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Sample records for impedance spectroscopic studies

  1. Dielectric and impedance spectroscopic studies of neodymium gallate

    NASA Astrophysics Data System (ADS)

    Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T. P.

    2016-05-01

    The AC electrical properties of a polycrystalline neodymium gallate, NdGaO3 (NGO), synthesized by the sol-gel method have been investigated by employing impedance spectroscopy in the frequency range from 42 Hz to 5 MHz and in the temperature range from 323 K to 593 K. The X-ray diffraction analysis shows that the compound crystallizes in the orthorhombic phase with Pbnm space group at room temperature. Two relaxation processes with different relaxation times are observed from the impedance as well as modulus spectroscopic measurements, which have been attributed to the grain and the grain boundary effects at different temperatures in NGO. The complex impedance data are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element in parallel. It has been observed that the value of the capacitance and the resistance associated with the grain boundary is higher than those associated with the grain. The temperature dependent electrical conductivity shows the negative temperature coefficient of resistance. The frequency dependent conductivity spectra are found to follow the power law.

  2. Impedance and modulus spectroscopic study of nano hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Jogiya, B. V.; Jethava, H. O.; Tank, K. P.; Raviya, V. R.; Joshi, M. J.

    2016-05-01

    Hydroxyapatite (Ca10 (PO4)6 (OH)2, HAP) is the main inorganic component of the hard tissues in bones and also important material for orthopedic and dental implant applications. Nano HAP is of great interest due to its various bio-medical applications. In the present work the nano HAP was synthesized by using surfactant mediated approach. Structure and morphology of the synthesized nano HAP was examined by the Powder XRD and TEM. Impedance study was carried out on pelletized sample in a frequency range of 100Hz to 20MHz at room temperature. The variation of dielectric constant, dielectric loss, and a.c. conductivity with frequency of applied field was studied. The Nyquist plot as well as modulus plot was drawn. The Nyquist plot showed two semicircle arcs, which indicated the presence of grain and grain boundary effect in the sample. The typical behavior of the Nyquist plot was represented by equivalent circuit having two parallel RC combinations in series.

  3. Electrical properties of double perovskite oxide Sr2LaSbO6: An impedance spectroscopic study

    NASA Astrophysics Data System (ADS)

    Dutta, Alo; Kumari, Premlata; Sinha, T. P.

    2015-09-01

    The Rietveld refinement of the room temperature x-ray diffraction pattern of double perovskite oxide, Sr2LaSbO6 (SLS) synthesized by the solid-state reaction technique shows monoclinic phase with P21/ n symmetry, which is substantiated by the Raman spectrum of the sample. The dielectric relaxation of SLS is investigated in the temperature range from 30°C to 300°C and in the frequency range from 50 Hz to 1 MHz. The Cole-Cole model is used to explain the dielectric relaxation of SLS. The most probable relaxation frequencies at various temperatures are found to obey the Arrhenius law with an activation energy of 0.36 eV, which indicates that the polaron hopping plays the main role in the dielectric relaxation of SLS. The complex impedance plane plots are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element. The frequency dependent conductivity spectra obey the power law. [Figure not available: see fulltext.

  4. The impedance spectroscopic study and dielectric relaxation in A(Ni1/3Ta2/3)O3 [A=Ba, Ca and Sr

    NASA Astrophysics Data System (ADS)

    Hoque, Md M.; Dutta, A.; Kumar, S.; Sinha, T. P.

    2012-09-01

    We present the results of impedance spectroscopic study with its analytical interpretations in the framework of electric modulus formalism for Barium Nickel Tantalate Ba(Ni1/3Ta2/3)O3 (BNT), Calcium Nickel Tantalate Ca(Ni1/3Ta2/3)O3 (CNT) and Strontium Nickel Tantalate Sr(Ni1/3Ta2/3)O3 (SNT) synthesized by the solid-state reaction technique. The results of powder X-ray diffraction study reveal that BNT and SNT crystallize in cubic structure with lattice parameter a=4.07 Å and 3.98 Å respectively, whereas CNT crystallizes in monoclinic structure having lattice parameters, a=5.71 Å, b=13.45 Å and c=5.47 Å with β=118.3°. The logarithmic angular frequency dependence of the real part of complex dielectric permittivity and loss tangent as a function of temperature indicate significant dielectric relaxation in the samples, which have been explained by the Debye theory. The frequency dependence of the loss peak and the imaginary part of electrical modulus are found to obey the Arrhenius law. The relaxation mechanism of these samples is modeled by the Cole-Cole equation. This confirms that the polarization mechanism in BNT, CNT and SNT is due to the bulk effect arising in semiconductive grains. The scaling behavior of imaginary part of electric modulus M″ suggests that the relaxation describes the same mechanism at various temperatures but relaxation frequency is strongly temperature dependent. The normalized peak positions of tan δ/tan δm and M″/M″m versus log ω for BNT, CNT and SNT do not overlap completely and are very close to each other. These indicate the presence of both long-range and localized relaxation. Due to their high dielectric constant and low loss tangent, these materials may find several technological applications such as in capacitors, resonators, filters and integrated circuits.

  5. Impedance spectroscopic characterization of gadolinium substituted cobalt ferrite ceramics

    SciTech Connect

    Rahman, Md. T. Ramana, C. V.

    2014-10-28

    Gadolinium (Gd) substituted cobalt ferrites (CoFe{sub 2−x}Gd{sub x}O{sub 4}, referred to CFGO) with variable Gd content (x = 0.0–0.4) have been synthesized by solid state ceramic method. The crystal structure and impedance properties of CFGO compounds have been evaluated. X-ray diffraction measurements indicate that CFGO crystallize in the inverse spinel phase. The CFGO compounds exhibit lattice expansion due to substitution of larger Gd ions into the crystal lattice. Impedance spectroscopy analysis was performed under a wide range of frequency (f = 20 Hz–1 MHz) and temperature (T = 303–573 K). Electrical properties of Gd incorporated Co ferrite ceramics are enhanced compared to pure CoFe{sub 2}O{sub 4} due to the lattice distortion. Impedance spectroscopic analysis illustrates the variation of bulk grain and grain-boundary contributions towards the electrical resistance and capacitance of CFGO materials with temperature. A two-layer heterogeneous model consisting of moderately conducting grain interior (ferrite-phase) regions separated by insulating grain boundaries (resistive-phase) accurately account for the observed temperature and frequency dependent electrical characteristic of CFGO ceramics.

  6. Electrochemical Impedance Spectroscopic Sensing of Methamphetamine by a Specific Aptamer

    PubMed Central

    Ebrahimi, Mohsen; Johari-Ahar, Mohammad; Hamzeiy, Hossein; Barar, Jaleh; Mashinchian, Omid; Omidi, Yadollah

    2012-01-01

    Introduction Electrochemical impedance spectroscopy (EIS) is a simple and highly sensitive technique that can be used for evaluation of the aptamer-target interaction even in a label-free approach. Methods To pursue the effectiveness of EIS, in the current study, the folding properties of specific aptamer for methamphetamine (METH) (i.e., aptaMETH) were evaluated in the presence of METH and amphetamine (Amph). Folded and unfolded aptaMETH was mounted on the gold electrode surface and the electron charge transfer was measured by EIS. Results The Ret of methamphetamine-aptaMETH was significantly increased in comparison with other folding conditions, indicating specific detection of METH by aptaMETH. Conclusion Based on these findings, methamphetamine-aptaMETH on the gold electrode surface displayed the most interfacial electrode resistance and thus the most folding situation. This clearly indicates that the aptaMETH can profoundly and specifically pinpoint METH; as a result we suggest utilization of this methodology for fast and cost-effective identification of METH. PMID:23678446

  7. Dielectric and impedance spectroscopic studies of 0.8BaTiO3-0.2Bi0.5K0.5TiO3 lead-free ceramics

    NASA Astrophysics Data System (ADS)

    Ramesh, M. N. V.; Ramesh, K. V.

    2015-06-01

    0.8BaTiO3-0.2Bi0.5K0.5TiO3 (BT-BKT20) lead-free ceramics were prepared by conventional solid state reaction method followed by high energy ball milling. The formation of a single phase tetragonal structure in the material was confirmed by X-ray diffraction. Frequency and temperature-dependent dielectric studies show relaxor behavior in the BT-BKT20 which was found to obey modified Curie-Weiss law with degree of diffuseness 1.573. Complex impedance and electric modulus spectroscopy studies reveal temperature-dependent relaxation process in the material. The Cole-Cole plots were measured at high temperatures at which grain effect was observed. Impedance and electric modulus spectroscopy studies show non-Debye kind of conductivity relaxation process in the present material. Activation energies were calculated from impedance and electric modulus spectroscopy and the values of activation energy indicated that the conduction is ionic in nature. AC and DC conductivity have been measured and studied at different temperatures.

  8. Spectroscopic study of sprites

    NASA Astrophysics Data System (ADS)

    Kanmae, Takeshi

    Optical emissions from sprites--large electric discharges in the mesosphere caused by intense lightning strokes--have been studied for decades. Studies have identified that sprite emissions are primarily composed of molecular band emissions of nitrogen and notably identified the near ultraviolet and blue emission from the N2+ First Negative system, which provided direct evidence of ionization in sprites. This implies that further evidence of the ionization may be provided by the visible and near infrared emission from the N2+ Meinel system, which is more accessible from ground-based platforms, though anticipated strong quenching in the mesosphere and below have made the presence of the emission somewhat controversial. To investigate the presence of the Meinel emission along the vertical extent of sprites, we made ground-based spectral observations in 2005. The observed spectra were mainly composed of the N2 First Positive system, and no or little indication of the Meinel bands were found. This study suggests that the quenching is indeed severe at sprite altitude, and it is difficult to study the ionization process in sprites via the Meinel emission. In addition, the data allowed us to investigate details of the First Positive emission from sprites. The observed First Positive spectra showed that the vibrational distribution of the upper state varies along the vertical extent of sprites, which is in agreement with previous reports, and furthermore this study indicates that the variation is associated with altitude, implying that collisional energy transfer processes play roles in exciting the First Positive emission, particularly at lower altitudes. Recent high-speed imaging observations have revealed the very dynamic nature of sprites: they develop within a few to 10 ms in forms of streamers and columnar glows. The underlying electron energies in these features have been inferred from their emissions in previous measurements, but they lacked either sufficient

  9. Nuclear spectroscopic studies

    SciTech Connect

    Bingham, C.R.; Guidry, M.W.; Riedinger, L.L.; Sorensen, S.P.

    1993-02-08

    The Nuclear Physics group at the University of Tennessee, Knoxville is involved in several aspects of heavy-ion physics including both nuclear structure and reaction mechanisms. While our main emphasis is on experimental problems involving heavy-ion accelerators, we have maintained a strong collaboration with several theorists in order to best pursue the physics of our measurements. During the last year we have led several experiments at the Holifield Heavy Ion Research Facility and participated in others at Argonne National Laboratory. Also, we continue to be very active in the collaboration to study ultra-relativistic heavy ion physics utilizing the SPS accelerator at CERN in Geneva, Switzerland and in a RHIC detector R D project. Our experimental work is in four broad areas: (1) the structure of nuclei at high angular momentum, (2) heavy-ion induced transfer reactions, (3) the structure of nuclei far from stability, and (4) ultra-relativistic heavy-ion physics. The results of studies in these particular areas will be described in this document in sections IIA, IIB, IIC, and IID, respectively. Areas (1), (3), and (4) concentrate on the structure of nuclear matter in extreme conditions of rotational motion, imbalance of neutrons and protons, or very high temperature and density. Area (2) pursues the transfer of nucleons to states with high angular momentum, both to learn about their structure and to understand the transfer of particles, energy, and angular momentum in collisions between heavy ions. An important component of our program is the strong emphasis on the theoretical aspects of nuclear structure and reactions.

  10. Impedance Spectroscopic Investigation of Proton Conductivity in Nafion Using Transient Electrochemical Atomic Force Microscopy (AFM)

    PubMed Central

    Hink, Steffen; Wagner, Norbert; Bessler, Wolfgang G.; Roduner, Emil

    2012-01-01

    Spatially resolved impedance spectroscopy of a Nafion polyelectrolyte membrane is performed employing a conductive and Pt-coated tip of an atomic force microscope as a point-like contact and electrode. The experiment is conducted by perturbing the system by a rectangular voltage step and measuring the incurred current, followed by Fourier transformation and plotting the impedance against the frequency in a conventional Bode diagram. To test the potential and limitations of this novel method, we present a feasibility study using an identical hydrogen atmosphere at a well-defined relative humidity on both sides of the membrane. It is demonstrated that good quality impedance spectra are obtained in a frequency range of 0.2–1000 Hz. The extracted polarization curves exhibit a maximum current which cannot be explained by typical diffusion effects. Simulation based on equivalent circuits requires a Nernst element for restricted diffusion in the membrane which suggests that this effect is based on the potential dependence of the electrolyte resistance in the high overpotential region. PMID:24958175

  11. Corrosion Study Using Electrochemical Impedance Spectroscopy

    NASA Technical Reports Server (NTRS)

    Farooq, Muhammad Umar

    2003-01-01

    Corrosion is a common phenomenon. It is the destructive result of chemical reaction between a metal or metal alloy and its environment. Stainless steel tubing is used at Kennedy Space Center for various supply lines which service the orbiter. The launch pads are also made of stainless steel. The environment at the launch site has very high chloride content due to the proximity to the Atlantic Ocean. Also, during a launch, the exhaust products in the solid rocket boosters include concentrated hydrogen chloride. The purpose of this project was to study various alloys by Electrochemical Impedance Spectroscopy in corrosive environments similar to the launch sites. This report includes data and analysis of the measurements for 304L, 254SMO and AL-6XN in primarily neutral 3.55% NaCl. One set of data for 304L in neutral 3.55%NaCl + 0.1N HCl is also included.

  12. AC impedance study of degradation of porous nickel battery electrodes

    NASA Technical Reports Server (NTRS)

    Lenhart, Stephen J.; Macdonald, D. D.; Pound, B. G.

    1987-01-01

    AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low.

  13. Alternating current impedance spectroscopic analysis of biofunctionalized vertically-aligned silica nanospring surface for biosensor applications

    NASA Astrophysics Data System (ADS)

    Timalsina, Yukta P.

    In this dissertation, a process of vertically-aligned (silica) nanosprings (VANS) based biosensor development is presented. Alternating current (AC) impedance spectroscopy has been used to analyze sensor response as a function of saline phosphate (SP) buffer and biological solutions. The sensor is a parallel plate capacitor consisting of two glass substrates coated with indium tin oxide (ITO), where the VANS [or randomly-aligned nanosprings (RANS)] grown on one substrate serve as the dielectric spacer layer. The response of a VANS device as a function of ionic concentration in SP buffer was examined and an equivalent circuit model was developed. The results demonstrated that VANS sensors exhibited greater sensitivity to the changes in SP concentration relative to the ITO sensors, which serve as controls. The biofunctionalized VANS surface via physisorption and the cross-linker method demonstrates the repeatability, specificity, and selectivity of the binding. The physisorption of biotinylated immunoglobulin G (B-IgG) onto the VANS surface simplifies the whole sensing procedure for the detection of glucose oxidase, since the avidin-conjugated glucose oxidase (Av-GOx) can directly be immobilized on the B-IgG. The cross linker method involves the covalent attachment of antibodies onto the functionalized VANS surface via imine bond. The experiments revealed that the VANS sensor response is solely the result of the interaction of target molecule i.e. mouse IgG with the probe layer, i.e. goat antimouse IgG (GalphaM IgG). It was determined that VANS-based sensors exhibit a greater magnitude of change between successive bio-layers relative to the controls above 100 Hz, which indicates that the addition of biomolecules inhibits the diffusion of ions and changes the effective dielectric response of the VANS via biomolecular polarization. The study of ionic transport in nanosprings suggested that conductance follows a scaling law. It was demonstrated that a VANS-based device

  14. Potentiostatic and ac impedance studies of the hydrogen electrodes used in Ni/H2 batteries

    NASA Technical Reports Server (NTRS)

    Le Helloco, Jean-Guy; Bojkov, Hristo; Parthasarathy, Arvind; Srinivasan, Supramaniam; Appleby, A. J.

    1992-01-01

    In a study of electrode activity for hydrogen evolution and hydrogen ionization, knowledge of the detailed kinetics and of the surface coverage by adsorbed hydrogen is essential. In the Ni/H2 battery, the hydrogen electrode is subjected to high hydrogen pressure; elucidation of the variation of kinetic parameters with hydrogen pressure is therefore of interest. Potentiostatic and ac impedance spectroscopic techniques were used in the present study. The equivalent circuit of the reaction, the kinetic parameters, and their pressure dependence have been determined.

  15. EPR and impedance spectroscopic investigations on lithium bismuth borate glasses containing nickel and vanadium ions

    NASA Astrophysics Data System (ADS)

    Yadav, Arti; Khasa, Satish; Hooda, Ashima; Dahiya, Manjeet S.; Agarwal, Ashish; Chand, Prem

    2016-03-01

    Glasses having composition 7NiO • 23Li2O • 20Bi2O3 • 50B2O3, 7V2O5 • 23Li2O • 20Bi2O3 • 50B2O3 and x(2NiO • V2O5) • (30 - x)Li2O • 50B2O3 • 20Bi2O3 (with x = 0, 2, 5, 7 & 10 mol%) prepared through melt-quench route are explored by analyzing density, impedance spectroscopy and electron paramagnetic resonance (EPR). It is found that both density and molar volume increase with an increase in substitution of 2NiO • V2O5 in the base glass matrix. Different dielectric parameters viz. dielectric loss (ε), electrical modulus (M), loss tangent (tanδ) etc. are evaluated and their variations with frequency and temperature are analyzed which reveals that these glasses exhibit a non-Debye relaxation behavior. A phenomenal description of the capacitive behavior is obtained by considering the circuitry as a parallel combination of bulk resistance (Rb) and constant phase element (CPE). The conduction mechanism is found to follow Quantum Mechanical Tunneling (QMT) model. Spin Hamiltonian Parameters (SHPs) and covalency rates are calculated from the EPR spectra of vanadyl ion. The observed EPR spectra confirmed that V4 + ion exists as vanadyl ion in the octahedral coordination with tetragonal compression.

  16. EPR and impedance spectroscopic investigations on lithium bismuth borate glasses containing nickel and vanadium ions.

    PubMed

    Yadav, Arti; Khasa, Satish; Hooda, Ashima; Dahiya, Manjeet S; Agarwal, Ashish; Chand, Prem

    2016-03-15

    Glasses having composition 7NiO∙23Li2O∙20Bi2O3∙50B2O3, 7V2O5∙23Li2O∙20Bi2O3∙50B2O3 and x(2NiO∙V2O5)∙(30-x)Li2O∙50B2O3∙20Bi2O3 (with x=0, 2, 5, 7 & 10 mol%) prepared through melt-quench route are explored by analyzing density, impedance spectroscopy and electron paramagnetic resonance (EPR). It is found that both density and molar volume increase with an increase in substitution of 2NiO∙V2O5 in the base glass matrix. Different dielectric parameters viz. dielectric loss (ε), electrical modulus (M), loss tangent (tanδ) etc. are evaluated and their variations with frequency and temperature are analyzed which reveals that these glasses exhibit a non-Debye relaxation behavior. A phenomenal description of the capacitive behavior is obtained by considering the circuitry as a parallel combination of bulk resistance (Rb) and constant phase element (CPE). The conduction mechanism is found to follow Quantum Mechanical Tunneling (QMT) model. Spin Hamiltonian Parameters (SHPs) and covalency rates are calculated from the EPR spectra of vanadyl ion. The observed EPR spectra confirmed that V(4+) ion exists as vanadyl ion in the octahedral coordination with tetragonal compression.

  17. Spectroscopic study in Z-pinch discharge

    SciTech Connect

    Garamoon, A.A.; Saudy, A.H.; Shark, W.

    1995-12-31

    The temporal variation of the emitted line intensity has been investigated, and thus an important information about the dynamic ionization stages in the Z-pinch discharge has been studied. Also the electron temperature Te, has been deduced by using a spectroscopic technique.

  18. Studying Young Stars with Large Spectroscopic Surveys

    NASA Astrophysics Data System (ADS)

    Martell, Sarah L.

    2016-01-01

    Galactic archaeology is the study of the history of star formation and chemical evolution in the Milky Way, based on present-day stellar populations. Studies of young stars are a key anchor point for Galactic archaeology, since quantities like the initial mass function and the star formation rate can be studied directly in young clusters and star forming regions. Conversely, massive spectroscopic Galactic archaeology surveys can be used as a data source for young star studies.

  19. Nuclear spectroscopic studies. Progress report

    SciTech Connect

    Bingham, C.R.; Guidry, M.W.; Riedinger, L.L.; Sorensen, S.P.

    1994-02-18

    The Nuclear Physics group at UTK is involved in heavy-ion physics including both nuclear structure and reaction mechanisms. During the last year experimental work has been in 3 broad areas: structure of nuclei at high angular momentum, structure of nuclei far from stability, and ultra-relativistic heavy-ion physics. Results in these areas are described in this document under: properties of high-spin states, study of low-energy levels of nuclei far from stability, and high-energy heavy-ion physics (PHENIX, etc.). Another important component of the work is theoretical interpretation of experimental results (Joint Institute for Heavy Ion Research).

  20. Spectroscopic study of Mentha oils

    NASA Astrophysics Data System (ADS)

    Rai, A. K.; Singh, A. K.

    The visible fluorescence and excitation spectra of Mentha oils (Japanese mint oil, peppermint oil and spearmint oil) have been recorded. Different physical constants which are characteristic of the fluorescent molecules have been calculated for all three oils. Results reveal that the same group of organic compounds dominate in the oils of peppermint and spearmint, whereas some different compound is present in Japanese mint oil. It is also found that the fluorescence intensity of these oils is comparable to that of Rhodamine 6G dye in methanol solution. Our studies suggest that Mentha oils may be a useful lasing material in the 450-600 nm wavelength range.

  1. Synthesis, dielectric behavior and impedance measurement studies of Cr-substituted Zn-Mn ferrites

    SciTech Connect

    Hankare, P.P.; Patil, R.P.; Garadkar, K.M.; Sasikala, R.; Chougule, B.K.

    2011-03-15

    Graphical abstract: Variation of dielectric constant with frequency. Research highlights: {yields} Sol-gel route synthesized spherical crystalline nanoparticles of ZnMn{sub 1-x}Cr{sub x}FeO{sub 4}. {yields} XRD, DTA, FTIR, SEM, dielectric and impedance study. {yields} The ferrites show concentration dependence of ac electrical conductivity. {yields} Impedance response is dominated by grain boundary behavior. -- Abstract: Nanocrystalline ZnMn{sub 1-x}Cr{sub x}FeO{sub 4} (1.0 {>=} x {>=} 0) ferrites were synthesized by sol-gel technique. X-ray diffraction (XRD) confirmed the formation of single phasic cubic spinel lattice for all the compositions studied. Lattice parameter shows a decreasing trend with an increase in Cr content in the compositions. Formation of spherical nanoparticles was revealed by scanning electron microscopy (SEM) analysis. Infrared spectroscopic studies revealed two main absorption bands in the range 400-800 cm{sup -1} arising due to tetrahedral (A) and octahedral (B) site vibrations. Dielectric constant, dielectric loss tangent, ac conductivity and complex impedance were measured as a function of frequency in the range 20 Hz to 1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. The role of chromium in modifying structural and dielectric properties of these ferrites has been explained.

  2. Nuclear spectroscopic studies. Progress report

    SciTech Connect

    Bingham, C.R.; Guidry, M.W.; Riedinger, L.L.; Sorensen, S.P.

    1993-02-08

    The Nuclear Physics group at the University of Tennessee, Knoxville is involved in several aspects of heavy-ion physics including both nuclear structure and reaction mechanisms. While our main emphasis is on experimental problems involving heavy-ion accelerators, we have maintained a strong collaboration with several theorists in order to best pursue the physics of our measurements. During the last year we have led several experiments at the Holifield Heavy Ion Research Facility and participated in others at Argonne National Laboratory. Also, we continue to be very active in the collaboration to study ultra-relativistic heavy ion physics utilizing the SPS accelerator at CERN in Geneva, Switzerland and in a RHIC detector R&D project. Our experimental work is in four broad areas: (1) the structure of nuclei at high angular momentum, (2) heavy-ion induced transfer reactions, (3) the structure of nuclei far from stability, and (4) ultra-relativistic heavy-ion physics. The results of studies in these particular areas will be described in this document in sections IIA, IIB, IIC, and IID, respectively. Areas (1), (3), and (4) concentrate on the structure of nuclear matter in extreme conditions of rotational motion, imbalance of neutrons and protons, or very high temperature and density. Area (2) pursues the transfer of nucleons to states with high angular momentum, both to learn about their structure and to understand the transfer of particles, energy, and angular momentum in collisions between heavy ions. An important component of our program is the strong emphasis on the theoretical aspects of nuclear structure and reactions.

  3. Spectroscopic study of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Curran, Seamus; Weldon, Declan N.; Blau, Werner J.; Zandbergen, Henny W.; Kastner, J.; Kuzmany, Hans

    1994-11-01

    We present a comprehensive experimental study of the vibrational spectra of nanotubes. There are two main lines observed in the Raman spectrum, one positioned at 1350 cm-1, the D line, and the other at 1580 cm-1, the G line. Both these lines are very similar to those seen with disordered graphite. The disorder induced D line is very weak compared to the G line which is indicative of high crystalline materials. The position and intensity of the D line strongly depends on the energy of the exciting laser. This dispersion effect was also observed for graphitic particles and may be explained by a photoselective resonance process of nanotubes with different sizes. There are two optically active modes in the Infrared spectrum for highly orientated polycrystalline graphite which are the E1u and A2u modes. The E1u mode is positioned at 1587 cm-1 while the A2u mode is positioned at 868 cm-1. The Infrared spectrum of the nanotubes shows both modes although the E1u mode is downshifted to 1575 cm-1.

  4. Integrated Spectroscopic Studies of MIL03346

    NASA Technical Reports Server (NTRS)

    Dyar, M. D.; Pieters, C. M.; Hiroi, T.; Lane, M. D.; Marchand, G. J.

    2005-01-01

    Spectroscopic studies of the SNC meteorites continue to be of great interest because they provide the only "ground truth" available for ongoing Mossbauer, thermal emittance, MidIR, nearIR, and visible spectral analysis of the martian surface. We present here results of an integrated series of measurements made on the same split of MIL03346, in order to expand our understanding of the properties of these materials and to relate them to other SNCs.

  5. Study of Influence of Electrode Geometry on Impedance Spectroscopy

    SciTech Connect

    Ahmed, Riaz; Reifsnider, Kenneth L

    2011-01-01

    Electrochemical Impedance Spectroscopy (EIS) is a powerful and proven tool for analyzing AC impedance response. A conventional three electrode EIS method was used to perform the investigation in the present study. Saturated potassium chloride solution was used as the electrolyte and three different material rods were used as working electrodes. Different configurations of electrode area were exposed to the electrolyte as an active area to investigate electrode geometry effects. Counter to working electrode distance was also altered while keeping the working electrode effective area constant to explore the AC response dependence on the variation of ion travel distance. Some controlled experiments were done to validate the experimental setup and to provide a control condition for comparison with experimental results. A frequency range of 100 mHz to 1 MHz was used for all experiments. In our analysis, we have found a noteworthy influence of electrode geometry on AC impedance response. For all electrodes, impedance decreases with the increase of effective area of the electrolyte. High frequency impedance is not as dependent on geometry as low frequency response. The observed phase shift angle drops in the high frequency region with increased working electrode area, whereas at low frequency the reverse is true. Resistance and capacitive reactance both decrease with an increase of area, but resistance response is more pronounce than reactance. For lower frequencies, small changes in working area produce very distinctive EIS variations. Electrode material as well as geometry was systematically varied in the present study. From these and other studies, we hope to develop a fundamental foundation for understanding specific changes in local geometry in fuel cell (and other) electrodes as a method of designing local morphology for specific performance.

  6. Vibrational spectroscopic study of fluticasone propionate

    NASA Astrophysics Data System (ADS)

    Ali, H. R. H.; Edwards, H. G. M.; Kendrick, J.; Scowen, I. J.

    2009-03-01

    Fluticasone propionate is a synthetic glucocorticoid with potent anti-inflammatory activity that has been used effectively in the treatment of chronic asthma. The present work reports a vibrational spectroscopic study of fluticasone propionate and gives proposed molecular assignments on the basis of ab initio calculations using BLYP density functional theory with a 6-31G* basis set and vibrational frequencies predicted within the quasi-harmonic approximation. Several spectral features and band intensities are explained. This study generated a library of information that can be employed to aid the process monitoring of fluticasone propionate.

  7. The platinum microelectrode/Nafion interface - An electrochemical impedance spectroscopic analysis of oxygen reduction kinetics and Nafion characteristics

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Arvind; Dave, Bhasker; Srinivasan, Supramaniam; Appleby, John A.; Martin, Charles R.

    1992-01-01

    The objectives of this study were to use electrochemical impedance spectroscopy (EIS) to study the oxygen-reduction reaction under lower humidification conditions than previously studied. The EIS technique permits the discrimination of electrode kinetics of oxygen reduction, mass transport of O2 in the membrane, and the electrical characteristics of the membrane. Electrode-kinetic parameters for the oxygen-reduction reaction, corrosion current densities for Pt, and double-layer capacitances were calculated. The production of water due to electrochemical reduction of oxygen greatly influenced the EIS response and the electrode kinetics at the Pt/Nafion interface. From the finite-length Warburg behavior, a measure of the diffusion coefficient of oxygen in Nafion and diffusion-layer thickness was obtained. An analysis of the EIS data in the high-frequency domain yielded membrane and interfacial characteristics such as ionic conductivity of the membrane, membrane grain-boundary capacitance and resistance, and uncompensated resistance.

  8. The Spectroscopic study of {sup 33}Ar

    SciTech Connect

    Adimi, N.; Dominguez-Reyes, R.; Alcorta, M.; Borge, M. J. G.; Perea, A.; Tengblad, O.; Bey, A.; Blank, B.; Dossat, C.; Giovinazzo, J.; Matea, I.; Fynbo, H. O. U.; Knudsen, H. H.; Suemmerer, K.

    2011-10-28

    The proton-rich nucleus {sup 33}Ar has been produced at the low-energy facility SPIRAL at GANIL. Spectroscopic studies of gamma and p emission of this nucleus were performed with the 'Silicon Cube' detection system. The analysis of proton and gamma singles and coincidence spectra allowed us to establish a complete decay scheme of this nucleus. The comparison of the Gamow-Teller strength distribution deduced from our experiment and the theoretical one obtained with the Shell Model permitted the determination of a quenching factor for the Gamow-Teller strength.

  9. Potassium polytitanate gas-sensor study by impedance spectroscopy.

    PubMed

    Fedorov, F S; Varezhnikov, A S; Kiselev, I; Kolesnichenko, V V; Burmistrov, I N; Sommer, M; Fuchs, D; Kübel, C; Gorokhovsky, A V; Sysoev, V V

    2015-10-15

    Nanocrystalline potassium polytitanates K2O·nTiO2·mH2O represent a new type of semiconducting compounds which are characterized by a high specific surface that makes them promising for use in gas sensors. In this work, we have studied potassium polytitanate mesoporous nanoparticle agglomerates placed over a SiO2/Si substrate equipped with multiple coplanar electrodes to measure the electrical response to various organic vapors, 1000 ppm of concentration, mixed with air by impedance spectrometry in range of the 10(-2)-10(6) Hz. The recorded impedance data for each sensor segment are associated with RC components of an equivalent circuit which are applied to selectively recognize the test vapors exploiting a "multisensor array" approach. PMID:26515008

  10. Impedance microflow cytometry for viability studies of microorganisms

    NASA Astrophysics Data System (ADS)

    Di Berardino, Marco; Hebeisen, Monika; Hessler, Thomas; Ziswiler, Adrian; Largiadèr, Stephanie; Schade, Grit

    2011-02-01

    Impedance-based Coulter counters and its derivatives are widely used cell analysis tools in many laboratories and use normally DC or low frequency AC to perform these electrical analyses. The emergence of micro-fabrication technologies in the last decade, however, provides a new means of measuring electrical properties of cells. Microfluidic approaches combined with impedance spectroscopy measurements in the radio frequency (RF) range increase sensitivity and information content and thus push single cell analyses beyond simple cell counting and sizing applications towards multiparametric cell characterization. Promising results have been shown already in the fields of cell differentiation and blood analysis. Here we emphasize the potential of this technology by presenting new data obtained from viability studies on microorganisms. Impedance measurements of several yeast and bacteria strains performed at frequencies around 10 MHz enable an easy discrimination between dead and viable cells. Moreover, cytotoxic effects of antibiotics and other reagents, as well as cell starvation can also be monitored easily. Control analyses performed with conventional flow cytometers using various fluorescent dyes (propidium iodide, oxonol) indicate a good correlation and further highlight the capability of this device. The label-free approach makes on the one hand the use of usually expensive fluorochromes obsolete, on the other hand practically eliminates laborious sample preparation procedures. Until now, online cell monitoring was limited to the determination of viable biomass, which provides rather poor information of a cell culture. Impedance microflow cytometry, besides other aspects, proposes a simple solution to these limitations and might become an important tool for bioprocess monitoring applications in the biotech industry.

  11. Study of surfactant-skin interactions by skin impedance measurements.

    PubMed

    Lu, Guojin; Moore, David J

    2012-02-01

    The stratum corneum (SC) plays a very critical physiological role as skin barrier in regulating water loss through the skin and protects the body from a wide range of physical and chemical exogenous insults. Surfactant-containing formulations can induce skin damage and irritation owing to surfactant absorption and penetration. It is generally accepted that reduction in skin barrier properties occurs only after surfactants have penetrated/permeated into the skin barrier. To mitigate the harshness of surfactant-based cleansing products, penetration/permeation of surfactants should be reduced. Skin impedance measurements have been taken in vitro on porcine skin using vertical Franz diffusion cells to investigate the impact of surfactants, temperature and pH on skin barrier integrity. These skin impedance results demonstrate excellent correlation with other published methods for assessing skin damage and irritation from different surfactant chemistry, concentration, pH, time of exposure and temperature. This study demonstrates that skin impedance can be utilized as a routine approach to screen surfactant-containing formulations for their propensity to compromise the skin barrier and hence likely lead to skin irritation. PMID:21923733

  12. Study of surfactant-skin interactions by skin impedance measurements.

    PubMed

    Lu, Guojin; Moore, David J

    2012-02-01

    The stratum corneum (SC) plays a very critical physiological role as skin barrier in regulating water loss through the skin and protects the body from a wide range of physical and chemical exogenous insults. Surfactant-containing formulations can induce skin damage and irritation owing to surfactant absorption and penetration. It is generally accepted that reduction in skin barrier properties occurs only after surfactants have penetrated/permeated into the skin barrier. To mitigate the harshness of surfactant-based cleansing products, penetration/permeation of surfactants should be reduced. Skin impedance measurements have been taken in vitro on porcine skin using vertical Franz diffusion cells to investigate the impact of surfactants, temperature and pH on skin barrier integrity. These skin impedance results demonstrate excellent correlation with other published methods for assessing skin damage and irritation from different surfactant chemistry, concentration, pH, time of exposure and temperature. This study demonstrates that skin impedance can be utilized as a routine approach to screen surfactant-containing formulations for their propensity to compromise the skin barrier and hence likely lead to skin irritation.

  13. X-ray photoelectron spectroscopic and electrochemical impedance spectroscopic analysis of RuO2-Ta2O5 thick film pH sensors.

    PubMed

    Manjakkal, Libu; Cvejin, Katarina; Kulawik, Jan; Zaraska, Krzysztof; Socha, Robert P; Szwagierczak, Dorota

    2016-08-10

    The paper reports on investigation of the pH sensing mechanism of thick film RuO2-Ta2O5 sensors by using X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Interdigitated conductimetric pH sensors were screen printed on alumina substrates. The microstructure and elemental composition of the films were examined by scanning electron microscopy and energy dispersive spectroscopy. The XPS studies revealed the presence of Ru ions at different oxidation states and the surface hydroxylation of the sensing layer increasing with increasing pH. The EIS analysis carried out in the frequency range 10 Hz-2 MHz showed that the electrical parameters of the sensitive electrodes in the low frequency range were distinctly dependent on pH. The charge transfer and ionic exchange occurring at metal oxide-solution interface were indicated as processes responsible for the sensing mechanism of thick film RuO2-Ta2O5 pH sensors.

  14. Spectroscopic study of solar twins and analogues

    NASA Astrophysics Data System (ADS)

    Datson, Juliet; Flynn, Chris; Portinari, Laura

    2015-02-01

    Context. Many large stellar surveys have been and are still being carried out, providing huge amounts of data, for which stellar physical parameters will be derived. Solar twins and analogues provide a means to test the calibration of these stellar catalogues because the Sun is the best-studied star and provides precise fundamental parameters. Solar twins should be centred on the solar values. Aims: This spectroscopic study of solar analogues selected from the Geneva-Copenhagen Survey (GCS) at a resolution of 48 000 provides effective temperatures and metallicities for these stars. We test whether our spectroscopic parameters, as well as the previous photometric calibrations, are properly centred on the Sun. In addition, we search for more solar twins in our sample. Methods: The methods used in this work are based on literature methods for solar twin searches and on methods we developed in previous work to distinguish the metallicity-temperature degeneracies in the differential comparison of spectra of solar analogues versus a reference solar reflection spectrum. Results: We derive spectroscopic parameters for 148 solar analogues (about 70 are new entries to the literature) and verify with a-posteriori differential tests that our values are well-centred on the solar values. We use our dataset to assess the two alternative calibrations of the GCS parameters; our methods favour the latest revision. We show that the choice of spectral line list or the choice of asteroid or time of observation does not affect the results. We also identify seven solar twins in our sample, three of which are published here for the first time. Conclusions: Our methods provide an independent means to differentially test the calibration of stellar catalogues around the values of a well-known benchmark star, which makes our work interesting for calibration tests of upcoming Galactic surveys. Based on observations made with ESO Telescopes at the La Silla Observatory under programme ID 077.D

  15. Impedance spectroscopic analysis of composite electrode from activated carbon/conductive materials/ruthenium oxide for supercapacitor applications

    SciTech Connect

    Taer, E.; Awitdrus,; Farma, R.; Deraman, M. Talib, I. A.; Ishak, M. M.; Omar, R.; Dolah, B. N. M.; Basri, N. H.; Othman, M. A. R.; Kanwal, S.

    2015-04-16

    Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H{sub 2}SO{sub 4} electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance of the AC electrodes from 3 to 7, 17, 32 F g{sup −1} respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g{sup −1}, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.

  16. Impedance spectroscopic analysis of composite electrode from activated carbon/conductive materials/ruthenium oxide for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Taer, E.; Deraman, M.; Talib, I. A.; Awitdrus, Farma, R.; Ishak, M. M.; Omar, R.; Dolah, B. N. M.; Basri, N. H.; Othman, M. A. R.; Kanwal, S.

    2015-04-01

    Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H2SO4 electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance of the AC electrodes from 3 to 7, 17, 32 F g-1 respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g-1, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.

  17. Predictive Mechanistic Model for the Electrical Impedance and Intensity-Modulated Photocurrent and Photovoltage Spectroscopic Responses of an Organic Bulk Heterojunction Solar Cell

    NASA Astrophysics Data System (ADS)

    Set, Ying Ting; Birgersson, Erik; Luther, Joachim

    2016-05-01

    We develop a predictive and mechanistic model for the intensity-modulated photocurrent spectroscopic (IMPS), intensity-modulated photovoltage spectroscopic (IMVS), and electrical impedance spectroscopic (EIS) responses of organic bulk heterojunction (BHJ) solar cells. Unlike the dominant analytical framework—equivalent circuit analysis—the model uses physical parameters that directly reflect the device's fundamental electronic mechanisms, eliminating the ambiguity associated with interpreting phenomenological parameters. Formulated in the frequency domain, the model is a computationally efficient tool for extracting parameters from the measured spectra. With a set of physical parameters representing a device, we predict the device's spectra (a) in techniques employing different methods of perturbing a device and (b) at different bias voltages and illumination intensities. The predicted spectra show good agreement with the measured ones. By quantifying the device's internal electric field and charge carrier concentration and relating them to the spectra, we determine that the IMPS responses at the short-circuit condition and the IMVS responses at the open-circuit condition directly reflect the charge carrier extraction and recombination, respectively. Furthermore, the EIS response indicates the device's recombination time scale at different bias voltages.

  18. Pore Characteristics of Chitosan Scaffolds Studied by Electrochemical Impedance Spectroscopy

    PubMed Central

    Tully-Dartez, Stephanie; Cardenas, Henry E.

    2010-01-01

    In this study, a novel approach, electrochemical impedance spectroscopy (EIS), was used to examine the pore characteristics of chitosan scaffolds under aqueous conditions. The EIS was run with a constant current of 0.1 mA with the frequency sweep of 106 to 10−4 Hz. The resulting complex impedance measurement was then used to calculate porosity, which was determined to be 71%. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), two commonly used methods for scaffold characterization, were used to independently evaluate the pore characteristics and compare with that of EIS. The SEM and MIP were performed and analyzed under standard conditions. The pore diameter values found by SEM and MIP are 107 μm and 82 μm, respectively, indicating that both the image-based (SEM) and pressure-based (MIP) analyses provide similar results. The porosity of 73% calculated by MIP is comparable to that of EIS. From these results, it can be suggested that EIS, a relatively nondestructive test, is able to obtain comparable data on pore characteristics, as compared to SEM and MIP. The advantage of the EIS as an nondestructive test is that it can be performed under physiologically relevant conditions, whereas SEM and MIP require dry samples and vacuum conditions for measurement. These benefits make EIS a viable option for the characterization and long-term observation of tissue-engineered scaffolds. PMID:19580421

  19. Ambulatory impedance cardiography in hypertension: a validation study.

    PubMed

    McFetridge-Durdle, Judith A; Routledge, Faye S; Parry, Monica J E; Dean, C R T; Tucker, B

    2008-09-01

    The management of hypertension is improved by knowledge of the hemodynamics underlying blood pressure. Impedance Cardiography (ICG) provides data on a range of hemodynamic variables that affect blood pressure. However, ICG captures only fixed descriptions of hemodynamic characteristics. Improvements in ambulatory technology have led to the development of the Ambulatory Impedance Monitor (AIM) which records hemodynamic data during the activities of daily living. The purpose of this study was to evaluate the sensitivity of the AIM to detect hemodynamic changes associated with postural shift in persons with hypertension. Using a repeated measures cross-over design, sitting and standing hemodynamic measures were taken in seventeen persons with hypertension while wearing the AIM-BpTRU system designed for standard office use and the AIM-Spacelabs system designed for ambulatory monitoring. Both AIM-blood pressure monitoring systems detected significant changes from sitting to standing posture in heart rate (p=0.03), stroke volume (p=0.002), left ventricular ejection time (p<0.001), systemic vascular resistance (p=0.03) and diastolic blood pressure (p<0.001). Additionally, both systems generated measures of cardiac function that were positively correlated (p<0.001) and not significantly different (p>0.05). Our findings support previous work and demonstrate that the AIM provides valid and reliable estimates of cardiac function in persons with hypertension. PMID:18234557

  20. Impact of hydrogen concentrations on the impedance spectroscopic behavior of Pd-sensitized ZnO nanorods

    PubMed Central

    2013-01-01

    ZnO nanorods were synthesized using a low-cost sol-gel spin coating technique. The synthesized nanorods were consisted of hexagonal phase having c-axis orientation. SEM images reflected perpendicular ZnO nanorods forming bridging network in some areas. The impact of different hydrogen concentrations on the Pd-sensitized ZnO nanorods was investigated using an impedance spectroscopy (IS). The grain boundary resistance (Rgb) significantly contributed to the sensing properties of hydrogen gas. The boundary resistance was decreased from 11.95 to 3.765 kΩ when the hydrogen concentration was increased from 40 to 360 ppm. IS gain curve showed a gain of 6.5 for 360 ppm of hydrogen at room temperature. Nyquist plot showed reduction in real part of impedance at low frequencies on exposure to different concentrations of hydrogen. Circuit equivalency was investigated by placing capacitors and resistors to identify the conduction mechanism according to complex impedance Nyquist plot. Variations in nanorod resistance and capacitance in response to the introduction of various concentrations of hydrogen gas were obtained from the alternating current impedance spectra. PMID:23399029

  1. Quadrupole resonance spectroscopic study of narcotic materials

    NASA Astrophysics Data System (ADS)

    Rayner, Timothy J.; West, Rebecca; Garroway, Allen N.; Lyndquist, R.; Yesinowski, James P.

    1997-02-01

    Bulk narcotic detection systems based upon Quadrupole Resonance Analysis (QRA) technology have a major advantage over imaging technologies, in that QRA is chemical-specific and consequently has a lower rate of false alarms. QRA is a magnetic resonance technology which occurs as a result of the inherent molecular properties of the atomic nuclei in crystalline and amorphous solids. The QRA response is characterized by 1) the precessional frequency of the nucleus, and 2) the nature of the electric field gradient experienced by the nucleus,due to its molecular environment. Another important detection parameter is linewidth, resonant quality. All of these parameters depend on sample purity and manufacturing process. Quantum Magnetics recently carried out a study on the QRA signatures of various narcotic materials with the support of the US Army, US Customs, and the Office of National Drug Control Policy. The aim of the study was to fully characterize the variation in QRA spectroscopic parameters of different samples of cocaine base and cocaine hydrochloride. The results from this study ar discussed here.

  2. Electrochemical impedance spectroscopy study on corrosion inhibition of benzyltriethylammonium chloride

    NASA Astrophysics Data System (ADS)

    Idris, Mohd Nazri; Daud, Abdul Razak; Othman, Norinsan Kamil

    2013-11-01

    Electrochemical Impedance Spectroscopy (EIS) was employed to study the corrosion inhibition behavior of benzyltriethylammonium chloride (BTC) for carbon steel corrosion. The inhibition efficiency was investigated in 1.0 M HCl solution at room temperature (25°C) by varying the BTC concentration. EIS results indicated that the double layer capacitance of electrolyte/carbon steel interface decreases with the increasing of BTC concentration and consequently enhances the polarization resistance of equivalence Randles circuit. The results indicated that inhibition efficiency of as high as 65% could be achieved when 10mM BTC was present in 1.0 M HCl solution as compared to inhibitor-free solution. The inhibition process of BTC on the carbon steel corrosion was found to obey Langmuir adsorption isotherm. This study revealed that BTC is suitable to be used as a corrosion inhibitor in acid media.

  3. Fundamental spectroscopic studies of carbenes and hydrocarbon radicals

    SciTech Connect

    Gottlieb, C.A.; Thaddeus, P.

    1993-12-01

    Highly reactive carbenes and carbon-chain radicals are studied at millimeter wavelengths by observing their rotational spectra. The purpose is to provide definitive spectroscopic identification, accurate spectroscopic constants in the lowest vibrational states, and reliable structures of the key intermediates in reactions leading to aromatic hydrocarbons and soot particles in combustion.

  4. Spectroscopic studies of microwave plasmas containing hexamethyldisiloxane

    NASA Astrophysics Data System (ADS)

    Nave, A. S. C.; Mitschker, F.; Awakowicz, P.; Röpcke, J.

    2016-10-01

    Low-pressure microwave discharges containing hexamethyldisiloxane (HMDSO) with admixtures of oxygen and nitrogen, used for the deposition of silicon containing films, have been studied spectroscopically. Optical emission spectroscopy (OES) in the visible spectral range has been combined with infrared laser absorption spectroscopy (IRLAS). The experiments were carried out in order to analyze the dependence of plasma chemical phenomena on power and gas mixture at relatively low pressures, up to 50 Pa, and power values, up to 2 kW. The evolution of the concentration of the methyl radical, CH3, and of seven stable molecules, HMDSO, CH4, C2H2, C2H4, C2H6, CO and CO2, was monitored in the plasma processes by in situ IRLAS using tunable lead salt diode lasers (TDL) and external-cavity quantum cascade lasers (EC-QCL) as radiation sources. To achieve reliable values for the gas temperature inside and outside the plasma bulk as well as for the temperature in the plasma hot and colder zones, which are of great importance for calculation of species concentrations, three different methods based on emission and absorption spectroscopy data of N2, CH3 and CO have been used. In this approach line profile analysis has been combined with spectral simulation methods. The concentrations of the various species, which were found to be in the range between 1011 to 1015 cm-3, are in the focus of interest. The influence of the discharge parameters power, pressure and gas mixture on the molecular concentrations has been studied. To achieve further insight into general plasma chemical aspects the dissociation of the HMDSO precursor gas including its fragmentation and conversion to the reaction products was analyzed in detail.

  5. Study of impedance spectra for dry and wet EarEEG electrodes.

    PubMed

    Kappel, Simon L; Kidmose, Preben

    2015-01-01

    EarEEG is a novel recordings concept where electrodes are embedded on the surface of an earpiece customized to the individual anatomical shape of the users ear. A key parameter for recording EEG signals of good quality is a stable and low impedance electrode-body interface. This study characterizes the impedance for dry and wet EarEEG electrodes in a study of 10 subjects. A custom made and automated setup was used to characterize the impedance spectrum from 0.1 Hz-2 kHz. The study of dry electrodes showed a mean (standard deviation) low frequency impedance of the canal electrodes of 1.2 MΩ (1.4 MΩ) and the high frequency impedance was 230 kΩ (220 kΩ). For wet electrodes the low frequency impedance was 34 kΩ (37 kΩ) and the high frequency impedance was 5.1 kΩ (4.4 kΩ). The high standard deviation of the impedance for dry electrodes imposes very high requirements for the input impedance of the amplifier in order to achieve an acceptable common-mode rejection. The wet electrode impedance was in line with what is typical for a wet electrode interface.

  6. Measurement uncertainty in pulmonary vascular input impedance and characteristic impedance estimated from pulsed-wave Doppler ultrasound and pressure: clinical studies on 57 pediatric patients.

    PubMed

    Tian, Lian; Hunter, Kendall S; Kirby, K Scott; Ivy, D Dunbar; Shandas, Robin

    2010-06-01

    Pulmonary vascular input impedance better characterizes right ventricular (RV) afterload and disease outcomes in pulmonary hypertension compared to the standard clinical diagnostic, pulmonary vascular resistance (PVR). Early efforts to measure impedance were not routine, involving open-chest measurement. Recently, the use of pulsed-wave (PW) Doppler-measured velocity to non-invasively estimate instantaneous flow has made impedance measurement more practical. One critical concern remains with clinical use: the measurement uncertainty, especially since previous studies only incorporated random error. This study utilized data from a large pediatric patient population to comprehensively examine the systematic and random error contributions to the total impedance uncertainty and determined the least error prone methodology to compute impedance from among four different methods. We found that the systematic error contributes greatly to the total uncertainty and that one of the four methods had significantly smaller propagated uncertainty; however, even when this best method is used, the uncertainty can be large for input impedance at high harmonics and for the characteristic impedance modulus. Finally, we found that uncertainty in impedance between normotensive and hypertensive patient groups displays no significant difference. It is concluded that clinical impedance measurement would be most improved by advancements in instrumentation, and the best computation method is proposed for future clinical use of the input impedance.

  7. Rapid Flow Analysis Studies with Spectroscopic Detectors.

    NASA Astrophysics Data System (ADS)

    Thalib, Amlius

    A rapid flow analysis study based on segmented flow and flow injection principles is described in this thesis. The main objective of this study was to establish the response characteristics in continuous flow analysis systems in order to improve sampling rates with several types of spectroscopic detectors. It was found from flame photometric studies that non-segmented flowing streams are applicable to rapid flow analysis with automatic sample aspiration. Calcium was used as a typical example and determined at sampling rates up to 360 h('-1) with a detection limit of 0.05 mg L(' -1). A rapid flow system is reported using direct aspiration for AAS analysis with both manual injection and automatic aspiration techniques, and found to give sampling rates of up to 600-720 samples h('-1). Speed of analysis was reduced by about 50% when using an external peristaltic pump in the flow system design, due to increased sample dispersion. A novel aspect of a rapid flow injection approach reported with ICPAES detection includes the method of injecting samples via a peristaltic pump with simultaneous computer data processing. Determination of serum cations (Na, K, Ca, Mg and Fe) was demonstrated as an example of an application of the technique at sampling rates of 240 h('-1). Precision and detection limits for 13 elements in a single standard solution are reported. The use of automated aspiration sampling is also reported in this method for comparison. Further studies on flow characteristics were carried out by a combination of the rapid flow system with very short sampling times as low as 2 seconds using UV-visible spectrophotometric detection. Analysis of human blood serum samples was used as an example where total protein and inorganic phosphate were determined at sampling rates of 240 h('-1) and 360 h('-1) respectively. The novel aspects of the results from these studies include the very rapid sample throughput developed with simple and inexpensive experimental approaches in

  8. An impedance study on admiralty brass dezincification originated by microbiologically influenced corrosion.

    PubMed

    Ibars, J R; Polo, J L; Moreno, D A; Ranninger, C; Bastidas, J M

    2004-09-30

    In this article we describe a field study of biofouling and microbiologically influenced corrosion (MIC) of admiralty brass heat exchanger tubes in contact with running fresh water on the river Tagus close to Almaraz nuclear power plant in Spain. Dezincification originated by biofouling and MIC was studied using impedance, polarization resistance, gravimetric, scanning electron microscopy (SEM), and X-ray diffraction (XRD) measurements. Close correlation was observed between the biofilms formed and the corrosion process (dezincification) using the different experimental techniques. Impedance data showed a capacitive behavior including two time constants. Kramers-Kronig (KK) transforms were used to validate impedance data. The admiralty tubes' impedance data satisfied the KK relations.

  9. An impedance study on admiralty brass dezincification originated by microbiologically influenced corrosion.

    PubMed

    Ibars, J R; Polo, J L; Moreno, D A; Ranninger, C; Bastidas, J M

    2004-09-30

    In this article we describe a field study of biofouling and microbiologically influenced corrosion (MIC) of admiralty brass heat exchanger tubes in contact with running fresh water on the river Tagus close to Almaraz nuclear power plant in Spain. Dezincification originated by biofouling and MIC was studied using impedance, polarization resistance, gravimetric, scanning electron microscopy (SEM), and X-ray diffraction (XRD) measurements. Close correlation was observed between the biofilms formed and the corrosion process (dezincification) using the different experimental techniques. Impedance data showed a capacitive behavior including two time constants. Kramers-Kronig (KK) transforms were used to validate impedance data. The admiralty tubes' impedance data satisfied the KK relations. PMID:15334412

  10. [Experimental study on electrical impedance properties of human hepatoma cells].

    PubMed

    Fang, Yun; Tang, Zhiyuan; Zhang, Qian; Zhao, Xin; Ma, Qing

    2014-10-01

    The AC impedance of human hepatoma SMMC-7721 cells were measured in our laboratory by Agilent 4294A impedance analyzer in the frequency range of 0.01-100 MHz. And then the effect of hematocrit on electrical impedance characteristics of hepatoma cells was observed by electrical impedance spectroscopy, Bode diagram, Nyquist diagram and Nichols diagram. The results showed that firstly, there is a frequency dependence, i.e., the increment of real part and the imaginary part of complex electrical impedance (δZ', δZ"), the increment of the amplitude modulus of complex electrical impedance (δ[Z *]) and phase angle (δθ) were all changed with the increasing frequency. Secondly, it showed cell volume fraction (CVF) dependence, i. e. , the increment of low-frequency limit (δZ'0, δ[Z*] 0), peak (δZ"(p), δθ(p)), area and radius (Nyquist diagram, Nichols diagram) were all increased along with the electric field frequency. Thirdly, there was the presence of two characteristic frequencies: the first characteristic frequency (f(c1)) and the second characteristic frequency (f(c2)), which were originated respectively in the polarization effects of two interfaces that the cell membrane and extracellular fluid, cell membrane and cytoplasm. A conclusion can be drawn that the electrical impedance spectroscopy is able to be used to observe the electrical characteristics of human hepatoma cells, and therefore this method can be used to investigate the electrophysiological mechanisms of liver cancer cells, and provide research tools and observation parameters, and it also has important theoretical value and potential applications for screening anticancer drugs. PMID:25764724

  11. Otosclerosis in a black child: diagnostic acoustic impedance studies.

    PubMed

    Schweitzer, V G; Lilly, D J

    1984-10-01

    Otosclerosis classically describes an osteodystrophic change in the bony labyrinth and stapes footplate, of autosomal dominant inheritance, reported rare under the age of 5, extremely "rare" in the Oriental and Black race, "non-existent" in the American Indian, and with a clinical incidence of 5 per 1000 Caucasians. The differential diagnosis of a non-effusion conductive hearing loss in a child should include otosclerosis, congenital malleus or footplate fixation, tympanosclerotic fixation, congenital cholesteatoma, lysis of the incus long process, Paget's disease, osteogenesis imperfecta, and fibromuscular hyperplasia of the renal artery. Presented is a case report of a 14-year-old black male with bilateral clinical otosclerosis and a persistent stapedial artery. Preoperative multiple-frequency tympanometry and Zwislocki acoustic reactance and resistance analysis demonstrated absence of the "W" resonance pattern on high-frequency tympanometry and the classic friction and stiffness patterns of otosclerotic fixation. Repeat multiple-frequency tympanometry testing post-stapedectomy demonstrated prosthesis articulation. Prosthesis position can be monitored postoperatively by these acoustic impedance studies. PMID:6500827

  12. Hygroscopic particle behavior studied by interdigitated array microelectrode impedance sensors.

    PubMed

    Schindelholz, Eric; Tsui, Lok-kun; Kelly, Robert G

    2014-01-01

    The hygroscopic behavior of soluble salts bears importance in many research fields including atmospheric sciences, corrosion, porous building materials, and pharmaceuticals. Several methods have been used to study deliquescence (solid to liquid) and efflorescence (liquid to solid) phase transitions of these salts. In this study, we measured the deliquescence and efflorescence RH values of single salt microparticles deposited on an interdigitated microelectrode sensor via electrical impedance. The salts examined were NaCl, LiCl, NaBr, KCl, and MgCl2. Measured values were in agreement with in situ optical microscopic observations and, with the exception of MgCl2, literature values. In the case of MgCl2, deliquescence occurred at 33% RH and 12-15% RH, with the latter range being previously unreported. The depressed deliquescence RH was hypothesized to be a result of the formation of a metastable MgCl2 hydrate. Incomplete efflorescence of MgCl2 was also observed after exposure to <1.5% RH for up to 22 h due to formation of solid shells which trapped fluid. The phenomena elucidated by these results provide an explanation for the anomalous water retention and uptake behavior of MgCl2 below 33% RH reported elsewhere in the literature. The results presented in this study validate the use of this method as an alternative or complementary method for study of bulk-phase transitions of substrate-deposited particles across a broad RH range. These findings also demonstrate the utility of this method for detection of fluid trapping which cannot be directly ascertained by gravimetric and line-of-sight techniques commonly used in the study of hygroscopic particles.

  13. Multimodal Spectroscopic Study of Amyloid Fibril Polymorphism.

    PubMed

    VandenAkker, Corianne C; Schleeger, Michael; Bruinen, Anne L; Deckert-Gaudig, Tanja; Velikov, Krassimir P; Heeren, Ron M A; Deckert, Volker; Bonn, Mischa; Koenderink, Gijsje H

    2016-09-01

    Amyloid fibrils are a large class of self-assembled protein aggregates that are formed from unstructured peptides and unfolded proteins. The fibrils are characterized by a universal β-sheet core stabilized by hydrogen bonds, but the molecular structure of the peptide subunits exposed on the fibril surface is variable. Here we show that multimodal spectroscopy using a range of bulk- and surface-sensitive techniques provides a powerful way to dissect variations in the molecular structure of polymorphic amyloid fibrils. As a model system, we use fibrils formed by the milk protein β-lactoglobulin, whose morphology can be tuned by varying the protein concentration during formation. We investigate the differences in the molecular structure and composition between long, straight fibrils versus short, wormlike fibrils. We show using mass spectrometry that the peptide composition of the two fibril types is similar. The overall molecular structure of the fibrils probed with various bulk-sensitive spectroscopic techniques shows a dominant contribution of the β-sheet core but no difference in structure between straight and wormlike fibrils. However, when probing specifically the surface of the fibrils with nanometer resolution using tip-enhanced Raman spectroscopy (TERS), we find that both fibril types exhibit a heterogeneous surface structure with mainly unordered or α-helical structures and that the surface of long, straight fibrils contains markedly more β-sheet structure than the surface of short, wormlike fibrils. This finding is consistent with previous surface-specific vibrational sum-frequency generation (VSFG) spectroscopic results ( VandenAkker et al. J. Am. Chem. Soc. , 2011 , 133 , 18030 - 18033 , DOI: 10.1021/ja206513r ). In conclusion, only advanced vibrational spectroscopic techniques sensitive to surface structure such as TERS and VSFG are able to reveal the difference in structure that underlies the distinct morphology and rigidity of different amyloid

  14. Synthesis and Characterization of Ba(Zr{sub x}Ti{sub 1-x})O{sub 3} Solid Solutions Using Impedance Spectroscopic Techniques

    SciTech Connect

    Bajpai, P. K.; Mohan, C. R. K.

    2011-11-22

    Technologically important solid solutions of Ba(Zr{sub x}Ti{sub 1-x})O{sub 3} are synthesized using conventional solid state route. Relatively dense and single phase ceramics are confirmed using X-ray diffraction. Homogeneous and micron size grain growth is characterized using SEM. Impedance spectroscopy is used to study the electrical properties of ceramics. Broad and diffuse impedance loss peak is observed above 250 deg. C, which shifts towards higher frequency with increase in temperature. The distribution of relaxation frequency may be associated with the B-site cationic disorder due to the random distribution of (Zr{sup 4+}/Ti{sup +4}) having different ionic radii. Impedance relaxation obeys the Arrhenius relation with activation energy, E{tau} is 0.31 eV and 0.48 eV for BZT compositions with x = 0.10 and 0.15 respectively. Equivalent circuit representation using two RC element coupled in parallel is used to analyse the impedance response.

  15. Impedance Spectroscopic Indication for Solid State Electrochemical Reaction in (CH3NH3)PbI3 Films.

    PubMed

    Zohar, Arava; Kedem, Nir; Levine, Igal; Zohar, Dorin; Vilan, Ayelet; Ehre, David; Hodes, Gary; Cahen, David

    2016-01-01

    Halide perovskite-based solar cells still have limited reproducibility, stability, and incomplete understanding of how they work. We track electronic processes in [CH3NH3]PbI3(Cl) ("perovskite") films in vacuo, and in N2, air, and O2, using impedance spectroscopy (IS), contact potential difference, and surface photovoltage measurements, providing direct evidence for perovskite sensitivity to the ambient environment. Two major characteristics of the perovskite IS response change with ambient environment, viz. -1- appearance of negative capacitance in vacuo or post-vacuo N2 exposure, indicating for the first time an electrochemical process in the perovskite, and -2- orders of magnitude decrease in the film resistance upon transferring the film from O2-rich ambient atmosphere to vacuum. The same change in ambient conditions also results in a 0.5 V decrease in the material work function. We suggest that facile adsorption of oxygen onto the film dedopes it from n-type toward intrinsic. These effects influence any material characterization, i.e., results may be ambient-dependent due to changes in the material's electrical properties and electrochemical reactivity, which can also affect material stability.

  16. Spectroscopic Study of Multiple IRAS Galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Hovhannisyan, L. R.; Sargsyan, L. A.

    2003-04-01

    Spectroscopic observations by the 2.6 m BAO telescope of IRAS galaxies identified on the basis of the First Byurakan Survey (BIG objects) are reported. Slit spectra were obtained for 16 objects, including components of 7 multiple systems and 2 individual galaxies. The red shifts were measured, and the radial velocities, distances, absolute stellar magnitudes, and infrared and far infrared luminosities were calculated. A diagnostic diagram has been constructed based on the intensity ratios of emission lines and the activity types of the objects have been determined. Two LINERs, five galaxies with composite spectra (Comp, one of which has Sy2 features) and seven HII regions were found. Two objects are ultraluminous IR galaxies (ULIG). It is shown that all the multiple systems are physical pairs or groups. The observed high IR luminosity confirms the view that ULIG/HLIGs may be associated with interactions of galaxies.

  17. Studies on Electrical behavior of Glucose using Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Juansah, Jajang; Yulianti, Wina

    2016-01-01

    In this work we report the electrical characteristics of glucose at different frequencies. We show the correlation between electrical properties (impedance, reactance, resistance and conductance) of glucose and glucose concentration. Electrical property measurements on glucose solution were performed in order to formulate the correlation. The measurements were conducted for frequencies between 50 Hz and 1 MHz. From the measurements, we developed a single-pole Cole-Cole graph as a function of glucose concentration.

  18. A Comparative Study of Four Impedance Eduction Methodologies Using Several Test Liners

    NASA Technical Reports Server (NTRS)

    Watson, Willie R.; Jones, Michael G.

    2013-01-01

    A comparative study of four commonly used impedance eduction methods is presented for a range of liner structures and test conditions. Two of the methods are restricted to uniform flow while the other two accommodate both uniform and boundary layer flows. Measurements on five liner structures (a rigid-wall insert, a ceramic tubular liner, a wire mesh liner, a low porosity conventional liner, and a high porosity conventional liner) are obtained using the NASA Langley Grazing Flow Impedance Tube. The educed impedance of each liner is presented for forty-two test conditions (three Mach numbers and fourteen frequencies). In addition, the effects of moving the acoustic source from upstream to downstream and the refractive effects of the mean boundary layer on the wire mesh liner are investigated. The primary conclusions of the study are that: (1) more accurate results are obtained for the upstream source, (2) the uniform flow methods produce nearly identical impedance spectra at and below Mach 0.3 but significant scatter in the educed impedance occurs at the higher Mach number, (3) there is better agreement in educed impedance among the methods for the conventional liners than for the rigid-wall insert, ceramic, or wire mesh liner, and (4) the refractive effects of the mean boundary layer on the educed impedance of the wire mesh liner are generally small except at Mach 0.5.

  19. Spectroscopic study of low-lying {sup 16}N levels

    SciTech Connect

    Bardayan, D. W.; Nesaraja, C. D.; Pain, S. D.; Smith, M. S.; O'Malley, P. D.; Cizewski, J. A.; Hatarik, R.; Peters, W. A.; Blackmon, J. C.; Chae, K. Y.; Jones, K. L.; Moazen, B. H.; Paulauskas, S.; Pittman, S. T.; Schmitt, K. T.; Chipps, K. A.; Kozub, R. L.; Shriner, J. F. Jr.; Matei, C.

    2008-11-15

    The magnitude of the {sup 15}N(n,{gamma}){sup 16}N reaction rate in asymptotic giant branch stars depends directly on the neutron spectroscopic factors of low-lying {sup 16}N levels. A new study of the {sup 15}N(d,p){sup 16}N reaction is reported populating the ground and first three excited states in {sup 16}N. The measured spectroscopic factors are near unity as expected from shell model calculations, resolving a long-standing discrepancy with earlier measurements that had never been confirmed or understood. Updated {sup 15}N(n,{gamma}){sup 16}N reaction rates are presented.

  20. Studies of deionization and impedance spectroscopy for blood analyzer

    NASA Astrophysics Data System (ADS)

    Kwong, Charlotte C.; Li, Nan; Ho, Chih-Ming

    2005-11-01

    Blood analysis provides vital information for health conditions. For instance, typical infection response is correlated to an elevated White Blood Cell (WBC) count, while low Red Blood Cell (RBC) count, hemoglobin and hematocrit are caused by anemia or internal bleeding. We are developing two essential modules, deionization (DI) chip and microfluidic cytometer with impedance spectroscopy flow, for enabling the realization of a single platform miniaturized blood analyzer. In the proposed analyzer, blood cells are preliminarily sorted by Dielectrophoretic (DEP) means into sub-groups, differentiated and counted by impedance spectroscopy in a flow cytometer. DEP techniques have been demonstrated to stretch DNA, align Carbon Nanotubes (CNT) and trap cells successfully. However, DEP manipulation does not function in biological media with high conductivity. The DI module is designed to account for this challenge. H Filter will serve as an ion extraction platform in a microchamber. Sample and buffer do not mix well in micro scale allowing the ions being extracted by diffusion without increasing the volume. This can keep the downstream processing time short. Micro scale hydrodynamic focusing is employed to place single cell passing along the central plane of the flow cytometer module. By applying an AC electrical field, suspended cells are polarized, membrane capacitance C m, cytoplasm conductivity σ c, and cytoplasm permittivity ɛ c will vary as functions of frequency. Tracing back the monitored current, the numbers of individual cell species can be evaluated.

  1. Transport and spectroscopic studies of liquid and polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Bopege, Dharshani Nimali

    Liquid and polymer electrolytes are interesting and important materials to study as they are used in Li rechargeable batteries and other electrochemical devices. It is essential to investigate the fundamental properties of electrolytes such as ionic conductivity, diffusion, and ionic association to enhance battery performance in different battery markets. This dissertation mainly focuses on the temperature-dependent charge and mass transport processes and ionic association of different electrolyte systems. Impedance spectroscopy and pulsed field gradient nuclear magnetic resonance spectroscopy were used to measure the ionic conductivity and diffusion coefficients of ketone and acetate based liquid electrolytes. In this study, charge and mass transport in non-aqueous liquid electrolytes have been viewed from an entirely different perspective by introducing the compensated Arrhenius formalism. Here, the conductivity and diffusion coefficient are written as an Arrhenius-like expression with a temperature-dependent static dielectric constant dependence in the exponential prefactor. The compensated Arrhenius formalism reported in this dissertation very accurately describes temperature-dependent conductivity data for acetate and ketone-based electrolytes as well as temperature-dependent diffusion data of pure solvents. We found that calculated average activation energies of ketone-based electrolytes are close to each other for both conductivity and diffusion data (in the range 24-26 kJ/mol). Also, this study shows that average activation energies of acetate-based electrolytes are higher than those for the ketone systems (in the range 33-37 kJ/mol). Further, we observed higher dielectric constants and ionic conductivities for both dilute and concentrated ketone solutions with temperature. Vibrational spectroscopy (Infrared and Raman) was used to probe intermolecular interactions in both polymer and liquid electrolytes, particularly those which contain lithium

  2. Impedance Scaling and Impedance Control

    NASA Astrophysics Data System (ADS)

    Chou, W.; Griffin, J.

    1997-05-01

    When a machine becomes really large, such as the Really Large Hadron Collider (RLHC),(G. W. Foster and E. Malamud, Fermilab-TM-1976 (June, 1996).) of which the circumference could reach the order of megameters, beam instability could be an essential bottleneck. This paper studies the scaling of the instability threshold vs. machine size when the coupling impedance scales in a ``normal'' way. It is shown that the beam would be intrinsically unstable for the RLHC. As a possible solution to this problem, it is proposed to introduce local impedance inserts for controlling the machine impedance. In the longitudinal plane, this could be done by using a heavily detuned rf cavity (e.g., a biconical structure), which could provide large imaginary impedance with the right sign (i.e., inductive or capacitive) while keeping the real part small. In the transverse direction, a carefully designed variation of the cross section of a beam pipe could generate negative impedance that would partially compensate the transverse impedance in one plane.

  3. Comparative Study of Impedance Eduction Methods, Part 2: NASA Tests and Methodology

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Watson, Willie R.; Howerton, Brian M.; Busse-Gerstengarbe, Stefan

    2013-01-01

    A number of methods have been developed at NASA Langley Research Center for eduction of the acoustic impedance of sound-absorbing liners mounted in the wall of a flow duct. This investigation uses methods based on the Pridmore-Brown and convected Helmholtz equations to study the acoustic behavior of a single-layer, conventional liner fabricated by the German Aerospace Center and tested in the NASA Langley Grazing Flow Impedance Tube. Two key assumptions are explored in this portion of the investigation. First, a comparison of results achieved with uniform-flow and shear-flow impedance eduction methods is considered. Also, an approach based on the Prony method is used to extend these methods from single-mode to multi-mode implementations. Finally, a detailed investigation into the effects of harmonic distortion on the educed impedance is performed, and the results are used to develop guidelines regarding acceptable levels of harmonic distortion

  4. Study of dielectric and impedance properties of Mn ferrites

    NASA Astrophysics Data System (ADS)

    Mujasam Batoo, Khalid

    2011-02-01

    The paper reports on the effect of Al substitution on the structural and electrical properties of bulk ferrite series of basic composition MnFe 2-2 xAl 2 xO 4 (0.0≤ x≤0.5) synthesized using solid state reaction method. XRD analysis confirms that all the samples exhibit single phase cubic spinel structure excluding presence of any secondary phase. The dielectric constant shows a normal behaviour with frequency, whereas the loss tangent exhibits an anomalous behaviour with frequency for all compositions. Variation of dielectric properties and ac conductivity with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and hopping of charge between Fe +2 and Fe +3 as well as between Mn +2 and Mn +3 ions at octahedral sites. The complex impedance plane spectra shows the presence of two semicircles up to x=0.2, and only one semicircle for the higher values of x. The analysis of the data shows that the resistive and capacitive properties of the Mn ferrite are mainly due to processes associated with grain and grain boundaries.

  5. Integrated Spectroscopic Studies of Hydrous Sulfate Minerals

    NASA Technical Reports Server (NTRS)

    Dyar, M. D.; Lane, M. D.; Bishop, J. L.; OConnor, V.; Cloutis, E.; Hiroi, T.

    2005-01-01

    Sulfate minerals have been identified in Martian meteorites and on Mars using a suite of instruments aboard the MER rovers. These results have confirmed previous groundbased observations and orbital measurements that suggested their presence. The orbiting OMEGA instrument on Mars Express is also finding evidence for sulfate. In order to better interpret remote-sensing data, we present here the results of a coordinated visible/near infrared (VNIR) reflectance, Moussbauer (MB), and thermal emittance study of wellcharacterized hydrous sulfate minerals.

  6. Spectroscopic Study of Microwave Induced Plasma

    SciTech Connect

    Jovicevic, S.

    2004-12-01

    The results of the spatial distribution studies of electron densities, excitation and rotational temperatures and atomic line intensities of various elements in an atmospheric pressure mini-MIP torch with tangential argon flow. The electron number density, ne, is determined from the width of the hydrogen H{beta} 486.13 nm line while excitation temperature, Texc, is evaluated from the Boltzmann plot of relative line intensities either of carrier gas-argon or neutral iron that is introduced in the form of aerosols in MIP, The rotational temperatures, Trot, are determined from the relative intensities of OH (R2 and Q1 branch) electronic band A2{sigma} - X2{pi} (0,0) and to N{sub 2}{sup +} first negative system B{sup 2} {sigma}{sub u}{sup +} - X{sup 2} {sigma}{sub g}{sup +} (P branch). For the selected input power of 100 W, the influence of hydrogen in the wet and desolvated aerosols and support gas and the corresponding changes of the electron density, excitation and rotational temperature distributions are studied. The influence of potassium, low ionization potential element, to the spatial distribution of ne, Texc and Trot is studied also. Spatial intensity distributions and maximum intensities for investigate atomic line are determinate for the same conditions.

  7. Progress report on nuclear spectroscopic studies

    SciTech Connect

    Bingham, C.R.; Guidry, M.W.; Riedinger, L.L.; Sorensen, S.P.

    1994-02-18

    The Nuclear Physics group at the University of Tennessee, Knoxville (UTK) is involved in several aspects of heavy-ion physics including both nuclear structure and reaction mechanisms. While the main emphasis is on experimental problems, the authors have maintained a strong collaboration with several theorists in order to best pursue the physics of their measurements. During the last year they have had several experiments at the ATLAS at Argonne National Laboratory, the GAMMASPHERE at the LBL 88 Cyclotron, and with the NORDBALL at the Niels Bohr Institute Tandem. Also, they continue to be very active in the WA93/98 collaboration studying ultra-relativistic heavy ion physics utilizing the SPS accelerator at CERN in Geneva, Switzerland and in the PHENIX Collaboration at the RHIC accelerator under construction at Brookhaven National Laboratory. During the last year their experimental work has been in three broad areas: (1) the structure of nuclei at high angular momentum, (2) the structure of nuclei far from stability, and (3) ultra-relativistic heavy-ion physics. The results of studies in these particular areas are described in this document. These studies concentrate on the structure of nuclear matter in extreme conditions of rotational motion, imbalance of neutrons and protons, or very high temperature and density. Another area of research is heavy-ion-induced transfer reactions, which utilize the transfer of nucleons to states with high angular momentum to learn about their structure and to understand the transfer of particles, energy, and angular momentum in collisions between heavy ions.

  8. Spectroscopic Studies of Atmospheric Aerosol Chemistry

    NASA Astrophysics Data System (ADS)

    Wamsley, R.; Leather, K.; Horn, A. B.; Percival, C.

    2008-12-01

    Particles are ubiquitous in the troposphere and are involved in chemical and physical processes affecting the composition of the atmosphere, climate, cloud albedo and human health (Finlayson-Pitts and Pitts, 2000). Organic species, such as alcohols, carboxylic acids, ketones, aldehydes, aromatics, alkenes and alkanes, originate both from anthropogenic and natural sources and comprise a large component of atmospheric particles. Gas-phase species, such as ozone, can oxidize these organics, changing the particle's oxygen-to carbon ratio and potentially altering its hygroscopicity, viscosity, morphology and reactivity. One reaction in particular, that between ozone and oleic acid, has been the focus of several recent studies and extensively researched by Ziemann (2005). Oleic acid reacts readily with ozone and has a low vapor pressure making this reaction convenient to study in the laboratory and has become the benchmark for studying heterogeneous reactions representing the oxidative processing of atmospheric organic aerosols. A critical source of uncertainty in reactivity estimates is a lack of understanding of the mechanism through which some VOCs are oxidized. This knowledge gap is especially critical for aromatic compounds. Because the intermediate reaction steps and products of aromatics oxidation are unknown, chemical mechanisms incorporate parameters estimated from environmental chamber experiments to represent their overall contribution to ozone formation, e.g. Volkamer et al. ( 2006). Previous studies of uncertainties in incremental reactivity estimates for VOCs found that the representation of aromatics chemistry contributed significantly to the estimated 40 - 50% uncertainties in the incremental reactivities of common aromatic compounds Carter et al. (2002). This study shows development of an effective IR method that can monitor the reaction and hence obtain the kinetics of the ozonolysis of an aromatic compound in the aerosol phase. The development of such

  9. Nonlinear spectroscopic studies of interfacial molecular ordering

    SciTech Connect

    Superfine, R.

    1991-07-01

    The second order nonlinear optical processes of second harmonic generation and sum frequency generation are powerful new probes of surfaces. They possess unusual surface sensitivity due to the symmetry properties of the nonlinear susceptibility. In particular, infrared-visible sum frequency generation (SFG) can obtain the vibrational spectrum of sub-monolayer coverages of molecules. In this thesis, we explore the unique information that can be obtained from SFG. We take advantage of the sensitivity of SFG to the conformation of alkane chains to study the interaction between adsorbed liquid crystal molecules and surfactant treated surfaces. The sign of the SFG susceptibility depends on the sign of the molecular polarizability and the orientation, up or down, of the molecule. We experimentally determine the sign of the susceptibility and use it to determine the absolute orientation to obtain the sign of the molecular polarizability and show that this quantity contains important information about the dynamics of molecular charge distributions. Finally, we study the vibrational spectra and the molecular orientation at the pure liquid/vapor interface of methanol and water and present the most detailed evidence yet obtained for the structure of the pure water surface. 32 refs., 4 figs., 2 tabs.

  10. Progress report on nuclear spectroscopic studies

    SciTech Connect

    Bingham, C.R.; Riedinger, L.L.; Sorensen, S.P.

    1996-01-16

    The experimental program in nuclear physics at the University of Tennessee, Knoxville, is led by Professors Carrol Bingham, Lee Riedinger, and Soren Sorenseni who respectively lead the studies of the exotic decay modes of nuclei far from stability, the program of high-spin research, and our effort in relativistic heavy-ion physics. Over the years, this broad program of research has been successful partially because of the shared University resources applied to this group effort. The proximity of the Oak Ridge National Laboratory has allowed us to build extremely strong programs of joint research, and in addition to play an important leadership role in the Joint Institute for Heavy Ion Research (JIHIR). Our experimental program is also very closely linked with those at other national laboratories: Argonne (collaborations involving the Fragment Mass Analyzer (FMA) and {gamma}-ray arrays), Brookhaven (the RHIC and Phenix projects), and Berkeley (GAMMASPHERE). We have worked closely with a variety of university groups in the last three years, especially those in the UNISOR and now UNIRIB collaborations. And, in all aspects of our program, we have maintained close collaborations with theorists, both to inspire the most exciting experiments to perform and to extract the pertinent physics from the results. The specific areas discussed in this report are: properties of high-spin states; study of low-energy levels of nuclei far from stability; and high energy heavy-ion physics.

  11. [FTIR spectroscopic studies of facial prosthetic adhesives].

    PubMed

    Kang, Biao; Yang, Qing-fang; Liang, Jian-feng; Zhao, Yi-min

    2008-10-01

    According to the composition of the traditional facial prosthetic adhesives, most of adhesives can be classified into two categories: acrylic polymer-based adhesive and silicone-based adhesive. In previous studies, measurements of various mechanical bond strengths were carried out, whereas the functional groups of the adhesives were evaluated seldom during the adhesion. In the present study the analysis of two facial prosthetic adhesives (Epithane and Secure Adhesive) was carried out by using infrared spectroscopy. Two adhesives in the form of fluid or semisolid were submitted to FTIR spectroscopy, respectively. The results showed that water and ammonia residue volatilized during the solidification of Epithane, and absorption peak reduction of carbonyl was due to the volatilization of acetate vinyl from Secure Adhesive. Similar silicone functional groups both in the silicone-based adhesive and in silicone elastomer could be the key to higher bond strength between silicone elastomer and skin with silicone-based adhesive. The position, shape of main absorption peaks of three adhesives didn't change, which showing that their main chemicals and basic structures didn't change during solidification. PMID:19123392

  12. Spectroscopic and quantum chemical studies on bromopyrazone

    NASA Astrophysics Data System (ADS)

    Gökce, Halil; Bahçeli, Semiha

    2014-12-01

    In this study, the FT-IR, micro-Raman and UV-vis. spectra of bromopyrazone molecule, C10H8BrN3O, (with synonym,1-phenyl-4-amino-5-bromopyridazon-(6) or 5-amino-4-bromo-2-phenyl-3(2H)-pyridazinone) were recorded experimentally. The molecular structure, vibrational wavenumbers, electronic transition absorption wavelengths in ethanol solvent, HOMOs and LUMOs analyses, molecular electrostatic potential (MEP), natural bond orbitals (NBO), nonlinear optical (NLO) properties and atomic charges of bromopyrazone molecule have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set in ground state. The obtained results show that the calculated vibrational frequencies and UV-vis. values are in a good agreement with experimental data.

  13. Spectroscopic studies of silver boro tellurite glasses

    SciTech Connect

    Kumar, E. Ramesh Kumari, K. Rajani Rao, B. Appa Bhikshamaiah, G.

    2014-04-24

    The FTIR absorption and Raman scattering studies were used to obtain the structural information of AgI−Ag{sub 2}O−[(1−x)B{sub 2}O{sub 3}−xTeO{sub 2}] (x=0 to 1 mol% in steps of 0.2) glasses. The glassy nature of the compounds has been confirmed by X-ray diffraction. FTIR and Raman spectra were recorded for all samples at room temperature. FTIR spectra which provides the information about the change in bond structure of the glasses. Raman spectra provide the effect of TeO{sub 2} on SBT glass system is that as increasing the concentration of TeO{sub 2} the band intensity at 707 cm{sup −1} increase.

  14. Spectroscopic study of acetylene and hydrogen cyanide

    NASA Astrophysics Data System (ADS)

    Rozario, Hoimonti Immaculata

    High-resolution molecular spectroscopy has been used to study acetylene line parameters and emission spectra of hydrogen cyanide. All acetylene spectra were recorded in our laboratory at the University of Lethbridge using a 3-channel tuneable diode laser spectrometer. N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the v1+v3 band of acetylene at seven temperatures in the range 213-333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters. The line-broadening and line-shift coefficients as well as their temperature-dependent parameters have been also evaluated theoretically, in the frame work of a semi-classical approach based on an exponential representation of the scattering operator, an intermolecular potential composed of electrostatic quadrupole--quadrupole and pairwise atom--atom interactions as well as on exact trajectories driven by an effective isotropic potential. The experimental results for both N2-broadening and shifting show good agreement with the theoretical results. We have studied the line intensities of the 1vl 20←0v120 band system from the HCN emission spectrum. The infrared emission spectrum of H12C 14N was measured at the Justus-Liebig University, Giessen, Germany. The emission spectrum was analyzed with the spectrum analysis software Symath running using Mathematica as a platform. This approach allowed us to retrieve information on band intensity parameters.

  15. Ultrafast spectroscopic studies of metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Hu, Min

    An important aim of nanoparticle research is to understand how the properties of materials depend on their size and shape. In this thesis, time-resolved spectroscopy has been used to measure the physical properties of nanometer sized objects, such as the characteristic time scale for heat dissipation and their elastic moduli. In our experiments, metal nanoparticles are excited with a sub-picosecond laser pulse, which causes a rapid increase in the lattice temperature. In the first project, the rate of heat dissipation from Au nanoparticles to their surroundings was examined for different size gold nanospheres in aqueous solution. Laser induced lattice heating can also impulsively excite the phonon modes of the particle that correlate with the expansion co-ordinates. For spherical Au particles the symmetric breathing mode is excited. Experimental results for ˜50 nm diameter Au particles were compared to a model calculation where the expansion coordinate is treated as a damped harmonic oscillator. This gives information about the excitation mechanism. In the second project, the extensional and breathing modes of cylindrical gold nanorods were studied by time-resolved spectroscopy. These experiments yield values for the elastic constants for the rods. Both the extensional mode and the breathing mode results show that gold nanorods produced by wet chemical techniques have a smaller elastic moduli than bulk gold. HR-TEM and SAED studies show that the rods have a 5-fold twinned structure with growth along the [110] crystal direction. However, neither the growth direction nor the twinning provide a simple explanation for the reduced elastic moduli measured in the experiments. In a final project, polydisperse silver nanoparticle samples were investigated. A signal due to coherently excited vibrational motion was observed. The analysis shows that the observed signal arises from the triangular-shaped particles, rather than the rods or spheres that are present in the sample

  16. Spectroscopic studies in open quantum systems

    PubMed

    Rotter; Persson; Pichugin; Seba

    2000-07-01

    The Hamiltonian H of an open quantum system is non-Hermitian. Its complex eigenvalues E(R) are the poles of the S matrix and provide both the energies and widths of the states. We illustrate the interplay between Re(H) and Im(H) by means of the different interference phenomena between two neighboring resonance states. Level repulsion may occur along the real or imaginary axis (the latter is called resonance trapping). In any case, the eigenvalues of the two states avoid crossing in the complex plane. We then calculate the poles of the S matrix and the corresponding wave functions for a rectangular microwave resonator with a scatter as a function of the area of the resonator as well as of the degree of opening to a waveguide. The calculations are performed by using the method of exterior complex scaling. Re(H) and Im(H) cause changes in the structure of the wave functions which are permanent, as a rule. The resonance picture obtained from the microwave resonator shows all the characteristic features known from the study of many-body systems in spite of the absence of two-body forces. The effects arising from the interplay between resonance trapping and level repulsion along the real axis are not involved in the statistical theory (random matrix theory).

  17. Fluorescence spectroscopic studies of DNA dynamics

    SciTech Connect

    Scalettar, B.A.

    1987-04-01

    Random solvent induced motions of DNA are manifest as nanosecond torsional oscillations of the helix backbone, nanosecond through millisecond bending deformations and overall rotational and translational diffusion of the polymer. Fluorescence spectroscopy is used to study this spectrum of DNA motions while ethidium monoazide was covalently bounded. The steady state fluorescence depolarization data indicate that the covalent monoazide/DNA complex exhibits internal motions characterized by an average angular amplitude of 26 degrees confirming reports of fast torsional oscillations in noncovalent ethidium bromide/DNA systems. Data obtained by use of a new polarized photobleaching recovery technique (FPR) reflect both the rotational dynamics of the polymer and the reversible photochemistry of the dye. To isolate the reorientational motion of the DNA, the FPR experiments were ran in two modes that differ only in the polarization of the bleaching light. A quotient function constructed from the data obtained in these two modes monitors only the rotational component of the FPR recovery. In specific applications those bending deformations of long DNA molecules that have characteristic relaxation times on the order of 100 microseconds have been resolved. A fluorescence correlation technique that relates fluctuations in particle number to center-of-mass motion was used to measure translational diffusion on coefficients of the plasmid PBR322 and a short oligomeric DNA. A theory that describes angular correlation in systems exhibiting cyclic, biologically directed reorientation and random Brownian rotation is developed.

  18. Integrated Spectroscopic Studies of Anhydrous Sulfate Minerals

    NASA Technical Reports Server (NTRS)

    Lane, M. D.; Bishop, J. L.; Dyar, M. D.; Cloutis, E.; Forray, F. L.; Hiroi, T.

    2005-01-01

    Sulfates have been identified in Martian soils and bedrock and are emerging as an important indicator for aqueous activity on Mars. Sulfate minerals can form in a variety of low-temperature (evaporitic; chemical-weathering) and high-temperature (volcanic/fumarolic; hydrothermal) environments and their formational environments can range from alkaline to acidic. Although sulfates generally form in the presence of water, not all sulfates are hydrous or contain water in their structures. Many of these anhydrous sulfates (Dana group 28; Strunz class 67A) are minerals that form as accompanying phases to the main minerals in ore deposits or as replacement deposits in sedimentary rocks. However, some form from thermal decomposition of OH or H2O-bearing sulfates, such as from the reaction [1]: jarosite = yavapaiite + Fe2O3 + H2O. Where known, the stability fields of these minerals all suggest that they would be stable under martian surface conditions [2]. Thus, anhydrous sulfate minerals may contribute to martian surface mineralogy, so they must be well-represented in spectral libraries used for interpretation of the Martian surface. We present here the preliminary results of an integrated study of emittance, reflectance, and Mossbauer spectroscopy of a suite of wel-lcharacterized anhydrous sulfates.

  19. Spectroscopic study of biologically active glasses

    NASA Astrophysics Data System (ADS)

    Szumera, M.; Wacławska, I.; Mozgawa, W.; Sitarz, M.

    2005-06-01

    It is known that the chemical activity phenomenon is characteristic for some inorganic glasses and they are able to participate in biological processes of living organisms (plants, animals and human bodies). An example here is the selective removal of silicate-phosphate glass components under the influence of biological solutions, which has been applied in designing glasses acting as ecological fertilizers of controlled release rate of the nutrients for plants. The structure of model silicate-phosphate glasses containing the different amounts of the glass network formers, i.e. Ca 2+ and Mg 2+, as a binding components were studied. These elements besides other are indispensable of the normal growth of plants. In order to establish the function and position occupied by the particular components in the glass structure, the glasses were examined by FTIR spectroscopy (with spectra decomposition) and XRD methods. It has been found that the increasing amount of MgO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes systematically from a structure of the cristobalite type to a structure corresponding to forsterite type. Whilst the increasing content of CaO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes from a structure typical for cristobalite through one similar to the structure of calcium orthophosphate, to a structure corresponding to calcium silicates. The changing character of domains structure is the reason of different chemical activity of glasses.

  20. Raman spectroscopic studies on screening of myopathies.

    PubMed

    Gautam, Rekha; Vanga, Sandeep; Madan, Aditi; Gayathri, Narayanappa; Nongthomba, Upendra; Umapathy, Siva

    2015-02-17

    Myopathies are among the major causes of mortality in the world. There is no complete cure for this heterogeneous group of diseases, but a sensitive, specific, and fast diagnostic tool may improve therapy effectiveness. In this study, Raman spectroscopy is applied to discriminate between muscle mutants in Drosophila on the basis of associated changes at the molecular level. Raman spectra were collected from indirect flight muscles of mutants, upheld(1) (up(1)), heldup(2) (hdp(2)), myosin heavy chain(7) (Mhc(7)), actin88F(KM88) (Act88F(KM88)), upheld(101) (up(101)), and Canton-S (CS) control group, for both 2 and 12 days old flies. Difference spectra (mutant minus control) of all the mutants showed an increase in nucleic acid and β-sheet and/or random coil protein content along with a decrease in α-helix protein. Interestingly, the 12th day samples of up(1) and Act88F(KM88) showed significantly higher levels of glycogen and carotenoids than CS. A principal components based linear discriminant analysis classification model was developed based on multidimensional Raman spectra, which classified the mutants according to their pathophysiology and yielded an overall accuracy of 97% and 93% for 2 and 12 days old flies, respectively. The up(1) and Act88F(KM88) (nemaline-myopathy) mutants form a group that is clearly separated in a linear discriminant plane from up(101) and hdp(2) (cardiomyopathy) mutants. Notably, Raman spectra from a human sample with nemaline-myopathy formed a cluster with the corresponding Drosophila mutant (up(1)). In conclusion, this is the first demonstration in which myopathies, despite their heterogeneity, were screened on the basis of biochemical differences using Raman spectroscopy. PMID:25583313

  1. Interactions of Isophorone Derivatives with DNA: Spectroscopic Studies

    PubMed Central

    Deiana, Marco; Matczyszyn, Katarzyna; Massin, Julien; Olesiak-Banska, Joanna; Andraud, Chantal; Samoc, Marek

    2015-01-01

    Interactions of three new isophorone derivatives, Isoa Isob and Isoc with salmon testes DNA have been investigated using UV-Vis, fluorescence and circular dichroism spectroscopic methods. All the studied compounds interact with DNA through intercalative binding mode. The stoichiometry of the isophorone/DNA adducts was found to be 1:1. The fluorescence quenching data revealed a binding interaction with the base pairs of DNA. The CD data indicate that all the investigated isophorones induce DNA modifications. PMID:26069963

  2. Age-related changes in ac-impedance spectroscopy studies of normal human dentine: further investigations.

    PubMed

    Eldarrat, A H; High, A S; Kale, G M

    2010-01-01

    One of the age-related changes occurring in dentine structure is the formation of peritubular dentine on the inner walls of dentinal tubules leading to complete closure of tubules. Ac-impedance is safe, fast and non-invasive technique. In the last decade, the popularity of the technique has increased in dental research. Several investigators have used the technique to detect tooth cracks and caries. The results of in vitro studies showed that ac-impedance technique was more advanced for caries detection than visual and radiographic methods. However, other studies demonstrated that the accuracy of impedance measurements can be affected by many factors such as remineralization after tooth eruption. A study has been published on effect of age on impedance measurements by the authors for two age groups by employing ac-impedance spectroscopy. Therefore, the aim of this study was to demonstrate the importance of this technique by conducting further investigations on dentine samples of wider age groups. Dentine samples were prepared from extracted sound third molars of known patient age. The ac-impedance measurements were carried out over a wide range of frequency. After performing all electrical measurements, dentine samples were examined under SEM to correlate the electrical measurements with their structure. Impedance measurements showed that there were differences in impedance between young and old dentine. One-way ANOVA of the means of resistance and capacitance for all age groups (20, 25, 30, 40 and 50 years old dentine) revealed a significant difference (ANOVA, P < 0.0001) as a function of age. Applying Tukey's post hoc test, to the same data showed that this difference was due to the 50 years old dentine for resistance and was due to the 40 and 50 years old dentine for capacitance which were statistically different to all other groups. SEM investigation of dentine samples showed that young dentine is characterized by open dentinal tubules distributed all over the

  3. Spectroscopic studies of cold, gas-phase biomolecular ions

    NASA Astrophysics Data System (ADS)

    Rizzo, Thomas R.; Stearns, Jaime A.; Boyarkin, Oleg V.

    While the marriage of mass spectrometry and laser spectroscopy is not new, developments over the last few years in this relationship have opened up new horizons for the spectroscopic study of biological molecules. The combination of electrospray ionisation for producing large biological molecules in the gas phase together with cooled ion traps and multiple-resonance laser schemes are allowing spectroscopic investigation of individual conformations of peptides with more than a dozen amino acids. Highly resolved infrared spectra of single conformations of such species provide important benchmarks for testing the accuracy of theoretical calculations. This review presents a number of techniques employed in our laboratory and in others for measuring the spectroscopy of cold, gas-phase protonated peptides. We show examples that demonstrate the power of these techniques and evaluate their extension to still larger biological molecules.

  4. Studies of longitudinal profile of electron bunches and impedance measurements at Indus-2 synchrotron radiation source

    NASA Astrophysics Data System (ADS)

    Garg, Akash Deep; Yadav, S.; Kumar, Mukesh; Shrivastava, B. B.; Karnewar, A. K.; Ojha, A.; Puntambekar, T. A.

    2016-04-01

    Indus-2 is a 3rd generation synchrotron radiation source at the Raja Ramanna Centre for Advanced Technology (RRCAT) in India. We study the longitudinal profile of electrons in Indus-2 by using dual sweep synchroscan streak camera at visible diagnostic beamline. In this paper, the longitudinal profiles of electron bunch are analyzed by filling beam current in a single bunch mode. These studies are carried at injection energy (550 MeV) and at ramped beam energy (2.5 GeV). The effects of the wakefield generated interactions between the circulating electrons and the surrounding vacuum chamber are analyzed in terms of measured effects on longitudinal beam distribution. The impedance of the storage ring is obtained by fitting the solutions of Haissinski equation to the measured bunch lengthening with different impedance models. The impedance of storage ring obtained by a series R+L impedance model indicates a resistance (R) of 1350±125 Ω, an inductance (L) of 180±25 nH and broadband impedance of 2.69 Ω. These results are also compared with the values obtained from measured synchronous phase advancing and scaling laws. These studies are very useful in better understanding and control of the electromagnetic interactions.

  5. Single cells and intracellular processes studied by a plasmonic-based electrochemical impedance microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Foley, Kyle; Shan, Xiaonan; Wang, Shaopeng; Eaton, Seron; Nagaraj, Vinay J.; Wiktor, Peter; Patel, Urmez; Tao, Nongjian

    2011-03-01

    Electrochemical impedance spectroscopy is a crucial tool for the detection and study of various biological substances, from DNA and proteins to viruses and bacteria. It does not require any labelling species, and methods based on it have been developed to study cellular processes (such as cell spreading, adhesion, invasion, toxicology and mobility). However, data have so far lacked spatial information, which is essential for investigating heterogeneous processes and imaging high-throughput microarrays. Here, we report an electrochemical impedance microscope based on surface plasmon resonance that resolves local impedance with submicrometre spatial resolution. We have used an electrochemical impedance microscope to monitor the dynamics of cellular processes (apoptosis and electroporation of individual cells) with millisecond time resolution. The high spatial and temporal resolution makes it possible to study individual cells, but also resolve subcellular structures and processes without labels, and with excellent detection sensitivity (~2 pS). We also describe a model that simulates cellular and electrochemical impedance microscope images based on local dielectric constant and conductivity.

  6. Single cells and intracellular processes studied by a plasmonic-based electrochemical impedance microscopy.

    PubMed

    Wang, Wei; Foley, Kyle; Shan, Xiaonan; Wang, Shaopeng; Eaton, Seron; Nagaraj, Vinay J; Wiktor, Peter; Patel, Urmez; Tao, Nongjian

    2011-03-01

    Electrochemical impedance spectroscopy is a crucial tool for the detection and study of various biological substances, from DNA and proteins to viruses and bacteria. It does not require any labelling species, and methods based on it have been developed to study cellular processes (such as cell spreading, adhesion, invasion, toxicology and mobility). However, data have so far lacked spatial information, which is essential for investigating heterogeneous processes and imaging high-throughput microarrays. Here, we report an electrochemical impedance microscope based on surface plasmon resonance that resolves local impedance with submicrometre spatial resolution. We have used an electrochemical impedance microscope to monitor the dynamics of cellular processes (apoptosis and electroporation of individual cells) with millisecond time resolution. The high spatial and temporal resolution makes it possible to study individual cells, but also resolve subcellular structures and processes without labels, and with excellent detection sensitivity (~2 pS). We also describe a model that simulates cellular and electrochemical impedance microscope images based on local dielectric constant and conductivity.

  7. Mapping Electrical Impedance Spectra of the Healthy Oral Mucosa: a Pilot Study

    PubMed Central

    Richter, Ivica; Alajbeg, Ivan; Boras, Vanja Vučićević; Rogulj, Ana Andabak

    2015-01-01

    Objective Electrical impedance is the resistance to the electric current flow through a tissue and depends on the tissue’s structure and chemical composition. The aim of this study was to map electrical impedance spectra for each region of the healthy oral mucosa. Materials and Methods Electrical impedance was measured in 30 participants with healthy oral mucosa. Measurements were performed in 14 points on the right and the left side of the oral cavity, and repeated after 7 and 14 days respectively. Results The lowest values were measured on the tongue dorsum and the highest values were measured on the hard palate. No significant differences were found between the right and the left side. Significantly higher values were found in females on the upper labial mucosa, tongue dorsum and the ventral tongue. Significant difference between smokers and non-smokers on the lower labial mucosa and floor of the mouth was found. Electrical impedance was negatively correlated with salivary flow on the upper labial mucosa, hard palate, tongue dorsum and sublingual mucosa. Higher variability of measurements was found at low frequencies. Conclusions Electrical impedance mostly depends on the degree of mucosal keratinization. Demographic and clinical factors probably affect its values. Further studies with bigger number of participants are required. PMID:27688418

  8. Mapping Electrical Impedance Spectra of the Healthy Oral Mucosa: a Pilot Study

    PubMed Central

    Richter, Ivica; Alajbeg, Ivan; Boras, Vanja Vučićević; Rogulj, Ana Andabak

    2015-01-01

    Objective Electrical impedance is the resistance to the electric current flow through a tissue and depends on the tissue’s structure and chemical composition. The aim of this study was to map electrical impedance spectra for each region of the healthy oral mucosa. Materials and Methods Electrical impedance was measured in 30 participants with healthy oral mucosa. Measurements were performed in 14 points on the right and the left side of the oral cavity, and repeated after 7 and 14 days respectively. Results The lowest values were measured on the tongue dorsum and the highest values were measured on the hard palate. No significant differences were found between the right and the left side. Significantly higher values were found in females on the upper labial mucosa, tongue dorsum and the ventral tongue. Significant difference between smokers and non-smokers on the lower labial mucosa and floor of the mouth was found. Electrical impedance was negatively correlated with salivary flow on the upper labial mucosa, hard palate, tongue dorsum and sublingual mucosa. Higher variability of measurements was found at low frequencies. Conclusions Electrical impedance mostly depends on the degree of mucosal keratinization. Demographic and clinical factors probably affect its values. Further studies with bigger number of participants are required.

  9. Monitoring of CRT by means of impedance multiple measurements - simulation studies

    NASA Astrophysics Data System (ADS)

    Lewandowska, M.; Wtorek, J.; Bujnowski, A.; Mierzejewski, L.

    2010-04-01

    Cardiac resynchronization therapy (CRT) is a very promising treatment for patients with congestive heart failure. An Impedance Cardiography (ICG) is used for evaluation of heart mechanical activity. A simulation study with the use of a FEM model was performed. The developed realistic model of the thorax, based on CT data obtained from examination of a 68-year-old man, consisted of 212 000 tetrahedral elements. Different configurations of electrodes allowing extraction of ventricular components from impedance signal were examined. The associated sensitivity distributions were calculated for different phases of heart contraction and blood distribution inside the thorax. These sensitivity distributions were compared to that obtained for a uniform model of the thorax described by average conductivity. The performed simulation studies proved that it is possible to extract ventricular components of impedance signal with a reasonable accuracy.

  10. The Influence of Nanopore Dimensions on the Electrochemical Properties of Nanopore Arrays Studied by Impedance Spectroscopy

    PubMed Central

    Kant, Krishna; Priest, Craig; Shapter, Joe G.; Losic, Dusan

    2014-01-01

    The understanding of the electrochemical properties of nanopores is the key factor for better understanding their performance and applications for nanopore-based sensing devices. In this study, the influence of pore dimensions of nanoporous alumina (NPA) membranes prepared by an anodization process and their electrochemical properties as a sensing platform using impedance spectroscopy was explored. NPA with four different pore diameters (25 nm, 45 nm and 65 nm) and lengths (5 μm to 20 μm) was used and their electrochemical properties were explored using different concentration of electrolyte solution (NaCl) ranging from 1 to 100 μM. Our results show that the impedance and resistance of nanopores are influenced by the concentration and ion species of electrolytes, while the capacitance is independent of them. It was found that nanopore diameters also have a significant influence on impedance due to changes in the thickness of the double layer inside the pores. PMID:25393785

  11. A new approach to the study of impedance characteristics of tympanic membrane.

    PubMed

    Bogomolov, A V; Dragan, S P

    2015-01-01

    A new approach to studying the tympanic membrane impedance characteristics, based on the analysis of polyharmonic acoustic signals reflected by the tympanic membrane, is described. For this purpose, the acoustic pressure and the phase difference between the acoustic vibrations in two sections of a waveguide sealingly connecting the external auditory meatus and a generator of polyharmonic audio signals is measured. By processing the results of measurements, the estimates of the frequency-dependent reflection coefficients, absorption coefficients, and components of the acoustic impedance of the tympanic membrane are calculated. The features that principally distinguish the developed approach from other approaches are the absence of the necessity to create a positive pressure in the external auditory meatus, the absence of ultrasonic radiation into the external auditory meatus and a high-intensity sound, and the possibility of direct measurement of the tympanic membrane impedance in the audio frequency range with any step. PMID:26518544

  12. Impedance study of membrane dehydration and compression in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Le Canut, Jean-Marc; Latham, Ruth; Mérida, Walter; Harrington, David A.

    Electrochemical impedance spectroscopy (EIS) is used to measure drying and rehydration in proton exchange membrane fuel cells running under load. The hysteresis between forward and backward acquisition of polarization curves is shown to be largely due to changes in the membrane resistance. Drying tests are carried out with hydrogen and simulated reformate (hydrogen and carbon dioxide), and quasi-periodic drying and rehydration conditions are studied. The membrane hydration state is clearly linked to the high-frequency arc in the impedance spectrum, which increases in size for dry conditions indicating an increase in membrane resistance. Changes in impedance spectra as external compression is applied to the cell assembly show that EIS can separate membrane and interfacial effects, and that changes in membrane resistance dominate. Reasons for the presence of a capacitance in parallel with the membrane resistance are discussed.

  13. Studies on LiFePO 4 as cathode material using impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Schmidt, Jan Philipp; Chrobak, Thorsten; Ender, Moses; Illig, Jörg; Klotz, Dino; Ivers-Tiffée, Ellen

    Lithium iron phosphate is a promising cathode material for the use in hybrid electrical vehicles (HEV) meeting the demands of good stability during cycling and safe operation due to reduced risk of thermal runaway. However, slow solid state diffusion and poor electrical conductivity reduce power capability. For further improvement, the identification of the rate determining processes is necessary. Electrochemical impedance spectroscopy (EIS) has proven to be a powerful tool for the characterization of electrochemical systems. In this contribution a deconvolution of the impedance with the distribution of relaxation times (DRTs) is used to obtain a better resolution in frequency domain. Therewith, the relevant loss processes are identified and an impedance model is developed. Using DRT and CNLS-fit allows the determination of time constants and polarization resistances of all relevant loss processes. Furthermore, their temperature behavior is studied and a physical interpretation is provided.

  14. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Bertram, F.; Zhang, F.; Evertsson, J.; Carlà, F.; Pan, J.; Messing, M. E.; Mikkelsen, A.; Nilsson, J.-O.; Lundgren, E.

    2014-07-01

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  15. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    SciTech Connect

    Bertram, F. Evertsson, J.; Messing, M. E.; Mikkelsen, A.; Lundgren, E.; Zhang, F.; Pan, J.; Carlà, F.; Nilsson, J.-O.

    2014-07-21

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  16. Spectroscopic and dynamical studies of highly energized small polyatomic molecules

    SciTech Connect

    Field, R.W.; Silbey, R.J.

    1993-12-01

    The authors have initiated a program to perform spectroscopic and dynamic studies of small molecules. Large amplitude motions in excited acetylene were discussed along with plans to record the dispersed fluorescence (DF) and the stimulated emission pumping (SEP) spectra. SEP spectra were reported for the formyl radical. A Fourier transform spectrometer was discussed with respect to its ability to probe the structure of radicals. This instrument is capable of performing studies using various techniques such as magnetic rotation spectroscopy and sub-Doppler sideband-OODR Zeman (SOODRZ) spectroscopy.

  17. A study on the impact of lithium-ion cell relaxation on electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Barai, Anup; Chouchelamane, Gael H.; Guo, Yue; McGordon, Andrew; Jennings, Paul

    2015-04-01

    Lithium-ion (Li-ion) batteries are of great interest to the automotive industry due to their higher power and energy density, higher cell voltage, longer cycle life and lower self-discharge compared to other battery chemistries. Electrochemical impedance spectroscopy is a powerful tool employed to investigate the fundamental electrochemical reactions within a Li-ion battery cell, which relates to state of charge, internal temperature and state of health. Its effectiveness has established it as a core method to study electrochemical behaviour of batteries in both off-line and on-line applications. In this work it is shown that in addition to state of charge, internal temperature and state of health, the time period between the removal of an electrical load and the impedance measurement affects the results. The study of five commercially available cells of varying capacities and electrode chemistries show that, regardless of cell type, maximum impedance change takes place within the first 4 h of the relaxation period. The root cause of this impedance change has been discussed from an electrochemical perspective.

  18. Electrochemical Impedance Spectroscopy Study on Corrosion Protection of Acrylate Nanocomposite on Mild Steel Doped Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Mahmud, M. R.; Akhir, M. M.; Shamsudin, M. S.; Afaah, A. N.; Aadila, A.; Asib, N. A. M.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Harun, M. K.; Rusop, M.; Abdullah, S.

    2015-05-01

    Acrylate:carbon nanotubes (A:CNTs) nanocomposite thin film was prepared by sol- gel technique. The corrosion coating protection of acrylate:carbon nanotubes (CNTs) nanocomposite thin film has been coated on mild steel characterised by electrochemical impedance spectrometer (EIS) measurement and equivalent circuit model are employed to analyse coating impedance for corrosion protection. In this study, 3.5 w/v % sodium chloride (NaCl) solution was immersed the acrylate:carbon nanotubes nanocomposite thin film. As the results, the surface morphology were found that there formation of carbon nanotubes with good distribution on acrylate-based coating. From EIS measurement, A:CNTs nanocomposite thin film with 0.4 w/v % contain of CNTs was exhibited the highest coating impedance from Nyquist graph after immersed in sodium chloride solution and may provide the excellent corrosion protection. The Bode plots have shown the impedance is high at the beginning from the time at high frequency and slightly decreases with value of frequency become smaller.

  19. Comparative study of electrolyte additives using electrochemical impedance spectroscopy on symmetric cells

    NASA Astrophysics Data System (ADS)

    Petibon, R.; Sinha, N. N.; Burns, J. C.; Aiken, C. P.; Ye, Hui; VanElzen, Collette M.; Jain, Gaurav; Trussler, S.; Dahn, J. R.

    2014-04-01

    The effect of various electrolyte additives and additive combinations added to a 1 M LiPF6 EC:EMC electrolyte on the positive and negative electrodes surface of 1 year old wound LiCoO2/graphite cells and Li[Ni0.4Mn0.4Co0.2])O2/graphite cells was studied using electrochemical impedance spectroscopy (EIS) on symmetric cells. The additives tested were: vinylene carbonate (VC), trimethoxyboroxine (TMOBX), fluoroethylene carbonate (FEC), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and H2O alone or in combination. In general, compared to control electrolyte, the additives tested reduced the impedance of the positive electrode and increased the impedance of the negative electrode with the exception of LiTFSI in Li[Ni0.4Mn0.4Co0.2]O2/graphite wound cells. Higher charge voltage led to higher positive electrode impedance, with the exception of 2%VC + 2% FEC, and 2% LiTFSI. In some cases, some additives when mixed with another controlled the formation of the SEI at one electrode, and shared the formation of the SEI at one electrode when mixed with a different additive.

  20. Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.

    PubMed

    Dhiman, Mopsy; Kapur, Pawan; Ganguli, Abhijit; Singla, Madan Lal

    2012-09-01

    In this study the sensing capabilities of a combination of metals and conducting polymer sensing/working electrodes for tea liquor prepared by addition of different compounds using an impedance mode in frequency range 1 Hz-100 KHz at 0.1 V potential has been carried out. Classification of six different tea liquor samples made by dissolving various compounds (black tea liquor + raw milk from milkman), (black tea liquor + sweetened clove syrup), (black tea liquor + sweetened ginger syrup), (black tea liquor + sweetened cardamom syrup), (black tea liquor + sweet chocolate syrup) and (black tea liquor + vanilla flavoured milk without sugar) using six different working electrodes in a multi electrode setup has been studied using impedance and further its PCA has been carried out. Working electrodes of Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC) and conducting polymer electrodes of Polyaniline (PANI) and Polypyrrole (PPY) grown on an ITO surface potentiostatically have been deployed in a three electrode set up. The impedance response of these tea liquor samples using number of working electrodes shows a decrease in the real and imaginary impedance values presented on nyquist plots depending upon the nature of the electrode and amount of dissolved salts present in compounds added to tea liquor/solution. The different sensing surfaces allowed a high cross-selectivity in response to the same analyte. From Principal Component Analysis (PCA) plots it was possible to classify tea liquor in 3-4 classes using conducting polymer electrodes; however tea liquors were well separated from the PCA plots employing the impedance data of both conducting polymer and metal electrodes. PMID:23035436

  1. Spectroscopy study of the dynamics of the transencephalic electrical impedance in the perinatal brain during hypoxia.

    PubMed

    Seoane, Fernando; Lindecrantz, Kaj; Olsson, Torsten; Kjellmer, Ingemar; Flisberg, Anders; Bågenholm, Ralph

    2005-10-01

    Hypoxia/ischaemia is the most common cause of brain damage in neonates. Thousands of newborn children suffer from perinatal asphyxia every year. The cells go through a response mechanism during hypoxia/ischaemia, to maintain the cellular viability and, as a response to the hypoxic/ischaemic insult, the composition and the structure of the cellular environment are altered. The alterations in the ionic concentration of the intra- and extracellular and the consequent cytotoxic oedema, cell swelling, modify the electrical properties of the constituted tissue. The changes produced can be easily measured using electrical impedance instrumentation. In this paper, we report the results from an impedance spectroscopy study on the effects of the hypoxia on the perinatal brain. The transencephalic impedance, both resistance and reactance, was measured in newborn piglets using the four-electrode method in the frequency range from 20 kHz to 750 kHz and the experimental results were compared with numerical results from a simulation of a suspension of cells during cell swelling. The experimental results make clear the frequency dependence of the bioelectrical impedance, confirm that the variation of resistance is more sensitive at low than at high frequencies and show that the reactance changes substantially during hypoxia. The resemblance between the experimental and numerical results proves the validity of modelling tissue as a suspension of cells and confirms the importance of the cellular oedema process in the alterations of the electrical properties of biological tissue. The study of the effects of hypoxia/ischaemia in the bioelectrical properties of tissue may lead to the development of useful clinical tools based on the application of bioelectrical impedance technology.

  2. Spectroscopic Studies on Eu3+ Doped Boro-Tellurite Glasses

    NASA Astrophysics Data System (ADS)

    Selvaraju, K.; Marimuthu, K.

    2011-07-01

    Eu3+ doped boro-tellurite glasses have been synthesized and its optical behavior have been studied and reported. The presence of varying tellurium dioxide content results changes in spectroscopic behavoir were explored through UV-VIS, and Luminescence spectra. The bonding parameters have been calculated based on the observed band positions of the absorption spectra. The Judd-Ofelt intensity parameters Ωλ (λ = 2, 4 and 6) have been determined through the luminescence spectra without applying any constraints and the results are presented. The Judd-Ofelt parameters have been used to determine various optical properties corresponding to 5D0→7FJ (J = 1,2,3 and 4) transitions of Eu3+ ions. The varying optical properties of the prepared glasses with the change in tellurium dioxide have been studied and compared with similar studies.

  3. Spectroscopic studies of carbon impurities in PISCES-A

    SciTech Connect

    Ra, Y.; Hirooka, Y.; Leung, W.K.; Conn, R.W. . Inst. of Plasma and Fusion Research); Pospieszczyk, A. . Inst. fuer Plasmaphysik)

    1989-08-01

    The graphite used for the limiter of the tokamak reactor produces carbon-containing molecular impurities as a result of the interactions with the edge plasma. The behavior of these molecular impurities has been studied using emission spectroscopy. The present study includes: finding molecular bands and atomic lines in the visible spectral range which can be used for the study of the molecular impurities, studying the breakup processes of the molecular impurities on their way from the source into the plasma, developing a spectroscopic diagnostic method for the absolute measurement of the molecular impurity flux resulting from graphite erosion. For these studies, carbon-containing molecules such as CH{sub 4}, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, and CO{sub 2} were injected into the tokamak-boundary,like plasma generated by PISCES-A. The spectrograms of these gases were taken. Many useful bands and lines were determined from the spectrograms. The breakup processes of these gases were studied by observing the spatial profiles of the emission of the molecules and their radicals for different plasma conditions. For the absolute measurement of the eroded molecular impurity flux, the photon efficiency of the lines and bands were found by measuring the absolute number of the emitted photons and injected gas molecules. The chemical sputtering yield of graphite by hydrogen plasma was spectroscopically measured using the previously obtained photon efficiencies. It showed good agreement with results obtained by weight loss measurements. 16 refs., 7 figs., 1 tab.

  4. Combined spectroscopic and quantum chemical studies of ezetimibe

    NASA Astrophysics Data System (ADS)

    Prajapati, Preeti; Pandey, Jaya; Shimpi, Manishkumar R.; Srivastava, Anubha; Tandon, Poonam; Velaga, Sitaram P.; Sinha, Kirti

    2016-12-01

    Ezetimibe (EZT) is a hypocholesterolemic agent used for the treatment of elevated blood cholesterol levels as it lowers the blood cholesterol by blocking the absorption of cholesterol in intestine. Study aims to combine experimental and computational methods to provide insights into the structural and vibrational spectroscopic properties of EZT which is important for explaining drug substance physical and biological properties. Computational study on molecular properties of ezetimibe is presented using density functional theory (DFT) with B3LYP functional and 6-311++G(d,p) basis set. A detailed vibrational assignment has been done for the observed IR and Raman spectra of EZT. In addition to the conformational study, hydrogen bonding and molecular docking studies have been also performed. For conformational studies, the double well potential energy curves have been plotted for the rotation around the six flexible bonds of the molecule. UV absorption spectrum was examined in methanol solvent and compared with calculated one in solvent environment (IEF-PCM) using TD-DFT/6-31G basis set. HOMO-LUMO energy gap of both the conformers have also been calculated in order to predict its chemical reactivity and stability. The stability of the molecule was also examined by means of natural bond analysis (NBO) analysis. To account for the chemical reactivity and site selectivity of the molecules, molecular electrostatic potential (MEPS) map has been plotted. The combination of experimental and calculated results provide an insight into the structural and vibrational spectroscopic properties of EZT. In order to give an insight for the biological activity of EZT, molecular docking of EZT with protein NPC1L1 has been done.

  5. Spectroscopic studies on the photochemical decarboxylation mechanisms of synthetic pyrethroids.

    PubMed

    Suzuki, Yusuke; Ishizaka, Shoji; Kitamura, Noboru

    2012-12-01

    A novel radical trapping technique combined with a fluorescence spectroscopic analysis has been employed to investigate the radical intermediates produced by photodecarboxylation of four synthetic pyrethroids: fenvalerate (SMD), fenpropathrin (DTL), cyphenothrin (GKL), and cypermethrin (AGT). Under photoirradiation at >290 nm, all pyrethroids underwent direct photolysis via homolytic cleavage of the carbon-oxygen bonds in the ester groups. The consumed amount of a nitroxide free radical, as a trapping agent for the intermediate radical of a pyrethroid, was determined by ESR, which was the measure of the reaction yield of a photochemically generated α-cyano-3-phenoxybenzyl radical common to all pyrethroids. The reactivities of the pyrethroids studied was in the sequence of SMD > DTL > GKL > AGT. Furthermore, nanosecond transient absorption spectroscopy demonstrated that geminate recombination of the radical pair within a solvent cage is the main deactivation route of the photochemically generated α-cyano-3-phenoxybenzyl radical common for all pyrethroids studied.

  6. [Spectroscopic studies on transition metal ions in colored diamonds].

    PubMed

    Meng, Yu-Fei; Peng, Ming-Sheng

    2004-07-01

    Transition metals like nickel, cobalt and iron have been often used as solvent catalysts in high pressure high temperature (HPHT) synthesis of diamond, and nickel and cobalt ions have been found in diamond lattice. Available studies indicated that nickel and cobalt ions could enter the lattice as interstitial or substitutional impurities and form complexes with nitrogen. Polarized microscopy, SEM-EDS, EPR, PL and FTIR have been used in this study to investigate six fancy color natural and synthetic diamonds in order to determine the spectroscopic characteristics and the existing forms of transition metal ions in colored diamond lattice. Cobalt-related optical centers were first found in natural chameleon diamonds, and some new nickel and cobalt-related optical and EPR centers have also been detected in these diamond samples.

  7. [Spectroscopic studies on transition metal ions in colored diamonds].

    PubMed

    Meng, Yu-Fei; Peng, Ming-Sheng

    2004-07-01

    Transition metals like nickel, cobalt and iron have been often used as solvent catalysts in high pressure high temperature (HPHT) synthesis of diamond, and nickel and cobalt ions have been found in diamond lattice. Available studies indicated that nickel and cobalt ions could enter the lattice as interstitial or substitutional impurities and form complexes with nitrogen. Polarized microscopy, SEM-EDS, EPR, PL and FTIR have been used in this study to investigate six fancy color natural and synthetic diamonds in order to determine the spectroscopic characteristics and the existing forms of transition metal ions in colored diamond lattice. Cobalt-related optical centers were first found in natural chameleon diamonds, and some new nickel and cobalt-related optical and EPR centers have also been detected in these diamond samples. PMID:15766067

  8. Electrochemical cell design for the impedance studies of chlorine evolution at DSA anodes

    NASA Astrophysics Data System (ADS)

    Silva, J. F.; Dias, A. C.; Araújo, P.; Brett, C. M. A.; Mendes, A.

    2016-08-01

    A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS) studies of chlorine evolution on Dimensionally Stable Anodes (DSA®) has been developed. Despite being considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolution at DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSA anode current densities for chlorine evolution because they allow gas accumulation at the electrode surface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at high sodium chloride concentration (5 mol dm-3 NaCl) and high current densities (up to 140 mA cm-2) were recorded. Additionally, polarization curves and voltammograms were obtained showing little or no noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolution reaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms.

  9. Electrochemical cell design for the impedance studies of chlorine evolution at DSA(®) anodes.

    PubMed

    Silva, J F; Dias, A C; Araújo, P; Brett, C M A; Mendes, A

    2016-08-01

    A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS) studies of chlorine evolution on Dimensionally Stable Anodes (DSA(®)) has been developed. Despite being considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolution at DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSA anode current densities for chlorine evolution because they allow gas accumulation at the electrode surface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at high sodium chloride concentration (5 mol dm(-3) NaCl) and high current densities (up to 140 mA cm(-2)) were recorded. Additionally, polarization curves and voltammograms were obtained showing little or no noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolution reaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms.

  10. Electrochemical cell design for the impedance studies of chlorine evolution at DSA(®) anodes.

    PubMed

    Silva, J F; Dias, A C; Araújo, P; Brett, C M A; Mendes, A

    2016-08-01

    A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS) studies of chlorine evolution on Dimensionally Stable Anodes (DSA(®)) has been developed. Despite being considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolution at DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSA anode current densities for chlorine evolution because they allow gas accumulation at the electrode surface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at high sodium chloride concentration (5 mol dm(-3) NaCl) and high current densities (up to 140 mA cm(-2)) were recorded. Additionally, polarization curves and voltammograms were obtained showing little or no noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolution reaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms. PMID:27587166

  11. A Spectroscopic-Based Laboratory Experiment for Protein Conformational Studies

    ERIC Educational Resources Information Center

    Ramos, Carlos Henrique I.

    2004-01-01

    This article describes a practical experiment for teaching basic spectroscopic techniques to introduce the topic of protein conformational change to students in the field of molecular biology, biochemistry, or structural biology. The spectroscopic methods employed in the experiment are absorbance, for protein concentration measurements, and…

  12. Electrical impedance measurements in the arm and the leg during a thirty day bed rest study

    NASA Technical Reports Server (NTRS)

    Cardus, David; Jaweed, Mazher; McTaggart, Wesley

    1995-01-01

    The need to detect, follow, and understand the effects of gravity on body fluid distribution is a constant stimulus to the quest for new techniques in this area of research. One of these techniques is electrical bioimpedance spectroscopy (BIS). Although not new, this is a technique whose applications to biomedical research are fairly recent. What is new is the development of instrumentation that has made practical the use of impedance spectroscopy in the biomedical setting, particularly in studies involving human subjects. The purpose of this paper is to report impedance spectroscopy observations made on a subject who was submitted to bed rest for a period of thirty days. These observations were made as part of a study on muscle atrophy during a thirty day head down bed rest. Since bed rest studies are very costly in human and financial terms, and technically difficult to realize, we felt that even though the present study deals only with a single case it was worthy of reporting because it illustrates kinds of questions impedance spectroscopy may help to answer in microgravity research.

  13. Molecular spectroscopic study for suggested mechanism of chrome tanned leather

    NASA Astrophysics Data System (ADS)

    Nashy, Elshahat H. A.; Osman, Osama; Mahmoud, Abdel Aziz; Ibrahim, Medhat

    2012-03-01

    Collagen represents the structural protein of the extracellular matrix, which gives strength of hides and/or skin under tanning process. Chrome tan is the most important tanning agent all over the world. The methods for production of leather evolved over several centuries as art and engineering with little understanding of the underlying science. The present work is devoted to suggest the most probable mechanistic action of chrome tan on hide proteins. First the affect of Cr upon hide protein is indicated by the studied mechanical properties. Then the spectroscopic characterization of the hide protein as well as chrome tanned leather was carried out with Horizontal Attenuated Total Reflection (HATR) FT-IR. The obtained results indicate how the chromium can attached with the active sites of collagen. Molecular modeling confirms that chromium can react with amino as well as carboxylate groups. Four schemes were obtained to describe the possible interactions of chrome tan with hide proteins.

  14. A detailed spectroscopic study of an Italian fresco

    SciTech Connect

    Barilaro, Donatella; Crupi, Vincenza; Majolino, Domenico; Barone, Germana; Ponterio, Rosina

    2005-02-15

    In the present work we characterized samples of plasters and pictorial layers taken from a fresco in the Acireale Cathedral. The fresco represents the Coronation of Saint Venera, patron saint of this Ionian town. By performing a detailed spectroscopic analysis of the plaster preparation layer by Fourier-transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD), and of the painting layer by FTIR and confocal Raman microspectroscopy, scanning electron microscopy+energy dispersive x-ray spectroscopy, and XRD, we were able to identify the pigments and the binders present. In particular, Raman investigation was crucial to the characterization of the pigments thanks to the high resolution of the confocal apparatus used. It is worth stressing that the simultaneous use of complementary techniques was able to provide more complete information for the conservation of the artifact we studied.

  15. Spectroscopic study of Gd nanostructures quantum confined in Fe corrals

    DOE PAGESBeta

    Cao, R. X.; Sun, L.; Miao, B. F.; Li, Q. L.; Zheng, C.; Wu, D.; You, B.; Zhang, W.; Han, P.; Bader, S. D.; et al

    2015-07-10

    Low dimensional nanostructures have attracted attention due to their rich physical properties and potential applications. The essential factor for their functionality is their electronic properties, which can be modified by quantum confinement. Here the electronic states of Gd atom trapped in open Fe corrals on Ag(111) were studied via scanning tunneling spectroscopy. A single spectroscopic peak above the Fermi level is observed after Gd adatoms are trapped inside Fe corrals, while two peaks appear in empty corrals. The single peak position is close to the higher energy peak of the empty corrals. These findings, attributed to quantum confinement of themore » corrals and Gd structures trapped inside, are supported by tight-binding calculations. As a result, this demonstrates and provides insights into atom trapping in open corrals of various diameters, giving an alternative approach to modify the properties of nano-objects.« less

  16. Raman spectroscopic study of "The Malatesta": a Renaissance painting?

    PubMed

    Edwards, Howell G M; Vandenabeele, Peter; Benoy, Timothy J

    2015-02-25

    Raman spectroscopic analysis of the pigments on an Italian painting described as a "Full Length Portrait of a Gentleman", known also as the "Malatesta", and attributed to the Renaissance period has established that these are consistent with the historical research provenance undertaken earlier. Evidence is found for the early 19th Century addition of chrome yellow to highlighted yellow ochre areas in comparison with a similar painting executed in 1801 by Sir Thomas Lawrence of John Kemble in the role of Hamlet, Prince of Denmark. The Raman data are novel in that no analytical studies have previously been made on this painting and reinforces the procedure whereby scientific analyses are accompanied by parallel historical research.

  17. Spectroscopic study of Gd nanostructures quantum confined in Fe corrals

    SciTech Connect

    Cao, R. X.; Sun, L.; Miao, B. F.; Li, Q. L.; Zheng, C.; Wu, D.; You, B.; Zhang, W.; Han, P.; Bader, S. D.; Zhang, W. Y.; Ding, H. F.

    2015-07-10

    Low dimensional nanostructures have attracted attention due to their rich physical properties and potential applications. The essential factor for their functionality is their electronic properties, which can be modified by quantum confinement. Here the electronic states of Gd atom trapped in open Fe corrals on Ag(111) were studied via scanning tunneling spectroscopy. A single spectroscopic peak above the Fermi level is observed after Gd adatoms are trapped inside Fe corrals, while two peaks appear in empty corrals. The single peak position is close to the higher energy peak of the empty corrals. These findings, attributed to quantum confinement of the corrals and Gd structures trapped inside, are supported by tight-binding calculations. As a result, this demonstrates and provides insights into atom trapping in open corrals of various diameters, giving an alternative approach to modify the properties of nano-objects.

  18. Spectroscopic study of photo and thermal destruction of riboflavin

    NASA Astrophysics Data System (ADS)

    Astanov, Salikh; Sharipov, Mirzo Z.; Fayzullaev, Askar R.; Kurtaliev, Eldar N.; Nizomov, Negmat

    2014-08-01

    Influence of temperature and light irradiation on the spectroscopic properties of aqueous solutions of riboflavin was studied using linear dichroism method, absorption and fluorescence spectroscopy. It was established that in a wide temperature range 290-423 K there is a decline of absorbance and fluorescence ability, which is explained by thermodestruction of riboflavin. It is shown that the proportion of molecules, which have undergone degradation, are in the range of 4-28%, and depends on the concentration and quantity of temperature effects. Introduction of hydrochloric and sulfuric acids, as well as different metal ions leads to an increase in the photostability of riboflavin solutions by 2-2.5 times. The observed phenomena are explained by the formation protonation form of riboflavin and a complex between the metal ions and oxygen atoms of the carbonyl group of riboflavin, respectively.

  19. Raman spectroscopic study of "The Malatesta": a Renaissance painting?

    PubMed

    Edwards, Howell G M; Vandenabeele, Peter; Benoy, Timothy J

    2015-02-25

    Raman spectroscopic analysis of the pigments on an Italian painting described as a "Full Length Portrait of a Gentleman", known also as the "Malatesta", and attributed to the Renaissance period has established that these are consistent with the historical research provenance undertaken earlier. Evidence is found for the early 19th Century addition of chrome yellow to highlighted yellow ochre areas in comparison with a similar painting executed in 1801 by Sir Thomas Lawrence of John Kemble in the role of Hamlet, Prince of Denmark. The Raman data are novel in that no analytical studies have previously been made on this painting and reinforces the procedure whereby scientific analyses are accompanied by parallel historical research. PMID:25194320

  20. Spectroscopic study of the peculiar galaxy IC 883

    NASA Astrophysics Data System (ADS)

    Yakovleva, V. A.; Merkulova, O. A.; Karataeva, G. M.; Shalyapina, L. V.; Yablokova, N. V.; Burenkov, A. N.

    2016-04-01

    We analyze new optical spectroscopic observations obtained at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences with the SCORPIO focal reducer (in the modes of a Fabry-Perot interferometer (FPI) and long-slit spectroscopy) and the Multi-Pupil Fiber Spectrograph for the galaxy IC 883. We have confirmed that the main body of the galaxy rotates around its minor axis. The positions of the dynamical axes of the stellar and gaseous components have been found to differ by ~10°. The velocities in the SE tail do not correspond to the circular rotation around the galaxy's minor axis. This structure is probably a fragment of an unwound curved spiral arm. Regions with high velocity dispersions and peculiarities in the velocity fields have been found along the minor axis. Our study of the age and metallicity of the galaxy's stellar population has shown that the mean values of these parameters in the stellar disk, except for the central region ( r ≤ 5"), are ≈1 Gyr and ≈-0.4 dex, respectively. Both young (2-5 × 108 yr) and old (5-10 × 109 yr) stellar populations are present in the circumnuclear region. Our analysis of the spectroscopic data for the bright feature 8" south of the nucleus coincident in position with a compact X-ray source has shown that this is apparently a dwarf galaxy or a remnant of a companion galaxy. Our FPI observations in the Hα emission line and direct images have revealed a region of ionized gas that together with the already known structures along the minor axis forms a clumpy tidal structure of ionized gas pulled from the companion galaxy. The results of our study confirm the previously proposed hypothesis that the observed peculiar structures were formed by the merger of two galaxies. However, it can be said that IC 883 does not belong to the class of polar-ring galaxies.

  1. Single cells and intracellular processes studied by a plasmonic-based electrochemical impedance microscopy

    PubMed Central

    Wang, Wei; Foley, Kyle; Shan, Xiaonan; Wang, Shaopeng; Eaton, Seron; Nagaraj, Vinay J; Wiktor, Peter; Patel, Urmez; Tao, Nongjian

    2012-01-01

    We report an electrochemical impedance microscope (EIM) based on surface plasmon resonance. The new EIM can resolve local impedance with sub-micron spatial resolution, and monitor dynamics of various processes, such as apoptosis and electroporation of individual cells with millisecond time resolution. The high spatial and temporal resolution images make it possible to not only study individual cells, but also resolve the sub-cellular structures and processes without labels. The detection sensitivity achieved with the current setup is ~2 pS, which is excellent considering the conductance of a single ion channel is in the range of 5–400 pS. We describe also a model that simulates the EIM images of cells based on local dielectric constant and conductivity. PMID:21336333

  2. Influence of heart motion on cardiac output estimation by means of electrical impedance tomography: a case study.

    PubMed

    Proença, Martin; Braun, Fabian; Rapin, Michael; Solà, Josep; Adler, Andy; Grychtol, Bartłomiej; Bohm, Stephan H; Lemay, Mathieu; Thiran, Jean-Philippe

    2015-06-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technique that can measure cardiac-related intra-thoracic impedance changes. EIT-based cardiac output estimation relies on the assumption that the amplitude of the impedance change in the ventricular region is representative of stroke volume (SV). However, other factors such as heart motion can significantly affect this ventricular impedance change. In the present case study, a magnetic resonance imaging-based dynamic bio-impedance model fitting the morphology of a single male subject was built. Simulations were performed to evaluate the contribution of heart motion and its influence on EIT-based SV estimation. Myocardial deformation was found to be the main contributor to the ventricular impedance change (56%). However, motion-induced impedance changes showed a strong correlation (r = 0.978) with left ventricular volume. We explained this by the quasi-incompressibility of blood and myocardium. As a result, EIT achieved excellent accuracy in estimating a wide range of simulated SV values (error distribution of 0.57 ± 2.19 ml (1.02 ± 2.62%) and correlation of r = 0.996 after a two-point calibration was applied to convert impedance values to millilitres). As the model was based on one single subject, the strong correlation found between motion-induced changes and ventricular volume remains to be verified in larger datasets.

  3. What Impedes or Enhances My Studying? The Interrelation between Approaches to Learning, Factors Influencing Study Progress and Earned Credits

    ERIC Educational Resources Information Center

    Hailikari, Telle Katriina; Parpala, Anna

    2014-01-01

    The aim of the study is to explore how students' experiences of enhancing and impeding factors and approaches to learning are related to students' study progress. A total of 93 students from the Faculty of Arts and Humanities participated in the study by answering a Learn-questionnaire regarding their experiences of the enhancing and…

  4. A study of concrete slab damage detection based on the electromechanical impedance method.

    PubMed

    Hu, Xianyan; Zhu, Hongping; Wang, Dansheng

    2014-10-23

    Piezoelectric lead zirconate titanate (PZT) is being gradually applied into practice as a new intelligent material for structural health monitoring. In order to study the damage detection properties of PZT on concrete slabs, simply supported reinforced concrete slabs with piezoelectric patches attached to their surfaces were chosen as the research objects and the Electromechanical Impedance method (EMI) was adopted for research. Five kinds of damage condition were designed to test the impedance values at different frequency bands. Consistent rules are found by calculation and analysis. Both the root mean square deviation (RMSD) and the correlation coefficient deviation (CCD) damage indices are capable of detecting the structural damage. The newly proposed damage index Ry/Rx can also predict the changes well. The numerical and experimental studies verify that the Electromechanical Impedance method can accurately predict changes in the amount of damage in reinforced concrete slabs. The damage index changes regularly with the distance of damages to the sensor. This relationship can be used to determine the damage location. The newly proposed damage index Ry/Rx is accurate in determining the damage location.

  5. A Study of Concrete Slab Damage Detection Based on the Electromechanical Impedance Method

    PubMed Central

    Hu, Xianyan; Zhu, Hongping; Wang, Dansheng

    2014-01-01

    Piezoelectric lead zirconate titanate (PZT) is being gradually applied into practice as a new intelligent material for structural health monitoring. In order to study the damage detection properties of PZT on concrete slabs, simply supported reinforced concrete slabs with piezoelectric patches attached to their surfaces were chosen as the research objects and the Electromechanical Impedance method (EMI) was adopted for research. Five kinds of damage condition were designed to test the impedance values at different frequency bands. Consistent rules are found by calculation and analysis. Both the root mean square deviation (RMSD) and the correlation coefficient deviation (CCD) damage indices are capable of detecting the structural damage. The newly proposed damage index Ry/Rx can also predict the changes well. The numerical and experimental studies verify that the Electromechanical Impedance method can accurately predict changes in the amount of damage in reinforced concrete slabs. The damage index changes regularly with the distance of damages to the sensor. This relationship can be used to determine the damage location. The newly proposed damage index Ry/Rx is accurate in determining the damage location. PMID:25341438

  6. Spectroscopic studies of glassy phospho-silicate materials

    NASA Astrophysics Data System (ADS)

    Sitarz, Maciej; Handke, Mirosław; Fojud, Zbigniew; Jurga, Stefan

    2005-06-01

    The aim of the work is to determine the internal structure of bioactive glasses based on structural studies. Due to the absence of the long-range order, the X-ray methods usually applied in the studies of crystalline materials are of low applicability in the investigations of glasses. Therefore, spectroscopic methods, such as IR and NMR, which make it possible to 'see' the short- and the middle-range order are extremely suitable in their studies. IR investigations have shown that the glasses studied exhibit non-uniform domain composition, which should facilitate their transformation into glass-crystalline state. Additionally, detailed NMR measurements have been carried out in order to determine the influence of glass structure on the course of its crystallization. These studies make it possible to verify the common opinions on the middle-range order (domains) in the glasses studied. The results obtained for 27Al and 31P are particularly promising. Changes in the environment of [SiO 4] 4-tetrahedra, which can be spatially connected with various numbers of [PO 4] 3- and [AlO 4] 5- tetrahedra cause the presence of various types of bridging bonds, such as Si-O-Si, Si-O-Al and Si-O-P. This in turn has significant impact on the number and the shape of the bands occurring in the spectra.

  7. Impedance Mismatch study between the Microwave Generator and the PUPR Plasma Machine

    NASA Astrophysics Data System (ADS)

    Gaudier, Jorge R.; Castellanos, Ligeia; Encarnación, Kabir; Zavala, Natyaliz; Rivera, Ramón; Farahat, Nader; Leal, Edberto

    2006-12-01

    Impedance mismatch inside the connection from the microwave power generator to the plasma machine is studied. A magnetron power generator transmits microwaves of 2.45 GHz and variable power from 50W to 5000W, through a flexible rectangular waveguide to heat plasma inside a Mirror Cusp devise located at the Polytechnic University of Puerto Rico. Before the production of plasma, the residual gas of the devise must be extracted by a vacuum system (5Torr or better), then Argon gas is injected to the machine. The microwaves heat the Argon ions to initiate ionization and plasma is produced. A dielectric wall is used inside the rectangular waveguide to isolate the plasma machine and maintain vacuum. Even though the dielectric will not block the wave propagation, some absorption of microwaves will occur. This absorption will cause reflection, reducing the efficiency of the power transfer. Typically a thin layer of Teflon is used, but measurements using this dielectric show a significant reflection of power back to the generator. Due to the high-power nature of the generator (5KW), this mismatch is not desirable. An electromagnetic field solver based on the Finite Difference Time Domain Method(FDTD) is used to model the rectangular waveguide connection. The characteristic impedance of the simulation is compared with the analytical formula expression and a good agreement is obtain. Furthermore the Teflon-loaded guide is modeled using the above program and the input impedance is computed. The reflection coefficient is calculated based on the transmission line theory with the characteristic and input impedances. Based on the simulation results it is possible to optimize the thickness, shape and dielectric constant of the material, in order to seal the connection with a better match.

  8. Impedance Mismatch study between the Microwave Generator and the PUPR Plasma Machine

    SciTech Connect

    Gaudier, Jorge R.; Castellanos, Ligeia; Encarnacion, Kabir; Zavala, Natyaliz; Rivera, Ramon; Farahat, Nader; Leal, Edberto

    2006-12-04

    Impedance mismatch inside the connection from the microwave power generator to the plasma machine is studied. A magnetron power generator transmits microwaves of 2.45 GHz and variable power from 50W to 5000W, through a flexible rectangular waveguide to heat plasma inside a Mirror Cusp devise located at the Polytechnic University of Puerto Rico. Before the production of plasma, the residual gas of the devise must be extracted by a vacuum system (5Torr or better), then Argon gas is injected to the machine. The microwaves heat the Argon ions to initiate ionization and plasma is produced. A dielectric wall is used inside the rectangular waveguide to isolate the plasma machine and maintain vacuum. Even though the dielectric will not block the wave propagation, some absorption of microwaves will occur. This absorption will cause reflection, reducing the efficiency of the power transfer. Typically a thin layer of Teflon is used, but measurements using this dielectric show a significant reflection of power back to the generator. Due to the high-power nature of the generator (5KW), this mismatch is not desirable. An electromagnetic field solver based on the Finite Difference Time Domain Method(FDTD) is used to model the rectangular waveguide connection. The characteristic impedance of the simulation is compared with the analytical formula expression and a good agreement is obtain. Furthermore the Teflon-loaded guide is modeled using the above program and the input impedance is computed. The reflection coefficient is calculated based on the transmission line theory with the characteristic and input impedances. Based on the simulation results it is possible to optimize the thickness, shape and dielectric constant of the material, in order to seal the connection with a better match.

  9. Thoracic artificial lung impedance studies using computational fluid dynamics and in vitro models.

    PubMed

    Schewe, Rebecca E; Khanafer, Khalil M; Orizondo, Ryan A; Cook, Keith E

    2012-03-01

    Current thoracic artificial lungs (TALs) possess blood flow impedances greater than the natural lungs, resulting in abnormal pulmonary hemodynamics when implanted. This study sought to reduce TAL impedance using computational fluid dynamics (CFD). CFD was performed on TAL models with inlet and outlet expansion and contraction angles, θ, of 15°, 45°, and 90°. Pulsatile blood flow was simulated for flow rates of 2-6 L/min, heart rates of 80 and 100 beats/min, and inlet pulsatilities of 3.75 and 2. Pressure and flow data were used to calculate the zeroth and first harmonic impedance moduli, Z(0) and Z(1), respectively. The 45° and 90° models were also tested in vitro under similar conditions. CFD results indicate Z(0) increases as stroke volume and θ increase. At 4 L/min, 100 beats/min, and a pulsatility of 3.75, Z(0) was 0.47, 0.61, and 0.79 mmHg/(L/min) for the 15°, 45°, and 90° devices, respectively. Velocity band and vector plots also indicate better flow patterns in the 45° device. At the same conditions, in vitro Z (0) were 0.69 ± 0.13 and 0.79 ± 0.10 mmHg/(L/min), respectively, for the 45° and 90° models. These Z(0) are 65% smaller than previous TAL designs. In vitro, Z(1) increased with flow rate but was small and unlikely to significantly affect hemodynamics. The optimal design for flow patterns and low impedance was the 45° model. PMID:22009316

  10. Effect of Yttrium Doping in Barium Zirconium Titanate Ceramics: A Structural, Impedance, and Modulus Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Badapanda, Tanmaya; Cavalcante, Laécio Santos; da Luz, Geraldo Eduardo; Batista, Nouga Cardoso; Anwar, Shahid; Longo, Elson

    2013-09-01

    In the current article, we studied the effect of yttrium [Y3+] ions' substitution on the structure and electric behavior of barium zirconate titanate (BZT) ceramics with a general formula [Ba1- x Y2 x/3](Zr0.25Ti0.75)O3 (BYZT) with [ x = 0, 0.025, and 0.05] which were prepared by the solid-state reaction method. X-ray diffraction patterns indicate that these ceramics have a single phase with a perovskite-type cubic structure. Rietveld refinement data confirmed [BaO12], [ZrO6], [TiO6], and [YO6] clusters in the cubic lattice. The Y3+ ions' effects on the electric conductivity behavior of BZT ceramics as a function of temperature and frequency are described, which are based on impedance spectroscopy analyses. The complex impedance plots display a double semicircle which highlights the influences of grain and grain boundary on the ceramics. Impedance analyses showed that the resistance decreased with the increasing temperature and resulted in a negative temperature coefficient of the resistance property in all compositions. Modulus plots represent a non-Debye-type dielectric relaxation which is related to the grain and grain boundary as well as temperature-dependent electric relaxation phenomenon and an enhancement in the mobility barrier by Y3+ ions. Moreover, the electric conductivity increases with the replacement of Ba2+ by Y3+ ions may be due to the rise in oxygen vacancies.

  11. Study of the Dynamics of Transcephalic Cerebral Impedance Data during Cardio-Vascular Surgery

    NASA Astrophysics Data System (ADS)

    Atefi, S. R.; Seoane, F.; Lindecrantz, K.

    2013-04-01

    Postoperative neurological deficits are one of the risks associated with cardio vascular surgery, necessitating development of new techniques for cerebral monitoring. In this study an experimental observation regarding the dynamics of transcephalic Electrical Bioimpedance (EBI) in patients undergoing cardiac surgery with and without extracorporeal circulation (ECC) was conducted to investigate the potential use of electrical Bioimpedance for cerebral monitoring in cardio vascular surgery. Tetrapolar transcephalic EBI measurements at single frequency of 50 kHz were recorded prior to and during cardio vascular surgery. The obtained results show that the transcephalic impedance decreases in both groups of patients as operation starts, however slight differences in these two groups were also observed with the cerebral impedance reduction in patients having no ECC being less common and not as pronounced as in the ECC group. Changes in the cerebral impedance were in agreement with changes of haematocrit and temperature. The origin of EBI changes is still unexplained however these results encourage us to continue investigating the application of electrical bioimpedance cerebral monitoring clinically.

  12. EPR Spectroscopic Studies of [FeFe]-Hydrogenase Maturation

    PubMed Central

    Suess, Daniel L. M.

    2015-01-01

    Proton reduction and H2 oxidation are key elementary reactions for solar fuel production. Hydrogenases interconvert H+ and H2 with remarkable efficiency and have therefore received much attention in this context. For [FeFe]-hydrogenases, catalysis occurs at a unique cofactor called the H-cluster. In this article, we discuss ways in which EPR spectroscopy has elucidated aspects of the bioassembly of the H-cluster, with a focus on four case studies: EPR spectroscopic identification of a radical en route to the CO and CN− ligands of the H-cluster, tracing 57Fe from the maturase HydG into the H-cluster, characterization of the auxiliary Fe–S cluster in HydG, and isotopic labeling of the CN− ligands of HydA for electronic structure studies of its Hox state. Advances in cell-free maturation protocols have enabled several of these mechanistic studies, and understanding H-cluster maturation may in turn provide insights leading to improvements in hydrogenase production for biotechnological applications. PMID:26508821

  13. Theoretical and experimental study of the input impedance of the cylindrical cavity-backed rectangular slot antennas

    NASA Technical Reports Server (NTRS)

    Li, Ming-Yi; Hummer, Kenneth A.; Chang, Kai

    1991-01-01

    The authors study the input impedance of a cylindrical cavity-backed slot antenna based on mode matching and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. The numerical results agree very well with measurements. Two resonant frequencies were found from the input impedance. One resonant frequency is attributed to the rectangular slot and the other is due to the cavity. The slot length controls the first resonant frequency and has a much stronger effect on the input impedance at the antenna operating frequency as compared with the cavity length.

  14. Particle in a Disk: A Spectroscopic and Computational Laboratory Exercise Studying the Polycyclic Aromatic Hydrocarbon Corannulene

    ERIC Educational Resources Information Center

    Frey, E. Ramsey; Sygula, Andrzej; Hammer, Nathan I.

    2014-01-01

    This laboratory exercise introduces undergraduate chemistry majors to the spectroscopic and theoretical study of the polycyclic aromatic hydrocarbon (PAH), corannulene. Students explore the spectroscopic properties of corannulene using UV-vis and Raman vibrational spectroscopies. They compare their experimental results to simulated vibrational…

  15. Body fat measurement by bioelectrical impedance and air displacement plethysmography: a cross-validation study to design bioelectrical impedance equations in Mexican adults

    PubMed Central

    Macias, Nayeli; Alemán-Mateo, Heliodoro; Esparza-Romero, Julián; Valencia, Mauro E

    2007-01-01

    Background The study of body composition in specific populations by techniques such as bio-impedance analysis (BIA) requires validation based on standard reference methods. The aim of this study was to develop and cross-validate a predictive equation for bioelectrical impedance using air displacement plethysmography (ADP) as standard method to measure body composition in Mexican adult men and women. Methods This study included 155 male and female subjects from northern Mexico, 20–50 years of age, from low, middle, and upper income levels. Body composition was measured by ADP. Body weight (BW, kg) and height (Ht, cm) were obtained by standard anthropometric techniques. Resistance, R (ohms) and reactance, Xc (ohms) were also measured. A random-split method was used to obtain two samples: one was used to derive the equation by the "all possible regressions" procedure and was cross-validated in the other sample to test predicted versus measured values of fat-free mass (FFM). Results and Discussion The final model was: FFM (kg) = 0.7374 * (Ht2 /R) + 0.1763 * (BW) - 0.1773 * (Age) + 0.1198 * (Xc) - 2.4658. R2 was 0.97; the square root of the mean square error (SRMSE) was 1.99 kg, and the pure error (PE) was 2.96. There was no difference between FFM predicted by the new equation (48.57 ± 10.9 kg) and that measured by ADP (48.43 ± 11.3 kg). The new equation did not differ from the line of identity, had a high R2 and a low SRMSE, and showed no significant bias (0.87 ± 2.84 kg). Conclusion The new bioelectrical impedance equation based on the two-compartment model (2C) was accurate, precise, and free of bias. This equation can be used to assess body composition and nutritional status in populations similar in anthropometric and physical characteristics to this sample. PMID:17697388

  16. Infrared Imaging, Spectroscopic, and Photometric Studies of Comets

    NASA Technical Reports Server (NTRS)

    Gehrz, Robert D.

    1997-01-01

    We have continued our program of infrared (IR) photometric, imaging, spectroscopic, and polarimetric temporal observations of comets to study the properties of comet dust and comet nuclei. During the first two years we digitized our IR data base on P/Halley and other recent comets to facilitate further analysis and comparison with other data bases, and found compelling evidence for the emission of a burst of small grains from P/Halley's nucleus at perihelion. We reported imaging and photometric observations of Comets Austin 1990 V and Swift-Tuttle 1992. The Swift-Tuttle 1992t observations included IR photometry, several 7-14 micron long-slit spectra of the coma and a time-sequence of more than 150 10 micron broadband images of the coma. An analysis of near-IR images of the inner coma of P/Halley obtained on three consecutive nights in 1986 March showed sunwardjets. We completed our analysis of IR imaging spectrosco-photometric data on comets. We also obtained observations of Comets Hyakutake 1996 B2 and Hale/Bopp 1995 01. We obtained infrared imaging, photometric, spectroscopic and polarimetric temporal observations of bright comets using a network of five telescopes, with emphasis on simultaneous observations of comets at many wavelengths with different instruments. Our program offers several unique advantages: 1) rapid observational response to new comets with dedicated infrared telescopes; 2) observations within a few degrees of the sun when comets are near perihelion and 3) access to advanced infrared array imagers and spectrometers. In particular, reduction, analysis, publication and archiving of our Jupiter/sl-9 and Comet Hyakutake infrared data received special emphasis. Instrumentation development included installation of the latest version of the innovative FORTH telescope control and a data acquisition system that enables us to control three telescopes remotely by telephone from anywhere in the world for comet observations in broad daylight. We have

  17. Spectroscopic Studies of Molecular Systems relevant in Astrobiology

    NASA Astrophysics Data System (ADS)

    Fornaro, Teresa

    2016-01-01

    In the Astrobiology context, the study of the physico-chemical interactions involving "building blocks of life" in plausible prebiotic and space-like conditions is fundamental to shed light on the processes that led to emergence of life on Earth as well as to molecular chemical evolution in space. In this PhD Thesis, such issues have been addressed both experimentally and computationally by employing vibrational spectroscopy, which has shown to be an effective tool to investigate the variety of intermolecular interactions that play a key role in self-assembling mechanisms of nucleic acid components and their binding to mineral surfaces. In particular, in order to dissect the contributions of the different interactions to the overall spectroscopic signals and shed light on the intricate experimental data, feasible computational protocols have been developed for the characterization of the spectroscopic properties of such complex systems. This study has been carried out through a multi-step strategy, starting the investigation from the spectroscopic properties of the isolated nucleobases, then studying the perturbation induced by the interaction with another molecule (molecular dimers), towards condensed phases like the molecular solid, up to the case of nucleic acid components adsorbed on minerals. A proper modeling of these weakly bound molecular systems has required, firstly, a validation of dispersion-corrected Density Functional Theory methods for simulating anharmonic vibrational properties. The isolated nucleobases and some of their dimers have been used as benchmark set for identifying a general, reliable and effective computational procedure based on fully anharmonic quantum mechanical computations of the vibrational wavenumbers and infrared intensities within the generalized second order vibrational perturbation theory (GVPT2) approach, combined with the cost-effective dispersion-corrected density functional B3LYP-D3, in conjunction with basis sets of

  18. Vibrational spectroscopic study of vinyl substituted polycyclic aromatic hydrocarbons.

    PubMed

    Maurya, Anju; Rastogi, Shantanu

    2015-12-01

    The mid infrared emission features observed in various astrophysical sources are attributed to polycyclic aromatic hydrocarbon (PAH) molecules. The models of emission spectra from a collection of PAHs show uncertainty in matching the 6.2 μm feature. This indicates the need to consider a larger variety of PAHs and PAH derivatives. Chemical pathways towards formation of PAHs in the astrophysical environments involve vinyl substituted PAHs as intermediate products. Vibrational spectroscopic study of vinyl-PAHs is reported in the present work. The vinyl group is substituted at similar positions in eight different PAHs. The obtained optimized structures show that vinyl substitution at 2 position in acenes gives planar geometry, while all other vinyl-PAHs are non-planar. Infrared spectra is simulated for neutrals as well as for cations. The results are compared with the spectra of corresponding plain PAHs and analyzed for possible match with astrophysical observations. New features, due to vinyl group in the composite spectra, identified at 6.64, 6.92, 7.27, 8.77 and 10.35 μm fall close to some sub features of the observed emission spectra. The paper provides data that may be used in the emission models particularly along proto planetary nebulae type cool objects. PMID:26117194

  19. Spectroscopic study of HNO3 dissociation on ice.

    PubMed

    Marchand, Patrick; Marcotte, Guillaume; Ayotte, Patrick

    2012-12-13

    A detailed spectroscopic study of HNO(3):H(2)O binary amorphous mixtures, and of the adsorption of HNO(3) onto ice, is reported. Using a classical optics model, the extent of intermixing and of ionic dissociation of adsorbed HNO(3), which forms a strong acid with liquid water, is determined as a function of HNO(3) coverage and temperature. Even at temperatures as low as 45 K, where intermixing is limited to at most a few molecular layers at the interface, ionic dissociation of adsorbed HNO(3) is observed to be extensive. While some amount of molecularly adsorbed HNO(3) is observed at the surface of ice at 45 K, its ionic dissociation occurs irreversibly upon heating the ice substrate to 120 K. The molecularly adsorbed state of HNO(3) is not restored upon cooling, suggesting HNO(3) is a metastable entity at the surface of ice. Therefore, despite ionic dissociation of HNO(3) being thermodynamically favored, it appears to be kinetically inhibited at the surface of amorphous solid water at temperatures below 120 K.

  20. A spectroscopic study of the globular Cluster NGC 4147

    NASA Astrophysics Data System (ADS)

    Villanova, S.; Monaco, L.; Moni Bidin, C.; Assmann, P.

    2016-08-01

    We present the abundance analysis for a sample of 18 red giant branch stars in the metal-poor globular cluster NGC 4147 based on medium- and high-resolution spectra. This is the first extensive spectroscopic study of this cluster. We derive abundances of C, N, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Y, Ba, and Eu. We find a metallicity of [Fe/H] = -1.84 ± 0.02 and an α-enhancement of +0.38 ± 0.05 (errors on the mean), typical of halo globular clusters in this metallicity regime. A significant spread is observed in the abundances of light elements C, N, O, Na, and Al. In particular, we found an Na-O anticorrelation and Na-Al correlation. The cluster contains only ˜15 per cent of stars that belong to the first generation (Na-poor and O-rich). This implies that it suffered a severe mass-loss during its lifetime. Its [Ca/Fe] and [Ti/Fe] mean values agree better with the Galactic halo trend than with the trend of extragalactic environments at the cluster metallicity. This possibly suggests that NGC 4147 is a genuine Galactic object at odd with what claimed by some author that proposed the cluster to be member of the Sagittarius dwarf galaxy. An antirelation between the light s-process element Y and Na may also be present.

  1. Molecular docking, spectroscopic studies and quantum calculations on nootropic drug.

    PubMed

    Uma Maheswari, J; Muthu, S; Sundius, Tom

    2014-04-01

    A systematic vibrational spectroscopic assignment and analysis of piracetam [(2-oxo-1-pyrrolidineacetamide)] have been carried out using FT-IR and FT-Raman spectral data. The vibrational analysis was aided by an electronic structure calculation based on the hybrid density functional method B3LYP using a 6-311G++(d,p) basis set. Molecular equilibrium geometries, electronic energies, IR and Raman intensities, and harmonic vibrational frequencies have been computed. The assignments are based on the experimental IR and Raman spectra, and a complete assignment of the observed spectra has been proposed. The UV-visible spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies and the maximum absorption wavelengths λmax were determined by the time-dependent DFT (TD-DFT) method. The geometrical parameters, vibrational frequencies and absorption wavelengths were compared with the experimental data. The complete vibrational assignments are performed on the basis of the potential energy distributions (PED) of the vibrational modes in terms of natural internal coordinates. The simulated FT-IR, FT-Raman, and UV spectra of the title compound have been constructed. Molecular docking studies have been carried out in the active site of piracetam by using Argus Lab. In addition, the potential energy surface, HOMO and LUMO energies, first-order hyperpolarizability and the molecular electrostatic potential have been computed.

  2. Raman spectroscopic studies of the cure of dicyclopentadiene (DCPD)

    NASA Astrophysics Data System (ADS)

    Barnes, S. E.; Brown, E. C.; Corrigan, N.; Coates, P. D.; Harkin-Jones, E.; Edwards, H. G. M.

    2005-10-01

    The cure of polydicyclopentadiene conducted by ring-opening metathesis polymerisation in the presence of a Grubbs catalyst was studied using non-invasive Raman spectroscopy. The spectra of the monomer precursor and polymerised product were fully characterised and all stages of polymerisation monitored. Because of the monomer's high reactivity, the cure process is adaptable to reaction injection moulding and reactive rotational moulding. The viscosity of the dicyclopentadiene undergoes a rapid change at the beginning of the polymerisation process and it is critical that the induction time of the viscosity increase is determined and controlled for successful manufacturing. The results from this work show non-invasive Raman spectroscopic monitoring to be an effective method for monitoring the degree of cure, paving the way for possible implementation of the technique as a method of real-time analysis for control and optimisation during reactive processing. Agreement is shown between Raman measurements and ultrasonic time of flight data acquired during the initial induction period of the curing process.

  3. Raman spectroscopic studies of the cure of dicyclopentadiene (DCPD).

    PubMed

    Barnes, S E; Brown, E C; Corrigan, N; Coates, P D; Harkin-Jones, E; Edwards, H G M

    2005-10-01

    The cure of polydicyclopentadiene conducted by ring-opening metathesis polymerisation in the presence of a Grubbs catalyst was studied using non-invasive Raman spectroscopy. The spectra of the monomer precursor and polymerised product were fully characterised and all stages of polymerisation monitored. Because of the monomer's high reactivity, the cure process is adaptable to reaction injection moulding and reactive rotational moulding. The viscosity of the dicyclopentadiene undergoes a rapid change at the beginning of the polymerisation process and it is critical that the induction time of the viscosity increase is determined and controlled for successful manufacturing. The results from this work show non-invasive Raman spectroscopic monitoring to be an effective method for monitoring the degree of cure, paving the way for possible implementation of the technique as a method of real-time analysis for control and optimisation during reactive processing. Agreement is shown between Raman measurements and ultrasonic time of flight data acquired during the initial induction period of the curing process.

  4. Spectroscopic Study on the Interaction of 4-dimethylaminochalcones with Phospholipids

    NASA Astrophysics Data System (ADS)

    Tomečková, V.; Revická, M.; Sassen, A.; Veliká, B.; Stupák, M.; Perjési, P.

    2014-11-01

    The ultraviolet-visible and fluorescence spectroscopic properties of 4'-dimethylaminochalcone ( 1a) and its cyclic analogs 2a-4a have been studied in the presence of phospholipid vesicles (i.e., egg yolk lecithin and dipalmitoylpho sphatidylcholine), bovine serum albumin (BSA), and lipoprotein particles (i.e., bovine serum albumin plus egg yolk lecithin). The spectral results showed that compounds 1a-4a formed hydrophobic interactions with the phospholipids, lipoproteins, and BSA at the polar/nonpolar interface. Compounds 3a and 4a exhibited the strongest hydrophobic interactions of all of the compounds tested towards the phospholipids. Compound 2a gave the best fluorescent fluorophore indicating interactions with the lipids, lipoproteins, and proteins. Fluorescent microscopic imaging of breast cancer cells treated with compounds 1a-4a revealed that they could be used to stain all of the cellular components and destroy the nuclear structure. Compounds 1a-4a were found to be concentrated predominantly on the surfaces of the liposomes and lipoproteins.

  5. Electron Impedances

    SciTech Connect

    P Cameron

    2011-12-31

    It is only recently, and particularly with the quantum Hall effect and the development of nanoelectronics, that impedances on the scale of molecules, atoms and single electrons have gained attention. In what follows the possibility that characteristic impedances might be defined for the photon and the single free electron is explored is some detail, the premise being that the concepts of electrical and mechanical impedances are relevant to the elementary particle. The scale invariant quantum Hall impedance is pivotal in this exploration, as is the two body problem and Mach's principle.

  6. Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone.

    PubMed

    Gu, Chunju; Katti, Dinesh R; Katti, Kalpana S

    2013-02-15

    Chemical pretreatment has been the prevailing sample preparation procedure for infrared (IR) spectroscopic studies on bone. However, experiments have indicated that chemical pretreatment can potentially affect the interactions between the components. Typically the IR techniques have involved transmission experiments. Here we report experimental studies using photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). As a nondestructive technique, PA-FTIR can detect absorbance spectrum from a sample at controllable sampling depth and with little or no sample preparation. Additionally, the coupling inert gas, helium, which is utilized in the PA-FTIR system, can inhibit bacteria growth of bone by displacing oxygen. Therefore, we used this technique to study the undisturbed human cortical bone. It is found that photoacoustic mode (linear-scan, LS-PA-FTIR) can obtain basically similar spectra of bone as compared to the traditional transmission mode, but it seems more sensitive to amide III and ν(2) carbonate bands. The ν(3) phosphate band is indicative of detailed mineral structure and symmetry of native bone. The PA-FTIR depth profiling experiments on human cortical bone also indicate the influence of water on OH band and the cutting effects on amide I and mineral bands. Our results indicate that phosphate ion geometry appears less symmetric in its undisturbed state as detected by the PA-FTIR as compared to higher symmetry observed using transmission techniques on disturbed samples. Moreover, the PA-FTIR spectra indicate a band at 1747 cm(-1) possibly resulting from CO stretching of lipids, cholesterol esters, and triglycerides from the arteries. Comparison of the spectra in transverse and longitudinal cross-sections demonstrates that, the surface area of the longitudinal section bone appears to have more organic matrix exposed and with higher mineral stoichiometry.

  7. Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone

    NASA Astrophysics Data System (ADS)

    Gu, Chunju; Katti, Dinesh R.; Katti, Kalpana S.

    2013-02-01

    Chemical pretreatment has been the prevailing sample preparation procedure for infrared (IR) spectroscopic studies on bone. However, experiments have indicated that chemical pretreatment can potentially affect the interactions between the components. Typically the IR techniques have involved transmission experiments. Here we report experimental studies using photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). As a nondestructive technique, PA-FTIR can detect absorbance spectrum from a sample at controllable sampling depth and with little or no sample preparation. Additionally, the coupling inert gas, helium, which is utilized in the PA-FTIR system, can inhibit bacteria growth of bone by displacing oxygen. Therefore, we used this technique to study the undisturbed human cortical bone. It is found that photoacoustic mode (linear-scan, LS-PA-FTIR) can obtain basically similar spectra of bone as compared to the traditional transmission mode, but it seems more sensitive to amide III and ν2 carbonate bands. The ν3 phosphate band is indicative of detailed mineral structure and symmetry of native bone. The PA-FTIR depth profiling experiments on human cortical bone also indicate the influence of water on OH band and the cutting effects on amide I and mineral bands. Our results indicate that phosphate ion geometry appears less symmetric in its undisturbed state as detected by the PA-FTIR as compared to higher symmetry observed using transmission techniques on disturbed samples. Moreover, the PA-FTIR spectra indicate a band at 1747 cm-1 possibly resulting from Cdbnd O stretching of lipids, cholesterol esters, and triglycerides from the arteries. Comparison of the spectra in transverse and longitudinal cross-sections demonstrates that, the surface area of the longitudinal section bone appears to have more organic matrix exposed and with higher mineral stoichiometry.

  8. Gastroesophageal reflux in asymptomatic obese subjects: An esophageal impedance-pH study

    PubMed Central

    Akyüz, Filiz; Uyanıkoglu, Ahmet; Ermis, Fatih; Arıcı, Serpil; Akyüz, Ümit; Baran, Bülent; Pinarbasi, Binnur; Gul, Nurdan

    2015-01-01

    AIM: To investigate the relationship between reflux and body mass index (BMI) in the asymptomatic obese population using the impedance-pH technique. METHODS: Gastroesophageal reflux is frequent in the obese population. However, the relationship between acid reflux and BMI in asymptomatic obese people is unclear. Forty-six obese (BMI > 25 kg/m2) people were enrolled in this prospective study. We evaluated the demographic findings and 24-h impedance pH values of the whole group. Gas, acid (pH < 4), weak acid (pH = 4-7) and weak alkaline (pH ≥ 7) reflux parameters were analyzed. RESULTS: The mean age of patients was 49.47 ± 12.24 years, and half of them were men. The mean BMI was 30.64 ± 3.95 kg/m2 (25.14-45.58 kg/m2). BMI of 23 was over 30 kg/m2. Seventeen patients had a comorbidity (hypertension, diabetes mellitus, or ischemic heart disease). Endoscopic examination revealed esophagitis in 13 of the 28 subjects (10 Grade A, 3 Grade B). The subjects were divided into two groups according to BMI (< 30 and > 30 kg/m2). Demographic and endoscopic findings, and impedance results were similar in these two groups. However, there was a positive correlation between BMI and total and supine pH < 4 episodes (P = 0.002, r = 0.414; P = 0.000, r = 0.542), pH < 4 reflux time (P = 0.015, r = 0.319; P = 0.003, r = 0.403), and DeMeester score (P = 0.012, r = 0.333). CONCLUSION: Acid reflux is correlated with BMI in asymptomatic obese individuals. PMID:25780302

  9. Effect of temperature on the methotrexate BSA interaction: Spectroscopic study

    NASA Astrophysics Data System (ADS)

    Sułkowska, A.; Maciążek, M.; Równicka, J.; Bojko, B.; Pentak, D.; Sułkowski, W. W.

    2007-05-01

    Rheumatoid arthritis (RA) is an autoimmune and chronic inflammatory illness which affects about one percent of the world's population. Methotrexate (4-amino-10-methylfolic acid) (MTX) also known as amethopterin is commonly used to treat rheumatoid arthritis (RA). It is transported in the circulary system as a complex with serum albumin. The aim of this study was to investigate the interactions of MTX with transporting protein with the use of spectroscopic methods. The binding of MTX to bovine serum albumin (BSA) was studied by monitoring the changes in the emission fluorescence spectra of protein in the presence of MTX at excitation wavelength of 280 nm and 295 nm. The quenching of protein fluorescence at temperature range from 298 K to 316 K was observed. Energy transfer between methotrexate and fluorophores contained in the serum albumin structure was found at the molar ratio MTX:BSA 7.5:1. The relative fluorescence intensity of BSA decreases with increase of temperature. Similar results were observed for BSA excited with 280 nm and 295 nm at the same temperature range. The presence of MTX seems to prevent these changes. Temperature dependence of the binding constant has been presented. The binding and quenching constants for equilibrium complex were calculated using Scatchard and Stern-Volmer method, respectively. The results show that MTX forms π-π complex with aromatic amino acid residues of BSA. The binding site for MTX on BSA was found to be situated in the hydrophobic IIA or IB subdomain where the Trps were located. The spontaneity of MTX-BSA complex formation in the temperature range 298-316 K was ascertained.

  10. LEAD SORPTION ON RUTHENIUM OXIDE: A MACROSCOPIC AND SPECTROSCOPIC STUDY

    EPA Science Inventory

    The sorption and desorption of Pb on RuO2 xH2O were examined kinetically and thermodynamically via spectroscopic and macroscopic investigations. X-ray absorption spectroscopy (XAS) was employed to determine the sorption mechanism with regard to identity of nearest atomic neighbo...

  11. Using two-dimensional impedance maps to study weak scattering in sparse random media.

    PubMed

    Luchies, Adam C; Oelze, Michael L

    2016-04-01

    Impedance maps (ZMs) have been proposed as a tool for modeling acoustic properties of tissue microstructure. Three-dimensional (3D) ZMs are constructed from a series of adjacent histological tissue slides that have been stained to emphasize acoustic impedance structures. The power spectrum of a 3DZM can be related to the ultrasound backscatter coefficient, which can be further reduced to a form factor. The goal of this study is to demonstrate the ability to estimate form factors using two-dimensional (2D) ZMs instead of 3DZMs, which have reduced computational and financial cost. The proposed method exploits the properties of isotropic media to estimate the correlation coefficient from slices before estimating the 3D volume power spectrum. Simulated sparse collections of objects were used to study the method by comparing the results obtained using 2DZMs to those predicted by theory. 2DZM analysis was conducted on normal rabbit liver histology and compared to 3DZM analysis of the same histology. The mean percent error between effective scatterer diameter estimates from 2DZMs and 3DZMs of rabbit liver histology was <10% when using three 2DZMs. The results suggest that 2DZMs are a feasible alternative to 3DZMs when estimating form factors for sparse collections of objects. PMID:27106304

  12. Intergrain connectivity of MgB{sub 2} ceramics studied by impedance analysis

    SciTech Connect

    Wang, C. C.; Wang, C.; Zeng, R.; Dou, S. X.

    2010-07-15

    First, by using of the conventional Rowell analysis, we demonstrated that the addition of nano BN particles can effectively eliminate MgO and pores in MgB{sub 2} resulting in a very high density and good connectivity of BN-doped MgB{sub 2}. Then, another method--low-frequency dielectric impedance analysis--was introduced to characterize the properties of the grain boundaries of MgB{sub 2}. A comparative impedance study was performed in the frequency range from 100 Hz to 100 MHz on pure and nano BN-doped MgB{sub 2}. The study revealed some following interesting results: (1) a dielectric resonance around frequency of 10{sup 8} in both samples was observed, which was argued to be related to an inductance-capacitance and (2) the pure sample has two dielectric relaxations originating from intergrains, while the doped sample has only one intergranular contribution. This convinces that the electric connectivity of the doped sample is really improved by the addition of nano BN particles. Our results indicate that dielectric technique may be a useful tool to characterize the grain boundary properties and grain boundary-related properties of MgB{sub 2}.

  13. Spectroscopic Studies of Molecular Systems relevant in Astrobiology

    NASA Astrophysics Data System (ADS)

    Fornaro, Teresa

    2016-01-01

    In the Astrobiology context, the study of the physico-chemical interactions involving "building blocks of life" in plausible prebiotic and space-like conditions is fundamental to shed light on the processes that led to emergence of life on Earth as well as to molecular chemical evolution in space. In this PhD Thesis, such issues have been addressed both experimentally and computationally by employing vibrational spectroscopy, which has shown to be an effective tool to investigate the variety of intermolecular interactions that play a key role in self-assembling mechanisms of nucleic acid components and their binding to mineral surfaces. In particular, in order to dissect the contributions of the different interactions to the overall spectroscopic signals and shed light on the intricate experimental data, feasible computational protocols have been developed for the characterization of the spectroscopic properties of such complex systems. This study has been carried out through a multi-step strategy, starting the investigation from the spectroscopic properties of the isolated nucleobases, then studying the perturbation induced by the interaction with another molecule (molecular dimers), towards condensed phases like the molecular solid, up to the case of nucleic acid components adsorbed on minerals. A proper modeling of these weakly bound molecular systems has required, firstly, a validation of dispersion-corrected Density Functional Theory methods for simulating anharmonic vibrational properties. The isolated nucleobases and some of their dimers have been used as benchmark set for identifying a general, reliable and effective computational procedure based on fully anharmonic quantum mechanical computations of the vibrational wavenumbers and infrared intensities within the generalized second order vibrational perturbation theory (GVPT2) approach, combined with the cost-effective dispersion-corrected density functional B3LYP-D3, in conjunction with basis sets of

  14. Spectroscopic studies on lambda cro protein-DNA interactions.

    PubMed

    Torigoe, C; Kidokoro, S; Takimoto, M; Kyogoku, Y; Wada, A

    1991-06-20

    Spectroscopic (circular dichroism and fluorescence) and thermodynamic studies were conducted on lambda Cro-DNA interactions. Some base substitutions were introduced to the operator and the effects on the conformation of the complex and thermodynamic parameters for dissociation of the complex were examined. It was found that, (1) in the specific binding of Cro with DNA which has a (pseudo) consensus sequence, DNA is overwound, while in non-specific binding it is unchanged, or rather unwound; (2) substitution of central base-pairs or the introduction of a mismatched base-pair at the center of the operator reduces the extent of DNA conformational change on Cro binding and lessens the stability of the Cro-DNA complex, even though there is apparently no direct interaction between Cro and DNA at these positions; (3) stability of the complex increases with the degree of DNA conformational change of the same type during binding; (4) in some cases of specific binding, there are three states in the dissociation of the complex as observed by salt titration: two conformational states for the complex depending on salt concentration and, in non-specific binding, dissociation is a two-state transition; (5) the number of ions involved in interactions between Cro and 17 base-pair DNA is about 7.7 for NaCl titrations; (6) dissociation free energy prediction of the Cro-DNA complex by simple addition of the dissociation free energy change of a single base-pair substitution agrees with our experimental results when DNA overwinding occurs during binding, i.e. in specific binding.

  15. Corrosion behaviour of galvanized steel and electroplating steel in aqueous solution: AC impedance study and XPS

    NASA Astrophysics Data System (ADS)

    Lebrini, M.; Fontaine, G.; Gengembre, L.; Traisnel, M.; Lerasle, O.; Genet, N.

    2008-08-01

    The efficiency of a new triazole derivative, namely, 2-{(2-hydroxyethyl)[(4-methyl-1 H-1,2,3-benzotriazol-1-yl)methyl]amino}ethanol (TTA) has been studied for corrosion inhibition of galvanized steel and electroplating steel in aqueous solution. Corrosion inhibition was studied using electrochemical impedance spectroscopy (EIS). These studies have shown that TTA was a very good inhibitor. Data obtained from EIS show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The corrosion behaviour of galvanized steel and electroplating steel in aqueous solution was also investigated in the presence of 4-methyl-1 H-benzotriazole (TTA unsubstituted) by EIS. These studies have shown that the ability of the molecule to adsorb on the steel surface was dependent on the group in triazole ring substituent. X-ray photoelectron spectroscopy surface analysis with TTA shows that it chemisorbed on surface of galvanized steel and electroplating steel.

  16. Application of electrochemical impedance spectroscopy: A phase behavior study of babassu biodiesel-based microemulsions.

    PubMed

    Pereira, Thulio C; Conceição, Carlos A F; Khan, Alamgir; Fernandes, Raquel M T; Ferreira, Maira S; Marques, Edmar P; Marques, Aldaléa L B

    2016-11-01

    Microemulsions are thermodynamically stable systems of two immiscible liquids, one aqueous and the other of organic nature, with a surfactant and/or co-surfactant adsorbed in the interface between the two phases. Biodiesel-based microemulsions, consisting of alkyl esters of fatty acids, open a new means of analysis for the application of electroanalytical techniques, and is advantageous as it eliminates the required pre-treatment of a sample. In this work, the phase behaviours of biodiesel-based microemulsions were investigated through the electrochemical impedance spectroscopy (EIS) technique. We observed thatan increase in the amount of biodiesel in the microemulsion formulation increases the resistance to charge transfer at the interface. Also, the electrical conductivity measurements revealed that a decrease or increase in electrical properties depends on the amount of biodiesel. EIS studies of the biodiesel-based microemulsion samples showed the presence of two capacitive arcs: one high-frequency and the other low-frequency. Thus, the formulation of microemulsions plays an important role in estimating the electrical properties through the electrochemical impedance spectroscopy technique.

  17. Mapping Electrochemical Heterogeneity at Iron Oxide Surfaces: A Local Electrochemical Impedance Study.

    PubMed

    Lucas, Marie; Boily, Jean-François

    2015-12-22

    Alternating current scanning electrochemical microscopy (AC-SECM) was used for the first time to map key electrochemical attributes of oriented hematite (α-Fe2O3) single crystal surfaces at the micron-scale. Localized electrochemical impedance spectra (LEIS) of the (001) and (012) faces provided insight into the spatial variations of local double layer capacitance (C(dl)) and charge transfer resistance (R(ad)). These parameters were extracted by LEIS measurements in the 0.4-8000 Hz range to probe the impedance response generated by the redistribution of water molecules and charge carriers (ions) under an applied AC. These were attributed to local variations in the local conductivity of the sample surfaces. Comparison with global EIS measurements on the same samples uncovered highly comparable frequency-resolved processes, that were broken down into contributions from the bulk hematite, the interface as well as the microelectrode/tip assembly. This work paves the way for new studies aimed at mapping electrochemical processes at the mesoscale on this environmentally and technologically important material.

  18. Studies of phase transition and impedance behavior of Ba(Zr, Ti)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Sateesh, P.; Omprakash, J.; Kumar, G. S.; Prasad, G.

    2015-02-01

    Ceramic samples of Barium Zirconium Titanate (BaZrxTi1-xO3 (BZT)) were synthesized by conventional solid-state reaction method with different concentrations of x(= 0.05 (BZT1), 0.10 (BZT2), 0.15 (BZT3), 0.20 (BZT4), 0.25 (BZT5), 0.30 (BZT6)). Phase confirmation of the samples was done by X-ray diffraction (XRD) technique. All the compositions are in cubic structure. XRD pattern was recorded for samples sintered at different sintering temperatures. Lattice parameters increased with addition of Zr+4. Doping with Zr+4 into Barium titanate resulted in interesting changes of electrical properties (dielectric, impedance and ferroelectiricity). The strong influence of Zr doping on the phase transition characteristics of the BZT ceramics was studied from the dielectric response of the samples. Diffusivity of phase transition of the BZT ceramic samples increase with Zr+4 concentration, indicating changes from normal to diffuse transition to relaxor phase transition behavior. Impedance spectroscopy reveals the presence of temperature-dependent grain, grain boundary effects. Polarization-Electricfield (PE) loop measurements are also done on the samples.

  19. Application of electrochemical impedance spectroscopy: A phase behavior study of babassu biodiesel-based microemulsions

    NASA Astrophysics Data System (ADS)

    Pereira, Thulio C.; Conceição, Carlos A. F.; Khan, Alamgir; Fernandes, Raquel M. T.; Ferreira, Maira S.; Marques, Edmar P.; Marques, Aldaléa L. B.

    2016-11-01

    Microemulsions are thermodynamically stable systems of two immiscible liquids, one aqueous and the other of organic nature, with a surfactant and/or co-surfactant adsorbed in the interface between the two phases. Biodiesel-based microemulsions, consisting of alkyl esters of fatty acids, open a new means of analysis for the application of electroanalytical techniques, and is advantageous as it eliminates the required pre-treatment of a sample. In this work, the phase behaviours of biodiesel-based microemulsions were investigated through the electrochemical impedance spectroscopy (EIS) technique. We observed thatan increase in the amount of biodiesel in the microemulsion formulation increases the resistance to charge transfer at the interface. Also, the electrical conductivity measurements revealed that a decrease or increase in electrical properties depends on the amount of biodiesel. EIS studies of the biodiesel-based microemulsion samples showed the presence of two capacitive arcs: one high-frequency and the other low-frequency. Thus, the formulation of microemulsions plays an important role in estimating the electrical properties through the electrochemical impedance spectroscopy technique.

  20. Application of electrochemical impedance spectroscopy: A phase behavior study of babassu biodiesel-based microemulsions.

    PubMed

    Pereira, Thulio C; Conceição, Carlos A F; Khan, Alamgir; Fernandes, Raquel M T; Ferreira, Maira S; Marques, Edmar P; Marques, Aldaléa L B

    2016-11-01

    Microemulsions are thermodynamically stable systems of two immiscible liquids, one aqueous and the other of organic nature, with a surfactant and/or co-surfactant adsorbed in the interface between the two phases. Biodiesel-based microemulsions, consisting of alkyl esters of fatty acids, open a new means of analysis for the application of electroanalytical techniques, and is advantageous as it eliminates the required pre-treatment of a sample. In this work, the phase behaviours of biodiesel-based microemulsions were investigated through the electrochemical impedance spectroscopy (EIS) technique. We observed thatan increase in the amount of biodiesel in the microemulsion formulation increases the resistance to charge transfer at the interface. Also, the electrical conductivity measurements revealed that a decrease or increase in electrical properties depends on the amount of biodiesel. EIS studies of the biodiesel-based microemulsion samples showed the presence of two capacitive arcs: one high-frequency and the other low-frequency. Thus, the formulation of microemulsions plays an important role in estimating the electrical properties through the electrochemical impedance spectroscopy technique. PMID:27276278

  1. Combined Impedance Probe and Langmuir Probe Studies of the Low-Latitude E Region

    NASA Technical Reports Server (NTRS)

    Rowland, D. E.; Pfaff, R. F.; Steigies, C. T.

    2008-01-01

    The EQUIS-2 sounding rocket and radar campaign, launched from Kwajalein Atoll in 2004, included a mission to study low-latitude irregularities and electrodynamics, led by NASA GSFC. This mission included two instrumented rockets launched into the nighttime E region (apogee near 120 km), which included comprehensive electrodynamics and neutral density instrumentation. These rockets carried the first of a new generation of impedance probes, that utilize a wide-band drive signal to simultaneously measure the impedance of an antenna in a plasma as a function of frequency from 7 kEIz to 4 MHz. at a rapid cadence. This technique promises to permit true plasma spectroscopy, and resulted in the identification of multiple plasma resonances and accurate measurements of the plasma density, even in the low density nighttime E region. We present analyses of the technique and resulting spectra, and show how these data may be combined with fixed-bias Langmuir Probe data to infer the temperature structure of the E region as well as providing accurate absolute calibrations for the very high time resolution fixed-bias probe data. The data is shown to agree well with data from ionosonde, the ALTAIR radar, and the Peruvian beacon experiment.

  2. Spectroscopic studies of cathode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Totir, Dana Alexa

    2000-10-01

    Structural changes that occur during electrochemical cycling of lithium-ion battery cathode materials have been investigated using in situ spectroscopic techniques. A new method was developed for the preparation of carbon and binder free cathodes utilizing powder materials of interest for commercial batteries. The extraordinary quality of the cyclic voltammetric curves recorded for this type of electrodes during the in situ measurements allows direct correlations to be made between the state of charge of the material and its structural and electronic characteristics. LiCoO2, LiMn2O4 and LiCo0.15Ni 0.85O2 electrodes were evaluated using cycling voltammetry and the mean diffusion coefficient for Li-ions in the lattice (DLi) was calculated for LiMn2O4. LiMn2O4 electrodes prepared by this technique have been studied in situ using Mn K-edge XAS. Data analysis for the species formed at different potentials indicated a contraction of the lattice associated with the increase in the oxidation state of manganese. In situ Raman spectra of particles of LiMn2O 4, and LiCoO2 embedded in Au and also of KS-44 graphite and carbon microfibers MCF28 embedded in thermally annealed Ni have been recorded as a function of the applied potential. Fe K-edge XAFS of pyrite electrodes in a Li/PEO(LiClO4)/FeS 2 cell and S K-edge XANES measurements of a FeS2 electrode in a non-aqueous electrolyte have been acquired as a function of the state of charge. The studies have clearly evidenced the formation of metallic Fe and Li2S as intermediates after 4 e- discharge and the formation of Li2FeS2 after 2 e- recharge. While Fe K-edge studies have indicated that there is no change in the Fe environment and oxidation state upon 4 e- recharge, the results obtained from S K-edge studies are inconclusive for this stage. Finally, in situ Co K-edge XAFS data were obtained for the first time during the electrochemical cycling of electrodeposited Co(OH) 2 films in alkaline solutions. The results support

  3. Spectroscopic studies of uranium species for environmental decontamination applications

    NASA Astrophysics Data System (ADS)

    Eng, Charlotte

    After the Cold War, Department of Energy began to concentrate its efforts on cleanup of former nuclear material processing facilities, especially uranium-contaminated groundwater and soil. This research aims to study uranium association to both organic and inorganic compounds found in the contaminated environment in the hopes that the information gathered can be applied to the development and optimization of cost-effective remediation techniques. Spectroscopic and electrochemical methods will be employed to examine the behavior of uranium in given conditions to further our understanding of its impact on the environment. Uranium found in groundwater and soil bind with various ligands, especially organic ligands present in the environment due to natural sources (e.g. metabolic by-products or degradation of plants and animals) or man-made sources (e.g. chelating agents used in operating or cleanup of uranium processing facilities). We selected reasonable analogs of naturally occurring matter and studied their structure, chemical and electrochemical behavior and found that the structure of uranyl complexes depends heavily on the nature of the ligand and environmental factors such as pH. Association of uranium-organic complexes with anaerobic bacteria, Clostridium sp. was studied to establish if the bacteria can effectively bioreduce uranium while going through normal bacterial activity. It was found that the nature of the organic ligand affected the bioavailability and toxicity of the uranium on the bacteria. In addition, we have found that the type of iron corrosion products and uranyl species present on the surface of corroded steel depended on various environmental factors, which subsequently affected the removal rate of uranium by a citric acid/hydrogen peroxide/deionized water cleaning process. The method was found to remove uranium from only the topmost corrosion layers and residual uranium could be found (a) deeper in the corrosion layers where it is occluded by

  4. Spectroscopic studies of the several isomers of UO3

    NASA Astrophysics Data System (ADS)

    Sweet, Lucas E.; Reilly, Dallas D.; Abrecht, David G.; Buck, Edgar C.; Meier, David E.; Su, Yin-Fong; Brauer, Carolyn S.; Schwantes, Jon M.; Tonkyn, Russell G.; Szecsody, James E.; Blake, Thomas A.; Johnson, Timothy J.

    2013-10-01

    Uranium trioxide is known to adopt seven different structural forms. While these structural forms have been well characterized using x-ray or neutron diffraction techniques, little work has been done to characterize their spectroscopic properties, particularly of the pure phases. Since the structural isomers of UO3 all have similar thermodynamic stabilities and most tend to hydrolyze under open atmospheric conditions, mixtures of UO3 phases and the hydrolysis products are common. Much effort went into isolating pure phases of UO3. Utilizing x-ray diffraction as a sample identification check, UV/Vis/NIR spectroscopic signatures of α-UO3, β-UO3, γ-UO3 and α-UO2(OH)2 products were obtained. The spectra of the pure phases can now be used to characterize typical samples of UO3, which are often mixtures of isomers.

  5. Spectroscopic Studies of the Several Isomers of UO3

    SciTech Connect

    Sweet, Lucas E.; Reilly, Dallas D.; Abrecht, David G.; Buck, Edgar C.; Meier, David E.; Su, Yin-Fong; Brauer, Carolyn S.; Schwantes, Jon M.; Tonkyn, Russell G.; Szecsody, James E.; Blake, Thomas A.; Johnson, Timothy J.

    2013-09-26

    Uranium trioxide is known to adopt seven different structural forms. While these structural forms have been well characterized using x-ray or neutron diffraction techniques, little work has been done to characterize their spectroscopic properties, particularly of the pure phases. Since the structural isomers of UO3 all have similar thermodynamic stabilities and most tend to hydrolyze under open atmospheric conditions, mixtures of UO3 phases and the hydrolysis products are common. Much effort went into isolating pure phases of UO3. Utilizing x-ray diffraction as a sample identification check, UV/Vis/NIR spectroscopic signatures of α-UO3, β-UO3, γ-UO3 and UO2(OH)2 products were obtained. The spectra of the pure phases can now be used to characterize typical samples of UO3, which are often mixtures of isomers.

  6. Fundamental spectroscopic studies of carbenes and hydrocarbon radicals

    SciTech Connect

    Thaddeus, P.; Gottlieb, C.

    1992-05-01

    This document details activities during this reporting period topics discussed are: The first spectroscopic identification of the HCCCO and DCCCO radicals; detection of new vibrationally excited states of the carbon chain radicals CCH and CCD and the three-membered carbene ring, cyclopropenylidene; determination of an accurate structure of the cumulene carbene H{sub 2}CCC; analysis the hyperfine structure in the SiC radical; and the undertaking of a systematic search for new sulfur bearing radicals.

  7. Spectroscopic ellipsometry study of novel nanostructured transparent conducting oxide structures

    NASA Astrophysics Data System (ADS)

    Khosroabadi, Akram A.; Norwood, R. A.

    2013-02-01

    Spectroscopic ellipsometry has been used to find the optical constants, including refractive index, extinction coefficient, thickness and volume fraction of nanostructured transparent conducting oxides including indium tin oxide (ITO) and indium zinc oxide (IZO). We observed sharp features in the ellipsometry data, with the spectral peaks and positions depending on the nanostructure dimensions and material. A superposition of Lorentzian oscillators and the effective medium approximation has been applied to determine the volume ratio of voids and nanopillars, thereby providing the effective optical constants.

  8. Structural, spectroscopic and theoretical study of novel ephedrinum salt

    NASA Astrophysics Data System (ADS)

    Ivanova, B.; Kolev, T.; Lamshöft, M.; Mayer-Figge, H.; Seidel, R.; Sheldrick, W. S.; Spiteller, M.

    2010-05-01

    Ephedrinum violurate dihydrate was synthesized, spectroscopically and structural elucidated. The data are compared with those of the free-base ephedrine hemihydrate. Discussion on the stable conformer of the ephedrinum cation is carried out. Quantum chemical calculations were performed for the theoretical elucidation of the conformational preference of the ephedrinum cation and its vibrational properties. The model systems neutral ephedrine hemihydrate ( 1) and violurate salt dihydrate ( 2) are elucidated.

  9. Spectroscopic studies of gas-phase molecular clusters

    NASA Astrophysics Data System (ADS)

    Wong, Chi-Kin

    Spectroscopic investigations of hydrogen-bonding and van der Waals' interactions in molecular clusters were studied by the techniques of infrared predissociation and resonance-enhanced multiphoton ionization spectroscopies (REMPI). Ab initio calculations were applied in conjunction for data interpretation. The infrared predissociation spectroscopy of CN-·(H 2O)n (n = 2--6) clusters was reported in the region of 2950--3850 cm-1. The hydrogen bondings for the C-site and N-site binding, and among the water molecules were identified for n = 2 to 4. A spectral transition was observed for n = 5 and 6, implying that the anion was surface-bound onto the water aggregates in larger clusters. The infrared predissociation spectroscopy of Br-·(NH 3) and I-·(NH3) n (n = 1--3) clusters was reported in the region of 3050--3450 cm-1. For the Br -·(NH3) complex, a dominating ionic NH stretch appeared at 3175 cm-1, and the weaker free NH stretch appeared at 3348 cm-1. The observed spectrum was consistent to the structure in which there was one nearly linear hydrogen bond between Br- and the NH3 moiety. For the I- ·(NH3) complex, five distinct IR absorption bands were observed in the spectrum. The spectrum was not consistent with basic frequency patterns of three geometries considered in the ab initio calculations---complex with one, two and three hydrogen bondings between I- and the NH3 moiety. Substantial inhomogenous broadening were displayed in the spectra for I- ·(NH3)n (n = 2--3), suggesting the presence of multiple isomers. The REMPI spectroscopy of the bound 4p 2pi 1/2 and 2pi3/2 states, and the dissociative 3d 2Sigma+1/2 state in the Al·Ar complex was reported. The dissociative spectrum at Al+ channel suggested the coupling of the 4p 2pi 1/2,3/2 states to the repulsive 3d 2Sigma+1/2 state. The spin-electronic coupling was further manifested in the dissociative Al+ spectrum of the 3d 2Sigma+1/2 state. Using the potential energy curves obtained from ab initio

  10. A Raman Spectroscopic Study of Kernite to 25 GPa

    NASA Astrophysics Data System (ADS)

    Silva, M. E.; O'Bannon, E. F., III; Williams, Q. C.

    2015-12-01

    A Raman spectroscopic study of kernite to 25 GPaMarcus Silva, Earl O'Bannon III, and Quentin Williams Department of Earth & Planetary Sciences, University of California Santa Cruz The Raman spectrum of kernite (Na2B4O6(OH)2·3(H2O)) has been characterized up to ~25 GPa in order to explore pressure-induced changes in a structurally novel mineral that contains mixed coordination borate groups (three- and four-fold), and both hydroxyl units and water. During compression, all of the ~30 modes monitored shift positively and monotonically until ~2.2 GPa where a few low frequency modes disappear and tetrahedral borate modes merge. The low frequency modes that disappear at ~2.2 GPa are likely associated with Na vibrations, and their disappearance suggests that dramatic changes occur in the Na sites at ~2.2 GPa. The merging of the boron bending and stretching modes at ~2.2 GPa suggests that the local symmetry of the BO4 tetrahedra changes at this pressure, and likely becomes more symmetric. The remaining modes shift positively up to ~7.4 GPa where a second notable change occurs. All but 5 modes (with initial frequencies of 150, 166, 289, 307, and 525 cm-1) disappear at ~7.4 GPa. This indicates that a second phase transition has occurred which affects both the BO3H and BO4­ groups: based on the loss of modes, this transition may be associated with disordering of the crystal. These 5 modes persist and shift monotonically up to ~25 GPa. On decompression, the 5 modes shift smoothly down to ~2.0 GPa where a few new modes appear in the spectrum. When fully decompressed to room pressure, the Raman spectrum of the recovered sample is significantly different from the ambient spectrum of the initial sample. Thus, our results are suggest a phase transition occurring at 2.2 GPa with changes in the Na and tetrahedral boron sites, followed by an additional transition at 7.4 GPa that may involve disordering of the crystal. In the latter transition, at least the BO3H groups appear to be

  11. NMR spectroscopic study of organic phosphate esters coprecipitated with calcite

    NASA Astrophysics Data System (ADS)

    Phillips, Brian L.; Zhang, Zelong; Kubista, Laura; Frisia, Silvia; Borsato, Andrea

    2016-06-01

    Organic phosphorus incorporated in calcite during laboratory precipitation experiments and in natural cave deposits was investigated by solid-state NMR spectroscopy. For calcite precipitated in the presence of organic phosphoesters of varying size and functionality, solid-state 31P{1H} CP/MAS NMR shows that the phosphoesters were incorporated intact into the solid. Systematic changes in the 31P NMR chemical shift of the phosphate group were observed between the solid phosphoester and that incorporated in the solid precipitate, yielding 31P NMR chemical shifts of the coprecipitates in the range of +1.8 to -2.2 ppm. These chemical shifts are distinct from that of similarly prepared calcite coprecipitated with inorganic phosphate, 3.5 ppm. Only minor changes were noted in the phosphoester 31P chemical shift anisotropy (CSA) which suggests no significant change in the local structure of the phosphate group, which is dominated by C-O-P bonding. Close spatial proximity of the organic phosphate group to calcite structural components was revealed by 31P/13C rotational echo double resonance (REDOR) experiments for coprecipitates prepared with 13C-labeled carbonate. All coprecipitates showed significant 31P dephasing effects upon 13C-irradiation, signaling atomic-scale proximity to carbonate carbon. The dephasing rate for smaller organophosphate molecules is similar to that observed for inorganic phosphate, whereas much slower dephasing was observed for larger molecules having long and/or bulky side-chains. This result suggests that small organic molecules can be tightly enclosed within the calcite structure, whereas significant structural disruption required to accommodate the larger organic molecules leads to longer phosphate-carbonate distances. Comparison of 31P NMR spectroscopic data from the synthetic coprecipitates with those from calcite moonmilk speleothems indicates that phosphorus occurs mainly as inorganic orthophosphate in the natural deposits, although small

  12. A study of gadolinia-doped ceria electrolyte by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Liu, Feng; Brinkman, Kyle; Reifsnider, Kenneth L.; Virkar, Anil V.

    2014-02-01

    Samples of Gd2O3-doped CeO2 (GDC) were fabricated by sintering of powder compacts. Impedance spectra were measured from 400 °C to 675 °C in air by electrochemical impedance spectroscopy (EIS). Above ∼500 °C, high frequency arc was not semicircular but could be fitted with a constant phase element (CPE). Above ∼625 °C, high frequency arc could not be resolved due to a significant contribution from the inductive load. The impedance spectra were described using a simple equivalent circuit which included the leads/instrument impedance. The leads/instrument impedance was measured over a range of frequencies and temperatures. The high frequency part of the impedance after subtracting leads/instrument impedance could be resolved even at the highest measurement temperature and was described by a semicircle representative of transport across grain boundaries. From these measurements, grain and grain boundary resistivities were determined. The corresponding activation energies were 0.69 eV and 1.11 eV, respectively. The grain boundary capacitance was nearly independent of temperature. The present results show that grain boundary effects can be described by a resistor and a capacitor. Relevant equivalent circuit parameters were obtained from intercepts, maxima and minima in impedance diagrams.

  13. A new application of electrical impedance spectroscopy for measuring glucose metabolism: a phantom study

    NASA Astrophysics Data System (ADS)

    Dhurjaty, Sreeram; Qiu, Yuchen; Tan, Maxine; Liu, Hong; Zheng, Bin

    2015-03-01

    Glucose metabolism relates to biochemical processes in living organisms and plays an important role in diabetes and cancer-metastasis. Although many methods are available for measuring glucose metabolism-activities, from simple blood tests to positron emission tomography, currently there is no robust and affordable device that enables monitoring of glucose levels in real-time. In this study we tested feasibility of applying a unique resonance-frequency based electronic impedance spectroscopy (REIS) device that has been, recently developed to measure and monitor glucose metabolism levels using a phantom study. In this new testing model, a multi-frequency electrical signal sequence is applied and scanned through the subject. When the positive reactance of an inductor inside the device cancels out the negative reactance of the capacitance of the subject, the electrical impedance reaches a minimum value and this frequency is defined as the resonance frequency. The REIS system has a 24-bit analog-to-digital signal convertor and a frequency-resolution of 100Hz. In the experiment, two probes are placed inside a 100cc container initially filled with distilled water. As we gradually added liquid-glucose in increments of 1cc (250mg), we measured resonance frequencies and minimum electrical signal values (where A/D was normalized to a full scale of 1V). The results showed that resonance frequencies monotonously decreased from 243kHz to 178kHz, while the minimum voltages increased from 405mV to 793mV as the added amount of glucose increased from 0 to 5cc. The study demonstrated the feasibility of applying this new REIS technology to measure and/or monitor glucose levels in real-time in future.

  14. The Pt(111)/electrolyte interface under oxygen reduction reaction conditions: an electrochemical impedance spectroscopy study.

    PubMed

    Bondarenko, Alexander S; Stephens, Ifan E L; Hansen, Heine A; Pérez-Alonso, Francisco J; Tripkovic, Vladimir; Johansson, Tobias P; Rossmeisl, Jan; Nørskov, Jens K; Chorkendorff, Ib

    2011-03-01

    The Pt(111)/electrolyte interface has been characterized during the oxygen reduction reaction (ORR) in 0.1 M HClO(4) using electrochemical impedance spectroscopy. The surface was studied within the potential region where adsorption of OH* and O* species occur without significant place exchange between the adsorbate and Pt surface atoms (0.45-1.15 V vs RHE). An equivalent electric circuit is proposed to model the Pt(111)/electrolyte interface under ORR conditions within the selected potential window. This equivalent circuit reflects three processes with different time constants, which occur simultaneously during the ORR at Pt(111). Density functional theory (DFT) calculations were used to correlate and interpret the results of the measurements. The calculations indicate that the coadsorption of ClO(4)* and Cl* with OH* is unlikely. Our analysis suggests that the two-dimensional (2D) structures formed in O(2)-free solution are also formed under ORR conditions. PMID:21244087

  15. Numerical Study of Three Dimensional Effects in Longitudinal Space-Charge Impedance

    SciTech Connect

    Halavanau, A.; Piot, P.

    2015-06-01

    Longitudinal space-charge (LSC) effects are generally considered as detrimental in free-electron lasers as they can seed instabilities. Such “microbunching instabilities” were recently shown to be potentially useful to support the generation of broadband coherent radiation pulses [1, 2]. Therefore there has been an increasing interest in devising accelerator beamlines capable of sustaining this LSC instability as a mechanism to produce a coherent light source. To date most of these studies have been carried out with a one-dimensional impedance model for the LSC. In this paper we use a N-body “Barnes-Hut” algorithm [3] to simulate the 3D space charge force in the beam combined with elegant [4] and explore the limitation of the 1D model often used

  16. Degradation of Bilayer Organic Light-Emitting Diodes Studied by Impedance Spectroscopy.

    PubMed

    Sato, Shuri; Takata, Masashi; Takada, Makoto; Naito, Hiroyoshi

    2016-04-01

    The degradation of bilayer organic light-emitting diodes (OLEDs) with a device structure of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) (hole transport layer) and tris-(8-hydroxyquinolate)aluminum (Alq3) (emissive layer and electron transport layer) has been studied by impedance spectroscopy and device simulation. Two modulus peaks are found in the modulus spectra of the OLEDs below the electroluminescence threshold. After aging of the OLEDs, the intensity of electroluminescence is degraded and the modulus peak due to the Alq3 layer is shifted to lower frequency, indicating that the resistance of the Alq3 layer is increased. Device simulation reveals that the increase in the resistance of the Alq3 layer is due to the decrease in the electron mobility in the Alq3 layer. PMID:27451634

  17. Impedance studies of a green blend polymer electrolyte based on PVA and Aloe-vera

    NASA Astrophysics Data System (ADS)

    Selvalakshmi, S.; Mathavan, T.; Vijaya, N.; Selvasekarapandian, Premalatha, M.; Monisha, S.

    2016-05-01

    The development of polymer electrolyte materials for energy generating and energy storage devices is a challenge today. A new type of blended green electrolyte based on Poly-vinyl alcohol (PVA) and Aloe-vera has been prepared by solution casting technique. The blending of polymers may lead to the increase in stability due to one polymer portraying itself as a mechanical stiffener and the other as a gelled matrix supported by the other. The prepared blend electrolytes were subjected to Ac impedance studies. It has been found out that the polymer film in which 1 gm of PVA was dissolved in 40 ml of Aloe-vera extract exhibits highest conductivity and its value is 3.08 × 10-4 S cm-1.

  18. Resonance Raman spectroscopic studies of enzymesubstrate intermediates at 5 K

    NASA Astrophysics Data System (ADS)

    Kim, Munsok; Carey, Paul R.

    1991-01-01

    A simple and versatile system for resonance Raman (RR) spectroscopic analysis of enzymesubstrate complexes at liquid helium temperatures is described. The system allows us to record high-quality RR spectra for dithioacyl papain intermediates (MeO-Phe-Gly- and MeO-Gly-Gly-Phe-Gly-C (dbnd S)S-papain) in ice matrices at 5 K. Based on established structure-spectra correlations, it is concluded that the active-site conformation of the intermediates about the φ', ψ' glycinic linkages and cysteine-25 side chain is B-G+-PH both in ice matrices at 5 K and in solution at room temperature.

  19. Picosecond flash spectroscopic studies on ultraviolet stabilizers and stabilized polymers

    NASA Technical Reports Server (NTRS)

    Scott, G. W.

    1982-01-01

    Spectroscopic and excited state decay kinetics are reported for monomeric and polymeric forms of ultraviolet stabilizers in the 2-(2'-hydroxyphenyl)-benzotriazole and 2-hydroxybenzophenone classes. For some of these molecules in various solvents at room temperature, (1) ground state absorption spectra, (2) emission spectra, (3) picosecond time-resolved transient absorption spectra, (4) ground state absorption recovery kinetics, (5) emission kinetics, and (6) transient absorption kinetics are reported. In the solid state at low temperatures, emission spectra and their temperature dependent kinetics up to approximately 200K as well as, in one case, the 12K excitation spectra of the observed dual emission are also reported.

  20. Spectroscopic study of the extremely fast rotating star 44 Geminorum

    NASA Astrophysics Data System (ADS)

    Iliev, L.; Vennes, S.; Kawka, A.; Kubat, J.; Nemeth, P.; Borisov, G.; KRaus, M.

    Stars with extremely fast rotation represent interesting challenge to modern understanding of the stellar evolution. The reasons why such a spin-up process should occur during the evolution to otherwise normal star are still not well understood. Already in the beginning of the XX century Otto Struve proposed that fast rotation of the group of stars spectroscopically classified as Be could be the main reason for the formation of observed disks of circumstellar material around them. This circumstellar material is responsible for the emission lines observed in the spectrum of Be-stars as well as for the whole complex of spectral and photometrical patterns called in general Be-phenomenon.

  1. Impedance calculation for ferrite inserts

    SciTech Connect

    Breitzmann, S.C.; Lee, S.Y.; Ng, K.Y.; /Fermilab

    2005-01-01

    Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.

  2. Study of Electrical Properties in SHI Irradiated 6H-SiC Crystals using Low Temperature Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Viswanathan, E.; Murugaraj, R.; Selvakumar, S.; Kanjilal, D.; Sivaji, K.

    2011-07-01

    In the present work, low temperature impedance measurements were made on the pristine and Ag12+ ions irradiated 6H-SiC samples. The conductivity properties were studied at low temperature. The activation energies were calculated from the Arrhenius plot of d.c conductivity and impedance relaxation time. The activation energy was comparatively higher for the irradiated samples and found to be electronic conduction. From the study we observe the lower conductivity values exhibited for 300 K irradiated sample due to severe damage than the 80 K irradiated sample. The damage production mechanism and the change in electrical properties are discussed.

  3. Computational Study on the Steady-state Impedance of Saturated-core Superconducting Fault Current Limiter

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Tang, Y.; Liang, S.; Ren, L.; Wang, Z.; Xu, Y.

    This paper presents the electromagnetic analysis of a high voltage saturated-core superconducting fault current limiter (SCSFCL). The numerical analyses of a three-dimensional (3D) model is shown, and the specific parameters are given. The model focus on the steady-state impedance of the limiter when connected to the power grid. It analyzed the dependence of steady-state impedance on the AC coil current, and the relationship between oil gap and coil inductance. The results suggest that, adding oil gap between slice of silicon steel can reduce the core cross-section, restrain the ultraharmonic and decrease the steady-state impedance. As the core cross-section of AC limb decreased from 4344 cm2 to 3983 cm2, the total harmonic distortion for voltage decreased from 2.4% to 1.8%, and the impedance decreased from 1.082 Ω to 1.069 Ω(Idc=400A,Iac=1296A).

  4. A PARAMETRIC STUDY OF BCS RF SURFACE IMPEDANCE WITH MAGNETIC FIELD USING THE XIAO CODE

    SciTech Connect

    Reece, Charles E.; Xiao, Binping

    2013-09-01

    A recent new analysis of field-dependent BCS rf surface impedance based on moving Cooper pairs has been presented.[1] Using this analysis coded in Mathematica TM, survey calculations have been completed which examine the sensitivities of this surface impedance to variation of the BCS material parameters and temperature. The results present a refined description of the "best theoretical" performance available to potential applications with corresponding materials.

  5. Study of High-Frequency Impedance of Small-Angle Tapers and Collimators

    SciTech Connect

    Stupakov, Gennady; Podobedov, B.; /Brookhaven

    2010-06-04

    Collimators and transitions in accelerator vacuum chambers often include small-angle tapering to lower the wakefields generated by the beam. While the low-frequency impedance is well described by Yokoya's formula (for axisymmetric geometry), much less is known about the behavior of the impedance in the high frequency limit. In this paper we develop an analytical approach to the highfrequency regime for round collimators and tapers. Our analytical results are compared with computer simulations using the code ECHO.

  6. Exploring How Substance Use Impedes Engagement along the HIV Care Continuum: A Qualitative Study

    PubMed Central

    Gwadz, Marya; de Guzman, Rebecca; Freeman, Robert; Kutnick, Alexandra; Silverman, Elizabeth; Leonard, Noelle R.; Ritchie, Amanda Spring; Muñoz-Plaza, Corinne; Salomon, Nadim; Wolfe, Hannah; Hilliard, Christopher; Cleland, Charles M.; Honig, Sylvie

    2016-01-01

    Drug use is associated with low uptake of HIV antiretroviral therapy (ART), an under-studied step in the HIV care continuum, and insufficient engagement in HIV primary care. However, the specific underlying mechanisms by which drug use impedes these HIV health outcomes are poorly understood. The present qualitative study addresses this gap in the literature, focusing on African-American/Black and Hispanic persons living with HIV (PLWH) who had delayed, declined, or discontinued ART and who also were generally poorly engaged in health care. Participants (N = 37) were purposively sampled from a larger study for maximum variation on HIV indices. They engaged in 1–2 h audio-recorded in-depth semi-structured interviews on HIV histories guided by a multilevel social-cognitive theory. Transcripts were analyzed using a systematic content analysis approach. Consistent with the existing literature, heavy substance use, but not casual or social use, impeded ART uptake, mainly by undermining confidence in medication management abilities and triggering depression. The confluence of African-American/Black or Hispanic race/ethnicity, poverty, and drug use was associated with high levels of perceived stigma and inferior treatment in health-care settings compared to their peers. Furthermore, providers were described as frequently assuming participants were selling their medications to buy drugs, which strained provider–patient relationships. High levels of medical distrust, common in this population, created fears of ART and of negative interactions between street drugs and ART, but participants could not easily discuss this concern with health-care providers. Barriers to ART initiation and HIV care were embedded in other structural- and social-level challenges, which disproportionately affect low-income African-American/Black and Hispanic PLWH (e.g., homelessness, violence). Yet, HIV management was cyclical. In collaboration with trusted providers and ancillary staff

  7. Exploring How Substance Use Impedes Engagement along the HIV Care Continuum: A Qualitative Study.

    PubMed

    Gwadz, Marya; de Guzman, Rebecca; Freeman, Robert; Kutnick, Alexandra; Silverman, Elizabeth; Leonard, Noelle R; Ritchie, Amanda Spring; Muñoz-Plaza, Corinne; Salomon, Nadim; Wolfe, Hannah; Hilliard, Christopher; Cleland, Charles M; Honig, Sylvie

    2016-01-01

    Drug use is associated with low uptake of HIV antiretroviral therapy (ART), an under-studied step in the HIV care continuum, and insufficient engagement in HIV primary care. However, the specific underlying mechanisms by which drug use impedes these HIV health outcomes are poorly understood. The present qualitative study addresses this gap in the literature, focusing on African-American/Black and Hispanic persons living with HIV (PLWH) who had delayed, declined, or discontinued ART and who also were generally poorly engaged in health care. Participants (N = 37) were purposively sampled from a larger study for maximum variation on HIV indices. They engaged in 1-2 h audio-recorded in-depth semi-structured interviews on HIV histories guided by a multilevel social-cognitive theory. Transcripts were analyzed using a systematic content analysis approach. Consistent with the existing literature, heavy substance use, but not casual or social use, impeded ART uptake, mainly by undermining confidence in medication management abilities and triggering depression. The confluence of African-American/Black or Hispanic race/ethnicity, poverty, and drug use was associated with high levels of perceived stigma and inferior treatment in health-care settings compared to their peers. Furthermore, providers were described as frequently assuming participants were selling their medications to buy drugs, which strained provider-patient relationships. High levels of medical distrust, common in this population, created fears of ART and of negative interactions between street drugs and ART, but participants could not easily discuss this concern with health-care providers. Barriers to ART initiation and HIV care were embedded in other structural- and social-level challenges, which disproportionately affect low-income African-American/Black and Hispanic PLWH (e.g., homelessness, violence). Yet, HIV management was cyclical. In collaboration with trusted providers and ancillary staff

  8. Exploring How Substance Use Impedes Engagement along the HIV Care Continuum: A Qualitative Study.

    PubMed

    Gwadz, Marya; de Guzman, Rebecca; Freeman, Robert; Kutnick, Alexandra; Silverman, Elizabeth; Leonard, Noelle R; Ritchie, Amanda Spring; Muñoz-Plaza, Corinne; Salomon, Nadim; Wolfe, Hannah; Hilliard, Christopher; Cleland, Charles M; Honig, Sylvie

    2016-01-01

    Drug use is associated with low uptake of HIV antiretroviral therapy (ART), an under-studied step in the HIV care continuum, and insufficient engagement in HIV primary care. However, the specific underlying mechanisms by which drug use impedes these HIV health outcomes are poorly understood. The present qualitative study addresses this gap in the literature, focusing on African-American/Black and Hispanic persons living with HIV (PLWH) who had delayed, declined, or discontinued ART and who also were generally poorly engaged in health care. Participants (N = 37) were purposively sampled from a larger study for maximum variation on HIV indices. They engaged in 1-2 h audio-recorded in-depth semi-structured interviews on HIV histories guided by a multilevel social-cognitive theory. Transcripts were analyzed using a systematic content analysis approach. Consistent with the existing literature, heavy substance use, but not casual or social use, impeded ART uptake, mainly by undermining confidence in medication management abilities and triggering depression. The confluence of African-American/Black or Hispanic race/ethnicity, poverty, and drug use was associated with high levels of perceived stigma and inferior treatment in health-care settings compared to their peers. Furthermore, providers were described as frequently assuming participants were selling their medications to buy drugs, which strained provider-patient relationships. High levels of medical distrust, common in this population, created fears of ART and of negative interactions between street drugs and ART, but participants could not easily discuss this concern with health-care providers. Barriers to ART initiation and HIV care were embedded in other structural- and social-level challenges, which disproportionately affect low-income African-American/Black and Hispanic PLWH (e.g., homelessness, violence). Yet, HIV management was cyclical. In collaboration with trusted providers and ancillary staff

  9. Using Spectroscopic Profiles to Study the Morphology of Comets

    NASA Astrophysics Data System (ADS)

    Harris, Ien; Pierce, Donna M.; Cochran, Anita L.

    2016-10-01

    We have used the integral-field unit spectrograph (the George and Cynthia Mitchell Spectrograph) on the 2.7m Harlan J. Smith telescope at McDonald Observatory to obtain spectroscopic images of the comae of several comets. The images were obtained for various radical species (C2, C3. CH, CN, NH2). Radial and azimuthal average profiles of the radical species were created to enhance any observed cometary coma morphological features. We compare the observed coma features across the observed species and over the different observation periods in order to constrain possible rotational states of the observed comets. We will present results for several comets, including 2009P1 (Garradd). This work was funded by NASA's Planetary Atmospheres program (Award No. NNX14AH186).

  10. Raman spectroscopic study of a genetically altered kidney cell

    NASA Astrophysics Data System (ADS)

    Joshi, Joel; Garcia, Francisco; Centeno, Silvia P.; Joshi, N. V.

    2008-02-01

    A Raman spectroscopic investigation of a genetically altered Human Embryonic Kidney Cell (HEK293) along with a pathologically normal cell has been carried out by a conventional method. The genetic alteration was carried out with a standard protocol by using a Green Fluorescence Protein (GFP). Raman spectra show that there are dramatic differences between the spectrum obtained from a genetically altered cell and that obtained from a pathologically normal cell. The former shows three broad bands; meanwhile the latter shows several sharp peaks corresponding to the ring vibrational modes of Phen, GFP and DNA. The present analysis provides an indication that the force field near Phen located at 64, 65 and 66 was altered during the genetic transformation. The Raman spectrum could be a direct experimental evidence for substantial modifications triggered due to the expression of specific genes.

  11. Feasibility studies of electrical impedance spectroscopy for monitoring tissue response to photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Wilson, Brian C.; Osterman, Kendra S.; Hoopes, P. Jack; Lilge, Lothar D.; Paulsen, Keith D.

    1998-05-01

    Electrical impedance spectroscopy (EIS) has been evaluated as a non- or minimally-invasive technique to monitor the acute tissue response to photodynamic therapy (PDT). In this study the EIS spectra of normal muscle tissue in the rat hind leg were monitored immediately before and at time intervals up to 96 hours post-PDT treatment with different photosensitizers (Photofrin, ALA-induced PpIX, BenzoPorphyrin Derivative), at varying photosensitizer and light doses. EIS measurements were made using a pair of solid matrix Ag-AgCl electrodes placed parallel to one another on either side of the muscle mass and interfaced to a precision LCR impedance meter scanning the frequency range 1 - 1000 KHz. Independent histological grading of tissue injury was performed on tissue sections from treated and untreated legs at the 96 hour end point. Significant and PDT dose-dependent changes in the EIS spectra following treatment were observed, including increases in conductivity which correlated with the immediate post-PDT edematous response with Photofrin and ALA and which resolved or partially-resolved over the measurement time course. Photofrin treatments exhibited a clear drug dose response at 96 hours that was evident in both the EIS spectra and the histological sections. These changes included significant tissue necrosis as well as edema, inflammation and early fibroplasia. The BPD data were less clear, but potentially quite interesting. Most striking were below unity ratios of treated-to-untreated muscle spectra components at 24 hours which reversed to above unity by 96 hours in the through skin measurements. This phenomenon is indicative of a tissue response distinctly different than that observed with Photofrin or ALA. These data also suggest that EIS measured changes are sensitive enough to detect differences in PDT-initiated tissue damage that may be photosensitize-specific. While the data are derived from a small number of animals, the findings are quite encouraging in

  12. Impedance studies of the thin film LiMn2O4/electrolyteinterface

    SciTech Connect

    Striebel, Kathryn A.; Sakai, E.; Cairns, Elton J.

    2001-04-07

    Room-temperature impedance measurements of a thin-film LiMn2O4/LiPF6-EC-DMC interface have been used to identify the spontaneous formation Li2Mn2O4 at the interface at room temperature at voltages of 3.7 and higher. The impedance of the LiMn2O4 films exhibited two time constants: at about 14 kHz and 60 to 200 Hz. The high frequency loop is dependent on film morphology and was attributed to the substrate/oxide interface. The low frequency behavior was dependent on both state-of-charge (SOC) and time at a given SOC. At full charge the impedance in this electrolyte was stable at room temperature over several days. At high lithium contents, film OCV and impedance tended to grow logarithmically with time, with lower rates for lower Mn3+ content in the film. The increased impedance was removed by oxidation of the film to 4.5V vs. Li/Li+. The observations are consistent with a reversible disproportionation of part of the LiMn2O4 into Li2Mn2O4 and a lithium-deficient spinel. With extended constant current cycling part of the Li2Mn2O4 degrades to the Mn2O3 and the process is no longer reversible.

  13. Study of Rust Effect on the Corrosion Behavior of Reinforcement Steel Using Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bensabra, Hakim; Azzouz, Noureddine

    2013-12-01

    Most studies on corrosion of steel reinforcement in concrete are conducted on steel samples with polished surface (free of all oxides) in order to reproduce the same experimental conditions. However, before embedding in concrete, the steel bars are often covered with natural oxides (rust), which are formed during exposure to the atmosphere. The presence of this rust may affect the electrochemical behavior of steel rebar in concrete. In order to understand the effect of rust on the corrosion behavior of reinforcement steel, potentiodynamic and electrochemical impedance spectroscopy (EIS) tests were carried out in a simulated concrete pore solution using steel samples with two different surface conditions: polished and rusted samples. The obtained results have shown that the presence of rust on the steel bar has a negative effect on its corrosion behavior, with or without the presence of chlorides. This detrimental effect can be explained by the fact that the rust provokes a decrease of the electrolyte resistance at the metal-concrete interface and reduces the repassivating ability. In addition, the rust layer acts as a barrier against the hydroxyl ion diffusion, which prevents the realkalinization phenomenon.

  14. High Resistivity Lipid Bilayers Assembled on Polyelectrolyte Multilayer Cushions: An Impedance Study.

    PubMed

    Diamanti, Eleftheria; Gregurec, Danijela; Rodríguez-Presa, María José; Gervasi, Claudio A; Azzaroni, Omar; Moya, Sergio E

    2016-06-28

    Supported membranes on top of polymer cushions are interesting models of biomembranes as cell membranes are supported on a polymer network of proteins and sugars. In this work lipid vesicles formed by a mixture of 30% 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 70% 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS) are assembled on top of a polyelectrolyte multilayer (PEM) cushion of poly(allylamine hydrochloride) (PAH) and poly(styrene sodium sulfonate) (PSS). The assembly results in the formation of a bilayer on top of the PEM as proven by means of the quartz crystal microbalance with dissipation technique (QCM-D) and by cryo-transmission electron microscopy (cryo-TEM). The electrical properties of the bilayer are studied by electrochemical impedance spectroscopy (EIS). The bilayer supported on the PEMs shows a high resistance, on the order of 10(7) Ω cm(2), which is indicative of a continuous, dense bilayer. Such resistance is comparable with the resistance of black lipid membranes. This is the first time that such values are obtained for lipid bilayers supported on PEMs. The assembly of polyelectrolytes on top of a lipid bilayer decreases the resistance of the bilayer up to 2 orders of magnitude. The assembly of the polyelectrolytes on the lipids induces defects or pores in the bilayer which in turn prompts a decrease in the measured resistance.

  15. High Resistivity Lipid Bilayers Assembled on Polyelectrolyte Multilayer Cushions: An Impedance Study.

    PubMed

    Diamanti, Eleftheria; Gregurec, Danijela; Rodríguez-Presa, María José; Gervasi, Claudio A; Azzaroni, Omar; Moya, Sergio E

    2016-06-28

    Supported membranes on top of polymer cushions are interesting models of biomembranes as cell membranes are supported on a polymer network of proteins and sugars. In this work lipid vesicles formed by a mixture of 30% 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 70% 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS) are assembled on top of a polyelectrolyte multilayer (PEM) cushion of poly(allylamine hydrochloride) (PAH) and poly(styrene sodium sulfonate) (PSS). The assembly results in the formation of a bilayer on top of the PEM as proven by means of the quartz crystal microbalance with dissipation technique (QCM-D) and by cryo-transmission electron microscopy (cryo-TEM). The electrical properties of the bilayer are studied by electrochemical impedance spectroscopy (EIS). The bilayer supported on the PEMs shows a high resistance, on the order of 10(7) Ω cm(2), which is indicative of a continuous, dense bilayer. Such resistance is comparable with the resistance of black lipid membranes. This is the first time that such values are obtained for lipid bilayers supported on PEMs. The assembly of polyelectrolytes on top of a lipid bilayer decreases the resistance of the bilayer up to 2 orders of magnitude. The assembly of the polyelectrolytes on the lipids induces defects or pores in the bilayer which in turn prompts a decrease in the measured resistance. PMID:27267089

  16. Spectroscopic ellipsometry studies of HF treated Si (100) surfaces

    NASA Astrophysics Data System (ADS)

    Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

    1993-06-01

    Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effect of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that, after a 20-sec 9:1 HF dip without rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed, in an ultrahigh vacuum chamber (UHV), and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface layer, after being heated to about 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

  17. Spectroscopic ellipsometry studies of HF treated Si (100) surfaces

    NASA Astrophysics Data System (ADS)

    Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

    1993-08-01

    Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effects of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that after a 20-s 9:1 HF dip without rinse, the Si(100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si(100) surface was observed, in an ultrahigh vacuum (UHV) chamber, and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface-layer, after being heated to approximately 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

  18. Spectroscopic studies of homogeneous precursors to atmospheric acids and aerosols

    SciTech Connect

    Leopold, K.R.; Canagaratna, M.; Phillips, J.A.; Goodfriend, H.

    1996-10-01

    A detailed understanding of the nucleation and growth of atmospheric particulates is benefitted by precise knowledge of the structure and energetics of small molecular aggregates. We present the results of microwave spectroscopic characterization of three binary clusters which are potential precursors in such processes: H{sub 2}O-SO{sub 3}, H{sub 3}N-SO{sub 3}, and H{sub 2}O-HNO{sub 3}. In addition to providing detailed structural information, we describe the nature of the bonding in these systems. For the SO{sub 3} complexes, the intermolecular interaction is weaker than a chemical bond, but stronger than a van der Waals bond. We discuss how this feature of these systems renders their structure and energetics unusually sensitive to the presence of additional binding partners, and infer that an accurate molecular-level description of cluster growth will need to account for this effect. The results are compared with published high level ab initio calculations for all three systems.

  19. Structural and spectroscopic studies of a model for catechol oxidase.

    PubMed

    Smith, Sarah J; Noble, Christopher J; Palmer, Randahl C; Hanson, Graeme R; Schenk, Gerhard; Gahan, Lawrence R; Riley, Mark J

    2008-05-01

    A binuclear copper complex, [Cu2(BPMP) (OAc)2][ClO4] x H2O, has been prepared using the binucleating ligand 2,6-bis[bis(pyridin-2-ylmethylamino)methyl]-4-methylphenol (H-BPMP). The X-ray crystal structure reveals the copper centers to have a five-coordinate square pyramidal geometry, with the acetate ligands bound terminally. The bridging phenolate occupies the apical position of the square-based pyramids and magnetic susceptibility, electron paramagnetic resonance (EPR) and variable-temperature variable-field magnetic circular dichroism (MCD) measurements indicate that the two centers are very weakly antiferromagnetically coupled (J = -0.6 cm(-1)). Simulation of the dipole-dipole-coupled EPR spectrum showed that in solution the Cu-O-Cu angle was increased from 126 degrees to 160 degrees and that the internuclear distance was larger than that observed crystallographically. The high-resolution spectroscopic information obtained has been correlated with a detailed ligand-field analysis to gain insight into the electronic structure of the complex. Symmetry arguments have been used to demonstrate that the sign of the MCD is characteristic of the tetragonally elongated environment. The complex also displays catecholase activity (k(cat) = 15 +/- 1.5 min(-1), K(M) = 6.4 +/- 1.8 mM), which is compared with other dicopper catechol oxidase models. PMID:18188615

  20. Optical spectroscopic studies of mononitrated benzo[a]pyrenes.

    PubMed

    Vyas, Shubham; Onchoke, Kefa K; Rajesh, Cheruvallil S; Hadad, Christopher M; Dutta, Prabir K

    2009-11-12

    Spectroscopic properties, including absorption, emission spectra, and excited-state lifetimes of the mononitrated benzo[a]pyrenes (NBaPs), specifically 1-, 3-, and 6-nitrobenzo[a]pyrenes (1-, 3-, and 6-NBaP), are reported, and correlations with structure are developed. With 1- and 3-NBaP, bathochromic shifts are observed in the absorption spectra. The quantum yields of emission display the following trend: BaP > 6-NBaP > 1-NBaP approximately 3-NBaP. Fluorescence lifetimes for nitrated BaPs were approximately 6 to 7 times shorter than that of BaP. With the help of time-dependent density functional theory (TD-DFT), assignments of the electronic transitions are proposed and are in good agreement with the electronic spectra for the NBaPs in methanol. On the basis of optimization of the triplet states, different photochemical consequences are discussed, and the observed fluorescence quenching is explained. Changes in the electron density distributions in the ground and excited states calculated at the second-order coupled-cluster level using the resolution-of-the-identity approximation (RI-CC2) provide information about the possible mechanism of photochemical reactions of NBaPs. Correlations between the orientation of the nitro group relative to the aromatic plane and the observed properties of the NBaP are discussed. PMID:19888776

  1. Acid doping of polyaniline: Spectroscopic and electrochemical studies

    SciTech Connect

    Hatchett, D.W.; Josowicz, M.; Janata, J.

    1999-12-16

    A detailed investigation of the acid doping behavior of polyaniline has led to a robust and reproducible procedure for controlled adjustment of the redox state of dry polyaniline films. The initial step in this procedure is the casting of PANI films from formic acid. The subsequent exchange of the trapped formic acid for other primary dopants obtained from mono- and polyprotic acids (e.g., CH{sub 3}COO{sup {minus}}, BF{sub 4}{sup {minus}}, HSO{sub 4}{sup {minus}}, SO{sub 4}{sup 2{minus}}, H{sub 2}PO{sub 4}{sup {minus}}, and HPO{sub 4}{sup 2{minus}}) is demonstrated. The voltammetric and the spectroscopic behavior of the PANI doped with different anions indicate that both the protons and the anions of dopant acids influence the structure and redox properties of the polymer. The redox state of PANI doped with homologous series of chloroacetic and carboxylic acids correlates with the pK{sub a} of the dopant acid. These results show that it is possible to prepare the polymer with a desired oxidation state according to the pK{sub a} of the dopant acid of a given homologous series. The exchange of the formic acid for both stronger and weaker doping acid can be repeatedly accomplished by electrochemical cycling.

  2. Crew Quarters (CQ) and Electromagnetic Interference (EMI) Measurement Facility Combined Impedance Study

    NASA Technical Reports Server (NTRS)

    Scully, Robert C.

    2011-01-01

    This report documents an investigation into observed failures associated with conducted susceptibility testing of Crew Quarters (CQ) hardware in the Johnson Space Center (JSC) Electromagnetic Interference (EMI) Measurement Facility, and the work accomplished to identify the source of the observed behavior. Investigation led to the conclusion that the hardware power input impedance was interacting with the facility power impedance leading to instability at the observed frequencies of susceptibility. Testing performed in other facilities did not show this same behavior, pointing back to the EMI Measurement Facility power as the potential root cause. A LISN emulating the Station power bus impedance was inserted into the power circuit, and the susceptibility was eliminated from the measurements.

  3. Comparative Study of Impedance Eduction Methods. Part 1; DLR Tests and Methodology

    NASA Technical Reports Server (NTRS)

    Busse-Gerstengarbe, Stefan; Bake, Friedrich; Enghardt, Lars; Jones, Michael G.

    2013-01-01

    The absorption efficiency of acoustic liners used in aircraft engines is characterized by the acoustic impedance. World wide, many grazing ow test rigs and eduction methods are available that provide values for that impedance. However, a direct comparison and assessment of the data of the di erent rigs and methods is often not possible because test objects and test conditions are quite di erent. Only a few papers provide a direct comparison. Therefore, this paper together with a companion paper, present data measured with a reference test object under similar conditions in the DLR and NASA grazing ow test rigs. Additionally, by applying the in-house methods Liner Impedance Non-Uniform ow Solving algorithm (LINUS, DLR) and Convected Helmhholtz Equation approach (CHE, NASA) on the data sets, similarities and differences due to underlying theory are identi ed and discussed.

  4. Synthesis and characterization of cancrinite-type zeolite, and its ionic conductivity study by AC impedance analysis

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Ben Saad, K.; Hamzaoui, A. H.

    2012-12-01

    The synthesis of cancrinite in the system NaOH-SiO2-Al2O3-NaHCO3-H2O was performed, according to methods described in the literature, in an autoclave under hydrothermal conditions at T = 473 K. The electrical properties of cancrinite-type zeolite pellets were investigated by complex impedance spectroscopy in the temperature range 465-800°C. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (1 Hz to 13 MHz). The real and imaginary parts of complex impedance trace semicircles in the complex plane are plotted. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The results of bulk electrical conductivity and its activation energy are presented. The modulus analysis suggests that the electrical transport processes in the material are very likely to be of electronic nature. Relaxation frequencies follow an Arrhenius behavior with activation energy values not comparable to those found for the electrical conductivity.

  5. Impedance spectroscopy study of anodic growth of zirconium oxide film in NaOH medium

    NASA Astrophysics Data System (ADS)

    Pauporté, T.; Finne, J.; Lincot, D.

    2005-06-01

    The growth of anodic oxide films on zirconium metal has been followed up to 300 V by electrochemical impedance spectroscopy and scanning electron microscopy. The maximum layer thickness is 720 nm, the dielectric constant of the film is measured at 19.5 and the growth constant is 2.4 nm V-1. Above 50 V, the presence of two impedance relaxations between 1 Hz and 200 kHz reveals a bilayered structure. This may be a consequence of a lower resistivity of the outer layer induced by some electrolytic solution infiltration into film defects.

  6. Spectroscopic studies of the small-amplitude Cepheid SU Cas

    NASA Astrophysics Data System (ADS)

    Usenko, I. A.; Klochkova, V. G.; Tavolzhanskaya, N. S.

    2013-09-01

    A new set of 16 high-resolution spectra for the small-amplitude Cepheid SU Cas obtained in 2007-2009 has allowed us to determine its atmospheric parameters ( T eff = 6345 ± 30 K, log g = 2.40, V t = 3.25 km s-1) and to measure its radial velocities. The latter were added to the general list of radial velocities (375 estimates) obtained in the last 90 years. Using a frequency analysis, we have refined the pulsation and orbital periods of the Cepheid. Apart from the well-known fundamental pulsation period [Figure not available: see fulltext.], we have detected a possible secondary period of [Figure not available: see fulltext.]. Their ratio of 0.96 suggests the existence of nonradial pulsations in the Cepheid's atmosphere. Based on photoelectric photometry in the last 60 years, we have shown that the effective temperature undergoes cyclic secular changes of ±200 K with an unknown period. The mean effective temperature T eff = 6395 ± 52 K estimated from photometric data agrees well with our estimate from spectroscopic data. The variations of the mean color index, effective temperature, and γ-velocity (in 90 years of observations) point to a possible orbital motion of the well-known hot companion with the most probable periods of [Figure not available: see fulltext.], [Figure not available: see fulltext.], and [Figure not available: see fulltext.]. The elemental abundances in the atmosphere of SU Cas confirm the conclusion that this Cepheid is a typical yellow supergiant after the first dredge-up. Our T eff estimate gives a radius of 32 R ⊙ and a distance of 455 pc for it, which is inconsistent with its membership in the open cluster Alessi 95. The question about the pulsation mode of SU Cas still remains open.

  7. In situ spectroscopic ellipsometry studies of hydrogen ion bombardment of crystalline silicon

    SciTech Connect

    Hu, Y.Z.; Li, M.; Conrad, K.; Andres, J.W.; Irene, E.A.; Denker, M.; Ray, M.; McGuire, G.

    1992-05-01

    Hydrogen-bombardment induced damage in single crystal silicon as a function of the substrate temperature, ion energy, and ion dose was studied using in situ spectroscopic ellipsometry over the photon energy range 2.0-5.5 eV under high vacuum conditions. The incident hydrogen ion energies were 300 and 1000 eV, and the doses were 10{sup 15}-10{sup 18} ions/cm{sup 2}. In situ spectroscopic ellipsometry results showed that the damage layer thicknesses for the samples bombarded at elevated temperatures are smaller than for samples bombarded at room temperature and subsequently annealed at the same elevated temperature. The diffusion coefficient for hydrogen in silicon of 6 x 10{sup {minus}15} cm{sup {minus}2}/s was obtained from the in situ spectroscopic ellipsometry data. 40 refs., 11 figs., 1 tab.

  8. Cell Electrical Impedance as a Novel Approach for Studies on Senescence Not Based on Biomarkers

    PubMed Central

    Cha, Jung-Joon; Park, Yangkyu; Yun, Joho; Kim, Hyeon Woo; Park, Chang-Ju; Kang, Giseok; Jung, Minhyun; Pak, Boryeong; Jin, Suk-Won

    2016-01-01

    Senescence of cardiac myocytes is frequently associated with heart diseases. To analyze senescence in cardiac myocytes, a number of biomarkers have been isolated. However, due to the complex nature of senescence, multiple markers are required for a single assay to accurately depict complex physiological changes associated with senescence. In single cells, changes in both cytoplasm and cell membrane during senescence can affect the changes in electrical impedance. Based on this phenomenon, we developed MEDoS, a novel microelectrochemical impedance spectroscopy for diagnosis of senescence, which allows us to precisely measure quantitative changes in electrical properties of aging cells. Using cardiac myocytes isolated from 3-, 6-, and 18-month-old isogenic zebrafish, we examined the efficacy of MEDoS and showed that MEDoS can identify discernible changes in electrical impedance. Taken together, our data demonstrated that electrical impedance in cells at different ages is distinct with quantitative values; these results were comparable with previously reported ones. Therefore, we propose that MEDoS be used as a new biomarker-independent methodology to obtain quantitative data on the biological senescence status of individual cells. PMID:27812531

  9. Spectroscopic Signatures and Structural Motifs of Dopamine: a Computational Study

    NASA Astrophysics Data System (ADS)

    Srivastava, Santosh Kumar; Singh, Vipin Bahadur

    2016-06-01

    Dopamine (DA) is an essential neurotransmitter in the central nervous system and it plays integral role in numerous brain functions including behaviour, cognition, emotion, working memory and associated learning. In the present work the conformational landscapes of neutral and protonated dopamine have been investigated in the gas phase and in aqueous solution by MP2 and DFT (M06-2X, ωB97X-D, B3LYP and B3LYP-D3) methods. Twenty lowest energy structures of neutral DA were subjected to geometry optimization and the gauche conformer, GIa, was found to be the lowest gas phase structure at the each level of theory in agreement with the experimental rotational spectroscopy. All folded gauche conformers (GI) where lone electron pair of the NH2 group is directed towards the π system of the aromatic ring ( 'non up' ) are found more stable in the gas phase. While in aqueous solution, all those gauche conformers (GII) where lone electron pair of the NH2 group is directed opposite from the π system of the aromatic ring ('up' structures) are stabilized significantly.Nine lowest energy structures, protonated at the amino group, are optimized at the same MP2/aug-cc-pVDZ level of theory. In the most stable gauche structures, g-1 and g+1, mainly electrostatic cation - π interaction is further stabilized by significant dispersion forces as predicted by the substantial differences between the DFT and dispersion corrected DFT-D3 calculations. In aqueous environment the intra-molecular cation- π distance in g-1 and g+1 isomers, slightly increases compared to the gas phase and the magnitude of the cation- π interaction is reduced relative to the gas phase, because solvation of the cation decreases its interaction energy with the π face of aromatic system. The IR intensity of the bound N-H+ stretching mode provides characteristic 'IR spectroscopic signatures' which can reflect the strength of cation- π interaction energy. The CC2 lowest lying S1 ( 1ππ* ) excited state of neutral

  10. Tethered bilayer lipid membranes studied by simultaneous attenuated total reflectance infrared spectroscopy and electrochemical impedance spectroscopy

    PubMed Central

    Erbe, Andreas; Bushby, Richard J.; Evans, Stephen D.; Jeuken, Lars J. C.

    2013-01-01

    The formation of tethered lipid bilayer membranes (tBLMs) from unilamelar vesicles of egg yolk phosphatidylcholine (EggPC) on mixed self–assembled monolayers (SAMs) from varying ratios of 6-mercaptohexanol and EO3Cholesteryl on gold has been monitored by simultaneous attenuated total reflectance fourier transform infrared (ATR–FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS). The influence of the lipid orientation (and hence the anisotropy) of lipids on a gold film on the dichroic ratio was studied by simulations of spectra with a matrix method for anisotropic layers. It is shown that for certain tilt angles of the dielectric tensor of the adsorbed anisotropic layer dispersive and negative absorption bands are possible. The experimental data indicates that the structure of the assemblies obtained varies with varying SAM composition. On SAMs with a high content of EO3Cholesteryl, tBLMs with reduced fluidity are formed. For SAMs with high content of 6-mercaptohexanol, the results are consistent with the adsorption of flattened vesicles, while spherical vesicles have been found in a small range of surface compositions. The kinetics of the adsorption process is consistent with the assumption of spherical vesicles as long–living intermediates for surfaces of high 6-mercaptohexanol content. No long–living spherical vesicles have been detected for surfaces with large fraction of EO3Cholesteryl tethers. The observed differences between the surfaces suggest that for the formation of tBLMs (unlike supported BLMs) no critical surface coverage of vesicles is needed prior to lipid bilayer formation. PMID:17388505

  11. Single cell studies of mouse embryonic stem cell (mESC) differentiation by electrical impedance measurements in a microfluidic device.

    PubMed

    Zhou, Ying; Basu, Srinjan; Laue, Ernest; Seshia, Ashwin A

    2016-07-15

    Biological populations of cells show considerable cell-to-cell variability. Study of single cells and analysis of cell heterogeneity are considered to be critical in understanding biological processes such as stem cell differentiation and cancer development. Recent advances in lab-on-a-chip techniques have allowed single-cell capture in microfluidic channels with the possibility of precise environmental control and high throughput of experiments with minimal usage of samples and reagents. In recent years, label-free techniques such as electrical impedance spectroscopy have emerged as a non-invasive approach to studying cell properties. In this study, we have designed and fabricated a microfluidic device that combines hydrodynamic trapping of single cells in pre-defined locations with the capability of running electrical impedance measurements within the same device. We have measured mouse embryonic stem cells (mESCs) at different states during differentiation (t=0h, 24h and 48h) and quantitatively analysed the changes in electrical parameters of cells during differentiation. A marked increase in the magnitude of the cell impedance is found during cell differentiation, which can be attributed to an increase in cell size. The analysis of the measurements shows that the nucleus-to-cytoplasm ratio decreases during this process. The degree of cell heterogeneity is observed to be the highest when the cells are at the transition state (24h), compare with cells at undifferentiated (0h) and fully differentiated (48h) states. The device enables highly efficient single cell trapping and provides sensitive, label-free electrical impedance measurements of individual cells, enabling the possibility of quantitatively analysing their physical state as well as studying the associated heterogeneity of a cell population.

  12. Single cell studies of mouse embryonic stem cell (mESC) differentiation by electrical impedance measurements in a microfluidic device

    PubMed Central

    Zhou, Ying; Basu, Srinjan; Laue, Ernest; Seshia, Ashwin A.

    2016-01-01

    Biological populations of cells show considerable cell-to-cell variability. Study of single cells and analysis of cell heterogeneity are considered to be critical in understanding biological processes such as stem cell differentiation and cancer development. Recent advances in lab-on-a-chip techniques have allowed single-cell capture in microfluidic channels with the possibility of precise environmental control and high throughput of experiments with minimal usage of samples and reagents. In recent years, label-free techniques such as electrical impedance spectroscopy have emerged as a non-invasive approach to studying cell properties. In this study, we have designed and fabricated a microfluidic device that combines hydrodynamic trapping of single cells in pre-defined locations with the capability of running electrical impedance measurements within the same device. We have measured mouse embryonic stem cells (mESCs) at different states during differentiation (t=0 h, 24 h and 48 h) and quantitatively analysed the changes in electrical parameters of cells during differentiation. A marked increase in the magnitude of the cell impedance is found during cell differentiation, which can be attributed to an increase in cell size. The analysis of the measurements shows that the nucleus-to-cytoplasm ratio decreases during this process. The degree of cell heterogeneity is observed to be the highest when the cells are at the transition state (24 h), compare with cells at undifferentiated (0 h) and fully differentiated (48 h) states. The device enables highly efficient single cell trapping and provides sensitive, label-free electrical impedance measurements of individual cells, enabling the possibility of quantitatively analysing their physical state as well as studying the associated heterogeneity of a cell population. PMID:26963790

  13. Report of the SSC impedance workshop

    SciTech Connect

    1985-10-28

    This workshop focused attention on the transverse, single-bunch instability and the detailed analysis of the broadband impedance which would drive it. Issues discussed included: (1) single bunch stability -- impact of impedance frequency shape, coupled-mode vs. fast blowup regimes, possible stopband structure; (2) numerical estimates of transverse impedance of inner bellows and sliding contact shielded bellows; (3) analytic estimates of pickup and kicker impedance contributions; and (4) feasibility studies of wire and beam measurements of component impedance.

  14. A study on calculation method for mechanical impedance of air spring

    NASA Astrophysics Data System (ADS)

    Changgeng, SHUAI; Penghui, LI; Rustighi, Emiliano

    2016-09-01

    This paper proposes an approximate analytic method of obtaining the mechanical impedance of air spring. The sound pressure distribution in cylindrical air spring is calculated based on the linear air wave theory. The influences of different boundary conditions on the acoustic pressure field distribution in cylindrical air spring are analysed. A 1-order ordinary differential matrix equation for the state vector of revolutionary shells under internal pressure is derived based on the non-moment theory of elastic thin shell. Referring to the transfer matrix method, a kind of expanded homogeneous capacity high precision integration method is introduced to solve the non-homogeneous matrix differential equation. Combined the solved stress field of shell with the calculated sound pressure field in air spring under the displacement harmonic excitation, the approximate analytical expression of the input and transfer mechanical impedance for the air spring can be achieved. The numerical simulation with the Comsol Multiphysics software verifies the correctness of theoretical analysis result.

  15. Microstructural studies of AgNbO{sub 3} ceramic by using complex impedance spectroscopy

    SciTech Connect

    Gangaprasad, K.; Rao, T. Durga; Niranjan, Manish K.; Asthana, Saket

    2015-06-24

    Lead-free piezoelectric silver niobate ceramic was synthesized by conventional solid state route. Room temperature X-ray diffraction pattern revealed that the sample crystallizes in single phase orthorhombic perovskite structure. Scanning electron micrographs of AgNbO{sub 3} ceramic showed that the average grain size is in the range 2–3 µm. The electrical properties were investigated by using impedance spectroscopy. Appearance of single semicircular arc in the Nyquist plot indicated the presence of grain contribution in the sample. Single RC parallel circuit model was employed to extract bulk capacitance (C{sub b}), resistance (R{sub b}) and electrical conductivity (σ{sub b}). The activation energy calculated from impedance and modulus data indicate that same types of charge carriers (oxygen vacancy movements) are responsible for conduction and relaxation.

  16. Microstructural studies of AgNbO3 ceramic by using complex impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Gangaprasad, K.; Rao, T. Durga; Niranjan, Manish K.; Asthana, Saket

    2015-06-01

    Lead-free piezoelectric silver niobate ceramic was synthesized by conventional solid state route. Room temperature X-ray diffraction pattern revealed that the sample crystallizes in single phase orthorhombic perovskite structure. Scanning electron micrographs of AgNbO3 ceramic showed that the average grain size is in the range 2-3 µm. The electrical properties were investigated by using impedance spectroscopy. Appearance of single semicircular arc in the Nyquist plot indicated the presence of grain contribution in the sample. Single RC parallel circuit model was employed to extract bulk capacitance (Cb), resistance (Rb) and electrical conductivity (σb). The activation energy calculated from impedance and modulus data indicate that same types of charge carriers (oxygen vacancy movements) are responsible for conduction and relaxation.

  17. An Experimental Study on the Effect of Temperature on Piezoelectric Sensors for Impedance-Based Structural Health Monitoring

    PubMed Central

    Baptista, Fabricio G.; Budoya, Danilo E.; de Almeida, Vinicius A. D.; Ulson, Jose Alfredo C.

    2014-01-01

    The electromechanical impedance (EMI) technique is considered to be one of the most promising methods for developing structural health monitoring (SHM) systems. This technique is simple to implement and uses small and inexpensive piezoelectric sensors. However, practical problems have hindered its application to real-world structures, and temperature effects have been cited in the literature as critical problems. In this paper, we present an experimental study of the effect of temperature on the electrical impedance of the piezoelectric sensors used in the EMI technique. We used 5H PZT (lead zirconate titanate) ceramic sensors, which are commonly used in the EMI technique. The experimental results showed that the temperature effects were strongly frequency-dependent, which may motivate future research in the SHM field. PMID:24434878

  18. Study on electromechanical impedance characteristics of part of structures made of CFRP

    NASA Astrophysics Data System (ADS)

    Malinowski, Paweł H.; Wandowski, Tomasz; Ostachowicz, Wiesław M.

    2016-04-01

    Carbon Fibre Reinforced Polymers (CFRP) are more and more used in many branches of industry. Researchers are developing numerous techniques of non-destructive assessment of the structures made out of CFRP such as guided waves, ultrasonics, laser induced fluorescence and others. In this research we focus on electromechanical impedance (EMI) technique. In this technique a piezoelectric sensor is either surface mounted or embedded into investigated host structure. The electrical quantities of the sensor are measured for wide frequency range. Due to piezoelectric effect the electrical response of the sensor is related to mechanical response of the structure to which the sensors is bonded to. In the reported research impedance spectra in the vicinity of the transducer thickness mode were investigated as well as the lower frequency range. The spectra that were analysed were gathered from samples with surface treatment such as thermal degradation and samples adhesively bonded with film adhesive with symmetric and unsymmetric bond. Moreover, the samples with modified adhesive bonds were investigated. These spectra for different cases were compared with reference measurement results gathered from pristine samples. Numerical indexes for comparison of the EMI characteristics were proposed. The comparison of the indexes was also conducted. In the experimental part of the research the piezoelectric transducer was mounted at the sample surface. Measurements were conducted using HIOKI Impedance Analyzer IM3570.

  19. Acoustic impedance studies in Triassic reservoirs in the Netherlands - application to development and exploration

    SciTech Connect

    Griffiths, M.; Ford, J.

    1995-08-01

    Simple and cost effective seismic forward modelling techniques have been used in conjunction with petrophysical and geological data to provide an integrated approach to understanding the seismic response of Triassic gas reservoirs onshore and offshore Netherlands. Analysis shows that for the Volpriehausen Sandstone in the offshore sector a relationship exists between reservoir acoustic impedance and porosity such that an increase in porosity leads to a decrease in acoustic impedance. Data can be sub-divided on the basis of fluid fill and cementation with trends for both gas and water cases. Regression analysis has defined the optimum relationship for each fluid case and these relationships have been used to predict the acoustic impedance profiles for a variety of reservoir scenarios. Modelling shows that the highest seismic amplitudes and the greatest relative amplitude variation with fluid fill are related to high porosity reservoir. In the onshore sector, analysis for the Roet Sandstone has shown that even small scale variations in reservoir properties can be recorded within the detail of the seismic response. Results from seismic forward modelling compare with amplitude variations observed in real data and suggest that, within the limitations of the dataset and methodology, the technique can be used to predict reservoir attributes from the seismic response. So far, the technique has been sucessfully applied to both exploration and field development projects.

  20. Ac Impedance Spectroscopic Studies on Li2xPb2xBaP2O7

    NASA Astrophysics Data System (ADS)

    Vijayakumar, M.; Selvasekarapandian, S.

    2002-12-01

    The complex diphosphate (P2O7)4- ions have been used as a building blocks in wide variety of crystal phases for a wide spectrum of physical and chemical properties. Lithium barium diphsophate doped with lead {Li2-xPb2xBaP2O7 (x = 0, 0.2 & 0.4)} has been prepared by solid state reaction method The conductivity is found to be decreasing with the doping of lead. The lithium ion dynamics parameters such as hopping frequency and relaxation frequency were calculated from the frequency dependent conductivity and modulus analysis.

  1. How specific Raman spectroscopic models are: a comparative study between different cancers

    NASA Astrophysics Data System (ADS)

    Singh, S. P.; Kumar, K. Kalyan; Chowdary, M. V. P.; Maheedhar, K.; Krishna, C. Murali

    2010-02-01

    Optical spectroscopic methods are being contemplated as adjunct/ alternative to existing 'Gold standard' of cancer diagnosis, histopathological examination. Several groups are actively pursuing diagnostic applications of Ramanspectroscopy in cancers. We have developed Raman spectroscopic models for diagnosis of breast, oral, stomach, colon and larynx cancers. So far, specificity and applicability of spectral- models has been limited to particular tissue origin. In this study we have evaluated explicitly of spectroscopic-models by analyzing spectra from already developed spectralmodels representing normal and malignant tissues of breast (46), cervix (52), colon (25), larynx (53), and oral (47). Spectral data was analyzed by Principal Component Analysis (PCA) using scores of factor, Mahalanobis distance and Spectral residuals as discriminating parameters. Multiparametric limit test approach was also explored. The preliminary unsupervised PCA of pooled data indicates that normal tissue types were always exclusive from their malignant counterparts. But when we consider tissue of different origin, large overlap among clusters was found. Supervised analysis by Mahalanobis distance and spectral residuals gave similar results. The 'limit test' approach where classification is based on match / mis-match of the given spectrum against all the available spectra has revealed that spectral models are very exclusive and specific. For example breast normal spectral model show matches only with breast normal spectra and mismatch to rest of the spectra. Same pattern was seen for most of spectral models. Therefore, results of the study indicate the exclusiveness and efficacy of Raman spectroscopic-models. Prospectively, these findings might open new application of Raman spectroscopic models in identifying a tumor as primary or metastatic.

  2. SPECTROSCOPIC STUDIES OF MATERIALS FOR ELECTROCHEMICAL ENERGY STORAGE

    SciTech Connect

    Greenbaum, Steven G.

    2014-03-01

    Several battery materials research projects were undertaken, suing NMR spectroscopy as a primary analytical tool. These include transport proerties of liquid and solid electrolytes and structural studies of Li ion electrodes.

  3. Structural, dielectric and impedance studies of polycrystalline La0.6Gd0.2Ca0.2MnO3

    NASA Astrophysics Data System (ADS)

    Nandan K., R.; Rubankumar, A.; Kalainathan, S.

    2016-05-01

    Polycrystalline materials of Gd doped La1-xCaxMnO3 were prepared by Sol-Gel technique using citric acid as a chelating agent at 9000 C. The single phase formation of Gd doped LCMO were determined by Powder XRD, dielectric studies and impedance studies is investigated. The existence of dielectric relaxation and release of space charges were observed in the dielectric constant and real part of impedance plots respectively. The shift in the peaks for imaginary part of impedance revealed the existence of relaxation process due to oxygen vacancy. The existence of single semicircle in the cole-cole plot confirms the dielectric relaxation in the prepared sample.

  4. Computational, electrochemical, and spectroscopic, studies of acetycholinesterase covalently attached to carbon nanotubes.

    PubMed

    Cabral, Murilo F; Barrios, Joseph D; Kataoka, Erica M; Machado, Sergio A S; Carrilho, Emanuel; Garcia, Carlos D; Ayon, Arturo A

    2013-03-01

    This manuscript describes results related to the characterization of electrodes modified with a composite of acetylcholinesterase covalently bound to carbon nanotubes (CNT). The characterization was performed by computational methods and complemented by cyclic voltammetry, infrared spectroscopy, and electrochemical impedance spectroscopy. In-silico simulations enabled the identification of the binding site and the calculation of the interaction energy. Besides complementing the computational studies, experimental results obtained by cyclic voltammetry showed that the addition of CNT to the surface of electrodes yielded significant increases in effective area and greatly facilitated the electron transfer reactions. These results are also in agreement with impedance spectroscopy data, which indicated a high apparent rate constant, even after the immobilization of the enzyme. These results lend new information about the physical and chemical properties of biointerfaces at the molecular level, specifically about the mechanism and consequences of the interaction of a model enzyme with CNT. PMID:23274156

  5. Fundamental spectroscopic studies of carbenes and hydrocarbon radicals

    SciTech Connect

    1999-03-12

    Determination of bond dissociation energies and heats of formation of hydrocarbon radicals and carbenes requires knowledge of their structures, but this is not provided by standard mass spectrometric studies; what is needed is high-resolution spectroscopy, often best achieved at centimeter and millimeter wavelengths. Nearly 60 reactive organic molecules were investigated in the period from 1988--1998.

  6. LEAD SORPTION ON RUTHENIUM OXIDE: A MACROSCOPIC AND SPECTROSCOPIC STUDY

    EPA Science Inventory

    Metal oxide phases play an important role in governing the sorption and desorption mechanisms of metals in water, soils, and sediments. Many researchers have examined the efficiency of Pb sorption on Mn, Fe, Al, Ti, and Si oxide surfaces. Most studies concluded that adsorption ...

  7. Models of Longitudinal Space-Charge Impedance for the Study of theMicrobunching Instability

    SciTech Connect

    Venturini, Marco

    2008-03-10

    A 1D model of space-charge impedance, assuming atransversely uniform beam with circular cross-section, has been proposedand is being extensively used in the modelling of the microbunchinginstability of relevance for the beam delivery systems of x-ray FELs. Inthis paper we investigate the limitation of the model when applied tostudying the effect of shot noise--one of the sources of themicrobunching instability. We make comparison witha fully 3D calculationand identify the upper end of the frequency spectrum for applicability ofthe 1D model. Relaxation of the assumptions regarding axis-symmetry anduniformity of the transverse density is also reviewed.

  8. Conceptual design study to determine optimal enclosure vent configuration for the Maunakea Spectroscopic Explorer (MSE)

    NASA Astrophysics Data System (ADS)

    Szeto, Kei; Vogiatzis, Konstantinos; Hangan, Horia; Jubayer, Chowdhury M.; Breckenridge, Craig; Loewen, Nathan; Bauman, Steven; Salmon, Derrick

    2014-07-01

    The Maunakea Spectroscopic Explorer (MSE; formerly Next Generation Canada-France-Hawaii Telescope) is a dedicated, 10m aperture, wide-field, fiber-fed multi-object spectroscopic facility proposed as an upgrade to the existing Canada-France-Hawaii Telescope on the summit of Mauna Kea. The enclosure vent configuration design study is the last of three studies to examine the technical feasibility of the proposed MSE baseline concept. The enclosure vent configuration study compares the aero-thermal performance of three enclosure ventilation configurations based on the predicted dome thermal seeing and air flow attenuation over the enclosure aperture opening of a Calotte design derived from computational fluid dynamics simulations. In addition, functional and operation considerations such as access and servicing of the three ventilation configurations is discussed.

  9. Raman spectroscopic study of sodium chloride water solutions

    NASA Astrophysics Data System (ADS)

    Furić, K.; Ciglenečki, I.; Ćosović, B.

    2000-09-01

    The Raman spectra of NaCl water solutions have been studied in the concentration range between 0 and 3.3 M using a difference technique. The temperature dependence of the spectral profiles observed for the O-H stretching in the high frequency region (between 2500 and 4000 cm -1) was also investigated in the narrow interval around a room temperature. Although the considered bandshape is not of a simple kind, the measured Id/ I0 ratio plotted versus NaCl concentration and temperature fits a straight line in both diagrams very satisfactorily. The linear dependence of Id/ I0 versus NaCl molarity was checked in the study of natural seawater samples for which discrepancies were found. These deviations were attributed to other organic and inorganic dissolved components in the seawater.

  10. Studies of tropical fruit ripening using three different spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Huang, Jing; Li, Tianqi; Wu, Xiuxiang; Svanberg, Sune; Svanberg, Katarina

    2014-06-01

    We present a noninvasive method to study fruit ripening. The method is based on the combination of reflectance and fluorescence spectroscopies, as well as gas in scattering media absorption spectroscopy (GASMAS). Chlorophyll and oxygen are two of the most important constituents in the fruit ripening process. Reflectance and fluorescence spectroscopies were used to quantify the changes of chlorophyll and other chromophores. GASMAS, based on tunable diode laser absorption spectroscopy, was used to measure free molecular oxygen in the fruit tissue at 760 nm, based on the fact that the free gases have much narrower spectral imprints than those of solid materials. The fruit maturation and ripening processes can be followed by studying the changes of chlorophyll and oxygen contents with these three techniques.

  11. Spectroscopic studies of model polar stratospheric cloud films

    NASA Technical Reports Server (NTRS)

    Tolbert, Margaret A.; Koehler, Birgit G.; Middlebrook, Ann M.

    1993-01-01

    Fourier transform infrared (FTIR) spectroscopy has been used to study nitric-acid/ice films representative of type I polar stratospheric clouds (PSCs). These studies reveal that in addition to amorphous nitric acid/ice mixtures, there are three stable stoichiometric hydrates of nitric acid: nitric-acid monohydrate (NAM), dihydrate (NAD), and trihydrate (NAT). We also observe two distinct crystalline forms of the trihydrate, which we denote alpha- and beta-NAT. These two forms appear to differ in their concentration of crystalline defects, but not in their chemical composition. In addition to probing the composition of type I PSCs, we have also used FTIR spectroscopy to study the interaction of HCl with model PSC films. In this work we find that for HCl pressures in the range 10 exp -5 to 10 exp -7 Torr, HCl is taken up by ice at 155 K to form a thin layer of HCl.6H2O. At 193 K, the uptake of HCl by ice was consistent with less than or equal to monolayer coverage. Uptake of HCl by alpha and beta-NAT at 175 K was also consistent with less than or equal to monolayer coverage.

  12. SPECTROSCOPIC STUDIES OF STRUCTURE, DYNAMICS AND REACTIVITY IN IONIC LIQUIDS.

    SciTech Connect

    WISHART,J.F.

    2007-11-30

    Ionic liquids (ILs) are a rapidly expanding family of condensed-phase media with important applications in energy production, nuclear fuel and waste processing, improving the efficiency and safety of industrial chemical processes, and pollution prevention. ILs are generally nonvolatile, noncombustible, highly conductive, recyclable and capable of dissolving a wide variety of materials. They are finding new uses in chemical synthesis, catalysis, separations chemistry, electrochemistry and other areas. Ionic liquids have dramatically different properties compared to conventional molecular solvents, and they provide a new and unusual environment to test our theoretical understanding of charge transfer and other reactions. We are interested in how IL properties influence physical and dynamical processes that determine the stability and lifetimes of reactive intermediates and thereby affect the courses of chemical reactions and product distributions. Successful use of ionic liquids in radiation-filled environments, where their safety advantages could be significant, requires an understanding of ionic liquid radiation chemistry. For example, characterizing the primary steps of IL radiolysis will reveal radiolytic degradation pathways and suggest ways to prevent them or mitigate their effects on the properties of the material. An understanding of ionic liquid radiation chemistry will also facilitate pulse radiolysis studies of general chemical reactivity in ILs, which will aid in the development of applications listed above. Very early in our radiolysis studies it became evident that slow solvation dynamics of the excess electron in ILs (which vary over a wide viscosity range) increases the importance of pre-solvated electron reactivity and consequently alters product distributions. Parallel studies of IL solvation phenomena using coumarin-153 dynamic Stokes shifts and polarization anisotropy decay rates are done to compare with electron solvation studies and to evaluate

  13. Raman and infrared spectroscopic study of turquoise minerals.

    PubMed

    Čejka, Jiří; Sejkora, Jiří; Macek, Ivo; Malíková, Radana; Wang, Lina; Scholz, Ricardo; Xi, Yunfei; Frost, Ray L

    2015-10-01

    Raman and infrared spectra of three well-defined turquoise samples, CuAl6(PO4)4(OH)8·4H2O, from Lavender Pit, Bisbee, Cochise county, Arizona; Kouroudaiko mine, Faleme river, Senegal and Lynch Station, Virginia were studied, interpreted and compared. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, water molecules and hydroxyl ions. Approximate O-H⋯O hydrogen bond lengths were inferred from the Raman and infrared spectra. No Raman and infrared bands attributable to the stretching and bending vibrations of (PO3OH)(2-) units were observed. PMID:25956330

  14. Raman and infrared spectroscopic study of turquoise minerals

    NASA Astrophysics Data System (ADS)

    Čejka, Jiří; Sejkora, Jiří; Macek, Ivo; Malíková, Radana; Wang, Lina; Scholz, Ricardo; Xi, Yunfei; Frost, Ray L.

    2015-10-01

    Raman and infrared spectra of three well-defined turquoise samples, CuAl6(PO4)4(OH)8·4H2O, from Lavender Pit, Bisbee, Cochise county, Arizona; Kouroudaiko mine, Faleme river, Senegal and Lynch Station, Virginia were studied, interpreted and compared. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, water molecules and hydroxyl ions. Approximate O-H⋯O hydrogen bond lengths were inferred from the Raman and infrared spectra. No Raman and infrared bands attributable to the stretching and bending vibrations of (PO3OH)2- units were observed.

  15. Raman and infrared spectroscopic study of turquoise minerals.

    PubMed

    Čejka, Jiří; Sejkora, Jiří; Macek, Ivo; Malíková, Radana; Wang, Lina; Scholz, Ricardo; Xi, Yunfei; Frost, Ray L

    2015-10-01

    Raman and infrared spectra of three well-defined turquoise samples, CuAl6(PO4)4(OH)8·4H2O, from Lavender Pit, Bisbee, Cochise county, Arizona; Kouroudaiko mine, Faleme river, Senegal and Lynch Station, Virginia were studied, interpreted and compared. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, water molecules and hydroxyl ions. Approximate O-H⋯O hydrogen bond lengths were inferred from the Raman and infrared spectra. No Raman and infrared bands attributable to the stretching and bending vibrations of (PO3OH)(2-) units were observed.

  16. Interaction studies of Epirubicin with DNA using spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Charak, Sonika; Jangir, Deepak K.; Tyagi, Gunjan; Mehrotra, Ranjana

    2011-08-01

    Epirubicin (EPR) is an anticancer chemotherapeutic drug which exerts its cytotoxic effect by inhibiting DNA synthesis and DNA replication. We report the structural and conformational effect of EPR binding on DNA duplex under physiological conditions. Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-visible) spectroscopy and circular dichroism (CD) spectroscopy were used to determine the binding mode and binding constant of EPR with DNA. The effect of EPR-DNA complexation on stability and secondary structure of DNA was studied. FTIR measurements showed that EPR-DNA interaction occurs through guanine and cytosine bases. External binding of EPR with DNA was observed through phosphate backbone. UV-visible measurements revealed the intercalative mode of binding of EPR with DNA. The binding constant was estimated to be K = 3.4 × 10 4 which is indicative of moderate binding between EPR and DNA helix. FTIR and CD studies suggested partial transition from B-conformation of DNA to A-conformation of DNA after EPR binding to DNA duplex.

  17. Thermo-active polymer nanocomposites: a spectroscopic study

    NASA Astrophysics Data System (ADS)

    Winter, A. Douglas; Larios, Eduardo; Jaye, Cherno; Fischer, Daniel A.; Omastová, Mária; Campo, Eva M.

    2014-09-01

    Photo- and thermo-mechanical actuation behaviour in specific polymer-carbon nanotube composites has been observed in recent years and studied at the macroscale. These systems may prove to be suitable components for a wide range of applications, from MOEMs and nanotechnology to neuroscience and tissue engineering. Absence of a unified model for actuation behaviour at a molecular level is hindering development of such smart materials. We observed thermomechanical actuation of ethylene-vinyl acetate | carbon nanotube composites through in situ near-edge X-ray absorption fine structure spectroscopy to correlate spectral trends with macroscopic observations. This paper presents spectra of composites and constituents at room temperature to identify resonances in a building block model, followed by spectra acquired during thermo-actuation. Effects of strain-induced filler alignment are also addressed. Spectral resonances associated with C=C and C=O groups underwent synchronised intensity variations during excitation, and were used to propose a conformational model of actuation based on carbon nanotube torsion. Future actuation studies on other active polymer nanocomposites will verify the universality of the proposed model.

  18. Spectroscopic studies on the interaction of bilirubin with liver cystatin.

    PubMed

    Shah, Aaliya; Bano, Bilqees

    2011-02-01

    Studies on the role of endogenous metabolites such as bilirubin and their interactions with biomolecules have attracted considerable attention over the past several years. In this work, the interaction of bilirubin (BR) with purified goat liver cystatin (LC) was studied using fluorescence and ultraviolet (UV) spectroscopy. The fluorescence data proved that the fluorescence quenching of liver cystatin by BR was the result of BR-cystatin complex formation. Stern-Volmer analysis of fluorescence quenching data showed the binding constant to be 9.27 x 10⁴ M⁻¹ and the number of binding sites to be close to unity. The conformation of the BR-cystatin complex was found to change upon varying the pH of the complex. The BR-cystatin complex was found to have reduced papain inhibitory activity. Photo-illumination of BR-cystatin complex causes perturbation in the micro-environment of goat liver cystatin as indicated by red-shift. This report summarizes our research efforts to reveal the mechanism of interaction of bilirubin with liver cystatin.

  19. Raman spectroscopic study of Lactarius spores (Russulales, Fungi)

    NASA Astrophysics Data System (ADS)

    De Gussem, Kris; Vandenabeele, Peter; Verbeken, Annemieke; Moens, Luc

    2005-10-01

    Fungi are important organisms in ecosystems, in industrial and pharmaceutical production and are valuable food sources as well. Classical identification is often time-consuming and specialistic. In this study, Raman spectroscopy is applied to the analysis of fungal spores of Lactarius, an economically and ecologically important genus of Basidiomycota. Raman spectra of spores of Lactarius controversus Pers.: Fr., Lactarius lacunarum (Romagn.) ex Hora, Lactarius quieticolor Romagn. and Lactarius quietus (Fr.: Fr.) Fr. are reported for the first time. The spectra of these species show large similarity. These spectra are studied and compared with the Raman spectra of reference substances known to occur in macrofungi, including saccharides, lipids and some minor compounds that may serve as specific biomarkers (adenine, ergosterol and glycine). Most Raman bands could be attributed to specific components. In agreement with the biological role of fungal spores, high amounts of lipids were observed, the main fatty acid being oleate. In addition to different types of lipids and phospholipids, the polysaccharides chitin and amylopectin could be detected as well. The presence of trehalose is not equivocally shown, due to overlapping bands. Raman band positions are reported for the observed bands of the different species and reference products.

  20. Photoacoustic FTIR spectroscopic study of undisturbed nacre from red abalone

    NASA Astrophysics Data System (ADS)

    Verma, Devendra; Katti, Kalpana; Katti, Dinesh

    2006-07-01

    In this work, photoacoustic Fourier transform infrared (PA-FTIR) spectroscopy has been utilized to study interfacial interactions of undisturbed nacre and nacre powder from red abalone shell. The spectra of both undisturbed nacre and nacre powder showed characteristic bands of aragonite and proteins. Although nacre powder and undisturbed nacre are chemically identical, PA-FTIR spectrum of undisturbed nacre is found to be significantly different from that of nacre powder. A broad and strong band is observed at around 1485 cm -1 in nacre powder. The intensity of this band is notably reduced in undisturbed nacre. This result is explained on the basis of interfacial interactions between aragonite platelets and acidic proteins. It is also observed that band at around 1788 cm -1 originates from three overlapping bands 1797, 1787 and 1778 cm -1. The band at around 1787 cm -1 is assigned to C dbnd O stretching of carboxylate groups of acidic proteins. The other two bands at 1797 and 1778 cm -1, originate from aragonite and have been assigned to combination bands, ν 3 + ν 4a and ν 3 + ν 4b, respectively. For the study of stratification in undisturbed nacre, PA-FTIR spectra have been collected in step scan mode. The variation in spectra with depth can be attributed to changes in conformation of proteins as well as interfacial interactions.

  1. Ligand exchange in quaternary alloyed nanocrystals--a spectroscopic study.

    PubMed

    Gabka, Grzegorz; Bujak, Piotr; Giedyk, Kamila; Kotwica, Kamil; Ostrowski, Andrzej; Malinowska, Karolina; Lisowski, Wojciech; Sobczak, Janusz W; Pron, Adam

    2014-11-14

    Exchange of initial, predominantly stearate ligands for pyridine in the first step and butylamine (BA) or 11-mercaptoundecanoic acid (MUA) in the second one was studied for alloyed quaternary Cu-In-Zn-S nanocrystals. The NMR results enabled us to demonstrate, for the first time, direct binding of the pyridine labile ligand to the nanocrystal surface as evidenced by paramagnetic shifts of the three signals attributed to its protons to 7.58, 7.95 and 8.75 ppm. XPS investigations indicated, in turn, a significant change in the composition of the nanocrystal surface upon the exchange of initial ligands for pyridine, which being enriched in indium in the 'as prepared' form became enriched in zinc after pyridine binding. This finding indicated that the first step of ligand exchange had to involve the removal of the surface layer enriched in indium with simultaneous exposure of a new, zinc-enriched layer. In the second ligand exchange step (replacement of pyridine with BA or MUA) the changes in the nanocrystal surface compositions were much less significant. The presence of zinc in the nanocrystal surface layer turned out necessary for effective binding of pyridine as shown by a comparative study of ligand exchange in Cu-In-Zn-S, Ag-In-Zn-S and CuInS2, carried out by complementary XPS and NMR investigations.

  2. Vibrational spectroscopic studies of adsorbates on bimetallic surfaces. Doctoral thesis

    SciTech Connect

    Kuhn, W.K.

    1992-12-01

    In this work, well-defined bimetallic surfaces have been studied using carbon monoxide adsorption in conjunction with infrared reflection absorption spectroscopy (IRAS). These studies have indicated that for CO adsorbed on Cu overlayers, the bond between the CO and the Cu adatoms is comprised of both pi-back-donation and polarization interaction components. The sum of the contributions from these effects determines the observed bond strength with the observed CO stretching frequency being determined by the relative contributions of the components. In addition, it was determined that IR spectra of adsorbed CO show a remarkable sensitivity to surface structure. Three-dimensional Cu clusters, well-ordered two dimensional Cu islands and isolated Cu atoms are distinctively characterized by their CO IR peaks. In addition, both disorder-order and order-order transitions are observed for the metal overlayers on the single crystal metal substrates. It was also observed that localized segregation and ordering of mixed Co and S overlayers on a Mo(110) substrate occurs upon annealing.

  3. Identification and derivatization of selected cathinones by spectroscopic studies.

    PubMed

    Nycz, Jacek E; Pazdziorek, Tadeusz; Malecki, Grzegorz; Szala, Marcin

    2016-09-01

    In this study we identified three novel hydrochloride salts of cathinones 2-(pyrrolidin-1-yl)-1-(5,6,7,8-tetrahydronaphthalen-2-yl)pentan-1-one (1a) (TH-PVP), 2-(methylamino)-1-(2-methylphenyl)-1-propanone (1b) (2-MMC) and 1-(4-chlorophenyl)-2-(methylamino)propan-1-one (1c) (4-CMC). Their properties have been examined through combinations of GC-MS, IR, NMR, electronic absorption spectroscopy and single crystal X-ray diffraction method. NMR solution spectra showed readily diagnostic H-1 and C-13 signals from methyl, N-methyl and carbonyl groups. Additionally the use of thionation and amination reactions for identification of selected cathinones was presented. PMID:27423024

  4. High resolution spectroscopic study of Be10Lambda;

    NASA Astrophysics Data System (ADS)

    Gogami, T.; Chen, C.; Kawama, D.; Achenbach, P.; Ahmidouch, A.; Albayrak, I.; Androic, D.; Asaturyan, A.; Asaturyan, R.; Ates, O.; Baturin, P.; Badui, R.; Boeglin, W.; Bono, J.; Brash, E.; Carter, P.; Chiba, A.; Christy, E.; Danagoulian, S.; de Leo, R.; Doi, D.; Elaasar, M.; Ent, R.; Fujii, Y.; Fujita, M.; Furic, M.; Gabrielyan, M.; Gan, L.; Garibaldi, F.; Gaskell, D.; Gasparian, A.; Han, Y.; Hashimoto, O.; Horn, T.; Hu, B.; Hungerford, Ed. V.; Jones, M.; Kanda, H.; Kaneta, M.; Kato, S.; Kawai, M.; Khanal, H.; Kohl, M.; Liyanage, A.; Luo, W.; Maeda, K.; Margaryan, A.; Markowitz, P.; Maruta, T.; Matsumura, A.; Maxwell, V.; Mkrtchyan, A.; Mkrtchyan, H.; Nagao, S.; Nakamura, S. N.; Narayan, A.; Neville, C.; Niculescu, G.; Niculescu, M. I.; Nunez, A.; Nuruzzaman, Okayasu, Y.; Petkovic, T.; Pochodzalla, J.; Qiu, X.; Reinhold, J.; Rodriguez, V. M.; Samanta, C.; Sawatzky, B.; Seva, T.; Shichijo, A.; Tadevosyan, V.; Tang, L.; Taniya, N.; Tsukada, K.; Veilleux, M.; Vulcan, W.; Wesselmann, F. R.; Wood, S. A.; Yamamoto, T.; Ya, L.; Ye, Z.; Yokota, K.; Yuan, L.; Zhamkochyan, S.; Zhu, L.; Hksjlab E05-115 Collaboration

    2016-03-01

    Spectroscopy of a Be10Lambda; hypernucleus was carried out at JLab Hall C using the (e ,e'K+) reaction. A new magnetic spectrometer system (SPL+HES+HKS), specifically designed for high resolution hypernuclear spectroscopy, was used to obtain an energy spectrum with a resolution of ˜0.78 MeV (FWHM). The well-calibrated spectrometer system of the present experiment using p (e ,e'K+)Λ ,Σ0 reactions allowed us to determine the energy levels; and the binding energy of the ground-state peak (mixture of 1- and 2- states) was found to be BΛ=8.55 ±0.07 (stat . ) ±0.11 (sys . ) MeV. The result indicates that the ground-state energy is shallower than that of an emulsion study by about 0.5 MeV which provides valuable experimental information on the charge symmetry breaking effect in the Λ N interaction.

  5. Enhanced Raman spectroscopic study of rotational isomers on metal surfaces

    NASA Technical Reports Server (NTRS)

    Loo, B. H.; Lee, Y. G.; Frazier, D. O.

    1986-01-01

    Surfaced-enhanced Raman spectroscopy has been used to study rotational isomers of succinonitrile and N-methyl-thioacetamide on Cu and Ag surfaces. Both the gauche and trans conformers of succinonitrile are found to chemisorb on the metal surface. The doubly degenerate nu(C-triple bond-N) in the free molecules is removed when succinonitrile adsorbs on copper, which indicates that the two (C-triple bond-N) groups are no longer chemically equivalent. Both conformers are found to coordinate to the copper surface through the pi system of one of the two (C-triple bond-N) groups. In the case of N-methyl-thioacetamide, the population of the cis isomer is greatly increased on Cu and Ag surfaces. This is probably due to surface-induced cis-trans isomerization, in which the predominant trans isomer is converted to the cis isomer.

  6. Spectroscopic structural studies of salicylic acid, salicylamide and aspirin

    NASA Astrophysics Data System (ADS)

    El-Shahawy, Anwar S.

    The electronic absorption spectra of the salicylic acid and the salicylamide molecules have been studied using SCF—CL calculations. The singlet and the triplet electronic transition energies have been calculated. The state functions of eight excited states for these molecules have been calculated in addition to the oscillator strengths, charge densities, ionization potentials and electron affinities. Our calculations lead to the presence of salicylic acid and salicylamide in the β-forms in which the carboxylic hydroxyl group or the amino group is directed toward the enolic hydroxyl group. The salicylic acid and the salicylamide molecules have the Cs point group symmetry, but the aspirin molecule has the C1 point group symmetry, in which the acetyl group does not lie in the plane of the salicylic acid molecule.

  7. Spectroscopic studies on the interaction of ofloxacin with metals

    NASA Astrophysics Data System (ADS)

    Sagdinc, S.; Bayarı, S.

    2004-03-01

    Several coordination compounds (1:1) formed between alkaline earth metal cations [Mg(II), Ca(II) and Ba(II)] and transition metal ions [Co(II), Ni(II) and Zn(II)] with oflocaxin were synthesized. The compounds have been characterized using elemental analysis, Fourier transform infrared (FT-IR) spectroscopy and 1H NMR spectra. The solid state samples of all complexes have been measured within the range 4000-400 cm -1. Based on normal mode calculations for complexes, the assignments of bands observed in FT-IR spectra of studied compounds have been done. Some significant differences in vibrational structure have been observed and discussed. The frequencies and intensities of some bands of the ofloxacin depend systematically on the second ionization potential of the metals.

  8. Raman spectroscopic study of plasma-treated salmon DNA

    SciTech Connect

    Lee, Geon Joon; Kim, Yong Hee; Choi, Eun Ha; Kwon, Young-Wan

    2013-01-14

    In this research, we studied the effect of plasma treatment on the optical/structural properties of the deoxyribonucleic acid (DNA) extracted from salmon sperm. DNA-cetyltrimethylammonium (CTMA) films were obtained by complexation of DNA with CTMA. Circular dichroism (CD) and Raman spectra indicated that DNA retained its double helical structure in the solid film. The Raman spectra exhibited several vibration modes corresponding to the nuclear bases and the deoxyribose-phosphate backbones of the DNA, as well as the alkylchains of CTMA. Dielectric-barrier-discharge (DBD) plasma treatment induced structural modification and damage to the DNA, as observed by changes in the ultraviolet-visible absorption, CD, and Raman spectra. The optical emission spectra of the DBD plasma confirmed that DNA modification was induced by plasma ions such as reactive oxygen species and reactive nitrogen species.

  9. Raman and infrared spectroscopic study of kamphaugite-(Y)

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Scholz, Ricardo

    2015-05-01

    We have studied the carbonate mineral kamphaugite-(Y)(CaY(CO3)2(OH)·H2O), a mineral which contains yttrium and specific rare earth elements. Chemical analysis shows the presence of Ca, Y and C. Back scattering SEM appears to indicate a single pure phase. The vibrational spectroscopy of kamphaugite-(Y) was obtained using a combination of Raman and infrared spectroscopy. Two distinct Raman bands observed at 1078 and 1088 cm-1 provide evidence for the non-equivalence of the carbonate anion in the kamphaugite-(Y) structure. Such a concept is supported by the number of bands assigned to the carbonate antisymmetric stretching mode. Multiple bands in the ν4 region offers further support for the non-equivalence of carbonate anions in the structure. Vibrational spectroscopy enables aspects of the structure of the mineral kamphaugite-(Y) to be assessed.

  10. Spectroscopic study of low-temperature hydrogen absorption in palladium

    SciTech Connect

    Ienaga, K. Takata, H.; Onishi, Y.; Inagaki, Y.; Kawae, T.; Tsujii, H.; Kimura, T.

    2015-01-12

    We report real-time detection of hydrogen (H) absorption in metallic palladium (Pd) nano-contacts immersed in liquid H{sub 2} using inelastic electron spectroscopy (IES). After introduction of liquid H{sub 2}, the spectra exhibit the time evolution from the pure Pd to the Pd hydride, indicating that H atoms are absorbed in Pd nano-contacts even at the temperature where the thermal process is not expected. The IES time and bias voltage dependences show that H absorption develops by applying bias voltage 30 ∼ 50 mV, which can be explained by quantum tunneling. The results represent that IES is a powerful method to study the kinetics of high density H on solid surface.

  11. Spectroscopic study of low-temperature hydrogen absorption in palladium

    NASA Astrophysics Data System (ADS)

    Ienaga, K.; Takata, H.; Onishi, Y.; Inagaki, Y.; Tsujii, H.; Kimura, T.; Kawae, T.

    2015-01-01

    We report real-time detection of hydrogen (H) absorption in metallic palladium (Pd) nano-contacts immersed in liquid H2 using inelastic electron spectroscopy (IES). After introduction of liquid H2, the spectra exhibit the time evolution from the pure Pd to the Pd hydride, indicating that H atoms are absorbed in Pd nano-contacts even at the temperature where the thermal process is not expected. The IES time and bias voltage dependences show that H absorption develops by applying bias voltage 30 ˜ 50 mV, which can be explained by quantum tunneling. The results represent that IES is a powerful method to study the kinetics of high density H on solid surface.

  12. Mechanism of Arsenic Adsorption Using Wheat Biomass -- a spectroscopic study

    NASA Astrophysics Data System (ADS)

    Calvo, Oscar; Manciu, Felicia; Maldonado, Josefina; Gardea-Torresdey, Jorge

    2006-10-01

    Arsenic is a trace element that is toxic to animals, humans included. Since the current Environmental Protection Agency guidelines regarding water quality standards indicate that arsenic concentrations in excess of 50 ppb are hazardous to welfare of humans, the search for new water remediation methods or improvements of previous methods have been a focus in environmental technology. Investigations of arsenic uptake have used wide range of sorbents including iron oxides and oxyhydroxides, for which it have been proved that arsenic shows high affinity. In this study, we used far-infrared spectroscopy to examine the arsenic reduction using biomaterials. pH dependence analysis by FTIR demonstrates the sorption of iron oxides and oxyhydroxides by the wheat biomass. The splitting of 350 cm-1 amorphous iron oxide vibrations is a direct proof of the arsenic uptake. In addition, there is evidence of sorption of arsenic at sulfhydryl group of cysteine existent in wheat.

  13. Spectroscopic studies of Yb3+-doped rare earth orthosilicate crystals

    NASA Astrophysics Data System (ADS)

    Campos, S.; Denoyer, A.; Jandl, S.; Viana, B.; Vivien, D.; Loiseau, P.; Ferrand, B.

    2004-06-01

    Infrared transmission and Raman scattering have been used to study Raman active phonons and crystal-field excitations in Yb3+-doped yttrium, lutetium and scandium orthosilicate crystals (Y2SiO5 (YSO), Lu2SiO5 (LSO) and Sc2SiO5 (SSO)), which belong to the same C2h6 crystallographic space group. Energy levels of the Yb3+ ion 2F5/2 manifold are presented. In the three hosts, Yb3+ ions experience high crystal field strength, particularly in Yb:SSO. Satellites in the infrared transmission spectra have been detected for the first time in the Yb3+-doped rare earth orthosilicates. They could be attributed to perturbed Yb3+ sites of the lattices or to magnetically coupled Yb3+ pairs.

  14. Raman spectroscopic studies of carbon in extra-terrestrial materials

    NASA Technical Reports Server (NTRS)

    Macklin, John; Brownlee, Donald; Chang, Sherwood; Bunch, Ted

    1990-01-01

    The measurements obtained here indicate ways in which micro-Raman spectroscopy can be used to elucidate structural characteristics and distribution of carbon in meteorites and interplanetary dust particles (IDPs). Existing information about structurally significant aspects of Raman measurements of graphite is combined with structurally relevant findings from the present micro-Raman studies of carbons prepared by carbonization of polyvinylidine chloride (PVDC) at various temperatures and natural material, as well as several acid residues from the Allende and Murchison meteorites in order to establish new spectra-structure relationships. Structural features of many of the materials in this study have been measured by x ray analysis and electron microscopy: thus, their structural differences can be directly correlated with differences in the Raman spectra. The spectral parameters consequently affirmed as indicators of structure are used as a measure of structure in materials that have unknown carbon structure, especially IDPs. The unique applicability of micro-Raman spectroscopy is realized not only in the ability to conveniently measure spectra of micron-size IDPs, but also micro-sized parts of an inhomogeneous material. Microcrystalline graphite is known to give Raman spectra that differ dependent on crystallite size (see e.g., Lespade, et. al., 1984, or Nemanich and Solin, 1979). The spectral changes that accompany decreasing particle size include increase in the ratio (R) of the intensity of the band near 1350 cm(-1) (D band) to that of the band near 1600 cm(-1) (G band) increase in the half width of the D band (wD) increase in the frequency maximum of the G band and increase in the half-width (wG) of the 2nd order band near 2700 cm(-1) (G) band.

  15. FTIR Spectroscopic Studies on Cross Linking of SU-8 Photoresist

    NASA Astrophysics Data System (ADS)

    Kalaiselvi, S. M. P.; Tan, T. L.; Rawat, R. S.; Lee, P.; Heussler, S. P.; Breese, M. B. H.

    2013-11-01

    The usage of chemically-amplified, negative tone SU-8 photoresist is numerous, spanning industrial, scientific and medical fields. Hence, in this study, some preliminary studies were conducted to understand the dosage and heat treatment requirements of the SU-8 photoresist essential for pattern generation using X-ray lithography. In this work, using Synchrotron as the X-ray source, SU-8 photoresist was characterized for X-ray lithography in terms of its process parameters such as X-ray exposure dose, post exposure bake (PEB) time and temperature for various photoresist thicknesses which is considered worthwhile in view of applications of SU-8 for the fabrication of very high aspect ratio micro structures. The process parameters were varied and the resultant cross linking of the molecular chains of the photoresist was accurately monitored using a Fourier Transform Infra-Red (FTIR) spectrometer and the results are discussed. The infrared absorption peak at 914 cm-1 in the spectrum of the SU-8 photoresist was found to be a useful indicator for the completion of cross linking in the SU-8 photoresist. Results show that the cross linking of the SU-8 photoresist is at a higher rate from 0 J/cm3 to 30 J/cm3 after which the peak almost saturates regardless of the PEB time. It is a good evidence for the validation of dosage requirement of SU-8 photoresist for effective completion of cross linking, which in turn is a requirement for efficient fabrication of micro and nano structures. An analogous behavior was also observed between the extent of cross linking and the PEB time and temperature. The rate of cross linking declines after a certain period of PEB time regardless of PEB temperature. The obtained results also show a definite relation between variation of the absorbance area of the peak at 914 cm-1 and the X-ray exposure dose.

  16. Raman spectroscopic study of ancient South African domestic clay pottery

    NASA Astrophysics Data System (ADS)

    Legodi, M. A.; de Waal, D.

    2007-01-01

    The technique of Raman spectroscopy was used to examine the composition of ancient African domestic clay pottery of South African origin. One sample from each of four archaeological sites including Rooiwal, Lydenburg, Makahane and Graskop was studied. Normal dispersive Raman spectroscopy was found to be the most effective analytical technique in this study. XRF, XRD and FT-IR spectroscopy were used as complementary techniques. All representative samples contained common features, which were characterised by kaolin (Al 2Si 2O 5(OH) 5), illite (KAl 4(Si 7AlO 20)(OH) 4), feldspar (K- and NaAlSi 3O 8), quartz (α-SiO 2), hematite (α-Fe 2O 3), montmorillonite (Mg 3(Si,Al) 4(OH) 2·4.5H 2O[Mg] 0.35), and calcium silicate (CaSiO 3). Gypsum (CaSO 4·2H 2O) and calcium carbonates (most likely calcite, CaCO 3) were detected by Raman spectroscopy in Lydenburg, Makahane and Graskop shards. Amorphous carbon (with accompanying phosphates) was observed in the Raman spectra of Lydenburg, Rooiwal and Makahane shards, while rutile (TiO 2) appeared only in Makahane shard. The Raman spectra of Lydenburg and Rooiwal shards further showed the presence of anhydrite (CaSO 4). The results showed that South African potters used a mixture of clays as raw materials. The firing temperature for most samples did not exceed 800 °C, which suggests the use of open fire. The reddish brown and grayish black colours were likely due to hematite and amorphous carbon, respectively.

  17. A combined complex electrical impedance and acoustic emission study in limestone samples under uniaxial loading

    NASA Astrophysics Data System (ADS)

    Saltas, V.; Fitilis, I.; Vallianatos, F.

    2014-12-01

    In the present work, complex electrical impedance measurements in the frequency range of 10 mHz to 1 MHz were carried out in conjunction with acoustic emission monitoring in limestone samples subjected to linear and stepped-like uniaxial loading, up to ultimate failure. Cole-Cole plots of the complex impedance during the stepped loading of limestone have been used to discriminate the contributions of grains interior, grain boundaries and electrode polarization effects to the overall electrical behavior. The latter is well-described with an equivalent-circuit model which comprises components of constant phase elements and resistances in parallel connection. Electrical conductivity increases upon uniaxial loading giving rise to negative values of effective activation volume. This is a strong experimental evidence for the generation of transient electric signals recorded prior to seismic events and may be attributed to charge transfer (proton conduction) due to cracks generation and propagation as a result of the applied stress. The time-series of ac-conductivity at two distinct frequencies (10 kHz, 200 kHz) during linear loading of limestone samples exhibits a strong correlation with the acoustic emission activity obeying the same general self-similar law for critical phenomena that has been reported for the energy release before materials fracture.

  18. A Comparison Study of Normal-Incidence Acoustic Impedance Measurements of a Perforate Liner

    NASA Technical Reports Server (NTRS)

    Schultz, Todd; Liu, Fei; Cattafesta, Louis; Sheplak, Mark; Jones, Michael

    2009-01-01

    The eduction of the acoustic impedance for liner configurations is fundamental to the reduction of noise from modern jet engines. Ultimately, this property must be measured accurately for use in analytical and numerical propagation models of aircraft engine noise. Thus any standardized measurement techniques must be validated by providing reliable and consistent results for different facilities and sample sizes. This paper compares normal-incidence acoustic impedance measurements using the two-microphone method of ten nominally identical individual liner samples from two facilities, namely 50.8 mm and 25.4 mm square waveguides at NASA Langley Research Center and the University of Florida, respectively. The liner chosen for this investigation is a simple single-degree-of-freedom perforate liner with resonance and anti-resonance frequencies near 1.1 kHz and 2.2 kHz, respectively. The results show that the ten measurements have the most variation around the anti-resonance frequency, where statistically significant differences exist between the averaged results from the two facilities. However, the sample-to-sample variation is comparable in magnitude to the predicted cross-sectional area-dependent cavity dissipation differences between facilities, providing evidence that the size of the present samples does not significantly influence the results away from anti-resonance.

  19. Hydrogen-terminated detonation nanodiamond: Impedance spectroscopy and thermal stability studies

    NASA Astrophysics Data System (ADS)

    Su, Shi; Li, Jiangling; Kundrát, Vojtěch; Abbot, Andrew M.; Ye, Haitao

    2013-01-01

    In this paper, we investigated the effect of hydrogen termination on the electrical properties and impedance spectra of detonation nanodiamond. The impedance spectra revealed that the hydrogen-termination process increases the electrical conductivity by four orders of magnitude at room temperature. An equivalent circuit has been proposed to correlate with the conduction mechanism. Arrhenius plot showed that there were two different activation energy levels located at 0.089 eV and 0.63 eV between 50 °C and 400 °C. The possible physical mechanism corresponding to these activation energy levels has been discussed. Hydrogen-terminated detonation nanodiamond has been further annealed at different temperatures prior to FTIR and XPS measurements in order to understand their thermal stability. The results demonstrated that the surface oxidization occurred between 100 °C and 150 °C. However, the C-H bonds could partially survive when the temperature reaches 400 °C in air.

  20. Study of metal corrosion using ac impedance techniques in the STS launch environment

    NASA Technical Reports Server (NTRS)

    Calle, Luz M.

    1989-01-01

    AC impedance measurements were performed to investigate the corrosion resistance of 19 alloys under conditions similar to the STS launch environment. The alloys were: Zirconium 702, Hastelloy C-22, Inconel 625, Hastelloy C-276, Hastelloy C-4, Inconel 600, 7Mo + N, Ferralium 255, Inco Alloy G-3, 20Cb-3, SS 904L, Inconel 825, SS 304LN, SS 316L, SS 317L, ES 2205, SS 304L, Hastelloy B-2, and Monel 400. AC impedance data were gathered for each alloy after one hour immersion time in each of the following three electrolyte solutions: 3.55 percent NaCl, 3.55 percent NaCl-0.1N HCl, and 3.55 percent NaCl-1.0N HCl. The data were analyzed qualitatively using the Nyquist plot and quantitatively using the Bode plot. Polarization resistance, Rp, values were obtained using the Bode plot. Zirconium 702 was the most corrosion resistant alloy in the three electrolytes. The ordering of the other alloys according the their resistance to corrosion varied as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of Zirconium 702 and Ferralium 255 increased as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of the other 17 alloys decreased as the concentration of the hyrdochloric acid in the electrolyte increased.

  1. Excitation induced spectroscopic study and quenching effect in cerium samarium codoped lithium aluminoborate glasses

    NASA Astrophysics Data System (ADS)

    Kaur, Parvinder; Kaur, Simranpreet; Singh, Gurinder Pal; Arora, Deepawali; Kumar, Sunil; Singh, D. P.

    2016-08-01

    Lithium aluminium borate host has been codoped with cerium and samarium to prepare glass by conventional melt quench technique. Their structural and spectroscopic investigation has been carried out using XRD, FTIR and density measurements. The UV-Vis absorption spectra and fluorescence spectra (λexc.=380 nm and 400 nm) have been studied for spectroscopic analysis. The amorphous nature of the prepared samples is shown by XRD. The density is increasing with addition of cerium at the expense of aluminium, keeping other components constant. FTIR study also shows the presence of compact and stable tetrahedral BO4 units thus supporting the density results. The UV- Vis absorption spectra show a shift of optical absorption edge towards longer wavelength along with an increase in intensity of peaks with rising samarium concentration. The fluorescence spectra show a blue shift and subsequent suppression of cerium peaks with addition of samarium.

  2. Spectroscopic study of excitations in pi-conjugated polymers

    NASA Astrophysics Data System (ADS)

    Yang, Cungeng

    This dissertation deals with spin-physics of photo excitations in pi-conjugated polymers. Optical and magneto-optical spectroscopies, including continuous wave and time-resolved photo-induced absorption, photoluminescence, electroluminescence, and their optically detected magnetic resonance, were used to study steady state and transient photogeneration, energy transfer, spin relaxation, and spin dependent recombination process in the time domain from tens of nanoseconds to tens of milliseconds in polymer materials including regio-random poly (3-hexyl-thiophene-2,5-diyl), regio-regular poly (3-hexyl-thiophene-2,5-diyl), poly (9,9-dioctyl-fluorenyl-2,7-diyl), poly (poly (2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) of various morphologies, and transition metal complex poly (Pt-quinoxene). Our studies provided the tools to clarify the physical pictures regarding two types of long-lived photoexcitations, namely polarons (both germinate polaron-pairs, and unpaired polarons) and triplet excitons, which are the major excitations in these exotic semiconductors in electrical and optical related applications. From measurements of transient fluorescence and transient fluorescence detected magnetic resonance we show that photogenerated geminate polaron pairs live up to hundreds of microseconds following laser pulsed excitation. This conclusion is in agreement with the delayed formation of triplet excitons that we measured by transient photoinduced absorption. It also agrees with the weak spin-lattice relaxation rate in polymers that we measured using the optically detected magnetic resonance dynamic in thin films and organic light emitting devices. Randomly captured nongeminate polaron pairs were shown to be the major source of optically detected magnetic resonance signal at steady, state. We found that the dynamics and magnitude of the signal depend on the spin-relaxation rate, generation rate and decay rate of the geminate pairs and nongeminate pairs. Importantly we

  3. Vibrationally resolved negative ion photoelectron spectroscopic studies of niobium clusters

    SciTech Connect

    Green, S.M.E.; Alex, S.; Leopold, D.G.

    1996-12-31

    Negative ion photoelectron spectroscopy provides a means of obtaining vibrational data for atoms and small molecules {open_quotes}chemisorbed{close_quotes} on size-selected metal clusters. In the present study, Nb{sub 3}O{sup -}, Nb{sub 4}O{sup -} and Nb{sub 4}CO{sup -} were prepared in a flowing afterglow ion-molecule reactor equipped with a metal cathode cluster source. The 488 nm photoelectron spectrum of the mass-selected Nb{sub 3}O{sup -} anions shows a vertical transition to the ground state of neutral Nb{sub 3}O, with weak progressions in the Nb{sub 3}-O stretching (710{+-}20 cm{sup -1} in Nb{sub 3}O) and Nb, bending (320{+-}15 cm{sup -1}-in both Nb{sub 3}O and Nb{sub 3}O{sup -}) vibrational modes. These results indicate that the Nb{sub 3}O{sup -} anion, like Nb{sub 3}O and Nb{sub 3}O{sup +}, has a planar Ca{sub 2v} structure with the O atom bridging two Nb atoms. The Nb{sub 4}O{sup -} spectrum shows resolved transitions to the ground state of Nb{sub 3}O and to an excited electronic state lying 3050{+-}20 cm{sup -1} higher in energy. In analogy with the Nb{sub 4}O results, the 670{+-}20 cm{sup -1} frequency observed for the Nb{sub 4}O ground state is assigned to a metal-oxygen stretching mode, and the 215{+-}15 cm{sup -1} and 195{+-}15 cm{sup -1} frequencies observed in the ground and excited states, respectively, to a bending mode of the metal cluster. The electron affinities of Nb{sub 3}O and Nb{sub 4}O are 1.402 and 1.178 ({+-}0.006) eV, respectively. Preliminary, ongoing studies of mass selected Nb{sub 4}CO{sup -} anions prepared under a variety of source conditions thus far suggest the presence of two isomers, one with a greatly weakened but intact CO bond as indicated by a very low CO stretching frequency of about 1300 cm{sup -1} and the other with the dissociated C and O atoms bound separately to the niobium cluster.

  4. Ir Spectroscopic Studies on Microsolvation of HCl by Water

    NASA Astrophysics Data System (ADS)

    Mani, Devendra; Schwan, Raffael; Fischer, Theo; Dey, Arghya; Kaufmann, Matin; Redlich, Britta; van der Meer, Lex; Schwaab, Gerhard; Havenith, Martina

    2016-06-01

    Acid dissociation reactions are at the heart of chemistry. These reactions are well understood at the macroscopic level. However, a microscopic level understanding is still in the early stages of development. Questions such as 'how many H_2O molecules are needed to dissociate one HCl molecule?' have been posed and explored both theoretically and experimentally.1-5 Most of the theoretical calculations predict that four H_2O molecules are sufficient to dissociate one HCl molecule, resulting in the formation of a solvent separated H_3O+(H_2O)3Cl- cluster.1-3 IR spectroscopy in helium nanodroplets has earlier been used to study this dissociation process.3-5 However, these studies were carried out in the region of O-H and H-Cl stretch, which is dominated by the spectral features of undissociated (HCl)m-(H_2O)n clusters. This contributed to the ambiguity in assigning the spectral features arising from the dissociated cluster.4,5 Recent predictions from Bowman's group, suggest the presence of a broad spectral feature (1300-1360 wn) for the H_3O+(H_2O)3Cl- cluster, corresponding to the umbrella motion of H_3O+ moiety.6 This region is expected to be free from the spectral features due to the undissociated clusters. In conjunction with the FELIX laboratory, we have performed experiments on the (HCl)m(H_2O)n (m=1-2, n≥4) clusters, aggregated in helium nanodroplets, in the 900-1700 wn region. Mass selective measurements on these clusters revealed the presence of a weak-broad feature which spans between 1000-1450 wn and depends on both HCl as well as H_2O concentration. Measurements are in progress for the different deuterated species. The details will be presented in the talk. References: 1) C.T. Lee et al., J. Chem. Phys., 104, 7081 (1996). 2) H. Forbert et al., J. Am. Chem. Soc., 133, 4062 (2011). 3) A. Gutberlet et al., Science, 324, 1545 (2009). 4) S. D. Flynn et al., J. Phys. Chem. Lett., 1, 2233 (2010). 5) M. Letzner et al., J. Chem. Phys., 139, 154304 (2013). 6) J. M

  5. Spectroscopic studies on the antioxidant activity of ellagic acid

    NASA Astrophysics Data System (ADS)

    Kilic, Ismail; Yeşiloğlu, Yeşim; Bayrak, Yüksel

    2014-09-01

    Ellagic acid (EA, C14H6O8) is a natural dietary polyphenol whose benefits in a variety of diseases shown in epidemiological and experimental studies involve anti-inflammation, anti-proliferation, anti-angiogenesis, anticarcinogenesis and anti-oxidation properties. In vitro radical scavenging and antioxidant capacity of EA were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2‧-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe2+) chelating activity and ferric ions (Fe3+) reducing ability. EA inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45 μg/mL concentration. On the other hand, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), α-tocopherol and ascorbic acid displayed 69.8%, 66.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, EA had an effective DPPH• scavenging, ABTSrad + scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power and ferrous ions (Fe2+) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that EA can be used in the pharmacological, food industry and medicine because of these properties.

  6. Spectroscopic and thermal studies of PS/PVAc blends

    NASA Astrophysics Data System (ADS)

    Elashmawi, I. S.; Hakeem, N. A.; Abdelrazek, E. M.

    2008-10-01

    Polystyrene and polyvinyl acetate (PS/PVAc) films were blended with different contents using casting method. The effect of PS content on PVAc blends was investigated by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Ultra violet and visible studies (UV/VIS), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Significant changes in FT-IR, XRD and DSC analysis are observed which reveals an interactions between the two polymers and PS/PVAc blends had good or certain miscibility. XRD scans show some changes in the intensity and the height of the amorphous halos with increased PS. UV/VIS analysis revealed that the optical band gap decreases with increasing content of PS from 5 to 4.11 eV. A single glass transition temperature for each blend was observed, this DSC results supported that the miscibility existed in the blend. The apparent activation energy (E) of the blends was evaluated using TGA analysis. The value of E was increased with the increase of PS content.

  7. High resolution spectroscopic study of BeΛ10

    DOE PAGESBeta

    Gogami, T.; Chen, C.; Kawama, D.; Achenbach, P.; Ahmidouch, A.; Albayrak, I.; Androic, D.; Asaturyan, A.; Asaturyan, R.; Ates, O.; et al

    2016-03-10

    Spectroscopy of amore » $$^{10}_{\\Lambda}$$Be hypernucleus was carried out at JLab Hall C using the $$(e,e^{\\prime}K^{+})$$ reaction. A new magnetic spectrometer system (SPL+HES+HKS), specifically designed for high resolution hypernuclear spectroscopy, was used to obtain an energy spectrum with a resolution of 0.78 MeV (FWHM). The well-calibrated spectrometer system of the present experiment using the $$p(e,e^{\\prime}K^{+})\\Lambda,\\Sigma^{0}$$ reactions allowed us to determine the energy levels, and the binding energy of the ground state peak (mixture of 1$$^{-}$$ and 2$$^{-}$$ states) was obtained to be B$$_{\\Lambda}$$=8.55$$\\pm$$0.07(stat.)$$\\pm$$0.11(sys.) MeV. Furthermore, the result indicates that the ground state energy is shallower than that of an emulsion study by about 0.5 MeV which provides valuable experimental information on charge symmetry breaking effect in the $$\\Lambda N$$ interaction.« less

  8. Oxidation of pyrite surfaces: a photoelectron spectroscopic study

    NASA Astrophysics Data System (ADS)

    Karthe, S.; Szargan, R.; Suoninen, E.

    1993-10-01

    Surfaces of pyrite (FeS 2) differently prepared in situ and ex situ have been studied before and after contact to air and air-saturated aqueous solutions of 4≤pH≤10 by means of photoelectron spectroscopy. Pyrite surfaces fractured or scraped in situ revealed FeS-like species concentrated in the surface region. Preparation (polishing, grinding, powdering) and prolonged oxidation in air mainly resulted in basic iron sulphate and iron oxide/hydroxide. A promoting effect of an increased surface roughness due to the preparation was observed for the formation of iron oxide/hydroxide compared with sulphate in contrast to the natural oxidation process. Oxidation in air also led to sulphur-rich species identified as iron-deficient regions below monolayer coverage. Similar regions were present at ground surfaces exposed to air-saturated solution of pH4 and pH5. In near-neutral to alkaline solution mainly iron hydroxy-oxide is formed the layer thickness of which was estimated in the range of 0.5 nm (pH5) to 1.7 nm (pH10).

  9. Spectroscopic study of neodymium doped lead-bismuth-borate glasses

    NASA Astrophysics Data System (ADS)

    Pasha, Altaf; Dayani, P.; Negalur, Mahesh; Swamy, Manjunatha; Abhiram, J.; Rajaramakrishna, R.

    2016-05-01

    This paper reports on different physical and optical properties of rare earth doped heavy metal oxide glasses. The glass composition of 10Bi2O3-30PbO-60B2O3-xNd2O3 where x = 0, 0.1, 0.2, 0.5 and 1 (in mol %) has been synthesized using melt-quenching technique. Refractive index measurements for these glasses were done and physical parameters were studied. Structural properties of these glasses were analysed through infrared spectra that was recorded between 1600cm-1 and 300cm-1 in transmission mode. The optical absorption spectra were recorded in the wavelength range from 300 to 700 nm. The transitions originated from ground state energy 4I9/2. The energy level analysis has been carried out by considering absorption spectral bands. The results thus obtained are comparable with reports on similar glasses, indicating that the prepared glasses may have potential laser applications.

  10. Spectroscopic studies of refractory and dielectric thin films

    SciTech Connect

    Truong, C.M.

    1993-01-01

    This work demonstrated the application of the techniques and methodology of surface science to investigate the mechanisms of thin film deposition processes on solid surfaces. The synthesis of boron nitride (BN) thin films was studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). In this model system, diborane (B[sub 2]H[sub 6]), ammonia (NH[sub 3]) and hydrazine (N[sub 2]H[sub 4]) were used as precursors to deposit BN thin films on a clean Ru(0001) surface. The result showed that ammonia reaction with diborane yielded only boron-rich boron nitride overlayers. However, stoichiometric BN films in excess of one monolayer could be produced when hydrazine was substituted for ammonia. The effects of oxygen on boron-rich and stoichiometric boron-nitrogen films were also examined. In the second part of this work, high resolution electron energy loss spectroscopy (HREELS) was used to characterize defect centers in MgO and in lithium-doped MgO thin films. The HREELS results showed that MgO thin films grown on Mo(100) were nearly defect-free at temperatures up to 1100 K. HREELS measurements indicated that annealings to higher temperatures induced F-type defect centers in the MgO films. The formation of [Li[sup +]O[sup [minus

  11. HPLC assisted Raman spectroscopic studies on bladder cancer

    NASA Astrophysics Data System (ADS)

    Zha, W. L.; Cheng, Y.; Yu, W.; Zhang, X. B.; Shen, A. G.; Hu, J. M.

    2015-04-01

    We applied confocal Raman spectroscopy to investigate 12 normal bladder tissues and 30 tumor tissues, and then depicted the spectral differences between the normal and the tumor tissues and the potential canceration mechanism with the aid of the high-performance liquid chromatographic (HPLC) technique. Normal tissues were demonstrated to contain higher tryptophan, cholesterol and lipid content, while bladder tumor tissues were rich in nucleic acids, collagen and carotenoids. In particular, β-carotene, one of the major types of carotenoids, was found through HPLC analysis of the extract of bladder tissues. The statistical software SPSS was applied to classify the spectra of the two types of tissues according to their differences. The sensitivity and specificity of 96.7 and 66.7% were obtained, respectively. In addition, different layers of the bladder wall including mucosa (lumps), muscle and adipose bladder tissue were analyzed by Raman mapping technique in response to previous Raman studies of bladder tissues. All of these will play an important role as a directive tool for the future diagnosis of bladder cancer in vivo.

  12. Vibrational spectroscopic properties of hydrogen bonded acetonitrile studied by DFT.

    PubMed

    Alía, Jose M; Edwards, Howell G M

    2005-09-01

    Vibrational properties (band position, Infrared and Raman intensities) of the acetonitrile C[triple bond]N stretching mode were studied in 27 gas-phase medium intensity (length range: = 1.71-2.05 angstroms; -deltaE range = 13-48 kJ/mol) hydrogen-bonded 1:1 complexes of CH3CN with organic and inorganic acids using density functional theory (DFT) calculations [B3LYP-6-31++G(2d,2p)]. Furthermore, general characteristics of the hydrogen bonds and vibrational changes in the OH stretching band of the acids were also considered. Experimentally observed blue-shifts of the C[triple bond]N stretching band promoted by the hydrogen bonding, which shortens the triple bond length, are very well reproduced and quantitatively depend on the hydrogen bond length. Both predicted enhancement of the infrared and Raman nu(C[triple bond]N) band intensities are in good agreement with the experimental results. Infrared band intensity increase is a direct function of the hydrogen bond energy. However, the predicted increase in the Raman band intensity increase is a more complex function, depending simultaneously on the characteristics of both the hydrogen bond (C[triple bond]N bond length) and the H-donating acid polarizability. Accounting for these two parameters, the calculated nu(C[triple bond]N) Raman intensities of the complexes are explained with a mean error of +/- 2.4%.

  13. Spectroscopic Studies on the Characterization of a Persian Playing Card.

    PubMed

    Holakooei, Parviz; Niknejad, Maryam; Vaccaro, Carmela

    2016-01-01

    This paper presents the results of our investigations on a playing card preserved at The Mūzih-i Āynih va Rushanāī in Yazd, Iran. Conducting micro X-ray fluorescence spectrometry (μ-XRF), micro-Raman spectroscopy (μ-Raman), infrared reflectography (IRR), ultraviolet fluorescence photography, radiography, and optical microscopy, various paints applied on the playing card were identified. According to our analytical studies, red, green, blue, black, and gold-like metallic paints were identified to be a red monoazo pigment (β-naphthol PR 53:1), chrome green, artificial ultramarine blue, carbon black, and brass powder (Dutch metal powder), respectively, dating the playing card to 1895 onward based on the manufacturing date of the red monoazo pigment. Barite was also shown to be mixed with the pigments as an extender. On the other hand, the portrait's face of the playing card was peculiarly blackened. Our analytical approach toward characterizing the blackened face showed that the black paint was achieved by carbon black and, in other words, the face was not blackened due to the darkening of Pb-bearing pigments. Moreover, it was shown that there was no underdrawing under the black face and the black paint was most probably executed in the same time with the other paints. Considering the possible use of the playing card, it was suggested not to remove the blackened face in the cleaning process since the black paint was a part of the integrity of the playing card.

  14. Spectroscopic studies of aluminosilicate formation in tank waste simulants

    SciTech Connect

    Su, Y.; Wang, L.; Bunker, B.C.; Windisch, C.F.

    1997-12-31

    Aluminosilicates are one of the major class of species controlling the volume of radioactive high-level waste that will be produced from future remediation at Hanford site. Here the authors present studies of the phases and structures of aluminosilicates as a function of sludge composition using X-ray powder diffraction, solid state {sup 27}Al and {sup 29}Si NMR, and Raman spectroscopy. The results show that the content of NaNO{sub 3} in solution has significant effects on the nature of the insoluble aluminosilicate phases produced. It was found that regardless of the initial Si:Al ratio, nitrate cancrinite was the main phase formed in the solution with pH of 13.5 and 5 M NaNO{sub 3}. However, at lower NaNO{sub 3} concentration with initial Si:Al ratios of 1.1, 2.2, and 11.0 in the solutions, a range of aluminosilicate zeolites was produced with Si:Al ratios of 1.1, 1.3, and 1.5, respectively. Lowering the solution pH appears to promote the formation of amorphous aluminosilicates. The results presented here are important for the prediction of the solubility and dissolution rate of Al in tank wastes.

  15. Synthesis, spectroscopic, thermogravimetric and antimicrobial studies of mixed ligands complexes

    NASA Astrophysics Data System (ADS)

    Mahmoud, Walaa H.; Mahmoud, Nessma F.; Mohamed, Gehad G.; El-Sonbati, Adel Z.; El-Bindary, Ashraf A.

    2015-09-01

    An interesting series of mixed ligand complexes have been synthesized by the reaction of metal chloride with guaifenesin (GFS) in the presence of 2-aminoacetic acid (HGly) (1:1:1 molar ratio). The elemental analysis, magnetic moments, molar conductance, spectral (UV-Vis, IR, 1H NMR and ESR) and thermal studies were used to characterize the isolated complexes. The molecular structure of GFS is optimized theoretically and the quantum chemical parameters are calculated. The IR showed that the ligand (GFS) acts as monobasic tridentate through the hydroxyl, phenoxy etheric and methoxy oxygen atoms and co-ligand (HGly) as monobasic bidentate through the deprotonated carboxylate oxygen atom and nitrogen atom of amino group. The molar conductivities showed that all the complexes are non-electrolytes except Cr(III) complex is electrolyte. Electronic and magnetic data proposed the octahedral structure for all complexes under investigation. ESR spectrum for Cu(II) revealed data which confirm the proposed structure. Antibacterial screening of the compounds were carried out in vitro on gram positive (Bacillus subtilis and Staphylococcus aureus), gram negative (Escherichia coli and Neisseria gonorrhoeae) bacteria and for in vitro antifungal activity against Candida albicans organism. However, some complexes showed more chemotherapeutic efficiency than the parent GFS drug. The complexes were also screened for their in vitro anticancer activity against the breast cell line (MFC7) and the results obtained showed that they exhibit a considerable anticancer activity.

  16. Cyclotetrapeptides with alternating ?-Ala residues: synthesis and spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Ngu-Schwemlein, Maria; Zhou, Zhe; Bowie, Toni; Eden, Rebecca

    2003-07-01

    Three cyclotetrapeptides, c[Leu- D-Ala-Xaa- D-Ala], where Xaa is Leu ( P1), Lys ( P2) and Glu ( P3) were synthesized and studied by 1H and 13C NMR and CD spectroscopy. These cyclotetrapeptides exhibit similar coupling constants, 3JHNHα, in the range of 8.56-9.93 Hz, commonly observed for β-turn structures. All amide proton chemical shifts for P1, P2 and P3 exhibited linear dependence on temperature with moderate temperature coefficients ranging from -3.1 to -9.8 ppb/K. Amide proton signal broadening was observed for all residues in P1, P2 and P3, indicating that they are solvent accessible. The number of resonance observed for P1 was half of the total counts, indicating a C2 symmetric conformation. P2 and P3 exhibit similar CD in solvents of varying dielectric constants and dilutions, with characteristic positive CD bands at ca. 210 and 222 nm, which correspond to a β-turn type structure. Small CD/temperature effect was also observed with isodichroic points, consistent with conformational stability and a well-populated cyclotetrapeptide energy state. These heterochiral cyclotetrapeptides consisting of alternating D-Ala residues adopt stabilized open β-turn conformations and may be useful as a ligand template for further functionalization.

  17. Borax methylene blue: a spectroscopic and staining study.

    PubMed

    Donaldson, P T; Russo, A; Reynolds, C; Lillie, R D

    1978-07-01

    Borax methylene blue is quite stable at room temperatures of 22-25 C. At 30 C polychroming is slow; during 50 days in a water bath at this temperature the absorption peak moves from 665 to 656 nm. At 35 C, the absorption peak reaches 660 nm in 7 days, 654 nm in 14. At 60 C polychroming is rapid, the absorption peak reaching 640-620 nm in 3 days. When the pH of the borax methylene blue solutions, normally about 9.0, is adjusted to pH 6.5, the absorption peak remains at 665 nm even when incubated at 60 C for extended periods. When used as a blood stain 0.4 ml borax methylene blue (1% methylene blue in 1% borax), 4 ml acetone, 2 ml borax-acid phosphate buffer to bring the solution to pH 6.5, and distilled water to make 40 ml, with 0.2 ml 1% eosin added just before using, an excellent Nocht-Giemsa type stain is achieved after 30 minutes staining. The material plasmodia P. falciparum, P. vivax, and P. berghei stain moderate blue with dark red chromatin and green to black pigment granules. The study confirms Malachowski's 1891 results and explains Gautier's 1896-98 failure to duplicate it.

  18. Spectroscopic Studies on the Characterization of a Persian Playing Card.

    PubMed

    Holakooei, Parviz; Niknejad, Maryam; Vaccaro, Carmela

    2016-01-01

    This paper presents the results of our investigations on a playing card preserved at The Mūzih-i Āynih va Rushanāī in Yazd, Iran. Conducting micro X-ray fluorescence spectrometry (μ-XRF), micro-Raman spectroscopy (μ-Raman), infrared reflectography (IRR), ultraviolet fluorescence photography, radiography, and optical microscopy, various paints applied on the playing card were identified. According to our analytical studies, red, green, blue, black, and gold-like metallic paints were identified to be a red monoazo pigment (β-naphthol PR 53:1), chrome green, artificial ultramarine blue, carbon black, and brass powder (Dutch metal powder), respectively, dating the playing card to 1895 onward based on the manufacturing date of the red monoazo pigment. Barite was also shown to be mixed with the pigments as an extender. On the other hand, the portrait's face of the playing card was peculiarly blackened. Our analytical approach toward characterizing the blackened face showed that the black paint was achieved by carbon black and, in other words, the face was not blackened due to the darkening of Pb-bearing pigments. Moreover, it was shown that there was no underdrawing under the black face and the black paint was most probably executed in the same time with the other paints. Considering the possible use of the playing card, it was suggested not to remove the blackened face in the cleaning process since the black paint was a part of the integrity of the playing card. PMID:26767645

  19. Raman spectroscopic study of the tellurite minerals: rajite and denningite.

    PubMed

    Frost, Ray L; Dickfos, Marilla J; Keeffe, Eloise C

    2008-12-15

    Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO3), (b) A(XO3).xH2O, (c) A2(XO3)3.xH2O, (d) A2(X2O5) and (e) A(X3O8). Raman spectroscopy has been used to study rajite and denningite, examples of group (d). Minerals of the tellurite group are porous zeolite-like materials. Raman bands for rajite observed at 740, and 676 and 667 cm(-1) are attributed to the nu1 (Te2O5)(2-) symmetric stretching mode and the nu3 (TeO3)(2-) antisymmetric stretching modes, respectively. A second rajite mineral sample provided a more complex Raman spectrum with Raman bands at 754 and 731 cm(-1) assigned to the nu1 (Te2O5)(2-) symmetric stretching modes and two bands at 652 and 603 cm(-1) are accounted for by the nu3 (Te2O5)(2-) antisymmetric stretching mode. The Raman spectrum of dennigite displays an intense band at 734 cm(-1) attributed to the nu1 (Te2O5)(2-) symmetric stretching mode with a second Raman band at 674 cm(-1) assigned to the nu3 (Te2O5)(2-) antisymmetric stretching mode. Raman bands for rajite, observed at (346, 370) and 438 cm(-1) are assigned to the (Te2O5)(2-)nu2 (A1) bending mode and nu4 (E) bending modes.

  20. Influence of environment on piroxicam polymorphism: vibrational spectroscopic study.

    PubMed

    Taddei, P; Torreggiani, A; Simoni, R

    2001-01-01

    FTIR and FT-Raman spectroscopies were used to evaluate the mechanism of transformation of piroxicam into its different forms (alpha, beta, and monohydrate), depending on the environment. These vibrational techniques allowed us to identify the forms of piroxicam that crystallize from different solvents at different cooling rates and the conformation of the drug in some of its derivatives: piroxicam hydrochloride, piroxicam thallium and sodium salt hemihydrates, and piroxicam sodium salt. The usefulness of Raman spectroscopy in characterizing piroxicam:beta-cyclodextrin (PbetaCD) inclusion compounds was described. The Raman spectrum of 1:2 PbetaCD was discussed in comparison with that of the corresponding piroxicam sodium salt containing inclusion compound (1:2 PNabetaCD) in order to study the influence of the piroxicam derivative used on the structure of the inclusion compound. The Raman results showed that in both of the inclusion compounds the piroxicam mainly assumes the zwitterionic structure typical of a monohydrate; therefore, the kind of derivative used does not affect the conformation of the drug in its inclusion compound. The effect of the method of synthesis utilized (freeze-drying or freeze-thaw cycling) to obtain 1:2.5 PbetaCD was investigated. The inclusion compound obtained by freeze-thaw cycling proved to be more crystalline and to contain a higher amount of the beta form than the freeze-dried inclusion compound. Raman spectroscopy proved to be a useful technique for evaluating the effectiveness of the manufacturing process in relation to the pharmaceutical properties of the drug and to the nondestructive and noninvasive on-line quality control of the industrial products.

  1. Electron spin resonance spectroscopic studies of radical cation reactions

    SciTech Connect

    Dai, S.

    1990-01-01

    A spin Hamiltonian suitable for theoretical analyses of ESR spectra is derived using the general effective Hamiltonian theory in the usual Schroedinger representation. The Permutation Indices method is extended to obtain the dynamic exchange equations used in ESR lineshape simulation. The correlation between [beta]-hydrogen coupling constants and their geometric orientations are derived using a perturbation method. The three electron bond model is extended to rationalize unimolecular rearrangements of radical cations. The ring-closed radical cations of 9,10-octalin oxide and synsesquinorbornene oxide have been characterized by ESR spectroscopy in the CFCl[sub 3] matrix at low temperature. The self-electron-transfer rate constants between the methyl viologen dication and cation have been determined by dynamic ESR lineshape simulations at room temperature in allyl alcohol, water, methanol and propargyl alcohol solvents. The radical cation formed by the radiolytic oxidation of allylamine in Freon matrices at 77 K is the 3-iminiopropyl distonic species(3-iminium-1-propyl radical). The nucleophilic endocylization of the but-3-en-1-ol radical cation to the protonated tetrahydrofuran-3-yl radical was observed in the radiolytic oxidation of but-3-en-1-ol in Freon matrices. ESR studies of the radiolytic oxidation of 1,5-hexdiyne have resulted in characterization the 1,5-hexadiyne radical cation isomerizing to the 1,2,4,5-hexatetraene radical cation. The symmetric (C[sub 2v]) bicyclo[3.3.0]-octa-2,6-diene-4,8-diyl(a bridged 1,4-bishomobenzene species) radical cation is produced by the radiolytic oxidation of semibullvalene in Freon matrices. The ring-opening 3,4-dimethylenecyclobutene radical cation to 1,2,4,5-hexatetraene radical cation was observed in the photolysis of 3,4-dimethylenecyclobutene radical cation. The cyclooctatetraene radical cation generated by radiolytic oxidation photoisomerizes to bicyclo[3.3.0]octa-2,6-diene-4,8-diyl radical cation.

  2. Synchronous fluorescence spectroscopic study of solvatochromic curcumin dye

    NASA Astrophysics Data System (ADS)

    Patra, Digambara; Barakat, Christelle

    2011-09-01

    Curcumin, the main yellow bioactive component of turmeric, has recently acquired attention by chemists due its wide range of potential biological applications as an antioxidant, an anti-inflammatory, and an anti-carcinogenic agent. This molecule fluoresces weakly and poorly soluble in water. In this detailed study of curcumin in thirteen different solvents, both the absorption and fluorescence spectra of curcumin was found to be broad, however, a narrower and simple synchronous fluorescence spectrum of curcumin was obtained at Δ λ = 10-20 nm. Lippert-Mataga plot of curcumin in different solvents illustrated two sets of linearity which is consistent with the plot of Stokes' shift vs. the ET30. When Stokes's shift in wavenumber scale was replaced by synchronous fluorescence maximum in nanometer scale, the solvent polarity dependency measured by λSFSmax vs. Lippert-Mataga plot or ET30 values offered similar trends as measured via Stokes' shift for protic and aprotic solvents for curcumin. Better linear correlation of λSFSmax vs. π* scale of solvent polarity was found compared to λabsmax or λemmax or Stokes' shift measurements. In Stokes' shift measurement both absorption/excitation as well as emission (fluorescence) spectra are required to compute the Stokes' shift in wavenumber scale, but measurement could be done in a very fast and simple way by taking a single scan of SFS avoiding calculation and obtain information about polarity of the solvent. Curcumin decay properties in all the solvents could be fitted well to a double-exponential decay function.

  3. Solvated crystalline forms of nevirapine: thermoanalytical and spectroscopic studies.

    PubMed

    Chadha, Renu; Arora, Poonam; Saini, Anupam; Jain, Dharamvir Singh

    2010-09-01

    The study is aimed at exploring the utility of thermoanalytical methods in the solid-state characterization of various crystalline forms of nevirapine. The different forms obtained by recrystallization of nevirapine from various solvents were identified using differential scanning calorimetry and thermogravimetric analysis (TGA). The appearance of desolvation peak accompanied by weight loss in TGA indicated the formation of solvates: hemi-ethanolate (Form I), hemi-acetonitrilate (Form II), hemi-chloroformate (Form III), hemi-THF solvate (Form IV), mixed hemi-ethanolate hemi-hydrate (Form V), and hemi-toluenate (Form VI). The higher desolvation temperatures of all the solvates except toluenate than their respective boiling point indicate tighter binding of solvent. Emphasis has been laid on the determination of heat capacity and heat of solution utilizing microreaction calorimeter to further distinguish the various forms. The enthalpy of solution (ΔH(sol)), an indirect measure of the lattice energy of a solid, was well correlated with the crystallinity of all the solid forms obtained. The magnitude of ΔH(sol) was found to be -14.14 kJ/mol for Form I and -2.83 kJ/mol for Form V in phosphate buffer of pH 2, exhibiting maximum ease of molecular release from the lattice in Form I. The heat capacity for solvation (ΔC(p)) was found to be positive, providing information about the state of solvent molecules in the host lattice. The solubility and dissolution rate of the forms were also found to be in agreement with their enthalpy of solution. Form (I), being the most exothermic, was found to be the most soluble of all the forms.

  4. Raman spectroscopic study of the uranyl tricarbonate mineral liebigite

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Erickson, Kristy L.; Weier, Matt L.; Carmody, Onuma; Čejka, Jiří

    2005-03-01

    Raman spectroscopy at 298 and 77 K has been employed to study the structure of the uranyl tricarbonates liebigite {Ca 2[UO 2(CO 3) 3]11H 2O}. The spectra of the samples are sample dependent and significant differences in the Raman spectra are obtained upon cooling to 77 K. It is proposed that the mineral undergoes a phase change upon cooling. Significant changes in the Raman spectra are observed in the hydroxyl stretching region and in the low wavenumber region. Two Raman bands are observed at 3468 and 3528 cm -1 showing the non-equivalence of the water units in the structure. Obtaining spectra at 77 K enables well resolved bands at 3530, 3501, 3482, 3463, 3443, 3405 and 3364 cm -1. Two well resolved bands at 1087 and 1073 cm -1 in the 298 K spectra become bands at 1093, 1076 and 1008 cm -1 in the 77 K spectrum proving the non-equivalence of the carbonate units. This non-equivalence is reflected in the observation of multiple bands in the carbonate bending regions. The (UO 2) 2+ units are characterised by the antisymmetric stretching vibrations at 902, 885 and 873 cm -1 and by the ν2 bending modes at 248 cm -1. Two bands near 820 cm -1 may be assigned to the ν1 (UO 2) 2+ symmetric stretching vibrations, however, a coincidence of these vibrations with the ν2 (CO 3) 2- out-of plane bending vibrations cannot be excluded. The use of Raman spectroscopy enables a better definition of the vibrational modes of liebigite and shows changes in the molecular structure upon reaching 77 K.

  5. Spectroscopic studies of Synechococcus sp PCC 7002 phycobilisome core mutants

    SciTech Connect

    Gindt, Y.M.

    1993-04-01

    The role of the L[sub cm] (I), [beta][sup 18] (II), and [alpha][sup AP-B] (III) chromoproteins in the phycobilisome (PBS) core was investigated using genetically engineered strains of Synechococcus missing different polypeptides. Intact cells, isolated PBS, and subcore preparations for each mutant were studied to determine the effect of that mutation on energy transfer within the PBS core and to the reaction centers. Three mutants lacked the II and/or III polypeptides, while the I chromophore was altered in others. A lower energy absorbing chromophore, A[sub max] = 695 nm, was substituted for the I chromophore. The deletion of the II and III subunits had no discernible effect on energy transfer from the PBS to PSII. In cells and isolated PBS, the altered I chromophore acts to quench the PBS complex and to redirect the energy which would be transferred to PSII. In the PBS and subcore preparations, deletion of the III subunit did not alter energy transfer within the core. The deletion of the II subunit from the PBS caused a small decrease in the excited state lifetimes of the final emitters indicating more disorder within the core. The I chromophore was found to absorb at 670nm and to emit at 683nm within the intact PBS. The II chromophore emits at 679nm while the III chromophore emits at 682nm. A strong interaction exists between the I chromophore and the II subunit. Upon deletion of the II subunit from the PBS core, the I chromophore emits at a higher energy. The II subunit could act to stabilize the I chromophore-binding pocket, or exciton coupling could be occurring between the two. The role of the III chromophore is still unclear at this time. The III chromophore does contribute to the RT emission of the isolated PBS, but it transfers energy to I at 77 K. One can conclude that the III subunit is adjacent to the trimer containing the I polypeptide.

  6. Spectroscopic studies of Synechococcus sp PCC 7002 phycobilisome core mutants

    SciTech Connect

    Gindt, Y.M.

    1993-04-01

    The role of the L{sub cm} (I), {beta}{sup 18} (II), and {alpha}{sup AP-B} (III) chromoproteins in the phycobilisome (PBS) core was investigated using genetically engineered strains of Synechococcus missing different polypeptides. Intact cells, isolated PBS, and subcore preparations for each mutant were studied to determine the effect of that mutation on energy transfer within the PBS core and to the reaction centers. Three mutants lacked the II and/or III polypeptides, while the I chromophore was altered in others. A lower energy absorbing chromophore, A{sub max} = 695 nm, was substituted for the I chromophore. The deletion of the II and III subunits had no discernible effect on energy transfer from the PBS to PSII. In cells and isolated PBS, the altered I chromophore acts to quench the PBS complex and to redirect the energy which would be transferred to PSII. In the PBS and subcore preparations, deletion of the III subunit did not alter energy transfer within the core. The deletion of the II subunit from the PBS caused a small decrease in the excited state lifetimes of the final emitters indicating more disorder within the core. The I chromophore was found to absorb at 670nm and to emit at 683nm within the intact PBS. The II chromophore emits at 679nm while the III chromophore emits at 682nm. A strong interaction exists between the I chromophore and the II subunit. Upon deletion of the II subunit from the PBS core, the I chromophore emits at a higher energy. The II subunit could act to stabilize the I chromophore-binding pocket, or exciton coupling could be occurring between the two. The role of the III chromophore is still unclear at this time. The III chromophore does contribute to the RT emission of the isolated PBS, but it transfers energy to I at 77 K. One can conclude that the III subunit is adjacent to the trimer containing the I polypeptide.

  7. A spectroscopic and dynamical study of binary and other Cepheids

    NASA Astrophysics Data System (ADS)

    Petterson, Orlon King Lee

    High resolution observations have been made of a number of southern Cepheids to make an observational and theoretical study of Cepheid variables using radial velocities. The stars studied were part of a long term programme to observe southern variable stars, from which a valuable database of radial velocities gathered over a long period were available. Sixteen échelle spectrograph orders in the wavelength region 5400 - 8600Å were used, which included a number of absorption lines covering a range of species and excitation potentials. The line bisector technique was used to measure stellar and telluric lines and to obtain radial velocities. To improve the precision of the radial velocities we used telluric lines to calibrate the observations to a common reference frame. The radial velocities have a precision of ~300ms-1 allowing the detection of velocity differences of ~1 kms-1 with confidence. The radial velocity data obtained at Mount John University Observatory (MJUO) was combined with data from various sources to determine the orbits of any Cepheids exhibiting orbital motion. The various orbital parameters were determined for a number of systems and where radial velocities for the companions exist, some estimate of the mass was made. The precision of the radial velocities obtained from MJUO also allowed us to search for line level effects for a number of species among the Cepheid spectra. A number of IAU standard stars were observed to calibrate the radial velocities obtained at MJUO to the IAU standard scale. The radial velocities from MJUO were found not to differ significantly from the IAU values. Binary Cepheids are particularly useful in the determination of Cepheid masses, which are still an active topic for astronomical research. The value of the MJUO data was that it provided a consistent set of data against which other sources of data could be compared. For 8 of the Cepheids new or improved orbital solutions were found. They are Y Car, YZ Car, AX Cir

  8. Electrical impedance tomography to evaluate air distribution prior to extubation in very-low-birth-weight infants: a feasibility study

    PubMed Central

    de Souza Rossi, Felipe; Yagui, Ana Cristina Zanon; Haddad, Luciana Branco; Deutsch, Alice D'Agostini; Rebello, Celso Moura

    2013-01-01

    OBJECTIVES: Nasal continuous positive airway pressure is used as a standard of care after extubation in very-low-birth-weight infants. A pressure of 5 cmH2O is usually applied regardless of individual differences in lung compliance. Current methods for evaluation of lung compliance and air distribution in the lungs are thus imprecise for preterm infants. This study used electrical impedance tomography to determine the feasibility of evaluating the positive end-expiratory pressure level associated with a more homogeneous air distribution within the lungs before extubation. METHODS: Ventilation homogeneity was defined by electrical impedance tomography as the ratio of ventilation between dependent and non-dependent lung areas. The best ventilation homogeneity was achieved when this ratio was equal to 1. Just before extubation, decremental expiratory pressure levels were applied (8, 7, 6 and 5 cmH20; 3 minutes each step), and the pressure that determined the best ventilation homogeneity was defined as the best positive end-expiratory pressure. RESULTS: The best positive end-expiratory pressure value was 6.3±1.1 cmH20, and the mean continuous positive airway pressure applied after extubation was 5.2±0.4 cmH20 (p = 0.002). The extubation failure rate was 21.4%. X-Ray and blood gases after extubation were also checked. CONCLUSION: This study demonstrates that electrical impedance tomography can be safely and successfully used in patients ready for extubation to suggest the best ventilation homogeneity, which is influenced by the level of expiratory pressure applied. In this feasibility study, the best lung compliance was found with pressure levels higher than the continuous positive airway pressure levels that are usually applied for routine extubation. PMID:23644854

  9. High-impedance wire grid method to study spatiotemporal behavior of hot electron clump generated in a plasma

    SciTech Connect

    Terasaka, K. Kato, Y.; Tanaka, M. Y.; Yoshimura, S.; Morisaki, T.; Furuta, K.; Aramaki, M.

    2014-11-15

    High-impedance Wire Grid (HIWG) detector has been developed to study spatiotemporal behavior of a hot electron clump generated in an electron cyclotron resonance (ECR) plasma. By measuring the floating potentials of the wire electrodes, and generating structure matrix made of geometrical means of the floating potentials, the HIWG detector reconstructs the spatial distribution of high-temperature electron clump at an arbitrary instant of time. Time slices of the spike event in floating potential revealed the growth and decay process of a hot spot occurs in an ECR plasma.

  10. A study on transmission characteristics and specific absorption rate using impedance-matched electrodes for various human body communication.

    PubMed

    Machida, Yuta; Yamamoto, Takahiko; Koshiji, Kohji

    2013-01-01

    Human body communication (HBC) is a new communication technology that has presented potential applications in health care and elderly support systems in recent years. In this study, which is focused on a wearable transmitter and receiver for HBC in a body area network (BAN), we performed electromagnetic field analysis and simulation using the finite difference time domain (FDTD) method with various models of the human body. Further we redesigned a number of impedance-matched electrodes to allow transmission without stubs or transformers. The specific absorption rate (SAR) and transmission characteristics S21 of these electrode structures were compared for several models.

  11. Transport in fuel cells: Electrochemical impedance spectroscopy and neutron imaging studies

    NASA Astrophysics Data System (ADS)

    Aaron, Douglas Scott

    This dissertation focuses on two powerful methods of performing in-situ studies of transport limitations in fuel cells. The first is electrochemical impedance spectroscopy (EIS) while the second is neutron imaging. Three fuel cell systems are studied in this work: polymer electrolyte membrane fuel cells (PEMFCs), microbial fuel cells (MFCs) and enzyme fuel cells (EFCs). The first experimental section of this dissertation focuses on application of EIS and neutron imaging to an operating PEMFC. The effects of cathode-side humidity and flow rate, as well as cell temperature and a transient response to cathode-side humidity, were studied for a PEMFC via EIS. It was found that increased air humidity in the cathode resulted in greatly reduced cathode resistance as well as a significant reduction in membrane resistance. The anode resistance was only slightly reduced in this case. Increased air flow rate was observed to have little effect on any resistance in the PEMFC, though slight reductions in both the anode and the cathode were observed. Increased cell temperature resulted in decreased cathode and anode resistances. Finally, the transient response to increased humidity exhibited unstable behavior for both the anode and the cathode resistances and the PEMFC power output. Neutron imaging allowed the calculation of water content throughout the PEMFC, showing a maximum in water content at the cathode gas diffusion layer - membrane interface. The second experimental section of this dissertation delves into the world of microbial fuel cells. Multiple long-term observations of changes in internal resistances were performed and illustrated the reduction in anode resistance as the bacterial community was established. Over this same time period, the cathode resistance was observed to have increased; these two phenomena suggest that the anode improved over time while the cathode suffered from degradation. Increased anode fluid ionic strength and flow rate both led to significant

  12. Impedance and self-discharge mechanism studies of nickel metal hydride batteries for energy storage applications

    NASA Astrophysics Data System (ADS)

    Zhu, Wenhua; Zhu, Ying; Tatarchuk, Bruce

    2013-04-01

    Nickel metal hydride battery packs have been found wide applications in the HEVs (hybrid electric vehicles) through the on-board rapid energy conservation and efficient storage to decrease the fossil fuel consumption rate and reduce CO2 emissions as well as other harmful exhaust gases. In comparison to the conventional Ni-Cd battery, the Ni-MH battery exhibits a relatively higher self-discharge rate. In general, there are quite a few factors that speed up the self-discharge of the electrodes in the sealed nickel metal hydride batteries. This disadvantage eventually reduces the overall efficiency of the energy conversion and storage system. In this work, ac impedance data were collected from the nickel metal hydride batteries. The self-discharge mechanism and battery capacity degradation were analyzed and discussed for further performance improvement.

  13. Exploring binding properties of sertraline with human serum albumin: Combination of spectroscopic and molecular modeling studies.

    PubMed

    Shahlaei, Mohsen; Rahimi, Behnoosh; Nowroozi, Amin; Ashrafi-Kooshk, Mohammad Reza; Sadrjavadi, Komail; Khodarahmi, Reza

    2015-12-01

    Human serum albumin (HSA)-drug binding is an important factor to determine half life and bioavailability of drugs. In the present research, the interaction of sertraline (SER) to HSA was investigated using combination of spectroscopic and molecular modeling techniques. Changes in the UV-Vis, CD and FT-IR spectra as well as a significant degree of tryptophan fluorescence quenching were observed upon SER-HSA interaction. Data obtained by spectroscopic methods along with the computational studies suggest that SER binds to residues located in subdomain IIA of HSA. Analysis of spectroscopic data represented the formation of 1:1 complex, significant binding affinity, negative values of entropy and enthalpy changes and the essential role of hydrophobic interactions in binding of SER to HSA. The binding models were demonstrated in the aspects of SER's conformation, active site interactions, important amino acids and hydrogen bonding. Computational mapping of the possible binding site of SER confirmed that the ligand to be bound in a large hydrophobic cavity of HSA. In accordance with experimental data, computational analyses indicated that SER binding does not alter the secondary structure of the protein. The results not only lead to a better understanding of interaction between SER and HSA but also provide useful data about the influence of SER on the protein conformation. PMID:26471709

  14. Spectroscopic studies of copper doped alkaline earth lead zinc phosphate glasses

    NASA Astrophysics Data System (ADS)

    Sastry, S. Sreehari; Rao, B. Rupa Venkateswara

    2014-02-01

    In this paper spectroscopic investigation of Cu2+ doped alkaline earth lead zinc phosphate glasses was done through the spectroscopic techniques like X-ray diffraction, Ultra Violet (UV) absorption Spectroscopy, Electron Paramagnetic Resonance (EPR - X band), Fourier Transform Infra Red (FTIR) and Raman Spectroscopy. Alkaline earth lead zinc phosphate glasses containing 0.1% copper oxide (CuO) were prepared by the melt quenching technique. Spectroscopic studies indicated that there is a greater possibility for the copper ions to exist in Cu2+ state in these glasses. The optical absorption spectra indicated that the absorption peak of Cu2+ is a function of composition. The maxima absorption peak was reported at 862 nm for strontium lead zinc phosphate glass. Bonding parameters were calculated for the optical and EPR data. All these spectral results indicated clearly that there are certain structural changes in the present glass system with different alkaline earth contents. The IR and Raman spectra noticed the breaking of the P-O-P bonds and creating more number of new P-O-Cu bonds.

  15. A photoelectron spectroscopic and computational study of the o-dicarbadodecaborane parent anion

    NASA Astrophysics Data System (ADS)

    Zhang, Xinxing; Bowen, Kit

    2016-06-01

    We report a combined photoelectron spectroscopic and computational study of the o-dicarbadodecaborane (o-carborane) parent anion, (C2B10H12)-. Previous studies that focused on the electrophilic nature of o-carborane led to tantalizing yet mixed results. In our study, we confirmed that o-carborane does in fact form a parent anion and that it has considerable stability. This anion is an isomer ("Anion iso 2") where unlike in neutral o-carborane, the two carbon atoms are not bound.

  16. Studies on the binding behavior of prodigiosin with bovine hemoglobin by multi-spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Tang, Jing; Yang, Chao; Zhou, Lin; Ma, Fei; Liu, Shuchao; Wei, Shaohua; Zhou, Jiahong; Zhou, Yanhuai

    2012-10-01

    In this article, the interaction mechanism of prodigiosin (PG) with bovine hemoglobin (BHb) is studied in detail using various spectroscopic technologies. UV-vis absorption and fluorescence spectra demonstrate the interaction process. The Stern-Volmer plot and the time-resolved fluorescence study suggest the quenching mechanism of fluorescence of BHb by PG is a static quenching procedure, and the hydrophobic interactions play a major role in binding of PG to BHb. Furthermore, synchronous fluorescence studies, Fourier transform infrared (FTIR) and circular dichroism (CD) spectra reveal that the conformation of BHb is changed after conjugation with PG.

  17. Studies on the binding behavior of prodigiosin with bovine hemoglobin by multi-spectroscopic techniques.

    PubMed

    Tang, Jing; Yang, Chao; Zhou, Lin; Ma, Fei; Liu, Shuchao; Wei, Shaohua; Zhou, Jiahong; Zhou, Yanhuai

    2012-10-01

    In this article, the interaction mechanism of prodigiosin (PG) with bovine hemoglobin (BHb) is studied in detail using various spectroscopic technologies. UV-vis absorption and fluorescence spectra demonstrate the interaction process. The Stern-Volmer plot and the time-resolved fluorescence study suggest the quenching mechanism of fluorescence of BHb by PG is a static quenching procedure, and the hydrophobic interactions play a major role in binding of PG to BHb. Furthermore, synchronous fluorescence studies, Fourier transform infrared (FTIR) and circular dichroism (CD) spectra reveal that the conformation of BHb is changed after conjugation with PG.

  18. Impedance spectroscopy study of a catechol-modified activated carbon electrode as active material in electrochemical capacitor

    NASA Astrophysics Data System (ADS)

    Cougnon, C.; Lebègue, E.; Pognon, G.

    2015-01-01

    Modified activated carbon (Norit S-50) electrodes with electrochemical double layer (EDL) capacitance and redox capacitance contributions to the electric charge storage were tested in 1 M H2SO4 to quantify the benefit and the limitation of the surface redox reactions on the electrochemical performances of the resulting pseudo-capacitive materials. The electrochemical performances of an electrochemically anodized carbon electrode and a catechol-modified carbon electrode, which make use both EDL capacitance of the porous structure of the carbon and redox capacitance, were compared to the performances obtained for the pristine carbon. Nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the BET surface area, pore size distribution, pore volume and average pore diameter. The electrochemical behavior of carbon materials was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The EIS data were discussed by using a complex capacitance model that allows defining the characteristic time constant, the global capacitance and the frequency at which the maximum charge stored is reached. The EIS measurements were achieved at different dc potential values where a redox activity occurs and the evolution of the capacitance and the capacitive relaxation time with the electrode potential are presented. Realistic galvanostatic charge/discharge measurements performed at different current rates corroborate the results obtained by impedance.

  19. Charge Carrier Conduction Mechanism in PbS Quantum Dot Solar Cells: Electrochemical Impedance Spectroscopy Study.

    PubMed

    Wang, Haowei; Wang, Yishan; He, Bo; Li, Weile; Sulaman, Muhammad; Xu, Junfeng; Yang, Shengyi; Tang, Yi; Zou, Bingsuo

    2016-07-20

    With its properties of bandgap tunability, low cost, and substrate compatibility, colloidal quantum dots (CQDs) are becoming promising materials for optoelectronic applications. Additionally, solution-processed organic, inorganic, and hybrid ligand-exchange technologies have been widely used in PbS CQDs solar cells, and currently the maximum certified power conversion efficiency of 9.9% has been reported by passivation treatment of molecular iodine. Presently, there are still some challenges, and the basic physical mechanism of charge carriers in CQDs-based solar cells is not clear. Electrochemical impedance spectroscopy is a monitoring technology for current by changing the frequency of applied alternating current voltage, and it provides an insight into its electrical properties that cannot be measured by direct current testing facilities. In this work, we used EIS to analyze the recombination resistance, carrier lifetime, capacitance, and conductivity of two typical PbS CQD solar cells Au/PbS-TBAl/ZnO/ITO and Au/PbS-EDT/PbS-TBAl/ZnO/ITO, in this way, to better understand the charge carriers conduction mechanism behind in PbS CQD solar cells, and it provides a guide to design high-performance quantum-dots solar cells. PMID:27176547

  20. Electrochemical Impedance Studies on Tribocorrosion Behavior of Plasma-Sprayed Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Liu, Zhe; Chu, Zhenhua; Chen, Xueguang; Dong, Yanchun; Yang, Yong; Li, Yingzhen; Yan, Dianran

    2015-06-01

    In this paper, the tribocorrosion of plasma-sprayed Al2O3 coatings in simulated seawater was investigated by electrochemical impedance spectroscopy (EIS) technique, complemented by scanning electron microscopy to observe the morphology of the tribocorrosion attack. Base on EIS of plasma-sprayed Al2O3 coatings undergoing long-time immersion in simulated seawater, the corrosion process of Al2O3 coatings can be divided into the earlier stage of immersion (up to 20 h) and the later stage (beyond 20 h). Then, the wear tests were carried out on the surface of Al2O3 coating undergoing different times of immersion to investigate the influence of wear on corrosion at different stages. The coexistence of wear and corrosion condition had been created by a boron nitride grinding head rotating on the surface of coatings corroded in simulated seawater. The measured EIS and the values of the fitting circuit elements showed that wear accelerated corrosion at the later stage, meanwhile, corrosion accelerated wear with the immersion time increasing.

  1. Sensitivity study of an ultrasound coupled transrectal electrical Impedance Tomography system for prostate imaging

    NASA Astrophysics Data System (ADS)

    Wan, Y.; Halter, R.; Borsic, A.; Manwaring, P.; Hartov, A.; Paulsen, K.

    2010-04-01

    In 2009, prostate cancer ranks as the most common cancer and the second most fatal cancer in men in the United States. Unfortunately, the current clinical diagnostic methods (e.g. prostate-specific antigen (PSA), digital rectal examination, endorectal MRI, transrectal ultrasound, biopsy) used for detecting and staging prostate cancer are limited. It has been shown that cancerous prostate tissue has significantly different electrical properties when compared to benign tissues. Based on these electrical property findings, a TransRectal Electrical Impedance Tomography (TREIT) system is proposed as a novel prostate imaging modality. The TREIT system is comprised of an array of electrodes interfaced with a clinical TransRectal UltraSound (TRUS) probe. We evaluate this imaging system through series of phantom imaging experiments to assess the system's ability to image high and low contrast objects at various positions. We found that the TREIT system can easily discern high contrast inclusions of 1 cm in diameter at distances centered at 2 times the radius of the TREIT probe away from the probe surface. Furthermore, this technology's ability to detect low contrast inclusions suggests that it has the potential to successfully detect prostate cancer.

  2. Electrical impedance myography for the assessment of children with muscular dystrophy: a preliminary study

    PubMed Central

    Rutkove, S B; Darras, B T

    2013-01-01

    Electrical impedance myography (EIM) provides a non-invasive approach for quantifying the severity of neuromuscular disease. Here we determine how well EIM data correlates to functional and ultrasound (US) measures of disease in children with Duchenne muscular dystrophy (DMD) and healthy subjects. Thirteen healthy boys, aged 2-12 years and 14 boys with DMD aged 4-12 years underwent both EIM and US measurements of deltoid, biceps, wrist flexors, quadriceps, tibialis anterior, and medial gastrocnemius. EIM measurements were performed with a custom-designed probe using a commercial multifrequency bioimpedance device. US luminosity data were quantified using a gray-scale analysis approach. Children also underwent the 6-minute walk test, timed tests and strength measurements. EIM and US data were combined across muscles. EIM 50 kHz phase was able to discriminate DMD children from healthy subjects with 98% accuracy. In the DMD patients, average EIM phase measurements also correlated well with standard functional measures. For example the 50 kHz phase correlated with the Northstar Ambulatory Assessment test (R = 0.83, p = 0.02). EIM 50 kHz phase and US correlated as well, with R = −0.79 (p < 0.001). These results show that EIM provides valuable objective measures Duchenne muscular dystrophy severity. PMID:23894248

  3. Effects of Operating Conditions on Internal Resistances in Enzyme Fuel Cells Studied via Electrochemical Impedance Spectroscopy

    SciTech Connect

    Aaron, D; Borole, Abhijeet P; Yiacoumi, Sotira; Tsouris, Costas

    2012-01-01

    Enzyme fuel cells (EFCs) offer some advantages over traditional precious-metal-catalyzed fuel cells, such as polymer electrolyte membrane fuel cells (PEMFCs). However, EFCs exhibit far less power output than PEMFCs and have relatively short life spans before materials must be replaced. In this work, electrochemical impedance spectroscopy (EIS) is used to analyze the internal resistances throughout the EFC at a variety of operating conditions. EIS analysis is focused primarily on the resistances of the anode, solution/membrane, and cathode. Increased enzyme loading results in improved power output and reductions in internal resistance. Conditions are identified for which enzyme loading does not limit the EFC performance. EIS experiments are also reported for EFCs operated continuously for 2 days; power output declines sharply over time, while all internal resistances increase. Drying of the cathode and enzyme/mediator degradation are believed to have contributed to this behavior. Finally, experiments are performed at varying air-humidification temperatures. Little effect on internal resistances or power output is observed. However, it is anticipated that increased air humidification can improve longevity by delivering more water to the cathode. Improvements to the enzymatic cathode are needed for EFC development. These improvements need to focus on improving transport rather than increasing enzyme loading.

  4. Charge Carrier Conduction Mechanism in PbS Quantum Dot Solar Cells: Electrochemical Impedance Spectroscopy Study.

    PubMed

    Wang, Haowei; Wang, Yishan; He, Bo; Li, Weile; Sulaman, Muhammad; Xu, Junfeng; Yang, Shengyi; Tang, Yi; Zou, Bingsuo

    2016-07-20

    With its properties of bandgap tunability, low cost, and substrate compatibility, colloidal quantum dots (CQDs) are becoming promising materials for optoelectronic applications. Additionally, solution-processed organic, inorganic, and hybrid ligand-exchange technologies have been widely used in PbS CQDs solar cells, and currently the maximum certified power conversion efficiency of 9.9% has been reported by passivation treatment of molecular iodine. Presently, there are still some challenges, and the basic physical mechanism of charge carriers in CQDs-based solar cells is not clear. Electrochemical impedance spectroscopy is a monitoring technology for current by changing the frequency of applied alternating current voltage, and it provides an insight into its electrical properties that cannot be measured by direct current testing facilities. In this work, we used EIS to analyze the recombination resistance, carrier lifetime, capacitance, and conductivity of two typical PbS CQD solar cells Au/PbS-TBAl/ZnO/ITO and Au/PbS-EDT/PbS-TBAl/ZnO/ITO, in this way, to better understand the charge carriers conduction mechanism behind in PbS CQD solar cells, and it provides a guide to design high-performance quantum-dots solar cells.

  5. Electrical impedance myography for the assessment of children with muscular dystrophy: a preliminary study

    NASA Astrophysics Data System (ADS)

    Rutkove, S. B.; Darras, B. T.

    2013-04-01

    Electrical impedance myography (EIM) provides a non-invasive approach for quantifying the severity of neuromuscular disease. Here we determine how well EIM data correlates to functional and ultrasound (US) measures of disease in children with Duchenne muscular dystrophy (DMD) and healthy subjects. Thirteen healthy boys, aged 2-12 years and 14 boys with DMD aged 4-12 years underwent both EIM and US measurements of deltoid, biceps, wrist flexors, quadriceps, tibialis anterior, and medial gastrocnemius. EIM measurements were performed with a custom-designed probe using a commercial multifrequency bioimpedance device. US luminosity data were quantified using a gray-scale analysis approach. Children also underwent the 6-minute walk test, timed tests and strength measurements. EIM and US data were combined across muscles. EIM 50 kHz phase was able to discriminate DMD children from healthy subjects with 98% accuracy. In the DMD patients, average EIM phase measurements also correlated well with standard functional measures. For example the 50 kHz phase correlated with the Northstar Ambulatory Assessment test (R = 0.83, p = 0.02). EIM 50 kHz phase and US correlated as well, with R = -0.79 (p < 0.001). These results show that EIM provides valuable objective measures Duchenne muscular dystrophy severity.

  6. Study of spectroscopic and thermal characteristics of nonlinear optical molecular crystals based on 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Pavlovetc, I. M.; Fokina, M. I.

    2016-08-01

    The paper presents the results of study of spectroscopic and thermal characteristics of molecular co-crystals: 2-aminopyridine-4-nitrophenol-4-mtrophenolate (2AP4N) and 2,6- diaminopyridine-4-nitrophenol-4nitrophenolate (26DAP4N). Crystals were successfully grown by slow evaporation technique. Optical transparency in the region of 190-1100 was found to be suitable for applications with cut off wavelengths 420 and 430 nm respectively. Thermogravimetric and differential thermal analysis show good quality and thermal stability for studied crystals. Kurtz and Perry powder technique proves that the crystals are acentric and have significant nonlinear optical response.

  7. Spectroscopic study of sub-barrier quasi-elastic nuclear reactions

    SciTech Connect

    Pass, C.N.; Evans, P.M.; Smith, A.E.; Stuttge, L.; Betts, R.R.; Lilley, J.S.; Connell, K.A.; Simpson, J.; Smith, J.R.; James, A.N.

    1988-01-01

    The technique developed in this paper is particularly well suited to the detailed spectroscopic study of low energy quasi-elastic nuclear reactions and by overcoming the limitations of conventional procedure, the prospect of detailed studies of inclusive reaction mechanism may be realised. With only limited statistics we find evidence for strong multistep character in the transfer of a single nucleon from spherical vibrational target to spherical projectile nuclei. The suggestive measurements reported here may be made definitive through extended runs based on this technique and experiments planned for the future offer the real prospect of developing a quantified interpretation of the reaction process. 9 refs. 5 figs.

  8. ADVANCES IN IMPEDANCE THEORY

    SciTech Connect

    Stupakov, G.; /SLAC

    2009-06-05

    We review recent progress in the following areas of the impedance theory: calculation of impedance of tapers and small angle collimators; optical approximation and parabolic equation for the high-frequency impedance; impedance due to resistive inserts in a perfectly conducting pipe.

  9. Impedance analysis of acupuncture points and pathways

    NASA Astrophysics Data System (ADS)

    Teplan, Michal; Kukučka, Marek; Ondrejkovičová, Alena

    2011-12-01

    Investigation of impedance characteristics of acupuncture points from acoustic to radio frequency range is addressed. Discernment and localization of acupuncture points in initial single subject study was unsuccessfully attempted by impedance map technique. Vector impedance analyses determined possible resonant zones in MHz region.

  10. Synthesis, spectroscopic characterizations, crystal structures and DFT studies of nalidixic acid carbonyl hydrazones derivatives

    NASA Astrophysics Data System (ADS)

    Bergamini, F. R. G.; Ribeiro, M. A.; Lancellotti, M.; Machado, D.; Miranda, P. C. M. L.; Cuin, A.; Formiga, A. L. B.; Corbi, P. P.

    2016-09-01

    This article describes the synthesis and characterization of the 1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carbohydrazide (hzd) and six carbonyl hydrazones derivatives of the nalidixic with 1H-pyrrol-2-ylmethylidene (hpyrr), 1H-imidazol-2-ylmethylidene (h2imi), pyridin-2-ylmethylidene (h2py), pyridin-3-ylmethylidene (h3py), pyridin-4-ylmethylidene(h4py) and (2-hydroxyphenyl)methylidene (hsali). The carbonyl hydrazones were characterized by elemental and ESI-QTOF-MS analyses, IR and detailed NMR spectroscopic measurements. The 2D NMR experiments allowed the unambiguous assignment of the hydrogen, carbon and nitrogen atoms, which have not been reported for nalidixic acid carbonyl hydrazone derivatives so far. Crystal structures of hzd and the new carbonyl hydrazones h2imi, hpyrr and h3py were determined by X-ray diffraction studies. Although the synthesis of hzd was reported decades ago, the hzd crystal structure have not been reported yet. Geometric optimizations of all the characterized structures were performed with the aid of DFT studies. Despite the fact that the hydrazones with 2-pyridine carboxylic acid (h2py) and salicyl aldehyde (hsali) were already reported by literature, a detailed spectroscopic study followed by DFT studies are also reported for such compounds in this manuscript. Antimicrobial studies of the compounds are also presented.

  11. The RbCs X(1)Sigma(+) Ground Electronic State: New Spectroscopic Study.

    PubMed

    Fellows; Gutterres; Campos; Vergès; Amiot

    1999-09-01

    In this paper a new spectroscopic investigation on the X(1)Sigma(+) electronic ground state of the RbCs molecule is reported. This study is conducted by using laser-induced fluorescence combined with Fourier transform spectroscopy (LIF-FTS). More than 23 000 spectral data are used in a global linear reduction to molecular constants. With these new and improved molecular constants, the potential energy curve has been calculated by the inverted perturbation approach (IPA). Accurate values for the dissociation energy and the long-range parameters have been derived. Copyright 1999 Academic Press.

  12. Thermal Physical, and Infrared Spectroscopic Studies on Glasses Prepared by Microwave Route

    SciTech Connect

    Jagadeesha, N.; Gowda, V. C. Veeranna; Chakradhar, R. P. S.; Reddy, C. Narayana

    2011-07-15

    This paper describes thermal, physical and spectroscopic properties of glasses prepared by a novel micro wave method. These studies exhibited a strong compositional dependent trend and existence of characteristic boro-vanadate groups in these glasses. The scheme of modification of borate and vanadate groups is controlled by Sanderson's electronegativity principle. Analysis of density and glass transition temperatures suggests the presence of characteristic four coordinated borate and diboro - vanadate groups in these glasses. The presence of [BO{sub 4/2}]{sup -} and [B{sub 2}V{sub 2}O{sub 9}]{sup 2-}) groups are confirmed by Infrared Spectroscopy of investigated glasses.

  13. Spectroscopic studies of amino acid ionic liquid-supported Schiff bases.

    PubMed

    Ossowicz, Paula; Janus, Ewa; Schroeder, Grzegorz; Rozwadowski, Zbigniew

    2013-04-29

    Amino acid ionic liquid-supported Schiff bases, derivatives of salicylaldehyde and various amino acids (L-threonine, L-valine, L-leucine, L-isoleucine and L-histidine) have been investigated by means of various spectroscopic techniques (NMR, UV-Vis, IR, MS) and deuterium isotope effects on ¹³C-NMR chemical shifts. The results have shown that in all studied amino acid ionic liquid-supported Schiff bases (except the L-histidine derivative) a proton transfer equilibrium exists and the presence of the COO⁻ group stabilizes the proton transferred NH-form.

  14. Quantitative carbon-13 nuclear magnetic resonance spectroscopic study of mobile residues in bacteriorhodopsin

    SciTech Connect

    Bowers, J.L.; Oldfield, E.

    1988-07-12

    The authors have used quantitative carbon-13 nuclear magnetic resonance (NMR) spectroscopy to study the dynamic structure of the backbone of bacteriorhodopsin in the purple membrane of Halobacterium halobium R/sub 1/ and JW-3. NMR experiments were performed using an internal sucrose quantitation standard on purple membranes in which one of the following /sup 13/C'-labeled amino acids had been biosynthetically incorporated: glycine, isoleucine, lysine, phenylalanine, and valine. The results suggest that the C-terminus of the polypeptide chain backbone, and possibly one of the connecting loops, undergoes rapid, large angle fluctuations. The results are compared with previous NMR and fluorescence spectroscopic data obtained on bacteriorhodopsin.

  15. Infrared and Raman spectroscopic studies on alkali borate glasses: evidence of mixed alkali effect.

    PubMed

    Padmaja, G; Kistaiah, P

    2009-03-19

    A lithium-potassium-borate glass system containing manganese and iron cations has been thoroughly investigated in order to obtain information about the mixed alkali effect and the structural role of both the manganese and iron in such glass hosts. Mixed alkali borate glasses of the (30 - x)Li(2)O - xK(2)O - 10CdO/ZnO - 59B(2)O(3) (x = 0, 10, 15, 20, and 30) doped with 1MnO(2)/1Fe(2)O(3) system were prepared by a melt quench technique. The amorphous phase of the prepared glass samples was confirmed from their X-ray diffraction. The spectroscopic properties of glass samples were studied using infrared (IR) and Raman spectroscopic techniques. The density of all the prepared glasses was measured using Archimedes principle. Molar volumes were estimated from the density data. IR spectra of these glasses revealed a dramatic variation of three- and four-coordinated boron structures as a function of mixed alkali concentration. The vibrations due to Li-O, K-O, and MnO(4)/FeO(4) arrangements are consistent in all the compositions and show a nonlinear variation in the intensity with alkali content. Raman spectra of different alkali combinations with CdO and ZnO present drastic changes in the intensity of various Raman bands. The observation of disappearance and reappearance of IR and Raman bands as a function of various alkali concentrations is an important result pertaining to the mixed alkali effect in borate glasses. Acting as complementary spectroscopic techniques, both types of measurements, IR and Raman, revealed that the network structure of the studied glasses is mainly based on BO(3) and BO(4) units placed in different structural groups, the BO(3) units being dominant. The measured IR and Raman spectra of different glasses are used to clarify the optical properties of the present glasses correlating them with their structure and composition. PMID:19235995

  16. Binding of copper to lysozyme: Spectroscopic, isothermal titration calorimetry and molecular docking studies.

    PubMed

    Jing, Mingyang; Song, Wei; Liu, Rutao

    2016-07-01

    Although copper is essential to all living organisms, its potential toxicity to human health have aroused wide concerns. Previous studies have reported copper could alter physical properties of lysozyme. The direct binding of copper with lysozyme might induce the conformational and functional changes of lysozyme and then influence the body's resistance to bacterial attack. To better understand the potential toxicity and toxic mechanisms of copper, the interaction of copper with lysozyme was investigated by biophysical methods including multi-spectroscopic measurements, isothermal titration calorimetry (ITC), molecular docking study and enzyme activity assay. Multi-spectroscopic measurements proved that copper quenched the intrinsic fluorescence of lysozyme in a static process accompanied by complex formation and conformational changes. The ITC results indicated that the binding interaction was a spontaneous process with approximately three thermodynamical binding sites at 298K and the hydrophobic force is the predominant driven force. The enzyme activity was obviously inhibited by the addition of copper with catalytic residues Glu 35 and Asp 52 locating at the binding sites. This study helps to elucidate the molecular mechanism of the interaction between copper and lysozyme and provides reference for toxicological studies of copper.

  17. Binding of copper to lysozyme: Spectroscopic, isothermal titration calorimetry and molecular docking studies.

    PubMed

    Jing, Mingyang; Song, Wei; Liu, Rutao

    2016-07-01

    Although copper is essential to all living organisms, its potential toxicity to human health have aroused wide concerns. Previous studies have reported copper could alter physical properties of lysozyme. The direct binding of copper with lysozyme might induce the conformational and functional changes of lysozyme and then influence the body's resistance to bacterial attack. To better understand the potential toxicity and toxic mechanisms of copper, the interaction of copper with lysozyme was investigated by biophysical methods including multi-spectroscopic measurements, isothermal titration calorimetry (ITC), molecular docking study and enzyme activity assay. Multi-spectroscopic measurements proved that copper quenched the intrinsic fluorescence of lysozyme in a static process accompanied by complex formation and conformational changes. The ITC results indicated that the binding interaction was a spontaneous process with approximately three thermodynamical binding sites at 298K and the hydrophobic force is the predominant driven force. The enzyme activity was obviously inhibited by the addition of copper with catalytic residues Glu 35 and Asp 52 locating at the binding sites. This study helps to elucidate the molecular mechanism of the interaction between copper and lysozyme and provides reference for toxicological studies of copper. PMID:27089183

  18. Binding of copper to lysozyme: Spectroscopic, isothermal titration calorimetry and molecular docking studies

    NASA Astrophysics Data System (ADS)

    Jing, Mingyang; Song, Wei; Liu, Rutao

    2016-07-01

    Although copper is essential to all living organisms, its potential toxicity to human health have aroused wide concerns. Previous studies have reported copper could alter physical properties of lysozyme. The direct binding of copper with lysozyme might induce the conformational and functional changes of lysozyme and then influence the body's resistance to bacterial attack. To better understand the potential toxicity and toxic mechanisms of copper, the interaction of copper with lysozyme was investigated by biophysical methods including multi-spectroscopic measurements, isothermal titration calorimetry (ITC), molecular docking study and enzyme activity assay. Multi-spectroscopic measurements proved that copper quenched the intrinsic fluorescence of lysozyme in a static process accompanied by complex formation and conformational changes. The ITC results indicated that the binding interaction was a spontaneous process with approximately three thermodynamical binding sites at 298 K and the hydrophobic force is the predominant driven force. The enzyme activity was obviously inhibited by the addition of copper with catalytic residues Glu 35 and Asp 52 locating at the binding sites. This study helps to elucidate the molecular mechanism of the interaction between copper and lysozyme and provides reference for toxicological studies of copper.

  19. Application of electrical impedance tomography in diagnosis of emphysema--a clinical study.

    PubMed

    Eyüboğlu, B M; Oner, A F; Baysal, U; Biber, C; Keyf, A I; Yilmaz, U; Erdoğan, Y

    1995-08-01

    In this paper, electrical impedance tomography (EIT) ventilation images from a group of 12 patients (11 patients with emphysema and one patient with only chronic obstructive pulmonary disease (COPD) (chronic bronchitis) and a group of 15 normal subjects were acquired using a Sheffield mark 1 EIT system, at the levels of second, fourth and sixth intercostal spaces. Patients were diagnosed based on CT scans of the thorax, pulmonary function tests and posteroanterior x-ray graphs. One of the patients with emphysema has also a malignant lung tumour. Ventilation-related conductivity changes at total lung capacity (TLC) relative to residual volume were measured quantitatively in EIT images. These quantitative values demonstrate marked differences compared to those values obtained from the EIT images of 15 normal subjects. The EIT images of the patients were also compared with the CT images. In addition to the visual examination of the EIT images a statistical confidence test is applied to compare the images of the patients with the images of the normal subjects. Prior to statistical analysis all images are normalized with TLC to minimize the effect of mismatch between the TLC of different subjects. A normal mean image is created by averaging the normalized images from the normal subjects, at each intercostal space level. Than a 95% confidence interval is defined for each normal mean image. For each image of the patients, a confidence test image, which represents the deviations from the 95% confidence interval of the normal mean image, is created. The regions with emphysematous bulla and parencyhma are detectable in the confidence test images as regions of positive and negative deviations from the confidence interval of the normal mean, respectively. In the test images, it is possible to differentiate emphysematous parenchyma from emphysematous bulla, tumour structure, and COPD. However, the emphysematous bulla, the tumour structure, and COPD result in the same type of

  20. Spectroscopic studies on chemical- and photo-responsive molecular machines and their bio-applications

    NASA Astrophysics Data System (ADS)

    Lau, Yuen Agnes

    2011-07-01

    The four chapters presented in this dissertation describe how various spectroscopic techniques are used: 1) to study the operation of molecular machines in solution, 2) to track the operation of molecular machines inside a single cell, and 3) to investigate the photo-decomposition pathway of a biological chromophore. Recent advances in nanotechnology have enriched the development of nano-scale molecular assemblies to be used as delivery platforms for biologically relevant molecules. Among all the molecular assemblies, molecular machines that are incorporated onto various domains of mesoporous silica nanoparticles (MSN) hold considerable potential as a reliable delivery system. Because the ease of functionalization enables chemical or photo-responsive molecular moieties to be covalently attached to the silica framework, these molecular assemblies, with defined mechanized properties, can perform specific functions under external stimuli (pH, redox, or light). While the primary function of these molecular machines is to deliver stored cargo molecules, the means of activation and the motif in which they operate are different. In the first and second chapters of this dissertation, two types of molecular machines, nanovalves and nanoimpellers, and their operations are studied. The ability to continuously monitor and image progression of molecular-based biological events in real-time can enhance our understanding of intracellular processes upon drug, protein and nucleic acid delivery. Using the photo-activated nanoimpeller described in the second chapter, the third chapter explores how it can be used to transport a nuclear staining agent, PI, inside a single cell. Nanoimpellers are made by functionalizing azobenzene molecules to the internal pore surface of MSN. The continuous cis/trans isomerizations are set in motion upon laser illumination at optimal wavelength(s), which facilitate cargo molecules to be expelled from the pores to the surrounding medium. By refining a

  1. Spectroscopic and structural study of the newly synthesized heteroligand complex of copper with creatinine and urea.

    PubMed

    Gangopadhyay, Debraj; Singh, Sachin Kumar; Sharma, Poornima; Mishra, Hirdyesh; Unnikrishnan, V K; Singh, Bachcha; Singh, Ranjan K

    2016-02-01

    Study of copper complex of creatinine and urea is very important in life science and medicine. In this paper, spectroscopic and structural study of a newly synthesized heteroligand complex of copper with creatinine and urea has been discussed. Structural studies have been carried out using DFT calculations and spectroscopic analyses were carried out by FT-IR, Raman, UV-vis absorption and fluorescence techniques. The copper complex of creatinine and the heteroligand complex were found to have much increased water solubility as compared to pure creatinine. The analysis of FT-IR and Raman spectra helps to understand the coordination properties of the two ligands and to determine the probable structure of the heteroligand complex. The LIBS spectra of the heteroligand complex reveal that the complex is free from other metal impurities. UV-visible absorption spectra and the fluorescence emission spectra of the aqueous solution of Cu-Crn-urea heteroligand complex at different solute concentrations have been analyzed and the complex is found to be rigid and stable in its monomeric form at very low concentrations.

  2. Spectroscopic and structural study of the newly synthesized heteroligand complex of copper with creatinine and urea

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, Debraj; Singh, Sachin Kumar; Sharma, Poornima; Mishra, Hirdyesh; Unnikrishnan, V. K.; Singh, Bachcha; Singh, Ranjan K.

    2016-02-01

    Study of copper complex of creatinine and urea is very important in life science and medicine. In this paper, spectroscopic and structural study of a newly synthesized heteroligand complex of copper with creatinine and urea has been discussed. Structural studies have been carried out using DFT calculations and spectroscopic analyses were carried out by FT-IR, Raman, UV-vis absorption and fluorescence techniques. The copper complex of creatinine and the heteroligand complex were found to have much increased water solubility as compared to pure creatinine. The analysis of FT-IR and Raman spectra helps to understand the coordination properties of the two ligands and to determine the probable structure of the heteroligand complex. The LIBS spectra of the heteroligand complex reveal that the complex is free from other metal impurities. UV-visible absorption spectra and the fluorescence emission spectra of the aqueous solution of Cu-Crn-urea heteroligand complex at different solute concentrations have been analyzed and the complex is found to be rigid and stable in its monomeric form at very low concentrations.

  3. Spectroscopic studies of drugs used in the treatment of malignant tumors in ophthalmology

    NASA Astrophysics Data System (ADS)

    Pascu, Mihail-Lucian; Carstocea, Benone D.; Staicu, Angela; Ionita, Marcel A.; Truica, Sorina; Pascu, Ruxandra

    2001-10-01

    Two classes of substances which may be used in the treatment of malignant tumors in ophthalmology are studied from the point of view of their spectroscopic properties: synthetic porphyrines such as TNP, TPP, TSPP and Zn-TSPP and cytostatics such as 5-fluorouracil. The absorption, excitation and fluorescence spectra of the porphyrins are measured in water and DMSO solutions to allow their efficient use in photodynamic therapy studies at irradiation with UV-laser light. A spectroscopic study of 5-fluorouracyl, a cytostatic drug used in the treatment of ophthalmologic tumors is reported. Absorption, fluorescence excitation/emission spectra were measured for solutions of 5-fluorouracyl at 5 X 10-5 M concentration. The effects of UV-VIS irradiation of on the 5-fluorouracyl solutions were investigated. The irradiation was performed with a classical Xe lamp having a power density of 11 mW/cm2, at time intervals between 15 min and 60 min. While the absorption is not affected by light irradiation, the fluorescence of the solutions is increasing with the irradiation duration.

  4. The Distance to the Massive Galactic Cluster Westerlund 2 from a Spectroscopic and HST Photometric Study

    NASA Astrophysics Data System (ADS)

    Vargas Álvarez, Carlos A.; Kobulnicky, Henry A.; Bradley, David R.; Kannappan, Sheila J.; Norris, Mark A.; Cool, Richard J.; Miller, Brendan P.

    2013-05-01

    We present a spectroscopic and photometric determination of the distance to the young Galactic open cluster Westerlund 2 using WFPC2 imaging from the Hubble Space Telescope (HST) and ground-based optical spectroscopy. HST imaging in the F336W, F439W, F555W, and F814W filters resolved many sources previously undetected in ground-based observations and yielded photometry for 1136 stars. We identified 15 new O-type stars, along with two probable binary systems, including MSP 188 (O3 + O5.5). We fit reddened spectral energy distributions based on the Padova isochrones to the photometric data to determine individual reddening parameters RV and AV for O-type stars in Wd2. We find average values langRV rang = 3.77 ± 0.09 and langAV rang = 6.51 ± 0.38 mag, which result in a smaller distance than most other spectroscopic and photometric studies. After a statistical distance correction accounting for close unresolved binaries (factor of 1.08), our spectroscopic and photometric data on 29 O-type stars yield that Westerlund 2 has a distance langdrang = 4.16 ± 0.07 (random) +0.26 (systematic) kpc. The cluster's age remains poorly constrained, with an upper limit of 3 Myr. Finally, we report evidence of a faint mid-IR polycyclic aromatic hydrocarbon ring surrounding the well-known binary candidate MSP 18, which appears to lie at the center of a secondary stellar grouping within Westerlund 2. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  5. THE DISTANCE TO THE MASSIVE GALACTIC CLUSTER WESTERLUND 2 FROM A SPECTROSCOPIC AND HST PHOTOMETRIC STUDY

    SciTech Connect

    Vargas Alvarez, Carlos A.; Kobulnicky, Henry A.; Bradley, David R.; Kannappan, Sheila J.; Norris, Mark A.; Cool, Richard J.; Miller, Brendan P. E-mail: chipk@uwyo.edu E-mail: sheila@physics.unc.edu E-mail: rcool@obs.carnegiescience.edu

    2013-05-15

    We present a spectroscopic and photometric determination of the distance to the young Galactic open cluster Westerlund 2 using WFPC2 imaging from the Hubble Space Telescope (HST) and ground-based optical spectroscopy. HST imaging in the F336W, F439W, F555W, and F814W filters resolved many sources previously undetected in ground-based observations and yielded photometry for 1136 stars. We identified 15 new O-type stars, along with two probable binary systems, including MSP 188 (O3 + O5.5). We fit reddened spectral energy distributions based on the Padova isochrones to the photometric data to determine individual reddening parameters R{sub V} and A{sub V} for O-type stars in Wd2. We find average values (R{sub V} ) = 3.77 {+-} 0.09 and (A{sub V} ) = 6.51 {+-} 0.38 mag, which result in a smaller distance than most other spectroscopic and photometric studies. After a statistical distance correction accounting for close unresolved binaries (factor of 1.08), our spectroscopic and photometric data on 29 O-type stars yield that Westerlund 2 has a distance (d) = 4.16 {+-} 0.07 (random) +0.26 (systematic) kpc. The cluster's age remains poorly constrained, with an upper limit of 3 Myr. Finally, we report evidence of a faint mid-IR polycyclic aromatic hydrocarbon ring surrounding the well-known binary candidate MSP 18, which appears to lie at the center of a secondary stellar grouping within Westerlund 2.

  6. AC impedance spectroscopy studies on solid-state sintered zinc aluminum oxide (ZnAl2O4) ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, B. Rajesh; Rao, T. Subba

    2012-07-01

    In the present investigation Zinc Aluminum Oxide (ZnAl2O4) is prepared by solid-state reaction technique. Dielectric constant (ɛ'), dielectric loss(tan δ), ac conductivity (σac) as a function of temperature are studied by varying frequencies from 100 Hz to 1MHz using an impedance analyzer. The dielectric constant and dielectric loss increases gradually with an increase of temperature, but it decreases with increase of frequency. The ac conductivity (σac) also increases with increases of frequency. The transition peaks for ZnAl2O4 are observed at 490°C, 510°C, 520°C for the frequencies 1 KHz, 10 KHz and 100 KHz. No transition peaks are found for the frequency 100 Hz and 1 MHz because of high conductive loss.

  7. Corrosion protection of copper by polypyrrole film studied by electrochemical impedance spectroscopy and the electrochemical quartz microbalance

    NASA Astrophysics Data System (ADS)

    Lei, Yanhua; Ohtsuka, Toshiaki; Sheng, Nan

    2015-12-01

    Polypyrrole (PPy) films were synthesized on copper in solution of sodium di-hydrogen phosphate and phytate for corrosion protection. The protection properties of PPy films were comparatively investigated in NaCl solution. During two months immersion, the PPy film doped with phytate anions, working as a cationic perm-selective membrane, inhibited the dissolution of copper to 1% of bare copper. Differently, the PPy film doped with di-hydrogen phosphate anions, possessing anionic perm-selectivity, was gradually reduced, and inhibited the dissolution to 7.8% of bare copper. Degradation of the PPy films was studied by comparing the electrochemical impedance spectroscopy change at different immersion time and Raman spectra change after immersion.

  8. Rapid Electron Transport Phenomenon in the Bis(terpyridine) Metal Complex Wire: Marcus Theory and Electrochemical Impedance Spectroscopy Study.

    PubMed

    Maeda, Hiroaki; Sakamoto, Ryota; Nishihara, Hiroshi

    2015-10-01

    The authors reported previously that bis(terpyiridne)iron(II) complex oligomer wires possess outstanding long-range intrawire electron transport ability. Here, molecular arrays of gold-electrode-bis(terpyridine)iron(II)-ferrocene are constructed by stepwise coordination as simple models of the oligomer wire system. The fast electron transfer between the terminal ferrocene and the gold electrode through the bis(terpyiridne)iron(II) complex unit is studied by potential step chronoamperometry (PSCA) and electrochemical impedance spectroscopy (EIS). Tafel plots derived from PSCA are analyzed based on Marcus theory. The plots reveal greater first-order electron transfer rate constant, weaker electronic coupling between the terminal ferrocene and the gold electrode, and smaller reorganization energy than shown by a conventional ferrocenylalkanethiol self-assembled monolayer. The electron transfer rate constants estimated by EIS agree with the PSCA results.

  9. Dopant effects on 2-ethyl-1-hexanol: A dual-channel impedance spectroscopy and neutron scattering study

    NASA Astrophysics Data System (ADS)

    Singh, Lokendra P.; Raihane, Ahmed; Alba-Simionesco, Christiane; Richert, Ranko

    2015-01-01

    A two-channel impedance technique has been used to study the relaxation behavior of 2-ethyl-1-hexanol with polar and non-polar dopants at the few percent concentration level over a wide temperature and frequency range. The non-polar dopants shift both the Debye and the primary structural relaxation time in the same direction, to shorter times for 3-methylpentane and to longer times for squalane, consistent with the relative glass transition temperatures (Tg) of the components. By contrast, polar dopants such as water or methanol modify the α-process towards slower dynamics and increased amplitude, while the Debye process is accelerated and with a decreased amplitude. This effect of adding water to alcohol is explained by water promoting more compact structures with reduced Kirkwood correlation factors. This picture is consistent with a shift in the neutron scattering pre-peak to lower scattering vectors and with simulation work on alcohol-water systems.

  10. Dopant effects on 2-ethyl-1-hexanol: a dual-channel impedance spectroscopy and neutron scattering study.

    PubMed

    Singh, Lokendra P; Raihane, Ahmed; Alba-Simionesco, Christiane; Richert, Ranko

    2015-01-01

    A two-channel impedance technique has been used to study the relaxation behavior of 2-ethyl-1-hexanol with polar and non-polar dopants at the few percent concentration level over a wide temperature and frequency range. The non-polar dopants shift both the Debye and the primary structural relaxation time in the same direction, to shorter times for 3-methylpentane and to longer times for squalane, consistent with the relative glass transition temperatures (Tg) of the components. By contrast, polar dopants such as water or methanol modify the α-process towards slower dynamics and increased amplitude, while the Debye process is accelerated and with a decreased amplitude. This effect of adding water to alcohol is explained by water promoting more compact structures with reduced Kirkwood correlation factors. This picture is consistent with a shift in the neutron scattering pre-peak to lower scattering vectors and with simulation work on alcohol-water systems.

  11. Study of caffeine as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    NASA Astrophysics Data System (ADS)

    Solehudin, Agus; Berman, Ega Taqwali; Nurdin, Isdiriayani

    2015-09-01

    The corrosion behaviour of steel surface in the absence and presence of caffeine in 3.5% NaCl solution containing dissolved H2S gas is studied using electrochemical impedance spectroscopy (EIS). The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H2S at different caffeine concentrations showed that corrosion rate of carbon steel decreases with increasing of caffeine concentrations from 0 to 0,1 mmol/l. Whereas, the corrosion rate increase with increasing of caffeine concentrations from 1 to 10 mmol/l. It is clear that no inhibition efficiency increases with increasing inhibitor concentration. The optimum value of inhibition efficiency was 90% at a caffeine concentration of 0.1 mmol/l. This suggests that caffeine's performance as a corrosion inhibitor is more effective at a concentration of 0.1 mmol/l.

  12. Dopant effects on 2-ethyl-1-hexanol: A dual-channel impedance spectroscopy and neutron scattering study

    SciTech Connect

    Singh, Lokendra P.; Richert, Ranko; Raihane, Ahmed; Alba-Simionesco, Christiane

    2015-01-07

    A two-channel impedance technique has been used to study the relaxation behavior of 2-ethyl-1-hexanol with polar and non-polar dopants at the few percent concentration level over a wide temperature and frequency range. The non-polar dopants shift both the Debye and the primary structural relaxation time in the same direction, to shorter times for 3-methylpentane and to longer times for squalane, consistent with the relative glass transition temperatures (T{sub g}) of the components. By contrast, polar dopants such as water or methanol modify the α-process towards slower dynamics and increased amplitude, while the Debye process is accelerated and with a decreased amplitude. This effect of adding water to alcohol is explained by water promoting more compact structures with reduced Kirkwood correlation factors. This picture is consistent with a shift in the neutron scattering pre-peak to lower scattering vectors and with simulation work on alcohol-water systems.

  13. Theoretical DFT study on spectroscopic signature and molecular dynamics of neurotransmitter and effect of hydrogen removal

    NASA Astrophysics Data System (ADS)

    Mukherjee, V.; Singh, N. P.; Yadav, R. A.

    2013-04-01

    Vibrational spectroscopic study has been made for the serotonin molecule and its deprotonated form. The Infrared and Raman spectra in optimum geometry of these two molecules are calculated using density functional theorem and the normal modes are assigned using potential energy distributions (PEDs) which are calculated using normal coordinate analysis method. The vibrational frequencies of these two molecules are reported and a comparison has been made. The effect of removal of the hydrogen atom from the serotonin molecule upon its geometry and vibrational frequencies are studied. Electronic structures of these two molecules are also studied using natural bond orbital (NBO) analysis. Theoretical Raman spectrum of serotonin at different exciting laser frequencies and at different temperatures are obtained and the results are discussed. Present study reveals that some wrong assignments had been made for serotonin molecule in earlier study.

  14. Inhibition of nickel precipitation by gluconate. 1: Kinetic studies and spectroscopic analyses

    SciTech Connect

    Hu, H.L.; Nikolaidis, N.P.; Grasso, D.

    1998-08-01

    The role of gluconate on nickel precipitation kinetics was evaluated through particle size distribution analyses, and the inhibition mechanisms were explored through spectroscopic studies. Batch kinetic studies showed that nickel precipitation does not achieve equilibrium within the time frame of typical process units. The molar ratio of gluconate to nickel had a profound effect on precipitation kinetics. A complete inhibition of nickel precipitation was observed when the molar concentration of gluconate was high, and a time-dependent resolubilization was observed at lower ratios. Particle size distribution indicated that nickel precipitates were colloidal in nature. Nucleation rates were promoted by the presence of gluconate; however, the removal efficiency decreased due to complexation reactions. Spectroscopic analysis of the solids suggested the presence of a mixture of two solids, a nickel-gluconate complex and a nickel hydroxide. The kinetics of the formation of the precipitates suggests that design of treatment units for the recovery of nickel in the metal finishing industry should be proceeded with advanced oxidation that would oxidize the organic impurities, before nickel recovery is accomplished.

  15. Laser spectroscopic and theoretical studies of the structures and encapsulation motifs of functional molecules

    SciTech Connect

    Ebata, Takayuki; Kusaka, Ryoji; Xantheas, Sotiris S.

    2015-01-22

    Extensive laser spectroscopic and theoretical studies have been recently carried out with the aim to reveal the structure and dynamics of encapsulation complexes in the gas phase. The characteristics of the encapsulation complexes are governed by the fact that (i) most of the host molecules are flexible and (ii) the complexes form high dimensional structures by using weak non-covalent interactions. These characteristics result in the possibility of the coexistence of many conformers in close energetic proximity. The combination of supersonic jet/laser spectroscopy and high level quantum chemical calculations is essential in tackling these challenging problems. In this report we describe our recent studies on the structures and dynamics of the encapsulation complexes formed by calix[4]arene (C4A), dibenzo-18-crown-6-ether (DB18C6), and benzo-18-crown-6-ether (B18C6) 'hosts' interacting with N{sub 2}, acetylene, water, and ammonia 'guest' molecules. The gaseous host-guest complexes are generated under jet-cooled conditions. We apply various laser spectroscopic methods to obtain the conformer- and isomer-specified electronic and IR spectra. The experimental results are complemented with quantum chemical calculations ranging from density functional theory to high level first principles calculations at the MP2 and CCSD(T) levels of theory. We discuss the possible conformations of the bare host molecules, the structural changes they undergo upon complexation, and the key interactions that are responsible in stabilizing the specific complexes.

  16. Laser Spectroscopic and Theoretical Studies of the Structures and Encapsulation Motifs of Functional Molecules

    SciTech Connect

    Ebata, Takayuki; Kusaka, Ryoji; Xantheas, Sotiris S.

    2015-02-01

    Extensive laser spectroscopic and theoretical studies have been recently carried out with the aim to reveal the structure and dynamics of encapsulation complexes in the gas phase. The characteristics of the encapsulation complexes are governed by the fact that (i) most of the host molecules are flexible and (ii) the complexes form high dimensional structures by using weak non-covalent interactions. These characteristics result in the possibility of the coexistence of many conformers in close energetic proximity. The combination of supersonic jet/laser spectroscopy and high level quantum chemical calculations is essential in tackling these challenging problems. In this report we describe our recent studies on the structures and dynamics of the encapsulation complexes formed by calix[4]arene (C4A), dibenzo-18-crown-6-ether (DB18C6), and benzo-18-crown-6-ether (B18C6) "hosts" interacting with N2, acetylene, water, and ammonia "guest" molecules. The gaseous host-guest complexes are generated under jet-cooled conditions. We apply various laser spectroscopic methods to obtain the conformer- and isomer-specified electronic and IR spectra. The experimental results are complemented with quantum chemical calculations ranging from density functional theory to high level first principles calculations at the MP2 and CCSD(T) levels of theory. We discuss the possible conformations of the bare host molecules, the structural changes they undergo upon complexation, and the key interactions that are responsible in stabilizing the specific complexes

  17. Laser spectroscopic and theoretical studies of the structures and encapsulation motifs of functional molecules

    NASA Astrophysics Data System (ADS)

    Ebata, Takayuki; Kusaka, Ryoji; Xantheas, Sotiris S.

    2015-01-01

    Extensive laser spectroscopic and theoretical studies have been recently carried out with the aim to reveal the structure and dynamics of encapsulation complexes in the gas phase. The characteristics of the encapsulation complexes are governed by the fact that (i) most of the host molecules are flexible and (ii) the complexes form high dimensional structures by using weak non-covalent interactions. These characteristics result in the possibility of the coexistence of many conformers in close energetic proximity. The combination of supersonic jet/laser spectroscopy and high level quantum chemical calculations is essential in tackling these challenging problems. In this report we describe our recent studies on the structures and dynamics of the encapsulation complexes formed by calix[4]arene (C4A), dibenzo-18-crown-6-ether (DB18C6), and benzo-18-crown-6-ether (B18C6) "hosts" interacting with N2, acetylene, water, and ammonia "guest" molecules. The gaseous host-guest complexes are generated under jet-cooled conditions. We apply various laser spectroscopic methods to obtain the conformer- and isomer-specified electronic and IR spectra. The experimental results are complemented with quantum chemical calculations ranging from density functional theory to high level first principles calculations at the MP2 and CCSD(T) levels of theory. We discuss the possible conformations of the bare host molecules, the structural changes they undergo upon complexation, and the key interactions that are responsible in stabilizing the specific complexes.

  18. [Fluorescence spectroscopic study of interaction between Fe-protoporphyrin in myoglobin and Cu(II) ions].

    PubMed

    Feng, Yu-ying; Yang, Hui; Gu, Xiao-tian; Jiang, Hui-jun; Lu, Tian-hong

    2003-06-01

    In this paper, the interaction between Cu(II) ions and Fe-protoporphyrin in horse-heart myoglobin (FePP-Mb) was studied. As a result, some of the Fe(II) ions in FePP-Mb were found to be replaced by Cu(II) ions forming CuPP-Mb, by adding Cu(II) ions into the myoglobin solution. The interaction became stronger when adding more Cu(II) ions into the myoglobin solution. By studying the metal ions' interaction with myoglobin proteins as macromolecules and discussing the interaction mechanism, this work provides a theoretical basis for the further study of hazardous metal ions' interaction with the human body and its mechanism. The fluorescence spectroscopic method used in this study has higher sensitivity than the ordinary UV and CD methods.

  19. Extra-cellular volume estimation by electrical impedance--phase measurement or curve fitting: a comparative study.

    PubMed

    Goovaerts, H G; Faes, T J; de Valk-de Roo, G W; ten Bolscher, M; Netelenbosch, J C; van der Vijgh, W J; Heethaar, R M

    1998-11-01

    In order to determine body fluid shifts between the intra- and extra-cellular spaces, multifrequency impedance measurement is performed. According to the Cole-Cole extrapolation, lumped values of intra- and extra-cellular conduction can be estimated which are commonly expressed in resistances Ri and Re respectively. For this purpose the magnitude and phase of the impedance under study are determined at a number of frequencies in the range between 5 kHz and 1 MHz. An approach to determine intra- and extra-cellular conduction on the basis of Bode analysis is presented in this article. On this basis, estimation of the ratio between intra- and extra-cellular conduction could be performed by phase measurement only, midrange in the bandwidth of interest. An important feature is that the relation between intra- and extra-cellular conduction can be continuously monitored by phase measurement and no curve fitting whatsoever is required. Based on a two frequency measurement determining Re at 4 kHz and phi(max) at 64 kHz it proved possible to estimate extra-cellular volume (ECV) more accurately compared with the estimation based on extrapolation according to the Cole-Cole model in 26 patients. Reference values of ECV were determined by sodium bromide. The results show a correlation of 0.90 with the reference method. The average error of ECV estimation was -3.6% (SD 8.4), whereas the Cole-Cole extrapolation showed an error of 13.2% (SD 9.5). An important feature of the proposed approach is that the relation between intra- and extra-cellular conduction can be continuously monitored by phase measurement and no curve fitting whatsoever is required.

  20. Low temperature FTIR, Raman, NMR spectroscopic and theoretical study of hydroxyethylammonium picrate

    NASA Astrophysics Data System (ADS)

    Sudharsana, N.; Sharma, A.; Kuş, N.; Fausto, R.; Luísa Ramos, M.; Krishnakumar, V.; Pal, R.; Guru Row, T. N.; Nagalakshmi, R.

    2016-01-01

    A combined experimental (infrared, Raman and NMR) and theoretical quantum chemical study is performed on the charge-transfer complex hydroxyethylammonium picrate (HEAP). The infrared (IR) spectra for HEAP were recorded at various temperatures, ranging from 16 K to 299 K, and the Raman spectrum was recorded at room temperature. A comparison of the experimental IR and Raman spectra with the corresponding calculated spectra was done, in order to facilitate interpretation of the experimental data. Formation of the HEAP complex is evidenced by the presence of the most prominent characteristic bands of the constituting groups of the charge-transfer complex [e.g., NH3+, CO- and NO2]. Vibrational spectroscopic analysis, together with natural bond orbital (NBO) and theoretical charge density analysis in the crystalline phase, was used to shed light on relevant structural details of HEAP resulting from deprotonation of picric acid followed by formation of a hydrogen bond of the N-H⋯OC type between the hydroxyethylammonium cation and the picrate. 13C and 1H NMR spectroscopic analysis are also presented for the DMSO-d6 solution of the compound revealing that in that medium the HEAP crystal dissolves forming the free picrate and hydroxyethylammonium ions. Finally, the electron excitation analysis of HEAP was performed in an attempt to determine the nature of the most important excited states responsible for the NLO properties exhibited by the compound.

  1. Studies on Nephrite and Jadeite Jades by Fourier Transform Infrared (ftir) and Raman Spectroscopic Techniques

    NASA Astrophysics Data System (ADS)

    Tan, T. L.; Ng, L. L.; Lim, L. C.

    2013-10-01

    The mineralogical properties of black nephrite jade from Western Australia are studied by Fourier transform infrared (FTIR) spectroscopy using both transmission and specular reflectance techniques in the 4000-400 cm-1 wavenumber region. The infrared absorption peaks in the 3700-3600 cm-1 region which are due to the O-H stretching mode provides a quantitative analysis of the Fe/(Fe+Mg) ratio in the mineral composition of jade samples. The Fe/(Fe+Mg) percentage in black nephrite is found to be higher than that in green nephrite, but comparable to that of actinolite (iron-rich nephrite). This implies that the mineralogy of black nephrite is closer to actinolite than tremolite. The jade is also characterized using Raman spectroscopy in the 1200-200 cm-1 region. Results from FTIR and Raman spectroscopic data of black nephrite jade are compared with those of green nephrite jade from New Zealand and jadeite jade from Myanmar. Black nephrite appears to have a slightly different chemical composition from green nephrite. Spectra from FTIR and Raman spectroscopic techniques were found to be useful in differentiating black nephrite, green nephrite, and green jadeite jades. Furthermore, data on refractive index, specific gravity, and hardness of black nephrite jade are measured and compared with those of green nephrite and of jadeite jade.

  2. A NEAR-INFRARED SPECTROSCOPIC STUDY OF YOUNG FIELD ULTRACOOL DWARFS

    SciTech Connect

    Allers, K. N.; Liu, Michael C.

    2013-08-01

    We present a near-infrared (0.9-2.4 {mu}m) spectroscopic study of 73 field ultracool dwarfs having spectroscopic and/or kinematic evidence of youth ( Almost-Equal-To 10-300 Myr). Our sample is composed of 48 low-resolution (R Almost-Equal-To 100) spectra and 41 moderate-resolution spectra (R {approx}> 750-2000). First, we establish a method for spectral typing M5-L7 dwarfs at near-IR wavelengths that is independent of gravity. We find that both visual and index-based classification in the near-IR provides consistent spectral types with optical spectral types, though with a small systematic offset in the case of visual classification at J and K band. Second, we examine features in the spectra of {approx}10 Myr ultracool dwarfs to define a set of gravity-sensitive indices based on FeH, VO, K I, Na I, and H-band continuum shape. We then create an index-based method for classifying the gravities of M6-L5 dwarfs that provides consistent results with gravity classifications from optical spectroscopy. Our index-based classification can distinguish between young and dusty objects. Guided by the resulting classifications, we propose a set of low-gravity spectral standards for the near-IR. Finally, we estimate the ages corresponding to our gravity classifications.

  3. Lanthanide and transition metal complexes of bioactive coumarins: molecular modeling and spectroscopic studies.

    PubMed

    Georgieva, I; Mihaylov, Tz; Trendafilova, N

    2014-06-01

    The present paper summarizes theoretical and spectroscopic investigations on a series of active coumarins and their lanthanide and transition metal complexes with application in medicine and pharmacy. Molecular modeling as well as IR, Raman, NMR and electronic spectral simulations at different levels of theory were performed to obtain important molecular descriptors: total energy, formation energy, binding energy, stability, conformations, structural parameters, electron density distribution, molecular electrostatic potential, Fukui functions, atomic charges, and reactive indexes. The computations are performed both in gas phase and in solution with consideration of the solvent effect on the molecular structural and energetic parameters. The investigations have shown that the advanced computational methods are reliable for prediction of the metal-coumarin binding mode, electron density distribution, thermodynamic properties as well as the strength and nature of the metal-coumarin interaction (not experimentally accessible) and correctly interpret the experimental spectroscopic data. Known results from biological tests for cytotoxic, antimicrobial, anti-fungal, spasmolytic and anti-HIV activities on the studied metal complexes are reported and discussed. PMID:24680836

  4. Design and validation of a multi-electrode bioimpedance system for enhancing spatial resolution of cellular impedance studies.

    PubMed

    Alexander, Frank A; Celestin, Michael; Price, Dorielle T; Nanjundan, Meera; Bhansali, Shekhar

    2013-07-01

    This paper reports the design and evaluation of a multi-electrode design that improves upon the statistical significance and spatial resolution of cellular impedance data measured using commercial electric cell-substrate impedance sensing (ECIS) systems. By evaluating cellular impedance using eight independent sensing electrodes, position-dependent impedance measurements can be recorded across the device and compare commonly used equivalent circuit and mathematical models for extraction of cell parameters. Data from the 8-electrode device was compared to data taken from commercial electric cell-substrate impedance sensing (ECIS) system by deriving a relationship between equivalent circuit and mathematically modelled parameters. The impedance systems were evaluated and compared by investigating the effects of arsenic trioxide (As2O3), a well-established chemotherapeutic agent, on ovarian cancer cells. Impedance spectroscopy, a non-destructive, label-free technique, was used to continuously measure the frequency-dependent cellular properties, without adversely affecting the cells. The importance of multiple measurements within a cell culture was demonstrated; and the data illustrated that the non-uniform response of cells within a culture required redundant measurements in order to obtain statistically significant data, especially for drug discovery applications. Also, a correlation between equivalent circuit modelling and mathematically modelled parameters was derived, allowing data to be compared across different modelling techniques.

  5. Quantitative infrared spectroscopic method for the study of the hydration of ions in aqueous solutions

    SciTech Connect

    Kristiansson, O.; Lindgren, J.; de Villepin, J.

    1988-05-05

    An infrared spectroscopic method for the study of the hydration of ions in aqueous solutions has been developed. OD stretching bands of isotopically dilute HDO molecules in the first hydration sphere of ions are obtained when the absorption from H/sub 2/O molecules and HDO molecules in the bulk water are removed by a double difference technique. The method is applied to aqueous solutions of Ni(ClO/sub 4/)/sub 2/, Ni(BF/sub 4/)/sub 2/, and Ni(PF/sub 6/)/sub 2/. Coordination numbers of 4.6 +/- 0.8 for the ClO/sub 4//sup -/ anion and 3.9 +/- 0.8 for the BF/sub 4//sup -/ anion are obtained. A systematic study of the influence of different salt and HDO concentrations has been undertaken. It is found that Lambert-Beer's law is valid in the concentration ranges studied.

  6. Spectroscopic study of N-acetylcysteine and N-acetylcystine/hydrogen peroxide complexation

    NASA Astrophysics Data System (ADS)

    Picquart, Michel; Abedinzadeh, Zohreh; Grajcar, Lydie; Baron, Marie Héléne

    1998-03-01

    A spectroscopic study of N-acetylcysteine (RSH) and N-acetylcystine (RSSR) has been performed using infrared absorption and Raman scattering in order to pinpoint the sites of complexation of these two species with H 2O 2. Molecules of RSH and RSSR were studied in KBr pellets, and in aqueous solutions of H 2O, D 2O and H 2O with H 2O 2 (1 mol l -1) to characterize the specific influence of the solvent molecules. A time-resolved Raman study was performed for RSH-H 2O 2 in aqueous solution at 1:1 molar ratio in order to observe the formation of RSSR and to discuss the mechanism of this redox reaction.

  7. Spectroscopic Studies on Eu{sup 3+} Doped Boro-Tellurite Glasses

    SciTech Connect

    Selvaraju, K.; Marimuthu, K.

    2011-07-15

    Eu{sup 3+} doped boro-tellurite glasses have been synthesized and its optical behavior have been studied and reported. The presence of varying tellurium dioxide content results changes in spectroscopic behavoir were explored through UV-VIS, and Luminescence spectra. The bonding parameters have been calculated based on the observed band positions of the absorption spectra. The Judd-Ofelt intensity parameters {Omega}{sub {lambda}} ({lambda} = 2, 4 and 6) have been determined through the luminescence spectra without applying any constraints and the results are presented. The Judd-Ofelt parameters have been used to determine various optical properties corresponding to {sup 5}D{sub 0}{yields}{sup 7}F{sub J}(J = 1,2,3 and 4) transitions of Eu{sup 3+} ions. The varying optical properties of the prepared glasses with the change in tellurium dioxide have been studied and compared with similar studies.

  8. Spectroscopic, crystallographic and theoretical studies of lasalocid complex with ammonia and benzylamine

    NASA Astrophysics Data System (ADS)

    Huczyński, Adam; Janczak, Jan; Rutkowski, Jacek; Brzezinski, Bogumil

    A natural antibiotic - Lasalocid is able to form stable complexes with ammonia and organic amines. New complexes of lasalocid with benzylamine and ammonia were obtained in the crystal forms and studied using X-ray, FT-IR, 1H NMR, 13C NMR and DFT methods. These studies have shown that in both complexes the proton is transferred from the carboxylic group to the amine group with the formation of a pseudo-cyclic structure of lasalocid anion complexing the protonated amine or NH4+ cation. The spectroscopic and DFT studies demonstrated that the structure of the complex formed between Lasalocid and benzylamine in the solid is also conserved in the solution and gas phase. In contrast, the structure of the complex formed between lasalocid and ammonium cation found in the solid state undergoes dissociation in chloroform solution accompanied with a change in the coordination form of the NH4+ cation.

  9. Impedance studies of Ni/Cd and Ni/H2 cells using the cell case as a reference electrode

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1989-01-01

    Impedance measurements have been made on several Ni/Cd and Ni/H2 flightweight cells using the case as a reference electrode. For these measurements the voltage of the case with respect to the anode or cathode is unimportant provided that it remains stable during the measurement of the impedance. In the cells measured so far, the voltages of the cell cases with respect to the individual electrodes differ from cell to cell even at the same overall cell voltage, but they remains stable with time. The measurements can thus be used to separate the cell impedance into the contributions of each electrode, allowing improved diagnosis of cell problems.

  10. Impedance studies of nickel/cadmium and nickel/hydrogen cells using the cell case as a reference electrode

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1990-01-01

    Impedance measurements have been made on several Ni/Cd and Ni/H2 flight-weight cells using the case as a reference electrode. For these measurements, the voltage of the case with respect to the anode or cathode is unimportant provided that it remains stable during the measurement of the impedance. In the cells measured so far, the voltage of the cell cases with respect to the individual electrodes differ from cell to cell, even at the same overall cell voltage, but they remain stable with time. The measurements can thus be used to separate the cell impedance into the contributions of each electrode, allowing improved diagnosis of cell problems.

  11. Preferential binding of fisetin to the native state of bovine serum albumin: spectroscopic and docking studies.

    PubMed

    Singha Roy, Atanu; Pandey, Nitin Kumar; Dasgupta, Swagata

    2013-04-01

    We have investigated the binding of the biologically important flavonoid fisetin with the carrier protein bovine serum albumin using multi-spectroscopic and molecular docking methods. The binding constants were found to be in the order of 10(4) M(-1) and the number of binding sites was determined as one. MALDI-TOF analyses showed that one fisetin molecule binds to a single bovine serum albumin (BSA) molecule which is also supported by fluorescence quenching studies. The negative Gibbs free energy change (∆G°) values point to a spontaneous binding process which occurs through the presence of electrostatic forces with hydrophobic association that results in a positive entropy change (+51.69 ± 1.18 J mol(-1) K(-1)). The unfolding and refolding of BSA in urea have been studied in absence and presence of fisetin using steady-state fluorescence and lifetime measurements. Urea denaturation studies indicate that fisetin is gradually released from its binding site on the protein. In the absence of urea, an increase in temperature that causes denaturation of the protein results in the release of fisetin from its bound state indicating that fisetin binds only to the native state of the protein. The circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopic studies showed an increase in % α-helix content of BSA after binding with fisetin. Site marker displacement studies in accordance with the molecular docking results suggested that fisetin binds in close proximity of the hydrophobic cavity in site 1 (subdomain IIA) of the protein. The PEARLS (Program of Energetic Analysis of Receptor Ligand System) has been used to estimate the interaction energy of fisetin with BSA and the results are in good correlation with the experimental findings.

  12. Photoreceptor pigments for photomovement of microorganisms: some spectroscopic and related studies.

    PubMed

    Lenci, F; Ghetti, F

    1989-02-01

    Optical spectroscopy of photoreceptor pigments can substantially contribute to our understanding of the molecular processes which are the basis of photoreception and sensory transduction in photomotile microorganisms. The main spectroscopic techniques are briefly illustrated, together with the most significant types of progress that can be achieved. A few "case examples" are discussed in some detail: Halobacterium, with particular attention to the contribution of flash photolysis studies to the identification and characterization of sensory rhodopsins; Euglena, and the role of in vivo microspectrofluorometry in confirming the flavin nature of its photoreceptor pigment; the first suggestions on the rhodopsin-like nature of the Chlamydomonas photosensing system; Stentor and Blepharisma and the contribution of static and time-resolved fluorescence studies to a molecular model of the primary events in their photoreceptor pigments (stentorin and blepharismin) and systems. PMID:2498475

  13. Dielectric studies of boron sub phthalocyanine chloride thin films by admittance spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Kalia, Sameer; Mahajan, Aman; Neerja, Sharma, Anshul Kumar; Kumar, Sanjeev; Bedi, R. K.

    2016-05-01

    The dielectric properties of Boron Sub Phthalocyanine Chloride (Cl-SubPc) thermally deposited on ITO substrate have been studied using admittance spectroscopic techniques. The I-V and capacitance -frequency (C-F) studies at various bias voltages reveal that the mobility of charge carriers decrease with bias voltage, however the conduction phenomenon still remain hopping in nature. From the differential susceptance curve, the contribution of the Schottky barrier contact in the charge carrier concentration was found to be absent. The mobility of charge carriers have been determined using differential susceptance variation and from the phase of admittance curve. The values obtained in two cases have been found to be in agreement with each other.

  14. Spectroscopic study of antileishmanial drug incubated in the promastigotes of Leishmania mexicana

    NASA Astrophysics Data System (ADS)

    Hung, J.; Castillo, J.; Jiménez, G.; Hasegawa, M.; Rodriguez, M.

    2003-11-01

    In this work we present spectroscopic study of Boldine (aporphine alkaloid) that possesses important biological activities, in particular, in interaction with the promastigotes of Leishmania mexicana. The results show the applicability of autofluorescence of this drug to determinate the possible mechanism of its biological action. The blue shift and hyperchromic effect in the emission spectrum of the drug in interaction with the parasite cells indicate an energy transference process between them. The morphological change of cell shape of the promastigotes treated with the drug is observed using confocal microscopy. This morphological cell-shape transformation evidences an important interaction between the drug studied and some protein of the parasite cell. Here we describe for the first time the fluorescence properties of the Boldine in the promastigotes of L. mexicana.

  15. Fundamental study of photoresist dissolution with real time spectroscopic ellipsometry and interferometry

    NASA Astrophysics Data System (ADS)

    Burns, Sean D.; Schmid, Gerard M.; Trinque, Brian C.; Willson, James; Wunderlich, Jennifer; Tsiartas, Pavlos C.; Taylor, James C.; Burns, Ryan L.; Wilson, C. Grant

    2003-06-01

    The use of in situ spectroscopic ellipsometry (SE) is demonstrated as a technique for studying photoresist dissolution. Experiments carried out using a J.A.Woollam M-2000 ellipsometer and a custom built cell designed for in situ film measurements show that bulk dissolution rate measurements using the SE technique agree with dissolution rate data obtained using multiwavelength interferometry. SE is also demonstrated as a method for measuring thin film dissolution rates, water sorption, and films that swell. An additional focus of this work was the topic of interfacial "gel" layer formation during photoresist dissolution. Ellipsometry and interferometry were used to test several photoresist resins, with an emphasis on phenolic polymers. Single and multiple layer models were used to analyze the data, and were compared to model calculations predicting formation of a gel layer. For the materials studied, interfacial gel layer formation in low molecular weight phenolic polymers was not detected, within the resolution of the experimental techniques (< 15 nm).

  16. Electronic properties of diphenyl-s-tetrazine and some related oligomers. An spectroscopic and theoretical study

    NASA Astrophysics Data System (ADS)

    Moral, Mónica; García, Gregorio; Peñas, Antonio; Garzón, Andrés; Granadino-Roldán, José M.; Melguizo, Manuel; Fernández-Gómez, Manuel

    2012-10-01

    This work presents a theoretical and spectroscopic study on the electronic and structural properties of the diphenyl-s-tetrazine molecule (Ph2Tz) and some oligomeric derivatives. Ph2Tz was synthesized through a variation of Pinner-type reaction which uses N-acetylcysteine as catalyst. Insight into the structure and electronic properties of the title compound was obtained through IR, Raman, UV-Vis spectra in different solvents, and theoretical calculations. Theoretical studies have been extended to different n-mers derivatives up to an ideal molecular wire through the oligomeric approximation, predicting this way electronic properties such as LUMO energy levels, electron affinity and reorganization energy in order to assess their possible applications in molecular electronics.

  17. Accurate molecular structure and spectroscopic properties for nucleobases: A combined computational - microwave investigation of 2-thiouracil as a case study

    PubMed Central

    Puzzarini, Cristina; Biczysko, Malgorzata; Barone, Vincenzo; Peña, Isabel; Cabezas, Carlos; Alonso, José L.

    2015-01-01

    The computational composite scheme purposely set up for accurately describing the electronic structure and spectroscopic properties of small biomolecules has been applied to the first study of the rotational spectrum of 2-thiouracil. The experimental investigation was made possible thanks to the combination of the laser ablation technique with Fourier Transform Microwave spectrometers. The joint experimental – computational study allowed us to determine accurate molecular structure and spectroscopic properties for the title molecule, but more important, it demonstrates a reliable approach for the accurate investigation of isolated small biomolecules. PMID:24002739

  18. FTIR spectroscopic studies of lipid dynamics in phytosphingosine ceramide models of the stratum corneum lipid matrix.

    PubMed

    Rerek, Mark E; Van Wyck, Dina; Mendelsohn, Richard; Moore, David J

    2005-03-01

    IR spectroscopic studies are reported for N-stearyl-D-erythro-phytosphingosine (Cer NP) and N-stearyl-2-hydroxy-D-erythro-phytosphingosine (Cer AP) in a hydrated model of the skin lipid barrier comprised of equimolar mixtures of each ceramide with cholesterol and d(35)-stearic acid. Examination of the methylene stretching, rocking and bending modes reveal some rotational freedom and hexagonal packing in both the ceramide and stearic acid chains. Analysis of the acid carbonyl stretch and the ceramide Amide I modes show both shift to higher frequencies, indicating weaker hydrogen bonding, in the mixed systems compared to the pure materials. For both systems, the fatty acid chain disordering temperatures are significantly increased from those of the pure acids. The observed behaviors of these phytosphingosine ceramide systems are fundamentally different from the previously reported analogous sphingosine ceramide systems. The implications of these observations for lipid organization in the stratum corneum are briefly discussed.

  19. Raman spectroscopic study on the excystation process in a single unicellular organism amoeba (Acanthamoeba polyphaga).

    PubMed

    Lin, Yu-Chung; Perevedentseva, Elena; Cheng, Chia-Liang

    2015-05-01

    An in vivo Raman spectroscopic study of amoeba (Acanthamoeba polyphaga) is presented. The changes of the spectra during the amoeba cyst activation and excystation are analyzed. The spectra show the changes of the relative intensities of bands corresponding to protein, lipid, and carotenoid components during cyst activation. The presence of carotenoids in the amoeba is observed via characteristic Raman bands. These signals in the Raman spectra are intense in cysts but decrease in intensity with cyst activation and exhibit a correlation with the life cycle of amoeba. This work demonstrates the feasibility of using Raman spectroscopy for the detection of single amoeba microorganisms in vivo and for the analysis of the amoeba life activity. The information obtained may have implications for the estimation of epidemiological situations and for the diagnostics and prognosis of the development of amoebic inflammations.

  20. Molecular interactions of flavonoids to pepsin: Insights from spectroscopic and molecular docking studies.

    PubMed

    Zeng, Hua-Jin; Yang, Ran; Liang, Huili; Qu, Ling-Bo

    2015-01-01

    In the work described on this paper, the inhibitory effect of 10 flavonoids on pepsin and the interactions between them were investigated by a combination of spectroscopic and molecular docking methods. The results indicated that all flavonoids could bind with pepsin to form flavonoid-pepsin complexes. The binding parameters obtained from the data at different temperatures revealed that flavonoids could spontaneously interact with pepsin mainly through electrostatic forces and hydrophobic interactions with one binding site. According to synchronous and three-dimensional fluorescence spectra and molecular docking results, all flavonoids bound directly into the enzyme cavity site and the binding influenced the microenvironment and conformation of the pepsin activity site which resulted in the reduced enzyme activity. The present study provides direct evidence at a molecular level to understand the mechanism of digestion caused by flavonoids.

  1. Spectroscopic-ellipsometric study of native oxide removal by liquid phase HF process

    NASA Astrophysics Data System (ADS)

    Kurhekar, Anil Sudhakar; Apte, Prakash R.

    2013-02-01

    Ex situ spectroscopic ellipsometry (SE) measurements have been employed to investigate the effect of liquid-phase hydrofluoric acid (HF) cleaning on Si<100> surfaces for microelectromechanical systems application. The hydrogen terminated (H-terminated) Si surface was realized as an equivalent dielectric layer, and SE measurements are performed. The SE analyses indicate that after a 20-s 100:5 HF dip with rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed and analyzed by the ex-situ SE. Evidence for desorption of the H-terminated Si surface layer is studied using Fourier transform infrared spectroscopy and ellipsometry, and discussed. This piece of work explains the usage of an ex situ, non-destructive technique capable of showing state of passivation, the H-termination of Si<100> surfaces.

  2. Phosphorus-31 nuclear magnetic resonance spectroscopic study of the canine pancreas: applications to acute alcoholic pancreatitis

    SciTech Connect

    Janes, N.; Clemens, J.A.; Glickson, J.D.; Cameron, J.L.

    1988-01-01

    The first nuclear magnetic resonance spectroscopic study of the canine pancreas is described. Both in-vivo, ex-vivo protocols and NMR observables are discussed. The stability of the ex-vivo preparation based on the NMR observables is established for at least four hours. The spectra obtained from the in-vivo and ex-vivo preparations exhibited similar metabolite ratios, further validating the model. Metabolite levels were unchanged by a 50% increase in perfusion rate. Only trace amounts of phosphocreatine were observed either in the intact gland or in extracts. Acute alcoholic pancreatitis was mimicked by free fatty acid infusion. Injury resulted in hyperamylasemia, edema (weight gain), increased hematocrit and perfusion pressure, and depressed levels of high energy phosphates.

  3. Raman spectroscopic study on the excystation process in a single unicellular organism amoeba (Acanthamoeba polyphaga)

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Chung; Perevedentseva, Elena; Cheng, Chia-Liang

    2015-05-01

    An in vivo Raman spectroscopic study of amoeba (Acanthamoeba polyphaga) is presented. The changes of the spectra during the amoeba cyst activation and excystation are analyzed. The spectra show the changes of the relative intensities of bands corresponding to protein, lipid, and carotenoid components during cyst activation. The presence of carotenoids in the amoeba is observed via characteristic Raman bands. These signals in the Raman spectra are intense in cysts but decrease in intensity with cyst activation and exhibit a correlation with the life cycle of amoeba. This work demonstrates the feasibility of using Raman spectroscopy for the detection of single amoeba microorganisms in vivo and for the analysis of the amoeba life activity. The information obtained may have implications for the estimation of epidemiological situations and for the diagnostics and prognosis of the development of amoebic inflammations.

  4. Wrapping Together Galactic Archaeology and Interstellar Medium Studies in Large Spectroscopic Surveys

    NASA Astrophysics Data System (ADS)

    Kos, J.

    2016-10-01

    The cold interstellar medium (ISM) in our galaxy is usually observed at wavelengths other than optical. But optical spectroscopic surveys of stars give unprecedented information that is valuable also for ISM studies because they cover millions of lines-of-sight penetrating regions in and out of the Galactic plane that most all-sky surveys. Big advantages are distances to observed stars from which we infer distances to clumps of the ISM. The ISM is detected as scarce absorptions of several atoms and simple molecules and also as diffuse interstellar bands (DIBs), weak but numerous absorption features at visible and near IR wavelengths. With the enormous amount of information the surveys provide we can start doing galactic archaeology from the ISM point of view. Even though the principles are very different for star and gas dynamics, the starting points are the same. Here we present some results that are the first steps toward the galactic archaeology of the ISM.

  5. Spectroscopic analyses of Fe and water in clays: A Martian surface weathering study

    NASA Technical Reports Server (NTRS)

    Bishop, J. L.; Pieters, Carle M.; Edwards, J. O.; Coyne, L. M.; Chang, S.

    1991-01-01

    Martian surface morphology suggests the presence of liquid H2O on Mars in the past. Reflectance spectra of the Martian surface include features which correspond to the crystal field transitions of iron, as well as features supporting the presence of ice and minerals containing structural OH and surface water. Researchers initiated further spectroscopic studies of surface iron and water and structural OH in clays in order to determine what remotely obtained spectra can indicate about the presence of clays on Mars based on a clearer understanding of the factors influencing the spectral features. Current technology allows researchers to better correlate the low frequency fundamental stretching and bending vibrations of O-H bonds with the diagnostic near infrared overtone and combination bands used in mineral characterization and identification.

  6. Spectroscopic studies on gallic acid and its azo derivatives and their iron(III) complexes.

    PubMed

    Masoud, Mamdouh S; Ali, Alaa E; Haggag, Sawsan S; Nasr, Nessma M

    2014-01-01

    Azo gallic derivatives and their iron(III) complexes were synthesized and characterized. The stereochemistry and the mode of bonding of the complexes were achieved based on elemental analysis, UV-Vis and IR. The thermal behaviors of the complexes were studied. The effect of pH on the electronic absorption spectra of gallic acid and its azo derivatives are discussed. Different spectroscopic methods (molar ratio, straight line method, continuous variation, slope ratio and successive method) are applied for determination of stoichiometry and pK values for the complex formation of gallic acid with iron(III) in aqueous media. Iron(III) complexes of gallic acid is formed with different ratio: 1:1, 1:2, 1:3 and 1:4 (M:L).

  7. Raman spectroscopic study of “The Malatesta”: A Renaissance painting?

    NASA Astrophysics Data System (ADS)

    Edwards, Howell G. M.; Vandenabeele, Peter; Benoy, Timothy J.

    2015-02-01

    Raman spectroscopic analysis of the pigments on an Italian painting described as a "Full Length Portrait of a Gentleman", known also as the "Malatesta", and attributed to the Renaissance period has established that these are consistent with the historical research provenance undertaken earlier. Evidence is found for the early 19th Century addition of chrome yellow to highlighted yellow ochre areas in comparison with a similar painting executed in 1801 by Sir Thomas Lawrence of John Kemble in the role of Hamlet, Prince of Denmark. The Raman data are novel in that no analytical studies have previously been made on this painting and reinforces the procedure whereby scientific analyses are accompanied by parallel historical research.

  8. Spectroscopic study of mixed oxide SAT 1- x:LA x perovskite crystals

    NASA Astrophysics Data System (ADS)

    Runka, T.; Łapsa, K.; Łapiński, A.; Aleksiyko, R.; Berkowski, M.; Drozdowski, M.

    2004-10-01

    Mixed perovskite crystals have been grown from multicomponent melts using the Czochralski method. The Raman, FT-IR and Brillouin investigations of perovskite (1- x)Sr(Al 0.5Ta 0.5)O 3: xLaAlO 3 crystals are reported. The measurements have been performed for several LA concentrations in the range 0.22≤ x≤0.36 at room temperature. The assignment of vibrational modes of IR and Raman spectra was proposed. The experimental results were correlated with structural data, obtained from X-ray diffraction study. The dependence of hypersonic velocity of transverse and longitudinal modes as a function of LA content was also determined. Spectroscopic investigations confirmed the disordered Al/Ta distribution, which increases with the increase of LA content.

  9. Spectroscopic and theoretical study of the o-vanillin hydrazone of the mycobactericidal drug isoniazid

    NASA Astrophysics Data System (ADS)

    González-Baró, Ana C.; Pis-Diez, Reinaldo; Parajón-Costa, Beatriz S.; Rey, Nicolás A.

    2012-01-01

    A complete and detailed study of the hydrazone obtained from condensation of antituberculous isoniazid (hydrazide of the isonicotinic acid, INH) and o-vanillin (2-hydroxy-3-methoxybenzaldehyde, o-HVa) is performed. It includes structural and spectroscopic analyses, comparing experimental and theoretical results. The compound was obtained as a chloride of the pyridinic salt (INHOVA +Cl -) but it will be referred as INHOVA for the sake of simplicity. The conformational space was searched and optimized geometries were determined both in gas phase and including solvent effects. Vibrational (IR and Raman), electronic and NMR spectra were registered and assigned with the help of computational methods based on the Density Functional Theory. Isoniazid hydrazones are good candidates for therapeutic agents against tuberculosis with conserved efficiency and lower toxicity and resistance than parent INH.

  10. The study of interaction between PFOA/PFOS and uracil by topology quality and spectroscopic analysis

    NASA Astrophysics Data System (ADS)

    Xu, Hui-Ying; Zhu, Jian-Qing; Wang, Wei; Xu, Xiao-Lu; Lu, Yin

    2014-02-01

    It has been established that perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) can be considered as emerging persistent organic pollutants. In recent years, there was increasing distribution of PFOA/PFOS in environmental systems, and accumulation and toxic effects of PFOA/PFOS in human body. In this paper, quantum chemistry methods were employed to study the interaction between perfluorinated organic pollutants and base (uracil). The results showed that there were four stable binding modes between the two perfluorinated compounds with uracil, especially the second mode which caused the most detrimental physiological functional response. NBO analysis showed that reactive hydrogen in the two perfluorinated compounds had the greatest effect on the hydrogen bond. The nature of the hydrogen bond formed between the two perfluorinated compounds and base was investigated using the AIM theory. The changes of spectroscopic properties in complexes were analyzed by IR and NMR spectra.

  11. Fe-complex of a tetraamido macrocyclic ligand: Spectroscopic characterization and catalytic oxidation studies

    NASA Astrophysics Data System (ADS)

    Sullivan, Shane Z.; Ghosh, Anindya; Biris, Alexandru S.; Pulla, Sharon; Brezden, Anna M.; Collom, Samulel L.; Woods, Ross M.; Munshi, Pradip; Schnackenberg, Laura; Pierce, Brad S.; Kannarpady, Ganesh K.

    2010-10-01

    This work presents the spectroscopic characterization and reaction studies of a Fe III-complex (2) of a tetraamido macrocyclic ligand (1, 15,15-dimethyl-5,8,13,17-tetrahydro-5,8,13,17-tetraaza-dibenzo[a,g]cyclotridecene-6,7,14,16-tetraone). 2 was characterized primarily by means of EPR. In agreement with the magnetic moment ( μeff = 3.87 BM), EPR spectroscopy of 2 shows signals consistent with S = 3/2 intermediate-spin ferric-iron. Besides EPR, mass spectrometry, UV/vis spectroscopy and cyclic voltammetry were used to further characterize 2. 2 is soluble in water and activates hydrogen peroxide under ambient conditions. 2 catalytically bleaches dyes, pulp and paper effluents and oxidizes several amines to their corresponding N-oxides with high turnover number and good yields.

  12. Spectroscopic-ellipsometric study of native oxide removal by liquid phase HF process

    PubMed Central

    Kurhekar, Anil Sudhakar; Apte, Prakash R

    2014-01-01

    Ex situ spectroscopic ellipsometry (SE) measurements have been employed to investigate the effect of liquid-phase hydrofluoric acid (HF) cleaning on Si<100> surfaces for microelectromechanical systems application. The hydrogen terminated (H-terminated) Si surface was realized as an equivalent dielectric layer, and SE measurements are performed. The SE analyses indicate that after a 20-s 100:5 HF dip with rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed and analyzed by the ex-situ SE. Evidence for desorption of the H-terminated Si surface layer is studied using Fourier transform infrared spectroscopy and ellipsometry, and discussed. This piece of work explains the usage of an ex situ, non-destructive technique capable of showing state of passivation, the H-termination of Si<100> surfaces. PMID:24619506

  13. Inhibitory effect of morin on tyrosinase: insights from spectroscopic and molecular docking studies.

    PubMed

    Wang, Yajie; Zhang, Guowen; Yan, Jiakai; Gong, Deming

    2014-11-15

    Tyrosinase is a key enzyme in the production of melanin in the human body, excessive accumulation of melanin can lead to skin disorders. Morin is an important bioactive flavonoid compound widely distributed in plants and foods of plant origin. In this study, the inhibitory kinetics of morin on tyrosinase and their binding mechanism were determined using spectroscopic and molecular docking techniques. The results indicate that morin reversibly inhibited tyrosinase in a competitive manner through a multi-phase kinetic process. Morin was found to bind to tyrosinase at a single binding site mainly by hydrogen bonds and van der Waals forces. Analysis of circular dichroism spectra revealed that the binding of morin to tyrosinase induced rearrangement and conformational changes of the enzyme. Moreover, molecular docking results suggested that morin competitively bound to the active site of tyrosinase with the substrate levodopa.

  14. Molecular spectroscopic studies on the interaction of morin with bovine serum albumin.

    PubMed

    Hu, Yan-Jun; Yue, Hua-Li; Li, Xiao-Ling; Zhang, Si-Si; Tang, E; Zhang, Li-Ping

    2012-07-01

    The interaction between morin and bovine serum albumin (BSA) was studied using molecular spectroscopic approach at different temperatures under imitated physiological conditions. Quenching of intrinsic tryptophanyl fluorescence of BSA with increasing morin concentration is the actuating tool in the analysis. The obtained quenching mechanisms, binding constants, binding sites and corresponding thermodynamic parameters at different temperatures indicate that the hydrophobic interaction play a major role in the morin-BSA association. Binding affinity between morin and BSA was determined using Scatchard equation and the modified Stern-Volmer equation, and the corresponding Structure-affinity relationships of flavonoids were discussed. Site marker competitive displacement experiments demonstrated that morin binds with high affinity to site II (subdomain IIIA) of BSA. Furthermore, the circular dichroism spectral results indicated that the conformation of BSA changed in the presence of morin. In addition, the effect of some common metal ions on the binding constant between morin and BSA was examined.

  15. Photophysics of α-furil at room temperature and 77 K: Spectroscopic and quantum chemical studies.

    PubMed

    Kundu, Pronab; Chattopadhyay, Nitin

    2016-06-21

    Steady state and time resolved spectroscopic measurements have been exploited to assign the emissions from different conformations of α-furil (2, 2'-furil) in solution phase at room temperature as well as cryogen (liquid nitrogen, LN2) frozen matrices of ethanol and methylcyclohexane. Room temperature studies reveal a single fluorescence from the trans-planar conformer of the fluorophore or two fluorescence bands coming from the trans-planar and the relaxed skew forms depending on excitation at the nπ(∗) or the ππ(∗) absorption band, respectively. Together with the fluorescence bands, the LN2 studies in both the solvents unambiguously ascertain two phosphorescence emissions with lifetimes 5 ± 0.3 ms (trans-planar triplet) and 81 ± 3 ms (relaxed skew triplet). Quantum chemical calculations have been performed using density functional theory at CAM-B3LYP/6-311++G(∗∗) level to prop up the spectroscopic surveillance. The simulated potential energy curves (PECs) illustrate that α-furil is capable of giving two emissions from each of the S1 and the T1 states-one corresponding to the trans-planar and the other to the relaxed skew conformation. Contrary to the other 1,2-dicarbonyl molecular systems like benzil and α-naphthil, α-furil does not exhibit any fluorescence from its second excited singlet (S2) state. This is ascribed to the proximity of the minimum of the PEC of the S2 state and the hill-top of the PEC of the S1 state. PMID:27334172

  16. Photophysics of α-furil at room temperature and 77 K: Spectroscopic and quantum chemical studies

    NASA Astrophysics Data System (ADS)

    Kundu, Pronab; Chattopadhyay, Nitin

    2016-06-01

    Steady state and time resolved spectroscopic measurements have been exploited to assign the emissions from different conformations of α-furil (2, 2'-furil) in solution phase at room temperature as well as cryogen (liquid nitrogen, LN2) frozen matrices of ethanol and methylcyclohexane. Room temperature studies reveal a single fluorescence from the trans-planar conformer of the fluorophore or two fluorescence bands coming from the trans-planar and the relaxed skew forms depending on excitation at the nπ∗ or the ππ∗ absorption band, respectively. Together with the fluorescence bands, the LN2 studies in both the solvents unambiguously ascertain two phosphorescence emissions with lifetimes 5 ± 0.3 ms (trans-planar triplet) and 81 ± 3 ms (relaxed skew triplet). Quantum chemical calculations have been performed using density functional theory at CAM-B3LYP/6-311++G∗∗ level to prop up the spectroscopic surveillance. The simulated potential energy curves (PECs) illustrate that α-furil is capable of giving two emissions from each of the S1 and the T1 states - one corresponding to the trans-planar and the other to the relaxed skew conformation. Contrary to the other 1,2-dicarbonyl molecular systems like benzil and α-naphthil, α-furil does not exhibit any fluorescence from its second excited singlet (S2) state. This is ascribed to the proximity of the minimum of the PEC of the S2 state and the hill-top of the PEC of the S1 state.

  17. Coupled cluster study of spectroscopic constants of ground states of heavy rare gas dimers with spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Tu, Zhe-Yan; Wang, Wen-Liang; Li, Ren-Zhong; Xia, Cai-Juan; Li, Lian-Bi

    2016-07-01

    The CCSD(T) approach based on two-component relativistic effective core potential with spin-orbit interaction just included in coupled cluster iteration is adopted to study the spectroscopic constants of ground states of Kr2, Xe2 and Rn2 dimers. The spectroscopic constants have significant basis set dependence. Extrapolation to the complete basis set limit provides the most accurate values. The spin-orbit interaction hardly affects the spectroscopic constants of Kr2 and Xe2. However, the equilibrium bond length is shortened about 0.013 Å and the dissociation energy is augmented about 18 cm-1 by the spin-orbit interaction for Rn2 in the complete basis set limit.

  18. Study of benzotriazole as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    NASA Astrophysics Data System (ADS)

    Solehudin, Agus; Nurdin, Isdiriayani

    2014-03-01

    Corrosion and inhibition studies on API 5LX65 carbon steel in chloride solution containing various concentrations of benzotriazole has been conducted at temperature of 70°C using Electrochemical Impedance Spectroscopy (EIS). Corroded carbon steel surface with and without inhibitor have been observed using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS). The objectives of this research are to study the performance of benzotriazole as corrosion inhibitors. The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H2S at different BTAH concentrations showed that corrosion rate of carbon steel decreases with increasing of BTAH concentrations from 0 to 10 mmol/l. The inhibition efficiency of BTAH was found to be affected by its concentration. The optimum efficiency obtained of BTAH is 93% at concentration of 5 mmol/l. The result of XRD and EDS analysis reveal the iron sulfide (FeS) formation on corroded carbon steel surface without inhibitor. The EDS spectrum show the Nitrogen (N) bond on carbon steel surface inhibited by BTAH.

  19. Study of benzotriazole as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    SciTech Connect

    Solehudin, Agus; Nurdin, Isdiriayani

    2014-03-24

    Corrosion and inhibition studies on API 5LX65 carbon steel in chloride solution containing various concentrations of benzotriazole has been conducted at temperature of 70°C using Electrochemical Impedance Spectroscopy (EIS). Corroded carbon steel surface with and without inhibitor have been observed using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS). The objectives of this research are to study the performance of benzotriazole as corrosion inhibitors. The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H{sub 2}S at different BTAH concentrations showed that corrosion rate of carbon steel decreases with increasing of BTAH concentrations from 0 to 10 mmol/l. The inhibition efficiency of BTAH was found to be affected by its concentration. The optimum efficiency obtained of BTAH is 93% at concentration of 5 mmol/l. The result of XRD and EDS analysis reveal the iron sulfide (FeS) formation on corroded carbon steel surface without inhibitor. The EDS spectrum show the Nitrogen (N) bond on carbon steel surface inhibited by BTAH.

  20. Corrosion Behavior of Surface-Treated Implant Ti-6Al-4V by Electrochemical Polarization and Impedance Studies

    NASA Astrophysics Data System (ADS)

    Paul, Subir; Yadav, Kasturi

    2011-04-01

    Implant materials for orthopedic and heart surgical services demand a better corrosion resistance material than the presently used titanium alloys, where protective oxide layer breaks down on a prolonged stay in aqueous physiological human body, giving rise to localized corrosion of pitting, crevice, and fretting corrosion. A few surface treatments on Ti alloy, in the form of anodization, passivation, and thermal oxidation, followed by soaking in Hank solution have been found to be very effective in bringing down the corrosion rate as well as producing high corrosion resistance surface film as reflected from electrochemical polarization, cyclic polarization, and Electrochemical Impedance Spectroscopy (EIS) studies. The XRD study revealed the presence of various types of oxides along with anatase and rutile on the surface, giving rise to high corrosion resistance film. While surface treatment of passivation and thermal oxidation could reduce the corrosion rate by 1/5th, anodization in 0.3 M phosphoric acid at 16 V versus stainless steel cathode drastically brought down the corrosion rate by less than ten times. The mechanism of corrosion behavior and formation of different surface films is better understood from the determination of EIS parameters derived from the best-fit equivalent circuit.

  1. Ethical Crossroads: A Study of Factors Impeding Professional Growth in Initial Teacher Education in Zimbabwe

    ERIC Educational Resources Information Center

    Mswazi, J. L.; Shumba, A.

    2008-01-01

    Research on current discourses on educational change in general and teacher education in particular have identified reasons why some teacher education courses fail to connect with trainees. This study sought to investigate factors that underlie pre-service teachers' resistance to an innovative religious and moral education course. A descriptive…

  2. Spectroscopic and theoretical studies on the excited state in diimine dithiolate complexes of platinum(II)

    SciTech Connect

    Zuleta, J.A.; Bevilacqua, J.M.; Eisenberg, R. ); Proserpio, D.M. ); Harvey, P.D. )

    1992-06-10

    The photophysical properties of a series of Pt(N-N)(S-S) complexes have been studied where (N-N) is either an [alpha],[alpha][prime]-diimine or saturated diamine chelating ligand and (S-S) is either a dithiolate chelating ligand or two monothiolate ligands in order to determine the orbital composition of the excited state. The solvent dependence of the absorption spectra of these complexes and the temperature dependence of their emission intensities and lifetimes have been examined while the ligands have been systematically varied. The electronic spectra are found to be dependent on whether or not the nitrogen chelating ligand is unsaturated (contains a vacant [pi]* orbital). On the basis of the spectroscopic data, the lowest energy absorption band in the diimine complexes is assigned as a metal-dithiolate to [pi]*(diimine) transition, whereas in the diamine complexes it is assigned as a metal-to-dithiolate MLCT transition. The only room-temperature emissive complexes are those that contain an [alpha],[alpha][prime]-diimine chelating ligand. The nature of the emission in these complexes at all temperatures depends on the dithiolate ligand, and the temperature dependence of the emission spectra has been examined. The nature of the HOMO and LUMO has been examined experimentally using cyclic voltammetry. On the basis of the electrochemical and spectroscopic data, the emission from all of the Pt(diimine)(S-S) complexes except those of 1,2-dithiolate maleonitriledithiolate (mnt) is assigned as a [sup 3](d(Pt)/p(S)-[pi]*(diimine)) transition, while, for the mnt complexes, it corresponds to a [sup 3](d(Pt)/p(S)-[pi]*(mnt)) transition. These assignments are supported by extended Hueckel molecular orbital calculations.

  3. Study on the interaction of catechins with human serum albumin using spectroscopic and electrophoretic techniques

    NASA Astrophysics Data System (ADS)

    Trnková, Lucie; Boušová, Iva; Staňková, Veronika; Dršata, Jaroslav

    2011-01-01

    The interaction between eight naturally occurring flavanols (catechin, epicatechin, gallocatechin, epigallocatechin, catechin gallate, epicatechin gallate, gallocatechin gallate, and epigallocatechin gallate) and human serum albumin (HSA) has been investigated by spectroscopic (fluorescence quenching and UV-Vis absorption) and electrophoretic (native and SDS PAGE) techniques under simulated physiological conditions (pH 7.40, 37 °C). The spectroscopic results confirmed the complex formation for the tested systems. The binding constants and the number of binding sites were obtained by analysis of fluorescence data. The strongest binding affinity to HSA was found for epicatechin gallate and decreased in the order epicatechin gallate ⩾ catechin gallate > epigallocatechin gallate > gallocatechin gallate ≫ epicatechin ⩾ catechin > gallocatechin ⩾ epigallocatechin. All free energy changes possessed negative sign indicating the spontaneity of catechin-HSA systems formation. The binding distances between the donor (HSA) and the acceptors (catechins) estimated by the Förster theory revealed that non-radiation energy transfer from HSA to catechins occurred with high possibility. According to results obtained by native PAGE, the galloylated catechins increased the electrophoretic mobility of HSA, which indicated the change in the molecular charge of HSA, whilst the non-galloylated catechins caused no changes. The ability of aggregation and cross-linking of tested catechins with HSA was not proved by SDS-PAGE. The relationship between the structure characteristics of all tested catechins (e.g. presence of the galloyl moiety on the C-ring, the number of hydroxyl groups on the B-ring, and the spatial arrangement of the substituents on the C-ring) and their binding properties to HSA is discussed. The presented study contributes to the current knowledge in the area of protein-ligand binding, particularly catechin-HSA interactions.

  4. Studies of multiple stellar systems - IV. The triple-lined spectroscopic system Gliese 644

    NASA Astrophysics Data System (ADS)

    Mazeh, Tsevi; Latham, David W.; Goldberg, Elad; Torres, Guillermo; Stefanik, Robert P.; Henry, Todd J.; Zucker, Shay; Gnat, Orly; Ofek, Eran O.

    2001-07-01

    We present a radial velocity study of the triple-lined system Gliese 644 and derive spectroscopic elements for the inner and outer orbits with periods of 2.9655 and 627d. We also utilize old visual data, as well as modern speckle and adaptive optics observations, to derive a new astrometric solution for the outer orbit. These two orbits together allow us to derive masses for each of the three components in the system: MA=0.410+/-0.028 (6.9 per cent), MBa=0.336+/-0.016 (4.7 per cent), and MBb=0.304+/-0.014 (4.7 per cent)Msolar. We suggest that the relative inclination of the two orbits is very small. Our individual masses and spectroscopic light ratios for the three M stars in the Gliese 644 system provide three points for the mass-luminosity relation near the bottom of the main sequence, where the relation is poorly determined. These three points agree well with theoretical models for solar metallicity and an age of 5Gyr. Our radial velocities for Gliese 643 and vB 8, two common proper motion companions of Gliese 644, support the interpretation that all five M stars are moving together in a physically bound group. We discuss possible scenarios for the formation and evolution of this configuration, such as the formation of all five stars in a sequence of fragmentation events leading directly to the hierarchical configuration now observed, versus formation in a small N cluster with subsequent dynamical evolution into the present hierarchical configuration.

  5. Spectroscopic study of gold nanoparticle formation through high intensity laser irradiation of solution

    SciTech Connect

    Nakamura, Takahiro Sato, Shunichi; Herbani, Yuliati; Ursescu, Daniel; Banici, Romeo; Dabu, Razvan Victor

    2013-08-15

    A spectroscopic study of the gold nanoparticle (NP) formation by high-intensity femtosecond laser irradiation of a gold ion solution was reported. The effect of varying energy density of the laser on the formation of gold NPs was also investigated. The surface plasmon resonance (SPR) peak of the gold nanocolloid in real-time UV-visible absorption spectra during laser irradiation showed a distinctive progress; the SPR absorption peak intensity increased after a certain irradiation time, reached a maximum and then gradually decreased. During this absorption variation, at the same time, the peak wavelength changed from 530 to 507 nm. According to an empirical equation derived from a large volume of experimental data, the estimated mean size of the gold NPs varied from 43.4 to 3.2 nm during the laser irradiation. The mean size of gold NPs formed at specific irradiation times by transmission electron microscopy showed the similar trend as that obtained in the spectroscopic analysis. From these observations, the formation mechanism of gold NPs during laser irradiation was considered to have two steps. The first is a reduction of gold ions by reactive species produced through a non-linear reaction during high intensity laser irradiation of the solution; the second is the laser fragmentation of produced gold particles into smaller pieces. The gold nanocolloid produced after the fragmentation by excess irradiation showed high stability for at least a week without the addition of any dispersant because of the negative charge on the surface of the nanoparticles probably due to the surface oxidation of gold nanoparticles. A higher laser intensity resulted in a higher efficiency of gold NPs fabrication, which was attributed to a larger effective volume of the reaction.

  6. Gastro-oesophageal reflux is common in oligosymptomatic patients with dental erosion: A pH-impedance and endoscopic study

    PubMed Central

    Materna, Andrea; Martig, Lukas; Lussi, Adrian

    2015-01-01

    Background Dental erosion is a complication of gastro-oesophageal reflux disease (GORD) according to the Montreal consensus statement. However, GORD has not been comprehensively characterized in patients with dental erosions and pH-impedance measures have not been reported. Objectives Characterize GORD in patients with dental erosions using 24-h multichannel intraluminal pH-impedance measurements (pH-MII) and endoscopy. Methods This single-centre study investigated reflux in successive patients presenting to dentists with dental erosion using pH-MII and endoscopy. Results Of the 374 patients, 298 (80%) reported GORD symptoms <2 per week, 72 (19%) had oesophagitis and 59 (16%) had a hiatal hernia. In the 349 with pH-MII the mean percentage time with a pH <4 (95% CI) was 11.0 (9.3–12.7), and 34.4% (31.9–36.9) for a pH <5.5, a critical threshold for dental tissue. The mean numbers of total, acidic and weakly acidic reflux episodes were 71 (63–79), 43 (38–49) and 31 (26–35), respectively. Of the reflux episodes, 19% (17–21) reached the proximal oesophagus. In 241 (69%) patients reflux was abnormal using published normal values for acid exposure time and reflux episodes. No significant associations between the severity of dental erosions and any reflux variables were found. The presence of GORD symptoms and of oesophagitis or a hiatal hernia was associated with greater reflux, but not with increased dental erosion scores. Conclusions Significant oligosymptomatic gastro-oesophageal reflux occurs in the majority of patients with dental erosion. The degree of dental erosion did not correlate with any of the accepted quantitative reflux indicators. Definition of clinically relevant reflux parameters by pH-MII for dental erosion and of treatment guidelines are outstanding. Gastroenterologists and dentists need to be aware of the widely prevalent association between dental erosion and atypical GORD. PMID:25922678

  7. Low temperature dielectric and impedance studies on magnetoelectric Pb(Fe0.5Nb0.5)O3 ceramic

    NASA Astrophysics Data System (ADS)

    Matteppanavar, Shidaling; Shivaraja, I.; Rayaprol, Sudhindra; Angadi, Basavaraj

    2016-05-01

    The structural, microstructural, low temperature dielectric and impedance properties of Pb(Fe0.5Nb0.5)O3 (PFN) ceramic prepared by single step solid-state reaction method have been investigated. Processing parameters such as calcination, sintering temperature and sintering durations were optimized to get better dielectric properties. It was found that the above ceramics sintered at 1050 °C for 4 hr exhibited single phase, maximum density and uniform microstructure. X-ray diffraction (XRD) and neutron diffraction (ND) reveals that the system exhibit single phase without any kind of secondary phases at room temperature (RT) with monoclinic crystal structure (Cm). Surface morphology of the compounds was studied by Scanning electron microscope (SEM). Impedance spectroscopy is used to study the electrical behaviour of PFN in the frequency range from 100Hz to 1MHz and in the temperature range from 120 to 293 K. The frequency-dependent electrical data are analyzed by impedance formalisms. The complex impedance shows the relaxation (conduction) mechanism in the sample.

  8. Spectroscopic and molecular docking studies on the interaction of troxerutin with DNA.

    PubMed

    Subastri, A; Ramamurthy, C H; Suyavaran, A; Mareeswaran, R; Lokeswara Rao, P; Harikrishna, M; Suresh Kumar, M; Sujatha, V; Thirunavukkarasu, C

    2015-01-01

    Troxerutin (TXER) is a derivative of naturally occurring bioflavonoid rutin. It possesses different biological activities in rising clinical world. The biological activity possessed by most of the drugs mainly targets on macromolecules. Hence, in the current study we have examined the interaction mechanism of TXER with calf thymus DNA (CT-DNA) by using various spectroscopic methods, isothermal titration calorimetry (ITC) and molecular docking studies. Further, DNA cleavage study was carried out to find the DNA protection activity of TXER. UV-absorption and emission spectroscopy showed low binding constant values via groove binding. Circular dichroism study indicates that TXER does not modify native B-form of DNA, and it retains the native B-conformation. Furthermore, no effective positive potential peak shift was observed in TXER-DNA complex during electrochemical analysis by which it represents an interaction of TXER with DNA through groove binding. Molecular docking study showed thymine guanine based interaction with docking score -7.09 kcal/mol. This result was compared to experimental ITC value. The DNA cleavage study illustrates that TXER does not cause any DNA damage as well as TXER showed DNA protection against hydroxyl radical induced DNA damage. From this study, we conclude that TXER interacts with DNA by fashion of groove binding.

  9. Electrochemical Impedance Spectroscopy study in micro-grain structured amorphous silicon anodes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Paloukis, Fotis; Elmasides, Costas; Farmakis, Filippos; Selinis, Petros; Neophytides, Stylianos G.; Georgoulas, Nikolaos

    2016-11-01

    In this paper, a study of the lithiation mechanism of micro-grain structured silicon anode is presented. Micro-grain amorphous silicon was deposited on special copper foil and it is shown that after several decades of galvanostatic cycles, it preserves its granular nature with minor degradation. In order to shed light on the lithiation mechanisms of the micro-grain silicon, Electrochemical Impedance Spectroscopy (EIS) was conducted on silicon half-cells at various State-of-Charge (SoC) and various discharging current values and the Solid-Electrolyte Interphase (SEI) RSEI and polarization resistance Rpol were determined. Results reveal that Rpol highly increases for cell voltages lower than 0.2 V and it strongly depends on the discharging C-rate. From X-ray Photoelectron Spectroscopy (XPS) measurements combined with surface sputtering, the existence of a LixSiyOz interlayer between SEI and silicon is confirmed, which is believed to play an important role to the lithium kinetics. Finally, combining our results, a lithiation mechanism of the micro-grain silicon anode is proposed.

  10. Detection of Non-Cavitated Occlusal Caries with Impedance Spectroscopy and Laser Fluorescence: an In Vitro Study

    PubMed Central

    Mortensen, Diana; Dannemand, Katrine; Twetman, Svante; Keller, Mette Kirstine

    2014-01-01

    Objective: To evaluate the performance of an impedance spectroscopy technology for detecting non-cavitated occlusal caries lesions in permanent teeth in vitro. The method was compared with a commonly used laser fluorescence device and validated against histology. Material and Methodology: A non-cavitated sample of 100 extracted posterior teeth was randomly selected and assessed for caries on enamel and dentin level with aid of CarioScan PRO (ACIS) and DIAGNOdent pen (LF pen) by three examiners. After the measurements, the extension of the lesion was histologically determined as gold standard. Sensitivity, specificity, accuracy and receiver-operating curves were calculated. Intra- and inter-examiner reproducibility was expressed by intra class correlation coefficients. Results: The histological caries prevalence was 99% and 41% exhibited dentin caries. The ACIS technique displayed high specificities but almost negligible sensitivities at readings >50. A similar pattern was noted for the LF pen at readings >30. The intra- and inter-examiner reproducibility varied between 0.47 and 0.98 and the values were generally lower for the ACIS technique than for the LF pen. The inter-examiner agreement reached excellent levels with both methods. Conclusions: In vitro,the ACIS technique showed a low ability to disclose occlusal caries lesions in the enamel and/or dentin of non-cavitated permanent molars. However, further in vivo studies of permanent occlusal surfaces are needed to mirror the clinical situation. PMID:24799965

  11. Electrochemical Impedance Studies on Single and Multi-Walled Carbon Nanotubes--Polymer Nanocomposites for Biosensors Development.

    PubMed

    Tertiş, Mihaela; Florea, Anca; Feier, Bogdan; Marian, Iuliu Ovidiu; Silaghi-Dumitrescu, Luminţa; Cristea, Alexandru; Săndulescu, Robert; Cristea, Cecilia

    2015-05-01

    Advances in nanoscience have allowed scientists to incorporate new nanomaterials in biosensing platforms. Carbon nanotubes are nanomaterials that facilitate the charge transfer between the bioelement and the transducer. Electrochemical impedance spectroscopy is a useful technique for the modified surface characterization. In the present approach electrochemical impedance spectroscopy was used to characterize the electrodes modified with different types of carbon nanotubes (single and multi-wall) according to their morphology and electrochemical behavior. By using Nyquist and Bode diagrams it was possible to assign the appropriate circuit considering all possible contributors. The charge transfer resistances as well as the time constants were calculated for all five types of investigated carbon nanotubes.

  12. Impedance spectroscopy of manganite films prepared by metalorganic chemical vapor deposition.

    PubMed

    Nakamura, Toshihiro; Homma, Kohei; Tachibana, Kunihide

    2011-09-01

    Polycrystalline Pr(1-x)CaxMnO3 (PCMO) films were prepared by liquid source metalorganic chemical vapor deposition using in situ infrared spectroscopic monitoring. The electric properties of the PCMO-based devices with Ni and Al electrodes (Ni-PCMO-Ni and Al-PCMO-Al devices) were studied by dc current-voltage (I-V) measurements and ac impedance spectroscopy. The current varied linearly with the applied voltage in Ni-PCMO-Ni devices, while nonlinear behavior was observed in I-V curves for Al-PCMO-Al devices. Impedance spectra were also different between Ni-PCMO-Ni and Al-PCMO-Al devices. The Cole-Cole plots for the Ni-PCMO-Ni devices showed only a single semicircular arc, which was assigned to the PCMO bulk impedance. Impedance spectra for the Al-PCMO-Al devices had two distinct components, which could be attributed to the PCMO bulk and to the interface between the PCMO film and the Al electrode, respectively. The bias dependence of the impedance spectra suggested that the resistance switching in the Al-PCMO-Al devices was mainly due to the resistance change in the interface between the film and the electrode. The metal electrode plays an important role in the resistance switching in the PCMO-based devices. The choice of the optimum metal electrodes is essential to the ReRAM application of the manganite-based devices.

  13. Static and time-resolved spectroscopic studies of low-symmetry Ru(II) polypyridyl complexes

    SciTech Connect

    Curtright, A.E.; McCusker, J.K.

    1999-09-02

    The spectroscopic and electrochemical properties of a series of four Ru{sup II} polypyridyl complexes are reported. Compounds of the form [Ru(dmb){sub x}(dea){sub 3{minus}x}]{sup 2+} (x = 0--3), where dmb is 4,4{prime}-dimethyl-2,2{prime}-bipyridine and dea is 4,4{prime}-bis(diethylamino)-2,2{prime}-bipyridine, have been prepared and studied using static and time-resolved electronic and vibrational spectroscopies as a prelude to femtosecond spectroscopic studies of excited-state dynamics. Static electronic spectra in CH{sub 3}CN solution reveal a systematic shift of the MLCT absorption envelope from a maximum of 458 nm in the case of [Ru(dmb){sub 3}]{sup 2+} to 518 nm for [Ru(dea){sub 3}]{sup 2+} with successive substitutions of dea for dmb, suggesting a dea-based chromophore as the lowest-energy species. However, analysis of static and time-resolved emission data indicates an energy gap ordering of [Ru(dmb){sub 3}]{sup 2+} > [Ru(dmb){sub 2}(dea)]{sup 2+} > [Ru(dea){sub 3}]{sup 2+} > [Ru(dmb)(DEA){sub 2}]{sup 2+}, at variance with the electronic structures inferred from the absorption spectra. Nanosecond time-resolved electronic absorption and time-resolved step-scan infrared data are used to resolve this apparent conflict and confirm localization of the long-lived {sup 3}MLCT state on dmb in all three complexes where this ligand is present, thus making the dea-based excited state unique to [Ru(dea){sub 3}]{sup 2+}. Electrochemical studies further reveal the origin of this result, where a strong influence of the dea ligand on the oxidative Ru{sup II/III} couple, due to {pi} donation from the diethylamino substituent, is observed. The electronic absorption spectra are then reexamined in light of the now well-determined excited-state electronic structure. The results serve to underscore the importance of complete characterization of the electronic structures of transition metal complexes before embarking on ultrafast studies of their excited-state properties.

  14. Spectroscopic studies on diamond like carbon films synthesized by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Panda, Madhusmita; Krishnan, R.; Ravindran, T. R.; Das, Arindam; Mangamma, G.; Dash, S.; Tyagi, A. K.

    2016-05-01

    Hydrogen free Diamond like Carbon (DLC) thin films enriched with C-C sp3 bonding were grown on Si (111) substrates at laser pulse energies varying from 100 to 400 mJ (DLC-100, DLC-200, DLC-300, DLC-400), by Pulsed Laser Ablation (PLA) utilizing an Nd:YAG laser operating at fundamental wavelength. Structural, optical and morphological evolutions as a function of laser pulse energy were studied by micro Raman, UV-Vis spectroscopic studies and Atomic Force Microscopy (AFM), respectively. Raman spectra analysis provided critical clues for the variation in sp3 content and optical energy gap. The sp3 content was estimated using the FWHM of the G peak and found to be in the range of 62-69%. The trend of evolution of sp3 content matches well with the evolution of ID/IG ratio with pulse energy. UV-Vis absorption study of DLC films revealed the variation of optical energy gap with laser pulse energy (1.88 - 2.23 eV), which matches well with the evolution of G-Peak position of the Raman spectra. AFM study revealed that roughness, size and density of particulate in DLC films increase with laser pulse energy.

  15. Binding of phenazinium dye safranin T to polyriboadenylic acid: spectroscopic and thermodynamic study.

    PubMed

    Pradhan, Ankur Bikash; Haque, Lucy; Roy, Snigdha; Das, Suman

    2014-01-01

    Here, we report results from experiments designed to explore the association of the phenazinium dye safranin T (ST, 3,7-diamino-2,8-dimethyl-5-phenylphenazinium chloride) with single and double stranded form of polyriboadenylic acid (hereafter poly-A) using several spectroscopic techniques. We demonstrate that the dye binds to single stranded polyriboadenylic acid (hereafter ss poly-A) with high affinity while it does not interact at all with the double stranded (ds) form of the polynucleotide. Fluorescence and absorption spectral studies reveal the molecular aspects of binding of ST to single stranded form of the polynucleotide. This observation is also supported by the circular dichroism study. Thermodynamic data obtained from temperature dependence of binding constant reveals that association is driven by negative enthalpy change and opposed by negative entropy change. Ferrocyanide quenching studies have shown intercalative binding of ST to ss poly-A. Experiments on viscosity measurements confirm the binding mode of the dye to be intercalative. The effect of [Na⁺] ion concentration on the binding process suggests the role of electrostatic forces in the complexation. Present studies reveal the utility of the dye in probing nucleic acid structure. PMID:24498422

  16. Spectroscopic studies of interaction between CuO nanoparticles and bovine serum albumin.

    PubMed

    Esfandfar, Paniz; Falahati, Mojtaba; Saboury, AliAkbar

    2016-09-01

    Recently, the great interests in manufacturing and application of metal oxide nanoparticles in commercial and industrial products have led to focus on the potential impact of these particles on biomacromolecules. In the present study, the interaction of copper oxide (CuO) nanoparticles with bovine serum albumin (BSA) was studied by spectroscopic techniques. The zeta potential value for BSA and CuO nanoparticles with average diameter of around 50 nm at concentration of 10 μM in the deionized (DI) water were -5.8 and -22.5 mV, respectively. Circular dichroism studies did not show any changes in the content of secondary structure of the protein after CuO nanoparticles interaction. Fluorescence data revealed that the fluorescence quenching of BSA by CuO nanoparticles was the result of the formed complex of CuO nanoparticles - BSA. Binding constants and other thermodynamic parameters were determined at three different temperatures. The hydrogen bond interactions are the predominant intermolecular forces to stabilize the CuO nanoparticle - BSA complex. This study provides important insight into the interaction of CuO nanoparticles with proteins, which may be of importance for further application of these nanoparticles in biomedical applications. PMID:26555383

  17. UV-visible and (1)H-(15)N NMR spectroscopic studies of colorimetric thiosemicarbazide anion sensors.

    PubMed

    Farrugia, Kristina N; Makuc, Damjan; Podborska, Agnieszka; Szaciłowski, Konrad; Plavec, Janez; Magri, David C

    2015-02-14

    Four model thiosemicarbazide anion chemosensors containing three N-H bonds, substituted with phenyl and/or 4-nitrophenyl units, were synthesised and studied for their anion binding abilities with hydroxide, fluoride, acetate, dihydrogen phosphate and chloride. The anion binding properties were studied in DMSO and 9 : 1 DMSO-H2O by UV-visible absorption and (1)H/(13)C/(15)N NMR spectroscopic techniques and corroborated with DFT studies. Significant changes were observed in the UV-visible absorption spectra with all anions, except for chloride, accompanied by dramatic colour changes visible to the naked eye. These changes were determined to be due to the deprotonation of the central N-H proton and not due to hydrogen bonding based on (1)H/(15)N NMR titration studies with acetate in DMSO-d6-0.5% water. Direct evidence for deprotonation was confirmed by the disappearance of the central thiourea proton and the formation of acetic acid. DFT and charge distribution calculations suggest that for all four compounds the central N-H proton is the most acidic. Hence, the anion chemosensors operate by a deprotonation mechanism of the central N-H proton rather than by hydrogen bonding as is often reported. PMID:25451865

  18. Wakefields and coupling impedances

    NASA Astrophysics Data System (ADS)

    Kurennoy, Sergey

    1995-02-01

    After a short introduction of the wake potentials and coupling impedances, a few new results in impedance calculations are discussed. The first example is a new analytical method for calculating impedances of axisymmetric structures in the low frequency range, below the cutoff frequency of the vacuum chamber. The second example demonstrates that even very small discontinuities on a smooth waveguide can result in appearance of trapped modes, with frequencies slightly below the waveguide cutoff frequency. The high-frequency (above the cutoff) behavior of the coupling impedance of many small discontinuities is discussed in the third example.

  19. Spectroscopic studies on sidewall carboxylic acid functionalization of multi-walled carbon nanotubes with valine.

    PubMed

    Deborah, M; Jawahar, A; Mathavan, T; Dhas, M Kumara; Benial, A Milton Franklin

    2015-03-15

    The valine functionalized multi-walled carbon nanotubes (MWCNTS) were prepared and characterized by using XRD, UV-Vis, FT-IR, EPR, SEM, and EDX, spectroscopic techniques. The enhanced XRD peak (002) intensity was observed for valine functionalized MWCNTs compared with oxidized MWCNTs, which is likely due to sample purification by acid washing. UV-Vis study shows the formation of valine functionalized MWCNTs. FT-IR study confirms the presence of functional groups of oxidized MWCNTs and valine functionalized MWCNTs. The ESR line shape analysis indicates that the observed EPR line shape is a Gaussian line shape. The g-values indicate that the systems are isotropic in nature. The morphology study was carried out for oxidized MWCNTs and valine functionalized MWCNTs by using SEM. The EDX spectra revealed that the high purity of oxidized MWCNTs and valine functionalized MWCNTs. The functionalization has been chosen because, functionalization of CNTs with amino acids makes them soluble and biocompatible. Thus, they have potential applications in the field of biosensors and targeted drug delivery.

  20. Raman spectroscopic study of keratin 8 knockdown oral squamous cell carcinoma derived cells

    NASA Astrophysics Data System (ADS)

    Singh, S. P.; Alam, Hunain; Dmello, Crismita; Vaidya, Milind M.; Krishna, C. Murali

    2012-03-01

    Keratins are one of most widely used markers for oral cancers. Keratin 8 and 18 are expressed in simple epithelia and perform both mechanical and regulatory functions. Their expression are not seen in normal oral tissues but are often expressed in oral squamous cell carcinoma. Aberrant expression of keratins 8 and 18 is most common change in human oral cancer. Optical-spectroscopic methods are sensitive to biochemical changes and being projected as novel diagnostic tools for cancer diagnosis. Aim of this study was to evaluate potentials of Raman spectroscopy in detecting minor changes associated with differential level of keratin expression in tongue-cancer-derived AW13516 cells. Knockdown clones for K8 were generated and synchronized by growing under serum-free conditions. Cell pellets of three independent experiments in duplicate were used for recording Raman spectra with fiberoptic-probe coupled HE-785 Raman-instrument. A total of 123 and 96 spectra from knockdown clones and vector controls respectively in 1200-1800 cm-1 region were successfully utilized for classification using LDA. Two separate clusters with classification-efficiency of ~95% were obtained. Leave-one-out cross-validation yielded ~63% efficiency. Findings of the study demonstrate the potentials of Raman spectroscopy in detecting even subtle changes such as variations in keratin expression levels. Future studies towards identifying Raman signals from keratin in oral cells can help in precise cancer diagnosis.

  1. Spectroscopic studies on the spontaneous assembly of phenosafranin on glycosaminoglycans templates

    NASA Astrophysics Data System (ADS)

    Zhang, Shuzhen; Zhao, Fenglin; Li, Na; Li, Ke'an; Tong, Shenyang

    2002-10-01

    Spectroscopic studies showed that binding of phenosafranin (PSF) molecules to glycosaminoglycans (GAGs) resulted in the following observations: (i) appearance of a 52.6 nm hypsochromic shift of the visible absorption band; (ii) static quenching of fluorescence from PSF; (iii) induction of strong circular dichroism (CD) signal of PSF. Stoichiometry of the PSF-GAGs complex was determined by spectrophotometric titration, spectrofluorimetric titration and MacIntosh extraction method. These studies demonstrated the formation of the extended helical PSF array aligned on the helical backbone of GAGs templates by electrostatic force, and the dimeric binding mode of PSF to each anionic site was proposed. The comparative studies between PSF-heparin (Hep) and PSF-chondroitin 4-sulfate (CS) complexes revealed that: (i) stoichiometry of PSF-Hep complex was 1.8 times of PSF-CS complex; (ii) Hep was more effective than CS (1.8 times) in decreasing the absorbance of PSF; and (iii) Stern-Volmer constants of the Hep-PSF system were greater than that of the CS-PSF system. These differences were attributed to the different charge density on the Hep and CS molecules, which in turn suggested that the electrostatic force was dominant in the interaction between PSF and GAGs.

  2. Emerging trends in X-ray spectroscopic studies of plasma produced by intense laser beams

    SciTech Connect

    Arora, V.; Chakera, J. A.; Naik, P. A.; Gupta, P. D.

    2015-07-31

    X-ray line emission from hot dense plasmas, produced by ultra-short high intensity laser systems, has been studied experimentally in recent years for applications in materials science as well as for back-lighter applications. By virtue of the CPA technology, several laser facilities delivering pulses with peak powers in excess of one petawatt (focused intensities > 10{sup 20} W-cm{sup −2}) have either been commissioned across the globe during the last few years or are presently under construction. On the other hand, hard x-ray sources on table top, generating ultra-short duration x-rays at a repetition rate up to 10 kHz, are routinely available for time resolved x-ray diffraction studies. In this paper, the recent experiments on x-ray spectroscopic studies of plasma produced by 45 fs, Ti:sapphire laser pulses (focused iintensity > 10{sup 18} W-cm{sup −2}) at RRCAT Indore will be presented.

  3. Spectroscopic and structural studies of energetically efficient transport in nanocontacts to NiSi nanowires

    NASA Astrophysics Data System (ADS)

    Stein, A.; Farhat, I. A. H.; Lacevic, N.; Bazuhair, S. K.; Azhar, S. S.; Isakovic, A. F.

    Understanding correlations between mechanical, thermal, structural and electronic transport properties of different nanocontact geometries to nanowires, such as Au/Cu-NiSi-Si, remain one of the major goals of nanodevices reliability and scalability research. Aiming to clarify the failure modes and processes that affect the energy efficiency of transport and switching in constrained nanocontact geometries, such as end contacts, we conducted the structural, spectroscopic, and noise correlation studies. We show how the spatial (in)homogeneity at and in the near vicinity of the interface affects the transport performance of the nanojunctions. Mobile Ni clusters are identified at the nanojunction interface via Raman spectromicroscopy and their influence on charge transport is analyzed. We also show that the noise correlation spectra and micro-X-ray stress-strain studies in the nanojunctions are effictive tools in predicting the energy efficiency of the nanojunctions. A computational study of the interfacial properties of metal/Ni-Si via DFT and MD simulations is implemented. Work supported by Mubadala-SRC # 2011-KJ-2190. A part of the work done at BNL-CFN, supported by DOE. A part of the work done at Cornell Univ.CFN and CCMR, supported by the NSF.

  4. Spectroscopic studies on sidewall carboxylic acid functionalization of multi-walled carbon nanotubes with valine

    NASA Astrophysics Data System (ADS)

    Deborah, M.; Jawahar, A.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin

    2015-03-01

    The valine functionalized multi-walled carbon nanotubes (MWCNTS) were prepared and characterized by using XRD, UV-Vis, FT-IR, EPR, SEM, and EDX, spectroscopic techniques. The enhanced XRD peak (0 0 2) intensity was observed for valine functionalized MWCNTs compared with oxidized MWCNTs, which is likely due to sample purification by acid washing. UV-Vis study shows the formation of valine functionalized MWCNTs. FT-IR study confirms the presence of functional groups of oxidized MWCNTs and valine functionalized MWCNTs. The ESR line shape analysis indicates that the observed EPR line shape is a Gaussian line shape. The g-values indicate that the systems are isotropic in nature. The morphology study was carried out for oxidized MWCNTs and valine functionalized MWCNTs by using SEM. The EDX spectra revealed that the high purity of oxidized MWCNTs and valine functionalized MWCNTs. The functionalization has been chosen because, functionalization of CNTs with amino acids makes them soluble and biocompatible. Thus, they have potential applications in the field of biosensors and targeted drug delivery.

  5. Structural studies of E. coli ribosomes by spectroscopic techniques: A specialized review

    NASA Astrophysics Data System (ADS)

    Bonicontro, Adalberto; Risuleo, Gianfranco

    2005-12-01

    We present a review on our interdisciplinary line of research based on strategies of molecular biology and biophysics. These have been applied to the study of the prokaryotic ribosome of the bacterium Escherichia coli. Our investigations on this organelle have continued for more than a decade and we have adopted different spectroscopic biophysical techniques such as: dielectric and fluorescence spectroscopy as well as light scattering (photon correlation spectroscopy). Here we report studies on the whole 70S ribosomes and on the separated subunits 30S and 50S. Our results evidence intrinsic structural features of the subunits: the small shows a more "floppy" structure, while the large one appears to be more rigid. Also, an inner "kernel" formed by the RNA/protein association is found within the ribosome. This kernel is surrounded by a ribonucleoprotein complex more exposed to the solvent. Initial analyses were done on the so called Kaldtschmit-Wittmann ribosome: more recently we have extended the studies to the "tight couple" ribosome known for its better functional performance in vitro. Data evidence a phenomenological correlation between the differential biological activity and the intrinsic structural properties of the two-ribosome species. Finally, investigations were also conducted on particles treated at sub-denaturing temperatures and on ribosomes partially deproteinized by salt treatment (ribosomal cores). Results suggest that the thermal treatment and the selective removal of proteins cause analogous structural alterations.

  6. Spectroscopic study of formation, evolution and interaction of M31 and M33 with star clusters

    NASA Astrophysics Data System (ADS)

    Fan, Zhou; Yang, Yanbin

    2016-02-01

    The recent studies show that the formation and evolution process of the nearby galaxies are still unclear. By using the Canada France Hawaii Telescope (CFHT) 3.6m telescope, the PanDAS shows complicated substructures (dwarf satellite galaxies, halo globular clusters, extended clusters, star streams, etc.) in the halo of M31 to ~150 kpc from the center of galaxy and M31-M33 interaction has been studied. In our work, we would like to investigate formation, evolution and interaction of M31 and M33, which are the nearest two spiral galaxies in Local Group. The star cluster systems of the two galaxies are good tracers to study the dynamics of the substructures and the interaction. Since 2010, the Xinglong 2.16m, Lijiang 2.4m and MMT 6.5m telescopes have been used for our spectroscopic observations. The radial velocities and Lick absorption-line indices can thus be measured with the spectroscopy and then ages, metallicities and masses of the star clusters can be fitted with the simple stellar population models. These parameters could be used as the input physical parameters for numerical simulations of M31-M33 interaction.

  7. [Spectroscopic studies on the binding of phenazopyridine hydrochloride and bovine serum albumin].

    PubMed

    Zhou, Hong; Chen, Chang-Yun; Xie, An-Jian

    2007-09-01

    The binding of phenazopyridine hydrochloride and bovine serum albumin under physiological conditions was studied by spectroscopic method. The quenching mechanism of the fluorescence of bovine serum albumin by phenazopyridine hydrochloride was studied with fluorescence and absorption spectroscopy. The binding constant Kb and the number of binding sites n were determined at different temperatures according to Scatchard equation, and the main binding force was discussed by thermodynamic equations. The effect of the drug on bovine serum albumin conformation was also studied by using synchronous fluorescence spectroscopy. The quenching mechanism of phenazopyridine hydrochloride to bovine serum albumin is static quenching and non-radiation energy transfer. The binding constants Kb at 15, 25 and 37 degrees C are 2.47 x 10(7), 9.15 x 10(6) and 4.36 x 10(6) mol(-1) with one binding site, respectively. The thermodynamic parameters of the reaction are DeltaH = -71.2 kJ x mol(-1), and DeltaS = 124.8 J x mol(-1) x K(-1). Binding phenazopyridine hydrochloride to bovine serum albumin is a spontaneous inter-molecular interaction in which entropy increases and Gibbs free energy decreases. The binding distance r between phenazopyridine hydrochloride and bovine serum albumin is 1.61 nm according to Forster theory of non-radiation energy transfer. The binding force is electrostatic interaction. Phenazopyridine hydrochloride can be deposited and transported by serum protein in vivo. Phenazopyridine hydrochloride does affect the serum protein conformation.

  8. An electrochemical study of corrosion protection by primer-topcoat systems on 4130 steel with ac impedance and dc methods

    NASA Technical Reports Server (NTRS)

    Mendrek, M. J.; Higgins, R. H.; Danford, M. D.

    1988-01-01

    To investigate metal surface corrosion and the breakdown of metal protective coatings, the ac impedance method is applied to six systems of primer coated and primer topcoated 4130 steel. Two primers were used: a zinc-rich epoxy primer and a red lead oxide epoxy primer. The epoxy-polyamine topcoat was used in four of the systems. The EG and G-PARC Model 368 ac impedance measurement system, along with dc measurements with the same system using the polarization resistance method, were used to monitor changing properties of coated 4230 steel disks immersed in 3.5 percent NaCl solutions buffered at pH 5.4 over periods of 40 to 60 days. The corrosion system can be represented by an electronic analog called an equivalent circuit consisting of resistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for the resistors and capacitors, that can be assigned in the equivalent circuit following a least-squares analysis of the data, describe changes that occur on the corroding metal surface and in the protective coatings. Two equivalent circuits have been determined that predict the correct Bode phase and magnitude of the experimental sample at different immersion times. The dc corrosion current density data are related to equivalent circuit element parameters. Methods for determining corrosion rate with ac impedance parameters are verified by the dc method.

  9. Infrared external reflection spectroscopic studies of phase transitions in Langmuir monolayers of stearyl alcohol

    NASA Astrophysics Data System (ADS)

    Buontempo, Joseph T.; Rice, Stuart A.

    1993-11-01

    There is a steadily growing body of evidence that much of the information available concerning the properties of Langmuir monolayers concerns systems which are not in a state of equilibrium. What are now known to be unrelaxed monolayers of stearyl alcohol exhibit a high surface pressure phase transition whose signature in the isotherm changes from a ``kink'' (0-8 °C), to a small nearly flat region (8-15 °C), and finally to another kink (at higher temperatures). We have carried out external reflection infrared spectroscopic studies of relaxed monolayers of stearyl alcohol along a representative isotherm from each of the mentioned temperature regions. The results of our studies indicate that in each region the surfactant hydrocarbon chain becomes more ordered (i.e., has fewer gauche conformations) as the surface pressure is increased. We find that (i) at 5 °C, throughout the surface pressure range where the change in intramolecular chain order occurs, the collective tilt of the hydrocarbon chains remains nearly constant. For this isotherm the kink signals the point at which the hydrocarbon chains have achieved a very high degree of intramolecular order, perhaps the all-trans limit. (ii) In the 11 °C monolayer, in the phase often referred to as ``superfluid'', the intramolecular disorder in the hydrocarbon chains is measurably greater than in the equivalent phases in the higher and lower temperature regions. We also show that in the relaxed monolayer the nearly flat portion of the isotherm observed in the unrelaxed monolayer is almost totally absent, leaving only a kink very similar to those observed at higher and lower temperatures. (iii) At 25 °C, although the hydrocarbon chains in the relaxed monolayer attain a relatively high degree of intramolecular order, the high surface pressure phase transition is not observed. Instead, the surface pressure levels off at a value below that at which the transition is expected, and below the equilibrium spreading pressure

  10. The Rio Tinto Mars Analogue site: An extremophilic Raman spectroscopic study

    NASA Astrophysics Data System (ADS)

    Edwards, Howell G. M.; Vandenabeele, Peter; Jorge-Villar, Susana E.; Carter, Elizabeth A.; Perez, Fernando Rull; Hargreaves, Michael D.

    2007-12-01

    The Rio Tinto site is recognised as a terrestrial Mars analogue because of the presence of jarosite and related sulfates which have recently been identified by the NASA Mars Exploration Rover "Opportunity" in the El Capitan region of Meridiani Planum on Mars. It has long been known that acidophilic microbial action is responsible for the deep blood-red colour of the water in Rio Tinto, where the pH varies from about 1.5 to 3.0 and the water is rich in iron and sulfur. Following recent Raman spectroscopic characterisation of the mineral phases of the Rio Tinto system, we report here a study of the biological components found in several specimens of deposited minerals and near the waterside that were collected during a GeoRaman VI Conference organized field trip in 2006. Key biosignatures were found for carotenoids, scytonemin and mycosporine-like amino acids, which are indicative of the biological colonisation of exposed mineral substrates; information from this study will be useful for targeting Martian sites using a miniaturized Raman instrument where the biosignatures of relict or extant life could remain in the geological record.

  11. Human hemoglobin structural and functional alterations and heme degradation upon interaction with benzene: A spectroscopic study

    NASA Astrophysics Data System (ADS)

    Hosseinzadeh, Reza; Moosavi-Movahedi, Ali Akbar

    2016-03-01

    Here, the effect of benzene on hemoglobin structure, stability and heme prosthetic group integrity was studied by different methods. These included UV-vis absorption spectrophotometry, normal and synchronous fluorescence techniques, and differential scanning calorimetry (DSC). Our results indicated that benzene has high hemolytic potential even at low concentrations. The UV-vis spectroscopic results demonstrated that benzene altered both the globin chain and the heme prosthetic group of hemoglobin increasing met- and deoxy-Hb, while decreasing oxy-Hb. However, with increasing benzene the concentration of all species decreased due to heme destruction. The spectrophotometric results show that benzene has a high potential for penetrating the hydrophobic pocket of hemoglobin. These results were consistent with the molecular docking simulation results of benzene-hHb. Aggregation and thermal denaturation studies show that the increased benzene concentration induced hemoglobin aggregation with a decrease in stability, which is consistent with the DSC results. Conventional fluorescence spectroscopy revealed that the heme degradation species were produced in the presence of benzene. The results of constant wavelength synchronous fluorescence spectroscopy (CWSFS) indicated that at least five heme-degraded species were produced. Together, our results indicated that benzene has adverse effects on hemoglobin structure and function, and heme degradation.

  12. Potentiometric and spectroscopic study of the interaction of 3d transition metal ions with inositol hexakisphosphate

    NASA Astrophysics Data System (ADS)

    Veiga, Nicolás; Macho, Israel; Gómez, Kerman; González, Gabriel; Kremer, Carlos; Torres, Julia

    2015-10-01

    Among myo-inositol phosphates, the most abundant in nature is the myo-inositol hexakisphosphate, InsP6. Although it is known to be vital to cell functioning, the biochemical research into its metabolism needs chemical and structural analysis of all the protonation, complexation and precipitation processes that it undergoes in the biological media. In view of its high negative charge at physiological level, our group has been leading a thorough research into the InsP6 chemical and structural behavior in the presence of the alkali and alkaline earth metal ions essential for life. The aim of this article is to extend these studies, dealing with the chemical and structural features of the InsP6 interaction with biologically relevant 3d transition metal ions (Fe(II), Fe(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)), in a non-interacting medium and under simulated physiological conditions. The metal-complex stability constants were determined by potentiometry, showing under ligand-excess conditions the formation of mononuclear species in different protonation states. Under metal ion excess, polymetallic species were detected for Fe(II), Fe(III), Zn(II) and Cu(II). Additionally, the 31P NMR and UV-vis spectroscopic studies provided interesting structural aspects of the strong metal ion-InsP6 interaction.

  13. Studies on the inclusion behavior of 9-Aminoacridine into cyclodextrins: Spectroscopic and theoretical evidences

    NASA Astrophysics Data System (ADS)

    Manivannan, C.; Vijay Solomon, R.; Venuvanalingam, P.; Renganathan, R.

    2013-02-01

    9-Aminoacridine (9-AA) is an important attractive pharmaceutical drug employed as chemotheraptic agent for wound dressings. However, 9-AA possesses limited solubility and rapid metabolic decomposition renders this potential drug to limit its applications. Here we propose cyclodextrins (CDs) as a drug carrier to improve the bioavailability, solubility of 9-AA. The interaction between 9-AA and CDs (α-CD and β-CD) has been studied using UV-Vis absorption, steady state time resolved fluorescence, 1H NMR and FT-IR spectroscopy techniques. The spectroscopic measurements show that 9-AA does not form stable complex with α-CD and also confirmed by DFT calculations. On the other hand, 9-AA forms inclusion complex with β-CD in a 1:1 stoichiometry ratio. Our DFT results suggest that 9-AA stabilizes inside the CD environment through hydrogen bonding that has unambiguously confirmed by AIM analysis. Thus our studies provide a useful insights in the development of Aminoacridine based drugs & its delivery through a suitable carrier like CDs.

  14. Mechanism and conformational studies of farrerol binding to bovine serum albumin by spectroscopic methods

    NASA Astrophysics Data System (ADS)

    Zhang, Guowen; Wang, Lin; Fu, Peng; Hu, Mingming

    2011-11-01

    The mechanism and conformational changes of farrerol binding to bovine serum albumin (BSA) were studied by spectroscopic methods including fluorescence quenching technique, UV-vis absorption, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The results of fluorescence titration revealed that farrerol could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The thermodynamic parameters enthalpy change and entropy change for the binding were calculated to be -29.92 kJ mol -1 and 5.06 J mol -1 K -1 according to the van't Hoff equation, which suggested that the both hydrophobic interactions and hydrogen bonds play major role in the binding of farrerol to BSA. The binding distance r deduced from the efficiency of energy transfer was 3.11 nm for farrerol-BSA system. The displacement experiments of site markers and the results of fluorescence anisotropy showed that warfarin and farrerol shared a common binding site I corresponding to the subdomain IIA of BSA. Furthermore, the studies of synchronous fluorescence, CD and FT-IR spectroscopy showed that the binding of farrerol to BSA induced conformational changes in BSA.

  15. The Rio Tinto Mars analogue site: an extremophilic Raman spectroscopic study.

    PubMed

    Edwards, Howell G M; Vandenabeele, Peter; Jorge-Villar, Susana E; Carter, Elizabeth A; Perez, Fernando Rull; Hargreaves, Michael D

    2007-12-15

    The Rio Tinto site is recognised as a terrestrial Mars analogue because of the presence of jarosite and related sulfates which have recently been identified by the NASA Mars Exploration Rover "Opportunity" in the El Capitan region of Meridiani Planum on Mars. It has long been known that acidophilic microbial action is responsible for the deep blood-red colour of the water in Rio Tinto, where the pH varies from about 1.5 to 3.0 and the water is rich in iron and sulfur. Following recent Raman spectroscopic characterisation of the mineral phases of the Rio Tinto system, we report here a study of the biological components found in several specimens of deposited minerals and near the waterside that were collected during a GeoRaman VI Conference organized field trip in 2006. Key biosignatures were found for carotenoids, scytonemin and mycosporine-like amino acids, which are indicative of the biological colonisation of exposed mineral substrates; information from this study will be useful for targeting Martian sites using a miniaturized Raman instrument where the biosignatures of relict or extant life could remain in the geological record.

  16. Measurement of moisture content in photovoltaic panel encapsulants using spectroscopic optical coherence tomography: a feasibility study

    NASA Astrophysics Data System (ADS)

    Rashtchi, Shabnam; Ruiz, Pablo D.; Wildman, Ricky; Ashcroft, Ian

    2012-10-01

    EVA, a copolymer of ethylene and vinyl acetate, is a common encapsulant material used in silicon-based PV modules. It contributes to the structural integrity of the modules, provides electrical insulation and also acts as an environmental barrier. However, water can diffuse through EVA into the modules, leading to swelling and chemical degradation, which can impact interfacial bonds, leading to delamination and allowing more ingress to occur that can eventually end up in accelerated corrosion and device failure. Fourier Transform infrared spectroscopy (FTIR) and gravimetric techniques have been used to quantify water concentration and the diffusion coefficient in free standing EVA films. However, these techniques cannot be applied to measure water content in PV modules deployed in the field, as the encapsulant is usually between a glass front sheet and a back sheet made of glass or multilayered films. In this paper we study the feasibility of combining FTIR and spectroscopic optical coherence tomography (SOCT) to measure water concentration of the EVA layer inside the modules. SOCT provides depth resolved spectral information and thus has the potential of measuring water absorption at different layers in the PV module. These depth-resolved measurements are necessary to inform predictive models developed to study the structural integrity, stability and durability of PV modules. The fundamental principle of the technique is explained, the optimum spectral ranges are identified and the feasibility of a SOCT system is discussed based on light source and detector characteristics. Other strategies are also considered.

  17. Spectroscopic study of humic acids fractionated by means of tangential ultrafiltration

    NASA Astrophysics Data System (ADS)

    Francioso, O.; Sánchez-Cortés, S.; Casarini, D.; Garcia-Ramos, J. V.; Ciavatta, C.; Gessa, C.

    2002-05-01

    Different chemical and spectroscopic techniques—diffuse reflectance infrared Fourier transform (DRIFT), surface-enhanced Raman spectroscopy (SERS), and 1H, 13C nuclear magnetic resonance (NMR) have been applied to investigate a peat humic acid (HA) separated by tangential ultrafiltration into different nominal molecular weight (NMW) fractions. Each fraction analyzed showed a characteristic DRIFT and NMR pattern. High nominal molecular weight fractions were mainly characterized by long chains of methyl and methylene groups and poorly substituted aromatic rings, while in low nominal molecular weight fractions (L-NMW), phenolic and oxygen-containing groups were predominant. A comparative study on fractions before and after treatment with 0.5 M HCl was carried out. Purified fractions showed either an increase in the carboxylate and phenolic OH groups or an improvement in signal-to-noise ratio of their NMR spectra. The SERS study of NMW fractions allowed significative information on structure and conformation of these fractions. In particular, L-NMW fractions showed a great structural modification, when different alkaline extractants or treatment with HCl were used. Humic-like substances obtained by catechol and gallic acid polymerization on metal surface were investigated using SERS. The SERS spectra of these polymers were compared and discussed with those of NMW HA fractions.

  18. Understanding the solid-state forms of fenofibrate--a spectroscopic and computational study.

    PubMed

    Heinz, Andrea; Gordon, Keith C; McGoverin, Cushla M; Rades, Thomas; Strachan, Clare J

    2009-01-01

    The aim of this study was to investigate the structure of different solid-state forms of fenofibrate, a drug that lacks strong intermolecular interactions such as hydrogen bonding. In addition to a structural analysis of crystalline and amorphous fenofibrate using infrared and Raman spectroscopy combined with density functional theory calculations [B3LYP 6-31G(d)], solid-state changes that occur upon recrystallization of amorphous fenofibrate were monitored and described using in situ Raman spectroscopy. A comparison of the calculated vibrational spectra of a fenofibrate monomer and two dimer structures with the experimental vibrational spectra of crystalline and amorphous fenofibrate revealed conformational differences in the orientation of the two benzyl rings in the fenofibrate molecule and structural differences between the different solid-state forms in aliphatic parts of the drug molecule. The spectroscopic analysis suggests that non-hydrogen-bonded drug molecules are likely to exhibit more random molecular orientations and conformations in the amorphous phase since the weak intermolecular interactions that occur between such molecules can easily be disrupted. In situ Raman spectroscopy and multivariate analysis revealed multiple solid-state forms of fenofibrate, including the metastable crystalline form II, which were structurally analyzed with reference to the quantum chemical calculations. Overall, the study showed that vibrational spectroscopy, multivariate analysis, and quantum chemical modeling are well suited to investigate and characterize the structure of drug substances that exhibit only small structural differences between different solid-state forms. PMID:18590814

  19. Spectroscopic Study of ThCl+ by Two-Photon Ionization

    NASA Astrophysics Data System (ADS)

    Bartlett, Joshua; VanGundy, Robert A.; Heaven, Michael; Peterson, Kirk

    2016-06-01

    Despite the irreplaceable role experimental data plays for evaluating the performance of computational predictions, diatomic actinide species have not received much spectroscopic attention. As an early actinide element, thorium-containing species are ideal candidates for these types of studies. The electronic structure is expected to be relatively simple compared to later actinides, and therefore allows straightforward assessment of calculations. Here, we have studied ThCl+ for the first time via resonant two-photon ionization of jet-cooled ThCl produced by laser ablation of the metal reacted with dilute Cl2. Laser-induced Fluorescence (LIF) spectra have been recorded for the neutral molecule from 16000 - 23500 cm-1 in search of a suitable intermediate state for subsequent two-photon ionization experiments. Monochromator dispersion of the fluorescence has recovered the ground state vibration and anharmonic constants of ThCl. Resonant Two-Photon Ionization (R2PI) within a time-of-flight mass spectrometer was used to confirm ThCl production, and Pulsed Field Ionization Zero Kinetic Energy photoelectron spectroscopy (PFI-ZEKE) has been performed to identify the ionization energy as well as several of the low-lying states of the ThCl+ molecule. These constants have been predicted at the CASPT2 and CCSD(T) levels of theory, and a discussion of the calculations' performance will be presented alongside the recorded spectra.

  20. Near infrared photometric and optical spectroscopic study of 22 low mass star clusters embedded in nebulae

    NASA Astrophysics Data System (ADS)

    Soares, J. B.; Bica, E.; Ahumada, A. V.; Clariá, J. J.

    2008-02-01

    Aims:Among the star clusters in the Galaxy, those embedded in nebulae represent the youngest group, which has only recently been explored. The analysis of a sample of 22 candidate embedded stellar systems in reflection nebulae and/or HII environments is presented. Methods: We employed optical spectroscopic observations of stars in the directions of the clusters carried out at CASLEO (Argentina) together with near infrared photometry from the 2MASS catalogue. Our analysis is based on source surface density, colour-colour diagrams and on theoretical pre-main sequence isochrones. We take into account the field star contamination by carrying out a statistical subtraction. Results: The studied objects have the characteristics of low mass systems. We derive their fundamental parameters. Most of the cluster ages are younger than 2 Myr. The studied embedded stellar systems in reflection nebulae and/or HII region complexes do not have stars of spectral types earlier than B. The total stellar masses locked in the clusters are in the range 20-220 M⊙. They are found to be gravitationally unstable and are expected to dissolve in a timescale of a few Myr. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.

  1. Spectroscopic study on binding of gentisic acid to bovine serum albumin.

    PubMed

    Garzón, Andrés; Bravo, Iván; Carrión-Jiménez, M Rosario; Rubio-Moraga, Ángela; Albaladejo, José

    2015-01-01

    The interaction of (gentisic acid) GA with (bovine serum albumin) BSA has been studied by different spectroscopic techniques. GA is a monoanionic specie at the working pH of 7.4, it was determined by combining UV-Vis absorption spectroscopy and theoretical calculations. A set of fluorescence quenching experiments at different temperatures was carried out employing the native fluorescence of BSA. A Stern-Volmer constant (KSV) of (2.07±0.12)×10(4) mol(-1) L and a binding constant (Ka) of (8.47±4.39)×10(3) were determined at 310 K. The static quenching caused by the BSA-GA complex formation seems to play a significant role in the overall quenching process. A single binding site on BSA for GA was observed. ΔH=-55.6±0.2 kJ mol(-1) and ΔS=-104.3±0.6 J mol(-1) K(-1) were determined in a set of experiments on the dependence of Ka with the temperature. The binding process is, therefore, spontaneous and enthalpy-driven. Van der Waals forces and hydrogen bonds could also play the major role in the binding mode. The secondary structure changes of BSA in the absence and presence of GA were studied by FTIR and UV-Vis absorption spectroscopy.

  2. Time Domain Reflectometric and spectroscopic studies on toluene + butyronitrile solution

    NASA Astrophysics Data System (ADS)

    Karthick, N. K.; Arivazhagan, G.; Kumbharkhane, A. C.; Joshi, Y. S.; Kannan, P. P.

    2016-03-01

    The dielectric parameters of toluene + butyronitrile solution have been obtained by time domain reflectometry (TDR) technique in the frequency range from 10 MHz to 30 GHz at 298 K. Spectroscopic (FTIR and 13C NMR) studies have also been carried out on the solution and the results of the studies show that neat butyronitrile is self-associative through C-H⋯N contacts and weak intermolecular forces of C-H⋯N and C-H⋯π type are operative in the solution. The obtained dielectric parameters such as Kirkwood correlation factor g, relaxation time τ etc. have been analyzed in view of these weak intermolecular forces. The weak non-covalent interactions between heteromolecules appear to have no influence on the ideality of εm vs X2 curve of the solution. Heteromolecular entities with weak intermolecular forces experience larger hindrance leading to longer relaxation time τ.

  3. The effect of refluxing on the alkoxide-based sodium potassium niobate sol-gel system: Thermal and spectroscopic studies

    SciTech Connect

    Chowdhury, Anirban; Bould, Jonathan; Londesborough, Michael G.S.; Milne, Steven J.

    2011-02-15

    A study on the effects of prolonged heating under reflux conditions of up to 70 h on alkoxides of sodium, potassium and niobium dissolved in 2-methoxyethanol for the synthesis of sols of composition Na{sub 0.5}K{sub 0.5}NbO{sub 3} (NKN) has been carried out using combined thermogravimetric-Fourier transform infrared spectroscopic analyses. Extended refluxing increases the homogeneity of the Na{sub 0.5}K{sub 0.5}NbO{sub 3} (NKN) system. Spectroscopic analyses on the non-refluxed and 70 h refluxed NKN gels reveal the existence of inorganic hydrated carbonates and bicarbonates, which we propose arise from the hydration and carbonation of the samples on standing in air. The X-ray diffraction patterns of these two types of gels show orthorhombic NKN phase evolutions at higher temperatures. -- Graphical abstract: Total organic evolution plots over time for NKN dried gels obtained under different refluxing times show different thermochemical behaviours and these were investigated by thermal and spectroscopic analysis tools to find a correlation between the extent of -M-O-M- chain link formation and the amount of solvent vapour (methoxyethanol) evolution. Display Omitted Research highlights: > Prolonged refluxing of sol-gel NKN precursor solutions improves final properties of an NKN system. > An NKN process thermo-chemistry with thermal and spectroscopic analysis tools was explored. > An FTIR of NKN gels reveals tendency of NKN systems for rehydration and recarbonation on standing.

  4. Enhanced capacitance of composite TiO2 nanotube/boron-doped diamond electrodes studied by impedance spectroscopy.

    PubMed

    Siuzdak, K; Bogdanowicz, R; Sawczak, M; Sobaszek, M

    2015-01-14

    We report on novel composite nanostructures based on boron-doped diamond thin films grown on top of TiO2 nanotubes. The nanostructures made of BDD-modified titania nanotubes showed an increase in activity and performance when used as electrodes in electrochemical environments. The BDD thin films (∼200-500 nm) were deposited using microwave plasma assisted chemical vapor deposition (MW PA CVD) onto anodically fabricated TiO2 nanotube arrays. The influence of boron-doping level, methane admixture and growth time on the performance of the Ti/TiO2/BDD electrode was studied in detail. Scanning electron microscopy (SEM) was applied to investigate the surface morphology and grain size distribution. Moreover, the chemical composition of TiO2/BDD electrodes was investigated by means of micro-Raman spectroscopy. The composite electrodes TiO2/BDD are characterized by a significantly higher capacitive current compared to BDD films deposited directly onto a Ti substrate. The novel composite electrode of TiO2 nanotube arrays overgrown by boron-doped diamond (BDD) immersed in 0.1 M NaNO3 can deliver a specific capacitance of 2.10, 4.79, and 7.46 mF cm(-2) at a scan rate of 10 mV s(-1) for a [B]/[C] ratio of 2k, 5k and 10k, respectively. The substantial improvement of electrochemical performance and the excellent rate capability could be attributed to the synergistic effect of TiO2 treatment in CH4 : H2 plasma and the high electrical conductivity of BDD layers. The analysis of electrochemical impedance spectra using an electric equivalent circuit allowed us to determine the surface area on the basis of the value of constant phase element.

  5. Enhanced capacitance of composite TiO2 nanotube/boron-doped diamond electrodes studied by impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Siuzdak, K.; Bogdanowicz, R.; Sawczak, M.; Sobaszek, M.

    2014-12-01

    We report on novel composite nanostructures based on boron-doped diamond thin films grown on top of TiO2 nanotubes. The nanostructures made of BDD-modified titania nanotubes showed an increase in activity and performance when used as electrodes in electrochemical environments. The BDD thin films (~200-500 nm) were deposited using microwave plasma assisted chemical vapor deposition (MW PA CVD) onto anodically fabricated TiO2 nanotube arrays. The influence of boron-doping level, methane admixture and growth time on the performance of the Ti/TiO2/BDD electrode was studied in detail. Scanning electron microscopy (SEM) was applied to investigate the surface morphology and grain size distribution. Moreover, the chemical composition of TiO2/BDD electrodes was investigated by means of micro-Raman spectroscopy. The composite electrodes TiO2/BDD are characterized by a significantly higher capacitive current compared to BDD films deposited directly onto a Ti substrate. The novel composite electrode of TiO2 nanotube arrays overgrown by boron-doped diamond (BDD) immersed in 0.1 M NaNO3 can deliver a specific capacitance of 2.10, 4.79, and 7.46 mF cm-2 at a scan rate of 10 mV s-1 for a [B]/[C] ratio of 2k, 5k and 10k, respectively. The substantial improvement of electrochemical performance and the excellent rate capability could be attributed to the synergistic effect of TiO2 treatment in CH4 : H2 plasma and the high electrical conductivity of BDD layers. The analysis of electrochemical impedance spectra using an electric equivalent circuit allowed us to determine the surface area on the basis of the value of constant phase element.

  6. Line-Mixing Relaxation Matrix model for spectroscopic and radiative transfer studies

    NASA Astrophysics Data System (ADS)

    Mendaza, Teresa; Martin-Torres, Javier

    2016-04-01

    We present a generic model to compute the Relaxation Matrix easily adaptable to any molecule and type of spectroscopic lines or bands in non-reactive molecule collisions regimes. It also provides the dipole moment of every transition and level population of the selected molecule. The model is based on the Energy-Corrected Sudden (ECS) approximation/theory introduced by DePristo (1980), and on previous Relaxation Matrix studies for the interaction between molecular ro-vibrational levels (Ben-Rueven, 1966), atoms (Rosenkranz, 1975), linear molecules (Strow and Reuter, 1994; Niro, Boulet and Hartmann, 2004), and symmetric but not linear molecules (Tran et al., 2006). The model is open source, and it is user-friendly. To the point that the user only has to select the wished molecule and vibrational band to perform the calculations. It reads the needed spectroscopic data from the HIgh-resolution TRANsmission molecular absorption (HITRAN) (Rothman et al., 2013) and ExoMol (Tennyson and Yurchenko, 2012). In this work we present an example of the calculations with our model for the case of the 2ν3 band of methane (CH4), and a comparison with a previous work (Tran et al., 2010). The data produced by our model can be used to characterise the line-mixing effects on ro-vibrational lines of the infrared emitters of any atmosphere, to calculate accurate absorption spectra, that are needed in the interpretation of atmospheric spectra, radiative transfer modelling and General Circulation Models (GCM). References [1] A.E. DePristo, Collisional influence on vibration-rotation spectral line shapes: A scaling theoretical analysis and simplification, J. Chem. Phys. 73(5), 1980. [2] A. Ben-Reuven, Impact broadening of microwave spectra, Phys. Rev. 145(1), 7-22, 1966. [3] P.W. Rosenkranz, Shape of the 5 mm Oxygen Band in the Atmosphere, IEEE Transactions on Antennas and Propagation, vol. AP-23, no. 4, pp. 498-506, 1975. [4] Strow, L.L., D.D. Tobin, and S.E. Hannon, A compilation of

  7. AN IMAGING AND SPECTROSCOPIC STUDY OF FOUR STRONG Mg II ABSORBERS REVEALED BY GRB 060418

    SciTech Connect

    Pollack, L. K.; Prochaska, J. X.; Chen, H.-W.; Bloom, J. S.

    2009-08-20

    We present results from an imaging and spectroscopic study of four strong Mg II absorbers of W(2796) {approx}> 1 A revealed by the afterglow of GRB 060418 at z{sub GRB} = 1.491. These absorbers, at z = 0.603, 0.656, 1.107, and z {sub GRB}, exhibit large ion abundances that suggest neutral gas columns characteristic of damped Ly{alpha} systems. The imaging data include optical images obtained using Low-Resolution Imaging Spectrometer (LRIS) on the Keck I telescope and using Advanced Camera for Surveys on board Hubble Space Telescope, and near-infrared H-band images obtained using Persson's Auxiliary Nasmyth Infrared Camera on the Magellan Baade Telescope and K'-band images obtained using NIRC2 with laser guide star adaptive optics on the Keck II telescope. These images reveal six distinct objects at {delta} {theta} {approx}< 3.''5 of the afterglow's position, two of which exhibit well-resolved mature disk morphology, one shows red colors, and three are blue compact sources. Follow-up spectroscopic observations using LRIS confirm that one of the disk galaxies coincides with the Mg II absorber at z = 0.656. The observed broadband spectral energy distributions of the second disk galaxy and the red source indicate that they are associated with the absorbers at z = 0.603 and z = 1.107, respectively. These results show that strong Mg II absorbers identified in gamma-ray burst (GRB) afterglow spectra are associated with typical galaxies of luminosity {approx}0.1 - 1 L{sub *} at impact parameter of {rho} {approx}< 10 h {sup -1} kpc. The close angular separation would preclude easy detections toward a bright quasar. Finally, we associate the remaining three blue compact sources with the GRB host galaxy, noting that they are likely star-forming knots located at projected distances of {rho} = 2 - 12 h {sup -1} kpc from the afterglow. At the afterglow's position, we derive a 2{sigma} upper limit to the underlying star-formation rate intensity of 0.0074 M{sub sun} yr{sup -1} kpc

  8. Characterizing the structure of lipodisq nanoparticles for membrane protein spectroscopic studies.

    PubMed

    Zhang, Rongfu; Sahu, Indra D; Liu, Lishan; Osatuke, Anna; Comer, Raven G; Dabney-Smith, Carole; Lorigan, Gary A

    2015-01-01

    Membrane protein spectroscopic studies are challenging due to the difficulty introduced in preparing homogenous and functional hydrophobic proteins incorporated into a lipid bilayer system. Traditional membrane mimics such as micelles or liposomes have proved to be powerful in solubilizing membrane proteins for biophysical studies, however, several drawbacks have limited their applications. Recently, a nanosized complex termed lipodisq nanoparticles was utilized as an alternative membrane mimic to overcome these caveats by providing a homogeneous lipid bilayer environment. Despite all the benefits that lipodisq nanoparticles could provide to enhance the biophysical studies of membrane proteins, structural characterization in different lipid compositions that closely mimic the native membrane environment is still lacking. In this study, the formation of lipodisq nanoparticles using different weight ratios of POPC/POPG lipids to SMA polymers was characterized via solid-state nuclear magnetic resonance (SSNMR) spectroscopy and dynamic light scattering (DLS). A critical weight ratio of (1/1.25) for the complete solubilization of POPC/POPG vesicles has been observed and POPC/POPG vesicles turned clear instantaneously upon the addition of the SMA polymer. The size of lipodisq nanoparticles formed from POPC/POPG lipids at this weight ratio of (1/1.25) was found to be about 30 nm in radius. We also showed that upon the complete solubilization of POPC/POPG vesicles by SMA polymers, the average size of the lipodisq nanoparticles is weight ratio dependent, when more SMA polymers were introduced, smaller lipodisq nanoparticles were obtained. The results of this study will be helpful for a variety of biophysical experiments when specific size of lipid disc is required. Further, this study will provide a proper path for researchers working on membrane proteins to obtain pertinent structure and dynamic information in a physiologically relevant membrane mimetic environment. PMID

  9. Characterizing the structure of lipodisq nanoparticles for membrane protein spectroscopic studies.

    PubMed

    Zhang, Rongfu; Sahu, Indra D; Liu, Lishan; Osatuke, Anna; Comer, Raven G; Dabney-Smith, Carole; Lorigan, Gary A

    2015-01-01

    Membrane protein spectroscopic studies are challenging due to the difficulty introduced in preparing homogenous and functional hydrophobic proteins incorporated into a lipid bilayer system. Traditional membrane mimics such as micelles or liposomes have proved to be powerful in solubilizing membrane proteins for biophysical studies, however, several drawbacks have limited their applications. Recently, a nanosized complex termed lipodisq nanoparticles was utilized as an alternative membrane mimic to overcome these caveats by providing a homogeneous lipid bilayer environment. Despite all the benefits that lipodisq nanoparticles could provide to enhance the biophysical studies of membrane proteins, structural characterization in different lipid compositions that closely mimic the native membrane environment is still lacking. In this study, the formation of lipodisq nanoparticles using different weight ratios of POPC/POPG lipids to SMA polymers was characterized via solid-state nuclear magnetic resonance (SSNMR) spectroscopy and dynamic light scattering (DLS). A critical weight ratio of (1/1.25) for the complete solubilization of POPC/POPG vesicles has been observed and POPC/POPG vesicles turned clear instantaneously upon the addition of the SMA polymer. The size of lipodisq nanoparticles formed from POPC/POPG lipids at this weight ratio of (1/1.25) was found to be about 30 nm in radius. We also showed that upon the complete solubilization of POPC/POPG vesicles by SMA polymers, the average size of the lipodisq nanoparticles is weight ratio dependent, when more SMA polymers were introduced, smaller lipodisq nanoparticles were obtained. The results of this study will be helpful for a variety of biophysical experiments when specific size of lipid disc is required. Further, this study will provide a proper path for researchers working on membrane proteins to obtain pertinent structure and dynamic information in a physiologically relevant membrane mimetic environment.

  10. Spectroscopic study of Be-shell stars: 4 Her and 88 Her

    NASA Astrophysics Data System (ADS)

    Bhat, Shruthi S.; Paul, K. T.; Subramaniam, Annapurni; Mathew, Blesson

    2016-05-01

    We present an optical spectroscopic study based on 41 spectra of 4 Her and 32 spectra of 88 Her, obtained over a period of 6 months. We estimate the rotational velocity of these stars from HeI lines in the blue spectral region (4000-4500 Å). We find that these stars are likely to be rotating at a fractional critical rotation of ˜0.80. We measure the average I p/I c ratio to quantify the strength of the Hα line and obtain 1.63 for 4 Her and 2.06 for 88 Her. The radius of the Hα emission region is estimated to be Rd/R* ˜5.0, assuming a Keplerian disk. These stars are thus found to be fast rotators with a relatively small Hα emission region. We detect V/R variation of the Hα spectral line during the observed period. We re-estimate the periods for both stars and obtain a period of ˜46 d and its harmonic of 23.095 d for 4 Her, and a period of ˜86 d for 88 Her. As these two cases are shell stars with binaries and have low Hα EW with the emission region closer to the central star, the V/R variation and a change in period may be an effect of the binary on the circumstellar disk.

  11. Toward High Performance Graphene-based Solar Cells: Spectroscopic Study on Doped Graphene

    NASA Astrophysics Data System (ADS)

    Chang, Jan-Kai; Hsu, Chen-Chih; Lin, Wei-Hsiang; Wu, Chih-I.; Yeh, Nai-Chang

    2015-03-01

    A polymer-free transfer method with in situ doping process for graphene, aiming at simple and efficient doping of residue-free graphene, has been developed to achieve stacked graphene/dopant intercalation films. The proposed facile strategy led to a tunable work function from 3.25 eV to 5.10 eV, enabling graphene anode and cathode for solar cell devices. Both hybrid and organic photovoltaics using graphene electrodes have been carried out with a series of optimization based on spectroscopic characterizations. Since aging of doped graphene is crucial to the lifetime of graphene-based solar cells, the doping-induced electronic state variation with time has been investigated via X-ray and ultra-violet photoemission spectroscopy analysis to gain insight in its electronic properties and stability. The doping effect developed in graphene has also been studied via Raman spectroscopy, including time evolution of the Raman D, G and 2D bands under normal and humid conditions for up to 30 days. This systematic investigation of aging effect provides better understanding and helps optimize the stacking of doped graphene films for achieving high performance graphene-based devices. This work is supported by NSC of R.O.C. (Dragon Gate Program) and NSF for the work at Caltech.

  12. Spectroscopic investigations, molecular interactions, and molecular docking studies on the potential inhibitor "thiophene-2-carboxylicacid".

    PubMed

    Karthick, T; Balachandran, V; Perumal, S

    2015-04-15

    Thiophene derivatives have been focused in the past decades due to their remarkable biological and pharmacological activities. In connection with that the conformational stability, spectroscopic characterization, molecular (inter- and intra-) interactions, and molecular docking studies on thiophene-2-carboxylicacid have been performed in this work by experimental FT-IR and theoretical quantum chemical computations. Experimentally recorded FT-IR spectrum in the region 4000-400 cm(-1) has been compared with the scaled theoretical spectrum and the spectral peaks have been assigned on the basis of potential energy distribution results obtained from MOLVIB program package. The conformational stability of monomer and dimer conformers has been examined. The presence of inter- and intramolecular interactions in the monomer and dimer conformers have been explained by natural bond orbital analysis. The UV-Vis spectra of the sample in different solvents have been simulated and solvent effects were predicted by polarisable continuum model with TD-DFT/B3LYP/6-31+G(d,p) method. To test the biological activity of the sample, molecular docking (ligand-protein) simulations have been performed using SWISSDOCK web server. The full fitness (FF) score and binding affinity values revealed that thiophene-2-carboxylicacid can act as potential inhibitor against inflammation.

  13. Synthesis and spectroscopic studies of some chromium and molybdenum derivatives of bis-(acetylacetone)ethylenediimine ligand

    NASA Astrophysics Data System (ADS)

    Ramadan, Ramadan M.; Abdel-Rahman, Laila H.; Ismael, Mohamed; Youssef, Teraze A.; Ali, Saadia A.

    2013-10-01

    Interaction of [Cr(CO)6] with bis-(acetylacetone)ethylenediimine Schiff base, H2acacen, under reduced pressure resulted in the formation of [Cr(CO)3(H2acacen)] derivative. The Schiff base acted as a tridentate and coordinated the metal through the nitrogen of the azomethine groups and one hydroxyl group. Reaction of [Mo(CO)6] with H2acacen under sunlight irradiation in presence of air gave the oxo derivative [Mo2O6(H2acacen)2]. The ligand acted as a bidentate and coordinated the metal through the two imine groups. In presence of 2,2'-bipyridine (bpy), the reaction of [Mo(CO)6] with H2acacen gave [Mo2O6(bpy)(H2acacec)]. The structures of the reported complexes were proposed on the basis of spectroscopic studies. The proposed structures were also verified by theoretical calculations based on accurate DFT approximations. Moreover, the relative reactivity was estimated using chemical descriptors analysis.

  14. Studies on the interaction of apigenin with calf thymus DNA by spectroscopic methods

    NASA Astrophysics Data System (ADS)

    Zhang, Shufang; Sun, Xuejun; Kong, Rongmei; Xu, Mingming

    2015-02-01

    The interaction between apigenin and calf thymus deoxyribonucleic acid (ctDNA) in a pH 7.4 Tris-HCl buffer solution was investigated by UV-Vis spectroscopy, fluorescence spectroscopy, DNA melting techniques, and viscosity measurements. It was found that apigenin molecules could intercalate into the base pairs of DNA, forming a apigenin-DNA complex with a binding constant of K310K = 6.4 × 104 L mol-1. The thermodynamic parameters enthalpy change (ΔH), entropy change (ΔS) and Gibbs free energy (ΔG) were calculated to be 7.36 × 104 J mol-1, 329 J K-1 mol-1 and -2.84 × 104 J mol-1 at 310 K, respectively. Hydrophobic interaction was the predominant intermolecular force in stabilizing the apigenin-DNA complex. Thermal denaturation study suggested that the stabilization of the ctDNA helix was increased when the apigenin binding to ctDNA as indicated by the increase in thermal denaturation temperature of ctDNA at around 5.0 °C in the presence of apigenin. Spectroscopic techniques together with melting techniques and viscosity determination provided evidences of intercalation mode of binding for the interaction between apigenin and ctDNA.

  15. Internal Photoemission and X-Ray Photoelectron Spectroscopic Studies of Sulfur-Passivated GaAs

    NASA Astrophysics Data System (ADS)

    Sato, Kenji; Ikoma, Hideaki

    1993-02-01

    Internal photoemission and X-ray photoelectron spectroscopic (XPS) measurements were performed to investigate the effect of sulfur passivation on the GaAs surface and the degradation of the GaAs surface exposed to air ambient after the passivation. The reverse bias dependence of the Schottky barrier height was very small in the as-sulfur-treated sample and was mainly explained by the image force lowering effect. However, it increased as this sample was exposed to air, indicating an increase in the interface state density. The XPS studies showed that both the Ga and As oxides were hardly observed in the sulfur-passivated samples. This indicates that sulfur passivation strongly suppresses oxidation of GaAs. However, a small amount of elemental arsenic was observed with a trace of the As suboxides (such as AsO) after exposure to air and it increased as the exposure time was increased. These results were probably correlated with the increase in the bias dependence of the Schottky barrier height in samples exposed to air after the passivation. Thermal oxidation of GaAs was found to be retarded by sulfur passivation until oxidation time was about 10 min at 300°C. A possible model of suppression of oxidation by sulfur passivation was also discussed.

  16. ATR-FTIR spectroscopic studies of boric acid adsorption on hydrous ferric oxide

    NASA Astrophysics Data System (ADS)

    Peak, Derek; Luther, George W.; Sparks, Donald L.

    2003-07-01

    Boron is an important micronutrient for plants, but high B levels in soils are often responsible for toxicity effects in plants. It is therefore important to understand reactions that may affect B availability in soils. In this study, Attenuated Total Reflectance Fourier transform Infrared (ATR-FTIR) spectroscopy was employed to investigate mechanisms of boric acid (B(OH) 3) and borate (B(OH) 4-) adsorption on hydrous ferric oxide (HFO). On the HFO surface, boric acid adsorbs via both physical adsorption (outer-sphere) and ligand exchange (inner-sphere) reactions. Both trigonal (boric acid) and tetrahedral (borate) boron are complexed on the HFO surface, and a mechanism where trigonal boric acid in solution reacts to form either trigonal or tetrahedral surface complexes is proposed based upon the spectroscopic results. The presence of outer-sphere boric acid complexes can be explained based on the Lewis acidity of the B metal center, and this complex has important implications for boron transport and availability. Outer-sphere boric acid is more likely to leach downward in soils in response to water flow. Outer-sphere boron would also be expected to be more available for plant uptake than more strongly bound boron complexes, and may more readily return to the soil solution when solution concentrations decrease.

  17. Structural, spectroscopic and DFT study of 4-methoxybenzohydrazide Schiff bases. A new series of polyfunctional ligands.

    PubMed

    Ferraresi-Curotto, Verónica; Echeverría, Gustavo A; Piro, Oscar E; Pis-Diez, Reinaldo; González-Baró, Ana C

    2015-02-25

    Five Schiff bases obtained from condensation of 4-methoxybenzohydrazide with related aldehydes, namely o-vanillin, vanillin, 5-bromovanillin, 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde were prepared. A detailed structural and spectroscopic study is reported. The crystal structures of four members of the family were determined and compared with one another. The hydrazones obtained from 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde resulted to be isomorphic to each other. The solid-state structures are stabilized by intra-molecular O-H⋯N interactions in salicylaldehyde derivatives between the O-H moiety from the aldehyde and the hydrazone nitrogen atom. All crystals are further stabilized by inter-molecular H-bonds mediated by the crystallization water molecule. A comparative analysis between experimental and theoretical results is presented. The conformational space was searched and geometries were optimized both in gas phase and including solvent effects. The structure is predicted for the compound for which the crystal structure was not determined. Infrared and electronic spectra were measured and assigned with the help of data obtained from computational methods based on the Density Functional Theory.

  18. Spectroscopic investigations, molecular interactions, and molecular docking studies on the potential inhibitor "thiophene-2-carboxylicacid"

    NASA Astrophysics Data System (ADS)

    Karthick, T.; Balachandran, V.; Perumal, S.

    2015-04-01

    Thiophene derivatives have been focused in the past decades due to their remarkable biological and pharmacological activities. In connection with that the conformational stability, spectroscopic characterization, molecular (inter- and intra-) interactions, and molecular docking studies on thiophene-2-carboxylicacid have been performed in this work by experimental FT-IR and theoretical quantum chemical computations. Experimentally recorded FT-IR spectrum in the region 4000-400 cm-1 has been compared with the scaled theoretical spectrum and the spectral peaks have been assigned on the basis of potential energy distribution results obtained from MOLVIB program package. The conformational stability of monomer and dimer conformers has been examined. The presence of inter- and intramolecular interactions in the monomer and dimer conformers have been explained by natural bond orbital analysis. The UV-Vis spectra of the sample in different solvents have been simulated and solvent effects were predicted by polarisable continuum model with TD-DFT/B3LYP/6-31+G(d,p) method. To test the biological activity of the sample, molecular docking (ligand-protein) simulations have been performed using SWISSDOCK web server. The full fitness (FF) score and binding affinity values revealed that thiophene-2-carboxylicacid can act as potential inhibitor against inflammation.

  19. Spectroscopic studies of the size and composition of single aerosol droplets

    NASA Astrophysics Data System (ADS)

    Reid, Jonathan P.; Meresman, Helena; Mitchem, Laura; Symes, Rachel

    The characterization of aerosol properties and processes, non-intrusively and directly, poses a severe analytical challenge. In order to understand the role of aerosols in often complex environments, it is necessary to probe the particles in situ and without perturbation. Sampling followed by end-of-line analysis can lead to perturbations in particle composition, morphology and size, particularly when analysing liquid aerosol droplets containing volatile components. Optical spectroscopy can provide a strategy for the direct assessment of particle size, composition and phase. We review here the application of linear and non-linear Raman spectroscopies in the characterization of liquid aerosol droplets. Spontaneous Raman scattering can allow the unambiguous identification of chemical components and the determination of droplet composition. Stimulated Raman spectroscopy can allow the determination of droplet size with nanometre accuracy and can allow the characterization of near-surface composition. When combined, the mixing state and homogeneity in droplet composition can be investigated. We highlight some applications of these spectroscopic techniques in studies of the kinetics of particle transformation, the equilibrium composition of aqueous aerosol droplets, and the coagulation and mixing state of organic and aqueous aerosol components. Specifically, we examine the heat and mass transfer accompanying the evaporation of volatile components from liquid droplets, the equilibrium size of aqueous/sodium chloride droplets with varying relative humidity, and the mixing of the immiscible decane and water components during droplet coagulation. We conclude by considering the potential of these techniques for improving our understanding of aerosol properties and processes.

  20. Spectroscopic studies of the interaction of bichromophoric cyanine dyes with DNA. Effect of ionic strength.

    PubMed

    Schaberle, Fábio A; Kuz'min, Vladimir A; Borissevitch, Iouri E

    2003-05-01

    Spectroscopic characteristics of a cyanine dye with two chromophores (biscyanine dye, BCD) in aqueous solutions and effects of NaCl and DNA upon these characteristics have been studied by optical absorption, circular dichroism (CD) and fluorescence spectroscopies. In homogeneous solutions, BCD is characterized by intense optical absorption (epsilon =1.33 x 10(5) M(-1) x cm(-1)) and weak fluorescence (phi(fl)=0.018) in the wavelength region greater than 600 nm. The dye forms H-aggregates at low concentrations (10(-6) M). NaCl stimulates the formation of both H- and J-aggregates of the dye at much lower dye concentrations, while DNA in low concentrations (<10(-6) M) stimulated the formation of just J-aggregates on the surface of the DNA molecule. Higher DNA concentrations induce the dye to disaggregate, and there exists an equilibrium between three dye forms: free monomers, J-aggregates and bound monomers, the maximum content of J-aggregates was observed at [DNA]/[BCD]=0.6+/-0.2 and total disaggregation at [DNA]/[BCD]=190+/-20. J-aggregates are characterized by phi(fl)=0.05 and bound monomers by phi(fl)=0.44. In the presence of NaCl, total disaggregation was observed at [DNA]/[BCD]=570+/-10 due to competition between Na(+) and the dye molecules for DNA electronegative binding sites.

  1. Application of spectroscopic techniques for the analysis of kidney stones: a pilot study

    NASA Astrophysics Data System (ADS)

    Shameem, K. M., Muhammed; Chawla, Arun; Bankapur, Aseefhali; Unnikrishnan, V. K.; Santhosh, C.

    2016-03-01

    Identification and characterization of kidney stone remains one of the important analytical tasks in the medical field. Kidney stone is a common health complication throughout the world, which may cause severe pain, obstruction and infection of urinary tract, and can lead to complete renal damage. It commonly occurs in both sexes regardless of age. Kidney stones have different composition, although each stones have a major single characteristic component. A complete understanding of a sample properties and their function can only be feasible by utilizing elemental and molecular information simultaneously. Two laser based analytical techniques; Laser Induced Breakdown spectroscopy (LIBS) and Raman spectroscopy have been used to study different types of kidney stones from different patients. LIBS and Raman spectroscopy are highly complementary spectroscopic techniques, which provide elemental and molecular information of a sample. Q-switched Nd:YAG laser at 355 nm laser having energy 17mJ per pulse at 10 Hz repetition rate was used for getting LIBS spectra. Raman measurements were carried out using a home assembled micro-Raman spectrometer. Using the recorded Raman spectra of kidney stones, we were able to differentiate different kinds of kidney stones. LIBS spectra of the same stones are showing the evidence of C, Ca, H, and O and also suggest the presence of certain pigments.

  2. A spectroscopic study of the Globular Cluster M28 (NGC 6626)

    NASA Astrophysics Data System (ADS)

    Villanova, S.; Moni Bidin, C.; Mauro, F.; Munoz, C.; Monaco, L.

    2016-10-01

    We present the abundance analysis for a sample of 17 red giant branch stars in the metal-poor globular cluster M28 based on high resolution spectra. This is the first extensive spectroscopic study of this cluster. We derive abundances of O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Ba, La, Ce, and Eu. We find a metallicity of [Fe/H]=-1.29±0.01 and an α-enhancement of +0.34±0.01 (errors on the mean), typical of Halo Globular Clusters in this metallicity regime. A large spread is observed in the abundances of light elements O, Na, and Al. Mg also shows an anticorrelation with Al with a significance of 3σ. The cluster shows a Na-O anticorrelation and a Na-Al correlation. This correlation is not linear but "segmented" and that the stars are not distributed continuously, but form at least 3 well separated sub-populations. In this aspect M28 resembles NGC 2808 that was found to host at least 5 sub-populations. The presence of a Mg-Al anticorrelation favor massive AGB stars as the main polluters responsible for the multiple-population phenomenon.

  3. Spectroscopic Study of Terahertz Generation in Mid-Infrared Quantum Cascade Lasers.

    PubMed

    Jiang, Yifan; Vijayraghavan, Karun; Jung, Seungyong; Jiang, Aiting; Kim, Jae Hyun; Demmerle, Frederic; Boehm, Gerhard; Amann, Markus C; Belkin, Mikhail A

    2016-02-16

    Terahertz quantum cascade laser sources based on intra-cavity difference-frequency generation are currently the only room-temperature mass-producible diode-laser-like emitters of coherent 1-6 THz radiation. Device performance has improved dramatically over the past few years to reach milliwatt-level power output and broad tuning from 1.2 to 5.9 THz, all at room-temperature. Terahertz output in these sources originates from intersubband optical nonlinearity in the laser active region. Here we report the first comprehensive spectroscopic study of the optical nonlinearity and investigate its dependence on the mid-infrared pump frequencies. Our work shows that the terahertz generation efficiency can vary by a factor of 2 or greater depending on the spectral position of the mid-infrared pumps for a fixed THz difference-frequency. We have also measured for the first time the linewidth for transitions between the lower quantum cascade laser states, which is critical for determining terahertz nonlinearity and predicting optical loss in quantum cascade laser waveguides.

  4. Structural, spectroscopic and DFT study of 4-methoxybenzohydrazide Schiff bases. A new series of polyfunctional ligands.

    PubMed

    Ferraresi-Curotto, Verónica; Echeverría, Gustavo A; Piro, Oscar E; Pis-Diez, Reinaldo; González-Baró, Ana C

    2015-02-25

    Five Schiff bases obtained from condensation of 4-methoxybenzohydrazide with related aldehydes, namely o-vanillin, vanillin, 5-bromovanillin, 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde were prepared. A detailed structural and spectroscopic study is reported. The crystal structures of four members of the family were determined and compared with one another. The hydrazones obtained from 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde resulted to be isomorphic to each other. The solid-state structures are stabilized by intra-molecular O-H⋯N interactions in salicylaldehyde derivatives between the O-H moiety from the aldehyde and the hydrazone nitrogen atom. All crystals are further stabilized by inter-molecular H-bonds mediated by the crystallization water molecule. A comparative analysis between experimental and theoretical results is presented. The conformational space was searched and geometries were optimized both in gas phase and including solvent effects. The structure is predicted for the compound for which the crystal structure was not determined. Infrared and electronic spectra were measured and assigned with the help of data obtained from computational methods based on the Density Functional Theory. PMID:25255482

  5. Study of Ellagic Acid as a Natural Elastase Inhibitor by Spectroscopic Methods

    NASA Astrophysics Data System (ADS)

    Xing, X.; Yang, X.; Cao, Yu.

    2016-03-01

    A new natural inhibitor, ellagic acid (EA), was developed, and its inhibition efficiency on elastase was studied by spectroscopic methods. The experimental results proved that EA is a potent elastase inhibitor with an IC50 value of 1.44 mg/mL by UV-vis spectroscopy, and the inhibition mechanism of elastase was confirmed by fluorescence quenching. The interacting between EA and elastase was mainly based on the static quenching owing to the complex formation when the concentration of EA was ≤40 μM. Fluorescence quenching mainly occurred via dynamic quenching with increasing EA concentration. The thermodynamic parameters such as ΔH and ΔS were calculated to be -86.35 kJ/mol and -165.88 J/mol · K, respectively, indicating that the interactions between EA and elastase were mainly due to van der Waals forces or hydrogen bonding. The synchronous fl uorescence spectra showed that binding of EA to elastase can induce conformational changes in elastase.

  6. Binding of the anticancer alkaloid sanguinarine with tRNA(phe): spectroscopic and calorimetric studies.

    PubMed

    Hossain, Maidul; Kabir, Ayesha; Suresh Kumar, Gopinatha

    2012-01-01

    The interaction of the natural plant alkaloid and anticancer agent sanguinarine with tRNA(phe) has been investigated by spectroscopic and calorimetric techniques. Sanguinarine iminium binds to tRNA(phe) cooperatively; alkanolamine does not bind but in presence of large tRNA(phe) concentration, a conversion from alkanolamine to iminium occurs resulting in concomitant binding of the latter. The binding affinity of the iminium to tRNA(phe) obtained from isothermal titration calorimetry was of the order of 10(5) M(-1), which is close to that evaluated from spectroscopy. The binding was driven largely by negative enthalpy and a smaller but favourable positive entropy change. The binding was dependent on the [Na(+)] concentration, but had a larger non-electrostatic contribution to the Gibbs energy. A small heat capacity value and the enthalpy-entropy compensation in the energetics of the interaction characterized the binding of the iminium form to tRNA(phe). This study confirms that the tRNA(phe) binding moiety is the iminium form of sanguinarine. PMID:22702734

  7. Dissolution of tablet-in-tablet formulations studied with ATR-FTIR spectroscopic imaging.

    PubMed

    Wray, Patrick S; Clarke, Graham S; Kazarian, Sergei G

    2013-03-12

    This work uses ATR-FTIR spectroscopic imaging to study the dissolution of delayed release and pH resistant compressed coating pharmaceutical tablets. Tablets with an inner core and outer shell were constructed using a custom designed compaction cell. The core of the delayed release tablets consisted of hydroxypropyl methylcellulose (HPMC) and caffeine. The shell consisted of microcrystalline cellulose (MCC) and glucose. The core of the pH resistant formulations was an ibuprofen and PEG melt and the shell was constructed from HPMC and a basic buffer. UV/vis spectroscopy was used to monitor the lag-time of drug release and visible optical video imaging was used as a complementary imaging technique with a larger field of view. Two delayed release mechanisms were established. For tablets with soluble shell sections, lag-time was dependent upon rapid shell dissolution. For tablets with less soluble shells, the lag-time was controlled by the rate of dissolution medium ingress through the shell and the subsequent expansion of the wet HPMC core. The pH resistant formulations prevented crystallization of the ibuprofen in the core during dissolution despite an acidic dissolution medium. FTIR imaging produced important information about the physical and chemical processes occurring at the interface between tablet sections during dissolution. PMID:23291036

  8. Spectroscopic and MD simulation studies on unfolding processes of mitochondrial carbonic anhydrase VA induced by urea.

    PubMed

    Idrees, Danish; Prakash, Amresh; Haque, Md Anzarul; Islam, Asimul; Ahmad, Faizan; Hassan, Md Imtaiyaz

    2016-09-01

    Carbonic anhydrase VA (CAVA) is primarily expressed in the mitochondria and involved in numerous physiological processes including lipogenesis, insulin secretion from pancreatic cells, ureagenesis, gluconeogenesis and neuronal transmission. To understand the biophysical properties of CAVA, we carried out a reversible urea-induced isothermal denaturation at pH 7.0 and 25°C. Spectroscopic probes, [θ]222 (mean residue ellipticity at 222 nm), F344 (Trp-fluorescence emission intensity at 344 nm) and Δε280 (difference absorption at 280 nm) were used to monitor the effect of urea on the structure and stability of CAVA. The urea-induced reversible denaturation curves were used to estimate [Formula: see text], Gibbs free energy in the absence of urea; Cm, the mid-point of the denaturation curve, i.e. molar urea concentration ([urea]) at which ΔGD = 0; and m, the slope (=∂ΔGD/∂[urea]). Coincidence of normalized transition curves of all optical properties suggests that unfolding/refolding of CAVA is a two-state process. We further performed 40 ns molecular dynamics simulation of CAVA to see the dynamics at different urea concentrations. An excellent agreement was observed between in silico and in vitro studies.

  9. Structural, spectroscopic and DFT study of 4-methoxybenzohydrazide Schiff bases. A new series of polyfunctional ligands

    NASA Astrophysics Data System (ADS)

    Ferraresi-Curotto, Verónica; Echeverría, Gustavo A.; Piro, Oscar E.; Pis-Diez, Reinaldo; González-Baró, Ana C.

    2015-02-01

    Five Schiff bases obtained from condensation of 4-methoxybenzohydrazide with related aldehydes, namely o-vanillin, vanillin, 5-bromovanillin, 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde were prepared. A detailed structural and spectroscopic study is reported. The crystal structures of four members of the family were determined and compared with one another. The hydrazones obtained from 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde resulted to be isomorphic to each other. The solid-state structures are stabilized by intra-molecular Osbnd H⋯N interactions in salicylaldehyde derivatives between the Osbnd H moiety from the aldehyde and the hydrazone nitrogen atom. All crystals are further stabilized by inter-molecular H-bonds mediated by the crystallization water molecule. A comparative analysis between experimental and theoretical results is presented. The conformational space was searched and geometries were optimized both in gas phase and including solvent effects. The structure is predicted for the compound for which the crystal structure was not determined. Infrared and electronic spectra were measured and assigned with the help of data obtained from computational methods based on the Density Functional Theory.

  10. Synthesis, spectroscopic characterization and electrochemical studies of Girard's T chromone complexes

    NASA Astrophysics Data System (ADS)

    Al-Saeedi, Sameerah I.; Alaghaz, Abdel-Nasser M. A.; Ammar, Reda A.

    2016-05-01

    Complexes of cobalt(II), nickel(II), copper(II) and zinc(II) of general composition [M(L)2] have been. The elemental analyses, molar conductance, spectral, magnetic moment and thermal measurements studies of the compounds led to the conclusion that the ligand acts as a tridentate manner (OON). The molar conductance of the metal complexes in fresh solution of DMSO lies in the range of 8.10-10.18 Ω-1 cm2 mol-1 indicating their non-electrolytic behavior. On the basis of analytical and spectroscopic techniques, octahedral geometry of the complexes was proposed. The ligand field parameters were calculated for Co(II), Ni(II) and Cu(II) complexes and their values were found in the range reported for a octahedral structure. The data show that the complexes have composition of ML2 type. The activation of thermodynamic parameters are calculated using different equations. The octahedral geometry of the complexes is confirmed using DFT method from DMOL3 calculations and ligand field parameters. The cyclic voltammograms of the Cu(II)/Co(II)/Ni(II) complexes investigated in DMSO solution exhibit metal centered electroactivity in the potential range -1.5 to +1.5 V. The electrochemical data obtained for Cu(II) complexes explains the change of structural arrangement of the ligand around Cu(II) ions.

  11. Spectroscopic studies of Wolf-Rayet stars. III - The WC subclass

    NASA Technical Reports Server (NTRS)

    Torres, A. V.; Conti, P. S.; Massey, P.

    1986-01-01

    Wolf-Rayet (W-R) stars, which are the descendants of massive O-type stars, can be subdivided into three groups depending on their spectral appearance. These groups include the nitrogen class (WN), the carbon class (WC), and the oxygen class (WO). The present paper is concerned with the WC stars. The assignment of WC subtypes has been based on visual inspections of photographic plates. One of the aims of this study is related to the quantification of the visual estimates. The measured ratios of equivalent widths and the FWHM of the 4650 A line for Galactic and LMC stars are presented, and the reclassification of some stars is proposed on this basis. In particular, it is shown that the majority of the LMC WC stars should logically be classified WC4 instead of WC5. Comments on individual stars are provided, and terminal velocities are discussed. It is attempted to give a complete overview of the most important spectroscopic features of the WC stars in the optical region.

  12. Spectroscopic study of Be-shell stars: 4 Her and 88 Her

    NASA Astrophysics Data System (ADS)

    Bhat, Shruthi S.; Paul, K. T.; Subramaniam, Annapurni; Mathew, Blesson

    2016-05-01

    We present an optical spectroscopic study based on 41 spectra of 4 Her and 32 spectra of 88 Her, obtained over a period of 6 months. We estimate the rotational velocity of these stars from HeI lines in the blue spectral region (4000–4500 Å). We find that these stars are likely to be rotating at a fractional critical rotation of ˜0.80. We measure the average I p/I c ratio to quantify the strength of the Hα line and obtain 1.63 for 4 Her and 2.06 for 88 Her. The radius of the Hα emission region is estimated to be Rd/R* ˜5.0, assuming a Keplerian disk. These stars are thus found to be fast rotators with a relatively small Hα emission region. We detect V/R variation of the Hα spectral line during the observed period. We re-estimate the periods for both stars and obtain a period of ˜46 d and its harmonic of 23.095 d for 4 Her, and a period of ˜86 d for 88 Her. As these two cases are shell stars with binaries and have low Hα EW with the emission region closer to the central star, the V/R variation and a change in period may be an effect of the binary on the circumstellar disk.

  13. Spectroscopic Study of Terahertz Generation in Mid-Infrared Quantum Cascade Lasers

    PubMed Central

    Jiang, Yifan; Vijayraghavan, Karun; Jung, Seungyong; Jiang, Aiting; Kim, Jae Hyun; Demmerle, Frederic; Boehm, Gerhard; Amann, Markus C.; Belkin, Mikhail A.

    2016-01-01

    Terahertz quantum cascade laser sources based on intra-cavity difference-frequency generation are currently the only room-temperature mass-producible diode-laser-like emitters of coherent 1–6 THz radiation. Device performance has improved dramatically over the past few years to reach milliwatt-level power output and broad tuning from 1.2 to 5.9 THz, all at room-temperature. Terahertz output in these sources originates from intersubband optical nonlinearity in the laser active region. Here we report the first comprehensive spectroscopic study of the optical nonlinearity and investigate its dependence on the mid-infrared pump frequencies. Our work shows that the terahertz generation efficiency can vary by a factor of 2 or greater depending on the spectral position of the mid-infrared pumps for a fixed THz difference-frequency. We have also measured for the first time the linewidth for transitions between the lower quantum cascade laser states, which is critical for determining terahertz nonlinearity and predicting optical loss in quantum cascade laser waveguides. PMID:26879901

  14. WIYN open cluster study. LX. Spectroscopic binary orbits in NGC 6819

    SciTech Connect

    Milliman, Katelyn E.; Mathieu, Robert D.; Gosnell, Natalie M.; Geller, Aaron M.; Meibom, Søren; Platais, Imants

    2014-08-01

    We present the current state of the WOCS radial-velocity (RV) survey for the rich open cluster NGC 6819 (2.5 Gyr) including 93 spectroscopic binary orbits with periods ranging from 1.5 to 8000 days. These results are the product of our ongoing RV survey of NGC 6819 using the Hydra Multi-Object Spectrograph on the WIYN 3.5 m telescope. We also include a detailed analysis of multiple prior sets of optical photometry for NGC 6819. Within a 1° field of view, our stellar sample includes the giant branch, the red clump, and blue straggler candidates, and extends to almost 2 mag below the main sequence (MS) turnoff. For each star observed in our survey we present all RV measurements, the average RV, and velocity variability information. Additionally, we discuss notable binaries from our sample, including eclipsing binaries (WOCS 23009, WOCS 24009, and WOCS 40007), stars noted in Kepler asteroseismology studies (WOCS 4008, WOCS 7009, and WOCS 8007), and potential descendants of past blue stragglers (WOCS 1006 and WOCS 6002). We find the incompleteness-corrected binary fraction for all MS binaries with periods less than 10{sup 4} days to be 22% ± 3% and a tidal circularization period of 6.2{sub −1.1}{sup +1.1} days for NGC 6819.

  15. Hunting the parent of the Orphan stream. II. The first high-resolution spectroscopic study

    SciTech Connect

    Casey, Andrew R.; Keller, Stefan C.; Da Costa, Gary; Maunder, Elizabeth; Frebel, Anna

    2014-03-20

    We present the first high-resolution spectroscopic study on the Orphan stream for five stream candidates, observed with the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Clay telescope. The targets were selected from the low-resolution catalog of Casey et al.: three high-probability members, one medium, and one low-probability stream candidate were observed. Our analysis indicates that the low- and medium-probability targets are metal-rich field stars. The remaining three high-probability targets range over ∼1 dex in metallicity, and are chemically distinct compared to the other two targets and all standard stars: low [α/Fe] abundance ratios are observed, and lower limits are ascertained for [Ba/Y], which sit well above the Milky Way trend. These chemical signatures demonstrate that the undiscovered parent system is unequivocally a dwarf spheroidal galaxy, consistent with dynamical constraints inferred from the stream width and arc. As such, we firmly exclude the proposed association between NGC 2419 and the Orphan stream. A wide range in metallicities adds to the similarities between the Orphan stream and Segue 1, although the low [α/Fe] abundance ratios in the Orphan stream are in tension with the high [α/Fe] values observed in Segue 1. Open questions remain before Segue 1 could possibly be claimed as the 'parent' of the Orphan stream. The parent system could well remain undiscovered in the southern sky.

  16. Spectroscopic study of partially-ordered semiconductor heterojunction under high pressure and high magnetic field

    SciTech Connect

    Yu, P.Y.; Martinez, G.; Zeman, J.; Uchida, K.

    2000-12-31

    Photoluminescence upconversion (PLU) is a phenomenon in which a sample emits photons with energy higher than that of the excitation photon. This effect has been observed in many materials including rare earth ions doped in insulating hosts and semiconductor heterostructures without using high power lasers as the excitation source. Recently, this effect has been observed also in partially CuPt-ordered GaInP{sub 2} epilayers grown on GaAs substrates. As a spectroscopic technique photoluminescence upconversion is particularly well suited for studying band alignment at heterojunction interface. The value of band-offset has been determined with meV precision using magneto-photoluminescence. Using the fact that the pressure coefficient of electrons in GaAs is higher than those in GaInP{sub 2} they have been able to manipulate the band-offset at the GaInP/GaAs interface. By converting the band-offset from Type I to Type II they were able to demonstrate that the efficiency of the upconversion process is greatly enhanced by a Type II band-offset.

  17. A combined spectroscopic and theoretical study of propofol.(H2O)3

    NASA Astrophysics Data System (ADS)

    León, Iker; Cocinero, Emilio J.; Millán, Judith; Rijs, Anouk M.; Usabiaga, Imanol; Lesarri, Alberto; Castaño, Fernando; Fernández, José A.

    2012-08-01

    Propofol (2,6-di-isopropylphenol) is probably the most widely used general anesthetic. Previous studies focused on its complexes containing 1 and 2 water molecules. In this work, propofol clusters containing three water molecules were formed using supersonic expansions and probed by means of a number of mass-resolved laser spectroscopic techniques. The 2-color REMPI spectrum of propofol.(H2O)3 contains contributions from at least two conformational isomers, as demonstrated by UV/UV hole burning. Using the infrared IR/UV double resonance technique, the IR spectrum of each isomer was obtained both in ground and first excited electronic states and interpreted in the light of density functional theory (DFT) calculations at M06-2X/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. The spectral analysis reveals that in both isomers the water molecules are forming cyclic hydrogen bond networks around propofol's OH moiety. Furthermore, some evidences point to the existence of isomerization processes, due to a complicated conformational landscape and the existence of multiple paths with low energy barriers connecting the different conformers. Such processes are discussed with the aid of DFT calculations.

  18. Photometric and spectroscopic study of low mass embedded star clusters in reflection nebulae

    NASA Astrophysics Data System (ADS)

    Soares, J. B.; Bica, E.; Ahumada, A. V.; Clariá, J. J.

    2005-02-01

    An analysis of the candidate embedded stellar systems in the reflection nebulae vdBH-RN 26, vdBH-RN} 38, vdBH-RN} 53a, GGD 20, ESO 95-RN 18 and NGC 6595 is presented. Optical spectroscopic data from CASLEO (Argentina) in conjunction with near infrared photometry from the 2MASS Point Source Catalogue were employed. The analysis is based on source surface density, colour-colour and colour-magnitude diagrams together with theoretical pre-main sequence isochrones. We take into account the field population affecting the analysis by carrying out a statistical subtraction. The fundamental parameters for the stellar systems were derived. The resulting ages are in the range 1-4 Myr and the objects are dominated by pre-main sequence stars. The observed masses locked in the clusters are less than 25 M⊙. The studied systems have no stars of spectral types earlier than B, indicating that star clusters do not necessarily evolve through an HII region phase. The relatively small locked mass combined with the fact that they are not numerous in catalogues suggests that these low mass clusters are not important donors of stars to the field populations. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.

  19. {sup 1}H NMR spectroscopic studies establish that heparanase is a retaining glycosidase

    SciTech Connect

    Wilson, Jennifer C.; Laloo, Andrew Elohim; Singh, Sanjesh; Ferro, Vito

    2014-01-03

    Highlights: •{sup 1}H and {sup 13}C NMR chemical shifts of fondaparinux were fully assigned by 1D and 2D NMR techniques. •Hydrolysis of fondaparinux by heparanase was monitored by {sup 1}H NMR spectroscopy. •Heparanase is established to be a retaining glycosidase. -- Abstract: Heparanase is an endo-β-glucuronidase that cleaves heparan sulfate side chains of proteoglycans in basement membranes and the extracellular matrix (ECM). Heparanase is implicated in several diverse pathological processes associated with ECM degradation such as metastasis, inflammation and angiogenesis and is thus an important target for anti-cancer and anti-inflammatory drug discovery. Heparanase has been classed as belonging to the clan A glycoside hydrolase family 79 based on sequence analysis, secondary structure predictions and mutagenic analysis, and thus it has been inferred that it is a retaining glycosidase. However, there has been no direct experimental evidence to support this conclusion. Herein we describe {sup 1}H NMR spectroscopic studies of the hydrolysis of the pentasaccharide substrate fondaparinux by heparanase, and provide conclusive evidence that heparanase hydrolyses its substrate with retention of configuration and is thus established as a retaining glycosidase. Knowledge of the mechanism of hydrolysis may have implications for future design of inhibitors for this important drug target.

  20. Spectroscopic Studies of Carotenoid-to-Bacteriochlorophyll Energy Transfer in LHRC Photosynthetic Complex from Roseiflexus castenholzii

    SciTech Connect

    Niedzwiedzki, Dariusz; Collins, Aaron M.; LaFountain, Amy M.; Enriquez, Miriam M.; Frank, Harry A.; Blankenship, R. E.

    2010-06-14

    Carotenoids present in the photosynthetic light-harvesting reaction center (LHRC) complex from chlorosome lacking filamentous anoxygenic phototroph, Roseiflexus castenholzii were purified and characterized for their photochemical properties. The LHRC from anaerobically grown cells contains five different carotenoids, methoxy-keto-myxocoxanthin, γ-carotene, and its three derivatives, whereas the LHRC from aerobically grown cells contains only three carotenoid pigments with methoxy-keto-myxocoxanthin being the dominant one. The spectroscopic properties and dynamics of excited singlet states of the carotenoids were studied by steady-state absorption, fluorescence and ultrafast time-resolved optical spectroscopy in organic solvent and in the intact LHRC complex. Time-resolved transient absorption spectroscopy performed in the near-infrared (NIR) on purified carotenoids combined with steady-state absorption spectroscopy led to the precise determination of values of the energies of the S1(21Ag-) excited state. Global and single wavelength fitting of the ultrafast spectral and temporal data sets of the carotenoids in solvents and in the LHRC revealed the pathways of de-excitation of the carotenoid excited states.

  1. Spectroscopic, luminescence, electrochemical and antimicrobial studies of lanthanide complexes of bis-benzimidazole derived ligands

    NASA Astrophysics Data System (ADS)

    Siddiqi, Zafar A.; Shahid, Anjuli M.; Khalid, Mohd.; Sharma, Prashant K.; Siddique, Armeen

    2013-04-01

    The lanthanide complexes of [1,2-bis(benzimidazole-2-yl)ethane dihydrochloride], L1·2HCl and [1,4-bis(benzimidazole-2-onium)butane dihydrochloride], L2·2HCl having molecular formulae [Ln(L1)2Cl3H2O] and [Ln(L2)2Cl3H2O]·2H2O (Ln = La3+, Pr3+, Nd3+ and Gd3+), respectively, were prepared and characterized through IR, 1H and 13C NMR, ESI-mass, UV-visible and luminescence spectroscopic techniques. TGA data suggested presence of the coordinated and the lattice water. The oscillator strengths of the f-f transitions and the covalency parameters (β, b1/2 and δ) have been evaluated from the electronic spectral data. The proposed octa coordinate geometry for the complexes has been ascertained from the molecular model computations. CV studies indicate formation of stable quasi-reversible redox couples PrIII/IV, Nd III/IV and GdIII/IV in solution. The in vitro antimicrobial activities of the complexes have been evaluated against gram +ve and gram -ve bacteria and fungi.

  2. Spectroscopic Studies of Cyclopentane under Extreme Conditions and Implications for the P-T Phase Diagram

    NASA Astrophysics Data System (ADS)

    Ma, Chunli; Liu, Zhenxian; Cui, Qiliang; Hemley, Russell

    2013-06-01

    Infrared (IR) spectroscopy and Raman scattering combined with diamond anvil cell (DAC) and cryogenic techniques have been employed to investigate cyclopentane up to 4 GPa in the temperature range of 100-350 K and isothermal compression up to 84 GPa at room temperature. Four phases including liquid, plastic phases I and II, and truly crystalline phase III are clearly identified in the P-T range studied based on the changes of the ring breathing mode and CH2 rocking modes. The phase diagram is extended to the pressure and temperature range of 0 - 4.0 GPa and 105 - 350 K. Further compression at room temperature up to 84 GPa, another high-pressure phase (IV) is observed based on the appearance of low frequency peaks related to the lattice vibrational modes in the synchrotron far-IR spectra. The spectroscopic results indicate that cyclopentane persists the orientation ordered crystalline phase up to 84 GPa at room temperature. This work was supported by NSF (DMR-0805056; EAR 06-49658, COMPRES) and DOE/ NNSA (DE-FC03-03N00144, CDAC). NSLS is supported by the DOE/BES (DE-AC02-98CH10886).

  3. Photometric and spectroscopic study of the intermediate-age open cluster NGC 2355

    NASA Astrophysics Data System (ADS)

    Donati, P.; Bragaglia, A.; Carretta, E.; D'Orazi, V.; Tosi, M.; Cusano, F.; Carini, R.

    2015-11-01

    In this paper we analyse the evolutionary status and properties of the old open cluster NGC 2355, located in the Galactic anticentre direction, as a part of the long-term programme Bologna Open Clusters Chemical Evolution. NGC 2355 was observed with the Large Binocular Camera at the Large Binocular Telescope using the Bessel B, V, and Ic filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram method, as done in other papers of this series. Additional spectroscopic observations with the Fibre-fed Echelle Spectrograph at the Nordic Optical Telescope of three giant stars were used to determine the chemical properties of the cluster. Our analysis shows that NGC 2355 has metallicity slightly less than solar, with [Fe/H]= -0.06 dex, age between 0.8 and 1 Gyr, reddening E(B - V) in the range 0.14-0.19 mag, and distance modulus (m - M)0 of about 11 mag. We also investigate the abundances of O, Na, Al, α, iron-peak, and neutron capture elements, showing that NGC 2355 falls within the abundance distribution of similar clusters (same age and metallicity). The Galactocentric distance of NGC 2355 places it at the border between two regimes of metallicity distribution; this makes it an important cluster for the study of the chemical properties and evolution of the disc.

  4. Layered structure of room-temperature ionic liquids in microemulsions by multinuclear NMR spectroscopic studies.

    PubMed

    Falcone, R Dario; Baruah, Bharat; Gaidamauskas, Ernestas; Rithner, Christopher D; Correa, N Mariano; Silber, Juana J; Crans, Debbie C; Levinger, Nancy E

    2011-06-01

    Microemulsions form in mixtures of polar, nonpolar, and amphiphilic molecules. Typical microemulsions employ water as the polar phase. However, microemulsions can form with a polar phase other than water, which hold promise to diversify the range of properties, and hence utility, of microemulsions. Here microemulsions formed by using a room-temperature ionic liquid (RTIL) as the polar phase were created and characterized by using multinuclear NMR spectroscopy. (1)H, (11)B, and (19)F NMR spectroscopy was applied to explore differences between microemulsions formed by using 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]) as the polar phase with a cationic surfactant, benzylhexadecyldimethylammonium chloride (BHDC), and a nonionic surfactant, Triton X-100 (TX-100). NMR spectroscopy showed distinct differences in the behavior of the RTIL as the charge of the surfactant head group varies in the different microemulsion environments. Minor changes in the chemical shifts were observed for [bmim](+) and [BF(4)](-) in the presence of TX-100 suggesting that the surfactant and the ionic liquid are separated in the microemulsion. The large changes in spectroscopic parameters observed are consistent with microstructure formation with layering of [bmim](+) and [BF(4)](-) and migration of Cl(-) within the BHDC microemulsions. Comparisons with NMR results for related ionic compounds in organic and aqueous environments as well as literature studies assisted the development of a simple organizational model for these microstructures. PMID:21547960

  5. Mediaeval cantorals in the Valladolid Biblioteca: FT-Raman spectroscopic study.

    PubMed

    Edwards, H G; Farwell, D W; Rull Perez, F; Medina Garcia, J

    2001-03-01

    Raman spectroscopic studies of three mediaeval cantorals in the Biblioteca of the University of Valladolid has revealed information about the pigments used on these large manuscripts. Although executed in a simple colour palette, very pure cinnabar was used as the major colourant, offsetting the carbon black of the verses and script. A dark blue colour was achieved using a mixture of azurite (basic copper carbonate) and carbon, whereas a light blue colour was azurite alone. A grey colour was achieved using azurite, carbon particles and a calcareous 'limewash'. A yellow pigment, used sparely in the cantorals was ascribed to saffron; unusually, there was no evidence for the presence of the yellow mineral pigments orpiment, realgar and massicot. In several regions of the vellum specimens, evidence for biodeterioration was observed through the signatures of hydrated calcium oxalate. We report for the first time the Raman spectra of pigment in situ on a vellum fragment, which also shows evidence of substrate bands; comparison of black and red pigmented regions of vellum specimens has shown the presence of calcium oxalate in the black pigmented script but not in the red pigment regions, which suggests that the cinnabar in the red-pigmented regions acts as a toxic protectant for the vellum substrate against biological colonisation processes.

  6. Spectroscopic studies on the oxidation of carbonyl compounds by OH radicals in the aqueous solution

    NASA Astrophysics Data System (ADS)

    Schaefer, T.; Herrmann, H.

    2009-04-01

    The atmospheric conversation and degradation of volatile organic compounds (VOCs) is often initiated by radical reactions. One of the most important radical in the atmosphere is the OH-radical. Oxidation reactions of water soluble organic compounds in the atmospheric aqueous phase (cloud droplets, fog, rain, deliquescent particles) can be as fast as in the gas phase, but lead to different reaction products or different product distributions. The objective of this work is to identify and characterize the various transient species formed in the oxidation of carbonyl compounds such as acetone. This characterization is necessary to measure rate constants of elementary reaction steps in the course of the degradation process. The spectroscopic and kinetic information obtained will allow a better understanding of the atmospheric fate of carbonyl compounds. In order to characterize the optical properties of the formed transient compounds (e.g. organic peroxy radicals) a laser photolysis long path absorption apparatus coupled with a CCD-camera / grating combination is used. With this technique time resolved spectra (at different delay times after the excimer laser pulse) of the reactants and products can be recorded. Within this contribution organic peroxy radical spectra of the following parent carbonyl compounds (a) acetone, (b) hydroxyacetone, (c) methylglyoxal and (d) pyruvic acid will be presented, discussed and compared with literature data. OH radicals were generated directly in the reaction cell by the photolysis of hydrogen peroxide (H2O2) at 248 nm. All reactions were studied at T = 298K in the aqueous solution.

  7. A spectroscopic study of uranyl-cytochrome b5/cytochrome c interactions

    NASA Astrophysics Data System (ADS)

    Sun, Mei-Hui; Liu, Shuang-Quan; Du, Ke-Jie; Nie, Chang-Ming; Lin, Ying-Wu

    2014-01-01

    Uranium is harmful to human health due to its radiation damage and the ability of uranyl ion (UO22+) to interact with various proteins and disturb their biological functions. Cytochrome b5 (cyt b5) is a highly negatively charged heme protein and plays a key role in mediating cytochrome c (cyt c) signaling in apoptosis by forming a dynamic cyt b5-cyt c complex. In previous molecular modeling study in combination with UV-Vis studies, we found that UO22+ is capable of binding to cyt b5 at surface residues, Glu37 and Glu43. In this study, we further investigated the structural consequences of cyt b5 and cyt c, as well as cyt b5-cyt c complex, upon uranyl binding, by fluorescence spectroscopic and circular dichroism techniques. Moreover, we proposed a uranyl binding site for cyt c at surface residues, Glu66 and Glu69, by performing a molecular modeling study. It was shown that uranyl binds to cyt b5 (KD = 10 μM), cyt c (KD = 87 μM), and cyt b5-cyt c complex (KD = 30 μM) with a different affinity, which slightly alters the protein conformation and disturbs the interaction of cyt b5-cyt c complex. Additionally, we investigated the functional consequences of uranyl binding to the protein surface, which decreases the inherent peroxidase activity of cyt c. The information of uranyl-cyt b5/cyt c interactions gained in this study likely provides a clue for the mechanism of uranyl toxicity.

  8. Near-infrared spectroscopic studies of self-forming lipids and nanovesicles

    NASA Astrophysics Data System (ADS)

    Bista, Rajan K.; Bruch, Reinhard F.

    2009-02-01

    Lipids and liposomes have remained an active research topic for several decades due to their significance as membrane model. Several vibrational spectroscopic techniques have been developed and employed to study the properties of lipids and liposomes. In this study, near-infrared (NIR) spectroscopy has been used to analyze a suite of synthesized PEGylated lipids trademarked as QuSomesTM. The three amphiphiles used in this study, differ in their apolar hydrophobic chain length and contain various units of polar polyethylene glycol (PEG) head groups. In contrast to conventional phospholipids, this new kind of lipids forms liposomes spontaneously upon hydration, without the supply of external activation energy. Whilst the NIR spectra of QuSomesTM show a common pattern, differences in the spectra are observed which enable the lipids to be distinguished. NIR absorption spectra of these new artificial lipids have been recorded in the spectral range of 4800-9000 cm-1 (~2100-1100 nm) by using a new miniaturized spectrometer based on micro-optical-electro-mechanical systems (MOEMS) technology. In particular, we have established specific band structures as "molecular fingerprints" corresponding to overtones and combinations vibrational modes involving mainly C-H and O-H functional groups for sample analysis of QuSomesTM. Moreover, we have demonstrated that the nanovesicles formed by such lipids in polar solvents show high stability and obey Beer's law at low concentration. The results reported in this study may find applications in various field including the development of lipids based drug delivery systems.

  9. Chelerythrine-lysozyme interaction: spectroscopic studies, thermodynamics and molecular modeling exploration.

    PubMed

    Jash, Chandrima; Basu, Pritha; Payghan, Pavan V; Ghoshal, Nanda; Kumar, Gopinatha Suresh

    2015-07-01

    The binding of the iminium and alkanolamine forms of chelerythrine to lysozyme (Lyz) was investigated by spectroscopy and docking studies. The thermodynamics of the binding was studied by calorimetry. Spectroscopic evidence suggested that Trp-62 and Trp-63 in the β-domain of the protein are closer to the binding site; moreover, the binding site was at a distance of 2.27 and 2.00 nm from the iminium and alkanolamine forms, respectively, according to the Forster theory of non-radiation energy transfer. The equilibrium binding constants for the iminium and alkanolamine forms at 298 K were evaluated to be 1.29 × 10(5) and 7.79 × 10(5) M(-1), respectively. The binding resulted in an alteration of the secondary structure of the protein with a distinct reduction of the helical organization. The binding of iminium was endothermic, involving electrostatic and hydrophobic interactions, while that of alkanolamine form was exothermic and dominated by hydrogen bonding interactions. Docking studies provided the atomistic details pertaining to the binding of both forms of chelerythrine and supported the higher binding in favour of the alkanolamine over the iminium. Furthermore, molecular dynamics study provided accurate insights regarding the binding of both chelerythrine forms in accordance with the experimental results obtained. Chelerythrine binding pocket involves the catalytic region and aggregation prone K-peptide region, which are sandwiched between one another. Overall, these results suggest that both the forms of the alkaloid bind to the protein but the neutral form has higher affinity than the cationic form.

  10. Origin of Capacity Fading in Nano-Sized Co3O4Electrodes: Electrochemical Impedance Spectroscopy Study

    PubMed Central

    2008-01-01

    Transition metal oxides have been suggested as innovative, high-energy electrode materials for lithium-ion batteries because their electrochemical conversion reactions can transfer two to six electrons. However, nano-sized transition metal oxides, especially Co3O4, exhibit drastic capacity decay during discharge/charge cycling, which hinders their practical use in lithium-ion batteries. Herein, we prepared nano-sized Co3O4with high crystallinity using a simple citrate-gel method and used electrochemical impedance spectroscopy method to examine the origin for the drastic capacity fading observed in the nano-sized Co3O4anode system. During cycling, AC impedance responses were collected at the first discharged state and at every subsequent tenth discharged state until the 100th cycle. By examining the separable relaxation time of each electrochemical reaction and the goodness-of-fit results, a direct relation between the charge transfer process and cycling performance was clearly observed.

  11. Line narrowing spectroscopic studies of DNA-carcinogen adducts and DNA-dye complexes

    SciTech Connect

    Suh, Myungkoo

    1995-12-06

    Laser-induced fluorescence line narrowing and non-line narrowing spectroscopic methods were applied to conformational studies of stable DNA adducts of the 7{beta}, 8{alpha}-dihydoxy-9{alpha}, l0{alpha}-epoxy-7,8,9, 10-tetrahydrobenzo[{alpha}]pyrene (anti-BPDE). Stereochemically distinct (+)-trans-, ({minus})-trans-, (+)-cis- and ({minus})-cis adducts of anti-BPDE bound to exocyclic amino group of the central guanine in an 11-mer oligonucleotide, exist in a mixture of conformations in frozen aqueous buffer matrices. The (+)-trans adduct adopts primarily an external conformation with a smaller fraction ( {approximately} 25 %) exists in a partially base-stacked conformation. Both cis adducts were found to be intercalated with significant {pi}-{pi} stacking interactions between the pyrenyl residues and the bases. Conformations of the trans-adduct of (+)-anti -BPDE in 11-mer oligonucleotides were studied as a function of flanking bases. In single stranded form the adduct at G{sub 2} or G{sub 3} (5 ft-flanking, base guanine) adopts a conformation with strong, interaction with the bases. In contrast, the adduct with a 5ft-flanking, thymine exists in a primarily helixexternal conformation. Similar differences were observed in the double stranded oligonucleotides. The nature of the 3ft-flanking base has little influence on the conformational equilibrium of the (+)-trans-anti BPDE-dG adduct. The formation and repair of BPDE-N{sup 2}-dG in DNA isolated from the skin of mice treated topically with benzo[{alpha}]pyrene (BP) was studied. Low-temperature fluorescence spectroscopy of the intact DNA identified the major adduct as (+)-trans-anti-BPDE-N-dG, and the minor adduct fraction consisted mainly of (+)-cis-anti-BPDE-N{sup 2}-dG.

  12. Synthesis and spectroscopic studies of the aminoglycoside (neomycin)--perylene conjugate binding to human telomeric DNA.

    PubMed

    Xue, Liang; Ranjan, Nihar; Arya, Dev P

    2011-04-12

    Synthesis of a novel perylene-neomycin conjugate (3) and the properties of its binding to human telomeric G-quadruplex DNA, 5'-d[AG3(T2AG3)3] (4), are reported. Various spectroscopic techniques were employed to characterize the binding of conjugate 3 to 4. A competition dialysis assay revealed that 3 preferentially binds to 4, in the presence of other nucleic acids, including DNA, RNA, DNA-RNA hybrids, and other higher-order structures (single strands, duplexes, triplexes, other G-quadruplexes, and the i-motif). UV thermal denaturation studies showed that thermal stabilization of 4 increases as a function of the increasing concentration of 3. The fluorescence intercalator displacement (FID) assay displayed a significantly tighter binding of 3 with 4 as compared to its parent constituents [220-fold stronger than neomycin (1) and 4.5-fold stronger than perylene diamine (2), respectively]. The binding of 3 with 4 resulted in pronounced changes in the molar ellipticity of the DNA absorption region as confirmed by circular dichroism. The UV-vis absorption studies of the binding of 3 to 4 resulted in a red shift in the spectrum of 3 as well as a marked hypochromic change in the perylene absorption region, suggesting that the ligand-quadruplex interaction involves stacking of the perylene moiety. Docking studies suggest that the perylene moiety serves as a bridge that end stacks on 4, making contacts with two thymine bases in the loop, while the two neomycin moieties branch into the grooves of 4.

  13. Optical properties of As33S67-xSex bulk glasses studied by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Orava, J.; Šik, J.; Wágner, T.; Frumar, M.

    2008-04-01

    Variable angle spectroscopic ellipsometry (VASE) was employed to study the optical properties of As33S67-xSex (x =0, 17, 33.5, 50, and 67at.%) bulk glasses in the UV-vis-NIR (near infrared) spectral region for photon energies from 0.54to4.13eV (photon wavelengths from 2300to300nm). For data analysis, we employed Tauc-Lorentz (TL) dispersion model in the entire measured near bandgap spectral region and standard Cauchy dispersion model in the spectral region below the bandgap. With increasing Se content (x) in the bulk glass, we observed a linear decrease in optical bandgap energy Egopt from 2.52±0.02eV for As33S67 to 1.75±0.01eV for As33Se67 and linear increase in refractive index nTL in the NIR spectral region, e.g., at 0.80eV from 2.327 for As33S67 to 2.758 for As33Se67. The amplitude A decreased with increasing Se content. The peak transition energy E0 and broadening C had a maximum value for x =33.5at.% and systematically decreased for higher S or Se content in glasses. Our study showed that TL model is suitable to describe dielectric functions of studied chalcogenide bulk glasses in the broad spectral region. The bulk glasses had a higher refractive index compared to thin films of corresponding composition. The bulk glasses with high S content had higher value of optical bandgap energy than was previously reported for thin films. The optical bandgap energy of glasses with higher Se content was very similar to the thin films.

  14. Manipulating the proton transfer process in molecular complexes: synthesis and spectroscopic studies.

    PubMed

    Panja, Sumit Kumar; Dwivedi, Nidhi; Saha, Satyen

    2016-08-01

    The proton transfer process in carefully designed molecular complexes has been investigated directly in the solid and solution phase. SCXRD studies have been employed to investigate the N-H-O bonding interaction sites of the molecular complexes, with additional experimental support from FTIR and Raman spectroscopic studies, to gain information on the relative position of hydrogen in between the N and O centers. Further, the proton transfer process in solution is studied using UV-Visible spectroscopy through monitoring the intramolecular charge transfer (ICT) process in these molecular complexes, which is primarily governed by the number of electron withdrawing groups (nitro groups) on proton donor moieties (NP, DNP and TNP). It is found that the magnitude of the ICT process depends on the extent of proton transfer, which on the other hand depends on the relative stabilities of the constituent species (phenolate species). A correlation is observed between an increase in the number of nitro groups and an increase in the melting point of the molecular complexes, indicating the enhancement of ionic character due to the proton transfer process. The aliphatic H-bonding is identified and monitored using (1)H-NMR spectroscopy, which reveals that the identity of molecular complexes in solution interestingly depends on the extent of proton transfer, in addition to the nature of the solvents. The aliphatic C-H-O H-bonding interaction between the oxygen atom of the nitro group and the alkyl hydrogen in piperidinium was also found to play a significant role in strengthening the primary interaction involving a hydrogen transfer process. The conductivity of the molecular complexes increases with an increase in the number of nitro groups, indicating the enhancement in ionic character of the molecular complexes. PMID:27424765

  15. Studies of the Use of Electrochemical Impedance Spectroscopy to Characterize and Assess the Performance of Lacquers Used to Protect Aluminum Sheet and Can Ends

    NASA Astrophysics Data System (ADS)

    Ali, Mohammad

    This study involved investigating the feasibility of using Electrochemical Impedance Spectroscopy to assess the performance of coatings used to protect aluminum in beverage containers, and developing an accelerated testing procedure. In the preliminary investigation, tests were performed to ensure that the EIS systems at hand are capable, functional and consistent. This was followed by EIS testing of kitchen-aluminum foil and high-impedance epoxy polymer as a baseline for chemically-active and chemically-inert systems. The ability of EIS to differentiate between intact and flawed coatings was tested by investigating deliberately damaged coatings. The effects of varying the pH and oxygen content on the performance of the coated aluminum samples were also tested. From this investigation, it has been concluded that EIS can be used to differentiate between intact and flawed coatings and detect corrosion before it is visually observable. Signatures of corrosion have been recorded and a preliminary testing procedure has been drawn.

  16. Electrical biopsy of irradiated intestinal tissue with a simple electrical impedance spectroscopy system for radiation enteropathy in rats--a pilot study.

    PubMed

    Huang, Yu-Jie; Huang, Eng-Yen; Lu, Yi-Yu; Chen, Cheng-Yu; Cheng, Kuo-Sheng

    2011-09-01

    Electrical impedance is one of the most often used parameters for characterizing material properties, especially in biomedical applications. Electrical impedance spectroscopy (EIS), used for revealing both resistive and capacitive characteristics, is good for use in tissue characterization. In this study, a portable and simple EIS system based on a commercially available chip was used to assess rat intestinal tissues following irradiation. The EIS results were fitted to a resistor and capacitor electrical circuit model to solve the electrical properties of the tissue. The variation in the tissue's electrical characteristics was compared to the morphological and histological findings. From the experimental results, it was clear that the electrical properties, based on receiver operation curve analysis, demonstrated good detection performance relative to the histological changes. The electrical parameters of the tissues could be used to distinguish the tissue's status for investigation, which introduced a concept of 'electrical biopsy', and this 'electrical biopsy' approach may be used to complement histological examinations.

  17. Effect of low-temperature conditions on passive layer growth in Li intercalation materials: In situ impedance study

    SciTech Connect

    Barsoukov, E.; Kim, J.H.; Kim, J.H.; Yoon, C.O.; Lee, H.

    1998-08-01

    Electrochemical impedance spectroscopy has been applied to investigate the formation of insulating layers at the surfaces of microscopic particles of mesocarbon microbeads (MCMB), graphite, and hard carbon during the first Li-intercalation into these materials at ambient temperature as well as at {minus}20 C. Investigations were carried out in a three-electrode sandwich cell, designed for impedance measurements in the frequency range 64 kHz to 5 mHz. The impedance spectra, obtained in the potential range 1.5 and 0.02 V during the first charge, were analyzed by complex nonlinear least square fits. A new model, taking into account the porous structure of the intercalation material, electrochemical processes at the interface, as well as spherical diffusion of Li ions toward the centers of the particles, has been used for this analysis. The first intercalation at {minus}20 C results in formation of an insulating layer, which is about 90 times thinner than in the room-temperature case, as concluded from an analysis of experimental results. The irreversible capacity loss, which is 1.3 times larger at {minus}20 C that at room temperature, is ascribed to the formation of a porous precipitate of electrolyte decomposition products on the particle surface. Additional Li intercalation at room temperature results in an irreversible capacity loss of 26% from the initial value, and formation of a composite layer, including low-temperature and room-temperature deposited components.

  18. Electrochemical impedance spectroscopy to study physiological changes affecting the red blood cell after invasion by malaria parasites.

    PubMed

    Ribaut, Clotilde; Reybier, Karine; Reynes, Olivier; Launay, Jérôme; Valentin, Alexis; Fabre, Paul Louis; Nepveu, Françoise

    2009-04-15

    The malaria parasite, Plasmodium falciparum, invades human erythrocytes and induces dramatic changes in the host cell. The idea of this work was to use RBC modified electrode to perform electrochemical impedance spectroscopy (EIS) with the aim of monitoring physiological changes affecting the erythrocyte after invasion by the malaria parasite. Impedance cell-based devices are potentially useful to give insight into cellular behavior and to detect morphological changes. The modelling of impedance plots (Nyquist diagram) in equivalent circuit taking into account the presence of the cellular layer, allowed us pointing out specific events associated with the development of the parasite such as (i) strong changes in the host cell cytoplasm illustrated by changes in the film capacity, (ii) perturbation of the ionic composition of the host cell illustrated by changes in the film resistance, (iii) releasing of reducer (lactic acid or heme) and an enhanced oxygen consumption characterized by changes in the charge transfer resistance and in the Warburg coefficient characteristic of the redox species diffusion. These results show that the RBC-based device may help to analyze strategic events in the malaria parasite development constituting a new tool in antimalarial research.

  19. Equilibrium, Kinetics, and Spectroscopic Studies of SF6 Hydrate in NaCl Electrolyte Solution.

    PubMed

    Seo, Youngrok; Moon, Donghyun; Lee, Changho; Park, Jeong-Woo; Kim, Byeong-Soo; Lee, Gang-Woo; Dotel, Pratik; Lee, Jong-Won; Cha, Minjun; Yoon, Ji-Ho

    2015-05-19

    Many studies have focused on desalination via hydrate formation; however, for their potential application, knowledge pertaining to thermodynamic stability, formation kinetics, and guest occupation behavior in clathrate hydrates needs to be determined. Herein, the phase equilibria of SF6 hydrates in the presence of NaCl solutions (0, 2, 4, and 10 wt %) were monitored in the temperature range of 277-286 K and under pressures of up to 1.4 MPa. The formation kinetics of SF6 hydrates in the presence of NaCl solutions (0, 2, and 4 wt %) was also investigated. Gas consumption curves of SF6 hydrates showed that a pure SF6 hydrate system allowed fast hydrate growth as well as high conversion yield, whereas SF6 hydrate in the presence of NaCl solutions showed retarded hydrate growth rate as well as low conversion yield. In addition, structural identification of SF6 hydrates with and without NaCl solutions was performed using spectroscopic tools such as Raman spectroscopy and X-ray diffraction. The Raman spectrometer was also used to evaluate the temperature-dependent release behavior of guest molecules in SF6 and SF6 + 4 wt % NaCl hydrates. The results indicate that whereas SF6 hydrate starts to decompose at around 240 K, the escape of SF6 molecules in SF6 + 4 wt % NaCl hydrate is initiated rapidly at around 205 K. The results of this study can provide a better understanding of guest-host interaction in electrolyte-containing systems. PMID:25893445

  20. A New Optical Cell for Spectroscopic Studies of Geofluids at Pressures up to 100 MPa

    NASA Astrophysics Data System (ADS)

    Chou, I.; Burruss, R. C.

    2003-12-01

    Interpretation of Raman and fluorescence spectra of hydrocarbon fluid inclusions and spectroscopic observations of reactions in hydrocarbon-water systems require high quality reference spectra of individual gases, gas mixtures, and hydrocarbon-water systems. We constructed a new optical cell from a square flexible fused silica capillary tube (300 μ m x 300 μ m with 100 μ m x 100 μ m cavity) and a high-pressure valve that allows studies of fluids at room temperature and pressures up to 100 MPa. The cell has several advantages over existing ones, including the hydrothermal diamond-anvil cell, and they are: (1) ability to directly load sample fluids and monitor pressure during investigation; (2) no optical distortion; (3) small cell volume suitable for samples of limited supply (e.g., commercially available gas mixtures); (4) high pressures can be achieved; (5) a high-magnification, high-numerical-aperture objective lens (e.g., 100x) with a short working distance can be used due to the thin wall of the capillary tube, and (6) a heating-cooling stage can be added, allowing for investigations at temperatures other than room temperature, particularly suitable for studies of gas hydrates. Raman spectra have been collected from the cell for methane, ethane, propane, n-butane, and also for two gas mixtures containing up to 9 components as a function of pressure up to 41 MPa. The spectra document the shift in Raman bands with pressure as well as constrain the detection limits for various gas species in the mixtures. Preliminary experiments on the diffusion of methane in water were conducted by monitoring the concentration of dissolved methane in water, as a function of time and distance from the vapor-water boundary, immediately after the perturbation of an equilibrium state induced by a sudden change in methane pressure.

  1. Study on the interaction between ginsenoside Rh2 and calf thymus DNA by spectroscopic techniques.

    PubMed

    Wu, Dudu; Chen, Zhi

    2015-12-01

    The interaction between ginsenoside Rh2 (G-Rh2) and calf thymus DNA (ctDNA) was investigated by spectroscopic methods including UV-vis absorption, fluorescence and circular dichroism (CD) spectroscopy, coupled with DNA melting techniques and viscosity measurements. Stern-Volmer plots at different temperatures proved that the quenching mechanism was a static quenching procedure. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) were calculated to be -22.83 KJ · mol(-1) and 15.11 J · mol(-1) · K(-1) by van 't Hoff equation, suggesting that hydrophobic force might play a major role in the binding of G-Rh2 to ctDNA. Moreover, the fluorescence quenching study with potassium iodide as quencher indicated that the KSV (Stern-Volmer quenching constant) value for the bound G-Rh2 with ctDNA was lower than the free G-Rh2. The relative viscosity of ctDNA increased with the addition of G-Rh2 and also the ctDNA melting temperature increased in the presence of G-Rh2. Denatured DNA studies showed that quenching by single-stranded DNA was less than that by double-stranded DNA. The observed changes in CD spectra also demonstrated that the intensities of the positive and negative bands decreased with the addition of G-Rh2. The experimental results suggest that G-Rh2 molecules bind to ctDNA via an intercalative binding mode.

  2. Study on the interaction between ginsenoside Rh2 and calf thymus DNA by spectroscopic techniques.

    PubMed

    Wu, Dudu; Chen, Zhi

    2015-12-01

    The interaction between ginsenoside Rh2 (G-Rh2) and calf thymus DNA (ctDNA) was investigated by spectroscopic methods including UV-vis absorption, fluorescence and circular dichroism (CD) spectroscopy, coupled with DNA melting techniques and viscosity measurements. Stern-Volmer plots at different temperatures proved that the quenching mechanism was a static quenching procedure. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) were calculated to be -22.83 KJ · mol(-1) and 15.11 J · mol(-1) · K(-1) by van 't Hoff equation, suggesting that hydrophobic force might play a major role in the binding of G-Rh2 to ctDNA. Moreover, the fluorescence quenching study with potassium iodide as quencher indicated that the KSV (Stern-Volmer quenching constant) value for the bound G-Rh2 with ctDNA was lower than the free G-Rh2. The relative viscosity of ctDNA increased with the addition of G-Rh2 and also the ctDNA melting temperature increased in the presence of G-Rh2. Denatured DNA studies showed that quenching by single-stranded DNA was less than that by double-stranded DNA. The observed changes in CD spectra also demonstrated that the intensities of the positive and negative bands decreased with the addition of G-Rh2. The experimental results suggest that G-Rh2 molecules bind to ctDNA via an intercalative binding mode. PMID:25727213

  3. Equilibrium, Kinetics, and Spectroscopic Studies of SF6 Hydrate in NaCl Electrolyte Solution.

    PubMed

    Seo, Youngrok; Moon, Donghyun; Lee, Changho; Park, Jeong-Woo; Kim, Byeong-Soo; Lee, Gang-Woo; Dotel, Pratik; Lee, Jong-Won; Cha, Minjun; Yoon, Ji-Ho

    2015-05-19

    Many studies have focused on desalination via hydrate formation; however, for their potential application, knowledge pertaining to thermodynamic stability, formation kinetics, and guest occupation behavior in clathrate hydrates needs to be determined. Herein, the phase equilibria of SF6 hydrates in the presence of NaCl solutions (0, 2, 4, and 10 wt %) were monitored in the temperature range of 277-286 K and under pressures of up to 1.4 MPa. The formation kinetics of SF6 hydrates in the presence of NaCl solutions (0, 2, and 4 wt %) was also investigated. Gas consumption curves of SF6 hydrates showed that a pure SF6 hydrate system allowed fast hydrate growth as well as high conversion yield, whereas SF6 hydrate in the presence of NaCl solutions showed retarded hydrate growth rate as well as low conversion yield. In addition, structural identification of SF6 hydrates with and without NaCl solutions was performed using spectroscopic tools such as Raman spectroscopy and X-ray diffraction. The Raman spectrometer was also used to evaluate the temperature-dependent release behavior of guest molecules in SF6 and SF6 + 4 wt % NaCl hydrates. The results indicate that whereas SF6 hydrate starts to decompose at around 240 K, the escape of SF6 molecules in SF6 + 4 wt % NaCl hydrate is initiated rapidly at around 205 K. The results of this study can provide a better understanding of guest-host interaction in electrolyte-containing systems.

  4. Spectroscopic Study of Methylglyoxal and its Hydrates : a Gaseous Precursor of Secondary Organic Aerosols.

    NASA Astrophysics Data System (ADS)

    Bteich, Sabath; Goubet, Manuel; Margulès, L.; Motiyenko, R. A.; Huet, T. R.

    2016-06-01

    Secondary organic aerosols (SOA) have a significant effect on climate change. They are mainly produced in the atmosphere by oxidation of gaseous precursors. Fu et al. have suggested trans-methylglyoxal (MG) as a possible precursor of SOA in the cloud for its presence in large quantities in the atmosphere. The characterization of SOAs precursors by laboratory spectroscopy allows providing elements for the understanding of the process of formation of these aerosols. For this purpose, we completed the existing pure rotational spectrum of MG in the 12-40 GHz range by new records in a supersonic jet in the 4-20 GHz range (FTMW) and at room temperature in the 150-500 GHz range (mm/submm-wave spectrometer). The analysis was made with the support of quantum chemistry calculations (MP2/CBS and B98/CBS using the Gaussian 09 software). The adjustment of the spectroscopic parameters, taking into account the internal rotation related to the presence of a methyl group, was performed using the RAM36 code. The spectra have been reproduced at the experimental precision up to maximal values of J and K_a equal to 85 and 35, respectively. The data obtained for the isolated molecule, both experimentally and theoretically, will allow the study of its hydrated complexes and, by comparison, will give access to (micro-) hydration properties. For this purpose, two stable complexes predicted by theoretical calculations will be studied. T.- M. Fu et al., J. Geophys. Res., 113, (2008). C.E. Dyltick-Brenzinger and A. Bauder, Chem. Phys. 30, 147 (1978).

  5. Calorimetric and spectroscopic studies on solvation energetics for H₂ storage in the CO₂/HCOOH system.

    PubMed

    Fink, Cornel; Katsyuba, Sergey; Laurenczy, Gabor

    2016-04-28

    Solvents playing a crucial role in many chemical reactions and additives can be used to shift the reaction equilibrium. Herein we study the enthalpy of mixing for selected solvents (aqueous, organic) and basic additives (amines, aqueous KOH) when mixed with formic acid with the aim to optimize hydrogen storage/delivery in the CO2/HCOOH system. Formic acid, resulting from carbon dioxide hydrogenation, reaches highest yields when effectively "removed" from the reaction equilibrium. In terms of energy efficiency, any heat released during CO2 hydrogenation has to be reused in the reverse reaction, during the production of hydrogen. In any scenario, the usage of basic chemicals, non-innocent solvents, causes higher energy release in CO2 hydrogenation, which has to be reused in the hydrogen delivery process. Therefore, the enthalpy of mixing is a valuable parameter for designing hydrogen storage devices since it allows the estimation of energy balance for the CO2 hydrogenation/H2 liberation cycle. The highest formic acid concentrations in direct catalytic CO2 hydrogenation under acidic conditions were reached in DMSO. DMSO exhibits considerably stronger interactions with formic acid compared to water as was observed in calorimetric measurements. This difference can be ascribed, at least partly, to stronger hydrogen bonding of FA to DMSO than to water in the corresponding solutions, examined by a combination of IR spectroscopic and quantum chemical studies. Furthermore, the investigation of DMSO/FA- and water/FA systems by (1)H- and (13)C-NMR spectroscopy revealed that only 1 : 1 aggregates are formed in the DMSO solutions of FA in a broad concentration range, while the stoichiometry and the number of the FA-water aggregates essentially depend on the concentration of aqueous solutions.

  6. Performance of Two Bioelectrical Impedance Analyses in the Diagnosis of Overweight and Obesity in Children and Adolescents: The FUPRECOL Study

    PubMed Central

    Ramírez-Vélez, Robinson; Correa-Bautista, Jorge Enrique; Martínez-Torres, Javier; González-Ruíz, Katherine; González-Jiménez, Emilio; Schmidt-RioValle, Jacqueline; Garcia-Hermoso, Antonio

    2016-01-01

    This study aimed to determine thresholds for percentage of body fat (BF%) corresponding to the cut-off values for overweight/obesity as recommended by the International Obesity Task Force (IOTF), using two bioelectrical impedance analyzers (BIA), and described the likelihood of increased cardiometabolic risk in our cohort defined by the IOTF and BF% status. Participants included 1165 children and adolescents (54.9% girls) from Bogotá (Colombia). Body mass index (BMI) was calculated from height and weight. BF% of each youth was assessed first using the Tanita BC-418® followed by a Tanita BF-689®. The sensitivity and specificity of both devices and their ability to correctly classify children as overweight/obesity (≥2 standard deviation), as defined by IOTF, was investigated using receiver operating characteristic (ROC) by sex and age groups (9–11, 12–14, and 13–17 years old); Area under curve (AUC) values were also reported. For girls, the optimal BF% threshold for classifying into overweight/obesity was found to be between 25.2 and 28.5 (AUC = 0.91–0.97) and 23.9 to 26.6 (AUC = 0.90–0.99) for Tanita BC-418® and Tanita BF-689®, respectively. For boys, the optimal threshold was between 16.5 and 21.1 (AUC = 0.93–0.96) and 15.8 to 20.6 (AUC = 0.92–0.94) by Tanita BC-418® and Tanita BF-689®, respectively. All AUC values for ROC curves were statistically significant and there were no differences between AUC values measured by both BIA devices. The BF% values associated with the IOTF-recommended BMI cut-off for overweight/obesity may require age- and sex-specific threshold values in Colombian children and adolescents aged 9–17 years and could be used as a surrogate method to identify individuals at risk of excess adiposity. PMID:27782039

  7. Spectroscopic and quantum chemical study of the structure of a new paramagnetic dimeric palladium(II,III) complex with creatine

    NASA Astrophysics Data System (ADS)

    Mitewa, Mariana; Enchev, Venelin; Bakalova, Tatyana

    2002-05-01

    The structure and coordination mode of the newly synthesized dimeric paramagnetic Pd(II,III) complex are studied using magneto-chemical, EPR and IR spectroscopic methods. In order to perform reliable assignment of the IR bands, the structure and IR spectrum of the free creatine were calculated using ab initio method. For calculation of the configuration of its deprotonated and doubly deprotonated forms the semiempirical AM1 method was used.

  8. Laser-Raman and FT-IR spectroscopic studies of peptide-analogues of silkmoth chorion protein segments.

    PubMed

    Benaki, D C; Aggeli, A; Chryssikos, G D; Yiannopoulos, Y D; Kamitsos, E I; Brumley, E; Case, S T; Boden, N; Hamodrakas, S J

    1998-07-01

    Silkmoth chorion, the proteinaceous major component of the eggshell, with extraordinary mechanical and physiological properties, consists of a complex set of proteins, which have a tripartite structure: a central, evolutionarily conserved, domain and two more variable 'arms'. Peptide-analogues of silkmoth chorion protein central domain segments have been synthesized. Laser-Raman and infrared spectroscopic studies suggest the preponderance of antiparallel beta-pleated sheet structure for these peptides, both in solution and in the solid state. PMID:9644596

  9. Microfabricated AC impedance sensor

    DOEpatents

    Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

    2002-01-01

    A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

  10. Esophageal Impedance Monitoring: Clinical Pearls and Pitfalls.

    PubMed

    Ravi, Karthik; Katzka, David A

    2016-09-01

    The development of intraluminal esophageal impedance monitoring has improved our ability to detect and measure gastroesophageal reflux without dependence on acid content. This ability to detect previously unrecognized weak or nonacid reflux episodes has had important clinical implications in the diagnosis and management of gastroesophageal reflux disease (GERD). In addition, with the ability to assess bolus transit within the esophageal lumen, impedance monitoring has enhanced the recognition and characterization of esophageal motility disorders in patients with nonobstructive dysphagia. The assessment of the intraluminal movement of gas and liquid has also been proven to be of diagnostic value in conditions such as rumination syndrome and excessive belching. Further, alternative applications of impedance monitoring, such as the measurement of mucosal impedance, have provided novel insights into assessing esophageal mucosal integrity changes as a consequence of inflammatory change. Future applications for esophageal impedance monitoring also hold promise in esophageal conditions other than GERD. However, despite all of the clinical benefits afforded by esophageal impedance monitoring, important clinical and technical shortcomings limit its diagnostic value and must be considered when interpreting study results. Overinterpretation of studies or application of impedance monitoring in patients can have deleterious clinical implications. This review will highlight the clinical benefits and limitations of esophageal impedance monitoring and provide clinical pearls and pitfalls associated with this technology.

  11. Esophageal Impedance Monitoring: Clinical Pearls and Pitfalls.

    PubMed

    Ravi, Karthik; Katzka, David A

    2016-09-01

    The development of intraluminal esophageal impedance monitoring has improved our ability to detect and measure gastroesophageal reflux without dependence on acid content. This ability to detect previously unrecognized weak or nonacid reflux episodes has had important clinical implications in the diagnosis and management of gastroesophageal reflux disease (GERD). In addition, with the ability to assess bolus transit within the esophageal lumen, impedance monitoring has enhanced the recognition and characterization of esophageal motility disorders in patients with nonobstructive dysphagia. The assessment of the intraluminal movement of gas and liquid has also been proven to be of diagnostic value in conditions such as rumination syndrome and excessive belching. Further, alternative applications of impedance monitoring, such as the measurement of mucosal impedance, have provided novel insights into assessing esophageal mucosal integrity changes as a consequence of inflammatory change. Future applications for esophageal impedance monitoring also hold promise in esophageal conditions other than GERD. However, despite all of the clinical benefits afforded by esophageal impedance monitoring, important clinical and technical shortcomings limit its diagnostic value and must be considered when interpreting study results. Overinterpretation of studies or application of impedance monitoring in patients can have deleterious clinical implications. This review will highlight the clinical benefits and limitations of esophageal impedance monitoring and provide clinical pearls and pitfalls associated with this technology. PMID:27325223

  12. AB Initio Study of the Structure and Spectroscopic Properties of Halogenated Thioperoxy Radicals

    NASA Technical Reports Server (NTRS)

    Munoz, Luis A.; Binning, R. C., Jr.; Weiner, Brad R.; Ishikawa, Yasuyuki

    1997-01-01

    Thioperoxy (XSO or XOS) radicals exist in a variety of chemical environments, and they have as a consequence drawn some interest. HSO, an important species in the chemistry of the troposphere, has been examined both experimentally. The halogenated (X = F, Cl or Br) peroxy species and isovalent thioperoxy species have been studied less, but they too are potentially interesting because oxidized sulfur species and halogen sources are present in the atmosphere. Learning the fate of XSO and XOS radicals is important to understanding the atmospheric oxidation chemistry of sulfur compounds. Of these, FSO and ClSO are particularly interesting because they have been directly detected spectroscopically. Recent studies in our laboratory on the photochemistry of thionyl halides (X2SO; where X = F or Cl) have suggested new ways to generate XSO species. The laser-induced photodissociation of thionyl fluoride, F2SO, at 193 nm and thionyl chloride, ClSO, at 248 nm is characterized by a radical mechanism, X2SO -> XSO + X. The structure of FSO has been characterized experimentally by Endo et cd. employing microwave spectroscopy. Using the unrestricted Hartree-Fock (UHF) self-consistent field (SCF) method, Sakai and Morokuma computed the electronic structure of the ground (sup 2)A" and the first excited (sup 2)A' states of FSO. Electron correlation was not taken into account in their study. In a laser photodissociation experiment, Huber et al. identified ClSO mass spectromctrically. ClSO has also been detected in low temperature matrices by EPR and in the gas phase by far IR laser magnetic resonance. Although the structure of FSO is known in detail, the only study, experimental or theoretical, of CISO has been an ab initio HFSCF study by Hinchliffe. Electron correlation corrections were also excluded from this study. In order to better understand the isomerization and dissociation dynamics of the radical species, we have performed ab initio correlated studies of the potential energy

  13. A preliminary study on the prediction of damaged areas on ordinary concrete and lightweight concrete using electromechanical impedance technique with different frequency ranges

    NASA Astrophysics Data System (ADS)

    Cho, K. J.; Na, S.; Jang, J. G.; Lee, H. K.

    2014-03-01

    The electromechanical impedance (EMI) method for NDE uses a single piezoelectric material to act as an actuator and a sensor simultaneously, and the EMI method is suitable for structures with complex surfaces. However, this technique still has wide range of problems which needs to be investigated. For one, locating damaged areas on a host structure precisely is known to be extremely difficult as this non-model based technique heavily relies on the variations in the impedance signatures. In this study, an attempt to locate the damaged areas on an ordinary concrete panel and a lightweight concrete panel using bottom ash is carried out by using different frequency ranges. Since the sensing range decreases as the excitation frequency of piezoelectric material increases, one can possibly predict the damaged areas by analyzing the impedance signatures from different frequency ranges. Statistical analysis method such as root mean square deviation (RMSD) is applied to determine the changes of the experimental structures, and the RMSD values of low frequency range and high frequency range are compared to verify the relationship between the frequency range and sensing range. Furthermore, the applicability of this method to locating the damaged areas is investigated on various materials including the lightweight concrete.

  14. Spectroscopic study on sorption of hydrogen sulfide by means of red soil.

    PubMed

    Ko, T H; Chu, H

    2005-07-01

    This paper reports the results of the characterization of red soils in relation to the sorption of H2S from coal gas at 500 degrees C by spectroscopic techniques in order to provide more information on red soils' structural change both before and after reaction. In addition, by-products analysis has also been studied using Fourier transform infrared (FTIR) spectroscopy. Before and after the experiments the red soils were characterized with X-ray powder diffraction (XRPD), energy dispersion spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and FTIR spectroscopy. XRPD results indicate that iron oxide species disappear from the original to reacted red soil. EDS analysis shows that a significant amount of sulfur is present in the reacted red soil, which is in agreement with the results of the elemental analysis and the calculated value based on breakthrough curve. XPS regression fitting results further indicate that sulfur retention may be associated with the iron oxides. S 2p XPS fittings point out that the major sulfur species present in the reacted red soil are composed of S(-2), elemental sulfur, polysulfide, sulfite and sulfate. Additionally, the binding energy of iron shifts to a lower position for the reacted red soil, which indicates that iron oxides in the original red soil have been converted into iron sulfide. Appreciable amounts of the by-products CO2, SO2 and COS are detected by on-line FTIR spectroscopy during the initial and later stages of the sorption process. The formation of CO2 is related to the water-shift reaction, and SO2 is probably attributable to the reaction of organic matters and H2S. The concentration of COS is quantified by GC/FPD and found it to be about 350 ppm, which is close to the equilibrium concentration of the reaction of inlet CO and H2S at a temperature of 500 degrees C.

  15. Spectroscopic study of extended star clusters in dwarf galaxy NGC 6822

    SciTech Connect

    Hwang, Narae; Kim, Sang Chul; Park, Hong Soo; Lee, Myung Gyoon; Lim, Sungsoon; Hodge, Paul W.; Weisz, Daniel; Miller, Bryan

    2014-03-01

    We present a spectroscopic study of the four extended star clusters (ESCs) in NGC 6822 based on the data obtained with the Gemini Multi-Object Spectrograph on the Gemini-South 8.1 m telescope. The radial velocities derived from the spectra range from –61.2 ± 20.4 km s{sup –1} (for C1) to –115.34 ± 57.9 km s{sup –1} (for C4) and, unlike the intermediate-age carbon stars, they do not display any sign of systematic rotation around NGC 6822. The ages and metallicities derived using the Lick indices show that the ESCs are old (≥8 Gyr) and metal poor ([Fe/H] ≲ –1.5). NGC 6822 is found to have both metal poor ([Fe/H] ≈–2.0) and metal rich ([Fe/H] ≈–0.9) star clusters within 15' (2 kpc) from the center, whereas only metal poor clusters are observed in the outer halo with r ≥ 20'(2.6 kpc). The kinematics, old ages, and low metallicities of ESCs suggest that ESCs may have accreted into the halo of NGC 6822. Based on the velocity distribution of ESCs, we have determined the total mass and the mass-to-light ratio of NGC 6822: M{sub N6822}=7.5{sub −0.1}{sup +4.5}×10{sup 9} M{sub ⊙} and (M/L){sub N6822}=75{sub −1}{sup +45}(M/L){sub ⊙}. It shows that NGC 6822 is one of the most dark matter dominated dwarf galaxies in the Local Group.

  16. High-Resolution Spectroscopic Studies of Complexes Formed by Medium-Size Organic Molecules.

    PubMed

    Becucci, Maurizio; Melandri, Sonia

    2016-05-11

    A wealth of structural and dynamical information has been obtained in the last 30 years from the study of high-resolution spectra of molecular clusters generated in a cold supersonic expansion by means of highly resolved spectroscopic methods. The data obtained, generally lead to determination of the structures of stable conformations. In addition, in the case of weakly bound molecular complexes, it is usual to observe the effects of internal motions due to the shallowness of the potential energy surfaces involved and the flexibility of the systems. In the case of electronic excitation experiments, also the effect of electronic distribution changes on both equilibrium structures and internal motions becomes accessible. The structural and dynamical information that can be obtained by applying suitable theoretical models to the analysis of these unusually complex spectra allows the determination and understanding of the driving forces involved in formation of the molecular complex. In this way, many types of non-covalent interactions have been characterized, from pure van der Waals interactions in complexes of rare gases to moderate-strength and weak hydrogen bonds and to the most recent halogen bonds and n-π interactions. The aim of this review is to underline how the different experimental and theoretical methods converge in giving a detailed picture of weak interactions in small molecular adducts involving medium-size molecules. The conclusions regarding geometries and energies can contribute to understanding of the different driving forces involved in the dynamics of the processes and can be exploited in all fields of chemistry and biochemistry, from design of new materials with novel properties to rational design of drugs. PMID:26986455

  17. Comparative FTIR spectroscopic study upon the hydration of lecithins and cephalins

    NASA Astrophysics Data System (ADS)

    Pohle, Walter; Selle, Carsten; Fritzsche, Hartmut; Bohl, Martin

    1997-06-01

    Fourier-transform infrared (FTIR) spectroscopy has been used to study the gradual hydration of films prepared from some ubiquitous phospholipids. The diacyl lecithins (PCs, DPPC and DOPC) and cephalins (PEs, DPPE and DOPE) are representative for compounds with saturated (palmitoyl) and unsaturated (oleoyl) hydrocarbon chains, respectively. The adsorption isotherms obtained spectroscopically reveal that lecithins take up more water than cephalins, independently of the nature of their acyl chains. Furthermore, whereas the two lecithins exhibit more or less substantial and continuous wavenumber shifts for the well-assigned infrared absorption bands arising from the vibrations of their polar parts, the cephalins show a significantly diverse pattern with characteristic differences determined by the chemical nature of their tails. DPPE is, as far as reflected by its IR-band parameters, completely invariant against hydration, i.e. no influence of the water imbibed by the film is visible. Such a finding can be interpreted in terms of a tight hydrogen-bonding network formed between the phosphate and ammonium groups of DPPE. This explanation is confirmed by the results of relevant quantum-chemical AM1 calculations another part of which is also suitable to rationalize the wavenumber downwards shifts of the PO -2 and CO stretching-vibration bands of lecithins observed upon hydration. DOPE differs from DPPE by undergoing rather dramatic hydration-induced wavenumber shifts of the IR bands due to its polar parts. Contrarily to the lecithins, however, these displacements are restricted to a very narrow range of water activities. This behaviour suggests the existence of a lyotropic phase transition ascribed to a conversion from H ∥ to P α occurring when the water content of DOPE is decreased.

  18. Hunting the Parent of the Orphan Stream. II. The First High-resolution Spectroscopic Study

    NASA Astrophysics Data System (ADS)

    Casey, Andrew R.; Keller, Stefan C.; Da Costa, Gary; Frebel, Anna; Maunder, Elizabeth

    2014-03-01

    We present the first high-resolution spectroscopic study on the Orphan stream for five stream candidates, observed with the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Clay telescope. The targets were selected from the low-resolution catalog of Casey et al.: three high-probability members, one medium, and one low-probability stream candidate were observed. Our analysis indicates that the low- and medium-probability targets are metal-rich field stars. The remaining three high-probability targets range over ~1 dex in metallicity, and are chemically distinct compared to the other two targets and all standard stars: low [α/Fe] abundance ratios are observed, and lower limits are ascertained for [Ba/Y], which sit well above the Milky Way trend. These chemical signatures demonstrate that the undiscovered parent system is unequivocally a dwarf spheroidal galaxy, consistent with dynamical constraints inferred from the stream width and arc. As such, we firmly exclude the proposed association between NGC 2419 and the Orphan stream. A wide range in metallicities adds to the similarities between the Orphan stream and Segue 1, although the low [α/Fe] abundance ratios in the Orphan stream are in tension with the high [α/Fe] values observed in Segue 1. Open questions remain before Segue 1 could possibly be claimed as the "parent" of the Orphan stream. The parent system could well remain undiscovered in the southern sky. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  19. Spectroscopic and Computational Studies of Light and Heat Generation in Semiconductor Nanomaterials

    NASA Astrophysics Data System (ADS)

    Hannah, Daniel C.

    In crystalline semiconductors, the reduction of material dimensions to the nanometer length scale often has a profound impact on the optical, structural, and thermal properties exhibited by the material. While the optical properties of semiconductor nanocrystals have been studied for over two decades, many fundamental questions persist regarding thermal processes in this material class. For example, on what time scale do excited charge carriers dissipate energy and into which degrees of freedom? How is heat generated during carrier thermalization transported out of the nanocrystal? Can these processes be manipulated by structural modification? In the first part of this thesis, we utilize a combination of ultrafast spectroscopic methods and computational modeling to answer these questions. Overall, our results indicate that heat generation begins with hole thermalization, and that the subsequent transport of heat is heavily influenced by the semiconductor surface structure and surface chemistry. These findings lead us to propose and demonstrate several methods of independently tuning nanocrystal optical and thermal properties. In the second part of this thesis, we investigate a long standing issue in nanoscience: the efficient emission of light by group-IV nanocrystals. Again, utilizing a combination of optical spectroscopy and theoretical modeling, we are able to attribute long-lived, band-edge photoluminescence from Si nanocrystals to emission from the crystalline core, which remains indirect-gap in character despite substantial quantum confinement. We also attribute rapid, high-energy photoluminescence to a persistent amorphous surface layer. Finally, we explore some of the interesting structural behavior exhibited by group-IV nanocrystals at high pressure.

  20. Galactic Soft X-ray Emission Revealed with Spectroscopic Study of Absorption and Emission Spectra

    NASA Astrophysics Data System (ADS)

    Yamasaki, Noriko Y.; Mitsuda, K.; Takei, Y.; Hagihara, T.; Yoshino, T.; Wang, Q. D.; Yao, Y.; McCammon, D.

    2010-03-01

    Spectroscopic study of Oxygen emission/absorption lines is a new tool to investigate the nature of the soft X-ray background. We investigated the emission spectra of 14 fields obtained by Suzaku, and detected OVII and OVIII lines separately. There is an almost isotropic OVII line emission with 2 LU intensity. As the attenuation length in the Galactic plane for that energy is short, that OVII emission should arise within 300 pc of our neighborhood. In comparison with the estimated emission measure for the local bubble, the most plausible origin of this component is the solar wind charge exchange with local interstellar materials. Another component presented from the correlation between the OVII and OVIII line intensity is a thermal emission with an apparent temperature of 0.2 keV with a field-to-field fluctuation of 10% in temperature, while the intensity varies about a factor of 4. By the combination analysis of the emission and the absorption spectra, we can investigate the density and the scale length of intervening plasma separately. We analyzed the Chanrdra grating spectra of LMC X-3 and PKS 2155-304, and emission spectra toward the line of sight by Suzaku. In both cases, the combined analysis showed that the hot plasma is not iso-thermal nor uniform. Assuming an exponential disk distribution, the thickness of the disk is as large as a few kpc. It suggests that there is a thick hot disk or hot halo surrounding our Galaxy, which is similar to X-ray hot haloes around several spiral galaxies.