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排序方式: 共有423条查询结果,搜索用时 15 毫秒
71.
72.
Block copolymers having poly(tetrachlorobisphenol-A adipate) (PTBA) and polystyrene (PS) sequences were synthesized were synthesized by photodegradation of an oxime-containing polyester in the presence of styrene. Crystallinity, melting behavior, and spherulitic growth rates were studied as a function of block compositions and molecular weights. A model was proposed based on a complete phase separation between the two components. The influence of the polymer composition on the spherulitic growth rate is described by introducing a supplementary pre-exponential factor into the equation for the growth rate. This parameter is a measure of the tortuosity of the actual path that has to be covered owing to the presence of the noncrystallizable blocks. 相似文献
73.
It has been proposed that there are degrees of freedom intrinsic to quantum critical points that can contribute to quantum critical physics. We point out that this conclusion is quite general below the upper critical dimension. We show that in (2+1)D antiferromagnets Skyrmion excitations are stable at criticality and identify them as the critical excitations. We find exact solutions composed of Skyrmion and anti-Skyrmion superpositions, which we call topolons. We include the topolons in the partition function and renormalize by integrating out small size topolons and short wavelength spin waves. We obtain a correlation length exponent nu=0.690 666 and anomalous dimension eta=0.0166. 相似文献
74.
Morone M Beverina L Abbotto A Silvestri F Collini E Ferrante C Bozio R Pagani GA 《Organic letters》2006,8(13):2719-2722
The microwave-enhanced synthesis, comparative singlet oxygen sensitization efficiency, and nonlinear optical characterization of a new beta-functionalized porphyrin and its copper complex are described. We show that the introduction of a donor-acceptor push-pull conjugated fragment in the beta position strongly perturbs the porphyrin electronic structure leading to a remarkable one- and two-photon NIR absorption enhancement. 相似文献
75.
Greta Petrella Camilla Montesano Sara Lentini Giorgia Ciufolini Domitilla Vanni Roberto Speziale Andrea Salonia Francesco Montorsi Vincenzo Summa Riccardo Vago Laura Orsatti Edith Monteagudo Daniel Oscar Cicero 《Molecules (Basel, Switzerland)》2021,26(14)
A new strategy that takes advantage of the synergism between NMR and UHPLC–HRMS yields accurate concentrations of a high number of compounds in biofluids to delineate a personalized metabolic profile (SYNHMET). Metabolite identification and quantification by this method result in a higher accuracy compared to the use of the two techniques separately, even in urine, one of the most challenging biofluids to characterize due to its complexity and variability. We quantified a total of 165 metabolites in the urine of healthy subjects, patients with chronic cystitis, and patients with bladder cancer, with a minimum number of missing values. This result was achieved without the use of analytical standards and calibration curves. A patient’s personalized profile can be mapped out from the final dataset’s concentrations by comparing them with known normal ranges. This detailed picture has potential applications in clinical practice to monitor a patient’s health status and disease progression. 相似文献
76.
E. Fazio E. Piperopoulos S.H. Abdul Rahim M. Lanza G. Faggio G. Mondio F. Neri A.M. Mezzasalma C. Milone S. Santangelo 《Current Applied Physics》2013,13(4):748-752
Pristine and annealed multi-walled C nanotubes are preliminarily tested as catalysts towards the degradation of p-coumaric acid with better performances than the widely used activated carbon. In order to clarify the origin of their different catalytic efficiency, the samples are analysed by means of high-resolution transmission electron microscopy, X-ray photoemission, reflection electron energy loss and micro-Raman spectroscopy. Chemical composition, mass density, bonding configurations and threefold- to fourfold-coordinated carbon bonding ratios are determined. The comparative discussion of the results obtained leads to attribute the higher catalytic activity of the pristine nanotubes to their larger sp2/sp3 carbon bonding fraction and greater amount of oxygen containing functional groups. 相似文献
77.
Raoul Walther Anna K. Winther Anne Sofie Fruergaard Wouter vandenAkker Lise Srensen Signe Maria Nielsen Morten T. JarlstadOlesen Yitao Dai Henrik S. Jeppesen Paolo Lamagni Aleksandr Savateev Sren Lykke Pedersen Camilla Kaas Frich Ccile Vigier‐Carrire Nina Lock Mandeep Singh Vipul Bansal Rikke L. Meyer Alexander N. Zelikin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):284-288
Nanozymes, nanoparticles that mimic the natural activity of enzymes, are intriguing academically and are important in the context of the Origin of Life. However, current nanozymes offer mimicry of a narrow range of mammalian enzymes, near‐exclusively performing redox reactions. We present an unexpected discovery of non‐proteinaceous enzymes based on metals, metal oxides, 1D/2D‐materials, and non‐metallic nanomaterials. The specific novelty of these findings lies in the identification of nanozymes with apparent mimicry of diverse mammalian enzymes, including unique pan‐glycosidases. Further novelty lies in the identification of the substrate scope for the lead candidates, specifically in the context of bioconversion of glucuronides, that is, human metabolites and privileged prodrugs in the field of enzyme‐prodrug therapies. Lastly, nanozymes are employed for conversion of glucuronide prodrugs into marketed anti‐inflammatory and antibacterial agents, as well as “nanozyme prodrug therapy” to mediate antibacterial measures. 相似文献
78.
Kemilly M. P. Pinheiro Roger C. Moreira Kariolanda C. A. Rezende Mrcio Talhavini Lucio P. L. Logrado Jos A. F. Baio Marcos R. V. Lanza Wendell K. T. Coltro 《Electrophoresis》2019,40(3):462-468
This study describes the development of an analytical methodology based on the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C4D) for the separation and detection of inorganic anions in post‐blast explosive residues. The best separation condition was achieved using a running buffer composed of 35 mmol/L lactic acid, 10 mmol/L histidine and 0.070 mmol/L cetyl(trimethyl ammonium) bromide. For C4D measurements, the highest sensitivity was obtained applying a 700 kHz sinusoidal wave with excitation voltage of 20 Vpp. The separation of Cl?, NO3?, NO2?, SO42?, ClO4? and ClO3? was performed within ca. 150 s with baseline resolution and efficiencies between 4.4 × 104 and 1.7 × 105 plates/m. The found limits of detection ranged between 2.5 and 9.5 μmol/L. Last, real samples of post‐blast explosive residues were analyzed on the ME‐C4D devices obtaining successfully the determination of Cl?, NO3? and SO42?. The achieved concentration values varied between 12.8–72.5 mg/L for Cl?, 1.7–293.1 mg/L for NO3? and 1.3–201.3 mg/L for SO42?. The data obtained using ME‐C4D devices were in good agreement with the concentrations found by ion chromatography. The approach reported herein has provided short analysis time, instrumental simplicity, good analytical performance and low cost. Furthermore, the ME‐C4D devices emerge as a powerful and portable analytical platform for on‐site analysis demonstrating to be a promising tool for the crime scene investigation. 相似文献
79.
Alessandro Marzani Erasmo Viola Francesco Lanza di Scalea 《Journal of sound and vibration》2008,318(3):488-505
A semi-analytical finite element (SAFE) method is presented for analyzing the wave propagation in viscoelastic axisymmetric waveguides. The approach extends a recent study presented by the authors, in which the general SAFE method was extended to account for material damping. The formulation presented in this paper uses the cylindrical coordinates to reduce the finite element discretization over the waveguide cross-section to a mono-dimensional mesh. The algorithm is validated by comparing the dispersion results with viscoelastic cases for which a Superposition of Partial Bulk Waves solution is known. The formulation accurately predicts dispersion properties and does not show any missing root. Applications to viscoelastic axisymmetric waveguides with varying mechanical and geometrical properties are presented. 相似文献
80.
A transgenic mouse overexpressing the human form of semicarbazide-sensitive amine oxidase (SSAO) is known to have an abnormal structure of the elastic laminae and the elastic fibres in the aorta. Compared to the non-transgenic littermates, the elastic laminae are less folded. In order to quantify the undulation of this structure, an image analysis program that identified the elastic laminae was developed. The program measures the area fraction in different sectors from a plane parallel to the aorta wall. Images were taken from unstained aorta specimens where the elastic laminae were visualised with phase contrast microscopy. A contextual operation of the images produced a local orientation estimation for every linear structure. The image was then thresholded in eight sectors from 0 degrees to 180 degrees , with different orientation angles. The results show that the area fraction of the elastic laminae was significantly lower for the transgenic mouse in all sectors measured except for two. At 0-25 degrees , no difference was seen. In the sector at 160-180 degrees , parallel to the aorta wall, the area fraction of elastic laminae was instead significantly higher in the transgenic mouse. A novel method is presented, developed for detection and quantification of pathological changes in the elastic laminae in the aorta wall. The method gave reliable results and is considered to be a useful tool for morphometric studies of aorta with this kind of altered morphology concerning the elastic laminae. When compared with tangent count, the control group had a significantly larger mean curvature. 相似文献