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101.
M. Trotta M. E. Carlotti M. Gallarate G. P. Zara E. Muntoni 《Journal of Dispersion Science and Technology》2013,34(7):1041-1045
Insulin-loaded solid lipid nanoparticles (SLN) were prepared according to a solvent dilution method from O/W emulsions using isovaleric acid as organic phase. Insulin was derivatized with fluorescein isothyocianate (FITC) obtaining a fluorescent marker to be used in in vivo experiments. FITC-insulin and native insulin–loaded SLN were quite similar with regard to their mean sizes and encapsulation efficiency. SLN intestinal uptake was then investigated administering FITC-insulin loaded SLN on healthy male Wistar rats. Significant drug accumulation within intestinal lymphatic system was recovered, but the immune system seems to play an important role in SLN degradation: further studies are necessary to improve the results on blood glucose level. 相似文献
102.
The precise and accurate determination of water in petroleum products—gasoline, diesel oil and aromatic hydrocarbons—is of significant importance for their normal functional and operational characteristics for economics as well as in meeting international requirements. The standard method ISO 12937 for the measurement of water by the coulometric Karl Fischer titration method was subject to within-laboratory assessment. Thereby it was established that the analytical procedure could not always be relied upon, especially when low levels of water were determined. The aim of this work is to assess each stage of the test procedure depending on the particular problems defined by the samples, using high-reactive Karl Fischer reagents and coulometric cells with and without a diaphragm, and to indicate the major factors causing the uncertainty. A reduced combined uncertainty was achieved by modifying the sample preparation step, the administration of the moisture in the coulometric cell, and sample injection manipulation. Experiments showed that the cell without the diaphragm ensures lower and uniform uncertainty of the measurements in the range of 0.01 to 10 mg H2O in comparison to the cell with a diaphragm and therefore is more appropriate for the determination of low water levels in the petroleum products. A procedure that utilized a mixture of the reagent and toluene (10:6) was able to resolve the problem of two phases of formation and reduced conductivity of the reagent in direct titration of diesel oils. The results suggest that the modified procedure ensures relative expanded uncertainty equal to or less than 2.0% (n=5, confidence interval close to 95%) and 99.4% recovery for petroleum products investigated in repeatability conditions. 相似文献
103.
Catalin Badea 《Advances in Mathematics》2007,211(2):766-793
We study increasing sequences of positive integers (nk)k?1 with the following property: every bounded linear operator T acting on a separable Banach (or Hilbert) space with supk?1‖Tnk‖<∞ has a countable set of unimodular eigenvalues. Whether this property holds or not depends on the distribution (modulo one) of sequences (nkα)k?1, α∈R, or on the growth of nk+1/nk. Counterexamples to some conjectures in linear dynamics are given. For instance, a Hilbert space operator which is frequently hypercyclic, chaotic, but not topologically mixing is constructed. The situation of C0-semigroups is also discussed. 相似文献
104.
Carmen Ioana Ladiu Ionel Catalin Popescu Lo Gorton 《Journal of Solid State Electrochemistry》2005,9(5):296-303
The basic electrochemistry of carbon paste electrodes modified with Meldola Blue adsorbed on zirconium phosphate (MB-ZP-CPEs) and their ability to oxidize NADH have been investigated. Three types of carbon powder (graphite and glassy carbon-type Sigradur K and G) were used to obtain MB-ZP-CPEs. On comparing cyclic voltammograms recorded at MB-ZP-CPEs, similarly prepared from the three different carbon powders, those made with Sigradur K exhibited the lowest background current, and the best MB electrochemistry, seen as the highest peak intensities and smallest peak separation. Using MB-ZP-CPEs based on Sigradur K a study on NADH oxidation was done focusing on the effect of the Ca2+ concentration in the contacting solution and on the addition of polyethyleneimine (PEI) into the paste. It can be stated that MB-ZP-CPEs based on Sigradur K and containing 1.23% (w/w) PEI exhibited the best behavior for NADH oxidation, measured by the highest electrocatalytic rate constant (8.2×103 M–1 s–1). 相似文献
105.
Zamfir AD Serb A Vukeli Ž Flangea C Schiopu C Fabris D Kalanj-Bognar S Capitan F Sisu E 《Journal of the American Society for Mass Spectrometry》2011,22(12):2145-2159
Gangliosides (GGs), sialic acid-containing glycosphingolipids, are known to be involved in the invasive/metastatic behavior
of brain tumor cells. Development of modern methods for determination of the variations in GG expression and structure during
neoplastic cell transformation is a priority in the field of biomedical analysis. In this context, we report here on the first
optimization and application of chip-based nanoelectrospray (NanoMate robot) mass spectrometry (MS) for the investigation
of gangliosides in a secondary brain tumor. In our work a native GG mixture extracted and purified from brain metastasis of
lung adenocarcinoma was screened by NanoMate robot coupled to a quadrupole time-of-flight MS. A native GG mixture from an
age-matched healthy brain tissue, sampled and analyzed under identical conditions, served as a control. Comparative MS analysis
demonstrated an evident dissimilarity in GG expression in the two tissue types. Brain metastasis is characterized by many
species having a reduced N-acetylneuraminic acid (Neu5Ac) content, however, modified by fucosylation or O-acetylation such as Fuc-GM4, Fuc-GM3, di-O-Ac-GM1, O-Ac-GM3. In contrast, healthy brain tissue is dominated by longer structures exhibiting from mono- to hexasialylated sugar
chains. Also, significant differences in ceramide composition were discovered. By tandem MS using collision-induced dissociation
at low energies, brain metastasis-associated GD3 (d18:1/18:0) species as well as an uncommon Fuc-GM1 (d18:1/18:0) detected
in the normal brain tissue could be structurally characterized. The novel protocol was able to provide a reliable compositional
and structural characterization with high analysis pace and at a sensitivity situated in the fmol range. 相似文献
106.
Langeroudi EG Petre CF Azizi A Proulx E Larachi F 《Journal of separation science》2011,34(13):1568-1573
A capillary electrophoretic (CE) protocol was developed for the separation and quantification of free cyanide and zinc cyanide complex, two key species in gold cyanidation of zinc-bearing sulfidic ores. Several common carrier electrolytes were implemented in an indirect UV detection method. The effect of electric field strength, injection volume, concentration of electro-osmotic flow (EOF) modifier and UV-absorbing agent in background electrolyte (BGE) was examined while peak height, peak area and noise were considered for optimization. The best results were obtained using a BGE that contained 35 mM sodium chromate, 12 mM free cyanide and 0.45 mM hexamethonium bromide at pH 10.5. Free cyanide concentration was compared to that measured with the conventional silver nitrate titration method in solutions containing free cyanides and weak cyano-complexes. The developed CE protocol proved very robust in capturing the concentration of free cyanides (4% error) unlike the titration method which exhibited substantial sensitivity to the interfering weak cyano-complexes (38% error). 相似文献
107.
Florica Papa Catalin Negrila Gianina Dobrescu Akane Miyazaki Ioan Balint 《天然气化学杂志》2011,20(5):537-542
Fine and well dispersed Pt-Cu bimetallic nanoparticles stabilized by polyvinyl pyrrolidone (PVP) were synthesized by alkaline polyol method. The molar ratio of Pt to Cu was 1 : 1. Further, the Pt-Cu bimetallic nanoparticles were supported on alumina and their catalytic behavior in methane combustion was investigated. The as-prepared as well as the supported Pt-Cu nanoparticles were characterized by transmission elec-tron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fractal analysis and X-ray diffraction (XRD). The dependence of methane combustion on the morphology and surface composition of Pt-Cu nanoparticles was analyzed based on the experimental results. 相似文献
108.
Bution ML Caetano FH Britto FB Tomaino Gomes GA Zara FJ 《Micron (Oxford, England : 1993)》2006,37(3):249-254
In this study we histologically and histochemically describe the ventriculus of Dolichoderus bispinosus. The epithelium consists of two basic cell types, highly basophilic generative cells, and digestive cells. The latter present several cytoplasmic vesicles, rich in acidic and neutral polysaccharides, and basic proteins. Also, these cells exhibit an apocrine secretion pattern. A mass of fibrous material is observed on the surface of the epithelium. Finally, we discuss the results obtained. 相似文献
109.
The evolution of elemental Hg from its environmental compounds has already been supposed to be an important process within the global mercury cycle. The present study characterizes the abiotic reduction of Hg(II) ions by typical river humic substances (HS) conventionally pre-isolated by the adsorbent XAD 8 from the "Rio Negro" near Manaus, Brazil. For the investigation of this reduction process a special reaction and Hg(0) trapping unit combined with cold-vapor atomic absorption spectrometry (CVAAS) was developed. Preconcentration of traces of mercury(II), if required, was obtained by a home-made FIA system using microcolumns filled with the Hg(II)-selective collector CheliteS(R) (Serva Company). The effect of environmentally relevant parameters such as the pH value, the Hg(II)/HS ratio and the HS concentration on the Hg(II) reduction process was studied as a function of the time. The Hg(0) production was highest at pH 8.0 and in the case of decreasing HS amounts (0.5 mg) when about 65% of initially 1.0 mug Hg(II) was reduced within 50 h. Moreover, the reduction efficiency of HS towards Hg(II) strongly depended on the HS concentration but hardly on the Hg(II)/HS ratio. The reduction kinetics followed a relatively slow two-step first-order mechanism with formal rate constants of about 0.1 and 0.02 h(-1), respectively. Based on these findings the possible relevance of the abiotic evolution of mercury in humic-rich aquatic environments is considered. 相似文献
110.
Many-electron effects often dramatically modify the properties of reduced dimensional systems. We report calculations, based on an ab initio many-electron Green's function approach, of electron-hole interaction effects on the optical spectra of small-diameter single-walled carbon nanotubes. Excitonic effects qualitatively alter the optical spectra of both semiconducting and metallic tubes. Excitons are bound by approximately 1 eV in the semiconducting (8,0) tube and by approximately 100 meV in the metallic (3,3) tube. These large many-electron effects explain the discrepancies between previous theories and experiments. 相似文献