Gd1.96-xYxEu0.04O3 (x=0.0, 0.49, 0.98, 1.47, 1.96 mol%) nanophosphors: Propellant combustion synthesis, structural and luminescence studies

Gd1.96-xYxEu0.04O3 (x = 0.0, 0.49, 0.98, 1.47, 1.96 mol%) nanophosphors were synthesized by propellant combustion method at low temperature (400 degrees C). The powder X-ray diffraction patterns of as formed Gd1.96Eu0.04O3 showed monoclinic phase, however with the addition of yttria it transforms from monoclinic to pure cubic phase. The porous nature increases with increase of yttria content. The particle size was estimated from Scherrer's and W-H plots which was found to be in the range 30-40 nm. These results were in well agreement with transmission electron microscopy studies. The optical band gap energies estimated were found to be in the range 5.32-5.49 eV. PL emission was recorded under 305 nm excitation show an intense emission peak at 611 nm along with other emission peaks at 582, 641 nm. These emission peaks were attributed to the transition of D-5(0) —> F-7(J) (J = 0, 1, 2, 3) of Eu3+ ions. It was observed that PL intensity increases with increase of Y content up to x = 0.98 and thereafter intensity decreases. CIE color co-ordinates indicates that at x = 1.47 an intense red bright color can be achieved, which could find a promising application in flat panel displays. The cubic and monoclinic phases show different thermoluminescence glow peak values measured under identical conditions. The response of the cubic phase to the applied dose showed good linearity, negligible fading, and simple glow curve structure than monoclinic phase indicating that suitability of this phosphor in dosimetric applications. (C) 2014 Elsevier B.V. All rights reserved.

Assessing GCM Convergence for India Using the Variable Convergence Score

General circulation models (GCMs) use transient climate simulations to predict climate conditions in the future. Coarse-grid resolutions and process uncertainties necessitate the use of downscaling models to simulate precipitation. However, in the downscaling models, with multiple GCMs now available, selecting an atmospheric variable from a particular model which is representative of the ensemble mean becomes an important consideration. The variable convergence score (VCS) provides a simple yet meaningful approach to address this issue, providing a mechanism to evaluate variables against each other with respect to the stability they exhibit in future climate simulations. In this study, VCS methodology is applied to 10 atmospheric variables of particular interest in downscaling precipitation over India and also on a regional basis. The nested bias-correction methodology is used to remove the systematic biases in the GCMs simulations, and a single VCS curve is developed for the entire country. The generated VCS curve is expected to assist in quantifying the variable performance across different GCMs, thus reducing the uncertainty in climate impact-assessment studies. The results indicate higher consistency across GCMs for pressure and temperature, and lower consistency for precipitation and related variables. Regional assessments, while broadly consistent with the overall results, indicate low convergence in atmospheric attributes for the Northeastern parts of India.

Effect of Input Source Energy on SASW Evaluation of Cement Concrete Pavement

A series of spectral analyses of surface waves (SASW) tests were conducted on a cement concrete pavement by dropping steel balls of four different values of diameter (D) varying between 25.4 and 76.2 mm. These tests were performed (1) by using different combinations of source to nearest receiver distance (S) and receiver spacing (X), and (2) for two different heights (H) of fall, namely, 0.25 and 0.50 m. The values of the maximum wavelength (lambda(max)) and minimum wavelength (lambda(min)) associated with the combined dispersion curve, corresponding to a particular combination of D and H, were noted to increase almost linearly with an increase in the magnitude of the input source energy (E). A continuous increase in strength and duration of the signals was noted to occur with an increase in the magnitude of D. Based on statistical analysis, two regression equations have been proposed to determine lambda(max) and lambda(min) for different values of source energy. It is concluded that the SASW technique is capable of producing nearly a unique dispersion curve irrespective of (1) diameters and heights of fall of the dropping masses used for producing the vibration, and (2) the spacing between different receivers. The results presented in this paper can be used to provide guidelines for deciding about the input source energy based on the required exploration zone of the pavement. (C) 2014 American Society of Civil Engineers.

Life Estimation of Electrothermally Stressed Epoxy Nanocomposites

Accelerated electrothermal aging tests were conducted at a constant temperature of 60 degrees C and at different stress levels of 6 kV/mm, 7 kV/mm and 8 kV/mm on unfilled epoxy and epoxy filled with 5 wt% of nano alumina. The leakage current through the samples were continuously monitored and the variation in tan delta values with aging duration was monitored to predict the impending failure and the time to failure of the samples. It is observed that the time to failure of epoxy alumina nanocomposite samples is significantly higher as compared to the unfilled epoxy. Data from the experiments has been analyzed graphically by plotting the Weibull probability and theoretically by the linear least square regression analysis. The characteristic life obtained from the least square regression analysis has been used to plot the inverse power law curve. From the inverse power law curve, the life of the epoxy insulation with and without nanofiller loading at a stress level of 3 kV/mm, i.e. within the midrange of the design stress level of rotating machine insulation, has been obtained by extrapolation. It is observed that the life of epoxy alumina nanocomposite of 5 wt% filler loading is nine times higher than that of the unfilled epoxy.

Propensity to Form Amyloid Fibrils Is Encoded as Excitations in the Free Energy Landscape of Monomeric Proteins

Protein aggregation, linked to many of diseases, is initiated when monomers access rogue conformations that are poised to form amyloid fibrils. We show, using simulations of src SH3 domain, that mechanical force enhances the population of the aggregation-prone (N*) states, which are rarely populated under force free native conditions but are encoded in the spectrum of native fluctuations. The folding phase diagrams of SH3 as a function of denaturant concentration (C]), mechanical force (f), and temperature exhibit an apparent two-state behavior, without revealing the presence of the elusive N* states. Interestingly, the phase boundaries separating the folded and unfolded states at all C] and f fall on a master curve, which can be quantitatively described using an analogy to superconductors in a magnetic field. The free energy profiles as a function of the molecular extension (R), which are accessible in pulling experiments, (R), reveal the presence of a native-like N* with a disordered solvent-exposed amino-terminal beta-strand. The structure of the N* state is identical with that found in Fyn SH3 by NMR dispersion experiments. We show that the timescale for fibril formation can be estimated from the population of the N* state, determined by the free energy gap separating the native structure and the N* state, a finding that can be used to assess fibril forming tendencies of proteins. The structures of the N* state are used to show that oligomer formation and likely route to fibrils occur by a domain-swap mechanism in SH3 domain. (C) 2014 Elsevier Ltd. All rights reserved.

Crack stability in edge-notched clamped beam specimens: modeling and experiments

Stability of a fracture toughness testing geometry is important to determine the crack trajectory and R-curve behavior of the specimen. Few configurations provide for inherent geometric stability, especially when the specimen being tested is brittle. We propose a new geometrical construction called the single edge notched clamped bend specimen (SENCB), a modified form of three point bending, yielding stable cracking under load control. It is shown to be particularly suitable for small-scale structures which cannot be made free-standing, (e.g., thin films, coatings). The SENCB is elastically clamped at the two ends to its parent material. A notch is inserted at the bottom center and loaded in bending, to fracture. Numerical simulations are carried out through extended finite element method to derive the geometrical factor f(a/W) and for different beam dimensions. Experimental corroborations of the FEM results are carried out on both micro-scale and macro-scale brittle specimens. A plot of vs a/W, is shown to rise initially and fall off, beyond a critical a/W ratio. The difference between conventional SENB and SENCB is highlighted in terms of and FEM simulated stress contours across the beam cross-section. The `s of bulk NiAl and Si determined experimentally are shown to match closely with literature values. Crack stability and R-curve effect is demonstrated in a PtNiAl bond coat sample and compared with predicted crack trajectories from the simulations. The stability of SENCB is shown for a critical range of a/W ratios, proving that it can be used to get controlled crack growth even in brittle samples under load control.

Substitution-Modulated Anticancer Activity of Half-Sandwich Ruthenium(II) Complexes with Heterocyclic Ancillary Ligands

Ten new organometallic half-sandwich ruthenium complexes with heterocyclic ligands have been synthesized (H1-H10). The substituents on the ancillary heterocyclic ligands were varied to understand the effect of substitution on anticancer activity. The crystallographic characterization of five complexes confirms that they adopt three-legged piano-stool structures and are stabilized by intramolecular hydrogen bonding. Complexes H2 and H3 also exhibit halogen bonding in the solid state. In aqueous media, the complexes form dinuclear ruthenium species. Complex H1 with a noncytotoxic heterocycle, 6-fluoro-2-mercaptobenzothiazole, and complex H11 with the unsubstituted 2-mercaptobenzothiazole are the most active against A2780 and KB cell lines. The substitution of the H atoms on the ancillary ligand with Cl or Br atoms leads to a decrease in the anticancer activity. With the exception of fluorine-substituted H5, the complexes with mercaptobenzoxazole (H6-H9) are inactive against all of the tested cell lines. Ruthenium complexes with mercaptonaphthimidazole (H10) and mercaptobenzimidazole (H13) do not show any anticancer activity. The active complexes show a biphasic melting curve when incubated with calf thymus (CT) DNA. These complexes only inhibit thioredoxin reductase (TrxR) enzyme activity to a small extent. The substitution of hydrogen atoms with fluorine atoms in the aromatic heterocyclic ligands on organometallic half-sandwich ruthenium complexes has the most beneficial effect on their anticancer activity.

Regimes of nonlinear depletion and regularity in the 3D Navier-Stokes equations

The periodic 3D Navier-Stokes equations are analyzed in terms of dimensionless, scaled, L-2m-norms of vorticity D-m (1 <= m <= infinity). The first in this hierarchy, D-1, is the global enstrophy. Three regimes naturally occur in the D-1-D-m plane. Solutions in the first regime, which lie between two concave curves, are shown to be regular, owing to strong nonlinear depletion. Moreover, numerical experiments have suggested, so far, that all dynamics lie in this heavily depleted regime 1]; new numerical evidence for this is presented. Estimates for the dimension of a global attractor and a corresponding inertial range are given for this regime. However, two more regimes can theoretically exist. In the second, which lies between the upper concave curve and a line, the depletion is insufficient to regularize solutions, so no more than Leray's weak solutions exist. In the third, which lies above this line, solutions are regular, but correspond to extreme initial conditions. The paper ends with a discussion on the possibility of transition between these regimes.

Magnetization-steps in Y2CoMnO6 double perovskite: The role of antisite disorder

Antisite disorder is observed to have significant impact on the magnetic properties of the double perovskite Y2CoMnO6 which has been recently identified as a multiferroic. A paramagnetic-ferromagnetic phase transition occurs in this material at T-c approximate to 75 K. At 2K, it displays a strong ferromagnetic hysteresis with a significant coercive field of H-c approximate to 15 kOe. Sharp steps are observed in the hysteresis curves recorded below 8K. In the temperature range 2K <= T <= 5K, the hysteresis loops are anomalous as the virgin curve lies outside the main loop. The field-cooling conditions as well as the rate of field-sweep are found to influence the steps. Quantitative analysis of the neutron diffraction data shows that at room temperature, Y2CoMnO6 consists of 62% of monoclinic P2(1)/n with nearly 70% antisite disorder and 38% Pnma. The bond valence sums indicate the presence of other valence states for Co and Mn which arise from disorder. We explain the origin of steps by using a model for pinning of magnetization at the antiphase boundaries created by antisite disorder. The steps in magnetization closely resemble the martensitic transformations found in intermetallics and display first-order characteristics as revealed in the Arrott's plots. (C) 2014 AIP Publishing LLC.

Influence of curvature on the device physics of thin film transistors on flexible substrates

Thin film transistors (TFTs) on elastomers promise flexible electronics with stretching and bending. Recently, there have been several experimental studies reporting the behavior of TFTs under bending and buckling. In the presence of stress, the insulator capacitance is influenced due to two reasons. The first is the variation in insulator thickness depending on the Poisson ratio and strain. The second is the geometric influence of the curvature of the insulator-semiconductor interface during bending or buckling. This paper models the role of curvature on TFT performance and brings to light an elegant result wherein the TFT characteristics is dependent on the area under the capacitance-distance curve. The paper compares models with simulations and explains several experimental findings reported in literature. (C) 2014 AIP Publishing LLC.

Surrogate Regret Bounds for Bipartite Ranking via Strongly Proper Losses

The problem of bipartite ranking, where instances are labeled positive or negative and the goal is to learn a scoring function that minimizes the probability of mis-ranking a pair of positive and negative instances (or equivalently, that maximizes the area under the ROC curve), has been widely studied in recent years. A dominant theoretical and algorithmic framework for the problem has been to reduce bipartite ranking to pairwise classification; in particular, it is well known that the bipartite ranking regret can be formulated as a pairwise classification regret, which in turn can be upper bounded using usual regret bounds for classification problems. Recently, Kotlowski et al. (2011) showed regret bounds for bipartite ranking in terms of the regret associated with balanced versions of the standard (non-pairwise) logistic and exponential losses. In this paper, we show that such (non-pairwise) surrogate regret bounds for bipartite ranking can be obtained in terms of a broad class of proper (composite) losses that we term as strongly proper. Our proof technique is much simpler than that of Kotlowski et al. (2011), and relies on properties of proper (composite) losses as elucidated recently by Reid and Williamson (2010, 2011) and others. Our result yields explicit surrogate bounds (with no hidden balancing terms) in terms of a variety of strongly proper losses, including for example logistic, exponential, squared and squared hinge losses as special cases. An important consequence is that standard algorithms minimizing a (non-pairwise) strongly proper loss, such as logistic regression and boosting algorithms (assuming a universal function class and appropriate regularization), are in fact consistent for bipartite ranking; moreover, our results allow us to quantify the bipartite ranking regret in terms of the corresponding surrogate regret. We also obtain tighter surrogate bounds under certain low-noise conditions via a recent result of Clemencon and Robbiano (2011).

Identifying functionally important cis-peptide containing segments in proteins and their utility in molecular function annotation

Cis-peptide embedded segments are rare in proteins but often highlight their important role in molecular function when they do occur. The high evolutionary conservation of these segments illustrates this observation almost universally, although no attempt has been made to systematically use this information for the purpose of function annotation. In the present study, we demonstrate how geometric clustering and level-specific Gene Ontology molecular-function terms (also known as annotations) can be used in a statistically significant manner to identify cis-embedded segments in a protein linked to its molecular function. The present study identifies novel cis-peptide fragments, which are subsequently used for fragment-based function annotation. Annotation recall benchmarks interpreted using the receiver-operator characteristic plot returned an area-under-curve >0.9, corroborating the utility of the annotation method. In addition, we identified cis-peptide fragments occurring in conjunction with functionally important trans-peptide fragments, providing additional insights into molecular function. We further illustrate the applicability of our method in function annotation where homology-based annotation transfer is not possible. The findings of the present study add to the repertoire of function annotation approaches and also facilitate engineering, design and allied studies around the cis-peptide neighborhood of proteins.

Role of interface curvature on stress distribution under indentation for ZrN/Zr multilayer coating

Contact damage in curved interface nano-layeredmetal/nitride (150 (ZrN)/10 (Zr) nm) multilayer is investigated in order to understand the role of interface morphology on contact damage under indentation. A finite element method (FEM) model was formulated with different wavelengths of 1000 nm, 500 nm, 250 nm and common height of 50 nm, which gives insight on the effect of different curvature on stress field generated under indentation. Elastic-plastic properties were assigned to the metal layer and substrate while the nitride layer was assigned perfectly elastic properties. Curved interface multilayers show delamination along the metal/nitride interface and vertical cracks emanating from the ends of the delamination. FEM revealed the presence of tensile stress normal to the interface even under the contact, along with tensile radial stresses, both present at the valley part of the curve, which leads to vertical cracks associated with interfacial delamination. Stress enhancement was seen to be relatively insensitive to curvature. (C) 2014 Elsevier B.V. All rights reserved.

Improved tuning of the extended concentric tube resonator for wide-band transmission loss

Transmission loss (TL) of a simple expansion chamber (SEC) consists of periodic domes with sharp troughs. This limits practical application of the SEC in the variable-speed automobile exhaust systems. Three-fourths of the troughs of the SEC can be lifted by appropriate tuning of the extended inlet/outlet lengths. However, such mufflers suffer from high back pressure and generation of aerodynamic noise due to free shear layers at the area discontinuities. Therefore, a perforate bridge is made between the extended inlet and outlet. It is shown that the TL curve of a concentric tube resonator (CTR) can also be lifted in a similar way by proper tuning of the extended unperforated lengths. Differential lengths have to be used to correct the inlet/outlet lengths in order to account for the perforate inertance. The resonance peak frequencies calculated by means of the 1-D analysis are compared with those of the 3-D FEM, and appropriate differential lengths are calculated. It is shown how different geometric characteristics of the muffler and mean flow affect the differential lengths. A general correlation is obtained for the differential lengths by considering seven relevant geometric and environmental parameters in a comprehensive parametric study. The resulting expressions would help in design of extended-tube CTR for wide-band TL. (C) 2014 Institute of Noise Control Engineering.

Open loop Model for WDM Links

Wavelength Division Multiplexing (WDM) techniques overfibrelinks helps to exploit the high bandwidth capacity of single mode fibres. A typical WDM link consisting of laser source, multiplexer/demultiplexer, amplifier and detectoris considered for obtaining the open loop gain model of the link. The methodology used here is to obtain individual component models using mathematical and different curve fitting techniques. These individual models are then combined to obtain the WDM link model. The objective is to deduce a single variable model for the WDM link in terms of input current to system. Thus it provides a black box solution for a link. The Root Mean Square Error (RMSE) associated with each of the approximated models is given for comparison. This will help the designer to select the suitable WDM link model during a complex link design.