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排序方式: 共有790条查询结果,搜索用时 15 毫秒
81.
Milica Sentic Stéphane Arbault Laurent Bouffier Dragan Manojlovic Alexander Kuhn Neso Sojic 《Chemical science》2015,6(8):4433-4437
Among luminescence techniques, electrogenerated chemiluminescence (ECL) provides a unique level of manipulation of the luminescent process by controlling the electrochemical trigger. Despite its attractiveness, ECL is by essence a 2D process where light emission is strictly confined to the electrode surface. To overcome this intrinsic limitation, we added a new spatial dimension to the ECL process by generating 3D ECL at the level of millions of micro-emitters dispersed in solution. Each single object is addressed remotely by bipolar electrochemistry and they generate collectively the luminescence in the bulk. Therefore, the entire volume of the solution produces light. To illustrate the generality of this concept, we extended it to a suspension of multi-walled carbon nanotubes where each one acts as an individual ECL nano-emitter. This approach enables a change of paradigm by switching from a surface-limited process to 3D electrogenerated light emission. 相似文献
82.
83.
Vukomanović M Skapin SD Poljanšek I Zagar E Kralj B Ignjatović N Uskoković D 《Colloids and surfaces. B, Biointerfaces》2011,82(2):414-421
The novel concept of a simultaneous, controlled release of a drug and a prodrug with different physico-chemical properties was applied in order to prolong the release period of antibiotics and estimate their high local concentrations, which are the necessary preconditions for the treatment of some chronic infection diseases. For this purpose poly(D,L-lactide-co-glycolide)/hydroxyapatite (PLGA/HAp) core-shell nanostructures were used as the carrier of clindamycin-base, as a drug, and clindamycin-2-phosphate, as a prodrug model. As a result, a two-step release was observed: the controlled release of the more soluble phosphate form and the sustained release of the less-soluble base form of clindamycin, resulting in a high overall concentration of the released drug during the period of 30 days in vitro. The HAp phase within the PLGA core-shells, applied as a drug carrier, delayed the process of the degradation of the polymer; however, the presence of the drug affected the process of degradation and this influence was the dominant factor in the control over the degradation of the polymer phase of PLGA/HAp and the consequent kinetics of the drug release. 相似文献
84.
Vukomanović M Zavašnik-Bergant T Bračko I Skapin SD Ignjatović N Radmilović V Uskoković D 《Colloids and surfaces. B, Biointerfaces》2011,87(2):226-235
A step-by-step analysis of the formation and the drug loading of the poly(D,L-lactide-co-glycolide)/hydroxyapatite (PLGA/HAp) composite was carried out in a perspective of the following parameters: the structure, the morphology and the adsorption/desorption properties of the composite's bioceramic part. The authors demonstrated the importance of the material's capacity to form a fine dispersion of solid HAp particles, as an initial step, for the further loading of the drug and for the formation of the core-shell structures. The nanometer-sized rods of HAp have the capacity of ensuring a rapid adsorption and a controlled desorption of the drug from their surface, and they can act as a nucleating site for the formation of polymeric cores. Each component of this material was labeled with fluorescence dye, which enabled an insight into the distribution of the components in the core-shells that were obtained as the final outcome. Such an analysis showed a high level of uniformity among the cores enclosed within polymeric shells. From a practical perspective, the labeling of each component of the composite can be regarded as an additional functionality of the material: labeling can enable us to monitor its action during the healing process. This ability to be easily detected is expected to enhance the procedure for the controlled delivery of antibiotics after their local implantation of carriers loaded with the antibiotic and to provide more careful control over this process. 相似文献
85.
Dalibor Stankovic Dragan Manojlovic Goran Roglic Sladjana Kostic‐Rajacic Ivan Andjelkovic Biljana Dojcinovic Jelena Mutic 《Electroanalysis》2011,23(8):1928-1933
The determination of Pb and Cd with a Nafion‐modified glassy carbon electrode and Cu‐DPABA complex (Cu‐DPABA–NA/GCE; DPABA is methyl 3,5‐bis{bis‐[(pyridin‐2‐yl)methyl]amino}methyl‐benzoate) as an alternative electrode for anodic stripping voltammetry was described. Pb and Cd were accumulated in acetate buffer pH 4 at a potential of ?1.4 V (vs. Ag/AgCl electrode) for 120 s followed by a DPASV scan from ?1.2 to ?0.2 V. Under optimum conditions the calibration curves were linear in the range of 4.8×10?9–5.0×10?5 and 5.0×10?9–5×10?5 mol L?1 for Pb and Cd, respectively. Detection limits were 1.8×10?9 and 1.2×10?9 mol L?1 for Pb and Cd, respectively. Different parameters and conditions, such as membrane ingredients, accumulation time, potential and pH value were optimized. A study of interfering substances was also performed. A significant increase in current was achieved at the modified electrode in comparison with the bare glassy carbon electrode. The validation of the proposed method was made by Pb and Cd determination in the certified reference material Groundwater CRM 610 (BCR, Community Bureau of Reference, Brussels, Belgium). The electrode was successfully applied for determination of Pb and Cd in river water with a high content of organic contaminants without any pretreatment. 相似文献
86.
87.
Dragan Dimitrovski Dragana Radosavljevi? Miloje Rajovi? Rade Stoiljkovi? 《Acta Mathematica Hungarica》2011,132(1-2):15-26
It is shown that Sturm theorems, formulated in the 1830??s ([1], [2], [3] and [4]) and valid for second order linear homogeneous differential equation L(y)??y??+a(x)y??+b(x)y=0, could as well be formulated for the class of nonhomogeneous linear differential equations L(y)=f(x). Criteria for the existence of oscillatory solutions of nonhomogeneous equations, as well as more exact locations of the zeros are given. 相似文献
88.
The problem is related to a fleet of military aircraft with a certain flying program in which the availability of the aircraft
sufficient to meet the flying program is a challenging issue. During the pre- or after-flight inspections, some component
failures of the aircraft may be found. In such cases, the aircraft are sent to the repair shop to be scheduled for maintenance
jobs, consisting of failure repairs or preventive maintenance tasks. The objective is to schedule the jobs in such a way that
sufficient number of aircrafts is available for the next flight programs. The main resource, as well as the main constraint,
in the shop is skilled-workforce. The problem is formulated as a mixed-integer mathematical programming model in which the
network flow structure is used to simulate the flow of aircraft between missions, hanger and repair shop. The proposed model
is solved using the classical Branch-and-Bound method and its performance is verified and analyzed in terms of a number of
test problems adopted from the real data. The results empirically supported practical utility of the proposed model. 相似文献
89.
Snežana Č. Živković-Zlatanović Dragan S. Djordjević Robin E. Harte 《Integral Equations and Operator Theory》2011,69(3):347-363
We consider left and right Browder operators, left and right Fredholm operators, spectra related with these operators, and
various operator quantities. 相似文献
90.
Ben Issa N Rajaković-Ognjanović VN Marinković AD Rajaković LV 《Analytica chimica acta》2011,(1):191-198
A simple and efficient method for separation and determination of inorganic arsenic (iAs) and organic arsenic (oAs) in drinking, natural and wastewater was developed. If arsenic is present in water prevailing forms are inorganic acids of As(III) and As(V). oAs can be found in traces as monomethylarsenic acid, MMA(V), and dimethylarsenic acid, DMAs(V). Three types of resins: a strong base anion exchange (SBAE) and two hybrid (HY) resins: HY-Fe and HY-AgCl, based on the activity of hydrated iron oxides and a silver chloride were investigated. It was found that the sorption processes (ion exchange, adsorption and chemisorptions) of arsenic species on SBAE (ion exchange) and HY resins depend on pH values of water. The quantitative separation of molecular and ionic forms of iAs and oAs was achieved by SBAE and pH adjustment, the molecular form of As(III) that exists in the water at pH <8.0 was not bonded with SBAE, which was convenient for direct determination of As(III) concentration in the effluent. HY-Fe resin retained all arsenic species except DMAs(V), which makes possible direct measurements of this specie in the effluent. HY-AgCl resin retained all iAs which was convenient for direct determination of oAs species concentration in the effluent. The selective bonding of arsenic species on three types of resins makes possible the development of the procedure for measuring and calculation of all arsenic species in water. In order to determine capacity of resins the preliminary investigations were performed in batch system and fixed bed flow system. Resin capacities were calculated according to breakthrough points in a fixed bed flow system which is the first step in designing of solid phase extraction (SPE) module for arsenic speciation separation and determination. Arsenic adsorption behavior in the presence of impurities showed tolerance with the respect to potential interference of anionic compounds commonly found in natural water. Proposed method was established performing standard procedures: with external standard, certified reference material and standard addition method. Two analytical techniques: the inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectroscopy-hydride generation (AAS-GH) were comparatively applied for the determination of arsenic in all arsenic species in water. ICP-MS detection limit was 0.2 μg L−1 and relative standard deviation (RSD) of all arsenic species investigated was between 3.5 and 5.1%. 相似文献