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991.
Silvia Todros Chiara Venturato Arturo N. Natali Giuseppe Pace Vito Di Noto 《Journal of Polymer Science.Polymer Physics》2014,52(20):1337-1346
The effect of steam on the micro‐phase structure and mechanical properties of different block copolymers used in biomedical devices is investigated via FT‐IR, tensile tests and dynamic mechanical analysis (DMA). Steam sterilization, commonly performed on medical devices and simulated in this work, affects the copolymers' morphology, due to high temperature and humidity conditions. FT‐IR analysis reveals that steam induces a modification in the crystalline conformations of copolymers with a pre‐existing hydrogen bonding network, that is, thermoplastic polyurethanes (TPU) and poly(ether‐block‐amide) (PEBA), while it does not significantly affect the domain conformation in styrenic block copolymers (SEBS), due to weak interaction with water. As a consequence, relevant changes of the mechanical properties, closely related to the microdomain structure, are found for TPU and PEBA after sterilization, while SEBS mechanical behavior remains stable, as demonstrated by tensile tests and DMA results. For this reason, SEBS is suggested as the best choice in terms of durability in biomedical applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1337–1346 相似文献
992.
Vito Fiandanese Giuseppe Marchese Francesco Naso 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):89-90
Abstract Synthetic, mechanistic, and stereochemical aspects of the reactions of cuprates with various systems are being investigated in these laboratories(1). The series of substrates includes several sulphonyl-activated compounds. 相似文献
993.
994.
995.
Giulia Infurna Giuseppe Cavallaro Giuseppe Lazzara Stefana Milioto Nadka Tzankova Dintcheva 《Molecules (Basel, Switzerland)》2021,26(11)
In the last two decades, the naturally occurring polysaccharides, such as chitosan and pectin, have gained great attention having potential applications in different sectors, from biomedical to new generation packaging. Currently, the chitosan and pectic have been proposed as suitable materials also for the formulation of films and coatings for cultural heritage protection, as well as packaging films. Therefore, the formulation of biopolymer films, considering only naturally occurring polymers and additives, is a current challenging trend. This work reports on the formulation of chitosan (CS), pectin (PC), and chitosan:pectin (CS:PC) films, also containing natural crosslinking and reinforcement agents, such as citric acid (CA) and halloysite nanotubes (HNT), through the solvent casting technique. The produced films are characterized through water contact angle measurements, infrared and UV–visible spectroscopy and tensile test, while the durability of the CS:PC films is evaluated subjecting the film to accelerated UVB exposure and monitoring the photo-oxidation degradation in time though infrared spectroscopy. All obtained results suggest that both crosslinking and reinforcement agents have beneficial effects on the wettability, rigidity, and photo-oxidation resistance of biopolymer films. Therefore, these biopolymer films, also containing naturally occurring additives, have good properties and performance and they are suitable as coverage films for cultural heritage protection. 相似文献
996.
The aim of this paper is to point out some new results concerning the ripple instability in the closed-loop control system using pulse width modulators (PWM), with natural sampling, as power amplifier. The presented analysis, based on the dual-input describing function method and the theoretical framework of Kepler’s problem, shows an equivalence between the computation of switching instants of the PWM and the eccentric anomaly of the planet orbit around the sun, giving a simple stability criterion and a sufficient condition for the absence of solutions of the harmonic balance equation and, therefore, the probable absence of limit cycles of a period of a multiple of that characteristic of the modulator. The derived stability criterion, by using the describing function method, is successively compared with the local stability of the closed-loop PWM system for first- and second-order plants. In the first case it has been formally proved that the proposed criterion ensures the local stability of an equilibrium point, while in the second one a Monte Carlo simulation has confirmed that the selection of the modulator parameters, according to the proposed criterion, gives an effective method to avoid limit cycles and to ensure the local stability. 相似文献
997.
Genetically Engineered Supercharged Polypeptide Fluids: Fast and Persistent Self‐Ordering Induced by Touch 下载免费PDF全文
Dr. Lei Zhang Chao Ma Jing Sun Dr. Baiqi Shao Prof. Giuseppe Portale Prof. Dong Chen Prof. Kai Liu Prof. Andreas Herrmann 《Angewandte Chemie (International ed. in English)》2018,57(23):6878-6882
Mechanically induced disorder–order transitions have been studied in fluid surfactant solutions or polymer thermotropic liquid crystals. However, isothermally induced ordered phases do not persist after cessation of shear, which limits their technological applicability. Moreover, no such stimuli‐responsive materials involving biomacromolecules have been reported although biopolymer liquids are gaining a lot of attention. A biological fluid system is introduced in which anionic polypeptides are complexed with cationic surfactants. The resulting fluids exhibited very sensitive isotropic–nematic transition triggered by shear. The formed liquid crystal was preserved after cessation of mechanical stimulus. Self‐ordering behavior of the material was achieved through water flow and finger pressing. The latter mechanical induction resulted in the formation of complex pattern that can be read out by birefringence, allowing the recording of fingerprint information. 相似文献
998.
Dr. Denise Lovison Dr. Dario Alessi Dr. Lorenzo Allegri Dr. Federica Baldan Dr. Maurizio Ballico Prof. Giuseppe Damante Dr. Marilisa Galasso Prof. Daniele Guardavaccaro Dr. Silvia Ruggieri Prof. Andrea Melchior Dr. Daniele Veclani Dr. Chiara Nardon Prof. Walter Baratta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(33):e202200200
The chiral cationic complex [Ru(η1-OAc)(CO)((R,R)-Skewphos)(phen)]OAc ( 2 R ), isolated from reaction of [Ru(η1-OAc)(η2-OAc)(R,R)-Skewphos)(CO)] ( 1 R ) with phen, reacts with NaOPiv and KSAc affording [RuX(CO)((R,R)-Skewphos)(phen)]Y (X=Y=OPiv 3 R ; X=SAc, Y=OAc 4 R ). The corresponding enantiomers 2 S - 4 S have been obtained from 1 S containing (S,S)-Skewphos. Reaction of 2 R and 2 S with (S)-cysteine and NaPF6 at pH=9 gives the diastereoisomers [Ru((S)-Cys)(CO)(PP)(phen)]PF6 (PP=(R,R)-Skewphos 2 R -Cys; (S,S)-Skewphos 2 S -Cys). The DFT energetic profile for 2 R with (S)-cysteine in H2O indicates that aquo and hydroxo species are involved in formation of 2 R -Cys. The stability of the ruthenium complexes in 0.9 % w/v NaCl solution, PBS and complete DMEM medium, as well as their n-octanol/water partition coefficient (logP), have been evaluated. The chiral complexes show high cytotoxic activity against SW1736, 8505 C, HCT-116 and A549 cell lines with EC50 values of 2.8–0.04 μM. The (R,R)-Skewphos derivatives show higher cytotoxicity compared to their enantiomers, 4 R (EC50=0.04 μM) being 14 times more cytotoxic than 4 S against the anaplastic thyroid cancer 8505 C cell line. 相似文献
999.
1000.
Given a bounded open subset of R
n, we prove the existence of a minimum point for a functional F defined on the family A() of all quasiopen subsets of , under the assumption that F is decreasing with respect to set inclusion and that F is lower semicontinuous on A() with respect to a suitable topology, related to the resolvents of the Laplace operator with Dirichlet boundary condition. Applications are given to the existence of sets of prescribed volume with minimal k
th eigenvalue (or with minimal capacity) with respect to a given elliptic operator. 相似文献