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121.
L’ubomír Ježo Martin Palou Jana Kozánková Tomáš Ifka 《Journal of Thermal Analysis and Calorimetry》2010,101(2):585-593
Isothermal conduction calorimetry, differential thermal analysis (DTA)–thermogravimetric analysis (TG) analysis, and SEM observations
have proved the activation effect of Ca(OH)2 released from the C3S hydration upon blast furnace slag (BFS). Five sample mixtures of BFS and C3S and two samples of pure BFS and C3S were submitted to reaction with water inside the calorimeter at room temperature. The values of hydration heat were recorded
up to 7 days. Samples were stored in humidity during 28 days and then were submitted to DTA–TG and SEM analysis. The effect
of Ca(OH)2 upon heat evolution of sample mixtures has been quantified and its influence upon the formation of new hydrates and microstructure
of pastes was evidenced. 相似文献
122.
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124.
Jana Madejová Martin Pentrák Helena Pálková Peter Komadel 《Vibrational Spectroscopy》2009,49(2):211-218
The benefit of near-infrared (NIR) spectroscopy in studies of acid-treated clay minerals is demonstrated. The effects of mineral type, composition and content of non-swelling interlayers on the dissolution rate are investigated. Detailed analysis of the NIR region is performed by comparing the first overtone (2νOH) and combination (ν + δ)OH bands with the fundamental stretching (ν) and bending (ν) vibrations. Spectra of acid-treated samples show a gradual decrease in the intensities of the structural OH overtone (near 7100 cm?1) and combination (4600–4300 cm?1) bands reflecting a fewer number of octahedral atoms. The appearance of the 2νSiOH vibration for terminal (isolated) SiOH groups near 7315 cm?1 indicates the formation of a protonated silica phase. The band near 7130 cm?1 remaining in the spectra of acid-treated samples is assigned to 2νHOSiOH of geminal silanol groups. Thus the creation of geminal silanols, previously detected by 29Si MAS-NMR spectroscopy in acid-treated hectorite, is confirmed also by NIR spectroscopy. The assignment of the 4555 cm?1 band to the (ν + δ)SiOH combination enabled calculation of the wavenumber for the SiO–H bending vibration (~810 cm?1) that is not observable in the mid-IR region due to overlapping with the Si–O band of amorphous silica (~800 cm?1). The NIR spectra confirm that trioctahedral hectorite is much more susceptible to dissolution in HCl than dioctahedral nontronite. The dissolution rate of kaolinite present in the Badin clay as an admixture is lower than that of the main mineral nontronite. The accessibility of the interlayers for protons significantly influences the stability of clay minerals in HCl. Mixed-layered mineral illite/smectite with only 30% of swelling interlayers dissolves more slowly than smectite of similar chemical composition containing mainly swelling interlayers. 相似文献
125.
In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G)
some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases
and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for
the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and
voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented
to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed
in these oscillations. 相似文献
126.
Csilla Mišľanová Jana Príbojová Martina Valachovičová Zuzana Žilinská 《Analytical letters》2017,50(15):2359-2368
Cyclosporine, tacrolimus, sirolimus, and everolimus are commonly used immunosuppressants following organ transplantation. Their monitoring is used to determine the optimal dose for therapeutic effectiveness and minimize toxicity. High-performance liquid chromatographic–tandem mass spectrometry with positive electrospray ionization and multiple reaction monitoring mode was validated for the determination of cyclosporine A, tacrolimus, sirolimus, and everolimus in whole blood. A C18 analytical column was employed with a gradient elution of pH 4.0 aqueous 10?mmol/L ammonium acetate and acetonitrile. For the pretreatment of whole blood, simple protein precipitation was used with methanol:zinc sulfate. The calibration curves were linear from 20.0 to 1000?ng/mL for cyclosporine A, 1.0 to 50?ng/mL for tacrolimus and sirolimus, and 1.0 to 30?ng/mL for everolimus. The intra-assay precision and inter-assay precision were less than 15%. The method provides reliable and reproducible results according to the linearity, precision, accuracy, recovery, and matrix effects. The method has been introduced to routine clinical practice in Slovakia for the determination of immunosuppressants in patients after kidney transplantation. 相似文献
127.
The spectroscopic investigation on anionic dye, Erythrosine ‘B’(EB) with three different types of surfactants such as CTAB
(cationic), sodium lauryl sulphate (SLS; anionic) and Triton X-100 (TX-100),Tween-20, 40, 60 and 80 (nonionic) in aqueous
media shows that EB forms a 1:1 molecular complex with TX-100, Tweens and CTAB. No interaction is observed between EB and
SLS. The thermodynamic and spectrophotometric properties of these complexes suggest that EB forms a strong charge transfer
(CT) complex with TX-100 and Tweens whereas the interaction of EB with CTAB is coulombic in nature. Photogalvanic and photoconductometric
studies also support the above interactions. In addition to this, the electron-donating ability among the nonionic surfactants,
i.e. TX-100 and Tweens towards dye, role of surface in CT interaction, the site of CT interaction and the intensity and stability
of CT interaction between EB and nonionic surfactants have been pointed out. 相似文献
128.
In this paper, green composites of the corn starch were developed by using resorcinol-formaldehyde (Rf) as the cross-linking agent and reinforced with graft copolymers Saccharaum spontaneum L(Ss) and methyl methacrylates (MMA) as principal monomer and its binary mixture with acrylamide (AAm), acrylonitrile(AN), acrylic acid (AA) prepared under micro-wave. The matrix and composites were found to be thermally more stable than the natural corn starch backbone. There was improvement in physico-chemical and mechanical properties of composite were found to exhibit better than matrix. Ss-g-poly(MMA)-MW reinforced composites were found to exhibit better tensile strength, on the other hand Ss-g-poly(MMA + AA)-MW reinforced composites showed maximum compressive strength and wear resistance than other graft copolymers reinforced composite and the basic matrix. Further the matrix and composites were subjected for biodegradation studies through soil composting method. Different stages of biodegradation were evaluated through FT-IR studies and scanning electron microscopic (SEM) techniques. 相似文献
129.
Anuva Samanta Bijan Kumar Paul Sankar Jana Nikhil Guchhait 《Photochemistry and photobiology》2010,86(5):1022-1029
The photophysical properties of 5-(4-fluorophenyl)-2-hydroxypyridine (FP2HP) at different pH and its fluorescence response toward different transition metal ions have been studied by steady-state absorption and emission spectroscopy in combination with quantum chemical calculations. Although keto-enol tautomerization is observed in the excited state, the molecule is weakly fluorescent due to the presence of electron-rich nitrogen atom and relatively electron-deficient fluorine atom, which may lead to photoinduced electron transfer process. In the presence of the transition metal ions, such as Zn2+, Cd2+, Hg2+, etc., the studied molecule exhibits changes in its absorption and emission properties. The present system shows fluorescence enhancement instead of usual quenching in presence of the transition metal ions, such as Fe2+ and Cu2+. Spectral observation leads to the interpretation that this structurally simple molecule can be effectively utilized as a chelation-enhanced fluorescence-based chemosensor for the detection of transition metal ions. The experimental findings corroborate well with theoretical calculations at Hartree–Fock level using 6-31G** and lanl2dz basis sets. 相似文献
130.
Hrdlovic P Donovalova J Stankovicova H Gaplovsky A 《Molecules (Basel, Switzerland)》2010,15(12):8915-8932
Absorption and fluorescence spectra of bichromophoric coumarins were investigated in different solvents and in polymer matrices. These bichromophoric coumarins were composed of a coumarin dimethylamino-substituted at position 7 or unsubstituted coumarin and phthalimide or a 1,8-naphthylimide linked with an iminomethyl bridge to the position 3 or 8 of the coumarin ring. Absorption spectra of 7-dimethylamino derivatives in position 3 of coumarin were quite similar, exhibiting broad bands around 430-440 nm like the parent compound 7-dimethylaminocoumarin-3-carbaldehyde. For coumarin derivatives substituted in position 8, the absorption maximum was shifted to shorter wavelength as for derivatives without position 7 dimethylamino substitution. The most intense fluorescence was observed for 7-(N,N-dimethylamino)-3-[(N-phtalimidoyl)iminomethyl]coumarin in polar solvent, while intense fluorescence was observed for 7-(N,N-dimethylamino)-3-[N-(1,3-dioxobenz[de]isoquinolinyl)iminomethyl]-coumarin in non polar solvent (chloroform), comparable with the fluorescence of 7-amino-4-methylcoumarin. Spectral measurements of bichromophoric coumarins in polymer matrices revealed that the maxima lies in between those for chloroform and methanol yielding more intense fluorescence then in solutions. Completely different solvent effects were observed for 7-(N,N-dimethylamino)-3-[N-(1,3-dioxobenz[de]isoquinolinyl)imino-methyl]coumarin and 7-(N,N-dimethylamino)-3-[(N-phtalimidoyl)iminomethyl]coumarin. With addition of polar methanol the intensity of fluorescence decreases, yielding a Stern-Volmer-like constant of 0.54 dm3 mol?1 for 7-(N,N-dimethylamino)-3-[N-(1,3-dioxo-benz[de]isoquinolinyl)iminomethyl]coumarin and an even higher one of 1.08 dm3·mol?1 for 7-dimethylaminocoumarin-3-carbaldehyde compared to the rather low one of 0.024 dm3 mol?1 for 7-amino-4-methylcoumarin. Contrary to this, addition of methanol under identical conditions brings about an increase in fluorescence intensity of 7-(N,N-dimethylamino)-3-[(N-phtalimidoyl)iminomethyl]coumarin (about 60-fold). The reasons for these different solvent effects are discussed. 相似文献