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1

Absorption and fluorescence spectroscopic characterization of BLUF domain of AppA from Rhodobacter sphaeroides  

NASA Astrophysics Data System (ADS)

The BLUF domain of the transcriptional anti-repressor protein AppA from the non-sulfur anoxyphototrophic purple bacterium Rhodobacter sphaeroides was characterized by absorption and emission spectroscopy. The BLUF domain constructs AppA 148 (consisting of amino-acid residues 1-148) and AppA 126 (amino-acid residues 1-126) are investigated. The cofactor of the investigated domains is found to consist of a mixture of the flavins riboflavin, FMN, and FAD. The dark-adapted domains exist in two different active receptor conformations (receptor states) with different sub-nanosecond fluorescence lifetimes (BLUF r,f and BLUF r,sl) and a small non-interacting conformation (BLUF nc). The active receptor conformations are transformed to putative signalling states (BLUF s,f and BLUF s,sl) of low fluorescence efficiency and picosecond fluorescence lifetime by blue-light excitation (light-adapted domains). In the dark at room temperature both signalling states recover back to the initial receptor states with a time constant of about 17 min. A quantum yield of signalling state formation of about 25% was determined by intensity dependent transmission measurements. A photo-cycle scheme is presented including photo-induced charge transfer complex formation, charge recombination, and protein binding pocket reorganisation.

Zirak, P.; Penzkofer, A.; Schiereis, T.; Hegemann, P.; Jung, A.; Schlichting, I.

2005-08-01

2

Absorption and emission spectroscopic characterization of BLUF protein Slr1694 from Synechocystis sp. PCC6803 with roseoflavin cofactor.  

PubMed

The wild-type BLUF protein Slr1694 from Synechocystis sp. PCC6803 (BLUF=blue-light sensor using FAD) has flavin adenosine dinucleotide (FAD) as natural cofactor. This light sensor causes positive phototaxis of the marine cyanobacterium. In this study the FAD cofactor of the wild-type Slr1694 was replaced by roseoflavin (RoF) and the roseoflavin derivatives RoFMN and RoFAD during heterologous expression in a riboflavin auxotrophic E. coli strain. An absorption and emission spectroscopic characterization of the cofactor-exchanged-Slr1694 (RoSlr) was carried out both under dark conditions and under illuminated conditions. The behaviour of RoF embedded in RoSlr in aqueous solution at pH 8 is compared with the behaviour of RoF in aqueous solution. The fluorescence of RoF and RoSlr is quenched by photo-induced twisted intra-molecular charge transfer at room temperature with stronger effect for RoF. The fluorescence quenching is diminished at liquid nitrogen temperature. Light exposure of RoSlr causes irreversible conversion of the protein embedded roseoflavins to 8-methylamino-flavins, 8-dimethylamino-lumichrome and 8-methylamino-lumichrome. PMID:19758819

Zirak, P; Penzkofer, A; Mathes, T; Hegemann, P

2009-11-01

3

Characterization of red sandalwood by ICP-MS analysis, optical absorption and EPR spectroscopic methods  

NASA Astrophysics Data System (ADS)

Red sandalwood sample was subjected to ICP-mass spectrometer analysis for the determination of minor elements. The ash of the sample was also analysed for the presence of major elements. The minor elements present include Cu (281.256), Ba (3722.064), Sr (6365.482), Rb (45.285), Ce (49.863), Zn (375.433) and Pb (80.944) all in ppt. The major elements detected are Cd, Fe, Mn and Ni. Optical absorption spectrum indicates that Fe(III) and Ni(II) are in tetragonal distortion with octahedral geo-metry. ESR (electron spin resonance) spectral analysis also confirms Fe(III) in tetragonal distortion, and the g-values observed for Fe(III) are 6.52, 2.63 and 1.92 and for Mn(II) is 1.99. NIR spectrum is due to carbonate overtones and harmonics and water fundamentals.

Reddy, S. L.; Reddy, N. C. G.; Reddy, R. R. S.; Reddy, G. S.; Rao, P. S.; Reddy, B. J.; Frost, R. L.

2006-09-01

4

Optical absorption in Ar + irradiated silicon studied through spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

The ion implantation induced damage on the optical absorption of band tail states in single crystal Si(1 0 0) have been investigated using a spectroscopic ellipsometer in the energy range 1.7-3.3 eV. The changes induced in the optical absorption coefficient of the material as it undergoes a crystalline to amorphous transformation with increasing fluence, was examined for fluences of Ar + ranging from 6 × 10 13 to 1 × 10 16 ions/cm 2. In the present paper, it is shown that for photon energies higher than the fundamental band gap ( Eg:Si=1.1 eV), the optical absorption follows an exponential behaviour with energy similar to Urbach rule which has hitherto been observed only below Eg. This exponential behaviour of optical absorption between the fundamental edge Eg and the first direct transition ( E1/ E0 critical point CP) at 3.3 eV is characterized by inverse logarithmic slope E01. It is shown that E01 which determines the extent of broadening in the absorption spectra of E1/ E0 CP depends on ion fluence and the underlying microstructure. The increase in broadening is attributed to loss of long range order, introduction of defects, amorphization, changes in microstructure and irradiation induced strain in the material.

Tripura Sundari, S.

2004-01-01

5

Spectroscopic characterization of Nd:Y2O3: application toward a differential absorption lidar system for remote sensing of ozone  

NASA Astrophysics Data System (ADS)

Neodymium-doped yttria (Nd:Y2O3) is investigated as a solid-state laser material for frequency-tripled generation of ultraviolet laser wavelengths for use in remote sensing of ozone. Emphasis is placed both on the spectroscopy of the fundamental wavelengths at ~0.914 ?m and ~0.946 ?m to assess their feasibility for laser oscillation and on the absorption spectroscopy in the 0.8-?m wavelength region for determination of suitable pump sources. The temperature dependence of the emission and absorption characteristics of Nd:Y2O3 are examined, since aggressive cooling may be required for efficient ~0.914-?m lasing due to its quasi four-level nature. Data for flash-lamp-pumped laser performance on the 4F3/2-->4I11/2 is presented for Nd:Y2O3 and compared with Nd:YAG. Diode-pumped threshold-fluence and threshold-pump energy estimates for Nd:Y2O3 lasing on the 4F3/2-->4I9/2 at 0.914 ?m and 0.946 ?m are calculated based on the data presented here. The measurements presented here for the Nd:Y2O3 indicate favorable absorption and emission properties. Favorable absorption properties in the ~0.8-?m pump wavelength are compatible with a variety of potential pump sources. Favorable emission properties at reduced temperatures near 150 K indicate that Nd:Y2O3 operating at 0.914 ?m and 0.946 ?m will have normal-mode laser thresholds similar to that of room-temperature Nd:YAG operating at 0.946 ?m. In Q-switched operation, however, Nd:Y2O3 is predicted to exceed the performance of Nd:YAG due to the lower 1.06/0.94 cross-section ratio, which helps to limit amplified spontaneous-emission effects. Although Nd:Y2O3 is not a new material, it has not been the topic of study due to growth problems associated with its high melting point. New advances in growth techniques and the favorable spectroscopic features of Nd:Y2O3 have inspired a new examination of this material.

Walsh, Brian M.; McMahon, John M.; Edwards, William C.; Barnes, Norman P.; Equall, Randy W.; Hutcheson, Ralph L.

2002-12-01

6

Spectroscopic characterization of alkaline earth uranyl carbonates  

SciTech Connect

A series of alkaline uranyl carbonates, M[UO{sub 2}(CO{sub 3}){sub 3}].nH{sub 2}O (M=Mg{sub 2}, Ca{sub 2}, Sr{sub 2}, Ba{sub 2}, Na{sub 2}Ca, and CaMg) was synthesized and characterized by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) after nitric acid digestion, X-ray powder diffraction (XRD), and thermal analysis (TGA/DTA). The molecular structure of these compounds was characterized by extended X-ray absorption fine-structure (EXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). Crystalline Ba{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}].6H{sub 2}O was obtained for the first time. The EXAFS analysis showed that this compound consists of (UO{sub 2})(CO{sub 3}){sub 3} clusters similar to the other alkaline earth uranyl carbonates. The average U-Ba distance is 3.90+/-0.02A.Fluorescence wavelengths and life times were measured using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The U-O bond distances determined by EXAFS, TRLFS, XPS, and Raman spectroscopy agree within the experimental uncertainties. The spectroscopic signatures observed could be useful for identifying uranyl carbonate species adsorbed on mineral surfaces.

Amayri, Samer [Institute of Nuclear Chemistry, Johannes Gutenberg-Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); Reich, Tobias [Institute of Nuclear Chemistry, Johannes Gutenberg-Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany)]. E-mail: tobias.reich@uni-mainz.de; Arnold, Thuro [Forschungszentrum Rossendorf e.V., Institute of Radiochemistry, P.O. Box 510119, 01314 Dresden (Germany); Geipel, Gerhard [Forschungszentrum Rossendorf e.V., Institute of Radiochemistry, P.O. Box 510119, 01314 Dresden (Germany); Bernhard, Gert [Forschungszentrum Rossendorf e.V., Institute of Radiochemistry, P.O. Box 510119, 01314 Dresden (Germany)

2005-02-15

7

Approaches to spectroscopic characterization of cations  

NASA Astrophysics Data System (ADS)

Ions, the essence of mass spectrometry, are on the whole spectroscopically rather poorly characterized. This situation has, however, been changing rapidly with the development and application of laser methods. One of the ways to obtain information on the electronic, vibrational and rotational structure of polyatomic catios is via their electronic transitions. This is the subject of this review. In the first part, earlier studies aimed at determining vibrational frequencies, as well as the geometry of such ions, are illustrated by a couple of examples. The bulk of the article outlines our current developments which aim at spectral characterization of mass-selected ions, including fragments. The first success has been the study of C+2. A new method enables mass selected ions, which are co-deposited with neon to form a 5K matrix, to be studied by measurement of their electronic absorption spectra. In a gas phase method, electronic transitions between bound states of an ion can be probed using a two-colour laser photon, absorption-dissociation approach, with fragment ion detection. Recent results illustrate the potential of these techniques.

Maier, John P.

1991-01-01

8

Infrared spectroscopic characterization of mineralized tissues  

PubMed Central

Vibrational spectroscopy (Infrared and Raman), and in particular micro-spectroscopy and micro-spectroscopic imaging has been used to characterize developmental changes in bone and other mineralized tissues, to monitor these changes in cell cultures, and to detect disease and drug-induced modifications. Examples of the use of infrared micro-spectroscopy and micro-spectroscopic imaging are discussed in this review.

Boskey, Adele L.; Mendelsohn, Richard

2006-01-01

9

X-ray absorption spectroscopic and magnetic characterization of cobalt-doped zinc oxide nanocrystals prepared by the molten-salt method  

Microsoft Academic Search

The local atomic arrangement and electronic structure of the Co-doped Zn1?xCoxO nanocrystal have been quantitatively examined along with its magnetic properties. According to our analysis using powder X-ray diffraction, electron microscopy, and Zn K-edge X-ray absorption spectroscopy (XAS), phase-pure wurzite-structured Zn1?xCoxO nanocrystals have been successfully synthesized via the molten-salt method. The Co K-edge XAS analysis clearly demonstrates that all the

Ah Reum Han; Seong-Ju Hwang; Yongnan Zhao; Young-Uk Kwon

2008-01-01

10

Spectroscopic characterization of visbreaking tars  

SciTech Connect

Visbreaking (VB) is a thermal cracking process, widely used in the refineries of Western Europe to obtain distillates (gasoil, naphtha) from a petroleum residue (feedstock). The visbroken residue (tar) is used to produce fuel oil, after addition of the appropriate amounts of cutter-stock. Even if the highest conversion of feedstock would be desirable, the severity of the VB process is limited by the stability of the resulting VB tars. The stability index (SI) here employed is: SI = I + V{sub cet}, where V{sub cet} is the maximum amount of n-cetane, expressed as ml of cetane for g of sample, that can be added before the flocculation of asphaltenes starts. VB tars having SI<1.1 are considered to be unstable and cannot be used in the preparation of fuel oils with the appropriate specifications. Several papers can be found in the literature dealing with the molecular changes occuring during the VB process. The present paper is aimed at verifying the amount of information that can be extracted from optical spectroscopies and, in particular, the possibility of directly monitoring the physico-chemical modifications caused by VB process. To this purpose a series of VB tars, produced from a single feedstock at different severities, were investigated by a number of spectroscopic techniques, viz.: NIR; UV-Vis; Fluorescence; {sup 1}H and {sup 13}C NUR, EPR.

Scotti, R.; Clericuzio, M.; Pirovano, C. [Eniricerche S.p.A., Milanese (Italy)

1995-12-31

11

Vibrational spectroscopic characterization of fluoroquinolones  

NASA Astrophysics Data System (ADS)

Quinolones are important gyrase inhibitors. Even though they are used as active agents in many antibiotics, the detailed mechanism of action on a molecular level is so far not known. It is of greatest interest to shed light on this drug-target interaction to provide useful information in the fight against growing resistances and obtain new insights for the development of new powerful drugs. To reach this goal, on a first step it is essential to understand the structural characteristics of the drugs and the effects that are caused by the environment in detail. In this work we report on Raman spectroscopical investigations of a variety of gyrase inhibitors (nalidixic acid, oxolinic acid, cinoxacin, flumequine, norfloxacin, ciprofloxacin, lomefloxacin, ofloxacin, enoxacin, sarafloxacin and moxifloxacin) by means of micro-Raman spectroscopy excited with various excitation wavelengths, both in the off-resonance region (532, 633, 830 and 1064 nm) and in the resonance region (resonance Raman spectroscopy at 244, 257 and 275 nm). Furthermore DFT calculations were performed to assign the vibrational modes, as well as for an identification of intramolecular hydrogen bonding motifs. The effect of small changes in the drug environment was studied by adding successively small amounts of water until physiological low concentrations of the drugs in aqueous solution were obtained. At these low concentrations resonance Raman spectroscopy proved to be a useful and sensitive technique. Supplementary information was obtained from IR and UV/vis spectroscopy.

Neugebauer, U.; Szeghalmi, A.; Schmitt, M.; Kiefer, W.; Popp, J.; Holzgrabe, U.

2005-05-01

12

Absorption spectroscopic studies on gamma irradiated bismuth borosilicate glasses  

NASA Astrophysics Data System (ADS)

FT-IR spectroscopic measurements have been employed to investigate the structural changes in quaternary xBi2O3-15 Na2O-(70 - x) B2O3-15 SiO2 glass system with x = 5, 10, 15, 20 and 25 (mol%). The effect of gamma irradiation in the dose range of 0.1-60 kGy on the infrared absorption spectra of these glasses is also reported. The IR spectra of the prepared samples show characteristic bands related to the sharing of triangular and tetrahedral borate and silicate groups together with Bi-O groups. The effect of the heavy metal oxide Bi2O3 on the glass composition is also studied.

Kaur, Ravneet; Singh, Surinder; Pandey, O. P.

2013-10-01

13

Spectroscopic Methods of Remote Sensing for Vegetation Characterization  

NASA Astrophysics Data System (ADS)

Imaging spectroscopy (IS), often referred to as hyperspectral remote sensing, is one of the latest innovations in a very long history of spectroscopy. Spectroscopic methods have been used for understanding the composition of the world around us, as well as, the solar system and distant parts of the universe. Continuous sampling of the electromagnetic spectrum in narrow bands is what separates IS from previous forms of remote sensing. Terrestrial imaging spectrometers often have hundreds of channels that cover the wavelength range of reflected solar radiation, including the visible, near-infrared (NIR), and shortwave infrared (SWIR) regions. In part due to the large number of channels, a wide variety of methods have been applied to extract information from IS data sets. These can be grouped into several broad classes, including: multi-channel indices, statistical procedures, full spectrum mixing models, and spectroscopic methods. Spectroscopic methods carry on the more than 150 year history of laboratory-based spectroscopy applied to material identification and characterization. Spectroscopic methods of IS relate the positions and shapes of spectral features resolved by airborne and spaceborne sensors to the biochemical and physical composition of vegetation in a pixel. The chlorophyll 680nm, water 980nm, water 1200nm, SWIR 1700nm, SWIR 2100nm, and SWIR 2300nm features have been the subject of study. Spectral feature analysis (SFA) involves isolating such an absorption feature using continuum removal (CR) and calculating descriptors of the feature, such as center position, depth, width, area, and asymmetry. SFA has been applied to quantify pigment and non-pigment biochemical concentrations in leaves, plants, and canopies. Spectral feature comparison (SFC) utilizes CR of features in each pixel's spectrum and linear regression with continuum-removed features in reference spectra in a library of known vegetation types to map vegetation species and communities. SFC has been applied to map the distributions of minerals in soils and rocks; however, its application to characterize vegetation cover has been less widespread than SFA. Using IS data and the USGS Processing Routines in IDL for Spectroscopic Measurements (PRISM; http://pubs.usgs.gov/of/2011/1155/), this talk will examine requirements for and limitations in applying SFA and SFC to characterize vegetation. A time series of Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) data collected in the marshes of Louisiana following the Deepwater Horizon oil spill will be used to examine the impact of varying leaf water content on the shapes of the SWIR 1700, 2100, and 2300 nm features and the implications of these changes on vegetation identification and biochemical estimation. The USGS collection of HyMap data over Afghanistan, the largest terrestrial coverage of IS data to date, will be used to demonstrate the characterization of vegetation in arid and semi-arid regions, in which chlorophyll absorption is often weak and soil and rock mineral absorption features overlap vegetation features. Hyperion data, overlapping the HyMap data, will be presented to illustrate the complications that arise when signal-to-noise is low. The benefits of and challenges to applying a spectroscopic remote sensing approach to imaging spectrometer data will be discussed.

Kokaly, R. F.

2013-12-01

14

Spectroscopic characterization of uranium in evaporation basin sediments  

SciTech Connect

Evaporation ponds in the San Joaquin Valley (SJV), CA, used for the containment of irrigation drainage waters contain elevated levels of uranium (U) resulting from the extensive leaching by carbonate-rich irrigation waters of the local agricultural soils that contain low levels of naturally-occurring U. The SJV ponds are subjected to changes in redox chemistry with cycles of drying and flooding. Past studies have shown that U in the SJV Pont 14 surface sediments is present as mostly the oxidized and soluble form, U(VI). However, the authors were uncertain whether the U in the soil was only present as a U oxide of mixed stoichiometry, such as U{sub 3}O{sub 8(s)} (pitchblende) or other species. Here they present characterization information, which includes wet chemical and in situ spectroscopic techniques (X-ray absorption near-edge structure (XANES) and low temperature time-resolved luminescence spectroscopies) for samples from two SJV Pond sediments. Surface sediments from SJV Pont 16 were characterized for average oxidation state of U with XANES spectroscopy. The wet chemical extractions and in situ spectroscopic techniques provided fundamental and basic knowledge about the fraction of U(IV) to U(VI), the speciation of luminescent U(VI), and the susceptibility of the sediment U species to leaching.

Duff, M.C.; Morris, D.E.; Hunter, D.B.; Bertsch, P.M.

2000-05-01

15

Spectroscopic characterizations of organic/inorganic nanocomposites  

NASA Astrophysics Data System (ADS)

In the present study, pure and 0.3 wt%, 0.4 wt%, as well as 0.5 wt% L-arginine doped potassium dihydrogen phosphate (KDP) crystals were grown using solution growth techniques and further subjected to infrared (IR) absorption and Raman studies for confirmation of chemical group functionalization for investigating the incorporation mechanism of the L-arginine organic material into the KDP crystal structure. Infrared spectroscopic analysis suggests that structural changes are occurring for the L-arginine molecule as a result of its interaction with the KPD crystal. Infrared spectroscopic technique confirms the disturbance of the N-H, C-H and C-N bonds of the amino acid, suggesting successful incorporation of L-arginine into the KDP crystals. Raman analysis also reveals modification of the N-H, C-H and C-N bonds of the amino acid, implying successful inclusion of L-arginine into the KDP crystals. With the help of Gaussian software, a prediction of possible incorporation mechanisms of the organic material was obtained from comparison of the simulated infrared and Raman vibrational spectra with the experimental results. Furthermore, we also studied the effect of L-arginine doping on the thermal stability of the grown KDP crystal by employing Thermo gravimetric analysis (TGA). TGA suggests that increasing the level of L-arginine doping speeds the decomposition process and it weakens the KDP crystal, which indicates successful doping of the KDP crystals with L-arginine amino acid. Urinary stones are one of the oldest and most widely spread diseases in humans, animals and birds. Many remedies have been employed through the ages for the treatment of urinary stones. Recent medicinal measures reflect the modern advances, which are based on surgical removal, percutaneous techniques and extracorporeal shock wave lithotripsy (ESWL). Although these procedures are valuable, they are quite expensive for most people. Furthermore, recurrence of these diseases is awfully frequent with these procedures and the patients have to be subjected to careful follow up for several years. In contrast, in traditional therapeutic systems, most of the remedies were taken from plants and they proved to be helpful. However, the rationale behind their use is not thoroughly established through systematic pharmacological and clinical studies. In this regard, in the present investigation, with a view towards acquiring more insights, we have performed a detailed study of kidney stone formation and growth inhibition based on a traditional medicine approach with herbal extracts. The intricacy of calculi formation (i.e. nucleation, transformation, and aggregation) in a natural system such as urine is replicated to a certain extent in the present study by using a simplified single diffusion gel growth technique. Crystals were synthesized in a static gel environment without and with the presence of 1% and 2% concentration of Rotula Aquatica Lour (RAL) herbal extracts and further subjected to Raman, infrared absorption, X-ray photoelectron spectroscopy (XPS), and photoluminescence to analyze the effects of RAL on the growth of manganese-based calculi. Raman spectroscopy clearly provided an indication of the newberyite type of crystal as well as information on the chemical interaction between crystal and inhibitor. It also indicates the presence of organic components due to the RAL plant material. Infrared absorption spectroscopy indicates the presence of a strong reflecting component in the inhibitor as well as the newberyite type of crystal. XPS results indicated the presence of metallic zinc in the crystal with inhibitor. Furthermore, a considerable increase in the intensity of the magnesium and oxygen lines are noticed with the addition of the herbal extract, which suggest that the inhibitor chemical composition includes a substantial quantity of Mg and O. XPS analysis also demonstrates the presence of modified phosphorus oxidation states and suggest that they might make a contribution, too. The photoluminescence spectra of the crystal with inhibitor indicate the p

Govani, Jayesh R.

16

Surface spectroscopic characterization of titanium implant materials  

NASA Astrophysics Data System (ADS)

Titanium is one of the most commonly used biomaterials for dental and orthopedic applications. Its excellent tissue compatibility is mainly due to the properties of the stable oxide layer which is present on the surface. This paper reports a detailed spectroscopic characterization of the surface composition of non-alloyed Ti implant materials, prepared according to procedures commonly used in clinical practice (machining, ultrasonic cleaning and sterilization). The main methods of characterization are XPS and AES, and complementary information is obtained by SIMS, EDX and NMA (nuclear microanalysis). The surface of the implants is found to consist of a thin surface oxide which is covered by a carbon-dominated contamination layer. By comparison with reference spectra from single crystal TiO 2 (rutile) the composition of the surface oxide is shown to be mainly TiO 2, with minor amounts of suboxides and TiN x. The thickness of the surface oxides is 2-6 nm, depending on the method of sterilization. The surface contamination layer is found to vary considerably from sample to sample and consists of mainly hydrocarbons with trace amounts of Ca, N, S, P, Cl. Some differences in surface composition between directly prepared surfaces, and some possible contamination sources, are identified and discussed shortly.

Lausmaa, Jukka; Kasemo, Bengt; Mattsson, Håkan

1990-04-01

17

Absorption and fluorescence spectroscopic investigations of PAC/humic substance-interactions in water  

NASA Astrophysics Data System (ADS)

Time-resolved emission spectra of humic substances of different origin have been recorded in order to extend our previous spectroscopic characterization of humic and fulvic acids in aqueous solution with stationary UV/Vis-absorption and fluorescence measurements. Instead of applying a fitting procedure, decay times are introduced as simple and robust experimental parameters for the quantitative description of fluorescence decays. The analysis of time-resolved emission spectra indicates a wavelength dependence of the fluorescence investigations of the interactions between pyrene and various humic substances in water. For all humic substances the quenching of pyrene fluorescence is dominated by a static quenching process, i.e. by a ground-state complexation. A significant influence of pH on the fluorescence quenching efficiencies is found, whereas no long-term changes of the interaction between pyrene and a humic substance are discernible. Time-resolved triplet- triplet absorption measurements reveal a decrease of chrysene triplet lifetime due to the presence of humic substances.

Zimmermann, Ute; Loehmannsroeben, Hans-Gerd; Skrivanek, Thomas

1997-05-01

18

Absorption and emission spectroscopic characterisation of 8-amino-riboflavin  

NASA Astrophysics Data System (ADS)

The flavin dye 8-amino-8-demethyl- D-riboflavin (AF) in the solvents water, DMSO, methanol, and chloroform/DMSO was studied by absorption and fluorescence spectroscopy. The first absorption band is red-shifted compared to riboflavin, and blue-shifted compared to roseoflavin (8-dimethylamino-8-demethyl-D-riboflavin). The fluorescence quantum yield of AF in the studied solvents varies between 20% and 50%. The fluorescence lifetimes were found to be in the 2-5 ns range. AF is well soluble in DMSO, weakly soluble in water and methanol, and practically insoluble in chloroform. The limited solubility causes AF aggregation, which was seen in differences between measured absorption spectra and fluorescence excitation spectra. Light scattering in the dye absorption region is discussed and approximate absorption cross-section spectra are determined from the combined measurement of transmission and fluorescence excitation spectra. The photo-stability of AF was studied by prolonged light exposure. The photo-degradation routes of AF are discussed.

Tyagi, A.; Zirak, P.; Penzkofer, A.; Mathes, T.; Hegemann, P.; Mack, M.; Ghisla, S.

2009-10-01

19

Application of Spectroscopic Methods for Characterization of the Composition of Piassava  

Microsoft Academic Search

AbstractSpectroscopic methods—infrared absorption, atomic emission spectroscopy, and x-ray diffraction—were used for the characterization of the organic and inorganic composition and structure of piassava. The analysis of the infrared spectra revealed that pias-sava fibers consist mainly of cellulose, lignin, and hemicellulose, and that this chemical composition is similar to that of jute. The infrared spectra together with the x-ray diffraction of

Z. A. El-Sayed

1995-01-01

20

X-ray absorption and magnetic resonance spectroscopic studies of LixV6O13  

Microsoft Academic Search

Polycrystalline LixV6O13 samples, 0.5<=x<=6, were prepared by chemical intercalation in n-butyl lithium and investigated spectroscopically by x-ray absorption, electron paramagnetic resonance (EPR), and 7Li solid state nuclear magnetic resonance (NMR). Both the EPR results and the vanadium K-edge x-ray absorption fine structure spectra show that the average oxidation state of the vanadium decreases with the addition of Li, and the

P. E. Stallworth; S. Kostov; M. L. Denboer; S. G. Greenbaum; C. Lampe-Onnerud

1998-01-01

21

Spectroscopic characterization of natural calcite minerals  

Microsoft Academic Search

The FT-IR, FT-Raman, NMR spectral data of ten different limestone samples have been compared. FT-IR and FT-Raman spectral data show that calcium carbonate in limestone, principally in the form of calcite, as identified by its main absorption bands at 1426, 1092, 876 and 712cm?1. The sharp diffractions at the d-spacings, 3.0348, 1.9166 and 1.8796 confirm the presence of calcite structure

S. Gunasekaran; G. Anbalagan

2007-01-01

22

Extraction, Purification, and Spectroscopic Characterization of a Mixture of Capsaicinoids  

ERIC Educational Resources Information Center

This laboratory experiment provides a safe and effective way to instruct undergraduate organic chemistry students about natural-product extraction, purification, and NMR spectroscopic characterization. On the first day, students extract dried habanero peppers with toluene, perform a pipet silica gel column to separate carotenoids from…

Wagner, Carl E.; Cahill, Thomas M.; Marshall, Pamela A.

2011-01-01

23

Spectroscopic characterization of natural humic substances  

NASA Astrophysics Data System (ADS)

The chemical composition and structure of humic substances were established based on spectroscopic studies (EDXS, SRATR FTIR, and 13C NMR). Humic acids were isolated from different matrices such as soils, compost, lignite, and commercial lignohumate. The btained results showed the highest content of aromatic groups in lignite and humic acids of Chernozem. The aromaticity degree (a) calculated from 13C NMR spectroscopy data decreased in the following order: lignite > Chernozems > lignohumate > Luvisols > compost > Cambisols. Infrared spectroscopy detected bands indicative of aliphatic groups (C-H at 2925 cm-1); aromatic groups (C=C at 1620 cm-1); phenolic groups (at 1404-1419 cm-1); and carboxyl and carbonyl groups (at 1225-1223 cm-1) in all studied humic acid samples. The main differences were found in the fingerprint region of 1700-1000 cm-1. The reactivity of humic acids given by the O/R ratio showed that the highest amount of n-alkyl groups were in the lignohumate samples. EDX spectroscopy indicated elements occurring in situ. Soil humic acids contained Fe, Cu, Zn, Ti, Ca, K, S, P, Si, and Br.

Hladký, J.; Pospíšilová, L.; Liptaj, T.

2013-03-01

24

Spectroscopic characterization of natural calcite minerals  

NASA Astrophysics Data System (ADS)

The FT-IR, FT-Raman, NMR spectral data of ten different limestone samples have been compared. FT-IR and FT-Raman spectral data show that calcium carbonate in limestone, principally in the form of calcite, as identified by its main absorption bands at 1426, 1092, 876 and 712 cm -1. The sharp diffractions at the d-spacings, 3.0348, 1.9166 and 1.8796 confirm the presence of calcite structure and the calculated lattice parameters are: a = 4.9781 Å, c = 17.1188 Å. The range of 13C chemical shifts for different limestone samples is very small, varying from 198.38 to 198.42 ppm. The observed chemical shifts are consistent with the identical C-O bonding in different limestone samples. 27Al MAS NMR spectra of the samples exhibit a central line at 1 ppm and another line at 60 ppm corresponding to octahedral and tetrahedral Al ions, respectively. The five component resonances were observed in 29Si MAS NMR spectrum of limestone and these resonances were assigned to Si (4 Al), Si (3 Al), Si (2 Al), Si (1 Al) and Si (0 Al) from low field to high field.

Gunasekaran, S.; Anbalagan, G.

2007-11-01

25

Vinylmercury Hydrides: Synthesis and Spectroscopic Characterization.  

PubMed

The first vinylmercury hydrides, and among them the parent compound, have been prepared by a chemoselective reduction of the corresponding vinylmercury chlorides with tributylstannane in the presence of a radical inhibitor. These hydrides have been characterized on the basis of their spectral data ((1)H, (13)C, and (199)Hg NMR spectroscopy and mass spectrometry). The photoelectron spectra of the ethenylmercury hydride displays bands at 9.79, 10.13, 11.41, and 13.20 eV. On the basis of photoelectron spectra and ab initio quantum chemical calculations some (d-p)pi interaction between the vinyl pi-system and the mercury d-orbitals could be concluded. Vinylmercury hydrides have been condensed and then revaporized in vacuum at low temperature, but they exhibit a very low stability at room temperature even diluted in toluene (tau(1/2) approximately 1 min); elemental mercury and the corresponding divinylmercury were formed under these conditions. PMID:11666808

Guillemin, Jean-Claude; Bellec, Nathalie; Szétsi, Sándor Kis; Nyulászi, László; Veszprémi, Tamás

1996-10-23

26

Optical Characterization of Thin Colloidal Gold Films by Spectroscopic Ellipsometry  

Microsoft Academic Search

Spectroscopic ellipsometry and atomic force microscopy (AFM) experiments are employed to characterize nanocolloidal gold films, self-assembled at APTES-derivatized Si\\/SiO2 surfaces. X-ray fluorescence measurements after deposition confirm that AFM provides a representative means to probe the absolute surface coverage. Optical properties of gold nanocrystal assemblies are investigated both ex situ after drying and in situ prior to evaporation of the solvent.

E. Stefan Kooij; Herbert Wormeester; E. A. Martijn Brouwer; Vroonhoven van Esther; Silfhout van Arend; Bene Poelsema

2002-01-01

27

Spectroscopic characterization of plasma during electrolytic oxidation (PEO) of aluminium  

Microsoft Academic Search

We present results of an optical emission spectroscopic study of Plasma during Electrolytic Oxidation (PEO) of aluminium in citric acid and in sodium–tungstate water solutions. The line shape analysis of the first two hydrogen Balmer lines indicates presence of two PEO processes characterized by relatively low electron number densities Ne?0.8×1015cm?3 and at 2.5×1016cm?3. Apart from these two Ne values, Ne?6.0×1016cm?3

J. Jovovi?; S. Stojadinovi?; N. M. Šišovi?; N. Konjevi?

2011-01-01

28

Optimization of hollow waveguides as absorption cells for spectroscopic gas sensing.  

PubMed

Flexible and low-loss hollow waveguide has many advantages as an absorption cell for spectroscopic gas sensing. The characteristics of the sensing system are dependent on the parameters of the hollow waveguide cell. In this paper, a mathematical model was proposed to analyze the waveguide cell by considering waveguide loss, effective optical path length, and signal-to-noise ratio of the system. Simulation results show that the gas absorption intensity and system sensitivity are dependent not only on the waveguide length but also on the bore-diameter, signal-to-noise ratio, and the concentration of the target gases. The results provide optimizing methods for the sensing system and algorithms for error compensation. Preliminary experiments on concentration detection of methane gas were carried out and measured data showed good agreements with the simulation results. PMID:23452494

Zhou, Jia-Qi; Lu, Wei-Jia; Yao, Zhang-Rui; Wei, Yu-Qing; Shi, Yi-Wei

2013-03-01

29

Spectroscope  

NSDL National Science Digital Library

In this activity, learners construct their own spectroscope as they explore and observe spectra from familiar light sources. Learners can be challenged to make technological improvements to their spectroscopes and/or participate in extension activities that expand their understanding of different kinds of spectra and sharpen their observing skills.

Observatory, Mcdonald

2008-01-01

30

X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin  

PubMed Central

Hemoglobin (Hb) is the heme-containing O2 transport protein essential for life in all vertebrates. The resting high-spin (S = 2) ferrous form, deoxy-Hb, combines with triplet O2, forming diamagnetic (S = 0) oxy-Hb. Understanding this electronic structure is the key first step in understanding transition metal–O2 interaction. However, despite intense spectroscopic and theoretical studies, the electronic structure description of oxy-Hb remains elusive, with at least three different descriptions proposed by Pauling, Weiss, and McClure-Goddard, based on theory, spectroscopy, and crystallography. Here, a combination of X-ray absorption spectroscopy and extended X-ray absorption fine structure, supported by density functional theory calculations, help resolve this debate. X-ray absorption spectroscopy data on solution and crystalline oxy-Hb indicate both geometric and electronic structure differences suggesting that two of the previous descriptions are correct for the Fe–O2 center in oxy-Hb. These results support the multiconfigurational nature of the ground state developed by theoretical results. Additionally, it is shown here that small differences in hydrogen bonding and solvation effects can tune the ground state, tipping it into one of the two probable configurations. These data underscore the importance of solution spectroscopy and show that the electronic structure in the crystalline form may not always reflect the true ground-state description in solution.

Wilson, Samuel A.; Green, Evan; Mathews, Irimpan I.; Benfatto, Maurizio; Hodgson, Keith O.; Hedman, Britt; Sarangi, Ritimukta

2013-01-01

31

Characterization of cytochrome c as marker for retinal cell degeneration by uv/vis spectroscopic imaging  

NASA Astrophysics Data System (ADS)

Retinal diseases like age-related macular degeneration have become an important cause of visual loss depending on increasing life expectancy and lifestyle habits. Due to the fact that no satisfying treatment exists, early diagnosis and prevention are the only possibilities to stop the degeneration. The protein cytochrome c (cyt c) is a suitable marker for degeneration processes and apoptosis because it is a part of the respiratory chain and involved in the apoptotic pathway. The determination of the local distribution and oxidative state of cyt c in living cells allows the characterization of cell degeneration processes. Since cyt c exhibits characteristic absorption bands between 400 and 650 nm wavelength, uv/vis in situ spectroscopic imaging was used for its characterization in retinal ganglion cells. The large amount of data, consisting of spatial and spectral information, was processed by multivariate data analysis. The challenge consists in the identification of the molecular information of cyt c. Baseline correction, principle component analysis (PCA) and cluster analysis (CA) were performed in order to identify cyt c within the spectral dataset. The combination of PCA and CA reveals cyt c and its oxidative state. The results demonstrate that uv/vis spectroscopic imaging in conjunction with sophisticated multivariate methods is a suitable tool to characterize cyt c under in situ conditions.

Hollmach, Julia; Schweizer, Julia; Steiner, Gerald; Knels, Lilla; Funk, Richard H. W.; Thalheim, Silko; Koch, Edmund

2011-06-01

32

Accurate dimensional characterization of periodic structures by spectroscopic Mueller polarimetry  

NASA Astrophysics Data System (ADS)

The potential of spectroscopic Mueller polarimetry for the dimensional characterization of periodic structures has already been discussed in several instances. With respect to standard scatterometry; the added value of the technique is related to the information contained in the 16 elements of the Mueller matrix, while usual scatterometry provides only two. The additional information can prove useful to decorrelate dimensional or optical parameters, and to assess the adequacy of the model describing the profiles to be reconstructed: if the model is adequate, the optimal values of the dimensional parameters must remain stable when the measurement conditions, and thus the input data, are varied. This issue has been addressed for a series of 1D gratings etched in bulk Si and characterized by a spectroscopic polarimeter operating in the visible (Horiba Jobin Yvon MM-16), as well as CD-SEM and state-of-the art CD-AFM. With the usual lamellar or trapezoidal models both the CD and thickness values exhibit up to 10 nm systematic variations with measurement conditions. In contrast, with an original model taking into account the non-flatness of the open areas between adjacent lines the parameters become consistent to within 2 nm, well below typical tool-to-tool offsets. The corresponding profiles are also compatible with the CD-AFM images.

Foldyna, M.; De Martino, A.; Cattelan, D.; Bogeat, F.; Licitra, C.; Foucher, J.; Barritault, P.; Hazart, J.

2008-11-01

33

UV spectroscopic characterization of dimethyl- and ethyl-substituted carbonyl oxides.  

PubMed

Dimethyl- and ethyl-substituted Criegee intermediates, (CH3)2COO and CH3CH2CHOO, are photolytically generated from diiodo precursors, detected by VUV photoionization at 118 nm, and spectroscopically characterized via UV-induced depletion of the m/z = 74 signals under jet-cooled conditions. In each case, UV excitation resonant with the B-X transition results in significant ground-state depletion, reflecting the large absorption cross section and rapid dynamics in the excited B state. The broad UV absorption spectra of both (CH3)2COO and CH3CH2CHOO peak at ~320 nm with absorption cross sections approaching ~4 × 10(-17) cm(2) molec(-1). The UV absorption spectra for (CH3)2COO and CH3CH2CHOO are similar to that reported previously for syn-CH3CHOO, suggesting analogous intramolecular interactions between the ?-H and terminal O of the COO groups. Hydroxyl radical products generated concurrently with the Criegee intermediates are detected by 1 + 1' resonance enhanced multiphoton ionization. The OH signals, scaled relative to those for the Criegee intermediates, are compared with prior studies of OH yield from alkene ozonolysis. The stationary points along the reaction coordinates from the alkyl-substituted Criegee intermediates to vinyl hydroperoxides and OH products are also computed to provide insight on the OH yields. PMID:24621008

Liu, Fang; Beames, Joseph M; Green, Amy M; Lester, Marsha I

2014-03-27

34

Spectroscope  

NSDL National Science Digital Library

In this activity (posted on March 12, 2011), learners follow the steps to construct a spectroscope, a tool used to analyze light and color. First, learners use relatively simple materials to construct the device. Then, learners look through their spectroscopes at a variety of different light sources including incandescents, LEDs, compact fluorescents, sun light, etc. and compare what they observe. This resource includes a few examples of how certain chemicals form different colors of light.

Center, Oakland D.

2011-01-01

35

Absorption and emission spectroscopic characterisation of a pyrene-flavin dyad  

NASA Astrophysics Data System (ADS)

The pyrene-flavin (isoalloxazine) dyad, PFD {C 44H 31N 5O 5; CA Index name: 1-pyrenepropanoic acid, ?-[[4,10-dihydro-2,4-dioxo-10-phenylbenzo[g]pteridin-3(2H)-yl)acetyl]amino]-, phenylmethyl ester, (?R)-(9Cl); CA Registry number: 618907-57-6}, dissolved in either dichloromethane or acetonitrile is characterized by absorption and emission spectroscopy. Absorption cross-section spectra, stimulated emission cross-section spectra, fluorescence quantum distributions, quantum yields, and degrees of fluorescence polarisation are determined. The fluorescence decay after femtosecond pulse excitation is determined by fluorescence up-conversion. The ground-state absorption recovery is determined by picosecond pump and probe transmission measurements. The dye photo-stability is investigated by observation of absorption spectral changes due to prolonged blue-light excitation. The absorption spectrum of PFD dyad resembles the superposition of the absorption of isoalloxazine (flavin) and 1-methylpyrene. Long-wavelength photo-excitation of the flavin moiety causes fluorescence quenching by ground-state electron transfer from pyrene to isoalloxazine. Short-wavelength photo-excitation of the pyrene moiety causes (i) excited-state electron transfer from pyrene to isoalloxazine, and (ii) Förster-type energy transfer from pyrene to flavin followed by ground-state electron transfer from pyrene to flavin.

Shirdel, J.; Penzkofer, A.; Procházka, R.; Shen, Z.; Strauss, J.; Daub, J.

2007-01-01

36

A surface-enhanced infrared absorption spectroscopic (SEIRAS) study of the oscillatory electro-oxidation of methanol on platinum  

Microsoft Academic Search

The oscillatory electro-oxidation of methanol was studied by means of in situ infrared (IR) spectroscopy in the attenuated total reflection (ATR) configuration using a platinum film on a Si prism as working electrode. The surface-enhanced infrared absorption (SEIRA) effect considerably improves the spectroscopic resolution, allowing at following the coverage of some adsorbing species during the galvanostatic oscillations. Carbon monoxide was

E. Boscheto; B. C. Batista; R. B. Lima; H. Varela

2010-01-01

37

GENERAL: Plasma characterization on carbon fiber cathode by spectroscopic diagnostics  

NASA Astrophysics Data System (ADS)

This paper mainly investigates plasma characterization on carbon fiber cathodes with and without cesium iodide (CsI) coating powered by a ~300 ns, ~200 kV accelerating pulse. It was found that the CsI layers can not only improve the diode voltage, but also maintain a stable perveance. This indicates a slowly changed diode gap or a low cathode plasma expansion velocity. By spectroscopic diagnostics, in the vicinity of the cathode surface the average plasma density and temperature were found to be ~3 × 1014 cm-3 and ~5 eV, respectively, for an electron current density of ~40 A/cm2. Furthermore, there exists a multicomponent plasma expansion toward the anode. The plasma expansion velocity, corresponding to the carbon and hydrogen ions, is estimated to be ~1.5 cm/?s. Most notably, Cs spectroscopic line was obtained only at the distance <= 0.5 mm from the cathode surface. Carbon and hydrogen ions are obtained up to the distance of 2.5 mm from the cathode surface. Cs ions almost remain at the vicinity of the cathode surface. These results show that the addition of CsI enables a slow cathode plasma expansion toward the anode, providing a positive prospect for developing long-pulse electron beam sources.

Liu, Lie; Li, Li-Min; Xu, Qi-Fu; Chang, Lei; Wen, Jian-Chun

2009-08-01

38

Characterization by spectroscopic Ellipsometry, the physical properties of silver nanoparticles.  

NASA Astrophysics Data System (ADS)

Physicists are able to change their minds through their experiments. I think it is time to go kick the curse and go further in research if we want a human future. I work in the Nano-Optics and Plasmonics research. I defined with ellipsomètrie the structure of new type of Nano particles of silver. It's same be act quickly to replace the old dirty leaded electronic-connexion chip and by the other hand to find a new way for the heath care of cancer disease by nanoparticles the next killers of bad cells. Silver nanoparticle layers are obtained by Spark Plasma Sintering are investigated as an alternative to lead alloy based material for solder joint in power mechatronics modules. These layers are characterized by mean of conventional techniques that is the dilatometry technique, the resistivity measurement through the van der Pauw method, and the flash laser technique. Furthermore, the nanoparticles of silver layer are deeply studied by UV-Visible spectroscopic ellipsometry. Spectroscopic angles parameters are determined in function of temperature and dielectric constants are deduced and analyzed through an optical model which takes into account a Drude and a Lorentz component within the Bruggeman effective medium approximation (EMA). The relaxation times and the electrical conductivity are plot in function of temperature. The obtained electrical conductivity give significant result in good agreement to those reported by four points electrical measurement method.

Coanga, Jean-Maurice

2013-04-01

39

In-situ spectroscopic investigation of infrared transmissive\\/absorptive electrochromic devices  

Microsoft Academic Search

Novel transmissive\\/absorptive electrochromic (EC) devices have been assembled using conjugated polymers on infrared-transparent electrodes made of single-wall carbon nanotubes (SWNTs). We will present results on the design, fabrication and characterization of sandwich type EC devices using dioxythiophene-based conjugated polymers (PXDOT). The polymers were prepared on the SWNT films using a potentiostatic electropolymerization method. The transmittance of the samples was measured

Maria Nikolou; Aubrey L. Dyer

2005-01-01

40

Spectroscopic characterization of dissolved organic matter isolated from rainwater.  

PubMed

Rainwater is a matrix containing extremely low concentrations (in the range of muM C) of dissolved organic carbon (DOC) and for its characterization, an efficient extraction procedure is essential. A recently developed procedure based on adsorption onto XAD-8 and XAD-4 resins in series was used in this work for the extraction and isolation of rainwater dissolved organic matter (DOM). Prior to the isolation and fractionation of DOM, and to obtain sufficient mass for the spectroscopic analyses, individual rainwater samples were batched together according to similar meteorological conditions on a total of three composed samples. The results of the isolation procedure indicated that the resin tandem procedure is not applicable for rainwater DOM since the XAD-4 resin caused samples contamination. On the other hand, the XAD-8 resin allowed DOM recoveries of 39.9-50.5% of the DOC of the original combined samples. This recovered organic fraction was characterized by UV-visible, molecular fluorescence, FTIR-ATR and 1H NMR spectroscopies. The chemical characterization of the rainwater DOM showed that the three samples consist mostly of hydroxylated and carboxylic acids with a predominantly aliphatic character, containing a minor component of aromatic structures. The obtained results suggest that the DOM in rainwater, and consequently in the precursor atmospheric particles, may have a secondary origin via the oxidation of volatile organic compounds from different origins. PMID:19091380

Santos, Patrícia S M; Otero, Marta; Duarte, Regina M B O; Duarte, Armando C

2009-02-01

41

Synthesis and electrochemical and spectroscopic characterization of biicosahedral Au25 clusters.  

PubMed

The synthesis and electrochemical and spectroscopic characterization of biicosahedral Au(25) clusters with a composition of [Au(25)(PPh(3))(10)(thiolate)(5)Cl(2)](2+) are described. The biicosahedral Au(25) clusters protected with various types of thiol ligands including alkanethiols, 2-phenylethanethiol, 11-mercaptoundecanoic acid, and 11-mercapto-1-undecanol were synthesized in high yields using a one-step, one-phase procedure in which Au(PPh(3))Cl is reduced with tert-butylamine-borane in the presence of the thiol ligand in a 3:1 v/v chloroform/ethanol solution. All biicosahedral Au(25) clusters prepared exhibit characteristic optical absorption and photoluminescence properties. The emission energy is found to be substantially smaller than the optical absorption energy gap of 1.82 eV, indicating a subgap energy luminescence. The electrochemical HOMO-LUMO gap (~1.54 eV) of the clusters is also substantially smaller than the optical absorption energy gap but rather similar to the emission energy. These electrochemical and optical properties of the biicosahedral Au(25) clusters are distinctly different from those of the Au(25)(thiolate)(18) clusters. PMID:22489959

Park, SunYoung; Lee, Dongil

2012-05-01

42

Near-infrared diode laser based spectroscopic detection of ammonia: a comparative study of photoacoustic and direct optical absorption methods  

NASA Technical Reports Server (NTRS)

A photoacoustic spectroscopic (PAS) and a direct optical absorption spectroscopic (OAS) gas sensor, both using continuous-wave room-temperature diode lasers operating at 1531.8 nm, were compared on the basis of ammonia detection. Excellent linear correlation between the detector signals of the two systems was found. Although the physical properties and the mode of operation of both sensors were significantly different, their performances were found to be remarkably similar, with a sub-ppm level minimum detectable concentration of ammonia and a fast response time in the range of a few minutes.

Bozoki, Zoltan; Mohacsi, Arpad; Szabo, Gabor; Bor, Zsolt; Erdelyi, Miklos; Chen, Weidong; Tittel, Frank K.

2002-01-01

43

Surface-Mediated Synthesis and Spectroscopic Characterization of Tantalum Clusters on Silica  

SciTech Connect

Tantalum clusters were synthesized on the surface of porous silica by treatment of adsorbed Ta(CH{sub 2}Ph){sub 5} in H{sub 2} at temperatures in the range of 523-723 K. The surface species were characterized by UV-vis, far-infrared, and extended X-ray absorption fine-structure (EXAFS) spectroscopies, each of which provided evidence of Ta-Ta bonds similar to those in well-characterized molecular tantalum clusters. The Ta-Ta distance determined by EXAFS spectroscopy was 2.93 Angstroms. The chemistry of the cluster synthesis is similar to that of syntheses of similar tantalum clusters in solution. The supported clusters formed at 523 K are characterized by an EXAFS first-shell Ta-Ta coordination number of nearly 2, indicative of tri-tantalum clusters, although it is expected that a mixture of clusters was present, and reduction in H2 at higher temperatures led to larger tantalum clusters. This is the first example of the surface-mediated synthesis of an early transition metal cluster, and the supported clusters reported here are the first to have been characterized by all three of the spectroscopic methods mentioned above. The similarity of the surface synthesis to that in solution points to opportunities to extend this new class of material to other early transition metal clusters on various supports.

Nemana,S.; Gates, B.

2006-01-01

44

Spectroscopic and electrochemical characterization of nanostructured optically transparent carbon electrodes.  

PubMed

The present paper describes the results related to the optical and electrochemical characterization of thin carbon films fabricated by spin coating and pyrolysis of AZ P4330-RS photoresist. The goal of this paper is to provide comprehensive information allowing for the rational selection of the conditions to fabricate optically transparent carbon electrodes (OTCE) with specific electrooptical properties. According to our results, these electrodes could be appropriate choices as electrochemical transducers to monitor electrophoretic separations. At the core of this manuscript is the development and critical evaluation of a new optical model to calculate the thickness of the OTCE by variable angle spectroscopic ellipsometry. Such data were complemented with topography and roughness (obtained by atomic force microscopy), electrochemical properties (obtained by cyclic voltammetry), electrical properties (obtained by electrochemical impedance spectroscopy), and structural composition (obtained by Raman spectroscopy). Although the described OTCE were used as substrates to investigate the effect of electrode potential on the real-time adsorption of proteins by ellipsometry, these results could enable the development of other biosensors that can be then integrated into various CE platforms. PMID:23595607

Benavidez, Tomás E; Garcia, Carlos D

2013-07-01

45

Adsorption and spectroscopic characterization of lactoferrin on hydroxyapatite nanocrystals.  

PubMed

Lactoferrin (LF), a well-characterized protein of blood plasma and milk with antioxidant, cariostatic, anticarcinogenic and anti-inflammatory properties, has been adsorbed onto biomimetic hydroxyapatite (HA) nanocrystals at two different pH values (7.4 and 9.0). The interaction was herein investigated by spectroscopic, thermal and microscopic techniques. The positive electrostatic surface potential of LF at pH 7.4 allows a strong surface interaction with the slightly negative HA nanocrystals and avoids the protein-protein interaction, leading to the formation of a coating protein monolayer. In contrast, at pH 9.0 the surface potential of LF is a mix of negative and positive zones favouring the protein-protein interaction and reducing the interaction with HA nanocrystals; as a result a double layer of coating protein was formed. These experimental findings are supported by the good fittings of the adsorption isotherms by different theoretical models according to Langmuir, Freundlich and Langmuir-Freundlich models. The nanosized HA does not appreciably affect the conformation of the adsorbed protein. In fact, using FT-Raman and FT-IR, we found that after adsorption the protein was only slightly unfolded with a small fraction of the ?-helix structure being converted into turn, while the ?-sheet content remained almost unchanged. The bioactive surface of HA functionalized with LF could be utilized to improve the material performance towards the biological environment for biomedical applications. PMID:21152600

Iafisco, Michele; Di Foggia, Michele; Bonora, Sergio; Prat, Maria; Roveri, Norberto

2011-01-28

46

Spectroscopic characterization of collagen cross-links in bone  

NASA Technical Reports Server (NTRS)

Collagen is the most abundant protein of the organic matrix in mineralizing tissues. One of its most critical properties is its cross-linking pattern. The intermolecular cross-linking provides the fibrillar matrices with mechanical properties such as tensile strength and viscoelasticity. In this study, Fourier transform infrared (FTIR) spectroscopy and FTIR imaging (FTIRI) analyses were performed in a series of biochemically characterized samples including purified collagen cross-linked peptides, demineralized bovine bone collagen from animals of different ages, collagen from vitamin B6-deficient chick homogenized bone and their age- and sex-matched controls, and histologically stained thin sections from normal human iliac crest biopsy specimens. One region of the FTIR spectrum of particular interest (the amide I spectral region) was resolved into its underlying components. Of these components, the relative percent area ratio of two subbands at approximately 1660 cm(-1) and approximately 1690 cm(-1) was related to collagen cross-links that are abundant in mineralized tissues (i.e., pyridinoline [Pyr] and dehydrodihydroxylysinonorleucine [deH-DHLNL]). This study shows that it is feasible to monitor Pyr and DHLNL collagen cross-links spatial distribution in mineralized tissues. The spectroscopic parameter established in this study may be used in FTIRI analyses, thus enabling the calculation of relative Pyr/DHLNL amounts in thin (approximately 5 microm) calcified tissue sections with a spatial resolution of approximately 7 microm.

Paschalis, E. P.; Verdelis, K.; Doty, S. B.; Boskey, A. L.; Mendelsohn, R.; Yamauchi, M.

2001-01-01

47

Synthesis, characterization, and spectroscopic investigation of benzoxazole conjugated Schiff bases.  

PubMed

Two Schiff bases were synthesized by reaction of 2-(4'-aminophenyl)benzoxazole derivatives with 4-N,N-diethylaminobenzaldehyde. UV-visible (UV-vis) and steady-state fluorescence in solution were applied in order to characterize its photophysical behavior. The Schiff bases present absorption in the UV region with fluorescence emission in the blue-green region, with a large Stokes' shift. The UV-vis data indicates that each dye behaves as two different chromophores in solution in the ground state. The fluorescence emission spectra of the dye 5a show that an intramolecular proton transfer (ESIPT) mechanism takes place in the excited state, whereas a twisted internal charge transfer (TICT) state is observed for the dye 5b. Theoretical calculations were performed in order to study the conformation and polarity of the molecules at their ground and excited electronic states. Using density functional theory (DFT) methods at theoretical levels BLYP/Aug-SV(P) for geometry optimizations and B3LYP/6-311++G(2d,p) for single-point energy evaluations, the calculations indicate that the lowest energy conformations are in all cases nonplanar and that the dipole moments of the excited state relaxed structures are much larger than those of the ground state structures, which corroborates the experimental UV-vis absorption results. PMID:21988352

Santos, Fabiano S; Costa, Tania M H; Stefani, Valter; Gonçalves, Paulo F B; Descalzo, Rodrigo R; Benvenutti, Edilson V; Rodembusch, Fabiano S

2011-11-24

48

PROCESSING OF HIGH LEVEL WASTE: SPECTROSCOPIC CHARACTERIZATION OF REDOX REACTIONS IN SUPERCRITICAL WATER  

EPA Science Inventory

Current efforts are focused on the oxidative dissolution of chromium compounds found in Hanford tank waste sludge. Samples of chromium oxides and hydroxides with varying degrees of hydration are being characterized using Raman, FTIR, and XPS spectroscopic techniques. Kinetics of ...

49

Ground-based Spectroscopic Characterization of Close-in Exoplanets  

NASA Astrophysics Data System (ADS)

High-contrast, high-resolution spectroscopy from ground-based facilities can directly detect and characterize the atmospheres of close-in exoplanets. These measurements complement space-based direct detections by probing planets and spectral regions inaccessible to current space-based instruments. We use the NIRSPEC spectrometer on the Keck II telescope to obtain near-infrared spectra containing the blended light of a planet and its parent star, with signal-to-noise of several thousand. These observations target exoplanet spectral signatures in the 3-5 micron regime where the planet/star flux ratio is most favorable to ground based observations. We correct for strong, variable telluric absorption using a forward modeling approach that combines a line-by-line radiative transfer code for synthesizing the terrestrial atmosphere with observations of telluric standards and the target star itself. We disentangle the stellar and planet flux using a two-dimensional correlation analysis that allows us to compare an observed planet spectrum against a suite of different planet models. By combining planet detections from multiple epochs we can solve for the dynamical planet mass and characterize the atmosphere over the range of orbital phases. Here, we will describe our recent direct detection of the non-transiting Neptune mass exoplanet 55 Cancri E and show preliminary results from tau Bootis.

Bender, Chad F.; Carr, J. S.; Barman, T. S.

2010-01-01

50

Theoretical modeling of the spectroscopic absorption properties of luciferin and oxyluciferin: A critical comparison with recent experimental studies  

NASA Astrophysics Data System (ADS)

Firefly luciferin and its oxidated form, oxyluciferin, are two heterocyclic compounds involved in the enzymatic reaction, catalyzed by redox proteins called luciferases, which provides the bioluminescence in a wide group of arthropods. Whereas the electronic absorption spectra of D-luciferin in water at different pHs are known since 1960s, only recently reliable experimental electronic spectra of oxyluciferin have become available. In addition oxyluciferin is involved in a triple chemical equilibria (deprotonation of the two hydroxyl groups and keto-enol tautomerism of the 4-hydroxythiazole ring), that obligates to select during an experiment a predominant species, tuning pH or solvent polarity besides introducing chemical modifications. In this study we report the absorption spectra of luciferin and oxyluciferin in each principal chemical form, calculated by means of perturbed matrix method (PMM), which allowed us to successfully introduce the effect of the solvent on the spectroscopic absorption properties, and compare the result with available experimental data.

Anselmi, Massimiliano; Marocchi, Simone; Aschi, Massimiliano; Amadei, Andrea

2012-01-01

51

In-situ spectroscopic investigation of infrared transmissive/absorptive electrochromic devices.  

NASA Astrophysics Data System (ADS)

Novel transmissive/absorptive electrochromic (EC) devices have been assembled using conjugated polymers on infrared-transparent electrodes made of single-wall carbon nanotubes (SWNTs). We will present results on the design, fabrication and characterization of sandwich type EC devices using dioxythiophene-based conjugated polymers (PXDOT). The polymers were prepared on the SWNT films using a potentiostatic electropolymerization method. The transmittance of the samples was measured over the infrared through visible energy range. To extract the optical constants of the polymer, we modeled all layers of this multilayer thin film structure using a Drude-Lorentz model. From the parameters obtained, we compute optical constants which yield information about the electronic structure of the neutral and doped states of the polymer. Evidence for polaron states at low doping and bipolaron states at maximum doping will be discussed.

Nikolou, Maria; Dyer, Aubrey L.

2005-03-01

52

Recent advances in chromatographic separation and spectroscopic characterization of the higher fullerenes C76 and C84.  

PubMed

The basic and the higher fullerenes were chromatographically isolated from the obtained series of carbon soot extracts, in increased yields, by the new, advanced methods, on Al2O3 columns. The elution was performed continuously, in one phase of each process, at ambient conditions, with the several different original hexane-toluene gradients. Various separation systems were used previously. The unique and the main, dominant absorption maxima of the purified higher fullerenes were registered in the spectral regions where they intensively absorb, applying the IR and UV/VIS techniques. All the observed absorption bands are in excellent agreement with theoretical calculations, indicating the achieved advancement in chromatographic separation and spectroscopic characterization. The isolated fullerenes are important for investigation of their remarkable optical and electronic properties, as well as for the numerous possible applications in chemistry, physics, biomedicine, diagnostic and therapeutic agents, sensors, polymers, nanophotonic materials, special lenses, optical limiting, organic field effect transistors, solar cells etc. PMID:24635208

Jovanovic, T; Koruga, Dj

2014-01-01

53

Combined Mössbauer spectroscopic, multi-edge X-ray absorption spectroscopic, and density functional theoretical study of the radical SAM enzyme spore photoproduct lyase.  

PubMed

Spore photoproduct lyase (SPL), a member of the radical S-adenosyl-L-methionine (SAM) superfamily, catalyzes the direct reversal of the spore photoproduct, a thymine dimer specific to bacterial spores, to two thymines. SPL requires SAM and a redox-active [4Fe-4S] cluster for catalysis. Mössbauer analysis of anaerobically purified SPL indicates the presence of a mixture of cluster states with the majority (40 %) as [2Fe-2S](2+) clusters and a smaller amount (15 %) as [4Fe-4S](2+) clusters. On reduction, the cluster content changes to primarily (60 %) [4Fe-4S](+). The speciation information from Mössbauer data allowed us to deconvolute iron and sulfur K-edge X-ray absorption spectra to uncover electronic (X-ray absorption near-edge structure, XANES) and geometric (extended X-ray absorption fine structure, EXAFS) structural features of the Fe-S clusters, and their interactions with SAM. The iron K-edge EXAFS data provide evidence for elongation of a [2Fe-2S] rhomb of the [4Fe-4S] cluster on binding SAM on the basis of an Fe···Fe scatterer at 3.0 Å. The XANES spectra of reduced SPL in the absence and presence of SAM overlay one another, indicating that SAM is not undergoing reductive cleavage. The X-ray absorption spectroscopy data for SPL samples and data for model complexes from the literature allowed the deconvolution of contributions from [2Fe-2S] and [4Fe-4S] clusters to the sulfur K-edge XANES spectra. The analysis of pre-edge features revealed electronic changes in the Fe-S clusters as a function of the presence of SAM. The spectroscopic findings were further corroborated by density functional theory calculations that provided insights into structural and electronic perturbations that can be correlated by considering the role of SAM as a catalyst or substrate. PMID:24532333

Silver, Sunshine C; Gardenghi, David J; Naik, Sunil G; Shepard, Eric M; Huynh, Boi Hanh; Szilagyi, Robert K; Broderick, Joan B

2014-03-01

54

White-light continuum probed femtosecond time-resolved absorption spectroscopic measurement of ?-carotene under high pressure  

NASA Astrophysics Data System (ADS)

We have performed a femtosecond time-resolved absorption spectroscopic experiment of ?-carotene in n-hexane solution under high pressure up to ˜1.0 GPa. Using white-light continuum in the visible spectral region as probe light, we found that the energy level of S1 state descends, whereas its lifetime becomes longer with the rising pressure. We ascribe this tendency deviating from the energy gap law to the viscosity effects on the Cdbnd C stretching vibrations, which is fully consistent with the microviscosity theory. This Letter may provide some insights on the light harvesting and photoprotection functions of carotenoids in photosynthetic organisms.

Liu, Wei-Long; Zheng, Zhi-Ren; Zhang, Jian-Ping; Wu, Wen-Zhi; Li, Ai-Hua; Zhang, Wei; Huo, Ming-Ming; Liu, Zhi-Guo; Zhu, Rui-Bin; Zhao, Lian-Cheng; Su, Wen-Hui

2012-04-01

55

Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry: Preprint  

SciTech Connect

We use in-situ and ex-situ spectroscopic ellipsometry to characterize the optical, electronic, and structural properties of individual layers and completed silicon heterojunction devices. The combination of in-situ measurements during thin film deposition with ex-situ measurements of completed devices allows us to understand both the growth dynamics of the materials and the effects of each processing step on material properties. In-situ ellipsometry measurements enable us to map out how the optical properties change with deposition conditions, pointing the way towards reducing the absorption loss and increasing device efficiency. We use the measured optical properties and thickness of the i-, n-, and p-layers in optical device modeling to determine how the material properties affect device performance. Our best solar energy conversion efficiencies are 16.9% for a non-textured, single-sided device with an aluminum back surface field contact on a p-type float zone silicon wafer, and 17.8% for a textured double-sided device on a p-type float zone silicon wafer.

Levi, D.; Iwaniczko, E.; Page, M.; Branz, H.; Wang, T.

2006-05-01

56

Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry  

SciTech Connect

We use in-situ and ex-situ spectroscopic ellipsometry to characterize the optical, electronic, and structural properties of individual layers and completed silicon heterojunction devices. The combination of in-situ measurements during thin film deposition with ex-situ measurements of completed devices allows us to understand both the growth dynamics of the materials and the effects of each processing step on material properties. In-situ ellipsometry measurements enable us to map out how the optical properties change with deposition conditions, pointing the way towards reducing the absorption loss and increasing device efficiency. We use the measured optical properties and thickness of the i-, n-, and p-layers in optical device modeling to determine how the material properties affect device performance. Our best solar energy conversion efficiencies are 16.9% for a non-textured, single-sided device with an aluminum back surface field contact on a p-type float zone silicon wafer, and 17.8% for a textured double-sided device on a p-type float zone silicon wafer.

Levi, D.; Iwaniczko, E.; Page, M.; Wang, Q.; Branz, H.; Wang, T.

2006-01-01

57

Spectroscopic characterization of alkali modified zinc-tellurite glasses doped with neodymium.  

PubMed

Neodymium doped zinc-tellurite glasses of composition TeO(2)-ZnO-Na(2)O-Li(2)O have been prepared and characterized for their thermal, structural and optical properties. Differential thermal analysis revealed reasonably good forming tendency of the glass composition. FTIR spectra were used to analyze the functional groups present in the glass. Judd-Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative lifetime, branching ratio and stimulated emission cross-section for (4)F(3/2)-->(4)I(9/2, 11/2, 13/2) transitions. The quantum efficiency of the (4)F(3/2) level is comparable to the typical values obtained for the Nd(2)O(3)-doped glasses. The decay properties for higher concentration of Nd(2)O(3) were analyzed using Inokuti-Hirayama model to investigate the non-radiative relaxation of the (4)F(3/2) emitting level. The experimental values of branching ratio and saturation intensity of (4)F(3/2)-->(4)I(11/2) transition and calculated spectroscopic quality factor indicate the favourable lasing action in these glasses. PMID:20570210

Rajeswari, R; Babu, S Surendra; Jayasankar, C K

2010-09-15

58

Spectroscopic characterizations of rare earth doped ceramics, nanocrystals, nanocrystal embedded polymeric hosts and their potential applications  

NASA Astrophysics Data System (ADS)

Trivalent rare earth (RE3+) ions have been used as an activator in laser host materials and in a wide variety of photonic applications. Of the competing hosts, one of the most well studied and successful host has been yttrium aluminum garnet Y3Al5O12 (YAG). In comparison to YAG, yttrium oxide (Y2O3) has shown promise as a potential laser medium due to its excellent optical, thermal and mechanical properties. As single crystals, Y2O3 system can be extremely difficult to grow due to the high melting temperature (˜2200°C) of the host. Alternatively, ceramic and nanocrystalline forms of Y2O3 have contributed to renewed interest in the material as laser host and more recently in biological and other photonic applications due to simplicity of fabrication. This work focuses on four RE 3+ ions, namely erbium, neodymium, holmium, europium doped into Y 2O3 and are selected due to their multi-frequency absorption properties and visible to near infrared emission characteristics. The chosen nanocrystalline material are embedded or coated in polymers that are biocompatible resulting in visible to near infrared fluorescent polymers. These materials are characterized through morphology studies and spectroscopic analyses of the absorption and emission spectra. Judd-Ofelt (J-O) and Crystal-Field (CF) techniques are applied to the systems and the results are compared to single crystal and ceramic forms and in some cases these analyses are reported for the first time for this host. Results of these analyses show that the addition of near infrared emitting rare earth nanocrystals to these polymers offers an attractive application to their existing biological applications.

Nash, Kelly Latrice

59

Spectroscopic characterization of novel multilayer mirrors intended for astronomical and laboratory applications  

NASA Astrophysics Data System (ADS)

We report measurements of the reflection spectra of (i) concave (spherical and parabolic) Mo/Si, Mg/Si, and Al/Zr multilayer mirrors (MMs) intended for imaging solar spectroscopy in the framework of the TESIS/CORONAS-FOTON Satellite Project and of (ii) an aperiodic Mo/Si MM optimized for maximum uniform reflectivity in the 125-250 Å range intended for laboratory applications. The reflection spectra were measured in the configuration of a transmission grating spectrometer employing the radiation of a tungsten laser-driven plasma as the source. The function of detectors was fulfilled by backside-illuminated CCDs coated with Al or Zr/Si multilayer absorption filters. High-intensity second-order interference reflection peaks at wavelengths of about 160 Å were revealed in the reflection spectra of the 304-Å Mo/Si MMs. By contrast, the second-order reflection peak in the spectra of the new-generation narrow-band (~12 Å FWHM) 304-Å Mg/Si MMs is substantially depressed. Manifestations of the NEXAFS structure of the L2, 3 absorption edges of Al and Al2O3 were observed in the spectra recorded. The broadband Mo/Si MM was employed as the focusing element of spectrometers in experiments involving (i) the charge exchange of multiply charged ions with the donor atoms of a rare-gas jet; (ii) the spectroscopic characterization of a debris-free soft X-ray radiation source excited by Nd laser pulses in a Xe jet (iii) near-IR-to-soft-X-ray frequency conversion (double Doppler effect) occurring in the retroreflection from the relativistic electron plasma wake wave (flying mirror) driven by a multiterawatt laser in a pulsed helium jet.

Ragozin, Eugene N.; Mednikov, Konstantin N.; Pertsov, Andrei A.; Pirozhkov, Alexander S.; Reva, Anton A.; Shestov, Sergei V.; Ul'Yanov, Artem S.; Vishnyakov, Eugene A.

2009-05-01

60

Spectroscopic characterization of extrasolar planets from ground-, space- and airborne-based observatories  

NASA Astrophysics Data System (ADS)

This thesis deals with techniques and results of observations of exoplanets from several platforms. In this work I present and then attempt solutions to particular issues and problems connected to ground- and space-based approaches to spectroscopic characterization of extrasolar planets. Furthermore, I present the future prospects of the airborne observatory, SOFIA, in this field of astronomy. The first part of this thesis covers results of an exploratory study to use near-infrared integral-field-spectroscopy to observe transiting extrasolar planets. I demonstrate how adaptive-optics assisted integral field spectroscopy compares with other spectroscopic techniques currently applied, foremost being slit spectroscopy. An advanced reduction method using elements of a spectral-differential decorrelation and optimized observation strategies is discussed. This concept was tested with K-Band time series observations of secondary eclipses of HD 209458b and HD 189733b obtained with the SINFONI at the Very Large Telescope (VLT), at spectral resolution of R~3000. In ground-based near infrared (NIR) observations, there is considerable likelihood of confusion between telluric absorption features and spectral features in the targeted object. I describe a detailed method that can cope with such confusion by a forward modelling approach employing Earth transmission models. In space-based transit spectroscopy with Hubble's NICMOS instrument, the main source of systematic noise is the perturbation in the instrument's configuration due to the near Earth orbital motion of the spacecraft. I present an extension to a pre-existing data analysis sequence that has allowed me to extract a NIR transmission spectrum of the hot-Neptune class planet GJ 436b from a data set that was highly corrupted by the above mentioned effects. Satisfyingly, I was able to obtain statistical consistency in spectra (acquired over a broad wavelength grid) over two distinct observing visits by HST. Earlier reductions were unable to achieve this feat. This work shows that systematic effecting the spectrophotometric light-curves in HST can be removed to levels needed to observe features in the relatively small scale-height atmospheres of hot Neptune class planets orbiting nearby stars. In the third and final part of this thesis, I develop and discuss possible science cases for the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) in the field of detection and characterization of extrasolar planets. The principle advantages of SOFIA and its suite of instrumentation is illustrated and possible targets are introduced. Possible next generation instrumentation (dedicated to exoplanetary science) is discussed.

Angerhausen, Daniel

2010-11-01

61

Characterization of potassium glycinate for carbon dioxide absorption purposes  

Microsoft Academic Search

Aqueous solutions of potassium glycinate were characterized for carbon dioxide absorption purposes. Density and viscosity of these solutions, with concentrations ranging from 0.1 to 3M, were determined at temperatures from 293 to 313K. Diffusivity of CO2 in solution was estimated applying the modified Stokes–Einstein relation. Solubilities of N2O at the same temperatures and concentrations were measured and the ion specific

A. F. Portugal; P. W. J. Derks; G. F. Versteeg; F. D. Magalhães; A. Mendes

2007-01-01

62

Interactions of doxorubicin with organized interfacial assemblies. 2. Spectroscopic characterization.  

PubMed

Doxorubicin is an anthracycline that has found wide use as a chemotherapeutic agent, with the primary limitation to its use being cardiotoxicity. Depending on the identity and location of pendent side groups, the anthracyclines exhibit varying degrees of chemotherapeutic activity and toxicity, and a key area of research activity lies in understanding how the structure of the anthracycline influences its interactions with amphiphilic interfaces. We have studied interactions between doxorubicin and interfacial adlayers of octadecylamine (C18NH2), dihexadecylphosphate (DHP), and both monolayers and bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) on mica using time- and frequency-resolved spectroscopic measurements. We report surface-enhanced resonance Raman data and fluorescence lifetime and anisotropy imaging data for doxorubicin at these interfaces. For all monolayers, there is a substantial interaction between doxorubicin and the interface. For DMPC bilayers, the extent of the interaction between doxorubicin and the interface depends on how the interface was formed. PMID:24175753

Nieciecka, Dorota; Królikowska, Agata; Setiawan, Iwan; Krysinski, Pawel; Blanchard, G J

2013-11-26

63

Comprehensive Spectroscopic Characterization of Model Aromatic Substituents of Lignin  

NASA Astrophysics Data System (ADS)

2,6-Dimethoxyphenol (2,6-DMP) is a model compound with aromatic substitution similar to that in sinapyl alcohol, one of the three monomers that make up lignin. 2,6-DMP has been studied combining several spectroscopic techniques that span the microwave, infrared and ultraviolet regions. Spectra from laser-induced fluorescence excitation, IR-UV hole-burning, fluorescence dip IR, dispersed fluorescence and rotational spectra have allowed us to develop more insight to the structural details, intramolecular H-bonding and electronic excited states of this sinapyl alcohol analog. Coupling in the CH stretch region, broadening effects in the IR spectra and Coriolis coupling due to the OH tunneling coordinate in the rotational spectrum will be shown as we present this diverse set of experimental data involving transitions between different vibronic, vibrational and rotational levels of the molecule. These features will be compared to those in 2-methoxyphenol and 4-methyl-2,6-DMP during the discussion.

Dean, Jacob C.; Vara, Vanesa Vaquero; Hotopp, Kelly M.; Dian, Brian C.; Zwier, Timothy S.

2012-06-01

64

Characterization of optically compressing diode array for spectroscopic applications  

NASA Astrophysics Data System (ADS)

Spectroscopic detection and classification techniques suffer from the collection of excessive data and utilize only a fraction of the information collected for classification. Compressed Sensing (CS) techniques have been utilized in optical, photonic, electronic and controls applications. This limits data collection to the essentials and reduces the hardware, software, and computational requirements. Applying CS to just the general computational system results in the collection of data which is ultimately discarded. The result is excessive power consumption, mass, physical sizes, and complexity. Compressive Sensing requires, at a minimum, a non-uniform encoding system with a non-linear decompression system for total reconstruction. Pseudorandom encoding is frequently preferred. Total reconstruction of a compressed signal has been shown to be very computational intensive and other optical-based techniques have been demonstrated to accelerate the result. Prior work has demonstrated that total reconstruction is not necessary for effective classification via PCA and other spectroscopic relevant techniques. Prior work revised the system design and modified the signal processing, both electronic and computational, to reduce system requirements. To propagate this savings back into the photonics and optical chain, it is necessary to further develop alternative techniques. In particular, a modification to the traditional LDA allows the contraction of primary optics. In this presentation an optical detector scheme is detailed. A number of configurations are considered with the most savings achieved by a spatial integrating version that allows the maintenance of optical and photonic SNR by collecting a number of photons greater than or equal to the traditional LDA. Since primary optical diameter is largely specified by the need to subtend an angle sufficient to overcome system noise, optical diameters can be reduced by up to an order of magnitude. This also mitigates optical diameter driven resolution at the detector plane. Some third order and higher issues exist and are addressed. Theoretical development with limited empirical support is to be presented.

Griffin, Steven T.

2013-10-01

65

Spectroscopic characterization of nanovesicles originating from self-forming synthetic PEGylated lipids  

Microsoft Academic Search

In this study, we have utilized the advantages of biophotonics and nanotechnology in conjunction with vibrational spectroscopic techniques to understand the various properties of biological macromolecules known as lipid bilayers or liposomes and nanovesicles. Liposomes are spherical particles that can encapsulate a fraction of the solvent into their interior. Liposomes are constructed of polar lipids which are characterized by having

Rajan K. Bista; Reinhard F. Bruch; Aaron M. Covington

2010-01-01

66

Absorption spectroscopic probe to investigate the interaction between Nd(III) and calf-thymus DNA  

NASA Astrophysics Data System (ADS)

The interaction between Nd(III) and Calf Thymus DNA (CT-DNA) in physiological buffer (pH 7.4) has been studied using absorption spectroscopy involving 4f-4f transition spectra in different aquated organic solvents. Complexation with CT-DNA is indicated by the changes in absorption intensity following the subsequent changes in the oscillator strengths of different 4f-4f bands and Judd-Ofelt intensity ( T?) parameters. The other spectral parameters namely Slator-Condon ( Fk's), nephelauxetic effect ( ?), bonding ( b1/2) and percent covalency ( ?) parameters are computed to correlate with the binding of Nd(III) with DNA. The absorption spectra of Nd(III) exhibited hyperchromism and red shift in the presence of DNA. The binding constant, Kb has been determined by absorption measurement. The relative viscosity of DNA decreased with the addition of Nd(III). Thermodynamic parameters have been calculated according to relevant absorption data and Van't Hoff equation. The characterisation of bonding mode has been studied in detail. The results suggested that the major interaction mode between Nd(III) and DNA was external electrostatic binding.

Devi, Ch. Victory; Singh, N. Rajmuhon

2011-03-01

67

Optical absorption and luminescence properties of Nd 3+ in mixed alkali borate glasses—Spectroscopic investigations  

Microsoft Academic Search

Spectroscopic investigations were performed on 67B2O3·xLi2O·(32-x)Na2O and 67B2O3.·xLi2O·(32-x)K2O (where x=8, 12, 16, 20 and 24) glasses containing 1mol% Nd2O3. Covalency was studied as a function of x using Judd-Ofelt intensity parameters that are related to the ligand field symmetry and the degree of bond covalency. Results show that covalency increases when the third component is added to the binary borate

Y. C. Ratnakaram; A. Vijaya kumar; D. Thirupathi Naidu; R. P. S. Chakradhar; K. P. Ramesh

2004-01-01

68

Saturated absorption inside a Fabry-Perot resonator - Spectroscopic and metrological applications  

NASA Astrophysics Data System (ADS)

A saturated absorption technique for spectroscopy and metrology based on the use of a Fabry-Perot resonator is presented and applications of the technique are reported. The method involves the placing of the absorption cell within a Fabry-Perot resonator, allowing a considerable increase in sensitivity if the reflection coefficient of the mirrors is close to 1. For saturated absorption spectroscopy of a weakly saturated dilute media, the signal level is doubled and a Gaussian beam is obtained, permitting the observation of weak and fine lines. The technique has been applied to the study of the high-resolution hyperfine structure of iodine around 612 nm, in which the hyperfine dissociation of the R(47) 9-2 line was observed, and to the improvement of the frequency stability and reproducibility of an iodine-stabilized He-Ne laser.

Cerez, P.; Brillet, A.; Man-Pichot, C.; Umezu, J.

1980-06-01

69

Three-photon absorption and vibrational spectroscopic study of 2-methylamino-5-chlorobenzophenone  

NASA Astrophysics Data System (ADS)

In this paper, the vibrational spectral analysis and three-photon absorption properties of an organic material of 2-methylamino-5-chlorobenzophenone have been reported. The geometry and harmonic vibrational wavenumbers are calculated with the help of B3LYP density functional theory method. The detailed interpretation of the vibrational spectra has been carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology (SQM). SQM force fields have also been used to calculate potential energy distribution (PED) in order to make conspicuous vibrational assignments. The nonlinear absorption properties have been investigated in ethanol solution at 532 nm using the Z-scan technique employing laser pulses of 5 ns duration. Open aperture Z-scan data reveal the presence of effective three-photon absorption for ns pulses at 532 nm resulting in a strong optical limiting behavior, indicating possible photonic applications.

Sajan, D.; Chaitanya, K.; Safakath, K.; Philip, Reji; Suthan, T.; Rajesh, N. P.

2013-04-01

70

Metallic and semiconductor nanoparticles: Synthesis, characterization and femtosecond laser spectroscopic studies  

Microsoft Academic Search

The optical properties and the femtosecond relaxation dynamics of metallic and semiconductor nanoparticles and their dependence on the particle shapes were studied. Metallic and semiconductor nanoparticles were synthesized and characterized using optical absorption and emission spectroscopy as well as the Transmission Electron Microscopy (TEM). The ultrafast relaxation dynamics and the transient absorption spectra have been monitored using femtosecond pump-probe experiment.

Mona Bakr Mohamed

2002-01-01

71

Characterization of cell-penetrating lipopeptide micelles by spectroscopic methods.  

PubMed

The transport of bioactive compounds to the site of action is a great challenge. A promising approach to overcome application-related problems is the development of targeting colloidal transport systems, such as micelles which are equipped with uptake mediating moieties. Here, we investigated a set of novel lipopeptides which exhibit a surfactant-like structure due to attachment of two palmitoyl chains to the N-terminus of cationic or anionic amino acid sequences. We analyzed the association behavior of these lipopeptides by using 5(6)-carboxyfluorescein (CF)-labeled derivatives as a fluorescent probe and different spectroscopic methods such as fluorescence anisotropy and fluorescence correlation spectroscopy (FCS). The photophysical properties as well as the diffusion and rotational movements of the CF-labeled lipopeptides were exploited to determine the cmc and the size of the micelles consisting of lipopeptides. We could distinguish cationic and anionic lipopeptides by their association behavior and by studying the interactions with mouse brain capillary endothelial cells (b.end3). The cationic derivatives turned out to be very strong surfactants with a very low cmc in the micromolar range (0.5-14 ?M). The unique combination of micelle-forming property and cell-penetrating ability can pave the road for the development of a novel class of efficient drug carrier systems. PMID:24188016

Gehne, Sören; Sydow, Karl; Dathe, Margitta; Kumke, Michael U

2013-11-21

72

Thermal, spectroscopic, and ab initio structural characterization of carprofen polymorphs.  

PubMed

Commercial and recrystallized polycrystalline samples of carprofen, a nonsteroidal anti-inflammatory drug, were studied by thermal, spectroscopic, and structural techniques. Our investigations demonstrated that recrystallized sample, stable at room temperature (RT), is a single polymorphic form of carprofen (polymorph I) that undergoes an isostructural polymorphic transformation by heating (polymorph II). Polymorph II remains then metastable at ambient conditions. Commercial sample is instead a mixture of polymorphs I and II. The thermodynamic relationships between the two polymorphs were determined through the construction of an energy/temperature diagram. The ab initio structural determination performed on synchrotron X-Ray powder diffraction patterns recorded at RT on both polymorphs allowed us to elucidate, for the first time, their crystal structure. Both crystallize in the monoclinic space group type P2(1) /c, and the unit cell similarity index and the volumetric isostructurality index indicate that the temperature-induced polymorphic transformation I ? II is isostructural. Polymorphs I and II are conformational polymorphs, sharing a very similar hydrogen bond network, but with different conformation of the propanoic skeleton, which produces two different packing. The small conformational change agrees with the low value of transition enthalpy obtained by differential scanning calorimetry measurements and the small internal energy computed with density functional methods. PMID:21246561

Bruni, Giovanna; Gozzo, Fabia; Capsoni, Doretta; Bini, Marcella; Macchi, Piero; Simoncic, Petra; Berbenni, Vittorio; Milanese, Chiara; Girella, Alessandro; Ferrari, Stefania; Marini, Amedeo

2011-06-01

73

Solution and single crystal spectroscopic characterization of (PPh 4) 2[Fe(CN) 5(imidazole)]·2H 2O  

NASA Astrophysics Data System (ADS)

The compound (PPh 4) 2[Fe III(CN) 5(im)]·2H 2O ( 1) together with its 13C labeled analogue have been synthesized (where im is imidazole) and characterized by UV/Vis, LD, IR, Raman and resonance Raman spectroscopy both in solution, powder and single crystalline form. The low spin state of the metal center, Fe III, was confirmed by MCD, EPR and 57Fe Mössbauer spectroscopies. Polarized Raman spectroscopic studies on a single crystal of 1 show the strong dependence of the stretching cyano ligand vibrations on crystal orientation relative to the direction of laser polarization and allows for assignment of all CN vibrational modes. Raman, UV/Vis absorption, LD and MCD spectroscopy both in the solid state and in solution state allowed for the discrimination of the effect of protonation of the imidazole ligand and hydrogen bonding to the cyano ligands on the complex. The combined spectroscopic data demonstrates that in addition to the protonation state of the imidazole, hydrogen bonding interactions with the cyano ligands both in the solid state as well as in solution have a profound influence on the electronic properties of 1.

Tchouka, Heloïse; Meetsma, Auke; Molnár, Gábor; Rechignat, Lionel; Browne, Wesley R.

2011-07-01

74

Spectroscopic characterization of ion-irradiated multi-layer graphenes  

NASA Astrophysics Data System (ADS)

Low-energy Ar ions (0.5-2 keV) were irradiated to multi-layer graphenes and the damage process, the local electronic states, and the degree of alignment of the basal plane, and the oxidation process upon ion irradiation were investigated by Raman spectroscopy, soft X-ray absorption spectroscopy (XAS) and in situ X-ray photoelectron spectroscopy (XPS). By Raman spectroscopy, we observed two stages similar to the case of irradiated graphite, which should relate to the accumulations of vacancies and turbulence of the basal plane, respectively. XAS analysis indicated that the number of sp2-hybridized carbon (sp2-C) atoms decreased after ion irradiation. Angle-resolved XAS revealed that the orientation parameter (OP) decreased with increasing ion energy and fluence, reflecting the turbulence of the basal plane under irradiation. In situ XPS shows the oxidation of the irradiated multi-layer graphenes after air exposure.

Tsukagoshi, Akira; Honda, Shin-ichi; Osugi, Ryo; Okada, Hiraku; Niibe, Masahito; Terasawa, Mititaka; Hirase, Ryuji; Izumi, Hirokazu; Yoshioka, Hideki; Niwase, Keisuke; Taguchi, Eiji; Lee, Kuei-Yi; Oura, Masaki

2013-11-01

75

X-ray absorption spectroscopic studies of mononuclear non-heme iron enzymes  

SciTech Connect

Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s{yields}3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been applied to the study of non-heme iron enzyme active sites.

Westre, T.E.

1996-01-01

76

X-ray absorption and emission spectroscopic investigation of Mn doped ZnO films  

Microsoft Academic Search

The electronic structure of (Zn,Mn)O films with different Mn concentrations has been investigated by element-selective soft X-ray absorption and emission spectroscopy. The band gap narrowing of (Zn,Mn)O with increase of Mn concentration (<20% Mn) is attributed to the Mn doping and sp–d exchange interactions. According to analysis of the O K? and resonant Mn L2,3 X-ray emission spectra, the splitting

J. Jin; G. S. Chang; Y. X. Zhou; X. Y. Zhang; D. W. Boukhvalov; E. Z. Kurmaev; A. Moewes

2011-01-01

77

Electron Spin Resonance and optical absorption spectroscopic studies of manganese centers in aluminium lead borate glasses  

NASA Astrophysics Data System (ADS)

Electron Spin Resonance (ESR) and optical absorption studies of 5Al2O3 + 75H3BO3 + (20-x)PbO + xMnSO4 (where x = 0.5, 1,1.5 and 2 mol% of MnSO4) glasses at room temperature have been studied. The ESR spectrum of all the glasses exhibits resonance signals with effective isotropic g values at ?2.0, 3.3 and 4.3. The ESR resonance signal at isotropic g ? 2.0 has been attributed to Mn2+ centers in an octahedral symmetry. The ESR resonance signals at isotropic g ? 3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn2+ ions. The zero-field splitting parameter (zfs) has been calculated from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits an intense band in the visible region and it has been attributed to 5Eg ? 5T2g transition of Mn3+centers in an octahedral environment. The optical band gap and the Urbach energies have been calculated from the ultraviolet absorption edges.

SivaRamaiah, G.; LakshmanaRao, J.

2012-12-01

78

Electron Spin Resonance and optical absorption spectroscopic studies of manganese centers in aluminium lead borate glasses.  

PubMed

Electron Spin Resonance (ESR) and optical absorption studies of 5Al(2)O(3)+75H(3)BO(3)+(20-x)PbO+xMnSO(4) (where x=0.5, 1,1.5 and 2 mol% of MnSO(4)) glasses at room temperature have been studied. The ESR spectrum of all the glasses exhibits resonance signals with effective isotropic g values at ?2.0, 3.3 and 4.3. The ESR resonance signal at isotropic g?2.0 has been attributed to Mn(2+) centers in an octahedral symmetry. The ESR resonance signals at isotropic g?3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn(2+) ions. The zero-field splitting parameter (zfs) has been calculated from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits an intense band in the visible region and it has been attributed to (5)E(g)?(5)T(2g) transition of Mn(3+)centers in an octahedral environment. The optical band gap and the Urbach energies have been calculated from the ultraviolet absorption edges. PMID:23000927

SivaRamaiah, G; LakshmanaRao, J

2012-12-01

79

Spectroscopic characterization of dissolved organic matter isolated from rainwater  

Microsoft Academic Search

Rainwater is a matrix containing extremely low concentrations (in the range of ?M C) of dissolved organic carbon (DOC) and for its characterization, an efficient extraction procedure is essential. A recently developed procedure based on adsorption onto XAD-8 and XAD-4 resins in series was used in this work for the extraction and isolation of rainwater dissolved organic matter (DOM). Prior

Patrícia S. M. Santos; Marta Otero; Regina M. B. O. Duarte; Armando C. Duarte

2009-01-01

80

Raman spectroscopic characterization of some commercially available carbon black materials  

Microsoft Academic Search

Some commercially available carbon black materials were characterized by Raman spectroscopy. The Raman spectra were recorded between 1000 and 1800 cm?1, which corresponds to the spectral region that provides the most valuable data on the microstructure of carbons. A comparative study of the intensity, bandwidth and frequency shifts of the D and G bands, as well as the broad amorphous

T. Jawhari; A. Roid; J. Casado

1995-01-01

81

Spectroscopic characterization of Fe2+-doped II-VI ternary and quaternary mid-IR laser active powders  

NASA Astrophysics Data System (ADS)

We report on spectroscopic characterization of laser active powders based on iron doped II-VI ternary and quaternary semiconductors for mid-IR laser applications. Iron doped Cd1-x MnxTe, Cd1-x MnxS, Cd1-xMnxSe, Cd0.5Mn0.5S0.5Se0.5 , Cd1-xZnxTe compounds with x=0.5-0.25, were prepared by using thermo diffusion technique. The starting binary powders were mixed in the appropriate molar ratios, sealed in evacuated (10-3 Torr) quartz ampoules, and annealed at 800-1000oC for several days. Samples composition, integrity, and grain size were characterized by micro-Raman and Xray diffraction and revealed a variation of the crystal field parameters depending on powder composition. Fe2+ photoluminescence was characterized by spectral band position (normalized with respect to the detection platform spectral sensitivity) and lifetime at different temperatures, enabling calculation of the absorption and emission crosssections. Practical utility of the developed powders was demonstrated by a room temperature random lasing of iron doped Cd0.5Zn0.5Te powders over 5620-6020 nm spectral range pumped by a 2.94 ?m radiation of a Q-switched Er:YAG laser. In summary, the following has been accomplished: (1) It was demonstrated that laser active Fe2+ doped ternary and quaternary II-VI materials can be produced by simple annealing of the commercially available binary powders omitting expensive and complicated crystal growth processes; (2) It is possible to effectively shift PL of Fe2+ in II-VI host materials towards shorter or longer wavelength by varying composition, type and amount of the second cation in ternary II-VI materials; (3) Major spectroscopic characteristics of Fe2+ doped II-VI ternary and quaternary compounds were obtained and their practical utility for mid-IR lasing demonstrated.

Martinez, A.; Martyshkin, D. V.; Fedorov, V. V.; Mirov, S. B.

2014-02-01

82

Synthesis, Spectroscopic and Thermal Characterization of New Sulfasalazine Metal Complexes  

Microsoft Academic Search

The complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) with sulfasalazine (H3L) were studied in the solution and in the solid states. The stability constants of the metal complexes were calculated pH-metrically. The solid products were isolated and characterized by elemental, i.r, molar conductance, magnetic moment, diffused reflectance and thermal analyses. The mono- and biscomplexes were isolated with the

Ahmed A. Soliman; Gehad G. Mohamed; Wafaa M. Hosny; Mohamed A. El-Mawgood

2005-01-01

83

Spectroscopic Characterization of Mineralogy Across Vesta: Evidence of Different Lithologies  

NASA Technical Reports Server (NTRS)

The average spectrum of Vesta, obtained by VIR in the range 0.25-5.1 microns, shows clear evidence of absorption bands due to pyroxenes and thermal emissions beyond 3.5 11m. Vesta shows considerable variability across its surface in terms of spectral reflectance and emission, band depths, bands widths and bands centers, reflecting a complex geological history. Vesta's average spectrum and inferred mineralogy resemble those of howardite meteorites. On a regional scale, significant deviations are seen: the south polar 500km Rheasilvia impact crater has a higher diogenitic component, and equatorial regions show a higher eucritic component. This lithologic distribution, with a concentration of Mg-pyroxenes in the Rheasilvia area, reinforces the hypothesis of a deeper diogenitic crust excavated by the impact that formed the Rheasilvia crater, and an upper eucritic crust, whose remnants are seen in the equatorial region. This scenario has implications for Vesta differentiation, consistent with magma ocean models. However, serial magmatism models could also have concentrated pyroxene cumulates in plutons emplaced within the lower crust,

De Sanotis, M. C.; Ammannito, E.; Filacchione, G.; Capria, M. T.; Tosi, F.; Capaccioni, F.; Zambon, F.; Carraro, F.; Fonte, S.; Frigeri, A.; Jaumann, R.; Magni, G.; Marchi, S.; McCord, T. B.; McFadden, L. A.; McSween, H. Y.; Mittlefehldt, D. W.; Nathues, A.; Palomba, E.; Pieters, C. M.; Raymond, C. A.; Russell, C. T.; Turrini, D.

2012-01-01

84

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of some fluoroquinolone antibacterials using ammonium reineckate  

NASA Astrophysics Data System (ADS)

Three accurate, rapid and simple atomic absorption spectrometric (AAS), conductometric and colorimetric methods were developed for the determination of gatifloxacin (GTF), moxifloxacin (MXF) and sparfloxacin (SPF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at ?max 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone. The optimizations of various experimental conditions were described. Optimum concentration ranges for the determination of GTF, MXF and SPF were 5.0-150, 40-440 ?g mL -1 and 0.10-1.5 mg mL -1 using atomic absorption (AAS), conductometric and colorimetric methods, respectively. Detection and quantification limits are ranges from 1.5 to 2.3 ?g mL -1 using AAS method or 30-45 ?g mL -1 using colorimetric method. The proposed procedures have been applied successfully to the analysis of these drugs in pharmaceutical formulations and the results are favourably comparable to the reference methods.

Al-Ghannam, Sheikha M.

2008-04-01

85

Resonance Raman spectroscopic characterization of compound III of lignin peroxidase  

SciTech Connect

Resonance Raman (RR) spectra of several compounds III of lignin peroxidase (LiP) have been measured at 90 K with Soret and visible excitation wavelengths. The samples include LiPIIIa (or oxyLiP) prepared by oxygenation of the ferrous enzyme, LiPIIIb generated by reaction of the native ferric enzyme with superoxide, LiPIIIc prepared from native LiP plus H{sub 2}O{sub 2} followed by removal of excess peroxide with catalase, and LiPIII made by addition of excess H{sub 2}O{sub 2} to the native enzyme. The RR spectra of these four products appear to be similar and, thus, indicate that the environments of these hexacoordinate, low-spin ferriheme species must also be very similar. Nonetheless, the Soret absorption band of LiPIII is red-shifted by 5 nm from the 414-nm maximum common to LiPIIIa, -b, and -c. Analysis of the iron-porphyrin vibrational frequencies indicates that the electronic structures for the various compounds III are consistent with an Fe{sup III}O{sub 2}{sup {center dot}-}formulation. The spectral changes observed between the oxygenated complex and the ferrous heme of lignin peroxidase are similar to those between oxymyoglobin and deoxymyoglobin. The contraction in the core sizes in compound III relative to the native peroxidase is analyzed and compared with that of other heme systems. The Fe-O{sub 2} stretching vibration of the oxygenated peroxidase is observed at 563 cm{sup {minus}1} and shifts of 538 cm{sup {minus}1} with {sup 18}O isotope. The Fe-histidine stretching vibration is observed at 245 cm{sup {minus}1} in ferrous peroxidase and appears to shift to 276 cm{sup {minus}1} in the oxygenated complex.

Mylrajan, M.; Valli, K.; Wariishi, Gold, M.H.; Loehr, T.M. (Oregon Graduate Institute of Science and Technology, Beaverton (USA))

1990-10-01

86

Mössbauer spectroscopic characterization of macromolecule-metallochlorophyll complexes  

NASA Astrophysics Data System (ADS)

The bis-adducts of iron chlorophylls with poly(4-vinylpyridine-costyrene) (PVP) have been prepared and characterized by 57Fe Mössbauer spectroscopy. The Mössbauer parameters of the PVP-adducts of iron chlorophylls are typical of low-spin iron(II) complexes. The central iron(III) ion is spontaneously reduced upon the axial coordination of PVP to iron(III) chlorophylls. The general tendency in the spontaneous reduction of the iron(III) chlorophylls has been interpreted in terms of the ?-donor and ?-acceptor power of the axial macromolecular ligand.

Inoue, H.; Fukuda, K.; Nonomura, Y.; Fluck, E.

1993-04-01

87

Electromagnetic characterization of planar metamaterials by oblique angle spectroscopic measurements  

NASA Astrophysics Data System (ADS)

Artificially structured metamaterials with unit-cell dimensions on the order of 1/10th of a wavelength (?/10) have been shown to be well approximated by an effective medium description which mimics a continuous material. In this paper we present data for transmission and reflection from a planar array of split-ring resonators (SRRs) at varying angles of incidence. We attempt to model the form of the angle—dependent response of the SRRs using the Fresnel equations formulated from effective medium theory—treating the array as a thin continuous anisotropic crystal. This model is then fit to experimental data taken on a planar array of split rings to gauge the model accuracy, and to produce values for the frequency-dependent permeability and permittivity of the experimental SRR array. Simultaneous fitting of the transmission and reflection at multiple angles helps to avoid multiple solutions for the permittivity and permeability. This forward fitting approach using multiple angles is advantageous, as it enables a characterization of the optical constants without the need for phase information, and it avoids many of the branch problems inherent in the numerical inversion methods used so far on metamaterials. The work presented here shows the feasibility of this method. A refined procedure will be particularly advantageous for experimental characterization of higher frequency structures (i.e., THz and above), where phase information is difficult or impossible to obtain.

Driscoll, T.; Basov, D. N.; Padilla, W. J.; Mock, J. J.; Smith, D. R.

2007-03-01

88

Application of spectroscopic ellipsometry and Mueller ellipsometry to optical characterization.  

PubMed

This article provides a brief overview of both established and novel ellipsometry techniques, as well as their applications. Ellipsometry is an indirect optical technique, in that information about the physical properties of a sample is obtained through modeling analysis. Standard ellipsometry is typically used to characterize optically isotropic bulk and/or layered materials. More advanced techniques such as Mueller ellipsometry, also known as polarimetry in the literature, are necessary for the complete and accurate characterization of anisotropic and/or depolarizing samples that occur in many instances, both in research and in real-life activities. In this article, we cover three main subject areas: Basic theory of polarization, standard ellipsometry, and Mueller ellipsometry. The first section is devoted to a short, pedagogical introduction of the formalisms used to describe light polarization. The second section is devoted to standard ellipsometry. The focus is on the experimental aspects, including both pros and cons of commercially available instruments. The third section is devoted to recent advances in Mueller ellipsometry. Application examples are provided in the second and third sections to illustrate how each technique works. PMID:23317664

Garcia-Caurel, Enric; De Martino, Antonello; Gaston, Jean-Paul; Yan, Li

2013-01-01

89

Raman spectroscopic instrumentation and plasmonic methods for material characterization  

NASA Astrophysics Data System (ADS)

The advent of nanotechnology has led to incredible growth in how we consume, make and approach advanced materials. By exploiting nanoscale material properties, unique control of optical, thermal, mechanical, and electrical characteristics becomes possible. This thesis describes the development of a novel localized surface plasmon resonant (LSPR) color sensitive photosensor, based on functionalization of gold nanoparticles onto tianium dioxide nanowires and sensing by a metal-semiconducting nanowire-metal photodiode structure. This LSPR photosensor has been integrated into a system that incorporates Raman spectroscopy, microfluidics, optical trapping, and sorting flow cytometry into a unique material characterization system called the microfluidic optical fiber trapping Raman sorting flow cytometer (MOFTRSFC). Raman spectroscopy is utilized as a powerful molecular characterization technique used to analyze biological, mineralogical and nanomaterial samples. To combat the inherently weak Raman signal, plasmonic methods have been applied to exploit surface enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR), increasing Raman intensity by up to 5 orders of magnitude. The resultant MOFTRSFC system is a prototype instrument that can effectively trap, analyze, and sort micron-sized dielectric particles and biological cells. Raman spectroscopy has been presented in several modalities, including the development of a portable near-infrared Raman spectrometer and other emerging technologies.

Tanaka, Kazuki

90

Crystal structure characterization as well as theoretical study of spectroscopic properties of novel Schiff bases containing pyrazole group.  

PubMed

A series of novel Schiff bases containing pyrazole group were synthesized using 1-aryl-3-methyl-4-benzoyl-5-pyrazolone and phenylenediamine as the starting materials. All as-synthesized Schiff bases were characterized by means of NMR, FT-IR, and MS; and the molecular geometries of two Schiff bases as typical examples were determined by means of single crystal X-ray diffraction. In the meantime, the ultraviolet-visible light absorption spectra and fluorescent spectra of various as-synthesized products were also measured. Moreover, the B3LYP/6-1G(d,p) method was used for the optimization of the ground state geometry of the Schiff bases; and the spectroscopic properties of the products were computed and compared with corresponding experimental data based on cc-pVTZ basis set of TD-B3LYP method. It has been found that all as-synthesized Schiff bases show a remarkable absorption peak in a wavelength range of 270-370 nm; and their maximum emission peaks are around 344 nm and 332 nm, respectively. PMID:22617219

Guo, Jia; Ren, Tiegang; Zhang, Jinglai; Li, Guihui; Li, Weijie; Yang, Lirong

2012-09-01

91

Spectroscopic characterization of chrysotile asbestos from different regions  

NASA Astrophysics Data System (ADS)

Chrysotile asbestos from different geographic regions was characterized by 57Fe Mössbauer and FT-IR spectroscopies, and FE-SEM coupled with EDS. Mössbauer spectra showed incorporation of Fe(II) and Fe(III) into the crystal structure of chrysotile. The Fe(II)/Fe(III) ratios were calculated. The Fe(II) occupied the octahedral Mg(II) positions. Broadening of Mössbauer lines corresponding to the Fe(III) doublet indicated a possible presence of Fe(III) in tetrahedral and octahedral positions. In all samples magnetite (Fe 3-xO 4) was found as associated mineral. Changes in the FT-IR spectra of chrysotiles were assigned to structural incorporation of metal ions, such as iron or aluminium ions. The morphology of chrysotile asbestos was inspected by FE-SEM.

Risti?, Mira; Czakó-Nagy, Ilona; Musi?, Svetozar; Vértes, Attila

2011-05-01

92

[Structural characterization and spectroscopic analysis of the aloin].  

PubMed

Aloe is widely used in various fields for its rich polysaccharides, proteins, amino acids, vitamins, active enzymes and trace beneficial elements to human body. However, the main active ingredient aloin is also an allergenic ingredient, which even may cause a severe allergic reaction In this study, infrared spectroscopy, Raman spectroscopy applied to the structural characterization of the aloin Density functional theory (DFT) is applied to the theoretical calculations using the B3LYP/6-31G (d) basis set vibration, which was helpful to understand the aloin molecular vibrational frequency. By comparing we choose the optimal experimental condition for water as solvent under alkaline conditions, the detection limit of the Aloin can reach a level of 5 ppm, which can be considered the theoretical basis for rapid detection of aloin content. PMID:24822406

Xie, Yun-Fei; Huan, Nan; Cao, Yuan-Yuan; Wang, He-Ya; Zhong, Ying; Yao, Wei-Rong; Qian, He

2014-02-01

93

GPI detailed spectroscopic and astrometric characterization of HR 8799cde.  

NASA Astrophysics Data System (ADS)

We are proposing deep high signal-to-noise ratio (SNR) Gemini Planet Imager (GPI) Y, J, H and K1/K2 spectroscopy/photometry of the three inner planets of HR 8799. With GPI's superior contrast, and our advanced data reduction and analysis pipeline, these observations will revolutionize our understanding of the system's planets by allowing, for the first time, detailed high-SNR near infrared spectroscopy of planet e, as well as complementary planet c and d spectroscopy at Y-, J-, H- and K-band. The data will also be used to derive highly accurate relative astrometry of the three planets, allowing for more precise orbital characterization and detection of acceleration, a key value to properly constrain the systemâ??s orbital configuration.

Marois, Christian; Draper, Zack; Barman, Travis; Konopacky, Quinn; Patience, Jennifer; Ingraham, Patrick; Macintosh, Bruce; Lafreniere, David; Matthews, Brenda

2014-08-01

94

Silicon Heterojunction Solar Cell Characterization and Optimization using in Situ and Ex Situ Spectroscopic Ellipsometry  

Microsoft Academic Search

We use in-situ and ex-situ spectroscopic ellipsometry to characterize the optical, electronic, and structural properties of individual layers and completed silicon heterojunction devices. The combination of in-situ measurements during thin film deposition with ex-situ measurements of completed devices allows us to understand both the growth dynamics of the materials and the effects of each processing step on material properties. In-situ

Dean Levi; Eugene Iwaniczko; Matthew Page; Qi Wang; Howard Branz; Tihu Wang

2006-01-01

95

Spectroscopic and microscopic characterization of biosensor surfaces with protein\\/amino-organosilane\\/silicon structure  

Microsoft Academic Search

Composition and structure of biorecognition protein layers created on silicon substrates modified with amino-organosilanes determine the sensitivity and specificity of silicon based biosensing devices. In the present work, diverse spectroscopic and microscopic methods were applied to characterize model biosensor surfaces, formed on Si3N4 or SiO2 by modification with (3-aminopropyl)triethoxysilane, coating with rabbit gamma-globulins (IgGs) through physical adsorption, blocking with bovine

K. Awsiuk; A. Bernasik; M. Kitsara; A. Budkowski; P. Petrou; S. Kakabakos; S. Prauzner-Bechcicki; J. Rysz; I. Raptis

96

EUV interferometric lithography and structural characterization of an EUV diffraction grating with nondestructive spectroscopic ellipsometry  

Microsoft Academic Search

In this study, we constructed an exposure platform to perform extreme ultraviolet interferometric lithography (EUVIL) exposure. This platform can be used to expose 1D and 2D gratings, simulating the line\\/space and contact\\/hole patterns, respectively. A transmission grating and an achromatic setup were utilized in the exposure. A simple and nondestructive optical characterization approach based on spectroscopic ellipsometry was proposed to

Chun-Hung Lin; Chi-Hao Fong; Yi-Ming Lin; Yin-Yu Lee; Hok-Sum Fung; Bor-Yuan Shew; Jiann Shieh

2011-01-01

97

Synthesis and spectroscopic characterization of copper zinc aluminum nanoferrite particles.  

PubMed

Copper doped zinc aluminum ferrites CuxZn1-x.(AlxFe2-x)O4 are synthesized by the solid-state reaction route and characterized by XRD, TEM, EPR and non linear optical spectroscopy techniques. The average particle size is found to be from 35 to 90nm and the unit cell parameter "a" is calculated as from 8.39 to 8.89Å. The cation distributions are estimated from X-ray diffraction intensities of various planes. The XRD studies have verified the quality of the synthesis of compounds and have shown the differences in the positions of the diffraction peaks due to the change in concentration of copper ions. TEM pictures clearly indicating that fundamental unit is composed of octahedral and tetrahedral blocks and joined strongly. The selected area electron diffraction (SAED) of the ferrite system shows best crystallinity is obtained when Cu content is very. Some of the d-plane spacings are exactly coinciding with XRD values. EPR spectra is compositional dependent at lower Al/Cu concentration EPR spectra is due to Fe(3+) and at a higher content of Al/Cu the EPR spectra is due to Cu(2+). Absence of EPR spectra at room temperature indicates that the sample is perfectly ferromagnetic. EPR results at low temperature indicate that the sample is paramagnetic, and that copper is placed in the tetragonal elongation (B) site with magnetically non-equivalent ions in the unit cell having strong exchange coupling between them. This property is useful in industrial applications. Nonlinear optical properties of the samples studied using 5ns laser pulses at 532nm employing the open aperture z-scan technique indicate that these ferrites are potential candidates for optical limiting applications. PMID:24632431

Lakshmi Reddy, S; Ravindra Reddy, T; Roy, Nivya; Philip, Reji; Montero, Ovidio Almanza; Endo, Tamio; Frost, Ray L

2014-06-01

98

Synthesis and spectroscopic characterization of copper zinc aluminum nanoferrite particles  

NASA Astrophysics Data System (ADS)

Copper doped zinc aluminum ferrites CuxZn1-x.(AlxFe2-x)O4 are synthesized by the solid-state reaction route and characterized by XRD, TEM, EPR and non linear optical spectroscopy techniques. The average particle size is found to be from 35 to 90 nm and the unit cell parameter “a” is calculated as from 8.39 to 8.89 Å. The cation distributions are estimated from X-ray diffraction intensities of various planes. The XRD studies have verified the quality of the synthesis of compounds and have shown the differences in the positions of the diffraction peaks due to the change in concentration of copper ions. TEM pictures clearly indicating that fundamental unit is composed of octahedral and tetrahedral blocks and joined strongly. The selected area electron diffraction (SAED) of the ferrite system shows best crystallinity is obtained when Cu content is very. Some of the d-plane spacings are exactly coinciding with XRD values. EPR spectra is compositional dependent at lower Al/Cu concentration EPR spectra is due to Fe3+ and at a higher content of Al/Cu the EPR spectra is due to Cu2+. Absence of EPR spectra at room temperature indicates that the sample is perfectly ferromagnetic. EPR results at low temperature indicate that the sample is paramagnetic, and that copper is placed in the tetragonal elongation (B) site with magnetically non-equivalent ions in the unit cell having strong exchange coupling between them. This property is useful in industrial applications. Nonlinear optical properties of the samples studied using 5 ns laser pulses at 532 nm employing the open aperture z-scan technique indicate that these ferrites are potential candidates for optical limiting applications.

Lakshmi Reddy, S.; Ravindra Reddy, T.; Roy, Nivya; Philip, Reji; Montero, Ovidio Almanza; Endo, Tamio; Frost, Ray L.

2014-06-01

99

Flash spectroscopic characterization of photosynthetic electron transport in isolated heterocysts  

SciTech Connect

Electron transport was studied in heterocysts of the filamentous cyanobacterium Anabaena 7120 using spectral and kinetic analysis of absorbance transients elicited by single turnover flashes. Consistent photosynthetic turnovers were observed only in the presence of an exogenous source of reductant; therefore measurements were routinely made under a gas phase containing H2. Prominent absorbance changes corresponding to the oxidation of cytochrome c (554 nm) and the reduction of cytochrome b563 (563 nm) were observed. Under the most reducing conditions (99% H2/1% O2) cytochrome b563 was partially reduced between flashes in a slow, dark reaction. At 10-15% O2, the slow, dark reduction of cytochrome b563 was eliminated. Cytochrome turnover ceased entirely at high O2 concentrations (30%) but was restored by the addition of 25 microM KCN, demonstrating an interaction between the photosynthetic and respiratory electron transfer chains. Strobilurin A slowed the re-reduction of cytochrome c and eliminated the appearance of reduced cytochrome b563 by blocking electron transfer between reduced plastoquinone and the cytochrome b/f complex. Inhibition at a second site was apparent with 2-(n-heptyl)-4-hydroxyquinoline N-oxide, which blocked the reoxidation of cytochrome b563 but had little effect on cytochrome c relaxation. In uncoupled heterocysts, the rates of cytochrome c re-reduction and cytochrome b563 reduction were equal. Additional unassigned absorbance changes at 475 nm, 515 nm, and 572 nm were partially characterized. No absorbance change corresponding to an electrochromic shift was observed.

Houchins, J.P.; Hind, G.

1983-07-01

100

Atomic absorption spectroscopic analysis of some Pakistani herbal medicinal products used in respiratory tract infections.  

PubMed

Heavy metals are one of the major causes of widespread occurrence of respiratory tract infections (RTIs). Unani system of medicines utilizing plant extracts and herbal medicinal products (HMPs) are known to have remedial potential in different RTIs (flue, cough, bronchitis, allergy, asthma, nasal and chest congestion). Being natural in origin chances of metal contamination cannot be ignored in Phytopharmaceuticals, therefore toxic metal contents (Pb, Cd, As, and Hg) were determined in some Pakistani branded HMPs being used in various RTIs through atomic absorption spectrophotometer. Research findings showed detectable levels of metals in all these formulations. Daily metals intakes via these HMPs were calculated as: 0.86-277.44 (Pb), 1.442-10.986 (Cd), 0.16-5.83 (As), and 0.00-0.09 ?g/ day (Hg). Prevalence of toxic metals in HMPs especially elevated levels of Pb and Cd, pose severe health risks to the consumers. Statistical interpretation of data using ANOVA followed by LSD (p<0.05), revealed significantly different metal concentrations among HMPs. To identify the metal contaminant of HMPs and highlight their toxic manifestations is the basic aim of this research. The study is not a bias to the beneficial effects of the Phytopharmaceuticals, rather is done to improve their quality and safety parameter according to the international health standards. PMID:22186337

Hina, Bushra; Rizwani, Ghazala Hafeez; Shareef, Huma; Ahmed, Maryam

2012-01-01

101

Biotransformations of anticancer ruthenium(III) complexes: an X-ray absorption spectroscopic study.  

PubMed

An anti-metastatic drug, NAMI-A ((ImH)[Ru(III) Cl4 (Im)(dmso)]; Im=imidazole, dmso=S-bound dimethylsulfoxide), and a cytotoxic drug, KP1019 ((IndH)[Ru(III) Cl4 (Ind)2 ]; Ind=indazole), are two Ru-based anticancer drugs in human clinical trials. Their reactivities under biologically relevant conditions, including aqueous buffers, protein solutions or gels (e.g, albumin, transferrin and collagen), undiluted blood serum, cell-culture medium and human liver (HepG2) cancer cells, were studied by Ru K-edge X-ray absorption spectroscopy (XAS). These XAS data were fitted from linear combinations of spectra of well-characterised Ru compounds. The absence of XAS data from the parent drugs in these fits points to profound changes in the coordination environments of Ru(III) . The fits point to the presence of Ru(IV/III) clusters and binding of Ru(III) to S-donor groups, amine/imine and carboxylato groups of proteins. Cellular uptake of KP1019 is approximately 20-fold higher than that of NAMI-A under the same conditions, but it diminishes drastically after the decomposition of KP1019 in cell-culture media, which indicate that the parent complex is taken in by cells through passive diffusion. PMID:23361836

Levina, Aviva; Aitken, Jade B; Gwee, Yee Yen; Lim, Zhi Jun; Liu, Mimi; Singharay, Anannya Mitra; Wong, Pok Fai; Lay, Peter A

2013-03-11

102

X-ray Absorption Spectroscopic Studies of High-Spin Nonheme (Alkylperoxo)iron(III) Intermediates  

SciTech Connect

The reactions of iron(II) complexes [Fe(Tpt-Bu,i-Pr)(OH)] (1a, Tpt-Bu,i-Pr = hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate), [Fe(6-Me2BPMCN)(OTf)2] (1b, 6-Me2BPMCN = N,N'-bis((2-methylpyridin-6-yl)methyl)-N,N'-dimethyl-trans-1,2-diaminocyclohexane), and [Fe(L8Py2)(OTf)](OTf) (1c, L8Py2 = 1,5-bis(pyridin-2-ylmethyl)-1,5-diazacyclooctane) with tert-BuOOH give rise to high-spin FeIII-OOR complexes. X-ray absorption spectra (XAS) of these high-spin species show characteristic features, distinct from those of low-spin Fe-OOR complexes. These include (1) an intense 1s {yields} 3d preedge feature, with an area around 20 units, (2) an edge energy, ranging from 7122 to 7126 eV, that is affected by the coordination environment, and (3) a 1.86-1.96 Angstroms Fe-OOR bond, compared to the 1.78 Angstroms Fe-OOR bond in low-spin complexes. These unique features likely arise from a flexible first coordination sphere in those complexes. The difference in Fe-OOR bond length may rationalize differences in reactivity between low-spin and high-spin FeIII-OOR species.

Shan,X.; Rohde, J.; Koehntop, K.; Zhou, Y.; Bukowski, M.; Costas, M.; Fujisawa, K.; Que, Jr., L.

2007-01-01

103

Separation of Normal and Premalignant Cervical Epithelial Cells Using Confocal Light Absorption and Scattering Spectroscopic Microscopy Ex Vivo  

PubMed Central

Confocal light absorption and scattering spectroscopic (CLASS) microscopy can detect changes in biochemicals and the morphology of cells. It is therefore used to detect high-grade cervical squamous intraepithelial lesion (HSIL) cells in the diagnosis of premalignant cervical lesions. Forty cervical samples from women with abnormal Pap smear test results were collected, and twenty cases were diagnosed as HSIL; the rest were normal or low-grade cervical squamous intraepithelial lesion (LSIL). The enlarged and condensed nuclei of HSIL cells as viewed under CLASS microscopy were much brighter and bigger than those of non-HSIL cells. Cytological elastic scattered light data was then collected at wavelengths between 400 and 1000?nm. Between 600?nm to 800?nm, the relative elastic scattered light intensity of HSIL cells was higher than that of the non-HSIL. Relative intensity peaks occurred at 700?nm and 800?nm. CLASS sensitivity and specificity results for HSIL and non-HSIL compared to cytology diagnoses were 80% and 90%, respectively. This study demonstrated that CLASS microscopy could effectively detect cervical precancerous lesions. Further study will verify this conclusion before the method is used in clinic for early detection of cervical cancer.

Yang, Ling; Liu, Wen-Tao; Wu, Hao; Wang, Cheng; Ping, Bo; Shi, Da-Ren

2011-01-01

104

Spectroscopic and Functional Characterization of Iron-Bound Forms of Azotobacter vinelandiiNifIscA†  

PubMed Central

The ability of Azotobacter vinelandii NifIscA to bind Fe has been investigated to assess the role of Fe-bound forms in NIF-specific Fe-S cluster biogenesis. NifIscA is shown to bind one Fe(III) or one Fe(II) per homodimer and the spectroscopic and redox properties of both the Fe(III)- and Fe(II)-bound forms have been characterized using the UV-visible absorption, CD and VTMCD, EPR, Mössbauer and resonance Raman spectroscopies. The results reveal a rhombic intermediate-spin (S = 3/2) Fe(III) center (E/D = 0.33, D = 3.5 ± 1.5cm?1) that is most likely 5-coordinate with two or three cysteinate ligands and a rhombic high spin (S = 2) Fe(II) center (E/D = 0.28, D = 7.6 cm?1) with properties similar to reduced rubredoxins or rubredoxin variants with three cysteinate and one or two oxygenic ligands. Iron-bound NifIscA undergoes reversible redox cycling between the Fe(III)/Fe(II) forms with a midpoint potential of +36 ±15 mV at pH 7.8 (versus NHE). L-cysteine is effective in mediating release of free Fe(II) from both the Fe(II)- and Fe(III)-bound forms of NifIscA. Fe(III)-bound NifIscA was also shown to a competent iron source for in vitro NifS-mediated [2Fe-2S] cluster assembly on the N-terminal domain of NifU, but the reaction occurs via cysteine-mediated release of free Fe(II) rather than direct iron transfer. The proposed roles of A-type proteins in storing Fe under aerobic growth conditions and serving as iron donors for cluster assembly on U-type scaffold proteins or maturation of biological [4Fe-4S] centers are discussed in light of these results.

Mapolelo, Daphne T.; Zhang, Bo; Naik, Sunil G.; Huynh, Boi Hanh; Johnson, Michael K.

2012-01-01

105

Absorption  

NSDL National Science Digital Library

The process of absorption is a cellular process (microscopic). Absorption cells line the stomach and intestine walls and allow small nutrients (broken down from the food we eat) to pass through and into our blood. The process of absorption is much like a leaking balloon filled with water. The balloon is the stomach or intestine, the tiny holes are the absorption cells, and the water is nutrients leaving.

Katie Hale (CSUF;)

2002-09-26

106

X-Ray Absorption Spectroscopic Studies of High-Spin Nonheme (Alkylperoxo)Iron(III) Intermediates  

SciTech Connect

The reactions of iron(II) complexes [Fe(Tp{sup t-Bu,i-Pr})(OH)] (1a, Tp{sup t-Bu,i-Pr} = hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate), [Fe(6-Me{sub 2}BPMCN)(OTf){sub 2}] (1b, 6-Me{sub 2}BPMCN = N,N'-bis((2-methylpyridin-6-yl)methyl)-N,N'-dimethyl-trans-1,2-diaminocyclohexane), and [Fe(L{sup 8}Py{sub 2})(OTf)](OTf) (1c, L{sup 8}Py{sub 2} = 1,5-bis(pyridin-2-ylmethyl)-1,5-diazacyclooctane) with tert-BuOOH give rise to high-spin Fe{sup III}-OOR complexes. X-ray absorption spectra (XAS) of these high-spin species show characteristic features, distinct from those of low-spin Fe-OOR complexes (Rohde, J.-U.; et al. J. Am. Chem. Soc. 2004, 126, 16750--16761). These include (1) an intense 1s {yields} 3d preedge feature, with an area around 20 units, (2) an edge energy, ranging from 7122 to 7126 eV, that is affected by the coordination environment, and (3) a 1.86--1.96 {angstrom} Fe-OOR bond, compared to the 1.78 {angstrom} Fe-OOR bond in low-spin complexes. These unique features likely arise from a flexible first coordination sphere in those complexes. The difference in Fe-OOR bond length may rationalize differences in reactivity between low-spin and high-spin Fe{sup III}-OOR species.

Shan, X.; Rohde, J.-U.; Koehntop, K.D.; Zhou, Y.; Bukowski, M.R.; Costas, M.; Fujisawa, K.; Que, L.; Jr.

2009-06-04

107

Characterization of the spatial resolution in two-photon spectroscopic techniques used for plasma diagnostics  

NASA Astrophysics Data System (ADS)

We report a detailed characterization of the spatial resolution provided by different two-photon absorption spectroscopy techniques used in plasma diagnostics: two-photon absorption laser induced fluorescence (TALIF) and two-photon optogalvanic spectroscopy. Well-understood and characterized spatial resolution has especial importance for a precise control of experimental conditions, and absolute measurements. Beam profiles recorded with high resolution allow calculating the beam propagation and irradiance distribution in the beams overlap, the resulting fluorescence and ionization yield, and the corresponding spatial resolution.

Garcia-Lechuga, M.; Fuentes, L. M.; Gruetzmacher, K.; Perez, C.; de la Rosa, M. I.

2013-11-01

108

Spectroscopic and electrochemical characterization of di- tert-butylated sterically hindered Schiff bases and their phenoxyl radicals  

NASA Astrophysics Data System (ADS)

A series of sterically hindered N-arylsalicylaldimines (SAs) previously prepared from substituted salicylaldehydes (X-Sal, where X = H, Cl, Br, NO 2, OH, OCH 3) and 2,6-di- t-butyl-1-hydroxyaniline (L xH) and 2,5-di- t-butylaniline (L x'H) were characterized by 1H and 13C NMR, UV-Vis and electrochemical methods. The electronic spectra (ES) (X = OH, OCH 3) in alcoholic solvents (MeOH, EtOH, PrOH, iso-PrOH) unlike other solvents exhibit a new absorption band in the region 630-675 nm ( ?=19-242 M -1 cm -1), which are not characteristic for other SA known in literature. The ESR studies of primary phenoxyl radicals generated from L xH by their oxidation with PbO 2 reveal that some of them with the time are converted to more stable secondary Coppinger's radical. The cyclic voltammograms of L xH and L x'H except NO 2-substituted ones in CH 3CN are similar and along with two or three irreversible anodic waves at the potentials ranging from 0.0 to +1.9 V versus Ag/AgCl, also display one or two irreversible reduction waves at potentials -0.6 to +0.5 V. A series of a new SA prepared from 3,5-di- t-butylsalicylaldehyde and mono-substituted anilines (X = H, o-, p-F, Cl, Br, OCH 3, p- t-butyl, 5,6-benzo) were characterized by analytical, spectroscopic (IR, UV-Vis, 1H and 13C NMR), and electrochemical techniques. The ES spectra of o-, p-Cl, p-Br, o-CH 3 and 5,6-benzo-substituted SA did not exhibit expected absorptions at 400-500 nm in alcoholic solutions.

Kasumov, V. T.; Medjidov, A. A.; Yayli, N.; Zeren, Y.

2004-11-01

109

Spectroscopic studies of dipyridamole derivatives in homogeneous solutions: Effects of solution composition on the electronic absorption and emission  

NASA Astrophysics Data System (ADS)

Electronic absorption and fluorescence spectra of three different dipyridamole (DIP) derivatives, RA 39, RA 14 and RA 25, were monitored in aqueous solution as a function of pH in the range 2-13. Extinction coefficients, quantum yields and fluorescence lifetimes were obtained in aqueous solutions at different pHs and in several other solvents. The absorption spectra are characterized by two broad bands centered at 405-415 nm and 290 nm for RA 39 and RA 14 and at 370 and 270 nm for RA 25. The first band used for fluorescence excitation has a value of ? ? 5 × 10 3 M -1 cm -1 characteristic of a ? ? ?* transition. An increase in pH is accompanied by both fluorescence and absorption sharp changes around pH 6 giving a p K ? 5.8 for RA 39 and RA 14, similar to the one observed for DIP. In the case of RA 25 two p Ks are observed below 6.5, namely a p K1 ? 2.25 and p K2 = 5.20. These changes are associated to protonation equilibria of nitrogens in the ?-conjugated system of the pyrimido—pyrimidine ring. At high pH a second transition is observed only in fluorescence with p K ? 12.5 for RA 39 which is similar to DIP and p K ? 12.1 for RA 25. For RA 14 this transition was not observed. Estimates of the p K* for the first singlet excited state showed that in comparison to the ground state p K ? 5.8 or 5.2 (RA 25), the excited state p K* is more acid by almost a unit. In the case of RA 25 and the lowest p K of 2.25, an excited state reaction, possibly of proton transfer, seems to take place since emission and absorption data give opposite effects for p K*.

Borges, Christiane Philippini Ferreira; Tabak, Marcel

1994-06-01

110

Characterization of ethiofos absorption in the rat small intestine.  

PubMed

The absorption characteristics of ethiofos were studied using the rat in situ intestine circulating perfusion technique. Slow absorption kinetics were observed for ethiofos with varying rates of absorption and metabolism/degradation in situ as a function of buffer and absorption enhancers. In most cases less than 10 per cent of the radiolabeled compound is lost from the circulating perfusate in 90 min. In addition, over the same time period greater than 40 per cent of the intact parent compound was lost by degradation. Much of the difference can be accounted for in the formation of the free thiol metabolite. WR-1065, suggesting ester hydrolysis or metabolic activity. Good stability was observed in all perfusate systems ex vivo indicating that the degradation occurs in situ. The disodium salt of ethylenediaminetetraacetic acid (EDTA) was shown to be an effective absorption enhancer of ethiofos. The enhancement of intestinal absorption by EDTA was dose-dependent resulting in a 20-fold increase in blood levels of ethiofos in the portal blood. Follow-up studies in the rhesus monkey confirm this observation. Salicylate and dimethylsulfoxide (DMSO) also resulted in absorption enhancement although to a lesser degree than that seen after EDTA treatment. Addition of several alkaline phosphatase inhibitors did not significantly improve absorption of ethiofos in the rat small intestine. Proposed mechanism(s) for intestinal absorption and absorption enhancement of ethiofos are discussed. PMID:1651790

Geary, R S; Swynnerton, N F; Timmons, S F; Mangold, D J

1991-05-01

111

Fe-complex of a tetraamido macrocyclic ligand: Spectroscopic characterization and catalytic oxidation studies  

NASA Astrophysics Data System (ADS)

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 ( ?eff = 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.

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

112

Strategies for the spectroscopic characterization of irradiated proteins and other biomolecules  

NASA Astrophysics Data System (ADS)

The molecular properties of proteins and other biomolecules have been investigated in aqueous solution, after preceding X- or UV-irradiation. Spectroscopic techniques (UV-Vis absorption, fluorescence, circular dichroism), size-exclusion chromatography, and other physicochemical techniques were applied to differentiate between various radiation effects. Numerous functional and structural changes of the irradiated samples could be monitored; the effects continued in the post-irradiation period. Modifications of radiation effects were achieved by various approaches. In particular, a variety of additives reduce the detrimental effects of radiation considerably. Typical hydroxyl radical scavengers act as potent protectives against X-irradiation, while compounds absorbing in the UV range protect biomolecules against UV light exposure. Thiols and ascorbate may provide a chemical repair of already damaged particles, restoring some of the original molecular features.

Durchschlag, H.

2001-05-01

113

Surfactant assisted synthesis and spectroscopic characterization of selenium nanoparticles in ambient conditions  

NASA Astrophysics Data System (ADS)

In this work, an attempt has been made to synthesize well-distributed stable selenium (Se) particles of nanosize dimensions via an aqueous micellar solution by the assistance of surfactants of two different polarities (anionic, sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and cationic, hexadecyltrimethylammonium bromide (CTAB)). The morphology of the particles was examined with transmission electron microscopy (TEM). X-ray analysis reveals that the particles have a monoclinic structure. The band gap of the particles was determined from UV-visible optical spectroscopic results. The size variation was estimated by employing a quantum confinement effect equation. The evolution of the selenium nanoparticles in AOT and CTAB micellar media was corroborated with the time-dependent absorption spectra. The influence of hydrazine hydrate concentrations on the formation kinetics of Se nanoparticles was also investigated. The capping ability of the surfactants has been quantitatively evaluated from Fourier transform infrared (FTIR) studies.

Mehta, S. K.; Chaudhary, Savita; Kumar, Sanjay; Bhasin, K. K.; Torigoe, Kanjiro; Sakai, Hideki; Abe, Masahiko

2008-07-01

114

Spectroscopic characterization of both aqueous and solid-state diacerhein/hydroxypropyl-?-cyclodextrin inclusion complexes  

NASA Astrophysics Data System (ADS)

Diacerhein, a poorly water soluble antirheumatic prodrug, was spectroscopically characterized to form inclusion complexes with hydroxypropyl-?-cyclodextrin (HP?CD) in both aqueous solution and in solid phase. Complexation with the hydrophilic carriers was used to improve the solubility and dissolution rate of the compound. The kinetics of the prodrug degradation to the active rhein in aqueous buffer solution were also investigated as a function of HP?CD concentration. The solid complexes prepared by different methods such as physical mixture, kneading, co-evaporation method and freeze dried method in 1:1 M ratio, were characterized by DSC and FTIR. The dissolution profiles of solid complexes were determined and compared with diacerhein alone and their physical mixture, in the simulated intestinal fluid at 37 °C. The accurate molecular spectroscopic characterization of diacerhein in the presence of different amounts of aqueous cyclodextrins was essential to determine the correct binding constants for the diacerhein/HP?CD system. The binding constants were also validated by UV spectrometry and HPLC procedure in order to compare the values from the different methods. Higuchi-Connors phase solubility method has proved not suitable when either the free or/and the complexed prodrug degrade in aqueous solution.

Petralito, Stefania; Zanardi, Iacopo; Spera, Romina; Memoli, Adriana; Travagli, Valter

2014-06-01

115

Spectroscopic characterization of both aqueous and solid-state diacerhein/hydroxypropyl-?-cyclodextrin inclusion complexes.  

PubMed

Diacerhein, a poorly water soluble antirheumatic prodrug, was spectroscopically characterized to form inclusion complexes with hydroxypropyl-?-cyclodextrin (HP?CD) in both aqueous solution and in solid phase. Complexation with the hydrophilic carriers was used to improve the solubility and dissolution rate of the compound. The kinetics of the prodrug degradation to the active rhein in aqueous buffer solution were also investigated as a function of HP?CD concentration. The solid complexes prepared by different methods such as physical mixture, kneading, co-evaporation method and freeze dried method in 1:1M ratio, were characterized by DSC and FTIR. The dissolution profiles of solid complexes were determined and compared with diacerhein alone and their physical mixture, in the simulated intestinal fluid at 37°C. The accurate molecular spectroscopic characterization of diacerhein in the presence of different amounts of aqueous cyclodextrins was essential to determine the correct binding constants for the diacerhein/HP?CD system. The binding constants were also validated by UV spectrometry and HPLC procedure in order to compare the values from the different methods. Higuchi-Connors phase solubility method has proved not suitable when either the free or/and the complexed prodrug degrade in aqueous solution. PMID:24632430

Petralito, Stefania; Zanardi, Iacopo; Spera, Romina; Memoli, Adriana; Travagli, Valter

2014-06-01

116

Spectroscopic characterization of biological agents using FTIR, normal Raman and surface-enhanced Raman spectroscopies  

NASA Astrophysics Data System (ADS)

FTIR, Raman spectroscopy and Surface Enhanced Raman Scattering (SERS) requires a minimum of sample allows fast identification of microorganisms. The use of this technique for characterizing the spectroscopic signatures of these agents and their stimulants has recently gained considerable attention due to the fact that these techniques can be easily adapted for standoff detection from considerable distances. The techniques also show high sensitivity and selectivity and offer near real time detection duty cycles. This research focuses in laying the grounds for the spectroscopic differentiation of Staphylococcus spp., Pseudomonas spp., Bacillus spp., Salmonella spp., Enterobacter aerogenes, Proteus mirabilis, Klebsiella pneumoniae, and E. coli, together with identification of their subspecies. In order to achieve the proponed objective, protocols to handle, cultivate and analyze the strains have been developed. Spectroscopic similarities and marked differences have been found for Spontaneous or Normal Raman spectra and for SERS using silver nanoparticles have been found. The use of principal component analysis (PCA), discriminate factor analysis (DFA) and a cluster analysis were used to evaluate the efficacy of identifying potential threat bacterial from their spectra collected on single bacteria. The DFA from the bacteria Raman spectra show a little discrimination between the diverse bacterial species however the results obtained from the SERS demonstrate to be high discrimination technique. The spectroscopic study will be extended to examine the spores produced by selected strains since these are more prone to be used as Biological Warfare Agents due to their increased mobility and possibility of airborne transport. Micro infrared spectroscopy as well as fiber coupled FTIR will also be used as possible sensors of target compounds.

Luna-Pineda, Tatiana; Soto-Feliciano, Kristina; De La Cruz-Montoya, Edwin; Pacheco Londoño, Leonardo C.; Ríos-Velázquez, Carlos; Hernández-Rivera, Samuel P.

2007-05-01

117

Processing of High Level Waste: Spectroscopic Characterization of Redox Reactions in Supercritical Water - Final Report  

SciTech Connect

Current efforts are focused on the oxidative dissolution of chromium compounds found in Hanford tank waste sludge. Samples of chromium oxides and hydroxides with varying degrees of hydration are being characterized using Raman, FTIR, and XPS spectroscopic techniques. Kinetics of oxidation reactions at subcritical and supercritical temperatures are being followed by Raman spectroscopy using a high temperature stainless steel cell with diamond windows. In these reactions both hydrogen peroxide and nitrate anions are used as the oxidizing species with Cr(III) compounds and organic compounds as reducing agents.

Arrington Jr., C. A.

2000-11-15

118

Spectroscopic characterization of bendazac and benzydamine: possible photochemical modes of action.  

PubMed

The involvement of near-UV light in cataract development suggests that potential anti-cataract drugs may display unusual spectroscopic properties. As bendazac impedes certain effects associated with lens opacification, we have characterized the singlet and triplet states of bendazac and its analog, benzydamine, by fluorescence and phosphorescence methods. These compounds have much shorter triplet state lifetimes compared to the triplet state lifetimes observed in proteins. Our results raise the possibility that the photoprotective action of these compounds may result from their ability to dissipate energy through the triplet state. We propose alternative modes for the photoprotective actions of these compounds. PMID:8619844

Jez, J M; Vanderkooi, J M; Laties, A M

1996-04-16

119

Synthesis and Surface-Spectroscopic Characterization of Photoisomerizable glyco-SAMs on Au(111).  

PubMed

Photoisomerizable glyco-SAMs (self-assembled monolayers), utilizing synthetic azobenzene glycoside derivatives were fabricated. The ultimate goal of this project is to assay the influence of the 3D arrangement of sugar ligands on cell adhesion, and eventually make cell adhesion photoswitchable. However, it is a prerequisite for any biological study on the spatial conditions of carbohydrate recognition, that photoisomerization of the surface molecules can be verified. Here, we employed IRRAS and XPS to spectroscopically characterize glyco-SAMs. In particular and unprecedented to date, we prove reversible E?Z?E isomerization of azobenzene glycoside-terminated SAMs. PMID:24954531

Chandrasekaran, Vijayanand; Jacob, Hanne; Petersen, Finn; Kathirvel, Ketheeswari; Tuczek, Felix; Lindhorst, Thisbe K

2014-07-01

120

Synthesis and spectroscopic characterization of Yb3+ in Ca1-XYbXF2+X crystals  

NASA Astrophysics Data System (ADS)

Ca1-XYbXF2+X crystals were grown by two different methods: simple melting under CF{4} atmosphere and laser heated pedestal growth (LHPG) method under Ar atmosphere. Spectroscopic characterization has been carried out to separate different crystallographic site in Ca1-XYbXF2+X crystals and to identify Stark's levels of Yb3+ transitions. Experimental decay time dependence of Yb3+ concentration was analyzed by using concentration gradient fiber in order to understand concentration quenching mechanisms. Energy transfer to unexpected rare earth impurities observed by up-conversion emission spectra in visible region under IR Yb3+ ion pumping seems to be an efficient process.

Ito, M.; Goutaudier, C.; Guyot, Y.; Lebbou, K.; Fukuda, T.; Boulon, G.

2004-11-01

121

Synthesis, spectroscopic characterization and hydroxylation of Mn(II) complexes with bis(2-pyridylmethyl)benzylamine.  

PubMed

Two new Mn(II) complexes of bis(2-pyridylmethyl)benzylamine (bpa) were synthesized and characterized by elemental analyses, IR and UV-visible spectroscopies, thermal analyses and ES-MS. These complexes are stable in air with the formula of [(pba)2Mn2Cl2(micro-Cl)2] (1) and [(pba)2Mn2(H2O)2(micro-Ac)2] (Ac)2 (2). The spectroscopic titration results show that the complexes could react with H2O2 resulting active oxidants, which could cause the intramolecular aromatic hydroxylation. The hydroxylated ligand (pba-OH) was confirmed by ES-MS and HPLC. PMID:19223230

Li, Jun-Feng; Chen, Qiu-Yun

2009-07-01

122

Spectroscopic Characterization of the Water Oxidation Intermediates in the Blue Dimer Ru-Based Catalyst for Artificial Photosynthesis  

NASA Astrophysics Data System (ADS)

Utilization of sunlight requires solar capture, light-to-energy conversion and storage. One effective way to store energy is to convert it into chemical energy by fuel-forming reactions, such as water splitting into hydrogen and oxygen. Ruthenium complexes are among few molecular-defined catalysts capable of water splitting. Mechanistic insights about such catalysts can be acquired by spectroscopic analysis of short-lived intermediates of catalytic water oxidation. Use of techniques such as EPR and X-ray absorption spectroscopy (XAS) are used to determine electronic requirements of catalytic water oxidation. About 30 years ago Meyer and coworkers reported first ruthenium-based catalyst for water oxidation, the ``blue dimer''. We performed EPR studies and characterized structures and electronic configurations of intermediates of water oxidation by the ``blue dimer''. Intermediates were prepared chemically by oxidation of Ru-complexes with defined number of Ce (IV) equivalents and freeze-quenched at controlled times. Changes in oxidation state of Ru atom were detected by XANES at Ru K-edges. K-edges are sensitive to changes in Ru oxidation state for Blue Dimer [3,3]^4+, [3,4]^4+, [3,4]'^4+ and [4,5]^3+ allowing a clear assignment of Ru oxidation state in intermediates. EXAFS demonstrated structural changes.

Moonshiram, Dooshaye; Pushkar, Yulia; Jurss, Jonah; Concepcion, Javier; Meyer, Thomas; Zakharova, Taisiya; Alperovich, Igor

2012-02-01

123

Spectroscopic investigation and characterization of polypyrrole film doped with [MeN 4] 2[Ni(dmit) 2] complex salt  

NASA Astrophysics Data System (ADS)

Polypyrrole doped with bis(1,3-dithiole-2-thione-4,5-dithiolate) nickellate (II) (PPy/[Ni(dmit) 2] 2-) was electropolymerized in acetonitrile solution and characterized by Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopies, as well as cyclic voltammetry (CV), conductivity, and scanning electron microscopy (SEM) measurements. Ionic desorption studies conducted by photon stimulated ion desorption (PSID) were also performed using synchrotron radiation at the S K-edge and time-of-flight mass spectrometry (ToF-MS) for ion analysis. The spectroscopic techniques indicated that the [Ni(dmit) 2] 2- was inserted onto the PPy backbone without modification during the electropolymerization process. Loss of electroactivity during the oxi-reduction processes indicated that the [Ni(dmit) 2] 2- leaves the film, undergoing anion exchange during the redox cycle. PPy/[Ni(dmit) 2] 2- exhibited higher intrinsic conductivity value than other PPy/M-dmit films studied previously. SEM measurements showed an irregular and heterogeneous surface with steps formation. PSID results showed that the species desorb through the X-ray induced electron stimulated desorption (XESD) mechanism while atomic sulfur species are mainly formed by Auger stimulated ion desorption (ASID). These results confirmed the presence of [Ni(dmit) 2] 2- at the topmost layers of the hybrid film.

Arantes, C.; Rocco, A. M.; Rocco, M. L. M.

2010-04-01

124

Characterization of the rare earth orthophosphates and Ce-doped LaPO4 by x ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

X-ray Absorption Spectroscopy (XAS) of the Rare Earth (RE) 3d levels yields sharp peaks near the edges as a result of strong, quasi-atomic 3d(sup 10)4f (yields) 3d(sup 9)4f(sup n+1) (M(sub 4,5)) transitions that contain a wealth of spectroscopic features. XAS is a useful technique for the characterization of 4f-occupancy, 4f-hybridization, and valence in RE-containing materials. The XAS measurements of the single crystal RE-orthophosphates, as well as a range of Ce doped (approximately 1-30%) LaPO4 hosts were performed at the 3d edge in the total electron yield mode at beamline 8-2 at the Stanford Synchrotron Radiation Laboratory (SSRL). The XAS spectra of the RE ions in the orthophosphate matrix generally resemble that of the corresponding RE metal and emphasize the major contribution of the trivalent state to the electronic transitions occurring at the 3d edge. There is no energy shift of the La and Ce absorption peaks with Ce doping and furthermore, no additional transitions are observed in either spectral region. However, accompanying the Ce doping there is a significant narrowing of the La absorption peak full width half maximum that contrasts to the Ce features that exhibit no contraction. The La and Ce spectra indicate that the Ce-doping of LaPO4 is purely substitutional.

Shuh, D. K.; Perry, D.; Terminello, L. J.; Boatner, L. A.; Abraham, M. M.

125

Crystal growth, structural and spectroscopic characterization of undoped and Yb 3+-doped oxyboroapatite fibers  

NASA Astrophysics Data System (ADS)

High quality undoped and Yb 3+-doped new calcium oxyboroapatite single crystals were obtained. The samples were grown in monocrystalline fiber form by using a fast and economical floating zone method under laser heating so-called LHPG for laser heated pedestal growth and were characterized by X-ray diffraction, IR spectroscopy and Raman spectroscopy. Yb 3+ absorption, emission and fluorescence decay studies were carried out both at low and room temperatures. Electronic energy level positions were interpreted by comparing absorption and emission spectra with those of vibronic sideband energy positions from Raman and IR absorption spectroscopies. Emission spectrum at low temperature and experimental fluorescence decays within ms range reveal Yb 3+ ion occupation within at least two different crystallographic sites of the apatite-type structure leading to a broad emission band at room temperature from 925 to 1200 nm, which seems of high interest for ultrashort laser pulse production.

Ternane, Riadh; Boulon, Georges; Guyot, Yannick; Thérèse Cohen-Adad, Marie; Trabelsi-Ayedi, Malika; Kbir-Ariguib, Najia

2003-04-01

126

Attempted Isolation, Spectroscopic Characterization, and Computational Study of Diazirinone (N2CO), its Analogs, and their Precursors  

NASA Astrophysics Data System (ADS)

Intrigued by the 2005 reported synthesis of diazirinone, we carried out further experimental and theoretical studies aimed at the detailed matrix-isolation and millimeter-wave spectroscopic characterizations. Diazirinone is a peculiar isoconjugate of two very stable molecules, CO and N2, which may be of astrochemical interest. Unfortunately, the previous reported methods of diazirinone generation did not yield this species, but rather its decomposition products. Encouraged by the many computational studies of the N2CO potential energy surface that all found diazirinone to be the lowest energy isomer, save its decomposition products, we proposed a new method of preparation of diazirinone from the photolysis or thermolysis of carbonyl diazide by loss of two nitrogen molecules. We were able to generate the highly explosive carbonyl diazide in sufficient yield from the reaction of triphosgene and sodium azide. This has allowed us to obtain a matrix-isolation and gas phase IR spectrum of carbonyl diazide which has a gas-phase lifetime of several days. We are currently engaged in the safe purification and distillation of our sample and obtaining a millimeter-wave spectrum of carbonyl diazide. We will attempt to photolyze or thermolyze this molecule to release diazirinone and characterize it by millimeter-wave spectroscopy to pave the way for possible astrochemical detection. In order to provide better mechanistic insight into the decomposition of carbonyl diazide to diazirinone, we have engaged in a DFT and ab initio computational study of several possible pathways. Our preliminary results suggest that of the pathways studied, a step-wise process in which an acyclic CON4 species is generated by loss of nitrogen followed by possible rearrangement and further loss of N2 is most likely. These results will be compared to the analogous reactions for azirinone (HC2NO), our next likely synthetic and spectroscopic target. The millimeter-wave absorption spectrometer used in this research project has been used previously for the investigation of numerous small inorganic molecules and ions. The apparatus consists of a three-meter Pyrex discharge chamber with cylindrical electrodes at each end. The discharge operates at mTorr pressures and at temperatures as low as 77 K. The microwave signal is generated by a Gunn-diode microwave source, which is then further amplified and multiplied to reach the desired frequencies. The signal is focused onto a liquid-helium-cooled indium antimonide detector.

Esselman, Brian J.; Nolan, Alex M.; Amberger, Brent K.; Shaffer, Chris J.; Woods, R. Claude; Stanton, John F.; McMahon, Robert J.

2010-11-01

127

Spectroscopic Characterization of the Excitation Energy Transfer in the Fucoxanthin–Chlorophyll Protein of Diatoms  

Microsoft Academic Search

We characterized the energy transfer pathways in the fucoxanthin–chlorophyll protein (FCP) complex of the diatom Cyclotella meneghiniana by conducting ultrafast transient absorption measurements. This light harvesting antenna has a distinct pigment composition and binds chlorophyll a (Chl-a), fucoxanthin and chlorophyll c (Chl-c) molecules in a 4:4:1 ratio. We find that upon excitation of fucoxanthin to its S2 state, a significant amount of

Emmanouil Papagiannakis; Ivo H. M. van Stokkum; Holger Fey; Claudia Büchel; Rienk van Grondelle

2005-01-01

128

A spectroscopic characterization of a monomeric analog of copper, zinc superoxide dismutase  

Microsoft Academic Search

A mutated protein of human Cu(II)2Zn(II)2 SOD in which residues Phe50 and Gly51 at the dimer interface were substituted by Glu's, thus producing a monomeric species, has been characterized by electronic absorption spectroscopy, EPR, relaxivity and1H NMR techniques. Such substitutions and\\/or accompanying remodeling and exposure of the dimer interface to solvent, alter the geometry of the active site: increases in

Ivano Bertini; Mario Piccioli; Maria Silvia Viezzoli; Choi Ying Chiu; Guy T. Mullenbach

1994-01-01

129

Spectroscopic Characterization of Plasma – Chemically Functionalized and Fluorophore-Labeled Polymer Surfaces  

Microsoft Academic Search

\\u000a The potential of spectrofluorometry and fluorescence microscopy for the characterization and quantification of different functionalities\\u000a like OH and NH2 groups at plasma-chemically modified polymer surfaces is assessed using traditional reactive dyes such as dansyl derivatives\\u000a and a sophisticated VIS-excitable chromogenic and fluorogenic pyrylium label showing binding-induced spectral and intensity\\u000a changes in absorption and emission. Aiming at an improved fluorometric surface

Katrin Hoffmann; Renate Mix; Joerg F. Friedrich; Ute Resch-Genger

130

Metallic and semiconductor nanoparticles: Synthesis, characterization and femtosecond laser spectroscopic studies  

NASA Astrophysics Data System (ADS)

The optical properties and the femtosecond relaxation dynamics of metallic and semiconductor nanoparticles and their dependence on the particle shapes were studied. Metallic and semiconductor nanoparticles were synthesized and characterized using optical absorption and emission spectroscopy as well as the Transmission Electron Microscopy (TEM). The ultrafast relaxation dynamics and the transient absorption spectra have been monitored using femtosecond pump-probe experiment. Regarding the shape dependent optical properties of metallic nanoparticles, gold nanospheres show surface plasmon absorption at 520 nm, however gold nanorods show two plasmon absorption bands due to the oscillation of the surface electrons along the transverse and the longitudinal modes. New absorption features appear, which are assigned to quadrupole resonance absorption along the short axis perpendicular to the triangular or hexagonal nanoplatelets. One of the most unique properties of gold nanorods is that they fluoresce with quantum yield enhancement one million times than the gold bulk due to the local field effect created by the longitudinal surface plasmon absorption (lightning nanorod effect). To study the effect of the surrounding matrix on the electron-phonon and phononphonon ultrafast relaxation dynamics of gold particles, the relaxation dynamics of the gold particles embedded in hydrogel and in organic gels have been compared. A large decrease in the phonon-phonon relaxation time was observed in the organic gel due to their lower thermal conductivity compared to water. The chemical interaction between the solvent molecules trapped inside the gel network and the gold particles surface enhances the rate of the heat transfer between the particles and the bath, giving rise a faster rate of relaxation. Shape dependent optical and ultrafast electron dynamics of semiconductor CdSe nanocrystals was studied. The femtosecond transient absorption spectra of CdSe nanorods show more spectral features than the dots of comparable diameter. This is due to breaking the near degeneracy in the spherical dots by elongation of the unique c-axis in the CdSe nanorods. The population and relaxation dynamics of the excited states in CdSe nanorods of different aspect ratios are studied using femtosecond transient absorption spectroscopy.

Mohamed, Mona Bakr

131

Spectroscopic Characterization of Highly Energetic Isofulminic Acid, Honc, by Experimental and Theoretical Approaches  

NASA Astrophysics Data System (ADS)

The highly energetic isomer isofulminic acid, HONC, calculated to lie more than 80 kcal/mol above HNCO has been characterized spectroscopically in its ground state by a combination of rotational spectroscopy and large-scale CCSD(T) electronic structure calculations. The fundamental rotational transition of HONC, H^{18}ONC, HON^{13}C, and DONC has been detected in the centimeter-wave band in a molecular beam by Fourier transform microwave spectroscopy, and effective rotational constants and nitrogen and deuterium quadrupole coupling constants have been derived for each isotopic species. All of the measured constants agree very well with those predicted from theoretical calculations of HONC. A number of other electronic and spectroscopic properties of isofulminic acid, including dipole moments, vibrational frequencies, and infrared intensities have also been calculated at the CCSD(T)/cc-pCVQZ level of theory. HONC is a good candidate for detection in space with radio telescopes because of its high polarity and because the more stable isomers, HNCO, HOCN, and HCNO have been identified in rich astronomical sources. M. S. Schuurman, S. R. Muir, W. D. Allan, and H. F. Schaefer III, J. Chem. Phys. 120, 11587 (2004).

McCarthy, M. C.; Thaddeus, P.; Mladenovic, Mirjana; Lewerenz, Marius

2009-06-01

132

Characterization of Special Glasses with Optical Absorption, Thermoluminescence and Electron Spin Resonance.  

National Technical Information Service (NTIS)

Alkaline borate glasses with technological interest were investigated and its characterizations in the borate glasses doped with copper were carried out. Optical absorption, thermoluminescence and electron spin resonance techniques have been used, particu...

E. F. Chinaglia M. L. F. Nascimento S. C. Trippe M. Matsuoka S. Watanabe

1994-01-01

133

Characterization of High Ge Content SiGe Heterostructures and Graded Alloy Layers Using Spectroscopic Ellipsometry  

NASA Technical Reports Server (NTRS)

Si(x)Ge(1-x)heterostructures on Si substrates have been widely studied due to the maturity of Si technology. However, work on Si(x)Ge)1-x) heterostructures on Ge substrates has not received much attention. A Si(x)Ge(1-x) layer on a Si substrate is under compressive strain while Si(x)Ge(1-x) on Ge is under tensile strain; thus the critical points will behave differently. In order to accurately characterize high Ge content Si(x)Ge(1-x) layers the energy shift algorithm used to calculate alloy compositions, has been modified. These results have been used along with variable angle spectroscopic ellipsometry (VASE) measurements to characterize Si(x)Ge(1-x)/Ge superlattices grown on Ge substrates. The results agree closely with high resolution x-ray diffraction measurements made on the same samples. The modified energy shift algorithm also allows the VASE analysis to be upgraded in order to characterize linearly graded layers. In this work VASE has been used to characterize graded Si(x)Ge(1-x) layers in terms of the total thickness, and the start and end alloy composition. Results are presented for a 1 micrometer Si(x)Ge(1-x) layer linearly graded in the range 0.5 less than or equal to x less than or equal to 1.0.

Heyd, A. R.; Alterovitz, S. A.; Croke, E. T.

1995-01-01

134

Chemical vapor deposition synthesis and Raman spectroscopic characterization of large-area graphene sheets.  

PubMed

We present a chemical vapor deposition (CVD) method to catalytically synthesize large-area, transferless, single- to few-layer graphene sheets using hexamethyldisilazane (HMDS) on a SiO2/Si substrate as a carbon source and thermally evaporated alternating Ni/Cu/Ni layers as a catalyst. The as-synthesized graphene films were characterized by Raman spectroscopic imaging to identify single- to few-layer sheets. This HMDS-derived graphene layer is continuous over the entire growth substrate, and single- to trilayer mixed sheets can be up to 30 ?m in the lateral dimension. With the synthetic CVD method proposed here, graphene can be grown into tailored shapes directly on a SiO2/Si surface through vapor priming of HMDS onto predefined photolithographic patterns. The transparent and conductive HMDS-derived graphene exhibits its potential for widespread electronic and opto-electronic applications. PMID:23461419

Liao, Chun-Da; Lu, Yi-Ying; Tamalampudi, Srinivasa Reddy; Cheng, Hung-Chieh; Chen, Yit-Tsong

2013-10-01

135

Variable angle spectroscopic ellipsometry - Application to GaAs-AlGaAs multilayer homogeneity characterization  

NASA Technical Reports Server (NTRS)

Variable angle spectroscopic ellipsometry has been applied to a GaAs-AlGaAs multilayer structure to obtain a three-dimensional characterization, using repetitive measurements at several spots on the same sample. The reproducibility of the layer thickness measurements is of order 10 A, while the lateral dimension is limited by beam diameter, presently of order 1 mm. Thus, the three-dimensional result mainly gives the sample homogeneity. In the present case three spots were used to scan the homogeneity over 1 in of a wafer which had molecular-beam epitaxially grown layers. The thickness of the AlGaAs, GaAs, and oxide layers and the Al concentration varied by 1 percent or less from edge to edge. This result was confirmed by two methods of data analysis. No evidence of an interfacial layer was observed on top of the AlGaAs.

Alterovitz, Samuel A.; Snyder, Paul G.; Merkel, Kenneth G.; Woollam, John A.; Radulescu, David C.

1988-01-01

136

Spectroscopic characterization of recently excavated archaeological potsherds from Tamilnadu, India with multi-analytical approach.  

PubMed

A combined analytical study of potsherds excavated from different archaeological sites of Tamilnadu (Kavalapatti, Nattapuraki and Thamaraikulam villages), India are analyzed by spectroscopic techniques such as FTIR, X-ray diffraction, thermogravimetric analysis (TGA) and Scanning Electron Microscope (SEM) coupled with Energy Dispersive Spectrometer (EDS). FTIR and XRD techniques have been attempted to characterize the mineralogical composition, firing temperature and firing conditions of the archaeological potsherds. Thermogravimetric analysis (TGA) is the complementary study to estimate the firing temperature from characteristic thermal reactions in potsherds under controlled firing in inert gas atmosphere. Further, Scanning Electron Microscopy (SEM) equipped and coupled with an Energy Dispersive Spectrometer (EDS) to analyze internal morphology and chemical composition of the potsherds was used. From the results of the above techniques, the firing temperatures of potsherds were found to be greater than 650°C. PMID:24929323

Raja Annamalai, G; Ravisankar, R; Rajalakshmi, A; Chandrasekaran, A; Rajan, K

2014-12-10

137

Spectroscopic Characterization of a Green Copper Site in a Single-Domain Cupredoxin  

PubMed Central

Cupredoxins are widespread copper-binding proteins, mainly involved in electron transfer pathways. They display a typical rigid greek key motif consisting of an eight stranded ?-sandwich. A fascinating feature of cupredoxins is the natural diversity of their copper center geometry. These geometry variations give rise to drastic changes in their color, such as blue, green, red or purple. Based on several spectroscopic and structural analyses, a connection between the geometry of their copper-binding site and their color has been proposed. However, little is known about the relationship between such diversity of copper center geometry in cupredoxins and possible implications for function. This has been difficult to assess, as only a few naturally occurring green and red copper sites have been described so far. We report herein the spectrocopic characterization of a novel kind of single domain cupredoxin of green color, involved in a respiratory pathway of the acidophilic organism Acidithiobacillus ferrooxidans. Biochemical and spectroscopic characterization coupled to bioinformatics analysis reveal the existence of some unusual features for this novel member of the green cupredoxin sub-family. This protein has the highest redox potential reported to date for a green-type cupredoxin. It has a constrained green copper site insensitive to pH or temperature variations. It is a green-type cupredoxin found for the first time in a respiratory pathway. These unique properties might be explained by a region of unknown function never found in other cupredoxins, and by an unusual length of the loop between the second and the fourth copper ligands. These discoveries will impact our knowledge on non-engineered green copper sites, whose involvement in respiratory chains seems more widespread than initially thought.

Roger, Magali; Biaso, Frederic; Castelle, Cindy J.; Bauzan, Marielle; Chaspoul, Florence; Lojou, Elisabeth; Sciara, Giuliano; Caffarri, Stefano; Giudici-Orticoni, Marie-Therese; Ilbert, Marianne

2014-01-01

138

Spectroscopic characterization of a green copper site in a single-domain cupredoxin.  

PubMed

Cupredoxins are widespread copper-binding proteins, mainly involved in electron transfer pathways. They display a typical rigid greek key motif consisting of an eight stranded ?-sandwich. A fascinating feature of cupredoxins is the natural diversity of their copper center geometry. These geometry variations give rise to drastic changes in their color, such as blue, green, red or purple. Based on several spectroscopic and structural analyses, a connection between the geometry of their copper-binding site and their color has been proposed. However, little is known about the relationship between such diversity of copper center geometry in cupredoxins and possible implications for function. This has been difficult to assess, as only a few naturally occurring green and red copper sites have been described so far. We report herein the spectrocopic characterization of a novel kind of single domain cupredoxin of green color, involved in a respiratory pathway of the acidophilic organism Acidithiobacillus ferrooxidans. Biochemical and spectroscopic characterization coupled to bioinformatics analysis reveal the existence of some unusual features for this novel member of the green cupredoxin sub-family. This protein has the highest redox potential reported to date for a green-type cupredoxin. It has a constrained green copper site insensitive to pH or temperature variations. It is a green-type cupredoxin found for the first time in a respiratory pathway. These unique properties might be explained by a region of unknown function never found in other cupredoxins, and by an unusual length of the loop between the second and the fourth copper ligands. These discoveries will impact our knowledge on non-engineered green copper sites, whose involvement in respiratory chains seems more widespread than initially thought. PMID:24932914

Roger, Magali; Biaso, Frédéric; Castelle, Cindy J; Bauzan, Marielle; Chaspoul, Florence; Lojou, Elisabeth; Sciara, Giuliano; Caffarri, Stefano; Giudici-Orticoni, Marie-Thérèse; Ilbert, Marianne

2014-01-01

139

Synthesis, characterization and spectroscopic behavior of novel 2-oxo-1,4-disubstituted-1,2,5,6-tetrahydrobenzo[h]quinoline-3-carbonitrile dyes.  

PubMed

Two synthetic pathways were adopted to synthesize the target 2-oxo-1,4-disubstituted-1,2,5,6-tetrahydro-benzo[h]quinoline-3-carbonitriles. Structure of the synthesized compounds has been characterized based on FT-IR, (1)H NMR, (13)C NMR and elemental analyses. UV-Vis and fluorescence spectroscopy measurements provided that all compounds are good absorbent and fluorescent. Fluorescence polarity study demonstrated that these compounds were sensitive to the polarity of the microenvironment provided by different solvents. In addition, spectroscopic and physicochemical parameters, including singlet absorption, extinction coefficient, Stokes shift, oscillator strength and dipole moment were investigated in order to explore the analytical potential of synthesized compounds. PMID:24934972

Khan, Salman A; Asiri, Abdullah M; Al-Thaqafy, Saad H; Faidallah, Hassan M; El-Daly, Samy A

2014-12-10

140

In situ X-ray absorption spectroscopic study for the electrochemical delithiation of a cathode LiFe 0.4Mn 0.6PO 4 material  

Microsoft Academic Search

The electronic and local atomic structural characterization of a promising cathode material, LiFe0.4Mn0.6PO4, for a lithium rechargeable battery was performed by in situ X-ray absorption fine structure (XAFS) on both Mn and Fe K-edges. Upon delithiation, the X-ray absorption near edge structure (XANES) spectra analysis showed that the Fe2+\\/Fe3+ electrochemical reaction was two times faster than that of Mn2+\\/Mn3+. The

Tatiana Nedoseykina; Min Gyu Kim; Seul-A. Park; Hyun-Soo Kim; Seong-Bae Kim; Jaephil Cho; Youngil Lee

2010-01-01

141

Characterization of the interaction between reserpine and bovine serum albumin: spectroscopic approaches.  

PubMed

The characteristics of the interaction between reserpine and bovine serum albumin (BSA) were studied by fluorescence, UV-vis absorption and Fourier transform infrared (FT-IR) spectroscopy. Spectroscopic analysis revealed that fluorescence quenching of BSA by reserpine was through a static quenching procedure. The binding constant K(A) of reserpine with BSA at 293, 301 and 309 K was 1.63, 1.78 and 2.35 x 10(5) moL(-1) L respectively, which indicated degree of binding force between reserpine and BSA. There was one binding site between reserpine and BSA. The entropy and enthalpy changes were positive, indicating that interaction of reserpine and BSA was driven mainly by hydrophobic forces. The average binding distance between the donor (BSA) and the acceptor (reserpine) was about 3.84 nm based on the Forster non-radiation energy transfer theory. Results of synchronous fluorescence and FT-IR spectra indicated that the conformation and microenvironment of BSA were changed by the binding of reserpine. The results may provide important insights into the physiological activity of reserpine. PMID:22329240

Wang, Tianhu; Zhao, Zhimin; Hua, Jin; Zhang, Jihua

2011-12-01

142

Absorption  

NSDL National Science Digital Library

This activity can be used to allow students to explore the concept of absorption using a variety of materials. Extensions include exploring how Native Americans used absorbtion in a number of ways. This inquiry activity was developed by a K-12 science teacher in the American Physiological SocietyÃÂs 1998 Frontiers in Physiology Program. The NSES Standards addressed by this activity are current as of the year of development. For more information on the Frontiers in Physiology Program, please visit www.frontiersinphys.org.

Katherine M Knudson (Polson Middle School)

1998-04-01

143

Raman and X-ray absorption spectroscopic studies of hydrothermally altered alkali-borosilicate nuclear waste glass  

NASA Astrophysics Data System (ADS)

Raman spectroscopy and X-ray absorption spectroscopy (XAS) are used to characterize structural changes that took place in hydrothermally altered (Na,K)-alumina-borosilicate glasses with different Na/K ratios, formulated as part of a durability study to investigate the behavior of glasses for nuclear waste storage. The hydrothermal experiments, or vapor hydration tests (VHT), were performed on each glass for 3 and 20 days at 200 °C to accelerate and approximate long-term alteration processes that may occur in a nuclear waste repository. Results found for both glasses and their VHT altered counterparts show little, if any, structural influence from the different starting Na/K ratios. X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and Raman spectroscopy indicate that the altered samples are mostly amorphous with small amounts of analcime-like and leucite-like crystals within 200 ?m of the sample surface and contain up to 9.7 wt.% water or OH. The Raman data are nearly identical for the amorphous portions of all altered VHT samples investigated, and indicate that two glass structural changes took place during alteration: one, partial depolymerization of the alumina-borosilicate network, and two, introduction of water or OH. Al and Si XAS data indicate tetrahedral AlO 4 and SiO 4 environments in the original glasses as well as in the altered samples. Small energy shifts of the Si K-edge also show that the altered VHT samples have less polymerized networks than the original glass. Na XAS data indicate expanded Na environments in the VHT samples with longer Na-O distances and more nearest-neighbor oxygen atoms, compared with the original glasses, which may be due to hydrous species introduced into the expanding Na-sites.

McKeown, David A.; Buechele, Andrew C.; Viragh, Carol; Pegg, Ian L.

2010-04-01

144

Characterization of Spectral Absorption Properties of Aerosols Using Satellite Observations  

NASA Technical Reports Server (NTRS)

The wavelength-dependence of aerosol absorption optical depth (AAOD) is generally represented in terms of the Angstrom Absorption Exponent (AAE), a parameter that describes the dependence of AAOD with wavelength. The AAE parameter is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses high spectral resolution measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measured reflectance (rho lambda) is approximately given by Beer's law rho lambda = rho (sub 0 lambda) e (exp -mtau (sub abs lambda)) where rho(sub 0 lambda) is the cloud reflectance, m is the geometric slant path and tau (sub abs lambda) is the spectral AAOD. The rho (sub 0 lambda) term is determined by means of radiative transfer calculations using as input the cloud optical depth derived as described in Torres et al. [JAS, 2012] that accounts for the effects of aerosol absorption. In the second step, corrections for molecular and aerosol scattering effects are applied to the cloud reflectance term, and the spectral AAOD is then derived by inverting the equation above. The proposed technique will be discussed in detail and application results will be presented. The technique can be easily applied to hyper-spectral satellite measurements that include UV such as OMI, GOME and SCIAMACHY, or to multi-spectral visible measurements by other sensors provided that the aerosol-above-cloud events are easily identified.

Torres, O.; Jethva, H.; Bhartia, P. K.; Ahn, C.

2012-01-01

145

FTIR spectroscopic characterization of Cu(II) coordination compounds with exopolysaccharide pullulan and its derivatives  

NASA Astrophysics Data System (ADS)

Pullulan is a water-soluble, extracellular neutral polysaccharide with a linear flexible chain of ?-(1 ? 6)-linked maltotriose units, the structure of which is intermediate between pullulan and amylose structures because of the co-existence of both ?-(1 ? 6) and ?-(1 ? 4)-glycosidic linkages in single compounds. In alkali solutions Cu(II) ion forms complexes with reduced low-molar pullulan (RLMP). The metal content and the solution composition depends on pH. The complexing process begins in a weak alkali solution (pH > 7), and involves OH groups in C(2) and C(3) or C(6) pullulan monomer units (?- D-glucopyranose). Complexes of Cu(II) ion with reduced low-molar pullulan were synthesized in the water solutions, at the boiling temperature and at different pH values (7.512). Fourier-Transform Infrared (FTIR) spectroscopic data of synthesized complexes are rare in literature. FTIR spectroscopic characterization (FTIR, LNT-FTIR, ATR-FTIR, and FTIR microspectroscopy) of Cu(II) ion complexes with RLMP ( M w 6000 g mol -1) was carried out in this work. The similarities of the ?(C sbnd H) range in a part of FTIR spectra indicate that there is no difference in the conformation of the C 1 glucopyranose (Glc) unit in the RLMP and synthesized Cu(II) complexes. The complexing Cu(II) ion with RLMP in the dependence from the pH form different types of complex (pH 7-8: Cu(II)(Glc) 2(H 2O) 2, pH 8-10: Cu(II)(Glc) 2(H 2O)(OH), pH 10-12: Cu(II)(Glc) 2(OH) 2).

Miti?, Ž.; Nikoli?, G. S.; Caki?, M.; Premovi?, P.; Ili?, Lj.

2009-04-01

146

Spectroscopic and microscopic characterization of biosensor surfaces with protein/amino-organosilane/silicon structure.  

PubMed

Composition and structure of biorecognition protein layers created on silicon substrates modified with amino-organosilanes determine the sensitivity and specificity of silicon based biosensing devices. In the present work, diverse spectroscopic and microscopic methods were applied to characterize model biosensor surfaces, formed on Si(3)N(4) or SiO(2) by modification with (3-aminopropyl)triethoxysilane, coating with rabbit gamma-globulins (IgGs) through physical adsorption, blocking with bovine serum albumin (BSA) and specific binding of an anti-rabbit IgG antibody. In addition, silanized substrates with directly adsorbed BSA or anti-rabbit IgG antibody were examined as reference surfaces. The protein/amino-organosilane/silicon structure of all surfaces was confirmed by X-ray photoelectron spectroscopy. Homogeneity of protein coverage was verified with near-field scanning optical microscope, working in reflection and fluorescence mode. Surface coverage with proteins was determined with angle-resolved XPS using a previously established bilayer approach. Inner structure of protein layers was examined with atomic force microscopy. Vertical arrangement of carbon functional groups was revealed by high resolution ARXPS. Combined spectroscopic and microscopic data reveal the complex character of interactions with the immobilized IgG molecules during blocking with BSA and immunoreaction with anti-IgG antibody. Within experimental error, neither surface coverage nor lateral structural scales of protein layer (provided by Fourier and auto-correlation analysis of topographic and phase images) increase during blocking procedure. On the other hand, coverage and all structural measures rise considerably after immunoreaction. In addition, it was found that polar functional groups orient towards substrate for all protein layers, independently of coverage, prior to and after both blocking and specific binding. PMID:22056253

Awsiuk, K; Bernasik, A; Kitsara, M; Budkowski, A; Petrou, P; Kakabakos, S; Prauzner-Bechcicki, S; Rysz, J; Raptis, I

2012-02-01

147

Energy absorption characterization of human enamel using nanoindentation.  

PubMed

Enamel is a natural composite, which has much higher toughness than its major component, crystalline hydroxyapatite. In this study, the energy absorption behavior of human sound enamel was investigated with nanoindentation techniques. A UMIS nanoindenter system as well as a Berkovich and two spherical indenters with nominal tip radii of 5 and 20 microm were used to indent enamel at different loading forces in the direction parallel to enamel prisms. Inelastic energy dissipation versus depth of indenter penetration (U%-h(p) curve) as well as a function of indentation strain (U%-epsilon curve) of enamel was determined. Enamel showed much higher energy absorption capacity than a ceramic material with equivalent modulus (fused silica). Even at the lowest forces (1 mN) for the 20 microm indenter, inelastic response was found. Additional tests done at different force loading rates illustrated that load rate has little influence on P-h response of enamel. The top surface of enamel has the plastic work of indentation of approximately 5.2 nJ/microm(3). The energy absorbing ability is influenced by the very small protein rich component that exists between the hydroxyapatite nanocrystals as well as within the sheath structure surrounding the enamel rods. PMID:17133444

He, Li Hong; Swain, Michael V

2007-05-01

148

Electrochemical and spectroscopic characterization of the novel charge-transfer ground state in diimine complexes of ytterbocene.  

PubMed

The novel charge-transfer ground state found in alpha,alpha'-diimine adducts of ytterbocene (C(5)Me(5))(2)Yb(L) [L = 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen)] in which an electron is spontaneously transferred from the f(14) metal center into the lowest unoccupied (pi*) molecular orbital (LUMO) of the diimine ligand to give an f(13)-L(*)(-) ground-state electronic configuration has been characterized by cyclic voltammetry, UV-vis-near-IR electronic absorption, and resonance Raman spectroscopies. The voltammetric data demonstrate that the diimine ligand LUMO is stabilized and the metal f orbital is destabilized by approximately 1.0 V each upon complexation for both bpy and phen adducts. The separation between the ligand-based oxidation wave (L(0/-)) and the metal-based reduction wave (Yb(3+/2+)) in the ytterbocene adducts is 0.79 V for both bpy and phen complexes. The UV-vis-near-IR absorption spectroscopic data for both the neutral adducts and the one-electron-oxidized complexes are consistent with those reported recently, but previously unreported bands in the near-IR have been recorded and assigned to ligand (pi*)-to-metal (f orbital) charge-transfer (LMCT) transitions. These optical electronic excited states are the converse of the ground-state charge-transfer process (e.g., f(13)-L(*-) <--> f(14)-L(0)). These new bands occur at approximately 5000 cm(-1) in both adducts, consistent with predictions from electrochemical data, and the spacings of the resolved vibronic bands in these transitions are consistent with the removal of an electron from the ligand pi* orbital. The unusually large intensity observed in the f --> f intraconfiguration transitions for the neutral phenanthroline adduct is discussed in terms of an intensity-borrowing mechanism involving the low-energy LMCT states. Raman vibrational data clearly reveal resonance enhancement for excitation into the low-lying pi* --> pi* ligand-localized excited states, and comparison of the vibrational energies with those reported for alkali-metal-reduced diimine ligands confirms that the ligands in the adducts are reduced radical anions. Differences in the resonance enhancement pattern for the modes in the bipyridine adduct with excitation into different pi* --> pi* levels illustrate the different nodal structures that exist in the various low-lying pi* orbitals. PMID:12950203

Da Re, Ryan E; Kuehl, Christopher J; Brown, Mac G; Rocha, Reginaldo C; Bauer, Eric D; John, Kevin D; Morris, David E; Shreve, Andrew P; Sarrao, John L

2003-09-01

149

Chemical, spectroscopic characterization, DFT studies and antibacterial activities in vitro of a new gold(I) complex with rimantadine  

NASA Astrophysics Data System (ADS)

A novel gold(I) complex with rimantadine (RTD) was obtained and structurally characterized by a set of chemical and spectroscopic analysis. 1H, 13C and 15N nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic measurements suggest coordination of the ligand to Au(I) through the N atom of the ethanamine group. Theoretical (DFT) calculations confirmed the IR assignments and permit proposing an optimized geometry for the complex. The gold(I)-rimantadine complex (Au-RTD) is soluble in methanol, ethanol, dimethylsulfoxide, acetone and acetonitrile. The preliminary kinetic studies based on UV-vis spectroscopic measurements indicate the stability of the compound in solution. Antibacterial activities of the complex were evaluated by an antibiogram assay. The Au-RTD complex showed an effective in vitro antibacterial activity against the Pseudomonas aeruginosa, Escherichia coli (Gram-negative), and Staphylococcus aureus (Gram-positive) bacterial strains.

Sucena, Suelen F.; Paiva, Raphael E. F.; Abbehausen, Camilla; Mattos, Ives B.; Lancellotti, Marcelo; Formiga, André L. B.; Corbi, Pedro P.

2012-04-01

150

Toward the characterization of biological toxins using field-based FT-IR spectroscopic instrumentation  

NASA Astrophysics Data System (ADS)

IR spectroscopy is a broadly applicable technique for the identification of covalent materials. Recent advances in instrumentation have made Fourier Transform infrared (FT-IR) spectroscopy available for field characterization of suspect materials. Presently, this instrumentation is broadly deployed and used for the identification of potential chemical hazards. This discussion concerns work towards expanding the analytical utility of field-based FT-IR spectrometry in the characterization of biological threats. Two classes of materials were studied - biologically produced chemical toxins which were non-peptide in nature and peptide toxin. The IR spectroscopic identification of aflatoxin-B1, trichothecene T2 mycotoxin, and strychnine was evaluated using the approach of spectral searching against large libraries of materials. For pure components, the IR method discriminated the above toxins at better than the 99% confidence level. The ability to identify non-peptide toxins in mixtures was also evaluated using a "spectral stripping" search approach. For the mixtures evaluated, this method was able to identify the mixture components from ca. 32K spectral library entries. Castor bean extract containing ricin was used as a representative peptide toxin. Due to similarity in protein spectra, a SIMCA pattern recognition methodology was evaluated for classifying peptide toxins. In addition to castor bean extract the method was validated using bovine serum albumin and myoglobin as simulants. The SIMCA approach was successful in correctly classifying these samples at the 95% confidence level.

Schiering, David W.; Walton, Robert B.; Brown, Christopher W.; Norman, Mark L.; Brewer, Joseph; Scott, James

2004-12-01

151

Characterization of porous low-k films using variable angle spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Variable angle spectroscopic ellipsometry (VASE™) is used as a tool to characterize properties such as optical constant, thickness, refractive index depth profile, and pore volume fraction of single and bilayer porous low-k films. The porous films were prepared using sacrificial pore generator (porogen) approach. Two sets of porous films with open- and closed-pore geometries were measured. Three models were used for data analysis: Cauchy, Bruggeman effective medium approximation (BEMA), and graded layer. Cauchy, a well-known model for transparent films, was used to obtain thickness and optical constant, whereas BEMA was utilized to calculate the pore volume fraction from the ellipsometric data. The Cauchy or BEMA models were then modified as graded layers, resulting in a better fit and a better understanding of the porous film. The depth profile of the porous film implied a more porous layer at the substrate-film interface. We found 3%-4% more porosity at the interface compared with the bulk for both films. This work shows that VASE™, a nondestructive measurement tool, can be used to characterize single- and multigraded layer porous films quickly and effectively.

Othman, M. T.; Lubguban, J. A.; Lubguban, A. A.; Gangopadhyay, S.; Miller, R. D.; Volksen, W.; Kim, H.-C.

2006-04-01

152

Characterization of SiGe/Ge heterostructures and graded layers using variable angle spectroscopic ellipsometry  

NASA Technical Reports Server (NTRS)

Variable angle spectroscopic ellipsometry (VASE) has been used to characterize Si(x)Ge(1-x)/Ge superlattices (SLs) grown on Ge substrates and thick Si(x)Ge(1-x)/Ge heterostructures grown on Si substrates. Our VASE analysis yielded the thicknesses and alloy compositions of all layers within the optical penetration depth of the surface. In addition, strain effects were observed in the VASE results for layers under both compressive and tensile strain. Results for the SL structures were found to be in close agreement with high resolution x-ray diffraction measurements made on the same samples. The VASE analysis has been upgraded to characterize linearly graded Si(x)Ge(1-x) buffer layers. The algorithm has been used to determine the total thickness of the buffer layer along with the start and end alloy composition by breaking the total thickness into many (typically more than 20) equal layers. Our ellipsometric results for 1 (mu)m buffer layers graded in the ranges 0.7 less than or = x less than or = 1.0, and 0.5 less than or = x less than or = 1.0 are presented, and compare favorably with the nominal values.

Croke, E. T.; Wang, K. L.; Heyd, A. R.; Alterovitz, S. A.; Lee, C. H.

1996-01-01

153

A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255. I. C IV absorption variability  

NASA Astrophysics Data System (ADS)

Context. Broad absorption lines indicate gas outflows with velocities from thousands of km s-1 to about 0.2 the speed of light, which may be present in all quasars and may play a major role in the evolution of the host galaxy. The variability of absorption patterns can provide information on changes in the density and velocity distributions of the absorbing gas and its ionisation status. Aims: We want to accurately follow the evolution in time of the luminosity and both the broad and narrow C IV absorption features of an individual object, the quasar APM 08279+5255, and analyse the correlations among these quantities. Methods: We have collected 23 photometrical and spectro-photometrical observations at the 1.82 m Telescope of the Asiago Observatory since 2003, plus 5 other spectra from the literature. We analysed the evolution in time of the equivalent width of the broad absorption feature and two narrow absorption systems, the correlation among them and with the R band magnitude. We performed a structure function analysis of the equivalent width variations. Results: We present an unprecedented monitoring of a broad absorption line quasar based on 28 epochs during 14 years. The shape of broad absorption feature shows relative stability, while its equivalent width slowly declines until it sharply increases during 2011. At the same time, the R magnitude stays almost constant until it sharply increases during 2011. The equivalent width of the narrow absorption redwards of the systemic redshift only shows a decline. Conclusions: The broad absorption behaviour suggests changes in the ionisation status as the main cause of variability. We show for the first time a correlation of this variability with the R band flux. The different behaviour of the narrow absorption system might be due to recombination time delay. The structure function of the absorption variability has a slope comparable with typical optical variability of quasars. This is consistent with variations of the 200 Å ionising flux originating in the inner part of the accretion disk.

Trevese, D.; Saturni, F. G.; Vagnetti, F.; Perna, M.; Paris, D.; Turriziani, S.

2013-09-01

154

Characterization of the oral absorption of several aminopenicillins: determination of intrinsic membrane absorption parameters in the rat intestine in situ  

NASA Technical Reports Server (NTRS)

The absorption mechanism of several penicillins was characterized using in situ single-pass intestinal perfusion in the rat. The intrinsic membrane parameters were determined using a modified boundary layer model (fitted value +/- S.E.): Jmax* = 11.78 +/- 1.88 mM, Km = 15.80 +/- 2.92 mM, Pm* = 0, Pc* = 0.75 +/- 0.04 for ampicillin; Jmax* = 0.044 +/- 0.018 mM, Km = 0.058 +/- 0.026 mM, Pm* = 0.558 +/- 0.051, Pc* = 0.757 +/- 0.088 for amoxicillin; and Jmax* = 16.30 +/- 3.40 mM, Km = 14.00 +/- 3.30 mM, Pm* = 0, Pc* = 1.14 +/- 0.05 for cyclacillin. All of the aminopenicillins studied demonstrated saturable absorption kinetics as indicated by their concentration-dependent wall permeabilities. Inhibition studies were performed to confirm the existence of a nonpassive absorption mechanism. The intrinsic wall permeability (Pw*) of 0.01 mM ampicillin was significantly lowered by 1 mM amoxicillin and the Pw* of 0.01 mM amoxicillin was reduced by 2 mM cephradine consistent with competitive inhibition.

Sinko, P. J.; Amidon, G. L.

1992-01-01

155

Characterization of Thermal Arc Generator RB3 Flows by Laser Absorption Spectroscopy and Pitot Probe  

Microsoft Academic Search

The thermal arc generator RB3 flows were characterized by laser absorption spectroscopy and Pitot probe measurement. Firstly, translational temperature and flow velocity distributions in an argon flow were deduced from measured absorption profile of ArI 772.42 nm. The averaged specific enthalpy and plasma power for TPS test region was estimated as 3.72±0.48 MJ\\/kg, 1.77±0.68 kW, respectively. Next, an air flow

Makoto MATSUI; Hiroki TAKAYANAGI; Andreas KNAPP; Georg HERDRICH; Kimiya KOMURASAKI; Yoshihiro ARAKAWA; Monika AUWETER-KURTZ

2008-01-01

156

Synthesis, Structural and Spectroscopic Characterization, and Reactivities of Mononuclear Cobalt(III)-Peroxo Complexes  

PubMed Central

Metal-dioxygen adducts are key intermediates detected in the catalytic cycles of dioxygen activation by metalloenzymes and biomimetic compounds. In this study, mononuclear cobalt(III)- peroxo complexes bearing tetraazamacrocyclic ligands, [Co(12-TMC)(O2)]+ and [Co(13-TMC)(O2)]+, were synthesized by reacting [Co(12-TMC)(CH3CN)]2+ and [Co(13-TMC)(CH3CN)]2+, respectively, with H2O2 in the presence of triethylamine. The mononuclear cobalt(III)-peroxo intermediates were isolated and characterized by various spectroscopic techniques and X-ray crystallography, and the structural and spectroscopic characterization demonstrated unambiguously that the peroxo ligand is bound in a side-on ?2 fashion. The O-O bond stretching frequency of [Co(12-TMC)(O2)]+ and [Co(13- TMC)(O2)]+ was determined to be 902 cm?1 by resonance Raman spectroscopy. The structural properties of the CoO2 core in both complexes are nearly identical; the O-O bond distances of [Co(12-TMC)(O2)]+ and [Co(13-TMC)(O2)]+ were 1.4389(17) Å and 1.438(6) Å, respectively. The cobalt(III)-peroxo complexes showed reactivities in the oxidation of aldehydes and O2-transfer reactions. In the aldehyde oxidation reactions, the nucleophilic reactivity of the cobalt-peroxo complexes was significantly dependent on the ring size of the macrocyclic ligands, with the reactivity of [Co(13-TMC)(O2)]+ > [Co(12-TMC)(O2)]+. In the O2-transfer reactions, the cobalt(III)-peroxo complexes transferred the bound peroxo group to a manganese(II) complex, affording the corresponding cobalt(II) and manganese(III)- peroxo complexes. The reactivity of the cobalt-peroxo complexes in O2-transfer was also significantly dependent on the ring size of tetraazamacrocycles, and the reactivity order in the O2-transfer reactions was the same as that observed in the aldehyde oxidation reactions.

Cho, Jaeheung; Sarangi, Ritimukta; Kang, Hye Yeon; Lee, Jung Yoon; Kubo, Minoru; Ogura, Takashi; Solomon, Edward I.; Nam, Wonwoo

2010-01-01

157

Absorption of CO2 in algal mass culture systems: a different characterization approach.  

PubMed

For the characterization of CO(2) absorption in aerated microalgal culture systems, a different approach based on K(L)a(O(2)) determination and transformation was studied. To confirm the validity of this method, the influence of reactions between CO(2) and compounds (OH(-), H(2)O, and NH(3)) present in the culture medium upon the absorption mechanism was evaluated under different physical and chemical culture conditions. Under these conditions, knowledge of the relative magnitudes of the diffusion and reaction kinetics permitted the evaluation of their relative importance. For the determination of the parameters required for the calculation of the CO(2) absorption constant, empirical correlations for K(L) (0) and a were used that had been previously verified with experimental data for O(2) absorption. Since, for the conditions studied, the absorption rate was shown to be independent of the chemical reactions taking place in the liquid phase, the K(L)a for CO(2) could be directly related to the K(L)a for O(2) by a simple factor that took into account the difference in aqueous diffusivity of the two gases. Thus, using methods developed for determining O(2) absorption in gas-liquid contactors, it is possible to adequately characterize CO(2) absorption for laboratory and pilot scale algal production systems. PMID:18600683

Talbot, P; Gortares, M P; Lencki, R W; de la Noüe, J

1991-04-15

158

Synergic use of TOMS and Aeronet Observations for Characterization of Aerosol Absorption  

NASA Technical Reports Server (NTRS)

The role of aerosol absorption on the radiative transfer balance of the earth-atmosphere system is one of the largest sources of uncertainty in the analysis of global climate change. Global measurements of aerosol single scattering albedo are, therefore, necessary to properly assess the radiative forcing effect of aerosols. Remote sensing of aerosol absorption is currently carried out using both ground (Aerosol Robotic Network) and space (Total Ozone Mapping Spectrometer) based observations. The satellite technique uses measurements of backscattered near ultraviolet radiation. Carbonaceous aerosols, resulting from the combustion of biomass, are one of the most predominant absorbing aerosol types in the atmosphere. In this presentation, TOMS and AERONET retrievals of single scattering albedo of carbonaceous aerosols, are compared for different environmental conditions: agriculture related biomass burning in South America and Africa and peat fires in Eastern Europe. The AERONET and TOMS derived aerosol absorption information are in good quantitative agreement. The most absorbing smoke is detected over the African Savanna. Aerosol absorption over the Brazilian rain forest is less absorbing. Absorption by aerosol particles resulting from peat fires in Eastern Europe is weaker than the absorption measured in Africa and South America. This analysis shows that the near UV satellite method of aerosol absorption characterization has the sensitivity to distinguish different levels of aerosol absorption. The analysis of the combined AERONET-TOMS observations shows a high degree of synergy between satellite and ground based observations.

Torres, O.; Bhartia, P. K.; Dubovik, O.; Holben, B.; Siniuk, A.

2003-01-01

159

Growth and Raman spectroscopic characterization of As 4S 4 (II) single crystals  

NASA Astrophysics Data System (ADS)

As described by Kutoglu (1976 [16]), single crystals of As 4S 4 (II) phase have been grown using a new two-step synthesis that drastically increases the reproducibility that is attainable in synthetic experiments. First, through photo-induced phase transformation, pararealgar powder is prepared as a precursor instead of AsS melt. Then it is dissolved and recrystallized from CS 2 solvent. Results show that single crystals of the As 4S 4 (II) phase were obtained reproducibly through the dissolution-recrystallization process. Single crystals of As 4S 4 (II) obtained using this method were translucent and showed a uniform yellow-orange color. The crystal exhibits a platelet-like shape as a thin film with well-developed faces (0 1 0) and (0 1¯ 0). The grown crystals are as large as 0.50×0.50×0.01 mm. They were characterized using powder and single crystal X-ray diffraction techniques to confirm the phase identification and the lattice parameters. The As 4S 4 (II) phase crystallizes in monoclinic system with cell parameters a=11.202(4) Å, b=9.954(4) Å, c=7.142(4) Å, ?=92.81(4)°, V=795.4(6) Å 3, which shows good agreement with the former value. Raman spectroscopic studies elucidated the behavior of the substance and the relation among phases of tetra-arsenic tetrasulfide.

Kyono, Atsushi

2010-11-01

160

Kinetic and spectroscopic characterization of 1-naphthol 2-hydroxylase from Pseudomonas sp. strain C5.  

PubMed

1-Naphthol 2-hydroxylase (1-NH) catalyzes the conversion of 1-naphthol to 1,2-dihydroxynaphthalene. 1-NH from carbaryl degrading Pseudomonas strain C5 was purified and characterized for its kinetic and spectroscopic properties. The enzyme was found to be NAD(P)H-dependent external flavin monooxygenase. Though the kinetic parameters of 1-NH from strain C5 appear to be similar to 1-NH enzyme from strains C4 and C6, however, they differ in their N-terminal sequences, mole content of flavin adenine dinucleotide (FAD), reconstitution of apoenzyme, and K i. 1-NH showed narrow substrate specificity with comparable hydroxylation efficiency on 1-naphthol and 5-amino 1-naphthol (~30 %) followed by 4-chloro 1-naphthol (~9 %). Salicylate was found to be the nonsubstrate effector. The flavin fluorescence of 1-NH was found to increase in the presence of 1-naphthol (K d?=?11.3 ?M) and salicylate (K d?=?1027 ?M). The circular dichroism (CD) spectra showed significant perturbations in the presence of NAD(P)H, whereas no changes were observed in the presence of 1-naphthol. Naphthalene, 1-chloronaphthalene, 2-napthol, and 2-naphthoic acid were found to be the mixed inhibitors. Chemical modification studies showed the probable involvement of His, Cys, and Tyr in the binding of 1-naphthol, whereas Trp was found to be involved in the binding of NAD(P)H. PMID:24599669

Trivedi, Vikas D; Majhi, Prabin; Phale, Prashant S

2014-04-01

161

Spectroscopic and Electrochemical Characterization of Nanostructured Optically-Transparent Carbon Electrodes  

PubMed Central

The present paper describes the results related to the optical and electrochemical characterization of thin carbon films fabricated by spin coating and pyrolysis of AZ P4330-RS photoresist. The goal of this paper is to provide comprehensive information allowing for the rational the selection of the conditions to fabricate optically-transparent carbon electrodes (OTCE) with specific electro-optical properties. According to our results, these electrodes could be appropriate choices as electrochemical transducers to monitor electrophoretic separations. At the core of this manuscript is the development and critical evaluation of a new optical model to calculate the thickness of the OTCE by variable angle spectroscopic ellipsometry (VASE). Such data was complemented with topography and roughness (obtained by AFM), electrochemical properties (obtained by cyclic voltammetry), electrical properties (obtained by electrochemical impedance spectroscopy), and structural composition (obtained by Raman spectroscopy). Although the described OTCE were used as substrates to investigate the effect of electrode potential on the real-time adsorption of proteins by ellipsometry, these results could enable the development of other biosensors that can be then integrated into various CE platforms.

Benavidez, Tomas E.; Garcia, Carlos D.

2013-01-01

162

Replacement of the axial histidine heme ligand with cysteine in nitrophorin I: Spectroscopic and crystallographic characterization  

PubMed Central

To evaluate the potential of using the heme containing lipocalin nitrophorin 1 as a template for protein engineering, we have replaced the native axial heme coordinating histidine residue with glycine, alanine and cysteine. We report here the characterization of the cysteine mutant H60C_NP1 by spectroscopic and crystallographic methods. The UV/Vis, resonance Raman, and magnetic circular dichroism spectra suggest weak thiolate coordination of the ferric heme in the H60C_NP1 mutant. Reduction to the ferrous state resulted in loss of cysteine coordination, while addition of exogenous imidazole ligands gave coordination changes that varied with the ligand. Depending on the substitution of the imidazole, three heme coordination states could be distinguished: 5-coordinate mono-imidazole, 6-coordinate bis-imidazole and 6-coordinate imidazole/thiolate. Ligand binding affinities were measured and found to be generally 2-3 orders of magnitude lower for the H60C mutant relative to NP1. Two crystal structures of the H60C_NP1 in complex with imidazole and histamine were solved to 1.7 Å and 1.96 Å resolution, respectively. Both structures show that the H60C mutation is well tolerated by the protein scaffold and suggest that heme-thiolate coordination in H60C_NP1 requires some movement of the heme within its binding cavity. This adjustment may be responsible for the ease with which the engineered heme-thiolate coordination can be displaced by exogenous ligands.

Vetter, Stefan W.; Terentis, Andrew C.; Osborne, Robert L.; Dawson, John H.

2008-01-01

163

Spectroscopic characterization and energy transfer process in cobalt and cobalt-iron co-doped ZnSe/ZnS crystals  

NASA Astrophysics Data System (ADS)

Cobalt doped II-VI wide band semiconductors (e.g. ZnSe, ZnS, CdSe) are promising media for infrared (IR) laser applications. They could be utilized as effective passive Q-switches for cavities of Alexandrite as well as Nd and Er lasers operating over 0.7-0.8, 1.3-1.6, and ~2.8 ?m spectral ranges. We report spectroscopic characterization of Co:ZnSe and Co:ZnS crystals. Absorption cross-sections were measured for 4A2(F) ? 4T1(P), 4A2(F) ? 4T1(F), and 4A2(F) ? 4T2(F) transitions with maximum absorption at 768(726), 1615(1500), 2690(2740) nm for ZnSe(ZnS) crystals, respectively. The calculated absorption cross-sections of the above transitions were estimated to be 64(56)×1019, 7.5(7.8)×1019, and 0.52(0.49)×1019 cm2 for ZnSe(ZnS) crystal hosts. In addition to the above applications the cobalt ions could be utilized for excitation of Fe2+ ions via resonance energy transfer process. Tunable room temperature lasing of Fe 2+ doped binary and ternary chalcogenides has been successfully demonstrated over 3.5-6 ?m spectral range. However, II-VI lasers based on Fe2+ active ions don't feature convenient commercially available pump sources (e.g. some Fe doped crystal hosts require pump wavelengths longer than 3 ?m). Therefore, the process of energy transfer from Co2+ to Fe2+ ions could enable utilization of commercially available visible and near-infrared pump sources. We report a spectroscopic characterization of iron-cobalt co-doped ZnS and ZnSe crystals over 14-300K temperature range. Mid-IR laser oscillation at 3.9 ?m(3.6 ?m) via energy transfer in the Co:Fe:ZnSe (Co:Fe:ZnS) co-doped crystals was demonstrated under cobalt excitation at 4A2(F) ? 4T1(P) (~0.7?m) and 4A2(F) ? 4T1(F) (~1.56 ?m) transitions.

Peppers, J.; Martyshkin, D. V.; Fedorov, V. V.; Mirov, S. B.

2014-02-01

164

Spectroscopic, molecular structure characterizations and quantum chemical computational studies of ( E)-5-(diethylamino)-2-[(2-fluorophenylimino)methyl]phenol  

Microsoft Academic Search

The molecular structure and spectroscopic properties of (E)-5-(diethylamino)-2-[(2-fluorophenylimino)methyl]phenol were characterized by X-ray diffraction, IR and UV\\/Vis spectroscopy. These properties of title compound were also investigated from calculative point of view. Geometry optimization in gas phase was performed using DFT method with B3LYP applying 6-311G(d,p) basis set and geometry optimizations in solvent media were performed with the same level of theory

Çigdem Albayrak; Rene Frank

2010-01-01

165

Chemical Characterization of Riverine Dissolved Organic Matter Using a Combination of Spectroscopic and Pyrolytic Methods  

NASA Astrophysics Data System (ADS)

It is now well established that riverine dissolved organic matter (DOM) play a major role in environmental processes. However natural organic matter exhibit different properties depending on their sources and the fractions considered. As a result chemical characterization of DOM has appeared essential for a better understanding of their reactivity. The purpose of this work was to characterize all of the DOM at molecular level, including the non-hydrolysable fraction, which is a major part of this OM. To this aim a new analytical approach had to be considered. A combination of spectroscopic and pyrolytic methods has been applied to various fractions of DOM originating from different catchments (French and Amazonian rivers). The fractions were termed hydrophilic, transphilic and colloids according to the IHSS fractionation procedure, and account for at least 70% of the total dissolved organic carbon. Solid state 13C NMR and FTIR afford information on the nature and relative abundance of the chemical functions occurring in macromolecules. Differential thermogravimetric analysis allows to determine the thermal behaviour of the studied material and hence to optimize analytical pyrolysis conditions. Curie point pyrolysis combined to gas chromatography and mass spectrometry leads to identification of characteristic pyrolysis products, some of them being specific of a macromolecular source. Additional information can be provided by thermochemolysis with tetramethylammonium hydroxide (TMAH). TMAH was shown to allow an increase in the efficiency of the cracking of macromolecular structures and an enhancement of the detection of the polar pyrolysis products especially due to methylation of the alcohol, phenol and acid groups. The results obtained have established the importance of terrestrial contribution to DOM. Hydrophobic fractions mainly originate from lignin-derived units, whereas transphilic fractions mostly contain cellulose units together with lignin derived ones and substantial amount of nitrogen-containing moieties. Characterization of colloidal fraction has indicated the presence of compounds from bacterial origin, especially specific nitrogen-containing molecules that are characteristic pyrolysis products of peptidoglycans, along with lignin-derived units. However pyrolysis has revealed significant differences in the detection of nitrogen-containing molecules, which do not parallel nitrogen content of the fractions. Moreover in hydrophobic and transphilic fractions the molecular structure of these compounds, which are mainly nitrogen- and oxygen- containing molecules, has not allowed to ascertain their origin. As the major biological sources of organic nitrogen (proteins, amino sugars, or tetrapyrrole pigments) involve differences in the main nitrogen functionality, two additional spectroscopic methods, namely X-ray photoelectron spectroscopy (XPS) and solid state 15N NMR, have been used to determine the nitrogen functional groups (amide, amine, and N-heterocycle) present in the different fractions of DOM. The combination of these two methods has revealed the occurrence of different functionality of nitrogen, with relative contributions depending on the considered fraction. It has also appeared that Curie point pyrolysis does not account for the presence of nitrogen in macromolecules with the same efficiency depending on the functional group involved. This study has highlighted the importance of combining different analytical approaches to obtain a whole insight into chemical structure of OM and avoid biased information.

Templier, J.; Derenne, S.

2006-12-01

166

An X-ray absorption spectroscopic structural investigation of the nickel site in Escherichia coli NikA protein  

SciTech Connect

Since the discovery of the involvement of Ni in the active site of the enzyme urease in 1975, the role of Ni in biology has been rapidly expanding. The list of nickel-dependent metalloenzymes now includes acetyl coenzyme A synthase/carbon monoxide dehydrogenase, methyl coenzyme M reductase, Ni/Fe hydrogenases, and superoxide dismutases from Streptomyces. Each of these enzymes appears to be dependent on several gene products that constitute a Ni-specific transport and metallocenter assembly system. The authors report here the results of an X-ray spectroscopic structural investigation of the Ni site in a Ni transport protein, the periplasmic Ni-binding protein, NikA, from Escherichia coli.

Allan, C.B.; Gu, Z.; Choudhury, S.B.; Al-Mjeni, F.; Sharma, M.L.; Maroney, M.J. [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemistry] [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemistry; Wu, L.F.; Mandrand-Berthelot, M.A. [CNRS-URA, Villeurbanne (France). Lab. de Genetique Moleculaire des Microorganismes] [CNRS-URA, Villeurbanne (France). Lab. de Genetique Moleculaire des Microorganismes

1998-11-02

167

Spectroscopic Determination of Leaf Biochemistry Using Band-Depth Analysis of Absorption Features and Stepwise Multiple Linear Regression  

Microsoft Academic Search

We develop a new method for estimating the biochemistry of plant material using spectroscopy. Normalized band depths calculated from the continuum-removed reflectance spectra of dried and ground leaves were used to estimate their concentrations of nitrogen, lignin, and cellulose. Stepwise multiple linear regression was used to select wavelengths in the broad absorption features centered at 1.73 ?m, 2.10 ?m, and

Raymond F. Kokaly; Roger N. Clark

1999-01-01

168

X-ray absorption and X-ray photoelectron spectroscopic studies of air-oxidized chromium nitride thin films  

Microsoft Academic Search

The surface oxidation of CrN thin films prepared by the cathode are ion plating method was studied by X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) using soft X-rays from synchrotron radiation. The results indicate that molecular nitrogen is formed in the interstitial position of the chromium oxide matrix at the initial stage of oxidation. On further oxidation, at

F. Esaka; H. Shimada; M. Imamura; N. Matsubayashi; T. Sato; A. Nishijima; A. Kawana; H. Ichimura; T. Kikuchi; K. Furuya

1996-01-01

169

Characterization of ion-implanted aluminum and iron by spectroscopic ellipsometry.  

National Technical Information Service (NTIS)

The change in the optical constants of aluminum alloy and iron samples caused by implantation with nitrogen and chromium ions has been investigated by spectroscopic ellipsometry. The objective is to develop a method for simple, non-destructive characteriz...

J. S. Brodkin W. Franzen R. J. Culbertson J. M. Williams

1990-01-01

170

Preparation and spectroscopic characterization of visible light sensitized N doped TiO{sub 2} (rutile)  

SciTech Connect

Nitrogen doped TiO{sub 2} represents one of the most promising material for photocatalitic degradation of environmental pollutants with visible light. However, at present, a great deal of activity is devoted to the anatase polymorph while few data about rutile are available. In the present paper we report an experimental characterization of N doped polycrystalline rutile TiO{sub 2} prepared via sol-gel synthesis. Nitrogen doping does not affect the valence band to conduction band separation but, generates intra band gap localized states which are responsible of the on set of visible light absorption. The intra band gap states correspond to a nitrogen containing defect similar but not coincident with that recently reported for N doped anatase. - Graphical abstract: Nitrogen doped TiO{sub 2} represents one of the most promising material for photocatalitic degradation of environmental pollutants with visible light. However, at present, a great deal of activity is devoted to the anatase polymorph while few data about rutile are available. In the present paper we report an experimental characterization of N doped polycrystalline rutile TiO{sub 2} prepared via sol-gel synthesis.

Livraghi, S.; Czoska, A.M. [Dipartimento di Chimica I.F.M. and NIS, Universita degli Studi di Torino, Via P. Giuria, 7, 10125 Torino (Italy); Paganini, M.C. [Dipartimento di Chimica I.F.M. and NIS, Universita degli Studi di Torino, Via P. Giuria, 7, 10125 Torino (Italy)], E-mail: mariacristina.paganini@unito.it; Giamello, E. [Dipartimento di Chimica I.F.M. and NIS, Universita degli Studi di Torino, Via P. Giuria, 7, 10125 Torino (Italy)

2009-01-15

171

Real time spectroscopic ellipsometry for characterization of thin film optical properties and microstructural evolution  

Microsoft Academic Search

A rotating polarizer multichannel ellipsometer was applied in spectroscopic (1.3 - 4.2 eV) investigations of thin films during deposition. In this review, two examples are selected which demonstrate real time spectroscopic ellipsometry. In the first, we compare results for amorphous silicon and germanium sputtered to approximately 50 A on native oxide-covered c-Si. For these films, the evolution of the effective

R. W. Collins; Ilsin An; H. V. Nguyen; T. Gu

1991-01-01

172

Elemental and spectroscopic characterization of fractions of an acidic extract of oil sands process water.  

PubMed

'Naphthenic acids' (NAs) in petroleum produced water and oil sands process water (OSPW), have been implicated in toxicological effects. However, many are not well characterized. A method for fractionation of NAs of an OSPW was used herein and a multi-method characterization of the fractions conducted. The unfractionated OSPW acidic extract was characterized by elemental analysis, electrospray ionization-Orbitrap-mass spectrometry (ESI-MS), and an esterified extract by Fourier Transform infrared (FTIR) and ultraviolet-visible (UV) absorption spectroscopy and by comprehensive multidimensional gas chromatography-MS (GCxGC-MS). Methyl esters were fractionated by argentation solid phase extraction (Ag(+) SPE) and fractions eluting with: hexane; diethyl ether: hexane and diethyl ether, examined. Each was weighed, examined by elemental analysis, FTIR, UV, GC-MS and GCxGC-MS (both nominal and high resolution MS). The ether fraction, containing sulfur, was also examined by GCxGC-sulfur chemiluminescence detection (GCxGC-SCD). The major ions detected by ESI-MS in the OSPW extract were assigned to alicyclic and aromatic 'O2' acids; sulfur was also present. Components recovered by Ag(+) SPE were also methyl esters of alicyclic and aromatic acids; these contained little sulfur or nitrogen. FTIR spectra showed that hydroxy acids and sulfoxides were absent or minor. UV spectra, along with the C/H ratio, further confirmed the aromaticity of the hexane:ether eluate. The more minor ether eluate contained further aromatics and 1.5% sulfur. FTIR spectra indicated free carboxylic acids, in addition to esters. Four major sulfur compounds were detected by GCxGC-SCD. GCxGC-high resolution MS indicated these were methyl esters of C18 S-containing, diaromatics with ?C3 carboxylic acid side chains. PMID:23856466

Jones, D; Scarlett, A G; West, C E; Frank, R A; Gieleciak, R; Hager, D; Pureveen, J; Tegelaar, E; Rowland, S J

2013-11-01

173

?-MnO 2/polyaniline composites: Preparation, characterization, and applications in microwave absorption  

NASA Astrophysics Data System (ADS)

MnO 2/doped polyaniline (PANI) is prepared by an in situ polymerization method using ?-MnO 2 as the addition agent and hydrochloric acid as the doping agent. Products are characterized by FT-IR, UV-vis, XRD, and TEM. Conductivity, electromagnetic properties, and microwave absorption properties are first discussed on the basis of structural characterization. The as-prepared products of MnO 2/PANI are partially crystalline in nature and spherical in pattern with grain sizes of 50-70 nm. MnO 2 particles are successfully decorated with doped PANI. MnO 2/PANI displays moderate electric conduction, excellent dielectric losses, and microwave absorption capabilities. Compared to pure MnO 2, the dielectric and reflection loss properties of MnO 2/PANI composites exhibit significant improvements, with an effective absorption band at 5 GHz under -10 dB and maximum reflection loss of -21 dB at 13.56 GHz. Pure MnO 2 shows an effective absorption band of 3 GHz under -10 dB and a maximum reflection loss of -14.20 dB at 11.5 GHz. Thus, MnO 2/PANI composites are found to be a promising microwave absorption material.

Jianjun, Hu; Yuping, Duan; Jia, Zhang; Hui, Jing; Shunhua, Liu; Weiping, Li

2011-05-01

174

X-ray absorption fine structure spectroscopic determination of plutonium speciation at the Rocky Flats environmental technology  

SciTech Connect

X-ray Absorption Fine Structure spectroscopy was used to probe the speciation of the ppm level Pu in thirteen soil and concrete samples from the Rocky Flats Environmental Technology Site in support of the site remediation effort that has been successfully completed since these measurements. In addition to X-ray Absorption Near Edge Spectra, two of the samples yielded Extended X-ray Absorption Fine Structure spectra that could be analyzed by curve-fits. Most of these spectra exhibited features consistent with PU(IV), and more specificaJly, PuO{sub 2+x}-type speciation. Two were ambiguous, possibly indicating that Pu that was originally present in a different form was transforming into PuO{sub 2+x}, and one was interpreted as demonstrating the presence of an unusual Pu(VI) compound, consistent with its source being spills from a PUREX purification line onto a concrete floor and the resultant extreme conditions. These experimental results therefore validated models that predicted that insoluble PuO{sub 2+x} would be the most stable form of Pu in equilibrium with air and water even when the source terms were most likely Pu metal with organic compounds or a Pu fire. A corollary of these models' predictions and other in situ observations is therefore that the minimal transport of Pu that occurred on the site was via the resuspension and mobilization of colloidal particles. Under these conditions, the small amounts of diffusely distributed Pu that were left on the site after its remediation pose only a negligible hazard.

Lezama-pacheco, Juan S [Los Alamos National Laboratory; Conradson, Steven D [Los Alamos National Laboratory; Clark, David L [Los Alamos National Laboratory

2008-01-01

175

Absorption spectroscopy characterization measurements of a laser-produced Na atomic beam  

SciTech Connect

This work describes a pulsed Na atomic beam source developed for spectroscopic diagnosis of a high-power ion diode on the Particle Beam Fusion Accelerator II. The goal is to produce a {approximately} 10{sup 12}-cm{sup {minus}3}-density Na atomic beam that can be injected into the diode acceleration gap to measure electric and magnetic fields from the Stark and Zeeman effects through laser-induced-fluorescence or absorption spectroscopy. A {approximately} 10 ns fwhm, 1.06 {micro}m, 0.6 J/cm{sup 2} laser incident through a glass slide heats a Na-bearing thin film, creating a plasma that generates a sodium vapor plume. A {approximately} 1 {micro}sec fwhm dye laser beam tuned to 5,890 {angstrom} is used for absorption measurement of the Na I resonant doublet by viewing parallel to the film surface. The dye laser light is coupled through a fiber to a spectrograph with a time-integrated CCD camera. A two-dimensional mapping of the Na vapor density is obtained through absorption measurements at different spatial locations. Time-of-flight and Doppler broadening of the absorption with {approximately} 0.1 {angstrom} spectral resolution indicate that the Na neutral vapor temperature is about 0.5 to 2 eV. Laser-induced-fluorescence from {approximately} 1 {times} 10{sup 12}-cm{sup {minus}3} Na I 3s-3p lines observed with a streaked spectrograph provides a signal level sufficient for {approximately} 0.06 {angstrom} wavelength shift measurements in a mock-up of an ion diode experiment.

Ching, C.H.; Bailey, J.E.; Lake, P.W.; Filuk, A.B.; Adams, R.G.; McKenney, J.

1996-06-01

176

Absorption and fluorescence spectroscopic characterisation of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry)  

NASA Astrophysics Data System (ADS)

The absorption and fluorescence behaviour of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry) in a pH 8 aqueous buffer solution is studied. The flavin adenine dinucleotide (FAD) cofactor of dCry is identified to be present in its oxidized form (FAD ox), and the 5,10-methenyltetrahydrofolate (MTHF) cofactor is found to be hydrolyzed and oxidized to 10-formyldihydrofolate (10-FDHF). The absorption and the fluorescence behaviour of dCry is investigated in the dark-adapted (receptor) state, the light-adapted (signalling) state, and under long-time violet light exposure. Photo-excitation of FAD ox in dCry causes a reductive electron transfer to the formation of anionic FAD semiquinone (FAD rad - ), and photo-excitation of the generated FAD rad - causes an oxidative electron transfer to the back formation of FAD ox. In light adapted dCry a photo-induced equilibrium between FAD ox and FAD rad - exists. The photo-cycle dynamics of signalling state formation and recovery is discussed. Quantum yields of photo-induced signalling state formation of about 0.2 and of photo-induced back-conversion of about 0.2 are determined. A recovery of FAD rad - to FAD ox in the dark with a time constant of 1.6 min at room temperature is found.

Shirdel, J.; Zirak, P.; Penzkofer, A.; Breitkreuz, H.; Wolf, E.

2008-09-01

177

Nuclear Magnetic Resonance and X-Ray Absorption Spectroscopic Studies of Lithium Insertion in Silver Vanadium Oxide Cathodes  

SciTech Connect

Structural studies have been carried out on Ag{sub 2}V{sub 4}O{sub 11} (silver vanadium oxide, SVO) and Li{sub x}Ag{sub 2}V{sub 4}O{sub 11}, lithiated SVO with x=0.72, 2.13, and 5.59 using nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy (XAS). Lithium-7 NMR indicates the formation of a solid electrolyte interphase layer on the x=0.72 sample and lithium intercalation into both octahedral and tetrahedral sites in the SVO lattice, and that most but not all of the Ag (I) is reduced prior to initiation of V(V) reduction. Vanadium-51 NMR studies of SVO and lithiated SVO show decreased crystallinity with increased lithiation, as previously reported. Silver XAS studies indicate the formation of metallic silver crystallites in all the lithiated samples. A comparison of X-ray absorption near edge spectroscopy spectra for vanadium in these samples with those of reference compounds shows that some reduction of vanadium (V) occurs in the lithiated SVO with x=0.72 and increases with further lithiation leading to the formation of V(IV) and V(III) species. The results of this study indicate that vanadium(V) reduction occurs in parallel with silver (I) reduction during the initial stages of SVO lithiation, leading ultimately to the formation of vanadium (IV) and (III) species with further lithiation.

Leifer,N.; Colon, A.; Martocci, k.; Greenbaum, S.; Alamgir, F.; Reddy, T.; Gleason, N.; Leising, R.; Takeuchi, E.

2007-01-01

178

Calibration method for spectroscopic systems  

DOEpatents

Calibration spots of optically-characterized material placed in the field of view of a spectroscopic system allow calibration of the spectroscopic system. Response from the calibration spots is measured and used to calibrate for varying spectroscopic system operating parameters. The accurate calibration achieved allows quantitative spectroscopic analysis of responses taken at different times, different excitation conditions, and of different targets. 3 figs.

Sandison, D.R.

1998-11-17

179

Spectroscopic determination of leaf biochemistry using band-depth analysis of absorption features and stepwise multiple linear regression  

USGS Publications Warehouse

We develop a new method for estimating the biochemistry of plant material using spectroscopy. Normalized band depths calculated from the continuum-removed reflectance spectra of dried and ground leaves were used to estimate their concentrations of nitrogen, lignin, and cellulose. Stepwise multiple linear regression was used to select wavelengths in the broad absorption features centered at 1.73 ??m, 2.10 ??m, and 2.30 ??m that were highly correlated with the chemistry of samples from eastern U.S. forests. Band depths of absorption features at these wavelengths were found to also be highly correlated with the chemistry of four other sites. A subset of data from the eastern U.S. forest sites was used to derive linear equations that were applied to the remaining data to successfully estimate their nitrogen, lignin, and cellulose concentrations. Correlations were highest for nitrogen (R2 from 0.75 to 0.94). The consistent results indicate the possibility of establishing a single equation capable of estimating the chemical concentrations in a wide variety of species from the reflectance spectra of dried leaves. The extension of this method to remote sensing was investigated. The effects of leaf water content, sensor signal-to-noise and bandpass, atmospheric effects, and background soil exposure were examined. Leaf water was found to be the greatest challenge to extending this empirical method to the analysis of fresh whole leaves and complete vegetation canopies. The influence of leaf water on reflectance spectra must be removed to within 10%. Other effects were reduced by continuum removal and normalization of band depths. If the effects of leaf water can be compensated for, it might be possible to extend this method to remote sensing data acquired by imaging spectrometers to give estimates of nitrogen, lignin, and cellulose concentrations over large areas for use in ecosystem studies.We develop a new method for estimating the biochemistry of plant material using spectroscopy. Normalized band depths calculated from the continuum-removed reflectance spectra of dried and ground leaves were used to estimate their concentrations of nitrogen, lignin, and cellulose. Stepwise multiple linear regression was used to select wavelengths in the broad absorption features centered at 1.73 ??m, 2.10 ??m, and 2.301 ??m that were highly correlated with the chemistry of samples from eastern U.S. forests. Band depths of absorption features at these wavelengths were found to also be highly correlated with the chemistry of four other sites. A subset of data from the eastern U.S. forest sites was used to derive linear equations that were applied to the remaining data to successfully estimate their nitrogen, lignin, and cellulose concentrations. Correlations were highest for nitrogen (R2 from 0.75 to 0.94). The consistent results indicate the possibility of establishing a single equation capable of estimating the chemical concentrations in a wide variety of species from the reflectance spectra of dried leaves. The extension of this method to remote sensing was investigated. The effects of leaf water content, sensor signal-to-noise and bandpass, atmospheric effects, and background soil exposure were examined. Leaf water was found to be the greatest challenge to extending this empirical method to the analysis of fresh whole leaves and complete vegetation canopies. The influence of leaf water on reflectance spectra must be removed to within 10%. Other effects were reduced by continuum removal and normalization of band depths. If the effects of leaf water can be compensated for, it might be possible to extend this method to remote sensing data acquired by imaging spectrometers to give estimates of nitrogen, lignin, and cellulose concentrations over large areas for use in ecosystem studies.

Kokaly, R. F.; Clark, R. N.

1999-01-01

180

Structural characterization of bimetallic nanomaterials with overlapping x-ray absorption edges  

NASA Astrophysics Data System (ADS)

We describe a data analysis method for extended x-ray absorption fine structure spectroscopy suitable for use with compounds of diverse form that contain overlapping absorption edges. This method employs direct concurrent analysis of the data—demonstrated here for cases involving two interfering metal edges—and does not utilize subtractive or data filtering strategies that have been previously used to address this challenge. Its generality and precision are demonstrated in analyses made on two model nanoscale samples: (1) a Ir-Pt nanoparticle system supported on ?-Al2O3 and (2) a hybrid system of Pt nanowires on which Au nanoparticles have been nucleated and grown at the nanowire tips, stacking faults, and twinning boundaries. The results obtained demonstrate the unique compositional and structural qualities of these two systems as well as the broader utility of the new x-ray absorption spectroscopy based protocol used to characterize them.

Menard, Laurent D.; Wang, Qi; Kang, Joo H.; Sealey, Andrew J.; Girolami, Gregory S.; Teng, Xiaowei; Frenkel, Anatoly I.; Nuzzo, Ralph G.

2009-08-01

181

Spectroscopic characterization of the excitation energy transfer in the fucoxanthin-chlorophyll protein of diatoms.  

PubMed

We characterized the energy transfer pathways in the fucoxanthin-chlorophyll protein (FCP) complex of the diatom Cyclotella meneghiniana by conducting ultrafast transient absorption measurements. This light harvesting antenna has a distinct pigment composition and binds chlorophyll a (Chl-a), fucoxanthin and chlorophyll c (Chl-c) molecules in a 4:4:1 ratio. We find that upon excitation of fucoxanthin to its S2 state, a significant amount of excitation energy is transferred rapidly to Chl-a. The ensuing dynamics illustrate the presence of a complex energy transfer network that also involves energy transfer from the unrelaxed or 'hot' intermediates. Chl-c to Chl-a energy transfer occurs on a timescale of a 100 fs. We observe no significant spectral evolution in the Chl-a region of the spectrum. We have applied global and target analysis to model the measured excited state dynamics and estimate the spectra of the states involved; the energy transfer network is discussed in relation to the pigment organization of the FCP complex. PMID:16172942

Papagiannakis, Emmanouil; H M van Stokkum, Ivo; Fey, Holger; Büchel, Claudia; van Grondelle, Rienk

2005-11-01

182

Spectroscopic characterization and catalytic activity of zeolite X containing occluded alkali species  

SciTech Connect

Samples of zeolite X containing occluded cesium oxide (prepared via decomposition of impregnated cesium acetate) and occluded alkali metal (prepared via decomposition of impregnated alkali azide) were synthesized, characterized, and tested as solid base catalysts. X-Ray absorption spectroscopy at the Cs L{sub III} edge was used to probe the local structure in zeolites containing exchangeable cesium cations and occluded cesium oxides. Since the Cs-O interatomic distances determined by EXAFS were similar in both the zeolites and reference compounds, the white line intensity was proposed to correlate with ionicity of the Cs-O bond. Infrared spectroscopy of adsorbed carbon dioxide and temperature-programmed desorption of CO{sub 2} confirmed that occlusion of cesium oxide in the zeolite pores created new strong base sites that were catalytically active in the decomposition of 2-propanol to acetone. Alkali metal-loaded zeolites were found to be catalysts for the side-chain alkenylation of o-xylene with 1,3-butadiene to form 5-o-tolyl-2-pentene. Results from ESR spectroscopy suggested that extralattice alkali metal clusters contribute to the formation of active species for alkenylation.

Doskocil, E.J.; Davis, R.J.

1999-12-10

183

Infrared spectroscopic, x-ray, and nanoscale characterization of strontium titanate thin films  

SciTech Connect

Attenuated total reflectance (ATR) measurements were performed using Fourier transform infrared (FTIR) spectroscopy in the ATR mode with a thallium iodobromide (KRS-5) crystal to measure the frequencies of the v{sub 3} and v{sub 4} phonon absorption bands in thin Sr titanate films deposited on single-crystal Y-Ba Cu oxide (YBCO), La aluminate, Mg oxide, and Sr titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements at frequencies above 400 cm{sup -1}. Atomic force microscopy (AFM) and x-ray diffraction (XRD) measurements were also made to further characterize the films. The measurements were repeated on single-crystal specimens of Sr titanate and the substrates for comparison. Softening in the frequency of the v{sub 4} transverse optical phonon in the lattice-mismatched films below the established value of 544 cm{sup -1} is indicative of the highly textured, polycrystalline ceramic nature of the films and is consistent with the XRD and AFM results.

Webb, J.D.; Moutinho, H.R.; Kazmerski, L.L. [National Renewable Energy Lab., Golden, CO (United States)] [National Renewable Energy Lab., Golden, CO (United States); Mueller, C.H.; Rivkin, T.V.; Treece, R.E. [Superconducting Core Technologies, Inc., Golden, CO (United States)] [Superconducting Core Technologies, Inc., Golden, CO (United States); Dalberth, M.; Rogers, C.T. [Colorado Univ., Boulder, CO (United States). Dept. of Physics] [Colorado Univ., Boulder, CO (United States). Dept. of Physics

1996-06-01

184

Infrared spectroscopic, x-ray, and nanoscale characterization of strontium titanate thin films  

SciTech Connect

Attenuated total reflectance (ATR) measurements were performed using Fourier transform infrared (FTIR) spectroscopy in the ATR mode with a thallium iodobromide (KRS-5) crystal to measure the frequencies of the {nu}{sub 3} and {nu}{sub 4} phonon absorption bands in thin strontium titanate films deposited on single-crystal yttrium-barium copper oxide (YBCO), lanthanum aluminate, magnesium oxide, and strontium titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements to be made at frequencies above 400 cm{sup {minus}1}. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements were also made to further characterize the films. The measurements were repeated on single-crystal specimens of strontium titanate and the substrates for comparison. Softening in the frequency of the {nu}{sub 4} transverse optical phonon in the lattice- mismatched films below the established value of 544 cm{sup {minus}1} is indicative of the highly textured, polycrystalline ceramic nature of the films and is consistent with the XRD and AFM results.

Webb, J.D.; Moutinho, H.R.; Kazmerski, L.L. [National Renewable Energy Lab., Golden, CO (United States); Mueller, C.H.; Rivkin, T.V.; Treece, R.E. [Superconducting Core Technologies, Inc., Golden, CO (United States); Dalberth, M.; Rogers, C.T. [Colorado Univ., Boulder, CO (United States). Dept. of Physics

1996-04-01

185

Infrared Spectroscopic, X-ray and Nanoscale Characterization of Strontium Titanate Thin Films  

SciTech Connect

Attenuated total reflectance (ATR) measurements were performed using Fourier transform infrared (FTIR) spectroscopy in the ATR mode with a thallium iodobromide (KRS-5) crystal to measure the frequencies of the v{sub 3} and v{sub 4} phonon absorption bands in thin strontium titanate films deposited on single-crystal yttrium-barium copper oxide (YBCO), lanthanum aluminate, magnesium oxide, and strontium titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements to be made at frequencies above 400 cm-1. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements were also made to further characterize the films. The measurements were repeated on single-crystal specimens of strontium titanate and the substrates for comparison. Softening in the frequency of the v{sub 4} transverse optical phonon in the lattice-mismatched films below the established value of 544 cm-1 is indicative of the highly textured, polycrystalline ceramic nature of the films and is consistent with the XRD and AFM results.

Webb, J. D.; Moutinho, H. R.; Kazmerski, L. L.; Mueller, C. H.; Rivkin, T. V.; Treece, R. E.; Dalberth, M.; Rogers, C. T.

1997-01-01

186

Synthesis and spectroscopic characterization of super-stable rhenium(V)porphyrins  

NASA Astrophysics Data System (ADS)

The preparation of rhenium(V) porphyrin complexes {?-oxo-bis[(oxo)(5,10,15,20-tetraphenyl-21H,23H-porphinato)rhenium(V)] [OReTPP]2O (1), (oxo)(phenoxo)(2,3,7,8,12,13,17,18-octaethyl-5-monophenyl-21H,23H-porphinato)rhenium(V) ORe(PhO)MPOEP (2), (cloro)(oxo)(2,3,7,8,12,13,17,18-octaethyl-5,15-diphenyl-21H,23H-porphinato)rhenium(V) ORe(Cl)5,15DPOEP (4), and (oxo)(phenoxo)(2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphinato)rhenium(V) ORe(PhO)OEP (5)} by the interaction of H2ReCl6 with corresponding porphyrin in boiling phenol is described. (Cloro)(oxo)(2,3,7,8,12,13,17,18-octaethyl-5-monophenyl-21H,23H-porphinato)rhenium(V) ORe(Cl)MPOEP (3) and (oxo)(chloro)(2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphinato)rhenium(V) ORe(Cl)OEP (6) have been prepared by the reaction of axial-ligand substitution from (2) and (5), respectively. Compounds (2-4) were newly synthesized. Characterization of the compounds (1-6) reported herein was made mainly by UV-Visible, IR, 1? NMR, 1H1H 2D COSY, 1H1H 2D DOSY, 1H1H 2D ROESY, 1H1H 2D TOCSY spectroscopic techniques and elemental analysis. The stability of the complexes in solutions when exposed to strong acids at the presence of atmospheric oxygen has been estimated. Compounds (2-4) and (6) show them super-stable since they do not undergo dissociation along MN bonds in concentrated H2SO4 under heating up to 363 K. Compounds (3) and (4) undergo one-electron oxidation to form stable ?-cation radicals ORe(HSO)P under these conditions. The products of the reaction between all studied porphyrins and concentrated H2SO4 were isolated in CHCl3 by reprecipitation onto ice and proved to be rhenium(V) complexes ORe(HSO4)P.

Bichan, N. G.; Tyulyaeva, E. Yu.; Khodov, I. A.; Lomova, T. N.

2014-03-01

187

In vitro characterization of the intestinal absorption of methylmercury using a Caco-2 cell model.  

PubMed

Methylmercury (CH3Hg) is one of the forms of mercury found in food, particularly in seafood. Exposure to CH3Hg is associated with neurotoxic effects during development. In addition, methylmercury has been classified by the International Agency for Research on Cancer as a possible human carcinogen. Although the diet is known to be the main source of exposure, few studies have characterized the mechanisms involved in the absorption of this contaminant. The present study examines the absorption process using the Caco-2 cell line as a model of the intestinal epithelium. The results indicate that transport across the intestinal cell monolayer in an absorptive direction occurs mainly through passive transcellular diffusion. This mechanism coexists with carrier-mediated transcellular transport, which has an active component. The participation of H(+)- and Na(+)-dependent transport was observed. Inhibition tests point to the possible participation of amino acid transporters (B(0,+) system, L system, and/or y(+)L system) and organic anion transporters (OATs). Our study suggests the participation in CH3Hg absorption of transporters that have already been identified as being responsible for the transport of this species in other systems, although further studies are needed to confirm their participation in intestinal absorption. It should be noted that CH3Hg experiences important cellular acumulation (48-78%). Considering the toxic nature of this contaminant, this fact could affect intestinal epithelium function. PMID:24397474

Vázquez, Marta; Vélez, Dinoraz; Devesa, Vicenta

2014-02-17

188

[The spectroscopic study of topaz].  

PubMed

In this paper, the natural gem material--Topaz (colorless transparent samples and reactor irradiation induced blue color samples) was studied on the spectroscopic analysis of Fourier transformation infrared spectrum (FTIR) and FT-Raman spectrum. The structure of topaz consists of OH groups and SiO4 groups. Si-O vibration spectrum was characterized with the group theoretical analysis. OH stretching modes of vibration showed many changes among the different color samples, the reason of the changes was explained. The color origin was preliminary investigated by ultra-violet and visible absorption spectrum. PMID:12953446

Wang, B; Tu, J

2000-02-01

189

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation  

NASA Astrophysics Data System (ADS)

Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at ?max 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 ?g ml -1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15±1.15, 99.30±1.40, 99.60±1.50, and 99.00±1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.

Ragab, Gamal H.; Amin, Alaa S.

2004-03-01

190

Spectroscopic determination of the toxicity, absorption, reduction, and translocation of Cr(VI) in two Magnoliopsida species.  

PubMed

Hexavalent chromium is a contaminant highly mobile in the environment that is toxic for plants at low concentrations. In this work, the physiological response of Convolvulus arvensis and Medicago truncatula plants to Cr(VI) treatments was compared. C. arvensis is a potential Cr hyperaccumulator well adapted to semiarid conditions that biotransform Cr(VI) to the less toxic Cr(III). M. truncatula is a model plant well adapted to semiarid conditions with a well studied genetic response to heavy metal stress. The results demonstrated that C. arvensis is more tolerant to Cr toxicity and has a higher Cr translocation to the leaves. The inductively coupled plasma optical emission spectroscopy results showed that C. arvensis plants treated with 10 mg Cr(VI) L(-1) accumulated 1512, 210, and 131 mg Cr kg(-1) in roots, stems, and leaves, respectively. While M. truncatula plants treated with the same Cr(VI) concentration accumulated 1081, 331, and 44 (mg Cr kg(-1)) in roots, stems, and leaves, respectively. Enzymatic assays demonstrated that Cr(VI) decreased ascorbate peroxidase activity and increased catalase activity in M. truncatula, while an opposite response was found in C. arvensis. The x-ray absorption spectroscopy studies showed that both plant species reduced Cr(VI) to the less toxic Cr(III). PMID:23487994

Montes, Milka O; Peralta-Videa, Jose R; Parsons, Jason G; Corral Diaz, Baltazar; Gardea-Torresdey, Jorge L

2013-01-01

191

X-ray absorption spectroscopic evidence for the complexation of Hg(II) by reduced sulfur in soil humic substances  

SciTech Connect

Analysis of Hg(II) complexed by a soil humic acid (HA) using synchrotron-based X-ray absorption spectroscopy (XAS) revealed the importance of reduces sulfur functional groups (thiol (R-SH) and disulfide (R-SS-R)/disulfane (R-SSH)) in humic substances in the complexation of Hg(II). A two-coordinate binding environment with one oxygen atom and one sulfur atom at distances of 2.02 and 2.38 {angstrom}, respectively, was found in the first coordination shell of Hg(II) complexed by humic acid. Model calculations show that a second coordination sphere could contain one carbon atom and a second sulfur atom at 2.78 and 2.93 {angstrom}, respectively. This suggests that in addition to thiol S, disulfide/disulfane S may be involved with the complexation of Hg(II) in soil organic matter. The appearance of carbon atom in the second coordination shell suggests that one O-containing ligand such as carboxyl and phenol ligands rather than H{sub 2}O molecule is bound to the Hg(II). The involvement of oxygen ligand in addition to the reduced S ligands in the complexation of Hg(II) is due to the low density of reduced S ligands in humic substances. The XAS results from this experiment provided direct molecular level evidence for the preference of reduced S functional groups over oxygen ligands by Hg(II) in the complexation with humic substances.

Xia, K. [Kansas State Univ., Manhattan, KS (United States). Dept. of Agronomy] [Kansas State Univ., Manhattan, KS (United States). Dept. of Agronomy; Skyllberg, U.L. [Swedish Univ. of Agricultural Sciences, Umeaa (Sweden). Dept. of Forest Ecology] [Swedish Univ. of Agricultural Sciences, Umeaa (Sweden). Dept. of Forest Ecology; Bleam, W.F.; Helmke, P.A. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Soil Science] [Univ. of Wisconsin, Madison, WI (United States). Dept. of Soil Science; Bloom, P.R.; Nater, E.A. [Univ. of Minnesota, St. Paul, MN (United States). Dept. of Soil, Water, and Climate] [Univ. of Minnesota, St. Paul, MN (United States). Dept. of Soil, Water, and Climate

1999-01-15

192

Synthesis, conformational and spectroscopic characterization of monomeric styrene derivatives having pendant p-substituted benzylic ether groups  

NASA Astrophysics Data System (ADS)

Three derivatives of styrene monomer, 4-chlorophenyl-4-vinylbenzyl ether (I), 4-methoxyphenyl-4-vinylbenzyl ether (II) and 4-ethylphenyl-4-vinylbenzyl ether (III) were synthesized. The synthesized two novel compounds (I and III) and one with undefined structural features were identified by experimental spectroscopic techniques and density functional approach. The optimized geometrical structure, vibrational and electronic transitions along with chemical shifts of those compounds were presented in this study. The vibrational spectra of investigated compounds were recorded in solid state with FT-IR spectrometry in the range of 4000-400 cm-1. The computational vibrational wavenumbers and also ground state equilibrium conformations were carried out by using density functional method with 6-311++G(d,p) basis set. Assignments of the fundamental vibrational modes were examined on the basis of the measured data and total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method. Isotropic chemical shift of hydrogen and carbon nuclei were investigated via observed 1H and 13C NMR spectra in deuterated DMSO solution and predicted data applied with gauge-invariant atomic orbitals (GIAOs) method. The UV absorption spectra of monomers were observed in the range of 200-800 nm in ethanol, and time dependent DFT method was used to obtain the electronic properties. A detailed description of spectroscopic behaviors of compound was given based on the comparison of experimental measurements and theoretical computations.

Cinar, Mehmet; Ozcan, Levent; Karabacak, Mehmet; Erol, Ibrahim

2013-07-01

193

Vibrational spectroscopic methods to characterize the bionanoparticles originating from newly developed self-forming synthetic PEGylated lipids (QuSomes)  

NASA Astrophysics Data System (ADS)

Vibrational spectroscopy has been used to elucidate the temperature dependence of structural and conformational changes in lipids and liposomes. In this work, the thermal properties of lipid-based nanovesicles originating from a newly developed self-forming synthetic PEGylated lipids has been investigated by variable-temperature Fourier-transform infrared (FTIR) absorption and Raman spectroscopic methods. Thermally-induced changes in infrared and Raman spectra of these artificial lipid based nanovesicles composed of 1,2-dimyristoyl-rac-glycerol-3-dodecaethylene glycol (GDM-12) and 1,2-distearoyl-rac-glycerol-3-triicosaethylene glycol (GDS-23) were acquired by using a thin layered FTIR spectrometer in conjunction with a unique custom built temperature-controlled demountable liquid cell and variable-temperature controlled Raman microscope, respectively. The lipids under consideration have long hydrophobic acyl chains and contain various units of hydrophilic polyethylene glycol headgroups. In contrast to conventional phospholipids, this new kind of lipid is forming liposomes or nanovesicles spontaneously upon hydration, without supplying external activation energy. We have found that the thermal stability of such PEGylated lipids and nanovesicles differs greatly depending upon the acyl chain-lengths as well as associated head group units. However, the thermal behavior observed from both spectroscopic vibrational techniques are in good agreement.

Bista, Rajan K.; Bruch, Reinhard F.; Covington, Aaron M.

2011-02-01

194

Raman Spectroscopic Characterization of CH_4 Density Over a Wide Range of Temperature and Pressure  

NASA Astrophysics Data System (ADS)

The relationship among the methane ?_1 band position, temperature, and density was obtained by in situ Raman spectroscopic method. A derived equation can be used to calculate the density of pure CH_4 in natural or synthetic CH_4-bearing inclusion.

Shang, L. B.; Chou, I.-M.; Burruss, R. C.; Hu, R. Z.; Bi, X. W.

2014-06-01

195

Preparation and structural, spectroscopic, thermal, and electrochemical characterizations of iron(III) compounds containing dipicolinate and 2-aminopyrimidine or acridine  

Microsoft Academic Search

Two new iron(III) compounds, (Hamp)[Fe(pydc)2]?·?2H2O (1) and (Hacr)[Fe(pydc)2]?·?2H2O (2) (pydc?=?pyridine-2,6-dicarboxylic acid, amp?=?2-aminopyrimidine, acr?=?acridine), have been hydrothermally synthesized. Both compounds were characterized by spectroscopic methods (IR, UV\\/Vis), and their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by thermogravimetric analysis\\/differential thermal analysis (TGA\\/DTA) methods. Compound 1 consists of Hamp cation and [Fe(pydc)2] anion and

Masoumeh Tabatabaee; Fatemeh Abbasi; Boris-Marko Kukovec; Navid Nasirizadeh

2011-01-01

196

Characterization of Mannitol Polymorphic Forms in Lyophilized Protein Formulations Using a Multivariate Curve Resolution (MCR)Based Raman Spectroscopic Method  

Microsoft Academic Search

Purpose  To develop a novel multivariate curve resolution (MCR)-based Raman spectroscopic method to characterize and quantify five\\u000a known mannitol solid-state forms in lyophilized protein formulations.\\u000a \\u000a \\u000a \\u000a Materials and Methods  The multivariate quantitation method was developed based on second derivative Raman spectra of three anhydrous crystalline\\u000a forms (?-, ?-, and ?-mannitol), a hemihydrate and an amorphous mannitol form. The method showed a 5% quantitation

Yong Xie; Wenjin Cao; Sampathkumar Krishnan; Hong Lin; Nina Cauchon

2008-01-01

197

Dichromated poly(vinyl alchohol)-xanthene dye systems: holographic characterization and electron spin resonance spectroscopic study  

NASA Astrophysics Data System (ADS)

Dichromated poly(vinyl alcohol)-xanthene dye (DCPVA-XD) systems have been employed as real-time holographic recording materials. In this paper, holographic characterization of dichromated poly(vinyl alcohol) with fluorescein (Fl), eosin Y (EY) and Rose Bengal (RB) is presented. In addition, a systematic ESR spectroscopic investigation was also performed on these systems. The photochemical evolution of Cr(V), Cr(III), polymer radical and dye radical in these systems has been monitored and a comparison is made.

Manivannan, Gurusamy; Changkakoti, Rupak; Lessard, Roger A.; Mailhot, Gilles; Bolte, Michel

1994-01-01

198

Lithium thiazolidine-4-carboxylate: synthesis, spectroscopic characterization and preliminary in vitro cytotoxic studies in human HeLa cells.  

PubMed

A new water-soluble lithium salt of thiazolidine-4-carboxylic acid was synthesized and characterized by chemical and spectroscopic techniques. Elemental and mass spectrometric (ESI-MS) analyses of the solid compound fit to the composition LiC(4)H(6)NSO(2). (1)H, (13)C nuclear magnetic resonance (NMR), [(1)H-(15)N] NMR and infrared (IR) analyses permitted to elucidate the structure of the compound. Biological activity was evaluated by cytotoxic analysis using HeLa cells. Determination of cell death was assessed using a tetrazolium salt colorimetric assay, which reflects the cells viability. PMID:18353709

Corbi, Pedro P; Andrade, Fabiana C; Massabni, Antonio C; Heinrich, Tassiele A; Souza, Pedro P C; Costa-Neto, Cláudio M

2008-12-01

199

Purification and spectroscopic characterization of photosystem II reaction center complexes isolated with or without Triton X-100.  

PubMed

The pigment composition of the isolated photosystem II reaction center complex in its most stable and pure form currently is a matter of considerable debate. In this contribution, we present a new method based on a combination of gel filtration chromatography and diode array detection to analyze the composition of photosystem II reaction center preparations. We show that the method is very sensitive for the detection of contaminants such as the core antenna protein CP47, pigment-free and denatured reaction center proteins, and unbound chlorophyll and pheophytin molecules. We also present a method by which the photosystem II reaction center complex is highly purified without using Triton X-100, and we show that in this preparation the contamination with CP47 is less than 0.1%. The results strongly indicate that the photosystem II reaction center complex in its most stable and pure form binds six chlorophyll a, two pheophytin a, and two beta-carotene molecules and that the main effect of Triton X-100 is the extraction of beta-carotene from the complex. Analysis of 4 K absorption and emission spectra indicates that the spectroscopic properties of this preparation are similar to those obtained by a short Triton X-100 treatment. In contrast, preparations obtained by long Triton X-100 treatment show decreased absorption of the shoulder at 684 nm in the 4 K absorption spectrum and an increased number of pigments that trap excitation energy at very low temperatures. We conclude that the 684 nm shoulder in the 4 K absorption spectrum should at least in part be attributed to the primary electron donor of photosystem II. PMID:8841130

Eijckelhoff, C; van Roon, H; Groot, M L; van Grondelle, R; Dekker, J P

1996-10-01

200

Synthesis, spectroscopic characterization and DNA nuclease activity of Cu(II) complexes derived from pyrazolone based NSO-donor Schiff base ligands.  

PubMed

Two neutral mononuclear Cu(II) complexes have been prepared in EtOH using Schiff bases derived from 4-toluoyl pyrazolone and thiosemicarbazide. Both the ligands have been characterized on the basis of elemental analysis, IR, (1)H NMR, (13)C NMR and mass spectral data. The molecular geometry of one of these ligands has been determined by single crystal X-ray study. It reveals that these ligands exist in amine-one tautomeric form in the solid state. Microanalytical data, Cu-estimation, molar conductivity, magnetic measurements, IR, UV-Visible, FAB-Mass, TG-DTA data and ESR spectral studies were used to confirm the structures of the complexes. Electronic absorption and IR spectra of the complexes suggest a square-planar geometry around the central metal ion. The interaction of complexes with pET30a plasmid DNA was investigated by spectroscopic measurements. Results suggest that the copper complexes bind to DNA via an intercalative mode and can quench the fluorescence intensity of EB bound to DNA. The interaction between the complexes and DNA has also been investigated by agarose gel electrophoresis, interestingly, we found that the copper(II) complexes can cleave circular plasmid DNA to nicked and linear forms. PMID:21993257

Vyas, Komal M; Joshi, Rushikesh G; Jadeja, R N; Prabha, C Ratna; Gupta, Vivek K

2011-12-15

201

Raman spectroscopic and visible absorption investigation of LiCrSi2O6 pyroxene under pressure.  

PubMed

The first observation of the vibrational spectrum of the synthetic pyroxene Li-kosmochlor (LiCrSi2O6) is reported herein. The Raman and visible spectra are reported as a function of pressure. Though the pyroxene retains its P21/c symmetry, changes in the Raman spectra are observed between 6.8 and 7.7 GPa, possibly due to the formation of an additional bond between Li and O3 or some other transition that retains the mineral's P21/c space group. Splitting of the peak appearing at approximately 700 cm(-1), used to characterize the P21/c phase in other studies, is not observed. Comparison is made with the Raman spectra of LiAlSi2O6 and LiFeSi2O6 in the P21/c phase and the visible spectra of NaCrSi2O6 at high pressures. PMID:18935826

Pommier, C J S; Redhammer, G J; Denton, M B; Downs, R T

2008-07-01

202

Anion pairs in room temperature ionic liquids predicted by molecular dynamics simulation, verified by spectroscopic characterization  

SciTech Connect

Molecular-level spectroscopic analyses of an aprotic and a protic room-temperature ionic liquid, BMIM OTf and BMIM HSO4, respectively, have been carried out with the aim of verifying molecular dynamics simulations that predict anion pair formation in these fluid structures. Fourier-transform infrared spectroscopy, Raman spectroscopy and nuclear magnetic resonance spectroscopy of various nuclei support the theoretically-determined average molecular arrangements.

Schwenzer, Birgit; Kerisit, Sebastien N.; Vijayakumar, M.

2014-01-01

203

Characterization of the influence of nitric oxide donors on intestinal absorption of macromolecules.  

PubMed

To characterize the influence of nitric oxide (NO) donors on the intestinal absorption of macromolecules, the relationship between the release rate of NO from NO donors and their absorption-enhancing effects and the effects of several scavengers and generators on the absorption-enhancing effects of NO donor were investigated. The t1/2 values of the NO release rate from 3-(2-hydroxy-1-methylethyl-2-nitrosohydrazino)-1-propanamine (NOC5), 3-(2-hydroxy-1-methylethyl-2-nitrosohydrazino)-N-methyl-1-propanamine (NOC7) and N-ethyl-2-(1-ethyl-hydroxy-2-nitrosohydrazino)-ethanamine (NOC12) are 25, 5 and 100min, respectively. The absorption-enhancing effects of NO donors on the absorption of fluorescein isothiocyanate dextrans with an average molecular weight of 4400 (FD-4) are NOC5 > NOC7 > NOC12 in the colon. The lowest enhancing effect of NOC12 may be due to the slow rate of NO release. The enhancing effect of NOC7 rapidly disappeared compared with the effect of NOC5. The results raise the possibility that the difference between NOC5 and NOC7 on enhancing effect is related to the t1/2 of the NO release. The NOC7-induced enhancing effect was prevented by the co-administration of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazole-1-oxyl-3-oxide sodium salt (C-PTIO), an NO scavenger; tiron, an O2(-) scavenger; mannitol, an OH* scavenger, and deferoxamine, peroxynitrate scavenger. Pyrogallol, an O2(-) generator, potentiated the NOC7-induced enhancing effect. These results support a role for peroxynitrate, and possibly OH*, in the NO donor-induced intestinal enhancing effect. PMID:15501005

Takahashi, Koichi; Numata, Nanako; Kinoshita, Natsumi; Utoguchi, Naoki; Mayumi, Tadanori; Mizuno, Nobuyasu

2004-11-22

204

X-ray Absorption Spectroscopic and Theoretical Studies on (L)2[Cu2(S2)n]2+ Complexes: Disulfide Versus Disulfide(o1-) Bonding  

PubMed Central

Cu K-, L- and S K-edge X-ray absorption spectroscopic (XAS) data have been combined with density functional theory (DFT) calculations on [{(TMPA)Cu}2S2](ClO4)2 (1), [{Cu[HB(3,5-Pri2pz)3]}2(S2)] (2) and [{(TMEDA)Cu}2(S2)2](OTf)2 (3) to obtain a quantitative description of their ground state wavefunctions. The Cu L-edge intensities give 63% and 37% Cu d-character in the ground state of 1 and 2, respectively while the S K-pre-edge intensities reflect 20% and 48% S character in their ground states. These data indicate a more than two-fold increase in the total disulfide bonding character in 2 relative to 1. The increase in the number of Cu-S bonds in 2 (µ-?2:?2 S22? bridge) compared to 1 ((µ-?1:?1 S22? bridge), dominantly determines the large increase in covalency and Cu-disulfide bond strength in 2. Cu K- and L- and S K-pre-edge energy positions directly demonstrate the CuII/(S2?)2 nature of 3. The two disulfide(•1?)’s in 3 undergo strong bonding interactions which destabilize the resultant filled antibonding ?* orbitals of the (S2?)2 fragment relative to the Cu 3d levels. This leads to an inverted bonding scheme in 3 with dominantly ligand based holes in its ground state, consistent with its description as a dicopper(II)-bis-disulfide(•1?) complex.

Sarangi, Ritimukta; York, John T.; Helton, Matthew E.; Fujisawa, Kiyoshi; Karlin, Kenneth D.; Tolman, William B.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.

2008-01-01

205

X-Ray Absorption Spectroscopic And Theoretical Studies on (L)(2)[Cu-2(S-2)N](2+) Complexes: Disulfide Versus Disulfide(Center Dot 1-) Bonding  

SciTech Connect

Cu K-, Cu L-, and S K-edge X-ray absorption spectroscopic (XAS) data have been combined with density functional theory (DFT) calculations on [{l_brace}(TMPA)Cu{r_brace}{sub 2}S{sub 2}](ClO{sub 4}){sub 2} (1), [{l_brace}Cu[HB(3,5-Pr{sub 2}{sup i}pz){sub 3}]{r_brace}{sub 2}(S{sub 2})] (2), and [{l_brace}(TMEDA)Cu{r_brace}{sub 2}(S{sub 2}){sub 2}](OTf){sub 2} (3) to obtain a quantitative description of their ground state wavefunctions. The Cu L-edge intensities give 63 and 37% Cu d-character in the ground state of 1 and 2, respectively, whereas the S K-pre-edge intensities reflect 20 and 48% S character in their ground states, respetively. These data indicate a more than 2-fold increase in the total disulfide bonding character in 2 relative to 1. The increase in the number of Cu?S bonds in 2 ({mu}-{eta}{sup 2}:{eta}{sup 2} S{sub 2}{sup 2-} bridge) compared to 1 ({mu}-{eta}{sup 1}:{eta}{sup 1} S{sub 2}{sup 2-} bridge) dominantly determines the large increase in covalency and Cu-disulfide bond strength in 2. Cu K- and L- and S K-pre-edge energy positions directly demonstrate the Cu{sup II}/(S{sub 2}{sup -}){sub 2} nature of 3. The two disulfide({center_dot}1?)'s in 3 undergo strong bonding interactions that destabilize the resultant filled antibonding {pi}* orbitals of the (S{sub 2}{sup -}){sub 2} fragment relative to the Cu 3d levels. This leads to an inverted bonding scheme in 3 with dominantly ligand-based holes in its ground state, consistent with its description as a dicopper(II)-bis-disulfide({center_dot}1?) complex.

Sarangi, R.; York, J.T.; Helton, M.E.; Fujisawa, K.; Karlin, K.D.; Tolman, W.B.; Hodgson, K.O.; Hedman, B.; Solomon, E.I.; /Stanford U., Chem. Dept. /SLAC, SSRL /Minnesota U. /Johns Hopkins U. /Tsukuba U.

2009-04-30

206

An integrated spectroscopic approach to the chemical characterization of pyrolysis oils  

SciTech Connect

The hydrocarbon (''oil'') fraction of a coal pyrolysis tar prepared by open column liquid chromatography (LC) was separated into 16 subfractions by a second LC run. The first 13 of these fractions were chosen for integrated spectroscopic analysis. Low voltage mass spectrometry (MS), infrared spectroscopy (IR), and proton (PMR) as well as carbon -13 nuclear magnetic resonance spectrometry (CMR) were performed on the 13 fractions. Computerized multivariate analysis procedures such as factor or discriminant analysis followed by canonical correlation techniques were used to extract the overlapping information from the analytical data.

Hoesterey, B.L.; Windig, W.; Meuzelaar, H.L.C.; Eyring, E.M.; Grant, D.M.; Pugmire, R.J.

1987-04-01

207

The PtAl(-) and PtAl2(-) anions: theoretical and photoelectron spectroscopic characterization.  

PubMed

We report a joint photoelectron spectroscopic and theoretical study of the PtAl(-) and PtAl2(-) anions. The ground state structures and electronic configurations of these species were identified to be C?v, (1)?(+) for PtAl(-), and C2v, (2)B1 for PtAl2(-). Structured anion photoelectron spectra of these clusters were recorded and interpreted using ab initio calculations. Good agreement between theory and experiment was found. All experimental features were successfully assigned to one-electron transitions from the ground state of the anions to the ground or excited states of the corresponding neutral species. PMID:24784279

Zhang, Xinxing; Ganteför, Gerd; Bowen, Kit H; Alexandrova, Anastassia N

2014-04-28

208

Spectroscopic and Computational Characterization of Substrate-Bound Mouse Cysteine Dioxygenase: Nature of the Ferrous and Ferric Cysteine Adducts and Mechanistic Implications †  

PubMed Central

Cysteine dioxygenase (CDO) is a mononuclear non-heme Fe-dependent dioxygenase that catalyzes the initial step of oxidative cysteine catabolism. Its active site consists of an Fe(II) ion ligated by three histidine residues from the protein, an interesting variation on the more common 2-His-1-carboxylate motif found in many other non-heme Fe(II)-dependent enzymes. Multiple structural and kinetic studies of CDO have been carried out recently, resulting in a variety of proposed catalytic mechanisms; however, many open questions remain regarding the structure/function relationships of this vital enzyme. In this study, resting and substrate-bound forms of CDO in the Fe(II) and Fe(III) states, both of which are proposed to have important roles in this enzyme’s catalytic mechanism, were characterized by utilizing various spectroscopic methods. The nature of the substrate/active-site interactions was also explored using the cysteine analog selenocysteine (Sec). Our electronic absorption, magnetic circular dichroism, and resonance Raman data exhibit features characteristic of direct S (or Se) ligation to both the high-spin Fe(II) and Fe(III) active-site ions. The resulting Cys (or Sec)-bound species were modeled and further characterized using density functional theory computations to generate experimentally validated geometric and electronic structure descriptions. Collectively, our results yield a more complete description of several catalytically relevant species and provide support for a reaction mechanism similar to that established for many structurally related 2-His-1-carboxylate Fe(II)-dependent dioxygenases.

Gardner, Jessica D.; Pierce, Brad S.; Fox, Brian G.; Brunold, Thomas C.

2010-01-01

209

Biochemical and spectroscopic characterization of the blue-green photoreceptor in Halobacterium halobium  

SciTech Connect

Spectroscopic evidence indicates the presence of a second sensory receptor sR-II in Halobacterium halobium, which causes a repellent response to blue-green light. Reactions with hydroxylamine and NaCNBH/sub 3/ and reconstitution of the bleached pigment with retinal show that it is very similar to the other retinylidene pigments bacteriorhodopsin, halorhodopsin, and especially the earlier-discovered phototaxis receptor, sensory rhodopsin, renamed sR-I587. The second sensory receptor, sR-II480, has an absorbance maximum at 480 nm and undergoes a cyclic photoreaction with a half-time of approximately 200 msec. Its predominant photocycle intermediate absorbs maximally near 360 nm. The receptor can be detected spectroscopically in the presence of sR-I587 and quantitated through its transient response to 450-nm excitation. It is selectively bleached by low hydroxylamine concentrations that are insufficient to bleach sR-I587 significantly. Its photochemical and phototactic activities can be restored by addition of retinal. The mobility of the receptor, on NaDodSO4/polyacrylamide gels, was similar or identical to that of sR-I587 and slightly faster than bacteriorhodopsin, yielding an apparent molecular mass of 23-24 kDa.

Scherrer, P.; McGinnis, K.; Bogomolni, R.A.

1987-01-01

210

Spectroscopic characterization of metal bound phytochelatin analogue (Glu-Cys)4-Gly.  

PubMed

The metal ion binding properties of a phytochelatin (PC) analogue, (Glu-Cys)4-Gly (named as EC4), have been studied by a divalent metal ion binding assay monitored by UV-visible spectroscopy, circular dichroism and NMR spectroscopy. Spectro- photometric titration with different divalent metal ions have revealed that the stiochoimetry of metal-bound EC4 was 1:1, and its metal binding affinities with different divalent metal ions in the order of Cd(II)>Cu(II)>Zn(II)>Pb(II)>Ni(II)>Co(II). UV-visible spectroscopic analysis of metal complexes indicated that four sulfur atoms in cysteine residues are attributable to ligand-to-metal charge transfer (LMCT) between divalent metal ions and EC4, and further confirmed by 1D H1 NMR study and Circular Dichroism. In addition, Circular Dichroism spectra of both free and metal-bound forms of EC4 revealed that metal coordination drives the nonapeptide chain to fold into a turned conformation. The comprehensive analysis of spectroscopic properties of the nonapeptide complexed with metal ions not only provides a fundamental description of the metal ion binding properties of PC analogue, but also shows a correlation between metal binding affinity of PC analogue and the induction activity of metal ions. PMID:16051366

Cheng, Yongsheng; Yan, Yong-Bin; Liu, Jinyuan

2005-10-01

211

Optical absorption under total internal reflection in the characterization of soot in diesel engine oils  

NASA Astrophysics Data System (ADS)

Optical absorption of infrared radiation under total internal reflection in a novel sensor has been utilized to investigate the soot contamination of diesel engine oil by response surface methodology in factorial experiments. Sensor response showed highly significant dependence on oil soot concentration and temperature, in which the effect of the soot was greatest. The soot contamination of the optical rod in engine oil was found to be a surface phenomenon which showed little or no dependence on bulk oil shearing displacement below 500 rpm. The quadratic effect of sensor response to soot concentration was very high due to the agglomeration of soot particles, derived from the high surface energy of carbon soot. Test results of this optical absorption technique were in conformance with those other oil analysis techniques such as UV spectrophotometry, total acid number, viscosimetry, optical microscopy and EPMA. The technique proved to be more reliable than RDE emission spectrometry which showed ambiguous results due to colloidal suspension of soot particles in oil. Optical absorption proved to be an effective criterion in characterizing the soot contamination of diesel engine oil.

Ossia, C. V.; Kong, H.; Markova, L. V.; Myshkin, N. K.

2009-01-01

212

Errors in spectroscopic measurements of SOâ due to nonexponential absorption of laser radiation, with application to the remote monitoring of atmospheric pollutants  

Microsoft Academic Search

Methods of measuring the concentration of atmospheric pollutants by laser absorption spectroscopy, such as differential absorption lidar (DIAL) and integrated long-path techniques, all rely on the validity of Beer's exponential absorption law. It is shown here that departures from this law occur if the probing laser has a bandwidth larger than the wavelength scale of structure in the absorption spectrum

D. J. Brassington; T. M. Moncrieff; R. C. Felton; B. W. Jolliffe; B. R. Marx; W. R. C. Rowley; P. T. Woods

1984-01-01

213

Time-resolved spectroscopic characterization of a novel photodecarboxylation reaction mediated by homolysis of a carbon ?-bond in flurbiprofen.  

PubMed

Flurbiprofen (Fp), a nonsteroidal anti-inflammatory drug (NSAID) currently in use for arthritis pain relief and in clinical trials for metastatic prostate cancer, can induce photosensitization and phototoxicity upon exposure to sunlight. The mechanisms responsible for Fp phototoxicity are poorly understood and deserve investigation. In this study, the photodecarboxylation reaction of Fp, which has been assumed to underpin its photoinduced side effects, was explored by femtosecond transient absorption (fs-TA), nanosecond transient absorption (ns-TA), and nanosecond time-resolved resonance Raman (ns-TR(3)) spectroscopic techniques in pure acetonitrile (MeCN) solvent. Density functional theory (DFT) calculations were also performed to facilitate the assignments of transient species. The resonance Raman and DFT calculation results reveal that the neutral form of Fp was the predominant species present in MeCN. Analysis of the ultraviolet/visible absorption spectrum and results from TD-DFT calculations indicate that the second excited singlet (S2) can be excited by 266 nm light. Due to its intrinsic instability, S2 rapidly underwent internal conversion (IC) to decay to the lowest lying excited singlet (S1), which was observed in the fs-TA spectra at very early delay times. Intriguingly, three distinct pathways for S1 decay seem to coexist. Specifically, other than fluorescence emission back to the ground state and transformation to the lowest triplet state T1 through intersystem crossing (ISC), the homolysis of the carbon ?-bond decarboxylation reaction proceeded simultaneously to give rise to two radical species, one being carboxyl and another being the residual, denoted as FpR. The coexistence of the triplet Fp (T1) and FpR species was verified by means of TR(3) spectra along with ns-TA spectra. As a consequence of its apparent high reactivity, the FpR intermediate was observed to undergo oxidation under oxygen-saturated conditions to yield another radical species, denoted as FOR, which subsequently underwent intramolecular hydrogen transfer (IHT) and dehydroxylation (DHO) to form a final product, which could react with the carboxyl from the decarboxylation reaction to generate a minor final product. TD-DFT and transient state (TS) calculations for predicting the absorption bands and activation energies of the transient species produced in the photodecarboxylation reaction have provided valuable mechanistic insights for the assignment of the intermediate species observed in the time-resolved spectroscopy experiments reported here. The results of the time-resolved spectroscopy experiments and DFT calculations were used to elucidate the reaction mechanisms and intermediates involved in the photochemistry of Fp. PMID:23750456

Su, Tao; Ma, Jiani; Wong, Naikei; Phillips, David Lee

2013-07-18

214

Characterization of a new modular decay total absorption gamma-ray spectrometer (DTAS) for FAIR  

NASA Astrophysics Data System (ADS)

Beta-decay studies are one of the main goals of the DEcay SPECtroscopy experiment (DESPEC) to be installed at the future Facility for Antiproton and Ion Research (FAIR). DESPEC aims at the study of nuclear structure of exotic nuclei. A new modular Decay Total Absorption gamma-ray Spectrometer (DTAS) is being built at IFIC and is specially adapted to studies at fragmentation facilities such as the Super Fragment Separator (Super-FRS) at FAIR. The designed spectrometer is composed of 16 identical NaI(Tl) scintillation crystals. This work focuses on the characterization of these independent modules, as an initial step for the characterization of the full spectrometer. Monte Carlo simulations have been performed in order to understand the detector response.

Pizá, A. Montaner; Taín, J. L.; Agramunt, J.; Algora, A.; Guadilla, V.; Marín, E.; Rice, S.; Rubio, B.

2013-06-01

215

Characterization of a new modular decay total absorption gamma-ray spectrometer (DTAS) for FAIR  

SciTech Connect

Beta-decay studies are one of the main goals of the DEcay SPECtroscopy experiment (DESPEC) to be installed at the future Facility for Antiproton and Ion Research (FAIR). DESPEC aims at the study of nuclear structure of exotic nuclei. A new modular Decay Total Absorption gamma-ray Spectrometer (DTAS) is being built at IFIC and is specially adapted to studies at fragmentation facilities such as the Super Fragment Separator (Super-FRS) at FAIR. The designed spectrometer is composed of 16 identical NaI(Tl) scintillation crystals. This work focuses on the characterization of these independent modules, as an initial step for the characterization of the full spectrometer. Monte Carlo simulations have been performed in order to understand the detector response.

Montaner Piza, A.; Tain, J. L.; Agramunt, J.; Algora, A.; Guadilla, V.; Marin, E.; Rice, S.; Rubio, B. [Instituto de Fisica Corpuscular, CSIC-Univ. de Valencia, Apdo. Correos 22085, E-46071 Valencia (Spain)

2013-06-10

216

Potential approaches to the spectroscopic characterization of high performance polymers exposed to energetic protons and heavy ions  

NASA Technical Reports Server (NTRS)

A potential limitation to human activity on the lunar surface or in deep space is the exposure of the crew to unacceptably high levels of penetrating space radiations. The radiations of most concerns for such missions are high-energy protons emitted during solar flares, and galactic cosmic rays which are high-energy ions ranging from protons to iron. The development of materials for effective shielding from energetic space radiations will clearly require a greater understanding of the underlying mechanisms of radiation-induced damage in bulk materials. This can be accomplished in part by the detailed spectroscopic characterization of bulk materials that were exposed to simulated space radiations. An experimental data base thus created can then be used in conjunction with existing radiation transport codes in the design and fabrication of effective radiation shielding materials. Electron Paramagnetic Resonance Spectroscopy was proven very useful in elucidating radiation effects in polymers (high performance polymers are often an important components of structural composites).

Suleman, Naushadalli K.

1991-01-01

217

Studies related to Norway spruce galactoglucomannans: chemical synthesis, conformation analysis, NMR spectroscopic characterization, and molecular recognition of model compounds.  

PubMed

Galactoglucomannan (GGM) is a polysaccharide mainly consisting of mannose, glucose, and galactose. GGM is the most abundant hemicellulose in the Norway spruce (Picea abies), but is also found in the cell wall of flax seeds, tobacco plants, and kiwifruit. Although several applications for GGM polysaccharides have been developed in pulp and paper manufacturing and the food and medical industries, attempts to synthesize and study distinct fragments of this polysaccharide have not been reported previously. Herein, the synthesis of one of the core trisaccharide units of GGM together with a less-abundant tetrasaccharide fragment is described. In addition, detailed NMR spectroscopic characterization of the model compounds, comparison of the spectral data with natural GGM, investigation of the acetyl-group migration phenomena that takes place in the polysaccharide by using small model compounds, and a binding study between the tetrasaccharide model fragment and a galactose-binding protein (the toxin viscumin) are reported. PMID:23008171

Ekholm, Filip S; Ardá, Ana; Eklund, Patrik; André, Sabine; Gabius, Hans-Joachim; Jiménez-Barbero, Jesús; Leino, Reko

2012-11-01

218

Synthesis, spectroscopic characterization and structural investigations of new adduct compound of carbazole with picric acid: DNA binding and antimicrobial studies  

NASA Astrophysics Data System (ADS)

Carbazole picrate (CP), a new organic compound has been synthesized, characterized by various analytical and spectroscopic technique such as FT-IR, UV-Vis, 1H and 13C NMR spectroscopy. An orthorhombic geometry was proposed based on single crystal XRD study. The thermal stability of the crystal was studied by using thermo-gravimetric and differential thermal analyses and found that it was stable up to 170 °C. Further, the newly synthesized title compound was tested for its in vitro antibacterial and antifungal activity against various bacterial and fungal species. Also, the compound was tested for its binding activity with Calf thymus (CT) DNA and the results show a considerable interaction between CP and CT-DNA.

Saravanabhavan, Munusamy; Sathya, Krishnan; Puranik, Vedavati G.; Sekar, Marimuthu

2014-01-01

219

In situ x-ray absorption spectroscopic study of the Li[Ni1/3Co1/3Mn1/3]O2 cathode material  

NASA Astrophysics Data System (ADS)

The layered LiNi1/3Co1/3Mn1/3O2 system has recently drawn considerable interest for use as a cathode material for rechargeable lithium batteries. In order to investigate the charge-compensation mechanism and structural perturbations occurring in the system during cycling, in situ x-ray absorption spectroscopy (XAS) measurements were performed utilizing a novel electrochemical in situ cell specifically designed for long term x-ray experiments. The cell was cycled at a moderate rate through a typical Li-ion battery operating voltage range (2.9-4.7 V). The electrode contained 2.025 mg of LiNi1/3Co1/3Mn1/3O2 on a 25-?m Al foil and had an area of 0.79 cm2. The x-ray absorption spectroscopy (XAS) measurements were performed at the Ni, Co, and the Mn edges at different states of charge (SOC) during cycling, revealing details about the response of the cathode to Li insertion and extraction processes. Changes of bond distance and coordination number of Ni, Co, and Mn absorbers as a function of the state of charge of the material were obtained from the extended x-ray-absorption fine structure (EXAFS) region of the spectra. The x-ray absorption near-edge structure (XANES) region was studied in order to characterize the oxidation states of the 3d transition metals during cycling (Li extraction/insertion). We found that oxidation states of transition metals in LiNi1/3Co1/3Mn1/3O2 are Ni2+, Co3+, and Mn4+, whereas during charging Ni2+ is oxidized to Ni4+ through an intermediate stage of Ni3+, Co3+ is oxidized almost to Co4+ and, utilizing Faraday's calculation and XAS results, the Co was found to be at Co3.92+ at the end of the charge, while Mn was found to be electrochemically inactive and remains as Mn4+. The EXAFS data that were collected continuously during cycling revealed details about the response of the cathode to Li insertion and extraction. These measurements on the LiNi1/3Co1/3Mn1/3O2 cathode confirmed that the material retains its symmetry and good structural short-range order leading to superior cycling.

Deb, Aniruddha; Bergmann, Uwe; Cramer, Stephen P.; Cairns, Elton J.

2005-06-01

220

Characterization of the SEI on a carbon film electrode by combinedEQCM and spectroscopic ellipsometry  

SciTech Connect

The electrochemical quartz crystal microbalance (EQCM) andcyclic voltammetry have been applied simultaneously to characterizeelectron-beam deposited carbon film electrodes in LiClO4 orLiPF6-containing mixed electrolytes of ethylene carbonate (EC) anddimethyl carbonate (DMC). The structure of the carbon electrode was foundto be amorphous/disordered using Raman spectroscopy. Cyclic voltammetryin LiClO4 / EC+DMC demonstrated features typical of Liintercalation/deintercalation into/from the disordered carbon electrode,and EQCM showed a corresponding mass increase/decrease. Contrary to thecase of LiClO4 / EC+DMC electrolyte, LiPF6/EC+DMC electrolyte showed noLi deintercalation out of the thin-film carbon electrode. Combined EQCMand spectroscopic ellipsometry data were compared, and the solidelectrolyte interphase density after the first cycle in LiClO4 /EC+DMCwas estimated to be 1.3 g/cm3.

evans@socrates.berkeley.edu

2002-01-01

221

Characterization of Arsenic Ultra-Shallow Junctions in Silicon Using Photocarrier Radiometry and Spectroscopic Ellipsometry  

NASA Astrophysics Data System (ADS)

Photocarrier radiometry (PCR) and spectroscopic ellipsometry (SE) techniques were employed to measure ultra-shallow junction (USJ) wafers. These USJ wafers were prepared by As+ ion implantation at energies of 0.5 keV to 5 keV, at a dose of 1 × 1015 As+/cm2 and spike annealing. The experimental data showed that the PCR signal versus implantation energy exhibits a monotonic behavior. The damaged layer of the as-implanted wafer and the recrystallization and activation of the post-annealed wafer were evaluated by SE in the spectral range from 0.27 ?m to 20 ?m. PCR and SE were shown to provide non-destructive metrology tools for process monitoring in USJ fabrication.

Huang, Qiuping; Li, Bincheng; Gao, Weidong

2012-11-01

222

Synthesis and spectroscopic characterization of copper(II) tetraazaiminooxime macrocyclic complexes—A tetragonal distortion analysis  

Microsoft Academic Search

Herein we describe the synthesis and spectroscopic (infrared and UV–vis) analysis of [CuII(dohpn)(L)]n+ (dohpn=imineoximic tetraazamacrocyclic ligand 2,3,9,10-tetramethyl-1,4,8,11-tetraazaundecane-1,3,8,10-tetraen-11-ol-1-olate) and L=SCN?, I?, Cl? (n=0) and 4-aminopyridine (ampy), 4,4?-bipyridine (bipy), imidazole (im), 2-aminopyrazine (ampz) and water (n=1+). The following order of the Jahn-Teller stabilization energy (cm?1) was observed: I?(6452)

Gisele Marina Protasiewyck; Fábio Souza Nunes

2006-01-01

223

Synthesis and spectroscopic characterization of copper(II) tetraazaiminooxime macrocyclic complexes—A tetragonal distortion analysis  

NASA Astrophysics Data System (ADS)

Herein we describe the synthesis and spectroscopic (infrared and UV-vis) analysis of [Cu II(dohpn)(L)] n+ (dohpn = imineoximic tetraazamacrocyclic ligand 2,3,9,10-tetramethyl-1,4,8,11-tetraazaundecane-1,3,8,10-tetraen-11-ol-1-olate) and L = SCN -, I -, Cl - ( n = 0) and 4-aminopyridine (ampy), 4,4'-bipyridine (bipy), imidazole (im), 2-aminopyrazine (ampz) and water ( n = 1+). The following order of the Jahn-Teller stabilization energy (cm -1) was observed: I -(6452) < Cl -(6477) < NCS -(6494) < ampy(6562) < im(6614) < bipy(6685) < ampz(6739) < H 2O(7813) and the energy of the crystal field transition was correlated with the tetragonal distortion in the structures.

Protasiewyck, Gisele Marina; Nunes, Fábio Souza

2006-11-01

224

Chemical and spectroscopic characterization of water extractable organic matter during vermicomposting of cattle dung.  

PubMed

This work illustrated the characteristics and transformation of water extractable organic matter (WEOM) during vermistabilization (Eisenia fetida) of cattle dung by means of chemical and spectroscopic methods. The independent experiment conducted in triplicate was sampled at the 0, 7, 14, 21, 35, 60 and 90days. Results showed that the DOC kept steady around 2.7gkg(-1) after day 60 and the DOC/DON ratio decreased from 19.77 to 5.26 till the end of vermicomposting. On the other hand, vermicomposting decreased the aliphatic, proteinaceous, carbohydrates components and increased the aromaticity and oxygen-containing functional groups in the WEOM. Moreover, fluorescence spectra and fluorescence regional integration (FRI) results indicated that protein-like groups were degraded and fulvic and humic acid-like compounds were evolved during the vermicomposting process. In all, this study suggested the suitability of WEOM for monitoring the organics transformation and assessing the maturity in the vermicomposting. PMID:23416619

Lv, Baoyi; Xing, Meiyan; Yang, Jian; Qi, Wensheng; Lu, Yongsen

2013-03-01

225

Characterization of novel lithium battery cathode materials by spectroscopic methods: the Li5+xFeO? system.  

PubMed

The novel, lithium-rich oxide-phase Li?FeO? (LFO) could, in theory, deliver a specific capacity >900 mAh/g when deployed as a cathode or cathode precursor in a battery with a lithium-based anode. However, research results to date on LFO indicate that less than one of the five Li? cations can be reversibly de-intercalated/re-intercalated during repetitive charging and discharging cycles. In the present research, the system Li5+xFeO? with x values in the range of 0.0-2.0 was investigated by a combination of Raman and X-ray absorption spectroscopic methods supported by X-ray diffraction (XRD) analysis in order to determine if the Li?FeO? lattice would accommodate additional Li? ions, with concomitant lowering of the valence on the FeIII cations. Both the Raman phonon spectra and the XRD patterns were invariant for all values of x, strongly indicating that additional Li? did not enter the Li?FeO? lattice. Also, Raman spectral results and high-resolution synchrotron XRD data revealed the presence of second-phase Li?O in all samples with x greater than 0.0. Synchrotron X-ray absorption spectroscopy at the Fe k? edge performed on the sample with a Li-Fe ratio of 7.0 (i.e., x = 2.0) showed no evidence for the presence of FeII. This resistance to accepting more lithium into the Li?FeO? structure is attributed to the exceedingly stable nature of high-spin FeIII in tetrahedral "FeIIIO?" structural units of Li?FeO?. Partial substitution of the FeIII with other cations could provide a path toward increasing the reversible Li? content of Li5xFeO?-type phases. PMID:23876729

Maroni, Victor A; Johnson, Christopher S; Rood, Shawn C M; Kropf, A Jeremy; Bass, Dean A

2013-08-01

226

Spectroscopic characterization of dissolved organic matter isolates from sediments and the association with phenanthrene binding affinity.  

PubMed

In this study, selected spectroscopic characteristics of sediment organic matter (SOM) were compared and discussed with respect to their different isolation methods, the source discrimination capabilities, and the association with the extent of phenanthrene binding. A total of 16 sediments were collected from three categorized locations including a costal lake, industrial areas, and upper streams, each of which is likely influenced by the organic sources of algal production, industrial effluent, and terrestrial input, respectively. The spectroscopic properties related to aromatic structures and terrestrial humic acids were more pronounced for alkaline extractable organic matter (AEOM) isolates than for the SOM isolates based on water soluble extracts and pore water. The three categorized sampling locations were the most differentiated in the AEOM isolates, suggesting AEOM may be the most representative SOM isolates in terms of describing the chemical properties and the organic sources of SOM. Parallel factor analysis (PARAFAC) based on fluorescence excitation-emission matrix (EEM) showed that a combination of three fluorescent groups could represent all the fluorescence features of SOM. The three categorized sampling locations were well discriminated by the percent distributions of humic-like fluorescent groups of the AEOM isolates. The relative distribution of terrestrial humic-like fluorophores was well correlated with the extent of phenanthrene binding (r=0.571; p<0.05), suggesting that the presence of humic acids in SOM may contribute to the enhancement of binding with hydrophobic organic contaminants in sediments. Principal component analysis (PCA) further demonstrated that the extent of SOM's binding affinity might be affected by the degree of biogeochemical transformation in SOM. PMID:24997951

Hur, Jin; Lee, Bo-Mi; Shin, Kyung-Hoon

2014-09-01

227

Synthesis and Spectroscopic Characterization of Water-Soluble Fluorescent Ag Nanoclusters  

PubMed Central

Water-soluble fluorescent Ag nanoclusters (NCs) were synthesized at room temperature with sodium dodecyl sulfonate (SDS) as a protective agent. The effects of synthetic conditions on the fluorescence properties of Ag NCs were investigated. The results show that the fluorescence intensity of Ag NCs strongly depends on the synthetic conditions, such as the molar ratio of AgNO3 versus SDS and sodium borohydride (NaBH4), the reaction time, and the pH value of the reaction solution. Under the optimum conditions, the as-prepared Ag NCs exist in face-centered-cubic phase with an average size of 2?nm. Fluorescence spectra of Ag NCs show emission peaks at 365?nm for different excitation wavelength. Resonant absorptions are observed at 203?nm and 277?nm in the absorption spectrum, which can be used to establish the electronic levels in the Ag NCs system.

Zheng, Chengzhi; Wang, Huiping; Liu, Lingzhi; Zhang, Manjun; Liang, Jiangong; Han, Heyou

2013-01-01

228

FTIR spectroscopic, thermal and XRD characterization of hydroxyapatite from new natural sources  

NASA Astrophysics Data System (ADS)

The inorganic constituents of 5 different plants (leaves and stalks) were investigated by using Fourier transformer infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal analysis including thermal gravimetric analysis (TGA), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). These plants are Catha edulis (Khat), basil, mint, green tea and trifolium. The absorption bands of carbonate ions CO 32- was exhibited at 1446 cm -1, and the phosphate ions PO 43- was assigned at 1105 and 1035 cm -1. At high temperatures (600, 700 and 600 °C) further absorption bands of the phosphate ions PO 43- was assigned at the frequencies 572, 617, 962, 1043 and 1110 cm -1 and the vibrational absorption band of the carbonate ions CO 32- was assigned at 871, 1416 and 1461 cm -1. X-ray diffraction and thermal analysis confirm the obtained results of FITR. Results showed that the main inorganic constituents of C. edulis and basil leaves are hydroxyapatite whereas the hydroxyapatite content in the other plant samples is less than that in case of C. edulis and basil plant leaves.

Shaltout, Abdallah A.; Allam, Moussa A.; Moharram, Mohamed A.

2011-12-01

229

Effect of steric hindrance on carbon dioxide absorption into new amine solutions: thermodynamic and spectroscopic verification through solubility and NMR analysis.  

PubMed

Acid gas absorption technology is of great importance in these days for the prevention of global warming and the resulting worldwide climate change. More efficient process design and development for the removal of acid gases has become important, together with the development of new absorbents as one of urgent areas of research in addressing global-warming problems. In the present work, aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), a sterically hindered amine, has been examined as a potential CO2 absorbent and compared with the most commonly used absorbent, monoethanolamine (MEA) solution, through equilibrium solubility measurements and 13C NMR spectroscopic analyses. The solubilities of CO2 in aqueous 10 mass % AHPD solutions were higher than those in aqueous 10 mass % MEA solutions above 4 kPa at 298.15 K, but below 4 kPa, the solubility behavior appeared to be the opposite. The solubility difference between these two solutions increased with the CO2 partial pressures above the crossover pressure. Equilibrated CO2-MEA-H2O and CO2-AHPD-H2O solutions at various CO2 partal pressures ranging from 0.01 to 3000 kPa were analyzed by 13C NMR spectroscopy to provide a more microscopic understanding of the reaction mechanisms in the two solutions. In the CO2-amine-H2O solutions, amine reacted with CO2 to form mainly the protonated amine (AMH+), bicarbonate ion (HCO3-), and carbamate anion (AMCO2-), where the quantitative ratio of bicarbonate ion to carbamate anion strongly influenced the CO2 loading in the amine solutions. A profusion of bicarbonate ions, but a very small amount of carbamate anions, was identified in the CO2-AHPD-H2O solution, whereas a considerable amount of carbamate anions was formed in the CO2-MEA-H2O solution. AHPD contains more hydroxyl groups than nonhindered MEA, and hence, the chemical shifts in its 13C NMR spectra were strongly influenced by the solution pH values. In contrast, MEA appeared to be insensitive to pH. The strong interrelations among CO2 solubility, CO2 partial pressure, bulkiness of the amine structure, and pH identified through the present experimental investigations can provide basic guidelines for finding new potential organic absorbents, including specifically designed amine chemicals. PMID:12731852

Park, Jung-Yeon; Yoon, Sang Jun; Lee, Huen

2003-04-15

230

Chemical Characterization of Riverine Dissolved Organic Matter Using a Combination of Spectroscopic and Pyrolytic Methods  

Microsoft Academic Search

It is now well established that riverine dissolved organic matter (DOM) play a major role in environmental processes. However natural organic matter exhibit different properties depending on their sources and the fractions considered. As a result chemical characterization of DOM has appeared essential for a better understanding of their reactivity. The purpose of this work was to characterize all of

J. Templier; S. Derenne

2006-01-01

231

Spectroscopic characterization of oils yielded from Brazilian offshore basins: Potential applications of remote sensing  

Microsoft Academic Search

Spectroscopy is the basis to detect and characterize offshore hydrocarbon (HC) seeps through optical remote sensing. Diagnostic spectral features of HCs are linked to their chemical composition and fundamental molecular vibrations (SWIR-TIR features), as well as overtones and combinations of these vibrations (VNIR-SWIR). These features allow for the characterization of oil, oil on water and emulsified oil. This work shows

Talita Lammoglia; Carlos Roberto de Souza Filho

2011-01-01

232

Synthesis, spectroscopic characterization, photochemical and photophysical properties and biological activities of ruthenium complexes with mono- and bi-dentate histamine ligand.  

PubMed

The monodentate cis-[Ru(phen)(2)(hist)(2)](2+)1R and the bidentate cis-[Ru(phen)(2)(hist)](2+)2A complexes were prepared and characterized using spectroscopic ((1)H, ((1)H-(1)H)COSY and ((1)H-(13)C)HSQC NMR, UV-vis, luminescence) techniques. The complexes presented absorption and emission in the visible region, as well as a tri-exponential emission decay. The complexes are soluble in aqueous and non-aqueous solution with solubility in a buffer solution of pH 7.4 of 1.14 × 10(-3) mol L(-1) for (1R + 2A) and 6.43 × 10(-4) mol L(-1) for 2A and lipophilicity measured in an aqueous-octanol solution of -1.14 and -0.96, respectively. Photolysis in the visible region in CH(3)CN converted the starting complexes into cis-[Ru(phen)(2)(CH(3)CN)(2)](2+). Histamine photorelease was also observed in pure water and in the presence of BSA (1.0 × 10(-6) mol L(-1)). The bidentate coordination of the histamine to the ruthenium center in relation to the monodentate coordination increased the photosubstitution quantum yield by a factor of 3. Pharmacological studies showed that the complexes present a moderate inhibition of AChE with an IC(50) of 21 ?mol L(-1) (referred to risvagtini, IC(50) 181 ?mol L(-1) and galantamine IC(50) 0.006 ?mol L(-1)) with no appreciable cytotoxicity toward to the HeLa cells (50% cell viability at 925 ?mol L(-1)). Cell uptake of the complexes into HeLa cells was detected by fluorescence confocal microscopy. Overall, the observation of a luminescent complex that penetrates the cell wall and has low cytotoxicity, but is reactive photochemically, releasing histamine when irradiated with visible light, are interesting features for application of these complexes as phototherapeutic agents. PMID:22539182

Cardoso, Carolina R; de Aguiar, Inara; Camilo, Mariana R; Lima, Márcia V S; Ito, Amando S; Baptista, Maurício S; Pavani, Christiane; Venâncio, Tiago; Carlos, Rose M

2012-06-14

233

High sensitivity spectroscopic and thermal characterization of cooling efficiency for optical refrigeration materials  

NASA Astrophysics Data System (ADS)

Since recent demonstration of cryogenic optical refrigeration, a need for reliable characterization tools of cooling performance of different materials is in high demand. We present our experimental apparatus that allows for temperature and wavelength dependent characterization of the materials' cooling efficiency and is based on highly sensitive spectral differencing technique or two-band differential spectral metrology (2B-DSM). First characterization of a 5% w.t. ytterbium-doped YLF crystal showed quantitative agreement with the current laser cooling model, as well as measured a minimum achievable temperature (MAT) at 110 K. Other materials and ion concentrations are also investigated and reported here.

Melgaard, Seth D.; Seletskiy, Denis V.; di Lieto, Alberto; Tonelli, Mauro; Sheik-Bahae, Mansoor

2012-02-01

234

Spectroscopic characterization of lanthanide octaethylporphyrin sandwich complexes. Effects of strong. pi. pi. interaction  

Microsoft Academic Search

Optical absorption and resonance Raman spectra are reported for the lanthanide sandwich porphyrins, Eu{sup III}(OEP)â, Nd{sup III}(OEP)â, and La{sup III}(OEP)â (OEP = octaethylporphyrin). These complexes contain a single hole in the porphyrin Ï system and are electronically similar to the Ce{sup IV} sandwich porphyrin cation radical Ce{sup IV}(OEP)â{sup +}. Variable-temperature (10-300 K) UV-vis and near-infrared (NIR) spectra are obtained for

John K. Duchowski; David F. Bocian

1990-01-01

235

Characterization of the binding of nevadensin to bovine serum albumin by optical spectroscopic technique  

NASA Astrophysics Data System (ADS)

Binding of nevadensin to bovine serum albumin (BSA) has been studied in detail at 298 and 310 K using spectrophotometric technique. The intrinsic fluorescence of BSA was strongly quenched by the addition of nevadensin and spectroscopic observations are mainly rationalized in terms of a static quenching process at lower concentration of nevadensin ( Cdrug/ CBSA < 1) and a combined quenching process at higher concentration of nevadensin ( Cdrug/ CBSA > 1). The binding parameters for the reaction at a pH above (7.40) or below (3.40) the isoelectric point have been calculated according to the double logarithm regression curve. The thermodynamic parameters ? H0, ? G0, ? S0 at different temperatures and binding mechanism of nevadensin to BSA at pH 7.40 and 3.40 were evaluated. The binding ability of nevadensin to BSA at pH 7.40 was stronger than that at pH 3.40. Steady fluorescence, synchronous fluorescence and circular dichroism (CD) were applied to investigate protein conformation. A value of 2.15 nm for the average distance r between nevadensin (acceptor) and tryptophan residues (Trp) of BSA (donor) was derived from the fluorescence resonance energy transfer. Moreover, influence of pH on the interaction nevadensin with BSA was investigated.

Yu, Zhaolian; Li, Daojin; Ji, Baoming; Chen, Jianjun

2008-10-01

236

Characterization of DC reactive magnetron sputtered NiO films using spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Thin NiO films were deposited at 500 °C on n-type Si(1 1 1) by a DC reactive magnetron sputtering in a gas mixture of oxygen and argon. The ratio between the flow rates of oxygen and argon was respectively set at 1:4, 1:2, and 1:1. The dependence of structures and optical properties of NiO films were investigated using grazing incidence X-ray diffraction and spectroscopic ellipsometry in the spectral region of 1.5-5.0 eV. Ni-rich NiO films were obtained when the ratio between the flow rates of oxygen and argon was 1:4 and 1:2 in sputtering process. And when the ratio was 1:1, a relatively pure NiO film was formed. The partial pressure of oxygen could significantly influence the thickness and roughness of films. Refractive index n, extinction coefficient k, and direct gap energy and indirect gap energy of the NiO films were also subject to the influence of the partial pressure of oxygen.

Peng, T. C.; Xiao, X. H.; Han, X. Y.; Zhou, X. D.; Wu, W.; Ren, F.; Jiang, C. Z.

2011-04-01

237

Spectroscopic characterization of ion collisions and trapping at laser-irradiated double-foil targets  

NASA Astrophysics Data System (ADS)

Precise X-ray spectroscopic investigation of the colliding plasmas produced at single-side laser-irradiated double-foil Al/Mg targets is reported. The spatially resolved, time-integrated line spectra of the Al Ly? group were measured using a high-dispersion vertical-geometry Johann spectrometer. The X-ray spectra were evaluated with the multilevel collisional-radiative code MARIA. The complex satellite-rich structure observed in the Al Ly? emission indicates a presence of relatively cold dense plasma close to the Al foil surface, hot plasma between both foils, and Al ion trapping close to the Mg foil. An unusual formation of the Al spectra at the Mg foil surface is discussed in terms of interaction of counter-propagating plasmas, in particular trapping, deceleration and thermalization of the Al ions in the colliding plasmas. The qualitative analysis of the observed spectral emission is supported by 2D hydrodynamic modeling and by time-resolved imaging of the expanding plasma. Prospective use of the J-satellite line shifts in diagnosis of colliding laser-produced plasmas is discussed.

Renner, O.; Rosmej, F. B.; Adámek, P.; Dalimier, E.; Delserieys, A.; Krouský, E.; Limpouch, J.; Liska, R.; Riley, D.; Schott, R.

2007-05-01

238

Evaluation of optical parameters and characterization of ultrasonically sprayed MgO films by spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

MgO is a chemically stable buffer layer and a good candidate with its unique optical and structural characteristics such as low refractive index and good lattice matching for the deposition of technologically important materials. In this work, we have produced MgO films by a low cost ultrasonic spray pyrolysis technique and tried to improve their characteristics by thermal annealing. MgO films have been obtained on glass substrates at 325 ± 5 °C and annealed at two different temperatures as 500 °C and 600 °C for 2 h. Elemental analyses have been made by energy-dispersive X-ray spectroscopy. Thicknesses, refractive indices and extinction coefficient values have been determined by spectroscopic ellipsometry technique using Cauchy-Urbach model. Band gap values of the films have been calculated using the absorbance spectra and optical method. X-ray diffraction patterns have been used to investigate the structural properties and to calculate lattice parameters. Atomic force microscope images have been taken to see the effect of thermal annealing on surface morphology. Electrical resistivity values of the films have been determined using a four-point probe set-up. As a result, annealing temperature has a strong effect on the mentioned properties and a low cost ultrasonic spray pyrolysis technique allows the production of new and alternative MgO buffer layers for technological applications.

Kurtaran, S.; Akyuz, I.; Atay, F.

2013-01-01

239

Spectroscopic characterization of a microplasma used as ionization source for ion mobility spectrometry  

NASA Astrophysics Data System (ADS)

We report a miniaturized excitation source for soft ionization of molecules based on a dielectric barrier discharge. An atmospheric plasma is established at the end of a 500 ?m diameter capillary using He as buffer gas. The plasma jet which comes out of the capillary is dependent on the gas flow rate. The mechanism of the production of N 2+ outside the capillary, which is relevant for the protonation of molecules and sustains the production of primary ions, is investigated by spatially resolved spectroscopic measurements throughout the plasma. Possible application of such miniaturized plasmas is the ionization of gaseous compounds under atmospheric pressure as an alternative to traditional APCI (atmospheric pressure chemical ionization). The miniaturized plasma was applied as ionization source for ion mobility spectrometry where the common sources are radioactive, thus limiting the place of installation. First measurements of gaseous compounds with such a plasma ion mobility spectrometer with promising results showed detection limits comparable or even better than those obtained using common radioactive ionization sources.

Michels, Antje; Tombrink, Sven; Vautz, Wolfgang; Miclea, Manuela; Franzke, Joachim

2007-11-01

240

Structural, spectroscopic, and electrochemical characterization of boron-doped diamond films from different provenances  

SciTech Connect

Morphological, spectroscopic, and electrochemical aspects of boron-doped diamond (BDD) films grown on silicon surfaces originating from three different laboratories have been examined by atomic force microscopy (AF), Raman scattering, Auger electron spectroscopy, and cyclic voltammetry in polyethylene oxide LiClO{sub 4} electrolytes in ultrahigh vacuum. All specimens displayed AFM images characteristic of diamond and Raman spectra consistent with a wide range of boron concentrations (10{sup 19} to 10{sup 21} B atom/cm{sup 3}), with no evidence for the presence of gross graphitic impurities. The cyclic voltammetry of two of the specimens (denoted as GV2 and CWRU), however, showed features at potentials positive to lithium bulk deposition attributed to lithium-ion intercalation/deintercalation phenomena in non-diamond carbon present as a surface impurity, perhaps at the grain boundaries. This finding is consistent with earlier results for a specimen of type GV2 in aqueous electrolytes for which rates of heterogeneous electron transfer for certain redox couples were found higher than those for nominally clean BDD surfaces.

Li, L.F.; Totir, D.A.; Vinokur, N.; Miller, B.; Chottiner, G.; Evans, E.A.; Angus, J.C.; Scherson, D.A. [Case Western Reserve Univ., Cleveland, OH (United States)

1998-05-01

241

Surface layer in composites containing 4- n-octyl-4'-cyanobiphenyl. FTIR spectroscopic characterization  

NASA Astrophysics Data System (ADS)

Composites containing 4- n-octyl-4'-cyanobiphenyl (8CB) either confined to nanopores of molecular sieves with very large pores or coating silica nanoparticles of aerosil type at high silica-to-8CB ratios are investigated by IR spectroscopy. Band shape analysis was performed in wavenumber regions in which the peaks due to CN stretching, CH stretching and CH out-of-plane vibrations appear. Some of molecules confined to molecular sieves show spectroscopic features characteristic to a bulk-like 8CB matter located in the centre of the pores or in the inter-grain space. Other features of the IR spectra are due to 8CB molecules located in the surface layer, mostly forming hydrogen bonds between their CN groups and surface OH groups. Another part of the 8CB molecules in the surface layer may also interact by ? electrons of the aromatic rings. Hydrogen bonding is less hindered for the molecules of the surface layers onto aerosil particles than inside pores of the molecular sieves. Comparison is also made with the case of composites based on molecular sieves with small pores.

Frunza, L.; Kosslick, H.; Bentrup, U.; Pitsch, I.; Fricke, R.; Frunza, S.; Schönhals, A.

2003-06-01

242

Minerals from Macedonia XXIII. Spectroscopic and structural characterization of schorl and beryl cyclosilicates.  

PubMed

IR and Raman spectroscopy study on two collected cyclosilicate species: schorl (from tourmaline group), Na(Fe,Mg)(3)Al(6)(BO(3))(3)Si(6)O(18)(OH,F)(4) and beryl (Be,Mg,Fe)(3)Al(2)Si(6)O(18) were carried out. Although beryl is nominally anhydrous mineral, vibrational results strongly indicate that H(2)O molecules exist in the structural channels. The number of vibrational bands and their frequencies revealed the presence of H(2)O type II, in which C(2) symmetry axis of the water molecule is parallel to the structural channel (and to the c-axis of beryl). On the other hand, it was found that observed bands in the IR and Raman OH stretching region of the other tourmaline varieties appear as a result of the cation combinations involving dominant presence of Mg and Fe cations in the Y structural sites. The strong indication derived from the vibrational spectroscopic results that the studied mineral represents a schorl variety, coincide very well with the results obtained by powder X-ray diffraction and X-ray microprobe analysis. Both minerals show IR spectral similarities in the region below 1500 cm(-1), whereas the resemblance between the Raman spectra (1500-100 cm(-1)) is less expressed confirming that these spectra are more sensitive to compositional changes and to structural disorder. The identification of both minerals was additionally supported by studying the powder X-ray diffraction diagrams. PMID:18722809

Makreski, Petre; Jovanovski, Gligor

2009-08-01

243

Characterization of the moisture absorption behavior of TiH/sub x//KClO/sub 4/  

SciTech Connect

The moisture absorption and desorption behavior of the TiH/sub 0.65//KClO/sub 4/ and TiH/sub 1.65/KClO/sub 4/ pyrotechnic powders are being investigated by mass balancing and nuclear magnetic resonance (NMR) spectroscopic techniques. Moisture absorption and desorption rates have been determined at various points between 50 and 100 percent relative humidities (% RH). Below 92% RH, appreciable moisture is no longer absorbed by these systems. These is a factor of 5 greater moisture absorption at the 95% RH level than at the 92% RH level (0.14 wt. % versus 0.686 wt. % for TiH/sub 0.65//KClO/sub 4/). The rate of moisture absorption is much slower (4 days to absorb maximum amount of moisture) than the rate of desorption (20 minutes for complete desorption). There is also a large difference in the magnitudes of proton spin-lattice relaxation times (211 milliseconds for TiH/sub 0.65//KClO/sub 4/ and 600 to 850 ms for TiH/sub 1.65//KClO/sub 4/). Future studies will concern the effects of the interactions between the titanium and hydrogen nuclei on the line-shape of the high-field (300 MHz), magic-angle sample spinnings, proton NMR spectra of these systems. A quantitative NMR technique for determining the moisture content of these powders will also be developed. 2 refs., 2 figs., 2 tabs.

Attalla, A.; Wang, P.S.

1986-07-01

244

Spectroscopic characterization of lanthanide octaethylporphyrin sandwich complexes. Effects of strong. pi. pi. interaction  

SciTech Connect

Optical absorption and resonance Raman spectra are reported for the lanthanide sandwich porphyrins, Eu{sup III}(OEP){sub 2}, Nd{sup III}(OEP){sub 2}, and La{sup III}(OEP){sub 2} (OEP = octaethylporphyrin). These complexes contain a single hole in the porphyrin {pi} system and are electronically similar to the Ce{sup IV} sandwich porphyrin cation radical Ce{sup IV}(OEP){sub 2}{sup +}. Variable-temperature (10-300 K) UV-vis and near-infrared (NIR) spectra are obtained for all four single-hole sandwiches. At high resolution and/or at low temperatures, well-resolved fine structure is observed on the intradimer charge-transfer bands (ca. 1,250 nm) of all the complexes. The absorption is dominated by a single Franck-Condon active vibration. This vibration is assigned as a mode, Q{sub AB}, which contains a significant amount of multicenter character and modulates interring separation. Vibronic analysis of the NIR band contours reveals that two system origins, separated by 400-700 cm{sup {minus}1} (depending on the complex), are present. The progressions built off the lower and higher energy origins exhibit spacings of {approximately} 250 and {approximately} 315 cm{sup {minus}1}, respectively.

Duchowski, J.K.; Bocian, D.F. (Carnegie Mellon Univ., Pittsburgh, PA (USA))

1990-04-25

245

Characterization of magnetic materials by low-field microwave absorption techniques  

NASA Astrophysics Data System (ADS)

A low-field non-resonant microwave absorption has recently been observed in a variety of magnetically ordered materials at low DC fields (-1000 Oe ? HDC?+1000 Oe), which is known as low-field microwave absorption (LFA). It has been shown that LFA is essentially similar to giant magnetoimpedance (GMI), and clearly different from ferromagnetic resonance (FMR). LFA strongly depends on the anisotropy field of the sample. In contrast with FMR (which can be described as the homogeneous precession of spins in the saturated state), LFA can be thought as a spin rotation process occurring during the magnetic saturation. In this work, we present a detailed study of the basic features of LFA in several types of materials: ferrites and amorphous microwires and ribbons; in particular the effects sample shape, temperature up to the Curie transition, the influence of easy axis and the effects of annealings. These examples show that once LFA is fully understood, it can become a powerful characterization tool.

Valenzuela, R.; Alvarez, G.; Montiel, H.; Gutiérrez, M. P.; Mata-Zamora, M. E.; Barrón, F.; Sánchez, A. Y.; Betancourt, I.; Zamorano, R.

246

Instrument for x-ray absorption spectroscopy with in situ electrical control characterizations  

SciTech Connect

We report a synchrotron-based setup capable of performing x-ray absorption spectroscopy and x-ray magnetic circular dichroism with simultaneous electrical control characterizations. The setup can enable research concerning electrical transport, element- and orbital-selective magnetization with an in situ fashion. It is a unique approach to the real-time change of spin-polarized electronic state of a material/device exhibiting magneto-electric responses. The performance of the setup was tested by probing the spin-polarized states of cobalt and oxygen of Zn{sub 1-x}Co{sub x}O dilute magnetic semiconductor under applied voltages, both at low (?20 K) and room temperatures, and signal variations upon the change of applied voltage were clearly detected.

Huang, Chun-Chao; Chang, Shu-Jui; Yang, Chao-Yao; Tseng, Yuan-Chieh [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan (China)] [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Chou, Hsiung [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)] [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

2013-12-15

247

Structural characterization of electrodeposited copper hexacyanoferrate films by using a spectroscopic multi-technique approach.  

PubMed

A deep structural investigation predominantly by X-ray spectroscopic techniques is conducted on films of copper hexacyanoferrate (CuHCF) deposited under different conditions, aimed at establishing structure-properties relationships. We show that the potentiodynamic electrosynthesis of CuHCF on carbon-based surfaces produces a highly disordered material, with a variable amount of Prussian Blue (PB). The subsequent Cu(2+) intercalation induces the partial conversion of PB into CuHCF, which explains the improved electrocatalytic properties after the intercalation process. Both Cu and Fe K-edge data have been recorded. For the sample with the lower amount of PB, we could perform a multiple edge data analysis to determine the local atomic environment around both metal centres using the same set of structural parameters. The presence of high multiplicity Cu-N-C-Fe linear chains has allowed us to determine accurately the local environment of Fe while fitting the Cu K-edge data only. Using this approach we have retrieved structural information around Fe for those samples in which the concomitant presence of PB would have made impossible the analysis of the Fe K-edge. The Fe-C, C-N and Cu-N bond distances have been found in agreement with those of the bulk structures, but higher values of [Fe(CN)(6)] vacancies for the building blocks have been evidenced, reaching a value of ~45% in one sample. XANES, Raman and SEM data agree with the model proposed for each studied electrode. PMID:22422097

Giorgetti, Marco; Guadagnini, Lorella; Tonelli, Domenica; Minicucci, Marco; Aquilanti, Giuliana

2012-04-28

248

The SiP molecule: The first observation and spectroscopic characterization  

NASA Astrophysics Data System (ADS)

SiP molecules have been produced in a molecular free jet apparatus by laser vaporizing a silicon rod in the presence of He doped with phosphine (PH3) gas. Excitation spectra have been observed in the 21200-22350 cm-1 range by monitoring laser induced fluorescence. Dispersed fluorescence spectra have been recorded out of the upper states of the excitation bands. The ground electronic state is X 2?i with the spin-orbit splitting A=-186.774(11) cm-1, the harmonic wavenumber ?e=615.7(6) cm-1, and the equilibrium internuclear distance re=2.0775(17) Å. Two excited electronic states, A 2?+ and B 2?+, are observed at T0=427.4(5) and 21317.1(1) cm-1, respectively. The harmonic wavenumbers, ?e, and the equilibrium internuclear distances, re, are 680(2) cm-1 and 1.9658(13) Å, respectively, for the A 2?+ state and 455(1) cm-1 and 2.1278(8) Å, respectively, for the B 2?+ state. For the X 2?i, A 2?+, and B 2?+ electronic states, RKR potentials have been generated. Franck-Condon factors for the B-X, B-A, and A-X systems have been calculated. A 2?+, v~X 2?1/2, v+1 perturbations have been observed. A deperturbation procedure has yielded the off-diagonal spin-orbit electronic matrix element equal to 51(8) cm-1. This work represents the first spectroscopic investigation of the SiP molecule.

Jakubek, Zygmunt J.; Nakhate, S. G.; Simard, Benoit

2002-04-01

249

Spectroscopic investigation and optical characterization of Eu3+ ions in K-Nb-Si glasses.  

PubMed

This paper reports on the effect of concentration of Eu(3+) ions in K2O-Nb2O5-SiO2-Eu2O3 (KNbSiEu) glasses prepared by the melt quenching technique. By using the Judd-Ofelt (JO) theory, the intensity parameters ?? (?=2, 4, 6) have been determined from the absorption and emission spectra of Eu(3+) ions under different constraints. The radiative properties of some of the excited states of Eu(3+) ions have been calculated. The decay curves of (5)D0 level exhibited single exponential for all the Eu(3+) ions concentrations. From these results, it is suggested that the strong red emission at 616 nm corresponding to the (5)D0?(7)F2 transition could be used for the development of optical display devices. PMID:24161859

Murali Mohan, M; Rama Moorthy, L; Ramachari, D; Jayasankar, C K

2014-01-24

250

Characterization of the Interaction between Eupatorin and Bovine Serum Albumin by Spectroscopic and Molecular Modeling Methods  

PubMed Central

This study investigated the interaction between eupatorin and bovine serum albumin (BSA) using ultraviolet-visible (UV-vis) absorption, fluorescence, synchronous fluorescence, circular dichroism (CD) spectroscopies, and molecular modeling at pH 7.4. Results of UV-vis and fluorescence spectroscopies illustrated that BSA fluorescence was quenched by eupatorin via a static quenching mechanism. Thermodynamic parameters revealed that hydrophobic and electrostatic interactions played major roles in the interaction. Moreover, the efficiency of energy transfer, and the distance between BSA and acceptor eupatorin, were calculated. The effects of eupatorin on the BSA conformation were analyzed using UV-vis, CD, and synchronous fluorescence. Finally, the binding of eupatorin to BSA was modeled using the molecular docking method.

Xu, Hongliang; Yao, Nannan; Xu, Haoran; Wang, Tianshi; Li, Guiying; Li, Zhengqiang

2013-01-01

251

Comparison and investigation of bovine hemoglobin binding to dihydroartemisinin and 9-hydroxy-dihydroartemisinin: Spectroscopic characterization  

NASA Astrophysics Data System (ADS)

The UV-vis absorption, steady state/time resolved fluorescence spectroscopy and synchronous fluorescence, circular dichroism (CD) spectroscopy are used to investigate the interaction mechanisms of dihydroartemisinin (DHA) and 9-hydroxy-dihydroartemisinin (9-OH DHA), respectively. The UV-vis studies present that DHA and 9-OH DHA can disturb the structure of bovine hemoglobin (BHb). Steady state/time resolved and synchronous fluorescence spectroscopy reveal that the binding constant of DHA with BHb is bigger than 9-OH DHA. CD spectra indicate DHA and 9-OH DHA can change the conformation of BHb. The comparison results suggest that the binding of BHb with DHA is more stable and stronger than 9-OH DHA.

Xiao, Mengsi; Han, Lina; Zhou, Lin; Zhou, Yanhuai; Huang, Xiaoqin; Ge, Xuefeng; Wei, Shaohua; Zhou, Jiahong; Wu, Heming; Shen, Jian

252

Synthesis of Novel Heteroquaterphenoquinones and Their Electrochemical, Structural, and Spectroscopic Characterization.  

PubMed

Novel heteroquaterphenoquinones, 5,5'-bis(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-5,5'-dihydro-2,2'-bithienyl (3) and its 2,2'-biselenienyl (4), 2,2'-bifuryl (5), and 2,2'-bi-N-methylpyrrolyl (6) analogues, were synthesized by a stepwise cross-coupling reaction or by a more convenient one-pot oxidative homocoupling reaction of heterocycle-substituted phenols. Despite a highly conjugation-extended system, the quinones 3-6 are very stable in the solid state and in solution in common organic solvents. These quinones undergo a reversible one-stage, two-electron reduction up to dianions and a two-stage, one-electron oxidation reaction up to dications. The E(1)(red) of these quinones increases with the increase in the aromaticity of the incorporated heterocycles. The E(1)(ox) of these quinones appears to be specified by the ionization potential of the incorporated heterocycles. Thus, the N-methylquinone 6 exhibiting the lowest E(1)(ox) value exhibits the smallest E(1)(sum) among the quinones 3-6. The quinone 5 was revealed to exist in an unusual O-cis conformation in the solid state by X-ray crystallography, whereas the quinone 3 exists in an S-trans conformation in the solid state. The cis and trans isomers are interconvertible in solution in 3-5, whereas only N-trans isomer was detected for 6 in (1)H NMR spectroscopy. The quinones 3-6 exhibit a very intense absorption maximum in the near-infrared region of 662-827 nm. Of these, the maximum absorption wave length of 6 shifts to a more bathochromic region by 149-165 nm than those of 3-5. The quinones 3-6 can be used as dyestuffs in various fields for laser-driven high-density optical storage media. PMID:11667412

Takahashi, Kazuko; Gunji, Atsushi; Yanagi, Kazunori; Miki, Misao

1996-07-12

253

Label-Free Characterization of Cancer-Activated Fibroblasts Using Infrared Spectroscopic Imaging  

Microsoft Academic Search

Glandular tumors arising in epithelial cells comprise the majority of solid human cancers. Glands are supported by stroma, which is activated in the proximity of a tumor. Activated stroma is often characterized by the molecular expression of ?-smooth muscle actin (?-SMA) within fibroblasts. However, the precise spatial and temporal evolution of chemical changes in fibroblasts upon epithelial tumor signaling is

S. E. Holton; M. J. Walsh; A. Kajdacsy-Balla; R. Bhargava

2011-01-01

254

Preparation and Spectroscopic Characterization of MoS2 and MoSe2 Nanoparticles  

Microsoft Academic Search

In this manuscript, we report an experiment for the upper division chemistry laboratory involving the synthesis and characterization of molybdenum (IV) chalcogenide nanoparticles. The reaction is a straightforward synthesis between molybdenum hexacarbonyl and sulfur or selenium. Students follow the progress of the reaction via monitoring the carbonyl stretch using Fourier transform infrared (FTIR) spectroscopy. The nanoparticles are found to absorb

Brian C. Helmly; Will E. Lynch; Delana A. Nivens

2007-01-01

255

Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants  

Microsoft Academic Search

Indium tin oxide (ITO) is a transparent conducting oxide in wide use today. ITO can be difficult to work with since this material displays a complicated (graded) microstructure, and the optical properties of ITO can vary widely with deposition conditions and post-deposition processing. For this reason it is common to characterize ITO films via optical measurements. However, accurate results are

R. A Synowicki

1998-01-01

256

Absorption and fluorescence properties of fluorescein  

Microsoft Academic Search

We have characterized the protolytic equilibria of fluorescein and determined the spectroscopic properties of its protolytic forms. The protolytic constants relating the chemical activities (which at low ionic strength equal concentrations) of the cation, neutral form, anion and dianion are pK1 = 2.08, pK2 = 4.31, and pK3 = 6.43. All forms have rather high molar absorptivities being ?437FH31 =

Robert Sjöback; Jan Nygren; Mikael Kubista

1995-01-01

257

Characterizing Protein Complexes with UV absorption, Light Scattering, and Refractive Index Detection.  

NASA Astrophysics Data System (ADS)

Many modern pharmaceuticals and naturally occurring biomolecules consist of complexes of proteins and polyethylene glycol or carbohydrates. In the case of vaccine development, these complexes are often used to induce or amplify immune responses. For protein therapeutics they are used to modify solubility and function, or to control the rate of degradation and elimination of a drug from the body. Characterizing the stoichiometry of these complexes is an important industrial problem that presents a formidable challenge to analytical instrument designers. Traditional analytical methods, such as using florescent tagging, chemical assays, and mass spectrometry perturb the system so dramatically that the complexes are often destroyed or uncontrollably modified by the measurement. A solution to this problem consists of fractionating the samples and then measuring the fractions using sequential non-invasive detectors that are sensitive to different components of the complex. We present results using UV absorption, which is primarily sensitive to the protein fraction, Light Scattering, which measures the total weight average molar mass, and Refractive Index detection, which measures the net concentration. We also present a solution of the problem inter-detector band-broadening problem that has heretofore made this approach impractical. Presented will be instrumentation and an analysis method that overcome these obstacles and make this technique a reliable and robust way of non-invasively characterizing these industrially important compounds.

Trainoff, Steven

2009-03-01

258

Infrared and Raman spectroscopic characterization of some organic substituted hybrid silicas.  

PubMed

Nine hybrid silicas bearing the organic substituent groups methyl, octyl, octadecyl, vinyl, phenyl, mercaptopropyl, isocyanatopropyl, chloropropyl and glycidoxypropyl were synthesized by an acid-catalyzed, hydrolytic sol-gel process. The resulting solid materials were characterized by their absorbance and attenuated total reflection (ATR) IR and Raman spectra. The latter technique proved to be particularly useful in the identification of the organic moieties in the hybrid silicas. The effect of the presence of the organic groups on the silica networks was also investigated - there were increases observed in both the SiOSi bond angles and bond lengths. Moreover, deconvolution of the IR-active antisymmetric SiOSi stretching bands permitted detection of the four- and six-membered siloxane rings present in the silicas. There proved to be a greater number of four-membered rings on the surfaces of the particles. Both IR and Raman spectroscopy proved to be invaluable in the characterization of these hybrid materials. PMID:24992921

Capeletti, Larissa B; Baibich, Ione M; Butler, Ian S; Dos Santos, João H Z

2014-12-10

259

Spectroscopic, scanning laser OBIC and IV\\/QE characterizations of browned EVA solar cells  

Microsoft Academic Search

The effects of ethylene-vinyl acetate (EVA) discoloration due to accelerated field or laboratory exposure on the encapsulated silicon (Si) solar cells or EVA\\/glass laminates were characterized quantitatively by using noninvasive, nondestructive ultraviolet-visible spectrophotometry, spectrocolorimetry, spectro-fluorometry, scanning laser OBIC (optical beam induced current) spectroscopy and current-voltage (I-V) and quantum efficiency (QE) measurements. The results show that the yellowness index (YI) measured

F. J. Pern; I. L. Eiisgruber; R. H. Micheels

1996-01-01

260

Synthesis and Spectroscopic Characterization of Silver(I) Complexes of Selenones  

Microsoft Academic Search

Silver(I) complexes of selenones, [LAgNO3] and [AgL2]NO3 (where L is imidazolidine-2-selenone or diazinane-2-selenone and their derivatives) have been prepared and characterized by elemental analysis, IR and NMR (H, C and Ag) spectroscopy. An upfield shift in the C=Se resonance of selenones in C NMR and a downfield shift in N-H resonance in H NMR are consistent with selenium coordination to

Saeed Ahmad; Anvarhusein A. Isab; Alan P. Arnold

2003-01-01

261

Spectroscopic ellipsometry characterization of HfxSiyOz films using the Cody-Lorentz parameterized model  

NASA Astrophysics Data System (ADS)

A parameterized, Kramers-Kronig consistent, Cody-Lorentz optical model is used to simulate the dielectric response of thin HfxSiyOz films. Optical constants are determined in the range 0.75-8.35 eV. The Cody-Lorentz model has three specific differences when compared to the previously employed Tauc-Lorentz model: (1) weak exponential absorption below the band gap, (2) a modified joint density-of-states, and (3) a restriction on the ?1(?) parameter. These three differences allow the Cody-Lorentz model to have an improved fit to experimental data. As a result of a more accurate optical model for HfxSiyOz, we were able to identify an interfacial layer with thickness in close agreement with transmission electron microscopy measurements. Use of the Tauc-Lorentz model when fitting the same experimental data could not identify an interfacial layer. Results are also discussed in which the Cody-Lorentz model shows sensitivity to varying degrees of silicate composition.

Price, J.; Hung, P. Y.; Rhoad, T.; Foran, B.; Diebold, A. C.

2004-09-01

262

Characterization of the interactions between tetracycline antibiotics and microbial extracellular polymeric substances with spectroscopic approaches.  

PubMed

The antibiotics have attracted global attentions for their impact on aquatic ecosystem. The knowledge about the fate of antibiotics encountering extracellular polymeric substances (EPS) is, however, limited. In this study, we investigated the interacting mechanisms of tetracycline (TC) to EPS extracted from aerobic activated sludge. The contributions of the main components of EPS, extracellular proteins, and polysaccharides were evaluated using bovine serum albumin and alginate sodium, respectively. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance indicated that hydroxyl, carboxyl, and amino groups were the domain chemical groups involved in the interaction between TC and EPS, and the binding of TC onto EPS changed the structure of these chemical groups, thus causing shifts in their UV-visible absorption spectra. In addition, we found that extracellular proteins, rather than polysaccharides, were the major active contents involved in the interaction. Three-dimensional excitation-emission matrix fluorescence spectroscopy showed that the fluorophores in EPS were clearly quenched by TC and the static quenching process was observed, implying the complex formation of TC and EPS. Furthermore, thermodynamic analysis indicated that the binding of TC with EPS is spontaneous and dominated by electrostatic forces. PMID:23979850

Song, Chao; Sun, Xue-Fei; Xing, Su-Fang; Xia, Peng-Fei; Shi, Yi-Jing; Wang, Shu-Guang

2014-02-01

263

Chemical leaching of an Indian bituminous coal and characterization of the products by vibrational spectroscopic techniques  

NASA Astrophysics Data System (ADS)

High volatile bituminous coal was demineralized by a chemical method. The vibrations of the "aromatics" structure of graphite, crystalline or non-crystalline, were observed in the spectra at the 1600 cm-1 region. The band at 1477 cm-1 is assigned as VR band, the band at 1392 cm-1 as VL band and the band at 1540 cm-1 as GR band. Graphite structure remains after chemical leaching liberates oxygenated functional groups and mineral groups. The silicate bands between 1010 and 1100 cm-1 are active in the infrared (IR) spectrum but inactive in the Raman spectrum. Absorption arising from C-H stretching in alkenes occurs in the region of 3000 to 2840 cm-1. Raman bands because of symmetric stretch of water molecules were also observed in the spectrum at 3250 cm-1 and 3450 cm-1. Scanning electron microscopy analysis revealed the presence of a graphite layer on the surface. Leaching of the sample with hydrofluoric acid decreases the mineral phase and increases the carbon content. The ash content is reduced by 84.5wt% with leaching from its initial value by mainly removing aluminum and silicate containing minerals.

Manoj, B.; Kunjomana, A. G.

2012-04-01

264

AN EMPIRICAL CHARACTERIZATION OF EXTENDED COOL GAS AROUND GALAXIES USING Mg II ABSORPTION FEATURES  

SciTech Connect

We report results from a survey of Mg II absorbers in the spectra of background quasi-stellar objects (QSOs) that are within close angular distances to a foreground galaxy at z < 0.5, using the Magellan Echellette Spectrograph. We have established a spectroscopic sample of 94 galaxies at a median redshift of (z) = 0.24 in fields around 70 distant background QSOs (z{sub QSO} > 0.6), 71 of which are in an 'isolated' environment with no known companions and located at {rho} {approx_lt} 120 h {sup -1} kpc from the line of sight of a background QSO. The rest-frame absolute B-band magnitudes span a range from M{sub B} - 5log h = -16.4 to M{sub B} - 5log h = -21.4 and rest-frame B{sub AB} - R{sub AB} colors range from B{sub AB} - R{sub AB} {approx} 0 to B{sub AB} - R{sub AB} {approx} 1.5. Of these 'isolated' galaxies, we find that 47 have corresponding Mg II absorbers in the spectra of background QSOs and rest-frame absorption equivalent width W{sub r} (2796) = 0.1-2.34 A, and 24 do not give rise to Mg II absorption to sensitive upper limits. Our analysis shows that (1) W{sub r} (2796) declines with increasing distance from 'isolated' galaxies but shows no clear trend in 'group' environments; (2) more luminous galaxies possess more extended Mg II absorbing halos with the gaseous radius scaled by B-band luminosity according to R{sub gas} = 75 x (L{sub B} /L{sub B{sub *}}){sup (0.35{+-}0.03)} h {sup -1} kpc; (3) there is little dependence between the observed absorber strength and galaxy intrinsic colors; and (4) within R{sub gas}, we find a mean covering fraction of ({kappa}{sub 0.3}) {approx} 70% for absorbers of W{sub r} (2796) {>=} 0.3 A and ({kappa}{sub 0.1}) {approx} 80% for absorbers of W{sub r} (2796) {>=} 0.1 A. The results confirm that extended Mg II absorbing halos are a common and generic feature around ordinary galaxies and that the gaseous radius is a fixed fraction of the dark matter halo radius. The lack of correlation between W{sub r} (2796) strength and galaxy colors suggests a lack of physical connection between the origin of extended Mg II halos and recent star formation history of the galaxies. Finally, we discuss the total gas mass in galactic halos as traced by Mg II absorbers. We also compare our results with previous studies.

Chen, Hsiao-Wen; Helsby, Jennifer E.; Gauthier, Jean-Rene [Department of Astronomy and Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States); Shectman, Stephen A.; Thompson, Ian B. [The Observatories of Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Tinker, Jeremy L., E-mail: hchen@oddjob.uchicago.ed [Berkeley Center for Cosmological Physics, University of California-Berkeley, Berkeley, CA (United States)

2010-05-10

265

Spectroscopic characterization of chromite from the Moa-Baracoa Ophiolitic Massif, Cuba.  

PubMed

The Cuban chromites with a spinel structure, FeCr2O4 have been studied using optical absorption and EPR spectroscopy. The spectral features in the electronic spectra are used to map the octahedral and tetrahedral co-ordinated cations. Bands due Cr3+ and Fe3+ ions could be distinguished from UV-vis spectrum. Chromite spectrum shows two spin allowed bands at 17,390 and 23,810 cm(-1) due to Cr3+ in octahedral field and they are assigned to 4A2g(F) --> 4T2g(F) and 4A2g(F) --> 4T1g(F) transitions. This is in conformity with the broad resonance of Cr3+ observed from EPR spectrum at g = 1.903 and a weak signal at g = 3.861 confirms Fe3+ impurity in the mineral. Bands of Fe3+ ion in the optical spectrum at 13,700, 18,870 and 28,570 cm(-1) are attributed to 6A1g(S) --> 4T1g(G), 6A1g(S) --> 4T2g(G) and 6A1g(S) --> 4T2g(P) transitions, respectively. Near-IR reflectance spectroscopy has been used effectively to show intense absorption bands caused by electronic spin allowed d-d transitions of Fe2+ in tetrahedral symmetry, in the region 5000-4000 cm(-1). The high frequency region (7500-6500 cm(-1)) is attributed to the overtones of hydroxyl stretching modes. Correlation between Raman spectral features and mineral chemistry are used to interpret the Raman data. The Raman spectrum of chromite shows three bands in the CrO stretching region at 730, 560 and 445 cm(-1). The most intense peak at 730 cm(-1) is identified as symmetric stretching vibrational mode, A1g(nu1) and the other two minor peaks at 560 and 445 cm(-1) are assigned to F2g(nu4) and E(g)(nu2) modes, respectively. Cation substitution in chromite results various changes both in Raman and IR spectra. In the low-wavenumber region of Raman spectrum a significant band at 250 cm(-1) with a component at 218 cm(-1) is attributed F2g(nu3) mode. The minor peaks at 195, 175, 160 cm(-1) might be due to E(g) and F2g symmetries. Broadening of the peak of A1g mode and shifting of the peak to higher wavenumber observed as a result of increasing the proportion of Al3+O6. The presence of water in the mineral shows bands in the IR spectrum at 3550, 3425, 3295, 1630 and 1455 cm(-1). The vibrational spectrum of chromite gives raise to four frequencies at 985, 770, 710 and 650 cm(-1). The first two frequencies nu1 and nu2 are related to the lattice vibrations of octahedral groups. Due to the influence of tetrahedral bivalent cation, vibrational interactions occur between nu3 and nu4 and hence the low frequency bands, nu3 and nu4 correspond to complex vibrations involving both octahedral and tetrahedral cations simultaneously. Cr3+ in Cuban natural chromites has highest CFSE (20,868 cm(-1)) when compared to other oxide minerals. PMID:15863040

Reddy, B Jagannadha; Frost, Ray L

2005-06-01

266

Spectroscopic, molecular structure characterizations and quantum chemical computational studies of ( E)-5-(diethylamino)-2-[(2-fluorophenylimino)methyl]phenol  

NASA Astrophysics Data System (ADS)

The molecular structure and spectroscopic properties of ( E)-5-(diethylamino)-2-[(2-fluorophenylimino)methyl]phenol were characterized by X-ray diffraction, IR and UV/Vis spectroscopy. These properties of title compound were also investigated from calculative point of view. Geometry optimization in gas phase was performed using DFT method with B3LYP applying 6-311G(d,p) basis set and geometry optimizations in solvent media were performed with the same level of theory by the polarizable continuum model (PCM). TD-DFT calculations starting from optimized geometry were carried out in both gas and solution phase to calculate excitation energies of title compound. In addition, while the non-linear optical properties were computed, thermodynamic properties were obtained at the optimized geometry with the same level of theory. The intramolecular proton transfer process from enol form to keto form was investigated using DFT method with B3LYP applying 6-311G(d,p) basis set. Transition state structure in EtOH was performed with the same level of theory by the polarizable continuum model (PCM).

Albayrak, Çi?dem; Frank, Rene

2010-12-01

267

Overexpression, Isolation, and Spectroscopic Characterization of the Bidirectional [NiFe] Hydrogenase from Synechocystis sp. PCC 6803*  

PubMed Central

The bidirectional [NiFe] hydrogenase of the cyanobacterium Synechocystis sp. PCC 6803 was purified to apparent homogeneity by a single affinity chromatography step using a Synechocystis mutant with a Strep-tag II fused to the C terminus of HoxF. To increase the yield of purified enzyme and to test its overexpression capacity in Synechocystis the psbAII promoter was inserted upstream of the hoxE gene. In addition, the accessory genes (hypF, C, D, E, A, and B) from Nostoc sp. PCC 7120 were expressed under control of the psbAII promoter. The respective strains show higher hydrogenase activities compared with the wild type. For the first time a Fourier transform infrared (FTIR) spectroscopic characterization of a [NiFe] hydrogenase from an oxygenic phototroph is presented, revealing that two cyanides and one carbon monoxide coordinate the iron of the active site. At least four different redox states of the active site were detected during the reversible activation/inactivation. Although these states appear similar to those observed in standard [NiFe] hydrogenases, no paramagnetic nickel state could be detected in the fully oxidized and reduced forms. Electron paramagnetic resonance spectroscopy confirms the presence of several iron-sulfur clusters after reductive activation. One [4Fe4S]+ and at least one [2Fe2S]+ cluster could be identified. Catalytic amounts of NADH or NADPH are sufficient to activate the reaction of this enzyme with hydrogen.

Germer, Frauke; Zebger, Ingo; Saggu, Miguel; Lendzian, Friedhelm; Schulz, Rudiger; Appel, Jens

2009-01-01

268

Synthesis, spectroscopic characterization and biological activity of cis-[Ru(hesperidin)(1,10?-phenanthroline)2](PF6) complex  

NASA Astrophysics Data System (ADS)

The new complex cis-[Ru(phen)2(hesperidin)](PF6), complex 1, was synthesized and characterized by analytical (ESI-MS+, EA (C, H, N)) and spectroscopic (FTIR, UV-vis, 1H and 13C NMR) techniques and cyclic voltammetry. Complex 1 is chemically stable in the solid state and in organic solvents such as ethanol, methanol, acetone, and acetonitrile, as shown by spectrophotometric analysis. 1 is also photochemically and chemically stable (pH effects) and more hydrosoluble (518.83 ± 0.91 g mL-1) than free hesperidin (5.92 g mL-1). In accordance with this, the lipophilicity value in aqueous-octanol solution for 1 was -1.28, indicating its high hydrophilic characteristic. Although complex 1 showed to be essentially noncytotoxic, IC50 > 1.0 mmol L-1 as evaluated in the human cervical cancer cells line HeLa, it exhibited a moderate capacity of inhibiting the catalytic activity of the acetylcholinaesterase enzyme, IC50 = 63.6 mol L-1. The Lineweaver-Burk plot and the respective secondary replot indicated that the AChE inhibition was noncompetitive and reversible. These findings shows that complexation of the hesperidin improves physicochemical characteristics and increases the perspectives for development and medical applications of new bioactive-metal complexes.

Oliveira, Regina M. M.; de Souza Daniel, Juliana F.; Carlos, Rose M.

2013-01-01

269

Optical spectroscopic approach as a rapid tool to characterize the interactions of retinoids with human nuclear receptors  

NASA Astrophysics Data System (ADS)

Retinoids are potent molecules that can affect a variety of fundamental biological processes including cell differentiation and proliferation and apoptosis. These molecules elicit their biological effects by activating a family of nuclear receptors which act as ligand-inducible transcription factors belonging to the steroid/thyroid receptor superfamily. Retinoic acid receptors form heterodimers in which response to ligand binding, both partners contribute to transactivation and/or DNA binding in vivo. Surface-enhanced Raman scattering (SERS), Fourier transform-SERS (FT-SERS), fluorescence and circular dichroism are proposed to rapidly give information on the interaction of the different RARs and RXRs with their specific ligands at physiological concentrations. FT-SERS data reveal a significant attenuation in intensity of the bands originating from the retinoic polyenic chain upon complexation. The spectrum is dominantly of the (Beta) - ionone ring. Fluorescence measurements supported the hydrophobic character of the ligand binding pocket and the circular dichroic data indicate that the protein helices extend upon ligand binding. These novel spectroscopic information are fully consistent with published x-ray crystallographic results and suggest that these techniques may be valuable additional tools to characterize the interactions of agonists and antagonists with residues of the ligand binding pocket retinoid receptor homo- and hetero-dimers.

Morjani, Hamid; Sockalingum, Ganesh D.; Beljebbar, Abdelilah; Manfait, Michel

1998-04-01

270

Synthesis and characterization of low-OH?fluor-chlorapatite: A single-crystal XRD and NMR spectroscopic study  

SciTech Connect

Los-OH apatite of the compositional range Ca{sub 4.99-5.06}(PO{sub 4}){sub 2.98-3.00}F{sub 0.51-0.48}Cl{sub 0.38-0.36}OH{sub 0.14-0.12} was synthesized and characterized structurally by synchrotron-based single-crystal X-ray diffraction (XRD), and multiple nuclear magnetic resonance (NMR) spectroscopic techniques. the average structure is hexagonal with space group P6{sub 3}/m. The presence of scattering in the single-crystal diffraction data set, which is incommensurate within the average hexagonal structure, suggests the presence of localized short-range monoclinic domains. Complex lineshapes in the {sup 31}P and {sup 19}F MAS NMR spectra are also consistent with the presence of an incommensurate phase. No evidence was detected for splitting of the Ca2 site into two distinct sites (as had been previously reported for hexagonal ternary apatities). Structure refinement and {sup 19}F{l_brace}{sup 35}Cl{r_brace} TRAPDOR NMR experiments verified intercolumnal neighboring of F and Cl atoms (inter-column distance of 2.62 {angstrom}) within this low-OH{sup -} apatite suggesting that long-range neighboring of F and Cl within the apatite anion channels is feasible.

McCubbin, Francis M.; Mason, Harris E.; Park, Hyunsoo; Phillips, Brian L.; Parise, John B.; Nekvasil, Hanna; Lindsley, Donald H. (SBU)

2008-12-12

271

Synthesis and spectroscopic characterization of a fluorescent pyrrole derivative containing electron acceptor and donor groups  

NASA Astrophysics Data System (ADS)

The synthesis and fluorescence characterization of a new pyrrole derivative (PyPDG) containing the electron donor-acceptor dansyl substituent is reported. The effects of temperature and solvent polarity on the steady-state fluorescence of this compound are investigated. Our results show that PyPDG exhibits desirable fluorescent properties which makes it a promising candidate to be used as the photoactive material in optical thermometry and thermography applications. Further, the electrochemical and emission properties of polymeric films obtained from the oxidation polymerization of PyPDG are also analyzed.

Almeida, A. K. A.; Monteiro, M. P.; Dias, J. M. M.; Omena, L.; da Silva, A. J. C.; Tonholo, J.; Mortimer, R. J.; Navarro, M.; Jacinto, C.; Ribeiro, A. S.; de Oliveira, I. N.

2014-07-01

272

Synthesis and spectroscopic characterization of a fluorescent pyrrole derivative containing electron acceptor and donor groups.  

PubMed

The synthesis and fluorescence characterization of a new pyrrole derivative (PyPDG) containing the electron donor-acceptor dansyl substituent is reported. The effects of temperature and solvent polarity on the steady-state fluorescence of this compound are investigated. Our results show that PyPDG exhibits desirable fluorescent properties which makes it a promising candidate to be used as the photoactive material in optical thermometry and thermography applications. Further, the electrochemical and emission properties of polymeric films obtained from the oxidation polymerization of PyPDG are also analyzed. PMID:24704598

Almeida, A K A; Monteiro, M P; Dias, J M M; Omena, L; da Silva, A J C; Tonholo, J; Mortimer, R J; Navarro, M; Jacinto, C; Ribeiro, A S; de Oliveira, I N

2014-07-15

273

Synthesis, Spectroscopic, and Thermal Characterization of Thiazole Metal Complexes: Biological Activity Studies  

Microsoft Academic Search

Metal complexes of the organic ligand with N azomethine and N thiazole donation sites, derived from 3-(2-(2-(2,6-dichlorobenzylidene)hydrazinyl)-4-oxo-4,5-dihydrothiazol-5-yl) acetic acid (H2L), with some transition metal ions, namely Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II), are reported. They are characterized based on elemental analyses, IR, H NMR, solid reflectance, magnetic moment, and molar conductance. The ionization constants are found to be 5.57

M. M. Omar; G. G. Mohamed; M. A. Badawy; M. M. Nassar; A. B. Kamel

2010-01-01

274

Spectroscopic and chromatographic characterization of triflusal delivery systems prepared by using supercritical impregnation technologies.  

PubMed

This study describes the development and evaluation of an analytical method for the characterization of triflusal (2-acetoxy-4-(trifluoromethyl) benzoic acid) dispersed in sustained delivery systems prepared using supercritical fluid impregnation technology. Characterization assays comprised the determination of the percentage of triflusal and its degradation product impregnated in polymeric supports and further monitoring of the releases of the two drug components over time in physiological conditions. Preliminary delivery profiles were monitored spectrophotometrically using a continuous-flow system. In this case, no selective wavelength for discriminating between triflusal and metabolite was found so that measurements at 225 nm provided overall profiles corresponding to the two compounds. For a more accurate study, a chromatographic method was developed for monitoring the evolution of the concentration of the two components independently. Triflusal and metabolite were separated in a C(18) column and 25 mM acetic acid/acetate (pH 5.0)+methanol (40/60v/v) mobile phase. Several triflusal-polymer samples were prepared under different experimental conditions and release features were evaluated. Excellent delivery systems were obtained with poly(methyl)methacrylate beads treated at 40 degrees C and 190 bar for 48 h using supercritical carbon dioxide as a solvent. These samples showed a constant sustained release of drug for several weeks. PMID:18093783

Argemí, Anna; López-Periago, Ana; Domingo, Concepción; Saurina, Javier

2008-02-13

275

Synthesis, characterization and multi-spectroscopic DNA interaction studies of a new platinum complex containing the drug metformin.  

PubMed

A new platinum(II) complex; [Pt(Met)(DMSO)Cl]Cl in which Met=metformin and DMSO: dimethylsulfoxide, was synthesized and characterized by (1)H NMR, IR, UV-Vis spectra, molar conductivity and computational methods. Binding interaction of this complex with calf thymus (CT) DNA has been investigated by using absorption, emission, circular dichroism, viscosity measurements, differential pulse voltammetry and cleavage studies by agarose gel electrophoresis. UV-Vis absorption studies showed hyperchromism. CD studies showed less perturbation on the base stacking and helicity bands in the CD spectrum of CT-DNA (B?C structural transition). In fluorimeteric studies, the Pt(II) complex can bind with DNA-NR complex and forms a new non-fluorescence adduct. The anodic peak current in the differential pulse voltammogram of the Pt(II) complex decreased gradually with the addition of DNA. Cleavage experiments showed that the Pt(II) complex does not induce any cleavage under the experimental setup. Finally all results indicated that Pt(II) complex interact with DNA via groove binding mode. PMID:24682051

Shahabadi, Nahid; Heidari, Leila

2014-07-15

276

Synthesis, characterization and multi-spectroscopic DNA interaction studies of a new platinum complex containing the drug metformin  

NASA Astrophysics Data System (ADS)

A new platinum(II) complex; [Pt(Met)(DMSO)Cl]Cl in which Met = metformin and DMSO: dimethylsulfoxide, was synthesized and characterized by 1H NMR, IR, UV-Vis spectra, molar conductivity and computational methods. Binding interaction of this complex with calf thymus (CT) DNA has been investigated by using absorption, emission, circular dichroism, viscosity measurements, differential pulse voltammetry and cleavage studies by agarose gel electrophoresis. UV-Vis absorption studies showed hyperchromism. CD studies showed less perturbation on the base stacking and helicity bands in the CD spectrum of CT-DNA (B ? C structural transition). In fluorimeteric studies, the Pt(II) complex can bind with DNA-NR complex and forms a new non-fluorescence adduct. The anodic peak current in the differential pulse voltammogram of the Pt(II) complex decreased gradually with the addition of DNA. Cleavage experiments showed that the Pt(II) complex does not induce any cleavage under the experimental setup. Finally all results indicated that Pt(II) complex interact with DNA via groove binding mode.

Shahabadi, Nahid; Heidari, Leila

2014-07-01

277

Versatile coordinative abilities of a new hybrid pteridine-thiosemicarbazone ligand: crystal structure, spectroscopic characterization, and luminescent properties.  

PubMed

The synthesis and characterization of the first thiosemicarbazone-lumazine (TSCLMH=the thiosemicarbazone of 6-acetyl-1,3,7-trimethyllumazine) hybrid ligand is reported. The influence of the conformation of this compound on its energy and the atomic contribution to the molecular orbitals have been theoretically investigated. Ni(II), Cu(I), Zn(II), and Cd(II) complexes of this ligand have been synthesized and characterized by elemental analysis, thermogravimetric studies, IR, 1H, 13C, and 15N NMR, and UV-vis-NIR spectroscopy, magnetic measurements, and X-ray crystallography. Four types of coordination modes for the ligand may be predicted: (a) double bidentate; (b) tetradentate; (c) tridentate; (d) bidentate. Structures of representative complexes of types a, b, and d have been determined by X-ray crystallography. In the [Cu(TSCLMH)]2(ClO4)2 complex, TSCLMH acts as a doubly bidentate bridging ligand forming a dimer with a Cu...Cu distance of 2.876 A. The geometry around the metal ion is trigonally distorted tetrahedral with a relatively long (four-atom) bridge between the metal centers instead of the shorter, mainly single atom, bridges present in other thiosemicarbazone derivatives complexes. In the [Cd(NO3)2(TSCLMH)(EtOH)] complex, the metal ion displays eight-coordinated geometry with the TSCLMH ligand acting in a tetradentate planar fashion and two nitrate anions, one monodentate and the other bidentate. The coordination polyhedron in [Cd(TSCLM)2(H2O)].MeOH.2H2O is a square pyramid with two monoanionic ligands acting as bidentate NS donors and a water molecule completing the coordination sphere. Fluorescence spectroscopic properties of TSCLMH have been studied as well as the changes in position and intensity of fluorescence bands caused by the complexation with different metal ions (Ni2+, Cu+, Zn2+, Cd2+). PMID:18186630

Jiménez-Pulido, Sonia B; Linares-Ordóñez, Fátima M; Moreno-Carretero, Miguel N; Quirós-Olozábal, Miguel

2008-02-01

278

Optical, laser spectroscopic, and electrical characterization of transion metal doped zinc selenide and zinc sulfide nano-and-microcrystals  

NASA Astrophysics Data System (ADS)

Middle-infrared lasers operating over a "molecular fingerprint" 2-15 mum spectral range are in great demand for a variety of applications. One of the best choices for lasing in the 2-5 mum spectral range is direct oscillation from divalent transition metal ions (TM2+: Cr 2+, Fe2+, Co2+)-doped wide bandgap II-VI semiconductor crystals. There are three major objectives in this dissertation: (1) Realize and study middle-infrared electroluminescence of n and p-type, Cr doped bulk ZnSe crystals. We have demonstrated a method of ZnSe crystals thermal-diffusion doping with donor (In, Zn, and Al) and acceptor (Cu, Ag, and N through CrN) impurities resulting in n and p-type conductivity of Cr:ZnSe. We are the first to our knowledge to obtain mid-IR electroluminescence in nominally p-type Cr:Ag:ZnSe, which could prove valuable for developing of novel mid-IR laser diodes. (2) En route to low dimensional gain material, develop simple method for making microscopic laser active Cr doped ZnSe, ZnS and CdSe powders, realize and study their laser spectroscopic characteristics. We have demonstrated a simple physical method of Cr2+:ZnSe, ZnS and CdSe powder fabrication with average sizes below ˜ 10mum and ˜1mum (eliminating stage of bulk crystal growth) and demonstrated first ever mid-IR random lasing on these powders under optical excitation. In addition, we have examine suspensions and polymer films impregnated with Cr:II-VI powders for random lasing in the mid-IR. The powder, suspension and polymer samples are fabricated and characterized through the measurement of photoluminescence (PL) spectra, PL kinetics, and lasing threshold energy. (3) En route to low dimensional gain material, develop method for making laser active Cr, Co, and Fe doped ZnSe and ZnS quantum dots (QD), realize and study their laser spectroscopic characteristics. We have demonstrated a novel method of TM doped II-VI QDs fabrication based on laser ablation in liquid and Ar environment. TM doped II-VI QDs demonstrated strong mid-IR luminescence. And we also demonstrated the first mid-IR (2-3 mum) random lasing at room temperature of Cr2+:ZnS QD powders. The results obtained in this work open a new pathway for development of low-cost optically and electrically pumped broadly tunable mid-IR laser sources. Keyword: Middle-Infrared lasers, Electroluminescence, Transition Metal ions, powder random lasers, nanocrystal lasers, Polymer film and Suspension.

Kim, Changsu

279

Mössbauer spectroscopic characterization of iron methyl pyropheophorbide a and its derivatives  

NASA Astrophysics Data System (ADS)

Two kinds of iron chlorophylls, i.e. (methyl pyropheophorbide a)iron(III) chloride and its bis-pyridine adduct, were prepared and characterized by57Fe Mössbauer spectroscopy. (Methyl pyropheophorbide a)iron(III) chloride gave an asymmetric quadrupole-split doublet typical of high-spin iron(III) chlorophylls, while its bis-pyridine adduct showed a symmetric quadrupole-split doublet characteristic of low-spin iron(II) chlorophylls. The isomer shift and quadrupole splitting obtained for (methyl pyropheophorbide a)iron(III) chloride and its bis-pyridine adduct have led to the following conclusions. The substitution of the bulky phytyl group for the methyl group hardly affects the electronic state of the iron(II,III) ion, but the elimination of the methoxycarbonyl group increases the planarity of the macrocyclic chlorin ligand.

Inoue, H.; Soeda, K.; Akahori, H.; Nonomura, Y.; Yoshioka, N.

1994-12-01

280

Molecular modelling, spectroscopic characterization and biological studies of tetraazamacrocyclic metal complexes.  

PubMed

Macrocyclic complexes of the type [MLX]X2; where L is (C30H28N4), a macrocyclic ligand, M=Cr(III) and Fe(III) and X=Cl-, CH3COO- or NO3-, have been synthesized by template condensation reaction of 1,8-diaminonaphthalene and acetylacetone in the presence of trivalent metal salts in a methanolic medium. The complexes have been formulated as [MLX]X2 due to 1:2 electrolytic nature of these complexes. The complexes have been characterized with the help of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, electronic, infrared, far infrared, Mass spectral studies and molecular modelling. Molecular weight of these complexes indicates their monomeric nature. On the basis of all these studies, a five coordinated square pyramidal geometry has been proposed for all these complexes. These metal complexes have also been screened for their in vitro antimicrobial activities. PMID:24769359

Rathi, Parveen; Sharma, Kavita; Singh, Dharam Pal

2014-09-15

281

Multiple parameter optimization and spectroscopic characterization of a dielectric barrier discharge in N2  

NASA Astrophysics Data System (ADS)

For surface treatments with plasma under atmospheric pressure, it is important to obtain a homogeneous discharge, ideally a glow discharge. Normally, a discharge under atmospheric pressure is filamentary. The aim of this work is to examine the influence of various parameters on the plasma properties and therefore on its homogeneity. For this purpose, the plasma was characterized by optical emission spectroscopy and electrical measurements. It was found that a smaller gap leads to more electronic excited species and to an increased plasma power. Furthermore, the reduction of the gap distance results in a lower rotational temperature and, above all, to an improved homogeneity of the plasma. The changes in the plasma properties with variation of the external parameters, such as gas flow or applied voltage, are much slighter with a smaller gap. Therefore, a plasma with a smaller gas gap can be run over a wider region without significant changes in its properties.

Meiners, Annette; Leck, Michael; Abel, Bernd

2009-11-01

282

Synthesis and spectroscopic characterization of gallic acid and some of its azo complexes  

NASA Astrophysics Data System (ADS)

A series of gallic acid and azo gallic acid complexes were prepared and characterized by elemental analysis, IR, electronic spectra and magnetic susceptibility. The complexes were of different geometries: Octahedral, Tetrahedral and Square Planar. ESR was studied for copper complexes. All of the prepared complexes were of isotropic nature. The thermal analyses of the complexes were studied by DTA and DSC techniques. The thermodynamic parameters and the thermal transitions, such as glass transitions, crystallization and melting temperatures for some ligands and their complexes were evaluated and discussed. The entropy change values, ?S#, showed that the transition states are more ordered than the reacting complexes. The biological activities of some ligands and their complexes are tested against Gram positive and Gram negative bacteria. The results showed that some complexes have a well considerable activity against different organisms.

Masoud, Mamdouh S.; Hagagg, Sawsan S.; Ali, Alaa E.; Nasr, Nessma M.

2012-04-01

283

Structural and spectroscopic characterization of prepared Ag2S nanoparticles with a novel sulfuring agent.  

PubMed

Ag2S nanoparticles were prepared by a solvothermal process via reaction of Ag(NO3) and a new sulfuring agent from class of thio Schiff-base (2-(benzylidene amino) benzenethiol (C13H11NS)) in presence of various solvents. Spectra such as X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SEAD), ultraviolet-visible (UV-Vis) spectroscopy, thermo gravimetric-differential thermal analysis (TG-DTA), and Fourier transform Infrared (FT-IR) employed to characterize the synthesized products. Results of this paper indicate that shape and size of the silver sulfide can be controlled by means of setting certain reaction parameters such as the reaction temperature, presence of surfactant, and type of solvent. Silver sulfide nanoparticles with different morphology and size successfully prepared. In addition, the growth mechanisms of the Ag2S nanoparticles discussed preliminarily. PMID:24973787

Shakouri-Arani, Maryam; Salavati-Niasari, Masoud

2014-12-10

284

Solution NMR spectroscopic characterization of human VDAC-2 in detergent micelles and lipid bilayer nanodiscs.  

PubMed

Three isoforms of the human voltage-dependent anion channel (VDAC), located in the outer mitochondrial membrane, are crucial regulators of mitochondrial function. Numerous studies have been carried out to elucidate biochemical properties, as well as the three-dimensional structure of VDAC-1. However, functional and structural studies of VDAC-2 and VDAC-3 at atomic resolution are still scarce. VDAC-2 is highly similar to VDAC-1 in amino acid sequence, but has substantially different biochemical functions and expression profiles. Here, we report the reconstitution of functional VDAC-2 in lauryldimethylamine-oxide (LDAO) detergent micelles and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayer nanodiscs. We find that VDAC-2 is properly folded in both membrane-mimicking systems and that structural and functional characterization by solution NMR spectroscopy is feasible. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism. PMID:22119777

Yu, Tsyr-Yan; Raschle, Thomas; Hiller, Sebastian; Wagner, Gerhard

2012-06-01

285

Spectroscopic ellipsometric characterization of TiAlN\\/TiAlON\\/Si 3N 4 tandem absorber for solar selective applications  

Microsoft Academic Search

Sputter deposited TiAlN\\/TiAlON\\/Si3N4 tandem absorber has been characterized by spectroscopic ellipsometry in the wavelength range of 450–1200nm. Each layer of the tandem absorber viz., TiAlN, TiAlON and Si3N4 has been deposited separately on copper substrate (Cu) and ellipsometric measurements have been carried out on each of these layers. The measured ellipsometric spectra were fitted with theoretically simulated spectra and the

A. Biswas; D. Bhattacharyya; H. C. Barshilia; N. Selvakumar; K. S. Rajam

2008-01-01

286

Isolation and Spectroscopic Characterization of Reactive Species in Atmospheric and Interstellar Reactions  

NASA Astrophysics Data System (ADS)

A critical element to the study of chemical reactions is the characterization of reaction intermediates. Methods have been developed to isolate these transient species in the gas phase and when combined with infrared spectroscopy have proven to be excellent tools for determining the structure and reactivity of key intermediates. The studies presented here exploit these technologies to better understand the chemistry of species involved in atmospheric and interstellar reactions. An excellent example of their utility is in the study of the formation of proton hydrates and HONO in the upper atmosphere by sequential addition of water molecules onto the nitrosonium ion. This reaction only proceeds to products after addition of the fourth water molecule, and isolation and characterization of the intermediate trihydrate, NO+(H 2O)3, shows that this species is formed in three isomeric forms, each with a different water network that controls the degree of bond formation between the nitrosonium ion and an activated water molecule. Many isomeric structures are also seen in the clustering reactions of acetylene which may be a mechanism for the formation of benzene cation in interstellar space. The spectroscopy of the trimer, (C2H2)3 + indicates that this species exists in two major isomer classes; covalent forms, one of which may be benzene, and an ion-molecule complex, comprised of a loosely bound acetylene on a dimer core. Interestingly, this dimer core is different from the cyclobutadiene-like structure observed in dimerized acetylene, and proves to be a robust species on the potential energy surface as it survives further clustering events. Two structural isomers of CO3 -and NO3 - are also investigated, and found to have drastically different infrared spectra which are analyzed in the context of their electronic structure. Isomers in these systems are prepared under different expansion conditions which accounts for their unique spectral signatures.

Relph, Rachael A.

287

Structural and spectroscopic characterization of E- and Z-isomers of azobenzene.  

PubMed

Monomers of azobenzene were isolated in argon matrices at 15 K and characterized by infrared spectroscopy and theoretical calculations. When the equilibrium vapors existing over the azobenzene crystals at room temperature were trapped in the matrix, only the thermodynamically most stable E-azobenzene was detected. In an attempt to convert E-azobenzene into the Z isomer, the matrix-isolated E-monomers were irradiated either by broad-band or narrow-band UV-visible light of different wavelengths, in the 600-200 nm range. However, no E-to-Z transformation was observed under these conditions. In an alternative experiment, E-azobenzene was irradiated by UV-visible broad-band light in the gas phase prior to trapping in a matrix. In this case, the E-to-Z photoisomerization occurred, and both E- and Z-azobenzene monomers were detected in the matrix sample. Subsequent irradiation of the matrix with narrow-band tunable visible or UV light (? < 550 nm) resulted in back conversion of Z-azobenzene into the E-form. The observed photoinduced E-to-Z isomerizations allowed for the reliable vibrational characterization of both azobenzene isomers. The two-dimensional potential energy surfaces of Z- and E-azobenzene were explored as functions of the torsional movement of the two phenyl rings. They exhibit large flat areas around the minima, for both isomers, allowing for large-amplitude zero-point torsional vibrations. For the Z-form, these vibrations were found to be responsible for significant changes in the equilibrium NN bond length (up to 0.3 pm). This also allowed to explain the experimentally observed frequency smearing of the N[double bond, length as m-dash]N stretching vibration in this isomer. PMID:24647717

Duarte, Luís; Fausto, Rui; Reva, Igor

2014-08-28

288

Characterization of the formaldehyde-H2O system using combined spectroscopic and mass spectrometry approaches  

NASA Astrophysics Data System (ADS)

The atmosphere is a multiphase reactor in which physical exchange processes, heterogeneous reactions and photochemical reactions take place. The oxygenated organics (formaldehyde, ethanol, acetone etc.) present at trace concentrations into the atmosphere are known to play an important role in atmospheric chemistry due for example to their contribution in the production of HOx radicals, which largely determine the lifetime of pollutants [1]. Further, it has been shown that the interaction of oxygenated organics with ice particles in the atmosphere has the potential to promote heterogeneous chemistry [2]. In the polar lower troposphere, formaldehyde (H2CO) was measured in concentrations that are much higher that those predicted by chemistry models [3]. The mechanism at the origin of the formaldehyde production remains however controversial as the incorporation / partitioning of H2CO in ice crystal has to be determined first. Incorporation of formaldehyde into ice can take place according to several different physical mechanisms like co-condensation, riming, adsorption/desorption. The partitioning of formaldehyde between the gas phase, the liquid and the solid phases is an important parameter that leads to a better understanding of the incorporation mechanisms. In our work, different experimental approaches are used to characterize the partitioning between the different phases in which the H2O-H2CO system exists. Recently, we investigated by mass spectrometry and infrared diode laser spectroscopy the vapor liquid equilibrium (VLE) of formaldehyde aqueous solutions of different concentrations at room temperature. From the data collected on the vapor pressures at atmospherically relevant formaldehyde concentrations, we derived the Henry's coefficients at 295 K [4]. In this study we present first results on the solubility of formaldehyde in ice. This allows a better characterization of the partitioning of formaldehyde vapors above supercooled droplets and/or ice at low temperatures (233-283K) and low dissolved fraction of formaldehyde. Also presented is the thermal evolution of thin structured films of condensed H2CO/H2O or H2CO/acid-doped (HNO3)-ice layers. This is examined using temperature programmed desorption (TPD) experiments and Raman spectroscopy. The results are compared with those obtained on co-condensed H2CO/H2O mixtures [5]. [1] Atkinson R., Atmospheric Environment, 2000, 34: 2063 [2] Abbatt J.P.D., Chem.Rev. 2003, 103: 4783 [3] Dominé F., Shepson P.B., Science, 2002, 297: 1506 [4] Oancea A. et al. Environ. Sci. Technol. in press [5] Chazallon B. et al. , Phys.Chem.Chem.Phys., 2008, 10: 702

Oancea, A.; Hanoune, B.; Facq, S.; Focsa, C.; Chazallon, B.

2009-04-01

289

Purification and spectroscopic characterization of a recombinant chloroplastic hemoglobin from the green unicellular alga Chlamydomonas eugametos.  

PubMed

Hemoglobins (Hb), which have the important task of delivering molecular oxygen by facilitating its reversible binding to the heme, are now thought to have evolved in all groups of organisms including prokaryotes, fungi, plants and animals. Our recent finding of a light-inducible chloroplastic Hb in the green unicellular alga Chlamydomonas eugametos has further extend this idea, while raising questions about the function that an Hb could play in a high oxygen environment such as in the chloroplast. In order to understand the role played by this new Hb, we have undertaken its biochemical characterization. To facilitate the characterization of Chlamydomonas Hb, which represents less than 0.01% of the soluble protein in the green alga, the protein has been expressed in Escherichia coli and purified to apparent homogeneity. The purified recombinant protein possesses a non-covalently bound iron-protoporphyrin IX heme. The oxy form of the recombinant Hb. purified directly from bacterial cells, is very stable, with a measured half-life of 7 days at pH 8 and has an ultraviolet/visible spectrum similar to those of the related cytoplasmic Hbs of the ciliated protozoa Paramecium and Tetrahymena and of the cyanobacterium Nostoc commune. In contrast to what has been reported for oxymyoglobins and oxyhemoglobins, the dioxygen molecule bound to the L1637 Hb can be reduced by the electron-transfer mediator phenazine methosulfate in the presence of NADPH, indicating that the heme pocket of Chlamydomonas Hb may be more accessible to small molecules. With regard to this we found that when the small reducing agent sodium dithionite is used to reduce the met form, it must be removed anaerobically from the Hb prior to oxygenation of the protein to stably produce the oxy form. Otherwise, the oxy form is obtained readily from the met form under an oxygenic atmosphere when ferredoxin and ferredoxin NADP+ reductase are used to enzymically reduce the Hb. Finally, the spectra of the deoxy and met forms were unusual, the heme being partly low-spin at physiological pH. These results confirm the existence of a reversible oxygen-binding protein in the chloroplast of C. eugametos. The unusual spectral and biochemical properties of the protein may reflect a specialized function for this Hb. PMID:9022709

Couture, M; Guertin, M

1996-12-15

290

Structural characterization of humic-like substances with conventional and surface-enhanced spectroscopic techniques  

NASA Astrophysics Data System (ADS)

Emission-excitation, synchronous fluorescence spectroscopy and surface-enhanced Raman scattering (SERS) combined with surface-enhanced fluorescence (SEF) were applied to aqueous solutions of a humic-like substance (HLS) extracted from earthworm faeces. All measurements were acquired in a wide range of pH (4-12) and analysed by the linear regression analysis. Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectra were also acquired to assist in the structural characterization of this HLS. The emission and excitation spectra allowed the identification of two main fluorophores in the analysed sample. Moreover, a close correlation between fluorescence intensities of each fluorophore with pH variation was observed. SERS and SEF, in agreement with the fluorescence spectroscopy, showed that the HLS at low pH values exists in an aggregated and coiled molecular structure while it is dispersed and uncoiled at alkaline conditions. The obtained spectra also evidenced that different conditions modify the functional groups exposed to the surrounding aqueous environment.

Carletti, Paolo; Roldán, Maria Lorena; Francioso, Ornella; Nardi, Serenella; Sanchez-Cortes, Santiago

2010-10-01

291

Raman, infrared and near-infrared spectroscopic characterization of the herderite-hydroxylherderite mineral series  

NASA Astrophysics Data System (ADS)

Natural single-crystal specimens of the herderite-hydroxylherderite series from Brazil, with general formula CaBePO4(F,OH), were investigated by electron microprobe, Raman, infrared and near-infrared spectroscopies. The minerals occur as secondary products in granitic pegmatites. Herderite and hydroxylherderite minerals show extensive solid solution formation. The Raman spectra of hydroxylherderite are characterized by bands at around 985 and 998 cm-1, assigned to ?1 symmetric stretching mode of the HOPO33- and PO43- units. Raman bands at around 1085, 1128 and 1138 cm-1 are attributed to both the HOP and PO antisymmetric stretching vibrations. The set of Raman bands observed at 563, 568, 577, 598, 616 and 633 cm-1 are assigned to the ?4 out of plane bending modes of the PO4 and H2PO4 units. The OH Raman stretching vibrations of hydroxylherderite were observed ranging from 3626 cm-1 to 3609 cm-1. The infrared stretching vibrations of hydroxylherderites were observed between 3606 cm-1 and 3599 cm-1. By using a Libowitzky type function, hydrogen bond distances based upon the OH stretching bands were calculated. Characteristic NIR bands at around 6961 and 7054 cm-1 were assigned to the first overtone of the fundamental, whilst NIR bands at 10,194 and 10,329 cm-1 are assigned to the second overtone of the fundamental OH stretching vibration. Insight into the structure of the herderite-hydroxylherderite series is assessed by vibrational spectroscopy.

Frost, Ray L.; Scholz, Ricardo; López, Andrés; Xi, Yunfei; Queiroz, Camila de Siqueira; Belotti, Fernanda M.; Filho, Mauro Cândido

2014-01-01

292

Mononuclear metal complexes of organic carboxylic acid derivatives: Synthesis, spectroscopic characterization, thermal investigation and antimicrobial activity  

NASA Astrophysics Data System (ADS)

Two Schiff base ligands bearing organic acid moiety, vis., N-(2-thienylmethylidene)-2-amino-4-chlorobenzoic acid (HL 1) and N-(2-hydroxybenzylidene)-2-amino-4-chlorobenzoic acid (H 2L 2) have been synthesized by the interaction of 2-thiophenecarboxaldehyde and 2-hydroxybenzaldehyde with 2-amino-4-chlorobenzoic acid. Co(II), Ni(II), Cu(II) and Zn(II) complexes of these ligands have been prepared. They are characterized on the basis of analytical data, molar conductance, IR, 1H NMR, UV-vis, mass spectra, magnetic measurements, thermal analysis and X-ray powder diffraction technique. The molar conductance data reveal that these complexes are non-electrolytes. The ligands are coordinated to the metal ions in a terdentate manner with ONO/ONS donor sites of the carbonyl oxygen, azomethine nitrogen and phenolic oxygen or thiophenic sulphur. An octahedral structure is proposed for the prepared metal complexes and some ligand field parameters ( Dq, B and ?) in addition to CFSE were calculated. The thermal stability of the metal complexes is evaluated. The Schiff base ligands and their metal complexes have been tested against four species of bacteria as well as four species of fungi and the results have been compared with some known antibiotics.

Abd El-Wahab, Zeinab H.

2007-05-01

293

Functionalized tellurols: synthesis, spectroscopic characterization by photoelectron spectroscopy, and quantum chemical study.  

PubMed

Ethene-, cyclopropane-, 3-butene-, and cyclopropanemethanetellurol have been synthesized by reaction of tributyltin hydride with the corresponding ditellurides and characterized by 1H, 13C, and 125Te NMR spectroscopy and high-resolution mass spectrometry. The tellurols of this series, with a gradually increasing distance between the tellurium atom and the unsaturated group, have been studied by photoelectron spectroscopy and quantum chemical calculations. Two stable conformations of ethenetellurol and cyclopropanetellurol, five of allyltellurol, and four of cyclopropanemethanetellurol were found. In the photoelectron spectrum of vinyltellurol, the huge split between the first two bands indicates a direct interaction between the tellurium lone electron pair and the double bond. In the allyl derivative, a hyperconjugation effect was found for the most stable conformers. In contrast to the vinyl compounds, no direct interaction between the lone electron pair of X (X = O, S, Se, and Te) and the three-membered ring could be observed in the cyclopropyl derivatives. A hyperconjugation-like effect, which is independent of the relative orientation of the X-H group, is found to increase from S to Te. Thus, the type and extent of the interaction between the TeH group and an unsaturated or cyclopropyl moiety are clarified while the first comparison of interactions between the nonradioactive unsaturated chalcogen derivatives is performed. PMID:18257551

Khater, Brahim; Guillemin, Jean-Claude; Bajor, Gábor; Veszprémi, Tamás

2008-03-01

294

Spectroscopic characterization of B/KNO3 diode-laser induced combustion.  

PubMed

The combustion of a B/KNO3 pyrotechnic mixture was characterized by its chemiluminescence for the first time. The reaction was initiated by a continuous wave (cw) diode laser inside a novel multipurpose reaction cell, whose design and construction are described. As in the case of the extensively studied oxidation of boron by O2, the most intense luminescence, recorded in the 400-600 nm range, is assigned to BO2. Its appearance delay time (10(-2) to 10(-1) s) equals that measured for the pressure increase and is shortened as the laser power is increased. A band observed at 355 nm appears at longer delay times than the BO2 bands. The band, and some weaker ones, may be assigned to BO, although some bands expected for BO (based on reaction between B atoms and O2) are absent from the spectra. This observation is discussed in the text, and possible emission from BN is discussed. If the band is assigned to BO, the absence of known bands may be due to specific E-V resonance energy transfer. Possible oxidation mechanisms consistent with the different delay ignition times are discussed. PMID:23679891

Sivan, J; Haas, Y

2013-11-21

295

Synthesis, characterization and spectroscopic investigation of Cr3+ doped wollastonite nanophosphor  

NASA Astrophysics Data System (ADS)

This work explores the preparation of nanocrystalline Cr3+ (1-5 mol%) doped CaSiO3 phosphors by solution combustion process and study of its photoluminescence (PL) behavior. The nanopowders are well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infra-red (FTIR) spectroscopy. PXRD results confirm monoclinic phase upon calcination at 950 °C for 3 h. SEM micrographs indicates that the powder is highly porous and agglomerated. The TEM images show the powder to consist of spherical shaped particles of size ?30-60 nm. Upon 323 nm excitation, the emission profile of CaSiO3:Cr3+ exhibits a narrow red emission peak at 641 nm due to 2E ? 4A2 transition and broad band at 722 nm due to 4T2g ? 4A2g. It is observed that PL intensity increases with increase in Cr3+ concentration and highest PL intensity is observed for 3 mol% doped sample. The PL intensity decreases with further increase in Cr3+ doping. This decrease in PL intensity beyond 3 mol% is ascribed to concentration quenching. Racah parameters are calculated to describe the effects of electron-electron repulsion within the crystal lattice. The parameters show 21% reduction in the Racah parameter of free ion and the complex, indicating the moderate nephelauxetic effect in the lattice.

Madesh Kumar, M.; Nagabhushana, H.; Nagabhushana, B. M.; Suriyamurthy, N.; Sharma, S. C.; Shivakumara, C.; Hari Krishna, R.

2014-07-01

296

Full elastic characterization of absorptive rubber using laser excited guided ultrasonic waves  

NASA Astrophysics Data System (ADS)

Because of the highly damping nature of rubber, it is difficult to characterize its dynamic elastic properties using classical methods. In this paper, an experimental approach employing laser excited guided acoustic waves is proposed to accurately determine the real and imaginary part of the longitudinal and shear elastic modulus of a rubber layer. From the spatiotemporal evolution of a propagating laser excited Lamb wave measured by a laser Doppler vibrometer, which is scanning along a line perpendicular to a line of excitation, the phase velocity dispersion curves in the wave number - frequency domain are obtained. The results are interpreted in the framework of a detailed semianalytical study, analyzing the influence of elastic damping on the Lamb dispersion curves. This analysis is exploited to adequately fit the experimental dispersion curves and thus extract information about the elastic moduli and absorption coefficients of the rubber plate. The results are validated by a pulse-echo measurement, and by guided wave propagation results with the rubber layer connected in a bi-layer plate configuration to non-damping plates.

Verstraeten, Bert; Xu, Xiadong; Martinez, Loïc; Glorieux, Christ

2012-05-01

297

(TAML)Fe**IV=O Complex in Aqueous Solution: Synthesis And Spectroscopic And Computational Characterization  

SciTech Connect

Recently, we reported the characterization of the S = 1/2 complex [Fe{sup V}(O)B*]{sup -}, where B* belongs to a family of tetraamido macrocyclic ligands (TAMLs) whose iron complexes activate peroxides for environmentally useful applications. The corresponding one-electron reduced species, [Fe{sup IV}(O)B*]{sup 2-} (2), has now been prepared in >95% yield in aqueous solution at pH > 12 by oxidation of [Fe{sup III}(H{sub 2}O)B*]{sup -} (1), with tert-butyl hydroperoxide. At room temperature, the monomeric species 2 is in a reversible, pH-dependent equilibrium with dimeric species [B*Fe{sup IV}?O?Fe{sup IV}B*]{sup 2-} (3), with a pK{sub a} near 10. In zero field, the Moessbauer spectrum of 2 exhibits a quadrupole doublet with {Delta}E{sub Q} = 3.95(3) mm/s and {delta} = ?0.19(2) mm/s, parameters consistent with a S = 1 Fe{sup IV} state. Studies in applied magnetic fields yielded the zero-field splitting parameter D = 24(3) cm{sup -1} together with the magnetic hyperfine tensor A/g{sub n}{beta}{sub n} = (?27, ?27, +2) T. Fe K-edge EXAFS analysis of 2 shows a scatterer at 1.69 (2) {angstrom}, a distance consistent with a Fe{sup IV} = O bond. DFT calculations for [Fe{sup IV}(O)B*]{sup 2-} reproduce the experimental data quite well. Further significant improvement was achieved by introducing hydrogen bonding of the axial oxygen with two solvent-water molecules. It is shown, using DFT, that the {sup 57}Fe hyperfine parameters of complex 2 give evidence for strong electron donation from B* to iron.

Chanda, A.; Shan, X.; Chakrabarti, M.; Ellis, W.C.; Popescu, D.L.; Oliveira, F.Tiago de; Wang, D.; Que, L.; Jr.; Collins, T.J.; Munck, E.; Bominaar, E.L.

2009-05-12

298

Comprehensive characterization of oil refinery effluent-derived humic substances using various spectroscopic approaches.  

PubMed

Refinery effluent-derived humic substances (HS) are important for developing refinery effluent reclamation techniques and studying the environmental chemistry of wastewater effluents. In this study, dissolved organic matter (DOM) from refinery effluent was concentrated using a portable reverse osmosis (RO) system. HS were isolated from RO retentates with XAD-8 resin. A variety of approaches such as specific UV absorbance at 254nm (SUV(254)), elemental analysis, size exclusion chromatography (SEC), solid-state cross polarization magic angle spinning (13)C nuclear magnetic resonance spectrometry ((13)C CPMAS NMR), Fourier transform infrared spectrometry (FTIR), and electrospray ionization/ion trap/mass spectrometry (ESI/ion trap/MS) were employed for characterization of HS. The portable RO system exhibited high yield and recovery of DOM for concentrating refinery effluent. The concentration of dissolved organic carbon (DOC) in the refinery effluent was 9.9mg/l, in which humic acids (HA) and fulvic acids (FA) accounted for 2.3% and 34.6%, respectively. Elemental and SUV(254) analyses indicated relative high amounts of aliphatic structures and low amounts of aromatic structures in refinery effluent-derived HS. Refinery effluent-derived HS displayed lower molecular weight than natural HS. The number-average molecular weight (M(n)) and the weight-average molecular weight (M(w)) of HA were 1069 and 2934, and those of FA were 679 and 1212 by SEC, respectively. By ESI/ion trap/MS, the M(n) and the M(w) of FA were 330 and 383. Four kinds of carbon structures (aliphatic, aromatic, heteroaliphatic, and carboxylic carbons) were found in refinery effluent-derived HS by (13)C NMR analysis. The quantitative results support the interpretation that these HS are rich in aliphatic carbons and poor in aromatic carbons. Proteinaceous materials were identified by FTIR analysis in refinery effluent-derived HS. PMID:15950039

Lingbo, Li; Song, Yan; Congbi, Han; Guangbo, Shan

2005-07-01

299

A thermodynamic, spectroscopic, and mechanical characterization of the wood-polypropylene interphase  

NASA Astrophysics Data System (ADS)

Extruded composites composed of wood and semicrystalline polyolefin thermoplastics are gaining acceptance for use in structural, exterior applications. Wood and polyolefins are inherently incompatible making the use of a coupling agent necessary for improved stiffness and strength. However, the improvements to properties are negated by the addition of processing lubricants used in extrusion. The mechanisms for degrading the properties of the composite are largely unknown. The goal of this research is characterize the mechanisms that lead to improvements in properties in wood-polypropylene (PP) composites with the use of a coupling agent, maleic anhydride polypropylene (MAPP), and the degradation of properties with the incorporation of lubricants, a polyester (OP), zinc stearate (ZnSt), and ethylene bisstearamide (EBS). A combination of experimental techniques was used to probe the impact crystal and amorphous polymer morphology has on the mechanical response of the system. The use of dynamic mechanical spectroscopy allowed for the determination molecular, interaction at the wood-PP interface and between polymer molecules in the bulk. The analysis revealed that MAPP improved the stiffness of the composite by several different mechanisms. MAPP improves crystal nucleation off the wood surface and created a large interphase that likely increases bending stiffness. In addition, there is improved interaction between matrix and filler leading to decreased mechanical damping. These effects are negated with the incorporation of ZnSt because of a reaction with the MAPP's polar groups. This leads to poor packing and nucleation of PP molecules at the wood surface leading to a decrease in strength and stiffness.

Harper, David Paul

300

Fluorescence spectroscopic characterization of dissolved organic matter fractions in soils in soil aquifer treatment.  

PubMed

This work investigated the effect of soil aquifer treatment (SAT) operation on the fluorescence characteristics of dissolved organic matter (DOM) fractions in soils through laboratory-scale soil columns with a 2-year operation. The resin adsorption technique (with XAD-8 and XAD-4 resins) was employed to characterize the dissolved organic matter in soils into five fractions, i.e., hydrophobic acid (HPO-A), hydrophobic neutral (HPO-N), transphilic acid (TPI-A), transphilic neutral (TPI-N), and hydrophilic fraction (HPI). The synchronous fluorescence spectra revealed the presence of soluble microbial byproduct- and humic acid-like components and polycyclic aromatic compounds in DOM in soils, and SAT operation resulted in the enrichment of these fluorescent materials in all DOM fractions in the surface soil (0-12.5 cm). More importantly, the quantitative method of fluorescence regional integration was used in the analysis of excitation-emission matrix (EEM) spectra of DOM fractions in soils. The cumulative EEM volume (? T, n ) results showed that SAT operation led to the enrichment of more fluorescent components in HPO-A and TPI-A, as well as the dominance of less fluorescent components in HPO-N, TPI-N, and HPI in the bottom soil (75-150 cm). Total ? T, n values, which were calculated as [Formula: see text], suggested an accumulation of fluorescent organic matter in the upper 75 cm of soil as a consequence of SAT operation. The distribution of volumetric fluorescence among five regions (i.e., P i, n ) results revealed that SAT caused the increased content of humic-like fluorophores as well as the decreased content of protein-like fluorophores in both HPO-A and TPI-A in soils. PMID:23054268

Xue, Shuang; Zhao, Qingliang; Wei, Liangliang; Song, Youtao; Tie, Mei

2013-06-01

301

Raman spectroscopic characterization of a synthetic, non-stoichiometric Cu-Ba uranyl phosphate.  

PubMed

Crystals of phases belonging to the autunite group (general formula X(2+)(UO2)2(X(5+)O4)2·nH2O), specifically the uranyl phosphates (X(5+)=P) metauranocircite (X(2+)=Ba(2+)), metatorbernite (X(2+)=Cu(2+)) and a barian metatorbenite phase (X(2+)=Cu(2+)/Ba(2+)), have been synthesized in a silica gel medium and characterized by Raman spectroscopy. The Raman spectra showed bands in the range 750-1100 cm(-1), which were attributed to the ?1 and ?3 (PO(4))(3-) and (UO(2))(2+) stretching vibrations. By using the wavenumbers of the most intense and well defined ?1 (UO(2))(2+) vibration, the U-O bonds lengths were calculated for the three uranyl phosphate minerals. The results are in good agreement with previous single crystal structure analysis data. Bands in the spectra from 350 to 700 cm(-1) were attributed to the (PO(4))(3-) bending modes. Moreover, in the range 70-350 cm(-1), two groups of bands could be defined. The first group, with vibrations at lower wavenumbers, was attributed to the lattice modes and the second group, from 150 to 350 cm(-1), was assigned to the ?2 (UO(2))(2+) bending mode. Finally, in the case of the barian metatorbernite, bands in the range 1500-3800 cm(-1) were assigned to the OH stretching and the ?2 bending vibrations of water molecules. In this phase, all the vibrations show bandshifts when compared to the vibrations in metatorbernite. These bandshifts can be related to transitional Cu-O and Ba-O bond lengths. PMID:23727673

Sánchez-Pastor, Nuria; Pinto, André J; Astilleros, José Manuel; Fernández-Díaz, Lurdes; Gonçalves, Mário A

2013-09-01

302

Spectroscopic and Functional Characterization of Iron-Sulfur Cluster-Bound Forms of Azotobacter vinelandii NifIscA†  

PubMed Central

The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of NifIscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV–visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii NifIscA, and the ability of NifIscA to accept clusters from NifU and to donate clusters to the apo form of the nitrogenase Fe-protein. The results show that NifIscA can rapidly and reversibly cycle between forms containing one [2Fe-2S]2+ and one [4Fe-4S]2+ cluster per homodimer via DTT-induced two-electron reductive coupling of two [2Fe-2S]2+ clusters and O2-induced [4Fe-4S]2+ oxidative cleavage. This unique type of cluster interconversion in response to cellular redox status and oxygen levels is likely to be important for the specific role of A-type proteins in the maturation of [4Fe-4S] cluster-containing proteins under aerobic growth or oxidative stress conditions. Only the [4Fe-4S]2+-NifIscA was competent for rapid activation of apo-nitrogenase Fe protein under anaerobic conditions. Apo-NifIscA was shown to accept clusters from [4Fe-4S] cluster-bound NifU via rapid intact cluster transfer, indicating a potential role as a cluster carrier for delivery of clusters assembled on NifU. Overall the results support the proposal that A-type proteins can function as carrier proteins for clusters assembled on U-type proteins and suggest that they are likely to supply [2Fe-2S] clusters rather than [4Fe-4S] for the maturation of [4Fe-4S] cluster-containing proteins under aerobic or oxidative stress growth conditions.

Mapolelo, Daphne T.; Zhang, Bo; Naik, Sunil G.; Huynh, Boi Hanh; Johnson, Michael K.

2012-01-01

303

Spectroscopic characterizations of a mixed surfactant mesophase and its application in materials synthesis  

NASA Astrophysics Data System (ADS)

A viscous lyotropic crystalline mesophase containing bis (2-ethylhexyl) sodium sulfosuccinate (AOT), alpha-phosphatidylcholine (lecithin), with comparable volume fractions of isooctane and water was characterized by Fourier-transform 31P and 1H nuclear magnetic resonance (NMR) spectroscopy. Shear alignment on the reverse hexagonal mesophase was reflected through both 31P NMR and 1H NMR spectra. A complicated 31P spectrum was observed as a result of superposition of chemical shifts according to the distribution of crystalline domains prior to shear. The initially disordered samples with polydomain structures became macroscopically aligned after Couette shear and the alignment retained for a long period of time. 31P NMR chemical shift anisotropy characteristics were used to elucidate orientation of the hexagonal phase. Interestingly, 1H NMR of the water, methyl and methylene groups exhibited spectral changes upon shear alignment closely corresponding with that of 31P NMR spectra. A reverse hexagonal to lamellar phase transition was manifested as an expanding of the expressed 31P NMR chemical shift anisotropy and an apparent reversal of the powder pattern with increasing water content and/or temperature. Correspondingly, 1H NMR spectra also experienced a spectral pattern transition as the water content or temperature was increased. These observations complement the findings of mesophase alignment obtained using small angle neutron scattering (SANS) and imply that 31P and 1H NMR spectroscopy can be used as probes to define microstructure and monitor orientation changes in this binary surfactant system. This is especially beneficial if these mesophases are used as templates for materials synthesis. The mesophase retains its alignment for extended periods allowing materials synthesis to be decoupled from the application of shear. Highly aligned string-like silica nanostructures were obtained through templated synthesis in the columnar hexagonal structure of the viscous lyotropic crystalline mesophase. A two-step procedure was used to first shear-align the surfactant mesophase, and then conduct synthesis under quiescent conditions in the mesophase. Polystyrene was post-grafted to the silica surface without disturbing its nanostring morphology. The coupling of materials synthesis in surfactant mesophases with processing techniques (e.g. extrusion) may result in functional materials, such as new catalyst support and membrane nanoarchitectures.

Liu, Limin

304

Synthesis, spectroscopic characterization and antimicrobial activity of binuclear metal complexes of a new asymmetrical Schiff base ligand: DNA binding affinity of copper(II) complexes.  

PubMed

The 1:1 condensation of o-acetoacetylphenol and 1,2-diaminopropane under condition of high dilution gives the mono-condensed Schiff base, (E)-3-(1-aminopropan-2-ylimino)-1-(2-hydroxyphenyl)butan-1-one. The mono-condensed Schiff base has been used for further condensation with isatin to obtain the new asymmetrical dicompartmental Schiff base ligand, (E)-3-(2-((E)-4-(2-hydroxyphenyl)-4-oxobutan-2-ylideneamino) propylimino)indolin-2-one (H3L) with a N2O3 donor set. Reactions of the ligand with metal salts give a series of new binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, (1)H and (13)C NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. The analytical and spectroscopic tools showed that the complexes can be formulated as: [(HL)(VO)2(SO4)(H2O)]·4H2O, [(HL)Fe2Cl4(H2O)3]·EtOH, [(HL)Fe2(ox)Cl2(H2O)3]·2H2O, [(L)M2(OAc)(H2O)m]·nH2O; M=Co, Ni or Cu, m=4, 0 and n=2, 3, [(HL)Cu2Cl]Cl·6H2O and [(L)(UO2)2(OAc)(H2O)3]·6H2O. The metal complexes exhibited octahedral geometrical arrangements except copper complexes that exhibited tetrahedral geometries and uranyl complex in which the metal ion is octa-coordinated. The Schiff base and its metal complexes were evaluated for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus), Gram negative bacteria (Escherichia coli) and fungi (Candida albicans and Aspergillus flavus). The ligand and some of its complexes were found to be biologically active. The DNA-binding properties of the copper complexes (6 and 7) have been investigated by electronic absorption, fluorescence and viscosity measurements. The results obtained indicate that these complexes bind to DNA via an intercalation binding mode with an intrinsic binding constant, Kb of 1.34×10(4) and 2.5×10(4) M(-1), respectively. PMID:23988527

Shebl, Magdy

2014-01-01

305

Fourier transform infrared and Raman spectroscopic characterization of homogeneous solution concentration gradients near a container wall at different temperatures  

NASA Technical Reports Server (NTRS)

Fourier transform infrared (FTIR) and Raman spectroscopic techniques were used to study the solution concentration gradient in succino nitrile-rich and water-rich homogeneous solutions. The spectroscopic data shows significant concentration dependency. Although FTIR-attenuated total reflectance could not yield surface spectra since the evanescent infrared wave penetrated deep into the bulk solution, it showed that water-rich clusters were decreased at higher temperatures. This result is consistent with the calorimetric results reported earlier.

Loo, B. H.; Burns, D. H.; Lee, Y. G. L.; Emerson, M. T.

1991-01-01

306

Spectroscopic characterization of bionanoparticles originating from newly developed self-forming synthetic PEGylated lipids (QuSomes)  

Microsoft Academic Search

In this work, we have aimed to merge the advantages of nanotechnology and biophotonics in conjunction with vibrational spectroscopic\\u000a techniques in order to understand the various aspects of new kinds of synthetic bionanoparticles originating from self-forming\\u000a synthetic biopolymers known as polyethylene glycol (PEG)ylated lipids. In particular, two complementary molecular spectroscopic\\u000a techniques based on thin-layered Fourier transform infrared and confocal laser

Rajan K. Bista; Reinhard F. Bruch; Aaron M. Covington

2010-01-01

307

Absorption spectroscopy using quantum cascade laser  

Microsoft Academic Search

Characteristic molecular and atomic absorption spectra in the middle infrared region are extensively used for chemical analysis and spectroscopic detection of gases. The absorption of electromagnetic radiation in this so- called ``fingerprint'' spectral region is due to the vibration-rotational bands of molecular structures. Various techniques have been developed for high resolution and high sensitivity absorption spectroscopic detection. In this dissertation,

Simin Cai

1999-01-01

308

Generation, characterization and spectroscopic use of ultrashort pulses fully tunable from the deep UV to the MIR  

NASA Astrophysics Data System (ADS)

The impressive work of Ian Walmsley has brought us invaluable new possibilities for the full characterization of ultrashort pulses. Spectroscopy of physical, chemical and biological relevance does, however, need pulses far from the 800 nm Ti:sapphire wavelength used for testing SPIDER and its advanced versions. Fortunately, optical parametric amplification (OPA) allows for easy generation of fully tunable pulses. I will review our efforts, highlighting noncollinear OPA, i.e. NOPA, for visible pulses shorter than 10 fs, mixing into the UV down to below 200 nm at 20 fs duration and novel hybrid schemes to efficiently reach the middle IR. I will show that these schemes can be used equally well from kHz to MHz repetition rates. The tunable ultrafast pulses in turn also demand improvements in characterization. The UV range led us to use difference frequency generation instead of the sum frequency mixing employed in the original SPIDER. The lack of proper beam splitters and auto-referencing led us to the use of two auxiliary pulses and the avoidance of any additional chirp added to the test pulse. We termed this zero-additional-phase SPIDER, i.e. ZAP-SPIDER. Lately, with increased use of UV pulses, we came to the conclusion, that the ubiquitous two-photon-absorption can well serve as nonlinearity, at least in UV autocorrelation measurement. How do we use this for full characterization? Hopefully, Ian will tell us! Since the proof is known to be in the eating, I will demonstrate the success of our technical efforts with examples taken from ultrafast molecular dynamics. Highly pronounced vibronic wavepackets in the product of ultrafast excited state proton transfer and the very primary processes leading to homolytic and heterolytic bond cleavage will serve as easy to comprehend illustrations.

Riedle, Eberhard

2011-03-01

309

Errors in spectroscopic measurements of SO/sub 2/ due to nonexponential absorption of laser radiation, with application to the remote monitoring of atmospheric pollutants  

SciTech Connect

Methods of measuring the concentration of atmospheric pollutants by laser absorption spectroscopy, such as differential absorption lidar (DIAL) and integrated long-path techniques, all rely on the validity of Beer's exponential absorption law. It is shown here that departures from this law occur if the probing laser has a bandwidth larger than the wavelength scale of structure in the absorption spectrum of the pollutant. A comprehensive experimental and theoretical treatment of the errors resulting from these departures is presented for the particular case of SO/sub 2/ monitoring at approx.300 nm. It is shown that the largest error occurs where the initial calibration measurement of absorption cross section is made at low pressure, in which case errors in excess of 5% in the cross section could occur for laser bandwidths >0.01 nm. Atmospheric measurements by DIAL or long-path methods are in most cases affected less, because pressure broadening smears the spectral structure, but when measuring high concentrations errors can exceed 5%.

Brassington, D.J.; Moncrieff, T.M.; Felton, R.C.; Jolliffe, B.W.; Marx, B.R.; Rowley, W.R.C.; Woods, P.T.

1984-02-01

310

Isolation, characterization, spectroscopic properties and quantum chemical computations of an important phytoalexin resveratrol as antioxidant component from Vitis labrusca L. and their chemical compositions.  

PubMed

In this study, isolation and characterization of trans-resveratrol (RES) as an antioxidant compound were carried out from VLE, VLG and VLS. Furthermore, antioxidant activities were evaluated by using six different methods. Finally, total phenolic, flavonoid, ascorbic acid, anthocyanin, lycopene, ?-carotene and vitamin E contents were carried out. In addition, the FT-IR, (13)C and (1)H NMR chemical shifts and UV-vis. spectra of trans-resveratrol were experimentally recorded. Quantum chemical computations such as the molecular geometry, vibrational frequencies, UV-vis. spectroscopic parameters, HOMOs-LUMOs energies, molecular electrostatic potential (MEP), natural bond orbitals (NBO) and nonlinear optics (NLO) properties of title molecule have been calculated by using DFT/B3PW91 method with 6-311++G(d,p) basis set in ground state for the first time. The obtained results show that the calculated spectroscopic data are in a good agreement with experimental data. PMID:24967544

Güder, Aytaç; Korkmaz, Halil; Gökce, Halil; Alpaslan, Yelda Bingöl; Alpaslan, Gökhan

2014-12-10

311

A theoretical framework for quantitatively characterizing sound field diffusion based on scattering coefficient and absorption coefficient of walls.  

PubMed

This paper describes the development of a theoretical framework for quantitatively characterizing sound field diffusion based on scattering coefficient and absorption coefficient of walls. The concepts of equivalent scattering area, equivalent scatter reflection area, average scattering coefficient and average scatter reflection coefficient are introduced in order to express all walls' capability of scatter in a room. Using these concepts and the mean free path, scatter-to-absorption ratio, mean scatter time and diffusion time are defined in order to evaluate degree of diffusion of a space. Furthermore the effect of spatial scattering objects to sound field diffusion is formulated. In addition the time variation of specular and scattered components in a room impulse response is formulated. The verification of these characterization methods was performed with computer simulations based on the sound ray tracing method. The results supported that the ideas presented are basically valid. PMID:20815450

Hanyu, Toshiki

2010-09-01

312

Chemical characterization of tribochemical and thermal films generated from neutral and basic ZDDPs using X-ray absorption spectroscopy  

Microsoft Academic Search

X-ray absorption near edge structure (XANES) spectroscopy at the phosphorus L-edge and sulphur L-edge has been used to characterize the chemical nature of tribochemical and thermally generated films from several ZDDP antiwear agents in the neutral and basic forms. Using the P and S L-edge XANES spectra of model compounds with known structure as fingerprints, the chemical structures of P

Marina Fuller; Zhanfeng Yin; Masoud Kasrai; G. Michael Bancroft; Elaine S. Yamaguchi; P. Ray Ryason; Pierre A. Willermet; Kim H. Tan

1997-01-01

313

Characterization of material inhomogeneities in Hg 1- xCd xTe epilayer by infrared absorption spectra  

NASA Astrophysics Data System (ADS)

From an inclusion model, the material inhomogeneities of Hg 1- xCd xTe epilayers were estimated from the anomalous free carrier absorption (FCA) spectra taking into account the composition-in-depth nonuniformity of epilayers. The obtained parameters of the inhomogeneities can also explain the anomalous Hall effect. The investigation offers a nondestructive, simple and reliable tool to characterize the quality of an Hg 1- xCd xTe epilayer.

Li, Biao; Gui, Yongsheng; Ye, Hongjuan; Chu, Junhao

1998-06-01

314

New opportunities in trace elements structural characterization: high-energy X-ray absorption near-edge structure spectroscopy.  

PubMed

Garnets in lower crustal mafic and ultramafic rocks usually contain rare-earth elements (REE) in trace concentrations. Direct characterization of REE at trace levels in natural garnets is not available in the literature because of the difficulty of obtaining structural information by means of conventional diffraction methods. Here, the characterization of Nd at trace levels (176-1029 p.p.m.) in a set of natural garnets performed by means of Nd K-edge X-ray absorption near-edge structure spectroscopy is presented, showing the capability of high-energy XANES for REE in trace structural determinations. PMID:11872928

Chaboy, J; Cotallo, E; Quartieri, S; Boscherini, F

2002-03-01

315

Synthesis, characterization and microwave absorption of carbon-coated Sn nanorods  

Microsoft Academic Search

Carbon-coated Sn nanorods have been synthesized by an arc-discharge method. The Sn\\/C–paraffin composite shows excellent electromagnetic (EM) absorption properties. Reflection losses exceeding ?20dB can be realized in any interval within the 2–18GHz range by choosing an appropriate thickness of the absorbent layer between 1.5 and 9mm. The EM-wave absorption properties of nanocomposite materials are illustrated in detail by means of

Z. H. Wang; Z. Han; D. Y. Geng; Z. D. Zhang

2010-01-01

316

Seismic and spectroscopic characterization of the solar-like pulsating CoRoT target HD 49385  

NASA Astrophysics Data System (ADS)

Context. The star HD 49385 is the first G-type solar-like pulsator observed in the seismology field of the space telescope CoRoT. The satellite collected 137 days of high-precision photometric data on this star, confirming that it presents solar-like oscillations. HD 49385 was also observed in spectroscopy with the NARVAL spectrograph in January 2009. Aims: Our goal is to characterize HD 49385 using both spectroscopic and seismic data. Methods: The fundamental stellar parameters of HD 49385 are derived with the semi-automatic software VWA, and the projected rotational velocity is estimated by fitting synthetic profiles to isolated lines in the observed spectrum. A maximum likelihood estimation is used to determine the parameters of the observed p modes. We perform a global fit, in which modes are fitted simultaneously over nine radial orders, with degrees ranging from ? = 0 to ? = 3 (36 individual modes). Results: Precise estimates of the atmospheric parameters (Teff, [M/H], log g) and of the ? sin i of HD 49385 are obtained. The seismic analysis of the star leads to a clear identification of the modes for degrees ? = 0,1,2. Around the maximum of the signal (? ? 1013 ?Hz), some peaks are found significant and compatible with the expected characteristics of ? = 3 modes. Our fit yields robust estimates of the frequencies, linewidths and amplitudes of the modes. We find amplitudes of ~5.6 ± 0.8 ppm for radial modes at the maximum of the signal. The lifetimes of the modes range from one day (at high frequency) to a bit more than two days (at low frequency). Significant peaks are found outside the identified ridges and are fitted. They are attributed to mixed modes. Based on data obtained from the CoRoT (Convection, Rotation and planetary Transits) space mission, developed by the French Space agency CNES in collaboration with the Science Programs of ESA, Austria, Belgium, Brazil, Germany and Spain.Based on data obtained using the Télescope Bernard Lyot at Observatoire du Pic du Midi, CNRS and Université Paul Sabatier, France.

Deheuvels, S.; Bruntt, H.; Michel, E.; Barban, C.; Verner, G.; Régulo, C.; Mosser, B.; Mathur, S.; Gaulme, P.; Garcia, R. A.; Boumier, P.; Appourchaux, T.; Samadi, R.; Catala, C.; Baudin, F.; Baglin, A.; Auvergne, M.; Roxburgh, I. W.; Pérez Hernández, F.

2010-06-01

317

Development of a UV extended real time spectroscopic ellipsometer and its use for characterization of boron nitride thin films  

NASA Astrophysics Data System (ADS)

A rotating polarizer multichannel ellipsometer has been optimized for operation well into the ultraviolet (uv) spectral range. With this instrument, 132 spectral points in the ellipsometric parameters (psi, Delta) over the photon energy range from 1.5 eV (827 nm) to 6.5 eV (191 nm) can be collected in a minimum acquisition time of 24.5 ms, corresponding to one optical cycle of the rotating polarizer. Averages over two and eighty optical cycles (obtained in 49 ms and 1.96 s, respectively) give standard deviations in (psi, Delta) less than (0.04°, 0.08°) and (0.007°, 0.015°) respectively, for the energy range from 3.5 to 6.0 eV, as determined from successive measurements of a stable thermally oxidized silicon wafer. The key modifications that enable the extended spectral range include (i) a tandem in-line Xe/D2 source configuration, (ii) MgF2 Rochon polarizers, (iii) a spectrograph with a grating blazed at 250 nm and two stages of internally-mounted order-sorting filters, and (iv) non-uniform grouping of the pixels of the photodiode array detector. These modifications can be readily incorporated in other real time ellipsometer designs, including the rotating compensator and dual rotating compensator. The new instrument is well suited for real time characterization of wide band gap materials including boron nitride (BN), amorphous silicon oxy nitrides (a-SiOxNy), tantalum oxide (Ta2O5) among others. As an example of the application of this instrument, results of real time spectroscopic ellipsometry studies are reported for the deposition of boron nitride films grown by reactive magnetron sputtering from targets of BN and boron carbide. With the aid of the extended spectral range, crystallographic phase determination of the layered structure of the BN films has been possible. We have study the effect of deposition conditions on the nucleation of cBN and its optical properties.

Zapien, Juan Antonio

318

Spectroscopic Evidence for and Characterization of a Trinuclear Ferroxidase Center in Bacterial Ferritin from Desulfovibrio vulgaris Hildenborough  

PubMed Central

Ferritins are ubiquitous and can be found in practically all organisms that utilize Fe. They are composed of 24 subunits forming a hollow sphere with an inner cavity of ~80 Å in diameter. The main function of ferritin is to oxidize the cytotoxic Fe2+ ions and store the oxidized Fe in the inner cavity. It has been established that the initial step of rapid oxidation of Fe2+ (ferroxidation) by H-type ferritins, found in vertebrates, occurs at a diiron binding center, termed ferroxidase center. In bacterial ferritins, however, X-ray crystallographic evidence and amino-acid sequence analysis revealed a trinuclear Fe binding center comprising a binuclear Fe binding center (sites A and B), homologous to the ferroxidase center of H-type ferritin, and an adjacent mononuclear Fe binding site (site C). In an effort to obtain further evidence supporting the presence of a trinuclear Fe binding center in bacterial ferritins and to gain information on the states of the iron bound to the trinuclear center, bacterial ferritin from Desulfovibrio vulgaris (DvFtn) and its E130A variant were loaded with sub-stoichiometric amounts of Fe2+ and products were characterized by Mössbauer and EPR spectroscopy. Four distinct Fe species were identified: a paramagnetic diferrous species, a diamagnetic diferrous species, a mixed valence Fe2+Fe3+ species and a mononuclear Fe2+ species. The latter three species were detected in the wild-type DvFtn, while the paramagnetic diferrous species was detected in the E130A variant. These observations can be rationally explained by the presence of a trinuclear Fe binding center, and the four Fe species can be properly assigned to the three Fe binding sites. Further, our spectroscopic data suggest that (1) the fully occupied trinuclear center supports an all ferrous state, (2) site B and C are bridged by a ?-OH group forming a diiron sub-center within the trinuclear center, and (3) this sub-center can afford both a mixed valence Fe2+Fe3+ state and a diferrous state. Mechanistic insights provided by these new findings are discussed and a minimal mechanistic scheme involving O-O bond cleavage is proposed.

Pereira, Alice S.; Timoteo, Cristina G.; Guilherme, Marcia; Folgosa, Filipe; Naik, Sunil G.; Duarte, Americo G.; Huynh, Boi Hanh; Tavares, Pedro

2012-01-01

319

Thermophysics Characterization of Multiply Ionized Air Plasma Absorption of Laser Radiation  

NASA Technical Reports Server (NTRS)

The impact of multiple ionization of air plasma on the inverse Bremsstrahlung absorption of laser radiation is investigated for air breathing laser propulsion. Thermochemical properties of multiply ionized air plasma species are computed for temperatures up to 200,000 deg K, using hydrogenic approximation of the electronic partition function; And those for neutral air molecules are also updated for temperatures up to 50,000 deg K, using available literature data. Three formulas for absorption are calculated and a general formula is recommended for multiple ionization absorption calculation. The plasma composition required for absorption calculation is obtained by increasing the degree of ionization sequentially, up to quadruple ionization, with a series of thermal equilibrium computations. The calculated second ionization absorption coefficient agrees reasonably well with that of available data. The importance of multiple ionization modeling is demonstrated with the finding that area under the quadruple ionization curve of absorption is found to be twice that of single ionization. The effort of this work is beneficial to the computational plasma aerodynamics modeling of laser lightcraft performance.

Wang, Ten-See; Rhodes, Robert; Turner, Jim (Technical Monitor)

2002-01-01

320

X-Ray Absorption And EPR Spectroscopic Studies of the Biotransformations of Chromium(Vi) in Mammalian Cells. Is Chromodulin An Artifact of Isolation Methods?  

SciTech Connect

Very different biological activities are usually ascribed to Cr(VI) (a toxin and carcinogen) and Cr(III) (an antidiabetic agent), although recent evidence suggests that both these types of actions are likely to arise from cellular uptake of varying concentrations of Cr(VI). The first systematic study of XANES spectra of Cr(III) complexes formed in Cr(VI)-treated mammalian cells (A549, HepG2, V79, and C2C12 cell lines), and in subcellular fractions of A549 cells, has been performed using a library of XANES spectra of model Cr(III) complexes. The results of multiple linear regression analyses of XANES spectra, in combination with multiple-scattering fits of XAFS spectra, indicate that Cr(III) formed in Cr(VI)-treated cells is most likely to bind to carboxylato, amine, and imidazole residues of amino acids, and to a lesser extent to hydroxo or aqua ligands. A combination of XANES and EPR spectroscopic data for Cr(VI)-treated cells indicates that the main component of Cr(III) formed in such cells is bound to high-molecular-mass ligands (>30 kDa, probably proteins), but significant redistribution of Cr(III) occurs during the cell lysis, which leads to the formation of a low-molecular-mass (<30 kDa) Cr(III)-containing fraction. The spectroscopic (XANES, XAFS, and EPR) properties of this fraction were strikingly similar to those of the purported natural Cr(III)-containing factor, chromodulin, that was reported to be isolated from the reaction of Cr(VI) with liver. These data support the hypothesis that a chromodulin-like species, which is formed from such a reaction, is an artifact of the reported isolation procedure.

Levina, A.; Harris, H.H.; Lay, P.A.; /Sydney U.

2007-07-10

321

Optical absorption and EPR spectroscopic studies of (30 - x)Li 2O- xK 2O-10CdO-59B 2O 3-1Fe 2O 3: An evidence for mixed alkali effect  

NASA Astrophysics Data System (ADS)

Optical absorption and EPR spectroscopic studies were carried on (30 - x)Li 2O- xK 2O-10CdO-59B 2O 3-1Fe 2O 3 ( x = 0-30) glass system to understand the effect of progressive doping of Li + ion with K + ion. Optical absorption results show typical spectra of Fe 3+ ions and the various optical parameters such as, optical band gap, Urbach energy, oxide ion polarizability, optical basicity and interaction parameter were evaluated from the experimental data. The observed optical band gap and Urbach energy values show large deviation from the linearity where as the other parameters show small deviation from the linearity with the progressive substitution of Li + ions with K + ions. The observed EPR spectra are representative of Fe 3+ ion in octahedral and axial fields in the glass network. The number of paramagnetic centers and paramagnetic susceptibility values were evaluated at different resonance lines for all the specimens and these parameters show non-additive nature with the progressive substitution of Li + ions with K + ions in the glass network. This is first ever observation of mixed alkali effect (MAE) in EPR and optical parameters of mixed alkali borate glasses.

Padmaja, G.; Kistaiah, P.

2010-12-01

322

Characterization and Processing of Organic Nonlinear Optical Materials using Ellipsometric, Waveguiding, and Absorption Spectroscopy Techniques  

NASA Astrophysics Data System (ADS)

The first focus of this work is to describe methods for characterizing organic electro-optic materials. Teng-Man Ellipsometry and Attenuated Total Internal Reflection are reviewed. Experimental techniques for these instruments are described and the calculation of an electro-optic activity is derived. The two techniques are compared; it has been found that in Situ Teng-Man ellipsometry is useful to determine poling conditions but not for reliably evaluating electro-optic activity. Attenuated Total Internal Reflection is found to provide very reliable and precise measurements of electro-optic activity and linear optical constants. As a reference, many materials systems have been evaluated and their electro-optic activities are recorded herein. Methods for fabricating devices for test by Teng-Man ellipsometry and Attenuated Total Internal Reflection are presented. A process for inducing Pockel's response via contact-geometry electric field poling is also described, along with modifications to the simple slab dielectric device to enhance the efficacy of poling. An additional method for enhancing the efficiency of poling is presented. This technique relies on the photoisomerization of azobenzene dyes under 532nm radiation to reduce the dimensionality accessible to chromophores doped into the azobenzene matrix. This effect is known as "Laser Assisted Poling" and is shown to increase poling efficiency by more than two fold. The second purpose of this work is to present an experimental technique to measure the order parameter = 3cos 2q -12 . This method is known as Variable-Angle Polarization-Referenced Absorption Spectroscopy (VAPRAS). The experimental apparatus used for VAPRAS introduces small alterations to a UV/Vis Spectrophotometer and an order parameter is derived by exclusively using classical models for transmittance. VAPRAS provides an effective refractive index for the electro-optic material film which is used to calculate the order of absorbers in the film. The results of the VAPRAS method are compared with rigorous (Jones Matrix) simulations of absorbance and Monte Carlo simulations of poling. Both comparisons conclude that the order is low, ? 0.05, and their agreement with theory is within experimental error. Theoretical simulations of poling are employed to relate the results of VAPRAS to a noncentrosymmetric order parameter . Finally, a solid-state first molecular hyperpolarizability is calculated from these values, measurements of electro-optic activity, linear optical constants and other secondary properties of the electro-optic material.

Olbricht, Benjamin C.

323

Spectroscopic studies of Wolf-Rayet stars with absorption lines. IV - The mass of CX Cephei \\/WN5+O\\/. V - HD 9974, a single WN3  

Microsoft Academic Search

A radial velocity study is presented of both the emission and absorption lines in the eclipsing Wolf-Rayet binary. The mass ratio is 2.3, and the minimum masses are 5 solar masses for the WN5 star and 12 solar masses for the O-type companion, which appears to be approximately of the O8 type or earlier. The W-R star fills its Roche

P. Massey; P. S. Conti

1981-01-01

324

Chemical, spectroscopic characterization, DFT studies and initial pharmacological assays of a silver(I) complex with N-acetyl- l-cysteine  

Microsoft Academic Search

A new silver(I) complex with N-acetyl-l-cysteine (NAC) of composition AgC5H8NO3S·H2O was synthesized and characterized by a set of chemical and spectroscopic measurements. Solid-state 13C nuclear magnetic resonance (SSNMR) and infrared (IR) analyses indicate the coordination of the ligand to Ag(I) through the sulfur atom. The Ag–NAC complex is slightly soluble in dimethyl sulfoxide. It is insoluble in water, methanol, ethanol,

Camilla Abbehausen; Tassiele A. Heinrich; Emiliana P. Abrão; Claudio M. Costa-Neto; Wilton R. Lustri; André L. B. Formiga; Pedro P. Corbi

2011-01-01

325

Molecular structures and spectroscopic characterization of cobalt(III) and nickel(II) complexes of N -(2-hydroxyethyl)-2-(thiophene-2-ylmethylene)-hydrazinecarbothioamide  

Microsoft Academic Search

Two complexes of a thiosemicarbazone ligand, namely N-(2-hydroxyethyl)-2-(thiophene-2-ylmethylene)-hydrazinecarbothioamide (HL), have been synthesized. The complexes have been\\u000a characterized by physico-chemical and spectroscopic methods. The crystal and molecular structures of [CoL3]·2MeOH (1) and [NiL2] (2) have been determined by X-ray diffraction studies. For both complexes, the metal is coordinated through the sulfur and azomethine\\u000a nitrogen atoms of the thiosemicarbazone. The ligand exists

Mohammad Hakimi; Reza Takjoo; Vahideh Erfaniyan; Esther Schuh; Fabian Mohr

2010-01-01

326

Two complexes of Co(II) and Pd(II) formed in reaction with a mono-oxazoline derivative. Spectroscopic characterization and cytotoxic evaluation  

NASA Astrophysics Data System (ADS)

Two coordination compounds obtained from 2-(4-ethoxyphenyl)-4,5-dihydro-1H-oxazole, L, [CoCl2(L)2] (1) and [OHsbnd CH2sbnd CH2sbnd NH3]2·[PdCl4] (2) were synthesized and characterized through elemental analysis, spectroscopic methods (FTIR, UV-Vis, 1H NMR) and X-ray diffraction. Cytotoxicity tests on PBMC and HeLa cells were performed in order to evaluate the potential applications of these compounds in medicine. Also, compound (2) exhibits ligand assisted luminescent properties that were determined in solid state.

Alexandru, Maria-Gabriela; Cirkovic Velickovic, Tanja; Krstic, Maja; Hrubaru, Madalina-Marina; Draghici, Constantin

2013-06-01

327

FT-IR spectroscopic assessment of gas-phase absorption of atmospheric molecular species at low concentrations and their associated adsorption effects on various material surfaces  

NASA Astrophysics Data System (ADS)

Changes in the infrared absorbance observed at levels of concentration in the subparts per million (sub-ppm) of atmospherically significant molecular species, such as HCl, SO2, NO2 and NH3, has been quantified as a function of pressure and temperature for the surface reactions of these gases with various materials (e.g. copper, aluminum, stainless steel and teflon). A Nicolet Magna-IR 550 Fourier transform infrared (FT-IR) spectrometer operating in the 400-4000 cm-1 region and fitted with a 10-meter multipass absorption cell and a deuterated triglycine sulfate (DTGS) detector has been used for recording the spectra. Tubing materials chosen are typically associated with the hardware of measuring instruments used to collect atmospheric trace gas samples. The FT-IR spectrometer has been used to determine the concentration levels at the inlet and outlet tubing of the absorption cell. Small changes in the species concentration down to sub-ppm levels have also been recorded in the 650-4000 cm-1 region using a liquid nitrogen-cooled Mercury Cadmium Telluride (MCT-A) detector interfaced with the FT-IR spectrometer. The associated adsorption effects at the various gas-solid interfaces in the measuring apparatus, including the `sticking' effects on the walls of the absorption cell, have been quantified. Carefully monitored pressure and temperature conditions were utilized to provide a controlled environment, so as to quantify minute changes in the absorption of infrared radiation due to variations in the concentration of the gas samples brought about by different adsorption effects. Values for the absorption coefficients of the different gas phase molecular species in the infrared region of interest were derived from the absorbance measurements. The degree of adsorption for specific gassolid interfaces and the kinetic theory of the adsorption process (assuming a mono-layer) enabled the determination of the corresponding rate constants. It is envisioned that the accurate determination of the adsorption coverage parameters and the Langmuir rate constants for the various gas-material combinations will aid in the refinement of precise values for the associated residence time and activation energies and thereby lead to the development of a comprehensive adsorption isotherm model for gas-surface interactions.

Dowdye, Edward Henry, Jr.

2000-11-01

328

Synthesis, characterization and microwave absorption properties of dendrite-like Fe3O4 embedded within amorphous sugar carbon matrix  

NASA Astrophysics Data System (ADS)

Magnetite dendrites/sugar carbon (MDs/SC) nanocomposites, embedding MDs within amorphous SC matrix, were prepared by simple carbonization-reduction method using ?-Fe2O3 dendrites (HDs) as precursor of MDs and sucrose as SC source, while still maintain the dendritic shape of the precursor. The morphology, composition, structure and static magnetic properties of the as-prepared MDs/SC nanocomposites were characterized by various techniques thoroughly. Particularly, the electromagnetic and microwave absorption properties of the MDs/SC and MDs paraffin composites (40 wt.%) were compared over 2-14 GHz. The results show that the microwave absorption performance of MDs/SC samples is comparable or even superior to that of MDs case. The absorption band with reflection loss (RL) below -20 dB for one of the MDs/SC samples can cover the whole X-band (8-12 GHz) with thickness of 1.8-2.4 mm when the content of MDs in the MDs/SC nanocomposite is 25.8 wt.%, and the minimum RL can reach -49.9 dB at 12.1 GHz when the layer thickness is only 1.9 mm. The excellent microwave absorption properties of the MDs/SC paraffin composites are attributed to the proper match between the complex permittivity and permeability, and the unique fractal structures of MDs.

Wu, Hao; Wang, Liuding; Wu, Hongjing

2014-01-01

329

An X-ray absorption spectroscopic study on mixed conductive La0.6Sr0.4Co0.8Fe0.2O(3-?) cathodes. I. Electrical conductivity and electronic structure.  

PubMed

The electrical conduction mechanism of mixed conductive perovskite oxides, La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-?), for cathode materials of solid oxide fuel cells has been investigated from electronic structural changes during oxygen vacancy formation. La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-?) was annealed under various oxygen partial pressures p(O(2))s at 1073 K and quenched. Iodometric titration indicated that the oxygen nonstoichiometry of La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-?) depended on the annealing p(O(2)), with more oxygen vacancies introduced at lower than at higher p(O(2))s. X-Ray absorption spectroscopic measurements were performed at the O K-, Co L-, Fe L-, Co K-, and Fe K-edges. The valence states of the Co and Fe ions were investigated by the X-ray absorption near edge structure (XANES) at the Co and Fe L(III)-edges. While the Fe average valence was almost constant, the valence of the Co ions decreased with oxygen vacancy introduction. The O K-edge XANES spectra indicated that electrons were injected into the Co 3d/O 2p hybridization state with oxygen vacancy introduction. Both absorption edges at the Co and Fe K-edge XANES shifted towards lower energies with oxygen vacancy introduction. The shift at the Co K-edge resulted from the decrease in the Co average valence and that at the Fe K-edge appeared to be caused by changes in the coordination environment around the Fe ions. The total conductivity of La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-?) decreased with decreasing p(O(2)), due to a decreasing hole concentration. PMID:21850304

Orikasa, Yuki; Ina, Toshiaki; Nakao, Takayuki; Mineshige, Atsushi; Amezawa, Koji; Oishi, Masatsugu; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

2011-10-01

330

Ultra-violet and visible absorption characterization of explosives by differential reflectometry.  

PubMed

This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R(2)>0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and ?-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials. PMID:23299022

Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E

2013-03-15

331

Ultra-violet and visible absorption characterization of explosives by differential reflectometry  

NASA Astrophysics Data System (ADS)

This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R2 > 0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and ?-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials.

Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E.

2013-03-01

332

Induced chirality upon binding of cis-parinaric acid to bovine ?-lactoglobulin: spectroscopic characterization of the complex  

Microsoft Academic Search

Binding of the polyunsaturated cis-parinaric acid to bovine ?-lactoglobulin (BLG) was studied by circular dichroism (CD), electronic absorption spectroscopy and mass spectrometry methods. Upon protein binding, the UV absorption band of parinaric acid is red shifted by ca. 5 nm, showing hypochromism and reduced vibrational fine structure, suggesting that the ligand binds as a monomer in non-planar geometry. In the

Ferenc Zsila; T??mea Imre; Pál T. Szabó; Zsolt Bikádi; Miklós Simonyi

2002-01-01

333

A promising method to characterize low-field microwave absorption in high- Tc superconducting cuprates  

NASA Astrophysics Data System (ADS)

Low-field microwave absorption in high- Tc superconducting cuprates situated in the electron spin resonance configuration was proposed to be originating from two mechanisms which were known as viscous fluxon motion and junction current oscillation, respectively. It was noted that microwave energy absorbed should be thermalized in the former but re-radiated in the latter. So, photoacoustic detection is a potentially feasible way to isolate the contribution to low-field microwave absorption by viscous fluxon motion from that by junction current oscillation. In this paper, a quantitative approach is taken to analyze the feasibility of this new idea.

Tang, S. Y.; Fung, P. C. W.

334

A promising method to characterize low-field microwave absorption in high-Tc superconducting cuprates  

NASA Astrophysics Data System (ADS)

Low-field microwave absorption in high-Tc superconducting cuprates situated in the electron spin resonance configuration was proposed to be originating from two mechanisms which were known as viscous fluxon motion and junction current oscillation, respectively. It was noted that microwave energy absorbed should be thermalized in the former but re-radiated in the latter. So, photoacoustic detection is a potentially feasible way to isolate the contribution to low-field microwave absorption by viscous fluxon motion from that by junction current oscillation. In this paper, a quantitative approach is taken to analyze the feasibility of this new idea.

Fung, P. C. W.; Tang, S. Y.

1995-02-01

335

Laser and Spectroscopic Properties of Chromium - Forsterite  

Microsoft Academic Search

This thesis describes the discovery of a new tunable solid state laser, chromium-doped forsterite (Cr:Mg _2SiO_4), its spectroscopic, quantum electronic and laser characteristics. The main goal of spectroscopic investigations was to identify optically active ions in chromium-doped forsterite. The spectroscopic studies performed on Cr:Mg _2SiO_4 crystals grown under different conditions include: measurements of the polarized absorption and fluorescence spectra, polarized

Vladimir Petricevic

1990-01-01

336

X-ray absorption spectroscopic study of LiCoO2 as the negative electrode of lithium-ion batteries.  

PubMed

Lithium cobalt oxide (LiCoO(2)) particles are modified using rotor blade grinding and re-annealing and used as the active electrode material versus lithium in the 3-0 V potential interval, in which a maximum capacity of 903 mA h g(-1) is achieved. X-ray absorption near edge structure spectra reveal the complete reduction of Co(3+) to Co metal at 0 V. Cell recharge leads to an incomplete reoxidation of cobalt. A maximum reversible capacity of 812 mA h g(-1) is obtained, although a poor capacity retention upon prolonged cycling may limit its application. PMID:16612798

Chadwick, Alan V; Savin, Shelley L P; Alcántara, Ricardo; Fernández Lisbona, Diego; Lavela, Pedro; Ortiz, Gregorio F; Tirado, José L

2006-05-12

337

Carbon K-edge X-ray absorption spectroscopic studies of structure and electronic properties of hydrocarbons adsorbed on Ni crystal surfaces  

NASA Astrophysics Data System (ADS)

Using the Plane Grating Monochromator of the U7A beamline at the National Synchrotron Light Source (NSLS), the carbon K-edge X-ray absorption spectra of a large number hydrocarbon molecules and their derivatives adsorbed on Ni single-crystal surfaces (Ni(111), Ni(110) and Ni(100)) have been examined. The molecules studied include saturated hydrocarbons C2H6 and C6H12, and unsaturated ones C2H4, C2H2, C6H6, C6H10, C5H5N and C5H5S. Under the experimental conditions (room temperature, saturated surface), it is found that all the C K-edge Near Edge X-ray Absorption Fine Structures (NEXAFS) of the surface species exhibit the 1s yields pi* and 1s yields sigma shape resonance characteristic of unsaturated molecules although an intense 1s yields pi* transition is not seen in the gas phase spectra for the saturated alkanes. some of the adsorbates also exhibit polarization dependent behavior in their C K-edge adsorption coefficient.

Sham, T. K.; Carr, R. G.; Eberhardt, W.; Garrett, R.; Baldwin, E.; Friend, C. M.

338

Characterization of preform raw materials for high power fiber lasers using LID absorption measurement technique  

Microsoft Academic Search

Two different concepts are introduced and compared to measure for the first time residual absorption in pure and doped fused silica fiber preform raw materials at 940 nm and 1550nm directly by means of the laser induced deflection (LID) technique in order to analyze the minimal achievable attenuation in high power fiber lasers based on the doped fused silica raw

Ch. Mühlig; S. Bublitz; St. Grimm; A. Langner; G. Schötz

2010-01-01

339

Characterization of ITO- and TiO xN y films by spectroscopic ellipsometry, spectraphotometry and XPS  

NASA Astrophysics Data System (ADS)

Within the last years, several new application for optical coatings were found. To assist R&D activities in the development of new films and coating sources, combination of different analytical techniques is required: spectraphotometry measures reflectance, transmittance and absorbance. Spectroscopic ellipsometry is applied to determine optical constants n( ?) and k( ?). For high absorbing TiN and TiON films for CRT display applications, these constants were evaluated by combination of photometry and ellipsometry. Spectroscopic ellipsometry is introduced in quality control of ITO films for flat panel displays. Differences of the optical constants indicate enhanced failure rate of the complete display systems. With X-ray photon spectrometry (XPS) depth profiling and electron microprobe (EMP) analysis, Na-diffusion from the glass substrates into the films is found to be a source of the failures. Additionally, AFM is applied to monitor film structures and measure surface roughness.

Bartella, J.; Schroeder, J.; Witting, K.

2001-07-01

340

Spectroscopic and Photophysical Characterization of Fluorescent Chemosensors for Monosaccharides Based on N -Phenylboronic Acid Derivatives of 1,8-Naphthalimide  

Microsoft Academic Search

Spectroscopic and photophysical properties of two fluorescent probes for monosaccharides are presented. Probes are based on the N-phenyl-1,8-naphthalimide structure having the boronic acid group [R-B(OH)2] in ortho in one case, and meta in the other case, positions of the N-phenyl group. Formation of the anionic form of the boronic acid group [R-B(OH)-3] induced a substantial decrease of the steady-state fluorescence

Nicolas DiCesare; Devi P. Adhikari; Justin J. Heynekamp; Michael D. Heagy; Joseph R. Lakowicz

2002-01-01

341

Spectroscopic Observations  

NSDL National Science Digital Library

This is a series of three activities about light and spectra. First, learners will construct their own spectroscope, observe common light sources, record the observed spectra, and compare their findings. Next, learners will use their spectroscopes to observe the spectra from different gas tubes and compare each observed spectrum to known spectra. Finally, they will observe a solar spectrum created by a prism, view a solar spectrum on paper, and attempt to determine the elements present in the Sun. This activity requires spectroscope posters and gratings available from the Stanford Solar Center (http://solar-center.stanford.edu/posters/), fluorescent and incandescent light sources, and emission lamps and power sources. This activity is from the Stanford Solar Center's All About the Sun: Sun and Stars activity guide for Grades 5-8 and can also accompany the Stanford Solar Center's Build Your Own Spectroscope activity.

342

X-ray fluorescence mapping and micro-XANES spectroscopic characterization of exhaust particulates emitted from auto engines burning MMT-added gasoline.  

PubMed

The elemental distribution and compositional homogeneity in auto exhaust particulates emitted from methylcyclopentadienyl manganese tricarbonyl-(MMT-)added gasoline engines have been investigated using a newly installed synchrotron X-ray microprobe. Two representative groups of exhaust particulate matter, as defined in a recent bulk X-ray absorption fine structure (XAFS) spectroscopic study at the Mn K-edge, were studied. The micro-X-ray absorption near-edge structure (XANES) spectra indicate a relatively homogeneous distribution of phases within a given particulate sample, down to a spatial extent of 40 microm (the resolution of microprobe). The micro-XANES also enabled analysis of several areas which displayed compositions different from the bulk sample, supporting the general theory describing manganese species formation in the exhaust. The ability to evaluate small regions also enabled direct verification of manganese sulfate from the S XANES despite the vast excess of sulfur present in other forms. The presence of a chloride compound, introduced through the sample dilution air and engine intake air, was also revealed. The study demonstrates the value of the combined X-ray microfluorescence with excitation by polychromatic radiation for elemental mapping and micro-XANES spectroscopy for chemical speciation in the study of dilute environmental materials containing low-Z constituents such as Cl, S, and P. PMID:11505987

Mölders, N; Schilling, P J; Wong, J; Roos, J W; Smith, I L

2001-08-01

343

Spectroscopic characterization of 78 DENIS ultracool dwarf candidates in the solar neighborhood and the Upper Scorpii OB association  

NASA Astrophysics Data System (ADS)

Aims: We search for new ultracool dwarfs and report here our observations of 78 ultracool dwarf candidates that have been photometrically selected using the DENIS survey point source catalogue. We analyze low-resolution optical spectroscopic observations to estimate spectral types of all candidates. Methods: We derive spectral types for each object using measurements of the PC3 spectral index as defined in Martín et al. They range from M6 to L3. The H? emission and NaI subordinate doublet (818.3 nm and 819.9 nm) equivalent widths are measured in the spectra to identify young stellar objects. Spectroscopic indices of TiO, VO, CrH, and FeH molecular features are also reported. Results: A rule-of-thumb criterion for selecting young very low-mass objects using the NaI doublet equivalent width is given. It is used to confirm seven new members of the Upper Sco OB association and two new members of the R Cr-A star-forming region. Four of our field objects are also classified as very young, but are not members of any known nearby young association. The frequency of lower-gravity young objects in our field ultracool sample is 8.5%. Our results provide the first spectroscopic classification for 42 ultracool dwarfs in the solar vicinity with spectrophotometric distances in the range 17 pc to 65 pc (3 of them being new L dwarfs within 20 pc).

Martín, E. L.; Phan-Bao, N.; Bessell, M.; Delfosse, X.; Forveille, T.; Magazzù, A.; Reylé, C.; Bouy, H.; Tata, R.

2010-07-01

344

The X-ray absorption spectroscopic model of the copper(II) imidazole complex ion in liquid aqueous solution: a strongly solvated square pyramid.  

PubMed

Cu K-edge extended X-ray absorption fine structure (EXAFS) and Minuit X-ray absorption near-edge structure (MXAN) analyses were combined to evaluate the structure of the copper(II) imidazole complex ion in liquid aqueous solution. Both methods converged to the same square-pyramidal inner coordination sphere [Cu(Im)(4)L(ax)](2+) (L(ax) indeterminate) with four equatorial nitrogen atoms at EXAFS, 2.02 ± 0.01 Å, and MXAN, 1.99 ± 0.03 Å. A short-axial N/O scatterer (L(ax)) was found at 2.12 ± 0.02 Å (EXAFS) or 2.14 ± 0.06 Å (MXAN). A second but very weak axial Cu-N/O interaction was found at 2.9 ± 0.1 Å (EXAFS) or 3.0 ± 0.1 Å (MXAN). In the MXAN fits, only a square-pyramidal structural model successfully reproduced the doubled maximum of the rising K-edge X-ray absorption spectrum, specifically excluding an octahedral model. Both EXAFS and MXAN also found eight outlying oxygen scatterers at 4.2 ± 0.3 Å that contributed significant intensity over the entire spectral energy range. Two prominent rising K-edge shoulders at 8987.1 and 8990.5 eV were found to reflect multiple scattering from the 3.0 Å axial scatterer and the imidazole rings, respectively. In the MXAN fits, the imidazole rings took in-plane rotationally staggered positions about copper. The combined (EXAFS and MXAN) model for the unconstrained cupric imidazole complex ion in liquid aqueous solution is an axially elongated square-pyramidal core, with a weak nonbonded interaction at the second axial coordination position and a solvation shell of eight nearest-neighbor water molecules. This core square-pyramidal motif has persisted through [Cu(H(2)O)(5)](2+), [Cu(NH(3))(4)(NH(3),H(2)O)](2+), (1, 2) and now [Cu(Im)(4)L(ax))](2+) and appears to be the geometry preferred by unconstrained aqueous-phase copper(II) complex ions. PMID:22316238

Frank, Patrick; Benfatto, Maurizio; Hedman, Britt; Hodgson, Keith O

2012-02-20

345

Aqueous Cadmium Chalcogenide Quantum Dots: Synthesis, Characterization, Spectroscopic Investigation of Electron Transfer Properties and Photovoltaic Device Performance  

NASA Astrophysics Data System (ADS)

The research presented in this thesis will focus on (1) synthesis and characterization of aqueous CdSe quantum dots (QDs) as alternatives to organic QDs; (2) the roles that linkers and capping groups play on the physical and optical properties of aqueous QDs; (3) performance of QD-sensitized solar cells (QDSSC) incorporating magic-sized clusters (MSCs) vs regular QDs (RQDs) and as a function of the molecular linkers between QDs and TiO2; and (4) the effect of the polysulfide electrolyte on QD-functionalized TiO 2 films and their performance in QDSSCs. The use of QDs as light harvesters has grown over the last few decades due to their unique properties. Water-dispersible QDs are of increasing interest because their syntheses are straightforward, environmentally-benign and more cost-effective. CdSe and CdS QDs were synthesized at room temperature under ambient conditions, by combining a Cd precursor and either Na2SeSO3 (for CdSe) or Na2S2O3 (for CdS), in basic aqueous reaction mixtures. Three different ligands were utilized as capping groups (cysteinate (Cys), mercaptopropionate (MP), and mercaptosuccinate (MS)). Changing the capping-agent, the reagent concentrations and the temperature changed the photophysical properties of the QDs. When Cys was used as the capping-agent, MSCs were formed. When high concentrations of Cys were used or when the reaction mixture was heated, RQDs were formed. When MP and MS were used in the synthesis of CdSe, RQDs were formed. In the synthesis of CdS, MS caused the formation of RQDs, and MP caused formation of a mixture of RQDs and MSCs. Transient absorption spectroscopy and photoelectrochemical experiments were performed to understand the influence of capping-agent and electronic properties (MSCs vs. RQDs) on the efficiency of electron transfer from photoexcited QDs to TiO2. The Cys-CdSe-functionalized TiO2 exhibited more efficient electron injection and/or slower recombination, leading to improved efficiency of QDSSCs. Devices made with Cys-CdSe RQDs exhibited higher efficiencies than QDSSCs with Cys-CdSe MSCs, indicating that the presence of Cys induces greater efficiency in QDSSCs. For QDSSCs, a polysulfide electrolyte is commonly used instead of I-/I3-. Effects of the polysulfide electrolyte and Na2S on CdSe-functionalized TiO2 films were explored to elucidate the chemistry that occurs when CdSe is exposed to the electrolyte in the QDSSCs. Photophysical changes to the CdSe-functionalized films occurred when exposed to the polysulfide electrolyte. Upon immersion of CdSe-functionalized TiO¬2 films into solutions of Na2S, an initial red shift in the absorption spectrum was observed, followed by a decrease and blue shift of the band. Based on XPS analysis of the films, it was determined that the S within the electrolyte (1) replaced Se or (2) bound to the CdSe-functionalized film without replacing Se. Photoelectrochemical measurements were acquired to analyze device performance with varying [S] within the electrolyte. Upon increase of S, the efficiency of the device increased and gave rise to a better fill factor in the photocurrent-photovoltage data collected.

Coughlin, Kathleen M.

346

X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials  

SciTech Connect

The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus and Methylosinus trichosporiwn has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the Fe(HI)Fe(IH) oxidized state of the hydroxylase from M. capsulatus consists of approximately 6 N and 0 atoms at an average distance of 2.04 {Angstrom}. The Fe-Fe distance was determined to be 3.4 {Angstrom}. No evidence for the presence of a short oxo bridge in the iron center of the oxidized hydroxylase was found, suggesting that the active site of MMO is significantly different from the active sites of the dinuclear iron proteins hemery and ribonucleotide reductase. In addition, the results of the first shell fits suggest that there are more oxygen than nitrogen donor ligands.

DeWitt, J.G.

1992-12-01

347

X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials  

SciTech Connect

The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus and Methylosinus trichosporiwn has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the Fe(HI)Fe(IH) oxidized state of the hydroxylase from M. capsulatus consists of approximately 6 N and 0 atoms at an average distance of 2.04 [Angstrom]. The Fe-Fe distance was determined to be 3.4 [Angstrom]. No evidence for the presence of a short oxo bridge in the iron center of the oxidized hydroxylase was found, suggesting that the active site of MMO is significantly different from the active sites of the dinuclear iron proteins hemery and ribonucleotide reductase. In addition, the results of the first shell fits suggest that there are more oxygen than nitrogen donor ligands.

DeWitt, J.G.

1992-12-01

348

Ã-X absorption of propargyl peroxy radical (H-C?C-CH2OO·): a cavity ring-down spectroscopic and computational study.  

PubMed

The Ã-X electronic absorption spectrum of propargyl peroxy radical has been recorded at room temperature by cavity ring-down spectroscopy. Electronic structure calculations predict two isomeric forms, acetylenic and allenic, with two stable conformers for each. The acetylenic trans conformer, with a band origin at 7631.8 ± 0.1 cm(-1), is definitively assigned on the basis of ab initio calculations and rotational simulations, and possible assignments for the acetylenic gauche and allenic trans forms are given. A fourth form, allenic cis, is not observed. Simulations based on calculated torsional potentials predict that the allenic trans form will have a long, poorly resolved progression in the OOCC torsional vibration, consistent with experimental observations. PMID:21050020

Thomas, Phillip S; Kline, Neal D; Miller, Terry A

2010-12-01

349

In situ X-ray Absorption Spectroscopic Investigation of the Electrochemical Conversion Reactions of CuF2-MoO3 Nanocomposite  

SciTech Connect

We have used X-ray absorption spectroscopy at the Cu K-edge to investigate the electrochemical conversion reaction of 20 nm size 85 wt% CuF{sub 2}-15 wt% MoO{sub 3} nanocomposite under in situ conditions. The nanocomposite was prepared by high energy milling. Upon discharge, the lithiation reaction with the nanocomposite resulted in the formation of nanophase metallic Cu, which is consistent with the conversion of CuF{sub 2} into Cu and LiF. Based on XANES and Fourier transforms of EXAFS spectra, we show that the discharge process proceeded via the formation of highly dispersed Cu particles. Based on the coordination number of the first shell of Cu, the average size of the Cu particles was estimated to be in the 1-3 nm range in the fully discharged state.

A Mansour; F Badway; W Yoon; K Chung; G Amatucci

2011-12-31

350

An X-ray absorption spectroscopic investigation of the geometry of Pt(IV) in H2PtCl6 ammonia solution  

NASA Astrophysics Data System (ADS)

The geometrical structure of noble metal cations has an important impact in many areas. Therefore, the structure of some noble cations in solution has been investigated in order to understand the relationship between the structure and property of noble metal cations in solution. In this contribution, the coordination chemistry of H2PtCl6 in ammonia solution was investigated by X-ray absorption spectroscopy (XAS). We found that Cl ligands around Pt with a Pt-Cl bond length of 2.32 Å are completely replaced by NH3 ligands with a Pt-N distance of 2.05 Å. Theoretical calculations point out the occurrence of both a Pt-Cl and a Pt-N orbital hybridization. The observed 'hybridization peak' and the post-edge feature have been assigned to the contribution of Cl and N d-states.

Chen, Shuangming; Wu, Yanfei; Tao, Shi; Cui, Peixin; Chu, Wangsheng; Chen, Xing; Wu, Ziyu

2013-06-01

351

Infrared reflection absorption spectroscopic study of adsorption structure of self-assembled monolayer film of trithiocyanuric acid on evaporated silver film  

Microsoft Academic Search

The self-assembled monolayer film of trithiocyanuric acid (TCA) on evaporated silver films was characterized by using FT-IRAS and ab initio DFT calculation. Three hydrogen atoms in the most stable geometry of TCA tautomers were bonded to nitrogen atoms in the cyanuric ring. Observed IR bands for TCA in KBr disc at room temperature suggested that the TCA has a trithione

Naoki Osaka; Megumi Ishitsuka; Toshihiko Hiaki

2009-01-01

352

Performance characterization and ground testing of an airborne CO2 differential absorption lidar system (phase II)  

Microsoft Academic Search

The Air Force Research Laboratory (AFRL) Active Remote Sensing Branch has developed the Laser Airborne Remote Sensing (LARS) system for chemical detection using the differential absorption lidar (DIAL) technique. The system is based on a high-power CO2 laser which can use either the standard 12C16O2 or the 13C16O2 carbon dioxide isotopes as the lasing medium, and has output energies of

Daniel C. Senft; Marsha J. Fox; Carla M. Hamilton; Dale A. Richter; N. S. Higdon; Brian T. Kelly

1999-01-01

353

Synthesis, Characterization, and Microwave Absorption Property of the SnO 2 Nanowire\\/Paraffin Composites  

Microsoft Academic Search

In this article, SnO2 nanowires (NWs) have been prepared and their microwave absorption properties have been investigated in detail. Complex permittivity\\u000a and permeability of the SnO2 NWs\\/paraffin composites have been measured in a frequency range of 0.1–18 GHz, and the measured results are compared with\\u000a that calculated from effective medium theory. The value of maximum reflection loss for the composites with

H. T. Feng; R. F. Zhuo; J. T. Chen; D. Yan; J. J. Feng; H. J. Li; S. Cheng; Z. G. Wu; J. Wang; P. X. Yan

2009-01-01

354

An X-ray absorption spectroscopic study of the metal site preference in Al1-xGaxFeO3  

NASA Astrophysics Data System (ADS)

Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO3 (Pna21; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al1-xGaxFeO3 was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L2,3-, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al1-xGaxFeO3 indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO3 than in GaFeO3, implying more anti-site disorder is present in AlFeO3.

Walker, James D. S.; Grosvenor, Andrew P.

2013-01-01

355

Transmission electron microscopic and X-ray absorption fine structure spectroscopic investigation of U repartition and speciation after accumulation in renal cells.  

PubMed

After environmental contamination, U accumulates in the kidneys and in bones, where it causes visible damage. Recent in vitro data prove that the occurrence of citrate increases U bioavailability without changing its speciation. Two hypotheses can explain the role of citrate: it either modifies the U intracellular metabolization pathway, or it acts on the transport of U through cell membrane. To understand which mechanisms lead to increased bioavailability, we studied the speciation of U after accumulation in NRK-52E kidney cells. U speciation was first identified in various exposure media, containing citrate or not, in which U was supplied as U carbonate. The influence of serum proteins was analyzed in order to detect the formation of macromolecular complexes of U. Transmission electron microscopy (TEM) was employed to follow the evolution of the U species distribution among precipitated and soluble forms. Finally, extended X-ray absorption fine structure spectroscopy (EXAFS) enabled the precipitates observed to be identified as U-phosphate. It also demonstrated that the intracellular soluble form of U is U carbonate. These results suggest that citrate does not change U metabolization but rather plays a role in the intracellular accumulation pathway. U speciation inside cells was directly and clearly identified for the first time. These results elucidate the role of U speciation in terms of its bioavailability and consequent health effects. PMID:18273650

Carrière, Marie; Proux, Olivier; Milgram, Sarah; Thiebault, Céline; Avoscan, Laure; Barre, Nicole; Den Auwer, Christophe; Gouget, Barbara

2008-06-01

356

In situ X-ray absorption spectroscopic investigation of the electrochemical conversion reactions of CuF{sub 2}-MoO{sub 3} nanocomposite  

SciTech Connect

We have used X-ray absorption spectroscopy at the Cu K-edge to investigate the electrochemical conversion reaction of 20 nm size 85 wt% CuF{sub 2}-15 wt% MoO{sub 3} nanocomposite under in situ conditions. The nanocomposite was prepared by high energy milling. Upon discharge, the lithiation reaction with the nanocomposite resulted in the formation of nanophase metallic Cu, which is consistent with the conversion of CuF{sub 2} into Cu and LiF. Based on XANES and Fourier transforms of EXAFS spectra, we show that the discharge process proceeded via the formation of highly dispersed Cu particles. Based on the coordination number of the first shell of Cu, the average size of the Cu particles was estimated to be in the 1-3 nm range in the fully discharged state. -- Graphical Abstract: Comparison of Fourier transform of in situ Cu K-edge EXAFS spectra for a fully discharged CuF{sub 2{center_dot}}MoO{sub 3} nanocomposite in a nonaqueous Li cell with that of a Cu foil. Quantitative analysis of the Fourier transforms confirmed that the discharge mechanism for the nanocomposite proceeds via the reaction CuF{sub 2}+2Li{yields}Cu+2LiF. The discharge product of Cu is in the form of highly dispersed nanoparticles. Display Omitted

Mansour, A.N., E-mail: Azzam.Mansour@navy.mi [Systems and Materials for Power and Protection Branch, Naval Surface Warfare Center, Carderock Division, 9500 MacArthur Boulevard, West Bethesda, MD 20817-5700 (United States); Badway, F. [Energy Storage Research Group, Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, North Brunswick, NJ 08902 (United States); Yoon, W.-S. [School of Advanced Materials Eng., Kookmin University, 861-1 Jeongneung-dong, Seongbuk-gu, Seoul 136-702 (Korea, Republic of); Chung, K.Y. [Battery Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Amatucci, G.G. [Energy Storage Research Group, Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, North Brunswick, NJ 08902 (United States)

2010-12-15

357

Quantitative spectroscopic and theoretical study of the optical absorption spectra of H2O, HOD, and D2O in the 125-145 nm region  

NASA Astrophysics Data System (ADS)

The room temperature absorption spectra of water and its isotopomers D2O and HOD have been determined in absolute cross section units in the 125 to 145 nm wavelength region using synchrotron radiation. The experimental results for these B~ band spectra are compared with results from quantum mechanical calculations using accurate diabatic ab initio potentials. A Monte Carlo sampling over the initial rotational states of the molecules is applied in order to calculate the cross sections at a temperature of 300 K. The overall rotation of the water molecule is treated exactly. Both for the experimental and for the theoretical spectrum an analysis is made in terms of a component attributed to rapid direct dissociation processes and a component attributed to longer-lived resonances. The agreement between the results from experiment and theory is excellent for H2O and D2O. In the case of HOD in the results of theory two more resonances are found at low energy. It is demonstrated that the width of the resonances of 0.04 eV is the result of overlapping and somewhat narrower resonances in the spectra of molecules differing in rotational ground state.

Cheng, Bing-Ming; Chung, Chao-Yu; Bahou, Mohammed; Lee, Yuan-Pern; Lee, L. C.; van Harrevelt, Rob; van Hemert, Marc C.

2004-01-01

358

A spectroscopic proton-exchange membrane fuel cell test setup allowing fluorescence x-ray absorption spectroscopy measurements during state-of-the-art cell tests  

NASA Astrophysics Data System (ADS)

A test setup for membrane-electrode-assemblies (MEAs) of proton exchange membrane fuel cells which allows in situ fluorescence x-ray absorption spectroscopy studies of one electrode with safe exclusion of contributions from the counter electrode is described. Interference by the counter electrode is excluded by a geometry including a small angle of incidence (< 6°) between primary beam and electrode layer. The cell has been constructed by introducing just minor modifications to an electrochemical state-of-the-art MEA test setup, which ensures realistic electrochemical test conditions. This is at the expense of significant intensity losses in the path of the incident beam, which calls for the brilliance of third-generation synchrotrons to provide meaningful data. In measurements on Pt/C and Pt-Co/C cathodes combined with Pt-C anodes (H2/O2 feed), good data quality was demonstrated both for the majority element Pt as well as for Co despite of a low areal Co density in the order of 0.02 mg/cm2.

Petrova, Olga; Kulp, Christian; van den Berg, Maurits W. E.; Klementiev, Konstantin V.; Otto, Bruno; Otto, Horst; Lopez, Marco; Bron, Michael; Grünert, Wolfgang

2011-04-01

359

Infrared reflection absorption spectroscopic study on the adsorption structures of ethylene on Ag(110) and atomic oxygen pre-covered Ag(110) surfaces  

NASA Astrophysics Data System (ADS)

Infrared reflection absorption spectra in the CH 2 out-of-plane wagging (?(CH 2)) vibration region were measured for ethylene (C 2H 4) adsorbed on Ag(110) as well as on the oxygen-induced p( n×1) reconstructed surfaces of Ag(110) ( n=2, 3, 4 and 6) at 80 K. C 2H 4 on Ag(110) gives a main peak at 955 cm -1, while on p(2×1)O-Ag(110) it exhibits a broad features of at least four components (997, 984, 970 and 954 cm -1) at saturation coverage. C 2H 4 on p( n×1)O-Ag(110) ( n=6, 4, 3) gives rise to a 972-976 cm -1 band at low exposures, shifting to 966-970 cm -1 at saturation coverage. The spectral changes are interpreted by assuming a pair of adsorption sites on both sides of the added Ag-O rows of the reconstructed surfaces.

Akita, Masato; Osaka, Naoki; Hiramoto, Shuji; Itoh, Koichi

1999-06-01

360

Characterization of SEI layers on LiMn2O4 cathodes with in-situ spectroscopic ellipsometry  

SciTech Connect

In situ spectroscopic ellipsometry was employed to study the initial stage of SEI layer formation on thin-film LiMn{sub 2}O{sub 4} electrodes. It was found that the SEI layer formed immediately upon exposure of the electrode to EC/DMC (1:1 by vol) 1.0 M LiPF{sub 6} electrolyte. The SEI layer thickness then increased in proportion to a logarithmic function of elapsed time. In comparison, the SEI layer thickness on a cycled electrode increased in proportion to a linear function of the number of cycles.

Lei, Jinglei; Li, Lingjie; Kostecki, Robert; Muller, Rolf; McLarnon, Frank

2004-08-30

361

Halo-substituted thiosemicarbazones and their copper(II), nickel(II) complexes: detailed spectroscopic characterization and study of antitumour activity against HepG2 human hepatoblastoma cells.  

PubMed

Copper(II) and nickel(II) complexes of two different halogen substituted thiosemicarbazone ligands were synthesized. The ligands 3,4-difluoroacetophenone thiosemicarbazone (1) and 2-bromo-4'-chloroacetophenone thiosemicarbazone (2) were characterized and confirmed spectroscopically by FT-IR, FT-Raman, UV-vis and fluorescence spectral analysis, while the respective copper(II) complexes [Cu(C9H9N3F2S)2Cl2] (1a), [Cu(C9H9N3ClBrS)2Cl2] (2a) and nickel(II) complexes [Ni(C9H9N3F2S)2] (1b), [Ni(C9H9N3ClBrS)2] (2b) were characterized by FT-IR, UV-vis and electron paramagnetic spectroscopy (EPR). The EPR spectra of the Cu(II) complexes provided the rhombic octahedral and axial symmetry of the complexes 1a and 2a respectively. For the complex 1a, the g values calculated as g1=2.1228, g2=2.0706 and g3=2.001 between 2900 and 3300 G. While for the complex 2a, a set of two resonance absorptions were observed. The synthesized compounds were tested for antitumor activity and showed that the ability to kill liver cancer cells significantly. Out of all the synthesized compounds, copper(II) complexes 1a and 2a showed high cytotoxic effect on liver cancer cells with 67.51% and 42.77% of cytotoxicity respectively at 100 ?M. PMID:24084484

Jagadeesh, M; Kalangi, Suresh K; Sivarama Krishna, L; Reddy, A Varada

2014-01-24

362

An X-ray absorption spectroscopic study of the effect of bond covalency on the electronic structure of Gd2Ti(2-x)Sn(x)O7.  

PubMed

The titanate and stannate pyrochlore-type oxides have been investigated because of their potential applications in different fields. Pyrochlore-type oxides exhibit a wide variety of properties such as fast ionic conduction, resistance to radiation induced structural damage, and ferro- and antiferro-magnetism. These properties mainly depend on the metal-oxygen bonding interactions and electronic structure of the materials, both of which can change with composition. The Gd2Ti(2-x)Sn(x)O7 (0 ? x ? 2) system was synthesized by the ceramic method and investigated by X-ray absorption near edge spectroscopy (XANES), which allows for the examination of the effect of substitution on bonding and the electronic structure of materials. Examination of metal K- and L3-edge XANES spectra from the Gd2Ti(2-x)Sn(x)O7 system allowed for the elucidation of how the metal-oxygen bond covalency effects the electronic structure of these materials with increasing Sn content. The ionic character of the Ti-O and Gd-O bonds increases while the Sn-O bond becomes more covalent as x increases in the formula, and resulted in changes in energy and/or line shape of the spectra. This study shows that the bonding interactions between metal and oxygen vary strongly with composition, which may affect the fast ionic conduction and resistance to radiation induced structural damage that has been previously reported for these materials. It was also observed in this study that the intensity of the intersite-hybrid peaks found in the pre-edge region of the Ti K-edge XANES spectra resulting from excitations of 1s electrons into next-nearest neighbour Ti 3d states decreased significantly with increasing Sn incorporation. PMID:23681175

Aluri, Esther Rani; Grosvenor, Andrew P

2013-07-01

363

Optical absorption and NMR spectroscopic studies on paramagnetic neodymium(III) complexes with ?-diketone and heterocyclic amines. The environment effect on 4f-4f hypersensitive transitions  

NASA Astrophysics Data System (ADS)

The optical absorption spectra of [Nd(acac) 3(H 2O) 2]·H 2O, [Nd(acac) 3bpy] and [Nd(acac) 3phen(H 2O) 2] (where acac = acetylacetone, bpy = 2,2'-bipyridyl and phen = 1,10-phenanthroline) complexes in the visible region, in a series of non-aqueous solvents (methanol, ethanol, isopropanol, chloroform, acetonitrile, pyridine, nitrobenzene and dimethylsulphoxide) have been analyzed. The transition 4G 5/2 ? 4I 9/2 (Nd-VI) located near the middle of the visible region (17,500 cm -1) is hypersensitive. Its behavior is in sharp contrast to many other typically weak and consistently unvaried, normal 4f-4f transitions. The oscillator strength of this transition for the chelate as well as its adducts with phen and bpy in any of the solvent employed is larger than the oscillator strength of Nd 3+ aqua-ion. It is most intense in pyridine for all the complexes studied and, therefore, pyridine is the most effective in promoting f-f spectral intensity. The band shape and oscillator strength of the hypersensitive transitions display pronounced changes as compared to Nd 3+ aqua-ion. The band shapes of the hypersensitive transitions show remarkable changes on passing from aqueous solution to various non-aqueous solutions, which is the result of change in the environment about the Nd(III) ion in the various solutions and suggests change in the environment about the Nd(III) ion in the various solutions and suggests coordination of solvent molecule(s), in some cases. A comparative account of hypersensitivity in the present complexes with those of other adducts of Nd(?-diketoenolate) 3 with heterocyclic amines is discussed. The NMR signals of heterocyclic amines have been shifted to high fields while the resonances due to acetylacetone moiety have moved to low fields. The paramagnetic shift in the complexes is dipolar in nature.

Ansari, A. A.; Irfanullah, M.; Iftikhar, K.

2007-08-01

364

Atomic structure and chemical order in Ge-As selenide and sulfoselenide glasses: An x-ray absorption fine structure spectroscopic study  

NASA Astrophysics Data System (ADS)

The nearest-neighbor coordination environments of Ge and As atoms in GexAsySe1-x-y glasses with x:y=1:2 and 1:1 and in Ge0.154As0.308 (S,Se)0.538 sulfoselenide glasses with wide-ranging Se contents have been studied with Ge and As K-edge extended x-ray absorption time spectra spectroscopy. The average coordination numbers of Ge and As atoms are found to be 4 and 3, respectively, in all glasses. The compositional makeup of the first coordination shells of Ge and As atoms indicate that chemical order is largely preserved in stoichiometric and Se-excess GexAsySe1-x-y glasses. On the other hand, chemical order is found to be strongly violated in the case of Se-deficient GexAsySe1-x-y glasses where the chalcogen deficiency is entirely taken up by the formation of As-As homopolar bonds at low and intermediate levels of Se deficiency. The Ge atoms take part in homopolar bonding only in strongly Se-deficient glasses indicating clustering of As atoms. In the case of sulfoselenide glasses the distribution of S and Se atoms in the first coordination shells of Ge and As atoms is found to be random, signifying a chemically ordered chalcogen ``sublattice.'' It is shown that the intermediate-range structural and topological aspects of such compositional variation of chemical order may play a central role in controlling properties such as the molar volume of chalcogenide glasses.

Sen, S.; Aitken, B. G.

2002-10-01

365

Synthesis and characterizations of ultra-small ZnS and Zn(1-x)Fe(x)S quantum dots in aqueous media and spectroscopic study of their interactions with bovine serum albumin.  

PubMed

This work reports a new experimental methodology for the synthesis of ultra small zinc sulfide and iron doped zinc sulfide quantum dots in aqueous media. The nanoparticles were obtained using a simple procedure based on the precipitation of ZnS in aqueous solution in the presence of 2-mercaptoethanol as a capping agent, at room temperature. The effect of Fe(3+) ion concentration as dopant on the optical properties of ZnS was studied. The size of quantum dots was determined to be about 1nm, using scanning tunneling microscopy. The synthesized nanoparticles were characterized by X-ray diffraction, UV-Vis absorption and photoluminescence emission spectroscopies. The presence and amount of iron impurity in the structure of Zn((1-x))Fe(x)S nanocrystals were confirmed by atomic absorption spectrometry. A blue shift in band-gap of ZnS was observed upon increasing incorporation of Fe(3+) ion in the iron doped zinc sulfide quantum dots. The photoluminescence investigations showed that, in the case of iron doped ZnS nanoparticles, the emission band of pure ZnS nanoparticles at 427nm shifts to 442nm with appearance of a new sharp emission band around 532nm. The X-ray diffraction analysis indicated that the iron doped nanoparticles are crystalline, with cubic zinc blend structure, having particle diameters of 1.7±022nm. Finally, the interaction of the synthesized nanoparticles with bovine serum albumin was investigated at pH 7.2. The UV-Vis absorption and fluorescence spectroscopic methods were applied to compare the optical properties of pure and iron doped ZnS quantum dots upon interaction with BSA. It was proved that, in both cases, the fluorescence quenching of BSA by the quantum dots is mainly a result of the formation of QDs-BSA complex in solution. In the steady-state fluorescence studies, the interaction parameters including binding constants (K(a)), number of binding sites (n), quenching constants ( [Formula: see text] ), and bimolecular quenching rate constants (k(q)) were determined at three different temperatures and the results were then used to evaluate the corresponding thermodynamic parameters ?H, ?S and ?G. PMID:21482179

Khani, Omid; Rajabi, Hamid Reza; Yousefi, Mohammad Hasan; Khosravi, Ali Azam; Jannesari, Mohammad; Shamsipur, Mojtaba

2011-07-01

366

Synthesis and characterizations of ultra-small ZnS and Zn (1- x) Fe xS quantum dots in aqueous media and spectroscopic study of their interactions with bovine serum albumin  

NASA Astrophysics Data System (ADS)

This work reports a new experimental methodology for the synthesis of ultra small zinc sulfide and iron doped zinc sulfide quantum dots in aqueous media. The nanoparticles were obtained using a simple procedure based on the precipitation of ZnS in aqueous solution in the presence of 2-mercaptoethanol as a capping agent, at room temperature. The effect of Fe 3+ ion concentration as dopant on the optical properties of ZnS was studied. The size of quantum dots was determined to be about 1 nm, using scanning tunneling microscopy. The synthesized nanoparticles were characterized by X-ray diffraction, UV-Vis absorption and photoluminescence emission spectroscopies. The presence and amount of iron impurity in the structure of Zn (1- x) Fe xS nanocrystals were confirmed by atomic absorption spectrometry. A blue shift in band-gap of ZnS was observed upon increasing incorporation of Fe 3+ ion in the iron doped zinc sulfide quantum dots. The photoluminescence investigations showed that, in the case of iron doped ZnS nanoparticles, the emission band of pure ZnS nanoparticles at 427 nm shifts to 442 nm with appearance of a new sharp emission band around 532 nm. The X-ray diffraction analysis indicated that the iron doped nanoparticles are crystalline, with cubic zinc blend structure, having particle diameters of 1.7 ± 022 nm. Finally, the interaction of the synthesized nanoparticles with bovine serum albumin was investigated at pH 7.2. The UV-Vis absorption and fluorescence spectroscopic methods were applied to compare the optical properties of pure and iron doped ZnS quantum dots upon interaction with BSA. It was proved that, in both cases, the fluorescence quenching of BSA by the quantum dots is mainly a result of the formation of QDs-BSA complex in solution. In the steady-state fluorescence studies, the interaction parameters including binding constants ( Ka), number of binding sites ( n), quenching constants ( KSV), and bimolecular quenching rate constants ( kq) were determined at three different temperatures and the results were then used to evaluate the corresponding thermodynamic parameters ? H, ? S and ? G.

Khani, Omid; Rajabi, Hamid Reza; Yousefi, Mohammad Hasan; Khosravi, Ali Azam; Jannesari, Mohammad; Shamsipur, Mojtaba

2011-07-01

367

Infrared and Raman imaging for characterizing complex biological materials: a comparative morpho-spectroscopic study of colon tissue.  

PubMed

Complementary diagnostic methods to conventional histopathology are currently being investigated for developing rapid and objective molecular-level understanding of various disorders, especially cancers. Spectral histopathology using vibrational spectroscopic imaging has been put in the frontline as potentially promising in this regard as it provides a "spectral fingerprint" of the biochemical composition of cells and tissues. In order to ascertain the feasible conditions of vibrational spectroscopic methods for tissue-imaging analysis, vibrational multimodal imaging (infrared transmission, infrared-attenuated total reflection, and Raman imaging) of the same colon tissue has been implemented. The spectral images acquired were subjected to multivariate clustering analysis in order to identify on a molecular level the constituent histological organization of the colon tissue such as the epithelium, connective tissue, etc., by comparing the cluster images with the histological reference images. Based on this study, a comparative analysis of important factors involved in the vibrational multimodal imaging approaches such as image resolution, time constraints, their advantages and limitations, and their applicability to biological tissues has been carried out. Out of the three different vibrational imaging modalities tested, infrared-attenuated total reflection mode of imaging appears to provide a good compromise between the tissue histology and the time constraints in achieving similar image contrast to that of Raman imaging at an approximately 33-fold faster measurement time. The present study demonstrates the advantages, the limitations of the important parameters involved in vibrational multimodal imaging approaches, and their potential application toward imaging of biological tissues. PMID:24405955

Nallala, Jayakrupakar; Piot, Olivier; Diebold, Marie-Danièle; Gobinet, Cyril; Bouché, Olivier; Manfait, Michel; Sockalingum, Ganesh D

2014-01-01

368

o-Nitrotyrosine and p-iodophenylalanine as spectroscopic probes for structural characterization of SH3 complexes.  

PubMed

High-throughput screening of protein-protein and protein-peptide interactions is of high interest both for biotechnological and pharmacological applications. Here, we propose the use of the noncoded amino acids o-nitrotyrosine and p-iodophenylalanine as spectroscopic probes in combination with circular dichroism and fluorescence quenching techniques (i.e., collisional quenching and resonance energy transfer) as a means to determine the peptide orientation in complexes with SH3 domains. Proline-rich peptides bind SH3 modules in two alternative orientations, according to their sequence motifs, classified as class I and class II. The method was tested on an SH3 domain from a yeast myosin that is known to recognize specifically class I peptides. We exploited the fluorescence quenching effects induced by o-nitrotyrosine and p-iodophenylalanine on the fluorescence signal of a highly conserved Trp residue, which is the signature of SH3 domains and sits directly in the binding pocket. In particular, we studied how the introduction of the two probes at different positions of the peptide sequence (i.e., N-terminally or C-terminally) influences the spectroscopic properties of the complex. This approach provides clear-cut evidence of the orientation of the binding peptide in the SH3 pocket. The chemical strategy outlined here can be easily extended to other protein modules, known to bind linear sequence motifs in a highly directional manner. PMID:17567746

De Filippis, Vincenzo; Draghi, Annamaria; Frasson, Roberta; Grandi, Claudio; Musi, Valeria; Fontana, Angelo; Pastore, Annalisa

2007-07-01

369

Absorption spectra and photovoltaic characterization of chlorophyllins as sensitizers for dye-sensitized solar cells.  

PubMed

Dye-sensitized solar cells (DSSCs) based on Chlorine-e6 (Chl-e6), a Chlorophyll a derivative, and Chl-e6 containing Cu, have been investigated by carrying out incident photon to current efficiency (IPCE) and current-voltage (I-V) measurements. The effect of the metallic ion and the influence of the solvent polarity on the dye aggregation and their absorption bands have been analysed by performing electronic absorption measurements. The dependence of the photoelectrochemical parameters of these DSSCs on the electrolyte by the addition of pyrimidine and/or pyrrole has been discussed in details. For the first time I-V curves for a DSSC based on copper Chl-e6 dye have been shown and compared with Zn based chlorophyllin. Furthermore, the performance of a Cu-Chl-e6 based DSSC has been deeply improved by a progressive optimization of the TiO2 multilayer photoanode overcoming the best data reported in literature so far for this dye. It's worth to emphasize that, the analysis reported in this paper supplies very useful information which paves the way to further detailed studies turned to the employment of natural pigments as sensitizers for solar cells. PMID:24892526

Calogero, Giuseppe; Citro, Ilaria; Crupi, Cristina; Di Marco, Gaetano

2014-11-11

370

Enhancement of oral bioavailability of tripterine through lipid nanospheres: preparation, characterization, and absorption evaluation.  

PubMed

Oral delivery of anticancer drugs remains challenging because of limited water-solubility and/or poor permeability. Here, we aimed to enhance the oral bioavailability of tripterine (TRI, a plant-derived anticancer compound) using lipid nanospheres (LNs) and to determine the mechanisms of oral absorption. TRI-loaded LNs (TRI-LNs) were prepared by rapid dispersion of an ethanol mixture of TRI, lecithin, sodium oleate, and soybean oil into water. The obtained LNs were 150 nm in size with a high value of entrapment efficiency (99.95%). TRI-LNs were fairly stable and the drug release was negligible (<0.2%) in simulated physiological fluid. The pharmacokinetic results showed that LNs significantly enhanced the oral bioavailability of TRI with a relative bioavailability of 224.88% (TRI suspensions was used as a reference). The mechanistic studies demonstrated that improved intestinal permeability and post-enterocyte lymphatic transport were mainly responsible for the enhanced oral absorption. Our findings suggested that LNs may be a viable oral carrier for poorly bioavailable drugs. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci. PMID:24700417

Zhang, Xingwang; Zhang, Tianpeng; Zhou, Xiaotong; Liu, Hongming; Sun, Hua; Ma, Zhiguo; Wu, Baojian

2014-06-01

371

Biochemical and spectroscopic characterization of the putative photoreceptor for phototaxis in amoebae of the cellular slime mould Dictyostelium discoideum  

Microsoft Academic Search

Using sucrose gradient centrifugation, anion exchange chromatography on a SMART system, isoelectric focusing (IEF) and sodium dodecylsulphate polycrylamide gel electrophoresis (SDS PAGE), a 45.5. kDa membrane protein was isolated from amoebae of the cellular slime mould Dictyostelium discoideum. The absorption spectrum of the isolated protein corresponds well with the action spectrum for the photoaccumulation of the amoebae of Dictyostelium discoideum

Thomas Schlenkrich; Peter Fleischmann; Donat-P. Häder

1995-01-01

372

Characterizing Quasar Outflows IV: Regulating Outflows Through X-ray and EUV Absorption  

NASA Astrophysics Data System (ADS)

Galaxy evolution models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 11000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) measurements of UV emission line and continuum parameters. In this poster, we add photometry from the GALEX All-sky imaging survey, as well as the Chandra and ROSAT archives. These provide coverage of the rest-frame extreme ultraviolet, and soft X-ray bands. In an accompanying poster, we have subjectively divided these quasars into four categories: broad absorption-line quasars (2700 objects), associated absorption-line quasars (1700 objects), reddened quasars (160 objects), and unabsorbed/unreddened quasars (6300 objects). We are interested in testing the radiative-driving hypothesis that requires a suppression of X-ray flux in order to transfer momentum efficiently to the UV-absorbing gas. Hence, we explore how absorption in both the extreme ultraviolet and the soft X-ray bands correlate with properties of the UV outflows, quasar property, and changes in SED shape. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the Astrophysics Data Analysis Program and by Chandra grant GO9-0120X.

Derseweh, Jeffrey; Ganguly, R.; Richmond, J. M.; Stark, M. A.; Christenson, D. H.; Robbins, J. M.; Townsend, S. L.

2012-05-01

373

Spectroscopic ellipsometric characterization of TiAlN/TiAlON/Si 3N 4 tandem absorber for solar selective applications  

NASA Astrophysics Data System (ADS)

Sputter deposited TiAlN/TiAlON/Si 3N 4 tandem absorber has been characterized by spectroscopic ellipsometry in the wavelength range of 450-1200 nm. Each layer of the tandem absorber viz., TiAlN, TiAlON and Si 3N 4 has been deposited separately on copper substrate (Cu) and ellipsometric measurements have been carried out on each of these layers. The measured ellipsometric spectra were fitted with theoretically simulated spectra and the sample structure and wavelength dispersion of optical constants of each layers have been determined. The ellipsometric measurements have also been carried out on the three-layer tandem absorber deposited on Cu substrate. By analyzing the ellipsometric data, depth profiling of the tandem absorber has been carried out using the derived optical constants of the individual layers.

Biswas, A.; Bhattacharyya, D.; Barshilia, H. C.; Selvakumar, N.; Rajam, K. S.

2008-01-01

374

Spectroscopic characterization of Co3O4 catalyst doped with CeO2 and PdO for methane catalytic combustion.  

PubMed

The study deals with the XPS, Raman and EDX characterization of a series of structured catalysts composed of cobalt oxides promoted by palladium and cerium oxides. The aim of the work was to relate the information gathered from spectroscopic analyses with the ones from kinetic tests of methane combustion to establish the basic structure-activity relationships for the catalysts studied. The most active catalyst was the cobalt oxide doped with little amount of palladium and wins a confrontation with pure palladium oxide catalyst which is commercially used in converters for methane. The analyses Raman and XPS analyses showed that this catalyst is composed of a cobalt spinel and palladium oxide. The quantitative approach to the composition of the catalysts by XPS and EDX methods revealed that the surface of palladium doped cobalt catalyst is enriched with palladium oxide which provides a great number of active centres for methane combustion indicated by kinetic parameters. PMID:24913565

Jod?owski, P J; J?drzejczyk, R J; Rogulska, A; Wach, A; Ku?trowski, P; Sitarz, M; Lojewski, T; Ko?odziej, A; Lojewska, J

2014-10-15

375

Characterization of carrier recombination and trapping processes in proton irradiated silicon by microwave absorption transients  

NASA Astrophysics Data System (ADS)

Carrier lifetime variations dependent on proton irradiation with fluences in the range from 5×10 12 to 10 15 cm -2 were investigated in high resistivity oxygenated silicon wafers and pad detectors. The fast recombination and slow trapping constituents within recombination transients have been distinguished by combining analyses of the excess carrier decay dependence on the excitation intensity, bias illumination and temperature, measured using the technique of microwave absorption by free carriers. Differences in the rate of formation and type of defects in the ranges of moderate and highest proton irradiation fluences have been revealed from the inverse lifetime dependence on irradiation fluence. The activation factors of the capture centres have been evaluated from carrier lifetime variations in the range of low and elevated temperatures.

Gaubas, E.; Vaitkus, J.; Niaura, G.; Härkönen, J.; Tuovinen, E.; Luukka, P.; Fretwurst, E.

2005-07-01

376

Structural characterization, absorption and photoluminescence study of symmetrical azomethines with long aliphatic chains  

NASA Astrophysics Data System (ADS)

In this study, we investigated structural and optical properties of three symmetrical azomethines bis(4-(4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 11-heptadecafluoroundecyloxy)benzylidene)benzene-1,4-diamine (SAz1), bis(4-(4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 11-heptadecafluoroundecyloxy)benzylidene)biphenyl-4,4?-diamine (SAz2) and 4,4?-methylenebis(N-(4-(octadecyloxy)benzylidene)benzenamine (SAz3). Electronic properties, such as orbital energies and resulting energy gap of the three symmetrical azomethines were calculated theoretically by density functional theory (DFT). The photoluminescence (PL) and absorption UV-vis properties of the azomethines were investigated in chloroform solution. The effect of excitation wavelength and concentration on the PL properties was detected as well. Azomethines emitted violet, blue or green light. The highest PL intensity was found for SAz1.

Iwan, Agnieszka; Schab-Balcerzak, Ewa; Grucela-Zajac, Marzena; Skorka, Lukasz

2014-01-01

377

Characterization of Thermal Radiative Properties of Nanofluids for Selective Absorption of Solar Radiation  

NASA Astrophysics Data System (ADS)

Nanofluids are used in device cooling, heat pipes, and other applications. Researchers in thermal engineering have extensively investigated the thermal conductivity and enhanced heat transfer of nanofluids. This study investigates the thermal radiative properties of nanofluids and discusses the characteristics of the selective absorption of solar radiation of nanofluids. Several kinds of nanoparticles are prepared using the two-step method, and the effects of dispersants, mass fractions, and nanoparticle materials on the radiative properties of nanofluids within the wavelength range of 300 nm to 2500 nm are analyzed. Dispersants can reduce the transmittance of water by <5 % within the visible spectrum. ZnO- and AlN-water nanofluids selectively absorb solar radiation, whereas ZrC- and TiN-water nanofluids absorb most of the solar radiation applied to them. The findings of this study are beneficial to research on the application of nanofluids in solar energy utilization.

Zhu, Qunzhi; Cui, Yun; Mu, Lijuan; Tang, Liqing

2013-12-01

378

Mercury transformations in chemical agent simulant as characterized by X-ray absorption fine spectroscopy.  

PubMed

Chemical analyses of U.S. stockpiled mustard chemical warfare agent show some agent destined for destruction contains mercury [L. Ember, Chem. Eng. News 82 (2004) 8]. Because of its toxicity, mercury must be removed from agent prior to incineration or be scrubbed from incineration exhaust to prevent release into the atmosphere. Understanding mercury/agent interactions is critical if either atmospheric or aqueous treatment processes are used. We investigate and compare the state of mercury in water to that in thiodiglycol, a mustard simulant, as co-contaminants are introduced. The effects of sodium hypochlorite and sodium hydroxide, common neutralization chemicals, on mercury in water and simulant with and without co-contaminants present are examined using X-ray absorption fine spectroscopy (XAFS). PMID:18970232

Skubal, Laura R; Biedron, Sandra G; Newville, Matthew; Schneider, John F; Milton, Stephen V; Pianetta, Piero; O'Neill, H Jack

2005-10-15

379

Characterization of Metalloproteins by High-throughput X-ray Absorption Spectroscopy  

SciTech Connect

High-throughput X-ray absorption spectroscopy was used to measure transition metal content based on quantitative detection of X-ray fluorescence signals for 3879 purified proteins from several hundred different protein families generated by the New York SGX Research Center for Structural Genomics. Approximately 9% of the proteins analyzed showed the presence of transition metal atoms (Zn, Cu, Ni, Co, Fe, or Mn) in stoichiometric amounts. The method is highly automated and highly reliable based on comparison of the results to crystal structure data derived from the same protein set. To leverage the experimental metalloprotein annotations, we used a sequence-based de novo prediction method, MetalDetector, to identify Cys and His residues that bind to transition metals for the redundancy reduced subset of 2411 sequences sharing <70% sequence identity and having at least one His or Cys. As the HT-XAS identifies metal type and protein binding, while the bioinformatics analysis identifies metal-binding residues, the results were combined to identify putative metal-binding sites in the proteins and their associated families. We explored the combination of this data with homology models to generate detailed structure models of metal-binding sites for representative proteins. Finally, we used extended X-ray absorption fine structure data from two of the purified Zn metalloproteins to validate predicted metalloprotein binding site structures. This combination of experimental and bioinformatics approaches provides comprehensive active site analysis on the genome scale for metalloproteins as a class, revealing new insights into metalloprotein structure and function.

W Shi; M Punta; J Bohon; J Sauder; R DMello; M Sullivan; J Toomey; D Abel; M Lippi; et al.

2011-12-31

380

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy.  

PubMed

Mining of mercury deposits located in the California Coast Range has resulted in the release of mercury to the local environment and water supplies. The solubility, transport, and potential bioavailability of mercury are controlled by its chemical speciation, which can be directly determined for samples with total mercury concentrations greater than 100 mg kg(-1) (ppm) using X-ray absorption spectroscopy (XAS). This technique has the additional benefits of being non-destructive to the sample, element-specific, relatively sensitive at low concentrations, and requiring minimal sample preparation. In this study, Hg L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra were collected for several mercury mine tailings (calcines) in the California Coast Range. Total mercury concentrations of samples analyzed ranged from 230 to 1060 ppm. Speciation data (mercury phases present and relative abundances) were obtained by comparing the spectra from heterogeneous, roasted (calcined) mine tailings samples with a spectral database of mercury minerals and sorbed mercury complexes. Speciation analyses were also conducted on known mixtures of pure mercury minerals in order to assess the quantitative accuracy of the technique. While some calcine samples were found to consist exclusively of mercuric sulfide, others contain additional, more soluble mercury phases, indicating a greater potential for the release of mercury into solution. Also, a correlation was observed between samples from hot-spring mercury deposits, in which chloride levels are elevated, and the presence of mercury-chloride species as detected by the speciation analysis. The speciation results demonstrate the ability of XAS to identify multiple mercury phases in a heterogeneous sample, with a quantitative accuracy of +/-25% for the mercury-containing phases considered. Use of this technique, in conjunction with standard microanalytical techniques such as X-ray diffraction and electron probe microanalysis, is beneficial in the prioritization and remediation of mercury-contaminated mine sites. PMID:11036987

Kim, C S; Brown, G E; Rytuba, J J

2000-10-16

381

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy  

USGS Publications Warehouse

Mining of mercury deposits located in the California Coast Range has resulted in the release of mercury to the local environment and water supplies. The solubility, transport, and potential bioavailability of mercury are controlled by its chemical speciation, which can be directly determined for samples with total mercury concentrations greater than 100 mg kg-1 (ppm) using X-ray absorption spectroscopy (XAS). This technique has the additional benefits of being non-destructive to the sample, element-specific, relatively sensitive at low concentrations, and requiring minimal sample preparation. In this study, Hg L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra were collected for several mercury mine tailings (calcines) in the California Coast Range. Total mercury concentrations of samples analyzed ranged from 230 to 1060 ppm. Speciation data (mercury phases present and relative abundances) were obtained by comparing the spectra from heterogeneous, roasted (calcined) mine tailings samples with a spectral database of mercury minerals and sorbed mercury complexes. Speciation analyses were also conducted on known mixtures of pure mercury minerals in order to assess the quantitative accuracy of the technique. While some calcine samples were found to consist exclusively of mercuric sulfide, others contain additional, more soluble mercury phases, indicating a greater potential for the release of mercury into solution. Also, a correlation was observed between samples from hot-spring mercury deposits, in which chloride levels are elevated, and the presence of mercury-chloride species as detected by the speciation analysis. The speciation results demonstrate the ability of XAS to identify multiple mercury phases in a heterogeneous sample, with a quantitative accuracy of ??25% for the mercury-containing phases considered. Use of this technique, in conjunction with standard microanalytical techniques such as X-ray diffraction and electron probe microanalysis, is beneficial in the prioritization and remediation of mercury-contaminated mine sites. (C) 2000 Elsevier Science B.V.

Kim, C. S.; Brown, Jr. , G. E.; Rytuba, J. J.

2000-01-01

382

CD Spectroscope  

NSDL National Science Digital Library

In this activity, learners use an old CD to construct a spectroscope, a device that separates light into its component colors. Learners will hold it up to various light sources to examine how different light has different color strengths. Use this activity to introduce learners to the color spectrum and the tools scientists use to study it.

University, Colorado S.

2009-01-01

383

Characterizing ablation and aerosol generation during elemental fractionation on absorption modified lithium tetraborate glasses using LA-ICP-MS.  

PubMed

The influence of sample matrix composition, absorption behavior and laser aerosol particle size distribution on elemental fractionation in laser ablation inductively coupled plasma mass spectrometry was studied for nanosecond laser ablation at a wavelength of 266 nm. To this end, lithium tetraborate glass samples with different iron oxide contents and trace amounts of a group of 11 elements were prepared synthetically. The samples were characterized in terms of optical absorbance, melting points, trace element concentrations and homogeneity. UV/VIS spectra showed that sample absorption rises with increasing Fe2O3 content. Crater depths and time-dependent particle size distributions were measured, and ablated and transported sample volumes were estimated. Furthermore, the laser aerosol was filtered using a particle separation device and transient ICP-MS signals were acquired with and without filtering the aerosol. The results demonstrate that the amount of ablated sample is related to the absorption coefficient of the sample and therefore to the optical penetration depth of the laser beam into the sample. The higher energy densities resulting from the shorter penetration depths result in smaller average particle sizes for highly absorbing samples, which allows more efficient transport to and atomization and excitation of the ablated material within the ICP. The particle size distribution changes continuously with ablation time, and larger particle fractions occur mainly at the beginning of the ablation, which leads to particle-related fractionation processes at the beginning of the transient signal. Exceeding a critical depth to diameter ratio, laser-related elemental fractionation processes occur. Changes in the volatile to non-volatile element intensity ratio after the aerosol is filtered indicate that particle size-related enrichment processes contribute to elemental fractionation. PMID:15616778

Weis, Peter; Beck, Horst P; Günther, Detlef

2005-01-01

384

Spectroscopic characterization of triple-decker lanthanide porphyrin sandwich complexes. Effects of strong. pi. pi. interactions in extended assemblies  

Microsoft Academic Search

Electrochemical, optical absorption, near-infrared, infrared, resonance Raman, and electron paramagnetic resonance data are reported for several neutral and singly oxidized triple-decker lanthanide porphyrin sandwich complexes Lnâ(OEP)â (Ln = La(III), Ce(III), Eu(III); OEP = octaethylporphyrin). The data indicate that there are strong ÏÏ interactions between the porphyrin macrocycles in all of the complexes. As a consequence, the hole in the porphyrin

John K. Duchowski; David F. Bocian

1990-01-01

385

Synthesis, characterization and theoretical study of new hetarylazopyrazolone dyes and investigation of their absorption spectra  

NASA Astrophysics Data System (ADS)

A series of hetarylazopyrazolone dyes were synthesized by coupling 1-(2-benzothiazolyl)-3-methylpyrazol-5-one with six heterocylic amines prepared in nitrosyl sulphuric acid. The dyes were characterized by spectral methods and elemental analysis. The solvatochromic properties of the dyes were investigated in various solvents. Additionally, acid-base, concentration, temperature and substituent effects on the visible absorbtion spectra were also examined.

Aktan, Ebru; Ertan, Nermin; Uyar, Tahsin

2014-02-01

386

Induced chirality upon binding of cis-parinaric acid to bovine beta-lactoglobulin: spectroscopic characterization of the complex.  

PubMed

Binding of the polyunsaturated cis-parinaric acid to bovine beta-lactoglobulin (BLG) was studied by circular dichroism (CD), electronic absorption spectroscopy and mass spectrometry methods. Upon protein binding, the UV absorption band of parinaric acid is red shifted by ca. 5 nm, showing hypochromism and reduced vibrational fine structure, suggesting that the ligand binds as a monomer in non-planar geometry. In the CD spectra measured at pH 7.36 and 8.5 a strong, negative Cotton band appears centered at 310 nm (Delta epsilon = -25 M(-1) cm(-1)) corresponding to the long-wavelength absorption band of cis-parinaric acid. The source of this induced optical activity is the helical distortion of the polyene chromophore caused by the chiral protein environment. From CD spectral data the value of the association constant was calculated to be 4.7 x 10(5) M(-1) at pH 7.36. CD and mass spectrometry measurements showed that parinaric acid binds weakly to BLG in acidic solution, though small peaks at mass 18,559 and 18,645 can be obtained in the reconstructed electrospray mass spectrum; these correspond to the binding of parinaric acid in 1:1 stoichiometry to both monomer variants of BLG B and A. The hydrophobic interior cavity of BLG was assigned as the primary binding site of cis-parinaric acid. PMID:12044875

Zsila, Ferenc; Imre, Tímea; Szabó, Pál T; Bikádi, Zsolt; Simonyi, Miklós

2002-06-01

387

Characterization of Cr3+ doped mixed alkali ions effect in zinc borate glasses - Physical and spectroscopic investigations  

NASA Astrophysics Data System (ADS)

The physical and structural properties of Cr3+ doped 19.9 ZnO + xLi2O + (30 - x) Na2O + 50B2O3 (5 ? x ? 25) (ZLNB) glasses have been studied. Powder X-ray diffraction patterns indicated the amorphous nature of the glass samples. The physical parameters of all the glasses were also evaluated with respect to the composition. They exhibit the non-linearity providing the evidence for mixed alkali ions effect. The infrared spectra of the glasses in the range 400-4000 cm-1 showed the presence of BO3 and BO4 local structures in all the glass systems. No boroxol ring formation was observed in the structure of these glasses. Optical absorption and electron paramagnetic resonance studies were carried out at room temperature. From the optical absorption data various optical parameters such as optical band gap, Urbach energy were evaluated. Crystal field and Racah parameters are evaluated from optical absorption spectra. The EPR spectra of Cr3+ doped ZLNB glasses exhibited resonance signals at g = 4.066 and g = 1.9779 characteristic of Cr3+ ions. The evaluated bonding parameters suggest the covalent nature.

Rama Sundari, G.; Pushpa Manjari, V.; Raghavendra Rao, T.; Satish, D. V.; Rama Krishna, Ch.; Venkata Reddy, Ch.; Ravikumar, R. V. S. S. N.

2014-06-01

388

Spectroscopic characterization of triple-decker lanthanide porphyrin sandwich complexes. Effects of strong. pi. pi. interactions in extended assemblies  

SciTech Connect

Electrochemical, optical absorption, near-infrared, infrared, resonance Raman, and electron paramagnetic resonance data are reported for several neutral and singly oxidized triple-decker lanthanide porphyrin sandwich complexes Ln{sub 2}(OEP){sub 3} (Ln = La(III), Ce(III), Eu(III); OEP = octaethylporphyrin). The data indicate that there are strong {pi}{pi} interactions between the porphyrin macrocycles in all of the complexes. As a consequence, the hole in the porphyrin {pi} system of the Ln{sub 2}(OEP){sub 3}{sup +} systems is delocalized over all three rings on the vibrational and electronic time scales. The singly oxidized complexes exhibit a characteristic electronic absorption band at very low energies (ca. 2200 nm). This absorption arises as a direct consequence of the strong {pi}{pi} interactions between the rings. A molecular orbital scheme is proposed that accounts for this low-energy feature as well as a number of other properties of the triple-decker sandwich complexes.

Duchowski, J.K.; Bocian, D.F. (Carnegie-Mellon Univ., Pittsburgh, PA (USA))

1990-11-21

389

Spectroscopic characterization of polyethyleneglycol modified superoxide dismutase: sup 1 H NMR studies on its Cu sub 2 Co sub 2 derivative  

SciTech Connect

Spectroscopic methods have been employed in order to understand the molecular basis of the decrease in enzymatic activity of the antiinflammatory enzyme copper-zinc superoxide dismutase (SOD) following the covalent binding of polyethyleneglycol (PEG) chains to the protein amino-groups. The PEG modification is a general method recently proposed to improve the therapeutic index of enzymes. 1H NMR spectra on the cobalt substituted PEG-modified SOD, Cu2Co2-PEG-SOD, have been recorded. The signals are quite broad with respect to the unmodified enzyme. This has been interpreted on the basis of the effect of molecular weight on the linewidth. The analysis has shown that the histidine hydrogens involved in metal binding at the enzyme active site are the same in both native and PEG-modified SOD. Similarly, circular dichroism and absorption spectra indicate that the overall conformation of the metal clusters is not perturbed upon modification. On the other hand, azide titration shows that the affinity constant of N-3 for SOD is largely reduced upon PEG modification (K = 154 M-1 and 75 M-1 for the native and modified SOD, respectively). These results indicate that the decrease in enzymatic activity upon surface modification with PEG is not caused by a perturbation of the active site geometry, but to a decrease in the channeling of the O2- ion towards the enzyme active site.

Banci, L.; Bertini, I.; Caliceti, P.; Monsu Scolaro, L.; Schiavon, O.; Veronese, F.M. (Univ. of Florence (Italy))

1990-06-01

390

Structural characterization of 1,1,3,3-tetramethylguanidinium chloride ionic liquid by reversible SO2 gas absorption.  

PubMed

A unique new ionic liquid-gas adduct solid state compound formed between 1,1,3,3-tetramethylguanidinium chloride ([tmgH]Cl) and sulfur dioxide has been characterized by X-ray diffraction and Raman spectroscopy. The structure contains SO2 molecules of near normal structure kept at their positions by Cl-S interactions. The crystals belong in the orthorhombic system, space group Pbcn, with unit cell dimensions of a = 15.6908(10) Å, b = 9.3865(6) Å, and c = 14.1494(9) Å, angles ? = ? = ? = 90°, and Z = 8 at 120 K. The [tmgH]Cl has a very high absorption capacity of nearly 3 mol of SO2 per mol of [tmgH]Cl at 1 bar of SO2 and at room temperature. However, part of the absorbed SO2 was liberated during the crystallization, probably because the crystal only accommodates one molecule of SO2 per [tmgH]Cl. The nature of the high absorption capacity of [tmgH]Cl as well as of the homologous compounds with bromide and iodide are discussed. Some of these salts may prove useful as reversible absorbents of SO2 in industrial flue gases. PMID:24088034

Berg, Rolf W; Harris, Pernille; Riisager, Anders; Fehrmann, Rasmus

2013-11-01

391

X-ray absorption and Mössbauer spectroscopies characterization of iron nanoclusters prepared by the gas aggregation technique.  

PubMed

Partially oxidized iron nanoclusters have been prepared by the gas-phase aggregation technique with typical sizes of 2-3 nm. This preparation technique has been reported to obtain clusters with interesting magnetic properties such as very large exchange bias. In this paper, a sample composition study carried out by Mössbauer and X-ray absorption spectroscopies is reported. The information reached by these techniques, which is based on the iron short range order, results to be an ideal way to have a characterization of the whole sample since the obtained data are an average over a very large amount of the clusters. In addition, our results indicate the presence of ferrihydrite, which is a compound typically ignored when studying this type of systems. PMID:23421253

Sánchez-Marcos, J; Laguna-Marco, M A; Martínez-Morillas, R; Céspedes, E; Menéndez, N; Jiménez-Villacorta, F; Prieto, C

2012-11-01

392

Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets  

PubMed Central

We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings.

Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

2008-01-01

393

Temporally resolved characterization of shock-heated foam target with Al absorption spectroscopy for fast electron transport study  

SciTech Connect

The CH foam plasma produced by a laser-driven shock wave has been characterized by a temporally resolved Al 1s-2p absorption spectroscopy technique. A 200 mg/cm{sup 3} foam target with Al dopant was developed for this experiment, which used an OMEGA EP [D. D. Meyerhof