamic inactivation of planktonic and biofilm cells of Candida albicans using Rose Bengal (RB) in combination with biogenic gold nanoparticles synthesized by the cell‐free filtrate of Penicillium funiculosum BL1 strain. Monodispersed colloidal gold nanoparticles coated with proteins were characterized by a number of techniques including SEM–EDS, TEM, UV–Vis absorption and fluorescence spectroscopy, as well as Fourier transform infrared spectroscopy to be 24 ± 3 nm spheres. A Xe lamp (output power of 20mW, delivering intensity of 53 mW cm?2) was used as a light source to study the effects of RB alone, the gold nanoparticles alone and the RB‐gold nanoparticle mixture on the viability of C. albicans cells. The most effective reduction in the number of planktonic cells was found after 30 min of Xe lamp light irradiation (95.4 J cm?2) and was 4.89 log10 that is 99.99% kill for the mixture of RB with gold nanoparticles compared with 2.19 log10 or 99.37% for RB alone. The biofilm cells were more resistant to photodynamic inactivation, and the highest effective reduction in the number of cells was found after 30 min of irradiation in the presence of the RB–gold nanoparticles mixture and was 1.53 log10, that is 97.04% kill compared with 0.6 log10 or 74.73% for RB. The probable mechanism of enhancement of RB‐mediated photodynamic fungicidal efficacy against C. albicans in the presence of biogenic gold nanoparticles is discussed leading to the conclusion that this process may have a multifaceted character. 相似文献
48.
ABSTRACTHere we report on the synthesis and mesomorphic properties of a series of imino-linked dimeric molecules. In order to improve our understanding of the structure–NTB phase correlations, we have studied the impact of geometric and electronic factors arising from varying mesogenic units, different spacer lengths and from the ratio (n/m) between the lengths of terminal chains (n) and spacer (m). From the perspective of the molecular geometry, the results show that the stability of the NTB phase results from increasing effective molecular bending and with the broadening of the mesogenic unit, in particular near the spacer, and that the n/m ratio plays a substantial role in conjunction with the specific mesogenic unit. A computational study of the electronic properties shows that a broadening of the mesogenic core in the vicinity of the spacer is associated with an increased anisotropy of the electrostatic potential distribution. Within a given series of materials our study suggests that the incidence of the NTB phase and its thermal stability are governed by the synergy of specific geometrical factors and the anisotropy of the electrostatic potential distribution of the mesogenic core. 相似文献
49.
Alexander M. Khenkin Dr. Irena Efremenko Dr. Lev Weiner Dr. Jan M. L. Martin Prof. Ronny Neumann Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(4):1356-1364
A polyoxometalate of the Keggin structure substituted with RuIII, 6Q5[RuIII(H2O)SiW11O39] in which 6Q=(C6H13)4N+, catalyzed the photoreduction of CO2 to CO with tertiary amines, preferentially Et3N, as reducing agents. A study of the coordination of CO2 to 6Q5[RuIII(H2O)SiW11O39] showed that 1) upon addition of CO2 the UV/Vis spectrum changed, 2) a rhombic signal was obtained in the EPR spectrum (gx=2.146, gy=2.100, and gz=1.935), and 3) the 13C NMR spectrum had a broadened peak of bound CO2 at 105.78 ppm (Δ1/2=122 Hz). It was concluded that CO2 coordinates to the RuIII active site in both the presence and absence of Et3N to yield 6Q5[RuIII(CO2)SiW11O39]. Electrochemical measurements showed the reduction of RuIII to RuII in 6Q5[RuIII(CO2)SiW11O39] at ?0.31 V versus SCE, but no such reduction was observed for 6Q5[RuIII(H2O)SiW11O39]. DFT‐calculated geometries optimized at the M06/PC1//PBE/AUG‐PC1//PBE/PC1‐DF level of theory showed that CO2 is preferably coordinated in a side‐on manner to RuIII in the polyoxometalate through formation of a Ru? O bond, further stabilized by the interaction of the electrophilic carbon atom of CO2 to an oxygen atom of the polyoxometalate. The end‐on CO2 bonding to RuIII is energetically less favorable but CO2 is considerably bent, thus favoring nucleophilic attack at the carbon atom and thereby stabilizing the carbon sp2 hybridization state. Formation of a O2C–NMe3 zwitterion, in turn, causes bending of CO2 and enhances the carbon sp2 hybridization. The synergetic effect of these two interactions stabilizes both Ru–O and C–N interactions and probably determines the promotional effect of an amine on the activation of CO2 by [RuIII(H2O)SiW11O39]5?. Electronic structure analysis showed that the polyoxometalate takes part in the activation of both CO2 and Et3N. A mechanistic pathway for photoreduction of CO2 is suggested based on the experimental and computed results. 相似文献
50.
The aim of this work was to study the possibility of simultaneous voltammetric determination of some disinfectants used as components in cosmetic products. The examined compounds were: triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol), chloramine-T (N-chloro-p-toluenesulfonamide sodium salt), 4-chloro-3-methylphenol and 2-mercaptobenzothiazole. Measurements were performed using glassy carbon electrode immersed in Britton-Robinson buffers which acted as supporting electrolytes. The dependence of oxidation and reduction potentials on pH was examined using cyclic voltammetry. Britton-Robinson buffer of pH 9.9 was chosen for further studies to ensure the best separation of compounds. The resultant oxidation potentials indicate the possibility to simultaneously determine some of the disinfectants.. Oxidation reactions of mixtures containing two compounds (4-chloro-3-methylphenol and chloramine-T, 2-mercaptobenzothiazole and 4-chloro-3-methylphenol, 2-mercaptobenzothiazole and triclosan) were recorded as differential pulse voltammograms. 相似文献