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排序方式: 共有436条查询结果,搜索用时 31 毫秒
41.
42.
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
43.
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
44.
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
45.
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
46.
47.
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
48.
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
49.
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
50.
Svetlana M. Stanišić Ljubiša M. Ignjatović Dragan D. Manojlović Biljana P. Dojčinović 《Central European Journal of Chemistry》2011,9(3):481-491
This paper presents the extraction of cations from a soil sample, type ranker on serpentinite, in deionized water, by use
of three different extraction techniques. The first extraction technique included the use of a rotary mixer, the second technique
involved the use of a microwave digestion system with different extraction temperatures, and the third technique employed
an ultrasonic bath with different extraction times. Ion chromatography was used for determining the concentration of Li, Na,
K, Ca, Mg and ammonium ions in soil extracts with subsequent determination of concentrations for all cations, except for ammonium
ion extraction, conducted by Inductively Coupled Plasma-Atomic Emission Spectrometry. The results of cation extractions showed
that microwave assisted extraction was most efficient for the Li, Na, K, Ca, Mg, Co, Mn, Ni, Pb and ammonium ions. Use of
a rotary mixer for extraction was most efficient for Cd and Zn ions, while use of ultrasound bath was most efficient for Cr,
Cu, Fe and Al ions. Several times higher amount of cations extracted by the most efficient, compared to the second best technique,
under optimal conditions, were noticed in the case of: Ca, Mg, Co, Mn, Fe, Al, and Zn ions. 相似文献