The effects of the oriented fiber filler particles on the microscopic properties of the matrix network chains were investigated by using nanofiber filler particles as reinforcing material. Monte Carlo Rotational Isomeric State simulations were carried out for filled poly(ethylene) (PE) networks to study the dependence of the conformational distribution functions of polymer chains and their elastomeric properties on filler loadings. We were especially interested how the excluded volume effect of the nanofiber particles and their orientation (specifically orientational anisotropy) in the matrix influence elastomeric properties of the network. Distribution functions of the end-to-end distances of polymer chains for both unfilled and filled networks were calculated. Effects of nanofiber reinforcements with varying fiber radii and fiber volume fractions were investigated. We have found that the presence of nanofibers significantly increase the non-Gaussian behavior of polymer chains in the composite. The anisotropic effects of the nanofibers on mechanical properties of polymeric composites were studied as a function of their relative orientation to the direction of deformation. The modulus (reduced nominal stress per unit strain) was calculated from the distribution of end-to-end distances of polymer chains using the Mark–Curro method. Relatively small amount of nanofibers was found to increase the normalized moduli of the composite. Our results are quite in satisfactory qualitative agreement with experimental data reported in the literature. This shows that computer simulations provide a powerful tool in predicting physical properties of composite materials. 相似文献
In this study, dithizone (diphenylthiocarbazone) has been separately radiolabeled with 131I and with 99mTc for preliminarily testing their radiopharmaceutical potentials on male albino rabbits. 131I-dithizone and 99mTc-dithizone were intravenously injected to rabbits via their ear veins after anesthetizing with a mixture of Alfazyne and
Alfamine (Serva) to determine their dynamic and static statuses in the metabolism. Also, 99mTc as pertechnetate and 131I as iodate were administered to rabbits as controls. Dynamic and static scintigrams were obtained using a gamma camera (Diacan
Instruments). Dynamic scintigrams were obtained over the first half hour with frames of 1 minute following the administrations
of the labeled compounds. Static images were obtained from posterior projection at different time intervals up to about 3
hours following the administration of the radiolabeled compounds. 99mTc-dithizone was significantly uptaken by the pancreas in contrast to free 99mTc. In the case of 131I-dithizone, the distribution of 131I activity in the metabolism was clearly different than the case of free 131I and the uptake of 131I-dithizone at the pancreas zone was also significant. These preliminary tests have clearly indicated that especially 99mTc-dithizone has a significant potential to be used as a pancreatic radiopharmaceutical. 相似文献
AbstractA set of bis(arylthio) substituted 5,8-quinolinedione derivatives were synthesized and investigated for their in vitro antimicrobial effect. The antibacterial and antifungal activities of 6,7-bis(arylthio)-5,8-quinolinedione (4a–f) and 6,7-bis(arylthio)-2-methyl-5,8-quinolinedione (5a–f) were evaluated against four gram-negative bacteria, three gram-positive bacteria, and three fungi strains. The bis(methoxyarylthio) 5,8-quinolinedione analogs presented better activity against especially gram-positive bacteria compared to bis(halogenarylthio) 5,8-quinolinedione analogs. Bis(3-methoxyarylthio) 5,8-quinolinedione (4e) had the same activity of the reference drug against Staphylococcus aureus. Bis(2-methoxyarylthio) 5,8-quinolinedione (4f) showed two-and-a half-fold better activity with 89.69?μM against Enterococcus faecalis, and two-fold better activity with 11.20?μM against Staphylococcus epidermidis. Bis(2-methoxyarylthio)-2-methyl-5,8-quinolinedione 5f exhibited five-fold higher antibacterial activity with 43.44?μM against E. faecalis and also eight-fold activity of the reference drug with 2.71?μM against S. epidermidis. 相似文献
Two new soluble vic-dioxime ligands, 4-isopropylanilineglyoxime (L1H2) and 4-benzylpiperidineglyoxime (L2H2) were prepared by reacting 4-isopropylaniline and 4-benzylpiperidine with anti-chloroglyoxime. Ten metal complexes were obtanied by reacting both ligands with Cu(II),Ni(II),Co(II), Zn(II), and Cd(II)
cations. The ligands and their metal complexes were elucidated by elemental analysis, IR, UV-vis, 1H NMR, and 13C NMR and also magnetic moments of the complexes were determined.
The text was submitted by the authors in English. 相似文献
With the increasing research in the field of contact mechanics, different types of contact models have been investigated by many researchers by employing various complex material models. To ascertain the orthotropy effect and modeling parameters on a receding contact model, the double frictional receding contact problem for an orthotropic bilayer loaded by a cylindrical punch is taken into account in this study. Assuming plane strain sliding conditions, the governing equations are found analytically using Fourier integral transformation technique. Then, the resulting singular integral equations are solved numerically using an iterative method. The weight function describing the asymptotic behavior of the stresses are investigated in detail and powers of the stress singularities are provided. To control the trustworthiness and correctness of the analytical formulation and to compare the resulting stress distributions and contact boundaries, a numerically efficient finite element method was employed using augmented Lagrange contact algorithm. The aim of this paper is to investigate the orthotropy effect, modeling parameters and coefficients of friction on the surface and interface stresses, surface and interface contact boundaries, powers of stress singularities, weight function and to provide highly parametric benchmark results for tribological community in designing wear resistant systems.
A model is presented for the impact with friction of a flexible body in translation and rotation. This model consists of a system of nonlinear differential equations which considers the multiple collisions as well as frictional effects at the contacting end, and allows one to predict the rigid and elastic body motion after the impact. The kinetic energy is derived by utilizing a generalized velocity field theory for elastic solids. The model uses a dry coefficient of friction and a nonlinear contact force. We introduce a finite number of vibrational modes to take into account the vibrational behavior of the body during impact. The vibrations, the multiple collisions, and the angle of incidence angle, are found to be important factors for the kinematics of frictional impact. Analytical and experimental results were compared to establish the accuracy of the model. 相似文献
The effects of asymmetry and the electric field on the
electronic subbands and the nonlinear intersubband optical
absorption of GaAs quantum wells represented by a P?schl-Teller
confining potential are studied. The potential itself can be made
asymmetric through a correct choice of its parameter set and this
adjustable asymmetry is important for optimizing the absorption. In
that way optimal cases can be created. We calculate the modified
wave functions and electronic subbands variationally. The linear and
the nonlinear optical intersubband absorption coefficients are
calculated. Numerical results for a typical GaAs quantum well are
presented. The nonlinear part of the absorption coefficient is
strongly modified by the asymmetry parameters while the electric
field affects it at smaller values of the parameters.
- 78.67.De Quantum wells 相似文献
Vocal cord paralysis is a disease that can cause voice disability and aspiration problems. Expanded polytetrafluoroethylene (ePTFE; Gore-Tex) has been widely used in cardiovascular and plastic surgery; however, its biocompatibility and safety have not been established precisely in the larynx. In this study, the biocompatibility and safety of ePTFE used in vocal cord medialization in the rabbit larynx were assessed. Type 1 thyroplasty with Gore-Tex was performed on one side of the larynx in eight rabbits. A sham procedure was applied on the contralateral side of their larynx. The rabbits were sacrificed after 6 months, and macroscopic and microscopic evaluations and comparisons were performed. No significant inflammatory response to Gore-Tex or displacement of the implant was seen. There was only a tiny fibrotic capsule surrounding the material in each specimen. Intense eosinophilic cell infiltration was seen surrounding one rabbit specimen. Gore-Tex seems to be a biocompatible, stable, and reversible material that can be safely used in laryngeal framework surgery. 相似文献
We study convex conic optimization problems in which the right-hand side and the cost vectors vary linearly as functions of a scalar parameter. We present a unifying geometric framework that subsumes the concept of the optimal partition in linear programming (LP) and semidefinite programming (SDP) and extends it to conic optimization. Similar to the optimal partition approach to sensitivity analysis in LP and SDP, the range of perturbations for which the optimal partition remains constant can be computed by solving two conic optimization problems. Under a weaker notion of nondegeneracy, this range is simply given by a minimum ratio test. We discuss briefly the properties of the optimal value function under such perturbations. 相似文献
The purpose of this paper is to introduce ideal minimal spaces and to investigate the relationships between minimal spaces
and ideal minimal spaces. We define some closed sets in these spaces to establish their relationships. Basic properties and
characterizations related to these sets are given. 相似文献