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101.
Joseph V Schulte F Rooch H Feldmann I Dörfel I Österle W Panne U Kneipp J 《Chemical communications (Cambridge, England)》2011,47(11):3236-3238
Silver nanoparticles were generated based on citrate reduction in the ultrastructure of the sporopollenin biopolymer of Ambrosia artemisiifolia (ragweed) and Secale cereale (rye). The nanoparticles enable the acquisition of SERS spectra and thereby a vibrational characterization of the local molecular structure of sporopollenin. 相似文献
102.
103.
Adina Jung Volkan Filiz Sofia Rangou Kristian Buhr Petra Merten Janina Hahn Juliana Clodt Clarissa Abetz Volker Abetz 《Macromolecular rapid communications》2013,34(7):610-615
The formation of integral asymmetric membranes from ABC triblock terpolymers by non‐solvent‐induced phase separation is shown. They are compared with the AB diblock copolymer precursors. Triblock terpolymers of polystyrene‐block‐poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (PS‐b‐P2VP‐b‐PEO) with two compositions are investigated. The third block supports the formation of a membrane in a case, where the corresponding diblock copolymer does not form a good membrane. In addition, the hydrophilicity is increased by the third block and due to the hydroxyl group the possibility of post‐functionalization is given. The morphologies are imaged by scanning electron microscopy. The influence of the PEO on the membrane properties is analyzed by water flux, retention, and dynamic contact angle measurements.
104.
Michael Quentin Dirk Blondin Janina Klasen Rotem Shlomo Lanzman Falk-Roland Miese Christian Arsov Peter Albers Gerald Antoch Hans-Jörg Wittsack 《Magnetic resonance imaging》2012
Purpose
To evaluate which mathematical model (monoexponential, biexponential, statistical, kurtosis) fits best to the diffusion-weighted signal in prostate magnetic resonance imaging (MRI).Materials and Methods
24 prostate 3-T MRI examinations of young volunteers (YV, n= 8), patients with biopsy proven prostate cancer (PC, n= 8) and an aged matched control group (AC, n= 8) were included. Diffusion-weighted imaging was performed using 11 b-values ranging from 0 to 800 s/mm2.Results
Monoexponential apparent diffusion coefficient (ADC) values were significantly (P<.001) lower in the peripheral (PZ) zone (1.18±0.16 mm2/s) and the central (CZ) zone (0.73±0.13 mm2/s) of YV compared to AC (PZ 1.92±0.17 mm2/s; CZ 1.35±0.21 mm2/s). In PC ADCmono values (0.61±0.06 mm2/s) were significantly (P<.001) lower than in the peripheral of central zone of AC. Using the statistical analysis (Akaike information criteria) in YV most pixels were best described by the biexponential model (82%), the statistical model, respectively kurtosis (93%) each compared to the monoexponential model. In PC the majority of pixels was best described by the monoexponential model (57%) compared to the biexponential model.Conclusion
Although a more complex model might provide a better fitting when multiple b-values are used, the monoexponential analyses for ADC calculation in prostate MRI is sufficient to discriminate prostate cancer from normal tissue using b-values ranging from 0 to 800 s/mm2. 相似文献105.
Steady-state spectroscopic studies of two ortho (-OCH3 and -OH) derivatives of methyl p-dimethylaminobenzoate have been performed. The absorption spectra of molecules under study are analyzed taking into consideration results of quantum chemical semiempirical calculations. The fluorescence spectra of these molecules possess in polar solvents two bands, i.e., the locally excited and intramolecular charge transfer (ICT) fluorescence band. Their intensity ratio as well as the fluorescence/phosphorescence intensity ratio determined at 77 K depends on the solvent polarity. Theoretical studies of the TICT phenomenon have been made in order to explain the dual emission of molecules under study. Calculated electric dipole moments of these molecules in the ground, S0, and excited, S1(LE) and S1(ICT) states, have been compared with experimentally determined data. Theoretically determined transition energies, ΔEi, oscillator strengths, fi, and electric dipole moments μS0, μS1(LE) and μS1(ICT) of the planar donor-acceptor (D/A) conformer agree with experimental data. According to Marcus theory inner- and outer-solvatation sphere reorganization energies (λout, λin) are calculated using the determined spectroscopic properties of molecules under study. 相似文献
106.
107.
Phenyltin compounds are known to be biologically active. Their chemical structure suggests that they are likely to interact with the lipid fraction of cell membranes. Using fluorescence and NMR techniques, the effect of phenyltin compounds on selected regions of model lipid bilayers formed from phosphatidylcholine was studied. The polarization of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) dipalmitoyl-L -phosphatidylethanolamine and desorption of praseodymium ions was used to probe the polar region, whereas the polarization of 1 - (4 - trimethylammoniumphenyl) - 6 - phenyl - 1,3,5-hexatriene p-toluenesulfonate measured the hydrophobic core of the membrane. In addition, changes in the N-(5-fluoresceinthiocarbanoly)dipalmitoyl - L - α - phosphatidyl - ethanolamine fluorescence intensity indicated the amount of charge introduced by organotin compounds to the membrane surface. There were no relevant changes of measured parameters when tetraphenyltin was introduced to the vesicle suspension. Diphenyltin chloride causes changes of the hydrophobic region, whereas the triphenyltin chloride seems to adsorb in the headgroup region of the lipid bilayer. When the hemolytic activity of phenyltin compounds was measured, triphenyltin chloride was the most effective whereas diphenyltin chloride was much less effective. Tetraphenyltin causes little damage. Based on the presented data, a correlation between activity of those compounds to hemolysis (and toxicity) and the location of the compound within the lipid bilayer could be proposed. In order to inflict damage on the plasma membrane, the compound has to penetrate the lipid bilayer. Tetraphenyltin does not partition into the lipid fraction; therefore its destructive effect is negligible. The partition of the compound into the lipid phase is not sufficient enough, by itself, to change the structure of the lipid bilayer to a biologically relevant degree. The hemolytic potency seems to be dependent on the location of the compound within the lipid bilayer. Triphenyltin chloride which adsorbs on the surface of the membrane, causes a high level of hemolysis, whereas diphenyltin chloride, which penetrates much deeper, seems to have only limited potency. © 1998 John Wiley & Sons, Ltd. 相似文献
108.
Marek J. Potrzebowski Jarosaw Baszczyk Wiesaw R. Majzner Micha W. Wieczorek Janina Baraniak Wojciech J. Stec 《Solid state nuclear magnetic resonance》1998,11(3-4):215-224
high resolution solid state NMR spectroscopy was employed to study structural properties of bis(diisopropoxyphosphorothioyl) diselenide 1 and bis(dineopentoxyphosphorothioyl) diselenide 2. The principal elements Tii of
effective dipolar/chemical shift tensor were calculated from spinning sideband intensities employing the WIN-MAS program. The values of anisotropy and asymmetry parameters reflect the distortion of the selenium environment. It was found that the T33 component mostly contributes to changes in the isotropic chemical shifts.
CP/MAS experiments were used to decide the assignment of space group by counting the number of crystallographically unique selenium centers in the unit cell. Crystals of diselenide 1 are triclinic, space group P
with a=8.485(3) Å, b=8.508(1) Å, c=8.511(2) Å, =98.835(15)°, β=111.653(24)°, γ=93.524(21)°, V=559.5(3) Å3, Dc=1.544(2) g/cm3 and Z=1. Refinement using 2222 reflections for 157 variables gives R=0.037. Crystals of diselenide 2 are triclinic, space group P1 with a=9.1418(8) Å, b=9.1465(8) Å, c=9.9200(9) Å, =74.751(8)°, β=74.629(7)°, γ=82.216(7)°, V=769.7(1) Å3, Dc=1.365(2) g/cm3 and Z=1. Refinement using 3316 reflections for 297 variables gives R=0.0272. 相似文献
109.
Jan Hendrik Kobarg Peter Maass Janina Oetjen Oren Tropp Eyal Hirsch Chen Sagiv Mohammad Golbabaee Pierre Vandergheynst 《Advances in Computational Mathematics》2014,40(3):667-682
This article does not present new mathematical results, it solely aims at discussing some numerical experiments with MALDI Imaging data. However, these experiments are based on and could not be done without the mathematical results obtained in the UNLocX project. They tackle two obstacles which presently prevent clinical routine applications of MALDI Imaging technology. In the last decade, matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) has developed into a powerful bioanalytical imaging modality. MALDI imaging data consists of a set of mass spectra, which are measured at different locations of a flat tissue sample. Hence, this technology is capable of revealing the full metabolic structure of the sample under investigation. Sampling resolution as well as spectral resolution is constantly increasing, presently a conventional 2D MALDI Imaging data requires up to 100 GB per dataset. A major challenge towards routine applications of MALDI Imaging in pharmaceutical or medical workflows is the high computational cost for evaluating and visualizing the information content of MALDI imaging data. This becomes even more critical in the near future when considering cohorts or 3D applications. Due to its size and complexity MALDI Imaging constitutes a challenging test case for high performance signal processing. In this article we will apply concepts and algorithms, which were developed within the UNLocX project, to MALDI Imaging data. In particular we will discuss a suitable phase space model for such data and report on implementations of the resulting transform coders using GPU technology. Within the MALDI Imaging workflow this leads to an efficient baseline removal and peak picking. The final goal of data processing in MALDI Imaging is the discrimination of regions having different metabolic structures. We introduce and discuss so-called soft-segmentation maps which are obtained by non-negative matrix factorization incorporating sparsity constraints. 相似文献
110.
N‐alkoxypyridinium salts as coinitiators in radical polymerization: Synthesis and Photochemical Properties 下载免费PDF全文
Janina Kabatc Katarzyna Kostrzewska Robert Dobosz Łukasz Orzeł Katarzyna Jurek 《Journal of polymer science. Part A, Polymer chemistry》2017,55(17):2840-2850
A few N‐alkoxypyridinium salts are developed as photoinitiators for efficient polymerization reactions. They are characterized by absorption properties below 300 nm, and generate alkoxy radicals on UV‐Vis light exposure. The squarylium dye was used as a blue‐light photosensitizer. Polymerization results are correlated with the photochemistry of N‐alkoxypyridinium salts. The quenching of the excited singlet state of squarylium dye by pyridinium salt and the formation of the semioxidized species of squaraine suggests an electron transfer from an excited dye to a coinitiator, and that the resulting oxygen‐centered radical initiates the polymerization process. The chemical mechanism was investigated by steady state photolysis and nanosecond laser flash photolysis experiments. Photoinitiating activity of new photoinitiators for initiation of polymerization of trimethylolpropane triacrylate in the UV‐blue light region was compared with photoinitiating ability of selected commercially available initiators. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2840–2850 相似文献