A mathematical formalism related to the approximate as well as the accurate interferometric data reduction schemes is briefly outlined and subsequently applied in the reconstruction of the assumed (Luneburg) axisymmetric refractive index distribution. The presented comparative analysis confirms the generally held opinion that the approximate methods (“straight-line” and Kokubun-Iga approaches) may provide quite reasonable results in the examination of refractively inhomogeneous disturbances characterized by weak gradient and moderate index variation. On the other hand, the accurate scheme for transverse interferometric data interpretation and reduction, based on the close-form correlation between the fringe shift and the deflection function, [1] remains the only method for reliable reconstruction of strongly refracting index profiles, independently of magnitude of refraction and ambiguity of the fringes. This fact is of considerable importance for transverse interferometry of fibers (preform rods) and/or GRIN-rod lenses characterized by high numerical apertures. 相似文献
In the paper, the computational complexity of several variants of the problem of isothermic DNA sequencing by hybridization, is analyzed. The isothermic sequencing is a recent method, in which isothermic oligonucleotide libraries are used during the hybridization with an unknown DNA fragment. The variants of the isothermic DNA sequencing problem with errors in the hybridization data, negative ones or positive ones, are proved to be strongly NP-hard. On the other hand, the polynomial time algorithm for the ideal case with no errors is proposed. 相似文献
Microtubules are regulated by microtubule‐associated proteins. However, little is known about the structure of microtubule‐associated proteins in complex with microtubules. Herein we show that the microtubule‐associated protein Tau, which is intrinsically disordered in solution, locally folds into a stable structure upon binding to microtubules. While Tau is highly flexible in solution and adopts a β‐sheet structure in amyloid fibrils, in complex with microtubules the conserved hexapeptides at the beginning of the Tau repeats two and three convert into a hairpin conformation. Thus, binding to microtubules stabilizes a unique conformation in Tau. 相似文献
Nucleotides, their analogues, and other phosphate esters and phosphoramidates often contain the triethylammonium cation as a counterion. We found that this may be lost during chromatographic purification or concentration of solutions, yielding products in acidic forms or containing sub-stoichiometric amounts of the counterion. This in turn may be detrimental, e.g., due to possible decomposition of a compound or inaccurate sample preparation. Correlations between the structure of studied compounds and their susceptibility for cation loss were analyzed. Modifications in preparative techniques were developed to obtain the studied compounds with stoichiometric anion to cation ratios.
Graphical Abstract Triethylammonium salts of phosphate esters and phosphoramidates may lose the cationic component during chromatography or evaporation of solvent
The self-consistent model of heat and mass transfer during convective drying of capillary porous media describing both the
first and the second periods of drying is presented in Musielak (Wydawnictwo Politechniki Poznańskiej, seria Rozprawy, nr
386 (2004a); Chem. Process Eng. 25, 393–409 (2004b)). The results of simulations of processes in steady conditions are shown (Musielak Wydawnictwo Politechniki
Poznańskiej, seria Rozprawy, nr 386 (2004a); Chem. Process Eng. 25, 393–409 (2004b)). The main aim of the present work is to compare experimental results with those from numerical simulations.
Three convective drying processes have been performed experimentally. The first and the second periods of drying are considered,
during which the humidity of air in the dryer changes due to evaporation. The first process is used to establish drying parameters,
whereafter the two remaining processes are simulated. Good agreement between experimental and simulation results is found,
both qualitative and quantitative. 相似文献
The photophysical properties of 5‐deazaalloxazine and 1,3‐dimethyl‐5‐deazaalloxazine were studied in different solvents. These compounds have higher values of fluorescence quantum yields and longer fluorescence lifetimes, compared to those obtained for their alloxazine analogs. Electronic structure and S0–Si transitions were investigated using the ab initio methods [MP2, CIS(D), EOM‐CCSD] with the correlation‐consistent basis sets. Also the time‐dependent density functional theory (TD‐DFT) has been employed. The lowest singlet excited states of 5‐deazaalloxazine and 1,3‐dimethyl‐5‐deazaalloxazine are predicted to have the π, π* character, whereas similar alloxazines have two close‐lying π, π* and n, π* transitions. Experimental steady‐state and time‐resolved spectral studies indicate formation of an isoalloxazinic excited state via excited‐state double‐proton transfer (ESDPT) catalyzed by an acetic acid molecule that forms a hydrogen bond complex with the 5‐deazaalloxazine molecule. Solvatochromism of both 5‐deazaalloxazine and its 1,3‐dimethyl substituted derivative was analyzed using the Kamlet–Taft scale and four‐parameter Catalán solvent scale. The most significant result of our studies is that the both scales show a strong influence of solvent acidity (hydrogen bond donating ability) on the emission properties of these compounds, indicating the importance of intermolecular solute–solvent hydrogen‐bonding interactions in their excited state. 相似文献
Herein, we report a new and convenient methodology for the synthesis of ortho-XCF2 arylphosphonates via Diels-Alder reaction of selected 1,3-butadienes with XCF2-≡-P(O)(OEt)2, followed by the aromatization of the cyclic vinylphosphonates obtained using the KMnO4/Al2O3 system. The reactivity of ortho-XCF2 arylphosphonates was then examined to give the respective dichlorides that were converted to the corresponding phosphonic acids, phosphine oxides or a carboxylic acid (upon hydrolysis of the CF2Br group). When ortho-XCF2 arylphosphonates (X=Br) were treated with Zn/CuBr and an electrophile, the dimeric product ArCFCFAr was isolated only. The lithiation of the CF2H group (X=H) allowed however to obtain products of nucleophilic substitution with various electrophiles. 相似文献
The preparation of iodo acid [closo-1-CB9H8-1-COOH-10-I]− (1) is optimized and scaled from 1 to 40 g of B10H14. The improved preparation of the [arachno-6-CB9H13-6-COOH]− (5) uses four times smaller volume and can be run conveniently in up to 40 g scale in a 3-L vessel. The optimized oxidation of 5 to [closo-2-CB9H9-2-COOH]− (4) requires less oxidant, 12 times smaller volume, and significantly shorter reaction time. The overall yields of the iodo acid 1 as the [NMe4]+ salt are typically 8-10% (10-12 g) for 40 g of B10H14. The iodo acid 1 was transformed to amino acid 8, then to dinitrogen acid 10, and finally to sulfonium acid 2[3] in overall yield of about 13%. The search for a more efficient phosphine ligand for the Pd-catalyzed amination process was not fruitful. Three routes to the sulfonium acid 2[n] were investigated, and the best yield of about 47% was obtained for Cs2CO3-assisted cycloalkylation. Liquid crystalline ester of acid 2[3] and 4-butoxyphenol was prepared and investigated. 相似文献