排序方式: 共有64条查询结果,搜索用时 15 毫秒
1.
CoSm(SeO3)2Cl, CuGd(SeO3)2Cl, MnSm(SeO3)2Cl, CuGd2(SeO3)4 and CuSm2(SeO3)4: Transition Metal containing Selenites of Samarium and Gadolinum The reaction of CoCl2, Sm2O3, and SeO2 in evacuated silica ampoules lead to blue single crystals of CoSm(SeO3)2Cl (triclinic, , Z = 4, a = 712.3(1), b = 889.5(2), c = 1216.2(2) pm, α = 72.25(1)°, β = 71.27(1)°, γ = 72.08(1)°, Rall = 0.0586). If MnCl2 is used in the reaction light pink single crystals of MnSm(SeO3)2Cl (triclinic, , Z = 2, a = 700.8(2), b = 724.1(2), c = 803.4(2) pm, α = 86.90(3)°, β = 71.57(3)°, γ = 64.33(3)°, Rall = 0.0875) are obtained. Green single crystals of CuGd2(SeO3)2Cl (triclinic, , Z = 4, a = 704.3(4), b = 909.6(4), c = 1201.0(7) pm, α = 70.84(4)°, β = 73.01(4)°, γ = 70.69(4)°, Rall = 0.0450) form analogously in the reaction of CuCl2 and Gd2O3 with SeO2. CoSm(SeO3)2Cl contains [CoO4Cl2] octahedra, which are connected via one edge and one vertex to infinite chains. The Mn2+ ions in MnSm(SeO3)2Cl are also octahedrally coordinated by four oxygen and two chlorine ligands. The linkage of the polyhedra to chains occurs exclusively via edges. Both, the cobalt and the manganese compound show the Sm3+ ions in eight and ninefold coordination of oxygen atoms and chloride ions. In CuGd(SeO3)2Cl the Cu2+ ions are coordinated by three oxygen atoms and one Cl— ion in a distorted square planar manner. One further Cl— and one further oxygen ligand complete the [CuO3Cl] units yielding significantly elongated octahedra. The latter are again connected to chains via two common edges. For the Gd3+ ions coordination numbers of ?8 + 1”? and nine were found. Single crystals of the deep blue selenites CuM2(SeO3)4 (M = Sm/Gd, monoclinic, P21/c, a = 1050.4(3)/1051.0(2), b = 696.6(2)/693.5(1), c = 822.5(2)/818.5(2) pm, β = 110.48(2)°/110.53(2)°, Rall = 0.0341/0.0531) can be obtained from reactions of the oxides Sm2O3 and Gd2O3, respectively, with CuO and SeO2. The crystal structure contains square planar [CuO4] groups and irregular [MO9] polyhedra. 相似文献
2.
3.
Farida Larit Khaled M. Elokely Manal A. Nael Samira Benyahia Francisco Len Stephen J. Cutler Mohammed M. Ghoneim 《Molecules (Basel, Switzerland)》2021,26(4)
The in vitro activity of L. donovani (promastigotes, axenic amastigotes and intracellular amastigotes in THP1 cells) and T. brucei, from the fractions obtained from the hydroalcoholic extract of the aerial part of Hypericum afrum and the isolated compounds, has been evaluated. The chloroform, ethyl acetate and n-butanol extracts showed significant antitrypanosomal activity towards T. brucei, with IC50 values of 12.35, 13.53 and 12.93 µg/mL and with IC90 values of 14.94, 19.31 and 18.67 µg/mL, respectively. The phytochemical investigation of the fractions led to the isolation and identification of quercetin (1), myricitrin (2), biapigenin (3), myricetin (4), hyperoside (5), myricetin-3-O-β-d-galactopyranoside (6) and myricetin-3’-O-β-d-glucopyranoside (7). Myricetin-3’-O-β-d-glucopyranoside (7) has been isolated for the first time from this genus. The chemical structures were elucidated by using comprehensive one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR) spectroscopic data, as well as high-resolution electrospray ionization mass spectrometry (HR-ESI–MS). These compounds have also been evaluated for their antiprotozoal activity. Quercetin (1) and myricetin (4) showed noteworthy activity against T. brucei, with IC50 and IC90 values of 7.52 and 5.71 µM, and 9.76 and 7.97 µM, respectively. The T. brucei hexokinase (TbHK1) enzyme was further explored as a potential target of quercetin and myricetin, using molecular modeling studies. This proposed mechanism assists in the exploration of new candidates for novel antitrypanosomal drugs. 相似文献
4.
Hamida Maachou Kheireddine Bal Youcef Bal Alexandre Chagnes Gerard Cote Djamel Aliouche 《Applied biochemistry and biotechnology》2012,168(6):1459-1475
Chitosan/hydroxyapatite composite microparticles were prepared by a solid-in-water-in-oil emulsification cross-linking method. The characteristics and activity in presence of simulated body fluid for 14 and 21?days were investigated. The size distribution, surface morphology, and microstructure of these biomaterials were evaluated. The scanning electron microscopy revealed an aggregate of microparticles with a particle size, ranged from 4 to 10???m. The deposited calcium phosphate was studied using X-ray diffraction analysis, Fourier transform infrared spectroscopy, and inductively coupled plasma/atomic emission?spectroscopy analysis of phosphorus. These results show that the mineral, formed on microparticles, was a mixture of carbonated hydroxyapatite and calcite. Scanning electron microscopy revealed that calcium phosphate crystals growth was in form of rods organized as concentric triangular packets interconnected to each other by junctions. Interaction between chitosan and growing carbonated hydroxyapatite and calcite crystals are responsible for a composite growth into triangular and spherical shapes. The results demonstrated that these microparticles were potential materials for bone repair. 相似文献
5.
Ilyes Jedidi Zohra Ferhat‐Hamida Geneviève Delmas 《Journal of Polymer Science.Polymer Physics》2007,45(15):1932-1949
A linear Union Carbide PE (UC) has been analyzed by nonstandard calorimetry with a common DSC calorimeter and a Setaram C80 calorimeter. Nonstandard calorimetry entails using a low rate of heating (0.5–1 K/min), a small mass (0.5–1.5 mg), and an open cell (O‐cell) instead of the standard C‐cell. Events in O‐cells overlap less and occur with a faster kinetics than in C‐cells. PE crystals are nascent, solution‐grown (S‐grown), press‐grown (P‐grown), and strained by extrusion. In Part A, the traces show that the phase‐changes in the melt, previously observed in a C80 calorimeter (slow T‐ramp) and characterized by ΔHnetwork, can be observed with a common DSC in nonstandard conditions. In Part B, the difference between the C‐ and O‐cells and the changes in the main peak enthalpy (ΔHortho) are of interest. The main result is that, in O‐cells, the value of ΔHortho around Tortho, exceeds unambiguously in certain conditions ΔHortho found for perfect orthorhombic crystals. The main endotherm contains then another contribution, namely ΔHnetwork. Crystal reorganization during the slow T‐ramp is followed in the C‐ and O‐cells on S‐grown crystals. In O‐cells, lamellar thickening observed in the slow‐ramp is more extensive. The ease of phase‐change depends on the sample history. It is as follows: strained‐part extruded > nascent > S‐grown > P‐grown. Co‐operative chain motions are more hindered in the standard C‐cells than in the O‐cells. In Part C, lower values of m succeed in bringing phase‐changes in P‐grown (O‐cells) samples. The origin of the events is discussed: three processes are thought to contribute to the phase‐changes namely, melting of strained short‐range order, activation of vibrations in the CH2 groups, and fast decay of chain orientation which occurs simultaneously with melting. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1932–1949, 2007 相似文献
6.
Although, the effects of ultrasonic irradiation on multiphase flow through porous media have been studied in the past few
decades, the physics of the acoustic interaction between fluid and rock is not yet well understood. Various mechanisms may
be responsible for enhancing the flow of oil through porous media in the presence of an acoustic field. Capillary related
mechanisms are peristaltic transport due to mechanical deformation of the pore walls, reduction of capillary forces due to
the destruction of surface films generated across pore boundaries, coalescence of oil drops due to Bjerknes forces, oscillation
and excitation of capillary trapped oil drops, forces generated by cavitating bubbles, and sonocapillary effects. Insight
into the physical principles governing the mobilization of oil by ultrasonic waves is vital for developing and implementing
novel techniques of oil extraction. This paper aims at identifying and analyzing the influence of high-frequency, high-intensity
ultrasonic radiation on capillary imbibition. Laboratory experiments were performed using cylindrical Berea sandstone and
Indiana limestone samples with all sides (quasi-co-current imbibition), and only one side (counter-current imbibition) contacting
with the aqueous phase. The oil saturated cores were placed in an ultrasonic bath, and brought into contact with the aqueous
phase. The recovery rate due to capillary imbibition was monitored against time. Air–water, mineral oil–brine, mineral oil–surfactant
solution and mineral oil-polymer solution experiments were run each exploring a separate physical process governing acoustic
stimulation. Water–air imbibition tests isolate the effect of ultrasound on wettability, capillarity and density, while oil–brine
imbibition experiments help outline the ultrasonic effect on viscosity and interfacial interaction between oil, rock and aqueous
phase. We find that ultrasonic irradiation enhances capillary imbibition recovery of oil for various fluid pairs, and that
such process is dependent on the interfacial tension and density of the fluids. Although more evidence is needed, some runs
hint that wettability was not altered substantially under ultrasound. Preliminary analysis of the imbibition recoveries also
suggests that ultrasound enhances surfactant solubility and reduce surfactant adsorption onto the rock matrix. Additionally,
counter-current experiments involving kerosene and brine in epoxy coated Berea sandstone showed a dramatic decline in recovery.
Therefore, the effectiveness of any ultrasonic application may strongly depend on the nature of interaction type, i.e., co-
or counter-current flow. A modified form of an exponential model was employed to fit the recovery curves in an attempt to
quantify the factors causing the incremental recovery by ultrasonic waves for different fluid pairs and rock types. 相似文献
7.
8.
S. Benalia M. Hachemaoui D. Rached R. Khenata N. Bettahar M. Benyahia 《Journal of Physics and Chemistry of Solids》2009,70(3-4):622-626
First-principles calculations have been used to investigate the structural, electronic and elastic properties of the filled skutterudite CeRu4P12, using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange-correlation energy is described in the local spin density approximation (LSDA) using the Perdew–Wang parameterization. The results of the electronic properties show that this compound is an indirect band gap material. A special interest has been made to the determination of the elastic constants since there have been no available experimental and theoretical data. The energy band gaps and their volume and pressure dependence are investigated. Our results of the ground-state electronic properties are found to agree with experimental results. 相似文献
9.
10.
Pouzot M Nicolai T Benyahia L Durand D 《Journal of colloid and interface science》2006,293(2):376-383
Non-linear mechanical behavior at large shear deformation was been investigated for heat-set beta-lactoglobulin gels at pH 7 and 0.1 M NaCl using both oscillatory shear and shear flow. These gels have a self-similar structure at length scales smaller than the correlation length of the gel with fractal dimension d(f)=2. Strain hardening is observed that can be well described using the model proposed by Gisler et al. [T.C. Gisler, R.C. Ball, D.A. Weitz, Phys. Rev. Let. 82 (1999) 1064] for fractal colloidal gels. The increase of the shear modulus normalized by the low strain value (G(0)) is independent of G(0). For weak gels the elasticity increases up to a factor of ten, while for strong gels the increase is very small. At higher deformation irreversible fracture occurs, which leads eventually to macroscopic failure of the gel. For weak gels formed at low concentrations the deformation at failure is about 2, independent of the shear modulus. For strong gels fracture occurs at approximately constant stress (2 x 10(3) Pa). 相似文献