Intensity dependent transmission dynamics in magnetic fluids

The time dependent transmission is observed when a laser beam passes through a thin layer of a magnetic fluid. We found that the transmission reaches a peak at a time that depends on the intensity of the incident beam-the peak position shifts to shorter time when the input intensity is increased. The peak value of transmitted power decreases with increasing magnetic field. A simplified model is provided to explain these complex dynamics

Nonlinear optical effects in ferrofluids induced by temperature and concentration cross coupling

Both experiment and numerical calculation were performed to study the nonlinear optical (NLO) effects in ferrofluids consisting of magnetic particles suspended in an organic solvent. We show that, in contrast to all the mechanisms responsible for NLO phenomena known so far, the novel NLO effects in ferrofluids in the zero applied field can be explained by the cross coupling between the temperature of the system and the concentration of particles through thermophoresis, which in turn leads to the spatial distribution of the refractive index. This NLO effect is enhanced by applying a moderate magnetic field whose mechanism is unclear so far

Dynamics of low-dimensional dipolar systems

Time decays of low-dimensional magnetic dipoles with anisotropic energy barriers were studied theoretically. We found that the dynamic behaviors are interaction specific. For a chain with ferromagnetic coupling, a single mode dominates and the decay is essentially exponential. For antiferromagnetic coupling, the dynamics can be characterized by two distinct groups of time scales. The spectrum results in a plateau in the decay of remanent magnetization. This novel behavior differs from the prediction of the mean-field theory. For a two-dimensional rectangular lattice, a transition between the bimodal decay and a quasilogarithmic decay occurs when the ratio of length to width varies

Ferrofluid 3-D Gyroscope and Light Modulator.

Apparatus and methods for passing a focused laser beam through a thin ferrofluid cell creates a spatial distribution in the refractive index of the ferrofluid and generates a diffraction ring patterns. Using a pair of perpendicularly placed ferrofluid cells, two sets of diffraction ring patterns can be produced on two viewing screens. Deformations in the diffraction patterns due to an acceleration can be viewed on the screens, providing a ferrofluid accelerometer. By applying an electric or a magnetic field on a thin ferrofluid sample, the light passing through the sample can be modulated by the field, providing a light modulator. The apparatus and method has applications for detecting acceleration information within a gyroscope and for use in toys

Crossover behavior in dynamics of frozen ferrofluids

The imaginary part of susceptibility, chi , in frozen ferrofluids was measured as functions of temperature, frequency, and concentration of magnetic particles. In a very dilute region, where magnetic interaction is negligible, the relaxation time is mainly determined by Neel\u27s relaxation in isolated particles and the frequency-dependent peak temperature in chi (T), T-p, obeys the Arrhenius law. In the moderate concentration range, T-p has a Vogel-Fulcher (VF) relaxation with the measuring frequency. However, for concentration larger than a certain value, deviation from VF law occurs. Simulations show that the VF relation could be attributed to Ising spin-glass-like random and frustrated interaction between magnetic moments of particles. We suggest that particle configuration before freezing is critical to determine the distribution of pair exchange parameters. For high concentration, there are more ferromagnetic than antiferromagnetic bonds. The deviation from VF law at high concentration could be due to short range correlation among spins

Mitochondrial nutrients improve immune dysfunction in the type 2 diabetic Goto-Kakizaki rats.

The development of type 2 diabetes is accompanied by decreased immune function and the mechanisms are unclear. We hypothesize that oxidative damage and mitochondrial dysfunction may play an important role in the immune dysfunction in diabetes. In the present study, we investigated this hypothesis in diabetic Goto-Kakizaki rats by treatment with a combination of four mitochondrial-targeting nutrients, namely, R-alpha-lipoic acid, acetyl-L-carnitine, nicotinamide and biotin. We first studied the effects of the combination of these four nutrients on immune function by examining cell proliferation in immune organs (spleen and thymus) and immunomodulating factors in the plasma. We then examined, in the plasma and thymus, oxidative damage biomarkers, including lipid peroxidation, protein oxidation, reactive oxygen species, calcium and antioxidant defence systems, mitochondrial potential and apoptosis-inducing factors (caspase 3, p53 and p21). We found that immune dysfunction in these animals is associated with increased oxidative damage and mitochondrial dysfunction and that the nutrient treatment effectively elevated immune function, decreased oxidative damage, enhanced mitochondrial function and inhibited the elevation of apoptosis factors. These effects are comparable to, or greater than, those of the anti-diabetic drug pioglitazone. These data suggest that a rational combination of mitochondrial-targeting nutrients may be effective in improving immune function in type 2 diabetes through enhancement of mitochondrial function, decreased oxidative damage, and delayed cell death in the immune organs and blood

Dipole interactions with random anisotropy in a frozen ferrofluid

Glassy behavior (including hysteresis, irreversibility, a peak in the zero-field-cooled magnetization, and nonexponential relaxation) is observed in a quenched ferrofluid system consisting of 50-angstrom magnetite particles. An Arrott plot, M^2 vs H/M, shows clear features of random anisotropy similar to what is found in amorphous ferromagnets. We discuss the glassy behavior in terms of both the random anisotropy and the dipole interactions, and we contrast the unusual response of our system with canonical spin glasses