Electric field control of diffraction and noise in dye-doped liquid crystals

We present results on permanent gratings in highly dye-doped liquid crystal cells without polymer coatings of the cells' surfaces. The surface-mediated gratings remain in cells for months without degradation of their quality. The peak diffraction efficiency can be controlled, enhanced or decreased, by applying low voltage AC field. At low frequencies, below 1 Hz, the diffracted signal can modulated by the AC field, but the time development of the signal shows a complex response. The enhancement of diffraction can be, however, observed at all frequencies we tested (0.1 Hz – 300 kHz). The permanent gratings cannot be removed by heating above the liquid crystal phase transition temperature as on cooling the diffraction efficiency is restored

Characterization of Liposomes for Cancer Cell Transfection

We have characterized a broad range of liposome formulations with varying DcChol:DOPE ratio. Subsequent addition of DcChol to liposomes increases its positive surface charge. However, loading the nuclear acids did not neutralize the overall negative surface potential to a similar extent. The liposomes were tested by transfection of DNA in living cancer cells

Strong optical force induced by morphology dependent resonances

We consider the resonant optical force acting on a pair of transparent microspheres by the excitation of the Morphology Dependent Resonance (MDR). The bonding and anti-bonding modes of the MDR correspond to strong attractions and repulsions respectively. The dependence of the force on separation and the role of absorption are discussed. At resonance, the force can be enhanced by orders of magnitude so that it will dominate over other relevant forces. We find that a stable binding configuration can be induced by the resonant optical force.Comment: 4 pages, 4 figure

Interactions between spherical nanoparticles optically trapped in Laguerre-Gaussian modes

When a Laguerre-Gaussian (LG) laser mode is used to trap nanoparticles, the spatial disposition of the particles about the beam axis is determined by a secondary mechanism that engages the input radiation with the interparticle potential. This analysis, based on the identification of a range-dependent laser-induced energy shift, elicits and details features that arise for spherical nanoparticles irradiated by a LG mode. Calculations of the absolute minima are performed for LG beams of variable topological charge, and the results are displayed graphically. It is shown that more complex ordered structures emerge on extension to three- and four-particle systems and that similar principles will apply to other kinds of radially structured optical mode. © 2005 Optical Society of America

Interplay Between Mitochondrial Proteins and Age-Associated Risk of Cardiovascular Diseases

Normal functioning of mitochondria is crucial for cardiac performance. Mitochondria undergo mitophagy (mitochondrial autophagy) and biogenesis, and mitochondrial proteins are subject to extensive post-translational modifications (PTMs). The state of mitochondrial homeostasis reflects overall cellular fitness and longevity. Perturbed mitochondria produce less adenosine triphosphate (ATP), release greater amounts of reactive molecules, and are more prone to apoptosis. Therefore mitochondrial turnover is an integral aspect of quality control in which dysfunctional mitochondria are selectively eliminated through mitophagy. Currently, the progressive deterioration of physiological functions is seen as accumulation of modified/damaged proteins with limiting regenerative ability throughout aging in myocardial cells. Mitochondrial stress response to reactive species was evaluated as electron transport chain (ETC) complexes, redox-active molecules, and their possible communication. Protein-protein interactions revealed a strong linkage between age and ETC protein subunits. Redox state was strongly affected in senescent mitochondria with shift in favor of more pro-oxidizing condition within cardiomyocytes. Assume all together, dysfunctional proteostasis can play a causative role in aging and restoration of protein homeostasis machinery is protective against aging and possibly age-related disorders

Localized vibrational modes in optically bound structures

We show, through analytical theory and rigorous numerical calculations, that optical binding can organize a collection of particles into stable one-dimensional lattice. This lattice, as well as other optically-bound structures, are shown to exhibit spatially localized vibrational eigenmodes. The origin of localization here is distinct from the usual mechanisms such as disorder, defect, or nonlinearity, but is a consequence of the long-ranged nature of optical binding. For an array of particles trapped by an interference pattern, the stable configuration is often dictated by the external light source, but our calculation revealed that inter-particle optical binding forces can have a profound influence on the dynamics.Comment: 4 pages, Optical Bindin

Increasingly transformed MCF-10A cells have a progressively tumor-like phenotype in three-dimensional basement membrane culture

<p>Abstract</p> <p>Background</p> <p>MCF-10A cells are near diploid and normal human mammary epithelial cells. In three-dimensional reconstituted basement membrane culture, they undergo a well-defined program of proliferation, differentiation, and growth arrest, forming acinar structures that recapitulate many aspects of mammary architecture <it>in vivo</it>. The pre-malignant MCF-10AT cells and malignant MCF-10CA1a lines were sequentially derived from the MCF-10A parental cell line first by expression of a constitutively active T24 H-Ras generating the MCF-10AT cell line. This was followed by repeated selection for increasingly aggressive tumor formation from cells recovered from xenograft tumors in immuno-compromised mice, generating the MCF-10CA1a cell line. When inoculated subcutaneously into the flanks of immuno-compromised mice, MCF-10AT cells occasionally form tumors, whereas MCF-10CA1a cells invariably form tumors with a shorter latency than MCF-10AT derived tumors.</p> <p>Results</p> <p>MCF-10AT cells grown in three-dimensional basement membrane culture form complex multi-acinar structures that produce a basement membrane but undergo delayed cell cycle arrest and have incomplete luminal development. MCF-10CA1a cells grown in three-dimensional basement membrane culture form large, hyper-proliferative masses, that retain few characteristics of MCF10A acini and more closely resemble tumors.</p> <p>Conclusion</p> <p>Here we report on the growth and differentiation properties of these three matched cell lines in three-dimensional basement membrane culture. Features of tissue morphogenesis were assessed, including proliferation, basement membrane formation, polarization of alpha-6 beta-4 integrin to the basement membrane, formation of cell:cell junctions, and apoptosis for luminal clearance. The matched series of normal MCF-10A, pre-malignant MCF-10AT, and malignant MCF-10CA1a cells offers a unique opportunity to study the mechanisms of malignant progression both in a three-dimensional microenvironment and in the same cell background.</p

Optically bound microscopic particles in one dimension

Counter-propagating light fields have the ability to create self-organized one-dimensional optically bound arrays of microscopic particles, where the light fields adapt to the particle locations and vice versa. We develop a theoretical model to describe this situation and show good agreement with recent experimental data (Phys. Rev. Lett. 89, 128301 (2002)) for two and three particles, if the scattering force is assumed to dominate the axial trapping of the particles. The extension of these ideas to two and three dimensional optically bound states is also discussed.Comment: 12 pages, incl. 5 figures, accepted by Phys. Rev.

Phase synchronization in tilted deterministic ratchets

We study phase synchronization for a ratchet system. We consider the deterministic dynamics of a particle in a tilted ratchet potential with an external periodic forcing, in the overdamped case. The ratchet potential has to be tilted in order to obtain a rotator or self-sustained nonlinear oscillator in the absence of external periodic forcing. This oscillator has an intrinsic frequency that can be entrained with the frequency of the external driving. We introduced a linear phase through a set of discrete time events and the associated average frequency, and show that this frequency can be synchronized with the frequency of the external driving. In this way, we can properly characterize the phenomenon of synchronization through Arnold tongues, which represent regions of synchronization in parameter space, and discuss their implications for transport in ratchets.Comment: 14 pages, 6 figures, Physica A, in pres