Kinetics of adsorption of methylene blue and rhodamine 6G on acrylic acid-based superabsorbents

Superabsorbent polymers (SAPs) of acrylic acid, sodium acrylate, and acrylamide (AM), crosslinked with ethylene glycol dimethacrylate, were synthesized by inverse suspension polymerization. The equilibrium swelling capacities of the SAPs were determined and these decreased with increasing AM content. The adsorption of the two cationic dyes, methylene blue and rhodamine 6G, on the dry as well as equilibrium swollen SAPs was investigated. The amount of the dye adsorbed at equilibrium per unit weight of the SAPs and the rate constants of adsorption were determined. The amount of the dye adsorbed at equilibrium by the SAPs decreased with increasing mol % of AM in the SAPs. The amount of the dye adsorbed at equilibrium was almost equal for the dry and equilibrium swollen SAPs. However, the equilibrium swollen SAPs adsorbed dyes at a higher rate than the dry SAPs. The higher rate of adsorption was attributed to the availability of all the anionic groups present in the fully elongated conformation of the SAPs in the equilibrium swollen state. The effect of initial dye concentration on the adsorption was also investigated and the adsorption was described by Langmuir adsorption isotherms. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Extracting Three Dimensional Surface Model of Human Kidney from the Visible Human Data Set using Free Software

Three dimensional digital model of a representative human kidney is needed for a surgical simulator that is capable of simulating a laparoscopic surgery involving kidney. Buying a three dimensional computer model of a representative human kidney, or reconstructing a human kidney from an image sequence using commercial software, both involve (sometimes significant amount of) money. In this paper, author has shown that one can obtain a three dimensional surface model of human kidney by making use of images from the Visible Human Data Set and a few free software packages (ImageJ, ITK-SNAP, and MeshLab in particular). Images from the Visible Human Data Set, and the software packages used here, both do not cost anything. Hence, the practice of extracting the geometry of a representative human kidney for free, as illustrated in the present work, could be a free alternative to the use of expensive commercial software or to the purchase of a digital model.

Dynamics of rotating composite beams: A comparative study between CNT reinforced polymer composite beams and laminated composite beams using spectral finite elements

This paper presents a spectral finite element formulation for uniform and tapered rotating CNT embedded polymer composite beams. The exact solution to the governing differential equation of a rotating Euler-Bernoulli beam with maximum centrifugal force is used as an interpolating function for the spectral element formulation. Free vibration and wave propagation analysis is carried out using the formulated spectral element. The present study shows the substantial effect of volume fraction and L/D ratio of CNTs in a beam on the natural frequency, impulse response and wave propagation characteristics of the rotating beam. It is found that the CNTs embedded in the matrix can make the rotating beam non-dispersive in nature at higher rotation speeds. Embedded CNTs can significantly alter the dynamics of polymer-nanocomposite beams. The results are also compared with those obtained for carbon fiber reinforced laminated composite rotating beams. It is observed that CNT reinforced rotating beams are superior in performance compared to laminated composite rotating beams. © 2012 Elsevier Ltd. All rights reserved.

Nonstoichiometry, defects and thermodynamic properties of YFeO3, YFe2O4 and Y3Fe5O12

Oxygen nonstoichiometry of three ternary oxides. YFeO3-delta, YFe2O4-alpha and Y3Fe5O12-theta. in the system Y-Fe-O was investigated as a function of oxygen partial pressure by thermogravimetry at high temperature. The defects responsible for nonstoichiometry were identified as oxygen vacancies for YFeO3-delta and YFe2O4-alpha although the manner of variation of nonstoichiometric parameter with oxygen partial pressure for these two oxides is quite different. Cation interstitials are the predominant defects in Y3Fe5O12-theta. Gibbs energies of formation of the three nonstoichiometric oxides were determined using solid-state electrochemical cells in the temperature range from 975 to 1475 K. YFe2O4-alpha was found to be stable only above 1391 K. Gibbs energies of formation of the three stoichiometric compounds from their component binary oxides were obtained by combining information from solid state cells with results of thermogravimetric analysis using the Gibbs-Duhem relation. The results can be summarized as: (1/2)Y2O3 + (1/2)Fe2O3 -> YFeO3;Delta G(f(ox))(O)(+/- 250)(J/mol) = 17, 126-8.263T (1/2)Y2O3 + FeO + (1/2)Fe2O3 -> YFe2O4;Delta G(f(ox))(O)(+/- 260)(J/mol) = -10,352-13.24T (3/2)Y2O3 + (5/2)Fe2O3 -> Y3Fe5O12;Delta G(f(ox))(O)(+/- 780)(J/mol) = -56, 647-31.091T. (C) 2012 Elsevier B.V. All rights reserved.

ATP release and autocrine signaling through P2X4 receptors regulate gamma delta T cell activation

Purinergic signaling plays a key role in a variety of physiological functions, including regulation of immune responses. Conventional alpha beta T cells release ATP upon TCR cross-linking; ATP binds to purinergic receptors expressed by these cells and triggers T cell activation in an autocrine and paracrine manner. Here, we studied whether similar purinergic signaling pathways also operate in the ``unconventional'' gamma delta T lymphocytes. We observed that gamma delta T cells purified from peripheral human blood rapidly release ATP upon in vitro stimulation with anti-CD3/CD28-coated beads or IPP. Pretreatment of gamma delta T cells with (10)panx-1, CBX, or Bf A reversed the stimulation-induced increase in extracellular ATP concentration, indicating that panx-1, connexin hemichannels, and vesicular exocytosis contribute to the controlled release of cellular ATP. Blockade of ATP release with (10)panx-1 inhibited Ca2+ signaling in response to TCR stimulation. qPCR revealed that gamma delta T cells predominantly express purinergic receptor subtypes A2a, P2X1, P2X4, P2X7, and P2Y11. We found that pharmacological inhibition of P2X4 receptors with TNP-ATP inhibited transcriptional up-regulation of TNF-alpha and IFN-gamma in gamma delta T cells stimulated with anti-CD3/CD28-coated beads or IPP. Our data thus indicate that purinergic signaling via P2X4 receptors plays an important role in orchestrating the functional response of circulating human gamma delta T cells. J. Leukoc. Biol. 92: 787-794; 2012.

Low-pass filters and differential tympanal tuning in a paleotropical bushcricket with an unusually low frequency call

Low-frequency sounds are advantageous for long-range acoustic signal transmission, but for small animals they constitute a challenge for signal detection and localization. The efficient detection of sound in insects is enhanced by mechanical resonance either in the tracheal or tympanal system before subsequent neuronal amplification. Making small structures resonant at low sound frequencies poses challenges for insects and has not been adequately studied. Similarly, detecting the direction of long-wavelength sound using interaural signal amplitude and/or phase differences is difficult for small animals. Pseudophylline bushcrickets predominantly call at high, often ultrasonic frequencies, but a few paleotropical species use lower frequencies. We investigated the mechanical frequency tuning of the tympana of one such species, Onomarchus uninotatus, a large bushcricket that produces a narrow bandwidth call at an unusually low carrier frequency of 3.2. kHz. Onomarchus uninotatus, like most bushcrickets, has two large tympanal membranes on each fore-tibia. We found that both these membranes vibrate like hinged flaps anchored at the dorsal wall and do not show higher modes of vibration in the frequency range investigated (1.5-20. kHz). The anterior tympanal membrane acts as a low-pass filter, attenuating sounds at frequencies above 3.5. kHz, in contrast to the high-pass filter characteristic of other bushcricket tympana. Responses to higher frequencies are partitioned to the posterior tympanal membrane, which shows maximal sensitivity at several broad frequency ranges, peaking at 3.1, 7.4 and 14.4. kHz. This partitioning between the two tympanal membranes constitutes an unusual feature of peripheral auditory processing in insects. The complex tracheal shape of O. uninotatus also deviates from the known tube or horn shapes associated with simple band-pass or high-pass amplification of tracheal input to the tympana. Interestingly, while the anterior tympanal membrane shows directional sensitivity at conspecific call frequencies, the posterior tympanal membrane is not directional at conspecific frequencies and instead shows directionality at higher frequencies.

Invisible decays of the lightest Higgs boson in supersymmetric models

We consider supersymmetric models in which the lightest Higgs scalar can decay invisibly consistent with the constraints on the 126 GeV state discovered at the CERN LHC. We consider the invisible decay in the minimal supersymmetric standard model (MSSM), as well its extension containing an additional chiral singlet superfield, the so-called next-to-minimal or nonminimal supersymmetric standard model (NMSSM). We consider the case of MSSM with both universal as well as nonuniversal gaugino masses at the grand unified scale, and find that only an E-6 grand unified model with unnaturally large representation can give rise to sufficiently light neutralinos which can possibly lead to the invisible decay h(0) -> (chi) over tilde (0)(1)(chi) over tilde (0)(1). Following this, we consider the case of NMSSM in detail, where we also find that it is not possible to have the invisible decay of the lightest Higgs scalar with universal gaugino masses at the grand unified scale. We delineate the regions of the NMSSM parameter space where it is possible for the lightest Higgs boson to have a mass of about 126 GeV, and then concentrate on the region where this Higgs can decay into light neutralinos, with the soft gaugino masses M-1 and M-2 as two independent parameters, unconstrained by grand unification. We also consider, simultaneously, the other important invisible Higgs decay channel in the NMSSM, namely the decay into the lightest CP-odd scalars, h(1) -> a(1)a(1), which is studied in detail. With the invisible Higgs branching ratio being constrained by the present LHC results, we find that mu(eff) < 170 GeV and M-1 < 80 GeV are disfavored in NMSSM for fixed values of the other input parameters. The dependence of our results on the parameters of NMSSM is discussed in detail.

On the densification mechanisms and properties of Cu-Pb and Cu-Pb-TiB2 nanocomposites densified using spark plasma sintering

The present paper is aimed to understand the sub-processes triggered by rapid heating during spark plasma sintering as well as to assess the extent to which densification and properties of metallic materials can be enhanced using such superfast consolidation process. Using nanocrystalline Cu-Pb as a model system, the influence of Pb as well as TiB2 addition on the densification mechanisms and properties are discussed. Importantly, a high hardness of 2 GPa is achieved in Cu-based nanocomposites. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

High Li storage capacity of poorly crystalline porous delta-MnO2 prepared by hydrothermal route

Poorly crystalline porous delta-MnO2 is synthesized by hydrothermal route from a neutral aqueous solution of KMnO4 at 180 degrees C and the reaction time of 24 h. The as-synthesized sample and also the sample heated at 300 degrees C have nanopetals morphology with large surface area. On heating at temperatures 400 degrees C, there is a decrease in BET surface area and also a change in morphology from nanopetals to clusters of nanorods. Furthermore, the poorly crystalline delta-MnO2 converts into well crystalline alpha-MnO2 phase. The electrochemical lithium intercalation and de-intercalation studies in a non-aqueous electrolyte provide a high discharge specific capacity (275 mAh g(-1)) at a specific current of 40 mA g(-1) for the poorly crystalline delta-MnO2 samples. The rate capability is also high. There is a decrease in capacity on repeated charge-discharge cycling. The specific capacity values of the crystalline alpha-MnO2 samples are considerably less than the values of poorly crystalline delta-MnO2 samples. Thus, the hydrothermal route facilitates preparation of poorly crystalline electrochemically active porous MnO2.

Topological saliency

Topological methods have been successfully used to identify features in scalar fields and to measure their importance. In this paper, we define a notion of topological saliency that captures the relative importance of a topological feature with respect to other features in its local neighborhood. Features are identified by extreme points of an input scalar field, and their importance measured by the so-called topological persistence. Computing the topological saliency of all features for varying neighborhood sizes results in a saliency plot that serves as a summary of relative importance of all topological features. We develop a convenient tool for users to interactively select and inspect features using the saliency plot. We demonstrate the use of topological saliency together with the rich information encoded in the saliency plot in several applications, including key feature identification, scalar field simplification, and feature clustering. (C) 2013 Elsevier Ltd. All rights reserved.

Employing synergistic interactions between few-layer WS2 and reduced graphene oxide to improve lithium storage, cyclability and rate capability of Li-ion batteries

The aim of the contribution is to introduce a high performance anode alternative to graphite for lithium-ion batteries (LiBs). A simple process was employed to synthesize uniform graphene-like few-layer tungsten sulfide (WS2) supported on reduced graphene oxide (RGO) through a hydrothermal synthesis route. The WS2-RGO (80:20 and 70:30) composites exhibited good enhanced electrochemical performance and excellent rate capability performance when used as anode materials for lithium-ion batteries. The specific capacity of the WS2-RGO composite delivered a capacity of 400-450 mAh g(-1) after 50 cycles when cycled at a current density of 100 mA g(-1). At 4000 mA g(-1), the composites showed a stable capacity of approximately 180-240 mAh g(-1), respectively. The noteworthy electrochemical performance of the composite is not additive, rather it is synergistic in the sense that the electrochemical performance is much superior compared to both WS2 and RGO. As the observed lithiation/delithiation for WS2-RGO is at a voltage 1.0 V (approximate to 0.1 V for graphite, Li* /Li), the lithium-ion battery with WS2-RGO is expected to possess high interface stability, safety and management of electrical energy is expected to be more efficient and economic. (C) 2013 Elsevier Ltd. All rights reserved.

A Secure and Efficient Authentication Protocol (SEAP) for MANETs with Membership Revocation

In this paper, we propose a novel authentication protocol for MANETs requiring stronger security. The protocol works on a two-tier network architecture with client nodes and authentication server nodes, and supports dynamic membership. We use an external membership granting server (MGS) to provide stronger security with dynamic membership. However, the external MGS in our protocol is semi-online instead of being online, i.e., the MGS cannot initiate a connection with a network node but any network node can communicate with the MGS whenever required. To ensure efficiency, the protocol uses symmetric key cryptography to implement the authentication service. However, to achieve storage scalability, the protocol uses a pseudo random function (PRF) to bind the secret key of a client to its identity using the secret key of its server. In addition, the protocol possesses an efficient server revocation mechanism along with an efficient server re-assignment mechanism, which makes the protocol robust against server node compromise.

Supercapacitors based on nitrogen-doped reduced graphene oxide and borocarbonitrides

Nitrogen-doped reduced giaphene oxide (RGO) samples with different nitrogen content, prepared by two different methods, as well as nitrogen-doped few-layer graphene have been investigated as supercapacitor electrodes. Two electrode measurements have been carried out both in aqueous (6 M KOH) and in ionic liquid media. Nitrogen-doped reduced graphene oxides exhibit satisfactory specific capacitance, the values reaching 126 F/g at a scan rate of 10 mV/s in aqueous medium. Besides providing supercapacitor characteristics, the study has shown the nitrogen content and surface area to be important factors. High surface-area borocarbonitrides, BxCyNz, prepared by the urea route appear to be excellent supercapacitor electrode materials. Thus, BC4.5N exhibits a specific capacitance of 169 F/g at a scan rate of 10 mV/s in aqueous medium. In an ionic liquid medium, nitrogen-doped RGO and BC4.5N exhibit specific capacitance values of 258 F/g and 240 F/g at a scan rate of 5 mV/s. The ionic liquid enables a larger operating voltage range of 0.0-2.5 V compared to 0.0-1 V in aqueous medium. (C) 2013 Elsevier Ltd. All rights reserved.

Large-Scale Elastic Net Regularized Linear Classification SVMs and Logistic Regression

Elastic Net Regularizers have shown much promise in designing sparse classifiers for linear classification. In this work, we propose an alternating optimization approach to solve the dual problems of elastic net regularized linear classification Support Vector Machines (SVMs) and logistic regression (LR). One of the sub-problems turns out to be a simple projection. The other sub-problem can be solved using dual coordinate descent methods developed for non-sparse L2-regularized linear SVMs and LR, without altering their iteration complexity and convergence properties. Experiments on very large datasets indicate that the proposed dual coordinate descent - projection (DCD-P) methods are fast and achieve comparable generalization performance after the first pass through the data, with extremely sparse models.

Fatigue crack propagation at concrete-concrete bi-material interfaces

This paper presents experimental and analytical studies on fatigue crack propagation in concrete-concrete cold jointed interface specimens. Beams of different sizes having jointed interface between two concretes with different elastic properties are tested under fatigue loading. The acoustic emission technique is used for monitoring the fatigue crack growth. It is observed that the interface having a higher moduli mismatch tends to behave in a brittle manner. The CMOD compliances at different loading cycles are measured and the equivalent crack lengths are determined from a finite element analysis. An analytical model for crack growth rate is proposed using the concepts of the dimensional analysis. (C) 2014 Elsevier Ltd. All rights reserved.