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81.
Guilherme S. Nunes 《Physics letters. A》2008,372(12):2048-2049
We point out that, when repulsive interactions between two fermions are not integrable, as the case may be for atomic fermions, the original Kohn-Sham density functional must be revised. 相似文献
82.
L.A. Valenzuela J.G.S. Duque C.T. Meneses W.C. Nunes M. Knobel 《Journal of Non》2008,354(42-44):4871-4873
We report structural and magnetic properties of fine particles embedded in an amorphous magnetic matrix. As-quenched amorphous Fe73.5Nb3CuSi13.5B9 ribbons (FINEMET) were submitted to the thermal treatments of several times (1 ? t ? 240 min) at 570 °C using a conventional furnace. The analyses of the X-ray diffraction patterns at room temperature reveal that our samples consist of single phase Fe3Si nanocrystals embedded in a residual amorphous phase. Magnetic measurements show that the saturation moment at T = 450 °C increases as a function of annealing time. This behavior is attributed to an increase of the fraction of nanocrystallites in the residual amorphous phase. 相似文献
83.
84.
85.
C. R. M. de Lima P. R. S. de Souza R. T. Stopilha W. A. de Morais G. T. M. Silva J. S. Nunes 《Journal of Dispersion Science and Technology》2018,39(1):83-91
Interpolyelectrolyte complex (IPEC) dispersions were prepared from chitosan and poly(sodium acrylate), NaPMA, by mixing their solutions, at different carboxyl-to-aminium molar ratios, rCA. Gyration radius was determined by small angle x-ray scattering (SAXS) and showed that, as rCA was increased, IPEC dimensions decreased and reached a minimum at rCA?=?0.75, which was considered the ratio at which IPEC cluster dimensions were minimum, following collapse, phase segregation, nucleation, and growth of larger particles. Pair distance distributions, P(r), became narrower up to rCA?=?0.75, increasing its width from this point. Relaxation-related parameters from dynamic light scattering (DLS) intensity correlation functions (ICFs) identified three main relaxation processes. The fast process, related to free polyelectrolyte molecules random motion disappeared as rCA, was increased. The other two relaxation processes also were a function of rCA and presented marked changes at rCA?=?0.75. At the same value of rCA, the energy of activation for the average relaxation rate showed the occurrence of a clear change in the nature of IPEC-related interactions. As hydrodynamic diameter, determined by DLS, was much larger than the gyration radius determined by SAXS, IPEC particles could be described as being composed by a core, rich in segregated, insoluble material, enveloped by IPEC soluble clusters, possibly in the form of water-rich gels. 相似文献
86.
The rectal administration of drugs has been an enduring medical practice for either the management of local or systemic conditions. Although mostly regarded as an alternative to other delivery routes, the colorectal mucosa offers an effective pathway for enhanced systemic bioavailability of many active molecules. The fairly stable physicochemical and enzymatic environment of the mucosa and the possibility of partially avoiding the hepatic first-pass effect are some of the potential advantages of rectal drug delivery. At the same time, higher drug levels of drugs can be achieved at colorectal fluids and tissues, which can aid management of local conditions. However, problems with patient acceptability as well as poor and erratic drug absorption may impair efficient use of the rectal drug delivery route. The valuable features of nanotechnology-based systems for mucosal use are well recognized, and their potential as carriers for drug delivery has already been proven for different medical applications/delivery routes. Although still limited, the development of rectal nanomedicines with therapeutic, diagnostic, and prophylactic purposes is steadily emerging and may circumvent some of the problems associated with the more standard delivery approaches. This review discusses the rationale behind the use of nanotechnology-based strategies for rectal drug delivery and provides a critical overview on the various types of nanosystems proposed so far. 相似文献
87.
Angela C. Raimondi Peter B. Hitchcock G. Jeffery Leigh Fábio S. Nunes 《Journal of chemical crystallography》2004,34(2):83-87
The crystal structure of the binuclear tetraiminediphenolate diiron(II) macrocyclic complex [Fe2(tidf)(CH3OH)4](ClO4)2 (tidf = tetraiminediphenolate ligand) is presented. The molecular structure (monoclinic, space group C2/c, Z = 4, a = 20.6903(14)Å, b = 11.0827(11) Å, c = 16.0494(15) Å, = 99.911(6) shows two iron(II) cores occupying distorted octahedral geometries with four methanol molecules bound axially. Main equatorial bond distances are 2.050(3) Å for Fe—O1 and 2.067(4) Å for Fe—N1 with a Fe Fe distance of 3.108(1) Å. Contrasting to the monoiron complex the macrocycle does not adopt a bent conformation being nearly coplanar with the maximum deviation from the least-squares plane of 0.18 Å. 相似文献
88.
Antonio Carlos Niedwieski Tai Hasegawa Fábio Souza Nunes 《Journal of chemical crystallography》2004,34(8):529-532
The title complex was prepared from the reaction of [V2(-Cl)3(thf)3]2[Zn2Cl6] with N,N,NN-tetraethylethane-1,2-diamine (teeda) in refluxing thf and its crystal structure exhibits two triangulo-[V3(-Cl)3(-Cl)(
3-OH)(thf)2(teeda)]+ cations bridged by two chlorides. The molecular structure (monoclinic, space group P2
1/n, Z = 2, a = 11.8005(7) Å, b = 18.7492(14) Å, c= 15.6253(9) Å, = 103.600(4) shows each vanadium site in a distorted octahedral geometry. V1 and V2 have two thf molecules bounded in cis configuration, and V3 completes the hexa-coordination with the diamine teeda. Main bond distances are 2.5149(12) Å for V(1)--Cl(1), 2.062(3) Å for V(1)-
3-O(3), 2.5554(12) Å for V(1)-
3-Cl(4), 2.140(3) Å for V(1)–O(1)(thf), 2.243(4) Å for V(3)–N(1)(teeda), and 3.0437(9) for V(1)···V(2). 相似文献
89.
Fábio S. Nunes Patricia de M. L. Murta Ivo Vencato Carlos J. da Cunha 《Journal of chemical crystallography》1997,27(12):721-725
The synthesis and crystal structure of the novel pentacoordinated complex [Cu(DOHPN)(IMI-DAZOLE)] (ClO4), (DOHPN=(3,3′-trimethylenedinitrilo bis 2-butanone oxime) are reported. The X-ray crystal structure (space groupP21/n, a=11.349(2) Å,b=14.241(3) Å,c= 12.635(3) Å; α=90°, β=100.21 (3)°, γ=90°) shows that the copper(II) ion occupies a distorted square-pyramidal geometry with the imidazole ligand occupying the axial position. The copper(II)-(N)imidazole distance is 2.125(3) Å and the copper(II)-tetraaza plane distance is 0.385/Å. The tetraaza ligand DOHPN adopts a “butterfly-like” geometry with a dihedral angle of 149.69°. The title complex is the first structurally characterized compound of the series [Cu(DOHPN)(axial ligand)]n+ where the axial ligand is a neutral N-heterocycle with known biological relevance. A comparison of the structural parameters with those observed when the axial ligand is H2O or NCS? (N-bonded) gives the following series with increasing metal-ligand interaction: H2O>IMIDAZOLE>NCS? (N-bonded). 相似文献
90.
Ishiruji FH Evans DJ Benedito FL Nunes FS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):1029-1033
Hexacyanoferrate(III) reacts with [FeII(meso)(CH3CN)2](ClO4)2.2CH3CN (meso=5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) in acetonitrile/water mixture producing the title complex, where three [Fe(meso)]2+ units are connected by two [Fe(CN)6](3-) anions. Molecular modeling (MM+) shows a fairly linear molecule and M?ssbauer data are consistent with two terminal pentacoordinated low spin iron(II)-meso units linked to one hexacoordinated low spin iron(II)-meso through two hexacoordinated low spin iron(III) units. Spectroscopic characterization showed a typical mixed-valence charge transfer band and the degree of electron coupling was calculated to be H(AB)=678 cm(-1). Magnetic properties exhibited an antiferromagnetic exchange interaction between the iron(III) ions with a coupling constant J= -44 cm(-1). 相似文献