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331.
We report a simulation study for bottle-brush polymers grafted on a rigid backbone. Using a standard coarse-grained bead-spring model extensive molecular dynamics simulations for such macromolecules under good solvent conditions are performed. We consider a broad range of parameters and present numerical results for the monomer density profile, density of the untethered ends of the grafted flexible backbones and the correlation function describing the range that neighboring grafted bottle-brushes are affected by the presence of the others due to the excluded-volume interactions. The end beads of the flexible backbones of the grafted bottle-brushes do not access the region close to the rigid backbone due to the presence of the side chains of the grafted bottle-brush polymers, which stretch the chains further in the radial directions. Although a number of different correlation lengths exist as a result of the complex structure of these macromolecules, their properties can be tuned with high accuracy in good solvents. Moreover, qualitative differences with 'typical' bottle-brushes are discussed. Our results provide a first approach to characterizing such complex macromolecules with a standard bead-spring model. 相似文献
332.
Lougiakis N Marakos P Pouli N Poul N Balzarini J 《Chemical & pharmaceutical bulletin》2008,56(6):775-780
The preparation of novel 5-amino or 7-hydroxy substituted pyrazolo[4,3-b]pyridine and pyrazolo[3,4-c]pyridine acyclic C-nucleosides is described. Their synthesis was carried out by condensation of suitably substituted lithiated picolines with 2-benzyloxyethoxymethylchloride followed by pyrazole ring annulation. The compounds were evaluated for their antiviral activity against a wide panel of viruses, but were found inactive at subtoxic concentrations. 相似文献
333.
Markos Koutmos Irene P. Georgakaki Panagiotis Tsiolis Dimitri Coucouvanis Prof. 《无机化学与普通化学杂志》2008,634(2):255-261
The synthesis of multimetallic M/S clusters by the reductive coupling of dimeric building blocks appears to be of general utility. In this paper we describe the synthesis and characterization of new single cubanes with cores such as [Mo2Fe2S4]2+ and [MoFe3S4]3+,2+. 相似文献
334.
Efthymia Symitsi Panagiotis Stamolampros George Daskalakis Nikolaos Korfiatis 《European Journal of Operational Research》2021,288(2):605-619
This paper investigates the informational value of online reviews posted by employees for their employer, a rather untapped source of online information from employees, using a sample of 349,550 reviews from 40,915 UK firms. We explore this novel form of electronic Word-of-Mouth (e-WOM) from different perspectives, namely: (i) its information content as a tool to identify the drivers of job satisfaction/dissatisfaction, (ii) its predictive ability on firm financial performance and (iii) its operational and managerial value. Our approach considers both the rating score as well as the review text through a probabilistic topic modeling method, providing also a roadmap to quantify and exploit employee big data analytics. The novelty of this study lies in the coupling of structured and unstructured data for deriving managerial insights through a battery of econometric, financial and operational research methodologies. Our empirical analyses reveal that employee online reviews have informational value and incremental predictability gains for a firm's internal and external stakeholders. The results indicate that when models integrate structured and unstructured big data there are leveraged opportunities for firms and managers to enhance the informativeness of decision support systems and in turn, gain competitive advantage. 相似文献
335.
We use isoperimetric inequalities combined with a new technique to prove upper bounds for the site percolation threshold of plane graphs with given minimum degree conditions. In the process we prove tight new isoperimetric bounds for certain classes of hyperbolic graphs. This establishes the vertex isoperimetric constant for all triangular and square hyperbolic lattices, answering a question of Lyons and Peres. We prove that plane graphs of minimum degree at least 7 have site percolation threshold bounded away from 1/2, which was conjectured by Benjamini and Schramm, and make progress on a conjecture of Angel, Benjamini, and Horesh that the critical probability is at most 1/2 for plane triangulations of minimum degree 6. We prove additional bounds for stronger minimum degree conditions, and for graphs without triangular faces. 相似文献
336.
Mullen W Albalat A Gonzalez J Zerefos P Siwy J Franke J Mischak H 《Electrophoresis》2012,33(4):567-574
One of the aims in the field of proteomics is the identification of a protein or polypeptide, or a range of these compounds, that could provide pre-symptomatic indication of the onset of a disease. A number of analytical techniques have been employed to try and achieve this end. These techniques have been applied to the complete range of body fluids and tissues that are readily available from clinical studies. Of these sample sources, the urinary low molecular weight peptidome has been shown to reflect changes in the health status of the individual. The alterations that occur in the polypeptide make up of urine, which reflect changes in biological status, are known as biomarkers. To be able to determine these changes no single technique has emerged that can cope with detecting the large number of peptides present and quantifying them over the wide concentration range they exist in. In this investigation, we made use of a single reflectron time of flight (RTOF)-MS analyser to which we first connected a CE system and then a nanoflow HPLC. Two pooled male and female standard urine samples were compared on these systems. Both techniques had similar results in terms of number of peptides detected and the mass range the peptides were detected over. The major differences in terms of biomarker research were the ability in CE to calibrate the migration time of the peptides to allow comparison between samples. In addition, CE was shown not to suffer from carry over from previous samples as was seen in the LC analysis. 相似文献
337.
Ivopoulos P Sotiropoulou M Bokias G Staikos G 《Langmuir : the ACS journal of surfaces and colloids》2006,22(22):9181-9186
Comb-type copolymers of poly(acrylic acid) grafted with poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPSA) side chains form with poly(ethylene glycol), at low pH, water-soluble hydrogen-bonding interpolymer complexes. Turbidimetry, viscometry, and dynamic light scattering measurements suggest that compact, negatively charged, colloidal nanoparticles are formed at pH<3.75. The influence of the structure of the graft copolymers and of the ionic strength of the solution on the size of these nanoparticles was investigated. It was found that their hydrodynamic radius decreases by increasing the molecular mass of the PAMPSA side chains of the graft copolymer and increases with increasing the ionic strength of the solution. 相似文献
338.
We have performed a variety of high-level electronic structure calculations on two moderately sized organic molecules and found considerable sensitivity of the intramolecular potential energy surface to the method employed. The gas-phase structure of tyrosine-glycine varies qualitatively between B3LYP and MP2 optimizations, producing different close contacts between the tyrosine ring and the glycine moiety. The relative energies of the 2-(acetylamino)benzamide conformations found in its two polymorphs can vary by over 20 kJ mol-1 between MP2 and B3LYP calculations, using the same basis set. It is shown by a novel analysis that the intramolecular equivalent of basis set superposition error competes with the errors in the intramolecular dispersion in causing this sensitivity. 相似文献
339.
Lancaster RW Karamertzanis PG Hulme AT Tocher DA Covey DF Price SL 《Chemical communications (Cambridge, England)》2006,(47):4921-4923
A computational prediction that mixing the synthetic mirror image of progesterone with its natural form would produce a specific racemic crystal structure was validated. 相似文献
340.
Panagiotis Sidiropoulos Nikos Nikolaidis Ioannis Pitas 《Chaos, solitons, and fractals》2009,42(5):2667-2674
Fragile watermarking is a popular method for image authentication. In such schemes, a fragile signal that is sensitive to manipulations is embedded in the image, so that it becomes undetectable after any modification of the original work. Most algorithms focus either on the ability to retrieve the original work after watermark detection (invertibility) or on detecting which image parts have been altered (localization). Furthermore, the majority of fragile watermarking schemes suffer from robustness flaws. We propose a new technique that combines localization and invertibility. Moreover, watermark dependency on the original image and the non-linear watermark embedding procedure guarantees that no malicious attacks will manage to create information leaks. 相似文献