Effect of residual stresses and metallographic stability on the over all performance of integral diaphragm material

The integral diaphragm pressure transducer consists of a diaphragm machined from precipitation hardened martensitic (APX4) steel. Its performance is quite significant as it depends upon various factors such as mechanical properties including induced residual stress levels, metallurgical and physical parameters due to different stages of processing involved. Hence, the measurement and analysis of residual stress becomes very important from the point of in-service assessment of a component. In the present work, the stress measurements have been done using the X-ray diffraction (XRD) technique, which is a non-destructive test (NDT). This method is more reliable and widely used compared to the other NDT techniques. The metallurgical aspects have been studied by adopting the conventional metallographic practices including examination of microstructure using light microscope. The dimensional measurements have been carried out using dimensional gauge. The results of the present investigation reveals that the diaphragm material after undergoing series of realization processes has yielded good amount of retained austenite in it. Also, the presence of higher compressive stresses induced in the transducer results in non-linearity, zero shift and dimensional instability. The problem of higher retained austenite content and higher compressive stress have been overcome by adopting a new realization process involving machining and cold and hot stabilization soak which has brought down the retained austenite content to about 5–6% and acceptable level of compressive stress in the range −100 to −150 MPa with fine tempered martensitic phase structure and good dimensional stability. The new realization process seems to be quite effective in terms of controlling retained austenite content, residual stress, metallurgical phase as well as dimensional stability and this may result in minimum zero shift of the diaphragm system.

Localized reversible nanoscale phase separation in Pr0.63Ca0.37MnO3 single crystal using a scanning tunneling microscope tip

We report the destabilization of the charge ordered insulating (COI) state in a localized region of Pr0.63Ca0.37MnO3 single crystal by current injection using a scanning tunneling microscope tip. This leads to controlled phase separation and formation of localized metallic nanoislands in the COI matrix which have been detected by local tunneling conductance mapping. The metallic regions thus created persist even after reducing the injected current to lower values. The original conductance state can be restored by injecting a current of similar magnitude but of opposite polarity. We thus achieve reversible nanoscale phase separation that gives rise to the possibility to "write, read, and erase" nanosized conducting regions in an insulating matrix with high spatial resolution. (c) 2007 American Institute of Physics.

Gelatin hydrogel electrolytes and their application to electrochemical supercapacitors

Gelatin hydrogel electrolytes (GHEs) with varying NaCl concentrations have been prepared by cross-linking an aqueous solution of gelatin with aqueous glutaraldehyde and characterized by scanning electron microscopy, differential scanning calorimetry, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic chronopotentiometry. Glass transition temperatures for GHEs range between 339.6 and 376.9 K depending on the dopant concentration. Ionic conductivity behavior of GHEs was studied with varying concentrations of gelatin, glutaraldehyde, and NaCl, and found to vary between 10(-3) and 10(-1) S cm(-1). GHEs have a potential window of about 1 V. Undoped and 0.25 N NaCl-doped GHEs follow Arrhenius equations with activation energy values of 1.94 and 1.88 x 10(-4) eV, respectively. Electrochemical supercapacitors (ESs) employing these GHEs in conjunction with Black Pearl Carbon electrodes are assembled and studied. Optimal values for capacitance, phase angle, and relaxation time constant of 81 F g(-1), 75 degrees, and 0.03 s are obtained for 3 N NaCl-doped GHE, respectively. ES with pristine GHE exhibits a cycle life of 4.3 h vs 4.7 h for the ES with 3 N NaCl-doped GHE. (c) 2007 The Electrochemical Society.

Gibbs Energy of Formation of MnO: Measurement and Assessment

Based on the measurements of Alcock and Zador, Grundy et al. estimated an uncertainty of the order of +/- 5 kJ mol(-1) for the standard Gibbs energy of formation of MnO in a recent assessment. Since the evaluation of thermodynamic data for the higher oxides Mn3O4, Mn2O3, and MnO2 depends on values for MnO, a redetermination of its Gibbs energy of formation was undertaken in the temperature range from 875 to 1300 K using a solid-state electrochemical cell incorporating yttria-doped thoria (YDT) as the solid electrolyte and Fe + Fe1-delta O as the reference electrode. The cell can be presented as Pt, Mn + MnO/YDT/Fe + Fe1+delta O, Pt Since the metals Fe and Mn undergo phase transitions in the temperature range of measurement, the reversible emf of the cell is represented by the three linear segments. Combining the emf with the oxygen potential for the reference electrode, the standard Gibbs energy of formation of MnO from alpha-Mn and gaseous diatomic oxygen in the temperature range from 875 to 980 K is obtained as: Delta G(f)(o)/Jmol(-1)(+/- 250) = -385624 + 73.071T From 980 to 1300 K the Gibbs energy of formation of MnO from beta-Mn and oxygen gas is given by: Delta G(f)(o)/Jmol(-1)(+/- 250) = -387850 + 75.36T The new data are in excellent agreement with the earlier measurements of Alcock and Zador. Grundy et al. incorrectly analyzed the data of Alcock and Zador showing relatively large difference (+/- 5 kJ mol(-1)) in Gibbs energies of MnO from their two cells with Fe + Fe1-delta O and Ni + NiO as reference electrodes. Thermodynamic data for MnO is reassessed in the light of the new measurements. A table of refined thermodynamic data for MnO from 298.15 to 2000 K is presented.

The influence of Zr/Ti content on the morphotropic phase boundary in the PZT-PZN system

A quantitative structural investigation was carried out on (1-y)PbZrxTi1-xO3-yPbZn(1/3)Nb(2/3)O(3) where y=0.1 and 0.2 ((1-y)PZT-yPZN). High resolution XRD data have been used for quantitative phase analysis. The nominal compositions were prepared by a two-step low temperature calcining solid-state method. The sintered samples show an average grain size of 1-2 mu m. It is demonstrated that the increase in the concentration of PZN leads to the shift of the morphotropic phase boundary (MPB) of PZT towards the PbZrO3 end member. In the present work, an effort has been made to quantitatively determine the MPB phase contents and to regain the coexistence of tetragonal and monoclinic phases by varying the value of x(i.e. Zr/Ti ratio). The width of the MPB becomes considerably larger for y=0.10 and 0.20 as compared to pure PZT. This is attributed to the considerably lower grain size of our samples resulting from the adopted preparation method. (C) 2010 Elsevier B.V. All rights reserved.

Effective models of two-flavor QCD: finite $\mu$ and $m_q$-dependence

We study effective models of chiral fields and Polyakov loop expected to describe the dynamics responsible for the phase structure of two-flavor QCD at finite temperature and density. We consider chiral sector described either using linear sigma model or Nambu-Jona-Lasinio model and study the phase diagram and determine the location of the critical point as a function of the explicit chiral symmetry breaking (i.e. the bare quark mass $m_q$). We also discuss the possible emergence of the quarkyonic phase in this model.

Deformation and crystallization of Zr-based amorphous alloys in homogeneous flow regime

The purpose of this study is to experimentally investigate the interaction of inelastic deformation and microstructural changes of two Zr-based bulk metallic glasses (BMGs): Zr41.25Ti13.75Cu12.5Ni10Be22.5 (commercially designated as Vitreloy 1 or Vit1) and Zr46.75Ti8.25Cu7.5Ni10Be27.5 (Vitreloy 4, Vit4). High-temperature uniaxial compression tests were performed on the two Zr alloys at various strain rates, followed by structural characterization using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Two distinct modes of mechanically induced atomic disordering in the two alloys were observed, with Vit1 featuring clear phase separation and crystallization after deformation as observed with TEM, while Vit4 showing only structural relaxation with no crystallization. The influence of the structural changes on the mechanical behaviors of the two materials was further investigated by jump-in-strain-rate tests, and flow softening was observed in Vit4. A free volume theory was applied to explain the deformation behaviors, and the activation volumes were calculated for both alloys.

Mechanical and Thermal Properties of Eva Blended with Biodegradable Ethyl Cellulose

In this study, biodegradable blend of Poly (Ethylene-co-Vinyl Acetate) (EVA) and Ethyl Cellulose (EC) were prepared. Ethylene vinyl alcohol (EVOH) copolymer was used as an interfacial compatibilizer to enhance adhesion between EVA and EC. The melt blended compatibilized biocomposites were examined for mechanical and thermal properties as per the ASTM standards. It has been found that the EC has a reinforcing effect on EVA leading to enhanced tensile strength and also impart biodegradability. Thus, a high loading of 50% EC could be added without compromising Much on the mechanical properties. Analysis of the tensile data using predictive theories showed an enhanced interaction of the dispersed phase (EC) and the matrix (EVA). The compatibilizing effects of EVOH on these blends were confirmed by the significant improvement in the mechanical properties comparable with neat EVA as also observed by SEM microscopy. The TGA thermograms exhibits two-stage degradation and as EC content increases, the onset temperature for thermal degradation reduces. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1044-1056, 2010

Dynamics and local structure of colossal magnetoresistance manganites

We report Extended X-ray Absorption Fine Structure and anelastic spectroscopy measurements on on hole doped manganese oxides La1-xCaxMnO3 which present the colossal magnetoresistance effect. EXAFS measurements were realized both in the absence and presence of an applied magnetic field of 1.1 Tesla, in a wide temperature range (between 330 and 77 K) and at various dopings (x = 0.25 and x = 0.33). The magnetic field orders the magnetic moments so favouring the electron mobility and the reduction of Mn-O octahedra distortions. We observe the presence of four short and two long Mn-O distances (1.93 and 2.05 Angstrom respectively) above and also below the metal-insulator phase transition. The overall distortion decreases but does not completely disappear in the metallic phase suggesting the possible coexistence of metallic and insulating regions at low temperatures. The magnetic field reduces the lattice distortions showing evidence of a microscopic counterpart of the macroscopic colossal magnetoresistance. We also present preliminary anelastic relaxation spectra in a wide temperature range from 900 K to 1 K on a sample with x = 0.40, in order to study the structural phase transitions and the lattice dynamics. A double peak has been observed at the metal-insulator transition in the imaginary part of Young's modulus. This double peak indicates that the metal-insulator transition could be a more complex phenomenon than a simple second order phase transition. In particular the peak at lower temperatures can be connected with the possible presence of inhomogeneous phase structures. Another intense dissipation peak has been observed corresponding to the structural orthorhombic-trigonal transition around 750 K.

Dynamic changes in mitogen-activated protein kinase (MAPK) activities in the corpus luteum of the bonnet monkey (Macaca radiata) during development, induced luteolysis, and simulated early pregnancy: A role for p38 MAPK in the regulation of luteal function

Changes in MAPK activities were examined in the corpus luteum (CL) during luteolysis and pregnancy, employing GnRH antagonist (Cetrorelix)-induced luteolysis, stages of CL, and hCG treatment to mimic early pregnancy as model systems in the bonnet monkey. We hypothesized that MAPKs could serve to phosphorylate critical phosphoproteins to regulate luteal function. Analysis of several indices for structural (caspase-3 activity and DNA fragmentation) and functional (progesterone and steroidogenic acute regulatory protein expression) changes in the CL revealed that the decreased luteal function observed during Cetrorelix treatment and late luteal phase was associated with increased caspase-3 activity and DNA fragmentation. As expected, human chorionic gonadotropin treatment dramatically increased luteal function, but the indices for structural changes were only partially attenuated. All three MAPKs appeared to be constitutively active in the mid-luteal-phase CL, and activities of ERK-1/2 and p38-MAPK (p38), but not Jun N-terminal kinase (JNK)-1/2, decreased significantly (P < 0.05) within 12 - 24 h after Cetrorelix treatment. During the late luteal phase, in contrast to decreased ERK-1/2 and p38 activities, JNK-1/2 activities increased significantly (P < 0.05). Although human chorionic gonadotropin treatment increased ERK-1/2 and p38 activities, it decreased JNK-1/2 activities. The activation status of p38 was correlated with the phosphorylation status of an upstream activator, MAPK kinase-3/6 and the expression of MAPK activated protein kinase-3, a downstream target. Intraluteal administration of p38 kinase inhibitor (SB203580), but not MAPK kinase-1/2 inhibitor (PD98059), decreased the luteal function. Together, these data suggest an important role for p38 in the regulation of CL function in primates.

Relay Selection and Data Transmission Throughput Tradeoff in Cooperative Systems

A common and practical paradigm in cooperative communications is the use of a dynamically selected 'best' relay to decode and forward information from a source to a destination. Such a system consists of two core phases: a relay selection phase, in which the system expends resources to select the best relay, and a data transmission phase, in which it uses the selected relay to forward data to the destination. In this paper, we study and optimize the trade-off between the selection and data transmission phase durations. We derive closed-form expressions for the overall throughput of a non-adaptive system that includes the selection phase overhead, and then optimize the selection and data transmission phase durations. Corresponding results are also derived for an adaptive system in which the relays can vary their transmission rates. Our results show that the optimal selection phase overhead can be significant even for fast selection algorithms. Furthermore, the optimal selection phase duration depends on the number of relays and whether adaptation is used.

Vitamin A and thyroxine carrier proteins in chicken plasma Steady-state control of the plasma level of free retinol-binding protein and free thyroxine

1. 1. The binding parameters of prealbumin-2 with retinol-binding protein and thyroxine (T4) revealed the existence of distinct and multiple sites for both retinol-binding protein and T4. 2. 2. From the analysis of binding parameters of retinol-binding protein with prealbumin-2 it is clear that under steady-state conditions about 99% of the holo-retinol-binding protein remains bound to prealbumin-2. 3. 3. Equilibrium dialysis studies on binding properties of thyroid hormones with prealbumin-2 revealed that it has a single high affinity site and three low affinity sites. 4. 4. The occurrence of three carrier proteins for thyroid hormones, thyroxine-binding globulin, prealbumin-2 and albumin has been demonstrated. However, the chicken thyroxine-binding globulin differs from human thyroxine-binding globulin by being relatively less acidic and occuring at a two-fold lower concentration. But the thyroid hormone binding parameters are comparable. 5. 5. Highly sensitive methods were developed for determination of T4 binding capacities of the various proteins and plasma level of total T4 by fractionation of carrier proteins and further quantitatively employing in electrophoresis and equilibrium dialysis. 6. 6. The thyroxine-binding proteins were found to be two types, one (viz., thyroxine-binding globulin) of great affinity but of low binding capacity, which mainly acts as reservoir of T4, and another (viz.,prealbumin-2) of low affinity but of high binding capacity, which can participate predominantly in the control of the free T4 pool.

Magnetically induced currents and magnetic response properties of molecules

The magnetically induced currents in organic monoring and multiring molecules, in Möbius shaped molecules and in inorganic all-metal molecules have been investigated by means of the Gauge-including magnetically induced currents (GIMIC) method. With the GIMIC method, the ring-current strengths and the ring-current density distributions can be calculated. For open-shell molecules, also the spin current can be obtained. The ring-current pathways and ring-current strengths can be used to understand the magnetic resonance properties of the molecules, to indirectly identify the effect of non-bonded interactions on NMR chemical shifts, to design new molecules with tailored properties and to discuss molecular aromaticity. In the thesis, the magnetic criterion for aromaticity has been adopted. According to this, a molecule which has a net diatropic ring current might be aromatic. Similarly, a molecule which has a net paratropic current might be antiaromatic. If the net current is zero, the molecule is nonaromatic. The electronic structure of the investigated molecules has been resolved by quantum chemical methods. The magnetically induced currents have been calculated with the GIMIC method at the density-functional theory (DFT) level, as well as at the self-consistent field Hartree-Fock (SCF-HF), at the Møller-Plesset perturbation theory of the second order (MP2) and at the coupled-cluster singles and doubles (CCSD) levels of theory. For closed-shell molecules, accurate ring-current strengths can be obtained with a reasonable computational cost at the DFT level and with rather small basis sets. For open-shell molecules, it is shown that correlated methods such as MP2 and CCSD might be needed to obtain reliable charge and spin currents. The basis set convergence has to be checked for open-shell molecules by performing calculations with large enough basis sets. The results discussed in the thesis have been published in eight papers. In addition, some previously unpublished results on the ring currents in the endohedral fullerene Sc3C2@C80 and in coronene are presented. It is shown that dynamical effects should be taken into account when modelling magnetic resonance parameters of endohedral metallofullerenes such as Sc3C2@C80. The ring-current strengths in a series of nano-sized hydrocarbon rings are related to static polarizabilities and to H-1 nuclear magnetic resonance (NMR) shieldings. In a case study on the possible aromaticity of a Möbius-shaped [16]annulene we found that, according to the magnetic criterion, the molecule is nonaromatic. The applicability of the GIMIC method to assign the aromatic character of molecules was confirmed in a study on the ring currents in simple monocylic aromatic, homoaromatic, antiaromatic, and nonaromatic hydrocarbons. Case studies on nanorings, hexaphyrins and [n]cycloparaphenylenes show that explicit calculations are needed to unravel the ring-current delocalization pathways in complex multiring molecules. The open-shell implementation of GIMIC was applied in studies on the charge currents and the spin currents in single-ring and bi-ring molecules with open shells. The aromaticity predictions that are made based on the GIMIC results are compared to other aromaticity criteria such as H-1 NMR shieldings and shifts, electric polarizabilities, bond-length alternation, as well as to predictions provided by the traditional Hückel (4n+2) rule and its more recent extensions that account for Möbius twisted molecules and for molecules with open shells.

Isolation and characterization of heat-stable allergens from shrimp (Penaeus indicus)

Shrimp are among the more common causes of immediate hypersensitivity reactions to food. To characterize better the allergenic substances within shrimp, extracts from heated shrimp were systematically examined with solid-phase radioimmunoassay and sera from patients clinically sensitive to shrimp. Two heat-stable protein allergens, designated as Sa-I and Sa-II, were identified from boiled shrimp (Penaeus indicus) extracts. Sa-I was isolated by ultrafiltration, Sephadex G-25, and diethylaminoethyl-Sephacel chromatography, whereas Sa-II, the major allergen, was purified by successive chromatography on diethylaminoethyl-Sephacel, Bio-Gel P-200, and Sepharose 4B columns. Sa-I, which was homogeneous by polyacrylamide gel electrophoresis (PAGE), elicited a single band on sodium dodecyl sulfate-PAGE corresponding to a molecular weight of 8.2 kd. Sa-II was also found to be homogeneous by PAGE, crossed immunoelectrophoresis, and immunoblotting. On sodium dodecyl sulfate-PAGE, it elicited a single band with a molecular weight of 34 kd. Sa-II was found to contain 301 amino acid residues and was particularly rich in glutamate/glutamine and aspartate/asparagine. Solid-phase radioimmunoassay-inhibition studies revealed that Sa-I and Sa-II share 54% of the allergenic epitopes, suggesting that Sa-I may be a fragment of Sa-II.SDS-PAGE, Sodium dodecyl sulfate-polyacrylamide gel electrophoresis; MW, Molecular weight; BSA, Bovine serum albumin; DEAE, Diethylaminoethyl; SPRIA, Solid-phase radioimmunoassay; CIE, Crossed immunoelectrophoresis .

Potentiometric determination of activities in the two-phase fields of the system Na2O---(α)Al2O3

Three compounds have been found to be stable in the pseudobinary system Na2O---(α)Al2O3 between 825 and 1400 K; two nonstoichiometric phases, β-alumina and β″-alumina, and NaAlO2. The homogeneity of β-alumina ranges from 9.5 to 11 mol% Na2O, while that of β″-alumina from 13.3 to 15.9 mol% Na2O at 1173 K. The activity of Na2O in the two-phase fields has been determined by a solid-state potentiometric technique. Since both β- and β″-alumina are fast sodium ion conductors, biphasic solid electrolyte tubes were used in these electrochemical measurements. The open circuit emf of the following cells were measured from 790 to 980 K: [GRAPHICS] The partial molar Gibbs' energy of Na2O relative to gamma-Na2O in the two-phase regions can be represented as: DELTA-GBAR(Na2O)(alpha- + beta-alumina) = -270,900 + 24.03 T, DELTA-GBAR(Na2O)(beta- + beta"-alumina) = -232,700 + 56.19 T, and DELTA-GBAR(Na2O)(beta"-alumina + NaAlO2) = -13,100 - 4.51 T J mol-1. Similar galvanic cells using a Au-Na alloy and a mixture of Co + CoAl(2+2x)O4+3x + (alpha)Al2O3 as electrodes were used at 1400 K. Thermodynamic data obtained in these studies are used to evaluate phase relations and partial pressure of sodium in the Na2O-(alpha) Al2O3 system as a function of oxygen partial pressure, composition and temperature.