Luminomagnetic Nd3+ doped fluorapatite coated Fe3O4 nanostructures for biomedical applications

Luminomagnetic nanostructured Nd³⁺ doped fluorapatite (FAP) coated Fe₃O₄ nanoparticles were produced by hydrothermal method. X-ray diffraction analysis indicates that the prepared nanoparticles contain both FAP and Fe₃O₄ phases. Electron microscope analysis shows the formation of nanoparticles of Fe₃O₄ encased in rod shaped FAP nanoparticles of average length 40 nm. Magnetic measurements confirm the room temperature superparamagnetic nature of the nanoparticles with saturation magnetization value up to 7.8 emu/g. The prepared nanoparticles display strong near infrared (NIR) emission at 1060 nm under 800 nm excitation. Cell viability studies for 72 hour demonstrate the survival rate of over 84% with 500 μg/mL concentration indicating the good cytocompatibility of the prepared materials. The present Nd³⁺ doped FAP coated Fe₃O₄ nanostructure provides an excellent multifunctional platform for diagnostics and therapeutic applications.     

LI-BIST: A Low-Cost Self-Test Scheme for SoC Logic Cores and Interconnects

For system-on-chips (SoC) using deep submicron (DSM) technologies, interconnects are becoming critical determinants for performance, reliability and power. Buses and long interconnects being susceptible to crosstalk noise, may lead to functional and timing failures. Existing at-speed interconnect crosstalk test methods propose inserting dedicated interconnect self-test structures in the SoC to generate vectors which have high crosstalk defect coverage. However, these methods may have a prohibitively high area overhead. To reduce this overhead, existing logic BIST structures like LFSRs could be reused to deliver interconnect tests. But, as shown by our experiments, use of LFSR tests achieve poor crosstalk defect coverage. Additionally, it has been shown that the power consumed during testing can potentially become a significant concern.In this paper, we present Logic-Interconnect BIST (LI-BIST), a comprehensive self-test solution for both the logic of the cores and the SoC interconnects. LI-BIST reuses existing logic BIST structures but generates high-quality tests for interconnect crosstalk defects, while minimizing the area overhead and interconnect power consumption. The application of the LI-BIST methodology on example SoCs indicates that LI-BIST is a viable, low-cost, yet comprehensive solution for testing SoCs.     

Chaos in mechanical systems — A review

In this paper, a review of the various developments in the field of chaotic dynamics with specific emphasis on chaos in structural and mechanical systems is presented. The paper discusses some known chaotic systems such as the Lorenz, Rössler, Ueda and Henon attractors as well as chaos in Duffing and Van der Pol oscillators. The paper also covers chaos in piecewise linear systems, impacting oscillators and flow induced vibrating systems. Topics such as bifurcations and routes to chaos, different ways of characterising chaos, domains of attraction and control of chaos are also discussed.     

High-sensitivity humidity sensor based on SnO2 nanoparticles synthesized by microwave irradiation method

Tin oxide hexagonal-shaped nanodiscs (SnO) and spherical nanoparticles (SnO₂) have been prepared by using a simple household microwave irradiation method with an operating frequency of 2.45 GHz. This technique permits us to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystallite size was evaluated from powder X-ray diffraction (XRD) studies and was in the 20 to 25 nm range. Transmission electron microscopy (TEM) analysis showed that the as prepared SnO form as hexagonal-shaped nanodiscs and upon subsequent annealing at 500 °C for 5 h in air, the SnO gets converted to spherical-shaped nanoparticles of SnO₂. The SnO₂ sample shows good sensitivity towards the relative humidity. The calculated response and recovery time were found to be 32 s and 25 s respectively. These results indicate promising applications of SnO₂ nanoparticles in a highly sensitive environmental monitoring and humidity controlled electronic devices. The samples were further subjected to thermal analyses (TG–DTA) and UV–VIS diffusion reflectance spectroscopy (DRS) studies.     

The influence of surface morphology of TiO2 coating on the performance of dye-sensitized solar cells

The optimization of solar energy conversion efficiency of dye-sensitized solar cells (DSSCs) was investigated by the tuning of TiO₂ photoelectrode's surface morphology. Double-layered TiO₂ photoelectrodes with four different structures were designed by the coating of TiO₂ suspension, incorporated with low and high molecular weight poly(ethylene glycol) as a binder. Among these four systems, P2P1, where P1 and P2 correspond to the molecular weight of 20,000 and 200,000, respectively, showed the highest efficiency under the conditions of identical film thickness and constant irradiation. This can be explained by the larger pore size and higher surface area of P2P1 TiO₂ electrode than the other materials as revealed by scanning electron microscopic (SEM) and Brunauer–Emmett–Teller (BET) analyses. Electrochemical Impedance Spectroscopy (EIS) analysis shows that P2P1 formulation displayed a smaller resistance than the others at the TiO₂/electrolyte interface. The best efficiency (η) of 9.04% with the short-circuit photocurrent density (J_sc) and open-circuit voltage (V_oc) of 18.9 mA/cm² and 0.74 V, respectively, was obtained for a solar cell by introducing the light-scattering particles to the TiO₂ nanoparticles matrix coated on FTO electrode having the sheet resistivity of 8 Ω/sq.     

Growth and Characterization of C60 Crystals from Pure C60 and Fullerite

Good quality C₆₀ crystals have been grown from high purity C₆₀ powder and fullerene mixture (C₆₀/C₇₀) by vacuum sublimation method. The grown crystals were characterized with Optical microscopy, SEM, powder XRD, High Performance Liquid Chromatography and Raman spectroscopic analyses.     

Antilipolytic actions of vanadate and insulin in rat adipocytes mediated by distinctly different mechanisms

Vanadate, which mimics the biological effects of insulin, also inhibits lipolysis in rat adipocytes. Here we demonstrate that the antilipolytic effect of vanadate differs from that of insulin at least by the five following criteria: 1) vanadate inhibits lipolysis mediated by high (supraphysiological) concentrations of catecholamines; 2) vanadate antagonizes (Bu)2cAMP-mediated lipolysis; 3) vanadate antagonizes isobutylmethylxanthine-dependent lipolysis, 4) vanadate inhibits lipolysis mediated by okadaic acid; and 5) wortmannin, which blocks the antilipolytic effect of insulin, fails to block vanadate-mediated antilipolysis. Vanadate does activate phosphoinositol 3-kinase, and wortmannin blocks this activation. Our working hypothesis assumes that all of the insulin-like effects of vanadate, including antilipolysis, are initiated by the inhibition of protein phosphotyrosine phosphatases (PTPases). Among documented PTPase inhibitors we found that VOSO4 (oxidation state +4), several organic vanadyl compounds (+4), zinc (Zn2+), tungstate (W), and molybdate (Mo) also had antilipolytic activity. The order of potency was vanadyl acetylacetonate > or = VOSO4 > or = NaVO3 > or = vanadyl-dipicolinate > Zn2+ > W > Mo, and it correlated better with the inhibition of adipose membranal-PTPases in cell-free experiments. We have concluded that the antilipolytic effect of vanadate is 1) mechanistically distinct from that of insulin, 2) independent of phosphoinositol 3-kinase activation, and 3) independent of the lipolytic cascade. We also strongly suggest that the antilipolytic effect of vanadate emanates from inhibiting adipose membranal, rather than cytosolic PTPases, and present preliminary data showing distinct differences in catalysis between these two PTPase categories. Overall, the study indicates that antilipolysis can be manifested via alternative, insulin-independent, signal-transducing pathways.     

Convex cost functions in blind equalization

Existing blind adaptive equalizers that use nonconvex cost functions and stochastic gradient descent suffer from lack of global convergence to an equalizer setup that removes sufficient ISI when an FIR equalizer is used. The authors impose convexity on the cost function and anchoring of the equalizer away from the all-zero setup. They establish that there exists a globally convergent blind equalization strategy for 1D pulse amplitude modulation (PAM) systems with bounded input data (discrete or continuous) even when the equalizer is truncated. The resulting cost function is a constrained l₁ norm of the joint impulse response of the channel and the equalizer. The results apply to arbitrary linear channels (provided there are no unit circle zeros) and apply regardless of the initial ISI (that is whether the eye is initially open or closed). They also show a globally convergent stochastic gradient scheme based on an implementable approximation of the l₁ cost function     

Influences of different TiO2 morphologies and solvents on the photovoltaic performance of dye-sensitized solar cells

The effects of TiO₂ photoelectrode's surface morphology and different solvents on the photovoltaic performance of dye-sensitized solar cells (DSSCs) were studied. By successive coating of TiO₂ suspension, composed of low and high molecular weight poly(ethylene)glycol (PEG) as a binder, double layered TiO₂ photoelectrodes with four different structures were obtained. Among the DSSCs with different TiO₂ electrodes, DSSC with P2P1 electrode (P2 and P1 correspond to PEG molecular weights of 20,000 and 200,000, respectively) showed higher performance under identical film thickness at a constant irradiation of 100 mW cm⁻², which may be correlated with large pore size and high surface area of the corresponding TiO₂ electrode. This was confirmed by electrochemical impedance spectroscopy (EIS) analysis of the DSSC and the transient photovoltage measurement of electrons in the TiO₂ electrode. Among the different solvents investigated here, the DSSC containing acetonitrile showed high conversion efficiency and the order of performance of the DSSCs with different solvents were AN > MPN > PC > GBL > DMA > DMF > DMSO. Better correlation was observed between the donor number of solvents and photoelectrochemical parameters of the DSSCs containing different solvents rather than the measured viscosity and dielectric constant of solvents. The reasons for the low performance of the DSSCs containing DMA, DMSO and DMF, respectively, were due to the negative shift of TiO₂ conduction band and the desorption of dye molecules from the TiO₂ photoelectrode by those solvents.