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53.
Igor Serša Slobodan Macura 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,135(2):466-477
We experimentally verified a recently proposed technique for the excitation of a complicated three-dimensional profile (CARVE,completelyarbitraryregionalvolumeexcitation). CARVE is based on a generalized DANTE RF pulse sequence and a synchronous string of gradient steps. Provided there is no limitation in the number of pulses, CARVE can generate an excitation profile of any shape with any resolution. However, hardware limitations and sample properties restrict the number of RF pulses and gradient steps and, thus, limit attainable resolution of the excitation profile. We theoretically and experimentally showed that spatial resolution can be increased by distributing a long sequence among several CARVE experiments and summing up their signals. This is particularly important for three-dimensional excitation profiles where ann-fold increase in resolution requires ann3-fold increase of the number of events in the sequence. The potential use of three-dimensional CARVE might be in spectroscopic imaging where the excitation profile can be tailored to match the shape of a selected organ or body part. 相似文献
54.
Djaković-Sekulić Tatjana Lj. Perišić-Janjić Nada U. Petrović Slobodan D. 《平面色谱法杂志一现代薄层色谱法》2003,16(2):147-153
JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of para-substituted amides of α-phenylacetic, benzoic, propanoic, and 2,2-dimethylpropanoic acid... 相似文献
55.
S.D. Bosanac 《Chemical physics letters》1984,103(6):484-486
Properties of rotational rainbows in the presence of multiple collisions are described. It is shown that if magnetic transitions are measured only one rainbow is observed. If magnetic transitions are not distinguished several rainbow peaks are found. 相似文献
56.
Onjia AE Milonjić SK Todorović M Loos-Neskovic C Fedoroff M Jones DJ 《Journal of colloid and interface science》2002,251(1):10-17
The surface properties of Ni and Cu hexacyanoferrates were investigated by the inverse gas chromatography method. Retentions of 10 organic compounds were measured at zero surface coverage in the temperature range 80 to 95 degrees C. The gas/solid partition coefficients and the related thermodynamic data of adsorption (standard free energy change, standard state enthalpies, and entropy changes) also at zero surface coverage were determined. The dispersive component of free surface energy of both hexacyanoferrates, at investigated temperatures, was calculated. The surface acid/base properties were also evaluated using polar adsorbates and the results obtained indicate that nickel hexacyanoferrate is more acidic than copper hexacyanoferrate. 相似文献
57.
Kutnjak Z Cordoyiannis G Nounesis G Lebar A Zalar B Zumer S 《The Journal of chemical physics》2005,122(22):224709
A lyotropic inverse micelle phase composed of water, thermotropic liquid-crystal octylcyanobiphenyl (8CB), and surfactant (DDAB) was studied by using high-resolution calorimetry on several mixtures with 3%, 8%, and 15% micelle concentration. Calorimetric results show strong depression of the isotropic to nematic (I-N) phase-transition temperature. Broad heat-capacity anomalies show the existence of a wide coexistence range of isotropic, nematic, and smectic-A phases, which mimics the behavior of a new nearly stable thermodynamic phase. An observation of the rather sharp almost bulklike nematic to smectic-A (N-A) transition at low-temperatures indicates that our heat capacity results are consistent with the phase separation scenario in which significant number of micelles is expelled during I-N conversion leaving almost pure nematic phase at lower temperatures. It was found that micelles get almost completely remixed on heating the mixture back to the isotropic phase. 相似文献
58.
Branko Kozuilić Ivančica Leuštek Branka Pavlović Pavao Mildner Slobodan Barbarić 《Applied biochemistry and biotechnology》1987,15(3):265-278
Each of the three high-mannose type glycoproteins studied, acid phosphatase, invertase, and glucose oxidase, could be specifically
cross-linked through its carbohydrate chains. The procedure involves periodate oxidation of carbohydrate residues followed
by reaction of the generated aldehyde groups with adipic acid dihydrazide as a cross-linker. The amount and size as well as
solubility of the formed polymers could be efficiently controlled by varying the reaction conditions, i.e., the oxidation
degree and the concentrations of glycoproteins, cross-linker, and hydrogen ions during the cross-linking reaction. It was
found that the quantity and size of polymers increased with oxidation degree and protein concentration and by lowering the
pH. When the protein concentration was above and pH below certain values, depending on the glycoenzyme, insoluble polymers
formed. The soluble cross-linked polymers retained a high level of original activity, and the minor decrease in specific activity
noticed was shown to occur during the periodate oxidation step. The cross-linked glycoenzymes are much more resistant to denaturation
by high temperature and by changes in pH, demonstrating the usefulness of this method in preparation of the stabilized glycoprotein
derivatives. 相似文献
59.
A new spectrofluorimetric determination of iridium(IV) with 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX) or 3-hydroxy-2-methyl-1-(4-tolyl)-4-pyridone (HY) is reported. Iridium(IV) react with HX or HY and chelates were extracted into chloroform or dichloromethane. The organic phase showed fluorescence. The fluorescence measurements to quantify iridium were carried out in its fluorescent band centred at λex=373 nm and λem=480 nm. Under optimal conditions, the calibration graphs were linear over the concentration range of 0.1-7.6 μg ml−1 of iridium for Ir(IV)-HX and 0.1-5.8 μg ml−1 for Ir(IV)-HY with a correlation coefficients of 0.999 and 0.992 and relative standard deviation of ±1.1%.The method is free from interference by Rh(III) and Pt(IV), which normally interfere with other methods. Iridium can be determined in the presence of 300-fold excess of rhodium(III) and 10-fold excess of platinum(IV).The method was applied successfully to the determination of iridium in some synthetic mixtures and mineral sample gave satisfactory results. 相似文献
60.
This paper describes the use of principal component analysis (PCA) to de-noise Raman spectra and considerably shorten data acquisition time in Raman mapping experiments. A solid dosage pharmaceutical material (bead) is mapped by a Raman line-mapping system. The mapping acquisition time was varied from 30 s (usually employed in practice) to only 3 s. Apparently excessive noise in the maps measured for 3 s is removed by PCA and the maps of all three components of the bead are then binarized and compared. It is found that spatial difference is negligible despite the remarkably different acquisition times employed. The spectra acquired for 3 s and reconstructed via PCA are found to largely overlap with the spectra acquired for 30 s. The signal to noise ratio of the Raman mapping spectra does not obey the expected root t dependence, thereby preventing straightforward estimation of the shortest usable acquisition time (which is to a lesser extent also a function of the binarization threshold). The results reveal that Raman microscopy can be considered a fast method for mapping some materials, in contrast to the established opinion that it is an inherently slow technique. 相似文献