A quaternary lead based perovskite structured materials with diffuse phase transition behavior

A lead based quaternary compound composed of 0.25(PbZr_0.52Ti_0.48O₃) + 0.25(PbFe_0.5Ta_0.5O₃) + 0.25 (PbF_0.67W_0.33O₃) + 0.25(PbFe_0.5Nb_0.5O₃) - (PZT-PFT-PFW-PFN) was synthesized by conventional solid-state reaction techniques. It showed moderate high dielectric constant, low dielectric loss, and two diffuse phase transitions, one below the room temperature ∼261 K and other above ∼410 K. X-ray diffraction (XRD) patterns revealed a tetragonal crystal structure at room temperature where as scanning electron micrograph (SEM) indicates inhomogeneous surface with an average grain size of 500 nm-3 μm. Well saturated ferroelectric hysteresis loops with good saturation polarization (spontaneous polarization, P_s ∼ 30.68 μC/cm²) were observed. Temperature-dependent ac conductivity displayed low conductivity with kink in spectra near the phase transition. In continuing search for developing new ferroelectric materials, in the present study we report stoichiometric compositions of complex perovskite ceramic materials: (PZT-PFT-PFW-PFN) with diffuse phase transition behavior. The crystal structure, dielectric properties, and ferroelectric properties were characterized by XRD, SEM, dielectric spectroscopy, and polarization. 1/? versus (T) plots revealed diffuse relaxor phase transition (DPT) behavior. The compositional variation on the phase transition temperature, dielectric constant, and ferroelectric to paraelectric phase transitions are discussed.     

Curcumin Prevents Cerebellar Hypoplasia and Restores the Behavior in Hyperbilirubinemic Gunn Rat by a Pleiotropic Effect on the Molecular Effectors of Brain Damage

Bilirubin toxicity to the central nervous system (CNS) is responsible for severe and permanent neurologic damage, resulting in hearing loss, cognitive, and movement impairment. Timely and effective management of severe neonatal hyperbilirubinemia by phototherapy or exchange transfusion is crucial for avoiding permanent neurological consequences, but these therapies are not always possible, particularly in low-income countries. To explore alternative options, we investigated a pharmaceutical approach focused on protecting the CNS from pigment toxicity, independently from serum bilirubin level. To this goal, we tested the ability of curcumin, a nutraceutical already used with relevant results in animal models as well as in clinics in other diseases, in the Gunn rat, the spontaneous model of neonatal hyperbilirubinemia. Curcumin treatment fully abolished the landmark cerebellar hypoplasia of Gunn rat, restoring the histological features, and reverting the behavioral abnormalities present in the hyperbilirubinemic rat. The protection was mediated by a multi-target action on the main bilirubin-induced pathological mechanism ongoing CNS damage (inflammation, redox imbalance, and glutamate neurotoxicity). If confirmed by independent studies, the result suggests the potential of curcumin as an alternative/complementary approach to bilirubin-induced brain damage in the clinical scenario.     

Rehabilitation and field testing of an FRP bridge deck on a truss bridge

A light-weight FRP deck was used, on an experimental basis, to replace a heavy deteriorated concrete deck improving the load rating of a 60-year old truss bridge located in Wellsburg, New York. This was the first such application in New York State. Load testing was conducted after installation of the FRP deck to study its behavior. Results indicated the conservative nature of the deck design, and no composite action between the deck and the superstructure. The study also shows that the joints are only partially effective in load transfer between panels.     

Modeling the dynamics of the mixed layer in solar ponds

A new model is proposed to explain the Nielsen's equilibrium condition. This model takes into account the effects of both turbulent entrainment and diffusion on the growth/erosion of the gradient zone. The existing turbulent entrainment model is modified to make it applicable near the equilibrium condition. The new model predictions indicate the dependence of the equilibrium condition on the mixed layer depth, apart from the salinity and temperature gradients in the gradient zone.     

Effects of nitrogen doping on the growth and properties of plasma-enhanced chemical-vapor-deposited diamond-like-carbon films

Nitrogen-doped diamond-like carbon (DLC) or amorphous hydrogenated carbon (a-C:H) films were grown by plasma enhanced chemical vapor deposition using methane and nitrogen gases as precursors. The effects of nitrogen trifluoride (NF₃) on these nitrogen-doped DLC films were also investigated. The deposition rate decreases sharply with the addition of nitrogen in the absence of NFF₃ due to dilution, while it increases in the presence of NFF₃ due, presumably, to the reduction of activated hydrogen species by the fluorine radical (F϶. X-ray photoelectron spectra reveal a nitrogen concentration in the range of 9.3 to 13.8% in these DLC films with a C Is electron binding energy of 287-288 eV, indicating the diamond-like structure. Infrared spectra of DLC films indicate the presence of amino groups (N-H) and nitrile and/or isonitrile (C= N) groups giving strong evidence of sp carbon. Diamond like carbon films deposited in CHF₄ +NF₄ (with and without NFF₃) have a lower refractive index, a lower bulk resistivity, and a lower optical bandgap than films deposited using CHF₄ due to a lower hydrogen content in the films. Moreover, the bulk resistivity of these films decreases by over four orders of magnitude and the optical bandgap decreases from 2.65 eV to about 0.75 eV following annealing at a temperature of 500°C.     

On Petri net models of infinite state supervisors

A class of supervisory control problems that require infinite state supervisors is considered, and Petri nets with inhibitor arcs (PNs) are introduced to model the supervisors. This PN-based approach to supervisory control is compared to automata-based approaches. The primary advantage of a PN-based supervisory controller is that it provides a finite representation of an infinite state supervisor. For verification, implementation, and testing reasons, a finite PN-based representation of an infinite state supervisor is preferred over an automata-based supervisor. It is shown that this modeling advantage is accompanied by a decision disadvantage, in that in general the controllability of a language that can be generated by the closed-loop system is undecidable     

Dielectric and pyroelectric properties of triglycine sulphate-polystyrene composites

A composite of Triglycine sulphate (TGS) and polystyrene has been fabricated by mixing different particle size TGS powders (75 μm to 400 μm) and polystyrene solution. The dielectric constant has been measured in the frequency range 0.1 to 100 KHz, and the pyroelectric current measurements were made by the Byer and Roundy direct method. Specific heat of the composite was determined by the differential them analysis (DTA) technique.

Particle size dependance of dielectric constant, pyroelectric coefficient and responsivity have been studied. Anomalies in ε' and P_y were observed even in the composite with the lowest particle size of TGS (75 μm). The surface effects have much greater influence on electrical properties but thermal properties are, not affected. This is indicated by a decrease in ε' and P^y with decreasing particle size of TGS, while specific heat of composite is almost independent of particle size.     

Suppression of buried oxide induced variability on digital performance of GeOI pMOSFETs using substrate bias scheme

Random variation in buried oxide thickness strongly affects the digital performance of ultra-thin body germanium-on-insulator MOSFETs. Dependencies of threshold voltage, ON-current, OFF-current and subthreshold slope of ultra-thin body germanium-on-insulator MOSFETs on three different BOX dielectrics are examined by employing well-calibrated Synopsys TCAD. The variation of threshold voltage and ON-current becomes less sensitive with high-k BOX dielectrics whereas smaller variation of OFF-current is observed for the device with low-k BOX dielectrics. The subthreshold slope remains almost unaltered for all BOX dielectrics. Furthermore, a positive substrate bias is found to suppress variability of digital performance parameters of GeOI p-MOSFETs.

     

Parallel Simulated Annealing Algorithms

Simulated annealing (SA) has been considered a good tool for complex nonlinear optimization problems. The technique has been widely applied to a variety of problems. However, a major disadvantage of the technique is that it is extremely slow and hence not suitable for complex optimization problems such as scheduling. There are many attempts to develop parallel versions of the algorithm. Many of these algorithms are problem dependent in nature. We present, in this paper, two general algorithms for SA. The algorithms have been applied to job shop scheduling problem (JSS) and the traveling salesman problem (TSP) and it has been observed that it is possible to achieve superlinear speedups using the algorithm.     

Optimum short-time polynomial regression for signal analysis

Sādhanā - We propose a short-time polynomial regression (STPR) for time-varying signal analysis. The advantage of using polynomials is that the notion of a spectrum is not needed and the...