Biomedical subjects

D Mihailovic

Publications and source records attributed to D Mihailovic.

At least 19 recordsLinked to original sources

PubMed2005

Kinetics of a superconductor excited with a femtosecond optical pulse.

Superconducting state dynamics following excitation of a superconductor with a femtosecond optical pulse is studied in terms of a phenomenological Rothwarf and Taylor model. Analytical solutions for various limiting cases are obtained. The model is found to account for the intensity and temperature dependence of both photoinduced quasiparticle density, as well as pair-breaking and superconducting state recovery dynamics in conventional as well as cuprate superconductors.

Journal Article↗

PubMed2005

Optical experimental evidence for a universal length scale for the dynamic charge inhomogeneity of cuprate superconductors.

Time-resolved optical experiments can give unique information on the characteristic length scales of dynamic charge inhomogeneity on femtosecond time scales. From data on the effective quasiparticle relaxation time tau(r) in La(2-x)SrxCuO4 and Nd(2-x)Ce(x)CuO4, we derive the temperature and doping dependence of the intrinsic phonon escape length l(e), which can be a direct measure of charge inhomogeneity. Remarkably, a common feature of both p- and n-type cuprates is that, as T --> Tc, l(e) approaches the superconducting coherence length l(e) --> xi(s)0. In the normal state l(e) is found to be in excellent agreement with the mean free path l(m) obtained from the resistivity data and structural coherence lengths l(s) from neutron scattering experiments, implying the existence of complex intrinsic textures on different length scales which may have a profound effect on the functional properties of these materials.

Journal Article↗

PubMed2005

Charged particles on a two-dimensional lattice subject to anisotropic Jahn-Teller interactions.

The properties of a system of charged particles on a 2D lattice, subject to an anisotropic Jahn-Teller-type interaction and 3D Coulomb repulsion, are investigated. In the mean-field approximation without Coulomb interaction, the system displays a phase transition of first order. When the long-range Coulomb interaction is included, Monte Carlo simulations show that the system displays very diverse mesoscopic textures, ranging from spatially disordered pairs to ordered arrays of stripes, or charged clusters, depending only on the ratio of the two interactions (and the particle density). Remarkably, charged objects with an even number of particles are more stable than with an odd number of particles. We suggest that the diverse functional behavior-including superconductivity-observed in oxides can be thought to arise from the self-organization of this type.

Journal Article↗

PubMed2003

Unusual magnetic state in lithium-doped MoS2 nanotubes.

We report on the very peculiar magnetic properties of an ensemble of very weakly coupled lithium-doped MoS2 nanotubes. The magnetic susceptibility chi of the system is nearly 3 orders of magnitude greater than in typical Pauli metals, yet there is no evidence for any instability which would alleviate this highly frustrated state. Instead, the material exhibits peculiar paramagnetic stability down to very low temperatures, with no evidence of a quantum critical point as T-->0 in spite of clear evidence for strongly correlated electron behavior. The exceptionally weak intertube interactions appear to lead to a realization of a near-ideal one-dimensional state in which fluctuations prevent the system from reordering magnetically or structurally.

Journal Article↗

PubMed2001

Critical exponents at the ferromagnetic transition in tetrakis(dimethylamino)ethylene-C(60) (TDAE- C(60)).

Critical exponents at the ferromagnetic transition were measured for the first time in an organic ferromagnetic material tetrakis(dimethylamino)ethylene fullerene[60] (TDAE- C(60)). From a complete magnetization-temperature-field data set near T(c) = 16.1+/-0.05, we determine the susceptibility and magnetization critical exponents gamma = 1.22+/-0.02 and beta = 0.75+/-0.03, respectively, and the field vs magnetization exponent at T(c) of delta = 2.28+/-0.14. Hyperscaling is found to be violated by Omega identical with d(')-d approximately -1/4, suggesting that the onset of ferromagnetism can be related to percolation of a particular contact configuration of C(60) molecular orientations.

Journal Article↗

PubMed2001

Self-assembly of subnanometer-diameter single-wall MoS2 nanotubes.

We report on the synthesis, structure, and self-assembly of single-wall subnanometer-diameter molybdenum disulfide tubes. The nanotubes are up to hundreds of micrometers long and display diverse self-assembly properties on different length scales, ranging from twisted bundles to regularly shaped "furry" forms. The bundles, which contain interstitial iodine, can be readily disassembled into individual molybdenum disulfide nanotubes. The synthesis was performed using a novel type of catalyzed transport reaction including C(60) as a growth promoter.

Journal Article↗

PubMed2000

Origin of ferromagnetic exchange interactions in a fullerene-organic compound.

Organic ferromagnets, which exhibit exchange interactions between unpaired electrons in pi-orbitals, are rare, and the origin of ferromagnetism in these compounds has so far remained unexplained. Tetrakis(dimethylamino)ethylene-fullerene[60] (TDAE-C60) shows a transition to a ferromagnetic state with fully saturated s = 1/2 molecular spins at the relatively high Curie temperature (for organic materials) of 16 K (ref. 4). It has been suggested that the orientations of the C60 molecules may be important for ferromagnetism in this material, but in the absence of structural data at low temperatures there has been little progress towards understanding these microscopic interactions. Here we report the results of a comparative structural study of two different magnetic forms of TDAE-C60 crystals at low temperatures, correlating the structural properties--in particular, the intermolecular orientations--with the magnetic properties. We find that both ferromagnetism and spin-glass-like ordering are possible in this material, and depend on the orientational state of C60 molecules. This resolves the apparent contradictions posed by different macroscopic measurements, and opens the way to a microscopic understanding of pi-electron ferromagnetic exchange interactions in organic materials.

Journal Article↗

PubMed1999

Protective effect of a bioflavonoid proanthocyanidin-BP1 in glycerol-induced acute renal failure in the rat: renal stereological study.

Renal ischemia as well as oxygen metabolites play an important role in renal injury during myoglobinuric acute renal failure (ARF). On the other hand, flavonoids, a diverse group of constituents naturally occurring in plants, have a strong antioxidative activity, and have been implicated in vascular relaxation. In this study the protective effect of a new bioflavonoid proanthocyanidin-BP1 (BP1), extracted from seeds of grapes, was evaluated in glycerol-induced ARF in rats. Stereological methods were used to quantify changes in renal morphology associated with ARF. Volume density of tubular lumen and intratubular cast formations, nuclear parameters (area, diameter, volume) of epithelial cells in the cortical proximal tubules, and glomerular parameters (surface area, diameter, volume, perimeter) were estimated on kidney sections of rats treated either with 50% glycerol (8 mL/kg i.m.) alone. BP1 (20 mg/kg i.p.) in addition to glycerol, or BP1 alone. It was noted that the volume density of tubular lumen and cast formations were significantly lower (p < 0.001) in kidneys of the rats treated with BP1 in addition to glycerol, compared with those treated with glycerol alone. There were no significant differences in glomerular and nuclear parameters between glycerol treated, and BP1 in addition to glycerol treated rats. Renal function was significantly improved in rats treated with BP1 in addition to glycerol. The results suggest that BP1 is a protective agent in glycerol model of ARF. This effect is probably due to the antioxidative activity of BP1 and reduced toxicity of myoglobin in renal tissue. Moreover, it is possible that the ability of BP1 to protect the kidney is dependent upon renal vascular relaxation. The potential beneficial effects of bioflavonoid-BP1 demonstrated in experimental ARF could be considered in therapy of myoglobinuric ARF.

Acute Kidney Injury↗

PubMed1998