Effects of external magnetic field on biodistribution of nanoparticles: A histological study

This study investigates the effect of external magnetic fields on the biodistribution of nanoparticles (NP). A NdFeB magnet of 2.4 kG was externally applied over the left femoral artery or right kidney. The 250 nm dextran-coated Fe₃O₄ NP was injected via tail vein in healthy rats, and organs were taken 1 or 24 h later. Prussian blue stain revealed that NP were more rapidly retained in the liver and spleen than in the lungs. NP aggregation observed in the kidney and femoral artery after application of external magnets was time dependent. Hollow organs such as the intestine, colon, and urinary bladder retained little NP.     

A non-equilibrium thermodynamic instability in shear-induced diffusion in polymer solutions

In the presence of shear flow, the constitutive equation for the diffusion flux in polymer solutions exhibits two kinds of coupling. One of these couplings comes from the viscous pressure contribution to the chemical potential, and the other one from the divergence of the viscous pressure tensor. The former contribution yields an effective diffusion coefficient depending on the viscous pressure, which may become negative in some circumstances. In such a case, an instability appears and the previously homogeneous system splits into two regions, with different solute concentrations – concentration banding. This separation depends on the polymer molecular mass and therefore it may provide a basis for the chromatographic separation of polymers of different molecular mass.     

An asymmetric feeding X-band active frequency-scanning leaky-wave antenna

An asymmetric feeding X-band active leaky-wave antennas is developed, to excite the first high order mode of the microstrip leaky wave antenna. One is the asymmetric feeding leaky-wave antenna which integrated with a HEMT oscillator, and the other is the frequency-tuned leaky-wave antenna which integrated with a varactortuned HEMT VCO. The microstrip leaky-wave antenna is operated in the first higher mode. To excite the first higher mode, the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the center of the microstrip leaky wave antenna. The design of these active leaky-wave antennas is discussed and the beam scanning phenomena of the antenna is presented. The HEMT oscillator frequency is controlled by tuning the varactor DC bias and the beam scanning is demonstrated. The measured scanning angle agree with prediction, it is close to 30° as the VCO frequency tuned from 8.06 GHz to 9GHz.     

Antibacterial activity and cytocompatibility of chitosan-N-hydroxy-2,3-propyl-N methyl-N,N-diallylammonium methyl sulfate

A water-soluble quaternary ammonium salt of chitosan, chitosan-N-hydroxy-2,3-propyl-N-methyl-N,N-diallylammonium methyl sulfate (MDAACS), was synthesized by reacting chitosan with methyl diallyl ammonium salt (MDAA). The results of water contact angle and swelling ratio showed that the membrane of MDAACS was more hydrophilic than chitosan. The antibacterial activities of MDAACS against Staphylococcus aureus and Klebsiella pneumoniae were evaluated with the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The results showed that the antibacterial activity of MDAACS was higher than that of chitosan. The cytocompatibility was evaluated in vitro with L929 fibroblast proliferation based on MTT colorimetric assay. The results showed that cell growth was much higher on MDAACS than on chitosan.     

Minimal-energy splines: I. Plane curves with angle constraints

This is the first in a series of papers on minimal-energy splines. The paper is devoted to plane minimal-energy splines with angle constraints. We first consider minimal-energy spline segments, then general minimal-energy spline curves. We formulate problems for minimal-energy spline segments and curves, prove the existence of solutions, justify the Lagrange multiplier rules, and obtain some nice properties (e.g., the infinite smoothness). Finally, we report our computational experience on minimal-energy splines.     

Critical temperatures of the anisotropic Heisenberg antiferromagnets

The first eight terms of the high temperature series expansions for the mean-square fluctuations of the magnetization variables are derived for the spin $\text{?}\text{1}\text{2}$ anisotropic Heisenberg antiferromagnets. The antiferromagnetic critical temperatures are determined for the s.c. and b.c.c. lattices.     

Four dimensional bolus tagging imaging of pulsatile flow

Inversion bolus tagging MR methods were used to provide a graphic depiction of the axial velocity in three spatial dimensions for pulsatile flow through complex geometries. Visualization of the flow field was readily apparent, and a train of tagged boli were depicted providing an immediate overview of the displacement of flowing fluid over the entire pulsatile cycle. Tagging efficiency obtained using adiabatic inversion pulses was improved compared to that with a windowed sinc pulse. Results from phantom experiments on steady flow were correlated with computational fluid dynamic (CFD) simulations. The use of 3D methods reduced spatial partial volume effects, and the displacement of boli in a steady flow experiment correlated well with CFD simulations. The use of adiabatic inversion pulses resulted in sharp edged inversion regions with good retention of longitudinal magnetization. However in order to keep the pulse duration short, of the order of 2-5 ms, a rather large RF amplitude had to be used. The inversion bolus tagging method is useful in visualizing the flow field in multiple levels for pulsatile fluid flowing through complex geometries, and may be useful in fluid dynamic applications.     

A dynamic analysis of modified compact-tension specimens using homalite-100 and polycarbonate plates

The dynamic fracture and crack-arrest responses of a modified compact-tension specimen (M-CT) machined from Homalite-100 and polycarbonate sheets were studied by dynamic photoelasticity, dynamic finite-element analysis and streaking photography. In contrast to some of the published results involving steel M-CT specimens, substantial dynamic effects were observed during rapid crack propagation in the Homalite-100 and polycarbonate M-CT specimens. The dynamic crack-arrest toughnesses.K _1a , were relatively constant and were about 80 percent and 50 percent of the corresponding fracture toughness,K _1c , of Homalite-100 and polycarbonate, respectively.