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991.
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
992.
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
993.
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
994.
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
995.
996.
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
997.
Carla Ciarcià Paolo Falsaperla Andrea Giacobbe Giuseppe Mulone 《Mathematical Methods in the Applied Sciences》2015,38(14):2937-2952
In this paper, we propose a mathematical model to study the dynamics of anorexic and bulimic populations. The model proposed takes into account, among other things, the effects of peers' influence, media influence, and education. We prove the existence of three possible equilibria that without media influences are disease‐free, bulimic‐endemic, and endemic. Neglecting media and education effects, we investigate the stability of such equilibria, and we prove that under the influence of media, only one of such equilibria persists and becomes a global attractor. Which of the three equilibria becomes global attractor depends on the other parameters. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
998.
The basic assumptions for the depth-dependent Ekman equations are presented. An analysis of three wind stress time series, from different geographical locations, is performed: The results lead to interpret the wind stress as a stochastic process, with components fluctuating with deterministic frequencies. The stochastic equations coupling wind stress and ocean currents are formulated; their solutions are stochastically bounded. Results of numerical simulations are given to show the main behaviors of the system. 相似文献
999.
Giuseppe Tresoldi Santo Di Pietro Dario Drommi Santo Lanza 《Transition Metal Chemistry》2010,35(2):151-158
The solvento species obtained by the treatment of cis-RuCl2(N,N-L)2 [L = di-2-pyridyl sulfide (dps), di-2-pyrimidyl sulfide (dprs)] with AgPF6, reacted with dithioethers L′ [L′ = 2,6-bis(2-pyridylthiomethyl)pyridine (pytmp), 2,6-bis(2-pyrimidylthiomethyl)pyridine (prtmp) and 2,6-bis{2-(4-methyl)pyrimidylthiomethyl}
pyridine (mprtmp)] to afford the compounds [Ru(N,N-L)2(N,S-L′)][PF6]2. The 1H NMR spectra indicate that L′ is chelated through S and N atoms with the formation of a four-membered ring. As a consequence, the ruthenium and sulfur
atoms are stereogenic centers with ∆ and Λ and (R) and (S) configurations, respectively. NMR spectra, at low temperatures, show that two invertomers, of similar abundance, as enantiomeric
couples ∆S, ΛR and ∆R, ΛS are present. In the methylene region, four AB systems are observed that in both the species contain
two non-equivalent methylene groups. Variable-temperature NMR spectra and EXSY experiments show that the sulfur inversion
produces an exchange between the invertomers. The one-dimensional band-shape analysis of the exchanging methylene signals
showed that the energy barriers for the process are in the 43–52 kJ mol−1 range. The possible mechanisms of the sulfur inversion are discussed. 相似文献
1000.
Mariaelena Ricca Vito Foderà Daniela Giacomazza Maurizio Leone Giuseppe Spadaro Clelia Dispenza 《Colloid and polymer science》2010,288(9):969-980
Poly(N-vinyl-2-pyrrolidone) (PVP) hydrogels have been synthesised from the aqueous solutions of the same linear polymer by two different
radiation sources: electron beams and UV rays. The present investigation couples conventional hydrogel characterisation techniques
with the study of the partition equilibria, fluorescence behaviour and release of two different molecular probes, 1-anilino-8-naphthalene
sulphonate (ANS) and Thioflavin T (ThT). The two probes have comparable molecular weight and different structural and optical
properties. The ‘chemical’ networks produced upon irradiation in different experimental conditions presented quite distinctive
mechanical spectra, yielded to different porous solids upon freeze-drying and showed specific rehydration ratios when ‘equilibrated’
in water. More interestingly, they offered ‘hydrophobic pockets’ to host the ANS molecules in a way that the probe is completely
occluded from water, making it fluoresce. Conversely, the generated PVP networks did not show any specific affinity towards
the hydrophilic ThT that was only barely untaken. 相似文献