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91.
On the directed hop-constrained shortest path problem 总被引:1,自引:0,他引:1
92.
Marjan Motiei Luis Pleno de Gouveia Tom opík Robert Vícha David koda Jaroslav Císa Reza Khalili Eva Domincov Bergerov Luk Münster Haojie Fei Vladimír Sedlaík Petr Sha 《Molecules (Basel, Switzerland)》2021,26(7)
The alkaline milieu of chronic wounds severely impairs the therapeutic effect of antibiotics, such as rifampicin; as such, the development of new drugs, or the smart delivery of existing drugs, is required. Herein, two innovative polyelectrolyte nanoparticles (PENs), composed of an amphiphilic chitosan core and a polycationic shell, were synthesized at alkaline pH, and in vitro performances were assessed by 1H NMR, elemental analysis, FT-IR, XRD, DSC, DLS, SEM, TEM, UV/Vis spectrophotometry, and HPLC. According to the results, the nanostructures exhibited different morphologies but similar physicochemical properties and release profiles. It was also hypothesized that the simultaneous use of the nanosystem and an antioxidant could be therapeutically beneficial. Therefore, the simultaneous effects of ascorbic acid and PENs were evaluated on the release profile and degradation of rifampicin, in which the results confirmed their synergistic protective effect at pH 8.5, as opposed to pH 7.4. Overall, this study highlighted the benefits of nanoparticulate development in the presence of antioxidants, at alkaline pH, as an efficient approach for decreasing rifampicin degradation. 相似文献
93.
A Passive Optical Network (PON) is a network technology for deploying access networks based on passive optical components. In a single PON access network, the client terminals are connected to a Central Office through optical splitters and interconnecting fibers where each splitter splits in equal parts the input optical signal coming from the Central Office over its different output fibers. In this paper, we consider PON topology solutions where the splitting ratio and the number of splitting stages are not constrained to a given target design but, instead, are decided based on the cost of the solutions. We present different Integer Linear Programming formulations to model this problem and provide computational results showing that the optimal solutions can be computed for realistic problem instances. In addition, we describe how the formulations can be adapted for the traditional PON topology approaches and present computational results showing that significant cost gains are obtained with the unconstrained splitting stage approach. 相似文献
94.
Mónica Rodríguez Jorge Xue Laura M. Gouveia Alejandro J. Müller A. Eduardo Sáez Julien Rigolini Bruno Grassl 《Colloids and surfaces. A, Physicochemical and engineering aspects》2011,373(1-3):66-73
Two groups of copolymers were synthesized from high molecular weight polyacrylamides. One group of copolymers consisted of sulfonated, anionic copolymers (PAM-S) of acrylamide with the sodium salt of 2-acryloamido-2-methyl-1-propane sulfonic acid, and the other consisted of zwitterionic copolymers (PAM-Z) of acrylamide with a sulfobetaine methacrylate monomer. The shear rheology of aqueous solutions of the copolymers and their mixtures was studied experimentally. Solutions of both copolymers exhibit shear thinning behavior in the range of concentrations explored. Solutions of mixtures of two copolymers (PAM-Z and PAM-S) exhibited a slight viscosity synergy at high relative contents of PAM-S. Addition of a relatively high concentration of an electrolyte (0.3 M NaCl) induces decreases in viscosity due to coil contraction and eliminates the synergy of the mixtures. Mixtures of the zwitterionic copolymer and a cationic surfactant, cetyl trimethylammonium p-toluene sulfonate (CTAT), were also studied. These solutions exhibit a strong synergistic effect at low-shear rates when the surfactant forms wormlike micelles. In addition, oscillatory shear measurements demonstrate that PAM-Z/CTAT mixtures are significantly more elastic than CTAT solutions, which indicates that PAM-Z is effective in promoting micelle entanglements, as reflected by the increase in relaxation time with PAM-Z content. 相似文献
95.
Sandra C. Gouveia Paula C. Castilho 《Rapid communications in mass spectrometry : RCM》2010,24(13):1851-1868
Helicrysum melaleucum is a medicinal plant traditionally used in the islands of the Macaronesia region for the treatment of respiratory diseases. In this work, the phenolic compounds of Helicrysum melaleucum plants collected in different geographical locations of Madeira Island and their morphological parts (total aerial parts, leaves, flowers and stems) were extracted and analyzed separately by high‐performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC‐DAD/ESI‐MSn). A total of 68 compounds were characterized based mainly on their UV and mass spectra. These included derivatives of O‐glycosylated flavonoids (flavonol and flavones type), quinic acid, caffeic acid, lignans and polyphenols. The flowers were found to be the morphological part with higher variety of phenolic compounds. The large differences in the phenolic composition of plants collected from different geographical locations allowed the identification of a few components, such as pinoresinol and methoxylated flavone derivatives, likely to be useful as geographical markers. Also, these results promote further comparison of the bioactivities of the different samples analyzed. This paper marks the first report on the chemical analysis of Helichrysum melaleucum species. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
96.
In this paper, we present a new formulation for the local access network expansion problem. Previously, we have shown that this problem can be seen as an extension of the well-known Capacitated Minimum Spanning Tree Problem and have presented and tested two flow-based models. By including additional information on the definition of the variables, we propose a new flow-based model that permits us to use effectively variable eliminations tests as well as coefficient reduction on some of the constraints. We present computational results for instances with up to 500 nodes in order to show the advantages of the new model in comparison with the others. 相似文献
97.
The thermal behavior of melt‐mixed polypropylene (PP)/poly(?‐caprolactone) (PCL) blends was investigated with differential scanning calorimetry, and it was quantitatively related to the morphology observed through scanning electron microscopy. The PP/PCL blends were immiscible in the whole composition range; however, some interesting phenomena were found. Blends with low PP contents crystallized in a fractionated fashion. By applying a self‐nucleation procedure, we demonstrated that this occurred because of a lack of highly active heterogeneities within the confined PP domains. On the other hand, PP acted as a nucleating agent for PCL, and when the PP content was reduced, the higher surface/volume ratio increased its nucleating activity. The nucleating effect was improved when the PP was self‐nucleated because of the better nucleating effect of PP annealed crystals. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1365–1379, 2007 相似文献
98.
Ulisses Barres de Almeida Elisabete M. de Gouveia Dal Pino 《Brazilian Journal of Physics》2013,43(5-6):328-340
Gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. Cherenkov Telescope Array (CTA) is an international initiative to build the next-generation ground-based gamma-ray observatory which will have a factor of 5–10 improvement in sensitivity in the 100-GeV–10-TeV range and an extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the Northern and another in the Southern Hemisphere) for full sky coverage and will be operated as an open observatory. It will provide a deep insight into the non-thermal high-energy Universe. In this talk, we will briefly present the major design concepts of CTA as well as its vast science case. 相似文献
99.
Second-order perturbation expansions are rearranged in a convenient form that justifies taking the smallest energy difference, for non-vanishing matrix elements, as the first approximation in the average energy denominator method. 相似文献
100.
Ana M. Reis Marcos V. D. Vermelho D rio L. Nic cio Evandro A. Gouveia Artur S. Gouveia-neto 《Fiber and Integrated Optics》1995,14(2):179-193
The generation of near-infrared and intense visible light through stimulated multi-wave mixing processes in single-mode silica-based optical fibers pumped by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 μm is described. The experimental results show that intense infrared light around 1.2 μm is produced via selp-hase-matched four-photon mixing at the minimum group velocity dispersion region of pure SiO2-core and P2O5-doped silica fibers. In the visible spectral region, from 580 nm to 600 nm, 20 W peak power 100-ps pulses were generated by pumping single spans of single-mode P2O5-doped and undoped SiO2-core fibers with 1.319-μm laser pulses. The signal light generated in such fibers propagated in the LP02 fiber mode and exhibited a threshold power that depended upon the fiber length and a critical length that was power dependent. Also, it exhibited an asymmetrical spectrum of a few nanometers bandwidth, with a long tail toward high frequencies. For GeO2-doped silica-based fibers, a multiple-wavelength visible signal propagating in several high-order fiber modes was generated. 相似文献