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71.
72.
73.
We present results of the deuteron nuclear magnetic resonance (NMR) and small-angle X-ray scattering (SAXS) study of ordering and phase transition behavior of octylcyanobiphenyl (8CB) liquid crystal confined to a controlled-pore glass (CPG) with nontreated and silanes-treated pore surfaces. The deuteron NMR spectra allowed to determine the degree of nematic liquid crystal ordering and also provided an indirect information on the confined 8CB smectic ordering via its influence on the nematic ordering. For the smectic phase these data are supplemented with measurements of the temperature dependence of the first-order SAXS diffraction pattern. The NMR results indicate that the average nematic and smectic order parameters of 8CB in the nontreated CPG are only weakly perturbed by the confinement. The SAXS data further suggest that in confined 8CB for both nontreated and silane-treated CPG a domainlike pattern appears in accordance with the Imry-Ma theorem. 相似文献
74.
Irena Ćaleta Marijeta Kralj Marko Marjanović Grace Karminski-Zamola 《Monatshefte für Chemie / Chemical Monthly》2008,139(5):569-573
A series of bis-styrylbenzothiazol-3-ium salts containing different substituents 4–12 were synthesized from 2-methylbenzothiazole by condensation of quaternary salts 1–3 with p-substituted benzaldehydes. All compounds were characterized by IR, 1H and 13C NMR, MS, and elemental analysis. Synthesized compounds 4–12 were screened for antitumor activities. Based on presented in vitro screening results we may conclude that compounds 4–6 and 9 showed the best cell growth inhibitory activity.
Correspondence: Grace Karminski-Zamola, Department of Organic Chemistry, Faculty of Chemical Engineering and Technology, Marulićev
trg 20, HR-10000 Zagreb, Croatia. 相似文献
75.
76.
The influence of sodium stearate (NaSt) on the precipitation of calcium carbonate during the semicontinuous process of slaked lime carbonation was studied in the systems in which process parameters, like concentration of total dissolved calcium, temperature, CO(2) flow rate and initial addition rate of slaked lime, were controlled. It was found that calcite was the only calcium carbonate polymorph that appeared under the investigated experimental conditions, while FT-IR spectroscopy and thermogravimetric analysis of samples confirmed the presence of stearate on the surface of precipitated calcium carbonate (PCC). Specific surface area of PCC increased with increasing stearate content: the highest value, s = 52.8 m(2) g(-1), was obtained at t = 20 degrees C, c(tot) = 17.0 mmol dm(-3) and the stearate content of m(NaSt)/m(CaO) = 0.03. It was also found that hydrophobic calcite crystals in the form of rhombohedral and scalenohedral morphology can be produced at m(NaSt)/m(CaO) > 0.01. The exception is the case of nanosized PCC production, when much higher concentration of NaSt is needed, m(NaSt)/m(CaO) = 0.22. Minimal amount of stearate necessary to build up the monolayer and corresponding cross sectional area of one stearate molecule were estimated for the obtained calcite morphologies. 相似文献
77.
The study of the smectic-A to chiral smectic-C(*) phase transition of the liquid crystal S-(+)-[4-(2(')-methyl butyl) phenyl 4(')-n-octylbiphenyl-4-carboxylate] (CE8) containing dispersed hydrophilic aerosils reveals novel properties, important to understanding quenched disorder and confinement in ferroelectric liquid crystals. Smectic layer compression leads to a distribution of transition temperatures inducing smearing of the macroscopic data across the transition. A pronounced confinement-induced pretransitional tilted order is observed. 相似文献
78.
79.
Kralj B Krizaj I Bukovec P Slejko S Milacic R 《Analytical and bioanalytical chemistry》2005,383(3):467-475
Speciation of Al in tea infusions was studied by size exclusion chromatography (SEC) and anion-exchange fast protein liquid
chromatography (FPLC). Fractions were collected throughout the chromatographic separations and Al was determined “off line”
by inductively coupled plasma optical emission spectroscopy (ICP–OES). Black, green, and red tea samples were investigated.
The total concentration of Al in tea infusions was determined by ICP–OES and ranged between 0.5 and 4 mg dm−3. The pH of tea infusions ranged between 5.3 and 5.5. Data from SEC–ICP–OES analysis indicated that 10–35% of total Al in
tea infusions was eluted at a retention volume corresponding to a molecular mass of approximately 3800 Da. The remaining Al
was adsorbed on the column resin. The same tea infusions were also analysed by anion-exchange FPLC–ICP–OES. It was found experimentally
that the same percentage of total Al as from the SEC column was eluted at a retention volume that corresponded to negatively
charged Al-citrate. The remaining Al was adsorbed on the column resin. Identification of Al-binding ligands eluting under
the chromatographic peak was performed by electrospray ionisation tandem mass spectrometry (ES–MS–MS) analysis. It was proven
that ionic Al species in tea infusions (10–35% of the total Al) corresponded to negatively charged Al-citrate. The remaining
species that was adsorbed on the SEC or FPLC columns was most probably bound to phenolic compounds. Speciation of Al in tea
with milk or lemon was also studied. Results for tea with milk indicated that Al-citrate was not transformed and that approximately
60% of total Al was transformed into high-molecular-mass Al species. This fraction was subjected to sodium dodecyl sulfonate
polyacryl gel electrophoresis (SDS–PAGE). The results indicated that Al was occluded by milk proteins (mostly caseins). When
citric acid was added to tea infusions the percentage of negatively charged Al-citrate remained either the same or increased
to 40% of total Al. 相似文献
80.
C. J. Proctor B. Kralj A. G. Brenton J. H. Beynon 《Journal of mass spectrometry : JMS》1980,15(12):619-631
Over thirty consecutive reactions of a type m1+ → m2+ → m3+ have been studied in a variety of organic compounds using a reversed geometry mass spectrometer. Two field free regions allow the separation of the two steps that make up the consecutive reaction sequence. Translational energy release measurements are used in the comparison of m2+ ions formed as a result of a high energy process in the ion source with m2+ ions formed as a product of a metastable decomposition. In some cases the structures of such ions have been found to be different. Examples have also been found where consecutive fragmentations of metastable ions do not occur although, when higher energy ions within the source are studied, the two-step reaction does take place. Furthermore, it has been found that a control over ion internal energy may be achieved by selecting portions of a peak due to the fragmentation of a metastable ion. Unimolecular reactions may then be used to study the reactivity of such ‘energy-selected’ ions; collision induced reactions can be used to study the structure of both the reactive and unreactive energy selected ions. 相似文献