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1

EMERGING INFRARED LASER ABSORPTION SPECTROSCOPIC  

E-print Network

. Internal and external cavity-enhanced spectroscopies are two methods to increase the magnitude-reflector), such as light detection and ranging (LIDAR), differential optical ab- sorption spectroscopy (DOAS), laser ABSORPTION SPECTROSCOPIC TECHNIQUES FOR GAS ANALYSIS spectroscopy (LIBS), and fiber optic or waveguide

2

Spectroscopic characterization of alkane radical cations—I. Electronic absorption spectra of 3-methylalkane radical cations  

NASA Astrophysics Data System (ADS)

Radical cations of various 3-methylalkanes (C 6-C 14) have been produced and stabilized by ?-irradiation of the corresponding neutral compounds in saturated chloroflourocarbon (1,1-diflourotetra-chloroethane and 1,1,2-trichlorotriflouroethane) and perflourocarbon (perflourohexane and perfluoro-methylcyclohexane) matrices at 77 K. The perfluorocarbon matrices appeared more suitable for studies of the lighter radical cations, whereas the chlorofluorocarbon matrices were more suited for studies of the heavier radical cations; intermediary cations could be studied in both types of matrices. After irradiation, electronic absorptions associated with both the matrix and the alkane additive were observed. Pure spectra of the 3-methylalkane radical cations were obtained by difference spectrometry, after selective elimination of these cations by illumination. The electronic absorption spectra of the 3-methylalkane radical cations consist in all cases of a single broad absorption band. The spectral position of this band shifts to longer wavelengths with increasing chain length; the maximum of the absorption band was found to be situated at 490 nm for 3-methylpentane radical cations and at 940 nm for 3-methyltridecane radical cations. The results are most interesting because they give direct information on the electronic absorption of 3-methylpentane radical cations. It was found that the molar extinction coefficients of these cations are not very much smaller than those of other 3-methylalkane radical cations and thus must be of the order of 10 3dm 3·mol -1·cm -1. From this it is deduced that the majority of positive ions trapped in irradiated pure 3-methylpentane glasses at 77 K are not parent cations.

van den Bosch, Ann; Stienlet, Dominique; Ceulemans, Jan

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

Start | View At a Glance | Author Index 348-3 An In Situ Real-Time Quick X-Ray Absorption Spectroscopic (Q-XAS) Investigation of  

E-print Network

Spectroscopic (Q-XAS) Investigation of Ni Precipitation On Al-Rich Soil Minerals. See more from this Division: S Ni K-edge extended X-ray absorption fine structure spectroscopic data to characterize the mechanisms

Sparks, Donald L.

5

Spectroscopic characterization of alkaline earth uranyl carbonates  

NASA Astrophysics Data System (ADS)

A series of alkaline uranyl carbonates, M[UO 2(CO 3) 3]· nH 2O ( M=Mg 2, Ca 2, Sr 2, Ba 2, Na 2Ca, 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 2[UO 2(CO 3) 3]·6H 2O was obtained for the first time. The EXAFS analysis showed that this compound consists of (UO 2)(CO 3) 3 clusters similar to the other alkaline earth uranyl carbonates. The average U-Ba distance is 3.90±0.02 Å.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; Reich, Tobias; Arnold, Thuro; Geipel, Gerhard; Bernhard, Gert

2005-02-01

6

Optical absorption in Ar + irradiated silicon studied through spectroscopic ellipsometry  

Microsoft Academic Search

The ion implantation induced damage on the optical absorption of band tail states in single crystal Si(100) 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

S. Tripura Sundari

2004-01-01

7

Optical absorption in Ar+ irradiated silicon studied through spectroscopic ellipsometry  

Microsoft Academic Search

The ion implantation induced damage on the optical absorption of band tail states in single crystal Si(100) 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

S. Tripura Sundari

2004-01-01

8

Spectroscopic characterization of streptavidin functionalized quantum dots  

Microsoft Academic Search

The spectroscopic properties of quantum dots can be strongly influenced by the conditions of their synthesis. In this work, we have characterized several spectroscopic properties of commercial, streptavidin functionalized quantum dots (QD525, lot 1005-0045, and QD585, lot 0905-0031, from Invitrogen). This is the first step in the development of calibration beads to be used in a generalizable quantification scheme of

Yang Wu; Gabriel P. Lopez; Larry A. Sklar; Tione Buranda

2007-01-01

9

Characterization of the physico-chemical properties of polymeric materials for aerospace flight. [differential thermal and atomic absorption spectroscopic analysis of nickel cadmium batteries  

NASA Technical Reports Server (NTRS)

Electrodes and electrolytes of nickel cadmium sealed batteries were analyzed. Different thermal analysis of negative and positive battery electrodes was conducted and the temperature ranges of occurrence of endotherms indicating decomposition of cadmium hydroxide and nickel hydroxide are identified. Atomic absorption spectroscopy was used to analyze electrodes and electrolytes for traces of nickel, cadmium, cobalt, and potassium. Calibration curves and data are given for each sample analyzed. Instrumentation and analytical procedures used for each method are described.

Rock, M.

1981-01-01

10

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

11

Spectroscopic characterization of manganese minerals  

NASA Astrophysics Data System (ADS)

Manganese minerals ardenite, alleghanyite and leucopoenicite originated from Madhya Pradesh, India, Nagano prefecture Japan, Sussex Country and Parker Shaft Franklin, Sussex Country, New Jersey respectively are used in the present work. In these minerals manganese is the major constituent and iron if present is in traces only. An EPR study of on all of the above samples confirms the presence of Mn(II) with g around 2.0. Optical absorption spectrum of the mineral alleghanyite indicates that Mn(II) is present in two different octahedral sites and in leucophoenicite Mn(II) is also in octahedral geometry. Ardenite mineral gives only a few Mn(II) bands. NIR results of the minerals ardenite, leucophoenicite and alleghanyite are due to hydroxyl and silicate anions which confirming the formulae of the minerals.

Lakshmi Reddy, S.; Padma Suvarna, K.; Udayabhaska Reddy, G.; Endo, Tamio; Frost, R. L.

2014-01-01

12

Intrinsic Absorption Properties in Active Galaxies Observed with the Far Ultraviolet Spectroscopic Explorer  

E-print Network

In a continuing survey of active galactic nuclei observed by the Far Ultraviolet Spectroscopic Explorer, we provide a deeper analysis of intrinsic absorption features found in 35 objects. Our survey is for low-redshift and moderate-luminosity objects, mostly Seyfert galaxies. We find a strong correlation between maximum radial velocity and luminosity. We also examine the relationships between equivalent width (EW), full width at half maximum, velocity: and continuum flux. The correlation between velocity and luminosity has been explored previously by Laor & Brandt, but at a significantly higher redshift and heavily weighted by broad absorption line quasars. We also have examined each object with multiple observations for variability in each of the aforementioned quantities, and have characterized the variation of EW with the continuum flux. In our survey, we find that variability of O VI lambda1032, lambda1038 is less common than of the UV doublets of CIV and N V seen at longer wavelengths, because the O VI absorption is usually saturated. Lyman beta absorption variability is more frequent. In a target-by-target examination we find that broad absorption line absorption and narrow absorption line absorbers are related in terms of maximum outflow velocity and luminosity, and both can be exhibited in similar luminosity objects. We also find one object that shows radial velocity change, seven objects that show equivalent width variability, and two objects that show either transverse velocity changes or a change in ionization.

Jay P. Dunn; D. Michael Crenshaw; S. B. Kraemer; M. L. Trippe

2008-07-01

13

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

14

Spectroscopic Characterization of Streptavidin Functionalized Quantum dots1  

PubMed Central

The spectroscopic properties of quantum dots can be strongly influenced by the conditions of their synthesis. In this work we have characterized several spectroscopic properties of commercial, streptavidin functionalized quantum dots (QD525, lot#1005-0045 and QD585, Lot#0905-0031 from Invitrogen). This is the first step in the development of calibration beads, to be used in a generalizable quantification scheme of multiple fluorescent tags in flow cytometry or microscopy applications. We used light absorption, photoexcitation, and emission spectra, together with excited-state lifetime measurements to characterize their spectroscopic behavior, concentrating on the 400-500nm wavelength ranges that are important in biological applications. Our data show an anomalous dependence of emission spectrum, lifetimes, and quantum yield (QY) on excitation wavelength that is particularly pronounced in the QD525. For QD525, QY values ranged from 0.2 at 480nm excitation up to 0.4 at 450nm and down again to 0.15 at 350nm. For QD585, QY values were constant at 0.2 between 500nm and 400nm, but dropped to 0.1 at 350nm. We attribute the wavelength dependences to heterogeneity in size and surface defects in the QD525, consistent with characteristics previously described in the chemistry literature. The results are discussed in the context of bridging the gap between what is currently known in the physical chemistry literature of quantum dots, and the quantitative needs of assay development in biological applications. PMID:17368555

Wu, Yang; Lopez, Gabriel P.; Sklar, Larry A.; Buranda, Tione

2007-01-01

15

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

16

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.

2009-12-01

17

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

18

Spectroscopic characterization and laser performance of diode-laser-pumped Nd: GdVO 4  

Microsoft Academic Search

We have carried out a detailed spectroscopic characterization of Nd: GdVO4, a new laser crystal with high effective absorption and emission cross sections. The accidental degeneracy of the upper4F3\\/2 laser level decreases the number of emission lines and creates -together with the anisotropic crystal field - high emission cross sections (7.6 × 10-19 cm2 at 1.06 µm and 300 K).

T. Jensen; V. G. Ostroumov; J.-P. Meyn; G. Huber; A. I. Zagumennyi; I. A. Shcherbakov

1994-01-01

19

X-ray-absorption spectroscopic studies of sodium polyphosphate glasses  

Microsoft Academic Search

A series of sodium polyphosphate glasses of composition Nan+2PnO3n+1 have been studied using synchrotron-radiation x-ray-absorption spectroscopy. High-resolution P L-edge and K-edge x-ray appearance near-edge structure (XANES) as well as K-edge extended x-ray-absorption fine structure (EXAFS) of the phosphates have been investigated. It has been found that while the K-edge XANES spectra of different phosphate glasses are similar, the L-edge XANES

Zhanfeng Yin; Masoud Kasrai; G. Michael Bancroft; Kim H. Tan; Xinghong Feng

1995-01-01

20

Application of Spectroscopic Ellipsometry and Mueller Ellipsometry to Optical Characterization  

E-print Network

Films; Mueller matrix INTRODUCTION The use of polarized light to characterize the optical propertiesApplication of Spectroscopic Ellipsometry and Mueller Ellipsometry to Optical Characterization E optically isotropic bulk and/or layered materials. More advanced techniques like Mueller ellipsometry, also

21

A compact, cost-effective diffuse reflectance spectroscopic imaging system for quantitative tissue absorption and scattering  

NASA Astrophysics Data System (ADS)

There is clinical utility for a wide-field, spectroscopic imaging device for quantitative tissue absorption and scattering in a number of applications. We present the design of a compact, cost-effective spectroscopic imaging system, which consists of a broadband source with bandpass filters and a light guide for illumination and an inexpensive array of silicon photodiodes for detection. A single-pixel version of the system was tested in liquid phantoms simulating a wide range of human breast tissue and optical properties can be extracted with absorption and reduced scattering errors of 12.6% and 4.7%, respectively. We show proof-of-concept for performing fast, wide-field spectroscopic imaging with a simple design. The design also allows for scaling and expansion into higher pixel number and density in future iterations of custom device design, which includes in-house photodiode array fabrication processes and integration of on-board current amplifier circuits.

Lo, Justin Y.; Yu, Bing; Kuech, Thomas F.; Ramanujam, Nirmala

2011-03-01

22

Spectroscopic characterization of matrix isolated transient species  

NASA Astrophysics Data System (ADS)

Part I describes the electronic spectra of various actinide containing compounds isolated in solid Ar using laser induced fluorescence (LIF) spectroscopy. The IR spectra for many of the same molecules were also recorded to aid in the identification of the fluorescing species in the LIF spectra. LIF spectra of UO2 isolated in solid Ar were recorded to investigate the interactions between actinide compounds and the rare gas matrix host. At the time of the experiments, it had been proposed that for UO2 and CUO, the interactions between the actinide containing molecule and Ar were strong enough to reorder the low-lying electronic states of the molecule. The experiments presented here showed no evidence of a reordering of low-lying electronic states based on comparison of the matrix spectra with theoretical predictions and gas phase spectra. An attempt to observe fluorescence from higher order uranium oxides was undertaken. A matrix was made by ablating U metal in a 1.0% O2/Ar mixture. UO3 was a probable molecule formed in the experiment. And, while absorptions belonging to UO3 were observed in IR spectra, LIF from the same matrix provided evidence that another molecule was fluorescing. Two different vibrational frequencies observed in the U-O symmetric stretching region were indicative of at least two low-lying electronic states in fluorescing molecule. UO3 is a closed shell molecule, and it is unlikely that it has any low-lying electronic states. Instead, the fluorescence was attributed to the open shell species (UO2)+(O2) -. LIF and IR spectra of thermally vaporized UCl4 isolated in solid Ar were recorded. UCl4 contains U(IV), which is the most stable oxidation state other than U(VI). Before these experiments, no fluorescence had been recorded that could be attributed to UCl4. Based on the observed vibrational frequencies in the fluorescence bands and the lifetime of the fluorescence, it was determine that there was at least two different fluorescing species. The short lived fluorescence was assigned to UCl 4, and the long-lived fluorescence was assigned to UOCl x. A low resolution map for the electronic levels in UOCl x was created. One of the first LIF studies of actinide containing molecules was performed by Grzybowski and Andrews[1] for UF6. While, the same group later recorded IR spectra for the UFx fragements[2], no fluorescence spectra were recorded. Spectra were recorded here of UF x fragments trapped in solid formed by either passing UF 6 through a microwave discharge or ablating U atoms into an F2 /Ar mixture. At the time of these experiments, the IR spectrometer was not available, and the molecules producing the fluorescence could not be deduced solely from the LIF spectra. A comparison with previous IR spectra[2] gave some indication of possible candidates. In all the experiments that investigated uranium containing matrices with IR spectroscopy, UN2 was observed. A search was undertaken to observe fluorescence from UN2. To insure a good yield of UN 2, 1% N2 was added to the carrier gas. The fluorescence spectra observed in these experiments was very intriguing, but was determined not to be coming from UN2, rather it appears to be coming from U atom clusters. However further experiments are necessary to confirm how many atoms are in the clusters. The final part of this thesis focuses on the electronic spectra of Xe-OH isolated solid Ar. Rare gas radical systems (Rg-X) such as Rg-OH are a good model system for studying weak, long range intermolecular interactions. It is known that when Rg=Xe, the strength of the interaction is much larger. For most Rg-OH complexes, the spectroscopic constants have been determined previously[3]. However, the constants for Xe-OH ares currently undetermined. Gas-phase studies were undertaken to determined these constants.[4] However, these experiments were in conflict with previous LIF spectra recorded in a matrix in which Goodman and Brus[5] observed that the A ? X emission band for Xe-OH is redshifted approximately 5,000 cm-1, which is unusually large. Additionally, they found

Lue, Christopher J.

23

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

24

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

25

Vibrational Spectroscopic Characterization of Hematite, Maghemite, and Magnetite Thin  

E-print Network

Vibrational Spectroscopic Characterization of Hematite, Maghemite, and Magnetite Thin Films University, 100 West 18th Avenue, Columbus, Ohio 43210 ABSTRACT Thin films of three iron oxide polymorphs, hematite, maghemite, and magnetite, were produced on KBr substrates using a conventional electron beam

26

Impedance spectroscopic characterization of solar cell  

NASA Astrophysics Data System (ADS)

Impedance spectroscopy is used to characterize a commercial solar cell, at various dc bias potentials, under illumination and dark conditions. Interesting features are observed in medium and low frequency range, at large bias potentials. All the models reported in literature utilize combinations of resistances and capacitances, but the results indicate that inductances are necessary to model the actual solar cell, since an inductive loop is observed in the medium frequency range, especially at large bias potential, both under illumination and dark conditions. A new circuit which captures all the trends semi quantitatively is proposed to model the data.

Gautham, S.; Ramanathan, S.

2014-10-01

27

Synthesis and spectroscopic characterization of gold nanoparticles  

NASA Astrophysics Data System (ADS)

Photoluminescent nanoparticles of gold with size 3, 4, 6, and 9 nm are prepared by borohydride/citrate reduction in presence of polyethylene glycol (PEG)/tannic acid. The prepared nanomaterials are characterized by UV-vis spectroscopy and dynamic light scattering (DLS) technique. Intense photoluminescence (PL) is observed in nanoparticles prepared by fast reduction with borohydride in presence of PEG. A red shift of PL emission from 408 to 456 nm is observed for the change of size from 4 to 6 nm. Increase in PL intensity is observed for all the nanoparticles on the addition of KCl. Citrate reduced gold colloid which consists of large particles of size ˜35 nm with anisotropic shapes showing two plasmon peaks is also prepared. The anisotropy is confirmed by TEM measurement. SERS activity of this colloid is tested using glutamic acid as an adsorbate probe. Assignment of the observed bands is given.

Philip, Daizy

2008-11-01

28

Spectroscopic characterization of laser-induced tin plasma S. S. Harilal,a  

E-print Network

Spectroscopic characterization of laser-induced tin plasma S. S. Harilal,a Beau O'Shay, and Mark. S 2005 Optical emission spectroscopic studies have been carried out on a tin plasma generated using 1064

Harilal, S. S.

29

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

30

Precision radial velocities of double-lined spectroscopic binaries with an iodine absorption cell  

E-print Network

A spectroscopic technique employing an iodine absorption cell (I_2) to superimpose a reference spectrum onto a stellar spectrum is currently the most widely adopted approach to obtain precision radial velocities of solar-type stars. It has been used to detect ~80 extrasolar planets out of ~130 know. Yet in its original version, it only allows us to measure precise radial velocities of single stars. In this paper, we present a novel method employing an I_2 absorption cell that enables us to accurately determine radial velocities of both components of double-lined binaries. Our preliminary results based on the data from the Keck I telescope and HIRES spectrograph demonstrate that 20-30 m/s radial velocity precision can be routinely obtained for "early" type binaries (F3-F8). For later type binaries, the precision reaches ~10 m/s. We discuss applications of the technique to stellar astronomy and searches for extrasolar planets in binary systems. In particular, we combine the interferometric data collected with the Palomar Testbed Interferometer with our preliminary precision velocities of the spectroscopic double-lined binary HD 4676 to demonstrate that with such a combination one can routinely obtain masses of the binary components accurate at least at the level of 1.0%.

Maciej Konacki

2005-02-25

31

Novel dipodal Schiff base compounds: Synthesis, characterization and spectroscopic studies  

NASA Astrophysics Data System (ADS)

Two novel dipodal Schiff base compounds 1,2-benzyloxy-bis-[2-(benzylideneamino)phenol, L1 and 1,2-benzyloxy-bis[3-(benzylideneamino)pyridine], L2 were synthesized. Their sensing actions were confirmed by UV-Vis absorbance and emission spectroscopic studies in presence of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sn(II), Cd(II) and Pb(II) in methanol medium (1 × 10-4 M). It was found that the dipodal compounds can selectively bind to Cu(II) and Pb(II) metal ions with a significant change in its emission and absorption spectra, while the addition of other metal ions (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sn(II), Cd(II) and Pb(II)) produces insignificant or minor changes. The host-guest complexes formed were determined by Job's plot method. As a chemosensor, L1 and L2 dipodal Schiff base compounds shows a specific selectivity towards Cu(II) and Pb(II) ions in according to all spectroscopic data.

Obali, Aslihan Yilmaz; Ucan, Halil Ismet

2015-02-01

32

Structural diversity of F/sub 430/ from methanobacterium thermoautotrophicum. A nickel x-ray absorption spectroscopic study  

SciTech Connect

Nickel metalloenzymes have been found in all methane-producing bacteria examined. Two hydrogenases from Methanobacterium thermoautotrophicum contain nickel which has been shown to be coordinated by S-containing ligands in one form. A compound called F/sub 430/ has been isolated from M. thermoautotrophicum, strain ..delta..H, and has been identified as the Ni-containing prosthetic group in protein component C of the S-methyl coenzyme-M reductase system. F/sub 430/ has been established to have a Ni(II)-tetrapyrrole structure, constituting the only known biological example of nickel in a tetrahydro reduced corphine. The detailed mechanistic role of F/sub 430/ in methyl group reduction has not been identified. We report here a Ni x-ray absorption spectroscopic (XAS) study of several forms of F/sub 430/ and component C isolated from M. thermoautotrophicum, strain ..delta..H. These preliminary results indicate that free F/sub 430/ is structurally distinct from the F/sub 430/-containing protein. Also, depending upon the conditions used, extraction of F/sub 430/ from the protein yields at least two structurally distinct forms, one similar to that in the intact protein and one similar to free F/sub 430/. Analysis of the extended x-ray absorption fine structure (EXAFS) data and comparison with a number of structurally characterized Ni(II) complexes provide evidence that the flexibility of the tetrapyrrole is responsible for the different structural forms.

Eidsness, M.K.; Sullivan, R.J.; Schwartz, J.R.; Hartzell, P.L.; Wolfe, R.S.; Flank, A.M.; Cramer, S.P.; Scott, R.A.

1986-05-28

33

Optical absorption and photoluminescence properties of Nd3+ doped mixed alkali phosphate glasses-spectroscopic investigations.  

PubMed

Spectroscopic investigations were performed on 68NH(4)H(2)PO(4).xLi(2)CO(3)(30-x)K(2)CO(3) and 68NH(4)H(2)PO(4).xNa(2)CO(3)(30-x)K(2)CO(3) (where x=5, 10, 15, 20 and 25) glasses containing 2 mol% Nd(2)O(3). Various spectroscopic parameters (Racah (E(1), E(2), E(3)), spin-orbit (xi(4f)) and configuration interaction (alpha)) are reported. Judd-Ofelt intensity parameters (Omega(2), Omega(4), Omega(6)) are calculated for Nd(3+) doped two mixed alkali phosphate glass matrices. From the magnitude of Judd-Ofelt parameters, covalency is studied as a function of x in the glass matrix. Using Judd-Ofelt intensity parameters, total radiative transition probabilities (A(T)), radiative lifetimes (tau(R)), branching ratios (beta) and integrated absorption cross sections (Sigma) have been computed for certain excited states of Nd(3+) in these mixed alkali phosphate glasses. Emission cross sections (sigma(P)) are calculated for the two transitions, (4)G(7/2)-->(4)I(11/2) and (4)G(7/2)-->(4)I(13/2) of Nd(3+) in these mixed alkali phosphate glasses. Optical band gaps (E(opt)) for direct and indirect transitions are reported. PMID:19010718

Ratnakaram, Y C; Srihari, N V; Kumar, A Vijaya; Naidu, D Thirupathi; Chakradhar, R P S

2009-02-01

34

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

35

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

36

Direct Spectroscopic Characterization of Non-Transiting Exoplanet Atmospheres  

NASA Astrophysics Data System (ADS)

We are using ground-based high-resolution spectroscopy in the thermal infrared to characterize molecular signatures in the atmospheres of non-transiting close-in exoplanets. Our observations target the strong methane and carbon monoxide absorption features, at 3.3 microns and 4.6 microns respectively, that result from the high temperatures in these planets' atmospheres. Using the NIRSPEC spectrometer on the Keck II telescope, we obtain very-high signal-to-noise spectroscopy with a spectral resolution of 25,000, that contains the blended light of a parent star and its known close-in planet companion. We precisely model both components and recover the planet contribution through a cross-correlation analysis. We will discuss early results from observations targeting methane absorption from the nearby exoplanet 55 Cancri b. We will also describe the techniques that are yielding high signal-to-noise spectra in the thermal infrared, and our detailed terrestrial absorption correction using a synthetic transmission function. This program expands the direct characterization of exoplanets beyond recent space-based transit measurements, in order to begin understanding the entire close-in population. CB is supported by an NRC Research Associateship Award at NRL; basic research in infrared astronomy at NRL is supported by 6.1 base funding.

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

2009-01-01

37

3.4 Spectroscopic Sensors Spectroscopy is the scientific study of the absorption, emission, or scattering of  

E-print Network

be influenced and modified by other phenomena, spectroscopy provides the potential for enhanced chemical analysis and sensing. The list of spectroscopic techniques and sub- techniques is large and continually spectroscopy · Auger electron spectroscopy · Cavity-ringdown laser absorption spectroscopy · Electron

38

Spectroscopic characterization of a contemporary Indian miniature painting.  

PubMed

A case study on a contemporary Indian miniature was carried out through the application of different spectroscopic techniques. Painting support, pigments, and dyes were largely characterized by means of energy dispersive x-ray fluorescence and Raman microspectroscopy directly on the artwork. Regarding golden motifs and silvered areas, for which these techniques have not provided enough information, scanning electron microscopy coupled with energy dispersive x-ray spectroscopy was used as a complementary technique. The painting support was identified as the Bombyx mori silk. Among the colorant matters, several pigments were identified such as chrome yellow, lithopone, hematite, lamp black, mica-titania pearlescent pigment, and tin-based metallic silver, and dyes such as phthalocyanine blue and the recent synthetic pigment red PR9 naphthol AS. All this materials will provide evidence in the support of the contemporary production of the artwork for future studies. PMID:24359650

Cardeira, Ana Mafalda; Longelin, Stéphane; Le Gac, Agnès; Nogueira, Isabel; Carvalho, Maria Luísa; Manso, Marta

2013-12-01

39

Thermal and Spectroscopic Characterization of a Proton Pumping Rhodopsin from an Extreme Thermophile*  

PubMed Central

So far retinylidene proteins (?rhodopsin) have not been discovered in thermophilic organisms. In this study we investigated and characterized a microbial rhodopsin derived from the extreme thermophilic bacterium Thermus thermophilus, which lives in a hot spring at around 75 °C. The gene for the retinylidene protein, named thermophilic rhodopsin (TR), was chemically synthesized with codon optimization. The codon optimized TR protein was functionally expressed in the cell membranes of Escherichia coli cells and showed active proton transport upon photoillumination. Spectroscopic measurements revealed that the purified TR bound only all-trans-retinal as a chromophore and showed an absorption maximum at 530 nm. In addition, TR exhibited both photocycle kinetics and pH-dependent absorption changes, which are characteristic of rhodopsins. Of note, time-dependent thermal denaturation experiments revealed that TR maintained its absorption even at 75 °C, and the denaturation rate constant of TR was much lower than those of other proton pumping rhodopsins such as archaerhodopsin-3 (200 ×), Haloquadratum walsbyi bacteriorhodopsin (by 10-times), and Gloeobacter rhodopsin (100 ×). Thus, these results suggest that microbial rhodopsins are also distributed among thermophilic organisms and have high stability. TR should allow the investigation of the molecular mechanisms of ion transport and protein folding. PMID:23740255

Tsukamoto, Takashi; Inoue, Keiichi; Kandori, Hideki; Sudo, Yuki

2013-01-01

40

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

41

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

42

Spectroscopic characterization of collagen cross-links in bone.  

PubMed

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. PMID:11585346

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

2001-10-01

43

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

44

Absorption line shape recovery beyond the detection bandwidth limit: application to the precision spectroscopic measurement of the Boltzmann constant  

E-print Network

A theoretical model of the influence of detection bandwidth properties on observed line shapes in laser absorption spectroscopy is described. The model predicts artificial frequency shifts, extra broadenings and line asymmetries which must be taken into account in order to obtain accurate central frequencies and other spectroscopic parameters. This reveals sources of systematic effects most probably underestimated so far potentially affecting spectroscopic measurements. This may impact many fields of research, from atmospheric and interstellar physics to precision spectroscopic measurements devoted to metrological applications, tests of quantum electrodynamics or other fundamental laws of nature. Our theoretical model is validated by linear absorption experiments performed on H2O and NH3 molecular lines recorded by precision laser spectroscopy in two distinct spectral regions, near- and mid-infrared. Possible means of recovering original line shape parameters or experimental conditions under which the detection bandwidth has a negligible impact, given a targeted accuracy, are proposed. Particular emphasis is put on the detection bandwidth adjustments required to use such high-quality molecular spectra for a spectroscopic determination of the Boltzmann constant at the 1 ppm level of accuracy.

François Rohart; Sinda Mejri; Papa Lat Tabara Sow; Sean K. Tokunaga; Christian Chardonnet; Benoît Darquié; H. Dinesan; E. Fasci; A. Castrillo; L. Gianfrani; Christophe Daussy

2014-07-09

45

Spectroscopic and photochemical characterization of a deep ocean proteorhodopsin.  

PubMed

A second group of proteorhodopsin-encoding genes (blue-absorbing proteorhodopsin, BPR) differing by 20-30% in predicted primary structure from the first-discovered green-absorbing (GPR) group has been detected in picoplankton from Hawaiian deep sea water. Here we compare BPR and GPR absorption spectra, photochemical reactions, and proton transport activity. The photochemical reaction cycle of Hawaiian deep ocean BPR in cells is 10-fold slower than that of GPR with very low accumulation of a deprotonated Schiff base intermediate in cells and exhibits mechanistic differences, some of which are due to its glutamine residue rather than leucine at position 105. In contrast to GPR and other characterized microbial rhodopsins, spectral titrations of BPR indicate that a second titratable group, in addition to the retinylidene Schiff base counterion Asp-97, modulates the absorption spectrum near neutral pH. Mutant analysis confirms that Asp-97 and Glu-108 are proton acceptor and proton donor, respectively, in retinylidene Schiff base proton transfer reactions during the BPR photocycle as previously shown for GPR, but BPR contains an alternative acceptor evident in its D97N mutant, possibly the same as the second titratable group modulating the absorption spectrum. BPR, similar to GPR, carries out outward light-driven proton transport in Escherichia coli vesicles but with a reduced translocation rate attributable to its slower photocycle. In energized E. coli cells at physiological pH, the net effect of BPR photocycling is to generate proton currents dominated by a triggered proton influx, rather than efflux as observed with GPR-containing cells. Reversal of the proton current with the K+-ionophore valinomycin supports that the influx is because of voltage-gated channels in the E. coli cell membrane. These observations demonstrate diversity in photochemistry and mechanism among proteorhodopsins. Calculations of photon fluence rates at different ocean depths show that the difference in photocycle rates between GPR and BPR as well as their different absorption maxima may be explained as an adaptation to the different light intensities available in their respective marine environments. Finally, the results raise the possibility of regulatory (i.e. sensory) rather than energy harvesting functions of some members of the proteorhodopsin family. PMID:12821661

Wang, Wei-Wu; Sineshchekov, Oleg A; Spudich, Elena N; Spudich, John L

2003-09-01

46

Confocal Light Absorption and Scattering Spectroscopic (CLASS) imaging: From cancer detection to sub-cellular function  

NASA Astrophysics Data System (ADS)

Light scattering spectroscopy (LSS), an optical technique that relates the spectroscopic properties of light elastically scattered by small particles to their size, refractive index and shape, has been recently successfully employed for sensing morphological and biochemical properties of epithelial tissues and cells in vivo. LSS does not require exogenous markers, is non-invasive, and, due to its multispectral nature, can sense biological structures well beyond the diffraction limit. All that makes LSS be a very good candidate to be used both in clinical medicine for in vivo detection of disease and in cell biology to monitor cell function on the organelle scale. Recently we developed two LSS-based imaging modalities: clinical Polarized LSS (PLSS) Endoscopic Technique for locating early pre-cancerous changes in GI tract and Confocal Light Absorption and Scattering Spectroscopic (CLASS) Microscopy for studying cells in vivo without exogenous markers. One important application of the clinical PLSS endoscopic instrument, a noncontact scanning imaging device compatible with the standard clinical endoscopes and capable of detecting dysplastic changes, is to serve as a guide for biopsy in Barrett's esophagus (BE). The instrument detects parallel and perpendicular components of the polarized light, backscattered from epithelial tissues, and determines characteristics of epithelial nuclei from the residual spectra. It also can find tissue oxygenation, hemoglobin content and other properties from the diffuse light component. By rapidly scanning esophagus the PLSS endoscopic instrument makes sure the entire BE portion is scanned and examined for the presence of dysplasia. CLASS microscopy, on the other hand, combines principles of light scattering spectroscopy (LSS) with confocal microscopy. Its main purpose is to image cells on organelle scale in vivo without the use of exogenous labels which may affect the cell function. The confocal geometry selects specific region and images are obtained by scanning the confocal volume across the sample. The new beam scanning CLASS microscope is a significant improvement over the previous proof-of-principle device. With this new device we have already performed experiments to monitor morphological changes in cells during apoptosis, differentiated fetal from maternal nucleated red blood cells, and detected plasmon scattering spectra of single gold nanorod.

Qiu, Le

47

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 ...

48

Amyloid oligomers: spectroscopic characterization of amyloidogenic protein states.  

PubMed

It is assumed that protein fibrils manifested in amyloidosis result from an aggregation reaction involving small misfolded protein sequences being in an 'oligomeric' or 'prefibrillar' state. This review covers recent optical spectroscopic studies of amyloid protein misfolding, oligomerization and amyloid fibril growth. Although amyloid fibrils have been studied using established protein-characterization techniques throughout the years, their oligomeric precursor states require sensitive detection in real-time. Here, fluorescent staining is commonly performed using thioflavin T and other small fluorescent molecules such as 4-(dicyanovinyl)- julolidine and 1-amino-8-naphtalene sulphonate that have high affinity to hydrophobic patches. Thus, populated oligomeric intermediates and related 'prefibrillar structures' have been reported for several human amyloidogenic systems, including amyloid-beta protein, prion protein, transthyretin, alpha-synuclein, apolipoprotein C-II and insulin. To obtain information on the progression of the intermediate states, these were monitored in terms of fluorescence parameters, such as anisotropy, and quantum efficiency changes upon protein binding. Recently, new antibody stains have allowed precise monitoring of the oligomer size and distributions using multicolor labelling and single molecule detection. Moreover, a pentameric thiophene derivative (p-FTAA) was reported to indicate early precursors during A-beta(1-40) fibrillation, and was also demonstrated in real-time visualization of cerebral protein aggregates in transgenic AD mouse models by multiphoton microscopy. Conclusively, molecular probes and optical spectroscopy are now entering a phase enabling the in vivo interrogation of the role of oligomers in amyloidosis. Such techniques used in parallel with in vitro experiments, of increasing detail, will probably couple structure to pathogenesis in the near future. PMID:20148961

Lindgren, Mikael; Hammarström, Per

2010-03-01

49

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin 1  

E-print Network

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been

van Stokkum, Ivo

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

Spectroscopic characterization of high k dielectrics: Applications to interface electronic structure and stability against chemical phase separation  

NASA Astrophysics Data System (ADS)

Extensive spectroscopic characterization of high k materials under consideration for replacing Si oxide as the gate dielectric in Si-based microelectronic devices has been accomplished. Band offset energies of Zr silicates with respect to Si have been determined as a function of silicate alloy composition by combining near-edge x-ray absorption fine structure spectroscopy, vacuum-ultraviolet spectroscopic ellipsometry, x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and ab initio calculations on cluster models. These studies provide insight that applies to both transition metal- and rare earth-based dielectrics, including binary oxides and silicate and aluminate alloys. Results have been used to estimate the electronic conduction through Hf silicate films as a function of alloy composition. Thermally induced chemical phase separation in Zr silicate films has been characterized using XPS, Fourier transform infrared spectroscopy, x-ray diffraction, high-resolution transmission electron microscopy, and extended x-ray absorption fine structure spectroscopy. Our results indicate separation into a noncrystalline, Si-rich phase and either nano- or microcrystalline ZrO2, depending on the original film stoichiometry. .

Krug, C.; Lucovsky, G.

2004-07-01

52

New advances in the use of infrared absorption spectroscopy for the characterization of heterogeneous catalytic reactions.  

PubMed

Infrared absorption spectroscopy has proven to be one of the most powerful spectroscopic techniques available for the characterization of catalytic systems. Although the history of IR absorption spectroscopy in catalysis is long, the technique continues to provide key fundamental information about a variety of catalysts and catalytic reactions, and to also offer novel options for the acquisition of new information on both reaction mechanisms and the nature of the solids used as catalysts. In this review, an overview is provided of the main contributions that have been derived from IR absorption spectroscopy studies of catalytic systems, and a discussion is included on new trends and new potential directions of research involving IR in catalysis. We start by briefly describing the power of Fourier-transform IR (FTIR) instruments and the main experimental IR setups available, namely, transmission (TIR), diffuse reflectance (DRIFTS), attenuated total reflection (ATR-IR), and reflection-absorption (RAIRS), for advancing research in catalysis. We then discuss the different environments under which IR characterization of catalysts is carried out, including in situ and operando studies of typical catalytic processes in gas-phase, research with model catalysts in ultrahigh vacuum (UHV) and so-called high-pressure cell instruments, and work involving liquid/solid interfaces. A presentation of the type of information extracted from IR data follows in terms of the identification of adsorbed intermediates, the characterization of the surfaces of the catalysts themselves, the quantitation of IR intensities to extract surface coverages, and the use of probe molecules to identify and titrate specific catalytic sites. Finally, the different options for carrying out kinetic studies with temporal resolution such as rapid-scan FTIR, step-scan FTIR, and the use of tunable lasers or synchrotron sources, and to obtain spatially resolved spectra, by sample rastering or by 2D imaging, are introduced. PMID:24424375

Zaera, Francisco

2014-11-21

53

Nanofluid optical property characterization: towards efficient direct absorption solar collectors  

PubMed Central

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 ?m). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ?10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase. PMID:21711750

2011-01-01

54

Nanofluid optical property characterization: towards efficient direct absorption solar collectors.  

PubMed

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 ?m). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ?10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase. PMID:21711750

Taylor, Robert A; Phelan, Patrick E; Otanicar, Todd P; Adrian, Ronald; Prasher, Ravi

2011-01-01

55

X-ray diffraction and absorption spectroscopic studies of copper mixed ligand complexes with aminophenol as one of the ligands  

NASA Astrophysics Data System (ADS)

X-ray diffraction (XRD) and X-ray absorption spectroscopic (XAS) studies have been conducted on two copper complexes, i.e., copper macrocyclic complex of succinic acid and ortho aminophenol (complex-1) and copper macrocyclic complex of pthalic acid and ortho aminophenol (complex-2). The diffraction pattern of the complexes have been recorded using Rigaku RINT-2000 X-ray diffractometer equipped with rotating anode X-ray tube operated at 40 kV and 100 mA. The X-ray absorption spectra of the complexes have been recorded at the K-edge of copper on Cauchois type bent crystal spectrograph having radius 0.4 m employing a mica crystal, oriented to reflect from (100) planes, for dispersion. The X-ray absorption near edge structure (XANES) parameters, viz., chemical shift, energy position of the principal absorption maximum and edge-width have been determined and discussed. From the extended X-ray absorption fine structure (EXAFS) data, the bond lengths have been calculated using three methods, namely, Levy's method, Lytle, Sayers and Stern's (LSS) method and Fourier transformation method. The results obtained have been compared with each other and discussed.

Mishra, A.; Jain, Garima; Patil, H.

2012-05-01

56

CDOM Characterization of Surface Waters and Groundwater in Tampa Bay, FL: A Spectroscopic and Radioisotopic Approach  

NASA Astrophysics Data System (ADS)

Carbonate platforms surrounding subtropical estuaries allow water and chemical constituents to be easily transferred between subsurface aquifers and overlying surficial waters. During times of low rainfall, a significant portion of the water found in the rivers that supply these estuaries originates from springs within the streams themselves. This fluctuation in headwater source often results in variability in the chemistry of the organic material and therefore CDOM optical properties. In addition to the impact of groundwater on stream chemistry, an estuary can be influenced by waters rising directly from beneath the estuary. In the Tampa Bay region, CDOM concentration and optical properties within groundwater wells suggest unique sources and biogeochemical pathways of organic material. Shallow aquifers resemble surface runoff in concentration of DOC and CDOM, as well as in CDOM spectral properties. In contrast, the deep aquifers show higher fluorescence efficiencies and blueshifting of fluorescence. Overall, the depth dependency indicates that CDOM in shallow groundwater has terrestrial sources whereas deep groundwater (where water is estimated to be >10,000 years old) has properties more similar to marine humics. Discussed here will be the results from a March-April 2006 study coupling spectroscopic and radioisotopic techniques to better characterize sources of CDOM in a subtropical estuary. Naturally occurring isotopes of radium (used as a proxy for groundwater contribution) were measured along with CDOM fluorescence, absorption and DOC. Discerning the contribution of CDOM via groundwater, river water and marine water will prove useful in understanding carbon cycling within the Tampa Bay region.

Conmy, R. N.; Coble, P. G.; Pyrtle, A. J.

2007-12-01

57

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

58

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

59

X-ray absorption fine structure spectroscopic study of uranium nitrides  

SciTech Connect

Uranium mononitride (UN), sesquinitride (U2N3) and dinitride (UN2) were characterized by extended X-Ray absorption fine structure spectroscopy. Analysis on UN indicate the presence of three uranium shells at distances of 3.46(3), 4.89(5) and 6.01(6) A and a nitrogen shell at a distance of 2.46(2) A . For U2N3, two absorbing uranium atoms at different crystallographic positions are present in the structure. One of the uranium atoms is surrounded by nitrogen atoms at 2.28(2) A and by uranium atoms at 3.66(4) and 3.95(4) A . The second type of uranium atom is surrounded by nitrogen atoms at 2.33(2) and 2.64(3) A and by uranium atoms at 3.66(4), 3.95(4) and 5.31(5) A . Results on UN2 indicate two uranium shells at 3.71(4) and 5.32(5) A and two nitrogen shells at 2.28(2).

Poineau, Frederic [University of Nevada, Las Vegas; Yeamans, Charles B. [University of California, Berkeley; Cerefice, Gary S. [University of Nevada, Las Vegas; Sattelberger, Alfred P [Argonne National Laboratory (ANL); Czerwinski, Ken R. [University of Nevada, Las Vegas

2012-01-01

60

Raman spectroscopic characterization on cervical neoplasm in biopsy direction  

NASA Astrophysics Data System (ADS)

Raman spectroscopy was applied to distinguish the spectroscopic information between normal cervical tissues (14) and cervical neoplasia (17), including low grade squamous intraepithelial lesions (6) and high grade squamous intraepithelial lesions (11). Standard pathological sections of these cervical tissues were measured from superficial to stroma layers. We have normalized significant Raman peaks, 1250 and 1579-1656 cm -1 by taking a ratio over a stationary Raman at 1004 cm -1, and successfully discriminated between normal and neoplasm cervical tissues.

Shin, Hsiao Hsin; Tsai, Yan Sheng; Wang, Tao Yuan; Chu, Shou Chia; Chiang, Huihua Kenny

2007-02-01

61

Self-assembled monolayers of benzylmercaptan and para-cyanobenzylmercaptan on gold: surface infrared spectroscopic characterization.  

PubMed

Self-assembled monolayers (SAMs) on gold substrates were prepared from benzylmercaptan (BM) and para-cyanobenzylmercaptan (pCBM), and the resulting surfaces were investigated using conventional infrared reflection-absorption spectroscopy (IRRAS) as well as polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). IRRAS data are analyzed by comparison with transmission IR spectra and theoretical (DFT) simulations. The spectroscopic results indicate the presence of well-ordered monolayers of BM and pCBM with an orientation perpendicular to the surface. IRRAS and PM-IRRAS data are compared to each other and the respective merits of both methods are discussed. PMID:20407711

Rajalingam, K; Hallmann, L; Strunskus, T; Bashir, A; Wöll, C; Tuczek, F

2010-05-01

62

The Crystalline Nanocluster Phase as a Medium for Structural and Spectroscopic Studies of Light Absorption of  

E-print Network

The Crystalline Nanocluster Phase as a Medium for Structural and Spectroscopic Studies of Light-3000 Received November 11, 2009; E-mail: coppens@buffalo.edu Abstract: The crystalline nanocluster phase was specifically aimed at examining the properties of the nanoclusters as models for TiO2 surfaces across which

Coppens, Philip

63

Spectroscopic characterization and detection of Ethyl Mercaptan in Orion  

E-print Network

New laboratory data of ethyl mercaptan, CH$_{3}$CH$_{2}$SH, in the millimeter and submillimeter-wave domains (up to 880 GHz) provided very precise values of the spectroscopic constants that allowed the detection of $gauche$-CH$_3$CH$_2$SH towards Orion KL. 77 unblended or slightly blended lines plus no missing transitions in the range 80-280 GHz support this identification. A detection of methyl mercaptan, CH$_{3}$SH, in the spectral survey of Orion KL is reported as well. Our column density results indicate that methyl mercaptan is $\\simeq$ 5 times more abundant than ethyl mercaptan in the hot core of Orion KL.

Kolesniková, L; Cernicharo, J; Alonso, J L; Daly, A M; Gordon, B P; Shipman, S T

2014-01-01

64

Regular paper Spectroscopic characterization of the excitation energy transfer  

E-print Network

meneghiniana by conducting ultrafast transient absorption measurements. This light harvesting antenna has network is discussed in relation to the pigment organization of the FCP complex. Abbreviations: Chl-transfer; LHC ­ light-harvesting complex; PCP ­ peridinin­ chlorophyll protein; SADS ­ species

van Stokkum, Ivo

65

Chemical and spectroscopic characterization of humic acids extracted from the bottom sediments of a Brazilian subtropical microbasin  

E-print Network

H values; (ii) fulvic acid (FA), the fraction soluble at all pH values; and (iii) humin, the fraction1 Chemical and spectroscopic characterization of humic acids extracted from the bottom sediments to chemically and spectroscopically characterize humic acids (HA) isolated from bottom sediment samples

Paris-Sud XI, Université de

66

Polarization-Modulated Infrared Reflection Absorption Spectroscopic Studies of a Hydrogen-Bonding Network at the Air-Water Interface  

E-print Network

absorption spectroscopy (PM-IRRAS). The molecular structure and orientation of the 1:1 hydrogen- bonding. Compared to the previous IRRAS studies on the similar monolayers, the sensitivity of PM- IRRAS is obviously improved. PM-IRRAS will likely become a powerful analytical technique for the characterization of molecular

Rusell, K.C.

67

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

68

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

PubMed

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 (F(k)'s), nephelauxetic effect (?), bonding (b(1/2)) 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, K(b) 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. PMID:21247794

Devi, Ch Victory; Singh, N Rajmuhon

2011-03-01

69

Synthesis and spectroscopic characterization of nanostructured thermoelectric materials  

NASA Astrophysics Data System (ADS)

Bismuth in the bulk form is a semimetal with a rhombohedral structure. It has a small band overlap between the conduction and valence bands and a highly anisotropic electron effective-mass tensor. Thermoelectric materials, in which one of the three dimensions is in the nanometer regime, exhibit unique quantum confinement properties and have generated much interest in recent years. Theoretical investigations have suggested that nanowires with diameters ? 10 nm will possess a figure-of-merit ZT > 2. Prior to this study, it has been shown that Bi nanowires with small enough diameters (˜10 nm), prepared via the pulsed laser vaporization method, undergo a transition from a semimetal with a small band overlap to a semiconductor with a small indirect band gap. Infrared absorption and UV-visible measurements were used to confirm this semimetal-to-semiconductor phase transition. In this thesis, we report the synthesis and optical characteristics of a variety of various potential thermoelectric materials including bismuth, nickel sulfide and cadmium sulfide. The infrared absorption in our Bi nanorods is blue-shifted in energy when compared to the corresponding spectra in bulk Bi, and when cooled down to liquid nitrogen temperatures, group theory suggests a strong temperature dependence in the Bi band structure. We also find that the Bi nanorod suspension displays excellent optical limiting properties at both 532 and 1064 nm excitations in the nanosecond laser pulse regime. We have also synthesized nickel sulfide nanoparticles with an average size of 5 nm by a one-step solid phase reaction. The intensity-dependent nonlinear transmission study was carried out using a 7 ns Nd:YAG laser at 532nm using Z-scan, and the nonlinear scattering was found to be the dominant mechanism for the observed response. Importantly, the modified Z-scan method allowed us to measure two competing mechanisms simultaneously - the optical limiting and saturable absorption in surface-modified nickel sulfide nanoparticles suspensions.

Reppert, Jason Brooks

70

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

PubMed

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 532nm using the Z-scan technique employing laser pulses of 5ns duration. Open aperture Z-scan data reveal the presence of effective three-photon absorption for ns pulses at 532nm resulting in a strong optical limiting behavior, indicating possible photonic applications. PMID:23410921

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

2013-04-01

71

X-ray absorption spectroscopic evidence for a unique nickel site in Clostridium thermoaceticum carbon monoxide dehydrogenase  

SciTech Connect

Carbon monoxide dehydrogenase (COdH) in Clostridium thermoaceticum is an ..cap alpha../sub 3/..beta../sub 3/ protein containing six nickels per molecule, in addition to a number of Fe-S clusters. Previous electron paramagnetic resonance (EPR) spectroscopic work has suggested that nickel is involved in binding CO forming an EPR-detectable species, which is probably a key intermediate in the oxidation of CO to CO/sub 2/ and in the synthesis of acetate. In order to better define the nature of this nickel site, Ni X-ray absorption spectra have been recorded and interpreted by comparison with model compounds. The extended X-ray absorption fine structure (EXAFS) spectrum for oxidized COdH is different from that of other Ni enzymes. Both the EXAFS and the X-ray absorption edge spectra suggest a Ni site containing substantial sulfur ligation. The Ni X-ray absorption edge spectrum of rubredoxin-oxidized COdH exhibits a characteristic shoulder with an inflection point at 8336 eV. Such a feature is absent in octahedral model compounds, whereas a well-resolved peak is observed in square-planar Ni complexes. A distinct 1s ..-->.. 3d transition at 8333 eV is observed in a tetrahedral model. The lack of correspondence suggests that square-pyramidal and distorted-square-planar geometries are plausible candidates for the COdH Ni site. Treatment of rubredoxin-oxidized COdH with hydrogenase and H/sub 2/ shifts the Ni edge to lower energies, indicating Ni-based reduction. 34 references, 3 figures.

Cramer, S.P.; Eidsness, M.K.; Pan, W.H.; Morton, T.A.; Ragsdale, S.W.; DerVartanian, D.V.; Ljungdahl, L.G.; Scott, R.A.

1987-07-29

72

Synthesis and spectroscopic characterization of cadmium sulfide nanowires  

NASA Astrophysics Data System (ADS)

Pulsed laser vaporization method has been used for preparing cadmium sulfide (CdS) nanowires of 50 -- 100 nm in diameter. The morphology and crystallinity of as-prepared CdS nanowires are studied by means of X-ray diffraction, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). Excellent ordering of the lattice planes perpendicular to the [001] plane has been observed. Photoacoustic (PA), UV-Vis, Raman, and photoluminescence spectroscopy have been used to measure the optical properties. PA spectra yielded a steeper absorption edge for as-prepared CdS nanowires when compared to the conventional optical absorption spectrum. The increased steepness might be attributed to the well-ordered structure and size distribution. The data shows that PA spectroscopy is an excellent technique to investigate opaque and highly light scattering samples. Raman data suggests increased exciton-LO phonon coupling in CdS nanowires. The appearance of a narrow photoluminescence peak at 491 nm (FWHM of 9 nm) and the absence of emission above 500 nm demonstrate the high quality of nanowires.

Kuthirummal, Narayanan; Reppert, Jason; Diehl, Brian; Rao, Apparao

2009-03-01

73

Photomask CD and LER characterization using Mueller matrix spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Critical dimension and line edge roughness on photomask arrays are determined with Mueller matrix spectroscopic ellipsometry. Arrays with large sinusoidal perturbations are measured for different azimuth angels and compared with simulations based on rigorous coupled wave analysis. Experiment and simulation show that line edge roughness leads to characteristic changes in the different Mueller matrix elements. The influence of line edge roughness is interpreted as an increase of isotropic character of the sample. The changes in the Mueller matrix elements are very similar when the arrays are statistically perturbed with rms roughness values in the nanometer range suggesting that the results on the sinusoidal test structures are also relevant for "real" mask errors. Critical dimension errors and line edge roughness have similar impact on the SE MM measurement. To distinguish between both deviations, a strategy based on the calculation of sensitivities and correlation coefficients for all Mueller matrix elements is shown. The Mueller matrix elements M13/M31 and M34/M43 are the most suitable elements due to their high sensitivities to critical dimension errors and line edge roughness and, at the same time, to a low correlation coefficient between both influences. From the simulated sensitivities, it is estimated that the measurement accuracy has to be in the order of 0.01 and 0.001 for the detection of 1 nm critical dimension error and 1 nm line edge roughness, respectively.

Heinrich, A.; Dirnstorfer, I.; Bischoff, J.; Meiner, K.; Ketelsen, H.; Richter, U.; Mikolajick, T.

2014-10-01

74

Spectroscopic Characterization of Aliphatic Moieties in Four Plant Cuticles  

Microsoft Academic Search

Aliphatic components of tomato, pepper, and apple fruit cuticles, and the leaf cuticles of mature olive trees, were characterized using elemental analysis, carbon (C) nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR). Cuticular fractions isolated for analyses included bulk, dewaxed, nonsaponifiable, and nonhydrolyzable cuticles. Results from C NMR and FTIR spectra indicate that the cuticles of all the

Elizabeth J. Johnson; Orna Dorot; Judong Liu; Benny Chefetz; Baoshan Xing

2007-01-01

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

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

77

Electrical and spectroscopic characterization of a surgical argon plasma discharge  

NASA Astrophysics Data System (ADS)

For electrosurgical procedures, the argon plasma coagulation (APC) discharge is a well-established atmospheric-pressure plasma tool for thermal haemostasis and devitalization of biological tissue. To characterize this plasma source, voltage-current measurements, microphotography, optical emission spectroscopy and numerical simulation are applied. Two discharge modes are established during the operation of the APC plasma source. A short transient spark discharge is ignited within the positive half period of the applied high voltage after a streamer channel connects the APC probe and the counter-electrode. During the second phase, which continues under negative high voltage, a glow discharge is stabilized in the plasma channel.

Keller, Sandra; Bibinov, Nikita; Neugebauer, Alexander; Awakowicz, Peter

2013-01-01

78

Characterizing Absorption Spectrum of Natural Rubidium by Using a Directly Modulated VCSEL  

E-print Network

Characterizing Absorption Spectrum of Natural Rubidium by Using a Directly Modulated VCSEL Ido Ben in the absorption profile of a medium containing system atoms. Moreover, the change leads to a very narrow spectra: the VCSEL output and the absorption. Two modulation side bands, separated by fhfs owe to coincide

Eisenstein, Gadi

79

[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

80

FTIR Spectroscopic Characterization Of II-VI Semiconductors  

NASA Technical Reports Server (NTRS)

Combination of commercial Fourier-transform infrared (FTIR) spectrometer with computer and special-purpose software constitutes highly automated facility for acquisition and processing of infrared transmission or reflection spectral image data. Intended principally to acquire transmission spectra of some compounds of elements in groups II and VI of periodic table. System used to characterize specimens of II/VI alloy semiconductors grown by directional solidification and quenching. Transmission-edge maps helpful in studies of flows, gradients of temperature, and coefficients of diffusion in solidifying melts. Data acquired by system include optical characteristics, and they both verify and complement data obtained by such other techniques as measurements of density and x-ray-dispersion analysis.

Perry, G. L. E.; Szofran, F. R.

1991-01-01

81

Crystal chemistry of sibutramine: thermal, diffractometric and spectroscopic characterization.  

PubMed

Monohydrated sibutramine hydrochloride is a widely used active ingredient for the treatment of obesity. An anhydrous form of sibutramine hydrochloride was prepared starting from its monohydrate form upon heating it at 140 degrees C for 15 min. This dehydration process was monitored using conventional TG/DSC methods. Heated above 190 degrees C, sibutramine hydrochloride sublimes and recrystallizes on the cold walls of the test tube, giving platelet shaped crystals suitable for single crystal X-ray diffraction analysis: monoclinic, P2(1)/n, a = 7.321(2) A, b = 25.456(5) A, c = 9.750(3) A, beta = 101.60(2) degrees , V = 1779.9(8) A(3), Z = 4. At variance, sibutramine free base was typically recovered as a viscous oily material, upon treatment of its hydrochloride salt in ethyl acetate solution. Recrystallization from hexane yielded a white polycrystalline powder, the structure of which was determined by unconventional ab initio X-ray powder diffraction analysis: triclinic, P-1, a = 8.6578(3) A, b = 9.3318(3) A, c = 11.1224(4) A, alpha = 110.434(3) degrees , beta = 100.159(3) degrees , gamma = 89.201(2) degrees , V = 827.76(5) A(3), Z = 2. Sibutramine, in its different crystalline environments, was also fully characterized by solid state (13)C NMR analyses. Additional spectral information was obtained by collecting spectra of a metastable, oily sample, before it slowly recrystallizes (within hours). PMID:18398902

Maccaroni, Elisabetta; Alberti, Enrica; Malpezzi, Luciana; Masciocchi, Norberto; Pellegatta, Cesare

2008-12-01

82

Spectroscopic and morphologic characterization of the dentin/adhesive interface  

NASA Astrophysics Data System (ADS)

The potential environmental risks associated with dental amalgams have forced many European countries to ban their use and turn to alternative materials, composite resins. The purpose of this study was to correlate morphologic characterization of the dentin/adhesive bond with chemical analyses using micro-FTIR and micro-Raman spectroscopy. A commercial dental adhesive was placed on dentin substrates cut from extracted, unerupted human third molars. Sections of the dentin/adhesive interface were investigated using IR radiation produced at the Aladdin synchrotron source; visible radiation from Kr+ laser was used for the micro-Raman spectroscopy and through the use of differentially staining in conjunction with light microscopy. Due to its limited spatial resolution and the unknown samples thickness the IR results cannot be used quantitatively in determining the extent of diffusion. The result from the micro-Raman spectroscopy and light microscopy indicate exposed protein at the dentin/adhesive interface. Using a laser that reduces background fluorescence, the micro-Raman spectroscopy provides quantitative chemical and morphologic information on the dentin/adhesive interface. The staining procedure is sensitive to sites of pure protein and complements the Raman results.

Lemor, R. M.; Kruger, Michael B.; Wieliczka, David M.; Swafford, Jim R.; Spencer, Paulette

1999-04-01

83

Spectroscopic and morphologic characterization of the dentin/adhesive interface  

NASA Astrophysics Data System (ADS)

The potential environmental risks associated with mercury release have forced many European countries to ban the use of dental amalgam. Alternative materials such as composite resins do not provide the clinical function for the length of time characteristically associated with dental amalgam. The weak link in the composite restoration is the dentin/adhesive bond. The purpose of this study was to correlate morphologic characterization of the dentin/adhesive bond with chemical analyses using micro- Fourier transform infrared and micro-Raman spectroscopy. A commercial dental adhesive was placed on dentin substrates cut from extracted, unerupted human third molars. Sections of the dentin/adhesive interface were investigated using infrared radiation produced at the Aladdin synchrotron source; visible radiation from a Kr+ laser was used for the micro-Raman spectroscopy. Sections of the dentin/adhesive interface, differentially stained to identify protein, mineral, and adhesive, were examined using light microscopy. Due to its limited spatial resolution and the unknown sample thickness the infrared results cannot be used quantitatively in determining the extent of diffusion. The results from the micro-Raman spectroscopy and light microscopy indicate exposed protein at the dentin/adhesive interface. Using a laser that reduces background fluorescence, the micro-Raman spectroscopy provides quantitative chemical and morphologic information on the dentin/adhesive interface. The staining procedure is sensitive to sites of pure protein and thus, complements the Raman results.

Lemor, R. M.; Kruger, Michael B.; Wieliczka, David M.; Swafford, Jim R.; Spencer, Paulette

1999-01-01

84

A new spectroscopic survey for damped Ly-alpha absorption lines from high-redshift galaxies  

NASA Astrophysics Data System (ADS)

New low-resolution (FWHM is approximately equal to 4-6 A) spectroscopy of a sample of 57 background QSOs is presented. These data are combined with similar low-resolution spectroscopy of 53 recently acquired background QSOs. The spectra are analyzed to generate a complete sample of absorption features which, if the features are assumed to be Ly-alpha lines, have restframe equivalent widths not less than 5 A. The mean number densities of the damped Ly-alpha absorbers are determined. The distribution of the number of damped Ly-alpha absorbers observed per background QSO spectrum is found to be consistent with what is expected for randomly distributed intervening objects. The number of lines of sight that exhibit two damped Ly-alpha lines is consistent with what is expected on Poisson statistics. No significant evidence for clustering of the damped Ly-alpha absorbers on velocity scales greater than 5000 km/s is found.

Lanzetta, Kenneth M.; Wolfe, Arthur M.; Turnshek, David A.; Lu, Limin; McMahon, Richard G.; Hazard, Cyril

1991-09-01

85

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

86

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

87

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

88

Atomic absorption spectroscopic measurements of silicon atom concentrations in electron cyclotron resonance silicon oxide deposition plasmas  

NASA Astrophysics Data System (ADS)

The silicon atom densities in both silane/oxygen and tetraethoxysilane (TEOS)/oxygen electron cyclotron resonance (ECR) plasmas were measured as functions of microwave power, pressure, and gas flow rates. An atomic absorption spectrometer with a Si hollow-cathode lamp was constructed for these measurements. Silicon atom densities in silane/oxygen ECR discharges increase with rising plasma density, and a strong correlation was found between the Si atom gas-phase abundance and the silicon oxide film deposition rate. The measured Si concentrations [(1-7)×1010 cm-3] were high enough to account for a significant part of the film growth in the silane based chemistry. In TEOS/O2 discharges Si atom concentrations were lower by an order of magnitude, so Si is probably not a major contributor to the growth rate in that case. The internal temperature of Si atoms was found to vary from 380 to 720 K with increasing microwave power (200-650 W).

Augustyniak, Edward; Chew, Kok Heng; Shohet, J. Leon; Woods, R. Claude

1999-01-01

89

Absorption-line-shape recovery beyond the detection-bandwidth limit: Application to the precision spectroscopic measurement of the Boltzmann constant  

NASA Astrophysics Data System (ADS)

A theoretical model of the influence of detection-bandwidth properties on observed line shapes in laser absorption spectroscopy is described. The model predicts artificial frequency shifts, extra broadenings, and line asymmetries that must be taken into account in order to obtain accurate central frequencies and other spectroscopic parameters. This reveals sources of systematic effects most probably underestimated, so far potentially affecting spectroscopic measurements. This may impact many fields of research, from atmospheric and interstellar physics to precision spectroscopic measurements devoted to metrological applications, tests of quantum electrodynamics, or other fundamental laws of nature. Our theoretical model is validated by linear absorption experiments performed on H2O and NH3 molecular lines recorded by precision laser spectroscopy in two distinct spectral regions, near- and midinfrared. Possible means of recovering original line-shape parameters or experimental conditions under which the detection bandwidth has a negligible impact, given a targeted accuracy, are proposed. Particular emphasis is put on the detection-bandwidth adjustments required to use such high-quality molecular spectra for a spectroscopic determination of the Boltzmann constant at the 1 ppm level of accuracy.

Rohart, F.; Mejri, S.; Sow, P. L. T.; Tokunaga, S. K.; Chardonnet, C.; Darquié, B.; Dinesan, H.; Fasci, E.; Castrillo, A.; Gianfrani, L.; Daussy, C.

2014-10-01

90

Fourier transform infrared spectroscopic characterization of mineralizing type I collagen enzymatic trivalent cross-links.  

PubMed

The most abundant protein of bone's organic matrix is collagen. One of its most important properties is its cross-linking pattern, which is responsible for the fibrillar matrices' mechanical properties such as tensile strength and viscoelasticity. We have previously described a spectroscopic method based on the resolution of the Amide I and II Fourier transform Infrared (FTIR) bands to their underlying constituent peaks, which allows the determination of divalent and pyridinoline (PYD) collagen cross-links in mineralized thin bone tissue sections with a spatial resolution of ~6.3 ?m. In the present study, we used FTIR analysis of a series of biochemically characterized collagen peptides, as well as skin, dentin, and predentin, to examine the potential reasons underlying discrepancies between two different analytical methodologies specifically related to spectral processing. The results identified a novel distinct FTIR underlying peak at ~1,680 cm(-1), correlated with deoxypyridinoline (DPD) content. Furthermore, the two different methods of spectral resolution result in widely different results, while only the method employing well-established spectroscopic routines for spectral resolution provided biologically relevant results, confirming our earlier studies relating the area of the underlying 1,660 cm(-1) with PYD content. The results of the present study describe a new peak that may be used to determine DPD content, confirm our earlier report relating spectroscopic parameters to PYD content, and highlight the importance of the selected spectral resolution methodology. PMID:25424977

Paschalis, E P; Gamsjaeger, S; Tatakis, D N; Hassler, N; Robins, S P; Klaushofer, K

2015-01-01

91

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

92

Analytical and spectroscopic characterization of humic acids extracted from sewage sludge, manure, and worm compost  

SciTech Connect

Humic acids extracted from sewage sludges, manure, and worm compost have been characterized by chemical and spectroscopic methods. Meaningful differences in the composition were revealed by FTIR, {sup 1}H, {sup 13}C NMR, and visible spectroscopies. These differences allow a differentiation among the products depending on the source from which they were obtained. Humic acid extracted from sewage sludges contains the highest percentage of aliphatic carbon, associated with polysaccharides and proteinaceous structures, and has characteristics close to those of aquatic humic acids. On the other hand, humic acids from manure and worm compost are similar to the humic acids originating from soil.

Deiana, S.; Gessa, C.; Manunza, B.; Seeber, R. (Universita di Sassari (Italy)); Rausa, R. (Eniricerche S.p.A., Milanese (Italy))

1990-07-01

93

Reactivity of Chromium(III) Nutritional Supplements in Biological Media: An X-Ray Absorption Spectroscopic Study  

SciTech Connect

Chromium(III) nutritional supplements are widely used due to their purported ability to enhance glucose metabolism, despite growing evidence on low activity and the potential genotoxicity of these compounds. Reactivities of Cr(III) complexes used in nutritional formulations, including [Cr3O(OCOEt)6(OH2)3]+ (A), [Cr(pic)3] (pic) = 2-pyridinecarboxylato(-) (B), and trans-[CrCl2(OH2)4]+ (CrCl3 {center_dot} 6H2O; C), in a range of natural and simulated biological media (artificial digestion systems, blood and its components, cell culture media, and intact L6 rat skeletal muscle cells) were studied by X-ray absorption near-edge structure (XANES) spectroscopy. The XANES spectroscopic data were processed by multiple linear-regression analyses with the use of a library of model Cr(III) compounds, and the results were corroborated by the results of X-ray absorption fine structure spectroscopy and electrospray mass spectrometry. Complexes A and B underwent extensive ligand-exchange reactions under conditions of combined gastric and intestinal digestion (in the presence of a semisynthetic meal, 3 h at 310 K), as well as in blood serum and in a cell culture medium (1-24 h at 310 K), with the formation of Cr(III) complexes with hydroxo and amino acid/protein ligands. Reactions of compounds A-C with cultured muscle cells led to similar ligand-exchange products, with at least part of Cr(III) bound to the surface of the cells. The reactions of B with serum greatly enhanced its propensity to be converted to Cr(VI) by biological oxidants (H2O2 or glucose oxidase system), which is proposed to be a major cause of both the insulin-enhancing activity and toxicity of Cr(III) compounds (Mulyani, I.; Levina, A.; Lay, P. A. Angew. Chem. Int. Ed. 2004, 43, 4504-4507). This finding enhances the current concern over the safety of consumption of large doses of Cr(III) supplements, particularly [Cr(pic)3].

Nguyen, A.; Mulyani, I.; Levina, A.; Lay, P.A.

2009-05-22

94

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.

2007-04-01

95

Synthesis, spectroscopic characterization, DFT studies and biological assays of a novel gold(I) complex with 2-mercaptothiazoline  

Microsoft Academic Search

A new gold(I) complex with 2-mercaptothiazoline (MTZ) with the coordination formula [AuCN(C3H5NS2)] was synthesized and characterized by chemical and spectroscopic measurements, DFT studies and biological assays. Infrared (IR) and 1H, 13C and 15N nuclear magnetic resonance (NMR) spectroscopic measurements indicate coordination of the ligand to gold(I) through the nitrogen atom. Studies based on DFT confirmed nitrogen coordination to gold(I) as

Camilla Abbehausen; Juliana F. Castro; Marcelle B. M. Spera; Tassiele A. Heinrich; Claudio M. Costa-Neto; Wilton R. Lustri; André L. B. Formiga; Pedro P. Corbi

2011-01-01

96

Silver sulfadoxinate: Synthesis, structural and spectroscopic characterizations, and preliminary antibacterial assays in vitro  

NASA Astrophysics Data System (ADS)

The sulfa drug sulfadoxine (SFX) reacted with Ag+ ions in aqueous solution, affording a new silver(I) complex (AgSFX), which was fully characterized by chemical, spectroscopic and structural methods. Elemental, ESI-TOF mass spectrometric and thermal analyses of AgSFX suggested a [Ag(C12H13N4O2S)] empirical formula. Infrared spectroscopic measurements indicated ligand coordination to Ag(I) through the nitrogen atoms of the (deprotonated) sulfonamide group and by the pyrimidine ring, as well as through oxygen atom(s) of the sulfonamide group. These hypotheses were corroborated by 13C and 15N SS-NMR spectroscopy and by an unconventional structural characterization based on X-ray powder diffraction data. The latter showed that AgSFX crystallizes as centrosymmetric dimers with a strong Ag⋯Ag interaction of 2.7435(6) Å, induced by the presence of exo-bidentate N,N? bridging ligands and the formation of an eight-membered ring of [AgNCN]2 sequence, nearly planar. Participation of oxygen atoms of the sulfonamide residues generates in the crystal a 1D coordination polymer, likely responsible for its very limited solubility in all common solvents. Besides the analytical, spectroscopic and structural description, the antibacterial properties of AgSFX were assayed using disc diffusion methods against Escherichia coli and Pseudomonas aeruginosa (Gram-negative), and Staphylococcus aureus (Gram-positive) bacterial strains. The AgSFX complex showed to be active against Gram-positive and Gram-negative bacterial strains, being comparable to the activities of silver sulfadiazine.

Zanvettor, Nina T.; Abbehausen, Camilla; Lustri, Wilton R.; Cuin, Alexandre; Masciocchi, Norberto; Corbi, Pedro P.

2015-02-01

97

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

98

Optical characterization of ferroelectric PZT thin films by variable angle spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Ferroelectric thin films are used as high dielectric constant capacitors, infrared detectors, piezoelectric transducers, optical modulators, optical waveguides, and nonvolatile memory chips for dynamic random access memory (DRAM) etc. While ferroelectric and dielectric properties of these films have been extensively investigated, their optical properties have been comparatively less studied and of limited use in quantitative evaluation of multilayer thin films. In this work we explored the variable angle spectroscopic ellipsometry (VASE) technique for its effectiveness in physical property characterization. The VASE combined with its computer modeling tool enables nondestructive, nonintrusive, and contactless optical means for optical characterization. Crystalline Lead Zirconium Titanate PbZr0.52Ti0.48O3 (PZT) thin films, fabricated on SrTiO3 layer atop of Si substrates, were characterized using VASE (J.A. Woollam; Lincoln, NE, USA) by determining the ellipsometric parameters ? and ? as a function of wavelengths (200-1000 nm) and incident angles (65°, 70°,75°) at room temperature. A physical representation of the multilayer system was constructed by a six layer model (analysis software WVASE32, J.A. Woollam) through a step-by-step method. Other physical properties characterized by several well-known techniques on structure, morphology and topographical features correspond well with the models developed using VASE alone. The technique and the methodology developed have shown promises in identifying the respective thickness and optical properties of multilayer thin film system, with limited input of processing or composition information.

Rahman, Md. Shafiqur; Garcia, Carlos D.; Bhalla, Amar; Guo, Ruyan

2014-09-01

99

FT-IR spectroscopic, thermal analysis of human urinary stones and their characterization  

NASA Astrophysics Data System (ADS)

In the present study, FT-IR, XRD, TGA-DTA spectral methods have been used to investigate the chemical compositions of urinary calculi. Multi-components of urinary calculi such as calcium oxalate, hydroxyl apatite, struvite and uric acid have been studied. The chemical compounds are identified by FT-IR spectroscopic technique. The mineral identification was confirmed by powder X-ray diffraction patterns as compared with JCPDS reported values. Thermal analysis techniques are considered the best techniques for the characterization and detection of endothermic and exothermic behaviors of the urinary stones. The percentages of each hydrate (COM and COD) are present together, in the presences of MAPH or UA. Finally, the present study suggests that the Urolithiasis is significant health problem in children, and is very common in some parts of the world, especially in India. So that present study is so useful and helpful to the scientific community for identification of latest human health problems and their remedies using spectroscopic techniques.

Selvaraju, R.; Raja, A.; Thiruppathi, G.

2015-02-01

100

Spectroscopic and Photophysical Properties of the Trioxatriangulenium  

E-print Network

1 Spectroscopic and Photophysical Properties of the Trioxatriangulenium Carbocation and its and absorption spectroscopic techniques. A significant difference is observed of the photophysical parameters

101

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

102

Chemical Vapor Deposition Synthesis and Raman Spectroscopic Characterization of Large-Area Graphene Sheets  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

103

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

104

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

105

The synthesis and spectroscopic characterization of nano calcium fluorapatite using tetra-butylammonium fluoride  

NASA Astrophysics Data System (ADS)

Pure homogeneous nano sized biocompatible fluorapatite (FAp) particles were synthesized by a wet chemical procedure using water soluble tetra-butylammonium fluoride (TBAF) without using high temperatures and any purification processes. Combination of the Bragg's law and the plane-spacing equation for the two high intensity lines, namely, (0 0 2) and (3 0 0), gives a = 9.3531 Å, c = 6.8841 Å, confirms the identity of the highly crystalline synthetic material as well as its purity. The effect of various pH's in crystal formation and on their size was also evaluated. The calculated crystallinities were excellent with a rate around 5.0. The synthesized nano FAp was fully characterized by spectroscopic techniques (XRD, SEM, EDS, BET, FT-IR and ICP-AES). The nitrogen adsorption-desorption isotherm showed a type IV diagram and calculation of the surface area was investigated as well.

Sheykhan, Mehdi; Heydari, Akbar; Ma'mani, Leila; Badiei, Alireza

2011-12-01

106

Raman spectroscopic and ESI-MS characterization of uranyl peroxide cage clusters.  

PubMed

Strategies for interpreting mass spectrometric and Raman spectroscopic data have been developed to study the structure and reactivity of uranyl peroxide cage clusters in aqueous solution. We demonstrate the efficacy of these methods using the three best-characterized uranyl peroxide clusters, {U24}, {U28}, and {U60}. Specifically, we show a correlation between uranyl-peroxo-uranyl dihedral bond angles and the position of the Raman band of the symmetric stretching mode of the peroxo ligand, develop methods for the assignment of the ESI mass spectra of uranyl peroxide cage clusters, and show that these methods are generally applicable for detecting these clusters in the solid state and solution and for extracting information about their bonding and composition without crystallization. PMID:24422479

McGrail, Brendan T; Sigmon, Ginger E; Jouffret, Laurent J; Andrews, Christopher R; Burns, Peter C

2014-02-01

107

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

108

Preparation and spectroscopic characterization of polarons and bipolarons of thiophene oligomers within the channels of pentasil zeolites: The evolution of organic radical ions into conducting polymers  

SciTech Connect

Pentasil zeolites such as ZSM-5 and Na-{beta} can be used as supporting matrices in which short-chain oligomers of polythiophene can be prepared, oxidatively doped to the conducting state, stabilized, and finally spectroscopically characterized. For the first time the evolution of the electronic structure of doped polythiophene from monomer to polymer has been observed directly for chain lengths between two and nine. Plots of the electronic absorption band energies for the polaron and bipolaron are found to be linear functions of inverse chain length. These results are extrapolated to infinite chain length to predict the positions of heretofore unobserved electronic transitions of bulk polythiophene. These extrapolations suggest that the lowest energy polaron and bipolaron levels of doped polythiophene are remarkably close in energy, implying that transient formation of polarons from bipolarons in energetically feasible and that this process could play a role in interchain charge hopping in this material.

Casper, J.V.; Ramamurthy, V.; Corbin, D.R. (E.I. du Pont de Nemours and Co., Wilmington, DE (USA))

1991-01-16

109

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

NASA Astrophysics Data System (ADS)

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, 1H NMR, 13C 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.

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

2014-12-01

110

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

111

Spectroscopic characterization of effective components anthraquinones in Chinese medicinal herbs binding with serum albumins  

NASA Astrophysics Data System (ADS)

The interactions of serum albumins such as human serum albumin (HSA) and bovine serum albumin (BSA) with emodin, rhein, aloe-emodin and aloin were assessed employing fluorescence quenching and absorption spectroscopic techniques. The results obtained revealed that there are relatively strong binding affinity for the four anthraquinones with HSA and BSA and the binding constants for the interactions of anthraquinones with HSA or BSA at 20 °C were obtained. Anthraquinone-albumin interactions were studied at different temperatures and in the presence of some metal ions. And the competition binding of anthraquinones with serum albumins was also discussed. The Stern-Volmer curves suggested that the quenching occurring in the reactions was the static quenching process. The binding distances and transfer efficiencies for each binding reactions were calculated according to the Föster theory of non-radiation energy transfer. Using thermodynamic equations, the main action forces of these reactions were also obtained. The reasons of the different binding affinities for different anthraquinone-albumin reactions were probed from the point of view of molecular structures.

Bi, Shuyun; Song, Daqian; Kan, Yuhe; Xu, Dong; Tian, Yuan; Zhou, Xin; Zhang, Hanqi

2005-11-01

112

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

113

Spectroscopic characterization of II-VI compounds and application to copper indium selenide-based solar cells  

Microsoft Academic Search

Structures consisting of CuInSe2 films, deposited on molybdenum-coated glass substrates and covered by CdS or ZnO thin films, for application in solar cells, have been characterized by spectroscopic ellipsometry, atomic force microscopy, photoluminescence and photovoltaic response. Computer aided simulations of the photovoltaic operation of these structures have been made to reinforce and complement the results of the characterization studies. The

Heriberto De Jesus Aguilar Juarez

1999-01-01

114

Transient Spectroscopic Characterization of the Genesis of a Ruthenium Complex Catalyst Supported on Zeolite Y  

SciTech Connect

A mononuclear ruthenium complex anchored to dealuminated zeolite HY, Ru(acac)(C{sub 2}H{sub 4}){sup 2+} (acac = acetylacetonate, C{sub 5}H{sub 7}O{sup 2}{sup -}), was characterized in flow reactors by transient infrared (IR) spectroscopy and Ru K edge X-ray absorption spectroscopy. The combined results show how the supported complex was converted into a form that catalyzes ethene conversion to butene. The formation of these species resulted from the removal of acac ligands from the ruthenium (as shown by IR and extended X-ray absorption fine structure (EXAFS) spectra) and the simultaneous decrease in the symmetry of the ruthenium complex, with the ruthenium remaining mononuclear and its oxidation state remaining essentially unchanged (as shown by EXAFS and X-ray absorption near-edge structure spectra). The removal of anionic acac ligands from the ruthenium was evidently compensated by the bonding of other anionic ligands, such as hydride from H2 in the feed stream, to form species suggested to be Ru(H)(C{sub 2}H{sub 4}){sub 2}{sup +}, which is coordinatively unsaturated and inferred to react with ethene, leading to the observed formation of butene in a catalytic process.

Ogino, Isao; Gates, Bruce C.; (UCD)

2010-01-12

115

IR spectroscopic characterization of oh defects in jadeite from a vein occurrence  

NASA Astrophysics Data System (ADS)

The role of OH defects in pyroxenes is of considerable geological interest in view of characterizing the chemistry of nominally anhydrous mineral phases likely to be present in the Earth's mantle. Pyroxene may indeed be the main storage site for hydrogen in the Earth's upper mantle, revealing concentrations ranging from about 100 to 1300 wt.ppm H2O (Ingrin and Skogby, 2000). The jadeite sample of the present study originates from the locality of the Clear Creek area, New Idria district, California (Coleman, 1961). Small colorless cleavage fragments of near end-member jadeite single-crystals found within veins of "white jadeite" were separated and oriented. Under the microscope the strongly elongated crystal fragment, 500 x 200 x 150 70?m in size, proved in parts to be free from impurities and inclusions. The OH defect incorporation mode in vein jadeite must also be considered for pyroxenes formed in mantle regions. IR spectroscopy provides an extremely sensitive method for detecting trace hydrogen bonded to oxygen, thus forming structural OH defects. In the present case it was necessary to use an FTIR microscope providing suitable measuring spot sizes for the absorption measurements. Using polarized IR radiation, the pleochroic scheme of the OH absorption bands allows to impose defined constraints on the OH orientation. Polarized single-crystal spectra of the oriented jadeite crystal fragment were recorded from 4000 to 2000 cm-1. Jadeite is characterized by two small but broad absorption bands centered at 3618 and 3556 cm-1. Both bands show a distinct pleochroism in the (010) plane. The maximum of absorption is observed when the angle between the E vector of the polarized radiation and the c-axis, measured within the positive a- and c-axis, amounts to 70o. In contrast, only a weak pleochroism was observed in (100) with a slightly stronger absorption parallel to the b-axis. Some similarities exist with the pleochroic behavior of group II bands in diopside, which occur around 3535, 3460, and 3355 cm-1 (Ingrin and Skogby, 2000), suggesting a partial replacement of the O2 oxygen atoms by OH groups with an OH dipole orientation pointing to the vicinity of vacant M2 sites also in jadeite. Literature Coleman RG (1961) J Petrol 2, 209 Ingrin J, Skogby H (2000) Eur J Mineral 12, 543 Acknowledgements: This work was partly supported by the EU through the Human Potential Program under Grant HPRN-CT-2000-0056.

Andrut, M.; Beran, A.; Wildner, M.

2003-04-01

116

Solution properties and spectroscopic characterization of polymeric precursors to SiNCB and BN ceramic materials  

SciTech Connect

Boron Nitride, BN, and composite SiNCB ceramic fibers are important structural materials because of their excellent thermal and oxidative stabilities. Consequently, polymeric materials as precursors to ceramic composites are receiving increasing attention. Characterization of these materials requires the ability to evaluate simultaneous molecular weight and compositional heterogeneity within the polymer. Size exclusion chromatography equipped with viscometric and refractive index detection as well as coupled to a LC-transform device for infrared absorption analysis has been employed to examine these heterogeneities. Using these combined approaches, the solution properties and the relative amounts of individual functional groups distributed through the molecular weight distribution of SiNCB and BN polymeric precursors were characterized. {copyright} {ital 1998 American Institute of Physics.}

Cortez, E.; Remsen, E; Chlanda, V. [Analytical Science Center, Monsanto Corporate Research, Monsanto Company, 800 North Lindbergh, St. Louis, Missouri 63167 (United States); Carrol, P. [Department of Chemistry and Laboratory for the Research on the Structure of Matter, University of Pennsylvania, Pennsylvania 19107-6323 (United States); Sneddon, L. [The Advanced Ceramics Program, Dow Corning Corporation, Midland, Michigan, 48686-0995 (United States)

1998-06-01

117

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

118

Development of Cellular Absorptive Tracers (CATs) for a Quantitative Characterization of Microbial Mass in Flow Systems  

SciTech Connect

We report on a new Cellular Absorptive Tracers (CATs) method, for a simple, non-destructive characterization of bacterial mass in flow systems. Results show that adsorption of a CAT molecule into the cellular mass results in its retardation during flow, which is a good, quantitative measure of the biomass quantity and distribution. No such methods are currently available for a quantitative characterization of cell mass.

Saripalli, Prasad; Brown, Christopher F.; Lindberg, Michael J.

2005-03-16

119

Characterization of molecular and biomolecular layers on diamond thin films by infrared reflection-absorption spectroscopy  

Microsoft Academic Search

We explore the use of single-bounce infrared reflection-absorption spectroscopy (IRRAS) to characterize molecular and biomolecular layers on doped and undoped diamond thin films on silicon substrates. Experimental measurements of thin layers of poly(methyl methacrylate) (PMMA) as a function of polarization and angle of incidence were used to characterize the intensity, frequency, and symmetry of the vibrational features. Fresnel multilayer reflectivity

Robert J. Hamers; Courtney Stavis; Ankit Pokhrel; Ryan Franking; Rose E. Ruther; Xiaoyu Wang; Michelle C. Cooperrider; Hongjun Zheng; John A. Carlisle; James E. Butler

2011-01-01

120

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. PMID:21062059

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

2010-01-01

121

Characterization of absorption spectrum of ethanol gas for use as terahertz alcohol sensor  

Microsoft Academic Search

The absorption spectra of pure ethanol gas and ethanol gas mixed with air were characterized for examining the use of ethanol gas as a terahertz alcohol sensor. A comparison of the spectra of both gases showed that the absorbance of the latter was ~1.3 times greater than that of the former.

J. Hamazaki; S. Saito; I. Hosako

2010-01-01

122

Spectroscopic characterization of high-energy and high fluence rate photon beams  

NASA Astrophysics Data System (ADS)

High-energy, high fluence rate photon sources are used in radiation oncology for the treatment of a variety of disease sites. Common dosimetry methods for characterizing these sources use energy-integrating devices; however, the most descriptive characterization of these sources are performed with devices that preserve the energy-specific information in the source output. This work used Monte-Carlo- (MC-) and measurement-based spectroscopic methods to characterize two therapeutic-level megavoltage photon sources. MC simulations were performed using the MCNP5 transport code and measurements were performed with a Compton-scattering (CS) technique. Because MC was used extensively in this work, some general MCNP5 investigations were performed to benchmark the techniques used. Limitations in the advanced variance reduction techniques, Doppler-broadening model, and use of phase space files were investigated. Based on the results of these investigations, recommendations were made for using each technique. The validity of the CS technique for use with megavoltage systems was demonstrated using MC simulations of a 6 MV linear accelerator field and measurements of a high dose rate 192Ir source. Following these initial demonstrations, the spectrum of a 60Co teletherapy unit was characterized. Simulations were performed to determine the spectrum's sensitivity to the source model. Multiple measurements were completed using a reverse-electrode germanium (REGe) detector with the CS spectrometry technique. The CS spectra were corrected for detector response and the CS geometry using a novel detector response function that was calculated using MCNP5. The detector response was unfolded using the Gold deconvolution method. Comparisons of the simulated and measured spectra showed agreement in terms of the peak positions, mean spectrum energy, and relative fluences under specific portions of the spectra. The spectrum of a 6 MV photon field from a Varian Clinac iX linear accelerator was also characterized. Simulations were performed to determine the spectrum's sensitivity to changes in the primary electron source parameters of mean energy, spot size, and divergence. In addition, measurements were performed using the CS technique with the REGe detector. These measurements demonstrated that the linac spectrum was detectable above background, and the CS signal was dependent on field size.

Bartol, Laura J.

123

[Biosynthesis of CdS quantum dots in Saccharomyces cerevisiae and spectroscopic characterization].  

PubMed

In the present work, CdS quantum dots (QDs) were successfully biosynthesized at room temperature by using saccharomyces cerevisiae yeast as a carrier. Fluorescence emission spectra, ultraviolet-visible (UV/Vis) absorption spectra, and inverted fluorescence microscope images confirmed that saccharomyces cerevisiae can be used to biosynthesize CdS QDs. The as-prepared CdS QDs show the fluorescence emission peak at 443 nm and emit blue-green fluorescence under UV light (with excitation at 365 nm). Transmission electron microscopy (TEM) was applied to characterize the as-prepared CdS QDs and the TEM results showed that the as-prepared CdS QDs had the structure of hexagonal wurtzite. Fluorescence emission spectrum and UV/Vis absorption spectrum were used as the performance indicatiors to study the effects of saccharomyces cerevisiae yeast incubation times, reactant Cd2+ concentrations and reaction times on CdS QDs synthesis. Saccharomyces cerevisiae yeast grown in early stable phase can get the highest fluorescence intensity of CdS QDs when they were co-cultured with 0.5 mmol x L(-1) of Cd2+ with 24 h incubation time. Furthermore, much more CdS QDs can be obtained by changing the culture medium during the synthesis process. PMID:22715791

Huang, Huai-qing; He, Ming-xin; Wang, Wen-xing; Liu, Jin-ling; Mi, Cong-cong; Xu, Shu-kun

2012-04-01

124

Spectroscopic networks  

NASA Astrophysics Data System (ADS)

Approaches related to graph theory are given which allow a better understanding of and yield routes for systematic enlargement and improvement of experimental spectroscopic line lists of molecules. The protocols are based on the fact that the information in line lists can be related to large-scale, weighted, undirected graphs, whereby the vertices are discrete energy levels, the edges are transitions, and the weights are transition intensities. The resulting graph is what one may call a spectroscopic network (SN). It is shown on the example of the HD16O isotopologue of the water molecule that both its measured and first-principles one-photon absorption SNs have a scale-free behavior with all of the usual consequences, including appearance of hubs, robustness, error tolerance, and the "small-world" property. The graph-theoretical view of molecular spectra offers several new ideas for improving the accuracy and robustness of the information systems containing high-resolution spectroscopic data.

Csaszar, A. G.; Furtenbacher, T.

2011-05-01

125

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. PMID:23595607

Benavidez, Tomas E.; Garcia, Carlos D.

2013-01-01

126

Structural and spectroscopic characterization of a thiosemicarbazidatodioxouranium(VI) complex: a combined experimental and DFT study.  

PubMed

The title thiosemicarbazidatodioxouranium(VI) compound was synthesized and characterized by FT-IR, NMR and UV-vis spectroscopies. Solid-state structure of the compound was confirmed by X-ray crystallography. Besides, the molecular geometry, vibrational frequencies and gauge-independent atomic orbital (GIAO) (1)H and (13)C NMR chemical shift values of the compound in the ground state have been calculated using the density functional theory (DFT/B3LYP) method with the 6-311++G(d,p) basis set for the C, H, Cl, N, O, S atoms and SDD pseudo-potential for the U atom, and compared with the experimental data. Using the TD-DFT method, electronic absorption spectra of the compound have been predicted at same level. As a result, a good agreement is obtained between the experimental and theoretical ones. PMID:25168237

?ahin, Musa; Özdemir, Nam?k; Bal-Demirci, Tülay; Ülküseven, Bahri; Dinçer, Muharrem; Soylu, Mustafa Serkan

2015-01-25

127

Structural and spectroscopic characterization of a thiosemicarbazidatodioxouranium(VI) complex: A combined experimental and DFT study  

NASA Astrophysics Data System (ADS)

The title thiosemicarbazidatodioxouranium(VI) compound was synthesized and characterized by FT-IR, NMR and UV-vis spectroscopies. Solid-state structure of the compound was confirmed by X-ray crystallography. Besides, the molecular geometry, vibrational frequencies and gauge-independent atomic orbital (GIAO) 1H and 13C NMR chemical shift values of the compound in the ground state have been calculated using the density functional theory (DFT/B3LYP) method with the 6-311++G(d,p) basis set for the C, H, Cl, N, O, S atoms and SDD pseudo-potential for the U atom, and compared with the experimental data. Using the TD-DFT method, electronic absorption spectra of the compound have been predicted at same level. As a result, a good agreement is obtained between the experimental and theoretical ones.

?ahin, Musa; Özdemir, Nam?k; Bal-Demirci, Tülay; Ülküseven, Bahri; Dinçer, Muharrem; Soylu, Mustafa Serkan

2015-01-01

128

Characterizing the structure of lipodisq nanoparticles for membrane protein spectroscopic studies.  

PubMed

Membrane protein spectroscopic studies are challenging due to the difficulty introduced in preparing homogenous and functional hydrophobic proteins incorporated into a lipid bilayer system. Traditional membrane mimics such as micelles or liposomes have proved to be powerful in solubilizing membrane proteins for biophysical studies, however, several drawbacks have limited their applications. Recently, a nanosized complex termed lipodisq nanoparticles was utilized as an alternative membrane mimic to overcome these caveats by providing a homogeneous lipid bilayer environment. Despite all the benefits that lipodisq nanoparticles could provide to enhance the biophysical studies of membrane proteins, structural characterization in different lipid compositions that closely mimic the native membrane environment is still lacking. In this study, the formation of lipodisq nanoparticles using different weight ratios of POPC/POPG lipids to SMA polymers was characterized via solid-state nuclear magnetic resonance (SSNMR) spectroscopy and dynamic light scattering (DLS). A critical weight ratio of (1/1.25) for the complete solubilization of POPC/POPG vesicles has been observed and POPC/POPG vesicles turned clear instantaneously upon the addition of the SMA polymer. The size of lipodisq nanoparticles formed from POPC/POPG lipids at this weight ratio of (1/1.25) was found to be about 30 nm in radius. We also showed that upon the complete solubilization of POPC/POPG vesicles by SMA polymers, the average size of the lipodisq nanoparticles is weight ratio dependent, when more SMA polymers were introduced, smaller lipodisq nanoparticles were obtained. The results of this study will be helpful for a variety of biophysical experiments when specific size of lipid disc is required. Further, this study will provide a proper path for researchers working on membrane proteins to obtain pertinent structure and dynamic information in a physiologically relevant membrane mimetic environment. PMID:24853657

Zhang, Rongfu; Sahu, Indra D; Liu, Lishan; Osatuke, Anna; Comer, Raven G; Dabney-Smith, Carole; Lorigan, Gary A

2015-01-01

129

Characterization of fresh and aged natural ingredients used in historical ointments by molecular spectroscopic techniques: IR, Raman and fluorescence.  

PubMed

Natural organic materials used to prepare pharmaceutical mixtures including ointments and balsams have been characterized by a combined non-destructive spectroscopic analytical approach. Three classes of materials which include vegetable oils (olive, almond and palm tree), gums (Arabic and Tragacanth) and beeswax are considered in this study according to their widespread use reported in ancient recipes. Micro-FTIR, micro-Raman and fluorescence spectroscopies have been applied to fresh and mildly thermally aged samples. Vibrational characterization of these organic compounds is reported together with tabulated frequencies, highlighting all spectral features and changes in spectra which occur following artificial aging. Synchronous fluorescence spectroscopy has been shown to be particularly useful for the assessment of changes in oils after aging; spectral difference between Tragacanth and Arabic gum could be due to variations in origin and processing of raw materials. Analysis of these materials using non-destructive spectroscopic techniques provided important analytical information which could be used to guide further study. PMID:21725834

Brambilla, L; Riedo, C; Baraldi, C; Nevin, A; Gamberini, M C; D'Andrea, C; Chiantore, O; Goidanich, S; Toniolo, L

2011-10-01

130

Molecular approach to the chemical characterization of fish-exuded kairomone: a Fourier transform infrared spectroscopic study  

Microsoft Academic Search

Diel vertical migration (DVM) bioassay-guided Fourier transform infrared spectroscopy can be a prominent non-destructive and\\u000a innovative approach for ecological studies. During the characterization of the nature of the fish-exuded kairomone, the peak\\u000a area results from the spectroscopic analysis of the control, fish-conditioned (F) and temperature incubated fish-conditioned\\u000a (IF) treatments of the DVM bioassays demonstrated that there was a strong correlation

Sara B. Akkas; Ayse O. Kepenek; Meryem Beklioglu; Feride Severcan

2010-01-01

131

Crystallographic and spectroscopic characterization and reactivities of a mononuclear non-haem iron(III)-superoxo complex.  

PubMed

Mononuclear non-haem iron(III)-superoxo species (Fe(III)-O2(-·)) have been implicated as key intermediates in the catalytic cycles of dioxygen activation by non-haem iron enzymes. Although non-haem iron(III)-superoxo species have been trapped and characterized spectroscopically in enzymatic and biomimetic reactions, no structural information has yet been obtained. Here we report the isolation, spectroscopic characterization and crystal structure of a mononuclear side-on (?(2)) iron(III)-superoxo complex with a tetraamido macrocyclic ligand. The non-haem iron(III)-superoxo species undergoes both electrophilic and nucleophilic oxidation reactions, as well as O2-transfer between metal complexes. In the O2-transfer reaction, the iron(III)-superoxo complex transfers the bound O2 unit to a manganese(III) analogue, resulting in the formation of a manganese(IV)-peroxo complex, which is characterized structurally and spectroscopically as a mononuclear side-on (?(2)) manganese(IV)-peroxo complex. The difference in the redox distribution between the metal ions and O2 in iron(III)-superoxo and manganese(IV)-peroxo complexes is rationalized using density functional theory calculations. PMID:25510711

Hong, Seungwoo; Sutherlin, Kyle D; Park, Jiyoung; Kwon, Eunji; Siegler, Maxime A; Solomon, Edward I; Nam, Wonwoo

2014-01-01

132

Characterization of dissolved organic matter during reactive transport: A column experiment with spectroscopic detection  

NASA Astrophysics Data System (ADS)

Al and Fe oxy-hydroxide minerals have been implicated in dissolved organic matter (DOM) stabilization. DOM solutions from a Pinus ponderosa forest floor (PPDOM) were used to irrigate polypropylene columns, 3.2 cm long by 0.9 cm diameter (total volume 2.0 cm3), that were packed with quartz sand (QS), gibbsite-quartz sand (Al-QS), and goethite-quartz sand (Fe-QS) mixtures. To investigate the mobilization and fractionation of DOM during reactive transport, effluent solutions were characterized by UV-Vis absorbance and excitation-emission matrix (EEM) fluorescence spectroscopies. Magnitude of PPDOM sorption followed the trend Al-QS > Fe-QS > QS during the initial transport. Effluent pH values suggest that ligand exchange is a primary mechanism for PPDOM sorption onto oxy-hydroxide minerals. Low molar absorptivity values were observed in effluent solutions of early pore volumes, indicating preferential mobilization of compounds with low aromatic character. Compounds traditionally characterized by EEM spectroscopy as being more highly humified were favorably absorbed onto the gibbsite and goethite surfaces. Humification index values (HIX) were also correlated with DOM aromaticity. HIX results suggest that the presence of low mass fractions of oxy-hydroxide minerals affect the preferential uptake of high molar mass constituents of PPDOM during reactive transport.

Vazquez, A.; Hernández, S.; Rasmussen, C.; Chorover, J.

2010-12-01

133

Melanin from the Nitrogen-Fixing Bacterium Azotobacter chroococcum: A Spectroscopic Characterization  

PubMed Central

Melanins, the ubiquitous hetero-polymer pigments found widely dispersed among various life forms, are usually dark brown/black in colour. Although melanins have variety of biological functions, including protection against ultraviolet radiation of sunlight and are used in medicine, cosmetics, extraction of melanin from the animal and plant kingdoms is not an easy task. Using complementary physicochemical techniques (i.e. MALDI-TOF, FTIR absorption and cross-polarization magic angle spinning solid-state 13C NMR), we report here the characterization of melanins extracted from the nitrogen-fixing non-virulent bacterium Azotobacter chroococcum, a safe viable source. Moreover, considering dihydroxyindole moiety as the main constituent, an effort is made to propose the putative molecular structure of the melanin hetero-polymer extracted from the bacterium. Characterization of the melanin obtained from Azotobacter chroococcum would provide an inspiration in extending research activities on these hetero-polymers and their use as protective agent against UV radiation. PMID:24416247

Banerjee, Raja

2014-01-01

134

Melanin from the nitrogen-fixing bacterium Azotobacter chroococcum: a spectroscopic characterization.  

PubMed

Melanins, the ubiquitous hetero-polymer pigments found widely dispersed among various life forms, are usually dark brown/black in colour. Although melanins have variety of biological functions, including protection against ultraviolet radiation of sunlight and are used in medicine, cosmetics, extraction of melanin from the animal and plant kingdoms is not an easy task. Using complementary physicochemical techniques (i.e. MALDI-TOF, FTIR absorption and cross-polarization magic angle spinning solid-state (13)C NMR), we report here the characterization of melanins extracted from the nitrogen-fixing non-virulent bacterium Azotobacter chroococcum, a safe viable source. Moreover, considering dihydroxyindole moiety as the main constituent, an effort is made to propose the putative molecular structure of the melanin hetero-polymer extracted from the bacterium. Characterization of the melanin obtained from Azotobacter chroococcum would provide an inspiration in extending research activities on these hetero-polymers and their use as protective agent against UV radiation. PMID:24416247

Banerjee, Aulie; Supakar, Subhrangshu; Banerjee, Raja

2014-01-01

135

Growth and spectroscopic characterization of monolayer and few-layer hexagonal boron nitride on metal substrates.  

PubMed

Atomically thin two dimensional hexagonal boron nitride (2D h-BN) is one of the key materials in the development of new van der Waals heterostructures due to its outstanding properties including an atomically smooth surface, high thermal conductivity, high mechanical strength, chemical inertness and high electrical resistance. The development of 2D h-BN growth is still in the early stages and largely depends on rapid and accurate characterization of the grown monolayer or few layers h-BN films. This paper demonstrates a new approach to characterizing monolayer h-BN films directly on metal substrates by grazing-incidence infrared reflection absorption spectroscopy (IRRAS). Using h-BN films grown by atmospheric-pressure chemical vapor deposition on Cu and Ni substrates, two new sub-bands are found for the A2u out-of-plane stretching mode. It is shown, using both experimental and computational methods, that the lower-energy sub-band is related to 2D h-BN coupled with substrate, while the higher energy sub-band is related to decoupled (or free-standing) 2D h-BN. It is further shown that this newly-observed fine structure in the A2u mode can be used to assess, quickly and easily, the homogeneity of the h-BN-metal interface and the effects of metal surface contamination on adhesion of the layer. PMID:25640166

Feigelson, Boris N; Bermudez, Victor M; Hite, Jennifer K; Robinson, Zachary R; Wheeler, Virginia D; Sridhara, Karthik; Hernández, Sandra C

2015-02-12

136

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

137

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

138

X-ray absorption spectroscopic studies of the active sites of nickel- and copper-containing metalloproteins  

SciTech Connect

X-ray absorption spectroscopy (XAS) is a useful tool for obtaining structural and chemical information about the active sites of metalloproteins and metalloenzymes. Information may be obtained from both the edge region and the extended X-ray absorption fine structure (EXAFS) or post-edge region of the K-edge X-ray absorption spectrum of a metal center in a compound. The edge contains information about the valence electronic structure of the atom that absorbs the X-rays. It is possible in some systems to infer the redox state of the metal atom in question, as well as the geometry and nature of ligands connected to it, from the features in the edge in a straightforward manner. The EXAFS modulations, being produced by the backscattering of the ejected photoelectron from the atoms surrounding the metal atom, provide, when analyzed, information about the number and type of neighbouring atoms, and the distances at which they occur. In this thesis, analysis of both the edge and EXAFS regions has been used to gain information about the active sites of various metalloproteins. The metalloproteins studied were plastocyanin (Pc), laccase and nickel carbon monoxide dehydrogenase (Ni CODH). Studies of Cu(I)-imidazole compounds, related to the protein hemocyanin, are also reported here.

Tan, G.O.

1993-06-01

139

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

140

Spectroscopic characterization of PET glycolysis and surface molecular orientation of polymers  

NASA Astrophysics Data System (ADS)

This dissertation seeks to develop novel polymer characterization techniques using UV and fluorescence spectroscopy. The first portion of the dissertation consists of monitoring the glycolytic depolymerization of poly(ethylene terephthalate), PET, using UV and fluorescence spectroscopy. The primary product of the glycolysis of PET is bis(hydroxyethyl) tereplithalate (BHET), along with other low molecular weight oligomers (degree of polymerization = 1--3). The UV absorption of the glycolized products occurs at 287 nm and is associated with the pi ? pi* transition of the tereplithalate moiety. This absorption band shows a linear increase with reaction time that corresponds to an increase in the concentration of glycolized products. BHET was selected as a model compound to represent the glycolized products and was used to calculate the concentration of glycolized products. When using excitation wavelengths of 300 nm and 340 nm, fluorescence emission spectra of the glycolized products were observed at 350 nm and 380 nm respectively. These emission bands also showed an increase in intensity corresponding to the concentration increase. Again, BHET was used as a model compound to simulate and calculate the concentration of the glycolized products. We determined the overall reaction to be second order and that the reaction rate is strongly dependent on the glycol concentration; an increase in the glycol concentration results in an increase in the reaction rate. The second portion of this dissertation consists of the characterization of surface molecular orientation of poly(ethylene terephthalate) (PET) and Kaptono films by UV reflection dichroism using a specular reflection accessory and a bifurcated fiber optic. The UV reflection peaks for PET and Kapton RTM occur at 257 nm and 310 nm respectively. The orientation function and dichroic ratio calculated using both specular reflection and the fiber optic agreed well with each other. Additionally, correct placement of the polarizer is essential in producing good results. When placed at either the source or detector side of the fiber, there was no evidence of orientation seen. However, placement at the common end shows good agreement with the results from the specular reflection accessory. These different results are a manifestation of the polarization/depolarization characteristics of the fiber optic.

Weir, Michael David

141

Solid-state NMR as a spectroscopic tool for characterizing phosphane-borane frustrated lewis pairs.  

PubMed

Frustrated Lewis pair (FLP) chemistry has provided a new strategy for small molecule binding and/or catalytic activation. It is based on the cooperative reaction behavior of Lewis acid and Lewis base centers that are in close proximity to each other (e.g., within the same molecule) but cannot form a direct bond because of geometrical constraints. The most prominent FLPs are based on intramolecular phosphane-borane adducts, whose catalytic properties can be tailored over wide ranges of reactivity and selectivity. For the structural and chemical design of such systems, a fundamental understanding needs to be developed on how structure, dynamics and covalent interactions between the Lewis centers influence the reactivity profile. Advanced solid-state nuclear magnetic resonance (NMR) spectroscopic techniques afford new opportunities for addressing this challenge. Following a general introduction into the fundamentals of NMR spectroscopy, this review discusses the different types of internal interactions - magnetic shielding, nuclear electric quadrupolar coupling, indirect spin-spin interactions, and "through-space" dipole-dipole couplings - influencing NMR spectra in the solid state. As discussed in detail, each type of interaction bears specific informational content with regard to structural issues in FLP chemistry. One of the most attractive features of solid-state NMR is the possibility of tailoring the effective Hamiltonian by manipulations in either physical space or spin space. Using such "decoupling" or "recoupling" techniques certain types of interactions can be selectively turned off for spectral simplification or turned on for selective evaluation. The present review summarizes the most important selective averaging techniques that have found applications in the characterization of FLPs. In a second step the interaction parameters need to be connected with structure and bonding information. As illustrated in this chapter, ab initio calculations using density functional theory (DFT) methods have become indispensable for this task. Based on this comprehensive strategy including advanced NMR methodology, computer simulations, and ab initio calculations, the present review illustrates the utility of (31)P and (11)B NMR chemical shifts, (11)B electric field gradient tensors, and (31)P-(11)B indirect and direct dipole-dipole interactions for characterizing intramolecular borane-phosphane FLPs, illustrating the potential of this method to (1) quantify the extent of boron-phosphorus bonding interactions (and hence the "degree of frustration") and (2) reveal specific structural details (i.e., boron-phosphorus distances and other local geometry aspects) relating to the catalytic activities of these exciting materials. PMID:23138688

Wiegand, Thomas; Eckert, Hellmut; Grimme, Stefan

2013-01-01

142

Synthesis, spectroscopic characterization and molecular modeling of a tetranuclear platinum(II) complex with thiazolidine-4-carboxylic acid  

NASA Astrophysics Data System (ADS)

The synthesis, spectroscopic characterization and molecular modeling of a novel tetranuclear platinum(II) complex with thiazolidine-4-carboxylic acid (THC) are described. Elemental analysis is consistent with the composition PtCl2C4H7NO2S·H2O. Infrared (IR) spectroscopic results and solid-state 13C and 15N nuclear magnetic resonance (NMR) data indicate coordination of the ligand to Pt(II) through the nitrogen and sulfur atoms. The square planar geometry of the platinum(II) complex is completed by chlorine atoms. Density functional theory (DFT) suggests the formation of a tetrameric cluster as the most probable structure, where each THC molecule bridges between two metal centers. The compound is insoluble in water.

Corbi, Pedro P.; Formiga, André L. B.; Bonk, Fábio A.; Quintão, Frederico A.; Ferraresi, Diego K. D.; Lustri, Wilton R.; Massabni, Antonio C.

2012-07-01

143

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

144

Characterisation of bhringaraj and guduchi herb by ICP-MS analysis, optical absorption, infrared and EPR spectroscopic methods  

NASA Astrophysics Data System (ADS)

Leaves of bhringaraj and guduchi herb of Kadapa district of Andhra Pradesh, India, are dried and powdered. ICP-MS analysis of samples indicates that copper is present in both the samples. An EPR study of guduchi sample also confirms the presence of Fe(III) whereas Eclipta alba confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum of guduchi indicates that Cu(II) is present in rhombically distorted octahedral environment. NIR and IR results are due to carbonate fundamentals.

Reddy, S. Lakshmi; Fayazuddin, Md.; Reddy, N. C. G.; Ahmad, Adeel; Reddy, G. Siva; Rao, P. Sambasiva; Reddy, B. Jagannatha; Frost, R. L.

2008-11-01

145

Characterisation of bhringaraj and guduchi herb by ICP-MS analysis, optical absorption, infrared and EPR spectroscopic methods.  

PubMed

Leaves of bhringaraj and guduchi herb of Kadapa district of Andhra Pradesh, India, are dried and powdered. ICP-MS analysis of samples indicates that copper is present in both the samples. An EPR study of guduchi sample also confirms the presence of Fe(III) whereas Eclipta alba confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum of guduchi indicates that Cu(II) is present in rhombically distorted octahedral environment. NIR and IR results are due to carbonate fundamentals. PMID:18280774

Reddy, S Lakshmi; Fayazuddin, Md; Reddy, N C G; Ahmad, Adeel; Reddy, G Siva; Rao, P Sambasiva; Reddy, B Jagannatha; Frost, R L

2008-11-01

146

Spectroscopic characterization and photobleaching kinetics of hypericin-N-methyl pyrrolidone formulations.  

PubMed

Hypericin (HY) is a promising photosensitizer in photodynamic therapy (PDT). It was recently reported that appropriate use of N-methyl pyrrolidone (NMP) enhanced in vivo PDT efficacy of HY and enhanced in vivo delivery of HY. This present study further investigates the use of NMP and other known non-toxic pharmaceutical additives, polyvinylpyrrolidone (PVP, K29/32) and copolyvidonum (S630), for formulating HY to enhance its delivery with photodynamic activity as a goal in mind. Hence, the first objective of this study was to characterize the solubilization of HY by NMP, K29/32 and S630. Thermodynamic considerations were used to explain the solvation process. Photobleaching is another important property of photosensitizers. There is no report on the photostability of HY in pharmaceutical formulations used for PDT. Therefore, the second objective of this study was to investigate the photobleaching of HY in these formulations. The fluorescence of HY was found to increase significantly in higher concentrations of NMP or when 5% of polymer was co-mixed with 5% of NMP solution. The photobleaching of HY in these formulations followed first-order kinetics. The loss of fluorescence paralleled to the loss of absorption of HY. The formulation of HY with 40% NMP was found to be the most stable. PMID:17077897

Saw, Constance Lay Lay; Olivo, Malini; Soo, Khee Chee; Heng, Paul Wan Sia

2006-11-01

147

Spectroscopic networks  

NASA Astrophysics Data System (ADS)

Approaches related to graph theory are investigated which allow a better understanding and yield routes for systematic enlargement and improvement of experimental spectroscopic line lists of molecules. The proposed protocols are based on the fact that quantum mechanics builds, in a simple and natural way, large-scale, weighted, undirected graphs, whereby the vertices are discrete energy levels, the edges are transitions, and the weights are transition intensities. A small part of molecular quantum mechanical graphs can be probed experimentally via high-resolution spectroscopic techniques, while the complete graph encompassing the full line list information for a given molecule can be obtained through sophisticated variational nuclear motion computations. Both approaches yield what one may call spectroscopic networks (SNs). It is shown on the example of the HD 16O isotopologue of the water molecule that both the measured and the computed one-photon absorption SNs have a scale-free behavior with all of the usual consequences, including appearance of hubs, robustness, error tolerance, and the "small-world" property. For the complete computed "deterministic" network the scale-free property holds if a realistic intensity cut-off is employed during its build-up, thus introducing "stochasticity". The graph-theoretical view of molecular spectra offers several new ideas for improving the accuracy and robustness of the information systems containing high-resolution spectroscopic data.

Császár, Attila G.; Furtenbacher, Tibor

2011-04-01

148

X-ray absorption spectroscopic investigation of the resting ferrous and cosubstrate-bound active sites of phenylalanine hydroxylase.  

PubMed

Previous studies of ferrous wild-type phenylalanine hydroxylase, [Fe(2+)]PAH(T)[], have shown the active site to be a six-coordinate distorted octahedral site. After the substrate and cofactor bind to the enzyme ([Fe(2+)]PAH(R)[L-Phe,5-deaza-6-MPH(4)]), the active site converts to a five-coordinate square pyramidal structure in which the identity of the missing ligand had not been previously determined. X-ray absorption spectroscopy (XAS) at the Fe K-edge further supports this coordination number change with the binding of both cosubstrates to the enzyme, and determines this to be due to the loss of a water ligand. PMID:12009881

Wasinger, Erik C; Miti?, Natasa; Hedman, Britt; Caradonna, John; Solomon, Edward I; Hodgson, Keith O

2002-05-21

149

Probing the Fermi Bubbles in Ultraviolet Absorption: A Spectroscopic Signature of the Milky Way's Biconical Nuclear Outflow  

NASA Astrophysics Data System (ADS)

Giant lobes of plasma extend ?55° above and below the Galactic center, glowing in emission from gamma rays (the Fermi Bubbles) to microwaves and polarized radio waves. We use ultraviolet absorption-line spectra from the Hubble Space Telescope to constrain the velocity of the outflowing gas within these regions, targeting the quasar PDS 456 (l, b = 10.°4, +11.°2). This sightline passes through a clear biconical structure seen in hard X-ray and gamma-ray emission near the base of the northern Fermi Bubble. We report two high-velocity metal absorption components, at v LSR = –235 and +250 km s–1, which cannot be explained by co-rotating gas in the Galactic disk or halo. Their velocities are suggestive of an origin on the front and back side of an expanding biconical outflow emanating from the Galactic center. We develop simple kinematic biconical outflow models that can explain the observed profiles with an outflow velocity of gsim900 km s–1 and a full opening angle of ?110° (matching the X-ray bicone). This indicates Galactic center activity over the last ?2.5-4.0 Myr, in line with age estimates of the Fermi Bubbles. The observations illustrate the use of UV spectroscopy to probe the properties of swept-up gas venting into the Fermi Bubbles. Based on observations taken under program 13448 of the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555, and under program 14B-299 of the NRAO Green Bank Telescope, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Fox, Andrew J.; Bordoloi, Rongmon; Savage, Blair D.; Lockman, Felix J.; Jenkins, Edward B.; Wakker, Bart P.; Bland-Hawthorn, Joss; Hernandez, Svea; Kim, Tae-Sun; Benjamin, Robert A.; Bowen, David V.; Tumlinson, Jason

2015-01-01

150

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

151

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

NASA Astrophysics Data System (ADS)

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 4H 6NSO 2. 1H, 13C nuclear magnetic resonance (NMR), [ 1H- 15N] 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.

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

2008-12-01

152

Compressed shell conditions extracted from spectroscopic analysis of Ti K-shell absorption spectra with evaluation of line self-emission  

NASA Astrophysics Data System (ADS)

Ti-doped tracer layers embedded in the shell at varying distances from the fuel-shell interface serve as a spectroscopic diagnostic for direct-drive experiments conducted at OMEGA. Detailed modeling of Ti K-shell absorption spectra produced in the tracer layer considers n = 1-2 transitions in F- through Li-like Ti ions in the 4400-4800 eV range, both including and excluding line self-emission. Testing the model on synthetic spectra generated from 1-D LILAC hydrodynamic simulations reveals that the model including self-emission best reproduces the simulation, while the model excluding self-emission overestimates electron temperature Te and density Ne to a higher degree for layers closer to the core. The prediction of the simulation that the magnitude of Te and duration of Ti absorption will be strongly tied to the distance of the layer from the core is consistent with the idea that regions of the shell close to the core are more significantly heated by thermal transport out of the hot dense core, but more distant regions are less affected by it. The simulation predicts more time variation in the observed Te, Ne conditions in the compressed shell than is observed in the experiment, analysis of which reveals conditions remain in the range Te = 400-600 eV and Ne = 3.0-10.0 × 1024 cm-3 for all but the most distant Ti-doped layer, with error bars ˜5% Te value and ˜10% Ne on average. The Te, Ne conditions of the simulation lead to a greater degree of ionization for zones close to the core than occurs experimentally, and less ionization for zones far from the core.

Johns, H. M.; Mancini, R. C.; Hakel, P.; Nagayama, T.; Smalyuk, V. A.; Regan, S. P.; Delettrez, J.

2014-08-01

153

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.

2011-03-01

154

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

155

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

156

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

157

Local structural studies of the cubic Cd1-xCaxO system through Cd K-edge extended X-ray absorption spectroscopic studies.  

PubMed

Cd K-edge extended X-ray absorption fine-structure spectroscopic studies were carried out on Cd(1-x)Ca(x)O (0 ? x ?0.9) solid solutions and the first and second nearest neighbour (NN) distances and their mean square relative displacement ?(2) were estimated. The first NN distance, d(Cd-O)(x), was found to be smaller than its expected value, a(x)/2, obtained from the X-ray diffraction measurements. It increases monotonically and non-linearly with a negative curvature, comparable with that of the a(x) value variation. The variation ?(2) of the 1NN with x is consistent with a disordered solid solution model. The 2NN distances d(Cd-Cd)(x) and d(Cd-Ca)(x) are found to follow the average values obtained by X-ray diffraction with d(Cd-Ca)(x) > d(Cd-Cd)(x). From detailed analysis it is argued that the solid solution exhibits a bimodal distribution of the 1NN distances, d(Cd-O)(x) and d(Ca-O)(x), and that the system belongs to a persistent type. PMID:22713887

Srihari, Velaga; Sridharan, V; Nomura, Masaharu; Sastry, V Sankara; Sundar, C S

2012-07-01

158

Local structural studies of the cubic Cd1–xCaxO system through Cd K-edge extended X-ray absorption spectroscopic studies  

PubMed Central

Cd K-edge extended X-ray absorption fine-structure spectroscopic studies were carried out on Cd1–xCaxO (0 ? x ?0.9) solid solutions and the first and second nearest neighbour (NN) distances and their mean square relative displacement ?2 were estimated. The first NN distance, d Cd–O(x), was found to be smaller than its expected value, a(x)/2, obtained from the X-ray diffraction measurements. It increases monotonically and non-linearly with a negative curvature, comparable with that of the a(x) value variation. The variation ?2 of the 1NN with x is consistent with a disordered solid solution model. The 2NN distances d Cd–Cd(x) and d Cd–Ca(x) are found to follow the average values obtained by X-ray diffraction with d Cd–Ca(x) > d Cd–Cd(x). From detailed analysis it is argued that the solid solution exhibits a bimodal distribution of the 1NN distances, d Cd–O(x) and d Ca–O(x), and that the system belongs to a persistent type. PMID:22713887

Srihari, Velaga; Sridharan, V.; Nomura, Masaharu; Sastry, V. Sankara; Sundar, C. S

2012-01-01

159

Optical absorption of Zn(V,Al)O thin films studied by spectroscopic ellipsometry from 1 to 6 eV  

NASA Astrophysics Data System (ADS)

Aerogel nanoparticles prepared with various Al concentrations were used as a target for the deposition of (V,Al) co-doped ZnO films by rf-magnetron sputtering on glass substrates. The influence of Al content on the structural and the optical properties of the Zn(V,Al)O films was investigated by X-ray diffraction and spectroscopic ellipsometry (SE). It is found that all films exhibit one high intensity (0 0 2) peak, indicating that they have c-axis preferred orientation due to self-texturing mechanism. SE measurements, used to determine the complex pseudo dielectric functions, were carried out at room temperature in the 1-6 eV photon energy region. The excitonic edge of the fundamental band gap (E0) transition in the imaginary part of the dielectric function of the Zn(V,Al)O films is observed around 3.5 eV and shows a dependence on the Al content. The E0 absorption edge of the Zn0.9-x V0.1AlxO alloys shows a blueshift from that of pure ZnO, reaching 389 meV for x = 0.02. This blueshift is interpreted by the Burstein-Moss effect. By analyzing the dielectric function, reduced effective mass m* of the Zn0.9-x V0.1AlxO alloy is extracted and shows good agreement with literature values.

Sayari, Amor; El Mir, Lassaad; Al-Heniti, Saleh; Al-Harbi, Talal; Yaghmour, Saud Jamil; Abdullah Al-Ghamdi, Ahmad

2013-06-01

160

An x-ray absorption spectroscopic study of the electronic structure and bonding of rare-earth orthoferrites  

NASA Astrophysics Data System (ADS)

Rare-earth orthoferrites, REFeO3 (RE=rare earth; Y), are tremendously adaptable compounds that are being investigated for use in a wide variety of applications including gas sensors, vehicle catalytic converters, and solid-oxide fuel cells. They also exhibit interesting magnetic properties such as high-temperature antiferromagnetism, making them useful for data storage applications. The compounds adopt a distorted perovskite-type structure where the tilt angle of the octahedra increases (Fe-O-Fe bond angle decreases) as the size of the rare-earth atom decreases. Despite intensive study of the physical properties of these compounds, very few studies have investigated how the bonding and electronic structure of these systems change with substitution of the RE. X-ray absorption near-edge spectroscopy (XANES) is a technique well-suited for such a study, and, in view of this, Fe L-, Fe K- and O K-edge spectra from a series of REFeO3 compounds (RE=La, Pr, Nd, Sm, Eu, Gd, Ho, Yb, Y) have been collected, and are presented here. Fe L-edge spectra show that Fe is octahedrally coordinated and that the Fe-centered octahedra do not appear to distort with changes in the identity of the RE. The Fe K-edge spectra contain an intersite hybrid peak, which is an ill-studied feature that is attributed to non-local transitions of 1s electrons to 3d states on the next-nearest-neighbor atom that are hybridized with 4p states on the absorbing atom through O 2p states. In this study, it is shown that the intensity of this feature is strongly dependent on the Fe-O-Fe bond angle; the lower the Fe-O-Fe bond angle, the less intense the intersite hybrid peak is.

Hayes, J. R.; Grosvenor, A. P.

2011-11-01

161

An x-ray absorption spectroscopic study of the electronic structure and bonding of rare-earth orthoferrites.  

PubMed

Rare-earth orthoferrites, REFeO? (RE D rare earth; Y), are tremendously adaptable compounds that are being investigated for use in a wide variety of applications including gas sensors, vehicle catalytic converters, and solid-oxide fuel cells. They also exhibit interesting magnetic properties such as high-temperature antiferromagnetism, making them useful for data storage applications. The compounds adopt a distorted perovskite-type structure where the tilt angle of the octahedra increases (Fe-O-Fe bond angle decreases) as the size of the rare-earth atom decreases. Despite intensive study of the physical properties of these compounds, very few studies have investigated how the bonding and electronic structure of these systems change with substitution of the RE. X-ray absorption near-edge spectroscopy (XANES) is a technique well-suited for such a study, and, in view of this, Fe L-, Fe K- and O K-edge spectra from a series of REFeO? compounds (RE D La, Pr, Nd, Sm, Eu, Gd, Ho, Yb, Y) have been collected, and are presented here. Fe L-edge spectra show that Fe is octahedrally coordinated and that the Fe-centered octahedra do not appear to distort with changes in the identity of the RE. The Fe K-edge spectra contain an intersite hybrid peak, which is an ill-studied feature that is attributed to non-local transitions of 1s electrons to 3d states on the next-nearest-neighbor atom that are hybridized with 4p states on the absorbing atom through O 2p states. In this study, it is shown that the intensity of this feature is strongly dependent on the Fe-O-Fe bond angle; the lower the Fe-O-Fe bond angle, the less intense the intersite hybrid peak is. PMID:22056809

Hayes, J R; Grosvenor, A P

2011-11-23

162

An x-ray absorption spectroscopic study of the electronic structure and bonding of rare-earth orthoferrites  

SciTech Connect

Rare-earth orthoferrites, REFeO{sub 3} (RE=rare earth; Y), are tremendously adaptable compounds that are being investigated for use in a wide variety of applications including gas sensors, vehicle catalytic converters, and solid-oxide fuel cells. They also exhibit interesting magnetic properties such as high-temperature antiferromagnetism, making them useful for data storage applications. The compounds adopt a distorted perovskite-type structure where the tilt angle of the octahedra increases (Fe-O-Fe bond angle decreases) as the size of the rare-earth atom decreases. Despite intensive study of the physical properties of these compounds, very few studies have investigated how the bonding and electronic structure of these systems change with substitution of the RE. X-ray absorption near-edge spectroscopy (XANES) is a technique well-suited for such a study, and, in view of this, Fe L-, Fe K- and O K-edge spectra from a series of REFeO{sub 3} compounds (RE=La, Pr, Nd, Sm, Eu, Gd, Ho, Yb, Y) have been collected, and are presented here. Fe L-edge spectra show that Fe is octahedrally coordinated and that the Fe-centered octahedra do not appear to distort with changes in the identity of the RE. The Fe K-edge spectra contain an intersite hybrid peak, which is an ill-studied feature that is attributed to non-local transitions of 1s electrons to 3d states on the next-nearest-neighbor atom that are hybridized with 4p states on the absorbing atom through O 2p states. In this study, it is shown that the intensity of this feature is strongly dependent on the Fe-O-Fe bond angle; the lower the Fe-O-Fe bond angle, the less intense the intersite hybrid peak is.

Hayes, J.R.; Grosvenor, A.P. (Saskatchewan)

2011-11-07

163

Nanoflaky MnO2/functionalized carbon nanotubes for supercapacitors: an in situ X-ray absorption spectroscopic investigation.  

PubMed

The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. C-CNT was found to have a lower edge plane structure and fewer defect sites than N-CNT. MnO2/C-CNT with a highly developed surface area exhibited favorable electrochemical performance. To determine the atomic/electronic structures of the MnO2/functionalized CNTs (MnO2/C-CNT and MnO/N-CNT) during the charge/discharge process, in situ X-ray absorption spectroscopy (XAS) measurements were made at the Mn K-edge. Both C-CNT and N-CNT are highly conductive. The effect of the scan rate on the capacitance behavior was also examined, revealing that the ?* state of CNT and the size of the tunnels in pseudo-capacitor materials (which facilitate conduction and the transport of electrolyte ions) are critical for the capacitive performance, and their role depends on the scan rate. In the slow charge/discharge process, MnO2/N-CNT has a more symmetrical rectangular cyclic voltammetry (CV) curve. In the fast charge/discharge process, MnO2/C-CNT with a highly developed surface provides fast electronic and ionic channels that support a reversible faradaic redox reaction between MnO2 nanoflakes and the electrolyte, significantly enhancing its capacitive performance over that of MnO2/N-CNT. The MnO2/C-CNT architecture has great potential for supercapacitor applications. The information that was obtained herein helps to elucidate CNT surface modification and the design of the MnO2/functionalized CNT interface with a view for the further development of supercapacitors. This work, and especially the combination of CV with in situ XAS measurements, will be of value to readers with an interest in nanomaterial, nanotechnology and their applications in energy storage. PMID:25511126

Chang, Han-Wei; Lu, Ying-Rui; Chen, Jeng-Lung; Chen, Chi-Liang; Lee, Jyh-Fu; Chen, Jin-Ming; Tsai, Yu-Chen; Chang, Chien-Min; Yeh, Ping-Hung; Chou, Wu-Ching; Liou, Ya-Hsuan; Dong, Chung-Li

2015-01-22

164

Nanoflaky MnO2/functionalized carbon nanotubes for supercapacitors: an in situ X-ray absorption spectroscopic investigation  

NASA Astrophysics Data System (ADS)

The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. C-CNT was found to have a lower edge plane structure and fewer defect sites than N-CNT. MnO2/C-CNT with a highly developed surface area exhibited favorable electrochemical performance. To determine the atomic/electronic structures of the MnO2/functionalized CNTs (MnO2/C-CNT and MnO/N-CNT) during the charge/discharge process, in situ X-ray absorption spectroscopy (XAS) measurements were made at the Mn K-edge. Both C-CNT and N-CNT are highly conductive. The effect of the scan rate on the capacitance behavior was also examined, revealing that the ?* state of CNT and the size of the tunnels in pseudo-capacitor materials (which facilitate conduction and the transport of electrolyte ions) are critical for the capacitive performance, and their role depends on the scan rate. In the slow charge/discharge process, MnO2/N-CNT has a more symmetrical rectangular cyclic voltammetry (CV) curve. In the fast charge/discharge process, MnO2/C-CNT with a highly developed surface provides fast electronic and ionic channels that support a reversible faradaic redox reaction between MnO2 nanoflakes and the electrolyte, significantly enhancing its capacitive performance over that of MnO2/N-CNT. The MnO2/C-CNT architecture has great potential for supercapacitor applications. The information that was obtained herein helps to elucidate CNT surface modification and the design of the MnO2/functionalized CNT interface with a view for the further development of supercapacitors. This work, and especially the combination of CV with in situ XAS measurements, will be of value to readers with an interest in nanomaterial, nanotechnology and their applications in energy storage.The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. C-CNT was found to have a lower edge plane structure and fewer defect sites than N-CNT. MnO2/C-CNT with a highly developed surface area exhibited favorable electrochemical performance. To determine the atomic/electronic structures of the MnO2/functionalized CNTs (MnO2/C-CNT and MnO/N-CNT) during the charge/discharge process, in situ X-ray absorption spectroscopy (XAS) measurements were made at the Mn K-edge. Both C-CNT and N-CNT are highly conductive. The effect of the scan rate on the capacitance behavior was also examined, revealing that the ?* state of CNT and the size of the tunnels in pseudo-capacitor materials (which facilitate conduction and the transport of electrolyte ions) are critical for the capacitive performance, and their role depends on the scan rate. In the slow charge/discharge process, MnO2/N-CNT has a more symmetrical rectangular cyclic voltammetry (CV) curve. In the fast charge/discharge process, MnO2/C-CNT with a highly developed surface provides fast electronic and ionic channels that support a reversible faradaic redox reaction between MnO2 nanoflakes and the electrolyte, significantly enhancing its capacitive performance over that of MnO2/N-CNT. The MnO2/C-CNT architecture has great potential for supercapacitor applications. The information that was obtained herein helps to elucidate CNT surface modification and the design of the MnO2/functionalized CNT interface with a view for the further development of supercapacitors. This work, and especially the combination of CV with in situ XAS measurements, will be of value to readers with an interest in nanomaterial, nanotechnology and their applications in energy storage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06439a

Chang, Han-Wei; Lu, Ying-Rui; Chen, Jeng-Lung; Chen, Chi-Liang; Lee, Jyh-Fu; Chen, Jin-Ming; Tsai, Yu-Chen; Chang, Chien-Min; Yeh, Ping-Hung; Chou, Wu-Ching; Liou, Ya-Hsuan; Dong, Chung-Li

2015-01-01

165

Self-Assembling of Redox-Active Atrazine Poly(ethylenimine) Conjugates – Interfacial Electrochemical and Spectroscopic Characterization  

Microsoft Academic Search

Thin films of polymers tethered with both atrazine haptens and ferrocenyl (Fc) probes were formed on polycrystalline gold electrodes by taking advantage of the facile formation of self-assembled monolayers (SAMs) of thiolates. These films were characterized by polarization modulation Fourier transform infrared reflection - absorption spectrometry (PM-IRRAS), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. The combination of these techniques gave

Zhaohui Chen; Michèle Salmain; Claire-Marie Pradier; Nathalie Fischer-Durand; Alain Pailleret; Fethi Bedioui; Sandrine Zannae

2006-01-01

166

Modified polyamines for CO{sub 2} absorption. Product preparation and characterization  

SciTech Connect

Aliphatic polyamines easily absorb acidic gases but unfortunately are not suitable for industrial application because their solutions are difficult to regenerate. Molecular modification is of primary importance to reduce their basicity and to allow their use in acid gas recovery processes. Various modified polyamines were prepared by reacting tetraethylenepentamine (TEPA) with formaldehyde and formaldehyde/phenol in various molar ratios. The physical and chemical characterization of the synthesized products showed a general reduction of basicity; the modification of TEPA with formaldehyde and phenol gave products with high CO{sub 2} absorption capacity and easier regeneration; moreover, the heat of reaction during CO{sub 2} absorption was reduced. The selected compound had a TEPA/CH{sub 2}O/C{sub 6}H{sub 5}OH ratio equal to 1/0.5/0.4. This new product showed higher cyclic capacity, higher absorption rate, and lower degradation compared with diethanolamine under the same experimental conditions. The product is stable, constant in composition, and suitable for industrial scale-up.

De Filippis, P.; Giavarini, C.; Maggi, C.; Rinaldi, G.; Silla, R.

2000-05-01

167

Infrared Absorption Spectroscopy of the Phenyl Juliusz G. Radziszewski,*, Mark R. Nimlos,*,  

E-print Network

Infrared Absorption Spectroscopy of the Phenyl Radical Juliusz G. Radziszewski,*, Mark R. Nimlos and combustion processes.1-3 Despite numerous attempts, spectroscopic characterization of C6H5 is far from com mol-1]. In this paper we report the infrared absorption spectrum of the phenyl radical in an argon

Ellison, Barney

168

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

169

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

170

Characterization of fine resolution field spectrometers using solar Fraunhofer lines and atmospheric absorption features.  

PubMed

The accurate spectral characterization of high-resolution spectrometers is required for correctly computing, interpreting, and comparing radiance and reflectance spectra acquired at different times or by different instruments. In this paper, we describe an algorithm for the spectral characterization of field spectrometer data using sharp atmospheric or solar absorption features present in the measured data. The algorithm retrieves systematic shifts in channel position and actual full width at half-maximum (FWHM) of the instrument by comparing data acquired during standard field spectroscopy measurement operations with a reference irradiance spectrum modeled with the MODTRAN4 radiative transfer code. Measurements from four different field spectrometers with spectral resolutions ranging from 0.05 to 3.5nm are processed and the results validated against laboratory calibration. An accurate retrieval of channel position and FWHM has been achieved, with an average error smaller than the instrument spectral sampling interval. PMID:20490248

Meroni, Michele; Busetto, Lorenzo; Guanter, Luis; Cogliati, Sergio; Crosta, Giovanni Franco; Migliavacca, Mirco; Panigada, Cinzia; Rossini, Micol; Colombo, Roberto

2010-05-20

171

X-ray Absorption Spectroscopic and Theoretical Studies on (L)2[Cu2(S2)n]2+ Complexes: Disulfide Versus Disulfide(•1?) 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. PMID:18076173

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

172

Electrochemical Kinetics and X-ray Absorption Spectroscopic Investigations of Oxygen Reduction on Chalcogen-Modified Ruthenium Catalysts in Alkaline Media  

SciTech Connect

The oxygen reduction reaction (ORR) in alkaline media has been investigated on chalcogen-modified ruthenium nanoparticles (Ru/C, Se/Ru/C, Se/RuMo/C, S/Ru/C, S/RuMo/C) synthesized in-house via aqueous routes. In acidic medium, it is well known that modification by a chalcogen prevents the oxidation of the underlying transition-metal (Ru) surface, thereby promoting direct molecular O{sub 2} adsorption on the Ru metal. On an unmodified Ru catalyst in alkaline media, the surface oxides on Ru mediate the 2e{sup -} reduction of molecular O{sub 2} to a stable peroxide anion (HO{sub 2}{sup -}) intermediate via an outer-sphere electron-transfer mechanism. This increases the activity of HO{sub 2}{sup -} near the electrode surface and decreases the overpotential for ORR by effectively carrying out the reduction of HO{sub 2}{sup -} to OH{sup -} at the oxide-free ruthenium metal site. An increase in ORR activity of Ru is observed by modification with a chalcogen; however, the increase is not as significant as observed in acidic media. Ternary additives, such as Mo, were found to significantly improve the stability of the chalcogen-modified catalysts. Detailed investigations of the ORR activity of this class of catalyst have been carried out in alkaline media along with comparisons to acidic media wherever necessary. A combination of electrochemical and X-ray absorption spectroscopic (EXAFS, XANES, {Delta}{mu}) studies has been performed in order to understand the structure/property relationships of these catalysts within the context of ORR in alkaline electrolytes.

N Ramaswamy; R Allen; S Mukerjee; Y

2011-12-31

173

Photoinduced isomerization of 23-oxosapogenins: conformational analysis and spectroscopic characterization of 22-isosapogenins.  

PubMed

The first synthesis of 22-isospirostane derivatives is described. They were obtained by photochemical isomerization of 23-oxosapogenins. The structure of 23-oxo-22-isotigogenin acetate (12) was proved by a single crystal X-ray diffraction, while structures of 23-oxo-22-isodiosgenin acetate (13) and 23-oxo-22-isosarsasapogenin acetate (14) were elucidated by spectroscopic methods. 22-Isodiosgenin acetate (17) was obtained by NaBH(4) reduction of the 23-oxo derivative 13 followed by the two-step Barton-McCombie deoxygenation procedure. Conformational analysis of 22-iso compounds was carried out with CD and NMR, as well as DFT calculations. PMID:23190388

Jastrz?bska, Izabella; Górecki, Marcin; Frelek, Jadwiga; Santillan, Rosa; Siergiejczyk, Leszek; Morzycki, Jacek W

2012-12-21

174

Characterization of personal RF electromagnetic field exposure and actual absorption for the general public.  

PubMed

In this paper, personal electromagnetic field exposure of the general public due to 12 different radiofrequency sources is characterized. Twenty-eight different realistic exposure scenarios based upon time, environment, activity, and location have been defined and a relevant number of measurements were performed with a personal exposure meter. Indoor exposure in office environments can be higher than outdoor exposure: 95th percentiles of field values due to WiFi ranged from 0.36 to 0.58 V m(-1), and for DECT values of 0.33 V m(-1) were measured. The downlink signals of GSM and DCS caused the highest outdoor exposures up to 0.52 V m(-1). The highest total field exposure occurred for mobile scenarios (inside a train or bus) from uplink signals of GSM and DCS (e.g., mobile phones) due to changing environmental conditions, handovers, and higher required transmitted signals from mobile phones due to penetration through windows while moving. A method to relate the exposure to the actual whole-body absorption in the human body is proposed. An application is shown where the actual absorption in a human body model due to a GSM downlink signal is determined. Fiftieth, 95th, and 99 th percentiles of the whole-body specific absorption rate (SAR) due to this GSM signal of 0.58 microW kg(-1), 2.08 microW kg(-1), and 5.01 microW kg(-1) are obtained for a 95th percentile of 0.26 V m(-1). A practical usable function is proposed for the relation between the whole-body SAR and the electric fields. The methodology of this paper enables epidemiological studies to make an analysis in combination with both electric field and actual whole-body SAR values and to compare exposure with basic restrictions. PMID:18695413

Joseph, W; Vermeeren, G; Verloock, L; Heredia, Mauricio Masache; Martens, Luc

2008-09-01

175

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

176

Synthesis, characterization and microwave absorption properties of polyaniline/Sm-doped strontium ferrite nanocomposite  

NASA Astrophysics Data System (ADS)

Sm-doped strontium ferrite nanopowders (SrSm0.3Fe11.7O19) and their composites of polyaniline (PANI)/SrSm0.3Fe11.7O19 with 10 wt% and 20 wt% ferrite were prepared by a sol-gel method and an in-situ polymerization process, respectively. The structure, magnetic properties and microwave absorption properties of the samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. The particle size of SrSm0.3Fe11.7O19 was about 35 nm by using XRD. The ferrite successfully packed by PANI. PANI/SrSm0.3Fe11.7O19 possessed the best absorption property with the optimum matching thickness of 3 mm in the frequency of 2-18 GHz. The value of the maximum reflection loss (RL) were -26.0 dB at 14.2 GHz with the 6.5 GHz bandwidth and -24.0 dB at 13.8 GHz with the 7.9 GHz bandwidth for the samples with 10 wt% and 20 wt% ferrite, respectively.

Luo, Juhua; Xu, Yang; Gao, Duoduo

2014-11-01

177

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

NASA Astrophysics Data System (ADS)

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 Zn1-xCoxO 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; Chou, Hsiung; Tseng, Yuan-Chieh

2013-12-01

178

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin 1  

NASA Astrophysics Data System (ADS)

The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm-1. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

Gauden, Magdalena; Crosson, Sean; van Stokkum, I. H. M.; van Grondelle, Rienk; Moffat, Keith; Kennis, John T. M.

2004-09-01

179

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

180

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin  

SciTech Connect

The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm{sup -1}. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

Gauden, Magdalena; Crosson, Sean; van Stokkum, I.H.; Grondelle, Rienkvan; Moffat, Keith; Kennis, John T. (UC)

2004-12-13

181

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. PMID:23762779

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

2013-01-01

182

Spectroscopic characterization and quantitative determination of atorvastatin calcium impurities by novel HPLC method  

NASA Astrophysics Data System (ADS)

Seven process related impurities were identified by LC-MS in the atorvastatin calcium drug substance. These impurities were identified by LC-MS. The structure of impurities was confirmed by modern spectroscopic techniques like 1H NMR and IR and physicochemical studies conducted by using synthesized authentic reference compounds. The synthesized reference samples of the impurity compounds were used for the quantitative HPLC determination. These impurities were detected by newly developed gradient, reverse phase high performance liquid chromatographic (HPLC) method. The system suitability of HPLC analysis established the validity of the separation. The analytical method was validated according to International Conference of Harmonization (ICH) with respect to specificity, precision, accuracy, linearity, robustness and stability of analytical solutions to demonstrate the power of newly developed HPLC method.

Gupta, Lokesh Kumar

2012-11-01

183

Characterization of the spectroscopic properties of the Cu,Co cluster in a prokaryotic superoxide dismutase.  

PubMed

A Cu,Co derivative of the Cu,ZnSOD from Photobacterium leiognathi, in which cobalt has been selectively substituted for zinc, has been prepared and spectroscopically investigated. The derivative shows three bands in the visible region at 530, 566, and 600 nm when copper is in the oxidized state. Reduction or depletion of the copper ion produce a shift of the band absorbing at 600 to 590 nm because of the detachment from copper of the imidazolate bridging the two metals when copper is in the oxidized state. Numerous isotropically shifted 1H NMR lines are observed when copper is oxidized, confirming the presence of the imidazolate bridge between the two metals. Comparison of the optical and the NMR spectra with those observed for the eukaryotic enzyme reveals the occurrence of slight but unambiguous differences diagnostic of a different degree of distortion of the metal cluster between the prokaryotic and eukaryotic enzymes. PMID:10334865

Venerini, F; Sette, M; Stroppolo, M E; De Martino, A; Desideri, A

1999-06-01

184

Spectroscopic and computational characterization of laccases and their substrate radical intermediates.  

PubMed

Laccases are multicopper oxidases which oxidize a wide variety of aromatic compounds with the concomitant reduction of oxygen to water as by-product. Due to their high stability and biochemical versatility, laccases are key enzymes to be used as eco-friendly biocatalyst in biotechnological applications. The presence of copper paramagnetic species in the catalytic site paired with the substrate radical species produced in the catalytic cycle makes laccases particularly attractive to be studied by spectroscopic approaches. In this review, the potentiality of a combined multifrequency electron paramagnetic spectroscopy /computational approach to gain information on the nature of the catalytic site and radical species is presented. The knowledge at molecular level of the enzyme oxidative process can be of great help to model new enzymes with increased efficiency and robustness. PMID:25595303

Pogni, Rebecca; Baratto, Maria Camilla; Sinicropi, Adalgisa; Basosi, Riccardo

2015-03-01

185

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

186

SEM, EDX, Infrared and Raman spectroscopic characterization of the silicate mineral yuksporite.  

PubMed

The mineral yuksporite (K,Ba)NaCa2(Si,Ti)4O11(F,OH)?H2O has been studied using the combination of SEM with EDX and vibrational spectroscopic techniques of Raman and infrared spectroscopy. Scanning electron microscopy shows a single pure phase with cleavage fragment up to 1.0mm. Chemical analysis gave Si, Al, K, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and REE. Raman bands are observed at 808, 871, 930, 954, 980 and 1087cm(-1) and are typical bands for a natural zeolite. Intense Raman bands are observed at 514, 643 and 668cm(-1). A very sharp band is observed at 3668cm(-1) and is attributed to the OH stretching vibration of OH units associated with Si and Ti. Raman bands resolved at 3298, 3460, 3562 and 3628cm(-1) are assigned to water stretching vibrations. PMID:25240833

Frost, Ray L; López, Andrés; Scholz, Ricardo; Theiss, Frederick L; Romano, Antônio Wilson

2015-02-25

187

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

188

SEM, EDX, Infrared and Raman spectroscopic characterization of the silicate mineral yuksporite  

NASA Astrophysics Data System (ADS)

The mineral yuksporite (K,Ba)NaCa2(Si,Ti)4O11(F,OH)?H2O has been studied using the combination of SEM with EDX and vibrational spectroscopic techniques of Raman and infrared spectroscopy. Scanning electron microscopy shows a single pure phase with cleavage fragment up to 1.0 mm. Chemical analysis gave Si, Al, K, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and REE. Raman bands are observed at 808, 871, 930, 954, 980 and 1087 cm-1 and are typical bands for a natural zeolite. Intense Raman bands are observed at 514, 643 and 668 cm-1. A very sharp band is observed at 3668 cm-1 and is attributed to the OH stretching vibration of OH units associated with Si and Ti. Raman bands resolved at 3298, 3460, 3562 and 3628 cm-1 are assigned to water stretching vibrations.

Frost, Ray L.; López, Andrés; Scholz, Ricardo; Theiss, Frederick L.; Romano, Antônio Wilson

2015-02-01

189

A Complete Spectroscopic Characterization of SO and its Isotopologues up to the Terahertz Domain  

NASA Astrophysics Data System (ADS)

In order to obtain accurate terahertz center frequencies for SO and its isotopologues, we have studied the absorption spectrum of SO, 34SO, and 33SO up to 2.5 THz using continuous-wave terahertz photomixing based on a frequency comb providing an accuracy down to 10 kHz. Sulfur monoxide was produced in a radio frequency discharge of air in a cell containing pure sulfur. Together with the strong absorption signal of the main isotopologue, transitions of 34SO (34S: 4.21%) and 33SO (33S: 0.75%) were observed in natural abundance. The newly observed transitions constitute an extension of the observed rotational quantum numbers of the molecule toward higher N values, allowing an improvement of the molecular parameters for the three species. An isotopically invariant fit has been performed based on pure rotational and ro-vibrational transitions of all SO isotopologues, enabling their accurate line position prediction at higher frequencies. Thanks to this new set of parameters, it is now possible to predict with very high accuracy the frequencies of the ro-vibrational lines. This should enable the research of SO in the mid-IR using ground-based IR telescopes, space-based telescope archives (Infrared Space Observatory, Spitzer), and future space missions such as the James Webb Space Telescope. This set of parameters is particularly well adapted for the detection of SO lines in O-rich evolved stars or in molecular clouds in absorption against bright IR sources.

Martin-Drumel, M. A.; Hindle, F.; Mouret, G.; Cuisset, A.; Cernicharo, J.

2015-02-01

190

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

191

Synthesis, spectroscopic, and electrochemical studies of 1,2-naphthalene-ring-fused tetraazachlorins, -bacteriochlorins, and -isobacteriochlorins: the separation and characterization of structural isomers.  

PubMed

1,2-Naphthalene-ring-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized. Procedures for the synthesis of the starting materials, that is, derivatives of 1,2-naphthalenedicarboxylic acid, have been reinvestigated and improved. Nine possible derivatives, including four, two, and three structural isomers of TACs, TABCs, and TAiBCs, respectively, were separated by using thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC), and the structure of each isomer was determined by (1)H NMR spectroscopy combined with the NOE technique. The formation ratio of each isomer was rationalized in terms of the intramolecular steric repulsion effect, which was predicted by geometry optimizations at the DFT level. The derived compounds were characterized by using IR, electronic, and magnetic circular dichroism (MCD) spectroscopy, and by electrochemical methods. Frequency calculations at the DFT level correctly reproduced the experimental IR spectra and, in particular, distinguished between the three isomers of the TAiBCs. In the electronic absorption and MCD spectra of the TAC and TABC species, the Q-band splits into two intense components similarly to the 2,3-naphthalene-fused derivatives described in our preceding paper, although no significant spectral differences were observed from species to species. On the other hand, the spectra of the TAiBCs showed moderate differences depending on the structure of the isomer. The spectroscopic properties as well as the electrochemical behavior of these chlorins resemble those of the corresponding benzene-fused derivatives rather than the 2,3-naphthalene-fused derivatives. Molecular-orbital and configuration-interaction calculations within the framework of the ZINDO/S method were helpful in the discussions of the above observations. PMID:15625670

Makarova, Elena A; Fukuda, Takamitsu; Luk Yanets, Evgeny A; Kobayashi, Nagao

2005-02-01

192

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

193

Complementary characterization of Ti-Si-C films by x-ray diffraction and absorption  

NASA Astrophysics Data System (ADS)

Advanced electronic devices based on III-N semiconductors, particularly these operated at the high power and high frequency or corrosive atmosphere, need elaboration of new technology for contacts metallization which are thermally and chemically stable. Performed studies aimed at the development of materials for applications in the improved metallization. Due to the unique combination of the metallic electro-thermal conductivity and ceramic resistance to oxidation and thermal stability, the MAX phases were chosen as the materials potentially applicable to this task. Particular interest lies in the MAX phases based on the Ti, Si and C or N atoms, especially on the Ti3SiC2 phase. The paper focuses on a comprehensive characterization of films grown by means of high-temperature magnetron Ti, Si and C co-sputtering. The complementary characterization by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) is presented. XRD studies pointed out the presence of several phases in the investigated samples, therefore XAS as an atomic sensitive probe was applied to examine the average atomic order around Ti atoms as a function of the technological parameters and to point towards proper procedures to achieve the appropriate stoichiometry around Ti atoms and finally the Ti3SiC2 phase.

Lawniczak-Jablonska, K.; Klepka, M. T.; Dynowska, E.; Wolska, A.; Borysiewicz, M. A.; Piotrowska, A.

2013-12-01

194

Spectroscopic and Chromatographic Characterization of Wastewater Organic Matter from a Biological Treatment Plant  

PubMed Central

Spectroscopic and chromatographic changes in dissolved organic matter (DOM) characteristics of influent and treated sewage were investigated for a wastewater treatment plant (WWTP) with a biological advanced process. Refractory DOM (R-DOM) was defined as the dissolved organic carbon concentrations of the samples after 28-day incubation for this study. Specific UV absorbance (SUVA), hydrophobicity, synchronous fluorescence spectra and molecular weight (MW) distributions were selected as DOM characteristics. The percent distribution of R-DOM for the effluent was much higher than that of the influent, indicating that biodegradable DOM was selectively removed during the process. Comparison of the influent versus the effluent sewage revealed that SUVA, fulvic-like fluorescence (FLF), humic-like fluorescence (HLF), the apparent MW values were enhanced during the treatment. This suggests that more aromatic and humic-like compounds were enriched during the biological process. No significant difference in the DOM characteristics was observed between the original effluent (i.e., prior to the incubation) and the influent sewage after the incubation. This result suggests that the major changes in wastewater DOM characteristics occurring during the biological advanced process were similar to those for simple microbial incubation. PMID:22315538

Park, Min-Hye; Lee, Tae-Hwan; Lee, Bo-Mi; Hur, Jin; Park, Dae-Hee

2010-01-01

195

Spectroscopic characterization of the iron-oxo intermediate in cytochrome P450.  

PubMed

From analogy to chloroperoxidase from Caldariomyces fumago, it is believed that the electronic structure of the intermediate iron-oxo species in the catalytic cycle of cytochrome P450 corresponds to an iron(IV) porphyrin-pi-cation radical (compound I). However, our recent studies on P450cam revealed that after 8 ms a tyrosine radical and iron(IV) were formed in the reaction of ferric P450 with external oxidants in the shunt pathway. The present study on the heme domain of P450BM3 (P450BMP) shows a similar result. In addition to a tyrosine radical, a contribution from a tryptophan radical was found in the electron paramagnetic resonance (EPR) spectra of P450BMP. Here we present comparative multi-frequency EPR (9.6, 94 and 285 GHz) and Mössbauer spectroscopic studies on freeze-quenched intermediates produced using peroxy acetic acid as oxidant for both P450 cytochromes. After 8 ms in both systems, amino acid radicals occurred instead of the proposed iron(IV) porphyrin-pi-cation radical, which may be transiently formed on a much faster time scale. These findings are discussed with respect to other heme thiolate proteins. Our studies demonstrate that intramolecular electron transfer from aromatic amino acids is a common feature in these enzymes. The electron transfer quenches the presumably transiently formed porphyrin-pi-cation radical, which makes it extremely difficult to trap compound I. PMID:16218876

Jung, Christiane; Schünemann, Volker; Lendzian, Friedhelm; Trautwein, Alfred X; Contzen, Jörg; Galander, Marcus; Böttger, Lars H; Richter, Matthias; Barra, Anne-Laure

2005-10-01

196

Surface spectroscopic characterization of the interaction between zinc ions and. gamma. -alumina  

SciTech Connect

Interaction of zinc ions with ..gamma..-alumina has been investigated using the surface spectroscopic techniques of X-ray photoelectron spectroscopy (ESCA or XPS) and low energy ion scattering spectroscopy (ISS). In addition, the bulk techniques of laser Raman spectroscopy (LRS) and X-ray diffraction (XRD) were employed. Surface characteristics of Zn/Al/sub 2/O/sub 3/ catalysts are affected by both metal loading and calcination temperature. The Zn/Al intensity ratio was examined as a function of zinc content and calcination temperature. Plots of both ESCA and ISS intensity ratios (Zn/Al) vs metal loading show changes in slope at high loadings, indicating a change in surface structure. ESCA, LRS, and XRD all show the ability to distinguish between ZnO and ZnAl/sub 2/O/sub 4/. Results indicate that at low zinc loadings (<20%), a strong interaction occurs between zinc and ..gamma..-alumina resulting in the formation of an aluminate type phase (i.e., a surface spinel). This interaction involves diffusion of zinc ions into the tetrahedral lattice sites of the support. At higher loadings, bulk-like ZnO segregates on top of the interaction species and the support. ESCA has also been used to study the effects of reduction and sulfiding on the catalysts.

Strohmeier, B.R.; Hercules, D.M.

1984-04-01

197

Spectroscopic and structural characterization of the [Fe(imidazole)(6)](2+) cation.  

PubMed

Spectroscopic, structural, and magnetic data are presented for Fe(C(3)H(4)N(2))(6)(NO(3))(2), which facilitate a precise definition of the electronic and molecular structure of the [Fe(Im)(6)](2+) cation. The structure was determined at 120(1) K by X-ray diffraction methods. The salt crystallizes in the trigonal space group R3 with unit-cell parameters a = 12.4380(14) A, c = 14.5511(18) A, and Z = 3. All the imidazole ligands are equivalent with an Fe-N bond distance of 2.204(1) A. Variable-temperature inelastic neutron scattering (INS) measurements identify a cold magnetic transition at 19.4(2) cm(-1) and a hot transition at 75.7(6) cm(-1). The data are interpreted using a ligand field Hamiltonian acting in the weak-field (5)D basis, from which the diagonal trigonal field splitting of the (5)T(2g) (O(h)) term is estimated as approximately 485 cm(-1), with the (5)A(g) (S(6)) component lower lying. High-field multifrequency (HFMF) EPR data and measurements of the magnetic susceptibility are also reported and can be satisfactorily modeled using the energies and wave functions derived from analysis of the INS data. The electronic and molecular structures are related through angular overlap model calculations, treating the imidazole ligand as a weak pi-donor. PMID:12950228

Carver, Graham; Tregenna-Piggott, Philip L W; Barra, Anne-Laure; Neels, Antonia; Stride, John A

2003-09-01

198

Synthesis, spectroscopic, structural and thermal characterizations of vanadyl(IV) adenine complex prospective as antidiabetic drug agent  

NASA Astrophysics Data System (ADS)

The vanadyl(IV) adenine complex; [VO(Adn)2]?SO4; was synthesized and characterized. The molar conductivity of this complex was measured in DMSO solution that showed an electrolyte nature. Spectroscopic investigation of the green solid complex studied here indicate that the adenine acts as a bidentate ligand, coordinated to vanadyl(IV) ions through the nitrogen atoms N7 and nitrogen atom of amino group. Thus, from the results presented the vanadyl(IV) complex has square pyramid geometry. Further characterizations using thermal analyses and scanning electron techniques was useful. The aim of this paper was to introduce a new drug model for the diabetic complications by synthesized a novel mononuclear vanadyl(IV) adenine complex to mimic insulin action and reducing blood sugar level. The antidiabetic ability of this complex was investigated in STZ-induced diabetic mice. The results suggested that VO(IV)/adenine complex has antidiabetic activity, it improved the lipid profile, it improved liver and kidney functions, also it ameliorated insulin hormone and blood glucose levels. The vanadyl(IV) complex possesses an antioxidant activity and this was clear through studying SOD, CAT, MDA, GSH and methionine synthase. The current results support the therapeutic potentiality of vanadyl(IV)/adenine complex for the management and treatment of diabetes.

El-Megharbel, Samy M.; Hamza, Reham Z.; Refat, Moamen S.

2015-01-01

199

Synthesis, spectroscopic, structural and thermal characterizations of vanadyl(IV) adenine complex prospective as antidiabetic drug agent.  

PubMed

The vanadyl(IV) adenine complex; [VO(Adn)2]?SO4; was synthesized and characterized. The molar conductivity of this complex was measured in DMSO solution that showed an electrolyte nature. Spectroscopic investigation of the green solid complex studied here indicate that the adenine acts as a bidentate ligand, coordinated to vanadyl(IV) ions through the nitrogen atoms N7 and nitrogen atom of amino group. Thus, from the results presented the vanadyl(IV) complex has square pyramid geometry. Further characterizations using thermal analyses and scanning electron techniques was useful. The aim of this paper was to introduce a new drug model for the diabetic complications by synthesized a novel mononuclear vanadyl(IV) adenine complex to mimic insulin action and reducing blood sugar level. The antidiabetic ability of this complex was investigated in STZ-induced diabetic mice. The results suggested that VO(IV)/adenine complex has antidiabetic activity, it improved the lipid profile, it improved liver and kidney functions, also it ameliorated insulin hormone and blood glucose levels. The vanadyl(IV) complex possesses an antioxidant activity and this was clear through studying SOD, CAT, MDA, GSH and methionine synthase. The current results support the therapeutic potentiality of vanadyl(IV)/adenine complex for the management and treatment of diabetes. PMID:25150436

El-Megharbel, Samy M; Hamza, Reham Z; Refat, Moamen S

2015-01-25

200

One-dimensional WO3 and its hydrate: One-step synthesis, structural and spectroscopic characterization  

NASA Astrophysics Data System (ADS)

We report on a one-step hydrothermal growth of one-dimensional (1D) WO3 nanostructures, using urea as 1D growth-directing agent and a precursor free of metals other than tungsten. By decreasing the pH of the starting solution, the size of the nanostructures was reduced significantly, this development being accompanied by the realization of phase pure hexagonal WO3 nanorods (elimination of monoclinic impurity phase) and a red shift in optical absorption edge. Surface analyses indicated the presence of reduced tungsten species in the WO3 nanostructures, which increased two-fold in a hydrated WO3 phase obtained with further decrease in pH. We suggest that oxygen vacancies are responsible for this defect state in WO3, while protons are responsible or contribute significantly to the same in the hydrated phase.

Iwu, Kingsley O.; Galeckas, Augustinas; Rauwel, Protima; Kuznetsov, Andrej Y.; Norby, Truls

2012-01-01

201

First-principles spectroscopic characterization of PbSe nanoparticles passivated with Fe complexes  

NASA Astrophysics Data System (ADS)

Given that defining characteristics of nanoparticles -- morphology, catalytic reactivity, optical and electronic properties -- are often dictated by their surfaces, it is informative to investigate how surface chemistry and structure change as different ligands are introduced to the surface. Starting with oleate-passivated PbSe nanoparticles, we remove the oleate ligands and replace them with an organometallic complex: cyclopentadienyl iron dicarbonyl. Measured and calculated x-ray photoemission core-level shifts indicate a charge transfer between surface Pb atoms and Fe atoms. We investigate the nature of this charge transfer in more detail through analysis of x-ray absorption spectra (XAS) at the Fe L-edge. Fe XAS are calculated from first-principles using a GW-based Bethe-Salpeter approach. The spectra reveal that the extent to which pi-backbonding is possible between the Fe and associated carbonyls varies with the charge density on the Fe atom.

Gilmore, Keith; Hammack, Aaron; Sawvel, April; Rosen, Evelyn; Ogletree, D. Frank; Urban, Jeffrey; Milliron, Delia; Helms, Brett; Cohen, Bruce; Prendergast, David

2012-02-01

202

Characterization of organic and inorganic optoelectronic semiconductor devices using advanced spectroscopic methods  

NASA Astrophysics Data System (ADS)

In this thesis, advanced spectroscopy methods are discussed and applied to gain understanding of the physical properties of organic conjugated molecules, II-VI thin film semiconductors, and vertical cavity surface emitting lasers (VCSEL). Experiments include single photon and two-photon excitation with lasers, with subsequent measurements of the absorption and photoluminescence, as well as photocurrent measurements using tungsten and xenon lamps, measuring the direct current and the alternating current of the devices. The materials are investigated in dissolved form (conjugated polymers), thin films (polymers, II-VI semiconductors), and complex layer structures (hybrid device, VCSEL). The experiments are analyzed and interpreted by newly developed or applied theories for two-photon saturation processes in semiconductors, bandgap shrinkage due to optically induced electron hole pairs, and the principle of detailed balance to describe the photoluminescence in thin film cadmium sulfide.

Schroeder, Raoul

203

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

204

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. PMID:23839090

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

2013-01-01

205

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

PubMed

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. PMID:23839090

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

2013-01-01

206

Structural, spectroscopic and magnetic characterization of undoped, Ni2+ doped ZnO nanopowders  

NASA Astrophysics Data System (ADS)

Structural, magnetic and optical properties of undoped and Ni2+ doped ZnO nanopowders have been prepared by sonochemical assistance. Powder XRD studies confirm the hexagonal structure of both undoped and Ni2+ doped of ZnO nanopowders and its average crystallite sizes are evaluated. Optical absorption and Electron Paramagnetic Resonance spectral data confirmed the site symmetry for Ni2+ ions as octahedral. Photoluminescence spectra exhibited the emission bands in ultraviolet and blue regions at an excitation wavelength of 328 nm. FT-IR spectra showed the characteristic vibrational bands of Zn-O. Vibrating sample magnetometer was used for the magnetic property investigations and indicates room temperature ferromagnetism which is intrinsic in nature and attributed to oxygen and/or Zn deficiencies.

Babu, B.; Sundari, G. Rama; Ravindranadh, K.; Yadav, M. Rajesh; Ravikumar, R. V. S. S. N.

2014-12-01

207

Spectroscopic characterization of the chemical composition of the potent sweetener Vartamil  

NASA Astrophysics Data System (ADS)

The chemical composition of the potent sweetener Vartamil was characterized using spectral methods. It was demonstrated that Vartamil is a mixture of saccharose chloro derivatives, the main one of which is 4,1',6'-trichloro-4,1',6'-trideoxygalactosaccharose (Sucralose).

Kolosova, T. E.; Prokhodchenko, L. K.; Pilipenko, V. V.; Suboch, V. P.

2008-03-01

208

Spectroscopic and microstructural characterization of solution chemistry effects in PZT thin film processing  

SciTech Connect

Ferroelectric PZT 53:47 thin films were prepared by two different solution deposition methodologies. Both routes utilized carboxylate and alkoxide precursors and acetic acid, which served as both a solvent and a chemical modifier. We have studied the effects of solution preparation conditions on film microstructure and ferroelectric properties, and have used NMR spectroscopy to characterize chemical differences between the two precursor solutions. Films prepared by a sequential precursor addition (SPA) process were characterized by slightly lossy hysteresis loops, with a P{sub r} of 18.7 {mu}C/cm{sup 2} and an E{sub c} of 55.2 kV/cm. Films prepared by an inverted mixing order (IMO) process were characterized by well saturated hysteresis loops, a P{sub r} of 26.2 {mu}C/cm{sup 2} and an E{sub c} of 43.3 kV/cm. While NMR investigations indicated that the chemical environments of both the proton and carbon species were similar for the two processes, differences in the amounts of by-products (esters, and therefore, water) formed were noted. These differences apparently impacted ceramic microstructure. Although both films were characterized by a columnar growth morphology, the SPA derived film displayed a residual pyrochlore layer at the film surface, which did not transform into the stable perovskite phase. The presence of this layer resulted in poor dielectric properties and lossy ferroelectric behavior.

Schwartz, R.W.; Assink, R.A.; Headley, T.J.

1992-03-01

209

Spectroscopic and microstructural characterization of solution chemistry effects in PZT thin film processing  

SciTech Connect

Ferroelectric PZT 53:47 thin films were prepared by two different solution deposition methodologies. Both routes utilized carboxylate and alkoxide precursors and acetic acid, which served as both a solvent and a chemical modifier. We have studied the effects of solution preparation conditions on film microstructure and ferroelectric properties, and have used NMR spectroscopy to characterize chemical differences between the two precursor solutions. Films prepared by a sequential precursor addition (SPA) process were characterized by slightly lossy hysteresis loops, with a P{sub r} of 18.7 {mu}C/cm{sup 2} and an E{sub c} of 55.2 kV/cm. Films prepared by an inverted mixing order (IMO) process were characterized by well saturated hysteresis loops, a P{sub r} of 26.2 {mu}C/cm{sup 2} and an E{sub c} of 43.3 kV/cm. While NMR investigations indicated that the chemical environments of both the proton and carbon species were similar for the two processes, differences in the amounts of by-products (esters, and therefore, water) formed were noted. These differences apparently impacted ceramic microstructure. Although both films were characterized by a columnar growth morphology, the SPA derived film displayed a residual pyrochlore layer at the film surface, which did not transform into the stable perovskite phase. The presence of this layer resulted in poor dielectric properties and lossy ferroelectric behavior.

Schwartz, R.W.; Assink, R.A.; Headley, T.J.

1992-01-01

210

Terahertz broadband spectroscopic investigations of amino acid  

NASA Astrophysics Data System (ADS)

We present an experimental terahertz (THz) spectroscopic investigation of amino acid using an air-breakdown-coherent detection (ABCD) system. The strong and ultra-broadband (0.1 to 10THz) terahertz radiations generated by two-color laser induced air plasma and measured by coherent heterodyne detection. The broadband THz reflection spectra of L-Lysine (C6H14N2O2) and L-Arginine (C6H14N2O2) are obtained. To solve the phase-retrieval problem in RTDS, the absorption signatures of the materials are extracted directly from the first derivative of the relative reflectance with respect to frequency. The absorption features of the two amino acids are characterized in the 0.5~6 THz region. It is found that both the two amino acids have an absorption peak at 1.10 THz.

Zhu, De-chong; Zhang, Liang-liang; Zhong, Hua; Zhang, Cun-lin

2011-08-01

211

Infrared and Raman spectroscopic characterization of some organic substituted hybrid silicas  

NASA Astrophysics Data System (ADS)

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 Sisbnd Osbnd Si bond angles and bond lengths. Moreover, deconvolution of the IR-active antisymmetric Sisbnd Osbnd Si 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.

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

2014-12-01

212

Arsenate Uptake by Calcite: Macroscopic and Spectroscopic Characterization of Adsorption and Incorporation Mechanisms  

SciTech Connect

Batch uptake experiments and X-ray element mapping and spectroscopic techniques were used to investigate As(V) (arsenate) uptake mechanisms by calcite, including adsorption and coprecipitation. Batch sorption experiments in calcite-equilibrated suspensions (pH 8.3; PCO{sub 2} = 10{sup -3.5} atm) reveal rapid initial sorption to calcite, with sorption rate gradually decreasing with time as available sorption sites decrease. An As(V)-calcite sorption isotherm determined after 24 h equilibration exhibits Langmuir-like behavior up to As concentrations of 300 {mu}M. Maximum distribution coefficient values (K{sub d}), derived from a best fit to a Langmuir model, are {approx}190 L kg{sup -1}. Calcite single crystals grown in the presence of As(V) show well-developed rhombohedral morphology with characteristic growth hillocks on (10{bar 1}4) surfaces at low As(V) concentrations ({<=}5 {mu}M), but habit modification is evident at As(V) concentrations {>=}30 {mu}M in the form of macrostep development preferentially on the - vicinal surfaces of growth hillocks. Micro-X-ray fluorescence element mapping of (10{bar 1}4) surfaces shows preferential incorporation of As in the - vicinal faces relative to + vicinals. EXAFS fit results for both adsorption and coprecipitation samples confirm that As occurs in the 5+ oxidation state in tetrahedral coordination with oxygen, i.e., as arsenate. For adsorption samples, As(V) forms inner-sphere surface complexes via corner-sharing with Ca octahedra. As(V) coprecipitated with calcite substitutes in carbonate sites but with As off-centered, as indicated by two Ca shells, and with likely disruption of local structure. The results indicate that As(V) interacts strongly with the calcite surface, similar to often-cited analog phosphate, and uptake can occur via both adsorption and coprecipitation reactions. Therefore, calcite may be effective for partial removal of dissolved arsenate from aquatic and soil systems.

Alexandratos,V.; Elzinga, E.; Reeder, R.

2007-01-01

213

Spectroscopic characterization of copper(II) complexes of indoxyl N(4)-methyl thiosemicarbazone  

NASA Astrophysics Data System (ADS)

New copper(II) complexes of indoxyl thiosemicarbazone (ITSC) of general composition CuL 2X 2 (where L: ITSC; X: Cl -, NO 3-, ClO 4-, NCS -) have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements and spectral (electronic, IR, EPR, 1H NMR , Mass) studies. Cyclic voltammetry measurements show quasi-reversible Cu 2+/Cu 1+ couple. Various physico-chemical techniques suggest a tetragonal structure for these copper(II) complexes.

Chandra, Sulekh; Kumar, Umendra

2004-10-01

214

Optical properties of perfluorocyclobutyl polymers. III. Spectroscopic characterization of rare-earth-doped perfluorocyclobutyl polymers  

NASA Astrophysics Data System (ADS)

We present a continuation of two previous studies [J. Opt. Soc. Am. B 20, 1838 (2003) and J. Opt. Soc. Am. B 21, 958 (2004)] on the optical characteristics of perfluorocyclobutyl-based polymers. Previously, the spectral dependences of the refractive index and the extinction coefficient have been calculated, and investigations were made into the theoretical and measured attenuation spectra of these polymers. Here, we report on the erbium-doped perfluorocyclobutyl aryl ether polymer 1,1,1-tris(4-trifluorovinyloxy)phenyl ethane. The absorption and fluorescence spectra are provided, including the Judd-Ofelt parameterization. The Judd-Ofelt parameters are found to be ?2=16.05×10-20 cm2, ?4=3.67×10-20 cm2, and ?6=3.59×10-20 cm2. These results are compared with those for a similar study on erbium-doped poly(methyl methacrylate), and conclusions are drawn concerning the effect of host properties in the 1550 nm region.

Gordon, Jennifer; Ballato, John; Smith, Dennis W., Jr.; Jin, Jianyong

2005-08-01

215

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

216

Characterization and spectroscopic applications of a high-efficiency Ho:YLF laser  

NASA Astrophysics Data System (ADS)

The development of a high-efficiency CW YLF laser doped with Er,Tm,Ho: and featuring a strongly focusing resonator that collects a high density of pump power on the active crystal is described. The emission is investigated at 2.06 microns and a tuning range both at liquid-nitrogen (77 K) and at dry-ice (210 K) temperature. The noise characteristics and the long-term power stability of the laser is studied with an eye to employing this source for high-resolution spectroscopy in the 2-micron wavelength region. The detection of several absorption lines of NH3 at low pressure is described. The output power of the laser as a function of the power impinging on the crystal for different transmission of the output mirror is illustrated. The best result obtained is 1.46 W output for 3.2 W of argon pump. The minimum threshold achieved is 3.5 mW with a 1-percent transmission mirror. It is concluded that it is possible to develop a highly efficient Ho:YLF laser featuring low noise and sufficient tunability for high-resolution spectroscopy in the 2-micron region.

di Lieto, A.; Neri, A.; Minguzzi, P.; Pozzi, F.; Tonelli, M.; Jenssen, H. P.

217

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

218

Novel isatinoxime molybdenum and chromium complexes: Synthesis, spectroscopic, and thermal characterization  

NASA Astrophysics Data System (ADS)

Reactions of molybdenum and chromium hexacarbonyls with isatin-3-oxime (H2L) in THF were carried out under sun light or according to the traditional thermal reflux synthetic routes. Di-?-oxo bimolybdenum complex, [Mo(H2L)(THF)(O)2]2 was successfully synthesized under the reflux conditions. However, the dichromium oxo complex, [Cr(H2L)(O)2]2 was prepared using the sun light route. The prepared complexes were characterized using elemental analysis, IR, mass spectrometry, UV-Vis spectra, thermal analysis, and magnetic measurements.

Nassar, Mostafa Y.; Attia, Attia S.; Adawy, Shaymaa; El-Shahat, M. F.

2012-10-01

219

Raman Spectroscopic Characterization of Rare Earth Ions Doped Bismuth-Based Glasses  

SciTech Connect

The xReO(1-x)[3Bi2O3{center_dot}PbO] glass systems with diferent rare earth ions (ReO = CeO2, Tb4O7) have been prepared and examined with the aim of determining their structural characteristics. Raman sprectroscopy and density measurements were used to characterize the samples. Raman spectroscopy data permitted to identify some of the structural units that built up the lead bismuthate vitreous network. Density data were used to calculate the Poisson's ratio in terms of the Makishima-Mackenzie model.

Pop, L.; Culea, E.; Bosca, M. [Department of Physics, Technical University of Cluj-Napoca (Romania); Culea, M. [Faculty of Physics, Babes-Bolyai University of Cluj-Napoca (Romania)

2007-04-23

220

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

221

Erbium-activated monolithic silica xerogels and silica-titania planar waveguides: optical and spectroscopic characterization  

NASA Astrophysics Data System (ADS)

Recent results obtained for Er2O3-SiO2 monolithic xerogels and erbium activated SiO2-TiO2 planar waveguides are presented. Monolithic erbium-activated silica xerogels with erbium content ranging from 0 up to 40000 ppm were prepared by the sol-gel technique. Samples were densified by thermal treatment in air at 950 degrees C for 120 hours. The densification degree and the relative content of hydroxyl groups were studied by NIR absorption and Raman spectroscopies. Emission at 1.5 micrometers , characteristic of the 4I13/2 yields 4I15/2 transition of Er3+ ions, was observed at room temperature for all monolithic samples upon continuous wave excitation at 980 nm. For the 5000 Er/Si ppm doped xerogel, an intense photoluminescence was observed with a lifetime of 8 ms for the metastable 4I13/2 level. Passive and erbium-activated SiO2-TiO2 planar waveguides, monomode at 632.8 nm, were prepared by a dip-coating technique. Some parameters such as H2O content, intermediate and final thermal treatments, and the molar ratio TiO2/SiO2 were modified during the preparation of the solution in order to minimize the final content of residual hydroxyl groups and the phase separation between silica and titania. Raman spectroscopy was used to check the structural properties of the waveguides. A lifetime of 7 ms was measured for the metastable 4I13/2 level in a 93SiO2-7TiO2 planar waveguide activated by 10000 ppm Er/(Si + Ti). The best value of the attenuation coefficient was of 0.5 dB/cm at 632.8 nm.

Zampedri, Luca; Tosello, Cristiana; Rossi, Flavio; Ronchin, Sabina; Rolli, Raffaella; Montagna, Maurizio; Chiasera, Alessandro; Righini, Giancarlo C.; Pelli, Stefano; Monteil, Andre; Chaussedent, Stephane; Bernard, Christope; Duverger, Claire; Ferrari, Maurizio; Armellini, Cristina

2001-04-01

222

UV spectroscopic characterization of an alkyl substituted Criegee intermediate CH3CHOO  

NASA Astrophysics Data System (ADS)

Ozonolysis of alkenes in the troposphere proceeds through a Criegee intermediate, or carbonyl oxide, which has only recently been detected in the gas phase. The present study focuses on the production of an alkyl-substituted Criegee intermediate, CH3CHOO, in a pulsed supersonic expansion, and then utilizes VUV photoionization at 118 nm and UV-induced depletion of the m/z = 60 signal to probe the B 1A' ? X 1A' transition. The UV-induced depletion approaches 100% near the peak of the profile at 320 nm, indicating rapid dynamics in the B state, and corresponds to a peak absorption cross section of ˜5 × 10-17 cm2 molecule-1. The electronic spectrum for CH3CHOO is similar to that reported recently for CH2OO, but shifted 15 nm to shorter wavelength, which will result in a longer tropospheric lifetime for CH3CHOO with respect to solar photolysis. Complementary electronic structure calculations (EOM-CCSD) are carried out for the B and X potentials of these Criegee intermediates along the O-O coordinate. An intramolecular interaction stabilizes the ground state of the syn-conformer of CH3CHOO relative to anti-CH3CHOO, and indicates that the syn-conformer will be the more abundant species in the expansion. The excited B electronic state of syn-CH3CHOO is also predicted to be destabilized relative to that for anti-CH3CHOO and CH2OO, in accord with the shift in the B-X transition observed experimentally. Hydroxyl radicals produced concurrently with the generation of the Criegee intermediates are detected by 1+1' resonance enhanced multiphoton ionization. The OH yield observed with CH3CHOO is 4-fold larger than that from CH2OO, consistent with prior studies of OH generation from alkene ozonolysis.

Beames, Joseph M.; Liu, Fang; Lu, Lu; Lester, Marsha I.

2013-06-01

223

Structures and spectroscopic characterization of calcium chloride-nicotinamide, -isonicotinamide, -picolinamide and praseodymium bromide-nicotinamide complexes  

NASA Astrophysics Data System (ADS)

The coordination structures formed by calcium complexes with nicotinamide (na), isonicotinamide (ina) and picolinamide (pa) and praseodymium bromide-na are reported. The structures of CaCl2·(C6H6N2O)2·2H2O (Ca-na), CaCl2·(C6H6N2O)2·4H2O (Ca-ina), CaCl2·(C6H6N2O)2·5H2O (Ca-pa) and PrBr3·(C6H6N2O)2·6H2O (PrBr-na) in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz and Raman spectroscopies. Carbonyl oxygen of nicotinamide is coordinated to Ca2+, but it is O-monodentate (carbonyl oxygen) and N,O-bidentate ligand (pyridyl nitrogen and carbonyl oxygen) for Pr3+ to form a chain structure in PrBr-na. For isonicotinamide, only carbonyl oxygen atom is coordinated to Ca2+. Pyridyl nitrogen and carbonyl oxygen of picolinamide are coordinated to Ca2+ to form a five-membered ring structure. The crystal structure and spectroscopic results indicate the differences of the coordination of Ca and Pr ions, the changes of hydrogen bonds and conformation of the ligands induced by complexation. Unlike transition metal ions, Sr2+ or lanthanide ions, Ca2+ is inclined to coordinate to carbonyl oxygen atoms of the ligands.

Xue, Junhui; Jiang, Ye; Li, Weihong; Yang, Limin; Xu, Yizhuang; Zhao, Guozhong; Zhang, Gaohui; Bu, Xiaoxia; Liu, Kexin; Chen, Jia'er; Wu, Jinguang

2015-02-01

224

Structures and spectroscopic characterization of calcium chloride-nicotinamide, -isonicotinamide, -picolinamide and praseodymium bromide-nicotinamide complexes.  

PubMed

The coordination structures formed by calcium complexes with nicotinamide (na), isonicotinamide (ina) and picolinamide (pa) and praseodymium bromide-na are reported. The structures of CaCl2·(C6H6N2O)2·2H2O (Ca-na), CaCl2·(C6H6N2O)2·4H2O (Ca-ina), CaCl2·(C6H6N2O)2·5H2O (Ca-pa) and PrBr3·(C6H6N2O)2·6H2O (PrBr-na) in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz and Raman spectroscopies. Carbonyl oxygen of nicotinamide is coordinated to Ca(2+), but it is O-monodentate (carbonyl oxygen) and N,O-bidentate ligand (pyridyl nitrogen and carbonyl oxygen) for Pr(3+) to form a chain structure in PrBr-na. For isonicotinamide, only carbonyl oxygen atom is coordinated to Ca(2+). Pyridyl nitrogen and carbonyl oxygen of picolinamide are coordinated to Ca(2+) to form a five-membered ring structure. The crystal structure and spectroscopic results indicate the differences of the coordination of Ca and Pr ions, the changes of hydrogen bonds and conformation of the ligands induced by complexation. Unlike transition metal ions, Sr(2+) or lanthanide ions, Ca(2+) is inclined to coordinate to carbonyl oxygen atoms of the ligands. PMID:25280333

Xue, Junhui; Jiang, Ye; Li, Weihong; Yang, Limin; Xu, Yizhuang; Zhao, Guozhong; Zhang, Gaohui; Bu, Xiaoxia; Liu, Kexin; Chen, Jia'er; Wu, Jinguang

2015-02-25

225

Spectroscopic characterization of intermetallic catalysts and correlations with methanation activity and laser mass spectrometry of organic compounds  

SciTech Connect

Spectroscopic techniques such as electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), ion scattering spectroscopy (ISS), scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) were used to characterize a number of intermetallic catalytic systems: Th/sub x/Ni/sub y/, Th/sub x/Co/sub y/ and Th Ni/sub x/Fe/sub 5-x/. The results are discussed in relation to methanation activity. Laser mass spectra (LMS) obtained for diquaternary ammonium salts do not show emission of doubly charged molecular ions. Instead, characteristic ions are formed by dehydrogenation (M-H)/sup +/ or dealkylation (M-CH/sub 3/)/sup +/ from the dication. In the case where coulombic repulsion between the two positive charges in the molecule is large, the charge separation process, M/sup 2 +/ ..-->.. M/sub 1//sup +/ + M/sub 2//sup +/, is favored over dehydrogenation and dealkylation. Emission of cluster ions occurs during laser irradiation of substituted pyridines even at threshold laser power density. The clusters generated include dimers and trimers, and appear in both positive ion and negative ion laser mass spectra.

Dang, T.A.

1983-01-01

226

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

227

Synthesis, spectroscopic characterization, biological screenings, DNA binding study and POM analyses of transition metal carboxylates.  

PubMed

This article contains the synthesis of a novel carboxylic acid derivative, its transition metal complexes and evaluation of biological applications. Six carboxylate complexes of transition metals, Zn(II) and Hg(II), have been successfully synthesized and characterized by FT-IR and NMR ((1)H, (13)C). The ligand, HL, (4-[(2,6-Diethylphenyl)amino]-4-oxobutanoic acid) was also characterized by single crystal X-ray analysis. The complexation occurs via oxygen atoms of the carboxylate moiety. FT-IR date show the bidentate nature of the carboxylate moiety of the ligand as the ?? value in all complexes is less than that of the free ligand. The ligand and its complexes were screened for antifungal and antileishmanial activities. The results showed that the ligand and its complexes are active with few exceptions. UV-visible spectroscopy and viscometry results reveal that the ligand and its complexes interact with the DNA via intercalative mode of interaction. A new and efficient strategy to identify the pharmacophores and anti-pharmacophores sites in carboxylate derivatives for the antibacterial/antifungal activity using Petra, Osiris and Molinspiration (POM) analyses was also carried out. PMID:25646895

Uddin, Noor; Sirajuddin, Muhammad; Uddin, Nizam; Tariq, Muhammad; Ullah, Hameed; Ali, Saqib; Tirmizi, Syed Ahmed; Khan, Abdur Rehman

2015-04-01

228

Spectroscopic characterization of discharge products in Li-Air cells with aprotic carbonate electrolytes  

SciTech Connect

Raman, infrared and X-ray photoelectron spectroscopies were used to characterize the thick coating of reaction products on carbon and MnO2 coated carbon cathodes produced during discharge of Li-air cells. The results show that neither Li2O2 or Li2O are major components of the insoluble discharge products; instead the products are largely composed of fluorine, lithium, and carbon, with surprisingly little oxygen. The complex reaction chemistry also appears to involve the formation of ethers or alkoxide products at the expense of the carbonate solvent molecules (ethylene carbonate and dimethylcarbonate). The irreversible discharge reaction is likely electrochemically promoted with Li-anion species and dissolved oxygen. Exactly how the molecular O2 participates in the reaction is unclear and requires further study. The addition of a conformal coating of MnO2 on the carbon lowers the cell s operating voltage, but does not alter the overall discharge chemistry.

Veith, Gabriel M [ORNL; Nanda, Jagjit [ORNL; Howe, Jane Y [ORNL; Dudney, Nancy J [ORNL

2011-01-01

229

Spectroscopic characterization of a masterpiece: The Manueline foral charter of Sintra  

NASA Astrophysics Data System (ADS)

The foral charter attributed by D. Manuel I of Portugal, in 1514, to the village of Sintra was studied using Energy Dispersive X-ray Fluorescence spectrometry, Raman and Infrared micro-spectroscopies. A complete characterization of the pictorial materials used in the production of this masterpiece allowed the identification of iron gall inks used in the written text; pigments such as malachite, azurite, lead white, cinnabar, yellow ochre, gold, silver and carbon black in the illuminations and letterings; filler and binder used in the production of coloring materials and inks. Gum and calcium carbonate were the most recurrent binder and filler identified in this study. Silvering and gilding were mostly obtained by applying ground silver and gold on parchment.

Manso, Marta; Gac, Agnès Le; Longelin, Stéphane; Pessanha, Sofia; Frade, José Carlos; Guerra, Mauro; Candeias, António José; Carvalho, Maria Luísa

2013-03-01

230

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

231

Spectroscopic characterization of magnetic Fe3O4@Au core shell nanoparticles.  

PubMed

The magnetic nanoparticles iron oxide (Fe3O4) nanoparticles and iron oxide/gold core-shell (Fe3O4/Au) nanoparticles were synthesized and their catalytic photo-degradation activity towards malathion as example of organophosphorus pesticides were reported. Iron oxide (Fe3O4) magnetic nanoparticle was successfully prepared through co-precipitation method by the reduction of ferric chloride (FeCl3) using ascorbic acid. The morphology of the prepared nanoparticles was characterized by the TEM and XRD (X-ray diffraction) techniques. Degradation of 10ppm of malathion in the presence of these nanoparticles under UV radiation was monitored using (HPLC) and UV-visible spectra. Fe3O4/Au nanoparticles showed higher efficiency in photo-degradation of malathion than Fe3O4 ones. PMID:25617979

Fouad, Dina M; El-Said, Waleed A; Mohamed, Mona B

2015-04-01

232

[Reflectance spectroscopic characterization of thallium wastewater treatment by pyrite and pyrite slag].  

PubMed

The surface hydroxyls in pyrite and slag were investigated, and the result showed that the hydroxyls in pyrite slag were induced by residual pyrite. The diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) indicated that the surface hydroxyls in pyrite and slag reacted with thallium ion in the process of wastewater treatment. The 3 550 cm(-1) peak and 3 402 cm(-1) peak weakened after pyrite and slag treatment, nevertheless the 3 550 cm(-1) peak lowered and shifted to higher frequencies by about 70 cm(-1) with slag treatment. The reflectance spectroscopy in visible region was used to characterize the change of particle and specific surface in these treatment process, and furthermore, the fact that the activity of both pyrite and slag increased in repetitive use was explained. PMID:17608189

Zhang, Ping; Chen, Yong-Heng; Liang, Min-Hua; Yao, Yan

2007-04-01

233

Synthesis, spectroscopic characterization and pH dependent photometric and electrochemical fate of Schiff bases.  

PubMed

A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synthesized and characterized by (1)H NMR, (13)C NMR, FTIR and UV-Vis spectroscopy. The results were compared with a structurally related Schiff base, 1-((4-chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of BPIMN and CPIMN was investigated in a wide pH range. The experimental findings were supported by quantum mechanical approach. The redox mechanistic pathways were proposed on the basis of results obtained electrochemical techniques. Moreover, pH dependent UV-Vis spectroscopy of BPIMN and CPIMN was carried out and the appearance of isosbestic points indicated the existence of these compounds in different tautomeric forms. PMID:25437845

Rauf, Abdur; Shah, Afzal; Abbas, Saghir; Rana, Usman Ali; Khan, Salah Ud-Din; Ali, Saqib; Zia-Ur-Rehman; Qureshi, Rumana; Kraatz, Heinz-Bernhard; Belanger-Gariepy, Francine

2015-03-01

234

Raman spectroscopic characterization of the core-rim structure in reaction bonded boron carbide ceramics  

NASA Astrophysics Data System (ADS)

Raman spectroscopy was used to characterize the microstructure of reaction bonded boron carbide ceramics. Compositional and structural gradation in the silicon-doped boron carbide phase (rim), which develops around the parent boron carbide region (core) due to the reaction between silicon and boron carbide, was evaluated using changes in Raman peak position and intensity. Peak shifting and intensity variation from the core to the rim region was attributed to changes in the boron carbide crystal structure based on experimental Raman observations and ab initio calculations reported in literature. The results were consistent with compositional analysis determined by energy dispersive spectroscopy. The Raman analysis revealed the substitution of silicon atoms first into the linear 3-atom chain, and then into icosahedral units of the boron carbide structure. Thus, micro-Raman spectroscopy provided a non-destructive means of identifying the preferential positions of Si atoms in the boron carbide lattice.

Jannotti, Phillip; Subhash, Ghatu; Zheng, James Q.; Halls, Virginia; Karandikar, Prashant G.; Salamone, S.; Aghajanian, Michael K.

2015-01-01

235

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

236

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

237

Synthesis and microwave absorption characterization of SiO2 coated Fe3O4-MWCNT composites.  

PubMed

This study investigated the microwave absorption properties of core-shell composites containing; iron oxide decorated carbon nanotubes (CNTs) and silica (SiO2@Fe3O4-MWCNTs) with various thicknesses of silica shells (7, 20 and 50 nm). Transmission electron microscopy (TEM) and X-ray diffraction results confirmed the formation of these core-shell structures. Microwave absorption characterization of the samples at the ranging band under consideration (the X-band) showed increased absorption and shifting of the peaks to lower frequencies compared to the uncoated sample (Fe3O4-MWCNTs). The minimum reflection loss decreased with increasing SiO2 thickness. The minimum reflection loss of the composite with an optimized thickness of the silica shell (7 nm) exceeded -41 dB at 8.7-9 GHz. PMID:25288483

Hekmatara, Hoda; Seifi, Majid; Forooraghi, Keyvan; Mirzaee, Sharareh

2014-11-21

238

Synthesis, characterization and spectroscopic studies of some boron-containing hydrogen storage materials  

NASA Astrophysics Data System (ADS)

In this dissertation the synthesis and characterization of boron-related nanostructures and dehydrogenation studies of metal borohydrides using FTIR are reported. Boron-related nanostructures are of interest because of their potential applications in nanoelectronics and in hydrogen storage. A low pressure chemical vapor deposition (LPCVD) apparatus was built in order to grow boron nanostructures. Various techniques, namely, Auger electron spectroscopy (AES), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were used to characterize the synthesized boron and boride nanostructures, and boron coated carbon nanotubes (CNTs). By the uncatalyzed pyrolysis of diborane, at relatively low temperature, crystalline boron nanoribbons were synthesized. Nickel-catalyzed growth also produced Ca, Sr and Y boride nanowires that were found to be crystalline. Amorphous boron coated CNTs were synthesized by LPCVD. Two growth mechanisms, vapor-liquid-solid (VLS) and vapor-solid (VS) were invoked to explain the observed nanostructures. A high vacuum apparatus for FTIR studies was built. The capabilities of the apparatus were first tested by acquiring low temperature and room temperature spectra of sodium and lithium borohydrides. The metal borohydrides are of high hydrogen content and dehydrogenation studies using FTIR were done. NaBH 4 and the K2B12H12 salt were studied. It was found that above its melting point (673 K), NaBH4 is probably converted to its B12H12-2 salt, which then loses all hydrogen to produce amorphous boron. This conversion of B 12H12-2 to boron clusters was confirmed through dehydrogenation studies of K2B12H12. Both SIMS and AES are surface sensitive techniques to study thin film surfaces and interfaces at nano-dimentions. Thin (9-10 mum) cadmium telluride films have application as the buffer layer on silicon substrates to form high quality mercury cadmium telluride (MCT) films. MCT films find applications in IR detectors and in photovoltaic cells. Due to the lattice mismatch it is necessary to grow CdTe films on a monolayer of arsenic and 20 nm thick ZnTe on silicon. The purpose of this study was to show the capabilities of the Scanning Auger Multiprobe PHI 600 in the qualitative analysis of CdTe, ZnTe and As films on Si and of an MCT film surface, which was grown on CdZnTe.

Jash, Panchatapa

239

Spectroscopic Characterizations of Molecularly-Linked Gold Nanoparticle Assemblies Upon Thermal Treatment  

SciTech Connect

Nanostructured gold catalysts have attracted increasing interest since the pioneer work of Haruta which demonstrated unusually high catalytic activities for CO oxidation when the nanoparticles were made less than {approx}10 nm diameter in size and supported on oxides. It is possible to use core-shell gold nanoparticles to construct the catalyst and activate the catalytic activity by applying a thermal-treatment process. The understanding of how the core-shell surface components reconstitute in such a catalytic activation process will have important implications in expanding this approach to the design and fabrication of nanostructured catalysts. We report herein the results of a study of decanethiolate-capped gold nanoparticles of 2-nm and 5-nm core sizes assembled on planar substrates using 1,9-nonanedithiol (NDT) and 11-mercaptoundecanoic acid (MUA) as molecular linkers were studied as a model system. XPS and IR are employed to detect the identity of surface species and to analyze the elemental composition or oxidation states of the nanomaterials, from which we derive structural information about the surface reconstitution of the core-shell nanostructured catalysts. Electrochemical methods are used to characterize the electrocatalytic activities.

Luo, Jin; Maye, Mathew M.; Han, Li; Kariuki, Nancy N.; Jones, V W.; Lin, Yuehe; Engelhard, Mark H.; Zhong, Chuan-Jian

2004-05-11

240

New copper(II) complexes with dopamine hydrochloride and vanillymandelic acid: Spectroscopic and thermal characterization  

NASA Astrophysics Data System (ADS)

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. The Cu(II) chelates with coupled products of dopamine hydrochloride (DO.HCl) and vanillymandelic acid (VMA) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical techniques namely IR, magnetic and UV-vis spectra are used to investigate the structure of these chelates. Cu(II) forms 1:1 (Cu:DO) and 1:2 (Cu:VMA) chelates. DO behave as a uninegative tridentate ligand in binding to the Cu(II) ion while VMA behaves as a uninegative bidentate ligand. IR spectra show that the DO is coordinated to the Cu(II) ion in a tridentate manner with ONO donor sites of the phenolic- OH, -NH and carbonyl- O, while VMA is coordinated with OO donor sites of the phenolic- OH and -NH. Magnetic moment measurements reveal the presence of Cu(II) chelates in octahedral and square planar geometries with DO and VMA, respectively. The thermal decomposition of Cu(II) complexes is studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed.

Mohamed, Gehad G.; Nour El-Dien, F. A.; El-Nahas, R. G.

2011-10-01

241

Synthesis, spectroscopic characterization, stability assessment and DNA-binding of new 2,6-piperidinedione derivatives.  

PubMed

This work reports on structural characterization of new antineoplaston (ANP) representatives, namely 3-(benzoylamino)-2,6-piperidinedione (BPD), 3-(4-methoxybenzoylamino)-2,6-piperidinedione (MPD) and 3-(p-nitrobenzoylamino)-2,6-piperidinedione (NPD). These compounds were prepared by reacting N-(4-substituted benzoyl)-glutamines with N-hydroxysuccinimide to afford the corresponding esters, which were heated to produce the corresponding 2,6-piperidinedione (PD) compounds. Non-destructive analytical procedures such as 1H NMR and NIR analyses confirmed the postulated chemical structures of these PD compounds. HPLC chromatograms at an ambient temperature or from solutions preheated at 30, 40 or 60 degrees C displayed only a single peak for each compound. Combination of heat with pH modification had virtually no effect on the obtained peaks, thus attesting to the stability and purity of these compounds. MS analysis displayed molecular mass ions indicative of BPD, MPD and NPD at m/z 233.4, 263.2 and 278.3, respectively. The fragmentation patterns using MS/MS analyses conformed to the structural and molecular formulae of the prepared compounds. Furthermore, preliminary biological assessments showed the capacity of these compounds to bind to the DNA. NPD, but not BMP or MPD, had a superior affinity to the DNA than the prototype ANP-A10. PMID:11718269

Abou-Zeid, L; El-Mowafy, A M; El-Kerdawy, M M; Hamza, H; Abdel-Hamid, M E

2001-10-01

242

Growth and spectroscopic characterization of a new organic nonlinear optical crystal: L-alaninium succinate.  

PubMed

A novel organic nonlinear optical (NLO) material, l-alaninium succinate, was synthesized by the standard method. The synthesized material was purified by repeated recrystallization. Single crystals were grown by slow evaporation technique using water as solvent. The grown crystals were characterized by FT-IR, FT-NMR and UV-vis-NIR techniques. The second harmonic generation (SHG) from the material was confirmed using Nd:YAG laser which shows that LAS has 23% SHG efficiency of that of the standard KDP. The UV-vis-NIR transmittance was recorded in the range from 190 to 1100nm. In this study, the lower cut-off is shifted towards UV region (190nm) which shows that LAS has good transmittance in region from 190 to 1100nm and it makes LAS for SHG. Functional groups present in the grown crystal were identified using FT-IR spectrum which gives confirmation of NH(3)(+) ion in LAS. The chemical structure of l-alaninium succinate was established by FT-NMR technique. PMID:19157964

Raja, C Ramachandra; Gokila, G; Joseph, A Antony

2009-05-01

243

Cytotoxic behavior and spectroscopic characterization of metal complexes of ethylacetoacetate bis(thiosemicarbazone) ligand.  

PubMed

Reaction of Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ion with 2,4-dihydrazino-thioamido-1-ethoxybutane led to the formation of mono and binuclear complexes. These complexes have been characterized by elemental analyses, IR, UV-Vis spectra, magnetic moments, molar conductances, (1)H NMR and mass spectra (ligand and its Zn(II) complex), thermal analyses (DTA and TGA) and ESR measurements. The IR data suggest the involvement of sulfur and azomethane nitrogen atoms in coordination to the central metal ion .The Molar conductances of the complexes in DMF are commensurate with their non-ionic character. The ESR spectra of Cu(II) complexes show axial type symmetry (d(x2-y2)) ground state with covalent bond character. On the basis of spectral studies, octahedral or tetrahedral geometry has been assigned to the metal complexes. Complexes have been tested invitro against tumor cells and number of microorganisms in order to assess their antitumor and antimicrobial properties. PMID:24011929

El-Tabl, Abdou Saad; El-wahed, Moshira Mohamed Abd; Rezk, Ahmed Mahmoud Salah Mahmoud

2014-01-01

244

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

245

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

246

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

PubMed

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 HOPO3(3-) and PO4(3-) 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. PMID:24076459

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

2014-01-24

247

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

NASA Astrophysics Data System (ADS)

Crystals of phases belonging to the autunite group (general formula X2+(UO2)2(X5+O4)2?nH2O), specifically the uranyl phosphates (X5+ = P) metauranocircite (X2+ = Ba2+), metatorbernite (X2+ = Cu2+) and a barian metatorbenite phase (X2+ = Cu2+/Ba2+), 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( and ( stretching vibrations. By using the wavenumbers of the most intense and well defined ?1( 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 ( 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( 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.

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

2013-09-01

248

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

249

Synthesis, structure, and spectroscopic characterization of three uranyl phosphates with unique structural units  

NASA Astrophysics Data System (ADS)

Single crystals of Zn4(OH)2[(UO2)(PO4)2(OH)2(H2O)] (UZnP), Cs[(UO2)(HPO4)NO3] (UCsP), and In3[(UO2)2(PO4)4OH(H2O)6].2H2O (UInP) were obtained from hydrothermal reactions and have been structurally and chemically characterized. UZnP crystallizes in space group Pbcn, a=8.8817(7), b=6.6109(5), c=19.569(1) Å; UCsP crystallizes in P-1, a=7.015(2), b=7.441(1), c=9.393(2) Å, ?=72.974(2), ?=74.261(2), ?=79.498(2); and UInP crystallizes in P-1, a=7.9856(5), b=9.159(1), c=9.2398(6) Å ?=101.289(1), ?=114.642(1), ?=99.203(2). The U6+ cations are present as (UO2)2+ uranyl ions coordinated by five O atoms to give pentagonal bipyramids. The structural unit in UZnP is a finite cluster containing a uranyl pentagonal bipyramid that shares corners with two phosphate tetrahedra. The structural unit in UCsP is composed of uranyl pentagonal bipyramids with one chelating nitrate group that are linked into chains by three bridging hydrogen phosphate tetrahedra. In UInP, the structural unit contains pairs of edge-sharing uranyl pentagonal bipyramids with two chelating phosphate tetrahedra that are linked into chains through two bridging phosphate tetrahedra. Indium octahedra link these uranyl phosphate chains into a 3-dimensional framework. All three compounds exhibit unique structural units that deviate from the typical layered structures observed in uranyl phosphate solid-state chemistry.

Wylie, Ernest M.; Dawes, Colleen M.; Burns, Peter C.

2012-12-01

250

Observation of a cw dark-field signal in an absorption spectroscopic experiment using a phase locked free-electron laser  

PubMed

We introduce a technique for ultrasensitive absorption spectroscopy using the GHz-rate pulse train from a phase-locked free-electron laser (FEL), in which the fractional power absorbed from one or more laser lines reappears as a signal on the dark background between the pulses emerging from the sample. Preliminary absorption experiments in 15 Torr cm of methane at 3.25 &mgr;m, using phase-locked pulses from the Mark III FEL, clearly reveal an interpulse beat signal due to absorption by adjacent molecular rotational lines which is generated only in the presence of interpulse phase coherence. PMID:11018958

Szarmes; Madey; Straub

2000-03-27

251

Observation of a cw Dark-Field Signal in an Absorption Spectroscopic Experiment Using a Phase Locked Free-Electron Laser  

NASA Astrophysics Data System (ADS)

We introduce a technique for ultrasensitive absorption spectroscopy using the GHz-rate pulse train from a phase-locked free-electron laser (FEL), in which the fractional power absorbed from one or more laser lines reappears as a signal on the dark background between the pulses emerging from the sample. Preliminary absorption experiments in 15 Torr cm of methane at 3.25 ?m, using phase-locked pulses from the Mark III FEL, clearly reveal an interpulse beat signal due to absorption by adjacent molecular rotational lines which is generated only in the presence of interpulse phase coherence.

Szarmes, Eric B.; Madey, John M. J.; Straub, Karl D.

2000-03-01

252

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

253

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

254

Synthesis, structure, and spectroscopic characterization of three uranyl phosphates with unique structural units  

SciTech Connect

Single crystals of Zn{sub 4}(OH){sub 2}[(UO{sub 2})(PO{sub 4}){sub 2}(OH){sub 2}(H{sub 2}O)] (UZnP), Cs[(UO{sub 2})(HPO{sub 4})NO{sub 3}] (UCsP), and In{sub 3}[(UO{sub 2}){sub 2}(PO{sub 4}){sub 4}OH(H{sub 2}O){sub 6}].2H{sub 2}O (UInP) were obtained from hydrothermal reactions and have been structurally and chemically characterized. UZnP crystallizes in space group Pbcn, a=8.8817(7), b=6.6109(5), c=19.569(1) A; UCsP crystallizes in P-1, a=7.015(2), b=7.441(1), c=9.393(2) A, {alpha}=72.974(2), {beta}=74.261(2), {gamma}=79.498(2); and UInP crystallizes in P-1, a=7.9856(5), b=9.159(1), c=9.2398(6) A {alpha}=101.289(1), {beta}=114.642(1), {gamma}=99.203(2). The U{sup 6+} cations are present as (UO{sub 2}){sup 2+} uranyl ions coordinated by five O atoms to give pentagonal bipyramids. The structural unit in UZnP is a finite cluster containing a uranyl pentagonal bipyramid that shares corners with two phosphate tetrahedra. The structural unit in UCsP is composed of uranyl pentagonal bipyramids with one chelating nitrate group that are linked into chains by three bridging hydrogen phosphate tetrahedra. In UInP, the structural unit contains pairs of edge-sharing uranyl pentagonal bipyramids with two chelating phosphate tetrahedra that are linked into chains through two bridging phosphate tetrahedra. Indium octahedra link these uranyl phosphate chains into a 3-dimensional framework. All three compounds exhibit unique structural units that deviate from the typical layered structures observed in uranyl phosphate solid-state chemistry. - Graphical abstract: Three new uranyl phosphates with unique structural units are reported. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Three new uranyl phosphates have been synthesized hydrothermally. Black-Right-Pointing-Pointer Single crystal analyses reveal unique structural units. Black-Right-Pointing-Pointer The dimensionality of these compounds deviate from typical U{sup 6+} layered structures.

Wylie, Ernest M.; Dawes, Colleen M. [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States)] [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Burns, Peter C., E-mail: pburns@nd.edu [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

2012-12-15

255

Observation of a cw Dark-Field Signal in an Absorption Spectroscopic Experiment Using a Phase Locked Free-Electron Laser  

Microsoft Academic Search

We introduce a technique for ultrasensitive absorption spectroscopy using the GHz-rate pulse train from a phase-locked free-electron laser (FEL), in which the fractional power absorbed from one or more laser lines reappears as a signal on the dark background between the pulses emerging from the sample. Preliminary absorption experiments in 15 Torr cm of methane at 3.25 mum, using phase-locked

Eric B. Szarmes; John M. J. Madey; Karl D. Straub

2000-01-01

256

Aminophenyl double decker silsesquioxanes: Spectroscopic elucidation, physical and thermal characterization, and their applications  

NASA Astrophysics Data System (ADS)

The incorporation of cage-like silsesquioxanes (SQ) to form polymers has demonstrated property enhancements in areas such as: thermal and mechanical characteristics, flame retardance, dielectric properties, and oxidative resistance. However, with most hybrid polymers investigated, the attached SQs are pendant with respect to the polymer backbone. A recently developed class of these nano-structured, cage-like silsesquioxanes, formally known as double decker silsesquioxanes (DDSQ), offers the opportunity to form hybrid polymers with SQ cages as a part of the polymer backbone. However, during the capping reaction, these functionalized DDSQs generate cis and trans isomers with respect to the 3D Si-O core. Therefore, it is logical to characterize properties, which will allow for optimization of capping reaction parameters, particularly if one isomer is favored over the other. Moreover, these characteristics are also relevant when reacting or incorporating these isomers, or mixtures thereof, with other molecules to form novel materials. In this dissertation, three aminophenyl DDSQs were synthesized. More specifically, two meta- aminophenyl DDSQs, which were differentiated according to the moiety attached to the D-Si (methyl or cyclohexyl), and one para-aminophenyl DDSQ with a methyl moiety were used. Chemical, physical, and thermal characteristics were evaluated for individual isomers as well as binary mixtures of different cis/trans ratios. The 1H NMR spectra of the cis and trans isomers of these DDSQ had not previously been assigned to a degree that allowed for quantification, which was necessary for these studies. Thus, 1H-29Si HMBC correlations were applied to facilitate 1H spectral assignments and also to confirm previous 29Si assignments. Using 1H NMR not only saves time and material over 29Si NMR, but also provides a more accurate quantification, thus allowing for the ratio of cis and trans isomers present in each compound to be determined. Solubility behavior was investigated for the individual isomers, such that separation techniques could be developed. It was found that cis isomers were 33 times more soluble than trans isomers for para-aminophenyl (R = methyl), and 22 times more soluble for the analogous meta-aminophenyl in a solution of THF and hexanes. For a more sterically hindered meta-aminophenyl (R = cyclohexyl), cis isomers were only 3.5 times more soluble, and the overall solubility was also the lowest. Phase diagrams representing solid-liquid melt equilibria of the binary cis/trans mixtures were developed. Single crystal x-ray diffraction data of isolated isomers helped to interpret the phase behavior. Both compounds with a methyl moiety exhibited eutectic phase diagrams. Their trans isomers were higher melting and exhibited larger packing density. Changing from para- to meta-aminophenyl shifted the solid-liquid equilibrium further from ideal, with decreased activity coefficients. Cyclohexyl DDSQ exhibited an isomorphic phase diagram (a complete solid-solution), attributed to cyclohexyl being more similar in size to the phenyl moieties. A specific application that was chosen for these DDSQ was high performance thermosetting oligoimides. They displayed advantages over their organic counterparts in areas such as the liquid to solid transition and viscosity, which improves the processing window. Additionally, they increased the overall degree of cross-linking leading to improved oxidative stability at elevated temperatures.

Schoen, Beth Whitney

257

Characterization of shear-thickening fluid-filled foam systems for use in energy absorption devices  

E-print Network

The absorption of energy during impacts is ubiquitous in society. From our car seats to body armor, the ability to divert or dissipate unwanted energy is an aspect that has many engineering challenges. One approach to this ...

Ramirez, Jose G. (Jose Guadalupe), 1980-

2004-01-01

258

Characterization of arsenic in oil shale and oil shale derivatives by X-ray absorption spectroscopy  

SciTech Connect

Arsenic must be removed from oil shales because of its effects on catalysts as well as the environmental problems associated with leaching. Difficulties in determining total arsenic content lead to an effort to find a method for best performing the analysis. It was found that the combination of X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) was adequate to provide quantitative information on arsenic at the ppm level.

Cramer, S.P.; Sisken, M.; George, G.N.; Brown, L.D.

1987-04-01

259

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

260

Non-ionic surfactants as novel intranasal absorption enhancers: in vitro and in vivo characterization.  

PubMed

Abstract Objective: To explore the potential of non-ionic surfactants as novel intranasal absorption enhancers. Methods: Taking sumatriptan succinate (SMS) as a model drug, influence of different non-ionic surfactants, including laurate sucrose ester (SE), cremophor EL and poloxamer 188, on the intranasal absorption of SMS was investigated using an in situ nasal perfusion technique in rats. Ciliotoxicity of the non-ionic surfactants was evaluated using an in situ toad palate model. In vivo behavior of the selected formulations was studied in rats. Results: All the non-ionic surfactants investigated increased the intranasal absorption of SMS remarkably but with varied extent and trend. Moreover, it was revealed that at the same concentration, laurate SE had better permeation-enhancing effect than that of cremophor EL and poloxamer 188. The ciliotoxicity results showed that all the non-ionic surfactants were regarded as safe at selected concentrations. Based on the in situ absorption data and ciliotoxicity results, the following three samples, 0.5% laurate SE, 0.1% cremophor EL and 0.5% poloxamer 188 were selected for in vivo absorption studies in rats. Among them, 0.5% laurate SE group presented the highest enhancing effect, followed by 0.1% cremophor EL and 0.5% poloxamer 188 group, with absolute bioavailability 29.99%, 22.64% and 20.90%, respectively. Conclusions: Laurate SE is a promising intranasal absorption enhancer. PMID:25347689

Li, Ying; Li, Jinfeng; Zhang, Xin; Ding, Jiaojiao; Mao, Shirui

2014-10-27

261

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

NASA Astrophysics Data System (ADS)

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, 13C and 1H 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.

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

2014-12-01

262

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

263

Description of the Role of Shot Noise in Spectroscopic Absorption and Emission Measurements with Photodiode and Photomultiplier Tube Detectors: Information for an Instrumental Analysis Course  

ERIC Educational Resources Information Center

A description of shot noise and the role it plays in absorption and emission measurements using photodiode and photomultiplier tube detection systems is presented. This description includes derivations of useful forms of the shot noise equation based on Poisson counting statistics. This approach can deepen student understanding of a fundamental…

McClain, Robert L.; Wright, John C.

2014-01-01

264

Characterization of the intestinal absorption of inorganic mercury in Caco-2 cells.  

PubMed

The main form of mercury exposure in the general population is through food. Intestinal absorption is therefore a key step in the penetration of mercury into the systemic circulation, and should be considered when evaluating exposure risk. Many studies have investigated the transport of mercury species in different cell lines, though the mechanisms underlying their intestinal absorption are not clear. This study evaluates the accumulation and transport of Hg(II), one of the mercury species ingested in food, using Caco-2 cells as intestinal epithelium model with the purpose of clarifying the mechanisms involved in its absorption. Hg(II) shows moderate absorption, and its transport fundamentally takes place via a carrier-mediated transcellular mechanism. The experiments indicate the participation of an energy-dependent transport mechanism. In addition, H(+)- and Na(+)-dependent transport is also observed. These data, together with those obtained from inhibition studies using specific substrates or inhibitors of different transporter families, suggest the participation of divalent cation and amino acid transporters, and even some organic anion transporters, in Hg(II) intestinal transport. An important cellular accumulation of up to 51% is observed - a situation which in view of the toxic nature of this species could affect intestinal mucosal function. This study contributes new information on the mechanisms of transport of Hg(II) at intestinal level, and which may be responsible for penetration of this mercurial form into the systemic circulation. PMID:25283090

Vázquez, M; Devesa, V; Vélez, D

2015-02-01

265

Characterization of in vivo absorption features of chlorophyte, phaeophyte and rhodophyte algal species  

Microsoft Academic Search

Despite the plentiful diversity of macroalgae in coastal environments, few studies have examined the in vivo absorption features of common marine macrophytes. Here we report on results of a survey of 12 central California common intertidal and subtidal taxa, representing Chlorophyta, Phaeophyta and Rhodophyta carried out in the summer of 1988. Computer-assisted analyses were used to obtain fourth-derivative spectra from

C. M. Smith; R. S. Alberte

1994-01-01

266

Unusual ionospheric absorption characterizing energetic electron precipitation into the South Atlantic Magnetic Anomaly  

Microsoft Academic Search

An imaging riometer (IRIS) was installed newly in the southern area of Brazil in order to investigate precipitation of energetic electrons into the South Atlantic Magnetic Anomaly (SAMA). An unusual ionospheric absorption event was observed in the nighttime (~20 h LT) near the maximum depression (Dst ~ -164 nT) and the following positive excursion during the strong geomagnetic storm on

Masanori Nishino; Kazuo Makita; Kiyofumi Yumoto; N. J. Schuch; M. A. Abdu

2002-01-01

267

Spectroscopic characterization of iron ores formed in different geological environments using FTIR, XPS, Mössbauer spectroscopy and thermoanalyses.  

PubMed

Application of thermoanalyses, FTIR, XPS and Mössbauer spectroscopic methods can differentiate between iron ores formed in different geological environments. Two types of iron ore are formed in shallow marine environments in the Bahariya Depression, Egypt, yellowish brown ooidal ironstones (type 1) and black mud and fossiliferous ironstones (type 2). Both types were subjected to subaerial weathering, producing a dark brown lateritic (pedogenic) iron ore (type 3). Microscopic investigation indicates goethite is the main mineral in types 1 and 3, while hematite is the main mineral in type 2 and also occurs in type 3. Thermoanalyses indicated the dehydroxylation endothermic peak of goethite of type 1 occurs between 329 and 345°C, while in type 3 occurs between 284 and 330°C. This variation can be attributed to the nanocrystalline nature of the pedogenic goethite. The presence of an exothermic peak at 754°C in type 3 is probably attributed to goethite-hematite phase transformation. FTIR spectroscopy indicated that goethite of type 1 is characterized by the presence of the ?-OH band between 799 and 802cm(-1), the ?-OH between 898 and 904cm(-1) and the bulk hydroxyl stretch between 3124 and 3133cm(-1). Goethite of type 3 is characterized by the absence of the bulk hydroxyl stretch band and the ?-OH and ?-OH are shifted to higher Wavenumbers that can attributed to a relative Al-for Fe-substitution. Hematite is identified by two IR bands; the first is between 464 and 475cm(-1) and at the second is between 540 and 557cm(-1). Quartz is identified in all iron ore types, nitrates are identified in types 1 and 2, but absent in type 3 and Kaolinite is identified in type 2. The Mössbauer spectrum of type 1 is fitted with one magnetic sextet corresponding to goethite with an isomer shift (IS)=0.374mms(-1), a quadruple splitting (QS)=-0.27mms(-1) and a hyperfine magnetic field (BHF)=?37. The Mössbauer spectrum of type 2 is fitted with one magnetic sextet corresponding to hematite with IS=0.363mms(-1), QS=-0.23mms(-1) and BHF=?50. The Mössbauer spectrum of type 3 is best fitted with a single doublet corresponding to ferrihydrite and one sextet corresponding to hematite. The XPS survey scans and the high resolution of the Fe 2p3/2 can differentiate between the yellowish-brown and green ooidal laminae of type 1. The XPS survey scans indicate the presence of Fe, O, C, N, Na, Cl, Ca and Si in all laminae, while S, Zn, Ti and P are only restricted to the green laminae. The high resolution of the Fe 2p3/2 indicates that Fe is linked to OH(-) ligand in the yellowish-brown laminae that correspond to goethite, while Fe is linked to SO4(2-) ligand in the green laminae. The XPS survey scans of types 2 and 3 indicate that Fe is linked to O(2-) ligand that corresponds to hematite. PMID:25467675

Salama, Walid; El Aref, Mourtada; Gaupp, Reinhard

2014-10-31

268

Spectroscopic characterization of iron ores formed in different geological environments using FTIR, XPS, Mössbauer spectroscopy and thermoanalyses  

NASA Astrophysics Data System (ADS)

Application of thermoanalyses, FTIR, XPS and Mössbauer spectroscopic methods can differentiate between iron ores formed in different geological environments. Two types of iron ore are formed in shallow marine environments in the Bahariya Depression, Egypt, yellowish brown ooidal ironstones (type 1) and black mud and fossiliferous ironstones (type 2). Both types were subjected to subaerial weathering, producing a dark brown lateritic (pedogenic) iron ore (type 3). Microscopic investigation indicates goethite is the main mineral in types 1 and 3, while hematite is the main mineral in type 2 and also occurs in type 3. Thermoanalyses indicated the dehydroxylation endothermic peak of goethite of type 1 occurs between 329 and 345 °C, while in type 3 occurs between 284 and 330 °C. This variation can be attributed to the nanocrystalline nature of the pedogenic goethite. The presence of an exothermic peak at 754 °C in type 3 is probably attributed to goethite-hematite phase transformation. FTIR spectroscopy indicated that goethite of type 1 is characterized by the presence of the ?-OH band between 799 and 802 cm-1, the ?-OH between 898 and 904 cm-1 and the bulk hydroxyl stretch between 3124 and 3133 cm-1. Goethite of type 3 is characterized by the absence of the bulk hydroxyl stretch band and the ?-OH and ?-OH are shifted to higher Wavenumbers that can attributed to a relative Al-for Fe-substitution. Hematite is identified by two IR bands; the first is between 464 and 475 cm-1 and at the second is between 540 and 557 cm-1. Quartz is identified in all iron ore types, nitrates are identified in types 1 and 2, but absent in type 3 and Kaolinite is identified in type 2. The Mössbauer spectrum of type 1 is fitted with one magnetic sextet corresponding to goethite with an isomer shift (IS) = 0.374 mm s-1, a quadruple splitting (QS) = -0.27 mm s-1 and a hyperfine magnetic field (BHF) = ?37. The Mössbauer spectrum of type 2 is fitted with one magnetic sextet corresponding to hematite with IS = 0.363 mm s-1, QS = -0.23 mm s-1 and BHF = ?50. The Mössbauer spectrum of type 3 is best fitted with a single doublet corresponding to ferrihydrite and one sextet corresponding to hematite. The XPS survey scans and the high resolution of the Fe 2p3/2 can differentiate between the yellowish-brown and green ooidal laminae of type 1. The XPS survey scans indicate the presence of Fe, O, C, N, Na, Cl, Ca and Si in all laminae, while S, Zn, Ti and P are only restricted to the green laminae. The high resolution of the Fe 2p3/2 indicates that Fe is linked to OH- ligand in the yellowish-brown laminae that correspond to goethite, while Fe is linked to SO42- ligand in the green laminae. The XPS survey scans of types 2 and 3 indicate that Fe is linked to O2- ligand that corresponds to hematite.

Salama, Walid; El Aref, Mourtada; Gaupp, Reinhard

2015-02-01

269

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

270

Sulphur characterization in coal from X-ray absorption near edge spectroscopy  

Microsoft Academic Search

High resolution (? 0.2 eV) S L-edge X-ray absorption near edge structure (XANES) spectra of several inorganic and organic sulphur model compounds are presented. The spectra were recorded in both total electron yield (TEY) and fluorescence yield (FY) modes. A qualitative interpretation is used to explain the origin of the fine features in the XANES spectra of certain model compounds.

M. Kasrai; J. R. Brown; G. M. Bancroft; Z. Yin; K. H. Tan

1996-01-01

271

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

272

Fabrication process and electromagnetic wave absorption characterization of a CNT/Ni/epoxy nanocomposite.  

PubMed

Since carbon nanotube (CNT) was first discovered in 1991, it has been considered as a viable type of conductive filler for electromagnetic wave absorption materials in the GHz range. In this paper, pearl-necklace-structure CNT/Ni nano-powders were fabricated by a polyol process as conductive fillers. Compared to synthesized CNT, pearl-necklace Ni-decorated CNT increased the electrical conductivity by an order of 1 due to the enhancement of the Ni-conductive network. Moreover, the decorated Ni particles prevented the agglomeration of CNTs by counterbalancing the Van der Walls interaction between the CNTs. A CNT/Ni nanocomposite showed a homogeneous dispersion in an epoxy-based matrix. This enhanced physical morphology and electrical properties lead to an increase in the loss tangent and reflection loss in the CNT/Ni/Epoxy nanocomposite compared to these characteristics of a CNT/Epoxy nanocomposite in range of 8-12 GHz. The electromagnetic wave absorption properties of CNT/Ni/epoxy nanocomposites will provide enormous opportunities for electronic applications where lightweight EMI shielding or electro-magnetic wave absorption properties are necessary. PMID:24245312

Ryu, Seongwoo; Mo, Chan Bin; Lee, Haeshin; Hong, Soon Hyung

2013-11-01

273

Light Absorption Properties of Brown Carbon from Fresh and Aged Biomass Burning Aerosols Characterized in a Smog Chamber  

NASA Astrophysics Data System (ADS)

Black carbon is an important particulate phase light absorber in the atmosphere. Recent studies have shown that some organic matter also absorb visible light, especially at short wavelengths. These organic compounds are referred to as "brown carbon". Biomass burning is a major contributor to brown carbon in atmospheric particulate matter; however, its optical properties are poorly characterized. We have conducted smog chamber experiments to investigate light absorption properties of brown carbon in primary and aged biomass burning emissions, namely the imaginary refractive index. The aging was performed in a smog chamber, where dilute emissions were exposed to UV lights to initiate photo-oxidation, which often produced substantial secondary organic aerosol. The experiments took place at Carnegie Mellon University (CMU) and at the US Fire Science Laboratory in Missoula, MT as part of the Fire Lab at Missoula field campaign (FLAME 2009). The CMU experiments simulated household wood burning (oak), and the FLAME experiments simulated wildland fires with fuels including gallberry, lodgepole pine, black spruce and ponderosa pine. Absorption coefficients were measured using an Aethalometer (Magee Scientific) at 7 different wavelengths ranging between 370 nm and 950 nm. The black carbon size distributions were measured using a Single Particle Soot Photometer (SP2, DMT), and total aerosol size distributions were measured using a Scanning Mobility Particle Sizer (SMPS, TSI). The absorption coefficients of both the fresh and aged aerosol were significantly larger, and had stronger wavelength dependence than what would be expected for black carbon alone, and for a black carbon core with a non-absorbing shell. This indicates that biomass burning organic aerosol should be classified as brown carbon. A (black carbon) core - (brown carbon) shell absorption model based on Mie theory was optimized to determine the shell imaginary refractive index which produces model outputs that fit measured absorption coefficients. The fresh and aged aerosol had similar optical properties, with shell imaginary refractive index ranging between 0.2 and 0.4 at 550 nm, and wavelength dependence between ?-2 and ?-3. These values correspond to absorption efficiencies comparable to black carbon at short visible wavelengths. Assuming a clear (non-absorbing) shell overestimates the single scattering albedo by up to a factor of 2, and underestimates the simple forcing efficiency by up to an order of magnitude.

Saleh, R.; Chuang, W.; Hennigan, C.; McMeeking, G. R.; Coe, H.; Donahue, N. M.; Robinson, A. L.

2011-12-01

274

Preformulation characterization and in vivo absorption in beagle dogs of JFD, a novel anti-obesity drug for oral delivery.  

PubMed

Abstract JFD (N-isoleucyl-4-methyl-1,1-cyclopropyl-1-(4-chlorine)phenyl-2-amylamine·HCl) is a novel investigational anti-obesity drug without obvious cardiotoxicity. The objective of this study was to characterize the key physicochemical properties of JFD, including solution-state characterization (ionization constant, partition coefficient, aqueous and pH-solubility profile), solid-state characterization (particle size, thermal analysis, crystallinity and hygroscopicity) and drug-excipient chemical compatibility. A supporting in vivo absorption study was also carried out in beagle dogs. JFD bulk powders are prismatic crystals with a low degree of crystallinity, particle sizes of which are within 2-10??m. JFD is highly hygroscopic, easily deliquesces to an amorphous glass solid and changes subsequently to another crystal form under an elevated moisture/temperature condition. Similar physical instability was also observed in real-time CheqSol solubility assay. pKa (7.49?±?0.01), log?P (5.10?±?0.02) and intrinsic solubility (S0) (1.75??g/ml) at 37?°C of JFD were obtained using potentiometric titration method. Based on these solution-state properties, JFD was estimated to be classified as BCS II, thus its dissolution rate may be an absorption-limiting step. Moreover, JFD was more chemically compatible with dibasic calcium phosphate, mannitol, hypromellose and colloidal silicon dioxide than with lactose and magnesium stearate. Further, JFD exhibited an acceptable pharmacokinetic profiling in beagle dogs and the pharmacokinetic parameters Tmax, Cmax, AUC0-t and absolute bioavailability were 1.60?±?0.81?h, 0.78?±?0.47??g/ml, 3.77?±?1.85??g·h/ml and 52.30?±?19.39%, respectively. The preformulation characterization provides valuable information for further development of oral administration of JFD. PMID:24694186

Fan, Yunzhou; Yang, Meiyan; Wang, Yuli; Li, Yanyou; Zhou, Yuanda; Chen, Xiaoping; Shan, Li; Wei, Jun; Gao, Chunsheng

2014-04-01

275

X-ray absorption spectroscopic studies of zinc in the N-terminal domain of HIV-2 integrase and model compounds.  

PubMed

X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) analysis, has been carried out at the Zn K edge of the N-terminal part of the integrase protein of the human immunodeficiency virus, type 2 (HIV-2), and of some zinc coordination compounds. In the presence of excess beta-mercaptoethanol, which was present in the NMR structure elucidation of the protein [Eijkelenboom et al. (1997), Curr. Biol. 7, 739-746; (2000), J. Biomol. NMR, 18, 119-28], the protein spectrum was nearly identical to that recorded in its absence. Comparison of the XANES of the protein with that of model compounds and literature data permits the conclusion that the Zn ion is four-coordinated. The major shell of the EXAFS provides evidence for a mixed (N or O as well as S) coordination sphere, while the minor shells indicate imidazole coordination. Our approach to the analysis of the EXAFS, including quantification of the imidazole by multiple scattering simulations with EXCURV92, was validated on the model compounds. An important result is that with multiple scattering simulations using restraints on the parameters of the imidazole rings the number of imidazoles and their orientation could be determined. The integrase spectra can be fitted with two sulfur ligands at 2.26 A (Debye-Waller-type factor 0.009 A(2)) and two imidazole ligands with the N atoms at 1.99 A (Debye-Waller-type factor 0.005 A(2)). The XAS-derived geometry is fully consistent with that found in the NMR structure determination and, allowing for the Volume contraction due to the temperature difference between the experiments, justifies the restraints applied in the structure calculation (Zn-S and Zn-N distances of 2.3 A and 2.0 A, respectively). PMID:12511797

Feiters, Martinus C; Eijkelenboom, Astrid P A M; Nolting, Hans Friedrich; Krebs, Bernt; van den Ent, Fusinita M I; Plasterk, Ronald H A; Kaptein, Robert; Boelens, Rolf

2003-01-01

276

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.

277

Brief communication: Mass spectroscopic characterization of tetracycline in the skeletal remains of an ancient population from Sudanese Nubia 350-550 CE.  

PubMed

Histological evidence of tetracycline use has been reported in an ancient X-Group population (350-550 CE) from Sudanese Nubia (Bassett et al., 1980). When bone samples were examined by fluorescent microscopy under UV light at 490 A yellow-green fluorophore deposition bands, similar to those produced by tetracycline, were observed, suggesting significant exposure of the population to the antibiotic. These reports were met skeptically with claims that the fluorescence was the result of postmortem taphonomic infiltration of bacteria and fungi. Herein, we report the acid extraction and mass spectroscopic characterization of the antibiotic tetracycline from these samples. The bone samples were demineralized in anhydrous hydrogen fluoride which dissolved the bone-complexed tetracycline, followed by isolation by solid phase extraction on reverse-phase media. Chemical characterization by high pressure liquid chromatography mass-spectroscopic procedures showed that the retention times and mass spectra of the bone extract were identical to tetracycline when treated similarly. These results indicate that a natural product tetracycline was detectable within the sampled bone and was converted to the acid-stable form, anhydrotetracycline, with a mass + H of 427.1 amu. Our findings show that the bone sampled is labeled by the antibiotic tetracycline, and that the NAX population ingested and were exposed to tetracycline-containing materials in their dietary regime. PMID:20564518

Nelson, Mark L; Dinardo, Andrew; Hochberg, Jeffery; Armelagos, George J

2010-09-01

278

Femtosecond transient absorption spectroscopic study of a carbonyl-containing carotenoid analogue, 2-(all-trans-retinylidene)-indan-1,3-dione.  

PubMed

The photophysical properties of a carbonyl-containing carotenoid analogue in an s-cis configuration, relative to the conjugated ? system, 2-(all-trans-retinylidene)-indan-1,3-dione (C20Ind), were investigated by femtosecond time-resolved spectroscopy in various solvents. The lifetime of the optically forbidden S(1) state of C20Ind becomes long as solvent polarity increases. This trend is completely opposite to the situation of S(1-ICT) dynamics of carbonyl-containing carotenoids, such as peridinin and fucoxanthin. Excitation energy dependence of the transient absorption measurements shows that the transient absorption spectra in nonpolar solvents were originated from two distinct transient species, while those in polar and protic solvents are due to a single transient species. By referring to the results of MNDO-PSDCI (modified neglect of differential overlap with partial single- and double-configuration interaction) calculations, we conclude: (1) in polar and protic solvents, the S(1) state is generated following excitation up to the S(2) state; (2) in nonpolar solvents, however, both the S(1) and the (1)n?* states are generated; and (3) C20Ind does not generate the S(1-ICT) state, despite the fact that it has two conjugated carbonyl groups. PMID:21361262

Kusumoto, Toshiyuki; Kosumi, Daisuke; Uragami, Chiasa; Frank, Harry A; Birge, Robert R; Cogdell, Richard J; Hashimoto, Hideki

2011-03-24

279

A femtosecond transient absorption spectroscopic study on a carbonyl-containing carotenoid analogue, 2-(all-trans-retinylidene)-indan-1,3-dione  

PubMed Central

The photophysical properties of a carbonyl-containing carotenoid analogue in an s-cis configuration, relative to the conjugated ? system, 2-(all-trans-retinylidene)-indan-1,3-dione (C20Ind), were investigated by femtosecond time-resolved spectroscopy in various solvents. The lifetime of the optically forbidden S1 state of C20Ind becomes long as solvent polarity increases. This trend is completely opposite to the situation of S1-ICT dynamics of carbonyl-containing carotenoids, such as peridinin and fucoxanthin. Excitation energy dependence of the transient absorption measurements shows that the transient absorption spectra in non-polar solvents were originated from two distinct transient species, while those in polar and protic solvents are due to a single transient species. By referring to the results of MNDO-PSDCI (modified neglect of differential overlap with partial single- and double-configuration interaction) calculations, we conclude: (1) In polar and protic solvents, the S1 state is generated following excitation up to the S2 state; (2) In non-polar solvents, however, both the S1 and 1n?* states are generated; and (3) C20Ind does not generate the S1-ICT state, despite the fact that it has two conjugated carbonyl groups. PMID:21361262

Kusumoto, Toshiyuki; Kosumi, Daisuke; Uragami, Chiasa; Frank, Harry A.; Birge, Robert R.; Cogdell, Richard J.; Hashimoto, Hideki

2011-01-01

280

Spectroscopic Diagnostics for AGNs  

E-print Network

A review of the spectroscopic tools needed to characterize AGNs is presented. This review focusses on ultraviolet, optical and infrared emission-line diagnostics specifically designed to help differentiate AGNs from starburst-dominated galaxies. The strengths and weaknesses of these methods are discussed in the context of on-going and future AGN surveys.

Sylvain Veilleux

2002-01-08

281

Absorption spectra and photovoltaic characterization of chlorophyllins as sensitizers for dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

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.

Calogero, Giuseppe; Citro, Ilaria; Crupi, Cristina; Di Marco, Gaetano

2014-11-01

282

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

283

Organic matter characterization by infrared spectroscopic methods in lake sediment records from boreal and subarctic Sweden: Implications for long-term carbon cycling  

NASA Astrophysics Data System (ADS)

Freshwater systems play an important role in the global carbon cycle. In this dynamic system, inorganic and organic carbon can be incorporated into biota, effluxed to the atmosphere or accumulated in sediments. The amount and composition of the carbon, derived from both aquatic and terrestrial sources, accumulated in sediments depend on the climatic and environmental conditions present in the lake and its catchment, and are thus sensitive to changes in, e.g., temperature, precipitation, vegetation and hydrological flow patterns. In this study, we show the application of infrared spectroscopic methods to qualitatively and quantitatively characterize organic matter stored in lake sediments with a focus on changes in the source of terrestrial-derived organic matter. Infrared spectroscopic methods facilitate a fast, cost-efficient and non-destructive analysis of minerogenic as well as organic sediment components. We applied three different infrared spectroscopic analyses - visible-near infrared spectroscopy (VNIRS; 25000-4000 cm-1), Fourier-transform infrared spectroscopy in the mid-IR region (FTIR; 3750-400 cm-1) and a combined Fourier-transformed infrared - thermal programmed desorption technique (FTIR-TPD; 3750-400 cm-1) - to Holocene sediment records from two Swedish lakes, Lång-Älgsjön and Lake Koukkel, to reconstruct past changes in the organic matter composition. The infrared spectral information of these records indicate sections of different organic matter composition reflecting varying stages of the lake and landscape development. An early-Holocene mire development around the boreal lake Lång-Älgsjön led to an increased input of organic matter from the catchment into the lake initiating an early natural lake acidification, whereas the subarctic Lake Koukkel has been affected by mire and potentially late-Holocene permafrost dynamics, which caused an increased and less variable input of allochthonous organic matter. Overall, variations in organic matter composition seem mainly driven by changes in the landscape rather than any direct effects of successive climate changes. Our findings emphasize that infrared spectroscopic methods are a promising tool for the fast and cost-effective characterization of organic matter in sediment samples, particularly with regard to the detection of qualitative differences between samples. An improved understanding of past variations in the organic matter composition and the related processes driving these changes is essential to further understand the interactions in the carbon cycle between the terrestrial and aquatic systems.

Meyer-Jacob, Carsten; Rosén, Peter; Bindler, Richard

2013-04-01

284

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

285

A novel strategy for site-directed chemical reactions in single stranded DNA--absorption and NMR spectroscopic studies of model compounds.  

PubMed Central

A new and simple model enabling a chemical species to be brought to a preselected site in single strand DNA is reported. Two oligonucleotides containing a propanediol linkage were hybridized to their complementary sequences with an extra-base opposite the propanediol derivative. Absorption studies results shown that the addition of a bisacridine derivative strongly increased the stabilities of both duplexes when added in a 1:1 ratio. NMR studies on one of these duplexes brought evidence of the intercalation of the bisacridine at the position involving the propanediol linkage. These results suggest that this system could be used to target a specific reaction at a preselected position using the bisacridine derivative as carrier for the reactive species. PMID:1408782

Asseline, U; Rozelle, T; Lancelot, G; Thuong, N T

1992-01-01

286

Preliminary characterization of calcium chemical environment in apatitic and non-apatitic calcium phosphates of biological interest by X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Several reports have mentioned the existence of non-apatitic environments of phosphate and carbonate ions in synthetic and biological poorly crystalline apatites. However there were no direct spectroscopic evidences for the existence of non-apatitic environment of calcium ions. X-ray Absorption Spectroscopy, at the K-edge of calcium, allows the discrimination between different calcium phosphates of biological interest despite great spectral similarities. A primary analysis of the spectra reveals the existence, in synthetic poorly crystalline apatites, of variable features related to the maturation stage of the sample and corresponding to the existence of non-apatitic environments of calcium ions. Although these features can also be found in several other calcium phosphate salts, and do not allow a clear identification of the ionic environments of calcium ions, they give a possibility to directly determine the maturity of poorly crystalline apatite from calcium X-ray Absorption Near Edge Structure spectra.

Eichert, D.; Salomé, M.; Banu, M.; Susini, J.; Rey, C.

2005-07-01

287

Chemical modification of TiO2 surfaces with methylsilanes and characterization by infrared absorption spectroscopy  

NASA Technical Reports Server (NTRS)

Infrared absorption spectra of methylsilanes bonded to a TiO2 powder were obtained. The reacting silanes include Me sub (4-n)SiX sub n (n=1-4; X=Cl, OMe) and hexamethyldisilazane (HMDS). Reactions were performed on hydroxylated-but-anhydrous TiO2 surfaces in the gas phase. IR spectra confirm the presence of a bonded silane layer. Terminal surface OH groups are found to react more readily than bridging OH groups. By-products of the modification adsorp tenaciously to the surface. The various silanes show only small differences in their ability to sequester surface OH groups. Following hydrolysis in moist air, Si-OH groups are observed only for the tetrafunctional silanes.

Finklea, H. O.; Vithanage, R.

1982-01-01

288

Characterization of hydrogen absorption/desorption states on lithium-carbon-hydrogen system by neutron diffraction  

NASA Astrophysics Data System (ADS)

The nanostructural hydrogenated graphite (CnanoHx) was synthesized from graphite by ball milling under hydrogen (H2) atmosphere. In this product, characteristic hydrogenated states in the form of polarized hydrocarbon groups (?CH, ?CH2, and ?CH3) are realized in the nanoscale. By synthesizing the composite of CnanoHx and lithium hydride (LiH), known as the Li ?C?H system, hydrogen was desorbed at 350°C, which is a lower temperature compared to the decomposition temperature of each component. It is considered that this hydrogen desorption would be induced by destabilization of each hydrogen absorbed state due to an interaction between the polarized C ?H groups in CnanoHx and LiH. Therefore, in order to understand the hydrogen absorption/desorption mechanism of the Li ?C?H system, it is an important issue to investigate the change in the C ?H groups during hydrogen absorption/desorption reactions in the composite. The correlations among atoms contained in this composite are examined by neutron diffraction measurements, where the protium/deuterium (H/D) isotopic substitution was used to clarify the location of hydrogen atoms in this composite. Some C ?D and Li ?D correlations are found from the radial distribution function [RDF(r)] obtained by the neutron diffraction for the CnanoDx and LiD composite. After dehydrogenation, C ?C triple bond and Li ?C bond, ascribed to lithium carbide (Li2C2), are observed. Furthermore, the RDF(r ) corresponding to rehydrogenated composite indicates the presence of not only the Li ?D correlation but also the C ?D one.

Miyaoka, Hiroki; Itoh, Keiji; Fukunaga, Toshiharu; Ichikawa, Takayuki; Kojima, Yoshitsugu; Fuji, Hironobu

2008-09-01

289

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, G.E., Jr.; Rytuba, J.J.

2000-01-01

290

An X-ray absorption spectroscopic study of the metal site preference in Al{sub 1-x}Ga{sub x}FeO{sub 3}  

SciTech Connect

Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO{sub 3} (Pna2{sub 1}; 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, Al{sub 1-x}Ga{sub x}FeO{sub 3} was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L{sub 2,3}-, 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 Al{sub 1-x}Ga{sub x}FeO{sub 3} 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 AlFeO{sub 3} than in GaFeO{sub 3}, implying more anti-site disorder is present in AlFeO{sub 3}. - Graphical abstract: Al{sub 1-x}Ga{sub x}FeO{sub 3} has been investigated by XANES. Through examination of Al L{sub 2,3}-, Ga K-, and Fe K-edge XANES spectra, it was found that more anti-site disorder of the Fe atoms is present in AlFeO{sub 3} compared to in GaFeO{sub 3}. Highlights: Black-Right-Pointing-Pointer Al{sub 1-x}Ga{sub x}FeO{sub 3} was investigated by X-ray absorption spectroscopy. Black-Right-Pointing-Pointer Ga prefers to occupy the tetrahedral site in Al{sub 1-x}Ga{sub x}FeO{sub 3}. Black-Right-Pointing-Pointer Fe prefers to occupy the octahedral sites in Al{sub 1-x}Ga{sub x}FeO{sub 3} as x increases. Black-Right-Pointing-Pointer More anti-site disorder is present in AlFeO{sub 3} compared to in GaFeO{sub 3.}.

Walker, James D.S. [Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5C9 (Canada); Grosvenor, Andrew P., E-mail: andrew.grosvenor@usask.ca [Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5C9 (Canada)

2013-01-15

291

Multi-steps infrared spectroscopic characterization of the effect of flowering on medicinal value of Cistanche tubulosa  

NASA Astrophysics Data System (ADS)

Multi-steps infrared spectroscopic methods, including conventional Fourier transform infrared spectroscopy (FT-IR), second derivative spectroscopy and two-dimensional infrared (2D-IR) correlation spectroscopy, have been proved to be effective methods to examine complicated mixture system such as Chinese herbal medicine. The focus of this paper is the investigation on the effect of flowering on the pharmaceutical components of Cistanche tubulosa by using the Multi-steps infrared spectroscopic method. Power-spectrum analysis is applied to improve the resolution of 2D-IR contour maps and much more details of overlapped peaks are detected. According to the results of FT-IR and second derivative spectra, the peak at 1732 cm -1 assigned to C dbnd O is stronger before flowering than that after flowering in the stem, while more C dbnd O groups are found in the top after flowering. The spectra of root change a lot in the process of flowering for the reason that many peaks shift and disappear after flowering. Seven peaks in the spectra of stem, which are assigned to different kinds of glycoside components, are distinguished by Power-spectra in the range of 900-1200 cm -1. The results provide a scientific explanation to the traditional experience that flowering consumes the pharmaceutical components in stem and the seeds absorb some nutrients of stem after flowering. In conclusion, the Multi-steps infrared spectroscopic method combined with Power-spectra is a promising method to investigate the flowering process of C. tubulosa and discriminate various parts of the herbal medicine.

Lai, Zuliang; Xu, Peng; Wu, Peiyi

2009-01-01

292

Optical characterization of CuIn1?xGaxSe2 alloy thin films by spectroscopic ellipsometry  

Microsoft Academic Search

Optical constants of polycrystalline thin film CuIn1?xGaxSe2 alloys with Ga\\/(Ga+In) ratios from 0 to 1 have been determined by spectroscopic ellipsometry over an energy range of 0.75–4.6 eV. CuIn1?xGaxSe2 films were deposited by simultaneous thermal evaporation of elemental copper, indium, gallium and selenium. X-ray diffraction measurements show that the CuIn1?xGaxSe2 films are single phase. Due to their high surface roughness,

P. D. Paulson; R. W. Birkmire; W. N. Shafarman

2003-01-01

293

Optical characterization of CuIn1-xGaxSe2 alloy thin films by spectroscopic ellipsometry  

Microsoft Academic Search

Optical constants of polycrystalline thin film CuIn1-xGaxSe2 alloys with Ga\\/(Ga+In) ratios from 0 to 1 have been determined by spectroscopic ellipsometry over an energy range of 0.75-4.6 eV. CuIn1-xGaxSe2 films were deposited by simultaneous thermal evaporation of elemental copper, indium, gallium and selenium. X-ray diffraction measurements show that the CuIn1-xGaxSe2 films are single phase. Due to their high surface roughness,

P. D. Paulson; R. W. Birkmire; W. N. Shafarman

2003-01-01

294

Characterization of esterase and alcohol dehydrogenase activity in skin. Metabolism of retinyl palmitate to retinol (vitamin A) during percutaneous absorption.  

PubMed

Retinyl palmitate, a widely used ingredient in cosmetic products, is promoted for its beneficial effects on the appearance of skin. Previous studies suggest that enzymes are available in skin to metabolize this ingredient during skin absorption. Esterase activity hydrolyzes retinyl palmitate to retinol (vitamin A), which is oxidized in many tissues to retinoic acid primarily by alcohol dehydrogenase. The activities of esterase and alcohol dehydrogenase were characterized in hairless guinea pig skin by using flow-through diffusion cells and radiolabeled model compounds (methyl salicylate and benzyl alcohol) previously shown to be metabolized by these enzymes. Methyl salicylate was hydrolyzed by esterase to a greater extent in viable skin than in nonviable skin. Glycine conjugation of salicylic acid and benzoic acid occurred only in viable skin. The metabolism of methyl salicylate and benzyl alcohol occurred to a greater extent in male guinea pig skin than in female guinea pig skin. The percutaneous absorption of both radiolabeled compounds was similar in viable and nonviable skin. About 30 and 18% of topically applied retinyl palmitate were absorbed from an acetone vehicle by hairless guinea pig skin and human skin, respectively. Less than 1% of the applied dose of this lipophilic compound diffused from skin into the receptor fluid. Retinol was the only detectable metabolite of retinyl palmitate in both hairless guinea pig and human skin. In human skin, 44% of the absorbed retinyl palmitate was hydrolyzed to retinol. The use of retinyl palmitate in cosmetic formulations may result in significant delivery of retinol into the skin. PMID:7971717

Boehnlein, J; Sakr, A; Lichtin, J L; Bronaugh, R L

1994-08-01

295

X-ray photoelectron and X-ray absorption spectroscopic study on ?-FeSi 2 thin films fabricated by ion beam sputter deposition  

NASA Astrophysics Data System (ADS)

A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of ?-FeSi 2 films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173 K are investigated. For the film fabricated at 873 K, Si 2p XPS spectra indicate the formation of a relatively thicker SiO 2 layer. In addition, Fe L-edge XAS spectra exhibit the formation of FeSi 2- X by preferential oxidation of Si or the presence of unreacted Fe. The results for the film fabricated at 1173 K imply the existence of FeSi 2 with ? and ? phases. In contrast, the results for the film fabricated at 973 K indicate the formation of relatively homogeneous ?-FeSi 2. These imply that the relatively excellent crystal property of the film fabricated at 973 K is due to the formation of homogeneous ?-FeSi 2. As a conclusion, the combination of XPS and XAS using synchrotron radiation is a powerful tool to elucidate the surface chemical states of thin films.

Esaka, F.; Yamamoto, H.; Matsubayashi, N.; Yamada, Y.; Sasase, M.; Yamaguchi, K.; Shamoto, S.; Magara, M.; Kimura, T.

2010-03-01

296

X-ray Absorption Spectroscopic and Computational Investigation of a Possible S···S Interaction in the [Cu3S2]3+ Core  

PubMed Central

The electronic structure of the [Cu3S2]3+ core of [(LCu)3(S)2]3+ (L = N,N,N?,N?-tetramethyl-2R,3R-cyclohexanediamine) is investigated using a combination of Cu and S K-edge X-ray absorption spectroscopy and calculations at the density functional and multireference second-order perturbation levels of theory. The results show that the [Cu3S2]3+ core is best described as having all copper centers close to, but more oxidized than, Cu2+, while the charge on the S2 fragment is between that of a sulfide (S2?) and a subsulfide (S23?) species. The [Cu3S2]3+ core thus is different from a previously described, analogous [Cu3O2]3+ core, which has a localized [(Cu3+Cu2+Cu2+)(O2?)2]3+ electronic structure. The difference in electronic structure between the two analogues is attributed to increased covalent overlap between the Cu 3d and S 3p orbitals and the increased radial distribution function of the S 3p orbital (relative to O 2p). These features result in donation of electron density from the S-S ?* to the Cu and result in some bonding interaction between the two S atoms at ~ 2.69 Å in [Cu3S2]3+, stabilizing a delocalized S=1 ground state. PMID:21923178

Sarangi, Ritimukta; Yang, Lei; Winikoff, Stuart G.; Gagliardi, Laura; Cramer, Christopher J.; Tolman, William B.; Solomon, Edward I.

2011-01-01

297

Combination of chiroptical, absorption and fluorescence spectroscopic methods reveals multiple, hydrophobicity-driven human serum albumin binding of the antimalarial atovaquone and related hydroxynaphthoquinone compounds.  

PubMed

High-affinity human serum albumin (HSA) binding of the C3-substituted antimalarial 2-hydroxy-1,4-naphthoquinone derivative atovaquone (ATQ) has been demonstrated and studied by circular dichroism (CD), UV/VIS absorption, fluorescence spectroscopy and affinity chromatography methods. The analysis of induced CD data generated upon HSA binding of ATQ revealed two high-affinity binding sites (K(a) ? 2 × 10(6) M(-1)). CD interaction studies and displacement of specific fluorescent and radioactive marker ligands indicated the contribution of both principal drug binding sites of HSA to complexation of ATQ, and also suggested the possibility of simultaneous binding of ATQ and some other drugs (e.g. warfarin, phenylbutazone, diazepam). Comparison of UV/VIS spectra of ATQ measured in aqueous solutions indicated the prevalence of the anionic species formed by dissociation of the 2-hydroxyl group. HSA binding of related natural hydroxynaphthoquinones, lapachol and lawsone also induces similar CD spectra. The much weaker binding affinity of lawsone (K(a) ? 10(4) M(-1)) bearing no C3 substituent highlights the importance of hydrophobic interactions in the strong HSA binding of ATQ and lapachol. Since neither drug exhibited significant binding to serum ?(1)-acid glycoprotein, HSA must be the principal plasma protein for the binding and transportation of 2-hydroxy-1,4-naphthoquinone-type compounds which are ionized at physiological pH values. PMID:20737064

Zsila, Ferenc; Fitos, Ilona

2010-11-01

298

Spectroscopic verification of zinc absorption and distribution in the desert plant Prosopis juliflora-velutina (velvet mesquite) treated with ZnO nanoparticles  

PubMed Central

The impact of metal nanoparticles (NPs) on biological systems, especially plants, is still not well understood. The aim of this research was to determine the effects of zinc oxide (ZnO) NPs in velvet mesquite (Prosopis juliflora-velutina). Mesquite seedlings were grown for 15 days in hydroponics with ZnO NPs (10 nm) at concentrations varying from 500 to 4000 mg L?1. Zinc concentrations in roots, stems and leaves were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Plant stress was examined by the specific activity of catalase (CAT) and ascorbate peroxidase (APOX); while the biotransformation of ZnO NPs and Zn distribution in tissues was determined by X-ray absorption spectroscopy (XAS) and micro X-ray fluorescence (?XRF), respectively. ICP-OES results showed that Zn concentrations in tissues (2102 ± 87, 1135 ± 56, and 628 ± 130 mg kg?1 d wt in roots, stems, and leaves, respectively) were found at 2000 mg ZnO NPs L?1. Stress tests showed that ZnO NPs increased CAT in roots, stems, and leaves, while APOX increased only in stems and leaves. XANES spectra demonstrated that ZnO NPs were not present in mesquite tissues, while Zn was found as Zn(II), resembling the spectra of Zn(NO3)2. The ?XRF analysis confirmed the presence of Zn in the vascular system of roots and leaves in ZnO NP treated plants. PMID:22820414

Hernandez-Viezcas, J.A.; Castillo-Michel, H.; Servin, A.D.; Peralta-Videa, J.R.; Gardea-Torresdey, J.L.

2012-01-01

299

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

300

Ground-based infrared spectroscopic measurements of carbonyl sulfide: Free tropospheric trends from a 24-year time series of solar absorption measurements  

NASA Astrophysics Data System (ADS)

Solar absorption spectra recorded over a 24-year time span have been analyzed to retrieve average free tropospheric mixing ratios of carbonyl sulfide (OCS). The measurements were recorded with the Fourier transform spectrometer located in the U.S. National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.09 km, lat. 31.9°N, long. 111.6°W), southwest of Tucson, Arizona, and were obtained on 167 days between May 1978 and February 2002, typically at 0.01-cm-1 spectral resolution. A best fit to the time series shows an average mixing ratio of 566 pptv (1 pptv = 10-12 per unit volume) between 2.09 and 10 km, a small but statistically significant long-term decrease equal to (-0.25 ± 0.04)% yr-1, 1 sigma, and a seasonal variation with a summer maximum, a winter minimum, and a peak amplitude of (1.3 ± 0.4)%, 1 sigma, relative to the mean. Although a statistically significant decline and seasonal variation have been detected, both are exceedingly small. The present results confirm and extend earlier studies showing that the OCS free tropospheric abundance at northern midlatitudes has remained nearly constant over the last decades.

Rinsland, C. P.; Goldman, A.; Mahieu, E.; Zander, R.; Notholt, J.; Jones, N. B.; Griffith, D. W. T.; Stephen, T. M.; Chiou, L. S.

2002-11-01

301

Structural features of titanate nanotubes/nanobelts revealed by Raman, X-ray absorption fine structure and electron diffraction characterizations.  

PubMed

High-purity nanotubes and nanobelts could be controllably obtained in hydrothermal treatments of anatase TiO(2) in concentrated NaOH solution depending on treating temperature and duration. Their structural features were studied employing X-ray diffraction, Raman, X-ray absorption fine structure, and electron diffraction characterizations. The results reveal that both the nanotubes and nanobelts might be of layered titanate structure. The similarity and difference among the nanotubes/nanobelts and other bulk titanates represented by trititanate H(2)Ti(3)O(7) and lepidocrocite-type H(0.7)Ti(1.825) square(0.175)O(4.0).H(2)O were also presented. PMID:16851687

Ma, Renzhi; Fukuda, Katsutoshi; Sasaki, Takayoshi; Osada, Minoru; Bando, Yoshio

2005-04-01

302

Gold Nanoclusters Entrapped in the Alpha-Cages of Y-Zeolites: Structural Characterization By X-Ray Absorption Spectroscopy  

SciTech Connect

Au(CH{sub 3}){sub 2}(C{sub 5}H{sub 7}O{sub 2}) was used as a precursor to synthesize mononuclear gold complexes in faujasites, NaY zeolite, and dealuminated Y zeolite. Treatment of these supported complexes in flowing helium as the temperature was increased led to the gradual reduction of the gold and formation of gold nanoclusters in each zeolite, which were characterized by X-ray absorption spectroscopy. After treatment at the highest temperature, 573 K, the average diameters of the gold clusters were approximately 10 and 8 {angstrom} in NaY zeolite and dealuminated Y zeolite, respectively; these clusters are smaller than the diameters of the {alpha}-cages of the zeolite. The results indicate that the supported clusters were trapped within these cages and that the cages limited their sizes; in contrast, clusters formed similarly on the surfaces of metal oxides are significantly larger than those formed in the zeolites.

Fierro-Gonzalez, J.C.; Hao, Y.; Gates, B.C.

2009-06-03

303

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. PMID:18463292

Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

2008-01-01

304

Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets  

SciTech Connect

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.

Saykally, Richard J; Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

2008-01-08

305

Spectroscopic characterization of co-precipitated arsenic- and iron-bearing sulfide phases at circum-neutral pH  

NASA Astrophysics Data System (ADS)

Precipitation of arsenic- and iron-sulfide phases from porewaters is an important mechanism for removing arsenic and other contaminant metals from solution, thus reducing their bioaccessibility and potential toxicity. Although sulfide phases form readily at low pH, the identity, crystallinity, and local structure of arsenic and iron co-precipitated phases that form at circum-neutral pH are less well known. In this study, co-precipitated As+Fe sulfide phases and end-member As-sulfides and Fe-sulfides were synthesized in batch experiments and in a gas-tight reaction vessel at 25°C. Reduced conditions were maintained by keeping a constant flow of a 95%N2 /5%H2 mixture gas. Fresh saturated solutions of 0.3 M Fe(II) or Fe(III), 0.3 M S2- and 0.2 M As(III) ions were mixed and pH was maintained at pH 4, 6 and 8 by small additions of concentrated HCl or NaOH. At different time intervals, aliquots were extracted from suspensions aged from hours to 1 month and analyzed for total iron, arsenic and sulfur (by ICP-OES and ICP-MS). The Fe-S-As precipitates were characterized by X-ray diffraction (XRD) and synchrotron X-ray absorption spectroscopy (XAS). X-ray diffraction and Fe k-edge EXAFS showed the precipitation of amorphous to poorly crystalline iron sulfide when Fe(II) was co-precipitated with sulfide (no arsenic) at pH 4, 6, and 8. The precipitate that formed in ~1-4 h was nanoparticle-sized and disordered mackinawite (FeS), which showed a characteristic broad, low-intensity Bragg peaks in the XRD patterns. After aging for ~7 d, XRD patterns showed a change to more crystalline mackinawite. In contrast, co-precipitation of As(III) with Fe(II) and sulfide resulted in x-ray amorphous (both synchrotron and laboratory XRD) precipitates for all pH and aging times (~4 h to 1 m). Arsenic and iron XANES and EXAFS spectra of precipitates at pH 4 showed a mixture of amorphous orpiment-type (As2S3) and mackinawite-type (FeS) phases. At pH 6 and 8, XANES showed As sulfide and a fraction of As(III) coordinated by oxygen, with a higher proportion of As(III)-O at pH 8 with arsenic EXAFS data showing two distinct coordination environments: oxygen atoms at 1.79 Å and sulfur atoms at 2.3, 3.2, and 3.5 Å, the latter consistent with the local structure of orpiment. When Fe(II) was co-precipitated with arsenic and sulfide, Fe EXAFS and XRD showed a mackinawite-type structure with evidence for formation of magnetite at pH 8. Arsenic EXAFS showed a mixture of arsenic sulfide and As(III)-O, with a higher proportion of As(III)-O at pH 8 than at pH 6. Also, analyses of the pH 6 and 8 supernatant solutions showed that ~95% of the iron, and 96-99% of arsenic and sulfur were precipitated with the highest arsenic uptake associated with the Fe(II) mixtures. Thus, at circum-neutral pH arsenic is effectively removed when combined with both iron and sulfide. A complicated mechanism of arsenic sequestration occurs through both rapid precipitation of amorphous arsenic sulfide phases and surface complexation. This differs from the precipitation dominated arsenic removal at low pH mixtures.

Illera, V.; Rivera, N. A.; O'Day, P. A.

2009-12-01

306

Spectroscopic ellipsometry study of Si nanocrystals embedded in a SiOx matrix: Modeling and optical characterization  

NASA Astrophysics Data System (ADS)

In this work, we report on a spectroscopic ellipsometry study of thin films of silicon nanocrystals embedded in a SiOx matrix that is performed to better understand how substoichiometric SiOx species affect the optical properties of these systems. The silicon nanocrystals are fabricated in a SiOx matrix by thermal annealing of magnetron-sputtered thin films in a wide range of x values (0 < x < 2) in order to produce every possible substoichiometric SiOx species in various fractions. A generic optical model to describe the thin film content with various SiOx volumetric fractions is developed and used to analyze the data obtained from the spectroscopic ellipsometry. Tauc-Lorentz and Bruggeman effective medium approximation models are employed to determine the ellipsometric angles (? and ?) and the complex dielectric function. We show that the optical properties of the nc-Si embedded in a SiOx matrix are highly dependent on the value of x and on the volumetric fractions of the substoichiometric SiOx species present in the system.

Ilday, Serim; Nogay, Gizem; Turan, Rasit

2014-11-01

307

Oxybenziporphyrins, oxypyriporphyrins, benzocarbaporphyrins, and their 23-oxa and 23-thia analogues: synthesis, spectroscopic characterization, metalation, and structural characterization of a palladium(II) organometallic derivative.  

PubMed

A series of nine porphyrin analogues have been synthesized using the "3 + 1" variant on the MacDonald condensation. Tripyrrane-type systems with a centrally unsubstituted pyrrole, furan, or thiophene ring were prepared using conventional methods, and these were condensed with indene-1,3-dicarbaldehyde, 5-formylsalicylaldehyde, or 3-hydroxy-2,6-pyridinedicarbaldehyde in the presence of TFA to generate benzocarba-, oxybenzi-, and oxypyriporphyrins, respectively. The furan-containing analogues proved to be highly basic and could only be isolated as the corresponding hydrochloride salts. All nine analogue systems showed porphyrin-like UV-vis spectra with one or two Soret absorptions near 400 nm and a series of weaker bands at longer wavelengths. These systems also showed large diatropic ring currents by proton NMR spectroscopy that were comparable to true porphyrins. In the presence of trace amounts of TFA, benzocarbaporphyrin 12 formed a monocation, and in 50% TFA a C-protonated dication was generated. The 23-oxacarbaporphyrin 14 gave a monocation in chloroform, although the free base was generated in 5% Et(3)N-chloroform. In 50% TFA-CHCl(3), 14 afforded a mixture of mono- and diprotonated species. Thiacarbaporphyrin 15 also formed a monocation in the presence of TFA, but C-protonation was relatively disfavored for this system. Nonetheless, in the presence of TFA-d, 12, 14, and 15 all showed rapid exchange of the internal NH and CH protons. Carbaporphyrin 12 also showed slow exchange at the meso-positions, but this process was not observed for its heteroanalogues 14 and 15. Protonation studies were also conducted for oxybenziporphyrins and oxypyriporphyrins 16-21. Oxacarbaporphyrin 14 was shown to be a superior organometallic ligand and afforded good yields of the related nickel(II) and palladium(II) derivatives under mild conditions. A low yield of the platinum(II) complex could also be isolated. All three complexes retained their aromatic character, although the Pd(II) derivative appeared to possess a slightly larger diatropic ring current. The palladium(II) complex 27 was further characterized by X-ray crystallography. The macrocyclic core was shown to be highly planar where the dihedral angles of the component pyrrole, furan and indene rings relative to the mean [18]annulene plane were all

Liu, Dachun; Ferrence, Gregory M; Lash, Timothy D

2004-09-01

308

X-ray absorption and photoelectron spectroscopic study of the association of As(III) with nanoparticulate FeS and FeS-coated sand.  

PubMed

Iron sulfide (FeS) has been demonstrated to have a high removal capacity for arsenic (As) in reducing environments. However, FeS may be present as a coating, rather than in nanoparticulate form, in both natural and engineered systems. Frequently, the removal capacity of coatings may be different than that of nanoparticulates in batch systems. To assess the differences in removal mechanisms between nanoparticulate FeS and FeS present as a coating, the solid phase products from the reaction of As(III) with FeS-coated sand and with suspensions of nanoparticulate (NP) FeS were determined using x-ray absorption spectroscopy and x-ray photoelectron spectroscopy. In reaction with NP FeS at pH 5, As(III) was reduced to As(II) to form realgar (AsS), while at pH 9, As(III) adsorbed as an As(III) thioarsenite species. In contrast, in the FeS-coated sand system, As(III) formed the solid phase orpiment (As(2)S(3)) at pH 5, but adsorbed as an As(III) arsenite species at pH 9. These different solid reaction products are attributed to differences in FeS concentration and the resultant redox (pe) differences in the FeS-coated sand system versus suspensions of NP FeS. These results point to the importance of accounting for differences in concentration and redox when making inferences for coatings based on batch suspension studies. PMID:21911241

Han, Young-Soo; Jeong, Hoon Y; Demond, Avery H; Hayes, Kim F

2011-11-01

309

Spectroscopic remote sensing of plant stress at leaf and canopy levels using the chlorophyll 680 nm absorption feature with continuum removal  

NASA Astrophysics Data System (ADS)

This paper explores the use of spectral feature analysis to detect plant stress in visible/near infrared wavelengths. A time series of close range leaf and canopy reflectance data of two plant species grown in hydrocarbon-contaminated soil was acquired with a portable spectrometer. The ProSpecTIR-VS airborne imaging spectrometer was used to obtain far range hyperspectral remote sensing data over the field experiment. Parameters describing the chlorophyll 680 nm absorption feature (depth, width, and area) were derived using continuum removal applied to the spectra. A new index, the Plant Stress Detection Index (PSDI), was calculated using continuum-removed values near the chlorophyll feature centre (680 nm) and on the green-edge (560 and 575 nm). Chlorophyll feature's depth, width and area, the PSDI and a narrow-band normalised difference vegetation index were evaluated for their ability to detect stressed plants. The objective was to analyse how the parameters/indices were affected by increasing degrees of plant stress and to examine their utility as plant stress indicators at the remote sensing level (e.g. airborne sensor). For leaf data, PSDI and the chlorophyll feature area revealed the highest percentage (67-70%) of stressed plants. The PSDI also proved to be the best constraint for detecting the stress in hydrocarbon-impacted plants with field canopy spectra and airborne imaging spectroscopy data. This was particularly true using thresholds based on the ASD canopy data and considering the combination of higher percentage of stressed plants detected (across the thresholds) and fewer false-positives.

Sanches, Ieda Del'Arco; Souza Filho, Carlos Roberto; Kokaly, Raymond Floyd

2014-11-01

310

Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide  

NASA Astrophysics Data System (ADS)

Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regard to their environment and the coolant. In this work the study of the atomic structure and next-neighbour environment of Am in the (Pu,U)O2 lattice in an irradiated (60 MW d kg-1) MOX sample was performed employing micro-X-ray fluorescence (µ-XRF) and micro-X-ray absorption fine structure (µ-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Am (˜0.66 wt%) are determined from the experimental data gained for the irradiated fuel material examined in its peripheral zone (rim) of the fuel. In the irradiated sample Am builds up as Am3+ species within an [AmO8]13- coordination environment (e.g. >90%) and no (<10%) Am(IV) or (V) can be detected in the rim zone. The occurrence of americium dioxide is avoided by the redox buffering activity of the uranium dioxide matrix.

Degueldre, Claude; Cozzo, Cedric; Martin, Matthias; Grolimund, Daniel; Mieszczynski, Cyprian

2013-06-01

311

Characterization of the Electronic Structure of Silicon Nanoparticles Using X-ray Absorption and Emission  

SciTech Connect

Resolving open questions regarding transport in nanostructures can have a huge impact on a broad range of future technologies such as light harvesting for energy. Silicon has potential to be used in many of these applications. Understanding how the band edges of nanostructures move as a function of size, surface termination and assembly is of fundamental importance in understanding the transport properties of these materials. In this thesis work I have investigated the change in the electronic structure of silicon nanoparticle assemblies as the surface termination is changed. Nanoparticles are synthesized using a thermal evaporation technique and sizes are determined using atomic force microscopy (AFM). By passivating the particles with molecules containing alcohol groups we are able to modify the size dependent band edge shifts. Both the valence and conduction bands are measured using synchrotron based x-ray absorption spectroscopy (XAS) and soft x-ray fluorescence (SXF) techniques. Particles synthesized via recrystallization of amorphous silicon/SiO{sub 2} multilayers of thicknesses below 10 nm are also investigated using the synchrotron techniques. These samples also show quantum confinement effects but the electronic structure is different from those synthesized via evaporation methods. The total bandgap is determined for all samples measured. The origins of these differences in the electronic structures are discussed.

Vaverka, A M

2008-07-15

312

Synthesis, Spectroscopic Characterization, X-Ray Structure, and DFT Calculations of Some New 1,4-Dihydro-2,6-Dimethyl-3,5 -Pyridinedicarboxamides  

PubMed Central

A series of novel 1,4-dihydro-2,6- dimethyl-3,5-pyridinedicarboxamides were synthesized and characterized by infrared absorption spectrum (IR), proton nuclear magnetic resonance (1H NMR), elemental analysis, ultraviolet spectrum (UV), and fluorescence techniques, together with X-ray single crystal diffraction. The results of density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations provided a reasonable explanation on the molecular structures, the molecular frontier orbital, and the spectra of electronic absorption and emission. The present work will be helpful to systematically understanding of the structures and the optical properties of 1,4-dihydropyridines for studying the structure-activity relationship and to develop new drugs and their analytical methods. PMID:24625887

Li, Yi; Liu, Yuan-Yuan; Chen, Xue-Jun; Xiong, Xiao-Hui; Li, Fang-Shi

2014-01-01

313

The purple Codex Rossanensis: spectroscopic characterization and first evidence of the use of the elderberry lake in a 6th century manuscript  

E-print Network

The Codex Rossanensis is a 6th century Bizantine illuminated manuscript written on purple parchment and conserved at the Museo Diocesano in Rossano Calabro, Italy. It is one of the oldest surviving illuminated manuscripts of the New Testament. The challenge of the analysis of the Codex Rossanensis lies in the lack of analytical information on the pictorial media used in the Early Middle Ages. Even though old-medieval illuminated manuscripts have been deeply studied from the historical standpoint, they have been rarely described in their material composition. This paper presents the results obtained during the measurements campaign (June 2012 - November 2013). The spectroscopic analyses performed by Raman, micro-FTIR and XRF allowed for the complete characterization of the pictorial palette, the inks, the support and the material used in a previous restoration treatment. To the author knowledge the article shows the first experimental evidence of the usage of the elderberry lake in a 6th century illuminated ma...

Bicchieri, Marina

2014-01-01

314

Spectroscopic characterization of Co3O4 catalyst doped with CeO2 and PdO for methane catalytic combustion  

NASA Astrophysics Data System (ADS)

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.

Jod?owski, P. J.; J?drzejczyk, R. J.; Rogulska, A.; Wach, A.; Ku?trowski, P.; Sitarz, M.; ?ojewski, T.; Ko?odziej, A.; ?ojewska, J.

2014-10-01

315

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; ?ojewski, T; Ko?odziej, A; ?ojewska, J

2014-10-15

316

Monitoring and characterization of compost obtained from household waste and pine sawdust in a facultative reactor by conventional and spectroscopic analyses.  

PubMed

This study proposes a new facultative reactor configuration for the treatment of organic household waste and pine sawdust. The process was monitored and the compost characterized by conventional (temperature, moisture, pH, ash content and ratio C/N) conjugated with spectroscopic analyses (ultraviolet (UV)/visible (Vis) and infrared (IR)) and germination index. The spectroscopy results revealed enrichment of carbon-carbon unsaturation structures and a degradation of the aliphatic structures. The results showed that stability of the final product was reached after 90 days and that the compost obtained presents substantial richness of stabilized organic matter and an absence of toxicity, so it may be considered as an organic fertilizer. Finally, this study led to the conclusion that the reactor proposed can be a promising technology for the management of organic household waste and sawdust. PMID:25106532

de Campos, Sandro Xavier; Resseti, Rolan Roney; Zittel, Rosimara

2014-12-01

317

Spectroscopic approach in the characterization of the copper(II) complexes of isatin-3,2'-quinolyl-hydrazones and their adducts  

NASA Astrophysics Data System (ADS)

Copper(II) complexes of isatin-3,2'-quinolyl-hydrazones of the type [Cu(L)X] (where X = Cl -, Br -, NO 3-, CH 3COO - and ClO 4-] and their adducts Cu(L)X.2Y [where Y = pyridine or dioxane and X = Cl -, Br -, NO 3- and ClO 4-] have been synthesized under controlled experimental conditions and characterized by using the modern spectroscopic and physicochemical techniques viz. IR, electronic, EPR, elemental analysis, magnetic moment susceptibility measurements and molar conductance, etc. On the basis of spectral studies a four coordinated square planer geometry is assigned for Cu(L)X type complexes whereas the adducts (Cu(L)X.2Y were found to have a six coordinated octahedral geometry.

Gupta, Lokesh Kumar; Bansal, Usha; Chandra, Sulekh

2006-10-01

318

Synthesis, spectroscopic characterization and magnetic properties of homo- and heterodinuclear complexes of transition and non-transition metal ions with a new Schiff base ligand.  

PubMed

Four homodinuclear complexes of Ni(II)-Ni(II), Cu(II)-Cu(II), Co(II)-Co(II) and Co(III)-Co(II) and five heterodinuclear complexes of Co(III)-Zn(II), Co(III)-Cu(II), Co(III)-Ni(II), Cu(II)-Zn(II) and Zn(II)-Cu(II) with the octadentate Schiff base compartmental ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine (H4fsatrien) have been synthesized. The complexes have been characterized with the help of elemental analyses, molecular weights, molar conductances, magnetic susceptibilities and spectroscopic (UV-vis, IR, ESR) data. Cryomagnetic data also helped to elucidate the structural features of the Cu(II) complexes. PMID:18650125

Sarkar, Saikat; Biswas, Susobhan; Dey, Kamalendu

2008-12-15

319

Study of a sample of faint Be stars in the exofield of CoRoT. I. Spectroscopic characterization  

NASA Astrophysics Data System (ADS)

Context. Be stars are probably the most rapid rotators among stars in the main sequence (MS) and, as such, are excellent candidates to study the incidence of the rotation on the characteristics of their non-radial pulsations, as well as on their internal structure. Pulsations are also thought to be possible mechanisms that help the mass ejection needed to build up the circumstellar disks of Be stars. Aims: The purpose of this paper is to identify a number of faint Be stars observed with the CoRoT satellite and to determine their fundamental parameters, which will enable us to study their pulsation properties as a function of the location in the HR diagram and to search for correlations with the light outbursts, which are possibly produced by discrete mass ejections. Methods: We identified those objects in the exofields of CoRoT presenting the Be phenomenon using H? surveys, as well as automated methods based on pulsation properties that we finally confirmed with FLAMES/GIRAFFE and X-shooter spectroscopic observations at VLT/ESO, and with near-IR photometry. The spectra were 1) corrected for the veiling effect, 2) treated with the GIRFIT code to determine apparent fundamental parameters, and 3) corrected with the FASTROT code for effects induced by the rapid rotation. Results: A list of 41 Be star candidates were found from photometric and spectroscopic criteria. The spectral coverage useful for determining the fundamental parameters was obtained for only about half of them. We then spectroscopically identified 21 Be stars, two probable Be stars, and two B stars contaminated by the Sh 2-284 nebulosity. A short description of the spectral characteristics of each star is given. The fundamental parameters and, in particular, the rotation frequency ?r (cycles per day) were all corrected for rotational effects at rotation rates ranging from ?/?c = 0.8 to 1.0. We have determined the positions of Be stars in the HR diagram and find two of them located beyond the MS phase. Conclusions: The well-determined fundamental parameters presented in this paper for a statistically reliable sample of Be stars will enable us in forthcoming papers to compare the properties of stars as pulsators either according to their location in different regions of the HR diagram or with those predicted from theory. Appendices are only available in electronic form at http://www.aanda.org

Semaan, T.; Hubert, A. M.; Zorec, J.; Martayan, C.; Frémat, Y.; Gutiérrez-Soto, J.; Fabregat, J.

2013-03-01

320

Reactivity-activity relationships of oral anti-diabetic vanadium complexes in gastrointestinal media: an X-ray absorption spectroscopic study.  

PubMed

The reactions of oral V(V/IV) anti-diabetic drugs within the gastrointestinal environment (particularly in the presence of food) are a crucial factor that affects their biological activities, but to date these have been poorly understood. In order to build up reactivity-activity relationships, the first detailed study of the reactivities of typical V-based anti-diabetics, Na3V(V)O4 (A), [V(IV)O(OH2)5](SO4) (B), [V(IV)O(ma)2] (C, ma = maltolato(-)) and (NH4)[V(V)(O)2(dipic)] (D, dipic = pyridine-2,5-dicarboxylato(2-)) with simulated gastrointestinal (GI) media in the presence or absence of food components has been performed by the use of XANES (X-ray absorption near edge structure) spectroscopy. Changes in speciation under conditions that simulate interactions in the GI tract have been discerned using correlations of XANES parameters that were based on a library of model V(V), V(IV), and V(III) complexes for preliminary assessment of the oxidation states and coordination numbers. More detailed speciation analyses were performed using multiple linear regression fits of XANES from the model complexes to XANES obtained from the reaction products from interactions with the GI media. Compounds B and D were relatively stable in the gastric environment (pH ? 2) in the absence of food, while C was mostly dissociated, and A was converted to [V10O28](6-). Sequential gastric and intestinal digestion in the absence of food converted A, B and D to poorly absorbed tetrahedral vanadates, while C formed five- or six-coordinate V(V) species where the maltolato ligands were likely to be partially retained. XANES obtained from gastric digestion of A-D in the presence of typical food components converged to that of a mixture of V(IV)-aqua, V(IV)-amino acid and V(III)-aqua complexes. Subsequent intestinal digestion led predominantly to V(IV) complexes that were assigned as citrato or complexes with 2-hydroxyacidato donor groups from other organic compounds, including certain carbohydrates. The absence of strong reductants (such as ascorbate) in the food increased the V(V) component in gastrointestinal digestion products. These results can be used to predict the oral bioavailability of various types of V(V/IV) anti-diabetics, and the effects of taking such drugs with food. PMID:25100248

Levina, Aviva; McLeod, Andrew I; Kremer, Lauren E; Aitken, Jade B; Glover, Christopher J; Johannessen, Bernt; Lay, Peter A

2014-10-01

321

Spectroscopic characterization of a neon surface-wave sustained (2.45 GHz) discharge at atmospheric pressure  

NASA Astrophysics Data System (ADS)

In this paper a spectroscopic study of a microwave (2.45 GHz) neon surface-wave sustained discharge (SWD) at atmospheric pressure in a quartz tube has been carried out in order to determine the plasma characteristic parameters (e.g. electron temperature and density, gas temperature, absorbed power per electron) and also to identify possible deviations from the thermodynamic equilibrium for this kind of microwave discharge. The results have been compared to experiments in the literature for other noble gas (helium and argon) SWDs generated under similar experimental conditions. Intermediate values between those of argon and helium plasmas were obtained for characteristic neon plasma parameters (temperatures and electron density). An important departure from the Saha equilibrium was exhibited by neon SWDs.

Sáinz, A.; García, M. C.

2008-09-01

322

The Time Domain Spectroscopic Survey: Spectroscopic Variability Investigations Within SDSS-IV/eBOSS  

NASA Astrophysics Data System (ADS)

The Time Domain Spectroscopic Survey (TDSS) is an SDSS-IV subproject that began summer 2014 and will continue for 4-6 years. Besides its main program to obtain initial characterization spectra of about 220,000 optical variables selected from PanSTARRS-1, the TDSS includes 9 separate smaller programs to study spectroscopic variability. We describe each of these Few-Epoch Spectroscopy (FES) programs, which target objects with existing SDSS spectroscopy amongst classes of quasars and stars of particular astrophysical interest. These include, in approximate order of decreasing sample size: Broad Absorption Line Quasars (BALQSOs), the most photometrically variable ("HyperVariable") quasars, high S/N normal broad line quasars, quasars with double-peaked or very asymmetric broad emission line profiles, Hypervariable stars, active ultracool (late-M and L-type) dwarf stars with Halpha emission, dwarf carbon stars, white dwarf/M dwarf spectroscopic binaries with Halpha emission, and binary supermassive black hole candidates from MgII broad line velocity shift analysis. We summarize herein the unique and diverse astrophysical investigations facilitated by these TDSS FES programs.

Green, Paul J.; Anderson, Scott F.; Morganson, Eric; Eracleous, Michael; Shen, Yue; Brandt, W. Niel; Ruan, John J.; Schmidt, Sarah J.; Badenes, Carles; West, Andrew A.; Ju, Wenhua; Greene, Jenny E.; Tdss, Panstarrs-1, Sdss-Iv

2015-01-01

323

Quest for Environmentally-Benign Ligands for Actinide Separations: Thermodynamic, Spectroscopic, and Structural Characterization of U(VI) Complexes with Oxa-Diamide and Related Ligands  

SciTech Connect

Complexation of U(VI) with N,N,N{prime},N{prime}-tetramethyl-3-oxa-glutaramide (TMOGA) and N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) was studied in comparison with their dicarboxylate analog, oxydiacetic acid (ODA). Thermodynamic parameters, including stability constants, enthalpy and entropy of complexation, were determined by spectrophotometry, potentiometry and calorimetry. Single-crystal X-ray diffractometry, EXAFS spectroscopy, FT-IR absorption and laser-induced luminescence spectroscopy were used to obtain structural information on the U(VI) complexes. Like ODA, TMOGA and DMOGA form tridentate U(VI) complexes, with three oxygen atoms (the amide, ether and/or carboxylate oxygen) coordinating to the linear UO{sub 2}{sup 2+} cation via the equatorial plane. The stability constants, enthalpy and entropy of complexation all decrease in the order ODA > DMOGA > TMOGA, showing that the complexation is entropy driven and the substitution of a carboxylate group with an amide group reduces the strength of complexation with U(VI) due to the decrease in the entropy of complexation. The trend in the thermodynamic stability of the complexes correlates very well with the structural and spectroscopic data obtained by single crystal XRD, FT-IR and laser-induced luminescence spectroscopy.

Advanced Light Source; Tian, Guoxin; Rao, Linfeng; Teat, Simon J.; Liu, Guokui

2009-01-05

324

Characterization of two quinone radicals in the NADH:ubiquinone oxidoreductase from Escherichia coli by a combined fluorescence spectroscopic and electrochemical approach.  

PubMed

The NADH:ubiquinone oxidoreductase (complex I) couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. It was proposed that the electron transfer involves quinoid groups localized at the end of the electron transfer chain. To identify these groups, fluorescence excitation and emission spectra of Escherichia coli complex I and its fragments, namely, the NADH dehydrogenase fragment containing the flavin mononucleotide and six iron-sulfur (Fe-S) clusters, and the quinone reductase fragment containing three Fe-S clusters were measured. Signals sensitive to reduction by either NADH or dithionite were detected within the complex and the quinone reductase fragment and attributed to the redox transition of protonated ubiquinone radicals. A fluorescence spectroscopic electrochemical redox titration revealed midpoint potentials of -37 and- 235 mV (vs the standard hydrogen electrode) for the redox transitions of the quinone radicals in complex I at pH 6 with an absorption around 325 nm and a fluorescence emission at 460/475 nm. The role of these cofactor(s) for electron transfer is discussed. PMID:24279322

Hielscher, Ruth; Yegres, Michelle; Voicescu, Mariana; Gnandt, Emmanuel; Friedrich, Thorsten; Hellwig, Petra

2013-12-17

325

Synthesis, characterization, spectroscopic and thermodynamic studies of charge transfer interaction of a new water-soluble cobalt(II) Schiff base complex with imidazole derivatives  

NASA Astrophysics Data System (ADS)

The water-soluble cobalt(II) tetradentate Schiff base complex [Co(II)L](ClO 4) 2, L: ( N, N'-bis{5-[(triphenylphosphonium)-methyl]salicylidine}- o-phenylenediamineperchlorate has been synthesized and characterized. This complex forms charge transfer (CT) complexes with imidazole and 1-methylimidazole. The formation constant, molar absorptivity ( ?'), and thermodynamic parameters for charge transfer complexes formation of cobalt(II) Schiff base complexes with imidazole derivatives were determined by using UV-vis spectrophotometric method in aqueous solutions at constant ionic strength ( I = 0.2 mol dm -3 KNO 3) at pH 6.0 and various temperatures between 292 and 315 K.

Boghaei, Davar M.; Askarizadeh, Elham; Bezaatpour, Abolfazl

2008-02-01

326

Characterizing a Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for Measurements of Atmospheric Ammonia  

Microsoft Academic Search

A compact, fast response Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC- TILDAS) for measurements of ammonia has been evaluated under both laboratory and field conditions. Absorption of radiation from a pulsed, thermoelectrically cooled QC laser occurs at reduced pressure in a 76 m path length, 0.5 L volume multiple pass absorption cell. Detection is achieved using a thermoelectrically

R. Ellis; J. G. Murphy; R. van Haarlem; E. Pattey; J. O'Brien

2009-01-01

327

One-dimensional WO{sub 3} and its hydrate: One-step synthesis, structural and spectroscopic characterization  

SciTech Connect

We report on a one-step hydrothermal growth of one-dimensional (1D) WO{sub 3} nanostructures, using urea as 1D growth-directing agent and a precursor free of metals other than tungsten. By decreasing the pH of the starting solution, the size of the nanostructures was reduced significantly, this development being accompanied by the realization of phase pure hexagonal WO{sub 3} nanorods (elimination of monoclinic impurity phase) and a red shift in optical absorption edge. Surface analyses indicated the presence of reduced tungsten species in the WO{sub 3} nanostructures, which increased two-fold in a hydrated WO{sub 3} phase obtained with further decrease in pH. We suggest that oxygen vacancies are responsible for this defect state in WO{sub 3}, while protons are responsible or contribute significantly to the same in the hydrated phase. - Graphical abstract: The figure illustrates the role of pH in morphological and absorption edge evolution of WO{sub 3} (hydrate) as well as the variation in the concentration of defect electrons between anhydrous and hydrated WO{sub 3}. Highlights: Black-Right-Pointing-Pointer WO{sub 3} nanorods prepared in a one step procedure. Black-Right-Pointing-Pointer HCl (aq) enables phase pure WO{sub 3} nanorods. Black-Right-Pointing-Pointer HCl (aq) induces significant reduction in dimension of and red shift in absorption edge of nanorods. Black-Right-Pointing-Pointer W{sup 5+} detected in hydrothermal WO{sub 3} phase, the concentration of which increases in the hydrated phase. Black-Right-Pointing-Pointer W{sup 5+} from the two phases due to different positive defects.

Iwu, Kingsley O., E-mail: k.o.iwu@smn.uio.no [Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo (Norway); Galeckas, Augustinas, E-mail: augustinas.galeckas@fys.uio.no [Department of Physics, University of Oslo, Centre for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Rauwel, Protima, E-mail: protima.singh@fys.uio.no [Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1126 Blindern, NO-0318 Oslo (Norway); Kuznetsov, Andrej Y., E-mail: andrej.kuznetsov@fys.uio.no [Department of Physics, University of Oslo, Centre for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Norby, Truls, E-mail: truls.norby@kjemi.uio.no [Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo (Norway)

2012-01-15

328

Single molecule spectroscopic characterization of a far-red fluorescent protein (HcRed) from the Anthozoa coral Heteractis crispa  

NASA Astrophysics Data System (ADS)

We report on the photophysical properties of a far-red intrinsic fluorescent protein by means of single molecule and ensemble spectroscopic methods. The green fluorescent protein (GFP) from Aequorea victoria is a popular fluorescent marker with genetically encoded fluorescence and which can be fused to any biological structure without affecting its function. GFP and its variants provide emission colors from blue to yellowish green. Red intrinsic fluorescent proteins from Anthozoa species represent a recent addition to the emission color palette provided by GFPs. Red intrinsic fluorescent markers are on high demand in protein-protein interaction studies based on fluorescence-resonance energy transfer or in multicolor tracking studies or in cellular investigations where autofluorescence possesses a problem. Here we address the photophysical properties of a far-red fluorescent protein (HcRed), a mutant engineered from a chromoprotein cloned from the sea anemone Heteractis crispa, by using a combination of ensemble and single molecule spectroscopic methods. We show evidence for the presence of HcRed protein as an oligomer and for incomplete maturation of its chromophore. Incomplete maturation results in the presence of an immature (yellow) species absorbing/fluorescing at 490/530-nm. This yellow chromophore is involved in a fast resonance-energy transfer with the mature (purple) chromophore. The mature chromophore of HcRed is found to adopt two conformations, a Transoriented form absorbing and 565-nm and non-fluorescent in solution and a Cis-oriented form absorbing at 590-nm and emitting at 645-nm. These two forms co-exist in solution in thermal equilibrium. Excitation-power dependence fluorescence correlation spectroscopy of HcRed shows evidence for singlet-triplet transitions in the microseconds time scale and for cis-trans isomerization occurring in a time scale of tens of microseconds. Single molecule fluorescence data recorded from immobilized HcRed proteins, all point to the presence of two classes of molecules: proteins with Cis and Trans-oriented chromophores. Immobilization of HcRed in water-filled pores of polyvinyl alcohol leads to a polymer matrix - protein barrel interaction which results in a 'freezing' of the chromophore in a stable conformation for which non-radiative deactivation pathways are either suppressed or reduced. As a result, proteins with both Cis- and Trans-oriented chromophores can be detected at the single molecule level. Polymer chain motion is suggested as a mediator for an eventual cis-trans isomerization of the chromophore in the case of single immobilized proteins.

Cotlet, Mircea; Habuchi, Satoshi; Whitier, Jennifer E.; Werner, James H.; De Schryver, Frans C.; Hofkens, Johan; Goodwin, Peter M.

2006-02-01

329

One protein, two chromophores: comparative spectroscopic characterization of 6,7-dimethyl-8-ribityllumazine and riboflavin bound to lumazine protein.  

PubMed

We investigated the lumazine protein from Photobacterium leiognathi in complex with its biologically active cofactor, 6,7-dimethyl-8-ribityllumazine, at different redox states and compared the results with samples containing a riboflavin cofactor. Using anaerobic photoreduction, we were able to record optical absorption kinetics from both cofactors in similar protein environments. It could be demonstrated that the protein is able to stabilize a neutral ribolumazine radical with ?35% yield. The ribolumazine radical state was further investigated by W-band continuous-wave EPR and X-band pulsed ENDOR spectroscopy. Here, both the principal values of the g-tensor and an almost complete mapping of the proton hyperfine couplings (hfcs) could be obtained. Remarkably, the g-tensor's principal components are similar to those of the respective riboflavin-containing protein; however, the proton hfcs show noticeable differences. Comparing time-resolved optical absorption and fluorescence data from ribolumazine-containing samples, solely fluorescence but no signs of any intermediate radical or a triplet state could be identified. This is in contrast to lumazine protein samples containing the riboflavin cofactor, for which a high yield of the photogenerated triplet state and some excited flavin radical could be detected using time-resolved spectroscopy. These results clearly demonstrate that ribolumazine is a redox-active molecule and could, in principle, be employed as a cofactor in other enzymatic reactions. PMID:25325849

Paulus, Bernd; Illarionov, Boris; Nohr, Daniel; Roellinger, Guillaume; Kacprzak, Sylwia; Fischer, Markus; Weber, Stefan; Bacher, Adelbert; Schleicher, Erik

2014-11-20

330

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

331

A combined spectroscopic and molecular docking approach to characterize binding interaction of megestrol acetate with bovine serum albumin.  

PubMed

The binding interactions between megestrol acetate (MA) and bovine serum albumin (BSA) under simulated physiological conditions (pH?7.4) were investigated by fluorescence spectroscopy, circular dichroism and molecular modeling. The results revealed that the intrinsic fluorescence of BSA was quenched by MA due to formation of the MA-BSA complex, which was rationalized in terms of a static quenching procedure. The binding constant (Kb ) and number of binding sites (n) for MA binding to BSA were 2.8?×?10(5) ?L/mol at 310?K and about 1 respectively. However, the binding of MA with BSA was a spontaneous process due to the negative ?G(0) in the binding process. The enthalpy change (?H(0) ) and entropy change (?S(0) ) were - 124.0?kJ/mol and -295.6?J/mol per K, respectively, indicating that the major interaction forces in the binding process of MA with BSA were van der Waals forces and hydrogen bonding. Based on the results of spectroscopic and molecular docking experiments, it can be deduced that MA inserts into the hydrophobic pocket located in subdomain IIIA (site II) of BSA. The binding of MA to BSA leads to a slight change in conformation of BSA but the BSA retained its secondary structure, while conformation of the MA has significant change after forming MA-BSA complex, suggesting that flexibility of the MA molecule supports the binding interaction of BSA with MA. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24852109

Shi, Jie-Hua; Zhu, Ying-Yao; Wang, Jing; Chen, Jun

2015-02-01

332

Some new [(thione)2Au(diamine)]Cl3 complexes: synthesis, spectroscopic characterization, computational and in vitro cytotoxic studies.  

PubMed

Recent advances in oncology are focused on developing new complexes of gold(III) with various ligands that show augmented anti-proliferative potential and reduced toxicity as compared to cis-platin. In this study, new Au(III) complexes of the type [(thione)2Au(diamine)]Cl3 are reported, where thione=1,3-imidazolidine-2-thione (Imt), 1,3-Diazinane-2-thione (Diaz) and diamine=1,2-diaminoethane (en), 1,3-diaminopropane (pn) or 1,4-diaminobutane (bn). The solid state IR as well as (13)C and (15)N NMR data indicate that Au(III) center is bonded via sulfur of thiocarbonyl SC site of the thiones and also chelated by the diamines from the trans side of coordinated thiones. Spectroscopic data are evaluated by comparisons with calculated data from the built and optimized structure by GAUSSIAN 09 at the RB3LYP level with LanL2DZ bases set. These new Au(III) complexes based on mixed thione and diamine ligands are very similar to the square planar structure of tetracoordinate [Au(en)2]Cl3complex. In this study, cytotoxicity data for these gold(III) complexes against C6 glioma cell lines are also reported, and the results indicate some complexes have cytotoxicity comparable to cis-platin. PMID:23876928

Al-Maythalony, Bassem A; Monim-ul-Mehboob, M; Altaf, Muhammad; Wazeer, Mohammed I M; Isab, Anvarhusein A; Altuwaijri, Saleh; Ahmed, Ayesha; Dhuna, Vikram; Bhatia, Gaurav; Dhuna, Kshitija; Kamboj, Sukhdev Singh

2013-11-01

333

Some new [(thione)2Au(diamine)]Cl3 complexes: Synthesis, spectroscopic characterization, computational and in vitro cytotoxic studies  

NASA Astrophysics Data System (ADS)

Recent advances in oncology are focused on developing new complexes of gold(III) with various ligands that show augmented anti-proliferative potential and reduced toxicity as compared to cis-platin. In this study, new Au(III) complexes of the type [(thione)2Au(diamine)]Cl3 are reported, where thione = 1,3-imidazolidine-2-thione (Imt), 1,3-Diazinane-2-thione (Diaz) and diamine = 1,2-diaminoethane (en), 1,3-diaminopropane (pn) or 1,4-diaminobutane (bn). The solid state IR as well as 13C and 15N NMR data indicate that Au(III) center is bonded via sulfur of thiocarbonyl Sdbnd Crbond2 site of the thiones and also chelated by the diamines from the trans side of coordinated thiones. Spectroscopic data are evaluated by comparisons with calculated data from the built and optimized structure by GAUSSIAN 09 at the RB3LYP level with LanL2DZ bases set. These new Au(III) complexes based on mixed thione and diamine ligands are very similar to the square planar structure of tetracoordinate [Au(en)2]Cl3complex. In this study, cytotoxicity data for these gold(III) complexes against C6 glioma cell lines are also reported, and the results indicate some complexes have cytotoxicity comparable to cis-platin.

Al-Maythalony, Bassem A.; Monim-ul-Mehboob, M.; Altaf, Muhammad; Wazeer, Mohammed I. M.; Isab, Anvarhusein A.; Altuwaijri, Saleh; Ahmed, Ayesha; Dhuna, Vikram; Bhatia, Gaurav; Dhuna, Kshitija; Kamboj, Sukhdev Singh

2013-11-01

334

Characterization of Copper(II) Interactions with Sinefungin, a Nucleoside Antibiotic: Combined Potentiometric, Spectroscopic and DFT Studies  

PubMed Central

Interactions between sinefungin and copper(II) ions were investigated. Stoichiometry and stability constants of the metal-free system and two mononuclear complexes present in solution were determined on the basis of potentiometric data analysis. The results were compared to the Cu(II)-ornithine system due to structural similarities between both molecules. Combined spectroscopic and theoretical studies allowed for determination of coordination pattern for the Cu(II)-sinefungin complexes. At acidic pH, copper is bound in “glycine-like” coordination mode, identical with that of ornithine. This involves ?-amino group and the carboxyl oxygen. At higher pH, a “bis-complex” is formed by two sinefungin molecules. The second ligand binds in equatorial position displacing two water molecules, what results in the stable {2N,2O} coordination. Both axial positions are supposed to be occupied by N1 nitrogen donors of adenine moiety, what is confirmed by DFT calculations. They interact indirectly with copper(II) through water molecules as the result of dominant syn conformation of purine. PMID:18273386

Jaworska, Maria; Lodowski, Piotr; Mucha, Ariel; Szczepanik, Wojciech; Valensin, Gianni; Cappannelli, Massimo; Je?owska-Bojczuk, Ma?gorzata

2007-01-01

335

Structural characterization of C-S-H and C-A-S-H samples-Part II: Local environment investigated by spectroscopic analyses  

SciTech Connect

Spectroscopic studies ({sup 1}H, {sup 23}Na and {sup 27}Al MAS NMR and Raman spectroscopy) have been used to characterize three series of C-S-H samples (0.8Spectroscopic investigations indicate that the main part of the Al atoms is readily incorporated into the interlayer region of the C-S-H structure. Al atoms are mainly inserted as four-fold coordinated aluminates in the dreierketten silicate chain (either in bridging or paired tetrahedra) at low Ca/Si ratio. Four-fold aluminates are progressively replaced by six-fold coordinated aluminates located into the interlayer region of the C-S-H structure and bonded to silicate chains. Investigation of the hydrogen bonding in C-S-H indicates that the main part of the hydrogen bonds is intra-main layer, and thus explains the low stacking cohesion of the C-S-H structure leading to its nanometric crystal size and the OD character of the tobermorite like structures. - Graphical abstract: The insertion of aluminum atoms into the C-S-H structure has been investigated by spectroscopic analyses ({sup 27}Al and {sup 1}H MAS NMR and Raman). The previously determined structural continuity, when increasing the C/S ratio from the C-S-H(I) type to the C-S-H(II) type, has been confirmed even in the presence of aluminum.

Renaudin, Guillaume, E-mail: guillaume.renaudin@ensccf.f [Clermont-Universite, Ecole Nationale Superieure de Chimie de Clermont-Ferrand, LMI, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere Cedex (France); Russias, Julie [Commissariat a l'Energie Atomique, DEN, Marcoule, Waste Treatment and Conditioning Research Department, F-30207 Bagnols sur Ceze (France); Leroux, Fabrice [Clermont Universite, UBP, Laboratoire des Materiaux Inorganiques, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere Cedex (France); Cau-dit-Coumes, Celine; Frizon, Fabien [Commissariat a l'Energie Atomique, DEN, Marcoule, Waste Treatment and Conditioning Research Department, F-30207 Bagnols sur Ceze (France)

2009-12-15

336

Structural characterization of C-S-H and C-A-S-H samples—Part II: Local environment investigated by spectroscopic analyses  

NASA Astrophysics Data System (ADS)

Spectroscopic studies ( 1H, 23Na and 27Al MAS NMR and Raman spectroscopy) have been used to characterize three series of C-S-H samples (0.8Spectroscopic investigations indicate that the main part of the Al atoms is readily incorporated into the interlayer region of the C-S-H structure. Al atoms are mainly inserted as four-fold coordinated aluminates in the dreierketten silicate chain (either in bridging or paired tetrahedra) at low Ca/Si ratio. Four-fold aluminates are progressively replaced by six-fold coordinated aluminates located into the interlayer region of the C-S-H structure and bonded to silicate chains. Investigation of the hydrogen bonding in C-S-H indicates that the main part of the hydrogen bonds is intra-main layer, and thus explains the low stacking cohesion of the C-S-H structure leading to its nanometric crystal size and the OD character of the tobermorite like structures.

Renaudin, Guillaume; Russias, Julie; Leroux, Fabrice; Cau-dit-Coumes, Céline; Frizon, Fabien

2009-12-01

337

13C-Methyl Formate: Observations of a Sample of High-mass Star-forming Regions Including orion-KL and Spectroscopic Characterization  

NASA Astrophysics Data System (ADS)

We have surveyed a sample of massive star-forming regions located over a range of distances from the Galactic center for methyl formate, HCOOCH3, and its isotopologues H13COOCH3 and HCOO13CH3. The observations were carried out with the APEX telescope in the frequency range 283.4-287.4 GHz. Based on the APEX observations, we report tentative detections of the 13C-methyl formate isotopologue HCOO13CH3 toward the following four massive star-forming regions: Sgr B2(N-LMH), NGC 6334 IRS 1, W51 e2, and G19.61-0.23. In addition, we have used the 1 mm ALMA science verification observations of Orion-KL and confirm the detection of the 13C-methyl formate species in Orion-KL and image its spatial distribution. Our analysis shows that the 12C/13C isotope ratio in methyl formate toward the Orion-KL Compact Ridge and Hot Core-SW components (68.4 ± 10.1 and 71.4 ± 7.8, respectively) are, for both the 13C-methyl formate isotopologues, commensurate with the average 12C/13C ratio of CO derived toward Orion-KL. Likewise, regarding the other sources, our results are consistent with the 12C/13C in CO. We also report the spectroscopic characterization, which includes a complete partition function, of the complex H13COOCH3 and HCOO13CH3 species. New spectroscopic data for both isotopomers H13COOCH3 and HCOO13CH3, presented in this study, have made it possible to measure this fundamentally important isotope ratio in a large organic molecule for the first time. This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut fur Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory (under program ID 089.F-9319).

Favre, Cécile; Carvajal, Miguel; Field, David; Jørgensen, Jes K.; Bisschop, Suzanne E.; Brouillet, Nathalie; Despois, Didier; Baudry, Alain; Kleiner, Isabelle; Bergin, Edwin A.; Crockett, Nathan R.; Neill, Justin L.; Margulès, Laurent; Huet, Thérèse R.; Demaison, Jean

2014-12-01

338

Synthesis, isolation, and spectroscopic characterization of holmium-based mixed-metal nitride clusterfullerenes: HoxSc3-xN@C80 (x=1, 2).  

PubMed

The synthesis, isolation and spectroscopic characterization of holmium-based mixed metal nitride clusterfullerenes Ho(x) Sc(3-x) N@C(80) (x=1, 2) are reported. Two isomers of Ho(x) Sc(3-x) N@C(80) (x=1, 2) were synthesized by the reactive gas atmosphere method and isolated by multistep recycling HPLC. The isomeric structures of Ho(x) Sc(3-x) N@C(80) (x=1, 2) were characterized by laser-desorption time-of-flight (LD-TOF) mass spectrometry and UV/Vis/NIR, FTIR and Raman spectroscopy. A comparative study of M(x) Sc(3-x) N@C(80) (M=Gd, Dy, Lu, Ho) demonstrates the dependence of their electronic and vibrational properties on the encaged metal. Despite the distinct perturbation induced by 4f(10) electrons, we report the first paramagnetic (13) C?NMR study on Ho(x) Sc(3-x) N@C(80) (I; x=1, 2) and confirm I(h) -symmetric cage structure. A (45) Sc NMR study on HoSc(2) N@C(80) (I, II) revealed a temperature-dependent chemical shift in the temperature range of 268-308?K. PMID:22745152

Zhang, Yang; Popov, Alexey A; Schiemenz, Sandra; Dunsch, Lothar

2012-07-27

339

Characterization of biochar-derived dissolved organic matter using UV-visible absorption and excitation-emission fluorescence spectroscopies.  

PubMed

In recent years, biochar has become of considerable interest for a variety of environmental applications. However, the feasibility of its application is entirely dependent on its physical and chemical properties, including the characteristics of biochar-derived dissolved organic matter (DOM). The goal of this study was to assess the use of optical analysis for the purpose of characterizing biochar-derived DOM. Three different biochars (slow pyrolysis birch and maple; fast pyrolysis maple) were produced and leached in distilled water over 17d. Samples were taken on days 3, 10, 13 and 17, filtered, and analyzed for DOC content. Samples were also subjected to optical analysis using UV-visible absorption and excitation-emission matrix (EEM) fluorescence spectroscopies. EEM fluorescence data were further analyzed using parallel factor analysis (PARAFAC). Absorbance and fluorescence results were combined and examined using principal component analysis (PCA). Significant differences in the water soluble organic carbon content were observed for all biochar types. The estimated aromaticity (SUVA254) and mean molecular weight (S275-295) of biochar-derived DOM were also found to differ based on biochar type. PARAFAC analysis identified three humic-like components and one protein-like component. Distinct DOM signatures were observed for each biochar type. Transformations in biochar DOM characteristics over time were also observed. The PCA showed a clear delineation in biochar types based on their optical properties. The results of this study indicate that optical analysis may provide valuable information regarding the characteristics of biochar-derived DOM. PMID:24359913

Jamieson, Tyler; Sager, Eric; Guéguen, Céline

2014-05-01

340

Characterization of Ligand Effects on Water Activation in Triarylphosphoine-Stabilized Pt Nanoparticle Catalysts by X-ray Absorption Spectroscopy  

SciTech Connect

The synthesis, preparation, and electrochemical characterization of triphenylphosphine triphosphonate (TPPTP) stabilized Pt particles have been reported previously with the observation that the TPPTP ligands increase the specific activity of Pt for the oxygen reduction reaction (ORR). In this work the ORR activity of the Pt/TPPTP electrocatalyst is probed by analyzing water activation with Pt L3-edge X-ray absorption spectroscopy and the EXAFS and Delta XANES analysis techniques. The results are compared with that for similarly prepared Pt/C and Pt stabilized by an oxidized TPPTP ligand (Pt/ox-TPPTP). The Pt particles in the Pt/TPPTP catalyst at 0.54 V (RHE) are complexed via the P (i.e., Pt-P

Gatewood,D.; Schull, T.; Baturina, O.; Pietron, J.; Garsany, Y.; Swider-Lyons, K.; Ramaker, D.

2008-01-01

341

CHARACTERIZATION OF A SAMPLE OF INTERMEDIATE-TYPE AGNs. I. SPECTROSCOPIC PROPERTIES AND SERENDIPITOUS DISCOVERY OF NEW DUAL AGNs  

SciTech Connect

A sample of 10 nearby intermediate-type active galactic nuclei (AGNs) drawn from the Sloan Digital Sky Survey is presented. The aim of this work is to provide estimations of the black hole (BH) mass for the sample galaxies from the dynamics of the broad-line region. For this purpose, a detailed spectroscopic analysis of the objects was done. Using Baldwin-Phillips-Terlevich diagnostic diagrams, we have carefully classified the objects as true intermediate-type AGNs and found that 80%{sup +7.2%} {sub -17.3%} are composite AGNs. The BH mass estimated for the sample is within 6.54 {+-} 0.16 < log M {sub BH} < 7.81 {+-} 0.14. Profile analysis shows that five objects (J120655.63+501737.1, J121607.08+504930.0, J141238.14+391836.5, J143031.18+524225.8, and J162952.88+242638.3) have narrow double-peaked emission lines in both the red (H{alpha}, [N II] {lambda}{lambda}6548,6583 and [S II] {lambda}{lambda}6716, 6731) and the blue (H{beta} and [O III] {lambda}{lambda}4959, 5007) regions of the spectra, with velocity differences ({Delta}V) between the double peaks within 114 km s{sup -1} < {Delta}V < 256 km s{sup -1}. Two of them, J121607.08+504930.0 and J141238.14+391836.5, are candidates for dual AGNs since their double-peaked emission lines are dominated by AGN activity. In searches of dual AGNs, type 1, type II, and intermediate-type AGNs should be carefully separated, due to the high serendipitous number of narrow double-peaked sources (50% {+-} 14.4%) found in our sample.

Benitez, Erika; Cruz-Gonzalez, Irene; Martinez, Benoni; Jimenez-Bailon, Elena [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, Mexico D.F. 04510 (Mexico)] [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, Mexico D.F. 04510 (Mexico); Mendez-Abreu, Jairo; Lopez-Martin, Luis [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain)] [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Fuentes-Carrera, Isaura [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional (ESFM-IPN), U.P. Adolfo Lopez Mateos, Mexico D.F. 07730 (Mexico)] [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional (ESFM-IPN), U.P. Adolfo Lopez Mateos, Mexico D.F. 07730 (Mexico); Leon-Tavares, Jonathan [Aalto University Metsaehovi Radio Observatory, Metsaehovintie 114, FI-02540, Kylmaelae (Finland)] [Aalto University Metsaehovi Radio Observatory, Metsaehovintie 114, FI-02540, Kylmaelae (Finland); Chavushyan, Vahram H., E-mail: erika@astro.unam.mx [Instituto Nacional de Astrofisica, Optica y Electronica, Apdo. Postal 51-216, 72000 Puebla (Mexico)

2013-01-20

342

Growth, characterization, vibrational spectroscopic and thermal studies of a new metallorganic non-linear optical crystal—Bisthiourea cadmium bromide  

NASA Astrophysics Data System (ADS)

Single crystals of bisthiourea cadmium bromide (BTCB), a new metallorganic material crystallizing in orthorhombic system were grown from slow evaporation solution growth. The grown crystals were characterized by X-ray diffraction, FTIR and FT-Raman spectral studies. The crystals were also subjected to TGA/DTA analysis and second harmonic generation test. The transmission characteristics of the crystal was also studied.

Ramachandraraja, C.; Sundararajan, R. S.

2008-12-01

343

Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts  

NASA Astrophysics Data System (ADS)

An ultra-high vacuum (UHV) setup for "real" and "inverse" model catalyst preparation, depth-resolved near-surface spectroscopic characterization, and quantification of catalytic activity and selectivity under technologically relevant conditions is described. Due to the all-quartz reactor attached directly to the UHV-chamber, transfer of the catalyst for in situ testing without intermediate contact to the ambient is possible. The design of the UHV-compatible re-circulating batch reactor setup allows the study of reaction kinetics under close to technically relevant catalytic conditions up to 1273 K without contact to metallic surfaces except those of the catalyst itself. With the attached differentially pumped exchangeable evaporators and the quartz-microbalance thickness monitoring equipment, a reproducible, versatile, and standardised sample preparation is possible. For three-dimensional near-surface sample characterization, the system is equipped with a hemispherical analyser for X-ray photoelectron spectroscopy (XPS), electron-beam or X-ray-excited Auger-electron spectroscopy, and low-energy ion scattering measurements. Due the dedicated geometry of the X-ray gun (54.7°, "magic angle") and the rotatable sample holder, depth analysis by angle-resolved XPS measurements can be performed. Thus, by the combination of characterisation methods with different information depths, a detailed three-dimensional picture of the electronic and geometric structure of the model catalyst can be obtained. To demonstrate the capability of the described system, comparative results for depth-resolved sample characterization and catalytic testing in methanol steam reforming on PdGa and PdZn near-surface intermetallic phases are shown.

Mayr, Lukas; Rameshan, Raffael; Klötzer, Bernhard; Penner, Simon; Rameshan, Christoph

2014-05-01

344

Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts.  

PubMed

An ultra-high vacuum (UHV) setup for "real" and "inverse" model catalyst preparation, depth-resolved near-surface spectroscopic characterization, and quantification of catalytic activity and selectivity under technologically relevant conditions is described. Due to the all-quartz reactor attached directly to the UHV-chamber, transfer of the catalyst for in situ testing without intermediate contact to the ambient is possible. The design of the UHV-compatible re-circulating batch reactor setup allows the study of reaction kinetics under close to technically relevant catalytic conditions up to 1273 K without contact to metallic surfaces except those of the catalyst itself. With the attached differentially pumped exchangeable evaporators and the quartz-microbalance thickness monitoring equipment, a reproducible, versatile, and standardised sample preparation is possible. For three-dimensional near-surface sample characterization, the system is equipped with a hemispherical analyser for X-ray photoelectron spectroscopy (XPS), electron-beam or X-ray-excited Auger-electron spectroscopy, and low-energy ion scattering measurements. Due the dedicated geometry of the X-ray gun (54.7°, "magic angle") and the rotatable sample holder, depth analysis by angle-resolved XPS measurements can be performed. Thus, by the combination of characterisation methods with different information depths, a detailed three-dimensional picture of the electronic and geometric structure of the model catalyst can be obtained. To demonstrate the capability of the described system, comparative results for depth-resolved sample characterization and catalytic testing in methanol steam reforming on PdGa and PdZn near-surface intermetallic phases are shown. PMID:24880412

Mayr, Lukas; Rameshan, Raffael; Klötzer, Bernhard; Penner, Simon; Rameshan, Christoph

2014-05-01

345

Infrared spectroscopic imaging with high spatial resolution and high sensitivity  

NASA Astrophysics Data System (ADS)

Polarization Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS) is a very sensitive imaging technique for the characterization of molecular films. In order to achieve a spatial resolution close to the diffraction limit a very small pinhole which acts as a point-source has to be used. However, such a small pinhole, the typical diameter would be app. 100 ?m, may reduces dramatically the intensity of the infrared beam. Using a common FTIR spectrometer the spatial resolution is mainly limited by the brilliance of the globar infrared source. Therefore, an improvement in lateral resolution requires a more brilliant light source. The free electron laser (FEL) is such a high brilliant infrared source. The combination of the FEL with the PM-IRRAS imaging system is a new approach to capture spectroscopic images with an excellent spatial resolution close to the diffraction limit. PM-IRRAS images of a self assembly monolayer of phosphonic acid molecules onto a microstructures gold / aluminum oxide surface where characterized. The spectroscopic image exhibits a spatial resolution of app. 5 ?m. An evaluation of characteristic absorbance bands of the phosphate group reveals that phosphonic acid molecules bound with a high degree of orientation but differently at the gold and aluminum oxide surfaces. However, the spectroscopic image reveals also several domains of disordering across the surface. Such domains have a dimension of only few micrometers and can be identified in a high resolved PM-IRRAS image.

Sablinskas, Valdas; Steiner, Gerald; Ceponkus, Justinas; Salzer, Reiner

2008-02-01

346

Spectroscopic database  

NASA Technical Reports Server (NTRS)

Several aspects of quantitative atmospheric spectroscopy are considered, using a classification of the molecules according to the gas amounts in the stratosphere and upper troposphere, and reviews of quantitative atmospheric high-resolution spectroscopic measurements and field measurements systems are given. Laboratory spectroscopy and spectral analysis and prediction are presented with a summary of current laboratory spectroscopy capabilities. Spectroscopic data requirements for accurate derivation of atmospheric composition are discussed, where examples are given for space-based remote sensing experiments of the atmosphere: the ATMOS (Atmospheric Trace Molecule) and UARS (Upper Atmosphere Research Satellite) experiment. A review of the basic parameters involved in the data compilations; a summary of information on line parameter compilations already in existence; and a summary of current laboratory spectroscopy studies are used to assess the data base.

Husson, N.; Barbe, A.; Brown, L. R.; Carli, B.; Goldman, A.; Pickett, H. M.; Roche, A. E.; Rothman, L. S.; Smith, M. A. H.

1985-01-01

347

Astrometric Spectroscopic  

E-print Network

The Astrometric and Spectroscopic Parallaxes of Three Dwarf Novae (SS Aur, U Gem, and SS Cyg) ­­­T, covering the region 2.18 to 2.30 µm, for U Gem and SS Aur, and lower resolution (15�/pix) for all three DN vs. M V for the three DN. The moderate resolution spectra of SS Aur, U Gem, and the late­type dwarf

Harrison, Thomas

348

Synthesis, spectroscopic characterization, antineoplastic, in vitro-cytotoxic, and antibacterial activities of mononuclear ruthenium(II) complexes  

Microsoft Academic Search

The synthesis, antineoplastic, cytotoxic, and antibacterial activities of Ru(II) complexes derived from quinazoline and thiosemicarbazone ligands are reported. These complexes have been prepared and characterized by UV-Vis, IR, H-NMR, FAB-mass spectroscopy, and elemental analysis. The ligands and resulting complexes were subjected to in vivo antineoplastic activity against a transplantable murine tumor cell line Ehrlich ascites carcinoma (EAC) and in vitro cytotoxic activity

Sreekanth Thota; Mohammad Imran; Manasa Udugula; Subhas Somalingappa Karki; Narasimha Kanjarla; Rajeshwar Yerra; Jan Balzarini; Erik De Clercq

2012-01-01

349

Growth, characterization, vibrational spectroscopic and thermal studies of a new metallorganic non-linear optical crystal-Bisthiourea cadmium bromide.  

PubMed

Single crystals of bisthiourea cadmium bromide (BTCB), a new metallorganic material crystallizing in orthorhombic system were grown from slow evaporation solution growth. The grown crystals were characterized by X-ray diffraction, FTIR and FT-Raman spectral studies. The crystals were also subjected to TGA/DTA analysis and second harmonic generation test. The transmission characteristics of the crystal was also studied. PMID:18487082

Ramachandraraja, C; Sundararajan, R S

2008-12-15

350

Spectroscopic characterization of ?-FeSi2 single crystals and homoepitaxial ?-FeSi2 films by XPS and XAS  

NASA Astrophysics Data System (ADS)

Chemical state analysis by a combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is performed for ?-FeSi2 single crystals and homoepitaxial ?-FeSi2 films. The Si 2p XPS and Fe L-edge XAS spectra imply that the annealing at 1173 K to remove native oxide layers on the crystal induces the formation of FeSi in the surface. The formation of FeSi is also confirmed by Si K-edge XAS analysis. For the homoepitaxial ?-FeSi2 films grown on the crystals, the Si K-edge XAS spectra indicate that structurally homogeneous ?-FeSi2 films can be grown on the ?-FeSi2 single crystals when the substrate temperatures of 973 and 1073 K are applied for molecular beam epitaxy (MBE). Consequently, it is indicated that the combination of XPS and XAS using synchrotron radiation is a useful tool to clarify chemical states of ?-FeSi2 single crystals and homoepitaxial ?-FeSi2 films, which is important to reveal optimized growth conditions of homoepitaxial films.

Esaka, F.; Yamamoto, H.; Udono, H.; Matsubayashi, N.; Yamaguchi, K.; Shamoto, S.; Magara, M.; Kimura, T.

2011-01-01

351

Synthesis and spectroscopic characterization of monometallic molybdenum (VI) complexes derived from bis(2-hydroxy-1-naphthaldehyde)succinoyldihydrazone  

NASA Astrophysics Data System (ADS)

Molybdenum complexes [(?2-O)2(MoO2)2(H4nsh)2]·2A·2C2H5OH (where A = O (1), py (2), 2-pic (3), 4-pic (4) and 5-pic (5)) have been synthesized in absolute ethanol from bis(2-hydroxy-1-naphthaldehyde)succinoyldihydrazone. The composition of the complexes has been deduced on the basis of the data obtained from elemental analyses and thermo-analytical data. All complexes are non-electrolyte in DMSO solution as evident from low value of molar conductance in the range 2.2-3.3 ?-1 cm2 mol-1. The complexes are diamagnetic and have molybdenum in +6 oxidation state. The dihydrazone coordinates to the molybdenum centre as a neutral bidentate ligand through two azomethine nitrogen atoms only. This is revealed by the downfield shift of ?(sbnd CHdbnd Nsbnd ) signals by 0.16-0.44 ppm as compared to that in the free dihydrazone. The carbon atoms closer to azomethine nitrogen atoms downfield shift confirming the coordination of azomethine nitrogen atoms. The ?(Cdbnd N) stretching vibrations also shift to lower frequency in the IR spectra of the complexes. Apart from the intra ligand bands, the complexes show a new absorption band in the region 421-423 nm attributed to charge-transfer transition from dihydrazone ligand to molybdenum centre. The dihydrazone is present in anti-cis conformation in all of the complexes. The complexes develop a new kind of intramolecular hydrogen bonding between naphtholic sbnd OH groups of coordinated dihydrazone.

Kumar, A.; Koch, A.; Borthakur, R.; Chakraborty, M.; De, A. K.; Phukan, A.; Bez, G.; Lal, R. A.

2014-04-01

352

Characterization of Ligand Effects on Water Activation in Triaryl Phospine Stabilized Pt Nanoparticle Catalysts by X-ray Absorption Spectroscopy  

SciTech Connect

The synthesis, preparation, and electrochemical characterization of triphenylphosphine triphosphonate (TPPTP) stabilized Pt particles have been reported previously with the observation that the TPPTP ligands increase the specific activity of Pt for the oxygen reduction reaction (ORR). In this work the ORR activity of the Pt/TPPTP electrocatalyst is probed by analyzing water activation with Pt L{sub 3}-edge X-ray absorption spectroscopy and the EXAFS and Delta XANES analysis techniques. The results are compared with that for similarly prepared Pt/C and Pt stabilized by an oxidized TPPTP ligand (Pt/ox-TPPTP). The Pt particles in the Pt/TPPTP catalyst at 0.54 V (RHE) are complexed via the P (i.e., Pt-P

Gatewood, D.; Schull, T; Baturina, O; Pietron, J; Garsany, Y; Swider-Lyons, K; Ramaker, D

2008-01-01

353

Physiological Characterization of Root Zn2+ Absorption and Translocation to Shoots in Zn Hyperaccumulator and Nonaccumulator Species of Thlaspi.  

PubMed Central

Radiotracer techniques were employed to characterize 65Zn2+ influx into the root symplasm and translocation to the shoot in Thlaspi caerulescens, a Zn hyperaccumulator, and Thlaspi arvense, a nonaccumulator. A protocol was developed that allowed us to quantify unidirectional 65Zn2+ influx across the root-cell plasma membrane (20 min of radioactive uptake followed by 15 min of desorption in a 100 [mu]M ZnCl2 + 5 mM CaCl2 solution). Concentration-dependent Zn2+ influx in both Thlaspi species yielded nonsaturating kinetic curves that could be resolved into linear and saturable components. The linear kinetic component was shown to be cell-wall-bound Zn2+ remaining in the root after desorption, and the saturable component was due to Zn2+ influx across the root-cell plasma membrane. This saturable component followed Michaelis-Menten kinetics, with similar apparent Michaelis constant values for T. caerulescens and T. arvense (8 and 6 [mu]M, respectively). However, the maximum initial velocity for Zn2+ influx in T. caerulescens root cells was 4.5-fold higher than for T. arvense, indicating that enhanced absorption into the root is one of the mechanisms involved in Zn hyperaccumulation. After 96 h 10-fold more 65Zn was translocated to the shoot of T. caerulescens compared with T. arvense. This indicates that transport sites other than entry into the root symplasm are also stimulated in T. caerulescens. We suggest that although increased root Zn2+ influx is a significant component, transport across the plasma membrane and tonoplast of leaf cells must also be critical sites for Zn hyperaccumulation in T. caerulescens. PMID:12226473

Lasat, M. M.; Baker, AJM.; Kochian, L. V.

1996-01-01

354

Hybrid glass and sol-gel integrated optical waveguides for absorption-based biosensing  

Microsoft Academic Search

A novel integrated optical planar waveguide platform for absorption-based biosensing is demonstrated. The platform integrates surface ion-exchanged channel waveguides with one-step UV patterned sol-gel structures to define the probing regions. Cytochrome c protein was utilized to characterize the device performance. Spectroscopically specific attenuation of approximately 2 dB in the guided signal occurred at 532nm for 1.4 cm long probing region.

Ismail E. Araci; Nasuhi Yurt; Seppo Honkanen; Sergio B. Mendez; Nasser Peyghambarian

2005-01-01

355

Vibrational spectroscopic characterization of the phosphate mineral ludlamite (Fe,Mn,Mg)3(PO4)2?4H2O - A mineral found in lithium bearing pegmatites  

NASA Astrophysics Data System (ADS)

The objective of this work is to analyze ludlamite (Fe,Mn,Mg)3(PO4)2?4H2O from Boa Vista mine, Galiléia, Brazil and to assess the molecular structure of the mineral. The phosphate mineral ludlamite has been characterized by EMP-WDS, Raman and infrared spectroscopic measurements. The mineral is shown to be a ferrous phosphate with some minor substitution of Mg and Mn. Raman bands at 917 and 950 cm-1 are assigned to the symmetric stretching mode of HOPO32- and PO43- units. Raman bands at 548, 564, 599 and 634 cm-1 are assigned to the ?4PO43- bending modes. Raman bands at 2605, 2730, 2896 and 3190 cm-1 and infrared bands at 2623, 2838, 3136 and 3185 cm-1 are attributed to water stretching vibrations. By using a Libowitzky empirical function, hydrogen bond distances are calculated from the OH stretching wavenumbers. Strong hydrogen bonds in the structure of ludlamite are observed as determined by their hydrogen bond distances. The application of infrared and Raman spectroscopy to the study of ludlamite enables the molecular structure of the pegmatite mineral ludlamite to be assessed.

Frost, Ray L.; Xi, Yunfei; Scholz, Ricardo; Belotti, Fernanda M.

2013-02-01

356

Synthesis, spectroscopic (FT-IR/NMR) characterization, X-ray structure and DFT studies on (E)-2-(1-phenylethylidene) hydrazinecarboximidamide nitrate hemimethanol  

NASA Astrophysics Data System (ADS)

The title molecular salt, (E)-2-(1-phenylethylidene) hydrazinecarboximidamide nitrate hemimethanol CHN4+·NO3-·0.5CHO, was synthesized and characterized by elemental analysis, FT-IR and NMT spectroscopies, and single-crystal X-ray diffraction technique. Quantum chemical calculations were performed to study the molecular and spectroscopic properties of the title compound, and the results were compared with the experimental findings. The calculated results show that the optimized geometry can well reproduce the crystal structure parameters, and the theoretical vibrational frequencies and GIAO 1H and 13C NMR chemical shifts show good agreement with experimental values. The dipole moment, linear polarizability and first hyperpolarizability values were also computed. The linear polarizabilities and first hyper polarizabilities of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. On the basis of the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H) and temperatures.

Özdemir, Nam?k; ?nkaya, Ersin; Sar?p?nar, Emin; Akyüz, Lale; ?lhan, ?lhan Özer; Ayd?n, Semiha; Dinçer, Muharrem; Büyükgüngör, Orhan

2013-10-01

357

Dissociative Binding of Carboxylic Acid Ligand on Nanoceria Surface in Aqueous Solution: A Joint in Situ Spectroscopic Characterization and First-Principles Study  

SciTech Connect

Carboxylic acid is a common ligand anchoring group to functionalize nanoparticle surfaces. Its binding structures and mechanisms as a function of the oxidation states of metal oxide nanoparticle surfaces are not well characterized experimentally. We present an in situ sum frequency generation vibrational spectroscopy (SFG-VS) study on the binding of deuterated acetic acid on ceria nanoparticles in the aqueous solution. In the SFG experiment, ceria nanoparticles were deposited on the flat surface of a CaF2 hemisphere in contact with acetic acid solutions. While the ceria nanoparticle deprotonated the acetic acid, the CaF2 surface could not. Thus, the binding of the deprotonated acetic acid on ceria can be selectively probed. SFG spectra revealed that the binding modes of the carboxylate group depend on the oxidation states of the ceria surfaces. SFG polarization analysis suggested that the bidentate chelating and bridging binding modes co-exist on the reduced ceria surfaces, while the oxidized ceria surfaces are dominated by the bidentate bridging mode. The direct spectroscopic evidence helps to clarify the binding structures and mechanisms on the ceria nanoparticles. Furthermore, the middle-infrared (IR) transparent CaF2 and its chemical inertness make CaF2 and similar substrate materials good candidates for direct SFG-VS measurement of nanoparticle surface reactions and binding chem-istry.

Lu, Zhou; Karakoti, Ajay S.; Velarde Ruiz Esparza, Luis A.; Wang, Weina; Yang, Ping; Thevuthasan, Suntharampillai; Wang, Hongfei

2013-11-21

358

Vibrational spectroscopic characterization of the phosphate mineral ludlamite (Fe,Mn,Mg)?(PO?)??4H?O - a mineral found in lithium bearing pegmatites.  

PubMed

The objective of this work is to analyze ludlamite (Fe,Mn,Mg)(3)(PO(4))(2)?4H(2)O from Boa Vista mine, Galiléia, Brazil and to assess the molecular structure of the mineral. The phosphate mineral ludlamite has been characterized by EMP-WDS, Raman and infrared spectroscopic measurements. The mineral is shown to be a ferrous phosphate with some minor substitution of Mg and Mn. Raman bands at 917 and 950 cm(-1) are assigned to the symmetric stretching mode of HOPO(3)(2-) and PO(4)(3-) units. Raman bands at 548, 564, 599 and 634 cm(-1) are assigned to the ?(4)PO(4)(3-) bending modes. Raman bands at 2605, 2730, 2896 and 3190 cm(-1) and infrared bands at 2623, 2838, 3136 and 3185 cm(-1) are attributed to water stretching vibrations. By using a Libowitzky empirical function, hydrogen bond distances are calculated from the OH stretching wavenumbers. Strong hydrogen bonds in the structure of ludlamite are observed as determined by their hydrogen bond distances. The application of infrared and Raman spectroscopy to the study of ludlamite enables the molecular structure of the pegmatite mineral ludlamite to be assessed. PMID:23257342

Frost, Ray L; Xi, Yunfei; Scholz, Ricardo; Belotti, Fernanda M

2013-02-15

359

Surface spectroscopic characterization of hydrodesulfurization catalysts, molybdenum-alumina catalysts, and Ni-W/Al/sub 2/O/sub 3/ catalysts, and molybdenum-titania catalysts  

SciTech Connect

X-ray photoelectron spectroscopy (ESCA), ion scattering spectroscopy (ISS), and x-ray diffraction have been used to characterize a series of sulfided and reduced MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ catalysts. ESCA and ISS have identified the presence of both MoS/sub 2/ and Mo(V) on a sulfided MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ catalyst. The octahedrally and tetrahedrally coordinated molybdenum on an oxidic MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ precursor catalyst show different sulfidation behavior. The distribution of nickel species on Ni/Al/sub 2/O/sub 3/ and Ni-W/Al/sub 2/O/sub 3/ catalysts have been studied using ESCA and ISS. Increases in the peak width asymmetry of an Ni 2p photoelectron spectra were observed for Ni/Al/sub 2/O/sub 3/ when the nickel content was increased. These changes were minimized when the tungsten concentration was increased from 15 to 24% WO/sub 3/. The surface structure of MoO/sub 3//TiO/sub 2/ catalysts have been investigated using several spectroscopic techniques: ESCA, ISS, x-ray diffraction, IR and Raman spectroscopy. Up to the concentration of 10wt% MoO/sub 3/, two types of molybdenum-titania surface interaction species are produced in roughly a 2:1 proportion.

Li, C.P.

1984-01-01

360

New route to the synthesis of bis[N-(2-aminoethyl) salicylaldiminato] chromium(III) chloride monohydrate Spectroscopic characterization, crystal structure and interaction with DNA.  

PubMed

The reaction of [Cr(urea)(6)]Cl(3).3H(2)O with H(2)salen (H(2)salen=N,N(')-ethylenebis(salicylaldimine) in water-methanol mixture (40:60v/v) under reflux yielded the complex bis[N-(2-aminoethyl)salicylaldiminato]chromium(III) chloride monohydrate, [Cr(aesaldmn)(2)]Cl.H(2)O. The complex was characterized by elemental analysis, molar conductance, magnetic susceptibility, spectroscopic (UV-vis and IR) data and X-ray diffraction studies. The new ligand, N-(2-aminoethyl)salicylaldimine, Haesaldmn, possibly resulted from the hydrolytic cleavage of one end of the H(2)salen ligand during reflux. Binding of this chromium(III) complex to CT DNA has been studied using UV-vis spectroscopy with an apparent binding constant of 2.68 x 10(3)M(-1). It shows that the binding mode is electrostatic while the emission of ethidium bromide to CT DNA in the absence and in the presence of the complex show that it binds DNA with partial intercalation. PMID:16524764

Biswas, Susobhan; Sarkar, Saikat; Dey, Kamalendu; Jana, Bimal; Basu, Tarakdas; Yap, Glenn P A; Kreisel, Kevin

2006-11-01

361

Modern spectroscopic technique in the characterization of biosensitive macrocyclic Schiff base ligand and its complexes: inhibitory activity against plantpathogenic fungi.  

PubMed

Complexes of the type [M(L)Cl2], where M = Co(II), Ni(II) and Cu(II) have been synthesized with a macrocyclic Schiff base ligand (1,4,5,7,10,11,12,15-octaaza,5,11,16,18-tetraphenyl, 3,4,12,13-tetramethyl cyclo-octadecane) derived from Schiff base (obtained by the condensation of 4-aminoantipyrine and dibenzoyl methane) and ethylenediamine. The ligand was characterized on the basis of elemental analysis, IR, (1)H NMR, EI Mass and molecular modeling studies while the complexes were characterized by elemental analysis, molar conductance measurements, magnetic susceptibility measurements, IR, electronic and EPR spectral studies. All the complexes are non-electrolyte in nature. The covalency factor (?) and coefficient factor (?) suggest the covalent nature of the complexes. The ligand and its metal complexes have shown antifungal activity with their LD50 values determined by probit analysis against two economically important fungal plant pathogens i.e. Macrophomina phaseolina and Fusarium solani. PMID:24161868

Tyagi, Monika; Chandra, Sulekh; Akhtar, Jameel; Chand, Dinesh

2014-01-24

362

Spectroscopic characterization and evaluation of SiO{sub 2}-overcoated silver islands as a SERS substrate  

SciTech Connect

Vacuum deposition of a 50-{Angstrom} layer of silver and a subsequent 50-{Angstrom} layer of SiO{sub 2} onto glass is shown to be a viable substrate for Surface-Enhanced Raman Spectroscopy (SERS) and a suitable model of silica surfaces. The model silica surface is characterized by SERS, Atomic Force Microscopy (AFM), and Auger Electron Spectroscopy (AES). SERS of pyridine adsorption onto the SiO{sub 2} overlayer was used to characterize differences between the silica and silver surfaces. Adsorption isotherm and kinetic data for surfactant adsorption at the silica/solution interface have been elucidated with SERS employing the SiO{sub 2}/Ag substrates. Surface roughness relative to the underlying silver-island film and general structure of the substrate was measured with contact mode AFM. AES was used to probe the silica surface for possible exposure of silver through pinholes in the silica overcoat; the {open_quotes}pinhole percentage{close_quotes} was determined to be {<=} 1%

Lacy, W.B.; Williams, J.M.; Wenzler, L.A. [Univ. of Utah, Salt Lake City, UT (United States)

1995-12-01

363

Diorganotin(IV) complexes of biologically potent 4( 3H)-quinazolinone derived Schiff bases: Synthesis, spectroscopic characterization, DNA interaction studies and antimicrobial activity  

NASA Astrophysics Data System (ADS)

Four Schiff base ligands and their corresponding organotin(IV) complexes have been synthesized and characterized by elemental analyses, IR, 1H NMR, MS and thermal studies. The Schiff bases are obtained by the condensation of 3-amino-2-methyl-4( 3H)-quinazolinone with different substituted aldehydes. The elemental analysis data suggest the stoichiometry to be 1:1 ratio formation. Infrared spectral data agreed with the coordination to the central metal ion through imine nitrogen, lactam oxygen and deprotonated phenolic oxygen atoms. All the synthesized compounds have been evaluated for antimicrobial activity against selected species of microorganisms. In addition, DNA binding/cleavage capacity of the compounds was analyzed by absorption spectroscopy, viscosity measurements and gel electrophoresis methods.

Prasad, Kollur Shiva; Kumar, Linganna Shiva; Chandan, Shivamallu; Jayalakshmi, Basvegowda; Revanasiddappa, Hosakere D.

2011-10-01

364

Spectroscopic characterization of a series of polyyne-iodine molecular complexes H(Ctbnd C)nH(I6) of n = 5-9  

NASA Astrophysics Data System (ADS)

A series of molecular complexes, C2nH2I6 (n = 5-9), formed from size-selected hydrogen-end-capped polyyne, H(Ctbnd C)nH, and iodine molecules was characterized by UV-vis and IR absorption spectroscopy for elucidating location and geometry of iodine atoms in the complex. The IR lines for the CH-stretching ?u fundamental at 3305 cm-1 and CH-bending ?u fundamental at 625 cm-1 for C2nH2 (n = 5-7) in CCl4 were red-shifted by 220 and 15 cm-1, respectively, for its complex of C2nH2I6. A few lines were intensified in the low-frequency region of 850-1450 cm-1 for CC-stretching ?u modes of polyynes in the complex.

Wada, Yoriko; Morisawa, Yusuke; Wakabayashi, Tomonari

2012-07-01

365

Heat loads from ICRF and LH wave absorption in the SOL: characterization on JET and implications for the ITER-Like Wall  

NASA Astrophysics Data System (ADS)

Heat loads from ICRF and LH wave absorption in the SOL are characterized on JET from the de-convolution of surface temperatures measured by infrared thermography. The spatial localization, quantitative estimates, parametric dependence and physical origin of the observed heat fluxes are documented. Implications of these observations are discussed for the operation of JET with an ITER-Like Wall, featuring Beryllium tiles with reduced power handling capability.

Colas, L.; Jacquet, Ph.; Mayoral, M.-L.; Arnoux, G.; Bobkov, V.; Brix, M.; Fursdon, M.; Goniche, M.; Graham, M.; Lerche, E.; Mailloux, J.; Monakhov, I.; Noble, C.; Ongena, J.; Petržilka, V.; Sirinelli, A.; Riccardo, V.; Vizvary, Z.

2011-12-01

366

Heat loads from ICRF and LH wave absorption in the SOL: characterization on JET and implications for the ITER-Like Wall  

SciTech Connect

Heat loads from ICRF and LH wave absorption in the SOL are characterized on JET from the de-convolution of surface temperatures measured by infrared thermography. The spatial localization, quantitative estimates, parametric dependence and physical origin of the observed heat fluxes are documented. Implications of these observations are discussed for the operation of JET with an ITER-Like Wall, featuring Beryllium tiles with reduced power handling capability.

Colas, L.; Arnoux, G.; Goniche, M. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Jacquet, Ph.; Mayoral, M.-L.; Brix, M.; Fursdon, M.; Graham, M.; Mailloux, J.; Monakhov, I.; Noble, C.; Sirinelli, A.; Riccardo, V.; Vizvary, Z. [Euratom/CCFE Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Bobkov, V. [Max-Planck-Institut fuer Plasmaphysik, EURATOM-Assoziation, Garching (Germany); Lerche, E.; Ongena, J. [Association EURATOM-Belgian State, ERM-KMS, Brussels (Belgium); Petrzilka, V. [Association EURATOM-IPP. CR, Za Slovankou 3, 182 21 Praha 8 (Czech Republic)

2011-12-23

367

Soliton absorption spectroscopy  

SciTech Connect

We analyze optical soliton propagation in the presence of weak absorption lines with much narrower linewidths as compared to the soliton spectrum width by using a perturbation analysis technique based on an integral representation in the spectral domain. The stable soliton acquires a spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary soliton propagation and to an absorber inside a passively mode-locked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurements in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improvement in the sensitivity and spectroscopic accuracy, which makes soliton absorption spectroscopy a promising measurement technique.

Kalashnikov, V. L.; Sorokin, E. [Institut fuer Photonik, TU Wien, Gusshausstr. 27/387, A-1040 Vienna (Austria)

2010-03-15

368

Spectroscopic characterizations and biological studies on newly synthesized Cu 2+ and Zn 2+ complexes of first and second generation dendrimers  

NASA Astrophysics Data System (ADS)

The novel Cu(II) and Zn(II) complexes of first and second generation poly(propylene amine) dendrimers (PPA), comprising 1,8-naphthalimde units on periphery have been synthesized. These new complexes were characterized by elemental analysis, molar conductivity, spectral methods (IR, 1H NMR and UV-vis spectra) and thermal analysis (TG and DTG) techniques. From elemental analysis as well as thermal studies it has found that the first generation dendrimer behaves as bidentate ligand and forming chelates with 1:2 (ligand:metal) and 1:4 (ligand:metal) stoichiometry for second generation dendrimer. Different kinetic parameters namely activation energy (? E*), enthalpy of activation (? H*), entropy of activation (? S*) and free energy change of activation (? G*) are calculated using Coats-Redfern equation. The antibacterial activity of dendrimers and their complexes was evaluated against some Gram positive and negative bacteria.

Refat, Moamen S.; El-Deen, Ibrahim M.; Grabchev, Ivo; Anwer, Zeinab M.; El-Ghol, Samir

2009-05-01

369

Spectroscopic characterization of cell membranes and their constituents of the plant-associated soil bacterium Azospirillum brasilense  

NASA Astrophysics Data System (ADS)

Structural and compositional features of bacterial membranes and some of their isolated constituents (cell surface lipopolysaccharide, phospholipids) of the plant-growth-promoting diazotrophic rhizobacterium Azospirillum brasilense (wild-type strain Sp245) were characterized using Fourier transform infrared (FTIR) spectroscopy and some other techniques. FTIR spectra of the cell membranes were shown to comprise the main vibration modes of the relevant lipopolysaccharide and protein components which are believed to be involved in associative plant-bacterium interactions, as well as of phospholipid constituents. The role and functions of metal cations in the structural organization and physicochemical properties of bacterial cell membranes are also discussed considering their accumulation in the membranes from the culture medium.

Kamnev, A. A.; Antonyuk, L. P.; Matora, L. Yu.; Serebrennikova, O. B.; Sumaroka, M. V.; Colina, M.; Renou-Gonnord, M.-F.; Ignatov, V. V.

1999-05-01

370

Spectroscopic detection  

DOEpatents

In embodiments, spectroscopic monitor monitors modulated light signals to detect low levels of contaminants and other compounds in the presence of background interference. The monitor uses a spectrometer that includes a transmissive modulator capable of causing different frequency ranges to move onto and off of the detector. The different ranges can include those with the desired signal and those selected to subtract background contributions from those with the desired signal. Embodiments of the system are particularly useful for monitoring metal concentrations in combustion effluent.

Woskov, Paul P. (Bedford, MA); Hadidi, Kamal (Cambridge, MA)

2003-01-01

371

Polyoxometalates functionalized by bisphosphonate ligands: synthesis, structural, magnetic, and spectroscopic characterizations and activity on tumor cell lines.  

PubMed

We report the synthesis and characterization of eight new Mo, W, or V-containing polyoxometalate (POM) bisphosphonate complexes with metal nuclearities ranging from 1 to 6. The compounds were synthesized in water by treating Mo(VI), W(VI), V(IV), or V(V) precursors with biologically active bisphosphonates H(2)O(3)PC(R)(OH)PO(3)H(2) (R = C(3)H(6)NH(2), Ale; R = CH(2)S(CH(3))(2), Sul and R = C(4)H(5)N(2), Zol, where Ale = alendronate, Sul = (2-Hydroxy-2,2-bis-phosphono-ethyl)-dimethyl-sulfonium and Zol = zoledronate). Mo(6)(Sul)(2) and Mo(6)(Zol)(2) contain two trinuclear Mo(VI) cores which can rotate around a central oxo group while Mo(Ale)(2) and W(Ale)(2) are mononuclear species. In V(5)(Ale)(2) and V(5)(Zol)(2) a central V(IV) ion is surrounded by two V(V) dimers bound to bisphosphonate ligands. V(6)(Ale)(4) can be viewed as the condensation of one V(5)(Ale)(2) with one additional V(IV) ion and two Ale ligands, while V(3)(Zol)(3) is a triangular V(IV) POM. These new POM bisphosphonates complexes were all characterized by single-crystal X-ray diffraction. The stability of the Mo and W POMs was studied by (31)P NMR spectroscopy and showed that all compounds except the mononuclear Mo(Ale)(2) and W(Ale)(2) were stable in solution. EPR measurements performed on the vanadium derivatives confirmed the oxidation state of the V ions and evidenced their stability in aqueous solution. Electrochemical studies on V(5)(Ale)(2) and V(5)(Zol)(2) showed reduction of V(V) to V(IV), and magnetic susceptibility investigations on V(3)(Zol)(3) enabled a detailed analysis of the magnetic interactions. The presence of zoledronate or vanadium correlated with the most potent activity (IC(50)~1-5 ?M) against three human tumor cell lines. PMID:22725619

El Moll, Hani; Zhu, Wei; Oldfield, Eric; Rodriguez-Albelo, L Marleny; Mialane, Pierre; Marrot, Jérôme; Vila, Neus; Mbomekallé, Israel Martyr; Rivière, Eric; Duboc, Carole; Dolbecq, Anne

2012-07-16

372

Entrapment of marine microalga, Isochrysis galbana, for biosorption of Cr(III) from aqueous solution: isotherms and spectroscopic characterization  

NASA Astrophysics Data System (ADS)

Microalga, Isochrysis galbana, biomass was entrapped into alginate gel by liquid curing method in the presence of Ca(II) ions. The biosorption of chromium(III) by the entrapped live algal biomass was studied in a batch system. The effect of initial cadmium concentration, pH, temperature and liquid and solid ratio on Cr(III) removal was investigated. The maximum experimental biosorption capacities for entrapped live algal biomass were found to be 335.27 mg Cr(III) g-1 of dry algal biomass. The kinetics of chromium biosorption was slow; approximately 75 % of biosorption took place in 2 h. The percent adsorption increased with increase in pH; pH 5 of the solution was found to favor adsorption very strongly. The equilibrium biosorption data were evaluated by Langmuir and Freundlich isotherm models, and was best described by Langmuir and Freundlich isotherms. The biosorbent was characterized and evaluated, the functional groups -OH, -COOH and C=O were involved in the biosorption process. Since binding capacity was relatively high for immobilized live algal biomass, those algal forms are to be considered as suitable biosorbent for the removal of chromium in wastewater treatment.

Kadimpati, Kishore Kumar; Mondithoka, Krishna Prasad; Bheemaraju, Sarada; Challa, Venkata Ramachandra Murthy

2013-03-01

373

Comparative studies, synthesis, spectroscopic and characterization of N-methylisatin-3-Girard's T and P hydrazone complexes  

NASA Astrophysics Data System (ADS)

Different types of complexes derived from the reactions of N-methylisatin Girard's T hydrazone, N,N,N-trimethyl-2-[(2z)-2-(1-methyl-2-oxo-1,2-dihydro-3H-indole-3-ylidene) hydrazino]-2-oxo-ethan ammonium chloride (MIGT) and N-methylisatin Girard's P hydrazone, 1-{2-(2z)-2-[(1-methyl-2-oxo-1,2-dihydro-3H-indole-3-ylidene) hydrazino]-2-oxoethyl}pyridinium chloride (MIGP) with Fe3+, Al3+, Sb3+ and Sn2+ salts were synthesized. The isolated complexes were characterized by elemental analyses, molar conductivities, spectral (IR, UV-Vis., 1H NMR, mass), magnetic moments and thermal measurements. The values of conductance suggest that the complexes are conducting in polar solvents (EtOH, H2O and DMF). The IR spectra suggest that the ligands coordinate in a bidentate and/or tridentate manner via the carbonyl groups of both N-methylisatin and Girard's T and/or P and the (Cdbnd N) group. The solvents inside and outside the coordination sphere were determined by weight loss and TGA methods. The octahedral geometry of the complexes is confirmed using spectral, magnetic and DFT method from DMOL3 calculations. The ligands and their metal complexes were tested against different strains of bacteria and fungi.

Azhari, Shaker J.; Salah, Sabah; Farag, Rabei S.; Mostafa, Mohsen M.

2015-02-01

374

Transition metal complexes of neocryptolepine analogues. Part I: Synthesis, spectroscopic characterization, and invitro anticancer activity of copper(II) complexes.  

PubMed

New generation of copper(II) complexes with aminoalkylaminoneocryptolepine as bidentate ligands has been synthesized and it is characterized by elemental analyses, magnetic moment, spectra (IR, UV-Vis, (1)H NMR and ESR) and thermal studies. The IR data suggest the coordination modes for ligands which behave as a bidentate with copper(II) ion. Based on the elemental analysis, magnetic studies, electronic and ESR data, binuclear square planar geometry was proposed for complexes 7a, 7b, square pyramidal for 9a, 9b and octahedral for 8a, 8b, 10a, 10b. The molar conductance in DMF solution indicates that all complexes are electrolyte except 7a and 7b. The ESR spectra of solid copper(II) complexes in powder form showed an axial symmetry with (2)B1g as a ground state and hyperfine structure. The thermal stability and degradation of the ligands and their metal complexes were studied employing DTA and TG methods. The metal-free ligands and their copper(II) complexes were tested for their in vitro anticancer activity against human colon carcinoma (HT-29). The results showed that the synthesized copper(II) complexes exhibited higher anticancer activity than their free ligands. Of all the studied copper(II) complexes, the bromo-substituted complex 9b exhibited high anticancer activity at low micromolar inhibitory concentrations (IC50=0.58?M), compared to the other complexes and the free ligands. PMID:24867072

Emam, Sanaa Moustafa; El Sayed, Ibrahim El Tantawy; Nassar, Nagla

2015-03-01

375

Spectroscopic characterization of TiC x films produced by pulsed laser deposition in CH 4 environments  

NASA Astrophysics Data System (ADS)

Titanium carbide (TiC x) thin films were grown on (1 0 0)-Si substrates by a pulsed laser deposition (PLD) method using a Ti target in methane gas. The films are characterized in situ by Auger (AES), electron energy loss (EELS) and X-ray photoelectron spectroscopies (XPS). It was found that the reaction between the ablated Ti species and CH 4 in the plasma plume influenced the C:Ti ratio. XPS numerical fitting for the C 1s transition revealed three Gaussians components. The main component, binding energy of 282.8 eV, is assigned to C making bonds with Ti, like in stoichiometric TiC. The second component, binding energy of 284.9 eV, is assigned to C?C bonds. A third component is found for films deposited at pressures higher than 25 mTorr at 286.5 eV. A post-deposition thermal treatment demonstrates that the Ti?C and C?C peaks are very stable, whereas, the third peak tends to decrease for temperatures higher than 200 °C. It is assumed that this last component is due to carbonyl complexes remnant in films. Finally, it can be concluded that the titanium carbide films processed by PLD is a chemically inhomogeneous material; mostly composed of sub-stoichiometric TiC and particulates of segregated carbon.

Soto, G.

2004-05-01

376

One pot synthesis of biologically active pregnane derivatives, their single crystal structures, spectroscopic characterization and theoretical calculations  

NASA Astrophysics Data System (ADS)

One pot allylic oxidation of 3?-acetoxypregna-5,16-diene-20-one (2) and nucleophilic addition at C-16 position of 3?-hydroxypregna-5,16-diene-20-one (3) yielded 3?-acetoxypregna-5,16-diene-7,20-dione (4) and 3?-hydroxy-16?-(5'-hydroxypentyloxy)-pregn-5-ene-20-one (5) respectively in high yield. A detailed theoretical study supported by X-ray analysis of compounds 4 and 5 has been carried out. Conformational analysis of compounds 4 and 5 was done with the help of crystal structure, which crystallize out in orthorhombic form having P212121 space group. Structural characterization of compounds 4 and 5 was done with the aid of 1H, 13C NMR, IR, UV, ESI-MS and ESI-HRMS. The molecular geometries and vibrational frequencies for compounds 4 and 5 in the ground state were calculated using the Density functional theory (DFT) with 6-31G(d,p) basis set and compared with experimental data. 1H and 13C nuclear magnetic resonance magnetic shifts of 4 and 5 were calculated using GIAO method and compared with the experimental data. UV-Vis spectra of both the compounds were recorded and electronic properties such as HOMO-LUMO energies were calculated by time dependent TD-DFT approach. The compounds were screened for their anti-hyperlipidemic and anti-oxidant activity.

Sethi, Arun; Bhatia, Akriti; Bhatia, Gitika; Shrivastava, Atul; Prakash, Rohit

2013-11-01

377

Influence of Galloyl Moiety in Interaction of Epicatechin with Bovine Serum Albumin: A Spectroscopic and Thermodynamic Characterization  

PubMed Central

The health benefits stemming from green tea are well known, but the exact mechanism of its biological activity is not elucidated. Epicatechin (EC) and epicatechin gallate (ECG) are two dietary catechins ubiquitously present in green tea. Serum albumins functionally carry these catechins through the circulatory system and eliminate reactive oxygen species (ROS) induced injury. In the present study ECG is observed to have higher antioxidant activity; which is attributed to the presence of galloyl moiety. The binding affinity of these catechins to bovine serum albumin (BSA) will govern the efficacy of their biological activity. EC and ECG bind with BSA with binding constants 1.0×106 M?1 and 6.6×107 M?1, respectively. Changes in secondary structure of BSA on interaction with EC and ECG have been identified by circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy. Thermodynamic characterization reveals the binding process to be exothermic, spontaneous and entropy driven. Mixed binding forces (hydrophobic, electrostatic and hydrogen bonding) exist between ECG and BSA. Binding site for EC is primarily site-II in sub-domain IIIA of BSA and for ECG; it is site-I in sub-domain IIA. ECG with its high antioxidant activity accompanied by high affinity for BSA could be a model in drug designing. PMID:22916242

Pal, Sandip; Saha, Chabita; Hossain, Maidul; Dey, Subrata Kumar; Kumar, Gopinatha Suresh

2012-01-01

378

Spectroscopic characterization of X-ray emitting young stars associated with the Sh 2-296 nebula  

E-print Network

We studied a sample of stars associated with the Sh 2-296 nebula, part of the reflection nebulae complex in the region of Canis Major (CMa R1). Our sample corresponds to optical counterparts of X-ray sources detected from observations with the XMM-Newton satellite, which revealed dozens of possible low-mass young stars not yet known in this region. A sample of 58 young star candidates were selected based on optical spectral features, mainly H{\\alpha} and lithium lines, observed with multi-objects spectroscopy performed by the Gemini South telescope. Among the candidates, we find 41 confirmed T Tauri and 15 very likely young stars. Based on the H{\\alpha} emission, the T Tauri stars were distinguished between classical (17%) and weak-lined (83%), but no significant difference was found in the age and mass distribution of these two classes. The characterization of the sample was complemented by near- and mid-infrared data, providing an estimate of ages and masses from the comparison with pre-main-sequence evolut...

Fernandes, B; Montmerle, T; Rojas, G

2015-01-01

379

[Three-dimensional excitation emission matrix fluorescence spectroscopic characterization of dissolved organic matter in water of coal-mining area].  

PubMed

Three-dimensional excitation emission matrix was applied to characterize the fluorescence properties of dissolved organic matter in various waters of Shilong coal-mining area. Fluorescence peak I (fulvic-like) and peak II (humic-like) were strong, while peak IV and peak V (protein-like) were weak or even undetected in some samples. Fluorescence peaks in various waters and different zones showed great difference in intensities and the fluorescence peaks in underground water tended to be much lower than those of surface waters. Furthermore, the fluorescence peaks of rivers and lakes were higher than those of mine drainage, and also the fluorescence peaks in coking zone and coal mining zone were higher than those in sewage-irrigated zone, or even much higher than those in farming zone. The reason may be that coal mining activities and coal industry can bring plenty of organic matter from coal to surroundings. Meanwhile, surface water would accept mine drainage, waste water of coal-washing and sewage from daily life easier than underground water, so surface water can be polluted seriously. Fluorescence peaks in waters from coal mining area are little influenced by pH of the water but can be influenced by the content of Ca2+ to water in some extent. PMID:18422146

Yang, Ce; Zhong, Ning-Ning; Shui, Yu-Lei; Wang, Fei-Yu; Chen, Dang-Yi

2008-01-01

380

Combination of chromatographic and spectroscopic methods for the isolation and characterization of polar guaianolides from Achillea asiatica.  

PubMed

Four polar guaianolides, 8alpha-angeloxy-2alpha,4alpha, 10beta-trihydroxy-6betaH,7alphaH, 11betaH-1(5)-guaien- 12,6alpha-olide; 8alpha-angeloxy-1beta,2beta:4beta,5beta-diepoxy- 10beta-hydroxy-6betaH,7alphaH,11betaH-12,6alpha-guaianolide; 8alpha-angeloxy-4alpha, 10beta-dihydroxy-2-oxo-6betaH, 7alphaH, 11betaH- 1(5)-guaien- 12,6alpha-olide and 8-desacetyl-matricarin, were isolated from Achillea asiatica and characterized by TLC, MS, IR, HPLC and diode array detection. Purified extracts were separated by means of flash chromatography. HPLC separations were achieved using different methanol-water gradients as mobile phase and LiChrospher 100-RP8 5 microm or Zorbax SB-C8 3.5 microm as stationary phases. The chromatographical data are compared to those of the proazulene 8alpha-tigloxy-artabsin which shows antiinflammatory effects. By means of these characteristics the identification of the guaianolides with potential antiphlogistic properties is also possible from other sources. PMID:11761000

Glasl, S; Gunbilig, D; Narantuya, S; Werner, I; Jurenitsch, J

2001-11-30

381

Spectroscopic Infrared Ellipsometry  

E-print Network

Spectroscopic Infrared Ellipsometry: Components, Calibration, and Application #12;CIP-DATA KONINKLIJKE BIBLIOTHEEK, DEN HAAG Boer, Johannes Henricus Wilhelmus Gerardus den Spectroscopic Infrared in Dutch. ISBN 90 386 0017 8 Subject headings: spectroscopy ellipsometry infrared. #12;Spectroscopic

Eindhoven, Technische Universiteit

382

Analytical studies on the charge transfer complexes of loperamide hydrochloride and trimebutine drugs. Spectroscopic and thermal characterization of CT complexes.  

PubMed

Charge transfer complexes of loperamide hydrochloride (LOP.HCl) and trimebutine (TB) drugs as electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as ?-acceptors in acetonitrile were investigated spectrophotometrically to determine the cited drugs in pure and dosage forms. The reaction gives highly coloured complex species which are measured spectrophotometrically at 460, 415 and 842nm in case of LOP.HCl and at 455, 414 and 842nm in case of TB using DDQ, TCNE and TCNQ reagents, respectively. The optimum experimental conditions have been studied carefully and optimized. Beer's law was obeyed over the concentration ranges of 47.70-381.6, 21.50-150.5 and 10.00-100.0?gmL(-1) for LOP.HCl and 37.85-264.9, 38.75-310.0 and 7.75-155.0?gmL(-1) for TB using DDQ, TCNE and TCNQ reagents, respectively. Sandell sensitivity, standard deviation, relative standard deviation, limit of detection and quantification were calculated. The obtained data refer to high accuracy and precision of the proposed method. These results are also confirmed by inter and intra-day precision with percent recovery of 99.18-101.1% and 99.32-101.4% in case of LOP.HCl and 98.00-102.0% and 97.50-101.4% in case of TB using DDQ, TCNE and TCNQ reagents for intra- and inter-day, respectively. These data were compared with those obtained using official methods for the determination of the cited drugs. The stability constants of the CT complexes were determined. The final products of the reaction were isolated and characterized using FT-IR, (1)H NMR, elemental analysis and thermogravimetric analysis (TG). The stoichiometry and apparent formation constant of the complexes formed were determined by applying the conventional spectrophotometric molar ratio method. PMID:24727166

Elqudaby, Hoda M; Mohamed, Gehad G; El-Din, Ghada M G

2014-08-14

383

Analytical studies on the charge transfer complexes of loperamide hydrochloride and trimebutine drugs. Spectroscopic and thermal characterization of CT complexes  

NASA Astrophysics Data System (ADS)

Charge transfer complexes of loperamide hydrochloride (LOP.HCl) and trimebutine (TB) drugs as electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as ?-acceptors in acetonitrile were investigated spectrophotometrically to determine the cited drugs in pure and dosage forms. The reaction gives highly coloured complex species which are measured spectrophotometrically at 460, 415 and 842 nm in case of LOP.HCl and at 455, 414 and 842 nm in case of TB using DDQ, TCNE and TCNQ reagents, respectively. The optimum experimental conditions have been studied carefully and optimized. Beer’s law was obeyed over the concentration ranges of 47.70-381.6, 21.50-150.5 and 10.00-100.0 ?g mL-1 for LOP.HCl and 37.85-264.9, 38.75-310.0 and 7.75-155.0 ?g mL-1 for TB using DDQ, TCNE and TCNQ reagents, respectively. Sandell sensitivity, standard deviation, relative standard deviation, limit of detection and quantification were calculated. The obtained data refer to high accuracy and precision of the proposed method. These results are also confirmed by inter and intra-day precision with percent recovery of 99.18-101.1% and 99.32-101.4% in case of LOP.HCl and 98.00-102.0% and 97.50-101.4% in case of TB using DDQ, TCNE and TCNQ reagents for intra- and inter-day, respectively. These data were compared with those obtained using official methods for the determination of the cited drugs. The stability constants of the CT complexes were determined. The final products of the reaction were isolated and characterized using FT-IR, 1H NMR, elemental analysis and thermogravimetric analysis (TG). The stoichiometry and apparent formation constant of the complexes formed were determined by applying the conventional spectrophotometric molar ratio method.

Elqudaby, Hoda M.; Mohamed, Gehad G.; El-Din, Ghada M. G.

2014-08-01

384

CO/FTIR Spectroscopic Characterization of Pd/ZnO/Al2O3 Catalysts for Methanol Steam Reforming  

SciTech Connect

An 8.8% Pd/ZnO/Al2O3 catalyst was either pretreated under O2 at 773 K followed by H2 at 293 K or under H2 at 773 K to obtain, respectively, a supported metallic Pd° catalyst (Pd°/ZnO/Al2O3) or a supported PdZn alloy catalyst (PdZn/ZnO/Al2O3). Both catalysts were studied by CO adsorption using FTIR spectroscopy. For the supported PdZn alloy catalyst (PdZn/ZnO/Al2O3), exposure to a mixture of methanol and steam, simulating methanol steam reforming reaction conditions, does not change the catalyst surface composition. This implies that the active sites are PdZn alloy like structures. The exposure of the catalyst to an oxidizing environment (O2 at 623 K) results in the break up of PdZn alloy, forming a readily reducible PdO with its metallic form being known as much less active and selective for methanol steam reforming. However, for the metallic Pd°/ZnO/Al2O3 catalyst, FTIR results indicate that metallic Pdº can transform to PdZn alloy under methanol steam reforming conditions. These results suggest that PdZn alloy, even after an accidental exposure to oxygen, can self repair to form the active PdZn alloy phase under methanol steam reforming conditions. Catalytic behavior of the PdZn/ZnO/Al2O3 catalyst also correlates well with the surface composition characterizations by FTIR/CO spectroscopy.

Lebarbier, Vanessa MC; Dagle, Robert A.; Conant, Travis; Vohs, John M.; Datye, Abhaya K.; Wang, Yong

2008-02-12

385

Micro-Spectroscopic Imaging and Characterization of Individually Identified Ice Nucleating Particles from a Case Field Study  

SciTech Connect

The effect of anthropogenic and biogenic organic particles on atmospheric glaciation processes is poorly understood. We use an optical microscopy (OM) setup to identify the location of ice nuclei (IN) active in immersion freezing and deposition ice nucleation for temperatures of 200-273 K within a large population of particles sampled from an ambient environment. Applying multi-modal micro-spectroscopy methods we characterize the physicochemical properties of individual IN in particle populations collected in central California. Chemical composition and mixing state analysis of particle populations are performed to identify characteristic particle-type classes. All particle-types contained organic material. Particles in these samples take up water at subsaturated conditions, induce immersion freezing at subsaturated and saturated conditions above 226 K, and act as deposition IN below 226 K. The identified IN belong to the most common particle-type classes observed in the field samples: organic coated sea salt, Na-rich, and secondary and refractory carbonaceous particles. Based on these observations, we suggest that the IN are not always particles with unique chemical composition and exceptional ice nucleation propensity; rather, they are common particles in the ambient particle population. Thus, particle composition and morphology alone are insufficient to assess their potential to act as IN. The results suggest that particle-type abundance is also a crucial factor in determining the ice nucleation efficiency of specific IN types. These findings emphasize that ubiquitous organic particles can induce ice nucleation under atmospherically relevant conditions and that they may play an important role in atmospheric glaciation processes.

Knopf, Daniel A.; Alpert, Peter A.; Wang, Bingbing; O'Brien, Rachel E.; Kelly, Stephen T.; Laskin, Alexander; Gilles, Mary K.; Moffet, Ryan C.

2014-09-03

386

Preparation, spectroscopic and thermal characterization of new metal complexes of verlipride drug. In vitro biological activity studies  

NASA Astrophysics Data System (ADS)

Metal complexes of the general formula [M(VER)2Cl2(H2O)2]·yH2O and [Cr(VER)2Cl2(H2O)2]Cl·H2O (where VER = verlipride, M = Mn(II) (y = 2), Co(II) (y = 2), Ni(II) (y = 2), Cu(II) (y = 1) and Zn(II) (y = 0)) are prepared and characterized based on elemental analyses, IR, 1H NMR, magnetic moment, molar conductance, and thermal analyses (TG and DTA) techniques. From the elemental analyses data, the complexes are formed in 1:2 [Metal]:[VER] ratio. The molar conductance data reveal that all the metal chelates are non-electrolytes except Cr(III) complex, it is 1:1 electrolyte. IR spectra show that VER is coordinated to the metal ions in a neutral monodentate manner with O donor site of the carbonyl O atom. On the basis of spectral studies and magnetic moment measurements an octahedral geometry has been assigned for the complexes. The thermal behavior of these chelates is studied using thermogravimetric analysis technique. The results obtained show that the complexes lose hydrated water, HCl and coordinated water molecules followed immediately by decomposition of the ligand molecules in the successive unseparate steps. The VER drug, in comparison to its metal complexes is also screened for its biological activity against Gram positive bacterial (Staphylococcus aureus) and Gram negative bacteria (Escherichia coli) and fungi (Candida albicans and Aspergillus flavus) in vitro. The activity data show that most of the metal complexes have antibacterial activity like or higher than that of the parent VER drug against one or more species.

Soliman, M. H.; Mohamed, Gehad G.

2012-06-01

387

In situ x-ray absorption spectroscopic study of the Li[Ni[subscript 1/3]Co[subscript 1/3]Mn[subscript 1/3  

SciTech Connect

The layered LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} 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 LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} on a 25-{micro}m Al foil and had an area of 0.79 cm{sup 2}. 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 LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} are Ni{sup 2+}, Co{sup 3+}, and Mn{sup 4+}, whereas during charging Ni{sup 2+} is oxidized to Ni{sup 4+} through an intermediate stage of Ni{sup 3+}, Co{sup 3+} is oxidized almost to Co{sup 4+} and, utilizing Faraday's calculation and XAS results, the Co was found to be at Co{sup 3.92+} at the end of the charge, while Mn was found to be electrochemically inactive and remains as Mn{sup 4+}. 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 LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} cathode confirmed that the material retains its symmetry and good structural short-range order leading to superior cycling.

Deb, A.; Bergmann, U.; Cramer, S.P.; Cairns, E.J. (SSRL); (LBNL)

2010-07-13

388

Spectroscopic characterization and biological activity of dihydrazone transition metal complexes: Crystal structure of 2,3-butanedione bis(isonicotinylhydrazone)  

NASA Astrophysics Data System (ADS)

Metal complexes of the chloride, nitrate and acetate salts of Co(II), Ni(II) Cu(II), Zn(II), Cd(II) or Hg(II) with 2,3-butanedione bis(isonicotinylhydrazone) [BBINH] have been synthesized and structurally characterized. The crystal of BBINH was solved to crystallize as monoclinic system with space group of P121/c14. The formulae of the complexes were assigned based on the elemental analysis and mass spectra. The formation of BBINH complexes depend on the metal anion used. All complexes are nonelectrolytes except for the complexes 2, 3, 4 are (1:1) and 13 and 14 which are 1:2 electrolytes. BBINH behaves as a neutral tetradentate (N2O2) in the chloride complexes of Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II). In [Co2(BBINH)(H2O)Cl3]Cl?H2O, BBINH has the same dentate but with the two Co(II) ions. In the acetate complexes, [Ni2(BBINH-2H)(H2O)2(OAc)2]?3H2O and [Cu2(BBINH-2H)(OAc)2]?5H2O, BBINH acts as a binegative tetradentate with the two metal ions. The ligand in the nitrate complexes acts as a neutral bidentate via the two hydrazone azomethine Cdbnd NHy; the nitrate ions are ionic in the Cd(II) and Zn(II) complexes and covalent in the Ni(II) complex. The data are supported by NMR (1H and 13C) spectra. The magnetic moments and electronic spectra of all complexes provide tetrahedral, square planar and/or octahedral structure. The decomposition of the complexes revealed the outer and inner solvents as well as the remaining residue based on TGA. The complexes have variable activities against some bacteria and fungi. The ligand is inactive against all tested organisms. The activity of Cd(II) and Hg(II) may be related to the geometry of the complexes.

El-Sayed, Ahmed E. M.; Al-Fulaij, O. A.; Elaasar, A. A.; El-Defrawy, M. M.; El-Asmy, A. A.

2015-01-01

389

X-ray photoelectron, Cu L3MM Auger and X-ray absorption spectroscopic studies of Cu nanoparticles produced in aqueous solutions: The effect of sample preparation techniques  

NASA Astrophysics Data System (ADS)

Stable sols of copper nanoparticles from 10 nm to 50 nm in diameter synthesized in aqueous solutions using several reducing agents and immobilized on pyrographite were characterized by XPS, Cu L3MM Auger and X-ray absorption spectroscopy (Cu L-edge TEY XANES and Cu K-edge XANES and EXAFS in transmission mode) along with UV-vis spectroscopy, AFM, TEM. It was found that the nanoparticles produced in the hydrazine hydrate and sodium borohydride assisted synthesis are composed of surface Cu(II) oxyhydroxides, and the shells formed by cuprite Cu2O and distorted Cu(I) oxide, which showed the Cu L-edge peak shifted to higher energies, above the metallic core. The relative amount of cuprite was usually larger in the hydrazine systems, but it depended on the sample preparation protocol. The nanoparticles prepared using ascorbic acid as a reactant consisted of rather thick Cu(II) overlayer and largely distorted Cu(I) oxide underneath. The post-synthetic sample handling notably affected the results; in particular, sedimentation (instead of drying of the colloidal solution) favored reduction of the oxide layers to metallic copper and agglomeration of the Cu particles in the precipitate, even in the case of ascorbic acid, while the colloidal particles in the supernatant were oxidized.

Saikova, Svetlana; Vorobyev, Sergey; Likhatski, Maxim; Romanchenko, Alexander; Erenburg, Simon; Trubina, Svetlana; Mikhlin, Yuri

2012-08-01

390

Synthesis, spectroscopic characterization, electrochemical behavior and computational analysis of mixed diamine ligand gold(III) complexes: antiproliferative and in vitro cytotoxic evaluations against human cancer cell lines.  

PubMed

The gold(III) complexes of the type [(DACH)Au(en)]Cl3, 1,2-Diaminocyclohexane ethylenediamine gold(III) chloride [where 1,2-DACH = cis-, trans-1,2- and S,S-1,2diaminocyclohexane and en = ethylenediamine] have been synthesized and characterized using various analytical and spectroscopic techniques including elemental analysis, UV-Vis and FTIR spectra; and solution as well as solid-state NMR measurements. The solid-state (13)C NMR shows that 1,2-diaminocyclohexane (1,2-DACH) and ethylenediamine (en) are strongly bound to the gold(III) center via N donor atoms. The stability of the mixed diamine ligand gold(III) was determined by (1)H and (13)C NMR spectra. Their electrochemical behavior was studied by cyclic voltammetry. The structural details and relative stabilities of the four possible isomers of the complexes were also reported at the B3LYP/LANL2DZ level of theory. The coordination sphere of these complexes around gold(III) center adopts distorted square planar geometry. The computational study also demonstrates that trans- conformations is slightly more stable than the cis-conformations. The antiproliferative effects and cytotoxic properties of the mixed diamine ligand gold(III) complexes were evaluated in vitro on human gastric SGC7901 and prostate PC3 cancer cells using MTT assay. The antiproliferative study of the gold(III) complexes on PC3 and SGC7901 cells indicate that complex 1 is the most effective antiproliferative agent among mixed ligand based gold(III) complexes 1-3. The IC50 data reveal that the in vitro cytotoxicity of complexes 1 and 3 against SGC7901 cancer cells are fairly better than that of cisplatin. PMID:25034122

Al-Jaroudi, Said S; Monim-ul-Mehboob, M; Altaf, Muhammad; Al-Saadi, Abdulaziz A; Wazeer, Mohammed I M; Altuwaijri, Saleh; Isab, Anvarhusein A

2014-12-01

391

Synthesis, spectroscopic characterization, electrochemistry and biological evaluation of some binuclear transition metal complexes of bicompartmental ONO donor ligands containing benzo[b]thiophene moiety  

NASA Astrophysics Data System (ADS)

A series of new binucleating Cu(II), Co(II), Ni(II) and Zn(II) complexes of bicompartmental ligands with ONO donor were synthesized. The ligands were obtained by the condensation of 3-chloro-6-substituted benzo[b]thiophene-2-carbohydrazides and 4,6-diacetylresorcinol. The synthesized ligands and their complexes were characterized by elemental analysis and various spectroscopic techniques. Elemental analysis, IR, 1H NMR, ESI-mass, UV-Visible, TG-DTA, magnetic measurements, molar conductance and powder-XRD data has been used to elucidate their structures. The bonding sites are the oxygen atom of amide carbonyl, azomethine nitrogen and phenolic oxygen for ligands 1 and 2. The binuclear nature of the complexes was confirmed by ESR spectral data. TG-DTA studies for some complexes showed the presence of coordinated water molecules and the final product is the metal oxide. All the complexes were investigated for their electrochemical activity, only the Cu(II) complexes showed the redox property. Cu(II) complexes were square planar, whereas Co(II), Ni(II) and Zn(II) complexes were octahedral. Powder-XRD pattern have been studied in order to test the degree of crystallinity of the complexes and unit cell calculations were made. In order to evaluate the effect of antimicrobial activity of metal ions upon chelation, both the ligands and their metal complexes were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The results showed that the metal complexes were found to be more active than free ligands. The DNA cleaving capacities of all the complexes were analyzed by agarose gel electrophoresis method against supercoiled plasmid DNA. Among the compounds tested for antioxidant capacity, ligand 1 displayed excellent activity than its metal complexes.

Mahendra Raj, K.; Vivekanand, B.; Nagesh, G. Y.; Mruthyunjayaswamy, B. H. M.

2014-02-01

392

A series of transition and non-transition metal complexes from a N?O? hexadentate Schiff base ligand: Synthesis, spectroscopic characterization and efficient antimicrobial activities.  

PubMed

Some transition and non-transition metal complexes of the hexadentate N?O? donor Schiff base ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine, abbreviated to H?fsatrien, have been synthesized. All the 14 metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic (UV-Vis, IR, NMR, ESR) data. The analytical data helped to elucidate the structures of the metal complexes. The Schiff base, H?fsatrien, is found to act as a dibasic hexadentate ligand using N?N?O? donor set of atoms (leaving the COOH group uncoordinated) leading to an octahedral geometry for the complexes around all the metal ions except VO²(+) and UO?²(+). However, surprisingly the same ligand functions as a neutral hexadentate and neutral tetradentate one towards UO?²(+) and VO²(+), respectively. In case of divalent metal complexes they have the general formula [M(H?fsatrien)] (where M stands for Cu, Co, Hg and Zn); for trivalent metal complexes it is [M(H?fsatrien)]X·nH?O (where M stands for Cr, Mn, Fe, Co and X stands for CH?COO, Cl, NO?, ClO?) and for the complexes of VO²(+) and UO?²(+), [M(H?fsatrien)]Y (where M=VO and Y=SO?); M=UO? and Y=2 NO?). The Schiff base ligand and most of the complexes have been screened in vitro to judge their antibacterial (Escherichia coli and Staphylococcus aureus) and antifungal (Aspergillus niger and Pencillium chrysogenum) activities. PMID:20801711

Sarkar, Saikat; Dey, Kamalendu

2010-11-01

393

Preparation and characterization of novel glass-ceramic tile with microwave absorption properties from iron ore tailings  

NASA Astrophysics Data System (ADS)

A novel glass-ceramic tile consisting of one glass-ceramic layer (GC) attaining microwave absorption properties atop ceramic substrate was prepared through quench-heat treatment route derived from iron ore tailings (IOTs) and commercial raw materials (purity range 73-99%). X-ray diffraction (XRD), SEM, Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Physical property measurement system (PPMS) and Vector network analyzer (VNA) measurements were carried out to investigate phase, microstructure, magnetic and microwave absorption aspects of the glass-ceramic layer. Roughly 80.6±1.7 wt% borosilicate glass and 19.4±1.7 wt% spinel ferrite with chemical formula of (Zn2+0.17Fe3+0.83)[Fe3+1.17Fe2+0.06Ni2+0.77]O4 were found among the tested samples. Absorption of Electromagnetic wave by 3 mm thick glass-ceramic layer at frequency of 2-18 GHz reached peak reflection loss (RL) of -17.61 dB (98.27% microwave absorption) at 10.31 GHz. Altering the thickness of the glass-ceramic layer can meet the requirements of different level of microwave absorption.

Yao, Rui; Liao, SongYi; Dai, ChangLu; Liu, YuChen; Chen, XiaoYu; Zheng, Feng

2015-03-01

394

Resolving Spectral Lines with a Periscope-Type DVD Spectroscope  

ERIC Educational Resources Information Center

A new type of DVD spectroscope, the periscope type, is described and the numerical analysis of the observed emission and absorption spectra is demonstrated. A small and thin mirror is put inside and an eighth part of a DVD is used as a grating. Using this improved DVD spectroscope, one can observe and photograph visible spectra more easily and…

Wakabayashi, Fumitaka

2008-01-01

395

Synthesis, spectroscopic characterization and biological activities of N4O2 Schiff base ligand and its metal complexes of Co(II), Ni(II), Cu(II) and Zn(II)  

NASA Astrophysics Data System (ADS)

The Schiff base ligand, bis(indoline-2-one)triethylenetetramine (L) obtained from condensation of triethylenetetramine and isatin was used to synthesize the complexes of type, [ML]Cl2 [M = Co(II), Ni(II), Cu(II) and Zn(II)]. L was characterized on the basis of the results of elemental analysis, FT-IR, 1H and 13C NMR, mass spectroscopic studies. The stoichiometry, bonding and stereochemistries of complexes were ascertained on the basis of results of elemental analysis, magnetic susceptibility values, molar conductance and various spectroscopic studies. EPR, UV-vis and magnetic moments revealed an octahedral geometry for complexes. L and its Cu(II) and Zn(II) complexes were screened for their antibacterial activity. Analgesic activity of Cu(II) and Zn(II) complexes was also tested in rats by tail flick method. Both complexes were found to possess good antibacterial and moderate analgesic activity.

Al-Resayes, Saud I.; Shakir, Mohammad; Abbasi, Ambreen; Amin, Kr. Mohammad Yusuf; Lateef, Abdul

396

Preparation, spectroscopic and thermal characterization of new charge-transfer complexes of ethidium bromide with ?-acceptors. In vitro biological activity studies.  

PubMed

Ethidium bromide (EtBr) is a strong DNA binder and has been widely used to probe DNA structure in drug-DNA and protein-DNA interaction. Four new charge-transfer (CT) complexes consisting of EtBr as donor and quinol (QL), picric acid (PA), tetracyanoquinodimethane (TCNQ) or dichlorodicyanobenzoquinone (DDQ) as acceptors, were synthesized and characterized by elemental analysis, electronic absorption, spectrophotometric titration, IR, Raman, (1)H NMR and X-ray powder diffraction (XRD) techniques. The stoichiometry of these complexes was found to be 1:2 ratio and having the formula [(EtBr)(acceptor)]. The thermal stability of the synthesized CT complexes was investigated using thermogravimetric (TG) analyses, and the morphology and particle size of these complexes were obtained from scanning electron microscopy (SEM). The CT complexes were also tested for its antibacterial activity against two Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis and two Gram-negative bacteria; Escherichia coli and Pseudomonas aeuroginosa strains by using Tetracycline as standard and antifungal property against Aspergillus flavus and Candida albicans by using amphotericin B as standard. The results were compared with the standard drugs and significant conclusions were obtained. The results indicated that the [(EtBr)(QL)2] complex had exerted excellent inhibitory activity against the growth of the tested bacterial strains. PMID:23542517

Eldaroti, Hala H; Gadir, Suad A; Refat, Moamen S; Adam, Abdel Majid A

2013-05-15

397

Preparation, characterization, spectroscopic (FT-IR, FT-Raman, UV and visible) studies, optical properties and Kubo gap analysis of In2O3 thin films  

NASA Astrophysics Data System (ADS)

Indium oxide (In2O3) thin films are successfully deposited on microscopic glass substrate at different temperatures by spray pyrolysis technique using Indium acetate as precursor solution. The physical properties of these films are characterized by XRD, SEM, AFM, UV-visible, PL and Photo acoustic measurements. XRD analysis revealed that the films are polycrystalline in nature having cubic crystal structure with a preferred grain orientation along (2 2 2) plane. The average transmittance in the visible region is found to vary from 60% to 93% depending upon the substrate temperature. The complete vibrational analysis has been carried out and the optimized parameters are calculated using HF and DFT (LSDA, B3LYP and B3PW91) methods with 3-21G(d,p) basis set for In2O3. The fundamental frequencies are calculated and assigned according to the experimental frequencies. Furthermore, 13C NMR and 1H NMR chemical shifts are calculated by using the gauge independent atomic orbital (GIAO) technique with HF/B3LYP/B3PW91 methods on same basis set. A study of the electronic properties; absorption wavelengths, excitation energy, dipole moment, Kubo gap (HOMO and LUMO) and frontier molecular orbital energies, are performed by HF and DFT methods. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) is executed. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the compound are calculated in gas phase.

Jothibas, M.; Manoharan, C.; Ramalingam, S.; Dhanapandian, S.; Johnson Jeyakumar, S.; Bououdina, M.

2013-10-01

398

Synthesis, spectroscopic characterization and structural studies of a new proton transfer (H-bonded) complex of o-phenylenediamine with L-tartaric acid  

NASA Astrophysics Data System (ADS)

A proton transfer or H-bonded (CT) complex of o-phenylenediamine (OPD) as donor with L-tartaric acid (TART) as acceptor was synthesized and characterized by spectral techniques such as FTIR, 1H NMR, elemental analysis, TGA-TDA, X-ray crystallography and spectrophotometric studies. The structural investigations exhibit that the cation [OPD+] and anion [TART-] are linked together through strong N+-H⋯O- type hydrogen bonds due to transfer of proton from acceptor to donor. Formed H-bonded complex exhibits well resolved proton transfer bands in the regions where neither donor nor acceptor has any absorption. The stoichiometry of the H-bonded complex (HBC) was found to be 1:1, determined by straight line methods. Spectrophotometric studies have been performed at room temperature and Benesi-Hildebrand equation was used to determine formation constant (KCT), molar extinction coefficient (?CT) and also transition energy (ECT) of the H-bonded complex. Spectrophotomeric and crystallographic studies have ascertained the formation of 1:1 H-bonded complex. Thermal analysis (TGA-DTA) was also used to confirm the thermal fragmentation and the stability of the synthesized H-bonded complex.

Khan, Ishaat M.; Ahmad, Afaq

2013-10-01

399

Spectroscopic characterization of cometary samples  

NASA Astrophysics Data System (ADS)

A summary of what is presently known from cometary vibrational spectroscopy is presented, along with some possible results to be anticipated from future non-sample-return cometary missions which, however, will leave a number of key questions unanswered. It is suggested that major efforts have to be made in the laboratory to properly prepare the analysis of returned cometary samples. Particular attention is given to Raman spectroscopy of cometary analogs (frozen gases and irradiated organic materials), performed applying sufficiently low laser power so as not to significantly alter the sample. Also discussed are attempts to use REELS, which may yield information not only on the elemental composition of the sample but also on its optical constants, especially in the FUV.

Strazzulla, G.; Baratta, G. A.; Compagnini, G.; Foti, G.

1991-04-01

400

Raman Spectroscopic Characterization of Graphene  

Microsoft Academic Search

The recent progress using Raman spectroscopy and imaging of graphene is reviewed. The intensity of the G band increases with increased graphene layers, and the shape of 2D band evolves into four peaks of bilayer graphene from a single peak of monolayer graphene. The G band will blue shift and become narrow with both electron and hole doping, whereas the

Bo Tang; Hu Guoxin; Hanyang Gao

2010-01-01