Experimental Study on Substrate Noise Effects of a Pulsed Clocking Scheme on PLL Performance

In this brief, the substrate noise effects of a pulsed clocking scheme on the output spur level, the phase noise, and the peak-to-peak (Pk-Pk) deterministic period jitter of an integer-N charge-pump phase-locked loop (PLL) are demonstrated experimentally. The phenomenon of noise coupling to the PLL is also explained through experiments. The PLL output frequency is 500 MHz and it is implemented in the 0.13-mu m CMOS technology. Measurements show a reduction of 12.53 dB in the PLL output spur level at an offset of 5 MHz and a reduction of 107 ps in the Pk-Pk deterministic period jitter upon reducing the duty cycle of the signal injected into the substrate from 50% to 20%. The results of the analyses suggest that using a pulsed clocking scheme for digital systems in mixed-signal integration along with other isolation techniques helps reduce the substrate noise effects on sensitive analog/radio-frequency circuits.

Prediction of breakout noise from an elliptical duct of finite length

This paper describes a predictive model for breakout noise from an elliptical duct or shell of finite length. The transmission mechanism is essentially that of ``mode coupling'', whereby higher structural modes in the duct walls get excited because of non-circularity of the wall. Effect of geometry has been taken care of by evaluating Fourier coefficients of the radius of curvature. The noise radiated from the duct walls is represented by that from a finite vibrating length of a semi infinite cylinder in a free field. Emphasis is on understanding the physics of the problem as well as analytical modeling. The analytical model is validated with 3-D FEM. Effects of the ovality, curvature, and axial terminations of the duct have been demonstrated. (C) 2010 Institute of Noise Control Engineering.

Analytical prediction of break-out noise from a reactive rectangular plenum with four flexible walls

This paper describes an analytical calculation of break-out noise from a rectangular plenum with four flexible walls by incorporating three-dimensional effects along with the acoustical and structural wave coupling phenomena. The breakout noise from rectangular plenums is important and the coupling between acoustic waves within the plenum and structural waves in the flexible plenum walls plays a critical role in prediction of the transverse transmission loss. The first step in breakout noise prediction is to calculate the inside plenum pressure field and the normal flexible plenum wall vibration by using an impedance-mobility approach, which results in a compact matrix formulation. In the impedance-mobility compact matrix (IMCM) approach, it is presumed that the coupled response can be described in terms of finite sets of the uncoupled acoustic subsystem and the structural subsystem. The flexible walls of the plenum are modeled as an unfolded plate to calculate natural frequencies and mode shapes of the uncoupled structural subsystem. The second step is to calculate the radiated sound power from the flexible walls using Kirchhoff-Helmholtz (KH) integral formulation. Analytical results are validated with finite element and boundary element (FEM-BEM) numerical models. (C) 2010 Acoustical Society of America. DOI: 10.1121/1.3463801]

Nonlinear electrical conduction and broad band noise in the charge-ordered rare earth manganate Nd0.5Ca0.5MnO3

Measurements of the dc transport properties and the low-frequency conductivity noise in films of charge-ordered Nd0.5Ca0.5MnO3 grown on Si substrate reveal the existence of a threshold field in the charge-ordered regime beyond which strong nonlinear conduction sets in along with a large broad band conductivity noise. Threshold-dependent conduction disappears as T --> T-CO, the charge-ordering temperature. This observation suggests that the charge-ordered state gets depinned at the onset of the nonlinear conduction. (C) 1999 American Institute of Physics. [S0003-6951(99)05247-X].

An oxidative cross-dehydrogenative-coupling reaction in water using molecular oxygen as the oxidant: vanadium catalyzed indolation of tetrahydroisoquinolines

An aerobic oxidative cross-dehydrogenative coupling reaction between sp(3) C-H and sp(2) C-H bonds is developed by employing a vanadium catalyst (10 mol%) in an aqueous medium using molecular oxygen as the oxidant. This environmentally benign strategy exhibits larger substrate scope and shows high regioselectivity.

Prediction of Breakout Noise from a Rectangular Duct with Compliant Walls

Breakout noise from HVAC ducts is important at low frequencies, and the coupling between the acoustic waves and the structural waves plays a critical role in the prediction of the transverse transmission loss. This paper describes the analytical calculation of breakout noise by incorporating three-dimensional effects along with the acoustical and structural wave coupling phenomena. The first step in the breakout noise prediction is to calculate the inside duct pressure field and the normal duct wall vibration by using the solution of the governing differential equations in terms of Green's function. The resultant equations are rearranged in terms of impedance and mobility, which results in a compact matrix formulation. The Green's function selected for the current problem is the cavity Green's function with modification of wave number in the longitudinal direction in order to incorporate the terminal impedance. The second step is to calculate the radiated sound power from the compliant duct walls by means of an ``equivalent unfolded plate'' model. The transverse transmission loss from the duct walls is calculated using the ratio of the incident power due to surface source inside the duct to the acoustic power radiated from the compliant duct walls. Analytical results are validated with the FE-BE numerical models.

Radiative and non-radiative effects of a substrate on localized plasmon resonance of particles

Experiments have shown strong effects of some substrates on the localized plasmons of metallic nano particles but they are inconclusive on the affecting parameters. Here, we have used discrete dipole approximation in conjunction with Sommerfeld integral relations to explain the effect of the substrates as a function of the parameters of incident radiation. The radiative coupling can both quench and enhance the resonance and its dependence on the angle and polarization of incident radiation with respect to the surface is shown. Non-radiative interaction with the substrate enhances the plasmon resonance of the particles and can shift the resonances from their free-space energies significantly. The non-radiative interaction of the substrate is sensitive to the shape of particles and polarization of incident radiation with respect to substrate. Our results show that the plasmon resonances in coupled and single particles can be significantly altered from their free-space resonances and are quenched or enhanced by the choice of substrate and polarization of incident radiation. (C) 2012 American Institute of Physics. http://dx.doi.org/10.1063/1.4736544]

Conductivity noise study of the insulator-metal transition and phase coexistence in epitaxial samarium nickelate thin films

Interaction between the lattice and the orbital degrees of freedom not only makes rare-earth nickelates unusually ``bad metal,'' but also introduces a temperature-driven insulator-metal phase transition. Here we investigate this insulator-metal phase transition in thin films of SmNiO3 using the slow time-dependent fluctuations (noise) in resistivity. The normalized magnitude of noise is found to be extremely large, being nearly eight orders of magnitude higher than thin films of common disordered metallic systems, and indicates electrical conduction via classical percolation in a spatially inhomogeneous medium. The higher-order statistics of the fluctuations indicate a strong non-Gaussian component of noise close to the transition, attributing the inhomogeneity to the coexistence of the metallic and insulating phases. Our experiment offers insight into the impact of lattice-orbital coupling on the microscopic mechanism of electron transport in the rare-earth nickelates.

A common stochastic accumulator with effector-dependent noise can explain eye-hand coordination

The computational architecture that enables the flexible coupling between otherwise independent eye and hand effector systems is not understood. By using a drift diffusion framework, in which variability of the reaction time (RT) distribution scales with mean RT, we tested the ability of a common stochastic accumulator to explain eye-hand coordination. Using a combination of behavior, computational modeling and electromyography, we show how a single stochastic accumulator to threshold, followed by noisy effector-dependent delays, explains eye-hand RT distributions and their correlation, while an alternate independent, interactive eye and hand accumulator model does not. Interestingly, the common accumulator model did not explain the RT distributions of the same subjects when they made eye and hand movements in isolation. Taken together, these data suggest that a dedicated circuit underlies coordinated eye-hand planning.

Interplay of Substrate Conductivity, Cellular Microenvironment, and Pulsatile Electrical Stimulation toward Osteogenesis of Human Mesenchymal Stem Cells in Vitro

The influences of physical stimuli such as surface elasticity, topography, and chemistry over mesenchymal stem cell proliferation and differentiation are well investigated. In this context, a fundamentally different approach was adopted, and we have demonstrated the interplay of inherent substrate conductivity, defined chemical composition of cellular microenvironment, and intermittent delivery of electric pulses to drive mesenchymal stem cell differentiation toward osteogenesis. For this, conducting polyaniline (PANI) substrates were coated with collagen type 1 (Coll) alone or in association with sulfated hyaluronan (sHya) to form artificial extracellular matrix (aECM), which mimics the native microenvironment of bone tissue. Further, bone marrow derived human mesenchymal stem cells (hMSCs) were cultured on these moderately conductive (10(-4)10(-3) S/cm) aECM coated PANI substrates and exposed intermittently to pulsed electric field (PEF) generated through transformer-like coupling (TLC) approach over 28 days. On the basis of critical analysis over an array of end points, it was inferred that Coll/sHya coated PANI (PANI/Coll/sHya) substrates had enhanced proliferative capacity of hMSCs up to 28 days in culture, even in the absence of PEF stimulation. On the contrary, the adopted PEF stimulation protocol (7 ms rectangular pulses, 3.6 mV/cm, 10 Hz) is shown to enhance osteogenic differentiation potential of hMSCs. Additionally, PEF stimulated hMSCs had also displayed different morphological characteristics as their nonstimulated counterparts. Concomitantly, earlier onset of ALP activity was also observed on PANI/Coll/sHya substrates and resulted in more calcium deposition. Moreover, real-time polymerase chain reaction results indicated higher mRNA levels of alkaline phosphatase and osteocalcin, whereas the expression of other osteogenic markers such as Runt-related transcription factor 2, Col1A, and osteopontin exhibited a dynamic pattern similar to control cells that are cultured in osteogenic medium. Taken together, our experimental results illustrate the interplay of multiple parameters such as substrate conductivity, electric field stimulation, and aECM coating on the modulation of hMSC proliferation and differentiation in vitro.

Morphological transitions and buckling characteristics in a nanoparticle-laden sessile droplet resting on a heated hydrophobic substrate

In this work, we have established the evaporation-liquid flow coupling mechanism by which sessile nanofluid droplets on a hydrophobic substrate evaporate and agglomerate to form unique morphological features under controlled external heating. It is well understood that evaporation coupled with internal liquid flow controls particle transport in a spatiotemporal sense. Flow characteristics inside the heated droplet are investigated and found to be driven by the buoyancy effects. Velocity magnitudes are observed to increase by an order at higher temperatures with similar looking flow profiles. The recirculating flow induced particle transport coupled with collision of particles and shear interaction between them leads to the formation of dome shaped viscoelastic shells of different dimensions depending on the surface temperature. These shells undergo sol-gel transition and subsequently undergo buckling instability leading to the formation of daughter cavities. With an increase in the surface temperature, droplets exhibit buckling from multiple sites over a larger sector in the top half of the droplet. Irrespective of the initial nanoparticle concentration and substrate temperature, growth of a daughter cavity (subsequent to buckling) inside the droplet is found to be controlled by the solvent evaporation rate from the droplet periphery and is shown to exhibit a universal trend.

Studies on elastic coupling parameters of fracture modes in orthotropic materials

The characterisation of cracks is usually done using the well known three basic fracture modes, namely opening, shearing and tearing modes. In isotropic materials these modes are uncoupled and provide a convenient way to define the fracture parameters. It is well known that these fracture modes are coupled in anisotropic materials. In the case of orthotropic materials also, coupling exists between the fracture modes, unless the crack plane coincides with one of the axes of orthotropy. The strength of coupling depends upon the orientation of the axes of orthotropy with respect to the crack plane and so the energy release rate components associated with each of the modes vary with crack orientation. The variation, of these energy release rate components with the crack orientation with respect to orthotropic axes, is analyzed in this paper. Results indicate that in addition to the orthotropic planes there exists other planes with reference to which fracture modes are uncoupled.

Thermodynamics of ligand (substrate end product) binding to endoxylanase from Chainia sp. (NCL-82-5-1): isothermal calorimetry and fluorescence titration studies

The binding of xylo-oligosaccharides to Chainia endoxylanase resulted in a decrease in fluorescence intensity of the enzyme with the formation of 1:1 complex. Equilibrium and thermodynamic parameters of ligand binding were determined by fluorescence titrations and titration calorimetry. The affinity of xylanase for the oligosaccharides increases in the order X-2 < X-3 < X-4 less than or equal to X-5. Contributions from the enthalpy towards the free energy change decreased with increasing chain length from X-2 to X-4, whereas an increase in entropy was observed, the change in enthalpy and entropy of binding being compensatory. The entropically driven binding process suggested that hydrophobic interactions as well as hydrogen bonds play a predominant role in ligand binding.

Pt metal-CeO2 interaction: Direct observation of redox coupling between Pt-0/Pt2+/Pt4+ and Ce4+/Ce3+ states in Ce0.98Pt0.02O2-delta catalyst by a combined electrochemical and x-ray photoelectron spectroscopy study

Pt ions-CeO2 interaction in Ce1-xPtxO2-delta (x=0.02) has been studied for the first time by electrochemical method combined with x-ray diffraction and x-ray photoelectron spectroscopy. Working electrodes made of CeO2 and Ce0.98Pt0.02O2-delta mixed with 30% carbon are treated electrochemically between 0.0-1.2 V in potentiostatic (chronoamperometry) and potentiodynamic (cyclic voltametry) mode with reference to saturated calomel electrode. Reversible oxidation of Pt-0 to Pt2+ and Pt4+ state due to the applied positive potential is coupled to simultaneous reversible reduction of Ce4+ to Ce3+ state. CeO2 reduces to CeO2-y (y=0.35) after applying 1.2 V, which is not reversible; Ce0.98Pt0.02O2-delta reaches a steady state with Pt2+:Pt4+ in the ratio of 0.60:0.40 and Ce4+:Ce3+ in the ratio of 0.55:0.45 giving a composition Ce0.98Pt0.02O1.74 at 1.2 V, which is reversible. Composition of Pt ion substituted compound is reversible between Ce0.98Pt0.02O1.95 to Ce0.98Pt0.02O1.74 within the potential range of 0.0-1.2 V. Thus, Ce0.98Pt0.02O2-delta forms a stable electrode for oxidation of H2O to O-2 unlike CeO2. A linear relation between oxidation of Pt2+ to Pt4+ with simultaneous reduction in Ce4+ to Ce3+ is observed demonstrating Pt-CeO2 metal support interaction is due to reversible Pt-0/Pt2+/Pt4+ interaction with Ce4+/Ce3+ redox couple.

Resistance Noise in Electrically Biased Bilayer Graphene

We demonstrate that the low-frequency resistance uctuations, or noise, in bilayer graphene is strongly connected to its band structure, and displays a minimum when the gap between the conduction and valence band is zero. Using double-gated bilayer graphene devices we have tuned the zero gap and charge neutrality points independently, which oers a versatile mechanism to investigate the low-energy band structure, charge localization and screening properties of bilayer graphene.