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111.
Selecting a cost optimum subset of discrete-value dispersion compensation modules (DV-DCMs) subject to maximum module count from an available set of DV-DCMs is a NP-hard problem. We derive a novel dynamic programming algorithm with pseudo-polynomial time bound and show that DV-DCM cost re-scaling can improve the running time. 相似文献
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113.
Abstract Aliphatic polyesters, such as poly(lactic acids), need high molecular weight for acceptable mechanical properties. This can be achieved through ring-opening polymerization of lactides. The lactide route is, however, relatively complicated, and alternative polymerization routes are of interest. In this paper we report the properties of a polymer made by a two-step process: first a condensation polymerization of lactic acid and then an increase of the molecular weight with diisocyanate. The end product is then a thermoplastic poly(ester-urethane). The hydroxylterminated prepolymer was made with condensation polymerization of L–lactic acid and a small amount of 1,4-butanediol. The polymerization was performed in the melt under nitrogen and reduced pressure. The preparation of poly(ester-urethane) was done in the melt using aliphatic diisocyanates as the chain extenders reacting with the end groups of the prepolymer. The polymer samples were carefully characterized, including preliminary degradation studies. The results indicate that this route to convert lactic acid into thermoplastic biodegradable polymer has high potential. Lactic acid is converted into a mechanically attractive polymer with high yield, which could make the polymer suitable for high volume applications. The mechanical properties of the poly(ester-urethane) are comparable with those of poly(lactides). Capillary rheometer measurements indicate that the polymer is processible both by injection molding and extrusion. 相似文献
114.
Elinor Meiby Malin Morin Zetterberg Sten Ohlson Víctor Agmo Hernández Katarina Edwards 《Analytical and bioanalytical chemistry》2013,405(14):4859-4869
Lipodisks, also referred to as polyethylene glycol (PEG)-stabilized bilayer disks, have previously been demonstrated to hold great potential as model membranes in drug partition studies. In this study, an HPLC-MS system with stably immobilized lipodisks is presented. Functionalized lipodisks were immobilized on two different HPLC support materials either covalently by reductive amination or by streptavidin–biotin binding. An analytical HPLC column with immobilized lipodisks was evaluated by analysis of mixtures containing 15 different drug compounds. The efficiency, reproducibility, and stability of the system were found to be excellent. In situ incorporation of cyclooxygenase-1 (COX-1) in immobilized lipodisks on a column was also achieved. Specific binding of COX-1 to the immobilized lipodisks was validated by interaction studies with QCM-D. These results, taken together, open up the possibility of studying ligand interactions with membrane proteins by weak affinity chromatography. 相似文献
115.
Hanrieder J Wicher G Bergquist J Andersson M Fex-Svenningsen A 《Analytical and bioanalytical chemistry》2011,401(1):135-147
The development of powerful analytical techniques for specific molecular characterization of neural cell types is of central
relevance in neuroscience research for elucidating cellular functions in the central nervous system (CNS). This study examines
the use of differential protein expression profiling of mammalian neural cells using direct analysis by means of matrix-assisted
laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). MALDI-MS analysis is rapid, sensitive, robust,
and specific for large biomolecules in complex matrices. Here, we describe a newly developed and straightforward methodology
for direct characterization of rodent CNS glial cells using MALDI-MS-based intact cell mass spectrometry (ICMS). This molecular
phenotyping approach enables monitoring of cell growth stages, (stem) cell differentiation, as well as probing cellular responses
towards different stimulations. Glial cells were separated into pure astroglial, microglial, and oligodendroglial cell cultures.
The intact cell suspensions were then analyzed directly by MALDI-TOF-MS, resulting in characteristic mass spectra profiles
that discriminated glial cell types using principal component analysis. Complementary proteomic experiments revealed the identity
of these signature proteins that were predominantly expressed in the different glial cell types, including histone H4 for
oligodendrocytes and S100-A10 for astrocytes. MALDI imaging MS was performed, and signature masses were employed as molecular
tracers for prediction of oligodendroglial and astroglial localization in brain tissue. The different cell type specific protein
distributions in tissue were validated using immunohistochemistry. ICMS of intact neuroglia is a simple and straightforward
approach for characterization and discrimination of different cell types with molecular specificity. 相似文献
116.
Svensson FR Abrahamsson M Strömberg N Ewing AG Lincoln P 《The journal of physical chemistry letters》2011,2(5):397-401
Ruthenium dipyridophenazine (dppz) complexes are sensitive luminescent probes for hydrophobic environments. Here, we apply multiple-frequency fluorescence lifetime imaging microscopy (FLIM) to Δ and Λ enantiomers of lipophilic ruthenium dppz complexes in live and fixed cells, and their different lifetime staining patterns are related to conventional intensity-based microscopy. Excited state lifetimes of the enantiomers determined from FLIM measurements correspond well with spectroscopically measured emission decay curves in pure microenvironments of DNA, phospholipid membrane or a model protein. We show that FLIM can be applied to monitor the long-lived excited states of ruthenium complex enantiomers and, combined with confocal microscopy, give new insight into their biomolecular binding and reveal differences in the microenvironment probed by the complexes. 相似文献
117.
S. B. Erenburg S. V. Trubina K. S. Zhuravlev T. V. Malin B. Pecz 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(9):1147-1150
Multilayered samples with extremely narrow GaN quantum wells in an AlN host are synthesized via ammonia MBE. The parameters of the microstructure are determined by means of EXAFS spectroscopy, high-resolution electron microscopy, and low-angle scattering. Their relationship to the morphology of GaN/AlN superlattices is established. The influence of growth conditions and the thickness of superlattices on their optical properties and mixing in the near-boundary layers is established. 相似文献
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119.
Malin Jonsson Andreas Ehn Moah Christensen Marcus Aldén Joakim Bood 《Applied physics. B, Lasers and optics》2014,115(1):35-43
A method for simultaneous measurements of fluorescence lifetimes of two species along a line is described. The experimental setup is based on picosecond laser pulses from two tunable optical parametric generator/optical parametric amplifier systems together with a streak camera. With an appropriate optical time delay between the two laser pulses, whose wavelengths are tuned to excite two different species, laser-induced fluorescence can be both detected temporally and spatially resolved by the streak camera. Hence, our method enables one-dimensional imaging of fluorescence lifetimes of two species in the same streak camera recording. The concept is demonstrated for fluorescence lifetime measurements of CO and OH in a laminar methane/air flame on a Bunsen-type burner. Measurements were taken in flames with four different equivalence ratios, namely ? = 0.9, 1.0, 1.15, and 1.25. The measured one-dimensional lifetime profiles generally agree well with lifetimes calculated from quenching cross sections found in the literature and quencher concentrations predicted by the GRI 3.0 mechanism. For OH, there is a systematic deviation of approximately 30 % between calculated and measured lifetimes. It is found that this is mainly due to the adiabatic assumption regarding the flame and uncertainty in H2O quenching cross section. This emphasizes the strength of measuring the quenching rates rather than relying on models. The measurement concept might be useful for single-shot measurements of fluorescence lifetimes of several species pairs of vital importance in combustion processes, hence allowing fluorescence signals to be corrected for quenching and ultimately yield quantitative concentration profiles. 相似文献
120.