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31.
High density polyethylene composites with curaua fibres were prepared using an intermeshing co-rotating extruder and two different coupling agents. The thermal stability of the components was studied by thermogravimetric and differential scanning analysis, as well as by the oxidation induction time. Maleic anhydride grafted polyethylene, used as coupling agent, affected the composite stability more markedly than did poly(ethylene-co-vinyl acetate). However, oxidation induction times were analogous for composites with and without coupling agents. Results also indicated that a higher fibre-matrix interaction precludes the crystallinity enhancement caused by the fibre. 相似文献
32.
33.
34.
Roberto Giuntini Antonio Ledda Francesco Paoli 《International Journal of Theoretical Physics》2017,56(12):3895-3911
35.
Miasnikova A Laschewsky A De Paoli G Papadakis CM Müller-Buschbaum P Funari SS 《Langmuir : the ACS journal of surfaces and colloids》2012,28(9):4479-4490
A series of symmetrical, thermo-responsive triblock copolymers was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization, and studied in aqueous solution with respect to their ability to form hydrogels. Triblock copolymers were composed of two identical, permanently hydrophobic outer blocks, made of low molar mass polystyrene, and of a hydrophilic inner block of variable length, consisting of poly(methoxy diethylene glycol acrylate) PMDEGA. The polymers exhibited a LCST-type phase transition in the range of 20-40 °C, which markedly depended on molar mass and concentration. Accordingly, the triblock copolymers behaved as amphiphiles at low temperatures, but became water-insoluble at high temperatures. The temperature dependent self-assembly of the amphiphilic block copolymers in aqueous solution was studied by turbidimetry and rheology at concentrations up to 30 wt %, to elucidate the impact of the inner thermoresponsive block on the gel properties. Additionally, small-angle X-ray scattering (SAXS) was performed to access the structural changes in the gel with temperature. For all polymers a gel phase was obtained at low temperatures, which underwent a gel-sol transition at intermediate temperatures, well below the cloud point where phase separation occurred. With increasing length of the PMDEGA inner block, the gel-sol transition shifts to markedly lower concentrations, as well as to higher transition temperatures. For the longest PMDEGA block studied (DP(n) about 450), gels had already formed at 3.5 wt % at low temperatures. The gel-sol transition of the hydrogels and the LCST-type phase transition of the hydrophilic inner block were found to be independent of each other. 相似文献
36.
A. S. Fonseca A. F. Teixeira G. A. Presta M. Geller S. S. Valença F. Paoli 《Laser Physics》2012,22(10):1635-1641
Biostimulative effect of low intensity laser in tissues has been described on a photobiological basis and clinical protocols are recommended for treatment of various diseases. The aim of this work was to evaluate effects of laser exposure on the survival of Escherichia coli cultures and plasmid topological forms. Escherichia coli cultures and plasmids were exposed to infrared laser to study bacterial survival and electrophoretic profile, respectively. Data indicate low intensity infrared laser: (i) had no effect on E. coli wild type, endonuclease IV, exonuclease III, formamidopyrimidine DNA glycosylase/MutM protein and endonuclease III deficient cultures, but decreased the survival of E. coli UvrA protein deficient cultures; (ii) there was no alteration in the electrophoretic profile of plasmids. Exposure to low intensity infrared laser decreases survival of Escherichia coli cultures deficient in nucleotide excision repair of DNA and this effect could depend on fluences, wavelength and tissues conditions. 相似文献
37.
L. Paoli 《Archive for Rational Mechanics and Analysis》2010,198(2):505-568
As in Paoli (Arch Rational Mech Anal, 2010), we consider a discrete mechanical system with a non-trivial mass matrix subjected to perfect unilateral constraints described by geometrical inequalities ${f_{\alpha}(q) \geqq 0, \alpha \in \{1, \ldots, \nu \}\, (\nu \geqq 1)}We consider a discrete mechanical system with a non-trivial mass matrix, subjected to perfect unilateral constraints described
by the geometrical inequalities
fa (q) \geqq 0, a ? {1, ..., n} (n\geqq 1){f_{\alpha} (q) \geqq 0, \alpha \in \{1, \dots, \nu\} (\nu \geqq 1)}. We assume that the transmission of the velocities at impact is governed by Newton’s Law with a coefficient of restitution
e = 0 (so that the impact is inelastic). We propose a time-discretization of the second order differential inclusion describing
the dynamics, which generalizes the scheme proposed in Paoli (J Differ Equ 211:247–281, 2005) and, for any admissible data,
we prove the convergence of approximate motions to a solution of the initial-value problem. 相似文献
38.
Nishant Peddagopu Anna L. Pellegrino Carmela Bonaccorso Patrizia Rossi Paola Paoli Graziella Malandrino 《Molecules (Basel, Switzerland)》2022,27(19)
Very few sodium complexes are available as precursors for the syntheses of sodium-based nanostructured materials. Herein, the diglyme, triglyme, and tetraglyme (CH3O(CH2CH2O)nCH3, n = 2–4) adducts of sodium hexafluoroacetylacetonate were synthesized in a single-step reaction and characterized by IR spectroscopy, 1H, and 13C NMR. Single-crystal X-ray diffraction studies provide evidence of the formation of the ionic oligomeric structure [Na4(hfa)6]2−•2[Na(diglyme2]+ when the diglyme is coordinated, while a mononuclear seven-coordinated complex Na(hfa)•tetraglyme is formed with the tetraglyme. Reaction with the monoglyme (CH3OCH2CH2OCH3) does not occur, and the unadducted polymeric structure [Na(hfa)]n forms, while the triglyme gives rise to a liquid adduct, Na(hfa)•triglyme•H2O. Thermal analysis data reveal great potentialities for their applications as precursors in metalorganic chemical vapor deposition (MOCVD) and sol-gel processes. As a proof-of-concept, the Na(hfa)•tetraglyme adduct was successfully applied to both the low-pressure MOCVD and the sol-gel/spin-coating synthesis of NaF films. 相似文献
39.
Ba5−xLaxNb4−xTixO15 solid solutions were prepared by solid state reaction method. Structural analysis for the stoichiometric phases was performed for x=0, 1, 2 and 3 by Rietveld analysis of neutron powder diffraction data. The x=0, 1 and 2 members could be refined in the space group P-3m1 (stacking sequence chhcc, polytypoid 5 H). There is a decrease in cell volume as x increases. La3+ occupies preferentially the A2 site (Wyckoff site 2d) and Ti4+ the B2 site (Wyckoff site 2c). As x increases there is an increase of the global instability index (GII) (which is a measure of the extent to which the BVS rule is violated over the whole structure) indicating the presence of intrinsic strains large enough to cause instability at room temperature. This strain is responsible for a structural change for the member with x=3, which could be refined in the space group P-3c1 (stacking sequence (chhcc)2, polytypoid 2×5H=10H). This change in space group is associated with a cooperative rotation of (Nb/Ti)O6 octahedra around the c-axis, necessary to accommodate the smaller La3+ ion in the cuboctahedral cavity. 相似文献
40.
A. Bencini A. Bianchi M. Micheloni P. Paoletti P. Dapporto P. Paoli E. Garcia-España 《Journal of inclusion phenomena and macrocyclic chemistry》1992,12(1-4):291-304
The interaction of PdCl
4
2–
with the macrocyclic ligands of the series [3k]aneN
k
has been studied both in solution and in the solid state. [18]aneN6 and [21]aneN7 form both mono- and binuclear Pd2+ complexes, whose stability constants have been determined in 0.5 mol dm–3 NaCl at 298.15 K. [21]aneN7 also forms, in solution, a trinuclear species in which an amino group deprotonates to bridge two Pd2+ ions, as observed in the solid state. The crystal structure of the complexes [Pd2([18]aneN6)Cl2][ClO4]2 and [Pd3([21]aneN7)Cl3][ClO4]2 · H2O have been solved by single crystal X-ray analysis. C12H30N6Cl4O8Pd2: monoclinic, space group C2/m,a = 10.876(2),b = 18.117(2),c = 7.043(2) Å, = 113.78(2)°,V = 1270(12) Å3,Z = 2,D
calc = 1.92 g cm-3, = 16.94 cm–1.R = 0.063,R
w = 0.059. C14H36N7CI5O9Pd3: orthorhombic, space groupPcab,a = 13.125(7),b = 13.213(3),c = 33.570(5) Å,V = 5822(3) Å3,Z = 8,D
calc = 2.15 g cm–3, = 21.20 cm–1.R = 0.074,R
w = 0.061. In very acidic solutions the polyammonium cations (H
k
[3k]aneN
k
)
k+
interact with PdCl
4
2–
forming second sphere coordinated species. These reactions have been followed by a microcalorimetric technique in 2 mol dm–3 HCl solutions. The slowness of the reactions of (H10[30]aneN10)10+ with PdCl
4
2–
has been interpreted in terms of inclusion of the anion into the receptor's cavity as shown by the crystal structure of [(PdCl4)(H10[30]aneN10)][PdCl4]2Cl4: triclinic, space group PT,a = 7.760(3),b = 11.448(4),c = 13.399(11) Å, = 96.31(8)°, = 104.50(6)°, = 92.30(3)°,Z = 1.R = 0.046 andR
w = 0.039.This paper is dedicated to the memory of the late Dr C. J. Pedersen. 相似文献