Self Injection length in La0.7 Ca0.3 Mno3-YBa 2Cu3O7-d ferromagnet- superconductor multi layer thin films

We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-d (YBCO). The heterojunctions were grown in situ by sequentially growing LCMO and YBCO films on LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 microns width were patterned both on the LAO (control) and LCMO side of the substrate. Critical current, Ic, was measured at 77K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed that while the control side showed a Jc of ~2 x 10E6 A/ cm2 the LCMO side showed about half the value for the same thickness (1800 A). The difference in Jc indicates that a certain thickness of YBCO has become 'effectively' normal due to self-injection. From the measurement of Jc at two different thickness' (1800 A and 1500 A) of YBCO both on the LAO as well as the LCMO side, the value of self-injection length (at 77K) was estimated to be ~900 A self-injection length has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection.Comment: 6 pages, one figure in .ps forma

Interleukin-10 Promotes Pathological Angiogenesis by Regulating Macrophage Response to Hypoxia during Development

Aberrant angiogenesis in the eye is the most common cause of blindness. The current study examined the role of interleukin-10 (IL-10) in ischemia-induced pathological angiogenesis called neovascularization during postnatal development. IL-10 deficiency resulted in significantly reduced pathological retinal angiogenesis. In contrast to the choroicapillaris where IL-10 interferes with macrophage influx, IL-10 did not prevent anti-angiogenic macrophages from migrating to the retina in response to hypoxia. Instead, IL-10 promoted retinal angiogenesis by altering macrophage angiogenic function, as macrophages from wild-type mice demonstrated increased vascular endothelial growth factor (VEGF) and nitric oxide (NO) compared to IL-10 deficient macrophages. IL-10 appears to directly affect macrophage responsiveness to hypoxia, as macrophages responded to hypoxia with increased levels of IL-10 and STAT3 phosphorylation as opposed to IL-10 deficient macrophages. Also, IL-10 deficient macrophages inhibited the proliferation of vascular endothelial cells in response to hypoxia while wild-type macrophages failed to do so. These findings suggest that hypoxia guides macrophage behavior to a pro-angiogenic phenotype via IL-10 activated pathways

Lithium suppression of tau induces brain iron accumulation and neurodegeneration

Lithium is a first-line therapy for bipolar affective disorder. However, various adverse effects, including a Parkinson-like hand tremor, often limit its use. The understanding of the neurobiological basis of these side effects is still very limited. Nigral iron elevation is also a feature of Parkinsonian degeneration that may be related to soluble tau reduction. We found that magnetic resonance imaging T2 relaxation time changes in subjects commenced on lithium therapy were consistent with iron elevation. In mice, lithium treatment lowers brain tau levels and increases nigral and cortical iron elevation that is closely associated with neurodegeneration, cognitive loss and parkinsonian features. In neuronal cultures lithium attenuates iron efflux by lowering tau protein that traffics amyloid precursor protein to facilitate iron efflux. Thus, tau- and amyloid protein precursor-knockout mice were protected against lithium-induced iron elevation and neurotoxicity. These findings challenge the appropriateness of lithium as a potential treatment for disorders where brain iron is elevated (for example, Alzheimer’s disease), and may explain lithium-associated motor symptoms in susceptible patients

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Effect of torsion arm dimensions on natural frequency of a torsion mirror

Micron-size torsion-mirrors, made in silicon, have been proposed and used in several optical communication applications. A very common structure used for torsion mirror, a framed diaphragm pivoted on two torsion wires, is analyzed for their frequency response as a function parameters of torsion wires, the silicon diaphragm and frame. The aim of the simulations is to obtain as high a natural frequency of vibration while maintaining a stiff frame around the diaphragm mirror. A set of optimum values of parameters could be determined for a given frequency of vibration

2-D simulation of multilayered MEMS structures

MEMS device structures, particularly those made using Surface-Micromachining, consist of thin layers of insulator, silicon, silicon dioxide, silicon nitride, metal or poly-silicon held at few points onto a thick silicon substrate. These heterogeneous layers resemble closely to laminas of composites used in building structures. For these heterogeneous material systems, involving Metal- Insulator-Semiconductor layers, there is usually an inherent two dimensional thermal contraction of the various layers upon cooling from a growth temperature of 1000 to 1200 C down to room temperature. The thermal stress, so developed, could result in static deformation as well change the dynamic characteristics of the micro-parts. Thin heteroepitaxial layers, with lattice mismatch with the single crystal substrate, can also result in a built in stress. External effects like electrostatic potentials and magnetic fields applied to a layered structure can also result in contractions or extensions of specific layers that respond to applied fields. A generic formulation of governing equations of equilibrium and compatibility has been developed for laminated structures with various in-built stress effects like difference in temperature of formation and use; difference in lattice constants of heteroepitaxial layers; effects that involve dimensional changes like piezoelectric effect and magnetostriction. This paper aims at demonstrating, through simulations of a test structure of a doubly suspended resonator, how these multi-layer structures could exploit the static deformations to result in a robust (temperature- insensitive) dynamic response. The static deformation for temperature changes in a bi-layer of aluminum and silicon dioxide is simulated on ANSYS. The results of ANSYS match very well with a fabricated test device

Micro-miniaturized electrophoresis DNA separator using MEMS

Conventional DNA separation procedures involve large sizes, high voltages and are unfit for large molecules. Proposed set-up constitutes two fold separation techniques, porous filter for fractionating strands on size and final run through microchannels (agarose, buffer solution) viscous enough for DNA electrophoresis. For arriving at the final set-up all the physical contradictions like voltage, viscosity of the fluid, length of the channel were analyzed. The physical set up consists around 20 microchannels (varying diameters) positioned at 500um (centre-to-centre spacing) assembling entire device within 1cm. Polymerase Chain Reaction (PCR) treated DNA assays, are fed to microchannel entrances. Mixture of DNA strands are then passed through magnetic filters. Filtering property of the filters is adjusted by regulating corresponding magnetic field strengths. Smallest strands pass through small pored filter, owing to high velocity (in electrophoresis), thus categorization being done. Proposal replaces conventional apparatus by miniaturized equipment, in ideal case disposable. Miniaturization reduced voltages requirement, solving high-voltage handling problems. Proposed apparatus can fractionate large (> 200kbp) molecules and even organic molecules

Design and Fabrication of Bulk Micro-machined, High Resilience, High-Q, High Tilt Angle, Low Driving Voltage, Flexure Beam Micro-mirrors on Mono-crystalline Silicon

We report the design, fabrication and characterization of electrically tunable, bulk micro machined, doubly clamped, circular cross-section flexure based square-plate Metal-On-Oxide, DC bias tension applied, resonant micro-mirrors for different frequencies starting from 1 kilohertz to 172 kilohertz on silicon {100} oriented wafers with high Q factors in the air, that have high resilience. Though silicon shows inherent reflective behavior, the surface quality of the top-deposited metal layer is treatment specific. The sputtered chrome-gold films have good light scattering properties, for precise measurements within 6x6 ROI matrixes for vibrometry and AFM. We introduce novel circular cross-section flexure hinges with the advantages of compact design, 5 fold better precision of rotation compared to similar constant cross-section flexure, lesser stiffness, and beam length and beam width that are less decisive for micro-manufacture. We have fabricated the device, with a double mask, replacing torsion beams with flexure beams. These suspended-in-air-in-trapezoidal-cavity square plate micro-mirrors fabricated on the silicon {100} oriented wafers, are electrically tunable at +/- 30 Volts, with onset of motion at as low as 3 Volts electrical potential, with the largest achieved tilt angle as high as 11 degrees and parabolic capacitance-voltage characteristics, that confirm the motion of the device in a cavity. The motion of these devices was recorded as a Doppler frequency shift. The result shows a slight improvement in mirror surface quality when resonant micro-mirrors are applied with bias tension, that deviates from the results presented in prior art. The micro-mirrors initially show inactivity in motion, which stabilizes later. The exact mechanism responsible for this initial inactivity is not known, we attribute it to the sluggish behavior of joined mechanical elements with large time constants, which slow down the vibrancy

Improvement in reliability of MEMS resonator using multi-layers

Many promising applications of MEMS based devices are in critical systems. Hence, their reliability has become an important issue. The techniques used for the fabrication of these devices give rise to large residual stresses. This coupled with their high speeds of operation make them prone to fatigue failure. The focus of this work is the improvement of reliability under fatigue loading using multi-layers. This paper demonstrates that by adjusting the thickness ratios, the stress in a multi-layered resonator can be prevented from alternating. Moreover, the peak stress can be minimized and performance can be improved in harsh environments